JP2013015428A - Inspection device, inspection method and manufacturing method of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inspection device capable of accurately inspecting a defect of a substrate on the basis of change in an angle of reflected light from an object to be inspected.SOLUTION: The inspection device of the present invention includes: a light source 11 for emitting infrared light; an optical system for making the infrared light emitted from the light source 11 incident substantially perpendicularly onto a wafer 30 as parallel light and guiding reflected light from the wafer 30; and IR cameras 19, 20 for detecting light except specularly reflected light among the reflected light guided by the optical system. An emitting end face of an optical fiber 13 for guiding the infrared light from the light source 11 is arranged at a pupil position of the optical system.

Description

  The present invention relates to an inspection apparatus, an inspection method, and a method for manufacturing a semiconductor device, which are suitable for surface shape inspection of a substrate, particularly inspection of a bonded substrate in which a support substrate is bonded to an element substrate.

  2. Description of the Related Art In recent years, through silicon vias (TSVs) have attracted attention as next-generation semiconductor packaging technologies that can simultaneously achieve miniaturization, high integration, and high performance of semiconductor devices. TSV is an electrode or wiring that penetrates the semiconductor chip vertically. By stacking a plurality of chips and connecting the chips with each other by TSV, it is possible to easily realize a reduction in size, capacity, and performance of a three-dimensional integrated circuit.

  When forming the vias, it is necessary to reduce the thickness of the wafer in order to reduce the processing time and reduce the pitch. Back surface grinding (back grinding) is performed to reduce the thickness of the wafer. If the thickness of the wafer is reduced, the wafer is likely to warp, making handling difficult. Therefore, a support substrate (support substrate) is bonded to the front surface of the wafer to polish the back surface of the wafer, and after the polishing is completed, the support substrate is removed from the wafer.

  The wafer and the support substrate are bonded together by an adhesive layer such as a resin. At this time, a foreign substance may enter between the wafer and the support substrate. In addition, air may remain between the wafer and the support substrate, and pores may be formed. When the wafer backside polishing process is performed in this state, there is a problem that the thickness of the wafer varies between a region where foreign matter and voids are present and another region. In the above-described three-dimensional semiconductor device, if the thickness of the wafer is different, connection between chips may not be achieved.

  In recent years, backside illumination technology (BSI: Backside Illumination) for CMOS (Complementally Metal Oxide Semiconductor) sensors has been developed. In BSI, light is collected from the wafer side on the back side of the sensor. Even in the manufacturing process of an image sensor that employs BSI, there is a process in which the back surface of the wafer is shaved while the support substrate is bonded to the wafer. In this case as well, the wafer thickness may vary due to foreign matter between the wafer and the support substrate. Thus, when the wafer thickness varies, there is a problem that sensitivity unevenness occurs.

  In order to solve such a problem, it is desired to detect foreign matter or the like between the wafer and the resin before performing the backside polishing process of the wafer. Conventionally, an inspection apparatus for inspecting a defect of an SOI (Silicon on Insulator) wafer in which two silicon wafers are bonded together has been proposed (Patent Document 1, Non-Patent Document 1). These inspection apparatuses irradiate the SOI wafer with infrared light and detect defects such as voids based on the transmitted or reflected light.

  When transmitted illumination is used as in Non-Patent Document 1, Fresnel reflection occurs in a portion where a void is generated, so that the intensity of transmitted light in this portion is weaker than that in a portion where no void is generated. A void existing between the substrates of the SOI wafer is detected from a difference in luminance between a portion where the void is generated and a portion where the void is not generated from an image obtained by imaging this.

Japanese Patent Laid-Open No. 7-161568

“Semiconductor Internal Observation System C9597-11”, Hamamatsu Photonics Co., Ltd., June 2010, Cat. No. SSMS0001J06

  In the inspection apparatus described above, both transmitted light of the illumination light and scattered / diffracted light are captured and imaged, and the defect is detected based on the difference in luminance between the defective portion and the non-defective portion. Only a small amount of scattered light is generated in the minute foreign matters and voids in the adhesive layer, and the difference in luminance is also minute. Therefore, there is a problem that it is difficult to detect such a minute defect. Further, it is difficult to determine whether a foreign object exists or a void exists from the acquired image.

  The present invention has been made against the background described above, and an object of the present invention is to provide an inspection apparatus, an inspection method, and a semiconductor device manufacturing method using the inspection apparatus that can accurately inspect defects to be inspected. Is to provide.

  The inspection apparatus according to the first aspect of the present invention includes a light source unit that emits infrared light, and the infrared light emitted from the light source unit is incident as a parallel light substantially perpendicularly on the inspection target, and the inspection target An optical system that guides the reflected light from the optical system, and a light detection unit that detects light other than the regular reflected light out of the reflected light guided by the optical system, and the front light source unit is disposed at the pupil position of the optical system It is what has been. Thereby, the defect of the inspection object can be inspected with high accuracy based on the change in the reflected light angle from the inspection object.

  An inspection apparatus according to a second aspect of the present invention is the inspection apparatus according to the above aspect, wherein the light detection unit includes two photodetectors, and the optical system transmits light other than the specularly reflected light. It is characterized by being guided to a photodetector. Thereby, based on the images acquired by the two imagers, the defect to be inspected can be inspected with high accuracy.

  The inspection apparatus according to a third aspect of the present invention is the inspection apparatus described above, wherein the optical system is arranged symmetrically with respect to an optical axis, and reflects light other than specularly reflected light from the inspection object, Two reflecting surfaces are respectively led to the two photodetectors. Thereby, the inspection of the surface shape of the inspection object can be performed based on the change in the reflected light angle from the inspection object.

