A method for establishing a fitting model for the growth rate of germanium-silicon

Abstract

The present invention relates to a method for establishing a germanium-silicon growth rate fitting model, which comprises the following steps: S1, providing an epitaxial device with a cavity; S2, setting process parameters, introducing process gas into the cavity, and growing a germanium-silicon epitaxial layer on a substrate; S3, obtaining the growth rate of the germanium-silicon epitaxial layer corresponding to the process parameters; S4, changing the process parameters, and repeating steps S2 to S3 to obtain the growth rate of the germanium-silicon epitaxial layer under the changed process parameters; S5, obtaining the germanium-silicon growth rate fitting model for the process parameters based on each process parameter and the growth rate corresponding to the process parameter; the fitting model proposed in the present invention can accurately infer the growth rate of the germanium-silicon epitaxial layer and is applicable to a wider range of processes.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor epitaxial equipment, and in particular to a method for establishing a germanium-silicon growth rate fitting model. Background Art

[0002] Silicon, as the most important semiconductor material, plays an irreplaceable role in the information industry. However, it suffers from drawbacks such as low carrier mobility and relatively slow device speeds. This requires epitaxial growth of other materials, the most common of which is silicon-germanium (SiGe). To save costs and time, it is often necessary to calculate SiGe epitaxial growth rates under different conditions based on experimental results and empirical data. Existing models for estimating growth rates are generally believed to conform to the Arrhenius equation, but this equation only agrees with experimental results within a certain temperature range, making it applicable only to a narrow range of process conditions.

[0003] In order to more accurately deduce the epitaxial growth rate of SiGe, it is necessary to obtain a more accurate fitting model that takes multiple factors into consideration. Summary of the Invention

[0004] The purpose of this invention is to provide a more accurate SiGe growth rate fitting model that takes into account multiple factors. The SiGe epitaxial layer growth rate in this invention refers to the growth rate of the SiGe epitaxial layer on a silicon substrate, which fluctuates under the influence of process conditions such as process temperature and process gas.

[0005] The method for establishing a germanium-silicon growth rate fitting model provided by the present invention comprises the following steps:

[0006] S1. Providing an epitaxial device having a cavity;

[0007] S2, setting process parameters, introducing process gas into the chamber, and growing a silicon-germanium epitaxial layer on the substrate;

[0008] S3, obtaining the growth rate of the silicon-germanium epitaxial layer corresponding to the process parameters;

[0009] S4, changing the process parameters, and repeating steps S2 to S3 to obtain a growth rate of the silicon-germanium epitaxial layer under the changed process parameters;

[0010] S5. Obtaining a germanium-silicon growth rate fitting model related to each process parameter according to each process parameter and the growth rate corresponding to the process parameter;

[0011] The silicon-germanium growth rate is the growth rate of the silicon-germanium epitaxial layer on the substrate, and the process gas includes a silicon-containing gas and a germanium-containing gas.

[0012] Furthermore, the process parameters include: process temperature, partial pressure of silicon-containing gas, and partial pressure of germanium-containing gas.

[0013] Furthermore, changing the process parameters includes: changing only the process temperature while keeping the partial pressure of the silicon-containing gas and the partial pressure of the germanium-containing gas unchanged, and changing only the partial pressure of the silicon-containing gas while keeping the process temperature and the ratio of the partial pressure of the germanium-containing gas to the partial pressure of the silicon-containing gas unchanged.

[0014] Furthermore, the process gas also includes a carrier gas.

[0015] As a preferred example, the silicon-containing gas includes one or more of SiH4, SiHCl3, SiH2Cl2 and SiCl4.

[0016] As a preferred example, the germanium-containing gas contains at least one of GeH4 and Ge2H6.

[0017] Furthermore, the partial pressure of the gas can be adjusted by adjusting the flow rate of the silicon-containing gas entering the cavity to adjust the partial pressure of the silicon-containing gas in the cavity; by adjusting the flow rate of the germanium-containing gas entering the cavity to adjust the partial pressure of the germanium-containing gas in the cavity.

[0018] Furthermore, the germanium-silicon growth rate fitting model is a function of the correlation between the germanium-silicon growth rate and the partial pressure of the silicon-containing gas, the partial pressure of the germanium-containing gas, and the process temperature.

[0019] Furthermore, the germanium-silicon growth rate fitting model is:

[0020]

[0021] Where GR represents the growth rate of germanium silicon, k1, k2, k3 are constants, R is the molar gas constant, Ea is the reaction activation energy, P Ge Represents the partial pressure of germanium-containing gas, P Si Represents the partial pressure of silicon-containing gas.

