Metal Edge Coverage and Control of Charge Accumulation in RF Sputtered Insulators

The successful application of rf sputtered SiO
2
in the passivation of silicon semiconductor devices depends in part on the proper control of ionic charge migration in the insulator during sputtering, and on the adequate coverage of metal line edges by the insulator. It is shown that an appropriate combination of target purity, substrate temperature control and phosphosilicate blocking layer thickness can be used to achieve ionic charge densities at the silicon-SiO
2
interface of less than 1×10
¹²
charges per square centimeter. The effects of argon ion bombardment are shown to be acceptably low for typical operating conditions. In a conventional system, the adequate coverage of metal line edges is shown to be influenced primarily by argon pressure and magnetic field. In a special system where the substrate potential can be varied, it has been shown that adequate edge coverage can be obtained at sufficiently negative potentials. These data are consistent with a mechanism requiring some resputtering to obtain the desired film coverage.