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Etching of Vertical Walled Patterns in (100) Silicon

IP.com Disclosure Number: IPCOM000076753D
Original Publication Date: 1972-Apr-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 24K

Publishing Venue

IBM

Related People

Schwuttke, GH: AUTHOR [+2]

Abstract

The fabrication of dielectrically isolated structures in silicon, such as "Beam Lead", Double Poly, and others requires the etching of grooves in the form of patterns into the silicon wafer. Grooves etched chemically into silicon surfaces have either sloped sides or round sides, as illustrated by Fig. 1. This type of processing may also lead to undercutting of the mask, as shown at a/2. The difficulties in producing vertically-walled grooves limit the component density achievable in an array. The fabrication of vertical-walled patterns in a silicon wafer of (100) or any other orientation is, therefore, desirable.

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Etching of Vertical Walled Patterns in (100) Silicon

The fabrication of dielectrically isolated structures in silicon, such as "Beam Lead", Double Poly, and others requires the etching of grooves in the form of patterns into the silicon wafer. Grooves etched chemically into silicon surfaces have either sloped sides or round sides, as illustrated by Fig. 1. This type of processing may also lead to undercutting of the mask, as shown at a/2. The difficulties in producing vertically-walled grooves limit the component density achievable in an array. The fabrication of vertical-walled patterns in a silicon wafer of (100) or any other orientation is, therefore, desirable.

Vertical-wall etching illustrated by Fig. 2 is achieved through silicon ion bombardment. High-energy Si+ bombardment of silicon converts the silicon into amorphous silicon soluble in HF. Vertical walled grooves are made as follows:

1) The desired mask is placed on the wafer surface and subsequently the slice is bombarded with high energy Si+ ions. The penetration (depth of groove) is determined by the ion energy. Typical values of ion penetration are approximately 1.5 m for 1 MeV.

2) After bombardment, the slice is placed in HF and the groove is rapidly etched out.

This etching technique is independent of crystal orientation, therefore, vertical walls can be etched on (100) or any other surface.

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