U.S. patent application number 16/427321 was filed with the patent office on 2020-12-03 for predicting local layout effects in circuit design patterns.
The applicant listed for this patent is International Business Machines Corporation. Invention is credited to Jing Sha, Dongbing Shao, Yufei Wu, Zheng Xu.
Application Number | 20200380088 16/427321 |
Document ID | / |
Family ID | 1000005220089 |
Filed Date | 2020-12-03 |
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United States Patent
Application |
20200380088 |
Kind Code |
A1 |
Sha; Jing ; et al. |
December 3, 2020 |
PREDICTING LOCAL LAYOUT EFFECTS IN CIRCUIT DESIGN PATTERNS
Abstract
A method for predicting local layout effect in a circuit design
pattern includes obtaining a plurality of circuit design patterns,
generating layout images from the circuit design patterns,
extracting feature vectors from the layout images by processing the
layout images in a computer vision machine learning algorithm,
comparing the feature vector extracted from a selected layout image
to clusters of feature vectors extracted from the layout images,
wherein the clusters of feature vectors include an in-range cluster
and an outlier cluster, and labelling a circuit design pattern
corresponding to the selected layout image, for which threshold
voltage has not been experimentally measured, as being an in-range
circuit design pattern or an outlier circuit design pattern, in
response to the selected layout image respectively correlating with
the in-range cluster or with the outlier cluster.
Inventors: |
Sha; Jing; (White Plains,
NY) ; Shao; Dongbing; (Wappingers Falls, NY) ;
Wu; Yufei; (Poughkeepsie, NY) ; Xu; Zheng;
(Wappingers Falls, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
International Business Machines Corporation |
Armonk |
NY |
US |
|
|
Family ID: |
1000005220089 |
Appl. No.: |
16/427321 |
Filed: |
May 30, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G06N 3/088 20130101;
G06N 20/00 20190101; G06N 3/0454 20130101; G06F 30/398 20200101;
G06K 9/6223 20130101 |
International
Class: |
G06F 17/50 20060101
G06F017/50; G06N 20/00 20060101 G06N020/00; G06N 3/08 20060101
G06N003/08; G06N 3/04 20060101 G06N003/04; G06K 9/62 20060101
G06K009/62 |
Claims
1. A method for rejecting a circuit design pattern that is
predicted to have local layout effect, comprising: obtaining a
plurality of circuit design patterns; generating a plurality of
layout images each corresponding to one of the plurality of circuit
design patterns; training a computer vision machine learning
algorithm in an unsupervised fashion to generate a training set of
feature vectors for the plurality of layout images; generating a
cluster plot of the training set of feature vectors; identifying an
in-range cluster and an outlier cluster on the cluster plot;
identifying a circuit design pattern that corresponds to a layout
image that produced a feature vector within the outlier cluster;
and rejecting the identified circuit design pattern.
2. The method of claim 1 further comprising: fabricating samples of
circuit design patterns that correspond to feature vectors present
in each of the clusters; and identifying the in-range cluster and
the outlier cluster based on experimental measurements of threshold
voltage for samples that are present in each of the clusters,
wherein experimental measurements for samples in the outlier
cluster indicate local layout effect.
3. The method of claim 2 further comprising using principal
component analysis for dimensionality reduction of the training set
of feature vectors.
4. The method of claim 1 further comprising: clustering the feature
vectors; and identifying the in-range cluster and the outlier
cluster based on the in-range cluster having more members than the
outlier cluster.
5. The method of claim 1 wherein partitional clustering is used to
cluster the feature vectors.
6. The method of claim 1 wherein the computer vision machine
learning algorithm includes an autoencoder that extracts the
feature vectors as intermediate codings from the layout images.
7. A method for rejecting circuit design patterns that are
predicted to have local layout effect, comprising: obtaining a
plurality of circuit design patterns; generating a plurality of
layout images each corresponding to one of the plurality of circuit
design patterns; training a computer vision machine learning
algorithm in an unsupervised fashion to generate a training set of
feature vectors for the plurality of layout images; generating a
cluster plot of the training set of feature vectors; identifying an
in-range cluster and an outlier cluster on the cluster plot;
obtaining an inference set of circuit design patterns; generating
an inference set of layout images each corresponding to one of the
inference set of circuit design patterns; using the computer vision
machine learning algorithm to generate an inference set of feature
vectors for the inference set of layout images; plotting on the
cluster plot the inference set of feature vectors; identifying
outlier members of the inference set of layout images that produced
feature vectors that overlie the outlier cluster on the cluster
plot; and rejecting circuit design patterns that correspond to the
outlier members of the inference set of layout images.
8. The method of claim 7 wherein identifying the in-range cluster
and the outlier cluster includes fabricating at least one sample of
a circuit design pattern from each of the clusters and
experimentally measuring threshold voltage of the at least one
sample from each of the clusters, wherein experimental measurements
for samples in the outlier cluster indicate local layout
effect.
9. The method of claim 7 wherein identifying the in-range cluster
and the outlier cluster includes counting a number of members in
each of the clusters.
10. The method of claim 7 wherein the cluster plot is a
2-dimensional cluster plot produced by reducing dimensionality of
the training set of feature vectors, and dimensionality of the
inference set of feature vectors is reduced before plotting the
inference set of feature vectors on the cluster plot.
11. The method of claim 7 wherein partitional clustering is used to
identify the in-range and outlier clusters.
12. The method of claim 7 wherein the computer vision machine
learning algorithm includes a convolutional neural network.
13. The method of claim 7 wherein the computer vision machine
learning algorithm includes an autoencoder that extracts the
feature vectors as intermediate codings from the layout images.
14. A method for rejecting a circuit design pattern that is
predicted to have local layout effect, comprising: obtaining a
plurality of circuit design patterns; generating layout images from
the circuit design patterns; extracting feature vectors from the
layout images by processing the layout images in a computer vision
machine learning algorithm; comparing the feature vector extracted
from a selected layout image to clusters of feature vectors
extracted from the layout images, wherein the clusters of feature
vectors include an in-range cluster and an outlier cluster; and
rejecting a circuit design pattern corresponding to the selected
layout image, for which threshold voltage has not been
experimentally measured, as being a circuit design pattern that is
predicted to have local layout effect, in response to the feature
vector of the selected layout image correlating with the outlier
cluster.
15. The method of claim 14 further comprising: fabricating samples
of at least some of the circuit design patterns; and identifying
the in-range cluster and the outlier cluster based on experimental
measurements of threshold voltage for samples that are present in
each of the clusters, wherein experimental measurements for samples
in the outlier cluster indicate local layout effect.
