157-nm lithography has gained significant momentum and worldwide support as the post-193 nm technology. Due to higher absorption at shorter wavelength, however, there are several critical issues including materials and reticle handling at 157-nm. These key technical areas are being studied at Intel in collaboration with worldwide industrial and academic partners. In this paper, we will report the progress on 157-nm specific mask technology development.
In this paper, the performance of the focused ion beam repair for a 193 nm DUV reticle is studied via wafer level data. The lithography tool used for wafer exposure is 193 nm Microstepper with NA of 0.6. The resist process used is the top surface imaging resist process. In the study, two different repair tools from different manufacturers were used to perform clear intrusion mask defect repairs. We found that in the case of a clear defect repair, due to the combination of defused carbon and gallium staining near the repair region, the effective mask critical dimension (CD) in that region is larger under the 193 nm exposure as compared to the actual repaired mask CD. As a result, a well controlled edge repair, i.e., the repaired patch lined-up well with a line or a contact edge, actually will induce a CD variation in the resist. For example, in the case of a 0.22 micrometer contact (1x), 6 nm (1x) constant CD reduction in resist throughout a range of focus and exposure dose was observed in a good repair as compared to that of a defect-free same size contact. When the repair patch is recessed slightly from the edge, the CD change is reduced as compared to the perfect edge alignment case. Based on this study, we found that it is preferable to recess the repaired patch slightly from the line edge in the case of clear defect repair.
Phase shifting masks (PSMs) have been shown to increase resolution in optical lithography as low as 0.25 micrometers . However, the production of defect-free PSMs remains a challenge. The increase in resolution decreases not only the maximum allowable chromium defect size, but also introduces phase defects that print at even smaller sizes than regular absorber defects. In addition to repairing smaller defects, PSM repair also has to deal with different new materials, and develop new approaches to defect metrology for transmission and shifter defects. A new focused ion beam (FIB) repair tool has been developed over the last year: the Micrion 8000PSMR. This paper describes the progress during this development with respect to imaging, absorber deposition, absorber removal, and quartz removal. Comparison to currently available laser repair tools is included where appropriate.
Phase shifting masks (PSMs) have proven to increase resolution in optical lithography. However, the production of defect free PSMs still remains a challenge. The increase in resolution not only decreases the maximum allowed chromium defect size, but also introduces phase defects which print at even smaller sizes than conventional defects. This paper will describe typical defects on quartz etched Rim shifting and Attenuated PSMs as well as the minimum requirements for repairing these defects during the process development phase. Finally, possible PSM repair methods using conventional mask repair techniques such as focused ion beam sputtering and laser ablation will be discussed.