JP6650341B2 - Sectional shape measurement method - Google Patents

Description

  The present invention relates to a cross-sectional shape measuring method for measuring a cross-sectional shape of a work such as a silicon wafer.

  2. Description of the Related Art Conventionally, a double-side polishing apparatus that polishes both sides of a wafer by rotating and revolving a carrier plate holding a wafer is known (see Patent Document 1).

  Such a double-side polishing apparatus includes a thickness measuring instrument capable of measuring the thickness of the wafer being polished, an upper surface plate having a through hole for measurement, a lower surface plate, a sun gear, an internal gear, and a carrier plate. The carrier plate is sandwiched between the upper platen and the lower platen, the carrier plate is meshed with the sun gear and the internal gear, and the carrier plate is rotated and revolved by rotating the sun gear and the internal gear. By rotating the lower platen, both surfaces of the wafer held on the carrier plate are polished.

  Further, the double-side polishing apparatus has a polishing step of polishing both sides of the wafer while rotating the carrier plate only by rotation, a measuring step of measuring the thickness of the wafer at a predetermined position during the polishing step, and a measuring step of the measuring step. Determining a polishing end time based on the measurement result.

JP 2015-47656 A

However, in such a polishing apparatus, there is a problem that the cross-sectional shape of the wafer (work) cannot be obtained because only the thickness of the wafer at a predetermined position is measured during the polishing process.
In the polishing process, it is required not only to finish a work to a desired thickness but also to finish it to a desired cross-sectional shape.
The cross-sectional shape of the wafer is evaluated by indices such as SFQR and GBIR. By obtaining a workpiece having a desired cross-sectional shape that satisfies the conditions based on these indices, the semiconductor device manufactured in the subsequent semiconductor device manufacturing process is obtained. The yield can be improved.
However, it is not possible to determine whether or not the cross-sectional shape of the work has been processed into a desired cross-sectional shape only by measuring the thickness of the work. Therefore, in order to obtain a work having a desired cross-sectional shape, a cross-sectional shape measuring method capable of measuring the cross-sectional shape of the work during polishing has been required.
In addition, the cross-sectional shape of the work includes the upper surface plate, the lower surface plate, the processing speed that can be set arbitrarily such as the rotation speed of the sun gear and the internal gear, the processing load, the supply amount and temperature of the polishing slurry, and the upper surface plate and the lower surface plate. It changes depending on the state of the processing surface (change in shape due to temperature change or wear), the actual temperature of the polishing slurry, the processing state that changes as needed with the progress of polishing, such as the rotation state of the work. Even if the workpiece is polished under the same processing conditions, the processing state is not always the same. In other words, even if the workpiece is polished under the same processing conditions, the processing state varies, so that a workpiece having a desired cross-sectional shape cannot be constantly obtained. Therefore, it is necessary to measure the cross-sectional shape of the work during the polishing process, and to control the processing conditions when the desired cross-sectional shape is not obtained. Therefore, in order to obtain a work having a desired cross-sectional shape, a cross-sectional shape measuring method capable of measuring the cross-sectional shape of the work during polishing has been required.

  An object of the present invention is to provide a cross-sectional shape measuring method capable of measuring a cross-sectional shape of a work during polishing.

  The present invention provides a cross-sectional shape measurement for measuring the thickness of a work to be polished by a rotatable surface plate by a thickness measuring means through a measurement hole provided in the surface plate to obtain a cross-sectional shape of the work. A method, wherein a plurality of thicknesses measured by the thickness measuring means and a plurality of in-plane positions obtained by the position calculating means for obtaining an in-plane position of the work whose thickness is measured by the thickness measuring means are respectively obtained. The thickness at each in-plane position is converted into a thickness at each predetermined radial position of the work corresponding to a radial distance from the center of the work to each in-plane position. The cross-sectional shape of the workpiece in the radial direction is obtained.

  According to the present invention, the cross-sectional shape of the work can be measured during the polishing. Therefore, polishing can be performed while grasping whether the cross-sectional shape of the work is processed to a desired cross-sectional shape, and when the cross-sectional shape is not the desired cross-sectional shape, the processing conditions can be controlled during polishing. Thereby, it is possible to constantly obtain a work having a desired cross-sectional shape.

FIG. 1 is an explanatory diagram showing a configuration of an embodiment of a polishing apparatus according to the present invention. FIG. 2 is an explanatory diagram showing a positional relationship among a sun gear, an internal gear, and a carrier plate shown in FIG. 1. FIG. 3 is a diagram showing a cross-sectional shape of a wafer obtained by the method of the first embodiment, where (A) is a plan view showing an in-plane position where the thickness of the wafer is measured, and (B) is a radial distance of the in-plane position. 7 is a graph in which mirror inversion processing and arithmetic processing are performed on each position and thickness on the axis corresponding to FIG. It is the figure which calculated | required the cross-sectional shape of the wafer by the method of 2nd Example, (A) is a top view which shows the in-plane position which measured the thickness of the wafer, (B) is the radial distance of the in-plane position. 6 is a graph in which arithmetic processing is performed on each position and thickness on an axis corresponding to FIG. FIG. 13 is a plan view showing an in-plane position where the thickness of the wafer is measured by the method of the third embodiment. It is the graph which calculated | required the cross-sectional shape of the wafer which has a taper by the method of 2nd Example, (A) is the 1st time graph, (B) is the 2nd time graph, (C) is the 3rd time graph. FIG. 6A is a graph obtained by performing mirror inversion processing and arithmetic processing by the method of the fourth embodiment on the graph shown in FIG. 6A, and FIG. 6B is a graph showing the method of the fourth embodiment on the graph shown in FIG. FIG. 6C is a graph obtained by performing the mirror inversion processing and the arithmetic processing by the method of the fourth embodiment on the graph shown in FIG. 6C. It is the graph which calculated | required the cross-sectional shape of the wafer which does not have a taper by the method of 4th Example, (A) is the graph which measured the thickness of the wafer, (B) is mirror inversion processing and arithmetic processing to the graph. It is a graph performed. It is the graph which calculated | required the cross-sectional shape of the wafer which has a taper by the method of 4th Example, (A) is the graph which measured the thickness of the wafer, (B) performed mirror inversion processing and arithmetic processing to the graph. It is a graph. 9 is a graph showing the cross-sectional shape of a tapered wafer obtained by the method of the second embodiment. 14 is a graph showing the cross-sectional shape of a tapered wafer obtained by the method of the fourth embodiment.

