JPWO2015105055A1 - Work thickness measuring apparatus, measuring method, and work polishing apparatus - Google Patents

Abstract

The workpiece thickness measuring device of the present invention is disposed opposite to a liquid immersion device that immerses at least a part of the polished workpiece in a liquid, and determines the distance to the surface of the portion of the workpiece immersed in the liquid. Two or more measuring instruments capable of being measured. Further, the method for measuring the thickness of the workpiece of the present invention includes a step of immersing at least a part of the workpiece after polishing in a liquid, and a state in which at least a part of the workpiece is immersed in the liquid and sandwiching the workpiece. And measuring the thickness of the workpiece with two or more measuring devices that can measure the distance to the surface of the part of the workpiece immersed in the liquid. The workpiece polishing apparatus according to the present invention includes a receiving unit that receives information on the thickness of the workpiece measured by the measurement apparatus or the measurement method, and switching or polishing of a polishing recipe based on the information on the thickness of the workpiece. A calculation unit that corrects the parameter of the condition.

Description

  The present invention relates to a workpiece thickness measuring apparatus, a measuring method, and a workpiece polishing apparatus, and in particular, a workpiece thickness measuring apparatus and measurement capable of measuring the thickness of the workpiece when the workpiece is wet. The present invention relates to a method, and a workpiece polishing apparatus using a measurement result by the measurement apparatus and the measurement method.

  Conventionally, in a manufacturing process of a silicon wafer which is a typical example of a workpiece to be polished, single-side polishing (finish polishing) for finishing the wafer to a predetermined thickness has been performed, and particularly high flatness is required. For a wafer having a diameter of 300 mm or more, a double-side polishing process is generally adopted in which the front and back surfaces of the wafer are simultaneously polished.

  Such polishing is greatly affected by the polishing environment, such as the timing of replacement of polishing sub-materials and the timing of equipment stoppage, and it is not possible to accurately grasp changes in the amount of polishing stock removal. There is a problem that the flatness and the density of LPD (Light Point Defects) vary.

  On the other hand, there is a method to measure the thickness of the wafer after polishing, grasp the change in the polishing allowance, feed back this change to the polishing apparatus, and switch the polishing recipe or correct the parameters of the polishing conditions. It has been proposed (see, for example, Patent Document 1).

JP 2003-68689 A

  However, since polishing is performed using polishing slurry or grinding water in the polishing process, the wafer is in a wet state after polishing. Therefore, the method of Patent Document 1 accurately measures the thickness of the wafer. Therefore, it was necessary to wait for the wafer to dry.

  Therefore, there is a time lag of several hours until the thickness of the wafer can be measured accurately, that is, until the drying process is completed, so that the wafer processed during that time can accurately control the polishing amount. If the next wafer is not polished until the drying process is completed in order to accurately control the polishing amount, there is a problem that the throughput of the polishing process decreases. Further, such a problem is a problem that can occur not only in a silicon wafer but also in general work that is polished by the same method.

  The present invention is intended to solve the above problem, and provides a workpiece thickness measuring apparatus and workpiece thickness measuring method capable of measuring the thickness of the workpiece while the workpiece is wet. For the purpose. Another object of the present invention is to provide a workpiece polishing apparatus capable of appropriately controlling the polishing amount while ensuring the throughput.

The gist configuration of the present invention is as follows.
The workpiece thickness measuring device of the present invention is disposed opposite to a liquid immersion device that immerses at least a part of the polished workpiece in a liquid, and determines the distance to the surface of the portion of the workpiece immersed in the liquid. And two or more measuring instruments capable of being measured.

  In the workpiece thickness measuring apparatus of the present invention, it is preferable to further include a support member for fixing the measuring device.

  Furthermore, in the workpiece thickness measuring apparatus of the present invention, it is preferable that the measuring device includes a cap at the tip.

  In addition, in the workpiece thickness measuring apparatus of the present invention, it is preferable that the liquid immersion device is a tank capable of accommodating the workpiece therein.

  In the workpiece thickness measuring apparatus according to the present invention, the tank is preferably made of quartz or plate glass.

  Furthermore, in the workpiece thickness measuring apparatus of the present invention, it is preferable that at least a part of the measuring instrument is inserted into the tank, and a gap is provided between the tank and the measuring instrument.

  Furthermore, in the workpiece thickness measuring apparatus of the present invention, the liquid immersion device is a liquid supply pipe capable of supplying the liquid so that at least a part of the workpiece is always immersed in the liquid. preferable.

