阅读说明：本技术 光波导元件及光波导器件 (Optical waveguide element and optical waveguide device ) 是由 本谷将之 宫崎德一 于 2019-09-26 设计创作，主要内容包括：在使用加工得薄的基板的光调制元件中,防止电连接时的基板破碎,从而防止连接不良、制造成品率下降。在具有形成有光波导和导体图案的光学基板和支承光学基板的支承基板的光波导元件中,导体图案包含作为进行电连接的范围而规定的至少一个电连接区域,光学基板在与电连接区域对应的部分具有以贯通光学基板的方式除去该光学基板的原材料而得到的基板除去部,电连接区域的至少一部分经由基板除去部形成在支承基板上。(In an optical modulation element using a substrate processed to be thin, the substrate is prevented from being broken during electrical connection, thereby preventing connection failure and reduction of manufacturing yield. In an optical waveguide element including an optical substrate on which an optical waveguide and a conductor pattern are formed and a support substrate supporting the optical substrate, the conductor pattern includes at least one electrical connection region defined as a range for electrical connection, the optical substrate includes a substrate removal portion formed by removing a material of the optical substrate so as to penetrate the optical substrate at a portion corresponding to the electrical connection region, and at least a portion of the electrical connection region is formed on the support substrate via the substrate removal portion.)

1. An optical waveguide element having:

an optical substrate formed with an optical waveguide and a conductor pattern; and

a support substrate supporting the optical substrate, wherein,

the conductor pattern includes at least one electrical connection region defined as a range in which electrical connection is performed,

the optical substrate has a substrate removing portion formed by removing a material of the optical substrate so as to penetrate the optical substrate at a portion corresponding to the electrical connection region,

at least a part of the electrical connection region is formed on the support substrate via the substrate removing portion.

2. The optical waveguide element of claim 1,

the thickness of the optical substrate is 10 μm or less.

3. The optical waveguide element according to claim 1 or 2, wherein,

the electrical connection region is a rectangular electrical connection pad configured as a part of the conductor pattern,

the conductor pattern includes a line portion connected to the electrical connection pad,

the electrical connection pad is formed in such a manner that a width measured in the same direction as a line width of the nearest line portion of the electrical connection pad is wide with respect to the line width,

at least a part of the electrical connection pad is formed on the support substrate via the substrate removing portion, and the substrate removing portion is disposed so that a boundary with another part of the optical substrate is not formed below the line portion.

4. The optical waveguide element according to any one of claims 1 to 3,

the substrate removing part is formed in a size including at least a circle having a diameter of 40 μm.

5. The optical waveguide element according to any one of claims 1 to 4,

the substrate removing portion is formed to have an opening at an outer edge of the optical substrate.

6. The optical waveguide element according to any one of claims 1 to 5,

the conductor pattern is formed to have a step at a portion corresponding to a boundary between the substrate removing portion and another portion of the optical substrate.

7. The optical waveguide element according to any one of claims 1 to 6,

at least two of the electrical connection regions are formed in the support substrate via one of the substrate removing portions.

8. The optical waveguide element of claim 7,

the conductor patterns include a signal conductor pattern for propagating an electric signal and a ground conductor pattern connected to a ground potential,

the at least two electrical connection regions include the electrical connection region of at least one of the signal conductor patterns and the electrical connection region of at least one of the ground conductor patterns.

9. The optical waveguide element according to any one of claims 1 to 8,

the substrate removing part is formed in a shape in which a boundary with another part of the optical substrate does not include a bend.

10. The optical waveguide element according to any one of claims 1 to 9,

the substrate removing portion is formed so as to include a portion where the conductor pattern is not formed in a range of the support substrate that can be visually recognized through the substrate removing portion.

11. The optical waveguide element according to any one of claims 1 to 10,

the electrical connection region is electrically connected to the other electrical connection region via a conductor disposed outside the optical substrate.

12. An optical waveguide device having:

the optical waveguide element of any one of claims 1 to 11; and

a housing for accommodating the optical waveguide element.

Technical Field

The present invention relates to an optical waveguide element and an optical waveguide device.

Background

In a high-speed and large-capacity optical fiber communication system, an optical transmitter incorporating a waveguide type optical modulator is frequently used. Wherein the LiNbO with the electro-optic effect₃An optical modulation element (hereinafter also referred to as LN) used for a substrate is widely used in a high-speed and large-capacity optical fiber communication system because it can realize optical modulation characteristics in a wide band with less optical loss as compared with a modulation element using a semiconductor material such as indium phosphide (InP), silicon (Si), or gallium arsenide (GaAs).

On the other hand, the modulation scheme of the optical fiber communication system is influenced by the recent trend of increasing the transmission capacity, and transmission formats such as QPSK (Quadrature Phase Shift Keying), DP-QPSK (Dual Polarization-Quadrature Phase Shift Keying), etc., in which Polarization multiplexing is introduced into multi-value modulation, are the mainstream.

The recent spread of internet services has further increased the amount of communication information, and studies on continuous high-speed and large-capacity optical communication systems have been progressing. On the other hand, the demand for miniaturization of the device is not changed, and the light modulation element itself needs to be miniaturized.

