JP2009130078A - Method and device of measuring thickness of soi layer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simply measure the thickness of an SOI layer with high accuracy when an SOI layer is formed by polishing an SOI wafer. <P>SOLUTION: After the SOI layers of a plurality of SOI wafers 10 stuck to the surface of a stick plate 21 by adhesive are polished, the stick plate 21 is dismounted from a polishing device and mounted on the X-Y stage 28 of a device for measuring the thickness of the SOI layers. A measuring beam in a predetermined wavelength region is then transmitted from a measuring light source through an optical fiber 29, and an SOI wafer 10 is irradiated with the measuring beam from an instrumentation head 30. Detection is performed over the wavelength region by a spectroscope with regard to optical interference information of reflected light 32a, i.e., the incident light 31 of a measuring beam reflected on the surface of the SOI layer, and reflected light 32b, i.e., the incident light 31 reflected on the boundary of the SOI layer and an insulating film. Thickness of the SOI layer is calculated from the optical interference information. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method and an apparatus for measuring the thickness of an SOI layer in an SOI (Silicon on Insulator) wafer having a bonded structure, and in particular, the thickness of the SOI layer can be easily measured with high accuracy in forming an SOI layer by polishing. The present invention also relates to a method and an apparatus for measuring the thickness of an SOI layer effective for controlling the polishing amount.

  Silicon wafers commonly referred to as SOI wafers are attracting attention as a substrate for semiconductor devices such as high-speed devices on which high-speed logic circuits including SRAM and high-voltage devices including power transistors are mounted. It has become to. As shown in FIG. 4, the SOI wafer 10 having a bonded structure has an SOI layer 13 which is an active layer of a silicon single crystal thin film formed on a support wafer 11 made of single crystal silicon via an insulating film 12. It has a structure. Then, in this SOI wafer manufacturing method, an active layer wafer is bonded and bonded to the support wafer 11 through, for example, a silicon oxide film formed by thermal oxidation, and the active layer wafer is thinned to form an SOI layer 13. There is a way to make it. Hereinafter, a wafer in which a support wafer and an active layer wafer are bonded and bonded via an insulating film, or a wafer in which the active layer wafer is an SOI layer are both referred to as SOI wafers.

  In the manufacturing process of the SOI wafer, the active layer wafer is formed into an SOI layer having an appropriate thickness suitable for the semiconductor device by a highly accurate processing method including a grinding process and a polishing process. Here, in the grinding process, a generally used processing method is used. For example, the active layer wafer is ground by rough grinding and precision grinding using a diamond grindstone to leave a predetermined polishing allowance. Finished.

  In the SOI wafer polishing step, the active layer wafer is polished and the thickness of the formed SOI layer is measured repeatedly in order to control the SOI layer 13 to a required thickness. Here, in the prior art, as shown in FIG. 5A, a plurality of SOI wafers 10 subjected to the above-mentioned grinding or the like are attached to one attaching plate 101 of the polishing apparatus with an adhesive such as an adhesive wax. The Here, an adhesive wax is spin-coated on the back surface of the support wafer 11 and fixed to the affixing plate 101. A plurality of SOI wafers 10 attached to one attachment plate 101 are simultaneously polished.

  Here, the polishing surface plate 103 to which the polishing cloth 102 is attached is brought into contact with the surface of the active layer wafer of the SOI wafer 10, and further, the polishing surface plate 103 is pressurized and rotated to act as described above by the action of the abrasive (slurry). The surface of the active layer wafer having the polishing allowance is polished. In this case, the polishing amount on the wafer surface is controlled by the polishing time. In this control method based on the polishing time, first, the polishing rate is measured in advance, the polishing time is estimated based on the polishing rate, and all the SOI wafers 10 are polished. In addition, in the estimation of the polishing time, the temporal change in the polishing rate due to the change with time of the polishing cloth and the slurry is taken into consideration.

