The combination of conductive topcoat ESPACER Z300 and positive tone CAR FEP171 was investigated in detail for the second level patterning of Alternating Aperture Phase Shift Masks (AAPSM) using e-beam lithography. Chrome load variations between 2 and 50% with the corresponding deviation of the second level pattern, homogeneously and unevenly distributed on the mask, had no significant impact on placement and overlay accuracy. No clear defect increasing could be measured when applying ESPACER top coat. The quartz etch selectivity of FEP171 was identically with the widely accepted laser resist IP3600 and a good etch depth linearity was achieved down to 200nm feature size. Finally, the performance of the developed process has been demonstrated on a 65nm node device design.
The aim is to apply e-beam lithography for second level imaging of Alternating Phase Shift Masks (altPSM) in the 65 nm node and below. Difficulties due to charging effects arise when exposing areas where the chromium absorber has been cleared away. In order to achieve correct pattern placement, the commercial water-soluble conductive ESPACER 300Z top coat from Showa Denka is applied in combination with chemically amplified resist of type FEP171. The paper describes the method and algorithm to test the efficacy of the material and the technological steps taken to avoid or reduce charge effects. The obtained overlay accuracy proves the ESPACER/FEP171 combination a promising approach for future altPSM manufacturing.
When e-beam lithography is applied for second level imaging of Alternating Phase Shift Masks charging effects on the cleared chrome absorber induces placement, overlay and pattern distortion of the second layer. The water soluble conductive to coat Showa Denko ESPACER 300Z has been evaluated in combination with the chemically amplified resist FEP171 for a charging eliminating patterning solution. Application of ESPACER on top of FEP171 kept the resist performance unchanged. Sensitivity, profile, resolution, CD-uniformity and post exposure delay of FEP171 have been investigated and no influence of ESPACER was detected. The bilayer system ESPACER and FEP171 was used for the second patterning of an altPSM test design and the technology performance was characterized. No difference has been figured out between placement of the second level and placement on a non-structured chrome layer. The achieved overlay accuracy proves the ESPACER/FEP171 combination as a promising approach for future altPSM manufacturing.
The new capillary spin (CAP-Spin) coating principle, realized in the STEAG HamaTech ASR5000, was evaluated for mask making using chemically amplified resists.
Basic correlations between coating parameters, resist thickness and film uniformity were figured out. We achieved a film thickness uniformity of close to 2% total range after a process optimization based on our investigation results with the positive tone resist JSR KRS-XE.
Finally, the performance of ASR coated blanks was assessed on the basis of a binary mask making process using the Fuji FEP171 resist. The ASR5000 was integrated in an advanced tool set and the patterned reticles have met the requirements of the 100nm Technology Node in terms of resolution and CD-uniformity. No correlation between thickness and CD distribution could be observed.
The evaluated post coating and post exposure delay influence of FEP171 also confirms the usability of the ASR5000 coated substrates for advanced mask making.
Positive tone chemically amplified resists CAP209, EP012M (TOK), KRS-XE (JSR) and FEP171 (Fuji) were evaluated for mask making. The investigations were performed on an advanced tool set comprising of a Steag coater ASR5000, Steag developer ASP5000, 50kV e-beam writer Leica SB350, UNAXIS MASK ETCHER III , STS ICP silicon etcher and a CD-SEM KLA8100. We investigated and compared resolution, sensitivity, resist slope, dark field loss, CD-uniformity, line edge roughness, and etch resistance of the evaluated resists. Furthermore, the influence of post coating delay, post exposure delay and other process parameters on the resist performance was determined.
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