U.S. patent number RE42,294 [Application Number 10/819,338] was granted by the patent office on 2011-04-12 for semiconductor integrated circuit designing method and system using a design rule modification.
This patent grant is currently assigned to Kabushiki Kaisha Toshiba. Invention is credited to Soichi Inoue, Toshiya Kotani, Satoshi Tanaka.
United States Patent |
RE42,294 |
Kotani , et al. |
April 12, 2011 |
Semiconductor integrated circuit designing method and system using
a design rule modification
Abstract
A method for designing a semiconductor integrated circuit is
provided which comprises compacting a design layout of a
semiconductor integrated circuit on the basis of a given design
rule to obtain a compacted pattern, predicting a pattern to be
formed at a surface area of a wafer for forming the semiconductor
integrated circuit on the basis of the compacted pattern, obtaining
an evaluated value by comparing the predicted pattern with the
compacted pattern, deciding whether the evaluated value satisfies a
predetermined condition, and modifying the design rule when the
evaluated value is decided as not satisfying the predetermined
condition.
Inventors: |
Kotani; Toshiya (Sagamihara,
JP), Tanaka; Satoshi (Kawasaki, JP), Inoue;
Soichi (Yokohama, JP) |
Assignee: |
Kabushiki Kaisha Toshiba
(Kawasaki-shi, JP)
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Family
ID: |
18697788 |
Appl.
No.: |
10/819,338 |
Filed: |
April 7, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
09892572 |
Jun 28, 2001 |
06507931 |
Jan 14, 2003 |
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Foreign Application Priority Data
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Jun 30, 2000 [JP] |
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2000-199839 |
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Current U.S.
Class: |
716/106; 716/119;
716/136; 716/111 |
Current CPC
Class: |
G06F
30/398 (20200101) |
Current International
Class: |
G06F
17/50 (20060101); G06F 11/22 (20060101); G06F
9/455 (20060101) |
Field of
Search: |
;716/2,4-5,8-10 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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3-108738 |
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May 1991 |
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JP |
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8-287959 |
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Nov 1996 |
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JP |
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2854551 |
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Nov 1998 |
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JP |
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2000-182921 |
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Jun 2000 |
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JP |
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1996-35135 |
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Oct 1996 |
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KR |
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1999-62811 |
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Jul 1999 |
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KR |
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Other References
John L. Nistler et al., "Large Area Optical Design Rule Checker for
Logic PSM Application," SPIE vol. 2254 Photomask and X-Ray Mask
Technology (1994), pp. 78-83. cited by other .
Chaitali Sengupta et al., "An Integrated CAD Framework Linking VLSI
Layout Editors and Process Simulators," SPIE vol. 2726, (1996) pp.
244-253. cited by other.
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Primary Examiner: Whitmore; Stacy A
Attorney, Agent or Firm: Finnegan, Henderson, Farabow,
Garrett & Dunner, L.L.P.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
.Iadd.This application Ser. No. 10/819,338, filed Apr. 7, 2004, is
a reissue application of U.S. Pat. No. 6,507,931. A continuation of
this reissue application was filed on Oct. 4, 2007, and was
accorded application Ser. No. 11/905,862. .Iaddend.This application
is .Iadd.also .Iaddend.based upon and claims the benefit of
priority from the prior Japanese Patent Application No.
2000-199839, filed Jun. 30, 2000, the entire contents of which are
.Iadd.also .Iaddend.incorporated herein by reference.
