New 193-nm resist resolution to 60 nm without phase shift

06/01/1998

New 193-nm resist,resolution to 60 nm without phase shift

A research group at Hyundai Electronics Industries (HEI) in South Korea has demonstrated the ability to print 60 nm (0.06-?m) isolated lines using a new single-layer 193-nm photoresist and traditional (nonphase shift) masks. The resist has shown good etch resistance and adhesion, and Hyundai officials say it should be usable for 0.13-?m processes.

Data on the advance was presented at the SPIE Symposium on Microlithography in Santa Clara, CA, but it received little attention at the time, in part because of the strong publicity generated by a group at the University of Texas that printed 80-nm features using a DuPont Photomasks phase shift mask. In both cases, the extremely narrow lines had a good deal of space on either side - 160 nm in the University of Texas work, and 180 nm in the Hyundai work. For 1:1 line-and-space patterns, which are more indicative of real-world conditions, the Hyundai group reported 120-nm capability, and the Texas group 140 nm.

Taken together, the two groups` work suggests that the extendibility of 193-nm lithography will not be limited by resist chemistries.

The HEI resist is based on a maleic anhydride alternating copolymer chemistry, with enhancements including an adhesion enhancer. The Texas group, as well as researchers at Hitachi, are pursuing a cyclic olefin polymer formula.

At the geometries involved, the resist patterns can have very high aspect ratios, and show a tendency to separate from the substrate. A key aspect of making 193-nm resists production-ready will be improving etch resistance - this will allow the use of thinner resist layers, thus reducing the aspect ratio. The Hyundai formula is said to have etch resistance similar to novolac-based products. Depth of focus was 0.4-?m; this was achieved at 140-nm lines and spaces with conventional illumination, and at 120 nm with off-axis quadrapole illumination.

Ki-Ho Baik, manager of HEI`s lithography group, said the material "should be applicable to 130-nm processes," and added that resolution, depth of focus, and sensitivity are no longer concerns. He added that HEI "has been putting a lot of effort into commercializing the resist through resists makers, so that it can be on hand in volume before full-field 193-nm scanners come in." - C.L.