JPH09262747A - Double grinding device for high brittle material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably support a work even when a cutting load is brought into an unbalanced state by supporting the work under machining by a hydrostatic holding member consisting of a pair of upper and lower hydrostatic pads ar ranged facing the upper and under surfaces of the work. SOLUTION: Hydrostatic holding members 3a and 3b arranged facing both the upper and under surfaces of a wafer 1 to support stably support the wafer 1 are positioned in two spots of the inside and the outside in a radial direction of cup grinding wheels 2a and 2b. In a cutting feed during processing, since hydrostatic pads 3a and 3b are also operated in linkage with cutting of the grinding wheels 2a and 2b through a wafer surface, even when the wafer 1 surface is continuously cut through cut-through by the grinding wheels 2a and 2b, a distance between each of hydrostatic pads 3a and 3b and the wafer 1 surface is kept in an excellent state, resulting in stable support of the wafer 1 by the hydrostatic holding members 3a and 3b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is suitable for accurately surface-grinding both sides of a disk-shaped workpiece made of a highly brittle material typified by a semiconductor wafer used for an IC substrate. The present invention relates to a double-sided grinding machine for highly brittle materials.

[0002]

2. Description of the Related Art In grinding (or polishing) the surface of a disk-shaped workpiece made of a highly brittle material, for example, a semiconductor wafer, the method of grinding the wafer surface one by one grinds by the stress received from the grinding tool. Since there is a problem that the inside wafer is warped, and as a result, high flatness grinding is not performed, simultaneous grinding of both surfaces of the wafer is generally performed. As a method of simultaneously grinding both sides of a wafer, a method of vertically supporting the wafer by a plurality of rollers and simultaneously grinding both sides of the wafer with a pair of grinding tools provided so as to face both sides of the wafer has been conventionally used. It was

However, since the roller for supporting the wafer is not generally a mechanism capable of coping with a high load in the vertical direction, each of a pair of grinding tools provided on both sides of the wafer during wafer grinding If the cutting load applied to the wafer is uneven, the wafer being processed will be warped, and the cutting amount on both sides of the wafer will also be uneven, so there is the problem that high-flatness grinding cannot be performed. It was Therefore,
To address this problem, several mechanisms have been devised to control the cutting loads of the pair of grinding tools to be equal.

As a method for equalizing the cutting loads of a pair of grinding tools provided on both sides of a wafer, for example, in Japanese Patent Laid-Open No. 57-54063, one grinding tool does not swing with respect to the tool rotating shaft. And the other grinding tool is configured so that the other grinding tool can be swung with respect to the tool rotation axis by the universal joint and can be moved in the tool rotation axis direction. With this configuration, the cutting load received by the wafer from the grinding tool configured so as not to swing with respect to the tool rotation axis and not move in the tool rotation axis direction is applied to the tool rotation axis by the universal joint. Since the grinding tool configured so that it can swing and move in the tool rotation axis direction changes according to the cutting load applied to the wafer, the cutting loads received from the respective grinding tools on both sides of the wafer become substantially equal, resulting in a flat surface. It is said that high-quality grinding will be performed.

[0005]

However, Japanese Patent Laid-Open No.
Even in the processing apparatus indicated by No. 54063, since the roller supporting the wafer does not have a mechanism capable of coping with a high load in the vertical direction, the wafer being processed is mainly paired with a pair of grinding plates provided facing each other on both sides of the wafer. It will be supported by the tool. Generally, since there are many minute irregularities on the surface of the wafer before the surface grinding process, the cutting load that the wafer being processed receives from each of the pair of grinding tools is not always equal. However, there is a problem in that it is unbalancedly supported, and as a result, grinding with high flatness cannot be performed.

An object of the present invention is to perform a double-sided simultaneous grinding of the surface of a disk-shaped work piece made of a highly brittle material typified by a semiconductor wafer. An object of the present invention is to provide a grinding device that stably supports a workpiece even when a cutting load received from a grinding tool becomes unbalanced, thereby performing double-sided grinding with high flatness.

