CN100444414C - Solar cell and its manufacturing method - Google Patents

Abstract

According to the first hand of the invention which is a solar battery which is an OECO solar battery using a silicon single crystal substrate, wherein the minimum depth h of each groove always meets a relational expression: h>=W1tan theta, the theta represents a depth direction along a semiconductor single crystal substrate, when watching along any sections which is perpendicular to the longitudinal direction of each groove, a straight line which is connected with a lower end portion of an electrode of a groove with a maximum depth and an upper end portion of the inner side surface of a same groove which does not form an electrode is formed, and an included angle between reference lines which are perpendicular to the depth direction, and the W1 represents a distance between the edge of two openings of the groove. According to a method for making the solar battery of the second hand of the invention, a plurality of grooves are formed on a first main surface of a p-type silicon single crystal substrate which is cut from a silicon single crystal ingot. First, a portion of knife edge of a groove dividing blade protrudes from the feeding surface of a flat substrate of a worktable in a predetermined height. The p-type silicon single crystal substrate moves to the rotational groove dividing blade along the feeding surface of the substrate, and the first main surface and the feeding surface of the substrate are kept closely contacting, and then an electrode is formed on only one side of the inner side surface of the groove which is divided at a horizontal direction of the groove.

Description

Solar cell and manufacture method thereof

The application is to be application number the dividing an application for the Chinese patent application of " solar cell and manufacture method thereof " that be No. 02806810.6 denomination of invention on March 19th, 2002 applying date.

Technical field

The present invention relates to a kind of solar cell and a kind of method of making this solar cell.

Background technology

Requirement to solar cell recently relates to higher efficient and lower cost simultaneously.OECO in this article (tiltedly evaporation contact) technology has attracted people's attention.OECO technology is the method by the manufacturing solar cell of people such as German Institut furSolarenergieforschung GmbH Hameln/Emmerthal (ISFH) r R.Heze proposition, and the representational Renewble Energy that is disclosed in, Vol 14, and p83 (1989) goes up (solar cell by the manufacturing of OECO technology often abbreviates the OECO battery hereinafter as).The manufacture method of OECO will be made a brief explanation with reference to Figure 12.The OECO battery is built into and makes have many parallel grooves 2 ' (to have rectangle, semicircle, triangle or its similar section form) be engraved in silicon single crystal substrate 24 ' and (abbreviate " semiconductor monocrystal substrate " hereinafter as, or simpler being called " substrate ") on the first type surface, as optical receiving surface, therefore every groove 2 ' has on the medial surface 2 ' a of the side when transverse direction is seen and is used to the electrode b ' that obtains to export after this first type surface.Normally delineate groove 2 ' with cast-cutting saw.Specifically, silicon single crystal substrate 24 ' is placed on the work top, keeps leaving a constant distance, form surface (optical receiving surface) at the groove of silicon single crystal substrate 24 ' and go up delineation groove 2 ' with the workbench surface by moving horizontally cast-cutting saw.The formation of one side, 2 ' a top electrode 6 ' of every groove 2 ' is realized that by vacuum evaporation this evaporation is carried out sideling with respect to the later first type surface as optical receiving surface 1 ' a of semiconductor monocrystal substrate 24 '.This technology can make electrode material be deposited on selectively on the last and outstanding top surface that the has fallen thing 2 ' b of all side 2 ' a of groove, and this is based on by groove itself and is applied to the shadow effect for the treatment of on the plated metal.The thickness of this plated metal has difference in the zone of outstanding bulge top surface 2 ' b with in the zone of inboard 2 ' a, therefore, then the corrosion process of evaporation technology can successfully be removed this metal thereby only stay electrode on the side, and the difference that its thickness equals in the side the last thickness of the top surface 2 ' b of thickness on the 2 ' a is equally thick.

This structure successfully is reduced to 5% of total approximately light receiving area to the shadow loss of solar cell.Because have the general solar cell that forms electrode with silk screen print method, to be subjected to about 12% big shadow loss usually, so, can know that the OECO solar cell has the shadow loss that obviously reduces, thereby obtain big energy conversion efficiency.

The solar cell of the practicality of paying can be classified by source material at present, is divided into silica-based (monocrystalline, polycrystalline and amorphous), based compound semiconductor, and other.In other material, what the most extensively make is monocrystal silicon substrate, and this is because they have good power conversion effect and low production cost.The silicon single crystal substrate that is used for solar cell cuts with the metal wire sawing normally that single crystal rod prepares, and single crystal rod obtains by Czochralski method (abbreviating " CZ method " hereinafter as) or floating melting zone method (abbreviating the F2 method hereinafter as).The substrate that cuts out by cast-cutting saw is used as by the substrate that cuts into and is used.

But it is disadvantageous cutting with the metal wire sawing, increase when the degree of depth of abrasive particle quantity in ingot is advanced in incision on the service position increases owing to being retained in, and these increases cutting width gradually.Therefore, semiconductor monocrystal substrate 24 ' will have such thickness, promptly reduce to finishing cutting edge (right-hand side the figure) from beginning cutting edge (left-hand side in the drawings).Therefore be appreciated that be favourable by the semiconductor monocrystal substrate 24 ' that cuts into by shortening that the process time reduces to production cost aspect sizable degree, but be disadvantageous aspect heterogeneous making semiconductor monocrystal substrate 24 '.Can reach the uniformity of 4 inch diameter substrate thickness and to resemble 20 to the 30 μ m manyly, and along with the increase of substrate diameter, this non-uniformity becomes bigger.

Any conventional method that goes up the delineation groove at the substrate 24 ' that is used to make solar cell is that success will follow in the constant depth of measuring on whole surface from optical receiving surface 1 ' that obtains groove 2 ', and this is because cause in uneven thickness in the substrate 24 '.More precisely, use edge of a knife type cast-cutting saw and cut, it keeps below it on edge of a knife constant reference in height, will be at substrate 24 ' delineate groove 2 ' deeplyer than thickness portion.

Have the substrate 24 ' of the non-homogeneous degree of depth,, will cause the aspect ratio design load of electrode 6 ' little, or unwanted metal deposition also can be on groove basal surface 2c ' by of the formation of above-mentioned gas-phase deposition at groove side 2 ' a top electrode 6 '.Electrode 6 ' with height littler than design load will upward produce bigger electricity at electrode 6 ' and lead loss.Metal formation at the groove basal surface will increase shadow loss, thereby the failure energy conversion efficiency.But, be used to remove the undue corrosion that deposits of metal and will reduce the area that electrode forms, thereby will increase resistance loss.As normal result, the two all causes the reduction of energy conversion efficiency shadow loss and resistance loss.

Except above-mentioned OECE solar cell, if the depth of groove of delineation is uneven in substrate 24 ', the solar cell of other type may cause the variation on characteristic in addition.Under the demonstration example situation of depth of groove greater than design load that is used for the electrode contact of delineating on the rear surface at solar cell, the boundary areas between electrode and substrate has increased, and this causes increasing in the recombination rate of boundary.In contrast, the degree of depth is less than design load, and this causes bad contact the between electrode and substrate, and this can increase contact resistance.In the depth of groove of delineating on the optical receiving surface of another solar cell is under the situation heterogeneous, and the variation of boundary areas causes the recombination rate difference on thickness direction and vertical plane inter normal direction.These variations on characteristic cause the variation of output voltage, and finally may reduce the output of solar cell.

So first purpose of the present invention is to provide according to OECO technology to have the electrode that forms suitably, so that positively suppress shadow loss and resistance loss.Second purpose of the present invention provides a kind of method that forms the manufacturing solar cell of groove in such as the OECO solar cell that has, and can easily make the greater efficiency that depth of groove is even and can realize solar cell with low cost.

