JP2008233473A - Thin film substrate manufacturing method - Google Patents

Abstract

It is an object of the present invention to provide a method for manufacturing a high-quality thin film substrate that can accurately measure the thickness of a substrate that has been thinned by processing the surface of the substrate and has little variation in film thickness. And
A method of manufacturing a thin film substrate according to the present invention includes a step of forming a recess having a predetermined depth on a part of one surface of one of two substrates, and one substrate provided with a recess. A substrate bonding step of bonding the surface of one substrate to one surface of the other substrate, and processing the surface of one substrate opposite to the bonding surface between the bonded one substrate and the other substrate, so that the depth of the recess is greater than the distance One of the surface processing step for making the thickness thick, the surface destruction step for breaking the portion where the concave portion is located on the surface of the processed one substrate and causing the concave portion to appear, and the surface of the processed one substrate and the surface breaking step A level difference measuring step for measuring a level difference with the surface of the other substrate exposed in the recess appearing on the surface of the substrate.
[Selection] Figure 1

Description

  The present invention relates to a method for manufacturing a thin film substrate used in a planar lightwave circuit, for example.

  In a method of manufacturing a substrate having a thin film by processing one side of the directly bonded substrates, it is important to measure the thickness of the thin film. Here, the direct bonding refers to bonding by atomic level covalent bonding between materials (see, for example, Patent Document 1).

  FIG. 4 is a schematic view showing a part of a process of a conventional method for manufacturing a thin film substrate. 4A and 4B are schematic cross-sectional views of the substrate in each step of the method for manufacturing a thin film substrate.

  In the conventional method for manufacturing a thin film substrate, as shown in FIG. 4A, after the two substrates 91 and 92 are directly bonded to each other, the surface of one substrate 91 is ground or polished, thereby obtaining the structure shown in FIG. As shown in FIG. Here, of the substrates 91 and 92 shown in FIG. 4A, the thickness of the substrate 92 on the non-thinning side is Ta, and the thickness of the substrate 91 on the thinning side is Tb. The thickness of the substrate 91 after thinning is defined as Tb ′. The thickness of the bonding substrate 100 is initially (Ta + Tb) as shown in FIG. 4 (a), and thereafter processing such as grinding or polishing is performed, and finally FIG. 4 (b). (Ta + Tb ′) as shown in FIG. The thickness Tb ′ of the thinned substrate 91 is the difference between the thickness (Ta + Tb ′) of the bonded substrate 100 after processing such as grinding or polishing and the thickness Ta of the substrate 92 ((Ta + Tb ′) − Ta). Can be obtained as The thickness of the substrate 91 after the thinning can be achieved by, for example, a stylus type thickness meter.

  In addition to the above-described method for manufacturing a thin film substrate, for example, there is a method of providing a plurality of recesses on the surface of one of two substrates (see, for example, Patent Document 2 or 3). First, after bonding the surface of one substrate provided with the recesses and the surface of the other substrate, one substrate is thinned. And it thins until a recessed part appears and it is set as a joining board | substrate. The thickness of the thinned substrate can be measured by observing the appearing recess with a microscope.

Japanese Patent No. 375236 Japanese Utility Model Publication No. 3-61331 JP 2004-22746 A

  However, in the conventional manufacturing method shown in FIG. 4, since the thickness Tb 'of the substrate 91 after thinning is measured by an indirect method, the accuracy may be significantly deteriorated. For example, when the thickness Ta of the substrate 92 is 500 μm and the thickness Tb ′ of the substrate 91 after thinning is 5 μm, the thickness of the substrate 91 after thinning is measured when measuring with a stylus type thickness meter. Depending on the accuracy (± 0.2 μm) and its reproducibility (± 0.2 μm), the accuracy of Tb ′ is significantly degraded, for example, 5 ± 0.4 μm.

  In addition, in the method of manufacturing a thin film substrate in which a concave portion is provided on one of the two substrates, waste liquid generated during processing such as grinding or polishing flows into the concave portion, and accurate measurement may not be possible. Moreover, it is necessary to form a recessed part deeper than the thickness of the thin film after thinning. For this reason, when a concave portion having a small size and a deep depth is formed, the surface of the polishing disk may be caught by the concave portion during polishing when the film is thinned, and the edge of the concave portion may be lost, resulting in an increase in polishing scratches.

