A film removal method in a molecular beam epitaxy process

Abstract

The present invention provides a film removal method in a molecular beam epitaxy process, which relates to the technical field of semiconductor manufacturing. The method includes: heating an InP substrate to a first film removal temperature under a preset As pressure condition; maintaining at the first film removal temperature for a first period of time; heating from the first film removal temperature to a second film removal temperature; maintaining at the second film removal temperature for a third period of time, and then the film removal process ends. By maintaining at the first film removal temperature slightly lower than the reference temperature for the first period of time, the substrate is fully heated while reducing the desorption of phosphorus. Due to the full heating, the time required for the complete desorption of surface oxides at the second film removal temperature is reduced, so that the surface defects of the epitaxial wafer can be significantly reduced and the surface quality of the epitaxial wafer can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor manufacturing, and particularly to a method for removing a film in a molecular beam epitaxy process. Background Art

[0002] For the molecular beam epitaxy (MBE) growth of InP-based epitaxial materials, first, the InP substrate needs to be subjected to a high-temperature film removal treatment in a molecular beam epitaxy equipment to remove the natural oxide on the surface of the InP substrate, and then, according to the device structure design, the corresponding epitaxial layer is deposited and grown. In the large-scale mass production of InP-based semiconductor devices, the quality of the molecular beam epitaxy high-temperature film removal process directly affects the surface defect density of the InP-based semiconductor device epitaxial wafer prepared, and further affects the yield and reliability of the final device. If the film removal time is too short, the surface oxide cannot be completely desorbed, which will lead to the formation of defects during the subsequent epitaxial growth process; if the film removal time is too long, phosphorus desorption will occur and a large number of InAs microcrystals will be formed, and these InAs microcrystals will also lead to the formation of defects during the subsequent epitaxial growth process. Therefore, whether the film removal time is too long or too short, the defect density of the substrate surface and the epitaxial wafer will increase. The more surface defects the epitaxial wafer has, the lower the yield of the device, and at the same time, the worse the reliability of the device.

[0003] Therefore, for the mass production of InP-based semiconductor device epitaxial wafers, a molecular beam epitaxy film removal process needs to be proposed to reduce the surface defect density of the InP-based semiconductor device epitaxial wafers and improve the quality of the InP-based semiconductor device epitaxial wafers. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for removing a film in a molecular beam epitaxy process to solve the problem of reducing surface defects caused by the film removal of the InP substrate, aiming at the above-mentioned deficiencies of the prior art.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] The present invention provides a method for removing a film in a molecular beam epitaxy process, which is used for removing the film from the InP substrate, and the method includes:

[0007] Step a: Under a preset As pressure condition, heat the InP substrate to a first film removal temperature, and the first film removal temperature is 4°C to 6°C lower than the previously obtained reference temperature, and the reference temperature is the substrate temperature when the InP substrate is heated and raised to the RHEED pattern showing a ×4 reconstruction stripe under the preset As pressure condition;

[0008] Step b: Keep for a first time period at the first film removal temperature, and the range of the first time period t1 is 6 min ≤ t1 ≤ 14 min;

[0009] Step c: Heat up from the first demolding temperature to the second demolding temperature. The time required for this heating process is the second time period. The range of the second time period t2 is 0.5 min ≤ t2 ≤ 2 min, and the range of the difference between the second demolding temperature and the reference temperature is greater than or equal to zero and less than or equal to 15°C;

[0010] Step d: Hold for the third time period at the second demolding temperature, and then the demolding process ends.

[0011] Optionally, step a includes: Under the preset As pressure condition, linearly heat up the temperature of the InP substrate to the preset temperature at the first preset rate. After the substrate temperature reaches the preset temperature, immediately linearly heat up to the first demolding temperature at the second preset rate. The first preset rate is greater than the second preset rate, and the preset temperature is 15°C to 20°C lower than the reference temperature T c lower.

[0012] Optionally, the range of the first preset rate is 50°C / min to 100°C / min, and the range of the second preset rate is 10°C / min to 30°C / min.

[0013] Optionally, the first demolding temperature is 5°C lower than the reference temperature T c lower.

