Browse Prior Art Database

Bubble Burst Etching

IP.com Disclosure Number: IPCOM000086562D
Original Publication Date: 1976-Sep-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Hutchins, GL: AUTHOR

Abstract

There are several problems associated with constant gas bubble agitation in etching tanks which cause poor control and uniformity in etching. When a large sample is etched, uniformity must be provided over that area to achieve desired results. Referring to the figure, if the bubble generator 11 (i.e., a box with one side having an array 14 of holes 16 through which N(2) is passed to generate bubbles) is powered by a constant flow of gas 15, the bubbles 12 generated do not come out of array 14 uniformly. Their flow pattern shifts due to inconsistencies in array 14 or liquid (etchant) filling some of the holes 16. Since resistance to gas flow is higher in holes 16, the gas prefers to go through holes 16 through which flow is occurring in another area of array 14.

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Bubble Burst Etching

There are several problems associated with constant gas bubble agitation in etching tanks which cause poor control and uniformity in etching. When a large sample is etched, uniformity must be provided over that area to achieve desired results. Referring to the figure, if the bubble generator 11 (i.e., a box with one side having an array 14 of holes 16 through which N(2) is passed to generate bubbles) is powered by a constant flow of gas 15, the bubbles 12 generated do not come out of array 14 uniformly. Their flow pattern shifts due to inconsistencies in array 14 or liquid (etchant) filling some of the holes 16. Since resistance to gas flow is higher in holes 16, the gas prefers to go through holes 16 through which flow is occurring in another area of array 14.

The bubble burst etcher, however, uses pulsating gas flows to power generator 11. There is a pressure drop associated with each pulse, and this pressure is adjusted to overcome resistance in holes 16 due to etching filling them between pulses. In fact, liquid filling holes between pulses helps to increase the initial pressure drop in the generator.

With the bubble burst etching one can provide agitation at the sample 21 so that a period of "dead" time occurs at the sample surface 20 when no bubbles remain there. This promotes uniformity because no bubbles 12 are hanging on the surface 20 to retard etching. Another feature of this "dead" time is that the etch rate without agitation is m...