Hereinafter, an example which is an embodiment of a polishing apparatus equipped with a cross-sectional shape measuring device for implementing the cross-sectional shape measuring method according to the present invention will be described with reference to the drawings.
[First embodiment]

A polishing apparatus 10 shown in FIG. 1 includes a polishing machine 20 for polishing both sides of a wafer (silicon wafer) W which is one of works, and a cross-sectional shape measuring apparatus 100 for measuring a radial cross-sectional shape of the wafer W during polishing. And a controller 300 for controlling driving devices M1 to M5, which will be described later, such that the cross-sectional shape becomes a target cross-sectional shape based on the radial cross-sectional shape of the wafer W measured by the cross-sectional shape measuring device 100. Have. Reference numeral 115 denotes a memory, and the memory 115 stores data obtained by the arithmetic unit 110 described later. Reference numeral 200 denotes a storage unit, which stores recipes indicating appropriate processing conditions for changing the cross-sectional shape to a target cross-sectional shape according to the obtained cross-sectional shape of the wafer W.
[Polishing machine]

  The polishing machine 20 includes an upper surface plate 21 and a lower surface plate 22 as a surface plate, a sun gear 23 rotatably disposed at the center of the upper surface plate 21 and the lower surface plate 22, and an upper surface plate 21 and a lower surface plate 22. And a carrier plate 30 disposed between the upper surface plate 21 and the lower surface plate 22 and provided with a work holding hole 30A (see FIG. 2). A polishing member 25 is provided on a lower surface of the upper stool 21, and a polishing member 26 is provided on an upper surface of the lower stool 22.

  The carrier plate 30 meshes with the sun gear 23 and the internal gear 24 as shown in FIG. 2, and rotates and revolves by rotation of the sun gear 23 and the internal gear 24. As the carrier plate 30 rotates and revolves, both surfaces of the wafer W disposed in the work holding holes 30A of the carrier plate 30 are polished by the polishing members 25 and 26.

  As shown in FIG. 1, the upper stool 21 is fixed to a rod 42 via a support stud 40 and a mounting member 41. The rod 42 is moved up and down by the driving device M1, and the upper platen 21 is moved up and down integrally by the up and down movement of the rod 42.

  On the other hand, the upper portion 43A of the drive shaft 43 penetrates the hole 23A at the center of the sun gear 23, and the sun gear 23 is fixed to the upper portion 43A, and the sun gear 23 rotates integrally with the drive shaft 43. It has become. The drive shaft 43 is rotated by the drive device M4, and the sun gear 23 is rotated integrally with the drive shaft 43 by the drive device M4.

  A drive shaft 44 rotated by the drive device M2 is inserted into the hole of the drive shaft 43, and an upper end portion 44A of the drive shaft 44 projects from the upper end of the drive shaft 43. A driver 45 is fixed to the upper end portion 44A, and the driver 45 rotates integrally with the drive shaft 44. A hook 46 provided on the upper stool 21 is engaged with the outer peripheral surface of the driver 45, and the upper stool 21 is integrally rotated by the rotation of the driver 45. The hook 46 is movable up and down with respect to the outer peripheral surface of the driver 45, whereby the upper platen 21 is movable up and down with respect to the driver 45.

  That is, the upper stool 21 moves up and down by the up and down movement of the rod 42 and rotates by the rotation of the drive shaft 44. That is, the upper stool 21 is rotated integrally with the drive shaft 44 by the drive device M2.

  A drive shaft 49 is formed below the center of the lower stool 22, and the drive shaft 43 is rotatably arranged in the drive shaft 49. The drive shaft 49 is rotated by the drive device M3, and the lower stool 22 is rotated integrally with the drive shaft 49 by the drive device M3.

  A drive shaft 47 is formed in the internal gear 24, and a drive shaft 49 is rotatably arranged in the drive shaft 47. The drive shaft 47 is rotated by the drive device M5, and the internal gear 24 is rotated integrally with the drive shaft 47 by the drive device M5.

  A measurement hole 50 is formed in the upper surface plate 21 at a position radially away from the center of the upper surface plate 21 by a predetermined distance. The measurement holes 50 are formed through the upper surface plate 21 and the polishing member 25, and a plurality of measurement holes 50 are formed at equal intervals along the circumferential direction of the position separated by the predetermined distance, but at least one measurement hole 50 is provided. I just need. Each measurement hole 50 is provided with a window member 51 that transmits infrared laser light as measurement light. The upper platen 21 is provided with a supply hole (not shown) for supplying the polishing slurry.

