Selective epitaxial growth method
By introducing DCS, GeH4, and SiH4 into the process chamber and conducting multiple sets of comparative experiments and selectivity verification, the problem of low growth rate or difficulty in achieving selectivity of low Ge content SiGe thin films was solved, achieving a balance between high growth rate and low Ge content, and improving production efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HUA HONG SEMICONDUCTOR MANUFACTURING (WUXI) LTD
- Filing Date
- 2026-01-07
- Publication Date
- 2026-05-12
AI Technical Summary
In the traditional low-Ge-content SiGe thin film growth process, the epitaxial growth rate is low or the selectivity is difficult to achieve, which affects the production efficiency.
By introducing DCS, GeH4, and SiH4 into the process chamber while keeping the flow rates of DCS and GeH4 constant and gradually increasing the flow rate of SiH4, multiple sets of comparative experiments were conducted to obtain the relationship between growth rate and Ge content, verify selectivity, and select an appropriate gas flow rate combination for selective epitaxial growth.
A balance was achieved between high growth rate and low Ge content, ensuring selective epitaxial growth and improving production efficiency.
Smart Images
Figure CN122028656A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of semiconductor manufacturing technology, specifically to a selective epitaxial growth method. Background Technology
[0002] Traditional selective epitaxy processes for germanium-silicon epitaxial layers (SiGe thin films) typically employ two gases: SiCl2H2 (also known as DCS) and GeH4. The Ge content in the deposited SiGe thin film is controlled by adjusting the flow ratio of GeH4 to DCS. GeH4 is not only the main component gas source, but the Ge atoms in GeH4 can also promote the decomposition of H, significantly affecting the growth rate of the SiGe thin film.
[0003] In BiCMOS (BJT and CMOS integration) processes, the base region of SiGe HBT (heterojunction bipolar transistor) devices requires controlling the Ge concentration gradient to create an accelerating electric field, thereby shortening electron transit time and improving the high-frequency performance of the device. However, for the growth of SiGe thin films with low Ge content, the GeH4 flow rate needs to be reduced to lower the Ge content during the introduction of DCS and GeH4 gases. This leads to a significant decrease in growth rate, affecting production efficiency. Furthermore, since DCS contains Cl, simply increasing the DCS flow rate will actually reduce the growth rate. On the other hand, if the faster-reacting SiH4 is used as the silicon source, the growth rate is too fast when combined with GeH4, making it difficult to achieve selectivity. Summary of the Invention
[0004] This application provides a selective epitaxial growth method that can solve at least one of the following problems in the traditional epitaxial growth process of low-Ge content SiGe films: the epitaxial growth rate of SiGe films is low, affecting production efficiency; or the epitaxial growth rate of SiGe films is too fast, making it difficult to achieve selectivity in SiGe films.
[0005] This application provides a selective epitaxial growth method, including: First step: Provide a silicon substrate, introduce DCS, GeH4 and SiH4 into the process chamber, and keep the flow rates of DCS and GeH4 constant while gradually increasing the flow rate of SiH4. Perform at least three sets of comparative experiments to form at least three different thicknesses of germanium-silicon epitaxial layers on the silicon substrate, wherein the flow rate of SiH4 is different in each set of comparative experiments. The second step: Based on the comparative experiment, obtain the relationship between SiH4 flow rate and the growth rate of the germanium-silicon epitaxial layer, as well as the relationship between germanium content and DCS flow rate, GeH4 flow rate, and SiH4 flow rate. The third step: Using an experimental substrate, DCS, GeH4 and SiH4 are introduced into the process chamber, and the flow rate of SiH4 or GeH4 is increased to verify whether the epitaxial growth of the germanium-silicon epitaxial layer is selective. The experimental substrate is not a silicon substrate. Fourth step: If the epitaxial growth of the germanium-silicon epitaxial layer is selective, then according to the relationship between the SiH4 flow rate and the growth rate of the germanium-silicon epitaxial layer, as well as the relationship between the germanium content and the DCS flow rate, the GeH4 flow rate, and the SiH4 flow rate, and according to the SiH4 and GeH4 flow rate windows that meet the requirements for selective growth, a suitable combination of DCS, GeH4, and SiH4 flow rates is selected to perform selective epitaxial growth on the silicon substrate.
