WO2011097676A1

WO2011097676A1 - Contact composition

Info

Publication number: WO2011097676A1
Application number: PCT/AU2011/000137
Authority: WO
Inventors: Stefan John Jarnason; Rhett Evans
Original assignee: Csg Solar Ag
Priority date: 2010-02-15
Filing date: 2011-02-10
Publication date: 2011-08-18

Abstract

A method of making contacts and forming a conduction layer in a semiconductor device, in particular to thin film semiconductor devices such as thin film photovoltaic devices. The process provides a region of semiconductor material contacted by a metal contact layer wherein the metal contact layer comprises a layer nickel :aluminium alloy. The nickel :aluminium alloy provides contact to the device and interconnection of individual devices with superior resistance to corrosion.

Description

"Contact composition"

Field of the Invention

The present invention relates generally to the field of semiconductor device fabrication and in particular the invention provides an improved processing step for use in a method of forming metal contacts to semiconductor devices and in particular to thin film semiconductor devices such as thin film photovoltaic devices.

Background of the Invention

A major advantage of thin-film photovoltaic (PV) modules over conventional wafer-based modules is the potential for low cost of production. A number of methods have been proposed for forming contacts in electronic devices, however in order to achieve low cost, some devices including some thin film photovoltaic devices use aluminium for both contacts and for device interconnection. Typically metallurgical pure aluminium is used for this purpose. Over time it has been found that such contacts can suffer from corrosion particularly when the device is used in a high humidity environment and even though the device is enclosed in a protective encapsulation.

Summary of the Invention

According to a first aspect the present invention provides a method of forming a connection layer, in an electronic device, the method comprising the steps of:

a) preparing a surface onto which the connection layer will be formed;

b) forming a nickel.aluminium alloy connection layer over the prepared surface.

According to a second aspect the present invention provides a semiconductor device comprising a region of semiconductor material and a metal contact in electrical contact with the semiconductor layer, the metal contact comprising a connection layer of nickel:aluminium alloy.

Preferably the device is a thin film silicon solar cell. Preferably also the method of applying the connection layer is by sputtering.

Preferably the electronic, device will be a photovoltaic device structure in a silicon film deposited on a glass substrate. The silicon film may comprise a first doped region having silicon of a first dopant polarity closest to the glass, a lightly doped or intrinsic region over the first doped region and a second doped region having silicon of a second dopant polarity opposite to the first dopant polarity over the lightly doped region.

The method preferably further comprises One or more of the following steps: 1) dividing the silicon film into a plurality of cell regions by forming cell isolation grooves;

2) forming a mask of organic resin in a layer over the silicon film;

3) forming a first set of openings in the mask to expose the silicon of the second dopant polarity in locations where contacts to the first doped region are required;

4) etching the silicon film through the first set of openings to expose at least some of the silicon of the first dopant polarity;

5) isolating the silicon of the first dopant polarity from silicon at the exposed edge of the silicon of the second dopant polarity by placing the substrate into an atmosphere comprising a vapour of a solvent of the organic resin whereby the organic resin softens and re-flows to reduce each opening of the first openings in size and to insulate the exposed edge of the silicon of the second dopant polarity;

6) forming a second set of openings in the mask in further locations where contacts to the silicon of the second dopant polarity are required;

7) forming the nickel:aluminium alloy layer over a surface of the mask and extending the alloy into each opening of the first set of openings to contact the silicon of the first dopant polarity and into the second set of openings to contact the silicon of the second dopant polarity, the alloy in the first set of openings being isolated from the exposed edge of the silicon of the second dopant polarity by the re-flowed resin;

8) forming isolation grooves in the alloy layer to separate the contacts to the silicon of the first dopant polarity from the contacts to the silicon of the second dopant polarity within each cell, whereby the alloy layer interconnects the silicon of the second dopant polarity of one of the cells to the silicon of the first dopant polarity of an adjacent one of the cells;

9) tabbing and encapsulation of the solar cells.

The photovoltaic device structure may further comprise one or more of the following features:

1) a plurality of cell regions divided by cell isolation grooves;

2) a layer of organic resin formed over the silicon film;

3) a first set of openings in the organic resin layer and extending through the silicon of the second dopant polarity to expose the silicon of the first dopant polarity in locations where contacts to the first doped region are required; 5) the organic resin extending over the edges of the openings in the silicon of the first dopant polarity to insulate the edges of the silicon of the first dopant polarity;

6) a second set of openings in the organic resin in further locations where contacts to the silicon of the second dopant polarity are required;

7) the nickehaluminium alloy layer extending over a surface of the organic resin layer and extending into each opening of the first set of openings to contact the silicon of the first dopant polarity and extending into the second set of openings to contact the silicon of the second dopant polarity, the alloy in the first set of openings being isolated from the exposed edges of the silicon of the second dopant polarity by the re-flowed resin;

8) isolation grooves in the alloy layer to separate the contacts to the silicon of the first dopant polarity from the contacts to the silicon of the second dopant polarity within each cell, whereby the alloy layer interconnects the silicon of the second dopant polarity of one of the cells to the silicon of the first dopant polarity of an adjacent one of the cells;

The nickel :aluminium alloy contact may be formed by various methods but one particularly preferred method is by sputtering. The nickel:aluminium alloy will have a composition of in the range of one of 10 - 100,000 or 100 - 100,000 or 1,000 - 100,000 or 10,000 - 100,000 or 10 - 10,000 or 100 - 10,000 parts per million nickel in aluminium (by weight) and preferably 1,000 - 10,000 or 2,000 - 10,000 or 3,000 - 10,000 or 4,000 - 10,000 or 5,000 - 10,000 or 6,000 - 10,000 or 7,000 - 10,000 or

8,000 - 10,000 or 9,000 - - 10,000 or 1,000 - 9,000 or 2,000 - - 9,000 or 3,000 - 9,000 or 4,000 - 9,000 or 5,000 - 9,000 or 6,000 - 9,000 or 7,000 - 9,000 or 8,000 - 9,000 or

1,000 - 8,000 or 2,000 - 8,000 or 3,000 - 8,000 or 4,000 - 8,000 or 5,000 - 8,000 or

6,000 - 8,000 or 7,000 - 8,000 or 1,000 - 7,000 or 2,000 - 7,000 or 3,000 - 7,000 or

4,000 - 7,000 or 5,000 - 7,000 or 6,000 - 7,000 or 1,000 - 6,000 or 2,000 - 6,000 or

3,000 - 6,000 or 4,000 - 6,000 or 5,000 - 6,000 or 1,000 - 5,000 or 2,000 - 5,000 or 3,000 - 5,000 or 4,000 - 5,000 or i;000 - 4,000 or 2,000 - 4,000 or 3,000 - 4,000 or

1,000 - 3,000 or 2,000 - 3,000 or 1,000 - 2,000 parts per million nickel in aluminium

