Optical probe and method of manufacturing the same, optical probe array, optical probe card

Abstract

Provided is an optical probe having a single-mode transmission mode and capable of efficiently measuring an optical device, an optical probe array, an optical probe card, and a manufacturing method of an optical probe. The optical probe (10) has a first region (11) and a second region (12) that are joined in a manner such that an optical waveguide having a single-mode transmission mode is continuous. The first region (11) that is continuous to a top end surface (100) opposite the optical device (20) includes a region that gradually narrows toward a region boundary (13) between the first region (11) and the second region (12) from a region in which the top end surface (100) has a maximum mode field diameter. The top end surface (100) is a curved surface, and a radius of curvature of the top end surface (100) is set so that a traveling direction of an optical signal (L) incident from the top end surface (100) is approximately parallel to a central axis direction of the optical waveguide.

Description

Technical Field

[0001] This invention relates to optical probes, optical probe arrays, optical probe cards, and methods for manufacturing optical probes used in the measurement of optical devices. Background Technology

[0002] Using silicon photonics technology, optical devices with optical signals as input and output are formed on a wafer. An optical probe is used to measure the characteristics of the optical device in its wafer-formed state. In this case, to reduce the loss of the optical signal transmitted between the optical device and the optical probe, the optical device and the optical probe are aligned and their mode fields are matched.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: U.S. Patent Application Publication No. 2006 / 0008226A1

[0006] Patent Document 2: Japanese Patent Application Publication No. 62-31136 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] When optical signals are transmitted in single-mode, the dimensions of the optical signal terminals of optical devices, the core diameter of optical probes, and the mode field diameter are on the order of several μm. Therefore, the tolerance for error in aligning the optical signal terminals of the optical devices with the top surface of the optical probes is low, making accurate alignment of the optical devices and probes difficult. As a result, in the measurement of optical devices, situations arise where the time required for alignment increases measurement time, or where inaccurate alignment leads to increased connection losses. Thus, in the case of single-mode optical signal transmission, there is a problem of inefficient measurement of optical devices.

[0009] In view of the above problems, the purpose of the present invention is to provide an optical probe, an optical probe array, an optical probe card, and a method for manufacturing an optical probe that has a single-mode transmission mode and can efficiently measure optical devices.

[0010] Solution for solving the problem

[0011] According to one aspect of the present invention, an optical probe is provided, comprising a first region and a second region, the first region and the second region being connected in a manner that enables a single-mode optical waveguide to transmit continuously. The first region, continuous to a top surface opposite the optical device, includes a region on the top surface where the maximum mode field diameter gradually narrows toward the boundary between the first region and the second region. The top surface is curved, and the radius of curvature of the top surface is set such that the direction of travel of the light signal incident from the top surface is approximately parallel to the central axis of the optical waveguide.

[0012] The effects of the invention

[0013] According to the present invention, an optical probe, an optical probe array, an optical probe card, and a method for manufacturing an optical probe are provided, which have a single-mode transmission mode and are capable of efficiently measuring optical devices. Attached Figure Description

[0014] Figure 1 This is a schematic cross-sectional view showing the structure of the optical probe according to the first embodiment.

[0015] Figure 2 This is a schematic diagram illustrating the angle of refraction at the top surface of the optical probe according to the first embodiment.

[0016] Figure 3 This is a diagram used to illustrate the maximum working distance.

[0017] Figure 4 It is a graph showing the relationship between the radius of curvature of the tip surface of the optical probe and the numerical aperture.

[0018] Figure 5 It is a graph showing the relationship between the radius of curvature of the top surface of the optical probe and the spot radius of the optical signal.

[0019] Figure 6 It is a graph showing the relationship between positional deviation and connection loss.

[0020] Figure 7 It is a graph showing the relationship between the radius of curvature of the top surface of the optical probe and the length of the light spot.

[0021] Figure 8A This is a schematic diagram (one of the embodiments) used to illustrate the manufacturing method of the optical probe involved in the first embodiment.

[0022] Figure 8B This is a schematic diagram (second one) illustrating the manufacturing method of the optical probe according to the first embodiment.

[0023] Figure 9A This is a schematic diagram showing the structure of the optical probe array according to the first embodiment.

[0024] Figure 9B This is a schematic top view showing an example of an optical waveguide for an optical device.

[0025] Figure 10 This is a schematic diagram showing the structure of the optical fiber of the comparative example.

[0026] Figure 11 This is a schematic diagram showing the structure of a measurement system using the optical probe according to the first embodiment.

[0027] Figure 12 This is a schematic diagram showing the structure of the measurement system involved in a variation of the first embodiment.

[0028] Figure 13 This is a schematic diagram showing the structure of the optical probe according to the second embodiment.

[0029] Figure 14 This is a schematic diagram illustrating the structure of an optical probe according to other embodiments.

