Dirk Beyer

90-nm mask making processes using the positive tone chemically amplified resist FEP171

A mask patterning technology for the 90nm technology node has been developed using the FujifilmARCH resist FEP171 and the state-of-the-art mask making tools SteagHamaTech mask coater ASR5000, Leica 50kV variable shaped e-beam writer SB350, SteagHamaTech developer ASR5000 and UNAXIS Mask Etcher III. A resist resolution of below 100nm dense lines and 150nm contact holes was demonstrated. The line width shrinking due to chrome etching varies between 25nm and 50nm per feature and a corresponding resolution of 125nm dense lines in a 105nm thick chrome absorber has been achieved. The global CD-uniformity with a 3σ of 7.7nm and a total range of 10.8nm met the requirements of the ITRS roadmap. The local uniformity with a 3σ of 3.8nm and a range of 5.6nm offers potential for future application of the Leica SB350. Applying of a new correction method taking electron scattering and process characeristics into account provides a linearity of 6.1nm. In addition, the line width of different featurees was kept in a range up to 12nm when the local pattern density was changed. The composite placement accuracy of 12nm fulfills already the requirements of the 65nm node. A special investigation proved the excellent fogging depression of the SB350.

Comparative evaluation of e-beam sensitive chemically amplified resists for 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.

Shaped beam technology for nano-imprint mask lithography

the Leica SB350MW 50keV shaped-beam e-beam lithography tool was used to write large-area 1X templates applicable in Step and Flash Imprint Lithography (S-FIL). This paper describes how information from the pattern analysis can be used to define the ZEP7000 resist exposure optimization technique for the SB350 MW tool together with the Motorola template pattern transfer process to obtain final template images in the transparent template. As a result of the complete process, well-resolved trenches measuring 33 nm and contacts as small as 44nm were obtained. Further improvements in the resist patterning will be possible by an adaptation of our standard proximity corrector (currently used in the 90 nm node maskmaking) with a high resolution upgrade.

Investigation of e-beam sensitive negative-tone chemically amplified resists for binary mask making

Negative-tone chemically amplified resists MES-EN1G (JSR), FEN-270 (Fujifilm ARCH), EN-024M (TOK) and NEB-22 (Sumitomo) were evaluated for binary mask making. The investigations were performed on an advanced tool set comprising a 50kV e-beam writer Leica SB350, a Steag Hamatech hot/cool plate module APB5000, a Steag Hamatech developer ASP5000, an UNAXIS MASK ETCHER III and a SEM LEO1560 with integrated CD measurement option. We investigated and compared the evaluated resists in terms of resolution, e-beam sensitivity, resist profile, post exposure bake sensitivity, CD-uniformity, line edge roughness, pattern fidelity and etch resistance. Furthermore, the influence of post coating delay and post exposure delay in vacuum and air was determined.

Evaluation of most recent chemically amplified resists for high resolution direct write using a Leica SB350 variable shaped beam writer

E-beam direct writing, one node ahead of advanced optical lithography, can be a time and cost effective option for early device and technology development as well as for fast prototyping. Because of the device complexity only a variable-shaped e-beam writer combined with sensitive chemically amplified resists (CAR) can be considered for this approach. We evaluated various pCARs and nCARs of all major suppliers for our goal to structure DRAMs of the 50nm node using the Leica SB350 e-beam writer. The most promising samples were selected for a process optimization by variation of bake and development conditions. Finally, one resist of each tonality met the most of our specifications like dense lines and contact holes resolution, sensitivity and vacuum stability.

A novel silicon detector for energetic electrons with improved linearity characteristics

This paper describes a novel silicon detector with improved linearity characteristics for energetic electrons up to 50 keV. The modified pn-junction detector stracture contains a buried implanted n(+) layer (N ∼ 1-5 × 1015 cm-3) in the n-type Si substrate, which is attributed by a near-surface high-field region in the depletion zone. To enable a high-field region of several micrometers depth, high-energy ion implantation with 31p ions of 10-30 MeV was used. The corresponding electric field distribution of the novel detector is characterized by a constant electric field strength of 10-50 kV/cm from the surface down to the depth of the buried implanted layer. Detectors with considerable improved linearity up to electron current densities of 20 A/cm2 were been fabricated, which have been tested at the e-beam writer SB 350 of Leica Microsystems Lithography for electrons of 50 keV.

Mask patterning process using the negative tone chemically amplified resist TOK OEBR-CAN024

Optimized process parameters using the TOK OEBR-CAN024 resist for high chrome load patterning have been determined. A tight linearity tolerance for opaque and clear features, independent on the local pattern density, was the goal of our process integration work. For this purpose we evaluated a new correction method taking into account electron scattering and process influences. The method is based on matching of measured pattern geometry by iterative back-simulation using multiple Gauss and/or exponential functions. The obtained control function acts as input for the proximity correction software PROXECCO. Approaches with different pattern oversize and two Cr thicknesses were accomplished and the results have been reported. Isolated opaque and clear lines could be realized in a very tight linearity range. The increasing line width of small dense lines, induced by the etching process, could be corrected only partially.

Alternating aperture phase shift mask process using e-beam lithography for the second level

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.

Avoidance/reduction of charging effects in case of partially insufficient substrate conductivity when using ESPACER 300Z

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.

Second-level imaging of advanced alternating phase-shift masks using e-beam lithography

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.