Silicon nitride film, preparation method thereof and semiconductor device

Abstract

The invention belongs to the technical field of semiconductors, and relates to a silicon nitride film, a preparation method thereof and a semiconductor device. The preparation method of the silicon nitride film comprises the following steps: (1) introducing precursor gas into a cavity which is vacuumized, and preheating a wafer to a deposition temperature at the same time; (2) depositing a silicon nitride film on the surface of the wafer; (3) vacuumizing the cavity, introducing nitrogen, and performing plasma treatment on the silicon nitride film; and (4) vacuumizing the cavity, and cooling to finish the preparation. After the nitrogen is introduced in the step (3), the pressure in the cavity is 2.0 torr to 3.0 torr; the power of the plasma treatment is 450 W to 550 W. According to the invention, the silicon nitride film obtained by deposition is subjected to plasma treatment, and the plasma treatment process is optimized, so that the silicon nitride film with good uniformity and low roughness is prepared.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, specifically to silicon nitride thin films, and particularly to a silicon nitride thin film, a preparation method thereof, and a semiconductor device. Background Art

[0002] In the process of semiconductor manufacturing, silicon nitride thin films have good stress characteristics and good visible light transmittance, and are often widely used as light-transmitting thin films in the fields of visible light and infrared windows. This requires a high light transmittance of the silicon nitride thin film. The light transmittance is affected by the film thickness and surface roughness. A thinner and less rough silicon nitride thin film can maximize the transmittance, thus meeting the application requirements that are extremely sensitive to light loss. However, due to process reasons and the characteristics of silicon nitride thin films during deposition, shallow pits and particles often appear on the surface, resulting in a large roughness. Therefore, it is urgently needed to be improved to reduce the roughness.

[0003] CN117488273A discloses a preparation method of a low-roughness thick silicon nitride thin film, which adopts a process combining LPCVD and high-temperature annealing. By adjusting the flow ratio of DCS and NH3, silicon nitride thin films with different refractive indexes are prepared; the high-temperature annealing process eliminates the stress in the silicon nitride thin film, reduces the hydrogen content in the silicon nitride thin film, reduces the light absorption effect of the silicon nitride waveguide, realizes the low roughness and low stress of the thick silicon nitride, and improves the light transmission efficiency of the silicon nitride thin film; the prepared silicon nitride thin film has a roughness within 1 nm, a refractive index of 2.05 - 2.1, a stress within 1000 MPa, and a silicon nitride thickness that can reach 500 nm, which can meet the requirements of silicon-based optoelectronic devices for silicon nitride thin films.

[0004] CN105070646A discloses a preparation method of a low-stress silicon nitride thin film, including the following steps: loading a wafer into a reaction chamber and then evacuating the reaction chamber, maintaining the vacuum degree of the reaction chamber at a preset vacuum degree and for a first preset duration; controlling the temperature value in the reaction chamber to a preset temperature value and for a second preset duration; respectively introducing a first flow rate of SiH4 gas, a second flow rate of NH3 gas, a third flow rate of N2 gas, and a fourth flow rate of He gas into the reaction chamber, and after introducing each gas, maintaining for a third preset duration; performing radio frequency ignition to make each gas form a plasma state and react with each other to generate a silicon nitride thin film on the surface of the wafer.

[0005] CN110473768A discloses a method for preparing a silicon nitride thin film. The preparation method includes alternately performing the following steps: Step 1), depositing a silicon nitride sub-film on the surface of a substrate by chemical vapor deposition; and Step 2), performing plasma surface treatment on the surface of the silicon nitride sub-film, wherein the ions used in the plasma surface treatment include nitrogen ions; wherein, the number of times of alternately performing Step 1) and Step 2) ranges from 2 to 5 times to obtain a silicon nitride thin film including a stack of multiple silicon nitride sub-films. In this invention, the required silicon nitride thin film to be deposited is divided into several silicon nitride sub-films and deposited layer by layer. By superimposing the contact interfaces, the original growth structure is disrupted, and the formation of pinhole defects can be inhibited.

