DE102010006329A1 - Use of applicator roll for structured applying of e.g. hydrofluoric acid on silicon wafer during manufacturing solar cells, using projections that exhibits outer surface, where medium is applied on silicon wafer under effect of dielectric - Google Patents

Abstract

The roll (1) has projections (3a-3c) exhibiting an outer surface (5) and arranged in a form of a mirror image of a structure. An element e.g. corrosive medium, is applied on a semiconductor substrate i.e. silicon wafer under thermal effect of a dielectric e.g. silicon nitride and thermally or wet-chemically produced silicon oxide. The dielectric is located on the corrosive medium on the semiconductor substrate and removed locally by the applied corrosive medium. Dopant diffuses into the semiconductor substrate in regions in which the dielectric is locally removed.

Description

The invention relates to a use of an applicator roll and an applicator roll according to the preamble of claim 10.

In the manufacture of semiconductor devices, particularly solar cell fabrication, there is an increasing need to apply etching or doping media on an industrial scale locally to semiconductor substrates. So far, this is realized by means of complex masking processes, in which those areas in which no immediate order is to take place, are provided with a protective layer. For this purpose, a protective layer is usually first applied over the whole area, which is subsequently opened locally by means of complex photolithographic processes or laser beam evaporation technologies at those locations where the etching or doping medium should come into contact with the semiconductor substrate.

Against this background, the object of the present invention is to provide a cost-effective option for local application of process media, in particular etching or doping agents.

This object is achieved by the use of an applicator roll according to the features of claim 1.

Furthermore, the invention is based on the object to provide an application roller suitable for the use according to the invention with which process media, in particular etching or doping media, can be reliably applied to a multiplicity of semiconductor substrates in a production line in a sufficiently high quality.

This object is achieved by an applicator roll having the features of claim 10.

Advantageous developments are each the subject of dependent claims.

In the use according to the invention, an applicator roll with an outer surface having elevations, on which the elevations are arranged in the form of a mirror image of a structure to be applied, for structured application of an element from a group consisting of an etching medium, a doping medium, a masking lacquer, a metal-containing paste and a heat-generating a dielectric-forming substance used on a semiconductor substrate.

In the structured application, the element is transferred from the elevations to the semiconductor substrate and thereby the structure to be applied is formed from the inserted element. The term of applying an element to a semiconductor substrate is to be understood to mean that the element is applied directly or indirectly to the semiconductor substrate. For example, the semiconductor substrate may be provided with a dielectric layer to which the element is applied.

As a result of the mirror-image arrangement of the elevations on the applicator roll, a structure is visible in a plan view of the outer surface of the applicator roll, which appears mirror-inverted relative to a structure applied to the semiconductor substrate by the applicator roll. The mirror image and the applied structure are, however, not necessarily completely congruent apart from the mirror-invertedness. Thus, for example, slight deviations may occur because an applied element, for example an applied etching solution, readily deliquesces on the semiconductor substrate or the elevations are deformed during the application of an element to the semiconductor substrate due to a contact pressure.

In the present case, a masking varnish is to be understood as meaning a flowable, curable medium which protects a semiconductor surface from the action of a process medium used during processing or further processing of the semiconductor substrate. The masking lacquer can protect the semiconductor surface, for example, from the action of an etching solution, a doping medium or a reactive gas.

In a preferred embodiment of the use according to the invention, the applicator roll is used for the structured application of a masking resist to the semiconductor substrate, and after the application of the masking resist, the semiconductor substrate is at least partially exposed to an etching medium. In areas not protected by the masking lacquer, the surface of the semiconductor substrate is textured by means of the etching medium. As the etching medium, for example, known texture etching solutions or a corrosive plasma can be used.

Under the action of heat, a dielectric-forming substances in the context of the present invention are, usually organic, substances which can be converted by heat into a dielectric in an annealing step.

It has been shown that the use according to the invention allows, as an expense, etching or doping media, masking lacquers, metal-containing pastes or a dielectric under the action of heat forming substances locally on semiconductor substrates, in particular on solar cell substrates such as silicon wafers.

The use according to the invention of an applicator roll for the structured application of a metal-containing paste can, inter alia, advantageously be used in the formation of metal contacts, in particular in the formation of metal contacts on solar cell substrates.

The use according to the invention of an applicator roll for the structured application of a substance which forms a dielectric under the action of heat makes it possible to form local dielectrics on the semiconductor substrate in a comfortable manner.

