# US 12,002,702 B2 · Wafer de-chucking detection and arcing prevention > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,002,702 B2 - Document ID: US12002702B2 - Status: Granted - Kind: B2 - Application number: 17/929,144 - Filed: 2022-09-01 - Published: 2022-12-29 - Granted: 2024-06-04 - Earliest claimed: 2018-12-12 - Assignees: Applied Materials, Inc. - Applicants: Applied Materials, Inc. - Inventors: Ganesh Balasubramanian; Byung Chul Yoon; Hemant Mungekar - Web page: https://patentgrep.com/patent/US12002702B2 ## CPC - H10P 72/722: {Details of electrostatic chucks} - H01J 37/32697: {Electrostatic control} - H01J 37/32715: {Workpiece holder} - H10P 72/0604: {Process monitoring, e.g. flow or thickness monitoring} - H10P 72/0616: {Monitoring of warpages, curvatures, damages, defects or the like} - H10P 74/23: {characterised by multiple measurements, corrections, marking or sorting processes} - H01J 2237/24564: Measurements of electric or magnetic variables, e.g. voltage, current, frequency - H01J 2237/24578: Spatial variables, e.g. position, distance - H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10 - H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H) ## Abstract Methods and systems of detection of wafer de-chucking in a semiconductor processing chamber are disclosed. Methods and systems of interdiction are also disclosed to prevent hardware and wafer damage during semiconductor fabrication if and when de-chucking is detected. In one embodiment, a de-chucking detection method is based on measuring change in imaginary impedance of a plasma circuit, along with measuring one or both of reflected RF power and arc count. In another embodiment, a possibility of imminent de-chucking is detected even before complete de-chucking occurs by analyzing the signature change in imaginary impedance. ## Claims ### Claim 1 A method of damage prevention for a semiconductor processing chamber, the method comprising: placing a wafer on an electrostatic chuck (ESC); creating plasma adjacent to the wafer inside the processing chamber; calculating, by a virtual sensor, a change in imaginary impedance (ΔZI) of a plasma circuit formed when the plasma is created inside the processing chamber; determining, by the virtual sensor, if the wafer is de-chucked from the ESC based on the change in imaginary impedance and further based on data from at least a first physical sensor or a second physical sensor; and performing a damage prevention action responsive to determining that the wafer is de-chucked. ### Claim 2 (depends on 1) The method of claim 1, wherein the determining further comprises: comparing, by a processor, the calculated ΔZI with a predetermined first threshold value to produce a first result, wherein the first result having a first value above the predetermined first threshold value indicates that the wafer is de-chucked. ### Claim 3 (depends on 2) The method of claim 2, wherein the method further comprises: measuring reflected RF power by the first physical sensor; measuring an arc count by the second physical sensor; comparing the measured reflected RF power with a predetermined second threshold value to produce a second result, wherein the second result having a second value above the predetermined second threshold value indicates that the wafer is de-chucked; comparing the measured arc count with a predetermined third threshold value to produce a third result, wherein the third result having a third value above the predetermined third threshold value at least partially indicates that the wafer is de-chucked; and determining, based on the first result, and at least one of the second result and the third result, whether it is safe to continue a plasma process without a risk of damaging at least one of the ESC and the wafer. ### Claim 4 (depends on 1) The method of claim 1, wherein performing the damage prevention action comprises: stopping a current plasma process. ### Claim 5 (depends on 1) The method of claim 1, further comprising: prior to placing the wafer on the ESC, measuring an incoming bow of the wafer; and adjusting a power of a DC source that powers the ESC according to the measured incoming bow of the wafer. ### Claim 6 (depends on 5) The method of claim 5, further comprising: monitoring a bow of the wafer as a current plasma process progresses in time; and adjusting the power of the DC source according to the monitored bow of the wafer to adjust electrostatic chucking force required to maintain contact with the ESC. ### Claim 7 A method of damage prevention for a semiconductor processing chamber, the method comprising: calculating, by a virtual sensor, a change in imaginary impedance (ΔZI) of a plasma circuit formed when plasma is created inside a processing chamber by a plasma source inside the processing chamber, wherein an electrostatic chuck (ESC) inside the processing chamber is configured to chuck a wafer; determining, by