High Velocity Aerosol Cleaning with Organic Solvents: Particle Removal and Substrate Damage

Abstract

High velocity aerosol cleaning using ultrapure water or dilute aqueous solutions (e.g. dilute ammonia) is common in semiconductor IC fabrication [1]. This process combines droplet impact forces with continuous liquid flow for improved cleaning efficiency of sub-100nm particles. As with any physically enhanced cleaning process, improved particle removal can be accompanied by increased substrate damage, especially to smaller (<80nm) features [2]. Solvents such as N-methylpyrrolidone (NMP) and tetrahydrofurfuryl alcohol (THFA) are used for resist strip applications [3]. It is possible, and sometimes useful, to deliver these solvents through the same spray nozzle normally used for aqueous spray cleaning. In this presentation we explore the particle removal and substrate damage performance of 2-ethoxyethanol (EGEE), NMP and THFA as used in a conventional aerosol spray cleaning system

Particle Removal and Damage Thresholds from Particle Removal and Damage Formation Frequency for High-Velocity-Aerosol Cleaning

“…The flux of damage events F D was determined for 30-70nm wide gate stack lines, 160nm tall. [3] According to these estimates, only a small fraction of the droplets contribute to particle removal, and not the majority of the droplets as predicted in [4]. For this cleaning condition only one droplet out of every 5000 droplets in the spray leads to particle removal compared to one and a half droplet out a million droplets leads to damage.…”

Uniformity of Particle Removal by Aerosol Spray

“…In semiconductor fabrication high speed aerosol spray is commonly used in single wafer cleaning tools to remove fine particles from wafer substrates. Ultrapure water or dilute chemical solutions [1,2] are atomized into a fine droplet stream by N 2 that is supplied to a nozzle. The droplet stream impacts on the wafer substrate with high speed, and the induced high shear stress is responsible for the removal of particles within the impingement region.…”

Cleaning and Damage Performance of Single Wafer Cleaning Tools using Physical Removal Forces

“…Physical cleaning methods, like aerosol spray and megasonic cleaning are currently used in front-end and back-end of line cleaning applications and show encouraging results in terms of particle removal (1)(2)(3)(4)(5). However, no reasonable comparison between different cleaning techniques is possible without parallel damage assessment on patterned substrates.…”