CN110685009A - Epitaxial growth apparatus and epitaxial growth method - Google Patents

Epitaxial growth apparatus and epitaxial growth method Download PDF

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CN110685009A
CN110685009A CN201910980116.9A CN201910980116A CN110685009A CN 110685009 A CN110685009 A CN 110685009A CN 201910980116 A CN201910980116 A CN 201910980116A CN 110685009 A CN110685009 A CN 110685009A
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wafer
epitaxial growth
faster
epitaxial
slower
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费璐
林志鑫
曹共柏
王华杰
董晨华
季文明
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Zing Semiconductor Corp
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Zing Semiconductor Corp
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Priority to TW109106864A priority patent/TWI740402B/en
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    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B25/00—Single-crystal growth by chemical reaction of reactive gases, e.g. chemical vapour-deposition growth
    • C30B25/02—Epitaxial-layer growth
    • C30B25/18—Epitaxial-layer growth characterised by the substrate
    • C30B25/20—Epitaxial-layer growth characterised by the substrate the substrate being of the same materials as the epitaxial layer
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B25/00—Single-crystal growth by chemical reaction of reactive gases, e.g. chemical vapour-deposition growth
    • C30B25/02—Epitaxial-layer growth
    • C30B25/16—Controlling or regulating
    • C30B25/165—Controlling or regulating the flow of the reactive gases
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/02—Elements
    • C30B29/06—Silicon

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  • Engineering & Computer Science (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Chemical Vapour Deposition (AREA)

Abstract

The invention provides an epitaxial growth apparatus and an epitaxial growth method. The epitaxial growth device is characterized in that a gas inlet allowing reaction gas for forming an epitaxial layer on a wafer to enter the growth chamber is formed in the growth chamber of the epitaxial growth device, when the edge part of the wafer subjected to the epitaxial growth process is provided with a fast region and a slow region with different crystal orientations, and the epitaxial layer grows faster in the fast region than in the slow region, the gas inlet rate of the reaction gas provided by the gas inlet when the fast region rotates to pass is smaller than that of the reaction gas provided by the gas inlet when the slow region rotates to pass. The epitaxial growth device can adjust the deposition of the epitaxial layer in different crystal directions, is beneficial to obtaining the epitaxial layer with uniform thickness, and improves the quality of the epitaxial wafer. The epitaxial growth method has the same or similar characteristics with the epitaxial growth device, the thickness uniformity of the epitaxial layer can be improved without changing the structure of the epitaxial growth device, the local flatness of the epitaxial wafer is reduced, and the flexibility is high.

Description

Epitaxial growth apparatus and epitaxial growth method
Technical Field
The invention relates to the field of epitaxial growth processes, in particular to an epitaxial growth device and an epitaxial growth method.
Background
Electronic device manufacturing has high requirements for flatness of the upper surface of a semiconductor wafer as a substrate, and is commonly evaluated by taking into account the focusing ability of a stepper on all areas of the wafer surface as a local flatness SFQR (least square/range of surface reference on site) parameter. Maximum local flatness SFQRmaxRepresents the maximum SFQR value of all the considered electronic component ranges on the semiconductor wafer. SFQRmaxThe reduction in value is advantageous for solving the problem of defocusing of the photolithography process, the problem of polishing uniformity of the CMP process, the problem of poor adhesion in the SOI adhesion process, and the like, which may be encountered in manufacturing electronic devices. The local flatness of the silicon wafer can be optimized by grinding, polishing, etc.
A semiconductor wafer commonly used as a substrate is a silicon epitaxial wafer, which is generally obtained by an epitaxial growth process of growing an epitaxial layer in the same crystal orientation and in a single crystal on a silicon wafer. Compared with a silicon wafer not comprising the epitaxial layer, the silicon epitaxial wafer has the advantages of lower defect density, better latch-up resistance and the like, and is suitable for manufacturing highly integrated electronic elements such as a microprocessor or a memory chip on the epitaxial layer. The local flatness of a silicon epitaxial wafer is related to the uniformity of the epitaxial layers deposited using an epitaxial growth process.
Currently, silicon epitaxial wafers are manufactured by placing a silicon wafer in a chamber of an epitaxial device, heating the silicon wafer by using a heat source, introducing a reaction gas into the chamber, decomposing the reaction gas at a high temperature on the surface of the wafer to form silicon, and depositing the silicon wafer on the surface of the silicon wafer to grow the silicon wafer to form an epitaxial layer.
