JP2008068388A - Electrostatically coupled type sensor, end point detection method using the same, and device thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatically coupled type sensor, an end point detection method and a device thereof which surely detects the polishing end point with high precision by providing an extremely suitable sensor to detect a polishing end point of a conductive film, reduces noise generation, uses low power consumption and reduces the cost. <P>SOLUTION: The electrostatically coupled type sensor 33 is composed of an oscillation circuit 36 composed of an inductor 34 and a capacitor 35, and a plurality of electrodes 37, 37 having a phase difference generated by disposing on both the ends of the inductor 34. The electrostatically coupled type sensor induces electrostatic coupling between the plurality of electrodes 37, 37 and the conductive film 28 by bringing the plurality of electrodes 37, 37 close to the conductive film 28 having a certain film thickness in parallel and oscillates with a resonance frequency corresponding to the change of a film thickness resistance value of the conductive film 28 through the electrostatic coupling. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrostatic coupling type sensor, an end point detection method and an end point detection apparatus using the same, and in particular, the polishing end point of a conductive film is highly accurate in CMP (Chemical Mechanical Polishing). In particular, the present invention relates to an electrostatic coupling type sensor capable of reliably detecting an end point, an end point detecting method and an end point detecting apparatus using the same.

  For example, the following eddy current sensors are known as conventional techniques related to an electrostatic coupling type sensor, an end point detection method using the same, and an end point detection apparatus. In this prior art, a conductive coil or a sensor coil (eddy current sensor) disposed in the vicinity of a substrate on which the conductive film is formed, and an alternating current signal of a constant frequency is supplied to the sensor coil to the conductive film. An AC signal source for forming an eddy current; and a detection circuit for measuring a reactance component and a resistance component including the conductive film, wherein the sensor coil includes an oscillation coil connected to the signal source, and the coil A detection coil disposed on the conductive film side; and a balance coil disposed on the opposite side of the oscillation coil to the conductive film side, wherein the detection coil and the balance coil are connected to be in opposite phases to each other. ing. A combined impedance is output from the resistance component and reactance component detected by the detection circuit, and a change in the film thickness of the conductive film is detected as a substantially linear relationship over a wide range from the change in the impedance. . (For example, refer to Patent Document 1).

As another conventional technique related to an electrostatic coupling type sensor, an end point detection method using the same, and an end point detection device, for example, the following distance measuring IC is known. This prior art includes an oscillator built in a package, and a planar inductor that is disposed in the package and is connected to the oscillator to specify the oscillation frequency of the oscillator. When a conductive material approaches the IC package surface, the planar inductor changes the oscillation frequency of the oscillator. The approaching distance of the conductive substance can be detected by detecting the oscillation frequency. In order to shorten the measurement time, a high-frequency current is passed through the planar inductor, and electrostatic induction generated on the surface is effectively used. Applications include control of the arm by measuring the position of the robot arm, pressure detection by storing it in the position detector (see, for example, Patent Document 2).
Japanese Patent No. 3578822 (page 3, FIGS. 1 to 11). Japanese Patent No. 3352619 (pages 2 to 4, FIG. 18).

  The oxide film formed on the semiconductor wafer is subjected to lithography and etching to form a groove pattern corresponding to the wiring pattern, and a conductive film made of Cu or the like for filling the groove pattern is formed thereon, A process for forming a wiring pattern by removing unnecessary portions of a conductive film by chemical mechanical polishing is known. In the formation of this wiring pattern, it is extremely important to reliably detect the polishing end point when the conductive film is removed to an appropriate thickness and stop the process. If the polishing of the conductive film is excessive, the resistance of the wiring increases, and if the polishing is insufficient, an insulation failure of the wiring is caused.

On the other hand, in the technique of monitoring the film thickness of the conductive film using eddy current, it is necessary to create a strong magnetic flux to cause eddy current, and the inductor has a three-dimensional shape. For this reason, there are generally the following problems when incorporating an eddy current sensor into a polishing apparatus or the like. As the current flowing through the coil increases, the power consumption increases and the power supply device also increases in size. Magnetic flux leaks to the periphery and noise is likely to occur. A process for winding the conductive wire in a coil shape is required, resulting in high costs.

