JP3990361B2 - Optical bench - Google Patents

Description

  The present invention relates to an optical bench which is a silicon substrate for mounting optical components. In particular, the present invention relates to a substrate for optically coupling an optical semiconductor element and an optical component such as an optical fiber or a lens and fixing them.

  Conventionally, an optical element mounting substrate for optically coupling an optical semiconductor element composed of a laser diode or a photodiode to an optical fiber or a lens, and an optical element mounting substrate capable of transmitting a high-frequency signal at a maximum transmission signal frequency of 10 GHz. There was a structure disclosed in Japanese Patent Laid-Open No. 2002-50821.

JP 2000-50821 A

  However, the optical element mounting substrate disclosed in the above conventional example has the following problems.

For signals with a frequency exceeding 10 GHz, a dielectric layer (for example, made of silicon oxide (SiO ₂ )) having a maximum film thickness of 10 μm is insufficient in thickness, so that transmission loss is suppressed (for example, 3 dB / cm or less). ) It is difficult to form a transmission line, that is, a thin film wiring pattern. Further, although the silicon substrate is specified to have a resistivity of 10,000 Ω · cm or more, a non-doped silicon substrate must be used to achieve this resistivity, and it is difficult to control the value. . Actually, it is easy to obtain a silicon substrate of 1000 Ω · cm or more, but it is difficult to specify a silicon substrate of 10000 Ω · cm or more. Further, since the transmission signal deterioration cannot be reduced without using such a specific resistivity substrate, not only the productivity is low but also the cost reduction is difficult to cope with.

  Next, since the dielectric layer is formed on the entire surface of the silicon substrate, a dielectric layer of about 10 μm is also formed inside the V groove for the optical fiber. Therefore, this dielectric layer is liable to reduce the accuracy of the shape of a highly accurate V groove formed by anisotropic etching of silicon. As a result, the mounting accuracy (passive alignment accuracy) of the optical fiber is likely to be lowered.

  Next, since the dielectric layer is formed only on one surface of the silicon substrate, the silicon substrate is likely to warp. As described above, since the dielectric layer is provided only on one surface of the silicon substrate, the warpage of the substrate is easily promoted by the temperature variation. As a result, the optical coupling between the laser diode and the optical fiber is likely to shift, and the coupling loss tends to increase.

  Therefore, the present invention provides a structure that can suppress or reduce transmission loss of a high-frequency signal of 10 GHz or more, and can use a general-purpose silicon substrate without the transmission loss depending on the resistivity of the silicon substrate. Furthermore, the accuracy of the V-groove for mounting the optical fiber and the lens is ensured, and at the same time, the structure in which the warpage of the substrate is difficult to occur, especially the increase in the warpage of the substrate due to the temperature fluctuation is suppressed. An object of the present invention is to provide a structure that suppresses an increase in optical coupling loss.

  As the above-mentioned invention, the present inventors have made an optical element mounting substrate (optical bench) in which the first glass substrate is bonded to the front surface of the silicon substrate and the second glass substrate is bonded to the back surface to substantially increase the thickness of the derivative layer. Proposed. However, when the glass substrate and the silicon substrate are bonded, air may remain blocked at the interface between them. After bonding, the silicon V-groove is covered with a glass substrate, and air is sealed. Therefore, in the manufacturing process for forming wirings and electrodes after bonding, there is a problem that the sealed air expands and contracts to affect the processing dimensional accuracy.

  The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

  Of the inventions disclosed in this application, the outline of typical ones will be briefly described as follows.

  In order to achieve the above object, the solving means in the present invention is as follows.

  The first means is a laser diode, a wiring electrically connected to the laser diode, a lens or an optical fiber optically connected to the laser diode, a photodiode optically connected to the laser diode, and the photodiode. An optical bench having an installation part for installing an electrically connected wiring, a silicon substrate, a first substrate installed on the surface of the silicon substrate, and a first substrate installed on the back surface of the silicon substrate A second substrate, the laser diode installation portion, the wiring, and the photodiode installation portion on the first substrate, the lens or the optical fiber installation portion on the silicon substrate, the lens or An optical bench comprising a groove that passes through an installation portion of the optical fiber and communicates with an outer peripheral end of the first substrate. .

  The second means is a laser diode, a wiring electrically connected to the laser diode, a lens or optical fiber optically connected to the laser diode, a photodiode optically connected to the laser diode, and the photodiode. An optical bench having an installation part for installing an electrically connected wiring, a silicon substrate, a first substrate installed on the surface of the silicon substrate, and a first substrate installed on the back surface of the silicon substrate A second substrate, the laser diode installation portion, the wiring, and the photodiode installation portion on the first substrate, the lens or the optical fiber installation portion on the silicon substrate, the lens or A groove communicating with the outer peripheral end of the first substrate through the optical fiber installation portion, in front of the silicon substrate; The opposite surface to the lens or the optical fiber installation part, a optical bench comprising a groove which communicates to the outer periphery of the first substrate.