  Then, the rotation of the polishing platen is stopped at the polishing time when the SOI layer 13 has a required thickness, and all the SOI wafers 10 are peeled off from the pasting plate 101. Next, as shown in FIG. 5B, the thickness of the SOI layer 13 is measured for each of the peeled SOI wafers 10.

  In the measurement of the thickness of the SOI layer 13, for example, an optical interference type film thickness measuring device such as NanoSpec (trade name) manufactured by Nanometric Co., Ltd. is used, and one SOI wafer 10 is placed on the sample stage 104 of the measuring device. The focal length of the microscopic head 105 movable up and down is adjusted. Then, visible light, for example, is transmitted from a measurement light source (not shown) of the measurement apparatus, and the SOI wafer 10 is irradiated from the microscopic head 105 of the measurement apparatus. Optical interference information by the reflected light from the surface of the SOI layer 13 and the surface of the insulating film 12 of the measurement light incident on the SOI wafer 10 is detected through a spectrometer. Then, the thickness of the SOI layer 13 is calculated from this optical interference information. In this case, since there is light absorption in the SOI layer 13, for example, the thickness is preferably 10 μm or less.

  As a method for measuring the thickness of the SOI layer 13 by spectral interference using the above-mentioned spectroscope, a Fourier transform infrared spectrophotometer is used in addition to the method of measuring a visible light spectrum using a dispersive spectroscope as described above. There is a method of analyzing an infrared spectral spectrum by (FTIR) (for example, see Patent Document 1). This method facilitates highly accurate thickness measurement even when the SOI layer 13 exceeds 10 μm.

  When the thickness of the SOI layer falls within an allowable range, the SOI wafer 10 is finished in the polishing process and sent to the next process such as a bevel process. On the other hand, the SOI wafer 10 whose thickness of the SOI layer deviates from the allowable range is pasted again to the pasting plate 101 with adhesive wax, and additional polishing processing is performed on the SOI layer 13. Here, among the SOI wafers 10 that have been subjected to the polishing process with a plurality of application plates, a wafer having a close SOI layer 13 thickness is newly attached to one application plate to perform additional polishing.

  Thus, in the polishing process of batch processing of a plurality of sheets, if excessive polishing is performed, the SOI wafer becomes unusable. Therefore, the polishing process and the SOI layer 13 are performed until the SOI layer 13 has a required thickness. The thickness measurement is repeated.

  However, in the polishing process of the SOI wafer using the SOI layer thickness measurement method, the manufacturing cost can be reduced by the batch processing. In the polishing process and the thickness measurement, the SOI plate is bonded to the affixing plate. Wafer stripping and pasting must be repeated. For this reason, the improvement in workability and productivity of the polishing process has been limited. In addition, the repeated peeling and sticking of the SOI wafer easily causes mechanical damage such as scratches and scratches on the surface of the SOI layer, or trace damage such as adsorption marks on the back surface of the SOI wafer in the thickness measurement. It was a factor to reduce the yield.

On the other hand, a polishing method and a polishing apparatus for monitoring the thickness of an SOI layer in a so-called in-line, in which a film thickness is measured while polishing an SOI wafer (see, for example, Patent Documents 2 and 3). However, these polishing methods are all single-wafer processing methods, and although the thickness control of the SOI layer is highly accurate, it is difficult to reduce the manufacturing cost compared to the batch processing.
Japanese Patent Laid-Open No. 5-308096 JP-A-8-216061 JP 2005-19920 A

  The present invention has been made in view of the above circumstances, and in the polishing process of batch-processed SOI wafers, the thickness of the SOI layer is set in a state where the SOI wafer is adhered to the affixing plate with an adhesive such as adhesive wax. An object of the present invention is to provide an SOI layer thickness measuring method and measuring apparatus which can be easily measured with high accuracy and are effective in controlling the polishing amount of the SOI layer.

