CN105200516A - Polycrystalline silicon ingot casting process capable of enhancing inclusion removing effect - Google Patents

Abstract

The invention relates to a heat-exchange-based polycrystalline silicon ingot casting process technology capable of enhancing an inclusion removing effect. According to such a method, a production process for producing a polycrystalline silicon ingot by heat exchange is improved, a heat insulation cage of a polycrystalline silicon ingot furnace is mainly improved, and an inclusion removing process is added in a polycrystalline silicon ingot production process. According to the process technology, the later period of the inclusion removing process is crossed and overlapped with a crystal growth preparation process, crystal growth time can be shortened, crystal growth efficiency can be improved, and time required by the whole polycrystalline silicon ingot production process is only 2 to 3 hours more than that required by an ordinary polycrystalline silicon ingot production process.

Description

A kind of polycrystalline silicon casting ingot process strengthening impurities removal effect

Technical field

The present invention relates to a kind of use heat strengthening impurities removal effect and exchange production polycrystalline silicon casting ingot process technology.

Background technology

At present, common use heat exchanges the processing method of producing polycrystalline silicon ingot casting: be directly placed in ingot casting crucible by polycrystalline silicon material, under vacuum conditions, top heater in polycrystalline silicon ingot or purifying furnace and the both sides well heater be positioned in the middle part of crucible are opened, polycrystalline furnace is heated up and is heated to about 1540 DEG C, by the time except the polycrystalline silicon material of crucible bottom 2cm thickness is molten, after all the other polycrystalline silicon materials all melt, directly enter the long brilliant stage, namely press certain speed and slowly continue to promote the thermal baffle aperture of surrounding to 8cm, temperature is reduced to 1450 DEG C, and then cool to 1400 DEG C gradually by stage gradient, till all melted silicons all crystallization.There are the following problems for this technique: (1) because bottom temp is low, the poor fluidity of melted silicon, and impurity, can not effectively impurities removal easily at congregate; (2) the resistivity distribution of whole silicon ingot can be caused uneven; The existence of impurity and resistivity distribution uneven, the dislocation desity of silicon ingot can be caused comparatively large, and and then affect minority carrier life time and the photoelectric transformation efficiency of polysilicon.

Summary of the invention

For above-mentioned prior art, the object of the present invention is to provide a kind of polycrystalline cast ingot Technology that can strengthen impurities removal effect, realize effective impurities removal, reduce the dislocation of polycrystal silicon ingot.

The inventive method improves in the production technique that polycrystalline silicon ingot casting is produced in heat exchange, the improvement mainly on the heat-insulation cage of polycrystalline ingot furnace, and increase an impurities removal process in polycrystalline cast ingot production process.Present invention process comprises the following steps:

1) bottom the heat-insulation cage of polycrystalline ingot furnace, two-layer heat insulation carbon felt collar is increased, simultaneously, one deck carbon felt is placed in the melted silicon same level position of heat-insulation cage surrounding, strengthen the effect of heat insulation in ingot casting production process, ensure that in crucible, polycrystalline liquation has stable thermograde in the polycrystalline cast ingot production processes such as melt, impurities removal, long crystalline substance;

2) polycrystalline ingot furnace intensification is being heated to about 1540 DEG C, by the time except the polycrystalline silicon material of crucible bottom 2cm thickness is molten, after all the other polycrystalline silicon materials all melt, open thermal baffle aperture to 4cm, temperature declines and controls 1460 DEG C ~ 1500 DEG C a certain values and continue 3 ~ 4 hours, keep the polycrystalline silicon material in crucible not continue the dark molten length that also do not start brilliant, make the abundant convection current of polysilicon liquation in crucible, impurity is pushed on polysilicon liquation face by convection current;

3) slowly promote thermal baffle to 6cm, temperature is reduced to 1450 DEG C, and continues half an hour;

4) slowly promote thermal baffle to 7cm, temperature is reduced to 1445 DEG C, and continues 2 hours 30 minutes;

5) slowly promote thermal baffle to 9cm, temperature is reduced to 1442 DEG C, and continues 5 hours;

6) slowly promote thermal baffle to 10cm, temperature is reduced to 1440 DEG C, and continues 2 hours;

7) slowly promote thermal baffle to 12cm, temperature is reduced to 1435 DEG C, and continues 5 hours;

8) then slowly promote thermal baffle to 15cm, temperature is reduced to 1432 DEG C, and continues 8 hours;

9) last, impurities removal end of processing enters into the long brilliant stage, till all melted silicons all crystallization.

Technical solution of the present invention is divided be clipped to 4cm by being opened thermal baffle aperture, 6cm, 7cm, 9cm, 10cm, 12cm, 15cm, control temperature drops to 1500 DEG C-1460 DEG C, 1450 DEG C, 1445 DEG C, 1442 DEG C, 1440 DEG C, 1435 DEG C, 1432 DEG C, and continue 0.50 hour ~ 8 hours, guarantee that the silicon material of crucible bottom can not melt, liquation in crucible also can not start long brilliant, make the abundant convection current of polysilicon liquation in crucible, impurity is pushed on polysilicon liquation face by convection current, impurity is pushed again to crucible edge and gathers be attached on sidewall of crucible, thus reach obvious impurities removal effect, decrease the dislocation of polycrystal silicon ingot, improve minority carrier life time and the photoelectric transformation efficiency of polycrystal silicon ingot.Later stage of the impurities removal process of the technical program and long brilliant set-up procedure juxtaposition, and can shorten the long brilliant time, improve long brilliant efficiency, whole polycrystalline cast ingot production process required time only than common polycrystalline ingot casting production process increase by 2 ~ 3 little time.