[0007]

In order to achieve this object, the present invention provides a means for supporting a workpiece being machined instead of a pair of grinding tools provided on opposite sides of the workpiece. By this, even if the cutting load received from each of the pair of grinding tools becomes unbalanced, the work piece can be stably supported.

That is, the present invention is a double-sided machine that grinds both sides of a workpiece simultaneously by a pair of annular grinding tools provided on the upper and lower sides of the disk-shaped workpiece made of a highly brittle material. In the grinding apparatus, the workpiece being ground is supported by a static pressure holding member composed of a pair of upper and lower static pressure pads provided so as to face the upper and lower surfaces of the workpiece. As a result, the work piece has a static pressure composed of a pair of upper and lower static pressure pads provided on the upper and lower surfaces of the work piece instead of the pair of grinding tools provided on the opposite surfaces of the work piece. It is supported by the holding member in a non-contact state.

Further, if the static pressure holding members are provided at two locations inside and outside in the radial direction of the annular grinding tool, the workpieces are subjected to respective cutting loads received by the pair of annular grinding tools. Even if an imbalance occurs, it is stably supported by static pressure holding members provided on both sides of the grindstone contact surface of the workpiece.

If a plurality of static pressure pockets are provided on the surfaces of the pair of upper and lower static pressure pads facing the surface of the workpiece, and a coolant discharge port is provided inside each static pressure pocket, The work piece is stably held by the pressure of the coolant discharged from multiple static pressure pockets provided in each static pressure pad, and the coolant that fills the surface of the work piece is generated during grinding. It also contributes to the discharge of cutting chips and the cooling of the workpiece.

Further, among the static pressure holding members, a static pressure pad (upper static pressure pad) provided facing the upper surface of the workpiece.
Is an interlocking movement with a grinding tool (upper grindstone) that processes the upper surface of the workpiece, and the static pressure pad (lower static pressure pad) that is provided facing the lower surface of the workpiece is the lower surface of the workpiece. By operating in tandem with the grinding tool (lower grindstone) for machining, when the grinding tool is cut and fed to the workpiece, even if the wafer surface continues to be ground due to the cutting of the grindstone, each static pressure pad The distance between the wafer and the wafer surface is kept good, and as a result, the static pressure holding member can stably support the wafer.

When the upper and lower static pressure pads are operated in association with the upper and lower grinding tools as described above, the distance between each static pressure pad and the wafer surface is maintained even if many grinding processes are performed. In order to keep good condition, it is necessary to minimize the wear amount of the abrasive grain layer of the annular grinding tool (the thickness of the abrasive grain layer decreases due to wear), but the annular shape is used for the purpose of reducing the grinding resistance. When the width of the abrasive grain layer of the grinding tool is set small, the abrasion amount of the abrasive grain layer becomes large. In order to deal with this, it is preferable to use diamond abrasive grains, which are less worn, as the material of the abrasive grain layer of the annular grinding tool.

During the grinding process, the work piece is supported by a static pressure holding member in the vertical direction and an annular outer peripheral support (carrier) in the horizontal direction. With this configuration, in the static pressure holding state of the workpiece during the grinding process, the grinding feed (upper grindstone) of the grinding tool (upper grindstone) for processing the upper surface of the workpiece is moved (slow speed descending).
Therefore, when the upper static pressure pad linked to this is lowered, the work piece should be held at the intermediate position between the upper static pressure pad and the lower static pressure pad while being supported in the horizontal direction by the carrier. It will descend slightly,
Therefore, the distance between the grinding tool (lower grindstone) for machining the lower surface of the workpiece and the lower surface of the workpiece is narrowed, and the upper surface of the workpiece is ground by the upper grindstone and the lower surface of the workpiece is ground by the lower grindstone at the same time. Like

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a grinding device being machined, including a positional relationship between a wafer (workpiece) 1, upper and lower grindstones (grinding tools) 2a and 2b, and upper and lower static pressure pads (static pressure holding members) 3a and 3b. It is a conceptual diagram showing the main part,
The upper figure is a plan sectional view and the lower figure is a side sectional view.

