Germanium virtual substrate epitaxy manufacturing method
By using low-temperature and high-temperature epitaxial growth of germanium films on silicon substrates and performing high-temperature in-situ annealing after each epitaxial, the problems of defects and dislocations of existing germanium imaginary substrate films are solved, and high quality is achieved The preparation of germanium imaginary substrate improves the production quality and optical performance of subsequent devices.
Patent Information
- Application Number
- CN202411530890.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-30
- Publication Date
- 2025-02-14
AI Technical Summary
The germanium film obtained by the existing germanium virtual substrate production method has many defects and dislocations or has rough surfaces, which affects the production quality and optical performance of subsequent devices.
The method of growing germanium films at low temperature and high temperature epitaxial is adopted, and high-temperature in-situ annealing is performed after each epitaxial, and cycles are performed to reduce point defects and mismatch dislocations, and finally a high-quality germanium imaginary substrate is obtained.
Through this method, the point defect density and mismatch dislocation density of the germanium film can be significantly reduced, the flatness and crystal quality of the film can be improved, and the dummy substrate performance of the subsequent epitaxial of the germanium tin film can be improved.
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Figure CN119433694A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of semiconductor production and application, and in particular to a germanium virtual substrate epitaxial manufacturing method. Background Art
[0002] In the semiconductor field of optoelectronic applications on CMOS logic chips, the IV group semiconductor germanium-tin alloy is triggering a widespread research boom. Compared with traditional silicon and germanium materials, germanium-tin exhibits more superior properties. Its carrier mobility and bandgap energy are not only higher, but also controllable. When the tin content exceeds 8%, the bandgap characteristics of the germanium-tin alloy will change from indirect bandgap to direct bandgap, which makes it an ideal choice for manufacturing group IV optoelectronic devices such as light-emitting diodes, lasers and high-speed photodetectors. With the continuous expansion of group IV electronic and photonic logic technology and the development of system-on-chip (SOC) integration, germanium-tin alloy is gradually becoming a star material in the future integrated circuit (IC) field. However, due to the large lattice mismatch between silicon materials and germanium-tin materials, epitaxial growth of germanium-tin thin films directly on silicon substrates will produce a large number of mismatch dislocations, which is not conducive to the manufacture of semiconductor devices. A feasible solution is to first epitaxially grow a germanium buffer layer on a silicon substrate as a virtual substrate, and then continue to epitaxially grow germanium-tin thin films on the germanium virtual substrate. In this way, the huge lattice mismatch between the germanium-tin material and the single crystal silicon substrate can be mitigated.
[0003] However, the germanium thin film obtained by the existing virtual substrate manufacturing method has many defects and dislocations or a rough surface, which affects the subsequent device manufacturing quality and optical performance. Summary of the invention
[0004] In view of the above problems existing in the prior art, the present invention proposes a germanium virtual substrate epitaxial manufacturing method, which mainly solves the problem that the germanium film obtained by the existing germanium virtual substrate manufacturing method has many defects and dislocations or a rough surface, which affects the subsequent device manufacturing quality and optical performance.
[0005] In order to achieve the above purpose and other purposes, the technical solution adopted by the present invention is as follows.
[0006] The present application provides a method for manufacturing germanium virtual substrate epitaxy, comprising: providing a substrate; sequentially performing low-temperature epitaxial and high-temperature epitaxial growth of a germanium film on the substrate to obtain a first sample, wherein the first sample comprises a low-temperature epitaxial germanium layer and a high-temperature epitaxial germanium layer stacked in sequence; performing high-temperature in-situ annealing on the first sample to eliminate point defects in the low-temperature epitaxial germanium layer and the high-temperature epitaxial germanium layer and to suppress misfit dislocations in the low-temperature epitaxial germanium layer; lowering the temperature of the substrate to a first target temperature for low-temperature epitaxial growth and then sequentially performing low-temperature epitaxial and high-temperature epitaxial growth of a germanium film to obtain a second sample; performing high-temperature in-situ annealing on the second sample to obtain a target epitaxial germanium film.
[0007] In one embodiment of the present application, the step of providing a substrate includes: sequentially cleaning, drying and deoxidizing a wafer to obtain the substrate.
