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DEEP TRENCH SUBSTRATE CONTACTS SELF-ALIGNED TO TRENCH ISOLATION

IP.com Disclosure Number: IPCOM000006170D
Original Publication Date: 1991-Jul-01
Included in the Prior Art Database: 2001-Dec-11
Document File: 2 page(s) / 65K

Publishing Venue

Motorola

Related People

Kent J. Cooper: AUTHOR [+5]

Abstract

Advanced Bipolar devices use trench isolation to increase both circuit density and device performance. In addition, some advanced Bipolar designs also require trench substrate contacts. Previously, the silicon trenches for device isolation and substrate contacts were fabricated with two separate etch steps. Using the following process, both isolation and substrate contact trenches are fabricated with a single etch step.

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MO7WROLA INC. Technical Developments Volume 13 July 1991

DEEP TRENCH SUBSTRATE CONTACTS SELF-ALIGNED TO TRENCH ISOLATION

by Kent J. Cooper, Bich-Yen Nguyen, Wayne Ray, Scott Roth and Barbara Vasquez

  Advanced Bipolar devices use trench isolation to increase both circuit density and device performance. In addition, some advanced Bipolar designs also require trench substrate contacts. Previously, the silicon trenches for device isolation and substrate contacts were fabricated with two separate etch steps. Using the following process, both isolation and substrate contact trenches are fabricated with a single etch step.

  Trenches are etched using an appropriate hard mask and an oxide liner is then grown on the exposed silicon surface of each trench. Polysilicon is then

deposited and etched back selectively to the trench hard mask, in order to planar& the trenches (Figure
1). Photoresist is then patterned such that only the isolation trenches are covered. The exposed poly- silicon in the contact trenches is then selectively removed with respect to the hard mask, photoresist, and the trench oxide liner. The oxide liner in the bottom of the contact trenches is then removed with an anisotropic oxide etch (Figure 2). After the photoresist mask is removed, polysilicon is deposited and etched back to form a planar trench to substrate contact, which is self-aligned with respect to the trench isolation (Figure 3).

FlGURF t

-

HARD MASK

POLYSILICON w OXIDE LINER

ISOLATION SUB...