[0014] Optionally, the range of the difference between the second demolding temperature and the reference temperature is greater than or equal to 5 and less than or equal to 15°C.

[0015] Optionally, the method further includes a demolding condition optimization step, and the demolding condition optimization step includes:

[0016] Step a1: Keep the second time period unchanged. For 3 different first time periods, calculate the corresponding third time period t3 according to the following relationship between the third time period t3 and the first time period t1, , respectively demold the InP substrate, and grow an epitaxial layer with a preset structure on the demolded InP substrate to obtain 3 corresponding epitaxial wafers, where m represents the expected minimum value of the previously obtained t3, n represents the expected maximum value of the previously obtained t3, k is a preset constant, and 0.2 ≤ k ≤ 0.3;

[0017] Step a2: Perform surface defect characterization tests on the 3 epitaxial wafers respectively to obtain the corresponding surface defect data of the 3 epitaxial wafers;

[0018] Step a3: Perform data fitting on the surface defect data and the 3 different first time periods to obtain the corresponding relationship between the surface defect data and the first time period;

[0019] Step a4: According to the corresponding relationship determined in step a3, within the value range of the first time period, calculate and determine the minimum value S of the surface defect data and the corresponding data tolerance range. The data tolerance range is from S to S×(1 + f%), where f is a real number between 5 and 15;

[0020] Step a5: Within the value range of the first time period, determine the sub - value range of the first time period corresponding to the data tolerance range;

[0021] Step a6: Within the sub - value range, in combination with the relationship formula between the third time period and the first time period in step a1, calculate the value of t1 and the value of t3 when the sum of t1 and t3 is the smallest, and use these values as the optimized values of the first time period and the third time period.

[0022] Optionally, in step a1, the values of the three different first time periods are 6 min, 10 min, and 14 min respectively.

[0023] Optionally, m = 3 min and n = 8 min.

[0024] Optionally, f = 10.

[0025] The beneficial effects of the present invention include:

[0026] The film - removing method in the molecular beam epitaxy process provided by the present invention includes: Step a: Under the preset As pressure condition, heat the InP substrate to the first film - removing temperature. The first film - removing temperature is 4°C to 6°C lower than the previously obtained reference temperature. The reference temperature is the substrate temperature when the InP substrate is heated to the RHEED pattern showing the ×4 reconstruction stripes under the preset As pressure condition; Step b: Maintain for the first time period at the first film - removing temperature. The range of the first time period t1 is 6 min ≤ t1 ≤ 14 min; Step c: Heat from the first film - removing temperature to the second film - removing temperature. The time required for this heating process is the second time period. The range of the second time period t2 is 0.5 min ≤ t2 ≤ 2 min. The difference between the second film - removing temperature and the reference temperature ranges from greater than or equal to zero and less than or equal to 15°C; Step d: Maintain for the third time period at the second film - removing temperature, and then the film - removing process ends. By maintaining for the first time period at the first film - removing temperature slightly lower than the reference temperature, while fully heating the substrate, the desorption of phosphorus is reduced. Due to the full heating, the time required for the complete desorption of surface oxides at the second film - removing temperature is reduced, thereby significantly reducing the surface defects of the epitaxial wafer and improving the surface quality of the epitaxial wafer. Description of the Drawings

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0028] Figure 1 The flowchart showing the film removal method in the molecular beam epitaxy process provided by the embodiment of the present invention is shown;

[0029] Figure 2 The schematic curve showing the change of the substrate temperature with time during the film removal process provided by the embodiment of the present invention is shown;

[0030] Figure 3 The schematic diagram showing the determination of the value sub-range of the first time period provided by the embodiment of the present invention is shown. Detailed implementation manners

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0032] InP-based semiconductor devices can be fabricated using molecular beam epitaxy technology. During the fabrication process, first, the InP substrate needs to be subjected to a high-temperature film removal treatment in a molecular beam epitaxy apparatus to remove the native oxide on the surface of the InP substrate, and then corresponding epitaxial layers are deposited and grown according to the device structure design. In the large-scale mass production of InP-based semiconductor devices, the quality of the molecular beam epitaxy high-temperature film removal process directly affects the surface defect density of the epitaxial wafers of the fabricated InP-based semiconductor devices, and thus affects the yield and reliability of the final devices. Too long or too short film removal time will increase the defect density on the substrate surface and the epitaxial wafer. The more surface defects on the epitaxial wafer, the lower the yield of the device, and at the same time, the worse the reliability of the device. Therefore, for the mass production of InP-based semiconductor devices, an optimization technology for the molecular beam epitaxy film removal process needs to be proposed to reduce the surface defect density of the epitaxial wafers of InP-based semiconductor devices and improve the quality of the epitaxial wafers of InP-based semiconductor devices.