The growth rate of the epitaxial layer is foundDepending on the growth orientation, i.e., the crystal orientation of the silicon wafer, the growth rate of the epitaxial layer may increase or decrease, particularly at the edge portion of the wafer, resulting in a difference in the thickness of the epitaxial layer. Taking a silicon wafer having a diameter of 300mm as an example and an upper surface thereof being, for example, a (001) crystal plane, experimental data have shown that at an edge portion 149mm away from the center of the wafer, a portion corresponding to the center of the wafer is formed<110>Within a certain range of crystal orientation, the thickness of the epitaxial layer is large over the entire wafer surface and corresponds to that of the wafer<100>Within a certain range of crystal orientation, the thickness of the epitaxial layer is small in the entire wafer surface, and the local flatness SFQR in the edge portion is large, which results in the maximum local flatness SFQR of the silicon epitaxial wafermaxThis is large, which causes deterioration in the quality of the silicon epitaxial wafer and also causes problems in the manufacture of electronic devices.
To address the problem of large local flatness SFQR of epitaxial layers, prior methods have mostly adjusted from changing the structure of the epitaxial growth apparatus, such as changing the design of the gas inlet or changing the design of the susceptor on which the wafer is mounted in order to change the gas flow. However, it is complicated to adjust the structure of the epitaxial growth apparatus in consideration of the influence on each functional part of the apparatus, and it is difficult to adjust the structure of the epitaxial growth apparatus which has been put into use in time in accordance with the actual process conditions, and flexibility is poor.
Disclosure of Invention
The invention provides an epitaxial growth apparatus and an epitaxial growth method, aiming to improve the thickness uniformity of an epitaxial layer formed on a wafer and reduce the local flatness (SFQR) so as to obtain an epitaxial wafer with higher quality.
According to one aspect of the present invention, an epitaxial growth apparatus is provided, which includes a growth chamber and a susceptor located in the growth chamber, the susceptor being configured to place a wafer and to rotate the wafer during epitaxial growth, the growth chamber being provided with a gas inlet allowing a reaction gas for forming an epitaxial layer on the wafer to enter the growth chamber; when the edge portion of the wafer has a faster region and a slower region different in crystal orientation and the epitaxial layer grows faster in the faster region than in the slower region, the gas inlet port provides a smaller inlet rate of the reaction gas when the faster region rotates past than when the slower region rotates past as the wafer rotates during the epitaxial growth.
Optionally, the inlet rate of the reactant gas provided by the inlet port varies in pulses with time, and the inlet rate of the reactant gas provided by the inlet port as the slower region rotates past is the peak of the pulse.
Optionally, the faster regions and the slower regions are alternately distributed at the edge portion of the wafer along the circumferential direction of the wafer, the edge portion of the wafer further includes transition regions, the transition regions are interposed between adjacent one of the faster regions and one of the slower regions, and the crystal orientation of the transition regions is such that the growth rate of the epitaxial layer at the transition regions is interposed between the faster regions and the slower regions.
Optionally, as the wafer rotates, the gas inlet rate of the reaction gas provided by the gas inlet gradually increases as the faster region, the transition region, and the slower region sequentially rotate to the gas inlet, and gradually decreases as the slower region, the transition region, and the faster region sequentially rotate to the gas inlet.
Optionally, the wafer is a single crystal silicon wafer, a silicon-on-insulator wafer, a strained silicon wafer, or a strained silicon-on-insulator wafer.
Optionally, the faster zone is located within a predetermined fan angle of the <110> crystal orientation of the wafer and the slower zone is located within a predetermined fan angle of the <100> crystal orientation of the wafer.
Optionally, the predetermined fan angle is 0-10 degrees.
Optionally, the reaction gas comprises SiH4、SiH2Cl2、SiHCl3And SiCl4At least one of (1).
Optionally, the rotation speed of the wafer is 40-60 rpm.
According to another aspect of the present invention, there is provided an epitaxial growth method, comprising the steps of:
placing a wafer in a growth chamber of an epitaxial growth device, wherein the edge part of the wafer is provided with a faster area and a slower area which have different crystal orientations, the epitaxial growth is faster in the faster area than in the slower area, and the growth chamber is provided with an air inlet; and rotating the wafer and performing epitaxial growth on the wafer, wherein reaction gas is conveyed into the growth chamber through the gas inlet to form an epitaxial layer on the wafer, and the gas inlet rate of the reaction gas is smaller when the reaction gas rotates through the gas inlet in the faster region than when the reaction gas rotates through the gas inlet in the slower region during the epitaxial growth.
Optionally, the rate of admission of the reactant gas is varied in pulses over time and the peak of the pulse is reached as the slower region rotates past the inlet.
Optionally, the gas inlet rate of the reactant gas varies with time in the form of one or a combination of two or more of a rectangular wave, a spike pulse, a sawtooth wave, a triangular wave, a sine wave, and a step wave.
Optionally, the faster zone is located within a predetermined fan angle of a first crystal orientation of the wafer, and the slower zone is located within a predetermined fan angle of a second crystal orientation of the wafer.
Optionally, the gas inlet rate of the reaction gas is 0-20L/min.
