CN103618026B - A kind of polysilicon micro-nano processing unit (plant) and method of gridding - Google Patents

Abstract

The invention discloses a gridded polycrystalline silicon micro-nano processing device and method. At present, the effect of preparing anti-reflection layer of polycrystalline silicon solar cells is not good. In the present invention, the output end of the ultrasonic generator controller is threadedly connected with the tail of the horn through the transducer, and the head of the horn is threaded with the tail of the plane ultrasonic tool head; the head of each plane ultrasonic tool head is Extending into the reaction observation chamber; the inner wall of the reaction observation chamber opposite to each planar ultrasonic tool head is respectively fixed with a sound wave reflection plate; the reaction container is arranged in the reaction observation chamber. The steps of the polysilicon micro-nano processing method of the present invention are as follows: inject the mixed acid solution into the reaction container, drive the planar ultrasonic tool head to form an ultrasonic standing wave, put the polysilicon material into the reaction container for preparation, and place it in a deionized solution for cleaning after preparation , encapsulation. The invention can improve the anti-reflection effect on the polysilicon surface, thereby improving the photoelectric conversion efficiency of the polysilicon photovoltaic cell.

Description

A gridded polysilicon micro-nano processing device and method

technical field

The invention belongs to the field of new solar energy and relates to the processing and production of polycrystalline silicon photovoltaic panels, in particular to a gridded polycrystalline silicon micro-nano processing device and method.

Background technique

New energy has become one of the important fields of research in the 21st century, and the application and popularization of solar energy has been highly valued by people. The energy of the sun is very rich. The energy irradiated on the earth every second is equivalent to 5 million tons of standard coal. If converted into electrical energy, it is about 3.8×10 ¹⁹ MW. Solar energy does not contain harmful substances and does not emit carbon dioxide. It has great development prospects , is an effective way for mankind to solve the current energy crisis. Until the 1990s, solar photovoltaic materials were mainly monocrystalline silicon. In the 1980s, the application of polycrystalline silicon grew rapidly due to its advantages of relatively low cost and high efficiency, and it continued to squeeze out the market for monocrystalline silicon. main solar cell material. Polycrystalline silicon solar cells are relatively mature and relatively low-cost solar cell technology at present. Due to the diversity of polycrystalline silicon grain orientations, traditional monocrystalline silicon textured surface preparation techniques cannot be used. How to prepare polycrystalline silicon solar cells for anti-reflection cheaply and reliably? Layer is one of the key technologies for the industrialization of polycrystalline silicon solar cells.

At present, the production technologies for producing polysilicon surfaces mainly include the following types:

1. Laser grooving: The method of laser grooving can be used to make an inverted pyramid structure on the surface of polysilicon. In the spectral range of 500-900nm, the reflectivity is 4-6%, which is equivalent to the double-layer anti-reflection coating on the surface. And the reflectance of the (100) surface monocrystalline silicon chemically made suede is 11%. The short-circuit current of the battery made of laser-made suede is about 4% higher than that of the smooth surface coated with double anti-reflection coatings (ZnS/MgF ₂ ), which is mainly because long-wave light (wavelength greater than 800nm) obliquely enters the battery. The problem of laser suede production is that the surface is damaged and some impurities are introduced during etching, and the surface damage layer must be removed by chemical treatment. The solar cell made by this method usually has a high short-circuit current, but the open-circuit voltage is not too high, mainly because the surface area of the cell increases, which causes the recombination current to increase.

2. Chemical grooving: use a mask (Si ₃ N ₄ or SiO ₂ ) for isotropic etching. The etching solution can be acidic etching solution or sodium hydroxide or potassium hydroxide solution with high concentration. This method cannot Formation of the kind of pointed cone-like structure formed by anisotropic etching. According to reports, the suede formed by this method has obvious anti-reflection effect on the spectral range of 700-1030 microns. However, the mask layer is generally formed at a higher temperature, which causes the performance of polycrystalline silicon materials to decline, especially for polycrystalline materials with lower quality, the minority carrier lifetime is shortened. The conversion efficiency of cells made on 225cm ² polysilicon by using this process reaches 16.4%. The mask layer can also be formed by screen printing.

3. Reactive ion etching (RIE): This method is a maskless etching process, and the reflectance of the formed suede surface is particularly low, and the reflectance in the spectral range of 450-1000 microns can be less than 2%. From an optical point of view, it is an ideal method, but the problem is that the silicon surface is seriously damaged, the open circuit voltage and fill factor of the battery decrease, and the process is complicated.