(by weight). When applying the contact by sputtering the sputtering source will be a nickel:aluminium target having a composition comprising the desired composition of the contact. The nickehaluminium alloy may be in the range of one of 90.000 - 99.999% aluminium and 0.001 - 10.000% nickel or 99.000 - 99.999% aluminium and 0.001 - 1.000% nickel or 99.900 - 99.999% aluminium and 0.001 - 0.100% nickel or 99.990 - 99.999% aluminium and 0.001 - 0.010% nickel or 90.000 - 99.990% aluminium and 0.010 - 10.000% nickel or 99.000 - 99.990% aluminium and 0.010 - 1.000% nickel or 99.900 - 99.990% aluminium and 0.010 - 0.100% nickel 90.000 - 99.900% aluminium and 0.100 - 10.000% nickel or 99.00 - 99.900% aluminium and 0.100 - 1.000% nickel or 90.000 - 99.000% aluminium and 1.000 - 10.000% nickel and preferably the nickel :aluminium alloy will be in the range of one of 99.0. - 99.9% aluminium and 0.1 - 1.0% nickel or 99.1 - 99.9% aluminium and 0.1 - 0.9% nickel or 99.2 - 99.9% aluminium and 0.1 - 0.8% nickel or 99.3 - 99.9% aluminium and 0.1 - 0.7% nickel or 99.4 - 99.9% aluminium and 0.1 - 0.6% nickel or 99.5 - 99.9% aluminium and 0.1 - 0.5% nickel or 99.6 - 99.9% aluminium and 0.1 - 0.4% nickel or 99.7 - 99.9% aluminium and 0.1 - 0.3% nickel or 99.8 - 99.9% aluminium and 0.1 - 0.2% nickel or 99.1 - 99.8% aluminium and 0.2 - 0.9% nickel or 99.2 - 99.8% aluminium and 0.2 - 0.8% nickel or 99.3 - 99.8% aluminium and 0.2 - 0.7% nickel or 99.4 - 99.8% aluminium and 0.2 - 0.6% nickel or 99.5 - 99.8% aluminium and 0.2 - 0.5% nickel or 99.6 - 99.8% aluminium and 0.2 - 0.4% nickel or 99.7 - 99.8% aluminium and 0.2 - 0.3% nickel or 99.1 - 99.7% aluminium and 0.3 - 0.9% nickel or 99.2 - 99.7% aluminium and 0.3 - 0.8% nickel or 99.3 - 99.7% aluminium and 0.3 - 0.7% nickel or 99.4 - 99,7% aluminium and 0.3 - 0.6% nickel or 99.5 - 99.7% aluminium and 0.3 - 0.5% nickel or 99.6 - 99.7% aluminium and 0.3 - 0.4% nickel or 99.1 - 99.6% aluminium and 0.4 - 0.9% nickel or 99.2 - 99.6% aluminium and 0.4 - 0.8% nickel or 99.3 - 99.6% aluminium and 0.4 - 0.7% nickel or 99.4 - 99.6% aluminium and 0.4 - 0.6% nickel or 99.5 - 99.6% aluminium and 0.4 - 0.5% nickel or

99.1 - 99.5% alvtminium and 0.5 - 0.9% nickel or 99.2 - 99.5% aluminium and 0.5 - 0.8% nickel or 99.3 - 99.5% aluminium and 0.5 - 0.7% nickel or 99.4 - 99.5% aluminium and 0.5 - 0.6% nickel or 99.1 - 99.4% aluminium and 0.6 - 0.9% nickel or

99.2 - 99.4% aluminium and 0.6 - 0.8% nickel or 99.3 - 99.4% aluminium and 0.6 - 0.7% nickel or 99.1 - 99.3% aluminium and 0.7 - 0.9% nickel or 99.2 - 99.3% aluminium and 0.7 - 0.8% nickel or 99.1 - 99.2% aluminium and 0.8 - 0.9% nickel (by weight). The composition of the nickel :aluminium alloy target is selected to obtain low resistance contacts to both dopant polarities of the cell while maintaining good corrosion protection properties.

The sputtered layer of nickel :aluminium alloy may be in the range of one of

0.05-0.5 um or 0.10 - 0.50 urn or 0.15 - 0.50 rn or 0.20 - 0.50 um or 0.25 - 0.50 um or 0.30 - 0.50 um or 0.35 - 0.50 um or 0.40 - 0.5 um or 0.45 - 0.50 um or 0.05 - 0.45 Mm or 0.10 - 0.45 um or 0.15 - 0.45 um or 0.20 - 0.45 um or 0.25 - 0.45 um or 0.30 -

0.45 um or 0.35 - 0.45 m or 0.40 - 0.45 um or 0.05 - 0.40 um or 0.10 - 0.40 um or 0.15 - 0.40 um or 0.20 - 0.40 um or 0.25 - 0.40 um or 0.30 - 0.40 um or 0.35 - 0.40 um or 0.05 - 0.35 um or 0.10 - 0.35 um or 0.15 - 0.35 um or 0.20 - 0.35 um or 0.25 - 0.35 um or 0.30 - 0.35 um or 0.05 - 0.30 um or 0.10 - 0.30 um or 0.15 - 0.30 Mm or 0.20 - 0.30 um or 0.25 - 0.30 um or 0.05 - 0.25 um or 0.10 - 0.25 um or 0.15 - 0.25 Mm or 0.20 - 0.25 um or 0.05 - 0.20 Mm or 0.10 - 0.20 um or 0.15 - 0.20 Mm or 0.05 - 0.15 um or 0.10 - 0.15 um or 0.05 - 0.10 Mm thick and preferably nominally 0.1 um (0.095-0.105 um or 0.096-0.105 um or 0.097-0.105 Mm or 0.098-0.105 um or 0.099- 0.105 um or 0.100-0.105 Mm or 0.101-0.105 m or 0.102-0.105 M or 0.103-0.105 m or 0.104-0.105 Mm or 0.095-0.104 Mm 0.096-0.104 Mm or 0.097-0.104 um or 0.098- 0.104 um or 0.099-0.104 um or 0.100-0.104 um or 0.101-0.104 um or 0.102-0.104 um or 0.103-0.104 um or 0.095-0.103 um or 0.096-0.103 um or 0.097-0.103 um or 0.098- 0.103 um or 0.099-0.103 um or 0.100-0.103 um or 0.101-0.103 Mm or 0.102-0.103 um or 0.095-0.102 um or 0.096-0.102 m or 0.097-0.102 Mm or 0.098-0.102 Mm or 0.099- 0.102 m or 0.100-0.102 Mm or 0.101-0.102 um or 0.095-0.101 Mm or 0.096-0.101 M or 0.097-0.101 m or 0.098-0.101 M or 0.099-0.101 um or 0.095-0.100 um or 0.096- 0.100 Mm or 0.097-0.100 um or 0.098-0.100 um or 0.099-0.100 Mm or 0.095-0.099 um or 0.096-0.099 um or 0.097-0.099 um or 0.098-0.099 um or 0.095-0.098 Mm or 0.096- 0.098 Mm or 0.097-0.098 Mm or 0.095-0.097 um or 0.096-0.097 um or 0.095-0.096 um) thick. The device is typically encapsulated in an encapsulation film such as a 0.4 mm thick EVA encapsulation with a 0.3 mm thick Tedlar-Polyester-EVA (TPE) encapsulation.