  In the workpiece thickness measuring apparatus of the present invention, it is preferable that the liquid supply pipe includes a liquid supply amount adjusting unit capable of adjusting an amount of supplying the liquid.

  Furthermore, in the workpiece thickness measuring device of the present invention, the workpiece thickness measuring device further includes a liquid introduction pipe disposed in close proximity to the workpiece thickness measurement location and sandwiching the workpiece, wherein at least the tip of the measuring instrument is It is preferable to be inserted into the liquid introduction tube.

  Here, in the workpiece thickness measuring apparatus of the present invention, the liquid is preferably water.

  In the workpiece thickness measuring apparatus of the present invention, it is preferable that the measuring instrument is an optical spectral interference measuring instrument.

Furthermore, in the workpiece thickness measuring apparatus of the present invention, it is preferable that the deformation amount of the tank is 50 nm or less when measuring the thickness of the workpiece.
Here, “the amount of deformation of the tank” refers to the amount of deformation at a point on the line where the two measuring devices face each other, and refers to the maximum displacement during the measurement time.

  In the workpiece thickness measuring apparatus of the present invention, it is preferable that a reinforcing plate is disposed in the tank.

  Furthermore, in the workpiece thickness measuring apparatus according to the present invention, the tank includes a drainage portion, a drainage amount measuring device for measuring a drainage amount from the drainage portion, and a drainage amount based on the measured drainage amount. And a controller for adjusting the amount of liquid.

  Here, the method for measuring the thickness of the workpiece of the present invention includes a step of immersing at least a part of the workpiece after polishing in a liquid, and a state in which at least a part of the workpiece is immersed in the liquid and sandwiching the workpiece And measuring the thickness of the workpiece with two or more measuring devices that can measure the distance to the surface of the part of the workpiece immersed in the liquid. .

  A workpiece polishing apparatus according to an aspect of the present invention is based on the workpiece thickness information measured by the workpiece thickness measuring device and the workpiece thickness information. And an arithmetic unit that switches a polishing recipe or corrects a parameter of a polishing condition.

  Furthermore, a workpiece polishing apparatus according to another aspect of the present invention is based on a receiving unit that receives the workpiece thickness information measured by the workpiece thickness measuring method, and the workpiece thickness information. And an arithmetic unit that switches a polishing recipe or corrects a parameter of a polishing condition.

  According to the present invention, it is possible to provide a workpiece thickness measuring device and a workpiece thickness measuring method capable of measuring the thickness of the workpiece while the workpiece is wet. Further, according to the present invention, it is possible to provide a workpiece polishing apparatus capable of appropriately controlling the polishing amount while ensuring the throughput.

(A) It is a schematic perspective view of the workpiece thickness measuring apparatus concerning the 1st Embodiment of this invention. (B) It is a figure which shows the principal part of the thickness measuring apparatus of the workpiece | work concerning the 1st Embodiment of this invention. (A) It is a schematic perspective view of the workpiece thickness measuring apparatus concerning the 2nd Embodiment of this invention. (B) It is a figure which shows the principal part of the thickness measuring apparatus of the workpiece | work concerning the 2nd Embodiment of this invention. (A) It is a schematic sectional drawing of the thickness measuring apparatus of the workpiece | work concerning the 3rd Embodiment of this invention. (B) It is sectional drawing which shows the principal part of the thickness measuring apparatus of the workpiece | work concerning the 3rd Embodiment of this invention. (A) It is a schematic sectional drawing of the thickness measuring apparatus of the workpiece | work concerning the 4th Embodiment of this invention. (B) It is sectional drawing which shows the principal part of the thickness measuring apparatus of the workpiece | work concerning the 4th Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Work thickness measuring device)
<First Embodiment>
FIG. 1A is a schematic perspective view of a workpiece thickness measuring apparatus according to the first embodiment of the present invention, and FIG. 1B is a workpiece thickness according to the first embodiment of the present invention. It is a figure which shows the principal part of a height measuring apparatus. As shown in FIG. 1A, the workpiece thickness measuring device 1 has a water tank 2 filled with water (pure water). This water tank 2 is a liquid immersion device that can accommodate a workpiece (a silicon wafer in this embodiment) W after polishing, and can immerse the entire wafer W or a part thereof in water.

