Methods for preparing standard silicon wafers and calibration methods for flatness measurement equipment

Abstract

This invention provides a method for preparing a standard silicon wafer and a method for calibrating a planarity measurement device, comprising: providing a silicon wafer; performing a first heat treatment on the silicon wafer to grow an oxide layer on the surface of the silicon wafer; and performing a second heat treatment on the silicon wafer after the oxide layer has grown to improve the surface roughness of the oxide layer through a high-temperature decomposition reaction; wherein the first heat treatment includes: heating to a first heat treatment temperature and maintaining the first heat treatment time in an atmosphere containing oxygen; the second heat treatment includes: heating to a second heat treatment temperature and maintaining the second heat treatment time in an atmosphere containing argon. The preparation method provided by this invention, by combining a two-step process of "thermal oxidation growth" and "high-temperature decomposition and reconstruction," creates a standard wafer surface that possesses both the purity of the thermal oxide layer and the specific and uniform surface roughness obtained through high-temperature decomposition, meeting the stringent calibration requirements of non-contact planarity measurement devices that are extremely sensitive to cleanliness.

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] Silicon wafers are supplied;

[0009] The silicon wafer is subjected to a first heat treatment to grow an oxide layer on the surface of the silicon wafer;

[0010] The silicon wafer after the oxide layer has been grown is subjected to a second heat treatment to improve the surface roughness of the oxide layer through a high-temperature decomposition reaction;

[0011] The first heat treatment includes: heating to a first heat treatment temperature and maintaining the temperature in an atmosphere containing oxygen for a first heat treatment duration; the second heat treatment includes: heating to a second heat treatment temperature and maintaining the temperature in an atmosphere containing argon for a second heat treatment duration.

[0012] Optionally, in the method for preparing the standard silicon wafer, the first heat treatment temperature is 800~1000℃, and the first heat treatment duration is 0.1~10h.

[0013] Optionally, in the method for preparing the standard silicon wafer, the first heat treatment lasts for 1 to 5 hours.

[0014] Optionally, in the method for preparing the standard silicon wafer, the atmosphere for the first heat treatment is pure oxygen or an atmosphere generated by the reaction of oxygen and hydrogen.

[0015] Optionally, in the method for preparing the standard silicon wafer, when the atmosphere of the first heat treatment is an atmosphere generated by the reaction of oxygen and hydrogen, the flow rate ratio of oxygen to hydrogen is 1:2.

[0016] Optionally, in the method for preparing the standard silicon wafer, the second heat treatment temperature is 1000~1300℃, and the second heat treatment duration is 0.1~5h.

[0017] Optionally, in the method for preparing the standard silicon wafer, the atmosphere for the second heat treatment is pure argon, a mixture of argon and hydrogen, or a mixture of argon and oxygen.

[0018] Optionally, in the method for preparing the standard silicon wafer, before subjecting the silicon wafer to the first heat treatment, the preparation method further includes:

[0019] The silicon wafer is loaded into a reaction chamber with a set loading temperature and held in an inert protective atmosphere for a set time.

[0020] After performing the second heat treatment on the silicon wafer, the preparation method further includes:

[0021] Under an inert protective atmosphere, the temperature inside the reaction chamber is reduced from the second heat treatment temperature to the unloading temperature.

[0022] Optionally, in the method for preparing the standard silicon wafer, the set loading temperature and the set unloading temperature are 400℃~700℃, and the set duration is 0.1min~60min.

[0023] The present invention also provides a calibration method for a flatness measuring device, comprising:

[0024] Provide a standard silicon wafer prepared using the preparation method described in any of the preceding claims;

[0025] 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,

[0026] The measurement error of the target measurement device is confirmed based on the measurement data.

[0027] 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.

[0028] 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: providing a silicon wafer; performing a first heat treatment on the silicon wafer to grow an oxide layer on its surface; and performing a second heat treatment on the silicon wafer after the oxide layer has grown to improve the surface roughness of the oxide layer through a high-temperature decomposition reaction. The first heat treatment includes: heating to a first heat treatment temperature and maintaining the temperature in an oxygen-containing atmosphere for a first heat treatment duration; the second heat treatment includes: heating to a second heat treatment temperature and maintaining the temperature in an argon-containing atmosphere for a second heat treatment duration. The preparation method provided by this invention, by combining a two-step process of "thermal oxidation growth" and "high-temperature decomposition and reconstruction," creates a standard wafer surface that possesses both the purity of the thermal oxide layer and the specific and uniform surface roughness obtained through high-temperature decomposition, meeting the stringent calibration requirements of non-contact planarity measurement devices such as surface light scattering instruments, which are extremely sensitive to cleanliness. Attached Figure Description

[0029] Figure 1 A flowchart illustrating a method for preparing a standard silicon wafer according to an embodiment of the present invention;

[0030] Figure 2 The image shows the atomic force microscope measurement results of three silicon wafers in Example 1 of this embodiment of the invention.

