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Proceedings Paper

Novel technique for submicron separation between metal lines
Author(s): Arvind Raghavan; S. K. Lahiri; Amitava DasGupta
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Paper Abstract

Realization of submicron features usually involves the use of sophisticated techniques like e-beam or x-ray lithography. A novel alternative technique of 'underetch and liftoff' has been developed using normal UV lithography in order to obtain submicron gap between metal lines. This technique is attractive since these small gaps can be realized irrespective of lithographic limitations. In this process, the first step involves the deposition of the first layer of metal. The next step is the coating of photoresist and opening windows. This is followed by etching of the first metal which results in an underetch. Subsequently the second metal layer is deposited. The final step is liftoff. As the photoresist is removed together with the second metal layer on top of it, it leaves behind a gap between the first and second metal layers equal to the amount of underetch while etching the first metal. Our experiments show that the underetch depends on the composition of the etchant, etching temperature, thickness of metal and time of etching. However, if etching is done for a sufficiently long time underetching stops. Hence, other factors have been standardized to obtain gaps of 0.5-0.7 micron for gold and aluminium metal lines. The small gaps between metal lines are useful in devices like charge coupled devices and metal insulator semiconductor tunnel transistors (MISTTs). MISTTs having high current gains have been successfully fabricated where the submicron emitter to collector separation was achieved using the above process. The technique where submicron gaps can be achieved using simple equipment, is expected to find a lot of use in semiconductor technology.

Paper Details

Date Published: 14 August 1997
PDF: 7 pages
Proc. SPIE 3183, Microlithographic Techniques in IC Fabrication, (14 August 1997); doi: 10.1117/12.280542
Show Author Affiliations
Arvind Raghavan, Univ. of Maryland/College Park (United States)
S. K. Lahiri, Indian Institute of Technology (India)
Amitava DasGupta, Indian Institute of Technology (India)

Published in SPIE Proceedings Vol. 3183:
Microlithographic Techniques in IC Fabrication
Soon Fatt Yoon; Raymond Yu; Chris A. Mack, Editor(s)

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