A Statistical Analysis of Copper Bottom Coverage of High-Aspect-Ratio Features Using Ionized Physical Vapor Deposition

Abstract—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 sput-tering 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 de-position rates of 1000A 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. Index Terms—Bottom coverage, copper, deposition, ionized physical vapor deposition, plasma, sputtering, statistics. I