Summary of the invention

For finishing above-mentioned first purpose, solar cell according to first aspect present invention is a kind of solar cell with optical receiving surface, this optical receiving surface is that first first type surface by the semiconductor monocrystal substrate with a plurality of almost parallel grooves that form thereon constitutes, each groove has the electrode that is used to draw output, this electrode is configured in its horizontal poor direction only to be had on the medial surface of a side, wherein

Relational expression below the minimum-depth h of every groove satisfies:

h ≥W ₁tanθ……(1)

In addition, the θ representative is along the thickness direction of semiconductor monocrystal substrate, be formed on one along perpendicular to any portion section of each groove longitudinal direction fluted bottom with the electrode on the depth capacity groove connect and do not have electrode to form straight line of thereon same groove medial surface upper end and, and W perpendicular to the angle between the reference line of thickness direction ₁Representative is by the recess width of distance definition between two edge of opening of groove.

As shown in Figure 4, at thickness direction along semiconductor monocrystal substrate 24, be formed on groove 2 a side 2a electrode 6 bottom LE and do not form straight line that the upper end of medial surface 2c of the same groove of electrode is connected thereon and perpendicular to the angle θ between the reference line of the thickness direction of substrate, corresponding to when forming electrode 6 by the oblique angle vapour deposition, gas phase incident (deposition angles) angle of electrode material.The minimum-depth h of each groove 2 relate to one its vertically have thickness distribution, find the depth of groove that measures on the minimum depth one.

The inventor finds after by extensive studies, such as the formation of groove basal surface top electrode and electrode not only divide the inconsistency that forms area, if the minimum-depth h of groove, the width W of groove ₁With the satisfied condition of showing out by formula (1) of angle θ, can avoid effectively.The solar cell that is built into like this, even the short groove that forms on the thinnest position that is formed on the substrate with non-uniform thickness is had with respect to the correct electrode that forms of thickness direction, with have never a resistance loss that surpasses required value, be enough degree of depth that can guarantee groove.This solar cell also is good reducing shadow loss effect direction, and this also is the real purpose of OECO solar cell.

For the mechanical strength that will guarantee that solar cell itself is enough, must guarantee the thickness of silicon single crystal substrate, for example, thick as 150 to 300 left and right sides μ m.For will reducing the production cost of solar cell, need to reduce substrate thickness certainly, only be that simple strategy may cause solar cell can not keep enough mechanical strengths with not achieving one's goal for forming of dark groove.In other words, would rather remain on mechanical strength on the high level, and assurance is by the depth of groove of the present invention's regulation.

And, if groove is to form like this, make and stay the uniform thickness of semiconductor monocrystal substrate in this observed each bottom portion of groove position of section, then can make mechanical strength planar even, and this have only the worry that has adequate thickness not on the certain location and cause substrate to break with regard to successfully having eliminated to be derived from.It should be noted, the variation that " the balanced thickness " in the content of this explanation refers to thickness drops on ± scope of 10 μ m within.

The advantage that forms groove on the direction of mentioning in front is following each point.The electrode that is formed on each groove 2 is referred to as finger electrode, and the busbar electrode by describing subsequently is joined to one another, and is used for being formed on the electric current collection along arranging groove direction.On the other hand, shown in Fig. 3 A and 3B, the thickest position of hypothesis semiconductor monocrystal substrate is P2 now, and the thinnest position is P1, being formed on the groove 2 that connects on P2 and the P1 rectilinear direction approx, to have the groove of being presented as 2 be the darkest in position P2 one side, and become more shallow depth distribution gradually towards position P1 side.The per unit groove length, the area that can form the groove medial surface of finger electrode diminishes towards position P1.

On the other hand, shown in Figure 14,15 and 16, solar cell 1 has the busbar electrode 30 that is used for collected current, it be formed on semiconductor monocrystal substrate 24 first first type surfaces in case across each groove 2 in order to be electrically connected with all electrodes 6 that are formed on each groove (see Fig. 1, below this paper, abbreviate " finger electrode " as).Can form busbar 30 to such an extent that make its inner surface configuration consistent, as shown in figure 18, or make it stop up each groove, as shown in figure 19 with all grooves 2.

Shown in Figure 14,15 and 16, the position that busbar electrode 30 forms is preferably determined approaching the thickest position P2 rather than the thinnest position P1.Because the zone for the area deficiency on the groove that forms finger electrode 6 can be favourable so form busbar electrode 30 near shaped position P2 busbar electrode 30 separately.When electric current leaves busbar electrode 30 and comes out, electrorheological in finger electrode 6 gets less, even have any reason that causes resistance loss, make that the actual resistance loss that produces is little owing to the voltage drop in the electrode that has only little current density.According to the groove arrangement of front, so might be aligned in the position that causes the shade groove on the flank side surface leaving busbar electrode 30.Even in gas-phase deposition, found area that electrode forms owing to the problem of technology accuracy makes it be slightly less than the target design value, because only leaving the shortage that to find on all positions of busbar 30 in electrode forming surface is long-pending, so resistance loss can take place hardly, be favourable in this.In being shown in Figure 14, any example of 15 and 16, now hypothesis semiconductor monocrystal substrate 24 is vertically divided equally by connecting the thickest position P2 and the drawn straight line DL of the thinnest position P1, and the entire portion of busbar electrode 30 drops among affiliated half of the thickest position P2.This structure to more efficiently position P1 be placed on influential to resistance loss, be favourable away from the terminal aspect of the finger electrode of busbar electrode 30.

Which position P1 and P2 busbar electrode 30 more approaches, and differentiates with the method that describes below in this manual.At first, as shown in figure 17, baseline L2 and L1 are drawn in position P2 and P1 respectively, make with the profile of semiconductor monocrystal substrate 24 to contact.Then perpendicular to baseline L2 draw a pair of area decision line L3 and L4, and its profile with semiconductor monocrystal substrate 24 is contacted, and perpendicular to baseline L1 draw a pair of area decision line L5 and L6, and its profile with semiconductor monocrystal substrate 24 is contacted, hypothesis is by busbar electrode 30 now, the area that baseline L2 and area decision line L3, L4 are enclosed is S2, and by busbar electrode 30, the area that baseline L1 and area decision line L5, L6 are enclosed is S1, if the relation of S2＞S1 is set up, think that then busbar 30 is closer locations P2.

As shown in Figure 3A, the longitudinal direction of each groove 2 preferably is in parallel with straight line L, or inclination angle at 45 or depart from a little a bit, straight line L is in along substrate first first type surface, and connect the thickest position P2 (thickness=h2) and the thinnest position P1 (thickness=h1) of semiconductor chip, and more preferably as far as possible to this place parallel (that is, above-mentioned angle be 0 ° as far as possible).This is that each groove is the darkest in position P2 side, and in contrast, is the most shallow in position P1 side because be in when parallel with groove 2 longitudinal directions as straight line L, and this resistance loss is reduced to minimum the most highlightedly.When the angle between straight line L and groove direction surpasses 45 °, cause the general deficiency of the degree of depth and result to cause being positioned at general deficiency, and this just increase resistance loss unfriendly at the groove inner area near the groove 2 of position P1.

Silicon single crystal substrate the best is elected the substrate material that is used for solar cell as.The silicon single crystal that great majority are made by the CZ method are＜100〉direction has a pull-up axle, makes that being used for the substrate surface direction that solar cell makes as substrate material generally has { the crystal orientation of 100} direction.Will be formed in plurality of grooves and to have and be bordering under the on-chip situation in 100} crystal orientation (abbreviate as hereinafter the 100} substrate), on its first type surface＜110〉direction on, as long as very little external force just can cause substrate to dissociate along groove, if and the section form of groove has the part that is tending towards concentrated stress, if or substrate kept many damages of producing in the process of delineation groove, then cause breaking.The existing formation direction and＜110 of stipulating each groove〉direction is inconsistent, makes it might improve the considerable degree of mechanical strength to of the solar cell that has obtained.

