CN117957635A - SiC P-type and low resistivity crystals, boules, wafers and devices and methods of making the same - Google Patents

Abstract

Doped SiOC liquid starting materials provide p-type polymer derived ceramic SiC crystalline materials, including ingots and wafers. p-type SiC electronic devices. Low resistivity SiC crystals, wafers and boules have phosphorus as a dopant. Polymer-derived ceramic doped SiC shaped charge source materials for vapor deposition growth of doped SiC crystals.

Description

SiC P-type and low resistivity crystals, boules, wafers and devices and methods of making the same

Cross Reference to Related Applications

The present application claims priority and benefit from U.S. c. ≡119 (e) (1) U.S. provisional application serial No. 63/220,132 filed on 7.9 of 2021 and U.S. provisional application serial No. 63/337,088 filed on 4.30 of 2022, the disclosures of which are incorporated herein by reference in their entireties.

Technical Field

The present invention relates to p-type SiC crystals, ingots, boules and wafers; low resistivity SiC crystals, ingots, boules, and wafers; methods of fabricating p-type SiC crystals, ingots, boules, and wafers; methods of making low resistivity SiC crystals, ingots, boules, and wafers; as well as devices made from these wafers and the use of these wafers.

Background

Pure crystalline silicon carbide (SiC) is electrically neutral, i.e. the positive and negative charges in the crystalline material are balanced. Generally, to be useful in the manufacture of semiconductor diodes and transistors, impurities are added to the SiC crystal during the SiC crystal growth process to create a charge imbalance within the crystal, which can affect the conductivity of the SiC. Impurity atoms that add positive charge to SiC are referred to as donor atoms. Typically, the donor atoms are identified by the columns to the right of the columns containing Si and C in the periodic table (e.g., column 15, V A). Typical donor atoms for SiC are nitrogen (N) and phosphorus (P). Impurity atoms that add negative charge to SiC are referred to as acceptor atoms. Typically, acceptor atoms are identified by the columns to the left of the columns containing Si and C in the periodic table (e.g., column 13 or III A). Typical acceptor atoms for SiC are boron (B) and aluminum (Al). SiC crystals will typically contain both donor and acceptor atomic impurities. For donor impurity atoms or acceptor impurity atoms, in order to affect the net charge in the crystal and become electrically active (i.e., affect the conductivity/resistivity of the crystal), the impurity atoms must generally replace Si atoms or C atoms at their positions in the crystal, and in this case, the impurity atoms are referred to as substitutional impurities. The impurity atoms may also be located at positions between the Si atoms and the C atoms. In this case, the impurity atoms are referred to as interstitial impurities, and may not affect the net charge in the crystal, may have less effect on the charge, and may not affect the net charge in the crystal in some cases. Thus, the terms "electroactive atomic impurity", "electroactive impurity" and "electroactive" are used to describe atoms added to SiC crystalline materials, including substitutional and interstitial atoms, that affect the net charge of the material (e.g., the crystal). Thus, all substituted impurities are electroactive impurities, and interstitial impurities may be electroactive impurities or non-electroactive impurities. Accordingly, the atomic concentration of the donor impurity or acceptor impurity (the ratio of the number of impurity atoms to the total number of atoms in the crystal) may be equal to or greater than the atomic concentration of the electroactive impurity (e.g., the substituted impurity atoms). When there are more electroactive (e.g., substituted) donor atoms than electroactive (e.g., substituted) acceptor atoms, the SiC crystal is n-type, n representing a negative, i.e., there is an excess of negative charge. In contrast, when there are more electroactive (e.g., substituted) acceptor atoms than donor atoms, the SiC crystal is p-type, with p representing a positive, i.e., there is an excess of positive charge in the SiC crystal.

Prior to the present invention, no commercially available p-type SiC substrates with diameters >100mm have been used to fabricate SiC semiconductor devices. It is believed that prior attempts to manufacture p-type SiC crystals do not provide a manufacturable process for producing high quality, low defect p-type SiC materials such as SiC crystals, siC ingots, and p-type SiC wafers cut from these ingots. Thus, prior to the present invention, the benefits of SiC semiconductor devices having p-type SiC materials were largely unavailable and commercially unavailable.

As used herein, unless otherwise indicated, there are two types of charge carriers in a semiconductor material, namely holes and electrons. Holes can be considered as "opposite" of electrons. Unlike negatively charged electrons, holes are positively charged, the number of holes is equal to electrons, but the polarity is opposite to the charge of electrons. Holes can sometimes be confusing because they are not physical particles like electrons, but rather lack electrons in atoms. As electrons leave their locations, holes can move from one atom to another in the semiconductor. Thus, by analogy, it is like a group of people standing in a row on a step. If the person who is in front walks up a step, the person leaves a void. When everyone walks up one step, the available steps (cavities) will move down on these steps. When an electron in an atom moves out of the valence band of the atom (typically the outermost electron shell that is completely filled with electrons) into the conduction band (the region in the atom where electrons can easily escape), a hole is formed, which typically occurs anywhere in the semiconductor.

As used herein, unless otherwise indicated, the terms "p-type," "p-type wafer," "p-type crystal," "p-type boule," and similar such terms are to be given their broadest possible meanings and are intended to include SiC crystalline materials having more electrically active acceptor atomic impurities (e.g., substituted acceptor atomic impurities) than electrically active donor atomic impurities (e.g., substituted donor impurity atoms). Thus, for example, siC crystalline materials having a net number of electroactive acceptor atoms per unit volume of from 1×10 ¹⁰/cm³ to 1×10 ²²/cm³, from about 1×10 ¹⁸/cm³ to 1×10 ²⁰/cm³, from about 1×10 ¹⁸/cm³ to 1×10 ²³/cm³, from about 1×10 ¹⁸/cm³ to 1×10 ²⁴/cm³, greater than about 1×10 ⁹/cm³, greater than about 1×10 ¹⁵/cm³, greater than about 1×10 ¹⁸/cm³, and greater than 1×10 ¹⁹/cm³ are characterized as p-type SiC crystalline materials.

In addition, unless otherwise indicated, to be considered a p-type SiC crystalline material, the net carrier concentration will have an excess of acceptor atomic impurities, as shown in equation (1)

(1)Nc＝N_D-N_A

Where Nc is the net concentration of carriers. N _D is the concentration of the electroactive donor impurity atoms. N _A is the concentration of electroactive acceptor impurity atoms. Conventionally, nc is negative for p-type materials, indicating the absence of electrons.

As used herein, unless otherwise indicated, the terms "p-type device," "p-type semiconductor," and similar such terms are to be given their broadest possible meaning and include any semiconductor, microelectronic device, or electronic device having a p-type layer or based on a p-type wafer, chip, or substrate.

As used herein, unless otherwise indicated, the term "p ⁺"、"p⁺ -type" and similar such terms refer to p-type crystalline SiC materials, e.g., p-type ingots, wafers, etc., which have a high content of dopants, e.g., are heavily doped (N _D>10¹⁸/cm³), and thus have a low resistivity (< 0.03 ohm-cm). Thus, the p ⁺ -type material may have an N _A,10¹⁸/cm³ of 10 ¹⁸/cm³ to about 10 ²⁰/cm³ to an N _A,N_D>10¹⁹/cm³ of about 10 ²¹/cm³, about 1 x 10 ¹⁸/cm³ to 1 x 10 ²³/cm³, about 1 x 10 ¹⁸/cm³ to 1 x 10 ²⁴/cm³, and an N _A of about 10 ²⁰/cm³. In general, the resistivity of the p ⁺ -type material may be equal to or less than 0.03 ohm-cm, less than about 0.025 ohm-cm, less than about 0.020 ohm-cm, less than about 0.015 ohm-cm, from about 0.030 ohm-cm to about 0.01 ohm-cm, from about 0.025 ohm-cm to about 0.008 ohm-cm, and from about 0.020 ohm-cm to about 0.005 ohm-cm.

As used herein, unless otherwise indicated, the term "p ^-"、"p^- type" and similar such terms refer to p-type crystalline materials, e.g., p-type ingots, wafers, etc., which have a small amount of dopant, e.g., lightly doped (N _D<10¹⁸/cm³), and thus have a higher resistivity. Typically, these resistivities are higher than 0.03 ohm-cm. Thus, the p ^- type material can have a value of N _A from 10 ¹⁸/cm³ to about 10 ¹⁰/cm³ and less. Typically, the resistivity of p ^- type materials can range from 0.03 ohm-cm to 10 ⁸ ohm-cm and greater.

As used herein, unless otherwise indicated, the terms "n-type", "n-type wafer", "n-type crystal", "n-type boule" and similar such terms are to be given their broadest possible meanings and shall include SiC crystalline materials having a negative charge with more electrically active donor atoms (e.g., substitutional donor atom impurities) than other types of impurity atoms. Thus, for example, siC crystalline materials having a net number of electroactive donor atoms per unit volume of from 1 x 10 ¹⁰/cm³ to 1 x 10 ²²/cm³, from about 1 x 10 ¹⁸/cm³ to 1 x 10 ²⁰/cm³, greater than about 1 x 10 ⁹/cm³, greater than about 1 x 10 ¹⁵/cm³, greater than about 1 x 10 ¹⁸/cm³, and greater than about 1 x 10 ¹⁹/cm³ are characterized as n-type SiC crystalline materials.

Further, unless otherwise indicated, considered as an n-type SiC crystalline material, the net carrier concentration will represent an excess of donor atom impurities, as shown in the equation. Conventionally, nc is positive for n-type materials, indicating electron excess.

The term "N ⁺"、"n⁺ type" and similar such terms refer to N-type materials, such as N-type ingots, wafers, etc., which have a high doping dose, such as heavily doped (N _A>10¹⁸/cm³), and thus have a low resistivity (< 0.03 ohm-cm). Typically, these resistivities may be equal to or lower than 0.03 ohm-cm.

The term "N ^-"、"n^- type" and similar such terms refer to N-type materials, such as N-type ingots, wafers, etc., which have a small amount of dopant, such as lightly doped (N _A<10¹⁸/cm³), and thus have a relatively high resistivity. Typically, these resistivities may be higher than 0.03 ohm-cm, and are typically equal to or higher than 0.03 ohm-cm.

As used herein, unless otherwise indicated, the terms "physical cavities," "physical voids," and "physical cavities" refer to physical properties, rather than electrical properties, and are used in a generic manner, such as to indicate the absence of material in a solid or surface, the structure or surface, and the absence of empty spaces in a surface or solid.

As used herein, unless otherwise indicated, "vapor deposition" ("VD"), "vapor deposition technique," "vapor deposition process," and similar such terms are to be given their broadest meanings and shall include processes such as converting a solid or liquid starting material into a gaseous or vapor state and then depositing the gas or vapor to form, e.g., grow, a solid material. As used herein, vapor deposition techniques will include by epitaxial growth, wherein the layer is provided by vapor phase (gaseous phase). Other types of vapor deposition techniques include: chemical vapor deposition ("CVD"); physical vapor deposition ("PVD"), plasma enhanced CVD, physical vapor transport ("PVT"), etc. Examples of vapor deposition apparatus would include hot wall chemical vapor deposition reactors, multi-furnace chemical vapor deposition reactors, chemical vapor deposition chimney reactors. Physical Vapor Transport (PVT) means and requires the use of at least one solid starting material that is sublimated to provide vapor (e.g., flux) for crystal growth.

As used herein, unless otherwise indicated, the term "vaporization temperature" will be given its broadest possible meaning and includes the temperature at which a material transitions from a liquid state to a gaseous state, from a solid state to a gaseous state, or both (e.g., solid to liquid to gaseous transitions occur over a very small temperature range, such as a range of less than about 20 ℃, less than about 10 ℃, and less than about 5 ℃). Unless specifically stated otherwise, the vaporization temperature will be the temperature corresponding to any particular pressure (e.g., one atmosphere, 0.5 atmospheres) at which this transition occurs. When discussing the vaporization temperature of a material in a particular application, method, or used in a particular device (such as a PVT device), the vaporization temperature will be at the pressure used or typically used in the application, method, or device, unless explicitly stated otherwise.

Silicon carbide generally does not have a liquid phase and is not in a liquid phase under typical PVT process conditions, but rather, silicon carbide sublimates under vacuum at temperatures above about 1700 ℃. (it should be noted that SiC can exist in the liquid phase at very high pressures.) generally, in industrial and commercial applications, conditions are established such that sublimation occurs at temperatures of about 2500 ℃ and above. When silicon carbide sublimates, it generally forms a vapor flux composed of various silicon and carbon, the composition of the vapor flux being a function of the source material and temperature and pressure. However, the present invention provides, among other things, the ability to control the ratio of these components by selecting a liquid starting material, such as a polysilocarb (polysilocarb) precursor, in addition to the use of a source material, such as a forming charge (SHAPED CHARGE), and the temperature and pressure during the PVT process.

As used herein, unless otherwise indicated, the terms "crystal," "ingot" and "boule" and similar such terms are to be given their broadest possible meaning and refer to the crystal structure as such: a diameter of about 50mm to about 250mm, a diameter greater than 100mm, a diameter greater than 250mm, and typically a diameter of about 150mm; and has a height (i.e., distance from seed end to tail end) of about 25mm to about 250mm, a height of about 75mm to about 150mm, a height of 75mm and greater, a height of about 100mm and greater, a height of about 150mm and greater, and typically a height of about 100mm to about 150 mm. The term "crystal" generally refers to a structure that is initially grown and then removed from the growth apparatus. The term "ingot" generally refers to crystals that have been treated (e.g., flattened) at one or both ends. The term "ingot" generally refers to an ingot that has been further processed, such as by forming a flat surface on the ingot, and is ready for use in a wafer processing (i.e., manufacturing wafers from the ingot). Generally, crystals are grown in vapor deposition devices using vapor deposition processes, and in particular PVT devices and processes.

Unless specifically stated otherwise or clear from the context, the terms crystal, ingot, and boule used in this specification are generally interchangeable; and in particular, the description of the nature, crystal structure, macroscopic and microscopic imperfections, and composition of one material in this specification is generally applicable to other materials.

As used herein, unless otherwise indicated, the terms "wafer," "SiC wafer," "p-type SiC wafer," "n-type SiC wafer," and similar such terms refer to a crystalline material that is a structure cut from a larger structure of the same crystalline material (e.g., a p-type SiC wafer cut from a p-type SiC boule). Generally, wafer 700 is a disk-like structure and may be circular or semi-circular 705 and may have one plane or more than one plane. The wafer has a top or top surface, a bottom or bottom surface, and a thickness. The outer edge of the wafer may be tapered, beveled, chamfered, square, rounded, etc.

Typically, siC wafers are formed by dicing the wafer generally transverse to the c-axis (growth axis) of the larger crystal (e.g., ingot). Typically, the wafer may be on the growth axis (i.e., on-axis) or at a few degrees to the axis (i.e., off-axis), typically about 0.1 degrees to about 5 degrees from the growth axis for off-axis wafers. The wafer may have a thickness of about 80 μm to about 600 μm and a diameter of about 50mm to about 250mm, preferably about 150mm. SiC wafers typically have a carbon face or surface, and a silicon face or surface when cut on-axis or slightly off-axis. The wafer may also be diced along the growth axis as well as in any other crystallographic direction of the growth axis.

Typically, prior to developing commercial SiC MOSFETs, the power industry (> 500V) was primarily based on the use of silicon (Si) IGBTs. These are bipolar devices and have low conduction losses, allowing them to handle high currents (amps) and high power (watts or W). However, they suffer from high power losses during the off phase (transition between on and off), limiting their operating frequency. The operating frequency is important because the higher the frequency, the smaller the passive components (e.g., inductance) of the converter/inverter, which helps reduce the volume and weight of the device. Reducing the volume or weight or both of these devices (MOSFETs and IGBTs) is a long standing problem in the art and is also an important indicator for end users. MOFETs are unipolar devices and therefore their switching losses are low (especially during the off phase). However, their on-resistance (conduction loss) is higher, increasing with increasing voltage, so IGBTs are favored at higher voltages (for Si, > 500V). Accordingly, the art has proposed a long-standing and unresolved paradigm for optimizing (i.e., minimizing) conduction losses and transition losses in semiconductor devices.

In addition, the transition of silicon-based devices to SiC-based devices faces a number and long-standing problems. In particular, the transition from p-type silicon devices to SiC-type devices (e.g., n-type for these initial previous attempts) requires significant expense, time, and difficulty to redesign the p-type silicon devices, e.g., circuits, masks, configurations, etc., so that n-type SiC can be used. The inability of the prior art to provide high quality p-type SiC wafers leaves an unresolved long-standing problem and need.

The history of power electronics and circuits began with semiconductor devices made of silicon.

Many designs of power supply circuits employ designs as well as p-channel and n-channel field effect transistors, the most common of which are MOSFETs, or metal oxide semiconductor field effect transistors. As used herein, unless otherwise indicated, a p-channel MOSFET is a MOSFET in which the channel of the MOSFET consists of a majority of holes as carriers. When the MOSFET is activated and turned on, most of the current is holes that move through the channel. Another type of MOSFET is an n-channel MOSFET, in which most of the carriers are electrons. There are two different ways of manufacturing an n-channel or p-channel MOSFET: enhancement MOSFET or depletion MOSFET.

When there is no voltage difference between the gate and source terminals, the depletion mode MOSFET is typically on (maximum current flows from source to drain). However, if a voltage is applied to its gate lead, the drain-source channel becomes more resistive until the gate voltage is so high that the transistor is completely turned off. The opposite is true of enhancement MOSFETs. When the gate-source voltage is 0V (vgs=0), it is normally off. However, if a voltage is applied to its gate lead, the resistance of the drain-source channel becomes small.

Typical applications of power devices are the design and manufacture of power circuits, i.e. inverters, converters and power supplies. These circuits are designed using either n-channel MOSFETs or p-channel MOSFETs or both. One example of the need for both types is an H-bridge power drive circuit whose function is to drive current through the load in either direction (i.e., drive a DC motor in an electric motor-guided vehicle, for example, forward or backward, or drive a motor in a purely electric vehicle).

To improve the energy efficiency of modern power management circuits, designers now employ silicon carbide MOSFETs based on 4H-SiC crystalline substrates. Silicon carbide MOSFETs offer the opportunity to design circuits that operate at higher voltages and high frequencies than circuits that use silicon MOSFETs. When SiC MOSFETs are used, the power supply circuit described above can typically operate at voltages ranging from 600V to above 10kV with current strengths ranging from 5A to above 200A.

Today, MOSFETs made of SiC can only be manufactured with n-type SiC substrates, since there is currently no commercial supply of p-type SiC substrates. Therefore, most SiC MOSFETs are made as n-channel devices. Because only SiC MOSFETs using n-type substrates are commercially available to date, siC MOSFETs cannot be deployed in all power circuit applications.

There has long been a need for a commercially viable n-channel IGBT (a variation of a MOSFET transistor) because such devices can provide lower on-resistance and/or higher blocking voltages than their p-channel counterparts. Furthermore, from a system perspective, an n-channel device with positive voltage polarity and similar to a conventional power MOSFET may be more attractive. Heretofore, p-type SiC materials formed as epitaxial layers on n-type SiC substrates have been used, and such devices have been manufactured by subsequently removing the substrates by grinding. These devices have proven unsatisfactory for several reasons, including because of the difficulty in requiring removal of the substrate. The present invention provides, inter alia, the ability to provide such SiC IGBT devices that are simple to manufacture and commercially acceptable.

There is a long felt need for SiC LDMOSFETs (lateral metal oxide semiconductor field effect transistors). These devices were developed on silicon for high power applications such as cellular and UHF broadcast transmissions have increased significantly. This is because Si LDMOSFETs have higher gain and better linearity than bipolar devices. However, prior to the present invention, this design was not realized in SiC because there was only an n-type SiC substrate, and historically any p-type epitaxially formed SiC substrate had too high a resistivity compared to silicon, resulting in undesirable LDMOSFET device performance.

In general, power MOSFETs tend to exhibit better performance when fabricated with n-channels rather than p-channels. However, to achieve higher performance, such devices typically require epitaxial growth on low resistivity p-type substrates. However, the p-type 4H-SiC substrates currently commercially available have a relatively high resistivity (2.5 ohm-cm) that is about two orders of magnitude higher than the n-type substrate. The advantages of n-channel SiC devices have long been sought after, but these advantages have not been realized due to the high resistivity found in existing p-type substrates. The p-type wafer of the present invention thus provides low resistivity, which addresses this long-standing need, and results in n-channel SiC devices having improved performance relative to devices fabricated with n-type SiC substrates.

As used herein, unless otherwise indicated, the term "specific gravity" (also referred to as "apparent density") will be given its broadest possible meaning, generally referring to the weight per unit structural volume, e.g., the spatial shape of a material. This property will include the internal porosity of the particles as part of their volume. In other techniques, the measurement may be with a low viscosity fluid that wets the particle surface.

