JP4493286B2 - Work polishing method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technique for polishing a disk-shaped workpiece such as a semiconductor wafer, and more specifically, when a workpiece reaches a target thickness, the polishing apparatus is automatically operated by using a sizing function. The present invention relates to a polishing technique for workpieces to be stopped.
[0002]
[Prior art]
Conventionally, as a polishing apparatus for polishing a disk-shaped workpiece such as a semiconductor wafer, a lapping apparatus, a polishing apparatus, a CMP (Chemical Mechanical Polishing) apparatus, or the like is known. These polishing apparatuses include a single-side polishing apparatus that presses a workpiece against one surface plate and polishes it, and a double-side polishing device that holds a workpiece between two upper and lower surface plates for polishing.
[0003]
Among these, as schematically shown in FIG. 7, the double-side polishing apparatus includes an annular upper surface plate 50 and lower surface plate 51 that are coaxially positioned, and a sun gear 52 that is positioned at the center of both surface plates 50, 51. And an internal gear 53 positioned so as to surround the two surface plates 50 and 51, and a plurality of carriers 54 positioned on the lower surface plate 51 and meshing with both the gears 52 and 53. The workpieces W held by the carriers 54 that rotate while revolving around the sun gear 52 while rotating the surface plates 50 and 51 and the gears 52 and 53 around the central axis with a motor (not shown) The both surface plates 50 and 51 are sandwiched and polished. At this time, abrasive slurry whose components are adjusted in accordance with the purpose of polishing is supplied between both surface plates 50 and 51.
[0004]
This type of polishing apparatus is usually equipped with a sizing mechanism that automatically stops the apparatus when the workpiece reaches a target thickness. A general sizing mechanism is equipped with a thickness sensor (transition sensor), which detects the thickness of the workpiece and stops the polishing machine when it reaches the target thickness. It is configured. In this case, the thickness of the workpiece W is not directly detected by the thickness sensor, but the upper and lower surface plates 50 and 51 are usually detected by detecting the position of the upper surface plate 50 that gradually descends with polishing. The interval S between them is detected as the thickness of the workpiece, and the polishing is terminated when the interval S becomes equal to the target thickness of the workpiece. The carrier 54 is thinner than the target thickness of the workpiece W. Therefore, the upper surface plate 50 does not come into contact with the carrier 54 at the end of polishing.
[0005]
On the other hand, in Patent Document 1, as another example of the sizing mechanism, the polishing apparatus is stopped by detecting that the upper surface plate is in contact with the carrier without using the thickness sensor as described above. Are disclosed. This utilizes the fact that the motor is overloaded when the upper surface plate comes into contact with the carrier. Use the carrier with the same thickness as the target thickness of the workpiece and change the load state of the motor that drives the upper surface plate. It is constantly monitored by a load detection sensor, and the motor is stopped when the upper surface plate comes into contact with the carrier and becomes overloaded.
[0006]
As described in Patent Document 1 described above, when such a carrier sizing method is used, the flatness of the workpiece is greatly improved as compared with the case where other sizing methods using a thickness sensor or the like are used. It is known. This has been confirmed by polishing experiments conducted by the present inventors. However, on the other hand, it has been found from experiments that this carrier sizing method is prone to malfunction.
[0007]
In other words, this carrier sizing method monitors the load state of the motor that drives the upper surface plate by the drive current, and detects the inflection point when the drive current increases when the upper surface plate contacts the carrier. In this case, the relationship between the processing time and the drive current is generally shown by a curve A in FIG. 4 from a polishing experiment conducted by the present inventors. The driving current changes drastically at the start of polishing. This is because the thickness of multiple workpieces is not uniform at the beginning of polishing, so the number of workpieces that touch the upper surface plate changes with polishing, Since the initial surface of the workpiece has large irregularities, it can be considered that the load applied to the upper surface plate fluctuates.
[0008]
After the above-mentioned period, the drive current gradually decreases on average, but it does not always decrease smoothly. As indicated by the inflection point a, the drive current temporarily increases. It decreases while changing in various forms, such as being in a horizontal state like the inflection point b. This is presumably because the load state fluctuates due to changes in the shape of the abrasive material accompanying polishing, the supply state thereof, or changes in the contact state between the workpiece and the surface plate. When the upper surface plate comes into contact with the carrier, the drive current starts to increase as indicated by the inflection point c, and this point becomes a normal inflection point indicating the polishing end point.