An optical head 101 is provided above a position radially separated from the center of the upper stool 21 by a predetermined distance. Each rotation of the upper stool 21 causes each measurement hole 50 to be located directly below the optical head 101. In addition, the infrared laser light emitted from the optical head 101 irradiates the wafer W through the window member 51.
[Cross section measuring device]

As shown in FIG. 1, the cross-sectional shape measuring device 100 irradiates an infrared laser beam, which is a measuring beam, to a wafer W through a window member 51 attached to a measuring hole 50 of the upper stool 21 and the wafer. The optical head 101 includes an optical head 101 that receives light reflected by W, a laser oscillator 102 that causes the optical head 101 to emit infrared laser light, an arithmetic unit 110, and a memory 115.
[memory]

The memory 115 stores the thickness of the wafer W determined by the thickness measuring unit 111 of the arithmetic unit 110 and the radial distance at the in-plane position determined by the position calculating unit 112 (the diameter from the center of the wafer W to the in-plane position). (Direction distance) and the cross-sectional shape of the wafer W obtained by the cross-sectional shape calculation unit 113.
[Computing device]

The arithmetic device 110 calculates a thickness measuring unit (thickness measuring means) 111 for measuring the thickness of the wafer W based on the reception of the reflected light from the optical head 101 and an in-plane position where the thickness of the wafer W is obtained. A position calculation unit (position calculation means) 112 for obtaining a radial distance from the center of the wafer W to an in-plane position obtained from the rotational positions of the sun gear 23 and the internal gear 24, and a thickness of the wafer W obtained by the thickness measurement unit 111. And a cross-sectional shape calculating unit 113 for calculating a cross-sectional shape of the wafer W based on the position and the radial distance at the in-plane position calculated by the position calculating unit 112.
[Thickness measurement section]

The thickness measuring unit 111 measures the reflection intensity on the surface of the wafer W of the wavelength tunable laser light that sweeps the wavelength at a high speed based on the reception of the reflected light from the optical head 101, for example, by measuring the light reflection interference method. The thickness of the wafer W is obtained by reconstructing the wavelength dispersion of the reflection (the state of interference of the light reflected on the front and back surfaces of the wafer) from this reflection intensity and performing frequency analysis.
[Position calculation unit]

The position calculation unit 112 obtains the position and the rotation speed of the carrier plate 30 based on the rotation positions of the sun gear 23 and the internal gear 24. That is, the revolving position and the rotation position of the carrier plate 30 are obtained, and based on the revolving position and the rotation position, the in-plane position of the wafer W directly below the optical head 101 is set to the origin of the center of the wafer W. It is obtained as a position in the X, Y coordinate system or as polar coordinates (r, θ). The radial distance from the center of the wafer W to the in-plane position is determined based on the determined in-plane position of the wafer W.
[Section shape calculation unit]

  The cross-sectional shape calculation unit 113 compares the data of the radial distance at each in-plane position of the wafer W stored in the memory 115 and the thickness at each of these in-plane positions with the wafer corresponding to the radial distance of each in-plane position. The W is converted into a thickness at each predetermined position in the radial direction of the W, and the sectional shape of the wafer W is obtained based on the thickness at these positions. The interval for obtaining the cross-sectional shape of the wafer W can be set arbitrarily. In this embodiment, for example, the cross-sectional shape of the wafer W is obtained based on the data of the in-plane position and the thickness obtained for 15 seconds, and a new shape is obtained at 15-second intervals. First, the sectional shape of the wafer W is determined.

  That is, the cross-sectional shape calculation unit 113 calculates the radial distances R1 to Rn at the respective in-plane positions Q1 to Qn of the wafer W stored in the memory 115 in the radial direction on the minus side (−150 to 0 mm) on the X axis. The thickness at each position on the minus side on the X axis corresponding to the distance is determined from the thickness of each in-plane position Q1 to Qn. That is, as shown in FIG. 3B, dots D1 to Dn indicating the thickness are obtained. The Z axis indicates the thickness, and no correspondence is established between the in-plane positions Q1 to Qn and the dots D1 to Dn.

  Further, the cross-sectional shape calculation unit 113 performs mirror inversion processing on the obtained dots D1 to Dn around the Z axis, and displays the dots D1 ′ to Dn indicating the thickness at each position on the plus side (0 to 150 mm) on the X axis. '.

  That is, the above-described conversion processing is processing for converting the thickness of each in-plane position Q1 to Qn into a thickness at each position on the minus side on the X axis, and converting each thickness on the minus side on the X axis to the origin. The mirror is inverted so as to be symmetrical with respect to, and is converted into each position on the positive side on the X axis, and the thickness of each position on the negative side on the X axis corresponding to each positive position on the X axis To convert the thickness into a thickness at each position on the plus side on the X-axis.

  Then, the cross-sectional shape calculation unit 113 obtains a polynomial approximate curve T1 based on each of the dots D1 to Dn and D1 'to Dn', and obtains the polynomial approximate curve T1 as a cross-sectional shape of the wafer W1 in the X-axis direction. .

