JP4303860B2 - Silicon wafer polishing equipment - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a polishing apparatus for polishing a silicon wafer.
[0002]
[Prior art]
In the conventional silicon wafer manufacturing process, the polishing of the silicon wafer is performed by a lapping process in which the wafer is obtained by cutting the silicon ingot to remove the processing distortion, and in order to ensure the parallelism of the surface. It is performed in a so-called polishing process called a chemical mechanical polishing process (CMP) for polishing the wafer surface to a mirror surface close to the stage.
In any of these processes, the surface flatness of the silicon wafer and the parallelism of the front and back surfaces of the wafer are extremely important factors, and various polishing methods have been developed so far.
[0003]
An example of a conventional polishing apparatus will be described with reference to FIG. In the figure, 51 is a polishing surface plate, and this polishing surface plate is connected to a rotating shaft 53 and is rotated by a rotation drive device (not shown). A polishing cloth 52 is attached to the surface of the polishing surface plate 51, and a polishing agent usually made of abrasive grains such as alumina or silicon carbide is supplied to hold the polishing agent on the surface of the polishing cloth. Yes. On the other hand, a polishing plate 54 is fixed to the rotating shaft 56 and is disposed so as to face the polishing cloth. A silicon wafer 55 to be polished is attached to the lower surface of the polishing plate 54 with an adhesive such as wax. Although not shown, the polishing plate 54 is pressurized downward by an air cylinder or dead weight, the silicon wafer 55 and the polishing cloth 52 are pressed against each other, and the rotating shafts 53 and 56 are in contact with each other. The surface of the silicon wafer 55 is polished by rotating and moving the silicon wafer 55 and the polishing pad 52 relatively.
[0004]
By the way, with such a pressurizing method using an air cylinder and dead weight, it is difficult to uniformly pressurize the surface of the polishing platen 51 and the polishing plate 54, and the surface of the polishing platen 51 and the surface of the polishing plate 54 It is extremely difficult to maintain parallelism.
Further, heat is generated between the silicon wafer 55 being polished and the polishing cloth 52, and this heat generates a temperature difference between the upper and lower surfaces of the polishing plate 54, and the polishing plate is heated downward in a convex shape as shown in FIG. As a result, the silicon wafer 55 bonded to the surface is also deformed. As a result, the silicon wafer 55 obtained as a result of polishing has a concave surface as shown in FIG. 7, and both surfaces are non-parallel. There is a problem that becomes.
As described above, the conventional polishing apparatus employing the pressurizing means such as the air cylinder and dead weight is insufficient in terms of in-plane uniformity of pressure and thermal deformation of the plate.
[0005]
In the above polishing apparatus, there is known an apparatus that pressurizes a silicon wafer using a fluid such as air or water. That is, the apparatus shown in FIG. 8 is a polishing apparatus using a fluid as a pressurizing means, in which 81 is a polishing surface plate and 82 is a polishing cloth. Then, there is a polishing plate 84 to which a silicon wafer 85 is attached so as to face these, and an elastic hollow body 87 is disposed on the polishing plate 84. A fluid such as air or water is press-fitted into the elastic hollow body 87, and the pressure applied to the elastic hollow body 87 is evenly transmitted to the polishing plate 84 according to the Pascal principle, and the silicon wafer 85 is polished. 82 is in pressure contact. Also in this polishing apparatus, the polishing cloth 82 and the silicon wafer 85 are relatively moved by the rotation shafts 83 and 88 to perform polishing.
[0006]
By the way, in such a polishing apparatus, the use of air as the pressurizing means is known as disclosed in, for example, JP-A-11-77519. However, since there is no means for controlling the heat generated by friction between the silicon wafer and the polishing cloth in this polishing apparatus, the plate is thermally deformed by the generated heat, and the parallelism of the polished silicon wafer surface is ensured. The drawback of being difficult to do is still not improved.
[0007]
In the above polishing apparatus, the use of water as the pressurizing means is known as disclosed in, for example, Japanese Utility Model Publication No. 62-165849. However, in this polishing apparatus, since the water used as the pressurizing means is an incompressible fluid, the damper action is poor, and when there is a sudden pressure change due to fluctuations in the rotational drive system, the water is filled. It is difficult for the elastic hollow body to absorb the pressure change, and the impact of the pressure change is directly transmitted to the silicon wafer and the polishing cloth, resulting in the deterioration of the stability of the polishing conditions, and the polishing management such as the polishing thickness becomes difficult. Become.
