Apparatus to detect fault conditions of a plasma processing reactor

Abstract

A method of fault detection for use in a plasma processing chamber is provided. The method comprises monitoring plasma parameters within a plasma chamber and analyzing the resulting information. Such analysis enables detection of failures and the diagnosis of failure modes in a plasma processing reactor during the course of wafer processing. The method comprises measuring the plasma parameters as a function of time and analyzing the resulting data. The data can be observed, characterized, compared with reference data, digitized, processed, or analyzed in any way to reveal a specific fault. Monitoring can be done with a detector such as a probe, which is preferably maintained within the plasma chamber substantively coplanar with a surface within the chamber, and directly measures net ion flux and other plasma parameters. The detector is preferably positioned at a grounded surface within the reactor such as a grounded showerhead electrode, and can be of a planar ion flux probe (PIF) type or a non-capacitive type. Chamber faults that can be detected include a build-up of process by-products in the process chamber, a helium leak, a match re-tuning event, a poor stabilization rate, and a loss of plasma confinement. If the detector is a probe, the probe can be embedded in a part of a plasma processing chamber and can comprises one or more gas feed-through holes.

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         16 . An apparatus for monitoring a plasma process wherein a plasma process is initiated within a plasma chamber, plasma parameter data on the plasma process is obtained by use of a planar ion flux (PIF) probe wherein a sensing surface of the probe is exposed to the plasma and is coextensive with a wall or component surface within the plasma chamber, and the plasma parameter data is evaluated for indications of a fault condition, wherein (a) the probe is embedded in the wall or in any of the following components of a plasma processing chamber: a showerhead electrode, a liner, a confinement ring, a focus ring, an electrode without gas outlets, a gas distribution plate and a substrate support, (b) the probe is heated by use of a temperature control component, (c) the probe is capable of compensating for differential wear rate between a sensing surface of the probe and an adjacent and surrounding surface of a chamber component in which the probe is embedded and/or (d) the probe is embedded in any of a capacitively coupled plasma processing chamber, an inductively-coupled plasma processing chamber and an electron cyclotron resonance plasma processing chamber. 
     
     
         17 . The apparatus of  claim 16 , wherein the PIF probe is embedded in the inner or outer electrode part of a multi-piece showerhead electrode assembly. 
     
     
         18 . The apparatus of  claim 16 , wherein the probe is located in a showerhead electrode and the probe comprises one or more gas feed-through holes creating a gas passage from the sensing surface, through, to the back surface of the probe and (a) the gas feed-through holes are positioned to approximate the overall gas distribution pattern that would exist in the absence of the probe or (b) the gas feed-through holes are positioned in the probe where they would otherwise be located in the showerhead electrode in the absence of the probe. 
     
     
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         21 . The apparatus of  claim 16 , further comprising a detection system which stores the plasma parameter data on a computer-readable storage medium system, filters the plasma parameter data, subjects the plasma parameter data to an algorithm, subjects the plasma parameter data to a mathematical operation, and compares the plasma parameter data to existing reference data, which results in an interpretation; and, the issuance of a status report and/or warning based on the interpretation. 
     
     
         22 . The apparatus of  claim 16 , wherein the probe is positioned in a recess extending into a radio frequency biased surface or at a grounded surface. 
     
     
         23 . The apparatus of  claim 16 , wherein the probe includes a temperature control component operable to heat or cool the probe. 
     
     
         24 . The apparatus of  claim 16 , wherein (a) the probe is operable to collect the plasma parameter data as a series of measurements during the course of processing a wafer, (b) collect post-RF ramp plasma density data and/or (c) identify a random retuning of an RF matching system of the plasma chamber. 
     
     
         25 . The apparatus of  claim 16 , wherein the probe is operable to detect (a) a change in the slope of the post-RF ramp plasma density data is used to indicate the plasma chamber fault condition is a build-up of process by-products in the process chamber, (b) an oscillation of the plasma density after an RF ramp of between about 5% and about 20% of the absolute value of the plasma density is used to indicate that the plasma chamber fault condition is a helium leak and/or (c) an oscillation of the plasma density of amplitude less than 5% of the absolute value of the plasma density and of duration less than 5 seconds, occurring after the RF ramp, is used to indicate that the plasma chamber fault condition is a random re-tuning of the matching system. 
     
     
         26 . The apparatus of  claim 21 , wherein (a) the status report and/or warning initiates a corrective step in the system, (b) the status report and/or warning records the interpretation in a log containing wafer history and/or (c) the status report and/or warning stops the processing of a wafer in the plasma chamber.