Thin film and its preparation method

Abstract

The present invention relates to a thin film and a preparation method thereof, belonging to the field of semiconductor technology. In the preparation method of the thin film, within a first preset time, a first reaction source and a second reaction source are introduced into a reaction chamber to form a first thin film. Then, within a second preset time, while stopping the introduction of the first reaction source, the amount of the second reaction source introduced is increased to maintain a stable state in the reaction chamber, and the remaining first reaction source and second reaction source continue to react completely to form a second thin film made of the same material as the first thin film. Then, within a third preset time, the wafer is cleaned to obtain a thin film structure on the wafer. Since the reaction environment in the reaction chamber is maintained in a stable state, the remaining first reaction source and second reaction source will not undergo incomplete reaction again, avoiding the possibility that the remaining first reaction source generates by-products and drops on the wafer to form bump defects, and improving the yield of the wafer.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and particularly to a thin film and a method for preparing the same. Background Art

[0002] In the existing semiconductor manufacturing process, during the process of depositing a mask layer on a wafer by using Plasma-Enhanced Chemical Vapor Deposition (PECVD for short), a cleaning process is carried out in the deposition chamber to prevent particulate matter from falling onto the wafer and causing bump defects.

[0003] In the existing process, during the process from the end of deposition to cleaning, the volume in the deposition chamber remains unchanged. When the radio frequency source is immediately turned off and the first reactant stops being introduced, while the introduction amount of the second reactant remains unchanged, the pressure in the deposition chamber will suddenly decrease. At this time, it will cause an instantaneous change in the ambient temperature in the deposition chamber. The instantaneous change in the ambient temperature will cause the remaining first reactant in the deposition chamber to react incompletely to generate by-products, which will fall onto the wafer to form bump defects, seriously affecting the yield of the wafer.

[0004] Based on this, how to reduce the bump defects generated during the deposition of thin films in the semiconductor manufacturing process has become a technical problem that needs to be urgently solved by those skilled in the art. Summary of the Invention

[0005] Based on this, it is necessary to provide a thin film and a method for preparing the same in view of the problem of bump defects generated during the deposition of thin films in the semiconductor manufacturing process.

[0006] To achieve the above object, on the one hand, the present invention provides a method for preparing a thin film, including:

[0007] Introduce a first reaction source and a second reaction source into the reaction chamber within a first preset time to form a first thin film on the wafer;

[0008] Within a second preset time, stop introducing the first reaction source into the reaction chamber, increase the amount of substance of the second reaction source introduced into the reaction chamber, so as to control the sum of the amount of substance of the first reaction source and the amount of substance of the second reaction source in the reaction chamber to remain unchanged. The remaining first reaction source in the reaction chamber reacts with the second reaction source to form a second thin film on the side of the first thin film away from the wafer; the material of the first thin film is the same as the material of the second thin film;

[0009] Within a third preset time, use the second reaction source as a cleaning gas to clean the wafer after the second thin film is formed.

[0010] In one embodiment, the radio frequency source in the reaction chamber is turned on both within the first preset time and within the second preset time.

[0011] In one embodiment, within the third preset time, the radio frequency source in the reaction chamber is turned off.

[0012] In one embodiment, the second preset time includes a first period and a second period;

[0013] In the first period, the amount of substance of the second reaction source is increased to a preset value;

[0014] In the second period, the amount of substance of the second reaction source is maintained at the preset value without change.

[0015] In one embodiment, within the third preset time, the second reaction source is continuously introduced into the reaction chamber.

[0016] In one embodiment, within the third preset time, the amount of substance of the second reaction source is the same as the amount of substance of the second reaction source at the end of the second preset time.

[0017] In one embodiment, within the third preset time, the reaction chamber is also evacuated.

[0018] In one embodiment, within the third preset time, after cleaning the wafer after forming the second thin film with the second reaction source as the cleaning gas, it further includes:

[0019] At the fourth preset time, the introduction of the second reaction source into the reaction chamber is stopped, and the pressure in the reaction chamber is maintained the same as the pressure in the reaction chamber at the end of the third preset time.

[0020] In one embodiment, the first reaction source includes a silicon source, and the second reaction source includes a nitrogen source and / or an oxygen source.

