Optical apparatus, inspection apparatus, and alignment method

Abstract

This reduces the time required for alignment processing, enabling efficient inspection of optical waveguides provided in optical integrated circuits. [Solution] This invention is an optical device for inspecting an optical integrated circuit, comprising: a light source that emits light; an illumination optical unit that shapes the light emitted by the light source into a predetermined shape; a modulation unit that receives the light shaped by the illumination optical unit and modulates the received light with the spatial light modulator to emit light having a predetermined pattern shape; and a light guide unit that guides the light emitted from the modulation unit to the input end of an optical waveguide provided in the optical integrated circuit.

Description

Technical Field

[0001] This invention relates to a technique for inspecting an optical integrated circuit, and more particularly to an alignment technique for optimizing the incident position of light incident on an optical waveguide for inspection.

Background Art

[0002] In semiconductor devices for information processing, as the functions and integration density increase, the amount of heat generated also increases, and further suppression of power consumption is strongly required. To meet such requirements, silicon photonics technology has attracted attention. This technology aims to provide low-loss and wide-bandwidth processing by providing a fine optical waveguide formed of a semiconductor material on a semiconductor device and using optical information transmission.

[0003] The optical waveguide used in an optical integrated circuit to which silicon photonics technology is applied has an end point that is a fine single-mode waveguide with a size of, for example, about 4 μm. Therefore, when inspecting the optical integrated circuit in the manufacturing process, for example, it is necessary to adjust the incident position of the inspection light incident on the optical waveguide with high resolution and accuracy.

[0004] The process of optimizing the incident position of the inspection light on the optical waveguide to align the optical axis between the optical system of the inspection apparatus and the optical waveguide is generally referred to as alignment processing (or simply alignment). In this regard, for example, Patent Document 1 describes a technique for inspecting an optical waveguide after performing alignment processing between the inspected optical waveguide and the inspection apparatus. In this prior art, an optical waveguide device to be inspected, an irradiation optical unit for injecting inspection light into one end of the optical waveguide, and a condensing optical unit for receiving light emitted from the other end of the optical waveguide are each attached to a movable stage. Then, the alignment for aligning the optical axes of these respective parts, that is, the alignment processing, is mechanically performed by a moving mechanism coupled to the movable stage.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Patent No. 6331196 specification [Overview of the project] [Problems that the invention aims to solve]

[0006] In the conventional technology described above, a moving mechanism with high positioning accuracy is required to achieve high-precision alignment, and the speed of this mechanism becomes the limiting factor in speeding up the alignment process. In particular, in actual optical devices such as optical integrated circuits, multiple channels of optical waveguides are often provided, and sequentially performing alignment on each of them takes a long time. For this reason, there is a need for a technology that can perform alignment in a shorter time and suppress the increase in processing time, especially for multiple-channel optical waveguides.

[0007] This invention has been made in view of the above-mentioned problems, and aims to propose a technology that significantly reduces the time required for alignment processing and enables efficient inspection of optical waveguides provided in optical integrated circuits. [Means for solving the problem]

[0008] One aspect of the present invention relates to an optical device for inspecting an optical integrated circuit. This optical device includes a light source that emits light, an illumination optical unit that shapes the light emitted by the light source into a predetermined shape, a modulation unit that receives the light shaped by the illumination optical unit and modulates the received light with the spatial light modulator to emit light having a predetermined pattern shape, and a light guide unit that guides the emitted light from the modulation unit to the input end of an optical waveguide provided in the optical integrated circuit.

[0009] In this optical device, the spatial light modulator forms an emitted light with a predetermined pattern shape, making it possible to emit a light beam with a smaller spot size from the light shaped by the illumination optics. For example, it is possible to emit a beam light with a spot size narrowed to the extent that waveguide mode coupling with the optical waveguide is possible. Furthermore, the spatial light modulator allows for electrical control to set the position from which the light is emitted. By changing the emission position of the light from the spatial light modulator, the incident position of the light on the optical waveguide also changes.

[0010] In other words, the positional relationship between the input end of the optical waveguide and the light directed towards it can be changed by electrical control without substantially relying on mechanical movement. This means that the alignment of the irradiation optical unit and the optical waveguide, which is performed by relative movement using mechanical movement in the conventional technology described above, can be replaced by positional changes using only electrical control. Therefore, compared to the conventional technology which involves mechanical movement, it becomes possible to perform the alignment process between the optical waveguide and the optical device that incidents light into it at a significantly faster speed.

[0011] Furthermore, by appropriately setting the modulation pattern of the spatial light modulator, it is possible to generate multiple small-diameter beams. This means that if the optical integrated circuit under inspection has multiple optical waveguides, it is possible to simultaneously inject light into them. In other words, even if the optical integrated circuit has multiple optical waveguides, it is possible to perform alignment processing on them in parallel, which can significantly reduce processing time compared to sequential processing.

[0012] Another aspect of the present invention relates to an inspection device for inspecting an optical integrated circuit. This inspection device comprises a holding unit for holding the optical integrated circuit to be inspected, a light emitting unit having the same configuration as the optical device described above and for injecting light as inspection light into the input terminal provided on the optical integrated circuit, a light receiving unit for receiving light emitted from the output terminal of the optical waveguide as light to be detected, and a control unit for controlling the spatial light modulator to adjust the incidence position of the inspection light to the input terminal.

[0013] In the inspection apparatus configured in this way, as described above, inspection light is incident on the optical waveguide while electrically controlling the incident position, and the light emitted from the optical integrated circuit is received, making it possible to determine the relationship between the incident position of the inspection light on the optical waveguide and the amount of light emitted from the optical integrated circuit. Using this result, it is possible to perform alignment processing between the light emission unit and the optical waveguide.

