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Full Phase Mask in Damascene Process

IP.com Disclosure Number: IPCOM000007569D
Publication Date: 2002-Apr-05
Document File: 7 page(s) / 91K

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The IP.com Prior Art Database

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IPCOM000007568D: IP.COM

Abstract

To provide optimal printing resolution, a full phase PSM mask can be used in a Damascene process. One feature of this full phase PSM is shifter cutting at corners, wherein a cut can be made in a shifter at the corner and the phase of one shifter segment can be switched. Another feature of this full phase PSM is the use of negative tone resist for the wafer.

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FULL PHASE MASK IN DAMASCENE PROCESS

Brief Summary of the Invention:
To provide optimal printing resolution, a full phase PSM
mask can be used in a Damascene process. One feature of
this full phase PSM is shifter cutting at corners, wherein
a cut can be made in a shifter at the corner and the phase
of one shifter segment can be switched. Another feature of
this full phase PSM is the use of negative tone resist for
the wafer.

Brief Background
A conventional metal process comprises depositing a metal
layer on a substrate and then depositing a positive tone
resist layer on the metal layer. The positive tone resist
is exposed using a clear field mask. Etching the metal
forms the desired pattern.

The semiconductor industry is moving from aluminum to
copper to enhance device performance at smaller critical
dimensions (e.g. at 0.13 microns).

Unfortunately, copper is very difficult to etch.
Therefore, a conventional metal process as described above
cannot be used. However, a Damascene process can be used
to form copper pattern. The Damascene process includes
forming an oxide layer on the substrate and then depositing
the positive tone resist layer on the oxide layer. The
positive tone resist can be exposed using a dark field
mask. Thus, etching the oxide forms the opposite pattern
than that desired. Copper can then be deposited and

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planarized (using a CMP operation), thereby forming the
desired pattern in copper.

Brief Description of the Figures
Figure P1 illustrates a phase-shift layout (left) that can
be used in a Damascene process and a resulting (i.e.
printed) image (right). The shifters in the phase-shift
layout are outlined in either green or burgundy to
represent different phases. Note that these shifters are
formed in a dark field mask, which is not shown to better
illustrate the shifters. This phase-shift layout
illustrates a T-intersection, which could form the gate of
a transistor. As shown, the right corner of the T-
intersection is cut, thereby allowing associated shifters
to be assigned opposite phases.

Note that the cut and phase switch can be used on any
region that includes a bend and tends to print large. In
other words, the cut and phase switch can be used on many
corners of the phase-shift layout.

To generate the image, a second mask (see Figure P3),
called a binary mask, has been used to expose the
extraneous feature that would otherwise print at the
corner.

In accordance with one feature of the invention, a negative
tone resist is used on the wafer. In other words, the
resist developer dissolves the non-irradiated regions,
thereby creating a "negative" image.

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The image in Figure P1 illustrates a 10...