As used herein, unless otherwise indicated, the term "actual density" (which may also be referred to as "true density") will be given its broadest possible meaning and generally means the weight per unit volume of material when no voids are present in the material. Such measurement and properties substantially eliminate any internal porosity of the material (i.e., below a detectable level of standard measurement techniques), e.g., it does not include any voids in the material.

As used herein, unless otherwise indicated, "room temperature" is 25 ℃. And "standard ambient temperature and pressure" is 25 ℃ and 1 atmosphere. Unless explicitly stated otherwise, all tests, test results, physical properties, and temperature-related and/or pressure-related values are provided at standard ambient temperatures and pressures, including viscosity.

In general, unless otherwise indicated, the terms "about" and "symbol" to "as used herein are intended to include the greater of a variation or range of ±10% and experimental or instrument errors associated with obtaining the stated values.

As used herein, unless otherwise indicated, the terms% by weight and% by mass are used interchangeably and refer to the weight of the first component as a percentage of the total weight, e.g., formulation, mixture, preform, material, structure or product. Unless explicitly stated otherwise, X/Y or XY are used to denote the weight% of X and the weight% of Y in the formulation. Unless explicitly stated otherwise, X/Y/Z or XYZ is used to denote the weight% of X, the weight% of Y and the weight% of Z in the formulation.

As used herein, unless otherwise indicated, "volume%" and "% volume" and similar such terms refer to the percentage of the volume of the first component to the total volume, such as a formulation, mixture, preform, material, structure, or product.

As used herein, unless explicitly stated otherwise, the term "source material" when used in the context of ingot growth, vapor deposition apparatus, epitaxy, and crystal growth and deposition processes shall be given its broadest possible definition and refers to powdered SiC material, siC space forms (e.g., shaped charges) or other forms of solid SiC material placed in a growth chamber or in an apparatus for crystal growth, epitaxy, or SiC vapor deposition and forming a flux.

As used herein, the terms "purity," "purity level," "impurity," and "contaminant" should be taken to be related and generally relate to undesired materials and are not intentionally added to the SiC material or polymer derivatization process to make SiC crystals. These terms do not include dopants (e.g., impurity atoms, atomic impurities, substitutional impurities, interstitial impurities, electroactive impurities, and the like), or other elements or materials that are intentionally added to or incorporated into the SiC crystal to provide or affect charge, semiconductor properties, or other properties and characteristics of the SiC crystal. These terms do not include the intended incorporation or incorporation of the starting material, polysilocarb precursor, cured material, first ceramic material, source material, and any predetermined material of one or more of these materials to provide the characteristics of the SiC crystal (and in particular the SiC wafer). In determining the purity and purity level, the amount of dopant will be considered (i.e., calculated) as part of the SiOC or SiC material. Thus, as so defined and as used herein, a dopant or doping material is not an "impurity". In this way, for example, a doped (e.g., with atomic impurities) SiOC material or doped (e.g., with atomic impurities) SiC material having only dopants and Si, O, and C, or having only dopants and Si and C, will be 100% pure.

As used herein, unless specifically stated otherwise, the terms "existing material," "current material," "currently available material," "existing vapor deposition apparatus," "current vapor deposition apparatus," and similar such terms refer to source materials and apparatus that were already present prior to the present invention. The use of this term should not be taken nor an admission of the prior art. It is merely a description of the current state of the art as a baseline or reference point from which significant and breakthrough improvements of embodiments of the present invention may be estimated, compared and measured.

The background section is intended to introduce various aspects of the art that may be associated with embodiments of the present invention. Accordingly, the above discussion in this section provides a framework for better understanding of the present invention and should not be deemed an admission of prior art.

Disclosure of Invention

The need for high temperature, high capacity and high performance semiconductor devices, power devices and electronics has been unmet and has long been and continues to grow. Silicon carbide (SiC) wafers provide substrates that meet the performance characteristics (e.g., high temperature, power, bandgap, etc.) preferred and required for these applications. However, prior to the present invention, p-type SiC crystals, p-SiC ingots, p-type SiC ingots, and p-type SiC wafers made from such ingots have not been commercially available and have not been available to a great extent. In particular, such p-type materials cannot be obtained by PVT processes. Thus, the advantages, benefits and potential of p-type SiC wafer based semiconductor devices have not been realized and, in particular, utilized in a commercially and economically acceptable manner.

Another long standing problem with previous attempts to dope SiC, including the incorporation of electroactive acceptor atoms into SiC crystals, is the lack of uniformity in the crystal or wafer from side to side and top to bottom. The present invention addresses and solves this long-standing problem by: methods, source materials, are provided for providing crystals having a highly uniform distribution of electroactive atomic impurities from side to side and top to bottom in embodiments of doped SiC crystals and wafers of the invention.

The present invention addresses these long-felt needs, inter alia, by: formulations, methods, and apparatus are provided for obtaining p-type SiC materials and semiconductor devices utilizing these p-type SiC materials.

The present invention addresses these problems and long-felt needs, inter alia, by providing compositions, materials, articles, devices, and processes taught, disclosed, and claimed herein.

The present invention addresses these problems and long-felt needs, among others, by providing high quality, low defect p-type SiC materials, including p-type SiC crystals, p-type SiC ingots, and p-type SiC wafers obtained from these ingots. The present invention addresses these problems and long-standing needs, inter alia, by providing p-type SiC materials, including p-type SiC crystals, p-type SiC ingots, p-type ingots, and p-type wafers, which are suitable for or useful in the economical manufacture, commercial manufacture, or both, of semiconductor devices. The present invention addresses these problems and long-felt needs, in particular, by providing advantages of SiC semiconductor devices with p-type SiC materials, and in particular, providing such devices in an economically and commercially viable manner, such that their uses and advantages can be widely achieved.

There is also a long-felt need for low resistivity SiC materials, including low resistivity SiC crystals, siC ingots, and SiC wafers obtained from these ingots, and in particular low resistivity SiC wafers and devices that may be built on or from these wafers. These low resistivity wafers may be p-type or n-type wafers. The present invention addresses these problems and long-standing needs, inter alia, by providing low resistivity SiC materials, including low resistivity SiC crystals, siC ingots, boules, and wafers, which are suitable for or useful in the economical manufacture, commercial manufacture, or both, of semiconductor devices.

Accordingly, there is provided a method of manufacturing a SiC crystal having predetermined electrical properties, the method comprising: placing a SiC source material in a vapor deposition apparatus; the SiC source material includes silicon, carbon, and dopants, wherein the dopants are selected to provide predetermined electrical properties to the SiC crystal; wherein the dopant is fixed in position in the source material relative to the silicon and carbon; adding an inert gas to the vapor deposition apparatus, and controlling the pressure in the vapor deposition apparatus; heating the SiC source material to thereby form a flux, wherein the flux comprises silicon, carbon, and dopants; and depositing the flux on a growth face of the SiC crystal to thereby grow the SiC crystal; wherein the SiC crystal has predetermined electrical properties.

Further, there is provided a method of manufacturing a p-type SiC crystal, the method including: placing a shaped charge SiC source material (SHAPED CHARGE SIC source material) in a vapor deposition apparatus; the shaped charge SiC source material consists essentially of silicon, carbon, and a quantity of acceptor atoms held in a certain position of the shaped charge SiC source material; wherein the acceptor atoms are fixed in position relative to the silicon and carbon in the forming material source material; heating the shaped charge SiC source material and thereby forming a flux by sublimation of the shaped charge source material; wherein the flux comprises silicon, carbon, and a portion of a quantity of acceptor atoms; and depositing flux on a growth face of the p-type SiC crystal to thereby grow the p-type SiC crystal; wherein at least some of the acceptor atoms in the flux form substitutional atomic impurities in the p-type SiC crystal.

Further, there is provided a method of manufacturing a low-resistivity n-type SiC crystal, the method including: placing a shaped charge of SiC source material in a vapor deposition apparatus; the shaped charge SiC source material consists essentially of silicon, carbon, and a quantity of donor atoms held in a certain position of the shaped charge SiC source material; wherein the acceptor atoms are fixed in position relative to the silicon and carbon in the forming material source material; heating the shaped charge SiC source material and thereby forming a flux by sublimation of the shaped charge source material; wherein the flux comprises silicon, carbon, and a portion of the quantity of acceptor atoms; and depositing flux on a growth face of the n-type SiC crystal to thereby grow the n-type SiC crystal; wherein at least some acceptor atoms in the donor atoms in the flux form substitutional atomic impurities in the n-type SiC crystal.

Further, a p-type SiC wafer is provided having a diameter of about 4 inches (100 mm) to about 6 inches (150 mm); a thickness of about 300 μm to about 600 μm; an acceptor atom; and a resistivity of about 0.015 to about 0.028 ohm-cm.

Additionally, a low resistivity n-type SiC boule is provided, the low resistivity n-type SiC boule having a diameter of at least about 4 inches (100 mm); a height of at least about 1 inch (25 mm); and includes donor atoms, wherein the donor atoms consist essentially of phosphorus.

Further, a low resistivity n-type SiC wafer is provided, the low resistivity n-type SiC wafer having a diameter of about 4 inches (100 mm) to about 6 inches (150 mm); a thickness of about 300 μm to about 600 μm; a donor atom; and a resistivity of 0.03 ohm-cm or less.

Furthermore, a liquid doped polysilocarb precursor material for producing p-type SiC crystals is provided, the liquid doped polysilocarb precursor material having: a dopant, wherein the dopant has one or more elements selected from group 13 of the periodic table, whereby the selected elements provide a number of acceptor atoms; silicon, carbon and oxygen; wherein the dopant is less than 10 weight percent of the total weight of the liquid doped polysilocarb precursor material; and wherein the liquid doped polysilocarb precursor material defines a negative potential net carrier concentration (pNc); wherein pNc = number of donor atoms-number of acceptor atoms.

Furthermore, a liquid doped polysilocarb precursor material for manufacturing low resistivity n-type SiC crystals is provided, the liquid doped polysilocarb precursor material having: a dopant, wherein the dopant has one or more elements selected from group 15 of the periodic table, whereby the selected elements provide a number of donor atoms; silicon, carbon and oxygen; wherein the dopant is less than 10 weight percent of the total weight of the liquid doped polysilocarb precursor material; and wherein the liquid doped polysilocarb precursor material defines a positive potential net carrier concentration (pNc); wherein pNc = number of donor atoms-number of acceptor atoms.

Further, provided are such methods, materials, boules, and wafers having one or more of the following features: wherein the source material consists essentially of silicon, carbon, and dopants; wherein the source material is comprised of silicon, carbon, and dopants; wherein the dopant comprises one or more elements of group 15 of the periodic table; wherein the dopant comprises phosphorus; wherein the dopant consists essentially of phosphorus; wherein the dopant consists of phosphorus; wherein the dopant comprises one or more elements of group 13 of the periodic table; wherein the dopant comprises boron; wherein the dopant consists essentially of boron; wherein the dopant consists of boron; wherein the dopant comprises aluminum; wherein the dopant consists essentially of aluminum; wherein the dopant consists of aluminum; wherein the predetermined electrical property comprises a net charge and the net charge is positive, whereby the crystal is a p-type crystal; wherein the predetermined electrical property comprises a net charge and the net charge is negative, whereby the crystal is an n-type crystal; wherein the predetermined electrical property comprises resistivity; wherein the predetermined electrical property comprises a resistivity of 0.013 ohm-cm and less; wherein the predetermined electrical property comprises a resistivity of 0.03 ohm-cm and less; wherein the predetermined electrical property comprises a resistivity of about 0.010 ohm-cm and less; wherein the predetermined electrical property comprises a resistivity of about 0.01 ohm-cm to about 0.001 ohm-cm; wherein the predetermined electrical property comprises a resistivity of about 0.009 ohm-cm to about 0.004 ohm-cm; wherein no other material is added to the flux after the flux is formed from the source material; wherein no other materials are added to the vapor deposition device; wherein the SiC source material is the sole source of dopant; and wherein no alloy is present and thus the process is alloy free.

Further, provided are such methods, materials, boules, and wafers having one or more of the following features: wherein the vapor deposition device is a physical vapor transport device; wherein the flux is a directional flux; wherein the SiC source material is a shaped charge; wherein the crystals have a diameter of at least about 100mm and a height of at least about 25 mm; wherein the crystals have a diameter of about 100mm to about 150mm and a height of about 25mm to about 125 mm; wherein an inert gas is added to the vapor deposition apparatus, and no other gas is added to the vapor deposition apparatus; wherein the p-type crystal has a diameter of at least about 100mm and a height of at least about 25 mm; wherein the p-type crystal has a diameter of about 100mm to about 150mm and a height of about 25mm to about 125 mm; wherein the p-type crystal has a resistivity of less than 2.0 ohm-cm; wherein the p-type crystal has a resistivity of 2.0 ohm-cm to about 0.1 ohm-cm; wherein the p-type crystal has a resistivity of 0.13 ohm-cm and less; wherein the p-type crystal has a resistivity of 0.013 ohm-cm to about 0.004 ohm-cm; wherein the p-type crystal has a resistivity of about 0.010 ohm-cm or less; wherein the p-type crystal has a resistivity of about 0.01 ohm-cm to about 0.001 ohm-cm; and wherein the p-type crystal has a resistivity of about 0.009 ohm-cm to about 0.004 ohm-cm.

Further, provided are such methods, materials, boules, and wafers having one or more of the following features: wherein during growth of the p-type crystal, the dopant remains fixed in the source material until the source material sublimates to form a flux; wherein the donor atom comprises one or more elements of group 15 of the periodic table; wherein the donor atom comprises phosphorus; wherein the donor atom consists essentially of phosphorus; wherein the donor atom consists of phosphorus; wherein the source material is the only source of acceptor atoms; wherein the vapor deposition device is a physical vapor transport device; wherein an inert gas is added to the vapor deposition apparatus, and no other gas is added to the vapor deposition apparatus; wherein the n-type crystal has a diameter of at least about 100mm and a height of at least about 25 mm; wherein during growth of the n-type crystal, acceptor atoms remain fixed in the source material until the source material sublimates to form a flux.

Additionally, the methods, materials, boules, and wafers are provided having one or more of the following features: p-type crystal growth on the C-plane including the SiC seed; p-type crystal growth on the S-face including SiC seed; including p-type crystal growth on the C-face of a SiC seed, wherein the SiC seed has a 4H or 6H polytype; including p-type crystal growth on the S-face of a SiC seed, where the SiC seed has a 4H or 6H polytype.

Drawings

Fig. 1 is a diagram of an embodiment of a 150mm p-type SiC crystal according to the invention.

Fig. 2A is a schematic plan view of an embodiment of a doped SiC wafer according to the invention.

Fig. 2B is a schematic cross-sectional view of the wafer of fig. 2A taken along line B-B.

Fig. 3 is a process flow diagram of an embodiment of a system and method according to the present invention.

Fig. 4 is a schematic cross-sectional schematic view of an embodiment of a vapor deposition apparatus and process according to the present invention.

Fig. 5 is a schematic cross-sectional schematic view of an embodiment of an N-channel E-MOSFET device utilizing a p-type SiC wafer according to the invention.

Fig. 6 is a schematic cross-sectional view of an embodiment of a P-channel E-MOSFET device utilizing a P-type SiC wafer according to the invention.

Fig. 7 is a schematic cross-sectional schematic diagram of an embodiment of an N-channel D-MOSFET device utilizing a p-type SiC wafer according to the invention.

Fig. 8 is a schematic cross-sectional schematic view of an embodiment of a P-channel D-MOSFET device utilizing a P-type SiC wafer according to the invention.

Fig. 9 is a schematic cross-sectional schematic diagram of an embodiment of an IGBT device according to the invention that utilizes a p-type SiC wafer.

Fig. 10 is a schematic cross-sectional schematic view of an embodiment of a Lateral Diffusion MOSFET (LDMOS) device utilizing a p-type SiC wafer according to the invention.

Fig. 11 is a schematic cross-sectional schematic view of an embodiment of a VMOS MOSFET device utilizing a p-type SiC wafer in accordance with the invention.

Fig. 12 is a schematic cross-sectional schematic diagram of an embodiment of a UMOS MOSFET device utilizing a p-type SiC wafer in accordance with the present invention.

Fig. 13 is a schematic cross-sectional schematic view of an embodiment of an IGTB device utilizing a p-type SiC wafer according to the invention.

Fig. 14 is a schematic cross-sectional view of an embodiment of a CMOS compound device utilizing a p-type SiC wafer according to the present invention.

Fig. 15 is a schematic cross-sectional view of an embodiment of a flash memory device utilizing a p-type SiC wafer according to the present invention.

Fig. 16 is a schematic cross-sectional view of a CMOS compound device utilizing a p-type SiC wafer according to the present invention.

Detailed Description

The present invention relates generally to silicon carbide (SiC) crystals, ingots, boules and wafers, processes for making such articles, and apparatuses made from or based on such wafers.

Embodiments of the invention generally relate to such crystals, ingots, boules and wafers manufactured using sublimation growth processes, such as Physical Vapor Transport (PVT) and devices performing sublimation growth processes (e.g., PVT devices), in polymer-derived ceramic based processes, the starting materials include polysilocarb precursor materials.

Embodiments of the present invention generally relate to p-type SiC crystals, including ingots, boules, and wafers, processes for fabricating these p-type articles, and devices made from or based on these p-type wafers. In particular, embodiments of the present invention relate to cubic p-type SiC crystals, ingots, boules, and wafers, processes for making these p-type articles, and devices made from or based on these p-type wafers. In particular, embodiments of the present invention relate to hexagonal p-type SiC crystals, including ingots, bars, and wafers, processes for fabricating these p-type articles, and devices made from or based on these p-type wafers.

Embodiments of the present invention generally relate to low resistivity SiC crystals, including ingots, boules, and wafers, processes for making such articles, and devices made from or based on such wafers. In particular, in embodiments, the present invention relates to n-type and p-type SiC wafers having a resistivity of 0.010 ohm-cm or less, and preferably a resistivity of 0.005 ohm-cm or less. These low resistivity wafers may be p-type or n-type wafers. In an embodiment, these low resistivity wafers have a cubic or hexagonal crystal structure, each wafer also being a p-type or n-type wafer.

Generally, embodiments of the present invention are based on or include polymer derived ceramic ("PDC") materials, products, and applications that typically use, are based on, or consist of PDC materials. Examples of PDC materials, formulations, precursors, starting materials, and apparatus and methods for making such materials can be found, for example, in U.S. patent nos. 9,657,409, 9,815,943, 10,091,370, 10,322,936, and 11,014,819, and U.S. patent publication nos. 2018/0290893 and 9,499,677, 9,481,781, 8,742,008, 8,119,057, 7,714,092, 7,087,656, 5,153,295, and 4,657,991, the entire disclosures of each of which are incorporated herein by reference.

The preferred PDC is a "polysilocarb" material, which is a PDC material comprising silicon (Si), oxygen (O), and carbon (C). Polysilocarb materials and methods of making such materials are disclosed and taught in U.S. patent nos. 9,815,943, 9,657,409, 10,322,936, 10,753,010, 11,014,819, and 11,091,370, and U.S. patent publication nos. 2018/0290893, the entire disclosures of each of which are incorporated herein by reference.

Embodiments of the present invention generally relate to a liquid-to-solid-to-ceramic-to-crystal process using a PDC liquid precursor material that is then cured to a solid material (e.g., plastic-like material, cured material). The solidified solid PDC material is converted (e.g., pyrolyzed) into a first PDC ceramic material, and then the first ceramic material is converted (e.g., pyrolyzed) into a PDC SiC source material. Typically, these steps or transitions are performed as separate heating operations, however, they may be performed in a single heating operation. The PDC SiC source material may also be formed as a shaped charge source material. The PDC SiC source material is then used to grow (e.g., by vapor deposition and preferably PVT) PDC SiC crystals. Typically, the precursor materials are liquids, however, they may be solid, dissolved solid, and molten.

In general, one or more dopants (e.g., additive materials, such as atomic impurities, intended to impart a predetermined property or properties to SiC crystalline materials (e.g., crystals, ingots, boules, and wafers)) may be added to the PDC material. These dopants are selected to provide a SiC crystal with predetermined properties, characteristics, or both (e.g., properties or characteristics associated with electrical or semiconductor) that then include ingots, boules, and wafers grown or made from PDC precursors. In a preferred embodiment, the predetermined electrical or semiconductor properties or characteristics include, for example: resistivity of the material; conductivity; crystal position (substituted or interstitial) and donor atoms (i.e. no electrons) and electron distribution; concentration, crystal position and distribution of electroactive atomic impurities; concentration, crystal position, ratio and distribution of substitutional and interstitial type atomic impurities; nc value; n _A value; and N _D, carrier concentration, ne, nh; and changes in the electron band structure result in changes in the valence or conduction band energy or fermi energy. These features will include p-type and low resistivity n-type or p-type crystals, as well as such articles having cubic or hexagonal crystal structures.