In order to improve this, it is necessary to use a material having a small elastic coefficient as an elastic hollow body that contains water. However, since a high pressure cannot be applied to an elastic hollow body using such a material, polishing is difficult. There is a problem that efficiency is lowered.
[0008]
[Problems to be solved by the invention]
The present invention has been made in consideration of the above circumstances, and is excellent in uniformity in polishing a silicon wafer, and further improves the polishing accuracy by preventing thermal deformation of the polishing plate and improves the processing efficiency. An object of the present invention is to provide a polishing apparatus capable of performing the above.
[0009]
[Means for Solving the Problems]
The present invention includes a polishing platen having a polishing cloth adhered to the surface thereof, a hollow cylindrical polishing plate head disposed opposite to the polishing platen, and a slidably inserted into the opening of the polishing plate head. An elastic hollow body disposed in a space surrounded by the polishing plate having a surface for adhering a silicon wafer facing the polishing platen, the space between the polishing plate and the polishing plate head, and contacting the polishing plate A first temperature sensor for measuring the surface temperature of the polishing cloth, a second temperature sensor for measuring a temperature at a boundary between the polishing plate and the elastic hollow body, and processing a signal from the temperature sensor A control device for controlling the temperature of the fluid supplied to the elastic hollow body by a control signal from the control device, and supplying the temperature-adjusted fluid to the elastic hollow body That comprises a pipe, in a silicon wafer polishing apparatus is relatively sliding the silicon wafer and the polishing pad to polish the silicon wafer, the elastic hollow body is provided so as to surround the inner chamber and the inner chamber is separated into the outer chamber, the air in the inner chamber, Ri configured double structure der as the outer chamber may accommodate a temperature-controlled fluid by the temperature adjustment unit, the temperature control unit Is a silicon wafer polishing apparatus characterized in that the temperature of the fluid is controlled so that the surface temperature of the polishing cloth is equal to the surface temperature of the polishing plate on the elastic hollow body side .
[0010]
Further, in the silicon wafer polishing apparatus, the fluid is water .
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic cross-sectional view of the polishing apparatus of the present invention. The polishing apparatus of the present invention is mainly composed of a polishing surface plate 1 and a polishing plate head 6.
The polishing surface plate 1 is fixed to a rotating shaft 3 positioned at the lower portion, and is connected to a rotation driving device (not shown) to be rotatable. Then, a polishing cloth 2 is attached to the surface to slidably contact the silicon wafer and polish it.
[0012]
A polishing plate head 6 is disposed facing the polishing surface plate 1. The polishing plate head 6 is coaxially fixed to a rotary shaft 10 positioned above the polishing plate head 6 and is freely rotatable by a rotation driving device (not shown) and adjusts the gap with the polishing platen. It can be moved up and down as much as possible. The polishing plate head 6 has a cylindrical hollow cylinder shape, and the double-structure elastic hollow body 7 and the polishing plate 4 are accommodated therein.
The double-structure elastic hollow body 7 is a hollow structure having a double structure formed of an elastic body such as rubber, and the inside thereof is separated into an inner chamber 8 and an outer chamber 9. These inner chamber 8 and outer chamber 9 can press-fit fluids such as gas and liquid through fluid supply pipes 11 and 13, respectively. These fluids can be press-fitted and discharged by valves 12 and 14 provided in the opening piping of the inner chamber 8 or the outer chamber 9.
The polishing plate 4 is slidably inserted into the opening of the polishing plate head 6, and the surface of the polishing plate 4 facing the polishing platen 1 is bonded to a silicon wafer by an adhesive such as wax. 5 is attached.
[0013]
In order to polish a silicon wafer using such a polishing apparatus, first, the silicon wafer 5 is adhered and held on the polishing plate 4. At this time, it is desirable to arrange the silicon wafer 5 at the periphery of the polishing plate 4 so as not to be positioned on the polishing plate rotation center axis in order to perform uniform polishing. Further, when a plurality of silicon wafers 5 are bonded and polished, the uniformity of polishing is further improved by arranging the silicon wafer 4 so as to be rotationally symmetric with respect to the rotation center axis of the polishing plate 4.
