CN109119338A

CN109119338A - A kind of highback polishing and efficient single crystal process

Info

Publication number: CN109119338A
Application number: CN201810887869.0A
Authority: CN
Inventors: 许成德; 陈健生; 李鑫
Original assignee: Hengdian Group DMEGC Magnetics Co Ltd
Current assignee: Hengdian Group DMEGC Magnetics Co Ltd
Priority date: 2018-08-06
Filing date: 2018-08-06
Publication date: 2019-01-01

Abstract

The present invention provides a kind of technique for being easy to produce in batches in conjunction with existing producing line, reinforce to silicon chip back side polishing action, and there is promotion to existing battery efficiency, PN junction after survivable diffusion is not easy to form " etching print " and influence battery appearance, stability has biggish guarantee etc., therefore carries on the back present invention employs chain type " acid+alkali+alkali " mode and throw technique.

Description

A kind of highback polishing and efficient single crystal process

Technical field

The present invention relates to photovoltaic industry solar energy single crystal cell piece wet etching correlative technology field, more particularly to one kind are new The highback that type etches chain type " sour throwing+alkali throwing+alkali is thrown " polishes and efficient single crystal process.

Background technique

Current commercialization monocrystalline common process battery manufacturing procedure approximately as: making herbs into wool → diffusion → etching → PE → printing, Sintering → testing efficiency.This commercialization monocrystalline solar cells manufacturing technology is relatively easy, mature, adapts to large-batch industrial Production, it is thus possible to be widely applied.

Commercialization monocrystalline common process battery chain type wet process acid etch making technology process and purpose are as follows at present: (1) silicon Piece uses HF+HNO in etching groove₃Nitration mixture removes the back side and surrounding PN junction, while the back side carries out just slightly acid polishing.(2) silicon wafer By washing 1 slot pure water cleaning.(3) porous silicon of KOH or NaOH solution removal silicon chip surface, and neutralize the acid of silicon chip surface. (4) silicon wafer is by washing 2 slot pure water cleaning.(5) HF removes the oxide layer of silicon wafer front surface, and neutralizes the alkali on silicon wafer.(6) silicon Piece is by washing 3 slot pure water cleaning.(7) silicon wafer completes making technology by the dry silicon wafer of drying tank.

Commercialization monocrystalline common process battery slot type wet process alkaline etching making technology process and purpose are as follows at present: (1) silicon Piece removes the back side and surrounding oxide layer in chain type HF slot, using HF.(2) silicon wafer is cleaned by chain type sink and drying tank is dry For silicon wafer (3) silicon wafer in slot-type device, aqueous slkali carries out burn into polishing to silicon chip back side and surrounding.(4) silicon wafer passes through groove-type water It washes.(5) silicon wafer passes through Dipping process, and HF removes the oxide layer of silicon wafer front surface, and neutralizes the alkali on silicon wafer.(6) silicon wafer passes through Slot type washing.(7) dry silicon wafer is dried, making technology is completed.

Since single crystal battery chain type wet process acid etch making technology is easy to operate by large-scale business processing procedure, but polish Effect is poor.And single crystal battery slot type wet process alkaline etching making technology back throwing effect is preferable, but processing procedure is cumbersome, equipment is mostly equal to be lacked Point.Therefore, it is necessary to invent a kind of novel etching technics, keep current etching technics effect further perfect.

Summary of the invention

The technical problem to be solved by the present invention is to overcome the above prior art, one kind is provided and is easy to and existing production Knot closes the technique of batch production, reinforces having promotion, survivable expansion to silicon chip back side polishing action, and to existing battery efficiency PN junction after dissipating is not easy to be formed " etching print " and influences battery appearance, stability have it is biggish ensure etc., therefore present invention chain type " acid+alkali+alkali " mode back throws technique.

The first object of the present invention is to provide a kind of high polishing process of chain type.By changing in conventional Schmid Equipment Foundations Manufacturing apparatus provides a kind of monocrystalline solar cells back polishing process.Reach backside reflection rate and promote 5%-50%, makes silicon chip back side Flannelette is more smooth, reaches mirror effect.