The wafer 1 which is the object to be processed has a substantially circular plane shape, but the outer periphery is not arcuate due to the orientation flat processing in the previous step. The wafer 1, which is a disk-shaped workpiece, is supported by a ring-shaped outer peripheral support (carrier) 6 in the horizontal direction, so that the carrier 6
The rotational driving force from the roller 7 for holding is transmitted. On the other hand, in the vertical direction, since the wafer 1 needs to be supported by the static pressure holding member 3, the structure of the carrier 6 supports the wafer 1 in a free state (movable in the vertical direction) in the vertical direction. It is supposed to do. That is, by setting the inner circumference of the carrier 6 slightly larger than the outer circumference of the wafer 1, a slight gap 8 is formed between the outer circumference of the wafer 1 and the inner circumference of the carrier 6 when the wafer 1 is supported by the carrier 6. As a result, the wafer 1 is supported by the carrier 6 in the horizontal direction but is free in the vertical direction. The carrier 6 is always supported by the roller 7, and only the wafer 1 is attached to and detached from the carrier 6 supported by the roller 7 during processing.

At least three rollers 7 are required to stably support the carrier 6 as shown in FIG. 1, but four or more rollers 7 may be provided if necessary. Further, in order to handle several types of wafers, each of the rollers 7 is movable in the horizontal direction according to the outer diameter of the carrier 6. A roller drive motor (not shown) is connected to one of the plurality of rollers 7, and the wafer 1 is rotated via the carrier 6 by driving the roller connected to the roller drive motor during processing. Thus, the entire surface of the wafer 1 is ground. The rollers not connected to the roller driving motor rotate together with the rotation of the wafer 1.

The annular grinding tool used as the grinding tool is in the shape of a dish, which is commonly called a cup grindstone, and the edge 9 of the dish contacts the surface of the wafer 1 for grinding. Since both surfaces of the wafer 1 are ground simultaneously in the present invention, two grinding tools are used as a pair. Further, in order to evenly grind both surfaces of the wafer 1, the pair of grinding tools 2a, 2b are the same in shape and material. The outer diameter of the cup grindstone used as the grinding tool is preferably sufficiently larger than the outer diameter of the wafer in order to efficiently process the wafer surface. Further, the width of the abrasive grain layer 5 of the cup grindstone as the grinding tool (the width of the edge portion 9 of the cup grindstone) is preferably as small as possible on condition that the grinding load received by the grinding tool is sufficiently endured. This is because the smaller the width of the abrasive layer of the cup grindstone as a grinding tool, the smaller the grinding resistance, and therefore the cracking of the wafer during processing can be prevented. Further, in order to reduce the increase in the wear amount of the abrasive grain layer 5 due to the reduction of the width of the abrasive grain layer, diamond abrasive grains are used as the material of the abrasive grain layer 5 because of the small wear amount of the abrasive grains.

A pair of grinding tools, that is, the upper grindstone 2a and the lower grindstone 2b are vertically symmetrically opposed to each other with respect to the wafer 1 in order to equalize the grinding load received from the grinding tool 2 on the upper and lower surfaces of the wafer during processing. To be done.
In other words, the rotary shafts 10 of the upper grindstone 2a and the lower grindstone 2b are arranged coaxially. Further, in order to grind the entire surface of the wafer 1 with these grinding tools, the rotation center 11 of the wafer 1 must be on the contact surface of the grinding tool 2 (on the edge 9 of the cup grindstone) or inside this. It will be clear from FIG. 1 that this is not the case. However, when the static pressure holding members (upper static pressure pad 3a, lower static pressure pad 3b) described below are provided at two locations inside and outside the annular grinding tools 2a, 2b in the radial direction, the static pressure holding is performed. Members 3a, 3b
Therefore, in order to stably support the wafer, it is preferable to set the rotary shaft 10 of the grinding tools 2a and 2b so that the rotation center 11 of the wafer 1 is located almost on the contact surface of the grinding tools 2a and 2b. Furthermore, the upper grindstone 2a and the lower grindstone 2b
The respective rotation directions of are set to be opposite to each other.
This is because when the upper grindstone 2a and the lower grindstone 2b are rotated in the same direction, a large horizontal pressing force is applied to the roller 7, so that the roller 7 is abraded severely. is there.

