JP2005120464A - Electrolytic processing apparatus and electrolytic processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect the endpoint of electrolytic processing stably with high precision and with a relatively simple construction. <P>SOLUTION: The electrolytic processing apparatus comprises: a holding section 42 for holding a processing object; a processing electrode 50 which can come close to or into contact with the processing object; a feeding electrode 52 for feeding electricity to the processing object; a fluid supply section 72 for supplying fluid between the processing object and at least one of the processing electrode and the feeding electrode; a processing power source 78 for applying a voltage between the processing electrode and the feeding electrode; a drive section for causing relative movement between the processing object and at at least one of the processing electrode and the feeding electrode; and an eddy current sensor 110 for detecting the thickness of the processing object from a change in eddy current loss, said sensor being disposed not in contact with or separately by an insulator from the processing electrode and/or the feeding electrode. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electrolytic processing apparatus and an electrolytic processing method, and more particularly, to an electrolytic processing apparatus and an electrolytic process used for processing a conductive material on a substrate surface such as a semiconductor wafer and removing impurities attached to the substrate surface. It relates to a processing method.

  In recent years, as a wiring material for forming a circuit on a substrate such as a semiconductor wafer, the movement of using copper (Cu) having low electrical resistivity and high electromigration resistance instead of aluminum or aluminum alloy has become prominent. . This type of copper wiring is generally formed by embedding copper in a fine recess provided on the surface of the substrate. As a method of forming this copper wiring, there are methods such as CVD, sputtering and plating, but in any case, copper is formed on almost the entire surface of the substrate, and unnecessary copper is formed by chemical mechanical polishing (CMP). To be removed.

1A to 1C show a manufacturing example of this type of copper wiring board W in the order of steps. First, as shown in FIG. 1A, an insulating film 2 such as an oxide film made of SiO ₂ or a low-k material film is deposited on a conductive layer 1a on a semiconductor substrate 1 on which a semiconductor element is formed. A contact hole 3 and a wiring groove 4 are formed in the insulating film 2 by lithography / etching technique, a barrier layer 5 made of TaN or the like is formed thereon, and a seed layer 7 is formed thereon as a power feeding layer for electrolytic plating. To do.

  Then, as shown in FIG. 1B, the surface of the substrate W is plated with copper to fill the contact holes 3 and the wiring grooves 4 with copper and to deposit a copper film 6 on the insulating film 2. . Thereafter, the copper film 6, the seed layer 7 and the barrier layer 5 on the insulating film 2 are removed by chemical mechanical polishing (CMP) to insulate the surface of the copper film 6 filled in the contact hole 3 and the wiring groove 4. The surface of the film 2 is substantially flush with the surface. As a result, a wiring made of the copper film 6 is formed as shown in FIG.

  In recent years, as the miniaturization and high precision have progressed in the components of all devices, and the manufacturing in the sub-micron region has become common, the influence of the processing method itself on the characteristics of the material has been increasing. Under these circumstances, the machining method in which the tool removes the workpiece while physically destroying it, as in conventional machining, because many defects are generated in the workpiece by machining. The properties of the work piece deteriorate. Therefore, it becomes a problem how the processing can be performed without impairing the characteristics of the material.

  Special processing methods developed as means for solving this problem include chemical polishing, electrolytic processing, and electrolytic polishing. In contrast to conventional physical processing, these processing methods perform removal processing or the like by causing a chemical dissolution reaction. Therefore, defects such as work-affected layers and dislocations due to plastic deformation do not occur, and the problem of performing processing without impairing the properties of the above-mentioned material is achieved.

  As an electrolytic process, a process for processing in ultrapure water using the catalytic action of an ion exchanger has been developed. As shown in FIG. 2, the ion exchanger 12 a attached to the machining electrode 14 and the ion exchanger 12 b attached to the power supply electrode 16 are brought into contact with or close to the surface of the workpiece 10, thereby processing the electrode 14. A fluid 18 such as ultrapure water is supplied from the fluid supply unit 19 between the processing electrode 14 and the power supply electrode 16 and the workpiece 10 while applying a voltage between the power supply electrode 16 and the power supply electrode 16. Thus, the surface layer of the workpiece 10 is removed.

  According to this electrolytic processing, water molecules 20 in a fluid 18 such as ultrapure water are dissociated into hydroxide ions 22 and hydrogen ions 24 by ion exchangers 12a and 12b. The workpiece 10 is supplied to the surface of the workpiece 10 facing the machining electrode 14 by the electric field between the workpiece 10 and the machining electrode 14 and the flow of a fluid 18 such as ultrapure water. The density of the nearby hydroxide ions 22 is increased, and the atoms 10 a of the workpiece 10 are reacted with the hydroxide ions 22. The reactant 26 generated by the reaction is dissolved in the fluid 18 such as ultrapure water and is removed from the workpiece 10 by the flow of the fluid 18 such as ultrapure water along the surface of the workpiece 10.

  Since the machining principle is based on chemical interaction between ions and the workpiece, the electrolytic machining can be removed while the electrode as a tool and the workpiece are not in contact with each other. Therefore, electrolytic machining has the advantage that it does not cause physical damage to the workpiece such as mechanical machining. However, on the other hand, since removal processing occurs even in a non-contact state, it is generally difficult to control the processing to be surely terminated particularly at the processing end point (when a desired processing amount is reached). In particular, when electrolytic processing is performed on a workpiece in which a plurality of substances (for example, copper and seed layers) having different electrical conductivities with processing, such as a semiconductor substrate, are exposed on the processing surface, the materials are exposed on the processing surface. Abrupt changes in the processing speed occur with changes in the area (working area) of different substances, and as a result, overprocessing tends to occur at the end of processing.

  For this reason, it is conceivable to suppress over-processing at the end of processing by controlling the current and voltage application methods in accordance with changes in the processing area of different substances. However, if the current and voltage application methods are controlled in response to changes in the work area of different materials, it is considered that the control becomes considerably complicated.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an electrolytic processing apparatus and an electrolytic processing method capable of detecting a processing end point of electrolytic processing with high accuracy and stability with a relatively simple configuration. And

  In order to achieve the above object, an electrolytic machining apparatus according to the present invention includes a machining electrode that is freely accessible to a workpiece, a feeding electrode that feeds power to the workpiece, and the workpiece and the machining electrode or the feeding electrode. A voltage is applied between at least one of the fluid supply unit for supplying either ultrapure water, pure water, a liquid having an electric conductivity of 500 μS / cm or less, or an electrolyte, and the processing electrode and the power supply electrode. A processing power source to be applied, a drive unit that relatively moves the workpiece and at least one of the processing electrode or the power feeding electrode, and the processing electrode and / or the power feeding electrode are disposed in a non-contact manner or via an insulator. And an eddy current sensor for detecting the thickness of the workpiece from a change in eddy current loss.

  In this way, the thickness of the workpiece during processing is changed from the change in eddy current loss by the eddy current sensor which is arranged in contact with the processing electrode and / or the feeding electrode via an insulating material to prevent a short circuit. By constantly detecting in-situ, the machining end point of electrolytic machining can be detected with high accuracy and stability with a relatively simple configuration.

  For example, if the eddy current sensor is arranged in the machining electrode when the machining electrode and the feeding electrode are arranged close to each other, only the portion of the eddy current sensor is not processed. Such an adverse effect can be prevented by arranging an eddy current sensor in In addition, by disposing an insulator between the feeding electrode and the eddy current sensor, the magnetic field of the eddy current sensor can be prevented from being affected by the feeding electrode. The number of eddy current sensors can be set arbitrarily.

  Another electrolytic processing apparatus of the present invention includes a machining electrode that is freely accessible to a workpiece, a feeding electrode that feeds power to the workpiece, and between the workpiece and at least one of the machining electrode or the feeding electrode. A voltage in which an off time is provided between the processing electrode and the power supply electrode, and a fluid supply part for supplying either ultrapure water, pure water, a liquid having an electric conductivity of 500 μS / cm or less, or an electrolyte A processing power source for applying a power, a drive unit for relatively moving the workpiece and at least one of the processing electrode or the power feeding electrode, and the processing electrode and / or the power feeding electrode arranged in a non-contact manner or via an insulator. And an eddy current sensor for detecting the thickness of the workpiece from a change in eddy current loss when the voltage of an arbitrary input form applied between the machining electrode and the feeding electrode is off. It is characterized by.

  In electrolytic machining, machining proceeds in a state where a voltage is applied between the machining electrode and the power supply electrode. For this reason, when the thickness of the workpiece is measured in a state where a voltage is applied between the machining electrode and the feeding electrode, a difference may occur between the measured thickness and the actual thickness. Also, when the thickness of the workpiece is measured using an eddy current sensor while applying a pulse voltage between the machining electrode and the feed electrode and performing electrolytic machining, the frequency of the applied pulse voltage is detected by the sensor. When the frequency approaches the frequency at which it oscillates for detection (AC of several tens of MHz), noise is likely to be mixed in the detection signal of the eddy current sensor.

  In this electrolytic processing apparatus, the thickness of the workpiece is detected by the eddy current sensor from the change in eddy current loss when the voltage of any input form applied between the processing electrode and the feeding electrode is off. Thus, precise machining amount control can be performed while reducing noise from being mixed into the detection signal of the sensor due to the voltage applied between the machining electrode and the power feeding electrode.

The voltage applied between the machining electrode and the power supply electrode is preferably a pulse voltage that periodically becomes zero.
Thus, by applying a pulse voltage between the machining electrode and the power supply electrode, it is possible to effectively suppress the occurrence of pits on the machining surface, and by setting the minimum potential of the pulse voltage to 0, When the periodically visiting voltage is 0 (off), the thickness of the workpiece can be measured at any time.

One or more eddy current sensors are arranged outside the processing electrode and the feeding electrode.
For example, if there is a space between the machining electrode and the feeding electrode where the eddy current sensor can be disposed without contacting these electrodes, the eddy current sensor can be disposed by placing the eddy current sensor in this space. The processing electrode and the power supply electrode can be disposed in a non-contact manner. The number of eddy current sensors can be set arbitrarily.

