DOUBLE-SIDE POLISHING APPARATUS FOR WORKPIECE AND DOUBLE-SIDE POLISHING METHOD FOR WORKPIECE

Abstract

This disclosure aims to provide a double-side polishing apparatus for a workpiece and a double-side polishing method for a workpiece, capable of suppressing roll-off of the outer peripheral shape of the workpiece. The temperature of polishing slurry is individually adjusted for each of a plurality of slurry supply systems.

Claims

1. A double-side polishing apparatus for a workpiece, comprising: an upper platen and a lower platen, and a plurality of slurry discharge ports provided in one or both of the upper platen and the lower platen, wherein the apparatus has a plurality of slurry supply systems formed by the plurality of slurry discharge ports, and each of the plurality of slurry supply systems is provided with a respective slurry temperature adjustment unit.

2. The double-side polishing apparatus for a workpiece according to claim 1, wherein the plurality of slurry discharge ports forming the plurality of slurry supply systems are arranged at different radial positions or regions of the platen.

3. The double-side polishing apparatus for a workpiece according to claim 1, wherein one or both of the upper platen and the lower platen are provided with a plurality of temperature measurement units configured to measure a temperature of a polishing surface of the workpiece, and the plurality of temperature measurement units are arranged at different radial positions or regions of the platen.

4. A double-side polishing method for a workpiece, comprising an individual temperature adjustment step in which a temperature of polishing slurry is individually adjusted for each of a plurality of slurry supply systems formed by a plurality of slurry discharge ports provided in one or both of an upper platen and a lower platen.

5. The double-side polishing method for a workpiece according to claim 4, wherein the plurality of slurry discharge ports forming the plurality of slurry supply systems are arranged at different radial positions or regions of the platen for each of the slurry supply systems, and in the individual temperature adjustment step, the temperature of polishing slurry is adjusted such that the polishing slurry discharged from the slurry discharge ports located at positions or regions closer to the center of the platen has a lower temperature.

6. The double-side polishing method for a workpiece according to claim 5, further comprising a temperature measurement step in which a temperature of a polishing surface of the workpiece is measured at different radial positions or regions of the platen, wherein, in the individual temperature adjustment step, the temperature of polishing slurry is adjusted such that a temperature difference between the different radial positions or regions measured in the temperature measurement step approaches a target temperature difference.

7. The double-side polishing method for a workpiece according to claim 6, wherein, in the individual temperature adjustment step, the temperature of polishing slurry is adjusted using an index T/D, which is obtained by dividing a temperature difference T between the different radial positions of the platen, measured in the temperature measurement step, by a difference D in a platen-to-platen distance between the upper platen and the lower platen at the different radial positions.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In the accompanying drawings:

[0024] FIG. 1 is a diagram illustrating an example of a double-side polishing apparatus for a workpiece according to one embodiment of the present disclosure;

[0025] FIG. 2A is a diagram for explaining heat generation when the upper platen and the lower platen are parallel;

[0026] FIG. 2B is a diagram for explaining heat generation when the upper platen and the lower platen become non-parallel during polishing;

[0027] FIG. 3 is a graph presenting the relationship between the in-plane temperature difference of the upper platen and the outer peripheral shape of the wafer after processing in Examples;

[0028] FIG. 4 is a graph presenting the results in Examples; and

[0029] FIG. 5 is a graph presenting the relationship between T/D and ESFQD in Examples.

DETAILED DESCRIPTION

[0030] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. First, a double-side polishing apparatus for a workpiece according to one embodiment of the present disclosure will be described.

Double-Side Polishing Apparatus for a Workpiece

[0031] FIG. 1 is a sectional view illustrating a double-side polishing apparatus for a workpiece according to one embodiment of the present disclosure. As illustrated in FIG. 1, the double-side polishing apparatus 1 includes a rotary platen 4 having an upper platen 2 and a lower platen 3, a sun gear 5 provided at the center of the rotary platen 4, an internal gear 6 provided at the outer peripheral portion of the rotary platen 4, and a carrier plate 7 provided between the upper platen 2 and the lower platen 3 and having one or more holding holes (not illustrated) for holding a workpiece.

