JP3673904B2 - Double-side grinding machine for thin disk-shaped workpieces - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a double-side grinding apparatus for thin disk-shaped workpieces, and more particularly to an apparatus for simultaneously grinding both surfaces of a thin disk-shaped workpiece such as a semiconductor wafer.
[0002]
[Prior art]
As a device that grinds both sides of a workpiece at the same time, a workpiece placed in a pocket of a rotating disk-shaped carrier is passed between a pair of rotating grinding wheels arranged so that the grinding surfaces of the end faces face each other. Is conventionally known. In this case, the outer diameter (diameter) of the grinding surface of the grinding wheel must be larger than the outer diameter of the workpiece. In addition, the carrier usually has a plurality of pockets formed at equal intervals on the circumference close to the outer periphery, and a part of the carrier enters between the pair of grinding wheels together with the wafer. Of course, the thickness of the carrier must be smaller than the distance between a pair of grinding wheels during grinding, that is, the finished thickness of the workpiece.
[0003]
By the way, currently used semiconductor wafers include those with an outer diameter of about 200 mm (8 inches) and those with an outer diameter of about 300 mm (12 inches), both of which have a thickness (finished dimension of grinding) of about 0.8 mm. Yes, it is very thin compared to the outer diameter. When such a wafer is ground with the above-described apparatus, since the outer diameter of the wafer is relatively large, the outer diameter of the grindstone increases, and the carrier that accommodates and rotates the wafer also increases. For this reason, an apparatus becomes large. In addition, since the wafer is thin, it is necessary to make the portion of the carrier that enters the grinding wheel together with the wafer very thin. Grinding force acts on the part of the carrier, especially the pocket, that enters between the grinding wheels, via the workpiece contained in the carrier. However, if this part is thinned, the strength decreases and the workpiece can be moved smoothly. It becomes difficult. For this reason, conventionally, double-side grinding of a wafer has been difficult.
[0004]
The same problem occurs in the case of a thin disk-shaped workpiece other than a wafer.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide an apparatus that can simultaneously and easily grind both surfaces of a thin disk-shaped workpiece and can be downsized.
[0006]
[Means for Solving the Problems and Effects of the Invention]
The apparatus according to the present invention comprises a pair of grinding wheels which are arranged and rotated so that the circular grinding surfaces of the end faces face each other and can move relative to each other in the axial direction, and processing surfaces on both sides of the thin disk-shaped workpiece. The workpiece is supported between the grinding surfaces so as to face the grinding surfaces of the pair of grinding wheels and a part and center of the outer periphery of the workpiece are located inside the outer circumference of the grinding surface. A workpiece rotation means for causing the workpiece rotation means to sandwich the portion of the workpiece that has come out from between the grinding wheels from both sides in the radial direction and to move in the circumferential direction of the workpiece. A pair of position holding belts arranged in such a manner, and these belts are provided with grooves for supporting the work in the axial direction and the radial direction by fitting the outer periphery of the work. Kutomo one is characterized in that said a drive belt for rotating the workpiece by being driven in the circumferential direction of the workpiece.
[0007]
The work is supported and rotated by the work rotation means such that a part of the outer periphery and the center thereof are located inside the outer periphery of the grinding surface, and a pair of grinding wheels respectively apply each grinding surface to each of the workpieces. It is rotated while being in contact with the processing surface. By rotating the grinding wheel, the work surface of the workpiece that is in contact with the grinding surface is ground, and the workpiece rotates with a part of the outer periphery and the center located inside the outer periphery of the grinding surface. During the rotation of the workpiece, the entire processing surface of the workpiece passes between the grinding surfaces and comes into contact with the grinding surface. For this reason, it is possible to simultaneously grind the entire processing surface of both surfaces by simply rotating the workpiece on the spot using a grinding wheel whose outer diameter is slightly larger than the radius of the workpiece. It is only necessary to rotate the workpiece on the spot, and it is not necessary to move it using a carrier as in the conventional case, so even a thin disk-shaped workpiece can be ground easily and reliably, and the device is compact. Is possible. In addition, it is possible to grind the entire work surface of the workpiece using a grinding wheel whose outer diameter is slightly larger than the radius of the work, and it is necessary to use a large grindstone whose outer diameter of the grinding surface is larger than the outer diameter of the workpiece. Therefore, it is possible to reduce the size of the apparatus from this point.