  Accordingly, an object of the present invention is to provide a method for manufacturing a high-quality thin film substrate that can accurately measure the thickness of a substrate that has been thinned by processing the surface of the substrate and that has little variation in film thickness. To do.

  In order to achieve the above object, the present invention provides a plurality of recesses in one of two substrates, and directly bonds the surface of the substrate provided with the recesses with the surface of the other substrate. After thinning the substrate, it was decided to destroy the portion where the concave portion was located on the surface of the one substrate to cause a gap to appear.

  Specifically, the method for manufacturing a thin film substrate according to the present invention includes a recess forming step in which a recess having a predetermined depth is provided on a part of one surface of one of two substrates, and the recess forming step. A substrate bonding step of bonding a surface of the one substrate provided with the recess to one surface of the other substrate of the two substrates, and the one substrate and the other substrate bonded in the substrate bonding step. A surface processing step of processing the surface of the one substrate opposite to the bonding surface to make the thickness thicker than a distance of the depth of the recess, and among the surfaces of the one substrate processed in the surface processing step A surface destruction step of destroying a portion where the concave portion is located and causing the concave portion to appear; a surface of the one substrate processed in the surface processing step; and the concave portion appearing on the surface of the one substrate in the surface destruction step Comprising a step measurement step of measuring the level difference between the exposed said other surface of the substrate.

  By performing the recess forming step, the substrate bonding step, and the surface processing step, a step from the surface of one substrate to the surface of the other substrate exposed in the recess appearing on the surface is formed. By measuring, the film thickness of one substrate can be measured directly. Further, by providing the surface destruction step, for example, the surface of the other substrate can be exposed to the recess in a state in which abrasive grains or waste liquid by grinding or polishing and waste liquid by etching are prevented from adhering to the recess. Therefore, in the step measurement process, it is possible to accurately measure the thickness of the thinned substrate by reducing the influence on the measurement error caused by the abrasive grains and waste liquid. This makes it possible to provide a high-quality thin film substrate with little variation in film thickness.

  In the thin film substrate manufacturing method, it is preferable that the method further includes a resurface processing step of processing the surface of the one substrate again to a predetermined thickness after the step measurement step.

  Thereby, if the surface is processed again based on the measurement result, the thickness of the substrate can be made closer to the desired thickness.

  Further, in the method for manufacturing the thin film substrate, the surface is provided while providing a plurality of the concave portions in the concave portion forming step, and changing the position of the concave portions appearing in the surface destruction step according to the positions where the concave portions are provided. It is desirable to repeat from the processing step to the step measurement step.

  As a result, the position where a new concave portion appears every time the surface destruction process is changed, so the step to the surface of the other newly appeared substrate reduces the influence on the measurement error due to abrasive grains and waste liquid from the previous process. Thus, it is possible to accurately measure the thickness of the thinned substrate multiple times.

  In the method for manufacturing a thin film substrate, it is preferable that a plurality of the recesses having different depths are provided in the recess forming step, and the steps from the surface processing step to the step measurement step are repeated.

  As a result, the position where a new concave portion appears every time the breaking process is changed, the difference in the measurement error due to abrasive grains and waste liquid from the previous process is reduced by the step to the surface of the other newly appeared substrate. It is possible to accurately measure the thickness of the thinned substrate multiple times. In addition, since the depths of the plurality of concave portions are changed, even when roughing one substrate, it is possible to perform surface processing while checking the thickness of one substrate one by one.

  The method for manufacturing a thin film substrate of the present invention can accurately measure the thickness of a substrate that has been thinned by processing the surface of the substrate, and can provide a high-quality thin film substrate with little variation in film thickness. It is.

  Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiment described below is an example of the configuration of the present invention, and the present invention is not limited to the following embodiment.