16. The method of claim 14 further comprising: clustering the
feature vectors; and identifying the in-range cluster and the
outlier cluster based on the in-range cluster having more members
than the outlier cluster.
17. The method of claim 16 wherein partitional clustering is used
to cluster the feature vectors.
18. The method of claim 14 wherein the computer vision machine
learning algorithm includes a convolutional neural network.
19. The method of claim 18 wherein the computer vision machine
learning algorithm is trained in a supervised fashion based on
measured values of threshold voltage for a majority of the circuit
design patterns.
20. The method of claim 14 wherein the computer vision machine
learning algorithm includes an autoencoder that extracts the
feature vectors as intermediate codings from the layout images.
Description
BACKGROUND
[0001] The present invention relates to the electrical, electronic,
and computer arts, and more specifically, to integrated circuit
design techniques.
[0002] In VLSI (very large scale integration) digital design,
electrical conductors (metal lines) interconnect the terminals of
the electronic components (such as cells, elements, objects, and
the like) in the integrated circuit, and vias are used to
interconnect the metal lines. As VLSI designs continue to reduce
the spacing between adjacent electronic components, increasing
proximity of electrically isolated electrical conductors and vias
can introduce unexpected electrical couplings between the
conductors and/or vias (by capacitance and/or inductance), a
phenomenon known as "local layout effect" ("LLE"). Local layout
effect is undesirable at least because it can cause circuit
threshold voltage to be out of its designed range. (Threshold
voltage is the minimum gate-to-source voltage V.sub.GS (th) that is
needed to create a conducting path between the source and drain
terminals. It is an important characteristic that determines proper
operation of a computational circuit. Out-of-range threshold
voltage can produce computational errors.)
[0003] In order to detect the presence of local layout effect, it
presently is required to measure threshold voltage experimentally
on a fully fabricated VLSI circuit. Efforts have been made to
simulate circuit performance before fabrication, in order to
predict a possibility of local layout effect; however, such efforts
have not yet produced confidence in their results. Problems with
attempting to simulate LLE arise in part because the phenomenon
itself can be caused by stochastic defects in circuit fabrication,
which are not accounted for in conventional circuit simulation
software.
SUMMARY
[0004] Principles of the invention provide techniques for
predicting local layout effects in circuit design patterns. In one
aspect, an exemplary method for rejecting a circuit design pattern
that is predicted to have local layout effect includes obtaining a
plurality of circuit design patterns, generating a plurality of
layout images each corresponding to one of the plurality of circuit
design patterns, training a computer vision machine learning
algorithm in an unsupervised fashion to generate a training set of
feature vectors for the plurality of layout images, generating a
cluster plot of the training set of feature vectors, and
identifying an in-range cluster and an outlier cluster on the
cluster plot. The method further includes identifying a circuit
design pattern that corresponds to a layout image that produced a
feature vector within the outlier cluster, and rejecting the
identified circuit design pattern. In one or more embodiments, the
cluster plot may be many-dimensional, i.e. in excess of three
dimensions.
[0005] In another aspect, an exemplary method for rejecting circuit
design patterns that are predicted to have local layout effect
includes obtaining a plurality of circuit design patterns;
generating a plurality of layout images each corresponding to one
of the plurality of circuit design patterns; training a computer
vision machine learning algorithm in an unsupervised fashion to
generate a training set of feature vectors for the plurality of
layout images; generating a cluster plot of the training set of
feature vectors; identifying an in-range cluster and an outlier
cluster on the cluster plot; obtaining an inference set of circuit
design patterns; generating an inference set of layout images each
corresponding to one of the inference set of circuit design
patterns; using the computer vision machine learning algorithm to
generate an inference set of feature vectors for the inference set
of layout images; plotting on the cluster plot the inference set of
feature vectors; identifying outlier members of the inference set
of layout images that produced feature vectors that overlie the
outlier cluster on the cluster plot; and rejecting circuit design
patterns that correspond to the outlier members of the inference
set of layout images.
[0006] In another aspect, an exemplary method for rejecting a
circuit design pattern that is predicted to have local layout
effect includes obtaining a plurality of circuit design patterns;
generating layout images from the circuit design patterns;
extracting feature vectors from the layout images by processing the
layout images in a computer vision machine learning algorithm;
comparing the feature vector extracted from a selected layout image
to clusters of feature vectors extracted from the layout images,
wherein the clusters of feature vectors include an in-range cluster
and an outlier cluster; and rejecting a circuit design pattern
corresponding to the selected layout image, for which threshold
voltage has not been experimentally measured, as being an outlier
circuit design pattern, in response to the feature vector of the
selected layout image correlating with the outlier cluster.
[0007] One or more embodiments of the invention or elements thereof
can be implemented in the form of a computer program product
including a computer readable storage medium with computer usable
program code for performing or facilitating the method steps
indicated. Furthermore, one or more embodiments of the invention or
elements thereof can be implemented in the form of a system (or
apparatus) including a memory that embodies computer executable
instructions, and at least one processor that is coupled to the
memory and operative by the instructions to perform or to
facilitate exemplary method steps. Yet further, in another aspect,
one or more embodiments of the invention or elements thereof can be
implemented in the form of means for carrying out one or more of
the method steps described herein; the means can include (i)
hardware module(s), (ii) software module(s) stored in a tangible
computer readable storage medium (or multiple such media) and
implemented on a hardware processor, or (iii) a combination of (i)
and (ii); any of (i)-(iii) implement the specific techniques set
forth herein.
[0008] As used herein, "facilitating" an action includes performing
the action, making the action easier, helping to carry the action
out, or causing the action to be performed. Thus, by way of example
and not limitation, instructions executing on one processor might
facilitate an action carried out by instructions executing on a
remote processor, by sending appropriate data or commands to cause
or aid the action to be performed. For the avoidance of doubt,
where an actor facilitates an action by other than performing the
action, the action is nevertheless performed by some entity or
combination of entities.
[0009] In view of the foregoing, techniques of the present
invention can provide substantial beneficial technical effects. For
example, one or more embodiments provide one or more of:
[0010] Efficient identification of circuit design patterns that
produce unacceptable shifts of threshold voltage.
[0011] Identification of in-range circuit design patterns and
outlier circuit design patterns before simulation, fabrication, or
testing of the designs.
