CN102953123A

CN102953123A - Diffusion furnaces employing ultra low mass transport systems

Info

Publication number: CN102953123A
Application number: CN2012102796986A
Authority: CN
Inventors: 理查·W·帕克斯; 路易斯·阿雷安卓·芮·加希亚; 彼得·G·拉给
Original assignee: TP SOLAR Inc
Current assignee: TP SOLAR Inc
Priority date: 2011-08-19
Filing date: 2012-08-07
Publication date: 2013-03-06
Anticipated expiration: 2032-08-07
Also published as: TW201314942A; TWI473290B; CN102953123B

Abstract

Multi-zone, solar cell diffusion furnaces having a plurality of radiant element (SiC) or/and high intensity IR lamp heated process zones, including baffle, ramp-up, firing, soaking and cooling zone(s). The transport of solar cell wafers, e.g., silicon, selenium, germanium or gallium-based solar cell wafers, through the furnace is implemented by use of an ultra low-mass, wafer transport system comprising laterally spaced shielded, synchronously driven, metal bands or chains carrying non-rotating alumina tubes suspended on wires between them. The wafers rest on raised circumferential standoffs spaced laterally along the alumina tubes, which reduces contamination. The high intensity IR flux rapidly photo-radiation conditions the wafers so that diffusion occurs>3 faster than conventional high-mass thermal furnaces. Longitudinal side wall heaters comprising coil heaters in Inconel sheaths inserted in carrier tubes are employed to insure even heating of wafer edges adjacent the side walls.

Description

The ultralow quality delivery system of anti-sagging drift stop and sidewall well heater diffusion furnace

Technical field

The present invention relates to continuous handling machinery, multilane formula (multi-lane) diffusion furnace be used for by use in 700-1100 ℃ of scope radiation resistance or/and the heating of IR lamp solar cell wafer is processed, so that the diffusion of P and/or B doping agent composition or/and be diffused into altogether in the silicon (or other advanced materials) in the wafer, forms the p-n junction upper layer thus or/and back of the body surface field layer.Specifically, the present invention relates to a kind of solar cell diffusion furnace, have one or more heating region and ultralow quality, low-frictional force, portion transverse wire suspension type alumina tube delivery system, add longitudinal side wall radiation heater and anti-sagging drift stop subassembly.

Background technology

Making silica-based solar cell needs laterally to cut down thin slice silicon with " wire saw " from silicon ingot, is used for forming coarse solar cell wafer.Subsequently these wafers (forming by crystal formation or by the polycrystalline that combines no matter be) are processed to form the level and smooth wafer of thickness in 140 to 330 micrometer ranges.Because suitable silicon is rare, trend is to make wafer thinner, and thickness is the 140-180 micron usually.

Raw wafers (raw wafer) with completion is processed into the functional solar cell that can produce by photovoltaic effect electricity subsequently.Wafer process comprises: be called the two stage process of diffusion, it produces semi-conduction " p-n " junction diode; Then be the 3rd technique, respectively silver and aluminium base slurry coating be screen-printed on the front and back of wafer in this technique, then burn till p-n junction grid and back contact, wherein these layers serve as respectively ohm collector electrode and ground connection.

Diffusion technique roughly comprises two stages: first stage is to the front of wafer and/or the dopant material of one or more type of backside coating (coating) and make these materials dry, then, second stage is in diffusion furnace, chamber or heating region the wafer that has been coated with to be heated (roasting), so that the doping agent composition is diffused in silicon (or other advanced materials) the wafer matrix, thereby form p-n junction layer or back contact.The diffusion furnace that the present invention relates to improve to some extent and sinter process, process and thermal profile.

In the situation that various phosphorus (P) or boron (B) source are arranged, at high temperature spread.Use phosphorus to produce the p-type knot at the top surface of wafer, and use boron to produce the N-shaped knot on back of the body surface.Mix " emtting electrode " layer that phosphorus silicon (P-doped Si) forms photovoltaic cell, that is, and the layer of electron emission when being exposed to sunlight (conventional photon source).As mentioned above, collect these electronics through the meticulous net of the metallic contact of silk screen printing, described metallic contact is to be sintered in the surface of battery by the metallization stove.

Order about phosphorus by High temperature diffusion technique and enter into wafer.The common 20-30 consuming time of current technique minute." electroactive " phosphorus is in addition formed low resistance contact.In common diffusion, to the back of the body surface-coated boron compound of wafer, and to the top surface phosphors coating compound of wafer.In the single roasting, wafer is heated, in order to boron and phosphorus are diffused in its corresponding basal surface and top surface altogether.

Spread and various cleaning, the ablation of laser edge and etch process so that after removing unwanted semiconducter junction from the two sides of wafer, with antireflecting coating (ARC) (normally silicon nitride (SiN3)) described wafer is coated with, this is normally undertaken by plasma enhanced chemical vapor deposition (PECVD).After ARC applied, battery was navy blue surface color (or brown, this depends on used coating material).ARC make wavelength approximately 0.6 micron the reflection of incident photon reduce to minimum.Be embedded into hydrogen in the silicon and luckily have the bulk defects in effect, the especially polycrystalline material of dummy defective owing to the formation of ARC.Described defective is some traps, and electron-hole pair can be recombinated in these traps, thereby reduces battery efficiency or power stage.

In IR metallization roasting process subsequently, high temperature (above 850 ℃) can make hydrogen spread from wafer and go back.Therefore, in order to prevent that described hydrogen from from wafer " venting ", needing roasting time shorter.Preferably hydrogen is caught and stayed (especially in the situation that polycrystalline material) in the block materials.

The diffusion stoving oven and the diffusion technique that the present invention relates to improve to some extent.The IR handling machinery stove and accessory that is currently available for these diffusion sinter processs has long heating chamber, and wherein a plurality of IR lamps separate in fact equably with the below in chip conveying system (wire guipure or ceramic roller handling machinery) top and (usually separate 1.5 ").By various forms of insulation, modal is the compression-type masonite, makes the insulation of heating region and outside atmosphere.Infrared rays (IR) lamp makes the temperature of the silicon wafer that imports into be elevated to about 700 ℃ to 950 ℃.Within 30 minute time length of diffusion technique, keep this temperature, then make the wafer cooling and it is transferred to next downstream process operation and equipment.

Current available diffusion furnace uses one of chip conveying system of two types usually: 1) high quality handling machinery, it comprises the heavy type (〉 350Kg of a plurality of static state (non-vertically moving)) the solid ceramic rotating roller; Or 2) the wire guipure of movable (vertically moving) is used for the roasting zone of transfer wafers by stove.For the metallic pollution that makes the wafer back surface is reduced to minimum or is prevented the metallic pollution on wafer back surface, the ceramic rotating roller stove of current preferred static state.The working width of these stoves is generally 1 to 2 meter, and the permission wafer also is emitted on band or the roller conveyor, therefore is called as " multilane formula " stove.Typical conventional diffusion furnace is about 400 " long, as to have 160 36 ", and wide IR lamp is placed on the roller top, and 100 to 160 lamps are placed on the roller below.

In the static solid rotating roller handling machinery stove of these high quality, IR lamp usefulness is elevated to diffusion temperature with the temperature of furnace chamber for a long time, and the scope of diffusion temperature is 700 ℃ to 950 ℃.Principle of operation obviously is such: it is hot that the IR lamp of roller below keeps roller, and wafer helps heat to be delivered to wafer with contacting of roller, and this heat transmission is to conduct by thermo-contact to carry out.Along handling machinery significant thermal profile is arranged, it raises in the ingress and reduces in the exit.

As for wire guipure handling machinery, must support band in the centre with silica tube, to prevent with sagging and the sliding surface of low-frictional force is provided.Because pipe covers the downside of wafer, in order to prevent occurring " cold " band on the wafer, pipe is arranged to herringbone pattern.Yet the price of pipe is very high, makes the mass penalty of conveyor system, and hinders the bottom heating region that enters stove.

Therefore, the solid rotary ceramic roller conveyor of the present art or wire guipure stove can't satisfy in control capital cost faster production and strengthen the demand of throughput.In order to compensate, make stove laterally wider, so just can in each stove zone, process the wafer of many circuits.The lamp that this needs again more to grow, price is higher, the mean time to failure, MTTF of these lamps is usually shorter in fact, thereby significantly increases running cost.Equally, the current power that can't increase lamp, this is because higher output can cause modulation element overheated, this is (mainly being in high quality solid ceramic roller conveyor system) that the thermal mass by stove causes.Overheated in order to prevent, reduce power density with thermopair, but this can cause the spectrum output of IR lamp emission that substantial variations (lower optical throughput and energy output) occurs.The optical throughput result who reduces needs again to reduce the speed of handling machinery band or the length (keeping simultaneously original tape speed) that prolongs stove, therefore makes processing slack-off.

Therefore, in the field of diffusion furnace and diffusion sinter process, following outstanding demand is arranged: significantly improve the clean of roasting zone and effectively use, better control and thermal profile to whole stove are provided, allow to improve the utilization of roasting energy, improve speed and the homogeneity of diffusion technique, when keeping or improving throughput, reduce the length of stove, and in the situation that the footprint area of stove reduces and energy, operation and maintenance cost are lower, realize these targets.

