Electron beam damage in the SiN membrane of an X-ray lithography mask

Abstract

The damage caused as a result of exposure to an electron beam of 20 to 50 kV acceleration voltage on the SiN membrane of an X-ray mask has been investigated. It determined that the optical and the mechanical properties of this material are modified and may potentially limit its use as a membrane in an X-ray mask structure for high density memory devices of giga bit dynamic random access memory (DRAM) level. In particular, after exposure to the electron beam of a 50 kV acceleration voltage and a dosage of 900 mu C/cm(2), the optical transmission of the SiN membrane fell by about 17% in the wavelength of 633 nm and the change of the out of plane distortion(OPD) on the 16 x 16 mm(2) membrane was observed. The difference in the mechanical deflection before and after exposure to the electron beam of 20kV to 50kV acceleration voltage on the membrane area of 800 x 800 mu m(2) was about 500 Angstrom to 200 Angstrom which was measured by the alpha-step (Tencor 200) with the stylus force of 19.6 dyn.