JPH10296619A - Polishing surface plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain the flatness of a surface plate optimum, improve polishing accuracy and enhance productivity by increasing the polishing speed. SOLUTION: This polishing surface plate 10 is constituted so that a level block 12, wherein a polishing face 11 is formed on the surface side of the polishing surface plate 10, is provided to polish the surface to be polished of a workpiece flat with the surface of the workpiece pressed against the polishing face 11. In this case, coolant flowing passages through which coolant flows in two layers in the depth direction are formed within the level block 12, and the thickness of a core layer section 15 corresponding to the part between the two layer coolant flow passages 20A and 20B is larger than the thickness of the top side layer section 14 corresponding to the part between the surface and the coolant flow passage 20A on the surface side and the thickness of the bottom side layer section 16 corresponding to the part between the back face 13, which is the opposite side of the surface side, and the coolant flow passage 20B on the side of the back face 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing surface plate, and more particularly, to a polishing surface for pressing a surface to be polished of an object to be polished to flatten the surface to be polished. The present invention relates to a polishing surface plate provided with a surface plate provided so as to be formed on a polishing plate.

This polishing surface plate is used by being mounted on a wafer polishing apparatus for polishing the surface of a wafer to be polished. Wafer polishing equipment includes polishing equipment,
And a wrapping device. For example, as shown in FIG. 5, the polishing apparatus basically has a polishing surface plate 52 having a polishing surface 51 for polishing the surface of the wafer 50, and is disposed to face the polishing surface plate 52 to remove the wafer 50. Holder 53 for holding wafer, polishing surface 5 of wafer 50
A contact / separation mechanism 54 for moving the wafer holding unit 53 and the polishing platen 52 toward and away from the wafer holder 50 so that the wafer 50 is held against the polishing surface 51 by a predetermined pressing force. The pressing mechanism 55 for pressing, the wafer holding portion 53 in a state where the wafer 50 is pressed against the polishing surface 51.
A drive mechanism 56 for relatively moving the (wafer 50) and the polishing platen 52 (polishing surface 51) by rotation and / or reciprocation is provided, and a supply mechanism of a liquid abrasive called a slurry is provided. . The polishing platen 52 is usually
A member constituting a polishing surface, such as a cloth or a felt-like cloth, or a sponge or a short brush-like member, is fixed on a surface of a surface plate (main body) made of a metal plate or a ceramic plate. Includes a surface plate receiving portion for receiving and supporting the surface plate. According to the polishing apparatus configured as described above, the surface of a thin plate-like wafer to be polished, for example, the surface of a silicon wafer for a semiconductor device can be mirror-polished and flattened.

[0003]

2. Description of the Related Art Conventionally, in a wafer polishing apparatus as described above, the main body of a polishing platen (hereinafter simply referred to as a "platen") has a high flatness in order to improve the polishing accuracy of the wafer. Required. In particular, since the flatness of a silicon wafer, which is a raw material of a semiconductor chip, is required to have a submicron precision, the surface plate is not allowed to be slightly deformed and its rigidity is required to be very high. In order to increase the rigidity, the material is selected or the plate thickness is increased. Generally, stainless steel is used as the material of the conventional surface plate in the case of a polishing apparatus because of its chemical resistance, and in the case of a lapping apparatus, cast iron is used.

[0004]

However, in the above-mentioned conventional polishing platen, the polished surface side of the platen is heated by heat generated when the surface of the object to be polished (wafer) rubs against the polished surface. It deformed due to thermal expansion, and the flatness of the polished surface at the start of polishing and after a certain period of time had changed. In other words, the temperature on the front side, which is the polished surface side of the surface plate, is high due to frictional heat, whereas the temperature on the back surface side of the surface plate is low, so that the surface side of the surface plate is warped in a convex shape. However, there was a problem that the flatness (polishing accuracy) cannot be improved. As a conventional example, when the polished surface of the surface plate becomes 40 degrees Celsius or more in a constant temperature room at room temperature of 24 degrees Celsius, there is a problem that the flatness of the polished surface is reduced and the wafer cannot be polished to a desired flatness.

