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Method for Planarizing Over Shallow Trenches Filled With Silicon Dioxide

IP.com Disclosure Number: IPCOM000099694D
Original Publication Date: 1990-Feb-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Bakeman, PE, Jr: AUTHOR [+3]

Abstract

By proper selection of processes and materials for filling planarizing, and etch stopping, superior planarization is achieved.

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Method for Planarizing Over Shallow Trenches Filled With Silicon Dioxide

       By proper selection of processes and materials for
filling planarizing, and etch stopping, superior planarization is
achieved.

      Referring to Fig. 1, a topology comprised of etched depressions
(trenches) in silicon substrate 10 and unetched regions having cap
silicon nitride (Si3N4) 12 is formed in a conventional process.
Then, conformal silicon dioxide (SiO2) 14 is deposited.  Thin
polysilicon 16 is conformally deposited next.  Conformal SiO2 18 is
deposited to complete the cross section shown in Fig. 1.

      Referring to Fig. 2, large trenched areas are protected by
photoresist and SiO2 18 is etched away from all other areas.
Photoresist is then stripped and conformal polysilicon 20 is
deposited and planarized to the level of the top of SiO2 18.
Polysilicon is removed rapidly while SiO2 is removed very slowly in a
chemical, mechanical polishing planarization process.  Thus, SiO2 18
becomes an effective planarization stop when regions of polysilicon
on the exposed surface become very small.

      Further planarization down to the level of the top surface of
nitride 12, as shown in Fig. 3, is achieved by using a reactive ion
etching process which etches polysilicon and SiO2 at about the same
rate.