CN108447770B - Preparation method of silicon dioxide film - Google Patents

Abstract

The invention provides a preparation method of a silicon dioxide film. First, a silicon substrate is provided. Secondly, the silicon substrate is placed into an oxidation furnace, and the temperature in the oxidation furnace is 1000-1200 ℃. Then, oxygen is introduced into the oxidation furnace, and the flow rate of the oxygen is 9slm/min-10 slm/min. And introducing oxygen into the oxidation furnace for 4-6 min, introducing hydrogen into the oxidation furnace and igniting, wherein the flow of the hydrogen is 14-14.6 slm/min, and forming a first silicon dioxide layer on the surface of the silicon substrate.

Description

Preparation method of silicon dioxide film

technical field

The invention relates to an electronic semiconductor process, in particular to a preparation method of a silicon dioxide film.

Background technique

In the semiconductor manufacturing technology, oxidation and chemical vapor deposition (CVD) are mostly used for the preparation of thin films. Thermal oxidation is a method of forming a silicon dioxide film on the surface of a silicon wafer at a high temperature. The purpose of thermal oxidation is to make a silicon dioxide film with certain quality requirements on the silicon wafer, which can protect, passivate, insulate, and buffer the silicon wafer or device.

In the existing semiconductor device manufacturing process, a wet oxygen process is commonly used, that is, a silicon dioxide film is grown on a silicon substrate by using oxygen gas to carry high-temperature water vapor. In the wet oxygen process, the purity of the high-temperature water vapor has an important influence on the process quality. The low purity of the water vapor will lead to high impurity content and poor film quality in the silicon dioxide film. In order to improve the purity of water, the combustion of hydrogen and oxygen (hydrogen-oxygen synthesis) is often used to produce high-purity water. In addition, in the process of preparing the silicon dioxide thin film, the flow rate of oxygen and hydrogen also have an important influence on the formation rate of the silicon dioxide thin film and the uniformity of the silicon dioxide thin film.

SUMMARY OF THE INVENTION

Based on this, it is necessary to provide a method for preparing a silicon dioxide thin film in order to improve the growth rate and uniformity of the silicon dioxide thin film.

The present invention provides a method for preparing a silicon dioxide film, the method comprising:

S100, providing a silicon substrate;

S200, putting the silicon substrate into an oxidation furnace, and raising the temperature in the oxidation furnace to a reaction temperature, where the reaction temperature is 1000°C-1200°C;

S300, feed oxygen into the oxidation furnace, and the flow rate of the oxygen is 9slm/min-10slm/min; and

S400, after feeding oxygen into the oxidation furnace for 4min-6min, feeding hydrogen into the oxidation furnace and igniting, the flow rate of the hydrogen is 14slm/min-14.6slm/min, on the surface of the silicon substrate A first silicon dioxide layer is formed.

In one embodiment, the S400 includes:

S410, after feeding oxygen 4min-6min into the oxidation furnace, start to feed hydrogen into the oxidation furnace, and the flow rate of the hydrogen is 4slm/min-8slm/min;

S420, after passing hydrogen into the oxidation furnace for 0.5min-1.5min, adjust the flow rate of the hydrogen to 14slm/min-14.6slm/min, and form a first silicon dioxide layer on the surface of the silicon substrate.

In one embodiment, in the S300, the oxygen flow rate is 9.53 slm/min.

In one embodiment, in the S400, the hydrogen flow rate is 14.3 slm/min.

In one embodiment, the S200 includes:

The S200 includes:

S210, providing an oxidation furnace, heating the oxidation furnace to a pretreatment temperature, and the pretreatment temperature is 800°C-900°C;

S220, after the oxidation furnace is heated to the pretreatment temperature, the silicon substrate is put into the oxidation furnace and nitrogen gas is introduced into the oxidation furnace;

S230, after maintaining the pretreatment temperature for 20min-40min, disconnect the nitrogen gas and raise the temperature in the oxidation furnace from the pretreatment temperature to the reaction temperature, where the reaction temperature is 1000°C-1200°C.