[0009]
Therefore, if the control device is set so that the polishing is terminated when the inflection point of the drive current is detected, the incorrect inflection points a and b appearing before the upper surface plate comes into contact with the carrier are properly set. Misidentified as an inflection point c and easily causes malfunction.
[0010]
Here, since the irregular inflection points a and b usually have a smaller degree of change in the drive current than the regular inflection point c, the polishing apparatus is used after confirming that the drive current has increased to some extent. If set to stop, it is possible to accurately detect a regular inflection point and prevent malfunction. However, in this case, since the timing of the end of polishing is greatly delayed, not only the work is excessively polished and the flatness is lowered, but also the carrier is also polished by a considerable amount and the life is likely to be reduced. .
[0011]
[Patent Document 1]
JP 2001-260015 A
[Patent Document 2]
JP 2002-144224 A
[Patent Document 3]
JP-A-6-71556
[Patent Document 4]
Japanese Patent Laid-Open No. 3-86466
[Patent Document 5]
JP-A-11-347926
[Patent Document 6]
Japanese Patent Laid-Open No. 5-138529
[Patent Document 7]
JP-A-9-262743
[0012]
[Problems to be solved by the invention]
The technical problem of the present invention is that, in the workpiece polishing using the carrier sizing method described above, when the change in the driving current of the motor accompanying the contact between the surface plate and the carrier is detected and the polishing is finished, the driving current is reduced. Even when there are a plurality of changing inflection points, it is possible to reliably detect a normal inflection point indicating the polishing end point and without causing a timing delay.
[0013]
[Means for Solving the Problems]
In order to solve the above problems, according to the present invention, a workpiece to be polished is held on a carrier having a thickness substantially the same as a target thickness after polishing of the workpiece, and is rotated by a surface plate driven by a motor. A method of polishing until the thickness is the same as that of the carrier, the function of detecting the driving current of the motor, the function of detecting an inflection point where the current value changes due to contact between the surface plate and the carrier, and polishing. Hold the control device with a function to end and the inflection point detection function of the control device after the workpiece polishing is started, When the difference between the measured thickness of the workpiece measured by the thickness sensor and the target thickness falls below a certain value, the inflection point detection function is switched on. Using the timing setting device, With the timing setting device There is provided a method for polishing a workpiece, wherein polishing is terminated when an inflection point is detected after the inflection point detection function of the control device is turned on.
[0014]
According to the polishing method of the present invention having the above configuration, the inflection point detection function of the control device is switched to the ON state immediately before the workpiece reaches the target thickness by the timing setting device, and the inflection point detected after the switching is performed. Since the polishing is finished, even if there are multiple incorrect inflection points due to the drive current changing during the polishing, the regular inflection point indicating the polishing end point is ensured and the timing is ensured. Detection can be performed without causing a delay, and the polishing apparatus can be accurately stopped at the polishing end point.
[0016]
Further, in order to carry out the above polishing method, according to the present invention, the polishing method has at least one surface plate for polishing the workpiece, and has a thickness substantially the same as the target thickness of the workpiece after polishing. A carrier configured to hold the workpiece therein and to contact the platen when the workpiece reaches a target thickness, at least one platen motor for individually driving the platen, A control device including a current detection device that detects a drive current of two or more surface plate motors, and an inflection point detection device that detects an inflection point at which the current value changes and ends polishing; It has a thickness sensor that measures the thickness of the workpiece, Hold the inflection point detection device of the control device in the off state for a while after starting the polishing of the workpiece, When the difference between the measured thickness of the workpiece measured by the thickness sensor and the target thickness falls below a certain value, There is provided a workpiece polishing apparatus having a timing setting device for switching an inflection point detection device to an ON state.
[0018]
According to one specific embodiment of the present invention, the polishing apparatus is a double-side polishing apparatus, and the double-side polishing apparatus includes two upper and lower surface plates and two surface plates that individually drive the surface plates. A motor for a panel, a sun gear and an internal gear, and the carrier that meshes with both gears and rotates while revolving between the upper and lower surface plates. It is connected to at least one of the two platen motors.