[0008]
In addition, the work can be reliably supported and rotated in the axial direction and the radial direction with only a pair of position holding belts provided with grooves, the configuration of the apparatus is simple, and further miniaturization is possible. There are two types of semiconductor wafers, one where the outer periphery is cut out in an arcuate shape and a flat portion for positioning is formed, and the other where this is not formed. Therefore, not only the wafer in which the positioning flat portion is not formed but also the wafer in which this is formed, the outer peripheral portion can be reliably supported and rotated.
[0009]
Therefore, according to the apparatus of the present invention, both surfaces of a thin disk-shaped workpiece can be ground simultaneously and easily, and the apparatus can be downsized.
[0010]
For example, the pair of position holding belts are respectively attached to a pair of openable and closable opening and closing members, and when the opening and closing members are closed, outer peripheral portions on both sides in the radial direction of the workpiece are fitted into the grooves of the belt. Has been made.
[0011]
In this way, the work can be easily held by the belt by closing the open / close member after the belt is positioned on both radial sides of the work with the open / close member open.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which the present invention is applied to double-side grinding of a semiconductor wafer will be described with reference to the drawings.
[0013]
FIG. 1 shows the overall configuration of a double-side grinding apparatus. This double-side grinding apparatus is intended for both a workpiece on which a positioning flat portion is not formed and a workpiece on which the workpiece is formed. The double-sided grinding machine is a horizontal axis double-sided surface grinding machine (1) with a workpiece rotation device (2) added as a workpiece rotation means. Details of the rotation device (2) are shown in FIGS. Yes. In the description of this embodiment, the front side of FIG. 1 is the front, the back side is the rear, and the left and right when viewing from the front, that is, the left and right of FIG.
[0014]
The grinding machine (1) includes a horizontal bed (3) and left and right grindstone heads (4) and (5) attached to the upper surface of the bed (3). The grindstone heads (4) and (5) are moved in the left-right direction independently from each other by an appropriate driving means (not shown). Horizontal grinding wheel shafts (6) and (7) are rotatably supported in the grinding wheel heads (4) and (5), respectively. The axes of the left and right grinding wheel shafts (6) and (7) are on one common horizontal line extending in the left-right direction. A cup-shaped left grinding wheel (8) is fixed to the tip of the grinding wheel shaft (6) that protrudes to the right from the left grinding wheel head (4), and the grinding wheel shaft (7 that projects to the left from the right grinding wheel head (5)) The right grinding wheel (9) of the same shape and dimensions is fixed to the tip of The annular vertical right end surface of the left grinding wheel (8) is the left circular grinding surface (8a), and the annular vertical left end surface of the right grinding wheel (9) is the right circular grinding surface (9a). ) (9a) face each other in a parallel state. In the case of this embodiment, the outer periphery of each grindstone (8) (9) and the outer periphery of each grinding surface (8a) (9a) coincide. When at least one of the left and right grindstone heads (4) and (5) moves in the left-right direction, the left and right grindstones (8) and (9) move relatively in the left-right direction, that is, in the axial direction. The left and right grindstone shafts (6) and (7) are rotated at the same speed in opposite directions by an appropriate drive means (not shown), so that the left and right grindstones (8) and (9) are rotated at the same speed in opposite directions. Rotated with. The other part of the grinding machine (1) can be configured in the same manner as a known horizontal-axis double-sided surface grinding machine.
