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Because of CD linearity requirements, proximity effect correction (PEC) will be mandatory for most critical layers when e-beam maskmaking is used. For the MEBES 5000 system, the method chosen for PEC is the GHOST"2'3 PEC algorithm.ABSTRACT Advanced reticle specifications for resolution, critical dimension (CD) control and CD linearity of 1 80-nm generation devices require large-scale improvements to maskmaking processes. The -200 nm of bias required with widely used wet etch processes will not meet these specifications. A solution to the high bias requirement of wet etch processing is to implement a plasma or dry etch process. Plasma etch processing has been shown to have little or no undercutting. However, some of the standard resists used with electron beam (e-beam) exposure of photomasks have poor dry etch characteristics. ZEP 7000 is an e-beam resist that has good dry etch resistance while exhibiting superior lithographic quality. In this paper, processes using ZEP 7000 resist and inductively coupled plasma (ICP) etching are described. The combination of these operations can result in zero bias or near zero bias process with e-beam exposure of photomasks.While the required dose for ZEP 7000 is higher than that of PBS, the higher beam current capability of newer e-beam systems, together with multipass writing strategies, enables the use of these slower resists without throughput penalty. Optimization of the development process was done using a two-component solvent developer. A puddle process was investigated for optimizing sensitivity, edge slope, resist loss, mean-to-target control, and CD uniformity. Dry etching with ICP has been shown to etch chromium films with good selectivity to the resist, give a highly anisotropic etch, and, most significantly, show insensitivity to loading effects. The net result of this effort is the development of a process that gives excellent CD control when meeting MEBES 5000 system requirements for 1 80-nm maskmaking. Data on resolution, CD control, and defects are presented using this process.

As photomask minimum feature size requirements continue to shrink, resist resolution limitations and their tradeoffs with exposure dose are critical factors. Recently, nearly every node needs a new electron beam resist, customized for exposure dose requirements while simultaneously meeting resolution specifications. Intel Mask Operations has an active program focused on screening new electron beam resists and processes. We discuss the performance metrics we use to evaluate materials and discuss the relative capabilities of the latest resists. We present fundamental resist metrics (resolution, LER and dose) as well as manufacturing process sensitivities.

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Previous papers have examined the use of ZEP 7000 resist with dry etch and the compatibility of this process with advanced MEBES writing tools.1'23 This paper details further advances made to this process and the improvements in critical dimension (CD) control that can be made by fine-tuning the process. This paper describes how isofocal dose is found experimentally and how a process is established using that dose. The advantage of running a process at or near isofocal4'5 is that it provides minimum CD variation. One disadvantage of running at isofocal is that data bias is usually required. With a higher dose than 8 iC/cm2, a new developer solvent from Nippon Zeon (ZED 750) is introduced to have a sufficient number of puddles and a long enough develop time to ensure good uniformity. Results of edge slope (i.e., sidewall profile) comparisons, resolution, and CD uniformity when using this process are presented and compared with results of the established process.Dry etching masks becomes increasingly important as the dimensions on the mask shrink in accordance with the SIA roadmap. The advantage of dry etch over wet etch is its anisotropy and, thus, a much reduced etch CD bias. One disadvantage of dry etch is the resist loss that occurs during plasma etching. The minimal resist thickness required for a dry etch process tends to be larger than that for wet etch. By choosing a different etch chemistry, significant improvements can be made in the selectivity during the dry etch, which is the ratio of the chrome etch rate relative to the ZEP 7000 resist etch rate. Improvements in selectivity may permit the use of thinner resists, resulting in a more robust process. Along with improved selectivity, the etch CD bias is decreased. This reduces the need to bias the data. Results from this alternative chemistry are shown.