CN107794569B - A kind of method and device thereof of polysilicon chip straight forming - Google Patents

Abstract

The invention relates to a method and a device for direct molding of a polycrystalline silicon wafer. The method specifically includes: using a crucible with controllable internal pressure, casting and pressing the molten silicon liquid into a specific mold cavity; the temperature of the directional solidified block is lower than the melting point of silicon; the supercooling of the silicon liquid in the directional solidified block Driven by high speed, it starts directional solidification from top to bottom and adsorbs on the formation surface of the directional solidification block; the formation surface has a fine suede structure, controllable nucleation, and the grown grain size is small and uniform; after solidification, take out Oriented solidified block with adsorbed silicon chips; adjust the pressure and temperature in the cavity of the directional solidified block to release the taken out silicon chips. The invention adopts the formation surface with fine textured structure to grow silicon wafers, replaces the complex wet texturing process, reduces the traditional process of manufacturing silicon wafers, improves the utilization rate of silicon materials, and effectively reduces the manufacturing cost of solar cells .

Description

A method and device for direct molding of polycrystalline silicon wafers

technical field

The invention relates to a method for direct molding of polycrystalline silicon wafers, specifically, silicon melt is directly exported from a crucible into a specific mold cavity and crystallized into silicon wafers on a directional solidified block forming surface with a textured structure.

Background technique

Polycrystalline silicon wafer is an important part of manufacturing solar cells, and its quality directly affects the photoelectric conversion efficiency of solar cells. The manufacturing cost of polycrystalline silicon wafers restricts the development of the photovoltaic industry, so improving the quality of polycrystalline silicon wafers and reducing their manufacturing costs are the only way to develop solar energy.

The traditional device for manufacturing directional solidified polysilicon is shown in Figure 4. In the figure, 1. Stainless steel shell, 2. Heat insulation cage, 3. Heater, 4. Argon gas, 5. Melt silicon, 6. Crystalline silicon, 7. Quartz crucible, 8. graphite tray, 9. directional solidified block, 10. bracket. The device adopts directional solidification from bottom to top. The method is to melt the polysilicon material in the crucible first, cool down through the bottom of the crucible, and directional solidify to form a polysilicon ingot, and use a diamond wire or a mortar wire to cut the polysilicon ingot to form a polysilicon wafer, and then clean the texture. The process forms the polycrystalline silicon wafers needed to make solar cells. First of all, because the bottom and side of the melt are in contact with the crucible during the solidification process, solidification occurs from the bottom of the side, and secondly, there is no induction at the beginning of solidification, and the grain orientation is different at the beginning of solidification. Eventually lead to the existence of inconsistent grain orientation. The crystal grain size of the silicon wafer obtained by the method is relatively large and uneven, and the crystal orientation is inconsistent. And there are a lot of waste and environmental pollution problems of crucible and silicon material in its manufacturing process. For example, the quartz crucible used in the growth process of each polysilicon ingot can only be used once, and a lot of silicon material, diamond wire or mortar wire will be wasted during the cutting process of the silicon ingot.

In modern technology, there are reports on the technology of directly growing silicon wafers. The method of growing silicon wafers is to use a specific crucible and an adsorption solidification device to directly grow silicon wafers from a silicon solution, and through the inhibition of nucleation and limitation of the adsorption solidification device The nature of heat flow grows silicon wafers with large grain sizes. Although this technology reduces the waste of materials to a certain extent, due to its simple structure, it cannot guarantee the control of temperature and pressure. The silicon wafers produced have a large grain size, many internal dislocations, and low photoelectric conversion efficiency. , and the silicon wafer growth thickness is not easy to control during the silicon wafer growth process.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art and provide a method for direct molding of polycrystalline silicon wafers. The method specifically includes: using a crucible with controllable internal pressure, casting and pressing the molten silicon liquid into a specific mold cavity; the temperature of the directional solidified block is lower than the melting point of silicon; the supercooling of the silicon liquid in the directional solidified block Driven by high speed, it starts directional solidification from top to bottom and adsorbs on the formation surface of the directional solidification block; the formation surface has a fine suede structure, controllable nucleation, and the grown grain size is small and uniform; after solidification, take out Oriented solidified block with adsorbed silicon slices; adjust the pressure and temperature in the cavity of the oriented solidified block to release the taken out silicon slices. The invention adopts the formation surface with fine textured structure to grow silicon wafers, replaces the complex wet texturing process, reduces the traditional process of manufacturing silicon wafers, improves the utilization rate of silicon materials, and effectively reduces the manufacturing cost of solar cells .

