Method for preparing SiO2 mask by using wet oxygen oxidation method

Abstract

The invention discloses a method for preparing a SiO2 mask by using a wet oxygen oxidation method. The method comprises the following steps: S1, carrying water vapor; S2, feeding a material into a pipe; S3, heating; the wet-oxygen oxidation method adopted by the invention is carried out under a high-temperature condition (the temperature is greater than or equal to 900 DEG C), and water vapor is used for reacting with the silicon wafer to generate the SiO2 mask. Compared with a dry oxidation method, the method has the advantages that the required temperature is low, the film growing speed is high, the film growing speed is more than two times of the dry oxidation speed at the same temperature, the reactant is water vapor, and compared with laughing gas of a PECVD (Plasma Enhanced Chemical Vapor Deposition) method, the method has almost no cost, and the method has certain advantages under the conditions at the present stage.

Description

Technical Field

[0001] The invention belongs to the field of solar energy materials, and in particular relates to a method for preparing a SiO2 mask. Background Art

[0002] As a commonly used barrier layer, SiO2 mask has the characteristics of simple preparation principle and good barrier effect. As a barrier layer, SiO2 mask has the characteristics of good film uniformity and simple removal (usually using HF cleaning), which is very compatible with the solar energy industry. It is often used as a barrier layer in diffusion processes such as phosphorus diffusion / boron diffusion and cleaning processes such as texturing / polishing in the solar cell industry.

[0003] The current methods for preparing SiO2 masks are usually dry oxygen oxidation and PECVD deposition. The dry oxygen oxidation method uses O2 to directly react with silicon wafers in a high temperature environment (≥1000°C) to prepare SiO2 masks. This method has high temperature requirements (at least 1000°C) and slow film growth. The PECVD method uses nitrous oxide and silane as special gases, and a chemical reaction occurs under a plasma-enhanced assisted scheme to generate a SiO2 mask. The disadvantage of this method is that it requires expensive nitrous oxide as a reaction gas, and the overall cost is relatively high. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing a SiO2 mask based on the prior art. Compared with the prior art, the present method has the advantages of low required temperature, fast film growth speed and low cost.

[0005] The purpose of the present invention can be achieved by the following measures:

[0006] A method for preparing a SiO2 mask using a wet oxygen oxidation method comprises the following steps:

[0007] S1. Carrying water vapor: Adjust the temperature in the wet oxygen generator to 30-95°C, introduce N2 and / or O2 gas into its inlet pipe, and after bubbling in the water in the wet oxygen generator, extract the water vapor carrying gas from its outlet pipe;

[0008] S2. Material feeding: Set the temperature in the high-temperature furnace tube to 700-750°C, send the silicon wafer into the high-temperature furnace tube, and keep the protective gas in the feeding process;

[0009] S3. Heating: Raise the temperature in the high-temperature furnace tube to 900-1050°C, and introduce protective gas or water vapor as a carrier gas during the heating process;

[0010] S4. Wet oxidation: The temperature in the high-temperature furnace tube is maintained at 900-1050°C, and water vapor is introduced into the carrier gas for 20-120 minutes for wet oxidation;

[0011] S5. Cooling: Cool the high-temperature furnace tube to below 800°C, introduce protective gas, and the material exits the tube.

[0012] In S1, preferably, the flow rate of the water vapor carrying gas is 1-5 slm; and the temperature in the wet oxygen generator is adjusted to 30-85°C.

[0013] In S2, preferably, N2 is used as the protective gas, and the N2 flow rate is 5-20slm.

[0014] In S3, preferably, the protective gas is N2, and the water vapor carrying gas is N2 and / or O2 gas carrying water vapor; the flow rate of the protective gas or the water vapor carrying gas is 1-5slm; and the temperature in the high-temperature furnace tube is raised to 900-1000°C.

[0015] In S4, preferably, the flow rate of the water vapor carrier gas is 1-5 slm. The present invention uses a temperature of 900-1050°C in the wet oxidation process. The present invention has a lower lower limit temperature in the wet oxidation process. The lower limit temperature required for wet oxidation is 900°C, while the existing dry oxidation requires a temperature of more than 1000°C. The time for passing the water vapor carrier gas for wet oxidation is controlled to be 20-70 minutes, more preferably 30-60 minutes.