  Third means includes a laser diode, a wiring electrically connected to the laser diode, a lens or an optical fiber optically connected to the laser diode, a photodiode optically connected to the laser diode, and the photodiode. An optical bench having an installation part for installing an electrically connected wiring, a silicon substrate, a first substrate installed on the surface of the silicon substrate, and a first substrate installed on the back surface of the silicon substrate A second substrate, the laser diode installation portion, the wiring, and the photodiode installation portion on the first substrate, the lens or the optical fiber installation portion on the silicon substrate, the lens or A groove communicating with the outer peripheral end of the first substrate through the installation portion of the optical fiber, and the first substrate and the Second substrate is the optical bench is a dielectric substrate.

  The fourth means includes a laser diode, a wiring electrically connected to the laser diode, a lens or an optical fiber optically connected to the laser diode, a photodiode optically connected to the laser diode, and the photodiode. An optical bench having an installation part for installing an electrically connected wiring, a silicon substrate, a first substrate installed on the surface of the silicon substrate, and a first substrate installed on the back surface of the silicon substrate A second substrate, the laser diode installation portion, the wiring, and the photodiode installation portion on the first substrate, the lens or the optical fiber installation portion on the silicon substrate, the lens or A groove communicating with the outer peripheral end of the first substrate through the optical fiber installation portion, in front of the silicon substrate; A groove communicating with the outer periphery of the first substrate is provided on a surface opposite to the lens or the optical fiber installation portion, and the first substrate and the second substrate are optical benches that are dielectric substrates. .

  The fifth means includes a laser diode, a wiring electrically connected to the laser diode, a lens or an optical fiber optically connected to the laser diode, a photodiode optically connected to the laser diode, and the photodiode. An optical bench having an installation part for installing an electrically connected wiring, a silicon substrate, a first substrate installed on the surface of the silicon substrate, and a first substrate installed on the back surface of the silicon substrate A second substrate, the laser diode installation portion, the wiring, and the photodiode installation portion on the first substrate, the lens or the optical fiber installation portion on the silicon substrate, the lens or A groove communicating with the outer peripheral end of the first substrate through the installation portion of the optical fiber, and the first substrate and the Second substrate is an optical bench is a glass substrate.

  Sixth means includes a laser diode, a wiring electrically connected to the laser diode, a lens or an optical fiber optically connected to the laser diode, a photodiode optically connected to the laser diode, and the photodiode. An optical bench having an installation part for installing an electrically connected wiring, a silicon substrate, a first substrate installed on the surface of the silicon substrate, and a first substrate installed on the back surface of the silicon substrate A second substrate, the laser diode installation portion, the wiring, and the photodiode installation portion on the first substrate, the lens or the optical fiber installation portion on the silicon substrate, the lens or A groove communicating with the outer peripheral end of the first substrate through the optical fiber installation portion, in front of the silicon substrate; The opposite surface to the lens or the optical fiber installation portion includes a groove that communicates to the outer periphery of said first substrate, said second substrate and said first substrate is the optical bench is a glass substrate.

  Further, the optical bench manufacturing method of the first to sixth means includes a step of forming an etching groove on the silicon substrate by anisotropic etching, and an outer peripheral edge of the silicon substrate through the etching groove on the silicon substrate. Forming a groove communicating with each other, bonding the silicon substrate, the first substrate, and the second substrate, and forming a laser diode installation portion, a wiring, and a photodiode installation portion on the first substrate. And a step of etching a part of the first substrate to expose the groove formed in the silicon substrate.

  Also, a laser diode, a wiring electrically connected to the laser diode, a lens or an optical fiber optically connected to the laser diode, a photodiode optically connected to the laser diode, and an electrical connection to the photodiode A laser diode module having an installation portion for installing wiring, the silicon substrate, a first substrate installed on the surface of the silicon substrate, and a second substrate installed on the back surface of the silicon substrate The laser diode on the first substrate, the wiring, the photodiode on the silicon substrate, the lens or the optical fiber on the silicon substrate, the lens or the optical fiber A groove communicating with the outer peripheral edge of the first substrate through the installation portion of the first substrate and the front of the first substrate The second substrate is a laser diode module with optical bench is a glass substrate.

  Further, a laser diode, a wiring electrically connected to the laser diode, a lens or an optical fiber optically connected to the laser diode, a photodiode optically connected to the laser diode, and an electrical connection to the photodiode A laser diode module having an installation portion for installing wiring, the silicon substrate, a first substrate installed on the surface of the silicon substrate, and a second substrate installed on the back surface of the silicon substrate The laser diode on the first substrate, the wiring, the photodiode on the silicon substrate, the lens or the optical fiber on the silicon substrate, the lens or the optical fiber A groove communicating with the outer peripheral end of the first substrate through the installation portion of the first substrate, A groove communicating with the outer periphery of the first substrate is provided on a surface opposite to the lens or the optical fiber installation portion, and the first substrate and the second substrate are mounted with an optical bench that is a glass substrate. This is a laser diode module.

