Dressing Apparatus, Dressing Method, and Method of Manufacturing Device Chips

The present invention relates to an apparatus for and a method of dressing grindstones, and a method of manufacturing device chips using the dressing apparatus and method.

Device chips that incorporate devices such as integrated circuits (ICs) are indispensable components in various electronic appliances such as cellular phones and personal computers, for example. The device chips are fabricated according to a sequence of steps of thinning down a semiconductor wafer with a plurality of devices constructed in a face side thereof and then dividing the semiconductor wafer to separate areas thereof that include the respective devices.

A semiconductor wafer as a workpiece is thinned down by a grinding apparatus, for example. The grinding apparatus thins down the workpiece by grinding its reverse side that is free of devices. The grinding apparatus includes a chuck table for holding the workpiece with its face side facing downwardly toward the chuck table and a vertical spindle on which a grinding wheel having grindstones is mounted. The grinding wheel is of an annular shape with the grindstones attached to its lower surface. The spindle has a lower end to which the grinding wheel is fixed and is rotatable about its central axis in unison with the grinding wheel.

Each of the grindstones secured to the grinding wheel is made of abrasive grains bound together by a bonding material. The bonding material includes a vitrified bond containing air bubbles or a resin bond, for example. The abrasive grains that are made of diamond or cubic boron nitride are dispersed in the bonding material, making up the grindstone.

The grinding apparatus thins down the workpiece, i.e., the semiconductor wafer, as follows.

The workpiece is placed on an upper surface of the chuck table that acts as a holding surface. The workpiece is held on the chuck table such that the face side of the workpiece where the devices are present faces downwardly toward the holding surface of the chuck table. In other words, the workpiece is held on the chuck table with its reverse side free of the devices being exposed upwardly.

The grinding wheel with the grindstones attached to its lower surface is positioned above the workpiece whose reverse side faces upwardly. The grinding wheel mounted on the spindle and the chuck table holding the workpiece start to rotate about their respective vertical axes. While the grinding wheel and the chuck table are rotating, the chuck table and the spindle are moved vertically toward each other. The grindstones on the lower surface of the rotating grinding wheel and the reverse side of the workpiece on the holding surface of the chuck table come into abrasive contact with each other, whereupon the abrasive grains exposed on lower surfaces of the grindstones grind the reverse side of the workpiece.

The abrasive grains continuously grind the reverse side of the workpiece while the chuck table and the spindle are moving vertically toward each other, thereby removing a layer of the reverse side of the workpiece and hence thinning down the workpiece by the predetermined thickness.

The grinding step as it goes on produces swarf from the workpiece and the grindstones, and the swarf is deposited on the grinding surfaces of the grindstones, tending to load the grindstones. In order for the grindstones to grind the workpiece without fail, some of the abrasive grains are required to be exposed from the bonding material on the grinding surfaces of the grindstones that contact the workpiece. The swarf deposited on the grinding surfaces is likely to be stuck between the exposed abrasive grains and makes the abrasive grains less exposed than they should. In addition, as the grindstones repeatedly grind workpieces, the abrasive grains exposed on the grinding surfaces of the grindstones are worn off or dulled over time.

For eliminating loading and dulling of the grindstones to recover their grinding capability, it is customary to scrape the grinding surfaces of the grindstones at appropriate timings to sharpen the grindstones for better grinding. Such a step is referred to as dressing (see, for example, JP 2021-121464A).

Although the grinding capability of grindstones mounted on the lower surface of a grinding wheel can be recovered by replacing the grinding wheel with another grinding wheel, the grinding surfaces of the grindstones on the replacing grinding wheel may have their positions or heights varied among themselves. In a case where the grinding surfaces of the grindstones vary in position, a dressing step is effective to align the positions of the grinding surfaces with each other.

The grindstones are dressed as follows. First, a dresser board is positioned below the grinding wheel mounted on the spindle. The dresser board is similar in nature to grindstones in that it includes abrasive grains that are hard enough to grind at least the bonding material of the grindstones, for example.

Then, while the dresser board and the grinding wheel are rotating respectively about their central axes, the dresser board and the spindle are vertically brought toward each other to bring the grinding surfaces of the grindstones and the upper surface of the dresser board into abrasive contact with each other. When the grindstones and the dresser board slide abrasively against each other, the upper surface of the dresser board is ground by the abrasive grains that are exposed on the grinding surfaces of the grindstones and the grinding surfaces of the grindstones are ground by the abrasive grains that are exposed on the upper surface of the dresser board.