Preferably, the method of the third aspect further includes the step of etching the silicon film in the second set of openings to remove damaged material from the surface of the silicon of the second dopant polarity before formation of the metal layer.

The organic resin is preferably novolac, but other similar resins are also suitable such as commonly available photoresists. The openings in the resin layer can be formed by chemical removal using solutions of caustic substances such as potassium hydroxide (KOH) or sodium hydroxide (NaOH). Other methods of making openings in the mask layer include laser ablation and photographic techniques (using photoresist).

Brief Description of the Drawings

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings (not drawn to scale) in which:

Fig. 1 is a diagram of a section through a semiconductor device after initial steps of applying an anti-reflection coating over a glass substrate and depositing a doped semiconductor film over the anti-reflection coating; Fig. 2 is the sectional view seen in Fig. 1 after a scribing step has been completed to form a cell separating groove dividing separate cell areas and insulating layers have been applied over the semiconductor layer;

Fig. 3 is a schematic diagram of an X-Y table with an inkjet print head fitted for directly applying the insulation etchant , using inkjet technology;

Fig. 4 is the sectional view seen in Fig. 2 (shifted slightly to the left), after a pattern of etchant has been directly deposited onto the insulating layer to open the insulating layer in areas where contacts to an underlying n⁺ type region of the semiconductor layer are required;

Fig. 5 is the sectional view seen in Fig. 4 after the insulation layer has been opened in the areas where contacts to the underlying n⁺ type region of the semiconductor layer are required;

Fig. 6 is the sectional view seen in Fig. 5 after further etching steps have been performed to remove some of the doped semiconductor film in the area where the contact to the underlying n⁺ type region of the semiconductor layer is required;

Fig. 7 is the sectional view seen in Fig. 6 after a reflow step to flow some of the insulating layer into the hole formed by removal of some of the doped semiconductor film in the area where a contact to the underlying n⁺ type region of the semiconductor layer are required. A pattern of caustic solution has been directly deposited onto the insulating layer to open the insulating layer in an area where a contact to an upper p⁺ type region of the semiconductor layer is required;

Fig. 8 is the sectional view seen in Fig. 7 after the caustic has opened the insulation layer in the areas where the contact to the upper p⁺ type region of the semiconductor layer is required;

Fig. 9 is the sectional view seen in Fig. 8 after further etching steps have been performed to clean the surface of the doped semiconductor film of damaged material in the areas where the contact to the upper p⁺ type region of the semiconductor layer is required;

Fig. 10 is the sectional view seen in Fig. 9 after a metal layer has been applied to contact the p⁺ and n⁺ type regions of the semiconductor material and to interconnect adjacent cells;

Fig. 11 is the sectional view seen in Fig. 10 after the metal layer has been interrupted to separate the contacts to the p⁺ & n⁺ type regions from each other within each cell;

Fig. 12 is a back view (silicon side) of part of the device of Fig. 11 ; and Fig. 13 is a diagram of a part of a completed device, illustrating the interconnection between adjacent cells and the encapsulation layer.

Detailed Description of the Preferred Embodiments

Referring to the drawings, Fig. 1 illustrates a part of a semiconductor structure

11 which is a precursor to the photovoltaic device fabrication process described below. The semiconductor structure 11 is formed as a thin semiconductor film applied to a substrate 22 in the form of a glass sheet to which a thin silicon nitride anti-reflection coating 71 has been applied. For optimal performance, the thin semiconductor film comprises a thin polycrystalline silicon film 12 formed with a total thickness in the range of 1 to 2μπα and preferably Ι.όμηι. The polycrystalline silicon film 12 has an upper p⁺ type region 13 which is 60nm thick, a lower n⁺ type region 15 which is 40nm thick, and a 1.5μπι thick intrinsic or lightly p type doped region 14 separating the p⁺ and n⁺ type regions. The sheet resistance in both n⁺ type and p⁺ type layers is preferably between 400 and 2500 Ω/ο, with no more than 2xl0¹⁴ cm^"2 boron in total. Typical values are around 750 Ω D for n⁺ type material and 1500 Ω/D for p⁺ type material. The thickness of the n⁺ type and p⁺ type layers is typically between 20 and 100 ran. The glass surface is preferably textured to promote light trapping, but this is not shown in the drawings for sake of clarity.

Division into cells

As seen in Fig. 2, the silicon film 12 is separated into cells by scribed isolation grooves 16. This is achieved by scanning a laser over the substrate in areas where isolation grooves 16 are required to define the boundaries of each photovoltaic cell. To scribe the grooves 16, the structure 11 is transferred to an X-Y stage (not shown) located under a laser operating at 1064 nm to produce focussed laser beam 73 which cuts the isolation grooves through the silicon. The laser beam is focussed to minimise the width of the groove, which is lost active area. Typically, a pulse energy of 0.11 mJ is required to fully ablate the silicon film and gives a groove width of 50 μπι. To ensure a continuous groove, successive pulses are overlapped by 50%. The optimum cell width is in the range of 5 to 8 mm and cell widths of 6mm are typical.

As seen in Fig. 2, two layers of insulation are preferably used on the surface of the silicon and are added after the laser scribing step described above. The first insulation layer is an optional thin but tough cap nitride 72. This layer protects the exposed silicon along the edges of the cell definition grooves 16 after laser scribing and passivates the surface of the silicon. The cap nitride 72 is preferably capable of being etched completely in a few minutes to allow access to the silicon at n type and p type contact locations and typically comprises 60 nm of silicon nitride deposited by PECVD at a temperature of 300 - 320°C.

Before the cap layer 72 is applied, the structure 11 is transferred to a tank containing a 5% solution (by weight) of hydrofluoric acid for one minute. This removes any remaining debris and any surface oxides that may have formed. The structure is rinsed in de-ionised water and dried.

The second insulation layer 17 is a thin layer of organic resin. The insulating resin is resistant to dilute solutions of hydrofluoric acid (HF) and potassium permanganate (ΚΜηθ4), and is preferably vacuum compatible to 10^"6 mbar. The insulation material most often used is novolac resin (AZ PI SO) similar to that used in photoresist (but without any photoactive compounds). The novolac resin is preferably loaded with 20 - 30% (by weight) white titania pigment (titanium dioxide) which improves coverage and gives it a white colour that improves its optical reflectivity to help trap light within the silicon. The resin layer 17 serves as an etch mask for etching steps described below and also covers over the rough jagged surface that is formed along the edges of the cell definition grooves 16, an area that is prone to pinholes in the cap nitride layer 72. The organic resin layer 17 also thermally and optically isolates the metal layer from the silicon to facilitate laser patterning of a metal layer in contact forming process steps described below.