The second object of the present invention is can effectively to promote single crystal battery efficiency.

To achieve the goals above, the invention adopts the following technical scheme:

A kind of polishing of highback and efficient single crystal process, the technique the following steps are included:

1) 156.75 × 156.75mm of monocrystalline silicon wafer is used, makes flannelette by conventional process for etching；

2) silicon wafer after making herbs into wool is selected into diffusion furnace PN junction and thickeies oxide coating process；

3) etching feeding uniformly sprays moisture film using the diffusion front of silicon wafer, swims on liquid level into No. 1 slot of etching, silicon wafer four Week, the back side uniformly with HF, HNO₃Medical fluid reaction is removed oxide layer, and preliminary acid polishing to silicon wafer surrounding, the back side；

4) silicon wafer is transmitted between No. 2 slots of No. 1 slot of etching and etching by idler wheel, by being lauched knife hydro-peening silicon wafer on two groups, and By air knife or catch up with water truck dryer silicon wafer；

5) silicon wafer is transmitted by idler wheel into No. 2 reactive tanks of etching, and silicon wafer is immersed in aqueous slkali using high temperature in No. 2 reactive tanks of etching Middle mode；Heating plate is mounted in the reservoir that No. 2 reactive tanks of etching and alkali slot share；Etch the storage of No. 2 reservoirs and alkali slot Liquid bath shares, and reservoir feed flow is divided into two, a part supply No. 2 reactive tanks of etching, a part supply alkali slot reactive tank；

6) silicon wafer is transmitted to 1 slot of washing by idler wheel, by being above lauched knife hydro-peening silicon wafer, and by catching up with water idler wheel to squeeze dring silicon Piece；

7) silicon wafer is transmitted by idler wheel into alkali slot, and silicon wafer reacts consistent with No. 2 reactive tanks of etching in alkali slot；

8) silicon wafer is transmitted to 2 slots of washing by idler wheel and subsequent acid tank, 3 slots of washing, drying tank complete etch process flow；

9) PECVD filming equipment is used, plates antireflection film in monocrystalline front, subsequent printing back is electric respectively on monocrystalline silicon piece Pole, Al-BSF, positive electrode, and be sintered and form Ohmic contact, re-test transfer efficiency.

In the technical scheme, the present invention is frequently encountered in the experimental study stage and can be blocked up by mud in No. 2 slot filter cores of etching Fill in phenomenon.

Script silicon wafer comes out from No. 1 slot of etching passes through turntable, directly into No. 2 slots of etching.It is anti-for etching 1 by analysis Answering slot medical fluid is HF, HNO₃, and etching No. 2 reactive tank medical fluids is C₄H₁₃NO, silicon wafer from No. 1 reactive tank of etching come out can by HF, HNO₃Bring No. 2 reactive tanks of etching, HF, HNO into₃Meeting and C₄H₁₃NO reaction generates salt, mud class to block No. 2 slot filter cores of etching. In order to solve this abnormal phenomenon, increase pure water cleaning silicon chip, Yi Jixin between No. 2 reactive tanks of No. 1 reactive tank and etching etching Increase air knife or water idler wheel is caught up with to make dry No. 2 reactive tanks of laggard etching of silicon wafer.Thus avoid as far as possible acid-base neutralization forming salt, Mud, to block pumping filter core.

The phase encounters efficiency and does not promote the phenomenon that declining instead the present invention before the test, the cell piece back side after theoretical polished backside Compound reduction, and can efficient absorption long-wave band light, make improved efficiency, rather than decline.Lead to efficiency decline through checking The reason is that the oxidated layer thickness of silicon chip surface is inadequate, C under the condition of high temperature₄H₁₃NO corrodes the oxide layer for breaking through silicon chip surface, and Continue to destroy PN junction, so as to cause efficiency decline.In order to solve this exception, the present invention spreads work using oxide layer is thickeied Skill increases to frontside oxide layer sufficiently thick, prevents C in etching 2 slots and alkali slot with sufficiently thick oxide layer₄H₁₃NO destroys PN Knot.

The present invention encounters 2 tank liquor positions of needs raising etching when the phase constructs before the test can be only achieved immersion mode.