(First embodiment)
FIG. 1 is a schematic view showing a part of the steps of the method for manufacturing a thin film substrate according to the present embodiment. FIG. 1A is a schematic surface view of one of two substrates in each step of the thin film substrate manufacturing method. Moreover, FIG.1 (b)-(d) is a schematic sectional drawing in the AA 'surface of Fig.1 (a) in each process of the manufacturing method of a thin film substrate.

(Recess formation process)
In the method of manufacturing the thin film substrate of FIG. 1, first, as shown in FIG. 1B, a recess 20a to a predetermined depth is formed on a part of one surface of one of the two substrates 31, 30. 20d is provided. As the two substrates 31 and 30, for example, LiNbO ₃ is applied as the substrate 31 on the side where the recesses 20a to 20d are provided, and LiTaO ₃ is applied as the substrate 30 to be bonded to the substrate 31 provided with the recesses 20a to 20d. it can. Further, LiNb _x Ta _1-x O ₃ or quartz can be applied as the substrate 30. In addition, the thickness of one of the two substrates 31 and 30 may be thicker than the design value of the thickness of the substrate 31 that is finally processed and thinned. The thickness of the other substrate 30 may be any size as long as it functions as a substrate that supports the substrate 20 during or after processing. For example, the thickness of one substrate 31 after processing The design value can be 100 times or more. In FIG. 1, the thickness of the substrate 30 is Ta, and the thickness of the substrate 31 is Tb.

  The recesses 20a to 20d can be provided, for example, by patterning on the surface of one substrate and removing a part of the surface of the substrate by 0.01 μm or more by dry etching. The shape of the recesses 20a to 20d may be any shape as long as the thickness of the substrate can be measured in a step measurement process described later. For example, as shown in FIG. 1A, the shape of the hole on the surface of the substrate 31 can be made into an L shape to form a prism shape in the depth direction. Alternatively, for example, the overall shape of the recess can be a cylindrical shape, a prismatic shape, a conical shape, or a pyramid shape. The depths of the recesses 20a to 20d are set to a predetermined depth according to the design value of the thickness of the substrate to be finally thinned.

  Further, at least one recess (corresponding to the recesses 20a to 20d) may be provided, and a plurality of recesses may be provided as shown in FIG. Moreover, you may arrange | position a recessed part (equivalent to the recessed parts 20a-20d) in any position in the board | substrate 31, regardless of the case of one or more. In the case where a plurality of recesses (corresponding to the recesses 20a to 20d) are provided, since the thickness of the substrate 31 can be measured at various positions in the step measurement process described later, It can be known whether 31 thickness is uniform. However, the number of the recesses (corresponding to the recesses 20a to 20d) is one or a plurality of cases. For example, when the manufactured thin film substrate is used for an element such as a planar lightwave circuit, the element of the substrate 31 It is necessary to provide it in the area excluding the part used as.

(Board bonding process)
Next, as shown in FIG. 1C, the surface of one substrate 31 provided with the recesses 20 a to 20 d in the above-described recess forming step is bonded to one surface of the other substrate 30 of the two substrates 31 and 30. To do. Hereinafter, a substrate formed by bonding the two substrates 31 and 30 is referred to as a bonded substrate 50. The bonding is preferably direct bonding. In some cases, an adhesive may be applied to at least one surface of the two substrates 31 and 30 to bond each other. However, in this case, it is necessary that the thickness of the adhesive is uniform and known. Therefore, if the bonding of the two substrates 31 and 30 is a direct bonding, the influence on the measurement error due to the bonding when the thickness of the substrate 31 is measured is small, and the measurement accuracy can be improved. Therefore, the processed thin film substrate can be made high quality.

(Surface machining process)
Next, as shown in FIG. 1D, the surface 24 of one substrate 31 opposite to the bonding surface 23 between the one substrate 31 and the other substrate 30 bonded in the substrate bonding step is processed. The thickness is set to Tb ′. The surface 24 of one of the bonded substrates 50 can be processed by, for example, grinding, polishing, dry etching, wet etching, or a combination thereof to reduce the thickness of the substrate 31. The thickness of the substrate 31 is set in accordance with the design value of the thickness of the substrate 31 to be finally thinned. However, it is necessary to be thicker than the distance of the depths of the recesses 20c and 20d appearing in the surface destruction process described later.