During the dressing step described above, it is desirable to appropriately control the relative movement of the dresser board and the grindstones in vertical directions, i.e., directions transverse to the directions along which the grindstones and the dresser board slide abrasively against each other, and the loads applied to the dresser board and the grindstones.

While the dresser board is dressing the grindstones, the dresser board and the grindstones are required to be pressed against each other under suitable forces. If the forces are too weak or the dresser board and the grindstones are not held in contact with each other, then the dresser board is unable to dress the grindstones smoothly. If the forces are too strong, then the dresser board and the grindstones are likely to be worn too much and consumed too early.

When the dresser board starts to dress the grindstones, it is necessary to move the dresser board and the grindstones closely toward each other. If the relative speed at which the dresser board and the grindstones move relatively to each other is too small, then it takes a long period of time to start dressing the grindstones, possibly adversely affecting the productivity, i.e., efficiency with which to dress the grindstones with the dresser board. On the other hand, if the relative speed is too large, then the dresser board and the grindstones are liable to impinge upon each other.

It is therefore an object of the present invention to provide a dressing apparatus, a dressing method, and a method of manufacturing device chips that are capable of appropriately controlling loads applied between a dresser board and grindstones at the time the dresser board and the grindstones move relatively to each other in directions transverse to the plane along which the grindstones and the dresser board slide abrasively against each other, i.e., at the time the dresser board dresses the grindstones.

In accordance with an aspect of the present invention, there is provided a dressing apparatus for dressing grindstones that grinds a workpiece by causing the grindstones and a dresser board to slide abrasively against each other, the dressing apparatus including a board holder for holding the dresser board, a moving mechanism for moving the board holder and the grindstones relatively to each other in a direction transverse to a plane along which the grindstones abrasively slide against the dresser board, and a measuring instrument for detecting a load applied to the dresser board.

In accordance with the aspect of the invention, preferably, the moving mechanism includes a mechanism for moving the board holder with respect to the grindstones, and the dressing apparatus further includes a measurement reference marker disposed in a path along which the dresser board is to be moved by the moving mechanism.

In accordance with the aspect of the invention, preferably, the moving mechanism includes an actuator for moving the board holder with respect to the grindstones, and the dressing apparatus further includes a guide for limiting movement of the board holder in directions transverse to the directions in which the actuator moves the board holder.

In accordance with the aspect of the invention, preferably, the dressing apparatus further includes a workpiece holder for holding the workpiece and a grinding actuator on which there is mounted a grinding wheel rotatable about its central axis, the grindstones being mounted on the grinding wheel, in which the grinding wheel is rotated to rotate the grindstones and the grinding actuator is operated to bring the grindstones into contact with the workpiece held by the workpiece holder thereby to grind the workpiece, and the grinding wheel is rotated to rotate the grindstones and the grinding actuator is operated to bring the grindstones into contact with the dresser board held by the board holder thereby to dress the grindstones.

In accordance with the aspect of the invention, preferably, the grinding wheel is rotated to rotate the grindstones and the grinding actuator is operated to bring the grindstones into contact with the dresser board thereby to dress the grindstones irrespectively of whether the grindstones are not grinding the workpiece or the grindstones are grinding the workpiece held by the workpiece holder.

In accordance with the aspect of the invention, the dressing apparatus further includes a liquid supply nozzle for supplying a liquid to the dresser board held by the board holder.

In accordance with the aspect of the invention, the dressing apparatus further a cleaning nozzle for supplying a fluid to the grindstones, in which the grinding wheel, the workpiece holder, and the board holder are disposed such that a path followed by the grindstones rotated by the grinding wheel when the grinding wheel is rotated overlaps a portion of the workpiece held by the workpiece holder and overlaps a portion of the dresser board held by the board holder as viewed in a direction transverse to a plane along which the grindstones are rotated, and the cleaning nozzle is disposed to supply the fluid at a position out of contact with the workpiece held by the workpiece holder and the dresser board held by the board holder on the path followed by the grindstones as viewed in the direction transverse to the plane along which the grindstones are rotated.

