Method for manufacturing standard silicon wafer and calibration method for flatness measuring apparatus

Abstract

This invention provides a method for preparing a standard silicon wafer and a method for calibrating a planarity measurement device. The preparation method includes: performing two consecutive heat treatments on the silicon wafer in a reaction chamber: first, performing a first heat treatment at high temperature in a reducing atmosphere to remove the surface oxide layer and contaminants and optimize its surface atomic arrangement structure; then, lowering the temperature to a lower target temperature and performing a second heat treatment in a hydrogen halide etching atmosphere to obtain a standard silicon wafer through etching. Since the standard silicon wafer is obtained by etching in a clean reaction chamber, its surface particle and metal impurity content is extremely low, and its surface roughness is specific and has excellent uniformity. This makes the standard silicon wafer suitable for the precise calibration of non-contact planarity measurement devices such as surface light scattering instruments, which are extremely sensitive to cleanliness, and it has a wide range of applications.

Description

Technical Field

[0001] This invention relates to the field of measurement, and in particular to a method for preparing a standard silicon wafer and a calibration method for a flatness measurement device. Background Technology

[0002] During wafer fabrication, surface roughness needs to be measured. To ensure the accuracy and stability of surface flatness measurement, standard wafers are required, and the measuring equipment needs to be calibrated regularly.

[0003] However, current calibration practices face technical bottlenecks:

[0004] The existing calibration standards are not clean enough, with a large number of particulate contaminants and metallic impurities on their surface. They are only suitable for calibration of contact testing equipment such as atomic force microscopes. However, when using contact testing equipment such as atomic force microscopes for measurement, there are drawbacks such as long measurement time (generally, if only a single 10μm×10μm point in the center is measured, the measurement time is about 15 minutes, while if it is shipped as a product, 21 points need to be measured, and the measurement time is about five hours), small measurement range, and susceptibility to vibration.

[0005] In addition, existing technologies make it difficult to repeatedly and controllably prepare standard sheets with specific roughness and excellent uniformity at the wafer level. Summary of the Invention

[0006] The purpose of this invention is to provide a standard silicon wafer preparation method and a calibration method for a flatness measurement device, so as to solve the problems of insufficient cleanliness of standard wafers, narrow applicability, and lack of controllable and uniform specific roughness in existing flatness measurement devices.

[0007] To address the above problems, this invention provides a method for preparing a standard silicon wafer, comprising:

[0008] A silicon wafer is provided and loaded into the reaction chamber;

[0009] The silicon wafer is subjected to a first heat treatment, the first heat treatment comprising: raising the temperature inside the reaction chamber from the loading temperature to a first target heat treatment temperature under an inert protective atmosphere, and maintaining the first heat treatment duration under a reducing atmosphere; and,

[0010] The silicon wafer is subjected to a second heat treatment, the second heat treatment comprising: reducing the temperature inside the reaction chamber from the first target heat treatment temperature to a second target heat treatment temperature, the second target heat treatment temperature being lower than the first target heat treatment temperature, and maintaining the second heat treatment for a duration in an etching atmosphere containing hydrogen halide, and then reducing the temperature inside the reaction chamber from the second target heat treatment temperature to the unloading temperature in an inert protective atmosphere.

[0011] Optionally, in the method for preparing the standard silicon wafer, the first target heat treatment temperature is 1000-1200℃, and the first heat treatment duration is 1-300s.

[0012] Optionally, in the method for preparing the standard silicon wafer, the first heat treatment duration is 60-200 s.

[0013] Optionally, in the method for preparing the standard silicon wafer, the second target heat treatment temperature is 800-1000℃, and the second heat treatment duration is greater than or equal to 1s.

[0014] Optionally, in the method for preparing the standard silicon wafer, the flow rate of hydrogen halide in the etching atmosphere is greater than or equal to 1 sccm.

[0015] Optionally, in the method for preparing the standard silicon wafer, the reducing atmosphere is pure hydrogen, or the reducing atmosphere is a mixture of hydrogen and an inert gas.

[0016] Optionally, in the method for preparing the standard silicon wafer, the hydrogen halide is at least one of hydrogen chloride, hydrogen bromide, hydrogen iodide, or hydrogen fluoride.

[0017] Optionally, in the method for preparing the standard silicon wafer, the loading temperature and the unloading temperature are 400℃-700℃; the heating rate when the temperature inside the reaction chamber is increased from the loading temperature to the first target heat treatment temperature and the cooling rate when the temperature inside the reaction chamber is decreased from the first target heat treatment temperature to the unloading temperature are 0.01-30℃ / min.

