JP4096469B2 - Optical receiver module and method of manufacturing optical receiver module - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical receiver module used for optical communication.
[0002]
[Prior art]
In recent years, optical modules have been actively developed in order to reduce the cost and size of optical integrated circuits in optical communications. In particular, attention is focused on module assembly by passive alignment mounting in which elements and optical fibers are mounted on a Si carrier without driving the elements.
[0003]
FIG. 29 is a cross-sectional view for explaining a conventional optical receiver module.
500 is a Si carrier, 501 is a V-groove formed on the Si carrier, 502 is an optical fiber, and 503 is a side-illuminated photodiode. Here, since the V-groove 501 is formed with high accuracy by alkali anisotropic etching, the optical fiber 502 fixed to the V-groove 501 is automatically positioned, and the positional accuracy in the height direction and the lateral direction is extremely high. high. Since the light receiving element 503 uses flip chip mounting utilizing the self-alignment effect by solder reflow, it can be mounted by passive alignment without driving the element.
[0004]
However, this conventional structure still has some problems. In particular, the following two points can be cited as major problems. The first problem is that it cannot be applied to a back-illuminated type light receiving element because it does not have a mechanism for converting the optical path of the irradiation light from the optical fiber. The second problem is that the optical fiber cannot be accurately positioned in the optical axis direction. Specifically, even if an end of the optical fiber is pressed against the end of the V-groove (reference numeral 504 in the figure) and positioned, the end of the V-groove (reference numeral 504 in the figure) also has an inclination of about 54.7 degrees. As a result, the tip is lifted and the optical axis is shifted. Therefore, there was no other way than positioning the optical fiber in the optical axis direction.
[0005]
The following techniques have been reported as techniques for solving these problems.
First, as a technique for solving the problem that it cannot be applied to the first surface or back-illuminated type light receiving element, the technique described in “Science Technical Report, EMD96-30, 1996, P.37” is used. There is. In this technique, as shown in FIG. 30, an optical fiber 603 is fixed to a V-groove 601 of a substrate 600, and an optical path of irradiation light from the optical fiber 603 is converted using an inclined surface 602 at the tip of the V-groove 601. The surface of the light receiving element 604 is irradiated.
[0006]
However, if this technique and the mounting of the light receiving element are combined with the flip chip mounting technique using the self-alignment effect by solder reflow, there remains a problem that it is difficult to cope with the irradiation of the back surface of the light receiving element. In particular, in the case of an IC in which a light receiving element integrates a transistor and a high-frequency matching circuit and uses a coplanar line as a wiring, it is necessary to irradiate received light from the back surface, avoiding the surface on which electrodes and pads are arranged. Therefore, the method shown in FIG. 30 is limited to an element mounted with the surface facing downward, that is, a surface incident type element.
[0007]
Next, as a technique related to positioning of the second optical fiber in the optical axis direction, “Passive alignment of a tapered laser with more than 50% coupling efficiency, Electronics Letters 27th April 1995 Vol.31 No.9 P.730 There is a technique described in "." As shown in FIG. 31, the end of the V-groove 700 on the element 701 side is cut by dicing to form a surface 703 perpendicular to the surface of the substrate 702, and the optical fiber 704 is pressed against the end surface 703. Thus, positioning in the optical axis direction is performed in addition to the vertical direction and the horizontal direction.
[0008]
However, this technique can be applied to a side-illuminated module. However, in the back-illuminated module as described above, it is necessary to convert the optical path of received light using the inclined surface of the V-groove end. Therefore, it is not applicable.
[0009]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to enable irradiation from the back surface of a light receiving element even when an optical receiving module is assembled by passive alignment mounting. Another object of the present invention is to position the optical fiber in the optical axis direction with high accuracy in an optical module that changes the optical path in the vertical direction by using the inclination of the tip surface of the V-groove.
[0010]
[Means for Solving the Problems]
According to the first aspect of the invention, the optical fiber is sandwiched between the bonded first and second Si substrates using the V-groove, and the received light from the optical fiber is applied to the reflection film at the tip of the V-groove. Then, the direction is changed in the vertical direction, and the light is received by the back-illuminated light receiving element flip-chip mounted in the concave portion of the first Si substrate.
