Browse Prior Art Database

Underlayer Resist for Improved Alignment Capability

IP.com Disclosure Number: IPCOM000120694D
Original Publication Date: 1991-May-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 1 page(s) / 66K

Publishing Venue

IBM

Related People

Brunsvold, WR: AUTHOR [+6]

Abstract

An underlayer resist formulation is disclosed which allows for stronger alignment signal intensities when using certain optical lithography tools.

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Underlayer Resist for Improved Alignment Capability

      An underlayer resist formulation is disclosed which allows for
stronger alignment signal intensities when using certain optical
lithography tools.

      Modern integrated circuits are built using layer by layer
fabrication processes, with each layer generally requiring a
lithographic pattern definition step.  Precise alignment between
successive patterns is critical to device performance.  On optical
lithography tools, alignment is often done using lasers which must
detect the alignment marks (fabricated at a previous level) through
the resist layer which is to be patterned.  In some cases multilayer
resist stacks are used, which consist of at least a top imaging layer
of photoresist and an underlayer which may planarize topography and
provide the necessary thickness to the resist mask (other layers
might be included as needed). A conventional choice for the
underlayer might be a photoresist, such as AZ135OJ* (* Trademark of
Hoechst Celanese), which has been baked "hardbaked" (i.e., baked at a
sufficiently high temperature to crosslink and insolubilize the
novolak resin in the resist).  The absorbance of several microns of
hardbaked AZ135OJ is sufficiently low at 633 nm (helium-neon laser
wavelength) to allow for a strong alignment signal, but alignment is
impractical at 442 nm (helium-cadmium laser wavelength) because of
high absorbance.

      The invention disclosed here is an underlayer resist co...