JP2007015107A - Polishing apparatus and polishing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten polishing time by detecting vibrations at the time of polishing with high sensitivity and accurately detecting unevenness of polishing in real time, to easily check the existence of waste, to normally transmit vibrations of the surface plate on radio, and to improve detecting performance of the vibration peculiar to polishing used for obtaining a polishing state, concerning a polishing apparatus. <P>SOLUTION: A polishing apparatus comprises a first surface plate 3, a second surface plate 2, an abrasive cloth 1a, a vibration detector 10, a driving mechanism 21, a transmitting portion 13, a receiving portion 14, and a signal analyzing portion 15, a controlling portion 17, an annular transmitting antenna 25 attached around a rotating shaft of the first surface plate 3 or the second surface plate 2 and connected to the transmitting portion 13, and a receiving antenna 26 attached to an extension line of the rotating shaft and connected to the receiving portion 14. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a polishing apparatus and a polishing method, and more particularly to a polishing apparatus and a polishing method used for planarizing an insulating film, a surface of a conductive film, and the like constituting a semiconductor element.

  The degree of integration of semiconductor devices such as semiconductor memory devices is increasing year by year, and multilayer wiring of internal circuits is further advanced. In order to make the wiring multi-layered, an interlayer insulating film on the wiring is planarized by using a chemical mechanical polishing (hereinafter referred to as CMP) technique. In the CMP technique, importance is attached to detection and automation of the polishing end point from the viewpoint of time and cost.

  However, since the polishing rate cannot be kept constant due to the deterioration of the polishing cloth and the like, the end time of the polishing could not be determined accurately even if it was controlled temporally. Therefore, until now, the operation of polishing for a short time, stopping the polishing and observing the polishing state of the object to be polished has been repeated until a flat surface is obtained. Such a method is not practical because it takes time and effort.

  Until now, the end point of CMP has been detected by detecting a change in torque of a motor that rotates a surface plate (also referred to as a head) and monitoring the frictional resistance of the polishing surface based on the change. However, since this method has no high-frequency components, it only obtains a positional and temporal average of the rubbing frictional force on the polished surface, so that the sensitivity is poor and it may not be used depending on the structure of the head. For example, in an airbag system having a structure in which the head and the housing are joined by an elastic body, the influence of the friction on the polishing surface is difficult to be transmitted to the rotating shaft, and the sensitivity is significantly lowered and is not practical.

In addition, there is a method of detecting an end point by measuring a polished object with an optical film thickness meter, but it cannot be detected in real time. Further, when the silicon nitride film and the SiO ₂ film are polished at the same time, the polishing film thickness cannot be measured with an optical film thickness meter.

  In view of this, it is proposed in Japanese Patent Laid-Open Nos. 6-320416 and 6-45299 to detect the end point of polishing based on changes in the rotational torque of the motor and the vibration of the surface plate. However, in those publications, it is not whether the polished surface is simply flattened, but the polishing progresses and foreign material is exposed to the polished surface, which changes the frictional resistance of the polished surface and changes the vibration. The end point is the time.

Japanese Laid-Open Patent Publication No. 6-320416 discloses a method of measuring distortion of a surface plate due to friction between a polishing surface and a polishing cloth with a strain sensor.
JP-A-6-320416 JP-A-6-45299 JP-A-6-320416

  However, in a polishing apparatus using a strain sensor, since vibration generated by polishing is small, mechanical vibration (sound) such as motor vibration of the polishing apparatus is mixed as background noise, so that sufficient sensitivity cannot be obtained. As a result, it is difficult to accurately detect the polishing state of the entire region of the polishing surface or detect the end point, and additional polishing is required after the basic polishing is finished.

  Further, when the distortion of the head caused by the friction between the polishing surface and the polishing cloth is measured by the distortion sensor, the distortion is not so large as to appear in the distortion sensor. In addition, even if the vibration of the polishing apparatus itself is reduced by a filter, it is the actual condition that a change in unevenness on the wafer surface cannot be detected by the strain sensor. This is because strain sensors are not sensitive to high vibration frequencies.

  In the conventional polishing apparatus, there is no objective index regarding the timing of the polishing cloth and the timing of replacement, and therefore, these operations are apt to be performed unnecessarily.

  Further, even if the polished surface is damaged by dust (foreign matter) during polishing, the presence of the scratch can be found only after the polishing object is taken out and observed with a microscope after polishing. No countermeasures have been taken against the generation and mixing of dust during polishing by CMP, and the evaluation was made indirectly by observing scratches on the polished surface.

  On the other hand, since the polishing evaluation is conventionally performed after the polishing is completed, even if dust is mixed in the initial stage of one lot (usually about 25 sheets) and the surface of the workpiece starts to be damaged, I didn't notice any garbage until the end. For this reason, since an object to be polished after entering dust that damages the polishing surface is naturally damaged, an object to be polished such as a semiconductor wafer is wasted. In addition, a part of the polished surface is missing and becomes dust, which may further increase dust.

  In addition, even if dust is present during polishing, the location cannot be specified. Therefore, the entire polishing cloth may be replaced in order to remove the dust. In such a case, it takes time and effort.

  Furthermore, in the above-mentioned patent publication, it is described that a signal for detecting the vibration of the surface plate is transmitted from the surface plate to the amplifier. However, when the signal transmission is to be performed wirelessly, The wireless signal is temporarily interrupted by the shaft of the motor for rotating the motor.

  By the way, the polishing amount depends on the shape of the pattern, and varies greatly depending on the polishing conditions such as the applied pressure, the number of rotations, the polishing liquid flow rate, and the surface condition of the polishing pad. Therefore, when the polishing amount is controlled by time, trial polishing is performed once for each lot and the polishing rate is checked, but this takes time. In addition, when a plurality of types of lots having different patterns are polished, the time occupied by the trial polishing increases and the throughput decreases.

  The object of the present invention is to detect vibrations during polishing with high sensitivity and accurately detect variations in polishing, reduce the polishing time in real time, and facilitate confirmation of the presence of dust, It is an object of the present invention to provide a polishing apparatus and a polishing method capable of normally transmitting vibrations of a surface plate wirelessly and improving the detection ability of vibration inherent to polishing used for capturing a polishing state.

  As illustrated in FIG. 15, the above-described problem includes a first surface plate 3 that supports an object to be polished, a second surface plate 2 that is disposed to face the first surface plate 3, A polishing cloth 1a affixed to the second surface plate 2, a vibration detector 10 attached to the first surface plate 3 or the second surface plate 2, and at least the first surface plate 3 or the first surface plate 2. Drive mechanism 21 for driving two surface plates 2, and attached to the first surface plate 3 or the second surface plate 2 on the side where the vibration detector 10 is attached, and by the vibration detector 10 Transmitter 13 for wirelessly transmitting detected information, receiver 14 for receiving a radio signal output from transmitter 13, and signal analysis connected to receiver 14 for analyzing the received radio signal Based on the signal from the unit 15 and the signal analyzing unit 15, the polishing stop and polishing conditions A control unit 17 that outputs at least a signal for instructing the change to the drive mechanism, and a rotary shaft of the first surface plate 3 or the second surface plate 2 to which the vibration detector 10 is attached. Further, the invention is solved by a polishing apparatus comprising an annular transmitting antenna 25 connected to the transmitting unit 13 and a receiving antenna 26 attached to the extension of the rotating shaft and connected to the receiving unit 14. .

  In this case, as illustrated in FIG. 19, the logarithmic amplifier 34 c for expanding the amplitude range of the vibration signal based on the output of the vibration detector 10 </ b> A and the output side of the receiving unit 14 are connected to the output from the receiving unit. And an anti-log amplifier 35 for converting an output signal.

  In the polishing apparatus described above, as illustrated in FIGS. 39 to 47, the first surface plate 3 that supports the object to be polished and the second surface plate disposed to face the first surface plate 3. 2, a polishing cloth 1 d affixed to the second surface plate 2, driving means 8 and 21 for periodically moving the first surface plate 3 within a certain range on the polishing cloth 1 d, and the first The vibration intensity of one surface plate 3 or the driving torque value of the driving means is divided by a function including the position component of the first surface plate, and the result is output as a polishing state signal. This is solved by a polishing apparatus characterized by having polishing end point detecting means 77 for differentiating the change in time with time and detecting the end of polishing based on the differential value.

  As illustrated in FIG. 48, the above-described problems are the surface plate 3 that supports the workpiece W, the polishing cloth 1 that polishes the workpiece W, and the friction between the polishing cloth 1 and the workpiece W. And a displacement detector 61-63 for measuring a change in displacement of the first surface plate 3 dragged in the moving direction of the polishing cloth 1 or the rotating direction of the surface plate.

  In this polishing apparatus, the flattening speed of the workpiece W flattened by friction with the polishing pad 1 is made to correspond to the output signals of the displacement detectors 61 to 63, and the change in the output signal is flattened. A polishing end point discriminating means 15 for discriminating the end point of polishing within a predetermined speed range or when a predetermined value is reached is provided.

  As illustrated in FIGS. 39 to 47, the above-mentioned problem includes a first surface plate that supports the object to be polished, a second surface plate that is disposed to face the first surface plate, and the first surface plate. In a polishing method using a polishing apparatus including a polishing cloth attached to a surface plate of 2, the first surface plate is periodically moved within a certain range on the polishing cloth by a driving means, and the first surface plate is moved. The value of the vibration intensity of one surface plate or the rotational torque of the driving means is divided by a function including the position component of the first surface plate, and the result is used as a polishing state signal. The problem is solved by a polishing method comprising a step of differentiating with time and ending polishing based on the differential value.

  In the above polishing method, the function is a proportional function proportional to a distance from a rotation center of the polishing pad. In the polishing cloth, when grooves or holes are formed at substantially equal density, the function is a function proportional to the square of the distance from the rotation center of the polishing cloth. Furthermore, the function includes the number of rotations of the second surface plate.

  As illustrated in FIGS. 26 to 28, the above-described problem includes a first surface plate that supports an object to be polished, a second surface plate that is disposed to face the first surface plate, and the first surface plate. In the polishing method of polishing the object to be polished with the polishing cloth using the polishing cloth attached to the surface plate of No. 2, the vibration detector detects the polishing of the first surface plate or the second surface plate. When the vibration detector detects an abnormal vibration intensity detected by the vibration detector, and the abnormality detection time of the vibration intensity is shorter than the rotation period of the second platen, This is solved by a polishing method comprising controlling the driving of a surface plate and the second surface plate.

(Work)
According to the present invention, when the output of the vibration detector that detects vibration during polishing is transmitted to the outside wirelessly, the transmitting antenna and the receiving antenna are arranged coaxially. Stable transmission / reception is performed even if it moves.

  Further, when power is supplied to the vibration detector or the transmitter attached to the surface plate, an annular conductor is attached around the shaft that rotates the surface plate, and power is supplied through a brush that contacts the annular conductor. As a result, troubles such as battery replacement and work stoppage due to power shortage are avoided. A commercially available slip ring may be used as the annular conductor.

  Furthermore, according to the present invention, when polishing, an abnormality in vibration intensity detected by a vibration detector attached to the surface plate is detected, and the abnormality detection time of vibration intensity is shorter than the rotation period of the surface plate. Since a signal analyzing unit for outputting a signal indicating the presence of dust is provided at the top, the occurrence of scratches due to dust on the polished surface of the object to be polished thereafter is prevented.

  Further, when the vibration intensity abnormality occurs longer than the period of the surface plate, it is a cause other than a scratch. Therefore, if the polishing is immediately stopped, the abnormal operation of the polishing apparatus due to a cause other than dust can be easily detected.

  In addition, when the vibration signal detected by the vibration detector is wirelessly sent to the control unit, the amplitude range of the vibration signal is expanded wirelessly via the logarithmic amplifier, and the vibration signal is restored with the inverse logarithmic amplifier after reception. The S / N ratio is improved.

  In addition, when the vibration detector detects vibration of the workpiece support plate that changes as the polishing progresses, if the supply of energy to drive the workpiece support plate is temporarily stopped during detection, background noise may occur. Can be significantly reduced, and the S / N ratio can be improved.