[0006] In the prior art, the processes for preparing high-quality silicon nitride thin films are usually complex or have strict requirements for process conditions. Therefore, it is of great significance to provide a simple method for preparing high-quality silicon nitride thin films. Summary of the Invention

[0007] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a silicon nitride thin film, a preparation method thereof, and a semiconductor device. By performing plasma treatment on the deposited silicon nitride thin film and optimizing the plasma treatment process, the present invention prepares a silicon nitride thin film with good uniformity and low roughness.

[0008] To achieve the purpose of this invention, the following technical solutions are adopted: In the first aspect, the present invention provides a method for preparing a silicon nitride thin film. The preparation method includes: (1) introducing a precursor gas into a chamber evacuated to a vacuum while preheating a wafer to a deposition temperature; (2) depositing a silicon nitride thin film on the surface of the wafer; (3) evacuating the chamber to a vacuum, introducing nitrogen gas, and performing plasma treatment on the silicon nitride thin film; (4) evacuating the chamber to a vacuum and cooling down to complete the preparation; after introducing nitrogen gas in step (3), the pressure in the chamber is 2.0 torr - 3.0 torr; the power of the plasma treatment in step (3) is 450 W - 550 W.

[0009] In the preparation method provided by the present invention, while preheating the wafer, a precursor gas is introduced. Under the pressure environment created by the precursor gas, the preheating effect of the wafer is better. And during the preheating process of the wafer, through the long-term stability of the precursor gas, the flow rate of the precursor gas, its distribution in the chamber, and the pressure distribution in the chamber are all more uniform, providing a good deposition environment for the subsequent deposition of the silicon nitride thin film.

[0010] The present invention performs plasma treatment on the deposited silicon nitride thin film. The nitrogen ions in the plasma (such as N +)(Under the acceleration of the electric field, bombarding the silicon nitride film enhances the atomic mobility in the silicon nitride film, enabling the removal of atoms or molecules from the convex regions on the surface of the silicon nitride film, promoting the ordered arrangement of deposited atoms and filling micro-defects, and suppressing grain coarsening and stress cracking caused by atomic migration at high temperatures. As a result, the surface undulation of the silicon nitride film is reduced, and a dense and smooth film structure is formed.)

[0011] (The present invention further optimizes the process of plasma treatment. First, before plasma treatment, the chamber is pumped to a vacuum to ensure that there is no residual ammonia and silane in the chamber, so that no new unstable silicon nitride film will be generated during the subsequent plasma treatment, avoiding the generation of particle contamination due to the unstable film generated during the plasma treatment, which affects the uniformity and roughness of the prepared silicon nitride film. In addition, the present invention optimizes the power and time of plasma treatment. Plasma treatment is carried out at a relatively low power of 450 W - 550 W, avoiding strong bombardment of the film, resulting in etching of the film. When the power is too high, Arcing (arc discharge) is likely to occur, leading to abnormal local film thickness and affecting the uniformity of the prepared silicon nitride film.)

[0012] (Preferably, the precursor gas in step (1) includes ammonia, silane, and nitrogen.)

[0013] (Preferably, after introducing the precursor gas in step (1), the pressure in the chamber is 1.0 torr - 5.0 torr.)

[0014] (Preferably, in the precursor gas of step (1), the flow rate of nitrogen is 1000 sccm - 2000 sccm.)

[0015] (Preferably, in the precursor gas of step (1), the flow rate of ammonia is 20 sccm - 40 sccm.)

[0016] (Preferably, in the precursor gas of step (1), the flow rate of silane is 10 sccm - 30 sccm.)

[0017] (Preferably, the deposition temperature is 300 °C - 400 °C.)

[0018] (Preferably, the heating rate of preheating is 15.0 °C / min - 20.0 °C / min.)

