CN102969395B

CN102969395B - Method for improving cracking resistance of silicon chip

Info

Publication number: CN102969395B
Application number: CN201210426846.2A
Authority: CN
Inventors: 周浪; 孟虹辰
Original assignee: Nanchang University
Current assignee: Nanchang University
Priority date: 2012-10-31
Filing date: 2012-10-31
Publication date: 2015-04-15
Anticipated expiration: 2032-10-31
Also published as: CN102969395A

Abstract

The invention provides a method for improving cracking resistance of a silicon chip and belongs the technical field of photovoltaic materials. The method is characterized in that the silicon chip is placed in an argon or nitrogen atmosphere, heated to 300-900 DEG C and then subjected to heat preservation for 0.2-4 hours, and then the silicon chip is cooled at the speed lower than 7 DEG C/min to a room temperature and then discharged from a furnace. The method is simple in operation, low in costs and capable of greatly improving cracking resistance of the silicon chip and particularly improving the cracking resistance to diamonds which are used for cutting the silicon chip, and the bending fracture strain of the silicon chip can be improved by over 90%; simultaneously, minority carrier lifetime of polycrystalline silicon chips is obviously prolonged; and chip cracking rates during silicon chip follow-up processing and solar battery manufacturing processes are reduced, and solar battery production costs are finally reduced.

Description

A kind of method improving silicon chip anti-fragmentation performance

Technical field

The invention belongs to photovoltaic material technical field.In particular to production and the modification of solar cell silicon chip.

Technical background

Solar photovoltaic electric power more than 85% is based on crystal silicon chip solar cell, and wherein more than 50% is polysilicon chip solar cell.Required polysilicon chip is obtained by the polycrystalline silicon ingot casting cutting of directional solidification.Industrial at present have two kinds of silicon chip cutting techniques: silicon carbide abrasive mortar mix steel wire cutting (hereinafter referred to as mortar cutting) is cut (hereinafter referred to as diamond cut) with consolidated diamond fret saw.The thickness of silicon chip is 0.16 ~ 0.22 mm, is thinning gradually with technical development general trend.Ubiquity die crack loss problem, particularly polysilicon chip in photovoltaic industry.Generally reflect according to industry, the fragment rate of mortar cutting silicon wafer monocrystalline silicon piece is generally 0.3 ~ 1.0%, and polysilicon chip then reaches 1.5 ~ 4.5%.We adopt the bending breaking strain of three power bending methods to two kinds of silicon chips to carry out measuring statistics, and find monocrystalline silicon piece bending breaking strain average out to 0.15%, polysilicon chip is then 0.11%.Can see that silicon chip bending breaking strain has its fragment rate to affect very significantly.

The production application of diamond cut silicon chip just just starts at present, although industry not yet draws its fragment rate horizontal data, but existing bending fracture test display, diamond cut polysilicon chip is perpendicular to the bending breaking strain average out to 0.065% on line of cut direction, be starkly lower than mortar cutting polysilicon chip (0.11%), its fragment rate level will be higher; Also Similar Problems is there is in diamond cut monocrystalline silicon piece perpendicular on line of cut direction.Diamond cut silicon chip technology because it is efficient, environmental protection, silicon chip surface damage little advantage and be expected to apply on a large scale, but fragment rate is higher may restrict its development, thus improves its anti-fragmentation performance particularly important.。

Solar cell is with up to now, and relevant silicon chip manufacturing enterprise and solar cell growth enterprise constantly make great efforts to reduce silicon chip fragment rate by relevant management link, but there is not yet the technology report that any active improvement improves silicon chip anti-fragmentation performance.

Summary of the invention

The object of this invention is to provide a kind of method of raising silicon chip anti-fragmentation performance of lower cost, particularly improve the method for diamond cut silicon chip anti-fragmentation performance.

The method of raising silicon chip anti-fragmentation performance of the present invention, is achieved through the following technical solutions.

Silicon chip is placed in argon gas or nitrogen atmosphere, is heated to 300 ~ 900 DEG C, be incubated 0.2 ~ 4 hour, then, come out of the stove silicon chip is cooled to room temperature lower than the speed of 7 DEG C/min.

In said process, under the condition of 300 ~ <600 DEG C, also silicon chip can be placed in air atmosphere.

The present invention is based on and a large amount of system experimentations of heat treatment on the impact of silicon chip breaking strain are researched and proposed.Research finds, not only high temperature more than 900 DEG C, to silicon chip heating and thermal insulation and Slow cooling in the comparatively large-temperature range being low to moderate 300 DEG C, can make the breaking strain of silicon chip be significantly improved, particularly to diamond cut silicon chip, very remarkable perpendicular to effect on line of cut direction at it; Research also shows, and improves heat treatment temperature, can't bring better treatment effect more than 900 DEG C.Fig. 1 illustrates two kinds of silicon chips heat treatment experiment result at 900 DEG C; Fig. 2 illustrates the heat treatment experiment result to diamond cut polysilicon silicon chip under series of temperature.

The technology of the present invention effect is: after the inventive method process, and the bending breaking strain of silicon chip significantly improves.Improve degree with diamond cut silicon chip comparatively mortar cutting silicon wafer be large; Be large to be comparatively parallel to line of cut direction perpendicular to line of cut direction.To the polysilicon chip of diamond cut, perpendicular on line of cut direction, can more than 90% be improved through its bending breaking strain of process of the present invention.

The result that silicon chip bending breaking strain improves, will make its anti-fragmentation performance improve, and fragment rate in silicon chip subsequent treatment and solar cell manufacturing process is reduced, final reduction solar cell production cost.