  According to still another polishing apparatus of the present invention, since it has a displacement detector that detects the position of the workpiece support disk during polishing, the frictional force between the polishing cloth and the workpiece is increased as the polishing proceeds. As a result, the position of the workpiece support plate changes, and the end point of polishing can be detected by the amount of change in the displacement. In this case, since the amount of change in the position of the workpiece support plate differs from the background noise in the vibration frequency band, detection with a good S / N ratio is possible without being affected by vibrations of the motor or the like.

  In the present invention, since a technique such as increasing vibration inherent in polishing or improving the S / N ratio is adopted, it is possible to make a determination such as detection of a polishing end point of a wafer having no foreign matter for detecting the polishing end point. Becomes easier.

  Accordingly, embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a configuration diagram showing a main part of a polishing apparatus according to a first embodiment of the present invention.

  The polishing apparatus includes a disk-shaped lower surface plate 2 that is rotated by a motor M, and a disk-shaped upper surface plate 3 that supports an object to be polished W via a suction pad (not shown). In the lower surface plate 2 and the upper surface plate 3, resonance portions 2a and 3a each formed of one or a plurality of cavities are formed. On the lower surface plate 2, a polishing cloth 1 that is in contact with the workpiece W is attached.

  The polishing cloth 1 is made of, for example, urethane foam and has a two-layer structure.

  In the upper layer portion of the polishing cloth 1, first grooves 4 having a depth of about 2 mm as shown in FIGS. 2 (a) and 2 (b) are formed at a plurality of locations. The rectangular region surrounded by the first groove 4 has a width of, for example, 20 mm, and serves as an excitation unit 5 that contacts the workpiece W during polishing and induces vibration. A second groove (cavity) 6 that overlaps the excitation unit 5 is formed in the lower layer portion of the polishing pad 1, and the second groove 6 resonates with the vibration of the excitation unit 5.

  The formation region of the first groove 4 is not particularly limited, but there are, for example, those shown in FIGS. 2 (a) and 2 (b). The first groove 4 shown in FIG. 2 (a) has a rectangular plane, and a plurality of grooves are formed in the cross direction. Moreover, the 1st groove | channel 4 shown in FIG.2 (b) is formed in multiple numbers by the length and breadth linearly.

  As shown in FIG. 3, the upper surface plate 3 is supported by a housing 8 having an internal cavity via an elastic portion 7 such as rubber or a spring, and moves differently from the housing 8. . The upper part of the housing 8 is fixed to the lower end of the shaft 9 that is rotated and moved up and down by the shaft drive unit 21. The casing 8, the upper surface plate 3, and the elastic portion 7 are also called a head as a whole, and the space inside the head has an internal pressure that can press the upper surface plate 3 against the polishing pad 1.

  A vibration detection element (hereinafter also referred to as an acceleration element) 10 is attached to the upper part or side part of the upper surface plate 3, and the output end of the vibration detection element 10 is connected to a transmitter 13 attached to the housing 8. Yes. For example, a piezoelectric element acceleration sensor is used as the vibration detection element 10.

  A head having a structure in which a space surrounded by the casing 8, the upper surface plate 3, and the elastic portion 7 is maintained at a predetermined pressure is called an airbag head. In the airbag type head, when the upper surface plate 3 is displaced upward, downward pressure is applied to the upper surface plate 3 to restore the original position. On the other hand, when the upper surface plate 3 is displaced downward, the upper surface plate 3 is displaced. A pressure is applied or an upward pressure is applied back to the original or maintained. The pressure is applied from the outside through a cavity in the shaft 9.

  Further, the transmitter 13 wirelessly transmits a signal of information about the vibration frequency and vibration intensity from the vibration detection element 10 to the receiver 14 and analyzes the vibration information received by the receiver 14 by the signal analysis unit 15. A natural vibration component (for example, a vibration component peculiar to the polishing apparatus) due to a cause other than polishing is subtracted from the power spectrum of the vibration frequency and vibration intensity obtained, and the result is displayed on the display unit 16 or via the drive control unit 17. The shaft 9 and the dresser 12 are moved, driven, stopped, or the amount of polishing liquid supplied from the nozzle 11 is controlled via the drive control unit 17.

  The surface of the polishing pad 1 is sharpened by the dresser 12. The vertical movement and rotation operation of the dresser 12 are controlled by the drive control unit 17.

  The rotational speed of the motor M that rotates the lower surface plate 2 is controlled by the drive control unit 17.

  Examples of the workpiece W to be polished by the above-described polishing apparatus include a wafer such as silicon, germanium, and a compound semiconductor, and a conductive film, an insulating film, and a metal film formed on such a wafer.

  A plurality of small holes may be formed in the polishing pad 1 instead of the first and second grooves described above.

  Next, the operation of the above-described polishing apparatus will be described by taking the polishing of a semiconductor wafer as an example.

  First, after the semiconductor wafer W is pasted on the lower surface of the upper surface plate 3 as the workpiece W, the lower surface plate 2 is rotated by a signal from the drive control unit 17. Further, the shaft 9 is rotated and lowered by a signal from the drive control unit 17 to press the semiconductor wafer W against the polishing pad 1. During the polishing, a polishing liquid is supplied to the polishing pad 1 through the nozzle 11.

  When polishing is started, the semiconductor wafer W vibrates due to the friction between the semiconductor wafer W and the polishing pad 1, so that the vibration part 5 formed on the polishing pad 1 vibrates, and the vibration is caused by the second groove 6 and the lower surface plate. 2 and amplified by the resonance of the resonance portions 2 a and 3 a of the upper surface plate 3 and transmitted to the vibration detecting element 10.

  As vibration input to the vibration detection element 10, there is a vibration component from the shaft drive unit 21 that drives the shaft 9 in addition to a vibration component due to friction. The natural vibration of the shaft drive unit 21 becomes noise of the vibration detection element 10 that detects frictional vibration. However, since the vibration detection element 10 is attached to the upper surface plate 3, the natural vibration of the shaft drive unit 21 transmitted to the shaft 9 and the housing 8 is attenuated by vibration absorption of the elastic body 7. As a result, the natural vibration of the shaft drive unit 21 transmitted to the upper surface plate 3 is weakened, so that noise input to the vibration detection element 10 is reduced.

  Vibration information such as vibration frequency and vibration intensity detected by the vibration detection element 10 is displayed on the display unit 16 via the transmitter 13, the receiver 14, and the signal analysis unit 15. On the display unit 16, for example, a power spectrum of vibration as shown in FIG. 4 is displayed. This power spectrum is obtained by subtracting natural vibration components caused by causes other than polishing by the signal analysis unit 15.

  It can be seen that, in the initial stage of polishing and in a state where unevenness exists on the entire polished surface, the vibration intensity is increased over a wide vibration frequency band from low frequency to high frequency as seen in FIG. When the polishing progresses and a part of the polished surface becomes locally flat, not only the vibration intensity decreases over the entire vibration frequency but also the attenuation of the vibration intensity at a low vibration frequency of about 500 Hz becomes remarkable. Low-frequency attenuation is a unique phenomenon that occurs when a part of the polishing surface is polished flat. When the entire surface is uniformly polished, high-frequency vibration intensity around 1000 Hz is attenuated. When a part of the polishing surface is flattened, the drive control unit 17 adjusts the rotation speed of the upper surface plate 3 and the lower surface plate 2, the pressure by the upper surface plate 3, etc. Reduce.

  Since vibration does not occur when the entire surface of the polished surface is uniformly flattened, the vibration intensity becomes almost zero in the entire vibration frequency band as shown in FIG.

  Thus, not only the vibration frequency band is wide and the vibration intensity is increased and the sensitivity is improved by the vibration induction of the excitation unit 5 provided on the polishing pad 1, but also the second groove 6 and the upper surface plate of the polishing pad 1 are improved. 3 and the resonance by the resonance parts 2a and 3a of the lower surface plate 2 are amplified.

  This makes it possible to amplify and detect the presence of fine irregularities on the polished surface. Due to the change in vibration, the polishing state can be detected even with minute irregularities of 0.05 μm or less on the polished surface, the situation of polishing variation on the polished surface can be accurately grasped, and the polishing pressure can be changed in the direction in which the variation decreases. By changing the number of rotations of the upper or lower surface plates 2 and 3, it can be automatically corrected to correct the polishing variation. As a result, it is possible to grasp the polishing state with high accuracy and to easily determine the end of polishing, or to eliminate additional polishing and improve the throughput.

  When the signal analysis unit 15 integrates the spectrum of the vibration intensity with respect to the vibration frequency, the integral value gradually decreases as the polishing progresses. Therefore, when the temporal change of the integral value disappears, it is determined that the polishing is finished and the signal analysis is performed. A signal indicating completion of polishing is sent from the unit 15 to the drive control unit 17, and the drive control unit 17 stops the rotation of the shaft 9 or raises the shaft 9 to cut off the contact between the semiconductor wafer W and the polishing pad 1. Finish polishing.

  If the integral value does not become completely zero at the end of polishing, the integral value becomes a preset reference value, or the temporal change of the integral value is smaller than the preset reference value. At this point, it may be determined that the polishing is finished.

  By the way, when the polishing cloth 1 is worn in a state where the polishing is not finished, the friction between the workpiece W and the excitation unit 5 is reduced and vibration is not generated, and the vibration intensity is rapidly attenuated to be almost the same as the state after the polishing is finished. Changes to characteristics. Such steep attenuation of vibration intensity is detected by the signal analysis unit 15 via the vibration detection element 10, the transmitter 13, and the receiver 14, and the signal analysis unit 15 determines that the polishing cloth 1 has deteriorated. In this case, polishing is stopped via the drive control unit 17 and the dresser 12 is driven to make the polishing cloth 1 conspicuous. Then, after finishing the sharpening, the polishing is resumed.

  When the surface of the polishing pad 1 becomes smooth, the vibration intensity in the band of 0 to several hundred Hz of the vibration frequency exists in the magnitude of several dB. Therefore, the presence and vibration of the vibration intensity in the vibration frequency band. It may be detected that the polishing cloth is worn based on the information on the change in strength.

  The deterioration standard of the polishing cloth may be a deterioration reference when the time from the start to the end of polishing is shorter than a preset time or when the temporal change of the integral value decreases beyond a specified value.

  Next, a process of polishing an insulating film covering the wiring of the semiconductor device using the above polishing apparatus will be described.

In the case of forming a wiring of a semiconductor device, first, after forming the first insulating film W ₂ on the semiconductor substrate W ₁ as shown in FIG. 5 (a), on the first insulating film W ₂ a metal film is formed, followed by patterning the metal film as shown in FIG. 5 (b) to form a wiring pattern W _3. Then, as shown in FIG. 6 (a), forming a second insulating film W ₄ for protecting the wiring pattern W _3. Step formed with the wiring pattern W ₃ by a first insulating film W ₂ appears as an uneven surface of the second insulating film W _4. Surface of the second insulating film W ₄ is polished to the end point is detected by the polishing apparatus described above, the polishing surface thereof became flat as shown in Figure 6 (b).

When the second insulating film W ₄ is, for example, a SiO ₂ film using TEOS, the polishing rate is high, so that the CVD is performed on the second insulating film W ₄ as shown in FIG. sometimes the silicon nitride film W ₅ is formed. Irregularities appear on the surface of the silicon nitride film W _5. Surface of the second insulating film W ₄ and the silicon nitride film W ₅ is polished to the end point is detected by the polishing apparatus of the present invention, the polishing surface thereof becomes flat as shown in FIG. 7 (b). Since silicon nitride is harder than SiO _2, the polishing amount when there is a silicon nitride film W ₅ is less than the polishing amount in the absence of the silicon nitride film W _5.

When polishing only the second insulating film W ₄ is the waveform of the vibration changes, to be input to the vibration detecting element 10 in these cases, as a polishing surface thereof FIG. 8 (a) ~ (c) Fig. As shown in FIG. 10, it becomes smaller as polishing proceeds.

