Robin Teitzel

Lithographic performance results for a new 50-kV electron-beam mask writer

Current pattern generation tool designs will be inadequate to meet the advanced requirements for next-generation masks, particularly at the 100 nm node. Etec Systems, Inc. has developed a complete raster-based patterning solution to provide improved resolution, critical dimension (CD) uniformity, positional accuracy, and throughput. This solution meets the challenges of the 130-nm device generation with extendibility to at least 100 nm devices. Our complete patterning solution includes an electron-beam (e-beam) pattern generation system and a new 50 kV process. The e-beam system includes a column with 50 kV accelerating voltage and a new graybeam writing technique. To accomplish this technique, a pulse-width modulated blanking system, per-pixel deflection, retrograde scanning, and multiphase and multipass writing are used. This combination of features results in markedly improved lithographic performance and enables the use of conventional high-contrast resists for faster process implementation. Additional significant innovations of this pattern generation system include a novel stage design, an integrated automated material handling system (AMHS), on-board diagnostics, and improved environmental/thermal management. We believe this comprehensive patterning solution offers the best combination of benefits to the user in terms of versatility and extendibility.

Next generation DUV ALTA mask patterning capabilities

The capability of the DUV ALTAÒ 4300 system has been extended by the development of two new optical subsystems: a 0.9 NA, 42X reduction lens and a high-bandwidth acousto-optic deflector based beam position and intensity correction servo. The PSM overlay performance has been improved by modifications to the software algorithms. Characterization data show improved resolution performance in line end shortening, through pitch CD bias and feature corner acuity. The AOD subsystem reduces stripe beam placement errors and random and systematic beam intensity errors. This has enabled local CD uniformity to be reduced to 4.3 nm (3σ) and global CD uniformity to be reduced to 5.8 nm (range/2). Second layer overlay performance is now 20 nm (max error). A split lot wafer evaluation has demonstrated the equivalence of unmodified ALTAÒ 4300 reticles to those printed on a 50 KeV electron beam system for a 130/110 nm device. Wafer lithography results show equivalent CD uniformity, depth of focus and pattern registration results.

ALTA 4700 system mask patterning performance improvements for X-architecture and wafer electrical performance interchangeability with 50kV E-beam

The capability and performance of the production-proven DUV ALTA 4300 system has been extended by the development of two new optical subsystems: a 0.9 NA, 42X reduction lens and a high-bandwidth acousto-optic deflector based beam position and intensity correction servo. The PSM overlay performance has been improved by modifications to the software algorithms. The enhanced performance, delivered by these subsystem improvements, has been introduced as a new product-the ALTA 4700. Characterization data show improved resolution performance in line end shortening, through pitch CD bias and feature corner acuity. The AOD subsystem reduces stripe beam placement errors and random and systematic beam intensity errors. This has enabled local CD uniformity to be reduced to 4.3 nm (3σ) and global CD uniformity to be reduced to 6 nm (3σ). Second layer overlay performance is now 20 nm (max error). This paper also demonstrates superior X-Architecture performance delivered by the ALTA 4700. Characterization data show global CD uniformity in 0°, 45°, 90°, and 135° orientations better than 6.5nm (3σ); mean CD control in all 4 orientations less than 3.6nm; and smooth angled lines through a wide range of angles. A split lot wafer evaluation demonstrates the equivalence of wafers produced DUV ALTA system reticles vs. those produced with reticles from a 50kV electron beam system. The evaluation shows the interchangeability of these two systems for 90nm Metal 1 applications-with no changes to the wafer OPC (originally optimized for the 50kV system). Characterization data focus on final wafer electrical performance-the performance characteristic that determines ultimate integrated circuit device yield.

DUV ALTA system aerial image enhancement for improved pattern fidelity

The ALTA 4300 system has been used to successfully write many advanced design layers previously only feasible with 50kV vector shaped beam tools. In order to further enlarge the application space of this high productivity an aerial image enhancement technique has been developed to deliver mask patterns that more closely match pattern data for corners and jogs. This image enhancement is done in real time in the ALTA system’s rasterizer by modifying the gray level mapping of pixels near the corner vertexes. SEM measurements of corner rounding with standard rasterization and the enhanced rasterization show an improvement of corner rounding radius from ~205 to ~132 nm. A direct comparison of SEM micrographs show no qualitative difference between vector scan mask features and those written with aerial image enhancement. This convincingly demonstrates that the ALTA 4300 system with the new image enhancement can write many layers requiring vector scan corner acuity.

Elements of an advanced pattern generator for 130- to 100-nm maskmaking

In response to next-generation mask requirements, Etec Systems, Inc has developed a complete raster-based patterning solution to meet the production needs of the 130 nm IC device generation as well as those for early 100 nm production. In developing this new MEBES system, we have aimed at versatility, extendability, and compatibility with conventional high-contrast resists and redesigned it form the ground up. This MEBES system incorporates many technological innovations, such as anew 50 kV electron-beam (e-beam) column, a new raster graybeam writing strategy, a new stage, an integrated automated material handling system, on-board diagnostics, and environmental/thermal control. A discussion of architectural details of the new MEBES system designed to meet the tight requirements of 130-100 nm technology nodes is presented. This comprehensive patterning solution offers the best combination of benefits to the user in terms of versatility, overall system throughput, and extendability. Initial throughput and lithographic performance benchmarks are also presented and are very promising in predicting the ability to meet critical dimension uniformity requirements of 10nm or better, as predicted by the ITRS requirements.

DUV ALTA system aerial image enhancement for improved pattern fidelity: phase II

The ALTA 4300 system has been used to successfully write many advanced designs previously only possible with 50kV VSB systems. In order to further enlarge the application space of this high productivity system, an aerial image enhancement technique has been developed to deliver mask patterns that more closely match the pattern data for corners and jogs. This image enhancement is done in real time in the ALTA systems rasterizer by modifying the gray level mapping of pixels near the corner vertexes. SEM measurements of corner rounding with standard rasterization and the enhanced rasterization show a 35% improvement of corner rounding radius from ~205 to ~132 nm. A direct comparison of SEM micrographs show little qualitative difference between vector scan mask features and those written with aerial image enhancement. This convincingly demonstrates that the ALTA 4300 system with the new image enhancement can write many layers requiring vector scan corner acuity.