WO2019237654A1

WO2019237654A1 - Method for growing oxide layer on silicon carbide substrate

Info

Publication number: WO2019237654A1
Application number: PCT/CN2018/115875
Authority: WO
Inventors: 何志
Original assignee: 重庆伟特森电子科技有限公司
Priority date: 2018-06-11
Filing date: 2018-11-16
Publication date: 2019-12-19
Also published as: CN108847384A

Abstract

Disclosed is a method for growing an oxide layer on a silicon carbide substrate. The method comprises the following steps: S1: covering a surface of a silicon carbide substrate (1) with a mask layer (2) and then carrying out a patterning treatment on the mask layer (2), so that a first region, which is to be oxidized, on the surface of the silicon carbide substrate (1) is exposed, and a second region to be oxidized thereof is covered by the mask layer (2); S2: implanting oxygen ions and nitrogen ions (3) into the first region, which is to be oxidized, to form an ion implantation layer (4) on the surface of the silicon carbide substrate (1); and S4: carrying out a high-temperature thermal oxidation treatment to form an oxide layer (5) on the surface of the silicon carbide substrate (1), wherein the thickness of the oxide layer (5) on the ion implantation layer (4) is greater than that of the oxide layer (5) in the remaining region of the surface of the silicon carbide substrate (1). According to the method, by means of the implantation of the oxygen ions, the silicon carbide surface is amorphized, so that the oxidation rate is improved; furthermore, by means of the implantation of the nitrogen ions, the interface state density of silicon dioxide and silicon carbide is reduced, so that the quality of an interface between the silicon dioxide and the silicon carbide can be improved.

Description

Method for growing oxide layer on silicon carbide substrate

Technical field

The present invention relates to the field of semiconductor technology, and more particularly, to a method for rapidly growing an oxide layer on a silicon carbide substrate (including an epitaxial layer).

Background technique

Silicon carbide (SiC) is a wide band gap semiconductor material, which has the advantages of high critical breakdown electric field strength, high saturation electron mobility, and high thermal conductivity. It is particularly suitable for high power power transmission and energy conversion technology. Power electronic devices made of SiC materials can carry high voltage and high current, and can work stably in harsh application environments such as high radiation and high temperature. SiC materials can be used to prepare rectifier devices such as Schottky diodes, PIN tubes, and also can be used to prepare switching devices such as MOSFET, JFET, IGBT. SiC materials are also widely used in MEMS devices.

In the semiconductor device manufacturing process, the oxidation process is a commonly used manufacturing process. The oxidation process can be used to grow a gate oxide layer, a sacrificial oxide layer, an isolation layer between electrodes, and a masking layer used for implantation or etching. SiC material is another semiconductor material that can directly grow SiO ₂ through thermal oxidation after Si material. This characteristic of SiC material brings unique advantages to the preparation of SiC devices.

However, the chemical properties of the SiC material itself are very stable, the oxidation rate of SiC is very slow, and a high oxidation temperature is required, which results in the growth of the oxide layer with a thickness of tens of nanometers is very slow, and the time and temperature required are much longer. Higher than common Si oxidation, the interface state of the resulting silicon oxide is problematic, while the growth of thicker oxide layers for isolation or shielding purposes is very difficult. At the same time, as the most commonly used isoform in SiC materials, 4H-SiC is an anisotropic material. The oxidation rate of different crystal planes varies greatly, among which the oxidation rate of Si crystal plane is the slowest, and that of C crystal plane is the lowest. The oxidation rate is the fastest. The oxidation rates of the a-plane and m-plane are slightly lower than the C-plane. In view of the relatively mature epitaxial technology of the Si crystal plane, the epitaxial wafers of the prior art are mainly epitaxial wafers based on the Si crystal plane. This results in that the oxide layer growth takes a long time when preparing high-voltage devices, and the oxidation rates of different parts of the device will be different It will have additional adverse effects on the device function and bring new challenges to the device structure and process design. In some cases, a technician may choose a method of directly depositing a dielectric layer on a silicon carbide epitaxial wafer. However, the quality of the oxide film deposited by this method is not high and the application range is small. In addition, after the dielectric layer is etched, structural sharp corners will be formed, which will cause electric field concentration and lead to device leakage or breakdown. It will not form a smooth transition structure like the natural oxide layer in the selected area. How to increase the oxidation speed of the oxide layer grown on the silicon carbide substrate has become a technical problem to be solved urgently by those skilled in the art.

