CN109107974B - A kind of cleaning method of quartz device for solar cell preparation - Google Patents

Abstract

The invention belongs to the technical field of solar cells. The invention discloses a method for cleaning a quartz device for solar cell preparation, which comprises the steps of cleaning a cleaning tank by acid, cleaning a high-temperature water washing tank by water, cleaning the normal-temperature water washing tank by water, drying and the like, wherein the acid cleaning is carried out by adopting mixed liquid medicine of hydrofluoric acid and ozone water, and the water cleaning is carried out by adopting ozone water. The invention is not only suitable for quartz devices in a diffusion process, but also suitable for cleaning the quartz devices in a film coating process; the invention can reduce the usage amount of hydrofluoric acid, hydrochloric acid and ozone water, and greatly reduce the time of the whole cleaning process; the invention can effectively clean the quartz device, reduce the pollution proportion and improve the efficiency.

Description

A kind of cleaning method of quartz device for solar cell preparation

technical field

The invention relates to the technical field of solar cells, in particular to a cleaning method for a quartz device used for solar cell preparation.

Background technique

The diffusion process is the process of forming a P-N junction in the production of crystalline silicon solar cells. The diffusion process of silicon wafer is a process in which elemental phosphorus is deposited on the surface of P-type crystalline silicon by chemical reaction between the diffusion source gas and the silicon wafer at high temperature. The chemical reaction formula is as follows:

2P ₂ O ₅ +5Si==5SiO ₂ +4P↓,

It can be seen from the above reaction formula that when POCl ₃ is thermally decomposed, if there is no external oxygen (O ₂ ) involved in its decomposition, it is not sufficient, and the generated PCl ₅ is not easy to decompose, and has a corrosive effect on silicon, destroying the silicon wafer. surface state. But in the presence of foreign O ₂ , PCl ₅ will be further decomposed into P ₂ O ₅ and release chlorine (Cl ₂ ), the reaction formula is as follows:

The generated P ₂ O ₅ further interacts with silicon to generate SiO ₂ and phosphorus atoms.

During the diffusion process, the silicon wafer is first inserted into the quartz boat, and then the quartz boat and the silicon wafer are put into the diffusion quartz tube for the diffusion process. After the diffusion is completed, the silicon wafer is taken out from the quartz boat, and then a new silicon wafer is inserted for the next batch of diffusion. Therefore, in the production process, the quartz device is reused. However, a layer of white powdery objects will be deposited on the surface of quartz devices used for a long time. The white powdery objects are composed of a mixture of phosphorus pentoxide, metaphosphoric acid, orthophosphoric acid, phosphorus pentachloride, dust, and silicon chip debris. When a quartz device is exposed to air, it chemically reacts with moisture in the air. The following is the reaction equation:

P ₂ O ₅ +H ₂ O (low temperature)==2HPO ₃ ,

P ₂ O ₅ +3H ₂ O (high temperature)==2H ₃ PO ₄ ,

PCl ₅ +H ₂ O (a small amount)==POCl ₃ +2HCl,

PCl ₅ +4H ₂ O (excess)==H ₃ PO ₄ +5HCl,

Quartz devices include: quartz tubes, quartz boats, waste pipes, exhaust gas cylinders, etc., which will not be explained further in the future.

When a large amount of mixture is generated on the surface of the quartz device, and after each diffusion process, a certain amount of diffused dust and particles will remain on the surface of the quartz device, which will affect the appearance of the silicon wafer after contact with the silicon wafer, such as: black printing on the card slot point, etc., and even reduce the cell efficiency in severe cases. Therefore, the quartz boat needs to be cleaned regularly.

The existing quartz device cleaning method is to first use hydrofluoric acid and hydrochloric acid mixed acid for pickling, then use pure water overflow for water washing, and finally dry; this kind of quartz device cleaning process has the following problems, the original acid The washing tank is designed without cover for easy operation. During the pickling process of the quartz device, hydrofluoric acid and hydrochloric acid volatilize, resulting in an unpleasant sour smell in the workshop, and the continuous volatilization of hydrofluoric acid and hydrochloric acid causes the concentration of the pickling tank to decline all the time. During the process, the acid washing and water washing time is too long, the use of hydrofluoric acid and hydrochloric acid chemicals is too much, the cleaned quartz equipment is not clean, and the cleaned quartz equipment has acid residues, which leads to EL pollution of the cells.

