Film and preparation method thereof

Abstract

The invention relates to a thin film and a preparation method thereof, and relates to the technical field of semiconductors, in the preparation method of the thin film, a first reaction source and a second reaction source are introduced into a reaction cavity within a first preset time to form a first thin film, and then, in a second preset time, introduction of the first reaction source is stopped while introduction of the second reaction source is stopped to form a second thin film; the amount of substance introduced into the second reaction source is increased, so that the environment in the reaction cavity is kept in a stable state, the remaining first reaction source and the remaining second reaction source continuously and completely react to form a second thin film made of the same material as the first thin film, and then the wafer is cleaned within third preset time to obtain the thin film structure on the wafer. The reaction environment in the reaction cavity is kept in a stable state, so that the residual first reaction source and the second reaction source do not react incompletely, the possibility that the residual first reaction source generates by-products due to incomplete reaction, the by-products fall on the wafer to form salient point defects is avoided, and the yield of the wafer is improved.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to a thin film and a method for preparing the same. Background Art

[0002] In the existing semiconductor manufacturing process, when a mask layer is deposited on a wafer using a plasma-enhanced chemical vapor deposition (PECVD) process, a cleaning process is performed in the deposition chamber to prevent particles from falling onto the wafer and causing bump defects.

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

[0004] Based on this, how to reduce the bump defects generated when depositing thin films in the semiconductor manufacturing process has become a technical problem that technical personnel in this field urgently need to solve. Summary of the invention

[0005] Based on this, it is necessary to provide a thin film and a method for preparing the same in order to solve the problem of bump defects generated when depositing thin films in semiconductor manufacturing processes.

[0006] In order to achieve the above object, on the one hand, the present invention provides a method for preparing a thin film, comprising:

[0007] 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;

[0008] 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, and the remaining first reaction source in the reaction chamber reacts with the second reaction source to form a second film on the 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;

[0009] 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.

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

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

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

[0013] During the first period, increasing the amount of the substance of the second reaction source to a preset value;

[0014] During the second period, the amount of the substance in the second reaction source is maintained at the preset value.

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

[0016] In one embodiment, 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.

[0017] In one of the embodiments, the reaction chamber is also evacuated during the third preset time.

[0018] In one embodiment, after the second reaction source is used as a cleaning gas to clean the wafer after the second film is formed within the third preset time, the method further includes:

[0019] 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.

[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 provided, which is prepared based on any of the above-mentioned thin film preparation methods.

[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 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 film on a wafer. Then, within a second preset time, the first reaction source is stopped from being introduced into the reaction chamber. Although the introduction of the first reaction source is stopped at this time, there are still first reaction sources that have not reacted completely in the chamber. In order to avoid the change in the amount of the substance in the reaction chamber, which leads to the change in the environment in the reaction chamber, and then the convex point defects caused by the incomplete reaction, the amount of the substance of the second reaction source introduced into the reaction chamber is increased, so that 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 remains unchanged, that is, the environment in the reaction chamber maintains a stable state, and the remaining first reaction source and the second reaction source continue to react completely to form a second film of the same material as the first film. Then, within a third preset time, the second reaction source is used as a cleaning gas to clean the wafer after the second film is formed, and a film structure on the wafer is obtained.

[0025] Since the reaction environment in the reaction chamber maintains a stable state, the remaining first reaction source and the second reaction source will no longer have an incomplete reaction, and a second film made of the same material as the first film is formed, thereby avoiding the possibility of the remaining first reaction source generating by-products due to incomplete reaction and falling on the wafer to form bump defects, thereby 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 the conventional technology, the drawings required for use in the embodiments or the conventional technology descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0027] Figure 1 A schematic diagram of a structure in which a bump defect is generated on an existing wafer;

[0028] Figure 2 It is a schematic diagram of the state inside an existing reaction chamber;

[0029] Figure 3 A schematic diagram of a process for preparing a thin film provided in an embodiment of the present application;

[0030] Figure 4 A schematic diagram of the gas flow rate of a reaction source provided in an embodiment of the present application;

