Micro-casted silicon carbide nano-imprinting stamp

Details Micro-casted silicon carbide nano-imprinting stamp Micro-casted silicon carbide nano-imprinting stamp

2002-10-24

2004-06-29

Mills, Gregory (Department: 1763)

Etching a substrate: processes

Pattern or design applied by transfer

C216S044000, C216S052000

Reexamination Certificate

active

06755984

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to a structure and a method of forming a hardened nano-imprinting stamp from silicon carbide. More specifically, the present invention relates to a structure and a method of forming a hardened nano-imprinting stamp using a micro-casting process.
BACKGROUND OF THE ART
Nano-imprinting lithography is a promising technique for obtaining nano-size (as small as a few tens of nanometers) patterns. A key step in forming the nano-size patterns is to first form an imprinting stamp that includes a pattern that complements the nano-sized patterns that are to be imprinted by the stamp.
In
FIG. 1
a
, a prior nano-imprint lithography process includes an imprinting stamp
200
having a plurality of imprint patterns
202
formed thereon. In
FIG. 1
b
, the imprint patterns
202
consists of a simple line and space pattern having a plurality of lines
204
separate by a plurality of spaces
206
between adjacent lines
204
. The imprint patterns
202
are carried by a substrate
211
. By pressing (see dashed arrow
201
) the imprinting stamp
200
into a specially designed mask layer
203
, a thickness of the mask layer
203
is modulated with respect to the imprint patterns
202
(see
FIG. 1
a
) such that the imprint patterns
202
are replicated in the mask layer
203
.
Typically, the mask layer
203
is made from a material such as a polymer. For instance, a photoresist material can be used for the mask layer
203
. The mask layer
203
is deposited on a supporting substrate
205
. Using a step and repeat process, the imprinting stamp
200
is pressed repeatedly onto the mask layer
203
to replicate the imprint patterns
202
in the mask layer
203
and to cover the whole area of the mask layer
203
.
In
FIG. 2
, after the step and repeat process, the mask layer
203
includes a plurality of nano-size impressions
207
that complement the shape of the imprint patterns
202
. Next, in
FIG. 3
, the mask layer
203
is anisotropically etched (i.e. a highly directional etch) to form nano-sized patterns
209
in the mask layer
203
. Typically, the supporting substrate
205
or another layer (not shown) positioned between the mask layer
203
and the supporting substrate
205
serves as an etch stop for the anisotropic etch.
In
FIG. 4
, each line
204
includes opposed side surfaces
204
s
, a top surface
204
t
, opposed face surfaces
204
f
, and edges
204
e
. A space
206
separates each line
204
. Typically, the imprint stamp
200
is made from a material such as silicon (Si). For example, the substrate
211
can be a silicon wafer and the line and space features (
204
,
206
) can be made from silicon (Si) or polysilicon (&agr;-Si). Silicon is the material of choice for nano-imprint stamps because there are well established microelectronics processes for manufacturing silicon based structures and circuits, and because silicon is readily available at a reasonable cost.
However, one of the disadvantages of the prior imprint stamp
200
is that silicon is a soft material and is subject to breakage, damage, and wear from repeated pressing steps into the mask layer
203
. In
FIG. 4
, a section E—E of the line feature
204
is particularly subject to wear, damage, and breakage due to repeated pressing steps. In
FIG. 5
, an enlarged view of the section E—E of
FIG. 4
illustrates that the edges
204
e
, the top surface
204
t
, the side surfaces
204
s
, and the face surfaces
204
f
are particularly susceptible to wear W from only a few pressing with the mask layer
203
.
In
FIG. 6
, the imprint stamp
200
is pressed
201
into the mask layer
203
so that the line features
204
are disposed in the mask layer
203
. Repeated pressing steps cause wear, damage, and breakage denoted as W at the edges
204
e
and the top surface
204
t
of the line features
204
. Only ten or fewer pressing steps can result in the imprint stamp
200
wearing to the point where it can no longer be used to form consistent, repeatable, and accurate imprint patterns
209
.
In
FIGS. 7
a
and
7
b
,a more detailed view of the wear to the line features
204
shows that the wear is most severe along the edges
204
e
and top surface
204
t
as those portions of the line features
204
contact the mask layer
203
first and have surface features that are substantially normal to the direction of pressing
201
. Accordingly, as illustrated in
FIGS. 8
a
and
8
b
, the line feature
204
quickly deteriorates from the ideal line feature
204
of
FIG. 8
a
to the worn out line features
204
of
FIG. 8
b
after only a few pressing cycles with the mask layer
203
.
Fabrication of the imprint stamp
200
is one of the most crucial and most expensive steps in the entire imprinting lithography process. Another disadvantage of the prior imprint stamp
200
is that a cost of manufacturing the imprint stamp
200
is not recouped because the imprint stamp
200
is damaged and/or wears out before an adequate number of pressing steps required to justify the manufacturing cost of the imprint stamp
200
can occur. Accordingly, the prior imprint stamp
200
is not economical to manufacture.
Consequently, there exists a need for a nano-size imprinting stamp that is resistant to wear, damage, and breakage. There is also an unmet need for a nano-size imprinting stamp that can retain consistent, repeatable, and accurate imprint patterns over multiple pressing steps so that the cost of manufacturing the nano-size imprinting stamp is recovered.
SUMMARY OF THE INVENTION
The micro-casted silicon carbide nano-imprinting stamp of the present invention solves the aforementioned disadvantages and limitations of the prior nano-imprinting stamps. The micro-casted silicon carbide nano-imprinting stamp of the present invention is stronger and tougher because silicon carbide is used as the material for the imprint stamp as opposed to the silicon material of the prior nano-imprinting stamps.
The micro-casted silicon carbide nano-imprinting stamp of the present invention has an increased service lifetime; therefore, the cost of manufacturing the micro-casted silicon carbide nano-imprinting stamp can be recovered because the stamp can withstand many pressing cycles without wearing out, breaking, or being damaged, unlike the prior nano-imprinting stamps that are made from silicon.


REFERENCES:
patent: 2003/0071016 (2003-04-01), Shih et al.

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