[0011]
Thus, by flip chip mounting of the light receiving element and fixing of the optical fiber by the V groove using two Si substrates, the relative position between the optical fiber and the light receiving element is maintained with high accuracy by passive alignment mounting. It is possible to perform backside irradiation.
[0012]
  AlsoThe invention according to claim 1According toThe optical fiber is sandwiched by the V-groove provided in the first Si substrate,Because the optical fiber is in contact with the oblique surface of the first Si substratePositioning between both Si substrates can be made more accurate.
[0019]
  Claim2According to the invention described in claim1In addition to the effects of the described invention, when the light receiving element is a transistor, the irradiation direction to the light receiving element is often the back surface, but at this time, it is more useful.
[0020]
  Claim3According to the invention described in claim 1,Or 2In addition to the operational effects of the invention described in the above, when the light receiving element is an IC composed of a transistor and a high frequency matching circuit, the irradiation direction to the light receiving element is often the back surface, but at this time, it becomes more useful. .
[0021]
  Claim4According to the invention described in claim2Or3In addition to the effects of the invention described in (1), when a coplanar line is used as the wiring of the light receiving element, the irradiation direction to the light receiving element is often the back surface, but at this time, it becomes more useful.
[0022]
  Claim5According to the invention described in claim 1,4In addition to the operational effects of the invention described in any one of the above, the light receiving element is formed on the semiconductor substrate having a band gap wavelength shorter than the wavelength of the received light, so that light can easily pass through the semiconductor substrate, This is preferable as a back-illuminated light receiving element.
[0023]
  Claim6According to the invention described in claim 1,5In addition to the operational effects of the invention described in any one of the above, since the light receiving element is formed on the InP substrate, light is easily transmitted through the substrate, which is preferable as a back-illuminated light receiving element.
[0024]
  Claim7According to the invention described in claim 1,6In addition to the operational effects of the invention described in any one of the above, it is possible to easily connect to a connector or the like by means of an electrode pad provided at the end of the wiring opposite to the light receiving element.
[0025]
  Claim8In the first Si substrate,Has a beveled surface at the tipOptical fiberPinchingV-groove forFormed,thisA recess for arranging the light receiving element is formed on an extension line in the extending direction of the V-groove, and a pad and an electric wiring for mounting the back-side illuminated light receiving element are formed inside the recess. A back-illuminated light receiving element is mounted on the first Si carrier andIs done. AlsoOptical fiber on the second Si substratePinchingA V-groove for use is formed, and a reflection film for optical path conversion is formed on the oblique surface at the tip of the V-groove to form a second Si carrier. AndWhile the tip of the optical fiber is in contact with the inclined surface of the tip of the V-groove formed in the first Si carrierThe first Si carrier and the second Si carrier are bonded together, and the optical fiber is sandwiched and fixed between the V grooves of both carriers.
As a result, the structure of the optical receiver module according to claim 1 can be obtained.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
[0030]
FIG. 1 shows a plan view of the optical receiver module in the present embodiment. FIG. 2 shows a vertical cross section taken along line AA in FIG. Further, FIG. 3 shows a view from the arrow B (left side view) in FIG. 1, and FIG. 4 shows a view from the arrow C (right side view) in FIG.
[0031]
As shown in FIG. 2, the optical receiver module includes a first Si substrate 1, a second Si substrate 2, a backside illuminated light receiving element 3, an optical fiber 4, a reflection film 5 for optical path conversion, and a light receiving element mounting pad 6. The wiring 7 is constituted. Then, the first Si substrate 1 and the second Si substrate 2 are bonded together with the optical fiber 4 sandwiched therebetween. The first Si substrate 1 constitutes a first Si carrier C1, and the second Si substrate 2 constitutes a second Si carrier C2.
[0032]
A recess 8 is formed on the surface (upper surface) of the first Si substrate 1. On the bottom surface 8a of the recess 8, the light receiving element mounting pad 6 and the wiring 7 are patterned. Further, as shown in FIG. 3, the back-illuminated light receiving element 3 is flip-chip mounted on the light receiving element mounting pad 6 inside the recess 8.