Dopants may be added to the liquid PDC precursor material, the solid solidified PDC material, the first PDC ceramic, and combinations and variations thereof. Dopants may also be added to or as part of the binder used to form the shaped charge, such as the spatial features of SiC, used as source material for growing SiC crystals in vapor deposition processes (e.g., PVT). The preparation and use of shaped charge SiC source materials for vapor deposition (e.g., PVT) growth of SiC crystals is disclosed and taught in U.S. patent publication No. 2018/0290893, the entire disclosure of which is incorporated herein by reference.

Generally, in embodiments of the present invention, the dopant is preferably a constituent of the PDC material, the SiC source material, and both. Thus, the dopant may: (i) Chemically bonded to the PDC material (e.g., partially polymer chains in the liquid PDC material, partially cured polymer in the solid cured PDC material, or both); (ii) It may be held (chemically, mechanically, or both) in a matrix of PDC material (e.g., nanocomposite), such as disclosed and taught in U.S. patent 10,633,400, the entire disclosure of which is incorporated herein by reference; (iii) It may be held (chemically, mechanically, or both) in the SiC source material; and (iv) combinations and variations of these.

The inclusion of dopants as an integral part of the SiC source material has several advantages over prior methods of introducing dopants into a crystal growth vapor deposition process. For example, having the dopant as part of the SiC source material allows the dopant to sublimate from the source material along with Si and C to form a flux in vapor deposition processes and apparatus (e.g., PVT). In this way, the dopant is not added separately to the flux after the flux is formed. Instead, the dopant is formed with the flux and is part of the flux. Adding dopants in the flux formation and as part of the flux formation may better control the overall process than adding dopants to the flux after the flux formation (e.g., by gas flow or separate sublimation of dopants). Thus, in general, preferred embodiments of the present invention avoid the need to separate the dopant source from the SiC source material. This would include avoiding the use of a dopant-based gas stream into the vapor deposition apparatus, the use of separate solid dopant sources in the vapor deposition apparatus, and combinations of these. It should be understood that in other embodiments, a separate dopant-based gas stream may be used, such as a gas stream with a second type of dopant.

Typically, the dopant (e.g., atomic impurity) is fixed in the SiC source material (e.g., forming material source material) and throughout the location, distribution, and both of the SiC source material. In addition, and preferably, the dopants remain fixed in predetermined locations and distributions, and preferably remain fixed throughout most and all of the vapor deposition process of growing SiC crystals. In this way, the dopant may be uniformly distributed throughout the SiC source material. It may be varied according to concentration, location and distribution within the SiC source material to account for variations in flux formation and SiC crystal growth. In the latter manner, the predetermined locations of the dopants are non-uniform, but result in a uniform distribution of dopants in the SiC crystal. In this manner, and in embodiments where the forming material source material is doped, a matrix of Si, C, and atomic impurities (e.g., donor atoms, acceptor atoms, or both) is provided. The doping profile charge is a porous matrix of Si, C and atomic impurities, wherein the matrix holds the atomic impurities, immobilizes the atomic impurities, or both.

When using an embodiment of a shaped charge SiC source material, the predetermined location and distribution of dopants (e.g., atomic impurities) remain fixed in the solid source material until the dopants sublimate with the solid source. Thus, in vapor deposition (e.g., PVT) processes and apparatus, the dopant may remain immobilized in the solid source material for at least 60%, 70%, 80%, 90%, and 100% of the crystal growth cycle to the extent that the solid source material has not sublimated. In other words, in these embodiments, the solid dopant does not shift its position relative to the solid SiC in the shaped charge during the growth cycle of the crystal.

Further, the predetermined location and distribution of dopants (e.g., atomic impurities) in the SiC source material (e.g., siC forming material source material) provides the ability to obtain a high ratio of substitutional impurities to interstitial impurities in the SiC crystal (i.e., greater or more efficient use of atomic impurities). This more efficient use of atomic impurities reduces adverse effects (e.g., stress) that interstitial impurities may cause in SiC crystals. Because SiC and doping elements co-sublimate as dopant atoms are exposed at the surface, incorporation on the growing ingot is better ensured at a uniform concentration throughout the growth.

It will be appreciated that by keeping the dopant (e.g., atomic impurity) "fixed" during the growth cycle of the crystal, it is relative to the non-sublimated portion of the source material (i.e., the remaining non-sublimated portion). As the source material sublimates during the vapor deposition process, the dopants also sublimate. In this way, the dopant is formed in and as part of the flux along with the Si and C-based components of the flux. Further, in this manner, and preferably, the dopant is not added separately to the flux after the flux is formed. Instead, the dopant is a component of the flux, even a component of the flux formation.

In general, embodiments of the present invention relate to formulations and methods for providing dopant source materials to fabricate a predetermined type of SiC wafer. In these embodiments, the starting material (e.g., precursor) is typically a liquid and then cured to a solid material. The solid starting material typically comprises a dopant (e.g., an atomic impurity). The solid starting material is then pyrolyzed into a ceramic containing the dopant. The ceramic is then further converted to SiC, which contains dopants, and forms the basis of source material for the growth of predetermined types of SiC crystals (e.g., p-type, low resistivity p-type, and low resistivity n-type). Each of these predetermined crystal types is then fabricated into SiC wafers, such as p-type, low resistivity p-type, and low resistivity n-type.

In general, preferred embodiments of the present invention relate to formulations that use a liquid comprising Si, O and C to form a liquid precursor material that is added with one or more dopants (e.g., atomic impurities) and thus contains the dopants. The one or more dopants are selected from elements and compounds that are intended to provide specific electrical, semiconducting, or both properties to the SiC crystals and wafers ultimately made from the liquid precursor material.

The dopant may be or be based on any element capable of forming an electroactive atomic impurity in the SiC crystal and wafer, any element that provides one or more predetermined electrical, semiconductor, or physical properties to the SiC crystal and wafer. For example, the dopant may Be or Be based on an element selected from group 13 IIIA of the periodic table (boron (B), aluminum (Al), etc.), an element selected from group 2 IIA (beryllium (Be), etc.), and an element selected from group 15 VA (nitrogen (N), phosphorus (P), arsenic (As), antimony (Ab), etc.). The dopant may also be selected from elements in group 16 VIA (e.g., oxygen (O), sulfur (S), etc.). The dopant may be selected from transition metals such as Ti, cr, mn, ni, fe, co and the like. In embodiments, the transition metal element may increase the properties of the crystalline material, thereby increasing the properties of the doped SiC wafer, which provides a new performance class in spintronics, photonic band gap, and electrochemical devices, among others.

Preferred dopants for fabricating p-type SiC crystals, ingots, boules and wafers are aluminum and boron. The preferred dopants for fabricating n-type low resistivity wafers are phosphorus, nitrogen, and in some cases sulfur, and combinations of phosphorus, sulfur, and nitrogen.

Although the present description focuses on SiC vapor deposition techniques, and in particular SiC PVT techniques, it should be appreciated that the present invention is not so limited and may be applied to other SiC crystal growth processes, joining processes, and other applications.

Precursor and source materials-typically

Embodiments of the present invention preferably use, are based on or are configured as PDC of "polysilocarb" materials, i.e. materials comprising silicon (Si), oxygen (O) and carbon (C), as well as embodiments of such materials that have been cured, embodiments of such materials that have been pyrolyzed, and embodiments of such materials that have been converted to SiC for use as a source material. Silicon oxycarbide materials, siOC compositions, and similar such terms refer to polysilocarb materials, and will include liquid materials, solid uncured materials, cured materials, ceramic materials, and combinations and variations of these materials, unless otherwise specified. Polysilocarb materials and methods of making such materials are disclosed and taught in U.S. patent nos. 9,815,943, 9,657,409, 10,322,936, 10,753,010, 11,014,819, and 11,091,370, and U.S. patent publication nos. 2018/0290893, the entire disclosures of each of which are incorporated herein by reference.

The polysilocarb material may have a high purity and an exceptionally high purity. Thus, they may be 99.99% pure, 99.999% pure, and 99.9999% pure. The polysilocarb material may also contain other elements. Specifically, in a preferred embodiment, the polysilocarb material comprises a dopant (e.g., an atomic impurity). (in making these percent purity calculations, the dopant is not considered an impurity, but is considered part of the SiC material in order to make percent purity calculations.) the polysilocarb material is made from one or more polysilocarb precursors or precursor formulations. The polysilocarb precursor formulation comprises one or more functionalized silicon polymers or monomers, a non-silicon based cross-linking agent, and possibly other ingredients such as inhibitors, catalysts, dopants, and other additives. The dopant may include, for example, one or more of metals, metalloids, metal complexes, alloys, and non-metals, and combinations and variations thereof.

Thus, for example, the p-type dopant may comprise or be based on one or more than one element selected from group 13 elements (boron, etc.). A particularly preferred dopant for fabricating p-type SiC crystals, ingots, boules and wafers is aluminum.

To produce low resistivity p-type crystals and wafers, the amount of dopant contained in the starting polysilocarb material should be sufficient to continue in the process to provide sufficient dopant in the SiC source material to provide sufficient electroactive atomic impurities in the p-type crystal material to have low resistivity. As used herein, unless otherwise specified, the "low resistivity" SiC p-type crystals, ingots, boules and wafers have a resistivity of 0.03 ohm-cm and less, about 0.010 ohm-cm and less, about 0.007 ohm-cm and less, about 0.005 ohm-cm and less, about 0.003 ohm-cm and less, about 0.01 ohm-cm to about 0.001 ohm-cm, about 0.009 ohm-cm to about 0.004 ohm-cm and about 0.006 ohm-cm to about 0.002 ohm-cm.

Preferred dopants for low resistivity n-type SiC crystalline materials are phosphorus, nitrogen, and sulfur (as double donors) and combinations thereof.

To produce low resistivity n-type crystals and wafers, the amount of dopant included in the starting polysilocarb material should be sufficient to continue in the process to provide sufficient dopant in the SiC source material to provide sufficient electroactive atomic impurities in the n-type crystal material to have low resistivity. As used herein, unless otherwise specified, the "low resistivity" SiC n-type crystals, ingots, boules, and wafers have a resistivity of 0.03 ohm-cm and less, about 0.010 ohm-cm and less, about 0.007 ohm-cm and less, about 0.005 ohm-cm and less, about 0.003 ohm-cm and less, about 0.01 ohm-cm to about 0.001 ohm-cm, about 0.009 ohm-cm to about 0.004 ohm-cm, and about 0.006 ohm-cm to about 0.002 ohm-cm.

Typically, the polysilocarb precursor formulation is initially liquid. The liquid precursor is cured to solid or semi-solid SiOC (i.e., a "cured material"). The solid or semi-solid SiOC is then pyrolysed to ceramic SiOC and then converted (further pyrolysed) to SiC. These processes and transformations may occur in single steps, or in separate or distinct steps, as well as combinations and variations thereof.

U.S. patent No. 11,091,370, the entire disclosure of which is incorporated herein by reference, discloses and teaches precursor formulations that can be used as starting materials to which dopants (e.g., donor atoms, acceptor atoms, or sources of both atoms) are added, as well as methods of making these precursor formulations. These formulations can provide carbon-rich SiC source materials and carbon-deficient SiC source materials. Depending on the type of donor or acceptor atoms and other conditions, a predetermined stoichiometry (e.g., rich in carbon, deficient in carbon) in the source material may be beneficial, e.g., a predetermined stoichiometry may result in more doping of the dopant as a substitutional impurity into the SiC crystal.

Precursor formulations can be made from a variety of precursors.

The precursor may be a siloxane backbone additive such as Methyl Hydrogen (MH), the chemical formula of which is shown below.

MH may have a molecular weight of about 400mw to about 10000mw, about 600mw to about 3000mw ("mw" may be measured as a weight average molecular weight in amu or g/mol), and may have a viscosity of preferably about 20cps to about 60 cps. The percentage of methylsiloxane units "X" may be from 1% to 100%. The percentage of dimethylsiloxane units "Y" may be from 0% to 99%. The precursors can be used to provide a backbone of crosslinked structure, as well as other features and characteristics, to cured preforms and ceramic materials. Such precursors may also be modified, inter alia, by reaction with unsaturated carbon compounds to produce new or additional precursors. Typically, the Methyl Hydrogen Fluid (MHF) has a minimum amount of "Y", and more preferably "Y" is zero in all practical applications.

The precursor may be a vinyl-substituted polydimethylsiloxane having the chemical formula shown below.

The molecular weight (mw) of the precursor may be about 400mw to about 10000mw, and may have a viscosity of preferably about 50cps to about 2000 cps. The percentage of methyl vinyl siloxane units "X" can be 1% to 100%. The percentage of dimethylsiloxane units "Y" may be from 0% to 99%. Preferably, X is about 100%. The precursors can be used to reduce crosslink density and improve toughness, as well as to cure other features and characteristics of the preform and ceramic materials.

The precursor may be vinyl-substituted and vinyl-terminated polydimethylsiloxanes having the chemical formula shown below.

The precursor may have a molecular weight (mw) of about 500mw to about 15000mw, and preferably a molecular weight of about 500mw to 1000mw, and may have a viscosity of preferably about 10cps to about 200 cps. The percentage of methyl vinyl siloxane units "X" can be 1% to 100%. The percentage of dimethylsiloxane units "Y" may be from 0% to 99%. The precursor may be used to provide branching and lower the curing temperature, as well as other features and characteristics of the cured preform and ceramic material.

The precursor may be a tetra-vinyl cyclotetrasiloxane (tetravinylcycloterasiloxane, "TV") having the chemical formula shown below.

The precursor may be a siloxane backbone additive such as methyl-terminated phenethyl polysiloxane (which may also be referred to as styrene vinyl xylyl polysiloxane) having the chemical formula shown below.

The molecular weight (mw) of the precursor may be from about 800mw to at least about 10000mw to at least about 20000mw, and may have a viscosity of preferably from about 50cps to about 350 cps. The percentage of styrene vinyl phenyl siloxane units "X" may be 1% to 60%. The percentage of dimethylsiloxane units "Y" may be 40% to 99%. The precursors can be used to provide improved toughness, reduce the reaction cure exotherm, change or modify the refractive index, adjust the refractive index of the polymer to match the refractive index of various types of glass, to provide other features and characteristics such as transparent glass fibers and cured preforms and ceramic materials.

The precursor may be divinylbenzene.

The precursor may also be any of the precursors and liquid starting materials disclosed and taught in U.S. patent No. 11,091,370.

Precursor formulations to which dopants (e.g., donors, acceptors, or sources of both atoms) can be added to provide doped SiC source materials include, for example, the following precursor formulations.

The precursor formulation was prepared by mixing together 41wt% of linear methyl hydrogen polysiloxane (methyl-hydrogen polysiloxane, MHF) and 59wt% of tetra vinyl cyclotetrasiloxane (TV).

The precursor formulation was made by mixing together 90% methyl-terminated phenylethyl polysiloxane (with 27% X) and 10% tv at room temperature. The precursor formulation had 1.05 moles of hydride, 0.38 moles of vinyl, 0.26 moles of phenyl and 1.17 moles of methyl. The precursor formulation had the following molar amounts of Si, C and O, based on 100g formulation.

	Molar (mol)	Molar ratio of Si, C and O (% of total moles in the molar column)
			Si	1.17	20％
C	3.47	60％
			O	1.17	20％

As calculated, after all CO was removed, siOC resulting from the formulation would have 2.31 moles of C calculated and have 98% excess of C.

The precursor formulation was made by mixing together 70% methyl-terminated phenylethyl polysiloxane (with 14% X) and 30% tv at room temperature. The precursor formulation had 0.93 moles of hydride, 0.48 moles of vinyl, 0.13 moles of phenyl and 1.28 moles of methyl. The precursor formulation had the following molar amounts of Si, C and O, based on 100g formulation.

	Molar (mol)	Molar ratio of Si, C and O (% of total moles in the molar column)
			Si	1.28	23％
C	3.05	54％
			O	1.28	23％

As calculated, after all CO was removed, siOC resulting from the formulation would have a calculated 1.77 mole of C and 38% excess of C.

The precursor formulation was made by mixing together 50% methyl-terminated phenylethyl polysiloxane (with 20% X) and 50% tv at room temperature. The precursor formulation had 0.67 moles of hydride, 0.68 moles of alkenyl groups of ethyl, 0.10 moles of phenyl groups and 1.25 moles of methyl groups. The precursor formulation had the following molar amounts of Si, C and O, based on 100g formulation.

	Molar (mol)	Molar ratio of Si, C and O (% of total moles in the molar column)
			Si	1.25	22％
C	3.18	56％
			O	1.25	22％

As calculated, after all CO was removed, siOC resulting from the formulation would have 1.93 moles of C calculated and have 55% excess of C.

The precursor formulation was made by mixing together 65% methyl-terminated phenylethyl polysiloxane (with 40% X) and 35% tv at room temperature. The precursor formulation had 0.65 mole of hydride, 0.66 mole of vinyl, 0.25 mole of phenyl and 1.06 mole of methyl. The precursor formulation had the following molar amounts of Si, C and O, based on 100g formulation.

	Molar (mol)	Molar ratio of Si, C and O (% of total moles in the molar column)
			Si	1.06	18％
C	3.87	54％
			O	1.06	28％

As calculated, after all CO was removed, siOC resulting from the formulation would have 2.81 moles of C calculated and have 166% excess C.

The precursor formulation was made by mixing 65% MHF and 35% dicyclopentadiene (DCPD) together at room temperature. The precursor formulation had 1.08 moles of hydride, 0.53 moles of vinyl, 0.0 moles of phenyl and 1.08 moles of methyl. The precursor formulation had the following molar amounts of Si, C and O, based on 100g formulation.

	Molar (mol)	Molar ratio of Si, C and O (% of total moles in the molar column)
			Si	1.08	18％
C	3.73	64％
			O	1.08	18％

As calculated, after all CO was removed, siOC resulting from the formulation would have 2.65 moles of C calculated and have 144% excess of C.

The precursor formulation was made by mixing 82% MHF and 18% dicyclopentadiene (DCPD) together at room temperature. The precursor formulation had 1.37 moles of hydride, 0.27 moles of vinyl, 0.0 moles of phenyl and 1.37 moles of methyl. The precursor formulation had the following molar amounts of Si, C and O, based on 100g formulation.

	Molar (mol)	Molar ratio of Si, C and O (% of total moles in the molar column)
			Si	1.37	25％
C	2.73	50％
			O	1.37	25％

As calculated, after all CO was removed, siOC resulting from the formulation would have 1.37 moles of C calculated and have 0% excess of C.

The precursor formulation was made by mixing together 46% MHF, 34% TV and 20% VT at room temperature. The precursor formulation had 0.77 moles of hydride, 0.40 moles of vinyl, 0.0 moles of phenyl and 1.43 moles of methyl. The precursor formulation had the following molar amounts of Si, C and O, based on 100g formulation.

	Molar (mol)	Molar ratio of Si, C and O (% of total moles in the molar column)
			Si	1.43	30％
C	1.95	40％
			O	1.43	30％

As calculated, after all CO was removed, siOC resulting from the formulation would have 0.53 moles of C calculated and have 63% C deficiency, or 63% C deficiency.

The precursor formulation was made by mixing together 70% MHF, 20% TV and 10% VT at room temperature. The precursor formulation had 1.17 moles of hydride, 0.23 moles of vinyl, 0.0 moles of phenyl and 1.53 moles of methyl. The precursor formulation had the following molar amounts of Si, C and O, based on 100g formulation.

	Molar (mol)	Molar ratio of Si, C and O (% of total moles in the molar column)
			Si	1.53	31％
C	1.87	38％
			O	1.53	31％

As calculated, after all CO was removed, siOC resulting from the formulation would have 0.33 moles of C calculated and have 78% C deficiency, or 78% C deficiency.

With 50% methyl-terminated phenylethyl polysiloxane (with 20% X) and 50% TV precursor formulation (95% MHF).

Precursor formulations with 54% methyl-terminated phenethyl polysiloxane (with 25% X) and 46% TV.

Precursor formulations with 57% methyl-terminated phenethyl polysiloxane (with 30% X) and 43% TV.

The precursor formulation may also be any of the precursor formulations disclosed and taught in U.S. patent No. 11,091,370.