The epitaxial growth device provided by the invention can carry out epitaxial growth on a wafer, the growth chamber is provided with the gas inlet, the gas inlet allows reaction gas for forming an epitaxial layer on the wafer to enter the growth chamber, and when the edge part of the wafer is provided with a faster area and a slower area with different crystal orientations and the epitaxial layer grows faster in the faster area than in the slower area, the gas inlet rate of the reaction gas provided by the gas inlet when the faster area rotates and passes is smaller than that of the reaction gas provided when the slower area rotates and passes along with the rotation of the wafer in the epitaxial growth process. The speed of the reaction gas input by the gas inlet of the epitaxial growth device is not constant, but changes along with the passing of different crystal orientation areas related to the growth rate on the wafer, so that the deposition of the epitaxial layer in the different crystal orientation areas can be adjusted, the epitaxial growth device is beneficial to obtaining the epitaxial layer with uniform thickness, reducing the local flatness of the epitaxial wafer and improving the quality of the epitaxial wafer.
The epitaxial growth method provided by the invention comprises the steps of firstly placing a wafer in a growth chamber, wherein the edge part of the wafer is provided with a faster area and a slower area which are different in crystal orientation, the epitaxial growth is faster in the faster area than in the slower area, the growth chamber is provided with an air inlet, then the wafer is rotated and subjected to epitaxial growth, and in the epitaxial growth process, the air inlet rate of reaction gas when the faster area of the wafer rotates and passes through the air inlet is greater than the air inlet rate when the slower area of the wafer rotates and passes through the air inlet. By adjusting the gas inlet rate of the reaction gas, the method is favorable for reversely adjusting the change condition of the epitaxial growth rate caused by different crystal orientations, namely the reaction gas supply is relatively increased in a slower region with slow epitaxial growth, and the reaction gas supply is relatively reduced in a faster region with fast epitaxial growth, so that the thickness uniformity of an epitaxial layer deposited on a wafer is improved, the local flatness of the epitaxial wafer is reduced, and the quality of the epitaxial wafer is improved. The epitaxial growth method provided by the invention can improve the quality of the epitaxial wafer under the condition of not changing the structure of the epitaxial growth device, and has high adjustment flexibility.
Drawings
FIG. 1 is a schematic crystal orientation diagram of a silicon wafer in an embodiment of the present invention.
FIG. 2 is a schematic diagram of the distribution of faster and slower regions on a silicon wafer in an embodiment of the present invention.
Fig. 3 is a partial cross-sectional view schematically illustrating an epitaxial growth apparatus according to an embodiment of the present invention.
Fig. 4 is a schematic flow chart of an epitaxial growth method according to an embodiment of the present invention.
Fig. 5 is a graph showing the intake rate of the reaction gas in the epitaxial growth method according to the embodiment of the present invention.
Description of reference numerals:
10-a growth chamber; 11-an air inlet; 20-a susceptor; 21-a groove; 30-wafer.
Detailed Description
The epitaxial growth apparatus and the epitaxial growth method according to the present invention will be described in further detail below with reference to the accompanying drawings and specific examples. The advantages and features of the present invention will become more apparent from the following description. It is to be noted that the drawings are in a very simplified form and are not to precise scale, which is merely intended to facilitate the clear description of the embodiments of the invention.
In the manufacturing process of semiconductor wafers, the semiconductor wafers formed by cutting are usually subjected to a grinding step, such as grinding or lapping, to round the mechanically sensitive edges, then polished and cleaned, and then vapor grown in an epitaxial growth apparatus on the upper surface of the wafer to form an epitaxial layer.
In an epitaxial growth process, a semiconductor wafer, such as a silicon wafer, is placed in an epitaxial growth apparatus to be rotated at a certain speed and heated, a reaction gas (e.g., TCS, trichlorosilane) is supplied as a source gas to the surface of the silicon wafer, decomposed into silicon and volatile byproducts at a temperature of about 600 to 1250 ℃, and an epitaxial layer of silicon is epitaxially grown on the silicon wafer. The epitaxial layer may be undoped or doped with boron, phosphorus, arsenic or antimony, as appropriate, using a suitable dopant gas to adjust the conductivity type and resistivity.
In order to improve the thickness uniformity of an epitaxial layer formed on a semiconductor wafer by epitaxial growth, in particular, the local flatness of the edge portion is optimized to reduce the maximum local flatness value SFQR on the epitaxial wafermaxHowever, adjusting the structure of the epitaxial growth apparatus needs to consider the influence on each functional component of the apparatus, and since the difficulty of adjusting the structural design of the apparatus in time according to the actual process conditions in production is high, the flexibility of this method is poor.