[0014] As described above, the alignment process performed in this manner can be executed at a higher speed than conventional techniques involving mechanical movement. Furthermore, even when there are multiple optical waveguides, the processing for each can be performed in parallel, thus suppressing the length of the processing time. In the most preferable state, the processing time for multiple optical waveguides can be the same as that for a single optical waveguide.

[0015] Another aspect of the present invention relates to a method for aligning an optical waveguide for characteristic testing of an optical integrated circuit. This alignment method modulates light emitted from a light source and shaped into a predetermined form using a spatial light modulator placed in the optical path of the optical waveguide to emit light with a predetermined pattern shape, and while changing the pattern shape of the emitted light by the spatial light modulator over time, the emitted light from the spatial light modulator is incident on the input end of the optical waveguide as test light, thereby scanning the incident position of the test light on the input end, and while scanning the test light, light emitted from the output end of the optical waveguide is received as light to be detected, and the emission position of the emitted light is set to the position where the amount of received light of the light to be detected is maximum when the test light is scanned.

[0016] Even in the alignment method configured as described above, by changing the emission position of the light emitted from the spatial light modulator over time, while scanning the light incident on the optical waveguide, the light emitted from the optical waveguide is received. Since it is considered that the received light amount becomes maximum in the state where alignment is achieved, the alignment process can be completed by setting the emission position of the light emitted from the spatial light modulator so that such conditions are satisfied. As described above, high-speed processing is possible, and even when there are a plurality of optical waveguides to be processed, an increase in processing time is suppressed.

Advantages of the Invention

[0017] As described above, according to the present invention, the time required for the alignment process can be significantly shortened.

Brief Description of the Drawings

[0018] [Figure 1] It is a block diagram showing a schematic configuration of an embodiment of an inspection apparatus according to the present invention. [Figure 2] It is a diagram for explaining the structure and operation of the light emitting unit in more detail. [Figure 3] It is a diagram schematically showing the structure of a MEMS phased array. [Figure 4] It is a diagram for explaining the principle of the alignment process in this embodiment. [Figure 5] It is a diagram for explaining another example of the structure of the light emitting unit. [Figure 6] It is a flowchart showing the alignment process and characteristic inspection of this embodiment. [Figure 7] It is a diagram showing the principle of the process for determining the scanning range.

Modes for Carrying Out the Invention

[0019] FIG. 1 is a block diagram showing a schematic configuration of an embodiment of an inspection apparatus according to the present invention. This inspection apparatus 1 is an apparatus for inspecting the characteristics of an optical waveguide incorporated in a substrate. More specifically, the inspection apparatus 1 uses, as a work W to be inspected, a semiconductor device in which an optical waveguide G is formed of a semiconductor material or the like on a semiconductor substrate S such as silicon, like an optical integrated circuit, to inspect the optical characteristics of the optical waveguide. The optical waveguide formed of a semiconductor material in this way is generally a single-mode waveguide.

[0020] The inspection apparatus 1 mainly includes a light emitting unit 3 that generates inspection light, a holding unit 5 that holds the work W, a light receiving unit 7 that receives light emitted from the work W, and a control unit 9 that controls the operations of these units. In FIG. 1, solid arrows indicate the optical path of light, and dotted arrows indicate the flow of electrical signals.

[0021] The light emitting unit 3 generates inspection light necessary for inspecting the optical waveguide and irradiates the work W with it. For this purpose, the light emitting unit 3 includes a light source 31, an illumination optical unit 33, a modulation unit 35 including a spatial light modulator 40, a projection optical unit 37, and a reflection mirror 39. The light source 31 is a laser light source that emits light having a wavelength through which the optical waveguide is transmissive, for example, infrared light in the T band. The illumination optical unit 33 shapes the laser light emitted from the light source 31 into a line beam.

[0022] The modulation unit 35 has a spatial light modulator 40, and modulates and outputs the line beam emitted from the illumination optical unit 33 by the spatial light modulator 40. This will be described in detail later. The modulated light beam is condensed by a projection optical unit 37 including a converging lens described later, the optical path is folded back substantially horizontally by the reflection mirror 39, and is irradiated onto the side surface of the work W held by the holding unit 5. The reflection mirror 39 contributes to the compactification of the light emitting unit 3 by folding back the optical path, and is used for the incident angle of light with respect to the work W by changing the inclination as necessary.

[0023] The holding unit 5 comprises a stage 51 that holds the workpiece W in a horizontal position and a stage moving unit 53 that moves the stage 51. The stage moving unit 53 moves the stage 51 in the XYZ-θ direction by an appropriate drive mechanism. Here, the XY plane is the horizontal plane, and the Z axis is the vertically upward direction. The θ direction is the rotational direction around the Z axis. The XYZ coordinate axes shown in Figure 1 indicate the position and direction of the stage 51 and the workpiece W, and are used in subsequent drawings to consistently show the direction.

[0024] In other words, the stage 51 is capable of horizontal and vertical movement, as well as rotation around a vertical axis. This allows the workpiece W held on the stage 51 to be positioned in a location suitable for inspection. Depending on the configuration of other parts of the apparatus, at least some of these movement axes may be omitted.

[0025] The light-receiving unit 7 receives light emitted from the optical waveguide G of the workpiece W. For this purpose, the light-receiving unit 7 includes a light receiver 73 that generates a signal corresponding to the amount of incident light, and a light-receiving optical unit 71 that collects the light emitted from the workpiece W and guides it to the light receiver 73. The light receiver 73 is a photosensor having at least one-dimensional, more preferably two-dimensional, positional resolution, and image sensors such as CCD sensors and CMOS sensors can be suitably applied.

