薄膜技术Film.ppt

Sputtering General System Schematic * DC Sputtering Plasma characteristics Usually inert gas like Ar used (no chemical component) Contains equal numbers of positive ions, neutrals and electrons (charge balanced) Most of voltage drop occurs near target electrode Called cathode sheath Ar+ ions accelerated across cathode sheath to target (negatively biased) Collisions liberate target atoms * DC Sputtering Plasma characteristics * DC Sputtering Sputtering Yield (Y): Number of atoms/molecules ejected from target/incident ion It is a function of ion mass, ion energy, target composition and angle of incidence. Compared to evaporation, Y doesn’t exhibit as strong of dependence on target material as vapor pressure does. Consequence ? controlling composition of compounds and alloys is much easier * Sputtering: General Processes * Sputtering Usually not configured as “point sources” Large targets used. Leads to uniform coating If target is off-angle and substrate is rotated, coatings are conformal Point Source Large area source * RF Sputtering Used when dielectric targets are required * Potential Drop Total DC Current must add to zero Mobility differences in electrons and ions leads to positive bias of plasma Geometry plays a role * Unequal Electrode Configuration Field highest at smallest electrode, highest current density there also Small targets lead to selective sputtering at target only. If substrate electrode is connected to chamber, then A2 is even larger, leading to more sputtering at the target. * Sputtering Use of RF power enables in-situ substrate cleaning Bias the substrate electrode with RF induces sputtering at that electrode RF power to substrate can also add sputtering component to deposition Inert ions become highly directional Used to enhance conformality * High Density Plasma Sputtering Uses RF coil to ionize sputtered atoms * HDP Sputtering Produces a narrow angular distribution of depositing species Useful in deep trench filling Conventional