OES diagnostics as a universal technique to control the Si etching structures profile in ICP

Area of Science:

• Materials Science
• Plasma Physics
• Spectroscopy

Background:

• Silicon etching is crucial for microfabrication.
• Controlling etching profiles is essential for device performance.
• Optical emission spectroscopy (OES) offers non-intrusive plasma monitoring.

Purpose of the Study:

• To demonstrate OES for estimating silicon etching profiles.
• To correlate OES intensity ratios with specific etching profiles.
• To investigate process parameter effects on etching characteristics.

Main Methods:

• Utilizing SF6/C4F8/O2 plasma for silicon etching.
• Measuring OES intensity ratios of oxygen (778.1 nm) and fluorine (685.8, 703.9 nm) lines.
• Analyzing etching profiles for various structure sizes and aspect ratios.

Main Results:

• An optimal O/F emission intensity ratio range (2-6) was identified for micro-structures (13-100 μm).
• A different optimal ratio range (1.5-2) was found for macro-structures (400-4000 μm).
• Process parameters influencing silicon/aluminum etch rates, profile wall angle, selectivity, and bowing were investigated.

Conclusions:

• OES is a highly efficient method for real-time estimation of silicon etching profiles.
• Specific O/F emission intensity ratios can guide the fabrication of directional micro- and macro-structures.
• Understanding process parameter influences is key to optimizing silicon etching for microelectronics.