Determining the orientation of a substrate in-situ
A method of processing a substrate includes polishing a front surface of a substrate on a first pad coupled to a first platen. The method further includes transferring the substrate from the first pad to a second pad coupled to a second platen with a carrier head. The method further includes moving the carrier head to a scan position to place an edge of the substrate above an orientation sensor disposed at a rotational center of the second pad. The method further includes scanning the edge of the substrate with the orientation sensor to produce a signal. The method further includes analyzing the signal to locate a reference mark of the substrate to determine a rotational orientation of the substrate relative to the carrier head.
1 . A method of processing a substrate, comprising:
polishing a front surface of a substrate on a first pad coupled to a first platen;
moving a carrier head to a scan position to place an edge of the substrate above an orientation sensor disposed at a rotational center of the first pad;
scanning the edge of the substrate with the orientation sensor to produce a signal; and
analyzing the signal to locate a reference mark of the substrate to determine a rotational orientation of the substrate relative to the carrier head, wherein analyzing the signal to locate the reference mark includes identifying a reference mark signature.
2 . The method of claim 1 , wherein the reference mark is a notch or a flat surface formed in the edge of the substrate.
3 . The method of claim 1 , wherein analyzing the signal to locate the reference mark includes:
determining one or more candidates for a portion of the substrate including the reference mark; and
analyzing the one or more candidates to identify the reference mark signature.
4 . The method of claim 3 , wherein the reference mark signature is a drop in intensity in the signal.
5 . The method of claim 4 , wherein the reference mark signature is identified by the drop in signal intensity that reaches or exceeds a threshold.
6 . The method of claim 1 , wherein analyzing the signal to locate the reference mark includes:
identifying at least one pair of candidates for a portion of the substrate including the reference mark that are located 180 degrees apart; and
analyzing each candidate in the pair of candidates to identify the reference mark signature.
7 . The method of claim 1 , wherein the reference mark signature is identified by comparing the signal to either a threshold or a pre-stored reference signal signature of the reference mark for the type of substrate.
8 . The method of claim 1 , wherein the reference mark signature is identified after a partial revolution of the carrier head.
9 . The method of claim 1 , further comprising:
polishing the front surface by rotating the first pad and the carrier head; and
monitoring the front surface with a plurality of endpoint sensors to determine an endpoint of the polishing of the front surface by the first pad.
10 . The method of claim 9 , wherein the monitoring of the front surface includes:
using the determined rotational orientation of the substrate relative to the carrier head to determine which portion of the front surface is being scanned by each endpoint sensor.
11 . The method of claim 9 , wherein the monitoring of the front surface includes:
moving each endpoint sensor along a scan path along the front surface a plurality of times to obtain end point data of the front surface along the scan path.
12 . The method of claim 9 , wherein the monitoring of the front surface includes:
transferring the substrate from the first pad to a second pad that is coupled to a second platen with a carrier head;
scanning the edge of the substrate as it is moved over an orientation sensor disposed at a rotational center of the second pad;
selecting a first die of a plurality of dies formed on the front surface; and
coordinating the rotation and position of the carrier head and the rotation of the second platen to scan the first die.
13 . A method of polishing a substrate, comprising:
scanning an edge of a substrate using an orientation sensor located at a rotational center of a platen;
analyzing data obtained by the orientation sensor to determine a location of a reference mark of the substrate in relation to a carrier head holding the substrate, wherein analyzing the signal to locate the reference mark includes identifying a reference mark signature;
polishing a front surface of the substrate; and
monitoring the front surface during polishing with an endpoint sensor embedded in the platen that scans the front surface, wherein monitoring the front surface includes identifying a portion of the front surface being scanned by the endpoint sensor using the determined location of the reference mark in relation to the carrier head.
14 . The method of claim 13 , wherein analyzing the data obtained by the orientation sensor to determine a location of the reference mark in relation to the carrier head includes:
identifying one or more candidates for a portion of the substrate including the reference mark that are located degrees apart; and
analyzing each candidate to identify the reference mark signature.
15 . The method of claim 13 , wherein analyzing the data obtained by the orientation sensor to determine a location of the reference mark in relation to the carrier head includes:
comparing the data to a threshold, wherein the location of the reference mark is determined when the threshold is met or exceeded.
16 . The method of claim 13 , wherein monitoring the front surface includes scanning the identifying portion of the front surface with the endpoint sensor a plurality of times during the polishing of the front surface.
17 . A polishing system, comprising:
a polishing station, including:
a platen including a polishing pad;
a carrier head configured to rotate a substrate;
an isotropic electromagnetic sensor embedded in the platen at the rotational center of the platen, wherein the isotropic electromagnetic sensor is configured to scan an edge of a substrate that includes a reference mark;
a plurality of endpoint sensors embedded in the platen around the isotropic electromagnetic sensor, each endpoint sensor configured to monitor a surface of the substrate being polished on the pad; and
a controller in communication with the isotropic electromagnetic sensor and the endpoint sensors, wherein the controller is configured to analyze data obtained by the isotropic electromagnetic sensor to identify a location of the reference mark relative to the carrier head.
18 . The polishing system of claim 17 , further comprising:
at least one of a metrology tool or a pre-alignment station configured to determine the location of the reference mark before polishing the substrate.