An original end point detection system was developed by making use of the skin effect in chemical mechanical polishing (CMP). The developed system utilizes a critical change in the eddy current due to the skin effect. The critical change is caused by the following two phases in the polishing process. The first phase is that the eddy current increases when the magnetic flux begins to penetrate the copper film as the film thickness reduces to less than `skin depth'. The next phase is that the eddy current fades out due to substantial elimination of the copper film by further polishing. Consequently, a prominent local maximum point of the eddy current emerges at the turning point between the two phases, which can be detected sensitively before the copper film is eliminated. It was demonstrated that the developed system gains a high sensitivity by making use of a critical change in the eddy current due to the skin effect without exposing the semiconductor device excessively to an intense magnetic flux.

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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A preliminary study of a tabletop multi-mode z-pinch x-ray souce is presented. The goal of development of this device was to obtain high densities and temperatures in plasmas of high atomic number elements with two different types of loads: vacuum spark and small (micronscale) wires. In the first mode, the device can be used for x-ray spectroscopic research and calibration of x-ray and vacuum ultraviolet (VUV) diagnostics instrumentation. In the second mode, single wire and x-pinch loads were applied. The device was developed on the basis of a W calibration source developed under a previous Sandia contract, and subsequently transferred to UNR. The existing system was substantially modified to lower the inductance and increase reliability. The system uses a railgap switch, a low-inductance vacuum interface, and a low-voltage (<25 kV), low-impedance, vacuum coaxial transmission line. Circuit modeling of the modified system predicted more than 100 kA into a plasma load from its DC-charged 3 microfarad, 25 kV capacitor bank, with a time to peak current of about 700 ns. This system is compact, and uses no transformer oil or deionized water. The total energy stored in the capacitors bank is up to 800 I with a charge voltage of up to 25 kV. The measured time to peak current is near 700 ns, and typical maximum current of 10&110 kA. The x-ray output energy, pulse duration, and x-ray images fram this plasma source were studied with PCD and XRD diodes and a time-gated pinhole camera. The work was supported by SNL and UNRAn extreme-ultraviolet (EUV) radiation source near the wavelength of 13.5 nm which utilizes a xenon-filled capillaty Z-pinch plasma is presented. The xenon plasma exhibits broadband emission characteristics that offer radiation near 1 I nm and 13.5 nm. A fast-several kA current derived from pulse compression circuit consisting of magnetic switch, a high voltage transformer and a static induction (SI) thyristor stack is applied across the capillary to produce the radiation. The EUV radiation and dynamics of pinching plasma in a capillaly are characterized by employing a photodiode measurement and a high-speed camera in the visible region. A gazing incidence spectrograph is also used to investigate spectral emission from the plasma and the scaling of this EUV light source for lithography.