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Moisture Detector Device by Appearance Change of Fluorocarbon Films

IP.com Disclosure Number: IPCOM000035279D
Original Publication Date: 1989-Jun-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 1 page(s) / 13K

Publishing Venue

IBM

Related People

Lindstroem, JL: AUTHOR [+3]

Abstract

Disclosed is a moisture detector device which uses the clearly visible change in appearance of a polymeric fluorocarbon film deposited on a silicon substrate upon exposure to moisture in the ambient. The appearance change is caused by loss of adhesion of the film to the substrate which causes it to wrinkle thereby inducing a marked reflectance change. This occurs almost instantly when a certain level of moisture is reached (such as by breathing on the film). This effect can be used as a reliable indicator if the moisture level in the ambient exceeded a certain value during the lifetime of the device.

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Moisture Detector Device by Appearance Change of Fluorocarbon Films

Disclosed is a moisture detector device which uses the clearly visible change in appearance of a polymeric fluorocarbon film deposited on a silicon substrate upon exposure to moisture in the ambient. The appearance change is caused by loss of adhesion of the film to the substrate which causes it to wrinkle thereby inducing a marked reflectance change. This occurs almost instantly when a certain level of moisture is reached (such as by breathing on the film). This effect can be used as a reliable indicator if the moisture level in the ambient exceeded a certain value during the lifetime of the device.

The structure consists of a fluorocarbon film of a thickness in excess of 500 nm on a silicon substrate. The fluorocarbon film consists primarily of fluorine, carbon and hydrogen. The fluorocarbon film is deposited in a 13.56 MHz rf flexible diode plasma etching/deposition system. A pressure of 250 mTorr during deposition, a constant 100 sccm flow of CF4/40%H2 gas, and 200 Watts of rf power. A dc bias of -140 Volts formed on the capacitively coupled electrode. In order to avoid unintentional contamination of the deposited film, a solid Teflon* electrode was used as wafer support. The deposition rate was greater than 10 nm/min. After a deposition of 200 nm of fluorocarbon film, the deposition was stopped for 40 minutes and the system was evacuated (below 10-6 Torr range). Interrupting the deposition of the fluorocarbon film was found to be necessary in order to maintain a smooth fluorocarbon film on silicon. Subsequently, the deposition was continued for another 20 minutes, stopped again for 40 minutes and finally continued for another 20 minutes. This pro...