JP3377860B2 - Polishing control device for semiconductor wafer - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor wafer polishing control apparatus suitable for, for example, a batch polishing type silicon wafer polisher, and particularly to a semiconductor wafer polishing control that enables high flatness polishing. It relates to the device.

[0002]

2. Description of the Related Art Conventionally, as a device for mirror-polishing the surface of a semiconductor wafer, a polishing device called a silicon wafer polisher configured as shown in FIG. 6 has been used. The polishing apparatus shown in this figure is of standard construction.

A centering bearing 2 is provided on the pressure shaft 1,
A pressure head 3 is attached to the centering bearing 2 so as to be swingable with respect to the pressure shaft 1 and rotatable with the pressure shaft 1.

Below the pressure head 3, there is mounted a block 4 as shown in FIG. 7, which is capable of simultaneously mounting a plurality of silicon wafers 5 (four in the figure) as a material to be polished. A surface plate 9 having a polishing pad 6 attached to the upper surface thereof is provided on the side facing the pressure head 3.

Therefore, when polishing the silicon wafer 5, the block 4 is pressed against the surface plate 9 with the silicon wafer 5 mounted, and the silicon wafer 5 is applied to the polishing pad 6 while rotating the pressing head 3. Slide it.

In this polishing process, the platen 9 is caused by the polishing heat generated by the friction between the silicon wafer 5 and the polishing liquid 17 supplied on the polishing pad 6 due to the pressing force and the chemical reaction.
There is a problem that it is difficult to polish the silicon wafer 5 with high flatness because the flatness and the temperature of the silicon wafer 5 change.

In order to suppress this temperature change, the polishing apparatus is provided with a cooling mechanism as shown in the figure. In a general cooling mechanism, the surface plate 9 has a water cooling jacket 1
0 is attached, cooling water having a constant temperature is supplied to the water cooling unit 11 via the supply system 14, and the cooling water in the cooling unit 11 is discharged via the drainage system 15. Further, the surface plate 9 and the water cooling jacket 10 are mounted on a thrust bearing 12 or the like mounted on a pedestal 13 in order to prevent the occurrence of vertical shake when rotating by the rotating shaft 16. In addition, the pressure applied from the pressure shaft 1 causes the surface plate 9
In order to prevent the flat surface of the plate from being deformed and to cool the surface plate 9 uniformly, the cooling jacket 10 is provided with ribs 18 as shown in FIG. 8, and the surface plate 9 and the water cooling jacket 10 are bolted. The structure is such that it is assembled with a bolt through the hole 19.

[0008]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
Even a conventional polishing apparatus having a rib structure for preventing the deformation of the above still has the following problems.

That is, the temperature of the cooling water is fixed by the heat of polishing until it reaches about 40 ° C., which is the temperature condition for obtaining proper polishing surface quality and polishing productivity of the silicon wafer 5. The surface temperature of the platen 9 rises from the start of polishing to the end of polishing, and the surface plate 9 is thermally deformed as the temperature rises.

FIG. 9 shows exaggeratedly that the surface plate 9 is generally thermally deformed to the lower surface side by thermal expansion. FIG. 10 shows that the silicon wafer 5 is moved to the center side of the block 4 due to the thermal deformation. It shows a state of being inclined and polished. In general, in order to prevent the silicon wafer 5 from being inclined and polished, the thermal deformation at each point of the surface plate 9 is predicted in advance from the deformation amount curve as shown in FIG. This deformation curve is processed so as to have a concave surface shape that is line-symmetric with respect to the reference level, and the temperature control of the polishing surface at the time of heating is performed so that the planar state of the surface plate 9 matches the block 4 in the temperature rising state. It corresponds by doing.

However, the surface plate 9 has a diameter of 1 to 1.5.
Since it is very large, it takes a lot of processing time to finish the surface plate 9 into a concave shape that is aimed at, and skilled processing operations are also required. Therefore, the processing work of the surface plate 9 is extremely complicated. There is a problem of becoming. Further, even if an ideal shape can be obtained by such processing, as shown in FIG. 12, the polishing apparatus repeats polishing and resting under cooling water of a constant temperature during use. The surface plate 9 is repeatedly displaced along with the polishing and the rest, and eventually the machining of high flatness reaches its limit.