As one of the measures for downsizing an optical modulator, for example, an optical modulator using a ridge waveguide (hereinafter, referred to as a ridge optical modulator) has been studied (for example, see patent document 1). In the ridge waveguide, after a substrate using LN is thinned, a desired stripe portion (ridge) is left by dry etching or the like and the other portion is thinned (for example, to a substrate thickness of 10 μm or less), whereby the effective refractive index of the ridge portion is increased as compared with the other portion to form an optical waveguide. In the ridge type optical modulation element, since the light-trapping portion is limited to the ridge portion, the interaction between light and electricity can be efficiently generated, as compared with an optical modulation element using an optical waveguide manufactured by metal diffusion of Ti or the like. As a result, the length of the interaction portion can be shortened, and the light modulation element can be downsized.

However, as a result of processing the substrate thickness as thin as about several tens of micrometers, a new problem is generated. That is, the optical modulator needs to be connected to electrical components such as a relay board and a connector for relaying connection to an external circuit by wire bonding, flip-chip bonding, or the like, for example, inside a housing that houses the optical modulator. In contrast, in the ridge-type optical modulation element, as a result of processing the substrate to be as thin as about several tens of micrometers, when electrical connection such as wire bonding or flip chip bonding is performed, cracks or chipping may occur in the substrate due to pressure or the like applied from the tip of the capillary of the wire bonder or the solder bump.

That is, for example, in a conventional optical modulator using a thin substrate such as a ridge-type optical modulator, there is a possibility that a problem such as a reduction in manufacturing yield due to a connection failure with an electrical component or the like occurs.

Prior art documents

Patent document

Patent document 1: japanese patent laid-open publication No. 2011-75917

Disclosure of Invention

Summary of the invention

Problems to be solved by the invention

From the above-described background, in an optical waveguide element using a thin substrate, such as a ridge-type optical modulation element, it is desired to prevent breakage of the substrate at the time of electrical connection, thereby preventing connection failure and a reduction in manufacturing yield.

Means for solving the problems

According to an aspect of the present invention, there is provided an optical waveguide element including: an optical substrate formed with an optical waveguide and a conductor pattern; and a support substrate that supports the optical substrate, wherein the conductor pattern includes at least one electrical connection region defined as a range in which electrical connection is to be performed, the optical substrate includes a substrate removal portion, which is obtained by removing a material of the optical substrate so as to penetrate the optical substrate, at a portion corresponding to the electrical connection region, and at least a portion of the electrical connection region is formed on the support substrate via the substrate removal portion.

According to another aspect of the present invention, the optical substrate has a thickness of 10 μm or less.

According to another aspect of the present invention, the electrical connection region is a rectangular electrical connection pad configured as a part of the conductor pattern, the conductor pattern includes a line portion connected to the electrical connection pad, the electrical connection pad is formed so as to have a width, which is measured in the same direction as the line width, with respect to the line width of the nearest line portion of the electrical connection pad, at least a part of the electrical connection pad is formed on the support substrate via the substrate removing portion, and the substrate removing portion is disposed so as not to form a boundary with another part of the optical substrate below the line portion.

According to another aspect of the present invention, the substrate removing part is formed in a size including at least a circle having a diameter of 40 μm.

According to another aspect of the present invention, the substrate removing portion is formed to have an opening at an outer edge of the optical substrate.

According to another aspect of the present invention, the conductor pattern is formed to have a step at a portion corresponding to a boundary between the substrate removing portion and another portion of the optical substrate.

According to another aspect of the present invention, at least two of the electrical connection regions are formed in the support substrate via one of the substrate-removed portions.

According to another aspect of the present invention, the conductor pattern includes a signal conductor pattern for propagating an electric signal and a ground conductor pattern connected to a ground potential, and the at least two electrical connection regions include the electrical connection region of at least one of the signal conductor patterns and the electrical connection region of at least one of the ground conductor patterns.

According to another aspect of the present invention, the substrate removing portion is formed in a shape in which a boundary with another portion of the optical substrate does not include a bend.

According to another aspect of the present invention, the substrate removing portion is formed so as to include a portion where the conductor pattern is not formed in a range of the support substrate that can be visually recognized through the substrate removing portion.

According to another aspect of the present invention, the electrical connection region is electrically connected to the other electrical connection region via a conductor disposed outside the optical substrate.

Another aspect of the present invention relates to an optical waveguide device having: any of the optical waveguide elements described above; a housing for accommodating the optical waveguide element.

The specification includes the entire contents of japanese patent application No. 2019-067619 filed on 29/3 in 2019.

Effects of the invention

According to the present invention, in an optical waveguide element using a thin substrate, such as a ridge-type optical modulation element, for example, it is possible to prevent breakage of the substrate at the time of electrical connection such as wire bonding in which pressure is applied to the substrate, thereby preventing connection failure and reduction in manufacturing yield.

Drawings

Fig. 1 is a diagram showing a structure of an optical modulation device according to an embodiment of the present invention.

Fig. 2 is a diagram showing a structure of an optical modulation element used in the optical modulation device shown in fig. 1.

Fig. 3 is a partial detailed view of a portion a of the light modulator shown in fig. 2.

Fig. 4 is a sectional view aa of the partial detail view shown in fig. 3.

Fig. 5 is a partial detailed view of a portion B of the light modulator shown in fig. 2.

Fig. 6 is a cross sectional view bb of the detail shown in fig. 5.

Fig. 7 is a partial detailed view of a portion C of the light modulation element shown in fig. 2.

Fig. 8 is a cross-sectional view cc of the partial detail view shown in fig. 7.

Fig. 9 is a cross-sectional view dd taken through the partial detail view shown in fig. 7.

Fig. 10 is a diagram showing an example of a structure in flip-chip bonding in the electrical connection region.

FIG. 11 is a cross-sectional view of the graph ee shown in FIG. 10.