  Further, in the conventional technology comprising a distance measuring IC, it is configured to include an oscillator and a planar inductor connected to the oscillator and specifying the oscillation frequency of the oscillator. The arm is controlled by position measurement, or stored in a position detector and used for pressure detection.

  Therefore, a sensor that is extremely suitable for detecting the polishing end point of the conductive film is provided to reliably detect the polishing end point with high accuracy, no noise is generated, low power consumption, and further cost reduction. Therefore, a technical problem to be solved arises, and the present invention aims to solve this problem.

  The present invention has been proposed in order to achieve the above object, and the invention according to claim 1 includes a plurality of oscillation circuits including an inductor and a capacitor, and a plurality of phase differences generated by disposing both ends of the inductor. The electrode is made in parallel and close to the conductive film having a certain film thickness, thereby causing electrostatic coupling between the electrode and the conductive film, and through the electrostatic coupling An electrostatic coupling sensor that oscillates at a resonance frequency corresponding to a change in film thickness resistance value of the conductive film is provided.

  According to this configuration, the oscillation circuit is a Colpitts type oscillation circuit whose oscillation frequency band is determined by the inductance of the inductor and the lumped capacitance of the capacitor. When the electrodes arranged at both ends of the inductor are brought close to the conductive film in parallel, the respective electrodes cause electrostatic induction on the conductive film side, and the electrodes and the conductive film are statically connected via the distributed capacitance. Electrocouple. As a result, an equivalent circuit in which the distributed capacitance and the film thickness resistance of the conductive film are added to the inductance and the lumped constant capacitance can be regarded as a parallel resonant circuit. The resonant frequency of this parallel resonant circuit is the value of ω (= 2πf) when the susceptance component in the admittance of the equivalent circuit becomes zero. In this susceptance, the film thickness resistance value (R) is related in the form of a time constant (Cm · R) that is a product of the distributed capacitance (Cm). Therefore, the electrostatic coupling type sensor oscillates at a resonance frequency corresponding to the change in the film thickness resistance value of the conductive film via the electrostatic coupling.

  According to a second aspect of the present invention, there is provided an oscillating circuit comprising a planar inductor and a capacitor, the planar inductor is disposed in parallel with a conductive film having a certain film thickness, and the planar inductor has a phase distribution. There is provided an electrostatic coupling type sensor that oscillates at a resonance frequency corresponding to a change in film thickness resistance value of the conductive film through electrostatic coupling between the conductive film and the conductive film.

  According to this configuration, the planar inductor has both functions of the inductor according to the first aspect of the present invention and each electrode disposed at both ends thereof. The oscillation circuit is a Colpitts type oscillation circuit whose oscillation frequency band is determined by the inductance of the planar inductor and the lumped capacitance of the capacitor. When a planar inductor is brought close to the conductive film in parallel, electrostatic induction is induced on the conductive film side due to the phase distribution of the planar inductor, and the planar inductor and the conductive film are efficiently electrostatically distributed via the distributed capacitance. Join. As a result, an equivalent circuit in which the distributed capacitance and the film thickness resistance of the conductive film are added to the inductance of the planar inductor and the lumped constant capacitance of the capacitor can be regarded as a parallel resonant circuit. Hereinafter, in substantially the same manner as the operation of the first aspect of the invention, the electrostatic coupling type sensor has a resonance frequency corresponding to a change in the film thickness resistance value of the conductive film through the electrostatic coupling that has been efficiently generated. Oscillates.

  The invention according to claim 3 is an end point detection method for detecting a polishing end point when the conductive film is polished to remove an appropriate thickness, and the electrostatic coupling type sensor according to claim 1 or 2 is used. The end point detection method used is provided.

  According to this configuration, in the electrostatic coupling type sensor according to claim 1 or 2, the distribution generated between the plurality of electrodes or the planar inductor and the conductive film in the inductance of the inductor or the planar inductor and the lumped constant capacitance of the capacitor. An equivalent circuit to which the capacitance and the film thickness resistance of the conductive film are added can be regarded as a parallel resonant circuit. The resonant frequency of this parallel resonant circuit is the value of ω (= 2πf) when the susceptance component in the admittance of the equivalent circuit becomes zero. In this susceptance, the film thickness resistance value (R) is related in the form of a time constant (Cm · R) which is a product of the distributed capacitance (Cm). On the other hand, this film thickness resistance value changes so as to increase as the film thickness decreases as the polishing of the conductive film proceeds. Therefore, when the relationship between the film thickness and the resonance frequency when the film thickness is changed is determined from the equivalent circuit, it can be seen that the resonance frequency can increase as the film thickness decreases. Based on the change that can increase the resonance frequency, the polishing end point when the appropriate thickness of the conductive film is removed by polishing is detected.

