7 July 1997 Effect of SiC x-ray masks on alignment accuracy of heterodyne alignment
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This paper describes the results of a study to investigate the applicability of silicon carbide (SiC) x-ray masks to an optical-heterodyne alignment technique. SiC was deposited at a thickness of 2 micrometer on a 4 inch silicon (Si) wafer. Its surface roughness was improved from 15 nm Ra (geometrical average) to 0.2 nm Ra using a polishing method. Using this SiC material, x-ray masks with Ta absorber patterns for alignment marks and overlay measurement were fabricated. To obtain a high overlay repeatability, we have deposited an anti- reflection coating (ARC) on both sides of the x-ray mask, which increased an optical transmission at a wavelength of 785 nm from 37% to 73%. We have also deposited an opaque coating (OPC) on the mask alignment mark. Using the x-ray mask, the overlay repeatability by mix-and-match method was evaluated. The overlay repeatability near the X, Y and (theta) alignment marks was 21 nm, 21 nm, and 49 nm (3 sigma) for the corresponding axes. The overlay repeatability of the X and Y directions was 61 nm and 54 nm (3 sigma) in a wafer. These results are equivalent to the results obtained using SiN x-ray masks. From these results, we consider that SiC x-ray masks are applicable to optical heterodyne alignment, and can also be used in practical x-ray lithography.
© (1997) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Hajime Aoyama, Hajime Aoyama, Fumiaki Kumasaka, Fumiaki Kumasaka, Yoshihisa Iba, Yoshihisa Iba, Takao Taguchi, Takao Taguchi, Masayuki Takeda, Masayuki Takeda, Masaki Yamabe, Masaki Yamabe, Makoto Fukuda, Makoto Fukuda, Masanori Suzuki, Masanori Suzuki, Kimiyoshi Deguchi, Kimiyoshi Deguchi, } "Effect of SiC x-ray masks on alignment accuracy of heterodyne alignment", Proc. SPIE 3048, Emerging Lithographic Technologies, (7 July 1997); doi: 10.1117/12.275796; https://doi.org/10.1117/12.275796

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