JP7051505B2 - Optical waveguide structure and its manufacturing method - Google Patents

Description

The present invention relates to an optical waveguide structure and a method for manufacturing the same.

In the optical waveguide structure, a technique is known in which the refractive index of the optical waveguide layer or the diffraction grating layer is changed by heating with a heater to change the laser oscillation wavelength (for example, Patent Document 1). Various techniques for increasing the efficiency of heating by the heater and suppressing the power consumption of the heater are disclosed. For example, Patent Documents 2 to 4 describe techniques for forming a deep mesa structure in a portion including an optical waveguide layer in order to prevent heat diffusion, arranging a high heat resistance layer under the optical waveguide layer, and forming a hollow waveguide structure. It has been disclosed.

When the portion including the optical waveguide layer has a deep mesa structure, grooves may be formed on both sides of the portion including the optical waveguide layer. The groove is usually filled with an insulating material such as polyimide, and the wiring for supplying power to the heater is arranged so as to pass over the insulating material.

On the other hand, Patent Document 5 discloses a waveguide structure including a ridge, a peninsula structure, and a conductive trace. In this waveguide structure, the peninsula structure is adjacent to the ridge so that there is a gap between the end face of the peninsula structure and the side wall of the ridge. Conductive traces are laid across the gap so that the conductive traces extend over the top surface of the peninsula and the top surface of the ridge.

International Publication No. 2016/152274 Japanese Patent No. 5303581 Japanese Patent No. 5303580 U.S. Pat. No. 7,778,295 Special Table 2017-502355

However, the surface of the insulating material that fills the groove may have low flatness. For example, the surface of the insulating material may have a shape in which the center is recessed and a shape in which the periphery is projected. If the wiring is arranged so as to pass through the surface of the insulating material having irregularities on the surface in this way, the wiring is distorted, and deterioration or disconnection of the wiring is likely to occur due to the temperature difference between when the power is turned on and when the power is not turned on. In some cases. In this case, the reliability of the optical waveguide structure is lowered.

The present invention has been made in view of the above, and an object of the present invention is to provide an optical waveguide structure having high heating efficiency by a heater and suppressing deterioration of reliability, and a method for manufacturing the same.

In order to solve the above-mentioned problems and achieve the object, the optical waveguide structure according to one aspect of the present invention includes an optical waveguide layer and a diffraction grating layer so as to extend in a predetermined length along one direction. A configured distributed reflection portion, a clad portion that surrounds the distributed reflection portion from above, below, left, and right, a heater arranged along the distributed reflection portion on the upper surface of the clad portion, and an electric heater. The clad portion is formed with vertical grooves extending along the distributed reflection portion on both the left and right sides of the distribution reflection portion, and these vertical grooves include the distribution reflection portion. A mesa portion having a mesa-shaped cross section is defined, the heater is arranged on the mesa portion, and at least one of the vertical grooves is a first groove portion having a predetermined groove width and the first groove portion. It has a second groove portion whose groove width is smaller than that of one groove portion, and the clad portion in the vicinity of at least one of the vertical grooves is an inner side wall far from the mesa portion in the vertical groove in a plan view. It has a convex portion that protrudes from the surface toward the mesa portion to form the second groove portion, and the wiring is passed over the convex portion and hung on the second groove portion, and is electrically connected to the heater. Is connected to.

In the optical waveguide structure according to one aspect of the present invention, at least one of the vertical grooves has a third groove portion adjacent to the convex portion and a groove width larger than that of the first groove portion, and the clad portion. Has a recess forming the third groove portion.

In the optical waveguide structure according to one aspect of the present invention, the convex portions are composed of a plurality of segments separated from each other in the projecting direction.

The optical waveguide structure according to one aspect of the present invention further includes a protective film that covers the inner surface of each of the flutes and the surface of the clad portion.

In the optical waveguide structure according to one aspect of the present invention, the protective film is thicker in the vicinity of the opening of the groove than the portion of the other protective film.

In the optical waveguide structure according to one aspect of the present invention, the protective film fills the second groove portion.

In the optical waveguide structure according to one aspect of the present invention, the width of the groove between the convex portion and the mesa portion is 3 μm or less.

