Fabrication of 1-Mbit DRAMs By Using X-Ray Lithography

Nobuyuki Yoshioka; Noriaki Ishio; Nobuo Fujiwara; Takahisa Eimori; Yaichiro Watakabe; Kenichi Kodama; Takashi Miyachi; Hisao Izawa

doi:10.1117/12.968529

1 August 1989 Fabrication of 1-Mbit DRAMs By Using X-Ray Lithography

Nobuyuki Yoshioka, Noriaki Ishio, Nobuo Fujiwara, Takahisa Eimori, Yaichiro Watakabe, Kenichi Kodama, Takashi Miyachi, Hisao Izawa

Author Affiliations +

Proceedings Volume 1089, Electron-Beam, X-Ray, and Ion-Beam Technology: Submicrometer Lithographies VIII; (1989) https://doi.org/10.1117/12.968529
Event: 1989 Santa Clara Symposium on Microlithography, 1989, San Jose, CA, United States

Abstract

Functional 1-Mbit DRAM devices were fabricated by using x-ray lithography. An x-ray stepper ( Nikon SX-5) which has a high brightness x-ray tube (10 kW) with a Pd rotating target was used for the fabrication of the devices. The alignment system is based upon the use of a linear diffraction grating as an alignment target. The mask-to-wafer alignment is performed by detecting the first-order diffraction beam of incident laser beams from the grating alignment target. The wafer diameter is 150 mm, the mask diameter is 75 mm, and the exposure field size is 25x25 mm². A W-Ti alloy absorber was used as an x-ray mask absorber. Since W-Ti absorber films can be controlled to have an internal stress of less than 1 x 10⁸ dyne/cm², the mask distortion was less than 0.1 μm for the 15x15 mm² field including two 1-Mbit DRAM chips. The x-ray lithography was applied to the contact process by using a novolak-based positive resist XPB. The XPB resist has high sensitivity, high resolution capability, and high dry etch resistance. The alignment error was less than 0.15μm in 3σ. A 1-Mbit DRAM with a bit yield of 99.5% was obtained. It was thus demonstrated that x-ray lithography technology has the potential for use in VLSI fabrication.

Citation Download Citation

Nobuyuki Yoshioka, Noriaki Ishio, Nobuo Fujiwara, Takahisa Eimori, Yaichiro Watakabe, Kenichi Kodama, Takashi Miyachi, and Hisao Izawa "Fabrication of 1-Mbit DRAMs By Using X-Ray Lithography", Proc. SPIE 1089, Electron-Beam, X-Ray, and Ion-Beam Technology: Submicrometer Lithographies VIII, (1 August 1989); https://doi.org/10.1117/12.968529

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available