JP2022086485A - Optical waveguide element, optical modulator, optical modulation module, and optical transmission device - Google Patents

Abstract

To provide an optical waveguide element which offers good bonding position accuracy without substrate etching even when the size and spacing of electrode pads are reduced.SOLUTION: An optical waveguide element is provided, comprising an optical waveguide and electrode pads with conductor wires bonded thereto provided on a substrate. Each electrode pad has a bonding area in which a conductor wire is bonded thereto, where an intermediate layer forming a step at a position surrounding the bonding area on the substrate is provided between the substrate and the electrode pad.SELECTED DRAWING: Figure 5

Description

The present invention relates to an optical waveguide element, an optical modulator, an optical modulation module, and an optical transmitter.

In a high-speed / large-capacity optical fiber communication system, light incorporating an optical modulation element as an optical waveguide element composed of an optical waveguide formed on a substrate and a control electrode for controlling an optical wave propagating through the optical waveguide. Modulators are often used. Among them, an optical modulation element using LiNbO ₃ (hereinafter, also referred to as LN) having an electro-optical effect as a substrate can realize a wide-band optical modulation characteristic with little light loss, and thus is a high-speed / large-capacity optical fiber. Widely used in communication systems.

In particular, the modulation method in the optical fiber communication system is multi-valued such as QPSK (Quadrature Phase Shift Keying), DP-QPSK (Dual Phaseization-Quadrature Phase Shift Keying), etc. in response to the recent trend of increasing transmission capacity. Transmission formats that incorporate phase shift keying into multi-value modulation have become the mainstream, and are being used in backbone optical transmission networks as well as in metro networks.

The acceleration of the spread of Internet services in recent years has led to a further increase in communication traffic, and studies on continuous high-speed and large-capacity optical communication systems are still underway. On the other hand, the demand for miniaturization of the device remains unchanged, and the miniaturization of the light modulation element itself is required. For example. When used, it is necessary to reduce the size of the light modulation element housed inside to about 1/3 as compared with the conventional one.

As one measure for miniaturizing the light modulation element, for example, a light modulation element using a rib-type waveguide (hereinafter referred to as a rib-type light modulation element) has been studied (see, for example, Patent Document 1). In the rib-guided waveguide, a substrate using LN is thinly processed, and then other portions are further thinned (for example, to a substrate thickness of 10 μm or less) while leaving a desired striped portion (rib) by dry etching or the like. As a result, the effective refractive index of the rib portion is made higher than that of the other portions to form an optical waveguide. In the rib-type light modulation element, the light confinement portion is limited to the rib portion as compared with the light modulation element using an optical waveguide manufactured by using metal diffusion such as Ti, so that the interaction between light and electricity Can be efficiently generated. As a result, the length of the interaction portion can be shortened, and the light modulation element can be miniaturized.

On the other hand, if the light modulation element is miniaturized, the area of the substrate on which the light modulation element is formed is reduced, the size of the electrode pads (bonding electrode pads) formed on the substrate is reduced, and the distance between the electrode pads is reduced. Reduction will also be required. The reduction of the electrode pad spacing limits the upper limit thickness of the electrode pad in order to improve the patterning accuracy of the electrode pad, and the thinner the electrode pad, the more bonding when the conductor wire is bonded onto the electrode pad. The strength is low. Therefore, it may be necessary to realize a technique that can more accurately determine the bonding position on the electrode pad without protruding from the electrode pad.

Patent Document 2 describes that a minute convex portion protruding in the surface direction or a minute concave portion recessed in the surface direction of the semiconductor element is formed at the center of each of the four sides of the rectangular electrode pad of the semiconductor element. Has been done. In this semiconductor element, when the center of the electrode pad is positioned at the center of the work of the wire bonding device, the vertical and horizontal lines of the cross cursor (crosshair cursor) are displayed in the work area image of the magnifying microscope provided in the wire bonding device. The position of the work is adjusted so as to pass through a pair of convex portions or concave portions provided on the two opposite left and right sides and the upper and lower two sides of the electrode pads, respectively. As a result, in this semiconductor element, the position of wire bonding can be adjusted with high accuracy.

Further, in Patent Document 3, in a semiconductor element, recesses such as a cross shape in a plan view are formed by etching the surface of the silicon substrate at two positions on the surface of the silicon substrate on which the electrode pads (bonding pads) are formed. It is described to form a pattern. In this semiconductor element, electrode pads are formed on each of the two recess patterns, and the step formed on the surface of the electrode pad by the recess pattern is used as a reference point for the wire bonding apparatus to grasp the connection location. Be done.

However, in the semiconductor element described in Patent Document 2, since a convex portion or a concave portion is formed in each of the electrode pads in the direction of the substrate surface, if the convex portion is formed, it becomes an obstacle in narrowing the distance between the electrode pads and the concave portion. When the above is formed, the bondable region is scraped, which can limit the reduction of the electrode pad area. Further, the semiconductor device described in Patent Document 3 requires a patterning step and some other steps for substrate etching, which may lead to a significant increase in process man-hours. In particular, when a concave pattern is formed on a substrate thinned to a thickness of 10 μm or less as described above, the formation of the concave portion by substrate etching causes a decrease in the strength of the substrate and affects the reliability as a device. obtain.

Japanese Unexamined Patent Publication No. 2011-75917 Japanese Unexamined Patent Publication No. 2000-12603 Japanese Patent No. 4352579

From the above background, it is required to realize a technique capable of achieving good bonding position accuracy without substrate etching even when the size and spacing of the electrode pads are reduced in the optical waveguide element.

One aspect of the present invention is an optical waveguide element provided on a substrate with an optical waveguide and an electrode pad including a bonding area to which a conductor wire is bonded, and a step is provided on the substrate at a position surrounding the bonding area. An intermediate layer to be formed is provided between the substrate and the electrode pad.
According to another aspect of the present invention, the step formed by the intermediate layer has a plan view shape of a circle, a plurality of arcs, a rectangle, a plurality of straight lines, or a plurality of bending lines surrounding the joint area. Including the part.
According to another aspect of the present invention, the step formed by the intermediate layer is a portion around the joint area where the height of the lower surface of the electrode pad measured from the surface of the substrate corresponds to the joint area. It is formed so as to be lower than the height of the portion.
According to another aspect of the invention, the intermediate layer has protrusions arranged around the junction area.
According to another aspect of the invention, the intermediate layer has through holes or recesses that open over the entire range of the joining area.
According to another aspect of the present invention, the step formed by the intermediate layer is a portion around the joint area where the height of the lower surface of the electrode pad measured from the surface of the substrate corresponds to the joint area. It is formed so as to be higher than the height of the portion.
According to another aspect of the present invention, the upper surface of the intermediate layer extends over the entire range of the joining area.
According to another aspect of the present invention, the intermediate layer has a convex portion protruding from the upper surface of the intermediate layer, and the uppermost surface thereof extends over the entire range of the joint area of the electrode pad. do.
According to another aspect of the present invention, the intermediate layer has a groove at a position surrounding the periphery of the joining area.
According to another aspect of the present invention, the electrode pad is formed so as to cover the entire intermediate layer.
According to another aspect of the present invention, the intermediate layer has a thickness of 1.0 μm or more.
According to another aspect of the invention, the intermediate layer is a resin.
According to another aspect of the invention, the resin is a thermosetting resin or a thermoplastic resin.
Another aspect of the present invention includes any of the above optical waveguide elements, which are optical waveguide elements that modulate light, a housing that houses the optical waveguide elements, and an optical fiber that inputs light to the optical waveguide elements. An optical modulator comprising an optical fiber that guides the light output by the optical waveguide element to the outside of the housing.
Another aspect of the present invention is an optical modulation module including any of the above optical waveguide elements, which is an optical modulation element that modulates light, and a drive circuit for driving the optical waveguide element.
Yet another aspect of the present invention is an optical transmission device comprising the above-mentioned light modulator or optical modulation module and an electronic circuit for generating an electric signal for causing the optical waveguide element to perform a modulation operation.

According to the present invention, in the optical waveguide element, even when the size and spacing of the electrode pads are reduced, good bonding position accuracy can be realized without accompanied by substrate etching.