[0022] As a preferred example, before step S2, a step of baking the substrate is also included.

[0023] As a preferred example, the baking step is: introducing hydrogen into the cavity, the baking process temperature is 800° C.-1200° C., and the purpose of baking is to remove moisture and residual carbon oxides on the surface of the substrate.

[0024] As a preferred example, the process temperature is 550°C-750°C.

[0025] Furthermore, the silicon germanium growth rate fitting model is used to infer the silicon germanium growth rate.

[0026] The fitting model proposed in the present invention can accurately infer the growth rate of the silicon-germanium epitaxial layer and is applicable to a wider process temperature range. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the epitaxial device structure of the present invention;

[0028] Figure 2 A flow chart for establishing a fitting model for the present invention;

[0029] Figure 3 It is a curve diagram of the fitting model of the present invention and the actual data;

[0030] Figure 4 Schematic diagram of epitaxial growth of silicon germanium. DETAILED DESCRIPTION

[0031] The following is a further detailed description of a method for establishing a germanium-silicon growth rate fitting model proposed by the present invention in conjunction with the accompanying drawings and specific embodiments. According to the following description, the advantages and features of the present invention will become clearer. It should be noted that the drawings are in a very simplified form and use non-precise proportions, which are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. In order to make the purposes, features and advantages of the present invention more obvious and easy to understand, please refer to the drawings. It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the implementation conditions of the present invention, so they have no technical significance. Any modification of the structure, change in the proportional relationship or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the efficacy and purpose that can be achieved by the present invention.

[0032] See also Figure 1 The method for establishing the germanium-silicon growth rate fitting model proposed in the present invention adopts the following method: Figure 1The epitaxial device shown is implemented, which includes a cavity formed by an upper dome 116 and a lower dome 108 made of quartz, and a base 105 for supporting a substrate 104 is provided in the cavity; a heating component 101 and a thermometer 102 are provided at the top and bottom of the cavity, and the heating component 101 uses infrared radiation to provide thermal energy to the cavity, and the process temperature in the cavity is changed by controlling the power of the heating component 101. The thermometer 102 is used to monitor the temperature near the substrate 104. The chamber further includes an upper liner 100, a lower liner 112, an upper flange 103, and a lower flange 107. The upper liner 100 and lower liner 112 are both quartz rings, positioned inside an upper dome 108 and a lower dome 116, respectively. The upper liner 100 is positioned above the lower liner 112, and has an inlet 113 for process gas 114 and an exhaust port 106 opposite the inlet 113, both located on the sides of the upper and lower liners 100 and 112. The process gas 114 includes a gas containing silicon and germanium and a carrier gas. The upper dome 116 is connected to the upper flange 103, which secures the upper dome 116 to the sidewall. The lower dome 108 is connected to the lower flange 107, which secures the lower dome 108 to the sidewall. A rotational support shaft 109, a support bracket 110, and a pin 111 are provided below the susceptor 105. The rotational support shaft 109 is used to support the rotation and elevation of the susceptor 105, and the support bracket 110 is used to support the pin 111 when the rotational support shaft 109 descends, thereby separating the substrate 104 from the susceptor 105 during transfer. Preheating rings 115 are also provided around the susceptor 105 to preheat the process gas 114 entering the chamber.

[0033] like Figure 2 FIG. 1 is a flow chart of a method for establishing a germanium-silicon growth rate fitting model proposed by the present invention, wherein the germanium-silicon growth rate represents the growth rate of the germanium-silicon epitaxial layer on the substrate. The method comprises the following steps:

[0034] S1. Provide an epitaxial device, wherein the cavity of the device has a base, and the substrate is placed on the base; optionally, the epitaxial device is Figure 1 Epitaxial equipment shown;

[0035] S2. Setting process parameters and introducing process gases into the cavity; the process gases include silicon-containing gas and germanium-containing gas, and the process gases are pyrolyzed at high temperature and then vapor-deposited on the substrate surface to form a germanium-silicon epitaxial layer;

[0036] S3. Obtaining a growth rate of the silicon-germanium epitaxial layer corresponding to the process parameters; optionally, the growth rate is calculated by dividing the thickness of the silicon-germanium epitaxial layer by the deposition time; specifically, after a period of epitaxial layer growth, the substrate is removed from the chamber, and the thickness of the silicon-germanium epitaxial layer during the period is measured using a measuring instrument, and the growth rate is calculated by dividing the thickness by the period;

[0037] S4, changing the process parameters, and repeating steps S2 to S3 to obtain a growth rate of the silicon-germanium epitaxial layer under the changed process parameters;

[0038] S5. Obtaining a germanium-silicon growth rate fitting model related to each process parameter according to each process parameter and the growth rate corresponding to the process parameter;

[0039] The obtained SiGe growth rate fitting model is used to infer the SiGe growth rate in a subsequent epitaxial process.