One embodiment variant of the use according to the invention provides that, for the purpose of local doping of the semiconductor substrate with the application roller, a doping medium is applied in a structured manner to the semiconductor substrate and dopant is diffused from the doping medium into the semiconductor substrate. In this way, a low-cost local doping of the semiconductor substrate can be realized. In some cases, it has proved to be advantageous to dry the applied doping medium against inward diffusion of the dopant. In many cases, however, can be dispensed with such a drying, without affecting this adversely.

A further development of this embodiment provides that before the structured application of the doping medium by means of a further application roller, a doping medium is applied flat to the semiconductor substrate and diffused into the semiconductor substrate. In conjunction with the subsequent local doping medium application and the diffusion of dopant from this locally applied doping medium, a two-stage doping and thus a selective emitter can be formed in this way in a cost-effective manner. The diffusion of the dopant from the locally applied doping medium is advantageously carried out under an oxygen-containing atmosphere. Doping with more than two stages can also be realized in a cost-effective manner by corresponding additional steps of the local doping medium application. The described development of the invention can be advantageously integrated into a line production.

In the present case, surface application is understood to mean application in which, in contrast to a structured application, no structure is formed. Instead, essentially a full-surface application is made to a side of the semiconductor substrate to be coated. Narrow border areas, however, can remain uncoated, for example.

One embodiment variant of the use according to the invention provides that an etching medium is applied in a patterned manner to the semiconductor substrate with the application roller and a surface texture is formed by local etching of the semiconductor substrate by means of the applied etching medium. In this way, for example, low-cost locally the coupling of light into a solar cell substrate can be improved. In this embodiment, applicator rollers may suitably be used whose elevations form a plurality of structures, each of which has an extension of a few micrometers.

Another embodiment provides that an etching medium is applied in a patterned manner to the semiconductor substrate with the application roller and layers formed on the semiconductor substrate are locally etched by means of the applied etching medium. For example, doped semiconductor layers may be formed on the semiconductor substrate, whether by diffusion of dopant into the semiconductor substrate or by applying a doped semiconductor layer. These can be locally etched with this embodiment of the invention and thus removed, which allows for back-contact solar cells a low-cost local separation of a pn junction.

A development of this embodiment provides that the etching medium is applied to a solar cell substrate, on which a dielectric is arranged. This dielectric is preferably silicon nitride or a thermally or wet-chemically generated oxide. The dielectric is further removed locally by means of the applied etching medium and in those areas in which the dielectric was locally removed, dopant is diffused into the solar cell substrate. The dielectric, in particular silicon nitride or thermally or wet-chemically produced silicon oxide, can serve as a diffusion barrier for the dopant, so that no dopant diffuses into the solar cell substrate in the regions covered by the dielectric. As illustrated by this development, the use according to the invention, inter alia, also makes possible a cost-effective configuration of a masking method in which a dielectric is used instead of a masking varnish for masking the semiconductor substrate.

If a dielectric is used which does not act as a diffusion barrier but only a layer which inhibits the diffusion of dopant but does not prevent it, a local selective removal of the dielectric by means of the applied etching medium in a single diffusion step can be used to form a selective emitter. In those areas where the dielectric has been removed, the dopant passes freely into the solar cell substrate and doped comparatively strong, while located in areas located below the dielectric only a small amount of dopant reach the solar cell substrate, so that there is a comparatively weak doping is formed. However, it is sometimes difficult to realize a sufficiently homogeneous weak doping in this way.

This problem of homogeneity can be circumvented by using a diffusion barrier dielectric. Thus, with the described development, for example, a multistage doping of a solar cell substrate, in particular a two-stage doping as in the case of a selective emitter, can be formed, for example, with low outlay on costs. For this purpose, surface dopant is diffused into the solar cell substrate prior to the arrangement of the dielectric on the solar cell substrate, and a comparatively weak doping is thereby formed. For flat diffusion of dopant, for example, by means of an applicator roll, a doping medium can be applied in a planar manner. After arranging and locally removing the dielectric, comparatively strong dopant is diffused in those regions in which the dielectric has been removed, the remaining dielectric serving as a diffusion barrier. The result is a two-stage or selective emitter. By multiple, successive local removal of the dielectric associated with diffusion of dopant in the opened regions, multi-stage dopants with more than two doping stages can obviously be formed.