Claims
What is claimed is:
1. A method for designing a semiconductor integrated circuit,
.Iadd.executed by a computer programmed to perform the method, the
method .Iaddend.comprising: compacting a design layout of a
semiconductor integrated circuit.Iadd., using a computer,
.Iaddend.on the basis of a given design rule .Iadd.of the
semiconductor integrated circuit .Iaddend.to obtain a compacted
pattern; predicting a pattern to be formed at a surface area of a
wafer for forming the semiconductor integrated circuit.Iadd., using
a computer, .Iaddend.on the basis of the compacted pattern;
obtaining an evaluated value.Iadd., using a computer, .Iaddend.by
comparing the predicted pattern with the compacted pattern;
deciding.Iadd., using a computer, .Iaddend.whether the evaluated
value satisfies a predetermined condition; and modifying the design
rule.Iadd., using a computer, .Iaddend.when the evaluated value is
decided as not satisfying the predetermined condition.
2. A method according to claim 1, wherein the pattern .Iadd.to be
.Iaddend.formed at a surface area of a wafer is predicted.Iadd.,
using a computer, .Iaddend.using data obtained by converting data
of the compacted pattern to mask data for photolithography or data
for electron beam lithography.
3. A method according to claim 1, wherein the pattern .Iadd.to be
.Iaddend.formed at a surface area of a wafer is predicted.Iadd.,
using a computer, .Iaddend.using at least one model selected from a
first prediction model, second prediction model and third
prediction model, the first prediction model being a model for
calculating a light exposed state of a resist on the wafer when the
compacted pattern is projected on the resist, the second prediction
model being a model for calculating a resist pattern configuration
after the resist has been developed, and the third prediction model
being a model for calculating a wafer surface configuration after
the wafer has been work-processed using the resist pattern.
4. A system .Iadd.having a computer readable medium including
instructions .Iaddend.for designing a semiconductor integrated
circuit, comprising: means for compacting a design layout of a
semiconductor integrated circuit on the basis of a given design
rule .Iadd.of the semiconductor integrated circuit .Iaddend.to
obtain a compacted pattern; means for predicting a pattern to be
formed at a surface area of a wafer for forming the semiconductor
integrated circuit on the basis of the compacted pattern; means for
obtaining an evaluated value by comparing the predicted pattern
with the compacted pattern; means for deciding whether the
evaluated value satisfies a predetermined condition; and means for
modifying the design rule when the evaluated value is decided as
not satisfying the predetermined condition.
5. A system according to claim 4, wherein the pattern .Iadd.to be
.Iaddend.formed at a surface area of a wafer is predicted using
data obtained by converting data of the compacted pattern to mask
data for lithography or data for electron beam lithography.
6. A system according to claim 4, wherein the pattern .Iadd.to be
.Iaddend.formed at a surface area of a wafer is predicted using at
least one model selected from a first prediction model, second
prediction model and third prediction model, the first prediction
model being a model for calculating a light exposed state of a
resist on the wafer when the compacted pattern is projected on the
resist, the second prediction model being a model for calculating a
resist pattern configuration after the resist has been developed,
and the third prediction model being a model for calculating a
wafer surface configuration after the wafer has been work-processed
using the resist pattern.
7. A .Iadd.non-transitory .Iaddend.computer readable .Iadd.storage
.Iaddend.medium .[.configured to store.]. .Iadd.encoded with a
computer program product storing .Iaddend.program instructions for
causing a computer to compact a design layout of a semiconductor
integrated circuit on the basis of a given design rule .Iadd.of the
semiconductor integrated circuit .Iaddend.to obtain a compacted
pattern, causing the computer to predict a pattern to be formed at
a surface area of a wafer for forming the semiconductor integrated
circuit on the basis of the compacted pattern, causing the computer
to obtain an evaluated value by comparing the predicted pattern
with the compacted pattern, causing the computer to decide whether
the evaluated value satisfies a predetermined condition, and
causing the computer to modify the design rule when the evaluated
value is decided as not satisfying the predetermined condition
.Iadd.the computer providing a modified design layout of a
semiconductor integrated circuit based on the modified design
rule.Iaddend..