[0032] Although not illustrated, a polishing pad is attached to the lower surface of the upper platen 2, which serves as a polishing surface thereof, and to the upper surface of the lower platen 3, which serves as a polishing surface thereof. In the example illustrated in FIG. 1, a recessed portion is provided at the center of the lower surface of the upper platen 2, and this portion has a sealed structure. The sun gear 5 and the lower platen 3 rotate independently of each other, and a gap between the sun gear 5 and the lower platen 3 is sealed so that the polishing slurry does not leak. As illustrated in FIG. 1, the upper surface of the sun gear 5 is positioned above the upper surface of the carrier plate 7.

[0033] Using this double-side polishing apparatus 1, a workpiece (e.g., a wafer) is held in one or more holding holes provided in the carrier plate 7, and the workpiece is sandwiched between the upper platen 2 and the lower platen 3 that constitute the rotary platen 4. While supplying polishing slurry onto the polishing pads (not illustrated) respectively attached to the upper platen 2 and the lower platen 3, the sun gear 5 and the internal gear 6 are rotated, thereby causing relative rotation between the rotary platen 4 and the carrier plate 7, and enabling simultaneous polishing of both surfaces of the workpiece.

[0034] In the double-side polishing apparatus 1, a plurality of slurry discharge ports 8 (8a, 8b) are provided in one or both of the upper platen 2 and the lower platen 3 (only in the upper platen 2 in the illustrated example). In the illustrated example, two slurry discharge ports 8a are arranged on the inner peripheral side of the upper platen 2. In this example, the two slurry discharge ports 8a are disposed symmetrically with respect to the center axis of rotation. The other two slurry discharge ports 8b are arranged on the outer peripheral side of the upper platen 2. Similarly, the two slurry discharge ports 8b are disposed symmetrically with respect to the center axis of rotation.

[0035] Each of the slurry discharge ports 8 is connected to a slurry supply pipe 9. Specifically, each of the slurry discharge ports 8a on the inner peripheral side is connected to a slurry supply pipe 9a, and each of the slurry discharge ports 8b on the outer peripheral side is connected to a slurry supply pipe 9b. The polishing slurry may be supplied from the slurry supply pipes 9 by a gravity feed method or a pressure feed method.

[0036] The double-side polishing apparatus 1 has a plurality of slurry supply systems formed by the plurality of slurry discharge ports 8. In the present example, the two slurry discharge ports 8a on the inner peripheral side form an inner slurry supply system, to which polishing slurry is supplied through two slurry supply pipes 9a, respectively. The two slurry discharge ports 8b on the outer peripheral side form an outer slurry supply system, to which polishing slurry is supplied through two slurry supply pipes 9b, respectively.

[0037] The plurality of slurry discharge ports 8 (in the present example, the inner slurry discharge ports 8a and the outer slurry discharge ports 8b) that form the plurality of slurry supply systems (in the present example, the inner slurry supply system and the outer slurry supply system) are arranged at different radial positions or regions of the platen. That is, in the present example, the inner slurry discharge ports 8a are located at positions or regions on the inner peripheral side of the upper platen 2 relative to the outer slurry discharge ports 8b.

[0038] In this double-side polishing apparatus 1, each of the plurality of slurry supply systems is provided with a respective slurry temperature adjustment unit 10. In the present example, the inner slurry supply system is provided with a slurry temperature adjustment unit 10a. By means of this slurry temperature adjustment unit 10a, the temperature of the polishing slurry supplied from the two slurry supply pipes 9a to the inner slurry discharge ports 8a connected to the respective slurry supply pipes 9a is individually adjusted (independently of the polishing slurry from the outer slurry supply pipes 9b). The outer slurry supply system is provided with another slurry temperature adjustment unit 10b (different from the slurry temperature adjustment unit 10a). By means of the slurry temperature adjustment unit 10b, the temperature of the polishing slurry supplied from the two slurry supply pipes 9b to the outer slurry discharge ports 8b connected to the respective slurry supply pipes 9b is individually adjusted (independently of the polishing slurry from the inner slurry supply pipes 9a). The slurry temperature adjustment unit 10 may employ a heating device and/or a cooling device.