Advantageously, in the described development for the purpose of diffusion of dopant into the solar cell substrate by means of a further application roller, a doping medium is applied to the surface of the dielectric and thereby doping medium in areas in which the dielectric was removed introduced. In the remaining regions, the solar cell substrate is protected by the dielectric against the diffusion of dopant from the dopant medium applied in a planar manner. The additional applicator roller used in this case need not have a structure. Drying of the doping medium applied by means of the further application roller before the diffusion of the dopant may be advantageous in individual applications. Due to the flat application of the doping medium, only a very coarse alignment of the solar cell substrate to the other applicator roll is required.

Alternatively, in the described development for the purpose of diffusion of dopant into the solar cell substrate by means of a further applicator roll a doping medium structured in those areas in which the dielectric was removed, applied and dopant from the doping medium are diffused into the solar cell substrate. Advantageously, a further application roller is used, which has elevations that represent substantially the same structure as the elevations of the applicator roll previously used for the application of the etching medium. The doping medium can thus be applied in a simple manner substantially in those regions in which the dielectric has been removed, and application of doping medium to other regions can be avoided, at least to a large extent. This alternative embodiment variant can advantageously be used in conjunction with dielectrics which have no diffusion barrier effect with respect to the dopant used.

Against this background, it is also conceivable that, although the elevations of the further applicator roll form substantially the same structure as the elevations of the applicator roll used for the application of the etching medium, they have a reduced cross-sectional area. This reduces the risk that the elevations of the further applicator roll will release doping medium onto the remaining dielectric or other areas not intended for a dopant medium application. In the choice of the structure of the further application roller, in particular the cross sections of the structure forming surveys, it has proved to be useful to take into account the properties of the doping medium used, in particular its flow behavior. This takes into account the fact that applied doping medium can also be brought, for example, by partially flowing the applied structure into areas in which no doping medium application is desired.

In the described alternative embodiment, it has proven advantageous to form line-like openings by the local removal of the dielectric. In a further development of the method, a silicon nitride layer is then applied to the solar cell substrate in a planar manner, using an etching medium according to the invention structuredly applied to the silicon nitride layer and locally removed by etching, but at least partially leaving the underlying dielectric layer. The etching medium is applied to the silicon nitride layer in such a way that linear openings are formed in the silicon nitride layer by the etching. These line-shaped openings in the silicon nitride layer are aligned such that they intersect with a projection in the plane of the line-like openings in the dielectric layer with these at a non-zero angle, preferably at an angle of about 90 °. Furthermore, in the linear openings in the Silicon nitride layer introduced and sintered a metal paste without glass frit. This results in the intersections of the line-shaped openings in the silicon nitride layer with the line-shaped openings in the dielectric layer selective contact of the solar cell substrate, which is heavily doped at a location formed in the manner described above selective emitter at this point. An error-prone alignment of linear openings in the dielectric layer with the local application of the doping medium and the metal-containing paste can be avoided in this way. Instead, only the line-shaped openings in the silicon nitride layer need to be aligned with the metal-containing paste. The latter can be applied structured in a preferred variant with an applicator roll. Alternatively, an application by means of known screen printing technology is conceivable.

In practice, it has proven useful in some cases to dry the doping medium before the diffusion of the dopant. This can be done in conventional drying ovens, especially dry-running ovens. However, such drying can generally be omitted.

In the case of the use according to the invention, in particular if an etching medium is to be applied directly or indirectly to a silicon wafer, it has proved advantageous to use as the etching medium a hydrofluoric acid-containing etching medium, preferably a solution containing hydrofluoric acid.

In the use according to the invention, it has proved useful to use a phosphoric acid or boric acid-containing doping medium, preferably a solution containing phosphoric acid or boric acid, as the doping medium.

The use according to the invention makes it possible to apply only comparatively small amounts of an etching or doping medium, so that a smaller amount of chemicals is needed compared to a full-surface media application or etching baths, which reduces the consumption of chemicals and also increases the safety at work. It has also been found that reactions that occur as a result of the etching or doping medium application often end in the depletion of at least one reaction species involved. Production processes can thus be made less susceptible to deviations from intended process times, for example etching times.

In industrial production, the semiconductor substrates are generally transported through a production line via known conveyor systems, such as roller conveyors, conveyor belts or lifting beam systems. Against this background, it has been found useful to use applicator rollers whose circumference is dimensioned at areas passing into contact with the respective semiconductor substrate in such a way that it corresponds to the longitudinal extent of an area to be provided with an etching or doping medium in the transport direction of the semiconductor substrate. In addition, it is conceivable to provide several order rollers whose circumference corresponds in each case only a part of said longitudinal extent in the transport direction of the semiconductor substrate.