[0016] In S5, preferably, the protective gas is N2.

[0017] The present invention adopts a wet oxidation scheme to prepare a SiO2 mask, and its core reaction equation is 2H2O+Si→SiO2+H2. In this scheme, water vapor is used as a core reactant, and its reaction temperature with silicon is lower, the reaction speed is faster, and the reactant is water vapor, which is cheaper. The use of this scheme can effectively reduce the oxidation time and temperature, and does not use expensive special gases such as laughing gas, so the cost is lower.

[0018] The wet oxidation long SiO2 mask process requires a wet oxygen generator device, which is used to provide the water vapor required for wet oxidation. Its structure is as follows Figure 1 As shown in the figure, the device is mainly used to carry water vapor into the high-temperature furnace tube. The principle is as follows: the device is a sealed device with inlet and outlet pipes, which is loaded with water inside and can be heated to maintain a constant temperature. N2 or O2 can be introduced into the inlet pipe and bubbled in the water. The introduced gas can carry water vapor out of the outlet pipe by bubbling in the water. The amount of water carried by the gas can be controlled by adjusting the temperature of the device (the set temperature is 30-95℃) (the saturated vapor pressure of water changes with temperature).

[0019] The preparation of the silicon dioxide mask adopts the high temperature furnace tube method. A specific process step is as follows:

[0020] 1. Material inlet pipe: The furnace temperature is set to (700-750℃), and the material is fed into the furnace tube. During the inlet process, N2 is kept as a protective gas. The N2 flow rate is 5-20slm.

[0021] 2. Heating: The furnace tube is heated to a specific temperature (900-1050℃) and maintained at normal pressure. During the heating process, protective gas N2 can be introduced, and N2 or O2 carrying water vapor can also be introduced as a pre-oxidation step. The flow rate of N2 and / or O2 carrying water vapor is 1-5slm. The water temperature setting value of the steam generator is 30-95℃.

[0022] 3. Wet oxidation: The temperature of the furnace tube is maintained at 900-1050℃ and the pressure is maintained. N2 or O2 or a mixture of N2 and O2 carrying water vapor is introduced, the flow rate of the gas carrying water vapor is set at 1-5slm, the water temperature of the steam generator is set at 30-95℃, and the time of passing the gas carrying water vapor is set at 20-120min.

[0023] In this process, parameters such as furnace temperature, gas flow rate carrying water vapor, and water temperature in the steam generator have a great influence on the wet oxidation rate. The relationship between the thickness of the generated SiO2 film and the temperature of the oxidation furnace is as follows: Figure 2 The relationship between the thickness of the generated SiO2 film and the flow rate of the gas carrying water vapor is as follows: Figure 3 The relationship between the thickness of the generated SiO2 film and the water temperature of the wet oxygen generator is as follows: Figure 4 The relationship between the thickness of the generated SiO2 film and the time of passing water vapor to carry gas is as follows: Figure 5 .

[0024] 4. Cooling: The furnace tube is cooled to below 800°C, protective N2 is introduced, the material is discharged from the tube, and the process is completed.

[0025] Beneficial effects of the present invention:

[0026] The wet oxygen oxidation method adopted by the present invention is carried out under high temperature conditions (temperature greater than or equal to 900° C.), using water vapor and silicon wafer to react to generate a SiO2 mask. Compared with the dry oxidation method, this method has a lower required temperature and a faster film growth rate. At the same temperature, the film growth rate is more than twice that of the dry oxygen oxidation rate. In addition, the reactant is water vapor, and compared with the laughing gas of the PECVD method, the method has almost no cost. Under current conditions, this method has certain advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The schematic diagram of the structure of the wet oxygen generator device is shown below;

[0028] Figure 2 This is the relationship between the thickness of the generated SiO2 film and the temperature of the oxidation furnace tube;

[0029] Figure 3 It is the relationship diagram between the thickness of the generated SiO2 film and the flow value of the gas carrying water vapor;

[0030] Figure 4 It is the relationship diagram between the thickness of the generated SiO2 film and the water temperature value of the wet oxygen generator;

[0031] Figure 5 This is a graph showing the relationship between the thickness of the generated SiO2 film and the time of passing water vapor to carry gas. DETAILED DESCRIPTION

[0032] The present invention can be better understood according to the following examples. However, it is easy for those skilled in the art to understand that the contents described in the examples are only used to illustrate the present invention, and should not and will not limit the present invention described in detail in the claims.