It is a figure which shows the structure of the optical modulator which concerns on 1st Embodiment of this invention. It is a figure which shows the structure of the light modulation element used in the light modulator shown in FIG. 1. It is a partial detailed view of the part A of the light modulation element shown in FIG. It is a partial detailed view of the part B shown in FIG. It is a VV cross-sectional arrow view of the part B shown in FIG. It is a figure which shows the example of the bonding position deviation in the part B shown in FIG. This is a modified example of the configuration of the B portion shown in FIG. It is a partial detailed view of part C shown in FIG. FIG. 8 is a cross-sectional view taken along the line IX-IX of part C shown in FIG. It is a partial detailed view of part D shown in FIG. FIG. 10 is a cross-sectional view taken along the line XI-XI of part D shown in FIG. It is a partial detailed view of part E shown in FIG. It is a cross-sectional view of XIII-XIII of the part E shown in FIG. It is a partial detailed view of the F part shown in FIG. FIG. 14 is a cross-sectional view taken along the line XV-XV of the F portion shown in FIG. It is a partial detailed view of the G part shown in FIG. 16 is a cross-sectional view taken along the line XVII-XVII of the G portion shown in FIG. It is a partial detailed view of the H part shown in FIG. FIG. 8 is a cross-sectional view taken along the line XIV-XIV of the H portion shown in FIG. It is a partial detailed view of the J part shown in FIG. FIG. 20 is a cross-sectional view taken along the line XXI-XXI of the J portion shown in FIG. It is a partial detailed view of the K part shown in FIG. FIG. 22 is a cross-sectional view taken along the line XXIII-XXIII of the K portion shown in FIG. 22. It is a partial detailed view of the M part shown in FIG. It is a figure which shows the structure of the optical modulation module which concerns on 2nd Embodiment of this invention. It is a figure which shows the structure of the optical transmission apparatus which concerns on 3rd Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[1. First Embodiment]
FIG. 1 is a diagram showing a configuration of an optical modulator 100 using an optical modulation element 104, which is an optical waveguide element according to the first embodiment of the present invention. The light modulator 100 includes a housing 102, a light modulation element 104 housed in the housing 102, and a relay board 106. The light modulation element 104 is, for example, a DP-QPSK modulator. Finally, a cover (not shown), which is a plate body, is fixed to the opening of the housing 102, and the inside thereof is hermetically sealed.

The light modulator 100 also has a signal pin 108 for inputting a high-frequency electric signal used for modulation of the light modulation element 104 and a signal pin 110 for inputting an electric signal used for adjusting the operating point of the light modulation element 104. And have.

Further, the light modulator 100 houses an input optical fiber 114 for inputting light into the housing 102 and an output optical fiber 120 for guiding the light modulated by the light modulation element 104 to the outside of the housing 102. It is held on the same surface of the body 102.

Here, the input optical fiber 114 and the output optical fiber 120 are fixed to the housing 102 via the supports 122 and 124, which are fixing members, respectively. The light input from the input optical fiber 114 is collimated by the lens 130 arranged in the support 122, and then input to the light modulation element 104 via the lens 134. However, this is only an example, and the light input to the light modulation element 104 is based on the prior art, for example, an input optical fiber 114 is introduced into the housing 102 via the support 122, and the introduced input light is introduced. It can also be performed by connecting the end face of the fiber 114 to the end face of the substrate 230 (described later) of the light modulation element 104.

The light modulator 100 also has an optical unit 116 that polarizes and synthesizes two modulated lights output from the light modulation element 104. The light after polarization synthesis output from the optical unit 116 is collected by the lens 118 arranged in the support 124 and coupled to the output optical fiber 120.

The relay board 106 uses a conductor pattern (not shown) formed on the relay board 106 to optical a high-frequency electric signal input from the signal pin 108 and an electric signal for adjusting an operating point input from the signal pin 110. It relays to the modulation element 104. The conductor pattern on the relay board 106 is connected to an electrode pad (described later) constituting one end of the electrode of the light modulation element 104, for example, by wire bonding. Further, the optical modulator 100 includes a terminator 112 having a predetermined impedance in the housing 102.

FIG. 2 is a diagram showing an example of the configuration of the light modulation element 104 housed in the housing 102 of the light modulator 100 shown in FIG. The size of the light modulation element 104 is, for example, 10 mm or more and 20 mm or less in the horizontal direction shown in the figure, and 2 mm or more and 5 mm or less in the vertical direction shown in the figure. The light modulation element 104 is composed of an optical waveguide (dotted line in the figure) formed on the substrate 230, and performs DP-QPSK modulation of, for example, 200 G. The substrate 230 is, for example, an X-cut LN substrate having an electro-optic effect, which is processed to a thickness of 20 μm or less (for example, 2 μm) and thinned. The LN substrate may be doped with MgO (magnesium oxide).

Further, the optical waveguide is a convex optical waveguide (for example, a rib type optical waveguide or a ridge type optical waveguide) composed of a band-shaped extending convex portion formed on the surface of the thinned substrate 230. Here, since the refractive index of the LN substrate may change locally due to the photoelastic effect when stress is applied, it is generally a Si (silicon) substrate, a glass substrate, or an LN in order to reinforce the mechanical strength of the entire substrate. It is adhered to a support plate such as. In this embodiment, as will be described later, the substrate 230 is adhered to the support plate 502 via the adhesive layer 500 (see, for example, FIG. 5).

The substrate 230 is, for example, rectangular and has two left and right sides 280a and 280b extending in the vertical direction and facing each other, and 280c and 280d the upper and lower sides extending in the left and right direction and facing each other. In FIG. 2, as shown by the coordinate axes shown in the upper right part of the drawing, the normal direction toward the back of the paper in FIG. 2 (from the front surface to the back surface) is the X direction, the right direction in the drawing is the Y direction, and the lower direction in the drawing. Is the Z direction. These coordinate axes correspond to, for example, the X-axis, the Y-axis, and the Z-axis, which are the crystal axes of the substrate 230, which is an LN substrate.

The light modulation element 104 has the same input light as the input waveguide 232 that receives the input light (arrow pointing to the right in the figure) from the input optical fiber 114 on the lower side in the figure of the left side 280a in the figure of the substrate 230. Includes a branched waveguide 234 that branches into two lights with light intensity. Further, the light modulation element 104 includes so-called nested Machzenda type optical waveguides 240a and 240b, which are two modulation units that modulate each light branched by the branch waveguide 234.

The nested Machzenda-type optical waveguides 240a and 240b include two Machzenda-type optical waveguides 244a, 246a, and 244b, 246b, which are provided one by one in two waveguide portions forming a pair of parallel waveguides, respectively. As a result, in the nested Machzenda type optical waveguides 240a and 240b, after each of the input lights branched into two by the branched waveguide 234 is QPSK-modulated, the modulated light (output) is used in the respective output waveguides 248a. Output from 248b to the left in the figure.

These two output lights are then polarization-synthesized by an optical unit 116 arranged outside the substrate 230 and combined into one light beam. Hereinafter, the input waveguide 232 and the branch waveguide 234 formed on the substrate 230 of the light modulation element 104, and the nested Machzenda type optical waveguides 240a and 240b and the Machzenda type optical waveguides 244a, 246a, 244b, and 246b included therein are included. The optical waveguides and the like are collectively referred to as optical waveguides 232 and the like. As described above, these optical waveguides 232 and the like are convex optical waveguides composed of convex portions extending in a band shape on the substrate 230.

A high-frequency electric signal is input on the substrate 230 for causing each of the four Machzenda-type optical waveguides 244a, 246a, 244b, and 246b constituting the nested Machzenda-type optical waveguides 240a and 240b to perform modulation operation. Signal electrodes 250a, 250b, 250c, 250d are provided. Here, the high-frequency electric signal input to the signal electrodes 250a, 250b, 250c, 250d is, for example, an electric signal in the microwave band.

The right side of the signal electrodes 250a, 250b, 250c, 250d extends to the right side side 280b of the substrate 230, and is connected to the electrode pads 252a, 252b, 252c, and 252d, respectively. Further, the left side of the signal electrodes 250a, 250b, 250c, 250d is bent downward in the drawing and extends to the side 280d of the substrate 230, and is connected to the electrode pads 252e, 252f, 252g, and 252h.

The signal electrodes 250a, 250b, 250c, and 250d form, for example, a coplanar transmission line having a predetermined impedance together with a ground conductor pattern (not shown) formed on the substrate 230 according to the prior art. The ground conductor pattern is provided so as not to be formed on the optical waveguide 232 or the like, and the plurality of regions of the ground conductor pattern divided and formed by the optical waveguide 232 or the like are separated from each other by wire bonding or the like. Can be connected.

The electrode pads 256a, 252b, 252c, and 252d arranged on the side 280b on the right side of the drawing are connected to the relay board 106 by wire bonding. Further, the electrode pads 252e, 252f, 252g, and 252h arranged on the lower side 280d in the drawing are connected to four terminating resistors (not shown) mounted on the terminating device 112 by wire bonding, respectively. As a result, the high-frequency electric signal input from the signal pin 108 to the electrode pads 256a, 252b, 252c, 252d via the relay board 106 becomes a traveling wave and propagates through the signal electrodes 250a, 250b, 250c, 250d, and Machzenda. The light waves propagating in the type optical waveguide 244a, 246a, 244b, and 246b are modulated respectively.

