CN-122028656-A - Selective epitaxial growth method

CN122028656ACN 122028656 ACN122028656 ACN 122028656ACN-122028656-A

Abstract

The application provides a selective epitaxial growth method, which comprises the steps of firstly keeping DCS and GeH 4 flow unchanged in a process chamber, gradually increasing SiH 4 flow, carrying out a plurality of groups of comparison experiments to obtain a relational expression between SiH 4 flow and growth rate of a germanium-silicon epitaxial layer, obtaining a relational expression between germanium content and DCS, geH 4 and SiH 4 flow, then verifying selectivity under different GeH 4 flow by using an experimental substrate, and finally selecting proper DCS, geH 4 and SiH 4 flow combinations for selective epitaxial growth according to the comparison experiments if the epitaxial growth of the germanium-silicon epitaxial layer has selectivity. According to the application, through a comparison experiment and a selectivity verification experiment, DCS and SiH 4 co-current growth with proper flow ratio is selected, so that the growth rate of the germanium-silicon epitaxial layer can be improved, the Ge content in the germanium-silicon epitaxial layer can be diluted, and the effective balance of high growth rate, low Ge content and selectivity can be realized.

Inventors

WANG MINGJIE
LU MINGHUI
Bao Saisai
DU BAOTIAN
HUI KESHI
ZHANG SHOULONG

Assignees

华虹半导体制造(无锡)有限公司
华虹半导体(无锡)有限公司

Dates

Publication Date: 20260512
Application Date: 20260107

Claims (11)

