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Process Resulting in Increased Contact Area Refractory Metal Stud to Aluminum Wiring

IP.com Disclosure Number: IPCOM000062151D
Original Publication Date: 1986-Oct-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 25K

Publishing Venue

IBM

Related People

Cronin, JE: AUTHOR [+2]

Abstract

A novel process sequence is described for creating a refractory metal stud to connect underlying conductive regions to an upper level of aluminum alloy wiring. The interface (contact) area between the refractory metal and the aluminum alloy wiring is a function of wiring metal thickness t and a linear function of metal stud (or via hole) radius r. In an environment of increasing wiring density where via holes must decrease in radius r and where thickness t is constant or increasing, the area of contact between the stud and the metal line is higher in this process than in processes which make this contact area a function of r2 . This advantage may be used in a trade-off between achieving a lower contact resistance or permitting larger alignment tolerance in aligning the wiring mask to studs.

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Process Resulting in Increased Contact Area Refractory Metal Stud to Aluminum Wiring

A novel process sequence is described for creating a refractory metal stud to connect underlying conductive regions to an upper level of aluminum alloy wiring. The interface (contact) area between the refractory metal and the aluminum alloy wiring is a function of wiring metal thickness t and a linear function of metal stud (or via hole) radius r. In an environment of increasing wiring density where via holes must decrease in radius r and where thickness t is constant or increasing, the area of contact between the stud and the metal line is higher in this process than in processes which make this contact area a function of r2 . This advantage may be used in a trade-off between achieving a lower contact resistance or permitting larger alignment tolerance in aligning the wiring mask to studs. In the cross-sectional figure, a conductive region 2 (e.g., a polysilicon line) on substrate 4 is first coated with an insulating film 6 (e.g., SiO2) and is polished to obtain a planar surface. Photoresist is applied, dried, photo exposed and developed to leave dots of photoresist on regions which are to be via holes or stud connections e.g., regions A and B in the figure. A blanket layer of aluminum alloy 8 is deposited to a thickness t, and lift-off is performed to expose insulator 6 in the A and B regions. Reactive ion etching (RIE) is used to form the via holes through insulator 6. A refra...