Here, the high-speed modulation operation is performed by further strengthening the interaction between the electric field formed by the signal electrodes 250a, 250b, 250c, 250d in the substrate 230 and the waveguide light propagating through the Machzenda type optical waveguides 244a, 246a, 244b, and 246b. The substrate 230 is formed to have a thickness of 20 μm or less, preferably 10 μm or less, so that the above can be performed at a lower voltage. In the present embodiment, for example, the thickness of the substrate 230 is 1.2 μm, and the height of the convex portion constituting the optical waveguide 232 and the like is 0.7 μm.

The light modulation element 104 is also provided with bias electrodes 254a, 254b, and 254c for compensating for fluctuations in the bias point due to so-called DC drift and adjusting the operating point. The bias electrode 254a is used to compensate for bias point fluctuations of the nested Machzenda type optical waveguides 240a and 240b. Further, the bias electrodes 254b and 254c are used to compensate for bias point fluctuations of the Machzenda type optical waveguides 244a, 246a, and 244b, 246b, respectively.

The bias electrode 254a extends to the upper side 280c in the drawing of the substrate 230 and is connected to the electrode pads 256a, 256b, 256c, and 256d. Further, the bias electrode 254b extends to the upper side 280c in the drawing of the substrate 230 and is connected to the electrode pads 256e, 256f, 256g, and 256h. Similarly, the bias electrode 254c extends to the upper side (280c) of the substrate 230 in the drawing and is connected to the electrode pads 256j, 256k, 256m, and 256n.

These electrode pads 256a, 256b, 256c, 256d, 256e, 256f, 256g, 256h, 256j, 256k, 256m, 256n are each connected to any of the signal pins 110 via the relay board 106, and these signal pins are connected to each other. It is connected to a bias control circuit provided outside the housing 102 via the 110. As a result, the bias electrodes 254a, 254b, and 254c are driven by the bias control circuit, and the operating point is adjusted so as to compensate the bias point variation for each corresponding Machzenda type optical waveguide.

Hereinafter, the signal electrodes 250a, 250b, 250c, and 250d are also collectively referred to as a signal electrode 250. Further, the bias electrodes 254a, 254b, and 254c are also collectively referred to as a bias electrode 254. Further, the electrode pads 252a, 252b, 252c, 252d, 252e, 252f, 252g, and 252h of the signal electrode 250 are collectively referred to as an electrode pad 252. Further, the electrode pads 256a, 256b, 256c, 256d, 256e, 256f, 256g, 256h, 256j, 256k, 256m, 256n of the bias electrode 254 are also collectively referred to as an electrode pad 256.

FIG. 3 is a partial detailed view of part A of the light modulation element 104 shown in FIG. In FIG. 3, the electrode pads 256a, 256b, 256c, 256d, 256e, 256f, 256g, 256h, 256j, 256k, 256m, 256n of the bias electrodes 254a, 254b, and 254c are connected to the respective electrode pads 256. Shown with wires (thick line in the figure).

In this embodiment, the electrode pad 256 is formed on an intermediate layer arranged on the substrate 230. Here, a portion composed of an intermediate layer and an electrode pad 256 formed on the intermediate layer is referred to as a bonding portion. Further, the area on the surface of the electrode pad 256 to which the conductor wire is to be joined shall be referred to as a joining area.

The light modulation element 104 according to the present embodiment is provided with an intermediate layer forming a step on the substrate 230 at a position surrounding the bonding area of the electrode pad 256 between the substrate 230 and the electrode pad 256. As a result, a step is formed on the upper surface of the electrode pad 256 formed on the intermediate layer at a position surrounding the joint area along the step of the intermediate layer.

Hereinafter, the configuration of each bonding portion including the electrode pads 256 will be described by taking some of the electrode pads 256 shown in FIG. 3 as an example.

[1.1 Configuration of part B]
First, as a first configuration example of the bonding portion, the configuration of the B portion shown in FIG. 3 will be described. FIG. 4 is a partial detailed view of the B portion. In FIG. 4, the conductor wire 310 is bonded to the electrode pad 256a.

The electrode pad 256a is formed on the intermediate layer 300a formed on the substrate 230. The material of the intermediate layer 300a may be non-metal or metal. In the present embodiment, the intermediate layer 300a is a thermosetting resin. The thermosetting resin constituting the intermediate layer 300a is, for example, a photoresist, which contains a coupling agent (crosslinking agent) and is a so-called photosensitive permanent film in which the crosslinking reaction proceeds and is cured by heat. can do.

The intermediate layer 300a forms a step on the substrate 230 at a position surrounding the bonding area. This step is formed so that the height of the lower surface of the electrode pad 256a measured from the surface of the substrate 230 is lower than the height of the peripheral portion of the bonding area in the portion corresponding to the bonding area.

Specifically, the intermediate layer 300a has a rectangular shape in a plan view and is formed in a size larger than that of the electrode pad 256a. And in particular, the intermediate layer 300a has a through hole 400a that opens over the entire range of the joining area. Here, the joining area of the electrode pad 256a is circular, and accordingly, the opening of the through hole 400a is formed in a circular shape in a plan view. However, the circular joining area is an example, and the joining area may be any shape other than the circular shape, for example, a rectangle or a polygon. In these cases, the shape of the opening of the through hole 400a may be formed, for example, a rectangle or a polygon according to the plan view shape of the joining area.

FIG. 5 is a cross-sectional view taken along the line VV of the portion B shown in FIG. The substrate 230 is fixed to the support plate 502 via the adhesive layer 500. Here, the support plate 502 is composed of, for example, a glass substrate, an LN substrate, a Si substrate, or the like.

An intermediate layer 300a having a through hole 400a is formed on the substrate 230, and the inner circumference of the through hole 400a constitutes a step formed on the substrate 230 at a position surrounding the joint area. Due to the through hole 400a, the lower surface of the electrode pad 256a is in contact with the upper surface of the intermediate layer 300a in the portion surrounding the bonding area, and is in contact with the surface of the substrate 230 lower than the upper surface in the portion corresponding to the bonding area. That is, the step formed by the inner circumference of the through hole 400a of the intermediate layer 300a is a portion around the joint area where the height of the lower surface of the electrode pad 256a measured from the surface of the substrate 230 corresponds to the joint area. It is formed so as to be lower than the height of.

Due to the presence of the through hole 400a, a recess 304a that defines the joint area is formed on the upper surface of the electrode pad 256a at a position corresponding to the through hole 400a. Specifically, the range of the bottom surface of the recess 304a corresponds to the joining area.

The recess 304a functions as a target when visually determining the bonding position in the bonding work of the conductor wire 310 to the upper surface of the electrode pad 256a, and can improve the setting accuracy of the bonding position in the wire bonding work. Further, since the recess 304a can be set to a size corresponding to the size of the electrode pad 256a by the opening size of the through hole 400a, good bonding in the bonding work even when the size and the interval of the electrode pad 256a are reduced. Positional accuracy can be achieved and manufacturing yield can be improved.

Further, since the recess 304a defining the bonding area is formed along the shape of the intermediate layer 300a arranged on the substrate 230 (the shape of the through hole 400a in the B portion), the substrate is different from the above-mentioned conventional technique. Good bonding position accuracy can be achieved without the etching of 230.

Further, when the intermediate layer 300a made of a resin is used as in the present embodiment, the stress due to the difference in the coefficient of thermal expansion between the substrate 230 and the metal of the electrode pad 256 can be alleviated by the resin. , It is advantageous from the viewpoint of mechanical strength and long-term reliability of the light modulation element 104. Further, since the thickness of the intermediate layer 300a made of such a resin can be easily formed to be thicker than that of the intermediate layer made of metal, the depth of the recess 304a can be easily controlled, and the recess 304a as the target is good. Visibility can be ensured. From the viewpoint of visibility, it is desirable that the thickness of the intermediate layer 300a is 1.0 μm or more. In the example of the portion B shown in FIG. 5, the intermediate layer 300a is formed with a thickness of 2.0 μm.

Further, according to the configuration of the portion B, the outer edge of the joint area is determined by the step formed by the inner circumference of the recess 304a. Therefore, for example, when the bonding position of the conductor wire 310 deviates beyond the range of the recess 304a, as shown in FIG. 6, the step formed by the recess 304a causes the melted portion of the conductor wire on the electrode pad 256a to be formed. The surface shape may collapse or tilt. Therefore, in the light modulation element 104, the inspection accuracy of the bonding position deviation after the bonding work can be improved as compared with the case where a flat electrode pad is used.

Here, the size of the recess 304a (that is, the size of the bonding area) is the size of the molten portion of the conductor wire 310 on, for example, the electrode pad 256a (for example, in ball bonding, at the tip of the conductor wire) from the viewpoint of improving the bonding position accuracy. The size of the molten ball to be formed) is preferably 1.2 times or more and 1.5 times or less.

In the present embodiment, by providing the through hole 400a in the intermediate layer 300a, the height of the lower surface of the electrode pad 256a measured from the surface of the substrate 230 corresponds to the joint area, and the height around the joint area. Although it is assumed that a step is formed so as to be lower than the height of the portion, the configuration of the intermediate layer 300a forming such a step is not limited to this.