One or more dopants (e.g., a composition or material based on or including atomic impurities to provide donor or acceptor atoms in the flux during the crystal growth process) may be added to the one or more liquid precursors and thus to the liquid precursor formulation, in which case the dopant will become part of the cured SiOC material and thus of the SiOC ceramic and SiC. The dopant may chemically react in the liquid state, i.e., chemically bond to the components of the liquid precursor. The dopant may be part of a mixture (e.g., a solution or suspension) of liquid polysilocarb precursors. In this case, the dopant may be chemically bonded to the polysilocarb material during the curing step and thus to the cured SiOC material (during the pyrolysis step) and thus to the ceramic SiOC material (or during the step of converting to SiC) and thus (chemically or mechanically) remain in the doped SiC source material, as well as combinations and variations of these steps. This is true for either p-type doped SiC source materials (which provide or grow p-type crystals) or low resistivity doped SiC source materials (which provide or grow low resistivity n-type or p-type crystals).

The dopant may be part of a mixture, such as a solid mixed with a cured material, siOC ceramic, or both, in which case the dopant may be chemically bonded to the SiOC material during one or more subsequent steps to provide a p-type doped SiC source material or a low resistivity SiC source material.

In general, in embodiments of the present invention, the dopant is preferably a constituent of the SiOC material, the SiC source material, and both. Thus, the dopant may: (i) Chemically bonded to the SiOC material (e.g., a portion of the polymer chains or composition of one or more liquid SiOC precursor materials, a partially cured polymer in the cured SiOC material, or both); (ii) It may be held (chemically, mechanically, or both) in a matrix of SiOC material (e.g., nanocomposite material), such as disclosed and taught in U.S. patent 10,633,400, the entire disclosure of which is incorporated herein by reference; (iii) It may be held (chemically, mechanically, or both) in the SiC source material; and (iv) combinations and variations of these.

In embodiments of starting materials, intermediate materials, and processes for providing p-type SiC materials, the dopant is covalently bonded to one or more of the Si, C, O atoms in the SiOC composition. Thus, for example, the cured SiOC material is converted to SiC, resulting in the dopant being covalently bonded to Si, C, or both, and uniformly distributed throughout the SiC source material (i.e., powder), the SiC shaped charge (if used), for a vapor deposition process, such as PVT, to grow p-type SiC crystals.

In general, two reactions can be employed to covalently incorporate dopant molecules into a polymer network: hydrosilylation and condensation reactions. Typically, the hydrosilylation reaction will employ a functional group of at least one olefin in the dopant molecule. For example, a preferred embodiment will have two such functional groups, most preferably 3 to 4. The condensation reaction will employ an alkoxide, alcohol, OR hydroxide group, -OR, where R is typically a small alkane OR hydrogen.

In some embodiments, graphene, graphite, amorphous carbon structures, and combinations and variations thereof are present in the Si-O-C ceramic upon pyrolysis. The distribution of silicon species consisting of SiOxCy structures (which result in SiO ₄、SiO₃C、SiO₂C₂、SiOC₃ and SiC ₄) is formed in different ratios, which results from precursor selection and its processing history. In these embodiments, the dopant may be bonded with the amorphous carbon structure between adjacent carbon and silicon atoms. Typically, for SiOC, in the ceramic state, the carbon is largely non-coordinated to the oxygen atoms, so oxygen is largely coordinated to the silicon, and the dopant will largely be coordinated to the silicon or carbon, depending on its starting structure.

In a preferred embodiment, the starting material for a vapor deposition process (e.g., PVT) to grow p-type crystals has a dopant of one or more elements selected from the elements of group 13 of the periodic table (boron, etc.). The dopant is covalently bonded to the Si, C, or both of the source material and is uniformly distributed throughout the source material. In a more preferred embodiment, the starting material is configured as a shaped charge, the dopants are distributed throughout the shaped charge in a predetermined manner, e.g. uniformly distributed in layers of different concentrations, etc. This source material is then used to perform a vapor deposition process, for example, as described in the "crystal growth-general" subsection of the present specification.

In a preferred embodiment, the starting material for a vapor deposition process (e.g., PVT) to grow low resistivity n-type crystals has a dopant of one or more elements selected from group 15 elements of the periodic table (nitrogen, etc.). The dopant is covalently bonded to the Si, C, or both of the source material and is uniformly distributed throughout the source material. In a more preferred embodiment, the starting material is configured as a shaped charge, the dopants are distributed throughout the shaped charge in a predetermined manner, e.g. uniformly distributed in layers of different concentrations, etc. This source material is then used to perform a vapor deposition process, for example, as described in the "crystal growth-general" subsection of the present specification.

In embodiments of the present p-type materials and processes, the dopant, acceptor impurity atoms are part of the SiC source material, e.g., chemically bonded, covalently bonded, or trapped within the SiC matrix. Furthermore, in this embodiment, the dopant and its acceptor impurity atoms are not present in the starting material in the form of an alloy. For example, the dopant may be aluminum, and the aluminum is present in the source material rather than as an alloy. Thus, and in this manner, during vapor deposition, e.g., flux formation, and thereafter, dopant and acceptor impurity atoms are not alloyed, or do not form alloys. It is believed that avoiding the use of alloys, this alloying step or alloy formation provides significant advantages over the prior art and provides improved crystal growth, formation and properties. (as used herein, an alloy is a substance made up of two or more metals or a metal and a non-metal intimately bonded, typically by melting together and dissolving each other upon melting, an alloy may have different metals present in a ratio of 99:1, 90:10, 80:20 to 50:50). The term "alloy free" or "non-alloyed" refers to the absence or absence of forming any alloy having a ratio of 90:10, 80:20 to 50:50. In embodiments, alloys having ratios of 99:1 to 91:9 can also be avoided, and thus these alloys are not present in the starting materials and are not found or formed in vapor deposition apparatus.

In one embodiment, the dopant may be a high purity aluminum/silicon alloy or an aluminum-doped silicon powder as a precursor component. The doped silicon powder may react with carbon to form an Al-doped SiC powder. Such powders can be formed into shaped charge source materials.

Turning to fig. 3, a schematic perspective flow chart of an embodiment of a system and method for fabricating a doped SiC source material (p-type doped source material, low resistivity p-type doped source material, or low resistivity n-type source material) that includes a shaped charge (e.g., a space feature) of doped SiC source material is provided. The SiC source material is derived from doped SiOC precursors and intermediate materials. The doped SiC source material and shaped charge preferably have a high purity (e.g., 3 pieces 9, 4 pieces 9, 5 pieces 9 or more, preferably 6 pieces 9 or more). Lines, valves, and internal surfaces of systems containing precursors and other materials are made of or coated with materials that do not contaminate (e.g., provide a source of contaminants) SiOC, derived SiC, and the spatial shapes of SiC.

In embodiments where only p-type dopants are used (i.e., dopants providing an acceptor atom source), the presence of any material considered or as a source of donor atoms (such as nitrogen) should be minimized, mitigated, and eliminated. (note that in other embodiments, nitrogen may be present in a lesser amount than the p-type dopant and still obtain a p-type source material, i.e., configured to grow crystals with negative Nc.)

Similarly, in embodiments where only n-type dopants (i.e., dopants providing a source of donor atoms) are used, the presence of any material that would be considered or act as a source of acceptor atoms (such as boron and aluminum) should be minimized, reduced, and eliminated. (it should be noted that in other embodiments, boron or aluminum may be present in a lesser amount than the n-type dopant and still obtain an n-type source material, i.e., configured to grow crystals with positive Nc.)

The reservoirs 150a, 150b contain liquid polysilocarb precursor and the dopants may be contained in a separate reservoir, hopper or bin 150 c. If multiple dopants are used, multiple tanks, hoppers or bins may also be present. The dopant may be added to the tank or mixer 152. In this embodiment, one or both of the precursors may be removed by distillation apparatus 151a and distillation apparatus 151b, or no precursor may be removed, to remove any contaminants from the liquid precursor. Care should be taken not to damage the dopant or otherwise affect its properties.

The liquid precursor and dopant are then transferred to a mixing vessel 152 where they are mixed to form a doped precursor batch (e.g., p-type, low resistivity p-type, or low resistivity n-type) and catalyzed. The precursor batch is then poured into container 153 (preferably in clean room environment 157 a) for placement in furnace 154. The furnace 154 may have a purge gas inlet 161 and an exhaust gas discharge line 162. Typically, the purge gas is an inert gas, such as argon. The liquid polysilocarb material is oven cured and the dopant is reacted with the polysilocarb material to incorporate the dopant into or as part of the cured polysilocarb material.

The solidified material (i.e., solid doped SiOC (e.g., p-type, low resistivity p-type, or low resistivity n-type)) is then transferred, preferably under clean room conditions, into one and preferably several pyrolysis furnaces 155a, 155b, 155c, where it is converted from doped SiOC to doped SiC source material (e.g., p-type, low resistivity p-type, or low resistivity n-type). (note that in this embodiment, the SiOC ceramic will be the phase formed upon transition to SiC in the furnace (e.g., 155 a). The furnace has purge gas inlet lines 158a, 158b, 158c, and two exhaust gas exhaust lines 159a and 160a, 159b and 160b, 159c and 160c, respectively. Typically, the purge gas is an inert gas, such as argon. The exhaust gas may be treated, cleaned and recycled starting material in an exhaust gas treatment assembly 163 having an inlet line 164, the exhaust gas treatment assembly 163 collecting exhaust gas from various units in the system.

The resulting doped SiC source material (e.g., p-type, low resistivity p-type, or low resistivity n-type) (as a powder) is then transferred to a spatial feature formation region 190, which is preferably in a clean room condition. In region 190, the doped SiC material is provided to a mixing vessel 172, the mixing vessel 172 having a mixing device 173 (e.g., blade, paddle, stirrer, etc.). The adhesive from the adhesive tank 170 is added to the container 172 via line 171. In mixing vessel 172, siC is mixed with a binder to form a slurry or mixture. The consistency of the slurry should facilitate the subsequent forming operation. The SiC-binder slurry is then transferred to a forming device 175 where the slurry is formed into a spatial shape, such as a pellet, disk, block, etc., and preferably formed as a doped shaped charge source material (e.g., p-type, low resistivity p-type, or low resistivity n-type) and fed into an oven 177 where the binder is cured to impart the desired strength to the spatial shape and preferably pyrolyzed.

The spatial shapes may then also be transferred to a packaging device 180, where they are packaged. Preferably, these operations are performed under clean room conditions, and more preferably, the operations are performed in separate clean rooms or clean room areas 190a, 190b, 190 c. The shaped charge may also be provided directly to a vapor deposition apparatus (e.g., PVT) for growing doped SiC crystals (e.g., p-type, low resistivity p-type, or low resistivity n-type).

Preferably, in the manufacture of p-doped SiC, low resistivity p-doped or low resistivity n-doped SiC source materials, in a preferred embodiment, the polysilocarb precursor and dopant may be mixed in clean air at about 1 atmosphere pressure.

Preferably, in the manufacture of SiC and materials used to manufacture SiC, the curing of the doped and preferably catalyzed precursor material occurs at a temperature in the range of about 20 ℃ to about 150 ℃, about 75 ℃ to about 125 ℃ and about 80 ℃ to 90 ℃, as well as variations and combinations of these temperatures, and all values within these temperature ranges. Curing is carried out for a period of time, preferably to produce a hard cured material. The curing may be carried out in air or an inert gas, and preferably the curing is carried out under argon at ambient pressure. Preferably, for high purity materials, the ovens, vessels, processing equipment, and other components of the curing apparatus are clean, contain substantially no and do not contribute to the cured material any elements or materials that are considered impurities or contaminants. It is noted that in a preferred embodiment, either the donor or acceptor atomic sources may be considered contaminants, depending on the type of crystal being grown.

Preferably, pyrolysis occurs at temperatures ranging from about 800 ℃ to about 1300 ℃, from about 900 ℃ to about 1200 ℃, and from about 950 ℃ to 1150 ℃ and all values within these temperature ranges when manufacturing doped SiC source materials (e.g., p-type, low resistivity p-type, or low resistivity n-type). Pyrolysis is carried out for a period of time, preferably resulting in complete pyrolysis of the cured doped SiOC material into a p-type doped SiC source material. Preferably, pyrolysis is conducted under an inert gas (e.g., argon), and more preferably under flowing argon at or about atmospheric pressure. The gas may flow at about 1200cc/min to about 200cc/min, about 800cc/min to about 400cc/min, about 500cc/min, and all values within these flow ranges. Preferably, the initial vacuum evacuation of the process furnace is completed to a reduced pressure of at least less than 1x 10 ^-3 torr and is re-pressurized with an inert gas (e.g., argon) to greater than or equal to 100 torr. More preferably, the vacuum evacuation is completed to a pressure below 1x 10 ^-5 torr prior to repressurization with the inert gas. The vacuum evacuation process can be completed anywhere from 0 to >4 times before proceeding. Preferably, for high purity materials, the furnace, vessel, processing equipment, and other components of the solidification equipment are clean, substantially free of, contain no, and do not contribute any elements or materials to the pyrolyzed material that are considered contaminants.

Pyrolysis may be carried out in any heating device that maintains the desired temperature and environmental control. Thus, for example, pyrolysis may be conducted using a high pressure furnace, a box furnace, a tube furnace, a crystal growth furnace, a graphite box furnace, an arc melting furnace, an induction furnace, a kiln, a MoSi ₂ heating element furnace, a carbon furnace, a vacuum furnace, a gas furnace, an electric furnace, direct heating, indirect heating, a fluidized bed, an RF furnace, a kiln, a tunnel kiln, a box kiln, a shuttle kiln, a coker, a laser, microwaves, other electromagnetic radiation, as well as combinations and variations of these and other heating devices and systems capable of achieving the desired temperatures for pyrolysis.

Preferably, the ceramic doped SiOC is converted to SiC in a subsequent or continuous pyrolysis or conversion step when the doped SiC source material is manufactured. The conversion step of the doped SiOC may be part of (e.g., performed continuously with) the pyrolysis of the doped SiOC cured material, or may be a completely separate step in time, location, and both. Depending on the type of SiC desired to be doped, the conversion step (from SiOC to SiC) may be carried out at about 1200 ℃ to about 2550 ℃ and about 1300 ℃ to 1700 ℃ and all values within these temperature ranges.

Generally, the formation of the beta form is advantageous over time at temperatures of about 1600 ℃ to 1900 ℃. At temperatures above 1900 ℃, the formation of the alpha form is advantageous over time. Preferably, the conversion is carried out under an inert gas (e.g., argon), and more preferably under flowing argon at or about atmospheric pressure. The gas may flow at about 600cc/min to about 10cc/min, about 300cc/min to about 50cc/min, about 80cc/min to about 40cc/min, and all values within these flow ranges. Preferably, for high purity materials, the furnaces, vessels, processing equipment, and other components of the curing apparatus are clean, contain substantially no and do not contribute to SiC any elements or materials that are considered impurities or contaminants.

The subsequent yield of doped SiC derived from doped SiOC is generally about 10% to 50%, typically 30% to 40%, but higher or lower ranges and all values within these percentage ranges can be obtained.

It should also be appreciated that the loss of dopant throughout the process, including during crystal growth, should be considered in suppressing the amount of dopant present in the doped SiOC precursor material (e.g., the mixer 152 or the cured solid SiOC). Thus, sufficient dopant should be present in the SiC source material to reach a predetermined dopant level, such as a predetermined amount of electrically active atoms in the crystal grown from the source material and thus the wafer made from the crystal, to provide predetermined and desired electrical and semiconductor properties of the crystal and wafer.

The binder used to form the space of the dopant forming source material (e.g., dopant forming material source material) may be any binder used to hold SiC in a predetermined shape during processing, curing, and subsequent use of the space shape. Embodiments of the binder may preferably be oxygen free. Embodiments of the binder may preferably be made of a material containing only carbon and hydrogen. Embodiments of the binder may be made of an oxygen-containing material. An example of a binder may be any sintering aid used to sinter SiC. An example of a binder may be fused silica. Examples of binders may be polysilocarb precursor materials, including all liquid precursors set forth in this specification. Combinations and variations of these and other materials may also be used as binders. The binder may also contain a dopant that may be the same as or different from the dopant in the SiC powder used to make the shaped charge.

The binder may be cured and pyrolyzed to the desired extent under the conditions used to cure the polysilocarb precursor, or under the conditions required to transform the binder into a sufficiently hard (e.g., tough) material to maintain the shape of the spatial features. Thus, curing, hardening, forming or structuring should be performed based on the characteristics of the binder, as the case may be.

Examples of oxygen-free binders include polyethylene, silicon metal, hydrocarbon waxes, polystyrene and polypropylene, and combinations and variations thereof.

Examples of embodiments of binders that include only carbon and hydrogen include polyethylene, hydrocarbon waxes, carbon or graphite powders, carbon black, HDPE, LDPE, UHDPE, and PP, as well as combinations and variations thereof.

Examples of oxygen-containing binders include boric acid, boric oxide, silica, polyols, polylactic acid, cellulosic materials, sugars and saccharides, polyesters, epoxy resins, silicones, silicates, silanes, silsesquioxanes, acetates such as Ethylene Vinyl Acetate (EVA), polyacrylates such as PMMA, and polymer-derived ceramic precursors, as well as combinations and variations thereof.

Examples of embodiments of binders as sintering aids include silicon, boron oxide, boric acid, boron carbide, silicon carbon powder (silicon and carbon powder), silica, silicate, and polymer-derived ceramic precursors, as well as combinations and variations thereof.

The binder should be selected so as not to interfere with or otherwise inhibit the growth of the dopant, doped SiC crystal, and the nature of the doped SiC crystal and wafer.

Examples of binders will include catalyzed and uncatalyzed precursor formulations disclosed and taught in U.S. patent nos. 9,815,943, 9,657,409, 10,322,936, 10,753,010, 11,014,819, and 11,091,370, and U.S. patent publication nos. 2018/0290893, the entire disclosures of each of which are incorporated herein by reference. Methods of curing these adhesives are disclosed and taught in these patents and published applications, the entire disclosures of each of which are incorporated herein by reference.

The ashratio (Ashbys) catalyst and others are largely unaffected by the aluminum doped precursor formulation. The phosphorous containing precursor formulation may result in some catalyst inhibition. The suppression of the catalyst by the dopant may be overcome by non-catalytic means (e.g., driving the reaction despite the absence of the catalyst), such as by compensating with more thermal energy during the curing process.

In a preferred embodiment, one or more polysilocarb precursor formulations disclosed and taught in the patents and published applications listed above are used to fabricate a doped space-shaped, e.g., shaped charge source material (e.g., p-type, low resistivity p-type, or low resistivity n-type). The binder is pyrolysed to SiC to provide a hard and durable doped shaped charge source material. The dopant in the shaped charge source material is fixed.

In one embodiment, the binder is the same polysilocarb precursor as used to make the SiC source material, with or without a dopant. Thus, the amount of dopant present in the binder may be from 0% to about 50%. The dopant in the binder may be used to adjust or fine tune the amount of dopant present in the particular doped SiC shaped charge source material.

It should be understood that although preferred, doped SiC crystals and ingots may be grown without the use of shaped charges, such as powder charges or starting materials derived directly from doped SiC polymers. Furthermore, less desirable forms of SiC powder (e.g., not made from polymer-derived ceramics) may be used to form the doped SiC shaped charge source material.

The ability to start with a doped liquid material (e.g., precursor batch) having substantially all of the building blocks required to fabricate doped SiC source material powders (e.g., not made from polymer-derived ceramics), such as Si and C and dopants, provides significant advantages in controlling contamination and fabricating predetermined ratios of Si, C and dopants in the doped source material to control and affect flux formation and crystal growth in PVT processes and devices. Based in part on the properties of the present polymer-derived p-doped SiC in vapor deposition apparatus and growing p-type crystals, it is theorized that polymer-derived SiC is different from non-polymer-derived SiC and that metal alloys, metal gases, or both have been previously used in the crystal growth process. Thus, the synergistic benefits in terms of crystal growth and purity, wafer yield, and equipment yield further result from one or more individual benefits of the polymer-derived ceramic source material, including bulk density, particle size, siC-doped phase (β vs. α), stoichiometry, oxygen content (very low to no, nor oxide layer), high (e.g., 99.999% purity), and ultra-high (99.9999%) purity.

Dopant material-typically

In general, the dopant may be any material or combination of materials that may be used in and that do not interfere with a PDC process (e.g., polysilocarb-based PDC) forming a SiC source material and that provide predetermined atomic impurities (e.g., donor atoms, acceptor atoms, and combinations thereof) in the SiC source material, which then serve to generate fluxes with the atomic impurities in a vapor deposition process and from which crystals are grown that also have the atomic impurities as electroactive atomic impurities.

Aluminum and boron are preferred atomic impurities for p-type crystals, ingots, boules and wafers, as well as p-type low resistivity crystals, ingots, boules and wafers, and thus preferred dopants are those materials capable of providing these atomic impurities.

