Browse Prior Art Database

Control of Edge Shape of Photoresist Images

IP.com Disclosure Number: IPCOM000109166D
Original Publication Date: 1992-Aug-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Cronin, JE: AUTHOR [+2]

Abstract

Focus of projection exposure systems is varied during exposure of photoresist to control edge shape of developed images. The technique may be applied as a continuously varied focal plane or, to provide more independent control over image shape and exposure dose, as a stepped focus and controlled exposure time at each step. An example of an application in which the technique provides benefit is in control of via hole edge taper.

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Control of Edge Shape of Photoresist Images

       Focus of projection exposure systems is varied during
exposure of photoresist to control edge shape of developed images.
The technique may be applied as a continuously varied focal plane or,
to provide more independent control over image shape and exposure
dose, as a stepped focus and controlled exposure time at each step.
An example of an application in which the technique provides benefit
is in control of via hole edge taper.

      Referring to Fig. 1, positive photoresist 2 on substrate 4 is
exposed in region A to an image focused to provide a minimum image
size in resist 2.  The projected image is then refocused and an
exposure is made to result in a slightly larger exposed image in
photoresist 2.  This process is repeated a number of times to provide
steps of increasing image size of exposed photoresist as shown.  This
process of step and expose is automated to provide repeatable
results.  After development and heat treatment of the resist, an edge
contour similar to that shown in Fig. 2 can be reproducibly formed by
this process.

      The technique may be employed on other than positive
photoresist to obtain different edge contour effects, e.g., edges
suitable for use in lift-off processing.