To solve the above problem, the only method in the prior art is to increase the oxidation temperature of SiC. Increasing the oxidation temperature of SiC makes the production of SiC devices require expensive equipment, the production capacity is extremely low, and the prepared oxide layer and the interface between the oxide layer and the silicon carbide substrate also have many functional problems. After the oxidation growth of silicon carbide, there are a large number of carbon clusters and silicon-carbon dangling bonds at the interface of silicon dioxide and silicon carbide. On the one hand, carbon clusters and silicon-carbon dangling bonds can trap channel electrons, making them unable to participate in current transport, thereby reducing the charge density of the surface inversion layer; on the other hand, at low fields, the carbon clusters and silicon- As a Coulomb scattering center, electrons captured by carbon dangling bonds can reduce the mobility of the surface inversion layer, thereby greatly hindering the development of silicon carbide power devices.

Therefore, there is a need to provide a method for rapidly growing an oxide layer on a silicon carbide substrate to increase the oxidation speed of SiC and improve the state of the oxide layer / silicon carbide interface.

Summary of the Invention

The technical problem to be solved by the present invention is to provide a method for rapidly growing an oxide layer on a silicon carbide substrate (including an epitaxial layer).

To solve the above technical problems, the invention adopts the following technical solutions:

A method for growing an oxide layer on a silicon carbide substrate includes the following steps:

S1: Covering a surface of the silicon carbide substrate with a mask layer, and then patterning the mask layer, so that a first region to be oxidized on the surface of the silicon carbide substrate is exposed, and a second region to be oxidized is exposed. Mask layer coverage

S2: implanting the oxygen ions and nitrogen ions into the first region to be oxidized, and forming an ion implantation layer on the surface of the silicon carbide substrate;

S4: performing a high-temperature thermal oxidation treatment to form an oxide layer on the surface of the silicon carbide substrate, and the thickness of the oxide layer of the ion implantation layer is greater than the oxidation of the remaining area on the surface of the silicon carbide substrate Layer thickness.

Preferably, after the step S2 and before the step S4, the method further includes the following steps: S3: After the oxygen ions and nitrogen ions are implanted, the mask layer is removed.

Preferably, the implantation energy of the oxygen ions is 10 keV to 1 MeV, and the implantation dose thereof is 1 × 10 ¹⁴ cm ^-2 to 1 × 10 ¹⁸ cm ^-2 ; the implantation energy of the nitrogen ions is 10 keV to 1 MeV, and the implantation dose thereof It is 1 × 10 ¹² cm ^-2 to 1 × 10 ¹⁵ cm ^-2 .

Preferably, the temperature of the high-temperature thermal oxidation treatment is 900 ° C to 2000 ° C.

To solve the above technical problems, the invention also adopts the following technical solutions:

S1: implanting oxygen ions and nitrogen ions into the silicon carbide substrate by ion implantation to form an ion implantation layer on the surface of the silicon carbide substrate;

S2: performing a high-temperature thermal oxidation treatment, so that the ion-implanted layer is oxidized to form an oxide layer.

Preferably, before the step S1, the method further includes the following steps: S0: depositing a cushion layer on the silicon carbide substrate.

Preferably, after the step S2, the following steps are further included: S3: The oxide layer 5 is removed by wet etching or dry etching.

Preferably, the implantation energy of the oxygen ions is less than or equal to 100 keV, the implantation dose thereof is 1 × 10 ¹² cm ^-2 to 1 × 10 ¹⁸ cm ^-2 , and the implantation temperature thereof is 0 to 1000 ° C .; The implantation energy is less than or equal to 100 keV, and the implantation dose is 1 × 10 ¹² cm ^-2 to 1 × 10 ¹⁵ cm ^-2 .

