JP2012228745A - Polishing apparatus and polishing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing apparatus adequately controlling a polishing allowance of a wafer with a simple structure.SOLUTION: The polishing apparatus 1 is provided with: a polishing head 3 formed by integrating a packing pad 32 with a retainer ring 33; a retainer liquid pressure-measuring means 35 measuring the retainer liquid pressure Fr which the retainer ring 33 receives from slurry P on a polishing pad 23 during polishing of a wafer W; and a parameter setting means setting at least one parameter among head pressurizing force Fh applied to the polishing head 3 on the basis of the retainer liquid pressure Fr measured by the retainer liquid pressure measuring means 35, the rotation number of a surface plate 22 and polishing time per one batch. A polishing control means controls at least one of a rotation-driving means and a polishing head pressurizing means on the basis of the parameter set by the parameter setting means.

Description

  The present invention relates to a polishing apparatus and a polishing method.

  As a polishing method used in a final polishing process of a semiconductor wafer (hereinafter referred to as a wafer), a method using a polishing head in which a wafer chuck and a retainer ring are integrated is known. In this polishing method, the wafer is held by the polishing head, the slurry is supplied onto the polishing pad, and the wafer is polished without bringing the retainer ring into contact with the polishing pad.

  On the other hand, a polishing apparatus is known in which a wafer chuck and a retainer ring are driven independently (for example, Patent Document 1). The polishing apparatus of Patent Document 1 includes a rubber film provided on a wafer chuck surface (back surface), and controls the pressure for pressing the wafer against the polishing pad by controlling the pressure in the rubber film.

JP 2009-107094 A

  By the way, when polishing the wafer without bringing the retainer ring into contact with the polishing pad, the polishing allowance (wafer removal) is caused by the wear of the retainer ring due to the slurry moving in and out of the retainer ring and the variation in the thickness of the wafer itself. ) Will vary. This is thought to be due to the following reasons.

That is, it is considered that when the wafer protrusion amount (the protrusion amount of the polished surface of the wafer from the lower surface of the retainer ring) increases, the retainer pad gap dimension (the dimension of the gap between the retainer ring and the polishing pad) also increases.
In addition, when the retainer pad gap size is increased, it is considered that the retainer hydraulic pressure acting on the lower surface of the retainer ring (the hydraulic pressure due to the slurry moving inside and outside the retainer ring) decreases from the viewpoint of fluid lubrication.
Therefore, it is considered that the retainer fluid pressure decreases as the wafer protrusion amount increases.
Further, the retainer liquid pressure acts in the opposite direction to the head pressure applied to the polishing head (pressure in the direction approaching the polishing pad). For this reason, the polishing pressure (pressure in the direction approaching the polishing pad) actually acting on the wafer is substantially equal to the value obtained by subtracting the retainer liquid pressure from the head pressure.

  When the wafer is sequentially polished with the head pressure, the number of rotations of the surface plate and polishing head, and the polishing time of one batch being constant, the retainer fluid pressure does not change unless the retainer pad gap dimension changes. For this reason, the polishing pressure does not change and the polishing allowance does not vary from batch to batch.

  However, actually, as described above, the amount of protrusion of the wafer varies due to wear of the retainer ring and variations in the thickness of the wafer, and the retainer fluid pressure also varies. With this variation in the retainer fluid pressure, the polishing pressure also varies, resulting in variations in the polishing allowance.

When using a polishing head that integrates the wafer chuck and retainer ring as described above, the relative position between the wafer chuck and the retainer ring cannot be changed, so the wafer protrusion amount can be controlled for each batch. Therefore, the above problems cannot be solved.
On the other hand, in the polishing apparatus described in Patent Document 1, the wafer chuck and the retainer ring can be controlled by independently driving the wafer chuck and the retainer ring, but the wafer chuck and the retainer ring can be controlled independently. Therefore, there is a problem in that the structure for driving is complicated and many sensors and control parts are required.

  An object of the present invention is to provide a polishing apparatus and a polishing method capable of appropriately controlling a wafer removal allowance with a simple configuration.