The optical waveguide structure according to one aspect of the present invention includes an optical waveguide layer and a diffraction grating layer, and has a distributed reflective portion configured to extend at a predetermined length along one direction and the distributed reflecting portion thereof. The clad portion includes a clad portion that surrounds the clad portion from the top, bottom, left, and right, a heater that is arranged along the distributed reflection portion on the upper surface of the clad portion, and a wiring that is electrically connected to the heater. Each of the left and right sides of the distributed reflection portion has vertical grooves extending along the distributed reflection portion, and these vertical grooves define a mesa portion having a mesa-shaped cross section including the distributed reflection portion. The heater is arranged on the mesa portion, and at least a part of at least one of the flutes is a first polymer having a convex surface formed on the bottom surface of the flute. The second polymer layer is filled with a layer and an insulating second polymer layer formed on the first polymer layer, and the wiring is exposed above the portion of the flute. It is electrically connected to the heater through the surface of the heater.

In the optical waveguide structure according to one aspect of the present invention, the diffraction grating layer is configured as a sampling diffraction grating, a phase shift diffraction grating, or a superstructured diffraction grating.

The method for manufacturing an optical waveguide structure according to one aspect of the present invention includes a light waveguide layer and a diffraction grating layer, a distributed reflection unit configured to extend at a predetermined length along one direction, and the distributed reflection. By forming a clad portion that surrounds the portion from the top, bottom, left, and right along the clad portion, and by forming vertical grooves extending along the distribution reflection portion on both the left and right sides of the distribution reflection portion, the clad portion is formed. A step of forming a mesa portion having a mesa-shaped cross section including a distributed reflection portion, a step of arranging a heater on the upper surface of the clad portion along the distributed reflection portion, and wiring electrically connected to the heater. Including the step of arranging the groove, when forming the groove, the inner side wall far from the mesa portion in the vertical groove in the clad portion in the vicinity thereof with respect to at least one of the vertical grooves. A first groove portion having a predetermined groove width and a second groove portion having a groove width smaller than that of the first groove portion and formed by the convex portion by forming a convex portion protruding from the surface toward the mesa portion. When arranging the wiring, the wiring is passed over the convex portion and hung on the second groove portion, and is electrically connected to the heater.

The method for manufacturing an optical waveguide structure according to one aspect of the present invention includes a light waveguide layer and a diffraction lattice layer, a distributed reflection unit configured to extend at a predetermined length along one direction, and the distributed reflection. By forming a clad portion that surrounds the portion from the top, bottom, left, and right along the clad portion, and by forming vertical grooves extending along the distribution reflection portion on both the left and right sides of the distribution reflection portion in the clad portion. A step of forming a mesa portion having a mesa-shaped cross section including a distributed reflection portion, and a first step in which the surface is convex on the bottom surface of at least one of the flutes in at least a part of the flutes. A step of supplying a polymer material and curing the first polymer material to form a first polymer layer, and supplying an insulating second polymer material on the first polymer layer to cure the second polymer material. The step of forming the second polymer layer and filling the part of the vertical groove, the step of arranging the heater on the upper surface of the clad portion along the distributed reflection portion, and the wiring of the vertical groove. Includes a step of arranging so as to electrically connect to the heater through the surface of the second polymer layer exposed on the portion of the.

According to the present invention, it is possible to realize an optical waveguide structure in which the heating efficiency by the heater is high and the decrease in reliability is suppressed.

FIG. 1 is a schematic top view of the optical waveguide structure according to the first embodiment. FIG. 2 is a diagram showing a part of the cross section taken along the line AA of FIG. FIG. 3 is a diagram showing a part of the cross section taken along the line BB of FIG. FIG. 4 is a diagram illustrating a method for manufacturing the optical waveguide structure shown in FIG. FIG. 5 is a schematic diagram illustrating the optical waveguide structure according to the second embodiment. FIG. 6 is a schematic diagram illustrating the optical waveguide structure according to the third embodiment. FIG. 7 is a schematic diagram illustrating the optical waveguide structure according to the fourth embodiment. FIG. 8 is a schematic top view of the optical waveguide structure according to the fifth embodiment. FIG. 9 is a diagram showing a part of the cross section taken along the line CC of FIG. FIG. 10 is a diagram illustrating a method for manufacturing the optical waveguide structure shown in FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to this embodiment. Further, in the description of the drawings, the same or corresponding elements are appropriately designated by the same reference numerals. In addition, it should be noted that the drawings are schematic, and the relationship between the dimensions of each element, the ratio of each element, etc. may differ from the reality. Even between the drawings, there may be parts where the relationship and ratio of the dimensions are different from each other.

