WO2002059981A2

WO2002059981A2 - Production of electrical connections in substrate openings on circuit units by means of angularly directed deposition of conducting layers

Info

Publication number: WO2002059981A2
Application number: PCT/DE2002/000208
Authority: WO
Inventors: Titus Rinke
Original assignee: Universität Stuttgart
Priority date: 2001-01-24
Filing date: 2002-01-23
Publication date: 2002-08-01
Also published as: DE10290245D2; WO2002059981A3; AU2002240791A1; DE10103114A1

Abstract

The method of production can, amongst others, be used for the production of solar modules, in which the individual solar cells are electrically connected in series. At least one recess (10) is thus produced in a semiconductor layered construct, containing a p-n junction and an electrically-conducting substance (Al) deposited in an essentially directed manner on a substrate section comprising the recess (10), whereby the deposition direction, running at a solid angle, is set at such an inclination that only a wall section within the recess (10) is covered by the electrically-conducting material and thus the front electrode layer (6) of a solar cell is electrically contacted with the rear electrode layer (11) of a solar cell neighbouring the above cell. By means of said method metallisation levels of multi-layered circuit boards can be electrically connected to each other.

Description

description

Establishing electrical connections in substrate openings of circuit units by means of directional deposition of conductive layers

The present invention relates to a production method for an electronic or optoelectronic circuit unit and in particular to an electrical contacting structure therein. In this method, an opening or depression is formed into a substrate surface in a substrate as an intermediate product of the circuit unit, and an electrically conductive substance is applied to a substrate section containing the depression. The method can be applied, for example, to the series connection of photovoltaic solar cells in a solar module or to the contacting between metallization levels of a multiple printed circuit board.

In the manufacture of electrical contacting structures for electronic or optoelectronic circuit units, there is often a problem due to the spatial density of the conductor track and metallization structures that are present or to be produced, in order to selectively and spatially selectively produce electrical connections between two or more contact connections. To achieve this, several structuring and deposition processes have to be carried out in a complex manner.

An example of such circuit units are so-called solar modules, which have a plurality of solar cells, in particular thin-film solar cells, which are to be connected in series by means of electrical contacting structures. To this end, numerous proposals have been published that enable such a series connection. US-A-5, 593, 901 describes a photovoltaic solar module and a method for its production, in which the individual layers are alternately deposited and mechanically structured on an insulating transparent substrate such as a glass substrate. First, a conductive transparent film is applied to the substrate plate and structured in a plurality of parallel front electrodes. Then a photovoltaic region made of a thin film of hydrogen-doped, amorphous silicon is applied to the front electrodes and the trenches between them in a conventional PIN structure. The semiconductor material in the trenches between the front electrodes ensures electrical isolation of the front electrodes from one another. Then, in the photovoltaic semiconductor layer taischen parallel trenches are produced, and the semiconductor layer thus patterned into a plurality of photovoltaic elements, which come _to lie respectively above the front electrode. Finally, a thin film of a conductive material is applied to the structured semiconductor layer and the trenches formed between the solar cells. The material of this conductive layer that fills the trenches in the semiconductor layer provides electrical connections between the conductive film and the front electrodes. By forming trenches in the conductive film, the latter is then structured into a plurality of back electrodes.

US Pat. No. 6,011,215 describes a further photovoltaic solar module which has a plurality of photovoltaic regions which are electrically connected in parallel with one another. This solar module has in particular a metallic substrate, an electrically insulating layer arranged on the substrate, an electrically conductive lower electrode layer on the insulating layer, a plurality of electrical vias defined in the lower electrode layer and the insulating layer, one on the lower electrode layer disposed Semiconductor layer and an upper transparent electrically conductive material layer. The insulating layer and the lower electrode layer are thus partially broken through by the plated-through holes and the front side contact formed by the upper electrode layer is connected to the conductive substrate by the vertical plated-through holes.

A publication by SI Mizuno et al. in "Technical Digest ll ^th photovoltaic solar energy Conference (Sapporo, 1999)", p. 745, describes the production of a separable epitaxial layer on a semiconductor wafer, to which a plastic film is glued after completion of the solar cell. This plastic film is cut through with the laser, a second laser beam then cuts vertically through the epitaxial membrane. Then the plastic film together with the epitaxial membrane is lifted off the wafer and the back of the module is encapsulated.

Finally, it should also be mentioned that in CuInGaSe ₂ - (CIGS) solar cell technology, a glass substrate is usually used, on which a molybdenum layer is applied. This molybdenum is then structured mechanically or by means of a laser beam, ie separated into individual strips. In a second step, the CIGS is applied and then also cut laterally offset to the molybdenum strips. After deposition of a buffer layer, a transparent front electrode is applied in a third step and then also cut laterally offset to the CIGS structuring.

The above-mentioned techniques for series connection in solar modules are either too complex to process or achieve poor or non-reproducible module efficiencies. On the other hand, however, a series connection of single cells to modules is necessary, since single cells only deliver a voltage of less than 1 volt and Modules with a voltage of more than 10 volts are usually in demand.