On the other hand, when polishing the second insulating film W ₄ and the silicon nitride film W ₅ , as shown in FIGS. 9A and 9B, the silicon nitride film W ₅ covering the whole in the initial state. It is partially lost as polishing proceeds, made from the portion that the second insulating film W ₄ is exposed. With further polishing the silicon nitride film W ₅ the first insulating film W _4, the end point of the polishing is detected when the polishing surface is flattened, the polishing is stopped. In that the polishing surface, as shown in FIG. 9 (c), to sometimes only the first insulating film W ₄ is exposed, in some cases part is left silicon nitride film W _5.

  The waveform of vibration input to the vibration detecting element 10 during the polishing is substantially as shown in FIG.

  Therefore, the above polishing apparatus does not capture the situation where the amplitude increases due to the change in film quality as described in JP-A-6-320416, and the vibration intensity increases as the flatness of the polishing surface improves. In this configuration, the phenomenon is detected, and the polishing end point is determined and the polishing is stopped when the decrease in vibration reaches a predetermined standard.

  Note that a plurality of the above-described vibration detection elements 10 may be attached to the upper surface plate 3. For example, the polishing state may be detected in more detail by separately detecting the vertical vibration and the horizontal vibration. Further, the vibration of the vibration detecting element 10 may be a horizontal vibration or a circumferential vibration instead of a vertical vibration. The circumferential vibration will be described in detail in the eighth and ninth embodiments. Alternatively, the vibration detection element 10 may be attached to the lower surface plate 3 instead of the upper surface plate 3. About the attachment location, the following embodiment is applied similarly.

(Second Embodiment)
FIG. 11 is a side view showing a second embodiment of the present invention.

  In the present embodiment, as shown in FIG. 11, a vibration detection element (acceleration element) 18 made of a piezoelectric material such as ceramic or quartz is interposed in the intermediate layer of the upper surface plate 3. As a result, it is possible to detect not only vibration perpendicular to the polishing surface of the workpiece W but also friction in the torsional direction generated along the surface of the polishing surface, that is, “shear friction force”. The shear friction force decreases sharply when a part of the polishing surface is locally flattened. Therefore, when it is desired to uniformly polish the entire surface, the polishing conditions (for example, polishing pressure and polishing speed) are set so as not to decrease rapidly. To eliminate the variation in polishing.

  The vibration detection element 18 of this embodiment is connected to the transmitter 13 as in the first embodiment. Further, the vibration detecting element 18 may be applied to a polishing apparatus in which the polishing pad 1 does not have the excitation unit 5.

(Third embodiment)
FIG. 12 is a side view showing a third embodiment of the present invention.

  In this embodiment, as shown in FIG. 12, a film-like pressure sensor 19 such as a strain gauge is interposed between the workpiece W and the upper surface plate 3. Thereby, the vibration frequency and vibration intensity in the vertical direction can be detected by detecting the change in pressure that the workpiece W receives in the direction perpendicular to the polishing surface as the change in electric resistance. As the pressure sensor 19, a type capable of detecting a pressure distribution may be used.

  The vibration detecting element 18 of this embodiment is connected to the transmitter 13 as in the first embodiment, but can also be applied to a polishing apparatus that does not have the above-described excitation unit on the polishing cloth.

(Fourth embodiment)
In the above-described embodiment, the object to be polished is attached to the upper surface plate, and the polishing cloth is attached to the lower surface plate. However, as shown in FIG. 13, the object to be polished W is attached to the lower surface plate 2, The polishing cloth 1 may be attached to the upper surface plate 3.

  Also in this embodiment, the polishing cloth 1 is provided with the excitation unit 5, and the vibration detection element 10 and the transmitter 13 are attached to the upper surface plate 3.

  In this embodiment, the polishing cloth 1 is also provided with the second groove 6 in the same manner as in the first embodiment, and the upper surface plate 3 and the lower surface plate 2 are provided with resonance portions 2a and 3a formed of cavities. May be.

(Fifth embodiment)
In the above-described embodiment, the upper surface plate is rotated by the shaft. However, as shown in FIG. 14, a so-called dead weight type polishing apparatus using the upper surface plate 20 without the rotation mechanism is used. In addition, the vibration detecting element 10 and the transmitter 13 may be mounted on the upper surface plate 20. In this case, the excitation unit 5 may be provided in the polishing cloth 1 on the lower surface plate 2, or the resonance portion including a cavity may be provided in the upper surface plate 20 and the lower surface plate 2.

  In FIG. 14, the same reference numerals as those in FIG. 1 denote the same elements.

(Sixth embodiment)
FIG. 15 is a side view of the sixth embodiment of the present invention. In this embodiment, a polishing apparatus having a structure for supplying power to a transmitter without using a battery and a structure for wirelessly connecting the transmitter and a receiver is shown. 15, the same reference numerals as those in FIG. 1 denote the same elements.

  In FIG. 15, a shaft drive unit 21 having a motor is attached on the shaft 9, and the shaft drive unit 21 is attached to the swing device 23 via an elastic body 22. The oscillating device 23 is connected to the belt 24 and is movably arranged vertically and horizontally along the upper surface of the polishing pad 1a.

  A vibration detecting element (for example, an acceleration sensor) 10 is attached to the upper surface plate 3 at a position separated from the center of the upper surface plate 3 by ¼ to ¾ of the surface plate radius. Further, at least one round of a transmitting antenna 25 connected to the transmitter 13 is formed on the outer peripheral surface of the housing 8 to which the transmitter 13 is attached. Further, at least one reception antenna 26 is formed on the outer peripheral surface of the oscillating device, and the reception antenna 26 receives the signal shown in FIG. 1 via the elastic body 22 and the signal line 27 arranged along the belt 24. Connected to the machine 14. The receiving antenna 26 is surrounded by a grounded shield wire 27a.

  On the other hand, an annular conductor 28 insulated from the surface is formed around the shaft 9, and a conductive brush 29 is in contact with the annular conductor 28, and the conductive brush 29 supplies power to the outside. Connected to the wiring. Further, an electric wire 30 is drawn out from the annular conductor 28 along the inside or outside of the shaft 9, and the electric wire 30 is connected to the power supply terminal of the transmitter 13. The electric wire 30 is covered with an insulator.

  In addition, when the elastic part 7 for supporting the upper surface plate 3 to the housing 8 is an insulator, the upper surface plate 3 is used to secure a ground potential between the upper surface plate 3 and the transmitter 13. Must be formed of a conductor, or metal should be vapor-deposited on the surface of the upper surface plate 3 and connected to the ground wire. As a result, only one electric wire 30 is required in the length direction of the shaft 9 which is the ground potential.

  According to such a polishing apparatus, even when the upper surface plate 3 is rotated by the shaft 9, the signal output from the transmitter 13 is transmitted wirelessly through the substantially annular transmitting antenna 25 around the upper surface plate 3. The Since the radio signal is input to the receiver 14 shown in FIG. 1 via the substantially annular receiving antenna 26 around the shaft driving unit 21, the radio signal is not disturbed by the shaft 9. In this case, even if the oscillating device 23 is oscillated, the transmitting antenna 25 and the receiving antenna 26 are simultaneously oscillated, and the transmitting antenna 25 is rotated. Note that the receiving antenna 26 does not rotate.

  The transmission antenna 25 and the reception antenna 26 can be transmitted and received if one of them is arranged in a substantially annular shape around the shaft 9. However, in order to avoid the instability of the transmission / reception state due to the swing of the shaft 9, it is possible to arrange both the transmitting antenna 25 and the receiving antenna 26 in a ring and arrange them coaxially as described above. preferable.

  On the other hand, since the power consumed by the transmitter 13 is supplied through the electric wire 30 arranged along the shaft 9, it is unnecessary to replace the battery for supplying power to the transmitter 13. Throughput can be improved by avoiding interruption of polishing due to shortage.

  Note that the polishing pad 1a may be one in which an excitation unit is formed as in the first embodiment. Moreover, you may employ | adopt the structure shown in 1st implementation except an electric power supply system and a signal transmission system.

(Seventh embodiment)
Since it is necessary to construct a management system when a plurality of polishing apparatuses shown in the first embodiment and the sixth embodiment are used and a plurality of objects to be polished are polished in parallel, the embodiment is shown in FIG. Based on

In FIG. 16, the above-described transmitters 13 for transmitting signals f _{1 to} fn having different frequencies are attached to a plurality of polishing apparatuses m _{1 to mn} having the above-described structure. The detection element 10 is connected. Moreover, those transmitters 13 are configured to transmit only a specific vibration frequency band using a filter.

  The signal output from each transmitter 13 is propagated wirelessly via the transmitting antenna 25 and the receiving antenna 26.

Signals f _{1 to} fn having different frequencies input to the receiving antenna 26 above the transmitting antenna 25 are input to the receiver 32 via the synthesizer 31. Each time the signal analyzer 33 requests a certain amount of received data, the receiver 32 tunes the signals f _{1 to} fn of the plurality of transmitters 13 in order in a time division manner, and transmits the tuned signals to the signal analyzer 33. In addition, it has an auto-tuning (automatic frequency control) mechanism. Since the auto-tuning mechanism is a mechanism that automatically keeps the fluctuation of the frequency of the signal to be tuned within the reference frequency range, even if the frequency of each of the signals f _{1 to} f n is slightly shifted due to a temperature change or the like, reception is impossible. Inconvenience is avoided. For this reason, even if the transmission frequency of the transmitter 13 fluctuates due to a temperature change or the like, it is always received in the best reception state.

Further, since the receiver 32 transmits the signals f _{1 to} f n having the same or closest frequency as the tuned signal to the signal analysis unit 33, the signal processing in the signal analysis unit 33 is normally performed.

The signal analysis unit 33 controls the drive control unit 17 of each of the polishing apparatuses m _{1 to mn} based on the information of the time-divided signals f _{1 to} f _n to drive, stop, adjust the pressure of the surface plate, or the surface plate. The number of rotations is adjusted, or the dresser is driven and stopped.

  The tuning is performed in the order of frequency and this is repeated many times.

  As described above, a plurality of polishing apparatuses can be managed efficiently and optimally.

(Eighth embodiment)
In this embodiment, a polishing apparatus that controls polishing by vibration in the circumferential direction (or rotation direction) of the polishing surface will be described. FIG. 17 is a side view of the polishing apparatus showing the eighth embodiment, and FIG. 18 is a bottom view of the head. In FIG. 17, the same reference numerals as those in FIGS. 1 and 15 denote the same elements, and the portions not shown have the same mechanism as in any of FIGS.

  In the present embodiment, the elastic body 7 that connects the airbag-type casing 8 and the upper surface plate 3 is not particularly limited in material. However, a multilayer structure rubber sheet sandwiching a cloth may be used, or the rubber may be used. If a plurality of sheets are used, a sheet having a high mechanical strength can be obtained.

  A vibration detecting element 10A is mounted on the upper surface plate 3, and is directed to detect minute vibrations in the circumferential direction of the upper surface plate 3 as shown in FIG. The vibration detection element 10A has a structure in which the direction of vibration to be detected can be selected by changing its direction. The vibration detection element 10 in the first to seventh embodiments described above is arranged in a direction to detect vertical vibration.

  The vibration detection element 10 is connected to the transmitter 13A on the housing 8 via a signal line. The signal output end of the transmitter 13A is connected to the annular transmitting antenna 25 on the outer peripheral surface of the housing 8, and the power supply end of the transmitter 13A is connected to the annular conductor 28 shown in FIG. The mechanism on the side that receives the radio signal output from the transmitting antenna 25 is configured to include the annular receiving antenna 26 shown in FIG.

  Note that reference numeral 34 in FIG. 17 indicates a circuit in which a first amplifier 34a, a filter 34b, and a second amplifier 34c described later are integrated.

  The circuit of the transmission system and the reception system is as shown in FIG.

  The vibration detection element 10A is connected to the transmitter 13A via a first amplifier 34a, a filter 34b, and a second amplifier 34c. The vibration detection element 10A has a sensitivity equivalent to 50 mV / G (about 50 μV / gal) or more and a noise level equivalent to 1 mG (about 1 gal) or less, and an acceleration sensor is used as the vibration detection element 10A. The resonance frequency is 20 kHz or more, or has a resonance at a frequency at which the vibration intensity changes with the progress of polishing.