[0031] Figure 5 A schematic diagram of the state inside a reaction chamber provided in an embodiment of the present application;

[0032] Figure 6 A schematic diagram of the change in the amount of substances of a first reaction source and a second reaction source in a reaction chamber provided in an embodiment of the present application;

[0033] Figure 7 A schematic diagram of another state inside a reaction chamber provided in an embodiment of the present application;

[0034] Figure 8 A schematic diagram of an existing method for forming a convex point defect;

[0035] Fig. 9 A schematic diagram of a structure for forming a second film provided in an embodiment of the present application;

[0036] Fig.10 A schematic diagram of the comparative structure of a convex defect on the surface of a thin film after a thin film is formed on a wafer provided in an embodiment of the present application.

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

[0038] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. Embodiments of the present application are provided 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, the purpose of providing these embodiments is 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 those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0040] When used herein, the singular forms "a", "an", and "said / the" may also include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include / comprise" or "have" etc. specify the presence of 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 technology, refer to Figure 1 , Figure 1 The schematic diagram of the structure of a conventional wafer having a bump defect is shown in FIG. The bump defect in the dotted box is a bump defect. This bump defect generated after a thin film is prepared on the wafer will seriously reduce the yield of the wafer. In the conventional preparation method, reference Figure 2 , Figure 2 It is a schematic diagram of the state in an existing reaction chamber; in the deposition stage x1, the RF source in the reaction chamber is turned on, and reaction source 1 and reaction source 2 are introduced, and the pressure in the reaction chamber is maintained at a certain state. In the cleaning stage x2, while the amount of reaction source 1 in the reaction chamber is closed, the pressure in the reaction chamber will be pumped to the bottom pressure. At this time, since reaction source 1 is no longer introduced, the sum of the amount of substance in reaction source 1 and reaction source 2 in the reaction chamber will decrease. In the reaction chamber, according to the ideal gas state equation PV=nRT, P is the pressure in the reaction chamber, V is the volume in the reaction chamber, n is the total amount of substance in the reaction chamber, R is the gas constant, and T is the temperature in the reaction chamber. The pressure in the reaction chamber is pumped down to the bottom pressure, and the total amount of substance n in the reaction chamber decreases, which causes an instantaneous change in the ambient temperature in the reaction chamber. At this time, the remaining reaction sources in the reaction chamber will form incompletely reacted by-products due to the change in the ambient temperature in the reaction chamber, and fall on the surface of the first film on one side of the wafer to form convex defects. Since the defects have been formed, even if cleaning is performed later, the convex defects that have been formed cannot be removed, affecting the final product yield.

[0042] The present application provides a method for preparing a thin film in order to solve the problem of convex point defects generated during thin film preparation.

[0043] Please refer to Figure 3 , Figure 3 A schematic diagram of a process for preparing a thin film provided in an embodiment of the present application; Figure 4 , Figure 4 A schematic diagram of a gas flow rate of a reaction source provided in an embodiment of the present application; the method for preparing the film includes:

[0044] S101: within a first preset time T1, a first reaction source and a second reaction source are introduced into a reaction chamber to form a first thin film on a wafer.

[0045] In this step, in order to prepare a thin film on a wafer, the wafer needs to be placed in a reaction chamber for thin film preparation, and the volume of the reaction chamber is fixed. Figure 3 The curve change in FIG. 1 is only the 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, and increase the amount of the substance of the second reaction source introduced into the reaction chamber 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, and the remaining first reaction source in the reaction chamber reacts with the second reaction source to form a second film on the 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.

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

[0048] In the method for preparing the thin film, within a first preset time T1, a first reaction source and a second reaction source are introduced into the reaction chamber to react with each other, thereby forming a first thin film on the wafer.

