JP5037255B2 - Grinding apparatus and observation method of grinding apparatus - Google Patents

Description

  The present invention relates to a grinding apparatus for observing a grinding state with grinding water containing grinding waste generated by grinding of a wafer, and an observation method for the grinding apparatus.

  A semiconductor wafer in which a number of devices such as IC and LSI are formed on the surface, and each device is partitioned by a line to be divided (street), the back surface is ground by a grinding machine and processed to a predetermined thickness. A dividing line is cut by a cutting device (dicing device) and divided into individual devices, which are used for electric devices such as mobile phones and personal computers.

  In order to reduce the size and weight of a semiconductor chip, a semiconductor wafer is usually cut along a predetermined dividing line and separated into individual devices (chips) by grinding the back surface of the wafer to obtain a predetermined chip. It is formed to a thickness.

  A grinding apparatus for grinding a back surface of a wafer includes a chuck table for holding a wafer, a grinding means for rotatably supporting a grinding wheel provided with a grinding wheel for grinding the wafer held by the chuck table, and a grinding region And a grinding water supply means for supplying the grinding water to the wafer, and the wafer can be processed to a predetermined thickness.

  However, the grinding device performs grinding by bringing the grinding means closer to the wafer held on the chuck table at a predetermined feed speed and bringing the grinding wheel of the grinding wheel into contact with the wafer to perform grinding. Has a problem that surface burn may occur on the wafer.

In order to solve this problem, Japanese Patent Application Laid-Open No. 7-249601 discloses a grinding apparatus that periodically and automatically cleans a grinding wheel to reduce the frequency of sharpening due to crushing of the grinding wheel. Has been.
JP 7-249601 A

  The grinding apparatus disclosed in Patent Document 1 aims to reduce the frequency of sharpening work (dressing) of the grinding wheel by automatically and periodically cleaning the grinding wheel, but the cleaning timing is set appropriately. There is a problem that it is difficult to do and lacks certainty.

  The present invention has been made in view of such a point, and an object of the present invention is to provide a grinding apparatus and a grinding apparatus observation method capable of constantly observing the state of the grinding apparatus.

According to the present invention, a grinding table having a chuck table for holding a wafer, a grinding wheel provided with a grinding wheel for grinding the wafer held by the chuck table, and a grinding water supply for supplying grinding water to a grinding region Means for observing the grinding state with grinding water containing grinding waste generated by grinding of the wafer held on the chuck table, the observation means comprising grinding waste A pH detection unit for detecting the pH of the grinding water, a temperature detection unit for detecting the temperature of the grinding water, and a particle size sensor for detecting the particle size of the grinding waste. There is provided a grinding apparatus characterized by observing the dressing time of a grinding wheel based on pH, temperature and the particle size of grinding waste contained in grinding water .

  Since the present invention is configured to observe the grinding state based on the grinding water containing grinding waste, the timing of dressing of the grinding wheel can be properly recognized.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an external perspective view of a grinding apparatus 2 for grinding the back surface of a wafer according to an embodiment of the present invention. The housing 4 of the grinding device 2 is composed of a horizontal housing part 6 and a vertical housing part 8.

  A pair of guide rails 12 and 14 extending in the vertical direction are fixed to the vertical housing portion 8. A grinding means (grinding unit) 16 is mounted along the pair of guide rails 12 and 14 so as to be movable in the vertical direction. The grinding unit 16 is attached to a moving base 18 that moves up and down along a pair of guide rails 12 and 14 via a support portion 20.

  The grinding unit 16 includes a spindle housing 22 attached to the support portion 20, a spindle 24 rotatably accommodated in the spindle housing 22, and a servo motor 26 that rotationally drives the spindle 24.

  As best shown in FIG. 4, a mounter 28 is fixed to the tip of the spindle 24, and a grinding wheel 30 is screwed to the mounter 28. The grinding wheel 30 is configured by adhering a plurality of grinding wheels 34 in which diamond abrasive grains or the like are hardened with an appropriate bonding agent such as resin bond or vitrified bond to a free end portion of a wheel base 32.

  Grinding water is supplied to the grinding means (grinding unit) 16 via a hose 36. Preferably, pure water is used as the grinding water. As shown in FIG. 4, the grinding water supplied from the hose 36 is formed in the grinding water supply hole 38 formed in the spindle 24, the space 40 formed in the mounter 28, and the wheel base 32 of the grinding wheel 30. It is supplied to the wafer W held on the grinding wheel 34 and the chuck table 54 via a plurality of grinding water supply nozzles 42.

