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 µC/cm2, 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 ×16 mm2 membrane was observed. The difference in the mechanical deflection before and after exposure to the electron beam of 20 kV to 50 kV acceleration voltage on the membrane area of 800 ×800 µm2 was about 500 Å to 200 Å which was measured by the α-step (Tencor 200) with the stylus force of 19.6 dyn.