JP2012006123A - Cleaning method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cleaning method effectively removing grinding dust clogging holes of a holding unit of a holding table formed of a porous ceramic and restoring a suction force of the holding unit.SOLUTION: After a ground workpiece is conveyed out of the holding unit 21 of the holding table 20, fluid mixture of water and air is supplied to the holding unit 21 and is blown out from the holding unit 21, the inside of the holding unit 21 is thereby cleaned, and the grinding dust clogging the holes inside the holding unit 21 is removed.

Description

  The present invention relates to a cleaning method for cleaning a holding portion of a holding table that is provided in a grinding apparatus and sucks and holds a workpiece to be ground by negative pressure.

  In a semiconductor device manufacturing process, a semiconductor wafer on which a large number of electronic circuits such as IC and LSI are formed on the front surface is ground by a grinding device before being divided into chips and thinned to a predetermined thickness. Yes. As a grinding apparatus for performing back surface grinding of a semiconductor wafer, a turntable disposed rotatably along a workpiece attachment / detachment region and a processing region, and disposed on the turntable and sequentially moved to the processing region, A plurality of holding tables that adsorb and hold the substrate by negative pressure action, and a grinding means provided with a grinding wheel that is disposed in the processing area and that grinds the back surface of the work held on the holding table positioned in the processing area Are known (see Patent Document 1).

JP-A-10-86048

  In the holding table, generally, a holding portion that holds a workpiece by suction is made of a porous ceramic. For this reason, there has been a problem that the grinding waste enters the hole of the holding portion and becomes clogged while repeating the grinding process, and the suction force is reduced.

  The present invention has been made in view of the above circumstances, and its main technical problem is to effectively remove grinding debris clogged in the hole of the holding part of the holding table made of porous ceramic, and An object of the present invention is to provide a cleaning method capable of recovering the suction force.

  The cleaning method of the present invention includes a holding table for holding a workpiece and a grinding means for grinding the workpiece held on the holding table, and the holding table is a porous ceramic that holds the workpiece by suction. The holding unit of the grinding apparatus having the formed holding unit, a frame surrounding the holding unit, and a suction communication path that communicates the holding unit with a suction source that generates a suction force in the holding unit is cleaned. In the cleaning method, the grinding apparatus includes an air communication path that communicates the holding unit with an air supply source that supplies air to the holding unit, and a water supply source that supplies water to the holding unit. A water communication passage for communicating, a step of holding the workpiece by the holding portion of the holding table, a step of grinding the workpiece held by the holding table by the grinding means, and after grinding Holding table A step of unloading the workpieces from the said holding part, characterized in that it comprises a, a step of washing the holder mixed fluid is supplied to the air and water in the holding portion of the holding table.

  According to the present invention, after the ground workpiece is carried out from the holding part of the holding table, by supplying a mixed fluid of air and water to the holding part, grinding waste clogged in the hole of the holding part is released. And the holding part is washed. For this reason, the suction force of the holding part is restored.

The work referred to in the present invention is not particularly limited. For example, semiconductor wafers made of silicon, gallium arsenide (GaAs), silicon carbide (SiC), etc., ceramics, glass, sapphire (Al ₂ O ₃ ) -based inorganic materials Substrate, plate-like metal or resin ductile material, flatness on the order of micron to submicron (TTV: total thickness variation-the entire surface to be ground of the workpiece measured in the thickness direction based on the surface to be ground of the workpiece Examples of various processing materials that require a difference between the maximum value and the minimum value).

  According to the present invention, it is possible to provide a cleaning method capable of effectively removing grinding dust clogged in the hole of the holding portion of the holding table made of porous ceramic and recovering the suction force of the holding portion. Play.