[0008] In one embodiment of the present application, the process conditions of the deoxidation treatment include: deoxidation for 30 minutes under heating to 1000° C. in a vacuum chamber.
[0009] In one embodiment of the present application, after the low-temperature epitaxy is completed, the epitaxial growth is not terminated, and the substrate temperature continues to be increased to the second target temperature of the high-temperature epitaxy based on a preset temperature increase gradient.
[0010] In one embodiment of the present application, the temperature of the germanium source is adjusted to 1150° C. during the low-temperature epitaxy.
[0011] The temperature of the germanium source is adjusted to 900° C. during the high temperature epitaxy.
[0012] In one embodiment of the present application, the first target temperature is not higher than 380°C.
[0013] In an embodiment of the present application, the second target temperature includes 600°C.
[0014] In an embodiment of the present application, the thicknesses of the low-temperature epitaxial germanium layer and the high-temperature epitaxial germanium layer are 150 nm and 200 nm, respectively.
[0015] In one embodiment of the present application, the process conditions of the high-temperature in-situ annealing include: raising the substrate temperature to 800° C. and performing in-situ annealing for 30 minutes.
[0016] The present application also provides a germanium virtual substrate, which is obtained based on the germanium virtual substrate epitaxial manufacturing method.
[0017] As described above, the epitaxial manufacturing method of a germanium virtual substrate and the germanium virtual substrate proposed in the present application have the following beneficial effects.
[0018] The present application performs low-temperature and high-temperature epitaxy on a substrate and then performs high-temperature in-situ annealing, and then performs low-temperature, high-temperature epitaxy and high-temperature annealing in a cycle to obtain a high-quality film. The point defect density of the low-temperature epitaxial germanium layer can be reduced after the first high-temperature annealing. The second low-temperature epitaxy is homogeneous epitaxy relative to the first sample, which makes the second low-temperature epitaxy almost free of mismatch dislocation, and the second low-temperature epitaxy can make the sample surface smooth, and a large number of point defects can be eliminated through the second high-temperature epitaxy. After the second high-temperature annealing, a germanium film with high crystal quality and low surface roughness can be obtained, which can be used as a virtual substrate for subsequent germanium-tin film epitaxy. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Figure 1The figure is a flow chart and a structural diagram of one of the conventional epitaxial germanium thin film methods.
[0020] Figure 2 It is a flow chart and a structural diagram of another traditional epitaxial germanium thin film method.
[0021] Figure 3 Schematic diagram of the process of epitaxial manufacturing method of germanium virtual substrate in one embodiment of the present application.
[0022] Figure 4 It is a flow chart of a method for epitaxially manufacturing a germanium virtual substrate and a corresponding structural chart in one embodiment of the present application.
[0023] Figure 5 Schematic diagram of the surface AFM of an intrinsic Si substrate wafer including the substrate surface roughness (RMS).
[0024] Figure 6 This is a HRXRD schematic diagram of the epitaxial germanium film in Example 1 of the present application.
[0025] Figure 7 is a surface AFM schematic diagram of the epitaxial germanium film in Example 1 of the present application;
[0026] Figure 8 This is a HRXRD schematic diagram of the epitaxial germanium film in Example 2 of the present application.
[0027] Fig. 9 This is a surface AFM schematic diagram of the epitaxial germanium film in Example 2 of the present application.
[0028] Fig.10 This is a schematic diagram of HRXRD of the epitaxial germanium film in Example 3 of the present application.
[0029] Fig.11 This is a surface AFM schematic diagram of the epitaxial germanium film in Example 3 of the present application. DETAILED DESCRIPTION
[0030] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.
[0031] It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and thus the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.
[0032] The inventors have found that:
[0033] Due to the huge lattice mismatch between silicon and germanium-tin materials, epitaxial growth of germanium-tin thin films directly on silicon substrates will produce a large number of mismatch dislocations, which is not conducive to the manufacture of semiconductor devices. A feasible solution is to first grow a germanium buffer layer on the silicon substrate as a virtual substrate, and then continue to grow the germanium-tin thin film on the germanium virtual substrate. In this way, the huge lattice mismatch between the germanium-tin material and the Si substrate can be alleviated.