The polynomial approximation curve T1 and the dots D1 to Dn and D1 'to Dn' can be displayed on the display unit 301 (see FIG. 1) as shown in FIG.
[Control device]

  The control device 300 reads a recipe indicating appropriate processing conditions for making the cross-sectional shape into a target cross-sectional shape from the storage unit 200 according to the radial cross-sectional shape of the wafer W obtained by the arithmetic device 110, and reads the recipe. The driving of the driving devices M1 to M5 is controlled during the polishing process based on the processing conditions of the recipe.

Further, the control device 300 controls the driving devices M1 to M5 and the arithmetic device 110.
[motion]

  Next, the operation of the polishing apparatus 10 configured as described above will be described.

  First, the wafer W is loaded into the work holding hole 30A (see FIG. 2) of the carrier plate 30, the upper platen 21 at the retract position is lowered, and the wafer W is sandwiched between the lower platen 22 and the upper platen 21.

  Next, double-side polishing is started. That is, the upper stool 21 and the lower stool 22 are rotated by the control of the driving devices M2 and M3 by the control device 300, and the upper stool 21 is pressed downward by the control of the driving device M1. Thus, the upper platen 21 presses the wafer W. Further, the sun gear 23 and the internal gear 24 are rotated by the control of the driving devices M4 and M5 by the control device 300, and the carrier plate 30 rotates and revolves.

  Both surfaces of the wafer W are polished by the rotation of the upper platen 21 and the lower platen 22 and the pressing of the upper platen 21. Further, both sides of the wafer W are polished by the rotation and revolving of the carrier plate 30. The upper surface plate 21 and the lower surface plate 22 are rotated at a high speed as the rotation speed is gradually increased. Further, the load on the wafer W by the upper platen 21 is also gradually increased, and the wafer W is pressed with a high load. Further, the rotation speeds of the sun gear 23 and the internal gear 24 are gradually increased, and the rotation speed and the revolution speed of the carrier plate 30 are also increased. Then, both surfaces of the wafer W are polished by the high-speed rotation of the upper stool 21, the lower stool 22, and the carrier plate 30 and the high load of the upper stool 21.

  On the other hand, the infrared laser light is emitted downward from the optical head 101 by the laser oscillator 102, and each time the measurement hole 50 comes directly below the optical head 101 due to the rotation of the upper surface plate 21, the infrared laser light is emitted from the measurement hole. The wafer W is irradiated through the window member 51 of the wafer 50, and the light reflected on the front and back surfaces of the wafer W enters the optical head 101 through the window member 51 of the measurement hole 50.

  Each time the optical head 101 receives the reflected light, the thickness measuring unit 111 calculates the thickness of the wafer W based on the interference light between the received light on the front surface and the reflected light on the back surface of the wafer W. On the other hand, the position calculation unit 112 calculates the in-plane position of the wafer W whose thickness has been determined, and calculates the radial distance at the in-plane position. Then, the thickness of the wafer W and the radial distance at the in-plane position of the wafer W from which the thickness is obtained are stored in the memory 115.

  The memory 115 stores data of the thickness of the wafer W and the radial distance at the in-plane position of the wafer W from which the thickness was obtained. That is, as shown in FIG. 3A, the memory 115 stores radial distances R1 to Rn at in-plane positions Q1 to Qn of the wafer W1 and thicknesses at these in-plane positions Q1 to Qn. Will be.

  The cross-sectional shape calculation unit 113 converts the data stored in the memory 115, that is, the data of the radial distances R1 to Rn at the in-plane positions Q1 to Qn of the wafer W1 and the thickness at the in-plane positions Q1 to Qn into the wafer. The W1 is converted into a thickness at each radial position on the minus side on the X-axis, and a cross-sectional shape of the wafer W1 in the X-axis direction is obtained based on the thickness at these positions.

  That is, the sectional shape calculation unit 113 calculates the thickness of each position on the minus side on the X axis of the wafer W1 corresponding to the radial distances R1 to Rn at the in-plane positions Q1 to Qn of the wafer W1 stored in the memory 115. Is obtained from the thicknesses of the in-plane positions Q1 to Qn, and as shown in FIG. 3B, dots D1 to Dn indicating the thicknesses of the respective positions on the minus side on the X axis are obtained.

  Further, the cross-sectional shape calculation unit 113 mirror-reverses the dots D1 to Dn indicating the thickness at each position on the minus side on the X axis around the Z axis, and calculates the thickness at each position on the plus side on the X axis. The dots D1 'to Dn' shown are obtained. That is, each position on the minus side on one X-axis is mirror-inverted so as to be symmetrical with respect to the origin O, and converted into each position on the plus side on the other X-axis. The thickness of each position on the side is obtained from the thickness of each in-plane position Q1 to Qn.

  Further, the cross-sectional shape calculation unit 113 obtains a polynomial approximate curve T1 based on each of the dots D1 to Dn and D1 'to Dn', and obtains the polynomial approximate curve T1 as a cross-sectional shape of the wafer W in the X-axis direction. The obtained cross-sectional shape of the wafer W in the X-axis direction is stored in the memory 115.

  Then, the polynomial approximation curve T1 and the dots D1 to Dn and D1 'to Dn' shown in FIG. 3B can be displayed on the display unit 301. With the display on the display section 301, the cross-sectional shape of the wafer W1 being polished can be grasped.

  Based on the cross-sectional shape of the wafer W obtained by the cross-sectional shape calculation unit 113, the control device 300 reads from the storage unit 200 a recipe indicating appropriate processing conditions for making this cross-sectional shape a target cross-sectional shape. The driving of each of the driving devices M1 to M5 is controlled during the polishing process based on the processing conditions.