[0026] The control unit 9 includes at least a processor 91 that executes a pre-prepared control program and controls the above-mentioned parts of the device to perform predetermined operations, and a storage unit 93 for storing various types of information. The processor 91 can be a combination of a central processing unit (CPU), a microprocessing unit (MPU), a graphics processing unit (GPU), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), etc. The storage unit 93 can be a combination of a memory such as RAM (Random Access Memory) for short-term data storage, and an HDD (Hard Disk Drive) and SSD (Solid-State Disk) for longer-term data storage. For example, a personal computer device with a general hardware configuration may be used as the control unit 9.

[0027] The control unit 9 positions the workpiece W in the appropriate position by controlling the holding unit 5. It also controls the light emission unit 3 to emit the inspection light necessary for inspection. Furthermore, it controls the light receiving unit 7 to receive a signal representing the amount of light received from the light receiving unit 7, and measures the optical characteristics of the optical waveguide G based on that signal.

[0028] Figure 2 is a diagram illustrating the structure and operation of the light emission section in more detail. Note that, for the purpose of explaining the principle, optical elements such as lenses are shown as single components in the diagram, but they may be configured as an optical system combining multiple optical elements. Also, in the diagram, the dashed line indicates the optical axis of the optical system constituting the light emission section 3, and the dotted line schematically shows the spread of the light rays.

[0029] The illumination optics unit 33 includes a cylindrical lens 331, a collimating lens 332, and a cylindrical lens 333, which are arranged in order along the optical path of the light emitted from the light source 31 in the (-X) direction. The cylindrical lens 331 has power in the Y direction but no power in the Z direction, and spreads the laser light emitted from the light source 31 in the Y direction. The spread laser light is then shaped into collimated light by the collimating lens 332. Therefore, the laser light emitted from the collimating lens 332 is a line beam with a flattened light intensity distribution with the Y direction as its longitudinal direction.

[0030] The line beam is focused in the Z direction by a cylindrical lens 333 that has power in the Z direction and converges to the reflective surface of a spatial light modulator 40 provided in the modulation unit 35. The spatial light modulator 40 is a MEMS (Micro Electro Mechanical Systems) phased array. The spatial light modulator 40 reflects light incident in the (-X) direction in the (-Z) direction and changes the reflection pattern according to control commands from the control unit 9, thereby spatially modulating the emitted light. The modulated light is focused by a focus lens 371 provided in the projection optics unit 37 and reflected back in the (+X) direction by a reflection mirror 39, and incident on the (-X) side end face of the workpiece W as inspection light. The focus lens 371 is positioned so that the inspection light is focused on the (-X) side end face of the workpiece W. As a result, the workpiece W is irradiated with an optical beam that is narrowed to less than or equal to the numerical aperture (NA) of the optical waveguide G as inspection light. In this embodiment, the projection optics unit 37 projects the image formed on the spatial light modulator 40 onto the (-X) side end face of the workpiece W, reducing its size.

[0031] Next, the configuration of the spatial light modulator 40 will be described. The spatial light modulator 40 is, for example, a movable ribbon-type MEMS (Micro Electro Mechanical Systems) phased array. In this embodiment, the MEMS phased array is used as a programmable one-dimensional diffraction grating type optical modulator that diffracts incident light and emits it, and changes the emission pattern over time. Hereinafter, the MEMS phased array may be referred to as a "diffractive optical element". As a diffractive optical element (DOE), for example, a GLV (Grating Light Valve; "GLV" is a registered trademark of Silicon Light Machines) element can be suitably applied.

[0032] Figure 3 is a schematic diagram showing the structure of a MEMS phased array. More specifically, Figure 3(a) is a schematic diagram showing the general configuration of a spatial light modulator 40, which is one form of a MEMS phased array. Figure 3(b) shows the possible states of the spatial light modulator 40. Figure 3(c) shows the operation of the spatial light modulator 40 in this embodiment.

[0033] As shown in Figure 3(a), the spatial light modulator 40 has a general configuration in which a plurality of movable ribbons 402 are arranged on a substrate 401, facing the surface of a flat bottom electrode 403, and spaced at regular intervals in a direction parallel to the surface of the bottom electrode 403. The upper surface of each movable ribbon 402 is a reflective surface that reflects light, for example, by a metal coating. Each of the movable ribbons 402 is fixed to the bottom electrode 403 at a regular interval. That is, the distance between the movable ribbons 402 and the bottom electrode 403 is defined by a pair of post anchors 404 erected on the substrate 401 so as to sandwich the bottom electrode 403.

[0034] In the following explanation, in order to consistently indicate the direction in the spatial light modulator 40 while distinguishing it from the spatial coordinates shown in Figure 1, etc., we will set up orthogonal coordinates as shown in Figure 3(a). Of the directions along the surface of the substrate 401, the longitudinal direction of each of the multiple movable ribbons 402 will be the Dx direction, and the arrangement direction of the movable ribbons 402 will be the Dy direction. In addition, the direction perpendicular to the surface of the substrate 401 will be the Dz direction.

[0035] In the spatial light modulator 40, numerous movable ribbons 402, whose longitudinal direction is the Dx direction, are arranged in the Dx direction. The overall length of the spatial light modulator 40, which is an assembly of these ribbons, is greater in the Dy direction than in the Dx direction. Therefore, when considering the spatial light modulator 40 as a whole, the Dy direction can be considered its longitudinal direction.

[0036] The movable ribbon 402 is displaceable relative to the bottom electrode 403. Specifically, as shown in Figure 3(b), when a control voltage V is applied between the movable ribbon 402 and the bottom electrode 403, the movable ribbon 402 deforms due to electrostatic force and is displaced in the direction of approaching and separating from the bottom electrode 403, i.e., in the Dz direction, as shown by the solid and dotted lines. The amount of displacement of the movable electrode 402 depends on the magnitude of the control voltage V. The modulation unit 35 is provided with a drive circuit (e.g., a CMOS driver) 351 that operates in response to a control command from the control unit 9, and the control voltage V is applied to the movable ribbon 402 from this drive circuit 351.