  The effects obtained by the representative ones of the inventions disclosed in the present application will be briefly described as follows.

  In the optical bench of the present invention, a silicon substrate and a glass substrate are anodically bonded, and a laser diode installation part, a photodiode installation part, and a wiring (transmission line) made of a thin film element are formed on the glass substrate surface. At this time, a groove communicating with the outer peripheral end of the silicon substrate is formed so as to pass through the lens of the silicon substrate or the etching groove for installing the optical fiber, so that the etching groove is in communication with the outside air without being blocked. Therefore, even if there is a temperature rise due to heat in the step of forming the above-mentioned laser diode installation part and photodiode installation part and a thin film element after forming a glass / silicon / glass three-layer substrate by anodic bonding, The optical bench can be manufactured with high accuracy without being affected by the expansion of the closed air. Therefore, even when the transmission signal is 10 GHz or more, a transmission line with suppressed loss can be easily formed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a perspective view of an optical bench according to a first embodiment of the present invention. The optical bench includes a silicon substrate 1, a first glass substrate 2, and a second glass substrate 3. The silicon substrate 1 is a thicker substrate than the first glass substrate 2 and the second glass substrate 3. The first glass substrate 2 and the second glass substrate 3 are dielectric substrates having approximately the same thickness, and are made of the same material glass. These dielectric substrates are insulating substrates having a higher resistivity than the semiconductor silicon substrate 1 as a matter of course.

The silicon substrate 1 and the first glass substrate 2 are joined via a natural oxide film 4, that is, a silicon oxide (SiO ₂ ) thin film, and the silicon substrate 1 and the second glass substrate 3 are similarly natural oxide films 4. That is, they are joined via a silicon oxide thin film. That is, the first glass substrate 2 and the second glass substrate 3 are located on the silicon oxide thin film of the natural oxide film 4. The silicon substrate 1 is a single crystal silicon substrate having a crystal plane orientation (100), and a natural oxide film 4, that is, a silicon oxide thin film is formed on the surface thereof, and an etching formed in part by anisotropic etching of silicon. A groove 5 and an inverted pyramid groove 6 are formed.

  An inverted pyramid groove 6 is formed so that the center line of the etching groove 5 in the vicinity of the etching groove 5 is axisymmetric. On the surface of the first glass substrate 2, a tantalum nitride thin film resistor 8, a tantalum oxide thin film capacitor 9, a laser diode common thin film electrode 10 for electrical connection with the laser diode, and a laser diode common thin film electrode 10 are provided. The formed AuSn solder thin film 11 for laser diode, which is a solder film for mounting the laser diode, the thin film electrode 14 for photodiode for electrical connection with the photodiode, the first common thin film electrode 12 for photodiode, and the first photodiode thin film electrode Two common thin film electrodes 13, a first AuSn solder thin film 17 for photodiodes, which is a solder film for mounting a photodiode formed on the thin film electrode 14 for photodiodes, and a first common thin film electrode 12 for photodiodes, on which the photodiode is mounted For solder film The second AuSn solder thin film 15 for the photodiode, the third AuSn solder thin film 16 for the photodiode, which is a solder film for mounting the photodiode formed on the common thin film electrode 13 for the photodiode, and the substrate when the laser diode is operating A thin film temperature sensor 18 for measuring the surface temperature and a glass etching groove 7 for reflecting the light emitted from the laser diode and allowing the light to enter the photodiode are formed.

  As shown in the figure, the tantalum nitride thin film resistor 8 and the tantalum oxide thin film capacitor 9 are formed in the vicinity of the position where the laser diode AuSn solder thin film 11 on which the laser diode is mounted is formed. A high-frequency electrical signal exceeding 10 GHz transmitted to the laser diode or photodiode is transmitted to the thin film elements such as the tantalum nitride thin film resistor 8 and the laser diode common thin film electrode 10. Further, the etching groove 5 is a groove used for mounting an optical fiber or a lens, and the inverted pyramid groove 6 is a marker groove used for determining a position for mounting the optical fiber or lens. For example, when a lens having a cylindrical outer shape is mounted in the etching groove 5, the mounting height of the lens, that is, the optical axis center of the lens is determined by the width of the etching groove 5. Because the etching groove 5 is formed by anisotropic etching of silicon, the side surface of the etching groove 5 is constituted by the {111} plane of the crystal plane of silicon, and an angle of 54.7 ° with the (100) plane of the bottom plane. It is because it always does.

