JPS5919672A - Working pressure control device for polishing apparatus - Google Patents

Abstract

PURPOSE:To control smoothly working pressure for high accuracy polishing in a working pressure control device used for polishing wafers or the like by using an apparatus for continuously changing the pressure to gradually increase or decrease the working pressure relative to time axis. CONSTITUTION:To gradually increase working pressure of a pair of surface tables 10, 11 to shift a polishing device from the pressure reducing working to the own weight one, the set voltage of a desired value setter 21 in a control device 20 is altered from Va to zero, the down signal is sent from a comparator 23 to an up-down counter 26 so that the counter 26 is subjected to substraction by pulses from a voltage frequency converter 25 according to which the control signal Vt is reduced and secondary pressure P2 in a lower cylinder chamber 13b is reduced toward zero to increase the working pressure of a upper surface table 10. The rate of increasing pressure determines pulse frequency from the converter 25 by the value of set voltage VR1 of an inclination setter 24 in the control device 20 to gradually increase with a proper gradient the working pressure reaching from the working pressure in the pressure reducing working to that in the own weight working.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polishing apparatus for polishing a workpiece such as a wafer, and more particularly to an apparatus for controlling the processing pressure of the workpiece.

71? IJ shing processing is generally performed under pressure because the higher the processing pressure is, the faster the polishing is done, and the processing pressure for wafers is 100 to 300 f/cn.
? is considered appropriate. However, if this processing pressure is applied to the wafer from the beginning of processing, there are problems such as scratches and cracks occurring, and insufficient accuracy in parallelism, flatness, etc. For this reason, generally, at the start of machining, the machining pressure is extremely light and a break-in operation is performed, and after some time has elapsed, the machining pressure is reduced to zero in two or three stages to the above-mentioned 100 to 300 rpm. I was trying to move it to .

By the way, this type of conventional equipment uses a preset pressure to clamp the workpiece at a pressure such as air pressure, which is controlled by a pressure setting device such as a plurality of pressure reducing valves, which is set to a pressure corresponding to the processing pressure for each step. The processing pressure was changed by sequentially applying pressure to the plate, but this method was not suitable for polishing wafers, which required delicate precision, and it was difficult to obtain high-quality sea urchins. There were no drawbacks.

The present invention has been made in view of the above-mentioned points, and uses a device capable of continuously changing pressure, such as an electro-pneumatic converter, to gradually increase or decrease the machining pressure over time, thereby increasing or decreasing the machining pressure over time. To provide a processing field force control device for a polishing device which allows pressure to be smoothly opened.

1 to 3 showing one embodiment of the present invention will be explained below. In FIG. 1, 1° is an upper surface plate, and 1° is a lower surface plate, which are rotated separately by drive devices not shown. Fixed position qxo is free rotation joint 1
The piston 14 of the cylinder 13 is connected to the piston 14 of the cylinder 13 via the piston 2, so that the piston 14 can move up and down. FiiJ upper and lower surfaces (Qfzo, polishing cloth 10a on the opposing surfaces of xz.

11a are provided, and these polishing cloths 10a.

A workpiece 15 such as a wafer is rotated through the upper and lower constant f4xo and zz via 11a. In addition,
The workpiece 15 is fitted into a carrier (not shown), and is moved along a predetermined trajectory between the polishing cloths 10a and 113 by revolving and rotating the carrier using a drive device (also not shown). The explanation of the mechanism will be omitted.

Upper and lower cylinder chambers 13a of the WiJ control cylinder 13.

13b is connected on four sides to a pneumatic pressure source 18 via a magnetic valve 16 and an electropneumatic converter 17. [The magnetic valve 16, in the neutral position shown in FIG. , 1st
When switched to the lower position 16m in the figure, the secondary side circuit 19 is connected to the lower cylinder chamber 13b, and the upper cylinder chamber 9 chamber 13m is opened to the atmosphere, and further switched to the upper position 16b in Figure 1. When the secondary side circuit 19 is connected to the upper cylinder chamber 13m, the lower cylinder chamber 13b is opened to the atmosphere. The electro-pneumatic converter 17 is a control device 2
The primary pressure P from the air pressure source 18 is converted into the secondary pressure Pt by the control signal V (tl) from the air pressure source 18.

