Development of Original End Point Detection System Utilizing Eddy Current Variation Due to Skin Effect in Chemical Mechanical Polishing

Fujita, Takashi; Kitade, Keita; Yokoyama, Tomoo

doi:10.1143/jjap.50.05ec09

Cited by 10 publications

(13 citation statements)

References 4 publications

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“…18 As it is known, under the condition that a metal film, represented by a copper film, is exposed to a directional and intense magnetic field, a local eddy current is generated in the surface of copper film. 19 Using this method, the eddy current generated in the copper film changes monotonically in proportion to film thickness. 19 In addition, this method is a non-contact technique, avoiding to scratch the wafer surface.…”

Section: A Measurement Methodsmentioning

confidence: 99%

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A reliable control system for measurement on film thickness in copper chemical mechanical planarization system

Zhao

et al. 2013

Review of Scientific Instruments

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In recent years, a variety of film thickness measurement techniques for copper chemical mechanical planarization (CMP) are subsequently proposed. In this paper, the eddy-current technique is used. In the control system of the CMP tool developed in the State Key Laboratory of Tribology, there are in situ module and off-line module for measurement subsystem. The in situ module can get the thickness of copper film on wafer surface in real time, and accurately judge when the CMP process should stop. This is called end-point detection. The off-line module is used for multi-points measurement after CMP process, in order to know the thickness of remained copper film. The whole control system is structured with two levels, and the physical connection between the upper and the lower is achieved by the industrial Ethernet. The process flow includes calibration and measurement, and there are different algorithms for two modules. In the process of software development, C++ is chosen as the programming language, in combination with Qt OpenSource to design two modules' GUI and OPC technology to implement the communication between the two levels. In addition, the drawing function is developed relying on Matlab, enriching the software functions of the off-line module. The result shows that the control system is running stably after repeated tests and practical operations for a long time.

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Section: A Measurement Methodsmentioning

confidence: 99%

“…19 Using this method, the eddy current generated in the copper film changes monotonically in proportion to film thickness. 19 In addition, this method is a non-contact technique, avoiding to scratch the wafer surface. Meanwhile, it can achieve in situ measurement of the copper film thickness on wafer surface in real time.…”

Section: A Measurement Methodsmentioning

confidence: 99%

A reliable control system for measurement on film thickness in copper chemical mechanical planarization system

Zhao

et al. 2013

Review of Scientific Instruments

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“…4,[8][9][10] According to the skin effect use, critical changes can be made in accordance with the copper film thickness. Figure 2 shows magnetic flux change by skin effect.…”

Section: Principles Of the Developed End Point Detection Systemmentioning

confidence: 99%

“…4 The main principle is to detect a local maximum point of eddy current based on skin effect in the course of the film reduction process by polishing.…”

Section: Primary Magnetic Fieldmentioning

confidence: 99%

“…3 In the former paper, authors reported that end point detection using eddy current due to skin effect was developed for copper chemical mechanical planarization process. 4 The operation principle was shown with the some simulation results. In addition, the paper shows that resonant frequency profile was reproduced at three times under same experimental condition precisely.…”

mentioning

confidence: 99%

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Verification of Operation Principle on End Point Detection by Skin Effect in Chemical Mechanical Planarization

Fujita

Kitade

2017

ECS J. Solid State Sci. Technol.

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An original eddy current sensor by making use of skin effect of copper film was developed for end point prediction in CMP (Chemical Mechanical Planarization). The main operation principle is based on detecting a local maximum point of eddy current due to skin effect in the course of film thickness reduction by CMP. This paper focuses on the verification of the operation principle. The verification evaluation using ferrite sheet supported that magnetic field passing through to a copper film is indispensable to operate the end point detection. From the result of both copper film process and tungsten film process, it was apparent that the resonant frequency profile depends on the skin depth of film material. The equivalent circuit model including the plane inductor and copper film indicates that a real part of an impedance of a plane inductor is proportion to the square of mutual inductance corresponding to eddy current induced. The simulation result of the real part of impedance of the plane inductor was a good agreement with actual resonant frequency profile. It was clarified that the operation principle of the end point detection is based on eddy current generation due to skin effect. End point detection technology that detects polishing end is essential for CMP (Chemical Mechanical Polishing) technology to stop polishing accurately without dishing and erosion caused by overpolishing. 1 As conventional methods on end point detection technology, there were some measures by means of motor torque measurement or observation of reflection rate change of light. 2 In particular, end point detection technology by eddy current has been widely used for copper CMP. 3 In the former paper, authors reported that end point detection using eddy current due to skin effect was developed for copper chemical mechanical planarization process. 4 The operation principle was shown with the some simulation results. In addition, the paper shows that resonant frequency profile was reproduced at three times under same experimental condition precisely. It was demonstrated that the end point system is quite sensitive and robust for actual polishing process. 5 The developed end point system has a great advantage on applying to actual end point detection, compared with the conventional end point system. 6,7 The advantages are as follows.(1) It was difficult for the conventional system to detect polishing end point precisely because eddy current fades out at the polishing end point. The developed system can detect the polishing end point easily because a local maximum point of eddy current emerges around skin depth just before cupper film elimination. (2) Under the developed end point system, even if the initial copper film thickness were uneven in the lot, the polishing end point can be detected accurately because the detection point is based on the remaining film thickness which corresponds to skin depth of the film material. (3) The magnetic field generated by developed end point system is feeble and spread out enough to pass through very th...

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Advanced CMP Process Control by Using Machine Learning Image Analysis

Hsu¹,

Chen²,

Yu³

et al. 2021

2021 IEEE International Interconnect Technology Conference (IITC)

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Development of Original End Point Detection System Utilizing Eddy Current Variation Due to Skin Effect in Chemical Mechanical Polishing

Cited by 10 publications

References 4 publications

A reliable control system for measurement on film thickness in copper chemical mechanical planarization system

A reliable control system for measurement on film thickness in copper chemical mechanical planarization system

Verification of Operation Principle on End Point Detection by Skin Effect in Chemical Mechanical Planarization

Advanced CMP Process Control by Using Machine Learning Image Analysis

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