  The polynomial approximation curve T1 and the dots D1 to Dn and D1 'to Dn' are obtained at intervals of 15 seconds in this embodiment, and the polynomial approximation curve T1 and the dots D1 to Dn, displayed on the display unit 301. D1 'to Dn' are updated every 15 seconds.

  Further, based on the cross-sectional shape of the new wafer W obtained every 15 seconds, the control device 300 reads from the storage unit 200 a recipe indicating an appropriate processing condition for changing the cross-sectional shape to the target cross-sectional shape. The driving of each of the driving devices M1 to M5 is controlled during the polishing process based on the processing conditions of the recipe. Therefore, it is possible to reliably and efficiently polish the cross section of the wafer W so as to have a target cross section.

  In the first embodiment, the measured in-plane positions Q1 to Qn of the wafer W1 are collected on the radius (minus side on the X axis) of the wafer W1, and the thickness of each position on the minus side on the X axis is measured. Are obtained as dots D1 to Dn, and the dots D1 to Dn are mirror-inverted around the Z axis to obtain dots D1 'to Dn' indicating the thickness of each position on the plus side on the X axis. Since the radial cross-sectional shape of the wafer W1 is obtained from the dots D1 to Dn and D1 'to Dn', the radial cross-sectional shape of the wafer W1 can be obtained even with a small number of data.

In the first embodiment, the measured in-plane positions Q1 to Qn of the wafer W1 are collected on the minus side on the X-axis of the wafer W1, and the thickness of each position on the minus side on the X-axis is obtained. The cross-sectional shape of the wafer W1 in the X-axis direction is obtained. Conversely, the positions of the in-plane positions Q1 to Qn are collected on the positive side on the X-axis, and the thickness of each position on the positive side on the X-axis is determined. After the calculation, the obtained thickness may be mirror-reversed around the Z axis, the thickness at each position on the minus side on the X axis may be obtained, and the cross-sectional shape of the wafer W1 in the X axis direction may be obtained.
[Second embodiment]

  FIG. 4 is an explanatory diagram showing a method for measuring the cross-sectional shape in the X-axis direction of the wafer W2 according to the second embodiment.

  In FIG. 4A, Q1a to Q8a and Q1b to Q6b indicate the in-plane positions of the wafer W2 where the thickness is measured.

  In the second embodiment, first, similarly to the first embodiment, the radial distance from the center O of the wafer W2 to the in-plane positions Q1a to Q8a and Q1b to Q6b is obtained.

  Next, among the in-plane positions Q1a to Q8a and Q1b to Q6b, the plus positions on the X-axis of the wafer W2 corresponding to the radial distances of the in-plane positions Q1a to Q8a on the plus side of the X-axis. The thickness is determined from the thickness of each in-plane position Q1a to Q8a. That is, as shown in FIG. 4B, dots D1a to D8a indicating the thickness at each position on the plus side on the X axis are obtained.

  Similarly, the thickness of each position on the minus side on the X axis of the wafer W2 corresponding to the radial distance between the in-plane positions Q1b to Q6b on the minus side of the X axis is the thickness of each in-plane position Q1b to Q6b. Ask from. That is, as shown in FIG. 4B, dots D1b to D6b indicating the thickness of each position on the minus side on the X axis are obtained.

  Then, a polynomial approximate curve T2 is determined based on the dots D1a to D8a and D1b to D6b, and the polynomial approximate curve T2 is determined as a cross-sectional shape of the wafer W2 in the X-axis direction.

  The dots D1a to D8a, D1b to D6b, and the polynomial approximation curve T2 are obtained by the cross-sectional shape calculation unit 113 (see FIG. 1) of the calculation device 110, as in the first embodiment.

  That is, the cross-sectional shape calculation unit 113 of the second embodiment determines the in-plane positions Q1a to Q8a on the plus side of the X-axis among the in-plane positions Q1a to Q8a and Q1b to Q6b based on the thickness and the radial distance. Is converted into the thickness at each position on the plus side on the X axis, and the thickness and radial direction of each of the in-plane positions Q1b to Q6b on the minus side of the X axis among the in-plane positions Q1a to Q8a and Q1b to Q6b Based on the distance, a process of converting into a thickness at each position on the minus side on the X-axis is performed, and a cross-sectional shape of the wafer W2 in the X-axis direction is obtained by this process.

In the second embodiment, the cross-sectional shape of the wafer W2 in the X-axis direction is obtained. However, the cross-sectional shape of the wafer W2 in the Y-axis direction may be obtained in the same manner. Based on the data of the cross-sectional shape in the Y-axis direction and the cross-sectional shape in the X-axis direction, the tendency of the surface shape of the wafer W2 can be grasped.
[Third embodiment]

  FIG. 5 is an explanatory diagram showing a method of measuring the cross-sectional shapes of the X axis and the Y axis, the first axis J1, and the second axis J2 of the wafer W3 of the third embodiment.

  In the third embodiment, based on the in-plane positions Q1c to Q7c within a predetermined range of, for example, 60 ° around the X-axis and the thickness of the in-plane positions Q1c to Q7c, the third embodiment is similar to the second embodiment. A dot (not shown) indicating the thickness of each position on the X-axis is obtained, and a polynomial approximation curve is obtained based on these dots to obtain a cross-sectional shape of the wafer W3 on the X-axis.