Further, a water cooling jacket 10 is in contact with the thrust bearing 12, and the concave shape of the surface plate 9 may change over time due to loosening or stretching of bolts or the like that attach the water cooling jacket 10 to the surface plate 9. There is. Therefore, in order to manage and maintain the concave shape of the surface plate 9, time is required for measuring the concave shape and performing repair processing, and the down time of the polishing apparatus becomes long, so that the work efficiency of wafer polishing is improved. There is a problem that it will decrease.

The temperature of the polishing surface of the surface plate 9 suitable for the matching is such that the properties (surface condition, etc.) of the polishing pad 9 change in the order of the number of polishing batches, and the time between polishing batches varies. Therefore, the temperature changes by 2 ° C to 5 ° C. When the desired polishing temperature changes, the polishing temperature and surface plate 9
Since the thermal deformation state of No. 2 changes significantly, it is necessary to adjust the polishing time in addition to adjusting the temperature and supply amount of the abrasive liquid 17 for temperature control. Such a large number of changes in operating conditions cause deterioration of the polished shape of the wafer,
This causes uneven polishing amount and inclination.

In order to solve the problems of the conventional polishing apparatus as described above, a method of arranging a hollow body on a block for the purpose of uniform pressure application at a wafer pressure head unit is proposed in Japanese Patent Laid-Open No. 63-52967. Although there is a technique disclosed in the publication, it is actually very difficult to obtain a flat wafer flatness only by taking measures against this polishing head alone. Further, the technology disclosed in Japanese Utility Model Laid-Open No. 60-56460 is
The temperature of the cooling water is adjusted so that the temperature during polishing becomes constant, so that the flatness of the polishing platen can be ensured.
Further, the technique disclosed in Japanese Patent Application Laid-Open No. 2-27721 improves the polishing accuracy of a wafer by monitoring the state of the polishing surface during polishing without contact. However, such a technique causes a new problem that it is theoretically difficult to perform high-precision flatness processing or economically difficult.

The present invention has been made in view of the above conventional problems, and is capable of suppressing thermal deformation of the surface plate as much as possible, relatively easily and economically, and has a very high precision silicon wafer. It is an object of the present invention to provide a semiconductor wafer polishing control device capable of performing the above polishing.

[0016]

The present invention for achieving the above object comprises a block for holding a material to be polished, and a surface plate arranged on the side of the block holding the material to be polished.
A pressing mechanism for pressing the block against the surface plate,
A polishing control apparatus for a semiconductor wafer used in a polishing apparatus, comprising: a slide drive mechanism for relatively sliding the block and the surface plate, and a cooling mechanism for cooling the surface plate, the polishing apparatus comprising: Polishing device control means for generally controlling the operation of the device, and the block and the surface plate when the polishing control device controls the polishing of the material to be polished.
Thermal deformation of the surface plate caused by relative sliding motion with
Control is applied to the cooling mechanism so that
Temperature higher than the temperature of the cooling water supplied when not
Cooling water supply means for supplying the cooling water of a certain degree.

This cooling water supply means, when the polishing control device controls the polishing of the material to be polished, causes the surface plate to be caused by the relative sliding motion between the block and the surface plate. In order to be able to correct the thermal deformation of the above, the cooling mechanism is supplied with cooling water at a temperature higher than the temperature of the cooling water supplied when the control is not performed.

[0018]

The cooling water supply means controls the heating means for heating the cooling water in the path for supplying the cooling water to the cooling mechanism, and the polishing controller for polishing the material to be polished. If the control is not performed, the heating means is operated, and if the control is not performed, the heating control means is inactivated.

[0020]

The heating control means controls the amount of heat generated by the heating means according to the amount of deformation of the surface plate.

[0022]

The operation of the polishing apparatus is generally controlled by the polishing apparatus control means. However, when the polishing apparatus control means controls the polishing of the material to be polished, the cooling mechanism is equipped with this polishing apparatus, for example. Cooling water having a temperature higher than the temperature of the cooling water supplied when the control is not performed. Therefore, it becomes possible to suppress the deformation of the surface plate that occurs during polishing, and it becomes possible to perform highly accurate flat surface polishing.

[0023]

The supply of the cooling water having different temperatures may be performed by selectively switching the paths in which the cooling water having different temperatures is stored in advance during polishing and during suspension.