FIG. 2 shows a specific example of the irJ electropneumatic converter 17 and the arsenic control device 20. 21 is a target value setting section that sets the desired secondary pressure P! The voltage EEV is generated according to the voltage EEV, and the voltage (2) is applied to the comparator 23 via the switch 22 in response to the operation signal. Note that this target value setting section 21 changes the target value according to a predetermined program as the operating time progresses, or changes the target value to the target value according to a predetermined program as the operating time progresses, or
), several types of target values are set in each target value setting section 21 according to the program, and each target value setting section 21 is selected and connected to the comparator 23 as the program progresses. There is. Reference numeral 24 denotes a slope setting unit, which sets the slope of the temporal change in the rate of increase or decrease of the secondary pressure P with respect to the time axis, that is, the secondary EEP, and is configured to generate 'KlfVRI according to the set value. It has become. With a 25V voltage frequency converter,
It generates a pulse with a frequency proportional to the voltage VRI from the slope setting section 24. Reference numeral 26 denotes an up/down counter, which uses a comparator 23 to determine whether the new target value set by the target value setting unit 21 increases or decreases with respect to the old target value, and determines whether the comparator 23 outputs an around f signal up or a down signal down. Depending on the temperature, either addition or subtraction is performed. Reference numeral 27 denotes a D/A converter, which generates a control signal ('RL) V(t) corresponding to the count number in the up/down counter 26. This control signal V (0 is applied to the comparator 23, and when the voltage matches the target value V, the up/down signal UP or the down signal dowyl is cut off and the up/down counter 26 stops counting. 1]/The control signal v (tl) from the converter 27 is applied to the force smoke section 171 of the electro-pneumatic converter 17.

The force smoke section 171 moves the flannel/4172 back and forth according to the value of the control signal V (t), changes the gap X between the tip of the nozzle 173 provided opposite to the flapper 172, and backpressures Pn of the nozzle 173. is changed according to the control signal v (t). The back [1:Pn is the primary pressure P that is led to the pressure control oil well 174 as a pilot pressure and is supplied from the air source 18 by this pressure control valve 174.

is set to the back pressure Pn, that is, the secondary IP having a value corresponding to the control signal V (t).

Next, the operation of this device will be explained. At the start of operation, 'K E Vmax corresponding to the highest pressure P, max of the secondary pressure P2 is set as the operating pressure in the target value setting unit 21. Therefore, the up/down counter 26 counts a number corresponding to the operating pressure P, max, and the control signal V (t) corresponding to the counted number is D/A.
The Furano 4172 taken out from the converter 27 and attached to the force smoke part 17 is brought closest to the tip of the nozzle 173 to increase the nozzle back pressure Pn and close the pressure control valve 1.
The secondary pressure Pt from 74 is increased to the operating pressure P, mix. In this state, when the four-way solenoid valve 16 shown in FIG. 1 is switched to the lower position J e a , the operating pressure P
The pressurized air to the max reaches the lower cylinder chamber 13b.
The piston 14 is raised to the free rotation joint 12.
The upper surface plate 10 is raised via the upper surface plate 10. After opening between the upper and lower surface plates 10 and 11 in this way, the polishing cloth I on the lower surface plate 11
The workpiece 15 is fitted into a hole in a carrier (not shown) on Is. Next, the four-way magnetic valve 16 is switched to the upper position 16b, pressurized air is supplied to the upper cylinder chamber 13a, the upper surface plate 10 is gently lowered, and the upper surface plate 10 is placed on the workpiece 15. rain down When the fixed position lX111o is lowered, switch the four-way solenoid valve 16 to the neutral position,
, 13b to the atmosphere. Therefore, when the four-way solenoid valve 16 is in the neutral position, no pressure acts on the piston 14, but the weight of the upper surface plate 1o acts on the workpiece 15. Due to the weight of the upper surface plate 10, the workpiece 1
The pressure acting between 5 and the upper and lower surface plates 10 and 11 is called self-weight pressure, and polishing using this self-8X royal force as described later is called dead-weight processing.