[0031] Figure 3 This is a schematic diagram comparing the roughness uniformity of three silicon wafers in Example 1 of the present invention;

[0032] Figure 4 The image shows the atomic force microscope measurement results of three silicon wafers in Example 2 of this embodiment of the invention;

[0033] Figure 5 This is a schematic diagram comparing the roughness uniformity of three silicon wafers in Example 2 of Embodiment 2 of the present invention;

[0034] Figure 6 The figures show the atomic force microscopy measurement results of three silicon wafers in Example 3 of this embodiment of the invention.

[0035] Figure 7 This is a schematic diagram comparing the roughness uniformity of three silicon wafers in Example 3 of the present invention;

[0036] Figure 8The figures show the atomic force microscopy measurement results of three silicon wafers in Example 4 of this embodiment of the invention.

[0037] Figure 9 This is a schematic diagram comparing the roughness uniformity of three silicon wafers in Example 4 of this embodiment of the invention. Detailed Implementation

[0038] 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.

[0039] like Figure 1 As shown, this embodiment of the invention provides a method for preparing a standard silicon wafer, comprising the following steps:

[0040] S1 provides silicon wafers;

[0041] S2, the silicon wafer is subjected to a first heat treatment to grow an oxide layer on the surface of the silicon wafer;

[0042] S3, the silicon wafer after the oxide layer has been grown is subjected to a second heat treatment to improve the surface roughness of the oxide layer through a high-temperature decomposition reaction.

[0043] The first heat treatment includes: heating to a first heat treatment temperature and maintaining the temperature in an atmosphere containing oxygen for a first heat treatment duration; the second heat treatment includes: heating to a second heat treatment temperature and maintaining the temperature in an atmosphere containing argon for a second heat treatment duration.

[0044] The preparation method provided in this invention combines a two-step process of "thermal oxidation growth" and "high-temperature decomposition and reconstruction" to create a standard sheet surface that has both the purity of the thermal oxidation layer and the specific and uniform surface roughness obtained through high-temperature decomposition. This meets the stringent calibration requirements of non-contact flatness measurement equipment such as surface light scattering instruments, which are extremely sensitive to cleanliness.

[0045] 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, the silicon wafer provided in step S1 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.

[0046] In this embodiment of the invention, in step S2, before performing the first heat treatment on the silicon wafer, it is preferable to first heat the reaction chamber to a set loading temperature, and then load the silicon wafer into the reaction chamber and maintain it for a set time under an inert protective atmosphere.

[0047] The set loading temperature can be selected from 400℃ to 700℃, preferably 500℃ to 600℃, the inert protective atmosphere can be, for example, pure argon (Ar), and the set duration can be selected from 0.1 to 60 min, preferably 10 to 30 min.

[0048] Then, the first heat treatment is performed: under an inert protective atmosphere, the heating rate is maintained at 0.01~30℃ / min, preferably 1~10℃ / min, to raise the temperature inside the reaction chamber from the loading temperature to the first heat treatment temperature, and the atmosphere inside the reaction chamber is switched to an atmosphere containing oxygen. The first heat treatment time is maintained at the first heat treatment temperature and the atmosphere containing oxygen.

[0049] The preferred temperature for the first heat treatment is 800~1000℃. The duration of the first heat treatment can be selected from 0.1~10h, preferably 1~5h. The atmosphere for the first heat treatment is pure oxygen; or, the atmosphere for the first heat treatment is a water vapor atmosphere generated by the reaction of oxygen and hydrogen, wherein the flow ratio of oxygen to hydrogen is 1:2.

[0050] Then, the second heat treatment is performed: the heating rate is maintained at 0.01~30℃ / min, preferably 1~10℃ / min, and the temperature is raised to the second target temperature, while the atmosphere of the reaction chamber is switched to an atmosphere containing argon.

[0051] The preferred temperature for the second heat treatment is 1000~1300℃. The preferred duration for the second heat treatment is 0.1~5h. The atmosphere for the second heat treatment is pure argon, a mixture of argon and hydrogen, or a mixture of argon and oxygen.