As shown in FIG. 1A, the workpiece thickness measuring apparatus 1 is arranged so as to be opposed to each other and can measure two or more distances to the surface of the portion immersed in the liquid of the wafer W ( Two measuring devices 3 are provided in the illustrated example. That is, one of the measuring devices 3 can measure the distance from the measuring device 3 to the front surface of the wafer W, and the other is the distance from the measuring device 3 to the back surface of the wafer W. Can be measured.
As shown in FIG. 1A, the workpiece thickness measuring apparatus 1 further includes a support member 4 that fixes the measuring device 3. In the illustrated example, the support member 4 is composed of four struts arranged so as to surround the water tank 2 and four rigid plate members that connect the struts, and the measuring device 3 is attached to the two opposing plate members. By being fixed, the distance between the measuring devices 3 facing each other is kept constant.
Thereby, the measuring device 3 measures the distance to the front surface of the wafer W and the distance to the back surface of the wafer W at a predetermined position of the wafer W, for example, by an arithmetic unit (not shown). The thickness of the wafer W at the predetermined position can be obtained.

Here, as shown in FIG. 1B, the water tank 2 is filled with water (pure water) 5 so that the entire surface is immersed in the water 5 and the wafer W is placed between the measuring instruments 3 facing each other. Is arranged. The wafer W is transferred into water using a transfer unit (not shown) in a state wetted with polishing slurry or grinding liquid after polishing.
Hereinafter, the operational effects of the first embodiment will be described.

  According to the workpiece thickness measuring apparatus 1 of the present embodiment, first, the wafer W is transferred into water in a wet state, and the thickness of the wafer W can be measured in a state in which the wafer W is immersed in water. Therefore, the throughput of the polishing process can be ensured as compared with the case where the thickness of the wafer W is measured after the wafer W is dried. In addition, by grasping the change in the amount of machining allowance by comparing with the thickness of the wafer W before polishing, and feeding it back to the polishing apparatus, the polishing recipe is changed and the parameters of the polishing conditions are corrected. The amount of polishing by can be controlled appropriately. The amount of machining allowance for polishing may be grasped by, for example, one wafer W, or may be grasped by, for example, statistically viewing a plurality of wafers W. Therefore, by using the measurement result according to the present embodiment, the flatness of the wafer W after polishing (particularly the flatness of the outer peripheral portion) and the density of the LPD can be improved. Furthermore, by managing the amount of polishing stock removal, it is possible to optimize the amount of disposable polishing slurry used and to reduce material costs.

In addition, by moving the wafer W in the radial direction of the wafer W by a transfer unit (not shown), it is possible to measure the thickness of the wafer W in all the surfaces within a certain diameter range of the wafer W. In this case, it is preferable that the water tank 2 has a large volume including the moving range of the wafer W. On the other hand, the thickness may be measured in the radius range of the wafer W. Alternatively, the thickness of the wafer W at an arbitrary position can be measured by moving the measuring device 3. In this case, the measuring instrument 3 is moved while keeping the distance between the opposing measuring instruments 3 constant.
Further, by providing a mechanism for rotating the wafer W in the transfer section, the thickness measurement at an arbitrary position of the wafer W, the thickness measurement at a radius range or a diameter range in an arbitrary direction, and the circumferential direction of the wafer W It is also possible to measure the in-plane thickness along.

  Further, in the present embodiment, the thickness of the wafer W is calculated from the distance to the surface of the wafer W using the two measuring devices 3 facing each other. For example, in the method of measuring the thickness of the wafer W by interference of reflected light on the front and back surfaces by irradiating a laser or the like from one side of the wafer W, the light does not transmit to the back surface when the impurity concentration in the silicon substrate is high, Although the thickness of the wafer may not be evaluated, in this embodiment, the thickness of the wafer W can be measured regardless of the impurity concentration of the wafer W.

  Here, in the present invention, as in this embodiment, the liquid is preferably water and particularly preferably pure water. This is because light is transmitted and does not chemically react with the wafer W or the measuring device 3.

  The measuring device 3 is preferably an optical spectral interference measuring device. This is because the distance from the measuring device 3 to the surface of the wafer W can be measured through a liquid such as water.

Here, in the example shown in FIGS. 1A and 1B, the measuring device 3 is disposed outside the water tank 2, and therefore the water tank 2 is preferably made of a material that transmits light.
Further, as shown in FIGS. 1A and 1B, the measuring device 3 can be used with high accuracy by providing a recess 2 a in the water tank 2 and reducing the distance between the wafer W and the measuring device 3. .

  As shown in FIGS. 1 (a) and 1 (b), when an air layer 7 is interposed between the underwater portion and the measuring device 3, if the water pressure changes due to movement of the wafer W in water or the like, the water tank 2 Is deformed, the ratio of the distance between the air layer 7 and the underwater portion is changed, and it is considered that a slight deviation occurs in the optical apparent distance. The present inventor newly found out that the thickness of the wafer W can be measured with higher accuracy by suppressing this.

