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Complementary Selective Writing by Direct-Write E-Beam/Optical Lithography Using Mixed Positive And Negative Resist

IP.com Disclosure Number: IPCOM000101347D
Original Publication Date: 1990-Aug-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 66K

Publishing Venue

IBM

Related People

Kaszuba, P: AUTHOR [+4]

Abstract

By selectively writing complex patterns on semiconductor wafers utilizing both optical and E-beam technologies, line capacity can be increased over that which is achievable with direct-write E-beam (DWEB) considering throughput restrictions without selective writing.

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Complementary Selective Writing by Direct-Write E-Beam/Optical Lithography Using Mixed Positive And Negative Resist

       By selectively writing complex patterns on semiconductor
wafers utilizing both optical and E-beam technologies, line capacity
can be increased over that which is achievable with direct-write
E-beam (DWEB) considering throughput restrictions without selective
writing.

      A DWEB tool is capable of 0.25 mm lithography, while current
excimer laser lithographic tools are limited to images larger than
0.5 mm. For this reason the DWEB is required for printing sub-0.5 mm
levels. Since the DWEB throughput is gated by pattern complexity and
area to be written, it can be increased by writing only selected
patterns on each wafer level.

      By splitting the critical levels into two complementary
patterns, the first consisting of sub-0.5-micron images to be exposed
by DWEB and the second (less critical) to be exposed optically, a
composite pattern can be generated, as shown in Fig. 1.

      The process implementation depends on the tone of resist to be
used. For the majority of levels of interest, DWEB requires a
negative resist and optical tools utilize a positive resist.
Referring to Fig.  2, the first resist is coated on the wafer,
optically exposed, developed and hard-baked to prevent reflow or
cracking during subsequent deposition of a barrier layer. (For the
polysilicon level, a barrier layer of oxide is used.) Next, a layer
of 1000-an...