Comprise according to the manufacture method of the solar cell of second aspect present invention and on a first type surface of semiconductor chip, to form a plurality of grooves at least, wherein can make groove delineation blade rotation, and the blade portion branch of the groove delineation blade that stretches out with the precalculated position is remained on the smooth substrate charging surface of workbench, and

On the first type surface of semiconductor chip, delineate groove, and first type surface is closely contacted with the maintenance of substrate charging surface, and, make mobile step with respect to the substrate charging surface of groove delineation blade along on thickness direction perpendicular to groove delineation blade.

In the method for above-mentioned manufacturing solar cell of the present invention, the substrate charging surface of first type surface and workbench that will form the semiconductor chip of groove thereon is closely to contact, as corollary, make the first type surface of semiconductor chip and substrate charging surface keeping parallelism.Simultaneously, blade portion branch by the outstanding groove delineation blade of predetermined altitude remains on the smooth substrate charging surface of workbench, like this, if semiconductor chip is moving with respect to the groove delineation blade that rotates perpendicular to groove delineation blade thickness direction, will form groove thereon on semiconductor chip maintenance and the surperficial parallel first type surface of substrate charging with uniform depth.Shadow effect between each adjacent grooves of OECO solar cell that this point is successfully balanced, and make and might in each groove, form the electrode that has near uniform-dimension.It is consistent with design load exactly that this also might form each electrode, thereby suppress resistance loss, shadow loss, or similar loss.The present invention also is successful aspect the depth of groove of the solar cell of equilibrium except that the OECO solar cell, like this, can suppress the characteristic variations of solar cell, and can avoid the minimizing of exporting.

In the present invention, groove delineation blade comprises a plurality of edge of a knife parts that connect together with one heart with fixing interval, and all edges of a knife part (, also abbreviating " the compound groove delineation edge of a knife " as in this paper back) is given prominence to smooth charging surface at workbench with identical height.Adopt such structure, semiconductor chip only moves once under integrated mode with respect to the compound groove delineation edge of a knife, just may form the groove that divides corresponding to a plurality of blade portion like this.Because the projecting height of each edge of a knife part is identical each other, the groove that forms all has the identical degree of depth.Because each edge of a knife partly is to link the compound groove delineation edge of a knife under fixing interval, so, a plurality of parallel groove of arranging with constant spacing on the first type surface of semiconductor chip, formed.Thereby allow although repeat repeatedly collective's groove formation formation groove on entire main surface, but viewpoint from productivity ratio, the blade portion mark of constructing the compound groove delineation edge of a knife is equal to or greater than the number that will form groove on semiconductor chip, then by mobile semiconductor chip relatively only be once just on entire main surface the formation groove be more favourable.

Spendable in the present invention workbench can be to have swarf to get rid of groove on its substrate charging surface.For the situation that forms groove on the first type surface of semiconductor chip, the part that will form groove in the substrate is with the edge of a knife scored part way of groove delineation blade, makes swarf form the result as groove and produces.If it is motionless that the swarf that produces like this keeps, then be between semiconductor chip and the workbench, thereby damaged needed contact between semiconductor chip and workbench.Specifically, semiconductor chip improves an amount of the particle size approximate swarf from workbench, and this point is slightly damaged on the charging surface of substrate workbench and will be formed parallel relation between the semiconductor chip first type surface of groove.This just makes and is formed on the first type surface upper groove degree of depth and can not remains unchanged.For example, produced the groove that forms behind a large amount of swarfs often become than those the incipient stage form relatively more shallow.

But, swarf is got rid of the formation of groove on the substrate charging surface of workbench, on the substrate charging of workbench surface with form thereon that always to keep needed tight contact this respect between the first type surface of semiconductor chip of groove be successful, even this is that then the swarf that is produced is sticked by these grooves because form the result and produce a large amount of swarfs as groove.The retaining groove degree of depth was constant during this point made finally and might be in early days forms with the groove in later stage.Therefore can resemble as described above reducing to the resistance loss of solar cell and the loss of resistance shadow, thereby can improve energy conversion efficiency.And swarf get rid of groove formation also to contact area between semiconductor chip and workbench reduce contribution is arranged, and the result of this point is the frictional resistance that reduces in the relatively moving of semiconductor chip.Therefore process efficiency that groove forms and productivity improve.

In the above-mentioned method for manufacturing solar battery, make the even of last depth of groove, and form on the surface in the solar cell of making distribution with depth of groove (between maximum and minimum value poor) at whole groove, can be suppressed to resemble substrate thickness distribution (between maximum ga(u)ge and minimum thickness poor) ± 5% or littler aspect be successful.

The accompanying drawing summary

Fig. 1 is the amplification sectional view that part illustrates an embodiment of solar cell of the present invention;

Fig. 2 A is first example of form of grooves;

Fig. 2 B is second example of form of grooves;

Fig. 2 C is the 3rd example of form of grooves;

Fig. 2 D is first example around angled part;

Fig. 2 E is second example around angled part;

Fig. 3 A is the schematic diagram that the monocrystal chip with non-uniform thickness is shown;

Fig. 3 B is illustrated in to be shown in the schematic diagram that forms the groove method on Fig. 3 A substrate;

Fig. 4 illustrates the schematic section that the present invention has the solar cell of enough degree of depth;

Fig. 5 A is the schematic diagram that is used to explain the method that determines the square-section depth of groove;

Fig. 5 B is the schematic diagram that is used to explain the method that determines the V-arrangement section grooves degree of depth;

Fig. 6 is the schematic section that the processing step that is used to make solar cell is shown;

Fig. 7 be illustrate be shown in example 1 form the figure of linear measure longimetry point at the thickness direction top electrode of substrate;

Fig. 8 is the figure that electrode height measurement result in the example 1 is shown;

Fig. 9 explains the schematic diagram that forms groove demonstration example method in the solar cell method of the present invention;

Figure 10 illustrates the present invention to make the schematic section that forms groove demonstration example method in the solar cell method;

Figure 11 explains in the present invention to make the schematic diagram that forms the modification example of groove in the solar cell method;

Figure 12 is the schematic diagram that is illustrated in sedimentation state in the OECO method for manufacturing solar battery;

Figure 13 is illustrated in the schematic diagram with non-uniform thickness substrate top electrode sedimentation state;

Figure 14 illustrates the plane graph that the busbar electrode forms first embodiment of state;

Figure 15 illustrates the plane graph that the busbar electrode forms second embodiment of state;

Figure 16 illustrates the plane graph that the busbar electrode forms the 3rd embodiment of state;

Figure 17 explains to differentiate which position P2 and P1 are the figure that draws closer together with the busbar electrode;

Figure 18 is the schematic section that first example that the longitudinal direction upper section of busbar electrode forms is shown; And

Figure 19 is the schematic diagram of second example that the longitudinal direction upper section form of busbar electrode is shown.

Embodiment

Below all paragraphs will be with reference to the accompanying drawings to realizing that optimal mode of the present invention is described.

(first embodiment)

Fig. 1 is that part illustrates the enlarged diagram according to an embodiment of first aspect present invention, solar cell 1 is to constitute like this, makes on the wide and about tens microns first first type surface 24a that are formed on the p type silicon single crystal substrate 24 that silicon single crystal ingot cuts out to the dark groove of 100 μ m abreast of a large amount of hundreds of microns.These grooves 2 can adopt a cover hundreds of to come whole delineation to the cutting knife that almost links with one heart, rotates together, allow also that herein the delineation operation is divided into several the wheel and carry out.

On the first first type surface 24a of substrate 24, by the phosphorus formation emitter thin layer 4 of thermal diffusion, in order to produce p-n junction as n type dopant with formation like this groove 2 thereon.On emitter thin layer 4, generally by the thin silicon dioxide film 5 of thermal oxidation technology formation as the tunnel insulation film.

