AVS 51st International Symposium
    Plasma Science and Technology Friday Sessions
       Session PS1+DI-FrM

Paper PS1+DI-FrM8
Evaluation of the Effectiveness of H@sub 2@ Plasmas in Removing Boron from Si After Etching of HfO@sub 2@ Films in BCl@sub 3@ Plasmas

Friday, November 19, 2004, 10:40 am, Room 213A

Session: High K and Difficult Materials Etch
Presenter: C. Wang, University of Houston
Authors: C. Wang, University of Houston
V.M. Donnelly, University of Houston
Correspondent: Click to Email
Etching of high dielectric constant ("high-K") materials in BCl@sub 3@-containing plasmas is challenging due in part to boron residue that deposits on the underlying Si or SiO@sub 2@ surface during the over-etching period. Boron is a p-type dopant and therefore it is best if it is removed prior to subsequent processing. We have investigated the effectiveness of H@sub 2@ plasmas in removing this boron-containing layer. Following etching of HfO@sub 2@ or Al@sub 2@O@sub 3@ thin films in a high-density BCl@sub 3@ plasma, including a 60s overetch period, samples were transferred under vacuum to a UHV chamber equipped with x-ray photoelectron spectroscopy (XPS). After observing B-coverages of ~1 x 10@super 15@ (equivalent of ~ 1 monolayer), the samples were transferred back to the plasma reactor for exposure to the H@sub 2@ cleaning plasma, and then re-examined by XPS. Optical emission spectroscopy was used to monitor B deposition on and removal from the plasma chamber walls. B deposition on the reactor walls during BCl@sub 3@ plasma exposure reached saturated coverage in ~2 min. Following this, the H@sub 2@ plasma removed half of this B layer in 90s, and 90 % in 320 s. B was rapidly removed (< 5s) from the BCl@sub 3@-over-etched Si surfaces provided that the walls were first cleaned in the H@sub 2@ plasma, with the Si sample held in the UHV chamber during the chamber cleaning process. Conversely, it took much longer (~170s) to remove all detectable B on the sample surface if the sample and the reactor chamber walls were cleaned in the H@sub 2@ plasma at the same time. Etching rates of SiO@sub 2@ and Si in the H@sub 2@ cleaning plasma will be reported. Mechanisms of B deposition on and removal from chamber walls and Si and SiO@sub 2@ surfaces will be discussed. A less effective sequential O@sub 2@/H@sub 2@ plasma cleaning process will also be presented. Supported by SRC and AMD Inc.