[0049] Then, within the second preset time T2, the first reaction source is stopped from being introduced into the reaction chamber. Although the introduction of the first reaction source is stopped at this time, there is still a first reaction source that has not been fully reacted in the chamber. In order to avoid the amount of the substance in the reaction chamber changing, thereby causing the change of the environment in the reaction chamber, and then causing the convex point defects caused by the incomplete reaction, the amount of the substance of the second reaction source introduced into the reaction chamber is increased, so that 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 remains unchanged, that is, the environment in the reaction chamber maintains a stable state. At this time, the remaining first reaction source and the second reaction source continue to react completely to form a second film that is the same material as the first film. Then, at the third preset time T3, the second reaction source is used as a cleaning gas to clean the wafer after the second film is formed to obtain a film structure on the wafer.

[0050] Since the reaction environment in the reaction chamber maintains a stable state, the remaining first reaction source and the second reaction source will no longer have an incomplete reaction, and a second film made of the same material as the first film is formed, thereby avoiding the possibility of the remaining first reaction source generating by-products due to incomplete reaction and falling on the wafer to form bump defects, thereby improving the yield of the wafer.

[0051] Based on the above embodiments, the existing method for preparing thin films (such as Figure 2 ) and the method for preparing the film of the present application are compared. Figure 5 , Figure 5 A schematic diagram of the state in a reaction chamber provided for an embodiment of the present application; in the present application, at the first preset time T1, the RF 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, the first reaction source and the second reaction source react, and a first film is formed on the surface of the wafer. It should be noted that within the first preset time T1, the amount of the first reaction source and the second reaction source introduced can ensure that the first film can be formed on the wafer, and no specific limitation is made. After the first film of the required thickness is generated within the first preset time T1, the first reaction source is stopped from being introduced into the reaction chamber, and the second preset time T2 is entered. The starting time point of the second preset time T2 is the ending time point of the first preset time T1.

[0052] During the second preset time T2, the RF source is ensured to be in the on stage. While the amount of the first reaction source in the reaction chamber is closed, the amount of the substance introduced into the reaction chamber by the second reaction source is increased, so that 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 remains unchanged. It should be noted that the amount of the substance of the second reaction source can be increased by increasing the flow rate of the second reaction source into the reaction chamber. At this time, the reaction chamber is not evacuated, and the amount of the substance 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 film is generated, the remaining first reaction source will continue to form a second film with the same material as the first film on the side of the first film away from the wafer with the second reaction source. If the ambient temperature in the reaction chamber does not change, the remaining first reaction source will not generate byproducts due to incomplete reaction, thereby forming convex defects.

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

[0054] In this embodiment, the present application Figure 5 Compared with the existing preparation method, the preparation method in the invention completely reacts the remaining first reaction source to form a second film made of the same material as the first film, thereby significantly reducing the formation of convex 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 a wafer, a 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] Optional, such as Figure 5 As shown, in another embodiment of the present application, the first preset time T1 is greater than the second preset time T2.

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

[0059] Optional, reference Figure 6 , Figure 6A schematic diagram of the change in the amount of substances of a first reaction source and a second reaction source in a reaction chamber provided in an 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, the amount of the substance of the second reaction source is increased to a preset value.

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

[0062] Specifically, Figure 6 As shown, in the present application, within the first preset time T1 and the second preset time T2, the sum of the amount of the substance of the first reaction source and the amount of the substance of the second reaction source remains unchanged, thereby ensuring 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 film. In the process of forming the second film, the first reaction source will gradually decrease within the first time period t1, and thereafter, in order not to form by-products, the second time period t2 needs to maintain a relatively stable state for a period of time.

[0063] At the beginning of the first time period t1, the inflow flow of the first reaction source is closed, and the amount of the substance of the second reaction source is increased in order 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, that is, when the remaining first reaction source reacts with the second reaction source, as the first reaction source is reacted, the amount of the substance of the first reaction source gradually decreases, and the amount of the 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, maintaining the environment in the reaction chamber in a stable state, and thus completely reacting the remaining first reaction source. It should be noted that the preset value is the sum of the amount of the substance of the first reaction source and the amount of the substance of the second reaction source within the first preset time T1.

