JP2009130077A - Method of manufacturing soi wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the production cost in a process for polishing an SOI wafer while enhancing the productivity. <P>SOLUTION: An SOI layer is polished and the thickness thereof is adjusted and controlled by repeating step S1 for sticking a plurality of SOI wafers to one stick plate, step S2 for polishing all SOI wafers, step S3 for measuring the thickness of the SOI layer under a state where the SOI layers are stuck to the stick plate, and step S4 for determining whether the thickness of the SOI layer falls within an allowable range. Only such an SOI wafer as falling within the allowable range is stripped from the stick plate and sent to a step following the polish step. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an SOI (Silicon on Insulator) wafer having a bonded structure, and more particularly to a method for manufacturing an SOI wafer that is low in cost and excellent in productivity.

  An SOI wafer with a bonded structure manufactured by bonding and bonding an active layer wafer to a support wafer made of single crystal silicon via an insulating film such as a silicon oxide film is a manufacturing method for high performance semiconductor devices. In particular, the semiconductor substrate has been attracting attention as a suitable semiconductor substrate. Various manufacturing methods have been studied as substrate materials for high-speed devices on which high-speed logic circuits including SRAM, for example, or high-voltage devices including power transistors are mounted.

  In the manufacturing process of the SOI wafer, the active layer wafer is converted into an active layer having an appropriate thickness (hereinafter also referred to as an SOI layer) suitable for the semiconductor device by a high-precision processing method including grinding and polishing. . Here, the grinding process is a generally used method. For example, the active layer wafer is ground by rough grinding and precision grinding using a diamond grindstone to a thickness that leaves a predetermined polishing allowance. Finish.

  In the polishing process, for example, the thickness control of the SOI layer is performed with high accuracy according to the flow chart of the process as shown in FIG. FIG. 4 is a process flow chart showing a polishing process of batch processing in which, for example, grinding is performed as a pre-process. First, in the process of step S10 in FIG. 4, the plurality of SOI wafers that have been subjected to the above-described grinding or the like are attached to one attaching plate of the polishing apparatus with an adhesive such as an adhesive wax. Here, the back surface of the support wafer is fixed to the pasting plate via an adhesive wax spin-coated on the back surface.

  Next, in the process of step S11, polishing of all the SOI wafers attached to one attachment plate is performed. Here, the polishing surface plate to which the polishing cloth is affixed is brought into contact with the active layer wafer surface of all the SOI wafers, and further, the polishing surface plate is pressurized and rotated, and the above-described polishing is performed by the action of the abrasive (slurry). The surface of the active layer wafer 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 SOI wafers 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.

  Next, the rotation of the polishing platen is stopped at the polishing time when the SOI layer has a required thickness. Then, in the step S12, all the SOI wafers are peeled from the pasting plate, and in the subsequent step S13, the thickness of the SOI layer of all the peeled SOI wafers is measured. Then, in the determination process of step S14, the SOI wafer in which the thickness of the SOI layer falls within the allowable range and becomes YES is sent to the next process such as bevel processing.

  On the other hand, the SOI wafer in which the thickness of the SOI layer deviates from the allowable range (usually thicker than the allowable range) and is NO is adhered to the application plate again with an adhesive wax in the process of step S15. An additional polishing process is applied to the SOI layer. Here, among the SOI wafers polished with a plurality of application plates, a wafer having a near SOI layer thickness is newly attached to one application plate to perform additional polishing.

  Then, after additional polishing for a predetermined time, the entire SOI wafer is peeled off from the affixing plate in the step S17, the thicknesses of all SOI layers in the step S18 are measured, and the SOI layer in the step S19 is measured. Judge whether the thickness is within the allowable range. Here, the SOI wafer for which the determination is YES is sent to the next process, the SOI wafer for which the determination is NO is returned to step S15, and the above-described process is repeated until the thickness of the SOI layer falls within an allowable range.

