Radiation imagery chemistry: process – composition – or product th – Radiation modifying product or process of making – Radiation mask
Reexamination Certificate
1999-10-28
2003-01-07
Huff, Mark F. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Radiation modifying product or process of making
Radiation mask
Reexamination Certificate
active
06503665
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a phase shift mask and a technique relevant thereto, and more specifically, it relates to a shading member provided on a phase shift mask employed for a step of exposing a semiconductor device.
2. Description of the Background Art
FIG. 10
schematically illustrates the structure of an exposure unit employed for a conventional step of exposing a semiconductor device. In this exposure unit, an exposure light source
21
emits exposure light
22
having a prescribed exposure wavelength. The emitted exposure light
22
is transmitted through condenser lenses
23
a
and
23
b
, and the exposure area thereof is adjusted by a blind
24
.
The exposure light
22
having the adjusted exposure area is transmitted through condenser lenses
23
c
and
23
d
, and thereafter transmitted through a phase shift mask (including a reticle mask throughout the specification)
25
formed with a prescribed pattern layout.
The exposure light
22
transmitted through the phase shift mask
25
is adjusted to a prescribed exposure area by projection lenses
26
a
and
26
b
and an NA diaphragm
28
, and thereafter exposes a semiconductor substrate
14
placed on a stage
30
.
The semiconductor substrate
14
is sequentially formed with exposed areas
31
and
32
due to X-Y directional movement of the stage
30
(step-and-repeat system), and the pattern layout of the phase shift mask
25
is exposed over the entire surface of the semiconductor substrate
14
.
The pattern layout of the phase shift mask
25
is roughly classified into an LSI circuit pattern area
27
and a non-exposed area
20
. The LSI circuit pattern area
27
is formed with a pattern structure by a phase shift method capable of exposing a fine pattern, in order to satisfy the recent requirement for refinement of semiconductor devices.
With reference to FIGS.
11
(A) and
11
(B), the basic principle of a halftone phase shift method, representing the phase shift method, is now described. FIG.
11
(A) is a sectional view of a halftone phase shift mask, and FIG.
11
(B) illustrates the intensity of exposure light transmitted through the halftone phase shift mask on a semiconductor substrate.
Referring to FIG.
11
(A), a transmission area
34
and a phase shifter area
33
are formed on a transparent substrate
4
in this halftone phase shift mask. Part of the exposure light transmitted through the phase shifter area
33
is so adjusted that the phase thereof is converted by 180° and the transmittance is about 2 to 40% with respect to that transmitted through the transmission area
34
. Thus, in the exposure light transmitted through the halftone phase shift mask having the structure shown in FIG.
11
(A), light components 180°
0
out of phase overlap and cancel with each other in the vicinity of the boundary between the phase shifter area
33
and the transmission area
34
. Consequently, an area having light intensity of zero is formed in the vicinity of the boundary between the phase shifter area
33
and the transmission area
33
, as shown on a light intensity curve
35
in FIG.
11
(
b
).
The intensity of the part of the exposure light transmitted through the phase shifter area
33
is adjusted to a level (line L
1
in FIG.
11
(B)) not exposing a target film provided on the semiconductor substrate, by adjusting the transmittance of the phase shifter area
33
. Thus, exposure of a fine pattern corresponding to the transmission area
34
provided on the halftone phase shift mask is enabled.
A halftone phase shift mask employing this halftone phase shift method is now described with reference to
FIGS. 12 and 13
.
FIG. 12
is a plan view of the halftone phase shift mask, and
FIG. 13
is a sectional view taken along the line X-X′ in FIG.
12
.
This halftone phase shift mask includes an LSI circuit pattern area
2
, a strip-shaped shading zone area
3
provided to enclose the LSI circuit pattern area
2
, and a non-exposure area
13
provided to enclose the shading zone area
3
.
The LSI circuit pattern area
2
is formed with an LSI circuit pattern employing the aforementioned halftone phase shift method. The shading zone area
3
is provided for shading light leaking through a clearance defined between the LSI circuit pattern area
2
and the blind
28
described with reference to FIG.
10
.
The principle of shading with the shading zone area
3
is now described with reference to
FIGS. 14 and 15
.
FIG. 14
is an enlarged plan view of a region enclosed with a circle A in
FIG. 12
, and
FIG. 15
is a sectional view taken along the line X-X′ in FIG.
14
.
The shading zone area
3
, formed by shading parts
3
a
and Hall patterns
3
b
of the same material as a phase shifter area (not shown) forming the LSI circuit pattern area
2
employing the halftone phase shift method, can reduce the intensity of exposure light transmitted therethrough to a level not exposing a target film due to the function/effect of the halftone phase shift method. The size of each Hall pattern
3
b
is set smaller than that of the pattern of the resolution limit of the exposure unit so that each side is several &mgr;m, for example. Therefore, the exposure light transmitted through the shading zone area
3
forms no image.
Consequently, the shading zone area
3
can substantially prevent the exposure light transmitted therethrough from leakage, for serving as a shading film.
The semiconductor substrate
14
is sequentially formed with the exposed areas
31
and
32
by the step-and-repeat system as described with reference to
FIG. 10
, so that a pattern
17
of the phase shift mask
25
is exposed over the entire surface of the semiconductor substrate
14
as shown in FIG.
16
.
As shown in
FIG. 17
, areas E irradiated with the exposure light transmitted through the shading zone area
3
are formed around a pattern
17
a
. When the pattern
17
of the phase shift mask
25
is sequentially exposed in the step-and-repeat system in order of the pattern
17
a
, a pattern
17
b
, a pattern
17
c
and a pattern
17
d
, for example, there are formed areas
15
a
where the areas E overlap with adjacent patterns and areas
15
b
where the areas E of four patterns overlap with each other.
In each area
15
a
, another area E is exposed (single exposure) on the original pattern exposure. In each area
15
b
, other three areas E are exposed (triple exposure) on the original exposure. Thus, particularly the area
15
b
is irradiated with exposure light having intensity exposing the target film as a result, to exert influence on the original pattern
17
.
Considering this in view of the halftone phase shift mask, it follows that the halftone phase shift mask latently has areas
18
causing single exposure on linear portions of the shading zone area
3
and areas
19
causing triple exposure on corner portions of the shading zone area
3
, as shown in FIG.
18
. In this regard, there has been proposed a countermeasure of providing shading members
36
preventing transmission of exposure light on the areas
19
causing triple exposure, to be enclosed with corner portions of the shading zone area
3
as shown in FIG.
19
.
However, this countermeasure is unpractical due to remarkable influence on the size of the fabricated semiconductor device.
If the shading members
36
are not formed on the shading zone area
3
but separately prepared and bonded with an adhesive or the like, the shading members
36
come into contact with both of a glass substrate
4
and the shading zone area
3
having different thermal expansion coefficients. When the glass substrate
4
and the shading zone area
3
are thermally expanded respectively, therefore, the shading members
36
are disadvantageously warped.
When the shading members
36
are provided to be enclosed with the corner portions of the shading zone area
3
, a shading zone of a different size must be prepared for every phase shift mask since the size of the LSI circuit pattern area
2
varies with the phase shift mask.
While the Hall
Huff Mark F.
McDermott & Will & Emery
Mohamedulla Saleha R.
LandOfFree
Phase shift mask and semiconductor device fabricated with... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Phase shift mask and semiconductor device fabricated with..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Phase shift mask and semiconductor device fabricated with... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3053374