Therefore, in the embodiment shown in FIGS. 1A and 1B, the water tank 2 is preferably made of quartz or plate glass. This is because quartz and plate glass are highly rigid materials, so that deformation of the water tank can be reduced. This is because the above inconvenience due to the presence of the air layer 7 can be avoided.
Further, in order to increase the rigidity of the water tank 2, it is preferable to increase the thickness of the water tank 2, specifically, it is preferably 8 mm or more, more preferably 10 mm or more, and more preferably 12 mm or more. Is particularly preferred.

  Furthermore, in the workpiece thickness measuring apparatus of the present invention, it is preferable that the deformation amount of the tank is 50 nm or less when measuring the thickness of the workpiece. This is because the thickness of the wafer W can be measured with higher accuracy. In addition, although the deformation amount of a tank is not specifically limited, it can measure using SIENCE F10 by Keyence Corporation.

In order to set the deformation amount of the tank to 50 nm or less, specifically, the measurement transmission window on the line where the two measuring devices 3 of the tank face each other (in the example shown in FIGS. 1A and 1B, It is preferable to have a reinforcing material (in the example shown in FIGS. 1A and 1B, the reinforcing plate 2b) around the recess 2a) of the water tank 2. This is because the tank can be reinforced with the reinforcing material and the deformation amount of the tank can be reduced.
Here, in order to enhance the reinforcing effect, the reinforcing material preferably covers at least the top, bottom, left and right of the transmission window for measurement, and it is even more preferable to reinforce the entire side surface of the tank. Further, it is preferable to use a metal such as SUS as the material of the reinforcing material.
Alternatively, the tank itself can be made of a metal such as SUS, except for the portion of the transmission window for measurement.

Moreover, in order to make the deformation amount of the tank 50 nm or less, the height of the liquid level in the tank (in the example shown in FIGS. 1A and 1B, the height of the water surface in the water tank 2) is constant. It is preferable to adjust so that.
Specifically, for example, in the example shown in FIGS. 1A and 1B, a drainage part (drainage part in this example) is provided in a tank (water tank 2 in this example), and the drainage part (in this example) The amount of drained liquid from the drainage unit (in this example, the amount of drainage) is measured by a drainage amount measuring device (drainage amount measuring device), and based on the measured amount of drained liquid (drainage amount), the control unit It is preferable to adjust the amount of drained liquid (amount of drainage) by controlling the amount (water supply amount) and / or the moving speed of the transfer unit that moves the wafer W.

<Second Embodiment>
FIG. 2A is a schematic perspective view of a workpiece thickness measuring apparatus according to the second embodiment of the present invention, and FIG. 2B is a workpiece thickness according to the second embodiment of the present invention. It is a figure which shows the principal part of a height measuring apparatus.
As shown in FIGS. 2 (a) and 2 (b), in the workpiece thickness measuring apparatus 1 of this embodiment, the tip of the measuring instrument 3 is inserted into the water tank 2, and between the water tank 2 and the measuring instrument 3. It differs from the embodiment shown in FIGS. 1A and 1B in that a gap 8 is provided. A cap 6 is provided at the tip of the measuring device 3, and the metal measuring device 3 is waterproofed by the cap 6, and an air layer 7 is formed between the tip of the measuring device 3 and the cap 6. .

According to the second embodiment, first, since the basic configuration is the same as that of the first embodiment, the same operational effects as those of the first embodiment described above can be achieved.
In addition, according to the second embodiment, the gap 8 is provided between the water tank 2 and the measuring instrument 3, and the water 5 in the water tank 2 leaks from the gap 8. Even when the water tank 2 is deformed, it does not interfere with the measuring device 3, and it is possible to suppress a change in the optical apparent distance due to a change in the ratio of the distance between the air layer 7 and the underwater portion. Therefore, according to the present embodiment, the above-described inconvenience due to the presence of the air layer 7 can be avoided. Further, according to the second embodiment, since the measuring device 3 can be brought close to the wafer W, an advantage of improvement in measurement accuracy can be obtained.
In the present embodiment, since the water 5 leaks from the water tank 2, it is preferable to increase the amount of water supplied into the water tank 2, but the turbulent flow of the water 5 occurs to vibrate the wafer W. Therefore, it is preferable to supply the water 5 to a degree slightly larger than the amount leaking from the gap 8 so as not to cause a measurement error.