[0040] According to a large number of experiments, the growth rate of the germanium silicon epitaxial layer is related to the process temperature, the partial pressure of the silicon-containing gas, and the partial pressure of the germanium-containing gas. Figure 4 Figure 2 shows a schematic diagram of growing a germanium-silicon epitaxial layer on a silicon substrate. After high-temperature pyrolysis, germanium- and silicon-containing gases are vapor-deposited on the silicon substrate surface to form an epitaxial layer. This process is greatly affected by the process temperature. Generally speaking, the higher the temperature, the faster the pyrolysis reaction of the gas, and the higher the deposition rate. In addition, the partial pressure of the germanium- and silicon-containing gases also affects the deposition rate. The present invention explores the factors that affect the deposition rate and establishes a fitting model that includes the above factors. Therefore, the process parameters in this example include: process temperature, partial pressure of silicon-containing gas, and partial pressure of germanium-containing gas.

[0041] In step S4, specifically, changing the process parameters includes: changing only the process temperature while maintaining the partial pressure of the silicon-containing gas and the partial pressure of the germanium-containing gas unchanged; and changing only the partial pressure of the silicon-containing gas while maintaining the process temperature and the ratio of the partial pressure of the germanium-containing gas to the partial pressure of the silicon-containing gas unchanged. Changing the process temperature can be achieved by adjusting the power of the heating component. The preferred range of the process temperature is 550°C-750°C, and the more preferred range is 600°C-700°C. Changing the gas partial pressure can be achieved by controlling the flow rate of each gas entering the chamber, such as reducing or increasing the flow rate of the silicon-containing gas to reduce or increase the partial pressure of the silicon-containing gas. In order to achieve the above-mentioned change of only the partial pressure of the silicon-containing gas while maintaining the ratio of the partial pressure of the germanium-containing gas to the partial pressure of the silicon-containing gas unchanged, the flow rates of the silicon-containing gas and the germanium-containing gas can be adjusted synchronously and proportionally to maintain the partial pressure ratio of the two gases unchanged.

[0042] In this example, the silicon-containing gas includes one or more of SiH₄, SiHCl₃, SiH₂Cl₂, and SiCl₄; the germanium-containing gas includes at least one of GeH₄ and Ge₂H₆. The process gas also includes a carrier gas, which can be hydrogen or helium. The silicon-containing and germanium-containing gases are mixed with the carrier gas and introduced into the chamber, where they are then pyrolyzed and vapor-deposited on the substrate surface to form a silicon-germanium epitaxial layer.

[0043] The present invention has experimentally found that the growth rate of germanium silicon is related to the partial pressure of silicon-containing gas, the partial pressure of germanium-containing gas, and the process temperature. Therefore, the germanium silicon growth rate fitting model is a function of the correlation between the growth rate of germanium silicon and the partial pressure of silicon-containing gas, the partial pressure of germanium-containing gas, and the process temperature. As for the specific form of the germanium silicon growth rate fitting model, Figure 3 A curve graph of the fitted model and the actual data is shown, as Figure 3 As shown, the actual growth rate curve can be obtained according to the experiment, and the Arrhenius formula reveals that: growth rate GR = Ke -Ea / RT Therefore, the fitting model of the growth rate of germanium-silicon based on the Arrhenius formula and experimental discovery is a function of the correlation between the growth rate of germanium-silicon and the partial pressure of silicon-containing gas, the partial pressure of germanium-containing gas and the process temperature. Figure 3 The actual growth rate curve is fitted.

[0044] It can be obtained that the fitting model can be expressed by the following function:

[0045]

[0046] Where GR represents the growth rate of germanium silicon, k1, k2, k3 are constants, R is the molar gas constant, Ea is the reaction activation energy, P Ge Represents the partial pressure of germanium-containing gas, P Si represents the partial pressure of silicon-containing gas, and T represents the process temperature.

[0047] In step S5, the germanium-silicon growth rate fitting model for the process parameters is obtained, specifically: each process parameter and the growth rate corresponding to the process parameter are substituted into the above function 1.1, and the constants k1, k2, and k3 in the function 1.1 can be calculated. The calculated constants k1, k2, and k3 are substituted into the function 1.1 to finally obtain the final germanium-silicon growth rate fitting model.