The technical solution adopted by the present invention to solve the technical problem is:

A method for direct molding of polycrystalline silicon wafers, comprising the steps of:

The first step, the addition of raw materials

Adding the polysilicon raw material into the crucible of the polysilicon sheet direct forming device;

The second step, the melting of raw materials

Vacuum the above crystal growth furnace to 1.33×10 ^-4 Pa～1.06×10 ^-4 Pa, start the heater to heat the crucible, and melt the silicon material in the crucible at 1785K～1835K, when the silicon material is completely melted, keep the temperature for 20min -30min; at the same time, set the temperature in the cavity of the directional solidified block to be 1685K～1690K, and the pressure to be 1.33×10 ^-4 Pa～5.33×10 ^-4 Pa;

The third step, the diversion of silicon liquid

Then pass argon gas into the crucible so that the air pressure in the crucible is 1.63×10 ⁵ Pa～1.83×10 ⁵ Pa, and the silicon solution in the crucible flows into the upper part of the mold cavity through the guide tube under capillary action and gas pressure. inside the box;

The fourth step, directional solidification

After the silicon liquid fills the holding box, the overflow hole on the top of the holding box has silicon liquid flowing out from the overflow port of the silicon liquid. At this time, the temperature and pressure in the upper directional solidified block cavity are lowered to make the temperature in the directional solidified block cavity 1073K～1290K , the pressure is 1.33×10 ^-4 Pa～1.06×10 ^-4 Pa, then the silicon liquid in the mold cavity is directional solidified from top to bottom;

The fifth step is to extract the directional solidified block

After 10-30 seconds after lowering to the set temperature and pressure, after the silicon liquid in the mold cavity is completely solidified, take out the directional solidified block adsorbed on the bottom of the polysilicon wafer;

Step 6, release and cut silicon wafer

Adjust the pressure in the cavity of the directional solidified block to 1.46×10 ⁷ Pa to 1.66×10 ⁷ Pa, and adjust the temperature to 1480K to 1500K. At this time, the silicon wafer is released under the action of the pressure in the cavity, and then the edge of the silicon wafer is cut with a laser Part, you can make a direct molding polysilicon wafer.

A polycrystalline silicon chip direct forming device, the device comprises a directional solidified block, a casting mold cavity, a thermal insulation screen, a heater, a crucible, a graphite support and a thermal insulation cage;

Among them, the mold cavity is directly below the directional solidified block; the lower half of the directional solidified block and the mold cavity are placed in the insulation screen together; the insulation screen is fixed on the top cover of the heat insulation cage; inside the heat insulation cage, The bottom plate of the heat insulation cage is a graphite support, and a crucible is placed on the graphite support; the top of the crucible is connected to the lower part of the top cover of the heat insulation cage, and a heater is arranged around it, and an argon hole is provided to the outside of the heat insulation cage;

The main body of the described directional solidified block is a hollow body, and the top of the hollow body is provided with a steel cover; the middle part of the outer wall of the hollow body is fixed with a limiting device; the bottom of the hollow body is a graphite layer, and the lower surface of the graphite layer is The forming surface, the material of the forming surface is sapphire material, the thickness is 3-4 μm, and there are pyramid-shaped protrusions with the same size and the top of the tower facing down, the pyramid height is 2-4 μm, the tower base is square, and the side length is 3-5 μm, the gap between the pyramid-shaped protrusions is 1-2 μm, and the coverage rate is 85-90%;

The composition of the mold cavity includes a storage box and a temperature regulator at its lower part; the structure of the storage box is a square funnel, and the inclination angle of the funnel is 10° to 15°; the top of the storage box is in the middle of the top of each side wall Each has an opening, and the front and rear symmetrical openings are the silicon liquid overflow ports after the silicon liquid is filled, and the left and right symmetrical openings are the silicon liquid inflow inlets, and each silicon liquid inflow inlet is equipped with a guide for transferring the silicon liquid Tube, the guide tube goes down, passes through the top cover of the heat insulation cage, and leads to the bottom of the crucible;

The height of the containing box in the cavity of the casting mold is 230 μm to 250 μm.