[0006] Optionally, in the selective epitaxial growth method, the first step includes: Provide a silicon substrate; DCS, GeH4 and SiH4 are introduced into the process chamber, with the initial flow rate of DCS being 150 sccm, the initial flow rate of GeH4 being 170 sccm and the initial flow rate of SiH4 being 50 sccm. Four sets of comparative experiments were conducted, keeping the initial flow rates of DCS and GeH4 constant. In each set of comparative experiments, the flow rate of SiH4 was gradually increased to form germanium-silicon epitaxial layers of four different thicknesses on the silicon substrate. Specifically, in the first set of comparative experiments, the flow rate of SiH4 was 50 sccm; in the second set, it was 75 sccm; in the third set, it was 100 sccm; and in the fourth set, it was 125 sccm.
[0007] Optionally, in the selective epitaxial growth method, the third step includes: An experimental substrate is provided, and DCS, GeH4 and SiH4 are introduced into a process chamber. While keeping the flow rates of DCS and GeH4 constant, the flow rate of SiH4 is gradually increased to verify whether the epitaxial growth of the germanium-silicon epitaxial layer is selective. The experimental substrate is not a silicon substrate. Continuing with the experimental substrate, DCS, GeH4, and SiH4 were introduced into the process chamber, while keeping the flow rates of DCS and SiH4 constant. The flow rate of GeH4 was gradually increased to further verify whether the epitaxial growth of the germanium-silicon epitaxial layer is selective.
[0008] Optionally, in the selective epitaxial growth method, the step of providing an experimental substrate, introducing DCS, GeH4, and SiH4 into a process chamber, and gradually increasing the flow rate of SiH4 while keeping the flow rates of DCS and GeH4 constant, to verify whether the epitaxial growth of the germanium-silicon epitaxial layer is selective includes: An experimental substrate is provided, and DCS, GeH4 and SiH4 are introduced into a process chamber. The flow rates of DCS and GeH4 are kept constant, while the flow rate of SiH4 is gradually increased. If a germanium-silicon epitaxial layer is directly formed on the experimental substrate in the initial stage of the experiment, then it is determined that the epitaxial growth of the germanium-silicon epitaxial layer is not selective. If no germanium-silicon epitaxial layer is formed on the experimental substrate in the initial stage of the experiment, and the germanium-silicon epitaxial layer only begins to form on the experimental substrate when the SiH4 flow rate increases to a certain value, then the epitaxial growth of the germanium-silicon epitaxial layer is determined to be selective.
[0009] Optionally, in the selective epitaxial growth method, the step of continuing to use the experimental substrate, introducing DCS, GeH4, and SiH4 into the process chamber, and keeping the flow rates of DCS and SiH4 constant while gradually increasing the flow rate of GeH4 to further verify whether the epitaxial growth of the germanium-silicon epitaxial layer is selective includes: Continuing to use the experimental substrate, DCS, GeH4 and SiH4 were introduced into the process chamber, while keeping the flow rates of DCS and SiH4 constant, and gradually increasing the flow rate of GeH4. If a germanium-silicon epitaxial layer is directly formed on the experimental substrate in the initial stage of the experiment, then it is determined that the epitaxial growth of the germanium-silicon epitaxial layer is not selective. If no germanium-silicon epitaxial layer is formed on the experimental substrate in the initial stage of the experiment, and the germanium-silicon epitaxial layer only begins to form on the experimental substrate when the flow rate of GeH4 increases to a certain value, then the epitaxial growth of the germanium-silicon epitaxial layer is determined to be selective.
[0010] Optionally, in the selective epitaxial growth method, the flow rate of SiH4 that meets the requirements for selective growth is less than 125 sccm; the flow rate window of GeH4 that meets the requirements for selective growth is less than 230 sccm.
[0011] Optionally, in the selective epitaxial growth method, in the second step, the relationship between the SiH4 flow rate and the growth rate of the germanium-silicon epitaxial layer is as follows: GR=0.0973*F SiH4 +2.9041; Where GR is the growth rate of the germanium-silicon epitaxial layer, and F SiH4 The flow rate of SiH4.
