FDSOI Transistor Co-Integration via Local Well Doping
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Solution Overview
Problem
Integrated circuits using FDSOI technology face challenges in co-integrating transistors with distinct threshold voltages without degrading consumption performance and increasing the risk of leakage currents due to singular points formed at junctions between semi-conducting wells with opposite dopings.
Innovation Solution
The integration of standard cells with transistors of different threshold voltages is achieved by aligning nMOS and pMOS transistors within the same row, using the same type of doping for wells in one cell and opposite types in another, and applying a bias circuit to control electrical biases, thereby minimizing leakage currents and maintaining optimal spatial distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If transistors with different threshold voltages are co-integrated in FDSOI technology, then circuit performance flexibility is improved, but leakage currents increase due to singular points at well junctions
Solution Approach 1:
The patent applies local quality by differentiating well doping types in specific local regions. First cells use wells of a first doping type while second cells use wells of a second doping type, creating localized doping variations that enable different threshold voltages without forming harmful singular points at junctions between opposite doping types.
Solution Approach 2:
The patent segments the integrated circuit into distinct first cells and second cells with different well doping configurations. This segmentation allows independent optimization of each cell type's threshold voltage characteristics while avoiding the formation of singular points at cell boundaries through proper doping type assignment.
2Adaptability or versatility
If various gate materials are integrated to produce transistors with distinct threshold voltages, then threshold voltage differentiation is achieved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent changes the doping type parameter of the wells rather than using different gate materials. By using wells of a first doping type in first cells and wells of a second doping type in second cells, the invention achieves threshold voltage differentiation through a single manufacturable process that varies only the doping parameter, not the gate material composition.
3Adaptability or versatility
If cells with distinct threshold voltages are co-integrated, then operating flexibility is improved, but electrical performance degradation occurs
Solution Approach 1:
The patent applies local quality by assigning specific doping types to specific cell regions. First cells containing transistors of a first type use wells of a first doping type, while second cells containing transistors of a second type use wells of a second doping type. This localized doping strategy optimizes electrical performance for each transistor type while maintaining overall circuit operating flexibility.
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 allows for the co-integration of transistors with different threshold voltages without degrading consumption performance, reducing the formation of singular points and leakage currents, and simplifying the design and fabrication of the circuit by reducing the length of electrical interconnections and avoiding the need for deep buried wells.
Implementation Method 1
applying a bias circuit to control electrical biases
Implementation Method 2
using the same type of doping for wells in one cell and opposite types in another
Data Source
AI summary
An integrated circuit includes a substrate with first and second cells having first and second FDSOI field-effect transistors. There are first and second ground planes, a buried oxide layer and first and second wells, under the ground planes. The first well and the first ground plane have the same doping and the second well and the second ground plane have the same doping. The first and second cells are adjoined and their transistors are aligned in a first direction. The wells of the first cell and the first well of the second cell are doped opposite of the second well. A control device applies a first electrical bias to the wells with the first doping and a second electrical bias to the well with the second doping. The transistors of the first cell and second cell have different threshold voltage levels.