Michael Dane Walters

US Patent:

50310178, Jul 9, 1991

Filed:

Jan 29, 1988

Appl. No.:

7/149766

Inventors:

Joseph Pernyeszi - Scotts Valley CA
Michael D. Walters - San Jose CA
Kevin Venor - Ft. Collins CO

Assignee:

Hewlett-Packard Company - Palo Alto CA

International Classification:

H01L 2702

US Classification:

357 41

Abstract:

An opaque shield is provided for integrated circuits and comprises reflective particles of titanium dioxide and light-absorbing particles of carbon black suspended in polyimide. The reflective particles increase the effective path length of light traversing the carrier so that a much lower concentration of carbon black is required to render the shield opaque. The concentration of carbon black can be low enough so that its conductivity does not impair operation of the integrated circuit. In addition to shielding the integrated circuit from light, the shield also protects the integrated circuit from contamination. A fluid precursor material is formed by mixing titanium dioxide and carbon black particles into a polyamic acid solution. This solution is diluted, filtered and vacuum distilled to yield a suspension free of over-sized particles. The resulting suspension can be applied and patterned using conventional semiconductor processing techniques.