<Third Embodiment>
FIG. 3A is a schematic cross-sectional view of a workpiece thickness measuring apparatus according to a third embodiment of the present invention, and FIG. 3B is a workpiece thickness according to the third embodiment of the present invention. It is sectional drawing which shows the principal part of a height measuring apparatus.
The third embodiment is an example in which the aquarium 2 itself is not used in order to eliminate the deformation of the aquarium 2 that causes the ratio of the optical apparent distance between the air layer 7 and the underwater portion to change.

Here, the liquid supply pipe 9 includes a liquid supply amount adjustment unit capable of adjusting the amount of water 5 to be supplied, and adjusts the supply amount of water 5 to a position where the thickness of the wafer W is measured. The water film 11 can be formed so that the measurement location is always immersed in the water 5.
Further, for example, as shown in FIG. 3A, the water 5 is introduced into the liquid introduction tube 10 from one end of the cylindrical liquid introduction tube 10 and flows through the liquid introduction tube 10.

  According to the third embodiment, first, at least a portion where the thickness of the wafer W is measured is immersed in water, so that the wafer W is underwater as in the first and second embodiments. The thickness of the wafer W can be measured in a state immersed in the wafer, and the throughput of the polishing process can be ensured as compared with the case where the thickness of the wafer W is measured after the wafer W is dried. In addition, by grasping the change in the amount of machining allowance by comparing with the thickness of the wafer W before polishing, and feeding it back to the polishing apparatus, the polishing recipe is changed and the parameters of the polishing conditions are corrected. The amount of polishing by can be controlled appropriately. By using the measurement result according to the present embodiment, the flatness of the wafer W after polishing (particularly the flatness of the outer peripheral portion) and the density of the LPD can be improved. Furthermore, by managing the amount of polishing stock removal, it is possible to optimize the amount of disposable polishing slurry used and to reduce material costs.

  Also in the third embodiment, the thickness of the wafer W in all the surfaces in a certain diameter range of the wafer W is measured by moving the wafer W in the radial direction of the wafer W by a transfer unit (not shown). Can do. Furthermore, according to the present embodiment, the thickness of the wafer W can be measured regardless of the impurity concentration of the wafer W, as in the first and second embodiments.

  According to the third embodiment, since the water tank 2 is not used, there is no error in the measurement of the thickness of the wafer W due to the deformation of the water tank 2 as described above, and therefore the air layer 7 is interposed. The above-mentioned inconvenience caused by this can be avoided. Further, the measuring device 3 can be used with high accuracy by bringing the measuring device 3 close to the wafer 3.

<Fourth Embodiment>
FIG. 4A is a schematic cross-sectional view of a workpiece thickness measuring apparatus according to the fourth embodiment of the present invention, and FIG. 4B is a workpiece thickness according to the fourth embodiment of the present invention. It is sectional drawing which shows the principal part of a height measuring apparatus.
In the fourth embodiment, as shown in FIG. 4A, the wafer W is opposed to the wafer W so that the radial direction is the horizontal direction (direction perpendicular to gravity). Thus, the second embodiment is different from the third embodiment in that two measuring devices 3 are arranged.
Also in the fourth embodiment, the same operational effects as in the third embodiment can be achieved.
In particular, according to the fourth embodiment, it is easy to hold the water film 11 on the upper surface of the wafer W. The water film 11 can be held by supplying water to the lower surface of the wafer W at a higher pressure.

(Work thickness measurement method)
As described with reference to FIGS. 1 to 4, the workpiece thickness measuring method according to the embodiment of the present invention includes a step of immersing at least a part of the polished wafer W in a liquid such as pure water. As a method for immersing the wafer W in the liquid, for example, as shown in FIGS. 1 and 2, the wafer W can be arranged in the water tank 2 using the water tank 2, or alternatively, as shown in FIGS. 3 and 4. Thus, for example, the water pressure may be increased by the liquid supply pipe 9 so that the water film 11 is formed on a part of the wafer W. Other methods can also be used.
Then, in a state where at least a part of the wafer W is immersed in the liquid, the wafer W is disposed by two or more measuring devices 3 which are arranged to face each other with the wafer W interposed therebetween and capable of measuring the distance to the surface of the wafer W. Measuring the thickness of the portion immersed in the liquid.

  According to the workpiece thickness measurement method of the present embodiment, the thickness of the wafer W can be measured while the wafer W is wet, and the thickness of the wafer W is measured after the wafer W is dried. As compared with the above, it is possible to ensure the throughput of polishing batch processing. In addition, by grasping the change in the amount of machining allowance by comparing with the thickness of the wafer W before polishing, and feeding it back to the polishing apparatus, the polishing recipe is changed and the parameters of the polishing conditions are corrected. The amount of polishing by can be controlled appropriately. By using the measurement result obtained by the method of this embodiment, the flatness of the wafer W after polishing (particularly the flatness of the outer peripheral portion) and the density of the LPD can be improved. Furthermore, by managing the amount of polishing stock removal, it is possible to optimize the amount of disposable polishing slurry used and to reduce material costs.

