Amorphous silicon thin film and its preparation method and application

Abstract

The present invention belongs to the field of semiconductor technology and relates to an amorphous silicon thin film and its preparation method and application. The preparation method comprises: (1) using a PECVD method to perform pre-deposition in a first mixed atmosphere of silane and hydrogen to obtain an amorphous silicon pre-deposition thin film; and (2) adjusting the flow rate of silane and hydrogen and performing main deposition in a second mixed atmosphere of silane and hydrogen to obtain the amorphous silicon thin film. The preparation method of the amorphous silicon thin film provided by the present invention is carried out in a mixed atmosphere of silane and hydrogen during PECVD, which can improve the uniformity of the amorphous silicon thin film and enhance the quality of the amorphous silicon thin film. Moreover, the present invention includes sequential pre-deposition and main deposition, and the pre-deposition improves the surface roughness of the amorphous silicon thin film, eliminates the frosted appearance, and meets the needs of industrial production.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor technology and relates to an amorphous silicon thin film and a preparation method and application thereof. Background Art

[0002] Amorphous silicon (a-Si) is a non-crystalline semiconductor with an atomic structure characterized by short-range order and long-range disorder. Compared to crystalline silicon (c-Si), it has a tunable band gap (1.7eV to 2.0eV), making it suitable for optoelectronic devices such as solar cells and thin-film transistors (TFTs). However, amorphous silicon has a high density of defect states and requires hydrogenation to produce hydrogenated amorphous silicon (a-Si:H) to passivate defects and improve optical properties.

[0003] In the solar cell field, a-Si:H as an intrinsic layer can efficiently absorb visible light and broaden the spectral response. It also offers low cost, excellent low-light performance, and soft light properties. When used for backside passivation of crystalline silicon, a-Si:H can reduce carrier recombination. In the display field, a-Si:H as a TFT channel layer can control pixel switching, making it suitable for large-size panels.

[0004] Traditional methods for producing amorphous silicon thin films include chemical vapor deposition (CVD), which typically requires temperatures exceeding 600°C and cannot be used to produce amorphous silicon films on substrates such as glass and plastic. Plasma-enhanced chemical vapor deposition (PECVD) offers the advantages of low production temperatures, tunable optoelectronic properties, and the ability to deposit over large areas.

[0005] CN115863490A discloses a method for depositing an intrinsic amorphous silicon thin film using PECVD, a battery preparation method, and a battery. The method comprises: using silane as a reaction gas to sequentially deposit a first intrinsic amorphous silicon film layer and a second intrinsic amorphous silicon film layer on a silicon wafer substrate, wherein the deposition rate V1 of the first intrinsic amorphous silicon film layer is 0.4 nm / s to 1.2 nm / s; the radio frequency power W2 of the second intrinsic amorphous silicon film layer is less than the radio frequency power W1 of the first intrinsic amorphous silicon film layer; and using a mixture of silane and hydrogen as a reaction gas to deposit a third intrinsic amorphous silicon film layer on the second intrinsic amorphous silicon film layer. Although the method improves the passivation effect by adjusting the radio frequency power, it does not regulate or improve the uniformity of the amorphous silicon film, making it difficult to meet the needs of industrial production.

[0006] Therefore, it is necessary to provide an amorphous silicon thin film that can improve surface roughness, enhance uniformity and meet the needs of industrial production, as well as a preparation method and application thereof. Summary of the Invention

[0007] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide an amorphous silicon film and its preparation method and application. The preparation method can improve the uniformity of the amorphous silicon film, improve the surface roughness of the amorphous silicon film, and improve the quality of the amorphous silicon film, so that the preparation of the amorphous silicon film meets the needs of industrial production.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a method for preparing an amorphous silicon thin film, the method comprising:

[0010] (1) Pre-deposition is performed in a first mixed atmosphere of silane and hydrogen using a PECVD method to obtain an amorphous silicon pre-deposition film;

[0011] (2) Adjusting the flow rates of silane and hydrogen, performing main deposition in a second mixed atmosphere of silane and hydrogen to obtain the amorphous silicon thin film.