[0033] A wet oxygen generator is used to produce water vapor carrying gas, the structure of which is as follows Figure 1 As shown. The principle is as follows: the device is a sealed device with inlet and outlet pipes, which is loaded with water and can be heated to maintain a constant temperature. N2 or O2, or a mixture of N2 and O2, can be introduced into the inlet pipe. The introduced gas can carry water vapor and be discharged from the outlet pipe by bubbling in the water. The amount of water carried by the gas can be controlled by adjusting the temperature in the wet oxygen generator (the set temperature is 30-95℃) (the saturated vapor pressure of water changes with temperature).

[0034] Example 1

[0035] A specific method for preparing a SiO2 mask by wet oxidation of the present invention comprises the following steps:

[0036] 1. Material feeding: The furnace temperature is set to 750℃, and the silicon wafer is fed into the furnace. N2 is kept as protective gas during the feeding process. The N2 flow rate is 15slm.

[0037] 2. Heating: The furnace tube is heated to 1000℃ and kept at normal pressure. N2 gas is introduced as a protective gas during the heating process. The N2 gas flow rate is 5slm. The heating time is 20min.

[0038] 3. Wet oxidation: The temperature of the furnace tube is maintained at 1000℃ and the pressure is maintained. The water vapor O2 is introduced, the flow rate of the gas carrying water vapor is set at 3slm, the water temperature of the wet oxygen generator is set at 80℃, and the time of passing the gas carrying water vapor is 60min (i.e. the film growth time).

[0039] 4. Cooling: The furnace tube is cooled to 750°C, protective N2 is introduced, and the material is discharged from the tube to complete the process. The thickness of the SiO2 mask made in this embodiment is 160nm.

[0040] Example 2

[0041] A specific method for preparing a SiO2 mask by wet oxidation of the present invention comprises the following steps:

[0042] 1. Material feeding: The furnace temperature is set to 750℃, and the silicon wafer is fed into the furnace. N2 is kept as protective gas during the feeding process. The N2 flow rate is 15slm.

[0043] 2. Heating: The furnace tube is heated to 1000℃ and kept at normal pressure. N2 gas is introduced as a protective gas during the heating process. The N2 gas flow rate is 5slm. The heating time is 20min.

[0044] 3. Wet oxidation: The furnace tube temperature is set at 900℃ / 950℃ / 1000℃ / 1050℃ respectively, and the pressure is kept at normal. The water vapor O2 is introduced, the flow rate of the gas carrying water vapor is set at 3slm, the water temperature of the wet oxygen generator is set at 80℃, and the time of passing the gas carrying water vapor is 60min.

[0045] 4. Cooling: The furnace tube is cooled to 750°C, and protective N2 is introduced. The material is discharged from the tube to complete the process. In this embodiment, different furnace tube temperatures of 900°C / 950°C / 1000°C / 1050°C are used to grow oxide layer thicknesses of 80nm / 115nm / 160nm / 215nm (such as Figure 2 ).

[0046] Example 3

[0047] A specific method for preparing a SiO2 mask by wet oxidation of the present invention comprises the following steps:

[0048] 1. Material feeding: The furnace temperature is set to 750℃, and the silicon wafer is fed into the furnace. N2 is kept as protective gas during the feeding process. The N2 flow rate is 15slm.

[0049] 2. Heating: The furnace tube is heated to 1000℃ and kept at normal pressure. N2 gas is introduced as a protective gas during the heating process. The N2 gas flow rate is 5slm. The heating time is 20min.

