Oxide Semiconductor Silicon Barrier for On-State Current
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Solution Overview
Problem
Transistors with oxide semiconductor films face increased resistance and decreased on-state current due to impurity entry, particularly silicon, at the interface with insulating films, which affects their performance and operation characteristics.
Innovation Solution
A semiconductor device structure is designed with an oxide semiconductor film where the silicon concentration at the interface with the insulating film is limited to 1.1 at. % or less within 5 nm, and the remaining film has a silicon concentration below 0.1 at. %, along with a gate electrode overlapping the oxide semiconductor film and source/drain electrodes connected to it, to minimize impurity impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If oxide semiconductor film is formed over insulating film containing silicon, then manufacturing is simplified and cost is reduced, but silicon impurities enter the oxide semiconductor film causing increased resistance and decreased on-state current
Solution Approach 1:
A silicon barrier film is introduced as an intermediary layer between the insulating film containing silicon and the oxide semiconductor film. This barrier film prevents silicon impurities from entering the oxide semiconductor film during formation, thereby maintaining high on-state current while still allowing the use of cost-effective insulating films containing silicon.
2Ease of manufacture
If oxide semiconductor film is formed over insulating film containing silicon, then manufacturing is simplified, but resistance of source and drain regions increases
Solution Approach 1:
The silicon barrier film serves as a protective intermediary that prevents silicon impurity diffusion into the oxide semiconductor film. This maintains the electrical resistance characteristics of source and drain regions at desired levels while preserving the manufacturing simplicity of using silicon-containing insulating films.
3Reliability
If impurity entry is suppressed by careful process design, then on-state current is maintained, but device complexity increases
Solution Approach 1:
The silicon barrier film provides a straightforward structural solution to prevent impurity entry. Rather than requiring complex process controls or multiple processing steps, the barrier film is simply formed between the insulating film and oxide semiconductor film, maintaining on-state current while adding minimal device complexity.
Data Source
AI summary
To suppress a decrease in on-state current in a semiconductor device including an oxide semiconductor. A semiconductor device includes an insulating film containing silicon, an oxide semiconductor film over the insulating film, a gate insulating film containing silicon over the oxide semiconductor film, a gate electrode which is over the gate insulating film and overlaps with at least the oxide semiconductor film, and a source electrode and a drain electrode which are electrically connected to the oxide semiconductor film. In the semiconductor device, the oxide semiconductor film which overlaps with at least the gate electrode includes a region in which a concentration of silicon distributed from an interface with the insulating film is lower than or equal to 1.1 at. %. In addition, a concentration of silicon contained in a remaining portion of the oxide semiconductor film except the region is lower than the concentration of silicon contained in the region.