The chemistry of metalorganic chemical vapor deposition from a copper alkoxide precursor
The chemistry of chemical vapor deposition from copper (II) dimethylaminoethoxide onto single crystal strontium titanate has been studied by in situ infrared analysis of the vapor phase in the reactor, and by simultaneous mass spectrometer analysis of the reactor outlet gas. Species condensed from the reactor outlet gas in a liquid nitrogen trap were analyzed by proton nuclear magnetic resonance. Chemical information was also obtained by Auger electron and X-ray photoelectron spectrometer analysis of the deposited films. Deposition chemistry was studied with respect to deposition temperature, presence of ultraviolet light, and presence of a reactive gas cofeed. The goal was to determine the reaction pathway and relate it to deposited film composition.
In a reduced pressure helium atmosphere, copper dimethylaminoethoxide deposits clean, conductive films of copper metal at 200°C. The ligands are eliminated by two interdependent reactions: β-hydride elimination produces dimethylaminoethanol, while reductive elimination produces dimethylaminoethanol. The minimum deposition temperature is 150°C. At substrate temperatures near 250°C some ligand fragmentation occurs, in addition to the clean elimination pathway, leading to carbon contamination of the deposited films.
The deposition chemistry of copper dimethylaminoethoxide is not affected by irradiation with ultraviolet light of wavelengths between 360 nm and 600 nm. The ultraviolet light source was a Spectronics B-100 UV lamp. A light source with higher power might affect deposition chemistry.
At a substrate temperature of 200°C in the presence of oxygen, dimethylaminoethanol and dimethylaminoethanol are not detected as products. Decomposition involves extensive ligand fragmentation, producing small amines and carbonyl species, carbon monoxide, and carbon dioxide. Films are free of carbon and nitrogen, because the ligand fragments are volatile and stable. Films are a mixture of copper metal and copper (I) oxide. Optimization of oxygen concentration in the reactor could lead to deposition of a pure copper oxide.