[0052] Then, the atmosphere inside the reaction chamber is switched to an inert protective atmosphere, and under the inert protective atmosphere (such as argon), the temperature inside the reaction chamber is reduced from the second heat treatment temperature to the unloading temperature.

[0053] 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 heat treatment temperature to the unloading temperature, the cooling rate can be selected from 0.01℃ to 30℃ / min, preferably 1℃ to 10℃ / min.

[0054] As can be seen from the detailed description of each step above, the manufacturing method provided by the embodiments of the present invention, from loading, heating, oxidation, high-temperature annealing to unloading, is carried out entirely within the reaction chamber and protected by inert gas or high-purity process gas, thus minimizing the introduction of external particles and metal impurities. This further ensures that the produced standard silicon wafers can be used for calibration of equipment such as surface light scattering instruments, which require extremely high cleanliness. Furthermore, through precise control of the heating rate, temperature, duration, and atmosphere, excellent uniformity and repeatability of the oxide layer thickness and surface roughness of the products within and between batches can be ensured, meeting the requirements for use as metrological calibration standard silicon wafers.

[0055] Furthermore, to further prevent the introduction of external particles and metal impurities, the preparation method provided in this embodiment may also include: cleaning the silicon wafer after the two-step heat treatment to remove metal or particulate contamination from the surface of the silicon wafer. The chemical reagents used for cleaning may include: SC~1 solution (volume ratio satisfying: NH4OH:H2O2:DIWater = 1:1:5, used for organic contamination and particle removal), SC~2 solution (volume ratio satisfying: HCl:H2O2:DIWater = 1:1:6, used for metal ion and oxide removal), the cleaning temperature is 20~40℃, and the cleaning time is 10~200s.

[0056] The preparation method provided in the embodiments of the present invention will be described by way of example below.

[0057] Example 1

[0058] Three silicon wafers in their initial states are provided, and the three initial silicon wafers are processed as shown in Table 1 to obtain silicon wafer 1, silicon wafer 2, and silicon wafer 3. Among them, silicon wafer 1 only undergoes a second heat treatment, silicon wafer 2 and silicon wafer 3 undergo a first heat treatment and a second heat treatment, respectively, and the conditions for the second heat treatment of the three silicon wafers are the same. The only difference between silicon wafer 2 and silicon wafer 3 is the duration of the first heat treatment, while all other conditions are the same.

[0059] Table 1

[0060]

[0061] Then as Figure 2 As shown in the figure, the surface roughness of each silicon wafer was characterized using atomic force microscopy. In the figure, the brighter the area, the higher the surface roughness, and the larger the corresponding value; the darker the area, the lower the surface roughness, and the smaller the corresponding value.

[0062] Further analysis Figure 2 The measurement results shown yielded the root mean square roughness (AFM RMS) of each silicon wafer surface. Figure 3 As shown, the root mean square roughness represents the root mean square value of the surface height, and its calculation formula is as follows:

[0063]

[0064] Where n represents the number of sampling points, 𝑍 𝑖 This represents the height of the i-th sampling point.

[0065] according to Figure 3 The comparison results and combination Figure 2 It can be seen that the oxidative pyrolysis method (including two process steps: "thermal oxidation growth" and "high-temperature decomposition and reconstruction") can produce silicon wafers with a certain roughness, and the time of the first heat treatment will affect the surface roughness of the final silicon wafer.

[0066] Example 2

[0067] Silicon wafer 2 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 wafer 4 and silicon wafer 5. Compared with silicon wafer 2, silicon wafer 4 and silicon wafer 5 have the same other process conditions, except for the temperature during the first heat treatment.

[0068] Table 2

[0069]

[0070] Then as Figure 4 As shown, the surface roughness of each silicon wafer was characterized using atomic force microscopy. Further analysis... Figure 4 The measurement results shown yielded the root mean square roughness (AFM RMS) of each silicon wafer surface. Figure 5 As shown in the image.

[0071] according to Figure 5 The comparison results and combined Figure 4 It can be concluded that the oxidative pyrolysis method can produce silicon wafers with a certain roughness, and the temperature of the first heat treatment affects the surface roughness of the final silicon wafer.

[0072] Example 3

[0073] Silicon wafer 2 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 wafer 6 and silicon wafer 7. Compared with silicon wafer 2, silicon wafer 6 and silicon wafer 7 have the same other process conditions, except for the temperature during the second heat treatment.

