Reaction of Copper Oxide and β-Diketone for In situ Cleaning of Metal Copper in a Copper Chemical Vapor Deposition Reactor

Abstract

For in situ cleaning of inner reactor walls of copper chemical vapor deposition chambers used in the copper wiring process of LSI, etching of the deposited metallic copper is carried out by three step processes of copper oxidation, complexation with β-diketone, and vaporization to allow evacuator. In this paper, reactions suitable for the latter two processes are described. Reactions of copper oxide with three kinds of β-diketone, hexafluoroacetylacetone (Hhfac), acetylacetone and dipivaloylmethane, were studied using thermogravimetry in the range from room temperature to 400°C. Only Hhfac reacted with copper oxide showing etching in the temperature range above 170°C. At 350°C the weight ratio etching rate was 0.29 wt%/min at atmospheric pressure and 0.06 wt%/min at 665 Pa. The evaporation rate of the reaction product, Cu(hfac)2, was 5.3 wt%/min at 150°C, which is sufficiently higher than the etching rate of copper oxide. Reactions are as follows: 2CuO→Cu2O+1/2O2, Cu2O+Hhfac→Cu(hfac)+CuOH, 2Cu(hfac)→Cu(hfac)2+Cu, and Cu+CuO→Cu2O.