When the polishing process is completed in this way, the set value of the target value setting section 2 is set to a value corresponding to the first stage process pressure pa shown in FIG.

However, in this example, as will be described later, the processing pressure (self-weight pressure) during NiJ self-weight processing is set to be the processing pressure Pb of the second stage 1@ shown in FIG. During machining, the secondary pressure P from the electro-pneumatic converter 17 is applied to the lower cylinder chamber 13b. The voltage Va set to the setting device 21 is set to a value corresponding to the absolute value of the difference between the second stage machining pressure Pb and the first stage machining pressure Pa.

The set value of the target value setter 2 changes from a high value V max corresponding to the first operation E P 2 max to a predetermined value corresponding to the machining pressure Pa during the first stage vacuum machining as shown in mJ. When the value Va is changed to a lower value, the comparator 23 sends a down signal down to the up/down counter 26. Therefore, the up/down counter 26 is decremented by the pulses sent from the voltage same wave number converter 25.
The count number in the up/down counter 26 gradually decreases, and the control signal V (t) output from the D/man converter 27 also gradually decreases, causing the gap between the flutter 172 and the nozzle tip 173 to decrease is opened to lower the nozzle back pressure Pn and lower the secondary pressure P. In this way, when the control signal v(1) reaches the voltage Va newly set in the target value setter 2, the down signal down turns OFF and the up/down counter 26 stops counting. Therefore, the count in the up/down counter 26 stops counting at a number corresponding to the set voltage Va, and thereafter remains at that number. Therefore, the secondary pressure P of the electropneumatic converter 17! is the pressure P according to the set voltage Va written in qrJ! a
is maintained.

In this way, the secondary pressure P of the electropneumatic converter 17! When P and a are determined to be the pressures P and a during the first stage of pressure reduction processing, the four-way solenoid valve 16
is switched to the lower position 16a, and the secondary pressure P, that is, the pressure P,a is supplied to the lower cylinder chamber 13b. These pressures P and a are insufficient pressures to raise the upper surface plate 1θ, and the workpiece 15 is simply caused by the own weight of the upper surface plate 10.
The pressure between the workpiece 15 and the upper and lower surface plates 10. The processing pressure is reduced to Pa during vacuum processing.

Next, the upper and lower surface plates 7 o and 11 are rotated by a drive device (not shown), and the workpiece 15 is moved by a carrier and its drive device (also not shown) to perform porin-lag processing. After the pressure reduction machining using the machining pressure Pa has been performed for a predetermined time t1, the set voltage of the target value setter 21 is changed to a value vb corresponding to the second stage machining pressure Pb shown in FIG.

However, in this embodiment, an example in which dead weight processing is performed in the second stage will be described. Therefore, the second stage setting tEEvb
is set to zero. 3. When the set voltage of the target value setter 2 is changed from Va to zero, the comparator 23 sends the down signal down to the up/down counter 26 again.

Therefore, the up/down counter 26 is subtracted by the pulses from the voltage IN wave number converter 25, and the number therein gradually decreases, and accordingly, IIIJ 1fll
The signal v(t) also decreases, causing the secondary pressure P acting on the lower cylinder chamber 13b to decrease from P,a toward zero. As the secondary pressure P decreases, the force acting on the upper surface plate 10 against its own weight decreases, so the processing pressure increases from Pa toward Pb as shown in FIG. The rate of increase in the processing pressure is determined by the rate at which the numerical value in the up/down counter 26 decreases. This up/down counter 2
The decreasing speed of the numbers in 6 is the electric FEM wave number converter 25
The frequency of this arm pulse is determined by the set voltage VRJ of the slope setting section 24, so by setting this set voltage vp1 to a desired value or changing the set voltage midway, The increase in the processing pressure from the processing pressure Pa during reduced pressure processing to the processing pressure Pb during self-weight processing can be gradually increased using an appropriate gradient or curve.

