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Photoresist Exposure Dose Measurement and Control Method

IP.com Disclosure Number: IPCOM000108252D
Original Publication Date: 1992-May-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 2 page(s) / 58K

Publishing Venue

IBM

Related People

Babinski, JP: AUTHOR

Abstract

By determining end point of change in level of actinic light reflected from beneath photoresist, proper dose is measured and may be used to avoid over or under exposure. Proper exposure dose is measured by this method regardless of thickness or chemical variations in photoresist coatings or variations in substrate properties from substrate to substrate.

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Photoresist Exposure Dose Measurement and Control Method

       By determining end point of change in level of actinic
light reflected from beneath photoresist, proper dose is measured and
may be used to avoid over or under exposure.  Proper exposure dose is
measured by this method regardless of thickness or chemical
variations in photoresist coatings or variations in substrate
properties from substrate to substrate.

      Referring to the figure, substrate 2, coated with photoresist
layer 4 is exposed to actinic light from fiber optics bundle 8.
Light reflected from the surface and from beneath layer 4 is
collected by fibers in bundle 8 and transmitted to photomultiplier
tube (PMT) 10.  Voltage signal from PMT 10 is presented in output
graph 12 as a function of time.  In actuality, the signal may be sent
to computer 14 for treatment to create good detection of exposure
endpoint at the time of zero change in reflected light intensity and
to provide feedback to stop exposure. Relative input light intensity
may also be sensed by means of partially reflecting mirror 16 and
detector 18.  Output signal from detector 16 may be sent to computer
14 for diagnostic purposes or to provide light source control.

      Since it is the cessation of change in signal detected at PMT
10 that is used and not the absolute value of intensity of reflected
light, the detection of dose endpoint is relatively unaffected by
surface reflectivity of the photoresist or of properties...