An electronic circuit unit, in which electrical contacts are made, is, for example, a multilayer printed circuit board in the literal sense used here. There is also a problem in the prior art with multilayer printed circuit boards in that printed circuit boards generally become more and more compact in construction and the individual conductor tracks become ever finer, so that the technology for their production approaches the manufacture of conductor tracks on integrated circuits. It is therefore becoming increasingly difficult to electrically connect different metallization levels in pairs or groups to one another within a multilayer printed circuit board.

The connection of the individual metallization levels of multilayer printed circuit boards is carried out conventionally by galvanically applying metal in so-called via holes. However, this method only enables the connection of two specific levels in a via hole. In this process, as much metal has to be electrodeposited until the thickening metal levels touch and thus establish electrical contact with one another.

From Japanese patent application JP 02310994 A, a method for applying a conductive material to a through contact of a printed circuit board is known, in which the printed circuit board is fastened on an axis of rotation, the through hole to be coated being arranged outside the axis of rotation. Then the printed circuit board is acted upon in a directed manner with conductive material, the deposition device being inclined with respect to the walls of the through hole. At the same time, the circuit board is rotated around its axis of rotation. Thus, not only the surface of the circuit board facing the evaporation source of the conductive substance but also the walls of the through hole coated evenly with the conductive substance. However, only the entire inner wall of the through hole can be coated. A selective application of the conductive substance to certain sections of the inner wall is not possible.

US Pat. No. 6,147,311 describes a multilayer printed circuit board in which the metallization levels are embedded between adhesive layers and in which electrically conductive particles are dispersed. Different metallization levels are connected to one another in that, with a suitable device, conductor tracks are bent at their ends through the adhesive layer against the conductor track of the adjacent metallization level, wherein the effect of the electrically conductive particles in the adhesive layer creates an electrical contact between the conductor tracks of the metallization levels. In order to contact conductor tracks of several metallization levels with one another, however, a corresponding number of bending steps are necessary. It is not possible to connect several metallization levels to one another with a single method step. This method is therefore too complex for more complicated contacting processes.

It is therefore the object of the present invention to provide a production method for an electronic or optoelectronic circuit unit, in particular for its electrical contacting structure, by means of which the circuit unit can be manufactured with less production outlay. In particular, it is an object of the present invention to produce a solar module in which a plurality of photovoltaic solar cells are connected to one another in series. Furthermore, it is a particular object of the present invention to produce a multilayer printed circuit board and to electrically contact different metallization levels with one another in pairs or groups. This object is achieved with the features of patent claim 1. Advantageous refinements and developments of the method according to the invention are specified in the subclaims.

An essential aspect of the method according to the invention is that an opening or depression is produced in a substrate, which is an intermediate product of the circuit unit to be produced, and the opening is subjected to the deposition of at least one electrically conductive substance. The deposition can be carried out, for example, by vapor deposition or sputtering of the electrically conductive substance from a suitable source.

The decisive factor here is that the deposition is carried out in an essentially directional manner, so that a section within the depression is not covered by the electrically conductive substance. This means that from an isotropic distribution of deposition directions, at least one spatial angle region must be masked out, which is directed towards this section that is not to be covered.

In general, this means that the deposition directions present during the deposition of the electrically conductive substance, which in practice extend over a certain solid angle, are skewed with respect to at least one wall of the substrate opening. This has a shadowing effect, so that within the substrate opening a wall and / or bottom section of the depression is not covered by the electrically conductive substance during the deposition. An ideal case is when the deposition is completely directed, ie there is only one deposition direction and this is inclined to the wall of the depression in question and directed away from it. In practice, this ideal case can hardly be achieved, since on the one hand the conductive substance is emitted from the source into a solid angle and the one direction would lead to an unacceptable reduction in material yield and throughput. On the other hand, the vapor deposition systems used are usually operated in such a way that the substrates to be vaporized are moved below the source during the vaporization, so that a solid angle of the deposition would result even with completely directed deposition on the part of the source. It will therefore mostly be important to set this solid angle by means of apertures attached to the outlet of the conductive substance from the source, possibly taking into account a distance traveled by the substrate during the vapor deposition, in such a way that the solid angle does not contain any deposition direction which points to the relevant wall of the recess is directed. In most cases, the deposition directions contained in the solid angle must be inclined to the wall in question and directed away from it.

However, this does not apply in general, but also depends on the aspect ratio of the recess (depth / width ratio). If the aspect ratio is large enough, deposition directions can also be present which are directed towards the wall in question, as long as there are deeper sections which cannot be reached by any deposition direction.

The term “essentially directed” should therefore be understood to mean that the deposition should not take place in an undirected manner and that, as explained above, certain solid angle regions should be masked out during the deposition.