The porosity of the graphite layer is 1%-80%; the thickness of the graphite layer is 150mm-160mm.

Substantive features of the present invention are:

In the present invention, the directional solidification block is a top-down solidification device, and its forming surface has a fine textured structure, and silicon wafers are grown on the forming surface, which replaces the complicated wet texturing process, and reduces the slicing and texturing of traditional silicon wafers. process flow. Among them, the use of the mold cavity and directional solidified block is the key. The mold cavity and the forming surface have four characteristics, high purity, high temperature resistance, high melting point, and high strength. A graphite layer with specific pores at the bottom of the directional solidified block controls the forming surface pressure. During the contact between the forming surface of the directional solidified block and the silicon melt, the forming surface and the silicon material are not easy to react, the pressure of the forming surface is lower than the pressure on the surface of the silicon melt material, and when the temperature of the directional solidified block is controlled to be lower than the melting point, the silicon melt is adsorbed and solidified at Directional solidification blocks form on the face. When the formation surface of the directional solidification block is separated from the silicon wafer, the pressure on the formation surface should be controlled to be greater than the pressure on the surface of the silicon material, so that the formed silicon wafer can be easily and completely separated from the formation surface.

The beneficial effects of the present invention are:

The traditional method of manufacturing polysilicon wafers is to first melt the polysilicon material in the crucible, cool down the bottom of the crucible, and directional solidify to form a polysilicon ingot, then use a diamond wire or a mortar wire to cut the polysilicon ingot to form a polysilicon wafer, and then perform a cleaning process to form a solar energy. Polycrystalline silicon wafers required for batteries. The invention adopts a fine textured texture, replaces the complex wet textured process, and reduces the traditional technological processes of slicing and texturing for silicon wafers.

Compared with the prior art, the present invention has the advantages that the fine textured structure replaces the complex wet texturing process, reduces the traditional process flow for manufacturing silicon wafers, improves the utilization rate of silicon materials, and effectively reduces the cost of solar cells. manufacturing cost. Compared with the traditional process, the new process saves the long-term power control during the crystal growth process and the finished product's texturing, slicing and other processing processes, and the total power consumption is less than two-thirds of the traditional process; water consumption is only one-fourth First, the cost of making solar cells has been reduced by about 40%.

Description of drawings

FIG. 1 is a schematic diagram of the overall structure of a method for direct molding of polycrystalline silicon wafers according to the present invention.

Fig. 2 is a schematic diagram of the structure of a directional solidified block in a device used in a method for direct molding of a polycrystalline silicon wafer according to the present invention.

3 is a schematic diagram of a mold cavity in a device used in a method for direct molding of polycrystalline silicon wafers according to the present invention.

Fig. 4 is a structure of a polycrystalline silicon ingot furnace body in a device used in a method for direct molding of polycrystalline silicon wafers according to the present invention.

FIG. 5 is a structure diagram of the textured surface of the polycrystalline silicon wafer obtained in Example 1. FIG.

Detailed ways

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

Please refer to Fig. 1 to Fig. 3, it is a kind of structure schematic diagram of polysilicon wafer direct molding device (abbreviation crystal growth furnace), and the embodiment shown in Fig. , heater 7, crucible 8, graphite support 9 and heat insulation cage 10;

Wherein, directly below the directional solidification block 1 is the casting mold cavity 2; the lower half of the directional solidification block 1 and the casting mold cavity 2 are placed in the insulation screen 3 together; the insulation screen 3 is fixed on the top cover of the heat insulation cage 10 ; Inside the heat-insulating cage 10, the base plate of the heat-insulating cage 10 is a graphite support 9, and a crucible 8 is placed on the graphite support 9; , and is provided with the argon vent 5 to the outside of the heat insulation cage 10;