In one embodiment, the S300 includes:

S310, between the temperature in the oxidation furnace rising from the pretreatment temperature to the reaction temperature, feeding oxygen into the oxidation furnace, and the flow rate of the oxygen is 10slm/min-15slm/min;

S320, after the temperature in the oxidation furnace is raised to the reaction temperature, the flow rate of the oxygen is adjusted to 9slm/min-10slm/min, and a second silicon dioxide layer is formed on the surface of the silicon substrate, The second silicon dioxide layer is disposed between the first silicon oxide layer and the silicon substrate.

In one embodiment, after S400, S500 is further included, the hydrogen is disconnected, and oxygen is continuously introduced into the oxidation furnace, and the flow rate of the oxygen is 9slm/min-10slm/min. The silicon oxide layer forms a third silicon dioxide layer away from the surface of the silicon substrate.

In one embodiment, the step S100 further includes S110, cleaning the silicon substrate with a cleaning solution.

In one embodiment, the cleaning solution is a mixed solution of H ₂ SO ₄ \H ₂ O ₂ , a mixed solution of NH ₄ OH\H ₂ O ₂ \H ₂ O, HCL\H ₂ O ₂ \H ₂ O One or more of the mixed solution and the HF solution.

In one embodiment, S600 is also included. After the first silicon dioxide layer is prepared, the temperature in the oxidation furnace is lowered to 800°C-900°C, and the cooling time is 60min-70min.

In the preparation method of the silicon dioxide film provided by the present invention, at the reaction temperature of 1000°C-1200°C, oxygen with a flow rate of 9slm/min-10slm/min and oxygen with a flow rate of 14slm/min-14.6slm/min are passed through. The hydrogen reacts to produce high-purity water vapor. The water vapor reaches the surface of the silicon substrate by means of diffusion, and reacts rapidly with silicon on the surface of the silicon substrate to form a first silicon dioxide layer. When the hydrogen is at a flow rate of 14slm/min-14.6slm/min, and the oxygen is at a flow rate of 9slm/min-10slm/min, the flow rates of the hydrogen and oxygen are appropriate, and the oxidation furnace has a better reaction atmosphere. , so that the first silicon dioxide layer can be prepared quickly and efficiently, and the uniformity of the prepared first silicon dioxide layer is greatly improved.

Description of drawings

1 is a flowchart of a method for preparing a silicon dioxide film provided by an embodiment of the present invention;

2 is a schematic diagram of a process reaction of a method for preparing a silicon dioxide film according to an embodiment of the present invention;

3 is a schematic diagram of a process reaction of a method for preparing a silicon dioxide film provided by another embodiment of the present invention;

4 is a schematic diagram of a process reaction of a method for preparing a silicon dioxide film provided by an embodiment of the present invention;

5 is a schematic diagram of a process reaction of a method for preparing a silicon dioxide film provided by an embodiment of the present invention;

6 is a schematic diagram of a temperature process of a method for preparing a silicon dioxide film provided by an embodiment of the present invention.

Description of reference numerals

110: Silicon substrate

120: first silicon dioxide layer

130: Second Silicon Dioxide Layer

140: Third silicon dioxide layer

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the following examples and the accompanying drawings will further describe the preparation method of the silicon dioxide film of the present invention in detail. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

The method for preparing the silicon dioxide film according to the embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

Referring to accompanying drawings 1 and 2, an embodiment of the present invention provides a method for preparing a silicon dioxide film, which includes the following steps:

S100, providing a silicon substrate 110;

S200, putting the silicon substrate 110 into an oxidation furnace, and raising the temperature in the oxidation furnace to a reaction temperature, where the reaction temperature is 1000°C-1200°C;

S300, feed oxygen into the oxidation furnace, and the flow rate of the oxygen is 9slm/min-10slm/min; and

S400, after feeding oxygen into the oxidation furnace for 4min-6min, feeding hydrogen into the oxidation furnace and igniting, the flow rate of the hydrogen is 14slm/min-14.6slm/min, and in the silicon substrate 110 A first silicon dioxide layer 120 is formed on the surface.

In the S100, the silicon substrate 110 may be a P-type silicon wafer or an N-type silicon wafer. The size, thickness and shape of the silicon substrate 110 are not limited and can be selected according to actual needs. In one embodiment, the thickness of the silicon substrate 110 is 400um-600um.