  In order to achieve the above object, a method for measuring the thickness of an SOI layer according to a first aspect of the present invention includes bonding a support wafer and an active layer wafer through an insulating film, and bonding the active layer wafer to the active layer wafer. A method for measuring the thickness of the SOI layer in manufacturing an SOI wafer having an SOI layer having a required thickness, wherein a plurality of SOI wafers are pasted from the back surface of the support wafer to the pasting plate surface with an adhesive, After the surface of the wafer for active layer of the SOI wafer is brought into sliding contact with the surface of the polishing surface plate to which the polishing cloth is pasted, and the surface of the wafer for active layer of the plurality of SOI wafers is polished by the action of the abrasive, the pasting plate Each of the SOI wafers in a state where the plurality of SOI wafers are pasted on the pasting plate. It has a thickness of the optically measured, that the structure.

  The SOI layer thickness measuring apparatus according to the second aspect of the invention is a method in which a support wafer and an active layer wafer are bonded and bonded via an insulating film, and the active layer wafer is bonded to an SOI having a required thickness. An apparatus for measuring the thickness of the SOI layer in manufacturing an SOI wafer to be layered, wherein a plurality of SOI wafers are adhered from the back surface of the support wafer by an adhesive, and the activity of the plurality of SOI wafers A wafer for layering is polished to form the SOI layer, and the measurement stage is placed with the SOI layer facing upward. The measuring stage is disposed above the affixing plate, and the measurement light is applied to the SOI layers of the plurality of SOI wafers. And a measurement head that receives reflected or transmitted light of the measurement light from the SOI layer, a measurement light source that emits the measurement light, and the measurement light A first optical fiber that transmits measurement light emitted from a light source to a measuring head; a spectroscope that divides the reflected light or transmitted light to measure intensity; and the reflected light or transmitted light from the measuring head to the spectrometer. And a second optical fiber that transmits light.

  With the configuration of the present invention, in the polishing process of batch-process SOI wafers, the thickness of the SOI layer can be easily measured with high accuracy in a state where the SOI wafer is attached to the application plate with an adhesive such as an adhesive wax. The polishing amount of the SOI layer can be controlled effectively. And in SOI wafer manufacture, low manufacturing cost and high productivity are ensured easily. In addition, damage such as scratches and scratches in the SOI layer in the polishing process is reduced, and the yield of SOI wafer products is improved.

  A preferred embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a side view of a polishing head portion of an SOI wafer polishing apparatus for explaining the polishing process in this embodiment. FIG. 2 is a side view showing a method for measuring the thickness of the SOI layer according to this embodiment, and FIG. 3 is a schematic configuration diagram showing an example of a thickness measuring apparatus for the SOI layer according to this embodiment. In the drawings, the same or similar parts are denoted by the same reference numerals, and a part of the overlapping description is omitted.

  For example, an SOI wafer in which a support wafer made of a silicon wafer having a diameter of 5 inches and a thickness of 600 to 800 μm and an active layer wafer made of a similar silicon wafer are bonded and bonded through a silicon oxide film having a thickness of about 1 μm. Prepare a large number of sheets. Then, in the pre-process of polishing, the outer peripheral grinding of these SOI wafers is performed, and the active layer wafer is further subjected to surface grinding to leave a predetermined polishing margin and thin the film as described above.

  Then, as shown in FIG. 1, the SOI wafer 10 is stuck to one sticking plate 21 of the polishing apparatus with an adhesive such as an adhesive wax. Here, as described in the prior art, the SOI wafer 10 is fixed to the affixing plate by an adhesive such as an adhesive wax spin-coated on the back surface of the support wafer 11.

  The affixing plate 21 is made of, for example, an alumina plate having a diameter of 300 mm, and is detachably attached to the upper surface of the support head 22 of the polishing apparatus, for example, with bolts. The polishing surface plate 23 of the polishing apparatus has a polishing cloth 24 attached to the lower surface thereof, and is disposed opposite to the attachment plate 21 so that it can be moved up and down 26 and rotated 27 by the polishing surface plate driving unit 25. . Here, the direction of the rotation 27 may be either forward or reverse.