  According to a fourth aspect of the present invention, there is provided an electrostatic for judging the polishing end point based on the peak of the resonance frequency obtained when the polishing state of the conductive film is monitored using the electrostatic coupling type sensor according to the first or second aspect. An end point detection method using a combined sensor is provided.

  According to this configuration, the film thickness when the film thickness resistance value (R) is changed from 0 to ∞ (thickness: thick → thin) in the equivalent circuit described in the operation of the invention of claim 3 When the relationship of the resonance frequency is simulated, it can be seen that the resonance frequency increases as the film thickness decreases, and a peak occurs in the resonance frequency in the region where the film thickness resistance value (R) is close to ∞. The polishing state of the conductive film is monitored, and the polishing end point is determined based on the peak of the resonance frequency.

  According to a fifth aspect of the present invention, a wafer on which a conductive film is formed is held on a polishing head, and the conductive film is pressed against a polishing pad provided on the surface of a rotating platen while rotating the polishing head. The electrostatic coupling according to claim 1, wherein the end point detection device detects the end point of polishing when an appropriate thickness is removed by monitoring the conductive film in chemical mechanical polishing for polishing the conductive film. End point detection using an electrostatic coupling type sensor constructed by incorporating a mold sensor into either the platen or the polishing head and detecting the polishing end point from a change in oscillation frequency of the electrostatic coupling type sensor. Providing equipment.

  According to this configuration, the electrostatic coupling type sensor according to claim 1 or 2 is incorporated in either the platen or the polishing head in the chemical mechanical polishing apparatus to monitor the polishing state of the conductive film, and the conductive film The polishing end point is detected when the appropriate thickness is removed.

  The invention according to claim 1 is composed of an oscillation circuit composed of an inductor and a capacitor, and a plurality of electrodes having a phase difference caused by being arranged at both ends of the inductor, and the electrodes have a certain thickness. By bringing them close to the film in parallel, electrostatic coupling is caused between the electrode and the conductive film, and the resonance frequency corresponding to the change in the film thickness resistance value of the conductive film is caused through the electrostatic coupling. Since it oscillates, it is possible to provide a sensor suitable for detecting the polishing end point of the conductive film by using a resonance frequency signal corresponding to a change in the film thickness resistance value of the conductive film as an oscillation output. Can do. In addition, an electrostatic coupling type sensor in which electrodes are respectively generated at both ends of the inductor has an advantage that the cost can be reduced because it is relatively inexpensive.

  According to a second aspect of the present invention, there is provided an oscillating circuit comprising a planar inductor and a capacitor, the planar inductor is disposed in parallel with a conductive film having a certain film thickness, and the planar inductor has a phase distribution. And the conductive film are caused to oscillate at a resonance frequency corresponding to a change in the film thickness resistance value of the conductive film via the electrostatic coupling. A sensor that is extremely suitable for detecting the polishing end point of the conductive film by generating a resonance frequency signal corresponding to a change in the film thickness resistance value of the conductive film through oscillation coupling that frequently occurs. There is an advantage that it can be provided.

  The invention according to claim 3 is an end point detection method for detecting a polishing end point when the conductive film is polished to remove an appropriate thickness, and the electrostatic coupling type sensor according to claim 1 or 2 is used. Since the end point detection is used, the resonance frequency changes in the increasing direction when the film thickness of the conductive film becomes thinner than the range affected by the skin effect.Based on this change, the appropriate thickness is obtained by polishing. There is an advantage that the polishing end point when it is removed can be detected with high accuracy.

  According to a fourth aspect of the present invention, the polishing end point is determined based on the peak of the resonance frequency obtained when the polishing state of the conductive film is monitored using the capacitive coupling sensor according to the first or second aspect. Therefore, the resonance frequency changes so as to increase as the film thickness of the conductive film becomes thinner, and a peak can occur in the region where the film thickness resistance value is close to ∞. There is an advantage that the polishing end point can be reliably detected with high accuracy when an appropriate thickness is removed by polishing.