[0033]
Here, as shown in FIG. 1, the end of the wiring 7 is a wide electrode pad 7a. Thus, the wiring 7 electrically connected to the light receiving element 3 is formed on the Si substrate 1 on the side where the light receiving element 3 is mounted, and an electrode is formed at the end of the wiring 7 opposite to the light receiving element 3. A pad 7a is provided. Then, the signal of the light receiving element 3 is extracted outside using the pad 6 and the wiring 7.
[0034]
A V-groove 10 is extended on the surface of the second Si substrate 2 (the lower surface in FIG. 2). One end of the V-groove 10 opens on the side surface of the substrate, the other end extends linearly inwardly of the substrate, and the tip is inclined. As described above, the second Si substrate 2 is bonded to the recess forming surface of the first Si substrate 1, but the tip of the second Si substrate 2 is inclined to the surface facing the first Si substrate 1. The V-groove 9 is extended.
[0035]
In the first Si substrate 1, a V groove 9 is formed at a position facing the V groove 10 of the second Si substrate 2. One end of the V-groove 9 also opens to the side surface of the substrate, and the other end extends linearly inward of the substrate. As shown in FIG. 4, the optical fiber 4 is sandwiched between the V groove 10 of the second Si substrate 2 and the V groove 9 of the first Si substrate 1. Specifically, a total of four points on both side walls of the V groove 10 and both side walls of the V groove 9 are supported in contact.
[0036]
The first Si substrate 1 is not provided with the V groove 9, and the optical fiber 4 is sandwiched between the V groove 10 of the second Si substrate 2 and the surface (flat surface) of the first Si substrate 1. In this case, a total of three points on both side walls of the V-groove 10 and the surface of the first Si substrate 1 are in contact and supported.
[0037]
As shown in FIG. 2, in the second Si substrate 2, a reflection film 5 for optical path conversion is formed on the oblique surface 10 a at the tip of the V groove 10. The reflection film 5 converts the optical path of the received light from the optical fiber 4 in the vertical direction. The received light from the reflective film 5 is received by the back-illuminated light receiving element 3 described above. That is, when the reception light from the optical fiber 4 is applied to the reflection film 5, the light is converted in the vertical direction, is applied to the back-illuminated light receiving element 3, and is converted into an electrical signal.
[0038]
With the optical receiver module having such a structure, it is possible to irradiate the light receiving element 3 with the back surface.
A specific configuration example of the back-side illuminated light receiving element 3 is shown in FIG. The light receiving element 3 is a HEMT type phototransistor, and FIG.
[0039]
In FIG. 5, on the semi-insulating InP substrate 101, i-In_0.52Al_0.48As buffer layer 102, i-In_0.53Ga_0.47As light absorption layer 103, i-In_0.80Ga_0.20As carrier running layer 104, i-In_0.52Al_0.48An As gate contact layer 105 is formed in order. However, i-In_0.52Al_0.48In the As gate contact layer 105, a δ-doped layer 106 made of Si is formed. On the gate contact layer 105, n-type In_0.53Ga_0.47An As cap layer 107 is formed. A source electrode 109 and a drain electrode 110 are formed on the upper surface of the cap layer 107 so as to exhibit ohmic characteristics. The gate electrode 108 is in contact with the gate contact layer 105 by etching the cap layer 107 so as to form a Schottky junction.
[0040]
When infrared light having a wavelength of 1.55 μm is incident, it passes through the substrate 101 and i-In_0.53Ga_0.47As light absorption layer 103 and i-In_0.80Ga_0.20It is absorbed by the As carrier traveling layer 104. Electrons generated by this light irradiation are i-In_0.80Ga_0.20It diffuses at high speed in the As carrier traveling layer 104.
[0041]
Further, a high-frequency matching circuit is formed in another area of the InP substrate 101 to form an IC (OEIC). Specifically, as shown in FIG. 6, for example, a coplanar type high-frequency transmission line 301 is connected to the gate electrode of the photoresponsive transistor (high electron mobility phototransistor) 300. Further, an output matching circuit 304 including a coplanar type high frequency transmission line 302 and a stub 303 is connected to the drain electrode. Further, capacitors 305 and 306 are connected to the stub 303 and the transmission line 301 for grounding a high-frequency signal.