When the up/down counter 26 continues to subtract and the value therein becomes zero, the control hm signal V (t) also becomes zero, the down signal down is turned OFF' to stop counting, and from then on the control signal V (t) is kept at zero. Therefore, electropneumatic converter 1
The secondary cE p t of No. 7 becomes zero, the machining pressure is smoothly changed from Pa to Pb, and the process shifts from vacuum machining to self-weight machining.

During this self-weight machining, 40,000 electric current (Shigeru valve 16 was moved to upper position 16b)
Switch to In this way, self-weight processing is performed for a certain period of time,
At time t from the start of machining, the set voltage of target value setter 210 is changed from zero to voltage VC corresponding to the third stage machining pressure Pc. This voltage VC is the processing pressure pb
The value corresponds to the difference between and Pc. Since this setting 1σ, change is a change from zero to a larger value VC,
By changing the set voltage, the converter 23 sends an up signal UP to the up/down counter 26. Therefore, this up/down counter 26 adds pulses of a predetermined ad wave number from the electro-pneumatic converter 25 and continues adding them until the control signal V (t) reaches the set voltage VC. Since the secondary pressure P2 of the wax which gradually increases the secondary EEP of 17 acts on the upper cylinder chamber 13a,
Due to this increase in the secondary pressure P, the machining pressure gradually increases from the pressure pb toward Pc as shown in FIG. 3, and becomes stable when the machining pressure Pc is reached. The processing pressure Pc at this third stage is the pressure at which the porin lag processing can be carried out most efficiently, and this third stage processing is called pressure processing.

The pressure processing is performed for a predetermined period of time, time t3 from the start of processing.
When this happens, the actual porin rug processing is completed and the cleaning process begins. In the subsequent rp step, the surface pressure between the workpiece 15 and the upper and lower surface plates 10.11, which corresponds to the machining pressure, is Pdl/1m-f shown in Figure i3. This surface pressure I'
As shown in FIG. 3, d is a value lower than the machining pressure pb during self-weight machining, so when the time reaches t, the set voltage V of the target value setting unit 21 is first changed to zero. do. By changing this set voltage V, the secondary pressure P of the electro-pneumatic converter 17! gradually decreases, and the surface pressure decreases to the machining pressure Pb during self-weight machining.

When the nuclear surface field drops to Pb, that is, when the secondary lfpt becomes zero, the four-way solenoid valve 16 is immediately moved to the lower position 16a.
At the same time, the set voltage V of the target value setting section 2 is changed to a voltage Vd according to the absolute value of the difference between the machining pressure Pb and the surface pressure Pd.
change to E. By changing the set voltage V of the target value setting section 21, the old secondary pressure P! increases again. At this time, since the second Suita P is acting on the lower cylinder chamber 13b by changing the VJ of the four-way solenoid valve 16 described in 1iJ, the surface pressure corresponding to the machining pressure is increased by the gradual increase of the secondary pressure P. It gradually decreases and becomes stable when the surface pressure reaches Pd, as shown in FIG. When the cleaning process is continued for a predetermined time due to this surface pressure Pd, and time t4 has elapsed from the start of machining, the set voltage (■) of the target value setting unit 21 is changed from the above-mentioned Vd to Vmaz corresponding to the above-mentioned operating pressure P, max. do. By changing this set voltage, the secondary pressure P, gradually increases toward P,max. Therefore, the surface pressure corresponding to the processing pressure 1iiJ increases by tυ16 from Pd toward zero. When this surface pressure approaches zero, the rotation of the upper and lower surface plates 10, 11 and the movement of the workpiece 15 by a carrier (not shown) are stopped. Even after these stops, the secondary pressure P continues to rise, and the surface pressure becomes zero. After that, the secondary pressure P continues to rise toward the operating pressure Pg-max, so the secondary pressure P,
The pushing up force of the upper surface plate 10 overcomes the dead weight pressure of the upper surface plate 10 and raises the stationary setting M1', making it possible to take out the workpiece 15 and completing the 7Jq ridging process.

Furthermore, the above-mentioned changes in the set voltage V of the target value setting section 21, switching of the 4-way electric 1 intake valve 16, and changes and adjustments of the set voltage VRz of the inclination setting section 24 are performed according to a program prepared in advance. done automatically.