(Surface destruction process)
Next, as shown in FIG. 1E, the portions where the recesses 20c and 20d are located in the surface 24 of the one substrate 31 processed in the above-described surface processing step are destroyed to make the recesses 20c and 20d appear. For example, the surface 24 of one of the bonding substrates 50 can be destroyed by applying an ultrasonic water flow to the surface 24 of the substrate 31 to cause the recesses 20c and 20d to appear. This is because the portions 25 and 26 where the recesses 20c and 20d are located in the surface 24 of the substrate 31 can be peeled off by an impact caused by bubble destruction of the ultrasonic water flow. Further, by making a difference between the pressure outside the bonding substrate 50 and the pressure inside the cavity by the recesses 20c and 20d, the surface 24 of the substrate 31 can be broken and the recesses 20c and 20d can appear. For example, it can be realized by pressurizing or depressurizing the entire bonded substrate 50 or by applying a laser to the portions 25 and 26 of the surface 24 of the substrate 31 where the recesses 20c and 20d are positioned. These are methods in which the portions 25 and 26 are destroyed by the difference in pressure between the inside of the recesses 20 c and 20 d and the outside of the bonding substrate 50. Thus, since the surface 24 of the substrate 31 is destroyed and the recesses 20c and 20d appear, it is possible to eliminate the need for the recesses 20c and 20d to appear in the surface processing step described above. Therefore, it is possible to prevent the bonding substrate 50 from being scratched by lacking the edges of the recesses 20c and 20d as in the prior art in the surface processing step. Therefore, in the above-described recess forming step, the recesses 20c and 20d can be formed in the vicinity of the center of the substrate 31, and the thickness of the substrate 31 after being thinned at a position suitable for evaluating the thickness of the substrate. Can be evaluated. Further, since the surface of the bonded substrate 50 is not scratched, the substrate 31 is provided with a plurality of recesses 20c and 20d in the recess forming step as described above, and the thickness of the substrate 31 after thinning is reduced. It is also possible to evaluate the internal distribution.

(Step measurement process)
Next, the surface 24 of one substrate 31 processed to have a thickness Tb ′ by the above-described surface processing step and the recesses 20c and 20d that appeared on the surface 24 of the one substrate 31 in the above-described surface destruction step were exposed. The step with respect to the surfaces 40c and 40d of the other substrate 30 is measured. The level difference between the surface 24 of the substrate 31 and the surfaces 40c and 40d of the substrate 31 exposed in the recesses 20c and 20d can be measured by, for example, a stylus type level meter or an optical thickness meter. A stylus type step gauge is a device that measures the level difference, surface roughness, waviness, etc. by tracing an object with a set constant low needle pressure using a stylus. It is an instrument that measures a step by tracing the object while irradiating the object with a laser and changing the reflection angle or reflection position of the reflected light. In the stylus type step meter, when the step between the substrates 31 and 30 is within 30 μm, it is possible to measure with accuracy of ± 0.1 μm or less. Further, if the concave portions 20c and 20d are formed in a conical shape or a pyramid shape in the concave portion forming step, the size of the entrance of the concave portions 20c and 20d appearing on the surface 24 of the processed substrate 31 and the concave portions 20c and 20d are formed. It is also possible to measure the level difference from the size of the surfaces 40c and 40d of the substrate 30 exposed to the surface.

  As described above, by performing the above-described recess forming step, substrate bonding step, and surface processing step, the other substrate 30 exposed from the surface 24 of one substrate 31 to the recesses 20c and 20d that appeared on the surface 24 is formed. The film thickness of one substrate 31 can be directly measured by measuring the steps up to the surfaces 40c and 40d. Further, by providing the surface destruction step, for example, the surfaces 40c and 40d of the other substrate 30 are formed in the recesses 20c and 20d in a state in which abrasive grains or waste liquid by grinding or polishing and waste liquid by etching are prevented from adhering to the recesses. Can be exposed. Therefore, in the step measurement process, it is possible to accurately measure the thickness of the thinned substrate 31 by reducing the influence on the measurement error due to abrasive grains and waste liquid. Therefore, even if the thickness Tb ′ of one substrate 31 after processing is set to 20 μm or less, for example, the accuracy of the desired thickness of the substrate 31 can be suppressed to within ± 0.1 μm. This makes it possible to provide a high-quality thin film substrate with little variation in film thickness.