[0018] The present invention also provides a calibration method for a flatness measuring device, comprising:

[0019] Provide a standard silicon wafer prepared using the preparation method described in any of the preceding claims;

[0020] The surface of the standard silicon wafer is measured using the target measurement device to be calibrated, in order to obtain surface roughness measurement data; and,

[0021] The measurement error of the target measurement device is confirmed based on the measurement data.

[0022] Optionally, in the calibration method of the flatness measurement equipment, the target measurement equipment includes a surface light scattering instrument, an atomic force microscope, and a scanning electron microscope.

[0023] In summary, this invention provides a method for preparing a standard silicon wafer and a method for calibrating a planarity measurement device. The preparation method includes: performing two consecutive heat treatments on the silicon wafer in a reaction chamber: first, a first heat treatment is performed at a high temperature in a reducing atmosphere to remove the surface oxide layer and contaminants and optimize its surface atomic arrangement structure; then, the temperature is lowered to a lower target temperature and a second heat treatment is performed in a hydrogen halide etching atmosphere to obtain a standard silicon wafer through etching. Since the standard silicon wafer is obtained by etching in a clean reaction chamber, its surface particle and metal impurity content is extremely low, and its surface roughness is specific and has excellent uniformity. This makes the standard silicon wafer suitable for the precise calibration of non-contact planarity measurement devices such as surface light scattering instruments, which are extremely sensitive to cleanliness, and it has a wide range of applications. Attached Figure Description

[0024] Figure 1 A flowchart illustrating a method for preparing a standard silicon wafer according to an embodiment of the present invention;

[0025] Figure 2 The above are the surface light scattering test results of three silicon wafers in Example 1 of this embodiment of the invention.

[0026] Figure 3 This is a comparative schematic diagram of the average haze on the surfaces of three silicon wafers in Example 1 of the present invention;

[0027] Figure 4 This is a schematic diagram comparing the roughness uniformity of three silicon wafers in Example 1 of the invention embodiment;

[0028] Figure 5 The above are the surface light scattering test results of three silicon wafers in Example 2 of this embodiment of the invention.

[0029] Figure 6 This is a comparative schematic diagram of the average haze on the surfaces of three silicon wafers in Example 2 of this embodiment of the invention;

[0030] Figure 7 This is a schematic diagram comparing the roughness uniformity of three silicon wafers in Example 2 of the invention embodiment;

[0031] Figure 8 The above are the surface light scattering test results of three silicon wafers in Example 3 of this embodiment of the invention.

[0032] Figure 9 This is a comparative schematic diagram of the average haze on the surfaces of three silicon wafers in Example 3 of this embodiment of the invention;

[0033] Figure 10 This is a schematic diagram comparing the roughness uniformity of three silicon wafers in Example 3 of the invention embodiment;

[0034] Figure 11The above are the surface light scattering test results of three silicon wafers in Example 4 of this embodiment of the invention.

[0035] Figure 12 This is a comparative schematic diagram of the average haze on the surfaces of three silicon wafers in Example 4 of this embodiment of the invention;

[0036] Figure 13 This is a schematic diagram comparing the roughness uniformity of three silicon wafers in Example 4 of the invention. Detailed Implementation

[0037] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, further illustrates the method for preparing a standard silicon wafer and the calibration method for a flatness measurement device provided by the present invention. It should be noted that the drawings are all in a very simplified form and use non-precise scales, used only to facilitate and clarify the illustration of the embodiments of the present invention. Furthermore, the structures shown in the drawings are often part of the actual structure. In particular, different figures may emphasize different aspects and sometimes use different scales. It should be understood that relative terms such as "above," "below," "top," and "bottom" shown in the drawings can be used to describe the relationships between various elements. These relative terms are intended to cover different orientations of elements other than those depicted in the drawings. For example, if the device is inverted relative to the view in the drawings, an element described as "above" another element will now be below that element. It should also be understood that, unless specifically stated or indicated, the terms "first," "second," "third," etc., in the specification are only used to distinguish various components, elements, steps, etc., in the specification, and are not used to indicate logical or sequential relationships between various components, elements, steps, etc.