Fig. 12 is a diagram showing a first modification of the substrate removing portion.

Fig. 13 is a diagram showing a second modification of the substrate removing portion.

Fig. 14 is a diagram showing a third modification of the substrate removing portion.

Fig. 15 is a diagram showing a first modification of the conductor pattern.

Fig. 16 is a diagram showing a second modification of the conductor pattern.

Fig. 17 is a diagram showing another example of the light modulation element of the present invention.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The optical waveguide element according to the embodiments described below is an optical modulation element formed using an LN substrate, but the optical waveguide element according to the present invention is not limited to this. The present invention is also applicable to optical waveguide elements having electrodes using a substrate having a photoelectric effect, a thermo-optical effect, or an acousto-optical effect, and optical waveguide elements having functions other than optical modulation, in addition to the LN substrate.

Fig. 1 is a diagram showing the structures of an optical waveguide element and an optical waveguide device according to an embodiment of the present invention. In the present embodiment, the optical waveguide element is an optical modulation element 102 that performs optical modulation using a mach-zehnder optical waveguide, and the optical waveguide device is an optical modulation device 100 using the optical modulation element 102.

The light modulation device 100 houses a light modulation element 102 inside a housing 104. A cover (not shown) as a plate is finally fixed to the case 104 at the opening thereof, and the inside thereof is hermetically sealed.

The optical modulation device 100 includes an input optical fiber 106 for inputting light into the housing 104, and an output optical fiber 108 for guiding the light modulated by the optical modulation element 102 to the outside of the housing 104.

The optical modulation device 100 further includes: a connector 110 for receiving a high-frequency electrical signal for causing the optical modulator 102 to perform an optical modulation operation from the outside; and a relay substrate 112 for relaying the high-frequency electrical signal received by the connector 110 to one end of the signal electrode of the optical modulator 102. The optical modulation device 100 includes a terminator 114, and the terminator 114 is connected to the other end of the signal electrode of the optical modulation element 102 and has a predetermined impedance to suppress reflection of an electrical signal. Here, the signal electrodes of the optical modulator 102 are electrically connected to the relay substrate 112 and the terminator 114 by bonding with, for example, metal wires.

The optical modulation device 100 includes pins 116 and 117 and relay substrates 118 and 115. The pins 116 input a bias voltage applied from the outside of the housing 104 to conductor patterns 230d and 230e, which are bias electrodes to be described later, provided in the light modulation element 102 via the relay substrate 118. The pin 117 outputs a signal detected by a photodetector 119 provided in the optical modulator 102 to an electronic circuit provided outside the housing 104 via the relay substrate 115. Here, the photodetector 119 is, for example, a Photodiode (PD), which receives light branched from an output waveguide of the mach-zehnder optical waveguide constituting the optical modulation element 102 and monitors the output light of the optical modulation element 102. The pins 116, 117 are, for example, glass terminals.

Fig. 2 is a diagram showing a structure of the optical modulator 102 as an optical waveguide element housed in the housing 104 of the optical modulator 100 shown in fig. 1.

The optical modulator 102 includes an optical substrate 220 made of, for example, LN, and a support substrate 222 supporting the optical substrate 220. An optical waveguide 224 (a dotted line of a thick line is illustrated) is formed on the optical substrate 220. The optical waveguide 224 is, for example, a mach-zehnder optical waveguide including two parallel waveguides 226a, 226 b. Here, in the present embodiment, the optical substrate 220 is formed to have a thickness of 10 μm or less, and the optical waveguide 224 is configured as a ridge type optical waveguide. The support substrate 222 is thicker than the optical substrate 220 so that the mechanical strength thereof is stronger than that of the optical substrate 220 processed to be thinner. In order to establish the ridge optical waveguide structure, the support substrate 222 is formed of a material having a refractive index lower than that of the optical substrate, such as quartz, sapphire, or optical glass, or a substrate in which a layer (SiO2 or the like) having a refractive index lower than that of the optical substrate 220 is laminated on the surface of a substrate having a refractive index equal to or higher than that of the optical substrate 220, such as Si or LN.

The optical substrate 220 also has conductor patterns 230a, 230b, 230c, 230d, 230e, 230f, and 230g (hereinafter, collectively referred to as the conductor patterns 230) formed thereon. The conductor pattern 230 constitutes an electrode for controlling the light wave propagating in the optical waveguide 224. Specifically, the conductor patterns 230a, 230b, and 230c are signal electrodes that change the refractive index of the parallel waveguides 226a and 226b in accordance with the high-frequency electrical waveform by the input high-frequency electrical signal. The conductor pattern 230a is a signal conductor pattern for propagating an electric signal, and the conductor patterns 230b and 230c are ground conductor patterns connected to a ground potential.

The conductor patterns 230d and 230e are bias electrodes for setting an operating point (reference point) based on the change in refractive index of the signal electrode by an input dc voltage. The conductor patterns 230f and 230g are connected to two electrodes of the photodetector 119.

The conductor pattern 230 is provided with, for example, electrical connection regions 240a, 240b, 240c, 240d, 240e, 240f, 240g, 240h, 240j, 240k, 240m, 240n, 240p, 240q, 240r, 240s, 240t, 240u, 240v, 240w, 240y1, 240y2, 240z1, and 240z2 (hereinafter, collectively referred to as the electrical connection regions 240) which are predetermined as ranges for electrical connection with the metal leads 242.