SUMMARY OF THE INVENTION

In order to solve the above problems, the present invention provides a cleaning method for a quartz device used for solar cell preparation, which can reduce the use of chemicals and greatly save water resources and cleaning time without reducing the cleaning quality.

For achieving the above object, the technical scheme adopted in the present invention is as follows:

A method for cleaning a quartz device for solar cell preparation, comprising the following steps:

a) Add hydrofluoric acid and ozone water mixed medicinal solution in the cleaning tank and heat, and put the quartz device into the cleaning tank to seal, soak and pickle;

b) adding ozone water to the high-temperature washing tank and heating, and soaking and cleaning the quartz device soaked and pickled in step a) in the high-temperature washing tank;

c) adding ozone water to the normal temperature water washing tank, and soaking and cleaning the quartz device soaked and cleaned in step b) in the normal temperature water washing tank at normal temperature;

d) Repeat step c) until the pH value of the normal temperature water washing tank is neutral, and the water washing is completed;

e) After the water washing is completed, the quartz device is taken out and dried to complete the cleaning process of the quartz device.

Preferably, the ozone content in the ozone water is 10-30 ppm.

Preferably, in the mixed chemical solution of hydrofluoric acid and ozone water, the volume ratio of hydrofluoric acid and ozone water is (1-2):(15-20).

Preferably, in step a), the temperature during soaking and pickling is controlled at 60-90° C., and 40KHz ultrasonic waves and bubbling are used to assist pickling.

Preferably, in step a), the soaking and pickling time is 15-40 minutes.

Preferably, in step b), the temperature during soaking and cleaning is controlled at 60-90° C., and 40KHz ultrasonic waves and bubbling are used to assist cleaning.

Preferably, in step b), the volume of the ozone water is kept at 200-250 L, and the soaking and cleaning time is 10-30 minutes.

Preferably, in step c), bubbling is used to assist cleaning during immersion cleaning.

Preferably, in step c), the volume of the ozone water is kept at 200-250 L, and the soaking and cleaning time is 10-30 minutes.

Preferably, in step e), nitrogen or compressed air is used to dry the taken out quartz device.

In step a), in order to speed up the pickling rate and strengthen the cleaning effect, the bottom of the cleaning tank is heated to make the quartz device pickled at a high temperature; hydrofluoric acid is a volatile acid, and ozone in ozone water will also decompose into oxygen volatilization. Go out, especially when the high-temperature bubbling is turned on, so the top of the cleaning tank is covered, and the cover is sealed to ensure that it can be effectively sealed even at high temperature, preventing the volatilization of hydrofluoric acid and the decomposition and volatilization of ozone.

In step b), in order to quickly and effectively remove the acid on the surface of the quartz device from the quartz device, ozone water is also used for cleaning at a high temperature, and hydrofluoric acid is rapidly dissolved in the ozone water at a high temperature, thereby effectively removing the surface of the quartz device. Hydrofluoride acid component.

Ozone water has a very strong oxidizing ability and has a very strong oxidizing property. The oxidation-reduction potential of ozone water is higher than that of sulfuric acid, hydrofluoric acid and hydrogen peroxide. Therefore, the use of ozone water to remove organics and metals is more efficient than traditional methods.

Therefore, the present invention has the following beneficial effects:

(1) the present invention is not only applicable to the quartz device cleaning of the diffusion process but also to the cleaning of the quartz device of the coating process;

(2) the present invention can reduce the usage amount of hydrofluoric acid, hydrochloric acid and ozone water, and greatly reduce the whole cleaning process time;

(3) The present invention can effectively clean the quartz device, reduce the pollution ratio, and improve the efficiency.

Detailed ways

The technical solutions of the present invention will be further described below in conjunction with specific embodiments.