  The polishing apparatus of the present invention includes a surface plate provided with a polishing pad, a polishing head in which a wafer chuck and a retainer ring for holding a wafer are integrated, and a rotation that relatively rotates the surface plate and the polishing head. A driving unit; a polishing head pressurizing unit that applies pressure to the polishing head to press the wafer against the polishing pad; and a polishing control unit that controls the rotation driving unit and the polishing head pressurizing unit. A polishing apparatus for polishing a wafer using slurry supplied onto the polishing pad without bringing the retainer ring into contact with the polishing pad, wherein the retainer ring is on the polishing pad during polishing of the wafer. A retainer hydraulic pressure measuring means for measuring the hydraulic pressure received from the slurry, and based on the hydraulic pressure measured by the retainer hydraulic pressure measuring means Parameter setting means for setting at least one parameter among a pressure applied to the polishing head, a rotation speed of the surface plate, and a polishing time, and the polishing control means is set by the parameter setting means. Based on the parameters, at least one of the rotation driving means and the polishing head pressurizing means is controlled.

  On the other hand, the polishing method of the present invention comprises a surface plate provided with a polishing pad, a polishing head in which a wafer chuck for holding a wafer and a retainer ring are integrated, and the surface plate and the polishing head relatively rotated. The retainer ring using a slurry supplied onto the polishing pad, and a rotation driving means for causing the polishing head to apply pressure to the polishing head so as to press the wafer against the polishing pad. A polishing method using a polishing apparatus that polishes a wafer without contacting the polishing pad with the polishing pad, and measures the hydraulic pressure that the retainer ring receives from the slurry on the polishing pad during polishing of the wafer. Retainer fluid pressure measuring means is provided, and the polishing is performed based on the fluid pressure measured by the retainer fluid pressure measuring device during polishing of the wafer. A parameter setting step for setting at least one parameter of a pressure applied to the head, a rotation speed of the surface plate, and a polishing time; and the rotation driving means and the parameter based on the parameters set in the parameter setting step And a polishing control step of controlling at least one of the polishing head pressurizing means.

In the above polishing apparatus and polishing method, a retainer liquid pressure measuring means for measuring the retainer liquid pressure is provided in a polishing apparatus including a polishing head in which a wafer chuck and a retainer ring are integrated. Then, based on the measurement result of the retainer measuring means, at least one parameter of the head pressing force (pressure applied to the polishing head), the surface plate rotation speed (the surface plate rotation speed), and the polishing time is determined. It is set.
For this reason, for example, even if the wafer protrusion amount changes with respect to the immediately preceding batch, the polishing allowance is set appropriately by setting the polishing conditions for the next batch based on the retainer fluid pressure that has a correlation with the wafer protrusion amount. Can be controlled. For example, if the head pressure is changed by controlling the polishing head pressurizing means, the wafer pressure changes, so that the polishing allowance can be controlled. Further, if the surface plate rotation speed is changed, the amount of slurry entering the retainer ring changes, so that the retainer hydraulic pressure also changes, and as a result, the polishing allowance can be controlled. Further, the polishing allowance can be controlled by changing the batch polishing time (polishing time per batch) by controlling the rotation driving means.
Further, since the polishing head in which the wafer chuck and the retainer ring are integrated is used, the configuration is not complicated.
Note that the setting process of the polishing conditions (head pressure, surface plate rotation speed, polishing time) based on the retainer liquid pressure may be performed a plurality of times in one batch instead of every batch (once per batch).

In the polishing apparatus of the present invention, the parameter setting unit calculates a predicted value of the wafer removal allowance according to the following formula (1) based on the hydraulic pressure measured by the retainer hydraulic pressure measuring unit, and the predicted value and It is preferable to set the at least one parameter so that a preset target value is equal.
X = A × {Fh− (Fr × Sr)} / Sw × R × T (1)
X: Predicted value of machining allowance A: Proportional constant Fh: Pressure applied to the polishing head Fr: Fluid pressure measured by the retainer fluid pressure measuring means Sr: Surface area of the surface facing the polishing pad of the retainer ring Sw: Cover of the wafer Surface area of polishing surface R: Number of rotations of surface plate T: Polishing time

According to the present invention, variation in the polishing allowance can be accurately suppressed by a simple method of simply substituting various parameters into Equation (1).
Note that that the predicted value and the target value are equal means that the predicted value and the target value substantially match, and is not limited to a case where the predicted value and the target value match completely.

In the polishing apparatus of the present invention, the polishing head is provided with a communication hole that connects a predetermined position of the polishing head and the lower surface of the retainer ring in the vertical direction, and the retainer fluid pressure measuring means includes the It is preferable that the opening is provided so as to close the opening at the upper end of the communication hole.
According to the present invention, the retainer hydraulic pressure measuring means is provided so as to close the opening surface at the upper end of the communication hole. For this reason, the slurry rising in the communication hole due to capillary action comes into contact with the retainer fluid pressure measuring means, whereby the retainer fluid pressure can be measured directly, and the measurement accuracy of the retainer fluid pressure can be increased. Therefore, the polishing allowance can be appropriately controlled.

