State of the art in focused ion-beam mask repair systems

Abstract

Focused ion beam (FIB) systems are commonly used to repair lithographic masks with features below one micron. We will summarize the development of focused ion beam mask repair systems starting from the original tools developed for photomasks approximately 10 years ago. The present state of the art in FIB mask repair systems is incorporated in two types of toolsone for repair of proximity print X-ray masks, and the other for repair of photomasks and some phase shift masks. Similarities of the two styles of systems include the gallium ion optics, the lithographic stage for accurate positioning, a thermal enclosure to minimize system drift, deflection and scanning electronics, and an interface to inspection data. The differences include the process chemistries, repair strategies, and imaging techniques. Examples of a variety of repaired defects on both X-ray and phase shift masks will be shown.Advanced masks such as those for EUV (Extreme Ultraviolet), DUV (Deep Ultraviolet), and SCALPEL (Scattering with Angular Limitation in Projection Electron Lithography) will have to be repaired should those technologies mature, and presumably with FIB tools. Preliminary research and development of advanced mask repair problems will be described and possible approaches will be suggested.

High resolution x-ray mask repair

“…[1][2][3] The 8000XR incorporates many of the processes and tooling developed on the prototype, and includes such improvements as a differential laser interferometer controlled stage and beam deflection system to improve repair placement and stability, along with numerous additional software automated features. 2,3 The prototype FIB uses a 60 nm beam of 100 keV Ga ϩ . The commercial FIB uses a 40 nm beam of 30-keV Ga ϩ .…”