[0039] Further, in the present embodiment, one or both of the upper platen 2 and the lower platen 3 (only on the upper platen 2 in the illustrated example) are provided with a plurality of (two in this example) temperature measurement units 11 (11a, 11b) configured to measure the temperature of the polishing surface of the workpiece. The plurality of temperature measurement units 11 (11a, 11b) are arranged at different radial positions or regions of the platen. In the illustrated example, the temperature measurement unit 11a is arranged on the inner peripheral side (of the lower portion) of the upper platen 2, and the temperature measurement unit 11b is arranged on the outer peripheral side (of the lower portion) of the upper platen 2. As illustrated in the figure, it is preferable to dispose the temperature measurement units 11 in the vicinity of the slurry discharge ports 8. In the illustrated example, the inner temperature measurement unit 11a is disposed near the inner slurry discharge port 8a, and the outer temperature measurement unit 11b is disposed near the outer slurry discharge port 8b. Any known temperature sensor may be used as the temperature measurement unit 11.

Double-Side Polishing Method for a Workpiece

[0040] Next, a double-side polishing method for a workpiece according to one embodiment of the present disclosure will be described. Although not particularly limited, the method can be executed, for example, using the double-side polishing apparatus for a workpiece described in the above embodiment.

[0041] The method of the present embodiment includes an individual temperature adjustment step in which the temperature of the polishing slurry is individually adjusted for each of a plurality of slurry supply systems formed by a plurality of slurry discharge ports 8 provided in one or both of the upper platen 2 and the lower platen 3. In the method of the present embodiment, the plurality of slurry discharge ports 8 forming the plurality of slurry supply systems are arranged at different radial positions or regions of the platen for each slurry supply system. In the present example, the inner slurry discharge ports 8a that form the inner slurry supply system are located at positions or regions on the inner peripheral side of the platen relative to the outer slurry discharge ports 8b that form the outer slurry supply system. In the individual temperature adjustment step, it is preferable to adjust the temperature of the polishing slurry such that the polishing slurry discharged from the slurry discharge ports 8 located at positions or regions closer to the center of the platen (in the present example, the inner slurry discharge ports 8a) has a lower temperature.

[0042] The effects of the present embodiment will be described below.

[0043] In double-side polishing, from a mechanical perspective, the relative speed between the rotary platen 4 and the workpiece becomes higher on the outer peripheral side than on the inner peripheral side of the rotary platen 4. When the relative speed increases, the polishing pad is less likely to deform and wrap around the outer peripheral region of the workpiece, which suppresses polishing of the outer peripheral region of the workpiece and thereby suppresses roll-off in the outer peripheral shape of the wafer.

Effects (Double-Side Polishing Apparatus for a Workpiece)

[0044] The double-side polishing apparatus 1 for a workpiece according to the present embodiment is provided with a plurality of slurry discharge ports 8 in one or both of the upper platen 2 and the lower platen 3, includes a plurality of slurry supply systems formed by the plurality of slurry discharge ports 8, and is further provided with a respective slurry temperature adjustment unit 10 for each of the slurry supply systems.

[0045] According to this configuration, the temperature of the polishing slurry can be individually adjusted for each of the slurry supply systems by the respective slurry temperature adjustment units 10. In particular, the temperature of the polishing slurry can be adjusted such that the slurry discharged from the slurry discharge ports 8 located closer to the center of the platen (in this example, the inner slurry discharge ports 8a) has a lower temperature.

[0046] As a result, based on the above-mentioned mechanical effect, the temperature on the outer peripheral side of the rotary platen 4 can be maintained relatively higher. This promotes chemical action on the outer peripheral side, thereby relatively enhancing polishing on the outer peripheral side. Consequently, polishing can be promoted under a condition where roll-off in the outer peripheral shape of the workpiece is suppressed, making it possible to suppress the roll-off at the outer peripheral shape of the workpiece upon completion of polishing.

[0047] In order to reliably obtain such effects, it is preferable that the plurality of slurry discharge ports 8 forming the plurality of slurry supply systems are arranged at different radial positions or regions of the platen.

[0048] In addition, it is also preferable that one or both of the upper platen 2 and the lower platen 3 are provided with a plurality of temperature measurement units 11 (11a, 11b) configured to measure the temperature of the polishing surface of the workpiece, and that the temperature measurement units 11 (11a, 11b) are arranged at different radial positions or regions of the platen. This is because measuring temperatures at different radial positions or regions (e.g., the inner peripheral side and outer peripheral side) of the platen and adjusting the polishing slurry temperature using the slurry temperature adjustment units 10 so that the temperature difference between the different radial positions or regions of the platen, obtained from the measurement results, approaches a predetermined target value allows the above-described effects to be obtained more reliably.

