To alleviate the difficulty of ion beam etching, it is essential to acquire the low gradient holographic photoresist grating masks as well as the high gradient ones (i.e. the rectangular holographic photoresist grating masks). According to the ion beam etching experiments, the low gradient photoresist grating masks can effectively eliminate the redeposition. The control of the profile of holographic photoresist grating masks is investigated in this paper. Considering the effects of developing time and temperature of the developer on the response of photoresist and adopting the combination of computer simulation and experiments, a low gradient photoresist grating mask: 30% duty cycle at bottom and 65° gradient can be fabricated. The study indicates the increase of the developing time causes the diminish of the threshold volume of exposure while the increase of the slope of the linearity of photoresist response; the rise of the temperature of the developer leads to both the increase of the threshold volume of exposure and the slope of the linearity of photoresist response. As a result non-1:1 interferential exposure and low-temperature development are required in the fabrication of low gradient photoresist grating masks. The 1:7 interferential exposure and 15°C- development have been adopted in this experiment.
[1]
L. Johnson,et al.
Asymmetric triangular grating profiles with 90 degrees groove angles produced by ion-beam erosion.
,
1981,
Applied optics.
[2]
Xu Xiang.
Holographic ion beam etched diffraction gratings
,
2004
.
[3]
Howard M. Smith.
Holographic Recording Materials
,
1977
.
[4]
Shaojun Fu,et al.
VUV and soft x-ray diffraction grating fabrication by holographic ion beam etching
,
2005,
SPIE/COS Photonics Asia.
[5]
B. Shore,et al.
High-efficiency fused-silica transmission gratings.
,
1997,
Optics letters.