[0015]
The rotating device (2) has a workpiece (wafer) (W) with both processed surfaces (a) and (b) facing the left and right ground surfaces (8a) and (9a) respectively, and a part of the outer periphery of the workpiece (W). The workpiece (W) is vertically supported and rotated between the left and right grinding surfaces (8a) (9a) so that the center (c) is located inside the outer periphery of the grinding surfaces (8a) (9a). And attached to a horizontal plate-like base (10) extending forward and backward at a position slightly above the grindstone heads (4) and (5).
[0016]
The base (10) is fixed to the bed (3) via an appropriate support (11) that does not hinder the movement of the grinding wheel head (4) (5), and a horizontal moving member (12) is attached to the upper surface of the base (10). ing. The moving member (12) is moved in the front-rear direction along the upper surface of the base (10) by an appropriate driving means (not shown). The moving member (12) extends vertically upward at the right end, and a vertical plate-like lifting member (13) extending in the vertical direction is attached to the right side surface thereof. The elevating member (13) is moved up and down along the right side surface of the moving member (12) by an appropriate driving means (not shown).
[0017]
On the right side surface of the elevating member (13), a pair of front and rear opening / closing members (14) parallel to the elevating member (13) and an air cylinder (15) for opening and closing the same are attached. . Pins (16) that extend horizontally to the right are fixed to the front and rear of the lower end of the elevating member (13), and the portions on the upper side of the opening and closing member (14) and on the outer side in the front and rear direction are attached to these pins (16) Each is pivotably attached. The cylinder (15) is mounted downward in the front-rear direction center of the upper part of the elevating member (13), and the tip (lower end) of the cylinder rod (15a) is opened and closed by a pair of links (17). The upper end portion of the member (14) is connected to a portion inward in the front-rear direction. A stopper (18) for regulating the rod (15a) is fixed to the lower end of the elevating member (13) directly below the cylinder (15) so that the vertical position can be adjusted. When the rod (15a) extends and moves to the lower end position where it hits the stopper (18), as shown in FIG. 3, the pair of opening and closing members (14) rotate to the closed position where the lower part is closed and the whole is almost vertical. To do. When the rod (15a) contracts and moves to the upper end position that is separated from the stopper (18) by a predetermined distance, the pair of opening and closing members (14) opens in the front and rear direction as shown in FIG. Rotate to the open position.
[0018]
Three grooved rollers (19) and (20) that rotate about a shaft extending horizontally to the right side on the right side surface of the part of each opening and closing member (14) protruding downward from the elevating member (13) Are attached, and endless position holding belts (21) and (22) are wound around three rollers (19) and (20) of each opening and closing member (14). The belts (21) and (22) support the outer periphery of the workpiece (W) protruding from between the grinding wheels (8) and (9) from both sides in the radial direction (front-rear direction) in the axial and radial directions. In addition, the workpiece (W) is rotated, and is made of a suitable flexible material such as rubber. Grooves (23) are formed on the outer peripheral surface of each belt (21) (22) to fit the outer peripheral portion of the work (W) and support it in the axial and radial directions. The cross section of the groove (23) has a trapezoidal shape with a wider bottom, and the width in the left-right direction of the opening is slightly smaller than the thickness of the workpiece (W). The rollers (19) and (20) are provided at two locations, the inner portion in the front-rear direction above and below the downward projecting portion of the opening / closing member (14), and at one location on the outer portion in the front-rear direction at the middle of the height It has been. The three rollers (20) of the rear opening / closing member (14) and the two rollers (19) on the rear side of the front opening / closing member (14) are centered on a pin (24) fixed to the opening / closing member (14). The rear belt (22) is a driven belt that moves in the length direction as the work (W) rotates. One roller (19) on the front side of the front opening / closing member (14) is a driving roller driven by an electric motor (25), and the front belt (21) applied thereto is driven in the length direction. This is a drive belt that rotates the workpiece (W). A long hole (26) extending in the front-rear direction in the closed position is formed in the downward projecting portion of the front opening / closing member (14), and the front side (right end) of the motor (25) disposed horizontally horizontally is formed in this long hole (26). The side portion is attached so that it can move in the length direction (front-rear direction) of the long hole (26) but does not move in the axial direction (left-right direction). A drive roller (19) is fixed to the tip of a motor shaft (not shown) protruding to the right from the opening / closing member (14). A spring built-in plunger (27) that biases the motor (25) forward is provided on the left side surface of the downward projecting portion of the front opening / closing member (14), thereby biasing the drive roller (19) forward. Thus, a predetermined tension is applied to the drive belt (21).