[0038] like Figure 1 As shown, this embodiment of the invention provides a method for preparing a standard silicon wafer, comprising the following steps:

[0039] S1, providing a silicon wafer and loading the silicon wafer into the reaction chamber;

[0040] S2, performing a first heat treatment on the silicon wafer, the first heat treatment comprising: raising the temperature inside the reaction chamber from the loading temperature to a first target heat treatment temperature under an inert protective atmosphere, and maintaining the first heat treatment duration under a reducing atmosphere; and,

[0041] S3, perform a second heat treatment on the silicon wafer, the second heat treatment comprising: reducing the temperature inside the reaction chamber from the first target heat treatment temperature to a second target heat treatment temperature, the second target heat treatment temperature being lower than the first target heat treatment temperature, and maintaining the second heat treatment for a duration in an etching atmosphere containing hydrogen halide, and then reducing the temperature inside the reaction chamber from the second target heat treatment temperature to the unloading temperature in an inert protective atmosphere.

[0042] In this embodiment of the invention, the silicon wafer is primarily made of silicon-based materials. Given that the vast majority of substrates used in semiconductor microelectronics manufacturing are single-crystal silicon wafers, in step S1, the silicon wafer can be a single-crystal silicon wafer obtained through the Czochralski method or the zone melting method. Specifically, a single-crystal silicon ingot is prepared by the Czochralski method or the zone melting method, and then subjected to mid-to-late stage processes such as rolling, slicing, chamfering, and grinding to obtain a single-crystal silicon wafer. In other embodiments, the silicon wafer can also be a polycrystalline silicon wafer, silicon-on-insulator (SiI) wafer, or other types of silicon-based wafers.

[0043] In step S1, when loading the silicon wafer into the reaction chamber, the loading temperature is optionally 400℃-700℃, preferably 500-600℃, and the atmosphere is an inert protective atmosphere, such as pure argon (Ar). After maintaining this temperature for a period of time, the process proceeds to step S2 for the first heat treatment. Optionally, the holding time at the loading temperature is 0.1-10 min, preferably 1 min.

[0044] In step S2, the temperature inside the reaction chamber is raised from the loading temperature to the first target heat treatment temperature under an inert protective atmosphere at a rate of 0.01-30℃ / min, preferably 1-10℃ / min. The atmosphere inside the reaction chamber is switched to a reducing atmosphere. The first heat treatment time is maintained at the first target heat treatment temperature and under the reducing atmosphere. Then, the process proceeds to step S3 for the second heat treatment.

[0045] The first target heat treatment temperature is preferably 1000-1200℃. The first heat treatment duration can be selected from 1-300s, preferably 60-200s. The reducing atmosphere can be pure hydrogen, or the reducing atmosphere can be a mixture of hydrogen and an inert gas, such as a mixture of hydrogen and argon.

[0046] In step S3, the second target heat treatment temperature during the second heat treatment should be lower than the first target heat treatment temperature. Therefore, after the first heat treatment is completed, the cooling rate is maintained at 0.01-30℃ / min, preferably 1-10℃ / min, to reduce the temperature inside the reaction chamber from the first target heat treatment temperature to the second target heat treatment temperature. The atmosphere inside the reaction chamber is also switched from a reducing atmosphere to an etching atmosphere containing hydrogen halide. The second heat treatment time is maintained at the second target heat treatment temperature and under the etching atmosphere. Then, the atmosphere inside the reaction chamber is switched to an inert protective atmosphere. Under the inert protective atmosphere (e.g., argon), the temperature inside the reaction chamber is reduced from the second target heat treatment temperature to the unloading temperature.

[0047] The second target heat treatment temperature is preferably 800-1000℃. The second heat treatment duration is preferably greater than or equal to 1 second. The hydrogen halide can be at least one of hydrogen chloride, hydrogen bromide, hydrogen iodide, or hydrogen fluoride. The flow rate of hydrogen halide in the etching atmosphere is optionally greater than or equal to 1 sccm, preferably 200-1500 sccm.

[0048] In this embodiment, the standard sheet needs to meet the requirements for both roughness and uniformity. Therefore, a higher etching gas flow rate is used. However, the etching gas flow rate is not necessarily better the higher it is. In this embodiment, by controlling the etching gas flow rate at 200~1500 sccm and controlling the temperature and time of heat treatment, a standard sheet that is both rough and uniform can be obtained.

[0049] The unloading temperature can be selected from 400℃ to 700℃, preferably 500℃ to 600℃. When the temperature inside the reaction chamber is reduced from the second target heat treatment temperature to the unloading temperature, the cooling rate can be selected from 0.01℃ to 30℃ / min, preferably 1℃ / min.

[0050] In addition, the entire heat treatment process can be carried out under normal pressure or under reduced pressure. During reduced pressure treatment, the gas pressure in the chamber is 1 torr-100 torr, preferably 15 torr.