FIG. 1 is a schematic crystal orientation diagram of a silicon wafer in an embodiment of the present invention. Referring to fig. 1, the top surface of the silicon wafer is usually one crystal plane in the {100} crystal plane family, so the top surface of the epitaxial layer formed by epitaxial growth on the silicon wafer is also one crystal plane in the {100} crystal plane family, and the top surface of the silicon wafer is taken as an example (100) crystal plane in fig. 1. According to the radius direction of the wafer, different crystal directions of the wafer are distributed periodically along the circumference, for example, the crystal direction <110> appears every 90 degrees in fig. 1, and the crystal direction <110> is rotated by 45 degrees (45 degrees) clockwise or counterclockwise to be the crystal direction <100 >.
Studies have shown that the growth rate of an epitaxial layer of a semiconductor wafer such as a silicon wafer is dependent on the crystal orientation, and the growth rate of the epitaxial layer is increased or decreased at intervals depending on the crystal orientation (i.e., the growth orientation of the epitaxial layer is different), and this dependence is manifested at the edge portion of the upper surface of the wafer. Taking the silicon wafer shown in fig. 1 as an example, the epitaxial layer in the edge region selectively grows faster within a certain sector angle of the crystal orientation <110> of the wafer, and grows slower within a certain sector angle of the crystal orientation <100> of the wafer, and in the range of crystal orientations (not shown in the figure) between the crystal orientation <110> and the crystal orientation <100>, the epitaxial layer as a whole grows slower than within the crystal orientation <110> and faster than within the crystal orientation <110> angle. The growth rate and crystal orientation related law of the epitaxial layer is not unique to the epitaxial growth process of the silicon wafer, and should exist in the epitaxial growth of other semiconductor wafers. Therefore, although the present embodiment is described primarily with reference to a silicon wafer as an example, it should be understood that the concepts and concepts of the present invention are equally applicable to epitaxial growth processes for other semiconductor wafers. For example, the semiconductor wafer described below may be a single crystal silicon wafer, a silicon-on-insulator wafer, a strained silicon-on-insulator wafer, or the like, and the material of the semiconductor wafer may also be a crystal of another element such as germanium.
FIG. 2 is a schematic diagram of the distribution of faster and slower regions on a silicon wafer in an embodiment of the present invention. Referring to fig. 2, since the growth rate of the epitaxial layer at the upper edge of the silicon wafer is related to the crystal orientation of the wafer, when the silicon wafer is epitaxially grown in a rotating state, a faster region i in which the epitaxial layer grows faster, a slower region iii in which the epitaxial layer grows slower, and a transition region ii in which the growth rate is between the faster region i and the slower region iii are circumferentially distributed within a certain angle corresponding to different crystal orientations. If not adjusted, the difference in the epitaxial layer growth rate at these several positions at the edge portion causes a significant difference in the epitaxial layer thickness, which causes problems of poor wafer flatness and degradation in the quality and yield of the epitaxial wafer. Thus, it is necessary to adjust the difference in growth thickness between the regions where the epitaxial growth rate is different on the wafer, particularly, the faster region i and the slower region iii.
The epitaxial growth apparatus of the present embodiment is first described below. The epitaxial growth device of the embodiment adjusts the gas inlet rate of the reaction gas provided by the gas inlet along with the rotation of the wafer according to the difference of the epitaxial layer growth rates, so as to achieve the purpose of adjusting the thickness of the epitaxial layer, and the structure of the epitaxial growth device is not changed.
Fig. 3 is a partial cross-sectional view schematically illustrating an epitaxial growth apparatus according to an embodiment of the present invention. Referring to fig. 2 and 3, the epitaxial growth apparatus of the present embodiment includes a growth chamber 10 (only a portion of which is shown) and a susceptor 20 (only a portion of which is shown) disposed in the growth chamber 10, the susceptor 20 being configured to hold a wafer 30 and rotate the wafer 30 during epitaxial growth, the susceptor generally rotating the wafer 30 about its center line in a horizontal plane. The wafers 30 have different crystal orientations so that the edge portions include a faster region i and a slower region iii distinguished by differences in crystal orientation growth, i.e., the epitaxial layer deposited on the wafer 30 grows faster in the faster region i than in the slower region iii. The growth chamber 10 is provided with a gas inlet 11 for delivering a reaction gas into the growth chamber 10, wherein the reaction gas is used for forming an epitaxial layer on the upper surface of the wafer 30 through vapor deposition, and specifically, in the epitaxial growth process, along with the rotation of the wafer 30, the gas inlet 11 provides a reaction gas inlet rate when the fast zone i rotates and passes through that is smaller than a reaction gas inlet rate when the slow zone iii rotates and passes through that.