  Similarly, the cross-sectional shapes on the Y-axis, the first axis J1, and the second axis J2 are obtained, and the cross-sectional shapes of these four axes can be displayed on the display unit 301. By setting the first axis J1 and the second axis J2 arbitrarily, a desired cross-sectional shape can be measured.

  The cross-sectional shape of the four axes in the third embodiment is obtained by the cross-sectional shape calculation unit 113 (see FIG. 1) of the arithmetic unit 110, as in the first embodiment.

  The cross-sectional shape calculation unit 113 of the third embodiment determines each position on the X-axis based on the thickness and the radial distance of each of the in-plane positions Q1c to Q7c within a predetermined range around the X-axis among the in-plane positions. And a thickness at each position on the Y-axis based on the thickness and the radial distance of each in-plane position within a predetermined range around the Y-axis among the in-plane positions. And a thickness at each position on the first axis J1 based on the thickness and radial distance of each in-plane position within a predetermined range around the first axis J1 among the in-plane positions. And a process of converting the in-plane position into a thickness at each position on the second axis J2 based on the thickness and the radial distance of each in-plane position within a predetermined range around the second axis J2. To obtain the cross-sectional shapes of the X-axis, the Y-axis, the first axis J1, and the second axis J2. Is shall.

According to the third embodiment, since the cross-sectional shape of four axes is obtained, the tendency of the surface shape of the wafer W can be grasped more accurately. By increasing the number of axes of the required cross-sectional shape, it is possible to more accurately grasp the tendency of the surface shape of the wafer W.
[Fourth embodiment]

  FIGS. 6A to 6C are curves (polynomial approximation curves) G3, G4, and G5 obtained by calculating the tapered wafer W in the same manner as in the second embodiment. Actually, there are a plurality of dots indicating the thickness along each of the curves G3, G4, and G5 (see FIG. 4B), but for convenience of description, the dots are omitted and the curves G3, G4, and G5 are used. explain. Hereinafter, other curves will be similarly described. The curve G3 is obtained from data obtained for the first time (first 15 seconds), the curve G4 is obtained from data obtained for the second time (second 15 seconds), and the curve G5 is obtained from data obtained for the third time (third 15 seconds). .

  As described above, when the wafer W has a taper, as shown by the curves G3, G4, and G5, the measured value is affected by the taper component depending on the data acquisition timing, the cross-sectional shape is different, and the measured value is rampant. The difference (PV value) between the maximum thickness P and the minimum thickness V of the wafer W increases. If the cross-sectional shapes differ depending on the data acquisition timing, it is difficult to determine the true cross-sectional shape, and it is not possible to determine whether or not a desired cross-sectional shape has been processed, and it is not possible to select a recipe. Further, if the PV value is large, it is difficult to determine whether the value is an apparent value due to the influence of the taper component or a true value due to the uneven shape. Judgment cannot be made, and a recipe cannot be selected.

  When the wafer W has a taper, the PV value increases. Therefore, when the PV value is equal to or more than a predetermined value, it is possible to perform a mirror inversion process and then draw a polynomial approximate curve. By drawing a polynomial approximation curve after performing mirror inversion processing, it is possible to cancel the taper component. However, the mirror inversion processing may be performed regardless of the PV value.

  The mirror inversion processing is performed by the cross-sectional shape calculation unit 113 (see FIG. 1) of the calculation device 110. This mirror inversion processing is to invert the thickness of each position symmetrically with respect to the origin with the center position of the wafer W as the origin, and the thickness of each inverted position and the thickness of each position before inversion are calculated. Then, a polynomial approximation curve is drawn based on the curve, and the sectional shape of the wafer W is obtained.

  That is, as shown in FIGS. 7A to 7C, curves G3 ′, G3 ′, obtained by performing mirror inversion processing on the curves G3, G4, and G5 of FIGS. Based on G4 ', G5' and the curves G3, G4, G5 before mirror inversion, the polynomial approximate curves T3, T4, T5 are obtained, and the cross-sectional shape of the wafer W on the X axis is obtained.

  As described above, since the polynomial approximate curve drawing processing is performed after the mirror inversion processing, the data acquisition timing changes as can be seen from the polynomial approximate curves T3, T4, and T5 in FIGS. Even in this case, it is possible to prevent a change in the cross-sectional shape and a ramp-up of the PV value.

  A curve G6 shown in FIG. 8A is a curve showing the thickness at each position on the X-axis when the cross-sectional shape of the wafer W is convex and has no taper. Then, the curve G6 is mirror-inverted around the Z axis to obtain a curve G6 'shown in FIG. 8B, and a polynomial approximation curve T6 is obtained based on the curve G6' and the curve G6 to obtain a wafer W. The cross-sectional shape on the X-axis is obtained.

  In this embodiment, the PV value of the curve G6 is 0.5 μm, and since the wafer W has no taper, only the convex component is reflected in the PV value.

  G7 shown in FIG. 9A is a curve showing the thickness at each position on the X-axis when the cross-sectional shape of the wafer W is convex and has a taper. Then, the curve G7 is mirror-inverted around the Z axis to obtain a curve G7 ', and a polynomial approximation curve T7 is obtained based on the curve G7' and the curve G7 to obtain a cross-sectional shape of the wafer W on the X axis. .

  The PV value of the curve G7 is 1.0 μm, but the PV value of the polynomial approximation curve T7 subjected to the mirror inversion processing is 0.5 μm.

