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Striation Free Resist Coating Process

IP.com Disclosure Number: IPCOM000083701D
Original Publication Date: 1975-Jul-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Mondou, ER: AUTHOR [+2]

Abstract

Resists are spin coated to yield striation-free coatings so that, when low-energy exposures require extended development times, small dimension image geometries are not distorted.

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Striation Free Resist Coating Process

Resists are spin coated to yield striation-free coatings so that, when low- energy exposures require extended development times, small dimension image geometries are not distorted.

Equilibrium spin times are determined for resist formulations, which comprise a phenol-formaldehyde novolac or resole resin and a diazo ketone sensitizer contained in an organic solvent. The equilibrium spin time is the point at a particular spin speed, where a longer spin time does not change the thickness of the coated resist layer.

The figure is a graph of resist thickness versus spin time for the resist, showing an equilibrium time in the range of 8 to 10 seconds. Spin times below the equilibrium point gives striation-free coatings.

The shorter the spin time, the longer the development time can be before striations can be detected. Spin speed of the resist solution can be altered to yield the required resist film thickness. For example, a dilute resist solution spun at a spin speed of 2,400 RPM for one half a second will produce a 1.2 micron thick film that can be force developed for extended periods of time, without producing significant striations. The coatings which are spun for short times are in effect not spun dry and are in a semifluid state.

The coated substrates are kept in a horizontal position when removed from the spinner and transferred to a prebaking step. Solvent removal is then completed in the normal time. The striations which...