Surface Modification Using Assisting Electrodes in Wire Electrical Discharge Machining for Silicon Wafer Preparation

Area of Science:

• Materials Science and Engineering
• Manufacturing Processes
• Surface Engineering

Background:

• Polycrystalline silicon wafer preparation is critical for semiconductor manufacturing.
• Traditional wire electrical discharge machining (WEDM) faces challenges with silicon's low conductivity.
• Surface modification during machining is needed to enhance efficiency and quality.

Purpose of the Study:

• To develop an in-process surface modification technique for polycrystalline silicon during WEDM.
• To enhance material removal rate and control surface topography.
• To optimize WEDM parameters for improved wafer preparation.

Main Methods:

• Utilized wire electrical discharge machining (WEDM) with assisting electrodes.
• Transferred aluminum particles to the polycrystalline silicon surface to enhance conductivity.
• Investigated the effect of aluminum deposition on material removal and surface characteristics.
• Performed parameter optimization for voltage, resistance, pulse-on time, and electrode thickness.

Main Results:

• Achieved significant aluminum deposition (~3.87 wt%) on the machined surface using 25 mm-thick electrodes.
• Demonstrated accelerated material removal rates (~9.42 mg/s) with acceptable surface roughness (S_a ~5.49 μm).
• Identified optimal parameters for minimal surface roughness (S_a 2.54 μm) at 80 V, 1.7 Ω, 30 μs pulse-on time, and 15 mm electrode thickness.
• Multiple objective optimization yielded 3.26 ± 0.61 wt% surface modification and a material removal rate of 7.08 ± 2.2 mg/min with S_a = 4.3 ± 1.67 μm.

Conclusions:

• In-process surface modification via aluminum transfer effectively enhances WEDM of polycrystalline silicon.
• The technique improves material removal efficiency while preserving surface integrity and texture.
• Optimized WEDM parameters offer a viable solution for advanced polycrystalline silicon wafer preparation.