In this embodiment, taking a silicon wafer as an example, with reference to fig. 1, since the growth rate of the epitaxial layer is related to the crystal orientation of the silicon wafer, according to the difference in crystal orientation growth, the edge portion of the silicon wafer includes the faster region i, the transition region ii, and the slower region iii that are periodically distributed, one of the faster region i, one of the slower region iii, and two of the transition regions ii are included in the same period, and the faster region i, the transition region ii, the slower region iii, and the transition region ii are sequentially connected in the circumferential direction, and the difference between two adjacent periods is 90 degrees. The above-mentioned faster zone i of the edge portion of the wafer may be set to a predetermined fan angle range of the <110> crystal orientation of the edge portion of the wafer 30, the slower zone iii may be set to a predetermined fan angle range of the <100> crystal orientation of the edge portion of the wafer 30, and the transition zone ii may be set to a region of the edge of the upper surface of the wafer between the faster zone i and the slower zone iii. The edge portion may be specifically set according to the specification of the wafer and experimental data, and for example, for a 300mm diameter silicon wafer, a region of 145mm to 150mm from the center point may be used as the edge portion of the wafer. The specific range of each interval may be set according to experimental data of a conventional epitaxial growth process (reaction gas is supplied into the process chamber at a constant supply rate during epitaxial growth) performed by an epitaxial apparatus of similar structure, for example, a range in which the thickness in the edge portion of the wafer exceeds the average thickness by 5% may be defined as a faster zone i, and a range in which the thickness is less than the average thickness by 5% may be defined as a slower zone iii, and the difference in thickness between the faster zone i and the slower zone iii is mainly caused by the difference in crystal orientation. As an example, the faster zone I can be arranged in a range of +/-5 degrees with a <110> crystal orientation as a central line, and the slower zone III can be arranged in a range of +/-5 degrees with a <100> crystal orientation as a central line, namely, the fan angles of the faster zone I and the slower zone III can be in a range of 0-10 degrees.
The susceptor 20 may be made of graphite, silicon carbide, or quartz. In the epitaxial growth process, the wafer 30 is usually fixed in the groove 21 on the susceptor 20, and the upper surface of the edge of the groove 21 may be higher than or flush with the upper surface of the wafer 30. The shape of the groove 21 may be a special shape considering the gas flow, for example, the bottom surface of the groove 21 may be designed to be a slope to adjust the growth rate of the epitaxial layer by changing the resistance of the gas flow. The epitaxial growth apparatus may be provided with heating means above and below the growth chamber 10 to heat the wafer 30 and the reaction gas in the growth chamber 10, thereby promoting decomposition of the reaction gas and vapor-phase deposition of the reaction gas on the wafer 30 to form an epitaxial layer. The susceptor and the heating member of the present embodiment may be of known design.
More than one gas inlet may be provided on the walls of the growth chamber 10 of the epitaxial growth apparatus to deliver process gases, including reactant gases (i.e., source gases) and carrier gases, from outside the chamber into the growth chamber 10 during the epitaxial growth process. The reaction gas used for the epitaxial growth process for the silicon wafer may include Silane (SiH)4) Dichlorosilane (SiH)2Cl2DCS), trichlorosilane (SiHCl)3TCS) or tetrachlorosilane (SiCl)4) Isosilicon compound gas, H2(Hydrogen) or inert gas may be used as carrier gas, which mainly serves to dilute the reactant gas, and a trace amount of dopant gas, such as B, may be included in the process gas2H4. In this embodiment, the reaction gas is, for example, trichlorosilane, TCS for short, and the carrier gas is, for example, H2. The growth chamber may be provided with a gas inlet for delivering an etching gas (e.g., gaseous HCl) for pretreating a wafer placed on the susceptor and for treating the susceptor after removal of the wafer to remove excess deposits.
In this embodiment, the gas inlet 11 for delivering the reaction gas provided in the growth chamber 10 of the epitaxial growth apparatus may be configured to only allow the reaction gas to enter the growth chamber 10, or may be configured to allow the mixed process gas including other gases to enter the growth chamber 10, and the reaction gas provided by the gas inlet 11 is not a continuous constant gas inlet rate, but is a gas inlet rate adjusted according to the region of the wafer 30 rotating past during the epitaxial growth process, and if the gas inlet 11 also delivers other process gases, the other gases may be delivered continuously or in a manner similar to the reaction gas inlet rate. In another embodiment, the growth chamber 10 may be provided with more than one gas inlet for allowing the reaction gas to enter the growth chamber, and some of the gas inlets may provide the reaction gas with a stable gas inlet rate during the epitaxial growth, and wherein the gas inlet 11 is provided with a gas inlet rate that varies according to the region of the wafer 30 that is faced during the epitaxial growth. The plurality of air inlets on the chamber wall may be arranged at an angle and spacing.
In the present embodiment, the horizontal distance L of the gas inlet 11 from the edge of the wafer 30 is, for example, about 5cm to 15cm, and the vertical distance H between the lower edge of the gas inlet 11 and the upper surface of the recess 21 of the susceptor 20 is, for example, about 1mm to 10 mm. In practice, the gas inlet 11 is provided mainly for uniform delivery of the reactant gas to the upper surface of the wafer.