[0012] Optionally, in the selective epitaxial growth method, the growth rate of the germanium-silicon epitaxial layer is calculated using the following formula: GR = L / t; Wherein, GR is the growth rate of the germanium-silicon epitaxial layer, L is the thickness of the germanium-silicon epitaxial layer, and t is the process time for epitaxially growing the germanium-silicon epitaxial layer.
[0013] Optionally, in the selective epitaxial growth method, in the second step, the relationship between the germanium content and the flow rate of the DCS, the flow rate of GeH4, and the flow rate of SiH4 is as follows: C Ge / (1-C) Ge =20.1*(F) GeH4 / (F SiH4 +F DCS -3.89; Among them, C Ge For germanium content, F GeH4 For the flow rate of GeH4, F SiH4 F represents the flow rate of SiH4. DCS This refers to the traffic of the DCS.
[0014] Optionally, in the selective epitaxial growth method, the experimental substrate is made of silicon nitride or silicon dioxide.
[0015] Optionally, in the selective epitaxial growth method, in the fourth step, HCl is also introduced into the process chamber while an appropriate proportion of DCS, GeH4 and SiH4 are introduced.
[0016] The technical solution of this application has at least the following advantages: This application provides a selective epitaxial growth method. First, DCS, GeH4, and SiH4 are introduced into a process chamber while keeping the DCS and GeH4 flow rates constant. The SiH4 flow rate is gradually increased, and multiple comparative experiments are conducted to obtain the relationship between SiH4 flow rate and the growth rate of the germanium-silicon epitaxial layer, as well as the relationship between germanium content and the DCS, GeH4, and SiH4 flow rates. Then, the selectivity under different GeH4 flow rates is verified using other experimental substrates. Finally, if the epitaxial growth of the germanium-silicon epitaxial layer exhibits selectivity, a suitable combination of DCS, GeH4, and SiH4 flow rates is selected based on the comparative experiments and the SiH4 and GeH4 flow rate windows that conform to selective growth, and selective epitaxial growth is performed on a silicon substrate. This application, through multiple comparative experiments and selectivity verification experiments, selects a suitable co-flow ratio of DCS and SiH4 dual silicon source gases, which not only improves the growth rate of the germanium-silicon epitaxial layer but also dilutes the Ge content in the germanium-silicon epitaxial layer, achieving an effective balance between high growth rate, low Ge content, and selectivity. Attached Figure Description
[0017] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0018] Figure 1 This is a flowchart of the selective epitaxial growth method according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the flow rate changes of SiH4 and GeH4 on an experimental substrate, as demonstrated in an embodiment of the present invention. Detailed Implementation
[0019] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0020] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0021] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components; and they can refer to a wireless connection or a wired connection. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.
[0022] Furthermore, the technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.
[0023] This application provides a selective epitaxial growth method, referencing... Figure 1 The selective epitaxial growth method includes: First, perform the first step S1: provide a silicon substrate, introduce DCS, GeH4 and SiH4 into the process chamber, and keep the flow rates of DCS and GeH4 constant while gradually increasing the flow rate of SiH4. Perform at least three sets of comparative experiments to form at least three different thicknesses of germanium-silicon epitaxial layers on the silicon substrate, wherein the flow rate of SiH4 is different in each set of comparative experiments.
[0024] In this embodiment, the first step S1 includes: Step S1.1: Provide a silicon substrate; Step S1.2: Introduce DCS, GeH4 and SiH4 into the process chamber, wherein the initial flow rate of DCS is 150 sccm, the initial flow rate of GeH4 is 170 sccm, and the initial flow rate of SiH4 is 50 sccm. Step S1.3: Perform four sets of comparative experiments, keeping the initial flow rate of DCS and GeH4 constant. In each set of comparative experiments, gradually increase the flow rate of SiH4 to form germanium-silicon epitaxial layers of four different thicknesses on the silicon substrate. Specifically, in the first set of comparative experiments, the flow rate of SiH4 is 50 sccm; in the second set, it is 75 sccm; in the third set, it is 100 sccm; and in the fourth set, it is 125 sccm.
[0025] Then, perform the second step S2: based on the comparative experiment, obtain the relationship between the SiH4 flow rate and the growth rate of the germanium-silicon epitaxial layer, as well as the relationship between the germanium content and the DCS flow rate, the GeH4 flow rate, and the SiH4 flow rate.