[0042]
Thus, when the transmission line 301 is connected to the gate side, the sensitivity of the radio signal taken out from the output port can be increased. For example, when intensity modulation of incident light is performed, a desired frequency signal can be extracted with high sensitivity by connecting the output matching circuit 304 to the drain side.
[0043]
Next, the operation of the optical receiving module will be described.
In FIG. 2, the optical fiber 4 is sandwiched between the bonded first and second Si substrates 1 and 2 using V grooves 9 and 10, and the received light from the optical fiber 4 is reflected at the tip of the V groove 10. The direction of the film 5 is changed in the vertical direction, and the light is received by the back-illuminated light receiving element 3 that is flip-chip mounted in the concave portion 8 of the first Si substrate 1.
[0044]
Here, since the light receiving element 3 is flip-chip mounting using a self-alignment effect by solder reflow, it can be positioned with high accuracy, and the optical fiber 4 and the first and second Si substrates 1 and 2 are provided with V grooves 9 and 10. Thus, the relative position is accurately determined. Therefore, the relative positions of the optical fiber 4, the optical path conversion reflecting film 5, and the light receiving element 3 are highly accurate, and the light received from the optical fiber 4 can be received by the light receiving element 3 efficiently.
[0045]
As described above, the flip-chip mounting of the light receiving element 3 and the fixing of the optical fiber 4 by the V grooves 9 and 10 using the two Si substrates 1 and 2 allow the relative positions of the optical fiber 4 and the light receiving element 3 to be changed by passive alignment mounting. The backside illumination to the light receiving element 3 can be performed while maintaining high accuracy. Further, since the V-groove 9 for holding the optical fiber is formed on the recess forming surface of the first Si substrate 1, the optical fiber 4 is held by the V-groove 9 and positioning between the Si substrates 1 and 2 is performed. Higher accuracy can be achieved.
[0046]
Furthermore, the light receiving element 3 is a transistor, and the irradiation direction to the light receiving element is the back surface. At this time, it is more useful. Also, when the light receiving element 3 is an IC composed of a transistor and a high-frequency matching circuit, the irradiation direction to the light receiving element is the back surface, which is more useful at this time. In addition, when a coplanar line is used as the wiring of the light receiving element 3, the irradiation direction to the light receiving element is the back surface, which is more useful at this time.
[0047]
Further, the light receiving element 3 is formed on a semiconductor substrate (InP substrate) having a band gap wavelength shorter than the wavelength of the received light, and light is easily transmitted through the semiconductor substrate, which is preferable as a back-illuminated light receiving element. . That is, the light receiving element 3 is formed on the InP substrate, and light is easily transmitted through the substrate, which is preferable as a back-illuminated light receiving element.
[0048]
Further, a wiring 7 electrically connected to the light receiving element 3 is formed on the Si substrate 1 on the side where the light receiving element 3 is mounted, and an electrode pad 7a is formed at the end of the wiring 7 opposite to the light receiving element 3. And can be easily connected to a connector or the like.
[0049]
Next, a method for manufacturing the optical receiving module will be described.
First, a manufacturing method on the first Si carrier C1 side will be described with reference to FIGS. 7 to 9, (a) shows a plane as shown in FIG. 1, and (b) shows a cross section taken along line AA of FIG. 1.
[0050]
As shown in FIGS. 7A and 7B, a first Si substrate 1 is prepared, and a V-groove 9 for fixing an optical fiber on the surface of the Si substrate 1 and an extension line in the extending direction of the V-groove 9. A recess 8 for arranging the light receiving element 3 is formed by etching. As the etching solution, KOH, TMAH (tetramethylammonium hydroxide), or the like is used. At this time, the depth of the V-groove 9 is set such that the core of the optical fiber 4 is not located below the upper surface of the V-groove 9 (see FIG. 2).
[0051]
Subsequently, as shown in FIGS. 8A and 8B, the flip chip mounting pad 6 and the electric wiring 7 are formed on the bottom surface 8 a of the recess 8. Specifically, for example, Ti / Au is deposited and lifted off to form the pad 6 and the wiring 7.
