In situ silicon-wafer temperature measurements during RF argon-ion plasma etching via fluoroptic thermometry

Abstract

In situ silicon-wafer temperature measurements during RF argon-ion plasma etching are reported for four different wafer cooling environments: (i) lying on the electrode; (ii) clamped to the electrode; with additional helium gas between wafer and electrode in both (i) and (ii), in order to enhance heat transfer. Fluoroptic thermometry is applied to measure the local surface temperature of the wafer during plasma processing. The measured heating and cooling curves can be fitted using a model which considers conductive heat losses only. Deviations are observed when high RF power is applied and surface temperatures higher than 120 degrees C are reached. The authors report on effective cooling via helium gas of the rear side of the wafer which is lying on an electrode without any clamping.

Analysis of passive calorimetric probe measurements at high energy influxes

“…The basis for all the common methods for the analysis of passive calorimetric probe measurements is the consideration of temporal temperature changes during the heating and the cooling phase of the calorimetric probe [9]:…”

“…4.3 is the linear method. At the beginning of the heating curve at the equilibrium temperature T eq the losses are negligible and the energy influx is proportional to the slope of the temperature curve leading to [9]:…”

“…With the assumptions of a constant incoming power, linear loss terms, and a constant temperature for the surrounding of the probe the shape of the signal for heating and cooling phases will be exponential [9,10]:…”

“…First, we explain the well-known linear and exponential methods [4,[9][10][11] and the underlying assumptions in detail, before we show for a typical measurement why these methods are not suitable for energy influxes in the order of 100 W/ cm 2 . Finally, we introduce a novel method by combining the linear and the exponential methods and show that this approach is suitable for the analysis of high energy influxes by a passive calorimetric probe.…”

In-Situ Measurement of the Relative Thermal Contributions of Chemical Reactions and Ions During Plasma Etching

“…In the chuck, a heat transfer fluid flows through channels at a relatively constant temperature maintained by a chiller / heater and feedback control algorithm. The use of Helium carrier gas improves heat transfer between the chuck and substrate, and changes in He pressure and flow serve as additional temperature control "knobs" as well as sources of variability (5,6). Demands for improved uniformity have recently prompted development of various multi-zoned chucks in which process non-uniformity can be compensated by independent temperature control in multiple radial zones (7).…”