研究目的
Investigating the direct wafer bonding (DWB) method with a thin bonding dielectric interface to fabricate Si high-k MOS optical modulators with a thin equivalent oxide thickness (EOT) and to suppress void generation on the bonded wafer during high-temperature annealing.
研究成果
The Al2O3/HfO2 bilayer enables void-less wafer bonding in conjunction with pre-bonding annealing at 700 °C. The density of voids is reduced by three orders of magnitude as compared with that in the case of using the Al2O3 bonding interface. Wafer bonding with thin Al2O3/HfO2 high-k bonding interface is promising for Si high-k MOS optical modulators.
研究不足
The high-temperature process is unacceptable for the bonded wafer using the Al2O3 bonding interfacial layer due to significant increase in void density when the annealing temperature is over 500 °C.
1：Experimental Design and Method Selection:
The study involved the use of Al2O3 and HfO2 as high-k dielectric bonding interfacial layers to suppress void generation during high-temperature annealing.
2：Sample Selection and Data Sources:
SOI wafers were bonded through high-k dielectric interfaces to form a Si=high-k=Si gate stack.
3：List of Experimental Equipment and Materials:
Atomic layer deposition (ALD) was used for depositing Al2O3 and HfO
4：Thermal desorption spectrometry (TDS) was used to analyze gases desorbed from high-k=SOI surfaces. Experimental Procedures and Operational Workflow:
After pre-cleaning with diluted HF, high-k materials were deposited on both wafers by ALD. Pre-bonding annealing was carried out at 400 or 700 °C for 20 min in vacuum. The substrate surface was cleaned with a mega-sonic before bonding. Post-bonding annealing was carried out up to 700 °C for 1 min.
5：Data Analysis Methods:
Infrared (IR) transmission images and microscopic images were used to confirm the bonding condition and void generation. TDS was used to determine the reason of void generation.
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