[0019]
According to another specific embodiment of the present invention, the polishing apparatus is a single-side polishing apparatus, and the single-side polishing apparatus includes one surface plate and a surface plate motor that drives the surface plate. And a pressure plate for pressing the work against the surface plate, and the carrier interposed between the surface plate and the pressure plate.
[0020]
Furthermore, according to the present invention, one surface plate for polishing the workpiece, at least one pressure plate for pressing the workpiece against the surface plate, and attached to the lower surface of the pressure plate, A carrier having a thickness substantially the same as a target thickness of a subsequent workpiece, holding the workpiece being polished, and configured to contact the surface plate when the workpiece reaches the target thickness; A driving current connected to at least one of a platen motor for driving the platen, a pressure plate motor for individually driving the pressure plates, and the platen motor and the pressure plate motor. A control device including a current detection device that detects the current and an inflection point detection device that detects an inflection point at which the current value changes and terminates polishing; It has a thickness sensor that measures the thickness of the workpiece, Hold the inflection point detection device of the control device in the off state for a while after starting the polishing of the workpiece, When the difference between the measured thickness of the workpiece measured by the thickness sensor and the target thickness falls below a certain value, There is provided a workpiece polishing apparatus having a timing setting device for switching an inflection point detection device to an ON state.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 schematically shows a first embodiment of a polishing apparatus according to the present invention. This first embodiment is a double-side polishing apparatus for polishing both surfaces of a disk-shaped workpiece W. This polishing apparatus 1A includes an annular upper surface plate 2 and lower surface plate 3 that are coaxially positioned, a sun gear 4 that is positioned at the center of both surface plates 2, 3, and the outer circumference of both surface plates 2, 3. And a plurality of carriers 6 that mesh with both the gears 4 and 5 while being placed on the lower surface plate 3. Each of these carriers 6 is formed to have a thickness substantially equal to the target thickness of the workpiece W, that is, the thickness after polishing. Each carrier 6 has a plurality of workpiece holding holes and is polished in each workpiece holding hole. The work W to be held is held in a fitted state.
[0022]
As can be seen from FIG. 2, a plurality of workpieces W held by each carrier 6 are sandwiched from both sides by upper and lower surface plates 2 and 3, and an abrasive slurry whose components are adjusted according to the purpose of polishing is fixed. The work W is made to have the same thickness as the carrier 6 on the work surface of these surface plates 2 and 3 which normally rotate in opposite directions while being supplied between the surface plates 2 and 3 from the supply hole 8 provided in the surface 2. It is polished until it reaches the end. The carrier 6 is rotated by revolving around the sun gear 4 by being driven by the both gears 4 and 5 during polishing. When the workpiece W is polished to the target thickness, the upper surface plate 2 comes into contact with each carrier 6 as shown in FIG. In other words, the point in time when the upper surface plate 2 contacts each carrier 6 is the polishing end point.
[0023]
The lower surface plate 3, the sun gear 4 and the internal gear 5 are respectively attached to the upper ends of the drive shafts 3a, 4a and 5a arranged coaxially, and the gears 3b, 4b and 5b at the lower ends of the drive shafts are respectively attached. The motors M2, M3, and M4 are coupled to each other, and each of these motors is controlled by the control device 11 so as to be driven in a predetermined rotation direction at a predetermined rotation speed.
[0024]
On the other hand, the upper surface plate 2 extends from the pressurizing cylinder 16 and the pressurizing cylinder 16 that applies pressure to the rod 15a of the elevating cylinder 15 attached to the body 14 of the polishing apparatus. Via a pressure plate 16a, a surface plate suspension 17 attached to the lower end of the pressure rod 16a, a plurality of studs 18 suspended from the surface plate suspension 17, and a relay plate 19 fixed to the lower end of the stud 18. The locking member 20 on the relay plate 19 is engaged with the driver 2c at the upper end of the drive shaft 2a in the illustrated lowered position. The drive shaft 2a is connected to a motor M1 through a gear 2b at the lower end thereof, and the motor M1 is connected to the control device 11, and the control device 11 controls the motor M1 to obtain a predetermined value. It is driven at a predetermined rotational speed in the rotational direction.
