SOI STI Stress Modeling via Body-Tie Mobility Multiplier
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Solution Overview
Problem
Current models, such as the BSIM4 SPICE model, are inadequate for accurately modeling stress effects in silicon-on-insulator (SOI) processes due to their inability to consider the impact of a body-tie on shallow trench isolation (STI) stress, which can lead to device leakage and defects in MOSFETs.
Innovation Solution
A method is developed to model STI stress effects in SOI technology by creating instance parameters defining the body-tie enclosure dimensions, generating a mobility multiplier using these parameters, and integrating them into a netlist for circuit simulation, allowing for accurate simulation of stress effects using tools like Calibre's well proximity effect capability and SPICE models.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the standard BSIM4 SPICE model is used to model STI stress effect, then the modeling process is simple and familiar, but the model accuracy is insufficient for SOI devices because it does not account for body-tie impact
Solution Approach 1:
The patent segments the STI stress modeling into two distinct parts: (1) the standard BSIM4 model for general MOSFET behavior, and (2) an additional mobility multiplier component specifically for capturing body-tie effects in SOI devices. This segmentation allows the complex SOI stress modeling to be built upon the familiar BSIM4 foundation without completely replacing it, thereby improving accuracy while managing complexity through modular addition.
Solution Approach 2:
The patent introduces a mobility multiplier as an intermediary component that bridges the gap between the standard BSIM4 model and the specific requirements for SOI stress modeling. This mobility multiplier acts as a mediator that captures the body-tie effects and modulates the carrier mobility accordingly, allowing the standard model to be enhanced without fundamental redesign.
2Device complexity
If the 1/LOD model is used to approximate stress effect, then the modeling is simplified, but it fails to consider body-tie impact and provides insufficient accuracy
Solution Approach 1:
The patent changes the key parameter from the simple LOD (length of outside diameter) to a comprehensive set of body-tie enclosure dimension parameters. By changing from a single geometric parameter to multiple parameters that specifically describe body-tie enclosure dimensions, the model captures the previously neglected body-tie impact while maintaining a systematic parameter-based approach.
3Measurement precision
If body-tie enclosure dimensions are precisely measured and modeled, then stress simulation accuracy is improved, but the number of parameters and model complexity increases
Solution Approach 1:
The patent applies local quality by focusing the detailed parameter measurement specifically on the body-tie enclosure dimensions rather than requiring precise measurement of all device parameters. The instance parameters are created locally at the body-tie enclosure region, capturing the critical stress-affecting geometry without requiring comprehensive parameterization of the entire device structure.
Data Source
AI summary
A method and system for modeling silicon-on-insulator shallow trench isolation stress effect is described. The method includes creating instance parameters that define dimensions of a body-tie enclosure of gate and gate-end. The instance parameters are added to a netlist. The netlist and a lookup table are used to generate a mobility multiplier. The mobility multiplier is added to the netlist and a circuit simulation program runs the netlist having the instance parameters and the mobility multiplier.