Originally 2 slot types of etching are using " idler wheel band liquid " mode, and medical fluid is coated in silicon chip back side by idler wheel rotation, to corrode The back side and surrounding, requirement can be reached by not needing high liquid level.This etch mode causes back side suede corrosion uneven, reflectivity Low disadvantage.No. 2 reactive tank front and rear baffles of etching are now improved, work liquid level will be promoted, silicon wafer is immersed in No. 2 reactive tanks of etching In, medical fluid can sufficiently be reacted with silicon chip back side, thus the efficient polished silicon slice back side.

Preferably, step 2) diffusion is changed on the basis of producing line diffusion technique, Producing line diffusion technique increases a step newly before going out boat, increases step newly and logical oxygen 1000-5000sccm, big N is arranged₂Logical 1000- 10000sccm, time are 3-30 minutes.

Preferably, silicon wafer uses " Overwater-floating " mode in etching 1 slot in step 3), silicon wafer swims in medical fluid surface, Silicon chip back side, surrounding can be with HF, HNO in etching groove₃Sufficiently reaction.

Preferably, silicon wafer goes out to etch No. 1 slot in step 4), into before No. 2 slots of etching, increases water knife, air knife or catch up with water Idler wheel, silicon wafer is sprayed pure water cleaning by water knife, and water idler wheel or the dry silicon wafer of air knife are caught up in use.

In the technical scheme, 1 slot of etching uses HF, HNO₃, and etch 2 slots and use C₄H₁₃NO, HF, HNO₃With C₄H₁₃NO It will participate in reacting generating salt, mud etc., newly surge and knife, air knife or catch up with water idler wheel that will greatly reduce the generation such as salt, mud.

Preferably, silicon wafer is immersed in No. 2 reactive tanks of etching in step 5), it is heated under the condition of high temperature using medical fluid C₄H₁₃NO solution, temperature control 50-90 DEG C.

In the technical scheme, C₄H₁₃The oxide layer reaction rate of NO and front side of silicon wafer is very slow, and C₄H₁₃NO and back Face has had been removed that the exposed pasc reaction rate of oxide layer is very rapid, and the thick oxide layer of front side of silicon wafer can effectively prevent C₄H₁₃NO is reacted with PN junction, to play the role of protecting PN junction, according to C₄H₁₃Both NO and silicon wafer tow sides reaction rate Difference, C₄H₁₃NO and the exposed silicon of silicon chip back side play the role of polishing, C₄H₁₃NO solution concentration is controlled in 0.5-50%.

Preferably, it is preferred that silicon wafer is transmitted by idler wheel into alkali slot, and principle is consistent with No. 2 slots of etching in 7)；Silicon wafer is leaching Steep C at high operating temperatures₄H₁₃NO solution.In the technical scheme, compared under chain type alkali slot room temperature general in industry using KOH or Person's NaOH solution has the advantages that polished backside effect is good.

Preferably, device used in the technique includes No. 1 slot of etching, No. 2 slots, sink and alkali slot, etching 1 are etched Water knife and air knife are equipped between No. 2 slots of number slot and etching or catches up with water idler wheel, and liquid storage trench bottom is equipped with heating plate, etches in No. 1 slot Portion, which is equipped with, to be etched No. 1 reservoir of No. 1 reactive tank and etching, etches inside No. 2 slots equipped with No. 2 reactive tanks of etching, and No. 2 reactions are etched It is equipped with baffle before and after slot, etches No. 2 slots and alkali slot shares reservoir, etches No. 1 slot, No. 2 slots of etching, sink and alkali slot and passes through rolling Wheel shape is at chain type technique.

The beneficial effects of the present invention are:

1. highback polishes etching technics using metal ion chemistry product are not included in chemicals, the metallic pollution of battery is played very Protective action well, and increase producing line stability；

2. providing a kind of efficient polishing process of novel etching chain type " sour throwing+alkali throwing+alkali is thrown "；

3. the present invention not will form " etching print " and influence battery appearance and lead to the gear that leaks electricity；

4. silicon wafer of the present invention is etching 1 slot, 2 slots of etching and reacting generation bubble in the back side with medical fluid in alkali slot, it is supported silicon The idler wheel of piece is eliminated in time in transmission process, thus back side flannelette is more uniform compared to slot type alkali throwing flannelette, smooth；

5. applicability of the present invention is extensive, not only currently popular PERC can also be combined in conjunction with conventional single battery process Battery process.