With the method according to the invention, a spatially selective deposition can accordingly be achieved in the recess. This spatially selective deposition of the electrically conductive substance in the substrate recess can be used in various ways to produce a contacting structure in a circuit unit. In any case, the spatially selectively deposited electrically conductive Substance in the substrate opening with one or more other electrically conductive layers are contacted. This can be done either by the fact that these electrically conductive layers are already present in the substrate opening and can be contacted by the electrically conductive substance during their deposition. However, it can also be provided that the electrically conductive substance is only contacted with the further electrically conductive layer after it has been deposited in the substrate opening. In the following, using the exemplary embodiments for different circuit units, these two variants of the production of the contacting structure will become clear.

According to a first embodiment, the circuit unit to be produced using the method according to the invention can be formed, for example, by a solar module from a plurality of laterally adjacent photovoltaic solar cells which are to be connected in series using the method according to the invention. In this regard, two types of embodiment of the method according to the invention can be distinguished from one another, by means of which different types of solar modules can be produced.

In a first embodiment, a metallization in the form of a plurality of electrically conductive layers spaced apart from one another is applied to a main surface of a semiconductor substrate. Subsequently, one or more recesses or openings are formed up to edge regions of one of two adjacent electrically conductive layers, and the deposition of the electrically conductive substance is then preferably carried out by inclining the deposition directions with respect to a wall to be shaded so that contact between the an electrically conductive layer arranged in the depression and a surface section adjacent to the depression and opposite the other of the two adjacent electrically conductive layers, or a surface section produced thereon metallization is brought about. The metallization of this surface section and the contacting of the surface section with the electrically conductive layer can also be effected simultaneously with the deposition. As a result of the inclination of the deposition directions) and the shading effect achieved thereby, the surface section located only on one side of the depression is contacted with the electrically conductive layer in the depression, while the surface section located on the other side of the depression is not contacted with the electrically conductive layer in the depression is contacted.

In a second embodiment for producing a solar module from a plurality of laterally adjacent and series-connected photovoltaic solar cells, at least one recess or opening is formed in the substrate surface in a substrate. Then, an electrically conductive substance is deposited on a surface section containing the depression, preferably by oblique deposition, so that as a result of the shading effect caused by the inclination of the deposition directions contained in the solid angle, the electrically conductive substance is not deposited on a side wall of the depression.

Then a semiconductor material layer is also deposited in a substantially directional manner on the surface section containing the depression, the inclination of the deposition directions contained in the solid angle being set in such a way that the portion of the depression not covered by the electrically conductive substance essentially also from the Semiconductor material layer is not covered. At the same time, care must be taken to ensure that an electrically conductive layer to be subsequently applied to the semiconductor material layer matches the one under the

Semiconductor material layer located electrically conductive substance can be contacted. For example in that a contact section of the deposited electrically conductive substance remains free during the deposition of the semiconductor material layer, which is contacted during the subsequent deposition of the electrically conductive layer. However, this contact section may also not be provided, and instead the semiconductor material layer may be deposited by suitable process control in such a way that it has through holes at one point through which electrical contacting between electrically conductive layers located on both sides of the layer is possible.

Finally, the further electrically conductive layer is deposited on the substrate section containing the depression in such a way that a section on the semiconductor material layer is not covered in the depression. In the depression, the electrically conductive substance deposited first is thus in electrical contact with the later deposited electrically conductive layer either at the mentioned contact section or through the through-holes contained in the semiconductor material layer.

The electrically conductive layer can advantageously also be applied by an oblique direction from deposition directions contained within a solid angle, this time the angle of the deposition directions being set such that the layer is not deposited as a result of the shading on a side wall of the depression, which is opposite to the side wall on which the electrically conductive substance was not deposited. However, it can also be provided that the electrically conductive layer is first deposited over the entire surface by an undirected deposition process and then part of the layer is removed again at a suitable point in a structuring step or by simple mechanical scribing. Solar cells are thus formed on the surface sections of the substrate on both sides of the depression and are connected to one another in series by the method according to the invention. By arranging several recesses, a plurality of solar cells can thus be connected in series.

In the last-described embodiment, the substrate can be formed by placing a structurable material layer, in particular one, on a carrier, in particular a glass, plastic or metal plate

Plastic such as polyimide is applied. For example, a polyimide acting as a positive resist or another suitable positive resist can be used, which is exposed to light of suitable wavelength for the purpose of producing the depressions and then developed.

CIGS, for example, can be used as a semiconductor material in this second embodiment.

In the first embodiment described above, use is therefore made of a variant of the invention in which the electrically conductive substance in the depression is contacted with an electrically conductive layer when it is deposited. In this case, the electrically conductive layer is already present in the depression, namely at the bottom of the depression. In the second embodiment described above, however, use is made of the other variant of the invention, in which the electrically conductive substance is only contacted with an electrically conductive layer after it has been deposited in the depression. In this case, the electrically conductive layer is only applied to the electrically conductive substance in the manner described above after it has been deposited.