The novolac resin is applied to each module to a thickness of 4 to 5 μπι using a spray coater. After the structure 11 is coated, it is passed under heat lamps to heat it to 90°C to cure. As seen in Fig. 2, the insulation layer 17 is applied over the cap layer 72 and extends into the cell separation grooves 16.

Opening mask and etching n type contact openings

In order to make electrical contact to the buried n⁺ type layer and the upper p⁺ type layer with a metal layer which will be subsequently formed, holes must be made through the novolac resin layer 17 and the cap nitride layer 72 in the locations where the n type "crater" contacts and the p type "dimple" contacts are required. Firstly with regard to the "crater" contacts to the buried n⁺ type silicon layer, as well opening the novolac resin layer 17 and the cap nitride layer 72, most of the silicon film 12 must be removed from areas beneath what will later become the n type metal pads to form the n type contact openings 32. Referring to Figs. 3, 4 and 5 ink-jet technology is used to open holes in the novolac resin layer 17 at the crater locations. To achieve this the structure 11 is loaded onto an X-Y stage equipped with an ink-jet head 91 having multiple nozzles with a nozzle spacing of 0.5 mm and controlled by controller 92. The glass is held down with a vacuum chuck and initially scanned to ensure that no point is deformed more than 1 mm above the stage. The glass is then scanned beneath the head 91 at a table speed of typically 400 mm/s. Droplets 76 of dilute (15% +/- 1% by weight) potassium hydroxide (KOH) (see figure 4) are dispensed at locations intended for n type 'crater' contacts. The odd-numbered nozzles fire in the odd-numbered cells, and the even-numbered nozzles fire in the even-numbered cells, so that within a given cell, the spacing between lines of droplets is 1 mm. The spacing between droplets within each line is 400 μπι, hence the rate of droplet release at a table speed of 400 mm/s is 1 kHz. The droplets are sized to etch circular openings in the resin layer that are about 100 μηι in diameter. The KOH solution removes the resin insulation 17 in the area of the droplet 76 after a few minutes to form the hole 32 seen in Fig. 5.

The openings 32 are spaced holes so that lateral continuity is maintained in the semiconductor layer after contact formation. The ink-jet printing process applies a droplet 76 of the caustic solution in a controlled manner to remove the insulation only where the n type contacts are to be formed. The caustic solution preferably contains potassium hydroxide (KOH) but can also use sodium hydroxide (NaOH) and includes glycerol for viscosity control.. The print head used for this purpose is a model 128ID, 64ID2 or 64-30 manufactured by Ink Jet Technologies Inc., and will print substances having a viscosity in the range 5 to 20 centipoise. The droplet size deposited by the print head is in the range of 20 to 240 picolitre corresponding to a deposited droplet diameter range of 50- 150uin. In the preferred embodiment the droplets are printed at a diameter of ΙΟΟμπι. It should be noted that novolac is an organic resin closely related to the resins used in photo-resist material and the etchant printing process described above will apply equally to the patterning of other such materials.

To extend the opening 32 into the silicon layer 12 as seen in Fig. 6, the structure 11 is rinsed in water to remove residual KOH from the ink-jet printing process, and it is then immersed in a tank containing a 5% solution (by weight) of hydrofluoric acid for 1 minute to remove the silicon nitride from the n type contact openings 32. The sheet is then directly transferred to a tank containing 1% hydrofluoric acid (HF) and 0.1% potassium permanganate (KMnO.)) (by weight) for 4 minutes. This time is long enough to remove all of the p⁺ type layer and etch down along grain boundaries to expose some of the n⁺ type layer for the silicon thicknesses stated above, however the time should be adjusted for different silicon layer thicknesses, silicon crystal quality and extent of surface texturing. The structure 11 is then rinsed in de-ionised water and dried. The resulting opening 32 in the silicon 12 has a rough bottom surface 82, in which some points may be etched through to the anti-reflection layer 71 and some ridges 83 extend into the lightly doped p type region 14 as seen in Fig. 6. However as Jong as some of the n⁺ type region is exposed, good contact can be made to the n⁺ type region. Because the p type region is very lightly doped in the area near the n⁺ type region there is insufficient lateral conductivity to cause shorting if some p type material is also left in the bottom of the hole 32.

Reflow of mask

Because the side walls of the hole 32 are passing through the p⁺ type region 13 and the lightly doped region 14, the walls need to be insulated to prevent shorting of the p-n junction. This is achieved by causing the insulation layer 17 to re-flow whereby a portion of the insulation layer 78 in the vicinity of the edge of the opening 32 flows into the hole to form a covering 79 over the walls as seen in Fig.7. To achieve this the sheet is passed through a zone containing a vapour of a suitable solvent. This causes the novolac resin of the insulating layer 17 to reflow, shrinking the size of the . crater openings 32. As the samples exit this zone, they are heated under heat lamps to a temperature of 90°C to drive out die remaining solvent.

The rate of re-flow will vary with the aggressiveness of the solvent used, the concentration and, temperature. There are many suitable, volatile solvents that will dissolve organic resins such as novolac, including substances such as acetone. Acetone is a suitable solvent for the process, but acts quite aggressively, requiring only a few seconds to cover the walls of the hole 32 with resin, and making it difficult to control the process accurately. The preferred solvent is propylene glycol monomethyl ether acetate (PGMEA) and the device is introduced into an atmosphere containing a saturated vapour of PGMEA at room temperature (e.g., 21° C) for 4 minutes until a slight shrinkage of the holes in the insulation is observed.

Opening mask and cleaning p type contact openings

A further set of holes 19 (see Fig.8) are then formed in the insulation layer 17, again using the printing and etching process described above with reference to figs. 3, 4 and 5. These openings are formed by printing droplets 81 of caustic solution onto the insulation (see Fig. 7) in the locations where p type contact "dimples" are required. Following the removal of the insulation layer 17 by the caustic solution to form the openings 19 (see Fig. 8), any residual caustic solution is washed off with water and the cap layer 72 removed in the openings 19 with an etch of 5% hydrofluoric acid (HF) (by weight) for 1 minute (note times of from 10 seconds to 10 minutes may be required to remove the nitride layer depending on its stoichiometry). Optionally, any damaged silicon material on the surface of the p⁺ type region 13 is then removed to allow good contact using an etch in 1% hydrofluoric acid (HF) and 0.1% potassium permanganate (KMnO-i) (by weight) for ten seconds followed by a rinse in de-ionised water to provide the slightly recessed contact "ciimple" 85 seen in Fig. 9. This length of etch is long enough to remove surface plasma damage without etching all the way through the p⁺ type layer 13. It is also short enough to have negligible impact on the n type contacts.