[0026] Preferably, in the second step, the relationship between the SiH4 flow rate and the growth rate of the germanium-silicon epitaxial layer is: GR = 0.0973 * F SiH4 +2.9041; Where GR is the growth rate of the germanium-silicon epitaxial layer, and F SiH4 The flow rate of SiH4.
[0027] Furthermore, the growth rate of the germanium-silicon epitaxial layer is calculated using the formula: GR = L / t; Wherein, GR is the growth rate of the germanium-silicon epitaxial layer, L is the thickness of the germanium-silicon epitaxial layer, and t is the process time for epitaxially growing the germanium-silicon epitaxial layer.
[0028] Preferably, in the second step, the relationship between the germanium content and the flow rate of the DCS, the flow rate of GeH4, and the flow rate of SiH4 is: C Ge / (1-C) Ge =20.1*(F) GeH4 / (F SiH4 +F DCS -3.89; Among them, C Ge For germanium content, F GeH4 For the flow rate of GeH4, F SiH4 F represents the flow rate of SiH4. DCS This refers to the traffic of the DCS.
[0029] Next, in the third step S3: using an experimental substrate, DCS, GeH4 and SiH4 are introduced into the process chamber, and the flow rate of SiH4 or GeH4 is increased to verify whether the epitaxial growth of the germanium-silicon epitaxial layer is selective. The experimental substrate is not a silicon substrate, that is, the experimental substrate is a non-silicon substrate.
[0030] Preferably, the third step S3 may specifically include: Step S3.1: Provide an experimental substrate, introduce DCS, GeH4 and SiH4 into the process chamber, and keep the flow rates of DCS and GeH4 constant while gradually increasing the flow rate of SiH4 to verify whether the epitaxial growth of the germanium-silicon epitaxial layer is selective. The experimental substrate is not a silicon substrate. Step S3.2: Continuing to use the experimental substrate, DCS, GeH4 and SiH4 are introduced into the process chamber, and the flow rates of DCS and SiH4 are kept constant while the flow rate of GeH4 is gradually increased to further verify whether the epitaxial growth of the germanium-silicon epitaxial layer is selective.
[0031] The experimental substrate is made of silicon nitride or silicon dioxide.
[0032] In this embodiment, step S3.1 may specifically include: Step S3.1.1: Provide an experimental substrate, and introduce DCS, GeH4 and SiH4 into the process chamber. The initial flow rate of DCS is 150 sccm, the initial flow rate of GeH4 is 170 sccm, and the initial flow rate of SiH4 is 50 sccm. Keep the flow rates of DCS and GeH4 constant, and gradually increase the flow rate of SiH4 (for example, by increasing the flow rate of SiH4 in increments of 25 sccm: 50 sccm, 75 sccm, 100 sccm, 125 sccm, etc.). Step S3.1.2: If a germanium-silicon epitaxial layer is directly formed on the experimental substrate in the initial stage of the experiment, then the epitaxial growth of the germanium-silicon epitaxial layer is determined to be non-selective; if a germanium-silicon epitaxial layer is not formed on the experimental substrate in the initial stage of the experiment, and the germanium-silicon epitaxial layer only begins to form on the experimental substrate when the SiH4 flow rate increases to a certain value, then the epitaxial growth of the germanium-silicon epitaxial layer is determined to be selective.
[0033] refer to Figure 2 , Figure 2 This is a schematic diagram of the flow rate changes of SiH4 and GeH4 on an experimental substrate for selective verification according to an embodiment of the present invention. In this embodiment, the experimental substrate is made of silicon nitride. After the SiH4 flow rate is increased to 125 sccm in step S3.1, a germanium-silicon epitaxial layer begins to grow on the experimental substrate, indicating that 125 sccm is the upper limit of the flow rate for the selective epitaxial growth process of SiH4. That is, the flow rate of SiH4 that meets the requirements for selective growth is less than 125 sccm.
