Focus Drilling and Attenuated Phase Shift Mask for Subwavelength Contact Window Printing Using Positive and Negative Resists

We have investigated the process latitude and resolution limit of printing contact windows using a high numerical aperture KrF stepper and attenuated phase shift mask (APSM). We show that both positive and negative resists can be used depending on the size of the window on the mask. The advantages and disadvantages of using the positive and negative resists are presented. A combination of APSM and focus drilling are shown to extend the focus latitude of subwavelength window printing.