4. Making anti-reflection film layer: For high-efficiency solar cells, the most common and effective method is to evaporate ZnS/MgF ₂ double-layer anti-reflection film. The optimal thickness depends on the thickness of the underlying oxide layer and the characteristics of the battery surface. For example, whether the surface is smooth or suede, the anti-reflection process also includes evaporation Ta ₂ O ₅ , PECVD deposition Si ₃ N ₃ and so on. ZnO conductive film can also be used as anti-reflection material. However, this kind of technical process is complicated, and when it is applied to industrial production, the cost is very high, which is not conducive to widespread application.

Contents of the invention

The purpose of the present invention is to address the deficiencies of the prior art, and to provide a gridded polysilicon micro-nano processing method, which uses the joint action of ultrasound and acid etching solution to process the polysilicon surface, optimizes the microstructure of the polysilicon surface, and improves the polysilicon surface. Surface anti-reflection effect, thereby improving the photoelectric conversion efficiency of polycrystalline silicon photovoltaic cells. Another object of the present invention is to provide an apparatus for use in the method.

The polysilicon micro-nano processing device of the present invention includes a control device, a planar supergene generation device and a reaction device.

The control device includes a plurality of ultrasonic generator controllers and cameras, and the input end of each ultrasonic generator controller and the camera are connected to a computer. The camera's camera is directed towards the reaction device.

Described planar ultrasonic generation device comprises transducer, horn, planar ultrasonic tool head; The output end of each ultrasonic generator controller is connected with the afterbody of a transducer, and the head of each transducer is connected with a The tails of the horns are threaded, and the head of each horn is threaded with the tail of a planar ultrasonic tool head.

The reaction device includes a reaction observation chamber, a sound wave reflection plate and a reaction container; the reaction observation chamber is a transparent airtight container, and the head of each plane ultrasonic tool head is stretched into the reaction observation chamber; the reaction observation chamber is connected to each A sound wave reflection plate is fixedly arranged on the opposite inner wall of the two planar ultrasonic tool heads. The reaction container is arranged in the reaction observation chamber, and is arranged between the planar ultrasonic tool head and the sound wave reflection plate.

The distance between the sound wave reflecting plate and the plane ultrasonic tool head is Among them, n is the number of planar ultrasonic tool heads, and the value is 2 to 4, and λ is the wavelength of ultrasonic in liquid; Wherein, v is the velocity of ultrasound in the liquid, f is the frequency of ultrasound used, the range of values is 40KHz-1MHz, and the power of ultrasound is 500-1000W.

The head of the planar ultrasonic tool head is square column.

The micro-nano processing method of polysilicon of the present invention, the steps are as follows:

Step 1. Mix the analytically pure hydrofluoric acid solution, the analytically pure nitric acid solution and deionized water into a mixed acid solution, and the volume ratio of the analytically pure hydrofluoric acid solution to the analytically pure nitric acid solution in the mixed acid solution is 0.1-0.9:1, The volume ratio of analytically pure hydrofluoric acid solution to deionized water is 0.1-0.4:1, and the mixed acid solution is injected into the reaction vessel.

Step 2. The planar ultrasonic tool head is driven by a computer program to form an ultrasonic standing wave in the mixed acid solution. After the liquid level of the mixed acid solution is calm and a stable ultrasonic standing wave grid is formed, the cleaned and pretreated polysilicon material is placed Put it into a reaction container for preparation, and the time is 1 to 10 minutes.

Step 3. Cleaning the silicon chip prepared in step 2 in a deionized solution for 1 to 2 minutes to remove acid residue on the surface of the silicon chip.

Step 4. The cleaned and processed silicon wafers are packaged to complete the production of silicon wafers.

Beneficial effects of the present invention:

1. The head of the plane ultrasonic tool head in the present invention is a square column, which can form a regular standing wave grid;

2. The present invention uses ultrasound to control irregularly moving ions to corrode the silicon surface to form a relatively uniform structure, optimize the microstructure of the polysilicon surface, improve the anti-reflection effect of the polysilicon surface, and thereby improve the photoelectric conversion efficiency of polysilicon photovoltaic cells;

3. The existence of ultrasonic waves intensifies the movement of ions in the solution, making the reaction proceed more quickly;

4. Compared with laser etching, the cost of ultrasonic device is lower.

Description of drawings

Fig. 1 is a schematic diagram of the system structure of the present invention;

Fig. 2-1 is the front view of the plane ultrasonic tool head in the present invention;

Figure 2-2 is a top view of Figure 2-1;

Fig. 3 is a reaction mechanism diagram of the present invention;

Fig. 4 is the microstructure of the polysilicon textured surface observed under the electron microscope at the scale of 10 microns after the ultrasonic test;

Fig. 5 adopts the method of the present invention to carry out the microstructure of the polysilicon textured surface observed under the 10 micron scale after the orthogonal ultrasonic test;

Fig. 6 is the microstructure of the polysilicon textured surface observed under the electron microscope at the scale of 50 micrometers after the orthogonal ultrasonic test is carried out by the method of the present invention.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

As shown in Figure 1, a gridded polysilicon micro-nano processing device includes a control device, a planar supersonic generation device and a reaction device.