In a further embodiment of the present invention, the circuit unit is formed by a multilayer printed circuit board. In the case of a multilayer printed circuit board, the method according to the invention is used in such a way that several metallization levels are electrically connected to one another in groups. The substrate is formed by a multilayer printed circuit board and in a section in which a connection of metallization levels is to take place, a depression is formed at least as far as the lowest metallization level to be connected. The electrically conductive substance is then deposited in such a way that at least one section located between the metallization levels to be connected is covered in the depression.

The embodiments and types of embodiment of the present invention are explained in more detail below with reference to the drawing figures. Show it:

1A-F process steps for producing a solar module with series-connected solar cells according to a first embodiment of the method according to the invention;

2A-D method steps for producing a solar module with series-connected solar cells according to a second embodiment of the method according to the invention;

3A, B manufacture of electrical contacting structures in multilayer printed circuit boards;

4A-H process steps in the manufacture and electrical contacting of a multilayer printed circuit board.

1A-F describes the production of a solar module in which, with the aid of the method according to the invention, a plurality of laterally adjacent photovoltaic modules Solar cells can be connected in series. Two laterally adjacent solar cells are each shown in a longitudinal section in the drawings.

The solar cells are made up of a thin layer of semiconductor material and are therefore called thin-film solar cells. A so-called transfer technique is used in the production, which is based on the transfer of thin, single-crystalline semiconductor layers from a wafer to a foreign substrate, such as a glass substrate. In the transfer process, a thin, single-crystal surface layer that can be separated from the wafer is processed to a certain stage, i.e. provided with electronic or optoelectronic components and then - generally with the aid of the foreign substrate - separated from the wafer. After this

The semiconductor wafer is available for a new cycle to separate the processed semiconductor layer.

The method according to the invention is based on the transfer process indicated in FIG. 1A, which is explained in more detail below. However, other transfer techniques can also be used.

The transfer technology used in the method according to FIGS. 1A-F is described, for example, in documents EP 0 797 258 or EP 0 993 029, which are hereby incorporated into the disclosure content of the present application. In the case of silicon, this transfer technique is based on the production of so-called quasi-monocrystalline silicon layers (QMS). The process begins with the production of a 1 - 2 μm thin, porous silicon layer on the surface of a single-crystalline silicon wafer 1. The silicon wafer 1 is electrochemically etched by a solution containing hydrofluoric acid. The porosity can be adjusted by the electrical current density during the etching. The layer near the surface with a relatively low porosity is later converted into the QMS layer 3. If this layer has reached the desired thickness, the current density is increased during the etching process, and a second buried, highly porous so-called separating layer 2 is created. This separating layer later serves to separate the QMS layer 3 from the wafer 1. This is made of fine, nanoscopically thin threads existing porous material is crystalline and has the same crystallographic orientation as the starting wafer. By heating to over 1000 ° C, the thin, thread-like structures accumulate to form a compact layer from which the QMS layer 3 with low porosity is formed.

The QMS layer 3 forms the basis of the thin-film solar cell. In principle, there are two ways to manufacture this thin-film solar cell. Either the QMS layer 3 itself serves as a solar cell layer and is suitably supplied with dopants of the opposite conductivity type without further semiconductor material being grown. The alternative shown in FIGS. 1A-F, on the other hand, is based on the fact that the QMS layer 3 itself serves only as a substrate layer for further epitaxial layers, from which the solar cell is then manufactured.

First, a high p-doping is set in the QMS layer 3 in order to enable a low ohmic contact resistance for the rear-side metallization to be applied later. A p ⁺ -doped intermediate layer 4 is then first applied to this p ⁺ -doped QMS layer 3. A p-doped absorber layer 5 is then grown on this. A CVD process, for example, can be used as the layer growth for the intermediate layer 4 and the absorber layer 5. A region close to the surface of the originally p-doped layer 5 is then converted by diffusing in an n-conductive material such as phosphorus into an n ⁺ - conductive surface layer 5.1, so that the p ⁺ doped layer 5.1 and the p-doped layer 5.2 - n-transition of the solar cell is made. The n ⁺ -doped layer can also be produced in other ways, in which for example by depositing an n ⁺ -doped, amorphous Si layer.

In the following figures, the substrate wafer 1 and the separating layer 2 have already been omitted for the sake of simplification, although the actual transfer of the thin-film solar cell to the foreign substrate does not follow until a later step.

1B shows how a number of electrode layers 6 are applied to the surface of the n ⁺ -doped layer 5.1. These electrode layers 6 are located on the edge of stripe-shaped areas which extend into the image plane and are formed by the individual solar cells. Since the electrode layers 6 are only arranged at the edge of these strip-shaped areas, they do not have to be transparent to the incident optical radiation. The actual solar cell is formed in each case by the area not covered by the electrode layer 6, in which the n ⁺ -doped Si layer lies on the surface. The electrical conductivity of the n ⁺ -doped layer is sufficient for the current transport up to the edge-side electrode layer 6. 1A-F show two adjacent electrode layers 6 in the section plane perpendicular to the longitudinal direction of the strip-shaped regions. Alternatively, it can also be provided that the electrode layers 6 each extend over the entire length of the strip-shaped regions, in which case the electrode layers 6 must be essentially transparent to the incident radiation. In practice, a middle path is chosen by arranging a number of electrode layers 6 in the form of contact fingers into the image plane, the spacing of which depends on the conductivity of the n ⁺ -doped layer.

