Reflection photomasks including buffer layer comprising...

Details Reflection photomasks including buffer layer comprising... Reflection photomasks including buffer layer comprising...

2001-10-12

2004-03-02

Rosasco, S. (Department: 1756)

Radiation imagery chemistry: process, composition, or product th

Radiation modifying product or process of making

Radiation mask

Reexamination Certificate

active

06699625

ABSTRACT:

RELATED APPLICATIONS
This application claims the benefit of Japanese Patent Application No. 2000-314292, filed Oct. 13, 2000, the disclosure of which is hereby incorporated herein by reference in its entirety as if set forth fully herein.
FIELD OF THE INVENTION
This invention relates to reflection photomasks that are used for integrated circuit manufacturing, and more particularly to reflection photomasks that are used with extreme ultraviolet radiation for integrated circuit manufacturing and methods of manufacturing and using the same.
BACKGROUND OF THE INVENTION
As integration densities of integrated circuit devices continue to increase, it may become increasingly difficult to fabricate fine linewidths using conventional photomasks. Thus, for example, exposure of a pattern size of about 250 nm may be performed using Deep UltraViolet (DUV) radiation at, for example, 248 nm. Moreover, other DUV technologies, which can use a radiation source of shorter wavelength than about 193 nm, can decrease the pattern size to between about 100 and about 130 nm. In order to expose pattern sizes of less than about 100 nm, for example pattern sizes of about 5 to about 70 nm, exposure wavelengths in the Extreme UltraViolet (EUV) region, also referred to as the “soft X-ray region”, may be used. EUV radiation may cover wavelengths of between about 10 nm to about 14 nm, for example about 13.4 run to about 13.5 nm.
EUV exposure may use a reflection photomask in contrast with conventional transmission photomasks, since many materials may have a large optical absorptivity in the EUV region. In general, an EUV reflection photomask may be obtained by forming a pattern in an absorber, which can absorb EUV radiation, on a reflection mirror having large reflectivity in the EUV region. Thus, the regions in which the surface of the reflection mirror is covered with the absorber pattern become absorption regions, and the regions in which the surface of the reflection mirror is exposed become reflection regions. The reflection layer generally comprises a plurality of alternating films comprising first and second materials, such as Mo/Si and/or Be/Si.
FIG. 11
shows an embodiment of a conventional reflection photomask
110
. A reflection layer
112
comprising a multi-layer film is formed on a substrate
111
such as a silicon and/or glass substrate. An absorber pattern
113
for EUV rays which comprises, for example, a TaN film having a predetermined pattern, is formed on the reflection layer
112
.
However, when directly forming the absorber pattern
113
on the reflection layer
112
, as shown in
FIG. 11
, the exposed portion of the surface of the reflection layer
112
may be etched and/or damaged, during patterning (etching) of the absorber. This damage may reduce the reflectivity.
As shown in
FIG. 16
, the above defects may be reduced or eliminated using Focused Ion Beams (FIB). For example, in
FIG. 16
, an etching residue portion
113
a
in the absorber pattern at the left side and a damaged portion
113
b
in an adjacent absorber pattern may be generated during patterning of the absorber pattern
113
. FIB can locally remove only the residue portion
113
a
by an etching operation. The damaged portion
113
b
of the pattern also may be locally traced by the absorber and buried by irradiating the FIB at a predetermined gas atmosphere. This process often is referred to as a mask repair process. Unfortunately, however, in the structure shown in
FIG. 11
, the FIB irradiation itself can damage the surface of the reflection layer during the mask repair process.
Damage can be reduced when patterning the absorber as described in Hoshino et al.,
Process Scheme for Removing Buffer Layer on Multilayer for EUVL Mask
, Proceedings of the SPIE, Vol. 4066, July 2000, pp. 124-130, the disclosure of which is hereby incorporated herein by reference in its entirety as if set forth fully herein. For example, as shown in
FIG. 12
herein, a buffer layer
123
comprising an SiO
x