[0030] Explanation of reference numerals in the attached figures

[0031] 10: Optical probe; 11: First region; 12: Second region; 15: Optical probe array; 20: Optical device; 30: Electrical probe; 40: Optical probe head; 41: Optical probe card; 100: Top surface; 101: Core; 102: Cladding layer; 111: Top surface; 112: Connector; 120: Resin film; 200: Wafer. Detailed Implementation

[0032] Next, embodiments of the present invention will be described with reference to the accompanying drawings. In the following drawings, the same or similar parts are labeled with the same or similar reference numerals. However, it should be noted that the drawings are schematic. Furthermore, the embodiments shown below illustrate apparatus and methods for embodying the technical concept of the present invention, and the embodiments of the present invention do not limit the construction, arrangement, etc., of structural components to the following description. Various modifications can be made to the embodiments of the present invention within the scope of the claims.

[0033] (First Implementation)

[0034] The optical probe 10 according to the first embodiment transmits and receives optical signals between itself and the optical device 20. The following describes the transmission of the optical signal L emitted from the optical device 20 and incident on the optical probe 10 within the optical waveguide of the optical probe 10. Figure 1 The end of the optical probe 10 is shown, which includes a top surface 100 opposite to the optical device 20 and through which the light signal L passes.

[0035] exist Figure 1In this design, the central axis C10 of the optical waveguide of the optical probe 10 is set as the Z-axis direction, and the plane perpendicular to the Z-axis direction is set as the XY plane. Additionally, Figure 1 The left-right direction of the paper is defined as the X-axis, and the direction perpendicular to the paper is defined as the Y-axis. Hereinafter, the X-axis, Y-axis, and Z-axis will be collectively referred to as the "XYZ-axis directions".

[0036] The optical probe 10 can employ optical fiber, or a structure combining optical fiber and a lens. The optical probe 10 has an optical waveguide with a single-mode transmission mode. The optical waveguide of the optical probe 10 has a structure in which a cladding portion 102 is arranged on the outer periphery of the core portion 101. Figure 1 The cladding diameter Dr shown is the outer diameter of the optical probe 10 including the cladding portion 102.

[0037] The top surface 100 of the optical probe 10 is optically connected to the optical signal terminal (not shown) of the emitted light signal L of the optical device 20. The top surface 100 is a convex surface with a radius of curvature R. The radius of curvature R will be described in detail later. The optical probe 10 is constructed such that the first region 11 and the second region 12 are continuous or connected. The first region 11 is continuous with the top surface 100, and the core diameter of the second region 12 is narrower than the core diameter of the first region 11. Here, the optical waveguide of the first region 11 is continuous with the optical waveguide of the second region 12. The first region 11 is a fixed range of the optical probe 10 extending from the top surface 100 along the central axis C10 of the optical waveguide of the optical probe 10 (hereinafter also referred to as the "central axis direction").

[0038] The mode field diameter at the top surface 100 of the optical probe 10 is designated as the "first MF diameter Ce". The first region 11 includes a region where the maximum mode field diameter is located at the top surface 100, gradually narrowing in a conical shape towards the boundary 13 between the first region 11 and the second region 12. At the boundary 13, the mode field diameter of the first region 11 coincides with that of the second region 12. The mode field diameter of the second region 12 is fixed along its central axis. The mode field diameter of the second region 12 is designated as the "second MF diameter Cd".

[0039] A light signal L with a radiation angle of 2α emitted from optical device 20 is incident at the incident point Q on the top surface 100. The light signal L passes through the incident point Q with a central half-angle of ω at the incident point and forms a refraction angle (β+ω) with the direction of the radius of curvature. Figure 2 As shown, angle β is the angle formed by the direction of travel of the light signal L that has passed through the top surface 100 and the direction of the central axis.

[0040] Optical probes 10 are arranged at working distances WD along the Z-axis starting from optical device 20. The working distance WD is set to the range within which optical probes 10 can receive the light signal L emitted from optical device 20. In other words, the working distance WD is set such that the incident range of the light signal L at the top surface 100 is inside the optical waveguide.

[0041] Figure 3 This shows the state where the distance between the optical probe 10 and the optical device 20 is the maximum configurable working distance (hereinafter referred to as "maximum working distance WDm"). The maximum radiation angle of the optical signal L at the maximum working distance WDm is set to 2αm. Therefore, the numerical aperture NA of the top surface 100 is sin(αm).

[0042] The radius of curvature R of the top surface 100 of the optical probe 10 is set such that the direction of travel of the light signal L incident from the top surface 100 is approximately parallel to the central axis of the optical waveguide of the optical probe 10. The radius of curvature R of the top surface 100 will be explained below.

[0043] The light signal L incident on the top surface 100 is refracted at a refraction angle (β+ω). According to Snell's law, the refractive index nr of the core 101 at the incident point Q where the light signal L is incident on the top surface 100 is given by the following equation (1):

[0044] sin(αm+ω)=nr×sin(β+ω)…(1)

[0045] Based on equation (1), we obtain the following equation (2):

[0046] αm=sin -1 (nr×sin(β+ω)}-ω…(2)

[0047] in,

[0048] NA=sin(αm)…(3)

[0049] By making the refractive index nr of the core 101 approximately equal to the refractive index nd of the cladding 102, the following equation (4) is obtained:

[0050] β=sin -1 {sin(α0) / nr}…(4)

[0051] In equation (4), sin(α0) is the numerical aperture of the top surface 100 assuming that the top surface 100 is flat.