[0025]
The control device 11 includes a current detection device 23 that detects the drive current of the upper surface plate motor M1, and an inflection point detection device that detects an inflection point at which the detected drive current changes and stops the polishing apparatus. 24. During the polishing of the workpiece, the driving current of the motor M1 is continuously monitored by the current detector 23, and when the inflection point of the driving current is detected by the inflection point detector 24, the inflection point is detected. The control device 11 is configured to stop the polishing device in response to a signal from the device 24.
[0026]
In FIG. 4, the relationship between the polishing time (seconds) of the workpiece W and the drive current of the upper surface plate motor M1 is shown as a curve A. The characteristics of this drive current are as described in the section of “Prior Art”, and as described there, the drive current gradually decreases on average after starting polishing, but it is not always necessary. It does not necessarily decrease smoothly, but temporarily shows an increasing tendency as shown at the inflection point a, or the gradient becomes gentle or close to zero as shown at the inflection point b. It decreases while changing in various ways. Then, when the workpiece W is polished to the target thickness and the upper surface plate 2 comes into contact with the carrier 6, the carrier 6 is sandwiched between both surface plates 2 and 3, and the contact pressure between the surface plate and the carrier increases. Since the load of the motor M1 increases, the drive current starts to increase as indicated by the inflection point c, and this point becomes a normal inflection point indicating the polishing end point.
[0027]
However, since the control device 11 is set to finish the polishing when the inflection point detection device 24 detects the inflection point of the drive current, it appears before the upper surface plate 2 contacts the carrier 6. Incorrect inflection points a and b may be mistaken as regular inflection points c, which may cause malfunction. Therefore, a timing setting device 25 is attached to the polishing apparatus in order to prevent such a malfunction. The timing setting device 25 keeps the inflection point detection device 24 in the control device 11 in an off state for a while after the start of polishing, and the inflection point detection device 24 immediately before the workpiece W reaches the target thickness. This is switched to the on state and is configured as follows.
[0028]
That is, the timing setting device 25 includes a thickness sensor (transition sensor) 27 that measures the thickness of the workpiece W. This thickness sensor 27 is attached to the inner upper end of the drive shaft 2a, detects the position of the upper surface plate 2 that descends as the polishing progresses, and obtains the interval between both surface plates 2, 3. The interval is detected as the thickness of the workpiece W. More specifically, the thickness sensor 27 is a contact type made of a magnetic scale or the like, and the tip of the stylus 27a extending upward and contractible is fixed to the upper surface plate 2 in an integral relationship. The change of the surface plate suspension 17 is brought into contact with a contact 17a on the lower surface of the panel suspension 17, and is converted into an electrical signal as a variation of the upper surface plate 2, and is taken out.
[0029]
However, the configuration and measurement method of the thickness sensor 27 are not limited to this. For example, a non-contact type thickness sensor using an air gauge, ultrasonic waves, light, or the like can be used, and the thickness sensor can be configured to directly detect the position of the upper surface plate.
[0030]
A curve B in FIG. 4 shows the relationship between the measured thickness of the workpiece W by the thickness sensor 27 (interval between both surface plates 2 and 3) and the polishing time. The slope of the curve at the initial stage of polishing is steepest because the thickness of the plurality of workpieces W is not uniform at first, so the number of workpieces W to be polished by the upper surface plate 2 is small, and the upper surface plate This is probably because the thickness of 2 is rapidly decreased and the measured thickness is also rapidly decreased. When all the workpieces W come into contact with the upper surface plate 2, the gradient becomes gentle with respect to the change point x, and the measured thickness decreases at a substantially constant rate. When the workpiece W is polished to the same thickness as the carrier 6, the upper surface plate 2 comes into contact with the carrier 6, so that the polishing rate decreases at the change point y and the gradient becomes gentler. Become. The change point y corresponds to the inflection point c in the drive current characteristic curve A.
[0031]
The measured thickness t of the workpiece W detected by the thickness sensor 27 is input to the timing setting device 25, where it is compared with a preset reference thickness T, and when the difference between them becomes zero. In other words, when the measured thickness t becomes equal to the reference thickness T, the inflection point detection device 24 is switched to the on state. The reference thickness T is a value slightly larger than the target thickness of the workpiece W, and the optimum value varies depending on the type of the workpiece W, the polishing conditions, and the like. It is desirable that the value is larger by several to tens of micrometers than the target thickness of W. Specifically, the difference between the reference thickness T and the target thickness is preferably about 2 to 15 μm, more preferably about 5 μm. From the motor drive current characteristic data obtained by various experiments, an inflection point of the drive current appears in the vicinity of the polishing end point while polishing such a thickness of about a dozen μm. This is due to the fact that it is difficult. However, it goes without saying that the reference value may be a numerical value other than this.