Dopant materials that provide aluminum in the source material (and then may provide aluminum atom electroactive impurities into the SiC crystal structure), for example, are typically: a reactive aluminum material; a non-reactive aluminum material; and pure alumina material.

Typically, reactive aluminum materials are added to liquid precursor materials (e.g., precursor formulations) and then chemically react with these precursor materials during the curing step. For example, the reactive aluminum material includes:

(i) Aluminum alkoxide: al (OR) ₃, wherein R is alkyl OR phenyl. The reaction with the polysilocarb precursor material is typically: 2Al (OR) ₃+6SiH→2Al-(O-Si～)₃ +6rh; (Note that "Si" and "Si-as used in these reactions represent reactive Si functional groups that are attached to a larger structure, such as a polymer backbone or ligand backbone, that is not shown in the reaction.)

(Ii) Aluminum hydroxide (R is hydrogen). The reaction with the polysilocarb precursor material is typically: 2Al (OH) ₃+6SiH→2Al-(O-Si～)₃+3H₂;

(iii) Bauxite, gibbsite, boehmite, diaspore. The reaction with the polysilocarb precursor material is typically: by the hydroxide function of these minerals, similar to (ii); and

(Iv) Trimethylaluminum. The reaction with the polysilocarb precursor material is typically: 2 (Al (Me) ₃)+3H₂O→Al₂O₃+6CH_4.

Typically, the non-reactive aluminum material is added to a liquid precursor material (e.g., a "precursor formulation"), but may also be added to a cured material, ceramic SiOC, siC source material, and combinations and variations of these materials. During pyrolysis, the non-reactive material is held by or incorporated into the SiOC and SiC ceramic materials. For example, the non-reactive material includes an aluminosilicate material. Examples of such materials include: mullite, kyanite, sillimanite, andalusite, blue line stone and other island silicate (Neosilicate) powders; kaolinite, halloysite, and pyrophyllite; a network silicate (Tectosilicates, feldspar); a zeolite.

Typically, pure alumina materials are added to liquid precursor materials (e.g., precursor formulations), but may also be added to cured materials, ceramic SiOC, siC source materials, and combinations and variations of these materials. During pyrolysis, the pure alumina material is held by or incorporated into SiOC and SiC ceramic materials. For example, pure alumina materials include alumina powder Al ₂O₃ and corundum (including sapphire, ruby, etc.).

All of the foregoing aluminum dopant materials provide aluminum, for example, in the form of a ceramic oxide, in the SiC source material, rather than an alloy.

For example, a dopant material that provides boron in the source material (and then may provide an electroactive impurity of boron atoms into the SiC crystal structure) is typically: a reactive boron material; a non-reactive boron material.

Typically, reactive boron materials are added to liquid precursor materials (e.g., precursor formulation (1)) and then chemically react with these precursor materials during the curing step. For example, the reactive boron material includes:

(i) Boric acid B (OH) ₃. The reaction with the polysilocarb precursor material is typically: 2B (OH) ₃ +6SiH

→2B-(O-Si～)₃+3H₂；

(Ii) Borax (box, na ₂B₄O₇·10H₂ O). The reaction with the Si O C precursor material is typically:

And (3) condensation reaction.

(Iii) Boric acid R-B (OH) ₂, wherein R is alkenyl, such as vinyl. The reaction with the polysilocarb precursor material is typically: condensation reaction; and

(Iv) Divinylboronic acid Vi-B (OH) -Vi. The reaction with the polysilocarb precursor material is typically:

B-Vi+～SiH→B-C-C-Si～。

Typically, the non-reactive boron material is added to the liquid precursor material (e.g., precursor formulation), but may also be added to the cured material, ceramic SiOC, siC source material, and combinations and variations of these materials. During pyrolysis, the non-reactive material is held by or incorporated into the SiOC and SiC ceramic materials. For example, non-reactive materials include: borosilicate glass; b ₂O₃; boron carbide.

For n-type crystals, ingots, bars and wafers, as well as n-type low resistivity crystals, ingots, bars and wafers, nitrogen and phosphorus are preferred atomic impurities, phosphorus is a particularly preferred atomic impurity, and thus preferred dopants are those materials capable of providing these atomic impurities.

Nitrogen-containing or nitrogen-providing materials may be added to the liquid precursor material (e.g., precursor formulation). Such dopants include amines; amides; azo and diazo; a carbamate; a urethane; a carbodiimide; heterocycles of C and N; urea; an isocyanate; as possible candidate functional groups. Nylon or other N-containing carbon-based polymers may also be added to the formulation to react during pyrolysis. However, it should be noted that adding too much nitrogen can introduce undesirable stresses, stacking faults, and related defects to the crystal.

Typically, reactive phosphorus materials are added to liquid precursor materials (e.g., precursor formulations) and then chemically react with these precursor materials during the curing step. For example, the reactive phosphorus material includes:

(i) Reactive oxides of P, such as (R) ₃ -phosphine oxide (r=alkyl, phenyl, styryl), include triphenylphosphine oxide as shown below

And phosphorus pentoxide as shown below

The reaction of polysilocarb precursor materials with these dopants is typically:

R₃-P＝P＊+～Si-H→～Si-O-P-R₃

(ii) Reactive organophosphines such as (R1) _n-(R2)_3-n organophosphines (where r1=alkenyl, styryl, r2=alkyl, phenyl). For example diphenylvinyl phosphine as shown below

The divinylbenzene-type phosphine shown below

Diphenylstyrylphosphine as shown below

Triallylphosphines, shown below, are examples of materials for which n=3

The reaction of polysilocarb precursor materials with these dopants is typically:

R₃-P＝C＝C+～Si-H→～Si-C-C-P-R₃

(iii) Phosphines, including PH ₃、PCl₃、PF₃ and PBr ₃.

The reaction of polysilocarb precursor materials with these dopants is typically:

PX ₃+3～SiH→P-(Si～)₃ +3HX, wherein X is halogen or hydrogen

(Iv) Acids, including phosphoric acid (H ₃PO₄); polyphosphoric acid (CAS# 8017-16-1); ammonium polyphosphate (CAS# 68333-79-9); p (OR) ₃, wherein R is any alkyl, OR phenyl OR hydrogen; o=p (OR) 3, wherein R is any alkyl OR phenyl group OR hydrogen; triisopropyl phosphite as shown below

Triisopropyl phosphate as shown below

The reaction of polysilocarb precursor materials with these dopants is typically:

2(OH)₃P＝O+6～Si-H→2(～Si-O)₃-P＝O+3H₂

Typically, the non-reactive phosphorus material is added to the liquid precursor material (e.g., precursor formulation), but may also be added to the cured material, ceramic SiOC, siC source material, and combinations and variations of these materials. During pyrolysis, the non-reactive material is held by or incorporated into the SiOC and SiC ceramic materials. For example, non-reactive materials include: the phosphate compounds are shown below

Wherein M+ is sodium, potassium, calcium, lithium, ammonium, etc.

Phosphorus pentoxide shown below

Such as phosphate minerals from group Apatitie (Ca ₅(PO₄)₃ R, where R is F, cl or OH),

Inorganic dopants containing both N and P may also be used. These dopants are added to the liquid precursor material (e.g., precursor formulation (1)), but may also be added to the cured material, ceramic SiOC, siC source material, and combinations and variations of these materials. The inorganic material is held by or incorporated into the SiOC and SiC ceramic materials during pyrolysis. These materials provide co-doping capability, providing both N and P from a single dopant source. For example, co-dopants include struvite ((NH ₄)MgPO₄·8H₂ O), a phosphorus nitride group material, phosphorus pentanitride (P ₃N₅),

Other co-dopants (sources of N and P) are cyclophosphazene compounds, polyphosphazene compounds and hexachlorotriphosphazene compounds. These co-dopants are added to liquid precursor materials (e.g., precursor formulations) and then chemically react with those precursor materials during curing, pyrolysis, or both steps.

Further, as described above, any of the foregoing dopants may be added to the binder used to form the doped SiC forming material source material.

The dopant may be added to the precursor formulation at a weight percent of about 1%, about 2%, about 2.5%, about 5%, 2% to about 10%, about 1% to about 10%, less than 15%, less than 10%, less than 8%, and about 2% to about 8%. The dopant may be added to the binder at a weight percent of about 1%, about 1% to about 10%, about 2%, about 2.5%, about 5%, 2% to about 10%, less than 15%, less than 10% and less than 8%, and about 2% to about 8%.

There will be some material loss during the curing step and each pyrolysis step will have, for example, yield loss. These yield losses will include losses of dopant material. Thus, in view of these yield losses, a sufficient amount of dopant should be added to provide the amount of dopant atoms needed in the SiC source material for flux formation and crystal growth.

Doped crystal growth-typically

Silicon carbide generally does not have a liquid phase, but rather it sublimates in vacuo at temperatures above about 1700 ℃ to 1800 ℃. Typically, in industrial and commercial applications, conditions are established such that sublimation occurs at temperatures of about 2500 ℃ and above. When silicon carbide sublimates, it generally forms a vapor consisting of several different kinds of silicon and carbon. Generally, the composition and form (e.g., forming charge), temperature and pressure of the source material determine the proportion of vapor phase components in the carbon silicide vapor.

The present invention provides, inter alia, for the presence of predetermined, preselected and controlled dopants (e.g., additives, elements, compounds intended to provide SiC wafers with specific predetermined properties) in SiOC starting materials, which are then present in SiC source materials, e.g., powders for vapor deposition crystal growth processes.

As silicon carbide sublimates, it typically forms vapors composed of various silicon and carbon species, such as Si, C, siC, si ₂ C and SiC ₂.

Generally, the present invention uses PVT methods and apparatus well understood and well known in the art (e.g., U.S. patent No. 4,866,005, the entire disclosure of which is incorporated herein by reference) to grow the present p-type crystals, low resistivity p-type crystals, and low resistivity n-type crystals. During sublimation crystal growth, an elemental source, typically composed of silicon and carbon or SiC powder, is sublimated to produce a vapor flux of silicon and carbon atoms, which then condenses on the seed crystal and eventually forms larger crystals. To control the electrical properties (e.g., resistivity/conductivity) of SiC crystals, impurity atoms are added to the vapor stream where they will be incorporated into the crystal along with silicon and carbon atoms. The incorporation of impurities in the crystal is affected by the seed temperature, pressure, seed face-silicon or carbon, and the atomic ratio of carbon to silicon in the vapor stream. The carbon to silicon ratio in the vapor stream is related to the design of the source material, the temperature and pressure at the source.

Silicon and aluminum have similar atomic sizes, and thus aluminum impurity atoms will be located predominantly at silicon sites (as electroactive atomic impurities), or interstitial sites, in the crystal. In order to increase the likelihood of aluminum atoms being located in the silicon site, a vapor stream with excess carbon is required.

In typical sublimation growth of SiC using existing non-PDC source materials, the vapor stream generally has more silicon than carbon. Therefore, aluminum atoms must compete with silicon atoms for silicon sites. This characteristic of SiC sublimation growth based on inorganic sources (such as silicon metal, graphite, or SiC mill sources) results in difficulty in incorporating sufficient aluminum into the crystal so that the conductivity of wafers cut from the crystal is useful for semiconductor device fabrication.

Embodiments of the present invention overcome this problem by, among other things, having the ability to provide the source material with excess carbon, and incorporating and retaining dopants into the source material. Thus, these doped PDC source materials can unexpectedly provide favorable flux conditions for efficient incorporation of p-type dopants in SiC crystals. This in turn enhances the electrical properties of the p-type crystal and makes the wafer cut from the crystal useful, of higher quality and excellent electrical properties, and particularly commercially useful for semiconductor device fabrication.

In an embodiment, the use of PDC forming material source materials is unexpected because their ability to influence and control the Si/C ratio of the flux provides the ability to produce Si/C ratios that are more likely to enhance the incorporation of p-type dopant atomic impurities into the crystal when grown on the C-face of the crystal. Although the Si/C ratio in the flux at the seed will decrease over time, it is unlikely that it will drop below the value 1, while enhancement of p-type dopant incorporation still occurs. Thus, embodiments of the present forming material source materials provide the ability to grow p-type SiC crystals using C or Si-face seed crystals in PVT processes. In particular, p-type crystals may be grown on C or Si faces, 4H or 6H seed crystals.

The preferred embodiment of the ingot is monocrystalline and has only a single polytype. It should be understood that embodiments of ingots having multiple polytypes, multiple crystals, and both are also contemplated by the present description.

In one embodiment, the liquid PDC starting material, preferably a polysilocarb precursor, and more preferably the liquid polysilocarb precursor, has been added to or included (e.g., chemically bonded, chemical composite, in solution, in the polymer backbone, in a mixture, etc.) a predetermined dopant to provide predetermined properties to the SiC crystal.

While the dopant is preferably present in the liquid starting material, it may also be added to, e.g., combined with or mixed with, the cured SiOC material, ceramic SiOC material, and shaped charge. In some cases, a dopant such as nitrogen may also be added as a gas during the SiC crystal growth process.

The dopant may be a single material, such as an element, or may be two, three or more elements, typically selected from the same column of the periodic table. It is believed that the use of a combination of different materials from the same column of the periodic table (and thus having similar electron valence structures, but slightly different sizes) reduces stress in the SiC crystal. This in turn provides better, high quality, more useful ingots and wafers.

Preferred dopants for fabricating p-type SiC crystals, ingots and wafers are those selected from group 13 elements (boron, etc.). The preferred dopant for fabricating p-type SiC crystals, ingots and wafers is aluminum.

Preferred dopants for fabricating n-type SiC crystals, ingots and wafers are elements selected from group 15 (nitrogen, etc.). Preferred dopants for fabricating n-type SiC crystals, ingots and wafers are nitrogen, phosphorus, and combinations thereof.

The use of phosphorus, as well as a combination of nitrogen and phosphorus as dopants (preferably in a liquid polysilocarb starting material) provides the ability to have a low resistivity SiC wafer.

In less preferred embodiments of doped crystals (e.g., p-type, low resistivity n-type), the dopant is not uniform over the length of the crystal. In this embodiment, the concentration of dopant (as an electroactive atomic impurity) varies from the bottom of the seed (the side where crystal growth begins) to the top side of the tail (the side where growth ends), which variation can vary radially (as a percentage of the maximum dopant concentration to the minimum dopant concentration for the crystal) in the range of about 300% to 5% across the crystal diameter.

In preferred embodiments, the use of embodiments of doped forming material source materials reduces these variations for both tail to seed (i.e., length or height of crystal) and radial (diameter across crystal) to about 100% to 5%, less than 200%, less than 150%, less than 100%, less than 50%, less than 25% and less than 10%. This reduction in variation can further be achieved in a consistent manner, wherein most and substantially all (i.e., greater than 90%) of the crystals grown in the PVT apparatus have the same minor variation.

In one embodiment, the doped SiC crystal (e.g., p-type, low resistivity n-type) has a substantially uniform dopant distribution throughout the structure of the crystal, which is achieved by using a predetermined doping forming material source material having dopants distributed in the forming charge in a manner that provides uniformity of dopants incorporated into the crystal. Thus, in embodiments of a crystal, ingot, bar, or wafer, the dopant concentration or electroactive atomic impurity concentration varies by less than about 10%, less than about 5%, less than about 2%, and less than 1% across the length (e.g., tail-side to seed-side ("top-to-bottom")) and radially (measured as it moves from side-to-side along the diameter). Thus, these crystalline materials exhibit the desired electrical properties as a whole and exhibit the same degree (e.g., p-type electrical behavior, p-type low-resistivity electrical behavior, n-type low-resistivity electrical behavior) to the same degree. This allows the crystal (e.g., ingot) to be converted into a SiC wafer, with the desired electrical behavior present throughout the wafer, and in particular throughout the thickness of the wafer. These materials have dopants or electroactive impurities (i.e., less than 10% change from top to bottom, side to side, as described above) substantially uniformly distributed throughout the material, referred to herein as "uniformly" or "homogeneously" doped SiC wafers, ingots, crystals or boules.

Thus, in an embodiment, the p-type SiC wafer is devoid of any n-type material layer. Furthermore, in a preferred embodiment, the p-type SiC wafer (also including p-type crystals and p-type ingots) has electronically active donor atoms distributed throughout the wafer (also including p-type crystals and p-type ingots), and in particular throughout the entire thickness of the wafer. Furthermore, in a preferred embodiment, the p-type SiC wafer (also including p-type crystals and p-type ingots) has electrically active atomic impurities distributed throughout the wafer (also including p-type crystals and p-type ingots), and specifically throughout the entire thickness of the wafer. These materials have dopants or electroactive impurities (i.e., less than 10% change from top to bottom, side to side, as described above) substantially uniformly distributed throughout the material, referred to herein as "uniform p-type SiC" wafers, ingots, crystals or boules. These homogeneous p-type SiC crystals, boules, ingots, and wafers also include p+ and p-types.

The low resistivity SiC wafers may be n-type and p-type. Preferably, for an n-type low resistivity SiC wafer, the dopant is phosphorus or a mixture of phosphorus and nitrogen. Preferably, the dopants in the low resistivity crystals, boules, ingots, and wafers are distributed throughout the crystal matrix with less than 100%, less than 50%, less than 25% variation, and more preferably are uniform low resistivity SiC materials.

Embodiments of methods and processes for growing a boule, such as vapor depositing SiC to form a single crystal boule of p-type SiC or low resistivity p-type or n-type SiC, that provides for being very flat, such as having a limited amount of curvature or curvature at the face of the boule. The very flat profile of the ingot is achieved mainly by using a preselected shape of the SiC wafer disk placed in the vapor deposition apparatus. The preselected shape (e.g., shaped charge) is configured such that the area of flux and the flow within that area remain constant throughout the ingot growth process during the vapor deposition process. In this way, the rate and amount of SiC deposition on the faces of the ingot as the ingot grows remains consistent and uniform during the ingot growth process. Thus, for example, when a 6 inch diameter ingot is grown, the area of flux flow will be 28.27 square inches, and during ingot growth, for example, a3 inch long ingot, a 4 inch long ingot, etc., the flow rate and amount of SiC flowing through this area will be uniform across the area. Even during this process, the amount and location of SiC available for sublimation in the crystal disk changes, the shape of the crystal disk directs the flux, e.g., the "directional flux," in a manner that maintains the flux uniformly flowing through the region immediately adjacent to the face of the ingot. Shaped charges for growing SiC crystals and use of the charges are disclosed and taught in U.S. patent publication No. 2018/0290893, the entire disclosure of which is incorporated herein by reference.

In one embodiment, the flux is not kept constant throughout the growth process. Thus, in this embodiment, the rate, distribution of flux across the growth surface is managed (e.g., controlled in a predetermined manner) to provide a predetermined growth of the ingot or growth surface area. Thus, for example, during the latter stages of growth, the flux may be directed in a predetermined manner to compensate for non-uniformities that occur in the growth of the ingot. In this example, the regions of greater flux in the early stages of growth have less flux in the later stages of growth; also, areas with less flux in the early stages of growth have greater flux in the later stages of growth. In this way, the final ingot growth face minimizes the curvature of the ingot face or maximizes the radius of curvature.

In one embodiment, using a controlled flux, and more preferably using a directional flux, a 4 to 8 inch diameter p-type SiC or low resistivity SiC boule may be provided having a characteristic shape defined by a trailing end having a positive radius of curvature when oriented above the seed end. SiC crystals having diameters of 4 to 8 inches typically have radii in the range of 10 to 200 inches.

In embodiments, the radius of curvature (i.e., the inverse of the curvature) of the tail may be at least about 6 inches, at least about 8 inches, at least about 20 inches, at least about 60 inches, and approaching infinity (i.e., planar), as well as all values within these ranges of values. In one embodiment, the radius of curvature (i.e., the inverse of the curvature) of a 6 inch ingot will be at least about 10 inches, at least about 15 inches, at least about 25 inches, at least about 60 inches, and near infinity (i.e., planar), and all values within these ranges of values. In one embodiment, the radius of curvature of the ingot face is at least 2 times the length of the ingot, at least 5 times the length of the ingot, at least 10 times the length of the ingot, at least 25 times the length of the ingot, up to and including the case where the ingot face is planar, and all values within this range.

In one embodiment, the flux may be controlled by pressure and temperature in addition to the composition and constitution of the PDC source material. For a given growth temperature, growth may be slowed by increasing the chamber pressure. The fastest rate is typically under "full" vacuum (e.g., the vacuum pump is on and the chamber pressure is kept as low as possible). Thus, for example, to grow a boule at 400 μm/hr, the growth may be performed at a temperature T1 at P1 under full vacuum, or may be performed at a temperature T2> T1, with argon partial pressure of several millibars to several tens millibars (P2 > P1). In this way, flux and growth rate can be "tuned".