[0019] (Preferably, the radio frequency power for depositing the silicon nitride film is 250 W - 350 W.)

[0020] (Preferably, the frequency of the radio frequency is 13.56 MHz.)

[0021] Preferably, the time for depositing the silicon nitride thin film is 200 s - 300 s.

[0022] Preferably, the flow rate of nitrogen gas introduced in step (3) is 2000 sccm - 3000 sccm.

[0023] Preferably, the time for plasma treatment is 15 s - 25 s.

[0024] Preferably, the equipment used in the preparation method is a single - chamber single - wafer equipment.

[0025] In a second aspect, the present invention provides a silicon nitride thin film, which is prepared by the preparation method as described in the first aspect; the thickness of the silicon nitride thin film is 400 nm - 600 nm.

[0026] In a third aspect, the present invention provides a semiconductor device, which includes the silicon nitride thin film as described in the second aspect.

[0027] Compared with the prior art, the present invention has the following beneficial effects: (1) By performing plasma treatment on the deposited silicon nitride thin film, the present invention promotes the ordered arrangement of deposited atoms and fills microscopic defects, inhibits grain coarsening and stress cracking caused by atomic migration at high temperatures, thereby reducing the surface undulation of the silicon nitride thin film and forming a dense and smooth thin - film structure.

[0028] (2) The present invention optimizes the process of plasma treatment. Before plasma treatment, the chamber is pumped to vacuum to ensure that there is no residual ammonia and silane in the chamber. Thus, during the subsequent plasma treatment process, no new unstable silicon nitride thin film will be generated, avoiding the generation of particle contamination caused by the unstable thin film generated during the plasma treatment, which affects the uniformity and roughness of the prepared silicon nitride thin film; moreover, the present invention also optimizes the power and time of plasma treatment, performing plasma treatment at a lower power, avoiding strong bombardment of the thin film and avoiding Arcing defects, thereby ensuring the preparation of a silicon nitride thin film with good uniformity and low roughness. Description of the Drawings

[0029] Figure 1 is the AFM morphology diagram of the surface of the silicon nitride thin film prepared in Example 1.

[0030] Figure 2 is the AFM morphology diagram of the surface of the silicon nitride thin film prepared in Example 2.

[0031] Figure 3 is the AFM morphology diagram of the surface of the silicon nitride thin film prepared in Example 3.

[0032] Figure 4 It is the AFM morphology diagram of the surface of the silicon nitride thin film prepared in Example 4.

[0033] Figure 5 It is the AFM morphology diagram of the surface of the silicon nitride thin film prepared in Example 5.

[0034] Figure 6 It is the AFM morphology diagram of the surface of the silicon nitride thin film prepared in Example 9.

[0035] Figure 7 It is the AFM morphology diagram of the surface of the silicon nitride thin film prepared in Comparative Example 1.

[0036] Figure 8 It is the AFM morphology diagram of the surface of the silicon nitride thin film prepared in Comparative Example 2. Detailed implementation manners

[0037] The technical solution of the present invention will be further described below through specific implementation manners. Those skilled in the art should understand that the described embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in this application are intended to cover non-exclusive inclusion.

[0039] In the description of this application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order or primary-secondary relationship of the indicated technical features. In the description of the embodiments of this application, "a plurality of" means more than two unless otherwise specifically defined.

[0040] In a specific implementation manner, the present invention provides a method for preparing a silicon nitride thin film, and the preparation method includes: (1) introducing a precursor gas into a cavity pumped to a vacuum, and simultaneously preheating a wafer to a deposition temperature; (2) depositing a silicon nitride thin film on the surface of the wafer; (3) pumping the cavity to a vacuum, introducing nitrogen gas, and performing plasma treatment on the silicon nitride thin film; (4) pumping the cavity to a vacuum, cooling down, and the preparation is completed; after introducing nitrogen gas in step (3), the pressure in the cavity is 2.0 torr - 3 torr; the power of the plasma treatment in step (3) is 450 W - 550 W.

