Browse Prior Art Database

Cell for Porous Silicon Applications

IP.com Disclosure Number: IPCOM000083555D
Original Publication Date: 1975-Jun-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 3 page(s) / 46K

Publishing Venue

IBM

Related People

DeRobertis, IJ: AUTHOR [+2]

Abstract

This cell is designed to optimize the formation of porous silicon by a process which anodically etches appropriate silicon regions in an electrolyte of HF and DI H(2)O. These porous regions are subsequently oxidized at low temperatures and short times to form dielectric isolation.

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Cell for Porous Silicon Applications

This cell is designed to optimize the formation of porous silicon by a process which anodically etches appropriate silicon regions in an electrolyte of HF and DI H(2)O. These porous regions are subsequently oxidized at low temperatures and short times to form dielectric isolation.

The cell produces a uniform porous layer on high-resistivity silicon wafers, removes reaction bubbles, eliminates electrolyte contamination by automatic fill and drain operations, eliminates ambient light and gives constant temperature control.

The bottom housing 1 is made of TEFLON* material having a vacuum port 3 and an electrical terminating screw 4 tied directly to a stainless steel vacuum chuck 2, which is pressed concentrically into housing 1.

Vacuum chuck 2 has three concentric rings and four slots 90 degrees apart for positive contact of the wafer to the vacuum chuck surface. It also has a vacuum port in line with vacuum port 3.

Upper housing 5 is made of TEFLON material having an integral groove 6, terminating to a drain port 8, an O-ring 7 to seal bottom housing 1 from upper housing 5. An input/output platinum tubing 9 has a brazed platinum wire, not shown, terminating at connection 10 for electrical purposes.

A cover 11 prevents ambient light from reaching the wafer surface.

A monostat pump 12 includes a regulated controlled flow rate switch and gage. The pump 12 produces a clockwise or counterclockwise selective rotation fluid flow.

A three way solenoid valve 13 is normally open. A container 14 having two nipples holds the electrolytic solution consisting of electronic hydrofluoric acid (HF) and deionized water (DI H(2)O). One nipple is for input/output of the electrolyte, and the other for electrolyte drain. The liquid circulation system further includes a container 15 with one nipple for waste, a `T' fitting 16, a normally closed two-way solenoid valve 17, a container 18 for holding H 0 gravity feed, and tubing 19 for transfer of liquids. Spring loaded clamps 20 seal bottom housing 1 to upper housing 5.

The operation of the cell is as follows: 1) Release the two clamps 20 and remove the upper housing 5 from the bottom housing 1. 2) Place a 2.250'...