[0048] After obtaining the final germanium-silicon growth rate fitting model, in the application, the process parameters (process temperature T, partial pressure of germanium-containing gas P Ge and the partial pressure P of the silicon-containing gas Si ) into the above final germanium-silicon growth rate fitting model to infer the silicon-germanium growth rate under the process parameters. Figure 3The predicted growth rate can be obtained through the final germanium-silicon growth rate fitting model. The deviation between the predicted growth rate and the actual growth rate is small, and the deviation percentage between the predicted growth rate and the actual growth rate is less than 2.5%, especially when the process temperature is below 925°C, the deviation is even less than 1%; the results show that the final germanium-silicon growth rate fitting model can accurately predict the actual growth rate of silicon germanium.

[0049] In other preferred embodiments, prior to step S2, a step of baking the substrate is further included. The baking step comprises introducing hydrogen into the chamber and baking at a temperature in the range of 800°C to 1200°C to remove moisture and residual carbon oxides from the surface of the silicon substrate. A more preferred baking process temperature range is 850°C to 1050°C.

[0050] In summary, the fitting model proposed in the present invention can accurately calculate the growth rate of the SiGe epitaxial layer, and the process of establishing the fitting model is simple.

[0051] Although the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description is not intended to limit the present invention. After reading the above description, various modifications and substitutions of the present invention will become apparent to those skilled in the art. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A method for establishing a fitting model for the growth rate of silicon germanium, wherein the silicon germanium growth rate is the growth rate of a silicon germanium epitaxial layer on a substrate, characterized in that: The method comprises the following steps: S1. Providing an epitaxial device having a cavity; S2, setting process parameters, introducing process gas into the cavity, and growing a silicon-germanium epitaxial layer on the substrate; S3, obtaining the growth rate of the silicon-germanium epitaxial layer corresponding to the process parameters; S4, changing the process parameters, and repeating steps S2 to S3 to obtain a growth rate of the silicon-germanium epitaxial layer under the changed process parameters; S5. Obtaining a germanium-silicon growth rate fitting model related to each process parameter according to each process parameter and the growth rate corresponding to the process parameter; Wherein, the process gas includes silicon-containing gas and germanium-containing gas; The process parameters include: process temperature, partial pressure of silicon-containing gas, partial pressure of germanium-containing gas; The germanium-silicon growth rate fitting model is: Where GR represents the growth rate of germanium silicon, k1, k2, k3 are constants, R is the molar gas constant, Ea is the reaction activation energy, P Ge Represents the partial pressure of germanium-containing gas, P Si represents the partial pressure of silicon-containing gas, and T represents the process temperature.

2. The method for establishing a germanium-silicon growth rate fitting model according to claim 1, wherein: Changing the process parameters includes: changing only the process temperature while keeping the partial pressures of the silicon-containing gas and the germanium-containing gas unchanged, and changing only the partial pressure of the silicon-containing gas while keeping the process temperature and the ratio of the partial pressures of the germanium-containing gas to the partial pressure of the silicon-containing gas unchanged.

3. The method for establishing a germanium-silicon growth rate fitting model according to claim 1, wherein: The process gas also includes a carrier gas.

4. The method for establishing a germanium-silicon growth rate fitting model according to claim 1, wherein: The silicon-containing gas includes one or more of SiH4, SiHCl3, SiH2Cl2 and SiCl4.

5. The method for establishing a germanium-silicon growth rate fitting model according to claim 1, wherein: The germanium-containing gas contains at least one of GeH4 and Ge2H6.

6. The method for establishing a germanium-silicon growth rate fitting model according to claim 2, wherein: The partial pressure of the silicon-containing gas in the cavity is adjusted by adjusting the flow rate of the silicon-containing gas entering the cavity; the partial pressure of the germanium-containing gas in the cavity is adjusted by adjusting the flow rate of the germanium-containing gas entering the cavity.

7. The method for establishing a germanium-silicon growth rate fitting model according to claim 6, wherein: The germanium-silicon growth rate fitting model is a function of the correlation between the germanium-silicon growth rate and the partial pressure of the silicon-containing gas, the partial pressure of the germanium-containing gas, and the process temperature.

8. The method for establishing a germanium-silicon growth rate fitting model according to claim 1, wherein: Before step S2, a step of baking the substrate is also included.

9. The method for establishing a germanium-silicon growth rate fitting model according to claim 8, wherein: The baking step includes: introducing hydrogen into the cavity, and the baking process temperature is 800° C.-1200° C.

10. The method for establishing a germanium-silicon growth rate fitting model according to claim 1, wherein: The process temperature is 550°C-750°C.

11. The method for establishing a germanium-silicon growth rate fitting model according to claim 1, wherein: The silicon germanium growth rate fitting model is used to estimate the silicon germanium growth rate.

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