In the polishing apparatus of the present invention, a plurality of the retainer fluid pressure measuring means are provided at equal intervals along the outer edge direction of the retainer ring, and the parameter setting means is a measurement result obtained by the plurality of retainer fluid pressure measuring means. Preferably, the at least one parameter is set based on an average value of.
Here, in actual polishing, the lower surface of the retainer ring and the polishing surface of the polishing pad may not be parallel due to the influence of the moment acting on the polishing head due to the rotation of the polishing head. Thus, when the retainer ring and the polishing pad are not parallel, there are a portion where the retainer pad gap size is large and the retainer fluid pressure is small, and a portion where the retainer pad gap size is small and the retainer fluid pressure is large. Therefore, in the case where one retainer fluid pressure measuring means is provided at one place of the retainer ring, the retainer fluid pressure is measured while rotating the retainer ring. Therefore, the retainer at one of a plurality of places with different retainer pad gap dimensions is used. The hydraulic pressure will be measured. For this reason, there is a possibility that the retainer fluid pressure varies depending on the measurement timing, and the polishing allowance cannot be controlled appropriately.
On the other hand, for example, in the case where four retainer fluid pressure measuring means are provided at equal intervals along the outer edge direction of the retainer ring, the average value of the retainer fluid pressure at four locations with different retainer pad gap dimensions is measured. The value is almost constant regardless of the timing. Therefore, even if the retainer ring and the polishing pad are not parallel, the polishing allowance can be appropriately controlled.

The sectional view of the polish device concerning one embodiment of the present invention. The top view which shows schematic structure of the grinding | polishing apparatus in the said one Embodiment. Sectional drawing of the backing pad and retainer ring in the said one Embodiment. Sectional drawing which shows the grinding | polishing state of the wafer in the said one Embodiment. The block diagram which shows schematic structure of the grinding | polishing apparatus in the said one Embodiment. The flowchart which shows the grinding | polishing process in the said one Embodiment. The graph which shows the relationship between the wafer protrusion amount and retainer hydraulic pressure which concern on Example 1 of this invention. 3 is a graph showing a relationship between a wafer protrusion amount and an experimental value and a predicted value of a polishing allowance in Example 1; The graph which shows the relationship between the surface plate rotation speed which concerns on Example 2 of this invention, and a retainer hydraulic pressure. The graph which shows the relationship between the surface plate rotation speed in Example 2 and the experimental value and predicted value of the grinding allowance.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In the present embodiment, a configuration in which the setting processing of polishing conditions (head pressure, surface plate rotation speed, polishing time) based on the retainer liquid pressure is performed for each batch (once per batch) will be described as an example. However, it may be performed a plurality of times in one batch.
[Configuration of polishing apparatus]
As shown in FIGS. 1 and 2, the polishing apparatus 1 is a single wafer type apparatus that finish-polishes the surface of a wafer W having a diameter of 300 mm. In addition, it is good also as the grinding | polishing apparatus 1 aiming at the wafer W whose diameter dimension is other than 300 mm.
The polishing apparatus 1 includes a polishing unit 2, four polishing heads 3, a polishing head driving unit 4 (see FIG. 5), a storage unit 5 (see FIG. 5), and a control unit 6 (see FIG. 5). Is provided.

The polishing unit 2 includes a surface plate rotation driving unit 21, a disk-shaped surface plate 22 provided on a rotation shaft of the surface plate rotation driving unit 21, and a finish polishing slurry supply unit (not shown).
A polishing pad 23 is provided on the upper surface of the surface plate 22. The final polishing slurry supply unit appropriately supplies the final polishing slurry P to the polishing surface of the polishing pad 23.

  The polishing head 3 includes a rotating shaft member 31 that rotates by driving of the polishing head driving unit 4, a backing pad 32 provided at the lower end of the rotating shaft member 31, and a retainer ring 33 provided on the lower surface of the backing pad 32. With. The rotating shaft member 31 includes a cylindrical shaft portion 311 extending vertically and a disk-shaped rotating frame portion 312 provided at the lower end of the shaft portion 311.