For example, instead of the intermediate layer 300a provided with the through hole 400a, as shown in FIG. 7, an intermediate layer 300a-1 having a recess 402a that does not penetrate to the surface of the substrate 230 may be used. The material of the intermediate layer 300a-1 may be a non-metal or a metal, and is, for example, a thermosetting resin similar to that of the intermediate layer 300a. In the configuration shown in FIG. 7, the intermediate layer 300a-1 is also arranged between the substrate 230 and the lower surface portion of the electrode pad 256a corresponding to the joining area. Therefore, for example, in the case of wire bonding, the stress applied to the substrate 230 from the tool of the wire bonder can be relaxed by the intermediate layer 300a-1. Such relaxation of stress is advantageous from the viewpoint of preventing mechanical damage or the like in the substrate 230 when the substrate 230 is configured as a thin plate having a thickness of 20 μm or less as in the present embodiment.

[1.2 Configuration of C part]
Next, as a second configuration example of the bonding portion, the configuration of the C portion shown in FIG. 3 will be described. FIG. 8 is a partial detailed view of the portion C including the electrode pad 256b.

The electrode pad 256b is formed on the intermediate layer 300b formed on the substrate 230. The material of the intermediate layer 300b may be a non-metal or a metal, and is, for example, a thermosetting resin similar to that of the intermediate layer 300a.

The intermediate layer 300b has the same configuration as the intermediate layer 300a of the portion B shown in FIG. 5, and forms a step on the substrate 230 at a position surrounding the joint area of the electrode pad 256b. However, the step formed by the intermediate layer 300b is different from the step formed by the intermediate layer 300a, and the height of the lower surface of the electrode pad 256a measured from the surface of the substrate 230 corresponds to the joining area. It is formed so as to be higher than the height of the surrounding part of the area.

Specifically, the intermediate layer 300b has the same configuration as the intermediate layer 300a, except that it does not have a through hole 400a and has a groove 404a at a position surrounding the joint area of the electrode pad 256b. Here, the joint area of the electrode pad 256b is circular, and correspondingly, the groove 404a is formed in an annular shape in a plan view so as to surround the circular joint area. However, the circular joining area is an example, and the joining area may be any shape other than the circular shape, for example, a rectangle or a polygon. In these cases, the plan view shape of the groove 404a may be formed, for example, a rectangle or a polygon according to the plan view shape of the joining area.

FIG. 9 is a cross-sectional view taken along the line C of FIG. 8 shown in FIG. The groove 404a opens on the upper surface of the intermediate layer 300b, penetrates the intermediate layer 300b, and reaches the substrate 230. Due to the inner circumference of the annular groove 404a, the intermediate layer 300b forms a step at a position surrounding the joint area of the electrode pad 256b.

Due to the groove 404a, the lower surface of the electrode pad 256a is in contact with the surface of the substrate 230 which is the bottom surface of the groove 404a in the peripheral portion of the bonding area, and is on the upper surface of the intermediate layer 300b higher than the bottom surface in the portion corresponding to the bonding area. It will come into contact. That is, the step formed by the intermediate layer 300b by the inner circumference of the groove 404a is a portion around the joint area where the height of the lower surface of the electrode pad 256b measured from the surface of the substrate 230 corresponds to the joint area. It is formed to be higher than the height of.

Due to the presence of the groove 404a, an annular recess 304b that defines a joining area is formed on the upper surface of the electrode pad 256b at a position corresponding to the groove 404a. Specifically, of the upper surface of the electrode pad 256b, the portion surrounded by the recess 304b (specifically, the portion surrounded by the inner circumference of the annular recess 304b) corresponds to the joining area.

Similar to the recess 304a in the portion B, the range surrounded by the recess 304b functions as a target when visually determining the bonding position in the bonding work of the conductor wire 310 to the upper surface of the electrode pad 256b, and in the wire bonding work. It is possible to improve the setting accuracy of the bonding position. Further, since the recess 304b can be set to a size corresponding to the size of the electrode pad 256b, even when the size and the interval of the electrode pad 256b are reduced, it supports the realization of good bonding position accuracy in the bonding work. It is possible to improve the manufacturing yield.

Further, since the recess 304b that defines the joining area is formed along the shape of the intermediate layer 300b (the shape of the groove 404a) arranged on the substrate 230, unlike the prior art, the substrate 230 is not etched. Good bonding position accuracy can be achieved.

Further, in particular, in the configuration of the C portion shown in FIG. 9, the lower surface of the joint area of the electrode pad 256b can be in contact with the uppermost surface of the intermediate layer 300b which does not form a groove or a recess, so that the middle portion of the lower portion of the joint area of the electrode pad 256b can be contacted. The thickness of the layer 300b can be made thicker than that shown in FIG. 7. Therefore, in the configuration of the C portion, the stress applied to the substrate 230 from the wire bonder tool is further relaxed as compared with the configuration shown in FIG. 7, and mechanical damage such as cracking of the substrate 230 during the bonding operation is more effectively performed. Can be prevented.

[1.3 Configuration of D part]
Next, as a third configuration example of the bonding portion, the configuration of the D portion shown in FIG. 3 will be described. FIG. 10 is a partial detailed view of the D portion including the electrode pads 256c and 256d. Further, FIG. 11 is a cross-sectional view taken along the line XI-XI of the portion D shown in FIG.

The D portion is a modification of the configuration of the B portion shown in FIGS. 4 and 5, and the intermediate layer 300c is formed across the two electrode pads 256c and 256d. That is, the intermediate layer 300c formed on the substrate 230 has the same configuration as the intermediate layer 300a of the B portion, except that two electrode pads 256c and 256d are formed on the intermediate layer 300c. The material of the intermediate layer 300c may be a non-metal or a metal, and is, for example, a thermosetting resin similar to that of the intermediate layer 300a.

Then, in the intermediate layer 300c, through holes are opened at the respective positions corresponding to the bonding areas of the electrode pads 256c and 256d, as in the intermediate layer 300a shown in FIGS. 4 and 5, in the entire range of these bonding areas. 400b and 400c are provided.

Due to the presence of the through holes 400b and 400c, recesses 304c and 304d defining the joining area are formed on the upper surfaces of the electrode pads 256c and 256d at positions corresponding to the through holes 400b and 400c, respectively.

In the configuration of the D portion, in addition to the effect in the C portion described above, the intermediate layer 300c is formed across the two electrode pads 256c and 256d, which facilitates the patterning step and is intermediate for each electrode pad 256. The distance between the electrode pads 256c and 256d can be narrower and closer to each other than in the configuration in which the layer 300a is provided. Further, since the intermediate layer 300c is formed in a larger area than the intermediate layer 300a, the adhesion strength of the intermediate layer 300c to the substrate 230 is improved, which is advantageous in terms of long-term reliability.

[1.4 Configuration of E part]
Next, as a fourth configuration example of the bonding portion, the configuration of the E portion shown in FIG. 3 will be described. FIG. 12 is a partial detailed view of the E portion including the electrode pad 256e. Further, FIG. 13 is a cross-sectional view taken along the line XIII-XIII of the part E shown in FIG.

The E part is a modification of the configuration of the B part shown in FIGS. 4 and 5. The intermediate layer 300d formed under the electrode pad 256e has the same structure as the intermediate layer 300a of the portion B shown in FIG. 4, but its size is smaller than the size of the electrode pad 256e, and the electrode pad 256e is the intermediate layer. It is formed so as to cover the entire 300e. The material of the intermediate layer 300d may be a non-metal or a metal, and is, for example, a thermosetting resin similar to that of the intermediate layer 300a.

The intermediate layer 300d has a through hole 400e similar to the through hole 400a provided in the intermediate layer 300a of the portion B shown in FIG. As a result, a recess 304e that defines the joint area is formed on the upper surface of the electrode pad 256e at a position corresponding to the through hole 400e. As a result, the same effect as that of the above-mentioned B portion can be obtained in the E portion as well, and good bonding position accuracy can be realized without etching the substrate 230.

In addition to this, in the configuration of the E portion, since the entire intermediate layer 300d is covered with the electrode pad 256e, for example, the gas that can be generated from the intermediate layer 300d made of resin is inside the housing 102 in the long-term operation. Leakage to the room is suppressed, and changes in the environmental atmosphere of the light modulation element 104 in the housing 102 are prevented.

[1.5 F section configuration]
Next, as a fifth configuration example of the bonding portion, the configuration of the F portion shown in FIG. 3 will be described. FIG. 14 is a partial detailed view of the F portion including the electrode pad 256 g. Further, FIG. 15 is a cross-sectional view taken along the line XV-XV of the F portion shown in FIG.