For example, the electrical connection regions 240a, 240b, 240y1, 240y2, 240z1, and 240z2 are so-called electrical connection pads (hereinafter, also simply referred to as pads) formed as rectangular conductors constituting a part of the conductor patterns 230d, 230e, 230f, and 230g, respectively. The electrical connection regions 240c and 240d are rectangular lands (illustrated as dotted rectangular portions) provided at the upper and lower ends of the conductor pattern 230a, respectively, and are connected to the line portion via transition patterns formed in the wedge shape, respectively.

For example, the electrical connection regions 240e, 240f, 240g, 240h, 240p, 240q, 240r, and 240s are not conductor pattern portions having a specific shape such as pads, but are defined as circular regions defined in a conductor plane constituting the wide conductor pattern 230 b. Similarly, the electrical connection regions 240j, 240k, 240m, 240n, 240t, 240u, 240v, and 240w are defined as circular regions defined in the conductor plane constituting the conductor pattern 230 c.

In particular, the optical modulator 102 of the present embodiment is provided with substrate removing portions 250a, 250b, 250c, 250d, 250g, 250h, 250m, 250n, 250p, 250q, 250r, 250s, 250t, 250u, 250v, 250w, 250y1, 250y2, 250z1, and 250z2 (hereinafter, collectively referred to as substrate removing portions 250) each of which is obtained by removing a material of the optical substrate 220 so as to penetrate the optical substrate 220 in the thickness direction, at portions corresponding to the electrical connection regions 240 of the optical substrate 220.

Here, substrate removing portions 250a, 250b, 250g, 250h, 250m, 250n, 250p, 250q, 250n, 250p, 250q, 250r, 250s, 250t, 250u, 250v, 250w, 250y1, 250y2, 250z1, and 250z2 are provided at portions corresponding to the electrical connection regions 240a, 240b, 240g, 240h, 240m, 240n, 240p, 240q, 240v, 240w, 240y1, 240y2, 240z1, and 240z2, respectively. One substrate removing portion 250c is provided in a portion corresponding to the electrical connection regions 240c, 240e, and 240j arranged in parallel on the lower side of the optical modulator 102, and one substrate removing portion 250d is provided in a portion corresponding to the electrical connection regions 240d, 240e, and 240k arranged in parallel on the upper side of the optical modulator 102.

At least a part of each of the electrical connection regions 240 is formed on the support substrate 222 via the corresponding substrate removing portion 250.

Here, in the present embodiment, the electrical connection regions 240 are provided as portions to which metal wires are bonded by wire bonding such as ball bonding or wedge bonding. The substrate removing portion 250 is formed in a size including a size of a wire bonding portion formed by the wire bonding and a size (contact size) considering a positional accuracy of the wire bonding in a plan view. In the present embodiment, the contact size is a circle having a diameter of 40 μm. That is, each of the substrate removing portions 250 is formed in a size including a circle having a diameter of at least 40 μm in a plan view.

The electrical connection region 240 can be electrically connected to other electrical connection regions 240 via conductors (e.g., metal leads 242) disposed outside the optical substrate 220, in addition to electrical components (e.g., the relay substrates 112 and 118 and the terminal 114) outside the optical substrate 220. For example, the electrical connection regions 240g and 240m, and 240h and 240n shown in fig. 2 are examples.

The light modulator 102 having the above-described structure is provided with the substrate removing portion 250 so as to penetrate the optical substrate 220 at a portion corresponding to the electrical connection region 240 in the optical substrate 220, and at least a portion of the electrical connection region 240 is formed on the support substrate 222 via the substrate removing portion 250. Therefore, for example, when bonding a metal wire to the electrical connection region 240, a pressure applied to the electrical connection region 240 by a capillary of a wire bonder is applied to the support substrate 222 via the substrate removing portion 250, without being applied to the optical substrate 220 that is processed to be thin. Therefore, in the optical modulator 102, it is possible to prevent the occurrence of chipping in the optical substrate 220 when the electrical connection with the conductor pattern 230 on the optical substrate 220 is performed, and to prevent a connection failure and a reduction in manufacturing yield.

Fig. 3 is a partial detailed view of a portion a of the light modulator 102 shown in fig. 2. Fig. 4 is a cross-sectional view of the portion a shown in fig. 3. The electrical connection region 240g is provided in a size equal to or larger than the contact size (a circle having a diameter of 40 μm) set in consideration of the positional accuracy of bonding and the like. The substrate removing portion 250g is provided as a through hole penetrating the optical substrate 220 in the thickness direction. In addition, since the substrate removing portion 250g is formed in a size including the electrical connection region 240g in a plan view, it is formed in a size including at least a circle having a diameter of 40 μm. In the range of the substrate-removed portion 250g, the electrical connection region 240g in the conductor pattern 230b and the periphery thereof are formed on the support substrate 222. Then, a metal lead 242 is inscribed in the electrical connection region 240g formed on the support substrate 222. In particular, in the vicinity of the conductor pattern through which a high-frequency signal propagates, it is preferable that the electrical connection region 240g and the pattern around it be formed of a conductor thicker than the optical substrate 220 in order to avoid the pattern being cut by the step of the substrate-removed portion.

Fig. 5 is a partial detailed view of a portion B of the light modulator 102 shown in fig. 2. Fig. 5 is a cross-sectional view of the B portion bb shown in fig. 6. As described above, the electrical connection region 240a is a so-called pad formed as a rectangular conductor constituting a part of the conductor pattern 230 d. The substrate removing portion 250a is provided as a through hole penetrating the optical substrate 220 in the thickness direction, similarly to the substrate removing portion 250g described above, and is formed in a circle size including at least 40 μm in a plan view.