[0034] In this embodiment, step S3.2 may specifically include: Step S3.2.1: Continuing to use the experimental substrate, DCS, GeH4, and SiH4 are introduced into the process chamber. The initial flow rate of DCS is 150 sccm, the initial flow rate of SiH4 is 115 sccm, and the initial flow rate of GeH4 is 170 sccm. While keeping the flow rates of DCS and SiH4 constant, the flow rate of GeH4 is gradually increased (GeH4 is increased in increments of 30 sccm: 170 sccm, 200 sccm, 230 sccm, 260 sccm, etc.). Step S3.2.2: If a germanium-silicon epitaxial layer is directly formed on the experimental substrate in the initial stage of the experiment, then the epitaxial growth of the germanium-silicon epitaxial layer is determined to be non-selective; if a germanium-silicon epitaxial layer is not formed on the experimental substrate in the initial stage of the experiment, and the germanium-silicon epitaxial layer only begins to form on the experimental substrate when the flow rate of GeH4 increases to a certain value, then the epitaxial growth of the germanium-silicon epitaxial layer is determined to be selective.
[0035] Continue to refer to Figure 2 In this embodiment, after the GeH4 flow rate in step S3.2 is increased to 230 sccm, a germanium-silicon epitaxial layer begins to grow on the experimental substrate, indicating that 230 sccm is the upper limit of the flow rate for the selective epitaxial growth process of GeH4, that is, the flow rate of GeH4 that meets the requirements for selective growth is less than 230 sccm.
[0036] Finally, the fourth step S4 is performed: if the epitaxial growth of the germanium-silicon epitaxial layer is selective, then according to the relationship between the SiH4 flow rate and the growth rate of the germanium-silicon epitaxial layer, as well as the relationship between the germanium content and the DCS flow rate, the GeH4 flow rate, and the SiH4 flow rate, and according to the SiH4 and GeH4 flow rate windows that meet the requirements for selective growth, a suitable combination of DCS, GeH4, and SiH4 flow rates is selected to perform selective epitaxial growth on the silicon substrate.
[0037] Based on the verification that the epitaxial growth of germanium-silicon epitaxial layers is selective, the inventors, according to the relationship between SiH4 flow rate and the growth rate of the germanium-silicon epitaxial layer, as well as the relationship between germanium content and DCS flow rate, GeH4 flow rate, and SiH4 flow rate, and based on the flow rate windows of SiH4 and GeH4 that conform to selective growth, specifically, maximize the growth rate of the germanium-silicon epitaxial layer, that is, set the flow rates of GeH4 and SiH4 as high as possible but not close to the upper limit (GeH4 flow rate < 230 sccm, SiH4 flow rate < 125 sccm), within this range, based on the actual requirements of germanium content, and according to the relationship between germanium content and DCS flow rate, GeH4 flow rate, and SiH4 flow rate (C... Ge / (1-C) Ge =20.1*(F) GeH4 / (FSiH4 +F DCS Select the specific flow rates for GeH4 and SiH4.
[0038] In this embodiment, the inventors experimentally discovered that the required germanium content in the germanium-silicon epitaxial layer is 9%. The flow rates of GeH4 and SiH4 are set as high as possible but not close to the upper limit (GeH4 flow rate < 230 sccm, SiH4 flow rate < 125 sccm). Based on the relationship between germanium content and the flow rates of DCS, GeH4, and SiH4, a suitable DCS, GeH4, and SiH4 flow rate ratio of 150:200:100 can be determined (see attached diagram). Figure 2 (The location marked with a yellow asterisk in the diagram) indicates that, in the fourth step, a DCS, GeH4, and SiH4 flow rate combination ratio of 150:200:100 is selected for selective epitaxial growth on a silicon substrate. Specifically, a DCS flow rate of 150 sccm, a GeH4 flow rate of 200 sccm, and a SiH4 flow rate of 100 sccm are selected for selective epitaxial growth on a silicon substrate.
[0039] Furthermore, in the fourth step, HCl is also introduced into the process chamber while an appropriate proportion of DCS, GeH4, and SiH4 are introduced.
[0040] Among them, (1) the decomposition deposition principle of DCS (SiH2Cl2) is: SiH2Cl2↔ SiCl2+H2↔ Si+HCl; (2) the decomposition deposition principle of SiH4 is: SiH4↔ Si+H2, where the decomposition reaction rate of SiH4 gas is greater than that of DCS; (3) the decomposition deposition principle of GeH4 is: GeH4↔Ge+H2, where Ge atoms can act as desorption centers, reducing the activation energy of H cracking, thereby accelerating the overall chemical reaction. Furthermore, since the surface free tension coefficients of silicon (Si) substrate and experimental substrate (silicon nitride or silicon dioxide) are different, nucleation is easier on the Si substrate during epitaxial growth, while nucleation is not easy on the experimental substrate (silicon nitride or silicon dioxide). Therefore, selective epitaxial growth of germanium-silicon epitaxial layer on Si substrate can be achieved by adjusting the flow rate of HCl.