.Iadd.8. A method for preparing a design rule for a semiconductor
integrated circuit, executed by a computer programmed to perform
the method, the method comprising: obtaining a pattern of a design
layout, using a computer, on the basis of a given design rule of
the semiconductor integrated circuit; predicting a pattern to be
formed at a surface area of a wafer for forming the semiconductor
integrated circuit, using a computer, on the basis of the obtained
pattern; obtaining an evaluated value, using a computer, by
comparing the predicted pattern with the obtained pattern; deciding
whether the evaluated value satisfies a predetermined condition,
using a computer; modifying the given design rule, using a
computer, when the evaluated value is decided as not satisfying the
predetermined condition; and determining the given design rule as a
fixed design rule for the semiconductor integrated circuit, using a
computer, when the evaluated value is decided as satisfying the
predetermined condition..Iaddend.
.Iadd.9. A method according to claim 8, wherein the pattern to be
formed at a surface area of a wafer is predicted, using a computer,
using data obtained by converting data of the obtained pattern to
mask data for photolithography or data for electron beam
lithography..Iaddend.
.Iadd.10. A method according to claim 8, wherein the pattern formed
at a surface area of a wafer is predicted, using a computer, using
at least one model selected from a first prediction model, a second
prediction model and a third prediction model, the first prediction
model being a model for calculating a light exposed state of a
resist on the wafer when the obtained pattern is projected on the
resist, the second prediction model being a model for calculating a
resist pattern configuration after the resist has been developed,
and the third prediction model being a model for calculating a
wafer surface configuration after the wafer has been work-processed
using the resist pattern configuration..Iaddend.
.Iadd.11. A layout used for producing a semiconductor integrated
circuit, comprising a layout pattern designed using the design rule
prepared by the method according to claim 8, instructions for
executing the method being stored on a computer readable medium,
wherein the layout is associated with the layout pattern produced
using the prepared design rule..Iaddend.
.Iadd.12. A layout according to claim 11, wherein the layout
pattern includes a standard cell pattern..Iaddend.
.Iadd.13. A layout according to claim 11, wherein the layout
pattern includes a pattern for placement and routing..Iaddend.
.Iadd.14. A method for designing a layout for a semiconductor
integrated circuit, executed by a computer programmed to perform
the method, the method comprising: obtaining a pattern of a design
layout, using a computer, on the basis of a given design rule of
the semiconductor integrated circuit; predicting a pattern to be
formed at a surface area of a wafer for forming the semiconductor
integrated circuit, using a computer, on the basis of the obtained
pattern; obtaining an evaluated value, using a computer, by
comparing the predicted pattern with the obtained pattern; deciding
whether the evaluated value satisfies a predetermined condition,
using a computer; modifying the given design rule, using a
computer, when the evaluated value is decided as not satisfying the
predetermined condition; determining the given design rule as a
fixed design rule for the semiconductor integrated circuit, using a
computer, when the evaluated value is decided as satisfying the
predetermined condition; and designing a layout pattern for the
semiconductor integrated circuit, using a computer, using the fixed
design rule..Iaddend.
.Iadd.15. A method according to claim 14, wherein the pattern to be
formed at a surface area of a wafer is predicted, using a computer,
using data obtained by converting data of the obtained pattern to
mask data for photolithography or data for electron beam
lithography..Iaddend.
.Iadd.16. A method according to claim 14, wherein the pattern to be
formed at a surface area of a wafer is predicted, using a computer,
using at least one model selected from a first prediction model, a
second prediction model and a third prediction model, the first
prediction model being a model for calculating a light exposed
state of a resist on the wafer when the obtained pattern is
projected on the resist, the second prediction model being a model
for calculating a resist pattern configuration after the resist has
been developed, and the third prediction model being a model for
calculating a wafer surface configuration after the wafer has been
work-processed using the resist pattern configuration..Iaddend.
.Iadd.17. A method according to claim 14, wherein the layout
pattern includes a standard cell pattern..Iaddend.
.Iadd.18. A method according to claim 14, wherein the layout
pattern includes a pattern for placement and routing..Iaddend.