[0019]
In this embodiment, the outer diameter of the grindstones (8) and (9) is about 70% of the outer diameter of the workpiece (W), and the center (c) of the workpiece (W) is the grinding surface ( 8a) It is located slightly inside (lower side) of the outer periphery of (9a).
[0020]
Although not shown, a work loading device and a work unloading device are provided at appropriate locations behind the grinding machine (1), and the base (10) of the rotation device (2) is connected to these loading and unloading devices. It extends up.
[0021]
In the above grinding apparatus, the workpiece (W) is ground for example as follows.
[0022]
During the grinding operation, the left and right grindstones (8) and (9) are always rotating. At the start of work, the left and right whetstones (8) and (9) move to a standby position that is separated from the left and right, and the elevating member (13) has the lowermost part of the opening and closing member (14) above the whetstones (8) and (9). The front and rear opening / closing members (14) are opened to the open position. First, in such a state, the moving member (12) moves to an upper position of the work carry-in device. In the workpiece carry-in apparatus, workpieces (W) are supplied one by one to a predetermined carry-in position in a vertical state with the machining surfaces (a) and (b) facing left and right. The moving member (12) stops when the belt (21) (22) of the opening / closing member (14) in the open position comes directly above the workpiece (W) in the loading position, and then the lifting member (13) Is lowered to a predetermined workpiece loading position. As a result, the work (W) enters the space between the front and rear belts (21) and (22). At this time, as shown in FIG. 6, the opposing portions of the front and rear belts (21) and (22) are separated from the front and rear outer peripheral portions of the workpiece (W) and are linear. Next, the elevating member (13) is lowered to the workpiece loading position, and the cylinder rod (15a) is extended to come into contact with the stopper (18), whereby the opening / closing member (14) is closed to the closed position. When the opening / closing member (14) is closed to the closed position, the front-rear width of the opposed portions of the front and rear belts (21), (22) is smaller than the diameter of the workpiece (W), but in the middle of closing the opening / closing member (14). First, the front and rear outer peripheral parts of the workpiece (W) fit into the grooves (23) of the belt (21) (22), and the opposite portions of the belt (21) (22) made of a flexible material are ) Bend outward in the front-rear direction along the outer periphery of In the case of this embodiment, when the opening / closing member (14) is closed to the closed position, each belt (21) (22) has a groove (23) that is about a quarter of the circumference before and after the workpiece (W). The workpiece (W) is held by the belts (21) and (22). When the opening / closing member (14) is closed to the closed position, the elevating member (13) is raised to the standby position. As a result, the work (W) is held by the belts (21) and (22) and lifted from the work carry-in device.
[0023]
If the elevating member (13) is raised to the standby position, the moving member (12) moves to a position above the line connecting the left and right grindstones (8) (9) and stops. When the moving member (12) stops, the elevating member (13) descends to a predetermined grinding work position, and the drive roller (19) rotates. As the drive roller (19) rotates, the drive belt (21) is driven in the length direction, and the opposite portion moves in the circumferential direction of the workpiece (W). Then, the outer periphery of the work (W) fitted in the groove (23) of the belt (21) is moved in the circumferential direction by the frictional force with the belt (21). Rotated. As the work (W) rotates, the outer peripheral part of the work (W) that fits in the groove (23) of the driven belt (22) also moves in the circumferential direction, and the opposite part of the driven belt (22) becomes the work (W). Is moved in the circumferential direction of the workpiece (W) by the friction force between the belt (22) and the belt (22) is moved in the length direction. As a result, the work (W) rotates about its center (c). When the elevating member (13) is lowered to the grinding work position, the work (W) enters the space between the left and right grindstones (8) and (9), and as shown in FIG. 3, the center of the work (W) ( c) is located slightly below (inside) the uppermost part of the outer periphery of the grinding surfaces (8a) and (9a).