In accordance with another aspect of the present invention, there is provided a dressing method of dressing grindstones for grinding a workpiece, using a dressing apparatus including a board holder for holding a dresser board, in which the dressing apparatus causes the dresser board held by the board holder and the grindstones to slide abrasively against each other, the dressing method including dressing the grindstones, using the dressing apparatus by measuring a load applied to the dresser board and pressing the board holder and the grindstones against each other in a direction transverse to a plane along which the grindstones and the dresser board slide abrasively against each other such that the measured load applied to the dresser board has a value falling within a predetermined numerical range.

In accordance with the other aspect of the present invention, the dressing apparatus further includes a moving mechanism for moving the board holder with respect to the grindstones in the direction transverse to the plane along which the grindstones and the dresser board slide abrasively against each other, and a measurement reference marker disposed in a path followed by the dresser board when the board holder is moved by the moving mechanism, and the dressing method further includes moving the board holder by the moving mechanism and recording information about a position of the board holder at the time the dresser board held by the board holder and the measurement reference marker contact each other, and controlling the distance that the board holder is moved by the moving mechanism on the basis of the recorded information about the position of the board holder.

In accordance with the other aspect of the present invention, the dressing apparatus further includes a moving mechanism for moving the board holder with respect to the grindstones in the direction transverse to the plane along which the grindstones and the dresser board slide abrasively against each other, and the dressing method further includes moving the board holder by the moving mechanism and recording information about the position of the board holder at the time the board holder or the dresser board held by the board holder and the grindstones contact each other, and controlling the distance that the board holder is moved by the moving mechanism on the basis of the recorded information about the position of the board holder.

In accordance with the other aspect of the present invention, the grindstones are dressed by using the dressing apparatus by either bringing the dresser board into contact with the grindstones while the grinding stones are grinding the workpiece or by bringing the dresser board into contact with the grindstones while the grinding stones are not grinding the workpiece.

In accordance with a further aspect of the present invention, there is provided a method of manufacturing device chips by dividing a workpiece, including dressing grindstones for grinding a workpiece, using a dressing apparatus including a board holder for holding a dresser board, in which the dressing apparatus causes the dresser board held by the board holder and the grindstones to slide abrasively against each other, grinding the workpiece by the grindstones dressed by using the dressing apparatus or grinding the workpiece by the grindstones while simultaneously the grindstones are being dressed by using the dressing apparatus, and after the workpiece is ground, dividing the workpiece into device chips, in which the grindstones are dressed by using the dressing apparatus by measuring a load applied to the dresser board, and pressing the board holder and the grindstones against each other in a direction transverse to a plane along which the grindstones and the dresser board slide abrasively against each other such that the measured load applied to the dresser board has a value falling within a predetermined numerical range.

In accordance with the further aspect of the present invention, the workpiece is divided along division initiating points formed in the workpiece into the device chips.

With the dressing apparatus, the dressing method, and the method of manufacturing device chips according to the respective aspects of the invention, it is possible to appropriately control the load applied between the dresser board and the grindstones when the dresser board and the grindstones are moved relatively to each other in the direction transverse to the plane along which the dresser board and the grindstones slide abrasively against each other to dress the grindstones or when the grindstones are dressed by the dresser board by measuring the load applied to the dresser board.

The above and other objects, features and advantages of the present invention and the manner of realizing them will become more apparent, and the invention itself will best be understood from a study of the following description and appended claims with reference to the attached drawings showing a preferred embodiment of the invention.

A dressing apparatus, a dressing method, and a method of manufacturing device chips according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. First, the dressing apparatus will be described below. The dressing apparatus according to the present embodiment is combined as a dressing function with a grinding apparatus, or stated otherwise, functions as a part of a grinding apparatus that dresses grindstones of the grinding apparatus. According to the present invention, however, the dressing apparatus may be separate from and independent of a grinding apparatus that includes grindstones to be dressed by the dressing apparatus.

schematically illustrates, in perspective view, partly in block form, a central portion of the dressing apparatus.schematically illustrate, respectively in perspective, front elevation, and sectional side elevation, a dressing assembly of the dressing apparatus illustrated in. In, some components including a power transmitting beltand guidesare omitted from illustration for the sake of brevity.

As illustrated in, the dressing apparatusincludes a grindstone handler, a workpiece handler, and a dressing assembly.

The grindstone handlerincludes a spindleas a grinding actuator and a moving mechanismfor moving the spindlein vertical directions or Z-directions.

