A Sono-Electrochemical Technique for Enhanced Particle Removal from Tantalum Surfaces

Abstract

Low power megasonics is of interest to semiconductor cleaning community due to minimal feature damage. In this work, megasonic field at low power density in conjunction with electrochemistry is used for enhanced removal of silica particles from tantalum wafers. Cleaning studies were conducted in air or argon saturated aqueous solutions at 0.5 W/cm 2 in the absence and presence of applied potentials of −1.5 V or −2.0 V to tantalum (vs Ag/AgCl). The improvement in particle removal efficiency is attributed to oscillating hydrogen bubbles formed from water reduction in vicinity of tantalum surface and grown to a resonant size under suitable acoustic conditions.

Review—Understanding and Controlling Electrochemical Effects in Wet Processing

“…1 In addition to hydrogen evolution, cathodic polarization would also result in the formation of hydroxide ions near the metallic surface that could provide some etching of the surface to enhance particle removal. 1 The sono-electrochemical technique has been used to clean Ta surfaces contaminated with silica particles. 1 In this study, a cathodic potential of ∼1.5 to 2 V (vs Ag/AgCl electrode) was applied to contaminated Ta surface immersed in DI water or KCl solution and exposed to 0.93 MHz sound field.…”

“…1 The sono-electrochemical technique has been used to clean Ta surfaces contaminated with silica particles. 1 In this study, a cathodic potential of ∼1.5 to 2 V (vs Ag/AgCl electrode) was applied to contaminated Ta surface immersed in DI water or KCl solution and exposed to 0.93 MHz sound field. Microscopic images of several areas on the sample were first obtained.…”

“…For example, simultaneous use of megasonic and electrochemical effects has recently shown to remove particles from conductive surfaces. 1 Electrically enhanced wetting (aka Electrowetting) has been suggested for liquid penetration in to narrow, high aspect ratio features. 2 …”

Coupling Supramolecular Assemblies and Reactive Oxygen Species (ROS) with Megasonic Action for Applications in Shallow Trench Isolation (STI) Post-Chemical Mechanical Planarization (p-CMP) Cleaning

“…To date, a majority of the cleaning chemistries used in megasonic cleaning have been redox chemistries that relied on the charge flipping mechanism (i.e., Ce 4+ to Ce 3+ ) and nonionic surfactants to remove particles from the surface. 29 , 30 …”

“…In addition to its noncontact modality, megasonic cleaning is beneficial for shrinking device nodes as its ability to reduce the boundary layer allows for the effective removal of submicron nanoparticles. To date, a majority of the cleaning chemistries used in megasonic cleaning have been redox chemistries that relied on the charge flipping mechanism (i.e., Ce 4+ to Ce 3+ ) and nonionic surfactants to remove particles from the surface. , …”