Resist Processes

Resist footing variation and compensation over nonplanar wafer

[+] Author Affiliations
Takashi Sato, Ayako Endo, Kohji Hashimoto, Soichi Inoue, Tsuyoshi Shibata, Yuuji Kobayashi

Semiconductor Company, Toshiba Corporation, 8 Shinsugita-cho, Isogo-ku, Yokohama, Kanagawa?235-8522, Japan E-mail: ta.sato@toshiba.co.jp

J. Micro/Nanolith. MEMS MOEMS. 3(3), 436-441 (Jul 01, 2004). doi:10.1117/1.1759327
History: Received Apr. 22, 2003; Revised Oct. 24, 2003; Accepted Nov. 17, 2003; Online July 19, 2004
Text Size: A A A

We report a problem regarding DUV lithography on topographical substrates and a solution for obtaining desired CD control and resist pattern shape. In our experiment, large footings for a 250-nm resist pattern are observed when the resist pattern is transferred over a polysilicon step pattern of 175 nm in height. This pattern error is not negligible regarding device performance. The exposure tool used is a KrF scanner of NA 0.6. The resist is 500 nm thick with no antireflective coating (ARC). Computer simulation is used to demonstrate the amount of the footing. A nonrigorous diffraction model did not recreate the footing appearance at the poly-Si step. However, a rigorous diffraction model of incident light in a cone recreated the footing amount at the poly-Si step faithfully. In this simulation, optical distribution in the resist over the nonplanar wafer is solved by the finite-difference time-domain (FDTD) method. Optical intensity at the sidewalls of the step differs between the two models. Experimental results as well as simulation results show that larger coherency results in larger footing. In the case of a large coherency, the illumination rays come from various directions to the wafer, and a large shadow area is likely to appear behind the steep step. We also propose a shadow model for simple footing simulation. As a consequence, optical behavior in the vicinity at the steep step has a strong impact on the resist footing. © 2004 Society of Photo-Optical Instrumentation Engineers.

© 2004 Society of Photo-Optical Instrumentation Engineers

Citation

Takashi Sato ; Ayako Endo ; Kohji Hashimoto ; Soichi Inoue ; Tsuyoshi Shibata, et al.
"Resist footing variation and compensation over nonplanar wafer", J. Micro/Nanolith. MEMS MOEMS. 3(3), 436-441 (Jul 01, 2004). ; http://dx.doi.org/10.1117/1.1759327


Tables

Access This Article
Sign in or Create a personal account to Buy this article ($20 for members, $25 for non-members).

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging & repositioning the boxes below.

Related Book Chapters

Topic Collections

Advertisement
  • Don't have an account?
  • Subscribe to the SPIE Digital Library
  • Create a FREE account to sign up for Digital Library content alerts and gain access to institutional subscriptions remotely.
Access This Article
Sign in or Create a personal account to Buy this article ($20 for members, $25 for non-members).
Access This Proceeding
Sign in or Create a personal account to Buy this article ($15 for members, $18 for non-members).
Access This Chapter

Access to SPIE eBooks is limited to subscribing institutions and is not available as part of a personal subscription. Print or electronic versions of individual SPIE books may be purchased via SPIE.org.