Method for improving thickness uniformity of amorphous silicon film

Abstract

The invention provides a method for improving thickness uniformity of an amorphous silicon film, which comprises the following steps: providing an initial amorphous silicon film layer, and recording initial process data for forming the initial amorphous silicon film layer, the initial process data comprising initial deposition pressure and initial carrier gas flow; the thickness of the initial amorphous silicon film layer is detected, and the thickness difference between the center area and the edge area of the initial amorphous silicon film layer is obtained; and changing the initial deposition pressure and the initial carrier gas flow based on the thickness difference to obtain target process data. Deposition pressure and carrier gas flow are debugged based on the thickness difference between the central area and the edge area of the amorphous silicon film layer, the deposition pressure and the carrier gas flow are reduced when the amorphous silicon film layer is concave and poor in uniformity, and the deposition pressure and the carrier gas flow are increased when the amorphous silicon film layer is convex and poor in uniformity. By changing the deposition pressure and the carrier gas flow to balance the reaction rate of the reaction gas in the central area and the edge area, the thickness uniformity is greatly improved, and the thickness uniformity can be adjusted to be within 3%.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductors and relates to a method for improving the uniformity of amorphous silicon film thickness. Background Art

[0002] Amorphous silicon (α-Si), also known as amorphous silicon, is a form of single silicon with lower melting point, density and hardness than crystalline silicon. The structural characteristics of amorphous silicon show short-range order and long-range disorder, and its regular tetrahedral molecular structure will produce many defects such as hanging chains and voids due to deformation. Amorphous silicon is widely used in solar cells, thin film transistors, sensors and microelectronic devices. In semiconductor technology, amorphous silicon with a thickness of more than 500nm is generally called thick amorphous silicon, and its thickness uniformity often exceeds 5%. Poor thickness uniformity directly affects the performance and application effect of the material.

[0003] Thick amorphous silicon generally uses the following two process debugging methods to improve thickness uniformity: the first is to adjust the height of the horizontal position (Process Spacing) during process deposition; the second is to adjust the gas flow of the reaction gas and the carrier gas. The existing debugging method can only adjust the thickness uniformity of the amorphous silicon film layer to 5%, and the thickness uniformity is difficult to further optimize. Summary of the invention

[0004] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a method for improving the uniformity of amorphous silicon film thickness, so as to solve the problem in the prior art that the thickness uniformity of the amorphous silicon film layer is difficult to be further optimized after being adjusted to more than 5%.

[0005] To achieve the above object and other related objects, the present invention provides a method for improving the uniformity of amorphous silicon film thickness, comprising the following steps:

[0006] Providing an initial amorphous silicon film layer, and recording initial process data for forming the initial amorphous silicon film layer, wherein the initial process data includes an initial deposition pressure and an initial carrier gas flow rate;

[0007] Detecting the thickness of the initial amorphous silicon film layer to obtain a thickness difference between a central region and an edge region of the initial amorphous silicon film layer;

[0008] The initial deposition pressure and the initial carrier gas flow rate are changed based on the thickness difference to obtain target process data, wherein the target process data includes a target deposition pressure and a target carrier gas flow rate, and a target amorphous silicon film layer is formed using the target process data as a growth condition.

[0009] Optionally, the thickness of the central region of the initial amorphous silicon film layer is less than the thickness of the edge region of the initial amorphous silicon film layer, and the initial deposition pressure and the initial carrier gas flow rate are reduced to obtain the target deposition pressure and the target carrier gas flow rate.

[0010] Optionally, the initial deposition pressure ranges from 4000 to 4400 mTorr, and the initial carrier gas flow rate ranges from 1000 to 1400 sccm; the target deposition pressure ranges from 2100 to 2500 mTorr, and the target carrier gas flow rate ranges from 800 to 1200 sccm.

[0011] Optionally, the thickness of the central region of the initial amorphous silicon film layer is greater than the thickness of the edge region of the initial amorphous silicon film layer, and the initial deposition pressure and the initial carrier gas flow rate are increased to obtain the target deposition pressure and the target carrier gas flow rate.

[0012] Optionally, the thickness of the initial amorphous silicon film layer is not less than 500 nm; and the thickness of the target amorphous silicon film layer is not less than 500 nm.

[0013] Optionally, in the initial process data, Ar gas is used as carrier gas.