[0012] The preparation method provided by the present invention includes pre-deposition and main deposition carried out in sequence under silane and hydrogen atmosphere conditions, wherein the pre-deposition can improve the surface roughness of the obtained amorphous silicon film, eliminate the frosted appearance, and also improve the uniformity of the amorphous silicon film; then, high-quality amorphous silicon film is obtained through main deposition to meet the needs of industrial production.

[0013] Preferably, in the first mixed atmosphere of silane and hydrogen in step (1), the flow ratio of silane to hydrogen is 1:1.3 to 1:3.

[0014] Preferably, in the first mixed atmosphere of silane and hydrogen in step (1), the flow rate of silane is 100 sccm to 150 sccm.

[0015] Preferably, in the first mixed atmosphere of silane and hydrogen in step (1), the flow rate of hydrogen is 200 sccm to 300 sccm.

[0016] Preferably, the pre-deposition pressure in step (1) is 0.6 torr to 1 torr.

[0017] Preferably, the pre-deposition temperature in step (1) is 250°C to 300°C.

[0018] Preferably, the radio frequency power of the pre-deposition in step (1) is 50W~100W.

[0019] Preferably, the pre-deposition time in step (1) is 2s to 4s.

[0020] Preferably, in the second mixed atmosphere in step (2), the flow ratio of silane to hydrogen is 1:2.6 to 1:3.3.

[0021] Preferably, in the second mixed atmosphere in step (2), the flow rate of silane is 200 sccm to 250 sccm.

[0022] Preferably, in the second mixed atmosphere in step (2), the flow rate of hydrogen is 600 sccm to 650 sccm.

[0023] Preferably, the pressure of the main deposition in step (2) is 4 torr to 5 torr.

[0024] Preferably, the temperature of the main deposition in step (2) is 250°C to 300°C;

[0025] Preferably, the RF power of the main deposition in step (2) is 200W~300W.

[0026] Preferably, the main deposition time in step (2) is 55s~65s.

[0027] In a second aspect, the present invention provides an amorphous silicon thin film, which is prepared by the preparation method described in the first aspect.

[0028] In a third aspect, the present invention provides a semiconductor device comprising the amorphous silicon thin film described in the second aspect.

[0029] The numerical range described in the present invention includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The preparation method provided by the present invention includes pre-deposition and main deposition carried out in sequence under silane and hydrogen atmosphere conditions, wherein the pre-deposition can improve the surface roughness of the obtained amorphous silicon film, eliminate the frosted appearance, and also improve the uniformity of the amorphous silicon film; then, high-quality amorphous silicon film is obtained through main deposition to meet the needs of industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a film thickness distribution diagram of the amorphous silicon thin film obtained in Example 1. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0034] An embodiment of the present invention provides a method for preparing an amorphous silicon thin film, the method comprising:

[0035] (1) Pre-deposition is performed in a first mixed atmosphere of silane and hydrogen using a PECVD method to obtain an amorphous silicon pre-deposition film;

[0036] (2) Adjusting the flow rates of silane and hydrogen, performing main deposition in a second mixed atmosphere of silane and hydrogen to obtain the amorphous silicon thin film.

[0037] The preparation method provided by the present invention includes pre-deposition and main deposition carried out in sequence under silane and hydrogen atmosphere conditions, wherein the pre-deposition can improve the surface roughness of the obtained amorphous silicon film, eliminate the frosted appearance, and also improve the uniformity of the amorphous silicon film; then, high-quality amorphous silicon film is obtained through main deposition to meet the needs of industrial production.