(Work polishing equipment)
A workpiece polishing apparatus according to an embodiment of the present invention includes a receiving unit (not shown) that receives information on the thickness of the wafer W measured by the above-described workpiece thickness measuring apparatus and measuring method, and a receiving unit. And an arithmetic unit (not shown) that performs polishing recipe switching or polishing parameter correction based on the received thickness information of the wafer W. Specifically, for example, the polishing time can be corrected by the calculation unit. The polishing apparatus may be a double-side polishing apparatus or a single-side polishing apparatus.
According to the workpiece polishing apparatus of the present embodiment, it is possible to appropriately control the polishing amount while ensuring the throughput. Therefore, the flatness of the workpiece after polishing (particularly the flatness of the outer peripheral portion) can be improved, and the density of defects such as LPD can also be reduced.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to said embodiment at all. Moreover, although the Example of this invention is described below, this invention is not limited to this Example at all.

Example 1
Tests were performed to measure the thickness of the polished silicon wafer using two different types of measuring instruments that measure the distance to the wafer. For polishing, a general single-side polishing apparatus was used. As shown in Table 1 below, two types of substrates, p− and p ++, having a diameter of 300 mm were used for the silicon wafer. Furthermore, Hamamatsu Photonics Optical MicroGauge (conventional example 1) is used as a type of measuring device for evaluating interference of reflected light on the front and back surfaces of the wafer in water, and can be used in the present invention. SI-F10 manufactured by Keyence Corporation was used as a measuring instrument capable of measuring the distance up to (Invention Example 1). Moreover, the thickness of the wafer was measured after drying using Nano Metro made by Kuroda as a comparison object (Comparative Example). Inventive Example 1 and Comparative Example were measured using an apparatus of a type in which a wafer is sandwiched between two measuring instruments as shown in FIG. On the other hand, as for the conventional example, the measuring device is arranged only on one side of the wafer.
Table 1 shows the evaluation results.

As shown in Table 1, p ^- the thickness of the substrate, the conventional example 1 and Inventive Example 1 were both able to measure the thickness of accurately wafer, the thickness of the p ⁺⁺ substrate, prior art 1 Then, while the measurement itself could not be performed, it can be seen that the thickness of the wafer could be measured with high accuracy in Invention Example 1.

(Example 2)
Next, the thickness of the wafer after single-side polishing is measured, SFQR (Site Front Last Square Range) when the polishing time is corrected by feeding it back to the single-side polishing apparatus, and the difference in SFQR before and after single-side polishing is measured. (ΔSFQR) was determined. Here, the single-side polishing apparatus includes a receiving unit that receives information on the measured thickness of the wafer, and a calculation unit that corrects the polishing time based on the received information on the thickness of the wafer. The configuration of is the same as that of a general single-side polishing apparatus. The silicon wafer subjected to polishing was a p ⁻ type silicon wafer having a diameter of 300 mm. SFQR refers to the in-site plane calculated by the least-squares method within the set site as a reference plane, and is placed horizontally on the + side from this plane (that is, with the main surface of the wafer facing up). It is a value evaluated for each site expressed as the sum of absolute values of the maximum displacement amounts on the upper side and the lower side. In Example 2, the inside of a 26 × 8 mm ² site size was measured using a flatness measuring device (manufactured by KLA-Tencor: WaferSight).
Here, since the polishing rate varies depending on the operation status of the polishing apparatus, the SFQR was evaluated in two cases, after being temporarily stopped and restarted and when continuously operating. The evaluation results are shown in Table 2 below. In Table 2, Invention Example 2 is a case where the above feedback is performed, and Conventional Example 2 is a case where the above feedback is not performed. In Table 2, when the sign of ΔSFQR is positive, it indicates that SFQR has deteriorated after single-side polishing. Note that the thickness of the wafer after single-side polishing was measured in the same manner as in Invention Example 1.

  As shown in Table 2, in Conventional Example 2, since the polishing time was fixed, ΔSFQR was large and the flatness was low when the single-side polishing apparatus was stopped and restarted. On the other hand, in Invention Example 2, since the information on the measured thickness of the polished wafer is fed back to the single-side polishing apparatus and the polishing time is adjusted (520 sec), ΔSFQR is small and flatness is maintained even after restarting the stop. It can be seen that the decrease was suppressed.

