Semiconductor Device LOD Optimization for Leakage and Speed
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Solution Overview
Problem
The performance of semiconductor devices is affected by the Length of Diffusion (LOD) effect, which varies the threshold voltage of field effect transistors based on the distance between the element isolation layer and the gate electrode, leading to inefficiencies in power consumption and operating speed.
Innovation Solution
The semiconductor device is designed with specific configurations of transistors and element isolation layers, where transistors with varying LOD values are strategically placed to optimize threshold voltages, reducing off-leakage currents and enhancing ON current and speed, by connecting transistors in parallel and series within distinct semiconductor regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If transistors are placed with larger distance between element isolation layer and gate electrode, then threshold voltage increases and off-leakage current decreases, but operating speed decreases
Solution Approach 1:
The semiconductor device divides transistors into multiple groups with different LOD values. Specifically, first and second transistors have a first LOD value optimized for low off-leakage current, while third and fourth transistors have a second LOD value optimized for high operating speed. This segmentation allows different parts of the device to be optimized for different performance criteria simultaneously.
Solution Approach 2:
Different transistors within the same device are assigned different local qualities in terms of their LOD values. The first and second transistors are configured with larger LOD values to minimize off-leakage current, while the third and fourth transistors are configured with smaller LOD values to maximize operating speed. This local differentiation resolves the contradiction by allowing each transistor to be optimized for its specific functional role.
2Speed
If transistors are placed with smaller distance between element isolation layer and gate electrode, then operating speed increases, but off-leakage current increases
Solution Approach 1:
The device segments transistors into functional groups with different LOD characteristics. Third and fourth transistors use a second LOD value (smaller distance) to achieve high operating speed for critical path operations, while first and second transistors use a first LOD value (larger distance) to minimize off-leakage current. This segmentation enables speed-critical sections to operate fast while other sections maintain low leakage.
Solution Approach 2:
The invention applies local quality by assigning different LOD values to different transistor locations based on their functional requirements. Transistors in speed-critical paths (third and fourth) have smaller LOD values for faster operation, while transistors where leakage is more critical (first and second) have larger LOD values. This localized optimization resolves the speed-leakage contradiction.
3Ease of manufacture
If uniform LOD value is used for all transistors, then manufacturing is simplified, but device performance is suboptimal
Solution Approach 1:
The invention changes the LOD parameter differently for different transistor groups to optimize overall device performance. By establishing that first and second transistors have a first LOD value and third and fourth transistors have a second LOD value, the device achieves superior performance compared to uniform LOD configurations. The manufacturing process is adapted to accommodate these different parameter settings through controlled distance variations.
Data Source
AI summary
A semiconductor device includes first, second and third semiconductor regions, each surrounded by an element isolation layer, first and second transistors of the first semiconductor region connected in parallel between first and second nodes, a third transistor of the second semiconductor region between the second node and the first transistor, and a fourth transistor of the third semiconductor region between the second node and the second transistor. Gates of the first and second transistors extend in a first direction and are spaced from each other in a second direction. A first distance which is equal to a longer of two distances between the element isolation layer and the gate electrode of the first transistor in the second direction, is greater than a second distance which is equal to a longer of two distances between the element isolation layer and the gate electrode of the third transistor in the second direction.