The main body of the directional solidification block 1 is a hollow body 12 made of steel, the horizontal section of the hollow body 12 is a square, and the top is provided with a steel cover 11 for feeding argon and vacuuming to control the internal pressure of the cavity The middle part of the outer wall of the cavity body 12 is fixed with a limiter 13 (i.e. a limit plate), and the limiter 13 is installed on the top of the insulation screen 3, and the limiter 13 in the process of taking out and putting into the directional solidified block is used A detachable device for fixing and directional solidified blocks; the bottom of the cavity body 12 is a graphite layer 14, and the lower surface of the graphite layer 14 is a forming surface 15, and the material of the forming surface 15 is sapphire material with a thickness of 3.5 μm. There are evenly distributed pyramid-shaped protrusions of the same material and size with the top of the tower downward. The height of the pyramid is 3 μm, the base of the tower is square, and the side length is 5 μm. The gap between the pyramid-shaped protrusions is 1-2 μm. The coverage rate is 85-90%.

The porosity of the graphite layer is 1%-80%; the thickness of the graphite layer is 150mm-160mm;

In order to make it easier to take out the silicon wafer, the composition of the mold cavity 2 includes a holding box and a temperature regulator 18 at its lower part; the structure of the holding box is a square funnel, and the inclination angle of the funnel is 10° to 15°; There is an opening in the middle of the top of the box and the top of each side wall. The front and rear symmetrical openings are the silicon liquid overflow ports 16 (height is 40 μm, and the width is 100 mm) after the silicon liquid is filled. The left and right symmetrical openings are the silicon liquid flow. Inlet 17 (height is 30 μm, width is 100mm), each silicon liquid inflow port 17 is all equipped with a guide pipe 4 for transferring silicon liquid, guide pipe 4 is downward, passes through the top cover of heat insulation cage 10 , pass into the bottom of the crucible 8;

The height of the housing box in the mold cavity 2 was 250 μm.

In the directional solidified block 1, the pressure in the cavity is adjusted from the top by the argon gas introduced, and there is a graphite layer 14 with a porosity of 1% to 80% at the bottom, and the pressure range is 1.33×10 ^-4 Pa～5.33×10 ^-4 Pa, argon gas can pass through the graphite layer, silicon liquid can not pass through the graphite layer, and a layer of sapphire material is installed on the lower surface of the graphite layer to form a pyramid-shaped convex structure at intervals Surface 15, the forming surface can withstand the high temperature environment of the silicon melt, and does not chemically react with the silicon melt. When the cavity of the directional solidified block is in a state of low temperature and low pressure (temperature 1273K, pressure 1.33×10 ^-4 Pa), since the thermal conductivity of graphite material is stronger than that of sapphire material, the silicon liquid will first be adsorbed on the surface of the graphite layer in the pyramid-shaped gap, Then carry out nucleation and growth, each pyramid gap is a nucleation center, the nucleation center is small and uniform, and finally the silicon liquid is directional solidified into a silicon wafer with a small and uniform grain size and a pyramid texture.

The crucible is a tungsten crucible.

The heat insulation cage is graphite carbon felt composite material.

The guide tube connecting the mold cavity and the crucible is made of a tungsten material guide tube surrounded by heat-insulating materials.

The cavity of the casting mold is made of tungsten material, its inner surface is very smooth, and the bottom is connected with a temperature control module.

A specific embodiment of a method for direct molding of a polycrystalline silicon wafer according to the present invention is given below. The specific embodiment is only used to describe the present invention in detail, and does not limit the protection scope of the claims of the present invention.

Example 1

A. Crystal growth furnace for direct molding of polycrystalline silicon wafers

The structure of the crystal growth furnace used for direct molding of polycrystalline silicon wafers is as above, mainly including graphite support, heat insulation cage, crucible, heater, draft tube, mold cavity, directional solidification block; heat insulation cage is made of graphite carbon felt and steel It is made of a hood, which has a good thermal insulation effect; the heater is wound on the outer surface of the crucible; the guide tube connects the crucible and the mold cavity, and its exterior is surrounded by thermal insulation materials; the side of the mold cavity has overflow holes, and the bottom There is a heater electrode to adjust the temperature; the directional solidification block is placed on the top of the mold cavity when the silicon wafer is solidified, and its side is equipped with a limit device, and the interior is filled with argon gas with adjustable pressure, and the bottom is made of porous graphite and sapphire materials;

Among them, the volume of the crucible is 0.2m ³ ; the height of the cavity is 32cm, and the length of the bottom side is 16cm; the height of the containing box is 250μm, and the bottom area is 15.6cm×15.6cm. The following examples are the same.