On the other hand, conventionally, as shown in FIGS. 6 (perspective sectional view) and FIG. 7 (plan sectional view), a cooling channel 60 through which a single layer of cooling water flows is provided inside a surface plate 52. The cooling water is supplied to the cooling channel 60 to prevent the surface plate 52 from overheating, thereby suppressing the deformation of the surface plate 52.
The arrows in the figure indicate the flow direction of the cooling water. The reason why the cooling flow path 50 is formed in a zigzag shape is to allow the cooling water to flow in a direction and to efficiently cool the entire surface. However, even with such cooling, the temperature gradient between the front surface (the surface on the polished surface side) and the back surface is unilaterally reduced as the surface becomes higher and moves toward the back surface. Therefore,
There is a problem that the surface side is elongated and the surface plate is inevitably deformed so that the entire surface side is convexly curved. In addition, it is conceivable to increase the cooling efficiency by adopting a shape structure that enhances heat dissipation, but if such a shape structure is adopted, the rigidity is reduced, and the accuracy of the polished surface is reduced due to the pressing force against the wafer. Will be. Also,
When low-temperature cooling water flows, the surface of the surface plate is cooled well, but the back surface is also cooled more than necessary, and as a result, the relationship of the temperature gradient between the surface and the back surface of the surface plate remains unchanged ,
Surface plate deformation is inevitable.

For this reason, conventionally, the polishing rate has been kept low so as to suppress the amount of heat generated by the friction between the surface of the wafer and the polished surface. (Note that in order to suppress the polishing rate, the pressing force for pressing the wafer against the polishing surface may be reduced, and the speed of the relative movement between the wafer and the polishing surface may be reduced.) There was a problem that the polishing efficiency could not be increased with the surface plate.

Accordingly, an object of the present invention is to provide a polishing surface plate that can maintain the flatness of the surface surface suitably, improve the polishing accuracy, and increase the polishing speed to improve the productivity.

[0008]

To achieve the above object, the present invention has the following arrangement. That is, the present invention
A polishing surface plate comprising a surface plate provided such that a surface to be polished is pressed against the surface to be polished and the surface to be polished is polished flat; Inside, a cooling channel through which the cooling liquid flows in two layers in the thickness direction is formed, and the thickness of the core layer portion corresponding to the portion of the space between the two layers of the cooling channel is the same as the surface. The thickness of the surface layer portion corresponding to the portion of the layer between the cooling channel on the front side and the portion of the layer interval between the back surface opposite to the front surface and the cooling channel on the back side. It is characterized in that it is thicker than the thickness of the back layer portion.

The two-layer cooling passages communicate with each other, and the cooling liquid flows in the order of the cooling passage on the front side and the cooling passage on the back side, so that the cooling liquid inevitably flows on the front side. The temperature of the cooling liquid flowing into the cooling flow path is lower than the temperature of the cooling liquid flowing into the cooling flow path on the back side, and the entire surface plate can be cooled in a well-balanced and efficient manner. Polishing accuracy for polishing the surface to be polished can be improved while maintaining the degree appropriately.

In addition, since the core layer, the surface layer, and the back layer are formed separately and three layers are laminated, they can be easily manufactured by a conventional processing method.

Further, the polishing plate according to the present invention is provided in a polishing apparatus for polishing or lapping the wafer, wherein the object to be polished is a wafer. Used for

[0012]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a perspective sectional view schematically showing one embodiment of a polishing platen used in a wafer polishing apparatus according to the present invention. In FIG. 1, a polishing surface 11 is provided so that a surface of a wafer to be polished is pressed against the surface of the wafer to be polished, and a polishing surface 11 for polishing the wafer surface flat is formed on the surface side. The internal structure of the platen body (hereinafter, simply referred to as “platen 12”) of the platen 10 is described in cross section. As is clear from the figure, a cooling channel 20 through which the cooling liquid flows in two layers in the thickness direction is formed inside the surface plate 12. A cloth or a felt-like cloth, a sponge or a short brush-like member, or the like is fixed to the surface of the surface plate 12, and the polishing surface 11 is configured by the cloth or the felt-like cloth.