[0050] 3. Wet oxidation: The temperature of the furnace tubes is set at 1000°C and maintained at normal pressure. Water vapor O2 is introduced, and the flow rate of the gas carrying water vapor is set at 1slm / 2slm / 3slm / 4slm respectively. The water temperature of the wet oxygen generator is set at 80°C, and the time of passing the gas carrying water vapor is 60 minutes.

[0051] 4. Cooling: The furnace tube is cooled to 750°C, and protective N2 is introduced. The material is discharged from the tube to complete the process. In this embodiment, different gas flow rates of water vapor are 1slm / 2slm / 3slm / 4slm to grow oxide layer thicknesses of 80nm / 130nm / 160nm / 180nm (such as Figure 3 ).

[0052] Example 4

[0053] A specific method for preparing a SiO2 mask by wet oxidation of the present invention comprises the following steps:

[0054] 1. Material feeding: The furnace temperature is set to 750℃, and the silicon wafer is fed into the furnace. N2 is kept as protective gas during the feeding process. The N2 flow rate is 15slm.

[0055] 2. Heating: The furnace tube is heated to 1000℃ and kept at normal pressure. N2 gas is introduced as a protective gas during the heating process. The N2 gas flow rate is 5slm. The heating time is 20min.

[0056] 3. Wet oxidation: The temperature of the furnace tubes is set to 1000℃ and the pressure is kept at normal. The water vapor O2 is introduced, and the flow rate of the gas carrying water vapor is set at 3slm. The water temperature of the wet oxygen generator is set at 20℃ / 40℃ / 60℃ / 80℃, and the time of passing the gas carrying water vapor is 60min.

[0057] 4. Cooling: The furnace tube is cooled to 750°C, protective N2 is introduced, and the material is discharged from the tube to complete the process. In this embodiment, different water temperature settings of the wet oxygen generator are 20°C / 40°C / 60°C / 80°C, and the thickness of the grown oxide layer is 58nm / 79nm / 112nm / 164nm respectively (such as Figure 4 ).

[0058] Example 5

[0059] A specific method for preparing a SiO2 mask by wet oxidation of the present invention comprises the following steps:

[0060] 1. Material feeding: The furnace temperature is set to 750℃, and the silicon wafer is fed into the furnace. N2 is kept as protective gas during the feeding process. The N2 flow rate is 15slm.

[0061] 2. Heating: The furnace tube is heated to 1000℃ and kept at normal pressure. N2 gas is introduced as a protective gas during the heating process. The N2 gas flow rate is 5slm. The heating time is 20min.

[0062] 3. Wet oxidation: The temperature of the furnace tube is set to 1000℃ and the pressure is kept at normal. The water vapor O2 is introduced, the flow rate of the gas carrying water vapor is set at 3slm, the water temperature of the wet oxygen generator is set at 80℃, and the time of passing the gas carrying water vapor is set to 30min / 40min / 50min / 60min.

[0063] 4. Cooling: The furnace tube is cooled to 750°C, and protective N2 is introduced. The material is discharged from the tube to complete the process. The different times of passing the gas carrying water vapor in this embodiment are 30min / 40min / 50min / 60min, respectively, and the thickness of the grown oxide layer is 81nm / 110nm / 138nm / 163nm (such as Figure 5 ).

[0064] Comparative Example 1

[0065] A method for preparing a SiO2 mask comprises the following steps:

[0066] 1. Material feeding: The furnace temperature is set to 750℃, and the silicon wafer is fed into the furnace. N2 is kept as protective gas during the feeding process. The N2 flow rate is 15slm.

[0067] 2. Heating: The furnace tube is heated to 1000℃ and kept at normal pressure. N2 gas is introduced as a protective gas during the heating process. The N2 gas flow rate is 5slm. The heating time is 20min.

[0068] 3. Dry oxidation: The temperature of the furnace tube is maintained at 1000°C and the pressure is maintained at normal pressure. Dry oxygen gas O2 is introduced at a flow rate of 3slm and the oxygen flow time is 60min.

[0069] 4. Cooling: The furnace tube is cooled to 750°C, protective N2 is introduced, and the material is discharged from the tube to complete the process. The thickness of the SiO2 mask made in this embodiment is 72nm.