  An inspection apparatus according to a fourth aspect of the present invention is the inspection apparatus described above, wherein at least one of the reflection surface and the inspection object is moved based on the luminance information respectively acquired by the two photodetectors. The moving mechanism to be further provided. Thereby, it becomes possible to improve the defect detection accuracy.

  An inspection apparatus according to a fifth aspect of the present invention is characterized in that, in the above-described inspection apparatus, the inspection object is a bonded substrate in which an element substrate and a support substrate are bonded together via an adhesive layer. is there. The present invention is particularly suitable for such inspection of an inspection object.

  The inspection apparatus according to a sixth aspect of the present invention is characterized in that, in the above-described inspection apparatus, the light source unit switches and emits a plurality of infrared lights having different wavelengths. As a result, the type of defect present in the inspection object can be determined.

  In the inspection apparatus according to a seventh aspect of the present invention, in the inspection apparatus, the light source unit includes infrared light having a wavelength reflected by the element substrate and infrared light having a wavelength transmitted through the element substrate. Are switched and output. Thereby, the kind of defect which exists between joining substrates can be discriminated.

  The inspection apparatus according to an eighth aspect of the present invention is the inspection apparatus described above, wherein the light detection unit includes four light detectors, and the optical system transmits light other than the regular reflection light to the four light beams. Each is led to a detector. Accordingly, it is possible to inspect the defect to be inspected more accurately based on the images acquired by the four imagers.

  An inspection apparatus according to a ninth aspect of the present invention is the inspection apparatus described above, wherein the optical system is arranged every 90 degrees around the optical axis and reflects light other than the regular reflection light from the inspection object. Four reflective surfaces led to the four photodetectors are provided. Thereby, based on the change of the reflected light angle from a test object, the surface shape of a test object can be test | inspected more accurately.

  An inspection apparatus according to a tenth aspect of the present invention is the inspection apparatus according to the above aspect, wherein the light source unit guides the infrared light, and an optical fiber having an emission end face disposed at a pupil position of the optical system. In addition.

  An inspection apparatus according to an eleventh aspect of the present invention is the inspection apparatus, wherein the light source unit irradiates the inspection object with planar infrared light, and the light detection unit displays an image of the inspection object. It is characterized by imaging.

  In the inspection apparatus according to a twelfth aspect of the present invention, in the inspection apparatus, the light source unit irradiates the inspection target with planar infrared light, and the light detection unit displays an image of the inspection target. The imaging mechanism picks up the image, and the moving mechanism moves at least one of the reflecting surface and the inspection object based on luminance information other than the defective portion in the image acquired by the light detection unit.

  The inspection apparatus according to a thirteenth aspect of the present invention is the inspection apparatus, wherein the light source unit further includes a rotatable rotating mirror that reflects the infrared light beam and performs line scanning on the inspection object. It is to be prepared. Thereby, defect detection sensitivity can be improved.

  In the inspection method according to the fourteenth aspect of the present invention, the infrared light emitted from the light source unit disposed at the pupil position of the optical system is incident on the inspection object as a parallel light substantially perpendicularly, and is reflected from the inspection object. Of the light, light other than the specularly reflected light is detected by the light detection unit, and the defect to be inspected is detected based on the luminance information obtained by the light detection unit. Thereby, the defect of the inspection object can be inspected with high accuracy based on the change in the reflected light angle from the inspection object.

  An inspection method according to a fifteenth aspect of the present invention guides light other than the regular reflection light to two light detectors having different light detection sections in the inspection method described above. Thereby, based on the images acquired by the two imagers, the defect to be inspected can be inspected with high accuracy.

  The inspection method according to a sixteenth aspect of the present invention is the inspection method described above, wherein the light other than the specularly reflected light from the inspection object is transmitted by the two reflecting surfaces arranged symmetrically with respect to the optical axis. The light is guided to two photodetectors having different detectors. Thereby, the inspection of the surface shape of the inspection object can be performed based on the change in the reflected light angle from the inspection object.

  An inspection method according to a seventeenth aspect of the present invention is the inspection method described above, wherein at least one of the reflecting surface and the inspection object is moved based on the luminance information respectively acquired by the two photodetectors. Let As a result, the result detection accuracy can be improved.

  An inspection method according to an eighteenth aspect of the present invention is characterized in that, in the above inspection method, a plurality of infrared lights having different wavelengths are switched and irradiated to the inspection object. As a result, the type of defect present in the inspection object can be determined.

  An inspection method according to a nineteenth aspect of the present invention is the inspection method described above, wherein the inspection target is a bonded substrate in which an element substrate and a support substrate are bonded together through an adhesive layer, and is reflected by the element substrate. The infrared light having a wavelength that is transmitted and the infrared light having a wavelength that is transmitted through the element substrate are switched to irradiate the inspection object. Thereby, the kind of defect which exists between joining substrates can be discriminated.

  In the inspection method according to a twentieth aspect of the present invention, in the above inspection method, light other than the specularly reflected light from the inspection object is guided to four photodetectors different in the light detection section. Accordingly, it is possible to inspect the defect to be inspected more accurately based on the images acquired by the four imagers.

  The inspection method according to a twenty-first aspect of the present invention is the inspection method described above, wherein light other than specularly reflected light from the inspection object is transmitted by the four reflecting surfaces arranged every 90 degrees around the optical axis. It leads to four different photodetectors. Thereby, based on the change of the reflected light angle from a test object, the surface shape of a test object can be test | inspected more accurately.