  The first amplifier 34a has an amplification factor of 500, the filter has a band pass of 10 Hz to 30 KHz, and the second amplifier 34c has an amplification factor of 1/50. For example, an FM transmitter is used as the transmitter 13A.

  Commercially available operational amplifiers can be applied to the amplifiers 34a and 34c, respectively. The filter 34b is a combination of a plurality of band pass filters having different center frequencies such as a graphic equalizer so that it can immediately respond to changes in the polishing conditions, the object to be polished, and changes in the vibration mode due to modification of the polishing apparatus. Alternatively, the transmittance of each vibration frequency band may be changed by using a programmable bandpass filter. An example of the characteristics of a filter using a graphic equalizer is shown in FIG. Each band-pass filter preferably uses an attenuation factor of 34 dB / oct or more and a bandwidth equal to or less than the center frequency or about 1 kHz.

  On the other hand, in the receiving system, the receiver 14 connected to the receiving antenna 26 has a processing unit 35 having the signal analysis unit 15 and the drive control unit 17 shown in FIG. 1, and the processing unit 35 is an FFT analyzer or a CPU board. Or it is comprised by what is called a personal computer. The processing unit 35 obtains a spectrum of vibration frequency from about 10 Hz to about 30 kHz, for example.

  The above is a description of the structure for measuring the vibration inherent to polishing. Actually, however, vibrations such as a motor for rotating the lower surface plate 2 and the upper surface plate 3 are input to the vibration detecting element 10A. . Therefore, it is preferable to have a structure in which the vibration of the upper surface plate 3 caused by the vibration of the polishing apparatus itself is 50 mG (about 50 gal) or less. What is necessary is just to measure the grinding | polishing vibration which acts on the upper surface plate 3 when using a flat wafer as the to-be-polished object W as a method of judging whether it is 50 mG or less.

  Next, detection of the polishing end point using the polishing apparatus having the above-described structure will be described.

  First, the lower surface plate 2 and the upper surface plate 3 are rotated, and the workpiece W pasted under the lower surface plate 2 is pressed against the polishing cloth 1 on the lower surface plate 2 to be polished. Start polishing. The polishing cloth 1 has a lattice-like groove 4 and a vibrating part 5 as described in the first embodiment.

  When the relationship between the frequency of vibration of 0 to 25 kHz in the circumferential direction of the upper surface plate 3 and the intensity of the vibration is changed depending on the polishing time, the result shown in FIG. 21 is obtained and the polishing proceeds. It can be seen that the vibration intensity decreases over the entire vibration frequency band.

  Accordingly, the vibration signal detected by the vibration detection element 10A is input to the processing unit 35 via the transmitter 13A, the receiver 14, and the like. The processing unit 35 compares the reference spectrum, which is a reference value, with the vibration signal being measured. For example, the ratio between the integrated value of the vibration intensity and the integrated value of the reference spectrum in a specific frequency range is equal to or less than a predetermined threshold value. Or when the amount of time change of the integrated value of the vibration intensity in a specific frequency range is equal to or less than a predetermined threshold value, it is determined that the polishing is finished.

  The detection accuracy of the vibration signal greatly affects the performance of the wireless transmitter 13A. The characteristics required for the first and second amplifiers 34a and 34c and the filter 34b and the vibration signal to be transmitted are determined according to the following procedure.

  First, the vibration strength of the upper surface plate 3 is measured by wire. Next, the amplification factor of the first amplifier 34a is determined so that the voltage obtained by amplifying the vibration intensity signal does not exceed the allowable input voltage of the filter 34b. Further, the amplification factor of the second amplifier 34c is determined so that the voltage obtained by amplifying the vibration intensity signal that has passed through the filter 34b does not exceed the allowable input voltage of the transmitter 13A.

  When determining the transmission frequency band of the vibration intensity frequency of the filter 34b, first, wireless transmission is performed while actually polishing, and the vibration frequency at which the vibration intensity does not change even when polishing progresses is determined. A transmission frequency band that does not allow transmission is determined. A vibration component whose vibration intensity does not change even when polishing progresses is vibration noise caused by the polishing apparatus itself.

  The deterioration of the polishing cloth 1 and the change in the concentration of the polishing liquid can be known by comparing the spectrum measured in advance and the shape of the actually measured spectrum. When these pieces of information are unnecessary and it is desired to know only the polishing end point, the vibration intensity signal in a specific frequency region is converted into a DC signal corresponding to the effective value before the transmitter 13A, and this is converted into the transmitter 13A. To the receiver 14.

  In order to expand the amplitude range when the vibration signal is wirelessly transmitted, the vibration signal is amplified by the logarithmic amplifier 34c, then wirelessly transmitted by the transmitter 13A, and the wireless signal is received by the receiver 14 and then received. The original signal may be reproduced with an antilogarithmic amplifier in the processing unit 35.

  In the present embodiment, the power is supplied to the oscillator 13A using the annular conductor 28 as shown in FIG. 15, but a battery may be used. Further, the transmitter 13A may transmit to the receiver 14 by wire using a signal annular conductor having the same structure as the annular conductor 28 used for power supply, instead of wireless. Furthermore, although the transmitter 13A is attached to the outside of the housing 8, it may be attached to the inside of the cavity in the housing 8 like the vibration detecting element 10.

  In FIG. 17, one upper surface plate 3 is arranged on one lower surface plate 2, but a plurality of upper surface plates are arranged on one lower surface plate 2, or When a polishing apparatus having a plurality of sets of the lower surface plate 2 and the upper surface plate 3 is used, the above-described configuration is provided for each head to control the polishing independently for each head. To.

  The amplifier and filter described in the present embodiment may be applied to the polishing apparatus of the first to seventh embodiments.

(Ninth embodiment)
In the above-described eighth embodiment, the case where one vibration detection element 10A is attached has been described. However, a weight having the same weight as the vibration detection element 10A or the second vibration detection element is placed on the upper surface plate 3 as a vibration detection element. When mounted so as to be symmetric with respect to 10A, the balance of the rotating upper surface plate 3 is improved, and vibration during rotation is stabilized.

  FIG. 22 shows an apparatus to which the second vibration detection element is attached. In this configuration, vibration noise of the two vibration detection elements 10A and 10B can be reduced by adopting a circuit configuration as shown below.

  The vibration noise is due to a vibration component perpendicular to the measurement direction. The vibration detection elements 10A and 10B generally have a sensitivity of several percent for vibration components that are perpendicular to the measurement direction. In the present embodiment, the vibration component in the perpendicular direction is vertical vibration.

  In FIG. 22, the two vertical vibration noises input to the two vibration detection elements 10A and 10B are in the opposite directions as shown in FIGS. 23 (a) and 23 (b), and in FIG. As shown in (b), the direction may be the same.

  When vertical vibration noise occurs in the reverse direction as shown in FIG. 23, as shown in FIG. 25A, the outputs of the first amplifiers 34d and 34e connected to the output terminals of the vibration detection elements 10A and 10B. The adder 36 is connected to the end, and the output end of the adder 36 is connected to the filter 34b. In this case, as shown by solid arrows in FIG. 22A, the two vibration detection elements 10A and 10B are arranged so as to detect the rotational vibration of the upper surface plate 3 in the same circumferential direction.

  By arranging the vibration detection elements 10A and 10B in this manner and inserting the addition circuit 36 on the output side of the first amplifiers 34d and 34e, the vibration noise in the vertical direction can be canceled and reduced, and the filter Since the circumferential vibration intensity input to 34b is doubled, the S / N ratio is improved.

  On the other hand, when vertical vibration noise in the same direction as shown in FIGS. 24A and 24B occurs, as shown in FIG. 25B, at the output ends of the vibration detection elements 10A and 10B. A subtractor 38 is connected to the output terminals of the connected first amplifiers 34d and 34e, and the output terminal of the subtractor 38 is connected to the filter 34b. In this case, as shown by the dashed arrows in FIG. 22 (a), the two vibration detecting elements 10A and 10B are arranged so as to detect the rotational vibration of the upper surface plate 3 in the opposite direction.

  By arranging the vibration detection elements 10A and 10B in this way and inserting the subtractor 38 on the output side of the first amplifiers 24d and 34e, the vibration noise in the reverse direction can be added to reduce the vibration noise. Moreover, since the absolute value of the circumferential vibration intensity detected in the reverse direction is doubled by the subtractor 38, the circumferential vibration intensity input to the filter 34b is doubled, and the S / N ratio is increased. Is improved.

  Whether the upper surface plate 3 exhibits longitudinal vibration as shown in FIGS. 23A and 23B or longitudinal vibration as shown in FIGS. 24A and 24B depends on the polishing apparatus and the polishing conditions. so different, it is necessary to investigate whether to take either of the longitudinal vibration in advance. For such vertical vibration, it is sufficient to change the mounting direction of the two vibration detection elements 10A and 10B, or to replace the signal adder and subtractor to select a configuration with the least noise.

  In this embodiment, the vibration component in the circumferential direction is set as the detection target and the vibration component in the vertical direction is excluded. However, when the vibration component in the vertical direction is set as the detection target, the vibration component in the circumferential direction is set. In this case, it is necessary to adjust the directions of the two vibration detection elements.

(10th Embodiment)
FIG. 26 is a side view showing the tenth embodiment of the present invention.

  This embodiment prevents the polishing surface from being damaged by dust during polishing and facilitates removal of dust. Examples of dust that damages the polished surface include silicon oxide contained in the polishing liquid that has been dried and solidified, and fragments of the object to be polished.

  In FIG. 26, a deadweight type upper surface plate 41 is used, and an acceleration detection element (vibration detection element) 42 is attached to the surface thereof. Further, for example, a semiconductor wafer is attached as an object to be polished W under the upper surface plate 41 and placed on a polishing cloth 44 attached to the lower surface plate 43.

  Further, a marker 45 having a high light reflectance is attached to the side of the lower surface plate 43, and whether or not the marker is in a predetermined position is detected by a marker position detector 46 on the side of the lower surface plate 43. The The marker detector 46 has a light emitting element and a light receiving element, and the amount of light received increases due to the reflected light from the marker 45, so the presence or absence of the marker 45 is detected.

  A signal from the acceleration sensor 42 of the upper surface plate 41 is input to the signal analysis unit 15 via the transmitter 13 and the receiver 14 described in the first embodiment.

  In the above polishing apparatus, the lower surface plate 43 is rotated to polish the workpiece W with the polishing cloth 44. In this case, the workpiece W is moved in a certain direction by an arm (not shown). The vibration information of the upper surface plate 41 detected by the acceleration sensor 42 during one rotation of the marker 45 is transmitted to the signal processing analysis unit 15 at least once via the transmitter 13 and the receiver 14 shown in FIG. Enter continuously.

  In the case of normal polishing, a spectrum of vibration frequency and vibration intensity as shown in FIG. 27A is obtained. However, if the polishing surface of the workpiece W is damaged by dust on the polishing pad 44, FIG. As shown in b), the vibration intensity increases at some frequencies. The spectrum that is a criterion for determination of increase may be examined in advance, or a spectrum before being damaged may be used.

  When the presence of dust is clarified due to such an abnormality in vibration intensity, the drive control unit 17 drives the dresser 12 while supplying water to the polishing pad 44 through the nozzle 11, and starts from the surface of the polishing pad 44. After discharging the dust to the outside of the lower surface plate 43, control is performed such that polishing is resumed again.

  By the way, when it is desired to specify the position of dust, the following processing is performed.

  When polishing, if the vibration information of the upper surface plate 41 is continuously input to the signal analysis unit 15, the marker detector 46 can detect when the marker 43 is detected, and this is recorded as the marker position on the time axis. When an abnormal signal is recorded at the same time, for example, characteristics as shown in FIG. 28 are obtained. Since the marker position appears at a constant cycle, when a scratch due to dust occurs on the polished surface, the time of occurrence of the abnormal signal is recorded on the time axis. Accordingly, the angle θ at which dust is generated is easily determined based on the line connecting the marker 45 to the center of the polishing pad 44 from the ratio of the time interval between the marker passage and the time from the marker passage time to the occurrence of the abnormal signal. I want to.

