In Situ Pre-Metallization Cleaning of CoSi₂ Contact-Hole Patterns with Optimized Etching Process.

Area of Science:

• Materials Science
• Semiconductor Manufacturing
• Plasma Physics

Background:

• In situ contact hole cleaning is vital for semiconductor device fabrication.
• Argon (Ar) sputter-etching is a common technique for pre-metallization cleaning.
• Controlling process variables is key to optimizing etch profiles, rates, and minimizing damage.

Purpose of the Study:

• To investigate the effects of Ar sputter-etching parameters on contact hole profiles.
• To analyze the influence on etching rates and substrate damage.
• To determine optimal conditions for Si and CoSi2 sublayer etching.

Main Methods:

• Systematic variation of Ar sputter-etching parameters: plasma power, RF power, and Ar flow rate.
• Analysis of contact hole profiles, etching rates (SiO2, Si, CoSi2), and selectivity ratios.
• Evaluation of physical damage linked to DC bias.

Main Results:

• Increased plasma power decreased DC bias but increased SiO2 etch rate; increased RF power raised both, with a more significant effect.
• Higher Ar flow rate reduced etch uniformity and slightly lowered DC bias.
• Si and CoSi2 sublayer etching showed Si losses up to 31.7 Å/s, strongly influenced by DC bias.
• Achieved Si/CoSi2 etch selectivity ratio of approximately 1:2.
• Nitride/oxide selectivity ratio was approximately 1:2.

Conclusions:

• Process parameter optimization, particularly RF and plasma power, is critical for controlling Ar sputter-etching in contact hole cleaning.
• DC bias is a key factor influencing physical damage and Si/CoSi2 etch speed.
• Optimized Ar sputter-etching can achieve desired selectivity ratios for different material layers.