In the epitaxial growth apparatus of the present embodiment, the gas inlet rate (or flow rate) of the reaction gas (e.g., TCS) provided by the gas inlet 11 is in a range of about 0 to 20L/min, and the gas inlet rate of the reaction gas varies depending on the region of the wafer 30 rotating through the gas inlet 11, so that the amount of the reaction gas allowed to pass through the gas inlet 11 is increased or decreased as the wafer 30 rotates. In order to compensate for the difference in epitaxial growth rate of the reactant gases due to the difference in crystal orientation at the edge portion of the wafer 30 during the decomposition and epitaxial growth on the wafer 30, in the present embodiment, the gas inlet 11 provides a smaller inlet rate of the reactant gases when the faster zone i of the wafer 30 rotates past than when the slower zone iii of the wafer 30 rotates past, so that the supply amount of the reactant gases to the faster zone i is smaller than that to the slower zone iii, and the effect of adjusting the epitaxial growth rates of the faster zone i and the slower zone iii is provided, thereby facilitating the achievement of the effect of improving the thickness uniformity of the epitaxial layer.
As an example, the time for wafer 30 to rotate through one crystal orientation cycle (the present embodiment includes the adjacent connected faster region, transition region, slower region and transition region) can be used as one delivery cycle of the reactant gas, wherein the inlet rate of the reaction gas supplied from the inlet port is minimized during one delivery cycle as the faster zone I of the edge portion of the wafer rotates past the inlet port 11 (i.e., as the edge of the wafer of the faster zone I faces the chamber wall below the inlet port 11) to reduce the supply of the reaction gas (e.g., to reduce the silicon element formed after the TCS decomposition), thereby reducing the deposition thickness of the epitaxial layer in the faster zone I, and when the slower zone III of the peripheral portion of the wafer rotates past the gas inlet 11, the gas inlet rate of the reaction gas supplied from the gas inlet is maximized within one delivery cycle, so as to increase the supply of the reaction gas and improve the deposition thickness of the epitaxial layer in the slower region III.
In order to provide a reaction gas supplied from the gas inlet 11 with a smaller inlet rate when the faster zone i rotates past the gas inlet 11 than when the slower zone iii rotates past the gas inlet 11, the inlet rate of the reaction gas supplied from the gas inlet 11 may be varied in time in the form of pulses and such that the inlet rate of the reaction gas supplied from the gas inlet 11 is the peak of the pulses when the slower zone iii rotates past the gas inlet 11. Specifically, the pulse form that can be used may be one or a combination of two or more of a rectangular wave, a sharp pulse, a sawtooth wave, a triangular wave, a sine wave, and a step wave. Referring to fig. 2, in the present embodiment, the region rotating through the gas inlet 11 during one rotation of the wafer 30 (i.e., during one rotation cycle) includes four faster zones i, four slower zones iii, and eight transition zones ii interposed therebetween, so that the gas inlet rate of the reaction gas supplied from the gas inlet 11 may be varied in four pulses in each rotation cycle according to the time point when the slower zone iii rotates through the gas inlet 11. The pulse frequency can vary from 1Hz to 200Hz, and the specific value can be determined according to the crystal orientation of the wafer and the rotation rate, for example, the rotation rate of the wafer 30 is about 40-60 rpm. In addition, considering the distance between the gas inlet 11 and the wafer 30 and the time elapsed for the reaction gas to reach the wafer from the gas inlet, the start time of the delivery pulse of the reaction gas supplied from the gas inlet 11 may be slightly advanced (for example, about 0.05s to 1s) from the time when the slower region iii of the wafer 30 rotates to the gas inlet, and an effect is achieved that the gas inlet rate of the reaction gas supplied from the gas inlet 11 is the peak of the pulse when the slower region iii rotates through the gas inlet 11.
In order to make the gas inlet rate of the supplied reaction gas when the faster zone i rotates through the gas inlet 11 smaller than the gas inlet rate when the slower zone iii rotates through the gas inlet 11, the reaction gas may be supplied in a continuously variable manner, specifically, during the epitaxial growth, as the wafer 30 rotates, the gas inlet rate of the reaction gas supplied from the gas inlet 11 gradually increases as the faster zone i, the transition zone ii, and the slower zone iii sequentially rotate to the gas inlet 11, and gradually decreases as the slower zone iii, the transition zone ii, and the faster zone i sequentially rotate to the gas inlet 11. The gradual increase or decrease in the intake rate of the reaction gas may be in a linear or non-linear manner.