[0034] See also Figure 1 , Figure 1 The figure is a flow chart and a structural diagram of one of the conventional epitaxial germanium thin film methods.
[0035] The method comprises the following steps:
[0036] 1-1. Use RCA (Radio Corporation of America) standard cleaning to remove organic matter, particles, metal and other pollutants on the surface of the silicon wafer, and passivate the surface of the silicon wafer;
[0037] 1-2, high temperature deoxidation to remove the passivation layer on the surface of the silicon wafer to obtain a clean substrate 101;
[0038] 1-3, epitaxially growing a germanium thin film 102 on 101 at a low temperature (~300°C);
[0039] 1-4. Perform 102 high temperature cycle annealing 2-3 times at a temperature range of 500-750°C to obtain a single crystal germanium film.
[0040] The low temperature in this epitaxial method causes a large number of point defects in the germanium layer 101 during its growth, forming non-radiative recombination centers and light scattering centers, which will have an adverse effect on the performance of the optical film. Although subsequent high-temperature annealing will reduce the defect density, the threading dislocations caused by lattice mismatch will extend and diffuse to the wafer surface, forming new non-radiative recombination centers.
[0041] See also Figure 2 , Figure 2 It is a flow chart and a structural diagram of another traditional epitaxial germanium thin film method.
[0042] The method comprises the following steps:
[0043] 2-1. Use RCA (Radio Corporation of America) standard cleaning to remove organic matter, particles, metal and other pollutants on the surface of the silicon wafer, and passivate the surface of the silicon wafer;
[0044] 2-2, high temperature deoxidation to remove the passivation layer on the surface of the silicon wafer to obtain a clean substrate 201;
[0045] 2-3. Low temperature (~300-350℃) epitaxial germanium film 202;
[0046] 2-4. Epitaxially grow the germanium film 203 at a high temperature (~450-550°C) to obtain a single crystal germanium film.
[0047] Although this epitaxial method suppresses dislocations and point defects in the low-temperature germanium layer 201, high-temperature growth will cause the surface roughness of the film 202 to increase significantly, which will affect the subsequent CMP process flow, resulting in uneven distribution of the optical film layers, affecting the light field distribution of the product, and thus causing product instability.
[0048] Based on the problems existing in the above existing methods, the present application proposes a germanium virtual substrate epitaxial manufacturing method and a germanium virtual substrate. The technical solution of the present application is described in detail below in conjunction with specific embodiments.
[0049] See also Figure 3 , Figure 3 The method provided in the embodiment of the present application comprises the following steps:
[0050] Step S300, providing a single crystal silicon substrate. Specifically, the substrate may be a silicon substrate. The step of providing the substrate may include: sequentially cleaning, drying and deoxidizing the wafer. During the deoxidation treatment, the wafer may be placed in a vacuum chamber and deoxidized at 1000° C. for 30 minutes, and then epitaxial growth may be performed on the wafer.
[0051] Step S310, sequentially growing a germanium thin film by low-temperature epitaxial growth and high-temperature epitaxial growth on the substrate to obtain a first sample, wherein the first sample comprises a low-temperature epitaxial germanium layer and a high-temperature epitaxial germanium layer stacked sequentially.
[0052] In one embodiment, after adjusting the substrate temperature to a first target temperature during low-temperature epitaxy, epitaxial growth is performed at a preset growth rate, wherein the first target temperature is not higher than 380°C. For example, the temperature of low-temperature epitaxy can be set to 330°C, 360°C, or 380°C, etc., and can be set and adjusted according to actual production application requirements, and is not limited here. The thickness of the low-temperature epitaxially grown germanium film (i.e., the thickness of the low-temperature epitaxial germanium layer) can be set to 150nm.
[0053] In one embodiment, after the low-temperature epitaxy is completed, the epitaxial growth is not terminated, and the substrate temperature is continued to be raised to the second target temperature of the high-temperature epitaxy based on the preset temperature rise gradient. The specific temperature rise gradient can be set and adjusted according to the actual application requirements, and is not limited here. The second target temperature can be set to 600°C. The thickness of the high-temperature epitaxial germanium layer obtained by the high-temperature epitaxy can include 200nm.
