FinFET Threshold Voltage Tuning via Selective Oxidation
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Solution Overview
Problem
In integrated circuits, the intentional mismatch in threshold voltages between short channel and long channel FinFET devices often differs from the anticipated mismatch, leading to operational characteristics that do not meet design expectations due to fabrication variations.
Innovation Solution
The method involves forming fins for short and long channel FinFET devices with initially uniform sizes and performing an oxidation process to selectively reduce the size of the channel portions, allowing for the adjustment of threshold voltages by controlling the size of the fins, thereby tuning the threshold voltage mismatch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If intentional threshold voltage mismatch is designed between short channel and long channel FinFET devices, then independent turning on and off of devices is enabled, but fabrication variations cause actual mismatch to deviate from anticipated mismatch, resulting in operational characteristics that do not meet design expectations
Solution Approach 1:
The patent applies preliminary action by performing selective oxidation on the channel portion of fins before final device formation. This pre-treatment modifies the channel dimensions in advance, allowing compensation for fabrication variations. The oxidation process is selectively applied to specific fins based on their channel length characteristics, enabling pre-adjustment of threshold voltages to achieve the desired mismatch ratio before subsequent fabrication steps occur.
Solution Approach 2:
The patent implements local quality by applying oxidation selectively to the channel portion of specific fins rather than uniformly treating all fins. The oxidation is localized to regions where threshold voltage adjustment is needed, with different oxidation conditions applied to short channel fins versus long channel fins. This localized treatment creates the intended threshold voltage mismatch while leaving other device regions unaffected.
2Speed
If short channel devices are used for fast switching speeds, then switching performance is improved, but off-state leakage current increases
Solution Approach 1:
The patent applies parameter changes by modifying the physical dimensions of the fin channel portions through selective oxidation. By controlling the oxidation conditions (time, temperature, atmosphere), the channel width and height can be precisely adjusted. This dimensional parameter change directly affects both switching speed and off-state leakage current, allowing optimization of the trade-off between these two parameters. The oxidation process enables continuous tuning of channel dimensions to achieve desired device characteristics.
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 enables precise control over threshold voltages, allowing for the achievement of desired voltage mismatches between short and long channel devices, improving the operational characteristics of integrated circuits by reducing off-state leakage currents and enhancing switching speeds.
Implementation Method 1
performing an oxidation process to form a sacrificial oxide material selectively on the channel portion of one of the first and second fins but not on the channel portion of the other of the first and second fins
Data Source
AI summary
One illustrative method disclosed herein includes, among other things, forming first and second fins for a short channel FinFET device (“SCD”) and a long channel FinFET device (“LCD”), performing an oxidation process to form a sacrificial oxide material selectively on the channel portion of one of the first and second fins but not on the channel portion of the other of the first and second fins, removing the sacrificial oxide material from the fin on which it is formed so as to produce a reduced-size channel portion on that fin that is less than the initial size of the channel portion of the other non-oxidized fin, and forming first and second gate structures for the SCD and LCD devices.