Obviously, the described embodiments are only some, but not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

In the present invention, unless otherwise specified, all equipment and raw materials can be purchased from the market or are commonly used in the industry. The methods in the following examples are conventional methods in the art unless otherwise specified.

The hydrofluoric acid and hydrochloric acid used in the following examples and comparative examples are all commercially available raw materials, wherein the concentration of hydrofluoric acid is 49 wt %, and the concentration of hydrochloric acid is 37 wt %.

Example 1

A method for cleaning a quartz device for solar cell preparation, comprising the following steps:

a) Add 10L of hydrofluoric acid and 150L of ozonated water into the cleaning tank and heat it to 60°C, put the quartz device into the cleaning tank, seal, soak and pickle for 15 minutes, and use 40KHz ultrasonic wave and drum Foam-assisted pickling;

b) Add ozone water to the high temperature washing tank and keep the volume of ozone water at 230L, heat to 60°C, soak and clean the quartz device soaked and pickled in step a) in the high temperature washing tank for 10 minutes, and use 40KHz ultrasonic wave and Bubble-assisted cleaning;

c) adding ozone water to the normal temperature water washing tank and keeping the volume of the ozone water at 230L, soaking and cleaning the quartz device after step b) in the normal temperature washing tank for 10 minutes at normal temperature, and using bubbling to assist cleaning;

d) repeating step c) once to the pH value of the normal temperature water washing tank is 7, and the water washing is completed;

e) After washing with water, take out the quartz device, and use nitrogen to dry the taken out quartz device to complete the quartz device cleaning process.

Wherein, the ozone content in the ozone water in the above process is 10ppm.

Example 2

A method for cleaning a quartz device for solar cell preparation, comprising the following steps:

a) Add 20L of hydrofluoric acid and 200L of ozone water into the cleaning tank and heat it to 90°C, put the quartz device into the cleaning tank, seal it, soak it in pickling for 30 minutes, and use 40KHz ultrasonic wave and drum Foam-assisted pickling;

b) Add ozone water to the high temperature washing tank and keep the volume of the ozone water at 250L, heat it to 90°C, soak and clean the quartz device soaked and pickled in step a) in the high temperature washing tank for 30 minutes, and use 40KHz ultrasonic wave and Bubble-assisted cleaning;

c) adding ozone water to the normal temperature water washing tank and keeping the volume of the ozone water at 250L, soaking and cleaning the quartz device after step b) in the normal temperature washing tank for 30 minutes at normal temperature, and using bubbling to assist cleaning;

d) repeating step c) once to the pH value of the normal temperature water washing tank is 7, and the water washing is completed;

e) After the water washing is completed, the quartz device is taken out, and the taken out quartz device is dried with compressed air to complete the quartz device cleaning process.

Wherein, the ozone content in the ozone water in the above process is 30ppm.

Example 3

A method for cleaning a quartz device for solar cell preparation, comprising the following steps:

a) Add 20L of hydrofluoric acid and 160L of ozone water into the cleaning tank and heat it to 70°C, put the quartz device into the cleaning tank, seal, soak and pickle for 40 minutes, and use 40KHz ultrasonic wave and drum Foam-assisted pickling;

b) Add ozone water to the high temperature washing tank and keep the volume of the ozone water at 200L, heat it to 80°C, soak and clean the quartz device soaked and pickled in step a) in the high temperature washing tank for 15 minutes, and use 40KHz ultrasonic wave and Bubble-assisted cleaning;

c) adding ozone water to the normal temperature water washing tank and keeping the volume of the ozone water at 200L, soaking and cleaning the quartz device after step b) in the normal temperature water washing tank for 15 minutes at normal temperature, and using bubbling to assist cleaning;

d) repeating step c) once to the pH value of the normal temperature water washing tank is 7, and the water washing is completed;

e) After washing with water, take out the quartz device, and use nitrogen to dry the taken out quartz device to complete the quartz device cleaning process.

Wherein, the ozone content in the ozone water in the above process is 20ppm.