[0054] In one embodiment, when performing low-temperature epitaxy, the germanium source temperature may be adjusted to 1150° C., and when performing high-temperature epitaxy, the germanium source temperature may be adjusted to 900° C. Epitaxial growth is performed at the corresponding germanium source temperature.
[0055] Step S320, performing high-temperature in-situ annealing on the first sample to eliminate point defects in the low-temperature epitaxial germanium layer and the high-temperature epitaxial germanium layer and suppress misfit dislocations in the low-temperature epitaxial germanium layer.
[0056] In one embodiment, the process conditions of high temperature annealing include: raising the substrate temperature to 800° C. and performing in-situ annealing for 30 minutes. The high temperature annealing eliminates point defects in the high temperature epitaxial germanium layer and suppresses misfit dislocations in the low temperature epitaxial germanium layer.
[0057] Step S330, after lowering the temperature of the substrate to the first target temperature of low-temperature epitaxial growth, low-temperature epitaxial growth and high-temperature epitaxial growth of germanium thin film are performed in sequence to obtain a second sample. Homogeneous epitaxy is performed on the sample after the first high-temperature epitaxy, and there is almost no misfit dislocation, which can greatly improve the crystal quality.
[0058] Step S340, performing high-temperature in-situ annealing on the second sample to obtain a target epitaxial germanium thin film.
[0059] See also Figure 4 , Figure 4 It is a flow chart of a method for epitaxially manufacturing a germanium virtual substrate and a corresponding structural chart in one embodiment of the present application.
[0060] The process steps of the manufacturing method are as follows:
[0061] 1) Use RCA (Radio Corporation of America) standard cleaning to remove organic matter, particles, metal and other pollutants on the surface of the silicon wafer, and passivate the surface of the silicon wafer;
[0062] 2) high temperature deoxidation to remove the passivation layer on the surface of the silicon wafer to obtain a clean substrate 301;
[0063] 3) low temperature epitaxial germanium film to obtain a first low temperature epitaxial germanium layer 302;
[0064] 4) high temperature epitaxial germanium film to obtain a first high temperature epitaxial germanium layer 303;
[0065] 5) High temperature in-situ annealing;
[0066] 6) After lowering the substrate temperature, epitaxially growing a germanium film again to obtain a second low-temperature epitaxial germanium layer 304;
[0067] 7) high temperature epitaxial germanium film to obtain a second high temperature epitaxial germanium layer 305;
[0068] 8) High temperature in-situ annealing to obtain the target epitaxial germanium virtual substrate film.
[0069] The present invention obtains a high-quality germanium virtual substrate film by a method of performing high-temperature in-situ annealing and recycle epitaxial annealing after low-temperature / high-temperature epitaxial germanium film on a silicon substrate. The first low-temperature epitaxial germanium layer 302 has a relatively high point defect, which can reduce the linear dislocation density caused by lattice mismatch. Under high temperature conditions, a first high-temperature epitaxial germanium layer 303 with good quality can be epitaxially grown on the low-temperature germanium. After the first high-temperature annealing, the point defect density in the first low-temperature epitaxial germanium layer 302 can be greatly reduced to obtain a single crystal germanium film with high crystal quality, but this sacrifices the flatness of the film. The second low-temperature epitaxial germanium layer 304 is homogeneous with respect to the first high-temperature epitaxial germanium layer 303 which has formed a single crystal for the first time. This makes it that the second epitaxial low-temperature germanium film 304 will hardly produce misfit dislocations, and the low-temperature epitaxy will make the film surface smooth. However, there are still a large number of point defects in the second low-temperature epitaxial germanium layer 304. The second high-temperature epitaxial germanium layer 305 is continuously grown epitaxially. Since the second low-temperature epitaxial germanium layer 304 is already a flat film, the roughness of the film 305 is also extremely low. After annealing again, an epitaxial germanium film with high crystal quality and extremely low surface roughness can be obtained, which can be used as a virtual substrate for the subsequent epitaxy of germanium-tin thin films.