[0037] The control voltage V supplied from the drive circuit 351 can be set individually for each movable ribbon 402. Therefore, the height of each movable ribbon 402 in the Dz direction can be individually controlled by the magnitude of the control voltage V. Consequently, when the surfaces of multiple movable ribbons 402 are viewed macroscopically, various uneven patterns can be realized due to the differences in the height of each movable ribbon 402.

[0038] For example, as shown in Figure 3(a), when all the movable ribbons 402 have the same surface height, the surfaces of the movable ribbons 402 as a whole form a planar mirror. That is, when light is incident on the surface of the movable ribbons 402, the specularly reflected light is emitted from the surface of the movable ribbons 402. In other words, the surface of the spatial light modulator 40, which is an assembly of movable ribbons 402, acts as a planar mirror.

[0039] On the other hand, if a step of one-quarter wavelength of light is created between adjacent movable ribbons 402, a half-wavelength difference in optical path length is created between the light reflected by each movable ribbon 402, and these lights cancel each other out and are not emitted to the outside. In this way, by individually controlling the displacement of each movable ribbon 402, it becomes possible to make the reflection pattern of light from the spatial light modulator 40 vary in various ways.

[0040] The use of the spatial light modulator 40 in this embodiment is shown in Figure 3(c). Specifically, the spatial light modulator 40 is arranged such that the longitudinal direction of the incident light, which is incident as a line beam LB, is the Dy direction, and by partially reflecting the line beam LB in the Dy direction, it emits a spot light beam SB with a small spot size in the Dy direction. By reflecting light from a plurality of discretely arranged movable ribbons 402, it is possible to generate multiple spot light beams SB simultaneously from a single line beam LB, as shown in Figure 3(c).

[0041] The relationship between the orientation of the spatial light modulator 40 in the real space where it is installed and its XYZ coordinates is as follows. First, the Dy direction, which is the longitudinal direction of the spatial light modulator 40, corresponds to the Y direction in real space. That is, the spatial light modulator 40 is positioned so that its longitudinal direction coincides with the longitudinal direction of the line beam LB. Therefore, the spatial light modulator 40 has resolution in the longitudinal direction of the incident line beam LB. Also, the incident direction of the line beam LB corresponds to the X direction, more specifically the (-X) direction, and the exit direction of the spot light beam SB corresponds to the Z direction, more specifically the (-Z) direction.

[0042] Thus, the spatial light modulator 40 in this embodiment generates multiple spot light beams SB from the line beam LB, that is, it has the function of multi-spotting the line beam. Since the movable ribbon 402 from which light is reflected can be arbitrarily changed by electrical control, the arrangement pattern of the spot light beams SB emitted from the spatial light modulator 40 can be set in various ways, and moreover, the arrangement pattern can be changed over time. For this reason, it is possible to simultaneously perform optical scanning of the irradiated object with multiple spot light beams.

[0043] When using the aforementioned GLV element as the spatial light modulator 40, products with a switching frequency of 100 kHz or higher are available, so by using such an element, this optical scanning can be performed at extremely high speed.

[0044] As will be explained below, in the inspection apparatus 1 of this embodiment, such high-speed optical scanning is applied to the alignment process between the apparatus and the workpiece W. That is, in the conventional technology, the relative position between the optical system of the apparatus and the workpiece is mechanically changed while inspection light is incident on the optical waveguide and the emitted light is detected, but in this embodiment, instead of such mechanical movement, optical scanning by a spatial light modulator 40 is used.

[0045] Figure 4 illustrates the principle of the alignment process in this embodiment. Figure 4(a) schematically shows the path of light during the alignment process. For the purpose of explaining the principle, some optical elements on the optical path that do not hinder the explanation are omitted in Figure 4(a), and the folding of the optical path is ignored. In this example, three optical waveguides G are provided on the workpiece W, with their input terminals on the (-X) side of the workpiece W and their output terminals on the (+X) side. In reality, the positional relationship between the input and output terminals of the optical waveguides is not limited to this, but in that case, the light receiving unit 7 should be positioned according to the position of the output terminals. In general structures, the input and output terminals of the optical waveguides are not fixedly defined and are interchangeable. Also, appropriate optical circuit elements, such as filters and switches, may be interposed in the optical waveguides G.

[0046] As described above, the line beam LB emitted from the illumination optics unit 33 is converted into one or more spot light beams SB by the spatial light modulator 40. Here, three spot light beams SB are emitted from the spatial light modulator 40 corresponding to the three optical waveguides G and irradiate the (-X) side surface of the workpiece W.

[0047] If the conditions for a spot light beam SB irradiated onto the input end of an optical waveguide G are met, the light will be transmitted through the optical waveguide G and emitted from the output end on the (+X) side. Conversely, the purpose of alignment processing is to adjust the incident position and direction of the spot light beam SB so that the light irradiated onto the input end is emitted from the output end. The conditions required for the incident light are as follows:

[0048] The optical waveguide formed in the optical integrated circuit is generally a single-mode waveguide, and therefore the incident spot light beam SB must have its optical center precisely aligned with the optical axis of the optical waveguide G. In addition, the incident light must be focused to less than or equal to the numerical aperture of the optical waveguide G. In this embodiment, the spot light beam SB emitted from the spatial light modulator 40 is shaped by the projection optics unit 37, and these conditions are satisfied by injecting it into the input end of the optical waveguide G as a converged light beam such that the irradiation range (for example, the range containing 90% of the total light intensity of the spot light beam SB) is contained within the end face of the optical waveguide G.