  In the polishing process of the SOI wafer 10, the polishing surface plate 23 is moved down to a predetermined position by the polishing surface plate driving unit 25, and the polishing layer 24 is used to move the surface of the active layer wafer that becomes the SOI layer 13 of all the SOI wafers 10. Further, the polishing platen 23 is pressed and rotated. Then, the surface of the active layer wafer having the above-described polishing allowance is polished by the slurry action impregnating the polishing pad 24 to form the SOI layer 13 having a required thickness, for example, about 10 μm.

  In this polishing process, as described in the prior art, the polishing amount on the surface of the active layer wafer is controlled by a predetermined polishing time, and the polishing time during which the active layer wafer becomes the SOI layer 13 having the required thickness. Stop the polishing platen and stop the polishing process.

  Then, the affixing plate 21 is detached from the support head 22, and the thickness measurement of the SOI layer 13 of all the SOI wafers 10 affixed to the affixing plate 21 surface is performed on the affixing plate 21. The thickness measurement of the SOI layer 13 in this pasting state will be described with reference to FIG.

  As shown in FIG. 2, the thickness of the SOI layer 13 according to the present embodiment is measured by, for example, mounting the detached attaching plate 21 almost horizontally on a stainless steel XY stage 28 that is movable in a wide range in the horizontal direction. Put. Then, the XY stage 28 is moved freely in the X direction or the Y direction, and the thickness measurement of the SOI layers 13 of all the SOI wafers 10 that are attached to the attaching plate 21 is performed.

  In this thickness measurement, measurement light in a predetermined wavelength region is transmitted from a measurement light source of the measurement device via, for example, an optical fiber 29 and irradiated to the SOI wafer 10 from the measurement head 30. Here, the optical interference information between the reflected light 32a in which the incident light 31 of the measurement light is reflected from the surface of the SOI layer 13 and the reflected light 32b in which the incident light 31 is reflected from the interface region between the SOI layer 13 and the insulating film 12 is described above. Detect through a spectrometer over wavelength range. Then, the thickness of the SOI layer 13 is calculated from this optical interference information.

In the method of measuring the thickness of the SOI layer 13 by the spectral interference method, for example, a measurement light in a predetermined wavelength region is used using a dispersion spectrometer. As shown in FIG. 4, when the interference light of the reflected light 32a and the reflected light 32b with respect to the incident light 21 having the wavelength λ in the wavelength region is measured, for example, the wavelengths λ _m and λ _{m + 1} satisfying the following equations are used. In this case, the intensity of the interference light is maximized.

2tn = mλ _m (1)
2tn = (m + 1) λ _{m + 1} (2)

From equations (1) and (2)
t = 1 / (2n) × [(1 / λ _{m + 1} ) − (1 / λ _m )] ⁻¹
_{= 1 / (2n) × (} k m + 1 -k m) -1 = 1 / (2nΔk) ··· (3)
Here, t is the thickness of the SOI layer 13, n is the refractive index of Si, m is a positive integer, k is the wave number of light, and Δk is the wave number interval at which the interference light becomes maximum.

  Therefore, for example, the thickness of the SOI layer 13 can be calculated based on the above equation (3) in the optical interference information.

  Here, the wavelength region of the measurement light is appropriately determined depending on the thickness of the SOI layer 13. The light transmittance due to Si increases as the wavelength λ becomes longer, and becomes extremely large when, for example, 800 nm or more. On the other hand, the measurement accuracy of the thickness of the SOI layer 13 is usually improved as the wavelength λ becomes shorter. In general, light interference can be clearly detected when the transmittance is 10% or more. For these reasons, for example, when the required thickness of the SOI layer 13 is about 10 μm or less, the measurement light is visible light or near infrared light, and when the thickness exceeds 10 μm, the measurement light is Is preferably in the wavelength region of infrared light of 800 nm to 1.9 μm. In this way, the accuracy of measuring the thickness of the SOI layer can be ± 5% or less of the required thickness of the SOI layer.