  An inspection method according to a twenty-second aspect of the present invention is characterized in that, in the inspection method described above, the inspection object is irradiated with planar infrared light to capture an image of the inspection object.

  An inspection method according to a twenty-third aspect of the present invention is the inspection method described above, wherein the inspection object is irradiated with planar infrared light to capture an image of the inspection object, and is acquired by the light detection unit. Based on the luminance information other than the defective portion in the image, at least one of the reflecting surface and the inspection object is moved.

  The inspection method according to a twenty-fourth aspect of the present invention is the inspection method according to any one of claims 14 to 21, wherein the inspection target is line-scanned by reflecting the infrared light beam by a rotating mirror. Inspection method described in 1.

  A method for manufacturing a semiconductor device according to a twenty-fifth aspect of the present invention uses the inspection method described above to inspect defects in a bonded substrate in which an element substrate and a support substrate are bonded together with an adhesive layer. The back surface of the element substrate in the bonded substrate after inspection is polished, and the support substrate is peeled off. Thereby, the quality of the semiconductor device manufactured using a bonded substrate can be improved.

  ADVANTAGE OF THE INVENTION According to this invention, the inspection apparatus which can test | inspect the defect of a board | substrate accurately based on the change of the reflected light angle from a test object, an inspection method, and the manufacturing method of a semiconductor device using the same can be provided. .

It is a figure which shows the structure of the inspection apparatus which concerns on Embodiment 1. FIG. It is a figure explaining the state which test | inspects a bonded substrate in the inspection apparatus which concerns on Embodiment 1. FIG. It is a figure explaining the state which test | inspects a bonded substrate in the inspection apparatus which concerns on Embodiment 1. FIG. It is a figure explaining the sensitivity of the inspection apparatus which concerns on Embodiment 1. FIG. It is a figure explaining the state which test | inspects the joining board | substrate in the test | inspection apparatus which concerns on Embodiment 2. FIG. It is a figure explaining the state which test | inspects the joining board | substrate in the test | inspection apparatus which concerns on Embodiment 2. FIG. It is a figure which shows the other structure of the mirror used in the test | inspection apparatus which concerns on this invention. It is a figure which shows the structure of the inspection apparatus which concerns on Embodiment 2. FIG. It is a figure explaining the state which test | inspects the joining board | substrate in the test | inspection apparatus which concerns on Embodiment 2. FIG.

  Hereinafter, embodiments to which the present invention can be applied will be described. The following description is to describe the embodiment of the present invention, and the present invention is not limited to the following embodiment. For clarity of explanation, the following description is omitted and simplified as appropriate. Moreover, those skilled in the art can easily change, add, and convert each element of the following embodiments within the scope of the present invention.

Embodiment 1 FIG.
The configuration of the inspection apparatus according to Embodiment 1 of the present invention will be described with reference to FIG. FIG. 1 is a diagram showing a configuration of an inspection apparatus 10 according to the present embodiment. As shown in FIG. 1, the inspection apparatus 10 includes a light source 11, a lens 12, an optical fiber 13, an objective lens 14, an XY stage 15, a mirror 16, imaging lenses 17, 18, IR cameras 19, 20, and a comparator. 21, a controller 22 and a stage 23.

  Here, the bonded substrate 30 will be described as an example of the inspection target. First, the bonded substrate 30 will be described. The bonding substrate 30 is an intermediate product in a manufacturing process of a semiconductor device having a through electrode. The bonding substrate 30 includes an element substrate 31, a metal pattern 32, a support substrate 33, and an adhesive layer 34. The element substrate 31 is a semiconductor substrate such as a silicon wafer. The element substrate 31 is formed with a through electrode (not shown) embedded in the substrate and a metal pattern 32 connected to the through electrode.

  A support substrate 33 is bonded to the surface of the element substrate 31 on which the metal pattern 32 of the element substrate 31 is formed via an adhesive layer 34. As the support substrate 33, for example, quartz, glass, or a silicon wafer is used. By polishing the back surface of the surface of the element substrate 31 on which the metal pattern 32 is formed and exposing the terminal surface of the through electrode, the support substrate 33 is removed, whereby a semiconductor device including the through electrode is manufactured.

  As the adhesive layer 34, a peelable material is used. When, for example, a thermoplastic adhesive is used as the adhesive layer 34, the support substrate 33 can be bonded and removed by softening the adhesive layer 34 by heating. The inspection apparatus 10 is particularly suitable for inspection of foreign matters or voids between the element substrate 31 and the support substrate 33 of the bonded substrate 30.

  When a foreign substance exists between the element substrate 31 and the support substrate 33, the thickness of the bonding substrate 30 is increased. At this time, when the back surface polishing is performed, the thickness of the element substrate 31 in the part where the foreign matter exists becomes thinner than the other part. Further, since the back surface polishing is performed by applying pressure, if a void exists between the element substrate 31 and the support substrate 33, the thickness of the portion of the bonding substrate 30 where the void exists during the back surface polishing is reduced. For this reason, the thickness of the element substrate 31 in the part where the void exists is thicker than the other part.

  The inspection apparatus 10 according to the present invention inspects the unevenness of the thickness of the bonding substrate 30, that is, the surface shape of the bonding substrate 30 before performing such back surface polishing of the bonding substrate 30. That is, the inspection apparatus 10 can inspect defects or voids that are concave or convex with respect to the surroundings in the bonded substrate 30.