Summary of the invention

The present invention has satisfied these demands in this field, the present invention relates to multizone solar cell diffusion furnace, described diffusion furnace has super low-quality movable delivery system, be used for transfer wafers by a plurality of heating and cooling zone, at least one inlet baffle zone of described district inclusion, the zone raises, then be one or more diffusion soaking zone in downstream and optional diffusion roasting zone, and one or more cooled region, be used for phosphorus or/and the front of boron dope agent and/or back side diffusion or/and common diffusion, thereby in wafer matrix, form p-type or N-shaped knot and/or back contact.

Exactly, the present invention relates to the ultralow quality activity delivery system of wafer stoving oven, described delivery system comprises anti-sagging drift stop and sidewall well heater, the wafer that the outside drawing lines along multi-thread tunnel-type crosses is heated uniformly guaranteeing.

As disclosing as an example, delivery system of the present invention has been described herein in two alternate embodiment: A) band/pin drive system; And B) roller chain/chain wheel drive system, its central roll chain/chain wheel drive system is currently preferred embodiment.In two embodiment, wafer vertically is being supported on the minor diameter hollow refractory tube of non-rotating in the process by process zone, and described refractory tube is on the suspension wire or bar that is carried on across the width of delivery system.In band/pin drive system, described opposite end wiry is by rack bearing, and described support is to be formed or invested on the rotating band by rotating band.In roller chain/chain wheel drive system, end wiry is installed in the hollow tube of chain link pivot.

In current preferred heating system, in the heating region of top, use transversal orientation formula IR lamp, and in the heating region of bottom, use the combination of IR lamp and resistive heating.In order to improve the Transverse Heated homogeneity of crossing over the stove width, resistance heater is placed on and two longitudinal side wall adjacents, described sidewall is oriented to be parallel with the medullary ray of stove and separates with described medullary ray, and the IR lamp laterally is placed on above or below the longitudinal side wall resistance heating element, be preferably the below.The longitudinal side wall resistance heater is arranged in silica tube, vitrified pipe or the stable SiC pipe, and described pipe is arranged near the handling machinery below.In 5 drawing lines or wider stove, described well heater is in order to keep the wafer in the

row

1 and 5 adjacent with corresponding sidewall to be in suitable diffusion temperature.This is particularly useful for common diffusion processing.

Use the advantage of high strength IR lamp isolation module to be, provide short wavelength, high-throughput IR light to regulate, thereby promote faster diffusion.In the present invention, should be understood that and mentioning high strength IR lamp (HI-IR) part, can use the radiant heater element of SiC radiation/again, the disclosure of HI-IR modulation element only as an example.

In the stove zone, (for example implement the advanced material solar cell wafer by using ultralow quality, delivery system activity (vertically moving), that protection is arranged, silicon, selenium, germanium or gallium based solar battery wafer) transport, described delivery system comprises two or more continuous loops that transport element that are spaced laterally apart, the described element that transports is included in narrow " band " of width on each side of wafer process travel path, described light with load capacity, diameter is little, the refractory tube of non-rotating, described refractory tube is to be suspended on to tie up on the wire between the described band.Described refractory tube is thin-walled, hard pottery or vitreous material, is preferably at least one that is selected from aluminum oxide, silicon-dioxide, the zirconium white.

Implement delivery system " band " with many example embodiment, first is the metal that is spaced laterally apart, Flat belt or the belt of horizontal orientation, and each band has a plurality of vertically extending supports, and described support vertically separates along band.Described rack bearing wire is installed with refractory tube on the described wire.Described wire is striden the horizontal expansion of wafer row inbound path between the support that mates is to (each is with a upper support).In the preferred embodiment, each band is the roller chain before the second project, and for example, firm bicycle type chain, this chain have hollow tube rather than solid Chain element.The refractory tube suspension wire is passed the chain pipe joint, and described end support wiry is in described chain pipe joint.In two embodiment, by the drive system hereinafter described in detail to transporting element or " band " carries out synchronized drive.The mobile wire that keeps can keeping synchronously having carried refractory tube that makes described band is parallel to each other and be straight, that is, and and with the wafer direct of travel quadrature along machining path.Can use suitable alignment roller or introducer.

Importantly, there is a significant advantage in ultralow mass transport device of the present invention system,, does not need to use the handling machinery support bar that is, therefore basically can not cover bottom wafer surface, this just makes in the situation that travelling speed is higher or furnace length is shorter carries out effectively altogether diffusion and become possibility.

In two embodiment, make wafer pass successively some zones of diffusion furnace, be positioned at simultaneously on the isolated annular ledge of refractory tube, this causes of reduced contamination.Described bearing can have the configuration of multiple exterior contour, for example, and combinations conical, circular (annular), vertical sharp-edged, inclination, double cone shape, square top, fin, rib and these shapes etc.Refractory materials preferably is selected from pyroceramic or vitreous material, described material can accurately configure by casting, dry-pressing, extruding or mechanical workout, and at least a in preferably comprise silicon-dioxide (comprising silica glass), aluminum oxide and the zirconium white.

The configuration in rising zone and/or roasting zone is unimportant to equipment of the present invention or working method, and IR lamp or resistance heating element have multiple arrangement.For example, in first embodiment, in the situation of the width of stove narrow (delivery system is narrow), or in the situation that the end face phosphorus doping is only arranged, can in all zones, use HI-IR radiation flux lamp to implement all heating.In these process application, randomly use the HI-IR zone, described HI-IR adopts in the zone IR lamp isolation module to raise the temperature to preferred soaking temperature.In other embodiments, comprise rising (buffering) some zones regional and the soaking zone and can be independently IR lamp heating-type zone.

In second embodiment; in the situation of the processing route at stove wide (delivery system is about 1 to 2 meter wide); or (wherein temperature is higher than 950 ℃ in the technique of mixing with boron or with phosphorus being mixed in the front and with boron being mixed in the back side; for example; in 1000-1100 ℃ scope); the baking heat element can be the resistance radial pattern, for example SiC bar or coil tube type element, and described element randomly is contained in protectiveness silica tube or again radiation (opaque) the ceramic mould pipe.

In each disposition of heating component embodiment, but the Hybrid Heating element namely, can use the radiating element of independently IR lamp, HI-IR radiation flux isolation module and resistance heat radiation/again.For example, input (baffle plate) zone that raises can be independently IR lamp, then is a HI-IR flux isolation module of choosing wantonly, then is the radiating element of high temperature resistant radiation/again in the second roasting zone and the soaking zone.The soaking zone may only be the extension in roasting zone.Equally, the roasting zone may be the extension in buffering or the zone that raises.That is, the title in zone is not determinative, implements selection to type, position and the number of the element of delivery system above and below and is in order to realize required maturing temperature and machine process (phosphorous diffusion, boron diffusion or both).

In inferior quality delivery system of the present invention, wafer can not run into wire guipure or ceramic roller, but is supported on the ceramic support, does not therefore have metallic pollution, can not form focus in the wafer, and wafer can not be biased to a side or opposite side as in the conventional roller conveyor system.In addition, diffusion technique of the present invention is the technique that high-radiation flux drives, rather than technique heat conduction, that wavelength is grown.

In first chip conveying system embodiment, delivery system side band comprises vertical evenly spaced drive hole.Each band is configured to Infinite Loop, and described ring comprises and transports section (be used for travel forward, pass process zone) and return section.One or more pin driving roll at the exit end place by stove carries out synchronized drive to described band.

The normally resistant to elevated temperatures metal of described band, for example, a member of austenitic nickel-based superalloy series, suitable embodiment is nichrome, that is, and nickel/Chrome metal powder of 80/20.Other carrying material comprises titanium, Inco nickel (for example 600 type Inco nickels) or other superalloys.Described band slides in the passage that protection is being arranged on each side of stove zone, and passage component is made of aluminum oxide, silicon-dioxide, quartz or other high temperature low-frictional force stupaliths, so that the heating of described band is reduced to minimum.Randomly by ambient air or cooled pressurized air are mapped to described bringing up described band is cooled off.

Transport among the embodiment at second, use roller chain rather than described band, and do not need vertical support frame.On the contrary, each end of suspension wire is installed in the tubular sleeve pivotal parts of side chain link.Each side chain in low-frictional force high temperature ceramic material slide block groove or passage in slide, perhaps straddle on the guiding ridge on the described slide block, and serve as introducer, the linearity that is used for keeping chain is followed the tracks of and proper alignment.The chain wheel drive system (two drive sprockets that are spaced laterally apart on the same drive shaft) of the outlet by being positioned at diffusion furnace or inlet end below drives described chain.Be positioned in chain wheel drive in the situation below the inlet end of return path, to the steel loose pulley sprocket wheel of changed course usefulness or there is the wheel of flange suitably to locate, obtain the tractive drive system.At the front end of stove, the second changed course loose pulley that is spaced laterally apart upwards forwards on the entrance loose pulley chain to, and described entrance loose pulley is got back on the processing route chain changed course, thereby forms the loop.Use suitable changed course loose pulley and/or roller, randomly described driving is positioned between the inlet end of stove and the exit end Anywhere.Can in the cooling section of stove and/or on return path, cool off described chain, preferably cool off by induction ventilation air or pressurized air.