[0024]
If the elevating member (13) is lowered to the grinding work position, the grindstone (8) (9) is moved in a direction approaching each other, and the grinding surfaces (8a) (9a) correspond to the corresponding machining surfaces (a) (b) ). As a result, the lower part of the workpiece (W) is sandwiched between the grindstones (8) and (9), and a part of the lower outer periphery of the workpiece (W) and the center (c) are ground to the grinding surface (8a) (9a ) Is located inside the outer circumference. Since the front-rear distance between the front and rear open / close members (14) in the closed position is larger than the outer diameter of the grindstone (8) (9), the grindstones (8) (9) and the open / close member (14) do not interfere with each other. The grindstones (8) and (9) are moved to a predetermined position determined by the finished dimensions of the workpiece (W) and stopped at that position for a predetermined time. During that time, the grindstones (8) and (9) are rotated to grind the work surfaces (a) and (b) of the workpiece (W) in contact with the grinding surfaces (8a) and (9a). The workpiece (W) rotates while the workpiece (W) makes one rotation by rotating with a part of the outer circumference and the center (c) positioned inside the outer circumference of the grinding surface (8a) (9a). ) The machining surface (a) (b) of the entire surface passes between the grinding surfaces (8a) and (9a) and comes into contact with the grinding surfaces (8a) and (9a). In the meantime, the entire surfaces of both processed surfaces (a) and (b) are ground simultaneously. During grinding, if necessary, the elevating member (13) is reciprocated in the vertical direction, so that the workpiece (W) is in the vertical direction, that is, parallel to the grinding surfaces (8a) (9a). Reciprocate in the direction connecting the center (c) of the workpiece (W) and the axis of the grindstone (8) (9). This reciprocating movement is performed within a range in which a part of the outer periphery on the lower side of the workpiece (W) and the center (c) are always located inside the outer periphery of the grinding surfaces (8a) and (9a). For example, the stroke of the reciprocating movement is about 5 mm. By reciprocating the workpiece (W) in this way, the flatness and surface roughness of the center of the workpiece (W) can be improved.
[0025]
When the grinding of the workpiece (W) is completed, the grindstones (8) and (9) move away from the workpiece (W) and further move to the left and right standby positions. When the grindstones (8) and (9) are separated from the workpiece (W), the drive roller (19) stops rotating and the elevating member (13) is raised to the standby position. When the drive roller (19) stops, the belts (21), (22) and the workpiece (W) also stop. When the elevating member (13) is raised to the standby position, the moving member (12) is moved to an upper position of the work unloading device, and the work (W) is positioned directly above the predetermined unloading position. When the moving member (12) stops, the elevating member (13) descends to a predetermined unloading position, the cylinder rod (15a) contracts, and the opening / closing member (14) opens to the open position. As a result, the work (W) moves away from the belts (21) and (22), is moved to the carry-out position, and is carried out by the carry-out device. When the opening / closing member (14) is opened and the workpiece (W) is released, the elevating member (13) is raised to the standby position, and thereafter, the above operation is repeated to perform grinding one after another.
[0026]
When the workpiece (W) is reciprocated during grinding, the reciprocating direction is the direction connecting the center (c) of the workpiece (W) and the axis of the grindstone (8) (9) or close to this as described above. Although the direction is desirable, it may be reciprocated in another direction parallel to the grinding surfaces (8a) and (9a).
