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Recessed Oxide Isolation Process

IP.com Disclosure Number: IPCOM000088426D
Original Publication Date: 1977-Jun-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Abbas, SA: AUTHOR

Abstract

This method for obtaining substantially vertical blocks of recessed silicon dioxide isolation is as follows: 1. Etch a hole 8 in silicon substrate 10 using reactive ion etch with silicon dioxide as a mask. It is preferred that the hole have sharp vertical walls, as shown in Fig. 1. The silicon dioxide mask can be stripped or left in place. 2. Oxidize the wafer to grow thermal silicon dioxide 12 in the range of 500 Angstrom. 3. Deposit by chemical vapor deposition (CVD) silicon nitride 14 in the range of 500 Angstrom to produce the structure of Fig. 2. 4. Evaporate polysilicon layer 16 to a thickness of about half the depth of the hole-to produce the structure of Fig. 3. Dip etch lightly if there is any polysilicon sticking to the sides of the hole in the upper half. 5.

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Recessed Oxide Isolation Process

This method for obtaining substantially vertical blocks of recessed silicon dioxide isolation is as follows: 1. Etch a hole 8 in silicon substrate 10 using reactive ion etch with silicon dioxide as a mask. It is preferred that the hole have sharp vertical walls, as shown in Fig. 1. The silicon dioxide mask can be stripped or left in place. 2. Oxidize the wafer to grow thermal silicon dioxide 12 in the range of 500 Angstrom. 3. Deposit by chemical vapor deposition (CVD) silicon nitride 14 in the range of 500 Angstrom to produce the structure of Fig. 2. 4. Evaporate polysilicon layer 16 to a thickness of about half the depth of the hole- to produce the structure of Fig. 3. Dip etch lightly if there is any polysilicon sticking to the sides of the hole in the upper half. 5. Apply photoresist and use a blockout mask slightly larger than the mask in Step 1, and etch polysilicon. Over- etch to remove the polysilicon on the top surface to produce the structure of Fig.4. In actual practice one can visually observe the polysilicon removed. Polysilicon in the hole is protected by photoresist. An alternative to photoresist is to use a thin thermal silicon dioxide on top of the polysilicon as a mask. Strip the photoresist or silicon dioxide. 6. Oxidize the polysilicon in the hole until it is planar with the surface of the wafer with the the silicon dioxide region 18, as shown in Fig. 5. The The only material to be oxidized is the polysilicon....