About high strength IR flux heating unit embodiment (use in the downstream in buffering and/or the zone that raises), the HI-IR zone makes temperature quick (approximately in 2 seconds) be elevated to the diffusion technique setting point, described diffusion technique setting point approximately 700 ℃ in about 950 ℃ scope, by with high strength short wavelength IR radiation flux the wafer surface that scribbles doping agent being shone the light adjusting is carried out on described surface simultaneously, so that velocity of diffusion is faster.Compare with long wavelength radiation technique, the long IR radiation flux of this embodiment radiothermy in diffusion technique, this causes throughput double or larger so that diffusion has been shortened half or morely process period.As an example, in operation, stove of the present invention can be finished diffusion processing in 6 minutes, and the speed of current common process is 12 to 14 minutes.Therefore, throughput is double or larger.In addition, the resistivity of battery p-n junction layer is not only more even on the wafer and be consistent in different chips, and in " optimum point " between the 45-100 ohm-sq centimetre.

An importance of rapid diffusion technique of the present invention is, in the situation that use the IR lamp, described IR lamp is substantially to be higher than operation (percentage ratio of maximum lamp rated output) under the power of conventional oven.In first embodiment, controller uses the algorithm take experience as the basis to be adjusted in each zone and the power of the lamp of top and bottom, described adjustment be according to default temperature required, only undertaken by voltage control.In second embodiment, monitor the temperature in the zone of each correspondence by thermopair, and adjust the voltage of lamp by the feedback loop control algolithm.In addition, monitoring voltage can not supplied excessive voltage to lamp to guarantee in the situation that thermopair loses efficacy.

Therefore in the static rotating roller stove of routine, lamp operates under the power of 5-20%, and the characteristics of described lamp are: regulate if do not carry out effective light, flux is lower and wavelength is longer so.

In the metal mesh belt stove of routine, subject matter is the metal ion pollution of wafer, and this is because wafer is located immediately on the wire netting or is arranged on the metal " point " that is incorporated into band.Even used ceramic ball coating at metal mesh belt, the metal ion cloud still can overflow from the net metal of described band, thereby the chemical property of solar cell layer is caused disadvantageous effect.Attempted being coated with the bottom of phosphorus dopant to wafer, to reduce the metallic pollution from metal mesh belt.Yet this causes forming the p-n junction layer in the bottom of wafer.This needs again extra processing step to etch away described bottom p-n junction layer.The normally batch treatment of described etching step, this will be with the extra time, thereby slowed down production rate.

Inferior quality vitrified pipe delivery system of the present invention is processed and is solved these problems.The first, metal transports the side that assembly (band or chain) is placed on the stove zone, and these arrangement of components become not to be subjected to element radiation [heat], and this has prolonged assembly life-span.The second, the transverse wire that transports usefulness protects fully in the inferior quality vitrified pipe, and described vitrified pipe is the non-rotating ceramic supporting element minimum with contacting of wafer.There are rotating band or the chain member of protection to guarantee the atmosphere of cleaning in conjunction with the wafer support wire that is protected by vitrified pipe, thereby make the roasting zone not have in fact metal ion pollution.The 3rd, vitrified pipe generally quality is more much lower than roller, although and right and wrong revolving, but movable, namely mobile in stove and outside stove, therefore do not have large static heat quality, large static heat quality required power reduction.In addition, because vitrified pipe is suspended on the wire, so if vitrified pipe vertically splits, vitrified pipe remains on the wire and do not need to make immediately stove to stop in order to change so.Compare, in the solid roll stove, when roller breakage, stove is stopped.At last, wafer does not contact with vitrified pipe, and above ceramic rib bearing was elevated to vitrified pipe, described bearing preferred disposition became only at edge's supporting wafers.

Contrast with the 5-20% operand power grade of the current available thermal diffusion furnace of above-mentioned routine, process implementing example of the present invention is used the IR lamp in 40-70% power or more high-power lower operation, consequently, lamp IR flux in the system of the present invention is higher in fact, and peak value remains in the short IR scope (being lower than approximately 1.4 microns), normally approximately 1.25 microns of IR wavelength peaks.4 to 5 times of being about in the above-mentioned conventional thermal diffusion furnace of the relative rate of flow that technique according to the present invention is produced by the IR lamp are large.Be enclosed in longitudinal electrical resistance heating unit in quartz, pottery or the stable SiC pipe by use, avoided the heat fade in two side drawing lines (for example, drawing lines 1 and 5).

As mentioned above, stove of the present invention raising or/and adopted the HI-IR lamp module in the HI-IR stove zone, randomly comprises the isolated form module in certain embodiments.Described module comprises the insulation reflector element with parallel horizontal (with the carriage direction crosscut) cooling/reverberator passage, and is placed in the middle in each in described passage of one or more IR lamp.Described passage is optionally covered by the transparent transmission window of IR, for example, and quartz, Vicor, Pyrex, Robax, other high temp glass, synthetic sapphire etc.Many IR of high strength lamp isolation module is arranged to face with each other and is spaced apart, a module is above stove handling machinery delivery system, and a module is randomly below described system, in order to define selected IR lamp heating-type technique roasting zone between described module, module lamp and cooling air channels and described zone isolation are opened.In the situation that use described window, described passage is preferably opened in its opposite end, discharges so that cooling draught enters.By manifold, introduce cooling gas at an end of each passage at least, and at the other end or in the centre at two ends cooling gas is discharged.

The transmittance plate window stops the lamp cooling air/gas of high pressure/high speed to enter and disturbs process island (delivery system of carrying silicon wafer passes described process island), and simultaneously permission is kept abundant cooling to lamp quartz and glass/quartz transmittance plate with a large amount of cooling gases.By isolation and cooling, the present invention allows the IR lamp in the housing deliquescing that usually can make lamp and becomes under the power grade of curved (this can reduction of service life) to operate.

In another embodiment, isolation module comprises the IR lamp that separates, and described IR lamp is with or without the passage reverberator, and the Robax type glass port that separates below described lamp is arranged, therefore, described window (above and below) comes the spatial separation of handling machinery (carrying described wafer) with lamp.

This isolation geometry adds the optional cooling to IR lamp of the present invention, and the power that allows lamp increases to the scope of 40-70% or higher from the current standard of the power density of 15-20%.In the situation of using 100 watts/inch conventional IR lamp, this cause raising and HI-IR roasting zone in rate of heating be increased to about 80-150 ℃/second from approximately 30 ℃/second (conventional oven).This makes rate of heating effectively increase 2 times to 4 times than the speed of conventional oven, and can not cause lamp to turn down, close or be out of shape.In addition, lamp isolation of the present invention/optional cooling system allows to increase the speed of handling machinery band.This causes output essence to increase, or allows to shorten the length (in the situation that output is identical) of stove, and this can reduce the footprint area of stove.

In order in the soaking zone, to keep high-throughput in order to carry out phosphorous diffusion by high lamp power density, to realize High-speed machining, remove heat from described zone.The cooling air stream direction in the soaking zone is from top to bottom, in order to suppress particle deposition on the top surface of wafer and to remove described particulate.Therefore, contrast with the static ceramic rotating roller conveyor system of high quality (wherein working method can not remove heat from process zone), in system of the present invention and technique, removed heat, in order to can keep high power density and allow high-throughput, short wavelength's IR wafer light to regulate, thereby described technique is accelerated.As if although removing of heat is perverse, high-throughput, short wavelength's IR has not only compensated removing of heat.

The power of heating unit (no matter be IR lamp or resistance (SiC) radiating element, top or bottom) is carried out independence adjust or adjust by group, control in each zone, to realize accurate thermograde.Can use take temperature regulation, voltage type power regulation or the hybrid system of thermopair as the basis, adopt aforesaid PID controller to realize temperature control.The power regulation of lamp is voltage type preferably, because this allows to be convenient to keep stable lamp power, to obtain preferred high IR intensity (radiation flux) value and always constant spectrum output.In addition, make lamp operation under high power density more increase the IR flux, and better spectral range is provided, its peak value is in the appropriate location.

About utilizing the common diffusion technique of delivery system of the present invention, exemplary process line is carried out following configuration: 1) with chip oriented one-tenth basal surface facing up; 2) boron dope agent is coated on the basal surface facing up of wafer and makes wafer dry; 3) wafer is carried out upside-down mounting (for example, with rotary upside-down mounting device), so that the top surface of wafer now facing up; 4) phosphorus dopant is coated on the top surface of wafer and makes wafer dry; 5) with the wafer transmission behind the codoped in diffusion furnace of the present invention; 6) disposable in stove wafer is carried out concurrent roasting, make the wafer cooling and it is transferred to ARC, slurry silk screen printing, drying and the metallization operations in downstream.Because inferior quality delivery system of the present invention does not obviously cover the bottom surface of wafer, so the bottom surface obtains suitable roasting, therefore boron diffusion occurs, in order to form subsequently back contact.

Transport the fail safe system: as an option of stove; the Lower Half of stove can possess sagging drift stop subassembly; in order to prevent from having carried suspension wire or bar excessive sag when losing efficacy of vitrified pipe and bearing; for example, this inefficacy is to elongate owing to the wire fracture or under the effect of stress or heat to cause.In present preferred embodiment, sagging drift stop subassembly comprises slider part, for example, is selected from silica tube, bar or band, described slider part and handling machinery transport the medullary ray parallel aligned in path, and described medullary ray is consistent with the longitudinal cenlerline of stove heating region.The sidewall of drift stop slider part and furnace chamber is spaced apart certain distance inwardly, and this distance makes described drift stop slider part align with the travel path of bearing and be spaced apart below described travel path.The vertical end of each of drift stop slider part is installed in the transverse wall in (for example) stove roasting zone, and like this, the top of slider part is in the over top of transverse wall.Therefore, if transport wire and the pipe subassembly is sagging, during this time, bearing can contact with slider part, along with the carrying out that transports slides along slider part, and jumps out the transverse wall of stove, and can sagging and fracture, or damages in addition delivery system.For example, the interval between the bottom of the top of drift stop slider part and bearing is about 1 to 2 centimetre.In addition, because drift stop slider part and bearing path are spaced apart alignedly, so the drift stop slider part can not cover wafer, but separate with the side of wafer.