Effects (Double-Side Polishing Method for a Workpiece)

[0049] The double-side polishing method for a workpiece according to the present embodiment includes an individual temperature adjustment step in which the temperature of polishing slurry is individually adjusted for each of the plurality of slurry supply systems formed by the plurality of slurry discharge ports provided in one or both of the upper platen 2 and the lower platen 3. By adjusting the temperature of the polishing slurry such that the slurry discharged from the slurry discharge ports located at positions or regions closer to the center of the platen has a lower temperature, it becomes possible to promote polishing under conditions in which roll-off at the outer peripheral shape of the workpiece is suppressed. As a result, the roll-off at the outer peripheral shape of the workpiece upon completion of polishing can be improved.

[0050] The method of the present disclosure preferably further includes a temperature measurement step in which the temperature of the polishing surface of the workpiece is measured at different radial positions or regions (e.g., the inner peripheral side and the outer peripheral side) of the platen. In the individual temperature adjustment step, the temperature of the polishing slurry is preferably adjusted such that the temperature difference between the different radial positions or regions measured in the temperature measurement step approaches a target temperature difference. This allows the above-described effect to be achieved more reliably.

[0051] FIG. 2A is a diagram illustrating heat generation when the upper platen and the lower platen are parallel, and FIG. 2B is a diagram illustrating heat generation when the upper platen and the lower platen become non-parallel during polishing.

[0052] Basically, among the temperatures in the polishing environment, the most dominant factor affecting the post-polishing shape of the workpiece is the temperature of the polishing slurry. However, for example, the temperature measurement unit 11 disposed on the upper platen 2 measures the temperature of the polishing surface not only based on the temperature of the polishing slurry, but also including the temperature of the polishing pad and, to a slight extent, the temperature of the workpiece.

[0053] As schematically illustrated in FIG. 2A, when the upper platen 2 and the lower platen 3 are parallel, the temperature of the polishing pad 12, which fluctuates due to friction, can be considered uniform over the surface of the platen. Assuming the relatively small influence of the temperature of the workpiece (wafer) W can be neglected, the measured temperature can be regarded as substantially the temperature of the polishing slurry. Thus, T=T.sub.ATB (where T.sub.A is the temperature on the inner peripheral side, and T.sub.B is the temperature on the outer peripheral side) can be considered as the difference (relative value) in the temperature of the polishing slurry between different radial positions of the platen.

[0054] On the other hand, as schematically illustrated in FIG. 2B, when the parallelism of the rotating platen 4 is lost for some reason during double-side polishing, the friction of the polishing pad 12 increases on either the inner or outer peripheral side of the platen, causing a temperature imbalance in the polishing pad 12. As a result, the temperature measured by the temperature measurement unit 11 reflects a higher contribution from the polishing pad 12 on either the inner or outer side, making it difficult to obtain the temperature difference of the polishing slurry alone. In FIG. 2B, an example is illustrated in which the friction increases on the outer peripheral side, and the thickness of the carrier plate 7 appears thinner on the outer side in the illustration. However, in practice, the thickness of the carrier plate 7 does not become thinner on the outer side; rather, the polishing pad 12, being an elastic body, sinks more on the outer side, resulting in higher friction there.

[0055] In the method of the present disclosure, it is preferable that, in the individual temperature adjustment step, the temperature of the polishing slurry is adjusted using an index T/D, which is obtained by dividing the temperature difference T between different radial positions of the platen, measured in the temperature measurement step, by the difference D in the platen-to-platen distance between the upper platen 2 and the lower platen 3 at those different radial positions.

[0056] For example, when the different radial positions of the platen refer to two points, namely an inner peripheral side and an outer peripheral side, the difference D is defined as the difference between the platen-to-platen distance D.sub.A at the position on the inner peripheral side and the platen-to-platen distance D.sub.B at the position on the outer peripheral side, i.e., D=D.sub.AD.sub.B.

[0057] When the parallelism of the rotating platen 4 is disturbed, the temperature of the polishing pad 12 depends on the radial distance of the platen, and in particular, the temperature difference between different radial positions of the platen is approximately proportional to the difference in platen-to-platen distance between those radial positions. Therefore, by normalizing the temperature difference T with the distance difference D (i.e., by dividing T by D), the influence of heat generated in the polishing pad due to the loss of parallelism of the rotating platen 4 can be eliminated, and only the temperature difference of the slurrywhich is the most dominant factor in determining the post-polishing shape of the workpiececan be obtained as a measurement value.