The individual solar cells are thus formed by the strip-shaped areas extending into the image plane defined, which are to be connected in series by electrically connecting the associated electrode layers 6. The following describes how the two solar cells shown are connected in series. In a corresponding manner, all other solar cells adjoining to the right and left of it are simultaneously connected in series with one another. 1B, two mesa trenches A are etched into the semiconductor layers down to the pn junction, as shown, in each case immediately adjacent to and along the edges of the strip-shaped electrode layers 6. The regions between the mesa trenches A thus define inactive areas of the solar module. As an alternative to this, the cells can be separated by scratching or by lateral structuring already being carried out in the previous step of diffusing in the n-conducting substance.

According to FIG. IC, a metal strip 7 is glued to one of two adjacent electrode layers 6 with a solder paste. This metal strip 7 extends in the lateral direction, starting from the attachment point on the electrode layer 6 in the direction of the adjacent electrode layer 6.

Then, as shown in FIG. ID, a glass substrate 9 is glued onto the structure obtained by means of a resin adhesive 8. The thin-film solar cell is then separated from the semiconductor wafer, the separating layer 2 possibly being dissolved by a temperature treatment step, so that the QMS layer 3 is now the lowest layer of the component.

Then, according to FIG. 1E, the individual solar cells are separated from one another by opening 6 or along the inactive zone in the direction of the strip-shaped electrodes

Indentations 10 in the semiconductor layer structure are each formed up to the metal strips 7. The depressions 10 can NEN can be shaped in various ways, for example mechanically by scratching or sawing, chemically by an etching attack. Between each pair of adjacent solar cells, a trench-shaped depression 10, which separates the solar cells and extends as far as the metal strip 7, is thus formed in the layer structure, so that the bottom of each depression 10 is formed by the metal strip 7 connected to the front electrode of one of the two adjacent solar cells.

As an alternative to this procedure, it can also be provided that instead of attaching the metal strip 7 to the electrode layer 6, the latter is already applied in the previous metallization step into the inactive region between the mesa trenches A. In this case, the recess 10 must be formed up to the electrode layer 6. If this is carried out, for example, by means of an etching step, the electrode layer 6 can be used as an etching stop layer.

The rear electrodes of the solar cells are then formed in a single self-adjusting method step according to FIG. 1F and these are electrically contacted at the same time with the front electrodes of the respectively adjacent solar cells. This is done by a directional deposition process of an electrically conductive substance, the deposition direction being inclined relative to the depression 10 or the walls thereof. Strictly speaking, it is only important that only one inner wall of the depression 10 is completely covered during the deposition, so that metallization is brought about only between the metal strip 7 and the surface section located on one side of the depression 10. The surface section located on the other side of the depression 10, on the other hand, should not be contacted with the metal strip 7 by the deposition process, ie the corresponding inner wall of the depression 10 should not be exposed to the electrically conductive substance, or at least one To have an interruption. The decisive criterion is therefore that the deposition direction is inclined with respect to the plane of this inner wall and leads away from this plane, so that, as can be seen from FIG. 1F, there is a shadowing effect with respect to this inner wall of the depression. Of course, the deposition process can also be carried out mirror-symmetrically to a plane of symmetry running perpendicularly through the image plane 3 through the depression 10, in which case the surface section of the QMS layer 3 located on the left side of the depression 10 is connected to the metal strip 7 by the metal deposition and the right-hand inner wall of the depression 10 is shaded by the deposition, so that the right-hand surface section of the QMS layer 3 is not connected to the metal strip 7.

Fig. 1F shows the idealized case of a deposition with a single, defined deposition direction. As already mentioned, in practice the deposition will always take place over a certain solid angle range.

Due to the deposition of the electrically conductive substance, rear electrode layers 1 are thus simultaneously produced for all existing solar cells in a single work step and these are connected to the metal strips 7 in the manner described by the inclined deposition, so that a series connection of the solar cells is provided. The deposition process is most easily carried out by vapor deposition, aluminum being used as the metal. For example, indium tin oxide (ITO) can be used as the metal for the front, transparent electrode layers 6. In addition, suitable antireflection layers can be applied to the outer surface of the glass substrate 9 or to internal interfaces between the materials. In the exemplary embodiment described above, a variant of the invention is therefore used in which there is already an electrically conductive layer in the form of the metal strip 7 at the bottom of the recess 10 in the recess 10 and the electrically conductive substance when it is deposited into the recess 10 with the latter electrically conductive layer is connected.

In the exemplary embodiment described below, a variant of the invention is described on the basis of the production of a further solar module, in which the electrically conductive substance is only contacted with a further electrically conductive layer after it has been deposited in substrate depressions.