Only forming electrode 6 on the side in direction sidewards on the silica membrane on the medial surface of groove 25.Electrode 6 is by utilizing vapor phase growing apparatus (for example to deposit a kind of electrode material on the medial surface of groove, such as aluminum metal) electrode that forms, in addition, in deposition process, to put substrate 24 to such an extent that on an essential at least or bigger angle, relatively tilt, so that electrode material is deposited on the medial surface, mainly be deposited on the side on the direction sidewards of each groove.Fallen on the top surface of thing 23 although too much electrode material also can deposit to be formed on 2,2 of each adjacent grooves outstanding in deposition process, crossed many parts and can remove with etchant solution such as hydrochloric acid solution.The thin layer of sin 7 that the entire portion that comprises the substrate 25 first type surface 24a of electrode 6 is used as protective film and antireflective film covers.

The cross section that each groove 2 can have perpendicular to its longitudinal direction is the profile of the rectangle shown in Fig. 2 A, semicircular profile shown in Fig. 2 B, any in the V external form shown in Fig. 2 C, this is that the blade cuts device can easily obtain by cutting because these morphologies can utilize on every side.

Having at groove 2 has the rectangle that is shown in Fig. 2 A on the sectional view perpendicular to its longitudinal direction, or has under the V profile situation that is shown in Fig. 2 C, and this profile has two marginal portion 2a, the 2b intersecting each other shown in Fig. 2 D or Fig. 2 E.In rectangular recess, marginal portion 2a and 2b correspond respectively to the bottom of the limit wall of groove, and shown in Fig. 2 D, the angle of intersection that the two is shown is 90 ° or about 90 °.On the other hand, the groove of formation V has marginal portion 2a, the 2b that intersects at the acute angle of bottom portion of groove.Both of these case all often causes stress to be concentrated, and if binding site acutangulates, then to reduce the intensity of solar cell.When cross-sectional shape is watched, do the defence measure of circular R1 and R2 on the position that crosses of marginal portion 2a, 2b, be successful now aspect the mechanical strength that further improves solar cell.

The degree of circular R1 and R2 preferably is arranged within the scope of enough effects that can guarantee to prevent that stress is concentrated, and it does not damage since groove geometry cause such as the effect that on series resistance, reduces, in addition, preferable scope, normally about 2 to 20 μ m.After with circumferential blade cutting or similar device delineation groove, can easily obtain this circle by chemical corrosion.Be available as and remove the damage that when groove is delineated, is produced and the same corrosive agent of the corrosion of usefulness is realized.Etching extent preferably within the scope of about 5 to 20 μ m, drops within the preferred range described above in order to make this circle.Usually use potassium hydroxide aqueous solution as chemical corrosion solution.

Simultaneously, by cut the substrate that obtains by Czochralski method (being called " CZ " method in this paper back) or the crystal ingot made of floating melting zone method (abbreviating " FZ " method in this paper back as) with the wire sawing, usually on thickness (Fig. 3 A) heterogeneous, in addition, there are 20 to 30 μ m many like that to 4 inches its variable quantities of substrate, and also will further increase bigger substrate.This is because cut with the wire sawing, cause a large amount of abrasive particles to stay the working position when the degree of depth increase of crystal ingot is advanced in cutting, and this point increases the width of cutting gradually.

If integrally be inscribed in the groove 2 on the substrate 24 with non-uniform thickness with cast-cutting saw, last groove 2 will have the non-homogeneous degree of depth as shown in the signal section figure of Fig. 4.In the technology of OECO, be decided by that at the electrode of a side direction (evaporation among the figure) the deposition angles θ in addition of depth of groove and vapour deposition is defined as one and is connected along semiconductor monocrystal substrate 24 thickness direction T to only on what zone of groove medial surface, finding, when (promptly along any portion section, seen in the drawings portion's section) when watching, perpendicular to each groove longitudinal direction (promptly, direction perpendicular to drawing) flutedly have the bottom LE of the electrode 6 that forms on the groove 2u of depth capacity in the middle of 2 and do not have electrode to form the straight line of the upper end TE of the same groove 2u medial surface 2c of (medial surface of electrodeless formation) thereon, with perpendicular to the angle between the reference line HL of substrate thickness direction.

For the groove 2 that is positioned at each adjacency, the height of the outstanding bulge 23 between 2 is under inadequate situation, the trial that forms electrode in needed zone causes the deposition of electrode material not only on the marginal portion 2a of outstanding bulge 23, and, on marginal portion 2b, do not deposit corresponding to bottom portion of groove according to the angle θ that deposits with not needing yet.This unnecessarily increases the zone that will be corroded by later corrosion, and can not obtain necessary electrode.

In the present invention, all groove parts always guarantee enough degree of depth, even on the position (P1 among Fig. 3 A) that substrate is the thinnest as shown in Figure 4, this degree of depth also enough prevents electro-deposition to the marginal portion 2b corresponding to bottom portion of groove.With reference now to Fig. 5 A,, when when observing perpendicular to any portion section of groove longitudinal direction, suppose that depth of groove is h, electrode height is he, and then the electrode height he useable definition in depth of groove direction (in the substrate thickness direction) is the recess width W of distance between two edge of opening of groove ₁Defined in the above deposition θ is expressed as follows:

h _e＝W ₁tanθ

So, if sufficiently big, make and satisfy following relational expression in the thinnest locational depth of groove h ' assurance:

h’≥W ₁tanθ

Then electrode 6 can not deposit on the marginal portion 2b corresponding to groove again.Owing to is minimum in the thinnest locational depth of groove, so the depth of groove h of what its position in office always satisfies formula (1), therefore, the present invention can prevent that groove arbitrarily from causing electrode 6 to be deposited on the marginal portion 2b corresponding to bottom portion of groove.

It should be noted that formula (1) is set up the V groove that is shown in Fig. 5 B is also approximate.Now a groove of alignment of assumed is the darkest groove during those are formed on the substrate, if on substrate the most shallow groove to have the degree of depth be that h or darker then electrode exceedingly or insufficiently form never.

Refer again to Fig. 1 now, on another first type surface 24b of solar cell 1, (, abbreviate " second first type surface " as in this paper back), form backplate 8, and, for example, in the middle of silicon nitride film 10 is placed on.Silicon nitride film forms as protective film, and can be formed by CVD (chemical vapour deposition (CVD)) technology.Form backplate 9 so that cover the entire portion of second first type surface, and form by the al deposition layer usually.Constitute backplate layer 8 make by contact permeate portion 10a contact with below silicon single crystal 24 this contact permeate portion 10a on its thickness direction through silicon nitride film 10.Although contact permeate portion 10a can form with photoetching, be in the present embodiment by the groove of machining delineation or the aperture that punches by laser processing.

In order to guarantee that solar cell itself has enough mechanical strengths, it is so thick that the thickness of silicon single crystal substrate 24 is chosen about 150 to 300 μ m.Because in order to reduce the production cost of solar cell, so understanding will reduce the thickness of substrate certainly, for an only simple strategy that forms dark groove may make solar cell can not keep enough mechanical strengths unwillingly.Just, general, would rather place restrictions on the degree of depth of groove is 100 μ m or more a little less, and guarantees by depth of groove given to this invention.

At Fig. 1, each groove of solar cell 1 be formed on the first first type surface 24a with＜110〉direction inconsistent directions on.This has improved the mechanical strength of solar cell 1.Know that in this manual if the crystallography main shaft of the substrate of Shi Yonging is to have to depart from＜100〉direction the inclination angle drift angle substrate at 6 ° of angles nearly, then any substrate is set as has { 100} crystal orientation here.

Ensuing all paragraphs will be retouched the demonstration methods of making this solar cell 1.

At first obtain p type silicon single crystal ingot in the HIGH-PURITY SILICON by the III family element such as boron or gallium is added to, { the p type silicon single crystal substrate in 100} crystal orientation splits from this crystalline substance and cuts out and have.Generally, p type silicon single crystal has the specific electric resistance of 0.5 to 5 Ω cm at sheet.Then, shown in Fig. 6 process (a), use the high speed rotating blade on, generally＜100 with＜110〉inconsistent direction〉direction, adopt high speed rotating cutter DS (Fig. 3 B), { forming on first first type surface of 100} substrate is a plurality of parallel groove 2 of 20 to 100 μ m deeply in the p type.Although all can prepare silicon single crystal substrate, in view of the mechanical strength of last substrate is more preferably prepared by the CZ method by among both any of CZ method or FZ method.Thick substrate thickness can guarantee enough mechanical strengths the 40 μ m although resemble, and after having considered to be convenient to cutting operation and will having delineated depth of groove thereon, better thickness is 150 to 300 μ m.

