Silicon wafer loading method for tubular ALD (atomic layer deposition)

Abstract

The invention relates to a silicon wafer loading method of a tubular ALD (atomic layer deposition), which is characterized in that airflow in a metal boat is adjusted by adjusting the insertion density of each row of silicon wafers in a metal carrier, specifically, even rows of silicon wafers are arranged in the metal carrier, and one of the following two silicon wafer loading modes is adopted in each row to load the silicon wafers; according to the first silicon wafer loading mode, silicon wafers are fully inserted in grooves in the two sides in a row of a metal carrier, and the silicon wafers are loaded in grooves in the middle in the row of the metal carrier one by one; according to the second silicon wafer loading mode, the silicon wafers are fully inserted in the middle groove in the row of the metal carrier, and the silicon wafers are loaded in the grooves in the two sides in the row of the metal carrier one by one. The method has the advantages that the method is reasonable in design, the gas flow in the metal boat is adjusted, and the source quantity of tail emission can be effectively increased, so that the aluminum oxide film deposition effect is improved, and the film uniformity is improved.

Description

TECHNICAL FIELD

[0001] The application relates to a silicon wafer loading method for improving the uniformity of an alumina passivation film prepared by a tubular ALD, and belongs to the technical field of ALD. BACKGROUND

[0002] ALD (atomic layer deposition) is a chemical vapor deposition film method based on ordered and surface self-limiting reactions. The film is formed by alternately pulsing gas precursors into a reaction chamber and causing gas-solid phase chemical adsorption reactions on the surface of a deposition substrate.

[0003] A typical process step of a batch tubular ALD is as follows: in the first step, a precursor gas is introduced; in the second step, an inert gas is introduced to purge the remaining precursor; in the third step, an oxidizing gas, usually ozone or water vapor, is introduced; and in the fourth step, an inert gas is introduced again to purge the remaining oxidizing gas. One cycle of the above steps completes the deposition of one layer of film, and the growth of the film, i.e. the deposition thickness, is ultimately controlled by controlling the number of cycles. The reaction gas is introduced for several seconds.

[0004] There are many factors that affect the film quality of tubular ALD, such as chamber pressure, gas distribution, and temperature distribution. In order to ensure uniformity of the film, the silicon wafers at all positions in the process chamber need to be as uniformly exposed to the reaction gas as possible.

[0005] In the existing photovoltaic industry, in order to improve productivity, a large number of silicon wafers are loaded into the ALD reaction chamber at one time, and these silicon wafers are usually uniformly loaded on a metal carrier, as shown in FIG. 1. Figure 1 After the reaction gas is introduced into the chamber, it flows from the flow uniformizer to the exhaust chamber. In the process of flowing, the reaction gas is continuously absorbed by the silicon wafers, so the concentration of the reaction gas gradually decreases. Inevitably, the concentration of the reaction gas gradually decreases from the flow uniformizer to the exhaust chamber, that is, the amount of reaction gas that the silicon wafers are exposed to gradually decreases, resulting in a gradual decrease in the film thickness.

[0006] Specifically, in the process of crystalline silicon solar cells, ALD is commonly used to prepare an alumina passivation film. The source of the tubular ALD equipment is mainly intermittent at the furnace port. According to the existing technology, the amount of source gradually decreases from the source to the end of the furnace, which affects the uniformity of the alumina film thickness. SUMMARY

[0007] The present application provides a silicon wafer loading method for tubular ALD, which aims to overcome the above-mentioned deficiencies in the prior art, improve the deposition effect of the alumina film, and improve the uniformity of the film.

[0008] The technical solution of the present application: a silicon wafer loading method of a tube type ALD, the airflow in the metal boat is adjusted by adjusting the density of the inserted silicon wafers in each row in the metal carrier, the tail source amount is improved, and the overall alumina film uniformity is improved.

[0009] Specifically, there are even rows in the metal carrier, and one of the following two silicon wafer loading methods is used for silicon wafer loading in each row, The first silicon wafer loading method is to insert silicon wafers in the grooves on both sides of the metal carrier, and to load silicon wafers one by one in the grooves in the middle of the metal carrier; The second silicon wafer loading method is to insert silicon wafers in the grooves in the middle of the metal carrier, and to load silicon wafers one by one in the grooves on both sides of the metal carrier.

[0010] Preferably, a certain number of rows in the metal carrier from the direction close to the flow uniforming plate to the direction of the pumping cavity adopt one of the silicon wafer loading methods, the adjacent same number of rows adopt the other silicon wafer loading method, and the two silicon wafer loading methods are alternately arranged.

[0011] The present application has the advantages that: the method is reasonable in design, the airflow in the metal boat is adjusted, the source amount of the tail row can be effectively increased, the alumina film deposition effect is improved, and the film uniformity is improved. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is a silicon wafer loading schematic diagram of a prior art tube type ALD.

[0013] Figure 2 is a silicon wafer loading schematic diagram of one embodiment of the silicon wafer loading method of the tube type ALD of the present application.

[0014] Figure 3 is Figure 2 a schematic diagram of the first silicon wafer loading method in the present application.

[0015] Figure 4 is Figure 2 a schematic diagram of the second silicon wafer loading method in the present application. DETAILED DESCRIPTION

[0016] The present application will be further described in detail below in combination with embodiments and specific implementation manners.

[0017] As Figures 2-4 shown, a silicon wafer loading method of a tube type ALD, there are even rows in the metal carrier, the number of grooves in each row of the metal carrier can be 2*(m+n), the number of grooves for loading silicon wafers is 2n, and the remaining empty grooves are 2m.

[0018] As Figure 3As shown in FIG. 1, as the first wafer loading mode, the slots on both sides of the metal carrier are filled with wafers, and the slots in the middle of the metal carrier are loaded with wafers one by one. Assuming that there are 4m slots in the middle of the metal carrier, there are 2m empty slots on both sides of the metal carrier.

[0019] As shown in FIG. 2, as the second wafer loading mode, the slots in the middle of the metal carrier are filled with wafers, and the slots on both sides of the metal carrier are loaded with wafers one by one. Assuming that there are 2m slots on both sides of the metal carrier, there are m empty slots on both sides of the metal carrier. Figure 4

[0020] In the above two modes, the positions of the metal carrier with empty slots have small resistance to the airflow, the airflow is larger, and the amount of carried precursors is larger, so that the amount of precursors reaching the tail row can be increased.

[0021] By adjusting the arrangement of the two wafer loading modes (wafer loading modes), the airflow distribution at each position can be adjusted, so that the amount of precursors reaching the tail row can be increased while ensuring the uniformity of the airflow in the metal carrier.

[0022] In specific production, a certain number of rows in the metal carrier from the direction close to the flow uniforming plate to the direction of the pumping cavity adopt one wafer loading mode, the adjacent rows of the same number adopt another wafer loading mode, and the two wafer loading modes are arranged alternately.

[0023] As shown in FIG. 3, as a specific embodiment, the metal carrier is divided into 6 rows, each row has 232 slots, and the number of wafers loaded in each row is 200. Figure 2 The airflow flows from the flow uniforming plate to the pumping cavity. Along the airflow direction, the loading modes of each row are in turn the second wafer loading mode, the second wafer loading mode, the first wafer loading mode, the first wafer loading mode, the second wafer loading mode, and the second wafer loading mode,

[0024] When the reaction gas flows from the flow uniforming plate to the pumping cavity, part of the gas will flow to the furnace tail through the sparse positions, and this wafer loading mode can improve the gas concentration at the furnace tail and improve the film thickness at the furnace tail. For the metal carrier with the above adjusted wafer loading density, 6pcs of silicon wafers at the furnace mouth and 6pcs of silicon wafers at the furnace tail are selected, an ellipsometer is used to measure the film thickness of the aluminum oxide film, and the results are shown in the following table.

[0025] The following table is the aluminum oxide film thickness table of the furnace mouth and the furnace tail.

[0026]

[0027]

[0028] ​​As can be seen from the table above, the silicon wafer loading method of the tubular ALD of the present invention results in a similar thickness of alumina film at various locations, which can effectively improve the uniformity of the film.

[0029] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the inventive concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A method for loading silicon wafers into a tubular ALD, characterized in that, The metal carrier contains an even number of rows, and each row uses one of the following two silicon wafer loading methods: The first method of loading silicon wafers involves filling the slots on both sides of a row of metal carriers with silicon wafers, while the middle slot of a row of metal carriers is filled with silicon wafers one after another. The second method of loading silicon wafers involves filling the middle slot of a row of metal carriers with silicon wafers, while the slots on both sides of the same row of metal carriers are filled with silicon wafers one after another.

2. The silicon wafer loading method for a tubular ALD as described in claim 1, characterized in that, The metal carrier contains a certain number of rows of silicon wafers arranged from the direction near the flow equalizer towards the air extraction chamber, each using one silicon wafer loading method. Adjacent rows of the same number of rows use another silicon wafer loading method, and the two silicon wafer loading methods are alternately arranged.

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