  The taper component is reflected on the convex component of the wafer W in the PV value of the curve G7, but the taper component is canceled out by performing the mirror inversion processing on the PV value of the polynomial approximate curve T7. Therefore, only the convex component is reflected on the PV value. Similarly, when the cross-sectional shape of the wafer W is concave, the taper component is canceled and only the concave component is reflected on the PV value.

  Therefore, it is possible to obtain a cross-sectional shape on the X-axis of the wafer W that reflects only the concavo-convex component from which the taper component has been removed.

  FIG. 10 shows an example in which a wafer W having a taper is measured and mirror inversion processing is not performed, and is based on data (dots) of the thickness of the wafer W at a position on the X-axis and the thickness. A polynomial approximation curve T8 is shown. As shown in FIG. 10, when the wafer W has a taper, the taper component affects the polynomial approximation curve T8.

  FIG. 11 shows an example in which a wafer W having a taper is measured and mirror inversion processing is performed. The data (dots) of the thickness of the wafer W at a position on the X axis and a polynomial based on this thickness are shown. An approximate curve T9 is shown. As shown in FIG. 11, even if the wafer W has a taper, the taper component is canceled from the polynomial approximation curve T9, and it can be seen that only the unevenness component of the wafer W is reflected.

  In this manner, as can be seen from the graph of FIG. 11, by performing the mirror inversion processing, the taper component can be canceled and only the concave and convex component of the wafer W can be reflected.

  In each of the above embodiments, the cross-sectional shape of the wafer W is obtained by acquiring the thickness from one wafer W and the radial distance at the in-plane position of the wafer W whose thickness has been obtained. Similarly, when polishing the wafer W, the cross-sectional shape of the wafer W can be obtained. For example, when five wafers W are simultaneously polished using five carrier plates 30, the respective thicknesses from the five wafers W and the diameters at the in-plane positions of the respective wafers W whose thicknesses have been determined are obtained. The direction distance is obtained, and the same processing as in the above embodiment is performed based on the data obtained from these five wafers W, whereby a single cross-sectional shape can be obtained. Further, the positions of the five wafers W can be obtained based on the rotational positions of the sun gear 23 and the internal gear 24 shown in FIG. Data can be obtained. By processing the data of the thickness and the radial distance at the in-plane position for each wafer W in the same manner as in the above embodiment, the cross-sectional shape of each of the five wafers W can be obtained.

  In the above embodiment, the measurement hole 50 is provided in the upper surface plate 21. However, the measurement hole is provided in the lower surface plate 22, and the lower surface of the wafer W is irradiated with infrared laser light from below to reduce the thickness of the wafer W. You may make it measure.

  In the above embodiment, the cross-sectional shape of the wafer W is obtained by the polynomial approximate curve drawing process. In addition to the polynomial approximate curve drawing process, the thickness at each position on the axis is averaged, such as a moving average process. Any method may be used as long as it can be visualized.

  In the above embodiment, the optical head 101 is provided above the upper stool 21, but the optical head 101 may be provided on the upper stool 21 and measure the cross-sectional shape of the wafer W while rotating with the upper stool 21. .

  Each of the above embodiments has described the polishing apparatus for polishing both sides of the wafer W, but the present invention is also applicable to a polishing apparatus for polishing only one side of the wafer W.

  In the above embodiment, the case where the cross-sectional shape of the wafer W is measured during the polishing and the processing conditions are controlled during the polishing is described. However, the cross-sectional shape of the wafer W is measured between the polishing and the polishing. Alternatively, the processing conditions in the next polishing may be controlled.

  Further, in the above-described embodiment, the case where the silicon wafer is polished has been described. However, the present invention is not limited thereto.

  The present invention is not limited to the above embodiment, and changes and additions of the design are allowed without departing from the gist of the invention according to each claim of the claims.

Reference Signs List 10 polishing device 20 polishing machine 21 upper surface plate (surface plate)
22 Lower surface plate (surface plate)
Reference Signs List 50 Measurement hole 100 Cross-sectional shape measuring device 101 Optical head 110 Computing device 111 Thickness measuring unit 112 Position calculating unit 113 Cross-sectional shape calculating unit 115 Memory 200 Storage unit W Wafer (work)

Claims (8)