The high speed rotating blade is the needed geometry according to groove, for example, from having the square-section, selects in semi-circular section and the cross section that becomes the angle.By the high speed rotating blade of mentioning in front,, when injecting cutting fluid, can delineate groove 2 on first first type surface at substrate 1 in the cutting speed of per second about 0.1 to 4cm.Also allowing with cutter is that wire is sawed and replaced the high speed rotating blade.

As consult Fig. 3 A and described in the above, in view of the electrode that will reduce to be formed on the groove inner surface) finger electrode) resistance loss, the longitudinal direction of each groove 2 is positioned at, with along first first type surface of substrate and connect the thickest position P2 of semiconductor chip ((the straight line L of thickness=h1) is parallel, or inclination angle at 45 or slightly depart from for thickness=h2) and the thinnest position P1.Be arranged under the parallel situation with the direction of groove 2 at straight line L, can form the groove that satisfies above-mentioned formula (1) by following description.At first be predetermined position P1 and P2 by the thickness distribution of measuring substrate.Follow shown in Fig. 3 B, substrate 24 is placed on makes on the workbench DT that the cut direction of high speed rotating blade DS is consistent with the connecting line of position P1 and P2.These two design loads that adopt recess width W1 and gas phase deposition angles θ are also W ₁Tan θ value is predetermined, and the depth of cut of high speed rotating blade DS is set then, makes that the recess width h ' on the P1 of position becomes greater than W ₁Therefore tan θ, is keeping enough thickness T ' (flesh is 40 μ m or more) under the bottom of each groove.The substrate thickness T ' that is retained under each groove 2 bottoms can be expressed as: h1-h '.

Next, the damage that forms the back at groove, in substrate, produces, remove with above-mentioned chemical corrosion.When groove has rectangle shown in Fig. 2 A or 2C or V-arrangement, be used to remove the etching condition of damage, preferably it being adjusted to can be suitably the groove rounding, shown in Fig. 2 D or 2E.After finishing the corrosion of removing damage, so, on the first type surface of substrate, having formed texture structure, it is that the method known by any crowd such as anisotropic etch method etc. is for reducing reflection loss as rough surface is realized.After forming texture, substrate is placed on such as cleaning in the acidic aqueous solution that contains hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid or their mixed liquor, from the viewpoint of economy and production efficiency, preferably in hydrochloric acid, clean.

Next, shown in process among Fig. 6 (b), after cleaning, at the surface portion formation transmitter layer 4 of substrate.The method that forms emitter layer can be to adopt phosphorus pentoxide, and the ion implantation that can directly inject phosphonium ion etc. is coated with barrier diffusion method for any kind, but from the economic point of view, preferably adopts the gas phase diffusion method of phosphoryl chloride phosphorus oxychloride.In a demonstration program, can be used in the phosphoryl chloride phosphorus oxychloride atmosphere about 850 ℃ anneals substrate forms n type emitter layer 4.The thickness of emitter layer 4 generally is about 0.5 μ m, and sheet resistance is in the scope of about 40 to 100 Ω/mouths.The phosphorus glass that is formed on the substrate surface part in this process is removed in hydrogen fluorine solution.

Then, on the second first type surface 24b side of substrate, form electrode.At first, shown in process among Fig. 6 (C), on the second first type surface 24b, form silicon nitride layer 8 as passivation film.Silicon nitride layer 8 can form with CVD (chemical vapour deposition (CVD)) technology.Can use normal pressure CVD technology in this article, decompression hot CVD technology, any silicon nitride layer 8 that forms in the optical cvd technology etc., wherein, the present invention especially selects indirect plasma CVD technology for use, because this technology can be carried out in about 350 to 400 ℃ low temperature range, and can reduce the surface recombination velocity of the silicon nitride layer 8 that will obtain.This technology should be noted that and to select the direct heat nitriding method for use, because can not provide enough thickness for last thin layer.

Then, shown in process among Fig. 6 (d), on the silicon nitride layer 8 that so forms, form the groove 8a that electrode connects, be similar to the sort of high speed rotating blade that is used for the groove delineation by use and make it can reach below p type silicon single crystal substrate.The shape of cutter is according to desired section form of groove, and generally from rectangular in form, the semicircle form and is selected in the form that becomes the angle.After so forming groove 8a, form electrode 9 then so that groove 8a is covered together in company with silicon nitride layer 8 on every side, shown in process among Fig. 6 (e).Though available silver or copper conduct the electrode material here, in view of economy and machinability, best is aluminium (comprising its alloy).But with sputter and these two kinds of methods of vapour deposition deposition of aluminum all.Be useful on is narrated in the technology of second first type surface 24b side formation electrode at this point and is finished.

Next, shown in process among Fig. 6 (F), on the first first type surface 24a, form silica membrane 5 by thermal oxidation method.Silicon dioxide layer 5 is used as at electrode on the first first type surface 24a and the tunnel insulation film between the substrate 24, and in order to make the tunnel effect optimization in preventing short circuit, preferable thickness is 0.5 to 3nm.Silica membrane 5 can be with comprising dry oxidation, wet oxidation, steam oxidation, the pyrolysis oxidation, any known method of oxidation or the like forms in chloride environment, and wherein preferable employing be dry oxidation, this be since this method can guarantee high-quality thin film and be easy to control thickness.

Having silica membrane 5 to form thereon substrate 24, groove 2 direction is watched sidewards the time, having only on the side in the inner surface of groove 2 by oblique angle vapour deposition worker joint, generally deposits to about 5 μ m and seeks sample and formed electrode 6 originally.Though here as electrode material, material is not so limited best employing aluminium (alloy that comprises it), also can use such as silver copper or similar basic he metal with it.More particularly, substrate 24 is placed in the vapor phase growing apparatus, its main shaft is tilted to be 70 ° to 89 ° away from reference position, in addition, the reference position is defined as the position of first first type surface to the evaporation source orientation, makes the bearing of trend of groove cross perpendicular to evaporation source.This layout successfully makes electrode material, when when horizontal direction is watched, mainly is deposited on having only on the side in groove 2 medial surfaces.The deposition preferably only the vacuum degree in device reach 2 * 10 ^-5Pa or lower just can carrying out afterwards, deposition velocity then is adjusted to 1.0 to 1.5nm/sec (but not limited).Next, shown in process among Fig. 6 (g), having electrode 6 depositions substrate 24 thereon, immersion contains in the acidic aqueous solution of hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid or its mixed solution, thereby remove the unwanted electrode material part that is deposited on outstanding bulge 23 tops that are disposed between each abut groove 2,2.

On the substrate 24 on finish after all technology, the method of knowing with the crowd, formation is shown in the busbar electrode 30 of Figure 14 to 16, and the silicon nitride film 7 as passivation film and antireflective film, generally thickness is deposited into 60 to 70nm and is formed uniformly on first first type surface on the 24a ((h) among Fig. 6), thereby form last solar cell 1 by indirect plasma CVD technology.

Figure 14 illustrates an exemplary example, and busbar electrode 30 is formed on along the periphery of semiconductor monocrystal substrate 24 with the arc figure in this example, and Figure 16 then forms along same periphery with the line pattern that tangles.