  In addition, in the measurement of the thickness of the SOI layer 13 by the spectral interference method, in addition to the method of measuring the visible light spectrum using the above-described dispersion spectrometer, the infrared spectral spectrum is measured by a Fourier transform infrared spectrophotometer. It may be a method of analyzing.

  In the measurement of the thickness of the SOI layer 13 of the present embodiment, since the XY stage 28 can move in a wide range horizontally, the thickness of the SOI layer 13 of all the SOI wafers 10 on the pasting plate 21 is quickly measured. . In the above embodiment, the same effect can be obtained even if the measurement head 30 scans in the XY direction. When this measuring head 30 is scanned, it is possible to measure a wide range of SOI wafers 10 as compared with the case where the XY stage 28 is used, and the area of the affixing plate 21 can be increased and the size can be increased.

  Further, the thickness of the SOI layer 13 is maintained while the plurality of SOI wafers 10 are stuck on the surface of the sticking plate 21 without peeling the SOI wafer 10 from the sticking plate 21 as in the case of the prior art. Therefore, the workability of thickness measurement is greatly improved.

  As described above, the affixing plate 21 detachably attached to the polishing apparatus can be used both as a polishing head for polishing an SOI wafer and a measurement stage for measuring the thickness of the SOI layer. Other materials that can be used for such affixing plate 21 include ceramics such as aluminum nitride, yttrium, zirconia, and yttrium aluminum garnet.

  In the polishing process of the SOI wafer, the SOI wafer 10 in which the thickness of the SOI layer 13 is within the allowable range is peeled off from the sticking plate 21 and sent to the next process such as bevel processing, for example. .

  On the other hand, the SOI wafer 10 in which the thickness of the SOI layer 13 deviates from the allowable range is left stuck on the sticking plate 21 and is subjected to an additional polishing process on the SOI layer 13. And the SOI layer thickness measurement of the sticking state is performed with the thickness measurement method of the SOI layer mentioned above. Further, it is determined whether the thickness of the SOI layer 13 is within an allowable range, and the above-described polishing process and thickness measurement are repeated until the thickness of the SOI layer 13 is within the allowable range.

  Next, an example of the SOI layer thickness measuring apparatus according to the present embodiment will be described with reference to FIG. The measurement apparatus includes, for example, a measurement light source 33, a beam splitter 34, a multi-branch optical fiber 35 for light projection, a multi-measurement head 36, a multi-branch optical fiber 37 for light reception, a measurement switch 38, a spectroscope 39, and a personal computer (PC). ) 40 is provided. Here, the measurement light source 33 and the beam splitter 34 are coupled by a light projecting fiber 41, and the measurement switch 38 and the spectroscope 39 are coupled by a light receiving fiber 42, respectively.

  As the measurement light source 33, for example, a light source lamp such as a halogen lamp, a heating bulb, a xenon lamp, or a photodiode array is used. Here, as described in the thickness measurement method, an optical filter may be inserted between the measurement light source 33 and the light projecting fiber 41 so that a predetermined wavelength region is extracted. The measurement light source 33 may emit laser light.

  As described above, when the required thickness of the SOI layer 13 is about 10 μm or less, the wavelength of the measurement light is changed from visible light of, for example, 500 to 900 nm to near infrared light. In this wavelength region, the transmittance with water is approximately 100%, and even if water remains on the SOI layer 13, there is no problem in measuring the thickness of the SOI layer. In addition, when the wavelength of the measurement light exceeds 900 nm, the transmittance in water changes depending on the wavelength. Therefore, when the thickness of the SOI layer 13 exceeds 10 μm, the measurement light has a red color of 800 nm to 1.9 μm. A wavelength band in which the transmittance is relatively high in the wavelength range of external light may be selected.