Reference numeral 20A denotes a cooling channel on the front side,
2 is provided on the side of the surface (polishing surface 11). Also,
Reference numeral 20B denotes a cooling channel on the back surface, which is provided on the back surface 13 side opposite to the polishing surface 11. Cooling channel 2
Since 0 is two layers, it can be cooled efficiently. The two cooling channels 20A and 20B communicate with each other through an interlayer channel 22, and the cooling liquid is first supplied to the front surface side cooling channel 20A as shown by the arrow in FIG. After cooling the surface 11, the cooling channel 20B on the back side passes through the interlayer channel 22.
Supplied to As described above, the cooling liquid is supplied to the cooling channel 2 on the front side.
0A, the temperature of the coolant flowing into the cooling channel 20A on the front side necessarily increases the temperature of the coolant flowing into the cooling channel 20B on the back side. Lower than. That is, since the coolant is warmed by passing through the cooling channel 20A on the front side, when the coolant flows to the cooling channel 20B on the back side, the coolant is more heated than when flowing into the cooling channel 20A on the front side. The temperature is naturally rising. Therefore, the cooling effect of the cooling liquid acts on the entire surface plate 12 in a well-balanced manner, so that thermal deformation of the surface plate 12 can be suppressed, and polishing accuracy can be suitably improved.

As shown in FIG. 1, the thickness of the core layer 15 corresponding to the space between the two cooling passages 20A and 20B corresponds to the polishing surface 11 and the cooling passage 20A on the front side. And the thickness of the back layer portion 16 corresponding to the portion between the surface opposite to the polished surface (back surface 13) and the cooling channel 20B on the back surface. Thicker than it is. For example, in the present embodiment, the thickness of the core layer 15 is set to be three times the thickness of the surface layer 14 or the thickness of the back layer 16. Since the rigidity of the member increases in proportion to the cube of the thickness, the rigidity of the core layer 15 is 27 times the rigidity of the surface layer 14 or the back layer 16. The core layer 15 is surrounded by the cooling water surrounded by the two cooling channels 20A and 20B. Therefore, the temperature of the core layer portion 15 is maintained between the two cooling passages 20A and 20B at a uniform temperature. Thereby, the thermal deformation of the core layer 15 can be suitably suppressed, and the rigidity of the core layer 15 that has not been thermally deformed is utilized to make use of the surface layer 14.
And it can control that back layer part 16 deforms. That is, even if the surface layer portion 14 and the back layer portion 16 are heated and thermally expanded, the force can be pulled by the highly rigid core layer portion 15 and confined as internal stress. As described above, the core layer portion 15 is prevented from being deformed by being surrounded by the cooling water, and the surface layer portion 14 and the back layer portion 16 are suppressed from being deformed even when heated according to the above-described principle.
Eventually, deformation due to heat as the entire surface plate 12 can be suppressed,
Polishing accuracy can be suitably improved.

This effect increases as the thickness of the core layer 15 increases as compared with the thickness of the surface layer 14 and the thickness of the back layer 16. As described above, since the rigidity of the core layer portion 15 can be suitably used, even if the temperature of the polishing surface 11 increases to some extent, the accuracy of the flatness of the polishing surface 11 does not decrease. For this reason, even if the polishing rate is increased, highly accurate polishing can be performed. As a result, the productivity for polishing can be significantly improved.

