Method of making an improved field oxide isolation structure for

Details Method of making an improved field oxide isolation structure for Method of making an improved field oxide isolation structure for

1997-06-30

2000-04-25

Bowers, Charles

Semiconductor device manufacturing: process

Formation of electrically isolated lateral semiconductive...

Recessed oxide by localized oxidation

438297, 438452, 438225, 257395, H01L 2176

Patent

active

06054368&

ABSTRACT:
A method and structure for forming a modified field oxide region having increased field oxide threshold voltages (V.sub.th) and/or reduced leakage currents between adjacent device areas is achieved. The method involves forming a field oxide using the conventional local oxidation of silicon (LOCOS) using a patterned silicon nitride layer as a barrier to oxidation. After forming the LOCOS field oxide by thermal oxidation and removing the silicon nitride, a conformal insulating layer composed of silicon oxide is deposited and anisotropically etched back to form sidewall insulating portions over the bird's beak on the edge of the LOCOS field oxide, thereby forming a new modified field oxide. P-channel implants are formed in the device areas. Then a second implant is used to implant through the modified field oxide to provide channel-stop regions with modified profiles that increase the field oxide V.sub.th and/or reduce leakage current between device areas. This improved field oxide/channel-stop structure is particularly useful for reducing the leakage current on DRAM cells thereby increasing the refresh cycle times.

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