The control device includes an ultrasonic generator controller 1 and a camera 2 , and the input ends of the two ultrasonic generator controllers 1 and the camera 2 are connected to a computer 3 . The camera head of camera 2 faces the reaction device.

As shown in Figures 1, 2-1 and 2-2, the planar ultrasonic generating device includes a transducer 4, a horn 5, and a planar ultrasonic tool head 6; the output end of each ultrasonic generator controller 1 is connected to a transducer The tail of the transducer 4 is connected, the head of each transducer 4 is threaded with the tail of a horn 5, and the head of each horn 5 is threaded with the tail of a planar ultrasonic tool head 6.

The reaction device comprises a reaction observation chamber 7, a sound wave reflection plate 8 and a reaction container 9; the reaction observation chamber 7 is a transparent airtight container, and the heads of the two plane ultrasonic tool heads 6 all extend into the reaction observation chamber 7, and the two planes The ultrasonic tool head 6 is vertically arranged along the horizontal direction, and the head of the planar ultrasonic tool head 6 is a square column; the inner wall of the reaction observation room 7 opposite to each planar ultrasonic tool head 6 is respectively fixed with a sound wave reflection plate 8 . The reaction container 9 is arranged in the reaction observation chamber 7 and is arranged between the planar ultrasonic tool head 6 and the sound wave reflection plate 8 .

The number n=2 of the planar ultrasonic tool heads, the velocity v of the ultrasonic wave in the liquid is 1500m/s, the computer program controls the planar ultrasonic tool head 6 to generate ultrasonic waves, the ultrasonic frequency f is 40KHz, and the power is 750W; It can be calculated that the distance between the sound wave reflection plate 8 and the corresponding planar ultrasonic tool head 6 is 37.5 mm.

The steps of a gridded polysilicon micro-nano processing method are as follows:

Step 1. Prepare analytically pure hydrofluoric acid solution, analytically pure nitric acid solution and deionized water in proportion to form a mixed acid solution and inject it into the reaction vessel 5 .

The mixed acid solution can be prepared in any of the following ways:

(1) Mix 0.1L analytical pure hydrofluoric acid solution, 1L analytical pure nitric acid solution and 1L deionized water;

(2) Mix 0.9L analytical pure hydrofluoric acid solution, 1L analytical pure nitric acid solution and 2.25L deionized water;

(3) 0.5L of analytically pure hydrofluoric acid solution, 1L of analytically pure nitric acid solution and 2.5L of deionized water.

Step 2. The planar ultrasonic tool head 6 is driven by a computer program to form ultrasonic standing waves in the mixed acid solution. After the liquid level of the mixed acid solution is calm and a stable orthogonal ultrasonic standing wave grid is formed, the cleaned and pretreated The polysilicon material is put into the reaction vessel 9 for preparation, and the preparation time is 4 minutes.

Step 3. Place the silicon chip prepared in step 2 into a deionized solution and clean it for 2 minutes to remove the acid residue on the surface of the silicon chip.

Step 4. The cleaned and processed silicon wafers are packaged to complete the production of silicon wafers.

The specific working process of the gridded polysilicon micro-nano processing device is as follows:

Turn on the computer 3, inject an appropriate amount of mixed acid into the reaction container 9, then turn on the ultrasonic generator controller 1, and adjust the computer program so that the two planar ultrasonic tool heads 6 emit ultrasonic waves, and the ultrasonic waves emitted by each planar ultrasonic tool head 6 are consistent with the Corresponding to the superimposition of the ultrasound reflected by the sound wave reflecting plate 8, thereby forming two sets of standing waves perpendicular to each other, and when a stable standing wave grid is formed on the liquid surface of the mixed acid solution, a silicon chip of an appropriate size is placed in the mixed acid solution During the reaction, the intensity of the reaction can be observed through the camera 2, and then the time for the reaction to be completely completed can be controlled.

The reaction observation chamber 9 is an airtight container to avoid the interference of the sound waves and air flow in the air to the test.

As shown in Figure 3, the reaction mechanism of the gridded polysilicon micro-nano processing method is as follows:

When fabricating the suede structure on the surface of polysilicon by acid etching, it is mainly the participation of fluoride ions, which belong to nanoparticles. Usually, fluoride ions collide randomly in water and move freely. Ultrasound is a high-frequency longitudinal mechanical wave. The effect of mechanical waves on nanoparticles and micron ion bubbles can be described by Newton’s second law: F _A is the force on ions in solution in a two-dimensional orthogonal ultrasonic field, and v is the force on ions in ultrasonic waves. The speed of the field, the arrow indicates the direction of the speed, and the orthogonal standing wave field is generated by two sets of orthogonal planar ultrasonic generating devices. The fluorine ion will be partially controlled by the sound field distribution form and the chemical action environment under the action of the standing wave of the sound field, so that Change the micro-etching processing position of fluorine ions to complete the texture structure on the polysilicon surface.