[0038] In the prior art, PECVD preparation of amorphous silicon thin films requires high radio frequency power and high voltage conditions, but this condition will lead to excessively high plasma density, generating SiH3 + and H + A large number of high-energy particles such as ions bombard the surface of the growing film, which will not only remove the deposited silicon atoms and cause local unevenness, but also lead to island growth and increase the surface roughness. Moreover, the process conditions of the existing technology will cause SiH4 to decompose prematurely to form silane polymers or silicon clusters such as Si2H6 and Si3H8. These particles fall on the substrate and cause the surface roughness. In addition, the existing technology cannot be carried out in a hydrogen atmosphere at higher pressures because high pressure will cause excessive incorporation or escape of hydrogen, resulting in increased stress in the film and the generation of microcracks.

[0039] In certain embodiments, the silane in step (1) is monosilane.

[0040] The present invention adopts a process of pre-deposition followed by main deposition. Compared with conventional PECVD process conditions, pre-deposition adopts lower RF power and pressure. First, low RF power and pressure can weaken ion energy, making the pre-deposition process more gentle, thereby promoting uniform nucleation and reducing surface defects; second, low pressure reduces the probability of gas phase collisions, forcing SiH4 to decompose mainly on the substrate surface, thereby inhibiting particle contamination and improving smoothness; third, low RF power and pressure can reduce the energy of active groups such as SiH3, so that after being adsorbed on the substrate, they still have sufficient migration time to find low-energy sites, forming a dense and flat pre-thin film; finally, low RF power reduces hydrogen etching of the film, reducing surface defects, and low pressure prevents excessive hydrogen incorporation or escape, resulting in increased stress in the film, causing microcracks and exacerbating roughness.

[0041] In some embodiments, in the first mixed atmosphere of silane and hydrogen in step (1), the flow ratio of silane to hydrogen is 1:1.3~1:3, for example, it can be 1:1.3, 1:1.5, 1:1.6, 1:1.8, 1:2, 1:2.4, 1:2.5, 1:2.7, 1:2.8 or 1:3, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0042] In some embodiments, in the first mixed atmosphere of silane and hydrogen in step (1), the flow rate of silane is 100 sccm to 150 sccm, for example, 100 sccm, 110 sccm, 120 sccm, 130 sccm, 140 sccm or 150 sccm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0043] In some embodiments, in the first mixed atmosphere of silane and hydrogen in step (1), the flow rate of hydrogen is 200 sccm to 300 sccm, for example, it can be 200 sccm, 210 sccm, 220 sccm, 230 sccm, 240 sccm, 250 sccm, 260 sccm, 270 sccm, 280 sccm, 290 sccm or 300 sccm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0044] In some embodiments, the pre-deposition pressure in step (1) is 0.6 torr to 1 torr, for example, 0.6 torr, 0.7 torr, 0.8 torr, 0.9 torr or 1 torr, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0045] The pressure of the pre-deposition process of the present invention is controlled by continuously introducing silane and hydrogen.

[0046] In some embodiments, the pre-deposition temperature in step (1) is 250°C to 300°C, for example, 250°C, 260°C, 270°C, 280°C, 290°C or 300°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0047] The preparation method provided by the present invention can be carried out under relatively low radio frequency power and gas pressure, and thus can appropriately increase the pre-deposition temperature and improve the quality of the amorphous silicon pre-deposited film, thereby facilitating the improvement of the quality of the amorphous silicon film.

[0048] In some embodiments, the RF power of the pre-deposition in step (1) is 50W~100W, for example, it can be 50W, 60W, 70W, 80W, 90W or 100W, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0049] In some embodiments, the pre-deposition time in step (1) is 2s to 4s, for example, 2s, 2.5s, 3s, 3.5s or 4s, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0050] In some embodiments, in the second mixed atmosphere of step (2), the flow ratio of silane to hydrogen is 1:2.6 to 1:3.3, for example, it can be 1:2.6, 1:2.7, 1:2.8, 1:2.9, 1:3, 1:3.1, 1:3.2 or 1:3.3, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0051] In some embodiments, in the second mixed atmosphere in step (2), the flow rate of silane is 200 sccm to 250 sccm, for example, 200 sccm, 210 sccm, 220 sccm, 230 sccm, 240 sccm or 250 sccm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0052] In some embodiments, in the second mixed atmosphere in step (2), the flow rate of hydrogen is 600 sccm~650 sccm, for example, it can be 600 sccm, 610 sccm, 620 sccm, 630 sccm, 640 sccm or 650 sccm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0053] In some embodiments, the pressure of the main deposition in step (2) is 4 torr to 5 torr, for example, 4 torr, 4.1 torr, 4.2 torr, 4.3 torr, 4.4 torr, 4.5 torr, 4.6 torr, 4.7 torr, 4.8 torr, 4.9 torr or 5 torr, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0054] The pressure of the main deposition process of the present invention is controlled by the flow rates of silane and hydrogen.