[0012] These and other features and advantages of the present
invention will become apparent from the following detailed
description of illustrative embodiments thereof, which is to be
read in connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 depicts a plot of threshold voltages corresponding to
various circuit design patterns, marked with horizontal lines to
indicate in-range values and outlier values of threshold
voltage;
[0014] FIG. 2 depicts plots of 2-dimensional principal component
analysis (PCA) results and corresponding Vt values, in pixel space
and in feature vector space, of in-range and outlier circuit design
patterns;
[0015] FIG. 3 depicts sample layout clip images of in-range and
outlier circuit design patterns;
[0016] FIG. 4 depicts a deep learning architecture for producing
feature vectors to be used in PCA, according to an exemplary
embodiment;
[0017] FIG. 5 depicts in a flowchart steps of a method for training
and using the deep learning architecture of FIG. 4;
[0018] FIG. 6 depicts another deep learning architecture for
producing feature vectors to be used in PCA, according to an
exemplary embodiment;
[0019] FIG. 7 depicts in a flowchart steps of a method for training
and using the deep learning architecture of FIG. 6;
[0020] FIG. 8 depicts in a flowchart steps of an overall circuit
design and fabrication process in which exemplary embodiments are
implemented; and
[0021] FIG. 9 depicts a computer system that may be useful in
implementing one or more aspects and/or elements of the
invention.
DETAILED DESCRIPTION
[0022] Surprisingly, an aspect of the present invention is that
local layout effect can be predicted without experimental
measurements of threshold voltage and without detailed simulation
of circuit performance. This unexpected ability to predict local
layout effect can be accomplished by framing the problem as a
computer vision problem, in which the power of neural networks can
be applied to clipped 3-D images of circuit design patterns.
[0023] Generally, a neural network includes a plurality of computer
processors that are configured to work together to implement one or
more machine learning algorithms. The implementation may be
synchronous or asynchronous. In a neural network, the processors
simulate thousands or millions of neurons, which are connected by
axons and synapses. Each connection is enforcing, inhibitory, or
neutral in its effect on the activation state of connected neural
units. Each individual neural unit has a summation function which
combines the values of all its inputs together. In some
implementations, there is a threshold function or limiting function
on at least some connections and/or on at least some neural units,
such that the signal must surpass the limit before propagating to
other neurons. A neural network can implement supervised,
unsupervised, or semi-supervised machine learning. There are many
types of neural network architecture. Two types are described below
as exemplary embodiments of the invention: a convolutional neural
network (CNN) and an autoencoder. Variations of these two types,
and other types, also may be suitable for implementing the
invention as will be understood by an ordinary skilled worker.
[0024] One or more embodiments include establishing a neural
network, training the neural network in an unsupervised fashion on
a set of clipped images of circuit design patterns ("layout
images"), clustering principal components of feature vectors
produced by the neural network for each of the layout images, and
identifying from a cluster plot those layout images that have
"outlier" principal components that are expected to correspond to
unusual values of threshold voltage (Vt). Other embodiments include
establishing a neural network, training the neural network in a
supervised fashion on layout images and corresponding measurements
of threshold voltage, and applying the trained neural network to
layout images for which threshold voltage has not been measured
("working images"), in order to predict whether local layout effect
will be present for circuit design patterns corresponding to each
of the working images. Yet other embodiments include establishing a
neural network, training the neural network in an unsupervised
fashion on a set of layout images, clustering principal components
of feature vectors produced by the neural network for each of the
layout images, experimentally measuring threshold voltage for a
sample of points from each cluster of feature vectors, and
categorizing the clusters as "in-range" or "outlier" based on the
experimental measurements.
[0025] For further understanding of the "in-range" and "outlier"
terminology, FIG. 1 depicts a plot of threshold voltages (vertical
axis) experimentally measured on various actually-fabricated
circuit design patterns (horizontal axis), marked with horizontal
dashed lines to indicate in-range values and outlier values of
threshold voltage (Vt). For example, in-range threshold voltages
range between about 125 millivolt (mV) and about 155 mV. Outlier
threshold voltages exceed 155 mV or fall below 125 mV. Other values
for in-range and outlier voltages may be appropriate depending on
design specifications of any given circuit.
[0026] According to one or more embodiments, dimensionality
reduction techniques assist in identifying "in-range" and "outlier"
groups of layout images. As one example, FIG. 2 depicts plots of
2-dimensional principal component analysis (PCA) results and
corresponding Vt values, in pixel space and in feature vector
space, of in-range and outlier circuit design patterns. In the left
hand plot 200 of FIG. 2 (2-dimensional PCA in pixel space), various
values of Vt are scattered across the plot without any clear
correlation between the principal components and the Vt values. By
contrast, in the right hand plot 201 of FIG. 2 (2-dimensional PCA
in feature vector space), values of Vt are clustered into an
in-range group 202 and an outlier group 204. The in-range group 202
is at the left side of the right hand plot 201, and includes
mid-range values of Vt, i.e. values between about 125 mV and about
155 mV. The outlier group 204 is at the right side of the right
hand plot 201, and includes extreme values of Vt, i.e. values in
excess of 155 mV or less than 125 mV. FIG. 2 demonstrates that
in-range and outlier circuit design patterns can be easily
separated into two clusters in the feature vector space, while they
are difficult to distinguish in the pixel space. Although PCA is
discussed with reference to FIG. 2, other dimensionality reduction
techniques equally are applicable, e.g., maximum variance
unfolding, diffusion mapping. Note also that there are conventional
modeling approaches to correct for the LLE effect, this function
was not turned on in the raw data used to generate FIG. 2.
[0027] FIG. 3 depicts sample layout clip images of in-range circuit
design patterns 300a, 300b, 300c, 300d (which produce in-range
values of Vt) and outlier circuit design patterns 302a, 302b, 302c,
302d (which produce high or low values of Vt). Features of the
layout images that correlate to in-range or high or low values of
Vt are not apparent to a human observer, but can be detected by
trained neural networks. The different regions in FIG. 3 correspond
to different design layers, such as device marker layers as well as
physical design layers such as source/drain regions and the
like.
[0028] FIG. 4 depicts a deep learning architecture 400 for
producing feature vectors, which then can be used for clustering
layout images, according to an exemplary embodiment. The
architecture 400 includes an image clipping module 402, which
receives circuit design patterns 403 and produces 3-D layout images
404. Embodiments provide for data preparation such that multi-layer
integrated layout patterns may be input to a CNN. In some
embodiments, the input for a CNN is a set of three-dimensional
(3-D) layout images corresponding to 2-D images of multi-layered
layouts that are stacked in a third dimension. Each of the stacked
images is a specific layer of a multi-layer integrated circuit
design pattern (e.g., the layout captured in a field of view
(FOV)). Since an image may be represented as a two-dimensional
(2-D) array of numbers, a 3-D layout image representing the
multi-layer integrated circuit design pattern is constructed by
stacking multiple layout images (e.g., 2-D layers) of the
integrated layout pattern in the third dimension, which corresponds
to the number of integrated layers. Digital images may have only
three (e.g., red, green and blue or RGB) or four (e.g., cyan,
magenta, yellow and key or CMYK) channels (e.g., in the third
dimension, with image width and height being the other two
dimensions). The 3-D layout images that are constructed in some
embodiments can go beyond these channel limitations of digital
images. The number of integrated layers can be as many or as few as
desired.
