Pellicle

Details Pellicle Pellicle

1999-10-12

2001-10-16

Thomas, Alexander S. (Department: 1772)

Stock material or miscellaneous articles

Display in frame or transparent casing; or diorama including...

Peripheral enclosure or frame

C430S005000

Reexamination Certificate

active

06303196

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a pellicle which is bonded to a mask used in a photolithography process to protect the mask which process is a part of method for semiconductor integrated circuit fabrication.
2. Description of the Related Art
A mask is an original plate of a circuit pattern used for the transfer of a circuit pattern of a semiconductor integrated circuit onto a wafer, that is, the mask is a glass substrate having an original circuit pattern fabricated of opaque thin membrane formed thereon. To transfer the circuit pattern onto the wafer, the mask is set above a wafer, then ultra violet light, X-rays or the like are irradiated onto the mask.
When foreign matter such as dust is adhering to the mask, the exact shape of the shadow of the foreign matter is transferred onto the wafer. Subsequently, defects are made in the circuit pattern transferred onto the wafer, resulting in a lowering of the reliability of the semiconductor integrated circuit. To prevent adhesion of foreign matter like this to the mask, a structure having a transparent protective membrane, called a pellicle, is mounted to the mask surface.
FIG. 3
is a partially sectional view showing a structure of a conventional pellicle. As shown in
FIG. 3
, a pellicle
30
comprises a pellicle membrane
31
which is a protective membrane fabricated from a transparent member, a pellicle frame
32
to hold the pellicle membrane
31
at a predetermined distance away from a surface of a mask
34
, and an adhesive
33
to fix the pellicle frame
32
to the surface of the mask
34
. The pellicle membrane
31
is fabricated from a transparent thin membrane formed from nitrocellulose or the like, and prevents adhesion of foreign matter from outside onto the surface of the mask
34
by being fixed at a predetermined distance away from the surface of the mask. Even when foreign matter does adhere to the pellicle membrane
31
, the shadow of the foreign matter is not transferred onto the wafer because the shadow of the foreign matter adhering to the pellicle membrane
31
is out of focus during exposure of the wafer since the pellicle membrane
31
and the mask
34
are spaced apart.
To mount this type of pellicle
30
to the mask
34
, first, a side of the pellicle
30
with the adhesive
33
applied thereto and a surface of the mask
34
having an original circuit pattern formed thereon, are positioned face-to-face. Then, the pellicle
30
is press-adhered to the mask
34
by the application of a force against the mask
34
from above the pellicle
30
.
However, when this type of pellicle
30
is fixed to the mask, the adhesive
33
is squeezed out due to the pressure applied to the pellicle
30
, and a part of the adhesive
33
from an end surface of the pellicle frame
32
adheres to the surface of the mask on the inside and outside of the pellicle frame
32
.
FIG. 4
is a schematic sectional view showing the squeezed adhesive
33
′ adhering to the surface of the mask
34
inside the pellicle frame
32
. The adhesive
33
′ adhering to the surface of the mask
34
inside the pellicle frame
32
, as shown in
FIG. 4
, deteriorates due to exposure to the light from an exposure apparatus and loses its tackiness, and may move near to the original pattern of the mask due to vibration during transportation of the mask or the like. The problem has arisen that this deteriorated adhesive
33
′ causes defects in the mask
34
by adhering to the original pattern of the mask
34
.
In order to solve this type of problem, the technology described in Japanese Patent Application Laid-Open (JP-A) No. 6-19124 provides a pellicle such as that shown in
FIG. 5
(
FIG. 5
shows a pellicle which is mounted to the opposite surface of the mask to that in FIG.
4
). A groove
41
a
is formed on an end surface of a pellicle frame
41
facing a mask
43
, and a pellicle is fixed to the mask
43
by an adhesive with which the groove
41
a
is filled. By utilizing this structure, bleeding of the adhesive onto the mask
43
inside the pellicle frame
41
is prevented.
However, in the pellicle structure described in the aforementioned JP-A-No. 6-19124, the problem has been that it is difficult to adjust the amount of the adhesive
42
to be placed in the groove
41
a.
For example, too small an amount of the adhesive
42
makes it difficult to sufficiently fix the pellicle on the surface of the mask
43
because the adhesive
42
is not able to fully contact the mask
43
. On the other hand, too large an amount of the adhesive
42
causes problems with the adhesive
42
being pushed out all over the end surface of the pellicle frame
41
from the groove
41
a
upon pressing the pellicle against the mask
43
, and the pushed-out adhesive
42
adheres to the mask
43
on the inside and outside of the pellicle frame
41
. There has been a further problem that when the adhesive
42
is placed in the groove
41
a
like this, the bonding area of the mask
43
and the adhesive
42
in the state shown in
FIG. 5
is too small for a sufficient bond strength to be obtained.
The aim of the present invention, therefore, is to provide a pellicle which does not cause lowering of reliability of the mask due to the adhesion of adhesive pushed out from a pellicle frame to a surface of a mask when fixing the pellicle to the mask.
SUMMARY OF THE INVENTION
The pellicle of the present invention is a pellicle stretched between a predetermined position and a surface of a mask, on the surface of which is formed an original pattern for transferring a circuit pattern onto a wafer using a photolithographic method, in order to prevent the adhesion of foreign matter to the original pattern formed on the surface of the mask, wherein the pellicle is provided with a pellicle frame. The pellicle includes a pellicle membrane that is transparent to exposure light, and a frame-shaped structure. The frame structure has a surface at a first end adhering to the periphery of the pellicle membrane and a surface of a second end adhering to the mask. The frame also has a notch portion running in the peripheral direction of the surface at the second end surface for allowing adhesive used during an adhesion process to escape in the peripheral direction.
Namely, the pellicle of the present invention has a notch formed along the peripheral direction of a surface of the pellicle frame, which surface is to be bonded to the mask. By applying the adhesive to the notch, the adhesive can be released to the outside when mounting the pellicle to the mask, so that adhesion of the adhesive to the original pattern of the mask can be prevented.
When adopting a pellicle with this type of structure, the notch may be a tapered surface that is sloped at a predetermined angle to the mask. Also, the notch may be shaped so as to have an arcuate sectional form.
When adopting a pellicle with this type of structure, said notch may be a tapered surface which is sloped at a predetermined angle to said mask. Also, the notch may be shaped so as to have an arcuate sectional form.


REFERENCES:
patent: 5820950 (1998-10-01), Wang

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