The backing pad 32 is formed in a disc shape having an outer diameter dimension substantially equal to that of the rotating frame portion 312, and as shown in FIG. 3, a PET film 321 (polyethylene terephthalate film) and one surface of the PET film 321 are formed. The urethane foam layer 322 is laminated. The backing pad 32 is bonded to the rotating frame portion 312 via a double-sided tape 323 provided on the PET film 321.
The wafer W is held by the backing pad 32 by water adsorption by the urethane foam layer 322.

  The retainer ring 33 is a member for preventing the wafer W from jumping out due to centrifugal force during polishing of the wafer W. The retainer ring 33 is provided on the outer peripheral edge of the urethane foam layer 322 of the backing pad 32 through the heat welding sheet 331 so as to surround the wafer W. The material of the retainer ring 33 is not particularly limited, and glass epoxy or the like can be used.

  Further, as shown in FIGS. 1, 2, and 4, four communication holes 34 are provided in the backing pad 32 and the retainer ring 33. The communication holes 34 penetrate the backing pad 32 and the retainer ring 33 in the thickness direction, and are provided at equal intervals along the outer edge direction of the retainer ring 33. That is, considering the polishing head 3 as a whole, the communication hole 34 is provided so as to communicate a predetermined position of the polishing head 3 and the lower surface of the retainer ring 33 in the vertical direction.

  Further, four retainer hydraulic pressure measuring means 35 are provided on the upper surface of the backing pad 32 so as to block the opening surfaces at the upper ends of the four communication holes 34. The retainer fluid pressure measuring means 35 is, for example, a diaphragm type pressure sensor, and measures the retainer fluid pressure Fr. Specifically, as shown in FIG. 4, the retainer fluid pressure measuring means 35 measures the pressure when the slurry P rising in the communication hole 34 due to capillary action comes into contact as the retainer fluid pressure Fr, and this measurement result Is output to the control means 6.

As shown in FIG. 5, the polishing head drive unit 4 includes a head rotation drive unit 41 that rotates the rotary shaft member 31, and a polishing head pressurization unit 42 that applies a head pressure Fh to the polishing head 3. The head rotation driving means 41 and the polishing head pressurizing means 42 are driven under the control of the control means 6.
The surface plate rotation driving means 21 and the head rotation driving means 41 constitute the rotation driving means of the present invention.

  Various information for polishing the wafer W is stored in the storage unit 5. The stored information includes head pressure Fh (see FIG. 4), surface plate rotation speed R (rotation speed of the surface plate 22), batch polishing time Tb (polishing time per batch), retainer ring 33 Examples include the surface area Sr of the lower surface (the surface facing the polishing pad 23), the surface area Sw of the surface to be polished of the wafer W, the target value of the polishing allowance, and the like. As will be described in detail later, the head pressure Fh, the platen rotation speed R, and the batch polishing time Tb are updated as necessary by the parameter setting means 62 described later of the control means 6.

  The control means 6 includes a polishing control means 61 and a parameter setting means 62 configured by processing a program and data stored in the storage means 5 by a CPU (Central Processing Unit).

The polishing control means 61 controls the polishing conditions based on the parameters stored in the storage means 5.
Specifically, the polishing control means 61 sets the surface plate rotation driving means 21 and the head rotation driving means 41 for each batch so that the surface plate rotation speed R and the batch polishing time Tb become the values stored in the storage means 5. Control at least one of them. Further, the polishing head pressure unit 42 is controlled for each batch so that the head pressure Fh becomes a value stored in the storage unit 5.

The parameter setting unit 62 calculates a predicted value X of the polishing allowance based on the retainer hydraulic pressure Fr measured by the retainer hydraulic pressure measuring unit 35 and the following formula (1) obtained in advance. The proportionality constant A is a value obtained in a preliminary experiment.
X = A × {Fh− (Fr × Sr)} / Sw × R × T (1)
X: Predicted value of polishing allowance A: Proportional constant Fh: Head pressure Fr: Retainer fluid pressure Sr: Surface area of the retainer ring facing the polishing pad Sw: Surface area of the polished surface of the wafer R: Surface plate rotation speed Tb: Batch polishing time

  When the parameter setting unit 62 determines that the predicted value X calculated based on the mathematical formula (1) is not equal to the target value stored in the storage unit 5, the predicted value X becomes equal to the target value. At least one parameter among the head pressing force Fh, the platen rotation speed R, and the batch polishing time Tb is changed and stored in the storage means 5.