[0032]
Instead of setting the reference thickness T in the timing setting device 25 as described above and comparing this with the measured thickness t of the workpiece W, the target thickness of the workpiece W is set, and this is compared with the measured thickness. And the inflection point detecting device 24 can be turned on when those deviations are below a certain value. The deviation at this time is set equal to the difference between the reference thickness and the target thickness described above.
[0033]
Thus, the inflection point detection device 24 is held in the OFF state for a while after the start of polishing by the timing setting device 25 and switched to the ON state immediately before the workpiece W reaches the target thickness. Therefore, no matter how much the drive current changes while the inflection point detection device 24 is in the OFF state, the polishing device will not stop due to malfunction. Then, after the inflection point detection device 24 is turned on, when the workpiece W is polished to the target thickness and the upper surface plate 2 comes into contact with each carrier 6, the upper surface plate motor is driven by an increase in load. Since the current increases as indicated by the inflection point c, the inflection point c is detected as the polishing end point by the inflection point detection device 24, a signal is sent to the control device 11, the polishing device is stopped, and the polishing is stopped. Ends. Therefore, the inflection point c is an inflection point that is detected first after the inflection point detecting device 24 is switched on.
[0034]
If the inflection point detection device 24 is switched to the ON state immediately before the workpiece W reaches the target thickness and the polishing apparatus is stopped at the inflection point c that is detected first as described above, Therefore, it is not necessary to compare the degree of change in the drive current between the incorrect inflection points a and b, and therefore it is necessary to wait until the drive current increases considerably to determine whether or not it is the normal inflection point c. For example, the polishing can be finished when the decreasing gradient of the drive current becomes almost zero or when the driving current starts to increase slightly. As a result, there is no longer a problem that the timing of finishing polishing is delayed, and the problem that the work W is excessively polished to lower the flatness or the carrier 6 is polished to reduce the life is solved. can do.
[0035]
FIG. 5 is an example of a flowchart for explaining the operation of the polishing apparatus of the first embodiment. When the workpiece W is set in the workpiece holding hole of each carrier 6 with the upper platen 2 raised, the upper platen 2 is lowered and the start button is pressed, and the operation of the control device 11 starts (step S00). ). In step S01, the supply of the abrasive slurry is started from a slurry supply device (not shown). In step S02, all the motors M1 to M4 are started to start polishing. At the same time, in step S03, the measurement of the thickness of the workpiece W by the timing setting device 25 is started, and the measured thickness t and the reference thickness T are compared as shown in step S04. Then, the loop of step S03 and step S04 is repeated until the measured thickness t and the reference thickness T become equal.
[0036]
When the measured thickness t of the workpiece W becomes equal to the reference thickness T, the inflection point detection device 24 is activated in step S05, and the upper surface plate driving motor detected by the current detection device 23 is driven in step S06. The current value Id is stored in the inflection point detection device 24 as a reference current value Ir. Next, in step S07, the driving current value Id detected by the current detecting device 23 is again taken into the inflection point detecting device 24. In step S08, the driving current value Id and the previously stored reference current value Ir are obtained. To be compared. If the drive current value Id is smaller than the reference current value Ir, the process proceeds to step S09, the drive current value Id previously captured is stored again as the reference current value Ir, the process returns to step 07 again, and the above operation is repeated. It is. When the drive current value Id becomes equal to or larger than the reference current value Ir, the process proceeds to step S10, where the polishing apparatus is stopped and the polishing is finished (step S99).
[0037]
In the above embodiment, the current detector 23 detects the drive current of the motor M1 for the upper platen. However, the workpiece W is polished to the target thickness and the upper platen 2 comes into contact with the carrier 6, When the carrier 6 is sandwiched between the two surface plates 2 and 3 and the contact pressure between the surface plate and the carrier increases, the drive current of the lower surface plate motor M2 also changes accordingly. The polishing apparatus can be stopped by detecting the drive current of the motor M2. Alternatively, the drive currents of both the upper surface plate motor M1 and the lower surface plate motor M2 are detected, and the polishing end point is detected at an optimal timing from the change in the current values, and the polishing apparatus is stopped. Is also possible.
