Silicided Source Drain Extensions Transistor Series Resistance
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Solution Overview
Problem
Conventional transistor structures experience significant series resistance and silicon damage due to unsilicided source and drain extension regions, which are degraded during contact etch, leading to increased junction leakage and standby current.
Innovation Solution
The implementation of silicide on both source and drain extension regions with a thickness less than that on the source and drain diffusion regions, acting as an etch stop layer and reducing series resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If unsilicided source and drain extension regions are formed between the transistor gate and silicided source and drain regions, then the transistor structure is simpler to manufacture, but the series resistance increases significantly degrading transistor performance
Solution Approach 1:
The patent applies silicide selectively to specific regions: the source and drain extension regions receive silicide treatment, while other regions maintain their original structure. This local modification reduces series resistance in critical areas without requiring complete silicidation of the entire transistor structure, thus balancing manufacturing simplicity with performance improvement
Solution Approach 2:
The silicide is formed on the source and drain extension regions before the contact etch process. This preliminary silicidation creates a protective layer that prevents silicon loss and damage during subsequent contact etching, ensuring the extension regions maintain their intended dimensions and electrical properties
2Manufacturing precision
If contact etch is performed with high selectivity to silicide, then the contact formation precision is improved, but the source and drain extensions suffer silicon loss and damage when contact lands on them
Solution Approach 1:
The patent forms silicide on the source and drain extension regions before contact etching. This silicide layer acts as a protective cushion that prevents the high-selectivity contact etch from removing silicon and dopant from the extension regions, thereby preventing silicon loss and damage while maintaining the high precision contact formation
Solution Approach 2:
The patent converts the potentially harmful effect of high-selectivity contact etch into a beneficial protective mechanism. By forming silicide on the extension regions first, the etch process selectively removes the silicide (which is then replaced or protected) rather than the silicon, thus protecting the extension regions from damage while maintaining precise contact alignment
3Adaptability or versatility
If contact is oversized or misaligned, then the contact design rule flexibility is improved, but the source and drain extensions suffer silicon loss and dopant removal causing higher series resistance
Solution Approach 1:
The silicide formed on the source and drain extension regions serves as a protective cushion against oversized or misaligned contacts. When contacts extend beyond their ideal boundaries, the silicide layer prevents the contact etch from removing silicon and dopant from the extension regions, maintaining electrical performance despite contact misalignment
Solution Approach 2:
The patent converts the potential harm of oversized or misaligned contacts into a beneficial outcome. The silicide layer on the extension regions causes the contact etch to selectively remove silicide rather than silicon, so even when contacts are oversized or misaligned, the extension regions remain intact and functional
4Ease of manufacture
If contact etch damages the silicon in the source and drain extension region, then the contact formation process is simpler, but junction leakage and standby current increase
Solution Approach 1:
The silicide formed on the source and drain extension regions acts as a protective cushion during contact etching. This preliminary silicidation prevents the contact etch from damaging the silicon in the extension regions, thereby preventing increased junction leakage and standby current while maintaining a relatively simple contact formation process
Solution Approach 2:
The silicide is formed on the extension regions before contact etching to prevent damage. This preliminary protective action ensures that the subsequent contact formation process does not cause silicon damage that would lead to increased leakage and standby current
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 enhances transistor performance by lowering series resistance and protecting the source and drain extensions from etch damage, thereby improving overall transistor efficiency and reliability.
Implementation Method 1
The silicide on the source/drain extension regions lowers the series resistance of the transistor giving the transistor a performance boost and protects the source/drain extension regions from silicon loss and silicon damage during contact etch
Implementation Method 2
The silicide on the source/drain extension regions lowers the series resistance of the transistor giving the transistor a performance boost
Data Source
AI summary
A transistor is formed in a semiconductor substrate with a gate over a channel region, source/drain extension regions in the substrate adjacent the channel region, and source/drain regions in the substrate adjacent the source/drain extension regions. Silicide is formed on the source/drain extension regions and the source/drain regions so that the silicide has a first thickness over the source/drain extension regions and a second thickness over source/drain regions, with the second thickness being greater than the first thickness. Silicide on the source/drain extension regions lowers transistor series resistance which boosts transistor performance and also protects the source/drain extension regions from silicon loss and silicon damage during contact etch.