B. Operation steps

The first step, the addition of raw materials

Add 400kg polysilicon raw material into the tungsten crucible of the crystal growth furnace used for the direct molding of polycrystalline silicon wafers described in A, and then seal the furnace body (that is, use carbon felt to fill and seal the gap between the crucible and the graphite support, and at the same time turn off the guide Flow tube and argon hole, the following examples are the same);

The second step, the melting of raw materials

Vacuumize the crucible 8 of the above-mentioned crystal growth furnace to 1.33×10 ^-4 Pa, start the heater described in A to heat the special crucible in the crystal growth furnace, the heating power is 105KW, and the heating temperature reaches 1785K for continuous heating for 15 hours. Completely melt the silicon material in the special heating crucible in the first step, and then maintain it for 20 minutes; at the same time, set the temperature in the cavity of the directional solidified block to 1685K and the pressure to 1.33×10 ^-4 Pa.

The third step, the diversion of silicon liquid

When the silicon material is completely melted, pass argon gas into the crucible so that the pressure in the crucible is 1.63×10 ⁵ Pa, and the silicon solution in the crucible flows into the mold cavity of the upper casting mold platform through the guide tube under capillary action and gas pressure Inside;

The fourth step, directional solidification

After the silicon liquid fills the mold cavity, the silicon liquid flows out from the overflow hole on the top. At this time, the guide tube is closed to prevent the silicon liquid from continuing to flow in. Reduce the temperature and pressure in the cavity of the upper directional solidified block (the temperature in the cavity is reduced by the temperature adjustment effect of the insulation screen 3, and argon gas is introduced into the cavity to change the pressure in the cavity, so as to achieve the required conditions for crystal growth.) The temperature in the directional solidified block cavity is 1273K, the pressure is 1.33×10 ^-4 Pa, and the silicon liquid in the mold cavity is directional solidified from top to bottom;

The fifth step is to extract the directional solidified block

After lowering the temperature and reducing the pressure for 20 seconds, after the silicon liquid in the mold cavity has completely solidified, take out the directional solidified block on which the polysilicon wafer is adsorbed on the formed surface;

Step 6, release and cut silicon wafer

Adjust the pressure in the cavity of the directional solidified block to 1.66×10 ⁷ Pa, and adjust the temperature to 1480K. At this time, the silicon wafer is released under the action of the pressure and high temperature in the cavity, and then laser cutting is used to trim the edge of the silicon wafer. The surrounding burrs are then polished to produce a direct-molded polysilicon wafer. The obtained silicon wafer has a thickness of 200 μm to 210 μm.

The textured structure of the obtained polycrystalline silicon wafer is shown in Figure 5, and it can be seen from the figure that the textured rate is close to 90%, which is in line with the expected result. Since the sapphire material formation surface of the directional solidified block acts as a nucleation site during the crystal growth process, it plays a role in inducing nucleation, thereby forming uniform small-sized grains. It is well known that small-sized grains form more grain boundaries and fewer dislocations. Combined with the influence of dislocations and grain boundaries, the photoelectric conversion efficiency of solar cells manufactured by small-sized uniform columnar crystals is higher.

Example 2

A. Crystal growth furnace for direct molding of polycrystalline silicon wafers

The structure of the crystal growth furnace used for direct molding of polycrystalline silicon wafers mainly includes graphite brackets, heat insulation cages, crucibles, heaters, draft tubes, mold cavities, and directional solidified blocks; heat insulation cages are made of graphite carbon felt and steel covers. It has a good thermal insulation effect; the heater is wound on the outer surface of the crucible; the guide tube connects the crucible and the mold cavity, and its exterior is surrounded by thermal insulation materials; the side of the mold cavity has an overflow hole, and the bottom has a temperature adjustment Heater electrode; the directional solidification block is placed on the top of the mold cavity when the silicon wafer is solidified, and its side is equipped with a limit device, and the interior is filled with argon gas with adjustable pressure, and the bottom is made of porous graphite and sapphire materials;