Preferably, the implantation energy of the oxygen ions is 10 keV to 1 MeV, and the implantation dose thereof is 1 × 10 ¹² cm ^-2 to 1 × 10 ¹⁸ cm ^-2 , and the implantation temperature thereof is 0 to 1000 ° C .; The energy is 10 keV to 1 MeV, and the implantation dose is 1 × 10 ¹² cm ^-2 to 1 × 10 ¹⁵ cm ^-2 .

Any range described in the present invention includes an end value and any value between the end values and an arbitrary subrange formed by the end value or any value between the end values.

Unless otherwise specified, each raw material in the present invention can be obtained through commercial purchase, and the equipment used in the present invention can be performed by using conventional equipment in the field or referring to the existing technology in the field.

Compared with the prior art, the present invention has the following beneficial effects:

According to the method for growing an oxide layer on a silicon carbide substrate of the present invention, the surface of the silicon carbide is made amorphous by the implantation of oxygen ions, the oxidation rate is increased, and the density of the interface state of silicon dioxide and silicon carbide is reduced by the implantation of nitrogen ions. Therefore, the silicon carbide-based LOCOS process can be realized, the electric field aggregation effect caused by the structure tip can be avoided, and the quality of the interface between silicon dioxide and silicon carbide can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

The specific embodiments of the present invention will be described in further detail below with reference to the drawings.

1 is a flowchart of a method for growing an oxide layer on a silicon carbide substrate according to Embodiment 1 of the present invention;

2-5 are schematic diagrams showing steps of a method for growing an oxide layer on a silicon carbide substrate according to Embodiment 1 of the present invention;

6 is a flowchart of a method for growing an oxide layer on a silicon carbide substrate according to Embodiment 2 of the present invention;

7-9 are schematic steps of a method for growing an oxide layer on a silicon carbide substrate provided in Embodiment 2 of the present invention;

10 is a flowchart of a method for growing an oxide layer on a silicon carbide substrate according to Embodiment 3 of the present invention;

11-14 are schematic steps of a method for growing an oxide layer on a silicon carbide substrate provided in Embodiment 3 of the present invention.

detailed description

In order to explain the present invention more clearly, the present invention is further described below with reference to preferred embodiments. Those skilled in the art should understand that what is specifically described below is illustrative and not restrictive, which should not limit the scope of protection of the present invention.

Example 1

This embodiment provides a method for growing an oxide layer on a silicon carbide substrate (including an epitaxial layer). As shown in FIG. 1, the method includes the following steps:

S1-1: The surface of the silicon carbide substrate 1 is covered with a masking layer 2, and then the masking layer 2 is patterned so that the first region to be oxidized on the surface of the silicon carbide substrate 1 is exposed, and the second region to be oxidized is exposed. The area is covered by the mask layer 2, as shown in FIG. 2;

S1-2: implanting oxygen ions and nitrogen ions 3 into the first region to be oxidized, as shown in FIG. 3, forming an ion implantation layer 4 on the surface of the silicon carbide substrate 1, as shown in FIG. 4;

S1-3: After the oxygen ions and nitrogen ions 3 are implanted, the mask layer 2 is removed, as shown in FIG. 4;

S1-4: performing a high-temperature thermal oxidation treatment, forming an oxide layer 5 on the surface of the silicon carbide substrate 1, and the thickness of the oxide layer 5 corresponding to the ion implantation layer 4 is greater than the thickness of the oxide layer 5 in the remaining area of the surface of the silicon carbide substrate As shown in Figure 5.

In this embodiment, the material of the mask layer 2 may be photoresist, silicon dioxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), or aluminum nitride (AlN), or may be made of photoresist. A mixture of any two or more of silicon dioxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), and aluminum nitride (AlN).