Detailed description of the invention

Fig. 1 is process flow chart of the invention.

Fig. 2 is the structural schematic diagram of present invention process device.

In figure, No. 11, etching slot；2, No. 2 slots are etched；3, No. 1 reactive tank is etched；4, No. 1 reservoir is etched；5,2 are etched Number reactive tank；6, sink；7, alkali slot；8, water knife；9, air knife or water idler wheel is caught up with；10, reservoir is shared；11, heating plate；12, it keeps off Plate；13, idler wheel.

Specific embodiment

Below in conjunction with specific embodiment and attached drawing, the present invention will be further explained:

Referring to Fig.1,156.75 × 156.75 type monocrystalline silicon piece 400 is selected to spread by conventional alkali process for etching using normal pressure Furnace diffusion production PN junction.On the basis of original diffusion technique, original diffusion technique, which goes out boat back, will increase a step process newly, increase newly Process time is 5 minutes, leads to O₂Flow is 5000sccm, big N₂Flow is 10000sccm.400 silicon wafers, use hair after diffusion Board formula is uniformly divided into the subsequent polishing test of 4 groups of carry out.

Referring to Fig. 2, device used in the present invention includes No. 1 slot 1 of etching, etches No. 2 slots 2, sink 6 and alkali slot 7, etching Water knife 8 and air knife are equipped between No. 2 slots of No. 1 slot and etching or catches up with water idler wheel 9, and liquid storage trench bottom is equipped with heating plate 11, etches No. 1 No. 2 reactive tanks 5 of etching, etching are equipped with equipped with No. 2 No. 1 reservoir 4 of No. 1 reactive tank 3 of etching and etching, etching slots inside inside slot It is equipped with baffle 12 before and after No. 2 reactive tanks, etches No. 2 slots and alkali slot shares reservoir 10, etches No. 1 slot, etching No. 2 slots, sinks Chain type technique is formed by idler wheel 13 with alkali slot.

Embodiment 1

A kind of highback polishing and efficient single crystal process, comprising the following steps:

1) select wherein the 1st group 100 diffusion after monocrystalline silicon piece, etching feeding at uniformly spray moisture film, etch No. 1 slot in With HF, HNO₃Mixed acid solution corrodes silicon wafer surrounding and the back side, and preliminary acid polishing；

2) silicon wafer is transmitted between No. 2 slots of No. 1 slot of etching and etching by idler wheel, by being lauched knife hydro-peening silicon wafer on two groups, and By air knife or catch up with water truck dryer silicon wafer；

3) silicon wafer is transmitted by idler wheel into No. 2 reactive tanks of etching, and silicon wafer is immersed in C using high temperature in No. 2 reactive tanks of etching₄H₁₃NO Mode in solution, it is 70 DEG C that silicon wafer, which is immersed in temperature, and concentration polishes in 1.0% solution；

4) silicon wafer is transmitted to 1 slot of washing by idler wheel, by being above lauched knife hydro-peening silicon wafer, and by catching up with water idler wheel to squeeze dring silicon Piece；

5) silicon wafer is transmitted by idler wheel into alkali slot, and silicon wafer is immersed in C using high temperature in alkali slot₄H₁₃Mode in NO solution, silicon wafer leaching Bubble is 70 DEG C in temperature, and concentration polishes in 1.0% solution；

6) silicon wafer is transmitted to 2 slots of washing by idler wheel and subsequent acid tank, 3 slots of washing, drying tank complete etch process flow；

7) PECVD filming equipment is used, plates antireflection film in monocrystalline front, subsequent printing back is electric respectively on monocrystalline silicon piece Pole, Al-BSF, positive electrode, and be sintered and form Ohmic contact, re-test transfer efficiency.

It illustrates: the back side being carried out to silicon wafer after etching and tests reflectivity, and efficiency survey is carried out to cell piece after sintering Examination.