[0041] In the preparation method provided by the present invention, while preheating the wafer, a precursor gas is introduced to form a pressure of 2.0 torr - 3.0 torr in the cavity. For example, it can be 2.0 torr, 2.2 torr, 2.4 torr, 2.6 torr, 2.8 torr or 3.0 torr, including but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0042] Under the pressure environment created by the precursor gas, the preheating effect of the wafer is better. And during the preheating process of the wafer, through the long-term stability of the precursor gas, the flow rate of the precursor gas, its distribution in the cavity, and the pressure distribution in the cavity become more uniform, providing a good deposition environment for the subsequent deposition of the silicon nitride thin film.

[0043] The present invention performs plasma treatment on the deposited silicon nitride thin film. The nitrogen ions (such as N + ) in the plasma bombard the silicon nitride thin film under the acceleration of the electric field, enhancing the atomic mobility in the silicon nitride thin film, capable of removing atoms or molecules on the convex regions of the silicon nitride thin film surface, promoting the orderly arrangement of deposited atoms and filling micro-defects, inhibiting grain coarsening and stress cracking caused by atomic migration at high temperatures, thereby reducing the surface undulation of the silicon nitride thin film and forming a dense and smooth film structure.

[0044] The present invention further optimizes the process of plasma treatment. First, before performing plasma treatment, the cavity is pumped to vacuum to ensure that there is no residual ammonia and silane in the cavity, so that no new unstable silicon nitride thin film will be generated during the subsequent plasma treatment process, avoiding the generation of particle contamination due to the unstable thin film generated during the plasma treatment process, which affects the uniformity and roughness of the prepared silicon nitride thin film. In addition, the present invention optimizes the power and time of plasma treatment. Plasma treatment is carried out at a lower power to avoid strong bombardment of the thin film, resulting in etching of the thin film. And when the power is too high, it is easy to cause Arcing (arc discharge), resulting in abnormal local thin film thickness, affecting the uniformity of the prepared silicon nitride thin film.

[0045] In the present invention, the power of plasma treatment on the silicon nitride thin film is 450 W - 550 W. For example, it can be 450 W, 460 W, 470 W, 480 W, 490 W, 500 W, 510 W, 520 W, 530 W, 540 W or 550 W, including but not limited to the listed values, and other unlisted values within the numerical range are equally applicable. In some embodiments, the precursor gas described in step (1) includes ammonia, silane and nitrogen.

[0046] In some embodiments, in the precursor gas of step (1), the flow rate of nitrogen is 1000 sccm - 2000 sccm, for example, it can be 1000 sccm, 1100 sccm, 1200 sccm, 1300 sccm, 1400 sccm, 1500 sccm, 1600 sccm, 1700 sccm, 1800 sccm, 1900 sccm or 2000 sccm, including but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0047] In some embodiments, in the precursor gas of step (1), the flow rate of ammonia is 20 sccm - 40 sccm, for example, it can be 20 sccm, 22 sccm, 24 sccm, 26 sccm, 28 sccm, 30 sccm, 32 sccm, 34 sccm, 36 sccm, 38 sccm or 40 sccm, including but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0048] In some embodiments, in the precursor gas of step (1), the flow rate of silane is 10 sccm - 30 sccm, for example, it can be 10 sccm, 12 sccm, 14 sccm, 16 sccm, 18 sccm, 20 sccm, 22 sccm, 24 sccm, 26 sccm, 28 sccm or 30 sccm, including but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0049] In some embodiments, after introducing the precursor gas in step (1), the pressure in the chamber is 1.0 torr - 5.0 torr, for example, it can be 1.0 torr, 1.5 torr, 2.0 torr, 2.5 torr, 3.0 torr, 3.5 torr, 4.0 torr, 4.5 torr or 5.0 torr, including but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0050] In some embodiments, the deposition temperature is 300 °C - 400 °C, for example, it can be 310 °C, 320 °C, 330 °C, 340 °C, 350 °C, 360 °C, 370 °C, 380 °C, 390 °C or 400 °C, including but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0051] In some embodiments, the heating rate of the preheating is 15.0 °C / min - 20.0 °C / min. For example, it can be 15.0 °C / min, 15.5 °C / min, 16.0 °C / min, 16.5 °C / min, 17.0 °C / min, 17.5 °C / min, 18.0 °C / min, 18.5 °C / min, 19.0 °C / min, 19.5 °C / min, or 20.0 °C / min. This includes but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0052] In some embodiments, the radio frequency power for depositing the silicon nitride film is 250 W - 350 W. For example, it can be 250 W, 260 W, 270 W, 280 W, 290 W, 300 W, 310 W, 320 W, 330 W, 340 W, or 350 W. This includes but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0053] In some embodiments, the frequency of the radio frequency is 13.56 MHz.

