Advanced Mask Aligner Lithography (AMALITH)

Starting in the early 1960s, mask aligners were the dominating lithography tool for the first 20 years of the semiconductor industry. In the early 1980s industry changed over to projection lithography. However, mask aligners were never sorted out. Still today hundreds of new mask aligners are sold each year. This continuing success of mask aligner lithography is related to two basic trends in lithography: (a) Costs for leading-edge lithography tools double approximately every 4.4 years; and (b) the number of lithography steps per wafer was increasing from a few litho-layers to more than 35 layers now. This explains why mask aligner lithography, a very robust and cost-effective solution for uncritical litho-layers, is still widely used today. Mask aligner systems have much evolved, from manual 1‘‘ aligner to fully automatic 300 mm cluster systems of today. Interestingly, the shadow-printing lithography process itself was never improved. Illumination systems of most commercially available mask aligners are still based on technology developed in the 1970s. SUSS MicroTec has now introduced a novel mask aligner illumination system, referred as MO Exposure Optics (MOEO) [1,2]. The MO Exposure Optics system is based on high-quality microlens arrays in Fused Silica. MO Exposure Optics stabilizes the illumination against misalignment of the lamp, provides improved light uniformity, telecentric illumination and allows freely shaping the angular spectrum of the illumination light. Full control and light shaping are the key to optimize mask aligner lithography beyond today’s limi