[0051] The preparation method provided in the embodiments of the present invention will be described by way of example below.

[0052] Example 1

[0053] Three silicon wafers in their initial states were provided, and they were processed as shown in Table 1 to obtain silicon wafer 1, silicon wafer 2, and silicon wafer 3. Silicon wafer 1 remained in its initial state, silicon wafer 2 underwent only a second heat treatment, and silicon wafer 3 underwent both a first and second heat treatment. The surface light scattering test results for silicon wafers 1, 2, and 3 are shown below. Figure 2 As shown. Figure 2 In this context, the shade of gray indicates the level of haze, which is used to characterize scattered energy. Darker gray indicates a lower haze value, while lighter gray indicates a higher haze value.

[0054] Table 1

[0055]

[0056] Further analysis of the measurement results, such as Figure 3 and Figure 4 It can be found that silicon wafers with specific roughness can be obtained by adjusting the heat treatment conditions, and the roughness has good uniformity. The silicon wafer 3 that has undergone the first heat treatment and the second heat treatment has better roughness uniformity.

[0057] in, Figure 3 The diagram illustrates the average haze values ​​on the surfaces of silicon wafers 1, 2, and 3. The average haze value is numerically equal to the ratio of the collected scattered energy to the total reflected energy. The magnitude of the average haze value reflects the overall roughness of the silicon wafer surface; the larger the value, the rougher the surface. Figure 4 This is a comparative diagram of the uniformity of roughness of three silicon wafers. The vertical axis represents the statistical uniformity of the haze value distribution at various points on the silicon wafer surface. The calculation formula can be: (Haze) 最大值 - Haze 最小值 ) / (2 × Haze 平均值 The value of the vertical axis is expressed as a standard deviation, or the higher the value of the vertical axis, the worse the uniformity.

[0058] Example 2

[0059] Silicon wafer 3 and two other silicon wafers in their initial states are provided. The two other silicon wafers in their initial states are processed as shown in Table 2 to obtain silicon wafers 4 and 5. Compared with silicon wafer 3, the other process conditions for silicon wafers 4 and 5 remain unchanged, except for the flow rate of the etching atmosphere during the second heat treatment. The surface light scattering test results of silicon wafers 3, 4, and 5 are as follows: Figure 5 As shown in the image.

[0060] Table 2

[0061]

[0062] Further analysis of the measurement results, such as Figure 6 and Figure 7 It can be observed that, under the condition of fixed heat treatment temperature and time, increasing the gas flow rate can increase the surface roughness of the silicon wafer, but at the same time it will affect the uniformity of the roughness.

[0063] Example 3

[0064] Silicon wafer 3 and two other silicon wafers in their initial states are provided. The two other silicon wafers in their initial states are processed as shown in Table 3 to obtain silicon wafers 6 and 7. Compared with silicon wafer 3, silicon wafers 6 and 7 have the same other process conditions, except for the temperature during the second heat treatment. The surface light scattering test results of silicon wafers 3, 6, and 7 are as follows: Figure 8 As shown in the image.

[0065] Table 3

[0066]

[0067] Further analysis of the measurement results, such as Figure 9 and Figure 10 It can be found that, under the condition that the heat treatment gas flow rate and time are fixed, increasing the heat treatment temperature is beneficial to improving the surface roughness of the silicon wafer, but it will affect the roughness uniformity.

[0068] Example 4

[0069] Silicon wafer 3 and two other silicon wafers in their initial states are provided. The two other silicon wafers in their initial states are processed as shown in Table 4 to obtain silicon wafers 8 and 9. Compared with silicon wafer 3, silicon wafers 8 and 9 have the same other process conditions, except for the time of the second heat treatment. The surface light scattering test results of silicon wafers 3, 8, and 9 are as follows: Figure 11 As shown in the image.

[0070] Table 4

[0071]

[0072] Further analysis of the measurement results, such as Figure 12 and Figure 13 It can be found that, under the condition of fixed heat treatment gas flow rate and temperature, increasing the heat treatment time is beneficial to improving the surface roughness of silicon wafers and also to increasing the roughness uniformity.

[0073] Based on the above examples, it can be seen that in practical applications, the heat treatment time, temperature, gas flow rate, etc., can be reasonably adjusted within the selectable range to meet the specific requirements for the surface roughness and roughness uniformity of standard silicon wafers.

[0074] Furthermore, embodiments of the present invention also provide a calibration method for a flatness measuring device, comprising:

[0075] A standard silicon wafer prepared using the preparation method provided in this invention is provided;

[0076] The surface of the standard silicon wafer is measured using the target measurement device to be calibrated, in order to obtain surface roughness measurement data; and,

[0077] The measurement error of the target measurement device is confirmed based on the measurement data.