[0021] On the other hand, a thin film is also provided, which is formed by the method for preparing a thin film according to any one of the above.

[0022] In one embodiment, the first preset time is greater than the second preset time.

[0023] Compared with the prior art, the above technical solution has the following unexpected technical effects:

[0024] In the method for preparing the thin film, within a first preset time, a first reaction source and a second reaction source are introduced into the reaction chamber to react, thereby forming a first thin film on the wafer. Then, within a second preset time, the introduction of the first reaction source into the reaction chamber is stopped. At this time, although the introduction of the first reaction source is stopped, there is still unreacted first reaction source in the chamber. To avoid changes in the amount of substances in the reaction chamber, which may lead to changes in the environment in the reaction chamber and further cause bump defects due to incomplete reactions, the amount of the second reaction source introduced into the reaction chamber is increased so that the sum of the amounts of the first reaction source and the second reaction source in the reaction chamber remains unchanged, that is, to keep the environment in the reaction chamber in a stable state. At this time, the remaining first reaction source and the second reaction source continue to react completely to form a second thin film with the same material as the first thin film. Then, within a third preset time, using the second reaction source as a cleaning gas, the wafer after the second thin film is formed is cleaned to obtain the thin film structure on the wafer.

[0025] Since the reaction environment in the reaction chamber is maintained in a stable state, the remaining first reaction source and the second reaction source will no longer experience incomplete reactions, forming a second thin film with the same material as the first thin film, avoiding the possibility that the remaining first reaction source generates by-products due to incomplete reaction and drops on the wafer to form bump defects, and improving the yield of the wafer. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or in the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0027] Figure 1 FIG. 12 is a schematic structural diagram of a bump defect generated on a wafer in the prior art;

[0028] Figure 2 FIG. 16 is a schematic diagram of the state in a reaction chamber in the prior art;

[0029] Figure 3 FIG. 20 is a schematic flowchart of a method for preparing a thin film provided by an embodiment of the present application;

[0030] Figure 4 FIG. 24 is a schematic diagram of the gas flow rate of a reaction source provided by an embodiment of the present application;

[0031] Figure 5 FIG. 28 is a schematic diagram of the state in a reaction chamber provided by an embodiment of the present application;

[0032] Figure 6 Schematic diagram of the change in the amount of substance of the first reaction source and the second reaction source in the reaction chamber provided by the embodiment of the present application;

[0033] Figure 7 Another schematic diagram of the state in the reaction chamber provided by the embodiment of the present application;

[0034] Figure 8 Schematic diagram of a conventional formation of bump defects;

[0035] Figure 9 Schematic diagram of a structure for forming a second thin film provided by the embodiment of the present application;

[0036] Figure 10 Schematic diagram of a comparative structure of bump defects on the surface of a thin film after forming the thin film on a wafer provided by the embodiment of the present application.

[0037] Explanation of reference numerals: T1 - first preset time; T2 - second preset time; T3 - third preset time; T4 - fourth preset time; t1 - first time period; t2 - second time period. Detailed implementation manners

[0038] To facilitate the understanding of the present application, the present application will be described more comprehensively below with reference to the relevant drawings. Embodiments of the present application are shown in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of the present application more thorough and comprehensive.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs. The terms used in the specification of the present application herein are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0040] As used herein, the singular forms "a", "an" and "the" may also include the plural forms unless the context clearly dictates otherwise. It should also be understood that the terms "comprising", "including" or "having", etc. specify the presence of the stated features, wholes, steps, operations, components, parts or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts or combinations thereof.

