Specifications

RELATIVE RATES OF SPUTTERING SOURCES VS DISTANCE

Rate data, for sputtering with small sources, is usually taken by making step samples and

then measuring them with either profilometer or interferometer. A quartz crystal micro-

balance type rate monitor may also be used. If a rate monitor is used, the geometry and the

density of the deposit must be taken into account. Because of the uncertainties of rate

monitor data, the most prudent course is to correlate the values taken with the rate monitor

with those taken by step sample method.

If the distance from the substrate to the target is changed and the power remains constant, the

change in deposition rate is a function of the ratio of the distances squared. For example, if the

rate at a 3” target to substrate distance is 15 Å/sec., the power is constant and the distance

changes from 3” to 4”, the rate drops to 8.4 Å/sec.

Rate at 3” = 15 Å/sec.,

Ratio for a change from 3” to 4” = 3

= 9/16 = 0.563

Ratio times Rate at 3” = 0.563 x 15 Å/sec = 8.4 Å/sec

Many factors affect deposition rate, but this is a reasonable approximation of the ef-

fect of distance.