The electrode pad 256 g is formed on the intermediate layer 300e formed on the substrate 230. The material of the intermediate layer 300e may be a non-metal or a metal, and is, for example, a thermosetting resin similar to that of the intermediate layer 300a.

Similar to the intermediate layer 300a, the intermediate layer 300e forms a step on the substrate 230 at a position surrounding the joint area. This step is formed so that the height of the lower surface of the electrode pad 256 g measured from the surface of the substrate 230 is lower than the height of the peripheral portion of the joint area in the portion corresponding to the joint area.

Specifically, the intermediate layer 300e has an annular shape whose plan view shape surrounds the periphery of the joint area of the electrode pad 256 g. Due to the annularly formed intermediate layer 300e, the lower surface of the electrode pad 256g is in contact with the upper surface of the intermediate layer 300e in the peripheral portion of the bonding area, and the surface of the substrate 230 lower than the upper surface in the portion corresponding to the bonding area. Will come into contact with. That is, the step formed by the inner peripheral side wall of the intermediate layer 300e formed in an annular shape is a circle surrounding the joining area, and the height of the lower surface of the electrode pad 256g measured from the surface of the substrate 230 corresponds to the joining area. It is formed so as to be lower than the height of the peripheral portion of the joint area.

As a result, a recess 304f that defines the joining area is formed on the upper surface of the electrode pad 256g in a range corresponding to the inside of the ring formed by the intermediate layer 300e. Specifically, the bottom surface of the recess 304f corresponds to the joining area.

Similar to the recess 304a in the B portion, the recess 304f functions as a target when the bonding position is visually determined in the bonding work of the conductor wire 310 to the upper surface of the electrode pad 256g, and the bonding position of the bonding position in the wire bonding work. The setting accuracy can be improved. Further, since the recess 304f can be set to a size corresponding to the size of the electrode pad 256 g, even when the size and the interval of the electrode pad 256 g are reduced, good bonding position accuracy in the bonding work is realized and manufactured. Yield can be improved.

Further, since the recess 304f that defines the bonding area is formed along the shape of the intermediate layer 300e arranged on the substrate 230, unlike the prior art, good bonding position accuracy is obtained without etching the substrate 230. It can be realized.

Further, in particular, in the configuration of the F portion shown in FIG. 15, since the intermediate layer 300 g is formed as a simple ring, the patterning step of the intermediate layer 300 g becomes easy. Further, when the intermediate layer 300 g is made of resin, the amount of resin remaining in the lower part of the electrode pad 256 g is reduced as compared with the intermediate layer 300 d in which the plan view is formed rectangular, so that the intermediate layer in long-term operation is intermediate. It is possible to further suppress gas leakage from the layer 300 g into the housing 102.

In the above description of the F portion, the intermediate layer 300e is described as being formed in an annular shape, but the intermediate layer 300e is a modified example of the intermediate layer 300d in which the outer shape of the rectangular shape in a plan view is modified to be circular. It can be said that there is. That is, the intermediate layer 300e can also be defined as a structure in which the plan view is formed in a circular shape and a through hole having a circular opening is formed in the center thereof.

Here, the intermediate layers 300a, 300b, 300c, 300d, and 300e shown in FIGS. 4 to 15 form a step having a circular plan view at a position surrounding the joint area on the substrate 230. The plan view shape of the step is not limited to a circle.

The step formed by such an intermediate layer may include one or more arbitrary shaped portions surrounding the periphery of the joining area. For example, the step may have a plan-like shape including a shape portion of a plurality of arcs, rectangles, a plurality of straight lines, or a plurality of bent lines (bending lines) surrounding the periphery of the joint area.

[Structure of 1.6 G part]
Next, as a sixth configuration example of the bonding portion, the configuration of the G portion shown in FIG. 3 will be described. The G portion is an example in which the plan view shape of the step formed by the intermediate layer is composed of a plurality of arcs surrounding the periphery of the joint area, and is a modification of the F portion shown in FIG. 14 in which the step is formed in a circular shape. Is.

FIG. 16 is a partial detailed view of the G portion including the electrode pad 256h. Further, FIG. 17 is a cross-sectional view taken along the line XVII-XVII of the G portion shown in FIG. The electrode pad 256h is formed on the intermediate layer 300f formed on the substrate 230. The intermediate layer 300f is composed of two intermediate layers 300f-1 and 300f-2 having an arcuate shape in a plan view. The arcuate inner peripheral side walls of the intermediate layers 300f-1 and 300f-2 form a step surrounding the periphery of the joint area of the electrode pad 256h. The material of the intermediate layer 300f may be a non-metal or a metal, and is, for example, a thermosetting resin similar to that of the intermediate layer 300a.

Due to the intermediate layer 300f forming a plurality of arcuate steps surrounding the joint area, most of the peripheral portion of the electrode pad 256h is in contact with the upper surface of the intermediate layer 300f, and the portion corresponding to the joint area is the said. It comes into contact with the surface of the substrate 230, which is lower than the upper surface. That is, the step formed by the inner peripheral side wall of the intermediate layer 300 g is such that the height of the lower surface of the electrode pad 256 g measured from the surface of the substrate 230 is higher than the height of the portion around the joint area in the portion corresponding to the joint area. It is formed to be low.

As a result, on the upper surface of the electrode pad 256h, a recess 304g that defines the joining area is formed in a range surrounded by the two arcuate steps of the intermediate layer 300g. Specifically, the bottom surface of the recess 304 g corresponds to the joining area.

Similar to the recess 304a in the B portion, the recess 304g functions as a target when the bonding position is visually determined in the bonding work of the conductor wire 310 to the upper surface of the electrode pad 256h, and the bonding position of the bonding position in the wire bonding work. The setting accuracy can be improved.

In the configuration of the G portion, the intermediate layer 300f is divided into two arc-shaped portions, but the number of arc-shaped portions is not limited to this. The intermediate layer 300f may be composed of an arcuate portion divided into any number of 3 or more. Further, from the viewpoint of effectively functioning the recess 304g as a target when determining the bonding position, the total length of the steps surrounding the bonding area formed by the intermediate layer 300f (that is, the arc portion constituting the intermediate layer 300f). It is desirable that the total length of the inner circumferences of the joints is, for example, 1/2 or more of the entire circumference of the joint area.

[Structure of 1.7 H part]
Next, as a seventh configuration example of the bonding portion, the configuration of the H portion shown in FIG. 3 will be described. The H portion is an example in which the plan view shape of the step formed by the intermediate layer is formed by a rectangle surrounding the periphery of the joint area, and is a modification of the F portion shown in FIG. 14 in which the step is formed in a circular shape. ..

FIG. 18 is a partial detailed view of the H portion including the electrode pad 256j. Further, FIG. 19 is a sectional view taken along the line XIX-XIX of the H portion shown in FIG. The electrode pad 256j is formed on the intermediate layer 300g formed on the substrate 230. The intermediate layer 300g has the same structure as the intermediate layer 300f except that it is formed in the shape of a rectangular frame in a plan view. The rectangular frame-shaped intermediate layer 300 g is a portion around the joint area where the height of the lower surface of the electrode pad 256j measured from the surface of the substrate 230 corresponds to the joint area by the inner peripheral portion of the rectangular frame. A step is formed at a position surrounding the joint area so as to be lower than the height of.

As a result, on the upper surface of the electrode pad 256j, a recess 304h that defines the joining area is formed in a range corresponding to the inside of the rectangular frame formed by the intermediate layer 300g. Specifically, the bottom surface of the recess 304h corresponds to the joining area.

Similar to the recess 304a in the B portion, the recess 304h functions as a target when the bonding position is visually determined in the bonding work of the conductor wire 310 to the upper surface of the electrode pad 256j, and the bonding position of the bonding position in the wire bonding work. The setting accuracy can be improved.

[1.8 J part structure]
Next, as an eighth configuration example of the bonding portion, the configuration of the J portion shown in FIG. 3 will be described. The G portion is an example in which the plan view shape of the step formed by the intermediate layer is composed of a plurality of bending lines surrounding the periphery of the joint area, and the H portion shown in FIG. 18 in which the step is formed in a rectangular frame shape. This is a modified example of. In the G portion, the bending line is four L-shaped lines surrounding the joint area of the rectangular shape in a plan view from the four corners.

FIG. 20 is a partial detailed view of the J portion including the electrode pad 256k. Further, FIG. 21 is a cross-sectional view taken along the line XXI-XXI of the J portion shown in FIG. 20. The electrode pad 256k is formed on the intermediate layer 300h formed on the substrate 230. The intermediate layer 300h is composed of the intermediate layers 300h-1, 300h-2, 300h-3, and 300h-4, which are four portions having an L-shaped plan view. The inner peripheral side wall of each L-shaped portion of the intermediate layer 300h constitutes a step surrounding the periphery of the joint area of the electrode pad 256k. The material of the intermediate layer 300h may be a non-metal or a metal, and is, for example, a thermosetting resin similar to that of the intermediate layer 300a.