[0055] In some embodiments, the temperature of the main deposition in step (2) is 250°C to 300°C, for example, it can be 250°C, 260°C, 270°C, 280°C, 290°C or 300°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0056] In some embodiments, the RF power of the main deposition in step (2) is 200W~300W, for example, it can be 200W, 210W, 220W, 230W, 240W, 250W, 260W, 270W, 280W, 290W or 300W, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0057] In some embodiments, the main deposition time in step (2) is 55s to 65s, for example, 55s, 56s, 58s, 60s, 62s, 64s or 65s, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0058] An embodiment of the present invention provides an amorphous silicon thin film, which is prepared by the preparation method described in any embodiment.

[0059] A certain embodiment of the present invention provides a semiconductor device, comprising the amorphous silicon thin film according to any one of the embodiments.

[0060] In order to clearly illustrate the technical solution of the present invention, in the following embodiments and comparative examples, PECVD adopts a single-cavity single-chip type device; the radio frequency system is AENI, the frequency is 13.56 MHz, and the substrate used for deposition is a silicon substrate.

[0061] Example 1

[0062] This embodiment provides a method for preparing an amorphous silicon thin film, comprising the following steps:

[0063] (1) Using the PECVD method, monosilane was introduced into the reaction chamber at a flow rate of 120 sccm and hydrogen was introduced at a flow rate of 250 sccm to stabilize the pressure in the reaction chamber at 0.8 torr; then, pre-deposition was performed at a temperature of 280°C and a radio frequency power of 80 W for 3 seconds to obtain an amorphous silicon pre-deposition film;

[0064] (2) Adjusting the flow rates of silane and hydrogen to 220 sccm for monosilane and 650 sccm for hydrogen, and stabilizing the pressure in the reaction chamber at 4.5 torr; then, performing main deposition at a temperature of 280°C and a radio frequency power of 250 W for 60 seconds to obtain the amorphous silicon film.

[0065] The film thickness distribution diagram of the amorphous silicon thin film obtained in this embodiment is as follows Figure 1 As shown by Figure 1 It can be seen that the thickness of the amorphous silicon thin film obtained in this embodiment is uniform.

[0066] Example 2

[0067] This embodiment provides a method for preparing an amorphous silicon thin film, comprising the following steps:

[0068] (1) Using the PECVD method, monosilane was introduced into the reaction chamber at a flow rate of 100 sccm and hydrogen was introduced at a flow rate of 200 sccm to stabilize the pressure in the reaction chamber at 0.6 Torr; then, pre-deposition was performed at a temperature of 250°C and a radio frequency power of 50 W for 4 seconds to obtain an amorphous silicon pre-deposition film;

[0069] (2) Adjusting the flow rates of monosilane and hydrogen to 200 sccm for silane and 600 sccm for hydrogen, and stabilizing the pressure in the reaction chamber at 4 Torr; then, performing main deposition at a temperature of 250°C and a radio frequency power of 200 W for 55 seconds to obtain the amorphous silicon film.