  Thus, since the angle between the side surface and the bottom surface of the etching groove 5 is constant, the center height of the lens is determined by the width of the etching groove 5. At this time, if the spot of the laser diode (light exit port) mounted on the first glass substrate 2 via the AuSn solder thin film 11 for laser diode and the center of the lens coincide with each other, the light can be coupled, and the light The axes match. What is necessary is just to obtain | require the width | variety of the etching groove | channel 5 so that these optical axes may correspond. Further, the positioning of the lens in the longitudinal direction can use the inverted pyramid groove 6 formed in the vicinity of the etching groove 5 as a reference marker.

  The silicon substrate 1 may have other orientations as long as it represents the plane orientation {100}, and the resistivity of the silicon substrate 1 may be any resistivity. Preferably, it is 1000 Ωcm or less. This is because the first glass substrate 2 that transmits a high-frequency signal of 10 GHz or more is a substrate that is sufficiently thicker than a thin film formed by sputtering or CVD (Chemical Vapor Deposition). This is because the resistivity of 1 does not affect the transmission characteristics of the high-frequency transmission line (electrode pattern) constituted by the thin film elements on the first glass substrate 2.

  Here, generally, the loss of the transmission line is divided into a conductor loss and a dielectric loss. In this embodiment, a transmission line made of a thin film element is formed on the first glass substrate 2 having a low dielectric loss, so that the conductor loss is almost dominant. If a thick metal film is used for the transmission line, the conductor loss can be almost ignored. In the present embodiment, the increase in the thickness of the metal film can be easily handled, so that the loss of the transmission line can be reduced.

The first glass substrate 2 and the second glass substrate 3 have a thermal expansion coefficient of approximately 33 × 10 ⁻⁷ / ° C. and are close to the thermal expansion coefficient (23.3 × 10 ⁻⁷ / ° C.) of the silicon substrate 1, Further, a glass (for example, borosilicate glass) containing a large amount of Na ₂ O of about 4% and capable of anodic bonding with the silicon substrate 1 is preferable.

As shown, an etching groove 5 and an inverted pyramid groove 6 formed by anisotropic etching of silicon are formed, and a natural oxide film 4, that is, a silicon oxide (SiO ₂ ) thin film is formed on the surface of the silicon substrate 1. One glass substrate 2 and second glass substrate 3 are anodically bonded to each other to have a three-layer structure of glass / silicon / glass. The first glass substrate 2 is anodically bonded to the surface of the silicon substrate 1 on which the etching grooves 5 and the inverted pyramid grooves 6 are formed, and the second glass substrate 3 is anodically bonded to the back surface of the silicon substrate 1. The first glass substrate 2 needs to have a shape such that the post-bonding etching groove 5 and the inverted pyramid groove 6 are not hidden in the silicon substrate 1. The shape of the first glass substrate 2 shown in FIG. 2 is an example, and may be any shape as long as it does not cover the etching groove 5 and the inverted pyramid groove 6.

  Further, a groove 20 is provided in the silicon substrate 1 so as to pass through the etching groove 5. This groove 20 is provided in order to prevent the etching groove 5 from becoming a sealed space when the silicon substrate 1 and the glass substrate 2 are anodic bonded. Therefore, as long as the groove 20 passes through the etching groove 5, the shape thereof may not be a straight line but may be a curved line.

  Since the structure of such an example is a structure in which the silicon substrate 1 is sandwiched between the first glass substrate 2 and the second glass substrate 3, it can be said that it is difficult to promote the warpage of the substrate due to temperature fluctuations. Because, if the first glass substrate 2 and the second glass substrate 3 are made of the same material, their linear expansion coefficients are the same. Therefore, the substrate is hardly warped only by extending in the longitudinal direction due to temperature fluctuations. It is.

  FIG. 2 is a perspective view of an optical bench showing another embodiment. The difference from the embodiment shown in FIG. 1 is that the depth of the groove 20 is deeper than the depth of the etching groove 5. Since the groove 20 is hung below the bottom surface of the etching groove 5, the effect of a relief groove that absorbs excess adhesive when a lens or an optical fiber is installed appears.

  FIG. 3 is a top view showing the silicon substrate 1 in which the etching groove 5 and the groove 20 are formed. The groove 20 passes through the etching groove 5 and communicates with the outer peripheral end of the silicon substrate 1 to prevent the etching groove 5 from being blocked by air. In addition, even during anodic bonding, there is an effect of preventing air clogging that results in poor bonding between the silicon substrate 1 and the glass substrate 2.

  FIG. 4 is a perspective view of an optical bench showing another embodiment. The groove 21 is also formed on the surface of the silicon substrate 1 to be bonded to the glass substrate 3, thereby preventing air blockage that causes bonding failure even in anodic bonding between the silicon substrate 1 and the glass substrate 3.

