Fabrication of high-aspect-ratio transmission grating using DDR process for 10 nm EUV resist evaluation by EUV interference lithography

Abstract

We have developed an EUV interference lithographic exposure tool to evaluate a resist. The target patterning size of this system is 10 nm and below in half pitch. Transmission grating fabrication is a key technology in EUV interference lithography. To replicate a 10-nm-line-and-space (L/S) resist pattern on a wafer, a 20-nm-L/S pattern is required for the transmission grating. The pitch size of the interference fringes is half the size of the absorber pattern of the transmission grating. For the chemically amplified positive tone resist process, instead of alkali development, organic development can be adopted to convert to a negative-tone chemical amplification resist process, and pattern collapse can be suppressed. In addition to this process, a dry development rinse (DDR) process is used. The DDR process with dry development successfully prevents pattern collapse at a high aspect pattern because there is no surface tension in the dry development of the DDR process. The EUV diffraction efficiencies of the fabricated gratings were measured to be 14%, 11% and 4% for 40, 30 and 20-nm-L/S pattern grating, respectively. Using these gratings, 20, 15 and 10 nm resist pattern might be replicated on a resist. And the diffraction efficiency was sufficient for interferometric exposure using synchrotron radiation.