Formation of metal contacts

The final stage of device fabrication involves depositing a metal layer and slicing it up So that it forms a plurality of independent electrical connections, each one collecting current from one line of p type dimple contacts and delivering it to a line of n type crater contacts in the adjacent cell. In this manner, monolithic series interconnection of the cells is achieved.

Before the metal layer is applied, the structure 11 is immersed into a tank containing a 0.2% solution (by weight) of hydrofluoric acid for 20 seconds. This acid removes the surface oxide from both the crater and dimple contacts. There is wide latitude for the strength and duration of this etch and hydrofluoric acid solution strengths of in the range of 0.05 to 0.5% (by weight) can be used by compensating the time of the etch within the range of 5 to 100 seconds. The structure is then rinsed in de-ionised water and dried.

Turning to Fig. 10, the contact metal for the n type and p type contacts is applied simultaneously by depositing a thin metal layer 28 over the insulation layer 17 and extending into the holes 32 and 19 to contact the surfaces 82 and 85 of the n⁺ type region 15 and p⁺ type region 13. The metal layer is preferably a thin layer of nickel:aluminium alloy, which makes good electrical contact to both n⁺ type and p⁺ type silicon, provides good lateral conductivity, and has high optical reflectance.

The nickel.aluminium alloy contact may be formed by various methods but one particularly preferred method is by sputtering. The nickel:aluminium alloy will have a composition of in the range of 10 - 100,000 parts per million nickel in aluminium and preferably 1000 - 10000 parts per million nickel in aluminium (by weight). When applying the contact by sputtering, the sputtering source will be a nicke aluminium target having a composition comprising the desired composition of the contact. The the nickel.aluminium alloy may be in the range of one of 90.000 - 99.999% aluminium and 0.001 - 10.000% nickel and preferably will be in the range of 99.0 - 99.9% aluminium and 0.1 - 1% nickel (by weight)

The sputtered layer of nicke aluminium alloy may be in the range 0.05-0.5 um and preferably nominally 0.1 um (0.095 - 0.105 um) thick.

Isolation of n an p type contacts

The isolation of the n type and p type contacts is achieved by using a laser 86 (see Fig. 10) to melt and/or evaporate the metal layer 28 to thereby form an isolation groove 31 as seen in Fig. 11. When the laser is pulsed on, a small amount of metal is ablated directly under the beam creating a hole 31.

The structure 11 is processed using a laser operating at 1064 nm to scribe the isolation grooves in the metal layer 28. The laser is adjusted so that it scribes through the metal layer 28 without damaging the silicon 12. These scribes 31 separate the n type contacts 32 from the p type contacts 19 within each cell, while retaining the series connection of each cell to its neighbours. Preferred laser conditions are a pulse energy of 0.12 mJ with the beam defocused to a diameter of about 100 μπι. The pulse overlap is 50% and the scribes are spaced 0.5 mm apart. In addition, there are discontinuous scribes 34 along each cell definition groove 16 (see Fig. 12).

Fig. 12 illustrates a rear view of a part of a device made by the process described above, from which it can be seen that each of the cells of the device 11 comprises an elongate photovoltaic element 35a, 35b, 35c, 35d divided across its long axis by a plurality of transverse metal isolation scribes 31 which isolate alternate sets of holes 19 and holes 32 respectively providing contacts to the p⁺ type and n⁺ type regions of the cell. The transverse scribes 31 are made as long substantially straight scribes extending over the length of the device such that each scribe crosses each elongate cell.

Following the formation of the first set of scribes 31, a further set of metal isolation scribes 34 are formed over the cell separation scribes 16 between adjacent cells 11, to isolate every second pair of cells. The metal isolation scribes 34 extending to either side of any one of the elongate transverse scribes 31 are offset by one cell with respect to those on the other side of the same transverse scribe 31 such that the cells become series connected by a matrix of connection links 36 with alternating offsets, connecting one set of p type contacts 19 of one cell 35 to a set of n type contacts 32 of an adjacent cell 35, as shown in Figure 12.

The metal isolation scribes 31 comprises a first set of long scribes transverse to the cells 35 from 50-200μπι wide, preferably about ΙΟΟμπι wide. The scribes are typically spaced on centres of 0.2-2.0mm and preferably about 0.5mm to form conducting strips about 0.2-1.9mm and preferably about 0.4mm wide. The isolation scribes 34 comprises a second set of interrupted scribes parallel to the long direction of the cells 35 and substantially coincident with the cell isolation grooves 16 in the silicon, The isolation scribes 34 are also from 50-200μιη wide, preferably about ΙΟΟμπι wide. It is equally possible to form the isolation scribes 34 before forming the transverse isolation scribes 31. The scribed areas are illustrated in Fig. 12 with cross-hatching.

Referring to Figure 13, which illustrates a portion of the completed structure, the device is typically encapsulated in an encapsulation film 88 such as a 0.4 mm thick EVA encapsulation or a 0.2 mm thick Tedlar-Polyester-EVA (TPE) encapsulation. Fig. 13 also shows the connection of an n type contact of one cell to the p type contact of an adjacent cell to provide a series connections of cells. In practice there may be several n type contacts grouped together and several p type contacts grouped together however for the sake of clarity only one of each is shown in each cell. The arrangement shown in Fig. 13 is also schematic as the isolation grooves 16 in the silicon and the isolation grooves 31 in the metal run perpendicularly to one another in practice as is seen in Fig. 12.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

1. A method of forming a connection layer, in an electronic device, the method comprising the steps of:

a) preparing a surface onto which the connection layer will be formed;

b) forming a rdckelraluminium alloy connection layer over the prepared surface.

2. The method of claim 1 wherein the nickel:aluminium alloy has a composition of in the range of one of 10 - 100,000 or 100 - 100,000 or 1,000 - 100,000 or 10,000 - 100,000 or 10 - 10,000 or 100 - 10,000 or 1,000 - 10,000 or 2,000 - 10,000 or 3,000 - 10,000 or 4,000 - 10,000 or 5,000 - 10,000 or 6,000 - 10,000 or 7,000 - 10,000 or

8,000 - 10,000 or 9,000 - - 10,000 or 1,000 - 9,000 or 2,000 - - 9,000 or 3,000 - 9,000 or

4,000 - 9,000 or 5,000 - 9,000 or 6,000 - 9,000 or 7,000 - 9,000 or 8,000 - 9,000 or

1,000 - 8,000 or 2,000 - 8,000 or 3,000 - 8,000 or 4,000 - 8,000 or 5,000 - 8,000 or 6,000 - 8,000 or 7,000 - 8,000 or 1,000 - 7,000 or 2,000 - 7,000 or 3,000 - 7,000 or

3,000 - 6,000 or 4,000 - 6,000 or 5,000 - 6,000 or 1,000 - 5,000 or 2,000 - 5,000 or

3,000 - 5,000 or 4,000 - 5,000 or 1,000 - 4,000 or 2,000 - 4,000 or 3,000 - 4,000 or

1,000 - 3,000 or 2,000 - 3,000 or 1,000 - 2,000 parts per million nickel in aluminium (by weight).

