# US 10,121,708 B2 · Systems and methods for detection of plasma instability by optical diagnosis

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- Number: US 10,121,708 B2
- Document ID: US10121708B2
- Status: Granted
- Kind: B2
- Application number: 15/074,953
- Filed: 2016-03-18
- Published: 2017-05-18
- Granted: 2018-11-06
- Earliest claimed: 2015-11-17
- Assignees: Lam Research Corporation
- Applicants: Lam Research Corporation
- Inventors: Yukinori Sakiyama; Edward Augustyniak; Douglas Keil
- Web page: https://patentgrep.com/patent/US10121708B2

## CPC

- H10P 74/23: {characterised by multiple measurements, corrections, marking or sorting processes}
- C23C 16/45565: {Shower nozzles}
- C23C 16/4585: {Devices at or outside the perimeter of the substrate support, e.g. clamping rings, shrouds}
- C23C 16/4586: {Elements in the interior of the support, e.g. electrodes, heating or cooling devices}
- C23C 16/50: using electric discharges {(generation and control of plasma in discharge tubes for surface treatment H01J37/32, H01J37/34)}
- C23C 16/509: using internal electrodes
- C23C 16/52: Controlling or regulating the coating process {(C23C16/45557, C23C16/279 take precedence)}
- H01J 37/32082: {Radio frequency generated discharge (H01J37/32357, H01J37/32366, H01J37/32394 and H01J37/32403 take precedence)}
- H01J 37/32091: {the radio frequency energy being capacitively coupled to the plasma}
- H01J 37/32137: {controlling of the discharge by modulation of energy}
- H01J 37/32715: {Workpiece holder}
- H01J 37/32935: {Monitoring and controlling tubes by information coming from the object and/or discharge}
- H01J 37/3299: {Feedback systems}
- H10P 14/6336: {in the presence of a plasma [PECVD]}
- H10P 14/6339: {deposition by cyclic CVD, e.g. ALD, ALE or pulsed CVD}
- H10P 34/40: with high-energy radiation
- H10P 50/242: {of Group IV materials}
- H10P 72/0421: {for drying etching}
- H10P 72/0466: {characterised by the construction of the load-lock chamber}
- H10P 72/70: for supporting or gripping
- H10P 74/203: {Structural properties, e.g. testing or measuring thicknesses, line widths, warpage, bond strengths or physical defects}
- H01J 2237/334: Etching
- H10P 14/69215: {the material being a silicon oxide, e.g. SiO2}
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
- C23C: COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04)
- H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H)

## Abstract

A wafer is positioned on a wafer support apparatus beneath an electrode such that a plasma generation region exists between the wafer and the electrode. Radiofrequency power is supplied to the electrode to generate a plasma within the plasma generation region. Optical emissions are collected from the plasma using one or more optical emission collection devices, such as optical fibers, charge coupled device cameras, photodiodes, or the like. The collected optical emissions are analyzed to determine whether or not an optical signature of a plasma instability exists in the collected optical emissions. Upon determining that the optical signature of the plasma instability does exist in the collected optical emissions, at least one plasma generation parameter is adjusted to mitigate formation of the plasma instability.

## Claims

### Claim 1

A method for plasma processing of a wafer, comprising:
having a wafer on a wafer support apparatus, the wafer support apparatus positioned beneath an electrode such that a plasma generation region exists between the wafer and the electrode;
supplying a process gas to the plasma generation region;
supplying radiofrequency power to the electrode to transform the process gas into a plasma within the plasma generation region;
collecting optical emissions from the plasma using one or more optical emission collection devices;
determining an intensity of optical emission at a first optical emission wavelength corresponding to excited neutral atoms of the process gas within the collected optical emissions over time, wherein first optical emission wavelength is selected such that the intensity of optical emission at the first optical emission wavelength corresponding to excited neutral atoms of the process gas remains substantially unchanged when a plasmoid is present within the plasma;
determining an intensity of optical emission at a second optical emission wavelength corresponding to excited ions of the process gas within the collected optical emissions over time, wherein the second optical emission wavelength is selected such that the intensity of optical emission at the second optical emission wavelength corresponding to excited ions of the process gas increases when the plasmoid is present within the plasma, wherein the first optical emission wavelength is different than the second optical emission wavelength;
determining an indicator ratio of the intensity of optical emission at the second optical emission wavelength corresponding to excited ions of the process gas to the intensity of optical emission at the first optical emission wavelength corresponding to excited neutral atoms of the process gas over time;
identifying an increase in the indicator ratio over time by a threshold amount that indicates a presence of the plasmoid within the plasma;
in response to identifying the increase in the indicator ratio over time by the threshold amount, operating a direct current power supply to supply electrical current to the wafer support apparatus and from the wafer support apparatus directly to an underside of the wafer during plasma processing of the wafer to mitigate formation of the plasmoid within the plasma.