  Note that the inspection apparatus according to the present invention is not limited to the inspection of the bonded substrate 30, and it is also possible to inspect the surface shape of another substrate. For example, the present invention can be applied to an inspection of an SOI (Silicon On Insulator) substrate in a manufacturing process of a backside illumination type CMOS image sensor. Further, not only the bonded substrate but also the surface shape of the substrate can be inspected.

  The light source 11 is a laser light source that emits infrared light applied to the bonding substrate 30. As the light source 11, for example, an SLED (Super luminescent Light Emitting Diode) or LD (Laser Diode) having a center wavelength of 1310 nm or 1550 nm can be used. Generally, since a silicon wafer is used as the support substrate 33 disposed on the side irradiated with the inspection light, a light source that emits infrared light having a wavelength that transmits silicon is used. As the light source 11, it is preferable to use SLED. Thereby, generation | occurrence | production of speckle noise can be suppressed.

  Infrared light emitted from the light source 11 is collected by the lens 12 and enters the incident end face of the optical fiber 13. Infrared light taken into the optical fiber is guided through the optical fiber and exits from the exit end face. As the optical fiber 13, for example, a single mode fiber having an outer diameter of 120 μm can be used. In the present embodiment, the light source unit described in the claims includes a light source 11, a lens 12, and an optical fiber 13.

  The light source unit is a point light source that emits infrared light from the emission end of the optical fiber 13. The exit end face of the optical fiber 13 is disposed at a position conjugate with the pupil position of the optical system described later. That is, the light emission position of the light source unit is a position conjugate with the pupil position of the optical system. In the present embodiment, the pupil of the optical system matches the exit pupil of the objective lens 14.

  Infrared light emitted from the emission end face of the optical fiber 13 enters the objective lens 14. The objective lens 14 irradiates the entire inspection region of the bonded substrate 30 with incident infrared light as parallel light. That is, the objective lens 14 plays a role as a collimating lens. The bonding substrate 30 is placed on the XY stage 15. Here, the bonding substrate 30 is placed on the XY stage 15 so that the element substrate 31 contacts the XY stage 15. The XY stage 15 is movable in the XY direction. As a result, the entire surface of the bonding substrate 30 can be scanned by the infrared light irradiated from the optical fiber 13.

  The surface of the bonding substrate 30 on which the infrared light is irradiated is a flat surface and is disposed substantially perpendicular to the parallel light guided by the objective lens 14. That is, the optical axis of the objective lens 14 is substantially perpendicular to the surface of the bonding substrate 30 on the side irradiated with infrared light. Therefore, the infrared light applied to the bonding substrate 30 is coherent illumination with NA = 0. When there is no defect between the element substrate 31 and the support substrate 33, each surface of the bonding substrate 30 (the surface of the element substrate 31, the back surface and the surface of the support substrate 33, the back surface) is substantially perpendicular to the optical axis. Yes. The parallel light specularly reflected by the bonding substrate 30 enters the objective lens 14 again, and is collected by the objective lens 14 on the exit end face of the optical fiber 13.

  In order to prevent return light noise, a Faraday isolator may be provided between the optical fiber 13 and the objective lens 14. Or you may make it shift the light which returns to the optical fiber 13 again to the direction (front-back direction in FIG. 1) in which the mirror 16 is not arrange | positioned.

  The mirror 16 reflects infrared light other than the infrared light regularly reflected by the bonding substrate 30 and guides it to the imaging lens 17 or 18. The mirror 16 has two reflecting surfaces 16a and 16b arranged symmetrically with respect to the optical axis. In the present embodiment, the mirror 16 is composed of two right angle mirrors. An optical fiber 13 is disposed between the two right angle mirrors.

  The hypotenuses of the two right-angle mirrors are reflecting surfaces 16a and 16b, respectively. The reflecting surface 16a and the reflecting surface 16b are arranged with a predetermined interval. The exit end face of the optical fiber 13 is disposed between the reflecting surface 16a and the reflecting surface 16b. The reflecting surface 16 a reflects the light incident on the reflecting surface 16 a from the bonding substrate 30 to enter the imaging lens 17 and guides it to the IR camera 19. The reflecting surface 16 b reflects the light incident on the reflecting surface 16 b from the bonding substrate 30 to enter the imaging lens 18 and guides it to the IR camera 20.

  The imaging lenses 17 and 18 image light other than the specularly reflected light from the bonded substrate 30 on the imaging surfaces of the IR cameras 19 and 20, respectively. Therefore, the optical system described in the claims includes the objective lens 14, the mirror 16, and the imaging lenses 17 and 18. The objective lens 14 serves as a collimating lens that guides infrared light from the light source 11 to the bonding substrate 30 as parallel light, and also serves as a telecentric lens.

  The two IR cameras 19 and 20 capture an image of the inspection area of the bonded substrate 30 formed by the optical system. A defect in the inspection region of the bonded substrate 30 can be detected based on the images acquired by the IR cameras 19 and 20.

  Here, with reference to FIGS. 2 and 3, a case where the foreign matter 35 exists as a defect between the element substrate 31 and the support substrate 33 of the bonding substrate 30 will be described. 2 and 3 are views for explaining a state in which the bonding substrate 30 in which the foreign matter 35 is present is inspected in the inspection apparatus 10.

  When there is no inclination in the inspection region, the infrared light incident on the bonding substrate 30 returns to the emission end face of the optical fiber 13. Therefore, when there is no defect in the inspection area of the bonded substrate 30, the images acquired by the IR cameras 19 and 20 are dark images as a whole.