[0070] Embodiment 1
[0071] The equipment used in the epitaxial manufacturing method of the virtual germanium substrate of the embodiment of the present application is a self-built dual-chamber ultra-high vacuum chemical vapor deposition (UHV-CVD) system, in which the growth chamber on one side of the system is equipped with a molecular beam epitaxy (MBE) beam source furnace. The beam source furnace used is intrinsic Ge (99.9999% purity) in a boron nitride (p-BN) crucible, and a four-inch single-sided polished n-type intrinsic Si (001) wafer is selected as the substrate for the epitaxial Ge film, with a resistivity of 0.1Ω.cm-1.2Ω.cm.
[0072] 1. Processing of Si substrate materials:
[0073] 1) Prepare liquid III H2SO4:H2O2=3:1 in a customized quartz cup to remove some metal and heavy organic pollution on the surface of the silicon wafer. Boil the silicon wafer in the solution for 10 minutes, then take it out and rinse it with deionized water 15 times to clean it.
[0074] 2) Soak the silicon wafer cleaned with solution III in DHF (HF:H2O=1:20) solution for 4 minutes to remove the oxide film on the surface of the silicon wafer and remove the metals such as Fe, Al, Zn attached to the surface of the silicon wafer. Then take it out and rinse it with deionized water 15 times to clean it.
[0075] 3) After DHF cleaning, prepare solution No. 1 NH4OH:H2O2:H2O=1:1:4 to remove particles on the surface of silicon substrate. Put the silicon wafer into the solution and boil it for 10 minutes, then take it out and rinse it with deionized water 15 times to clean it.
[0076] 4) Soak the silicon wafer after cleaning with solution I in DHF (HF:H2O=1:20) solution for 4 minutes to remove oxidation on the surface of the silicon wafer, then take it out and rinse it with deionized water 15 times to clean it.
[0077] 5) Finally, HPM solution II was prepared with HCl:H2O2:H2O=1:1:4 to remove metal contamination such as Na, Fe, and Mg on the surface of the silicon wafer. The silicon wafer was placed in the solution and boiled for 10 minutes, and a SiO2 passivation film was formed on the surface of the silicon wafer again. Finally, the silicon wafer was rinsed with deionized water 15 times.
[0078] 2. Epitaxial growth of Ge thin film:
[0079] 1) After cleaning, the silicon wafer is dried at 4000 rpm for 30 seconds and then placed in the deposition system. It is then baked at 200°C to remove residual moisture on the surface of the substrate. The sample is then placed in the growth chamber, where the background vacuum is 1x10-7Pa. Before epitaxial growth, deoxidation treatment can be performed at 1000°C in the vacuum chamber for 30 minutes.
[0080] 2) adjusting the germanium source temperature to 1150°C, the sample holder rotation speed to 10 rpm, the substrate temperature to 330°C, and epitaxially growing a 150 nm germanium film on a silicon (001) substrate at an epitaxial rate of 1.2 nm / min;
[0081] 3) Linearly increase the substrate temperature (do not terminate the epitaxial process during this process) to 600°C at a heating rate of 5°C / min, and continue to grow a 200nm germanium film;
[0082] 4) Pause the epitaxial germanium film, reduce the germanium source temperature to 900°C, maintain the cooling rate at 2-5°C / min, increase the substrate temperature to 800°C for in-situ annealing for 30 minutes, and the first epitaxial germanium film is completed;
[0083] 5) Lower the substrate temperature to 330°C, raise the germanium source temperature to 1150°C again, and continue to grow a 150nm germanium film;
[0084] 6) Linearly increase the substrate temperature (do not terminate the epitaxial process during this process) to 600°C at a heating rate of 5°C / min, and continue to grow a 200nm germanium film;
[0085] 7) Pause the epitaxial germanium film, reduce the germanium source temperature to 900°C, maintain the cooling rate at 2-5°C / min, increase the substrate temperature to 800°C for in-situ annealing for 30 minutes, and the second epitaxial germanium film is completed.
[0086] 8) The epitaxial germanium film was subjected to HRXRD and AFM tests. Figure 6 It can be seen that the epitaxial germanium film is a single crystal film with high crystal quality. Figure 7 It can be seen that the surface of the epitaxial germanium film is flat, with a roughness (RMS) of 0.56nm, which is close to Figure 5 Silicon substrate RMS = 0.208nm.