Example 4

A method for cleaning a quartz device for solar cell preparation, comprising the following steps:

a) Add 16L of hydrofluoric acid and 160L of ozone water into the cleaning tank and heat it to 80°C, put the quartz device into the cleaning tank, seal it, soak it in pickling for 40 minutes, and use 40KHz ultrasonic wave and drum Foam-assisted pickling;

b) Add ozone water to the high temperature washing tank and keep the volume of the ozone water at 200L, heat it to 80°C, soak and clean the quartz device soaked and pickled in step a) in the high temperature washing tank for 15 minutes, and use 40KHz ultrasonic wave and Bubble-assisted cleaning;

c) adding ozone water to the normal temperature water washing tank and keeping the volume of the ozone water at 200L, soaking and cleaning the quartz device after step b) in the normal temperature water washing tank for 15 minutes at normal temperature, and using bubbling to assist cleaning;

d) repeating step c) once to the pH value of the normal temperature water washing tank is 7, and the water washing is completed;

e) After the water washing is completed, the quartz device is taken out, and the taken out quartz device is dried with compressed air to complete the quartz device cleaning process.

Wherein, the ozone content in the ozone water in the above process is 20ppm.

Example 5

A method for cleaning a quartz device for solar cell preparation, comprising the following steps:

a) Add 12L of hydrofluoric acid and 160L of ozone water into the cleaning tank and heat it to 90°C, put the quartz device into the cleaning tank, seal, soak and pickle for 40 minutes, and use 40KHz ultrasonic wave and drum Foam-assisted pickling;

b) Add ozone water to the high temperature washing tank and keep the volume of the ozone water at 200L, heat it to 80°C, soak and clean the quartz device soaked and pickled in step a) in the high temperature washing tank for 15 minutes, and use 40KHz ultrasonic wave and Bubble-assisted cleaning;

c) adding ozone water to the normal temperature water washing tank and keeping the volume of the ozone water at 200L, soaking and cleaning the quartz device after step b) in the normal temperature water washing tank for 15 minutes at normal temperature, and using bubbling to assist cleaning;

d) repeating step c) once to the pH value of the normal temperature water washing tank is 7, and the water washing is completed;

e) After washing with water, take out the quartz device, and use nitrogen to dry the taken out quartz device to complete the quartz device cleaning process.

Wherein, the ozone content in the ozone water in the above process is 20ppm.

Comparative ratio

1) Add the mixed medicinal solution of 32 liters of hydrofluoric acid, 16 liters of hydrochloric acid, and 160 liters of water in the cleaning tank, soak the quartz device at room temperature for 90 minutes, and use a frequency of 40KHz ultrasonic waves and bubbling assistance. Cleaning, the cleaning tank is open;

2) Take out the pickled quartz device and put it in the water washing tank 1 to use overflow mode, use 500 liters of pure water, the cleaning time is 40min, and the frequency is 40KHz ultrasonic wave, and bubbling auxiliary cleaning;

3) Put the quartz device in the water washing tank 2 and use the overflow mode, use 500 liters of pure water, the cleaning time is 40min, and the frequency is 40KHz ultrasonic wave, and bubbling auxiliary cleaning;

4) Put the quartz device in the water washing tank 3 and use the overflow mode, use 500 liters of pure water, the cleaning time is 40min, and the frequency is 40KHz ultrasonic wave, and bubbling auxiliary cleaning;

5) Use pH test paper to test the water tank until it is neutral, and use this as the judgment standard;

6) After the water washing is completed, take out the quartz boat and use nitrogen or compressed air to blow it to dry to complete the quartz boat cleaning process.

Cleaning efficiency and effect test:

Select six groups of quartz boats that need to be cleaned, respectively use the methods in the above-mentioned embodiments 1 to 5 and the comparative example to clean, and record the data such as how much hydrofluoric acid and ozone water are consumed in total; then select P-type 156.75 × 156.75 monocrystalline silicon The 6,000 pieces are divided into 6 groups by the conventional alkali texturing process after the suede is made, and then the quartz boats cleaned in the above manner are used for diffusion treatment, and data such as efficiency and pollution are tracked.