[0070] Example 3

[0071] This embodiment provides a method for preparing an amorphous silicon thin film, comprising the following steps:

[0072] (1) Using the PECVD method, monosilane was introduced into the reaction chamber at a flow rate of 150 sccm and hydrogen was introduced at a flow rate of 300 sccm to stabilize the pressure in the reaction chamber at 1 Torr; then, pre-deposition was performed at a temperature of 300°C and a radio frequency power of 100 W for 2 seconds to obtain an amorphous silicon pre-deposition film;

[0073] (2) Adjusting the flow rates of monosilane and hydrogen to 250 sccm for silane and 650 sccm for hydrogen, and stabilizing the pressure in the reaction chamber at 5 Torr; then, performing main deposition at a temperature of 300°C and a radio frequency power of 300 W for 65 seconds to obtain the amorphous silicon film.

[0074] Example 4

[0075] This embodiment provides a method for preparing an amorphous silicon thin film, which is the same as that of Example 1 except that the pre-deposition temperature is 200°C.

[0076] Example 5

[0077] This embodiment provides a method for preparing an amorphous silicon thin film, which is the same as that of Example 1 except that the pre-deposition temperature is 350°C.

[0078] Example 6

[0079] This embodiment provides a method for preparing an amorphous silicon thin film, which is the same as that of Example 1 except that the radio frequency power of the pre-deposition is 150 W.

[0080] Example 7

[0081] This embodiment provides a method for preparing an amorphous silicon thin film, which is the same as that of Example 1 except that the flow rates of monosilane and hydrogen are reduced in equal proportions so that the pre-deposition pressure is 0.3 Torr.

[0082] Example 8

[0083] This embodiment provides a method for preparing an amorphous silicon thin film, which is the same as that of Example 1 except that the flow rates of monosilane and hydrogen are increased in equal proportions so that the pre-deposition pressure is 1.5 Torr.

[0084] Example 9

[0085] This embodiment provides a method for preparing an amorphous silicon thin film, which is the same as that of Example 1 except that the flow rates of monosilane and hydrogen are reduced in equal proportions so that the pressure of the main deposition is 3.5 Torr.

[0086] Example 10

[0087] This embodiment provides a method for preparing an amorphous silicon thin film. The method is the same as that of Example 1 except that the flow rates of monosilane and hydrogen are increased in equal proportions so that the pressure of the main deposition is 5.5 Torr.

[0088] Example 11

[0089] This embodiment provides a method for preparing an amorphous silicon thin film, which is the same as that of embodiment 1 except that the main deposition temperature is 200°C.

[0090] Example 12

[0091] This embodiment provides a method for preparing an amorphous silicon thin film. Except that the main deposition temperature is 350°C, the rest is the same as that of embodiment 1.

[0092] Example 13

[0093] This embodiment provides a method for preparing an amorphous silicon thin film, which is the same as that of Example 1 except that the radio frequency power of the main deposition is 150 W.

[0094] Example 14

[0095] This embodiment provides a method for preparing an amorphous silicon thin film, which is the same as that of Example 1 except that the radio frequency power of the main deposition is 350 W.

[0096] Comparative Example 1

[0097] This comparative example provides a method for preparing an amorphous silicon thin film, which is the same as Example 1 except that only monosilane is introduced during pre-deposition.

[0098] Comparative Example 2

[0099] This comparative example provides a method for preparing an amorphous silicon thin film, comprising the following steps:

[0100] The PECVD method is used to set the flow rate of monosilane to 220 sccm and the flow rate of hydrogen to 650 sccm in the reaction chamber, so that the pressure in the reaction chamber is stabilized at 4.5 torr; then, the main deposition is performed at a temperature of 280°C and a radio frequency power of 250 W for 60 seconds to obtain the amorphous silicon film.

[0101] Performance Characterization

[0102] Ellipsometer was used to test the average thickness, uniformity and refractive index of the film; atomic force microscope was used to test the average thickness, uniformity and refractive index of the film. (AFM) The surface roughness of the film was tested respectively; the internal stress of the film was tested respectively using a stress meter. The average thickness, uniformity, refractive index, surface roughness and internal stress of the amorphous silicon thin films obtained in the above examples and comparative examples were measured, and the results are shown in Table 1.