[0052] By satisfying the following equation (5), the direction of travel of the light signal L incident from the top surface 100 is approximately parallel to the direction of the central axis:

[0053] ω=sin -1 (Ce / R)…(5)

[0054] Therefore, the radius of curvature R of the top surface 100 of the optical probe 10 is set to satisfy the following relationship (6):

[0055] R=Ce / sin(ω)…(6)

[0056] The maximum working distance WDm is expressed by the formula WDm = Ce / tan(αm). Therefore, the working distance WD satisfies the following formula (7):

[0057] WD≤Ce / tan(αm)…(7)

[0058] Furthermore, the radius of curvature R and the cladding diameter Dr of the optical probe 10 satisfy the following equation (8):

[0059] R≥Dr / 2…(8)

[0060] By satisfying the relationship in equation (8), it is possible to prevent the optical signal L transmitted in the optical probe 10 from leaking out from the side of the optical probe 10.

[0061] Figure 4 The relationship between the radius of curvature R of the top surface 100 and the numerical aperture NA is shown for cases where the first MF diameter Ce of the optical probe 10 is 20 μm, 30 μm, and 40 μm. For example... Figure 4 As shown, the smaller the radius of curvature R, the larger the numerical aperture NA. Furthermore, the larger the first MF diameter Ce, the larger the numerical aperture NA. For example, to achieve a numerical aperture NA of 0.2 for the top surface 100, the radius of curvature R is set as follows: With a first MF diameter Ce of 20 μm, the radius of curvature R is set to approximately 30 μm. With a first MF diameter Ce of 30 μm, the radius of curvature R is set to approximately 40 μm. With a first MF diameter Ce of 40 μm, the radius of curvature R is set to approximately 55 μm.

[0062] Figure 5 This illustrates the relationship between the radius of curvature R of the top surface 100 of the optical probe 10 and the radius ω0 of the light spot L passing through the top surface 100. For example... Figure 5As shown, the smaller the radius of curvature R of the top surface 100, the smaller the spot radius ω0. Furthermore, when the first MF diameter Ce of the optical probe 10 is 20 μm, 30 μm, or 40 μm, the larger the first MF diameter Ce, the smaller the spot radius ω0. To efficiently optically connect the optical device 20 to the optical probe 10, the spot diameter is set to be the same size as the optical signal terminal. Therefore, for example, when the size of the optical signal terminal of the optical device 20 is 4 μm, the spot radius ω0 is set to 2 μm. In this case, when the first MF diameter Ce is 30 μm, the radius of curvature R is set to approximately 30 μm, and when the first MF diameter Ce is 40 μm, the radius of curvature R is set to approximately 45 μm.

[0063] Figure 6 The relationship between the positional deviation D of the central axis C10 of the optical probe 10 and the optical axis C20 of the optical signal L in the X-axis or Y-axis direction is shown for cases where the diameter Ce of the first MF is 20 μm, 30 μm, and 40 μm, and the connection loss S of the optical signal L. Furthermore, Figure 6 The curve for Cd = 10 μm represents the connection loss in a single-mode fiber with a fixed mode field diameter of 10 μm. Here, the numerical aperture NA of the top facet 100 is 0.17, and the working distance WD is 25 μm.

[0064] like Figure 6 As shown, the larger the diameter Ce of the first MF, the smaller the variation of the connection loss S relative to the position deviation D. According to... Figure 6 The positional deviation D, which suppresses the variation in connection loss S to within 0.1 dB, is as follows: When the diameter Ce of the first MF is 20 μm, 2.5 (μm) ≥ D ≥ -2.5 μm. When the diameter Ce of the first MF is 30 μm, 3.5 μm ≥ D ≥ -3.5 μm. When the diameter Ce of the first MF is 40 μm, 5.0 μm ≥ D ≥ -5.0 μm.

[0065] In an optical probe array composed of multiple optical probes 10 arranged in a row, errors occur at various positions where the optical probes 10 are positioned within the array. Therefore, by using optical probes 10 in the optical probe array that exhibit small variations in connection loss relative to positional deviations, variations in connection loss during measurements using the optical device 20 employing the optical probe array can be reduced. Thus, by using optical probes 10 with a large first MF diameter Ce in the optical probe array, variations in connection loss S dependent on positional deviation D can be reduced. For example, an optical probe array can also be constructed using optical probes 10 with a first MF diameter Ce of 30 μm to 40 μm.

[0066] Furthermore, the range of positional deviation D used to reduce the variation in connection loss S can be changed by adjusting the working distance WD. That is, the shorter the working distance WD, the larger the range of positional deviation D that can reduce the variation in connection loss S to within 0.1 dB.

