Paper PS-ThP10
Quick Estimation of Deposition Rate for a Sputter System

Thursday, November 1, 2012, 6:00 pm, Room Central Hall

Here we present a practical estimation on deposition rate for a sputter system. The sputter system consists of four sputter sources in a high vacuum chamber, with an independent power supply for each sputter source. Quick estimation of deposition rate could be helpful for efficient experimental planning and reducing the number of experiments and time.

First, theory: Our early JAP paper* disclosed an energy balance model and derived a sputter rate = k (P –P_o). The physical meaning is that the sputter rate has a linear relationship with plasma source power P, with a nearly constant offset P_o, and constant slope k. Here we present several different materials results which illustrate the good fit between deposition rate and power within the working range of 100W to 550W.

Second, P_o estimation: The physical meaning of P_o is the power consumed to sustain plasma, which is dependent on the plasma boundary condition (chamber/plasma source geometry), ion diffusion co-efficient, electron temperature etc. In this situation, since the plasma ion is primarily Agon ion with fixed chamber geometry, P_ois nearly constant within the range of 25 to 52 W. With a simple estimation of 39W, an error of only 13W could be introduced. For a typical 200~400W experimental condition, the error from this estimation is small (2~5% error).

Third, slope k estimation: The different materials trends with slope k are calculated M/D *Y* V and plotted. (M: is the atomic weight, D: is the density, Y: is the sputter yield at 300V for Argon ion, and V is the DC voltage of the sputter source). The model assumes that the slope k is proportional to the sputter yield at the DC voltage, and converts the mass to volume for thin film thickness based on the deposition rate calculation. In our case, DC voltage V is close to 300V, so that sputter yields at 300V were used. However, further investigation showed that the simple sputter yield might not be accurate enough, and the correction for the sputter DC voltage could provide a better fit. The slope k trend agreed well with model estimation M/D*Y *V. Thus, results here implied that the slope k could be estimated for different materials.

Thus, a quick deposition rate estimation method was derived in comparison with experiments, which is expressed as:dep rate= M/D*Y*V * k’ *(P-P_o), and K’ and P_o are chamber specific that need to be experimentally determined. Once calibrated from one experiment, the deposition rates of other materials can be estimated from this formula.

In addition, this study could be helpful in applying to other chambers and sputter sources for a quick deposition rate estimation, even for alloy target or reactive sputtering.