In the eddy current sensor, a sensor coil that generates an eddy current in the workpiece and an oscillation circuit that is connected to the sensor coil and generates a variable frequency corresponding to the eddy current loss are integrally configured. It is preferable.
Thereby, signal transmission with low impedance (50Ω) becomes possible, and stable operation can be performed without picking up noise accompanying rotation of the processing table or the like. Further, by arranging the oscillation circuit (substrate) in a direction orthogonal to the sensor coil, it is possible to detect eddy current loss using a high oscillation frequency in the VHF band.

  The eddy current sensor is formed in the workpiece, a sensor coil disposed in the vicinity of the workpiece, a signal source that supplies an AC signal to the sensor coil to form an eddy current in the workpiece, and And a detection circuit for detecting the eddy current by the sensor coil.

  Thereby, it is possible to detect a change in the film thickness of the region with a good linear sensitivity by observing a change in the resistance component in the very thin region, for example, while the oscillation frequency is fixed. In addition, by looking at the change in the reactance component in the relatively thick film thickness region of the conductive film, it is possible to detect the change in the film thickness in that region linearly with good sensitivity. In addition, by detecting changes in impedance including resistance and reactance components, it is possible to detect changes in film thickness from a very thin film thickness to a relatively thick film thickness in a wide dynamic range with good sensitivity. Is possible.

  Therefore, it is possible to detect eddy current loss in a conductive film having a high specific resistance and a thin film thickness. For example, by detecting the electrolytic processing state of an angstrom-order thin film such as tantalum (Ta) constituting the barrier layer, The processing end point can be detected with high accuracy.

It is preferable to arrange a ferromagnetic body around the sensor coil.
By arranging the ferromagnetic material around the sensor coil in this way, the magnetic field due to the magnetic lines of force can be reduced, and a thin insulator can be used correspondingly.

It is preferable that a contact member is disposed between the workpiece and at least one of the processing electrode or the feeding electrode.
This contact member is made of, for example, a member containing an electrolyte, an insulator or a conductive pad, or any combination thereof. The member containing an electrolyte is made of, for example, an ion exchanger or a material containing an ion exchange substance.

  Thus, by disposing the ion exchanger between the workpiece and at least one of the processing electrode or the feeding electrode, the water molecule dissociation reaction is caused by the interaction between the functional group in the ion exchanger and the water molecule. The activation energy can be reduced, the dissociation of water can be promoted, and the processing speed can be improved.

  In the electrolytic processing method of the present invention, a workpiece to be fed by a power supply electrode is brought close to the machining electrode, and ultrapure water, pure water, or electricity is provided between the workpiece and at least one of the machining electrode or the power feeding electrode. Supplying either a liquid having a conductivity of 500 μS / cm or less or an electrolytic solution, and applying a voltage between the processing electrode and the power supply electrode, at least the workpiece and the processing electrode or the power supply electrode One of them is relatively moved, and the thickness of the workpiece is detected by an eddy current sensor from a change in eddy current loss.

  In another electrolytic processing method of the present invention, a workpiece is brought close to a processing electrode, and ultrapure water, pure water is provided between the workpiece and at least one of the processing electrode or a feeding electrode that supplies power to the workpiece. While supplying either water, a liquid having an electric conductivity of 500 μS / cm or less, or an electrolytic solution, and applying a voltage with an off time between the processing electrode and the feeding electrode, Relative movement of the machining electrode or at least one of the power supply electrodes causes the thickness of the workpiece to be vortexed when the voltage of any input form applied between the machining electrode and the power supply electrode is off. It is detected by an eddy current sensor from a change in current loss.

According to the present invention, the thickness of a workpiece during electrolytic processing is detected from a change in eddy current loss by an eddy current sensor arranged in a non-contact manner on a machining electrode and a power supply electrode, so that a relatively simple configuration is achieved. Thus, the processing end point of electrolytic processing can be detected with high accuracy and stability.
In particular, by detecting the thickness of the workpiece with an eddy current sensor when the voltage of an arbitrary input form applied between the machining electrode and the feeding electrode is off, for example, between the machining electrode and the feeding electrode. When a pulse voltage is applied to the sensor, precise processing amount control can be performed while reducing noise from being mixed into the detection signal of the sensor.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 3 is a plan layout view of a substrate processing apparatus including the electrolytic processing apparatus according to the embodiment of the present invention. In this example, an example is shown in which a conductive film such as a copper film or a barrier layer formed on the surface of the substrate is processed (polished) by an electrolytic processing apparatus. It is.

  As shown in FIG. 3, this substrate processing apparatus includes, for example, a cassette containing a substrate W having a copper film 6 as a conductive film (workpiece) and a barrier layer 5 on the surface, as shown in FIG. A pair of load / unload units 30 as a loading / unloading unit for loading / unloading, a first cleaning device 31a for performing primary cleaning of the substrate, a second cleaning device 31b for performing secondary cleaning (finish cleaning) of the substrate, A reversing machine 32 for reversing the substrate W and an electrolytic processing apparatus 34 are provided. These devices are arranged in series, and a transfer robot 36 as a transfer device that transfers the substrate W between these devices and transfers is arranged in parallel with these devices. Further, a control unit 38 that controls the electrolytic processing device 34 is disposed adjacent to the load / unload unit 30 during the electrolytic processing by the electrolytic processing device 34.

4 is a longitudinal sectional view of the electrolytic processing apparatus 34 shown in FIG. 3, and FIG. 5 is a plan view of FIG. As shown in FIG. 4, the electrolytic processing apparatus 34 includes a substrate holding portion 42 that is suspended from a free end of a swing arm 40 that is swingable in a horizontal direction and sucks and holds the substrate W downward (face-down). A processing table 44 made of a disc-shaped insulator and having the fan-shaped processing electrode 50 and the feeding electrode 52 shown in FIG. 5 alternately embedded with the processing electrode 50 and the surface (upper surface) of the feeding electrode 52 exposed. It is prepared at the top and bottom. A membrane-like ion exchanger 56 is attached to the upper surface of the processing table 44 so as to integrally cover the surfaces of the processing electrode 50 and the feeding electrode 52.
In this example, as the processing table 44 having the processing electrode 50 and the feeding electrode 52, a processing table 44 having a diameter more than twice the diameter of the substrate W held by the substrate holding part 42 is used. An example in which electrolytic processing is performed is shown.

  The ion exchanger 56 is made of, for example, a nonwoven fabric provided with an anion exchange group or a cation exchange group. The cation exchanger is preferably one that bears a strongly acidic cation exchange group (sulfonic acid group), but may be one that bears a weak acid cation exchange group (carboxyl group). The anion exchanger is preferably one carrying a strong basic anion exchange group (quaternary ammonium group), but may be one carrying a weak basic anion exchange group (tertiary or lower amino group).

  Here, for example, a nonwoven fabric provided with a strong base anion exchange group is obtained by a so-called radiation graft polymerization method in which a polyolefin nonwoven fabric having a fiber diameter of 20 to 50 μm and a porosity of about 90% is irradiated with γ rays and then graft polymerization is performed. The graft chain is introduced, and then the introduced graft chain is aminated to introduce a quaternary ammonium group. The capacity of the ion exchange group to be introduced is determined by the amount of graft chains to be introduced. In order to perform the graft polymerization, for example, using monomers such as acrylic acid, styrene, glycidyl methacrylate, sodium styrenesulfonate, chloromethylstyrene, and the like, by controlling the monomer concentration, reaction temperature, and reaction time, The amount of grafting to be polymerized can be controlled. Therefore, the ratio of the weight after graft polymerization to the weight of the material before graft polymerization is called the graft ratio. This graft ratio can be up to 500%, and the ion exchange groups introduced after graft polymerization are A maximum of 5 meq / g is possible.

  The nonwoven fabric provided with the strongly acidic cation exchange group was irradiated with γ-rays on a polyolefin nonwoven fabric having a fiber diameter of 20 to 50 μm and a porosity of about 90%, in the same manner as the method of providing the strongly basic anion exchange group. A graft chain is introduced by a so-called radiation graft polymerization method in which post-graft polymerization is performed, and then the introduced graft chain is treated with, for example, heated sulfuric acid to introduce a sulfonic acid group. Moreover, a phosphoric acid group can be introduce | transduced if it processes with the heated phosphoric acid. Here, the graft ratio can be 500% at the maximum, and the ion exchange group introduced after the graft polymerization can be 5 meq / g at the maximum.

  Examples of the material of the ion exchanger 56 include polyolefin polymers such as polyethylene and polypropylene, and other organic polymers. Moreover, as a raw material form, a woven fabric, a sheet | seat, a porous material, a short fiber, etc. other than a nonwoven fabric are mentioned.

  Here, polyethylene and polypropylene can be subjected to graft polymerization by generating radicals in the material by first irradiating the material with radiation (γ rays and electron beams) (pre-irradiation) and then reacting with the monomer. . Thereby, a graft chain having high uniformity and few impurities can be formed. On the other hand, other organic polymers can be radically polymerized by impregnating the monomer and irradiating (simultaneously irradiating) radiation (γ rays, electron beams, ultraviolet rays). In this case, it is not uniform, but can be applied to most materials.

  As described above, the ion exchanger 56 is composed of a nonwoven fabric provided with an anion exchange group or a cation exchange group, so that liquid such as pure water, ultrapure water, or an electrolytic solution freely moves inside the nonwoven fabric, and the nonwoven fabric It becomes possible to easily reach an active site having an internal water decomposition catalytic action, and many water molecules are dissociated into hydrogen ions and hydroxide ions. Furthermore, since hydroxide ions generated by dissociation are efficiently transported to the surface of the processing electrode 50 with the movement of liquid such as pure water, ultrapure water, or electrolytic solution, a high current can be obtained even at a low applied voltage.