It is a perspective view of a grinding device which has a holding part of a holding table cleaned with a cleaning method concerning one embodiment of the present invention. It is a disassembled perspective view of the holding table. It is sectional drawing of the same holding table. It is a top view which shows the positional relationship of the workpiece | work located in the process position, and the grinding process means. It is a piping diagram for holding | maintenance part washing | cleaning and workpiece | work adsorption | suction holding | maintenance provided in the grinding apparatus of one Embodiment.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
(1) Configuration of Grinding Apparatus A grinding apparatus according to an embodiment will be described with reference to FIG. The grinding apparatus 10 uses, for example, a disk-shaped semiconductor wafer having a thickness of about 700 μm as a workpiece, and horizontally holds such a workpiece on a vacuum chuck type holding table 20 so as to process a workpiece surface. Is exposed to the upper side and the workpiece surface is ground by the grinding means 30 to process the workpiece to a predetermined thickness. The holding table 20 has a holding part 21 on the surface side for adsorbing and holding the work by a negative pressure action, and in this embodiment, the holding part 21 is cleaned together with the grinding of the work.

  The grinding device 10 has a rectangular parallelepiped device base that is long in the X direction. A rectangular table base 25 is provided on the apparatus base 11 so as to be movable in the X direction. A vacuum chuck type holding table 20 is supported on the table base 25 so as to be rotatable about the Z direction (vertical direction) as the rotation axis direction.

  As shown in FIGS. 2 and 3, the holding table 20 includes a frame body 22 formed in a disk shape with a solid material such as stainless steel, and the holding section 21 surrounded by the frame body 22. I have. The frame body 22 is formed in a dish shape having an outer peripheral edge portion 221 and a bottom portion 222, and a suction hole 223 is formed through the center of the bottom portion 222. The suction hole 223 communicates with a suction source 70 that generates a suction force in the holding unit 21 via a supply / suction tube unit 63 and a suction tube unit 73 shown in FIG.

  An annular step portion 224 that is continuous with the bottom portion 222 is formed on the inner peripheral surface of the outer peripheral edge portion 221 of the frame body 22, and a plurality of partitions 225 having the same height as the step portion 224 are formed on the bottom portion 222. A plurality are formed in the radial direction. In this case, the partitions 225 are concentrically centered around the suction hole 223 and intermittently arranged in the circumferential direction. A plurality of suction grooves 226 along the radial direction and the circumferential direction are formed between the partitions 225 and between the outermost partition 225 and the step portion 224. These suction grooves 226 communicate with the suction holes 223.

  The holding portion 21 is formed in a disk shape from porous ceramic, and is fitted to the upper portion of the frame body 22 while being placed on the step portion 224 and each partition 225. As shown in FIG. 3, the upper surface of the holding portion 21 is flush with the horizontal upper surface of the outer peripheral edge portion 221 of the frame body 22, and the upper surface of the holding portion 21 is configured as a holding surface 211 that holds the workpiece 1 by suction. Has been. The suction groove 226 of the frame 22 is covered with the holding part 21, and the suction groove 226 and the suction hole 223 constitute a suction communication path that allows the holding part 21 to communicate with the suction source 70.

  The holding table 20 is reciprocated between the loading / unloading position at the front end (X1 side) and the processing position on the back side (X2 side) by moving the table base 25 in the X direction in FIG. . The apparatus base 11 is provided with a moving mechanism for moving the table base 25 in the X direction, and the table base 25 is provided with a rotation drive mechanism for rotating the holding table 20 (all not shown). On both sides of the table base 25 in the moving direction, a telescopic bellows-like cover 12 is provided that covers the moving path of the table base 25 and prevents grinding dust or the like from falling into the apparatus base 11.

  The holding table 20 is initially positioned at the carry-in / out position, and a work is placed on the holding surface 211 of the holding unit 21 of the holding table 20 by the operator. Then, the suction source 70 is operated, and thereby the workpiece is sucked and held on the holding surface 211 by the negative pressure generated on the holding surface 211 (step of holding the workpiece). The workpiece has the same diameter as the holding portion 21 and is placed concentrically on the holding surface 211. The operation in which the suction source 70 operates and the work is sucked and held by the holding portion 21 will be described later.

  When the workpiece is sucked and held by the holding portion 21 of the holding table 20, the table base 25 is moved in the X2 direction in FIG. 1, and the workpiece is positioned at the machining position and is disposed opposite to the upper grinding means 30.

