Selective wet etching of gold-tin based solder
AssigneeCree, Inc.
InventorAshay Chitnis
Life of this patent
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Abstract
The present invention is directed to post-deposition, wet etch processes for patterning AuSn solder material and devices fabricated using such processes. The processes can be applied to uniform AuSn layers to generate submicron patterning of thin AuSn layers having a wide variety of features. The use of multiple etching steps that alternate between different mixes of chemicals enables the etch to proceed effectively, and the same or similar processes can be used to etch under bump metallization. The processes are simple, cost-effective, do not contaminate equipment or tools, and are compatible with standard cleanroom fabrication processes.
Claims21
A method for fabricating an electronic device using selective wet etching, the method comprising:
- providing at least one wafer comprising at least one first surface;
- depositing at least one first layer comprising solder material adjacent to the at least one first surface, wherein the solder material comprises composite AuSn;
- depositing at least one second layer comprising etch mask material on said at least one first layer comprising solder material;
- introducing a plurality of liquid etching compositions to the at least one first layer comprising solder material, each of said plurality of liquid etching compositions comprising a different chemical composition, said plurality of liquid etching compositions introduced in a repeating, alternating fashion;
- and
- etching the at least one layer comprising solder material for a period of time sufficient to selectively etch at least one portion of the at least one solder layer with the plurality of liquid etching compositions;
- wherein selective wet etching is achieved using a wet etch process comprising:
- introducing the at least one first layer to at least one composition comprising at least one of HF, HCl and HNO3;
- and
- introducing the at least one first layer to at least one composition comprising aqua-regia.
A method for selective wet etching at least one blanket layer comprising AuSn solder material, the method comprising:
- repeatedly introducing the at least one blanket layer comprising AuSn solder material to a first etch composition comprising aqua-regia, wherein an etch mask layer is on said at least one blanket layer;
- and
- repeatedly introducing the at least one layer comprising AuSn solder material to a second composition comprising at least one of HF, HCl and HNO3 when said at least one layer is not being introduced to said first etch composition;
- wherein introduction of the second composition comprising at least one of HF, HC, and HNO3 alternates with the introduction of the first composition comprising aqua-regia.
A method for selectively wet etching a AuSn composite layer of solder material using repeated, alternating etchants, the method comprising:
- forming a mask layer on the solder layer, said mask layer comprising openings to said solder layer;
- a first etching of said solder layer through said mask layer openings using a first etch comprising a first chemical composition;
- a second etching of said solder layer through said mask opening using a second etch comprising a second chemical composition, said first and second etchings occurring at different times;
- wherein said first chemical composition comprises at least one of HF, HCl, and HNO3 or aqua-regia;
- and
- wherein said second chemical composition comprises at least one of HF, HCl, and HNO3 or aqua-regia.
Dependencies are inferred from the claim text.