[0033] Figure 1 The flowchart showing the film removal method in the molecular beam epitaxy process provided by the embodiment of the present invention is shown. The present invention provides a film removal method in the molecular beam epitaxy process, which is used to remove the film from the InP substrate when growing the epitaxial wafer of the InP-based semiconductor device by molecular beam epitaxy, as Figure 1As shown, the method includes:

[0034] Step a: Under a preset As pressure condition, heat the InP substrate to a first demolding temperature T1. The first demolding temperature T1 is 4°C to 6°C lower than a previously obtained reference temperature T c , and the reference temperature T c is the substrate temperature when the InP substrate is heated and raised to the RHEED pattern showing a ×4 reconstruction stripe under the preset As pressure condition. Optionally, the first demolding temperature T1 is 5°C lower than the reference temperature T c .

[0035] Generally, different As pressure conditions correspond to different optimal demolding conditions. All the demolding processes involved in the embodiments of the present invention are carried out under the same preset As pressure condition. Optionally, the pressure range of the preset As pressure is: greater than or equal to 1×10 -6 Torr and less than or equal to 6×10 -6 Torr. For example, the preset As pressure can be 1×10 -6 Torr, 2×10 -6 Torr, or 6×10 -6 Torr, or other values within the above range. It should be noted that the temperatures described in this application are all the thermocouple temperatures obtained through the thermocouples used to sense the temperatures of the corresponding components in the molecular beam epitaxy equipment. For example, generally, for the same molecular beam epitaxy equipment, the reference temperature T c of the InP substrate of the same specification is stable and unchanged. Therefore, the reference temperature T c of any specification of the InP substrate can be obtained in advance.

[0036] Step b: Maintain for a first time period t1 at the first demolding temperature T1. The range of the first time period t1 is 6 min ≤ t1 ≤ 14 min.

[0037] Step c: Heat from the first demolding temperature T1 to a second demolding temperature T2. The time required for this heating process is the second time period t2. The range of the second time period t2 is 0.5 min ≤ t2 ≤ 2 min. The difference between the second demolding temperature T2 and the reference temperature T c is in the range of greater than or equal to zero and less than or equal to 15°C, that is, T c ≤ T2 ≤ T c +15°C. Optionally, the difference between the second demolding temperature T2 and the reference temperature T c is in the range of greater than or equal to 5 and less than or equal to 15°C, that is, T c +5°C ≤ T2 ≤ T c +15°C.

[0038] Step d: Maintain for a third time period t3 at the second demolding temperature T2, and then the demolding process ends.

[0039] In the conventional demolding technique, the InP substrate is directly heated (e.g., linearly heated) from the temperature before demolding to a predetermined demolding temperature (equivalent to the second demolding temperature T2 in the present application) and maintained for a predetermined demolding time. When the substrate temperature reaches the predetermined demolding temperature, the oxide film starts to desorb. If the demolding time is too short, the surface oxide cannot be completely desorbed, which will lead to the formation of defects in the subsequent epitaxial growth process; if the demolding time is too long, phosphorus desorption will occur and a large number of InAs microcrystals will be formed, and these InAs microcrystals will also cause the formation of defects in the subsequent epitaxial growth process. Therefore, in the conventional technique, the surface defects are reduced by optimizing the demolding time (equivalent to the third time period in the present application). Since it takes a certain time for the oxide to be completely desorbed, during the entire demolding process, phosphorus desorption will occur in the region where the oxide desorbs earlier. Although the optimization of the demolding time in the conventional technique can improve the surface defects, this improvement is limited and it is difficult to further reduce the surface defects.