(Embodiment 1)
FIG. 1 is a schematic top view of the optical waveguide structure according to the first embodiment. FIG. 2 is a diagram showing a part of the cross section taken along the line AA of FIG. The optical waveguide structure 100 includes a laminated portion 101, a heater 103, and wirings 104 and 105. Trench grooves 102a and 102b are formed in the laminated portion 101. Further, the optical waveguide structure 100 includes two optical waveguide portions 110a and 110b and a distributed reflection unit 120 connected between the two optical waveguide portions 110a and 110b.

The laminated portion 101 is arranged on a substrate 100a made of n-type InP, and is configured by laminating a plurality of semiconductor layers. As shown in FIG. 2, in the laminated portion 101, a lower clad layer 100b made of n-type InP and also functioning as a buffer layer is laminated. A diffraction grating layer 100c is laminated on the lower clad layer 100b. The diffraction grating layer 100c is configured as, for example, a sampling diffraction grating, a phase shift diffraction grating, or a superstructured diffraction grating. The diffraction grating layer 100c is composed of an n-type GaInAsP having a bandgap wavelength shorter than the 1.55 μm band, for example, 1.3 μm, and an n-type InP. A spacer layer 100d made of n-type InP is laminated on the diffraction grating layer 100c. An optical waveguide layer 100e is laminated on the spacer layer 100d. The optical waveguide layer 100e is made of GaInAsP having a bandgap wavelength shorter than the 1.55 μm band, for example, 1.3 μm.

A first upper clad layer 100f made of p-type InP is laminated on the optical waveguide layer 100e. The upper part of the lower clad layer 100b, the diffraction grating layer 100c, the spacer layer 100d, the optical waveguide layer 100e, and the first upper clad layer 100f are suitable for optical waveguide of 1.55 μm band light in a single mode by etching or the like. It has a mesa structure M1 having a width W1 (for example, 2 μm). Both sides of the mesa structure M1 (in the left-right direction of the paper surface) are embedded with a current blocking structure composed of a lower embedded layer 100 g made of p-type InP and an upper embedded layer 100h made of n-type InP, so-called embedded. A mesa structure is formed. Further, a second upper clad layer 100i made of p-type InP is laminated on the first upper clad layer 100f and the upper embedded layer 100h.

The distributed reflection unit 120 includes an optical waveguide layer 100e, a spacer layer 100d, and a diffraction grating layer 100c, and is configured to extend in a predetermined length along one direction. The first upper clad layer 100f and the second upper clad layer 100i integrally function as an upper clad layer. The lower clad layer 100b, the upper clad layer, the lower embedded layer 100 g, and the upper embedded layer 100h are adjacent to each other so as to surround the distributed reflection portion 120 from above, below, left, and right, and function as the clad portion 106. do.

In the laminated portion 101, in each region where the two optical waveguide portions 110a and 110b are formed, the semiconductor layer made of the same n-type GaInAsP as the diffraction grating layer 100 is laminated instead of the diffraction grating layer 100c. It has become.

The trench grooves 102a and 102b are vertical grooves extending along the distributed reflection portion 120 on both the left and right sides of the distributed reflection portion 120 in the clad portion 106, respectively. These trench grooves 102a and 102b define a mesa portion M2 having a cross-sectional shape of a mesa shape and a width W2, including the distributed reflection portion 120. The width W2 is, for example, 3 μm. Further, the optical waveguide structure 100 includes a protective film 100j that covers the inner surface of each of the trench grooves 102a and 102b and the surface of the clad portion 106. The protective film 100j is made of a dielectric such as SiNx, in which SiNx has a lower refractive index than that of the clad portion 106. The thickness of the protective film 100j is, for example, 300 nm.

The heater 103 has a structure in which, for example, a Ti film, a Pt film, and an Au film are laminated, and is arranged along the distributed reflection portion 120 on the surface of the upper protective film 100j formed on the clad portion 106 in the mesa portion M2. Has been done.

The trench grooves 102a include a first groove portion 102aa having a predetermined groove width, second groove portions 102ab and 102ac having a groove width smaller than that of the first groove portion 102aa, and a third groove portion 102ad having a groove width larger than that of the first groove portion 102aa. It has 102ae, 102af, and 102ag.