In the above step S1-2, the implantation energy of oxygen ions is 10 keV to 1 MeV, and the implantation dose thereof is 1 × 10 ¹⁴ cm ^-2 to 1 × 10 ¹⁸ cm ^-2 . In the above step S1-2, the implantation energy of the nitrogen ions is 10 keV to 1 MeV, and the implantation dose thereof is 1 × 10 ¹² cm ^-2 to 1 × 10 ¹⁵ cm ^-2 .

In the above step S1-2, for the peripheral region (not shown) of the region where the ion implanted layer 4 is located, although it is not directly implanted with oxygen ions and nitrogen ions, the diffusion of oxygen ions causes the oxygen element concentration in the region The oxygen element concentration is higher than the silicon carbide material itself, and the diffusion of nitrogen ions causes the nitrogen element concentration in the region to be higher than that of the silicon carbide material itself. In this embodiment, the regions around the region where the ion implantation layer 4 is located, where the oxygen element concentration and the nitrogen element concentration are respectively higher than the oxygen element concentration and the nitrogen element concentration of the silicon carbide material itself, are referred to as oxygen-rich nitrogen-rich regions.

In the above step S1-2, the region where the ion implantation layer 4 is formed includes an ion implantation damaged region (not shown in the figure) and the above-mentioned oxygen-rich nitrogen-rich region (not shown in the figure).

In the above step S1-4, the temperature of the high-temperature thermal oxidation treatment is 900 ° C to 2000 ° C.

In the above step S1-4, all the oxygen ions of the ion implantation layer 4 are oxidized by the high-temperature thermal oxidation treatment to avoid the implanted oxygen ions remaining.

In the above step S1-4, during the high-temperature thermal oxidation treatment, the interface between the formed oxide layer 5 and the silicon carbide substrate 1 is nitrided, so that nitrogen atoms are accumulated at the interface between the silicon dioxide and the silicon carbide. Therefore, the carbon clusters at the interface between silicon dioxide and silicon carbide can be decomposed, and the interface state density can be reduced.

In the above step S1-4, due to the oxygen ion and nitrogen ion implantation and the edge effect of oxidation itself, during the above-mentioned high-temperature thermal oxidation treatment, at the junction between the first region to be oxidized and the second region to be oxidized, the oxide layer The thickness of 5 transitions gently, forming a "bird's beak" structure, thereby avoiding the adverse consequences caused by sudden changes in the thickness of the oxide layer.

In a preferred implementation manner of this embodiment, the above method does not include the above step S1-3, that is, the mask layer 2 remains until after the above step S1-4 is performed a high temperature thermal oxidation treatment. Accordingly, in the above step S1-4, the oxide layer 5 is not formed on the surface of the silicon carbide substrate 1 except the ion implantation layer 4 (that is, the area covered by the mask layer) or its thickness is very thin.

In the step S1-4, the oxide layer 5 is a silicon dioxide layer.

Example 2

As shown in FIG. 6, this embodiment provides a method for growing an oxide layer on a silicon carbide substrate (including an epitaxial layer). The method can rapidly grow high quality and excellent quality on a silicon carbide substrate (including an epitaxial layer). Interface oxide layer, the method includes the following steps:

S2-1: Oxygen and nitrogen ions 3 are implanted into the silicon carbide substrate 1 by ion implantation. As shown in FIG. 7, an ion implantation layer 4 is formed on the surface of the silicon carbide substrate 1, as shown in FIG. 8. ;

S2-2: performing a high-temperature thermal oxidation treatment, so that the ion implantation layer 4 is oxidized to form an oxide layer 5, as shown in FIG. 9.

In a preferred implementation manner of this embodiment, before the above step S2-1, the method further includes the following steps: S2-0: depositing a cushion layer on the silicon carbide substrate 1. In this embodiment, in the above step S2-1, oxygen ions and nitrogen ions 3 are injected into the silicon carbide substrate 1 through the above-mentioned cushion layer. Due to the blocking effect of the cushion layer, the oxygen ions and nitrogen ions 3 are in the silicon carbide substrate. The implantation depth in the wafer 1 is reduced compared to the case without a cushion. Preferably, the material of the cushion layer is silicon dioxide.