The elevations of the applicator roll are to be matched to the etching or doping medium used in such a way that the desired structural dimensions can be ensured. In order to achieve clear and precisely delimited structures, or a uniform doping, of the semiconductor substrate, the etching or doping medium must be applied in a uniform amount to the semiconductor substrate. This requires a suitable feeding of the application roller with the respective etching or doping medium.

This can for example be realized by the applicator roll is brought into contact with an additional donor roll. For example, the donor roll may be wetted by a nozzle system or the like with the etching or doping medium and further transfers the medium to the applicator roll.

Alternatively, it may be provided that the application roller is arranged in part within the etching or doping medium held in a container, so that during rotations of the application roller at least its elevations are moved through the etching or doping medium and thereby wetted. The recorded etching or doping medium can then be further applied to the semiconductor substrate.

Particularly advantageous is the use of an applicator roll according to the invention has been found according to claims 10 to 15.

The application roller according to the invention provides an outer surface having elevations on which the elevations are arranged in the form of a mirror image of a structure to be applied, wherein the elevations can be fed from an inner region of the applicator roll from a coating liquid.

Such an applicator roll allows for a comparatively long time a uniform and thus reliable application of an etching or doping medium on a variety of semiconductor substrates.

In one embodiment of the applicator roll according to the invention, the elevations are at least partially formed from a foam.

In a further development of the invention, the foam extends at least in sections into the interior of the applicator roll. In this way, the etching or doping medium can pass through the cavities of the foam to the outer surface, so that no separate openings or channels are required. If the cavities in the foam are dimensioned such that capillary effects promote the transport of the etching or doping medium to the outer surface of the applicator roll, this is advantageous for a uniform application of the etching or doping medium.

An advantageous embodiment variant of the applicator roll according to the invention provides that at least part of the elevations, preferably all elevations, are provided with openings through which the application liquid can flow, which openings are connected to the inner area of the applicator roll. As a result, the etching or doping medium used can be supplied to the elevations. Such openings may be provided in particular also in elevations of foam, which extends at least in sections into the inner region of the applicator roll.

In a preferred embodiment of the applicator roll according to the invention whose inner region can be placed under pressure. As a result, the supply of the application liquid from the interior to the elevations can be improved.

Another embodiment variant provides a squeegee arranged at least partially in the inner region of the application roller, by means of which a film can be guided along a wall of the inner region. This embodiment variant is particularly advantageous when using a high-viscosity coating liquid.

In the following the invention will be explained in more detail with reference to figures. Insofar as appropriate, identical elements are provided with the same reference numerals herein. Show it:

1 Side view of a first embodiment of an applicator roller according to the invention in a schematic representation

2 Schematic sectional view through the applicator roll 1

3 : Another embodiment of an applicator roller according to the invention in a schematic representation

4a : Schematic sectional view of the applicator roll 3

4b : Schematic sectional view through an applicator roll similar to those from 3

5a . 5b : Embodiment of an inventive use of an applicator roll in a schematic representation

6a to 6d A second exemplary embodiment of the use of an applicator roll according to the invention in a schematic representation

7a A third embodiment of the inventive use of an applicator roll in a schematic representation

7b : Front views to the schematic representations of the 7a

8th : A fourth embodiment of the inventive use of an applicator roll in a schematic representation

1 shows a schematic representation of a side view of a first embodiment of an applicator roll according to the invention 1 , This has three surveys 3a . 3b . 3c which are each completely from an outer surface 5 the applicator roll 1 take off. This illustrates, among other things 2 which is a sectional view through the applicator roll 1 out 1 represents along the line AA. In 2 is the applicator roll radius 13 away from the surveys 3a . 3b . 3c shown in dashed lines. This clarifies that the survey 3a completely from the outer surface 5 the applicator roll lifts.