B. Operation steps

The first step, the addition of raw materials

Add 400kg of polysilicon raw material into the tungsten crucible of the crystal growth furnace used for the direct molding of polysilicon wafers described in A, and then seal the furnace body;

The second step, the melting of raw materials

Vacuumize the crucible 8 of the above-mentioned crystal growth furnace to 1.33×10 ^-4 Pa, start the heater described in A to heat the special crucible in the crystal growth furnace, the heating power is 105KW, and the heating temperature reaches 1785K for continuous heating for 15 hours. Completely melt the silicon material in the special heating crucible in the first step, and then maintain it for 20 minutes; at the same time, set the temperature in the cavity of the directional solidified block to 1685K and the pressure to 1.33×10 ^-4 Pa.

The third step, the diversion of silicon liquid

When the silicon material is completely melted, pass argon gas into the crucible so that the pressure in the crucible is 1.63×10 ⁵ Pa, and the silicon solution in the crucible flows into the mold cavity of the upper casting mold platform through the guide tube under capillary action and gas pressure Inside;

The fourth step, directional solidification

After the silicon liquid fills the mold cavity, the silicon liquid flows out from the overflow hole on the top. At this time, the guide tube is closed to prevent the silicon liquid from continuing to flow in. Reduce the temperature and pressure in the cavity of the upper directional solidified block (the temperature in the cavity is reduced by the temperature adjustment effect of the insulation screen 3, and argon gas is introduced into the cavity to change the pressure in the cavity, so as to achieve the required conditions for crystal growth.) The temperature in the directional solidified block cavity is 1173K, the pressure is 1.06×10 ^-4 Pa, and the silicon liquid in the mold cavity is directional solidified from top to bottom;

The fifth step is to extract the directional solidified block

After lowering the temperature and reducing the pressure for 15 seconds, after the silicon liquid in the mold cavity has completely solidified, take out the directional solidified block on which the polysilicon wafer is adsorbed on the formed surface;

Step 6, release and cut silicon wafer

Adjust the pressure in the cavity of the directional solidified block to 1.66×10 ⁷ Pa, and adjust the temperature to 1480K. At this time, the silicon wafer is released under the action of the pressure and high temperature in the cavity, and then laser cutting is used to trim the edge of the silicon wafer. The surrounding burrs are then polished to produce a direct-molded polysilicon wafer. The obtained silicon wafer has a thickness of 200 μm to 210 μm.

The textured structure of the obtained polycrystalline silicon wafer is the same as in Example 1.

Example 3

A. Crystal growth furnace for direct molding of polycrystalline silicon wafers

The structure of the crystal growth furnace used for direct molding of polycrystalline silicon wafers mainly includes graphite brackets, heat insulation cages, crucibles, heaters, draft tubes, mold cavities, and directional solidified blocks; heat insulation cages are made of graphite carbon felt and steel covers. It has a good thermal insulation effect; the heater is wound on the outer surface of the crucible; the guide tube connects the crucible and the mold cavity, and its exterior is surrounded by thermal insulation materials; the side of the mold cavity has an overflow hole, and the bottom has a temperature adjustment Heater electrode; the directional solidification block is placed on the top of the mold cavity when the silicon wafer is solidified, and its side is equipped with a limit device, and the interior is filled with argon gas with adjustable pressure, and the bottom is made of porous graphite and sapphire materials;

B. Operation steps

The first step, the addition of raw materials

Add 400kg of polysilicon raw material into the tungsten crucible of the crystal growth furnace used for the direct molding of polysilicon wafers described in A, and then seal the furnace body;

The second step, the melting of raw materials

Vacuumize the crucible 8 of the above-mentioned crystal growth furnace to 1.33×10 ^-4 Pa, start the heater described in A to heat the special crucible in the crystal growth furnace, the heating power is 105KW, and the heating temperature reaches 1785K for continuous heating for 15 hours. Completely melt the silicon material in the special heating crucible in the first step, and then maintain it for 20 minutes; at the same time, set the temperature in the cavity of the directional solidified block to 1685K and the pressure to 1.33×10 ^-4 Pa.

