Yoshihiko Okamoto

New phase-shifting mask technology for quarter-micron photolithography

A new phase shifting mask technology that will remarkable improve the resolution of photolithography is proposed. This new phase shifting mask has a two layer structure, which consists of a ordinary transmission pattern substrate and a phase shifting pattern substrate. These two substrates are fabricated independently. Then, two substrates are overlapped with each other. The imaging plane of the projection lens using this phase shifting mask is shifted by a small amount to the projection lens. However, this mask is very little spherical aberration. In addition, particles on the back surface of the transmission pattern substrate and the phase shifting pattern substrate are prevented from being transferred. Then, a quarter micron resist pattern can be obtained even by an i-line stepper with a resolution capability of 0.45 micrometers . This new phase shifting mask is an extremely attractive tool for quarter micron photolithography.