film is formed under an absorber pattern
124
in a photomask
120
. When the photomask
120
is manufactured, a reflection layer
122
comprising a multi-layer film is formed on a substrate
121
, as shown in
FIG. 13A. A
buffer layer
123
a
is formed on the reflection layer
122
, as shown in FIG.
13
B. An absorber layer
124
a
is formed on the buffer layer
123
a
, as shown in FIG.
13
C.
As shown in
FIG. 13D
, the absorber pattern
124
is formed by patterning the absorber layer
124
a
by photolithography. A two stage etching method is used for patterning. First, dry etching is performed. In particular, the buffer layer
123
a
is etched after the absorber layer
124
a
, as shown in FIG.
13
E. Etching is stopped in a state where the buffer layer
123
a
still remains. Wet etching is then performed. In particular, the surface of the reflection layer
122
is exposed by completely removing the remaining buffer layer
123
a
, as shown in FIG.
13
F. Accordingly, it is possible to reduce the amount of over-etching of the surface of the reflection layer by using a wet etching process having etching selectivity higher than that of the dry etching.
Damage also can be reduced when pattering the absorber as described in Mangat et al.,
EUV Mask Fabrication With Cr Absorber
, Proceedings of the SPIE, Vol. 3997, July 2000, pp. 76-82, the disclosure of which is hereby incorporated herein by reference in its entirety as if set forth fully herein. For example, as shown in
FIG. 14
herein, in a photomask
140
, a buffer layer
144
comprising an SiON film is formed under an absorber pattern
145
. Furthermore, an etch stop layer
143
, comprising a Cr film of about 10 nm in thickness, is formed under the buffer layer
144
. When the photomask
140
is manufactured, a reflection layer
142
comprising a multi-layer film is formed on a substrate
141
, as shown in FIG.
15
A. An etch stop layer
143
a
is formed on the reflection layer
142
, as shown in
FIG. 15B. A
buffer layer
144
a
is formed on the etch stop layer
143
a
, as shown in FIG.
15
C. An absorber layer
145
a
is further formed on the buffer layer
144
a
, as shown in FIG.
15
D.
After forming the absorber pattern
145
by patterning the absorber layer
145
a
by photolithography, as shown in
FIG. 15E
, the buffer layer
144
a
is etched, as shown in FIG.
15
F. Since the etching selectivity of the SiON film can be high with respect to Cr, etching of the buffer layer
144
a
can stop at the surface of the etch stop layer
143
a
. As shown in
FIG. 15G
, the surface of the reflection layer
142
is exposed by removing the etch stop layer
143
a
. Accordingly, the surface of the reflection layer may not be over-etched during etching of the buffer layer by using the etch stop layer.
Unfortunately, the Hoshino et al. technique may use a complicated two-stage etching. It may be difficult to control the dry/wet etching process and the surface of the reflection layer may be damaged.
Moreover, the Mangat et al. technique also may complicate fabrication due to the etch stop layer. It may be possible to prevent the surface of the reflection layer from being over-etched during etching of the buffer layer by forming the etch stop layer. However, the surface of the reflection layer may be over-etched when the etch stop layer is removed subsequently. For example, when the etch stop layer comprising Cr remains on the reflection region, the etch stop layer may need to be removed since the optical absorptivity of the Cr film is strong and reflection on the surface of the reflection layer may be reduced. However, since etching selectivity of Cr with respect to the surface of the reflection layer may be low, the surface of the reflection layer may be over-etched.
SUMMARY OF THE INVENTION
Reflection photomasks, according to some embodiments of the invention, add a buffer layer comprising at least one Group VIII metal between the reflection layer and the absorber pattern that is configured to absorb extreme ultraviolet rays therein. In particular, some embodiments of reflection photomasks accord

Affiliated with

Also associated with

Rating

Reflection photomasks including buffer layer comprising... does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Reflection photomasks including buffer layer comprising..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Reflection photomasks including buffer layer comprising... will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3214666