[0041] Based on the content in the background art, refer to Figure 1 , Figure 1 Schematic diagram of a structure for generating bump defects on a conventional wafer; the bump defects are in the dashed box. Such bump defects generated after preparing a thin film on the wafer will seriously reduce the yield of the wafer. In the existing preparation method, refer toFigure 2 , Figure 2 is a schematic diagram of the state inside an existing reaction chamber; during the deposition stage x1, the radio frequency source inside the reaction chamber is turned on, and the first reaction source and the second reaction source are introduced. The pressure inside the reaction chamber is maintained at a certain state. During the cleaning stage x2, while the introduction amount of the first reaction source inside the reaction chamber is turned off, the pressure inside the reaction chamber is pumped down to the low pressure. At this time, since the first reaction source is no longer introduced, the sum of the amounts of substance of the first reaction source and the second reaction source inside the reaction chamber will decrease. According to the ideal gas state equation PV = nRT inside the reaction chamber, where P is the pressure inside the reaction chamber, V is the volume inside the reaction chamber, n is the total amount of substance in the reaction chamber, R is the gas constant, and T is the temperature inside the reaction chamber. When the pressure inside the reaction chamber is pumped down to the low pressure and the total amount of substance n inside the reaction chamber decreases, it will cause an instantaneous change in the ambient temperature inside the reaction chamber. At this time, the remaining first reaction source inside the reaction chamber will form unreacted by-products due to the change in the ambient temperature inside the reaction chamber, and fall on the surface of the first film on one side of the wafer to form bump defects. Since the defects have been formed, even if subsequent cleaning is carried out, the already formed bump defects cannot be removed, affecting the final product yield.

[0042] In view of the problem of bump defects generated during film preparation, the present application provides a method for preparing a film.

[0043] Please refer to Figure 3 , Figure 3 which is a schematic flow chart of a method for preparing a film provided by an embodiment of the present application; refer to Figure 4 , Figure 4 which is a schematic diagram of the gas flow rate of a reaction source provided by an embodiment of the present application; the method for preparing this film includes:

[0044] S101: Within a first preset time T1, introduce the first reaction source and the second reaction source into the reaction chamber to form a first film on the wafer.

[0045] In this step, to prepare a film on the wafer, the wafer needs to be placed in the reaction chamber for film preparation, and the volume inside this reaction chamber is fixed. Figure 3 The curve change in [[ ]] is only the introduction flow rate state when the first reaction source and the second reaction source are introduced into the reaction chamber.

[0046] S102: Within a second preset time T2, stop introducing the first reaction source into the reaction chamber, increase the amount of substance of the second reaction source introduced into the reaction chamber, so as to control the sum of the amounts of substance of the first reaction source and the second reaction source inside the reaction chamber to remain unchanged. The remaining first reaction source and the second reaction source inside the reaction chamber react to form a second film on the side of the first film facing away from the wafer; the material of the first film is the same as the material of the second film.

[0047] S103: Within a third preset time T3, use the second reaction source as the cleaning gas to clean the wafer after the second thin film is formed.

[0048] In the method for preparing this thin film, within a first preset time T1, introduce a first reaction source and a second reaction source into the reaction chamber to cause them to react, thereby forming a first thin film on the wafer.

[0049] Then, within a second preset time T2, stop introducing the first reaction source into the reaction chamber. At this time, although the introduction of the first reaction source is stopped, there is still unreacted first reaction source in the chamber. To avoid changes in the amount of substances in the reaction chamber, which may lead to changes in the environment in the reaction chamber and further cause bump defects due to incomplete reactions, increase the amount of the second reaction source introduced into the reaction chamber so that the sum of the amounts of the first reaction source and the second reaction source in the reaction chamber remains unchanged, that is, to keep the environment in the reaction chamber in a stable state. At this time, the remaining first reaction source and the second reaction source continue to react completely to form a second thin film with the same material as the first thin film. Then, at the third preset time T3, use the second reaction source as the cleaning gas to clean the wafer after the second thin film is formed, obtaining the thin film structure on the wafer.

[0050] Since the reaction environment in the reaction chamber is maintained in a stable state, the remaining first reaction source and the second reaction source will no longer experience incomplete reactions, forming a second thin film with the same material as the first thin film, avoiding the possibility that the remaining first reaction source generates by-products and drops on the wafer to form bump defects, and improving the yield of the wafer.

[0051] Based on the above embodiments, compare the existing method for preparing a thin film (as Figure 2 shown) with the method for preparing a thin film in this application. Refer to Figure 5 , Figure 5 which is a schematic diagram of the state in the reaction chamber provided by the embodiment of this application; in this application, at the first preset time T1, the radio frequency source in the reaction chamber is turned on, and the first reaction source and the second reaction source are introduced. The pressure in the reaction chamber is maintained at a certain state, and the first reaction source and the second reaction source react to form a first thin film on the wafer surface. It should be noted that within the first preset time T1, the introduction amounts of the first reaction source and the second reaction source only need to ensure that a first thin film can be formed on the wafer, and no specific limitations are made. After a first thin film with the required thickness is generated within the first preset time T1, stop introducing the first reaction source into the reaction chamber and enter the second preset time T2. The start time point of the second preset time T2 is the end time point of the first preset time T1.

