Body Bias Isolation Structures for Transistor Performance
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Solution Overview
Problem
Integrated circuits face challenges in efficiently managing power consumption due to poor isolation structures between transistor body regions, leading to increased power demands and thermal management issues, which limits the granularity of selective body bias adjustments.
Innovation Solution
The implementation of body bias isolation structures using shallow trench isolation (STI) trenches and nitride masks for dopant implantation, allowing for independent biasing of transistor body regions while minimizing circuit real estate consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If isolation structures are made larger to improve body bias isolation between regions, then isolation effectiveness is improved, but circuit real estate consumption increases
Solution Approach 1:
The patent transitions from planar isolation structures to three-dimensional trench isolation structures. By etching trenches into the substrate and filling them with insulating material, the isolation is extended into the vertical dimension, achieving better electrical isolation between body regions without proportionally increasing the horizontal area footprint.
Solution Approach 2:
The isolation structures use composite construction combining the semiconductor substrate material with insulating materials (such as oxide or nitride) filled in the trenches. This composite approach provides both mechanical support from the substrate and electrical isolation from the insulating material, achieving effective isolation in a compact structure.
2Loss of energy
If selective body bias control is implemented to reduce power consumption, then power efficiency is improved, but the granularity of bias adjustment is limited by isolation structure efficiency
Solution Approach 1:
The patent divides the semiconductor substrate into multiple independently biasable body regions using trench isolation structures. Each region can be independently biased through separate body terminals, allowing selective power management for different functional blocks (e.g., biasing non-critical regions to reduce leakage while maintaining forward bias in critical performance regions).
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
This approach enables optimized transistor performance by allowing forward body biases in critical regions for speed and reverse body biases in non-critical regions to reduce power consumption, thereby balancing power efficiency and performance without excessive area usage.
Implementation Method 1
A nitride mask may be used as an etch mask when forming the trenches.
Implementation Method 2
The nitride mask may also be used as an implant mask when implanting dopant at the bottom of the trenches.
Implementation Method 3
The implanted dopant forms doped regions at the bottom of the trenches.
Data Source
AI summary
An integrated circuit is provided with transistor body regions that may be independently biased. Some of the bodies may be forward body biased to lower threshold voltages and increase transistor switching speed. Some of the bodies may be reverse body biased to increase threshold voltages and decrease leakage current. The integrated circuit may be formed on a silicon substrate. Body bias isolation structures may be formed in the silicon substrate to isolate the bodies from each other. Body bias isolation structures may be formed from shallow trench isolation trenches. Doped regions may be formed at the bottom of the trenches using ion implantation. Oxide may be used to fill the trenches above the doped region. A deep well may be formed under the body regions. The deep well may contact the doped regions that are formed at the bottom of the trenches.