The trench groove 102b has a first groove portion 102ba, 102bb having a predetermined groove width, a second groove portion 102bc having a groove width smaller than that of the first groove portions 102ba, 102bb, and a second groove portion having a groove width larger than that of the first groove portions 102ba, 102bb. It has three grooves 102bd and 102be. The groove width of the first groove portions 102aa, 102ba, 102bb (for example, the groove width W3 shown in FIG. 2) is, for example, 20 μm. Here, it is assumed that the boundaries of the structures of the trench grooves 102a and 102b are defined by the surface of the protective film 100j provided on the side surface of the vertical groove carved in the clad portion 106. Therefore, the groove widths of the trench grooves 102a and 102b are the distances between the surfaces of the protective films 100j facing each other in the grooves as shown by the widths W3, W4 and the like in FIG.

Further, with respect to the trench groove 102a, the clad portion 106 in the vicinity thereof projects from the inner side wall far from the mesa portion M2 in the trench groove 102a toward the mesa portion M2 to form the second groove portions 102ab and 102ac, respectively. It has convex portions 101a and 101b. Further, the clad portion 106 has recesses 101c, 101d, 101e, 101f forming the third groove portions 102ad, 102ae, 102af, and 102ag, respectively, in the trench groove 102a. The recesses 101c, 101d, 101e, 101f are formed so that the third groove portions 102ad, 102ae, 102af, 102ag are adjacent to any of the convex portions 101a, 101b.

Further, with respect to the trench groove 102b, the clad portion 106 in the vicinity thereof protrudes from the inner side wall far from the mesa portion M2 in the trench groove 102b toward the mesa portion M2 to form the second groove portion 102bc. It has 101 g. Further, the clad portion 106 has recesses 101h and 101i forming the third groove portions 102bd and 102be, respectively, in the trench groove 102b. The recesses 101h and 101i are formed so that the third groove portions 102bd and 102be are adjacent to the convex portions 101g.

The wiring 104 has, for example, a thickness of 1 μm and has two arm portions 104a and 104b extending from the main body serving as an electrode pad. The arm portion 104a passes over the convex portion 101a, spans the second groove portion 102ab, and is electrically connected to the heater 103. The arm portion 104b passes over the convex portion 101b, is hung on the second groove portion 102ac, and is electrically connected to the heater 103. The arm portions 104a and 104b are connected to both ends of the heater 103 in the longitudinal direction, respectively.

The wiring 105 has an arm portion 105a extending from the main body serving as an electrode pad. The arm portion 105a passes over the convex portion 101g, is hung on the second groove portion 102bc, and is electrically connected to the heater 103. The arm portion 105a is connected to the vicinity of the center in the longitudinal direction of the heater 103.

The wirings 104 and 105 are configured to include a conductive material such as Au.

When an electric current is passed through the wirings 104 and 105, the electric current is supplied to the heater 103 to generate heat and heat the distributed reflection unit 120. As a result, the refractive index of the distributed reflection unit 120 changes, so that the reflection wavelength characteristic of the distributed reflection unit 120 can be changed.

In the optical waveguide structure 100, the arm portions 104a, 104b, and 105a of the wirings 104 and 105 pass over the convex portions 101a and 101b, respectively, and are passed over the second groove portions 102ab, 102ac, and 102bc, and are electrically connected to the heater 103. Is connected to. As a result, the arm portions 104a, 104b, and 105a are less likely to be distorted, so that deterioration and disconnection are less likely to occur. As a result, the decrease in reliability of the optical waveguide structure 100 is suppressed.

The groove width of the second groove portions 102ab, 102ac, 102bc (for example, the groove width W4 shown in FIG. 2) is preferably, for example, 3 μm or less, for example, about 1 μm in order to prevent distortion from being applied to the arm portions 104a, 104b, 105a. ..

As shown in FIG. 2, the arm portion 104a may not be completely linear, and the portion spanned by the second groove portion 102ab may bend due to its own weight. By adjusting the groove width W4, the portion may be bent. The bending can be made to the extent that there is no problem with deterioration or disconnection of the arm portion 104a.

Further, in the optical waveguide structure 100, a current can be passed through the heater 103 in a current path passing through the arm portion 104a and the arm portion 105a, and a current can be passed through the current path passing through the arm portion 104b and the arm portion 105a. .. In this case, a current flows in parallel between the arm portion 104a and the arm portion 105a of the heater 103 and the portion between the arm portion 104b and the arm portion 105a. As a result, the length of the current flowing through the heater 103 in each current path can be made shorter than the total length of the heater 103. As a result, the electric resistance received by the current in the heater 103 can be reduced, and the heat generation efficiency is increased.