The cooling water supply means is composed of heating means for heating the cooling water in the path for supplying the cooling water to the cooling mechanism and heating control means for controlling the amount of heat generated by the heating means. The heating means in the case of such a configuration operates the heating means when the polishing control device controls the polishing of the material to be polished, while the heating means operates when the control is not performed. Control is performed so that the heating means is inactivated.

[0026]

If the heating means is controlled by the heating control means so as to generate heat according to the amount of deformation of the surface plate,
Further, highly accurate flat surface polishing can be performed.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a semiconductor wafer polishing control apparatus according to the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a schematic structure of a semiconductor wafer polishing controller according to the present invention. The polishing apparatus 30 shown by blocks in the figure is one that has been conventionally used, and has the same configuration as that described in FIGS. 6 to 8, for example. is there. The polishing control device 35 controls the operation of the polishing device 30, and functions as a polishing control means. The cooling water temperature control device 40 has a cooling mechanism provided in the polishing device 30, specifically, a function of controlling the temperature of the cooling water supplied to the water cooling jacket 10 shown in FIG. It functions as a cooling water supply means. The cooling water whose temperature is controlled by the cooling water temperature control device 40 is pump 46 or pump 47.
Are supplied to the water cooling jacket 10.

The cooling water temperature controller 40 is the polishing controller 3
It has a function of producing cooling water of different temperatures based on the polishing signal and the rest signal output from the device 5. The cooling water temperature control device 40 operates as in the flowchart shown in FIG. The cooling water temperature control device 40 inputs the polishing signal output from the polishing control device 35 when the polishing device 30 is polishing a silicon wafer (S
1) If this polishing signal is input, raise the cooling water temperature to, for example, about 25 ° C. (S2), and pump 4
6 to the water cooling jacket 10. By supplying the cooling water whose temperature has been raised in this manner, it becomes possible to suppress the surface plate 9 from being deformed as shown in FIG. 9 due to heat generation during polishing. This is because if the cooling water having a high water temperature is supplied to the water cooling jacket 10, the surface plate 9 can be made into a concave shape due to the thermal expansion of the water cooling jacket 10, and the surface plate 9 is deformed into a convex shape by the heat of polishing. This is because the thermal deformation of the board 9 can be offset.

On the other hand, the cooling water temperature control device 40 inputs the pause signal output from the polishing control device 35 when the polishing device 30 is not polishing the silicon wafer (S1), and this pause signal is input. If so, the cooling water temperature is lowered to about 20 ° C. (S4), and the water is supplied to the water cooling jacket 10 by the pump 46 (S3). As a result, the temperature difference between the surface of the surface of the surface plate 9 which is rapidly cooled after the polishing and the side of the water cooling jacket 10 can be reduced.

The cooling water temperature control device 40 operating as described above has different temperatures for the cooling water supplied through the same cooling path depending on whether the polishing signal is input or the pause signal is input. It has the function of producing cooling water inside. Specifically, a temperature control device is provided in the path from the cooling water tank to the pump 46, which is capable of adjusting the temperature of the cooling water flowing through this path within a certain temperature range. By performing the above control, the amount of displacement of the surface plate 9 can be suppressed to some extent as shown in FIG. It is obvious that this displacement amount is reduced when compared with FIG. 12 showing the displacement amount of the surface plate 9 when the cooling water temperature is kept constant as in the conventional case.

In the above example, the temperature of the cooling water is adjusted to about 25 ° C. while polishing is being performed, and is adjusted to about 20 ° C. when not being polished. The temperature may be set according to the material of the surface plate 9 and the polishing condition of the silicon wafer so that the adverse effect due to its thermal deformation is minimized, and is not particularly limited to this temperature.

For example, as shown in FIG. 3, the flatness of the surface plate 9 changes linearly with respect to the reference level in accordance with the temperature of the cooling water as shown in the figure. If you select a cooling water temperature that matches the level,
High flatness polishing is possible. Further, in the above embodiment, the case of the internal slip is illustrated, but in the case of the external slip, since the deformation opposite to the case of the internal slip must be considered,
In this case, supply cooling water with low water temperature during polishing,
Supply warmed cooling water at rest.