  As shown in FIG. 2, in the part where the foreign material 35 exists, a part of the support substrate 33 rises and an inclination occurs. As shown in FIG. 2, when the inspection region has a slope that rises to the right, the infrared light incident on the inclined portion does not return to the emission end face of the optical fiber 13 but enters the reflecting surface 16 b of the mirror 16. This infrared light is reflected by the reflecting surface 16 b and guided to the IR camera 20 by the imaging lens 18.

  On the other hand, infrared light incident on a portion having no inclination in the inspection region returns to the emission end face of the optical fiber 13. Therefore, in the image acquired by the IR camera 20, only the portion where the inclination exists on the surface of the element substrate 31 which is the inspection target surface is bright and the other portion is dark. That is, the inspection apparatus 10 is an inspection apparatus for dark field illumination. Thus, in the inspection apparatus 10 according to the present invention, it is possible to inspect a defect of the inspection object based on the change in the reflected light angle from the inspection object. Also, the dark field illumination inspection apparatus has an effect of suppressing shot noise because the background light is dark.

  The size of the defect to be detected is usually several μm to several tens of μm. When there is the foreign material 35, the element substrate 31 or the support substrate 33 is inclined in a region larger than the size of the foreign material 35. For this reason, compared with the case where the foreign material 35 itself is detected, the pixel size of the IR cameras 19 and 20 can be increased. For example, the pixel size of the IR cameras 19 and 20 can be set to 50 μm. As a result, it is possible to reduce the time required for defect detection of the entire bonded substrate 30 and perform inspection at high speed.

  As shown in FIG. 3, when the inspection region has a slope that rises to the left, the infrared light incident on the inclined portion does not return to the emission end face of the optical fiber 13 but enters the reflecting surface 16 a of the mirror 16. This infrared light is reflected by the reflecting surface 16 a and guided to the IR camera 19 by the imaging lens 17. Similarly to the above, the infrared light incident on the portion having no inclination in the inspection region returns to the emission end face of the optical fiber 13. Therefore, in the image acquired by the IR camera 19, only the portion where the inclination exists on the surface of the element substrate 31 which is the inspection target surface is bright and the other portion is dark.

  As described above, in the present embodiment, the same region of the bonding substrate 30 can be observed simultaneously by two other IR cameras 19 and 20. The direction of the tilt generated in the support substrate 33 can be specified depending on which IR camera has detected the defect. As described above, in the present embodiment, the two reflected surfaces 16a and 16b and the two IR cameras 19 and 20 reflected symmetrically with respect to the optical axis are provided, so that the reflected light from the bonded substrate 30 is obtained. The surface shape can be inspected based on the change in angle.

  In the example shown in FIGS. 2 and 3, a part of the support substrate 33 is raised at the portion where the foreign material 35 exists and is inclined, but the element substrate 31 may be deformed. Even in such a case, since the infrared light transmitted through the support substrate 33 is reflected by the tilted element substrate 31 and the metal pattern 32, a defect can be detected. When there are portions that are not perpendicular to the infrared light irradiated on the front and back surfaces of the element substrate 31 and the support substrate 33 and the metal pattern 32, the light reflected from the portions is detected by the IR cameras 19 and 20. .

  In addition, when a void exists between the element substrate 31 and the support substrate 33, each surface of the element substrate 31 and the support substrate 33 is perpendicular to the irradiated infrared light, but the void surface is in red. Oblique light, that is, oblique to the optical axis. In this case, the light reflected or refracted on the void surface is shifted laterally at the pupil position and reflected by the mirror 16 and detected by the IR camera 19 or 20. Therefore, as described above, a defective portion where a void exists is observed as a bright portion in the image.

  Conventionally, in the inspection of the bonded substrate, a defect is detected by a change in luminance of infrared reflected light or transmitted light. For this reason, there is a problem that it is difficult to detect a defect because only a minute scattered light is generated in a minute foreign matter or void inside the adhesive layer, and this luminance change is also minute. In the present invention, since the defect is inspected based on the change in the reflected light angle, even a minute foreign substance or void inside the adhesive layer 34 can be detected with high sensitivity.

  The detection of the defect can be visually determined based on the images acquired by the IR cameras 19 and 20. Or you may provide the defect determination part which determines a defect using these images. The defect determination unit can determine a defect when the difference between the luminance of the portion having no defect and the luminance of the portion having the defect exceeds a certain threshold. Or you may determine with a defect, when the difference of the brightness | luminance in the image acquired with the two cameras 19 and 20 observing the same place exceeds a certain threshold value.

  Note that, due to the influence of scattered light and diffracted light by the metal pattern 32 formed on the element substrate 31, a pseudo defect that is determined to have a defect even though there is no defect may be detected. . Such diffracted light and scattered light often have a large angle with the optical axis. Therefore, it is preferable to reduce the size of the mirror 16 so as to prevent detection of pseudo defects. Alternatively, it is possible to provide a stop so that diffracted light and scattered light do not enter the mirror 16. Thereby, defect detection accuracy can be improved.

  Further, diffracted light and scattered light may be detected in the same manner by the two IR cameras 19 and 20 arranged on the left and right. Therefore, when there is a difference between the images obtained from the IR cameras 19 and 20, it may be determined as a defect. Further, since the metal pattern 32 is a repetitive pattern, it may not be determined that a defect detected at a constant interval, such as a Die to Die inspection or a Die to reference inspection, is a defect.

