Determination of gain for eddy current sensor

Patent metadata

Field	Value
Publication number	US-10207386-B2
Application number	US-201615046270-A
Country	US
Kind code	B2
Filing date	Feb 17, 2016
Priority date	Oct 29, 2013
Publication date	Feb 19, 2019
Grant date	Feb 19, 2019

Abstract

A method of controlling polishing includes polishing a substrate at a first polishing station, monitoring the substrate with a first eddy current monitoring system to generate a first signal, determining an ending value of the first signal for an end of polishing of the substrate at the first polishing station, determining a first temperature at the first polishing station, polishing the substrate at a second polishing station, monitoring the substrate with a second eddy current monitoring system to generate a second signal, determining a starting value of the second signal for a start of polishing of the substrate at the second polishing station, determining a gain for the second polishing station based on the ending value, the starting value and the first temperature, and calculating a third signal based on the second signal and the gain.

First claim

What is claimed is:

1. A polishing system, comprising:
a first polishing station including a first platen to support a first polishing pad, a first in-situ eddy current monitoring system including a first sensor to generate a first signal depending on a thickness of a conductive layer on a substrate, and a first temperature sensor;
a second polishing station including a second platen to support a second polishing pad and a second in-situ eddy current monitoring system including a second sensor to generate a second signal depending on the thickness of the conductive layer on the substrate;
a carrier head to hold the substrate; and
a controller configured to
determine an ending value of the first signal for an end of polishing of the substrate at the first polishing station;
receive a second signal from a second eddy current monitoring system during polishing of the substrate at the second polishing station;
determine a starting value of the second signal for a start of polishing of the substrate at the second polishing station;
determine a gain for the second polishing station based on the ending value, the starting value and a first temperature measured by the first temperature sensor;
for at least a portion of the second signal collected during polishing of at least one substrate at the second polishing station, calculate a third signal based on the second signal and the gain;
determine at least one of a polishing endpoint or an adjustment to a polishing parameter for the at least one substrate based on the third signal; and
at least one of cause the second polishing station to halt polishing at the polishing endpoint or adjust the polishing parameter at the second polishing station by the adjustment.

2. The system of claim 1 , wherein the controller is configured to calculate the gain based on the resistivity of the conductive layer being polished.

3. A polishing system, comprising:
a first polishing station including a first platen to support a first polishing pad, a first in-situ eddy current monitoring system including a first sensor to generate a first signal depending on a thickness of a conductive layer on a substrate, and a first temperature sensor;
a second polishing station including a second platen to support a second polishing pad, a second in-situ eddy current monitoring system including a second sensor to generate a second signal depending on the thickness of the conductive layer on the substrate, and a second temperature sensor in the second polishing station;
a carrier head to hold the substrate; and
a controller configured to
receive a second signal from a second eddy current monitoring system during polishing of the substrate at the second polishing station;
determine a starting value of the second signal for a start of polishing of the substrate at the second polishing station;
determine a gain for the second polishing station based on the starting value and a first temperature measured by the first temperature sensor, and wherein the controller is configured to determine the gain based on a second temperature measured by the second temperature sensor;
for at least a portion of the second signal collected during polishing of at least one substrate at the second polishing station, calculate a third signal based on the second signal and the gain;
determine at least one of a polishing endpoint or an adjustment to a polishing parameter for the at least one substrate based on the third signal; and
at least one of cause the second polishing station to halt polishing at the polishing endpoint or adjust the polishing parameter at the second polishing station by the adjustment.

4. The system of claim 3 , wherein the controller is configured to determine a first thickness from an ending value of the first signal and a calibration function relating thickness to signal strength.

5. The system of claim 4 , wherein the controller is configured to determine an adjusted thickness based on the first thickness, the first temperature and the second temperature.

6. The system of claim 5 , wherein the controller is configured to determine the adjusted thickness where the adjusted thickness T′ satisfies
T=T 1*[1+alpha( TE post TE ini )]

where T1 is the first thickness, TE post is the first temperature, TE ini is the second temperature, and alpha is a resistivity factor for a material of layer being polished.

7. The system of claim 3 , wherein the first temperature sensor is positioned to measure a temperature of the first polishing pad at the first polishing station and the second temperature is positioned to measure a temperature of the second polishing pad at the second polishing station.

8. The system of claim 3 , wherein the first temperature sensor is positioned to measure a temperature of a layer being polished at the first polishing station and the second temperature sensor is positioned to measure a temperature of the layer being polished at the second polishing station.

9. A polishing system, comprising:
a rotatable platen to support a polishing pad;
a carrier head to hold a first substrate against the polishing pad;
an in-situ eddy current monitoring system including a sensor to generate a first signal depending on a thickness of a conductive layer on the first substrate; and
a controller configured to
receive a measurement of an initial thickness of the conductive layer before polishing,
receive the first signal from the sensor,
determine a starting value of the first signal for a portion of the first signal corresponding to the first substrate at a start of polishing of the first substrate,
determine a gain based on the starting value and the measurement of the initial thickness of the conductive layer on the first substrate,
for at least a portion of a signal collected during polishing of the first substrate or a subsequent substrate calculate a second signal based on the first signal and the gain,
determine at least one of a polishing endpoint or an adjustment to a polishing parameter for the first substrate or the subsequent substrate based on the second signal, and
at least one of cause the polishing system to halt polishing at the polishing endpoint or cause the polishing system to adjust the polishing parameter by the adjustment.

10. The system of claim 9 , wherein the controller is configured to determine a desired value of the signal for a conductive layer of the initial thickness from a calibration function relating thickness to signal strength and the measurement of the initial thickness.

11. The system of claim 10 , wherein the controller is configured to determine the gain by calculating a multiplier N according to

N
=

(

D
-
K

)

(

S
-
K

)

where D is the desired value, S is the starting value, and K is a constant representing a value of the calibration function for zero thickness.

12. The system of claim 11 , wherein the controller is configured to determine the gain by multiplying an old gain by N.

13. The system of claim 9 , wherein the controller is configured to calculate the second signal V′ where the second signal V′ satisfies V′=V*G+K where V is the first s

Assignees

• Applied Materials Inc

Inventors

• Xu Kun
• Shen Shih-Haur
• Swedek Boguslaw A
• Carlsson Ingemar
• Bennett Doyle E
• Tu Wen-Chiang
• Iravani Hassan G
• Liu Tzu-Yu

Classifications

• H10P74/238

  comprising acting in response to an ongoing measurement without interruption of processing, e.g. endpoint detection or in-situ thickness measurement · CPC title

• H10P74/207

  Electrical properties, e.g. testing or measuring of resistance, deep levels or capacitance-voltage characteristics · CPC title

• H10P72/0602

  Temperature monitoring · CPC title

• H10P72/0428

  Apparatus for mechanical treatment or grinding or cutting · CPC title

• H10P52/403

  of conductive or resistive materials · CPC title