In being shown in the exemplary example of Figure 15, busbar electrode 30 is arranged such that whole groove battle arrays are opened the finger electrode 2 that belongs to each groove 2 in the part groove array 40 that comprises long recess 2 ' in 2 to be divided at the 2a of first of the thickest position P2 side with in the thinnest position P1 side, than the long second portion 2b of first 2a.The position of busbar electrode 30 also is adjusted to and makes in the 2a of first, and long groove 2 has long length.More particularly, dispose busbar electrode 30 parallelly with above-mentioned straight line DL in part groove array 40, groove 2 long in groove array 40 has long length in the 2a of first.Though long groove 2 has long finger electrodes 2, so often have bigger resistance loss, but the position of above-described busbar electrode 30 is such as making the long position of primary importance 2a, reducing aspect the resistance loss is more favourable, because correspondingly, can shorten second portion 2b.

Has uniform width although be shown in the busbar electrode 30 of Figure 14 to 16, but preferably busbar electrode 30 is widened towards a position, being useful on the lead metal silk of drawing output on this position will connect, because this part is bordering on the lead metal silk, can make contributions to electric current collection, thereby have mobile than big electric current.Be connected to along wire in the exemplary example of first end part of busbar electrode 30 at a handle, can form this electrode 30, make and partly to widen towards first end from the second end section.Be connected at another lead metal in the exemplary example of mid point on the longitudinal direction of busbar electrode 30, can form this electrode 30 to such an extent that feasiblely all be broadened towards mid point from two end points.

Form in the existing available method of busbar electrode 30, comprise such as forming electrode pattern by metallide or such as the metallochemistry plating of nickel (Ni) (but or both combinations, follow metallide after resembling chemical plating); Such as forming electrode pattern by the vapour deposition that resembles metallic aluminium (Al); Starch and form printed pattern such as form the metal contain Ni or its similar metal by silk screen printing, thereby this printed pattern of sintering forms electrode then; And be attached to semiconductor monocrystal substrate (as also available heat adjustment of needs) with pressurization such as the electrode metal lamina strip that Al or its similar metal are made.Being combined in of sheet metal tape made the sheet metal tape closely touched and tended to cause difficulty when existing finger electrode forms in the above groove inner surface, so may cause the problem of guaranteeing conductivity.If like this, form metal slurry thin layer on a face of sheet metal tape, and make in conjunction with being good in metal slurry thin layer one side, the metal slurry that stops up groove here can help the foundation that electricity is led between finger electrode and sheet metal tape.In this example, also have preferably because guarantee the bonding force of electrode and after the combination of sheet metal tape, carry out sintering.

(second embodiment)

To the embodiment of manufacturing solar cell method according to a second aspect of the invention be described.Target solar cell in a second embodiment remains and is similar to first embodiment, is shown in the OECO battery of Fig. 1.The employing edge of a knife of mentioning in front is to first embodiment of mo(u)ld top half, high speed rotating blade, according to the inhomogeneities in substrate thickness, dare to allow the degree of depth of groove 2 change and replace restriction, be applied at the thinnest position depth of groove h ' so that reduce shadow loss and the electrode resistance loss by formula (1) statement.In contrast, present second aspect purpose is even as far as possible depth of groove within single substrate.

In the present embodiment, obtained the iii group element such as boron or gallium is incorporated in the HIGH-PURITY SILICON, and passed through the p type silicon single crystal ingot of CZ method or the making of FZ method, and cut out p type silicon single crystal substrate 24 from this crystal ingot.To the regulation resistance of p type silicon single crystal substrate 24 and substrate thickness with in first embodiment, describe those be identical.It should be noted at present embodiment, also available polycrystal silicon ingot, and by the crowd know such as the HEM method, any silicon ingot of casting method and EFG manufactured.

Then, as shown in Figure 9, adopt groove delineation blade on the first first type surface 24a of substrate 24, to form a plurality of grooves 2.More particularly, stationary work-table 12 rises so that the charging surface 12a of semiconductor monocrystal substrate 24 is placed in guiding thereon.The edge of a knife part 13 that is used for delineating the rotating blade of groove side by side is attached on the fixing spacing, so that rotate together, thereby constitute the compound groove delineation edge of a knife 15, give prominence to identical projecting height h from the opening 14 on the substrate charging surface 12a that is formed on workbench 12 and the compound groove delineation edge of a knife 15 is set to feasible each edge of a knife part 13 that can allow.The first first type surface 24a that will form groove 2 in the above be put into the substrate charging of workbench 12 surface 12a closely contact, then semiconductor monocrystal substrate 24 with perpendicular to the thickness direction of edge of a knife part 13, move (as the feedstock direction of in Fig. 9, pointing out 9) to the compound groove delineation edge of a knife 15 that rotates around axis 16.When the semiconductor monocrystal substrate 24 that when the second first type surface 24b is clamped by chuck, moves here.It should be noted that Fig. 9 has enlarged the thickness of semiconductor monocrystal substrate 24, and the thickness of actual semiconductor monocrystal substrate resemble its diameter 1/500 little (being equally applicable to above-mentioned Figure 13 and Figure 10 that mentions later and 11).

According to this technology, has identical depth of groove H, recess width W1 and flute pitch W2, they are equivalent to edge of a knife part respectively from the outstanding height h of substrate charging surface 12a, a plurality of grooves of the thickness W1 of edge of a knife part 13 and edge of a knife spacing W2 are even also can form on the semiconductor monocrystal substrate 24 of the non-uniform thickness that has as shown in figure 10.According to will can normally changing the structure and the position of the compound groove delineation edge of a knife 15 in the groove 2 needed styles of semiconductor monocrystal substrate 24 formation.A typical structure of the compound groove delineation edge of a knife relates to 100 to 200 number of edge of a knife part 13, several projecting height h that pick up 100 μ m of edge of a knife part 13, and the edge of a knife spacing W2 about the hundreds of micron.Existing available edge of a knife part 13 comprises the diamond edge of a knife (is that 5 μ m are to the even bonding surface of the diamond abrasive particle of 10 μ m such as having and have particle size).When watching in the portion's section that is comprising rotation axis, employing has rectangle, semicircle, the edge of a knife part 13 of any of V and U section form can successfully form the groove corresponding to any the section form of those edge of a knife parts when watching perpendicular to the groove longitudinal direction.Adopt the edge of a knife part 13 that so constitutes (and the compound groove delineation edge of a knife that partly constitutes by the edge of a knife that connects together), when injecting cutting fluid to the delineation position, the first first type surface 24a of substrate 23 can cut in the cutting speed of per second 0.1 to 4cm usually.

Delineating also at the first first type surface upper groove of solar cell, the workbench 2 ' of the available Figure 11 of being shown in carries out.The substrate charging surface 12 ' a of workbench 12 ' has formation swarf within it to get rid of groove 17.This swarf is got rid of groove 17, and to have wide respectively be 0.5 to 5mm, and length is 10 to 30cm and is 1 to arrive the rectangle of 10mm deeply, and aim at 1 to 10mm spacing at substrate charging surface 12 ' a equably, and this is brought into contact semiconductor monocrystal substrate 24 usefulness.Because swarf is got rid of the formation of groove 17, substrate charging surface 12 ' a and semiconductor monocrystal substrate 24 have a contact zone that has reduced, and this point to reduce frictional resistance in basic 24 move be favourable, and so boost productivity.Got rid of in the groove 17 fall into into swarf at the swarf that produces along with the carrying out of groove delineation, this point also is favourable between the primary principal plane that may rest on semiconductor monocrystal substrate 24 and substrate charging surface 12 ' a and no longer include.This point has helped to keep desired tight state of contact between first first type surface of semiconductor monocrystal substrate 24 and substrate charging surface 12 ' a, and the degree of depth of last groove 2 on the first first type surface 24a is remained unchanged.Should be noted that the formation direction of the swarf eliminating groove 17 that is formed on substrate charging surface 12 ', more preferably inconsistent with the substrate feedstock direction.Under the situation that swarf eliminating groove 17 is housed, the swarf that produces along with the carrying out of groove delineation, often stay on the substrate charging surface 12 ' a of workbench 12 ', then along with semiconductor monocrystal substrate 24 moving on same direction moved along feedstock direction.Aim at the swarf of the feedstock direction 9 inconsistent directions of substrate 24 and get rid of groove 17 swarf that successfully sticks finally.

