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US 2003/0192025 A1Published application
Automated flow in PSM phase assignment
AssigneeNumerical Technologies, Inc.
InventorHua-Yu Liu
Life of this patent
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AssigneeNumerical Technologies, Inc.
InventorHua-Yu Liu
Estimating the term…
An automated phase assignment method is described that allows multiple rules for defining phase shifters to be used within a single cell. The rules for defining phase shifters can be sequenced. Then for a cell, the rules can be recursively applied. At each stage if the number of phase conflicts is below a threshold, then portions of the cell having conflicts are masked and processed using the next less aggressive rule set. This in turn leads to phase shifting masks with greater variation in phase shifter shapes and sizes. When the mask is used to fabricate integrated circuits (ICs), the resulting IC may have a greater number of small transistors and other features than a mask defined using only a single rule set per cell. Additional benefits can include better process latitude during IC fabrication and improved yield.
A method of automatically applying phase shifting rule sets to a layout, the method comprising:
A method for manufacturing an integrated circuit, the method comprising:
A phase shifting mask for fabricating an integrated circuit, the phase shifting mask comprising:
An integrated circuit exhibiting enhanced performance, the enhanced performance resulting from exposing a phase shifting mask formed using a layout, the layout including a plurality of cells, wherein at least one cell includes multiple phase shifting rule sets applied automatically by a system to facilitate fabrication of a higher percentage of gates using the most aggressive phase shifting rules than could be fabricated if only a single set of parameters was used for forming the gates.
A system of providing phase assignment, the system comprising:
An output file regarding phase assignment in a layout, the output file including:
A computer program product comprising:
A method of automatically applying phase shifting rule sets to a layout, the method comprising:
Dependencies are inferred from the claim text.
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Circuit design: circuit design at the physical level
Computing and data processing
Term end not estimated
1. Field of the Invention
The invention relates to a phase shifting mask (PSM) process, and particularly to an automated flow in PSM phase assignment.
2. Description of the Related Art
FIG. 1A illustrates a simplified layout including a plurality of features with their associated shifters, wherein phase conflicts exist in both intra-cell and inter-cell regions of the layout.
FIG. 1B illustrates one analysis pattern, i.e. a grid of uniform squares, which defines a plurality of cells.
FIG. 1C illustrates another analysis pattern that defines a plurality of non-uniform cells.
FIGS. 2A-2D illustrate a methodology 200 in which different rule sets can be applied to different regions of a single cell, thereby advantageously allowing more aggressive rule sets to be used more frequently. In methodology 200, a process can receive user input and/or include default settings in step 201. The user input can include, for example, layout and parameter information. Parameter information (explained in further detail in reference to FIGS. 3A, 3B, and 4) can include, for example, shifter widths, endcap margins, and fieldcap margins associated with each rule set. In one embodiment where user input is not provided, default parameter settings can be provided automatically by a system.
If all cells have not been phase shifted, as determined in step 202, then step 203 attempts to phase shift the next cell with the 1st rule set (i.e. the most aggressive rule set). If using the 1st rule set does not cause a phase conflict, as determined in step 204, then the cell can be phase shifted with the 1st rule set in step 205 and the process can return to step 202. However, if a phase conflict does arise as a result of the 1st rule set, then step 206 determines whether the number/percentage of phase conflicts is greater than a first limit X(1). The number of phase conflicts can be calculated by counting the phase conflicts within the cell. The percentage of phase conflicts can be calculated by dividing the number of phase conflicts in a cell by the total number of features that can be defined using phase shifting in that cell. Note that methodology 200 is equally applicable to numbers or percentages. For ease of reference, the term “number” will be used for purposes of describing the limit X(n) in FIGS. 2A-2D and will mean either the number or percentage of phase conflicts.
If the number of phase conflicts is less than the first limit X(1), then any area with a phase conflict is masked in step 207 and the remainder of the cell can be phase shifted with the 1st rule set in step 208. Step 209 attempts to phase shift the masked areas with a 2nd rule set (i.e. a rule set less aggressive than the 1st rule set). Note that if the number of phase conflicts is more than the first limit X(1), then step 210 attempts to phase shift the whole cell with the 2nd rule. Following either step 209 or 210, step 211 determines whether any phase conflicts are present.