[0049] In current optical integrated circuits, the cross-sectional size of optical waveguides is mainly around 3 to 5 μm. When using the GLV element described above as the spatial light modulator 40, it is possible to generate a spot light beam SB with a spot size of this magnitude by combining it with an appropriate optical system (e.g., a reduction optical system). In this embodiment, the spot size of the spot light beam SB is adjusted by appropriately setting the number of movable ribbons 402 that form one spot light beam SB and the beam projection magnification in the projection optical unit 37.

[0050] However, adjustment is required separately to align the optical center with the optical axis of the optical waveguide G. For this adjustment, the optical scanning by the spatial light modulator 40 described above is used. That is, as shown in Figure 4(a), the position of the spot light beam SB can be changed in the Y direction by controlling the spatial light modulator 40. Then, as shown by the dotted circle in Figure 4(b), the incident position of the spot light beam SB, which is the inspection light, with respect to the input end of the optical waveguide G is scanned in the Y direction by the spatial light modulator 40, and the emitted light Lo from the output end at each time is received by the light receiving unit 7 as the light to be detected, and the amount of received light is determined. This makes it possible to determine the correlation between the incident position of the inspection light and the corresponding amount of light to be detected.

[0051] When the amount of received light is at its maximum, the optical center of the spot light beam SB and the optical axis of the optical waveguide G are considered to be in the best alignment. Therefore, the objective of the alignment process is achieved by determining the incident position of the spot light beam SB when the amount of received light is at its maximum and identifying the reflection pattern of the spatial light modulator 40 necessary to cause the spot light beam SB to be incident at this position. In other words, if the line beam LB is incident while the spatial light modulator 40 is controlled to produce the reflection pattern thus identified, the spot light beam SB will be irradiated onto the input end with its optical center in good alignment with the optical axis of the optical waveguide G.

[0052] In this type of processing, changing the incident position of the spot light beam SB relative to the optical waveguide G does not require mechanical movement between them, and the switching speed of the reflection pattern of the spatial light modulator 40, controlled by an electrical control signal, becomes the limiting factor in the processing. Since such switching is much faster than mechanical movement, the time required for alignment processing is also greatly reduced.

[0053] As mentioned above, the spot light beam SB can be emitted from each position of the spatial light modulator 40 at any timing, and it is also possible to emit multiple spot light beams SB independently of each other. Therefore, it is possible to perform alignment processing for multiple optical waveguides G (specifically, optical scanning, detection of the amount of received light, and determination of the reflection pattern based thereon) in parallel. As a result, even when multiple optical waveguides G are provided in the optical integrated circuit, the increase in processing time can be suppressed.

[0054] In this explanation, we described the case where alignment is performed by optical scanning in the X direction. However, there may be cases where the position of the optical waveguide changes in the Z direction due to, for example, warping of the workpiece W, and alignment is required in this direction. In this case, by using a spatial optical modulator with two-dimensional resolution, it is possible to achieve two-dimensional optical scanning of the optical waveguide G, as shown in Figure 4(c). Then, from the detection results of the amount of received light in the Y and Z directions, a two-dimensional reflection pattern that maximizes the amount of received light can be determined.

[0055] Suitable two-dimensional spatial light modulators include, for example, Silicon Light Machines' PLV (Planar Light Valve; "PLV" is a registered trademark of the company) elements, or LCOS (Liquid Crystal on Silicon) elements, which are a type of liquid crystal optical element.

[0056] Figure 5 illustrates another example of the structure of the light emission unit. More specifically, Figure 5 shows an example configuration of a light emission unit capable of performing two-dimensional optical scanning with respect to the optical waveguide G. The illumination optical unit 33b in the example configuration shown in Figure 5 includes a convex lens 331b, a concave lens 332b, a convex lens 333b, and a polarizer 334 arranged in order along the optical path of light emitted from the light source 31 in the (-X) direction. In addition, a two-dimensional spatial light modulation element, such as an LCOS element, is provided as the spatial light modulator 40b of the modulation unit 35.

[0057] Light emitted from the light source 31 is shaped into a Gaussian beam of a predetermined size by the convex lens 331b, concave lens 332b, and convex lens 333b of the illumination optics unit 33b. Here, "shaping" the light includes not only changing the shape of the beam in cross-sectional view, but also expanding or contracting the beam diameter. For example, a light beam with a rectangular or elliptical cross-sectional shape and an appropriate spot size is shaped by the illumination optics unit 33b. The polarizer 334 aligns the polarization of the light incident on the spatial light modulator 40b by transmitting light of a specific polarization.

[0058] The spatial light modulator 40b generates multiple spot light beams SB by phase-modulating the light incident from the illumination optical unit 31b at a reflective surface. The spot light beams SB formed in the illumination optical unit 40b are incident on the input end of the optical waveguide G in the workpiece W via the projection optical unit 37 and the reflective mirror 39. The projection optical unit 37 converges the multiple spot light beams SB at the input end of the optical waveguide G. The reflective mirror 39 then reflects the spot light beams SB in the (+X) direction and incidents them on the (-X) side end face of the workpiece W as inspection light.

[0059] The spatial light modulator 40b can change the incident position of the spot light beam SB into the optical waveguide G in either the Y or Z direction by controlling the phase modulation pattern of the LCOS element.

[0060] When light emitted from the output end of an optical waveguide is received by an optical fiber, the optical axes of the optical waveguide and the optical fiber must also be aligned on the output side. In this embodiment, since the light emitted from the optical waveguide is received by a one-dimensional or two-dimensional image sensor, precise alignment processing on the output side is not necessary as long as the emitted light does not fall outside the receiving area of ​​the image sensor.