The third step, the diversion of silicon liquid

When the silicon material is completely melted, pass argon gas into the crucible so that the pressure in the crucible is 1.63×10 ⁵ Pa, and the silicon solution in the crucible flows into the mold cavity of the upper casting mold platform through the guide tube under capillary action and gas pressure Inside;

The fourth step, directional solidification

After the silicon liquid fills the mold cavity, the silicon liquid flows out from the overflow hole on the top. At this time, the guide tube is closed to prevent the silicon liquid from continuing to flow in. Reduce the temperature and pressure in the cavity of the upper directional solidified block (the temperature in the cavity is reduced by the temperature adjustment effect of the insulation screen 3, and argon gas is introduced into the cavity to change the pressure in the cavity, so as to achieve the required conditions for crystal growth.) The temperature in the directional solidified block cavity is 1073K, the pressure is 1.33×10 ^-4 Pa, and the silicon liquid in the mold cavity is directional solidified from top to bottom;

The fifth step is to extract the directional solidified block

After lowering the temperature and reducing the pressure for 10 seconds, after the silicon liquid in the mold cavity has completely solidified, take out the directional solidified block on which the polysilicon wafer is adsorbed on the formed surface;

Step 6, release and cut silicon wafer

Adjust the pressure in the cavity of the directional solidified block to 1.66×10 ⁷ Pa, and adjust the temperature to 1480K. At this time, the silicon wafer is released under the action of the pressure and high temperature in the cavity, and then laser cutting is used to trim the edge of the silicon wafer. The surrounding burrs are then polished to produce a direct-molded polysilicon wafer. The obtained silicon wafer has a thickness of 200 μm to 210 μm.

The textured structure of the obtained polycrystalline silicon wafer is the same as in Example 1.

The specific embodiments described above have further described the technical solutions and implementation methods of the present invention in detail. The above examples are not only used in the present invention, and all equivalent modifications, equivalent replacements, and improvements are carried out within the spirit and principles of the present invention. etc. should be within the protection scope of the present invention.

Matters not covered in the present invention are known technologies.

Claims (4)

1. a kind of method of polysilicon chip straight forming, it is characterized in that this method comprises the following steps:

The first step, the addition of raw material

Polycrystalline silicon raw material is added in the crucible of the polysilicon chip straight forming device；

Second step, the fusing of raw material

Above-mentioned crystal growing furnace is evacuated to 1.33 × 10^-4Pa~1.06 × 10^-4Pa starts heater heating crucible, In 1785K-1835K, the silicon material in fusion crucible keep temperature 20min-30min after silicon material is melted completely；It is fixed to concurrently set The temperature intracavitary to coagulated mass is 1685K-1690K, and pressure is 1.33 × 10^-4Pa~5.33 × 10^-4Pa；

Third step, the water conservancy diversion of silicon liquid

Then lead to argon gas into crucible, make in crucible air pressure 1.63 × 10⁵Pa~1.83 × 10⁵Pa, the silicon solution in crucible exist It is flowed into the accommodating case of mold die cavity on top under capillarity and gas pressure by diversion pipe；

4th step, directional solidification

After silicon liquid fills up accommodating case, the overflow hole at the top of accommodating case has silicon liquid to flow out from silicon liquid overflow port, and it is fixed to reduce top at this time To the intracavitary temperature of coagulated mass and pressure, make oriented solidified blocks cavity temperature 1073K~1290K, pressure 1.33 × 10^-4Pa~ 1.06×10^-4Pa, the then directional solidification from top to bottom of the silicon liquid in die cavity；

5th step extracts oriented solidified blocks

After being reduced to the temperature and pressure of setting after 10~30 seconds, after the silicon liquid in die cavity solidifies completely, bottom absorption is taken out There are the oriented solidified blocks of polysilicon chip；

6th step, release and cutting silicon wafer

The intracavitary pressure of oriented solidified blocks is adjusted to 1.46 × 10⁷Pa~1.66 × 10⁷Pa, temperature are adjusted to 1480K~1500K, this When silicon wafer be released under the action of cavity pressure, then using laser cutting silicon chip edge part, can be prepared by it is a kind of directly Molding polysilicon chip；