3. The method of claim 1 or 2 wherein the nicke aluminium alloy contact is formed by sputtering.

4. The method of claim 1, 2, or 3 wherein a sputtering source for the sputtering process is a nickel:aluminium target having a composition comprising the desired composition of the contact.

5. The method of claim 4 wherein the nickehaluminium alloy of the sputtering target is in the range of one of 90.000 - 99.999% aluminium and 0.001 - 10.000% nickel or 99.000 - 99.999% aluminium and 0.001 - 1.000% nickel or 99.900 - 99.999% aluminium and 0.001 - 0.100% nickel or 99.990 - 99.999% aluminium and 0.001 - 0.010% nickel or 90.000 - 99.990% aluminium and 0.010 - 10.000% nickel or 99.000 - 99.990% aluminium and 0.010 - 1.000% nickel or 99.900 - 99.990% aluminium and 0.010 - 0.100% nickel 90.000 - 99.900% aluminium and 0.100 - 10.000% nickel or 99.00 - 99.900% aluminium and 0.100 - 1.000% nickel or 90.000 - 99.000% aluminium and 1.000 - 10.000% nickel or 99.1 - 99.9% aluminium and 0.1 - 0.9% nickel or 99.2 - 99.9% aluminium and 0.1 - 0.8% nickel or 99.3 - 99.9% aluminium and 0.1 - 0.7% nickel or 99.4 - 99.9% aluminium and 0.1 - 0.6% nickel or

99.5 - 99.9% aluminium and 0.1 - 0.5% nickel or 99.6 - 99.9% aluminium and 0.1 - 0.4% nickel or 99.7 - 99.9% aluminium and 0.1 - 0.3% nickel or 99.8 - 99.9% aluminium and 0.1 - 0.2% nickel or 99.1 - 99.8% aluminium and 0.2 - 0.9% nickel or 99.2 - 99.8% aluminium and 0.2 - 0.8% nickel or 99.3 - 99.8% aluminium and 0.2 - 0.7% nickel or 99.4 - 99.8% alviminium and 0.2 - 0.6% nickel or 99.5 - 99.8% aluminium and 0.2 - 0.5% nickel or 99.6 - 99.8% aluminium and 0.2 - 0.4% nickel or 99.7 - 99.8% -duininium and 0.2 - 0.3% nickel or 99.1 - 99.7% aluminium and 0.3 - 0.9% nickel or 99.2 - 99.7% aluminium and 0.3 - 0.8% nickel or 99.3 - 99.7% aluminium and 0.3 - 0.7% nickel or 99.4 - 99.7% aluminium and 0.3 - 0.6% nickel or 99.5 - 99.7% aluminium and 0.3 - 0.5% nickel or 99.6 - 99.7% aluminium and 0.3 - 0.4% nickel or 99.1 - 99.6% aluminium and 0.4 - 0.9% nickel or 99.2 - 99.6% aluminium and 0.4 - 0.8% nickel or 99.3 - 99.6% aluminium and 0.4 - 0.7% nickel or 99.4 - 99.6% aluminium and 0.4 - 0.6% nickel or 99.5 - 99.6% aluminium and 0.4 - 0.5% nickel or 99.1 - 99.5% aluminium and 0.5 - 0.9% nickel or 99.2 - 99.5% aluminium and 0.5 - 0.8% nickel or 99.3 - 99.5% aluminium and 0.5 - 0.7% nickel or 99.4 - 99.5% aluminium and 0.5 - 0.6% nickel or 99.1 - 99.4% aluminium and 0.6 - 0.9% nickel or 99.2 - 99.4% aluminium and 0.6 - 0.8% nickel or 99.3 - 99.4% aluminium and 0.6 - 0.7% nickel or 99.1 - 99.3% aluminium and 0.7 - 0.9% nickel or 99.2 - 99.3% aluminium and 0.7 - 0.8% nickel or 99.1 - 99.2% aluminium and 0.8 - 0.9% nickel (by weight).

6. The method of claim 4 or 5 wherein sputtered layer of nickel :aluminium alloy is in the range of one of 0.05 - 0.50 um or 0.10 - 0.50 um or 0.15 - 0.50 um or 0.20 - 0.50 um or 0.25 - 0.50 um or 0.30 - 0.50 um or 0.35 - 0.50 um or 0.40 - 0.5 μιη or 0.45 - 0.50 um or 0.05 - 0.45 μιη or 0.10 - 0.45 um or 0.15 - 0.45 Mm or 0.20 - 0.45 um or 0.25 - 0.45 um or 0.30 - 0.45 μιη or 0.35 - 0.45 μτη or 0.40 - 0.45 um or 0.05 - 0.40 um or 0.10 - 0.40 μπι or 0.15 - 0.40 μιη or 0.20 - 0.40 μιη or 0.25 - 0.40 μπι or 0.30 - 0.40 μπι or 0.35 - 0.40 μτη or 0.05 - 0.35 \x or 0.10 - 0.35 μηι or 0.15 - 0.35 μπι or 0.20 - 0.35 μιη or 0.25 - 0.35 μιη or 0.30 - 0.35 μπι or 0.05 - 0.30 μπι or 0.10 - 0.30 μιη or 0.15 - 0.30 μπι or 0.20 - 0.30 μπι or 0.25 - 0.30 μιη or 0.05 - 0.25 μιη or 0.10 - 0.25 um or 0.15 - 0.25 μπι or 0.20 - 0.25 um or 0.05 - 0.20 μηι or 0.10 - 0.20 μπι or 0.15 - 0.20 μιη or 0.05 - 0.15 μπι or 0.10 - 0.15 μπι or 0.05 - 0.10 an or 0.095- 0.105 m or 0.096-0.105 μηι or 0.097-0.105 μπι or 0.098-0.105 μπι or 0.099-0.105 μπι or 0.100-0.105 μπι or 0.101-0.105 μιη or 0.102-0.105 μηι or 0.103-0.105 μπι or 0.104- 0.105 μι^η or 0.095-0.104 μπι 0.096-0.104 μπι or 0.097-0.104 μιη or 0.098-0.104 μπι or 0.099-0.104 μτη or 0.100-0.104 μχη or 0.101-0.104 um or 0.102-0.104 μπι or 0.103- 0.104 μιη or 0.095-0.103 μπι or 0.096-0.103 μηι or 0.097-0.103 um or 0.098-0.103 μπι or 0.099-0.103 μτη or 0.100-0.103 μτη or 0.101-0.103 um or 0.102-0.103 um or 0.095- 0.102 um or 0.096-0.102 um or 0.097-0.102 um or 0.098-0.102 um or 0.099-0.102 μπι or 0.100-0.102 um or 0.101-0.102 μπι or 0.095-0.101 μm or 0.096-0.101 um or 0.097- 0.101 m or 0.098-0.101 μm or 0.099-0.101 um or 0.095-0.100 um or 0.096-0.100 μm or 0.097-0.100 μτη or 0.098-0.100 μπι or 0.099-0.100 μιη or 0.095-0.099 μπι or 0.096- 0.099 μτη or 0.097-0.099 μπι or 0.098-0.099 μτη or 0.095-0.098 μτη or 0.096-0.098 um or 0.097-0.098 um or 0.095-0.097 um or 0.096-0.097 um or 0.095-0.096 um thick. 8. The method as claimed in any one of claims 1-7 wherein the device is encapsulated in an encapsulating film.

