APPARATUS AND METHOD FOR CURRENT SENSING USING EMBEDDED ELECTRODES
An in-situ current sensing apparatus for a plasma processing system has one or more sections defining a plasma channel, the plasma processing system configured to form a plasma in the plasma channel using a process gas. The in-situ current sensing apparatus includes an assembly including an electrically conductive housing coupled to a dielectric coating layer, wherein a surface of the dielectric coating layer is configured to physically contact at least one of the process gas or the plasma in the plasma channel. The in-situ current sensing apparatus also includes a current probe, inductively or electrically connected to the assembly, for sensing a capacitively-coupled current within the assembly caused by the formation of plasma in the plasma channel. The in-situ current-sensing apparatus further includes at least one dielectric break for electrically isolating the assembly from the one or more sections. The assembly may include an electrode embedded within the housing.
1 . An in-situ current sensing apparatus for a plasma processing system comprising one or more sections defining a plasma channel, the plasma processing system configured to form a plasma in the plasma channel using a process gas, the in-situ current sensing apparatus comprising:
an assembly including an electrically conductive housing coupled to a dielectric coating layer, wherein a surface of the dielectric coating layer is configured to physically contact at least one of the process gas or the plasma in the plasma channel;
a current probe, inductively or electrically connected to the assembly, for sensing a capacitively-coupled current within the assembly caused by the formation of plasma in the plasma channel; and
at least one dielectric break for electrically isolating the assembly from the one or more sections.
2 . The apparatus of claim 1 , wherein the electrically conductive housing includes one or more electrically conductive flanges coupled to the dielectric coating layer.
3 . The apparatus of claim 2 , wherein the current probe is connected to one of the one or more flanges.
4 . The apparatus of claim 2 , wherein the assembly further includes an electrode embedded within the housing between an insulation layer and a dielectric barrier layer, the dielectric barrier layer adapted to contact the plasma in the plasma channel.
5 . The apparatus of claim 4 , wherein the current probe is inductively or electrically coupled to the electrode.
6 . The apparatus of claim 1 , wherein the current probe is inductively or electrically coupled to the housing.
7 . The apparatus of claim 1 , wherein the assembly is configured to be electrically coupled to ground for sensing the capacitively coupled current.
8 . The apparatus of claim 1 , wherein the assembly is configured to be switched between electrically coupled to ground and electrically floating.
9 . The apparatus of claim 1 , further comprising a controller electrically coupled to the current probe and configured to receive the sensed current from the current probe.
10 . The apparatus of claim 9 , wherein the controller is further configured to calculate a thickness of the dielectric coating layer based on the sensed current.
11 . The apparatus of claim 9 , wherein the controller is further configured to detect a change in composition of the process gas based on the sensed current.
12 . The apparatus of claim 9 , wherein the controller is further configured to determine stability of the plasma in the plasma channel.
13 . The apparatus of claim 1 , wherein the one or more sections of the plasma processing system include at least one input section, a plurality of mid-block sections and at least one output section, the assembly being one of the mid-block sections of the plasma processing system.
14 . The apparatus of claim 13 , wherein the at least one dielectric break includes:
a first dielectric break located at an interface between the one mid-block section and the at least one input section; and
a second dielectric break located at an interface between the one mid-block section and the at least one output section,
wherein the first and second dielectric breaks are configured to electrically isolate the one mid-block section from the input and output sections.
15 . A method for performing in-situ current sensing in a plasma processing apparatus comprising one or more sections defining a plasma channel, the method comprising:
coupling a current-sensing device to the plasma processing apparatus, wherein the current-sensing device includes an assembly comprising an electrically conductive housing coupled to a dielectric coating layer and a current probe inductively or electrically connected to the assembly;
contacting, by a surface of the dielectric coating layer of the current-sensing device, at least one of a process gas or a plasma in the plasma channel;
electrically isolating the current-sensing device from the one or more sections of the plasma processing apparatus;
electrically grounding the current-sensing device; and
sensing, by the current probe, a capacitive current in the assembly.
16 . The method of claim 15 , wherein the assembly of the current-sensing device further includes (i) at least one flange defined by the housing, the at least one flange coupled to the dielectric coating layer; and (ii) an electrode embedded in the housing between an insulating layer and a dielectric barrier layer, the dielectric barrier layer adapted to contact at least one of the plasma gas or the plasma in the plasma channel.
17 . The method of claim 16 , further comprising using the embedded electrode to ignite the plasma in the plasma channel in a plasma ignition process, wherein the embedded electrode is electrically floating during the plasma ignition process.
18 . The method of claim 17 , wherein sensing the capacitive current by the current probe is performed after the plasma ignition process by electrically grounding one of the embedded electrode and the conductive housing.
19 . The method of claim 18 , wherein the current probe is one of inductively coupled to a grounding path and electrically connected between ground and one of the embedded electrode and the conductive housing to sense the capacitive current.
20 . The method of claim 18 , wherein the current probe is one of inductively coupled to a grounding path and electrically connected between ground and the at least one flange of the assembly to sense the capacitive current.
21 . The method of claim 18 , further comprising detecting erosion in a thickness of the dielectric coating layer using the sensed current.
22 . The method of claim 18 , further comprising detecting a change in composition of the process gas using the sensed current.
23 . The method of claim 18 , further comprising detecting a degree of stability of the plasma in the plasma channel using the sensed current.
24 . The method of claim 15 , wherein the current-sensing device is integrally formed with the plasma processing apparatus such that the current-sensing device is one of the one or more sections.