[0038]
FIG. 6 conceptually shows a second embodiment of the present invention. A polishing apparatus 1B of the second embodiment is a single-side polishing apparatus for polishing one side of a workpiece W. This single-side polishing apparatus includes one surface plate 30 that rotates around a vertical central axis, and at least one pressure plate 31 that presses the work W against a work surface formed on the upper surface of the surface plate 30. Have.
[0039]
The surface plate 30 has a drive shaft 30 a connected to a surface plate motor M 5, and the motor M 5 is connected to the control device 33. The control device 33 has the same configuration as the control device 11 of the first embodiment, and includes a current detection device 34 that detects the drive current of the motor M5, and an inflection point at which the detected drive current changes. And an inflection point detecting device 35 for stopping the polishing apparatus, and the operation thereof is substantially the same as in the first embodiment.
[0040]
Further, the pressure plate 31 is supported by a lift mechanism (not shown) and is movable up and down, and the pressure plate 31 is connected to an individual pressure plate motor M6 controlled by the control device 33 so as to have a center axis. A carrier 36 that holds the workpiece W is fixedly or detachably attached to the lower surface of the pressure plate 31. In the carrier 36, the height h protruding from the work contact surface 31 a of the pressure plate 31 is a substantial thickness, and the thickness h is formed to be the same as the target thickness of the work W. Accordingly, when the workpiece W is polished to the target thickness, the lower surface of the carrier 36 comes into contact with the surface plate 30.
[0041]
Further, a thickness sensor 37 for detecting the thickness of the workpiece W is attached to the pressure plate 31, and the thickness sensor 37 is connected to a timing setting device 38. , Connected to the control device 33. The operation of the timing setting device 38 is substantially the same as in the first embodiment.
[0042]
The illustrated thickness sensor 37 is a non-contact type sensor such as an air gauge, an ultrasonic type, or an optical type so as to detect an interval between the work contact surface 31 a of the pressure plate 31 and the surface plate 30. Although it is configured, a method of directly detecting the thickness of the workpiece W may be used.
In the figure, reference numeral 39 denotes a supply nozzle for supplying an abrasive to the center of the upper surface of the surface plate 30.
[0043]
Also in this second embodiment, instead of detecting the drive current of the surface plate motor M5 by the current detection device 34, the drive current of any one or more pressure plate motors M6 is detected and the polishing end point is detected. Alternatively, the drive currents of both the surface plate motor M5 and the one or more pressure plate motors M6 are detected simultaneously, and an appropriate polishing end point is determined from the inflection point of those currents. It can also be configured to detect and stop the polishing apparatus.
[0044]
In each of the above embodiments, the timing setting devices 25 and 38 have the thickness sensors 27 and 37, and the thickness sensor measures the thickness of the workpiece, and the inflection point detection device based on the measured thickness. Although the timing for turning on and off 24 and 35 is determined, a timer is used in place of the thickness sensors 27 and 37, and with this timer, the thickness of the workpiece is kept for a while from the start of polishing. Until the target thickness is approached, the inflection point detection devices 24 and 35 are held in an off state, and when the workpiece thickness approaches the target thickness, the inflection point detection devices 24 and 35 are turned on. It can also be set to switch to a state. The set time in this case varies depending on the type and thickness of the workpiece, the polishing conditions, and the like, but an appropriate time can be known from a workpiece polishing experiment performed in advance or an empirical rule regarding past polishing. For example, when polishing is performed based on the data shown in FIG. 4, the time should be set so that the inflection point detection device is turned on about 350 seconds after the start of polishing.
[0045]
【The invention's effect】
As described above, according to the present invention, in the polishing of a workpiece by the carrier sizing method, when the change in the driving current of the motor accompanying the contact between the surface plate and the carrier is detected and the polishing is finished, the driving current changes. Even when there are multiple inflection points, the regular inflection point indicating the polishing end point can be reliably detected without causing a timing delay, and as a result, the polishing apparatus can accurately detect the polishing end point without causing malfunction. Can be stopped.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a first embodiment of a polishing apparatus according to the present invention.