Due to the intermediate layer 300h forming a plurality of L-shaped steps surrounding the joint area, most of the peripheral portion of the electrode pad 256k is in contact with the upper surface of the intermediate layer 300h in the portion corresponding to the joint area. It comes into contact with the surface of the substrate 230 lower than the upper surface. That is, the step formed by the inner peripheral side wall of the intermediate layer 300h is such that the height of the lower surface of the electrode pad 256k measured from the surface of the substrate 230 is higher than the height of the portion around the joining area in the portion corresponding to the joining area. It is formed to be low.

As a result, a recess 304j that defines the joint area is formed on the upper surface of the electrode pad 256k in a range surrounded by the four L-shaped steps of the intermediate layer 300h. Specifically, the bottom surface of the recess 304j corresponds to the joining area.

Similar to the recess 304a in the B portion, the recess 304j functions as a target when the bonding position is visually determined in the bonding work of the conductor wire 310 to the upper surface of the electrode pad 256k, and the bonding position of the bonding position in the wire bonding work. The setting accuracy can be improved.

In the configuration of the J portion, as an example of the bending line included in the plan view shape of the step, four L-shaped lines surrounding the joint area of the plan view rectangle from the four corners are shown, but the bending line included in the step is L-shaped. It is not limited to the shape. The bending line of the step is not limited to the one composed of two straight lines including one bending point and opening at 90 degrees, such as an L-shape, depending on the plan view shape of the joint area, and any number of them. It may be composed of a plurality of straight portions or curved portions including bending points and each of which opens at an arbitrary angle.

[Structure of 1.9 K part]
Next, as an eighth configuration example of the bonding portion, the configuration of the K portion shown in FIG. 3 will be described. FIG. 22 is a partial detailed view of the K portion including the electrode pad 256 m. Further, FIG. 23 is a cross-sectional view taken along the line XXIII-XXIII of the K portion shown in FIG. 22.

The electrode pad 256m is formed on the intermediate layer 300j formed on the substrate 230. The material of the intermediate layer 300j may be a non-metal or a metal, and is, for example, a thermosetting resin similar to that of the intermediate layer 300a.

The intermediate layer 300j forms a step on the substrate 230 at a position surrounding the bonding area. This step is formed so that the height of the lower surface of the electrode pad 256 m measured from the surface of the substrate 230 is higher than the height of the peripheral portion of the joint area in the portion corresponding to the joint area.

Specifically, the intermediate layer 300j has a circular shape whose upper surface in plan view extends over the entire range of the joining area of the electrode pad 256 m. With this intermediate layer 300j, the lower surface of the electrode pad 256m is in contact with the upper surface of the intermediate layer 300j in the portion corresponding to the bonding area, and is in contact with the surface of the substrate 230 lower than the upper surface in the portion around the bonding area. .. That is, the step formed by the outer peripheral side wall of the intermediate layer 300j is such that the height of the lower surface of the electrode pad 256 m measured from the surface of the substrate 230 is higher than the height of the peripheral portion of the joint area in the portion corresponding to the joint area. It is formed to be high.

As a result, on the upper surface of the electrode pad 256m, a convex portion 600 defining the joining area is formed on the upper portion of the intermediate layer 300j. Specifically, the upper surface of the convex portion 600 corresponds to the joining area.

Similar to the recess 304a in the B portion, the convex portion 600 functions as a target when visually determining the bonding position in the bonding work of the conductor wire 310 to the upper surface of the electrode pad 256m, and the bonding position in the wire bonding work. The setting accuracy of can be improved.
[Structure of 1.10 M part]
Next, as a ninth configuration example of the bonding portion, the configuration of the M portion shown in FIG. 3 will be described. The M portion is a modification of the K portion shown in FIG. 22, and the plan view shape of the intermediate layer is formed not as a circle but as a rectangle.

FIG. 24 is a partial detailed view of the M portion including the electrode pad 256n. Since the cross section of the M portion is the same as the cross section of the K portion shown in FIG. 23, the illustration is omitted. The electrode pad 256n is formed on the intermediate layer 300k formed on the substrate 230. The material of the intermediate layer 300k may be a non-metal or a metal, and is, for example, a thermosetting resin similar to that of the intermediate layer 300a.

Similar to the intermediate layer 300j, the intermediate layer 300k has an upper surface extending over the entire range of the joining area, but is different from the intermediate layer 300j in that its plan view is rectangular. As a result, the intermediate layer 300k forms a step on the substrate 230 at a position surrounding the bonding area. This step is formed so that the height of the lower surface of the electrode pad 256n measured from the surface of the substrate 230 is higher than the height of the peripheral portion of the joint area in the portion corresponding to the joint area.

As a result, on the upper surface of the electrode pad 256n, a convex portion that defines the joining area is formed, similar to the convex portion 600 shown in FIG. 24.

Similar to the recess 304a in the B portion, the convex portion functions as a target when visually determining the bonding position in the bonding work of the conductor wire 310 to the upper surface of the electrode pad 256n, and the bonding position in the wire bonding work. The setting accuracy can be improved.

In the case of forming an intermediate layer extending over the entire range of the joint area such as the intermediate layer 300j of the K portion shown in FIG. 22 and the intermediate layer 300k of the M portion shown in FIG. 24, the plan view of the intermediate layer is formed. The shape is not limited to a circle and a rectangle, and may be any shape (for example, a polygon) depending on the shape of the joint area.

Hereinafter, the intermediate layers 300a, 300b, 300c, 300d, 300f, 300g, 300h, 300j, and 300k are collectively referred to as the intermediate layer 300. Further, the depressions 304a, 304b, 304c, 304d, 304e, 304f, 304g, 304h, 304j are collectively referred to as the depression 304.

In the light modulation element 104 having the above configuration, the intermediate layer 300 forms a step around the bonding area, so that a recess 34 or a convex portion 600 having a step defining the bonding area is formed on the upper surface of the electrode pad 256. To. These recesses 304 and convex portions 600 function as targets when the bonding position is visually determined in the bonding work, and improve the bonding position accuracy during the bonding work. Therefore, the size and / or spacing of the electrode pads can be reduced to further reduce the size of the light modulation element 104. As a result, in the optical modulator 100, it is possible to improve the mounting density of the components accommodated inside the housing 102 and to reduce the size of the housing 102.

The configuration for improving the bonding position accuracy by forming a step surrounding the bonding area on the electrode pad 256 by the intermediate layer 300 as described above is suitable when the distance between the electrode pads 256 is 10 μm or less. It is particularly useful when the interval is 5 μm or less. Further, the above configuration is suitable for an electrode pad having a side of 300 μm or less from the viewpoint of the size of the electrode pad 256, and is particularly useful when the side is 200 μm or less.

[2. Second embodiment]
Next, a second embodiment of the present invention will be described. This embodiment is an optical modulation module 1000 using the light modulation element 104 included in the light modulator 100 according to the first embodiment. FIG. 25 is a diagram showing the configuration of the optical modulation module 1000 according to the present embodiment. In FIG. 25, the same components as the optical modulator 100 according to the first embodiment shown in FIG. 1 shall be shown using the same reference numerals as those shown in FIG. 1, and the above-mentioned description of FIG. 1 will be described. Use it.

The optical modulation module 1000 has the same configuration as the optical modulator 100 shown in FIG. 1, but differs from the optical modulator 100 in that it includes a circuit board 1006 instead of the relay board 106. The circuit board 1006 includes a drive circuit 1008. The drive circuit 1008 generates a high-frequency electric signal for driving the light modulation element 104 based on, for example, a modulation signal supplied from the outside via the signal pin 108, and outputs the generated high-frequency electric signal to the light modulation element 104. do.

The light modulation module 1000 having the above configuration includes a light modulation element 104 having an electrode pad 256 formed on the intermediate layer 300, similarly to the light modulator 100 according to the first embodiment described above. Therefore, in the optical modulation module 1000, similarly to the optical modulator 100, it is possible to improve the mounting density of the components accommodated inside the housing 102 and to reduce the size of the housing 102.

[3. Third Embodiment]
Next, a third embodiment of the present invention will be described. This embodiment is an optical transmission device 1100 equipped with the optical modulator 100 according to the first embodiment. FIG. 26 is a diagram showing a configuration of an optical transmission device 1100 according to the present embodiment. The light transmission device 1100 includes an optical modulator 100, a light source 1104 that incidents light on the light modulator 100, a modulator driving unit 1106, and a modulation signal generation unit 1108. The above-mentioned optical modulation module 1000 can also be used instead of the light modulator 100 and the modulator drive unit 1106.

The modulation signal generation unit 1108 is an electronic circuit that generates an electric signal for causing the optical modulator 100 to perform a modulation operation, and based on transmission data given from the outside, the optical modulator 100 is subjected to light according to the modulation data. A modulation signal, which is a high-frequency signal for performing a modulation operation, is generated and output to the modulator drive unit 1106.