[0041] In this embodiment, in the fourth step, the appropriate flow rate ratio of DCS, GeH4, SiH4, and HCl can be selected as 150:200:100:70. Specifically, the DCS flow rate is 150 sccm; the GeH4 flow rate is 200 sccm; the SiH4 flow rate is 100 sccm; and the HCl flow rate is 70 sccm.
[0042] In this application, DCS, GeH4, and SiH4 are first introduced into the process chamber while keeping the DCS and GeH4 flow rates constant. The SiH4 flow rate is then gradually increased, and multiple comparative experiments are conducted to obtain the relationship between the SiH4 flow rate and the growth rate of the germanium-silicon epitaxial layer, as well as the relationship between the germanium content and the DCS, GeH4, and SiH4 flow rates. Then, the selectivity under different GeH4 flow rates is verified using other experimental substrates. Finally, if the epitaxial growth of the germanium-silicon epitaxial layer exhibits selectivity, a suitable combination of DCS, GeH4, and SiH4 flow rates is selected based on the comparative experiments and the SiH4 and GeH4 flow rate windows that conform to selective growth, and selective epitaxial growth is performed on a silicon substrate. The selective epitaxial growth method provided in this application can achieve a balance between the three major factors of Ge content, growth rate, and selectivity, significantly shortening the growth time of germanium-silicon epitaxial layers with low Ge content while ensuring selective growth.
[0043] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this application.
Claims
1. A selective epitaxial growth method, characterized in that, include: First step: Provide a silicon substrate, introduce DCS, GeH4 and SiH4 into the process chamber, and keep the flow rates of DCS and GeH4 constant while gradually increasing the flow rate of SiH4. Perform at least three sets of comparative experiments to form at least three different thicknesses of germanium-silicon epitaxial layers on the silicon substrate, wherein the flow rate of SiH4 is different in each set of comparative experiments. The second step: Based on the comparative experiment, obtain the relationship between SiH4 flow rate and the growth rate of the germanium-silicon epitaxial layer, as well as the relationship between germanium content and DCS flow rate, GeH4 flow rate, and SiH4 flow rate. The third step: Using an experimental substrate, DCS, GeH4 and SiH4 are introduced into the process chamber, and the flow rate of SiH4 or GeH4 is increased to verify whether the epitaxial growth of the germanium-silicon epitaxial layer is selective. The experimental substrate is not a silicon substrate. Fourth step: If the epitaxial growth of the germanium-silicon epitaxial layer is selective, then according to the relationship between the SiH4 flow rate and the growth rate of the germanium-silicon epitaxial layer, as well as the relationship between the germanium content and the DCS flow rate, the GeH4 flow rate, and the SiH4 flow rate, and according to the SiH4 and GeH4 flow rate windows that meet the requirements for selective growth, a suitable combination of DCS, GeH4, and SiH4 flow rates is selected to perform selective epitaxial growth on the silicon substrate.
2. The selective epitaxial growth method according to claim 1, characterized in that, The first step includes: Provide a silicon substrate; DCS, GeH4 and SiH4 are introduced into the process chamber, with the initial flow rate of DCS being 150 sccm, the initial flow rate of GeH4 being 170 sccm and the initial flow rate of SiH4 being 50 sccm. Four sets of comparative experiments were conducted, keeping the initial flow rates of DCS and GeH4 constant. In each set of comparative experiments, the flow rate of SiH4 was gradually increased to form germanium-silicon epitaxial layers of four different thicknesses on the silicon substrate. Specifically, in the first set of comparative experiments, the flow rate of SiH4 was 50 sccm; in the second set, it was 75 sccm; in the third set, it was 100 sccm; and in the fourth set, it was 125 sccm.
