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Isolated Resistor Having Doped Polysilicon Contacts and Method for Manufacture

IP.com Disclosure Number: IPCOM000050837D
Original Publication Date: 1982-Dec-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 61K

Publishing Venue

IBM

Related People

Barson, F: AUTHOR [+4]

Abstract

Semiconductor resistors may be isolated, in one form, by ion implanting a substrate with an appropriate impurity, within a ring of isolating material, typically silicon dioxide. One technique for forming an isolating ring is known as deep dielectric isolation (DDI), described, for example, in U.S. Patent 4,256,514.

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Isolated Resistor Having Doped Polysilicon Contacts and Method for Manufacture

Semiconductor resistors may be isolated, in one form, by ion implanting a substrate with an appropriate impurity, within a ring of isolating material, typically silicon dioxide. One technique for forming an isolating ring is known as deep dielectric isolation (DDI), described, for example, in U.S. Patent 4,256,514.

Some non-planarity may exist across the surface of the substrate after forming the DDI regions. In some instances, isolation 20 may project as much as 5,000 A or so above or below the semiconductor surface 21 (Fig. 1). When a doped polysilicon conductor 23 is formed across the resistor region and reactive ion etched (RIE) to form a contact 25, some unwanted polysilicon 27 may remain. In effect, the RIE process causes a polysilicon to be formed along the isolation as a sidewall enclosing the resistor. The sidewall may cause the resistor to be shunted between contacts, as well as provide unwanted dopant at the resistor edges. It is desirable to eliminate the unwanted sidewalls while providing protection for the remainder of the resistor.

In Fig. 2, a transistor region 10 and a resistor region 12 are formed in an N+ layer 16 and an N layer 14 epitaxially formed on a substrate 18. Isolation regions 22 and 24 are formed in the transistor region 10, and isolation region 26 is formed in the resistor region by the processes described in U.S. Patent 4,256,514. The region 30 between the isolation regions 26 is implanted with a suitable dopant to form a P-type resist...