Transistor Gate Shape Layout for Optical Proximity Correction
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Solution Overview
Problem
Nanometer-scale semiconductor fabrication technologies result in non-uniform transistor gate shapes due to optical effects, leading to undesirable operating characteristics such as current crowding, excessive leakage currents, and overheating, which complicate circuit design and are not adequately addressed by existing Optical Proximity Correction (OPC) methods.
Innovation Solution
A system that generates a transistor layout by determining a transistor gate shape based on a library of correlated operating characteristics, allowing for the selection and scaling of parameterized library elements to achieve desired operating characteristics, including uniform threshold voltage and current distribution, and post-processing to approximate the desired gate shape during optical proximity correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If nanometer-scale semiconductor fabrication technologies are used to increase transistor density, then the number of transistors on IC chips increases and cost decreases, but optical effects cause non-uniform gate shapes leading to current crowding, excessive leakage, and overheating
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing optimal gate shapes in a library that account for optical effects before actual transistor design. The system determines gate shapes that will produce uniform fabricated dimensions despite optical distortions during lithography, allowing designers to directly select pre-optimized shapes without real-time correction.
Solution Approach 2:
The patent employs parameter changes by modifying gate shape parameters (width, length, curvature) based on correlation data that maps drawn dimensions to fabricated dimensions. The system adjusts gate shape parameters to compensate for optical effects, transforming the gate shape from a simple rectangle to optimized contours that achieve uniform threshold voltage and current distribution.
2Manufacturing precision
If Optical Proximity Correction (OPC) is used to adjust drawn transistor gate shape, then fabricated gate shape becomes substantially rectangular, but transistors with smaller feature sizes still exhibit non-uniform threshold voltage and current density
Solution Approach 1:
The patent implements feedback by using measured correlation data between drawn and fabricated transistor characteristics to inform gate shape selection. The library contains experimentally determined relationships that feed back into the design process, allowing the system to select gate shapes that will produce desired fabricated characteristics based on prior measurements and observations.
Solution Approach 2:
The patent applies preliminary action by pre-determining gate shapes through correlation studies and storing them in a library. Instead of applying corrective transformations during design, the system pre-calculates optimal shapes that directly achieve uniform threshold voltage and current density, eliminating the need for subsequent OPC adjustments.
3Manufacturing precision
If transistor gate shape is adjusted to achieve uniform fabricated shape, then rectangular gate shape is obtained, but the transistor's operating characteristics become a non-linear function of channel width complicating circuit design
Solution Approach 1:
The patent employs parameter changes by selecting gate shapes with specific dimensional parameters that create linear relationships between channel width and operating characteristics. The library contains gate shapes parameterized to achieve proportional scaling of drive strength with width, allowing circuit designers to use standard linear design models rather than dealing with non-linear functions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system ensures that fabricated transistors achieve desired operating characteristics, such as uniform threshold voltage and proportional drive strength, simplifying circuit design and reducing manufacturing complexities by accounting for optical effects in the gate shape generation process.
Implementation Method 1
optical effects, such as interference and fringing, can cause the shape of a feature to be different than the intended shape of the feature
Data Source
AI summary
A system that generates a layout for a transistor is presented. During operation, the system receives a transistor library which includes operating characteristics of fabricated transistors correlated to transistor gate shapes. The system also receives one or more desired operating characteristics for the transistor. Next, the system determines a transistor gate shape for the transistor based on the transistor library so that a fabricated transistor with the transistor gate shape substantially achieves the one or more desired operating characteristics. The system then generates the layout for the transistor which includes the transistor gate shape.