In the range of the substrate removing portion 250a, a part of the electrical connection region 240a is formed on the support substrate 222 via the substrate removing portion 250 a. Then, the metal wire 242 is bonded to a portion of the electrical connection region 240a formed on the support substrate 222 via the substrate removing portion 250 a.

The substrate removing portion 250a may be formed so as to include the entire pad constituting the electrical connection region 240a, and thus the entire electrical connection region 240a, depending on the size of the pad or the size of the contact. In this case, the entire electrical connection region 240a is formed on the support substrate 222 via the substrate removing portion 250 a.

That is, the electrical connection region 240 may be formed at least partially on the support substrate 222 via the substrate removing portion 250, as long as the portion of the electrical connection region 240 corresponding to the size of the contact is formed on the support substrate 222.

Fig. 7 is a partial detailed view of a portion C of the light modulator 102 shown in fig. 2. Fig. 8 and 9 are a cross-sectional view cc and a cross-sectional view dd, respectively, of the C portion shown in fig. 7. The electrical connection regions 240e and 240j are defined as circular regions defined in the conductor planes constituting the wide conductor patterns 230b and 230c, which are ground conductor patterns. The electrical connection region 240c is formed as a rectangular land (in fig. 7, a rectangular portion hatched with right oblique lines) provided at the end portion on the lower side in the drawing of the conductor pattern 230a serving as a signal conductor pattern. These electrical connection regions 240e, 240c, and 240j are arranged in the left-right direction in the figure in the vicinity of the outer edge of the lower side of the figure of the optical substrate 220.

One substrate removing portion 250c is provided for the three electrical connection regions 240e, 240c, and 240 j. That is, the substrate removing unit 250c is different from the substrate removing units 250g and 250a described above in that the substrate removing unit 250c is provided for the plurality of electrical connection regions 240e, 240c, and 240 j. The substrate removing portion 250c is configured to penetrate the optical substrate 220 in the thickness direction, similarly to the substrate removing portions 250g and 250a described above, but is configured to have a rectangular cutout having an opening at the outer edge of the optical substrate 220, unlike the substrate removing portions 250g and 250 a.

The electrical connection regions 240e and 240j, which are defined in a circular shape in the conductor plane constituting the conductor patterns 230b and 230c, are provided in a size equal to or larger than the contact size (for example, a circle having a diameter of 40 μm) in the same manner as the electrical connection region 240g described above. Since the substrate removing portion 250c is formed to include the electrical connection regions 240e and 240j, it is formed to include a contact size region included in the electrical connection regions 240e and 240 j.

The conductor pattern 230a as a signal conductor pattern includes a line portion 230a-1 (hatched portion with diagonal lines in the figure) connected to an electrical connection region 240c formed as a pad at an end thereof. Also, the electrical connection region 240c is connected to the line portion 230a-1 via a transition pattern 230a-2 provided in a shape that changes into a wedge shape in the width direction thereof, for example.

In addition, the electrical connection region 240c provided as the pad is formed to be wider than a width W2 measured in the same direction as the line width W1 of the nearest line portion 230a-1 of the electrical connection region 240 c.

At least a part of the electrical connection region 240c as the pad is formed on the support substrate 222 via the substrate removing portion 250 c. The substrate removing portion 250c is disposed, for example, below the transition pattern 230a-2 so that the boundary 250c-1 with the other portion of the optical substrate 220 is not formed below the line portion 230 a-1.

In the configuration of the C portion of the light modulator 102, since the plurality of electrical connection regions 240 are formed on the support substrate 222 by the single substrate removing portion 250, the number of through holes and cutouts provided in the optical substrate 220 can be reduced. Therefore, the processing steps of the optical substrate 220 can be simplified, and the cost can be reduced. In addition, since the substrate removing portion 250c does not have the boundary 250c-1 formed below the fine-patterned line segment 230a-1, disconnection, a defective shape, and the like of the line segment 230a-1 can be prevented.

In the above-described section C, one substrate removing portion 250C is provided for the three electrical connection regions 240e, 240C, and 240j, but the present invention is not limited thereto. One substrate removing part 250 may be provided for at least two electrical connection regions 240, and at least a part of each of the at least two electrical connection regions 240 may be formed on the support substrate 222 via the one substrate removing part.

Similarly to the above-described section C, the at least two electrical connection regions 240 provided in the single substrate removing portion 250 may include the electrical connection region 240 of the conductor pattern 230 as at least one signal conductor pattern and the electrical connection region 240 of the conductor pattern 230 as at least one ground conductor pattern.

With this configuration, for example, when two substrate removing portions 250 are provided separately and adjacently to two electrical connection regions, i.e., a signal conductor pattern and a ground conductor pattern, which constitute a signal line and are arranged in parallel and accessible, it is possible to prevent the optical substrate 220 between the two substrate removing portions 250 from being broken or chipped.

In the present embodiment, the metal lead 242 is connected to the electrical connection region 240, but the present invention is not limited to this. The electrical connection regions 240 may be connected via solder bumps by, for example, flip chip bonding. Fig. 10 is a diagram showing an example of a structure in which such connection by flip-chip bonding is performed with respect to the electrical connection region 240. Fig. 10 is a view showing a detailed view of the portion C corresponding to fig. 7 of the connection portion with the electrical connection regions 240e, 240C, and 240 j. In fig. 10, the same components as those in fig. 7 are denoted by the same reference numerals as those in fig. 7.