FIG. 4 shows another embodiment of the present invention, in which the charging voltage of the capacitor 30 is applied to the electro-pneumatic converter 17 as a control signal V (t), and the voltage applied to the capacitor 30 is set to a target value. The setting section 21a can be used to sequentially change the voltage applied to the capacitor 30, and the slope setting section 24a can appropriately determine the charging and discharging currents associated with changes in the voltage applied to the capacitor 30 to set the gradual increase and decrease ratios to predetermined values. This is what I did. - "In other words, when the set voltage VRI of the target value setting section 21a is increased, the main power supply 3 is connected to the target value setting section 218X, the first trannosk 32, the resistors 34, 35,
Current flows to the capacitor 30 via the first diode 36 and the pace and collector of the second transistor 33,
Charging 41 of this capacitor 30! The current flowing from the main power supply 31 to the capacitor 30 is controlled by the voltage applied from the auxiliary power supply 38 to the pace of the first transistor 32 via the ramp setting B 24 a, The rate of increase of the charging N voltage of 30, that is, the control signal V(t) is set to a predetermined value, and when the control signal, that is, the charging voltage V(t) reaches the set voltage R, charging of the capacitor 30 is stopped. The control signal V (t) is stabilized at a value equal to the set chamber EEvR. On the other hand, when the set voltage VIlz of the target value setting section 21a is decreased, the voltage from the capacitor 30 to the second transistor 33 and the resistor 35
, 34, second diode 37, first transistor 320
It is discharged to the lower output line via the base, collector and target value setting section 21a, lowering the control signal vH. The value of the discharge current at this time, that is, the control signal V
(t) is calculated from the slope setting section 24a by the auxiliary power source 38.
is controlled by the voltage applied to the second transistor 33 through the gate.

The embodiment described above shows an example in which the pressure supplied to the cylinder 13 is electrically controlled, but the pressure may also be changed mechanically at a predetermined speed. Various separate image methods may be employed. In addition, in the former embodiment described above, since the processing pressure Pb of the second stage shown in FIG. Voltage Va, Vc according to the absolute value of the difference with pressure pb as a reference
An example was shown in which the setting value is set to the target value setting unit 21.
When all machining processes are performed only by depressurization machining in which secondary IfP is applied to the lower cylinder chamber 13b, or by pressurization machining in the opposite manner, N'll W + Membrane setting value each machining pressure P8. Pb.

It may be simply decreased or increased depending on Pc and Pd.

As described above, according to the present invention, it is possible to smoothly change the processing pressure during polishing from the initial low pressure to the optimum processing pressure, and it is possible to perform scratch-free polishing with higher precision. It is possible to provide an effective processing output side device.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing a specific example of the pressure control section, FIG. 3 is a characteristic diagram showing an example of changes in processing pressure during polishing processing, and FIG. FIG. 4 is a schematic circuit diagram showing another embodiment of the present invention. 10.11...Surface plate, 13...Cylinder, 15...
. 16... 4-way solenoid valve, 17... telegraph converter, 17... force smoke section, 172... 7 lattice, 173... nozzle, 174... I pressure Skin control valve, 18... Air pressure source, 20.20a... Collateral device,
21.21 a... Target value setting section, 23 ゛°° comparator, 24, 24a... Inclination setting section, 25...
Voltage frequency converter, 26... Up/down counter, 27... D/person converter, 30... Capacitor. Applicant's Representative Patent Attorney Takehiko Suzue Figure 1 "-1 = 22 Nienie - 11" Figure 3

Claims (2)

[Claims] (1) In a polishing device that can change the relative pressing force between a pair of surface plates that clamp a workpiece, a means for changing the pressing force is provided to gradually increase or decrease the pressing force with respect to a time axis. A processing pressure limiting device for a polishing device, which is characterized by: (2) The pressing force changing means includes a pressing force target value setting section,
2. The processing pressure differentiating device for a boring machine according to claim 1, further comprising a slope setting section for setting a gradual increase or decrease rate on the way to a target value.