[Operation of polishing equipment]
Next, a polishing process for the wafer W will be described as an operation of the polishing apparatus 1 described above.
First, when a command for starting the polishing of the wafer W is set and inputted to the polishing control means 61 of the control means 6 constituting the polishing apparatus 1, parameters stored in the storage means 5 as shown in FIG. (Head pressure Fh, surface plate rotation speed R, batch polishing time Tb) is read (step S1). Then, based on the parameters read in step S1, the surface plate rotation driving means 21, the head rotation driving means 41, and the polishing head pressurizing means 42 are controlled to start polishing the wafer W (step S2). In the polishing in step S2, as shown in FIG. 4, the wafer W is polished without bringing the retainer ring 33 and the polishing pad 23 into contact with each other.

Thereafter, the four retainer fluid pressure measuring means 35 measure the retainer fluid pressure Fr based on the contact state with the slurry P rising through the communication hole 34 (step S3), and set the measurement result as a parameter. Output to means 62.
When the parameter setting means 62 acquires the retainer hydraulic pressure measurement results from the four retainer hydraulic pressure measuring means 35, the parameter setting means 62 calculates an average value of the four retainer hydraulic pressures Fr (step S4).
In addition, since the measurement result of the retainer fluid pressure Fr is always output from the retainer fluid pressure measuring unit 35, the parameter setting unit 62 calculates the average value of the retainer fluid pressure Fr acquired after a predetermined time has elapsed from the start of polishing.

Then, the parameter setting unit 62 substitutes the average value of the retainer hydraulic pressure Fr and various information stored in the storage unit 5 into the mathematical formula (1), thereby predicting the polishing allowance of the wafer W being polished. X is calculated (step S5).
Thereafter, the parameter setting unit 62 determines whether or not the calculated predicted value X is equal to the target value stored in the storage unit 5 (step S6).
In this step S6, if the parameter setting means 62 determines that they are not equal, the head pressure Fh, so that the predicted value X when it is assumed that the retainer hydraulic pressure Fr does not change in the next batch becomes equal to the target value. At least one parameter of the platen rotation speed R and the batch polishing time Tb is set, and the parameter of the next batch stored in the storage unit 5 is updated (step S7).

  Here, the reason why the predicted value X is not equal to the target value is that the head pressure Fh has changed with respect to the immediately preceding batch. The reason why the head pressing force Fh changes is that the wafer protrusion amount Hd changes due to wear of the retainer ring 33, variation in the thickness dimension of the wafer W, and collapse of the backing pad 32 due to repeated water adsorption of the wafer W. In addition, the retainer hydraulic pressure Fr may change with this change.

In step S7, when the predicted value X is smaller than the target value and the polishing allowance needs to be increased, the parameter setting means 62 at least one of the head pressure Fh, the surface plate rotation speed R, and the batch polishing time Tb. Increase. On the other hand, when the predicted value X is larger than the target value and it is necessary to reduce the polishing allowance, at least one of the head pressure Fh, the surface plate rotation speed R, and the batch polishing time Tb is reduced.
Thus, the polishing allowance can be controlled by changing the polishing pressure Fw by changing the head pressure Fh. Also, the polishing allowance can be controlled by changing the retainer hydraulic pressure Fr by changing the surface plate rotation speed R and changing the polishing pressure Fw. Further, the polishing allowance can be controlled by changing the batch polishing time Tb.
Note that “the predicted value X and the target value are equal” in step S6 and step S7 means that the predicted value X and the target value substantially match, and are limited to only when they completely match. It is not something.

Then, after the parameter is updated in step S7, or after it is determined in step S6 that the predicted value X is equal to the target value, the polishing control unit 61 determines that the batch polishing time Tb before the update has elapsed. Then, the polishing is finished (step S8), and it is determined whether or not the next batch polishing process is performed (step S9). In step S9, when it is determined that the polishing control unit 61 does not perform the polishing process, the polishing process ends. When it is determined that the polishing control unit 61 determines to perform the process, the process returns to step S1 to perform the polishing process for the next batch.
Here, when the parameter is updated by performing the process of step S7, the polishing control means 61 reads the updated parameter. On the other hand, when the process of step S7 is not performed and the parameter is not updated, the polishing control unit 61 reads the same parameter as that of the immediately preceding batch. Note that when the parameters are not updated, the polishing control unit 61 does not have to perform the process of reading the parameters of the storage unit 5.