[0061] Figure 6 is a flowchart showing the processing details of the alignment process and characteristic inspection based on the results of the alignment process in this embodiment, based on the above principle. This process is realized by the processor 91 of the control unit 9 executing a procedure defined in a predetermined control program and causing each part of the device to operate cooperatively. First, the workpiece W, which is the object to be inspected, is brought into the device and placed on the stage 51 (step S101). Each part of the device is set to its initial state (step S102). For example, the stage 51 is positioned at a predetermined initial position.

[0062] Next, alignment adjustment is performed to position the workpiece W within the apparatus at a predetermined specified position (step S103). The content of the alignment adjustment is arbitrary. For example, a technique can be applied in which alignment marks are pre-marked on the workpiece W, and the stage 51 is moved based on the results of position detection obtained by imaging these marks with a camera or the like.

[0063] Furthermore, if the design data for the workpiece W is available, alignment adjustment can be performed as follows. Specifically, at least one, more preferably two, of the optical waveguides G provided in the workpiece W are predetermined as reference waveguides, and inspection light is irradiated from the light emission unit 3 toward the position of the input end of the reference waveguide determined from the design data, while the light emitted from the reference waveguide is detected by the light receiving unit 7. The control unit 9 operates the stage moving unit 53 to position the stage 51 so that the amount of received light is maximized. Alignment adjustment can be performed in this way. This method is particularly effective for tilt around the θ axis (Figure 1).

[0064] Next, the position of the optical waveguide G provided in the workpiece W is detected, and based on the result, the range in which the optical scan will be performed in step S106 described later is determined (steps S104, S105). Note that if the position of the optical waveguide G can be determined in advance from the design data, these processing steps can be omitted. In this process, the end face of the workpiece W is optically scanned at a relatively coarse pitch, and the amount of light received by the light receiving unit 7 is detected (step S104). If the input end of the optical waveguide G is at the incident position of the inspection light, the light will be emitted from the output end of the optical waveguide G. By detecting this, it is possible to estimate the approximate position of the optical waveguide G even if its position is unknown.

[0065] Figure 7 shows the principle of the process for determining the scanning range. Here, we consider an example where five optical waveguides G are arranged on the workpiece G at an uneven pitch. As shown in Figure (a), the end face of the workpiece G is optically scanned by changing the incident position of the inspection light in the Y direction over time, and the amount of light received by the light receiving unit 7 (detected light) is detected at each position (step S104). Then, as shown in Figure (c), a peak in light intensity appears near the position where the optical waveguide G is provided. In other words, it can be estimated that an optical waveguide G is provided near such a peak.

[0066] Furthermore, in optical scanning using the spatial light modulator 40, it is possible to simultaneously incident multiple inspection beams on different positions of the object being scanned. For this reason, as shown in Figure (b), the scanning range of the workpiece W may be divided into multiple blocks, and optical scanning of these blocks may be performed in parallel. This reduces the time required to optically scan the entire workpiece W by half. Here, the workpiece W is scanned in two blocks, but it may also be divided into three or more blocks, which will further reduce the required time.

[0067] As a further method to shorten processing time, instead of sequential optical scanning, for example, multiple spot light beams SB may be simultaneously irradiated in the Y direction at regular intervals, and the amount of light received at each position may be detected. This method is particularly effective when the arrangement pitch of optical waveguides G in the workpiece W is relatively wide.

[0068] At this stage, a relatively coarse optical scan is performed, so the peak position does not necessarily indicate the optimal position for alignment. Also, the peak height varies depending on the incident light position. Thus, the detected peaks only indicate regions where there is a high probability that an optical waveguide G exists. Therefore, as shown in Figure (d), a relatively narrow scanning range including the peak position of the received light intensity is set for each peak (step S105), and a narrow-pitch optical scan is performed within these scanning ranges to achieve high-precision alignment.

[0069] In other words, partial optical scanning is performed for each of the scanning ranges set in step S105 at a narrower pitch than in step S104, and the amount of received light is detected (step S106). The scanning pitch and the positional resolution of the light receiving unit 7 are the main factors that determine the accuracy of the alignment process. When GLV is used as the spatial light modulator 40, it is possible to achieve a beam diameter of 4 μm or less for the spot light beam SB and a scanning pitch of about (1 / 3) of the beam diameter.

[0070] Then, for each peak in the obtained light intensity profile, its peak position, that is, the position where the light intensity is maximum, is identified (step S107). The position thus identified can be said to represent the incident position of the inspection light when alignment is achieved for each optical waveguide G.

[0071] From these results, the optimal reflection pattern for the spatial light modulator 40 for the characteristic test to be performed later can be determined. For each optical waveguide G, the reflection pattern that allows the test light to be incident at a position where the light intensity of the light to be detected is maximum corresponds to the "optimal" reflection pattern. The determined reflection pattern can be stored in the storage unit 93 as a control amount for each movable ribbon 402 to realize it. By controlling each movable ribbon 402 of the spatial light modulator 40 based on the stored control amount, the reflection pattern is set to the optimal one (step S108), and then the characteristic test is performed in that state (step S109), so that the characteristic test can be performed with alignment achieved in each of the optical waveguides G.

[0072] The content of the characteristic inspection is arbitrary, and various physical properties necessary for evaluating the optical characteristics of the optical waveguide can be measured. Commonly used optical characteristics that represent the quality of an optical waveguide include insertion loss, near-field pattern (NFP), far-field pattern (FFP), and polarization characteristics, and these evaluation items can also be measured in the characteristic inspection in step S109.