The spindleincludes a substantially cylindrical member extending along its central axis in vertical directions or Z-directions and rotatable about the central axis. The spindlehas a lower end on which a grinding wheelis mounted. The grinding wheelis securely attached to the lower end of the spindlein axial alignment with the spindle. When the spindleis rotated about its vertical central axis by an electric motor, not depicted, coupled to the spindle, the grinding wheelis also rotated in unison with the spindlein a horizontal plane or an XY-plane about a central axis thereof aligned with the vertical central axis of the spindle.

The terms “vertical” and “horizontal” used herein mean not only strictly vertical and horizontal, but also substantially vertical and horizontal, covering slight deviations such as inclinations and curvatures from strictly vertical and horizontal directions. The vertical directions and the horizontal plane are also referred to as “Z-directions” and “XY-plane” respectively herein.

The grinding wheelrefers to a disk-shaped component with a plurality of grindstonesattached thereto. The grindstonesare arranged in an annular array on a lower surface of the grinding wheel. The grinding wheelis mounted on the lower end of the spindlesuch that the lower surface of the grinding wheelon which the grindstonesare disposed face downwardly.

The moving mechanismincludes a mechanism for moving the grindstonesand a workpieceto be ground thereby relatively to each other in vertical directions or Z-directions transverse to the plane along which the grindstonesand the workpieceslide abrasively against each other at the time the grindstonesgrind the workpiece. The moving mechanismalso functions as a mechanism for moving the grindstonesand a dresser boardfor dressing the grindstonesrelatively to each other in vertical directions or Z-directions transverse to the plane along which the grindstonesand the dresser boardslide abrasively against each other at the time the grindstonesare dressed by the dresser board.

The moving mechanismincludes a ball screw, not depicted, extending in vertical directions and a stepping motor, not depicted, for rotating the ball screw about its vertical central axis. When the stepping motor is energized, it rotates the ball screw to move the spindleupwardly or downwardly in the vertical directions. According to the present invention, the moving mechanismis not restricted to the structural details described above, but may be any of various mechanisms for moving the spindle, i.e., the grinding actuator, vertically.

According to the present embodiment, the moving mechanism for moving the grindstonesand the workpiecerelatively to each other in vertical directions or Z-directions is illustrated as a mechanism for moving the spindle, i.e., the grindstones, toward and away from the workpiece. Alternatively, or additionally, the moving mechanism may include a mechanism for moving the workpiecetoward and away from the spindle.

According to the present embodiment, furthermore, the moving mechanism for moving the grindstonesand the dresser boardrelatively to each other in vertical directions or Z-directions includes, in addition to the moving mechanismfor moving the grindstones, i.e., the spindle, a moving mechanism(see) for moving the dresser boardin the dressing assembly. The structure and function of the moving mechanismwill be described in detail later.

As illustrated in, the workpiece handlerincludes a chuck tableas a workpiece holder for holding the workpieceand a support tablethat supports the chuck tablethereon.

The workpieceincludes, for example, a disk-shaped wafer made of a semiconductor material such as silicon. However, the workpieceis not limited to any particular materials, shapes, structures, sizes, kinds, and uses. For example, the workpiecemay include a wafer made of GaAs, InP, GaN, or SiC, glass, ceramic, resin, or metal. Moreover, the workpiecemay include an object other than a wafer, e.g., any of various objects that can be ground by the grindstones.

The chuck tableas the workpiece holder has an upper surface as a holding surfacefor holding the workpieceby attracting the lower surface of the workpieceunder suction. The chuck tablehouses therein a mechanism, not depicted, for developing a negative pressure between the holding surfaceand the object thereon to attract the lower surface of the workpieceunder suction.

The support tableincludes a rotary table with the chuck tablemounted on an upper surface thereof. The support tableis rotatable about an axis along vertical directions or Z-directions. The support tablemay additionally be movable upwardly and downwardly along vertical directions or Z-directions.

The chuck tableis disposed on the support tableat a position offset from the axis about which the support tableis rotatable. In other words, when the support tableis rotated, the chuck tableis angularly moved in a horizontal plane, i.e., an XY-plane, with respect to the spindleand the grinding wheelof the grindstone handler.

The chuck tableis rotatably supported on the support tablefor rotation about its central axis along vertical directions or Z-directions.

As illustrated in, the dressing assemblyincludes a chuck tableas a board holder for holding the dresser board, a support tablethat supports the chuck tablethereon, the moving mechanismfor moving the chuck tableand the support tablealong vertical directions, i.e., Z-directions, with respect to the grinding wheeland the grindstones, and an auxiliary supportthat supports the support tablethereon.