Comparison of Experiments with a Lumped Parameter Model of the Plasma Assisted Chemical Vapor Deposition of Copper

Abstract

Experiments show that pure copper films can be formed at temperatures below 190 °C by H2 plasma assisted chemically vapor deposited copper(II)-hexafluoroacetylacetonate. A fundamental surface reaction mechanism has been derived for the reaction between dissociatively adsorbed precursor and atomic hydrogen produced in the plasma. The mechanism suggests that the deposition rate is proportional to [Cu(HFA),] 1/2 [H] and film purity improves with an increase in atomic hydrogen concentration. A new lumped parameter model has also been developed that agrees very well with experiments, to relate the operating conditions to the concentrations of Cu(HFA)2 and atomic hydrogen. Our model shows that at temperatures above 200 °C, surface recombination of atomic hydrogen decreases adsorbed [H] leading to copper films possessing high resistivity. It also indicates that at plasma powers above 60 W, high electron concentrations lead to the gasphase decomposition of the precursor and high film resistivity. An apparent activation energy of 5.0 kcal/mol is also suggested for the deposition, by the experiments and the reactor model.

Preparation of thin copper films from the vapour phase of volatile copper(I) and copper(II) derivatives by the CVD method

“…192 Step 4 is the limiting step of the entire process. 192,193 A somewhat simplified version of this mechanism was suggested earlier. 194 It was noted that the irreversibility of the entire process begins in the step where metallic copper adsorbed on the substrate appears.…”

“…A model of decomposition of Cu(HFA) 2 with the use of hydrogen plasma was described. 193 It was noted that in this process the hydrogen plasma is mainly electropositive and consists of cations, i.e., H + , H 2 and H 3 , electrons and hydrogen atoms. The overall process occurs according to the five-step mechanism discussed above; however, both the hydrogen atoms adsorbed on the substrate and the hydrogen atoms from the gas phase can participate in the limiting fourth step.…”

“…At high electric field power, decomposition of HFA fragments starts, the process becomes more complicated and strong contamination of films with carbon and fluorine is observed. 193 The decomposition mechanisms of other fluorinated copper(II) b-diketonates in CVD processes have almost not been studied. It was shown 189 that H(FOD) is the main product of Cu(FOD) 2 decomposition in the vapour phase.…”