  Therefore, if the signal analysis unit 15 sends a drive signal to the drive control unit 17 to drive the dresser 122 and drive the dresser 12 on the surface of the polishing pad 44 at least along the normal line of the angle θ, dust is removed. It takes a short time.

  If an abnormal signal is generated at the same position after the dresser, or an abnormal signal is generated at the same position even after the workpiece W is replaced, polishing is immediately stopped and an abnormal signal is generated. The worker is informed and the worker removes the cause of the abnormal signal. Thereby, since the polishing of the next workpiece W can be started in a normal state, the number of the workpieces W, for example, semiconductor wafers that are wasted is reduced, and the polishing efficiency is improved.

  By the way, as shown in FIG. 28, if the abnormal signal stops within one period of the marker, it can be understood that the abnormal signal is caused by dust. However, if it continues for more than one cycle, there is a high possibility of occurrence of an abnormal signal due to a cause other than dust. In this case, the polishing is completely stopped by the signal analysis unit, and an abnormal signal sound is output simultaneously with the stop command. It is necessary to inform the worker so that the

(Eleventh embodiment)
In the present embodiment, an apparatus for improving the S / N ratio of the output of the vibration detection element and the S / N ratio of the vibration input to the vibration detection element will be described with reference to FIGS. Vibration noise input to the vibration detection element is vibration other than vibration caused by friction between the workpiece W and the polishing pad 1 and is mainly generated from the motor. Such noise is hereinafter referred to as background noise.

  29 to 35, the vibration detection element 10 is placed at the center of the upper surface of the upper surface plate (the bottom plate of the head) 3 because the relative speed between the vibration detection object W and the polishing pad 1 is stably detected. This is because the error becomes smaller. The basic structure of the present embodiment is the same as that of the first or seventh embodiment, and the same reference numerals as those of the embodiments indicate the same elements.

  FIG. 29 employs a structure in which the vibration detecting element 10 is surrounded by a soundproof / sound absorbing material 50 through a gap in a cavity in the casing 8 of the head. The soundproofing / sound absorbing material 50 is made of an elastic material such as an accordion spring, rubber, or a porous resin that allows the upper surface plate 3 to freely vibrate.

  By adopting such a configuration, it is possible to improve the S / N ratio input to the vibration detection element 10 by preventing and absorbing background noise transmitted through the space in the housing 8. In addition, since a gap is formed between the soundproofing / sound absorbing material 50 and the vibration detecting element 10, new noise due to friction between the soundproofing / sound absorbing material 50 and the vibration detecting element 10 does not occur.

  If the natural vibration frequency of the upper surface plate 3 and the vibration frequency of the background noise are not matched, the S / N ratio is further improved.

  Note that reference numeral 51 in FIG. 29 denotes an inner sheet interposed between the upper surface plate 3 and the workpiece W in order to absorb the thickness variation of the workpiece W.

  FIG. 30 shows a device in which a resonance plate 52 is interposed between the vibration detecting element 10 and the upper surface plate 3 shown in FIG. The resonance plate 52 resonates at a specific vibration frequency to be measured, and is formed of, for example, a spring coil.

  According to this, background noise having a frequency different from the resonance frequency of the resonance plate 52 is shielded by the resonance plate 52 and is prevented from being input to the vibration detection element 10. The N ratio is improved.

  FIG. 31 shows an apparatus in which an amplifier 53 is attached to the side of the resonator 10 shown in FIG.

  When the impedance of the vibration detection element 10 itself is high, if the connection wiring to the amplifier 53 is long, noise easily enters the output signal of the vibration detection element 10, but the resonator 10 and the amplifier 53 are mounted on the upper surface plate 3. As a result, the connection wiring can be shortened to significantly reduce the noise applied to the vibration signal, thereby improving the S / N ratio.

  In the head of the polishing apparatus shown in FIG. 32, a hole 54 is formed in both the upper surface plate 3 and the inner sheet 51, and the vibration detecting element 10 and the object W to be detected are formed in the hole 54. A vibration transmitting needle 55 that is in contact with is inserted. The vibration generated in the detected object W due to the friction with the polishing pad 1 is transmitted to the vibration detecting element 10 through the vibration transmitting needle 55 without being absorbed by the inner sheet 51, and is input to the vibration detecting element 10. The vibration intensity is increased and the S / N ratio is improved.

  33, a diaphragm 56 is interposed between the vibration detecting element 10 shown in FIG. 29 and the upper surface plate 3, and a second vibration detecting element 57 for background measurement is mounted on the housing 8. Device. The background noise signal output from the second vibration detection element 57 is converted to an opposite phase by the vibration control unit 58, and then the vibration control unit 58 causes the diaphragm 56 to have the same waveform as that of the opposite phase signal. It is a device designed to vibrate. The diaphragm 56 is made of, for example, a piezoelectric material such as a piezo element.

  According to this apparatus, the vibration generated by the diaphragm 56 cancels the background noise input to the vibration detection element 10, so that the vibration generated by the polishing cloth 1 and the workpiece W is selectively applied to the vibration detection element 10. It becomes possible to input, and the S / N ratio is greatly improved.

Incidentally, the resonance frequency f ₀ of the vibration detecting element 10 is 5-10 times more sensitive than the other frequencies. However, the frequency f _{1 of} the vibration to be detected may not match the resonance frequency f ₀ . In this case, as shown in FIG. 34, the vibration of the detected frequency f ₁ is input to the frequency conversion circuit 59, and the vibration is performed with the same intensity as or proportional to the vibration frequency f ₁ detected by the frequency conversion circuit 59. By oscillating the plate 56 at the frequency f ₀ and feeding back the vibration at the frequency f ₀ to the vibration detecting element 10, highly sensitive vibration detection becomes possible. In this case, the processing as shown in the first or sixth embodiment is performed for the vibration having the frequency f ₀ .

  35, a plurality of vibration detection elements 10 shown in FIG. 29 are arranged on the upper surface plate 3, and a diaphragm 52 is individually interposed between the vibration detection elements 10 and the upper surface plate 3. In FIG. Device. Then, by applying a certain signal to each diaphragm 52, the vibration detection element 10 having the highest sensitivity for the frequency of vibration to be detected is selected by a selection circuit (not shown). Like to do.

  This avoids variations in the characteristics of the vibration detection element 10 and allows the vibration detection element 10 to be selected by another electric circuit instead of the deteriorated vibration detection element 10, thereby reducing the labor of replacing the vibration detection element 10. Can do.

  As a method other than the above for improving the S / N ratio, the power supply to a part or all of the motors of the polishing apparatus may be stopped at the time of vibration detection, which greatly reduces the background noise. The stop time is set to several seconds or less, and if it is about this time, the polishing process is continued because the head and the lower surface plate 2 rotate due to inertia. In addition, a time of several seconds or less is sufficient for vibration detection, and there is no problem in vibration detection. The power supply to the motor is stopped by a control signal from the drive control unit 17 as shown in FIG.

  Further, the output of the vibration detecting element 10 is taken out through the amplifier and filter as shown in the eighth embodiment, or is taken out after A / D conversion, thereby reducing noise generated in the signal transmission system. can do. When wirelessly transmitting an A / D converted signal, an A / D converter (not shown) is interposed between the oscillator 13A and the vibration detection element 10A shown in FIG.

  Further, when the head is oscillating, the background noise due to the oscillation becomes large at a place where the direction of the head changes, so that detection of vibration is avoided.

As an example of each vibration detection element, there are piezoelectric element acceleration sensor model names CE507M101 and CE507M301 of US Vibrometer, and when these sensors are used, as shown in FIG. 36, a resonance with high sensitivity can be obtained. preferably, detecting the vibration intensity at the frequency f _0. This can also be applied to the above-described embodiments.

  Next, the measurement results are shown in FIGS.

  FIG. 37 is an example showing how the frequency spectrum of vibration changes over time. According to this, it can be seen that the vibration intensity decreases with the lapse of the polishing time.

  FIG. 38 shows a spectrum as shown in FIG. 37, in which a spectrum in a specific frequency range is integrated, and a difference between integrated values for every lapse of a fixed time is calculated. According to this, it can be seen that as the polishing time elapses, the amount of change in the integrated value decreases and the flattening by polishing proceeds. The end point of polishing is when the change of the integrated value is lost. This determination of the end point can also be applied to the above-described embodiments.

(Twelfth embodiment)
FIG. 39 (a) is a cross-sectional view showing a mechanical part of a polishing apparatus according to a twelfth embodiment of the present invention, and FIG. 39 (b) is a plan view showing a lower surface plate. FIG. 40 is a circuit diagram showing a signal processing portion of the polishing apparatus according to the twelfth embodiment of the present invention. In these drawings, the same reference numerals as those in FIGS. 1 and 15 denote the same elements.

  In FIG. 39 (a), a position detector 61 for detecting the position of the upper surface plate 3 is arranged on the side of the shaft drive unit 21. The position detector 61 includes a light emitting element 61 a that irradiates light to the detection plate 62 attached to the shaft driving unit 21 and a light receiving element 61 b that receives reflected light from the detection plate 62. The position detector 61 measures the distance L from the shaft drive unit 21 in accordance with the amount of incident light of the light receiving element 61b, and inputs the measurement data to a computer 77 described later. For example, a semiconductor laser is used as the light emitting element 61a, and a photodiode is used as the light receiving element 61b.

  A polishing cloth 1 d having a plurality of grooves 4 a cut vertically and horizontally is attached to the lower surface plate 2, and the polishing cloth 1 d is rotated together with the lower surface plate 2 by the motor M during polishing. On the polishing cloth 1d, during polishing, the upper surface plate 3 reciprocates between points a and b, and the upper surface plate 3 rotates at a constant speed. The reciprocation and rotation of the upper surface plate 3 are transmitted from the shaft driving unit 21 via the elastic body 7, the housing 8, and the shaft 9. The operation of the shaft drive unit 21 is controlled by the drive control unit 17 in the same manner as in the first embodiment.

  As shown in FIG. 40, a voltage is applied to the output end of the vibration detecting element 10 attached to the upper surface plate 3 via a rectifier 63, and further, via a capacitor 64, an amplifier 65, a low pass filter 66 and a high pass filter 67. Connected to the FM transmitter 34B. The vibration signal output from the vibration detection element 10 is mechanically and electrically noise-removed by a capacitor 64, amplified by an amplifier 65, narrowed to a specific frequency band by a low-pass filter 66 and a high-pass filter 67, and FM. Input to the transmitter 34B. The specific frequency band is, for example, 8 kHz to 18 kHz when the low-pass filter 66 removes vibration signals of 18 kHz or more and the high-pass filter 67 removes vibration signals of 8 kHz or less.

  The FM transmitter 34 </ b> B transmits the vibration signal from the transmitting antenna 25 around the housing 8 to the FM receiver 69 wirelessly.

  The vibration signal input to the receiving antenna 26 attached around the shaft drive unit 21 is received by the FM receiver 69 as shown in FIG.

  A recording device 70 is connected to the output end of the FM receiver 69, and the vibration signal data stored in the recording device 70 is used for creation of a data library, frequency analysis, adjustment of a processing circuit, and the like. The output terminal of the FM receiver 69 is connected to a computer 77 via a 1 kHz high pass filter 71, a first amplifier 72, a rectifier circuit 73, a 0.5 Hz low pass filter 74, a second amplifier 75, and an A / D converter 76. It is connected to the. The high-pass filter 71 cuts the direct current component of the vibration signal, and the rectifier circuit 73 and the low-pass filter 74 integrate the specific frequency band of the vibration signal to obtain the effective value of the frequency.

  In the computer 77 described above, the vibration signal is calculated and displayed according to the flowchart of FIG.

  First, a case where the polishing object W is polished only by the rotation of the upper surface plate 3 without moving the rotation center of the upper surface plate 3 on the polishing cloth surface will be described.

