Browse Prior Art Database

Critical Dimension and Profile Control of Photoresist Images

IP.com Disclosure Number: IPCOM000062030D
Original Publication Date: 1986-Oct-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Knight, S: AUTHOR [+2]

Abstract

By interrupting the development process, the "induction period" (time before any removal of unexposed photoresist is observed) is utilized more than once to allow complete removal of the exposed photoresist before any significant amount of unexposed photoresist is removed. This procedure preserves size of small exposed regions in areas of thin photoresist while small exposed regions in thick photoresist areas are completely cleaned out. The procedure also results in steeper hole walls in the developed photoresist. Spin-applied, solvent-cast photoresist tends to planarize over the topography of integrated circuits. As a result, thickness of the cured photoresist can vary by a factor of two in different areas of a wafer.

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Critical Dimension and Profile Control of Photoresist Images

By interrupting the development process, the "induction period" (time before any removal of unexposed photoresist is observed) is utilized more than once to allow complete removal of the exposed photoresist before any significant amount of unexposed photoresist is removed. This procedure preserves size of small exposed regions in areas of thin photoresist while small exposed regions in thick photoresist areas are completely cleaned out. The procedure also results in steeper hole walls in the developed photoresist. Spin-applied, solvent-cast photoresist tends to planarize over the topography of integrated circuits. As a result, thickness of the cured photoresist can vary by a factor of two in different areas of a wafer. An opening at the bottom of a small hole in thin photoresist regions will become larger than mask dimensions when similar hole sizes must be completely opened in thick resist regions. This enlargement occurs because, after an induction period, unexposed photoresist is dissolved by the developer. The figure is a plot of photoresist development time T versus the thickness t of photoresist remaining. Increasing time is to the right on the horizontal axis, and decreasing thickness is downward on the vertical axis. Removal by development to zero thickness of a first, thin photoresist region is found at horizontal line E.P.1 (end point 1). Removal by development to zero thickness of a second photoresist region, having twice the thickness of the first photoresist region, is found at the horizontal axis of the plot E.P.2 (end point 2). Curve 2 indicates thickness of exposed photoresist remaining as a function of development time. Curve 4 indicates thickness of unexposed photoresist remaining as a function of uninterrupted development tim...