In the illustrated example, a relay board 112' configured to be flip-chip bonded is used instead of the relay board 112. Fig. 11 is a cross-sectional view of fig. 10 in an ee state. The relay substrate 112 'connects an electrode (not shown) provided on the back surface (lower surface in the figure in fig. 11) of the relay substrate 112' to, for example, the electrode connection region 240j via a solder bump 243. In this configuration, since the pressure applied from the relay substrate 112' via the solder bump 243 is applied not to the optical substrate 220 but to the support substrate 222 at the time of flip-chip bonding, it is possible to prevent the occurrence of damage such as breakage of the optical substrate 220, and prevent poor connection and reduction in manufacturing yield, as in the case of performing connection by the metal lead 242 described above.

The shape of the substrate removing portion, that is, the shape of the boundary between the substrate removing portion and the other portion of the optical substrate 220 is not limited to the rectangular shape shown in fig. 2, 3, 5, and 7. Fig. 12 and 13 show first and second modified examples of the substrate removing unit 250. Fig. 12 and 13 are views corresponding to fig. 3 showing a portion a of fig. 2.

Although substrate removing unit 1050g shown in fig. 12 has the same configuration as substrate removing unit 250g, it is different from substrate removing unit 250g in that bent portions at four corners of a rectangular shape are curved. The substrate removing unit 1150g shown in fig. 13 has the same configuration as the substrate removing unit 250g, but is different from the substrate removing unit 250g in that it is configured in a circular shape instead of a rectangular shape. Since the substrate removing portions 1050g and 1150g are formed in a shape (shape having a continuous curvature without corners) in which the boundary does not include a bend (shape having a curvature without corners) in which stress is easily concentrated due to a change in temperature in the manufacturing process or a change in the use environment temperature, it is possible to prevent the occurrence of cracks in the optical substrate at the removing portion in the manufacturing process of the optical substrate 220 and improve mechanical stability. The shape of the substrate removing portion is not limited to this, and may be, for example, an oval or a polygon.

The substrate removing portion may be formed so as to include a portion of the support substrate 222 where the conductor pattern 230 is not formed, within a range on the support substrate 222 that can be visually recognized through the substrate removing portion. Fig. 14 is a diagram showing such a third modification of the substrate removing section 250. Fig. 14 is a view corresponding to fig. 5 showing a part B of fig. 2. Although the substrate removing part 1250a shown in fig. 14 has the same configuration as the substrate removing part 250a, the lateral width thereof in the figure extends beyond the width of the electrical connection region 240a, and the region on the support substrate 222 where the electrical connection region 240a is not formed is included in a range that can be visually recognized through the substrate removing part 1250 a.

Accordingly, when the electrical connection region 240a is electrically connected, for example, when the metal wire 242 is bonded, the position of the substrate removing portion 250a can be visually confirmed, and therefore, the electrical connection can be performed at the position of the electrical connection region 240a in the substrate removing portion 250a with high accuracy.

In fig. 4, 6, 8, and 9 showing the above-described embodiment, the upper surface of the conductor pattern 230 formed on the upper portion of the substrate removing portion 250 is flat, but the present invention is not limited thereto. The conductor pattern 230 may be formed to have a step at a portion corresponding to a boundary between the substrate removing portion and another portion of the optical substrate 220.

Fig. 15 and 16 show first and second modified examples of the conductor pattern 230. Although the conductor patterns 1330a and 1430a shown in fig. 15 and 16 have the same configuration as the conductor pattern 230a, they are different in that portions corresponding to the positions of the boundaries between the left and right sides of the substrate removing portion 250a shown in the figure, that is, in that the two boundary portions 1332 and 1432 (both of which are within the ellipse of the dotted line shown in the figure) have steps. Here, the step of the boundary portion 1332 has a bent portion in the cross-sectional view shown in fig. 15, whereas the step of the boundary portion 1432 is formed of a curved line in the cross-sectional view shown in fig. 16.

Since the conductor patterns 1330a and 1430a as shown in fig. 15 and 16 have a step at a portion corresponding to the boundary of the substrate removing portion 250, the position of the substrate removing portion 250a can be visually confirmed by the step formed at the boundary 1332 and 1432 of the conductor patterns 1330a and 1430a when the electrical connection is performed in the electrical connection region 240a, for example, when the metal lead 242 is bonded. Therefore, the electrical connection can be performed with high accuracy at the position of the portion of the electrical connection region 240a in the substrate removing portion 250 a.

The present invention is not limited to the configurations of the above-described embodiments and modifications thereof, and can be implemented in various forms without departing from the scope of the invention.

For example, although the optical modulation element 102 in which the optical waveguide 224 is formed on the optical substrate 220 that is an LN substrate is shown as the optical waveguide element in the present embodiment, the optical waveguide 224 constitutes a single mach-zehnder optical waveguide including a pair of parallel waveguides 226a and 226b, the optical waveguide element to which the present invention is applied is not limited to this.

The optical waveguide element may be made of a material other than LN, which is thin enough to cause mechanical breakage such as chipping during electrical connection.

The optical waveguide element forming the substrate removing portion of the present invention may have a structure in which an LN substrate is used as an optical substrate as in the present embodiment, or may have an optical waveguide formed with a more complicated structure. For example, the optical waveguide element may be an optical modulation element 1502 for DP-QPSK modulation configured using two so-called nested mach-zehnder optical waveguides as shown in fig. 17.