It can be seen that the epitaxial growth apparatus of the present embodiment changes the gas inlet rate of the reaction gas provided by the gas inlet by adapting to the crystal orientation change of the rotating wafer to reversely adjust the change of the epitaxial growth rate caused by the difference of the crystal orientations, specifically, the reaction gas supply is relatively increased in the slow zone of the epitaxial growth, and the reaction gas supply is relatively decreased in the fast zone of the epitaxial growth, which has the effect of stabilizing the deposition rate of the epitaxial layer, thereby facilitating to obtain the epitaxial layer with uniform thickness, reducing the local flatness of the obtained epitaxial wafer, and improving the quality of the epitaxial wafer. Further, for the transition region ii of the edge portion of the wafer, since the growth rate of the epitaxial layer in this region is between the faster region i and the slower region iii, the intake rate of the reaction gas supplied from the intake port 11 when the transition region ii rotates through the intake port 11 can take a value between the intake rates of the reaction gas supplied when the faster region i and the slower region iii rotate through the intake port 11. Of course, the gas inlet rate of the supplied reaction gas can be further adjusted by the above-mentioned adjustment manner when the gas inlet 11 rotates to pass through each of the smaller regions having different crystal orientations and different epitaxial growth rates within the range of the transition region ii.
With the above epitaxial growth apparatus, in the faster zone i at the edge portion of the wafer 30, the growth of the epitaxial layer is accelerated due to the crystal orientation on the one hand, but on the other hand, the deposition amount is reduced due to the smaller gas intake rate of the reaction gas supplied from the gas inlet 11, which helps to suppress the tendency of the thickness increase of the faster zone i due to the faster growth, so that the epitaxial layer in this zone grows at the average growth rate over the entire wafer. Similarly, in the slower region iii of the edge portion of the wafer 30, the growth of the epitaxial layer is slowed down due to the crystal orientation, but the deposition amount is increased due to the larger gas inlet rate of the reaction gas supplied from the gas inlet 11, which helps to suppress the thickness reduction tendency of the slower region iii due to the slower growth, so that the epitaxial layer in this region grows at the average growth rate over the entire wafer.
The epitaxial growth method of the present embodiment is described below. Fig. 4 is a schematic flow chart of an epitaxial growth method according to an embodiment of the present invention. Referring to fig. 1 to 4, the present embodiment further includes an epitaxial growth method, including:
first step S1: placing a wafer 30 in a growth chamber 10 of an epitaxial growth apparatus, wherein the edge part of the wafer 30 has a faster zone I and a slower zone III which have different crystal orientations and the epitaxial growth is faster in the faster zone I than in the slower zone III, and the growth chamber is provided with an air inlet 11;
second step S2: and rotating the wafer 30 and carrying out epitaxial growth on the wafer 30, wherein reaction gas is conveyed into the growth chamber 10 through the gas inlet 11 to form an epitaxial layer on the wafer 30, and the gas inlet rate of the reaction gas is smaller when the reaction gas rotates through the gas inlet 11 in the faster zone I than when the reaction gas rotates through the gas inlet 11 in the slower zone III during the epitaxial growth.
The epitaxial growth method of the present embodiment employs the same concept as the above-described epitaxial growth apparatus, that is, an epitaxial growth process is performed by placing the wafer 30 on the susceptor 20 in the epitaxial growth apparatus, rotating the wafer 30 with the susceptor 20, and then introducing the reaction gas into the reaction chamber 10 through the gas inlet 11 on the growth chamber 10 (the epitaxial growth process may also include some conventional steps, such as heating). Wherein, the wafer 30 rotates along with the susceptor 20 during the epitaxial growth process, so that the crystal orientation towards the gas inlet 11 periodically changes, for example, in fig. 2, the faster zone i, the transition zone ii and the slower zone iii with different crystal orientations periodically rotate through the gas inlet 11, the epitaxial growth method of the present embodiment changes the gas inlet rate of the reaction gas according to the area of the wafer 30 passing through the gas inlet 11, and the gas inlet rate of the reaction gas when the faster zone i rotates through the gas inlet 11 is smaller than that when the slower zone iii rotates through the gas inlet 11, so as to adjust the growth thickness difference of the epitaxial layer caused by the different crystal orientations.
Fig. 5 is a graph showing the intake rate of the reaction gas in the epitaxial growth method according to the embodiment of the present invention. Referring to fig. 5, in the epitaxial growth process, the conventional epitaxial growth method uses a continuous supply of the reaction gas, and in the epitaxial growth method of the present embodiment, the reaction gas is supplied at a rate that varies according to the edge region passing through the gas inlet (i.e., the growth crystal orientation varies). Particularly, in one rotation period, when the fast zone i at the edge portion of the wafer 30 rotates through the gas inlet 11, the gas inlet rate of the reaction gas is relatively small to reduce the decomposition amount of the reaction gas, thereby reducing the thickness of the epitaxial layer deposited at the fast zone i, and when the slow zone iii at the edge portion of the wafer 30 rotates through the gas inlet 11, the gas inlet rate of the reaction gas is relatively large to increase the decomposition amount of the reaction gas, thereby improving the thickness of the epitaxial layer deposited at the slow zone iii, thereby helping to obtain the epitaxial layer with uniform thickness, reducing the local flatness of the epitaxial wafer, and improving the quality of the epitaxial wafer. The epitaxial growth method provided by the embodiment can improve the quality of the epitaxial wafer without changing the structure of the epitaxial growth device, and has high adjustment flexibility.
