Development of a wafer positioning system for the Sandia extreme ultraviolet lithography tool
A wafer positioning system was recently developed by Sandia National Laboratories for an Extreme Ultraviolet Lithography (EUVL) tool. The system, which utilizes a magnetically levitated fine stage to provide ultra-precise positioning in all six degrees of freedom, incorporates technological improvements resulting from four years of prototype development. This paper describes the design, implementation, and functional capability of the system. Specifics regarding control system electronics, including software and control algorithm structure, as well as performance design goals and test results are presented. Potential system enhancements, some of which are in process, are also discussed.
Six degree of freedom fine motion positioning stage based on magnetic levitation
The design of a magnetically suspended six degree of freedom positioning system capable of nanometer positioning is presented. The sample holder is controlled in six degrees of freedom (DOF) over 300 micrometers of travel in X, Y and Z directions. A design and control summary, and test results indicating stability and power dissipation are included in the paper. The system is vacuum compatible, uses commercially available materials, and requires minimal assembly and setup.
Wafer steppers for the 64-M and 256-Mbit memory generations
Optical wafer steppers are used in the fabrication of submicron and subhalf micron integrated circuits. The SIA Technology Roadmap has outlined the major requirements steppers must meet for the 64M and 256Mbit memory generations. These include 0.35 μm and 0.25 μm resolution over 22 and 27 mm square image fields. This article outlines these requirements and explores the impact on wafer stepper design and use. Stepper cost of ownership will be considered including the contribution of the reticle to the overall cost of the process. Two major trends can be discerned. First, the requirement of 0.25 μm imaging over fields larger than a square inch forces the adoption of step and scan technologies as the cost and size of full field lenses grow noncompetitive. Second, in order to reduce the overall cost of ownership of the photolithography process, the industry is adopting mix-and-match strategies using high NA steppers to print critical mask layers and high speed, low NA, wide field steppers to print non-critical layers.