[0087] Embodiment 2
[0088] The equipment used in the epitaxial manufacturing method of the virtual germanium substrate of the embodiment of the present application is a self-built dual-chamber ultra-high vacuum chemical vapor deposition (UHV-CVD) system, in which the growth chamber on one side of the system is equipped with a molecular beam epitaxy (MBE) beam source furnace. The beam source furnace used is intrinsic Ge (99.9999% purity) in a boron nitride (p-BN) crucible, and a four-inch single-sided polished n-type intrinsic Si (001) wafer is selected as the substrate for the epitaxial Ge film, with a resistivity of 0.1Ω.cm-1.2Ω.cm.
[0089] 1. Processing of Si substrate materials:
[0090] 1) Prepare liquid III H2SO4:H2O2=3:1 in a customized quartz cup to remove some metal and heavy organic pollution on the surface of the silicon wafer. Boil the silicon wafer in the solution for 10 minutes, then take it out and rinse it with deionized water 15 times to clean it.
[0091] 2) Soak the silicon wafer cleaned with solution III in DHF (HF:H2O=1:20) solution for 4 minutes to remove the oxide film on the surface of the silicon wafer and remove the metals such as Fe, Al, Zn attached to the surface of the silicon wafer. Then take it out and rinse it with deionized water 15 times to clean it.
[0092] 3) After DHF cleaning, prepare solution I of NH4OH:H2O2:H2O=1:1:4 to remove particles on the surface of silicon substrate. Put the silicon wafer into the solution and boil it for 10 minutes, then take it out and rinse it with deionized water 15 times to clean it.
[0093] 4) Soak the silicon wafer after cleaning with solution I in DHF (HF:H2O=1:20) solution for 4 minutes to remove oxidation on the surface of the silicon wafer, then take it out and rinse it with deionized water 15 times to clean it.
[0094] 5) Finally, HPM solution II was prepared with HCl:H2O2:H2O=1:1:4 to remove metal contamination such as Na, Fe, and Mg on the surface of the silicon wafer. The silicon wafer was placed in the solution and boiled for 10 minutes, and a SiO2 passivation film was formed on the surface of the silicon wafer again. Finally, the silicon wafer was rinsed with deionized water 15 times.
[0095] 2. Epitaxial growth of Ge thin film:
[0096] 1) After cleaning, the silicon wafer is dried at 4000 rpm for 30 seconds and then placed in the deposition system. It is then baked at 200°C to remove residual moisture on the surface of the substrate. The sample is then placed in the growth chamber, where the background vacuum is 1x10-7Pa. Before epitaxial growth, deoxidation treatment can be performed at 1000°C in the vacuum chamber for 30 minutes.
[0097] 2) adjusting the germanium source temperature to 1150°C, the sample holder rotation speed to 10 rpm, the substrate temperature to 360°C, and epitaxially growing a 150 nm germanium film on a silicon (001) substrate at an epitaxial rate of 1.2 nm / min;
[0098] 3) Linearly increase the substrate temperature (do not terminate the epitaxial process during this process) to 600°C at a heating rate of 5°C / min, and continue to grow a 200nm germanium film;
[0099] 4) Pause the epitaxial germanium film, reduce the germanium source temperature to 900°C, maintain the cooling rate at 2-5°C / min, increase the substrate temperature to 800°C for in-situ annealing for 30 minutes, and the first epitaxial germanium film is completed;
[0100] 5) Lower the substrate temperature to 360°C, raise the germanium source temperature to 1150°C again, and continue to grow a 150nm germanium film;
[0101] 6) Linearly increase the substrate temperature (do not terminate the epitaxial process during this process) to 600°C at a heating rate of 5°C / min, and continue to grow a 200nm germanium film;
[0102] 7) Pause the epitaxial germanium film, reduce the germanium source temperature to 900°C, maintain the cooling rate at 2-5°C / min, increase the substrate temperature to 800°C for in-situ annealing for 30 minutes, and the second epitaxial germanium film is completed.
[0103] 8) The epitaxial germanium film was subjected to HRXRD and AFM tests. Figure 8It can be seen that the epitaxial germanium film is a single crystal film with high crystal quality. Fig. 9 It can be seen that the surface of the epitaxial germanium film is flat, with a roughness (RMS) of 0.30nm, which is close to Figure 5 The silicon substrate RMS = 0.208 nm, which is lower in flatness than the first example.