The light modulation element 1502 is composed of an optical substrate 1520 which is an LN substrate similar to the optical substrate 220, and a support substrate 222 bonded to the optical substrate 1520. An optical waveguide 1524 is formed on the optical substrate 1520. Here, the optical waveguide 1524 is formed of two so-called nested mach-zehnder optical waveguides, and includes two parallel waveguide groups 1526a and 1526b each formed of four parallel waveguides and formed of two nested mach-zehnder optical waveguides.

In addition, conductor patterns 1530a, 1530b, 1530c, 1530d, 1530e, 1530f (hereinafter, collectively referred to as the conductor patterns 1530) are formed on the optical substrate 1520. Here, the conductor patterns 1530a and 1530b are signal electrodes for controlling light waves propagating through the parallel waveguide groups 1526a and 1526b, respectively, and the conductor patterns 1530c, 1530d, 1530e, and 1530f are bias electrodes.

Further, similarly to the conductor pattern 230 of the optical modulator 102 which is the optical waveguide element of the above-described embodiment, the conductor pattern 1530 includes at least one electrical connection region which is defined as a range in which electrical connection is performed by the metal lead 242, for example. Here, the electrically connected portion by the metal lead 242 is indicated by a solid circle at the end of the metal lead 242 in fig. 17. In fig. 17, all the metal leads are not labeled with the reference numeral 242 for the sake of avoiding redundant description and facilitating understanding. The same figure as the figure labeled with the reference numeral 242 represents the metal lead 242, and the solid circles at the ends of the respective metal leads represented on the optical substrate 1520 are understood to be the portions defining the electrical connection regions.

In the light modulation element 1502, similarly to the light modulation element 102, the optical substrate 1520 has a substrate removing portion formed by removing a material of the optical substrate so as to penetrate the optical substrate 1520 in a portion corresponding to the electrical connection region, and at least a portion of the electrical connection region can be formed on the support substrate 222 via the substrate removing portion.

In the optical modulation element 1502 shown in fig. 17, light incident on the optical waveguide 1524 from the left side in the figure is output from the right side in the figure as two output lights subjected to QPSK modulation, respectively. The two output beams are combined by polarization synthesis by appropriate spatial optics in accordance with the prior art to form a single beam of light, which is directed to a transmission fiber, for example, coupled to an optical fiber.

In the above-described embodiment, the electrical connection used in the electrical connection region 240 is an electrical connection with a metal lead, but the present invention is not limited to this. The electrical connection may be made to a conductor lead other than a metal lead, a conductor tape including a metal tape, or a solder bump in flip chip bonding, for example, depending on the type of the electrical connection. In these connections, a stronger pressure is required for the connection than in the case of using a lead wire, and therefore the structure of the present application can be applied more appropriately.

In the above-described embodiment, the contact size is a circle having a diameter of 40 μm, but the contact size is not limited to this. The contact size may be set to another size or another shape according to the type of electrical connection used in the electrical connection region 240.

As described above, the optical modulator 102 as the optical waveguide device according to the present embodiment includes the optical substrate 220 on which the optical waveguide 224 and the conductor pattern 230 are formed, and the support substrate 222 that supports the optical substrate 220. The conductor pattern 230 includes at least one electrical connection region 240 defined as a range in which electrical connection is performed. The optical substrate 220 includes a substrate removing portion 250, which is obtained by removing a material of the optical substrate 220 so as to penetrate the optical substrate 220, in a portion corresponding to the electrical connection region 240. At least a part of the electrical connection region 240 is formed on the support substrate 222 via the substrate removing portion 250.

According to this configuration, when, for example, a metal wire 242 is bonded to the electrical connection region 240, a pressing force applied to the electrical connection region 240 by a capillary of a wire bonder is applied to the support substrate 222 via the substrate removing portion 250, without being applied to the optical substrate 220 that is processed to be thin. Therefore, in the optical modulator 102, the optical substrate 220 can be prevented from being broken when the electrical connection with the conductor pattern 230 on the optical substrate 220 is performed, and a connection failure and a reduction in manufacturing yield can be prevented.

In the light modulator 102, the thickness of the optical substrate 220 is 10 μm or less. According to this configuration, in the optical waveguide element including the ridge-type optical waveguide formed on the optical substrate 220 that is processed to be thin, for example, the occurrence of breakage of the optical substrate 220 can be prevented, and connection failure and reduction in manufacturing yield can be prevented. In the description so far, although the thickness of the optical substrate is set to 10 μm or less, the above-described effects can be more exhibited when the thickness is 5 μm or less, and the effects can be more exhibited when the thickness is 2 μm or less.

In the optical modulator 102, for example, the electrical connection region 240c is a rectangular electrical connection pad configured as a part of the conductor pattern 230a, and the conductor pattern 230a includes a line portion 230a-1 connected to the electrical connection region 240c as the electrical connection pad. The electrical connection region 240c as an electrical connection pad is formed in such a manner that a width W2 measured in the same direction as the line width W1 with respect to the line width W1 of its nearest line portion 230a-1 is wide. At least a part of the electrical connection region 240c as an electrical connection pad is formed on the support substrate 222 via the substrate removing portion 250 c. The substrate removing portion 250c is disposed so that a boundary 250c-1 with the other portion of the optical substrate 220 is not formed below the line portion 230 a-1.

According to this structure, the occurrence of disconnection or the like of the line portion 230a-1 can be prevented.

In the light modulator 102, the substrate removing portion 250 is formed in a size including at least a circle having a diameter of 40 μm. According to this configuration, even when the electrical connection region 240 is electrically connected by wire bonding, it is possible to effectively avoid the pressing of the capillary of the wire bonder to the optical substrate 220.