  According to a fifth aspect of the present invention, a wafer on which a conductive film is formed is held on a polishing head, and the conductive film is pressed against a polishing pad provided on the surface of a rotating platen while rotating the polishing head. The electrostatic coupling according to claim 1, wherein the end point detection device detects the end point of polishing when an appropriate thickness is removed by monitoring the conductive film in chemical mechanical polishing for polishing the conductive film. Since the type sensor is incorporated into either the platen or the polishing head and configured to detect the polishing end point from a change in the oscillation frequency of the capacitively coupled sensor, the capacitively coupled sensor is a chemical mechanical polisher. By incorporating it into either the platen or polishing head in the equipment, the polishing status of the conductive film can be monitored appropriately, and polishing when the conductive film is removed to the proper thickness There is an advantage that it is possible to reliably detect point.

  The purpose of providing a sensor that is extremely suitable for detecting the polishing end point of a conductive film, reliably detecting the polishing end point with high accuracy, generating no noise, reducing power consumption, and further reducing costs. In order to achieve the above, an oscillation circuit composed of an inductor and a capacitor, and a plurality of electrodes having a phase difference generated by disposing them at both ends of the inductor, the electrodes are formed into a conductive film having a certain film thickness. By bringing them close to each other in parallel, electrostatic coupling occurs between the electrode and the conductive film, and oscillation occurs at a resonance frequency corresponding to a change in film thickness resistance value of the conductive film via the electrostatic coupling. This was realized by determining the polishing end point based on the peak of the resonance frequency obtained when the polishing state of the conductive film was monitored using an electrostatic coupling type sensor.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view of a chemical mechanical polishing apparatus in which an end point detection device using an electrostatic coupling type sensor is incorporated, FIG. 2 is an enlarged vertical sectional view of a polishing head, and FIG. 3 is an electrostatic coupling type sensor incorporated in a platen. FIG. 4 is a schematic configuration diagram for explaining a state in which the electrostatic coupling type sensor is incorporated in the polishing head.

First, the configuration of the end point detection apparatus using the electrostatic coupling type sensor according to the present embodiment will be described from the configuration of the chemical mechanical polishing apparatus. In FIG. 1, a chemical mechanical polishing apparatus 1 mainly includes a platen 2 and
And a polishing head 3. The platen 2 is formed in a disk shape, and a rotary shaft 4 is connected to the center of the lower surface thereof. The platen 2 rotates in the direction of arrow A when the motor 5 is driven. A polishing pad 6 is adhered to the upper surface of the platen 2, and an abrasive (slurry) is supplied onto the polishing pad 6 from a nozzle (not shown).

  As shown in FIG. 2, the polishing head 3 is mainly composed of a head body 7, a carrier 8, a retainer ring 9, a retainer ring pressing means 10, an elastic sheet 11, a carrier pressing means 16, and control means such as air. .

  The head body 7 is formed in a disk shape, and a rotary shaft 12 (see FIG. 1) is connected to the center of the upper surface thereof. The head body 7 is attached to the rotary shaft 12 and is driven by a motor (not shown) to rotate in the direction of arrow B in FIG.

  The carrier 8 is formed in a disc shape, and is disposed in the center of the head body 7. A dry plate 13 is provided between the center of the upper surface of the carrier 8 and the lower center of the head body 7, and rotation is transmitted from the head body 7 via the pins 14 and 14.

  An operating transformer main body 15a is fixed between the center lower part of the dry plate 13 and the center upper part of the carrier 8, and the core 15b of the operating transformer 15 is fixed to the center upper part of the carrier 8 and is not shown. A polishing state signal of a conductive film made of Cu or the like connected to the control unit and formed on the wafer W (lower side in FIG. 2) is output to the control unit.

  A carrier pressing member 16a is provided at the peripheral edge of the upper surface of the carrier 8, and a pressing force is transmitted from the carrier pressing means 16 to the carrier 8 through the carrier pressing member 16a.

  An air outlet 19 for injecting air from the air float line 17 to the elastic sheet 11 is provided on the lower surface of the carrier 8. The air float line 17 is connected to an air supply pump 21 which is an air supply source through an air filter 20 and an automatic opening / closing valve V1. Air is blown out from the air outlet 19 by switching the automatic opening / closing valve V1.

