Photoresist Component Extraction Measurements |
| The intimate contact between the lens, water and photoresist raised the possibility of small molecule resist components – residual casting solvent (RCS), PAGs and base quenchers – being leached from the film by the immersion water. This could lead to contamination of the lens and/or degradation of the resist performance. To address this issue, an extremely sensitive measurement technique was needed to quantify the small amount of extraction expected. Therefore, a radiochemical analysis was developed to provide high sensitivity, precision and selectivity. |
| For this analysis, a typical casting solvent and a PAG were synthesized with a carbon-14 containing precursor. The resulting radiolabeled resist components were then individually incorporated into model 193 nm resist formulations, provided by resist vendors TOK (Japan) and AZ Clariant (Somerville, NJ). Films of these resists were cast onto 2 in Si wafers and immersed in deionized water for 30 s to 30 min. The immersion water was then counted using liquid scintillation counting to determine the amount of each component that was extracted. A blank sample was also counted to determine the background noise level. The results of these measurements are shown as the counting rate, counts per minute (CPM), in Figures 1 and 2. |
| The measurements of immersion water placed on resist films containing labeled casting solvent show that no statistically detectable, above background, amount of RCS was extracted in 30 min. However, the results from the 14C-PAG experiments show that a small, but detectable, amount of PAG was extracted. The extraction was evident after 30 s of immersion, and the amount extracted did not increase with immersion time. To confirm this, the experiment was repeated with a 30 s prerinse before immersion. |
| Figure 3 shows that the prerinse water contained a detectable amount of 14C-PAG comparable to the amount seen in Fig. 3, and that the immersion water did not contain any statistically detectable PAG. The amount of extracted PAG was determined to be approximately 40 ng/cm2, based on the surface area of resist that was immersed. |
| Continue to Ionic Additives for Second Generation Immersion Fluid |
| References |
| 1. X. Yan, G. Liu, M.D. Dickey, and C.G. Willson. “Preparation of porous polymer membranes using nano- or micro-pillar arrays as templates.” Polymer, 2004. 45: p.8469-74. |
| 2. T.W. Holcombe, M.D. Dickey, and C.G. Willson. “Durable fluorinated mono-layers for Indium-Tin Oxide” Langmuir (submit Feb 2006). |