[0070] By comparing Comparative Example 1 with Examples 1 and 5, it can be seen that the film growth rate of the present method is fast, and the film growth rate can be more than twice the dry oxygen oxidation rate at the same temperature.

[0071] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that it is still possible to modify the technical solutions described in the aforementioned embodiments, or to perform equivalent replacements on some of the technical features therein. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a SiO2 mask using a wet oxygen oxidation method, characterized in that It includes the following steps: S1. Carrying water vapor: Adjust the temperature in the wet oxygen generator to 30-95°C, introduce N2 and / or O2 gas into its inlet pipe, and after bubbling in the water in the wet oxygen generator, extract the water vapor carrying gas from its outlet pipe; S2. Material feeding: Set the temperature in the high-temperature furnace tube to 700-750°C, send the silicon wafer into the high-temperature furnace tube, and keep the protective gas in the feeding process; S3. Heating: The temperature of the high temperature furnace tube is raised to 900-1050°C, and a protective gas is introduced during the heating process, or the water vapor is introduced to carry the gas; S4. Wet oxidation: The temperature in the high temperature furnace tube is maintained at 900-1050°C, and the water vapor carrying gas is introduced for 20-120min for wet oxidation; S5. Cooling: Cool the high-temperature furnace tube to below 800° C., introduce protective gas, and discharge the material from the tube.

2. The method for preparing a SiO2 mask using a wet oxygen oxidation method according to claim 1, characterized in that In S1, the flow rate of the water vapor carrying gas is 1 to 5 slm.

3. The method for preparing a SiO2 mask using a wet oxygen oxidation method according to claim 1, characterized in that In S1, the temperature in the wet oxygen generator is adjusted to 30-85°C.

4. The method for preparing a SiO2 mask using a wet oxygen oxidation method according to claim 1, characterized in that In S2, N2 is used as the protective gas, and the flow rate of N2 is 5 to 20 slm.

5. The method for preparing a SiO2 mask using a wet oxygen oxidation method according to claim 1, characterized in that In S3, the protective gas is N2, and the flow rate of the protective gas or the water vapor carrying gas is 1 to 5 slm.

6. The method for preparing a SiO2 mask using a wet oxygen oxidation method according to claim 1, characterized in that In S3, the temperature in the high temperature furnace tube is raised to 900-1000°C.

7. The method for preparing a SiO2 mask using a wet oxygen oxidation method according to claim 1, characterized in that In S4, the flow rate of the water vapor carrying gas is 1 to 5 slm, and the time for passing the water vapor carrying gas for wet oxidation is 20 to 70 minutes.

8. The method for preparing a SiO2 mask using a wet oxygen oxidation method according to claim 7, characterized in that In S4, the time for introducing the water vapor carrying gas for wet oxidation is 30 to 60 minutes.

9. The method for preparing a SiO2 mask using a wet oxygen oxidation method according to claim 1, characterized in that In S5, the protective gas is N2.

10. The method for preparing a SiO2 mask using a wet oxygen oxidation method according to claim 1, characterized in that The steps include:

1. Material inlet pipe: The furnace tube temperature is set to 700-750℃, and the material is fed into the furnace tube. During the inlet process, N2 is kept as a protective gas, and the N2 flow rate is 5-20slm; 2. Heating: The furnace tube is heated to 900-1050°C and maintained at normal pressure. During the heating process, protective gas N2 is introduced, or N2 and / or O2 carrying water vapor is introduced as a pre-oxidation step; the flow rate of N2 and / or O2 carrying water vapor is 1-5slm; the water temperature setting value of the water vapor generator is 30-95°C; 3. Wet oxidation: The temperature of the furnace tube is maintained at 900-1050°C and the normal pressure state; the N2 and / or O2 gas carrying water vapor is introduced, the gas flow rate is set at 1-5slm, the water temperature of the steam generator is set at 30-95°C, and the time of passing the N2 and / or O2 gas carrying water vapor is set to 20-120min; 4. Cooling: The furnace tube is cooled to below 800°C, protective N2 is introduced, and the material is discharged from the tube.

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