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Method to Reduce Bird's Beak Formation in Recessed Oxide Isolation Using Polysilicon

IP.com Disclosure Number: IPCOM000041706D
Original Publication Date: 1984-Mar-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 42K

Publishing Venue

IBM

Related People

Cahng, HJ: AUTHOR [+2]

Abstract

Conventional recessed oxide isolation techniques create a "bird's beak" formation, as discussed in U.S. 3,900,350 and 3,970,486. The following semiconductor process minimizes the formation of this "bird's beak" region in the fabrication of a recessed oxide isolation. Fig. 1 shows the first stage in the process where a silicon semiconductor substrate 2 has formed on its surface a layer of silicon dioxide 4 and a layer of silicon nitride 6 which will serve as a mask on the substrate 2 for the formation of the pad region where the recessed oxide will be grown. In this process step, the silicon dioxide layer 4 should be etched to minimize undercutting so that the subsequent deposition of a layer of polycrystalline silicon will conform to the etched edge of the layers 4 and 6. Fig.

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Method to Reduce Bird's Beak Formation in Recessed Oxide Isolation Using Polysilicon

Conventional recessed oxide isolation techniques create a "bird's beak" formation, as discussed in U.S. 3,900,350 and 3,970,486. The following semiconductor process minimizes the formation of this "bird's beak" region in the fabrication of a recessed oxide isolation. Fig. 1 shows the first stage in the process where a silicon semiconductor substrate 2 has formed on its surface a layer of silicon dioxide 4 and a layer of silicon nitride 6 which will serve as a mask on the substrate 2 for the formation of the pad region where the recessed oxide will be grown. In this process step, the silicon dioxide layer 4 should be etched to minimize undercutting so that the subsequent deposition of a layer of polycrystalline silicon will conform to the etched edge of the layers 4 and 6. Fig. 2 illustrates the next stage in the semiconductor process wherein a layer of polycrystalline silicon 10 is deposited conformly on the exposed surfaces of the semiconductor substrate 2 through the etched window 8 and over the layer of silicon nitride 6 and the portion of the silicon dioxide layer 4 exposed as the sidewall of the window 8. This can be performed by a chemical vapor deposition technique. The thickness of the polycrystalline silicon layer 10 can be varied depending upon the thickness of the oxide layer 4 and nitride layer 6 and the desired thickness of the recessed oxide to be grown in the window area 8, and also the length of the "bird's beak" region required. Fig. 3 illustrates the next stage in the semiconductor process wherein the polycrystalline silicon layer 10 is etched using a directional etching technique, such as reactive ion etching, so that the upper surface of the silicon nitride layer 6 is exposed again and the polycrystalline silicon regions 1...