[0067] Figure 7 This illustrates the relationship between the radius of curvature R of the top surface 100 of the optical probe 10 and the length of the range along the central axis where the spot radius ω0 is fixed (hereinafter referred to as the "spot length H"). Twice the spot length H is the focal depth of the optical signal L. For example... Figure 7 As shown, the larger the radius of curvature R, the longer the spot length H. Additionally, the larger the diameter Ce of the first MF, the shorter the spot length H.

[0068] For example, if the size of the optical signal terminal of the optical device 20 is 4 μm, the spot radius ω0 is set to 2 μm. According to... Figure 5 When the first MF diameter Ce is 30 μm and the spot radius ω0 is set to 2 μm, the radius of curvature R is 30 μm. In this case, according to Figure 7 The spot length H is 5 μm, so the focal depth is 10 μm. Therefore, even if the working distance varies by about 10 μm along the Z-axis, the connection loss remains almost unchanged. Thus, the optical probe 10, which satisfies the relationship in equation (6), can increase the tolerance for positional deviations in the Z-axis direction.

[0069] However, there exists a situation where the central axis C10 of the optical probe 10 is not parallel to the optical axis C20 of the optical signal L, but rather intersects with it. The angle formed by the central axis C10 and the optical axis C20 in this situation is referred to as the "tilt angle." The angular deviation of the incident angle of the optical signal L at the top surface 100 caused by the tilt angle is also referred to as the "rotational deviation." Due to the tilt angle, a change in the characteristics of the optical signal L transmitted in the optical probe 10 is also considered (hereinafter referred to as "incident variation").

[0070] However, in the optical probe 10, the direction of travel of the light signal L passing through the top surface 100 is approximately parallel to the central axis. Therefore, incident variations caused by tilt angles can be suppressed, allowing the light signal L to be stably incident on the optical probe 10. In other words, the optical probe 10 has a large tolerance for rotational deviations. Therefore, according to the optical probe 10, even when the central axis C10 and the optical axis C20 are not parallel, connection loss of the light signal L can be suppressed.

[0071] As explained above, the optical probe 10 according to the first embodiment improves the tolerance for positional deviations in the X-axis and Y-axis directions by having a first region 11 with an enlarged mode field diameter. Furthermore, since the top surface 100 is a curved surface satisfying equation (6), the travel direction of the light signal L incident on the top surface 100 is approximately parallel to the central axis C10 of the optical probe 10. Therefore, in the optical probe 10, the loss variation is reduced when the working distance WD changes from a predetermined distance. In other words, the tolerance for positional deviations in the Z-axis direction is improved. Moreover, in the optical probe 10, the tolerance for rotational deviations caused by the tilt angle is large.

[0072] Therefore, the tolerance for positional and rotational deviations in the XYZ axis directions is improved by using the optical probe 10. This reduces the time required for alignment between the optical probe 10 and the optical device 20, eliminating the need for precise alignment as needed. Furthermore, by using the optical probe 10, the characteristics of the light signal L emitted by the optical device 20 can be measured stably and accurately. Therefore, the optical device 20 can be measured efficiently using the optical probe 10, which has a single-mode transmission mode for the light signal L.

[0073] Reference Figures 8A-8B The manufacturing method of the optical probe 10 will be explained below. Furthermore, the manufacturing method described below is just one example; of course, the optical probe 10 can be manufactured by various other manufacturing methods, including its variations.

[0074] First, prepare an optical fiber whose mode field diameter tapers gradually from one end along the central axis. For example, in an optical fiber having an optical waveguide composed of a core 101 and a cladding 102, such as... Figure 8A The first region 11 is formed as shown. The first region 11 can be formed by methods such as locally heating the core 101. For example, one end of a single-mode fiber with a cladding diameter of Dr and a mode field diameter of the second MF diameter Cd is heated to approximately 1200°C to 1400°C. Through this heating process, an additive that increases the refractive index present in the core 101 diffuses, causing the core 101 to expand radially. This forms the first region 11 with a mode field diameter of the top surface equal to the first MF diameter Ce. The diffused additive is, for example, germanium (Ge).

[0075] Next, using an end face grinder, precision grinding machine, or similar equipment, the end of the first region 11, which is fixed by a fixture, is ground into a conical shape. This forms... Figure 8A The conical region 110 is shown by the dashed line.

[0076] Subsequently, using the top of the cone as an axis, the surface of the conical region 110 is machined into a convex curved surface through methods such as electrical discharge machining (EDM) heating and precision grinding, as shown below. Figure 8B The top surface 100 is formed as shown. At this point, it can be done as follows: Figure 8B As shown, the area with diameter Lc centered on the central axis C10 is machined into a curved surface, and the outer edge region 103 of the area machined into a curved surface is made into a cone shape.

[0077] In the process of machining the surface of the conical region 110 into a convex surface, the top surface 100 is formed such that the radius of curvature R of the top surface 100 satisfies the relationship of equation (6). As a result, the direction of travel of the light signal L incident from the top surface 100 is approximately parallel to the central axis direction of the optical waveguide of the optical probe 10. The optical probe 10 is manufactured in this way.

