The complexity of photomasks is rapidly increasing as semiconductor devices are scaled down and optical proximity correction (OPC) becomes commonplace. Raster scan architectures are well suited to the challenge of maintaining mask throughput despite these trends. Electron-beam techniques have the resolution to support OPC requirements into the foreseeable future. The MEBES® eXara mask pattern generator combines the resolution of a finely focused electron probe with the productivity and accuracy of Raster Graybeam patterning. Features below 100nm can be created, and OPC designs are produced with consistent fidelity. Write time is independent of resist sensitivity, allowing high-dose processes to be extended, and relaxing sensitivity constraints on advanced chemically amplified resists. The system is designed for the production of 100nm photomasks, and will support the development of 70nm masks.
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.
The decision by the Semiconductor Industry Association (SIA) to accelerate the continuing evolution to smaller linewidths is consistent with the commitment by Etec Systems, Inc. to rapidly develop new technologies for pattern generation systems with improved resolution, critical dimension (CD) uniformity, positional accuracy, and throughput. Current pattern generation designs are inadequate to meet the more advanced requirements for masks, particularly at or below the 100 nm node. Major changes to all pattern generation tools will be essential to meet future market requirements. An electron-beam (e-beam) system that is designed to meet the challenges for 130 - 100 nm device generation with extendibility to the 70-nm range will be discussed. This system has an architecture that includes a graybeam writing strategy, a new state system, and improved thermal management. Detailed changes include a pulse width modulated blanking system, per-pixel deflection, retrograde scanning multipass writing, and a column with a 50 kV accelerating voltage that supports a dose of up to 45 (mu) C/cm2 with minimal amounts of resist heating. This paper examines current issues, our approach to meeting International Technology Roadmap for Semiconductors (ITRS) requirements, and some preliminary results from a new pattern generator.
The semiconductor industry utilizes complex patterning tools to achieve the patterning of fine features. These tools require stiff, lightweight, dimensionally stable components in order to reliably pattern photomasks and wafers. Traditionally, these tools have used metals, ceramics, and low expansion glasses. However, a new class of materials, high performance composites, has demonstrated promise for replacing these materials. This paper discusses the design, manufacturing, and test of a carbon fiber composite stage component of an electron beam lithography tool.
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.
Finite element (FE) numerical models were proposed to simulate and predict substrate thermal expansion in photomask substrates and were found to be computationally expensive and dependent on the mask-writing strategy. The present work describes a newly developed model that predicts and corrects for the substrate heating effects in the photomask. This prosed model provides a practical way of predicting in-plane distortions during real-time patterning that is not limited to nay writing strategy or pattern density distribution. The main advantage of this model is that it significantly reduces the computational time by using the linear superposition theory. By adopting the concept of linear superposition, pattern placement errors of mask substrate scan be determined at any time during writing using lookup tables from precomputed FE models. IF the thermal distortion of the substrate at the time during writing using lookup tables from, precomputed FE models. IF the thermal distortion of the substrate at the time of writing is known, beam deflection can be introduced to correct for the distorted substrate. The result predicted by the linear superposition FE model showed a difference of less than 10 percent compared with those predicted using a real-time calculated Fe mode, in a worst case scenario. The accuracy of the linear superposition FE model was found to be partially dependent on the size of the simulated patterning field. The results presented in this paper illustrate the effect of other parameters on the performance of the newly developed model, such as the shape of the patterning fields and pattern coverage uniformity. The overview of this work focuses on fused silica mask substrate materials.
System architecture choices for an advanced mask writer (100 - 130 nm) have been evaluated. To compare and contrast variably shaped beam vector architecture with raster-based architecture, factors such as beam accelerating voltage and its effects on lithographic performance and system throughput for complex patterns have been studied. The results indicate that while both architectures have strengths and weaknesses, in the final analysis, raster-based systems offer the best combination of benefits to the user in terms of versatility and overall system throughput. Furthermore, other system requirements needed to support the challenges of the next generation mask writers are discussed. An architecture that includes a 50 kV raster graybeam (RGB), based architecture, a new writing strategy, a new stage system, an advanced environmental/thermal control management system, an automated material handling system, and a new resist and process is proposed.
The semiconductor industry utilizes complex patterning tools to achieve the patterning of fine features. These tools require stiff, lightweight, dimensionally stable components in order to reliably pattern photomasks and wafers. Traditionally, these tools have used metals, ceramics, and low expansion glasses. However, a new class of materials, high performance composites, have demonstrated promise for replacing these materials. This paper discusses the design, manufacturing, and test of a carbon fiber composite stage component of an electron beam lithography tool.
Finite element (FE) models have been created to investigate mechanical distortions associated with mask blank fabrication and mounting in a horizontal orientation. A modal analysis was completed to quantify the natural frequencies for the mask blank as a predictive tool for possible vibration prevention or control. By modeling the substrate with layers associated with the mask fabrication process and then by prestressing these layers, the resulting out-of-plane distortions (OPD) and in-plane distortions (IPD) can be determined. Utilizing these models, the magnitude of the maximum IPD and OPD due to gravity have been determined as a function of the mounting location to optimize the mounting position.