Further, in the optical waveguide structure 100, since the convex portions 101a, 101b, 101g are close to the mesa portion M2, the heat given by the heater 103 may be transferred to the convex portions 101a, 101b, 101g and radiated. be. Therefore, the third groove portions 102ad and 102ae are adjacent to the convex portion 101a, the third groove portions 102af and 102ag are adjacent to the convex portion 101b, and the third groove portions 102bd and 102be are adjacent to the convex portion 101g. As a result, the lengths of the convex portions 101a, 101b, 101g are substantially lengthened to increase the thermal resistance as much as possible, and heat dissipation from the convex portions 101a, 101b, 101g is suppressed. The groove width of the third groove portions 102ad, 102ae, 102af, 102ag (for example, the groove width W5 shown in FIG. 3) is preferably 3 μm or more, for example.

As described above, in the optical waveguide structure 100, the heating efficiency by the heater 103 is high, and the deterioration of reliability is suppressed.

(Production method)
The optical waveguide structure 100 can be manufactured, for example, by the following process. First, in the region where the distributed reflection portion 120 should be formed, as shown in FIG. 4A, a known metal organic chemical vapor deposition (MOCVD) method and photolithography technique are applied on the substrate 100a. And etching, the lower clad layer 100b, the diffraction lattice layer 100c, the spacer layer 100d, the optical waveguide layer 100e, the first upper clad layer 100f, the lower embedded layer 100 g, the upper embedded layer 100h, the second upper clad layer 100i. To form a structure containing the mesa structure M1. That is, a clad that includes an optical waveguide layer 100e and a diffraction grating layer 100c and is configured to extend in a predetermined length along one direction, and a clad that surrounds the distributed reflection unit 120 from above, below, left, and right along the distributed reflection unit 120. The step of forming the portion 106 is performed. In each region where the optical waveguides 110a and 110b should be formed, a semiconductor layer made of the same p-type GaInAsP as the diffraction grating layer 100 is laminated instead of the diffraction grating layer 100c.

Subsequently, after depositing the SiN film on the entire surface, the SiN film is patterned. After that, dry etching is performed using the SiN film as a mask to form the trench grooves 102a and 102b and the mesa portion M2. That is, by forming trench grooves 102a and 102b in the clad portion 106 along both sides of the distributed reflection portion 120, a step of forming the mesa portion M2 including the distributed reflection portion 120 is performed. Subsequently, the protective film 100j is formed by using the CVD method. FIG. 4B shows a state after the protective film 100j is formed. When forming the trench grooves 102a, 102b, by forming the convex portions 101a, 101b, 101g, the first groove portions 102aa, 102ba, 102bb, the second groove portions 102ab, 102ac, 102bc, and the third groove portion are formed. It forms 102ad, 102ae, 102af, 102ag, 102bd, 102be.

Subsequently, for example, a step of arranging the heater 103 along the distributed reflection portion 120 on the clad portion 106 and a step of arranging the wirings 104 and 105 electrically connected to the heater 103 using, for example, a thin-film deposition method and a lift-off method. And do. At this time, the arm portions 104a, 104b, 105a of the wirings 104, 105 are passed over any of the convex portions 101a, 101b, 101g and passed over any of the second groove portions 102ab, 102ac, 102bc, and are passed to the heater 103. Connect electrically. After that, the optical waveguide structure 100 is completed by appropriately performing the necessary steps in manufacturing the semiconductor element.

(Embodiment 2)
FIG. 5 is a schematic diagram illustrating the optical waveguide structure according to the second embodiment, and is an enlarged view of a part on the right side of the structure corresponding to FIG. The optical waveguide structure 100A has a structure in which the protective film 100j is replaced with the protective film 100Aj in the optical waveguide structure 100 according to the first embodiment.

The protective film 100Aj has a thick film portion 100Aja whose thickness is thicker than other portions of the protective film 100Aj in the vicinity of the opening of the trench groove 102a. As a result, the groove width W6 of the second groove portion 102ab is smaller than the groove width W4 in the optical waveguide structure 100. As a result, the arm portion 104a is less likely to be distorted, so that deterioration and disconnection are less likely to occur. As a result, the decrease in reliability of the optical waveguide structure 100 is further suppressed.

In order to form such a thick film portion 107Aja, the flow rate and pressure of the raw material gas of the protective film in the CVD method may be adjusted.