[0054] In some embodiments, the time for depositing the silicon nitride film is 200 s - 300 s. For example, it can be 200 s, 210 s, 220 s, 230 s, 240 s, 250 s, 260 s, 270 s, 280 s, 290 s, or 300 s. This includes but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0055] In some embodiments, the flow rate of the nitrogen gas introduced in step (3) is 2000 sccm - 3000 sccm. For example, it can be 2000 sccm, 2100 sccm, 2200 sccm, 2300 sccm, 2400 sccm, 2500 sccm, 2600 sccm, 2700 sccm, 2800 sccm, 2900 sccm, or 3000 sccm. This includes but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0056] In some embodiments, the time for the plasma treatment is 15 s - 25 s. For example, it can be 15 s, 16 s, 17 s, 18 s, 19 s, 20 s, 21 s, 22 s, 23 s, 24 s, or 25 s. This includes but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0057] In some embodiments, the equipment used in the preparation method is a single - chamber single - wafer equipment.

[0058] In another specific embodiment, the present invention provides a silicon nitride thin film, which is prepared by the preparation method described in the foregoing specific embodiment; the thickness of the silicon nitride thin film is 400 nm - 600 nm, for example, it can be 400 nm, 420 nm, 440 nm, 460 nm, 480 nm, 500 nm, 520 nm, 540 nm, 560 nm, 580 nm or 600 nm, including but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0059] In yet another specific embodiment, the present invention provides a semiconductor device, which includes the silicon nitride thin film described in the above another specific embodiment. Example 1

[0060] This example provides a preparation method of a silicon nitride thin film, and the preparation method includes: (1) Select a single-chamber single-wafer type device, clean the PECVD chamber, evacuate it to vacuum, and then introduce 1500 sccm of nitrogen, 30 sccm of ammonia, and 20 sccm of silane into the chamber. Keep the pressure in the chamber at 1.9 torr, and at the same time, preheat the wafer to 400 °C at a heating rate of 18 °C / min.

[0061] (2) Control the radio frequency frequency at 13.56 MHz and the radio frequency power at 300 W. Deposit a silicon nitride thin film on the wafer surface for 250 s to obtain a silicon nitride thin film with a thickness of 500 nm.

[0062] (3) Evacuate the chamber to vacuum again, introduce nitrogen with a flow rate of 2500 sccm, keep the pressure in the chamber at 2.5 torr, and perform plasma treatment on the silicon nitride thin film. The power of the plasma treatment is 500 W and the time is 20 s.

[0063] (4) Evacuate the chamber to vacuum and cool it down to room temperature to complete the preparation of the silicon nitride thin film.