In the computer 77, and sequentially samples the effective value of the vibration signal to be input consecutively at the rate of 10 per second (10 Hz), then calculates the 10 average values of the data D ₁ sampled, the average value It is referred to as a point data _{D 2.}

Then, the point so bumpy line is obtained when it is time to image display data D _2, the mean displays the calculated point value data D ₃ of the five points data D ₂ to smoothly display the line Get. In this case, when to obtain the average of 5 points data D ₂ while advancing one at point data D ₂ to the calculated forward, the point display data D ₃ becomes one obtained that in one second. Such an average is called a moving average.

  The point display data obtained by the moving average is sequentially drawn on the image display unit 77D of the computer, and a vibration intensity curve is obtained by drawing a plurality of point display data.

Incidentally, the sampled data D _1, as deduced from the embodiment described above, so that we gently attenuated as it travels to the polishing in the case of only the upper surface plate 3 simply rotates.

However, the operation is the upper surface plate 3 other than rotation, for example in the case with a reciprocating motion on the polishing cloth 1d is the point display data D ₃ is to include an AC component as shown by a chain line in FIG. 42 (a) Therefore, it becomes difficult to detect the end point of polishing. For example, if the curve of the alternate long and short dash line in FIG. 42 (a) is differentiated into a curve like the alternate long and short dash line in FIG. 42 (b), the time when the differential value becomes zero cannot be determined as the polishing end point. .

Therefore, when the upper surface plate 3 reciprocates between the points a · point b on the polishing cloth 1d performs correction dividing the data D ₁ of the effective value sampled at 10Hz with η respectively correction factor, then When the point data D ₂ and the point display data D ₃ are obtained and then the point display data D ₃ is displayed on the image display unit 77D, a curve indicated by a solid line in FIG. 42 (a) is obtained. A curve indicating the derivative of the curve is obtained by a solid line in FIG. Usually, since the period of the reciprocating operation is a higher order of several tens of seconds, it may be divided by the correction function for the point data D _2.

When the rotating upper surface plate 3 reciprocates between two points a and b in the diameter direction from the rotation center O ₀ of the lower surface plate 2, as shown in FIG. 39 (b). the temporal variation of the distance r becomes as shown in FIG. 43 (a), the correction coefficient η becomes r ² / r ₁ ² as shown in FIG. 43 (b). For example, when the distance between the points a and b is 32 mm and the moving speed v of the upper surface plate 3 is 2 mm / second, the period T of the waveform in FIG. 43B is 32 seconds. _{R 1} in this case is 134mm.

  Such a correction coefficient η is determined as follows.

  Considering that the minute portion P of the polishing surface of the object to be polished W at the distance r from the rotation center of the polishing pad 1d is rubbed by the polishing cloth 1d rotating at the angular velocity ω, the relative relationship between the minute portion P and the polishing pad 1d. The speed is a function of rω. This distance r is obtained based on position data from the position detector 61. The minute portion P is the center of rotation of the upper surface plate 3.

  Further, as shown in FIGS. 44 (a) and 44 (b), the surface of the polishing pad 1d has a groove 4e or a small hole 4f formed at a constant density. The number of times p of contact of the minute portion P with the groove 4e or the small hole 4f during one rotation is a function of rω. In addition, as shown in FIGS. 44 (c) and 44 (d), when the groove 4g or the small hole 4h extends radially from the center of rotation of the polishing pad 1d, a minute amount of the polishing pad 1d rotates once. The contact frequency p at which the portion P contacts the groove 4G or the small hole 4H is a function of ω. In addition, when using the polishing cloth in which the groove | channel and the small hole are not formed, it becomes unnecessary to consider the influence by the groove | channel and small hole of the micro part P. FIG.

  Therefore, the product of the above-described relative speed rω and the number of times of contact p is defined as a correction function η. The basis of the correction function η is as shown in Table 1.

It should be noted that factors such as the type of polishing liquid and the material of the polishing cloth are considered to hardly change during polishing, and therefore are not included in the correction coefficient η. In addition, when the upper surface plate 3 is not accompanied by an operation other than rotation, r is constant, so r is set to 1, and the rotation number of the upper surface plate 3 is generally not changed during polishing. The correction function η may be determined with ω = 1. Further, the correction function η may include a coefficient. For example, as shown in FIGS. 39B and 43B, the distance r may be divided by the distance r ₁ (constant).

As described above, the corrected sampled data Ds, as shown in FIG. 41, after being averaged with 10 Hz, is converted into point data D _2, then is converted into the point display data D _3. Then, the point display data D _3, in the image display unit 77d, is displayed in relation to the polishing time and vibration intensity as shown by the solid line in example FIG. 42 (a).

Further, the differential value of the drawn curve based on the point display data D ₃ is in the computer 77 (dV / dt) or time variation ΔV is calculated. The calculation result is displayed on the image display unit 77d as a curve, for example, as a solid line in FIG.

Calculation of the time variation amount ΔV of the point display data, for example, represented by the value obtained by subtracting the display data D ₃ from the display the current point data D ₃ 10-th previous point. In this example, the time change amount ΔV is displayed as one data per second.

  The point of time when the differential value (dV / dt) or the time variation ΔV becomes zero or more is set as the polishing end point, and the end point detection result is displayed on the image display unit 77D.

  The computer 77 that performs the calculation and display as described above functions as the drive control unit 17 shown in the first embodiment, and therefore instructs the shaft drive unit 21 to stop polishing when the polishing end point is detected.

Incidentally, the locus where the upper surface plate 3 back and forth between two points a, b on the polishing cloth 1d is not necessarily from the rotation center O ₀ of the polishing cloth 1d in the radial direction. For example, as shown in FIG. 45 (a), it exists as a linear trajectory perpendicular to the diameter direction, or as shown in FIG. 46 (a), the upper surface plate 3 is swung by the arm of the robot. Thus, the locus of the upper surface plate 3 may be arcuate.

In these cases, the distance r between the rotation center of the upper surface plate 3 and the rotation center O ₀ of the polishing pad 1d is temporally as shown in FIG. 45 (b) in the case of the locus shown in FIG. 45 (a). In the case of the locus shown in FIG. 46 (a), the time changes as shown in FIG. 46 (b).

  In the computer 77, the distance r at the time of measuring the effective value is calculated based on the data detected by the position detector 61 and used as the correction function η.

By the way, when only the rotational movement is given to the upper surface plate 3, it is not necessary to consider the correction function η, and the curve based on the point display data is as shown in FIG. Is as shown in FIG. 47 (a) and 47 (b), a curve A shows a state in which a SiO ₂ film formed using TEOS is polished, and a curve B indicates that silicon nitride is further formed on the SiO ₂ film. A state in which the films are polished after the films are formed is shown.

  In the above description, the detection of the polishing end point based on the vibration intensity of the upper surface plate 3 has been described. However, the progress of polishing is also captured as a change in the torque of the motor built in the shaft drive unit 21. Therefore, as described above, the effective value of the torque can be obtained, and the polishing status can be grasped or the end point can be detected by means for sampling or correcting the effective value.

(13th Embodiment)
In this embodiment, instead of measuring vibration (sound) due to friction between the head and the polishing pad, an example of an apparatus that measures the polishing state and the polishing end point based on the change in the frictional force between the head and the polishing pad. Show.

  FIG. 48 is a sectional view and a bottom view showing the main part of the twelfth embodiment. 48, the same reference numerals as those in FIGS. 1, 15, and 17 denote the same elements.

  48 (a) and 48 (b), the lower surface plate 2 on which the polishing pad 1 is bonded to the upper surface is rotated by the shaft drive unit 21 at a predetermined number of rotations. Further, the workpiece W to be polished by being pressed against the upper surface of the polishing pad 1 is attached to the lower surface of the metal upper surface plate 3 at the bottom of the airbag type head via the inner pad 51. . A side wall 3 b is fixed around the upper surface plate 3, and the side wall 3 b and the head casing (support) 8 are connected via an elastic portion 7. A cylindrical shaft 9 for rotating the housing 8 is attached to the center of the housing 8. Further, a cylindrical head cover 80 is non-rotatably attached around the shaft 9 and the housing 8 to prevent the head from being contaminated by the polishing liquid.

  On the upper surface of the upper surface plate 3, an inclined surface (not shown) is formed for converting the amount of lateral displacement (displacement) of the upper surface plate into the amount of displacement in the vertical direction.

  A first displacement detector 81 for detecting the displacement of the side wall 3 b of the upper surface plate 3 is attached to the bottom surface of the housing 8, and the displacement of the side wall 3 b of the upper surface plate 3 is attached to the bottom surface of the head cover 80. A second displacement detector 82 is attached to detect the above, and further, the ceiling surface in the housing 8 above the inclined surface of the upper surface plate 3 detects the displacement of the distance from the inclined surface. The third displacement detector 83 is attached.

  The first, second, and third displacement detectors 81-83 are stylus-type displacement meters that detect the displacement amount by the expansion and contraction of the needle, and the displacement amount by the change amount of the capacitor due to the change in the distance from the upper surface plate side wall 3b. , An eddy current displacement meter that detects the amount of displacement by the amount of change in magnetic flux density due to a change in the distance to the upper surface plate side wall 3b, an optical displacement meter that detects the distance by reflection of light, etc. is there.

  A plurality of such first to third displacement detectors 81 to 83 may be arranged as shown in the bottom view of the head in FIG. Further, it is not necessary to provide all of the first to third displacement detectors 81 to 83 as shown in FIGS. 48 (a) and 48 (b), and at least one may be attached.

  The outputs of the first to third displacement detectors 81 to 83 are connected to the transmitter 13b via the amplifiers 34a and 34c and the filter 34b as shown in FIG. 19, and the detection signals oscillated from the transmitter 13b are received. The processing unit 35 is configured to input to the processing unit 35 via the machine 14, and the processing unit 35 determines the polishing end point or changes the polishing condition based on the change of the displacement signal.

  Although not particularly illustrated, a polishing liquid supply nozzle and a dresser are disposed above the polishing pad 1 as in the above-described embodiment.

  Further, the first and second displacement detectors 81 and 82 may be protected with a transparent cover so as not to be exposed to polishing liquid or water. Since the third displacement detector 83 is disposed in the housing 8, no cover is necessary.

  Next, the polishing end point detection using such a polishing apparatus will be described.

  First, when a flat standard wafer is attached to the lower surface of the inner pad 51 to perform a polishing operation, the position of the upper surface plate 3 changes from FIG. 49 (a) to FIG. 49 (c). The displacement signals of the first to third displacement detectors 81 to 83 at this time are recorded as reference signals. The standard wafer is removed after measuring the reference signal.

  Next, when a wafer on which an interlayer film is formed as an object to be polished W is attached to the lower surface of the inner pad 51 and the polishing operation is performed, the upper surface plate 3 existing at the position of FIG. Along with the movement, it is displaced as shown in FIG. The reason why the upper surface plate 3 is displaced is that the friction applied between the workpiece W and the polishing pad 1 is large, so that the stress applied to the elastic body 7 around the upper surface plate 3 is greatly reduced. For this reason, the upper surface plate 3 is biased so as to be pulled in the moving direction of the housing 8. This is set as the initial state, and at this time, the displacement amount detected by the first to third displacement detectors 81 to 83 is set to the maximum value.

  As the polishing continues, the friction between the workpiece W and the polishing pad 1 gradually decreases with time, and the upper surface plate 3 is positioned closer to the center of the housing 8 as shown in FIG. Become. Further, the change of the upper surface plate 3 is also reduced, and as shown in FIG. 50, the change amount of the displacement detected by the first to third displacement detectors 81 to 83 is gradually reduced and finally the change amount is zero. Or it becomes close to zero, and polishing is stopped in this state. The polishing is stopped by lifting the housing 3 to reduce the polishing pressure or by separating the workpiece W from the polishing cloth 1.

  If it is difficult to detect the end point due to the amount of change in the displacement of the upper surface plate 3, the polishing is completed when the displacement amount and the reference signal match or when there is almost no difference, as shown in FIG. It is good also as a point. As an example where it is difficult to detect the end point, for example, when a foreign substance for end point detection is formed in the workpiece W, the displacement may be further increased when the foreign substance is exposed after being flattened. .