[0027]
On the wafer, there is a complete circular shape in which the flat portion for positioning as shown by the solid line in FIG. 3 is not formed, and a flat portion for positioning (f) in one place on the outer periphery as shown by the chain line in FIG. There are some of the cut-off circles. However, in the above grinding apparatus, the outer peripheral portion of the wafer is fitted into the groove (23) made of a flexible material, and the belt (21) (22) is matched to the shape of the outer periphery of the wafer. Therefore, not only the wafer in which the positioning flat portion is not formed but also the wafer in which the positioning flat portion is formed, the outer peripheral portion can be reliably supported and rotated.
[0028]
The left and right grindstones (8) and (9) are normally rotated at the same speed as in the above embodiment.For example, when it is desired to change the grinding allowance distribution of the left and right machining surfaces (a) and (b), In some cases, grinding can be performed by changing the rotational speed of the left and right grindstones (8) and (9). It is also possible to perform grinding by rotating the left and right grindstones (8) and (9) in the same direction.
[0029]
There may be a plurality of drive rollers (19) for driving the drive belt (21). Further, both of the pair of belts (21) and (22) may be used as drive belts.
[0030]
In the above embodiment, the pair of opening / closing members (14) are opened and closed by rotation, but may be opened and closed by parallel movement, for example. Further, the means for supporting the belts (21) and (22) is arbitrary, and it is not always necessary to attach them to the opening / closing member.
[0031]
In the above embodiment, the horizontal axis double-sided grinding apparatus in which the axis of the grinding wheel is horizontal is shown, but the axis of the grinding wheel is vertical in the same configuration as described above. .
[0032]
The present invention can also be applied to grinding thin disk-shaped workpieces other than semiconductor wafers.
[Brief description of the drawings]
FIG. 1 is a schematic front view of a double-side grinding apparatus showing an embodiment of the present invention.
FIG. 2 is an enlarged front view showing a main part of the work rotation device of FIG. 1;
FIG. 3 is a cross-sectional view taken along the line III-III in FIG.
4 is a cross-sectional view taken along the line IV-IV in FIG. 3;
FIG. 5 is a cross-sectional view showing a part of FIG. 4 further enlarged.
FIG. 6 is a drawing corresponding to FIG. 3 showing a state in which the opening / closing member is opened.
[Explanation of symbols]
(2) Workpiece rotation device (means)
(8) (9) Grinding wheel
(8a) (9a) Ground surface
(14) Opening / closing member
(21) (22) Position retention belt
(23) Groove
(W) Workpiece (semiconductor wafer)
(a) (b) Machined surface
(c) Center

Claims (2)

A pair of grinding wheels that are arranged so that the circular grinding surfaces of the end faces face each other and can move relatively in the axial direction are rotated, and the processing surfaces on both sides of the thin plate-like workpiece are the pair of grinding wheels. A workpiece rotation means for supporting and rotating the workpiece between the grinding surfaces so as to face the grinding surface of the grindstone and to have a part and center of the outer periphery of the workpiece located inside the outer circumference of the grinding surface. The workpiece rotation means is disposed so as to be able to move in the circumferential direction of the workpiece while sandwiching the portion of the workpiece protruding from between the grinding wheels from both sides in the radial direction. A pair of position holding belts are provided, and these belts are provided with grooves for supporting the work in the axial direction and the radial direction by fitting the outer periphery of the work, and at least one of the belts Double-side grinding apparatus of the thin disk-shaped workpiece, characterized in that the drive belt for rotating the workpiece by being driven in the circumferential direction of the click. The pair of position holding belts are respectively attached to a pair of openable and closable opening and closing members, and when the opening and closing members are closed, outer peripheral portions on both sides in the radial direction of the workpiece are fitted into the grooves of the belt. The double-sided grinding apparatus for thin disk-shaped workpieces according to claim 1, wherein:

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