FIG. 2 is an enlarged view of a main part of FIG. 2 showing a state during polishing.
FIG. 3 is an enlarged view of a main part of FIG. 2 showing a state of a polishing end point.
FIG. 4 is a diagram showing the relationship between polishing time, motor drive current, and workpiece thickness.
FIG. 5 is a flowchart for explaining the operation of the polishing apparatus according to the first embodiment;
FIG. 6 is a sectional view of an essential part schematically showing a second embodiment of the polishing apparatus according to the present invention.
FIG. 7 is a cross-sectional view schematically showing a conventional polishing apparatus.
[Explanation of symbols]
1A, 1B polishing equipment
2, 3, 30 Surface plate
4 Sun gear
5 Internal gear
6,36 carriers
11, 33 Control device
23, 34 Current detection device
24, 35 Inflection point detector
25, 38 Timing setting device
27, 37 Thickness sensor
M1, M2, M3, M4, M5, M6 motor
W Work
t Measurement thickness
T standard thickness

Claims (5)

A method in which a workpiece to be polished is held on a carrier having a thickness substantially the same as a target thickness after polishing of the workpiece, and is polished until the thickness becomes the same as that of the carrier by a surface plate driven by a motor. Because
A control device having a function of detecting the driving current of the motor, a function of detecting an inflection point where the current value changes due to contact between the surface plate and the carrier, and a function of terminating polishing; The inflection point detection function of the control device is kept in the off state, and the inflection point detection function is turned on when the difference between the measured thickness of the workpiece measured by the thickness sensor and the target thickness is below a certain value. A timing setting device for switching to a state, and polishing is terminated when an inflection point is detected after the inflection point detection function of the control device is turned on by the timing setting device . Polishing method. At least one surface plate for polishing the workpiece;
The workpiece has a thickness substantially equal to the target thickness of the workpiece after polishing, and is configured to hold the workpiece being polished and to contact the surface plate when the workpiece reaches the target thickness. A carrier,
At least one platen motor for individually driving the platen;
A control device including a current detection device that detects a driving current of one or more surface plate motors, and an inflection point detection device that detects an inflection point at which the current value changes and ends polishing;
It has a thickness sensor that measures the thickness of the workpiece, holds the inflection point detection device of the control device in an off state for a while after the workpiece polishing starts , and measures the workpiece measured by the thickness sensor A timing setting device that switches the inflection point detection device to an on state when the difference between the thickness and the target thickness is a certain value or less ;
An apparatus for polishing a workpiece, comprising: The polishing apparatus is a double-side polishing apparatus, and the double-side polishing apparatus includes two upper and lower surface plates, two surface plate motors that individually drive these surface plates, a sun gear and an internal gear, And the carrier that rotates while revolving between upper and lower surface plates engaged with both gears, and the current detection device of the control device is connected to at least one of the two surface plate motors. The polishing apparatus according to claim 2 . The polishing apparatus is a single-side polishing apparatus, and the single-side polishing apparatus includes one surface plate, a surface plate motor for driving the surface plate, a pressure plate for pressing a workpiece against the surface plate, and these The polishing apparatus according to claim 2 , further comprising the carrier interposed between the surface plate and the pressure plate. One surface plate for polishing the workpiece;
At least one pressure plate for pressing the workpiece against the surface plate;
It is attached to the lower surface of the pressure plate, has substantially the same thickness as the target thickness of the workpiece after polishing, holds the workpiece being polished, and when the workpiece reaches the target thickness A carrier configured to contact the surface plate;
A surface plate motor for driving the surface plate, and a pressure plate motor for individually driving the pressure plates;
A current detector connected to at least one of the surface plate motor and the pressure plate motor to detect a driving current, and an inflection point detection for detecting an inflection point at which the current value changes and terminating polishing. A control device comprising a device,
It has a thickness sensor that measures the thickness of the workpiece, holds the inflection point detection device of the control device in an off state for a while after the workpiece polishing starts , and measures the workpiece measured by the thickness sensor A timing setting device that switches the inflection point detection device to an on state when the difference between the thickness and the target thickness is a certain value or less ;
An apparatus for polishing a workpiece, comprising:

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