A DIAZOQUINONE POSITIVE PHOTORESIST FOR X-RAY-LITHOGRAPHY

Diazoquinone photoresists are very reliable materials for photolithogr aphy. They have been used extensively by the electronic industry becau se of their reliability, stability, and ease of operation; and a large body of information has been gathered regarding their application and use. Therefore, it would be natural to extend their use to the field of x-ray lithography. Unfortunately, the response of these resists to x-ray radiation is poor, and requires 1.2 J/cm(2). Such a dose is too high for practical applications. Amplified resists have been used succ essfully in x-ray lithography, but this came with the usual environmen tal sensitivity of the amplified resists. Here we report the modificat ion of diazoquinone resists for x-ray lithography, This was accomplish ed by substituting hydrogen atoms in the photoactive compound (PAC) by iodine. The attachment was carried out in two ways. In the first appr oach, we used iodine containing moieties to bridge several conventiona l diazonaphthoquinone sulfonates. Some of these bridging groups contai ned one iodine atom, while others contained more. We were able to dete rmine the relationship between the number of iodine atoms in the PAC t o the x-ray lithography sensitivity. The second approach was to synthe size a new diazonaphthoquinone where one of the hydrogen atoms on the naphthalene ring was substituted with an iodine atom. This modificatio n enabled us to understand the importance of the proximity effect of t he iodine to the diazoquinone group. It was found that placing one iod ine atom next to the diazoquinone group produces an improvement that i s equivalent to placing three iodine atoms on the bridge. The describe d modifications lead to considerable improvement in the sensitivity of the resist. This article describes the synthetic methods employed and the corresponding lithographic results. (C) 1995 American Vacuum Soci ety.