  Here, when the ion exchanger 56 is configured with one provided with either an anion exchange group or a cation exchange group, not only the material to be processed that can be subjected to electrolytic processing is limited, but also impurities are likely to be generated depending on the polarity. Therefore, the ion exchanger 56 may be configured integrally by concentrically arranging an anion exchanger having an anion exchange group and a cation exchanger having a cation exchange group. The anion exchanger having an anion exchange group and the cation exchanger having a cation exchange group may be stacked perpendicular to the processing surface of the substrate to be processed, but may be formed in a fan shape and alternately arranged. . Alternatively, such problems can be solved by adding both anion exchange groups and cation exchange groups to the ion exchanger 56 itself.

  Examples of such ion exchangers include amphoteric ion exchangers in which anion exchange groups and cation exchange groups are arbitrarily distributed, and bipolar ions in which cation exchange groups and anion exchange groups are present in layers. Examples of the exchanger include a mosaic ion exchanger in which a portion where a cation exchange group is present and a portion where an anion exchange group is present are arranged in parallel in the thickness direction. Of course, the ion exchanger 56 provided with either an anion exchange group or a cation exchange group may be used in accordance with the material to be processed.

  As shown in FIG. 4, the swing arm 40 moves up and down via a ball screw 62 as the vertical movement motor 60 is driven, and rotates at the upper end of a swing shaft 66 that rotates as the swing motor 64 is driven. It is connected. The substrate holder 42 is connected to a rotation motor 68 attached to the free end of the swing arm 40, and rotates (spins) as the rotation motor 68 is driven.

  The processing table 44 is directly connected to the hollow motor 70 and rotates (spins) as the hollow motor 70 is driven. A through hole (not shown) as a pure water supply unit that supplies pure water, more preferably ultrapure water, is provided in the center of the processing table 44. The through hole is connected to a pure water supply pipe (not shown) extending inside the hollow portion of the hollow motor 70. Pure water or ultrapure water is supplied through the through hole and then supplied to the entire processing surface through an ion exchanger 56 having water absorption.

  Further, as shown in FIG. 5, a pure water nozzle having a plurality of supply ports for supplying pure water, more preferably ultrapure water, is provided above the processing table 44 along the diameter direction of the processing table 44. 72 is arranged. Thereby, pure water, more preferably ultrapure water is simultaneously supplied to the surface of the substrate W from the vertical direction of the substrate W. Here, pure water is, for example, water having an electric conductivity of 10 μS / cm or less (1 atm, converted at 25 ° C.), and ultrapure water is, for example, water having an electric conductivity of 0.1 μS / cm or less. A liquid having an electric conductivity of 500 μS / cm or less or an arbitrary electrolytic solution may be used instead of pure water. By supplying the processing liquid during processing, processing instability due to processing products, gas generation, and the like can be removed, and uniform and reproducible processing can be obtained.

  In this example, as shown in FIGS. 4 and 5, a fan-shaped electrode plate 74 is disposed on the processing table 44, and the slip ring is attached to the electrode plate 74 facing the substrate W held by the substrate holding portion 42 during processing. By alternately connecting the cathode and anode of the machining power source 78 via 76, the electrode plate 74 connected to the cathode of the machining power source 78 becomes the machining electrode 50, and the electrode plate 74 connected to the anode becomes the feeding electrode 52. I am doing so. This is because, for example, in copper, an electrolytic processing action occurs on the cathode side, and depending on the material to be processed, the cathode side may be a feeding electrode and the anode side may be a processing electrode. That is, when the material to be processed is, for example, copper, molybdenum, or iron, an electrolytic processing action occurs on the cathode side. Therefore, the electrode plate 74 connected to the cathode of the processing power supply 78 becomes the processing electrode 50 and the electrode connected to the anode. The plate 74 is made to be the feeding electrode 52. On the other hand, in the case of aluminum or silicon, for example, an electrolytic processing action occurs on the anode side. Therefore, the electrode connected to the anode of the electrode can be used as a processing electrode, and the cathode side can be used as a feeding electrode.

  In this way, the processing electrode 50 and the power supply electrode 52 are divided and provided alternately along the circumferential direction of the processing table 44, thereby eliminating the need for a fixed power supply portion to the conductive film (workpiece) of the substrate. Thus, the entire surface of the substrate can be processed. Furthermore, by changing the positive and negative in a pulse shape, the electrolytic product can be dissolved, and the flatness can be improved by the multiplicity of processing repetition.

  Here, the processing electrode 50 and the feeding electrode 52 generally have a problem of oxidation or elution due to an electrolytic reaction. For this reason, carbon, a relatively inactive noble metal, conductive oxide, or conductive ceramic is used as a material for the processing electrode 50 and the feeding electrode 52 rather than metals and metal compounds widely used for electrodes. Is preferred. As an electrode made of this noble metal, for example, titanium is used as the base electrode material, platinum or iridium is attached to the surface by plating or coating, and sintering is performed at a high temperature to maintain stability and strength. Can be mentioned. Ceramic products are generally obtained by heat treatment using inorganic materials as raw materials, and products having various characteristics are made using various nonmetals, metal oxides, carbides and nitrides as raw materials. Some of these are conductive ceramics. When the electrode is oxidized, the electrical resistance value of the electrode increases, leading to an increase in applied voltage. Thus, by protecting the electrode surface with a material that is difficult to oxidize such as platinum or a conductive oxide such as iridium, the electrode is protected. A decrease in conductivity due to oxidation of the material can be prevented.

  Here, for example, when electrolytic processing of copper is performed using an ion exchanger 56 to which a cation exchange group is added, copper saturates the ion exchange group of the ion exchanger (cation exchanger) 56 after the processing is completed. Therefore, the processing efficiency when performing the next processing is deteriorated. Further, when electrolytic processing of copper is performed using an ion exchanger 56 to which an anion exchange group is added, fine particles of copper oxide are generated and adhered to the surface of the ion exchanger (anion exchanger) 56. The surface of the next processing substrate may be contaminated.

  Therefore, in this example, a regeneration unit 80 that regenerates the ion exchanger 56 is provided, and these effects are removed by regenerating the ion exchanger 56 by the regeneration unit 80 during processing. That is, the reproducing unit 80 includes a swing arm 82 having the same configuration as that of the swing arm 40 provided at an opposing position across the processing table 44 of the swing arm 40 that holds the substrate holding unit 42, and the swing arm 40. The reproducing head 84 is held at the free end of the arm 82, and a reproducing electrode 86 is attached to the lower surface of the reproducing head 84.

  Then, by applying a potential opposite to that at the time of processing to the ion exchanger 56 via the regeneration power supply 88, that is, the regeneration electrode 86 is connected to the cathode of the regeneration power supply 88 and the electrode plate facing the regeneration electrode 86. 74 is connected to the anode of the regeneration power supply 88 via the slip ring 90 and a voltage is applied between the regeneration electrode 88 and the electrode plate 74, so that ions positioned between the regeneration electrode 88 and the electrode plate 74 are applied. The dissolution of deposits such as copper adhering to the exchanger 56 is promoted, whereby the ion exchanger 56 can be regenerated during processing. In this case, the regenerated ion exchanger 56 is rinsed with pure water or ultrapure water that is supplied between the regenerating electrode 86 and the processing table 44 and removed by suction.

  Inside the processing table 44, an eddy current sensor 110 that detects the thickness of a workpiece such as a conductive film from a change in eddy current loss and detects a processing end point is an electrode plate 74 that serves as a feeding electrode 52. It is arranged through the inside. That is, a recess 44a is provided at a position penetrating through the electrode plate 74 serving as the feeding electrode 52 of the processing table 44, and the eddy current sensor 110 surrounded by the insulator 94 is accommodated in the recess 44a. Are arranged. A coaxial cable 115 extending from the eddy current sensor 110 is connected to the control unit 38. Accordingly, the thickness (film thickness) of a workpiece such as a conductive film during processing can be constantly detected in-situ from changes in eddy current loss by the eddy current sensor 110. It is like that. The number of eddy current sensors 110 can be set arbitrarily.

  Thus, by preventing the eddy current sensor 110 from coming into contact with the power supply electrode 52, a short circuit with the power supply electrode 52 of the eddy current sensor 110 is prevented, and the periphery of the eddy current sensor 110 is surrounded by the insulator 94. Thus, the magnetic field of the eddy current sensor 110 can be prevented from being affected by the power supply electrode 52. It is preferable to use the insulator 94 made of a ferromagnetic material, thereby reducing the magnetic field due to the lines of magnetic force, and accordingly, the insulator 94 having a small thickness can be used.

  If the eddy current sensor is arranged in the machining electrode when the machining electrode 50 and the feeding electrode 52 are arranged close to each other as in this example, the machining of only the portion of the eddy current sensor is not performed. However, such an adverse effect can be prevented by arranging an eddy current sensor in the power supply electrode.

  As described below, when the current applied between the machining electrode and the feeding electrode is changed to a pulse or an alternating current, an alternating current is also generated in the workpiece (conductive film) such as a copper film. Is on the order of several kHz, and on the other hand, the current passed through the eddy current sensor is on the order of several MHz, so that the influence of the pulse or alternating current can be treated as an error when detecting on the sensor side.

  FIG. 6 schematically shows the structure of the eddy current sensor 110. In the eddy current sensor 110, a sensor coil 111 that generates an eddy current in a conductive film and an oscillation circuit (substrate) 112 that is connected to the sensor coil 111 and oscillates a variable frequency in response to eddy current loss are integrated. It is configured. The sensor coil 111 and the oscillation circuit 112 are housed in the box body 113. The dimensions of the box 113 are, for example, about 20 mm or less in length and width and about 10 mm or less in height. A coaxial cable 115 having an impedance of about 50Ω is connected to the oscillation circuit 112, thereby supplying a direct current power to the eddy current sensor 110. The coaxial cable 115 serves as an output line that outputs an oscillation signal.