[0058] Accordingly, even when the parallelism of the rotating platen 4 is disturbed, the slurry temperature can be adjusted with high accuracy, thereby further suppressing the roll-off of the outer peripheral shape of the workpiece upon completion of polishing.

[0059] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments in any way. For example, in the above embodiment, the slurry discharge ports 8a and 8b that respectively form different slurry supply systems are arranged along the same straight line, but they may instead be located on different straight lines (i.e., disposed at different circumferential positions). Further, the number of slurry supply systems is not limited to two and may be, for example, three or more. In the case of three slurry supply systems, for example, an inner peripheral slurry supply system, an outer peripheral slurry supply system, and an intermediate slurry supply system located at a radial position between the inner and outer systems may be provided, and the temperature of the polishing slurry can be adjusted such that it decreases in the order of the outer peripheral slurry supply system, the intermediate slurry supply system, and the inner peripheral slurry supply system.

[0060] Even when the slurry discharge ports are located at different radial positions on the platen, if they belong to the same radial region, they may be controlled to have the same temperature. For example, when the radius of the wafer is divided into an inner peripheral region and an outer peripheral region, and two slurry discharge ports 8 are arranged in each region, it is apparent that adjusting the two slurry discharge ports 8a belonging to the inner peripheral region to the same lower temperature, and the two slurry discharge ports 8b belonging to the outer peripheral region to the same higher temperature does not deviate from the scope and spirit of the present disclosure. Such regional settings can be appropriately selected in terms of the number and range of the regions and are not limited to the above example.

[0061] Various other modifications and changes may also be made.

[0062] Examples of the present disclosure are described below. However, the present disclosure is not limited to the following Examples in any way.

EXAMPLES

[0063] In order to confirm the effects of the present disclosure, double-side polishing was performed using a double-side polishing apparatus for a workpiece, the apparatus being provided with two temperature measurement units arranged on the upper platen side and two slurry supply systems capable of individually controlling the temperature of the polishing slurry supplied thereto.

[0064] First, based on the temperature measurements at the two points, the relationship between the in-plane temperature difference of the upper platen and the outer peripheral shape of the wafer after processing was examined. This relationship is presented in FIG. 3.

[0065] As illustrated in FIG. 3, it was confirmed that the roll-off of the outer peripheral shape of the wafer is promoted as the temperature on the inner peripheral side of the platen increases (i.e., as the value on the horizontal axis in FIG. 3 increases, toward the right side of the figure).

[0066] Based on this result, the temperature difference between the inner and outer peripheral sides of the platen, when the temperatures of the two slurry supply systems are individually controlled, was set to inner peripheral side-outer peripheral side =0.5 C. so as to correspond to a target ESFQD (Edge Site Flatness Front reference least sQuare Deviation) value. It should be noted that ESFQD Mean EE1 in FIG. 3 indicates the average ESFQD value in the area of a 300 mm semiconductor wafer excluding the outermost 1 mm peripheral region. The ESFQD Mean EE 1 was measured using the WaferSight 2 manufactured by KLA-Tencor. The temperature was measured using a temperature sensor provided in the upper platen of the double-side polishing apparatus.

[0067] FIG. 4 is a graph comparing the results of the outer peripheral shape of wafers between an example in which the temperatures of the two slurry supply systems were individually adjusted, and a comparative example in which such temperature adjustment was not performed. It can be seen that, in the example, the roll-off of the outer peripheral shape of the wafer was suppressed compared to the comparative example.

[0068] FIG. 5 is a graph providing the relationship between T/D and ESFQD Mean EE1. Furthermore, the difference D in the platen-to-platen distance between two points at the position on the inner peripheral side and the outer peripheral side was measured. By dividing the measured in-plane temperature difference T on the platen by the D value, the index T/D was calculated, and its relationship with the outer peripheral shape of the wafer (ESFQD Mean EE1) was examined. As a result, it was confirmed that the correlation with the outer peripheral shape of the wafer improved when using T/D as an index, compared to using only the in-plane temperature difference T as the index.