The cooling liquid is supplied to the two-layer cooling passage 20.
The mode of supplying to A and 20B is not limited to the above embodiment. For example, a two-layer cooling flow path 20
A and 20B may not be connected to each other, and may have a structure in which the coolant is separately supplied. In this case, the cooling channel 20 on the front side
A, the temperature of the coolant flowing into the cooling channel 20 on the back side
B so as to be lower than the temperature of the coolant flowing into B.
A single coolant supply may be used. Further, from the viewpoint of making the temperature of the entire surface plate 12 more uniform, which is the gist of the present invention, the temperature of the back surface 13 is increased in accordance with the increased temperature of the polishing surface 11 of the surface plate 12. It is also possible to supply a high-temperature liquid (for example, temperature-adjusted water adjusted to a predetermined constant temperature) to the cooling channel 20A on the front side. Incidentally, a semiconductor device manufacturing factory for processing a wafer is provided with a plurality of temperature-regulated water supply devices so that water (temperature-regulated water) adjusted to a constant temperature can be obtained at various temperatures. And two types of temperature-regulated water can be obtained. Therefore, in the case described above, it is possible to easily supply temperature-regulated water having different temperatures to the front-side cooling passage 20A and the rear-side cooling passage 20B.

[0017]

Next, a more specific embodiment will be described with reference to FIGS. This embodiment has basically the same configuration as the embodiment of FIG.
4 and an example in which the back layer portion 16 is formed separately and three layers are laminated. 2 is a side sectional view, FIG. 3 is a sectional view taken along line XX of FIG. 2, and shows a cooling channel 20A on the front side, and FIG. 4 is a sectional view taken along line YY of FIG. The cooling channel 20B on the side is shown.

The surface layer portion 14 is formed in a disk shape as a whole, and has a lower surface formed with a groove serving as a cooling channel 20A on the front surface side. As shown in FIG. 3, the grooves are formed in a fan-shaped plane obtained by dividing a circle into three, and three grooves are provided on the lower surface of the surface layer portion 14. The leading shape of the groove is a zigzag in which one end of the groove starts straight from the center of the disk, is linearly drawn out to the outer peripheral portion, and a plurality of arcs successively decreasing concentrically from the outer peripheral portion of the disk toward the inside. When it comes to the center of the disk, it is again drawn straight out to the outer periphery. With this shape, cooling is performed efficiently and from the surface with a high peripheral speed, so that uniform cooling can be achieved. In addition, a portion located at the center of the disk at one end of the groove is provided with an inflow port 23 for cooling water as a cooling liquid.
become. Further, a portion located at the other end of the groove on the outer periphery of the disk is an outlet 24 which communicates with the interlayer flow path 22 of the core layer portion 15 and discharges cooling water to the cooling flow path 20B on the back side. .

The core layer 15 is formed in a disk shape as a whole, and both sides are formed flat. A through-hole is formed at the center of the disc and communicates in the thickness direction and passes through a water supply conduit 40 that supplies cooling water to the cooling channel 20A on the front side. Also, on the outer periphery of the disk, the outlet 2 of the surface layer portion 14 is provided.
At positions corresponding to No. 4, through holes serving as interlayer flow paths 22 are formed. The core layer portion 15 is set to have a thickness twice that of the surface layer portion 14 and a back layer portion 16 to be described later, and its rigidity is eight times. Flatness can be suitably maintained.

The back layer 16 is formed in a disk shape as a whole, and has a groove formed on the upper surface thereof to be the cooling channel 20B on the back side. As shown in FIG. 4, the groove has a shape drawn in a fan-shaped plane obtained by dividing a circle into three, and three grooves are provided. The routing shape is such that one end of the groove starts from the outer peripheral portion of the disk, and is extended in a zigzag shape in which a plurality of arcs are successively reduced concentrically from the outer peripheral portion toward the inside of the disk, and the center of the disk is formed. It has a shape communicating with the opening of the part. Efficient with this shape,
In addition, since cooling is performed from a surface having a high peripheral speed, uniform cooling can be achieved. A portion located at one end of the groove at the outer periphery of the disk is an inflow port 25 which communicates with the interlayer flow path 22 of the core layer portion 15 and in which cooling water flows into the cooling flow path 20B on the back side. The other end of the groove, which is located at the center of the disk, is a cooling water outlet 26.