  Next, a method of manufacturing the optical bench having the structure shown in FIG. 4 will be described with reference to FIGS. 5 (a) and 5 (b). In this manufacturing method, a plurality of differently shaped grooves (grooves having different depths or grooves having different sizes) are formed in a silicon substrate by anisotropic etching of silicon, and then a glass substrate is bonded to the silicon substrate. However, after a thin film element such as a thin film resistor or a thin film electrode is formed on the glass substrate, the glass substrate is etched by dry etching.

  Here, FIG. 5A and FIG. 5B are cross-sectional views shown for easy understanding of a method of manufacturing an optical bench having a characteristic structure. Therefore, it does not coincide with the cross section of the optical bench shown in FIG. The manufacturing method will be described in accordance with steps a) to h) in FIGS. 5 (a) and 5 (b).

a) The silicon substrate 1 before processing is shown. A natural oxide film 4 has already been formed.

b) First, a silicon nitride / silicon oxide (Si ₃ N ₄ / SiO ₂ ) laminated film (not shown) is formed on both surfaces of the silicon substrate 1 having a crystal plane orientation (100). The SiO ₂ film (for example, film thickness 120 nm) is a thermal oxide film formed by thermal oxidation, and the Si ₃ N ₄ film (for example, film thickness 160 nm) is a film formed by a low pressure CVD (Chemical Vapor Deposition) method. is there. Next, an opening for forming the etching groove 5 and the inverted pyramid groove 6 is provided in the Si ₃ N ₄ / SiO ₂ laminated film. In this method, photolithography (resist coating, exposure, development, resist pattern formation and transfer of a pattern to a Si ₃ N ₄ / SiO ₂ laminated film using the resist as a mask agent) used in conventional semiconductor technology is applied. RIE (Reactive Ion Etching) is applied to the etching of the Si ₃ N ₄ / SiO ₂ laminated film. Thereafter, anisotropic etching of silicon is performed with a 40 wt% potassium hydroxide aqueous solution (temperature: 70 ° C.). At this time, the etching is performed until the etching groove 5 has a desired depth, for example, 450 μm. The inverted pyramid groove 6 (not shown in FIG. 5) has a small mask opening by the Si ₃ N ₄ / SiO ₂ laminated film, so that the {111} plane appears before the etching depth of the etching groove 5 reaches 450 μm. Thus, a V-shaped groove, that is, an inverted pyramid shape is formed, and the etching is apparently stopped. As described above, the formation of differently shaped grooves (grooves having different depths and grooves having different sizes) by anisotropic etching of silicon is limited by the etching of the groove having the deepest depth. Can be formed. Next, the Si ₃ N ₄ / SiO ₂ laminated film is sequentially peeled using hot phosphoric acid and BHF (HF + NH ₄ F mixed aqueous solution). Thereafter, when the silicon substrate 1 is left in the atmosphere, natural oxide films 4 are formed on the front and back surfaces of the silicon substrate 1.

c) Grooves 20 and 21 are formed by dicing. Here, the method for forming the grooves 20 and 21 may be a wet etching method, a dry etching method, or a sandblasting method after forming a groove pattern mask. The advantage of dicing is that it is not necessary to form a mask. However, as the number of grooves 20 and 21 increases, process time is required. On the other hand, the wet etching, the dry etching, and the sand blasting method require a mask, but a large number of grooves 20 and 21 can be formed at the same time.

d) Next, the silicon substrate 1 and the borosilicate glass containing a large amount of Na ₂ O of about 4% are bonded to each other inside the first glass substrate 2 having a linear expansion coefficient close to that of the silicon substrate 1 by anodic bonding. The bonding conditions depend on the thickness of the glass substrate 2, but a substrate heating temperature of 300 ° C. or higher and an applied voltage of 50 V or higher are preferable. Further, the second glass substrate 3 and the silicon substrate 1 having the same thickness as the first glass substrate 2 are bonded by the same method. At this time, the first glass substrate 2 and the second glass substrate 3 are laminated on the silicon substrate 1 on the heater, a voltage is applied to and bonded to the first glass substrate 2, and then the second glass substrate 3. It is better to apply a voltage to and bond to each other. By this method, the warpage of the substrate due to bonding can be reduced as much as possible.

