Oxide Semiconductor Transistor Side Contact
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Solution Overview
Problem
Conventional fin-type transistors with oxide semiconductor materials face challenges in reducing on-state current and variations in electrical characteristics due to high contact resistance and miniaturization, leading to increased power consumption and instability.
Innovation Solution
A semiconductor element with an oxide semiconductor layer and low-resistance regions, where the electrode is electrically connected to the side surfaces of the low-resistance regions through grooves, reducing contact resistance and increasing the contact area, and the gate electrode covers the top and side surfaces of the channel formation region with a gate insulating film in between.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If oxide semiconductor material is used for an active layer to reduce off-state current, then off-state current is reduced to extremely low levels, but contact resistance to metal film electrodes increases
Solution Approach 1:
The patent applies local quality by creating low-resistance regions with different doping concentrations in specific areas of the oxide semiconductor layer. The channel formation region maintains low doping for low off-state current, while source and drain regions have higher doping for reduced contact resistance, allowing each region to have optimized properties for its specific function
Solution Approach 2:
The patent transitions from planar contact to three-dimensional contact by having electrodes extend into grooves and contact the oxide semiconductor layer from the side surfaces and bottom surfaces. This multi-dimensional contact approach increases the effective contact area without increasing the planar footprint, thereby reducing contact resistance while maintaining the low off-state current benefit
2Volume of moving object
If fin-type transistor structure is miniaturized to reduce device size, then device integration is improved, but on-state current decreases and variations in electrical characteristics increase due to contact resistance
Solution Approach 1:
The patent addresses miniaturization challenges by moving from two-dimensional planar contact to three-dimensional contact structures. Electrodes are formed to extend into grooves and contact the oxide semiconductor layer from multiple surfaces (top, side, and bottom), effectively increasing the contact area in three dimensions. This allows fin-type transistors to be miniaturized while maintaining stable electrical characteristics through enhanced contact area that compensates for the reduced device dimensions
3Reliability
If electrode contact area with oxide semiconductor layer is increased to reduce contact resistance, then on-state current is maintained, but device area increases
Solution Approach 1:
The patent resolves the area conflict by utilizing three-dimensional space for electrode contact. Instead of increasing the planar contact area, electrodes are formed to extend vertically and laterally into grooves, contacting the oxide semiconductor layer from multiple surfaces. This multi-dimensional contact approach increases the effective contact area (reducing contact resistance) without proportionally increasing the planar device footprint, as the additional contact area is achieved in the vertical dimension through groove structures
Data Source
AI summary
A structure including an oxide semiconductor layer which is provided over an insulating surface and includes a channel formation region and a pair of low-resistance regions between which the channel formation region is positioned, a gate insulating film covering a top surface and a side surface of the oxide semiconductor layer, a gate electrode covering a top surface and a side surface of the channel formation region with the gate insulating film positioned therebetween, and electrodes electrically connected to the low-resistance regions is employed. The electrodes are electrically connected to at least side surfaces of the low-resistance regions, so that contact resistance with the source electrode and the drain electrode is reduced.