The sidewall heating of outside drawing lines:

In at present preferred heating system, in the heating region of top, use transversal orientation formula IR lamp, and in the heating region of bottom, use the combination of IR lamp and resistive heating.In order to improve the Transverse Heated homogeneity of crossing over the stove width, resistance heater is placed on and two longitudinal side wall adjacents, described sidewall is oriented to be parallel with the medullary ray of stove and separates with described medullary ray, and the IR lamp laterally is placed on above or below the longitudinal side wall resistance heating element, be preferably the below.The longitudinal side wall resistance heater is arranged in silica tube, vitrified pipe or the stable SiC pipe, and described pipe is arranged near the handling machinery below.In 5 drawing lines or wider stove, described well heater is in order to keep the wafer in the

drawing lines

The sidewall well heater is in order to the furnace temperature of finishing with the sidewall adjacent, and this is because for preventing that lamp is burnt, IR lamp heating unit has not also just stopped to sidewall.If IR lamp heating unit extends in the lateral wall insulation thing, insulant can cause the local temperature of lamp to surpass the safety operation value so.Resistor-type longitudinal side wall well heater can be not luminous as main transversal I R lamp, but under the lower-wattage grade, operate to adjust the temperature of sidewall near zone, namely, lip temperature, make described temperature enough high, to compensate the power that loses in the lamp end and to pass the lateral wall insulation thing to any loss of stove outside.

Because the operation of lower-wattage, described vertical well heater can be placed on the horizontal plane top of main IR lamp and near sidewall, the interval is generally approximately 1 to 5 centimetre.In the situation that diffusion furnace uses inferior quality delivery system of the present invention, described vertical well heater also can be placed on the summary below on handling machinery plane, and approximately the horizontal plane than vitrified pipe hangs down 1 to 3 centimetre, and described vitrified pipe comprises the chip conveying support component.

Exemplary sidewall heating unit comprises the coil pipe resistance heating element, and described coil pipe resistance heating element is enclosed in the Inco nickel sheath and passes through MgO powder and described jacket insulation.Described element is inserted in transparent, the translucent or opaque silica tube of possibility subsequently; Because described element may not need in visible spectrum or near " luminous " (this depends on required output rating), so carrying pipe transparency is unimportant.In addition, an important safety using the carrying pipe to provide is characterised in that, described pipe serves as electric guard shield or isolator in order to avoid get an electric shock.Can use the heating unit of other types as the longitudinal side wall heating unit, described element comprises that to be incorporated into the power of carrying in the pipe be 1 to 3 kilowatt simple nichrome wire air-coil.Can control described sidewall heating unit by standard SCR controller.

Description of drawings

Fig. 1 is the schematic diagram of first embodiment of diffusion furnace of the present invention, has illustrated entrance transitional region, baffle area or/and roasting zone, at least one soaking zone, cooled region and the inferior quality transfer system that raises the zone, chooses wantonly with side-view;

Fig. 2 is the isometric view of inferior quality delivery system of the present invention (transporting for banding pattern in this embodiment), described delivery system is installed in some heating regions of diffusion furnace, wherein the front inlet end of stove has also illustrated the wafer on the alumina-supported pipe on the right side among the figure;

Fig. 3 A is that the band among Fig. 2 transports the equidistant enlarged view of embodiment in the regional HI-IR lamp zone with choosing wantonly of inlet baffle, is depicted as and passes described stove transporting two exemplary wafer;

Fig. 3 B is the isometric view of looking up of compresses lower section, is depicted as the exhaust manifold for the soaking zone;

Fig. 4 A is the amplification isometric view that transports from the band that Fig. 3 A decomposes out, is used for illustrating details;

Fig. 4 B transports the rack assembly of embodiment and the amplification isometric view of the most advanced and sophisticated retainer of bent wire for band;

Fig. 5 is the schematic side view of stove of the present invention, and the below is the temperature that forms in the respective regions graph outline to the time;

Fig. 6 has illustrated that with figure spectrum output is the key of the speed of IR lamp heating-type diffusion technique, wherein Fig. 6 A illustrates the spectrum output of inferior quality delivery system of the present invention to wavelength with relative intensity, and Fig. 6 B illustrates the contrastive spectrum output of high quality solid ceramic roller system to wavelength with identical relative intensity;

Fig. 7 is the schematic diagram of second embodiment of diffusion furnace of the present invention, is depicted as some process zones and chain drive-type chip conveying system;

Fig. 8 is the equidistant enlarged view of the chain delivery system in the stove process zone, is depicted as two exemplary wafer and passes transporting of described stove;

Fig. 9 is the amplification isometric view that chain drives details, is depicted as suspension wire and vitrified pipe and how is installed in the hollow chain pipe;

Figure 10 A is the vertical cross section that passes the line 10A/B-10A/B of Fig. 9, is depicted as first embodiment of the slider plate introducer that drives for chain, is passage in this embodiment;

Figure 10 B is the vertical cross section that passes the line 10A/B-10A/B of Fig. 9, is depicted as second embodiment of the slider plate introducer that drives for chain, is rib in this embodiment;

Figure 11 A is the vertical cross section that passes suspension wire and alumina tube, is depicted as the 3rd embodiment of wafer support;

Figure 11 B is the vertical cross section that passes suspension wire and alumina tube, is depicted as the 4th embodiment of wafer support configuration;

Figure 12 A is horizontal front view, be depicted as sagging drift stop slider part with respect to transport vitrified pipe, locus and the arrangement of bearing and groups of metal filaments component;

Figure 12 B is the isometric view of diffusion furnace bottom section of the present invention, and described diffusion furnace bottom section is equipped with a pair of sagging drift stop slide block;

Figure 13 is for making boron and phosphorus be diffused into altogether the schematic diagram of the process production line of wafer, and this altogether diffusion is the part that silicon wafer is processed into solar cell;

Figure 14 is the horizontal schematic diagram that adopts conveyor system of the present invention and adopt the stove of longitudinal side wall resistance heater in the bottom action of soaking zone;

Figure 15 is the alternative illustrative examples that adopts the stove of the present invention of longitudinal side wall well heater in top and lower region; And

Figure 16 is the isometric view of furnace system of the present invention, is depicted as in exemplary soaking zone the longitudinal side wall well heater is placed on above the IR lamp.

Embodiment

The following specifically describes the present invention has been described as an example, rather than as the restriction to scope of the present invention, equivalent or principle.This description will clearly make the those skilled in the art can carry out and use the present invention, and described some embodiment of the present invention, adaptation form, version, alternative form and purposes, wherein comprised the situation that is considered at present commercial embodiment.

Fig. 1 is the schematic diagram of diffusion furnace 10 of the present invention, diffusion furnace 10 comprises framework and shell 12, it has compresses lower section 14 and top section 16, framework 12 randomly disposes the linear brake lifters (referring to Fig. 2 and Fig. 3) that separates along the outside, be used for making top section 16 to raise with respect to compresses lower section, in order to allow lamp/subassembly and delivery system keeped in repair.Stove 10 comprises following a plurality of section or zone, from entrance or front end 18(in this drawing, and the left side) to outlet or rear (downstream) end 20(right side), be followed successively by:

IT, that is, and from the entrance transmission ends 18 of the doping agent applicator unit (not shown) of upstream;

B-1, that is, the inlet baffle zone, it uses one or more pressurized air cutter subassembly 22; The B-l zone randomly comprises the zone that raises, and one or more heating unit (not shown) is contained in the rising zone, is used for making chip temperature to be elevated to approximately 500 ℃ from envrionment temperature;

FZ, that is, initial roasting zone is used for making chip temperature be elevated to diffusion temperature, diffusion temperature approximately 900 ℃ in about 1100 ℃ scope, this depends on that spread is phosphorus, boron or both; FZ can further be subdivided into two or more zones, for example;

HI-IR zone, that is, high strength IR lamp array is preferably top or/and lower isolation reflector lamp subassembly 24-U, 24-L, is used for obtaining up to about 950 ℃ temperature then being;

HTZ, that is, high-temperature area heats it with resistance radiation (SiC) element 27, is used for obtaining the temperature up to 1100 ℃, and this depends on that spread is phosphorus, boron or both;

S, that is, the soaking zone has the upper and lower IR lamp or resistance element 26-U, the 26-L that separate;

B-2, that is, the outlet damper zone has air knife subassembly 22;

C, that is, cooled region does not have resistance element or IR lamp usually; And

OT, namely, the outlet transmission region, be used for spread wafer transmission after the roasting to for the processing units that carries out silk screen printing, then described processing units silk screen printing collector electrode finger piece and bus and go up overleaf silk screen printing back contact (not shown) on the front carry out roasting to form ohmic contact.The outlet transmission region optionally comprises the top adjacent with outlet of still (right side) or/and bottom air knife subassembly.