  Here, the sensor coil 111 has an air-core spiral shape, for example, one having about two turns is employed. The oscillation circuit 112 is arranged so as to be orthogonal to the air-core spiral sensor coil 111. This prevents the sensor coil 111 from generating eddy currents in the conductive material on the oscillation circuit (substrate) 112. That is, if the sensor coil 111 is arranged in parallel with the oscillation circuit 112, the magnetic flux generated from the sensor coil 111 generates an eddy current inside the conductive material or the like on the circuit board, and the eddy current sensor 110 has the eddy current loss. As a result, the accuracy deteriorates. Also in the oscillation circuit (substrate) 112, it is not preferable in terms of operation that an eddy current is generated in the conductive material on the substrate. By arranging the sensor coil 111 and the oscillation circuit (substrate) 112 at right angles, it becomes possible to accurately measure eddy current loss at a high oscillation frequency of about 200 MHz, as will be described later.

  For example, a Colpitts type oscillation circuit is adopted as the oscillation circuit 112, and a tank circuit is formed by the inductance of the sensor coil 111 and the capacitance of the capacitor of the oscillation circuit 112, and the oscillation frequency is determined by the oscillation frequency of the tank circuit. Here, the reactance component of the equivalent impedance of the sensor coil changes corresponding to the eddy current loss, and thereby the oscillation frequency changes.

  In this example, by selecting the inductance value of the sensor coil 111 and the capacitance value of the capacitor of the oscillation circuit 112, the oscillation frequency in the VHF band of about 200 MHz is set. By selecting this oscillation frequency, detection sensitivity corresponding to the specific resistance of the conductive film that generates eddy current loss can be obtained. That is, examples of the conductive film to be subjected to electrolytic processing include a barrier layer generally made of tantalum (Ta) and a copper film formed on the surface of the barrier layer. Here, the specific resistance of tantalum (Ta) is about 160 Ωm, the specific resistance of copper (Cu) is about 1.6 Ωm, and there is a difference of about 100 times.

  Here, when the conductive film is copper (Cu), the oscillation frequency is about 20 MHz as shown in FIG. That is, when the copper (Cu) film thickness is sufficiently large, an oscillation frequency of about 20.7 MHz is obtained, and when the copper (Cu) film is almost removed, the oscillation frequency is about 20.0 MHz. It becomes. For this reason, a sufficient detection width with a difference between the case where the film thickness is sufficient and the case where the film thickness is not sufficient is about 0.7 MHz.

  On the other hand, in the case of the tantalum (Ta) film used as the barrier layer, as shown in FIG. 7B, when the tantalum (Ta) film is sufficiently thick, the oscillation frequency is about 187 MHz. When the film thickness of the tantalum (Ta) film becomes almost zero, the oscillation frequency is about 184 MHz. In this case as well, a sufficient detection width of about 3 MHz can be obtained as described above.

  Here, the film thickness of the tantalum (Ta) film serving as the barrier layer is angstrom order, and the film thickness of copper (Cu) is μm order. According to the eddy current sensor 110, it is possible to detect the progress of the electrolytic processing of an extremely thin tantalum (Ta) film forming the barrier layer. In other words, in the detection of a copper film with an oscillation frequency of 7 MHz, the end point of electrolytic processing has an error of, for example, about 1000 mm, but the end point of electrolytic processing of a very thin tantalum (Ta) layer is By detecting as about 180 MHz, it is possible to detect the electrolytic processing end point of the barrier layer having a film thickness of angstrom order. Thereby, the detection accuracy of the end point of electrolytic processing can be improved markedly.

  FIG. 8 shows an eddy current loss detection circuit by the eddy current sensor 110. The eddy current sensor 110 includes a sensor coil 111, capacitors 116 and 117 that form a tank circuit with the sensor coil 111, and an active circuit element 118 including a transistor and the like. The capacitance is composed of a fixed capacitor (capacitor) 116 and a variable capacitor (capacitor) 117, and the variable capacitor 117 constitutes an automatic frequency adjustment circuit as will be described later. A frequency divider or subtracter 161 and a distribution board 154 that performs waveform conversion are connected to the eddy current sensor 110 via a coaxial cable 115.

  Here, as described above, the coaxial cable 115 serves as both a power supply line and a signal line. The eddy current sensor 110 is connected to the oscillation signal detection unit via a coupling capacitor, and is connected to the interface board from the interface board side. Power is supplied. Here, the frequency divider changes the detected oscillation frequency. However, according to the subtracter, the resolution can be improved by subtracting and removing many portions of the fixed amount with respect to the change.

  The oscillation signal detector in the processor 155 detects the progress of electrolytic processing from changes in eddy current loss accompanying the progress of electrolytic processing, and approximately two methods described below are employed. The first method detects a change in the oscillation frequency of the oscillation signal. As shown in FIGS. 7A and 7B, when the electrolytic processing of the conductive film proceeds, the eddy current loss changes accordingly, and the equivalent resistance value of the sensor coil changes. Therefore, since the oscillation frequency of the oscillation circuit changes, a signal corresponding to the frequency of the detection width is displayed on the monitor by dividing the oscillation signal by a frequency divider or subtracting it by a subtracter. . Thereby, a transition graph of the frequency trajectory as shown in FIGS. 7A and 7B is obtained.

  When the film thickness is sufficiently thick, the change in eddy current loss with the progress of electrolytic processing (elapse of time t) is small, and therefore the change in oscillation frequency is also small. As electrolytic processing progresses and the remaining film thickness of the conductive film decreases, the eddy current loss decreases rapidly. For this reason, the oscillation frequency also drops rapidly. When the remaining conductive film is completely removed, the processing of the underlying insulating film (oxide film) proceeds, but the conductive film itself does not exist, so the oscillation frequency becomes substantially constant. Therefore, the point at which the oscillation frequency rapidly decreases and then changes to a substantially constant value is the end point of electrolytic processing. By performing differential processing after moving average processing the output of the eddy current sensor 110 and observing the result of the differential processing, it is possible to detect the end point of electrolytic processing with high accuracy.

  Moreover, when the eddy current sensor 110 detects that the film thickness is thin, the recipe for electrolytic processing can be changed. That is, when the eddy current sensor 110 detects that the film thickness has reached a predetermined thickness, a signal is sent from the eddy current sensor 110 to the control unit 38, and the control unit 38 changes the operating conditions of electrolytic processing. Assuming that the processing conditions from the initial stage of electrolytic processing to the predetermined film thickness are the first processing conditions, the second processing condition after the eddy current sensor detects the predetermined film thickness is (1) than the first processing condition. The contact between the substrate and the processing electrode is shortened (2) The voltage applied to the feeding electrode and the processing electrode is reduced (3) The electrical conductivity of the processing liquid is reduced, or any combination is selected, Executed.

  Then, the oscillation frequency detected by the oscillation signal detection unit is transmitted to the control circuit, and the capacitance value of the variable capacitor (varicap) 117 is changed, thereby automatically shifting the oscillation frequency by automatic frequency tuning. Correction can be performed. This suppresses fluctuations in the self-oscillation frequency of the sensor, eliminates individual differences between the sensors, stabilizes the sensitivity of the output signal frequency from the eddy current sensor 110, and eliminates variations due to manufacturing accuracy of the eddy current sensor 110 itself. be able to.

  In order to stabilize the oscillation amplitude of the oscillation circuit using the automatic amplitude control (ALC) method and make the amplitude constant, a high frequency amplitude detector 124 is provided in the oscillation signal detector as shown in FIG. The magnitude of the detected signal is compared with the reference amplitude signal by the comparator 125. Accordingly, the amplitude can be controlled to be constant by operating the attenuator 126. By introducing such a circuit, the operation and S / N ratio at the time of TTL level signal conversion from the high-frequency signal of the eddy current sensor can be stabilized.

  The oscillating frequency signal of the eddy current sensor 110 is regarded as a time gradient change of the frequency, that is, a time differential signal of the oscillating frequency is calculated, and the end point of electrolytic processing can be determined based on this feature point. FIG. 10A shows the transition locus of the oscillation frequency itself with respect to time t, and FIG. 10B shows the transition locus of this differential value. Here, A indicates a metal layer (copper film) clear, B indicates a barrier first layer clear, and C indicates a barrier second layer clear. In this way, even if the change of the oscillation frequency itself is slight, by observing this differential value, it becomes easy to detect the electrolytic processing end point of the barrier layer having a film thickness of angstrom order.

  In the second eddy current loss detection method, the resistance component of the equivalent impedance of the eddy current loss of the sensor coil 111 is directly measured by an LCR meter. By using an LCR meter as the signal detection unit in FIG. 8, the resistance component R is displayed on the horizontal axis and the reactance component X is displayed on the vertical axis, as shown in FIG. 11. As the eddy current loss of the conductive film changes with the progress of electrolytic processing, it is possible to observe how the locus of the resistance value R and the reactance value X changes with the change of the eddy current loss of the conductive film.

That is, point B shows a large amount of residual film and large eddy current loss, and point A disappears as the electroconductive film progresses with the progress of electrolytic processing, eddy current loss disappears, and is fixed from the impedance meter side. This is a state where only resistance is present. As shown in FIG. 11, the impedance change of the sensor is
ΔR >> ΔX
Note that the resistance component (ΔR) changes much more greatly than the reactance component (ΔX). When the eddy current sensor measurement result deviates from a predetermined range during the operation of the electrolytic processing apparatus, it is determined that the sensor has failed and an error signal is generated. And the influence at the time of abnormality can be stopped to the minimum by stopping electrolytic processing.

  Next, substrate processing (electrolytic processing) using the substrate processing apparatus provided with the electrolytic processing apparatus 34 in this embodiment will be described. First, for example, as shown in FIG. 1B, a cassette containing a substrate W on which a copper film 6 and a barrier layer 5 are formed as a conductive film (workpiece) on the surface is set in a load / unload section 30. Then, one substrate W is taken out from the cassette by the transfer robot 36. The transport robot 36 transports the taken-out substrate W to the reversing machine 32 as necessary, and reverses the substrate W so that the surface on which the conductive film (copper film 6) is formed faces downward.

  The transport robot 36 receives the inverted substrate W, transports it to the electrolytic processing apparatus 34, and holds it by suction on the substrate holder 42. Then, the substrate holding part 42 holding the substrate W is moved to the processing position just above the processing table 44 by moving the swing arm 40. Next, the vertical movement motor 60 is driven to lower the substrate holding unit 42, and the substrate W held by the substrate holding unit 42 is brought into contact with or close to the surface of the ion exchanger 56 on the processing table 44.