  As shown in FIG. 1, the grinding means 30 is disposed on the front side of the column 13 erected on the rear end portion (X2 side end portion) of the apparatus base 11. A slider 15 is attached to the front surface of the column 13 through a pair of Z-axis guides 14 so as to be movable up and down along the Z direction. A grinding means 30 is fixed to the slider 15.

  The grinding means 30 is a flange-shaped wheel provided at the lower end of a spindle shaft, in which a spindle shaft (not shown) is coaxially and rotatably incorporated in a cylindrical spindle housing 31 whose axial direction extends in the Z direction. A grinding wheel 33 is detachably fixed to the mount 32. A motor part 34 is provided at the upper end of the spindle housing 31, and the spindle shaft is rotationally driven by the motor part 34.

  The grinding wheel 33 is composed of an annular base portion 331 that is detachably fixed to the lower surface of the wheel mount 32, and a large number of grindstones 332 that are annularly arranged and fixed to the outer peripheral portion of the lower surface of the base portion 331. It is what is done. As the grindstone 332, a material suitable for the workpiece is used, for example, a diamond grindstone formed by solidifying diamond abrasive grains with a binder such as a metal bond or a resin bond. The grinding wheel 33 is rotationally driven integrally with the spindle shaft by the motor unit 34.

  In the grinding means 30, the spindle housing 31 is fixed to the slider 15 via the holder 35 in a state where the wheel mount 32 is disposed below and the axial direction is parallel to the Z direction. The slider 15 includes a ball screw 361 that is disposed between the pair of Z-axis guides 14 and that is coupled to the slider 15 while being screwed together, and a servo motor 362 that rotationally drives the ball screw 361. It is driven up and down by the processing feed means 36. Therefore, the grinding means 30 is moved up and down integrally with the slider 15 by the work feeding means 36.

  The workpiece positioned at the machining position is ground at the workpiece surface exposed by the grinding means 30 and thinned to a target thickness (step of grinding the workpiece). Grinding by the grinding means 30 is performed together with the slider 15 by the work feeding means 36 while rotating the grinding wheel 33 by operating the motor unit 34 and rotating the holding table 20 in one direction to rotate the workpiece. This is done by lowering the means 30 and pressing the grindstone 332 of the rotating grinding wheel 33 against the work surface of the workpiece. At the time of grinding, for the purpose of lubrication, cooling, cleaning, etc., a grinding fluid is supplied from the base portion 331 of the grinding wheel to the work surface of the workpiece.

  FIG. 4 shows the positional relationship in the horizontal direction between the workpiece 1 and the grinding wheel 33 positioned at the machining position. As shown in the figure, the grinding outer diameter of the grinding wheel 33 (the outermost diameter of the rotation trajectory of the grindstone 332) is set to be approximately the same as the diameter of the workpiece 1. Further, the processing position of the workpiece 1 is set to a position where the cutting edge which is the lower surface of the grindstone 332 passes through the rotation center of the rotating workpiece 1. Then, the entire work surface is ground by pressing the grindstone 332 of the grinding wheel 33 against the work surface of the work 1 while rotating the holding table 20 in one direction to rotate the work 1.

  The thickness of the workpiece during grinding is measured by a thickness measuring means (not shown). The machining feed operation of the grinding means 30 by the machining feed means 36 is controlled based on the thickness measurement values measured one by one by the thickness measuring means. When the measured thickness value reaches the target value, the grinding means 30 is raised to separate the grindstone 332 from the workpiece, and the grinding process is terminated. After completion of the grinding process, the table base 25 is moved in the X1 direction in FIG. 1 to return the workpiece to the carry-in / out position and stop the rotation of the holding table 20. Then, the holding and holding of the work by the holding table 20 is released, and the ground work is carried out from the holding table 20 and transferred to the next process (process for carrying out the work).

(2) Cleaning of holding part After the work is carried out from the holding part 21 of the holding table 20, the holding part 21 is then cleaned. The grinding apparatus 10 has a piping system for cleaning the holding unit 21 shown in FIG. First, this piping system will be described.