The upstream and downstream of stove of the present invention is low temperature transport tape 28-U(upstream) and the 28-D(downstream), described band is connected to anti-reflecting layer applicator, screen process press, then is the metallization stove.These low temperature transport tapes 28-U is connected with the drive system 30 of stove 10 of the present invention with 28-D.

In first embodiment, the inferior quality drive system 30 of stove of the present invention comprises: pin driving roll 32(drives by the electric motor 34 of the outlet that is arranged in stove (right side) end and chain or with 36), chip conveying band subassembly 38, idle roll 40 and the tension system 44 that comprises tensioning roller 42.Tension system 44 comprises the automatic tension loop expansion pipe spring that serves as snubber, is used for helping prevent getting loose.It should be noted that by this to drive geometry, haul along feed path F from left to right and be with 38 to pass regional.

Stove of the present invention comprises: a plurality of high-tension rooms, and it has defined the intra-zone of shell 12; And a plurality of air manifolds, it comprises entrance and venting port, is used for environment or forced air are flow to into regional, such as arrow I(entrance) and the E(venting port) shown in, in order in each zone, keep suitable temperature.In addition, in the situation that isolation lamp/subassembly 24-U and 24-L(are using) the passage of reflector body in forced air is provided so that be arranged in the lamp cooling in the described passage.The surface of each among high-intensity lamp subassembly 24-U and the 24-L is covered by a slice vitreous silica, so that sealing reverberator passage separates itself and the wafer of just accepting the light adjusting in the HI-IR zone.The cooling of this lamp allows lamp approximately moving under 60% to 100% the peak power, and this is far above present available competitive unit.This provides immediately heat rising and high strength IR irradiation to wafer, is elevated to 700 ℃ of diffuse of peak values to 950 ℃ (phosphorous diffusions) from envrionment temperature and regulates temperature, and the high-strength light adjusting is provided.

The yardstick of Fig. 1 be so that can't illustrate in each position solid thermal insulating material 46, but those skilled in the art will appreciate that, shell comprises necessary insulating material configuration block.Randomly provide and pass insulant and enter air inversion (being illustrated by arrow 48) in the zone, described air inversion is opposite with hot-fluid.From the insulant extract heat and heat is recycled to the zone, this is the very high heat exchange operation of efficient to air when entering.It should be noted that lamp 26-U and 26-L or resistance element 27 are illustrated into staggered, in order to uniform heating and/or IR photon field to be provided; Randomly lamp 26-U and 26-L or resistance element 27 cannot be arranged to staggeredly.

Forward now inferior quality delivery system 30 to, Fig. 2 illustrates stove 12 with isometric view, has wherein removed exterior panel and insulant in order to illustrate the framework of compresses lower section 14, and described compresses lower section 14 has inlet end 18(lower right) and exit end 20(upper left side).For the sake of clarity, do not illustrate entrance and exit transport tape 28-U and 28-D.Four angles at the siding track 52 of stove have illustrated carriage and riser 50; These carriages and riser 50 are in order to show from compresses lower section 14(figure) to promote top section 16(not shown in the figures) to part (for example, lamp, resistance heating element, delivery system element etc.) check, adjustment, maintenance and repair/replacing.Compresses lower section 14 comprises siding track 52, lateral wall insulation piece 46-S and insulant interior region block 54.For the details of mictium 38 not, do not illustrate the collets in the place ahead, described collets are positioned at the front end of baffle area B-1 and B-1 and high strength IR zone HI-IR is separated, and the rear end that is positioned at cooled region C.

Collets 56 form the bottom in some zones.These bottom collets 56 have the aperture usually, are slit 88 herein, and these apertures add that the high-tension room (not shown) of bottom below allows to extract the waste gas of heat out with ID fan (not shown).This airflow has removed heat from regional, thereby allows the operation of element (lamp, SiC bar or coil pipe) to produce higher output, and allows to extract pollutent out, because airflow is from top to bottom.This hot gas/airflow pattern causes the pollutant level in stove zone to reduce, and therefore causes product cleaner.

Illustrated aperture 58 among the lateral wall insulation piece 46-S of siding track 52 in the presence of and far-end, described aperture 58 be for resistance element 27 is installed or/and high strength fluorescent tube 26(for clarity sake, only illustrated in every kind of element) and be used for connecting electrical lead, described element/lamp is across the width in stove zone.The delivery air chamber 60 that is used for high strength IR lamp zone, bottom 24-L by circuit 62 with compressed air-feed to the ring between reverberator passage and the lamp, and on demand below be discharged to the outside, or be discharged in the adjacent soaking zone, downstream.

For clarity sake, only illustrated the part of inferior quality active transmission band system 30 at right-hand member.Pin rodent in the idle roll that separates 40 of side band 38 and drive system 30 closes.Only can see idle roll 40 and driving roll thereunder 32 in cooled region C inside.Illustrated two wafer W-l and W-2 at inlet end (right side), described wafer is placed on the lateral oxidation aluminum pipe 64, is positioned at transmission and passes on the position of stove.

Fig. 3 A is the amplification isometric view of inlet end 18 of the stove 10 of Fig. 2, is depicted as the part with delivery system 30 of two wafer W-l of carrying and W-2.What two of delivery system 30 separated is with 38 to be arranged in the U-shaped passage 66, and described U-shaped passage 66 is formed in the top of left and right side wall collets 46-S.Each band comprises the hole 68 that accurately separates, pin 90 engagements of described hole 68 and idle roll 40.The support 70 of erectting also separates regularly along described band, described support 70 bearing metal silks 72, and vitrified pipe 64 is placed on the described wire 72.Exemplary wire is that diameter is 0.080 " nichrome.Bearing 84(is ring herein in this embodiment) be arranged on, be installed on the pipe 64, or be formed in the pipe 64, and be spaced laterally apart along described pipe.In transporting the process of passing stove 10, wafer is positioned on the seat rings, like this, wafer back surface with transport contacting seldom between the subassembly element, referring to the footprint area 96 among Fig. 4 A.

In the situation that pipe 64 fractures or split, wire 72 can holding tubes 64, until replace tubes 64 more.Because the hole 68 in the band is demarcated with the pin 90 in the roller (driving roll and idle roll), the support of each band moves by the relation of parallel aligned, so alumina tube keeps supplying with direct of travel (as shown by arrow F) crosscut with wafer.

Fig. 3 B is the below isometric view of the compresses lower section 12 of stove, for clarity sake, has removed framework.Bottom collets 56 are across side frame 52, and described bottom collets 56 have air vent channels 88(Fig. 3 A and can find out).Steel plate 100 comes with the bottom interval of collets 56, and this is spaced apart warm air the collector high-tension room is provided.Exhaust manifold subassembly 102 is connected to described high-tension room (spaces between 56 and 100) by the collar 104 on the end of transverse tube 106.The other end of transverse tube is connected to collector pipeline 108, and described pipeline 108 gives off hot gas from vapor pipe or flue tube 110.

Fig. 4 A has illustrated inferior quality delivery system 30 with isometric view, and U-shaped combination of channels part 74, and this embodiment is with 38 to move in described U-shaped combination of channels part 74.Fig. 4 B is the feature of the single-side stand subassembly of Fig. 4 A.

Each is with 38 to be supported on the quartzy slider part 74, and the cross section of described slider part 74 is U-shapeds and has shorter vertical side wall.Pair of holders tape member 76 is adhered on the top of U-shaped arm with the pyroceramic clay, described retainer tape member 76 is to be made by quartz, aluminum oxide or other high temperature fiber type stupaliths, so fully overlapping in order to remain on band in the passage and protect described band by physical means, making it can not touch heating unit, is cold thereby keep described band.Randomly environment for use compression ambient air cools off described band.

Support 70 comprises the vertical leg 80 that is fastened on the vertical salient 78, and described salient 78 is by to bring eleven punch 11 92 into formed from described.Leg 80 and salient 78 can tighten together by any appropriate ways, for example, by spot welding, by the alignment salient and leg hole 94 rivet or use screw fastening.The upper end of rack leg 80 is with one or more auricle 82, and each auricle has a hole, and refractory metal silk or bar 72 are inserted in the described hole.Alumina tube 64 is in described wire slip and by described wire carrying.Each pipe randomly comprises a plurality of support parts that are spaced laterally apart 84, is ring herein, and wafer is positioned on the support part 84, shown in the footprint area 96 among Fig. 4 A.

Seat rings 84 can have multiple cross-sectional configuration, and scope is: simple flat surfaces annulus (as shown in Fig. 4 A) is to the gradual shrinkage profile, and for example, cross-sectional profiles is the profile of bell-shaped curve shape.Various profiles are referring to Figure 10 A, Figure 10 B, Figure 11 A and Figure 11 B.It should be noted that in Fig. 4 B, the bent tip 86 of wire 72 is contained between two auricles, thus the locking wire, and to prevent transverse shifting wiry, this transverse shifting can cause the other end (right side) to fall down from the auricle of right side support.It should be noted that in Fig. 4 A, right side wiry has fully extended through the outside auricle of its corresponding support.Use has free-ended wire and can allow wire length to enlarge and shortening, and can not fall down in the hole from auricle.