The upper grindstone 2a and the lower grindstone 2b are respectively
A feed mechanism (not shown) for moving these in the vertical direction is provided. This feed mechanism is used for separating the upper grindstone 2a and the lower grindstone 2b from the wafer 1 when the wafer 1 is attached and detached, and is also used for cutting or feeding the grindstone to the wafer 1 during processing. In the case of surface grinding of a wafer, cutting feed needs to be performed in units of microns, so a servomotor is used as a feed mechanism and this is controlled by a numerical controller.

The static pressure holding member, which is an important component of the present invention, is composed of a pair of upper and lower static pressure pads 3a and 3b provided so as to face both upper and lower surfaces of the wafer 1. In order to stably support the wafer 1, the static pressure holding members 3a and 3b are preferably provided at two locations on the inner side and the outer side in the radial direction of the cup grindstones 2a and 2b as grinding tools. In these two static pressure holding members, upper and lower static pressure pads 3a, 3b
A plurality of static pressure pockets 4 are provided on the surface facing the surface of the wafer 1, and a coolant discharge port (not shown) is provided inside each static pressure pocket 4. An interval of several tens of μm is provided between the surface of the wafer 1 and the surface of each of the static pressure pads 3a and 3b, and a coolant of a specified pressure is discharged from the coolant discharge port of each static pressure pocket 4, thereby the inside of each static pressure pocket, Further, the gap between the wafer surface and the static pressure pad is filled with the coolant, and as a result, the wafer 1 is statically held in a non-contact state between the upper and lower static pressure pads 3a and 3b. Needless to say, at this time, the coolant that fills the wafer surface also contributes to discharge of chips generated during grinding and cooling of the wafer 1.

Here, the wafer 1 is the static pressure holding members 3a, 3a.
The following conditions are necessary for the static pressure to be stably maintained by b. One of the conditions is that the upper and lower static pressure pads 3a and 3b of the static pressure holding members 3a and 3b must have the same shape. This is because the static pressure of the wafer 1 is maintained by the static pressure applied to the wafer 1 of the upper and lower static pressure pads 3a and 3b being equal, so that the shapes of the static pressure pads 3a and 3b are symmetrical with respect to the wafer 1. It is easy to see that it must be configured to However, the shape of the static pressure pockets 4 may be symmetrical with respect to the wafer 1, and the plurality of static pressure pockets in one static pressure pad need not have the same shape. Another condition is that the pressure of the coolant discharged from the static pressure pockets 4 of the upper and lower static pressure pads 3a and 3b, which are symmetrical with respect to the wafer 1, must be equalized. It is clear that this condition is also necessary in order to equalize the static pressure applied to the wafer 1 by the upper and lower static pressure pads 3a and 3b. The pressure of the coolant discharged from each does not need to be equal to each other.

In this way, the wafer 1 is held by the static pressure holding member 3
In order to maintain a stable static pressure by a and 3b, the static pressure pads 3a and 3b symmetrically positioned with respect to the wafer 1 have the same shape, and the static pressure pads 3a and 3b symmetrically positioned with respect to the wafer 1 are used. The pressures of the coolant discharged from the pockets must be equal, but the shapes of the two static pressure holding members arranged inside and outside in the radial direction of the cup grindstone do not necessarily have to be equal. However, in order for the wafer 1 to be stably held by the static pressure holding member,
Since the holding forces of these two static pressure holding members should be equal, when the two static pressure holding members have different shapes, the discharge pressure of the coolant is adjusted to hold the two static pressure holding members. It is necessary to take measures to equalize the power.