With the technology process that explain in first embodiment with those, that be illustrated in process among Fig. 6 (a) to (h) after the groove delineation is identical, and obtainable solar cell 1 is identical with the solar cell that is shown in Fig. 1 also.According to this method of the present invention, the groove 2 with even degree of depth can be formed on first first type surface of substrate 24.This point is successfully balanced is applied to the shadow effect of each groove of adjacent grooves 2 in the OECO solar cell, and the result can make electrode 6 deposit to each groove 2 with equal amount.So each electrode 6 deposits to each groove 2 with equal amount.Form so each electrode 6 can conform to design load exactly, and suppressed resistance loss and shadow loss.

Should note, the edge of a knife partial shape of above-mentioned groove delineation cutter and the shape of workbench, structure and configuration will never limit the present invention, in this respect, be receivable according to those of skill in the art's technological know-how to its any normal modification.

Be also noted that the present invention never is subjected to the restriction of embodiment till now, and, may be used on certainly among the embodiment of any pattern not deviating under the spirit of the present invention.For example, although the two solar cell of all having demonstrated and having made of first and second embodiment by OECO technology, but the present invention is not limited, and except the OECO battery, also may be used on any other solar cell, at least need delineate groove on an one first type surface with regard to them, that is can estimate in the inhibition aspect the battery behavior variation with in the place that reduces of output facet.

The present invention will be described in further detail according to special example.

(example 1)

Be used to make solar cell obtain containing III family element gallium as impurity element, p type monocrystalline silicon piece (diameter=4 inch that are used to make solar cell, minimum thickness=270 μ m, maximum ga(u)ge=300 μ m, resistivity=0.5 Ω cm), and thickness distribution is to survey in advance with micrometer.According to measurement result, form as shown in Figure 3 a plurality of parallel grooves 2 parallel with the thinnest position line square-section that have with the thickest position connecting wafer with cast-cutting saw (high speed rotating tool).Thick in the edge of a knife part of the grinding blade of this employing is that 450 μ m, diameter are 50mm, and the edge of a knife spacing of 50 μ m is arranged.Be the thickness of grinding blade of 450 μ m and 5 ° the deposition angles that the back will be described according to the rules, the minimum-depth of groove h is defined as 50 μ m.Process conditions in this regulation comprise that the rotating speed of grinding blade is that 50rpm and wafer charging rate are 1mm/s, wherein to delineation position supply cold water.Wafer is inhaled past by the vacuum cup on the working surface opposite face.For relatively, the wafer with uniform thickness is similarly processed under identical condition forms groove (relatively wafer 1).

Wafer corrodes with potassium hydroxide solution after groove is drawn quarter, thereby removes the thin layer of damaged, and forms silicon nitride film 8 overleaf with plasma CVD technology.By thermal diffusion V group element phosphorus is introduced surface one side that receives light then, have the n that sheet resistance is 100 Ω/mouths thereby form ⁺District 4.Then with executing the rotor sheet processing back side to be formed for the groove 8a of electrode contact.And to form thick by vapor deposition of aluminum be the electrode 9 of 2 μ m.Then, forming thick by thermal oxidation on the surface that receives light is the tunnel oxidation film 5 of 2nm, then from tilting 5 ° of vapour depositions as the aluminium of electrode material, be the electrode 6 of 7 μ m thereby form thick on the side having only of the medial surface of groove perpendicular to the longitudinal direction of parallel groove and with wafer surface.Corrode with phosphate aqueous solution then and remove the unwanted metal part that also on the top surface of outstanding bulge, deposits.Form wide busbar electrode then; so that be connected with each electrode; purpose is to provide antireflection means and the surface protection that tackles sunlight; pass through plasma CVD; forming thick on the surface that receives sunlight is the silicon nitride film of 7 to 70 μ m, thereby has made solar cell of the present invention (invention battery 1) and be used for the solar cell (comparison battery 1) of comparison.

So the output characteristic of the solar cell of making is (the luminous intensity 1KW/m that adopts the sunlight simulator to measure ², spectrum: the AM1.5 sphere) measurement result of output characteristic is shown in table 1.

Table 1

	Short circuit current (A)	Open circuit voltage (V)	Duty factor (%)	Maximum output (W)
					Invention battery 1	3.03	0.677	76.0	1.55
Compare battery 1	3.05	0.680	76.8	1.59

The result who proposes from above has tangible difference at invention battery 1 with on relatively not having between the battery 1 to find exporting.This point is pointed out, solar cell of the present invention, even wafer thickness is inhomogeneous, also can successfully obtain to compare battery uniformly with wafer thickness has identical height output.

Next, the height (at the height of substrate thickness direction) of the groove medial surface top electrode of invention battery 1 is measured at SEMT.Measurement result is shown in Fig. 8.Measurement is being shown in making on 9 points altogether of Fig. 7, and one of them some a is at the center, and other all some b then is placed on to i around the center of 3.5cm diameter circle, begins in the position that forms direction along groove, is spaced by 45 ° later on.Arrow SL points out to cut the direction of silicon single crystal ingot among Fig. 7, and substrate from the position 12 to position 13 attenuation gradually.

From the result of this measurement, the standard deviation of electrode height is found to be 1.7, and when the difference that is transformed on electrode sections is long-pending, it equals peaked about 10%.The electrode resistance loss of considering now conventional solar cells is about 5% of output, and estimate the influence that changes at above-mentioned substrate sectional area only for resemble output about 0.5% little.Therefore conclusion is that this degree change can not influence the energy conversion efficiency of solar cell greatly, and can ignore.

(example 2)

Be used to make solar cell, contain III family element boron as the p type monocrystalline silicon piece 1 of impurity element (diameter=4 inch, minimum thickness=270 μ m, maximum ga(u)ge=300 μ m forms the parallel groove with square-section with cast-cutting saw on the surface of the reception sunlight of resistivity=2.0 Ω cm.Form groove, make the thickest position of it and connecting wafer and a straight line parallel of thin value.The edge of a knife part of grinding blade is thick as used herein is 450 μ m, and diameter is 50mm and to have edge of a knife spacing be 50 μ m, identical with example 1.Grinding blade thickness according to the rules is that 450 μ m and deposition angles are 5 °, and then the minimum thickness of groove is that h is restricted to 50 μ m.Process conditions in this regulation comprise that the rotating speed of grinding blade is that 60rpm and wafer charging rate are 1.5mm/s, wherein have cold feed to arrive the delineation position.Wafer is by being held surperficial excessively straight suction dish at working surface.For relatively, also made at the longitudinal direction of groove perpendicular to the thickest position of connecting wafer and the wafer (promptly perpendicular to the groove direction that is shown in Fig. 3) (comparison wafer 2) of a straight line of thin position.Then two kinds of wafers all be subjected to example 1 in those similar manufacture crafts, thereby make solar cell of the present invention (invention battery 2) and with the solar cell of making comparisons (relatively battery 2).

So the output characteristic of the solar cell of making is measured (luminous intensity: 1KW/m with the sunlight simulator ², spectrum: the AM1.5 sphere) measurement result of output characteristic is shown in table 2.

Table 2

	Short circuit current (A)	Open circuit voltage (V)	Duty factor (%)	Maximum output (W)
					Invention battery 2	3.03	0.680	76.7	1.58
Compare battery 2	3.01	0.677	74.8	1.52

The duty factor that invention battery 2 shows it is big approximately by 1.9% than battery frequently, and show higher output.Thereby reach a conclusion, adopting the present invention is successful obtaining higher output facet.

This solar cell has also been measured I-E characteristic according to four-end method in absolute dark, thereby has estimated series resistance.Measurement result is shown in table 3.

