Optical resists have been optimized for e-beam direct writing in order to enhance process compatibility. Drawbacks of optical positive resist (such as AZ-2400) for e-beam application are the following: (1) It is readily converted to a negative image when exposed to the high doses required for fiducial mask detection (multiple scans over a localized region), and (2) this negatively converted region is difficult to remove. The ratio Dg**i/Dp is proposed as a measure of rating positive resists for ease of conversion. As this ratio becomes larger, the likelihood of forming a negative image in the resist becomes smaller. The values for AZ-2400 and RE-5000p were 15 and 40, respectively. Conversion mechanisms were examined and two important factors were found: (1) The sensitizer contribution to negative image conversion was small, and (2) methylene group density in novolak was a dominant factor. Considering the above factors, a new positive novolak e-beam resist PER-1 has been developed with a Dg**i/Dp ratio of 285. Quarter-micron patterns are easily delineated in PER-1 with a variable-shaped e-beam system.
|Number of pages||4|
|Journal||Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures|
|Publication status||Published - 1986 Jan|
ASJC Scopus subject areas
- Condensed Matter Physics
- Electrical and Electronic Engineering