[0078] In the process of machining the surface of the conical region 110 into a curved surface, methods such as heating and melting using high-frequency discharge or carbon dioxide (CO2) laser, or precision grinding using a grinding machine, can be employed. Alternatively, heating and melting can be performed after grinding to machine the surface of the conical region 110 into a curved surface. By performing heating and melting after grinding, the surface roughness caused by grinding is improved, and the connection loss caused by surface scattering of the light signal L at the top surface 100 is reduced.

[0079] For example, the core diameter of the first region 11 can be set to approximately 25 μm, and the first MF diameter Ce can be set to approximately 30 μm. Alternatively, the core diameter of the second region 12 can be set to approximately 8 μm, and the second MF diameter Cd can be set to approximately 10 μm.

[0080] By using an optical probe array with multiple optical probes 10 arranged in a structure for measuring the optical device 20, multiple optical signal terminals can be simultaneously aligned with each optical probe 10. Therefore, by using the optical probe array, the characteristics of the optical device 20 can be measured in a short time. In other words, by connecting the optical probes 10 to the optical signal terminals in a multi-core manner using the optical probe array, the time required for alignment can be significantly reduced compared to the measurement method of aligning each optical probe 10 to the optical signal terminals one by one.

[0081] When multiple optical probes 10 are arranged to form an optical probe array, errors may occur in the position of the optical probes 10 disposed in the optical probe array. However, the optical probes 10 have a large tolerance for positional and rotational deviations in the XYZ axis directions. Therefore, with the optical probe array composed of optical probes 10, even if the relative position of the optical probes 10 and the optical device 20 changes, or if the central axis C10 and the optical axis C20 form an angle and intersect, the incident variation of the optical signal L can be reduced. Therefore, by using an optical probe array composed of optical probes 10, the optical signal terminals of the multiple optical devices 20 formed on the wafer can be easily aligned with the optical probes 10 within a range that reduces incident variation.

[0082] In other words, by using an optical probe array composed of optical probes 10 for measurement, and simultaneously aligning multiple optical devices 20, the measurement time can be shortened and connection losses reduced. As a result, the measurement and evaluation of the optical devices 20 can be easily performed, improving both yield and productivity.

[0083] Figure 9A An example of an optical probe array consisting of optical probe 10 is shown. Figure 9A The diagram shows an optical probe array 15 with four optical probes 10 arranged in a row, but the number of optical probes 10 constituting the optical probe array is not limited to four.

[0084] Figure 9A The optical device 20 shown is a structure in which optical signal terminals 21, each with an input and output end formed by a diffraction grating, are arranged at equal intervals. An input light signal emitted from the top surface 100 of the optical probe 10 is incident on an optical signal terminal 21 located at a working distance WD from the top surface 100 of the optical probe 10. The input light signal incident on the optical signal terminal 21 is deflected by the diffraction grating at the input and output ends and then transmitted within an optical waveguide (not shown) formed in the optical device 20. The input light signal is then transmitted to functional components such as a light-receiving element, an optical switch, and a modulation element disposed inside the optical device 20. For example, such as… Figure 9B As shown, the optical waveguide 22 that transmits the optical signal from the optical signal terminal 21 to the functional components of the optical device 20 is a cone shape with a gradually thinning mode field diameter.

[0085] On the other hand, the light output signal emitted from the diffraction grating of the light signal terminal 21 of the optical device 20 is incident on the top surface 100 of the optical probe 10. The light output signal transmitted inside the optical probe 10 is incident on the photoelectric conversion unit 50. The photoelectric conversion unit 50 converts the light output signal into an electrical signal and amplifies it.

[0086] Regarding the optical probe 10 constituting the optical probe array 15, the mode field diameter of the top surface 100 is enlarged, and the top surface 100 is a curved surface with a radius of curvature R. Therefore, even if positional deviations or rotational deviations occur between the optical probe 10 and the optical signal terminal 21 in the XYZ axis directions, the loss variation is small. Therefore, the optical probe array 15 can be used to achieve stable and high-precision measurement and short processing time. Furthermore, the allowable deviation for suppressing loss variation within a specified tolerance range can be adjusted by setting the working distance WD. By setting the working distance WD within the range that satisfies the relationship WD≤WDm=Ce / tan(αm), the allowable deviation can be increased.

[0087] In addition, Figure 9A The diagram shows an example of an optical probe array 15 with optical probes 10 arranged in a row, but the optical probe array 15 can also be other structures. For example, the optical probe array 15 can also be a structure in which optical probes 10 are arranged in the X-axis direction and the Y-axis direction respectively, and multiple optical probes 10 are arranged in an array.

