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.

Present Status of EUV Interference Lithography at NewSUBARU

“…In Japan, the EUV-IL exposure tool was developed at BL09b beamline at NewSUBARU synchrotron light facility, which was used for the EUV patterning tool to evaluate resist performance [6][7][8][9][10][11][12]. In this study, it is reported that the current results and status of this EUV-IL tool, especially the improvements in the exposure shot number increase by improving the grating holder design and exposure process automation by developing the specific software program.…”

The Measurement of the Refractive Index <i>n</i> and <i>k</i> Value of the EUV Resist by EUV Reflectivity Measurement Method

“…As a result, we could investigate the conditions for reducing LER and for enhancing resolution [7,8]. We hereby report on the methods of calculating the refractive index n and k values of photoresist with EUV light (13.5 nm), which has been difficult to measure until now, and the Dill B parameter, which is an absorption parameter, by focusing on the reflectance measurement method.…”