Each of the surveys 3a . 3b . 3c is with openings 9a . 9b . 9c . 9d . 9e . 9f . 9g . 9h Mistake. Of these, the openings extend 9b . 9d . 9f and 9h into an interior area 7 the applicator roll 1 into it. The openings 9a . 9c . 9e and 9g By contrast, they only extend to one channel 11 which the openings 9a . 9b . 9c . 9d . 9e . 9f . 9g . 9h connects with each other. The openings 9a . 9b . 9c . 9d . 9e . 9f . 9g . 9h as well as the canal 11 are flowed through by a coating liquid. This can therefore be based on the interior 7 directly or indirectly via the channel 11 to all openings 9a . 9b . 9c . 9 . 9e . 9f . 9g . 9h reach. The surveys 3a . 3b . 3c is thus of the interior 7 the applicator roll 1 from a contract liquid fed. The surveys 3a . 3b . 3c as well as the other parts of the applicator roll 1 can be made of basically any material, in particular of solid materials.

The 3 and the associated sectional view along the line BB 3 illustrate in schematic representations another embodiment of an applicator roll according to the invention 21 , This applicator roll 21 again has surveys 23a . 23b . 23c . 23d . 23e . 23f on which on the outside surface 5 the applicator roll 21 are arranged.

While the surveys 3a . 3b . 3c the applicator roll 1 out 1 represent a structure of parallel lines to be applied form the surveys 23a . 23b . 23c . 23d . 23e . 23f the applicator roll 21 out 3 parallel lines and to perpendicular cross lines from. In the embodiment of 1 consists of the structure to be applied thus from parallel lines, in the embodiment of 3 from parallel lines and perpendicular cross lines. Since the structures to be applied are mirror-symmetrical in both cases, the structure to be applied relative to the surface is a mirror image of the elevations 3a . 3b . 3c in 1 , or the surveys 23a . 23b . 23c . 23d . 23e . 23f in 3 , not immediately recognizable.

In the embodiment of 3 and 4a are the surveys 23a . 23b . 23c . 23d . 23e . 23f made of a foam. As 4a the example of the survey 23a Illustrated, are the surveys 23a . 23c and 23d formed from an annular foam that extends into the interior 7 the applicator roll 21 extends. Due to this configuration can in the embodiment of 3 and 4a to be dispensed with openings, which the elevations to the interior 7 connect. Instead, the application fluid through the cavities in the foam of the surveys 23a . 23c . 23d passed through to the outside. In principle, however, openings may also be provided in elevations formed from foam.

4b Illustrates a schematic representation of another embodiment of an applicator roll according to the invention. Their side view essentially corresponds to that of the applicator roll 21 out 3 , However, the cross section deviates from that of the applicator roll 21 out 3 as in a comparison of the sectional views 4a and 4b becomes visible. Although in the embodiment of 4b the assessment 23a ' also made of foam, but this does not extend as in the case of 4a to the interior 7 the applicator roll. Instead, a hollow core roll 25 provided with core openings 27a . 27b . 27c . 27d which is on your part to the interior 7 extend. The core openings 27a . 27b . 27c . 27d borders in the 4b shown way to the survey 23a ' at. Application liquid can thus from the interior 7 over the core openings 27a . 27b . 27c . 27d the foam of the survey 23a ' reach and through its cavities to the outer surface of the survey 23a ' reach.

To support the supply of application liquid from the inside 7 in the surveys is the interior of the embodiments of the 1 to 4b can be placed under positive pressure. In addition, in the embodiment of 4b a squeegee 29 indoor 7 arranged the applicator roll. Diesel squeegee 29 is rotatable about a squeegee axis 31 stored and has at her the hollow core 25 facing side a foil 33 on, which by rotation of the squeegee 29 around the squeegee axis 31 on a wall 26 of the hollow core roll 25 and thus the interior 7 is feasible along. By rotation of the squeegee 29 around the squeegee axis 31 can therefore be in the interior 7 arranged application liquid through the core openings 27a . 27b . 27c . 27d be pressed and in this way the supply of coating liquid to the surveys realized or at least supported.

It's obvious that the doctoring technology is off 4b also in the design variants of 1 to 4a can be provided.

5a illustrates an embodiment of the inventive use of an applicator roll 41 , According to this embodiment, the applicator roll 41 surveys 43a . 43b . 43c by which a texture etching solution 47 , For example, a hydrofluoric acid etching etching solution 47 , structured on a silicon wafer 45 is applied. As a result of this application of texture etching solution, the silicon wafer, which may be a solar cell substrate, for example, is locally etched. The applicator roll 41 For example, could be fed by a donor roller, not shown, which with the applicator roll 41 in contact and the texture etching solution 47 transfers to this. The donor roll could in turn be from a nozzle system or the like with the texture etching solution 47 be wetted.