(Embodiment 3)
6A and 6B are schematic views illustrating the optical waveguide structure according to the third embodiment, FIG. 6A is a diagram corresponding to FIG. 2, and FIG. 6B is a top view. The optical waveguide structure 100B has a configuration in which the convex portion 101a is replaced with the convex portion 101Ba in the optical waveguide structure 100 according to the first embodiment.

The convex portion 101Ba is composed of a plurality of segments 101Baa separated from each other in the protruding direction. The segments 101Baa are separated by a groove 101Bab. As a result, the thermal resistance of the convex portion 101Ba in the protruding direction can be made extremely high, so that heat dissipation from the mesa portion M2 to the convex portion 101Ba can be further suppressed, and the heating efficiency of the heater 103 can be further improved. The other convex portions 101b and 101g may be replaced with the same convex portions as the convex portions 101Ba.

(Embodiment 4)
FIG. 7 is a schematic diagram illustrating the optical waveguide structure according to the fourth embodiment, and is a diagram corresponding to FIG. 2. In this optical waveguide structure 100C, the protective film 100j has a structure in which the second groove portion 102ab is filled. As described above, in the case of the structure in which the protective film 100j fills the second groove portion 102ab, the groove width of the second groove portion 102ab before forming the protective film 100j is sufficiently narrow. As a result, when the second groove portion 102ab is filled with the protective film 100j, the unevenness of the surface of the protective film 100j is small. As a result, deterioration and disconnection of the wiring (arm portion 104a) are less likely to occur.

When the optical waveguide structure 100C is manufactured, it is preferable that the groove width of the second groove portion 102ab before forming the protective film 100j is about 0.5 μm to 3 μm. The other second groove portions 102ac and 102bc may also be filled with the protective film 100j.

(Embodiment 5)
FIG. 8 is a schematic top view of the optical waveguide structure according to the first embodiment. FIG. 9 is a diagram showing a part of the cross section taken along the line CC of FIG. The optical waveguide structure 100D has a structure in which the trench grooves 102a and 102b are replaced with the trench grooves 102Da and 102Db, respectively, and the polymer layer 107 is added in the optical waveguide structure 100 according to the first embodiment.

That is, the optical waveguide structure 100D includes an optical waveguide layer 100e and a diffraction grating layer 100c, and includes a distributed reflection unit 120 configured to extend in a predetermined length along one direction, and optical waveguide units 110a and 110b. It has a laminated portion 101D including an adjacent clad portion 106 so as to surround the optical waveguide portions 110a and 110b and the distributed reflection portion 120 from above, below, left and right along the optical waveguide portions 110a and 110b. The optical waveguide structure 100D further includes a heater 103 arranged along the distributed reflection portion 120 on the upper surface of the clad portion 106 of the laminated portion 101D, and wirings 104 and 105 electrically connected to the heater 103. ing. Then, trench grooves 102Da and 102Db, which are vertical grooves extending along the distributed reflection portion 120, are formed on both the left and right sides of the distribution reflection portion 120 in the clad portion 106. These trench grooves 102Da and 102bD define a mesa portion M2 including the distributed reflection portion 120 and having a mesa shape in cross section.

At least a part of the trench groove 102Da and the trench groove 102Db is filled with the polymer layer 107.

As shown in FIG. 9, the polymer layer 107 is formed on the first polymer layer 107a having a convex surface formed on the bottom surface of the groove (shown for the trench groove 102Da in the figure) and the first polymer layer 107a. It has an insulating second polymer layer 107b. That is, in the polymer layer 107, the second polymer layer 107b forms the outermost surface. Both the first polymer layer 107a and the second polymer layer 107b have a refractive index lower than that of the clad portion 106, and are polyimide, which is a photosensitive polymer in the present embodiment.

The arm portion 104a of the wiring 104 is electrically connected to the heater 103 through the surface of the second polymer layer 107b exposed above a part of the trench groove 102Da. The arm portion 104b of the wiring 104 is also electrically connected to the heater 103 through the surface of the second polymer layer 107b exposed above a part of the trench groove 102Da. The arm portion 105a of the wiring 105 is also electrically connected to the heater 103 through the surface of the second polymer layer 107b exposed above a part of the trench groove 102Db.

As described above, the surface of the insulating material that fills the groove may have a shape in which the center is recessed and a shape in which the periphery is projected. On the other hand, in the polymer layer 107, by forming the first polymer layer 107a in a convex shape, the action of denting the center of the surface of the second polymer layer 107b is offset. Further, by canceling the action of denting the center in this way, the action of forming a protruding shape at the periphery is also suppressed. As a result, the flatness of the surface of the polymer layer 107 is increased, and even if wiring (arm portions 104a, 104b, 105a) is passed over the polymer layer 107, distortion is less likely to be applied, and deterioration and disconnection are less likely to occur. As a result, the decrease in reliability of the optical waveguide structure 100D is suppressed.