In the S200, the oxidation furnace is a device for preparing silicon dioxide thin films. The oxidation furnace includes an ignition furnace, an ignition gun, a synthesis chamber and a thermocouple group. The main body of the synthesis chamber is built into the ignition furnace, and the gas outlet end of the synthesis chamber extends to the outside of the ignition furnace and communicates with the quartz tube. The intake end of the synthesis chamber extends to the outside of the ignition furnace and is fitted with an ignition gun, and the intake end of the ignition gun is provided with a hydrogen intake pipe. The intake end of the synthesis chamber is provided with an oxygen intake pipe, and the thermocouple components are installed on the ignition furnace and the ignition gun.

In the S200, the silicon substrate 110 is put into the oxidation furnace. The temperature in the oxidation furnace is the reaction temperature, and the reaction temperature is 1000°C-1200°C, preferably 1050°C. When the reaction temperature is increased, the reaction speed is accelerated, and the production rate of the silicon dioxide film can be improved.

In the S400, the first silicon dioxide layer 120 is a wet oxygen layer of a silicon dioxide film prepared by a hydrogen-oxygen synthesis method. When oxygen is introduced into the oxidation furnace for 4min-6min, after the measurement indication of the measuring meter used to measure the oxygen flow rate tends to be stable, hydrogen is introduced into the oxidation furnace and ignited. The flow is 4slm/min-8slm/min. This can avoid explosion due to excessive hydrogen and oxygen ratio due to inaccurate flow measurement when the flowmeter is activated instantaneously, thereby ensuring high safety in the preparation process of the silicon dioxide film.

In this embodiment, the silicon dioxide film preparation method, at a reaction temperature of 1000°C-1200°C, passes oxygen with a flow rate of 9slm/min-10slm/min and oxygen with a flow rate of 14slm/min-14.6slm/min The hydrogen reacts to produce high-purity water vapor. The water vapor can diffuse to the surface of the silicon substrate 110 and react with silicon to form the first silicon dioxide layer 120 . When the flow rate of the hydrogen is 14slm/min-14.6slm/min, and the flow rate of the oxygen is 9slm/min-10slm/min, the hydrogen can react with the oxygen to generate more water vapor, which can A stable water vapor environment is rapidly formed in the oxidation furnace, so that the first silicon dioxide layer 120 with better uniformity can be efficiently prepared, and the prepared silicon dioxide thin film has better uniformity big improvement.

In one embodiment, the S400 includes:

S410, after passing oxygen 4min-6min into described oxidation furnace, start to pass into hydrogen in described oxidation furnace, and the flow rate of described hydrogen is 4slm/min-8slm/min; And

S420, after passing hydrogen into the oxidation furnace for 0.5min-1.5min, adjusting the flow rate of the hydrogen to 14slm/min-14.6slm/min, and forming a first silicon dioxide layer on the surface of the silicon substrate 110 120.

In the present embodiment, oxygen is introduced first, and the flow rate of the oxygen is 9slm/min-10slm/min. After the oxygen is introduced for 4min-6min, the hydrogen is started to be introduced. The hydrogen reacts with the oxygen to generate water vapor, and the water vapor diffuses to the surface of the silicon substrate 110 and reacts with silicon to form the first silicon dioxide layer 120 . The flow rate of the hydrogen is 4slm/min-8slm/min, and after the flow rate is 4slm/min-8slm/min of hydrogen for 0.5min-1.5min, after the measurement indication of the flowmeter is stable, the flow rate of the hydrogen is Adjusted to 14slm/min-14.6slm/min. This can effectively avoid explosion due to inaccurate flow measurement when the flowmeter is activated instantaneously, thereby ensuring high safety in the preparation process of the first silicon dioxide layer 120 .

In one embodiment, in the S300, the oxygen flow rate is 9.53 slm/min.

In this embodiment, the flow rate of the oxygen is 9.53 slm/min, and the flow rate of the hydrogen gas is 14 slm/min-14.6 slm/min, preferably 14.3 slm/min. The flow rates of the hydrogen and oxygen are appropriate, and the hydrogen and oxygen can react to generate more water vapor, so that a stable water vapor environment can be quickly formed in the oxidation furnace, so as to prepare a uniform water vapor. The first silicon dioxide layer 120 .

In one embodiment, in the S400, the flow rate of the hydrogen gas is 14.3 slm/min.