[0052]
Subsequently, as shown in FIGS. 9A and 9B, AuSn solder is formed on the pad 6, and the back-illuminated light receiving element 3 is disposed with the active portion facing down, that is, with the light receiving surface facing upward. Further, reflow is performed at 280 ° C. or higher to fix (mount) the backside illuminated light receiving element 3. Further, the optical fiber 4 is fixed to the V groove 9 with an adhesive or the like. This is the first Si carrier.
[0053]
Next, a manufacturing method on the second Si carrier C2 side will be described with reference to FIG. 10, (a) shows a plane as shown in FIG. 1, and (b) shows a cross section taken along line AA of FIG.
[0054]
As shown in FIGS. 10A and 10B, a second Si substrate 2 is prepared, and a V-groove 10 for fixing an optical fiber is formed on the surface thereof in the same process as that for the first Si substrate 1. To do. However, the depth of the V-groove 10 is a depth at which the core of the optical fiber 4 is located below the upper surface of the V-groove 10 (see FIG. 2).
[0055]
Then, the reflective film 5 for optical path conversion is formed on the inclined surface 10a at the end of the V groove 10 by Ti / Au deposition and lift-off (or Ti / Au deposition and Ti / Au etching). This becomes the second Si carrier.
[0056]
The second Si carrier (substrate 2) formed in this way is overlaid on the first carrier (substrate 1) so that the optical fiber 4 fits into the V-groove 10 as shown in FIGS. Fix with resin or adhesive. That is, the first Si carrier (substrate 1) and the second Si carrier (substrate 2) are bonded together, and the optical fiber 4 is sandwiched and fixed between the V grooves 9 and 10 of both carriers.
[0057]
In this way, the optical receiving module is completed.
FIG. 11 shows an application example. In FIG. 11, the front end surface of the first Si substrate 1 at the V groove 9 is perpendicular to the surface of the substrate 1, and the front end surface of the optical fiber 4 is in contact with the vertical surface 20a. That is, the side surface 20a close to the light receiving element 3 in the V-groove 9 is perpendicular to the substrate surface, and the vertical surface 20a positions the tip of the optical fiber 4 in the optical axis direction.
[0058]
As described above, since the V groove 9 of the first Si substrate 1 is provided with the stopper (groove 20) in the optical axis direction of the optical fiber 4, the optical fiber 4, the first and second Si substrates 1, 2 are provided. Since the relative position in the optical axis direction is uniquely determined, the accuracy becomes high.
[0059]
12 and 13 show other application examples. 12 and 13, the V-groove 30 of the second Si substrate 2 includes a V-groove 31 for positioning the optical fiber 4 and a V-groove 32 for optical path conversion. The opening width of the V-groove 32 is smaller than that of the positioning V-groove 31 (W1 <W2 in FIG. 13). Further, a fiber stopper groove 33 is formed between the V grooves 31 and 32. The fiber stopper groove 33 communicates with both the V grooves 31, 32, and the side surfaces 33a, 33b thereof are perpendicular to the substrate surface and deeper than the fiber positioning V groove 31 (in FIG. 12, D1> D2). Of the side surfaces 33 a and 33 b of the fiber stopper groove 33, the tip surface of the optical fiber 4 is in contact with the optical fiber stopper surface 33 a formed at the boundary between the fiber stopper groove 33 and the optical path changing V groove 32. In this way, the optical fiber 4 is positioned in the optical axis direction. Therefore, since the V-groove 30 of the second Si substrate 2 is provided with a stopper in the optical axis direction of the optical fiber 4, the optical fiber 4, the first and second Si substrates 1 and 2, relative to each other in the optical axis direction. Since the position is uniquely determined, high accuracy is obtained.
(Second Embodiment)
Next, the second embodiment will be described focusing on the differences from the first embodiment.
[0060]
FIG. 14 shows a cross-sectional view of the optical receiver module in the present embodiment.
The optical receiver module includes a first Si substrate 41, a second Si substrate 42, a backside illuminated light receiving element 43, an optical fiber 44, a reflection film 45 for optical path conversion, a backside illuminated light receiving element mounting pad 46, and a wiring 47. It is configured. The second Si substrate 42 is mounted on the first Si substrate 41 by self-alignment by solder reflow using the bumps 52 with the optical fiber 44 sandwiched therebetween. The first Si substrate 41 constitutes a first Si carrier C11, and the second Si substrate 42 constitutes a second Si carrier C12.