[0014]
Next, relative positioning between the polishing platen 1 and the polishing plate head 6 and press-fitting of fluid into the inner chamber 8 and the outer chamber 9 of the double structure elastic hollow body 7 are performed. At this time, it is necessary to use a gas and a liquid in combination as the fluid. The contact pressure between the silicon wafer 4 and the polishing pad 2 is determined by the pressure of the fluid sealed in the double-structure elastic hollow body 7, and the polishing speed is determined.
The polishing apparatus set in this manner is relatively rotated and moved by the rotary shafts 3 and 10 connected to the polishing surface plate 1 and the polishing plate head 6 in the same manner as the conventional polishing apparatus for polishing. At this time, it is desirable to hold a polishing agent containing abrasive grains such as alumina or silicon carbide in the polishing cloth 2, and further improvement of polishing efficiency can be expected by supplying the polishing agent during polishing. .
[0015]
In the above embodiment, polishing is performed without controlling the temperature of the polishing plate. However, the temperature between the silicon wafer side surface and the double-structure elastic hollow body side surface of the polishing plate by the polishing heat between the polishing cloth and the silicon wafer. The difference may cause thermal deformation of the polishing plate. In order to suppress this, it is desirable to adjust the temperature of the polishing plate. A more preferred embodiment of the present invention will be described with reference to FIG. In this more preferred embodiment, the temperature can be adjusted by flowing a temperature-controlled fluid through an outer chamber in contact with the double-structured elastic hollow body polishing plate. Such a polishing apparatus of the present invention is obtained by adding means for measuring the temperature of the polishing plate surface and means for controlling the temperature of the polishing plate surface based on the result to the polishing apparatus of the present invention shown in FIG. is there.
[0016]
In the present invention, in order to control the temperature of the polishing plate, it is necessary to accurately grasp the temperatures of the upper and lower surfaces of the polishing plate, but it is difficult to measure the surface of the polishing plate on the silicon wafer side. Therefore, in the present invention, with respect to the silicon wafer side surface of the polishing plate, the temperature of the polishing cloth surface, which is approximate to the temperature of the silicon wafer side surface of the polishing plate, is measured by a radiation temperature sensor. That is, in the polishing apparatus of this embodiment shown in FIG. 2, reference numeral 15 denotes a radiation temperature sensor which is a first temperature sensor for measuring the surface temperature of the polishing pad 2 in a non-contact manner, and its output is sent to the temperature sensor interface 17. .
[0017]
The temperature of the surface of the polishing plate 4 on the side of the double-structured elastic hollow body 7 is a contact temperature such as a thermocouple as a second temperature sensor on the contact surface between the polishing plate 4 and the double-structured elastic hollow body 7. Install sensor 16 and measure. The output signal from the temperature sensor 16 is output to the temperature sensor interface 18, but since the polishing plate head 6 is a rotating body, signal transmission between the temperature sensor 16 and the temperature sensor interface 18 is a signal extraction. A wireless interface that does not require wires can also be used.
[0018]
The output signals of these two temperature sensors 15 and 16 are sent to the control device 19 via the temperature sensor interfaces 17 and 18. Then, the control device 19 compares the surface temperature of the polishing pad 2 with the temperature of the boundary surface between the elastic hollow body 7 of the polishing plate 4 based on the information of these two temperature sensors 15 and 16, and FIG. As shown, the temperature of the fluid as the heat exchange medium is controlled by the temperature control unit so that the polishing cloth surface temperature T ₁ and the elastic hollow body side surface temperature T _{2 of the} polishing plate are substantially equal, and the heat exchange medium fluid is doubled. The temperature is adjusted by press-fitting into and flowing through the outer chamber 9 of the structural elastic hollow body. In this case, water having a relatively large heat capacity is appropriate as the heat exchange medium fluid. In this case, it is desirable to enclose air having a small elastic coefficient in the inner chamber. Further, it is desirable that the heat exchange medium fluid be recycled to the temperature control unit 20 after heat exchange.