The modulator driving unit 1106 amplifies the modulation signal input from the modulation signal generation unit 1108 to drive the four signal electrodes 250a, 250b, 250c, 250d of the optical modulation element 104 included in the optical modulator 100. Outputs four high frequency electrical signals. As described above, instead of the light modulator 100 and the modulator drive unit 1106, the optical modulation module 1000 is provided with a drive circuit 1008 including a circuit corresponding to, for example, the modulator drive unit 1106 inside the housing 102. Can also be used.

The four high-frequency electric signals are input to the signal pins 108 of the light modulator 100 to drive the light modulation element 104. As a result, the light output from the light source 1104 is, for example, DP-QPSK modulated by the light modulator 100, becomes modulated light, and is output from the optical transmission device 1100.

In particular, in the light transmission device 1100, the light modulator 100 including the light modulation element 104 having the electrode pad 256 formed on the intermediate layer 300, similarly to the light modulator 100 according to the first embodiment described above. Alternatively, since the light modulation module 1000 is used, the size of these light modulators 100 or the light modulation module 1000 can be made smaller, and the device size can be made smaller.

The present invention is not limited to the configuration of the above embodiment and its alternative configuration, and can be implemented in various embodiments without departing from the gist thereof.

For example, in the first embodiment described above, the B, C, D, E, F, G, H, J, and K parts of the light modulation element 104 shown in FIGS. 2 and 3 The configuration of the bonding portion between the electrode pad 256 of the bias electrode 254 and the conductor wire has been described by taking the M portion (hereinafter, also collectively referred to as the B portion or the like) as an example, but the configuration of these bonding portions is a signal electrode. The same can be applied to the bonding portion between the electrode pad 252 of 250 and the conductor wire. For example, the intermediate layer 300a shown in FIG. 4 is formed in the lower part of the electrode pad 252a of the signal electrode 250a, and the same recess as the recess 304a shown in FIG. 5 is formed in the electrode pad 252a to serve as a target for bonding alignment. can do.

Further, in the bonding portions shown in the B portion, the C portion, the D portion, the E portion, the F portion, the G portion, the H portion, the J portion, the K portion, and the M portion, intermediate layers having different shapes are formed under the electrode pad 256. The 300 is formed, and the target of the bonding alignment at the time of wire bonding is formed on the upper surface of the electrode pad 256 in different embodiments. However, the electrode pads 256 and 252 in the light modulation element 104 and the conductor wire are used. The configuration of the bonding portion of the above is not limited to this. As the bonding portion in the light modulation element 104, the configurations of any of a plurality of different bonding portions shown in the B portion or the like may be mixed in the entire electrode pads 256 and 252, or any of the bonding portions shown in the B portion or the like. All the bonding portions may be configured by using the configuration of one bonding portion.

Further, in the bonding portions shown in the B portion, the C portion, the D portion, the E portion, the F portion, the G portion, the H portion, the J portion, the K portion, and the M portion, the lower surface of the electrode pad 256 is at least a part thereof. Although it is assumed that it is formed in contact with the surface of the substrate 230, the configuration of the bonding portion is not limited to this. For example, in FIGS. 5, 9, 11, 13, 13, 15, 17, 19, and 21, a part of the intermediate layer 300 is also provided in a portion where the lower surface of the electrode pad 256 is in contact with the surface of the substrate 230. It can be assumed that the entire electrode pad 256 formed is formed on the intermediate layer 300.

In this case, the intermediate layer 300 includes protrusions or recesses arranged around the joining area of the electrode pad 256. For example, in the configuration of the C portion shown in FIG. 9, when a part of the intermediate layer 300b is formed also in the portion where the lower surface of the electrode pad 256b is in contact with the surface of the substrate 230, the groove 404a is formed around the joint area. It is configured as an annular recess formed in the intermediate layer 300b so as to surround it. That is, the intermediate layer 300b may have recesses arranged around the joining area.

Further, for example, in the configuration of the F portion shown in FIG. 15, when a part of the intermediate layer 300f is formed also in a portion where the lower surface of the electrode pad 256 g is in contact with the surface of the substrate 230, the intermediate layer 300e is shown in FIG. It may be configured to have a convex portion having a plan view shape of an annulus surrounding the periphery of the joint area shown by the dotted line. That is, the intermediate layer 300e may have convex portions arranged around the joining area.

Further, in the configuration of the K portion shown in FIG. 23, a part of the intermediate layer 300j may be formed also in a portion where the lower surface of the electrode pad 256 m is in contact with the surface of the substrate 230. In this case, the intermediate layer 300j may be configured to have a convex portion having a circular shape extending in the entire range of the joint area shown by the dotted line in FIG. 22 in a plan view shape. That is, the intermediate layer 300j may be configured as having a convex portion protruding from the upper surface of the intermediate layer 300j and having a convex portion whose uppermost surface extends over the entire range of the joining area.

Further, in the configuration of the G portion shown in FIGS. 16 and 17, the intermediate layer 300f constitutes a step that surrounds the periphery of the joint area by two portions having an arc shape in a plan view, and the J portion shown in FIGS. 20 and 21. In the configuration of, the intermediate layer 300h constitutes a step that surrounds the periphery of the joint area by four portions having an L-shaped plan view, but the intermediate layer that surrounds the periphery of the junction area by a plurality of portions has this configuration. Is not limited. For example, the intermediate layer may be divided into three or five or more portions, and the inner peripheral side walls of those portions may form a step surrounding the joint area. The shape of such a divided intermediate layer, and thus the plan view shape of the step, may include, for example, three or more arcs surrounding a circular joint area or a plurality of linear shapes tangent to the circumference of the circle. Further, for example, when the joint area can be defined as a region forming a polygon, the plan view shape of the step is divided into two sides including a linear shape along the side of the polygon and the apex of the polygon. The shape portion of the bending line extending along the line (an L-shaped bending line such as the intermediate layer 300j of the H portion is an example thereof) may be included.

Further, the groove formed in the intermediate layer 300b of the C portion shown in FIGS. 8 and 9 is assumed to be annular, but the shape of the groove is not limited to this. Such a groove can be a groove having an arbitrary plan view shape. Further, the groove does not have to be formed in a continuous manner, and may be formed in a divided manner. A step formed by such a divided groove is one in which its planar shape includes a shape portion of a plurality of arcs, rectangles, a plurality of straight lines, or a plurality of bending lines surrounding a joint area. can do.

Further, in the above-described embodiment, the intermediate layer 300 is composed of, for example, a thermosetting resin which is a photoresist, but the material of the intermediate layer 300 is not limited to this. As described above, the intermediate layer 300 may be metal or non-metal. For example, when composed of a resin, the intermediate layer 300 is not limited to a thermosetting resin, but is an arbitrary resin such as a thermoplastic resin. Can be. Further, for example, the intermediate layer 300 may be configured in multiple layers by using the same or different materials.

Further, in the above-described embodiment, the substrate 230 is an X-cut LN substrate, but the substrate 230 is not limited to this. For example, the substrate 230 may be a Z-cut LN substrate. In this case, the signal electrode 250 and the bias electrode 254 may be formed on the buffer layer (for example, the SiO ₂ layer) formed on the substrate 230.

Further, the material of the substrate 230 is assumed to be an LN substrate, but the material of the substrate 230 is not limited to this. For example, the substrate 230 may be a semiconductor substrate such as InP, GaAs, or Si. Further, the substrate 230 may be configured by using any material having an electro-optical effect (for example, a ferroelectric substance or a polymer material).

Further, the substrate 230 may have a hybrid configuration in which the end faces of a plurality of substrates configured by using different materials are abutted and joined. For example, the substrate 230 may have a hybrid configuration of a quartz substrate and an LN substrate, an input waveguide 232, an output waveguide 248a, 248b, etc. may be configured on the quartz substrate, and another optical waveguide may be configured on the LN substrate. ..

Further, in the above-described embodiment, as an example, the configuration of the portion forming the electrode pad 256 in the light modulation element 104 which is an optical waveguide element has been described, but the applicable range of the configuration of the configuration of the electrode pad forming portion described above is. It is not limited to the optical waveguide element. The configuration of the electrode pad forming portion of the present invention can be applied not only to an optical waveguide element but also to a substrate used for a receiving module, a light source, or the like. In addition, the optical waveguide element, the light modulator, the optical modulation module, and the optical transmitter described above, and the optical transmission / reception module in which the light source and the receiver for demodulating the received optical modulation signal are mounted on the same board and theirs. It is also possible to use an optical transmitter / receiver housed in the same housing.

As described above, the light modulation element 104 constituting the light modulator 100 according to the first embodiment described above includes an optical waveguide 232 and the like, an electrode pad 256 including a bonding area to which the conductor wire 310 is bonded, and the like. Is an optical waveguide element provided on the substrate 230. The light modulation element 104 is provided with an intermediate layer 300 forming a step on the substrate 230 at a position surrounding the bonding area between the substrate 230 and the electrode pad 256.