[0064] The roughness of the silicon nitride thin film prepared in this example is 0.426 nm, and the surface AFM morphology diagram is as Figure 1 shown. Example 2

[0065] This example provides a preparation method of a silicon nitride thin film, and the preparation method includes: (1) Select a single-chamber single-wafer type device, clean the PECVD chamber, evacuate it to vacuum, and then introduce 2000 sccm of nitrogen, 40 sccm of ammonia, and 30 sccm of silane into the chamber. Keep the pressure in the chamber at 5.0 torr, and at the same time, preheat the wafer to 350 °C at a heating rate of 20 °C / min.

[0066] (2) Control the radio frequency at 13.56 MHz and the radio frequency power at 350 W. Deposit a silicon nitride film on the wafer surface for 300 s to obtain a silicon nitride film with a thickness of 600 nm.

[0067] (3) Evacuate the chamber to vacuum again, introduce nitrogen with a flow rate of 2650 sccm, keep the pressure in the chamber at 3.0 torr, and perform plasma treatment on the silicon nitride film. The power of the plasma treatment is 550 W and the time is 25 s.

[0068] (4) Evacuate the chamber to vacuum and cool it down to room temperature to complete the preparation of the silicon nitride film.

[0069] The roughness of the silicon nitride film prepared in this example is 0.439 nm, and the surface AFM morphology is as shown in Figure 2 shown. Example 3

[0070] This example provides a method for preparing a silicon nitride film, and the preparation method includes: (1) Select a single-chamber single-wafer type device, clean the PECVD chamber, evacuate it to vacuum, and then introduce 1000 sccm of nitrogen, 20 sccm of ammonia, and 10 sccm of silane into the chamber. Keep the pressure in the chamber at 1.0 torr, and at the same time, preheat the wafer to 300 °C at a heating rate of 15 °C / min.

[0071] (2) Control the radio frequency at 13.56 MHz and the radio frequency power at 250 W. Deposit a silicon nitride film on the wafer surface for 200 s to obtain a silicon nitride film with a thickness of 400 nm.

[0072] (3) Evacuate the chamber to vacuum again, introduce nitrogen with a flow rate of 2350 sccm, keep the pressure in the chamber at 2.0 torr, and perform plasma treatment on the silicon nitride film. The power of the plasma treatment is 450 W and the time is 15 s.

[0073] (4) Evacuate the chamber to vacuum and cool it down to room temperature to complete the preparation of the silicon nitride film.

[0074] The roughness of the silicon nitride film prepared in this example is 0.397 nm, and the surface AFM morphology is as shown inFigure 3 as shown Example 4

[0075] This example provides a method for preparing a silicon nitride thin film. Except that after introducing nitrogen in step (3), the pressure in the cavity is maintained at 1.5 torr, the rest are the same as those in Example 1.

[0076] The roughness of the silicon nitride thin film prepared in this example is 0.623 nm, and the surface AFM morphology diagram is as Figure 4 shown Example 5

[0077] This example provides a method for preparing a silicon nitride thin film. Except that after introducing nitrogen in step (3), the pressure in the cavity is maintained at 3.5 torr, the rest are the same as those in Example 1.

[0078] The roughness of the silicon nitride thin film prepared in this example is 0.525 nm, and the surface AFM morphology diagram is as Figure 5 shown Example 6

[0079] This example provides a method for preparing a silicon nitride thin film. Except that the power of the plasma treatment in step (3) is 350 W, the rest are the same as those in Example 1.

[0080] The roughness of the silicon nitride thin film prepared in this example is 0.712 nm. Example 7

[0081] This example provides a method for preparing a silicon nitride thin film. Except that the power of the plasma treatment in step (3) is 650 W, the rest are the same as those in Example 1.

[0082] The roughness of the silicon nitride thin film prepared in this example is 0.536 nm. Example 8

[0083] This example provides a method for preparing a silicon nitride thin film. Except that the time of the plasma treatment in step (3) is 10 s, the rest are the same as those in Example 1.