  Here, when using a liquid having a large resistance value, such as ultrapure water, the electrical resistance is reduced by bringing the ion exchanger 56 into contact with the substrate W, and the applied voltage may be small. Power consumption can also be reduced. This “contact” does not mean “pressing” in order to apply physical energy (stress) to the workpiece as in CMP, for example. Therefore, in the electrolytic processing apparatus according to the present embodiment, the vertical movement motor 60 is used for contact or proximity of the substrate W to the processing table 44. For example, in the CMP apparatus, there is a pressing mechanism that positively presses the substrate and the polishing member. Not done. This is the same in each embodiment described later.

  That is, in CMP, the substrate is generally pressed against the polishing surface with a pressing force of about 20 to 50 kPa. Here, for example, the ion exchanger 56 may be brought into contact with the substrate W with a pressure of 20 kPa or less. Even at a pressure of 10 kPa or less, a sufficient removal processing effect can be obtained.

  Even in the reproducing unit 80, in a similar manner, the swing arm 82 is moved to move the reproducing head 84 to a reproducing position immediately above the processing table 44, and is further lowered to perform reproduction attached to the lower surface of the reproducing head 84. The power supply 88 is brought into contact with or close to the surface of the ion exchanger 56 on the processing table 44.

  In this state, in the electrode plate 74 at a position facing the substrate W held by the substrate holding part 42, the cathode of the machining power source 78 is connected to the machining electrode 50 and the anode of the machining power source 78 is connected via the slip ring 76. A predetermined voltage is applied between the machining electrode 50 and the power supply electrode 52 by connecting to the power supply electrode 52. Further, in the reproducing unit 80, the reproducing electrode 86 is connected to the cathode of the reproducing power source 88, and the electrode plate 74 facing the reproducing electrode 86 is connected to the anode of the reproducing power source 88 through the slip ring 90, respectively. A predetermined voltage is applied between the electrode 88 and the electrode plate 74. Then, the substrate holder 42 and the processing table 44 are rotated together.

  At the same time, pure water, preferably ultrapure water is applied to the upper surface of the processing table 44 from the lower side of the processing table 44 through a through hole provided in the processing table 44, and the processing table is supplied from the upper side of the processing table 44 by the pure water nozzle 72. 44. Pure water, preferably ultrapure water, is simultaneously supplied to the upper surface of 44, and pure water between the processing table 44 and the substrate W held by the substrate holding unit 42 and between the processing table 44 and the regeneration electrode 86, Preferably, ultrapure water is filled. Further, in the regeneration unit 80, pure water, preferably ultrapure water is supplied and sucked between the processing table 44 and the regeneration electrode 86.

  Thereby, electrolytic processing by the processing electrode 50 of the conductive film (copper film 6 or barrier film 5) provided on the substrate W is performed by hydrogen ions or hydroxide ions generated by the ion exchanger 56, and at the same time, Regeneration by the regeneration unit 80 of the ion exchanger 56 is performed. Here, by allowing pure water or ultrapure water to flow inside the ion exchanger 56, a large amount of hydrogen ions or hydroxide ions are generated and supplied to the surface of the substrate W, thereby improving efficiency. It is possible to perform good electrolytic processing.

  That is, by allowing pure water or ultrapure water to flow inside the ion exchanger 56, sufficient water is supplied to the functional group that promotes the dissociation reaction of water (a sulfonic acid group in the case of a strongly acidic cation exchange material). As a result, the amount of dissociation of water molecules can be increased, and the processing products (including gas) generated by the reaction with hydroxide ions (or OH radicals) can be removed by the flow of water to increase the processing efficiency. . Therefore, a flow of pure water or ultrapure water is necessary, and the flow of pure water or ultrapure water is preferably uniform and uniform. By making the flow uniform and uniform, it is possible to supply ions. In addition, it is possible to achieve uniformity and uniformity of removal of processed products, and thus uniformity and uniformity of processing efficiency.

At this time, the film thickness of the conductive film (copper film 6 or barrier layer 5) being processed is measured in-situ by the eddy current sensor 110 provided on the processing table 44, and the measurement result is obtained. Based on this, the end point of the electrochemical machining is detected.
Then, after the electrolytic processing is completed, the processing power supply 78 and the processing power supply 78 of the regeneration power supply 88 are disconnected, the rotation of the substrate holding unit 42 and the processing table 44 is stopped, and then the substrate holding unit 42 is raised and shaken. The moving arm 40 is swung, and the substrate W after the electrolytic processing is transferred to the transfer robot 36. The transport robot 36 that has received the substrate transports the substrate to the reversing machine 32 and reverses it as necessary, transports the substrate to the first cleaning machine 31a, and transports the primary cleaning of the substrate to the second cleaning machine 31b. Then, secondary cleaning (finish cleaning) of the substrate is sequentially performed and dried, and the dried substrate W is returned to the cassette of the load / unload unit 30.

  When electrolytic machining is performed without interposing an ion exchanger between the machining electrode and the workpiece, the electrical resistance is proportional to the “distance between the workpiece and the machining electrode (distance between electrodes)”. . This is because the ion travel distance is reduced, and the required energy is reduced accordingly. For example, for ultrapure water (18.25 MΩ · cm), the electrical resistance is 18.25 MΩ (0.54 μA at a voltage of 10 V) when the distance between the electrodes is 1 cm, and the electrical resistance is 1.825 kΩ (0.55 μA when the distance between the electrodes is 1 μm). 5.4 mA) at a voltage of 10V.

  In addition, when an ion exchanger is interposed between the machining electrode and the workpiece, the electrical resistance is basically the same as that described above when the ion exchanger is brought close to the workpiece without contacting it. Similarly, it is proportional to “distance between workpiece and ion exchanger surface”. However, when the workpiece is brought into contact with the ion exchanger, the electric resistance is further reduced. This is because the ion concentration differs greatly between the inside and the outside of the ion exchanger.

That is, inside the ion exchanger, the ionization reaction of ultrapure water is promoted by the catalytic action, and the concentration of ions (H ⁺ and OH ⁻ ) increases. Therefore, the inside of the ion exchanger becomes a special field in which a high concentration of ions is accumulated (or can be) due to the presence of ion exchange groups. On the other hand, since there is no ion exchange group outside the ion exchanger, the increased ions try to return to the original (H ₂ O), and the ion concentration is significantly reduced.
Therefore, when the ion exchanger is brought into contact with the workpiece, the electrical resistance is kept at a constant low level regardless of the distance between the workpiece and the machining electrode when the ion exchanger is in contact with the workpiece. Can do.

  In this example, pure water, preferably ultrapure water is supplied between the processing table 44 and the substrate W. By performing electrolytic processing using pure water or ultrapure water that does not contain an electrolyte in this way, it is possible to prevent the impurities such as the electrolyte from adhering to or remaining on the surface of the substrate W. . Further, since copper ions and the like dissolved by electrolysis are immediately captured by the ion exchanger 56 by an ion exchange reaction, the dissolved copper ions and the like are deposited again on other portions of the substrate W or oxidized to form fine particles. The surface of the substrate W is not contaminated.

  Since ultrapure water has a large specific resistance and it is difficult for current to flow, the electrical resistance can be reduced by shortening the distance between the electrode and the workpiece as much as possible, or by sandwiching an ion exchanger between the electrode and the workpiece. Although it is reduced, the electric resistance can be further reduced and the power consumption can be reduced by further combining the electrolytic solution. In the processing with the electrolytic solution, the processed part of the workpiece covers a slightly wider range than the processing electrode. However, in the combination of ultrapure water and ion exchanger, almost no current flows through the ultrapure water. Only the area within which the machining electrode and the ion exchanger are projected is processed.

Moreover, you may use the electrolyte solution which added the electrolyte to the pure water or the ultrapure water instead of the pure water or the ultrapure water. By using the electrolytic solution, the electric resistance can be further reduced and the power consumption can be reduced. Examples of the electrolytic solution include neutral salts such as NaCl and Na ₂ SO ₄ , acids such as HCl and H ₂ SO ₄ , and alkali solutions such as ammonia. What is necessary is just to select and use suitably. When the electrolytic solution is used, it is preferable that a slight gap is provided between the substrate W and the ion exchanger 56 so as not to be in contact.

  Furthermore, instead of pure water or ultrapure water, a surfactant or the like is added to pure water or ultrapure water, and the electric conductivity is 500 μS / cm or less, preferably 50 μS / cm or less, more preferably 0. A liquid having a specific resistance of 10 MΩ · cm or less may be used. In this way, by adding a surfactant to pure water or ultrapure water, a layer having a uniform suppressing action to prevent the movement of ions is formed at the interface between the substrate W and the ion exchanger 56. The flatness of the processed surface can be improved by reducing the concentration of ion exchange (dissolution of metal). Here, the surfactant concentration is desirably 100 ppm or less. If the value of the electrical conductivity is too high, the current efficiency is lowered and the processing speed is slowed down. However, the electrical conductivity is 500 μS / cm or less, preferably 50 μS / cm or less, more preferably 0.1 μS / cm or less. A desired processing speed can be obtained by using a liquid having

Further, the ion exchanger 56 is sandwiched between the substrate W, the processing electrode 50, and the feeding electrode 52, so that the processing speed is greatly improved. That is, ultrapure water electrochemical processing is based on chemical interaction between hydroxide ions in ultrapure water and the material to be processed. However, since the hydroxide ion concentration, which is a reactive species contained in ultrapure water, is as small as 10 ⁻⁷ mol / L at room temperature and pressure, reactions other than removal processing reactions (oxide film formation, etc.) It is conceivable that the removal processing efficiency is reduced by the above. For this reason, in order to perform the removal processing reaction with high efficiency, it is necessary to increase the hydroxide ions. Thus, as a method of increasing hydroxide ions, there is a method of promoting the dissociation reaction of ultrapure water with a catalyst material, and an ion exchanger is an effective catalyst material. Specifically, the activation energy related to the dissociation reaction of water molecules is reduced by the interaction between the functional groups in the ion exchanger and the water molecules. Thereby, dissociation of water can be promoted and the processing speed can be improved.