In embodiments, polymer derived doped SiC imparts better polytype stability in p-type SiC or low resistivity SiC ingots, because the flux composition is more consistent over time. This embodiment (i.e., controlled polytype stability) is valuable and important to the ingot manufacturer because the movement of the polytype in mid-growth means that only a portion of the ingot is the original polytype, which typically has an adverse effect on the electronic properties, which in turn affect the device performance of the chip made from it.

Turning to fig. 4, a schematic cross-sectional view of an apparatus for growing p-type or low resistivity p-type or n-type SiC crystals and crystal structures is shown. Vapor deposition apparatus and methods, and in particular PVT apparatus and methods using PDC SiC source material, are disclosed and taught in U.S. patent No. 10,753,010 and published patent application No. 2018/0290893, the entire disclosures of each of which are incorporated herein by reference. The vapor deposition apparatus 1800 is a container having side walls 1808, a bottom or bottom wall 1809, and a top or top wall 1810. The walls 1808, 1809, 1810 may have ports 1806, 1807, 1805, which may be openings, nozzles, valves, which may control or allow gas flow into and out of the apparatus 1800. The apparatus 1800 is associated with a heating element 1804. The heating element may be configured and operated to provide a single temperature zone or multiple temperature zones within the device 1800. Inside the apparatus 1800 is a shaped charge 1801 made of doped SiC particles that together form a doped SiC spatial feature (it is noted that in one embodiment, the dopant may be incorporated into or be part of the binder used to form the SiC spatial feature).

The shaped charge 1801 may have a predetermined porosity and density. The SiC particles may have a predetermined porosity and density. The SiC particles are preferably held together by a binder. The shaped charge 1801 may be carbon-rich, carbon-lean, or stoichiometric. The shaped charge 1801 may have a carbon-rich, carbon-lean, or stoichiometric region or layer. Preferably, the SiC particles are SiOC polymer derived SiC. Non-polymer derived SiC may also be used as part or all of the shaped charge. The shaped charge 1801 has a height and cross-section or diameter 1820 as shown by arrow 1821. The shaped charge 1801 has an upper or top surface 1823 and a bottom surface 1824. In this embodiment, the shaped charge 1801 is shown as a top and bottom flat cylinder; it should be appreciated that any spatial form contemplated by the present description may be used in the apparatus 1800.

At the top 1810 of the apparatus 1800 is a seed 1802, which may have the same doping type and amount as would be expected to be found in crystals grown on the seed 1800. The seed 1800 has a surface 1802a. The seed 1802 has a cross-section or diameter 1822 and a height 1823. In some embodiments, a seed crystal may be mounted on movable stage 1803 to adjust the distance between surface 1802a and surface 1823.

The diameter 1820 of the shaped charge 1801 may be greater than, less than, or equal to the diameter 1822 of the seed 1802.

In operation, heating element 1804 increases the temperature of shaped charge 1801 to the point where SiC and dopant sublimate. This sublimation results in the formation of gases having various silicon and carbon and dopants. Such gas (i.e., flux) is present in the region 1850 between surfaces 1802a and 1823. Flux may also be present within the shaped charge 1801, depending on porosity or other factors. The flux rises in the device 1800 through region 1850, where the flux deposits p-type SiC, or n-type or p-type low resistivity SiC, on the surface 1802a in region 1850. Surface 1802a must be maintained at a sufficiently cool temperature to deposit gaseous silicon carbon species and dopant atomic impurities on its surface to form doped SiC crystals. In this way, the seed 1802 is grown into a p-type or n-type or p-type low resistivity SiC crystal by continuously adding the grown SiC and dopants in a polytype-matched crystal orientation on its surface. Thus, unless adjusted by the platform 1803 (which is shown in the fully retracted position), during ingot growth, the surface 1803 will grow toward the bottom 1809, thereby reducing the distance between the surface 1802a and the bottom 1809. The shape of the shaped charge may be used to create a predetermined temperature differential within the shaped charge during the vapor deposition process. Such predetermined temperature differences may address, reduce, and eliminate the deleterious effects of passivation, which is the condition of matter accumulation in the shaped charge during the process that reduces or prevents vapor formation.

In embodiments where only p-type dopants are used, the presence of any material (such as nitrogen) that is considered or serves as a source of donor atoms should be minimized, reduced, and eliminated. (note that in other embodiments, nitrogen may be present in a lesser amount than the p-type dopant and still obtain a p-type source material, i.e., configured to grow crystals with negative Nc.)

Theoretically, the sublimation and deposition processes occur at the surface and inside of the spatial features of the source material itself (e.g., shaped charges) and follow naturally occurring thermal gradients in the source material, or the thermal gradients may be determined by the shape of the spatial features. In one embodiment, the binder material may preferably remain present and maintain the shape and integrity of the spatial features during the sublimation temperature and thus not sublimate at or below the sublimation temperature of SiC. Such thermal gradients are typically from the outside to the inside. Theoretically, the material is continually sublimated and redeposited on adjacent particles, and in this way undergoes reflow or solid "fractionation" or "fractional sublimation" of the si—c species and dopants.

Further theoretically, in one embodiment, the spatial features and their predetermined gradients may allow some heavier impurities to be trapped behind the bottom of the growth chamber within the spatial feature structure, while lighter elements sublimate with the si—c vapor and are carried to the seed crystal. This theoretically provides the ability to release dopants or other additives at predetermined times during the process or growth cycle.

In one embodiment, the shaped charge provides a more consistent flux formation rate for a given temperature. The shape of the shaped charge can be tailored to provide a more uniform temperature throughout the shape, allowing a higher volume fraction of the shape to sublimate immediately, driving a higher flux rate at the seed/vapor interface at a given temperature than a standard powder stack or cylindrical body of powder. Thus, growth of polytypes requiring a lower temperature growth process will not be limited to slower growth rates.

The sublimation rate is in grams/hr. The flux is in grams/cm ² -hr (i.e., the rate at which a material passes through a region). Thus, the critical area is the flux area corresponding to the instantaneous surface area of the ingot growth surface (e.g., the face of the ingot where SiC is deposited). Typically, the flux area and the area of the ingot face are about the same, and these areas are typically slightly smaller than the cross-sectional area of the growth chamber of the vapor deposition apparatus.

For the purposes of calculation and such analysis, it is assumed for ease of calculation that the cross-sectional area of the growth chamber is the same as the area of the flux and the area of the ingot face. Thus, the growth rate (μm/hr) of the ingot may also be equivalent to the vapor flux- μm/hr- > g/hr (density of fully dense SiC 3.21 g/cc) through the surface area (cm ²) of the ingot. In situ measurements may be done via X-ray imaging or X-ray Computed Tomography (CT). In addition, the average growth rate can be determined by weighing the ingot before/after growth.

Typical commercial growth rates are from 200 μm/hr to 500 μm/hr. Embodiments of the present process and space-variant far exceed these existing commercial rates while providing equal and higher quality ingots. For example, embodiments of the present invention may have a growth rate of about 550 μm/hr to about 11000 μm/hr, about 800 μm/hr to about 1000 μm/hr, about 900 μm/hr to about 1100 μm/hr, about 700 μm/hr, about 800 μm/hr, about 900 μm/hr, about 1000 μm/hr, 1100 μm/hr at high and low pressures. It is contemplated that higher rates may be used as well as lower rates, and all rates within these ranges.

Typically, the growth rate is driven by 1) the temperature and 2) the pressure of the supplied gas (Ar, N ₂, etc.). For any given temperature, higher gas pressure dilutes the vapor pressure of the silicon-carbon species at the seed and ingot surfaces and slows the growth rate. Thus, pressure can be used to "dial-in" growth rate.

Thus, given a constant temperature, embodiments of the spatial features (e.g., shaped charges) can maintain a consistent flux generation rate (e.g., constant) throughout the operation of p-type SiC or low resistivity SiC crystal growth, including such crystals having diameters of about 4 inches to about 10 inches, about 6 inches to about 8 inches, about 4 inches, about 6 inches, about 8 inches, and larger and smaller diameters, and all diameters within these value ranges. Embodiments of the spatial features may maintain the flux generation rate at a given constant temperature throughout the p-type SiC or low resistivity SiC crystal growth process, thereby maintaining the ingot growth rate at a constant rate, a rate of less than about 0.001% change, a rate of less than about 0.01% change, a rate of less than about 1% change, a rate of less than about 5% change, a rate of less than about 20% change, a rate of about 0.001% change to about 15% change, a rate of about 0.01% change to about 5% change, and combinations and variations of these, and all values within these ranges of values during crystal growth. In an embodiment, at a constant temperature, the flux formation rate is maintained at: about 99.999% to about 60% of its maximum rate; about 99% to about 95% of its maximum rate; about 99.99% to about 80% of its maximum rate; about 99% to about 70% of its maximum rate; about 95% to about 70% of its maximum rate; about 99% to about 95% of its maximum rate; and combinations and variations of these, as well as all values within these percentage ranges, during ingot growth.

The embodiments provide different stoichiometries, binder contents, dopant contents and distribution of the two powders throughout a body, e.g., layers, regions, areas with different types of powder starting materials, different binders and combinations and variants thereof. This predetermined distribution of different stoichiometry, binder content, and both provides several advantages, including: as the source material is consumed from the outside inwards, the customization of the sublimated composition results in less variation of the composition from the beginning to the end of the growth cycle. Such predetermined distribution of different stoichiometry, binder content, and both may also improve stability of the polytype, as the constituent compositions of the vapor are consistent.

Embodiments of the invention include the use of doped SiC in the fabrication of p-type SiC or low resistivity SiC wafers for electronic and semiconductor applications. Doped (preferably high purity) SiC is required in vapor deposition apparatus and processes that produce p-type SiC or low resistivity SiC crystals and p-type SiC or low resistivity SiC wafers for later use.

Embodiments of the present polysilocarb p-type SiC or low resistivity SiC, and p-type SiC or low resistivity SiC ingots, p-type SiC or low resistivity SiC wafers, and other structures made from polysilocarb-derived SiC, exhibit polymorphism, and one-dimensional polymorphism is commonly referred to as polytype. Thus, polysilocarb-derived p-type SiC or low resistivity SiC may be present in many theoretically infinite different polytypes. As used herein, unless specifically stated otherwise, the terms polytype, and the like will be given their broadest possible meaning and will include a variety of different frameworks, structures, or arrangements through which silicon carbide tetrahedra (SiC ₄) is configured. Generally, these polytypes fall into two categories-alpha (α) and beta (β).

Examples of alpha-type polysilocarb derived p-type SiC or low resistivity SiC generally include hexagonal (H), rhombohedral (R), trigonal (T) structures, and may include combinations of these structures. Beta-type generally comprises a cubic (C) or sphalerite structure. Thus, for example, the polytypes of polysilocarb-derived p-type SiC or low resistivity SiC will include: 3C-SiC (beta-SiC or beta 3C-SiC) with the stacking sequence of ABCABC … …;2H-SiC, the stacking sequence of which is ABAB … …;4H-SiC, the stacking sequence of which is ABCBABCB … …; and 6H-SiC (a common form of alpha silicon carbide, alpha 6H-SiC), in a stacking order of ABCACBABCACB … …. Examples of other forms of alpha silicon carbide include 8H, 10H, 16H, 18H, 19H, 15R, 21R, 24H, 33R, 39R, 27R, 48H, and 51R.

Examples of polysilocarb-derived p-type SiC or low resistivity SiC may be polycrystalline or mono-crystalline. In general, in polycrystalline materials, grain boundaries exist as interfaces between two grains or crystallites of the material. These grain boundaries may be between the same polytypes with different crystal orientations, or between different polytypes with the same or different crystal orientations, as well as combinations and variations thereof. The single crystal structure consists of a single polytype and is substantially free of grain boundaries. In a preferred embodiment, the p-type SiC or low resistivity SiC is monocrystalline.

Embodiments of the present methods produce ingots, preferably monocrystalline p-type SiC or low resistivity SiC ingots. The length of these ingots may be about 1/2 inch to about 5 inches, about 1/2 inch to about 3 inches, about 1 inch to about 2 inches, greater than about 1/2 inches, greater than about 1 inch, and greater than about 2 inches. Larger and smaller sizes are contemplated as well as all values within these size ranges. The boule may have a cross-section, such as a diameter, of about 1/2 inch to about 9 inches, about 2 inches to about 8 inches, about 1 inch to about 6 inches, greater than about 1 inch, greater than about 2 inches, greater than about 4 inches, about 6 inches and about 8 inches, about 12 inches and about 18 inches. Other sizes are contemplated as well as all values within these size ranges.

P-type and low resistivity type wafers-typically

In general, a process for manufacturing electronic components from p-type SiC or low resistivity SiC ingots includes cutting p-type SiC or low resistivity SiC single crystal ingots into thin wafers. The SiC wafer produced is the starting point for manufacturing SiC-based semiconductor devices. SEMI (www.semi.org) has developed and released specifications for SiC wafers of various diameters up to 150 mm. These criteria are well known and understood by those skilled in the art. Because of the existing limitations of the SiC industry in commercializing p-type SiC crystals and wafers, and only n-type nitrogen doped SiC crystals and wafers, the most well known method of manufacturing SiC wafers suitable for use in manufacturing semiconductor devices is based on SiC n-type wafers, and can be used to manufacture p-type, n-type low resistivity and p-type low resistivity wafers.

Embodiments of the doped wafers of the present invention have a diameter of the boule cut therefrom and typically have a thickness of about 100 μm to about 500 μm. Preferably, the p-type electrical properties or low resistivity properties are distributed over the entire length of the ingot or the entire thickness of the wafer. More preferably, the p-type electrical properties or low resistivity properties are uniformly distributed throughout the length of the ingot or throughout the thickness of the wafer. One or both sides of the p-type SiC or low resistivity SiC wafer are then polished. The polished wafer is then used as a substrate for fabricating microelectronic semiconductor devices. Thus, p-type SiC or low resistivity SiC wafers are used as substrates for microelectronic devices built on the wafer. The fabrication of these microelectronic devices includes microfabrication processing steps such as epitaxial growth, doping or ion implantation, etching, deposition of various materials, photolithographic patterning, and the like. Once made from p-type SiC or low resistivity SiC wafers, the wafer (and thus the individual microcircuits) are separated into individual semiconductor devices in a process called dicing. These devices are then used to fabricate a variety of large semiconductors and electronic devices, for example, incorporated into these devices.

Examples of the present methods and resulting p-type SiC or low resistivity SiC wafers include, inter alia, about 2 inch diameter wafers and smaller wafers, about 3 inch diameter wafers, about 4 inch diameter wafers, about 5 inch diameter wafers, about 6 inch diameter wafers, about 7 inch diameter wafers, about 12 inch diameter wafers and possibly larger wafers, about 2 inch to about 8 inch diameter wafers, about 4 inch to about 6 inch diameter wafers, squares, circles and other shapes, about 1 square inch, about 4 square inches, about 8 square inches, about 10 square inches, about 12 square inches, about 30 square inches, about 50 square inches and larger and smaller surface areas per side, about 100 μm thickness, about 200 μm thickness, about 300 μm thickness, about 500 μm thickness, about 700 μm thickness, about 50 μm to about 800 μm thickness, about 100 μm to about 700 μm thickness, about 100 μm to about 400 μm thickness, about 400 μm to about 300 μm thickness and smaller and combinations thereof, and variations thereof having values in the range of about 100 μm to about 300 μm and smaller.

Embodiments of the present method and resulting cut and polished p-type SiC or low resistivity SiC wafers may also include a means for inducing ingot growth (i.e., as a "seed") whereby the remainder of the grown ingot matches the structure. The p-type SiC or low resistivity SiC wafer or p-type SiC or low resistivity SiC seed may be, inter alia, about 2 inch diameter wafers and smaller wafers, about 3 inch diameter wafers, about 4 inch diameter wafers, about 5 inch diameter wafers, about 6 inch diameter wafers, about 7 inch diameter wafers, about 12 inch diameter wafers and possibly larger wafers, about 2 inch to about 8 inch diameter wafers, about 4 inch to about 6 inch diameter wafers, squares, circles and other shapes, about 4 square inches, about 8 square inches, about 12 square inches, about 30 square inches, about 50 square inches and larger and smaller surface areas per side, about 100 μm thickness, about 200 μm thickness, about 300 μm thickness, about 500 μm thickness, about 1500 μm thickness, about 2500 μm thickness, about 50 μm to about 2000 μm thickness, about 500 μm to about 1800 μm thickness, about 800 μm to about 1200 μm thickness, about 500 μm to about 1500 μm thickness and about 500 μm thickness to about 1200 μm thickness and smaller and the range of these and smaller surface areas within the range of about 1500 μm to about 500 μm and smaller.

Embodiments of the present p-type SiC or low resistivity SiC boules, p-type SiC or low resistivity SiC wafers, and microelectronic devices fabricated from these wafers find application and use in, inter alia, diodes, wideband amplifiers, military communications, radar, telecommunications, data links and tactical data links, satellite communications and point-to-point radio power electronics, LEDs, lasers, lighting and sensors. Additionally, these embodiments may find application and use in transistors, such as High Electron Mobility Transistors (HEMTs), including HEMT-based Monolithic Microwave Integrated Circuits (MMICs) and IGBTs. These transistors can employ distributed (traveling wave) amplifier design methods, taking advantage of the larger band gap of SiC, enabling extremely wide bandwidths in small footprints. Accordingly, embodiments of the present invention will include SiC, siC boules, siC wafers, and microelectronic devices fabricated from these wafers made from or otherwise based on these methods, vapor deposition techniques, and polymers described below.

Embodiments of polysilocarb-derived p-type SiC or low resistivity SiC (particularly high purity SiC) have a number of unique properties that make them advantageous and desirable for use in, inter alia, electronics, solar and power transmission industries and applications. They can be used as very stable p-type or low resistivity semiconductor materials and are suitable for a variety of demanding applications including high power, high frequency, high temperature and corrosive environments and uses. Polymer derived p-type SiC or low resistivity SiC is a very hard material with a young's modulus of 424GPa.

In one embodiment, if the dopant is to be added to the material, the dopant may be added by way of a precursor and thus be present in a controlled manner and amount to grow into a boule or other structure. Embodiments of the precursor formulation may have a dopant or compound that carries and incorporates the dopant into the ceramic and then into the converted SiC so that the dopant is available and in a usable form in the vapor deposition process.

Additionally, dopants or other additives provide tailored or predetermined properties to wafers, layers, and structures made from embodiments of polymer-derived SiC. In these embodiments, such property enhancing additives are not considered impurities, as they are intended to be in the final product, which is desired in the final product. The property enhancing additive may be incorporated into the liquid precursor material. Depending on the nature of the property enhancing additive, it may be part of the precursor backbone, it may be compounded or part of a compound to incorporate it into a liquid precursor, or it may exist in other forms that enable it to survive (e.g., in a form that enables its function to be present in the final material as intended). The property enhancing additive may also be added as a coating to the SiC or SiOC powder material, may be added as a vapor or gas during processing, or may be in powder form and mixed with polymer derived SiC or SiOC particles, etc. In one embodiment, the property enhancing additive comprises or is part of a binder for the spatial shape. In one embodiment, the property enhancing additive may be a coating on the spatial feature. Furthermore, the form and manner in which the property enhancing additive is present should preferably be such that it has minimal, more preferably no, adverse effect on the process conditions, the process time and the quality of the final product.

P-type devices-typically

These p-type SiC wafers provide the ability to fabricate circuits, semiconductor devices, and chips previously designed with silicon p-type wafers, and do so with only the need to rewrite or rewrite the circuit or chip design. Thus, in one embodiment, a circuit or device is provided that directly builds a design using a p-type silicon substrate, instead of using a device made of SiC p-type wafers, without the need to modify, configure or adjust the silicon device-based circuit.

In this way, embodiments of the present invention address the problems faced by power circuit designers when exploiting the full advantage of SiC devices by: a manufacturable method is provided to produce 4H-SiC or 6H-SiC p-type substrates (e.g., wafers) with low defects, resistivity properties, and substrate diameters consistent with the requirements of current manufacturing equipment, such as Schottky Barrier Diodes (SBDs), junction barrier schottky diodes (JBS), and MOSFETs, as well as transistors such as gate turn-off transistors (GTOs) and Integrated Gate Bipolar Transistors (IGBTs), as well as variations and other types of these transistors and devices. Embodiments of the present invention are capable of fabricating p-type substrates that are diameter and resistivity matched, and preferably exceed p-type substrates currently commercially produced from n-type SiC crystals. The p-type wafers disclosed and taught herein provide device manufacturers with the ability to extend the application of SiC to, and thus make possible, devices currently manufactured with, all voltage and current intensity ranges from n-type SiC to p-type SiC. Based on the p-type wafers disclosed and taught herein, designers of power circuits will now be able to extend the advantages of SiC devices to all power management applications, among other things, of all voltage range, voltage polarity, and current intensity circuit designs.