[0061]
A recess 48 is formed on the surface (the lower surface in the drawing) of the second Si substrate 42. On the bottom surface 48a of the recess 48, the light receiving element mounting pad 46 and the wiring 47 are patterned. The end of the wiring 47 is a wide electrode pad 47a as in the first embodiment. In addition, the back-side illuminated light receiving element 43 is flip-chip mounted on the light receiving element mounting pad 46 inside the recess 48.
[0062]
Thus, the wiring 47 electrically connected to the light receiving element 43 is formed on the Si substrate 42 on the side where the light receiving element 43 is mounted, and an electrode pad is formed at the end of the wiring 47 opposite to the light receiving element 43. 47a is provided. Then, the signal of the light receiving element 43 is extracted outside using the pad 46 and the wiring 47.
[0063]
A V groove 49 is formed on the surface (upper surface) of the first Si substrate 41. One end of the V-groove 49 opens on the side surface of the substrate, the other end extends linearly inward of the substrate, and the tip is inclined. An optical fiber 44 is fixed in the V groove 49.
[0064]
In the first Si substrate 41, a reflection film 45 for optical path conversion is formed on the oblique surface 49 a at the tip of the V groove 49. Then, the optical path of the received light from the optical fiber 44 is converted in the vertical direction by the reflective film 45. This light is applied to the back-side illuminated light receiving element 43 and converted into an electrical signal.
[0065]
With the optical receiver module having such a structure, the light receiving element 43 can be irradiated with the back surface.
Next, the operation of the optical receiving module will be described.
[0066]
The optical fiber 44 is fixed in the V groove 49 of the first Si substrate 41, and the second Si substrate 42 is mounted on the first Si substrate 41 by self-alignment by solder reflow using bumps 52. The direction of the received light from 44 is changed in the vertical direction by the reflection film 45 at the tip of the V-groove 49, and the back-illuminated light receiving element 43 flip-chip mounted in the concave portion 48 of the second Si substrate 42. Received light.
[0067]
Here, since the light receiving element 43 is flip-chip mounting using a self-alignment effect by solder reflow, the light receiving element 43 can be positioned with high accuracy with respect to the second Si substrate 42. Also, the second Si substrate 42 is also obtained by solder reflow. It is bonded to the first Si substrate 41 by flip-chip mounting using the self-alignment effect, and the optical fiber 44 is positioned on the first Si substrate 41 by the V-groove 49. Therefore, the relative position of the optical fiber 44, the optical path changing reflection film 45, and the light receiving element 43 is highly accurate, and the light received from the optical fiber 44 can be received by the light receiving element 43 efficiently.
[0068]
As described above, the flip-chip mounting of the light receiving element 43, the self-alignment effect of both the Si substrates 41 and 42, and the fixing of the optical fiber 44 by the V groove 49 formed in the Si substrate 41, the optical fiber 44 and the light receiving element by the passive alignment mounting. The back surface irradiation to the light receiving element 43 can be performed while maintaining the relative position of 43 with high accuracy.
[0069]
Next, a method for manufacturing the optical receiving module will be described.
First, as shown in FIGS. 15A and 15B, a pad (first pad) 50 made of Ti / Au is formed on the outer periphery of the substrate on the first Si substrate 41. Then, SnPb solder bumps 52 are formed on the pads 50.
[0070]
Further, as shown in FIGS. 16A and 16B, a V groove 49 for fixing an optical fiber is formed on the first Si substrate 41 by etching using an etching solution such as KOH or TMAH. At this time, the depth of the V groove 49 is set to a depth at which the core of the optical fiber 44 is positioned below the upper surface of the V groove 49 (see FIG. 14). Then, a reflective film 45 for optical path conversion is formed on the tip inclined portion 49a of the V groove 49 by Ti / Au vapor deposition and lift-off (or Ti / Au vapor deposition and Ti / Au etching).
[0071]
Thereafter, as shown in FIGS. 17A and 17B, the optical fiber 44 is fixed inside the V groove 49 with an adhesive or the like. This is the first Si carrier.