3. The selective epitaxial growth method according to claim 1, characterized in that, The third step includes: An experimental substrate is provided, and DCS, GeH4 and SiH4 are introduced into a process chamber. While keeping the flow rates of DCS and GeH4 constant, the flow rate of SiH4 is gradually increased to verify whether the epitaxial growth of the germanium-silicon epitaxial layer is selective. The experimental substrate is not a silicon substrate. Continuing with the experimental substrate, DCS, GeH4, and SiH4 were introduced into the process chamber, while keeping the flow rates of DCS and SiH4 constant. The flow rate of GeH4 was gradually increased to further verify whether the epitaxial growth of the germanium-silicon epitaxial layer is selective.
4. The selective epitaxial growth method according to claim 3, characterized in that, The steps of providing an experimental substrate, introducing DCS, GeH4, and SiH4 into a process chamber, and gradually increasing the flow rate of SiH4 while keeping the flow rates of DCS and GeH4 constant to verify whether the epitaxial growth of the germanium-silicon epitaxial layer is selective include: An experimental substrate is provided, and DCS, GeH4 and SiH4 are introduced into a process chamber. The flow rates of DCS and GeH4 are kept constant, while the flow rate of SiH4 is gradually increased. If a germanium-silicon epitaxial layer is directly formed on the experimental substrate in the initial stage of the experiment, then it is determined that the epitaxial growth of the germanium-silicon epitaxial layer is not selective. If no germanium-silicon epitaxial layer is formed on the experimental substrate in the initial stage of the experiment, and the germanium-silicon epitaxial layer only begins to form on the experimental substrate when the SiH4 flow rate increases to a certain value, then the epitaxial growth of the germanium-silicon epitaxial layer is determined to be selective.
5. The selective epitaxial growth method according to claim 3, characterized in that, The step of continuing to use the experimental substrate, introducing DCS, GeH4, and SiH4 into the process chamber, and gradually increasing the flow rate of GeH4 while keeping the flow rates of DCS and SiH4 constant, to further verify whether the epitaxial growth of the germanium-silicon epitaxial layer is selective includes: Continuing to use the experimental substrate, DCS, GeH4 and SiH4 were introduced into the process chamber, while keeping the flow rates of DCS and SiH4 constant, and gradually increasing the flow rate of GeH4. If a germanium-silicon epitaxial layer is directly formed on the experimental substrate in the initial stage of the experiment, then it is determined that the epitaxial growth of the germanium-silicon epitaxial layer is not selective. If no germanium-silicon epitaxial layer is formed on the experimental substrate in the initial stage of the experiment, and the germanium-silicon epitaxial layer only begins to form on the experimental substrate when the flow rate of GeH4 increases to a certain value, then the epitaxial growth of the germanium-silicon epitaxial layer is determined to be selective.
6. The selective epitaxial growth method according to claim 3, characterized in that, The flow rate for selectively grown SiH4 is less than 125 sccm; the flow rate window for selectively grown GeH4 is less than 230 sccm.
7. The selective epitaxial growth method according to claim 1, characterized in that, In the second step, the relationship between the SiH4 flow rate and the growth rate of the germanium-silicon epitaxial layer is as follows: GR=0.0973*F SiH4 +2.9041; Where GR is the growth rate of the germanium-silicon epitaxial layer, and F SiH4 The flow rate of SiH4.
8. The selective epitaxial growth method according to claim 7, characterized in that, The formula for calculating the growth rate of the germanium-silicon epitaxial layer is as follows: GR = L / t; Wherein, GR is the growth rate of the germanium-silicon epitaxial layer, L is the thickness of the germanium-silicon epitaxial layer, and t is the process time for epitaxially growing the germanium-silicon epitaxial layer.
9. The selective epitaxial growth method according to claim 1, characterized in that, In the second step, the relationship between germanium content and the flow rate of DCS, the flow rate of GeH4, and the flow rate of SiH4 is as follows: C Ge / (1-C Ge )=20.1*(F GeH4 / (F SiH4 +F DCS ))-3.89; Among them, C Ge For germanium content, F GeH4 For the flow rate of GeH4, F SiH4 F represents the flow rate of SiH4. DCS This refers to the traffic of the DCS.
10. The selective epitaxial growth method according to claim 1 or 3, characterized in that, The experimental substrate is made of silicon nitride or silicon dioxide.
11. The selective epitaxial growth method according to claim 1, characterized in that, In the fourth step, HCl is introduced into the process chamber along with appropriate proportions of DCS, GeH4, and SiH4.