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Luminescence Measurement of Photoresist Thickness

IP.com Disclosure Number: IPCOM000062486D
Original Publication Date: 1986-Nov-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Batchelder, JS: AUTHOR

Abstract

Photoresist luminescence can be used to measure resist thickness on rough substrates like glass-epoxy and ceramic. Low power light pulse excitation can either induce the photoresist itself or a luminescent dye dissolved in the photoresist to emit light proportional to the photoresist thickness. The required light intensities would be well below those intensities required for photoresist exposure. Organic materials luminesce (emit fluorescence or phosphorescence) when excited by utlraviolet light. For low levels of excitation, the amount of luminescence is proportional to the amount of ultraviolet light absorbed.

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Luminescence Measurement of Photoresist Thickness

Photoresist luminescence can be used to measure resist thickness on rough substrates like glass-epoxy and ceramic. Low power light pulse excitation can either induce the photoresist itself or a luminescent dye dissolved in the photoresist to emit light proportional to the photoresist thickness. The required light intensities would be well below those intensities required for photoresist exposure. Organic materials luminesce (emit fluorescence or phosphorescence) when excited by utlraviolet light. For low levels of excitation, the amount of luminescence is proportional to the amount of ultraviolet light absorbed. By causing the photoresist layer to absorb ultraviolet light at a rate small enough such that the absorption of the entire film can be taken to be linear in thickness, the amount of luminescence will then be proportional to the film thickness. Optionally, a very dilute concentration of an organic laser dye can be added to the photoresist to affect ultraviolet absorption. The figure shows one possible embodiment of the optical layout for using this method. The output from a low power mercury lamp 1 is focussed by an elliptical mirror 2 onto a tuning fork chopper 3. The chopped excitation is then collimated and filtered by lenses 4 to only pass 435 nm light. This beam is then reflected off of a dichroic beam splitter 5 and focussed by a lens 7 onto the sample 6. The emission from the sample 6 then passes thr...