[0052] Ensure that the radio frequency source is in the on stage within the second preset time T2. While closing the input amount of the first reaction source in the reaction chamber, increase the amount of the second reaction source introduced into the reaction chamber so that the sum of the amount of the first reaction source and the amount of the second reaction source in the reaction chamber remains unchanged. It should be noted that increasing the amount of the second reaction source can be achieved by increasing the flow rate of the second reaction source into the reaction chamber. At this time, the reaction chamber is not evacuated, and increasing the amount of the second reaction source can also ensure that the pressure in the reaction chamber remains unchanged. According to the ideal gas state equation, the ambient temperature in the reaction chamber will not change. After the first thin film is formed, the remaining first reaction source and the second reaction source will continue to form a second thin film with the same material as the first thin film on the side of the first thin film facing away from the wafer. Since the ambient temperature in the reaction chamber does not change, the remaining first reaction source will not generate by-products due to incomplete reaction, thus avoiding the formation of bump defects.

[0053] Then, at the third preset time T3, use the second reaction source as the cleaning gas to clean the wafer after the second thin film is formed, which can further remove other impurities, thereby greatly increasing the yield of the wafer.

[0054] In this embodiment, the present application Figure 5 The preparation method in this application compared with the existing preparation method completely reacts the remaining first reaction source to form a second thin film with the same material as the first thin film, significantly reducing the formation of bump defects.

[0055] Optionally, in another embodiment of the application, the radio frequency source in the reaction chamber is turned on both within the first preset time T1 and within the second preset time T2.

[0056] Specifically, to deposit a thin film on the wafer, the radio frequency source needs to be turned on to ensure that the first reaction source and the second reaction source in the reaction chamber can react.

[0057] Optionally, as Figure 5 shown, in another embodiment of the present application, the first preset time T1 is greater than the second preset time T2.

[0058] Specifically, within the second preset time T2, since the introduction of the first reaction source has been stopped, the amount of the remaining first reaction source is small, and the reaction duration is shorter than the duration of forming the first thin film. Of course, the thickness of the formed first thin film is also greater than the thickness of the second thin film. It should be noted that the materials of the first thin film and the second thin film are the same, so it will not affect the structure of the finally formed thin film.

[0059] Optionally, refer to Figure 6 , Figure 6Schematic diagram of the change in the amount of substance of the first reaction source and the second reaction source in the reaction chamber provided by the embodiment of the present application; in another embodiment of the present application, the second preset time T2 includes a first time period t1 and a second time period t2.

[0060] In the first time period t1, increase the amount of substance of the second reaction source to a preset value.

[0061] In the second time period t2, keep the amount of substance of the second reaction source unchanged at the preset value.

[0062] Specifically, as Figure 6 shown, in the present application, within the first preset time T1 and the second preset time T2, the sum of the amount of substance of the first reaction source and the amount of substance of the second reaction source remains unchanged, so as to ensure that the environment in the reaction chamber is in a stable state. The second preset time T2 is mainly to completely react the remaining first reaction source in the reaction chamber to form a second thin film. During the formation of the second thin film, within the first time period t1, the first reaction source will gradually decrease. After that, in order not to form by-products in the second time period t2, a relatively stable state needs to be maintained for a period of time.

[0063] At the beginning of the first time period t1, the inlet flow rate of the first reaction source is closed, and the amount of substance of the second reaction source is increased to control the sum of the amount of substance of the first reaction source and the amount of substance of the second reaction source in the reaction chamber to remain unchanged. That is to say, when the remaining first reaction source reacts with the second reaction source, as the first reaction source is reacted, the amount of substance of the first reaction source gradually decreases, and the amount of substance of the second reaction source gradually increases to the preset value, ensuring that the total amount of substance in the reaction chamber remains unchanged and maintaining the environment in the reaction chamber in a stable state, so as to completely react the remaining first reaction source. It should be noted that this preset value is the sum of the amount of substance of the first reaction source and the amount of substance of the second reaction source within the first preset time T1.