.Iadd.19. A method for manufacturing a semiconductor device,
comprising projecting a pattern corresponding to the layout
designed by the method according to claim 14, onto a photoresist on
a semiconductor substrate..Iaddend.
.Iadd.20. A method according to claim 1, wherein the given design
rule defines a distance between patterns in different layers of the
semiconductor integrated circuit..Iaddend.
.Iadd.21. A system according to claim 4, wherein the given design
rule defines a distance between patterns in different layers of the
semiconductor integrated circuit..Iaddend.
.Iadd.22. The non-transitory computer readable storage medium
according to claim 7, wherein the given design rule defines a
distance between patterns in different layers of the semiconductor
integrated circuit..Iaddend.
.Iadd.23. A method according to claim 8, wherein the given design
rule defines a distance between patterns in different layers of the
semiconductor integrated circuit..Iaddend.
.Iadd.24. A layout according to claim 11, wherein the given design
rule defines a distance between patterns in different layers of the
semiconductor integrated circuit..Iaddend.
.Iadd.25. A method according to claim 14, wherein the given design
rule defines a distance between patterns in different layers of the
semiconductor integrated circuit..Iaddend.
.Iadd.26. A method according to claim 19, wherein the given design
rule defines a distance between patterns in different layers of the
semiconductor integrated circuit..Iaddend.
.Iadd.27. A method for manufacturing a semiconductor device,
comprising: forming a circuit pattern on a semiconductor wafer
based on the layout designed by the method according to claim
14..Iaddend.
.Iadd.28. A computer program product configured to store program
instructions for causing a computer to perform the method according
to claim 14..Iaddend.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor integrated circuit
designing method and system and, in particular, to a semiconductor
integrated circuit designing rule.
2. Description of the Related Art
In recent years, a marked advance has been made in the
manufacturing technology of a semiconductor integrated circuit and
the semiconductor integrated circuit of minimal working dimensions
in the order of 0.20 .mu.m has been mass produced. This very fine
work process has been realized by a very fine pattern forming
technology such as mask process technology, photolithography
technology and etching technology.
At those time periods when a pattern size of the semiconductor
circuit was adequately large, it was only necessary to prepare a
mask pattern using a desired LSI pattern as an as-designed pattern.
This mask pattern was transferred by a projection optical system on
a photoresist on a wafer and, with a developed photoresist used as
a mask, etching was performed. By doing so, it was possible to form
a substantially as-designed pattern on the wafer.
With the ever advancing microminiaturization of patterns, however,
it has been difficult to faithfully form that pattern and problems
arise in that pattern configurations on the wafer are not formed as
designed. In order to solve this problem, consideration has been
paid to a CD shift in each process and a procedure (hereinafter
referred to as a mask data processing) for forming a mask pattern
different from a designed pattern has become important so as to
allow a pattern configuration on the wafer to be formed as an
as-designed pattern.
As the mask data processing, there are pattern calculation
processing, mask data processing/preparation (MDP) processing for
varying a mask pattern by a design rule checker (D.R.C.), etc., and
optical proximity correction (OPC) processing for correcting an
optical proximity effect (OPC), etc. By these, the mask pattern can
be properly corrected such that pattern dimensions on the wafer are
matched to the desired dimensions.
In a device, such as a logic device, requiring a short turn-around
time (TAT), a greater processing time taken in the mask data
processing provides a major increase in the TAT. In order to
decrease the processing time for the mask data processing, it is
necessary to make the design rule less strict, but, if this is so
done, the chip size is increased.
In order to attain both an improved TAT and a reduced chip size, it
is important that detailed discussions be held between the designer
and the process developer about less strict design rule and
time-reduced mask data processing. In the logic device requiring a
greater time in a library development of cells or micro-cores,
etc., it is necessary that, at an earlier time stage in which a
process is not completely determined, the design rule be determined
with the use of a lithography simulation, etc. Since the designer
does the library development on the basis of a determined design
rule, if the design rule is modified after the library development
has been started, then it is necessary to re-design it on the basis
of the modified design rule.