[0104] Embodiment 3
[0105] The equipment used in the epitaxial manufacturing method of the virtual germanium substrate provided in the embodiment of the present application is a self-built dual-chamber ultra-high vacuum chemical vapor deposition (UHV-CVD) system, in which the growth chamber on one side of the system is equipped with a molecular beam epitaxy (MBE) beam source furnace. The beam source furnace used is intrinsic Ge (99.9999% purity) in a boron nitride (p-BN) crucible, and a four-inch single-sided polished n-type intrinsic Si (001) wafer is selected as the substrate for the epitaxial Ge film, with a resistivity of 0.1Ω.cm-1.2Ω.cm.
[0106] 1. Processing of Si substrate materials:
[0107] 1) Prepare liquid III H2SO4:H2O2=3:1 in a customized quartz cup to remove some metal and heavy organic pollution on the surface of the silicon wafer. Boil the silicon wafer in the solution for 10 minutes, then take it out and rinse it with deionized water 15 times to clean it.
[0108] 2) Soak the silicon wafer cleaned with solution III in DHF (HF:H2O=1:20) solution for 4 minutes to remove the oxide film on the surface of the silicon wafer and remove the metals such as Fe, Al, Zn attached to the surface of the silicon wafer. Then take it out and rinse it with deionized water 15 times to clean it.
[0109] 3) After DHF cleaning, prepare solution No. 1 NH4OH:H2O2:H2O=1:1:4 to remove particles on the surface of silicon substrate. Put the silicon wafer into the solution and boil it for 10 minutes, then take it out and rinse it with deionized water 15 times to clean it.
[0110] 4) Soak the silicon wafer after cleaning with solution I in DHF (HF:H2O=1:20) solution for 4 minutes to remove oxidation on the surface of the silicon wafer, then take it out and rinse it with deionized water 15 times to clean it.
[0111] 5) Finally, HPM solution II was prepared with HCl:H2O2:H2O=1:1:4 to remove metal contamination such as Na, Fe, and Mg on the surface of the silicon wafer. The silicon wafer was placed in the solution and boiled for 10 minutes, and a SiO2 passivation film was formed on the surface of the silicon wafer again. Finally, the silicon wafer was rinsed with deionized water 15 times.
[0112] 2. Epitaxial growth of Ge thin film:
[0113] 1) After cleaning, the silicon wafer is dried at 4000 rpm for 30 seconds and then placed in the deposition system. It is then baked at 200°C to remove residual moisture on the surface of the substrate. The sample is then placed in the growth chamber, where the background vacuum is 1x10-7Pa. Before epitaxial growth, deoxidation treatment can be performed at 1000°C in the vacuum chamber for 30 minutes.
[0114] 2) adjusting the germanium source temperature to 1150°C, the sample holder rotation speed to 10 rpm, the substrate temperature to 380°C, and epitaxially growing a 150 nm germanium film on a silicon (001) substrate at an epitaxial rate of 1.2 nm / min;
[0115] 3) Linearly increase the substrate temperature (do not terminate the epitaxial process during this process) to 600°C at a heating rate of 5°C / min, and continue to grow a 200nm germanium film;
[0116] 4) Pause the epitaxial germanium film, reduce the germanium source temperature to 900°C, maintain the cooling rate at 2-5°C / min, increase the substrate temperature to 800°C for in-situ annealing for 30 minutes, and the first epitaxial germanium film is completed;
[0117] 5) Lower the substrate temperature to 380°C, raise the germanium source temperature to 1150°C again, and continue to grow a 150nm germanium film;
[0118] 6) Linearly increase the substrate temperature (do not terminate the epitaxial process during this process) to 600°C at a heating rate of 5°C / min, and continue to grow a 200nm germanium film;
[0119] 7) Pause the epitaxial germanium film, reduce the germanium source temperature to 900°C, maintain the cooling rate at 2-5°C / min, increase the substrate temperature to 800°C for in-situ annealing for 30 minutes, and the second epitaxial germanium film is completed.