This internal slip means that when the thermal deformation of the surface plate 9 changes as shown in FIG. 9, a tapered polishing state as shown in FIG. 10 is obtained. The internal slip occurs due to the difference in the coefficient of thermal expansion between the material of the surface plate 9 and the material of the water cooling jacket 10. Therefore, when the coefficient of thermal expansion of both materials is opposite to the case where the internal expansion occurs, an external deviation occurs in which the outer side is excessively shaved contrary to the case shown in FIG. When this external deviation occurs, it is necessary to restore the concave warp, so cooling water having a low water temperature is supplied during polishing.

In the above embodiment, the temperature of the cooling water flowing in the same path is adjusted depending on whether the polishing signal is input or the pause signal is input. In the case of the different embodiment, as shown in FIG. 1, the dedicated paths for the cooling water of different temperatures are provided inside the cooling water temperature control device 40 and the cooling water temperature control device 4 respectively.
It is provided from 0 to the water cooling jacket 10 of the polishing apparatus 30, and dedicated pumps 46 and 47 are arranged on each path. In the cooling water temperature control device 40, in the path from the cooling water tank to the pump 46, a temperature control device capable of adjusting the temperature of the cooling water flowing through this path to, for example, about 20 ° C., and the cooling water. Provided in the path from the tank to the pump 47 is a temperature controller capable of adjusting the temperature of the cooling water flowing through this path to a temperature of, for example, about 25 ° C., and when a polishing signal is input and when a pause signal is input. It is provided with a function of selectively switching the pump 47 or the pump 46 depending on whether it is input.

Cooling water temperature control device 40 according to this embodiment
Operates like the flowchart shown in FIG.

The cooling water temperature control device 40 inputs the polishing signal output from the polishing control device 35 when the polishing device 30 is polishing a silicon wafer (S11), and when this polishing signal is input. For example, a pump 47 for supplying cooling water at 25 ° C. is selectively operated (S1
2) The cooling water heated to about 25 ° C. is supplied to the water cooling jacket 10 (S13). By supplying the cooling water whose temperature has been raised in this manner, it becomes possible to suppress the surface plate 9 from being deformed as shown in FIG. 9 due to heat generation during polishing. This is because if the cooling water having a high water temperature is supplied to the water cooling jacket 10, the surface plate 9 can be made into a concave shape by the thermal expansion of the water cooling jacket 10, and a constant shape which is likely to be deformed into a convex shape by the polishing heat. This is because the thermal deformation of the board 9 can be offset.

On the other hand, the cooling water temperature control device 40, when the polishing device 30 is not polishing the silicon wafer,
For example, the pump 46 that supplies cooling water at 20 ° C. is switched from the pump 47 to operate (S14), and cooling water having a water temperature of about 20 ° C. is supplied to the water cooling jacket 10 (S1).
3). As a result, the temperature difference between the surface of the surface of the surface plate 9 which is rapidly cooled after the polishing and the side of the water cooling jacket 10 can be reduced.

Also, in the above embodiment, the case of the internal slip has been illustrated, but in the case of the external slip, the deformation opposite to the case of the internal slip must be taken into consideration. Cooling water with a low water temperature is sometimes supplied, and warmed cooling water is supplied at rest. That is, the operation timings of the pump 46 and the pump 47 may be reversed between polishing and rest.

Further, unlike the above-described two embodiments, the next embodiment is such that the cooling water temperature can be changed to an arbitrary temperature according to the deformation amount of the surface plate 9 during polishing. Is.

In this embodiment, the same construction as that of the first embodiment is adopted. The cooling water temperature control device 40 has a cooling mechanism provided in the polishing device 30, specifically, a function of controlling the temperature of the cooling water supplied to the water cooling jacket 10 shown in FIG. It functions as a cooling water supply means. Further, the cooling water temperature control device 40 is provided with heating means for heating the cooling water supplied by the pump 46, and heating control means for controlling the heat generation amount of the heating means according to the deformation amount of the surface plate 9. There is. Therefore, the cooling water temperature control device 40 in the case of the present embodiment functions as the cooling water supply means and the heating means and the heating control means at the same time.

An electric heater can be exemplified as a suitable heating means. The displacement amount of the surface plate 9 may be recognized by using, for example, a monitor device that can recognize the displacement without contact.

