Apparatus and method for sensing RF signals from RF plasma processing equipment
A sensing device for monitoring electromagnetic radiation emanating from a plasma processing system. The sensing device may, for example, comprise at least two of a first probe for detecting a time varying RF electric field, a second probe for detecting a time varying RF magnetic field, and an optical probe for detecting the modulated light emission. The sensing device may, for example, further comprise a signal processing unit configured to receive a signal from each probe and to monitor the electromagnetic radiation with respect to only a single frequency of each signal.
1 . A sensing device for monitoring electromagnetic radiation emanating from a plasma processing system comprising at least two of:
(i) a first probe for detecting a time varying RF electric field;
(ii) a second probe for detecting a time varying RF magnetic field; and
(iii) an optical probe for detecting the modulated light emission; and the sensing device further comprising:
a signal processing unit configured to receive a signal from each probe, monitor the electromagnetic radiation with respect to only a single frequency of each signal, continuously determine the amplitude of each signal from each probe to produce amplitude data, and analyse the amplitude data to determine a changing average amplitude according to a high speed detection mode, wherein the high speed detection mode enabling pulse profile monitoring without the need for synchronisation with a TTL signal.
2 . A sensing device for monitoring electromagnetic radiation emanating from a plasma processing system comprising at least two of:
(i) a first probe for detecting a time varying RF electric field;
(ii) a second probe for detecting a time varying RF magnetic field; and
(iii) an optical probe for detecting the modulated light emission; and the sensing device further comprising:
a signal processing unit configured to receive a signal from each probe, monitor the electromagnetic radiation with respect to only a single frequency of each signal, continuously determine the amplitude of each signal from each probe to produce amplitude data, analyse the amplitude data to determine a changing average amplitude according to a high speed detection mode, and identify a high speed event based on the analysis of the amplitude data according to the high speed detection mode, the high speed event including a RF arc event or an RF pulse event.
3 . The sensing device of claim 1 wherein the signal processing unit is further configured to identify a high speed event based on the analysis of the amplitude data according to the high speed detection mode.
4 . The sensing device of claim 3 wherein the signal processing unit is further configured to store amplitude data corresponding to the identified high speed event.
5 . The sensing device of claim 4 wherein the signal processing unit is further configured to store amplitude data for a predetermined time period corresponding to the identified high speed event.
6 . The sensing device of claim 5 wherein the signal processing unit is further configured to discard amplitude data determined to not correspond to an identified high speed event.
7 . The sensing device of claim 1 wherein the signal processing unit is further configured to average the amplitude data of each signal over a predetermined time period.
8 . The sensing device of claim 7 wherein the signal processing unit is further configured to store the averaged amplitude data corresponding to the predetermined time period.
9 . The sensing device of claim 1 wherein the signal processing unit includes an in-quadrature module and a local oscillator, the in-quadrature module configured to multiply each signal from each probe by a signal from the local oscillator in order to select the single frequency.
10 . The sensing device of claim 9 wherein the signal processing unit includes a phase lock loop configured to tune the local oscillator so that it tracks each signal from each probe between a lower and upper frequency limit.
11 . The sensing device of claim 9 wherein the signal processing unit further includes a filter and averaging module configured to convert the output signals from the in-quadrature module to average values and remove modulation from the output signals to produce a signal vector for each signal.
12 . The sensing device of claim 11 wherein the signal processing unit further includes a vectoring block, configured to phase rotate the signal vectors in unison to produce a voltage signal vector on the real axis and having zero phase.
13 . The sensing device of claim 12 wherein the signal processing unit further includes a first in first out buffer configured to store the signal vectors after processing by the vectoring block.
14 . The sensing device of claim 1 wherein when a plasma process is pulsed the signal processing unit is configured to analyse amplitude data with respect to at least one of the signals and store parameters of a pulse based on the amplitude data.
15 . The sensing device of claim 3 wherein the signal processing unit is further configured to average the amplitude data of each signal over a predetermined time period.
16 . The sensing device of claim 4 wherein the signal processing unit is further configured to average the amplitude data of each signal over a predetermined time period.
17 . The sensing device of claim 5 wherein the signal processing unit is further configured to average the amplitude data of each signal over a predetermined time period.
18 . The sensing device of claim 7 wherein averaging the amplitude data of each signal over a predetermined time period includes averaging 1000 samples over a 1 ms time period.