Method for selective removal of a material from a wafer's alignment marks
Patent 5271798 Issued on December 21, 1993. Estimated Expiration Date: 
March 29, 2013. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
March 29, 2013. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent ReferencesMethod of etching back of tungsten layers on semiconductor wafers, and solution therefore Process for removal of residues remaining after etching polysilicon layer in formation of integrated circuit structure Process for etching a semiconductor device using an improved protective etching mask Mechanical lift-off process of a metal layer on a polymer Patent #: 5234539 InventorsApplicationNo. 039810 filed on 03/29/1993US Classes:438/745, Liquid phase etching257/E21.314, Using mask (EPO)257/E23.179, Marks applied to semiconductor devices or parts, e.g., registration marks, test patterns, alignment structures, wafer maps (EPO)438/975SUBSTRATE OR MASK ALIGNING FEATUREExaminersPrimary: Powell, William A.Attorney, Agent or FirmInternational ClassesB44C 001/22C23F 001/00 C03C 015/00 AbstractThe present invention remedies the problems associated with selective etching of material, and in particular tungsten, by locally removing the material (e.g. tungsten) from the alignment marks through wet etching without the need for any photo steps. Either before or after chemical mechanical polishing, the wafers are flatly aligned and a tungsten etching agent is introduced through an etchant dispensing apparatus onto the alignment marks. Since an alignment mark is normally a few hundred microns in size and there is a large unused silicon real estate around the alignment marks, the alignment constraints vis-a-vis etchant dispensing apparatus and wafer are not very critical and tungsten plugs in the live dice are easily protected from the wet etch. After the etch, the etching byproduct is removed by suction and the wafer is cleaned by being rinsed in distilled water.Other References
| |