[0120] 8) The epitaxial germanium film was subjected to HRXRD and AFM tests. Fig.10 It can be seen that the epitaxial germanium film is a single crystal film with high crystal quality. Fig.11 It can be seen that the surface of the epitaxial germanium film is flat, with a roughness (RMS) of 0.22nm, which is completely close to Figure 5 The silicon substrate RMS = 0.208nm, and an epitaxial germanium film with high crystal quality and high surface flatness was obtained.
[0121] refer to Figure 5-11 As shown, the HRXRD and AFM characterization images obtained in the embodiments of the present application show that after reasonable temperature control, the crystal quality of the epitaxial germanium film is high and the surface flatness is almost close to that of the substrate, which can be used as a virtual substrate for the subsequent external GeSn film to complete the optical thin film manufacturing process.
[0122] In one embodiment, the present application further provides a germanium virtual substrate, which is obtained based on the aforementioned germanium virtual substrate epitaxial manufacturing method, and the specific manufacturing process is not repeated here.
[0123] The present invention is described in detail above through specific implementation methods and examples, and at the same time, feasible evidence is given, but it does not constitute a limitation of the present invention. Without departing from the principle of the present invention, those skilled in the art can also make many modifications and changes, such as changing the epitaxial method to CVD, sputtering, etc., which should also be regarded as the protection scope of the present invention.
Claims
1. A method for epitaxially manufacturing a germanium virtual substrate, characterized in that: include: Providing a single crystal silicon substrate; Growing a germanium film on the substrate by low-temperature epitaxy and high-temperature epitaxy in sequence to obtain a first sample, wherein the first sample comprises a low-temperature epitaxial germanium layer and a high-temperature epitaxial germanium layer stacked in sequence; Performing high-temperature in-situ annealing on the first sample to eliminate point defects in the low-temperature epitaxial germanium layer and the high-temperature epitaxial germanium layer and suppress misfit dislocations in the low-temperature epitaxial germanium layer; After lowering the temperature of the substrate to a first target temperature for low-temperature epitaxial growth, sequentially growing a germanium thin film by low-temperature epitaxy and high-temperature epitaxy to obtain a second sample; The second sample is subjected to high-temperature in-situ annealing to obtain a target epitaxial germanium virtual substrate film.
2. The method for epitaxially manufacturing a germanium virtual substrate according to claim 1, characterized in that: The step of providing a single crystal silicon substrate comprises: The wafer is sequentially cleaned, dried and deoxidized to obtain the substrate.
3. The method for epitaxially manufacturing a germanium virtual substrate according to claim 2, characterized in that: The process conditions of the deoxidation treatment include: heating to 1000° C. in a vacuum chamber and deoxidizing for 30 minutes.
4. The method for epitaxially manufacturing a germanium virtual substrate according to claim 1, characterized in that: After the low-temperature epitaxy is completed, the epitaxial growth is not terminated, and the substrate temperature continues to be increased to the second target temperature of the high-temperature epitaxy based on a preset temperature increase gradient.
5. The method for epitaxially manufacturing a germanium virtual substrate according to claim 4, characterized in that: When performing the low-temperature epitaxy, the temperature of the germanium source is adjusted to 1150° C., and when performing the high-temperature epitaxy, the temperature of the germanium source is adjusted to 900° C.
6. The method for epitaxially manufacturing a germanium virtual substrate according to claim 1, characterized in that: The first target temperature is not higher than 380°C.
7. The method for epitaxially manufacturing a germanium virtual substrate according to claim 4, characterized in that: The second target temperature comprises 600°C.
8. The method for epitaxially manufacturing a germanium virtual substrate according to any one of claims 1 to 6, characterized in that: The thicknesses of the low-temperature epitaxial germanium layer and the high-temperature epitaxial germanium layer are 150 nm and 200 nm respectively.
9. The method for epitaxially manufacturing a germanium virtual substrate according to claim 1, characterized in that: The process conditions of the high temperature in-situ annealing include: raising the substrate temperature to 800° C. and performing in-situ annealing for 30 minutes.
10. A germanium virtual substrate, characterized in that: The germanium virtual substrate is obtained based on the germanium virtual substrate epitaxial manufacturing method according to any one of claims 1-9.