  Referring again to FIG. 1, the grinding apparatus 2 includes a grinding unit feed mechanism 44 that moves the grinding unit 16 in the vertical direction along the pair of guide rails 12 and 14. The grinding unit feed mechanism 44 includes a ball screw 46 and a pulse motor 48 fixed to one end of the ball screw 46. When the pulse motor 48 is pulse-driven, the ball screw 46 rotates and the moving base 18 is moved in the vertical direction via the nut of the ball screw 46 fixed inside the moving base 18.

  A chuck table unit 50 is disposed in the recess 10 of the horizontal housing portion 6. As shown in FIG. 2, the chuck table unit 50 includes a support base 52 and a chuck table 54 that is rotatably disposed on the support base 52. The chuck table unit 50 further includes a cover 56 having a hole through which the chuck table 54 is inserted.

  The chuck table unit 50 is moved in the front-rear direction of the grinding apparatus 2 by the chuck table moving mechanism 58. The chuck table moving mechanism 58 includes a ball screw 60 and a pulse motor 64 connected to one end of a screw shaft 62 of the ball screw 60.

  When the pulse motor 64 is pulse-driven, the screw shaft 62 of the ball screw 60 rotates, and the support base 52 having a nut screwed to the screw shaft 62 moves in the front-rear direction of the grinding device 2. Therefore, the chuck table 54 also moves in the front-rear direction according to the rotation direction of the pulse motor 64.

  As shown in FIG. 1, the pair of guide rails 66 and 68 and the chuck table moving mechanism 58 shown in FIG. 2 are covered with bellows 70 and 72. That is, the front end portion of the bellows 70 is fixed to the front wall that defines the recess 10, and the rear end portion is fixed to the front end surface of the cover 56. The rear end of the bellows 72 is fixed to the vertical housing portion 8, and the front end thereof is fixed to the rear end surface of the cover 56.

  In the horizontal housing portion 6 of the housing 4, a first wafer cassette 74, a second wafer cassette 76, a wafer transport means 78, a wafer temporary mounting means 80, a wafer carry-in means 82, and a wafer carry-out means 84 are provided. A cleaning means 86 is provided. Further, an operation means 88 is provided in front of the housing 4 for an operator to input grinding conditions and the like.

  Further, a cleaning water spray nozzle 90 for cleaning the chuck table 54 is provided at the approximate center of the horizontal housing portion 6. The cleaning water jet nozzle 90 ejects cleaning water toward the wafer after grinding held by the chuck table 54 in a state where the chuck table unit 54 is positioned in the wafer carry-in / carry-out region.

  In the recess 10 of the housing 4, a drain port 92 is provided for draining the grinding water containing the grinding waste of the wafer W by the grinding wheel 32. As shown in FIG. 4, the drain port 92 includes a pH sensor 94 for detecting the pH of the grinding water, a concentration sensor 96 for detecting the concentration of the grinding water containing grinding waste, and a temperature sensor for detecting the temperature of the grinding water. 98 is provided. Although not shown in particular, a particle size sensor for detecting the particle size of the grinding scraps may be provided.

  Detection outputs of the pH sensor 94, the concentration sensor 96, and the temperature sensor 98 are input to the controller 100. The controller 100 is connected to display means 102 such as an LCD. The pH sensor 94, the concentration sensor 96, the temperature sensor 98, and the controller 100 constitute observation means.

  The grinding operation of the grinding device 2 configured as described above will be described below. The wafer housed in the first wafer cassette 74 is a semiconductor wafer having a protective tape mounted on the front surface side (surface on which the circuit is formed), and therefore the wafer is positioned with the back surface positioned on the upper side. Housed in the first cassette 74. As described above, the first wafer cassette 74 that accommodates a plurality of semiconductor wafers is mounted with a predetermined cassette of the housing 4 in the carry-in area.

  When all of the unprocessed semiconductor wafers contained in the first wafer cassette 74 placed in the cassette carry-in area are carried out, a plurality of semiconductor wafers are accommodated in place of the empty wafer cassette 74. A new first wafer cassette 74 is manually placed in the cassette loading area.

  On the other hand, when a predetermined number of ground semiconductor wafers are loaded into the second wafer cassette 76 placed in the predetermined cassette unloading area of the housing 4, the second wafer cassette 76 is manually unloaded. A new empty second wafer cassette 76 is placed in the cassette unloading area.