The resulting result illustrates the schematic representation of the 5b , As can be seen, the local etching in those areas where the texture etch solution 47 was applied, a surface texture 49 educated. This can be used, for example, in solar cells to increase the light coupling.

The 6a to 6d illustrate another embodiment of the use of an applicator roll according to the invention. In this embodiment, a semiconductor substrate, in the present case a silicon wafer 45 , locally doped. For this purpose, by means of 1 known application roller 1 initially structured one phosphoric acid solution 51 on the silicon substrate 45 applied. As in 6b shown, the applied phosphoric acid solution is subsequently in a schematically indicated dry-running furnace 53 dried, although in principle also other drying ovens can be used. However, such a drying process is not mandatory. Partly better results can be achieved if the drying process is omitted. In the following, in a continuous diffusion furnace 57 which is in 6c is shown schematically and obviously can be replaced by diffusion ovens of another type, phosphorus from the dried phosphoric acid solution 55 in the silicon wafer 45 diffused. As a result, a two-stage doping results together with a weak n-type doping which is essentially present even before the diffusion of the phos- phorus from the dried phosphoric acid solution. This is schematically in 6d represented by the dashed line.

Said dashed line in 6d illustrates weaker doped areas 60 which, in essence, by the already before the diffusion of phosphorus from the dried phosphoric acid solution 55 existing n-type doping are formed, as well as more heavily doped regions 59 , which by diffusion of phosphorus from the dried phosphoric acid solution 55 according to 6c were trained. 6d thus shows a two-stage doping, which also readily dopants with more than two stages can be formed. A two-stage doping according to the illustration of 6d For example, in solar cells, it can be used as a selective emitter. As a matter of principle, obviously p-type dopings or dopings of different types can be combined with each other.

The 7a and 7b show a schematic representation of another embodiment of a use according to the invention. According to this is first by means of a mandrel 61 structures an etching medium onto a thermally or wet-chemically produced silicon oxide layer 63 applied 100 which is on a silicon wafer 45 is arranged. 7b illustrates this process step schematically in a side view. The applied etching medium is both in the 7a as well as in the 7b for better clarity, not shown.

The 7a and 7b illustrate the processes in a line production in which the silicon wafer is transported further in the production line. In the 7a and 7b this is by means of the transport direction 65 indicated. This transport direction 65 At the same time, this indicates the chronological sequence of the various process steps.

Accordingly, in the following, the silicon oxide 63 locally removed 102 by locally etching the silicon oxide by means of the applied etching medium. As a result, as in 7b recognizable, openings in the silicon oxide 63 ,

Furthermore, by means of a further application roller 67 one of the sake of clarity only partially phosphoric acid solution shown in places 51 applied flat 104 , As from the schematic representation of 7b becomes clear is thereby as another application roller 67 an applicator roll 67 used, which has no surveys. The surface of the applicator roll 67 has a certain flexibility. For example, it may consist of foam or have a foam sheath. Since silicon oxide layer with a thickness of a few to a few hundred nanometers is also much thinner compared to the silicon wafer than the schematic representation of 7a and 7b initially expect, comes the surface of the applicator roll 67 during structured ordering 104 the phosphoric acid solution 51 contrary to the simplified schematic representation of 7b both with the surface of the silicon oxide 63 as well as in those areas where the silica 63 was removed locally 102 , with the solar cell substrate 45 in contact. Thus, phosphoric acid solution becomes 52 on these areas as well as on the silicon oxide 63 applied 104 ,

After the structured application 104 the phosphoric acid solution 51 this is in the dry-running furnace 53 dried 106 , This drying step 106 is optional and not mandatory. With and without drying step good results could be achieved. Depending on the process, a drying step or its elimination may prove more favorable. As the phosphoric acid solution 51 was applied flat 104 , it is also after the drying step 106 both in those areas where the silica 63 was removed 102 , as well as on the silicon oxide 63 available.

The following is in a continuous diffusion furnace 57 Phosphorus from, when using a drying step 106 meanwhile dried, phosphoric acid solution 51 in the silicon wafer 45 diffused 108 , As 7b in which simplifying the dry-running furnace 53 as well as the diffusion continuous furnace 57 are not shown, can be seen are due to the Phosphoreindiffusion 108 in those areas in which the phosphoric acid solution 51 during the area application 104 was applied to the solar cell substrate 104 , more heavily doped areas 60 educated.