e) A tantalum nitride thin film resistor 8, a tantalum oxide thin film capacitor 9 (not shown in FIG. 5B), a laser diode common thin film electrode 10, and a laser diode AuSn solder thin film 11 (see FIG. 5 (b), photodiode thin film electrode 14 (not shown in FIG. 5 (b)), photodiode first common thin film electrode 12 (not shown in FIG. 5 (b)), photodiode first electrode Two common thin film electrodes 13 (not shown in FIG. 5B), a first AuSn solder thin film 17 for photodiodes (not shown in FIG. 5B), and a second AuSn solder thin film 15 for photodiodes (FIG. 5B). ), A third AuSn solder thin film 16 for photodiodes (not shown in FIG. 5B) and a thin film temperature sensor 18 (not shown in FIG. 5B) are formed. First, a thin film (not shown) of Au (for example, film thickness 3 μm) / Pt (for example, film thickness 300 nm) / Ti (for example, film thickness 100 nm) is formed. Either a sputtering method or a vacuum evaporation method is applied as the film forming method. In this case, a metal film other than this may be used as long as it is a metal film, or a single layer film such as an Al thin film or a Cr thin film may be used. However, the metal film on the outermost surface is preferably a thick film having a thickness of about 3 μm in order to reduce / suppress the conductor loss of the transmission line composed of the thin film pattern.

  Next, a resist pattern is formed by photolithography, and the Au / Pt / Ti thin film is etched by ion milling using the resist pattern as a mask. Thereafter, the resist is stripped using a stripping solution and oxygen ashing to form a laser diode common thin film electrode 10, a photodiode thin film electrode 14, a photodiode first common thin film electrode 12, and a photodiode second common thin film electrode 13. .

  Next, a tantalum nitride thin film, a tantalum oxide thin film, an upper Au / Pt / Ti thin film for a thin film capacitor, and a Pt / Ti thin film for a thin film temperature sensor are formed by a lift-off method. At this time, the tantalum nitride thin film and the tantalum oxide thin film can be formed by sputtering. For the sputtering in this case, the former applies a reactive sputtering method in which a small amount of nitrogen gas is introduced into an argon atmosphere, and the latter applies a reactive sputtering method in which an oxygen gas is introduced into an argon atmosphere. can do. The Pt / Ti thin film can be formed using either a sputtering method or a vacuum deposition method. Thus, each thin film element is formed on the first glass substrate 2.

f) For example, a negative resist having a high viscosity of about 1000 cp is applied on the first glass substrate 2, and the thick film resist pattern 25 is obtained by photolithography. The thickness of the thick film resist pattern 25 is, for example, about 100 μm. At this time, the resist openings 26 and 27 for forming the etching opening 28 and the glass etching groove 7 may be formed at the same time.

g) The etching opening 28 and the glass etching groove 7 are formed in the first glass substrate 2 by dry ICP (Inductively Coupled Plasma) dry etching of glass.

h) The thick film resist pattern 25 is stripped by oxygen ashing and a resist stripping solution. Next, a positive resist (not shown) is applied to the substrate surface by spray coating. Thereafter, a resist pattern (not shown) is formed by photolithography. At this time, the resist pattern includes an AuSn solder thin film 11 for a laser diode (not shown in FIG. 5B), a first AuSn solder thin film 17 for a photodiode (not shown in FIG. 5B), and a second photodiode. This resist pattern corresponds to the AuSn solder thin film 15 (not shown in FIG. 5B) and the third AuSn solder thin film 16 for photodiode (not shown in FIG. 5B). An AuSn solder thin film (for example, Au thin film: 80%, Sn thin film: 20%) is a laminated thin film of an Au thin film and a Sn thin film, and the total film thickness is 3 μm. This is formed using a vacuum deposition method, and each pattern is formed by a lift-off method.

  The optical bench of the present invention can be obtained by sequentially performing the above steps.

  As another manufacturing method, before the anodic bonding step between the silicon substrate 1 and the glass substrates 2 and 3 shown in d) above, the etching openings 28 and the glass etching grooves 7 of the glass substrate are processed in advance, Then, there is a method in which anodic bonding is performed and the ICP dry etching process of glass f) and g) is eliminated.

  Further, since anodic bonding is selected as a method for bonding the silicon substrate and the dielectric substrate, the dielectric substrate is a glass substrate, but a bonding method other than anodic bonding may be used. For example, an Au film is formed on the bonding surface by vapor deposition or sputtering, the surfaces of the Au film and the Au film are cleaned in a vacuum, and contacted immediately after that, and bonded at a high temperature of about 1000 ° C. It may be a method. In cases other than anodic bonding, a dielectric material other than glass can be used.

  FIG. 6 is a diagram showing dicing lines 30 and 31 for cutting out the optical bench manufactured by the manufacturing method of FIGS. 5A and 5B for each chip.

  Dicing lines 30 and 31 are indicated by hatching. By simultaneously cutting the silicon substrate 1 and the anodic bonded glass substrates 2 and 3 along the dicing lines 30 and 31, the optical bench is separated for each chip. According to this cutting method, the groove 20 remains on the silicon substrate 1. The remaining groove 20 is effective as a retracting groove for excess adhesive when the lens or optical fiber is mounted.