  The semiconductor wafer accommodated in the first wafer cassette 74 is conveyed by the vertical movement and forward / backward movement of the wafer conveyance means 78 and is placed on the wafer temporary placement means 80. The wafer placed on the temporary wafer placement means 80 is centered here, and then the chuck table of the chuck table unit 50 positioned in the wafer carry-in / out area by the turning operation of the wafer carry-in means 82. 54 and is sucked and held by the chuck table 54.

  When the chuck table 54 sucks and holds the wafer in this way, the chuck table moving mechanism 58 is operated to move the chuck table unit 54 and position it in the grinding area behind the apparatus.

  When the chuck table unit 50 is positioned in the grinding area, the center of the wafer held by the chuck table 54 is positioned slightly beyond the outer circumference circle of the grinding wheel 30.

  Next, the chuck table 54 is rotated at, for example, about 100 to 300 rpm, the servo motor 26 is driven to rotate the grinding wheel 30 at 4000 to 7000 rpm, and the pulse motor 48 of the grinding unit feed mechanism 44 is driven to rotate forward. The grinding unit 16 is lowered.

  Then, as shown in FIG. 4, the back surface of the wafer W is ground by pressing the grinding wheel 34 of the grinding wheel 30 against the back surface (surface to be ground) of the wafer W on the chuck table 54 with a predetermined load. By grinding in this way for a predetermined time, the wafer W is ground to a predetermined thickness.

  When grinding is completed, the chuck table moving mechanism 58 is driven to position the chuck table 54 in the wafer carry-in / carry-out region. If the chuck table 54 is positioned in the wafer carry-in / out area, the water to be ground (rear surface) of the ground wafer W that is ground and held by the chuck table 54 by spraying the cleaning water from the cleaning water spray nozzle 90. In addition to cleaning, the chuck table 54 after the wafer W is carried out is cleaned.

  After the wafer held by the chuck table 54 is released, the wafer W is transferred to the cleaning means 86 by the wafer unloading means 84. The wafer conveyed to the cleaning means 86 is cleaned and spin-dried here. Next, the wafer is stored in a predetermined position of the second wafer cassette 76 by the wafer transport means 78.

  When the back surfaces of many wafers are ground in this way, the working end portion of the grinding wheel 30 is clogged. Therefore, in this embodiment, a pH sensor 94, a concentration sensor 96, and a temperature sensor 98 are provided in the drain port 92, and the grinding state is observed by these sensors.

  That is, the controller 100 performs a predetermined calculation based on the detection outputs of the pH sensor 94, the concentration sensor 96, and the temperature sensor 98, and displays on the display means 102 the dressing display 104 that indicates that the dressing time of the grinding wheel 30 has come. A motor abnormality display 106 for informing the abnormality of the motor 26, a grinding water abnormality display 108 for informing the abnormality of the grinding water, and the like are performed.

  That is, according to the present embodiment, the grinding state of the grinding means (grinding unit) 16 can be observed by detecting the pH of the grinding water containing grinding waste, the concentration of the grinding water, or the temperature of the grinding water. The dressing time of the grinding wheel 34 can be displayed on the display means 102.

1 is an external perspective view of a grinding apparatus according to an embodiment of the present invention. It is a perspective view of a chuck table unit and a chuck table feed mechanism. It is a perspective view of the grinding wheel seen from the lower side. It is a partial cross section block diagram which shows the principal part of this invention.

Explanation of symbols

2 Grinding device 16 Grinding means (grinding unit)
24 spindle 26 servo motor 30 grinding wheel 34 grinding wheel 36 hose 42 grinding water supply nozzle 50 chuck table unit 54 chuck table 92 drain port 94 pH sensor 96 concentration sensor 98 temperature sensor 100 controller 102 display means

Claims (1)

A chuck table for holding a wafer, a grinding means having a grinding wheel provided with a grinding wheel for grinding a wafer held by the chuck table, and a grinding water supply means for supplying grinding water to a grinding region are provided. A grinding device,
Comprising observation means for observing the grinding state with grinding water containing grinding waste generated by grinding of the wafer held on the chuck table ;
The observation means has a pH detection unit for detecting the pH of the grinding water containing grinding waste, a temperature detection unit for detecting the temperature of the grinding water, and a particle size sensor for detecting the particle size of the grinding waste, The observing means observes the dressing time of the grinding wheel based on the pH and temperature of the grinding water and the particle size of the grinding waste contained in the grinding water .

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