[0040] In the demolding method provided by the present application, at the first demolding temperature T1 which is 4°C to 6°C lower than the reference temperature T c it is necessary to maintain for the first time period (6 min to 14 min). By adding this maintenance process, compared with the effect in the conventional technique, the actual test results show that the method of the present application can significantly reduce the surface defects. The reason may be as follows: Since the first demolding temperature T1 is lower than the second demolding temperature T2 actually used for the oxide film desorption, during the maintenance at the first demolding temperature T1, while fully heating the substrate, the phosphorus desorption can be significantly reduced. Since it has been maintained at the first demolding temperature T1 for 6 min to 14 min, sufficient heating of the substrate is achieved. Therefore, when the substrate temperature rises to the second demolding temperature T2, the oxide on the substrate surface will immediately start to desorb and the desorption is relatively uniform. At the same time, the total time required for the complete desorption of the oxide can be reduced, thereby significantly reducing the surface defect density. It has been experimentally verified that when the first demolding temperature T1 is 4°C to 6°C lower than the reference temperature T c the effect of significantly reducing the surface defect density can be achieved. If the first demolding temperature T1 is too much lower than the reference temperature T c sufficient heating of the substrate cannot be achieved, which will not affect the subsequent oxide desorption time. If the first demolding temperature T1 is too close to the reference temperature T c or greater than the reference temperature T c, it will lead to an increase in the desorption of phosphorus in the first time period. Similarly, the range of the first time period is also a consideration factor. If the first time period is less than 6 minutes, sufficient heating of the substrate cannot be achieved; if the first time period is too long (e.g., greater than 14 minutes), it will result in unnecessary waste of growth machine time.

[0041] Optionally, step a includes: under a preset As pressure condition, linearly increasing the temperature of the InP substrate to a preset temperature at a first preset rate. After the substrate temperature reaches the preset temperature, immediately linearly increase the temperature to a first demolding temperature T1 at a second preset rate. The first preset rate is greater than the second preset rate, and the preset temperature is 15 °C to 20 °C lower than the reference temperature T c . Optionally, the rate range of the first preset rate is 50 °C / min to 100 °C / min, and the rate range of the second preset rate is 10 °C / min to 30 °C / min. By introducing the preset temperature, rapid heating can be achieved during the process of increasing the temperature to the preset temperature, reducing the heating time. Then, during the process of increasing the temperature from the preset temperature to the first demolding temperature T1, the heating rate is reduced to avoid temperature overshoot.

[0042] The specific demolding heating process is as Figure 2 shown. From the start of demolding to time f1, the substrate temperature is increased to the preset temperature T0 at the first preset rate. After the substrate temperature reaches the preset temperature T0, immediately increase the temperature to the first demolding temperature T1 at the second preset rate. The process of increasing the temperature from the preset temperature T0 to the first demolding temperature T1 corresponds to the time from time f1 to time f2. Then, maintain the first time period at the first demolding temperature T1, and this process corresponds to the time from time f2 to time f3. The process of increasing the temperature from the first demolding temperature T1 to the second demolding temperature T2 corresponds to the time from time f3 to time f4. The process of maintaining the third time period at the second demolding temperature T2 corresponds to the time from time f4 to time f5. At time f5, the demolding process ends.

[0043] In summary, by maintaining the first time period at the first demolding temperature slightly lower than the reference temperature, the present method fully heats the substrate while reducing the desorption of phosphorus. Due to the sufficient heating, the desorption of the surface oxide of the substrate is relatively uniform, reducing the time required for the complete desorption of the surface oxide at the second demolding temperature, thereby significantly reducing the surface defects of the epitaxial wafer and improving the surface quality of the epitaxial wafer.

[0044] Optionally, the method further includes a demolding condition optimization step for optimizing the durations of the first time period and the third time period.

