John M Algots

Liquid metal micro-droplet generator for laser produced plasma target delivery used in an extreme ultra-violet source

The implementation of a Laser Produced Plasma Extreme Ultra-Violet (LPP EUV) source requires a high-power laser focused onto a target. In order to minimize the required laser input power the target material must have a high conversion efficiency to 13.5 nanometer radiation. Ideally, a pulsed laser is used and the target should be delivered in small uniform volumes to a point in space at high repetition rates. The small volumes minimize the amount of debris, the high repetition rates enable higher power systems and the free space delivery alleviates thermal issues and allows large collection angles. It has been demonstrated that lithium and tin have very high conversion efficiencies and system solutions exist to use these materials. In this paper we describe the requirements and performance of a liquid metal micro-droplet target generator capable of dispensing both lithium and tin. Finally it is shown that the current generator performance is sufficient to support stable source operation.

Wavelength stabilization in an excimer laser source using piezoelectric active vibration control

Excimer laser light sources for photolithography are subject to a cycle of ever-tightening precision requirements, dictated by the design-rule shrinks planned into the industry roadmap. But pulse-to-pulse stability of the center wavelength of the emitted light is limited by the presence of vibration in key components and structures. This paper covers the application of Active Vibration Control (AVC) technology to an excimer laser to mitigate the effects unwanted vibration, and enable compliance with anticipated future stability specifications. The laser system is described, from a structural-dynamics point of view. A systematic approach to vibration diagnostics is presented, with experimental results to support key conclusions regarding the types and sources of vibrations. Next, analytical assessment of active control performance is discussed, followed by breadboard-type implementation results showing reductions of > 30% in a key stability performance metric.