  A hole 22 is formed in the lower surface of the carrier 8 for blowing out vacuum and, if necessary, DIW (pure water) or air. The suction of the air is performed by driving the vacuum pump 23, and an automatic opening / closing valve V2 is provided in the vacuum line 24. By switching the automatic opening / closing valve V2, vacuum and DIW are fed via the vacuum line 24. Is done.

  Air supply from the air float line 17, vacuum action from the vacuum line 24, DIW supply and the like are executed by command signals from the control unit.

  The carrier pressing means 16 is disposed at the peripheral edge of the central portion of the lower surface of the head main body 7 and applies a pressing force to the carrier pressing member 16a, thereby transmitting the pressing force to the carrier 8 coupled thereto. The carrier pressing means 16 is preferably composed of a rubber sheet airbag 25 that expands and contracts by air intake and exhaust. The air bag 25 is connected to an air supply mechanism (not shown) for supplying air.

  The retainer ring 9 is formed in a ring shape and disposed on the outer periphery of the carrier 8. The retainer ring 9 is attached to a retainer ring holder 27 provided in the polishing head 3, and the elastic sheet 11 is stretched on the inner peripheral portion thereof.

  The elastic sheet 11 is formed in a circular shape, and a plurality of holes 22 are opened. The elastic sheet 11 is stretched on the inner side of the retainer ring 9 by sandwiching the peripheral portion between the retainer ring 9 and the retainer ring holder 27.

  An air chamber 29 is formed between the carrier 8 and the elastic sheet 11 below the carrier 8 on which the elastic sheet 11 is stretched. The wafer W on which the conductive film is formed is pressed against the carrier 8 through the air chamber 29. The retainer ring holder 27 is attached to an attachment member 30 formed in a ring shape via a snap ring 31. A retainer ring pressing member 10 a is connected to the mounting member 30. The retainer ring 9 is transmitted with the pressing force from the retainer ring pressing means 10 via the retainer ring pressing member 10a.

  The retainer ring pressing means 10 is disposed on the outer peripheral portion of the lower surface of the head body 7 and applies a pressing force to the retainer ring pressing member 10 a to press the retainer ring 9 coupled thereto against the polishing pad 6. The retainer ring pressing means 10 is preferably constituted by a rubber sheet airbag 16b, similar to the carrier pressing means 16. An air supply mechanism (not shown) for supplying air is connected to the airbag 16b.

  As shown in FIGS. 3 and 4, an electrostatic for detecting the polishing end point of the conductive film on the upper part of the platen 2 or the carrier 8 of the polishing head 3 in the chemical mechanical polishing apparatus 1. A combined sensor S is incorporated. When the electrostatic coupling type sensor S is incorporated on the platen 2 side, a polishing end point detection signal from the electrostatic coupling type sensor S is output to the outside via the slip ring 32.

  FIG. 5 shows a configuration example of a capacitively coupled sensor having a basic configuration, and FIG. 6 shows an equivalent circuit thereof. The capacitive coupling sensor 33 of this configuration example mainly includes an oscillation circuit 36 including an inductor 34 and a capacitor 35, and two electrodes 37 and 37 having a phase difference caused by being connected to both ends of the inductor 34. It is configured as.

Oscillation circuit 36, the oscillation frequency band f is, as shown in the following equation (1), which is an oscillation circuit of the Colpitts like determined by the capacitance C ₀ of the inductance L and lumped capacitor of the inductor 34.

    When the electrodes 37 and 37 disposed at both ends of the inductor 34 are brought close to the conductive film 28 in parallel, the respective electrodes 37 and 37 cause electrostatic induction on the conductive film 28 side, and are distributed via the distributed capacitance 2Cm. The electrodes 37 and 37 and the conductive film 28 are electrostatically coupled.

  Here, when the film thickness of the conductive film 28 is sufficiently thick, the conductive film 28 can be considered as a conductor having almost no resistance. However, in a region where the film thickness is extremely thin, the film thickness resistance R Cannot be ignored. The equivalent circuit of FIG. 6 shows a circuit in consideration of the film thickness resistance R and the distributed capacitance 2Cm.

  When the admittance Y is obtained from this equivalent circuit, it can be written as in equation (2).

  Therefore, the susceptance B is as shown in Equation (3).