In order to solve such a problem, a compaction tool has been
proposed (for example, Jpn. Pat. Appln. KOKAI Nos. 3-108738 and
8-287959) by which a design rule can be readily modified. This
compaction tool is such that, if the design rule is modified, each
portion of a design pattern can be individually reduced or modified
so as to satisfy such a "modified" design rule.
When, on the other hand, the design rule is determined, its work
processes are performed by only preparing a basic pattern close to
an actual device pattern, predicting a pattern configuration on the
wafer, by lithography simulation, etc., on the basis of the basic
pattern and determining the design rule on the basis of results of
such predictions.
However, the basic pattern used in the determination of the design
rule does not always reflect the detail of a practical device
pattern and there are cases where an actual device pattern is not
formed, as designed, at those kinds of patterns not fully predicted
by the simulation. Further, due to an increase in the number of
design rules, an increase in choices of process procedures and the
complexity of the data processing procedure, various factors need
to be considered so as to determine individual design rules, and
much time and effort is needed to determine the design rules. Still
further, there are cases where the process procedure and data
processing procedure cannot be determined until a design rule is
proposed. It is, therefore, also necessary to prepare a plurality
of design rules corresponding to the process procedure and data
processing procedure.
Although, as set out above, the compaction tool capable of a faster
design rule modification has been proposed, it is necessary to
initially determine the design rules upon the processing by the
compaction tool. Since, however, various difficulties as set out
above have been encountered in determining the design rules, much
time and effort is needed to determine the design rule. Further,
the once-determined design rule is not always optimal and, when a
practical device pattern is prepared with the use of the design
pattern compacted by the compaction tool, there is a risk that the
desired device pattern will not be obtained.
BRIEF SUMMARY OF THE INVENTION
In a first aspect of the present invention, a method for designing
a semiconductor integrated circuit is provided which comprises
compacting a design layout of a semiconductor integrated circuit on
the basis of a given design rule to obtain a compacted pattern,
predicting a pattern to be formed at a surface area of a wafer for
forming the semiconductor integrated circuit on the basis of the
compacted pattern, obtaining an evaluated value by comparing the
predicted pattern with the compacted pattern, deciding whether the
evaluated value satisfies a predetermined condition, and modifying
the design rule when the evaluated value is decided as not
satisfying the predetermined condition.
In a second aspect of the present invention, a system for designing
a semiconductor integrated circuit is provided which comprises
means for compacting a design layout of a semiconductor integrated
circuit on the basis of a given design rule to obtain a compacted
pattern, means for predicting a pattern to be formed at a surface
area of a wafer for forming the semiconductor integrated circuit on
the basis of the compacted pattern, means for obtaining an
evaluated value by comparing the predicted pattern with the
compacted pattern, means for deciding whether the evaluated value
satisfies a predetermined condition, and means for modifying the
design rule when the evaluated value is decided as not satisfying
the predetermined condition.
In a third aspect of the present invention, a computer readable
medium is provided which is configured to store program
instructions for causing a computer to compact a design layout of a
semiconductor integrated circuit on the basis of a given design
rule to obtain a compacted pattern, causing the computer to predict
a pattern to be formed at a surface area of a wafer for forming the
semiconductor integrated circuit on the basis of the compacted
pattern, causing the computer to obtain an evaluated value by
comparing the predicted pattern with the compacted pattern, causing
the computer to decide whether the evaluated value satisfies a
predetermined condition, and causing the computer to modify the
design rule when the evaluated value is decided as not satisfying
the predetermined condition.