  FIG. 7 is a diagram showing a cutting method other than that in FIG. The dicing line 30 is set so as to be in the groove 20, and after the optical bench is cut into each chip, the optical bench is formed with no groove 20 left.

  FIG. 8 is a top view showing a structure for forming the groove 22 of another optical bench. In the case of such a groove 22, the optical bench wiring and the laser diode shown in FIGS. 1, 2, and 4 and the groove 22 overlap with each other. However, the optical bench of the present invention has a glass substrate 2. Since the above-described wiring, laser diode, and the like are mounted on the groove 22, the groove 22 is on the back side of the mounting surface of the glass substrate 2, and there is no problem with the arrangement of the groove 22. As described above, the groove can be freely formed on the silicon substrate 1.

  FIG. 9 is a perspective view in which the optical fiber alignment reflector 40 and the aspherical lens 41 are mounted on the optical bench shown in FIGS. Laser diodes and wiring are omitted. A reflecting plate 40 is set in the groove 20, and the aspherical lens 41 is aligned using the reflecting plate 40. Therefore, if the groove 20 is used as a groove for the reflecting plate 40 set, it is effective for alignment of the aspherical lens and the optical fiber and can be optically aligned. Can be set.

  An optical filter (not shown) can be set instead of the reflection 40 set in the groove 20.

  FIG. 10 is a schematic diagram showing a state when the laser diode 32, the photodiode 33, and the aspherical lens 41 are mounted on the optical bench shown in FIG. The aspheric lens 41 is fixed to the etching groove 5 with an adhesive. The laser diode 32 and the photodiode 33 apply heat to the AuSn solder thin film 11 for laser diode, the first AuSn solder thin film 17 for photodiode, the second AuSn solder thin film 15 for photodiode, and the third AuSn solder thin film 16 for photodiode to melt them. The optical bench is fixed to the first glass substrate 2 by reflowing. At that time, the laser diode 32, the photodiode 33, and the aspherical lens 41 are fixed by passive alignment so that the optical axes thereof coincide. In order for these optical axes to coincide, of course, the width of the etching groove 5, the thickness of the first glass substrate 2, the position on the first glass substrate 2 where the laser diode 32 is mounted, and the photodiode are mounted. The position on the first glass substrate 2 and the position where the etching groove 5 is formed are determined in advance. In order to transmit an optical signal to the outside by applying a high-frequency electric signal of 10 GHz or more to the optical bench on which each optical component is mounted, each component is electrically connected by wire bonding. Since high frequency electrical signals are handled, the tantalum nitride thin film resistor 8, the tantalum oxide thin film capacitor 9, the laser diode common thin film electrode 10, and the photodiode thin film electrode 14 are used so that the length of each wire 34 for electrical connection is shortened. The first common thin-film electrode 12 for photodiode, the second common thin-film electrode 13 for photodiode, and the thin-film temperature sensor 18 are previously formed at optimal positions. Here, the tantalum nitride thin film resistor 8 serves as a function of eliminating electrical signal damping and terminating resistance. The electrical signal is converted into an optical signal by the laser diode 32, and the optical signal emitted from the laser diode 32 is transmitted to the outside such as an optical fiber through the aspheric lens 41. At this time, the optical signal emitted from the laser diode 32 is monitored by the photodiode 33. Here, wiring inside the optical bench or wiring outside the optical bench is shown by the wire 34, but this is not restrictive. It is also possible to form a through hole in the optical bench and electrically connect each element with a via-hole wiring filled with a metal. In this case, the distortion of the waveform of the high-frequency electrical signal due to the influence of the parasitic inductance of the wire 34 can be corrected.

  FIG. 11 is a schematic diagram showing an example in which the optical bench shown in FIG. 1 is mounted on a butterfly type laser diode module.

  A laser diode 32 and a photodiode 33 are mounted on the first glass substrate 2, an aspheric lens 41 is mounted on the silicon substrate 1, and an optical bench is mounted in the package 35. Although not shown, a cooling Peltier element for suppressing heat generation of the laser diode 32 is mounted below the optical bench. A high-frequency electrical signal of 10 GHz or higher is applied to the optical bench via a connector 39 having excellent high-frequency characteristics. An optical signal from the laser diode 32 is transmitted to the outside through an optical fiber 38 fixed by an aspheric lens 41, a collimator lens 36, and a ferrule 37. With such a configuration, the optical bench of the present invention is applied to a laser diode module.

  A potassium hydroxide aqueous solution was used to form the etching groove 5 and the inverted pyramid groove 6 for mounting the aspherical lens on the silicon substrate 1 constituting the optical bench described above, but TMAH (tetramethylammonium hydroxide) or Another etching solution capable of anisotropic etching of silicon such as EDP (ethylenediamine pyrocatechol water) may be applied. However, an aqueous potassium hydroxide solution is suitable from the viewpoint of etching shape and handling.

