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Dyed Resist to Enhance Undercut Angles Attainable on Reduction Projection Printers

IP.com Disclosure Number: IPCOM000060444D
Original Publication Date: 1986-Apr-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Barber, JR: AUTHOR [+7]

Abstract

The addition of an absorbing dye to a photoresist in a lift-off process will allow steeper undercut angles in the resulting photoresist pedestal. Steeper undercut angles minimize the possibility of metal bridging during metal deposition. Referring to Fig. 1, photoresist 10 without dye is deposited on substrate 12. When exposed to ultraviolet radiation through mask 14 having transparent area 16, photoresist 10 is exposed in area W. The intensity profile I of the incident radiation is superimposed on the figure to illustrate that the distribution of intensity is not uniform over the area of exposure. As the intensity decreases from the peak at the center of the exposed area, a threshold is reached where the radiation will no longer penetrate the entire thickness of the photoresist layer 10.

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Dyed Resist to Enhance Undercut Angles Attainable on Reduction Projection Printers

The addition of an absorbing dye to a photoresist in a lift-off process will allow steeper undercut angles in the resulting photoresist pedestal. Steeper undercut angles minimize the possibility of metal bridging during metal deposition. Referring to Fig. 1, photoresist 10 without dye is deposited on substrate 12. When exposed to ultraviolet radiation through mask 14 having transparent area 16, photoresist 10 is exposed in area W. The intensity profile I of the incident radiation is superimposed on the figure to illustrate that the distribution of intensity is not uniform over the area of exposure. As the intensity decreases from the peak at the center of the exposed area, a threshold is reached where the radiation will no longer penetrate the entire thickness of the photoresist layer
10. This decrease in the penetration of the radiation causes sloped sidewalls 20 when the photoresist is developed and unexposed portions dissolved, leaving the photoresist pedestal 18. The addition of a radiation-absorbing dye to the photoresist 10 in Fig. 2 will reduce the penetration of the radiation as you move away from the peak intensity, thereby giving a steeper sidewall 22 to the resist pedestal 18.

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