  The ion exchanger 56 may be omitted, and pure water or ultrapure water may be supplied between the substrate W and the processing electrode 50 and the power supply electrode 52. Thus, if the ion exchanger 56 is omitted, the processing speed is slow, but it is particularly effective for removing an extremely thin film by electrolytic processing. In addition, extra impurities such as electrolytes do not adhere to or remain on the surface of the substrate W.

  Further, in this example, the ion exchanger 56 is brought into contact with or close to the substrate W during electrolytic processing. In a state where the ion exchanger 56 and the substrate W are close to each other, although depending on the size of the gap, the electric resistance is large to some extent, so that the voltage when the required current density is applied increases. However, on the other hand, since it is non-contact, it is easy to make a flow of pure water or ultrapure water along the surface of the substrate W, and reaction products on the substrate surface can be removed with high efficiency. On the other hand, when the ion exchanger 56 is brought into contact with the substrate W, the electric resistance becomes extremely small, the applied voltage is small, and the power consumption can be reduced.

  Further, when the voltage is increased to increase the processing speed and the current density is increased, a discharge may occur when the resistance between the electrode and the substrate (workpiece) is large. When electric discharge occurs, pitching occurs on the surface of the workpiece, and the uniformity and flattening of the processed surface becomes difficult. On the other hand, when the ion exchanger 56 is brought into contact with the substrate W, the electrical resistance is extremely small, so that such discharge can be prevented from occurring.

  In this example, the ion exchanger 56 is used as a member containing an electrolyte. Instead of the ion exchanger 56, another contact member may be used, and the electrolytic processing may be performed while the contact member is in contact with the surface of the substrate W. Examples of the contact member include an insulator or a conductive pad. Moreover, you may use combining arbitrarily the member containing electrolytes, such as an ion exchanger, an insulator, and an electroconductive pad.

  FIG. 12 shows an electrolytic processing apparatus 34a according to another embodiment of the present invention. The processing table 44 is a rectangular and fixed type, and the substrate holding part 42 is vertically movable and reciprocates along a horizontal plane without swinging. An example is shown. That is, on the upper surface of the rectangular processing table 44, electrode plates 74 extending over the entire length in the width direction are arranged in parallel at a predetermined pitch while being spaced apart from each other. Are alternately connected so that the electrode plate 74 connected to the cathode of the processing electrode 78 becomes the processing electrode 50, and the electrode plate 74 connected to the anode of the processing electrode 78 becomes the feeding electrode 52.

  On the other hand, the substrate holding part 42 is held at the free end of the vertical movement arm 40a that moves up and down via a ball screw as the vertical movement motor 60a is driven, and rotates along with the rotation of the rotation motor 68. As the reciprocating motor 60a is driven, it reciprocates in the direction orthogonal to the electrode plate 74 integrally with the vertical movement arm 40a via the ball screw 62a. Although not shown, the upper surfaces of the processing electrode 50 and the feeding electrode 52 are covered with an ion exchanger.

  An eddy current sensor 110 is disposed between the machining electrode 50 and the power feeding electrode 52 and surrounded by an insulator 94. Thus, when there is a space in which the eddy current sensor 110 can be disposed without contacting the electrodes 50 and 52 between the processing electrode 50 and the power supply electrode 52, the eddy current sensor 110 is in this space. By arranging the eddy current sensor 110, it is possible to arrange the eddy current sensor 110 in a non-contact manner on the machining electrode 50 and the feeding electrode 52. The number of eddy current sensors 110 can be set arbitrarily.

  The electrolytic processing apparatus 34a rotates the substrate W through the substrate holding unit 42 while simultaneously driving the reciprocating motor 60a while the substrate W held by the substrate holding unit 42 is in contact with or close to the ion exchanger. Then, pure water or ultrapure water is supplied to the upper surface of the processing table 44 while reciprocating the substrate holder 42, and a predetermined voltage is applied between the processing electrode 50 and the power supply electrode 52. Thereby, the surface of the substrate W is electrolytically processed, and at the same time, the eddy current sensor 110 provided on the processing table 44 allows the film thickness of the conductive film (copper film 6 or barrier film 5) being processed to be in situ ( In-situ) is always measured, and the end point of the electrochemical machining is detected based on the measurement result.

  FIG. 13A shows another example of the eddy current sensor. The eddy current sensor includes, for example, a sensor coil 202 disposed in the vicinity of a conductive film 201 to be detected such as a copper film 6 and a barrier layer 5 formed on the surface of the substrate W illustrated in FIG. An AC signal source 203 connected to the sensor coil 202 is provided. Here, the conductive film to be detected is, for example, a copper film 6 having a thickness of about 0 to 1 μm formed on the substrate W shown in FIG. Is the barrier layer 5 of angstrom order. The barrier layer 5 is a high resistance layer made of Ta, TaN, and Tin. The sensor coil 202 is a coil of one to several turns, and is disposed in the vicinity of, for example, about 10 to 20 mm with respect to the conductive film to be detected. The AC signal source 203 is an oscillator having a fixed frequency of about 8 to 32 MHz. For example, a crystal oscillator is used.

  A synchronous detection circuit 205 that detects eddy currents formed in the conductive film 201 by the sensor coil 202 is connected to the end of the sensor coil 202. The synchronous detection circuit 205 can measure the impedance of the sensor coil 202 side including the conductive film 201.

FIG. 13B shows an equivalent circuit among the AC signal source 203, the sensor coil 202, and the conductive film 201. The current I ₁ flows through the sensor coil 202 due to the AC voltage supplied from the AC signal source 203. A current flows through the coil 202 disposed in the vicinity of the conductive film 201, and this magnetic flux interlinks with the conductive film 201, thereby forming a mutual inductance M therebetween, and an eddy current I ₂ in the conductive film 201. Flows. Here, R1 is an equivalent resistance on the primary side including the sensor coil 202, and L1 is a self-inductance on the primary side similarly including the sensor coil 202. On the conductive film 202 side, R2 is an equivalent resistance corresponding to eddy current loss, and L2 is its self-inductance. The impedance Z when the sensor coil side is viewed from the terminals a and b of the AC signal source 203 varies depending on the magnitude of the eddy current loss formed in the conductive film 201.

FIG. 14 shows a change in impedance Z as viewed from the AC signal source side. The horizontal axis is the resistance component (R), and the vertical axis is the reactance component (X). Point A is when the film thickness is extremely large, for example, 100 μm or more. In this case, the impedance Z when the sensor coil 202 side is viewed from the terminals a and b of the AC signal source 203 has an extremely large eddy current in the conductive film 201 disposed in the vicinity of the sensor coil 202, and the sensor coil 202. The resistance component (R ₂ ) and the reactance component jω (M + L ₂ ) connected in parallel with each other become extremely small. Accordingly, both the resistance component (R) and the reactance component (X) are reduced.

As the electrolytic processing proceeds and the conductive film 201 becomes thinner, the impedance Z viewed from the sensor coil input ends (terminals a and b) increases in the resistance component (R ₂ ) and the reactance component jω (M + L ₂ ). To do. A point where the resistance component (R) of the impedance Z viewed from the sensor coil input end is maximized is indicated by B. At this time, the eddy current loss seen from the sensor coil input end is maximized. As the electrolytic processing further proceeds and the conductive film 201 becomes thinner, the eddy current decreases and the resistance component viewed from the sensor coil input end gradually decreases because the eddy current loss gradually decreases. When all of the conductive film 201 is removed by electrolytic processing, there is no eddy current loss, the resistance component (R ₂ ) equivalently connected in parallel becomes infinite, and the resistance of the sensor coil itself Only the component (R ₁ ) remains. The reactance component (X) at this time is the reactance component (L ₁ ) of the sensor coil itself. This state is indicated by point C.

  Actually, for example, when a buried wiring made of copper or the like is formed in a wiring groove provided in a silicon oxide film by a so-called damascene process, tantalum nitride (TaN), titanium nitride (TiN) or the like is formed on the silicon oxide film. The barrier layer is provided, and a metal wiring such as copper or tungsten having high conductivity is provided thereon. Therefore, in the electrolytic processing of these conductive films, it is important to detect the end point of the electrolytic processing of the barrier layer. However, as described above, the barrier layer is made of a very thin film having a relatively low conductivity such as tantalum nitride (TaN) or titanium nitride (TiN) and a film thickness on the order of angstroms.

  In the eddy current sensor of this example, it is possible to easily detect the film thickness in the vicinity of the electrolytic processing end point of such a barrier layer. That is, a point D shown in FIG. 14 shows a position where the film thickness is about 1000 mm, for example, and the resistance component changes greatly corresponding to the film thickness change toward the point C where the film thickness becomes zero. And changes substantially linearly. At this time, as shown in FIG. 14, the reactance component (X) has an extremely small change amount compared to the resistance component. For this reason, in the conventional eddy current sensor based on the principle that the film thickness is detected based on the change in the oscillation frequency caused by the change in the reactance component, the change in the oscillation frequency is extremely small with respect to the change in the film thickness. For this reason, in order to increase the resolution of frequency change, it is necessary to increase the frequency. However, according to this eddy current sensor, the change in the film thickness is detected by observing the change in the resistance component while the oscillation frequency remains fixed. It becomes possible to observe the processing state clearly.

  FIGS. 15A to 15C show detection results of the film thickness of a fine conductive layer on the order of angstroms. The horizontal axis represents the remaining film thickness, the solid line on the vertical axis represents the resistance component (R), and the dotted line represents the reactance component (X). FIG. 15A shows data relating to the tungsten (W) film, and it can be seen that the change in the film thickness can be clearly detected by observing the change in the resistance component with a fine remaining film thickness of 1000 mm or less. FIG. 15B shows data relating to a titanium nitride (TiN) film, and similarly, a change in film thickness can be clearly detected in a region of 1000 mm or less. FIG.15 (c) is data regarding a titanium (Ti) film, and as shown in FIG.15 (c), while the film thickness changes from 500 to 0 mm, the resistance component changes greatly, The change in the film thickness can be detected clearly.