  Since the equivalent circuit of FIG. 6 can be regarded as a parallel resonance circuit, the value of ω (= 2πf) when the susceptance B = 0 is the resonance frequency. From equation (3), the film thickness resistance R is always related to the resonance condition in the form of a time constant (Cm · R) which is the product of the distributed capacitance Cm. Therefore, it can be seen that the capacitive coupling sensor 33 sees the film thickness resistance R through the distributed capacitance Cm.

  Here, the equivalent circuit of FIG. 6 is applied to a simulator, and the relationship between the film thickness and the resonance frequency when the film thickness resistance R is changed from 0 to ∞ (film thickness: thick to thin) is shown in FIG. Show. From FIG. 7, it can be seen that the resonance frequency increases as the film thickness decreases, and that the peak P can occur in the resonance frequency in the region where the film thickness resistance R is close to ∞. Also in the experimental result, the change characteristic of the resonance frequency almost the same as that in FIG. 7 is obtained.

  FIG. 8 shows another configuration example of a capacitively coupled sensor having a planar inductor. The planar inductor 39 in the electrostatic coupling sensor 38 of this configuration example has both functions of the inductor 34 in the electrostatic coupling sensor 33 shown in FIG. 5 and the electrodes 37 and 37 disposed at both ends thereof. . The planar inductor 39 is formed in a meander type on a substrate 39a made of an insulating material using a conductive material such as Cu. The planar inductor 39 may be formed in a spiral type in addition to the meander type shown in the figure.

  The oscillation circuit 40 is a Colpitts type oscillation circuit whose oscillation frequency band f is determined by the inductance of the planar inductor 39 and the lumped constant capacitance of the capacitor 41.

  When the planar inductor 39 is brought close to the conductive film in parallel, electrostatic induction is caused on the conductive film side by the phase distribution of the planar inductor 39, and the planar inductor 39 and the conductive film are efficiently connected via the distributed capacitance. Electrostatic coupling well. As a result, an equivalent circuit obtained by adding the distributed capacitance and the film thickness resistance of the conductive film to the inductance of the planar inductor 39 and the lumped constant capacitance of the capacitor 41 can be regarded as a parallel resonant circuit.

  Hereinafter, in substantially the same manner as the electrostatic coupling type sensor 33 shown in FIG. 5, the electrostatic coupling type sensor 38 responds to a change in the film thickness resistance value of the conductive film through the electrostatic coupling that is efficiently generated. Oscillating at the resonance frequency thus obtained, the change characteristic of the resonance frequency similar to that shown in FIG. 7 can be obtained with respect to the change of the film thickness of the conductive film.

8 includes an amplifier 42 composed of an operational amplifier, a feedback network 43 composed of resistors, etc., and a frequency counter 44 in addition to the planar inductor 39 and the capacitor 41. Yes. A resonance frequency signal serving as a detection signal for the polishing end point is output from the frequency counter 44.

  Next, the polishing action and the end point detection operation of the chemical mechanical polishing apparatus incorporating the end point detection apparatus using the electrostatic coupling type sensor configured as described above will be described. The electrostatic coupling type sensor used may be any of those shown in FIG. 5 or FIG. 8, but in this end point detection operation, the electrostatic coupling type sensor 38 shown in FIG. The case where 38 is incorporated in the upper part of the platen 2 will be described.

  First, the conductive film 28 waiting on the predetermined position is placed on the non-polished wafer W by a moving mechanism (not shown) of the polishing head 3. Then, the vacuum line 24 of the polishing head 3 is operated, and the air chamber 29 on the lower surface of the elastic sheet 11 is evacuated through the vacuum port 19a and the hole 22 (vacuum hole), whereby the conductive film 28 is unpolished. The wafer W is sucked and held, and the moving mechanism carries the polishing head 3 on which the conductive film 28 sucks and holds the unpolished wafer W onto the platen 2, and the conductive film 28 polishes the wafer W. It is placed on the platen 2 so as to contact the pad 6.

  When the polishing operation of the conductive film 28 on the upper portion of the wafer W is completed, the vacuum line 24 sucks and holds the wafer W by the polishing head 3 again by the operation of the vacuum line 24 and transports it to a cleaning device (not shown). Sometimes used.

  Next, the operation of the vacuum line 24 is released, and air is supplied to the airbag 25 from a pump (not shown) to inflate the airbag 25. At the same time, air is supplied to the air chamber 29 from the air outlet 19 provided in the carrier 8. Thereby, the internal pressure of the air chamber 29 becomes high.