In a preferred implementation manner of this embodiment, before step S2-0, the method may further include the following steps: depositing a masking layer 2 on the silicon carbide substrate 1, and then masking the masking layer 2 by photolithography. The patterning process is performed so that the first region to be oxidized on the surface of the silicon carbide substrate 1 is exposed, and the second region to be oxidized is covered by the mask layer 2 (same as in Embodiment 1, FIG. 2). In this embodiment, in the above step S2-1, oxygen ions and nitrogen ions 3 are implanted only into the first area to be oxidized, and the second areas to be oxidized are not implanted with oxygen ions and nitrogen ions 3 due to the shielding of the mask layer 2. (Same as Embodiment 1, FIG. 3 and FIG. 4).

In a preferred embodiment of the present embodiment, the step S2-1, the implantation energy of oxygen ions is less than or equal of 100 keV, the implantation dose of oxygen ions is 1 × 10 ¹² cm ^-2 to 1 × 10 cm ¹⁸ ^{- 2.} The implantation temperature of oxygen ions is 0 to 1000 ° C. In the above step S2-1, the implantation energy of the nitrogen ions is less than or equal to 100 keV, and the implantation dose of the nitrogen ions is 1 × 10 ¹² cm ^-2 to 1 × 10 ¹⁵ cm ^-2 .

In a preferred implementation manner of this embodiment, in step S2-2, the temperature of the high-temperature thermal oxidation treatment is 900 ° C to 2000 ° C.

In the step S2-2, the oxide layer 5 is a silicon dioxide layer.

In a preferred implementation manner of this embodiment, the material of the mask layer 2 may be photoresist, silicon dioxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), or aluminum nitride (AlN). It may be a mixture composed of any two or more of a photoresist, silicon dioxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), and aluminum nitride (AlN).

Example 3

As shown in FIG. 10, this embodiment provides a method for growing an oxide layer on a silicon carbide substrate (including an epitaxial layer). The method can rapidly grow a sacrificial oxide layer on a silicon carbide substrate (including an epitaxial layer). The method includes the following steps:

S3-1: Oxygen and nitrogen ions 3 are implanted into the silicon carbide substrate 1 by ion implantation. As shown in FIG. 11, an ion implantation layer 4 is formed on the surface of the silicon carbide substrate 1, as shown in FIG. 12. ;

S3-2: performing a high-temperature thermal oxidation treatment so that the ion-implanted layer 4 is oxidized to form an oxide layer 5, as shown in FIG. 13;

S3-3: The above-mentioned oxide layer 5 is removed by wet etching or dry etching, as shown in FIG. 14.

In a preferred implementation manner of this embodiment, before the above step S3-1, the method may further include the following steps: S3-0: a mask layer 2 is deposited on the silicon carbide substrate 1, and The mask layer 2 is patterned so that the first region to be oxidized on the surface of the silicon carbide substrate 1 is exposed, and the second region to be oxidized is covered by the mask layer 2 (same as in Embodiment 1, FIG. 2). In this embodiment, in the above step S3-1, oxygen ions and nitrogen ions 3 are implanted only into the first area to be oxidized, and the second areas to be oxidized will not be implanted with oxygen ions and nitrogen ions 3 due to the shielding of the mask layer 2. (Same as Embodiment 1, FIG. 3 and FIG. 4).

In a preferred implementation manner of this embodiment, in step S3-1 above, the implantation energy of oxygen ions is 10 keV to 1 MeV, and the implantation dose of oxygen ions is 1 × 10 ¹² cm ^-2 to 1 × 10 ¹⁸ cm ^-2 The implantation temperature of oxygen ions is 0 to 1000 ° C. In the above step S3-1, the implantation energy of the nitrogen ions is 10 keV to 1 MeV, and the implantation dose of the nitrogen ions is 1 × 10 ¹² cm ^-2 to 1 × 10 ¹⁵ cm ^-2 .