[0029] In conventional circuit simulation/analysis, there is no
reason to pre-process a circuit design pattern to produce layout
images, because the visual appearance of the circuit layout plays
no role in the numerical simulation of circuit performance.
Furthermore, due to the scale and complexity of VLSI circuits,
layout images are meaningless to human engineers. Thus, the
pre-processing accomplished by the image clipping module 402 makes
sense only in context of the current invention, which employs
neural networks to accomplish deep visual analysis of the 3-D
layout images 404.
[0030] The architecture 400 also includes a deep convolutional
neural network (i.e. a computer vision machine learning algorithm)
406, which receives the layout images 404 and outputs
classification labels 408. The neural network 406 includes a
penultimate layer 410 that generates feature vectors 411, which are
input to an ultimate classification layer 412 that generates the
classification labels 408. In supervised embodiments, the
classification labels 408 for the training layout images correspond
to measured values of threshold voltage Vt, i.e. "in-range,"
"high," or "low."
[0031] The deep neural network 406 can be trained to classify
layout images in a training set, for which threshold voltages have
been experimentally measured, into "in-range" and "outlier"
categories. There may be multiple "outlier" categories, e.g.,
"high" and "low" categories. At a penultimate layer of the trained
neural network, it will produce n-dimensional feature vectors for
each of the layout images. At an inference stage following
training, the trained CNN can be applied to an inference set of
layout images, for which threshold voltages have not been
experimentally measured, and can classify those working layout
images into "high," "low," or "in-range" categories based on the
n-dimensional feature vectors that the CNN produces for each of the
inference set of layout images.
[0032] FIG. 5 depicts, in a flowchart, steps of a method 500 for
training and using the deep learning architecture 400 of FIG. 4.
Steps 501-513 include training. At 501, obtain a training set of
circuit design patterns 403 and at 502 generate layout images 404
from the circuit design patterns. At 503, run the neural network
406 in a supervised manner on the set of layout images 404 to
generate classifications 408 that correspond to values of threshold
voltage (Vt) measured for each of the actually-fabricated circuit
design patterns 403 (e.g., "high," "low," or "in-range"). At 504,
extract the feature vectors 411 from the penultimate layer 410. At
506, undertake dimensionality reduction (e.g., principal component
analysis (PCA), kernel PCA, isomapping, maximum variance unfolding,
diffusion mapping, locally linear embedding, Laplacian
eigenmapping, Hessian locally linear embedding, local tangent space
analysis, summon mapping, multilayer autoencoders, locally linear
coordination, manifold charting) of the feature vectors 411. At
508, generate a cluster plot of the dimensionality reduction (e.g.,
PCA) results. Note that dimensionality reduction is non-essential.
In one or more embodiments, the feature vectors can be clustered
without reducing dimensionality. Indeed, clustering does not
require dimensionality reduction of feature vectors. Dimensionality
reduction is optional and is appropriate in one or more embodiments
for visualization which requires data of no more than three
dimensions.
[0033] At 510, identify distinct clusters (in-range and outlier) on
the cluster plot. At 512, correlate measured Vt values to each of
the distinct clusters. At 513, confirm that each of the distinct
clusters has a corresponding range or ranges of Vt values, e.g., at
least most of the layout images that are grouped in an in-range
cluster have in-range Vt values and at least most of the layout
images that are grouped in one or more outlier clusters have
extreme (outlier) Vt values.
[0034] Steps 514-526 include implementation. At 514, obtain an
inference set of circuit design patterns for which Vt has not been
measured. At 515, generate an inference set of layout images from
the inference set of circuit design patterns. At 516, run the
neural network 406 again on the inference set of layout images. At
518, extract the feature vectors for the inference set. At 520,
generate reduced dimension feature vectors by performing
dimensionality reduction on the feature vectors of the inference
set. At 522, overlay the reduced dimension feature vectors from 520
onto the cluster plot from 508. At 524, identify members of the
inference set that overlie an in-range cluster of the cluster plot
and identify members of the inference set that overlie an outlier
cluster of the cluster plot. At 526, reject the circuit design
patterns that correspond to those members of the inference set that
overlie any of the outlier cluster(s). Note, again, that
dimensionality reduction is not essential, that the cluster plot
may be many-dimensional (i.e. more than three dimensions), and
that, in one or more embodiments, feature vectors can be clustered
without reducing dimensionality.
[0035] FIG. 6 depicts another deep learning architecture 600 for
producing feature vectors to be used in PCA, according to an
exemplary embodiment. The architecture 600 includes an image
clipping module 602, which receives circuit design patterns 603 and
produces layout images 604, and also includes an encoder 606 (which
can be but not limited to a set of convolutional neural network
layers and/or fully connected layers) and a decoder 607 (which can
be but not limited to a set of convolutional neural network layers
and/or fully connected layers). Together, the encoder 606 and the
decoder 607 form an autoencoder as further described below. The
encoder 606 receives the layout images 604 and outputs feature
vectors (intermediate codings) 611. The decoder 607 receives the
feature vectors 611 and maps them back onto the layout images 604.
As an example of operation, the autoencoder can be trained (in an
unsupervised fashion) to produce codings from layout images, then
to map the codings back onto the layout images. Architecturally,
the autoencoder can have a form similar to that of a fully
connected neural network, with an input layer, an output layer, and
one or more hidden layers connecting the input and output layers.
However, as a person skilled in the art will recognize, the
autoencoder can include convolutional layers, or other types of
computation layers different from a fully connected neural network.
In the autoencoder, unlike most other types of neural network, the
output layer has the same number of neurons as the input layer, and
the hidden layers are trained for first encoding and then
reconstructing the inputs to the autoencoder, instead of iterating
to find weights to match the inputs to manually identified labels.
Accordingly, autoencoders generate "unsupervised" learning models.
