Radiation imagery chemistry: process – composition – or product th – Radiation modifying product or process of making – Radiation mask
Reexamination Certificate
2002-07-19
2004-05-11
Young, Christopher G. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Radiation modifying product or process of making
Radiation mask
C430S030000, C430S296000, C430S942000
Reexamination Certificate
active
06733932
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a mask lithography data generation method for manufacturing an electron beam exposure mask that is used when manufacturing a semiconductor device, and in particular to a mask lithography data generation method for lithography by a vector-type electron-beam exposing apparatus.
2. Description of the Related Art
During the manufacturing process of a semiconductor device, a process that forms the components of the semiconductor device by forming a pattern of a predetermined form in a thin conducting or insulating layer is performed as follows. First, a thin layer that is to be processed is formed. A resist is then formed as a layer on this thin layer and the resist is selectively exposed through electron beam (EB) lithography (wafer lithography) using a mask in which the predetermined pattern has been formed. After this, the resist is developed to selectively remove parts of the resist, thereby forming a resist pattern. The thin layer is then selectively removed by means such as etching with the resist pattern as a mask.
The mask used in wafer lithography mentioned above is also manufactured by EB lithography (mask lithography). In more detail, a resist is formed on a mask material, a pattern is drawn in the resist by an electron beam, and then the resist is developed to remove parts of the resist and so form a pattern. Means, such as etching or the like, is then used to selectively remove parts of the mask material, with the resist in which the pattern has been formed as a mask. By doing so, a mask in which a predetermined pattern has been formed is produced.
With the high integration of semiconductor devices in recent years, the patterns formed on wafers are becoming increasingly fine. As one example, the smallest dimensions for forming patterns are in the process of switching from 0.18 &mgr;m to 0.10 &mgr;m. As a result, the masks used of EB lithography need to be made increasingly fine.
When the masks used for EB lithography are made fine, however, there is the problem of the proximity effect causing decreases in the formation precision of the resist pattern.
FIG. 1A
is a plan view showing one example of a mask that is used during conventional EB lithography (wafer lithography), while
FIG. 1B
is a plan view showing the form of a resist pattern that is formed by this mask.
FIG. 2
is a plan view showing the form of the mask after correction. As shown in
FIG. 1A
, the mask
61
is provided with an opening
62
. The width A of the opening
62
is 400 nm, for example. When another opening, opening
63
, is formed at a position next to the opening
62
and a resist pattern is formed by performing lithography using the mask
61
with a projection magnification on the wafer of (¼) times, for example, the form of the resist pattern
64
, which corresponds to the opening
62
, is not a resemblance
62
a
of the opening
62
, and ends up narrower than the resemblance
62
a,
for example.
For this reason, the form of the opening
62
formed in the mask
61
is conventionally corrected in advance to become the opening
62
b,
as shown in FIG.
2
. The form of the opening
62
b
is produced by adding a corrective part
62
c
to the original opening
62
. The opening
62
may be 400 nm wide, for example, and the corrective part
62
c
may be 20 nm wide, for example. When lithography is performed at a projection magnification of (¼) times using this mask
61
, in the resist pattern formed on the wafer, the width of the region corresponding to the opening
62
is 100 nm, and the width of the region corresponding to the corrective part
62
c
is 5 nm.
EB exposing apparatuses include raster-type EB exposing apparatuses that perform lithography by scanning an electron beam and vector-type EB exposing apparatuses that divide a pattern into rectangles and shoot an electron beam separately at each rectangle. Of these, vector-type EB exposing apparatuses are capable of drawing with higher precision, so that vector-type EB exposing apparatuses are used when producing a mask by forming a fine pattern in a mask material. In order to manufacture a mask using a vector-type EB exposing apparatus, it is necessary to generate mask lithography data, in which the pattern for forming the mask is divided into rectangles, in advance. A mask is then manufactured by performing EB lithography (mask lithography) on a mask material based on this mask lithography data.
FIG.
3
A and
FIG. 3B
show a method of dividing the opening
62
b.
When EB lithography is performed using the mask
61
(see
FIG. 2
) in which the opening
62
b
has been formed, an electron beam is shot with the opening
62
b
having been divided into rectangles. As shown in
FIG. 3A
, one example of how the opening
62
b
can be divided divides the opening
62
b
into the opening
62
and the corrective part
62
c.
However, if the corrective part
62
c
is narrow, there is the problem that the width precision of the EB lithography falls.
FIG. 4A and 4B
are graphs showing the influence of the width of a rectangle produced by the division on the EB output characteristics, with the horizontal axis showing positions in the horizontal direction in a divided rectangle and the vertical axis showing the EB output.
FIG. 4A
shows the case of a rectangle whose width X is large, while
FIG. 4B
shows the case of a rectangle whose width X is small. As shown in
FIG. 4A
, when the width X of a rectangle is large, for example, 25 nm or more on the wafer, an approximately equal EB output is obtained across the width direction. Conversely, as shown in
FIG. 4B
, when the width X of a rectangle is small, for example, below 25 nm on the wafer, the EB output at the ends of the rectangle is low, with the EB output in the central part of the rectangle also falling. This is to say, there is a drop in the EB output characteristics. For this reason, there is a drop in the width precision of the EB exposure, so that the formation precision of the mask pattern also falls, resulting in a drop in the formation precision for semiconductor devices.
Due to the above, it is necessary to shoot the electron beam having divided the opening
62
b
without forming a shape with a narrow width (hereafter referred to as a “minute shape”), such as that shown in FIG.
3
A. As shown in
FIG. 3B
, dividing the opening
62
b
into the rectangles
68
a,
68
b,
and
68
c
does not produce any minute shapes, so that there is no fall in the EB output characteristics. Conventionally, methods of generating lithography data that divide mask patterns in this way to avoid producing any minute shapes are used.
FIG. 5
is a block diagram showing a conventional mask lithography data generation apparatus. As shown in
FIG. 5
, the conventional mask lithography data generation apparatus
50
includes a rectangle division processing unit
52
, a minute shape removal processing unit
53
, and a mask lithography data converting unit
55
. The following describes a conventional method of generating mask lithography data.
First, layout data
51
is generated. The layout data
51
is two-dimensional coordinate data showing the form of the opening
62
b
shown in
FIG. 2
, for example. Next, the layout data
51
is inputted into the rectangle division processing unit
52
, and a rectangle division process is performed on the layout data
51
. By doing so, a pattern corresponding to the opening
62
b
is divided as shown in
FIG. 3A
, for example, into a plurality of rectangles, or more specifically, the opening
62
and the corrective part
62
c.
At this point, the rectangle corresponding to the corrective part
62
c
has a narrow width, making it a minute shape.
Next, the layout data that has been subjected to the rectangle division process is inputted into the minute shape removal processing unit
53
. By doing so, the pattern divided into rectangles as shown in
FIG. 3A
is redivided into rectangles as shown in
FIG. 3B
, so as to remove the minute shape (the part corresponding to the corrective pa
Hamamoto Takeshi
Tonooka Youji
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