FORMATION OF COPPER THIN-FILMS BY A LOW KINETIC-ENERGY PARTICLE PROCESS

Low kinetic energy particle bombardment of a growing film surface has been employed to grow high-quality copper thin films on silicon and SiO2 with ideal metal/substrate interface characteristics. It is shown that the energy of Ar ions concurrently bombarding a growing film surface determines the crystal structure of the film. Under relatively low-energy ion bombardment conditions, (100)- or (111)-oriented Cu films are grown epitaxially on (100) Si or (111) Si surfaces, respectively. On the other hand, completely (111)-oriented films are obtained either on (100) Si, (111) Si, or SiO2 surfaces when large ion bombardment energies are employed. It has been found that (111)-oriented films thus created on SiO2 are metastable and easily transform by thermal annealing into completely (100)-oriented films with large grains of about 100-mu-m. This unique transformation phenomenon has been successfully applied to the formation of almost single-crystal (100)-oriented Cu islands on SiO2. In situ substrate surface cleaning by extremely low energy Ar ion bombardment has enabled the formation of ideal metal/silicon contacts without any postmetallization alloying heat cycles. Excellent adhesion of Cu thin films on SiO2 has also been demonstrated by the employment of the in situ substrate surface cleaning.