The three layers of the surface layer 14, the core layer 15, and the back layer 16 are fastened together by a large number of bolts 28 and fixed together. Reference numeral 29 denotes a ring-shaped packing which seals water-tightly between layer portions that are in close contact with each other.
In order to secure the rigidity of the platen 12, it is preferable that the three layers are completely adhered to each other, and it is preferable that the three layers be formed of an integral material without any discontinuity. It is difficult to form with high accuracy, and the manufacturing cost is high. On the other hand, if three layers are formed in a superposed manner as in the present embodiment, it is possible to manufacture easily and accurately. In addition, 3
In order to integrate the members of the layer, instead of using bolts as in the present embodiment, using a method of joining the two by raising the temperature by joining the metal surfaces in a vacuum space, a so-called joining method by metal diffusion. Is also good.

Reference numeral 18 denotes a surface platen, which is removably mounted on the platen 12. In this embodiment, it is detachably fixed by the clamp 19, but it may be detachably fixed by suction using a vacuum device. A cloth or a felt-like cloth, a sponge or a short brush-like member is fixed to the surface of the surface platen 18, and the polishing surface 1 is fixed.
1 is configured. The reason for using such a surface platen 18 is to facilitate maintenance management of the polished surface 11. That is, there is an advantage that maintenance can be facilitated since the cloth can be detached and replaced externally when the cloth or the like is replaced. However, it is a matter of course that the polishing surface 11 may be formed by directly attaching a cloth to the surface of the surface plate 12 without using the surface layer surface plate. When the polishing surface 11 is formed in such a manner, the cooling effect by the cooling water appears more directly on the polishing surface 11, and is effective in suppressing thermal deformation due to frictional heat during polishing.

The platen 12 and the surface plate 18 may be formed of a ceramic plate or a metal plate. If the surface plate 12 is a ceramic plate, the weight can be reduced and the rigidity can be improved. For example, if the platen 12 is a ceramic mainly composed of alumina, the density is about 3.9 g / cc, which is about half of the density (about 7.9 g / cc) of the cast iron material. Therefore, the weight can be reduced to about half, and the maintenance management work at the time of replacing the cloth or the like can be easily performed. As ceramics, there are ceramics mainly composed of silicon carbide in addition to those mainly composed of alumina. The material of the platen is preferably high in rigidity as described above, has a small coefficient of thermal expansion and a high thermal conductivity, because it is difficult to deform.

Reference numeral 30 denotes a base, which supports the platen 12 via a bearing 32 so as to be rotatable about an axis. 3
Reference numeral 4 denotes a drive shaft, which is fixed to the back surface of the surface plate 12;
2 is provided to extend in a direction perpendicular to the surface 2 (downward in FIG. 2). The drive shaft 34 is connected to a rotary drive motor disposed below the platen 12, and rotates the polishing platen 10 about an axis by its driving force. Also,
The base 30 itself may be swingably supported by another base member so that the platen 12 swings. As the swinging motion, a motion such as a linear reciprocating motion or a turning motion that does not rotate may be adopted. This makes it possible to polish the wafer more uniformly.

Numeral 40 denotes a water supply pipe, which communicates with the cooling channel 20A on the front side so as to supply cooling water to the cooling channel 20A on the front side. Reference numeral 42 denotes a discharge pipe, which communicates with the cooling channel 20B on the back side so as to be discharged from the cooling channel 20B on the back side. The water supply pipe 40 and the discharge pipe 42 are connected to a cooling water supply / discharge unit. For example, a cooling water supply source may be connected to the water supply line 40, and a suction device may be connected to the discharge line 42 to circulate the cooling water through the cooling channel 20. A trochoid pump can be used as the suction device. In the case of suction, there is an advantage that no matter how much the degree of vacuum is raised, only one atmosphere is attained, and the deformation of the polishing platen does not exceed a certain level. However, it goes without saying that a high-pressure flow may be used.

The water supply line 40 and the discharge line 42 pass through the inside of the drive shaft 34 and are connected to the cooling water supply / discharge means via a distributor section provided below the drive shaft 34. The distributor is a mechanism that supplies and discharges the cooling water through the water supply pipe 40 and the discharge pipe 42 without leaking the cooling water even when the drive shaft 34 rotates, and can use a known technique. Reference numeral 45 denotes a cover,
It is mounted on the side surface so as to extend to the back surface side to prevent the slurry from scattering and protects the rotation drive mechanism that rotates the platen 12.