[0064] In the second time period t2, keep the amount of substance of the second reaction source unchanged at the preset value. This process is set to ensure that the first reaction source is completely reacted. After the first reaction source is completely reacted, there will be no bump defects caused by the dropping of by-products generated by the remaining first reaction source, further improving the yield of the wafer.

[0065] Optionally, in another embodiment of the present application, the first reaction source includes a silicon source, and the second reaction source includes a nitrogen source and / or an oxygen source.

[0066] Specifically, in this embodiment, preparing the thin film may involve depositing a mask layer on the wafer. The mask layer may be a silicon oxide and / or silicon nitride thin film. The silicon source, as well as the nitrogen source and / or oxygen source introduced into the reaction chamber, can be controlled to deposit the required thin film. It should be noted that the silicon source may include, but is not limited to, SiH4, and the nitrogen source and / or oxygen source include, but are not limited to, N2 and / or N2O. Only examples are given here.

[0067] Optionally, in another embodiment of the present application, within the third preset time T3, the radio frequency source in the reaction chamber is turned off.

[0068] It should be noted that the third preset time T3 is the cleaning stage. To ensure that no bump defects caused by other impurities occur subsequently, the reaction chamber is cleaned. During this process, turning off the radio frequency source of the reaction chamber can avoid damaging the reaction chamber.

[0069] Optionally, as Figure 6 shown, in another embodiment of the present application, within the third preset time T3, the amount of substance of the second reaction source is the same as that of the second reaction source at the end of the second preset time T2.

[0070] Specifically, at the third preset time T3, although the thin film has been deposited, it is still necessary to maintain the stability in the reaction chamber to clean the wafer. Therefore, the second reaction source is continuously introduced. At this time, the introduction amount and the amount of substance of the second reaction source can be not adjusted because theoretically the first reaction source has been completely reacted at this time. So the amount of substance of the second reaction source is the same as that of the second reaction source at the end of the second preset time T2.

[0071] It should be noted that in another embodiment, the amount of substance of the second reaction source may vary within the third preset time T3. For example, the amount of substance of the second reaction source may gradually decrease within the third preset time T3, or the amount of substance of the second reaction source may also decrease in a stepped manner within the third preset time T3, etc. No specific description is given here, and only examples are given above.

[0072] Optionally, as Figure 5 shown in another embodiment of the present application, within the third preset time T3, the reaction chamber is also evacuated.

[0073] Specifically, the reaction chamber has a TV valve. Within the third preset time T3, the angle of the TV valve is controlled to evacuate the reaction chamber and pump the pressure in the reaction chamber to a low pressure to ensure that the chamber is in a relatively stable state.

[0074] Optionally, referring to Figure 7 , Figure 7Another schematic diagram of the state inside the reaction chamber provided by the embodiment of the present application; in another embodiment of the present application, within the third preset time T3, after cleaning the wafer after forming the second thin film with the second reaction source as the cleaning gas, it further includes:

[0075] At the fourth preset time T4, stop introducing the second reaction source into the reaction chamber, and maintain the pressure inside the reaction chamber the same as the pressure inside the reaction chamber at the end of the third preset time T3.

[0076] Specifically, within the fourth preset time T4 after the cleaning is completed, take out the wafer from the reaction chamber. Since the thin film preparation process has ended, the second reaction source is no longer introduced into the reaction chamber. At this time, keep the pressure inside the reaction chamber at the state of the pressure inside the reaction chamber at the end of the third preset time T3 to provide an environment for subsequent preparation.

[0077] Based on the above embodiments, the present application also explains the formation process of bump defects and the second thin film. Refer to Figure 8 , Figure 8 which is a schematic diagram of forming bump defects in the prior art; refer to Figure 9 , Figure 9 which is a schematic diagram of a structure for forming the second thin film provided by the embodiment of the present application. It can be seen from Figure 8 that due to the changes in the amount of substance and the pressure inside the reaction chamber, the environment inside the reaction chamber suddenly changes. After the first reaction source stops being introduced, the remaining first reaction source inside the reaction chamber will form bump defects due to the sudden change of the environment; as shown in Figure 9 , in the present application, since the environment inside the reaction chamber is ensured to be in a stable state, the remaining first reaction source inside the reaction chamber will continuously react with the second reaction source to form a continuous thin film, that is, the second thin film. When the first reaction source is completely reacted, bump defects caused by the first reaction source will no longer appear.