1. A method of selective epitaxial growth comprising: Providing a silicon substrate, introducing DCS, geH 4 and SiH 4 into a process chamber, keeping the flow of the DCS and the flow of GeH 4 unchanged, gradually increasing the flow of SiH 4 , and performing at least three groups of comparison experiments to form at least three germanium-silicon epitaxial layers with different thicknesses on the silicon substrate, wherein the flow of SiH 4 in each group of comparison experiments is different; Obtaining a relational expression between SiH 4 flow rate and growth rate of the germanium-silicon epitaxial layer, and obtaining a relational expression between germanium content and DCS flow rate, geH 4 flow rate and SiH 4 flow rate according to the comparative experiment; Step three, using an experimental substrate, introducing DCS, geH 4 and SiH 4 into a process chamber, increasing the flow of SiH 4 or GeH 4 , and verifying whether the epitaxial growth of the germanium-silicon epitaxial layer has selectivity or not, wherein the experimental substrate is not a silicon substrate; And a fourth step of selecting proper DCS, geH 4 and SiH 4 flow combinations according to the relation between the SiH 4 flow and the growth rate of the germanium-silicon epitaxial layer and the relation between the germanium content and DCS flow, the GeH 4 flow and the SiH 4 flow and according to the flow windows of SiH 4 and GeH 4 which are in accordance with the selective growth, and carrying out selective epitaxial growth on the silicon substrate.
2. The selective epitaxial growth method of claim 1, wherein the first step comprises: Providing a silicon substrate; Introducing DCS, geH 4 and SiH 4 into a process chamber, wherein the initial flow rate of the DCS is 150sccm, the initial flow rate of GeH 4 is 170sccm, and the initial flow rate of SiH 4 is 50sccm; Four sets of comparison experiments were performed, each of which gradually increased the flow rate of SiH 4 while maintaining the initial flow rate of DCS and the initial flow rate of GeH 4 , to form four thicknesses of silicon germanium epitaxial layers on the silicon substrate, wherein the flow rate of SiH 4 in the first set of comparison experiments was 50sccm, the flow rate of SiH 4 in the second set of comparison experiments was 75sccm, the flow rate of SiH 4 in the third set of comparison experiments was 100sccm, and the flow rate of SiH 4 in the fourth set of comparison experiments was 125sccm.
3. The selective epitaxial growth method according to claim 1, characterized in that the third step comprises: Providing an experimental substrate, introducing DCS, geH 4 and SiH 4 into a process chamber, keeping the flow of the DCS and the flow of GeH 4 unchanged, gradually increasing the flow of SiH 4 , and verifying whether the epitaxial growth of the germanium-silicon epitaxial layer has selectivity or not, wherein the experimental substrate is not a silicon substrate; And continuing to utilize the experimental substrate, introducing DCS, geH 4 and SiH 4 into the process chamber, keeping the flow of the DCS and the flow of SiH 4 unchanged, gradually increasing the flow of GeH 4 , and further verifying whether the epitaxial growth of the germanium-silicon epitaxial layer has selectivity.
4. The method of claim 3, wherein providing an experimental substrate, introducing DCS, geH 4 and SiH 4 into the process chamber, maintaining the flow rate of DCS and the flow rate of GeH 4 unchanged, gradually increasing the flow rate of SiH 4 , and verifying whether the epitaxial growth of the sige epitaxial layer is selective comprises: Providing an experimental substrate, introducing DCS, geH 4 and SiH 4 into the process chamber, keeping the flow of the DCS and the flow of GeH 4 unchanged, and gradually increasing the flow of SiH 4 ; If the germanium-silicon epitaxial layer is directly formed on the experimental substrate in the initial stage of the experiment, determining that the epitaxial growth of the germanium-silicon epitaxial layer has no selectivity; If the germanium-silicon epitaxial layer is not formed on the experimental substrate in the initial stage of the experiment, and the germanium-silicon epitaxial layer starts to be formed on the experimental substrate when the flow rate of SiH 4 is increased to a certain value, the epitaxial growth of the germanium-silicon epitaxial layer is determined to have selectivity.
5. The selective epitaxial growth method of claim 3, wherein the step of continuing to utilize the experimental substrate, introducing DCS, geH 4 and SiH 4 into the process chamber, maintaining the flow of DCS and the flow of SiH 4 unchanged, gradually increasing the flow of GeH 4 , and further verifying whether the epitaxial growth of the sige epitaxial layer is selective comprises: continuing to utilize the experimental substrate, introducing DCS, geH 4 and SiH 4 into the process chamber, keeping the flow of the DCS and the flow of SiH 4 unchanged, and gradually increasing the flow of GeH 4 ; If the germanium-silicon epitaxial layer is directly formed on the experimental substrate in the initial stage of the experiment, determining that the epitaxial growth of the germanium-silicon epitaxial layer has no selectivity; If the germanium-silicon epitaxial layer is not formed on the experimental substrate in the initial stage of the experiment, and the germanium-silicon epitaxial layer starts to be formed on the experimental substrate when the flow rate of GeH 4 is increased to a certain value, the epitaxial growth of the germanium-silicon epitaxial layer is determined to have selectivity.
6. The method of claim 3, wherein the flow rate of the SiH 4 is less than 125sccm, and the flow rate window of the GeH 4 is less than 230sccm.
7. The selective epitaxial growth method of claim 1, wherein in the second step, a relationship between SiH 4 flow rate and growth rate of the silicon germanium epitaxial layer is: GR=0.0973*F SiH4 +2.9041; Wherein GR is a growth rate of the sige epitaxial layer, and F SiH4 is a flow rate of SiH 4 .
8. The selective epitaxial growth method of claim 7, wherein the growth rate of the sige epitaxial layer is calculated by the formula: GR=L/t; wherein GR is a growth rate of the sige epitaxial layer, L is a thickness of the sige epitaxial layer, and t is a process time for epitaxially growing the sige epitaxial layer.
9. The selective epitaxial growth method according to claim 1, wherein in the second step, a relation between the germanium content and the flow rate of DCS, the flow rate of GeH 4 , the flow rate of SiH 4 is: C Ge /（1－C Ge ）=20.1*（F GeH4 /（F SiH4 ＋F DCS ))-3.89; Wherein, C Ge is germanium content, F GeH4 is GeH 4 flow, F SiH4 is SiH 4 flow, and F DCS is DCS flow.
10. A selective epitaxial growth method according to claim 1 or 3, wherein the experimental substrate is made of silicon nitride or silicon dioxide.
11. The selective epitaxial growth method of claim 1, wherein in the fourth step, HCl is introduced simultaneously with the introduction of DCS, geH 4 and SiH 4 in the proper proportions into the process chamber.