By selecting the number of neurons in each hidden layer, and by
selecting a number of hidden layers, the autoencoder compresses the
input data (e.g., 3-D layout images) into intermediate codings and
subsequently decompresses the codings to generate reconstructed
images that are similar to the 3-D layout images. The reconstructed
images per se are not necessarily pertinent in one or more
embodiments; instead, the intermediate codings are features
extracted from the input 3-D layout images. Then, at an inference
or implementation stage following training, new codings or features
could be extracted by the trained autoencoder from any new incoming
layout images, after which clustering and visualization techniques
can be applied to the intermediate codings (extracted features) to
generate a plot of in-range and outlier clusters corresponding to
in-range layout images and outlier layout images. The outlier
layout images then can be disparaged as problematic designs and the
corresponding circuit design patterns can be rejected. Optionally,
actual threshold voltages may be experimentally measured for
samples of circuit design patterns taken from each cluster of
layout images. The experimental measurements then may be used to
validate the cluster labels--e.g., if a cluster tentatively was
labelled "in-range" but the majority of measured samples actually
were out of range, then the cluster would be re-labelled as
"outlier."
[0036] FIG. 7 depicts in a flowchart steps of a method 700 for
training and using the deep learning architecture of FIG. 6. Steps
701-713 include training. At 701, obtain a training set of circuit
design patterns 603. At 702, generate layout images 604 from the
training set of circuit design patterns. At 703, run the encoder
606 on the set of layout images 604 to generate the feature vectors
611 and run the decoder 607 to map the feature vectors back onto
the layout images 604. At 704, extract the feature vectors 611 from
the encoder 606. At 706, undertake dimensionality reduction (e.g.,
principal component analysis (PCA)) of the feature vectors 611. (As
mentioned above, dimensionality reduction is an optional step. It
is possible to cluster feature vectors without reducing
dimensionality. Such clustering could produce a 2-, 3-, or
many-dimensional cluster plot at step 708.) At 708, generate a
cluster plot of the reduced dimension feature vectors. At 710,
identify distinct clusters (in-range and outlier) on the cluster
plot, for example, using machine vision to segment the data into
distinct clusters. At 712, correlate measured Vt values to each of
the distinct clusters. At 713, confirm that each of the distinct
clusters has a corresponding range or ranges of Vt values, e.g.,
each of the layout images that is grouped in an in-range cluster
has an in-range Vt value and each of the layout images that is
grouped in one or more outlier clusters has an extreme (outlier) Vt
value.
[0037] Steps 714-726 include implementation. At 714 obtain an
inference set of circuit design patterns for which no Vt values
have been measured, and at 715 generate an inference set of layout
images based on those circuit design patterns. At 716, run the
encoder 606 again on the inference set of layout images. At 718,
extract the feature vectors for the inference set. At 720,
optionally, reduce dimensionality of the feature vectors of the
inference set. At 722, overlay the reduced dimension feature
vectors from 720 onto the cluster plot from 708. At 724, identify
members of the inference set that overlie an in-range cluster of
the cluster plot and identify members of the inference set that
overlie an outlier cluster of the cluster plot. At 726, reject the
circuit design patterns that correspond to those members of the
inference set that overlie any of the outlier cluster(s).
[0038] In one or more embodiments, classification labels are not
essential. Without classifying layout images, clusters can be
identified in the feature space, and it can be assumed that a
majority cluster will be the in-range cluster. In case
classification labels are desired to validate this assumption, the
clusters can be categorized by testing samples from each sample
after clustering. Thus, an autoencoder process might be preferred
if pre-existing labels were not available, however a CNN might be
preferable in case a large corpus of threshold voltage measurements
already were available.
[0039] In the unsupervised protocol, it is helpful, but not
essential, to obtain actual measurements of threshold voltage.
Optionally, dimensionality reduction and clustering can be used
alone to identify "in-range" (majority) and "outlier" (minority)
clusters of feature vectors for various layout images.
[0040] Also, in the unsupervised protocol it is not essential to
have separate training and inference sets of circuit design
patterns and layout images. Instead, after feature vectors
(intermediate codings) have been extracted from an initial set of
layout images, and after clusters have been identified using
dimensionality reduction techniques, a few experimental
measurements of threshold voltages can be taken for a sampling of
actually-fabricated circuit designs corresponding to each of the
clusters. Then, based on the experimental measurements, clusters
and their members (including non-fabricated circuit design patterns
for which threshold voltage has not been measured) can be
identified as "in-range" or "high" or "low."
[0041] In one or more embodiments, the feature extraction aspect is
helpful for a circuit designer to obtain insight as to what circuit
features might trigger local layout effect. Then it might be
possible to eliminate LLE by changing single features of a circuit
design. Also, clustering on feature vectors can give clarity where
confidence of the classification labels is moderate.
[0042] It is worth noting that conventional modeling methods employ
"numbers in" and "numbers out." However, it is difficult to
quantize design "style," and even if this was possible, too many
numbers would be needed to describe a layout design.
Advantageously, one or more embodiments overcome the need for
quantizing layout style and directly use layout(s) as inputs, and
thus are more convenient, accurate, and/or easy.
[0043] FIG. 8 depicts an example high-level Electronic Design
Automation (EDA) tool flow 900, which is responsible for creating
an optimized microprocessor (or other IC) design to be
manufactured. A designer could start with a high-level logic
description 901 of the circuit (e.g. VHDL or Verilog). The logic
synthesis tool 903 compiles the logic, and optimizes it without any
sense of its physical representation, and with estimated timing
information. The placement tool 905 takes the logical description
and places each component, looking to minimize congestion in each
area of the design. The clock synthesis tool 907 optimizes the
clock tree network by cloning/balancing/buffering the latches or
registers. The timing closure step 909 performs a number of
optimizations on the design, including buffering, wire tuning, and
circuit repowering; its goal is to produce a design which is
routable, without timing violations, and without excess power
consumption. The routing stage 911 takes the placed/optimized
design, and determines how to create wires to connect all of the
components, without causing manufacturing violations. Post-route
timing closure 913 performs another set of optimizations to resolve
any violations that are remaining after the routing. Design
finishing 915 then adds extra metal shapes to the netlist, to
conform with manufacturing requirements. The checking steps 917
analyze whether the design is violating any requirements such as
manufacturing, timing, power, electromigration or noise, and the
like. When the design is clean, the final step 919 is to generate a
layout for the design, representing all the shapes to be fabricated
in the design to be fabricated 921.
[0044] Generally, embodiments of the present invention apply
machine learning computer vision to the visual appearance of layout
images produced from a circuit design pattern. Accordingly,
embodiments are implemented subsequent to step 919 of generating a
layout, so that the layout image(s) can be obtained and input to
the neural network. Thus, in case a circuit design pattern is
rejected based on the result of an embodiment of the invention,
then the process of FIG. 8 would revert back to a previous step
such as the routing stage 911. It is at this time that it would be
particularly helpful for a circuit designer to review the features
extracted by embodiments of the invention, in order to gain insight
as to how to adjust the circuit design pattern.