The groove widths of the trench grooves 102Da and the trench grooves 102Db (for example, the groove width W7 shown in FIG. 9) are preferably about 5 μm to 15 μm in order to facilitate the formation of the convex shape of the first polymer layer 107a. Further, in the present embodiment, only a part of the trench grooves 102Da and 102Db is filled with the polymer layer 107, but the entire trench grooves 102Da and 102Db may be filled with the polymer layer 107.

(Production method)
The optical waveguide structure 100D can be manufactured, for example, by the following process. First, as in the manufacturing process of the optical waveguide structure 100 described with reference to FIG. 4, a step of forming a distributed reflection unit 120, an optical waveguide portions 110a and 110b, and a clad portion 106 surrounding them from above, below, left and right. I do. .. Subsequently, the trench grooves 102Da and 102Db and the mesa portion M2 are formed. Subsequently, the protective film 100j is formed by using the CVD method. Subsequently, as shown in FIG. 10A, the first polymer material is cured so that the surface becomes convex on the bottom surface of a predetermined portion (shown for the trench groove 102Da in the figure) in the trench grooves 102Da and 102Db. Supply the previous polyimide. After that, the polyimide is thermoset to obtain the first polymer layer 107a. Subsequently, as shown in FIG. 10B, uncured polyimide, which is a second polymer material, is supplied onto the first polymer layer 107, and this is thermoset to form the second polymer layer 107b, and the trench groove 102Da is obtained. , Part of 102Db is filled.

After that, the optical waveguide structure 100D is formed by performing a step of arranging the heater 103 and a step of arranging the wirings 104 and 105 electrically connected to the heater 103, and further performing necessary steps in manufacturing the semiconductor element as appropriate. Complete.

In the first to third embodiments, the second groove may be filled with an insulating material such as polyimide. As in the fourth embodiment, the groove width of the second groove of the first to third embodiments is sufficiently narrow. , The unevenness of the surface when filled with an insulating material is small. As a result, deterioration and disconnection are less likely to occur even when wiring is passed over the insulating material. Further, in the first embodiment, both of the two trench grooves have the first groove portion, the second groove portion, and the third groove portion, but at least one of the two trench grooves is the first groove portion, the second groove portion, and the third groove portion. It may have a groove portion. The same applies to the second and third embodiments. Further, in the fifth embodiment, at least a part of both of the two trench grooves is filled with the polymer layer, but at least one part of the two trench grooves may be filled with the polymer layer.

Further, in the above embodiment, the diffraction grating layer is located on the substrate side with respect to the optical waveguide layer, but it may be located on the side opposite to the substrate. Further, in the above embodiment, both sides of the distributed reflection portion may not be embedded with a semiconductor such as a current blocking structure, and the mesa portion may have a high mesa structure. In this case, there is no clad portion adjacent to both sides of the mesa portion, and the clad portion is composed of an adjacent lower clad layer, a first upper clad layer, and a second upper clad layer so as to sandwich the distributed reflection portion.

Further, the present invention is not limited to the above embodiments. The present invention also includes a configuration in which the above-mentioned components are appropriately combined. Further, further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspect of the present invention is not limited to the above embodiment, and various modifications can be made.

100 Optical waveguide structure 100a Substrate 100b Lower clad layer 100c Diffraction grating layer 100d Spacer layer 100e Optical waveguide layer 100f First upper clad layer 100g Lower embedded layer 100h Upper embedded layer 100i Second upper clad layer 100j Protective film 101 Laminated portion 101a , 101b, 101g Convex 101c, 101d, 101e, 101f, 101h Recess 102a, 102b Trench groove 102aa, 102ba, 102bb First groove 102ab, 102ac, 102bc Second groove 102ad, 102ae, 102af, 102ag, 102bd, 102be 3rd Groove 103 Heater 104, 105 Wiring 104a, 104b, 105a Arm 106 Clad 107 Polymer layer 107a First polymer layer 107b Second polymer layer 108a, 108b Polyimide 110 Optical waveguide 120 Distributed reflection M1 Mesa structure M2 Mesa W1, W2 width W3, W4, W5, W6, W7 Groove width