[Effects of Embodiment]
In the present embodiment as described above, the following operational effects can be achieved.
(1) Based on the retainer fluid pressure measured by the retainer fluid pressure measuring means 35, the polishing apparatus 1 determines at least one parameter of the head pressure Fh, the surface plate rotation speed R, and the batch polishing time Tb. Control.
For this reason, even if the wafer protrusion amount Hd changes with respect to the immediately preceding batch, the polishing condition of the next batch is controlled according to the retainer fluid pressure Fr that has a correlation with the wafer protrusion amount Hd. Can be controlled. Furthermore, since the polishing head 3 in which the backing pad 32 and the retainer ring 33 are integrated is used, the configuration is not complicated.

(2) The parameter setting means 62 sets the head pressure Fh, the surface plate rotation speed R, and the batch so that the predicted value X of the polishing allowance calculated based on the formula (1) is equal to the target value. At least one parameter of the polishing time Tb is set.
For this reason, the variation in the polishing allowance for each wafer W can be accurately suppressed by a simple method of simply substituting various parameters into Equation (1).

(3) A communication hole 34 that communicates the backing pad 32 and the retainer ring 33 in the vertical direction is provided, and a retainer hydraulic pressure measuring means 35 is provided so as to close the opening surface of the upper end of the communication hole 34.
For this reason, the retainer fluid pressure measuring means 35 can directly measure the retainer fluid pressure Fr by contact with the slurry P rising in the communication hole 34. Therefore, the measurement accuracy of the retainer hydraulic pressure Fr can be increased, and the polishing allowance can be appropriately controlled.

(4) Four retainer hydraulic pressure measuring means 35 are provided at equal intervals along the outer edge direction of the retainer ring 33. The parameter setting means 62 sets parameters based on the average value of the measurement results obtained by the four retainer hydraulic pressure measurement means 35.
For this reason, even when the lower surface of the retainer ring 33 and the polishing surface of the polishing pad 23 are not parallel due to the influence of a rotational moment or the like, an average which is substantially the same value regardless of the measurement timing of the retainer hydraulic pressure Fr. The predicted value can be calculated based on the value, and the polishing allowance can be appropriately controlled.

[Other Embodiments]
The present invention is not limited to the above-described embodiment, and various improvements and design changes can be made without departing from the scope of the present invention.
That is, the mathematical expression (1) is used as the relational expression for calculating the predicted value of the polishing allowance. For example, a parameter having a correlation with the retainer hydraulic pressure Fr is newly introduced, and the mathematical expression (1) is used. The predicted value of the polishing allowance may be calculated using a relational expression different from.
Further, when the newly measured retainer fluid pressure Fr is larger than the retainer fluid pressure Fr measured in the immediately preceding batch, at least one parameter of the head pressure Fh, the surface plate rotation speed R, and the batch polishing time Tb. May be increased by a preset value.

Further, the number of retainer fluid pressure measuring means 35 provided in one polishing head 3 may be 3 or less, or 5 or more. Further, the communication hole 34 may be penetrated to the upper end surface of the rotary frame portion 312 and the retainer hydraulic pressure measuring means 35 may be provided on the upper end surface.
Furthermore, a planar pressure sensor may be applied as the retainer fluid pressure measuring means, and the pressure sensor may be provided on the lower surface of the retainer ring 33.
Further, a suction type wafer chuck may be used in place of the water adsorption type backing pad 32.

  Further, the replacement time of the retainer ring 33 may be determined based on the result of the retainer fluid pressure measurement by the retainer fluid pressure measuring means 35. That is, as the wear amount of the retainer ring 33 increases, the retainer pad gap dimension Hp increases and the retainer hydraulic pressure Fr decreases. Based on this relationship, it may be determined that it is time to replace the retainer ring 33 when the retainer hydraulic pressure Fr becomes equal to or less than a threshold value. If it is determined that it is time to replace, the operator may be informed that the polishing operation is once ended and the retainer ring 33 is replaced.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
In the present embodiment, an experiment was conducted to check whether or not the predicted value X of the polishing allowance calculated based on Equation (1) matches the actual polishing allowance.