  As described above, in the polishing process of batch processing, if excessive polishing is performed, the SOI wafer becomes unusable. Therefore, the adjustment polishing and the film thickness measurement are repeated until the active layer has a required thickness. It will be necessary.

  However, in the conventional SOI wafer polishing process, the manufacturing cost can be reduced by the batch processing. However, in the above-described adjustment polishing and film thickness measurement, the SOI wafer must be repeatedly peeled off and pasted to the pasting plate. Don't be. For this reason, the improvement in workability and productivity of the polishing process has been limited. In addition, repeated peeling and sticking of SOI wafers can easily cause mechanical damage such as scratches and scratches in the SOI layer, or trace damage such as suction marks on the back side of the SOI wafer in thickness measurement, and can increase the yield of SOI wafer products. It was a factor to reduce.

On the other hand, a polishing method and an apparatus for monitoring the thickness of the SOI layer in a so-called in-line, in which the film thickness is measured during polishing of the SOI wafer, are disclosed (for example, refer to Patent Documents 1 and 2). However, any of these polishing methods is a single wafer processing method, 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.
JP-A-8-216061 JP 2005-19920 A

  The present invention has been made in view of the above-described circumstances. In the polishing process for manufacturing an SOI wafer having a bonded structure, the batch processing of the SOI wafer is possible, and the SOI wafer is repeatedly peeled and bonded to the bonding plate. An object of the present invention is to provide a method for manufacturing an SOI wafer that is low in cost and excellent in productivity.

  In order to achieve the above object, a method for producing an SOI wafer according to the present invention includes bonding a support wafer and an active layer wafer through an insulating film, and bonding the active layer wafer to a predetermined thickness. In the method of manufacturing an SOI wafer to be an SOI layer, a step of attaching a plurality of SOI wafers to the surface of one affixing plate from the back surface of the support wafer with an adhesive, and the wafer for active layers of the plurality of SOI wafers The surface is brought into sliding contact with the surface of the polishing surface plate to which the polishing cloth is attached, and the surface of the active layer wafer surface of the plurality of SOI wafers is polished by the action of an abrasive, and the attachment is performed from a polishing apparatus that holds the attachment plate. Removing the plate and optically measuring the thickness of the SOI layer in a state where the SOI wafer is attached to the application plate; It has the adjusted to control the thickness of the SOI layer by an optical measuring thickness of the polishing and the SOI layer of the active layer wafer surface, has a structure.

  In a preferred aspect of the invention, the affixing plate is an alumina plate. In the measurement of the optical thickness of the SOI layer, the intensity of reflected light or transmitted light of the measurement light irradiated from the measurement light source to the SOI layer is measured.

  The configuration of the present invention enables batch processing of SOI wafers in the polishing process for manufacturing an SOI wafer having a bonded structure, and is excellent in productivity at low cost without repeating peeling and sticking of the SOI wafer to the bonding plate. Further, it is easy to manufacture SOI wafers. In addition, since the damage such as scratches and scratches on the SOI layer in the polishing process is reduced, the yield of SOI wafer products is improved.

  Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a flowchart of a polishing process showing a method for manufacturing an SOI wafer according to the present embodiment. FIG. 2 is a side view showing the polishing process of the SOI wafer for explaining the polishing process in the present embodiment, and FIG. 3 is for explaining the optical measurement of the SOI layer thickness in the present embodiment. It is a schematic block diagram which shows a film thickness measurement system.

  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 together via a silicon oxide film having a thickness of about 1 μm. Prepare a large number of sheets. Then, in the pre-process, the outer peripheral grinding of these SOI wafers is performed, and the active layer wafer is subjected to surface grinding to leave a predetermined polishing margin as described above and reduce the thickness to, for example, 15 to 20 μm.

  Then, as shown in FIG. 1, in the subsequent step S1 of the polishing process, a plurality of SOI wafers having the above polishing allowance are bonded to one bonding plate of the polishing apparatus with an adhesive such as an adhesive wax. Here, as explained in the prior art, the back surface of the support wafer is fixed to the affixing plate via the adhesive wax spin-coated on the back surface of the support wafer.