  Due to the expansion of the air bag 25, the conductive film 28 and the retainer ring 9 on the wafer W are pressed against the polishing pad 6 with a predetermined pressure. In this state, the platen 2 is rotated in the direction of arrow A in FIG. 1 and the polishing head 3 is rotated in the direction of arrow B in FIG. Then, slurry is supplied from a nozzle (not shown) onto the rotating polishing pad 6 to polish the conductive film 28 on the wafer W.

  Then, the electrostatic coupling type sensor 38 monitors the change in film thickness accompanying the progress of polishing on the conductive film 28 on the wafer W being polished, and detects the polishing end point as follows. The monitoring of the change in film thickness of the conductive film 28 will be described with reference to FIG. The target sample is obtained by forming a conductive film 28 made of Cu on the wafer W via an insulating film and a barrier layer.

  Due to the phase distribution of the planar inductor 39 in the capacitive coupling sensor 38 incorporated in the platen 2, electrostatic induction is caused on the conductive film 28 side above the wafer W. The film 28 is efficiently electrostatically coupled. The electrostatic coupling type sensor 38 oscillates at a resonance frequency corresponding to a change in film thickness resistance value of the conductive film 28 as the polishing progresses through the efficiently generated electrostatic coupling.

  As the film thickness decreases, the film thickness resistance value of the conductive film 28 gradually increases, and the resonance frequency can gradually increase with this (part f in FIG. 7). When polishing proceeds until the conductive film 28 disappears, the film thickness resistance value of the conductive film 28 increases and the resonance frequency increases rapidly (portion u in FIG. 7), and the film thickness resistance value is close to ∞. , A peak P may occur at the resonance frequency. By capturing the peak P, which is a clear change in the resonance frequency, the polishing end point can be reliably detected when an appropriate thickness is removed by polishing.

After detecting the polishing end point, the platen 2 is rotated, for example, about 10 rotations to stop the rotation, and the polishing operation of the conductive film 28 on the wafer W is stopped. For the portion f in FIG. 7, the conductive film 28 is not required if a roughing polishing with an increased polishing rate is performed and then the polishing process is shifted to a final polishing with a reduced polishing rate. The removal operation of the part can be performed efficiently.

  An in-plane film thickness distribution feedback system that feeds back a polishing parameter such as a polishing pressure or a zone pressure in the next polishing from a polishing state of the conductive film 28 obtained by using the capacitive coupling sensor 33 or 38. Can be built.

  The state of polishing of the conductive film 28 is monitored in real time using the capacitive coupling sensor 33 or 38, and the polishing parameters such as polishing pressure or zone pressure are determined in real time from the distribution in the wafer surface of the film thickness obtained at that time. A real-time in-plane film thickness distribution control system can be constructed.

  Using the electrostatic coupling type sensor 33 or 38, the polishing state of the conductive film 28 is monitored in real time, and the polishing rate or the polishing shape is detected to construct an automatic interval system that controls the dressing and head cleaning in real time. can do.

  In addition, an extremely high performance semiconductor device can be manufactured by the end point detection device equipped with at least one of the in-plane film thickness distribution feedback system, the real-time in-plane film thickness distribution control system, and the automatic interval system. .

  As described above, in the electrostatic coupling type sensor and the end point detection method and end point detection apparatus using the same according to the present embodiment, the electrostatic coupling type sensors 33 and 38 change the film thickness resistance value of the conductive film 28. By using the resonance frequency signal corresponding to the oscillation output as an oscillation output, a sensor suitable for detecting the polishing end point of the conductive film 28 can be provided.

  The electrostatic coupling type sensor 33 having the configuration in which the electrodes 37 and 37 are respectively disposed at both ends of the inductor 34 can be reduced in cost because it is relatively inexpensive.

  The capacitive coupling sensor 38 including the planar inductor 39 generates a resonance frequency signal corresponding to a change in the film thickness resistance value of the conductive film 28 as an oscillation output through the electrostatic coupling efficiently generated by the planar inductor 39. As a result, a sensor that is extremely suitable for detecting the polishing end point of the conductive film 28 can be provided.