The key character of the band of delivery system of the present invention and chain embodiment is its ultralow quality, easily installs, easily keeps clean, the point of contact when transporting wafer and pass stove on the wafer seldom, and easily safeguard.As shown in Fig. 4 A; because there are so many fully closely wires at interval to come to provide support for wafer; so damaged pipe and/or wire usually can be waited until when the shut-down of mapping out and be changed, because lose a pipe or wire can not have a strong impact on production throughput.

In stove embodiment of the present invention, (in several seconds) are heated to wafer in the diffusion temperature scope or near the diffusion temperature scope as quick as thought, in described embodiment, using high strength IR lamp or isolation module with the entrance adjacent or the downstream that are right after at stove of the present invention.With high strength short wavelength IR quantity of radiant energy wafer is carried out light and regulate, described quantity of radiant energy is about 4 to 5 times of present roller stove greatly or is larger, and therefore the diffusion speed of carrying out is faster.As an example, in stove of the present invention, temperature reached diffusion temperature in several seconds.The more important thing is, by in the HI-IR zone, using isolation module, and owing to can under high voltage, give described HI-IR zone and the element power supply of soaking zone, IR flux in technological process is higher, and finish diffusion being less than in 6 to 8 minutes, this time span is 1/2nd to 1/3rd of present system.

Fig. 5 and Fig. 6 illustrate these principles.The top part of Fig. 5 has schematically illustrated stove of the present invention with side-view, and the below is the temperature that forms in the respective regions graph outline to the time; Dashed curve P is when only carrying out phosphorous diffusion by the heating of IR lamp in the front in order to forming the p-n junction layer, the temperature profile in the stove of the present invention.Solid-line curve shows, the carrying out temperature and will exceed approximately 200 ℃ of the boron diffusion of carrying out in order to form back contact in the stove of the present invention, and need heat at least some zones with resistance element (the SiC bar that for example discloses).It should be noted that the IR lamp of stove of the present invention or the extremely steep profile that resistance element produces, this can make wafer reach fast the technological temperature of phosphorus (and/or boron) diffusion.That uses the heating of IR lamp shows the phosphorous diffusion curve of following substantially dotted outline at commercially available contrastive solid ceramic roller stove, is designated as " P.A. " (prior art) at figure.Because roller has been hot, so lamp is adjusted under lower-wattage operation (referring to Fig. 6 B, the below) automatically, therefore cause the temperature profile slope in fact and obviously lower, and it is longer to reach time of temperature, has grown approximately several minutes in stove.The most important aspect of the graphic representation of this Fig. 5 is, when using stove of the present invention, finish the speed faster in fact (point on the ordinate zou " D terminal point ") of diffusion, wafer is proceeded cooling and is transferred to silk screen printing (point " XFER " on the ordinate zou).

Compare, contrastive prior art phosphoric diffusion technology (dotted line among Fig. 5) is proceeded soaking under lower-wattage is set, and the time is much longer, points to shown in the right arrow on the dotted line as described.The common time spent of high strength IR radiation flux phosphoric diffusion technology of the present invention is 1/2 to 1/3 of the conventional thermal conduction process time.Therefore, throughput is higher in fact, and compares with the conventional oven that equates output (400 " long multiply by 36 " are wide), furnace volume much smaller (length is less than 300 ", and width is half).

Fig. 6 A and Fig. 6 B have illustrated that with figure spectrum output is the key of improving IR diffusion technique speed in light adjusting, rising and HI-IR zone.The spectrum output of lamp changes with the power of lamp, can be expressed as the percentage ratio of the maximum power capabilities of lamp.Fig. 6 A illustrates the spectrum curve of output of inferior quality delivery system of the present invention to wavelength with relative intensity.Upper curve is theoretical maximum T, has illustrated the IR peak value and be approximately 1.2 microns and relative intensity and be approximately 12.5.It should be noted that visible spectrum VS in the left side, with dashed lines illustrates.The lower curve that is designated as " the present invention " shows, in the of the present invention ultralow quality delivery system that uses the HI-IR lamp module, can use the modulating voltage Controlling System approximately operating the IR lamp under the 40-100% rated maximum (showing approximately 40-70% herein), and the maximum of intensity at peak value place is 8.

Compare, Fig. 6 B illustrates the contrastive spectrum output of high quality solid ceramic roller system to wavelength with identical relative intensity.In this contradistinction system that hot Monitoring and Controlling feedback system is moved with thermocouple type, lamp must approximately move under 20% the power.Yet relative intensity is index and reduces, and under about 1.8 peak strength, the peak value that is designated as " PA " is displaced to more close 1.75 microns, and this radiation flux is below 1/4th of technique of the present invention.In the conventional system, be displaced to longer wavelength, lower energy spectrum profile is also very important.

Therefore, in system of the present invention, lamp can be in more high-power lower operation, thereby causes relative intensity to increase to 4 to 5 times.The IR intensity that is applied to quickly this increase on the wafer is regulated wafer, to promote phosphorus or/and boron is diffused in the advanced wafer material quickly, ties accordingly and back contact thereby form.Therefore, in system of the present invention, the higher and sufficiently long of holding time of IR intensity is in order to process faster.

Fig. 7 relates to second embodiment of ultralow quality delivery system of the present invention to Figure 10 B, this embodiment adopts a pair of chain that separates, and wafer support wire and vitrified pipe hang from described chain.Among Fig. 7, the description of above Fig. 1 being carried out is applicable to number identical part.It should be noted that IT and B1 zone are combined into the zone that raises in this embodiment, in described rising zone, make chip temperature be elevated to approximately 500 ℃ to 900 ℃ from room temperature, in the situation that rising district inclusion HI-IR isolation lamp module is 900 ℃.Be roasting zone after this, described roasting zone raises the temperature to approximately 950-1100 ℃ of diffusion processing temperature, and this depends on that what spread is phosphorus or boron, or both.As shown in the figure, the exemplary resistance SiC element that discloses is adopted in the roasting zone.In the soaking zone, keep the roasting set point temperatures, chaotic for preventing making figure, do not illustrate heating unit, but see also Fig. 1 and Fig. 5.As shown in the figure, cooled region is divided into two sub regions CZ-1 and CZ-2, but CZ-2 can be externally.

In Fig. 7 and Fig. 8, transport by roller chain 112, provide the sprocket wheel 114 of power that roller chain 112 is moved by electric motor 34, described electric motor 34 is positioned at the exit end below of stove 20.Loose pulley (being sprocket wheel or flanged the wheel in this case) 40A-40C is arranged in the upstream of entrance, exit and return path R, with so that shown in chain in the driving ring change direction.The spring offset tension force and the loose pulley system 44 that are arranged in driving mechanism 30 downstreams provide suitable tension force.Being provided with deflector roll 116 and slideway piece 74 along chain link, is straight in order to keep described path.Air knife 22 provides cooled compressed air to described chain in cooled region or outside the cooled region.In addition, pipe water cooler 118 can be set in returning section, be used for described chain is further cooled off.

Figure 8 shows that two chain 112-L(left sides that separate) and the 112-R(right side) how to be supported in the groove or passage 120 in the slide block 74.The transverse wire 72 that supports vitrified pipe 64 has end 122, and described terminal 122 pass tubulose chain link sleeve pipe 124.Wire 72 separates approximately 1 " (2.5 centimetres).

Fig. 9 is the enlarged view that shows the alternately property chain link installation of wire 72.Middle chain link has solid pintle 126.All be covered with among chain link roller 128(Fig. 9 on chain link sleeve pipe 124 and the pintle 126 and do not show; Being shown among Figure 10 A and Figure 10 B) free end 122 wiry ends in the fastening piece 130,140 of the type of pushing away or screw-type nut or other types, to prevent described wire from sleeve pipe 124, fall down (referring to Figure 10 A, 10B).

Figure 10 A and Figure 10 B illustrate two embodiment of slider plate 74.Among Figure 10 A, slider plate comprises groove or passage 120, and chain 112 is supported in described groove or the passage 120.The free end 122 of wire 72 has screw thread, is used for receiving lock nut 130.Shown optional spacing washer 132.Bearing 84 has the inverted-V-shaped periphery, so wafer support is on circumferential ridge 134.Among Figure 10 B, slider plate 74 comprises the ridge 136 that can have various configurations, and described configuration comprises linear pattern or shaped form (inclination) sidewall.The side chain link of chain 112 straddles on ridge 136 and by ridge 136 and guides.In this embodiment, slider plate 74 does not have outer lateral mass 138 usually, and described plate is smooth in the both sides of described ridge, as has defined shown in the dotted line of side piece 138.In addition, the tip 122 of wire 72 ends in the type of lid or pushes away type nut 140.In this embodiment, the profile of bearing is the gradual shrinkage top, and cross section is half-sine wave.

Figure 11 A and Figure 11 B are depicted as two other embodiment of bearing 84, and Figure 11 A is depicted as asymmetric fin-shaped bearing, and described bearing has outside surface (right side of ridge 134) and the side surface vertical or that tilt of inclination.Figure 11 B is depicted as the embodiment of the current best form of bearing, that is, the both sides gradual shrinkage is conical, randomly has 134, two tapered side of circumferential rib to converge at place, described summit at the place, summit.Described rib or long inclined-plane all provide support wafer product, as respectively by shown in the position of wafer W-1 and W-2, this depend on bearing 84 along the interval of pipe 64 width than (wafer) product.Very large such as fruit product, basal surface is positioned on the described rib so, shown in wafer W-l (also referring to 96 among Fig. 4 A), and does not have shown in the wafer W-2 so widely such as fruit product, and so only the outside lower edge of product is positioned at (as shown in the figure) on the inclined-plane.This bearing is bonded on the vitrified pipe 64 rather than is integrally formed.The vertical height of bearing optionally changes, in order to adapt to various transporting and stove design and configuration.