  Next, in the process of step S2, polishing of all SOI wafers attached to one attachment plate is performed.

  This polishing process will be described with reference to FIG. As shown in FIG. 2, for example, an affixing plate 11 made of an alumina plate with a diameter of 300 mmφ has a plurality of SOI wafers 12 affixed to the upper surface with an adhesive such as an adhesive wax, and a bolt or the like is placed on the support head 13 of the polishing apparatus. Can be attached detachably. The polishing surface plate 14 of the polishing apparatus has a polishing cloth 15 attached to the lower surface thereof, and is disposed opposite to the attachment plate 11 so that the polishing platen drive unit 16 can move up and down 17 and rotate 18. . The SOI wafer 12 has a bonded structure of the active layer wafer 12a, the insulating film 12b, and the support wafer 12c, which have been surface-ground. Here, the direction of the rotation 18 may be either forward or reverse.

  In the polishing process of the SOI wafer 12, the polishing surface plate drive unit 16 lowers the polishing surface plate 14 to a predetermined position so that the polishing cloth 15 is in sliding contact with the surfaces of the active layer wafers 12a of all the SOI wafers 12. Apply pressure and rotation to the platen. Then, the surface of the active layer wafer 12a having the above-described polishing allowance is polished by a slurry action impregnating the polishing pad 15 to obtain an SOI layer having a required thickness, eg, about 10 μm.

  In this polishing process, the amount of polishing of the surface of the active layer wafer 12a is controlled by a predetermined polishing time, as described in the prior art. Here, the polishing time is estimated based on the polishing rate measured in advance, and all the SOI wafers 12 are polished. In the estimation of the polishing time, the temporal change of the polishing rate due to the temporal change of the polishing pad 15 and the slurry is taken into consideration. Then, the rotation of the polishing platen is stopped at the polishing time when the active layer wafer 12a becomes the SOI layer having the required thickness, and the polishing process is stopped.

  Next, the affixing plate 11 is detached from the support head 13, and in the process of step S3, the thickness measurement of the SOI layers of all the SOI wafers 12 affixed to the upper surface of the affixing plate 11 is performed in the affixed state. The measurement of the SOI layer thickness in this pasting state will be described with reference to FIG.

  In the step of measuring the SOI layer thickness in the affixed state in step S3, the detached affixing plate 11 is placed almost horizontally on, for example, a stainless steel XY stage 19 of the SOI layer thickness measuring device. Then, for example, measurement light of infrared white light is transmitted from the measurement light source 20 of the measurement apparatus via the half mirror 21 and the optical fiber 22 and is irradiated to the SOI wafer 12 from the measurement head 23 fixed to the measurement apparatus. The light intensity of the measurement light incident on the SOI wafer 12 is analyzed through the spectroscope 24 via the optical fiber 22 and the half mirror 21 for the reflected light or transmitted light of the SOI surface, the insulating film 12b or the attaching plate 11. Here, the spectroscope 24 includes a diffraction grating for performing wavelength spectroscopy and a light receiving sensor such as a CCD array. The infrared white light is suitable as measurement light that is sufficiently transmitted because the light absorption coefficient of the SOI wafer 12 made of silicon is small.

  Here, when the required thickness of the SOI layer is as thin as 5 μm or less, for example, even if the measurement light is visible light, it can be used because it passes through at least the thin SOI layer and the insulating film 12b. In the light intensity analysis, for example, the thickness of the SOI layer is calculated by a well-known optical interference method.

  In the measurement of the thickness of the SOI layer, since the XY stage 19 can move in a wide range horizontally, the thickness of the SOI layer of all the SOI wafers 12 on the attaching plate 11 is measured quickly.

  As described above, the affixing plate 11 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 an affixing plate include ceramics such as aluminum nitride, yttrium, zirconia, and yttrium aluminum garnet.