[0073] Performing the above process only once may not be sufficient to inspect all waveguides G on the workpiece W. For example, this may occur if the size of the workpiece W is larger than the width of the line beam LB that the light emission unit 3 can generate, or if the input ends of the optical waveguides G are located on multiple end faces of the workpiece W. Therefore, if there are any optical waveguides G on the workpiece W that have not yet been inspected (NO in step S110), the stage movement unit 53 is activated to change the position of the workpiece W so that the uninspected optical waveguides G can be inspected (step S111), and the process from step S103 onwards is repeated. Once all optical waveguides G have been inspected (YES in step S110), the inspection of the current workpiece W is considered complete.

[0074] As described above, in this embodiment, when performing characteristic testing of an optical waveguide provided in an optical integrated circuit, alignment processing using optical scanning by a spatial light modulator 40 is performed. Specifically, a line beam LB whose longitudinal direction is aligned with the direction in which the spatial light modulator 40 has resolution is incident on the spatial light modulator 40, and the spatial light modulator 40 generates one or more spot light beams SB with smaller spot sizes from the line beam LB.

[0075] The spot light beams SB generated in this way are each irradiated onto the optical waveguide G of the workpiece W as inspection light, and as the incident position changes over time, the optical waveguide G is optically scanned, and the conditions under which the amount of transmitted light is maximized are searched for. By realizing the conditions under which the amount of light is maximized in this way, the purpose of the alignment process is achieved.

[0076] Compared to conventional techniques that mechanically change the incident position of the inspection light, optical scanning using the spatial light modulator 40 is significantly faster, and furthermore, it is possible to perform processing on multiple optical waveguides in parallel and independently. For this reason, in this embodiment, alignment processing and characteristic inspection of the optical waveguide based on the results can be realized in a much shorter time than in conventional techniques. According to the inventors' findings, in the inspection apparatus 1 of this embodiment, the time required for alignment processing per optical waveguide channel is less than 100 msec, and moreover, since parallel processing is possible, the required time does not increase significantly even if the number of channels increases.

[0077] Furthermore, the light to be detected, emitted from the optical waveguide, is received by a photosensor with one-dimensional or two-dimensional positional resolution, and the amount of received light at each position is determined. Therefore, precise positioning on the receiving side is not required. This also contributes to shortening processing time.

[0078] As described above, in this embodiment, the inspection device 1 corresponds to the "inspection device" of the present invention, and of which the light emission unit 3 corresponds to the "optical device" and "light emission unit" of the present invention. Furthermore, in the light emission unit 3, the light source 31 and the illumination optical unit 33 (33b) function as the "light source" and "illumination optical unit" of the present invention, respectively, while the projection optical unit 37 and the reflection mirror 39 function together as the "light guide unit" of the present invention. In addition, the modulation unit 35 functions as the "modulation unit" of the present invention, and of which the spatial light modulators 40 and 40b function as the "spatial light modulator" of the present invention.

[0079] Furthermore, the light-receiving unit 7 and the control unit 9 in the above embodiment function as the "light-receiving unit" and "control unit" of the present invention, respectively. The holding unit 5 functions as the "holding unit" of the present invention, and of these, the stage moving unit 53 functions as the "relative moving unit" of the present invention.

[0080] It should be noted that the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the invention. For example, although the above embodiment is an inspection device 1 incorporating a light emission unit 3, it is also possible to implement the light emission unit 3 alone as an "optical device" of the present invention, provided that it is combined with an external control device.

[0081] For example, in the light emission unit 3 of the above embodiment, the light emitted horizontally from the light source 31 is reflected downward by the spatial light modulator 40, and then reflected horizontally again by the reflective mirror 39 before being incident on the workpiece W. These are measures to avoid increasing the size of the light emission unit 3 and are not essential requirements. Optical elements for further reversing the optical path may also be added as appropriate.

[0082] Furthermore, in the above embodiment, a GLV element (one-dimensional) or a PLV element (two-dimensional) is used as the spatial light modulator 40. However, other devices capable of achieving similar spatial light modulation at high speed may be used as the optical modulator.

[0083] For example, in the above embodiment, the stage 51 that holds the workpiece W is configured to be movable relative to the light emitting unit 3 and the light receiving unit 7, but instead of this, or in addition to this, at least one of the light emitting unit 3 and the light receiving unit 7 may be configured to move relative to the stage 51. In other words, the "relative movement unit" of the present invention is not limited to moving the "holding unit" as in the above embodiment, but may also move the "light emitting unit".

[0084] Furthermore, in the above embodiment, the optical characteristics of the optical waveguide are inspected based on the reception result of the detected light emitted from the optical waveguide. However, the optical device of the present invention can also be used to inspect optical integrated circuits. That is, inspection light may be incident on the input terminal of an optical waveguide provided in an optical integrated circuit, and the detected light emitted through the circuit in the optical integrated circuit may be received to inspect characteristics such as delay and dispersion in the optical integrated circuit.

[0085] As described above with examples of specific embodiments, in the present invention, for example, a diffraction grating type optical modulator may be used as the spatial light modulator. Such an element is particularly suitable for the purpose of the present invention because it can programmatically control the diffraction of light produced by the diffraction grating to realize various reflection patterns.

[0086] Furthermore, for example, the optical device according to the present invention may further include a control unit that controls a spatial light modulator to change the pattern shape of the emitted light over time. With such a configuration, by changing the position of the emitted light through electrical control of the spatial light modulator, high-speed optical scanning of the object to be illuminated can be achieved. By utilizing this, it is possible to perform alignment processing to optimize the incident position of light into the optical waveguide in a short time.

[0087] In this case, the control unit may set the pattern shape of the emitted light so that multiple light beams are emitted from the spatial light modulator. This makes it possible to perform optical scanning on multiple optical waveguides in parallel, for example, when an optical integrated circuit is provided with multiple optical waveguides. In other words, the alignment process for multiple optical waveguides can be performed in parallel in time, thereby shortening the processing time for the entire optical integrated circuit.