In the surrounding areas, the remaining silicon oxide layer worked 63 during the diffusing 108 of the phosphorus from the phosphoric acid solution 51 as a diffusion barrier, so that it remains essentially in an n-type doping with a lower dopant concentration, which already, as in 7b schematically indicated by the dashed line, was initially present. The result is thus a two-stage doping from weaker doped areas 60 and more heavily doped areas 59 and thus a selective emitter.

In principle, p-type dopings or dopings of different types can obviously also be combined with one another. The dopants or media should then be selected accordingly.

Finally, with a metallization device 69 For example, by means of a known screen printing device, a metallization 71 on the more heavily doped areas 59 upset 110 , Alternatively, the metallization device 69 provide an applicator roll having an elevations outer surface, on which the elevations are arranged in the form of a mirror image of the structure to be applied, so that the metallization can be applied structured with this applicator roll 110 ,

On a representation of the doping concentration corresponding to the dashed line in 7b was in 7a omitted for the sake of clarity. The remaining silica 63 may be used hereinafter, for example, as an antireflection coating or surface passivation layer. Advantageously, an anti-reflection coating can be applied to the solar cell substrate, in particular a silicon nitride layer, in a manner known per se prior to application of the metallization.

8th shows a schematic representation of a fourth embodiment of the inventive use of an applicator roll. According to this is first by means of another applicator roll 67 which has no elevations, surface boric acid solution as a doping medium on a silicon wafer used as a solar cell substrate 45 applied 112 , The boric acid solution is not shown for the sake of clarity. There 8th again schematically shows the sequence in a line production, the transport direction is again by the arrow 65 shown. Accordingly, in the following, in a first continuous diffusion furnace 57a Boron from the applied boric acid solution in the silicon wafer 45 diffused 114 , As a result, a planar boron doping 73 formed, as indicated schematically by a dashed line.

In addition, by means of the applicator roll 61 for the purpose of local doping of the silicon wafer 45 Boric acid solution structured on the silicon wafer 45 applied 116 , The boric acid solution is again not shown for reasons of clarity. The following is in a second continuous diffusion furnace 57b Boron from the structured applied boric acid solution diffused into the silicon wafer 118 , As a result, a selective emitter with more heavily doped regions results 59 and weaker areas 60 , The more heavily doped areas 59 can subsequently in a similar manner as in connection with the more heavily doped areas 7b be metallized described. An antireflection coating may be provided. Obviously, in the embodiment of the 8th use a doping medium other than boric acid solution, for example, a phosphorus-containing medium.

LIST OF REFERENCE NUMBERS

1

applicator roll

3a

survey

3b

survey

5

outer surface

7

interior

9a

opening

9b

opening

9c

opening

9d

opening

9e

opening

9f

opening

9g

opening

9h

opening

11

channel

13

Applicator roll radius away from elevations

21

applicator roll

23a

survey

23a '

survey

23b

survey

23c

survey

23d

survey

23e

survey

23f

survey

25

Rolling hollow core

26

wall

27a

core opening

27b

core opening

27c

core opening

27d

core opening

29

doctor

31

blade axis

33

foil

41

applicator roll

43a

survey

43b

survey

43c

survey

45

silicon chip

47

Texturätzlösung

49

surface texture

51

phosphoric acid solution

53

Dry continuous furnace

55

dried phosphoric acid solution

57

Diffusion continuous furnace

57a

Diffusion continuous furnace

57b

Diffusion continuous furnace

59

more heavily doped area

60

weaker endowed area

61

applicator roll

63

silica

65

transport direction

67

further application roller

69

metallizing

71

metallization

73

Planar boron doping

100

Structured application of etching medium

102

Local removal of silica

104

Flat application of phosphoric acid solution

106

Dry phosphoric acid solution

108

Indiffusion Phosphorus

110

Apply metallization

112

Surface application Boric acid solution

114

Indiffusion boron

116

Structured application boric acid solution

118

Indiffusion boron

Claims (15)

