Browse Prior Art Database

ROI Isolation Process to Minimize Bird's Beak

IP.com Disclosure Number: IPCOM000045080D
Original Publication Date: 1983-Jan-01
Included in the Prior Art Database: 2005-Feb-06
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Barson, F: AUTHOR

Abstract

The growth of bird's beak during selective recessed oxide isolation (ROI), oxidation is particularly troublesome in small, high speed devices, since the structure wastes significant lateral space and does not permit minimum device size.

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ROI Isolation Process to Minimize Bird's Beak

The growth of bird's beak during selective recessed oxide isolation (ROI), oxidation is particularly troublesome in small, high speed devices, since the structure wastes significant lateral space and does not permit minimum device size.

The problem may be improved by using a conventional SIO(2)/Si(3)N(4) mask for selective oxidation but with a subsequent reactive ion etch (RIE) etch- back to remove most of the bird's beak after its formation. By adjusting the RIE conditions properly, with a 2:1 etch rate ratio of SiO(2) :Si, a substantially planar silicon surface can be obtained adjacent to the residual bird's beak while greatly reducing the lateral extent of the bird's beak itself.

A conventional recessed oxide isolation is produced as usual by masking with SiO(2)/Si(3)N(4) layers 12, 14, etching out some silicon, and growing a thick ROI isolation oxide thermally. However, the amount of silicon removed prior to oxidation is less than that required for a full R0I process, so that the silicon dioxide surface 16 is slightly higher than the adjacent surface, as shown in Fig. 1. The bird's beak is shown with the angles alpha and beta from the initial silicon surface level 19.

The silicon nitride layer 14 is etched off in hot H(3)PO(4), and the structure Is subjected to RIE at conditions which give a relative etch rate of SiO(2):Si approximately equal to 2:1, as shown by the original surface in dashed line and the final su...