|
Phase-shift technology has been expected to be a useful method to improve the resolution of optical lithography. The absorptive phase shifter patterns has been formed with a two-layers structure of a SiO2 film to control the phase shifting and a thin Cr film to control the transmittance. If the absorptive shifter of a single-layer film is realized, the fabrication process will become as simple as that of conventional mask. Attenuated single-layer phase shift mask blanks have been proposed instead of the masks of two-layer structure of a Cr/SiO2/substrate. But the attenuated single-layer phase shift mask blanks with shifting angle of 180 degree(s) and with 5 approximately 20% transmittance for the exposure wave length have not been realized on production level. We selected an oxide or an oxi-nitride film of Cr or MoSi as materials for the attenuated single-layer phase shifter. And we have developed to produce the attenuated single-layer phase shift mask blanks which has fabrication capability and chemical durability as a mask material on 5' or 6' quartz substrate. Of course the defects of the attenuated single-layer phase shifter can be repaired with the combination of conventional methods using the focused ion beam and the laser beam. Their thickness are less than a half of two-layer film of conventional masks so that edge shape can be improved at the mask fabrication process. These films are deposited using DC magnetron sputtering process with Cr or MoSi target with Ar + O2 or Ar + O2 + N2 gas. The refractive index (n) and the extinction coefficient (k) of the film are controlled by the deposition condition such as sputtering current, sputtering pressure, oxygen supply, nitrogen supply and so on. Performances are examined such as: (1) variation of transmittance and phase value within a plate, (2) particle and pinhole density, (3) chemical durability, and (4) dry etching rate. It is confirmed that the blanks satisfy the performances of conventional mask blanks level. In this paper, deposition condition and characteristics of the attenuated single-layer phase shift mask blanks will be described.
|
