SOLAR CELL METALLIZATION USING INLINE ELECTROLESS PLATING

• US 20100124619A1
• Filed: 11/14/2008
• Published: 05/20/2010
• Est. Priority Date: 11/14/2008
• Status: Active Grant

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Palo Alto Research Center, Inc. (Xerox Holdings Corp.)
• Inventors: LITTAU, Karl A., ELROD, Scott A., XU, Baomin
• Granted Patent: US 9,150,966 B2
• Time in Patent Office: Days
• US Class Current: 427/554
• CPC Class Codes: C23C 18/161 from plating step, e.g. inkjet
• CPC Class Codes: C23C 18/1632 Features specific for the apparatus, e.g. layout of cells and of its equipment, multiple cells
• CPC Class Codes: C23C 18/165 Multilayered product layered product B32B
• CPC Class Codes: C23C 18/1651 Two or more layers only obtained by electroless plating
• CPC Class Codes: C23C 18/1653 Two or more layers with at least one layer obtained by electroless plating and one layer obtained by electroplating
• CPC Class Codes: C23C 18/31 Coating with metals
• CPC Class Codes: H01L 31/022425 for solar cells
• CPC Class Codes: Y02E 10/50 Photovoltaic [PV] energy

Abstract

Inline methods for forming a photovoltaic cell electrode structure, wherein the photovoltaic cell includes a semiconductor substrate having a passivation layer thereon, includes providing a plurality of contact openings through the passivation layer to the semiconductor substrate, selectively plating a contact metal into the plurality of contact openings by printing electroless plating solution into the plurality of contact openings to deposit the contact metal, depositing a metal containing material on the deposited contact metal, and firing the deposited contact metal and the deposited metal containing material. The metal containing material may include a paste containing a silver or silver alloy along with a glass frit and is substantially free to completely free of lead. The methods may also use light activation of the passivation layer or use seed layers to assist in the plating.

Claims

1. A method for forming a photovoltaic cell electrode structure, wherein the photovoltaic cell comprises a semiconductor substrate having a passivation layer thereon, the method comprising:

providing a plurality of contact openings through the passivation layer to the semiconductor substrate;

selectively plating a contact metal into the plurality of contact openings to deposit the contact metal by printing electroless plating solution directly into the contact openings;

depositing at least one metal containing layer over the deposited contact metal to form metal gridlines; and

firing the deposited contact metal and the at least one deposited metal containing layer.

2. The method according to claim 1, wherein the printing is done with an inkjet printer.

3. The method according to claim 1, wherein the plurality of contact openings are formed by laser ablation of the passivation layer.

4. The method according to claim 1, wherein the plurality of contact openings are formed by chemical etching.

5. The method according to claim 1, wherein the contact metal comprises one or more of nickel, cobalt, titanium, tantalum, tungsten, molybdenum, and palladium.

6. The method according to claim 1, wherein the composition of the electroless plating solution contains one or more chemicals which can remove residuals of the passivation layer.

7. The method according to claim 1, wherein the composition of the electroless plating solution contains doping materials which are also deposited into the contact openings and form a self-doping region around the contact openings after firing.

8. The method according to claim 1, wherein the at least one metal containing layer comprises a paste containing a silver or silver alloy.

9. The method according to claim 8, wherein the paste further comprises a glass frit and is substantially free to completely free of lead or lead oxide.

10. The method according to claim 1, wherein the method further comprises forming a buffer layer over the deposited contact metal prior to depositing the at least one metal containing layer.

11. The method according to claim 1, wherein the depositing at least one metal containing layer over the deposited contact metal comprises screen printing, extrusion, pad printing, jet printing or dispensing a metal containing paste over the deposited contact metal layer.

12. The method according to claim 1, wherein the depositing at least one metal containing layer over the deposited contact metal comprises electroless plating, electroplating, or light induced plating one or more metal containing layers over the deposited contact metal layer.

13. The method according to claim 1, wherein the firing is conducted at about 200°

C. to about 1000°

C.

14. The method according to claim 1, wherein the method further comprises light activating portions of the surface of the passivation layer surrounding one or more of the plurality of contact openings, wherein the selective plating of the contact metal into the plurality of contact openings also deposits the contact metal onto the light activated portions of the passivation layer.

15. The method according to claim 14, wherein the light activating comprises application of a laser to the passivation layer surface, wherein the light activating laser has an energy density to activate the surface but not to destroy the passivation layer.

16. The method according to claim 1, wherein the method further comprises depositing a light sensitive seed layer on the passivation layer prior to forming the plurality of contact openings in the passivation layer, and light activating the seed layer in portions on and surrounding one or more of the plurality of contact openings, wherein the selective plating of the contact metal deposits the contact metal at light activated portions of the seed layer and in the plurality of contact openings.

17. The method according to claim 16, wherein the seed layer comprises an organometallic material.

18. The method according to claim 1, wherein the method further comprises depositing a self-assembled monolayer material on the passivation layer following forming the plurality of contact openings in the passivation layer at portions on and surrounding one or more of the plurality of contact openings, and wherein the selective plating of the contact metal deposits the contact metal on the self-assembled monolayer and in the plurality of contact openings.

19. The method according to claim 1, wherein the process further comprises depositing a further metal containing material on the deposited metal containing material, the further metal containing material having a conductivity greater than a conductivity of the deposited metal containing material, and wherein the firing fires the deposited contact metal, the deposited metal containing material, and the further deposited metal containing material.

20. The method according to claim 1, wherein the semiconductor substrate comprises a silicon wafer and the passivation layer comprises silicon nitride.

21. An inline system for forming a photovoltaic cell electrode structure, wherein the photovoltaic cell electrode structure comprises a semiconductor substrate having a passivation layer thereon, the inline system comprising:

a contact opening forming device for providing a plurality of contact openings through the passivation layer to the semiconductor substrate,

a printing device, located downstream from the contact opening forming device, for selectively printing electroless plating solution directly into the contact openings to form contact metal in the plurality of contact openings,

a heating device to heat the substrate following the printing by the printing device,

a metallic gridline deposition device, located downstream from the heating device, for depositing metallic gridlines over the contact metal, and

a furnace device for firing the metallic gridlines and the substrate with the contact metal,

wherein the inline system retains the photovoltaic cell electrode structure within the system during processing by the foregoing devices.

22. The inline system according to claim 21, wherein the system further comprises one or more additional printing devices for selectively printing a self-assembled monolayer and/or a catalyst material into the contact openings, wherein the one or more additional printing devices are before the printing device for selectively printing electroless plating solution directly into the contact openings.

23. A method to form a metal-based pattern on a substrate comprising:

providing a substrate;

selectively printing electroless plating solution onto the substrate in an image-wise fashion;

heating the substrate to activate the printed electroless plating solution.

24. The method according to claim 23, wherein the printing is done by an inkjet printer.

25. The method according to claim 23, wherein the method further comprises selectively printing one or more additional types of plating solutions onto the substrate in an image-wise fashion, so that more than one kind of metal is deposited on the substrate.

26. The method according to claim 23, wherein the substrate does not have selectivity for electroless plating deposition.