A cross-sectional shape measuring method for measuring a thickness of a work to be polished by a rotatable surface plate by a thickness measuring means through a measurement hole provided in the surface plate to obtain a cross-sectional shape of the work. hand,
A plurality of thicknesses measured by the thickness measuring means and a plurality of in-plane positions obtained by the position calculating means for obtaining an in-plane position of the work whose thickness is measured by the thickness measuring means are respectively obtained,
The thickness at each in-plane position is converted to a thickness at each position in a predetermined radial direction of the work corresponding to a radial distance from the center of the work to each in-plane position, and the predetermined diameter is in obtaining the cross-sectional shape in the direction of the workpiece,
The predetermined radial direction is an X-axis direction set with the center of the work as an origin,
The conversion process is a process of converting the thickness at each position in one radial direction on the minus side or plus side of the X axis,
The one radial position is inverted to be symmetrical with respect to the origin and converted to the other radial position, and the one radial position corresponding to the other radial position. A process of converting the thickness of each position in the direction into the thickness of each position in the other radial direction,
A cross-sectional shape measuring method, wherein a cross-sectional shape of the work in the X-axis direction is obtained by these processes . A cross-sectional shape measuring method for measuring a thickness of a work to be polished by a rotatable surface plate by a thickness measuring means through a measurement hole provided in the surface plate to obtain a cross-sectional shape of the work. hand,
A plurality of thicknesses measured by the thickness measuring means and a plurality of in-plane positions obtained by the position calculating means for obtaining an in-plane position of the work whose thickness is measured by the thickness measuring means are respectively obtained,
The thickness at each in-plane position is converted to a thickness at each position in a predetermined radial direction of the work corresponding to a radial distance from the center of the work to each in-plane position, and the predetermined diameter is When determining the cross-sectional shape of the workpiece in the direction
The predetermined radial direction is an X-axis direction set with the center of the work as an origin,
The conversion process, based on the thickness of each in-plane position on the plus side in the X-axis direction and the radial distance of the in-plane positions, the thickness at each position on the plus side on the X-axis,
Based on the thickness and the radial distance of each in-plane position on the minus side in the X-axis direction among the in-plane positions, a process of converting into a thickness at each position on the minus side on the X-axis,
These processes, cross-sectional shape measuring how to and obtains the X-axis direction of the cross-sectional shape of the workpiece. A cross-sectional shape measuring method for measuring a thickness of a work to be polished by a rotatable surface plate by a thickness measuring means through a measurement hole provided in the surface plate to obtain a cross-sectional shape of the work. hand,
A plurality of thicknesses measured by the thickness measuring means and a plurality of in-plane positions obtained by the position calculating means for obtaining an in-plane position of the work whose thickness is measured by the thickness measuring means are respectively obtained,
The thickness at each in-plane position is converted to a thickness at each position in a predetermined radial direction of the work corresponding to a radial distance from the center of the work to each in-plane position, and the predetermined diameter is When determining the cross-sectional shape of the workpiece in the direction
The predetermined radial direction is an X-axis direction and a Y-axis direction set with the center of the work as an origin,
The conversion process is a process of converting the thickness at each position on the X axis based on the thickness and the radial distance of each in-plane position within a predetermined range around the X axis among the in-plane positions. A process of converting the in-plane position into a thickness at each position on the Y-axis based on a thickness and a radial distance of each in-plane position within a predetermined range around the Y-axis among the in-plane positions;
These processes, cross-sectional shape measuring how to and finding the X-axis direction of the cross-sectional shape of the workpiece and the Y-axis direction of the cross-sectional shape. A cross-sectional shape measuring method for measuring a thickness of a work to be polished by a rotatable surface plate by a thickness measuring means through a measurement hole provided in the surface plate to obtain a cross-sectional shape of the work. hand,
A plurality of thicknesses measured by the thickness measuring means and a plurality of in-plane positions obtained by the position calculating means for obtaining an in-plane position of the work whose thickness is measured by the thickness measuring means are respectively obtained,
The thickness at each in-plane position is converted to a thickness at each position in a predetermined radial direction of the work corresponding to a radial distance from the center of the work to each in-plane position, and the predetermined diameter is When determining the cross-sectional shape of the workpiece in the direction
The predetermined radial direction is an X-axis direction set with the center of the work as the origin, and passes through the origin and forms a predetermined angle with respect to the X-axis. One axis direction,
The conversion process is a process of converting the thickness at each position on the X axis based on the thickness and the radial distance of each in-plane position within a predetermined range around the X axis among the in-plane positions. Converting a thickness at each position on the first axis based on a thickness and a radial distance of each in-plane position within a predetermined range around the first axis among the in-plane positions; And
These processes, cross-sectional shape measuring how to and obtains the X-axis direction of the cross-sectional shape of the workpiece and said first axial sectional shape. A cross-sectional shape measuring method for measuring a thickness of a work to be polished by a rotatable surface plate by a thickness measuring means through a measurement hole provided in the surface plate to obtain a cross-sectional shape of the work. hand,
A plurality of thicknesses measured by the thickness measuring means and a plurality of in-plane positions obtained by the position calculating means for obtaining an in-plane position of the work whose thickness is measured by the thickness measuring means are respectively obtained,
The thickness at each in-plane position is converted to a thickness at each position in a predetermined radial direction of the work corresponding to a radial distance from the center of the work to each in-plane position, and the predetermined diameter is When determining the cross-sectional shape of the workpiece in the direction
Among the acquired thicknesses of the plurality of in-plane positions, when a difference between a maximum value and a minimum value of the thickness is a predetermined value or more, the center of the work is set as an origin, and the work is symmetric with respect to the origin. each position is inverted and a thickness of each position this inversion, wherein a cross sectional shape measured way to the determination of the workpiece cross section from a thickness of each position before inversion. Among the acquired thicknesses of the plurality of in-plane positions, when a difference between a maximum value and a minimum value of the thickness is a predetermined value or more, the center of the work is set as an origin, and the work is symmetric with respect to the origin. each position is inverted and a thickness of each position this inversion, according to any one of claims 1 to 4, characterized in that obtaining the inverted previous workpiece cross section from a thickness of each position Cross section shape measurement method.   The cross-sectional shape measuring method according to any one of claims 1 to 6, wherein the cross-sectional shape of the work is obtained by a polynomial approximation curve. A plurality of thicknesses measured by the thickness measuring means and a plurality of in-plane positions obtained by the position calculating means are obtained at predetermined time intervals,
The cross-sectional shape measuring method according to any one of claims 1 to 7, wherein a cross-sectional shape of the work is obtained every predetermined time.