[0088] Furthermore, a light receiving unit may be provided to receive light emitted from the output terminal of the optical waveguide as the light to be detected. With such a configuration, it is possible to optimize the operation of the spatial light modulator by feeding back the result of the light receiving unit's reception of the light to be detected to the control of the spatial light modulator. For example, if the light receiving unit detects the incident position and the amount of incident light of the light to be detected, it is possible to determine the incident position of the inspection light necessary to achieve alignment with the optical waveguide from the result.

[0089] Furthermore, in the inspection apparatus of the present invention, the control unit sets the emission position of the emitted light to a position where the amount of detected light is maximized when the inspection light is scanned, and the inspection light is incident on the input terminal to receive the detected light with the light receiving unit, and the characteristics of the optical waveguide can be inspected based on the light receiving result.

[0090] Furthermore, the inspection apparatus of the present invention may further include a relative movement unit that adjusts the optical path of incident light to the optical waveguide by changing the relative position between the holding unit and the light emission unit. With such a configuration, it is possible to roughly adjust the positional relationship between the holding unit and the light emission unit by operating the relative movement unit. In addition, by changing the region of the optical integrated circuit that is subjected to processing, it is possible to process a wider area. [Industrial applicability]

[0091] This invention is suitably applicable, for example, to the purpose of inspecting the optical properties of optical integrated circuits, and is particularly effective for high-speed inspection of optical integrated circuits having multiple single-mode optical waveguides. [Explanation of Symbols]

[0092] 1. Inspection device 3 Light emission section (optical device, light emission section) 5 Holding part 7 Light receiving section 9. Control Unit 31 Light source 33,33b Illumination optics section 37 Projection optical section (light guiding section) 39 Reflecting mirror (light guide part) 35 Modulation section 40,40b Spatial Light Modulator 51 stages 53 Stage Movement Section (Relative Movement Section)

Claims

1. An optical device for inspecting optical integrated circuits, A light source that emits light, An illumination optical unit that shapes the light emitted by the aforementioned light source into a predetermined shape, A modulation unit having a spatial light modulator that receives light shaped by the illumination optical unit, modulates the received light with the spatial light modulator and emits it as emitted light having a predetermined pattern shape, A light guide unit that guides the light emitted from the modulation unit to the input terminal of the optical waveguide provided in the optical integrated circuit. An optical device equipped with the following features.

2. The illumination optical unit has an optical system that shapes the light emitted by the light source into a line beam. The optical apparatus according to claim 1, wherein the modulation unit has a diffraction grating type optical modulation element having a resolution in the longitudinal direction of the line beam as the spatial light modulator.

3. The illumination optical unit has an optical system that shapes the light emitted by the light source into a rectangular or elliptical shape. The optical apparatus according to claim 1, wherein the modulation unit has a liquid crystal optical element as the spatial light modulator.

4. The optical apparatus according to any one of claims 1 to 3, further comprising a control unit that controls the spatial light modulator to change the pattern shape of the light emitted from the spatial light modulator over time.

5. The optical apparatus according to claim 4, wherein the control unit emits the emitted light, which includes a plurality of light beams, from the spatial light modulator by setting the pattern shape.

6. The optical device according to claim 4, further comprising a light receiving unit that receives light emitted from an output terminal corresponding to the optical waveguide as light to be detected in the optical integrated circuit.

7. The optical apparatus according to claim 6, wherein the control unit detects the incident position and the amount of incident light of the detected light received by the light receiving unit.

8. An inspection device for inspecting optical integrated circuits, A holding part that holds the optical integrated circuit to be inspected, Having the same configuration as the optical apparatus described in any one of claims 1 to 3, the optical device includes a light emission unit that incidents light as inspection light onto the input end of the optical waveguide, The optical integrated circuit includes a light receiving unit that receives light emitted from the output terminal corresponding to the optical waveguide as light to be detected, A control unit that controls the spatial light modulator and adjusts the incident position of the inspection light to the input terminal, An inspection device equipped with the following features.

9. The inspection apparatus according to claim 8, wherein the control unit scans the incident position of the inspection light on the input terminal by changing the emission position of the emitted light from the spatial light modulator over time.

10. The inspection apparatus according to claim 9, wherein the control unit performs scanning of the inspection light with respect to each of the plurality of optical waveguides provided in the optical integrated circuit in parallel in time.

11. The control unit, The emission position of the emitted light is set to the position where the amount of light received by the detected light is maximized when the inspection light is scanned. The inspection apparatus according to claim 9, wherein the inspection light is incident on the input terminal and the light receiving unit receives the light to be detected, and the characteristics of the optical waveguide are inspected based on the light reception result.

12. The inspection apparatus according to claim 9, further comprising a relative movement unit that adjusts the optical path of incident light to the optical waveguide by changing the relative position between the holding unit and the light emitting unit.

13. A method for centering an optical waveguide for characteristic testing of an optical integrated circuit, Light emitted from a light source and shaped into a predetermined form is modulated by a spatial light modulator placed in the optical path of the light to emit light with a predetermined pattern shape. By changing the pattern shape of the emitted light from the spatial light modulator over time and injecting the emitted light from the spatial light modulator into the input terminal of the optical waveguide as inspection light, the incidence position of the inspection light on the input terminal is scanned. While scanning the aforementioned inspection light, the light emitted from the output terminal of the optical waveguide is received as the light to be detected. A method for adjusting the alignment, wherein the emission position of the emitted light is set to the position where the amount of light received by the detected light is maximum when the inspection light is scanned.

14. The alignment method according to claim 13, wherein the scanning of the inspection light for each of the plurality of optical waveguides provided in the optical integrated circuit is performed in parallel in time.

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