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Coating Narrow Resistive Lines to Increase Electromigration Resistance

IP.com Disclosure Number: IPCOM000083192D
Original Publication Date: 1975-Apr-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

Berenbaum, L: AUTHOR

Abstract

Fig. 1 shows a typical cross section of an in-process wafer, wherein a well-known photoresist lift-off technique is utilized to produce thin resistive lines or stripes which are coated with suitable coating materials, such as Cr, Ti, or Ni, to reduce electromigration. With the lift-off process, a photoresist layer is spun onto a wafer, exposed by an electron beam, and developed so that shallow trenches exist.

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Coating Narrow Resistive Lines to Increase Electromigration Resistance

Fig. 1 shows a typical cross section of an in-process wafer, wherein a well- known photoresist lift-off technique is utilized to produce thin resistive lines or stripes which are coated with suitable coating materials, such as Cr, Ti, or Ni, to reduce electromigration. With the lift-off process, a photoresist layer is spun onto a wafer, exposed by an electron beam, and developed so that shallow trenches exist.

The conductive material is then deposited in the trenches, a coating material is applied and the photoresist is subsequently removed to expose the coated stripes. A disadvantage of the technique is that the coatings are generally applied only to the top surface of the stripe, leaving the edges of the stripe exposed.

Fig. 2 shows a similar cross section of an in-process wafer, wherein an improved technique is utilized to produce fully coated stripes. In the technique of Fig. 2, the photoresist layer is spun on the wafer and exposed in the usual fashion. After the metal is deposited in the trenches, a process step is applied to cause the photoresist to shrink. This can be accomplished by application of heat, chemicals or by electron bombardment of the photoresist along the stripes.

The shrinkage causes the trench to open slightly wider to expose the base of the conductive stripe. Since the edges of the stripe are sloped, the subsequently deposited coating film covers the entire striped sur...