[0045] By way of clarification, FIGS. 5 and 7 include training and
implementation (inference). Data for training, or a training
dataset, can have corresponding labels associated in the case of
CNN classification. It is used as input to a machine learning (ML)
model to be "trained" to determine model parameters. Once this
training step is finished, the ML model is fixed, i.e. model
parameters will not change afterwards (in the inference step). Data
for inference is new data, never seen by the model, which is to be
"inferenced" for a label by the model. Such a label is generated by
passing the data through the fixed model. Any new data for a
trained model to predict a label is data for inference.
Accordingly, reference is made herein to training sets and
inference sets.
[0046] Given the discussion thus far, and with reference to the
accompanying drawing Figures, it will be appreciated that, in
general terms, an exemplary method 500 for rejecting a circuit
design pattern that is predicted to have local layout effect
includes at 701 obtaining a plurality of circuit design patterns
403; at 702 generating a plurality of layout images 404 each
corresponding to one of the plurality circuit design patterns; at
703 training a computer vision machine learning algorithm in an
unsupervised fashion to generate a training set of feature vectors
or encodings 611 for the plurality of layout images; and at 704
extracting feature vectors 611 from the layout images. The
exemplary method also includes at 708 generating a cluster plot of
the feature vectors. Then at 710 the method further includes
identifying an in-range cluster and an outlier cluster on the
cluster plot. At 724 the method includes identifying a circuit
design pattern that corresponds to a layout image that produced a
feature vector within the outlier cluster, and at 726 rejecting the
identified circuit design pattern.
[0047] In one or more embodiments, the exemplary method also
includes actually fabricating samples of circuit design patterns
that correspond to feature vectors present in each of the clusters;
and identifying the in-range cluster and the outlier cluster based
on experimental measurements of threshold voltage for
actually-fabricated circuit design patterns that are present in
each of the clusters.
[0048] In one or more embodiments, principal component analysis
(PCA) is used for dimensionality reduction of the feature
vectors.
[0049] In one or more embodiments, partitional clustering (e.g.,
k-means clustering) is used to cluster the feature vectors.
Alternatively, density based clustering or hierarchical clustering
can be used. After clustering the feature vectors, the in-range
cluster and the outlier cluster may be identified based on a
heuristic such as the in-range cluster having a certain number more
members than each of the outlier cluster(s) (e.g., a simple
majority, 10% more, 70% to 30%, 80% to 20%) or having greater
density than the outlier cluster(s). Other suitable heuristics will
be apparent to the skilled worker. The most direct heuristic is to
actually fabricate sample circuit designs represented in each
cluster, measure threshold voltages, and determine on that basis
which cluster is "in-range" and which cluster(s) are
"outliers."
[0050] In one or more embodiments, the computer vision machine
learning algorithm includes an autoencoder. In other embodiments,
the computer vision machine learning algorithm includes a
combination of a CNN with an autoencoder.
[0051] According to another aspect, an exemplary method for
rejecting circuit design patterns that are predicted to have local
layout effect includes at 701 obtaining a plurality of circuit
design patterns 603; at 702 generating a plurality of layout images
604 each corresponding to one of the plurality of circuit design
patterns; at 703 training a computer vision machine learning
algorithm in an unsupervised fashion to generate a training set of
feature vectors 611 for the plurality of layout images; and at 708
generating a cluster plot of the feature vectors. At 710 the method
includes identifying an in-range cluster and an outlier cluster on
the cluster plot. The exemplary method also includes at 714
obtaining an inference set of circuit design patterns; at 715
generating an inference set of layout images each corresponding to
one of the inference set of circuit design patterns; at 718 using
the computer vision machine learning algorithm to generate an
inference set of feature vectors for the inference set of layout
images; at 722 plotting on the cluster plot the inference set of
feature vectors; and at 724 identifying outlier members of the
inference set of layout images that produced feature vectors that
overlie the outlier cluster on the cluster plot. Further, at 726
the method includes rejecting circuit design patterns that
correspond to the outlier members of the inference set of layout
images.
[0052] In one or more embodiments, identifying the in-range cluster
and the outlier cluster includes actually fabricating samples of
circuit design patterns from each of the clusters and
experimentally measuring threshold voltage of at least one sample
from each of the clusters. In one or more embodiments, identifying
the in-range cluster and the outlier cluster includes counting a
number of members in each of the clusters. In one or more
embodiments, partitional clustering is used to identify the
in-range and outlier clusters.
[0053] In one or more embodiments, the cluster plot is a
2-dimensional cluster plot that is obtained by reducing
dimensionality of the feature vectors.
[0054] In one or more embodiments, the computer vision machine
learning algorithm includes a convolutional neural network (CNN).
In other embodiments, the computer vision machine learning
algorithm includes an autoencoder. In other embodiments, the
computer vision machine learning algorithm includes a combination
of a CNN with an autoencoder.
[0055] Another aspect provides an exemplary method for rejecting a
circuit design pattern that is predicted to have local layout
effect, which includes at 501 obtaining a plurality of circuit
design patterns; at 502 generating layout images from the circuit
design patterns; at 504 extracting feature vectors from the layout
images by processing the layout images in a computer vision machine
learning algorithm; at 522 comparing the feature vector extracted
from a selected layout image to clusters of feature vectors
extracted from the layout images, wherein the clusters of feature
vectors include an in-range cluster and an outlier cluster; and at
526 rejecting a circuit design pattern corresponding to the
selected layout image, for which threshold voltage has not been
experimentally measured, as being an outlier circuit design
pattern, in response to the feature vector of the selected layout
image correlating with the outlier cluster.
[0056] In one or more embodiments, the computer vision machine
learning algorithm is trained in a supervised fashion based on
measured values of threshold voltage for a majority of the circuit
design patterns.
[0057] One or more embodiments of the invention, or elements
thereof, can be implemented in the form of an apparatus including a
memory and at least one processor that is coupled to the memory and
operative to perform exemplary method steps, or in the form of a
non-transitory computer readable medium embodying computer
executable instructions which when executed by a computer cause the
computer to perform exemplary method steps. FIG. 9 depicts a
computer system that may be useful in implementing one or more
aspects and/or elements of the invention, also representative of a
cloud computing node according to an embodiment of the present
invention.
[0058] Referring now to FIG. 9, cloud computing node 10 is only one
example of a suitable cloud computing node and is not intended to
suggest any limitation as to the scope of use or functionality of
embodiments of the invention described herein. Regardless, cloud
computing node 10 is capable of being implemented and/or performing
any of the functionality set forth hereinabove.
[0059] In cloud computing node 10 there is a computer system/server
12, which is operational with numerous other general purpose or
special purpose computing system environments or configurations.