(Example 3)
Next, the thickness of the wafer after single-side polishing was measured, and it was fed back to the single-side polishing apparatus to evaluate the LPD density when the polishing time was corrected. The LPD density was evaluated using a particle counter (KLA-Tencor SP2). Here, the single-side polishing apparatus includes a receiving unit that receives information on the measured thickness of the wafer, and a calculation unit that corrects the polishing time based on the received information on the thickness of the wafer. The configuration of is the same as that of a general single-side polishing apparatus. The silicon wafer subjected to polishing was a p ⁻ type silicon wafer having a diameter of 300 mm. Since the polishing rate varies depending on the operation status of the polishing apparatus, the LPD density was evaluated in two cases: after stopping and restarting, and when continuously operating. The evaluation results are shown in Table 3 below. In Table 3, Invention Example 3 is a case where the above feedback is performed, and Conventional Example 3 is a case where the above feedback is not performed. The thickness of the wafer after single-side polishing was measured in the same manner as in Invention Example 1.

  As shown in Table 3, in the conventional example 3, since the polishing time was fixed, when the single-side polishing apparatus was stopped and restarted, the LPD density was large and many defects were generated. It can be seen that the information on the thickness of the wafer after polishing was fed back to the single-side polishing apparatus and the polishing time was adjusted (520 sec), so that the generation of LPD could be suppressed even after restarting. Moreover, by managing the amount of machining allowance for polishing, the amount of disposable polishing slurry used can be optimized, and material costs can be reduced.

Example 4
Next, the measurement error of the wafer thickness when the material and thickness of the water tank were changed and the deformation amount of the water tank were monitored and evaluated. A p ⁺⁺ type substrate having a diameter of 300 mm was used as a silicon wafer used for polishing. For polishing, a general single-side polishing apparatus was used. Here, the measurement error is when the measurement is performed using the Keyence SI-F10 in the apparatus shown in FIG. 1 and when the thickness of the wafer is measured after drying using the nanometer manufactured by Kuroda. Ten measurements were performed, and the maximum difference between the measurement results was defined as a measurement error. Moreover, the deformation amount of the water tank was monitored during measurement time using SI-F10 made by Keyence, and the maximum displacement during that time was defined as the deformation amount of the water tank.
The evaluation results are shown in Table 4 below. In Table 4, “measurement error” is expressed as a relative index when the case of acrylic resin (thickness 8 mm) is set to 100, and the smaller the value, the smaller the “measurement error”. As shown in FIG. 1, the metal reinforcement is performed by attaching a SUS reinforcing plate to the water tank, and the drainage amount control is to adjust the water supply amount and the wafer moving speed by monitoring the drainage amount. It was done by.

As shown in Table 4, it is understood that when quartz is used, the amount of deformation of the water tank can be greatly reduced, thereby greatly improving the measurement error. It can also be seen that the thicker the water tank, the smaller the amount of deformation of the water tank and the smaller the measurement error.
It can also be seen that the metal reinforcement further reduced the amount of deformation of the water tank and further reduced the measurement error. Furthermore, it can be seen that by controlling the amount of drainage of water, the amount of deformation of the water tank is further reduced, and the measurement error is further reduced.

(Example 5)
Next, the measurement error of the wafer thickness when the water tank shown in FIG. 2 was used was evaluated by comparison with the measurement error when the water tank shown in FIG. 1 (but not having a reinforcing plate) was used. . The evaluation method is the same as in Example 4. The material and thickness of the water tank were the same. In Table 5, “measurement error” is shown as a relative value when the case of FIG. 1 is set to 100, and a smaller numerical value means a smaller error. In this embodiment, the wastewater amount control is not performed.

  When the apparatus shown in FIG. 2 is used, since the water tank has a gap and the deformation of the water tank does not interfere with the measuring instrument, it can be seen that the measurement error can be greatly reduced as shown in Table 5. .

(Example 6)
Next, the wafer thickness measurement error in the case of using the apparatus shown in FIG. 3 was evaluated in comparison with the measurement error in the case of using the water tank shown in FIG. 1 (without a reinforcing plate). . The evaluation method is the same as in Examples 4 and 5. In Table 6, “measurement error” is shown as a relative value when the case of FIG. 1 is set to 100, and a smaller numerical value means a smaller error. In this embodiment, the wastewater amount control is not performed.

  As shown in Table 6, when the apparatus shown in FIG. 3 is used, the measurement error can be greatly reduced because the water tank itself that causes the measurement error is not used.

