Computer-aided design and analysis of circuits and semiconductor – Nanotechnology related integrated circuit design
Reexamination Certificate
2001-04-19
2003-02-11
Phan, Trong (Department: 2818)
Computer-aided design and analysis of circuits and semiconductor
Nanotechnology related integrated circuit design
C716S030000
Reexamination Certificate
active
06519759
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a photomask pattern shape correction method to the photomask pattern shape correction method for modifying and correcting a pattern deformation, and a corrected photomask.
DESCRIPTION OF THE RELATED ART
Conventionally, a photomask pattern shape correction method is, for example, applied to modification and correction of a pattern deformation which is caused in a pattern formed with photolithography (photo etching) by the optical proximity effect of the optical system at the time of its formation.
The conventional photomask pattern shape correction method is shown in FIG.
1
. When a wiring layer of an angle
3
is to be corrected, a correction figure (A)
31
, a correction figure (B)
32
are added for correction by putting a notch
33
on the corner
3
. The size of the correction figure (A)
31
and the correction figure (B)
32
is set to the same dimensions of a size a
3
and a size b
3
. Moreover, a gate width W, and an interval G
1
and an interval G
2
between the correction figures are not taken into consideration when the correction figures are added.
SUMMARY OF THE INVENTION
However, the photomask formation of the above described conventional correction figure is accompanied by a problem that the shape of a photoresist is not correctly formed under a predetermined condition by means of optical proximity effect.
Against the above described problem thus arisen, an addition of a suitable correction figure is required. As an example, a photoresist shape example is shown in FIG.
2
. In the correction method applied in the
FIG. 2
, a large size of the correction figure maximizes the effect of reducing a roundness of the corner
3
of a wire resist pattern
55
of
FIG. 2
in the photoresist attributable to the optical proximity effect. As a result, taper
51
is produced which make a part of the gate portion to taper, causing adverse effects. When the correction figure is made small so as not to cause any adverse effect, there arises the problem that the roundness of the wire resist pattern
55
in the photoresist at the corner portion is not sufficiently made small and the correction of the optical proximity effect is not sufficiently obtained.
Moreover, when the wiring width is small and the interval between the correction figures is narrow, the taper
52
of the photoresist becomes large, thereby raising a new problem that a risk of disconnecting the wire is committed.
FIG. 2
shows that one side (edge) of the wiring width narrowing is considered only. However, in general the narrowing of the wiring width is caused in both sides of wiring layer, thereby the wiring layer width is much narrower.
It is the object of the present invention to provide the photomask pattern shape correction method for suitably modifying and correcting the pattern deformation (narrowing, rounding or the like) caused by the optical proximity effect.
In order to achieve such an object, the photomask pattern shape correction method of the invention is characterized in that, in the photomask pattern shape correction method of the wiring layer wherein correcting a photomask pattern on corner portions of a wiring layer by a optical proximity effect, said corner portions corresponding to exterior angles of said wiring layer except for any angle of approximate 180°, wherein
a first correction figure is applied when a distance between said corner portion and a gate electrode is within a predetermined range of distance; and
a second correction figure is applied when the distance between said corner portion and said gate electrode is over the predetermined range of distance.
Moreover, the size of the correction figure which determines whether a correction figure is to be added depending on the width of the above described pattern gate, the interval between the gates, the interval between the correction figures and the size of the wiring pattern width may take the size of the correction figure for an edge in the same direction as the gate direction and the size of the correction figure for the edge in the different direction from the gate direction as mutually different size, and the size of the correction figure for the edge in the same direction as the gate direction may be made smaller than the size of the correction figure for the edge in the different direction from the gate direction, or only the correction figure of the different direction from the gate direction may be formed and the correction figure for the edge of the same direction as the gate direction may be not formed.
The photomask pattern shape correction method of the invention according to claim
6
is characterized in that it comprises a step (S
1
) of extracting an corner (
1
) where the exterior angle of the wiring layer pattern is an angle of 90 degrees, which is out of the diffusion layer and where the distance from the gate is within a predetermined value (Rm) and the interval between the gates is equal to or more than the predetermined value (Pm), a step (S
2
) of adding a predetermined correction figure A to the edge in the gate direction of the extracted corner (
1
) and the correction figure B to the edge not in the gate direction respectively, a step (S
3
) of calculating the interval G
1
between the correction figure B and an adjacent correction figure, a step (S
4
) of checking whether the interval G
1
calculated at the step (S
3
) is equal to or more than the predetermined value (G
1
m) and a step (S
6
) of eliminating the correction figure A and the correction figure B when the result of the checking does not satisfy “G1>G1m”, thereby the formation of the correction figure A and the correction figure B is performed.
REFERENCES:
patent: 5350704 (1994-09-01), Anderson et al.
patent: 6099582 (2000-08-01), Haruki
patent: 6221539 (2001-04-01), Kotani et al.
patent: 6335981 (2002-01-01), Harazaki
patent: 6340542 (2002-01-01), Inoue et al.
Katten Muchin Zavis & Rosenman
NEC Corporation
Phan Trong
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