[0088] Compared to measurements using optical probe 10, measurements using a probe that does not enlarge the mode field diameter at the top surface are more efficient. Figure 10 When measuring optical devices 20 using the single-mode fiber 10a of the comparative example, the following problems arise. Regarding fiber 10a, the mode field diameter is fixed along the central axis from the end formed into a conical shape. In measuring optical devices 20 using fiber 10a, precise sub-micron level control with six degrees of freedom—including positional adjustments in each of the XYZ axes and micro-adjustments of rotation along each axis—is required to align fiber 10a with the optical device 20. Therefore, when fiber 10a is arranged to form an optical probe array, it is difficult to simultaneously measure multiple optical devices 20 by precisely aligning each fiber 10a individually. Consequently, using fiber 10a in measuring multiple optical devices 20 formed on a wafer is time-consuming and labor-intensive. Therefore, evaluation and measurement of optical devices 20 using fiber 10a suffers from poor productivity, making mass production difficult.

[0089] On the other hand, the optical probe 10 has a large tolerance for errors in the XYZ axis alignment and the position alignment based on rotation centered on the X and Y axes for adjusting the tilt angle. Therefore, when the optical probe 10 is used in an optical probe array, the alignment of the optical probe array with the optical device 20 can be performed in a short time due to the simplification, and the variation in loss can be reduced.

[0090] Figure 11 The diagram shows a structural example of a measurement system using the optical probe 10. Figure 11The measurement system shown includes an optical probe head 40 that holds the optical probes 10. The optical probe head 40 holds an optical probe array 15 in which a plurality of optical probes 10 are arranged in an array. That is, although not shown, the optical probes 10 are also arranged at equal intervals in the optical probe array 15 along the Y-axis direction, in the same way as the X-axis direction.

[0091] Figure 11 The measurement system shown is used to measure a plurality of optical devices 20 arrayed on a wafer 200 mounted on a stage 60. The positions of the optical probes 10 arranged in the optical probe array 15 correspond to the positions of the optical devices 20 formed on the wafer 200.

[0092] The optical probe head 40 is moved in the Z-axis direction by the control of the optical probe drive device 45. This allows for fine adjustment of the distance along the Z-axis between the top surface 100 of the optical probe 10 and the optical device 20. The stage 60 can also be moved by the stage drive device 61 to align the optical probe head 40 and the optical device 20 in the X and Y axes. Furthermore, the stage 60 is rotated about the Z-axis by the stage drive device 61, thereby adjusting the position of the optical device 20 relative to the optical probe 10 in the rotation direction about the Z-axis (hereinafter referred to as the "Z-axis rotation direction"). Alternatively, the position of the stage 60 can be fixed, allowing the optical probe head 40 to move in the X, Y, and Z axes.

[0093] As mentioned above, it is possible to pass through Figure 11 The measurement system shown is used to align the optical probe 10 with the optical device 20. Alternatively, the position of the optical probe head 40 can be fixed, and the stage 60 can be moved along the X-axis, Y-axis, Z-axis, or the rotational direction of the Z-axis or X-axis and Y-axis. In this way, various adjustment methods can be used for aligning the optical probe 10 with the optical device 20.

[0094] After the optical probe 10 and the optical device 20 are aligned, via Figure 11 The measurement system shown transmits optical signals to measure the optical device 20. For example, the optical probe 10 receives the optical signal L emitted by the optical device 20.

[0095] Optical probe 10 is connected to photoelectric conversion unit 50, which has photoelectric conversion module 51 and electrical connection terminal 52. The light signal L emitted from optical device 20 is transmitted via optical probe 10 to photoelectric conversion module 51, which is optically connected to optical probe 10. Photoelectric conversion module 51 converts the light signal L into an electrical signal and outputs the converted electrical signal to electrical connection terminal 52. Electrical connection terminal 52 is electrically connected to a tester (not shown). Photoelectric conversion unit 50 sends the electrical signal obtained by photoelectric conversion of light signal L to tester via electrical connection terminal 52.

[0096] The photoelectric conversion module 51 can be of various types, such as those that convert light signal L into electrical signal using a photodetector or similar device, and those that split light signal L using a diffraction grating device and detect wavelength changes based on the diffraction angle direction. The type of photoelectric conversion module 51 used varies depending on the measurement application. Furthermore, the light signal L can be branched off from the photoelectric conversion module 51 to perform multiple measurements simultaneously. By using the photoelectric conversion unit 50 to perform photoelectric conversion of the output of the optical probe 10 near the optical probe head 40, the measurement system can be simplified, the measurement time can be increased, and the repeatability of the measured values ​​can be improved. Thus, the optical device 20 can be measured using an optical probe card 41 that includes the optical probe 10 and the optical probe head 40 holding the optical probe 10.

[0097] <Variation Example>

[0098] To measure the characteristics of the optical device 20 that transmits electrical and optical signals in wafer condition, it is possible to... Figure 12 As shown, the optical probe 10 is used in combination with the electrical probe 30 for transmitting electrical signals. The electrical probe 30 is, for example, a cantilever type, a vertical needle type, or a vertical spring type. The electrical probe 30 is held by the electrical probe head 31.

