Application Of A Multiple Wavelength Absorption Endpoint System In Photomask Dry Etcher

Recently dry etcher system is a key process technology in preparation of photomasks for next generation microelectronic device and endpoint detection system is an important part of the dry etch process, because mask CD (critical dimension) control of Cr mask is more critical issues than before. In this paper, we describe real time endpoint system which is operated by optical emission multiple wavelength absorption for dry etch process of binary photomask. The end point detection system absorbs optical emission signal in real time, using optical cable from plasma chamber in dry etcher, and the signal is absorbed 200similar to800mn wavelength for a lot of grating manufactured by etch angle. The signal detects endpoint of process by association of one or several wavelength. We have tested newly developed EPD (end point detection) system and installed at PKL's dry etcher system(Clean Plasma 6000 1), using various open area Cr mask with ZEP7000(3000Angstrom) resist. This study showed that multiple wavelength absorption technique is enough to detect endpoint down to 2% Cr loading masks and the EPD signal reproducibility was within 2% of EPD time at the same patterned masks.