  When examining such a displacement of the surface plate, the change in the output signals of the displacement detectors 81 to 83 is gentle and may be measured as a DC component. Further, when the detection signals of the displacement detectors 81 to 83 have a low frequency of several tens of Hz as the casing 8, the upper surface plate 3, and the polishing cloth 1 rotate, only the low frequency component is extracted as the detection signal. That's fine. Since high-frequency signals such as background noise are removed by the filter, the sensitivity of the displacement detectors 81 to 83 is higher than that of the vibration detection element 10. When the detection signal is direct current, or when the frequency band is as narrow as about 0 to 100 Hz, the transmission accuracy to the detector is better than in the case of high frequency, so it is more sensitive than the vibration measurement described above. Measurement becomes possible.

  By the way, since the first displacement detector 81 rotates in synchronization with the head, the range to be measured by the upper surface plate 3 does not change, so that it is not affected by variations in the shape of the upper surface plate 3. However, since the distance between the first displacement detector 81 and the upper surface plate 3 changes while the upper surface plate 3 makes one rotation, the intensity and direction of the displacement signal periodically corresponds to the rotation frequency. Change. The rotation frequency is about 100 Hz at the maximum, and since it synchronizes with the rotation of the head, the S / N ratio is not deteriorated.

  The second displacement detector 82 can linearly detect the amount of change of the upper surface plate 3 without the displacement signal changing periodically, but is easily affected by variations in the shape of the housing 8 and the upper surface plate 3.

  The third displacement detector 83 uses the vertical movement of the slope formed on the upper surface plate 3 as a detection target, but eliminates such a slope and detects the vertical movement of the upper surface of the upper surface plate 3 as a detection target. It is good.

  By attaching a plurality of such displacement detectors 81 to 82, measuring the displacement of the front and rear, the left and right, and the top and bottom of the casing 8 and the upper surface plate 3, various types of information are received. By combining these forces, it is possible to obtain more information on wafer dropping, wafer breakage, and polishing conditions (polishing liquid supply, polishing cloth abnormality, pressure change, rotation speed change, etc.).

  Further, if hemispherical protrusions 91 and 92 as shown in FIGS. 52 (a) and 52 (b) or depressions (not shown) are formed at the detection location on the side wall 3b of the upper surface plate 3, multiple directions in the same location are formed. Displacement can be detected.

  When a plurality of objects to be polished W are polished simultaneously, a plurality of heads shown in FIG. 39 are activated simultaneously. When the variation in polishing under each head is 10% or less, it is not necessary to detect the polishing end point with all the heads, and the displacement detectors 81 to 83 and the above-described implementations may be applied to some heads (or one). It is only necessary to attach the vibration detecting element 10 of the form. In this case, good results can be obtained by stopping the polishing of all the heads when the heads to which the displacement detectors 81 to 83 or the vibration detecting element 10 are attached reach the end point. The polishing may be excessively performed for a predetermined time after reaching the end point.

  Also, in order to attach vibration detection elements and displacement detectors to all the heads, the heads (upper surface plate 3) are raised in the order in which the polishing end point detection is completed, the polishing is stopped, and waiting until all the polishing is completed. May be.

  A command to stop polishing a plurality of heads is issued by the control units 17 and 35 shown in FIGS.

  As described above, according to the present invention, since a mechanism for inducing vibration during polishing is formed on the polishing cloth, the vibration intensity of vibration generated during polishing is increased and vibration that can be detected by the vibration detection element is also provided. The frequency band becomes wider, the polishing conditions can be precisely controlled, and the polishing end point can be easily detected. As such a mechanism, there is a mechanism in which a plurality of grooves are formed in a polishing cloth and vibration is induced in a region surrounded by the grooves.

  In this case, if a cavity is formed in the polishing cloth or the surface plate, the induced vibration during polishing is amplified, and the change in vibration intensity of vibration detection can be easily grasped.

  In addition, frequency information is analyzed for the vibration information obtained from the vibration detection element, and the vibration intensity obtained by subtracting the natural vibration component due to causes other than polishing is integrated for each time, and when the integrated value falls below the reference value or the integrated value Since the polishing is stopped by the signal analysis means for sending a polishing stop signal at any time when the temporal change is below the reference value, the end point of the polishing can be easily detected.

  In the signal analysis means, the polishing cloth deterioration signal is generated either in the case where the time from the start of polishing to the stop of polishing is shorter than the set time, or in the case where the temporal change in the integral value has decreased beyond a specified value. Since a signal indicating this is output, it is easy to determine whether the polishing is finished or the polishing cloth is deteriorated, and the polishing operation can be optimized.

  When polishing, when the rate of decrease in vibration intensity at a specific vibration frequency is larger than that of other vibration frequencies, it has been experimentally confirmed that polishing is not performed uniformly. Polishing can be optimized by changing the polishing conditions so that the polishing is made uniform by detecting such attenuation of vibration intensity.

  Furthermore, the amount of vibration attenuation by the vibration detector at the time of polishing is regarded as an effective value, and the change in this effective value is measured every time, and the integrated value of the change or the amount of change over a certain time becomes zero or more. When the polishing end point is detected, and the first surface plate is accompanied by an operation of moving on the polishing cloth in addition to the rotation, an effective value is obtained by a function including the position of the first surface plate. If the detection signal is corrected by dividing, the end point of polishing can be detected quickly and accurately.

  In addition, according to the present invention, when the output of the vibration detecting element that detects vibration during polishing is transmitted to the outside wirelessly, the transmitting antenna and the receiving antenna are arranged coaxially, so that the antenna rotates. Transmission and reception can be stabilized even in a state where there is a swing or swing.

  Further, when power is supplied to the vibration detection element or the transmission unit attached to the surface plate, an annular conductor is attached around the shaft that rotates the surface plate, and power is supplied through a brush that contacts the annular conductor. As a result, it is possible to avoid situations such as trouble of battery replacement and work stoppage due to power shortage.

  Further, according to the present invention, since an automatic frequency control mechanism is used when performing a plurality of polishings simultaneously and transmitting / receiving polishing information wirelessly, a stable reception state can be achieved even if frequency fluctuations due to temperature changes occur. it can.

  Furthermore, according to the present invention, when polishing, an abnormality in the vibration intensity detected by the vibration detection element attached to the surface plate is detected, and the abnormality detection time of the vibration intensity is shorter than the rotation period of the surface plate. Since a signal analyzing unit that outputs a signal indicating the presence of dust is provided on the surface, it is possible to prevent the occurrence of scratches due to dust on the polished surface of the object to be polished thereafter.

  According to still another aspect of the present invention, in a structure having an air bag type upper surface plate that is damped from a casing that is kept secret by being hollow, the vibration detecting element that detects circumferential vibration is provided. Since it is attached to the upper surface plate and polishing is terminated by changing the vibration intensity or vibration spectrum signal output from the vibration detecting element, the vibration strength in the rotational direction of the air bag type upper surface plate and its Knowing the change in the spectrum makes it easy to determine the change in the polishing state.

  In addition, when the signal from the vibration detection element is output to the control unit via the bandpass filter, the vibration component depending on the vibration of the frequency unique to the polishing apparatus is removed in accordance with the polishing apparatus and the polishing conditions, Only vibrations generated by actual polishing can be selected.

  In addition, when the vibration signal detected by the vibration detection element is wirelessly sent to the control unit, the amplitude range of the vibration signal is expanded via the logarithmic amplifier, and the vibration signal is restored by the inverse logarithmic amplifier after reception. The S / N ratio is improved.

  When the output signal from the vibration detection element is small, the output signal can be increased by connecting a plurality of vibration detection elements. Moreover, since the unnecessary vibration components are increased by the plurality of vibration detection elements, the direction and arrangement of the vibration detection elements are selected so that the unnecessary vibration components cancel each other and the necessary vibration components are added. Therefore, noise due to unnecessary vibration components can be reduced and the S / N ratio can be improved.

  Further, according to another polishing apparatus of the present invention, when the vibration detecting element detects the vibration of the workpiece support plate that changes with the progress of polishing, the soundproofing material is disposed around the vibration detecting element. Therefore, the S / N ratio can be improved by suppressing the input of background noise such as a motor to the vibration detecting element.

  In addition, when the vibration detecting element detects the vibration of the workpiece support plate that changes with the progress of polishing, the vibration frequency to be detected is converted to the maximum sensitivity frequency of the vibration detecting element. The N ratio can be improved.

  In addition, when the vibration detecting element detects the vibration of the workpiece support plate that changes with the progress of polishing, the vibration plate having the same natural frequency as the vibration frequency to be detected is vibrated with the workpiece support plate. Since it is interposed between the detection elements, the detection vibration input to the vibration detection element can be resonated and amplified, and the S / N ratio is improved.

  In addition, when the vibration detecting element detects the vibration of the object support plate that changes with the progress of polishing, a vibration transmitting body that penetrates the object support plate and contacts the vibration detection element and the object to be polished is provided. Therefore, the vibration transmission efficiency from the object to be polished to the vibration detecting element is improved, and the S / N can be improved.

  In addition, when the vibration detection element detects the vibration of the workpiece support plate that changes with the progress of polishing, the supply of energy for driving the workpiece support plate is temporarily stopped during detection. Background noise can be greatly reduced and the S / N ratio can be improved.

  In addition, when the vibration detecting element detects the vibration of the workpiece support plate that changes with the progress of polishing, the vibration frequency to be detected is different from the vibration frequency of the background noise, Since the natural vibration frequency and the vibration frequency to be detected are the same, the S / N ratio can be improved.

  In addition, when the vibration detection element detects the vibration of the object support plate that changes with the progress of polishing, a vibration plate that vibrates in the opposite phase to the background noise is interposed between the object support plate and the vibration detection element. Therefore, it is possible to improve the S / N ratio by eliminating the input of background noise to the vibration detecting element.

  In addition, when detecting the vibration of the workpiece support plate, which changes as the polishing progresses, with the vibration detection element, it is possible to select multiple vibration detection elements on the workpiece support plate, so that the vibration detection element can fail. The trouble of exchange by can be reduced.

  According to still another polishing apparatus of the present invention, since it has a displacement detector that detects the position of the workpiece support disk during polishing, the frictional force between the polishing cloth and the workpiece is increased as the polishing proceeds. As a result, the position of the workpiece support plate changes, and the end point of polishing can be detected by the amount of change in the displacement. In this case, since the amount of change in the position of the workpiece support plate differs from the background noise in the vibration frequency band, detection with a good S / N ratio is possible without being affected by vibrations of the motor or the like.

