A statistical analysis of copper bottom coverage of high-aspect-ratio features using ionized physical vapor deposition

Ionized physical vapor deposition (IPVD) is a new method for depositing metal into high-aspect-ratio features used as interconnects in microelectronic fabrication. It is similar to sputtering except that a portion of the metal flux to the substrate is ionized. We show how a high ionized-metal-flux fraction (IMFF) at the deposition location improves the bottom coverage of deposited metal films. To measure IMFF, a tool was developed, that biased the front surface of a microbalance crystal directly so as to repel ions. Cu IMFFs to the substrate of greater than 90 % along with deposition rates of 1000 /spl Aring//min can be achieved. A statistical model for both IMFF and total metal flux as a function of four control variables, chamber height, Ar pressure, ionizer power, and sputter power, was developed.