研究目的
To study the effect of macro-scale mechanical stress on room temperature photoluminescence signals in silicon wafers and monitor stress relaxation over time.
研究成果
Macro-scale mechanical stress significantly affects RTPL intensity in Si wafers, with changes persisting for up to 450 days. Stress memorization can lead to up to 26% intensity increases, impacting electronic properties. Findings highlight the need for careful stress management in device storage and packaging to prevent performance variations.
研究不足
Difficulty in accurately quantifying mechanical stress due to variable contact areas; potential surface contamination over long periods; reliance on RTPL without calibrated stress measurement methods like Raman spectroscopy; uncertainty in force measurements (approximately 50 g).
1：Experimental Design and Method Selection:
The study involved applying localized mechanical stress to silicon wafers using polypropylene springs in containers and measuring RTPL spectra to observe changes and relaxation over time. Theoretical models for stress effects on electronic properties were considered.
2：Sample Selection and Data Sources:
Fifteen single-side polished (SSP) and ten double-side polished (DSP) Si wafers with 50 mm diameter, various resistivities (1–100 Ω cm), and thickness around 300 μm were used. Wafers were stored in containers with different stress levels applied.
3：List of Experimental Equipment and Materials:
Equipment includes a thermoelectrically cooled spectrograph system (WaferMasters MPL-300), FSM 128L system for wafer bow measurements, polypropylene springs, stainless-steel washers, and containers. Materials include Si wafers and polypropylene.
4：Experimental Procedures and Operational Workflow:
Wafers were placed in containers with springs; stress was applied by tightening lids with or without washers. RTPL measurements were conducted using 650 nm and 830 nm excitation lasers at fixed powers and exposure times. Wafer mapping and line scans were performed periodically up to 450 days after stress removal.
5：Data Analysis Methods:
RTPL intensity maps and line scans were analyzed for uniformity and changes over time. Statistical methods included standard deviation calculations for intensity uniformity.
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