On an electrically insulating solid-state substrate 20 (FIG. 2A), such as a glass substrate, a material layer 21 that can be structured by lithographic techniques, for example a layer of a positive resist, for example a polyimide layer designed as a positive resist, is first applied. The material layer 21 is then structured in such a way that a family of parallel lines is written into the material layer 21 with oblique exposure and then developed. This produces trench-shaped depressions 22, one of which is shown in FIG. 2A in a cross section perpendicular to its longitudinal direction. The depressions 22 are intended to use the method according to the invention to make electrical contact with the solar cells still to be formed in series with one another. In the exemplary embodiment shown, the recess 22 has inclined walls. As will be seen later, this is not absolutely necessary, but it simplifies the creation of the shading effects in the subsequent deposition processes.

According to FIG. 2B, the entire surface containing the depressions 22 is subjected to a deposition process of an electrically conductive capable substance, in the present case molybdenum (Mo), exposed. The deposition directions are again set in such a way according to the invention that there is a shadowing effect with respect to one of the walls or a section thereof. 2B shows the ideal case in which there is only a single deposition direction, which is inclined to the wall to be shadowed and directed away from it.

In the case shown, the left-hand inner walls of the depressions 22 are thus shaded, so that the molybdenum does not precipitate on these walls. It is clear from this that the left-hand inner wall of the recess 22, which is not to be coated, can also be a straight wall, but then the solid angle of the deposition directions must be rotated accordingly, so that there is again a shading effect with respect to this wall. In any case, if the inner wall to be shaded is at an angle ß with respect to the plane, the deposition directions should generally be at an angle α> ß to the plane (right-hand side). If the aspect ratio of the depression 22 is large enough, "this condition is not mandatory. Rather, in this case it is sufficient to hide a certain solid angle in a defined manner, so that there is an interruption of the deposited layer 23 on the left-hand wall of the depression 22.

The layers deposited on the surface sections of the polyimide layer on both sides of the depression 22 serve as rear-side electrode layers 23 of the solar cells still to be manufactured.

The semiconductor material of the solar cells is then applied according to FIG. 2C. In the present example, p-type CIGS is evaporated onto the surface and then a donor substance is diffused into a region of the evaporated semiconductor layer 24 near the surface, see above that a pn junction is formed immediately below the surface of the semiconductor layer 24. The deposition of the semiconductor material CIGS is also carried out in a directed manner. The direction of deposition is adjusted again so that there is a shading effect with respect to the left-hand inner wall of the recess 22, so that the semiconductor material is essentially not deposited on this inner wall. In general, the semiconductor material on the section on which the electrically conductive substance has not been deposited is also at least partially not deposited.

In addition, the semiconductor material must be deposited in such a way that an electrically conductive layer subsequently deposited thereon can form contact with the lower electrically conductive substance. This can be achieved, for example, by increasing the shading effect during the deposition of the semiconductor layer 24 compared to the previous deposition of the molybdenum, so that a so-called contact section 23a of the deposited molybdenum layer is not covered by the semiconductor layer 24 on the bottom of the recess 22. In order to increase the shadowing effect, an angle of the deposition directions of γ> α can be set during the deposition of the CIGS. In the present case, γ = 90 °, however, as has already been stated above, this angle and also the angle α can also be larger if the inner wall of the depression 22 to be kept free is a straight wall. 2C again shows the ideal case of deposition of the semiconductor material along a single deposition direction.

As an alternative to the production of the contact section 23a, it can also be provided that the semiconductor material is deposited on at least a section of the depression 22 in such a way that it has through holes (pinholes) through which the subsequently deposited electrically conductive layer 25 (FIG. 2D) also has through contacts the layer below 23 can form. For this, the right-hand wall of the recess 22 is a suitable section in the selected exemplary embodiment. The deposition of the semiconductor material takes place at this wall at a relatively small angle if — as shown — the deposition direction is directed perpendicularly from above onto the depression 22. Experience has shown that such a small deposition angle only results in rod-shaped depositions on the wall in question. Correspondingly, through holes are formed between them, which enable through contacts in the manner described. The electrically conductive layer 25 can then be deposited over the entire surface, for example, and subsequently an interruption can be incised on the right-hand surface section. In this embodiment variant, no contact section 23a would have to be provided for the deposition of the semiconductor material layer.

In a last method step, an electrically conductive and transparent layer of ZnO, ITO or the like, which forms the front electrode layers 25, is then applied according to FIG. 2D. This is also preferably done by a directional deposition process, in which this time the deposition directions are set such that the right-hand inner wall of the recess 22 is shaded, so that no material is deposited thereon. Since in the present case the right-hand inner wall of the recess 22 also makes an angle β with respect to the plane, the direction of deposition must be set with an angle δ <β. It is also clear here that the corresponding inner wall of the recess 22 to be shaded can also be a straight wall, so that in this case the deposition direction would have to be set at an angle δ <90 °.

Opposite the shaded wall, a front-side electrode layer 25 is formed on the corresponding surface section of the semiconductor layer 24 and this is covered by covering the left-hand inner wall of the recess 22 with the contact. Clock section 23a of the electrode layer 23 contacted. Thus, the solar cells formed on both sides of the recess 22 are connected in series with one another.

