System and method for monitoring chemical mechanical polishing

A method of operating an apparatus for chemical mechanical polishing, the method comprising:

• placing a set of microphones including at least three microphones in or around a process chamber, wherein the set of microphones including at least one infrasonic microphone, at least one acoustic microphone, and at least one ultrasonic microphone, and wherein the at least one infrasonic microphone is disposed on or adjacent to a top wall of the process chamber, the at least one acoustic microphone is disposed on or adjacent to sidewalls of the process chamber, and the at least one ultrasonic microphone includes a first ultrasonic microphone disposed on or adjacent a bottom surface of the process chamber and a second ultrasonic microphone disposed between the top wall and the bottom surface of the process chamber;
• adjusting band-widths and central frequencies of the at least three microphones so that a strength of sound signals received or detected at the microphones are maximized;
• receiving simultaneously, at each of the at least three microphones, an initiate signal from a process controller, the process controller synchronizing the initiate signal with a start of a chemical mechanical polishing operation;
• detecting, using the at least three microphones, sound in the process chamber during the chemical mechanical polishing operation and upon receipt of the initiate signal;
• obtaining electrical signals corresponding to the detected sounds using the at least three microphones;
• transmitting the electrical signals to a signal processor using the set of microphones;
• processing, at the signal processor, the electrical signals received from the set of microphones to detect a sound pattern in the electrical signals received from the set of microphones;
• generating a feedback signal based on the sound pattern;
• and
• transmitting the feedback signal to a process controller configured to control the operation of the apparatus.

An apparatus for monitoring a chemical mechanical polishing process, the apparatus comprising:

• a process controller configured to control parameters of the chemical mechanical polishing process performed in a process chamber, wherein a rotatable platen is disposed inside the process chamber, and a wafer carrier is disposed on the rotatable platen and configured to retain a wafer for polishing;
• a set of microphones disposed in or around a process chamber of the apparatus, the set of microphones configured to detect sound in the process chamber during the process and to transmit an electrical signal corresponding to the detected sound, the electrical signals from the set of microphones being unsynchronized with each other,
• wherein the set of microphones includes at least one infrasonic microphone disposed on or adjacent to a top wall of the process chamber, at least one acoustic microphone disposed on or adjacent to sidewalls of the process chamber, and at least one ultrasonic microphone disposed on a bottom-side of the rotatable platen;
• and
• a signal processor configured to transmit, to each microphone, a timing signal having a frequency disjoint from the frequencies of the electrical signals generated by the set of microphones, receive a combined signal including a combination of the timing signal and a corresponding unsynchronized electrical signal from each of the microphones, separate each of the combined signals to recover the unsynchronized electrical signal and the timing signal, align the unsynchronized electrical signals according to the recovered timing signal to produce synchronized electrical signals, process the electrical signal to enable detection of an event during a chemical mechanical polishing operation, and in response to detecting the event, transmit a feedback signal corresponding to the detected event to the process controller,
• wherein the process controller is further configured to receive the feedback signal and initiate a change in one or more parameters of the process based on the received feedback signal, calculate a distance of a source of the sound from each microphone of the set of microphones, and calculate a location of the source of the sound.