  As for the oscillation frequency of the AC signal source, it is desirable to increase the oscillation frequency to, for example, about 32 MHz when detecting a barrier layer having a relatively low conductivity. By increasing the oscillation frequency, the change in the thickness of the barrier layer of 0 to 250 mm can be clearly observed. On the other hand, for a metal having a relatively high conductivity such as a copper film, for example, it is possible to clearly detect a change in film thickness even at an oscillation frequency as low as about 8 MHz. In the case of a tungsten film, an oscillation frequency of about 16 MHz is preferable. As described above, it is preferable to select an oscillation frequency corresponding to the type of electrolytic processing target film.

  In each example shown in FIGS. 15A to 15C, the change in the reactance component (X) is extremely small with respect to the change in the resistance component (R). In the example of detecting the thickness of the barrier layer, the change in the reactance component (X) was 0.005% in the tantalum film when the remaining film thickness was 0 mm and 250 mm. On the other hand, the change of the resistance component (R) was 1.8%. Therefore, the detection sensitivity is improved about 360 times as compared with the method of looking at the change of the reactance component.

FIG. 16 shows a measurement circuit example of the impedance Z when the sensor coil side is viewed from the AC signal source side. The film thickness detection example described above mainly focuses on the change in the resistance component (R). However, in the impedance Z measurement circuit shown in FIG. 16, the resistance component (R) and reactance accompanying the change in the film thickness. Component (X), amplitude output (Z), and phase output (tan ⁻¹ R / X) can be extracted. Therefore, by using these signal outputs, it is possible to check the progress of the multifaceted electrolytic processing, for example, by measuring the film thickness according to the amplitude.

  The sensor coil 202 is disposed in the vicinity of the substrate W provided with the conductive film to be detected. A signal source 203 that supplies an AC signal to the sensor coil 202 is a fixed-frequency oscillator made of a crystal oscillator, and supplies a voltage having a fixed frequency of 8, 16, and 32 MHz, for example. The AC voltage formed by the signal source 203 is supplied to the sensor coil 202 via the band pass filter 302. A signal detected at the terminal of the sensor coil 202 is input to a synchronous detection unit including a cos synchronous detection circuit 305 and a sin synchronous detection circuit 306 via a high frequency amplifier 303 and a phase shift circuit 304, and the cos component and sin of the detection signal are detected. Ingredients are extracted. Here, two signals of the in-phase component (0 °) and the quadrature component (90 °) of the signal source 203 are formed from the oscillation signal formed by the AC signal source 203 by the phase shift circuit 304, and each is cos synchronous detection. The circuit 305 and the sin synchronous detection circuit 306 are introduced to perform the above-described synchronous detection.

From the synchronously detected signal, unnecessary high frequency components higher than the signal component are removed by the low-pass filters 307 and 308, and the resistance component (R) output as the cos synchronous detection output and the reactance component (X as the sin synchronous detection output) ) Outputs are taken out respectively. Also, the vector operation circuit 309 obtains an amplitude output (√R ² + X ² ) from the resistance component (R) output and the reactance component (X) output. Similarly, the vector operation circuit 310 obtains a phase output (tan ⁻¹ R / X) from the resistance component output and the reactance component output.

  FIG. 17 shows a configuration example of a sensor coil in the eddy current sensor. The sensor coil 210 is obtained by separating a coil for forming an eddy current in a conductive film and a coil for detecting an eddy current in the conductive film, and a three-layer coil 212 wound around a bobbin 211. , 213, 214. Here, the central coil 212 is an oscillation coil connected to the AC signal source 203. The oscillation coil 212 forms an eddy current in the conductive film on the substrate W disposed in the vicinity by a magnetic field generated by the current supplied from the AC signal source 203. A detection coil 213 is disposed above the bobbin 211 (on the conductive film side), and detects a magnetic field generated by an eddy current formed in the conductive film. A balance coil 214 is disposed on the opposite side of the oscillation coil 212 from the detection coil 213.

  In this example, the coils 212, 213, and 214 are formed by coils having the same number of turns (for example, 4 turns), and the detection coil 213 and the balance coil 214 are connected in opposite phases. Therefore, it is wired so that the generated electromotive forces cancel each other with respect to the same magnetic flux interlinked with the coils 213 and 214. The diameter of the coils 212, 213, 214 is, for example, about 15 mm.

  FIG. 18 shows a connection example of each coil. The detection coil 213 and the balance coil 214 constitute a series circuit as described above, and both ends thereof are connected to a resistance bridge circuit 217 including a variable resistor 216 as shown in FIG. By adjusting the resistance value of the variable resistor 216, the output voltage of the series circuit composed of the coils 213 and 214 can be adjusted to zero when there is no conductive film. The coil 212 is connected to the AC signal source 203 and generates an alternating magnetic flux, thereby forming an eddy current in a conductive film disposed in the vicinity. That is, when there is no conductive film in the vicinity of the sensor coil 210 and no eddy current is formed here, the output of the series circuit composed of the coils 213 and 214 connected in opposite phases is zero. The variable resistor 216 is adjusted. Therefore, even if the coil 212 generates an alternating magnetic flux, no output appears in the series circuit of the coils 213 and 214 connected in opposite phases.

  When the conductive film is present in the vicinity of the detection coil 213, the magnetic flux generated by the eddy current formed in the conductive film is linked to the detection coil 213 and the balance coil 214, but the detection coil 213 is more conductive. Since it is arranged at a position close to the conductive film, the balance of the induced voltages generated in the coils 213 and 214 is lost, and thereby the interlinkage magnetic flux formed by the eddy current of the conductive film can be detected. That is, the zero point can be adjusted by separating the series circuit of the detection coil 213 and the balance coil 214 from the oscillation coil 212 connected to the AC signal source and adjusting the balance with the resistance bridge circuit. . Therefore, since it is possible to detect the eddy current flowing in the conductive film from the zero state, the detection sensitivity of the eddy current in the conductive film is enhanced. As a result, it is possible to detect the magnitude of the eddy current formed in the conductive film with a wide dynamic range.

  FIG. 19A shows a change in reactance component (X = ωL) with respect to the change in the film thickness of the conductive film, out of the synchronous detection output appearing on the detection terminal side of the sensor coil 210 accompanying the change in the film thickness of the conductive film. Indicates. The relationship of the change in reactance component to the change in film thickness changes as the reactance component X is illustrated as the film thickness changes from thicker to thinner. That is, as for the film thickness of the conductive film, the change in reactance component (X = ωL) is small in the region (a) where the thickness is very thin, and the change in reactance component (X = ωL) in the region (b) where the film thickness is thick. Will grow. Further, in the region (c) having a film thickness larger than that, the change in the reactance component (X = ωL) is saturated.

  FIG. 19B shows a change in the resistance component R with respect to the change in the film thickness of the conductive film, out of the synchronous detection output appearing on the detection terminal side of the sensor coil 210 accompanying the change in the film thickness of the conductive film. The relationship of the change of the resistance component R with respect to the change of the film thickness changes as shown in the figure as the film thickness changes from the thicker to the thinner. That is, the output of the resistance component R changes greatly linearly in the region (a) of the ultrathin film thickness, and the change of the resistance component R is saturated when the region (b) of a certain thickness is reached. In (c), the output of the resistance component R decreases. Here, in the case of a copper film, the point (a) shows about 1000 Å, the point (b) shows 2000-3000 、, and the point (c) shows 5000 Å or more.

  The combined impedance Z corresponding to the film thickness of the conductive film can be output by the vector arithmetic circuit by squaring and squaring the outputs of the resistance component and the reactance component. FIG. 19C shows the relationship between the film thickness of the conductive film and the synthetic impedance Z. As apparent from FIG. 19 (c), in the synthetic impedance Z, the region where the output changes linearly with respect to the change in the film thickness is the resistance component or reactance component of FIG. 19 (a) or (b) alone. Compared to the measurement, it expands significantly. That is, according to the synthetic impedance Z, the film thickness of the conductive film having a wide dynamic range can be measured.

  In each of the above examples, a voltage is applied from the machining power source 58 between the machining electrode 50 and the feeding electrode 52 to perform electrolytic machining of a workpiece such as a conductive film. During this electrolytic machining, an eddy current sensor is used. The thickness (film thickness) of a workpiece such as a conductive film is measured. In the electrolytic processing, the processing proceeds in a state where a voltage is applied between the processing electrode 50 and the feeding electrode 52. For this reason, if the thickness of the workpiece is measured in a state where a voltage is applied between the machining electrode 50 and the feeding electrode 52, a difference may occur between the measured thickness and the actual thickness. .

  In addition, it is found that by performing electrolytic machining by applying a pulse voltage whose voltage fluctuates periodically between the machining electrode 50 and the power supply electrode 52, generation of pits on the machining surface can be effectively suppressed. ing. As described above, when the eddy current sensor is used to measure the thickness of the workpiece while applying electrolytic processing by applying a pulse voltage between the machining electrode 50 and the feeding electrode 52, the pulse voltage to be applied is measured. Becomes close to the frequency at which the sensor itself oscillates for detection (for example, alternating current of several tens of MHz), noise is likely to be mixed into the detection signal of the eddy current sensor.

  Therefore, as a machining power source 58 that applies a voltage between the machining electrode 50 and the feeding electrode 52, for example, a pulse voltage that periodically repeats the voltage V1 (on) and the voltage 0 (off) shown in FIG. 20 is applied. When a bipolar power supply is used and the pulse voltage periodically reaches 0, that is, when no voltage is applied between the machining electrode 50 and the power supply electrode 52, the eddy current sensor is turned on, the conductive film, etc. The thickness (film thickness) of the workpiece may be measured as needed.