  In addition, after the step measurement step, a resurface processing step for processing the surface of the one substrate 31 to a predetermined thickness can be performed again. Thereby, if the surface is processed again based on the measurement result, the thickness of the substrate 31 can be made closer to the desired thickness.

(Second embodiment)
FIG. 2 is a schematic view showing a part of the steps of the method for manufacturing the thin film substrate according to the present embodiment. 2A to 2C are schematic cross-sectional views of the substrate in each step of the thin film substrate manufacturing method. Further, FIG. 2 shows a part of a process that is additionally performed after the surface breaking process described in the first embodiment.

  In the present embodiment, a plurality of recesses 21c, 21d, and 21e are provided in the recess forming step in the first embodiment described above. Although FIG. 2 shows an embodiment in which three recesses 21c, 21d, and 21e having the same depth are provided, it is sufficient that there are at least two or more recesses (recesses corresponding to the recesses 21c, 21d, and 21e).

  In this embodiment, after measuring the level difference between the surface 24 of one substrate 31 of the bonding substrate 51 shown in FIG. 2A and the surface of the other substrate 40e exposed to the recess 21e, a surface processing step is further performed. The thickness is set to Tb ″ as shown in FIG. Thereafter, a surface breaking process is performed, and another recess 21 d appears on the surface 24 of one substrate 31 as shown in FIG. And a level | step difference measurement process is performed and the level | step difference between the surface 24 of one board | substrate 31 and the surface 40d of the other board | substrate 30 exposed to the recessed part 21d which appeared in FIG.2 (c) is measured. In other words, in the present embodiment, according to the position where the recesses 21c, 21d, and 21e are provided, the position of the recesses that appear in the surface destruction process is changed from the recesses 21e to the recesses 21d. Repeat until the step measurement process. In addition, about each method of a surface processing process, a surface destruction process, and a level | step difference measurement process, since it is the same as that of 1st embodiment, description is abbreviate | omitted.

  Thereby, in order to change the position where a new concave portion (the concave portion 21e or the concave portion 21d) appears every time the surface destruction process is performed, the step to the surface (the front surface 40e or the surface 40d) of the other newly appeared substrate 30 It is possible to accurately measure the thickness of the thinned substrate 31 a plurality of times by reducing the influence on the measurement error caused by the abrasive grains and the waste liquid 41 in the process. In particular, if the depths of the plurality of recesses 21c, 21d, and 21e are the same or substantially the same in the recess forming process, the surface processing is performed little by little in the surface processing process after the step measurement process is finished, and the surface breaking process is performed immediately. Since other recesses (from the recesses 21e to the recesses 21d) can appear, the thickness of the substrate 31 can be finely adjusted in the surface processing step.

  Furthermore, a plurality of recesses may be provided in a dispersed manner in the recess forming step, and some of the plurality of recesses may be dispersed in the surface breaking step. Thus, since it is possible to finely adjust the substrate while knowing whether the substrate surface is uniform, it is possible to provide a higher quality thin film substrate with little variation in film thickness.

(Third embodiment)
FIG. 3 is a schematic view showing a part of the steps of the method for manufacturing the thin film substrate according to the present embodiment. 3A to 3D are schematic cross-sectional views of the substrate in each step of the thin film substrate manufacturing method. Further, FIG. 3 shows a part of a process that is additionally performed after the surface breaking process described in the first embodiment.

  In the present embodiment, a plurality of recesses 22c, 22d, and 22e having different depths are provided in the recess forming step in the first embodiment described above. FIG. 3 shows a configuration in which three recesses 22c, 22d, and 22e having different depths are provided, but there are at least two recesses (recesses corresponding to the recesses 22c, 22d, and 22e) having different depths. That's all you need.