Description

Selective epitaxial growth method Technical Field The application relates to the technical field of semiconductor manufacturing, in particular to a selective epitaxial growth method. Background The conventional selective epitaxy process of a germanium-silicon epitaxial layer (SiGe film) generally adopts two gases, namely SiCl 2H2(SiCl2H2 and GeH 4, and the Ge content in the deposited SiGe film is controlled by adjusting the flow ratio of GeH 4 and DCS, wherein GeH 4 is not only a main component gas source, but also Ge atoms in GeH 4 can promote the cracking of H, and the growth rate of the SiGe film is obviously influenced. In BiCMOS (BJT) and CMOS (complementary metal oxide semiconductor) integrated process flows, the Base region (Base region) of SiGe HBT (heterojunction bipolar transistor) devices requires control of the Ge concentration gradient to form an accelerating electric field to shorten the electron transit time, thereby improving the high frequency performance of the devices. However, in the process of growing SiGe film with low Ge content, the flow of GeH 4 needs to be reduced to reduce the Ge content in the process of introducing DCS and GeH 4, which can greatly reduce the growth rate and affect the production efficiency, and furthermore, the Cl content in DCS can reduce the growth rate if the DCS flow is singly increased, and if SiH 4 with faster reaction is fully adopted as a silicon source, the growth rate is too fast after being matched with GeH 4, so that the selectivity is difficult to realize. Disclosure of Invention The application provides a selective epitaxial growth method, which can solve at least one of the problems that the epitaxial growth rate of a SiGe film is low, the production efficiency is affected, or the epitaxial growth rate of the SiGe film is high, the selectivity of the SiGe film is difficult to realize and the like in the conventional epitaxial growth process of the SiGe film with low Ge content. The embodiment of the application provides a selective epitaxial growth method, which comprises the following steps: Providing a silicon substrate, introducing DCS, geH 4 and SiH 4 into a process chamber, keeping the flow of the DCS and the flow of GeH 4 unchanged, gradually increasing the flow of SiH 4, and performing at least three groups of comparison experiments to form at least three germanium-silicon epitaxial layers with different thicknesses on the silicon substrate, wherein the flow of SiH 4 in each group of comparison experiments is different; Obtaining a relational expression between SiH 4 flow rate and growth rate of the germanium-silicon epitaxial layer, and obtaining a relational expression between germanium content and DCS flow rate, geH 4 flow rate and SiH 4 flow rate according to the comparative experiment; Step three, using an experimental substrate, introducing DCS, geH 4 and SiH 4 into a process chamber, increasing the flow of SiH 4 or GeH 4, and verifying whether the epitaxial growth of the germanium-silicon epitaxial layer has selectivity or not, wherein the experimental substrate is not a silicon substrate; And a fourth step of selecting proper DCS, geH 4 and SiH 4 flow combinations according to the relation between the SiH 4 flow and the growth rate of the germanium-silicon epitaxial layer and the relation between the germanium content and DCS flow, the GeH 4 flow and the SiH 4 flow and according to the flow windows of SiH 4 and GeH 4 which are in accordance with the selective growth, and carrying out selective epitaxial growth on the silicon substrate. Optionally, in the selective epitaxial growth method, the first step includes: Providing a silicon substrate; Introducing DCS, geH 4 and SiH 4 into a process chamber, wherein the initial flow rate of the DCS is 150sccm, the initial flow rate of GeH 4 is 170sccm, and the initial flow rate of SiH 4 is 50sccm; Four sets of comparison experiments were performed, each of which gradually increased the flow rate of SiH 4 while maintaining the initial flow rate of DCS and the initial flow rate of GeH 4, to form four thicknesses of silicon germanium epitaxial layers on the silicon substrate, wherein the flow rate of SiH 4 in the first set of comparison experiments was 50sccm, the flow rate of SiH 4 in the second set of comparison experiments was 75sccm, the flow rate of SiH 4 in the third set of comparison experiments was 100sccm, and the flow rate of SiH 4 in the fourth set of comparison experiments was 125sccm. Optionally, in the selective epitaxial growth method, the third step includes: Providing an experimental substrate, introducing DCS, geH 4 and SiH 4 into a process chamber, keeping the flow of the DCS and the flow of GeH 4 unchanged, gradually increasing the flow of SiH 4, and verifying whether the epitaxial growth of the germanium-silicon epitaxial layer has selectivity or not, wherein the experimental substrate is not a silicon substrate; And continuing to utilize the experimental substrate, introdu