[0099] For example, for an optical device 20, a probe unit is configured including a pair of optical probes 10 and an electrical probe 30. The probe unit is arranged corresponding to the position of the optical device 20 formed on the wafer 200. Furthermore, in Figure 12 The example shown illustrates a case where there is one optical probe 10 and one electrical probe 30 constituting a probe unit. The number of optical probes 10 and electrical probes 30 included in the probe unit is determined according to the structure of the optical device 20 and the measurement content.

[0100] exist Figure 12In the example shown, a composite probe card 42 is used to measure the optical device 20. The composite probe card 42 includes an optical probe 10, an optical probe head 40, an electrical probe 30, and an electrical probe head 31. For example, the probe unit is used to measure the optical device 20 as follows. An electrical signal output from a tester (not shown) is applied to the electrical signal terminal of the optical device 20 via the electrical probe 30. Then, the optical probe 10 receives the optical signal L emitted from the optical signal terminal of the optical device 20. By using the composite probe card 42 with multiple probe units, the optical probe 10 can be connected to the optical signal terminal of the optical device 20 in a multi-core manner, and the characteristics of multiple optical devices 20 can be measured with a single alignment. Alternatively, the optical signal emitted from the optical probe 10 can be incident on the incident end of the optical device 20, where the optical signal undergoes photoelectric conversion, and the resulting electrical signal is measured via the electrical probe 30. This improves the efficiency of measuring the optical device 20.

[0101] In the measurement of the optical device 20 using the composite probe card 42, the tolerance for positional and rotational deviations in the XYZ axis directions is also large by using the optical probe 10. Therefore, based on the measurement using the composite probe card 42, stable input-output characteristics can be obtained for the light signals L emitted by each of the multiple optical devices 20. In addition, the light receiving characteristics, switching characteristics, and oscillation characteristics of the optical device 20 can be measured by sending and receiving both light and electrical signals between the tester and the optical device 20.

[0102] (Second Implementation)

[0103] In the optical probe 10 according to the second embodiment, such as Figure 13 As shown, the first region 11 has a structure that joins a top portion 111, which extends to the top surface 100, with a connecting portion 112, which connects to the second region 12. The central axis C10 of the top portion 111 and the connecting portion 112 is aligned. The mode field diameter of the top portion 111 is fixed to a first MF diameter Ce. The mode field diameter of the connecting portion 112 at the joint surface where the top portion 111 and the connecting portion 112 join is less than or equal to the mode field diameter of the top portion 111. Furthermore, the connecting portion 112 has a region where the mode field diameter gradually narrows from the joint surface with the top portion 111 along the central axis of the optical waveguide.

[0104] For example, the tip portion 111 uses a graded-index (GI) optical fiber whose first tip surface 100 is processed into a curved surface with a radius of curvature R. Furthermore, the second tip surface of the tip portion 111 is fused to the tip surface of the enlarged core portion 101 of the connector portion 112. The connector portion 112, for example, uses an optical fiber.

[0105] The length T of the top end portion 111 along the central axis is set such that the light signal L incident from the top surface 100 passes parallel to the central axis direction through the joint surface between the top end portion 111 and the connecting portion 112.

[0106] For example, when using a GI-type optical fiber in the tip portion 111, the length T of the tip portion 111 is set to the spacing length at which the optical signal L can be incident the most. The spacing length is equivalent to one period (2π) of the optical path length within the lens. Assuming the spacing length P is 0.25 spacing, then T = 2πP / √A (√A: the refractive index distribution constant of the GI-type optical fiber). Thus, after the optical signal L travels approximately parallel to the central axis direction in the tip portion 111, it is incident as parallel light parallel to the central axis direction at the joint surface between the tip portion 111 and the connecting portion 112.

[0107] According to the optical probe 10 of the second embodiment, by joining a GI-type optical fiber having a top surface 100 with an optical fiber having an enlarged core 101, the working distance WD can be increased, and the incident range of the optical signal L at the top surface 100 can be expanded. Apart from this, the second embodiment is the same as the first embodiment, and repeated descriptions are omitted.

[0108] (Other implementation methods)

[0109] As described above, the present invention has been illustrated by way of embodiments, but it should not be construed that the discussion and drawings, which form part of this disclosure, are limiting of the invention. Based on this disclosure, those skilled in the art will understand various alternative embodiments, examples, and techniques.

[0110] For example, the above describes an example of using single-mode fiber in optical probe 10, but the fiber used in optical probe 10 is not limited to single-mode fiber. For example, polarization-maintaining fiber, dispersion-shifting fiber, photonic crystal fiber, etc., can also be used in optical probe 10. Furthermore, optical probe 10 can also be a waveguide structure with a core formed within a substrate. A photoelectric conversion unit can also be integrated using a multi-core optical probe array obtained by optical probe 10 with waveguides and fine electrical wiring patterns formed within or on a substrate, and an electrical probe array identical to the optical probe array. In this way, the entire measurement system can be miniaturized and integrated, and the optical probe 10, electrical probe 30, and optical device 20 of wafer 200 can be integrated into one unit via a substrate. Therefore, it is effective for miniaturized measurement structures that eliminate or reduce positional adjustments.