  Then, in the determination process of step S4, the SOI wafer whose SOI layer thickness is within the allowable range and becomes YES is peeled off from the affixing plate 11 in the process of step S5, for example, bevel processing or the like. To the next process. In this case, a new ground SOI wafer may be pasted on the pasting plate 11 from which the SOI wafer 12 has been peeled off.

  On the other hand, the SOI wafer in which the thickness of the SOI layer deviates from the allowable range and becomes NO is left stuck on the sticking plate 11, and an additional polishing process is performed on these SOI layers in the step S6. . Next, in the step S7, the SOI layer thickness in the pasted state is measured in exactly the same manner as described in step S3. Then, in the process of step S8, it is determined whether the thickness of the SOI layer is within an allowable range, and the SOI wafer in which the determination is YES is peeled off from the sticking plate 11 in the process of step S9. And send it to the next process. Here, the SOI wafer for which the determination is NO is returned to step S6, and the above-described steps are repeated until the thickness of the SOI layer falls within the allowable range.

  In the above embodiment, in the polishing process of the active layer wafer by batch processing of SOI wafers, the affixing plate becomes a polishing head for polishing processing of the SOI wafer and becomes a measurement stage for measuring the thickness of the SOI layer. Then, after the polishing process, the thickness of the SOI layer is measured with the SOI wafer attached to a detachable attaching plate. For this reason, unlike the conventional technique, the peeling and sticking of the SOI wafer to the sticking plate is not repeated, and the workability and productivity in the processing process of the SOI wafer are greatly improved. In addition, since it is a batch process, it is easy to reduce manufacturing costs. 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.

  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.

  In the polishing step of the above embodiment, as shown in FIG. 2, the case of polishing using a polishing apparatus in which the affixing plate 11 is on the lower side and the polishing platen 14 is disposed on the upper side is described. The polishing process may be performed using a polishing apparatus in which the polishing surface plate 14 is on the lower side and the sticking plate 11 is disposed on the upper side.

It is a flowchart of the grinding | polishing process which shows the manufacturing method of the SOI wafer concerning embodiment of this invention. It is a side view which shows the grinding | polishing process of a SOI wafer in order to use for description of the grinding | polishing process in embodiment of this invention. It is a schematic block diagram which shows a film thickness measurement system in order to use for description of the optical measurement of SOI layer thickness in embodiment of this invention. It is a flowchart of the grinding | polishing process which shows the manufacturing method of the SOI wafer in a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Adhesion plate 12 SOI wafer 12a Active layer wafer 12b Insulating film 12c Support body wafer 13 Support head 14 Polishing surface plate 15 Polishing cloth 16 Polishing surface plate drive part 17 Vertical movement 18 Rotation 19 XY stage 20 Measurement light source 21 Half Mirror 22 Optical fiber 23 Measuring head 24 Spectrometer

Claims (3)

In the method for manufacturing an SOI wafer, the support wafer and the active layer wafer are bonded and bonded via an insulating film, and the active layer wafer is made into an SOI layer having a predetermined thickness.
A step of adhering a plurality of SOI wafers from the back surface of the support wafer to the surface of one affixing plate with an adhesive;
Sliding the active layer wafer surface of the plurality of SOI wafers to the polishing surface plate surface to which a polishing cloth is attached, and polishing the active layer wafer surface of the plurality of SOI wafers by the action of an abrasive;
Removing the application plate from a polishing apparatus that holds the application plate, and optically measuring the thickness of the SOI layer in a state where the SOI wafer is applied to the application plate.
A method for manufacturing an SOI wafer, comprising adjusting and controlling the thickness of the SOI layer by polishing the surface of the active layer wafer and optically measuring the thickness of the SOI layer.   The method for manufacturing an SOI wafer according to claim 1, wherein the attaching plate is an alumina plate.   The optical thickness of the SOI layer is measured by measuring the intensity of reflected light or transmitted light of measurement light irradiated on the SOI layer from a measurement light source. Manufacturing method of SOI wafer.

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