Layout quality gauge for integrated circuit design
First Claim
1. A system for assessing and enforcing layout quality in terms of uniformity of gate lengths derived from wafer shapes in very large scale integrated chip (VLSI) design, the system comprising:
- a processor configured for;
receiving as input a layout of a VLSI chip;
obtaining a description of a plurality of gates on the layout, comprising obtaining a threshold value for a predetermined uniformity of gate length; and
obtaining a description of process variability specifying process conditions;
a shape processor configured for obtaining wafer shapes to compute gates over the layout for each process point in a process window;
the processor further configured for;
describing the layout by measuring the device dependent electrically-equivalent gate lengths of said plurality of gates from their corresponding wafer shapes;
measuring the device dependent electrically-equivalent gate lengths of said plurality of gates from their corresponding wafer shapes that are equivalent with respect to device off-current;
determining any gate within said plurality of gates that violates the predetermined uniformity of gate length threshold; and
flagging the gates that violate the threshold as outliers, wherein the flagging comprises placing a marker on the layout where the outlier is located; and
a tool for generating a histogram of gate lengths across the layout and across the process window, wherein a number and magnitude of the violation serves as a layout quality gauge.
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Accused Products
Abstract
A method for layout design includes steps or acts of: receiving a layout for design of an integrated circuit chip; designing mask shapes for the layout; transmitting the mask shapes to a litho simulator for generating wafer shapes; receiving the wafer shapes; calculating electrically equivalent gate lengths for the wafer shapes; analyzing the gate lengths to check for conformity against a threshold value, wherein the threshold value represents a desired value of electrically equivalent gate lengths; placing markers on the layout at those locations where the gate length violates the threshold value; and generating a histogram of gate lengths for comparing layouts for electrically equivalent gate lengths for layout quality.
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Citations
18 Claims
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1. A system for assessing and enforcing layout quality in terms of uniformity of gate lengths derived from wafer shapes in very large scale integrated chip (VLSI) design, the system comprising:
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a processor configured for; receiving as input a layout of a VLSI chip; obtaining a description of a plurality of gates on the layout, comprising obtaining a threshold value for a predetermined uniformity of gate length; and obtaining a description of process variability specifying process conditions; a shape processor configured for obtaining wafer shapes to compute gates over the layout for each process point in a process window; the processor further configured for; describing the layout by measuring the device dependent electrically-equivalent gate lengths of said plurality of gates from their corresponding wafer shapes; measuring the device dependent electrically-equivalent gate lengths of said plurality of gates from their corresponding wafer shapes that are equivalent with respect to device off-current; determining any gate within said plurality of gates that violates the predetermined uniformity of gate length threshold; and flagging the gates that violate the threshold as outliers, wherein the flagging comprises placing a marker on the layout where the outlier is located; and a tool for generating a histogram of gate lengths across the layout and across the process window, wherein a number and magnitude of the violation serves as a layout quality gauge. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method for layout design, the method comprising steps of:
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using a processor for;
receiving a layout for design of an integrated circuit chip;obtaining a description of process variability specifying process conditions; obtaining mask shapes designed for the layout, subject to the specified process conditions to compute gates over the layout for each process point in a process window; transmitting the mask shapes to a litho simulator for generating wafer shapes; receiving the wafer shapes from the litho simulator; calculating electrically equivalent gate lengths for the wafer shapes; analyzing the gate lengths for conformance to threshold values, wherein the threshold values represent acceptable values of electrically equivalent gate lengths; placing markers on the layout at those locations where the gate length violates the threshold value; and generating a histogram of the gate lengths for comparing the layout to other layouts for layout quality by checking conformity to specified variations of electrically equivalent gate lengths. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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18. A computer program product tangibly embodied on a non-transitory computer readable medium and storing code that, when executed, causes a computer to perform a method comprising:
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receive a layout for design of an integrated circuit chip; obtaining a description of process variability specifying process conditions; obtain mask shapes designed for the layout, subject to the specified process conditions to compute gates over the layout for each process point in a process window; transmit the mask shapes to a litho simulator for generating wafer shapes; receive the generated wafer shapes from the litho simulator; calculate electrically equivalent gate lengths for the wafer shapes; analyze the gate lengths to check conformity against a threshold value, wherein the threshold value represents a desired value of electrically equivalent gate length; place markers on the layout at those locations where the gate length violates the threshold value; and generate a histogram of gate lengths for comparing the layout to other layouts for layout quality by checking conformity to specified variation of electrically equivalent gate lengths.
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Specification