In the manufacture of semiconductor devices, the substrate,
usually Silicon, is oxidized to form an oxide layer at the surface prior to
device fabrication. This oxide layer (such as SiO2 grown on a Si (100)) surface
typically grows completely amorphous with little ordering in the first atomic
layers near the interface. This can lead to thickness and structural variations
that can affect the electronic performance of devices using these oxides.
To overcome this problem, researchers at Arizona State
University have developed a method to grow such oxide layers in an ordered
manner, to significantly enhance the material and electronic properties of
semiconductor devices. Using a newly developed method, up to 80% of an ordered
phase is obtained in SiO2 thin films ranging in thickness from approximately
1.25 to 30 nm grown on Si (100) surfaces. With respect to these thin films,
capacitance-voltage measurements on MOS structures indicate a dramatic
improvement in flat-band voltages along with a decrease in fixed charge in the
oxide, and especially increased carrier lifetime under the oxide. This also
lowers the interface state density.
Further enhancements to the process allow one to obtain a
higher degree of perfection resulting in improvements to the surface optical
properties as well. This process also lends itself to good control of the growth
kinetics of the oxide layer thereby opening up the possibility of much improved
control over the electrical properties of resultant devices. This process is
also useful for improving the oxide surfaces of alternative semiconductor
systems such as GaAs and SiGe, which are known to exhibit notoriously high
defect densities.
Potential Applications
- Improved carrier lifetimes in MOSFETs Low temperature
epitaxy on Si for materials including SiGe, SiGeC, SiGeSn,
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- GaAs, high-k dielectrics, peroskovites, silicides and
metals.
- Improved layers for light sensors, mirrors, light
detectors and solar cells.
Benefits and Advantages
- Low defect density at the substrate/oxide interface.
- Enhanced carrier lifetimes.
- Enhanced reliability and long-term performance of oxide
films.
- High chemical stability and resistance to surface
contamination – allowing wider processing window.
- Low temperature process epitaxy.
- Improved optical absorption properties.
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