Critical dimension uniformity is one of the key parameters to define the performance of electron beam lithography as well as the other lithography technologies. The characteristics of poly-butene-sulfone (PBS), a positive-type electron resist, have been investigated from the view-point of critical dimension control, using two types of electron beam lithography systems which use Gaussian spot and variable-shaped beams. It has been elucidated that the sensitivity of the PBS has a strong relationship with humidity during development. When the humidity changes from 30% to 32%, the sensitivity increases corresponding to the increase of 1 µ C/cm2 dosage. A very good critical dimension uniformity of less than 0.04 µ m has been attained using a variable-shaped beam at 30% humidity. The spot beam can also obtain a good pattern width uniformity at 32% humidity and 4.5 µ C/cm2 dosage. It is expected to correct the proximity effect in PBS by selecting the electron dosage related to humidity.

A new fabrication process of T-shaped gates has been developed using a deep-UV/electron-beam/deep-UV (DUV/EB/DUV) tri-layer resist system and electron-beam lithography for the first time. The simple process accomplished a submicron T-shaped gate by a single exposure and a single development step. The narrow/wide/narrow opening of the DUV/EB/DUV resist structure can be accurately controlled by the e-beam dosage and the development conditions. Differences in the sensitivities of the DUV resist and the EB resist were investigated. Due to the lower sensitivity of the adopted DUV resist to the electron beam, the smaller opening of the DUV resist layer was obtained. The higher sensitivity of the EB resist resulted in a wider opening in the middle resist layer. A 0.15-µm-gate-length T-shaped gate can be easily formed by the short-process-time and low-production-cost hybrid DUV/EB/DUV resist approach.

Si x N y /Ni thin film green mask blanks were developed , and are now going to be used to replace general chromium film used for binary mask as well as to replace molydium silicide embedded material for AttPSM for I-line (365 nm), KrF (248 nm), ArF (193 nm) and Contact/Proximity lithography. A bilayer structure of a 1 nm thick opaque, conductive nickel layer and a Si x N y layer is proposed for binary and phase-shifting mask. With the good controlling of plasma CVD of Si x N y under silane (50 sccm), ammonia (5 sccm) and nitrogen (100 sccm), the pressure is 250 mTorr. and RF frequency 13.56 MHz and power 50 W. Si x N y has enough deposition latitude to meet the requirements as an embedded layer for required phase shift 180 degree, and the T% in 193, 248 and 365 nm can be adjusted between 2 % to 20 % for binary and phase shifting mask usage. Ni can be deposited by E-gun, its sheet resistance Rs is less than 1.435 kΩ/square. Jeol ebeam system and I-line stepper are used to evaluate these thin film green mask blanks, feature size less than 200 nm half pitch pattern and 0.558 μm pitch contact hole can be printed. Transmission spectrums of various thickness of Si x N y film are inspected by using UV spectrometer and FTIR. Optical constants of the Si x N y film are measured by n & k meter and surface roughness is inspected by using Atomic Force Microscope (AFM).

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