In a preferred implementation manner of this embodiment, in step S3-2, the temperature of the high-temperature thermal oxidation treatment is 900 ° C to 2000 ° C.

In the step S3-2, the oxide layer 5 is a silicon dioxide layer.

Obviously, the foregoing embodiments of the present invention are merely examples for clearly explaining the present invention, and are not intended to limit the embodiments of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made on the basis of the above description. Not all implementations can be exhausted here. Any obvious changes or variations that are derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

A method for growing an oxide layer on a silicon carbide substrate includes the following steps:

S1: covering a surface of the silicon carbide substrate (1) with a mask layer (2), and then patterning the mask layer (2), so that the first surface of the silicon carbide substrate (1) is first The area to be oxidized is exposed, and the second area to be oxidized is covered by the mask layer (2);

S2: implanting the oxygen ions and nitrogen ions (3) into the first region to be oxidized, and forming an ion implantation layer (4) on the surface of the silicon carbide substrate (1);

S4: performing a high temperature thermal oxidation treatment, forming an oxide layer (5) on the surface of the silicon carbide substrate (1), and the thickness of the oxide layer (5) of the ion implantation layer (4) is greater than The thickness of the oxide layer (5) in the remaining area of the surface of the silicon carbide substrate (1).
The method for growing an oxide layer on a silicon carbide substrate according to claim 1, further comprising the following steps after the step S2 and before the step S4:

S3: After the oxygen ions and nitrogen ions (3) are implanted, the mask layer (2) is removed.
The method for growing an oxide layer on a silicon carbide substrate according to claim 1 or 2, wherein the implantation energy of said oxygen ions is 10keV to 1MeV, and the implantation dose thereof is 1 × 10 14 cm -2 to 1 × 10 18 cm -2 ; the implantation energy of the nitrogen ions is 10 keV to 1 MeV, and the implantation dose thereof is 1 × 10 12 cm -2 to 1 × 10 15 cm -2 .
The method for growing an oxide layer on a silicon carbide substrate according to claim 1 or 2, wherein a temperature of the high-temperature thermal oxidation treatment is 900 ° C to 2000 ° C.
A method for growing an oxide layer on a silicon carbide substrate includes the following steps:

S1: implanting oxygen ions and nitrogen ions (3) into the silicon carbide substrate (1) by ion implantation, and forming an ion implantation layer (4) on the surface of the silicon carbide substrate (1);

S2: performing a high-temperature thermal oxidation treatment so that the ion-implanted layer (4) is oxidized to form an oxide layer (5).
The method for growing an oxide layer on a silicon carbide substrate according to claim 5, further comprising the following steps before the step S1:

S0: depositing a pad layer on the silicon carbide substrate (1).
The method for growing an oxide layer on a silicon carbide substrate according to claim 5, further comprising the following steps after the step S2:

S3: removing the oxide layer (5) by wet etching or dry etching.
The method for growing an oxide layer on a silicon carbide substrate according to claim 5 or 6, wherein the implantation energy of the oxygen ions is less than or equal to 100 keV, and the implantation dose thereof is 1 × 10 12 cm -2 to 1 × 10 18 cm -2 , the implantation temperature of which is 0 to 1000 ° C .; the implantation energy of the nitrogen ions is less than or equal to 100 keV, and the implantation dose is 1 × 10 12 cm -2 to 1 × 10 15 cm -2 .
The method for growing an oxide layer on a silicon carbide substrate according to claim 5 or 7, wherein the implantation energy of the oxygen ions is 10keV to 1MeV, and the implantation dose thereof is 1 × 10 12 cm -2 to 1 × 10 18 cm -2 , the implantation temperature is 0 to 1000 ° C .; the nitrogen ion implantation energy is 10 keV to 1 MeV, and the implantation dose is 1 × 10 12 cm -2 to 1 × 10 15 cm -2 .
The method for growing an oxide layer on a silicon carbide substrate according to any one of claims 5 to 7, wherein the temperature of the high-temperature thermal oxidation treatment is 900 ° C to 2000 ° C.