A NOVEL X-RAY MASK FOR MIX-AND-MATCH OF OPTICAL AND X-RAY-LITHOGRAPHYAPPLIED IN SOI DEVICE FABRICATION

This paper reports on an application of a novel X-ray mask with a back -side alignment mark for fabricating of 0.15-mu m SOI p-MOSFETs in a m ix-and-match process of optical and synchrotron radiation X-ray lithog raphy. Optical alignment signals generated from the alignment marks on an X-ray mask and a wafer play an important role in obtaining high al ignment accuracy. In this paper, a novel structure of the X-ray mask t o improve the alignment signal of the mask and to minimize the optical interference effect on the SiN membrane is discussed. For Karl Suss X RS 200 X-ray stepper, the alignment result for synchrotron radiation l ithography with the novel X-ray mask applied to fabricate SOI devices was sigma(x) = 0.023 mu m and sigma(y) = 0.025 mu m. The saturation dr ain current I-d,I-sat was about 100 mu A/mu m, and the threshold volta ge V-T was about 0.4 V. The breakdown voltage BVdss between the source and the drain was measured at V-G = 0 V and I-D = 10 nA was larger th an 4 V.