[0014] As described above, in the method for improving the thickness uniformity of amorphous silicon film of the present invention, the deposition pressure and carrier gas flow rate are adjusted based on the thickness difference between the central area and the edge area of ​​the amorphous silicon film layer. When the amorphous silicon film layer is "concave" with poor uniformity, the deposition pressure and carrier gas flow rate are reduced. When the amorphous silicon film layer is "convex" with poor uniformity, the deposition pressure and carrier gas flow rate are increased. By changing the deposition pressure and the carrier gas flow rate to balance the reaction rate of the reaction gas in the central area and the edge area of ​​the wafer, the thickness uniformity can be greatly improved, and the thickness uniformity can be adjusted to within 3%. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Shown is a flow chart of a method for improving the uniformity of amorphous silicon film thickness in an embodiment of the present invention.

[0016] Figure 2 It is a schematic diagram showing the formation of an initial amorphous silicon film layer on a wafer according to an embodiment of the present invention.

[0017] Figure 3 It is a schematic diagram showing the formation of a target amorphous silicon film layer on a wafer according to an embodiment of the present invention.

[0018] Component number description

[0019] 1 Initial amorphous silicon film layer

[0020] 2 Wafer

[0021] 3 Target amorphous silicon film layer

[0022] 4 Wafer

[0023] Steps S1 to S3 DETAILED DESCRIPTION

[0024] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0025] See also Figure 1 It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0026] This embodiment provides a method for improving the thickness uniformity of amorphous silicon film. Figure 1 , shown as a process flow chart of the method, comprising the following steps:

[0027] S1: providing an initial amorphous silicon film layer, and recording initial process data for forming the initial amorphous silicon film layer, wherein the initial process data includes an initial deposition pressure and an initial carrier gas flow rate.

[0028] S2: Detecting the thickness of the initial amorphous silicon film layer to obtain a thickness difference between a central region and an edge region of the initial amorphous silicon film layer;

[0029] S3: Changing the initial deposition pressure and the initial carrier gas flow rate based on the thickness difference to obtain target process data, wherein the target process data includes a target deposition pressure and a target carrier gas flow rate, and forming a target amorphous silicon film layer using the target process data as growth conditions.

[0030] The method for improving the uniformity of amorphous silicon film thickness in this embodiment is described in detail below with reference to specific drawings.

[0031] First, see Figure 2 , executing step S1: providing an initial amorphous silicon film layer 1, and recording initial process data for forming the initial amorphous silicon film layer 1, wherein the initial process data includes an initial deposition pressure and an initial carrier gas flow rate.

[0032] As an example, a wafer 2 is provided, and the initial amorphous silicon film layer 1 is formed on the wafer 2 using the initial process data as growth conditions.

[0033] As an example, in the initial process data, Ar gas is used as a carrier gas, and silane (SiH 4 ) is used as a reaction gas, wherein SiH 4 removes H ions by a reduction reaction under high temperature and high pressure to form the initial amorphous silicon film layer 1 .

[0034] As an example, in this embodiment, the initial deposition pressure ranges from 4000 to 4400 mTorr, and the initial carrier gas flow rate ranges from 1000 to 1400 sccm; specifically, the initial deposition pressure is 4200 mTorr, and the initial carrier gas flow rate is 1200 sccm.

[0035] As an example, the thickness of the initial amorphous silicon film layer 1 is not less than 500 nm, that is, the initial amorphous silicon film layer 1 is a thick amorphous silicon film layer.

[0036] Next, step S2 is performed: detecting the thickness of the initial amorphous silicon film layer 1 to obtain the thickness difference between the central area and the edge area of ​​the initial amorphous silicon film layer 1 .

[0037] As an example, the thickness of the initial amorphous silicon film layer 1 is detected by using ellipsometry, surface detection, Rutherford backscattering spectroscopy or any other suitable method. In this embodiment, the thickness of the central region of the initial amorphous silicon film layer 1 is less than the thickness of the edge region, that is, the initial amorphous silicon film layer 1 is "concave" and has poor uniformity; specifically, in this embodiment, the maximum film thickness of the initial amorphous silicon film layer 1 is The minimum film thickness is 7128.69, and the thickness uniformity is 7.82%.

[0038] Next, see Figure 3 , execute step S3: change the initial deposition pressure and the initial carrier gas flow rate based on the thickness difference to obtain target process data, the target process data including the target deposition pressure and the target carrier gas flow rate, and form the target amorphous silicon film layer 3 with the target process data as the growth condition.

[0039] As an example, the thickness of the central area of ​​the initial amorphous silicon film layer 1 is less than the thickness of the edge area of ​​the initial amorphous silicon film layer 1, the initial deposition pressure and the initial carrier gas flow rate are reduced, and multiple adjustments are made to find the optimal values ​​of the deposition pressure and the carrier gas flow rate to obtain the target deposition pressure and the target carrier gas flow rate.