[0103] Table 1

[0104]

[0105] As can be seen from Table 1, the amorphous silicon thin film prepared by the preferred technical solution of the present invention has a uniformity of film thickness controlled at 1.2%~1.7%, a refractive index controlled at 4.05~4.08, a surface roughness that can be controlled at 0.9nm~1.0nm, and an internal stress controlled at -46MPa~-70MPa.

[0106] Comparison of Examples 4 and 5 with Example 1 shows that the pre-deposition temperature affects the thickness uniformity and surface roughness of the resulting amorphous silicon film. Specifically, when the pre-deposition temperature is too low, the thickness uniformity of the resulting amorphous silicon film increases from 1.7% to 2.6%, and the surface roughness increases from 0.9nm to 1.9nm. When the pre-deposition temperature is too high, the thickness uniformity of the resulting amorphous silicon film increases from 1.7% to 2.9%, and the surface roughness increases from 0.9nm to 2.0nm. Therefore, as a preferred technical solution, it is necessary to control the pre-deposition temperature to 250°C to 300°C.

[0107] Comparison of Example 6 with Example 1 shows that the pre-deposition RF power affects the thickness uniformity, refractive index, and surface roughness of the resulting amorphous silicon film. Specifically, when the pre-deposition RF power is too low, the thickness uniformity of the resulting amorphous silicon film increases from 1.7% to 2.4%, the refractive index decreases from 4.05 to 3.99, and the surface roughness increases from 0.9 nm to 1.8 nm. Therefore, as a preferred technical solution, the pre-deposition RF power needs to be controlled to 50 W to 100 W.

[0108] Comparison of Examples 7 and 8 with Example 1 shows that the pre-deposition pressure primarily affects the thickness uniformity and surface roughness of the resulting amorphous silicon film. Specifically, when the pre-deposition pressure is too low, the thickness uniformity of the resulting amorphous silicon film increases from 1.7% to 3.4%, and the surface roughness increases from 0.9 nm to 1.9 nm. When the pre-deposition pressure is too high, the thickness uniformity of the resulting amorphous silicon film increases from 1.7% to 2.3%, and the surface roughness increases from 0.9 nm to 2.1 nm. Therefore, as a preferred technical solution, the pre-deposition pressure needs to be controlled to be between 0.6 torr and 1 torr.

[0109] Comparison of Examples 9 and 10 with Example 1 shows that the main deposition pressure primarily affects the thickness uniformity and surface roughness of the resulting amorphous silicon film. Specifically, when the main deposition pressure is too low, the thickness uniformity of the resulting amorphous silicon film increases from 1.7% to 2.9%, and the surface roughness increases from 0.9 nm to 2.4 nm. When the main deposition pressure is too high, the thickness uniformity of the resulting amorphous silicon film increases from 1.7% to 2.7%, and the surface roughness increases from 0.9 nm to 2.1 nm. Therefore, as a preferred technical solution, the main deposition pressure needs to be controlled to be between 4 torr and 5 torr.

[0110] Comparison of Example 11 and Example 12 with Example 1 shows that the main deposition temperature primarily affects the thickness uniformity and surface roughness of the resulting amorphous silicon film. Specifically, when the main deposition temperature is too low, the thickness uniformity of the resulting amorphous silicon film increases from 1.7% to 2.5%, and the surface roughness increases from 0.9nm to 1.8nm. When the main deposition temperature is too high, the thickness uniformity of the resulting amorphous silicon film increases from 1.7% to 3.0%, and the surface roughness increases from 0.9nm to 2.0nm. Therefore, as a preferred technical solution, the main deposition temperature needs to be controlled between 250°C and 300°C.