The polysilicon chip straight forming device, the device include oriented solidified blocks, mold die cavity, heat protection screen, heater, earthenware Crucible, graphite holders and heat-insulation cage；

Wherein, the underface of oriented solidified blocks is mold die cavity；The lower half of oriented solidified blocks and mold die cavity are placed in guarantor together Among Wen Ping；Heat protection screen is fixed on the top cover of heat-insulation cage；The inside of heat-insulation cage is graphite holders, stone on the bottom plate of heat-insulation cage Crucible is placed on black bracket；The top of crucible is connected with the top cover lower part of heat-insulation cage, and having heaters is arranged in surrounding, and is provided with Outside logical argon gas hole to heat-insulation cage；

The main body of the oriented solidified blocks is cavity body, is provided with steel cage at the top of cavity body；The middle part of the outer wall of cavity body It is fixed with limiting device；The bottom of cavity body is graphite linings, and the lower surface of graphite linings is forming face, the material of the forming face The pyramid shape protrusion that size is identical, tower top is downward is distributed with above with a thickness of 3~4 μm for sapphire material, pyramid is high It is 2~4 μm, column foot is square, and side length is 3~5 μm, and the gap between pyramid shape protrusion is 1~2 μm, coverage rate 85 ~90%；

The composition of the mold die cavity includes the thermosistor of accommodating case and its underpart；The square funnel of the structure of accommodating case Shape, the tilt angles of funnel are 10 °~15 °；Respectively there are an opening, front and back among the top of accommodating case and each top side wall Symmetrical opening is the silicon liquid overflow port after silicon liquid is filled up, and symmetrical opening is silicon liquid inflow entrance, each silicon liquid inflow entrance It is mounted on the diversion pipe for being used for transmission silicon liquid, diversion pipe is downward, across the top cover of heat-insulation cage, is passed into the bottom of crucible Portion.

2. a kind of polysilicon chip straight forming device, it is characterized in that the device include oriented solidified blocks, mold die cavity, heat protection screen, Heater, crucible, graphite holders and heat-insulation cage；

Wherein, the underface of oriented solidified blocks is mold die cavity；The lower half of oriented solidified blocks and mold die cavity are placed in guarantor together Among Wen Ping；Heat protection screen is fixed on the top cover of heat-insulation cage；The inside of heat-insulation cage is graphite holders, stone on the bottom plate of heat-insulation cage Crucible is placed on black bracket；The top of crucible is connected with the top cover lower part of heat-insulation cage, and having heaters is arranged in surrounding, and is provided with Outside logical argon gas hole to heat-insulation cage；

The main body of the oriented solidified blocks is cavity body, is provided with steel cage at the top of cavity body；The middle part of the outer wall of cavity body It is fixed with limiting device；The bottom of cavity body is graphite linings, and the lower surface of graphite linings is forming face, the material of the forming face The pyramid shape protrusion that size is identical, tower top is downward is distributed with above with a thickness of 3~4 μm for sapphire material, pyramid is high It is 2~4 μm, column foot is square, and side length is 3~5 μm, and the gap between pyramid shape protrusion is 1~2 μm, coverage rate 85 ~90%；

The composition of the mold die cavity includes the thermosistor of accommodating case and its underpart；The square funnel of the structure of accommodating case Shape, the tilt angles of funnel are 10 °~15 °；Respectively there are an opening, front and back among the top of accommodating case and each top side wall Symmetrical opening is the silicon liquid overflow port after silicon liquid is filled up, and symmetrical opening is silicon liquid inflow entrance, each silicon liquid inflow entrance It is mounted on the diversion pipe for being used for transmission silicon liquid, diversion pipe is downward, across the top cover of heat-insulation cage, is passed into the bottom of crucible Portion.

3. polysilicon chip straight forming device as claimed in claim 2, it is characterized in that accommodating case in the mold die cavity Height is 230 μm~250 μm.

4. polysilicon chip straight forming device as claimed in claim 2, it is characterized in that the porosity of the graphite linings is 1% ~80%；Graphite linings are with a thickness of 150mm~160mm.