the virtual sensor, if the wafer is de-chucked based on the change in imaginary impedance and further based on data from at least a first physical sensor or a second physical sensor; and performing a damage prevention action responsive to determining that the wafer is de-chucked. ### Claim 8 (depends on 7) The method of claim 7, further comprising: comparing the calculated ΔZI with a predetermined first threshold value to produce a first result, wherein the first result having a first value above the predetermined first threshold value indicates that the wafer is de-chucked. ### Claim 9 (depends on 8) The method of claim 8, wherein the first physical sensor comprises a reflected RF power sensor that measures a power difference between a set point of an RF generator and an amount of power delivered by the RF generator. ### Claim 10 (depends on 9) The method of claim 9, wherein the second physical sensor comprises an arc count sensor that measures a number of arcs in the semiconductor processing chamber when plasma is on. ### Claim 11 (depends on 10) The method of claim 10, further comprising: comparing the measured reflected RF power with a predetermined second threshold value to produce a second result, wherein the second result having a second value above the predetermined second threshold value indicates that the wafer is de-chucked; comparing the measured arc count with a predetermined third threshold value to produce a third result, wherein the third result having a third value above the predetermined third threshold value at least partially indicates that the wafer is de-chucked; and determining, based on the first result, and at least one of the second result and the third result, whether the wafer is de-chucked. ### Claim 12 (depends on 8) The method of claim 8, wherein the damage prevention action comprises: stopping a current plasma process. ### Claim 13 (depends on 8) The method of claim 8, further comprising: storing, in a memory, values of A and B, wherein A is an ideal value of the imaginary impedance when the wafer has proper contact with the ESC, and B is an offset from A that indicates an imminent loss of contact of the wafer from the ESC. ### Claim 14 (depends on 13) The method of claim 13, further comprising: comparing a measured value of imaginary impedance over a time window with a predetermined value of (A-B); and predicting, based on a result of the comparing, a possibility of imminent wafer de-chucking. ### Claim 15 (depends on 14) The method of claim 14, further comprising: measuring, by an additional sensor, a bow of the wafer, based on which a power of a DC source that powers the ESC is varied. ### Claim 16 A method comprising: calculating, by a virtual sensor, a change in imaginary impedance (ΔZI) of a plasma circuit formed while a plasma is created inside a processing chamber, wherein a wafer is chucked by an electrostatic chuck (ESC) inside the processing chamber; determining, by the virtual sensor, if the wafer is de-chucked based on the change in imaginary impedance and further based on data from at least a first physical sensor or a second physical sensor; and performing a damage prevention action responsive to determining that the wafer is de-chucked. ### Claim 17 (depends on 16) The method of claim 16, further comprising: comparing the calculated ΔZI with a predetermined first threshold value to produce a first result, wherein the first result having a first value above the predetermined first threshold value indicates that the wafer is de-chucked. ### Claim 18 (depends on 17) The method of claim 17, further comprising: comparing a measured reflected RF power with a predetermined second threshold value to produce a second result, wherein the second result having a second value above the predetermined second threshold value indicates that the wafer is de-chucked; comparing a measured arc count with a predetermined third threshold value to produce a third result, wherein the third result having a third value above the predetermined third threshold value at least partially indicates that the wafer is de-chucked; and determining, based on the first result, and at least one of the second result and the third result, whether it is safe to continue a current plasma process without a risk of damaging at least one of the ESC and the wafer. ### Claim 19 (depends on 17) The method of claim 17, further comprising: storing, in a memory, values of A and B, wherein A is an ideal value of the imaginary impedance when the wafer has proper contact with the ESC, and B is an offset from A that indicates an imminent loss of contact of the wafer from the ESC. ### Claim 20 (depends on 17) The method of claim 17, further comprising: comparing a measured value of imaginary impedance over a time window with a predetermined value of (A-B); and predicting, based on a result of the comparing, a possibility of imminent wafer de-chucking.