Optimisation of dHF-based Cleaning Recipes: TO REMOVE OR NOT TO REMOVE A PARTICLE?

摘要

In this paper it is described how dHF-based cleaning recipes, such as the Imec-ciean, have to be optimized in order to have a good particle removal performance and at the same time minimize the (re-)deposition of particles. The mechanism behind the deposition and removal of particles on a wafer surface is described in terms of van der Waals and electrostatic interaction forces. It is shown that the first oxidizing step during an 'Imec'-clean can chemically modify particles and hence influence the particle removal efficiency. In order to make the cleaning recipe independent upon this first oxidizing step and obtain an optimal removal for all kinds of particles and substrates, the final rinse step has to be optimized. This is achieved by rinsing at a low pH, where the electrostatic attraction forces are shielded, and in combination with megasonic irradiation to overcome the van der Waals attraction that otherwise will cause the particles to re-deposit.