In the case of such a configuration, the cooling water temperature control device 40 detects the displacement amount of the surface plate 9 based on the signal input from the monitor device, and the displacement amount is corrected to the reference level. Thus, the amount of electricity supplied to the heater, which is the heating means, is controlled to adjust the temperature of the cooling water supplied to the water cooling jacket 10. The relationship between the displacement amount and the cooling water temperature to be supplied is determined based on the relationship between the flatness of the surface plate 9 and the cooling water temperature as shown in FIG. For example, in the case of external slip and when the displacement amount of the surface plate 9 is −10 μm, cooling water is heated to about 25 ° C. and supplied. Of course, the temperature of this cooling water is controlled so as to follow the amount of displacement of the surface plate 9 that changes momentarily from the start to the end of polishing. Therefore, as compared with the above-described embodiment in which the cooling water is simply switched to the cooling water at a constant temperature during the polishing and during the rest, the one in the present embodiment can perform very precise control, and as a result, the high flatness can be obtained. The wafer can be polished.

[0045]

As described in the foregoing, according to claim 1 wherein
According to the present invention described in Item 3 , the following effects can be obtained.

(1) Cooling water supplied during rest during polishing
Since the cooling water having a higher temperature is supplied, the displacement amount of the surface plate generated during polishing can be minimized.

(2) Since the cooling water having an appropriate temperature is supplied based on the displacement amount of the surface plate during polishing, the ever-changing displacement of the surface plate can be corrected in real time.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a semiconductor wafer polishing control apparatus according to the present invention.

FIG. 2 is an operation flowchart according to the first embodiment.

FIG. 3 is a diagram showing the relationship between the flatness of the surface plate and the cooling water temperature.

FIG. 4 is a diagram schematically showing a state of displacement of a surface plate during a polishing pause process in the first embodiment.

FIG. 5 is an operation flowchart according to the second embodiment.

FIG. 6 is a diagram showing a schematic configuration of a conventional polishing apparatus.

FIG. 7 is a diagram showing an arrangement state of silicon wafers mounted on a block.

FIG. 8 is a plan view showing the water cooling jacket shown in FIG.

FIG. 9 is a cross-sectional view of essential parts showing an exaggerated state of thermal deformation in a polishing process by a conventional polishing apparatus.

FIG. 10 is a view showing a cross section of a silicon wafer that has been brought into an internally slipped state by polishing.

FIG. 11 is a diagram showing the amount of deformation of each part of the surface plate in the conventional polishing apparatus.

FIG. 12 is a diagram schematically showing a state of displacement of a surface plate in a polishing pause process in a conventional polishing apparatus.

[Explanation of symbols]

1 ... Pressure shaft, 3 ... Pressure head, 4 ... block, 5 ... Silicon wafer, 6 ... polishing pad, 9 ... surface plate, 10 ... water cooling jacket, 11 ... water cooling part, 12 ... Thrust bearing, 13 ... frame, 16 ... Rotation axis, 30 ... Polishing device, 35 ... Polishing control device, 40 ... Cooling water temperature control device, 46, 47 ... Pumps.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 61-13631 (JP, A) JP 6-99350 (JP, A) JP 60-201868 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H01L 21/304 B24B 37/00

Claims (3)

(57) [Claims] 1. A block for holding a material to be polished, a surface plate arranged on a side of the block holding the material to be polished, a pressure mechanism for pressing the block against the surface plate, A polishing control apparatus for a semiconductor wafer used in a polishing apparatus, comprising: a slide drive mechanism that relatively slides a block and the surface plate; and a cooling mechanism that cools the surface plate. Polishing device control means for collectively controlling the operation of the block, and when the polishing control device controls the polishing of the material to be polished , the relative position between the block and the surface plate.
The thermal deformation of the surface plate caused by the sliding motion can be corrected.
So that the cooling mechanism does not have this control
Cooling water at a temperature higher than that of the cooling water supplied in the case
And a cooling water supply means for supplying the cooling water. 2. The cooling water supply means is provided in the cooling mechanism.
Heating that heats the cooling water in the cooling water supply path
Means and the polishing control device polishes the material to be polished.
If control is in progress,
On the other hand, if the control is not performed, the heating means should be turned off.
A contractor including heating control means to be activated.
Polishing control apparatus for a semiconductor wafer according to Motomeko 1. 3. The heating control means is a deformation amount of the surface plate.
The heating value of the heating means is controlled according to
The polishing control apparatus for a semiconductor wafer according to claim 2 .