[0078] The standard silicon wafer surface roughness has a known standard value. By comparing the measurement data of the target measurement device to be calibrated with this standard value, the measurement error of the target measurement device can be confirmed.

[0079] Optionally, the target measurement device can be a device that uses a non-contact optical measurement method to measure roughness, such as a localized light scattering (LLS) instrument, or a device that uses a contact or near-field scanning surface topography measurement method to measure roughness, such as an atomic force microscope or a scanning electron microscope. When the target measurement device is a surface light scattering instrument, its scattered light receiving channel can be DWN, DNN, DW1O, DW2O, or DNO.

[0080] In summary, the embodiments of the present invention provide a method for preparing a standard silicon wafer and a method for calibrating a planarity measurement device. The preparation method includes: performing two consecutive heat treatments on the silicon wafer in a reaction chamber: firstly, performing a first heat treatment at high temperature in a reducing atmosphere to remove the surface oxide layer and contaminants and optimize its surface atomic arrangement structure; then, lowering the temperature to a lower target temperature and performing a second heat treatment in a hydrogen halide etching atmosphere to obtain a standard silicon wafer through etching. Since the standard silicon wafer is obtained by etching in a clean reaction chamber, its surface particle and metal impurity content is extremely low, and its surface roughness is specific and has excellent uniformity. This makes the standard silicon wafer suitable for the precise calibration of non-contact planarity measurement devices such as surface light scattering instruments that are extremely sensitive to cleanliness, and it has a wide range of applications.

[0081] The above description is merely a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the claims.

Claims

1. A method for preparing a standard silicon wafer, characterized in that, include: A silicon wafer is provided and loaded into the reaction chamber; The silicon wafer is subjected to a first heat treatment, the first heat treatment comprising: raising the temperature inside the reaction chamber from the loading temperature to a first target heat treatment temperature under an inert protective atmosphere, and maintaining the first heat treatment duration under a reducing atmosphere; and, The silicon wafer is subjected to a second heat treatment, the second heat treatment comprising: reducing the temperature inside the reaction chamber from the first target heat treatment temperature to a second target heat treatment temperature, the second target heat treatment temperature being lower than the first target heat treatment temperature, and maintaining the second heat treatment for a duration in an etching atmosphere containing hydrogen halide, and then reducing the temperature inside the reaction chamber from the second target heat treatment temperature to the unloading temperature in an inert protective atmosphere.

2. The method for preparing a standard silicon wafer as described in claim 1, characterized in that, The first target heat treatment temperature is 1000-1200℃, and the first heat treatment duration is 1-300s.

3. The method for preparing a standard silicon wafer as described in claim 2, characterized in that, The duration of the first heat treatment is 60-200 seconds.

4. The method for preparing a standard silicon wafer as described in claim 1, characterized in that, The second target heat treatment temperature is 800-1000℃, and the second heat treatment duration is greater than or equal to 1s.

5. The method for preparing a standard silicon wafer as described in claim 1, characterized in that, The flow rate of hydrogen halide in the etching atmosphere is greater than or equal to 1 sccm.

6. The method for preparing a standard silicon wafer as described in claim 1, characterized in that, The reducing atmosphere is pure hydrogen, or a mixture of hydrogen and an inert gas.

7. The method for preparing a standard silicon wafer as described in claim 1, characterized in that, The hydrogen halide is at least one of hydrogen chloride, hydrogen bromide, hydrogen iodide, or hydrogen fluoride.

8. The method for preparing a standard silicon wafer as described in claim 1, characterized in that, The loading temperature and the unloading temperature are 400℃-700℃; the heating rate when the temperature inside the reaction chamber is increased from the loading temperature to the first target heat treatment temperature and the cooling rate when the temperature inside the reaction chamber is decreased from the first target heat treatment temperature to the unloading temperature are 0.01-30℃ / min.

9. A calibration method for a leveling measurement device, characterized in that, include: A standard silicon wafer prepared using the preparation method according to any one of claims 1 to 8 is provided; The surface of the standard silicon wafer is measured using the target measurement device to be calibrated, in order to obtain surface roughness measurement data; and, The measurement error of the target measurement device is confirmed based on the measurement data.

10. The calibration method for the leveling measurement equipment as described in claim 9, characterized in that, The target measurement equipment includes a surface light scattering instrument, an atomic force microscope, and a scanning electron microscope.

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