It should be noted that the embodiments in the present specification are described in a progressive manner, and for the methods disclosed in the embodiments, since the methods correspond to the structures disclosed in the embodiments, the relevant parts may be referred to each other.
The above description is only for the purpose of describing the preferred embodiments of the present invention and is not intended to limit the scope of the claims of the present invention, and any person skilled in the art can make possible the variations and modifications of the technical solutions of the present invention using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention, and therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention belong to the protection scope of the technical solutions of the present invention.

Claims (14)

1. An epitaxial growth device is characterized by comprising a growth chamber and a susceptor positioned in the growth chamber, wherein the susceptor is used for placing a wafer and driving the wafer to rotate in the epitaxial growth process, the growth chamber is provided with a gas inlet, and the gas inlet allows reaction gas for forming an epitaxial layer on the wafer to enter the growth chamber; when the edge portion of the wafer has a faster region and a slower region different in crystal orientation and the epitaxial layer grows faster in the faster region than in the slower region, the gas inlet port provides a smaller inlet rate of the reaction gas when the faster region rotates past than when the slower region rotates past as the wafer rotates during the epitaxial growth.
2. The epitaxial growth apparatus of claim 1 wherein the gas inlet provides a reactive gas whose inlet rate varies in pulses over time and the inlet rate of the reactive gas is the peak of the pulses as the slower region rotates past.
3. The epitaxial growth apparatus of claim 1, wherein the faster zones and the slower zones are alternately spaced along a circumferential direction of the wafer at an edge portion of the wafer, the edge portion of the wafer further comprising transition zones interposed between adjacent ones of the faster zones and ones of the slower zones, the transition zones having a crystal orientation such that a growth rate of the epitaxial layer at the transition zones is interposed between the faster zones and the slower zones.
4. An epitaxial growth apparatus according to claim 3 wherein as the wafer rotates, the gas inlet provides a reaction gas with a gas inlet rate that gradually increases as the faster zone, the transition zone, the slower zone sequentially rotate to the gas inlet and gradually decreases as the slower zone, the transition zone, and the faster zone sequentially rotate to the gas inlet.
5. An epitaxial growth device according to any one of claims 1 to 4 wherein the wafer is a single crystal silicon wafer, a silicon-on-insulator wafer, a strained silicon wafer or a strained silicon-on-insulator wafer.
6. Epitaxial growth apparatus according to claim 5, characterized in that the faster zone is located within a predetermined fan angle of the <110> crystal orientation of the wafer and the slower zone is located within a predetermined fan angle of the <100> crystal orientation of the wafer.
7. An epitaxial growth apparatus according to claim 6 wherein the predetermined fan angle is 0 to 10 degrees.
8. The epitaxial growth apparatus of claim 5, wherein the reaction gas comprises SiH4、SiH2Cl2、SiHCl3And SiCl4At least one of (1).
9. An epitaxial growth apparatus according to any one of claims 1 to 4 characterised in that the rotation rate of the wafer is in the range 40 to 60 revolutions per minute.
10. An epitaxial growth method, comprising:
placing a wafer in a growth chamber of an epitaxial growth device, wherein the edge part of the wafer is provided with a faster area and a slower area which have different crystal orientations, the epitaxial growth is faster in the faster area than in the slower area, and the growth chamber is provided with an air inlet; and
and rotating the wafer and carrying out epitaxial growth on the wafer, wherein reaction gas is conveyed into the growth chamber through the gas inlet to form an epitaxial layer on the wafer, and the gas inlet rate of the reaction gas is smaller when the reaction gas rotates through the gas inlet in the faster area than when the reaction gas rotates through the gas inlet in the slower area in the epitaxial growth process.
11. The epitaxial growth method of claim 10 wherein the rate of the reaction gas feed is pulsed over time and the peak of the pulse is reached as the slower region rotates past the feed.
12. The epitaxial growth method of claim 11 wherein the rate of the reaction gas being fed varies with time in the form of one or a combination of two or more of a rectangular wave, a spike, a sawtooth wave, a triangular wave, a sine wave and a stepped wave.
13. The epitaxial growth method of claim 10 wherein the faster zone is located within a predetermined fan angle of a first crystal orientation of the wafer and the slower zone is located within a predetermined fan angle of a second crystal orientation of the wafer.
14. The epitaxial growth method of claim 10 wherein the reaction gas is introduced at a rate of 0 to 20L/min.
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