研究目的
Investigating the possibility of passivating the silicon surface using Al2O3 layers with a much lower thermal budget for bulk lifetime studies without altering the silicon bulk properties.
研究成果
The study concludes that combining low-temperature post-deposition annealing of th-ALD Al2O3 layers or th-ALD/PA-ALD stacks with Corona charging is effective for achieving excellent surface passivation for bulk lifetime studies, with stable Seff values achievable even at low thermal budgets.
研究不足
The study demonstrates that while low-temperature annealing combined with Corona charging can achieve excellent surface passivation, the process requires careful control of annealing times and temperatures. UV illumination improves surface passivation but to a lesser extent compared to Corona charging.
1:Experimental Design and Method Selection:
The study focuses on the surface passivation provided by atomic-layer-deposited (ALD) Al2O3 using a low-temperature activation. Alternative methods to build up the negative charge, either by depositing external negative charges via the Corona method or by using UV light, are investigated.
2:Sample Selection and Data Sources:
1.3-Ωcm p-type float-zone silicon (FZ-Si) wafers with a thickness of 300 μm are used. All wafers receive an RCA clean, an oxidation step at 1050°C, and after removal of the oxide in HF a phosphorus diffusion at 850°C.
3:3-Ωcm p-type float-zone silicon (FZ-Si) wafers with a thickness of 300 μm are used. All wafers receive an RCA clean, an oxidation step at 1050°C, and after removal of the oxide in HF a phosphorus diffusion at 850°C.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Samples are passivated by Al2O3 layers deposited using plasma-assisted atomic layer deposition (PA-ALD) or thermal ALD (th-ALD). Effective carrier lifetimes are measured using the photoconductance decay (PCD) method.
4:Experimental Procedures and Operational Workflow:
Samples are annealed at different temperatures, some receive a Corona charge deposition or are illuminated using an UV LED array to improve the surface passivation.
5:Data Analysis Methods:
From the measured lifetime, the surface recombination velocity Seff is deduced using the equation Seff = W/2(1/τeff?1/τb), where W is the wafer thickness, τeff is the measured effective lifetime and τb the intrinsic bulk lifetime.
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