### Claim 2 (depends on 1)

The method for plasma processing of the wafer as recited in claim 1, wherein the plasmoid is characterized by an area of higher density plasma surrounded by larger volumes of normal density plasma.

### Claim 3 (depends on 1)

The method for plasma processing of the wafer as recited in claim 1, wherein the process gas is a bombardment gas.

### Claim 4 (depends on 1)

The method for plasma processing of the wafer as recited in claim 1, further comprising:
controlling a pressure within the plasma generation region within a range extending from about 1 Torr to about 3 Torr.

### Claim 5 (depends on 4)

The method for plasma processing of the wafer as recited in claim 4, further comprising:
controlling a distance as measured perpendicularly between the wafer support apparatus and the electrode to be within a range extending from about 0.3 inch to about 0.5 inch.

### Claim 6 (depends on 1)

The method for plasma processing of the wafer as recited in claim 1, wherein the threshold amount is at least three.

### Claim 7 (depends on 1)

The method for plasma processing of the wafer as recited in claim 1, wherein the threshold amount is at least 5, or wherein the threshold amount is at least 7, or wherein the threshold amount is at least 9, or wherein the threshold amount is at least 10.

### Claim 8 (depends on 1)

The method for plasma processing of the wafer as recited in claim 1, wherein the process gas is argon, and
wherein the intensity of optical emission at the first optical emission wavelength corresponding to excited neutral atoms of the process gas is determined at a wavelength of about 750 nanometers, and
wherein the intensity of optical emission at the second optical emission wavelength corresponding to excited ions of the process gas is determined at a wavelength of about 480 nanometers.

### Claim 9 (depends on 1)

The method for plasma processing of the wafer as recited in claim 1, wherein identifying the increase in the indicator ratio over time by the threshold amount that indicates the presence of the plasmoid within the plasma is done following completion of the plasma processing of the wafer in which the optical emissions were collected.

### Claim 10 (depends on 1)

The method for plasma processing of the wafer as recited in claim 1, wherein identifying the increase in the indicator ratio over time by the threshold amount that indicates the presence of the plasmoid within the plasma is done in real-time during the plasma processing of the wafer in which the optical emissions were collected.

### Claim 11 (depends on 10)

The method for plasma processing of the wafer as recited in claim 10, further comprising:
in response to identifying the increase in the indicator ratio over time by the threshold amount, reducing an amount of radiofrequency power supplied to the electrode.

### Claim 12 (depends on 10)

The method for plasma processing of the wafer as recited in claim 10, further comprising:
in response to identifying that the indicator ratio has not increased over time by the threshold amount, increasing an amount of radiofrequency power supplied to the electrode.

### Claim 13 (depends on 1)

The method for plasma processing of the wafer as recited in claim 1, wherein the amount of the electrical current is within a range extending up to about 100 milliAmperes.

### Claim 14 (depends on 1)

The method for plasma processing of the wafer as recited in claim 1, wherein operating the direct current power supply to supply electrical current to the wafer support apparatus includes connecting a positive terminal of the direct current power supply to the wafer support apparatus.

### Claim 15 (depends on 14)

The method for plasma processing of the wafer as recited in claim 14, wherein operating the direct current power supply to supply electrical current to the wafer support apparatus includes supplying a voltage within a range extending from about −10 Volts to about +50 Volts to the wafer support apparatus.

### Claim 16 (depends on 1)

The method for plasma processing of the wafer as recited in claim 1, wherein the plasmoid is initiated and sustained by high energy electrons.

### Claim 17 (depends on 1)

The method for plasma processing of the wafer as recited in claim 1, wherein the intensity of optical emission at the first optical emission wavelength is determined at a specific location within the plasma generation region, and wherein the intensity of optical emission at the second optical emission wavelength is also determined at the specific location within the plasma generation region, such that the indicator ratio is determined for the specific location within the plasma generation region, and
wherein the electrical current is supplied to a portion of the underside of the wafer located below the specific location within the plasma generation region to provide localized mitigation of the plasmoid within the plasma.