[0040] As an example, in this embodiment, the target deposition pressure ranges from 2100 to 2500 mTorr, and the target carrier gas flow rate ranges from 800 to 1200 sccm; specifically, the target deposition pressure is 2300 mTorr, and the target carrier gas flow rate is 1000 sccm.

[0041] As an example, a wafer 4 is provided, and the target amorphous silicon film layer 3 is formed on the wafer 4 using the target process data as the growth condition. In this embodiment, the maximum film thickness of the target amorphous silicon film layer 3 is The minimum film thickness is The thickness uniformity was 2.57%.

[0042] As an example, in the case where the thick amorphous silicon layer is "concave" with poor uniformity, reducing the deposition pressure and carrier gas flow rate can help slow down the growth rate of the film in the edge area, making the thickness of the edge area and the center area closer, thereby optimizing the thickness uniformity of the thick amorphous silicon film layer.

[0043] It should be noted that this embodiment only lists that the thickness of the central area of ​​the initial amorphous silicon film layer 1 is less than the thickness of the edge area. In another example, the thickness of the central area of ​​the initial amorphous silicon film layer 1 is greater than the thickness of the edge area, that is, the initial amorphous silicon film layer 1 is "convex" and has poor uniformity. In this case, the deposition pressure and the carrier gas flow rate are increased, and the optimal values ​​of the deposition pressure and the carrier gas flow rate are debugged multiple times to obtain the target deposition pressure and the target carrier gas flow rate. By increasing the deposition pressure and the carrier gas flow rate, it is helpful to increase the growth rate of the film in the edge area, so that the thickness of the edge area and the center area are closer, and the thickness uniformity of the thick amorphous silicon film layer is optimized.

[0044] In summary, in the method for improving the uniformity of amorphous silicon film thickness of the present invention, the deposition pressure and carrier gas flow rate are adjusted based on the thickness difference between the central area and the edge area of ​​the amorphous silicon film layer. When the amorphous silicon film layer is "concave" and the uniformity is poor, the deposition pressure and carrier gas flow rate are reduced. When the amorphous silicon film layer is "convex" and the uniformity is poor, the deposition pressure and carrier gas flow rate are increased. By changing the deposition pressure and carrier gas flow rate to balance the reaction rate of the reaction gas in the central area and the edge area of ​​the wafer, the thickness uniformity can be greatly improved, and the thickness uniformity can be adjusted to within 3%. Therefore, the present application effectively overcomes various shortcomings in the prior art and has a high industrial utilization value.

[0045] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A method for improving the uniformity of amorphous silicon film thickness, characterized in that: The following steps are involved: Providing an initial amorphous silicon film layer, and recording initial process data for forming the initial amorphous silicon film layer, wherein the initial process data includes an initial deposition pressure and an initial carrier gas flow rate; Detecting the thickness of the initial amorphous silicon film layer to obtain a thickness difference between a central region and an edge region of the initial amorphous silicon film layer; The initial deposition pressure and the initial carrier gas flow rate are changed based on the thickness difference to obtain target process data, wherein the target process data includes a target deposition pressure and a target carrier gas flow rate, and a target amorphous silicon film layer is formed using the target process data as a growth condition.

2. The method for improving the uniformity of amorphous silicon film thickness according to claim 1, characterized in that: The thickness of the central region of the initial amorphous silicon film layer is less than the thickness of the edge region of the initial amorphous silicon film layer, and the initial deposition pressure and the initial carrier gas flow rate are reduced to obtain the target deposition pressure and the target carrier gas flow rate.

3. The method for improving the uniformity of amorphous silicon film thickness according to claim 2, characterized in that: The initial deposition pressure ranges from 4000 to 4400 mTorr, and the initial carrier gas flow rate ranges from 1000 to 1400 sccm; the target deposition pressure ranges from 2100 to 2500 mTorr, and the target carrier gas flow rate ranges from 800 to 1200 sccm.

4. The method for improving the uniformity of amorphous silicon film thickness according to claim 1, characterized in that: The thickness of the central region of the initial amorphous silicon film layer is greater than the thickness of the edge region of the initial amorphous silicon film layer, and the initial deposition pressure and the initial carrier gas flow rate are increased to obtain the target deposition pressure and the target carrier gas flow rate.

5. The method for improving the uniformity of amorphous silicon film thickness according to claim 1, characterized in that: The thickness of the initial amorphous silicon film layer is not less than 500 nm; the thickness of the target amorphous silicon film layer is not less than 500 nm.

6. The method for improving the uniformity of amorphous silicon film thickness according to claim 1, characterized in that: In the initial process data, Ar gas is used as carrier gas.

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