Of these two static pressure holding members, the static pressure pad, that is, the upper static pressure pad 3a provided so as to face the upper surface of the wafer 1 is interlocked with a grinding tool for processing the upper surface of the wafer, that is, the upper grindstone 2a. The static pressure pad, that is, the lower static pressure pad 3b provided so as to face the lower surface of the wafer 1 is configured to operate in conjunction with a grinding tool that processes the lower surface of the wafer, that is, the lower grindstone 2b. For example, the mounting base of the upper static pressure pad 3a of each of the two static pressure holding members is the same as the mounting base of the upper grindstone 2a, and
The mounting bases of the lower static pressure pads 3b of the individual static pressure holding members are installed in the same manner as the mounting bases of the lower grindstone 2b. With this configuration, when the wafer 1 is attached and detached, the upper grindstone 2a and the lower grindstone 2b are separated from the wafer mounting surface, and the upper static pressure pad 3a and the lower static pressure pad 3b are also separated. It is easier to get out,
During cutting feed during processing, since each static pressure pad operates in conjunction with the cutting of the grindstone on the wafer surface, even if the wafer surface continues to be ground by the cutting of the grindstone, the gap between each static pressure pad and the wafer surface Is maintained satisfactorily, and as a result, the static pressure holding members 3a and 3b can continue to stably support the wafer 1.

When the upper and lower grindstones 2a, 2b contact the wafer surface, there is no sufficient gap between the upper and lower static pressure pads 3a, 3b and the wafer surface to hold the wafer 1 under static pressure. Therefore, the lower surface (grinding portion) of the upper grindstone 2a is located below the surface of the upper static pressure pad 3a by this gap, and similarly, the upper surface (grinding portion) of the lower grindstone 2b is also lower static pressure pad. It must be located above the surface of 3b.

By the way, when several tens to several hundreds of wafers 1 are continuously processed, a cup grindstone 2a as a grinding tool,
Since the abrasive grain layer 5 of 2b gradually wears, each static pressure pad 3
The distances between a and 3b and the wafer surface become closer as the processing is repeated, and as a result, the static pressure holding member 3 cannot support the wafer well, and each static pressure pad 3a constituting the static pressure holding member, A state in which 3b contacts the wafer surface may occur. As described above, if diamond abrasive grains with a small amount of wear are used as the material of the abrasive grain layer 5 of the cup grindstones 2a, 2b as the grinding tool, the above state will not be achieved unless a large number of wafers are processed. Then
Further, since the life of the cup grindstone as a grinding tool is usually extended before the above state is reached, it is not necessary to adjust the height of the static pressure pad with respect to wear of the abrasive grain layer 5. However, when a material having a relatively large amount of wear is used as the material of the abrasive grain layer 5, a means for adjusting the height of each static pressure pad 3a, 3b is required to cope with the wear of the abrasive grain layer 5. Becomes

Next, an embodiment of a grinding method using the above-mentioned double-sided grinding machine will be described with reference to the flow chart shown in FIG.

I. A servo motor (not shown) for driving the lower grindstone 2b is operated to position the lower grindstone 2b in the vertical direction at a position corresponding to the thickness of the wafer 1 (step 2).
1). At this time, the lower static pressure pad 3 that interlocks with the lower grindstone 2b
b will also be positioned at the same time. When the wafer 1 is carried in and out of the carrier 6, the wafer 1 is supported by the carrier 6 but is not held in static pressure, and as described above, the carrier 6 supports the wafer 1 only in the horizontal direction. Therefore, the loaded wafer 1 is placed on the upper surfaces of the lower grindstone 2b and the lower static pressure pad 3b. Therefore, even when the wafer 1 is not held under static pressure,
The positioning position of the lower grindstone 2b must be set so that the wafer 1 is supported by the lower grindstone 2b, the lower static pressure pad 3b, and the carrier 6. Incidentally, the positioning operation of the lower grindstone 2b is unnecessary thereafter unless the type of the wafer 1 is changed.