  In this embodiment, after measuring the level difference between the surface 24 of one substrate 31 of the bonding substrate 52 shown in FIG. 3A and the surface 40e of the other substrate 30 exposed in the recess 22e, a surface processing step is further performed. As shown in FIG. 3B, the thickness is set to Tb ″. Thereafter, a surface breaking process is performed, and another recess 22d appears on the surface 24 of one substrate 31 as shown in FIG. Then, a level difference measurement step is performed to measure the level difference between the surface 24 of one substrate 31 and the surface 40d of the other substrate 30 exposed in the recess 22d that appears in FIG. That is, in this embodiment, the process from the surface processing step to the step measurement step is repeated. In addition, about each method of a surface processing process, a surface destruction process, and a level | step difference measurement process, since it is the same as that of 1st embodiment, description is abbreviate | omitted.

  Thereby, in order to change the position at which a new concave portion (the concave portion 22e or the concave portion 22d) appears every time the destruction process is performed, a step up to the surface (the front surface 40e or the front surface 40d) of the other newly appearing substrate 30 is used. The thickness of the thinned substrate 31 can be accurately measured a plurality of times by reducing the influence on the measurement error caused by the abrasive grains and the waste liquid 41. In addition, since the depths of the plurality of recesses 22c, 22d, and 22e are changed, even when one substrate 31 is rough-cut, the surface processing can be performed while checking the thickness of the surface 24 of the one substrate 31 one by one.

  Furthermore, a plurality of recesses may be provided in a dispersed manner in the recess forming step, and some of the plurality of recesses may be dispersed in the surface breaking step. Thus, since it is possible to finely adjust the substrate while knowing whether the substrate surface is uniform, it is possible to provide a higher quality thin film substrate with little variation in film thickness.

  The method for producing a thin film substrate of the present invention can be used as a method for producing a thin film substrate in a planar lightwave circuit.

It is the schematic which showed a part of process of the manufacturing method of the thin film substrate which concerns on one Embodiment. It is the schematic which showed a part of process of the manufacturing method of the thin film substrate which concerns on one Embodiment. It is the schematic which showed a part of process of the manufacturing method of the thin film substrate which concerns on one Embodiment. It is the schematic which showed a part of process of the manufacturing method of the conventional thin film substrate.

Explanation of symbols

20a, 20b, 20c, 20d: recesses 21a, 21b, 21c, 21d: recesses 22a, 22b, 22c, 22d: recesses 23: bonding surface 24: surface 25, 26: portion 30, 31: substrates 40a, 40b, 40c, 40d: surface 41: abrasive grains and waste liquids 50, 51, 52, 100: bonded substrate 90, 91: substrate

Claims (4)

A recess forming step in which a recess having a predetermined depth is provided on a part of one surface of one of the two substrates;
A substrate bonding step of bonding the surface of the one substrate provided with the recess in the recess forming step to one side of the other substrate of the two substrates;
Surface processing for processing the surface of the one substrate on the opposite side to the bonding surface between the one substrate and the other substrate bonded in the substrate bonding step so as to have a thickness thicker than the depth distance of the recess. Process,
A surface destruction step of destroying a portion where the concave portion is located in the surface of the one substrate processed in the surface processing step and causing the concave portion to appear;
A step measuring step for measuring a step between the surface of the one substrate processed in the surface processing step and the surface of the other substrate exposed in the recess appearing on the surface of the one substrate in the surface breaking step;
A method of manufacturing a thin film substrate comprising:   2. The method of manufacturing a thin film substrate according to claim 1, further comprising a resurface processing step of processing the surface of the one substrate again to a predetermined thickness after the step measurement step. Providing the plurality of recesses in the recess forming step;
2. The thin film according to claim 1, wherein the steps from the surface processing step to the step measurement step are repeated while changing the position of the concave portion that appears in the surface destruction step according to the position where the concave portion is provided. A method for manufacturing a substrate. A plurality of the recesses having different depths from each other in the recess forming step are provided,
The method for manufacturing a thin film substrate according to claim 1, wherein the steps from the surface processing step to the step measurement step are repeated.

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