(2-1) Piping system Reference numerals 40 and 50 in FIG. 5 denote a water supply source and an air supply source, respectively. A water supply pipe part 41 is connected to the water supply source 40, and an air supply pipe part 51 is connected to the air supply source 50. The water supply pipe part 41 and the air supply pipe part 51 are joined at a joining point 60, and a joining pipe part 61 on the downstream side of the joining point 60 is connected to the holding table 20 via the supply / suction pipe part 63. The frame body 22 is connected to the suction hole 223. A solenoid valve 62 is provided in the junction pipe portion 61.

  In the water supply pipe section 41 and the air supply pipe section 51, open / close valves 42 and 52 are provided in the vicinity of the water supply source 40 and the air supply source 50, respectively. A water flow meter 43 and a check valve 44 are provided from the upstream side between the open / close valve 42 and the junction 60 in the water supply pipe 41, and the open / close valve 52 and the junction 60 in the air supply pipe 51 are connected. An air flow meter 53 and a check valve 54 are provided between them on the upstream side.

  Further, a suction air supply pipe portion 71 branches from between the open / close valve 52 and the air flow meter 53 in the air supply pipe portion 51. An exhaust port 72 is provided at the end of the suction air supply pipe 71. A suction pipe portion 73 branched from the supply / suction tube portion 63 is joined to the suction air supply pipe portion 71, and the joining point generates a suction source 70 that generates a suction force on the holding portion 21 of the holding table 20. It is configured as.

  A solenoid valve 74 is provided in the middle of the suction pipe portion 73. When the solenoid valve 74 is opened and the solenoid valve 62 of the merging pipe portion 61 is closed, the open / close valve 52 is opened and air is supplied from the air supply source 50 to the air supply pipe portion 51. Due to the flow of air that flows through 71 and is discharged from the exhaust port 72, the suction pipe portion 73 becomes negative pressure. Then, the negative pressure of the suction pipe portion 73 is transmitted to the holding portion 21 through the supply / suction pipe portion 63, the suction hole 223 of the frame body 22, and the suction groove 226, and suction force is generated in the holding portion 21. . In the above-mentioned “step of holding the workpiece”, the suction source 70 is brought into an operating state in this manner, whereby a negative pressure is generated on the holding surface 211 of the holding portion 21 and the workpiece is sucked and held on the holding surface 211. .

  In FIG. 5, the supply path of water or water and air is indicated by a one-dot chain line, the supply path of air is indicated by a solid line, and the suction path for generating a suction force on the holding portion 21 of the holding table 20 is indicated by a broken line. In this embodiment, the water supply pipe portion 41, the merging pipe portion 61 and the supply / suction pipe portion 63 constitute the water communication passage of the present invention, and the air supply pipe portion 51, the merging pipe portion 61 and the supply / suction pipe portion 63. Thus, the air communication path of the present invention is configured.

(2-2) Step of Cleaning the Holding Unit When the workpiece is returned to the loading / unloading position after the grinding process is finished, the solenoid valve 74 of the suction pipe portion 73 is closed to stop the operation state of the suction source 70, thereby holding the holding table. The suction holding of the work by the 20 holding portions 21 is released. Thereafter, the holding unit 21 is washed by the following operation.

  That is, the open / close valves 42 and 52 of the water supply pipe 41 and the air supply pipe 51 are opened while the solenoid valve 62 of the merging pipe 61 is opened and the solenoid valve 74 of the suction pipe 73 is closed. And Then, the water supplied from the water supply source 40 passes through the water supply pipe 41 and reaches the solenoid valve 62 of the merge pipe 61, and the air supplied from the air supply 50 joins through the air supply pipe 51. The solenoid valve 62 of the pipe part 61 is reached.

