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Threshold Voltage Adjustment by Varying Ge Content in SiGe p-Channel for Single Metal Shared Gate Complementary FET
Chong-Jhe Sun1, Chen-Han Wu1, Yi-Ju Yao1
1Department of Engineering and System Science, National Tsing Hua University, Hsinchu 30013, Taiwan.
Nanomaterials (Basel, Switzerland)
|October 27, 2022
Summary
We adjusted the threshold voltage (VT) in advanced transistors by controlling Germanium (Ge) content in silicon-germanium (SiGe) channels. This method effectively addresses work function metal filling challenges in scaled MOSFETs.
Area of Science:
- Materials Science
- Electrical Engineering
- Semiconductor Physics
Background:
- Scaling limitations in Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) necessitate novel approaches for device performance control.
- Work function metal (WFM) filling presents a significant challenge in highly scaled complementary field-effect transistors (CFETs).
- Precise threshold voltage (VT) adjustment is critical for optimizing transistor functionality and circuit performance.
Purpose of the Study:
- To demonstrate a method for adjusting the threshold voltage (VT) in N1 CFETs by controlling Germanium (Ge) content within the SiGe p-channel.
- To address the work function metal (WFM) filling issue in highly scaled MOSFETs.
- To investigate the tunability of VT in a single WFM shared gate N1 CFET using Ge content modulation.
Main Methods:
- Utilized a single WFM shared gate N1 CFET structure to study the proposed Ge content method.
- Controlled the Ge content in the SiGe p-channel to adjust the threshold voltage (VT).
- Analyzed the energy band configuration of Si1-xGex to correlate with experimental VT shifts.
Main Results:
- Demonstrated a clear relationship between Ge mole fraction and the p-type threshold voltage (VTP), observing a shift of 5 mV/Ge%.
- Validated the experimental VT tunability with theoretical energy band calculations for Si1-xGex.
- Presented a well-designed voltage transfer curve and inverter transient response for the CFET inverter with Ge-content-adjusted VT.
- Successfully constructed a 6T-Static Random-Access Memory (SRAM) using the designed CFET inverter, achieving a large static noise margin (SNM) of approximately 120 mV at a supply voltage (VDD) of 0.5 V.
Conclusions:
- Controlling Ge content in the SiGe p-channel is an effective method for adjusting VT in N1 CFETs.
- This approach successfully mitigates WFM filling issues in scaled MOSFETs.
- The demonstrated CFET inverter and 6T-SRAM exhibit promising performance characteristics for future integrated circuits.
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