  The beam splitter 34 is composed of an optical element such as a half mirror array, for example, and branches the measurement light transmitted from the measurement light source 33 via the light projecting fiber 41 into a large number (five in FIG. 3). A multi-branched optical fiber 35 is coupled. The light projecting multi-branch optical fiber 35 and the light projecting fiber 41 constitute a first optical fiber.

  The multi-measurement head 36 is composed of a plurality (five in FIG. 3) of measurement heads. Here, each measurement head irradiates the measurement light transmitted from each optical fiber of the branching optical fiber 35 for projection toward the surface of the SOI layer 13 of the SOI wafer 10. Further, as described above, it has a function of receiving reflected light from the SOI layer 13. The reflected light from the SOI layer 13 received from the multi-measuring head 36 is sent to the measurement switching unit 38 through the multi-branch optical fiber 37 for light reception. The light projecting branch optical fiber 35 and the light receiving multi-branch optical fiber 37 are configured by so-called bundle-type fibers and are connected to the multi-measurement head 36.

  The measurement switching unit 38 is composed of an optical element including an optical switch or the like, switches the reflected light transmitted through the multi-branch optical fiber 37 for receiving light, and transmits the reflected light to the spectroscope 39 through the light receiving fiber 42. It is supposed to be. The light receiving multi-branch optical fiber 37 and the light receiving fiber 42 constitute a second optical fiber.

  The spectroscope 39 includes a diffraction grating that performs wavelength spectroscopy and a light receiving sensor such as a CCD array. The reflected light from the SOI layer 13 transmitted through the light receiving fiber 42 is spectrally separated for each wavelength by the diffraction grating, and is collectively received by the CCD array as optical interference information for each wavelength. It has a configuration. The spectroscope 39 acquires the light interference information from the multi-measurement head 36 at a high speed by the switching operation of the measurement switching unit 38.

  The PC 40 calculates the thickness of the SOI layer 13, maps the thickness of the SOI layer on the SOI wafer 10, analyzes the distribution thereof based on the optical interference information acquired by the spectroscope 39, and the like. The result of is output. Further, the PC 40 performs all drive control of the measuring apparatus including, for example, the switching operation of the measurement switching unit 38 and the scanning of the XY stage 28. For example, the thickness of the SOI layer 13 is measured in accordance with input information to the PC 40 such as measurement points on the SOI wafer in mapping measurement.

  In the measurement apparatus, the structure having the multi-branch optical fiber, the multi-measurement head, etc. has been described so that the thickness mapping measurement of the SOI layer 13 can be performed at high speed. However, the structure having the measurement head 30 as described in FIG. It doesn't matter.

  Similarly to the method for measuring the thickness of the SOI layer, in the measurement apparatus, the XY stage 28 may be fixed and the multi-measurement head 36 may scan in the XY direction. Absent.

  In the above embodiment, in the polishing process of the active layer wafer by batch processing of SOI wafers, the affixing plate is also used as a polishing head for polishing the SOI wafer and a measurement stage for measuring the thickness of the SOI layer. Then, the thickness of the SOI layer is measured by an optical interference method while the SOI wafer is stuck on the sticking plate detached after the polishing process. This method for measuring the thickness of the SOI layer does not repeat the peeling and sticking of the SOI wafer to the sticking plate as in the prior art, greatly improving the workability and productivity in the polishing process of the SOI wafer, This is extremely effective in controlling the polishing amount of the SOI layer.

  In addition, mechanical damage such as scratches and scratches in the SOI layer, which has occurred in the prior art, or trace damage such as adsorption traces on the back surface of the SOI wafer in thickness measurement is eliminated, and the yield of SOI wafer products is improved.

  The SOI layer thickness measuring apparatus of the present embodiment can perform the mapping measurement of the thickness of the SOI layer 13 at high speed and with high accuracy, and does not require focusing between the measurement head and the SOI layer. Furthermore, even if moisture remains on the surface of the SOI layer, there is no hindrance in the measurement, and the thickness can be measured very simply. For these reasons, workability in measuring the thickness of the SOI layer is greatly improved.

