Low Z substrates for cost effective high-energy, stacked exposures

 Commercial application of the “direct” LIGA process requires solving two critical issues: throughput and price. Stacking of PMMA sheets bonded to substrates and exposed simultaneously with hard X-ray has been suggested recently. This paper presents a comparison of potential low Z substrates for stacked exposures in deep X-ray lithography based on elements of the second row of the periodic table. The transmission of various substrates considered for such an application have been calculated and experimentally determined. The transmission properties of materias such a beryllium, carbon, boron and compounds are by far better than that of silicon at lower photon energies typically used in LIGA applications, but this gain decreases with increasing photon energy. In stacked exposures, however, even small gains provide significant decrease in exposure time. Received: 25 August 1997/Accepted: 3 September 1997