Double Gate Transistor Charge Density Calculation Under Strong Forward Back Bias
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Solution Overview
Problem
Existing compact models for ultra-thin body transistors, such as FinFETs and UTBB MOSFETs, are not realistic when strong forward back bias is applied, as they assume the interface between the body and buried oxide is always depleted, leading to inaccurate device characteristics.
Innovation Solution
A computer-implemented method for determining charge densities in the front and/or back gates of double gate transistors using a physical processor, involving initial estimates and corrections based on Taylor development of a function to accurately calculate charge densities across a wide range of geometries and biases, including strong forward back bias scenarios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the interface between the body and buried oxide is assumed always depleted (as in existing compact models), then the model is simple and works for reverse and low forward back bias, but the model becomes unrealistic and inaccurate when strong forward back bias is applied
Solution Approach 1:
The patent applies the dynamics principle by making the interface condition dynamic rather than static. The interface between the body and buried oxide transitions from depleted to inverted based on the applied back bias conditions. The model dynamically adjusts the interface state (depleted or inverted) according to the operating conditions, allowing it to accurately represent both reverse/low forward bias and strong forward bias scenarios without requiring separate models.
2Adaptability or versatility
If a compact model describes transistor behavior for a wide range of back bias, then it provides useful design information, but it requires complex calculations that may not account for inversion at the back interface under strong forward back bias
Solution Approach 1:
The patent applies parameter changes by modifying the key parameter of interface charge density based on the applied bias conditions. The model changes the physical state parameter (depleted vs. inverted) of the back interface according to the back bias voltage, allowing accurate description across the full range of operating conditions. This parameter-based approach enables the model to adapt to different bias regimes without becoming overly complex.
Data Source
AI summary
A computer implemented method for calculating a charge density q1 of a first gate of a double gate transistor comprising a thin body with a first and a second gate interface, the method including determining, using a physical processor, an initial estimate q1,init of the charge density of the first gate; performing, using the physical processor, at least two basic corrections of the initial estimate based on a Taylor development of a function fzero(q1) able to be nullified by a correct value of the charge density q1 of the first gate.