FIG. 1 is a configuration diagram illustrating a polishing apparatus according to a first embodiment of the present invention. FIGS. 2A and 2B are plan views showing grooves of the polishing cloth applied to the polishing apparatus according to the first embodiment of the present invention. FIG. 3 is a perspective view in which a head used in the polishing apparatus according to the first embodiment of the present invention is partially cut. FIG. 4 is a spectrum showing the relationship between the vibration frequency and the vibration intensity detected by the vibration detecting element in the process of polishing using the polishing apparatus according to the first embodiment of the present invention. FIGS. 5A and 5B are cross-sectional views showing a part of the process of manufacturing the semiconductor device. 6A and 6B are cross-sectional views showing a first example of polishing an insulating film of a semiconductor device using the polishing apparatus of the first embodiment of the present invention. FIGS. 7A and 7B are cross-sectional views showing a second example of polishing an insulating film of a semiconductor device using the polishing apparatus according to the first embodiment of the present invention. 8A to 8C are cross-sectional views showing a first example of the transition of polishing of the insulating film of the semiconductor device using the polishing apparatus of the first embodiment of the present invention. 9A to 9C are cross-sectional views showing a second example of the transition of polishing the insulating film of the semiconductor device using the polishing apparatus according to the first embodiment of the present invention. FIG. 10 is a waveform diagram showing a change in vibration output from the vibration detection element of the polishing apparatus according to the first embodiment of the present invention. FIG. 11 is a side view showing a head portion of a polishing apparatus according to the second embodiment of the present invention. FIG. 12 is a side view showing the head portion of the polishing apparatus according to the second embodiment of the present invention. FIG. 13 is a side view showing a head portion of a polishing apparatus according to the third embodiment of the present invention. FIG. 14 is a side view showing a head portion of a polishing apparatus according to the fifth embodiment of the present invention. FIG. 15 (a) is a side view showing a polishing apparatus according to a sixth embodiment of the present invention, and FIG. 15 (b) is a perspective view showing the positional relationship between the transmitting antenna and the receiving antenna. FIG. 16 is a block diagram showing a circuit configuration of a polishing apparatus according to a seventh embodiment of the present invention. FIG. 17 is a side view showing a polishing apparatus according to an eighth embodiment of the present invention. FIG. 18 is a bottom view of the upper surface plate of the polishing apparatus according to the eighth embodiment of the present invention. FIG. 19 is a block diagram showing a signal system of the polishing apparatus according to the eighth embodiment of the present invention. FIG. 20 is a diagram illustrating an example of the relationship between the pass frequency and the signal transmittance of a plurality of bandpass filters applied to the polishing apparatus according to the eighth embodiment of the present invention. FIG. 21 is a spectrum showing the relationship between the vibration frequency and the vibration intensity detected by the vibration detection element of the polishing apparatus according to the eighth embodiment of the present invention. 22 (a) and 22 (b) are a side view of a polishing apparatus according to a ninth embodiment of the present invention and a bottom view of an upper surface plate of the polishing apparatus. 23 (a) and 23 (b) are side views showing a first example of vertical vibration of the upper surface plate of the polishing apparatus according to the ninth embodiment of the present invention. 24A and 24B are side views showing a second example of the vertical vibration of the upper surface plate of the polishing apparatus according to the ninth embodiment of the present invention. FIGS. 25A and 25B are block diagrams showing two examples of signal systems applied to the ninth embodiment of the present invention. FIGS. 26A and 26B are a side view and a plan view of a polishing apparatus according to a tenth embodiment of the present invention. 27A and 27B are spectra showing the relationship between the vibration frequency and the vibration intensity according to the tenth embodiment of the present invention. FIG. 28 is a spectrum diagram showing an abnormal signal due to dust by the polishing apparatus according to the tenth embodiment of the present invention and other abnormal signals. FIG. 29 is a partial cross-sectional view showing an example in which a sound absorbing material is provided in the head in the polishing apparatus according to the eleventh embodiment of the present invention. FIG. 30 is a partial cross-sectional view showing an example in which a vibrating body is attached to the bottom of a vibration detecting element in the polishing apparatus according to the eleventh embodiment of the present invention. FIG. 31 is a partial cross-sectional view showing an example in which a vibrating body is attached to the bottom of a vibration detecting element in the polishing apparatus according to the eleventh embodiment of the present invention. FIG. 32 is a partial cross-sectional view showing an example in which a vibration transmitting needle is interposed between a vibration detecting element and a detected object in the polishing apparatus according to the eleventh embodiment of the present invention. FIG. 33 is a partial cross-sectional view showing an example in which a circuit for removing noise vibration input to the vibration detecting element is provided in the polishing apparatus according to the eleventh embodiment of the present invention. FIG. 34 is a partial cross-sectional view showing an example in which a circuit for changing the vibration frequency input to the vibration detecting element is provided in the polishing apparatus according to the eleventh embodiment of the present invention. FIG. 35 is a partial cross-sectional view showing an example in which a plurality of vibration detection elements and vibration plates attached to the bottom surface thereof are provided in the polishing apparatus according to the eleventh embodiment of the present invention. FIG. 36 is a characteristic diagram showing the relationship between the vibration frequency and sensitivity of the vibration detecting element applied to the polishing apparatus of the present invention. FIG. 37 is a spectrum showing the relationship between the frequency and intensity of the natural vibration detected by the polishing apparatus according to the eleventh embodiment of the present invention. FIG. 38 is a characteristic diagram showing the amount of change over time of the integral value of the spectrum of the natural vibration detected by the polishing apparatus according to the eleventh embodiment of the present invention. 39 (a) and 39 (b) are a side view of a polishing apparatus according to a twelfth embodiment of the present invention, and a plan view showing a lower surface plate and a polishing cloth. FIG. 40 is a block diagram showing a signal system of the polishing apparatus according to the twelfth embodiment of the present invention. FIG. 41 is a block diagram showing signal processing of the computer of the polishing apparatus according to the twelfth embodiment of the present invention. FIG. 42 (a) is a diagram showing the vibration intensity curve before correction and the corrected vibration intensity curve displayed by averaging the sampling data in the polishing apparatus according to the twelfth embodiment of the present invention, and FIG. ) Is a diagram showing a differentiated curve of the vibration intensity curve before and after correction. FIG. 43 (a) shows a change in the distance r between the rotation center of the upper surface plate and the rotation center of the polishing cloth when the upper surface plate moves in the diameter direction of the polishing cloth in the polishing apparatus of the twelfth embodiment of the present invention. FIG. 43 (b) is a waveform diagram of a correction function using the distance r. 44 (a) to 44 (d) are plan views showing variations of the polishing cloth used in the polishing apparatus according to the twelfth embodiment of the present invention. FIG. 45 (a) is a plan view showing a second example of the movement trajectory of the upper surface plate in the polishing apparatus of the twelfth embodiment of the present invention, and FIG. 45 (b) is a diagram of the upper surface plate on the movement trajectory. It is a wave form diagram which shows the change of the distance r of a rotation center and the rotation center of polishing cloth. 46 (a) is a plan view showing a third example of the movement trajectory of the upper surface plate in the polishing apparatus of the twelfth embodiment of the present invention, and FIG. 46 (b) is a diagram of the upper surface plate on the movement trajectory. It is a wave form diagram which shows the change of the distance r of a rotation center and the rotation center of polishing cloth. FIG. 47 (a) shows a vibration intensity curve showing temporal changes when the upper surface plate does not move on the polishing cloth in the polishing apparatus of the twelfth embodiment of the present invention, and FIG. 47 (b) shows the vibration intensity curve. Is a differential curve. 48 (a) and 48 (b) are a sectional view and a bottom view showing the main part of the polishing apparatus according to the thirteenth embodiment of the present invention. 49 (a) to 49 (c) are bottom views showing changes due to polishing of the bottom surface of the head of the polishing apparatus according to the thirteenth embodiment of the present invention. FIG. 50 is a diagram showing the amount of change in the displacement of the upper surface plate with the progress of polishing in the polishing apparatus according to the thirteenth embodiment of the present invention. FIG. 51 is a diagram showing a comparison between the amount of change in the displacement of the upper surface plate due to the progress of polishing and the reference signal in the polishing apparatus according to the thirteenth embodiment of the present invention. 52 (a) and 52 (b) are partial cross-sectional views of the head showing a state where protrusions are formed in the vibration detection region in the polishing apparatus according to the thirteenth embodiment of the present invention.

Explanation of symbols

1, 1d Polishing cloth 2 Lower surface plate 2a Cavity 3 Upper surface plate 3a Cavity 3b Side wall 4 First groove 5 Second groove 6 Second groove (cavity)
7 Elastic part 8 Indicator 9 Shaft 10, 10A, 10B Vibration detection element 11 Nozzle 12 Dresser 13, 13A Transmitter 14 Receiver 15 Drive control part 16 Display part 21 Shaft drive part 22 Elastic part 23 Oscillating device 24 Belt 25 Feed Reliable antenna 26 Receiving antenna 27 Signal line 28 Ring conductor 29 Brush 30 Electric wire 31 Synthesizer 32 Receiver 33 Signal analysis units 34a, 34d, 34e First amplifier 34b Filter 34c Second amplifier 34B FM transmitter 35 Processing unit 41 Upper platen 42 Acceleration sensor 43 Lower platen 44 Polishing cloth 45 Marker 46 Marker detector 50 Soundproof / sound absorbing material 51 Inner sheet 52 Resonant plate 53 Amplifier 54 Hole 55 Vibration transmitting needle 56 Vibration plate 57 Vibration detection element 58 Vibration Control unit 59 Frequency conversion circuit 61 Position detector 62 Detection plate 63 Rectifier 64 Capacitor 65 Amplifier 66 Low pass filter 67 High pass filter 69 FM receiver 70 Recording device 71 Filter 72 First amplifier 73 Rectifier circuit 74 Low pass filter 75 Second amplifier 76 A / D converter 77 Computer 81, 82, 83 Displacement Detector 91, 92 Protrusion

Claims (10)

A first surface plate for supporting an object to be polished;
A second surface plate disposed opposite to the first surface plate;
An abrasive cloth affixed to the second surface plate;
A vibration detector attached to the first surface plate or the second surface plate;
A drive mechanism for driving at least the first platen or the second platen;
A transmitter that is attached to the first surface plate or the second surface plate on the side on which the vibration detector is mounted, and that wirelessly transmits vibration information detected by the vibration detector;
A receiver for receiving a radio signal output from the transmitter;
A signal analysis unit connected to the reception unit for analyzing the received radio signal;
Based on a signal from the signal analysis unit, a control unit that outputs at least a signal instructing to stop polishing or change polishing conditions to the drive mechanism;
An annular transmission antenna attached around the rotation axis of the first surface plate or the second surface plate to which the vibration detector is attached, and connected to the transmission unit;
A polishing apparatus comprising: a receiving antenna attached on an extension of the rotating shaft and connected to the receiving unit. A logarithmic amplifier for expanding the amplitude range of the vibration signal based on the output of the vibration detector;
The polishing apparatus according to claim 1, further comprising: an antilogarithmic amplifier that is connected to an output side of the receiving unit and converts an output signal from the receiving unit. A first surface plate for supporting an object to be polished;
A second surface plate disposed opposite to the first surface plate;
An abrasive cloth affixed to the second surface plate;
Drive means for periodically moving the first surface plate within a certain range on the polishing cloth;
The value of the vibration intensity of the first surface plate or the driving torque of the driving means is divided by a function including the position component of the first surface plate, and the result is used as a polishing state signal. A polishing apparatus comprising: a polishing end point detecting means for differentiating the change with time and detecting the end of polishing based on the differential value. A surface plate that supports the object to be polished;
Supporting the peripheral part of the surface plate via an elastic body, and a casing having a hollow inside,
A polishing cloth for polishing the polishing object;
A displacement detector for measuring a relative position of the surface plate with respect to the casing, which is dragged in a movement direction of the polishing cloth or a movement direction of the casing by friction between the polishing cloth and the object to be polished. Polishing equipment.   The flattening speed of the polishing object flattened by friction with the polishing cloth is made to correspond to the output signal of the displacement detector, and the change in the output signal is within a predetermined range of the flattening speed or a predetermined 5. The polishing apparatus according to claim 4, further comprising a polishing end point discriminating means for discriminating when the value reaches a polishing end point. Polishing provided with the 1st surface plate which supports a grinding | polishing target object, the 2nd surface plate arrange | positioned facing this 1st surface plate, and the polishing cloth affixed on this 2nd surface plate In a polishing method using an apparatus,
By the driving means, the first surface plate is periodically moved within a certain range on the polishing cloth,
The value of the vibration intensity of the first surface plate or the rotational torque of the driving means is divided by a function including the position component of the first surface plate, and the result is used as a polishing state signal. A polishing method characterized by including a step of differentiating a change with time and ending polishing based on the differential value.   The polishing method according to claim 6, wherein the function is a proportional function proportional to a distance from a rotation center of the polishing pad.   The groove is provided with substantially equal density in the polishing cloth, and the function is a function proportional to the square of the distance from the rotation center of the polishing cloth. Polishing method.   The polishing method according to claim 6, wherein the function includes a rotation speed of the second surface plate. Using a first surface plate that supports an object to be polished, a second surface plate disposed opposite to the first surface plate, and a polishing cloth attached to the second surface plate, In the polishing method for polishing the polishing object with the polishing cloth,
A vibration detector detects vibrations during polishing of the first surface plate or the second surface plate,
When an abnormality in vibration intensity detected by the vibration detector is detected, and the abnormality detection time of the vibration intensity is shorter than the rotation period of the second surface plate, the first surface plate and the second surface plate are detected. A polishing method comprising controlling driving of a surface plate.

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