DUV laser lithography for photomask fabrication

Abstract

Figure 1. Application space for i-line, DUV and e-beam lithography platforms is plotted as a function of feature size (primary / assist) and CD uniformity. The poly-gate line is based on gate level specifications for 180nm, 130nm and 90nm technology nodes. ABSTRACTIn the recent past significant work has been done to isolate and characterize suitable single layer Chemically Amplified Resist (CAR) systems for DUV printing applicable to photomask fabrication. This work is complicated by the inherent instability of most DUV CAR systems, particularly in air, showing unacceptable CD degradation over the normal photomask write time in today's DUV mask pattern generators. The high reflectivity of most photomask substrates at DUV wavelengths, creating unacceptable standing waves in the photo resist profile, further compounds this problem.A single layer CAR system suitable for 90nm technology node mask fabrication with DUV printing has been characterized and optimized. Results of this optimization in terms of relevant mask making parameters will be detailed. Furthermore, comparison of the properties of this resist system to other commercially available systems, including FEP-171, will be shown.The pattern fidelity of DUV laser generated masks has been studied in considerable detail. A demonstration of the capabilities of the Etec Systems ALTA™ 4300 will be shown.The pattern fidelity achieved will be compared/contrasted to that achieved with today's leading edge 50KeV vector scan e-beam systems. Advanced methods for modulating the DUV printed patterns' fidelity will be detailed.Finally, the cost and cycle time implications of inserting the DUV laser pattern generator into the mask manufacturing flow will be discussed.

Evaluation of a new-generation photomask develop system for CAR

“…Additionally, linearity data observed here was similar to another established PEK130 DUV process at one of AMTC's partner companies. 5 Contact linearity was not measured in this evaluation.…”

“…These trends contrast those from another established PEK130 DUV process at one of AMTC's partner companies, yet average CD deviation ranges for these feature types were similar between these two processes. 5 The largest CD deviations usually occurred at the lowest (<25%) and highest (>75%) local loads and both feature types had smaller CD deviations between 13 and 88% loading. Average CD deviation ranges for isolated lines on all test pattern #2 masks decreased more than 50% from 10.5nm over the entire local loading range to 5.1nm within the 13-88% range (likewise 9.5nm decreased to 7.7nm for dense spaces).…”

“…Despite these higher than expected CDU results, ranges for all feature types in test pattern #2 masks from Figure 3.21 were very similar to test masks results on another established PEK130 DUV process at one of AMTC's partner companies. 5 Furthermore, several 130nm node logic product masks exposed at DUV with PEK130, met all chrome CD specifications after develop on the TEL alpha develop tool.…”

“…Test pattern #2 was a different array of die covering 108x126mm, each with a fill pattern and CD cell, yet each die could vary in local load, allowing CD observations as a function of local load. 5 Several DRAM and logic product masks were also processed on the TEL alpha develop tool and examined for CDU and defect performance as part of this evaluation.…”

Pattern fidelity enhancement with OPC pattern generation on laser lithography

“…Corner Pull Back, Area Percentile, the percentage of pattern area to retangle area (P/R ratio) and etc. 1,3,4,5 . In our study we used Area Loss as the metric of contact hole quality.…”