[0064] In the second time period t2, the amount of the substance in the second reaction source is kept unchanged at a 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 remaining by-products generated by the first reaction source falling off, 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, the thin film can be prepared by depositing a mask layer on a wafer, and the mask layer can be a silicon oxide and / or silicon nitride thin film, and the silicon source and the nitrogen source and / or the oxygen source introduced into the reaction chamber can be controlled to deposit and form the required thin film. It should be noted that the silicon source can include but is not limited to SiH4, and the nitrogen source and / or the oxygen source include but are not limited to N2 and / or N2O, which are only exemplified here.

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

[0068] It should be noted that the third preset time T3 is a cleaning stage, and the reaction chamber is cleaned to ensure that no bump defects caused by other impurities will occur in the future. In this process, the RF source of the reaction chamber is turned off to avoid damage to the reaction chamber.

[0069] Optional, such as Figure 6 As shown, in another embodiment of the present application, within the third preset time T3, 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 T2.

[0070] Specifically, at the third preset time T3, although the thin film has been deposited, it is still necessary to maintain stability in the reaction chamber to clean the wafer. Therefore, the second reaction source is continuously introduced. At this time, the introduction amount of the second reaction source and the amount of substance do not need to be adjusted, because the first reaction source has theoretically been completely reacted at this time, so the amount of substance in the second reaction source at this time is the same as the amount of substance in 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 the substance in the second reaction source may change within the third preset time T3. For example, the amount of the substance in the second reaction source may gradually decrease within the third preset time T3, or the amount of the substance in the second reaction source may also decrease in a step-like manner within the third preset time T3, etc., which is not described in detail here, and the above is only for example.

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

[0073] Specifically, the reaction chamber is provided with a TV valve. Within the third preset time T3, the angle of the TV valve is controlled to evacuate the reaction chamber to reduce the pressure in the reaction chamber to the bottom pressure to ensure that the chamber is in a relatively stable state.

[0074] Optional, reference Figure 7 , Figure 7A schematic diagram of another state in a reaction chamber provided in an embodiment of the present application; in another embodiment of the present application, within a third preset time T3, after the wafer after the second film is formed is cleaned using the second reaction source as the cleaning gas, the method further includes:

[0075] At the fourth preset time T4, 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 T3.

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

[0077] Based on the above embodiments, the present application also describes the formation process of the convex point defect and the second film. Figure 8 , Figure 8 A schematic diagram of an existing method for forming a bump defect; Fig. 9 , Fig. 9 A schematic diagram of a structure for forming a second film provided in an embodiment of the present application. Figure 8 It can be seen from the figure that due to the change in the amount of the substance and the pressure in the reaction chamber, the environment in the reaction chamber suddenly changes. After the first reaction source stops flowing, the remaining first reaction source in the reaction chamber will form a convex defect due to the sudden change in the environment. Fig. 9 As shown, in the present application, since the environment in the reaction chamber is ensured to remain in a stable state, the remaining first reaction source in the reaction chamber will continue to react with the second reaction source to form a continuous film, i.e., the second film. The first reaction source is completely reacted, and the convex point 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 the bump defects after the film is actually prepared by the present method, referring to Fig.10 , Fig.10 A schematic diagram of a comparative structure of a convex defect on a surface of a thin film after a thin film is formed on a wafer provided in an embodiment of the present application; Fig.10 Figure a is a schematic diagram of the actual convex defect after the existing film is formed, and Figure b is a schematic diagram of the actual convex defect after the film is formed in the present application. It can be seen that the existing convex defects are more, while the convex defects after the film is formed on the wafer using the present method are significantly less, which improves the problem of convex defects when the film is formed on the wafer. Based on the comparison results, the present application significantly improves the effect of convex defects and improves the yield of the wafers produced in the end.

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

[0080] In this embodiment, since the reaction environment in the reaction chamber maintains a stable state, the remaining first reaction source and the second reaction source will no longer have an incomplete reaction, and a second film made of the same material as the first film is formed, thereby avoiding the possibility that the remaining first reaction source will not completely react and generate by-products that fall 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 the terms "some embodiments", "another embodiment", etc. means that the specific features, structures, materials or characteristics described in conjunction 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-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features of the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0083] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached 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, and the remaining first reaction source in the reaction chamber reacts with the second reaction source to form a second film on the 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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