Embodiment

Embodiment 1: the polycrystalline silicon material that different quality is filled a prescription by a certain percentage is placed in ingot casting crucible, under vacuum conditions, top heater in polycrystalline silicon ingot or purifying furnace and the both sides well heater be positioned in the middle part of crucible are opened, polycrystalline furnace is heated up and is heated to about 1540 DEG C, by the time except the polycrystalline silicon material of crucible bottom 2cm thickness is molten, after all the other polycrystalline silicon materials all melt, directly enter the long brilliant stage, namely press certain speed and slowly continue to promote the thermal baffle aperture of surrounding to 8cm, temperature is reduced to 1450 DEG C, and then cool to 1400 DEG C gradually by stage gradient, till all melted silicons all crystallization.The electrical performance indexes of the ingot casting obtained is as shown in table 1.

Table 1

Embodiment 2: increase two-layer heat insulation carbon felt collar bottom the heat-insulation cage of polycrystalline ingot furnace, simultaneously, one deck carbon felt is placed in the melted silicon same level position of heat-insulation cage surrounding, strengthen the effect of heat insulation in ingot casting production process, ensure that in crucible, polycrystalline liquation has stable thermograde in the polycrystalline cast ingot production processes such as melt, impurities removal, long crystalline substance, polycrystalline silicon material of filling a prescription same with embodiment 1 equal quality is placed in ingot casting crucible by certain proportioning, under vacuum conditions, top heater in polycrystalline silicon ingot or purifying furnace and the both sides well heater be positioned in the middle part of crucible are opened, again polycrystalline ingot furnace is heated up and be heated to about 1540 DEG C, by the time except the polycrystalline silicon material of crucible bottom 2cm thickness is molten, after all the other polycrystalline silicon materials all melt, open thermal baffle aperture to 4cm, temperature declines and controls 1460 DEG C ~ 1500 DEG C a certain values and continue 3 ~ 4 hours, the polycrystalline silicon material in crucible is kept not continue the dark molten length that also do not start brilliant, make the abundant convection current of polysilicon liquation in crucible, impurity is pushed on polysilicon liquation face by convection current, then slowly promote thermal baffle to 6cm, temperature is reduced to 1450 DEG C, and continues half an hour, then slowly promote thermal baffle to 7cm, temperature is reduced to 1445 DEG C, and continues 2 hours 30 minutes, then slowly promote thermal baffle to 9cm, temperature is reduced to 1442 DEG C, and continues 5 hours, then slowly promote thermal baffle to 10cm, temperature is reduced to 1440 DEG C, and continues 2 hours, then slowly promote thermal baffle to 12cm, temperature is reduced to 1435 DEG C, and continues 5 hours, then slowly promote thermal baffle to 15cm, temperature is reduced to 1432 DEG C, and continues 8 hours, finally, impurities removal end of processing enters into the long brilliant stage, till all melted silicons all crystallization.The electrical performance indexes of the ingot casting obtained is as shown in table 1.

Table 2

Finally, above it should be pointed out that, embodiments of the present invention are explained in detail, but in the ken that possesses of one skilled in the relevant art of the present invention, various change under the various prerequisite not departing from present inventive concept can be made.

Claims (1)

1. the polycrystalline silicon casting ingot process strengthening impurities removal effect comprises the following steps:

1) bottom the heat-insulation cage of polycrystalline ingot furnace, two-layer heat insulation carbon felt collar is increased, simultaneously, one deck carbon felt is placed in the melted silicon same level position of heat-insulation cage surrounding, strengthen the effect of heat insulation in ingot casting production process, ensure that in crucible, polycrystalline liquation has stable thermograde in the polycrystalline cast ingot production processes such as melt, impurities removal, long crystalline substance;

2) polycrystalline ingot furnace intensification is being heated to about 1540 DEG C, by the time except the polycrystalline silicon material of crucible bottom 2cm thickness is molten, after all the other polycrystalline silicon materials all melt, open thermal baffle aperture to 4cm, temperature declines and controls 1460 DEG C ~ 1500 DEG C a certain values and continue 3 ~ 4 hours, keep the polycrystalline silicon material in crucible not continue the dark molten length that also do not start brilliant, make the abundant convection current of polysilicon liquation in crucible, impurity is pushed on polysilicon liquation face by convection current;

3) slowly promote thermal baffle to 6cm, temperature is reduced to 1450 DEG C, and continues half an hour;

4) slowly promote thermal baffle to 7cm, temperature is reduced to 1445 DEG C, and continues 2 hours 30 minutes;

5) slowly promote thermal baffle to 9cm, temperature is reduced to 1442 DEG C, and continues 5 hours;

6) slowly promote thermal baffle to 10cm, temperature is reduced to 1440 DEG C, and continues 2 hours;

7) slowly promote thermal baffle to 12cm, temperature is reduced to 1435 DEG C, and continues 5 hours;

8) then slowly promote thermal baffle to 15cm, temperature is reduced to 1432 DEG C, and continues 8 hours;

9) last, impurities removal end of processing enters into the long brilliant stage, till all melted silicons all crystallization.