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Influence of Oxygen upon Radiation Durability of SiN X-ray Mask Membranes

The radiation durability of a SiN X-ray mask membrane prepared by low pressure chemical vapor deposition (LPCVD) has been investigated. It is shown that the radiation durability of SiN films is marginally affected by their N/Si compositions, crystalline structures or film stress, but is drastically affected by the oxygen concentration in the film. Mask pattern displacement seems to be changed by breaking the Si–O bonds. A SiN membrane with an oxygen concentration below 1% is found to be stable under X-ray irradiation at a dosage of up to 5 kJ/cm2. Consequently, control of the oxygen concentration during the LPCVD process is vital to obtain high durability SiN X-ray masks.