Figure 12 A and Figure 12 B have illustrated the optional fail safe system that transports, and described system comprises the sagging drift stop that is arranged in side by side bearing travel path below.Figure 12 A is depicted as locus and the arrangement of the sagging drift stop slider part 144 that transports the subassembly below, and the described subassembly that transports comprises driving chain 112, vitrified pipe 64, bearing 84 and wire 72.

As shown in Figure 12 A, sagging drift stop subassembly 144 is in order to prevent from having carried suspension wire or bar 72 excessive sag when losing efficacy of vitrified pipe 64 and bearing 84, for example, this inefficacy is because wire ruptures under the effect of stress or heat or elongation causes.In exemplary embodiment, sagging drift stop comprises slider part 144, for example, is selected from silica tube, bar or band, handling machinery shown in described slider part 144 and the arrow F transports the medullary ray parallel aligned in path, and described medullary ray is consistent with the longitudinal cenlerline in stove roasting zone.Drift stop slider part 144 and inside spaced apart certain distance of the sidewall of furnace chamber, this distance makes described drift stop slider part 144 align with the travel path of selected bearing and is spaced apart below described travel path.In the vertical recess 146 of holding in the transverse wall 54 that is installed in stove roasting zone 23 of each of drift stop slider part, like this, the top of slider part is spaced apart in the over top of transverse wall 54.Therefore, if transport wire and the pipe subassembly is sagging, during this time, bearing 84 can contact with slider part, along with the carrying out that transports slides along slider part, and skips the transverse wall of stove, and can be not sagging and rupture, or damages in addition delivery system.For example, the interval between the bottom of the top of drift stop slider part 144 and bearing 134 is about 1 to 2 centimetre.In addition, because drift stop slider part and bearing path are spaced apart alignedly, so the drift stop slider part can not cover wafer (referring to wafer W-1 and the W-2 of Figure 11 B), but separate with the side of wafer.

Figure 12 A also shows, above each conveyer chain slider plate 74 in its insulative sidewall piece 46S, below or a side be provided with compressed air pipe 148, be used for providing to the bottom of slide block 74 cooling air and provide cooling air by the hole 150 in the slider plate 74 to driving chain 112.

Figure 12 B is depicted as the bottom section 14 that width is the exemplary diffusion furnace 10 of 5 drawing lines, described bottom section 14 is equipped with a pair of sagging drift stop slide block 144, each sagging drift stop slide block 144 and a series of bearings 84 and column alignment and spaced apart below described bearing 84.Can place lateral clearance protective shield 152 at the width of entrance end span stove, upwards then when horizontal product transports horizontal plane, to guarantee again any sagging gap wiry transporting to alter course into.

Figure 13 shows that process production line 154, it comprises the first doping device equipment Do-1, is used for mixing with the basal surface of boron doped compositions (arrow B) to the silicon wafer of preparation.After with boron wafer being mixed in Do-1 and making the wafer drying, the described wafer of counter-rotating in upside-down mounting device 158 is so that the top surface of wafer facing up.Then the supine wafer transmission in top after will reversing is to the second doping device equipment Do-2, phosphorus doping composition (arrow P) is applied on the top surface of wafer in this doping device equipment Do-2 and makes wafer dry.Then will carry out wafer transmission after the dual coating to diffusion furnace 10 of the present invention with boron/phosphorus, carry out such as common diffusion roasting mentioned above herein, in the cooling section of stove, cool off, and be transferred to antireflecting coating device A RC 158, in antireflecting coating device A RC 158, apply antireflecting coating by plasma enhanced chemical vapor deposition, for example SiN3.After applying ARC, wafer transmission is arrived printing station, in printing station, printing press/moisture eliminator equipment 160 is coated to silver-based paste " ink " on the top surface of mixing after phosphorus/diffusion and (only when needed, the aluminium base slurry of back contact is coated on the basal surface after boron-doping/diffusion with the form of the meticulous circuit that separates; The boron-doping basal surface does not need aluminium base back contact slurry usually).Then will " after the printing " wafer transmission to moisture eliminator 162, moisture eliminator 162 is burnt the organic binder bond in the slurry under being no more than approximately 600-650 ℃ of fixed temperature, as shown in the figure, give off VOC at 164 places, waste gas condensation is got off or in thermal oxidizer, burnout.With the printing after wafer transmission to the metallization stove 166 in, in metallization stove 166, wafer carried out roasting so that optionally back of the body contact slurry flow in the successive layers, and form the fine grid of ohm collector electrode in the front, described grid is burnt in the p-n junction layer, but does not pass the p-n junction layer.The battery 168 of gained is proceeded each cleaning, deburring and test procedure, then forms band and is assembled into array, so that the solar panel that lamination becomes to finish between each glass coating.

Figure 14 has illustrated the horizontal homogeneity that improves the heating in the regional (mainly being the soaking zone) with the longitudinal side wall well heater to Figure 16, so that at the corresponding drawing lines of the sidewall of close stove (for example, be in the stove of 5 drawing lines at width, drawing lines 1 and 5) wafer that transports in is in processing temperature, and this temperature is uniform at its width.Description to identical parts among Fig. 1 and Fig. 7 and zone is applicable to Figure 15.In this embodiment, the stove zone is the zone 19 that raises, and then is a plurality of soaking zone S 1, S2 ... then Sn is at least one cooled region CZ, and for example C1 is or/and C2.Lamp 26U in the described zone and 26L provide high IR flux to regulate and heat.The regional 19(upper and lower that raises is respectively 19U and 19L) make in wafer is elevated to approximately 500 ℃ to 700 ℃ or higher scope fast from envrionment temperature.The first soaking zone S1 makes front and back, end face and the bottom surface of wafer be elevated to required diffusion temperature, and described diffusion temperature is in the scope of approximately 950 ℃ (phosphorus doping is only arranged) to approximately 1100 ℃ (codopeds of phosphorus and boron).Remaining soaking zone S2-Sn keeps required diffusion processing set point temperatures.Then in one or more cooled region C1, C2 etc., wafer is cooled off.In this embodiment, in the Lower Half of regional S1, S2, and in regional C1 (when regional C1 was replaced by soaking zone Sn, Sn was S3 in this embodiment), above lamp, arrange sidewall well heater 170.

Figure 15 shows that and in top and lower region, use sidewall well heater 170U and 170L.In this embodiment, in rising zone, bottom, use sidewall well heater 170L.In all shown soaking zones, use well heater.

Figure 16 shows that 3 line tunnel-types, described stove is transfer wafers W-1, W-2 and W-3 on direction F.Identical among remaining parts numbering and Fig. 3 A.In the soaking zone, be respectively applied to right and left side wall two

sidewall well heater

170R, 170L is shown as with its

sidewall

46R and 46L is adjacent and above transverse lower portion lamp 26L.Described sidewall well heater optionally extends in raise zone 19 or the optional roasting zone.Described sidewall well heater is placed on from sidewall 46R, the 46L of correspondence distance 172 places of selecting in advance, and the scope of described distance 172 is approximately 1 centimetre to approximately 5 centimetres.Described sidewall well heater can be supported in the recess 173 that cuts out in the transvers earea block 54, or is supported in the through hole (not shown) in described.As shown in the figure, described sidewall well heater comprises outer quartz tube 174, and bar or coil tube type resistance element ITS are placed in the described outer quartz tube 174.The outer rim (edge of the most

close sidewall

46R and 46L) that these sidewall well heaters are guaranteed wafer W-l in the drawing lines 1 and the wafer W-3 in the drawing lines 3 one by one border land obtains homogeneous heating.

The diffusion furnace of the present invention of the application's case is widely used in the solar cell manufacturing industry, namely, be applicable to following processing step: to solar cell wafer carry out roasting so that phosphorus or/and boron diffusion and being diffused into altogether in the wafer matrix, thereby form p-n junction layer or conductivity back of the body upper layer.Described system obviously is the improvement to current available stove, thereby provide higher throughput, this be because: process period is shorter in fact, cover still less, energy requirement is lower, the technique of wafer is polluted still less, and the homogeneity that p-n junction layer and boron-doping are carried on the back in the upper layer improves to some extent.Therefore, system of the present invention obviously might be used as making diffuse dopants in the solar cell advanced material wafer equipment and the new standard of method.