[0078] In addition, the present application also provides a comparison of the results of bump defects after actually preparing a thin film using this method. Refer to Figure 10 , Figure 10 which is a comparative structure schematic diagram of bump defects on the surface of a thin film after forming the thin film on a wafer provided by the embodiment of the present application; Figure 10 In Figure a of , it is an actual schematic diagram of bump defects after forming the existing thin film, and in Figure b of , it is an actual schematic diagram of bump defects after forming the thin film of the present application. It can be seen that there are more existing bump defects, while the bump defects after forming the thin film on the wafer using this method are significantly fewer, improving the problem of generating bump defects when forming the thin film on the wafer. Based on the comparison results, it is obtained that the present application significantly improves the effect of bump defects and improves the yield of the finally produced wafers.

[0079] The present application also provides a thin film, which is formed based on the above-mentioned method for preparing a thin film. It should be noted that this thin film is the first thin film and the second thin film described above.

[0080] In this embodiment, since the reaction environment in the reaction chamber is maintained in a stable state, the remaining first reaction source and second reaction source will no longer undergo incomplete reactions, forming a second thin film with the same material as the first thin film. This avoids the possibility that the remaining first reaction source generates by-products due to incomplete reaction and drops on the wafer to form bump defects, thereby improving the yield of the wafer.

[0081] In the description of this specification, the description with reference to terms such as "some embodiments", "another embodiment", etc. means that the specific features, structures, materials or features described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic description of the above terms does not necessarily refer to the same embodiment or example.

[0082] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features of the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0083] The above-described embodiments only represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method for preparing a thin film, characterized in that: include: Introducing a first reaction source and a second reaction source into the reaction chamber within a first preset time to form a first film on the wafer; Within a second preset time, the first reaction source is stopped from being introduced into the reaction chamber, and the amount of the substance of the second reaction source introduced into the reaction chamber is increased to control the sum of the amount of the substance of the first reaction source and the amount of the substance of the second reaction source in the reaction chamber to remain unchanged, the reaction environment in the reaction chamber is maintained in a stable state, the remaining first reaction source in the reaction chamber reacts with the second reaction source to form a second film on a side of the first film away from the wafer; the material of the first film is the same as the material of the second film; During a third preset time, the second reaction source is used as a cleaning gas to clean the wafer after the second film is formed.

2. The method for preparing a thin film according to claim 1, characterized in that: The radio frequency source in the reaction chamber is turned on during the first preset time and the second preset time.

3. The method for preparing a thin film according to claim 2, characterized in that: During the third preset time, the radio frequency source in the reaction chamber is turned off.

4. The method for preparing a thin film according to claim 1, characterized in that: The second preset time includes a first period and a second period; During the first period, increasing the amount of the substance of the second reaction source to a preset value; During the second period, the amount of the substance in the second reaction source is maintained at the preset value.

5. The method for preparing a thin film according to claim 1, characterized in that: During the third preset time, the second reaction source is continuously introduced into the reaction chamber.

6. The method for preparing a thin film according to claim 5, characterized in that: During the third preset time, the amount of the substance in the second reaction source is the same as the amount of the substance in the second reaction source at the end of the second preset time.

7. The method for preparing a thin film according to claim 5, characterized in that: The reaction chamber is also evacuated during the third preset time.

8. The method for preparing a thin film according to claim 1, characterized in that: After the wafer after the second film is formed is cleaned by using the second reaction source as a cleaning gas within the third preset time, the method further includes: At a fourth preset time, the introduction of the second reaction source into the reaction chamber is stopped, and the pressure in the reaction chamber is maintained to be the same as the pressure in the reaction chamber at the end of the third preset time.

9. The method for preparing a thin film according to claim 1, characterized in that: The first reaction source includes a silicon source, and the second reaction source includes a nitrogen source and / or an oxygen source.

10. The method for preparing a thin film according to claim 1, characterized in that: The first preset time is greater than the second preset time.

11. A film, characterized in that: The film is prepared by the method for preparing the film according to any one of claims 1 to 10.

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