[Example 1]

First, the polishing apparatus 1 according to the embodiment was prepared.
An experiment was conducted to examine the relationship between the wafer protrusion amount Hd, the retainer hydraulic pressure Fr, and the polishing allowance.
Specifically, the head pressure Fh and the polishing time T were fixed to predetermined values, and the surface plate rotation speed R was fixed to 18 rpm. Then, the wafer W was held by the polishing head 3 so that the wafer protrusion amount Hd became a predetermined value, polishing was performed, and the retainer hydraulic pressure Fr (Pa) during the polishing was measured. Further, the polishing allowance of the wafer W after polishing was measured.
Also, the retainer hydraulic pressure Fr during polishing and the polishing allowance were measured in the same manner by changing the wafer protrusion amount Hd.
FIG. 7 shows the relationship between the wafer protrusion amount Hd and the retainer hydraulic pressure Fr.
FIG. 8 shows the relationship between the wafer protrusion amount Hd and the polishing removal experimental value Y.

Next, for example, the retainer fluid pressure Fr when the wafer protrusion amount Hd is 30 μm and the experimental value Y of the polishing allowance, and the values of the parameters used in the above experiment (head pressure Fh, retainer ring surface area Sr, wafer) By substituting the surface area Sw of W, the platen rotation speed R, and the batch polishing time Tb) into the following formula (2), the assumed number B when the wafer protrusion amount Hd is 30 μm was obtained. Equation (2) is obtained by modifying Equation (1), using the assumed number B instead of the proportional constant A, and using the experimental value Y instead of the predicted value X.
B = Y / {Fh− (Fr−Sr)} × Sr / R / T (2)
Similarly, for each wafer protrusion amount Hd performed in the above experiment, an assumed number B was obtained based on Equation (2). And the average value of the assumed number B calculated | required with respect to each wafer protrusion amount Hd was determined as the proportionality constant A of Formula (1).

Next, the proportionality constant A determined based on the formula (2), the retainer hydraulic pressure Fr when the wafer protrusion amount Hd is 30 μm, and the values of the parameters used in the experiment are substituted into the formula (1). Thus, the predicted value X of the polishing allowance when the wafer protrusion amount Hd was 30 μm was obtained. Similarly, for each wafer protrusion amount Hd performed in the above-described experiment, a predicted value X of the polishing allowance was obtained based on Equation (1). The obtained predicted value X is shown in FIG.
As shown in FIG. 8, it was confirmed that the predicted value X of the polishing allowance and the experimental value Y almost coincided.

[Example 2]
Using the same polishing apparatus as in Example 1, an experiment was conducted to examine the relationship between the platen rotation speed R, the retainer hydraulic pressure Fr, and the polishing allowance.
Specifically, the head pressure Fh and the batch polishing time Tb were fixed, and the wafer protrusion amount Hd was fixed to 130 μm. Then, polishing was performed under conditions such that the platen rotational speed R was a predetermined value, and the retainer fluid pressure Fr (Pa) during the polishing was measured. Further, the polishing allowance of the wafer W after polishing was measured.
Further, the surface plate rotation speed R was changed, and the retainer hydraulic pressure Fr during polishing and the polishing allowance were measured in the same manner.
FIG. 9 shows the relationship between the surface plate rotation speed R and the retainer hydraulic pressure Fr.
Further, FIG. 10 shows the relationship between the platen rotation speed R and the polishing removal experimental value Y.

Next, for example, the retainer hydraulic pressure Fr when the platen rotational speed R is 12 rpm, the experimental value Y of the polishing allowance, and the values of the parameters used in the above experiments (the head pressure Fh, the surface area Sr of the retainer ring, By substituting the surface area Sw of the wafer W and the batch polishing time Tb) and the value 12 rpm of the surface plate rotation speed R into the formula (2), the assumed number B when the surface plate rotation speed R is 12 rpm is obtained. Asked.
Similarly, for each platen rotation speed R performed in the above experiment, an assumed number B is obtained based on Equation (2), and an average value of the assumed number B obtained for each of the platen rotation speeds R is obtained. , And determined as the proportionality constant A in Equation (1).

Next, the determined proportionality constant A, the retainer hydraulic pressure Fr when the platen rotation speed R is 12 rpm, the values of the parameters used in the experiment, and the value of the platen rotation speed R of 12 rpm are obtained. Substituting into Equation (1), the predicted value X of the polishing allowance when the platen rotation speed R is 12 rpm was determined. Similarly, for each surface plate rotation speed R performed in the above experiment, a predicted value X of the polishing allowance was obtained based on Expression (1). The obtained predicted value X is shown in FIG.
As shown in FIG. 10, it was confirmed that the predicted value X of the polishing allowance and the experimental value Y almost coincided.
Note that, as shown in FIG. 10, the polishing allowance gradually decreases when the platen rotation speed R becomes 22 rpm or more because the retainer fluid pressure Fr increases and the polishing pressure Fw decreases.