Table 3

	Series resistance (Ω cm 2)
		Invention battery 2	1.18
Compare battery 2	1.73

As can be seen from the results, invention battery 2 reaches 0.55 Ω cm with the difference of the series resistance that compares battery 2 ²Therefore think that aforementioned difference aspect duty factor is poor owing to aspect the series resistance.As for mentioning the OECO battery, by groove being formed to such an extent that parallel the resistance loss that just can successfully reduce finger electrode, and therefore can increase output with the thickest point of connecting wafer and the straight line of the thinnest point.

(example 3)

Be used to make solar cell, contain the p type monocrystalline silicon substrate (10cm of III family element gallium as impurity element ², substrate thickness=300 μ m, resistivity=0.5 Ω cm, varied in thickness=maximum 25 μ m) the surface of reception sunlight on, manufacture method according to the present invention forms a plurality of grooves with square-section.The thickness of the edge of a knife of groove delineation blade part is 450 μ m as used herein, and diameter is 50mm, and to connect together and keep edge of a knife spacing be 50 μ m, thereby has constituted the compound groove delineation edge of a knife.This compound groove delineation edge of a knife is arranged on that projecting height h is the place of 50 μ m above the workbench.Process conditions in this regulation comprise that the rotating speed of the compound groove delineation edge of a knife is 50rpm, and the substrate charging rate is 1mm/s.The vacuum cup on surperficial excessively (second first type surface) of first first type surface of wafer by forming groove in the above holds, and puts first first type surface to such an extent that closely contact with the substrate charging surface of workbench.Then, substrate is along moving on the direction perpendicular to the thickness direction of the groove delineation edge of a knife, and cold water is added to the position of work as with reference to the top explanation of doing of figure 9, thus on the semiconductor monocrystal substrate a plurality of grooves of formation.The semiconductor monocrystal substrate that obtains in this technology is referred to as the invention substrate.

As a comparison, another chip semiconductor monocrystal chip is fixed on the workbench, can allows the groove delineation edge of a knife nibble on the upper surface that stays in substrate, then, being parallel to the mobile groove delineation edge of a knife on the substrate charging surface direction of workbench, form groove according to conventional methods thereby form.The semiconductor monocrystal substrate that obtains in this technology is referred to as the comparison substrate.

Then, corrode each substrate, thereby remove affected layer, and using plasma CVD device forms silicon nitride film on the rear surface with potassium hydroxide aqueous solution.Then, V group element phosphorus is introduced into surface one side that receives light as impurity, has the n type emitter layer that sheet resistance is 100 Ω/ thereby form by thermal diffusion.Forming thick on the rear surface by vapor deposition of aluminum then is the electrode of 2 μ m.Next, forming thick by thermal oxidation on the surface that receives light is the tunnel oxidation film of 2 μ m, then from direction perpendicular to the longitudinal direction of parallel groove, and with first first type surface, the 5 place's vapor deposition of aluminum that tilt, be the electrode of 5 μ m only on a side, forming thick on the two sides of groove then.Then, on the top surface of outstanding bulge between each abut groove, also depositing unwanted metal part, remove by adopting the broad corrosion of phosphoric acid water.Purpose is to provide antireflection measure and the surface protection that tackles sunlight, and forming thickness by plasma CVD on the surface that receives light is the silicon nitride film of 70nm, thereby has made solar cell.

The I-E characteristic of this solar cell is with sunlight simulator (luminous intensity: 1KW/m ², spectrum: the AM1.5 sphere) measure.The various characteristics that obtains from the I-E characteristic derivation is shown in table 4.

Table 4

	Short circuit current (A)	Open circuit voltage (V)	Duty factor (%)	Maximum output (W)
					Invention battery 3	3.90	0.675	77.0	2.03
Compare battery 3	3.94	0.680	71.3	1.91

As found from the results, the duty factor (the curve factor of current-voltage curve) that invention battery 3 illustrates it frequently than battery 3 want big by 5.7%, this points out high maximum output.Next, observe the electrode that is formed on the solar cell surface with SEM.With the invention battery compare, find relatively battery 3 on the surface of whole reception light, reach about 15 μ m in the short maximum of groove battery electrode height.Be shown in main poor owing to duty factor of output difference in the superincumbent table 4.Think that the difference on duty factor is because the increase of the series resistance that the long-pending shortage of revealing by the SEM observation of electrode sections causes causes.

From with in view of be clearly, the present invention is at the almost balanced height that is formed on all finger electrodes on the groove medial surface, being successful aspect the variation of the surface portion that is suppressed at whole reception light only.This just makes might make the electrode that can suppress series resistance, and obtains the solar cell of high output.

(example 4)

Delineation is to adopt the workbench that is shown in Figure 11 to carry out according to groove according to the present invention, has formation thereon on this workbench, and wide be 2mm, be the parallel swarf eliminating groove of 5mm deeply, is that 2mm is parallel to the substrate feedstock direction and forms with the flute pitch.At this used substrate is the p type monocrystalline silicon substrate that is used to make solar cell, and it is square as impurity element (10cm) that it contains the boron of III family element, substrate thickness=250 μ m, resistivity=1.0 Ω cm, varied in thickness=maximum 20 μ m).At this used groove delineation blade is to be that 450 μ m and diameter are that the blade portion of the square-section of 50mm is grouped into by having thickness, and these edges of a knife parts connect together again to the edge of a knife spacing that is keeping 50 μ m, thereby constitute the compound groove delineation edge of a knife.This compound groove delineation edge of a knife is arranged on that projecting height is 50 μ m places above the workbench.Here Gui Ding process conditions comprise that the rotating speed of the compound groove delineation edge of a knife is that 60rpm and substrate charging rate are 1.25mm/s, and by coming mobile substrate with the same described in the example 3, groove are formed on first first type surface.

The experiment of another groove delineation also is to adopt not have the workbench that swarf is got rid of groove, carries out under identical condition.Having processed has each sample of 50, but and acceptance rate to be assumes samples do not have glass and fragment after the groove delineation, and sample decides as receiving such as the set point with depth of groove the nonuniformity that departs from not to be arranged.When use does not have the workbench of swarf eliminating groove, but the discovery acceptance rate is 83%, but when using the workbench with swarf eliminating groove, but find that acceptance rate is 98%, but reach 15% with this acceptance rate improvement.This has just proved the improvement aspect productivity ratio.

Claims (6)

1. a method of making solar cell is characterized in that, comprises the step that forms a plurality of grooves at least on a first type surface of semiconductor chip, wherein

Groove delineation blade can rotate under the outstanding one predetermined height on the smooth substrate charging surface of workbench in edge of a knife part that retaining groove is delineated blade, and

Delineation groove on a first type surface of semiconductor chip and keep tight contact the on first type surface and substrate charging surface, and along the substrate charging surface with respect to groove delineation blade, mobile substrate on the direction of delineating the blade thickness direction perpendicular to groove.

2. the method for manufacturing solar cell as claimed in claim 1 is characterized in that, comprises a plurality of blade portion that link on fixing spacing, with one heart in the described groove delineation blade, and can rotate together; And

Adopt the edge of a knife part of outstanding sustained height on a first type surface of semiconductor chip, to form a plurality of grooves in groups with fixing spacing.

3. the method for manufacturing solar cell as claimed in claim 1 or 2 is characterized in that, described workbench has swarf and gets rid of groove on its substrate charging surface.

4. as the method for manufacturing solar cell as described in arbitrary claim in the claim 1 to 2, it is characterized in that described workbench is fixed when rising at the guiding of substrates charge gauge, substrate is fixed when holding on the opposite of first type surface one side; And

Groove is to be moved towards fixing groove delineation blade and delineate by holding fixing substrate.

5. the method for the manufacturing solar cell described in claim 3 is characterized in that, described workbench is fixed when rising at the guiding of substrates charge gauge, and substrate is fixed when holding on the opposite of first type surface one side; And

Groove is to be moved towards fixing groove delineation blade and delineate by holding fixing substrate.

6. pass through the solar cell that the described method of arbitrary claim is made in claim 1 to 5.

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