Examples of well-known computing systems, environments, and/or
configurations that may be suitable for use with computer
system/server 12 include, but are not limited to, personal computer
systems, server computer systems, thin clients, thick clients,
handheld or laptop devices, multiprocessor systems,
microprocessor-based systems, set top boxes, programmable consumer
electronics, network PCs, minicomputer systems, mainframe computer
systems, and distributed cloud computing environments that include
any of the above systems or devices, and the like.
[0060] Computer system/server 12 may be described in the general
context of computer system executable instructions, such as program
modules, being executed by a computer system. Generally, program
modules may include routines, programs, objects, components, logic,
data structures, and so on that perform particular tasks or
implement particular abstract data types. Computer system/server 12
may be practiced in distributed cloud computing environments where
tasks are performed by remote processing devices that are linked
through a communications network. In a distributed cloud computing
environment, program modules may be located in both local and
remote computer system storage media including memory storage
devices.
[0061] As shown in FIG. 9, computer system/server 12 in cloud
computing node 10 is shown in the form of a general-purpose
computing device. The components of computer system/server 12 may
include, but are not limited to, one or more processors or
processing units 16, a system memory 28, and a bus 18 that couples
various system components including system memory 28 to processor
16.
[0062] Bus 18 represents one or more of any of several types of bus
structures, including a memory bus or memory controller, a
peripheral bus, an accelerated graphics port, and a processor or
local bus using any of a variety of bus architectures. By way of
example, and not limitation, such architectures include Industry
Standard Architecture (ISA) bus, Micro Channel Architecture (MCA)
bus, Enhanced ISA (EISA) bus, Video Electronics Standards
Association (VESA) local bus, and Peripheral Component Interconnect
(PCI) bus.
[0063] Computer system/server 12 typically includes a variety of
computer system readable media. Such media may be any available
media that is accessible by computer system/server 12, and it
includes both volatile and non-volatile media, removable and
non-removable media.
[0064] System memory 28 can include computer system readable media
in the form of volatile memory, such as random access memory (RAM)
30 and/or cache memory 32. Computer system/server 12 may further
include other removable/non-removable, volatile/non-volatile
computer system storage media. By way of example only, storage
system 34 can be provided for reading from and writing to a
non-removable, non-volatile magnetic media (not shown and typically
called a "hard drive"). Although not shown, a magnetic disk drive
for reading from and writing to a removable, non-volatile magnetic
disk (e.g., a "floppy disk"), and an optical disk drive for reading
from or writing to a removable, non-volatile optical disk such as a
CD-ROM, DVD-ROM or other optical media can be provided. In such
instances, each can be connected to bus 18 by one or more data
media interfaces. As will be further depicted and described below,
memory 28 may include at least one program product having a set
(e.g., at least one) of program modules that are configured to
carry out the functions of embodiments of the invention.
[0065] Program/utility 40, having a set (at least one) of program
modules 42, may be stored in memory 28 by way of example, and not
limitation, as well as an operating system, one or more application
programs, other program modules, and program data. Each of the
operating system, one or more application programs, other program
modules, and program data or some combination thereof, may include
an implementation of a networking environment. Program modules 42
generally carry out the functions and/or methodologies of
embodiments of the invention as described herein.
[0066] Computer system/server 12 may also communicate with one or
more external devices 14 such as a keyboard, a pointing device, a
display 24, etc.; one or more devices that enable a user to
interact with computer system/server 12; and/or any devices (e.g.,
network card, modem, etc.) that enable computer system/server 12 to
communicate with one or more other computing devices. Such
communication can occur via Input/Output (I/O) interfaces 22. Still
yet, computer system/server 12 can communicate with one or more
networks such as a local area network (LAN), a general wide area
network (WAN), and/or a public network (e.g., the Internet) via
network adapter 20. As depicted, network adapter 20 communicates
with the other components of computer system/server 12 via bus 18.
It should be understood that although not shown, other hardware
and/or software components could be used in conjunction with
computer system/server 12. Examples, include, but are not limited
to: microcode, device drivers, redundant processing units, and
external disk drive arrays, RAID systems, tape drives, and data
archival storage systems, etc.
[0067] Thus, one or more embodiments can make use of software
running on a general purpose computer or workstation. With
reference to FIG. 9, such an implementation might employ, for
example, a processor 16, a memory 28, and an input/output interface
22 to a display 24 and external device(s) 14 such as a keyboard, a
pointing device, or the like. The term "processor" as used herein
is intended to include any processing device, such as, for example,
one that includes a CPU (central processing unit) and/or other
forms of processing circuitry. Further, the term "processor" may
refer to more than one individual processor. The term "memory" is
intended to include memory associated with a processor or CPU, such
as, for example, RAM (random access memory) 30, ROM (read only
memory), a fixed memory device (for example, hard drive 34), a
removable memory device (for example, diskette), a flash memory and
the like. In addition, the phrase "input/output interface" as used
herein, is intended to contemplate an interface to, for example,
one or more mechanisms for inputting data to the processing unit
(for example, mouse), and one or more mechanisms for providing
results associated with the processing unit (for example, printer).
The processor 16, memory 28, and input/output interface 22 can be
interconnected, for example, via bus 18 as part of a data
processing unit 12. Suitable interconnections, for example via bus
18, can also be provided to a network interface 20, such as a
network card, which can be provided to interface with a computer
network, and to a media interface, such as a diskette or CD-ROM
drive, which can be provided to interface with suitable media.
[0068] Accordingly, computer software including instructions or
code for performing the methodologies of the invention, as
described herein, may be stored in one or more of the associated
memory devices (for example, ROM, fixed or removable memory) and,
when ready to be utilized, loaded in part or in whole (for example,
into RAM) and implemented by a CPU. Such software could include,
but is not limited to, firmware, resident software, microcode, and
the like.
[0069] A data processing system suitable for storing and/or
executing program code will include at least one processor 16
coupled directly or indirectly to memory elements 28 through a
system bus 18. The memory elements can include local memory
employed during actual implementation of the program code, bulk
storage, and cache memories 32 which provide temporary storage of
at least some program code in order to reduce the number of times
code must be retrieved from bulk storage during implementation.
[0070] Input/output or I/O devices (including but not limited to
keyboards, displays, pointing devices, and the like) can be coupled
to the system either directly or through intervening I/O
controllers.
[0071] Network adapters 20 may also be coupled to the system to
enable the data processing system to become coupled to other data
processing systems or remote printers or storage devices through
intervening private or public networks. Modems, cable modem and
Ethernet cards are just a few of the currently available types of
network adapters.
[0072] As used herein, including the claims, a "server" includes a
physical data processing system (for example, system 12 as shown in
FIG. 9) running a server program. It will be understood that such a
physical server may or may not include a display and keyboard.