  Based on the above, based on the retainer fluid pressure Fr measured by the retainer fluid pressure measuring means 35 and the mathematical expression (1), the head pressure Fh is set so that the predicted value X of the polishing allowance is equal to the target value. It was confirmed that the polishing allowance could be appropriately controlled by setting at least one parameter among the platen rotation speed R and the batch polishing time Tb.

DESCRIPTION OF SYMBOLS 1 ... Polishing apparatus 3 ... Polishing head 21 ... The surface plate rotation drive means which comprises a rotation drive means 22 ... The surface plate 23 ... Polishing pad 32 ... The backing pad as a wafer chuck 33 ... Retainer ring 34 ... Communication hole 35 ... Retainer hydraulic pressure Measuring means 41... Head rotation driving means constituting the rotational drive means 42... Polishing head pressurizing means 61... Polishing control means 62 ... Parameter setting means P ... Slurry W ... Wafer

Claims (5)

A surface plate provided with a polishing pad;
A polishing head integrated with a wafer chuck for holding a wafer and a retainer ring; and
Rotation drive means for relatively rotating the surface plate and the polishing head;
Polishing head pressurizing means for applying pressure to the polishing head so as to press the wafer against the polishing pad;
Polishing control means for controlling the rotation driving means and the polishing head pressurizing means, and polishing the wafer without bringing the retainer ring and the polishing pad into contact with each other using the slurry supplied onto the polishing pad. A polishing apparatus that performs
Retainer fluid pressure measuring means for measuring the fluid pressure that the retainer ring receives from the slurry on the polishing pad during polishing of the wafer;
Parameter setting means for setting at least one parameter of the pressure applied to the polishing head, the rotation speed of the surface plate, and the polishing time based on the liquid pressure measured by the retainer liquid pressure measuring means; With
The polishing apparatus, wherein the polishing control unit controls at least one of the rotation driving unit and the polishing head pressurizing unit based on the parameter set by the parameter setting unit. The polishing apparatus according to claim 1, wherein
The parameter setting means calculates a predicted value of the wafer removal allowance by the following mathematical formula (1) based on the hydraulic pressure measured by the retainer hydraulic pressure measuring means, and the predicted value and a preset target value The polishing apparatus is characterized in that the at least one parameter is set so as to be equal to each other.
X = A × {Fh− (Fr × Sr)} / Sw × R × T (1)
X: Predicted value of machining allowance A: Proportional constant Fh: Pressure applied to the polishing head Fr: Fluid pressure measured by the retainer fluid pressure measuring means Sr: Surface area of the surface facing the polishing pad of the retainer ring Sw: Cover of the wafer Surface area of polishing surface R: Number of rotations of surface plate T: Polishing time The polishing apparatus according to claim 1 or 2,
The polishing head is provided with a communication hole that communicates a predetermined position of the polishing head and the lower surface of the retainer ring in the vertical direction,
The polishing apparatus according to claim 1, wherein the retainer fluid pressure measuring means is provided so as to close an open surface opening at an upper end of the communication hole. In the polishing apparatus according to any one of claims 1 to 3,
A plurality of the retainer hydraulic pressure measuring means are provided at equal intervals along the outer edge direction of the retainer ring,
The polishing apparatus, wherein the parameter setting means sets the at least one parameter based on an average value of measurement results obtained by a plurality of retainer fluid pressure measurement means. A surface plate provided with a polishing pad;
A polishing head integrated with a wafer chuck for holding a wafer and a retainer ring; and
Rotation drive means for relatively rotating the surface plate and the polishing head;
A polishing head pressurizing unit for applying pressure to the polishing head so as to press the wafer against the polishing pad, and using the slurry supplied onto the polishing pad, the retainer ring and the polishing pad A polishing method using a polishing apparatus that polishes a wafer without contact,
The polishing apparatus is provided with a retainer fluid pressure measuring means for measuring the fluid pressure that the retainer ring receives from the slurry on the polishing pad during wafer polishing,
During polishing of the wafer, based on the liquid pressure measured by the retainer liquid pressure measuring means, at least one parameter of the pressure applied to the polishing head, the rotation speed of the surface plate, and the polishing time is set. Parameter setting process to
A polishing method comprising: performing a polishing control step of controlling at least one of the rotation driving unit and the polishing head pressurizing unit based on the parameter set in the parameter setting step.

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