  FIG. 12 is a cross-sectional view of an optical bench showing another embodiment of the present invention. The dicing for separating the individual optical benches is to cut the first glass substrate 2, the natural oxide film 4, the silicon substrate 1 and the second glass substrate 3. Since the toughness is different, it is necessary to change the rotation speed and feed rate of the dicing blade during glass cutting and silicon cutting, which increases the number of processes and may cause edge chipping or cracks in the cut portion. If you try to cut at the same blade rotation speed and feed speed, chipping and cracking will increase further. In particular, since wiring and electrodes are formed on the surface on the etching groove 5 side, chipping and cracking are not preferable. Some cracks and cracks are allowed on the surface opposite to the etching groove 5. From the above, as shown in FIG. 12, when forming the etching opening in the first glass substrate 2 in the steps g) and f) of FIG. 5B, the etching opening 50 is simultaneously formed in the dicing line portion. Form. Thereby, only the silicon substrate 1 can be diced, and the first glass substrate 2 will not be chipped or cracked. The second glass substrate 3 may be cut as it is under the same dicing conditions as the silicon substrate 1 or may be left uncut and divided. Since the natural oxide film 4 is thin, it can be ignored.

  FIG. 13 is an explanatory view of an optical bench in which a glass etching opening 51 is provided in a portion of a dicing line when separating the optical bench, as in FIG. A high-quality optical bench having no chipping or cracking on the opposite surface of the etching groove 5 can be manufactured.

  In the present invention, dry etching is used for the etching opening of the glass in the present invention. However, the etching opening is not particularly limited, and may be wet etching.

  Although the invention made by the present inventor has been specifically described based on the above-described embodiment, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. Of course.

It is a perspective view of the optical bench which is the 1st example of the present invention. It is a perspective view of the optical bench which is the other Example of this invention. It is a top view of the silicon substrate 1 which is one Example of this invention. It is a perspective view of the optical bench which shows the other Example. FIG. 5 is a process flow diagram showing a manufacturing process of the optical bench shown in FIG. 4. FIG. 6 is a process flow diagram showing a manufacturing process of the optical bench following FIG. It is a figure which shows the dicing line for cutting out the optical bench which is an Example of this invention for every chip | tip. It is a figure which shows the dicing line for cutting out the optical bench which is the other Example of this invention for every chip | tip. It is a top view which shows the formation structure of the groove | channel of the optical bench which is the other Example of this invention. It is the perspective view which mounts the reflecting plate for positioning of an optical fiber, and an aspherical lens on an optical bench. It is a perspective view when a laser diode, a photodiode, and a ball lens are mounted on the optical bench of the present invention. It is a top view when an optical bench of the present invention is mounted on a laser diode module. It is sectional drawing of the optical bench which shows the other Example of this invention. It is sectional drawing of the optical bench which shows the other Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Silicon substrate, 2 ... 1st glass substrate, 3 ... 2nd glass substrate, 4 ... Natural oxide film, 5 ... Etching groove, 6 ... Reverse pyramid groove, 7 ... Glass etching groove, 8 ... Tantalum nitride thin film resistance DESCRIPTION OF SYMBOLS 9 ... Tantalum oxide thin film capacitor, 10 ... Common thin film electrode for laser diodes, 11 ... AuSn solder thin film for laser diodes, 12 ... First common thin film electrode for photodiodes, 13 ... Second common thin film electrode for photodiodes, 14 ... For photodiodes Thin film electrode, 15 ... second AuSn solder thin film for photodiode, 16 ... third AuSn solder thin film for photodiode, 17 ... first AuSn solder thin film for photodiode, 18 ... thin film temperature sensor, 20 ... groove, 21 ... groove, 22 ... groove 25 ... thick film resist pattern, 26 ... resist opening, 27 ... resist opening, 28 ... etch 41, aspherical lens, 32 ... laser diode, 33 ... photodiode, 34 ... wire, 35 ... package, 36 ... collimator lens, 37 ... ferrule, 38 ... optical fiber, 39 ... connector, 40 ... reflector, 50, 51 ... etching openings, 30, 31 ... dicing lines.

Claims (1)

A silicon substrate;
A first substrate that is a dielectric substrate or a glass substrate disposed on the first surface of the silicon substrate via an oxide film ;
A second substrate that is a dielectric substrate or a glass substrate disposed on the second surface opposite to the first surface of the silicon substrate via an oxide film ;
Wiring installed on the first substrate;
An installation groove provided on the first surface of the silicon substrate and used for installation of a lens or an optical fiber;
A first groove that passes through the installation groove and communicates with an outer peripheral end of the silicon substrate;
An optical bench having a second groove communicating with the second surface of the silicon substrate up to an outer peripheral end of the silicon substrate.

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