Additional objects and advantages of the invention will be set
forth in the description which follows, and in part will be obvious
from the description, or may be learned by practice of the
invention. The objects and advantages of the invention may be
realized and obtained by means of the instrumentalities and
combinations particularly pointed out hereinafter.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
The accompanying drawings, which are incorporated in and constitute
a part of the specification, illustrate presently embodiments of
the invention, and together with the general description given
above and the detailed description of the embodiments given below,
serve to explain the principles of the invention.
FIG. 1 is a functional block diagram showing a concept of a
designing system according to an embodiment of the present
invention; .[.and.].
FIG. 2 is a flow chart showing an operation process of a designing
method according to an example of the present invention.[...].
.Iadd.; and.Iaddend.
.Iadd.FIG. 3 is an illustration of a computer having its operation
controlled by a program loaded from a storage medium..Iaddend.
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described below with
reference to the drawing.
FIG. 1 is a functional block diagram showing a concept of a
designing system according to an embodiment of the present
invention.
In the present system, a compaction tool 11 and simulator 12
coexist. The compaction tool 11 compacts a design layout so as to
make the design layout area as small as possible. The simulator 12
predicts a pattern configuration formed at a surface area of a
semiconductor wafer on the basis of the design layout.
To the compaction tool 11, a design rule table 13 for defining a
design rule of a given generation and a design rule preparing
pattern 14 for use in a design rule calculation are inputted. In
the compaction tool 11, the design rule preparing pattern 14 is
compacted in accordance with the design rule defined by the design
rule table 13 and a "compacted" pattern is outputted to the
simulator 12.
The simulator 12 includes the following simulators. A first is a
lithography simulator (fight intensity simulator or electron beam
exposing simulator, etc.) for calculating a light exposed state on
a wafer surface when a mask pattern is transferred by a light
exposure device onto a resist formed on a wafer. A second is a
simulator for calculating a pattern configuration of the resist
which, after being pattern-transferred, is developed. A third is a
simulator for calculating a configuration on a wafer surface
following a pattern-working process (etching) done on the wafer
surface area with a "developed" resist pattern used as a mask. A
wafer surface pattern configuration is predicted, by the simulator
12, in the case of a given process condition being selected. It is
noted that a device simulators for deciding a design rule or an LVS
(Layout Versus Schematics) for comparing layout data with a circuit
design may also be included if necessary.
In the present system, the compacted pattern data is converted to
data for photolithography or electron beam lithography and a
simulation is carried out using the "converted" data. Further, the
present system has a mask data processing system 15 for performing
mask data processing such as MDP processing, OPC processing, etc.,
and can perform mask data processing on a design pattern compacted
by the compaction tool 11. By performing the simulation on the thus
mask data processed pattern, it is possible to clarify a relation
between an actually executable mask data processing and a definable
design rule.
A wafer surface area's pattern configuration predicted by the
simulator 12 and design pattern compacted by the compaction tool 11
are compared by a comparing/evaluating means 16. A great/small
relation, etc., between an evaluated value obtained based on a
result of comparison and an initially given reference value 17 is
decided by a deciding means 18. In the case where a result of
decision satisfies a predetermined condition, an earlier defined
design rule is determined by a design rule determining means 19 as
being a design rule of a device now under consideration. In the
case where the result of decision does not satisfy the
predetermined condition, the earlier defined design rule is
modified (changed) by a design rule modifying (changing) means 20
to a new design rule and the new design rule is fed back to the
design rule table 13.
Now the operation of the designing system according to the
embodiment of the present invention will be explained below with
reference to a flow chart shown in FIG. 2.
First, the design rule table and design rule preparing pattern are
input to the compaction tool. The compaction tool compacts the
designed pattern so as to satisfy a design rule designated by the
design rule table (S1). As a design rule used as an initial value
in the design rule table can be made of a rule obtained by
uniformly shrinking, for example, a design rule of a previous
generation. It is desirable that the design rule can prepare the
same pattern shape as actual device pattern shape as possible. In a
logic device, for example, it is desirable to use a standard cell
pattern, etc. In the case of it being larger in scale, use is
desirably made of a logic device pattern also involving the
interconnection of an overlaying layer by a P&R (placement and
routing) step.