[0074] Table 3

[0075]

[0076] Then as Figure 6 As shown, the surface roughness of each silicon wafer was characterized using atomic force microscopy, and further analysis was performed. Figure 6 The measurement results shown yielded the root mean square roughness (AFM RMS) of each silicon wafer surface. Figure 7 As shown in the image.

[0077] according to Figure 7 The comparison results and combined Figure 6 It can be concluded that the oxidative pyrolysis method can produce silicon wafers with a certain roughness, and the temperature of the second heat treatment step will affect the surface roughness of the final silicon wafer.

[0078] Example 4

[0079] Silicon wafer 2 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 wafer 8 and silicon wafer 9. Compared with silicon wafer 2, silicon wafer 8 and silicon wafer 9 have the same other process conditions, except for the time of the second heat treatment.

[0080] Table 4

[0081]

[0082] Then as Figure 8 As shown, the surface roughness of each silicon wafer was characterized using atomic force microscopy, and further analysis was performed. Figure 8 The measurement results shown yielded the root mean square roughness (AFM RMS) of each silicon wafer surface. Figure 9 As shown in the image.

[0083] according to Figure 9 The comparison results and combined Figure 8It can be concluded that the oxidative pyrolysis method can produce silicon wafers with a certain roughness, and the time of the second heat treatment step will affect the surface roughness of the final silicon wafer.

[0084] 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.

[0085] Furthermore, embodiments of the present invention also provide a calibration method for a flatness measuring device, comprising:

[0086] A standard silicon wafer prepared using the preparation method provided in this invention is provided.

[0087] 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,

[0088] The measurement error of the target measurement device is confirmed based on the measurement data.

[0089] 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.

[0090] 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.

[0091] In summary, the standard silicon wafer preparation method and the flatness measurement equipment calibration method provided in this embodiment of the invention combine the two-step process of "thermal oxidation growth" and "high-temperature decomposition and reconstruction" to create a standard wafer surface that has both the purity of the thermal oxidation layer and the specific and uniform surface roughness obtained through high-temperature decomposition. This meets the stringent calibration requirements of non-contact flatness measurement equipment such as surface light scattering instruments, which are extremely sensitive to cleanliness.

[0092] 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: Silicon wafers are supplied; The silicon wafer is subjected to a first heat treatment to grow an oxide layer on the surface of the silicon wafer; The silicon wafer after the oxide layer has been grown is subjected to a second heat treatment to improve the surface roughness of the oxide layer through a high-temperature decomposition reaction; The first heat treatment includes: heating to a first heat treatment temperature and maintaining the temperature in an atmosphere containing oxygen for a first heat treatment duration; the second heat treatment includes: heating to a second heat treatment temperature and maintaining the temperature in an atmosphere containing argon for a second heat treatment duration.

2. The method for preparing a standard silicon wafer as described in claim 1, characterized in that, The first heat treatment temperature is 800~1000℃, and the first heat treatment duration is 0.1~10h.

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 1 to 5 hours.

4. The method for preparing a standard silicon wafer as described in claim 1, characterized in that, The atmosphere for the first heat treatment is pure oxygen; or, the atmosphere for the first heat treatment is water vapor generated by the reaction of oxygen and hydrogen.

5. The method for preparing a standard silicon wafer as described in claim 4, characterized in that, When the atmosphere for the first heat treatment is the atmosphere generated by the reaction of oxygen and hydrogen, the flow rate ratio of oxygen to hydrogen is 1:

2.

6. The method for preparing a standard silicon wafer as described in claim 1, characterized in that, The second heat treatment temperature is 1000~1300℃, and the second heat treatment duration is 0.1~5h.

7. The method for preparing a standard silicon wafer as described in claim 1, characterized in that, The atmosphere for the second heat treatment is pure argon, a mixture of argon and hydrogen, or a mixture of argon and oxygen.

8. The method for preparing a standard silicon wafer as described in claim 1, characterized in that, Before subjecting the silicon wafer to the first heat treatment, the preparation method further includes: The silicon wafer is loaded into a reaction chamber with a set loading temperature and held in an inert protective atmosphere for a set time. After performing the second heat treatment on the silicon wafer, the preparation method further includes: Under an inert protective atmosphere, the temperature inside the reaction chamber is reduced from the second heat treatment temperature to the unloading temperature.

9. The method for preparing a standard silicon wafer as described in claim 8, characterized in that, The set loading temperature and the set unloading temperature are 400℃~700℃, and the set duration is 0.1min~60min.

10. A calibration method for a leveling measurement device, characterized in that, include: Provide a standard silicon wafer prepared using the preparation method according to any one of claims 1 to 9; 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.

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