Oxide NMOS Channel Materials for Low Leakage and Higher Mobility
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Solution Overview
Problem
Current semiconductor transistor devices using silicon channels face limitations in carrier mobility and are prone to high off-state leakage due to small band gaps, leading to reduced gate control and operational inefficiencies, especially in group III-V semiconductor materials which suffer from lattice mismatch and crystalline defects on silicon substrates.
Innovation Solution
Integration of high mobility, wide band gap semiconductor oxides as alternate channel materials for n-channel devices, such as indium gallium zinc oxide (IGZO), which offer wider band gaps and higher electron mobility than silicon, reducing off-state leakage and enhancing performance without the need for crystalline substrates, and using native silicon or germanium for p-channel devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silicon channel material is used in NMOS devices, then manufacturing compatibility is maintained, but electron mobility is limited and off-state leakage increases
Solution Approach 1:
The patent employs composite material structures by integrating semiconductor oxide materials (such as IGZO, ZnO, Ga2O3) with conventional silicon-based CMOS processes. The oxide channel layer is deposited on silicon substrates using standard fabrication techniques, creating a hybrid structure that combines the wide bandgap properties of oxides with the manufacturing maturity of silicon technology. This resolves the contradiction by achieving low off-state leakage through oxide materials while maintaining ease of manufacture through compatibility with existing silicon CMOS fabrication processes.
2Speed
If group III-V semiconductor materials are used to increase carrier mobility, then electron mobility improves, but lattice mismatch and crystalline defects occur on silicon substrates
Solution Approach 1:
The patent changes the material parameter from conventional semiconductors to semiconductor oxides with wide bandgaps. By selecting oxide materials that can be deposited as amorphous or polycrystalline films rather than requiring single-crystal growth, the patent achieves high electron mobility without the lattice mismatch problems that plague group III-V materials on silicon. This parameter change resolves the contradiction by decoupling mobility improvement from crystalline structure stability requirements.
3Reliability
If wider band gap materials are used to reduce off-state leakage, then gate control improves, but manufacturing complexity increases
Solution Approach 1:
The patent segments the fabrication process into distinct deposition and annealing stages that are compatible with standard CMOS workflows. The oxide channel is deposited using established techniques such as sputtering or atomic layer deposition, followed by controlled annealing to activate carriers and form the conductive channel. This segmentation of the manufacturing process resolves the contradiction by achieving improved gate control through wide bandgap materials while keeping the overall fabrication complexity manageable through integration with existing process modules.
Data Source
AI summary
Techniques are disclosed for integrating semiconductor oxide materials as alternate channel materials for n-channel devices in integrated circuits. The semiconductor oxide material may have a wider band gap than the band gap of silicon. Additionally or alternatively, the high mobility, wide band gap semiconductor oxide material may have a higher electron mobility than silicon. The use of such semiconductor oxide materials can provide improved NMOS channel performance in the form of less off-state leakage and, in some instances, improved electron mobility as compared to silicon NMOS channels.