  The resonance frequency at which the capacitive coupling sensors 33 and 38 oscillate changes so as to increase as the film thickness of the conductive film 28 decreases, and in the region where the film thickness resistance value of the conductive film 28 is close to ∞. Since a peak can occur, the polishing end point when an appropriate thickness is removed by polishing can be reliably detected with high accuracy on the basis of the peak of the resonance frequency.

  The present invention can be variously modified without departing from the spirit of the present invention, and the present invention naturally extends to the modified ones.

FIG. 1 shows an electrostatic coupling type sensor according to an embodiment of the present invention, an end point detection method and an end point detection apparatus using the same.
The perspective view of the chemical mechanical polishing apparatus with which the end point detection apparatus using an electrostatic coupling type sensor was integrated. FIG. 2 is an enlarged longitudinal sectional view of a polishing head in the chemical mechanical polishing apparatus of FIG. 1. The schematic block diagram of FIG. 1 for demonstrating the state in which the electrostatic coupling type sensor was integrated in the platen. The schematic block diagram of FIG. 1 for demonstrating the state in which the electrostatic coupling type sensor was integrated in the grinding | polishing head. FIG. 2 is a circuit diagram of the capacitively coupled sensor of FIG. 1 having a basic configuration. FIG. 6 is a circuit diagram showing an equivalent circuit of the capacitive coupling sensor of FIG. 5. The characteristic view which shows the example of a change of the resonant frequency with respect to the film thickness of the electroconductive film by the electrostatic coupling type sensor of FIG. The block diagram which shows the other structural example of the capacitive coupling sensor of FIG. 1 provided with the planar inductor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Chemical mechanical polishing apparatus 2 Platen 3 Polishing head 4 Rotating shaft 5 Motor 6 Polishing pad 7 Head main body 8 Carrier 9 Retainer ring 10 Retainer ring pressing means 11 Elastic sheet 12 Rotating shaft 13 Dry plate 14 Pin 15 Actuation transformer 16 Carrier pressing means 17 Air Float Line 19 Air Blowout Port 20 Air Filter 21 Air Supply Pump 22 Hole 23 Vacuum Pump 24 Vacuum Line 25 Airbag 27 Retainer Ring Holder 28 Conductive Film 29 Air Chamber 30 Mounting Member 31 Snap Ring 32 Slip Ring 33 Electrostatic Coupling Type Sensor 34 Inductor 35 Capacitor 36 Oscillator circuit 37 Electrode 38 Electrostatic coupling sensor 39 Planar inductor 40 Oscillator circuit 41 Capacitor 42 Amplifier 43 Feedback network Click 44 frequency counter W wafer

Claims (5)

  An oscillation circuit composed of an inductor and a capacitor, and a plurality of electrodes having a phase difference generated by disposing them at both ends of the inductor, and by bringing the electrodes close to each other in parallel with a conductive film having a certain film thickness Static electricity is generated between the electrode and the conductive film, and oscillates at a resonance frequency corresponding to a change in film thickness resistance value of the conductive film via the electrostatic coupling. Electro-coupled sensor.   An oscillation circuit comprising a planar inductor and a capacitor is provided, the planar inductor is placed in parallel and close to a conductive film having a certain film thickness, and the phase distribution of the planar inductor causes a gap between the planar inductor and the conductive film. An electrostatic coupling type sensor that oscillates at a resonance frequency corresponding to a change in film thickness resistance value of the conductive film via the electrostatic coupling. An end point detection method for detecting an end point of polishing when an appropriate thickness is removed by polishing a conductive film,
The end point detection method using the electrostatic coupling type sensor of Claim 1 or 2.   3. An electrostatic coupling type sensor characterized in that a polishing end point is determined on the basis of a peak of a resonance frequency obtained when the polishing state of a conductive film is monitored using the electrostatic coupling type sensor according to claim 1. End point detection method using. A chemical machine that holds a wafer on which a conductive film is formed on a polishing head and polishes the conductive film by pressing the conductive film against a polishing pad provided on the surface of a rotating platen while rotating the polishing head An end point detection device that monitors the conductive film in polishing and detects a polishing end point when an appropriate thickness is removed,
3. The electrostatic coupling sensor according to claim 1 or 2 is incorporated into either the platen or the polishing head, and the polishing end point is detected from a change in oscillation frequency of the electrostatic coupling sensor. An end point detection apparatus using an electrostatic coupling type sensor.