An apparatus and method for diagnostics of netural radicals in plasma

Patent metadata

Field	Value
Publication number	US-2016198558-A1
Application number	US-201414912035-A
Country	US
Kind code	A1
Filing date	Jul 30, 2014
Priority date	Aug 12, 2013
Publication date	Jul 7, 2016
Grant date	—

Abstract

An apparatus for diagnostics of neutral radicals in plasma, the apparatus comprising: a portable probe configured to be attached to and extend into a plasma chamber to obtain information from plasma contained in the plasma chamber, the probe comprising a metallic rod configured to be biased with an alternating current voltage applied to the probe to obtain current measurements; a transparent dielectric sleeve having a large bandgap configured to allow light transmission to obtain optical emission spectra from the plasma; and an insulated thermocouple junction provided in the metallic rod, the thermocouple junction configured to measure equilibrium temperature of the probe.

First claim

1 . An apparatus for diagnostics of neutral radicals in plasma, the apparatus comprising:
a portable probe configured to be attached to and extend into a plasma chamber to obtain information from plasma contained in the plasma chamber, the probe comprising
a metallic rod configured to be biased with an alternating current voltage applied to the probe to obtain current measurements;
a transparent dielectric sleeve having a large bandgap configured to allow light transmission to obtain optical emission spectra from the plasma; and
an insulated thermocouple junction provided in the metallic rod, the thermocouple junction configured to measure equilibrium temperature of the probe.

2 . The apparatus of claim 1 , wherein the alternating current voltage is configured to be changeable when obtaining current measurements.

3 . The apparatus of claim 1 , further comprising a vacuum manipulator configured for attaching the probe to the plasma chamber and for manipulating the position of the probe in the plasma chamber, the vacuum manipulator comprising
a drive shaft configured to be connected to the probe and a number of flexible bellows connected between the drive shaft and the wall of the vacuum chamber via vacuum gaskets.

4 . The apparatus of claim 3 , wherein the vacuum manipulator is configured to allow swing, rotation, forward and backward movement of the probe in the plasma chamber without affecting vacuum level of the plasma chamber.

5 . The apparatus of claim 1 , further comprising a computer configured to analyse information obtained by the probe and to determine the type, density and temperature of neutral radicals in the plasma.

6 . The apparatus of claim 5 , wherein the computer is further configured to calculate, from current-voltage characteristics obtained via the probe, at least one of: electron and ion currents, electro energy distribution, plasma potential, electron temperature, ion temperature, electron heating, ion heating, ohmic heating and cooling of neutral radicals.

7 . The apparatus of claim 6 , wherein the computer is further configured to fit cooling of neutral radicals vs temperature of the probe linearly to determine the temperature of the neutral radicals.

8 . The apparatus of claim 5 , wherein the computer is further configured to, from the optical emission spectra, identify the type of radiative radicals that exist in the plasma and to calculate the density of the neutral radicals.

9 . A method of performing diagnostics of neutral radicals in plasma, the method comprising the steps of:
(a) obtaining current measurements from the plasma via a metallic rod of a portable probe extended into a plasma chamber containing the plasma, the metallic rod being biased with an alternating current voltage; (b) obtaining optical emission spectra from the plasma via a transparent dielectric sleeve of the portable probe, the transparent dielectric sleeve having a large bandgap configured to allow light transmission; and (c) measuring equilibrium temperature of the probe via an insulated thermocouple junction provided in the metallic rod.

10 . The method of claim 9 , further comprising changing the alternating current voltage when performing step (a).

11 . The method of claim 9 , further comprising the steps of:
(d) analysing information obtained by the probe; and (e) determining the type, density and temperature of neutral radicals in the plasma.

12 . The method of claim 11 , wherein step (d) further comprises calculating, from current-voltage characteristics obtained via the probe, at least one of: electron and ion currents, electro energy distribution, plasma potential, electron temperature, ion temperature, electron heating, ion heating, ohmic heating and cooling of neutral radicals.

13 . The method of claim 12 , wherein step (e) further comprises fitting cooling of neutral radicals vs temperature of the probe linearly to determine the temperature of the neutral radicals.

14 . The method of claim 12 , wherein step (e) further comprises, from the optical emission spectra, identifying the type of radiative radicals that exist in the plasma and calculating the density of the neutral radicals.

Assignees

• Univ Nanyang Tech

Inventors

• Chan Chia Sern
• Xu Shuyan
• Rutkevych Pavlo
• Xu Luxiang

Classifications

• H01J37/32954

  Electron temperature measurement · CPC title

• H05H1/0081

  by electric means · CPC title

• H05H1/0037 Primary

  by spectrometry · CPC title

• H01J37/32972

  Spectral analysis · CPC title