[0111] In addition, such as Figure 14As shown, the surface of the cladding portion 102 can also be covered with a resin film 120. By covering the outer side of the optical probe 10 with the resin film 120, the mechanical strength of the optical probe 10 is improved. Furthermore, since the outer side of the optical probe 10 is covered with the resin film 120, moisture intrusion and absorption into the optical probe 10 are prevented. Therefore, material degradation of the optical probe 10 caused by moisture intrusion can be prevented, and increased connection loss can be prevented. The resin film 120 is, for example, a polyimide film with a thickness of a few μm.

[0112] Therefore, the present invention naturally includes various embodiments not described herein.

Claims

1. An optical probe for transmitting and receiving optical signals between itself and an optical device, the optical probe being used to measure characteristics of the optical device in a wafer-formed state, characterized in that... The device comprises a first region and a second region, which are connected in a manner that enables a single-mode optical waveguide to be transmitted continuously. The optical waveguide is composed of a core and a cladding portion disposed on the outer periphery of the core. The first region, which extends to the top surface opposite the optical device, includes a region on the top surface where the mode field diameter is at its maximum and gradually narrows toward the boundary between the first region and the second region. The top surface is curved, and the radius of curvature of the top surface is set such that the direction of travel of the optical signal incident from the top surface is approximately parallel to the central axis of the optical waveguide immediately after the optical signal passes through the top surface. Assuming the radius of curvature of the top surface is R, the numerical aperture of the top surface is NA, the mode field diameter (i.e., the first MF diameter) of the top surface is Ce, the radiation angle of the light signal incident on the top surface is 2αm, the refractive index of the core at the incident point of the light signal on the top surface is nr, the central half-angle at the incident point of the top surface is ω, the refraction angle of the light signal at the incident point is (ω+β), and the top surface is flat, the numerical aperture sin(α0) of the top surface satisfies the following relationship: R = Ce / sin(ω) NA = sin(αm) αm=sin -1 {nr×sin(ω+β)}-ω β=sin -1 {sin(α0) / nr}.

2. The optical probe according to claim 1, characterized in that, At the boundary of the region, the diameter of the mold field in the first region is the same as the diameter of the mold field in the second region.

3. The optical probe according to claim 1, characterized in that, The working distance WD between the optical device and the top surface, the mode field diameter Ce of the top surface (i.e., the first MF diameter), and the radiation angle 2αm of the light signal incident on the top surface satisfy the following relationship: WD≤Ce / tan(αm).

4. The optical probe according to claim 1, characterized in that, The radius of curvature R of the top surface and the cladding diameter Dr of the optical probe satisfy the following relationship: R≥Dr / 2.

5. The optical probe according to claim 1, characterized in that, The surface of the cladding portion is covered by a resin film.

6. The optical probe according to claim 1, characterized in that, The first region has a structure that joins the top portion, which is continuous to the top surface, with the connecting portion, which is connected to the second region. The diameter of the mold field at the top is fixed. The mold field diameter of the connecting portion is less than or equal to the mold field diameter of the top end portion at the mating surface where it engages with the top end portion, and the connecting portion has a region where the mold field diameter gradually narrows from the mating surface along the central axis. The length of the top end along the central axis is set such that the light signal incident from the top end passes through the joint surface parallel to the central axis.

7. An optical probe array, characterized in that, It is constructed by arranging a plurality of optical probes according to any one of claims 1 to 6.

8. An optical probe card, characterized in that, have: The optical probe according to any one of claims 1 to 6; and The optical probe head is held in place by the optical probe.

9. A method for manufacturing an optical probe, the optical probe being used to measure the characteristics of an optical device formed on a wafer, the optical waveguide of the optical probe comprising a core and a cladding portion disposed on the outer periphery of the core, the transmission mode of the optical waveguide being single-mode, the manufacturing method being characterized by comprising the following steps: Prepare an optical fiber with a region whose mode field diameter gradually narrows from one end along the central axis. One end is ground into a conical shape to form a conical region; as well as Using the cone-shaped apex as an axis, the top surface of the cone-shaped region is machined into a convex curved surface. The radius of curvature of the top surface is set such that the direction of travel of the light signal incident on the top surface is approximately parallel to the central axis of the optical waveguide immediately after the light signal passes through the top surface. Assuming the radius of curvature of the top surface is R, the numerical aperture of the top surface is NA, the mode field diameter (i.e., the first MF diameter) of the top surface is Ce, the radiation angle of the light signal incident on the top surface is 2αm, the refractive index of the core at the incident point of the light signal on the top surface is nr, the central half-angle at the incident point of the top surface is ω, the refraction angle of the light signal at the incident point is (ω+β), and the top surface is flat, the numerical aperture sin(α0) of the top surface satisfies the following relationship: R = Ce / sin(ω) NA = sin(αm) αm=sin -1 {nr×sin(ω+β)}-ω β=sin -1 {sin(α0) / nr}.

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