Claims (6)

A distributed reflector that includes an optical waveguide layer and a diffraction grating layer and is configured to extend at a predetermined length along one direction.
A clad portion that surrounds the distributed reflection portion from above, below, left, and right along it,
A heater arranged along the distributed reflection portion on the upper surface of the clad portion, and
The wiring electrically connected to the heater and
Equipped with
The clad portion is formed with vertical grooves extending along the distributed reflection portion on both the left and right sides of the distributed reflection portion, and these vertical grooves have a mesa-shaped cross-sectional shape including the distribution reflection portion. Is defined and
The heater is arranged on the mesa portion, and the heater is arranged on the mesa portion.
At least one of the vertical grooves has a first groove portion having a predetermined groove width and a second groove portion having a groove width smaller than that of the first groove portion.
With respect to at least one of the vertical grooves, the clad portion in the vicinity thereof projects from the inner side wall far from the mesa portion in the vertical groove toward the mesa portion to form the second groove portion. It has a convex part and
The wiring is passed over the convex portion and hung on the second groove portion, and is electrically connected to the heater.
The wiring is connected to a position between the first arm portion and the second arm portion connected to the separated positions in the longitudinal direction of the heater and the first arm portion and the second arm portion in the longitudinal direction of the heater. It has a third arm portion, and is parallel to the portion between the first arm portion and the third arm portion of the heater and the portion between the second arm portion and the third arm portion. The length of the current flowing through the heater in the current path of each of the parts is shorter than the total length of the heater.
A protective film covering the inner surface of each of the flutes and the surface of the clad portion is further provided.
The protective film has a thickness in the vicinity of the opening of the vertical groove thicker than that of the other protective film, and the groove width of the second groove is the thickness in the vicinity of the opening of the vertical groove of the protective film. Is smaller than the groove width of the second groove portion when the thickness is not thicker than that of the other protective film portion.
Optical waveguide structure. The at least one of the vertical grooves has a third groove portion adjacent to the convex portion and having a groove width larger than that of the first groove portion.
The optical waveguide structure according to claim 1, wherein the clad portion has a recess forming the third groove portion. The optical waveguide structure according to claim 1 or 2, wherein the convex portion is composed of a plurality of segments separated from each other by a groove in the protruding direction. The optical waveguide structure according to any one of claims 1 to 3 , wherein the width of the second groove portion between the convex portion and the mesa portion is 3 μm or less. The optical waveguide structure according to any one of claims 1 to 4 , wherein the diffraction grating layer is configured as a sampling diffraction grating, a phase shift diffraction grating, or a superstructured diffraction grating. A distributed reflection portion including an optical waveguide layer and a diffraction grating layer, which is configured to extend at a predetermined length along one direction, and a clad portion that surrounds the distributed reflection portion from above, below, left, and right are formed. And the process to do
A step of forming a mesa portion having a mesa-shaped cross-sectional shape including the distributed reflection portion by forming vertical grooves extending along the distributed reflection portion on the left and right sides of the distributed reflection portion, respectively.
A step of arranging a heater on the upper surface of the clad portion along the distributed reflection portion, and
The process of arranging the wiring electrically connected to the heater and
Including
When forming the groove, the clad portion in the vicinity of at least one of the vertical grooves projects from the inner side wall far from the mesa portion in the vertical groove toward the mesa portion in a plan view. By forming the convex portion, a first groove portion having a predetermined groove width and a second groove portion having a groove width smaller than that of the first groove portion and formed by the convex portion are formed.
When arranging the wiring, the wiring is passed over the convex portion and hung on the second groove portion, and is electrically connected to the heater.
The wiring is connected to a position between the first arm portion and the second arm portion connected to the separated positions in the longitudinal direction of the heater and the first arm portion and the second arm portion in the longitudinal direction of the heater. It has a third arm portion, and is parallel to the portion between the first arm portion and the third arm portion of the heater and the portion between the second arm portion and the third arm portion. The length of the current flowing through the heater in the current path of each of the parts is shorter than the total length of the heater.
A protective film covering the inner surface of each of the vertical grooves and the surface of the clad portion is further formed, and the protective film is thicker in the vicinity of the opening of the vertical groove than the other protective film portions. The groove width of the second groove portion is smaller than the groove width of the second groove portion when the thickness of the protective film in the vicinity of the opening of the vertical groove is not thicker than that of the other protective film portion.
A method for manufacturing an optical waveguide structure.

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