Embodiment 2

1) select wherein the 2nd group 100 diffusion after monocrystalline silicon piece, etching feeding at uniformly spray moisture film, etch No. 1 slot in With HF, HNO₃Mixed acid solution corrodes silicon wafer surrounding and the back side, and preliminary acid polishing；

2) silicon wafer is transmitted between 2 slots of 1 slot of etching and etching by idler wheel, by being lauched knife hydro-peening silicon wafer on two groups, and is passed through Air knife catches up with water truck dryer silicon wafer；

3) silicon wafer is transmitted by idler wheel into No. 2 reactive tanks of etching, and silicon wafer is immersed in C using high temperature in No. 2 reactive tanks of etching₄H₁₃NO Mode in solution, it is 75 DEG C that silicon wafer, which is immersed in temperature, and concentration polishes in 2.0% solution；

5) silicon wafer is transmitted by idler wheel into alkali slot, and silicon wafer is immersed in C using high temperature in alkali slot₄H₁₃Mode in NO solution；Silicon wafer leaching Bubble is 75 DEG C in temperature, and concentration polishes in 2.0% solution；

Embodiment 3

1) select wherein the 3rd group 100 diffusion after monocrystalline silicon piece, etching feeding at uniformly spray moisture film, etch No. 1 slot in With HF, HNO₃Mixed acid solution corrodes silicon wafer surrounding and the back side, and preliminary acid polishing；

3) silicon wafer is transmitted by idler wheel into No. 2 reactive tanks of etching, and silicon wafer is immersed in C using high temperature in No. 2 reactive tanks of etching₄H₁₃NO Mode in solution, it is 80 DEG C that silicon wafer, which is immersed in temperature, and concentration polishes in 3.0% solution；

5) silicon wafer is transmitted by idler wheel into alkali slot, and silicon wafer is immersed in C using high temperature in alkali slot₄H₁₃Mode in NO solution, silicon wafer leaching Bubble is 80 DEG C in temperature, and concentration polishes in 3.0% solution；

Comparative example

Comparative example and 1,2,3 difference of embodiment are as follows: the 4th group 100 use the harsh etching technique of conventional chain type after diffusion, that is, carry on the back Face is not thrown by back, and other processes are consistent with embodiment.

Silicon chip back side reflectivity and finished battery electrical property, efficiency pair is made after embodiment 1,2,3 and comparative example etching Than as shown in the table:

1 illustrated embodiment 1,2,3 of table is compared with silicon chip back side reflectivity after comparative example etching:

As can be seen from Table 1 Novel back throw process example 1,2,3 and classical acid etching technics comparative example reflectivity it is high 7.3%, 10.1%, it 12.3% differs, it can be seen that Novel back throws technique has advantage very much.

2 illustrated embodiment 1,2,3 of table is compared with comparative example finished battery electrical property, efficiency variance value:

Classification	Uoc(mV)	Isc(A)	FF (%)	Eta (%)
					Comparison	0	0	0	0
Embodiment 1	0.0004	0.023	0.03	0.07
					Embodiment 2	0.0008	0.033	0.06	0.11
Embodiment 3	0.001	0.042	0.09	0.14

From 2 electrical property of table, efficiency data combination table 1 it can be seen that as backside reflection rate is promoted, ascendant trend is presented in efficiency, Middle Uoc, Isc, FF have different degrees of rising.1,2,3 silicon wafer of embodiment carries out back polishing, improves silicon chip back side reflectivity, Increase the absorption of the general middle medium-long wave band of sunlight.Thus efficiency and electrical property have promotion.