Embodiments of the invention may have or utilize one or more embodiments, features, functions, parameters, components, processes, or systems set forth in the precursor and source materials-typically, dopant crystal growth-typically, p-type and low resistivity type wafers-typically, p-type devices-typically teachings, and one or more embodiments, features, functions, parameters, components, processes, or systems in the examples and figures.

Example

The following examples are provided to illustrate various embodiments of the systems, processes, compositions, applications, and materials of the present invention. These examples are for illustrative purposes, may be prophetic, and should not be considered and should not limit the scope of the invention. Unless explicitly stated otherwise, percentages used in the examples are, for example, weight percentages of the total of a formulation, mixture, product, or structure. Unless explicitly stated otherwise, X/Y or XY are used to represent% of X and% of Y in the formulation. Unless explicitly stated otherwise, X/Y/Z or XYZ are used to denote% of X,% of Y and% of Z in the formulation.

Example 1

In one embodiment, a dispersion of 2.5wt% 5 μm mullite powder (MU-101, micrometer metal) is added to a precursor formulation of 41% MHF and 59% TV formulation with 30ppb Pt as the archratio catalyst. The doped precursor formulation is cured and then pyrolysed to SiC. The SiC powder is then made into a shaped charge by using the doped precursor formulation as a shaped charge binder, molding the shaped charge, and then curing the body into a green body. The green body is pyrolysed and converted into doped SiC forming material source material. Further details are set forth in examples 1A through 1D.

Example 1A

As shown in table 1, a liquid Al doping precursor formulation for manufacturing a p-type SiC source material for growing p-type SiC crystals.

Watch (1)

The ratio of the weight of mullite to the weight of the precursor formulation was targeted at 2.5%

* 41% By weight of linear methyl hydrogen polysiloxane (MHF) and 59% by weight of tetravinyl cyclotetrasiloxane (TV).

Example 1B

As shown in table 2, the cured Al-doped precursor formulation from example 1A was pyrolyzed to provide an Al-doped SiC material.

Table 2.

Example 1C

As shown in table 3, the ceramic Al-doped SiC material from example 1B was shaped into a space-shaped body and cured. Mullite is added with a binder to form a spatial shape.

TABLE 3 Table 3

* 41% By weight of linear methylhydrogen polysiloxane (MHF) and 59% by weight of tetravinyl cyclotetrasiloxane (TV)

Example 1D

As shown in table 4, the solidified spatial features of example 1C were pyrolyzed to provide an Al-doped SiC shaped charge source material for PVT growth of p-type SiC crystals.

TABLE 4 Table 4

Weight before pyrolysis (g)	Weight after pyrolysis (g)	Yield rate
			3264.9	2925.4	89.60％

Example 2

The same general formulation and procedure as examples 1A to 1D were followed except that triallylphosphine was added to the liquid precursor formulation in place of the aluminum dopant (the weight percent of triallylphosphine to the precursor formulation was 1% to 15%), and a binder (the weight percent of triallylphosphine to the P-doped SiC powder and binder was 1% to 15%) was also added to form a solidified P-doped SiC spatial form, which was then pyrolyzed to form a P-doped SiC shaped charge source material. The P-doped SiC forming material source material is used for PVT growth of low resistivity n-type SiC crystals.

Example 3

Turning to fig. 1, a photograph of a p-type SiC crystal having a diameter of about 150mm is shown. The crystal was grown using PVT process and apparatus and using an Al-doped SiC shaped charge source material of the type in example 1D. The p-type crystal had 70ppm of Al. The p-type crystal had 5.5X10 ¹⁸ aluminum atoms/cc. The crystals have a length of about 23 mm. A thin sheet of the crystal was prepared and polished to a blue/violet color when viewed in transmission. No evidence of the switch of polytype from 4H to another polytype was observed.

Example 4

Turning to fig. 2A, a schematic plan view of a doped SiC wafer 700 is shown. Fig. 2B is a cross-sectional view of wafer 700 along line B-B. Wafer 700 may be a p-type SiC wafer, wafer 700 may be a low resistivity p-type SiC wafer, or wafer 700 may be a low resistivity n-type SiC wafer. Wafer 700 is a disk-like crystal structure having a semicircular shape 705 with a planar surface 706. It should be appreciated that the wafer may be circular or may have more than one plane. Wafer 700 has edge 730. Wafer 700 has a top or top surface 710, a bottom or bottom surface 711, and a thickness indicated by arrow 712. The top and bottom surfaces of wafer 700 and the entire thickness 712 are doped SiC crystals. It should be understood that one surface is typically the C-face of the SiC crystal and the other surface is the Si-face of the SiC crystal. One or both surfaces may be polished and finished for device fabrication. The outer edge 730 of the wafer 700 may be tapered, beveled, chamfered, square, rounded, etc.

Wafer 700 is cut from a doped SiC boule having a length significantly greater than thickness 712 (e.g., 10 times, 20 times, 50 times, 70 times, or more) of wafer 700.

Thus, wafer 700 is not a thin doped SiC layer grown or deposited on a substrate layer of a different type of material, and then the substrate layer is removed from the thin doped SiC layer. Such thin (e.g., less than 1mm, less than 0.5 mm) substrate growth doped SiC layers have electrical and physical properties that are distinct from the doped SiC wafers cut from the doped SiC boule upon removal of the substrate. Such a substrate grown thin doped layer has unacceptable stresses in the material, exhibits warpage and curvature, and is generally unsuitable for any kind of semiconductor device fabrication.

Example 5

6 Inch (150 mm) p-type SiC wafers. Polytype 4H. And (3) doping agent Al. The crystal orientation is <0001> +/-0.5 degrees. The thickness is 325 μm to 500 μm. Tortuosity (Bow) <40 μm. Warp (Warp) <60 μm. TTV <15 μm. SBIR (LTV) (average 10 mm. Times.10 mm) <4 μm. MPD (microtubule) <0.2cm ^-2. TSD (THREADING SCREW DENSITY, screw density) <500cm ^-2. BPD (basal plane dislocation) <500cm ^-2. The resistivity is 0.015 ohm-cm to 0.028 ohm-cm.

Example 6

6 Inch (150 mm) low resistivity p-type SiC wafers. Polytype 4H. And (3) doping agent Al. The crystal orientation is <0001> +/-0.5 degrees. The thickness is 325 μm to 500 μm. Tortuosity (Bow) <40 μm. Warp (Warp) <60 μm. TTV <15 μm. SBIR (LTV) (average 10 mm. Times.10 mm) <4 μm. MPD (microtubule) <0.2cm ^-2. TSD (screw density) <500cm ^-2. BPD (basal plane dislocation) <500cm ^-2. The resistivity is 0.010 ohm-cm to 0.003 ohm-cm.

Example 7

6 Inch (150 mm) p-type SiC wafers. Polytype 6H. And (3) doping agent Al. The crystal orientation is <0001> +/-0.5 degrees. The thickness is 325 μm to 500 μm. Tortuosity (Bow) <40 μm. Warp (Warp) <60 μm. TTV <15 μm. SBIR (LTV) (average 10 mm. Times.10 mm) <4 μm. MPD (microtubule) <0.2cm ^-2. TSD (screw density) <500cm ^-2. BPD (basal plane dislocation) <500cm ^-2. The resistivity is 0.015 ohm-cm to 0.028 ohm-cm.

Example 8

6 Inch (150 mm) low resistivity p-type SiC wafers. Polytype 6H. And (3) doping agent Al. The crystal orientation is <0001> +/-0.5 degrees. The thickness is 325 μm to 500 μm. Tortuosity (Bow) <40 μm. Warp (Warp) <60 μm. TTV <15 μm. SBIR (LTV) (average 10 mm. Times.10 mm) <4 μm. MPD (microtubule) <0.2cm ^-2. TSD (screw density) <500cm ^-2. BPD (basal plane dislocation) <500cm ^-2. The resistivity is 0.010 ohm-cm to 0.003 ohm-cm.

Example 9

6 Inch (150 mm) low resistivity n-type SiC wafers. Polytype 4H. A dopant P. The crystal orientation is <0001> +/-0.5 degrees. The thickness is 325 μm to 500 μm. Tortuosity (Bow) <40 μm. Warp (Warp) <60 μm. TTV <15 μm. SBIR (LTV) (average 10 mm. Times.10 mm) <4 μm. MPD (microtubule) <0.2cm ^-2. TSD (screw density) <500cm ^-2. BPD (basal plane dislocation) <500cm ^-2. The resistivity is 0.010 ohm-cm to 0.003 ohm-cm.

Example 10

6 Inch (150 mm) low resistivity n-type SiC wafers. Polytype 6H. A dopant P. The crystal orientation is <0001> +/-0.5 degrees. The thickness is 325 μm to 500 μm. Tortuosity (Bow) <40 μm. Warp (Warp) <60 μm. TTV <15 μm. SBIR (LTV) (average 10 mm. Times.10 mm) <4 μm. MPD (microtubule) <0.2cm ^-2. TSD (screw density) <500cm ^-2. BPD (basal plane dislocation) <500cm ^-2. The resistivity is 0.010 ohm-cm to 0.003 ohm-cm.

Example 11

Turning to fig. 5, a schematic diagram of an N-channel E-MOSFET device 500 using a p-type SiC wafer is shown. The device 500 has a gate 512, a metal electrode 505, a metal oxide layer 504. The device 500 has a source 509, a drain 508 and a body 510. The circuit 511 is formed between the source 509 and the body 510. The source 509 is connected to the n-type SiC 502 through a metal electrode. The drain 508 is connected to the n-type SiC 503 through a metal electrode. The apparatus 500 has a p-type substrate 501 made of a p-type wafer sliced from a p-type ingot. The metal oxide layer 507 is adjacent to the p-type substrate 501. The body 510 is connected to the p-type substrate 501 through an electrode 507.

Example 12

Turning to fig. 6, a schematic diagram of a P-channel E-MOSFET device 600 using a P-type SiC wafer is shown. The device 600 has a gate 612, a metal electrode 605, a metal oxide layer 604. The device 600 has a source 609, a drain 608, and a body 610. The circuit 611 is formed between the source 609 and the body 610. Source 609 is connected to p-type SiC 602 through a metal electrode. The drain 608 is connected to the p-type SiC 603 through a metal electrode. The p-type SiC 602, 603 is made of p-type wafers cut from p-type boules. The device 600 has an n-type substrate 601. The metal oxide layer 607 is adjacent to the n-type substrate 601. The body 610 is connected to the n-type substrate 601 through an electrode 607.

Example 13

Turning to fig. 7, a schematic diagram of an N-channel D-MOSFET device 750 using a p-type SiC wafer is shown. The device 750 has a gate 762, a metal electrode 755, a metal oxide layer 754. The device 750 has a source 759, a drain 758, and a body 760. The circuit 761 is formed between the source 759 and the body 760. Source 759 is connected to n-type SiC 752 through a metal electrode. The drain 758 is connected to n-type SiC 753 through a metal electrode. The device 750 has an N-channel 751 with a channel length as indicated by arrow 764. The apparatus 750 has a p-type substrate 763 made of a p-type wafer sliced from a p-type boule. The metal oxide layer 756 is adjacent to the p-type substrate 763 and a portion of the N-channel 751. The body 760 is connected to a p-type substrate 763 through an electrode 757.

Example 14

Turning to fig. 8, a schematic diagram of a P-channel D-MOSFET device 800 using a P-type SiC wafer is shown. The device 800 has a gate 812, a metal electrode 805, a metal oxide layer 804. The device 800 has a source 809, a drain 808, and a body 810. A circuit 811 is formed between the source 809 and the body 810. Source 809 is connected to p-type SiC 802 through a metal electrode. Drain 808 is connected to p-type SiC 803 through a metal electrode. The p-type SiC 802 and 803 are made of p-type wafers cut from p-type ingots. The apparatus 800 has a P-channel 801 made from a P-type wafer sliced from a P-type ingot. Arrow 814 represents the channel length. The device 800 has an n-type substrate 813. The metal oxide layer 806 is adjacent to the n-type substrate 813 and a portion of the P-channel 801. Base 810 is connected to n-type substrate 813 through electrode 807.

Example 15

Turning to fig. 9, a cross-sectional schematic diagram of a SiC IGBT device 900 is shown. The apparatus 900 is based on a p+ type wafer cut from a p+ type ingot, which forms a layer 901, as well as other p-type materials in the multi-layer structure of the apparatus 900. Other layers of the device may also be based on PDC n-type SiC wafers.

Example 16

Turning to fig. 10, a schematic cross-sectional view of a SiC Laterally Diffused MOSFET (LDMOS) device 1000 is shown. The apparatus 1000 is based on a p+ type wafer cut from a p+ type ingot, which forms a layer 1001, as well as other p-type materials in the multilayer structure of the apparatus 1000. Other layers of the device may also be based on PDC n-type SiC wafers.

Example 17

Turning to fig. 11, a schematic cross-sectional view of a SiC VMOS MOSFET device 1100 is shown. The device 1100 is based on a p-type wafer cut from a p-type ingot that forms the p-type material in the multilayer structure of the device 1100. Other layers of the device may also be based on PDC n-type SiC wafers.

Example 18

Turning to fig. 12, a cross-sectional schematic diagram of a SiC UMOS MOSFET device 1200 is shown. The apparatus 1200 is based on a p-type wafer cut from a p-type ingot that forms the p-type material in the multi-layer structure of the apparatus 1200. Other layers of the device may also be based on PDC n-type SiC wafers.

Example 19

Turning to fig. 13, a cross-sectional schematic diagram of a SiC IGBT device 1300 is shown. The apparatus 1000 is based on a p-type wafer cut from a p-type ingot that forms a p-substrate layer, as well as other p-type materials in the multi-layer structure of the apparatus 1300. Other layers of the device may also be based on PDC n-type SiC wafers.

Example 20

Turning to fig. 14, a schematic cross-sectional view of a SiC CMOS compound device 1400 is shown. The apparatus 1400 is based on a p-type wafer cut from a p-type ingot that forms the p-substrate layer in the multi-layer and component structure of the apparatus 1400. Here, PMOS devices and NMOS devices are built on a common p-type substrate based on a p-type wafer diced from a p-type boule. Shallow trench isolation (ST) provides electrical isolation between these devices. The multi-layered metal lines are routed as interconnect devices to form circuits on the chip. Capacitors, resistors, and inductors may also be integrated into the compound device 1400.

Example 21

Turning to fig. 15, a cross-sectional schematic diagram of a SiC flash memory device 1500 is shown. Prior to the present invention, it was believed that flash memory devices could not be made of SiC. SiC flash memory device 1500 has a source 1501, a bit line 1502, a word line control gate 1503, a floating gate 1504, an n-type SiC feature 1505, a second n-type SiC feature 1506, and a p-type layer 1507 based on a p-type wafer cut from a p-type boule.

Example 22

Turning to fig. 16, an embodiment of a SiC CMOS compound device 1600 is shown. Such devices are used as analog and mixed signal devices. The apparatus has a p-type substrate layer based on a p-type wafer sliced from a p-type ingot.

Example 23

Lower resistivity SiC wafers provide significant advantages when used in production equipment because costly processing steps (e.g., grinding or thinning SiC substrates) are not required, while minimal, preferably no design changes are required to the circuitry.

Example 24

The lower resistivity SiC wafers also have a resistivity between 1 ohm-cm and 5 milliohm-cm.

Example 25

Nitrogen is much smaller than silicon. Thus, in theory, smaller impurity atoms may occupy carbon sites in the crystal and larger impurity atoms may occupy silicon sites. During SiC crystal growth, nitrogen may occupy one or both of the Si or C sites in the crystal.

Typically, doped SiC wafers may have 100 to 1000 parts per million of nitrogen dopant. Theoretically, only one of every 100 nitrogen atoms supplied during growth is absorbed into the crystal, i.e., becomes an electroactive atomic impurity. Thus, the source must be significantly higher than the desired dopant level. (the "absorption" of dopants into the lattice is known as site competition). However, the amount of nitrogen that can be put into the crystal is limited, and too much can distort the crystal, thereby creating stress. In the past, higher concentrations of nitrogen doping to reduce resistivity resulted in a large number of stacking faults and other crystal quality defects that negatively impacted epitaxy and device performance. The size of the phosphorus is closer to that of the silicon atom. Thus, in theory, within the SiC lattice, phosphorus will replace silicon (as opposed to nitrogen replacing carbon) and much less stress will be introduced (and fewer defects because the formation of defects is driven by the stress in the crystal). Thus, theoretically, the preferred amount of phosphorus dopant will be less than 10% of the nitrogen dopant required in the source material used to fabricate the phosphorus doped n-type SiC wafer, based on the dopant required. In a preferred embodiment, the process obtains >1% phosphorus from the source material as an electroactive atomic impurity into the SiC crystal.

Example 26

In sublimation processes for growing SiC crystals, typically more Si vapor than C vapor makes it suitable for incorporation of nitrogen, but at the same time high Si vapor concentrations are not suitable for incorporation of aluminum or boron to make p-type materials. However, theoretically, 1 of nitrogen or phosphorus is incorporated as a dopant per 100 atoms, while only 1 of boron or aluminum is incorporated per 1000 atoms.

Thus, for efficient incorporation, the doping source should be theoretically equal to or higher than the vapor pressure of silicon. Aluminum is a good dopant for p-type wafers because its vapor pressure is higher than that of silicon. Aluminum and silicon are arranged adjacent to each other in the periodic table (in fact, atoms of the same size).

Example 27

Existing 4H silicon carbide p-type materials (grown as epitaxial layers on a substrate (typically n-type SiC)) can be used to fabricate n-channel IGBTs, generally lacking the quality and conductivity of working well in IGBTs, and in particular, of working as commercially acceptable IGBTs. The present invention addresses and solves this problem, inter alia, by providing a p-type SiC wafer sliced from a p-type SiC boule that provides the ability to fabricate commercially acceptable and operable SiC IGBT devices.

Example 28

There is a long felt need for SiC LDMOSFETs (lateral metal oxide semiconductor field effect transistors). These devices are developed on silicon for high power applications such as cellular and UHF broadcast transmissions, and the demand for such devices is growing. This is because silicon LDMOSFETs have higher gain and better linearity than bipolar devices. However, prior to the present invention, devices of this design or type could not be made of or based on SiC because there were only n-type SiC substrates, and historically any p-type epitaxially formed SiC substrates had too high a resistivity compared to silicon, resulting in undesirable LDMOSFET device performance. The present invention addresses and solves this problem, inter alia, by providing a p-type SiC wafer sliced from a p-type SiC boule that provides the ability to fabricate commercially acceptable and operable SiC LDMOSFET devices.

Example 29

A polysilocarb precursor formulation having one or more dopants with a predetermined amount of acceptor impurity atoms and a predetermined amount of donor impurity atoms. In this way, the SiC source material has a predetermined amount of acceptor and donor impurity atoms, and thus a predetermined ratio of acceptor impurity atoms and donor impurity atoms. The predetermined ratio in turn provides a predetermined Nc value for doped SiC grown from the source material.

Example 30

In embodiments of polysilocarb precursors, si-OH functional siloxanes and silanes are used for the incorporation of most Al-OH, P-OH or B-OH functional groups without releasing hydrogen. For example, the following reaction is shown:

～Si-OH+～B-OH→～Si-O-B～+H2O

Example 31

SiC IGBTs having voltage capability greater than 10kV and greater than 100 kV.

Example 32

Medium voltage SiC IGBTs having a voltage capability of about 2 kV.

Example 33

4 Inch (100 mm) p-type SiC wafers. Polytype 4H. And (3) doping agent Al. The crystal orientation is <0001> +/-0.5 degrees. The thickness is 325 μm to 500 μm. Tortuosity (Bow) <40 μm. Warp (Warp) <60 μm. TTV <15 μm. SBIR (LTV) (average 10 mm. Times.10 mm) <4 μm. MPD (microtubule) <0.2cm ^-2. TSD (screw density) <500cm ^-2. BPD (basal plane dislocation) <500cm ^-2. The resistivity is 0.015 ohm-cm to 0.028 ohm-cm.

Example 34

4 Inch (100 mm) low resistivity p-type SiC wafers. Polytype 4H. And (3) doping agent Al. The crystal orientation is <0001> +/-0.5 degrees. The thickness is 325 μm to 500 μm. Tortuosity (Bow) <40 μm. Warp (Warp) <60 μm. TTV <15 μm. SBIR (LTV) (average 10 mm. Times.10 mm) <4 μm. MPD (microtubule) <0.2cm ^-2. TSD (screw density) <500cm ^-2. BPD (basal plane dislocation) <500cm ^-2. The resistivity is 0.010 ohm-cm to 0.003 ohm-cm.

