EUV Flare Variation Reduction with Dummy Fill for Negative-tone Photoresist Process
Date Issued
2016
Date
2016
Author(s)
Chen, Tai-Yu
Abstract
In the semiconductor manufacturing process, one of the most important techniques is photo lithography. The light with 193nm wavelength has the physical limitation problem on resolution. Extreme Ultraviolet Lithograph (EUVL) is one of the promising Next Generation Lithography (NGL) technologies. Most of foundries have invested considerable resources in the NGL technology. In this thesis we will mention one of the critical issues is EUV flare which is an undesirable scattered light due to the optical surface roughness. The high level EUV flare and the large flare variation could affect the control of critical dimension (CD) uniformity. However, previous work has reported that 0.2% change in flare level may cause 2 nm change in CD. There is a way to reduce flare variation and flare level for the process by using dummy fill for positive-tone photoresist process. We used the similar idea to reduce flare variation for negative- tone photoresist process. There is a mask different between negative-tone and positive-tone photoresist that negative-tone photoresist used dark field mask. For dark field mask process, the pattern or dummy fill are increasing the reflective area on the mask and the flare level on wafer, so we cannot decrease flare level by adding dummy fill. The distribution of dummy fill will be different that the dummy fill will accumulate in the middle for bright field mask, but in our case the dummy fill will accumulate on the edge for dark field mask process. We use a progressive method to reduce flare variation by insert dummy fill on low flare level region. Experimental results show that our process can reduce the flare variation by 40%, which may contribute to the better control of CD uniformity. This thesis presents the first work that reduce the flare variation for the negative-tone photoresist process.
Subjects
Lithography
Extreme Ultraviolet Lithograph
EUV flare
negative-tone photoresist process
dark field mask
Type
thesis
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