  Although the preferred embodiments of the present invention have been described above, the above-described embodiments do not limit the present invention. Those skilled in the art can make various modifications and changes in specific embodiments without departing from the technical idea and technical scope of the present invention.

It is a side view of the polish head part of the SOI wafer polish device for using for explanation of polish processing in the embodiment of the present invention. It is a side view which shows the thickness measuring method of the SOI layer concerning this embodiment of this invention. It is a schematic block diagram which shows an example of the thickness measuring apparatus of the SOI layer concerning this embodiment of this invention. It is sectional drawing which shows a common SOI wafer. It is explanatory drawing for using for description of grinding | polishing processing in a prior art, (a) is a side view of the grinding | polishing head part in grinding | polishing processing of an SOI wafer, (b) is a measuring part in thickness measurement of the SOI layer of an SOI wafer. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 SOI wafer 11 Wafer for support body 12 Insulating film 13 SOI layer 21 Adhering plate 22 Support head 23 Polishing surface plate 24 Polishing cloth 25 Polishing surface plate drive part 26 Vertical movement 27 Rotation 28 XY stage 29 Optical fiber 30 Measuring head 31 Incident Light 32a Reflected light from the SOI layer surface 32b Reflected light from the insulating film surface 33 Measuring light source 34 Beam splitter 35 Multi-branched optical fiber for light projection 36 Multi-measuring head 37 Multi-branched optical fiber for light-receiving 38 Measurement switcher 39 Spectroscope 40 Personal computer 41 Light emitting fiber 42 Light receiving fiber

Claims (4)

This is a method for measuring the thickness of the SOI layer in manufacturing an SOI wafer, in which a support wafer and an active layer wafer are bonded and bonded together via an insulating film to make the active layer wafer an SOI layer having a required thickness. And
A plurality of SOI wafers are pasted from the back surface of the support wafer to the affixing plate surface with an adhesive, and the active layer wafer surfaces of the plurality of SOI wafers are brought into sliding contact with a polishing surface plate surface to which a polishing cloth is adhered, and polished. After polishing the active layer wafer surface of the plurality of SOI wafers by the action of the agent,
An SOI layer characterized in that the thickness of each SOI layer is optically measured in a state where the affixing plate is detached from a polishing apparatus that holds the affixing plate, and the plurality of SOI wafers are affixed to the affixing plate. Thickness measurement method.   2. The SOI layer according to claim 1, wherein in the measurement of the optical thickness of the SOI layer, the intensity of reflected light or transmitted light of measurement light irradiated on the SOI layer from a measurement light source is measured. Thickness measurement method. An apparatus for measuring the thickness of an SOI layer in manufacturing an SOI wafer, in which a wafer for a support and an wafer for an active layer are bonded to each other through an insulating film to make the wafer for an active layer an SOI layer having a required thickness. And
A bonding plate in which a plurality of SOI wafers are bonded from the back surface of the support wafer by an adhesive is used to polish the active layer wafer of the plurality of SOI wafers to form the SOI layer, and then the SOI layer is placed upward. A measurement stage placed on the
A measurement head that is disposed above the affixing plate and irradiates the SOI layer of the plurality of SOI wafers with measurement light and receives reflected or transmitted light of the measurement light from the SOI layer;
A measurement light source for emitting the measurement light;
A first optical fiber for transmitting the measurement light emitted from the measurement light source to the measuring head;
A spectroscope for spectrally measuring the reflected light or transmitted light and measuring the intensity;
A second optical fiber for transmitting the reflected light or transmitted light from the measuring head to the spectrometer;
An SOI layer thickness measuring apparatus comprising: 4. The SOI layer thickness measuring apparatus according to claim 3, wherein the thickness of the SOI layer is calculated from optical interference information in the reflected light or transmitted light.

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