[0084] The roughness of the silicon nitride thin film prepared in this example is 0.812 nm. Example 9

[0085] This example provides a method for preparing a silicon nitride thin film. Except that the time of the plasma treatment in step (3) is 30 s, the rest are the same as those in Example 1.

[0086] The roughness of the silicon nitride thin film prepared in this embodiment is 0.601 nm, and the surface AFM morphology diagram is as Figure 6 shown. Comparative Example 1

[0087] This comparative example provides a method for preparing a silicon nitride thin film. Except for not performing step (3), the rest are the same as those in Example 1.

[0088] The roughness of the silicon nitride thin film prepared in this comparative example is 0.890 nm, and the AFM morphology diagram of the prepared silicon nitride thin film is as Figure 7 shown. Comparative Example 2

[0089] This comparative example provides a method for preparing a silicon nitride thin film. Except that in step (3), the cavity is not evacuated again, but the ammonia gas and silane are directly stopped, the rest are the same as those in Example 1.

[0090] The roughness of the silicon nitride thin film prepared in this comparison is 1.010 nm, and the surface AFM morphology diagram is as Figure 8 shown.

[0091] Performance test: The roughness of the silicon nitride thin films prepared in all the above examples and comparative examples was tested by atomic force microscopy (AFM). The test results are shown in Table 1. The AFM morphology diagrams of the silicon nitride thin films prepared in Examples 1 to 5, Example 9 and Comparative Examples 1 to 2 are shown in Figures 1 to 8 .

[0092] The thickness of the silicon nitride thin films prepared in all the above examples and comparative examples was tested by a film thickness gauge, and the uniformity of the film thickness was calculated. The test results are shown in Table 1.

[0093] Table 1

[0094] The applicant declares that the above description is only a specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for preparing a silicon nitride thin film, characterized in that, The preparation method includes: (1) Introduce precursor gases into a cavity evacuated to a vacuum, and at the same time preheat the wafer to the deposition temperature; (2) Deposit a silicon nitride film on the surface of the wafer; (3) Evacuate the cavity to a vacuum, introduce nitrogen gas, and perform plasma treatment on the silicon nitride film; (4) Evacuate the cavity to a vacuum, cool down, and the preparation is completed; After introducing nitrogen gas in step (3), the pressure in the cavity is 2.0 torr - 3.0 torr; The power of the plasma treatment in step (3) is 450 W - 550 W.

2. The preparation method according to claim 1, characterized in that, The precursor gases in step (1) include ammonia, silane, and nitrogen; And / or, after introducing the precursor gases in step (1), the pressure in the cavity is 1.0 torr - 5.0 torr.

3. The preparation method according to claim 2, characterized in that, In the precursor gases in step (1), the flow rate of nitrogen is 1000 sccm - 2000 sccm; the flow rate of ammonia is 20 sccm - 40 sccm, and the flow rate of silane is 10 sccm - 30 sccm.

4. The preparation method according to claim 1, characterized in that, The deposition temperature is 300 °C - 400 °C; And / or, the heating rate of the preheating is 15.0 °C / min - 20.0 °C / min.

5. The preparation method according to claim 1, characterized in that, The radio frequency power for depositing the silicon nitride film is 250 W - 350 W.

6. The preparation method according to claim 1, characterized in that, The time for depositing the silicon nitride film is 200 s - 300 s.

7. The preparation method according to claim 1, characterized in that, The flow rate of nitrogen gas introduced in step (3) is 2000 sccm - 3000 sccm; And / or, the time for the plasma treatment is 15 s - 25 s.

8. The preparation method according to any one of claims 1-7, characterized in that, The equipment used in the preparation method is a single - chamber single - wafer equipment.

9. A silicon nitride thin film, characterized in that, The silicon nitride film is prepared by the preparation method according to any one of claims 1 - 8; the thickness of the silicon nitride film is 400 nm - 600 nm.

10. A semiconductor device, characterized in that, The semiconductor device includes the silicon nitride film as described in claim 9.

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