Figures 4, 5 and 6 are comparisons of test results:

Figure 4 shows that the silicon wafer has passed through 4 minutes of no ultrasonic test when the volume ratio of analytical pure hydrofluoric acid solution (HF): analytical pure nitric acid solution (HNO3): deionized water (H2O) is 2:15:5, and the electron microscope The textured microstructure of polysilicon observed at the scale of 10 microns.

Figure 5 shows the 4-minute orthogonal ultrasonic test of silicon wafers when the volume ratio of analytical pure hydrofluoric acid solution (HF): analytical pure nitric acid solution (HNO ₃ ): deionized water (H ₂ O) is 2:15:5 , and the polysilicon textured microstructure observed at the scale of 10 microns under the electron microscope.

Figure 6 shows the 4-minute orthogonal ultrasonic test of silicon wafers when the volume ratio of analytically pure hydrofluoric acid solution (HF): analytically pure nitric acid solution (HNO ₃ ): deionized water (H ₂ O) is 2:15:5 , and the polysilicon textured microstructure observed at the scale of 50 microns under the electron microscope.

It can be seen that the orthogonal ultrasonic test using the gridded polysilicon micro-nano processing method can form a relatively uniform microstructure on the silicon surface, which can improve the anti-reflection effect of the polysilicon surface, thereby improving the photoelectric conversion efficiency of polysilicon photovoltaic cells.

In step 2 of the method, the preparation time of putting the cleaned and pretreated polysilicon material into the reaction vessel can be selected within the range of 1 to 10 minutes; You can choose within the range of ~2 minutes.

Claims (3)

1. A gridded polysilicon micro-nano processing device, comprising a control device, a planar ultrasonic generating device and a reaction device, characterized in that: The control device includes a plurality of ultrasonic generator controllers and cameras, and the input end and the camera of each ultrasonic generator controller are connected to the computer; the camera head of the video camera faces the reaction device; Described planar ultrasonic generating device comprises transducer, horn, planar ultrasonic tool head; The output end of each ultrasonic generator controller is connected with the afterbody of a transducer, and the head of each transducer is connected with a The tail of the horn is threaded, and the head of each horn is threaded with the tail of a planar ultrasonic tool head; The reaction device includes a reaction observation chamber, a sound wave reflection plate and a reaction container; the reaction observation chamber is a transparent airtight container, and the head of each plane ultrasonic tool head is stretched into the reaction observation chamber; the reaction observation chamber is connected to each A sound wave reflection plate is fixedly arranged on the opposite inner wall of the two planar ultrasonic tool heads; the reaction container is arranged in the reaction observation room, and is arranged between the planar ultrasonic tool head and the sound wave reflector; The distance between the sound wave reflecting plate and the plane ultrasonic tool head is Among them, n is the number of planar ultrasonic tool heads, and the value is 2 to 4, and λ is the wavelength of ultrasonic in liquid; Wherein, v is the velocity of ultrasound in the liquid, f is the frequency of ultrasound used, the range of values is 40KHz-1MHz, and the power of ultrasound is 500-1000W. 2 . The gridded polysilicon micro-nano machining device according to claim 1 , wherein the head of the planar ultrasonic tool head is in the shape of a square column. 3 . 3. A micro-nano-processing method adopting the micro-nano-processing device according to claim 1 to form gridded polysilicon, characterized in that: the steps of the method are as follows: Step 1. Mix analytical pure hydrofluoric acid solution, analytical pure nitric acid solution and deionized water into a mixed acid solution, the volume ratio of analytical pure hydrofluoric acid solution to analytical pure nitric acid solution in the mixed acid solution is 0.1-0.9:1, The volume ratio of analytically pure hydrofluoric acid solution to deionized water is 0.1-0.4:1, and the mixed acid solution is injected into the reaction vessel; Step 2. Two planar ultrasonic tool heads are driven by a computer program to emit ultrasonic waves, and the ultrasonic waves emitted by each planar ultrasonic tool head are superimposed with the ultrasonic waves reflected by the corresponding sound wave reflector, thus forming two sets of ultrasonic stations perpendicular to each other in the mixed acid solution. Wave, after the liquid level of the mixed acid solution is calm to form a stable ultrasonic standing wave grid, put the cleaned and pretreated polysilicon material into the reaction container for preparation, and the time is 1 to 10 minutes; Step 3. Washing the polysilicon material prepared in step 2 in a deionized solution for 1 to 2 minutes to remove the acid residue on the surface of the polysilicon material; Step 4. Packaging the cleaned and processed polysilicon material to complete the production of the polysilicon material.