II. Wafer 1 by a loading / unloading device (not shown)
Is inserted into the carrier 6 (step 22). At this time, the upper grindstone 2a and the upper static pressure pad 3a which operates in conjunction with the upper grindstone 2a
Are located above and away from the processing position so as not to interfere with the insertion of the wafer 1 into the carrier 6. Since the carrier 6 supports the wafer 1 only in the horizontal direction as described above, the wafer 1 inserted in the carrier 6 is placed in contact with the upper surfaces of the lower grindstone 2b and the lower static pressure pad 3b which are positioned. Will be.

III. The coolant is discharged from each of the static pressure pads 3a and 3b (step 23). At this time, wafer 1
Is due to the coolant discharged from the lower static pressure pad 3b,
It will float slightly above the upper surfaces of the lower grindstone 2b and the lower static pressure pad 3b. The discharge pressure of the coolant at this time needs to be suppressed to such an extent that the wafer 1 does not project above the carrier 6. Since the upper static pressure pad 3a is still far above the wafer 1, the wafer 1 is not kept under static pressure. At this time, however, the coolant discharged from the upper static pressure pad 3a is Grinding stone 2b and lower static pressure pad 3
The wafer 1 floating above b is prevented from jumping above the carrier 6.

IV. A roller driving motor (not shown) is driven to rotate the wafer 1 supported by the carrier 6 and rotate the upper grindstone 2a and the lower grindstone 2b (step 24). At this time, the wafer floats slightly above the upper surfaces of the lower grindstone 2b and the lower static pressure pad 3b and rotates. Further, as described above, the rotating directions of the upper grindstone 2a and the lower grindstone 2b are opposite to each other with respect to the wafer 1.

V. The upper grindstone 2a is fast-forwarded and lowered, and the wafer 1 is held under static pressure between the upper static pressure pad 3a that has descended in conjunction with the upper grindstone 2a and the lower static pressure pad 3b that has already been positioned (step 25). ). At this time, the rapid feed descent end position of the upper grindstone 2a is set to a position opposite to the positioning position of the lower grindstone 3a when the vertical position of the carrier 6 is used as a reference. As a result, the vertical position of the wafer 1 held under static pressure substantially coincides with the horizontal center position of the carrier 6 that supports the wafer 1 in a free state in the vertical direction. Is supported by the static pressure holding members 3a, 3b in a non-contact state, and is also supported by the carrier 6 in the horizontal direction.

VI. The upper grindstone 2a is further lowered at a very low speed, and both surfaces of the wafer 1 are ground by the upper grindstone 2a and the lower grindstone 2b while the wafer 1 is held at a static pressure (step 2).
6). Here, the upper and lower grindstones 2a, 2 in this step
The state of b, the upper and lower static pressure pads 3a and 3b, and the wafer 1 will be described in detail. As described above, the wafer 1 is supported by the carrier 6 in the horizontal direction but is free in the vertical direction. Further, in the static pressure holding state, the wafer 1 is held at an intermediate position between the upper static pressure pad 3a and the lower static pressure pad 3b. Therefore, in the static pressure holding state, the upper static pressure pad 3 interlocked with the upper grindstone 2a by the grinding feed (slow descent).
When a is lowered, the wafer 1 is supported by the carrier 6 in the horizontal direction, but is slightly lowered so as to be held at an intermediate position between the upper static pressure pad 3a and the lower static pressure pad 3b. It will be. In other words, in the static pressure holding state, the distance between the upper surface of the wafer and the upper static pressure pad and the distance between the lower surface of the wafer and the lower static pressure pad are always kept equal to each other. The distance between the upper and lower grindstones, that is, the distance between the upper grindstone and the upper surface of the wafer and the distance between the lower grindstone and the lower surface of the wafer are always equal.
Therefore, by lowering only the upper grindstone 2a, the gap between the lower grindstone 2b and the lower surface of the wafer is narrowed, and the upper surface of the wafer is ground by the upper grindstone 2a and the lower surface of the wafer is ground by the lower grindstone 2b. At this time, the amount of grinding of the upper surface of the wafer by the upper grindstone 2a and the amount of grinding of the lower surface of the wafer by the lower grindstone 2b are equal. That is, upper whetstone 2
It is possible to simultaneously control the depth of cut to the lower surface of the wafer by the lower grindstone 2b only by controlling the depth of cut to the upper surface of the wafer by a.