Then, mask data processing is performed on the compacted pattern
(S2). Since the assumed MDP processing and OPC processing differ
from layer to layer, the mask data processing method is determined,
taking into consideration the actual processing capability and
TAT.
Then, a pattern configuration finally formed on a surface area of
the wafer is predicted from the mask pattern prepared by the mask
data processing with the use of the simulator mounted on the system
(S3).
Then, those partially evaluated values such as a deviation amount
of a line-width dimension from a desired dimension and a shortened
amount of a dimension at a line end are calculated from the
predicted pattern configuration and "compacted" design pattern.
Further, the chip area, compaction shrink rate, etc., are also
calculated as evaluation values (S4).
Then a reference evaluation value initially determined for each
evaluation value is inputted (S5). Further, the calculated
evaluation value and reference evaluation value are compared and it
is decided whether or not the evaluation value satisfies the
condition of the reference evaluation value (S6). In the case where
the evaluation value satisfies the condition of the reference
evaluation value, the earlier defined design rule is determined as
the design rule of the device now under consideration (S7).
Then, a design rule exerting an influence on the calculated
evaluation value is decided and this design rule is extracted (S8).
In the case where, for example, a shortened amount of a gate layer
portion projecting from a diffusion layer is greater than a
reference evaluation value, the design rule defining a distance
from the gate's forward end to the diffusion layer is so set larger
as to satisfy the condition of the reference evaluation value. In
the case where a contact hole is situated at a corner of the
diffusion layer, since there is a risk that an electrical
conduction will fail between the contact hole and the diffusion
layer due to a rounding at the corner of the diffusion layer, the
design rule defining a distance from the end of the diffusion layer
to the contact hole is so set larger as to satisfy the reference
evaluation value. Further, a route defining a chip size on a device
is checked and a design rule exerting an influence on the route is
extracted.
Then, the extracted design rule is modified toward a direction
satisfying the condition of the reference evaluation value.
Further, the modified design rule is fed back to the design rule
table and the design rule of the design rule table is so modified
as to allow at least one evaluation value to satisfy the condition
of the reference evaluation value (S9).
By doing so, the above-mentioned steps are repeated until the
calculated evaluation value satisfies the condition of the
reference evaluation value.
By the way, the above-mentioned designing method can be realized by
a computer having its operation controlled by a program loaded from
a storage medium such as a magnetic disk.Iadd., as shown in FIG.
3.Iaddend..
According to the present embodiment, as set out above, the values
of the design rules can be calculated with the use of an actual
device pattern and it is, therefore, possible to calculate an exact
design rule, in a shorter period of time, compatible with processes
actually in use. Further, since this is a design rule also taking
into consideration the mask data processing assumed to be done with
an actual device, it is possible to compromise between the mask
data processing time and the chip size increase resulting from less
strict design rule. By providing the reference evaluation value, a
faster decision is made for OK (good) or NG (no good) and, in
addition, a readier numerical evaluation is also made on the design
rule. Further, by distinguishing between the design rule exerting
an influence on the evaluation value and other design rules, it is
easier to decide whether any given design rule should be set
stricter or any given design rule should be set more lenient and,
by doing so, it is possible to easily judge to which patterns
specific attention should be paid during the work-processing and
mask data processing.
It is to be noted that the design rules may be prepared not only
using the compaction tool and simulator as set out above but also
additionally preparing an actual mask and performing a transfer
test, etc.
Additional advantages and modifications will readily occur to those
skilled in the art. Therefore, the invention in its broader aspects
is not limited to the specific details and representative
embodiments shown and described herein. Accordingly, various
modifications may be made without departing from the spirit or
scope of the general inventive concept as defined by the appended
claims and their equivalents.
* * * * *