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Improved Isolation Process for Cmos Technology

IP.com Disclosure Number: IPCOM000044095D
Original Publication Date: 1984-Nov-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 2 page(s) / 52K

Publishing Venue

IBM

Related People

Mohler, RL: AUTHOR [+2]

Abstract

The need to improve circuit density mandates the use of a field oxidation process capable of yielding a shorter "bird's beak" than existing semi-recessed oxide (SROX) processes. However, any process which relies on an oxidation masking material not capable of withstanding the physical and chemical environment of n-well drive-in processes could not be implemented without giving up the dual self-aligned field tailor implant feature. This article describes a process which not only provides much less bird's beak than current SROX processes but significantly reduces boron depletion in the field regions and boron encroachment in the device regions. Following initial preparation of the substrate 11 and epitaxy 12, a pad oxide film 13 of approximately 50 nm thickness is grown.

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Improved Isolation Process for Cmos Technology

The need to improve circuit density mandates the use of a field oxidation process capable of yielding a shorter "bird's beak" than existing semi-recessed oxide (SROX) processes. However, any process which relies on an oxidation masking material not capable of withstanding the physical and chemical environment of n-well drive-in processes could not be implemented without giving up the dual self-aligned field tailor implant feature. This article describes a process which not only provides much less bird's beak than current SROX processes but significantly reduces boron depletion in the field regions and boron encroachment in the device regions. Following initial preparation of the substrate 11 and epitaxy 12, a pad oxide film 13 of approximately 50 nm thickness is grown. Photoresist 14 is applied and patterned in a lift-off profile; the resist pattern 14 is used as an implant mask for the n-well implant 15, and then as a lift- off mask for an evaporation of approximately 300 - 400 nm Si 16, resulting in the structure shown in Fig. 1. The photoresist 14 is lifted off, and the n-well 15 drive- in process is performed. Then, photoresist 17 is applied and patterned in a lift-off profile such that windows 18 are created where field oxidation is to be prevented, resulting in the structure shown in Fig. 2. Selective directional etching is used to open windows 18 in the evaporated Si 16 over the n-well regions 15. Then, MgO 19...