As an alternative to the oblique deposition in the last deposition step, the metal can also first be deposited over the entire surface and then a structuring step can be carried out in which a section of the layer deposited on the right inner wall of the depression 22 or on the right-hand surface section near the depression 22 25 is removed again, for example, by mechanical scribing. Instead of mechanical scribing, obliquely directed sputter etching can also be carried out, in which the left-hand wall of the recess can serve as a mask. Due to the shallow incidence of the etching beam, the desired interruption is preferentially etched on the right-hand wall of the depression in the upper region. In production, this may be more efficient than mechanical scribing, which usually has to be carried out individually for each cell.

During production, care must also be taken to ensure that there is no short circuit between the electrode layers 23 and 25 on the left-hand edge of the depression 22. This danger can be countered, for example, by vapor-depositing from the right at a very shallow angle either further semiconductor material, that is to say CIGS in the exemplary embodiment chosen, or any insulating material. Due to the flat vapor deposition angle1, the deposition takes place preferably at the critical left edge, while no deposition takes place on the remaining surface. Then the electrically conductive layer 25 can be deposited without the risk of a short circuit with the layer 23 at the critical left edge.

The embodiment of the method according to the invention described above is particularly advantageous since it Individual solar cells can be interconnected with just one structuring step, which can be done at the very beginning before the substrates are introduced into the vacuum chamber. The other processes take place in a self-adjusting manner and can be carried out in succession without breaking the vacuum. If it is necessary to cut through the transparent conductive layer 25, two structuring steps are necessary, but this step takes place after the vacuum processes. This method thus enables the production of a thin-film solar module without the deposition of the layers having to be interrupted by structuring.

Positive photosensitive polyimide can, for example, be applied to the glass substrate or any other substrate using the roller coat method (roller coating). The depressions 22 can then be produced in such a way that lines are written into the polyimide layer using a blue-emitting laser diode or a corresponding LED via mirrors or diffraction patterns, so that in each case obliquely exposed areas arise. With this procedure, the cell area which is inactivated by the formation of the depressions 22 can be reduced to structure widths of, for example, 20 μm, which can be produced with a laser beam without any problems. Furthermore, a defined layer of polyimide may remain in the exposed area during the development of the polyimide. As a result, an insulating film remains on the substrate 20, so that an electrically conductive substrate 20 can also be used in the manufacture of the solar module. In addition, the polyimide can be exposed with an interference pattern, so that surface structures can be formed after development, which are also transferred into the later deposited semiconductor layer 24. By means of such surface structures, multiple reflection can be generated on the surface exposed to the light, through which the efficiency can be increased. As an alternative to using a material layer to be structured, such as the polyimide layer, the trench-like depressions 22 can also be embossed or scratched directly into the substrate 20 or produced with a laser beam.

With regard to the semiconductor material in the above-described solar modules, it goes without saying that the pn junction can also be produced in the reverse order, so that a p ⁺ -doped layer is produced as the top layer.

The embodiments of the invention described below relate to another embodiment of a circuit unit, namely a multilayer printed circuit board. Here again a variant of the method according to the invention comes into play, in which the electrically conductive substance applied with an oblique deposition direction is already contacted with an electrically conductive layer present in the recess when it is deposited into the depression.

3A, B show the case in which a multiple printed circuit board 30 is first completed and then various metallization planes arranged in it are connected to one another with the aid of the method according to the invention.

In the exemplary embodiment shown, the multiple circuit board 30 produced has four metallization levels ad, which are to be electrically contacted with one another in a certain way. For this purpose, a recess 31 is formed at a suitable point in the multiple circuit board 30 up to at least the lowest metallization level to be connected. If, for example, the task is to connect interconnects of the metallization levels a and b to one another, the depression 31 is formed at a point at which this depression 31 can be exposed on a first inner wall of these metallization levels. If at the same time a further task consists in making electrical contact with the metallization levels b and d, the depression 31 should be determined in such a way that conductor tracks of the metallization levels b and d are exposed on a second inner wall opposite the first interior wall. Then, in a first method step (A), an electrical connection between the metallization levels a and b can be brought about by a first oblique deposition in which the second inner wall is shaded and only the first inner wall is coated. Subsequently, in a second oblique deposition step (B), in which the first inner wall is shadowed and only the second inner wall is coated, an electrical contact between the metallization levels b and d can be effected.

The embodiment of FIGS. 3A, B shows a depression 31 with straight side walls. However, it can also be provided that the depression is inclined with respect to the plane of the multilayer printed circuit board, i.e. has inclined inner walls. In this case, the direction of the deposition must be determined accordingly in order to achieve a desired shading effect with respect to a specific inner wall.

The preceding exemplary embodiment shows how a conventional multilayer printed circuit board 30 can be produced and then electrically contacted in the desired manner using the method according to the invention. 4A-G it is shown below how the goal of selective electrical contacting can already be achieved during the production of a multilayer printed circuit board.