9. The method as claimed in claim 8 wherein the device is encapsulated in an encapsulation film of a 0.4 mm thick EVA encapsulation with a 0.3 mm thick Tedlar- Polyester-EVA (TPE) encapsulation.

10. The method as claimed in any one of claims 1 - 9, further comprising one or more of the following steps:

1) dividing the silicon film into a plurality of cell regions by forming cell isolation grooves;

2) forming a mask of organic resin in a layer over the silicon film;

7) forming the nicke aluminium alloy layer over a surface of the mask and extending the alloy into each opening of the first set of openings to contact the silicon of the first dopant polarity and into the second set of openings to contact the silicon of the second dopant polarity, the alloy in the first set of openings being isolated from the exposed edge of the silicon of the second dopant polarity by the re-flowed resin; 8) forming isolation grooves in the alloy layer to separate the contacts to the silicon of the first dopant polarity from the contacts to the silicon of the second dopant polarity within each cell, whereby the alloy layer interconnects the silicon of the second dopant polarity of one of the cells to the silicon of the first dopant polarity of an adjacent one of the cells;

9) tabbing and encapsulation of the solar cells.

11. The method of claim 10 wherein the step of etching the silicon film in the second set of openings to remove damaged material from the svirface of the silicon of the second dopant polarity before formation of the metal layer.

12. The method of claim 10 or 11 wherein organic resin is novolac.

13. The method of claim 10, 11 or 12 wherein the openings in the resin layer are formed by chemical removal using a solution of a caustic substance.

14. The method of claim 10, 11, 12 or 13 wherein the caustic substance is potassium hydroxide (KOH) or sodium hydroxide (NaOH).

15. The method as claimed in any one of claims 1 - 14 wherein the device is a thin film silicon solar cell.

16. The method as claimed in any one of claims 1 - 15 wherein the electronic device is a photovoltaic device structure in a silicon film deposited on a glass substrate.

17. The method of claim 16 wherein the silicon film comprises a first doped region having silicon of a first dopant polarity closest to the glass, a lightly doped or intrinsic region over the first doped region and a second doped region having silicon of a second dopant polarity opposite to the first dopant polarity over the lightly doped region.

18. A semiconductor device comprising a region of semiconductor material and a metal contact in electrical contact with the semiconductor layer, the metal contact comprising a connection layer of mckel:aluminium alloy.

19. The semiconductor device of claim 18 wherein the nickel :alummium alloy has a composition of in the range of one of 10 - 100,000 or 100 - 100,000 or 1,000 - 100,000 or 10,000 - 100,000 or 10 - 10,000 or 100 - 10,000 or 1,000 - 10,000 or 2,000 - 10,000 or 3,000 - 10,000 or 4,000 - 10,000 or 5,000 - 10,000 or 6,000 - 10,000 or 7,000 - 10,000 or 8,000 - 10,000 or 9,000 - 10,000 or 1 ,000 - 9,000 or 2,000 - 9,000 or 3,000 - 9,000 or 4,000 - 9,000 or 5,000 - 9,000 or 6,000 - 9,000 or 7,000 - 9,000 or 8,000 - 9,000 or 1,000 - 8,000 or 2,000 - 8,000 or 3,000 - 8,000 or 4,000 - 8,000 or 5,000 - 8,000 or 6,000 - 8,000 or 7,000 - 8,000 or 1,000 - 7,000 or 2,000 - 7,000 or 3,000 - 7,000 or 4,000 - 7,000 or 5,000 - 7,000 or 6,000 - 7,000 or 1,000 - 6,000 or 2,000 - 6,000 or 3,000 - 6,000 or 4,000 - 6,000 or 5,000 - 6,000 or 1,000 - 5,000 or 2,000 - 5,000 or 3,000 - 5,000 or 4,000 - 5,000 or 1,000 - 4,000 or 2,000 - 4,000 or 3,000 - 4,000 or 1,000 - 3,000 or 2,000 - 3,000 or 1,000 - 2,000 parts per million nickel in aluminium (by weight).

20. The semiconductor device of claim 18 or 19 wherein the nickel:aluminium alloy connection layer is a sputtered layer.

21. The semiconductor device of claim 20 wherein the nickel:duminium alloy of the sputtered layer is in the range of one of 90.000 - 99.999% aluminium and 0.001 - 10.000% nickel or 99.000 - 99.999% aluminium and 0.001 - 1.000% nickel or 99.900 - 99.999% alurninium and 0.001 - 0.100% nickel or 99.990 - 99.999% aliiminium and 0.001 - 0.010% nickel or 90.000 - 99.990% alurninium and 0.010 - 10.000% nickel or 99.000 - 99.990% aluminium and 0.010 - 1.000% nickel or 99.900 - 99.990% aluminium and 0.010 - 0.100% nickel 90.000 - 99.900% aluminium and 0.100 - 10.000% nickel or 99.00 - 99.900% aluminium and 0.100 - 1.000% nickel or 90.000 - 99.000% alumimum and 1.000 - 10.000% nickel or 99.1 - 99.9% aluminium and 0.1 - 0.9% nickel or 99.2 - 99.9% aluminium and 0.1 - 0.8% nickel or 99.3 - 99.9% aluminium and 0.1 - 0.7% nickel or 99.4 - 99.9% aluminium and 0.1 - 0.6% nickel or 99.5 - 99.9% aluminium and 0.1 - 0.5% nickel or 99.6 - 99.9% aluminium and 0.1 - 0.4% nickel or 99.7 - 99.9% alumimum and 0.1 - 0.3% nickel or 99.8 - 99.9% aluminium and 0.1 - 0.2% nickel or 99.1 - 99.8% aluminium and 0.2 - 0.9% nickel or 99.2 - 99.8% alurninium and 0.2 - 0.8% nickel or 99.3 - 99.8% aluminium and 0.2 - 0.7% nickel or 99.4 - 99.8% aluminium and 0.2 - 0.6% nickel or 99.5 - 99.8% aluminium and 0.2 - 0.5% nickel or 99.6 - 99.8% aluminium and 0.2 - 0.4% nickel or 99.7 - 99.8% aluminium and 0.2 - 0.3% nickel or 99.1 - 99.7% aluminium and 0.3 - 0.9% nickel or 99.2 - 99.7% aluminium and 0.3 - 0.8% nickel or 99.3 - 99.7% aluminium and 0.3 - 0.7% nickel or 99.4 - 99.7% aluminium and 0.3 - 0.6% nickel or 99.5 - 99.7% aluminium and 0.3 - 0.5% nickel or 99.6 - 99.7% aluminium and 0.3 - 0.4% nickel or 99.1 - 99.6% aluminium and 0.4 - 0.9% nickel or 99.2 - 99.6% aluminium and 0.4 - 0.8% nickel or 99.3 - 99.6% aluminium and 0.4 - 0.7% nickel or 99.4 - 99.6% aluminium and 0.4 - 0.6% nickel or 99.5 - 99.6% aluminium and 0.4 - 0.5% nickel or 99.1 - 99.5% aluminium and 0.5 - 0.9% nickel or 99.2 - 99.5% aluminium and 0.5 - 0.8% nickel or 99.3 - 99.5% aluminium and 0.5 - 0.7% nickel or 99.4 - 99.5% aluminium and 0.5 - 0.6% nickel or 99.1 - 99.4% aluminium and 0.6 - 0.9% nickel or 99.2 - 99.4% alurninium and 0.6 - 0.8% nickel or 99.3 - 99.4% aluminium and 0.6 - 0.7% nickel or 99.1 - 99.3% aluminium and 0.7 - 0.9% nickel or 99.2 - 99.3% aluminium and 0.7 - 0.8% nickel or 99.1 - 99.2% aluminium and 0.8 - 0.9% nickel (by weight).