Test Results:

The consumption chemicals of Examples 1 to 5 and the comparative example are as follows in Table 1:

Table 1

Use the quartz boats obtained after cleaning in Examples 1 to 5 and the comparative example to make 6 groups of chips after texturing respectively. The data such as card groove printing, number of black spots, efficiency and pollution are as follows in Table 2:

Table 2

It can be seen from the comprehensive comparative example and the comparative group:

1. Using the new method of cleaning quartz devices to clean the quartz boat consumes significantly less chemicals than the original method of cleaning quartz devices;

2. The time to clean the quartz boat using the new method of cleaning quartz devices is obviously at least 90 minutes shorter than that of the original method of cleaning quartz devices;

3. Using the new method of cleaning quartz devices to clean the quartz boat for diffusion is obviously 0.2 to 0.3% less polluted than the original method of cleaning quartz devices to clean the quartz boat for diffusion;

4. Using the new method of cleaning quartz devices to clean the quartz boat for diffusion is obviously 0.3-0.7% less than the original method of cleaning the quartz boat for diffusion card groove printing;

5. The diffusion efficiency of cleaning the quartz boat using the new method of cleaning quartz devices is obviously 0.02%-0.03% higher than that of the original method of cleaning quartz devices.

It should be understood that for those skilled in the art, improvements or changes can be made according to the above description, and all these improvements and changes should fall within the protection scope of the appended claims of the present invention.

Claims (10)

1. A method for cleaning a quartz device for solar cell preparation is characterized by comprising the following steps:

a) adding mixed liquid medicine of hydrofluoric acid and ozone water into the cleaning tank, heating, and placing the quartz device into the cleaning tank for sealing, soaking and pickling;

b) adding ozone water into a high-temperature rinsing bath, heating, and soaking and cleaning the quartz device soaked and pickled in the step a) in the high-temperature rinsing bath;

c) adding ozone water into the normal-temperature water washing tank, and soaking and washing the quartz device soaked and washed in the step b) in the normal-temperature water washing tank at normal temperature;

d) repeating the step c) until the pH value of the normal-temperature rinsing bath is neutral, and finishing rinsing;

e) and taking out the quartz device after the water washing is finished, and drying to finish the cleaning process of the quartz device.

2. The method for cleaning a quartz device for solar cell production according to claim 1, characterized in that:

the ozone content in the ozone water is 10-30 ppm.

3. The method for cleaning a quartz device for solar cell production according to claim 1 or 2, characterized in that:

in the mixed liquid medicine of hydrofluoric acid and ozone water, the volume ratio of hydrofluoric acid to ozone water is (1-2): (15-20).

4. The method for cleaning a quartz device for solar cell production according to claim 1, characterized in that:

in the step a), the temperature is controlled to be 60-90 ℃ during soaking and pickling, and 40KHz ultrasonic waves and bubbling are used for assisting pickling.

5. The method for cleaning a quartz device for solar cell production according to claim 1, characterized in that:

in the step a), the soaking and pickling time is 15-40 minutes.

6. The method for cleaning a quartz device for solar cell production according to claim 1, characterized in that:

in the step b), the temperature is controlled to be 60-90 ℃ during soaking and cleaning, and 40KHz ultrasonic waves and bubbling are used for assisting cleaning.

7. The method for cleaning a quartz device for solar cell production according to claim 1, characterized in that:

in the step b), the volume of the ozone water is kept to be 200-250L, and the soaking and cleaning time is 10-30 minutes.

8. The method for cleaning a quartz device for solar cell production according to claim 1, characterized in that:

in the step c), bubbling is used for assisting in cleaning during soaking.

9. The method for cleaning a quartz device for solar cell production according to claim 1, characterized in that:

in the step c), the volume of the ozone water is kept to be 200-250L, and the soaking and cleaning time is 10-30 minutes.

10. The method for cleaning a quartz device for solar cell production according to claim 1, characterized in that:

in the step e), the taken quartz device is dried by adopting nitrogen or compressed air.