[0073] One or more embodiments can be at least partially
implemented in the context of a cloud or virtual machine
environment, although this is exemplary and non-limiting; the
system of FIG. 9 is also representative of non-cloud
implementations.
[0074] It should be noted that any of the methods described herein
can include an additional step of providing a system comprising
distinct software modules embodied on a computer readable storage
medium; the modules can include, for example, any or all of the
appropriate elements depicted in the block diagrams and/or
described herein; by way of example and not limitation, any one,
some or all of the modules/blocks and or sub-modules/sub-blocks
described. The method steps can then be carried out using the
distinct software modules and/or sub-modules of the system, as
described above, executing on one or more hardware processors such
as 16. Further, a computer program product can include a
computer-readable storage medium with code adapted to be
implemented to carry out one or more method steps described herein,
including the provision of the system with the distinct software
modules.
[0075] Exemplary System and Article of Manufacture Details
[0076] The present invention may be a system, a method, and/or a
computer program product at any possible technical detail level of
integration. The computer program product may include a computer
readable storage medium (or media) having computer readable program
instructions thereon for causing a processor to carry out aspects
of the present invention.
[0077] The computer readable storage medium can be a tangible
device that can retain and store instructions for use by an
instruction execution device. The computer readable storage medium
may be, for example, but is not limited to, an electronic storage
device, a magnetic storage device, an optical storage device, an
electromagnetic storage device, a semiconductor storage device, or
any suitable combination of the foregoing. A non-exhaustive list of
more specific examples of the computer readable storage medium
includes the following: a portable computer diskette, a hard disk,
a random access memory (RAM), a read-only memory (ROM), an erasable
programmable read-only memory (EPROM or Flash memory), a static
random access memory (SRAM), a portable compact disc read-only
memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a
floppy disk, a mechanically encoded device such as punch-cards or
raised structures in a groove having instructions recorded thereon,
and any suitable combination of the foregoing. A computer readable
storage medium, as used herein, is not to be construed as being
transitory signals per se, such as radio waves or other freely
propagating electromagnetic waves, electromagnetic waves
propagating through a waveguide or other transmission media (e.g.,
light pulses passing through a fiber-optic cable), or electrical
signals transmitted through a wire.
[0078] Computer readable program instructions described herein can
be downloaded to respective computing/processing devices from a
computer readable storage medium or to an external computer or
external storage device via a network, for example, the Internet, a
local area network, a wide area network and/or a wireless network.
The network may comprise copper transmission cables, optical
transmission fibers, wireless transmission, routers, firewalls,
switches, gateway computers and/or edge servers. A network adapter
card or network interface in each computing/processing device
receives computer readable program instructions from the network
and forwards the computer readable program instructions for storage
in a computer readable storage medium within the respective
computing/processing device.
[0079] Computer readable program instructions for carrying out
operations of the present invention may be assembler instructions,
instruction-set-architecture (ISA) instructions, machine
instructions, machine dependent instructions, microcode, firmware
instructions, state-setting data, configuration data for integrated
circuitry, or either source code or object code written in any
combination of one or more programming languages, including an
object oriented programming language such as Smalltalk, C++, or the
like, and procedural programming languages, such as the "C"
programming language or similar programming languages. The computer
readable program instructions may execute entirely on the user's
computer, partly on the user's computer, as a stand-alone software
package, partly on the user's computer and partly on a remote
computer or entirely on the remote computer or server. In the
latter scenario, the remote computer may be connected to the user's
computer through any type of network, including a local area
network (LAN) or a wide area network (WAN), or the connection may
be made to an external computer (for example, through the Internet
using an Internet Service Provider). In some embodiments,
electronic circuitry including, for example, programmable logic
circuitry, field-programmable gate arrays (FPGA), or programmable
logic arrays (PLA) may execute the computer readable program
instructions by utilizing state information of the computer
readable program instructions to personalize the electronic
circuitry, in order to perform aspects of the present
invention.
[0080] Aspects of the present invention are described herein with
reference to flowchart illustrations and/or block diagrams of
methods, apparatus (systems), and computer program products
according to embodiments of the invention. It will be understood
that each block of the flowchart illustrations and/or block
diagrams, and combinations of blocks in the flowchart illustrations
and/or block diagrams, can be implemented by computer readable
program instructions.
[0081] These computer readable program instructions may be provided
to a processor of a general purpose computer, special purpose
computer, or other programmable data processing apparatus to
produce a machine, such that the instructions, which execute via
the processor of the computer or other programmable data processing
apparatus, create means for implementing the functions/acts
specified in the flowchart and/or block diagram block or blocks.
These computer readable program instructions may also be stored in
a computer readable storage medium that can direct a computer, a
programmable data processing apparatus, and/or other devices to
function in a particular manner, such that the computer readable
storage medium having instructions stored therein comprises an
article of manufacture including instructions which implement
aspects of the function/act specified in the flowchart and/or block
diagram block or blocks.
[0082] The computer readable program instructions may also be
loaded onto a computer, other programmable data processing
apparatus, or other device to cause a series of operational steps
to be performed on the computer, other programmable apparatus or
other device to produce a computer implemented process, such that
the instructions which execute on the computer, other programmable
apparatus, or other device implement the functions/acts specified
in the flowchart and/or block diagram block or blocks.
[0083] The flowchart and block diagrams in the Figures illustrate
the architecture, functionality, and operation of possible
implementations of systems, methods, and computer program products
according to various embodiments of the present invention. In this
regard, each block in the flowchart or block diagrams may represent
a module, segment, or portion of instructions, which comprises one
or more executable instructions for implementing the specified
logical function(s). In some alternative implementations, the
functions noted in the blocks may occur out of the order noted in
the Figures. For example, two blocks shown in succession may, in
fact, be executed substantially concurrently, or the blocks may
sometimes be executed in the reverse order, depending upon the
functionality involved. It will also be noted that each block of
the block diagrams and/or flowchart illustration, and combinations
of blocks in the block diagrams and/or flowchart illustration, can
be implemented by special purpose hardware-based systems that
perform the specified functions or acts or carry out combinations
of special purpose hardware and computer instructions.
[0084] The descriptions of the various embodiments of the present
invention have been presented for purposes of illustration, but are
not intended to be exhaustive or limited to the embodiments
disclosed. Many modifications and variations will be apparent to
those of ordinary skill in the art without departing from the scope
and spirit of the described embodiments. The terminology used
herein was chosen to best explain the principles of the
embodiments, the practical application or technical improvement
over technologies found in the marketplace, or to enable others of
ordinary skill in the art to understand the embodiments disclosed
herein.
* * * * *