  Water and air merge at the merge point 60 and pass through the solenoid valve 62 to become a mixed fluid. The mixed fluid of water and air flows through the supply / suction pipe portion 63 and reaches the holding portion 21 through the suction hole 223 of the frame body 22 and the suction groove 226. The mixed fluid blows upward from the holding surface 211 through the hole in the holding unit 21 from the lower surface of the holding unit 21. As a result, the hole in the holding part 21 is washed, and when grinding waste generated during grinding of the workpiece enters the hole and is clogged, the grinding waste is discharged and removed from the holding part 21.

  In addition, as shown in FIG. 3, there is a case where the grinding dust 2 adheres to and accumulates in an inner corner portion formed by the bottom portion 222 of the frame body 22 and the partition 225 or the step portion 224. Such grinding scraps 2 are difficult to be removed by simple fluid contact, but are easily separated and removed by covering the suction grooves 226 with a mixed fluid in a bubble shape by flowing in a labyrinth.

  The pressure and flow rate of water supplied from the water supply source 40 and the pressure and flow rate of air supplied from the air supply source 50 when washing the holding unit 21 are appropriately set so that an appropriate mixed fluid is generated. Set to For example, the ratio of the flow rate of water and air is preferably about water: air = 7: 3, and the actual flow rate is about 20.0 L / min for water and about 8.6 L / min for air. The pressure is preferably 0.2 to 0.3 MPa (preferably around 0.3 MPa) for water and 0.5 to 0.8 MPa for air. The flow rate of water can be controlled while checking the water flow meter 43, and the flow rate of air can be controlled while checking the air flow meter 53. Moreover, the pressure of water and air is controlled while confirming with each pressure gauge (not shown).

  When the cleaning process for supplying the mixed fluid to the holding unit 21 is performed for a predetermined time, the solenoid valve 62 of the merging pipe portion 61 is closed to stop the supply of the mixed fluid. In this state, a new workpiece is placed on the holding portion 21 of the holding table 20, and the solenoid valve 74 of the suction pipe portion 73 is opened to operate the suction source 70, and the above grinding process is repeated.

(2-3) Effect of One Embodiment According to the present embodiment, after a ground workpiece is carried out from the holding portion 21 of the holding table 20, a mixed fluid of water and air is supplied to the holding portion 21 and held. By blowing out from the portion 21, the hole in the holding portion 21 is washed, and when the grinding dust is clogged in the hole, the grinding dust is removed from the holding portion 21. For this reason, the clogging of the holding part 21 due to the grinding dust is eliminated, and the suction force of the holding part 21 is recovered.

  The holding unit 21 may be cleaned every time one workpiece is ground, or intermittently every time a predetermined number of workpieces are ground. Furthermore, it may be performed at a stage where the reduction of the suction force of the holding portion 21 is recognized.

DESCRIPTION OF SYMBOLS 1 ... Work 10 ... Grinding device 20 ... Holding table 21 ... Holding part 22 ... Frame body 223 ... Suction hole (suction communication path)
226 ... Suction groove (suction communication path)
DESCRIPTION OF SYMBOLS 30 ... Grinding means 40 ... Water supply source 41 ... Water supply pipe part (water communication channel)
50 ... Air supply source 51 ... Air supply pipe (air communication passage)
61 ... Junction pipe section (water communication passage)
63 ... Supply / suction pipe section (water communication passage)
70 ... suction source

Claims (1)

A holding table for holding the workpiece, and a grinding means for grinding the workpiece held on the holding table,
The holding table includes a holding portion formed of a porous ceramic for sucking and holding a workpiece, a frame surrounding the holding portion, and a suction communication that connects the holding portion to a suction source that generates a suction force in the holding portion. A cleaning method for cleaning the holding part of the grinding device having a passage,
The grinding apparatus includes:
An air communication path for communicating the holding unit with an air supply source for supplying air to the holding unit;
A water communication path for communicating the holding unit with a water supply source for supplying water to the holding unit;
Have
Holding the workpiece with the holding portion of the holding table;
Grinding the workpiece held on the holding table with the grinding means;
A step of unloading the workpiece from the holding portion of the holding table after grinding;
Supplying a mixed fluid of air and water to the holding unit of the holding table to wash the holding unit;
A cleaning method comprising:

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