Here, the defect detection sensitivity in the inspection apparatus 10 will be described with reference to FIG. FIG. 4 is a diagram for explaining the defect detection sensitivity of the inspection apparatus 10. Here, it is assumed that the bonding substrate 30 has a convex defect. If the distance from the objective lens 14 to the bonding substrate 30 is d, and the distance from the output end face of the optical fiber 13 to one of the reflection surfaces 16a of the mirror 16 is d, the surface of the bonding substrate 30 having a defect that can be detected by the inspection apparatus 10. The height from is expressed by the following equation.
2Δ = d / f

  For example, when f = 250 mm and d = 0.5 mm, Δ = 1/1000. As described above, according to the present invention, even a slight inclination caused by a foreign substance can be detected with high sensitivity. The distance between the reflecting surfaces 16a and 16b is preferably as narrow as possible. The sensitivity can be improved as the distance between the reflecting surfaces 16a and 16b is narrower. It is also possible to change the defect detection sensitivity by changing the positions of the two right-angle mirrors.

  Here, returning to FIG. 1, further components of the inspection apparatus 10 will be described. The inspection apparatus 10 further includes a comparator 21, a controller 22, and a stage 23 in addition to the components described above. In order to detect a slight inclination of the bonding substrate 30, it is important to illuminate the bonding substrate 30 at a correct angle. Therefore, in the present embodiment, servo control is performed so that the overall brightness of images acquired by the two IR cameras 19 and 20 is equal.

  The comparator 21 calculates the average brightness of the images acquired by the IR cameras 19 and 20 and compares them. When the acquired image includes a defective portion that is brighter than the other portions, the comparator 21 calculates an average luminance excluding the defective portion. The controller 22 moves the stage 23 to which the mirror 16 is attached based on the comparison result by the comparator 21.

  That is, the controller 22 moves the mirror 16 based on luminance information other than the defective portion in the image. The controller 22 has, for example, a PID control function that performs proportional control, integral control, and derivative control. Thereby, infrared light can be irradiated perpendicularly to the bonding substrate 30, and defects can be detected more accurately.

  In the present embodiment, the mirror 16 is moved. However, a tilt mechanism is provided on the XY stage 15, and control is performed to equalize the overall brightness of images detected by the two cameras. You may make it perform.

Embodiment 2. FIG.
An inspection apparatus according to Embodiment 2 of the present invention will be described with reference to FIGS. 5 and 6 are diagrams illustrating a state in which the bonded substrate is inspected in the inspection apparatus 10A according to Embodiment 2 of the present invention. The inspection apparatus 10A can determine the type of detected defect.

  In the present embodiment, the light source 11 switches and emits a plurality of infrared lights having different wavelengths. The light source 11 switches between infrared light having a wavelength reflected by the support substrate 33 and infrared light having a wavelength that passes through the support substrate 33 and emits the light. For example, the light source 11 emits infrared light having two wavelengths, center wavelengths of 1310 nm and 980 nm, according to control.

  As the support substrate 33 arranged on the side irradiated with the inspection light, a silicon wafer is usually used. When a void exists between the element substrate 31 and the support substrate 33, each surface of the element substrate 31 and the support substrate 33 is perpendicular to the irradiated infrared light, but the void surface corresponds to the infrared light. It becomes diagonal to.

  As shown in FIG. 5, when infrared light having a center wavelength of 1310 nm that passes through the support substrate 33 is emitted from the light source 11, the light reflected or refracted on the void surface is shifted laterally at the pupil position and reflected by the mirror 16. Then, it is detected by the IR camera 19 or 20. Therefore, a defective portion where a void exists is observed as a bright portion in the image.

  On the other hand, as shown in FIG. 6, when infrared light having a central wavelength of 980 nm reflected from the support substrate 33 is emitted from the light source, the irradiated infrared light is perpendicular to the infrared light. And is returned to the exit end face of the optical fiber 13. Therefore, the image acquired by the IR camera 20 is a dark image as a whole. As described above, when the support substrate 33 itself is not tilted and there is a void defect, the images acquired by the IR cameras 19 and 20 are different by switching the wavelength.

  On the other hand, as described in the first embodiment, when there is a defect due to foreign matter between the element substrate 31 and the support substrate 33 and there is an inclined surface on the surface of the support substrate 33, the light source 11 Even if the wavelength of the emitted infrared light is switched, an image with a bright defect portion where foreign matter is present is obtained. In this way, it is possible to determine whether there is a void or a foreign substance between the element substrate 31 and the support substrate 33 by switching the wavelength that transmits through the support substrate 33 and the wavelength that is reflected.

  In the above embodiment, two right-angle mirrors are used as the mirror 16, but the present invention is not limited to this. As shown in FIG. 7, two parallel plate mirrors may be used instead of the two right-angle mirrors. In this case, the infrared light emitted from the light source 11 and collected by the lens 12 is arranged between the reflecting surfaces 16 a and 16 b of the mirror 16 without using the optical fiber 13. As a result, the distance between the reflecting surfaces 16a and 16b can be shortened compared with the case of using the optical fiber 13, and the inspection sensitivity can be further improved.

  Further, the mirror 16 may have more than two reflecting surfaces. For example, the mirror 16 may have four reflecting surfaces arranged every 90 degrees around the optical axis. As such a mirror 16, for example, a mirror having four pyramidal reflection surfaces can be used. An infrared light emitting part of the light source part is provided at the apex of the pyramidal mirror 16. For example, the exit end face of the optical fiber 13 is arranged at the apex of the pyramid mirror 16.

