Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2000-10-24
2002-06-11
Chaudhari, Chandra (Department: 2813)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S618000, C430S030000, C430S311000
Reexamination Certificate
active
06403477
ABSTRACT:
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to a method for correcting an optical proximity effect and, more particularly, to an optical proximity effect correction method for correcting the shape of a corner portion of a mask interconnect pattern to be transferred onto a photoresist film by a photolithographic technique.
(b) Description of the Related Art
Along with reduction in design rule for semiconductor devices, patterns for forming the semiconductor devices, such as patterns for gate electrodes, interconnect layers and contact holes, have been more and more reduced in the dimensions thereof Accordingly, mask patterns formed on an exposure mask, which are used for patterning the gate electrodes, interconnect layers and contact holes by photolithography, have also been more and more reduced in the dimensions thereof.
In an optical exposure in photolithography, When a mask pattern which has been reduced in dimensions to a degree close to the critical resolution of an exposure system is exposed and transferred onto a photoresist film, or the like, adjacent light beams optically interfere with each other during forming finely patterned regions which are in close proximity to each other. As a result, the exposed image is distorted. Thus, it is not possible to precisely transfer the mask pattern of the exposure mask. Generally, this is called an “optical proximity effect”.
If an optical proximity effect occurs in the exposure transfer process, the design pattern cannot be precisely transferred onto the photoresist film by using the mask pattern, whereby it is not possible to obtain device characteristics as desired in the design stage of the semiconductor device.
In view of the above, the mask pattern is generally subjected to a correction for compensating for the optical proximity effect in order to suppress the optical proximity effect and thus to precisely transfer the mask pattern of the exposure mask onto the photoresist film.
Now, referring to some of attached drawings, the phenomenon of an optical proximity effect and a correction method therefor will be briefly described.
FIGS. 1A and 1B
are schematic diagrams respectively illustrating a mask interconnect pattern of an exposure mask, and an actual interconnect pattern which has been distorted by the optical proximity effect after exposing and transferring the mask interconnect pattern onto a photoresist film.
FIGS. 2A and 2B
are schematic diagrams respectively illustrating a mask interconnect pattern which has been corrected so as to compensate for the optical proximity effect, and an actual interconnect pattern obtained therefrom.
A desired design interconnect pattern, i.e., a mask interconnect pattern
11
of an exposure mask which is in a predetermined relationship with (e.g., in a constant dimensional proportion to) the desired design interconnect pattern, is an L-shaped pattern having a straight portion
12
and a corner portion
13
which is bent in a direction at 90° with respect to the straight portion
12
, as illustrated in
FIG. 1A
, and the pattern is arranged so that the corner portion
13
of the interconnect pattern
11
is positioned above a contact hole
14
. The outer corner located at the outer periphery of the corner portion
13
has a bend angle &thgr;
1
of 90° as measured from within the interconnect pattern
11
, and is the inner corner located at the inner periphery of the corner portion
13
has a bend angle &thgr;
2
of 270°.
When the mask interconnect pattern
11
as illustrated in
FIG. 1A
is exposed and transferred onto the photoresist film, the interconnect pattern
16
obtained by the transfer process has round corners on the outer and inner peripheries of each of the corner portions
13
. That is, each corner of the corner portion
13
is rounded by the optical proximity effect, as illustrated in
FIG. 1B
, thereby causing a deviation with respect to the contact hole
14
. As a result, the contact area between the interconnect pattern
16
and the contact hole pattern
14
is reduced, whereby the contact resistance may increase and even a connection failure may occur therebetween.
In view of the above, a mask pattern having such a correcting pattern as to compensate for the optical proximity effect is used in the conventional technique in order to suppress the optical proximity effect.
For example, in Japanese Patent Laid-Open Publication No. Sho-10-229124, in order to suppress the above-described optical proximity effect, an additional correction pattern
17
or an “L”-shaped additional pattern is added to the outer corner of the corner portion
13
of the mask interconnect pattern
11
, and a cutout correction pattern
18
or a “L”-shaped cutout pattern is provided on the inner corner of the corner portion
13
.
By using such an exposure mask having a mask interconnect pattern for which the optical proximity effect has been corrected, it is possible to obtain a transferred interconnect pattern
19
close to the desired mask interconnect pattern
11
, as illustrated in FIG.
2
B.
The respective dimensions of the additional correction pattern and the cutout correction pattern which are provided in the mask pattern of the exposure mask in order to provide the correction of the optical proximity effect are determined by experiments, etc., for each of desired L-shaped interconnect patterns.
For example, as for the cutout correction pattern
20
provided on each inner corner of the corner portion
13
shown in
FIG. 3
, the cutout correction pattern
20
is generally an “L”-shaped pattern having two legs extending in two directions along the inner periphery of the corner portion
13
. The two legs of the “L”-shaped pattern
20
meet each other at a right angle, and have a length of L and a width of W, as illustrated in FIG.
3
.
The dimensions L and W of the cutout correction pattern are predetermined by experiments, etc., for each of the process conditions and the widths of the interconnects to be used, so as to eliminate the optical proximity effect as much as possible by providing a suitable correction. These dimensions are recited in a so-called “optical proximity effect correction rule”.
An interconnect pattern provided in a semiconductor device is basically formed by an L-shaped pattern which includes a straight portion and a corner portion. An ordinary interconnect pattern has generally no outer corner or inner corner having a bend angle other than 90° and 270°. Thus, for the purpose of designing and fabricating semiconductor devices, it is practically correct that any outer corner formed at the outer periphery of the corner portion has a bend angle of 90° and an inner corner formed at the inner periphery of the corner portion has a bend angle of 270°.
Therefore, in the conventional technique, when providing an optical proximity effect correction for a mask interconnect pattern, a cutout correction pattern having predetermined dimensions was equally applied to the inner corner portion of the corner portion of L-shaped interconnect pattern with reference to the predefined optical proximity effect correction rule.
For example, when designing a mask interconnect pattern for representing a simulation design interconnect pattern
22
as illustrated in
FIG. 4
, the design interconnect pattern
22
is scanned along the layout of the design interconnect pattern. In this process, each time one of corner portions
23
to
31
is extracted, a cutout correction pattern and an additional correction pattern based on to the optical proximity effect correction rule is automatically and equally provided to the inner corner and the outer corner of the one of the extracted corner portions
23
to
31
.
In
FIG. 4
, numeral
32
denotes a straight portion between adjacent corner portions
24
and
25
, numeral
33
denotes a straight portion between adjacent corner portions
27
and
28
, numeral
34
denotes a straight portion between adjacent corner portions
30
and
31
, and numeral
35
denotes a diffused region. Each of the straight portion
32
betw
Chaudhari Chandra
McGinn & Gibb PLLC
Smoot Stephen W.
LandOfFree
Method for correcting an optical proximity effect in an... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for correcting an optical proximity effect in an..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for correcting an optical proximity effect in an... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2934149