Claims

1. a high-back polishing and high-efficiency single crystal process, wherein the process comprises the following steps:

1) Using a single crystal 156.75×156.75mm silicon wafer, the textured surface is made by a conventional texturing process;

2) Put the silicon wafer after texturing into the diffusion furnace to make PN junction, and select the thickening oxide layer process;

3) Etching and feeding use the diffusion front of the silicon wafer to spray a water film evenly, enter the etching tank No. 1 to float on the liquid surface, and evenly react with the HF and HNO ₃ liquids around the silicon wafer and the back. Removal of oxide layer on the back, and preliminary acid polishing;

4) The silicon wafer is transferred between the etching slot No. 1 and the etching slot No. 2 through the roller, and the silicon wafer is sprayed and washed by two sets of upper and lower water jets, and the silicon wafer is dried by the air knife or the water-rushing roller;

5) The silicon wafer is transported into the etching No. 2 reaction tank through the roller, and the silicon wafer is immersed in an alkali solution at a high temperature in the etching No. 2 reaction tank; the heating plate is installed in the storage solution shared by the etching No. 2 reaction tank and the alkali tank In the tank; the No. 2 etching liquid storage tank is shared with the liquid storage tank of the alkali tank, the liquid supply of the liquid storage tank is divided into two parts, a part is supplied to the etching No. 2 reaction tank, and the other part is supplied to the alkali tank reaction tank;

6) The silicon wafer is transferred to the water washing tank 1 through the roller, sprayed and washed by the upper and lower water jets, and the silicon wafer is squeezed and dried by the water rushing roller;

7) The silicon wafer is transported into the alkali tank through the roller, and the reaction of the silicon wafer in the alkali tank is the same as that of etching the No. 2 reaction tank;

8) The silicon wafer is transferred to the water washing tank 2 and the subsequent acid tank, the water washing tank 3, and the drying tank through the roller to complete the etching process;

9) Using PECVD coating equipment, coat the anti-reflection film on the front of the single crystal, and then print the back electrode, aluminum back field, and positive electrode on the single crystal silicon wafer respectively, and sinter to form an ohmic contact, and then test the conversion efficiency.

2. a kind of high back polishing and high-efficiency single crystal process according to claim 1, is characterized in that, step 2) diffusion adopts thickening oxide layer process, is to change on the basis of production line diffusion process, production line diffusion A new step is added before the craft is out of the boat. The new step is set to pass oxygen 1000-5000sccm, large N ₂ pass 1000-10000sccm, and the time is 3-30 minutes.

3. A kind of high-back polishing and high-efficiency single crystal process according to claim 1, it is characterized in that, in step 3), silicon wafer adopts "water floating" mode in etching 1 groove, and silicon wafer floats on the surface of medicinal liquid , the back and surrounding of the silicon wafer can fully react with HF and HNO ₃ in the etching groove.

4. a kind of high back polishing and high-efficiency single crystal process according to claim 1, is characterized in that, in step 4), silicon wafer goes out to etch No. 1 groove, before entering and etch No. 2 groove, increase water jet, wind The silicon wafer is cleaned with pure water sprayed by the water jet, and the silicon wafer is dried by using the water rushing roller or the air knife.

5. a kind of high-back polishing and high-efficiency single crystal process according to claim 1, is characterized in that, in step 5), silicon wafer is immersed in etching No. 2 reaction tank, and using medicinal liquid is to be heated to C under high temperature state ₄ H ₁₃ NO solution, temperature controlled at 50-90°C.

6. a kind of high back polishing and high-efficiency single crystal process according to claim 1, is characterized in that, in preferably 7), silicon wafer is transported into alkali tank by roller, and the principle is consistent with etching No. 2 groove; Soak in C ₄ H ₁₃ NO solution at high temperature.

7. A high-back polishing and high-efficiency single crystal process according to claim 1, wherein the device used in the process comprises etching No. 1 groove (1), etching No. 2 groove (2), The water tank (6) and the alkali tank (7), between the etching tank No. 1 and the etching tank No. 2 are provided with a water knife (8) and an air knife or a water rushing roller (9), and a heating plate is provided at the bottom of the liquid storage tank (11), the No. 1 etching tank is provided with the etching No. 1 reaction tank (3) and the etching No. 1 liquid storage tank (4), and the etching No. 2 tank is provided with the etching No. 2 reaction tank (5) , There are baffle plates (12) before and after the etching No. 2 reaction tank, the etching No. 2 tank and the alkali tank share a liquid storage tank (10), the etching No. 1 tank, the etching No. 2 tank, the water tank and the alkali tank pass the roller (13) forming a chain process.