The polishing surface plate described above can be suitably used for a polishing apparatus for a wafer whose object is a wafer. As a wafer polishing apparatus, there is a polishing apparatus or a lapping apparatus. Further, the present invention is not limited to a surface plate having an upper surface serving as a polished surface as in the above-described embodiment, and may be used as a surface plate having a lower surface serving as a polished surface.
Further, it is needless to say that the present invention can be used for upper and lower platens of a double-side polishing machine for polishing both surfaces of a workpiece. Further, it is needless to say that the present invention is not limited to use in a single-wafer apparatus for polishing a single wafer, but may be used in a batch-type apparatus for holding and polishing a plurality of wafers with one plate. As described above, various preferred embodiments of the present invention have been described, but the present invention is not limited to these embodiments.
Of course, many more modifications can be made without departing from the spirit of the invention.

[0028]

According to the polishing platen of the present invention, a cooling flow path through which the cooling liquid flows in two layers in the thickness direction is formed inside the platen. The surface plate can be cooled as a whole with good balance and efficiency. Further, since the thickness of the core layer is larger than the thickness of the surface layer and the back layer, 2
Utilizing the rigidity of the core layer, which is kept at a uniform temperature between the cooling passages of the layers and the thermal deformation is suitably suppressed, the deformation of the surface layer and the back layer can be suppressed, and the deformation of the entire surface plate can be reduced. It can be suppressed suitably. For this reason, according to the present invention, it is possible to maintain the flatness of the surface plate appropriately, improve the polishing accuracy, and increase the polishing rate to improve the productivity.

[Brief description of the drawings]

FIG. 1 is a perspective sectional view schematically illustrating the principle of a polishing platen according to the present invention.

FIG. 2 is a cross-sectional view showing one embodiment of a polishing platen according to the present invention.

FIG. 3 is a cross-sectional view illustrating a cooling channel on the front side of the embodiment of FIG. 2;
It is a line sectional view.

FIG. 4 is a YY diagram showing a cooling channel on the back surface side of the embodiment of FIG. 2;
It is a line sectional view.

FIG. 5 is a schematic view of a polishing apparatus to which the polishing surface plate according to the present invention is attached.

FIG. 6 is a perspective sectional view schematically illustrating a conventional polishing platen.

FIG. 7 is a cross-sectional view illustrating a cooling channel of a conventional polishing platen.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Polishing surface plate 11 Polishing surface 12 Surface plate 13 Back surface 14 Surface layer portion 15 Core layer portion 16 Back layer portion 20A Cooling flow path on front side 20B Cooling flow path on back side 22 Interlayer flow path 28 Volt 40 Water supply pipe 42 Drainage Pipeline

Claims (4)

[Claims] 1. A polishing surface plate provided with a surface plate provided such that a surface to be polished is pressed against the surface to be polished and the surface to be polished is polished flat. In the surface plate, a cooling channel through which a cooling liquid flows in two layers in the thickness direction is formed inside the surface plate, and a thickness of a core layer portion corresponding to a portion of a layer interval of the two layers of cooling channels is provided. Has a thickness of a surface layer portion corresponding to a portion of a layer interval between the front surface and the cooling channel on the front surface side, and a layer of a back surface opposite to the front surface and a cooling channel on the back surface side. A polishing platen having a thickness greater than a thickness of a back layer portion corresponding to a space portion. 2. The cooling passage of the two layers communicates with each other, and the cooling liquid flows in the order of the cooling passage on the front surface side and the cooling passage on the back surface side. Polishing surface plate as described. 3. The polishing platen according to claim 1, wherein the core layer, the surface layer, and the back layer are formed separately, and three layers are laminated. . 4. The polishing surface plate according to claim 1, wherein the object to be polished is a wafer, and the polishing object is provided in a polishing apparatus for polishing or lapping the wafer.