[0019]
In the polishing apparatus, the temperature sensors 15 and 16 are usually output as analog signals, and the controller 19 is the simplest means using a digital arithmetic processing unit. Therefore, the temperature sensor interface needs to fulfill the function of an analog-digital converter.
[0020]
As described above, when the temperature of the polishing plate is not adjusted in the silicon wafer polishing apparatus, as shown in FIG. 3, the temperature on both the front and back surfaces of the polishing plate increases according to the operation time of the polishing apparatus. The difference becomes large, and the polishing plate is thermally deformed to cause deformation of the polished silicon wafer as described above. In this embodiment of the silicon wafer polishing apparatus shown in FIG. 2, the polishing plate shown in FIG. The surface temperature is adjusted so as not to cause a difference in temperature between the front and back surfaces to prevent thermal deformation of the polishing plate and improve the polishing accuracy of the polished silicon wafer.
[0021]
【The invention's effect】
The polishing apparatus of the present invention can apply uniform pressure to the polishing plate to which the silicon wafer is bonded, further uniformize the temperature distribution generated in the polishing plate, and suppress thermal deformation of the polishing plate. Therefore, when the polishing apparatus of the present invention is applied to the processing of a silicon wafer, the flatness of the silicon wafer can be improved.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of a polishing apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view of a polishing apparatus according to a more preferred embodiment of the present invention.
FIG. 3 is a graph showing the relationship between the polishing time and the temperature of the polishing plate surface for explaining one embodiment of the present invention.
FIG. 4 is a graph showing the relationship between the polishing temperature and the temperature of the polishing plate surface for explaining one embodiment of the present invention.
FIG. 5 is a schematic sectional view of a conventional polishing apparatus.
FIG. 6 is a diagram showing thermal deformation of a polishing plate in a conventional polishing apparatus.
FIG. 7 is a diagram showing the shape of a silicon wafer polished using a polishing plate thermally deformed in a conventional polishing apparatus.
FIG. 8 is a schematic sectional view of another conventional polishing apparatus.
[Explanation of symbols]
1,51,81. Polishing surface plate 2, 52, 82. Polishing cloth 3, 10, 53, 56, 83, 88. Rotating shaft 4, 54, 84. Polishing plates 5, 55, 85. 5. Silicon wafer 6. Polishing plate head 7. Double structure elastic hollow body Inner room9. Outside room 10. Rotating shafts 11,13. Fluid injection piping 12,14. Valve 15. Radiation temperature sensor 16. Temperature sensor 17,18. 18. Temperature sensor interface Control device 20. Temperature control unit 87. Elastic hollow body

Claims (2)

A polishing surface plate with a polishing cloth adhered to the surface, a hollow cylindrical polishing plate head disposed opposite to the polishing surface plate, and a polishing surface plate slidably inserted into the opening portion of the polishing plate head A polishing plate having a surface for adhering a silicon wafer opposite to the substrate, an elastic hollow body disposed in a space surrounded by the polishing plate and the polishing plate head, and in contact with the polishing plate , and the polishing A first temperature sensor for measuring the surface temperature of the cloth; a second temperature sensor for measuring a temperature at a boundary between the polishing plate and the elastic hollow body; and a control for processing a signal from the temperature sensor A temperature control unit for controlling the temperature of the fluid supplied to the elastic hollow body by a control signal from the control device, and a pipe for supplying the temperature-controlled fluid to the elastic hollow body by the temperature control unit In the silicon wafer polishing apparatus for polishing the silicon wafer by relatively sliding the silicon wafer and the polishing cloth, the elastic hollow body is provided in the outer chamber provided so as to surround the inner chamber and the inner chamber. are separated, the air in the inner chamber, Ri configured double structure der as the outer chamber may accommodate a temperature-controlled fluid by the temperature adjustment unit, the temperature control unit, said A silicon wafer polishing apparatus, wherein the temperature of the fluid is controlled so that the surface temperature of the polishing cloth and the elastic hollow body side surface temperature of the polishing plate are equal .   The silicon wafer polishing apparatus according to claim 1, wherein the fluid is water.

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