According to this configuration, in an optical waveguide element such as a light modulation element, good bonding position accuracy can be realized without substrate etching even when the size and spacing of the electrode pads are reduced. Therefore, the distance between the electrode pads used for bonding can be further narrowed, and the optical waveguide element can be made smaller.

Further, the step formed by the intermediate layer 300 may be configured such that its plan view shape includes a shape portion of a circle, a plurality of arcs, a rectangle, a plurality of straight lines, or a plurality of bending lines surrounding the periphery of the joint area. According to this configuration, since the step can be configured by using various planar views, the degree of freedom in designing the intermediate layer can be improved.

Further, in the light modulation element 104, the step formed by the intermediate layer 300 is a portion around the junction area where the height of the lower surface of the electrode pad 256 measured from the surface of the substrate 230 corresponds to the junction area. It is formed to be lower than the height. According to this configuration, when the electrode pad 256 is formed on the intermediate layer 300, the recess 304 indicating the joining area can be formed on the upper surface of the electrode pad 256. Thereby, the recess 304 can be used as a target for bonding alignment, and the bonding position accuracy can be improved.

Further, the intermediate layer 300 may be configured to have convex portions arranged around the joining area. Further, the intermediate layer 300 may be configured to have a through hole or a recess that opens over the entire range of the joining area. According to these configurations, the intermediate layer 300 can be easily configured with a simple three-dimensional shape.

Further, in the step formed by the intermediate layer 300, the height of the lower surface of the electrode pad measured from the surface of the substrate is higher than the height of the peripheral portion of the joint area in the portion corresponding to the joint area. It is formed like this. According to this configuration, when the electrode pad 256 is formed on the intermediate layer 300, a recess 304 indicating the outer periphery of the bonding area and a convex portion 600 indicating the range of the bonding area can be formed on the upper surface of the electrode pad 256. can. Thereby, the recess 304 and the convex portion 600 can be used as a target for bonding alignment, and the bonding position accuracy can be improved.

Further, the upper surfaces of the intermediate layers 300j and 300k extend over the entire range of the joining area. As a modification thereof, the intermediate layer 300 shall have a convex portion protruding from the upper surface of the intermediate layer 300, and the uppermost surface of the convex portion shall extend over the entire range of the bonding area of the electrode pad 256. be able to. Further, the intermediate layer 300b has a groove 404a at a position surrounding the periphery of the joining area. According to these configurations, the intermediate layer 300 can be easily configured with a simple three-dimensional shape.

Further, the electrode pad 256 may be formed so as to cover the entire intermediate layer 300. According to this configuration, for example, it is possible to prevent gas from leaking from the intermediate layer 300 made of resin into the inner chamber of the housing 102, and to change the environmental atmosphere of the light modulation element 104 in the housing 102. It can be prevented and long-term reliability can be improved.

The thickness of the intermediate layer 300 is 1.0 μm or more. According to this configuration, a clear step indicating the joining area can be formed on the electrode pad 256.

Further, the intermediate layer 300 is a resin. According to this configuration, the intermediate layer 300 having a thickness of submicron or more, which is difficult to form with a metal, can be easily formed, and a clear step indicating a bonding area can be easily formed on the electrode pad 256. ..

Further, the intermediate layer 300 can be made of a thermosetting resin or a thermoplastic resin. According to this structure, the intermediate layer can be formed by using a wide variety of resins.

Further, the light modulator 100 includes an optical modulation element 104, which is an optical waveguide element that modulates light, a housing 102 that houses the light modulation element 104, and an input optical fiber 114 that inputs light to the light modulation element 104. , An output optical fiber 120 that guides the light output by the light modulation element 104 to the outside of the housing 102. According to this configuration, it is possible to realize a small-sized optical modulator with good characteristics by using the light modulation element 104 whose bonding position accuracy is improved and further miniaturization is possible.

Further, the light modulation module 1000 according to the second embodiment includes an optical modulation element 104 that modulates light, which is an optical waveguide element, and a drive circuit 1008 that drives the light modulation element 104.
Further, the optical transmission device 1100 according to the third embodiment is a modulation signal generation which is an electronic circuit for generating an electric signal for causing the light modulator 100 or the optical modulation module 1000 and the light modulation element 104 to perform a modulation operation. A unit 1108 is provided.

According to these configurations, the optical modulation module 1000 and the optical transmitter 1100 having good characteristics can be realized.

100 ... Optical modulator, 102 ... Housing, 104 ... Optical modulation element, 106 ... Relay board, 108, 110 ... Signal pin, 112 ... Terminator, 114 ... Input optical fiber, 116 ... Optical unit, 118, 130, 134 ... Lens, 120 ... Output optical fiber, 122, 124 ... Support, 230 ... Substrate, 232 ... Input waveguide, 234 ... Branch waveguide, 240a, 240b ... Nested Mach Zenda type optical waveguide, 244a, 244b, 246a, 246b ... Mach Zenda type optical waveguide 248a, 248b ... Output waveguide, 250a, 250b, 250c, 250d ... Signal electrode, 252a, 252b, 252c, 252d, 252e, 252f, 252g, 252h, 256a, 256b, 256c, 256d, 256e, 256f, 256g, 256h, 256j, 256k, 256m, 256n ... Electrode pad, 254a, 254b, 254c ... Bias electrode, 300a, 300a-1, 300b, 300c, 300d, 300e, 300f, 300f-1, 300f-2, 300g, 300h, 300h-1, 300h-2, 300h-3, 300h-4, 300j, 300k ... Intermediate layer, 304a, 304b, 304c, 304d, 304e, 304f, 304g, 304h, 304j ... Recess, 400a, 400b , 400c, 400d, 400e ... Through hole, 402a ... concave, 404a ... groove, 500 ... adhesive layer, 502 ... support plate, 600 ... convex, 1000 ... optical modulation module, 1006 ... circuit board, 1008 ... drive circuit, 1100 ... Optical transmitter, 1104 ... Light source, 1106 ... Modulator drive unit, 1108 ... Modulation signal generation unit.

Claims (16)

An optical waveguide element having an optical waveguide and an electrode pad including a bonding area to which a conductor wire is bonded on a substrate.
An intermediate layer that forms a step on the substrate at a position surrounding the joint area is provided between the substrate and the electrode pad.
Optical waveguide element. The step formed by the intermediate layer has a plan-like shape including a shape portion of a circle, a plurality of arcs, a rectangle, a plurality of straight lines, or a plurality of bending lines surrounding the joint area.
The optical waveguide element according to claim 1. The step formed by the intermediate layer is such that the height of the lower surface of the electrode pad measured from the surface of the substrate is lower than the height of the peripheral portion of the joint area in the portion corresponding to the joint area. Formed,
The optical waveguide element according to claim 1 or 2. The intermediate layer has protrusions arranged around the joint area.
The optical waveguide element according to claim 3. The intermediate layer has through holes or recesses that open over the entire range of the joining area.
The optical waveguide element according to claim 3. The step formed by the intermediate layer is such that the height of the lower surface of the electrode pad measured from the surface of the substrate is higher than the height of the peripheral portion of the joint area in the portion corresponding to the joint area. Formed,
The optical waveguide element according to claim 1 or 2. The upper surface of the intermediate layer extends over the entire range of the joining area.
The optical waveguide element according to claim 6. The intermediate layer has a convex portion protruding from the upper surface of the intermediate layer.
The uppermost surface of the convex portion extends over the entire range of the joint area of the electrode pad.
The optical waveguide element according to claim 6. The intermediate layer has a groove at a position surrounding the joint area.
The optical waveguide element according to claim 6. The electrode pad is formed so as to cover the entire intermediate layer.
The optical waveguide element according to any one of claims 1 to 9. The optical waveguide element according to any one of claims 1 to 10, wherein the intermediate layer has a thickness of 1.0 μm or more. The optical waveguide element according to any one of claims 1 to 11, wherein the intermediate layer is a resin. The resin is a thermosetting resin or a thermoplastic resin.
The optical waveguide element according to claim 12. The optical waveguide element according to any one of claims 1 to 13, which is an optical modulation element that modulates light.
A housing for accommodating the optical waveguide element and
An optical fiber that inputs light to the optical waveguide element,
An optical fiber that guides the light output by the optical waveguide element to the outside of the housing,
An optical modulator equipped with. The optical modulation module comprising the optical waveguide element according to any one of claims 1 to 13, which is an optical modulation element that modulates light, and a drive circuit for driving the optical waveguide element. The light modulator according to claim 14 or the optical modulation module according to claim 15.
An electronic circuit that generates an electric signal for causing the optical waveguide element to perform a modulation operation,
An optical transmitter equipped with.

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