  As described above, when a voltage is not applied between the machining electrode 50 and the feeding electrode 52, that is, when the electrolytic machining is not in progress, the thickness (film thickness) of a workpiece such as a conductive film is measured using an eddy current sensor. By measuring with, precise machining amount control can be performed. In addition, even when the frequency of the pulse voltage applied between the machining electrode 50 and the power supply electrode 52 approaches the frequency that the sensor itself oscillates for detection (for example, alternating current of several tens of MHz), the detection signal of the eddy current sensor It is possible to reduce noise mixing. Furthermore, by setting the minimum potential of the pulse voltage to 0, the thickness of the workpiece can be measured as needed when the periodically visiting voltage is 0 (off).

  Note that a power supply other than the bipolar power supply, for example, a DC power supply that periodically turns on and off current by timer and relay control may be used as the power supply to apply the pulse voltage. Alternatively, a 50/60 Hz AC power source supplied to a factory or home may be connected to a circuit incorporating a diode to cut the AC current by half a wave. Furthermore, a pulse voltage may be formed by applying a bias voltage to the AC voltage. A means capable of supplying a periodically changing voltage (potential) using a thyristor, a capacitor, and a diode may be used. Moreover, the switching power supply generally marketed can also be used. A programmable power supply and a sequence control power supply that can control the waveform can be used particularly preferably.

In this example, a square wave is used as the pulse voltage applied between the machining electrode 50 and the power supply electrode 52, but a sine wave, a triangular wave, a sawtooth wave, a step wave, or the like may be used.
In addition, while performing electrolytic machining while using a continuous direct current (DC) between the machining electrode 50 and the power supply electrode 52 without using a pulse voltage, the time during which the voltage is off during the electrochemical machining, that is, A time during which a direct current (DC) does not flow between the processing electrode 50 and the feeding electrode 52 may be provided, and the thickness of the workpiece may be measured by an eddy current sensor when the voltage is off.

It is a figure which shows the example which forms copper wiring in order of a process. It is a figure attached | subjected to description of the principle of the electrolytic processing provided with the ion exchanger. It is a top view which shows the substrate processing apparatus provided with the electrolytic processing apparatus of embodiment of this invention. It is a longitudinal cross-sectional view of the electrolytic processing apparatus shown in FIG. FIG. 5 is a plan view of FIG. 4. It is a see-through | perspective perspective view which shows schematic structure of an eddy current sensor. It is a graph which shows the change of the oscillation frequency accompanying the progress of the electrolytic processing in the eddy current sensor shown in FIG. It is a figure which shows the detection circuit of the oscillation signal of an eddy current sensor. It is a figure which shows the amplitude adjustment circuit in FIG. (A) is a figure which shows the transition locus | trajectory of an oscillation frequency, (b) is a figure which shows the transition locus | trajectory of the time differential value of an oscillation frequency. It is a figure which shows the transition locus | trajectory of the equivalent impedance by a LCR meter. It is a top view of the partial cutting | disconnection which shows the electrolytic processing apparatus of other embodiment of this invention. (A) is a figure which shows the structure of another eddy current sensor, (b) is an equivalent circuit of (a). It is a figure which shows the transition locus | trajectory of the resistance component (R) and reactance component (X) accompanying the change of the film thickness by the eddy current sensor shown to Fig.13 (a). It is a figure which shows the example of a change of the resistance component (R) and the reactance component (X) accompanying the change of the film thickness by the eddy current sensor shown to Fig.13 (a). It is a figure which shows the structural example of a synchronous detection circuit. It is a figure which shows the structural example of a sensor coil. It is a figure which shows the example of a connection of the sensor coil shown in FIG. (A) is a graph showing changes in reactance components in the conductive film thickness and synchronous detection output, and (b) shows changes in resistance components in the conductive film thickness and synchronous detection output. (C) shows the change of the impedance (amplitude) of the film thickness of the conductive film and the synchronous detection output. It is a figure which shows the relationship between the timing of the measurement by the pulse voltage applied between a process electrode and a feed electrode, and an eddy current sensor.

Explanation of symbols

5 Barrier layer (workpiece)
6 Copper film (workpiece)
30 Loading / Unloading Unit 32 Reversing Machine 34, 34a Electrolytic Processing Device 36 Transfer Robot 38 Control Unit 39 Washing / Drying Unit 40 Swing Arm 40a Vertical Moving Arm 42 Substrate Holding Unit 44 Processing Table 50 Processing Electrode 52 Feed Electrode 56 Ion Exchange Body 66 Oscillating shaft 70 Hollow motor 72 Pure water nozzle 74 Electrode plates 76, 90 Slip ring 78 Processing power source 80 Reproducing part 82 Oscillating arm 84 Reproducing head 86 Regenerating electrode 88 Regenerating power source 94 Insulator 110 Eddy current sensors 111, 202, 210 sensor coil 113 oscillation circuit 113 box 115 coaxial cable 203 signal source 205 synchronous detection circuit 211 bobbin 212, 213, 214 coil 216 variable resistance 217 resistance bridge circuit

Claims (19)

A machining electrode that is freely accessible to the workpiece;
A feeding electrode for feeding power to the workpiece;
A fluid supply unit for supplying either ultrapure water, pure water, a liquid having an electric conductivity of 500 μS / cm or less, or an electrolytic solution between the workpiece and at least one of the processing electrode or the feeding electrode;
A machining power source for applying a voltage between the machining electrode and the feeding electrode;
A drive unit that relatively moves the workpiece and at least one of the processing electrode or the feeding electrode;
Electrolytic machining comprising: an eddy current sensor that is disposed in a non-contact manner or via an insulator on the machining electrode and / or the power supply electrode and detects the thickness of the workpiece from a change in eddy current loss apparatus. A machining electrode freely accessible to the workpiece;
A feeding electrode for feeding power to the workpiece;
A fluid supply unit for supplying either ultrapure water, pure water, a liquid having an electric conductivity of 500 μS / cm or less, or an electrolytic solution between the workpiece and at least one of the processing electrode or the feeding electrode;
A machining power source for applying a voltage with an off time between the machining electrode and the feeding electrode;
A drive unit that relatively moves the workpiece and at least one of the processing electrode or the feeding electrode;
The processing electrode and / or the feeding electrode is arranged in a non-contact manner or via an insulator, and any input form voltage applied between the processing electrode and the feeding electrode is turned off when eddy current loss occurs. An electrolytic processing apparatus comprising: an eddy current sensor that detects a thickness of the workpiece from a change.   The electrolytic processing apparatus according to claim 2, wherein the voltage applied between the processing electrode and the feeding electrode is a pulse voltage that periodically becomes zero.   4. The electrolytic processing apparatus according to claim 1, wherein at least one of the eddy current sensors is disposed outside the processing electrode and the power feeding electrode. 5.   In the eddy current sensor, a sensor coil that generates an eddy current in the workpiece and an oscillation circuit that is connected to the sensor coil and generates a variable frequency corresponding to the eddy current loss are integrally configured. The electrolytic processing apparatus according to claim 1, wherein:   The eddy current sensor is formed on the work piece, a sensor coil disposed in the vicinity of the work piece, a signal source that supplies an alternating current signal to the sensor coil to form an eddy current in the work piece, and the work piece. 5. The electrolytic processing apparatus according to claim 1, further comprising a detection circuit that detects the eddy current detected by the sensor coil.   The electrolytic processing apparatus according to claim 5, wherein a ferromagnetic material is disposed around the sensor coil.   The electrolytic processing apparatus according to claim 1, wherein a contact member is disposed between the workpiece and at least one of the processing electrode and the power feeding electrode.   The electrolytic processing apparatus according to claim 8, wherein the contact member is formed of any one of a member including an electrolyte, an insulator, a conductive pad, or any combination thereof.   The electrolytic processing apparatus according to claim 9, wherein the member including the electrolyte is made of a material including an ion exchanger or an ion exchange substance. Bring the workpiece close to the machining electrode,
Supply either ultrapure water, pure water, a liquid having an electric conductivity of 500 μS / cm or less, or an electrolytic solution between the workpiece and at least one of the machining electrode or a power feeding electrode that feeds the workpiece. And
While applying a voltage between the machining electrode and the feeding electrode, the workpiece and at least one of the machining electrode or the feeding electrode are relatively moved,
An electrolytic machining method, wherein the thickness of the workpiece is detected by an eddy current sensor from a change in eddy current loss. Bring the workpiece close to the machining electrode,
Supply either ultrapure water, pure water, a liquid having an electric conductivity of 500 μS / cm or less, or an electrolytic solution between the workpiece and at least one of the machining electrode or a power feeding electrode that feeds the workpiece. And
While applying a voltage with an off time between the processing electrode and the power supply electrode, the workpiece and at least one of the processing electrode or the power supply electrode are relatively moved,
A thickness of a workpiece is detected by an eddy current sensor from a change in eddy current loss when a voltage of an arbitrary input form applied between the machining electrode and the feeding electrode is off. Electrolytic processing method.   13. The electrolytic machining method according to claim 12, wherein the voltage applied between the machining electrode and the power feeding electrode is a pulse voltage that periodically becomes zero.   The electrolytic processing method according to claim 11, wherein the eddy current sensor is disposed in a non-contact manner or via an insulator on the processing electrode and / or the feeding electrode.   In the eddy current sensor, a sensor coil that generates an eddy current in the workpiece and an oscillation circuit that is connected to the sensor coil and generates a variable frequency corresponding to the eddy current loss are integrally configured. The electrolytic processing method according to any one of claims 11 to 14, wherein:   The eddy current sensor is formed on the workpiece, a sensor coil disposed in the vicinity of the workpiece, a signal source that supplies an AC signal to the sensor coil to form an eddy current in the workpiece, and The electrolytic processing method according to claim 11, further comprising: a detection circuit that detects the eddy current by the sensor coil.   17. The electrolytic processing method according to claim 11, wherein a contact member is disposed between the workpiece and at least one of the processing electrode and the power feeding electrode.   The electrolytic processing method according to claim 17, wherein the contact member is formed of any one of an electrolyte-containing member, an insulator, a conductive pad, or any combination thereof.   The electrolytic processing method according to claim 18, wherein the member including the electrolyte is made of a material including an ion exchanger or an ion exchange material.

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