15 July 1999 Efficiency increase for laser structuring using mask projection
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Mask based structuring in excimer laser applications is costly if mask with a small ratio of the hole pattern area compared to the whole illuminated area are used. In this case, the major part of the laser beam is reflected or absorbed at the mask. The herein presented system shapes the reflected part of the beam and guides it onto the mask again. This principle has been realized for up to eight irradiations of the mask. In order to achieve high quality ablation result both the beam divergence as well as the homogeneity play an important role. Therefore, a special homogenizer was developed which converts the excimer laser beam efficiency into a flat-top profile with negligible influence on the beam quality. The achieved optical resolution keeps within 2 micrometers and the homogeneity is sufficient to achieve nearly the same structure quality over the entire image field. Providing that the transmitting areas of the mask do not exceed a few per cent of the total irradiated area. An efficiency enhancement by more than a factor of five was achieved for eight mask irradiation passes compared to a single irradiation.
© (1999) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Knut Jasper, Knut Jasper, Peter Berger, Peter Berger, Helmut Huegel, Helmut Huegel, "Efficiency increase for laser structuring using mask projection", Proc. SPIE 3618, Laser Applications in Microelectronic and Optoelectronic Manufacturing IV, (15 July 1999); doi: 10.1117/12.352702; https://doi.org/10.1117/12.352702

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