  Then, four IR cameras that receive the reflected light from these four reflecting surfaces are provided. By imaging with these four IR cameras, it is possible to capture the deformation of the bonding substrate 30 in the vertical and horizontal directions. Thereby, it becomes possible to inspect the defect of the bonded substrate 30, that is, the surface shape more accurately.

Embodiment 2. FIG.
The configuration of the inspection apparatus according to Embodiment 2 of the present invention will be described with reference to FIG. FIG. 8 is a diagram showing a configuration of the inspection apparatus 10A according to the present embodiment. In FIG. 8, the same components as those in FIGS. 1 to 7 are denoted by the same reference numerals, and repeated description is omitted. As illustrated in FIG. 8, the inspection apparatus 10 </ b> A includes a light source 11, an objective lens 14, a mirror 16, imaging lenses 17 and 18, an optical scanner 40, and line sensors 42 and 43.

  The optical scanner 40 is disposed between the reflecting surfaces 16a and 16b of the two parallel flat mirrors. The optical scanner 40 includes a rotation mirror 41 that rotates about a rotation axis. As the rotating mirror, for example, a micro electro mechanical system (MEMS) mirror, a polygon mirror, or the like can be used. A gap (slit) is formed between the reflecting surfaces 16a and 16b, and the rotating mirror 41 is disposed in this gap. In the present embodiment, the light source unit described in the claims includes a light source 11 and a rotating mirror 41.

  The infrared light emitted from the light source 11 is reflected by the rotating mirror 41 and enters the objective lens 14. In the present embodiment, the rotating mirror 41 is the emission end face of the light source unit. The rotating mirror 41 is arranged at a position conjugate with a pupil position of an optical system described later. That is, the rotating mirror 41 is disposed on the pupil of the objective lens 14.

  The objective lens 14 collimates the incident infrared light and irradiates the bonding substrate 30 with a spot. By rotating the rotation mirror 41 of the optical scanner 40 about the rotation axis, line scanning can be performed with the beam collimated by the objective lens 14.

  The surface of the bonding substrate 30 on which the infrared light is irradiated is a flat surface, and is disposed substantially perpendicular to the beam guided by the objective lens 14. When there is no defect between the element substrate 31 and the support substrate 33, each surface of the bonding substrate 30 (the surface of the element substrate 31, the back surface and the surface of the support substrate 33, the back surface) is substantially perpendicular to the optical axis. Yes. The beam specularly reflected by the bonded substrate 30 enters the objective lens 14 again and is guided to the exit end face of the rotating mirror 41 by the objective lens 14.

  The mirror 16 reflects infrared light other than the infrared light regularly reflected by the bonding substrate 30 and guides it to the imaging lens 17 or 18. The imaging lenses 17 and 18 guide light other than the regular reflection light from the bonded substrate 30 to the imaging surfaces of the line sensors 42 and 43, respectively. Therefore, in the present embodiment, the optical system described in the claims includes the objective lens 14, the mirror 16, and the imaging lenses 17 and 18.

  The objective lens 14 serves as a collimating lens that guides infrared light from the light source 11 to the bonding substrate 30 as parallel light, and also serves as a telecentric lens. The line sensors 42 and 43 detect light reflected by the mirror 16. Based on the detection results of the line sensors 42 and 43, defects in the inspection region of the bonded substrate 30 can be detected.

  Here, an example in which reflected light from the bonding substrate 30 is detected by the line sensors 42 and 43 will be described with reference to FIG. FIG. 9 is a diagram for explaining a state in which the bonding substrate 30 is being inspected in the inspection apparatus according to the second embodiment.

  When there is no defect in the bonding substrate 30, the infrared light incident on the bonding substrate 30 is regularly reflected and returns to the direction of the rotating mirror 41. Therefore, when there is no defect in the inspection region of the bonded substrate 30, the luminance detected by the line sensors 42 and 43 becomes relatively dark.

  As shown in FIG. 9, when there is a defect in the bonding substrate 30, incident infrared light does not return to the direction of the rotating mirror 41 and enters the reflecting surface 16 a or 16 b of the mirror 16. In the example of FIG. 9, the infrared light is reflected by the reflecting surface 16 a and is guided to the line sensor 42 by the imaging lens 18. As described above, in the detection result of the line sensor 42, the brightness of the region where the defect exists is higher than the region where the defect does not exist.

  Since the surface illumination method is used in the first embodiment, if the telecentricity of the objective lens 14 is poor, the light emitted from the objective lens 14 is not perpendicular to the bonding substrate 30, and the reflected light from the bonding substrate 30 is not reflected. It may return to a place shifted in the width direction of the gap between the reflecting surfaces 16a and 16b on the pupil. When this shifted reflected light is incident on the mirror 16, a false detection of a defect occurs. In order to prevent this, if the interval between the reflecting surfaces 16a and 16b is increased, the defect detection sensitivity may be lowered.

  In the present embodiment, the infrared light reflected by the rotating mirror 41 is incident on a line passing through the center of the objective lens 14. For this reason, even if the telecentricity of the objective lens 14 is poor, the reflected light reflected by the bonded substrate 30 is shifted in the longitudinal direction of the gap formed between the reflecting surfaces 16a and 16b on the pupil. For this reason, even if the gap between the reflecting surfaces 16 a and 16 b is narrowed, the reflected light from the bonding substrate 30 does not enter the line sensors 42 and 43. Thus, the gap between the reflecting surfaces 16a and 16b can be narrowed, and the defect detection sensitivity can be improved.