22. The semiconductor device of claim 20 or 21 wherein sputtered layer of nickel-.aluminium alloy is in the range of one of 0.05 - 0.50 um or 0.10 - 0.50 um or 0.15 - 0.50 um or 0.20 - 0.50 um or 0.25 - 0.50 um or 0.30 - 0.50 um or 0.35 - 0.50 um or 0.40 - 0.5 um or 0.45 - 0.50 um or 0.05 - 0.45 um or 0.10 - 0.45 um or 0.15 - 0.45 Mm or 0.20 - 0.45 um or 0.25 - 0.45 um or 0.30 - 0.45 um or 0.35 - 0.45 um or 0.40 - 0.45 um or 0.05 - 0.40 um or 0.10 - 0.40 um or 0.15 - 0.40 Mm or 0.20 - 0.40 um or 0.25 - 0.40 um or 0.30 - 0.40 um or 0.35 - 0.40 um or 0.05 - 0.35 um or 0.10 - 0.35 um or 0.15 - 0.35 um or 0.20 - 0.35 um or 0.25 - 0.35 um or 0.30 - 0.35 Mm or 0.05 - 0.30 Mm or 0.10 - 0.30 um or 0.15 - 0.30 um or 0.20 - 0.30 m or 0.25 - 0.30 m or 0.05 - 0.25 M or 0.10 - 0.25 Mm or 0.15 - 0.25 or 0.20 - 0.25 Mm or 0.05 - 0.20 um or 0.10 - 0.20 um or 0.15 - 0.20 um or 0.05 - 0.15 um or 0.10 - 0.15 um or 0.05 - 0.10 um or 0.095-0.105 um or 0.096-0.105 Mm or 0.097-0.105 um or 0.098- 0.105 Mm or 0.099-0.105 um or 0.100-0.105 um or 0.101-0.105 m or 0.102-0.105 um or 0.103-0.105 Mm or 0.104-0.105 Mm or 0.095-0.104 μτη 0.096-0.104 um or 0.097- 0.104 um or 0.098-0.104 um or 0.099-0.104 Mm or 0.100-0.104 Mm or 0.101-0.104 m or 0.102-0.104 m or 0.103-0.104 Mm or 0.095-0.103 um or 0.096-0.103 m or 0.097- 0.103 um or 0.098-0.103 Mm or 0.099-0.103 or 0.100-0.103 Mm or 0.101-0.103 Mm or 0.102-0.103 um or 0.095-0.102 um or 0.096-0.102 Mm or 0.097-0.102 Mm or 0.098- 0.102 Mm or 0.099-0.102 m or 0.100-0.102 Mm or 0.101-0.102 Mm or 0.095-0.101 Mm or 0.096-0.101 Mm or 0.097-0.101 m or 0.098-0.101 Mm or 0.099-0.101 Mm or 0.095- 0.100 Mm or 0.096-0.100 um or 0.097-0.100 um or 0.098-0.100 um or 0.099-0.100 Mm or 0.095-0.099 um or 0.096-0.099 um or 0.097-0.099 um or 0.098-0.099 Mm or 0.095- 0.098 m or 0.096-0.098 μιη or 0.097-0.098 um or 0.095-0.097 um or 0.096-0.097 um or 0.095-0.096 μπι thick.

23. The semiconductor device as claimed in any one of claims 18 - 22 wherein the semiconductor device is encapsulated in an encapsulating film.

24. The semiconductor device as claimed in claim 23 wherein the semiconductor device is encapsulated in an encapsulation film of a 0.4 mm thick EVA encapsulation with a 0.3 mm thick Tedlar-Polyester-EVA (TPE) encapsulation.

25. The semiconductor device as claimed in any one of claims 18 - 24, further comprising:

1) a plurality of cell regions divided by cell isolation grooves;

2) a layer of organic resin formed over the silicon film;

3) a first set of openings in the organic resin layer and extending through the silicon of the second dopant polarity to expose the silicon of the first dopant polarity in locations where contacts to the first doped region are required; 5) the. organic resin extending over the edges of the openings in the silicon of the first dopant polarity to insulate the edges of the silicon of the first dopant polarity;

7) the nickel'.aluminium alloy layer extending over a surface of the organic resin layer and extending into each opening of the first set of openings to contact the silicon of the first dopant polarity and extending into the second set of openings to contact the silicon of the second dopant polarity, the alloy in the first set of openings being isolated from the exposed edges of the silicon of the second dopant polarity by the re-flowed resin;

26. The semiconductor device of claim 25 wherein organic resin is novolac.

27. The semiconductor device as claimed in any one of claims 18 - 26 wherein the device is a thin film silicon solar cell.

28. The semiconductor device as claimed in any one of claims 18 - 27 wherein the electronic device is a photovoltaic device structure in a silicon film deposited on a glass substrate.

29. The semiconductor device of claim 28 wherein the silicon film comprises a first doped region having silicon of a first dopant polarity closest to the glass, a lightly doped or intrinsic region over the first doped region and a second doped region having silicon of a second dopant polarity opposite to the first dopant polarity over the lightly doped region.