EB (electron beam) resist is widely used for the EUV (extreme ultraviolet) mask production. Tighter pitch size and smaller pattern features are required on EUV mask for the next generation EUV patterning. One of the most critical issues for EB lithography process is the stochastic issue which is induced by low density of quanta due to high energy of e-beam exposure. Such stochastic can induce the heterogeneity of various reactions in the photoresist. As a result, serious performance degradation is caused in key lithographic areas such as LWR (line width roughness), LCDU (local critical dimension uniformity), and resolution. It’s well known that quanta stochastic can be reduced by high dose condition. Thus, demand of high dose EB resist has been risen for further performance improvement. The previous studies showed the typical positive-tone chemically amplified resist (PCAR) comprising the PHS(polyhydroxystyrene) based polymer improved the lithographic performance up to 200μC/cm2, however, the performance was degraded in the high dose area over 250μC/cm2. These studies also suggested that the performance degradation could be caused by the cross-linking effect and decreasing the acid generation contrast induced by high dose. In this study, several PCAR formulations having the different materials were studied under Point-beam and MBMW (multi-beam mask writer) conditions to investigate the acid generation contrast influence on the lithographic performance. We have developed the new high acid generation PCAR and demonstrated the better LCDU and resolution performance on EUV blanks under the multi-beam condition compared with the typical PCAR.
EB (electron beam) resist is widely used for the EUV (extreme ultraviolet) mask production. Tighter pitch size and smaller pattern features are required on EUV mask for the next generation EUV patterning. A novel, high dose, positive-tone chemically amplified resist (pCAR) using PHS (polyhydroxystyrene) based polymer has been developed with improved resolution performance as verified by Point-beam writer and Multi-beam mask writer (MBMW). In this study, several high dissolution contrast pCAR formulations were studied under Point-beam conditions to investigate the impact of the chemical blur and the chemical stochastics on lithographic performance. For suppressing the chemical blur in the pCAR after exposure, formulations using larger size PAG (photo acid generator) could improve the resolution performance due to reduced acid diffusivity. For reducing the chemical stochastics, higher PAG loading pCAR and the low sensitivity pCAR were investigated. Improved resolution and LWR (line width roughness) performances were obtained by these pCAR up to approximately 200μC/cm2 under Point-beam condition. On the other hand, the lithographic performance was degraded at 270μC/cm2. Analytical results of PAG decomposition ratio by HPLC (high performance liquid chromatography) suggested the possibility that decreased acid concentration gradient could degrade lithographic performance when the pCAR sensitivity is too low. The investigation of different dissolution contrast pCAR showed that higher dissolution contrast pCAR with higher Rmax (maximum dissolution rate) resulted in improved resolution performance. According to this study, efforts to minimize the chemical blur and stochastics, and to maximize the photoresist contrast were the key factors for designing high-performing, low sensitivity pCAR. The verification results of the ultimate resolution of the representative pCAR with 60nm film thickness were also described in this paper under MBMW and mask process conditions. HP (half pitch) 21nm line and space pattern could be resolved without pattern collapse. The small ring pattern with a 10.5nm pattern width was nicely resolved as the smallest feature.
EB (electron beam) resist is widely used for the EUV (extreme ultraviolet) mask production. Tighter pitch size and smaller pattern features are required on EUV mask for the next generation EUV patterning. A novel, high dose, positive-tone chemically amplified resist (pCAR) using PHS (polyhydroxystyrene) based polymer has been developed with improved resolution performance as verified by Point-beam writer and Multi-beam mask writer (MBMW). In this study, several high dissolution contrast pCAR formulations were studied under Point-beam conditions to investigate the impact of the chemical blur and the chemical stochastics on lithographic performance. For suppressing the chemical blur in the pCAR after exposure, formulations using larger size PAG (photo acid generator) could improve the resolution performance due to reduced acid diffusivity. For reducing the chemical stochastics, higher PAG loading pCAR and the slower sensitivity pCAR were investigated. Improved resolution and LWR (line width roughness) performances were obtained by these pCAR up to approximately 200μC/cm2 under Point-beam condition. On the other hand, the lithographic performance was degraded at 270μC/cm2. Analytical results of PAG decomposition ratio by HPLC suggested the possibility that decreased acid generation contrast could degrade lithographic performance when the pCAR sensitivity is too slow. The investigation of different dissolution contrast pCAR showed that higher dissolution contrast pCAR with higher Rmax resulted in improved resolution performance. According to this study, efforts to minimize the chemical blur and stochastics, and to maximize the photoresist contrast were the key factors for designing high-performing, low sensitivity pCAR. The verification results of the ultimate resolution of the representative pCAR with 60nm film thickness were also described in this paper under MBMW and mask process conditions. HP21nm line and space pattern could be resolved without pattern collapse. The small ring pattern with a 10.5nm pattern width was nicely resolved as the smallest feature.
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