Use of an applicator roll ( 1 ; 41 ; 61 . 67 ) with a survey ( 3a . 3b . 3c ) outer surface ( 5 ) on which the surveys ( 31 . 3b . 3c ) are arranged in the form of a mirror image of a structure to be applied, for structured application ( 100 ; 104 ) of an element from a group consisting of an etching medium ( 47 ), a doping medium ( 51 ), a masking varnish, a metal-containing paste and a heat-imparting dielectric substance on a semiconductor substrate (US Pat. 45 ). Use according to claim 1, characterized in that as semiconductor substrate ( 45 ) a solar cell substrate ( 45 ), preferably a silicon wafer ( 45 ). Use according to one of the preceding claims, characterized in that, for the purpose of local doping of the semiconductor substrate ( 45 ) with the applicator roll ( 1 ; 67 ) a doping medium ( 51 ) structured on the semiconductor substrate ( 45 ) ( 116 ) and dopant from the doping medium into the semiconductor substrate ( 45 ) diffused ( 118 ), wherein the applied doping medium is preferably dried before the diffusion of the dopant. Use according to claim 3, characterized in that before the structured application ( 116 ) of the doping medium by means of a further application roller ( 67 ) a doping medium flat on the semiconductor substrate ( 45 ) ( 112 ) and in the semiconductor substrate ( 45 ) is diffused ( 114 ). Use according to one of claims 1 to 2, characterized in that with the applicator roll ( 41 ) an etching medium ( 47 ) structured on the semiconductor substrate ( 45 ) and by local etching of the semiconductor substrate ( 45 ) by means of the applied etching medium ( 47 ) a surface texture ( 49 ) is formed. Use according to one of claims 1 to 2, characterized in that with the applicator roll ( 61 ) an etching medium structured on the semiconductor substrate ( 45 ) is applied ( 100 ) and on the semiconductor substrate ( 45 ) trained layers ( 63 ) are locally etched by means of the applied etching medium ( 102 ). Use according to claim 5, characterized in that - the etching medium is applied to a solar cell substrate ( 45 ) is applied, on which a dielectric ( 63 ), preferably silicon nitride or an oxide ( 63 ), - the dielectric ( 63 ) is removed locally by means of the applied etching medium ( 102 ), - and in those areas in which the dielectric ( 63 ) was removed locally ( 102 ), Dopant in the solar cell substrate ( 45 ) is diffused ( 108 ). Use according to claim 7, characterized in that for the purpose of diffusion ( 108 ) of dopant into the solar cell substrate ( 45 ) by means of a further application roller ( 67 ) a doping medium ( 51 ) is applied flat to the dielectric ( 104 ) while doping medium in areas in which the dielectric ( 63 ) was removed ( 102 ), ( 104 ) and in these areas dopant from the doping medium ( 51 ) into the solar cell substrate ( 45 ) diffused ( 108 ) becomes. Use according to one of the preceding claims, characterized in that an applicator roll ( 1 ) is used according to one of the following claims. Application roller ( 1 ; 21 ) with a survey ( 3a . 3b . 3c ; 23a . 23b . 23c . 23d . 23e . 23f ; 23a ' ) outer surface ( 5 ) on which the surveys ( 3a . 3b . 3c ; 23a . 23b . 23c . 23d . 23e . 23f ; 23a ' ) are arranged in the form of a mirror image of a structure to be applied, characterized in that the elevations ( 3a . 3b . 3c ; 23a . 23b . 23c . 23d . 23e . 23f ; 23a ' ) from an interior area ( 7 ) of the applicator roll ( 1 ; 21 ) From a contract liquid can be supplied. Application roller ( 21 ) according to claim 10, characterized in that the elevations ( 23a . 23b . 23c . 23d . 23e . 23f ; 23a ' ) are formed at least in part of a foam. Application roller ( 1 ) according to one of claims 10 to 11, characterized in that at least part of the elevations ( 3a . 3b . 3c ), preferably all surveys ( 3a . 3b . 3c ), with openings through which the application liquid can flow ( 9a . 9b . 9c . 9d . 9e . 9f . 9g . 9h ), which with the interior ( 7 ) of the applicator roll ( 1 ) are connected. Application roller ( 1 ) according to claim 12, characterized in that at least a part of the openings ( 3a . 3b . 3c ) by means of at least one channel through which the application liquid can flow ( 11 ) is interconnected. Application roller ( 1 ; 21 ) according to one of claims 10 to 13, characterized in that the interior area ( 7 ) of the applicator roll ( 1 ; 21 ) can be placed under pressure. Applicator roll according to one of claims 10 to 14, characterized by at least one at least partially in the interior ( 7 ) of the applicator roll arranged doctor blade ( 29 ), by means of which a film ( 33 ) on a wall ( 26 ) of the interior ( 7 ) Is feasible along.

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