AVS 66th International Symposium & Exhibition
    Plasma Science and Technology Division Thursday Sessions
       Session PS-ThM

Paper PS-ThM11
In-situ Measurement of Deposited Tilm Thickness and Electron Density by Double Curling Probe

Thursday, October 24, 2019, 11:20 am, Room B131

Session: Plasma Diagnostics and Sources II
Presenter: Daisuke Ogawa, Chubu University, Japan
Authors: D. Ogawa, Chubu University, Japan
Y. Sakiyama, Lam Research Corporation
K. Nakamura, Chubu University, Japan
H. Sugai, Nagoya Industrial Science Research Institute, Japan
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We developed a technique for measuring the thickness of a deposited film and electron density of a processing plasma simultaneously during a process with the use of two curling probes (CPs). As might be already known, CP is one of the microwave resonators which has a spiral-shaped slot antenna to make resonance. The resonance frequency (RF) depends on the geometry of the probe (the length and diameter of the antenna) and material of the antenna cover, etc., and the RF shifts to a higher frequency as electron density increases. Also, our recent research showed that CP can find the thickness of the film deposited after a plasma processing through the observed shift of RF when a dielectric constant of the film is known. In a deposition process operated in semiconductor industries, a film deposits not only on the processing substrate but also on a CP. The deposition shifts the RF lower, but the plasma shifts the RF higher. As a result, the observed shift in RF corresponds to a summation of the two shifts. This summation makes it difficult for us to discriminate the two shifts, but a pair of different-sized CPs (double CP) enables discrimination of the two shifts caused in the same plasma with the identical film thickness. We so far derived the equation giving the two shifts based on the previous theory. In order to confirm the solution of the equation, we performed a simple model experiment of deposition in an argon plasma, inserting two CPs covered with a polyimide film of known thickness (55-micrometer). We first measured the original RFs of the two probes with no polyimide film and no plasma exposure. And then, we measured the RF of each CP with a layer of the polyimide film and with plasma exposure. Finally, we derived the film thickness and electron density from the four RFs: the result revealed almost the same film thickness as the 55-micrometer polyimide film and the electron density of 2×10 cm-3 which decently matches with the Langmuir probe data. In this presentation, we will show our latest results using the double CPs with the industrial application in mind.