[0045] The demolding condition optimization step includes:

[0046] Step a1: Keep the second time period unchanged. For 3 different first time periods, calculate the corresponding third time period t3 according to the following relationship between the third time period t3 and the first time period t1. , respectively demold the InP substrate, and grow an epitaxial layer with a preset structure on the demolded InP substrate to obtain 3 corresponding epitaxial wafers. Here, m represents the expected minimum value of the pre-obtained t3, n represents the expected maximum value of the pre-obtained t3, k is a preset constant, and 0.2 ≤ k ≤ 0.3. Optionally, in step a1, the values of the 3 different first time periods are 6 min, 10 min, and 14 min respectively. The present application does not limit the specific structure of the preset structure. For example, an epitaxial structure including materials such as InP, InGaAs, and InAlAs can be grown, as long as the structures used in the three epitaxial growths for the 3 different first time periods are the same.

[0047] Step a2: Perform surface defect characterization tests on the 3 epitaxial wafers respectively to obtain the surface defect data corresponding to the 3 epitaxial wafers. Step a3: Fit the surface defect data and the 3 different first time periods to obtain the corresponding relationship between the surface defect data and the first time period. Step a4: According to the corresponding relationship determined in step a3, within the value range of the first time period, calculate and determine the minimum value S of the surface defect data and the corresponding data tolerance range. The data tolerance range is from S to S×(1 + f%), where f is a real number from 5 to 15. Optionally, f = 10. Step a5: Within the value range of the first time period, determine the value sub-range of the first time period corresponding to the data tolerance range. Step a6: Within the value sub-range, in combination with the relationship between the third time period and the first time period in step a1, calculate the value of t1 and the value of t3 when the sum of t1 and t3 is the smallest, and use this value as the optimized value of the first time period and the third time period.

[0048] Since the temperature increase amplitude within the second time period is not large itself (about 5°C to 20°C) and the duration is short, the second time period remains unchanged during the optimization process. For example, the second time period can be fixed at 1 min. According to experience, the minimum and maximum values of the third time period can be expected. Here, the minimum value means that if it is less than this minimum value, defects caused by incomplete desorption of the oxide film will be significantly found; the maximum value means that if it exceeds this maximum value, defects caused by InAs microcrystals due to phosphorus desorption will be significantly found. For example, according to experience, the expected minimum value m = 3 min can be set, and the expected maximum value n = 8 min can be set.

[0049] After setting the values of m and n, for any first time period, there theoretically exists a corresponding optimal third time period. The relationship between the corresponding optimal third time period and the first time period is discussed below. As the first time period increases, the corresponding optimal third time period decreases, but the minimum value is m; as the first time period decreases, the corresponding optimal third time period increases, but the maximum value is n. Thus, a relational expression can be established to approximately represent the value of the optimal third time period t3 corresponding to the first time period t1. The optimal third time period here means that for any first time period, within the value range of the third time period, the third time period corresponding to the least surface defects. By establishing the above relational expression, when optimizing the time period in the demolding process, the variables can be reduced to only one (i.e., the first time period). In this case, only three experiments are needed to obtain the data for optimizing the first time period (i.e., the data obtained in step a2), then the corresponding relationship is established in step a3, and the minimum value S is determined in step a4, thus avoiding a large number of experiments when optimizing two or more variables and greatly reducing the optimization cost. Considering the errors caused by various reasons such as random factors, the expected optimal surface defect data within the range of S to S×(1 + f%) are all considered acceptable. Therefore, for S to S×(1 + f%), that is, for the data tolerance range, the value sub-range of the corresponding first time period can be determined.

[0050] As Figure 3 shown, the surface defect data is the number of surface defects per unit area, the experimental test data is the data corresponding to the black dots, and the fitting corresponding relationship curve (the dotted line in the figure) is obtained by data fitting. The minimum value S on the corresponding relationship curve is determined, then the data tolerance range is determined, and finally the value sub-range of the first time period corresponding to the data tolerance range can be determined as st1 to st2. It can be considered that for any value of the first time period within this value sub-range, the corresponding obtained surface defect data is optimal. To save the total demolding time and machine time, the relationship between the third time period and the first time period in step a1 can be combined to calculate the value of t1 and the value of t3 when the sum of t1 and t3 is the smallest, and these values are used as the optimized values of the first time period and the third time period. In the subsequent demolding process, using the optimized values of the first time period and the third time period can not only obtain smaller surface defect data, but also reduce the total demolding time and avoid unnecessary time waste.