The multilayer printed circuit board is built up alternately with the deposition of metallization levels or insulator layers and the implementation of the method according to the invention. First, according to step A, on a circuit board sub- strat a first metal layer a produced for example by vapor deposition. The conductor tracks are then structured conventionally, for example by using a dry film resist and etching back or by applying photoresist and subsequent vapor deposition and a lift-off process. Then, in accordance with step B, an insulation layer is applied and a recess 41 is introduced into it either using photolithographic or mechanical methods (drilling). In a further step C, the second metal layer b is deposited, for example by oblique vapor deposition, and structured again as described above, it being possible to achieve an interconnection between the metal layers a and b. A repeated repetition of the deposition of an insulator layer and a metal layer thus leads to a multilayer printed circuit board 40 with defined connections between individual layers.

Claims

claims

1. Production method for an electronic or optoelectronic circuit unit, in particular for its electrical contact structure, in which a.) A depression (10;) in a substrate (3, 4, 5; 21; 30).

22; 31; 41) is generated, and b.) An electrically conductive substance is deposited on a substrate section containing the depression in a substantially directional manner so that a section within the depression is not covered by the electrically conductive substance, and c.) The electrically conductive substance Substance in the depression during or after its deposition is contacted with an electrically conductive layer (7; 25; 32).

2. The method of claim 1, d a d u r c h g e k e n n z e i c h n e t that

- in method step b.) the deposition directions present during the deposition of the electrically conductive substance extend over a certain solid angle and

- are inclined with respect to at least one wall of the substrate opening and are directed away from this wall.

3. The method according to claim 1 or 2, d a du r c h g e k e n n z e i c h n e t that

- The depression is formed to a depth in which the electrically conductive layer (7; 32) is arranged and the electrically conductive substance is contacted with the electrically conductive layer (7; 32) when it is deposited.

4. The method according to claim 3, characterized in that - the circuit unit is a solar module from a plurality of laterally adjacent photovoltaic solar cells which are connected in series with the method, wherein a plurality of electrically conductive electrode layers (6) spaced apart from one another are applied to a main surface of the semiconductor substrate (3, 4, 5),

- From the opposite main surface of the substrate one or more depressions (10) each up to edge areas of one of two adjacent electrode layers

(6) be molded, and

- The deposition of the electrically conductive substance is carried out so that contact between the in the recess (10) arranged electrically conductive layer

(7) and a surface section adjacent to the depression and opposite the other electrode layer (6) is brought about.

5. The method according to claim 4, d a dur c h g e k e n n z e i c hn e t that

- an electrode layer at the same time as deposition

(11) on the surface section and the contacting of the electrode layer (11) with the electrically conductive layer (7) in the recess (10).

6. The method according to claim 1, that a d e r c h g e k e n n z e i c h n e t that

- The circuit unit is a solar module from a plurality of laterally adjacent photovoltaic solar cells, which are connected in series with the method, wherein

- After the deposition of the electrically conductive substance in method step b.), a semiconductor material layer (24) is deposited in a substantially directional manner on the substrate section containing the depression (22), the portion of the depression (22) not covered by the electrically conductive substance is also at least partially not covered by the semiconductor material layer (24), and the semiconductor material layer (24) is deposited in such a way that it leaves an opening to the electrically conductive substance on at least one section, - Then according to step c. ) a further electrically conductive layer (25) is deposited on the substrate section containing the depression (22) in such a way that a section on the semiconductor material layer (24) is not covered by the electrically conductive layer (25).

7. The method according to claim 6, characterized in that - the substrate (20, 21) is formed by a structurable material layer (21), in particular from a, on a carrier (20), in particular a glass, plastic or metal plate Plastic such as polyimide is applied.

8. The method according to claim 7, that the material layer (21) for producing the depression (22) is exposed and structured.

9. The method according to any one of claims 6 to 8, d a d u r c h g e k e n n z e i c h n t that

- The further electrically conductive layer (25) is deposited in a directed manner, the deposition direction being inclined with respect to the wall of the depression (22) closest to the portion not to be covered and being directed away from it.

10. The method according to any one of claims 6 to 8, d a d u r c h g e k e n n z e i c h n e t that

- The further electrically conductive layer (25) is deposited over the entire surface and then a section on the semiconductor material layer is removed.

11. The method according to claim 1, dadurchgekennzeic hn et that - The circuit unit is a multilayer printed circuit board (30, 40), in which several metallization levels (ad) are electrically connected to one another in groups using the method, the substrate being formed by a multilayer printed circuit board (30) or an intermediate product to form a multilayer printed circuit board (40) , and in a section in which a connection of metallization levels is to take place, a depression is formed at least as far as the lowest metallization level to be connected, and

- The deposition of the electrically conductive substance takes place in such a way that at least one section located between the metallization levels to be connected is covered in the depression (31, 41).

12. The method according to any one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that - the deposition is carried out by vapor deposition, sputtering or a CVD process.