VII. After grinding the preset depth of cut, the upper grindstone 2a is slightly lifted (several tens of μm) from the upper surface of the wafer (step 27). Before stopping the rotation of the upper and lower grindstones 2a and 2b, the upper and lower grindstones 2a and 2b must be separated from the wafer surface, but when the upper grindstone 2a is rapidly raised, the static pressure holding state of the wafer 1 is released. At the moment, the wafer 1 jumps upward, and in order to prevent this phenomenon, the upper grindstone 2a is slightly raised from the upper surface of the wafer to the extent that the static pressure holding state is not released.

VIII. The rotations of the upper grindstone 2a and the lower grindstone 2b are stopped, and the roller drive motor is stopped to stop the rotation of the wafer 1 (step 28). This is because in order to stop the rotation of the wafer 1 stably and quickly, it is better to stop the wafer 1 when the wafer 1 is still in the static pressure holding state.

IX. The discharge of the coolant from each static pressure pad 3a, 3b is stopped (step 29). As a result, the wafer 1 is released from the static pressure holding state and placed on the lower grindstone 2b and the lower static pressure pad 3b.

X. Raise the upper grindstone 2a (step 3
0). The ascending completion position at this time refers to a position where the upper grindstone 2a and the upper static pressure pad 3a do not interfere with the taking-out of the wafer 1 from the carrier 6 by an unillustrated loading / unloading device.

XI. Wafer 1 by a loading / unloading device (not shown)
Is removed from the carrier 6 (step 31).

The configuration of the double-sided grinding apparatus to which the present invention is applied and the double-sided grinding method using the double-sided grinding apparatus have been described above. In the present embodiment, the application to a work piece made of a highly brittle material such as a semiconductor wafer has been described, but it can be applied to a metal material typified by steel or aluminum or a non-metal material such as glass (lens). Application is also possible within the technical scope of the present invention. In particular, when performing double-sided grinding on the surface of a work piece that is easily cracked or damaged, such as a lens, by holding the work piece under static pressure in a non-contact state with a static pressure holding member, the work piece is cut by a grinding tool (or The grinding feed amount of the grinding tool can be set to a minimum so that the grinding load received from the grinding tool) can be minimized. As a result, cracking of the work piece during processing can be prevented and the surface of the work piece after processing is completed. It is possible to minimize grinding scratches. Further, in the present embodiment, the static pressure holding by the coolant pressure has been described, but instead of this, the static pressure holding by the air pressure can obtain substantially the same effect as that of the present embodiment. However, in this case, it is necessary to separately provide a coolant supply means.