In this embodiment, the flow rate of the oxygen is an optimum flow rate of 9.53 slm/min, and the flow rate of the hydrogen gas is an optimum flow rate of 14.3 slm/min. The hydrogen and the oxygen can react to generate a large amount of water vapor, and a stable water vapor environment can be rapidly formed in the oxidation furnace, thereby preparing a silicon dioxide film with good uniformity. Uniformity can be achieved within ±2%.

和

的二氧化硅薄膜。从表1中数据可以看出在氢气流量为14.3slm/min，并且氧气流量为9.53slm/min条件下制备的所述二氧化硅薄膜的均匀性较好，都能达到±2％以内。Please refer to Table 1, in one embodiment, under the condition that the flow rate of oxygen is 9.53slm/min and the flow rate of hydrogen is 14.3slm/min, after 37.5min and 20min, a thickness of

and

silicon dioxide film. From the data in Table 1, it can be seen that the uniformity of the silicon dioxide film prepared under the condition that the hydrogen flow rate is 14.3 slm/min and the oxygen flow rate is 9.53 slm/min is good, all within ±2%.

Table 1 Process parameters and uniformity of silicon dioxide films grown at 37.5 min and 20 min

time temperature(℃) H₂ traffic O₂ traffic In-chip uniformity wafer-to-sheet uniformity 37.5min 1050 14.3 9.53 ≤±0.97% ±0.34% 20min 1050 14.3 9.53 ≤±1.35% ±0.7%

In one embodiment, the S200 includes:

S210, providing an oxidation furnace, heating the oxidation furnace to a pretreatment temperature, and the pretreatment temperature is 800°C-900°C;

S220, after the oxidation furnace is heated to the pretreatment temperature, the silicon substrate 110 is put into the oxidation furnace and nitrogen gas is introduced into the oxidation furnace; and

S230, after maintaining the pretreatment temperature for 20min-40min, disconnect the nitrogen gas and raise the temperature in the oxidation furnace from the pretreatment temperature to the reaction temperature, where the reaction temperature is 1000°C-1200°C.

In this embodiment, the oxidation furnace is heated to a pretreatment temperature of 800° C. to 900° C., so that the reaction efficiency can be improved during the production of silicon dioxide thin films. The silicon substrate 110 is put into the oxidation furnace, and nitrogen gas is introduced into the oxidation furnace, and other inert gases may also be introduced, which is not limited herein. The nitrogen gas is used to purge the impurities in the oxidation furnace to ensure the high purity of the silicon dioxide film. The oxidation furnace maintains the pretreatment temperature of 800°C-900°C for about 20min-40min, and after the temperature in the furnace is constant and reaches a stable state, the oxidation furnace is heated to the reaction temperature, and the reaction temperature is 1000°C -1200℃. When the temperature in the oxidation furnace is raised to the reaction temperature of 1000°C to 1200°C, the preparation of the second silicon dioxide layer 130 can be ensured in an optimal temperature range, so that the rapid preparation of the second silicon dioxide layer 130 can be ensured. The second silicon dioxide layer 130 .

In one embodiment, the S300 includes:

S310, between the temperature in the oxidation furnace rising from the pretreatment temperature to the reaction temperature, feeding oxygen into the oxidation furnace, and the flow rate of the oxygen is 10slm/min-15slm/min;

S320, after the temperature in the oxidation furnace is raised to the reaction temperature, the flow rate of the oxygen is adjusted to 9slm/min-10slm/min, and a second silicon dioxide layer is formed on the surface of the silicon substrate 110 130 , the second silicon dioxide layer 130 is disposed between the first silicon oxide layer 120 and the silicon substrate 110 .

Please refer to Fig. 3 and Fig. 4. In this embodiment, when the temperature in the oxidation furnace increases from the pretreatment temperature of 800°C to 900°C to the reaction temperature of 1000°C to 1200°C, the During the process of raising the temperature to the reaction temperature, oxygen gas is introduced, so as to carry out the synthesis process of the second silicon dioxide layer 130 . The second silicon dioxide layer 130 is the first dry oxygen layer of the silicon dioxide thin film. The oxygen diffuses to the surface of the silicon substrate 110 to react with silicon, thereby generating the second silicon dioxide layer 130 . In this embodiment, the silicon dioxide film may be entirely composed of the second silicon dioxide layer 130 prepared by diffusing oxygen to the surface of the silicon substrate 110 and reacting with silicon, or may be composed of the first silicon dioxide layer The silicon layer 120 and the second silicon dioxide layer 130 are formed together, which is not limited herein.

In this embodiment, the oxygen flow rate for preparing the second silicon dioxide layer 130 is 10 slm/min-15 slm/min. In this way, the oxidation furnace has a relatively stable oxygen atmosphere, and the synthesis reaction of the second silicon dioxide layer 130 can be carried out well, so that the second silicon dioxide layer 130 with better uniformity can be prepared. After the temperature in the oxidation furnace rises to the reaction temperature, the flow rate of the oxygen is adjusted to 9slm/min-10slm/min. This can ensure that the oxygen is reacted to prepare the first silicon dioxide layer 120 at the optimal temperature of 1000°C-1200°C and the flow rate of 9slm/min-10slm/min. The preparation time of the first silicon dioxide layer 120 It is greatly shortened, and the uniformity of the prepared silicon dioxide film is also greatly improved.

In one embodiment, it also includes S500, disconnecting the hydrogen, and continuing to feed oxygen into the oxidation furnace, the flow rate of the oxygen is 9slm/min-10slm/min, and the first silicon dioxide layer 120 is far away from the A third silicon dioxide layer 140 is formed on the surface of the silicon substrate 110 .

Referring to FIG. 5 and FIG. 6 , in this embodiment, after the preparation of the first silicon dioxide layer 120 is completed, the hydrogen gas is disconnected, and the oxygen gas is continuously supplied to perform the third silicon dioxide layer 140 preparation, the third silicon dioxide layer 140 is the second dry oxygen layer of the silicon dioxide thin film.

In one embodiment, the silicon dioxide film obtained by the method has a dry-wet-dry layered structure. The silicon dioxide film is composed of the first silicon dioxide layer 120 , the second silicon dioxide layer 130 and the third silicon dioxide layer 140 together. The first dry oxygen layer 130 and the second dry oxygen layer 140 can increase the density of the silicon dioxide film. The growth rate of the first dry oxygen layer 130 and the second dry oxygen layer 140 is slower than that of the wet oxygen layer 120. Considering the preparation cost of the silicon dioxide film, the second dry oxygen layer 140 and the second dry oxygen layer 140 are relatively slow. The thickness of the first dry oxygen layer 130 should not exceed 700 angstroms. Therefore, when the thicknesses of the second dry oxygen layer 140 and the first dry oxygen layer 130 do not exceed 700 angstroms, the silicon dioxide film has better compactness, and the preparation of the silicon dioxide film lower cost.

In this embodiment, the oxygen flow rate for preparing the third silicon dioxide layer 140 is 9 slm/min-10 slm/min, preferably 9.53 slm/min. Continue to prepare the third silicon dioxide layer 140 on the surface of the first silicon dioxide layer 120, which can increase the density of the silicon dioxide thin film.

In one embodiment, after S100, S110 is further included, and the silicon substrate 110 is cleaned with a cleaning solution.

There may be contamination impurities on the surface of the silicon substrate 110, including organic matter and inorganic matter. These impurities exist on the surface of the silicon substrate 110 in atomic state, ionic state, thin film form or particle form. In order to completely remove these impurities and to generate a high-purity silicon dioxide film, in this embodiment, the silicon substrate 110 is cleaned with a cleaning solution.

In one embodiment, the cleaning solution includes a mixed solution of H ₂ SO ₄ \H ₂ O ₂ , a mixed solution of NH ₄ OH\H ₂ O ₂ \H ₂ O, and a mixed solution of HCL\H ₂ O ₂ \H ₂ O One or more of solution and HF solution.

In this embodiment, the selection of the cleaning liquid is selected according to the removal of different types of impurities. The mixed solution of H ₂ SO ₄ \H ₂ O ₂ can be used to remove heavy organic impurities. NH ₄ OH\H ₂ O ₂ \H ₂ O mixed solution can be used to remove organic matter, inorganic matter and metal ions. The mixed solution of HCL\H ₂ O ₂ \H ₂ O can be used to remove metal ions such as aluminum, iron, and sodium. HF solution can be used to remove metal ions and native oxide layers.

In one embodiment, after the S600, after the silicon dioxide film is prepared, the temperature in the oxidation furnace is lowered to 800°C-900°C for 60min-70min.

Referring to FIG. 6, in this embodiment, after the S600, after the silicon dioxide film is prepared, the temperature in the oxidation furnace is lowered from the reaction temperature of 1000°C-1200°C to 800°C-900°C °C. In the process of reducing the reaction temperature from 1000°C-1200°C to 800°C-900°C, nitrogen can be introduced for cooling, or other inert gas can be introduced, which is not limited here. By reducing the temperature in the oxidation furnace, it is possible to avoid potential safety hazards caused by the temperature in the reaction furnace being too high.

The technical features of the above-described embodiments can be combined arbitrarily. In order to make the description clear, all possible combinations of the technical features in the above-described embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, all It should be considered as the range described in this specification.

The above-mentioned embodiments only represent several embodiments of the present invention, and the descriptions thereof are specific and detailed, but should not be construed as a limitation on the scope of the patent of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can also be made, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention should be subject to the appended claims.

Claims (8)

1. A method for preparing a silicon dioxide film, comprising: S100, providing a silicon substrate (110); S200, putting the silicon substrate (110) into an oxidation furnace, and raising the temperature in the oxidation furnace from a preset temperature to a reaction temperature, where the reaction temperature is 1000°C-1200°C; S310, before the temperature in the oxidation furnace is increased from the preset temperature to the reaction temperature, oxygen is introduced into the oxidation furnace, and the flow rate of the oxygen is 10slm/min-15slm/min, and in the A second silicon dioxide layer (130) is formed on the surface of the silicon substrate (110), and the second silicon dioxide layer (130) is disposed on the surface of the silicon substrate (110); S320, after the temperature in the oxidation furnace is raised to the reaction temperature, the flow rate of the oxygen is adjusted to 9slm/min-10slm/min; S410, after feeding oxygen 4min-6min into the oxidation furnace, start feeding hydrogen into the oxidation furnace, and ignite, and the flow rate of the hydrogen is 4slm/min-8slm/min; S420, feeding hydrogen into the oxidation furnace for 0.5min-1.5min, adjusting the flow rate of the hydrogen to 14slm/min-14.6slm/min, and forming the first silicon dioxide layer on the surface of the second silicon dioxide layer (130). A silicon dioxide layer (120). 2 . The method for preparing a silicon dioxide film according to claim 1 , wherein, in the S320 , the flow rate of the oxygen gas is 9.53 slm/min. 3 . 3 . The method for preparing a silicon dioxide film according to claim 2 , wherein, in the S420 , the flow rate of the hydrogen gas is 14.3 slm/min. 4 . 4. The method for preparing a silicon dioxide film according to claim 1, wherein the S200 comprises: S210, providing an oxidation furnace, heating the oxidation furnace to a pretreatment temperature, and the pretreatment temperature is 800°C-900°C; S220, after the oxidation furnace is heated to the pretreatment temperature, the silicon substrate (110) is put into the oxidation furnace and nitrogen gas is introduced into the oxidation furnace; S230, after maintaining the pretreatment temperature for 20min-40min, disconnect the nitrogen gas and raise the temperature in the oxidation furnace from the pretreatment temperature to the reaction temperature, where the reaction temperature is 1000°C-1200°C. 5. the preparation method of silicon dioxide film as claimed in claim 1, is characterized in that, also comprises: S500, disconnects hydrogen, continues to feed oxygen into described oxidation furnace, and the flow rate of described oxygen is 9slm/min -10 slm/min, a third silicon dioxide layer (140) is formed on the surface of the first silicon dioxide layer (120) away from the silicon substrate (110). 6 . The method for preparing a silicon dioxide film according to claim 1 , wherein after the S100 , the method further comprises: S110 , cleaning the silicon substrate ( 110 ) with a cleaning solution. 7 . 7. The preparation method of silicon dioxide film according to claim 6, wherein the cleaning solution is a mixed solution of H ₂ SO ₄ \H ₂ O ₂ , NH ₄ OH\H ₂ O ₂ \H ₂ One or more of O mixed solution, HCL\H ₂ O ₂ \H ₂ O mixed solution and HF solution. 8. the preparation method of the silicon dioxide film as described in any one of claim 1-7, is characterized in that, also comprises: S600, after the preparation of the first silicon dioxide layer is completed, the temperature in the oxidation furnace is lowered to 800°C-900°C, and the cooling time is 60min-70min.

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