[0051] The above embodiments are only for illustrating the technical concept and characteristics of the present invention, and the purpose is to enable those of ordinary skill in the art to understand the content of the present invention and implement it. It should not be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims

1. A film stripping method in a molecular beam epitaxy process, characterized in that: The method is used to strip an InP substrate, and the method comprises: Step a: Under the preset As pressure condition, the InP substrate is heated to a first stripping temperature, which is 4°C to 6°C lower than the pre-obtained reference temperature. The reference temperature is the substrate temperature when the InP substrate is heated to a temperature when the RHEED pattern shows ×4 reconstruction stripes under the preset As pressure condition. The preset As pressure range is: greater than or equal to 1×10 -6 Torr, and less than or equal to 6×10 -6 Torr; Step b, maintaining the first time period at the first demolding temperature, wherein the first time period t1 is in the range of 6 min ≤ t1 ≤ 14 min; Step c, heating from the first demolding temperature to the second demolding temperature, the time required for the heating process is the second time period, the range of the second time period t2 is 0.5min ≤ t2 ≤ 2 min, and the range of the difference between the second demolding temperature and the reference temperature is greater than or equal to zero and less than or equal to 15°C; Step d, maintaining the second demolding temperature for a third period of time, and then the demolding process ends.

2. The film stripping method in the molecular beam epitaxy process according to claim 1, characterized in that: Step a includes: under a preset As pressure condition, linearly increasing the temperature of the InP substrate at a first preset rate to a preset temperature, and immediately linearly increasing the temperature at a second preset rate to a first stripping temperature after the substrate temperature reaches the preset temperature, the first preset rate is greater than the second preset rate, and the preset temperature is 15°C to 20°C lower than the reference temperature.

3. The film stripping method in the molecular beam epitaxy process according to claim 2, characterized in that: The first preset rate ranges from 50° C. / min to 100° C. / min, and the second preset rate ranges from 10° C. / min to 30° C. / min.

4. The film stripping method in the molecular beam epitaxy process according to claim 1, characterized in that: The first demolding temperature is 5°C lower than the reference temperature.

5. The film stripping method in the molecular beam epitaxy process according to claim 1, characterized in that: The difference between the second demolding temperature and the reference temperature is in the range of 5 or more and 15° C. or less.

6. The film stripping method in the molecular beam epitaxy process according to claim 1 or 5, characterized in that: The method further comprises a step of optimizing the stripping conditions, wherein the step of optimizing the stripping conditions comprises: Step a1, the second time period is fixed unchanged, for three different first time periods, the corresponding third time period t3 is calculated according to the following relationship between the third time period t3 and the first time period t1, , respectively stripping the InP substrates, and growing epitaxial layers of a preset structure on the stripped InP substrates to obtain three corresponding epitaxial wafers, wherein m represents the expected minimum value of t3 obtained in advance, n represents the expected maximum value of t3 obtained in advance, k is a preset constant, and 0.2≤k≤0.3; Step a2, performing surface defect characterization tests on the three epitaxial wafers respectively to obtain surface defect data corresponding to the three epitaxial wafers; Step a3, performing data fitting on the surface defect data and the three different first time periods to obtain a corresponding relationship between the surface defect data and the first time periods; Step a4, according to the corresponding relationship determined in step a3, within the value range of the first time period, calculate and determine the minimum value S of the surface defect data and the corresponding data tolerance range, the data tolerance range is S to S×(1+f%), and f is a real number from 5 to 15; Step a5: determining a value sub-range of the first time period corresponding to the data tolerance range within the value range of the first time period; Step a6, within the value sub-range, combined with the relationship between the third time period and the first time period in step a1, calculate the value of t1 and the value of t3 corresponding to the minimum sum of t1 and t3, and use the value as the optimized value of the first time period and the third time period.

7. The film stripping method in the molecular beam epitaxy process according to claim 6, characterized in that: In the step a1, the values ​​of the three different first time periods are 6 min, 10 min, and 14 min respectively.

8. The film stripping method in the molecular beam epitaxy process according to claim 6, characterized in that: m=3 min, and n=8 min.

9. The film stripping method in the molecular beam epitaxy process according to claim 6, characterized in that: f=10。

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