Accompanying drawing explanation

Fig. 1 is the present invention's two kinds of silicon chips heat treatment experiment results at 900 DEG C.In 900 DEG C/2 hours argon gas, before and after process, various silicon chip is being parallel to line of cut direction and perpendicular to the bending breaking strain (ε on line of cut direction _c, adopt 3 bending methods to measure).

Fig. 2 is the heat treatment experiment result to diamond cut silicon chip under different temperatures of the present invention.Before and after the process of lower 2 hours of different temperatures, diamond cut silicon chip is perpendicular to the bending breaking strain (ε on line of cut direction _c, adopt 3 bending methods to measure).

Embodiment

The present invention will be described further by following examples.The present invention includes but be not limited to the following example.

Embodiment 1.

Get mortar cutting polysilicon chip, become 78 x 8 mm with laser scribing means scribing ²the test piece of size strip; Its rectangular direction respectively along silicon chip line of cut direction with perpendicular to silicon chip line of cut direction, each 20; Test piece scribing edge all with No. 600 carborundum papers along the polishing deburring of rectangular direction.Often kind of test piece is got 10 and be incubated 2 hours in argon gas at 900 DEG C, afterwards with stove cooling, ensures that cooldown rate is lower than 7 DEG C/min in process.Various silicon chip is carried out one by one 3 bending experiments, record its breaking strain, and average, result is as shown in table 1.Make mortar cut polysilicon chip breaking strain in the two directions do heat treatment to be all significantly increased.

Table 1 mortar cutting polysilicon chip is 2 hours process front and back breaking strain value (x10 in 900 DEG C of argon gas ^-3)

	Be parallel to line of cut	Perpendicular to line of cut
			Before process	1.33	1.10
After process	1.71	1.66
			Relative increase	29%	51%

Embodiment 2.

Get diamond cut polysilicon chip, become 78 x 8 mm with laser scribing means scribing ²the test piece of size strip; Its rectangular direction respectively along silicon chip line of cut direction with perpendicular to silicon chip line of cut direction, each 20; Test piece scribing edge all with No. 600 carborundum papers along the polishing deburring of rectangular direction.Often kind of test piece is got 10 and be incubated 2 hours in argon gas at 600 DEG C, afterwards with stove cooling, ensures that cooldown rate is lower than 7 DEG C/min in process.Various silicon chip is carried out one by one 3 bending experiments, record its breaking strain, and average, result is as shown in table 2.Do heat treatment, diamond cut polysilicon chip breaking strain in the two directions is all significantly increased.

Table 2 diamond cut polysilicon chip is 2 hours process front and back breaking strain mean value (x10 in 600 DEG C of argon gas ^-3)

	Be parallel to line of cut	Perpendicular to line of cut
			Before process	1.50	0.65
After process	2.00	1.27
			Relative increase	33%	95%

Embodiment 3.

Get diamond cut polysilicon chip, become 78 x 8 mm with laser scribing means scribing ²the test piece of size strip; Its rectangular direction respectively along silicon chip line of cut direction with perpendicular to silicon chip line of cut direction, each 10; Test piece scribing edge all with No. 600 carborundum papers along the polishing deburring of rectangular direction.Often kind of test piece is incubated 2 hours in air at 300 DEG C, cools afterwards with stove.Various silicon chip is carried out one by one 3 bending experiments, record its breaking strain, and average, result is as shown in table 3.Can see, make diamond cut polysilicon chip breaking strain in the two directions have considerable raising do heat treatment.

Table 3 diamond cut polysilicon chip is 2 hours process front and back breaking strain mean value (x10 in 300 DEG C of air ^-3)

	Be parallel to line of cut	Perpendicular to line of cut
			Before process	1.50	0.65
After process	1.68	0.76
			Relative increase	12%	17%

Embodiment 4.

Get diamond cut monocrystalline silicon piece, become 78 x 8 mm with laser scribing means scribing ²the test piece of size strip; Its rectangular direction respectively along silicon chip line of cut direction with perpendicular to silicon chip line of cut direction, each 10; Test piece scribing edge all with No. 600 carborundum papers along the polishing deburring of rectangular direction.Often kind of test piece is incubated 2 hours in nitrogen at 600 DEG C, cools afterwards with stove.Various silicon chip is carried out one by one 3 bending experiments, record its breaking strain, and average, result is as shown in table 4.Can see, make diamond cut polysilicon chip breaking strain in the two directions have considerable raising do heat treatment.

Table 4 diamond cut monocrystalline silicon piece is 2 hours process front and back breaking strain mean value (x10 in 600 DEG C of nitrogen ^-3)

	Be parallel to line of cut	Perpendicular to line of cut
			Before process	1.67	1.04
After process	1.85	1.64
			Relative increase	11%	58%

Claims

1. improve a method for silicon chip of solar cell anti-fragmentation performance, it is characterized in that silicon chip to be placed in argon gas or nitrogen atmosphere, be heated to 300 ~ 900 DEG C, be incubated 0.2 ~ 4 hour, then, come out of the stove silicon chip is cooled to room temperature lower than the speed of 7 DEG C/min.

2. improve a method for silicon chip of solar cell anti-fragmentation performance, it is characterized in that silicon chip to be placed in air atmosphere, be heated to 300 ~ 600 DEG C, be incubated 0.2 ~ 4 hour, then, come out of the stove silicon chip is cooled to room temperature lower than the speed of 7 DEG C/min.