[0111] Comparison of Example 13 and Example 14 with Example 1 shows that the main deposition RF power mainly affects the thickness uniformity and surface roughness of the resulting amorphous silicon film. Specifically, when the main deposition temperature is too low, the thickness uniformity of the resulting amorphous silicon film increases from 1.7% to 2.8%, and the surface roughness increases from 0.9nm to 1.9nm. When the main deposition temperature is too high, the thickness uniformity of the resulting amorphous silicon film increases from 1.7% to 2.4%, and the surface roughness increases from 0.9nm to 2.1nm. Therefore, as a preferred technical solution, it is necessary to control the main deposition RF power to 200W~300W.

[0112] It can be seen from Comparative Example 1 and Example 1 that the simultaneous use of monosilane and hydrogen during pre-deposition is beneficial to improving the thickness uniformity of the obtained amorphous silicon film and reducing the surface roughness. When only monosilane is introduced, the thickness uniformity of the obtained amorphous silicon film is increased from 1.7% to 2.5%, and the surface roughness is increased from 0.9nm to 1.8nm, and the quality of the amorphous silicon film is reduced.

[0113] It can be seen from Comparative Example 2 and Example 1 that pre-deposition is beneficial to improving the thickness uniformity of the obtained amorphous silicon film and reducing the surface roughness. When only main deposition is performed, the thickness uniformity of the obtained amorphous silicon film is increased from 1.7% to 2.2%, and the surface roughness is increased from 0.9nm to 3.2nm, and the quality of the amorphous silicon film is reduced.

[0114] In summary, the preparation method provided by the present invention includes pre-deposition and main deposition carried out in sequence under silane and hydrogen atmosphere conditions, wherein the pre-deposition can improve the surface roughness of the obtained amorphous silicon film, eliminate the frosted appearance, and improve the uniformity of the amorphous silicon film; then, high-quality amorphous silicon film is obtained through main deposition to meet the needs of industrial production.

[0115] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection 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 scope of protection and disclosure of the present invention.

Claims

1. A method for preparing an amorphous silicon thin film, characterized in that: The preparation method is: (1) Pre-deposition is performed in a first mixed atmosphere of silane and hydrogen using a PECVD method to obtain an amorphous silicon pre-deposition film; The pre-deposition pressure is 0.6 torr to 1 torr, and the radio frequency power is 50W to 100W; The pre-deposition temperature is 250° C. to 300° C.; (2) adjusting the flow rates of silane and hydrogen, and performing main deposition in a second mixed atmosphere of silane and hydrogen to obtain the amorphous silicon thin film; The main deposition pressure is 4 torr to 5 torr, and the radio frequency power is 200W to 300W; The main deposition temperature is 250°C to 300°C.

2. The preparation method according to claim 1, characterized in that In the first mixed atmosphere of silane and hydrogen in step (1), the flow ratio of silane to hydrogen is 1:1.3 to 1:

3.

3. The preparation method according to claim 2, characterized in that In the first mixed atmosphere of silane and hydrogen in step (1), the flow rate of silane is 100 sccm to 150 sccm; And / or, in the first mixed atmosphere of silane and hydrogen in step (1), the flow rate of hydrogen is 200 sccm~300 sccm.

4. The preparation method according to any one of claims 1 to 3, characterized in that The pre-deposition time in step (1) is 2s to 4s.

5. The preparation method according to claim 4, characterized in that In step (2), the flow ratio of silane to hydrogen in the second mixed atmosphere is 1:2.6 to 1:3.

3.

6. The preparation method according to claim 4, characterized in that In step (2), the flow rate of silane in the second mixed atmosphere is 200 sccm to 250 sccm; And / or, in the second mixed atmosphere in step (2), the flow rate of hydrogen is 600 sccm~650 sccm.

7. The preparation method according to claim 5 or 6, characterized in that: The main deposition time in step (2) is 55s~65s.

8. An amorphous silicon thin film, characterized in that: The amorphous silicon thin film is prepared by the preparation method according to any one of claims 1 to 7.

9. A semiconductor device, characterized in that: The semiconductor device comprises the amorphous silicon thin film according to claim 8.

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