Parts list (this parts list be provide for convenient examination and can be in the situation that obtain allowing to delete)

Claims

1. continuous handling machinery diffusion furnace that is used for the processing solar cell wafer, described diffusion furnace comprises with exercisable array configuration:

A) a plurality of heating and cooling are regional, and described zone is next directed to the order of outlet of still by the stove entrance,

I) described zone is arranged by syntopy, so that by the continuous vertical processing conveyor path of described region deviding, described path is oriented in the plane of level substantially, in the described zone each comprises the outer side wall that separates, the processing volume is defined between the described outer side wall, and described processing volume is divided into regional upper part and regional lower part along the horizontal plane that is parallel to substantially described machining path plane;

Ii) described heating region comprises the heating unit that is selected from IR lamp and resistance radiating element, and described heating unit is oriented and the crosscut of described vertical processing conveyor path, in order to heat described processing volume;

Iii) the heating unit of described transversal orientation is arranged at least some of described heating region, is arranged at least one of described regional upper part and described regional lower part;

Iv) at least one pair of resistance heating element, described resistance heating element is arranged in described regional lower part or/and at least one in upper part, described resistance radiating element is oriented to be parallel with described vertical processing conveyor path, of each centering be arranged to described outer side wall in one adjacent;

B) inferior quality conveyor system is used for the reception solar cell wafer and makes solar cell wafer pass described zone along described vertical machining path from described stove entrance moving to described outlet of still, and described conveyor system comprises:

I) a plurality of refractory metal silks that separate, described wire are oriented and described vertical machining path crosscut, and described length wiry defines the useful chip conveying width that passes described stove zone between the described sidewall of described conveyor system;

Ii) diameter is little, wall is thin, the refractory tube of non-rotating, described refractory tube is suspended on the described wire, in order to when by described conveyor system described chip conveying being passed described stove zone, described wafer being provided support, and avoid the metal vapors that emits from described wire in order to protect described wafer in fact fully;

Iii) the development length of described refractory tube is the most of at least of described described length wiry, and is positioned to only expose described short relative side wiry at described wire;

Iv) a pair of separate transport parts, one is transported arrangements of components and becomes adjacent with described each end wiry, described each of transporting in the parts forms continuous loop, described continuous loop passes the described vertical machining path from the stove entrance to described outlet of still, then gets back to described entrance at the extra-regional return path of described stove;

V) described each of transporting in the parts comprises a plurality of storage members that separate equably along described each of transporting in the parts continuous loop, each described storage member is configured to removable and keeps described described short side wiry, and described wire cloth is set to strides the described width that transports and be suspended on described transporting between the parts; And

C) be arranged in the extra-regional drive system of described stove, described drive system arrangements becomes described two of engagement to transport parts, with along with the described parts that transport carry described a plurality of refractory tube and are suspended on the synchronizing moving that wire between the described storage member realizes passing described zone, in the furnace operating process, on described refractory tube, described chip conveying is passed described zone so that described wafer is processed.

2. continuous handling machinery diffusion furnace according to claim 1, wherein said delivery system comprises at least one in the following:

A) be selected from band and the ring type parts of roller chain;

B) wherein when using band, described band comprises vertically extending support, and described wire end is accommodated in the described support;

C) wherein when using the roller chain, described roller chain comprises the tubular pivot chain link, and described wire end is accommodated in the described chain link.

3. continuous handling machinery diffusion furnace according to claim 1, wherein said second area part is mounted to and is fixed in the framework and can't moves, described stove comprises the powerpropelled vertical-lift parts of a plurality of usefulness, described vertical-lift arrangements of components becomes to be connected to described upper and lower half stove area part, described vertical-lift parts are through arranging to promote described upper half area part with respect to described fixing half area part, thereby expose stove heating region inside and allow to enter described stove heating region inside, in order to check on demand, adjust, maintenance and repair.

4. continuous handling machinery diffusion furnace according to claim 1, wherein said upper part is mounted to and is fixed in the framework and can't moves, described stove comprises the powerpropelled vertical-lift parts of a plurality of usefulness, described vertical-lift arrangements of components becomes to be connected to described upper and lower half stove area part, described vertical-lift parts are through arranging to reduce described half area part with respect to described fixing upper half area part, thereby expose described stove heating region inside and allow to enter described stove heating region inside, in order to check on demand, adjust, maintenance and repair.

5. continuous handling machinery diffusion furnace according to claim 1, comprise sagging drift stop subassembly, described sagging drift stop subassembly is installed at least some lower part in the described stove zone, and be arranged to spaced apart below described bearing and with described bearing and column alignment.

6. the continuous diffusion of a photovoltaic (PV) solar cell wafer or altogether diffusion layer roasting method, described wafer has basal surface and top surface, said method comprising the steps of:

A) at least one in described bottom wafer surface and the described wafer top surface applies at least one doping agent composition, to produce a plurality of wafers, mixed by one deck doping agent composition at least one in described top surface and basal surface of described wafer;

B) transport wafer behind described a plurality of described codoped, from the stove entrance to outlet of still, pass successively a plurality of heating and cooling zone, described zone is arranged by syntopy, in order to define continuous vertical processing conveyor path, described path is oriented in the plane of level substantially, and the described top surface of described chip oriented one-tenth facing up;

C) transport in the step at the described wafer of inferior quality conveyor system upper support described, described conveyor system comprises the little non-rotating refractory tube of diameter, described refractory tube supports described wafer, described refractory tube is suspended on the wire, the second vertical outer side of described wire from first vertical outer side of described stove to described stove be across described wafer process path, and described wafer constantly advances by selected speed and passes described zone;

D) in described heating region directly by be mapped to IR lamp radiation on described top surface and the basal surface and hot resistance radiation or again at least one in the radiation described wafer is heated, the time of heating is enough to promote described doping agent to be diffused into the described wafer substrate material from described coating layer, thereby finishes the p-n junction top surface layer and carry on the back at least one the formation contact in the bottom surface layer; And

E) keep uniform heat across described wafer process path by the resistance radiation that applies from the longitudinal electrical resistance heating unit, described longitudinal electrical resistance heating unit is arranged in in the described heating region at least one, and is adjacent with described outer side wall and be parallel to described outer side wall.

7. method according to claim 6, wherein said heating region is divided into top heating region part and bottom heating region part along the plane that is parallel to substantially described machining path horizontal plane, and the resistance heating element from be arranged at least one bottom heating region part applies heat.

8. one kind is used in diffusion and metallization step silicon wafer being carried out hot worked equipment, and described wafer has top surface and basal surface, and described equipment comprises with exercisable array configuration:

A) at least one doping device module is used for applying doped compositions, and described doped compositions is selected from least one in boron dope agent composition and the phosphorus dopant composition;

B) continuous handling machinery IR lamp heating-type diffusion furnace, silicon wafer after described diffusion furnace mixes from described doping device module reception, described diffusion furnace has long and narrow heating region, described heating region is divided equally at the handling machinery interbedded water and is slit into top part and bottom part, and described diffusion furnace comprises lifting gear, described lifting gear allows described top part and bottom part relative movement, in order to can enter the inside of described heating region, described stove is applicable to the silicon wafer after mixing is spread roasting;

C) antireflecting coating module, described antireflecting coating module arrangement is in the downstream of described diffusion furnace, in order to the silicon wafer after described diffusion furnace reception diffusion roasting, and comprise for the member that applies antireflecting coating (ARC) at least top surface of described silicon wafer;

D) printing press/drier module, described printing press/drier module is arranged in the downstream of described antireflecting coating module, in order to receive the silicon wafer of the described ARC of scribbling, described printing press/drier module comprises for the member that applies back of the body contact slurry and the wafer after the collector electrode circuit of printed with fine on the described top surface prints with generation to described basal surface;

E) drier module, the wafer and the wafer after the zone of IR lamp heating is with described printing that are used for receiving after the described printing are heated to up to approximately 650 ℃, in order to burn the volatility organic binder bond the described slurry on the described top surface of the silicon wafer after described printing and the basal surface and the circuit; And

F) metallization stove, described metallization stove and accessory has long and narrow heating region, described heating region is divided equally at described handling machinery interbedded water and is slit into top part and bottom part, and described metallization stove comprises lifting gear, described lifting gear allows described top part and bottom part relative movement, in order to can enter the inside of described heating region, described stove is applicable to the silicon wafer after the printing is carried out IR lamp heating-type metallization roasting, burns approximately 750 ℃ in about 1100 ℃ scope; Thereby produce the silicon wafer that can be processed into solar panel array, described processing comprises cleaning, test and lamination.

9. according to claim 8 for silicon wafer is carried out hot worked equipment, wherein said diffusion furnace comprises:

A) a plurality of heating and cooling are regional, described zone is to come directed by the stove entrance to the order of outlet of still, described zone arranges by syntopy, so that by the continuous vertical processing conveyor path of described region deviding, described path is oriented in the plane of level substantially;

I) a plurality of refractory metal silks that separate, described wire are oriented and described vertical machining path crosscut, and described length wiry defines the useful chip conveying width in the described stove of passing of described conveyor system zone;

Iii) the development length of described refractory tube is the most of at least of described length wiry, and is positioned to only expose described short relative side wiry at described wire;

C) be arranged in the extra-regional drive system of described stove, described drive system arrangements becomes described two of engagement to transport parts, with along with the described parts that transport carry described a plurality of refractory tube and are suspended on the synchronizing moving that wire between the described storage member realizes passing described zone, in the furnace operating process, on described refractory tube, described chip conveying is passed described zone.

10. according to claim 9 for silicon wafer is carried out hot worked equipment, it comprises: the first doping device module is used for applying the boron dope agent compound to the described basal surface of described wafer; And the second doping device module, be used for the described top surface phosphors coating doping agent compound to described wafer, wafer after described the first doping device module will be mixed supplies to upside-down mounting device module, described upside-down mounting device module has be used to the described wafer that reverses so that described top surface member facing up, and the wafer that the top surface after the described counter-rotating makes progress is transferred to described the second doping device module.