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Tapering Metallurgy Edges

IP.com Disclosure Number: IPCOM000077975D
Original Publication Date: 1972-Oct-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Turnbull, RC: AUTHOR

Abstract

The etched metal stripe encountered in first and second level metallurgies of integrated circuit devices provides a step which is difficult to cover with successive glassing operations. The problem presented by a steep metal edge is particularly troublesome, when the metallurgy layer is etched by subtractive sputtered etching.

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Tapering Metallurgy Edges

The etched metal stripe encountered in first and second level metallurgies of integrated circuit devices provides a step which is difficult to cover with successive glassing operations. The problem presented by a steep metal edge is particularly troublesome, when the metallurgy layer is etched by subtractive sputtered etching.

A method for achieving a tapered edge in fabricating aluminum inter- connection metallurgy consists of subtractive etching of the blanket aluminum layer employing a KTFR* photoresist, which has been deposited and prebaked at 100 degrees C for 30 minutes, exposed and developed, and post-baked at 165 degrees C for 45 minutes. The first step is subetching, using a conventional aluminum etchant bath which includes H(3)PO(4)-800 ml, HNO(3)-50 ml, HC(2)H(3)O(2)-50 ml, and H(2)O-100 ml, at 40-50 degrees C. Subsequently, the subetched metallized wafer is placed in a hot etchant bath at a temperature of 40-70 degrees C. The etchant bath is basically similar to the aforementioned etchant bath, except that it includes NH(4)F.HF in the range of 0.665 to 5.325 g. The use of ammonium bifluoride in the second etchant bath adversely affects the adherence of the KTFR photoresist, allowing a controlled lateral undercutting of the photoresist by the ammonium bifluoride in the etchant bath. In the original etchant bath no significant undercutting occurs, since ammonium bifluoride is not present.

A second method of tapering the side wa...