Example 35

6 Inch (150 mm) p-type SiC wafers. Polytype 6H. And (3) doping agent Al. The crystal orientation is <0001> +/-0.5 degrees. The thickness is 325 μm to 500 μm. Tortuosity (Bow) <40 μm. Warp (Warp) <60 μm. TTV <15 μm. SBIR (LTV) (average 10 mm. Times.10 mm) <4 μm. MPD (microtubule) <0.2cm ^-2. TSD (screw density) <500cm ^-2. BPD (basal plane dislocation) <500cm ^-2. The resistivity is 0.015 ohm-cm to 0.028 ohm-cm.

Example 36

6 Inch (150 mm) low resistivity p-type SiC wafers. Polytype 6H. And (3) doping agent Al. The crystal orientation is <0001> +/-0.5 degrees. The thickness is 325 μm to 500 μm. Tortuosity (Bow) <40 μm. Warp (Warp) <60 μm. TTV <15 μm. SBIR (LTV) (average 10 mm. Times.10 mm) <4 μm. MPD (microtubule) <0.2cm ^-2. TSD (screw density) <500cm ^-2. BPD (basal plane dislocation) <500cm ^-2. The resistivity is 0.010 ohm-cm to 0.003 ohm-cm.

Example 37

4 Inch (100 mm) p-type SiC wafers. Polytype 4H. And (3) doping agent Al. The crystal orientation is <0001> +/-0.5 degrees. The thickness is 325 μm to 500 μm. Tortuosity (Bow) <40 μm. Warp (Warp) <60 μm. TTV <15 μm. SBIR (LTV) (average 10 mm. Times.10 mm) <4 μm. MPD (microtubule) <0.2cm ^-2. TSD (screw density) <500cm ^-2. BPD (basal plane dislocation) <500cm ^-2. The wafer has an N _A from 10 ¹⁸/cm³ to about 10 ¹⁹/cm³.

Example 38

6 Inch (150 mm) p-type SiC wafers. Polytype 4H. And (3) doping agent Al. The crystal orientation is <0001> +/-0.5 degrees. The thickness is 325 μm to 500 μm. Tortuosity (Bow) <40 μm. Warp (Warp) <60 μm. TTV <15 μm. SBIR (LTV) (average 10 mm. Times.10 mm) <4 μm. MPD (microtubule) <0.2cm ^-2. TSD (screw density) <500cm ^-2. BPD (basal plane dislocation) <500cm ^-2. The wafer has an N _A from 10 ¹⁸/cm³ to about 10 ¹⁹/cm³.

Example 39

6 Inch (150 mm) p-type SiC wafers. Polytype 6H. And (3) doping agent Al. The crystal orientation is <0001> +/-0.5 degrees. The thickness is 325 μm to 500 μm. Tortuosity (Bow) <40 μm. Warp (Warp) <60 μm. TTV <15 μm. SBIR (LTV) (average 10 mm. Times.10 mm) <4 μm. MPD (microtubule) <0.2cm ^-2. TSD (screw density) <500cm ^-2. BPD (basal plane dislocation) <500cm ^-2. The wafer has an N _A from 10 ¹⁸/cm³ to about 10 ¹⁹/cm³.

Example 40

4 Inch (100 mm) p-type SiC wafers. Polytype 4H. And (3) doping agent Al. The crystal orientation is <0001> +/-0.5 degrees. The thickness is 325 μm to 500 μm. Tortuosity (Bow) <40 μm. Warp (Warp) <60 μm. TTV <15 μm. SBIR (LTV) (average 10 mm. Times.10 mm) <4 μm. MPD (microtubule) <0.2cm ^-2. TSD (screw density) <500cm ^-2. BPD (basal plane dislocation) <500cm ^-2. The wafer has an N _A from 10 ¹⁸/cm³ to about 10 ¹⁹/cm³.

Example 41

4 Inch (100 mm) p-type SiC wafers. Polytype 6H. And (3) doping agent Al. The crystal orientation is <0001> +/-0.5 degrees. The thickness is 325 μm to 500 μm. Tortuosity (Bow) <40 μm. Warp (Warp) <60 μm. TTV <15 μm. SBIR (LTV) (average 10 mm. Times.10 mm) <4 μm. MPD (microtubule) <0.2cm ^-2. TSD (screw density) <500cm ^-2. BPD (basal plane dislocation) <500cm ^-2. The wafer has an N _A from 10 ¹⁸/cm³ to about 10 ¹⁹/cm³.

Example 42

4 Inch (100 mm) low resistivity n-type SiC wafers. Polytype 4H. A dopant P. The crystal orientation is <0001> +/-0.5 degrees. The thickness is 325 μm to 500 μm. Tortuosity (Bow) <40 μm. Warp (Warp) <60 μm. TTV <15 μm. SBIR (LTV) (average 10 mm. Times.10 mm) <4 μm. MPD (microtubule) <0.2cm ^-2. TSD (screw density) <500cm ^-2. BPD (basal plane dislocation) <500cm ^-2. The resistivity is 0.010 ohm-cm to 0.003 ohm-cm.

Example 43

4 Inch (100 mm) low resistivity p-type SiC wafers. Polytype 6H. A dopant P. The crystal orientation is <0001> +/-0.5 degrees. The thickness is 325 μm to 500 μm. Tortuosity (Bow) <40 μm. Warp (Warp) <60 μm. TTV <15 μm. SBIR (LTV) (average 10 mm. Times.10 mm) <4 μm. MPD (microtubule) <0.2cm ^-2. TSD (screw density) <500cm ^-2. BPD (basal plane dislocation) <500cm ^-2. The resistivity is 0.010 ohm-cm to 0.003 ohm-cm.

Example 44

6 Inch (150 mm) low resistivity n-type SiC wafers. Polytype 4H. A dopant P. The crystal orientation is <0001> +/-0.5 degrees. The thickness is 325 μm to 500 μm. Tortuosity (Bow) <40 μm. Warp (Warp) <60 μm. TTV <15 μm. SBIR (LTV) (average 10 mm. Times.10 mm) <4 μm. MPD (microtubule) <0.2cm ^-2. TSD (screw density) <500cm ^-2. BPD (basal plane dislocation) <500cm ^-2. The resistivity is 0.010 ohm-cm to 0.003 ohm-cm.

Example 45

6 Inch (150 mm) low resistivity p-type SiC wafers. Polytype 6H. A dopant P. The crystal orientation is <0001> +/-0.5 degrees. The thickness is 325 μm to 500 μm. Tortuosity (Bow) <40 μm. Warp (Warp) <60 μm. TTV <15 μm. SBIR (LTV) (average 10 mm. Times.10 mm) <4 μm. MPD (microtubule) <0.2cm ^-2. TSD (screw density) <500cm ^-2. BPD (basal plane dislocation) <500cm ^-2. The resistivity is 0.010 ohm-cm to 0.003 ohm-cm.

Example 46

4 Inch (100 mm) low resistivity n-type SiC wafers. Polytype 4H. A dopant P. The crystal orientation is <0001> +/-0.5 degrees. The thickness is 325 μm to 500 μm. Tortuosity (Bow) <40 μm. Warp (Warp) <60 μm. TTV <15 μm. SBIR (LTV) (average 10 mm. Times.10 mm) <4 μm. MPD (microtubule) <0.2cm ^-2. TSD (screw density) <500cm ^-2. BPD (basal plane dislocation) <500cm ^-2. The resistivity is 0.010 ohm-cm to 0.003 ohm-cm.

Example 47

4 Inch (100 mm) low resistivity p-type SiC wafers. Polytype 6H. A dopant P. The crystal orientation is <0001> +/-0.5 degrees. The thickness is 325 μm to 500 μm. Tortuosity (Bow) <40 μm. Warp (Warp) <60 μm. TTV <15 μm. SBIR (LTV) (average 10 mm. Times.10 mm) <4 μm. MPD (microtubule) <0.2cm ^-2. TSD (screw density) <500cm ^-2. BPD (basal plane dislocation) <500cm ^-2. The resistivity is 0.010 ohm-cm to 0.003 ohm-cm.

Example 48

6 Inch (150 mm) low resistivity n-type SiC wafers. Polytype 4H. A dopant P. The crystal orientation is <0001> +/-0.5 degrees. The thickness is 325 μm to 500 μm. Tortuosity (Bow) <40 μm. Warp (Warp) <60 μm. TTV <15 μm. SBIR (LTV) (average 10 mm. Times.10 mm) <4 μm. MPD (microtubule) <0.2cm ^-2. TSD (screw density) <500cm ^-2. BPD (basal plane dislocation) <500cm ^-2. The resistivity is 0.010 ohm-cm to 0.003 ohm-cm.

Example 49

6 Inch (150 mm) low resistivity p-type SiC wafers. Polytype 6H. A dopant P. The crystal orientation is <0001> +/-0.5 degrees. The thickness is 325 μm to 500 μm. Tortuosity (Bow) <40 μm. Warp (Warp) <60 μm. TTV <15 μm. SBIR (LTV) (average 10 mm. Times.10 mm) <4 μm. MPD (microtubule) <0.2cm ^-2. TSD (screw density) <500cm ^-2. BPD (basal plane dislocation) <500cm ^-2. The resistivity is 0.010 ohm-cm to 0.003 ohm-cm.

Title and examples

It should be understood that the headings used in this specification are for clarity and not limitation in any way. Accordingly, the processes and disclosure described under one heading should be read in the context of the entire specification, including various examples. The use of headings in this specification should not be construed as limiting the scope of the invention.

It should be noted that there is no need to provide or set forth a theory of novel and breakthrough processes, materials, properties or other beneficial features and properties that are the subject of or associated with the embodiments of the present invention. However, various theories are provided in this specification to further advance the art in this field. These theories presented in this specification, unless explicitly stated otherwise, in no way limit, restrict or narrow the scope of the claimed invention. These theories may not be needed or practiced with the present invention. It should also be appreciated that the present invention can yield new and heretofore unknown theories to explain the functional characteristics of embodiments of the methods, articles, materials, devices and systems of the present invention; and these latter teachings should not be taken as limiting the scope of the invention.

The various embodiments of the formulations, compositions, articles, plastics, ceramics, materials, parts, wafers, boules, spatial structures, uses, applications, equipment, methods, activities, and operations set forth in this specification may be used in a variety of other fields and in a variety of other activities, uses, and embodiments. Additionally, these embodiments may be used, for example, to: existing systems, articles, compositions, materials, operations, or activities; may be used in future developed systems, articles, compositions, material handling or activities; and such systems, articles, compositions, materials, operations, or activities that may be modified based in part on the teachings of the present specification. Furthermore, the various embodiments and examples set forth in this specification may be used in whole or in part with each other, as well as in different and various combinations. Thus, for example, the configurations provided in the various embodiments of the present description may be used with one another. For example, components having embodiments of A, A' and B and components having embodiments of a ", C, and D may be used together in various combinations, such as A, C, D, and A, A", C, and D, etc., in accordance with the teachings of the present specification. Therefore, the scope of protection provided by the present invention should not be limited to the particular embodiments, configurations, or arrangements set forth in the particular embodiments, examples, or embodiments in the particular drawings.

The present invention may be embodied in other forms than those specifically disclosed herein without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive.

Claims (67)

1. A method of manufacturing a SiC crystal having predetermined electrical properties, the method comprising:

a) Placing a SiC source material in a vapor deposition apparatus;

b) The SiC source material includes silicon, carbon and dopants,

I) Wherein the dopant is selected to provide the SiC crystal with the predetermined electrical property;

ii) wherein the dopant is fixed in position in the source material relative to the silicon and the carbon;

c) Adding an inert gas to the vapor deposition apparatus, and controlling the pressure in the vapor deposition apparatus;

d) Heating the SiC source material to thereby form a flux, wherein the flux comprises silicon, carbon, and dopants; and

E) Depositing the flux on a growth face of a SiC crystal to thereby grow the SiC crystal;

a) Wherein the SiC crystal has the predetermined electrical property.

2. The method of claim 1, wherein the source material consists essentially of silicon, carbon, and the dopant.

3. The method of claim 1, wherein the source material consists of silicon, carbon, and the dopant.

4. The method of claim 1, wherein the dopant comprises one or more elements of group 15 of the periodic table.

5. A method according to any one of claims 1 to 3, wherein the dopant comprises phosphorus.

6. A method according to any one of claims 1 to 3, wherein the dopant consists essentially of phosphorus.

7. A method according to any one of claims 1 to 3, wherein the dopant consists of phosphorus.

8. The method of claim 1, wherein the dopant comprises one or more elements of group 13 of the periodic table.

9. A method according to any one of claims 1 to 3, wherein the dopant comprises boron.

10. A method according to any one of claims 1 to 3, wherein the dopant consists essentially of boron.

11. A method according to any one of claims 1 to 3, wherein the dopant consists of boron.

12. A method according to any one of claims 1 to 3, wherein the dopant comprises aluminium.

13. A method according to any one of claims 1 to 3, wherein the dopant consists essentially of aluminium.

14. A method according to any one of claims 1 to 3, wherein the dopant consists of aluminium.

15. The method of any one of claims 1 to 3 and 8 to 14, wherein the predetermined electrical property comprises a net charge and the net charge is positive, whereby the crystal is a p-type crystal.

16. The method of any one of claims 1 to 9, wherein the predetermined electrical property comprises a net charge and the net charge is negative, whereby the crystal is an n-type crystal.

17. The method of any one of claims 1 to 16, wherein the predetermined electrical property comprises resistivity.

18. The method of any one of claims 1 to 17, wherein the predetermined electrical property comprises a resistivity of 0.013 ohm-cm and less.

19. The method of any one of claims 1 to 17, wherein the predetermined electrical property comprises a resistivity of about 0.010 ohm-cm and less.

20. The method of any one of claims 1 to 17, wherein the predetermined electrical property comprises a resistivity of about 0.01 ohm-cm to about 0.001 ohm-cm.

21. The method of any one of claims 1 to 17, wherein the predetermined electrical property comprises a resistivity of about 0.009 ohm-cm to about 0.004 ohm-cm.

22. The method of any one of claims 1 to 21, wherein no other material is added to the flux after the flux is formed from the source material.

23. The method of any one of claims 1 to 22, wherein no other material is added to the vapor deposition apparatus.

24. The method of any one of claims 1 to 23, wherein the SiC source material is the sole source of the dopant.

25. The method of any one of claims 1 to 24, wherein no alloy is present and whereby the method is alloy-free.

26. The method of any one of claims 1 to 25, wherein the vapor deposition apparatus is a physical vapor transport apparatus.

27. The method of any one of claims 1 to 26, wherein the flux is a directional flux.

28. The method of any one of claims 1 to 27, wherein the SiC source material is a shaped charge.

29. The method of any one of claims 1 to 28, wherein the crystals have a diameter of at least about 100mm and a height of at least about 25 mm.

30. The method of any one of claims 1 to 29, wherein the crystals have a diameter of about 100mm to about 150mm and a height of about 25mm to about 125 mm.

31. A method of manufacturing a p-type SiC crystal, the method comprising:

a) Placing a shaped charge of SiC source material in a vapor deposition apparatus;

b) The shaped charge SiC source material consists essentially of silicon, carbon, and a quantity of acceptor atoms held in a position of the shaped charge SiC source material;

c) Wherein the acceptor atoms are fixed in position in the forming material source material relative to the silicon and the carbon;

d) Heating the forming charge SiC source material and thereby forming a flux by sublimation of the forming charge source material; wherein the flux comprises silicon, carbon, and a portion of the quantity of acceptor atoms; and

E) Depositing the flux on a growth face of a p-type SiC crystal to thereby grow the p-type SiC crystal; wherein at least some of the acceptor atoms in the flux form substitutional atomic impurities in the p-type SiC crystal.

32. The method of claim 31, wherein the acceptor atom comprises boron.

33. The method of any one of claims 31 and 33, wherein the acceptor atom comprises aluminum.

34. The method of any one of claims 31 to 33, wherein the source material does not comprise an alloy.

35. The method of any one of claims 31 to 34, wherein the source material is the only source of acceptor atoms.

36. The method of any one of claims 31 to 35, wherein the vapor deposition apparatus is a physical vapor transport apparatus.

37. The method of any one of claims 31 to 36, wherein an inert gas is added to the vapor deposition apparatus and no other gas is added to the vapor deposition apparatus.

38. The method of any one of claims 31 to 37, wherein the p-type crystal has a diameter of at least about 100mm and a height of at least about 25 mm.

39. The method of any one of claims 31 to 37, wherein the p-type crystal has a diameter of about 100mm to about 150mm and a height of about 25mm to about 125 mm.

40. The method of any one of claims 31 to 39, wherein the p-type crystal has a resistivity of less than 2.0 ohm-cm.

41. The method of any one of claims 31 to 39, wherein the p-type crystal has a resistivity of 2.0 ohm-cm to about 0.1 ohm-cm.

42. The method of any one of claims 31 to 39, wherein the p-type crystal has a resistivity of 0.13 ohm-cm and less.

43. The method of any one of claims 31 to 39, wherein the p-type crystal has a resistivity of 0.013 ohm-cm to about 0.004 ohm-cm.

44. The method of any one of claims 31 to 39, wherein the p-type crystal has a resistivity of about 0.010 ohm-cm and less.

45. The method of any one of claims 31 to 39, wherein the p-type crystal has a resistivity of about 0.01 ohm-cm to about 0.001 ohm-cm.

46. The method of any one of claims 31 to 39, wherein the p-type crystal has a resistivity of about 0.009 ohm-cm to about 0.004 ohm-cm.

47. The method of any of claims 31 to 46, wherein during the growth of the p-type crystal, the dopant remains fixed in the source material until the source material sublimates to form the flux.

48. A method of manufacturing a low resistivity n-type SiC crystal, the method comprising:

a) Placing a shaped charge of SiC source material in a vapor deposition apparatus;

b) The shaped charge SiC source material consists essentially of silicon, carbon, and a quantity of donor atoms held in a location of the shaped charge SiC source material;

c) Wherein the acceptor atoms are fixed in position in the forming material source material relative to the silicon and the carbon;

d) Heating the forming charge SiC source material and thereby forming a flux by sublimation of the forming charge source material; wherein the flux comprises silicon, carbon, and a portion of the quantity of acceptor atoms; and

E) Depositing the flux on a growth face of the n-type SiC crystal to thereby grow the n-type SiC crystal;

Wherein at least some of the donor atoms in the flux form substitutional atomic impurities in the n-type SiC crystal.

49. The method of claim 48, wherein the donor atom comprises one or more of the elements of group 15 of the periodic table.

50. The method of any one of claims 48 to 49, wherein the donor atom comprises phosphorus.

51. The method of any one of claims 48 to 50, wherein the donor atom consists essentially of phosphorus.

52. The method of any one of claims 48 to 51, wherein the donor atom consists of phosphorus.

53. The method of any one of claims 48 to 52, wherein the source material is the only source of acceptor atoms.

54. The method of any one of claims 48 to 53 wherein the vapor deposition apparatus is a physical vapor transport apparatus.

55. The method of any one of claims 48 to 54, wherein an inert gas is added to the vapor deposition apparatus and no other gas is added to the vapor deposition apparatus.

56. The method of any one of claims 48 to 55, wherein the n-type crystal has a diameter of at least about 100mm and a height of at least about 25 mm.

57. The method of any one of claims 48 to 56, wherein the n-type crystal has a diameter of about 100mm to about 150mm and a height of about 25mm to about 125 mm.

58. The method of any one of claims 48 to 57, wherein the n-type crystal has a resistivity of 0.013 ohm-cm and less.

59. The method of any one of claims 48 to 57, wherein the n-type crystal has a resistivity of 0.013 ohm-cm to 0.004 ohm-cm.

60. The method of any one of claims 48 to 57, wherein the n-type crystal has a resistivity of about 0.010 ohm-cm and less.

61. The method of any one of claims 48 to 57 wherein the n-type crystal has a resistivity of about 0.01 ohm-cm to about 0.001 ohm-cm.

62. The method of any one of claims 48 to 57 wherein the n-type crystal has a resistivity of about 0.009 ohm-cm to about 0.004 ohm-cm.

63. The method of any of claims 48 to 62, wherein during the growth of the n-type crystal, the acceptor atoms remain fixed in the source material until the source material sublimates to form the flux.

64. A method according to any preceding claim comprising p-type crystal growth on the C-face of the SiC seed.

65. A method according to any preceding claim comprising p-type crystal growth on the S-face of the SiC seed.

66. A method according to any preceding claim comprising p-type crystal growth on the C-face of a SiC seed, wherein the SiC seed has a 4H or 6H polytype.

67. A method according to any preceding claim comprising p-type crystal growth on the S-face of a SiC seed, wherein the SiC seed has a 4H or 6H polytype.