  Also in the present embodiment, as described in FIG. 1, the comparator 21, the controller 22 and the like may be provided to perform servo control so that the luminance detected by the two line sensors 42 and 43 is equal. Good. Thereby, it becomes possible to detect a defect more accurately.

DESCRIPTION OF SYMBOLS 10 Inspection apparatus 11 Light source 12 Lens 13 Optical fiber 14 Objective lens 15 XY stage 16 Mirror 16a Reflecting surface 16b Reflecting surface 17 Imaging lens 18 Imaging lens 19 IR camera 20 IR camera 21 Comparator 22 Controller 23 Stage 30 Joint substrate 31 Element Substrate 32 Metal Pattern 33 Support Substrate 34 Adhesive Layer 35 Foreign Material 36 Void 40 Optical Scanner 41 Rotating Mirror 42 Line Sensor 43 Line Sensor

Claims (25)

A light source that emits infrared light;
An optical system that causes the infrared light emitted from the light source unit to enter the inspection target as parallel light substantially perpendicularly, and guides reflected light from the inspection target;
A light detection unit that detects light other than regular reflection light among the reflected light guided by the optical system;
The front light source unit is an inspection apparatus arranged at a pupil position of the optical system. The light detection unit has two light detectors,
The inspection apparatus according to claim 1, wherein the optical system guides light other than the specularly reflected light to the two photodetectors.   The optical system includes two reflecting surfaces that are arranged symmetrically with respect to an optical axis and reflect light other than specularly reflected light from the inspection target and guide the light to the two photodetectors, respectively. The inspection device described.   The inspection apparatus according to claim 3, further comprising a moving mechanism that moves at least one of the reflection surface and the inspection target based on luminance information respectively acquired by the two photodetectors.   The inspection apparatus according to claim 1, wherein the inspection target is a bonded substrate in which an element substrate and a support substrate are bonded to each other through an adhesive layer.   The inspection apparatus according to claim 1, wherein the light source unit switches and emits a plurality of infrared lights having different wavelengths.   The inspection apparatus according to claim 5, wherein the light source unit switches between infrared light having a wavelength reflected by the element substrate and infrared light having a wavelength transmitted through the element substrate. The light detection unit has four light detectors,
The inspection apparatus according to claim 1, wherein the optical system guides light other than the regular reflection light to the four photodetectors.   The optical system includes four reflecting surfaces that are arranged every 90 degrees around an optical axis and reflect light other than specularly reflected light from the inspection target and guide the light to the four photodetectors, respectively. The inspection device described in 1.   The inspection apparatus according to claim 1, wherein the light source unit further includes an optical fiber that guides the infrared light and has an emission end face disposed at a pupil position of the optical system. The light source unit irradiates the inspection object with planar infrared light,
The inspection apparatus according to any one of 1 to 10, wherein the light detection unit captures an image of the inspection target. The light source unit irradiates the inspection object with planar infrared light,
The light detection unit captures an image of the inspection target,
The inspection according to claim 4 or 9, wherein the moving mechanism moves at least one of the reflection surface and the inspection target based on luminance information other than a defective portion in the image acquired by the light detection unit. apparatus.   The inspection apparatus according to claim 1, wherein the light source unit further includes a rotatable mirror that reflects the beam of infrared light and performs line scanning on the inspection object. Infrared light emitted from the light source unit arranged at the pupil position of the optical system is incident as a parallel light on the inspection object substantially perpendicularly,
Of the reflected light from the inspection object, light other than regular reflected light is detected by the light detection unit,
An inspection method for detecting a defect to be inspected based on luminance information obtained by the light detection unit.   The inspection method according to claim 14, wherein lights other than the regular reflection light are respectively guided to two photodetectors having different light detection units.   The two reflecting surfaces arranged symmetrically with respect to the optical axis guide light other than the specularly reflected light from the inspection object to two different photodetectors of the light detection unit, respectively. 15. The inspection method according to 15.   The inspection method according to claim 16, wherein at least one of the reflection surface and the inspection object is moved based on luminance information respectively acquired by the two photodetectors.   The inspection method according to any one of claims 14 to 17, wherein a plurality of infrared lights having different wavelengths are switched and emitted to the inspection target.   The inspection target is a bonded substrate in which an element substrate and a support substrate are bonded to each other via an adhesive layer, and infrared light having a wavelength reflected by the element substrate and infrared light having a wavelength that transmits the element substrate. The inspection method according to any one of claims 14 to 18, wherein:   20. The inspection method according to claim 14, wherein light other than the specularly reflected light from the inspection target is guided to four photodetectors different from each other in the light detection unit.   21. The inspection method according to claim 20, wherein light other than specularly reflected light from the inspection object is guided to the four different photodetectors by four reflective surfaces arranged every 90 degrees around the optical axis.   The inspection method according to any one of 14 to 21, wherein the inspection object is irradiated with planar infrared light to capture an image of the inspection object. Irradiating the inspection object with planar infrared light to capture an image of the inspection object,
The inspection method according to claim 16 or 21, wherein at least one of the reflection surface and the inspection target is moved based on luminance information other than a defective portion in the image acquired by the light detection unit.   The inspection method according to any one of claims 14 to 21, wherein the inspection target is line-scanned by reflecting the infrared light beam by a rotating mirror. Using the inspection method according to claim 14 to 24, the defect inspection of the bonded substrate in which the element substrate and the support substrate are bonded together through an adhesive layer is performed,
Polish the back of the element substrate in the bonded substrate after inspection,
A method of manufacturing a semiconductor device for peeling off the support substrate.

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