[0039]

According to the present invention, in simultaneous double-sided grinding of the surface of a disk-shaped work piece made of a highly brittle material typified by a semiconductor wafer, it is provided so as to face both the upper and lower surfaces of the work piece. Since the workpiece to be ground is supported by the static pressure holding member composed of a pair of upper and lower static pressure pads, the workpiece is a pair of grinding tools provided facing each other on both sides of the workpiece. Instead of, the static pressure holding member came to be supported in a non-contact state. In particular, when the static pressure holding members are provided at two positions inside and outside in the radial direction of the annular grinding tool, the cutting load received from each of the pair of grinding tools provided facing both sides of the workpiece. Even if the balance is unbalanced, the workpiece can be stably supported by the two static pressure holding members provided on both sides of the grinding stone contact surface of the workpiece, and as a result, double-sided grinding with high flatness. It became possible to process.

Further, according to the present invention, the workpiece being machined is supported by the static pressure holding member instead of the pair of grinding tools provided so as to face both sides of the workpiece. It is possible to adjust the cutting load of both upper and lower grindstones so that the grinding resistance becomes smaller, and as a result, it is possible to prevent the workpiece from cracking during machining and to minimize the grinding scratches on the surface of the workpiece after machining is complete. It became possible to suppress.

Further, in the case where the workpiece is supported only by a pair of grinding tools provided so as to face both sides of the workpiece as in the prior art, in order to equalize the grinding amount on both sides of the workpiece. The pair of grinding tools have to grind both sides of the work piece with equal pressing force, which is difficult to control with a highly brittle material such as a wafer having irregularities on the surface. If the workpiece is supported in a non-contact state by the static pressure holding members provided so as to face both sides of the workpiece as described above, one of the cutting amounts preset by the numerical controller can be used. Both sides of the work piece can be equally ground by simply giving it to a grinding tool, which makes control easier than in the prior art.

[Brief description of drawings]

FIG. 1 includes a positional relationship among a wafer (workpiece), upper and lower grindstones (grinding tool), and a static pressure holding member in the present invention,
It is a conceptual diagram which shows the principal part of a grinding device.

FIG. 2 is a flowchart showing an embodiment of a grinding method using a double-sided grinding device according to the present invention.

[Explanation of symbols]

 1 Wafer (workpiece) 2a Upper grindstone (grinding tool) 2b Lower grindstone (grinding tool) 3a Upper static pressure pad (static pressure holding member) 3b Lower static pressure pad (static pressure holding member) 4 Static pressure pocket 5 Abrasive grains Layer 6 Carrier (peripheral support)

Claims (6)

[Claims] 1. A double-sided grinding machine for simultaneously grinding both sides of a workpiece by a pair of annular grinding tools provided to face both upper and lower sides of a disk-shaped workpiece made of a highly brittle material. Both sides of a highly brittle material characterized in that the workpiece being processed is supported by a static pressure holding member composed of a pair of upper and lower static pressure pads provided so as to face the upper and lower surfaces of the workpiece. Grinding equipment. 2. The double-side grinding device for a highly brittle material according to claim 1, wherein the static pressure holding members are provided at two locations inside and outside the annular grinding tool in the radial direction. 3. A plurality of static pressure pockets are provided on the surface of each of the static pressure pads facing the surface of the workpiece, and a coolant discharge port is provided inside each static pressure pocket. The double-sided grinding device for a highly brittle material according to 1 or 2. 4. A static pressure pad of the static pressure holding member, which is provided so as to face the upper surface of the workpiece, interlocks with a grinding tool for machining the upper surface of the workpiece of the annular grinding tool. And the static pressure pad provided so as to face the lower surface of the workpiece is designed to operate in conjunction with the grinding tool for machining the lower surface of the workpiece among the annular grinding tools. The double-sided grinding device for a highly brittle material according to any one of claims 1 to 3. 5. The double-sided grinding apparatus for highly brittle material according to claim 1, wherein diamond abrasive grains are used as a material of the abrasive grain layer of the annular grinding tool. 6. During the grinding process, the workpiece is supported by the static pressure holding member in the vertical direction and is supported by an annular outer peripheral support (carrier) in the horizontal direction. The double-sided grinding device for a highly brittle material according to claim 4 or 5, characterized in that: