# US 11,079,459 B2 · Resistivity-based calibration of in-situ electromagnetic inductive monitoring

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- Number: US 11,079,459 B2
- Document ID: US11079459B2
- Status: Granted
- Kind: B2
- Application number: 15/867,543
- Filed: 2018-01-10
- Published: 2018-07-19
- Granted: 2021-08-03
- Earliest claimed: 2017-01-13
- Assignees: Applied Materials, Inc.
- Applicants: Applied Materials, Inc.
- Inventors: Kun Xu; Ingemar Carlsson; Shih-Haur Shen; Boguslaw A. Swedek; Tzu-Yu Liu
- Web page: https://patentgrep.com/patent/US11079459B2

## CPC

- G01R 35/005: {Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references (G01R33/0035, G01R35/002 take precedence)}
- B24B 37/005: Control means for lapping machines or devices
- B24B 37/042: {operating processes therefor}
- C09G 1/00: Polishing compositions (French polish C09F11/00; detergents C11D)
- C09G 1/02: containing abrasives or grinding agents {(abrasives as such C09K3/14; polishing of semi-conductors H10P52/40)}
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)
- B24B: MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING (grinding of gear teeth B23F, of screw-threads B23G1/36; by electro-erosion B23H; abrasive or related blasting B24C; tools for grinding, buffing or sharpening B24D; polishing compositions C09G1/00; abrasives C09K3/14; electrolytic etching or polishing C25F3/00; grinding arrangements for use on assembled railway tracks E01B31/17); DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- C09G: POLISHING COMPOSITIONS (French polish C09F11/00); SKI WAXES

## Abstract

A first resistivity value and a correlation function relating thickness of a conductive layer having the first resistivity value to a signal from an in-situ monitoring system are stored. A second resistivity value for a conductive layer on a substrate is received. A sequence of signal values that depend on thickness of the conductive layer is received from an in-situ electromagnetic induction monitoring system that monitors the substrate during polishing. A sequence of thickness values is generated based on the sequence of signal values and the correlation function. For at least some thickness values of the sequence of thickness values adjusted thickness values are generated that compensate for variation between the first resistivity value and the second resistivity value to generate a sequence of adjusted thickness values. A polishing endpoint is detected or an adjustment for a polishing parameter is determined based on the sequence of adjusted thickness values.

## Claims

### Claim 1

A method of calibrating an in-situ electromagnetic induction monitoring system, comprising:
storing a correlation function relating thicknesses of a conductive layer to signal values from the in-situ electromagnetic induction monitoring system and storing a first value representing an electrical resistivity at which the correlation function applies;
receiving a sheet resistance measurement of a first conductive layer on a calibration substrate, the first conductive layer having an electrical resistivity at a second value;
measuring the first conductive layer on the calibration substrate using the in-situ electromagnetic induction monitoring system to generate a first signal value measurement;
making a measurement in the absence of a substrate having an outer conductive layer using the in-situ electromagnetic induction monitoring system to generate a second signal value measurement; and
calculating based on the first value representing the electrical resistivity at which the correlation function applies, the sheet resistance measurement, the first signal value measurement, and the second signal value measurement, an offset and a gain to apply to signals from the in-situ electromagnetic induction monitoring system to compensate for variation between the electrical resistivity at which the correlation function applies and the electrical resistivity of the first conductive layer.

### Claim 2 (depends on 1)

The method of claim 1, comprising:
receiving a third value representing an electrical resistivity of a second conductive layer on a second substrate;
receiving a sequence of signal values that depend on thickness of the second conductive layer from the in-situ electromagnetic induction monitoring system that monitors the second substrate during polishing;
generating a sequence of adjusted signal values by applying the offset and gain to the signal values from the sequence of signal values;
generating a sequence of thickness values based on the sequence of adjusted signal values and the correlation function;
for at least some thickness values of the sequence of thickness values, generating adjusted thickness values that compensates for variation between the electrical resistivity at which the correlation function applies and the electrical resistivity of the second conductive layer to generate a sequence of adjusted thickness values; and
at least one of detecting a polishing endpoint or determining an adjustment for a polishing parameter based on the sequence of adjusted thickness values.

### Claim 3 (depends on 2)

The method of claim 2, wherein applying the gain comprises calculating an adjusted signal value S′ that satisfies
S′=G*S−ΔK
where G is the gain and ΔK is the offset.

### Claim 4 (depends on 3)

The method of claim 3, comprising calculating the gain G satisfies
G=(SDH−SDL)/(S1−S2)
where S1 is the first signal value measurement, S2 is the second signal value measurement, and SDH is a desired high signal value for the second conductive layer and SDL is a desired low signal value for the absence of the second conductive layer.

### Claim 5 (depends on 4)

The method of claim 4, comprising calculating the desired high signal value SDH that satisfies
S
DH
=
W
1
·
(
ρ
0
Rs
CAL
)
2
+
W
2
·
(
ρ
0
Rs
CAL
)
+
W
3
.
where ρ0 is the first value, RsCAL is the sheet resistance measurement, and W1, W2 and W3 are coefficients.

### Claim 6 (depends on 5)

The method of claim 5, wherein the correlation function satisfies
S=W1·D2+W2·D+W3
where S is the signal value, and D is thickness.

### Claim 7

A computer program product for calibrating an in-situ electromagnetic induction monitoring system, the computer program product tangibly encoded on a non-transitory computer readable media, comprising instructions to cause a computer system to:
store a correlation function relating thicknesses of a conductive layer to signal values from the in-situ electromagnetic induction monitoring system and store a first value representing an electrical resistivity at which the correlation function applies;
receive a sheet resistance measurement of a first conductive layer on a calibration substrate, the first conductive layer having an electrical resistivity at a second value;
receive a first signal value measurement of the first conductive layer on the calibration substrate from the in-situ electromagnetic induction monitoring system;
receive a second signal value measurement in the absence of a substrate having an outer conductive layer from the in-situ electromagnetic induction monitoring system; and
calculate based on the first value representing the electrical resistivity at which the correlation function applies, the sheet resistance measurement, the first signal value measurement, and the second signal value measurement, an offset and a gain to apply to signals from the in-situ electromagnetic induction monitoring system to compensate for variation between the electrical resistivity at which the correlation function applies and the electrical resistivity of the first conductive layer.

### Claim 8 (depends on 7)

The computer program product of claim 7, comprising instructions to:
receive a third value representing an electrical resistivity of a second conductive layer on a second substrate;
receive a sequence of signal values that depend on thickness of the second conductive layer from the in-situ electromagnetic induction monitoring system that monitors the second substrate during polishing;
generate a sequence of adjusted signal values by applying the offset and gain to the signal values from the sequence of signal values;
generate a sequence of thickness values based on the sequence of adjusted signal values and the correlation function;
for at least some thickness values of the sequence of thickness values, generate adjusted thickness values that compensates for variation between the electrical resistivity at which the correlation function applies and the electrical resistivity of the second conductive layer to generate a sequence of adjusted thickness values; and
at least one of detect a polishing endpoint or determine an adjustment for a polishing parameter based on the sequence of adjusted thickness values.

### Claim 9 (depends on 8)

The computer program product of claim 8, wherein instructions to apply the gain comprise instructions to calculate an adjusted signal value S′ that satisfies
S′=G*S−ΔK
where G is the gain and ΔK is the offset.

### Claim 10 (depends on 9)

The computer program product of claim 9, comprising instructions to calculate the gain G that satisfy
G=(SDH−SDL)/(S1−S2)
where S1 is the first signal value measurement, S2 is the second signal value measurement, and SDH is a desired high signal value for the second conductive layer and SDL is a desired low signal value for the absence of the second conductive layer.

### Claim 11 (depends on 10)

The computer program product of claim 10, comprising instructions to calculate the desired high signal value SDH that satisfy
S
DH
=
W
1
·
(
ρ
0
Rs
CAL
)
2
+
W
2
·
(
ρ
0
Rs
CAL
)
+
W
3
.
where ρ0 is the first value, RsCAL is the sheet resistance measurement, and W1, W2 and W3 are coefficients.

### Claim 12 (depends on 11)

The computer program product of claim 11, wherein the correlation function satisfies
S=W1·D2+W2·D+W3
where S is the signal value, and D is thickness.

### Claim 13

A polishing system, comprising:
a rotatable platen to support a polishing pad;
a carrier head to hold a substrate against the polishing pad;
an in-situ electromagnetic induction monitoring system including a sensor to generate a sequence of signal values that depend on a thickness of a conductive layer on the substrate; and
a controller configured to
store a correlation function relating thicknesses of a conductive layer to signal values from the in-situ electromagnetic induction monitoring system and store a first value representing an electrical resistivity at which the correlation function applies,
receive a sheet resistance measurement of a first conductive layer on a calibration substrate, the first conductive layer having an electrical resistivity at a second value;
receive a first signal value measurement of the first conductive layer on the calibration substrate from the in-situ electromagnetic induction monitoring system;
receive a second signal value measurement in the absence of a substrate having an outer conductive layer from the in-situ electromagnetic induction monitoring system; and
calculate based on the first value representing the electrical resistivity at which the correlation function applies, the sheet resistance measurement, the first signal value measurement, and the second signal value measurement, an offset and a gain to apply to signals from the in-situ electromagnetic induction monitoring system to compensate for variation between the electrical resistivity at which the correlation function applies and the electrical resistivity of the first conductive layer.

### Claim 14 (depends on 13)

The system of claim 13, wherein the controller is configured to:
receive a third value representing an electrical resistivity of a second conductive layer on a second substrate;
receive a sequence of signal values that depend on thickness of the second conductive layer from the in-situ electromagnetic induction monitoring system that monitors the second substrate during polishing;
generate a sequence of adjusted signal values by applying the offset and gain to the signal values from the sequence of signal values;
generate a sequence of thickness values based on the sequence of adjusted signal values and the correlation function;
for at least some thickness values of the sequence of thickness values, generate adjusted thickness values that compensates for variation between the electrical resistivity at which the correlation function applies and the electrical resistivity of the second conductive layer to generate a sequence of adjusted thickness values; and
at least one of detect a polishing endpoint or determine an adjustment for a polishing parameter based on the sequence of adjusted thickness values.

### Claim 15 (depends on 14)

The system of claim 14, wherein the controller is configure to apply the gain to calculate an adjusted signal value S′ that satisfies
S′=G*S−ΔK
where G is the gain and ΔK is the offset.

### Claim 16 (depends on 15)

The system of claim 15, wherein the controller is configured the gain G that satisfies
G=(SDH−SDL)/(S1−S2)
where S1 is the first signal value measurement, S2 is the second signal value measurement, and SDH is a desired high signal value for the second conductive layer and SDL is a desired low signal value for the absence of the second conductive layer.

### Claim 17 (depends on 16)

The system of claim 16, wherein the controller is configured to calculate the desired high signal value SDH that satisfies
S
DH
=
W
1
·
(
ρ
0
Rs
CAL
)
2
+
W
2
·
(
ρ
0
Rs
CAL
)
+
W
3
.
where ρ0 is the first value, RsCAL is the sheet resistance measurement, and W1, W2 and W3 are coefficients.

### Claim 18 (depends on 17)

The system of claim 17, wherein the correlation function satisfies
S=W1·D2+W2·D+W3
where S is the signal value, and D is thickness.