(Example 7)
Next, as in Example 2, the thickness of the wafer after single-side polishing was measured, and SFQR (Site Front Last Square Range) when the polishing time was corrected by feeding it back to the single-side polishing apparatus was measured. The difference in SFQR before and after single-side polishing (ΔSFQR) was determined. The test was performed in three ways: when not performing both metal reinforcement and drainage control, performing only metal reinforcement, and performing both metal reinforcement and drainage control. Note that the thickness of the wafer after single-side polishing was measured in the same manner as in Invention Example 1.
In Table 7, the evaluation results are shown as relative values of the standard deviation of ΔSFQR, where 100 is the case where neither metal reinforcement nor drainage control is performed, and the smaller the value, the better the variation.
In addition, metal reinforcement and drainage amount control were performed by the same method as Example 4.

  As shown in Table 7, the relative value of the standard deviation of ΔSFQR can be further reduced by performing metal reinforcement, and the relative value of the standard deviation of ΔSFQR is further reduced by performing metal reinforcement and drainage control. I understand that I was able to.

DESCRIPTION OF SYMBOLS 1 Work thickness measuring apparatus 2 Water tank 3 Measuring device 4 Support member 5 Water 6 Cap 7 Air layer 8 Crevice 9 Liquid supply pipe 10 Liquid introduction pipe 11 Water film W Workpiece (wafer)

Claims (17)

A liquid immersion device that immerses at least a part of the workpiece after polishing in a liquid;
Two or more measuring devices which are arranged opposite to each other and capable of measuring the distance to the surface of the part immersed in the liquid of the workpiece, and comprising a workpiece thickness measuring device.   The workpiece thickness measuring apparatus according to claim 1, further comprising a support member for fixing the measuring instrument.   The workpiece measuring device according to claim 1, wherein the measuring device includes a cap at a tip.   The said liquid immersion device is a thickness measuring apparatus of the workpiece | work as described in any one of Claims 1-3 which is a tank which can accommodate the said workpiece | work inside.   The workpiece thickness measuring device according to claim 4, wherein the tank is made of quartz or plate glass. At least a part of the measuring device is inserted into the tank,
The workpiece thickness measuring apparatus according to claim 4, wherein a gap is provided between the tank and the measuring instrument.   The thickness measurement of the workpiece according to any one of claims 1 to 3, wherein the liquid immersion device is a liquid supply pipe capable of supplying the liquid so that at least a part of the workpiece is always immersed in the liquid. apparatus.   The workpiece thickness measuring device according to claim 7, wherein the liquid supply pipe includes a liquid supply amount adjusting unit capable of adjusting an amount of supplying the liquid. Further comprising a liquid introduction pipe disposed in close proximity to the workpiece thickness measurement location and sandwiching the workpiece;
The work thickness measuring device according to claim 7 or 8, wherein at least a tip of the measuring device is inserted into the liquid introduction tube.   The workpiece thickness measurement apparatus according to any one of claims 1 to 9, wherein the liquid is water.   The workpiece measuring device according to claim 1, wherein the measuring device is an optical spectral interference measuring device.   The workpiece thickness measuring device according to claim 4 or 5, wherein the deformation amount of the tank is 50 nm or less when the thickness of the workpiece is measured.   The workpiece thickness measuring device according to claim 12, wherein a reinforcing plate is disposed in the tank.   The tank includes a drained liquid part, a drained liquid amount measuring device that measures a drained liquid amount from the drained liquid part, and a control unit that adjusts the drained liquid amount based on the measured drained liquid amount. Item 14. The workpiece thickness measuring apparatus according to Item 12 or 13. Immersing at least a part of the polished workpiece in a liquid;
Two or more measurements in which at least a part of the workpiece is immersed in the liquid and arranged opposite to each other with the workpiece interposed therebetween, and the distance to the surface of the portion of the workpiece immersed in the liquid can be measured Measuring the thickness of the workpiece by means of a vessel, and a method for measuring the thickness of the workpiece. A receiving unit that receives information on the thickness of the workpiece measured by the workpiece thickness measuring device according to any one of claims 1 to 14,
An apparatus for polishing a workpiece, comprising: an arithmetic unit that switches a polishing recipe or corrects a parameter of a polishing condition based on information on the thickness of the workpiece. A receiver for receiving information on the thickness of the workpiece measured by the workpiece thickness measuring method according to claim 15;
An apparatus for polishing a workpiece, comprising: an arithmetic unit that switches a polishing recipe or corrects a parameter of a polishing condition based on information on the thickness of the workpiece.

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