In the light modulator 102, for example, the substrate removing portion 250c is formed to have an opening at the outer edge of the optical substrate 220. With this configuration, the outer edge portion of the optical substrate 220, which is likely to be broken or chipped, can be simplified in configuration, and the mechanical strength of the outer edge portion can be ensured.

In the light modulator 102, as the conductor patterns, conductor patterns 1330a and 1430a having steps at the boundary portions 1332 and 1432 corresponding to the boundary between the substrate removing portion 250 and the other portion of the optical substrate 220 may be used. According to this configuration, when the electrical connection region 240a is electrically connected, for example, when the metal lead 242 is bonded, the position of the substrate removing portion 250a can be visually checked by the step formed at the boundary portion of the conductor pattern 230, and therefore, the electrical connection can be performed at the position of the electrical connection region 240a in the substrate removing portion 250a with high accuracy.

In the light modulator 102, at least two electrical connection regions 240 can be formed on the support substrate 222 via one substrate removal portion 250. According to this configuration, the number of substrate removing portions 250 provided in the optical substrate 220 can be reduced, and the manufacturing process of the optical substrate 220 can be simplified to reduce the cost.

In the optical modulator 102, the conductor pattern 230 includes, for example, a conductor pattern 230a serving as a signal conductor pattern through which an electric signal propagates, and conductor patterns 230b and 230c serving as ground conductor patterns connected to a ground potential. Also, the at least two electrical connection regions 240 may include at least one electrical connection region of the signal conductor pattern (e.g., the electrical connection region 240c) and at least one electrical connection region of the ground conductor pattern (e.g., the electrical connection regions 240e and/or 240 j).

With this configuration, it is possible to prevent the portion of the optical substrate 220 between the two substrate removing portions 250 from being broken or chipped, which would otherwise occur when the two substrate removing portions 250 are provided adjacent to each other separately for the two electrical connection regions, i.e., the signal conductor pattern and the ground conductor pattern, which constitute the signal line and are arranged in parallel and accessible.

In the light modulator 102, the substrate removing portion 250 may be formed in a shape in which the boundary with the other portion of the optical substrate 220 does not include a bend. According to this configuration, the substrate removing portion does not include a bend at the boundary where stress is likely to concentrate due to processing strain or fluctuation of the environmental temperature, and thus the mechanical stability of the optical substrate 220 can be improved.

In the light modulator 102, the substrate removing portion 250 may be formed so as to include a portion where the conductor pattern 230 is not formed in a range on the support substrate 222 that can be visually recognized through the substrate removing portion 250. According to this configuration, when the electrical connection region 240a is electrically connected, for example, when the metal wire 242 is bonded, the position of the substrate removing portion 250a can be visually confirmed, and therefore, the electrical connection can be performed at the position of the electrical connection region 240a in the substrate removing portion 250a with high accuracy.

In the optical modulator 102, the electrical connection region 240 is electrically connected to another electrical connection region 240 via a conductor, for example, a metal lead 242, which is disposed outside the optical substrate 220. According to this configuration, since the electrical connection between the conductor patterns 230 in the optical substrate 220 can be freely performed without fear of damage to the optical substrate 220, the degree of freedom in designing the optical modulator 102 can be improved.

In the optical modulator 102, in addition to the conductor leads such as the metal leads 242, a conductor ribbon or a solder bump can be connected to the electrical connection region 240. With this configuration, the optical substrate 220 can be prevented from being damaged, and the conductor pattern 230 can be electrically connected to various conductors.

The optical modulation device 100 as an optical waveguide device according to the present embodiment includes the optical modulation element 102 as any one of the optical waveguide elements described above and a housing that houses the optical modulation element. According to this configuration, since the probability of occurrence of breakage of the optical substrate 220 can be reduced and electrical connection with a good manufacturing yield can be performed, an optical waveguide device with high reliability can be stably produced at low cost.

Description of the reference symbols

100 … optical modulation device, 102, 1502 … optical modulation element, 104 … housing, 106 … input optical fiber, 108 … output optical fiber, 110 … connector, 112', 115, 118, 1512a, 1512b, 1518a, 1518b, 1518c, 1518d … relay substrate, 114, 1514a, 1514b … terminator, 116, 117 … pin, 119 … photodetector, 220, 1520 … optical substrate, 222 … support substrate, 224, 1524 … optical waveguide, 226a, 226b … parallel waveguide, 230a, 230b, 230c, 230d, 230e, 1330a, 1430a, 1530b, 1530c, 1530d, 1530e, 1530f … conductor pattern, 230a-1 … line portion, 230a-2 … transition pattern, 240a, 240b, 240c, 240d, 240e, 240f, 240g, 240j, 240k, 240m, 240r, 240m, 240t, 240m, 240r, 240m, 240r, 240b, 240r, 240b, 240r, 240b, 230c, 230b, 230c, 240b, 230c, 230b, 230c, 230b, 230c, 230b, 230c, 230b, and 240b, 240, 240u, 240v, 240w, 240y1, 240y2, 240z1, 240z2 … electrical connection regions, 242 … metal leads, 243 … solder bumps, 250a, 250b, 250c, 250d, 250g, 250h, 250m, 250n, 250p, 250q, 250r, 250s, 250t, 250u, 250v, 250w, 250y1, 250y2, 250z1, 250z2, 1050g, 1150g, 1250a … substrate removal, 250c-1 … interface, 1332, 1522 1432 … interface, and 1526a, 1526b … parallel waveguide sets.