On the other hand, as shown in FIGS. 18A and 18B, a second Si substrate 42 is prepared, and a pad (second pad) 51 made of Ti / Au is formed on the outer periphery of the substrate on the upper surface thereof. Then, as shown in FIGS. 19A and 19B, a recess 48 for arranging the back-side illuminated light receiving element is formed on the second Si substrate 42 by wet etching or dry etching.
[0072]
After that, as shown in FIGS. 20A and 20B, a pad (third pad) 46 and an electric wiring 47 for mounting the back-side illuminated light receiving element 43 on the bottom surface 48a of the recess 48 are made of Ti / Au or the like. Form with.
[0073]
Subsequently, as shown in FIGS. 21A and 21B, AuSn solder is formed on the pad 46, and the back-side illuminated light receiving element 43 is disposed with the active portion facing down, that is, with the light receiving surface facing upward. To do. Thereafter, reflow is performed at 280 ° C. or higher to fix (mount) the backside illuminated light receiving element 43. This becomes the second Si carrier.
[0074]
Then, as shown in FIG. 14, the second Si carrier (substrate 42) formed in this way is arranged so that the pad 51 and the pad 50 of the first Si carrier (substrate 41) are aligned. That is, the second Si carrier (substrate 42) is positioned on the first Si carrier (substrate 41) so that the pads 50 and 51 are positioned via the solder bumps 52. Thereafter, the first Si carrier (substrate 41) and the second Si carrier (substrate 42) are joined by reflowing at a temperature at which the AuSn solder does not melt at 190 ° C. or higher.
[0075]
Thereby, an optical receiving module is formed.
(Third embodiment)
Next, the third embodiment will be described with a focus on differences from the first embodiment.
[0076]
FIG. 22 shows a plan view of the optical receiver module of this embodiment, and FIG. 23 shows a longitudinal sectional view taken along the line DD of FIG. Further, FIG. 24 shows a Si substrate (Si carrier) 60.
[0077]
As shown in FIG. 24, the basic configuration of the Si substrate (carrier) 60 includes a first V groove 61 for positioning an optical fiber extending on the surface of the Si substrate 60 whose plane orientation is (100), On the extended line of the V-groove 61, a second V-groove 62 for optical path conversion having an opening width smaller than that of the V-groove 61 is extended. Further, a fiber stopper groove 63 is formed between the V grooves 61 and 62. The fiber stopper groove 63 communicates with both the V grooves 61, 62, and its side surface is perpendicular to the substrate surface and is deeper than the positioning V groove 61. The fiber stopper groove 63 is for positioning the optical fiber in the optical axis direction. In addition, a reflective film 64 that converts the optical path of the received light from the optical fiber 66 in the vertical direction is formed on the oblique surface at the tip of the optical path converting V-groove 62.
[0078]
22 and 23, using this Si substrate (Si carrier) 60, the optical fiber 66 is fixed to the optical fiber positioning V-groove 61 in a state in which the front end surface is in contact with the side surface 63a of the fiber stopper groove 63. Has been. That is, the distal end portion of the optical fiber 66 is positioned in the optical axis direction by the optical fiber stopper surface 63 a formed at the boundary between the fiber stopper groove 63 and the optical path changing V groove 62. Further, a surface irradiation type light receiving element 65 is disposed on the upper surface of the Si substrate 60 to receive the received light from the reflective film 64.
[0079]
Next, the operation of the optical receiving module will be described.
The optical fiber 66 is fixed to the fiber positioning V-groove 61 with the tip surface of the optical fiber 66 in contact with the side surface 63 a of the fiber stopper groove 63, and the received light from the optical fiber 66 is applied to the reflection film 64 at the tip of the V-groove 62. Thus, the direction is changed in the vertical direction, and the light receiving element 65 receives the light.
[0080]
As described above, the optical fiber 66 is fixed with high accuracy in the optical axis direction in addition to the horizontal direction and the vertical direction. Therefore, the relative position of the light receiving element 65 and the optical fiber 66 becomes more accurate, and good coupling can be obtained.
[0081]
Next, the manufacturing method will be described.
First, as shown in FIGS. 25A and 25B, a nitride film 70 is formed on the Si substrate 60, and then photolithography and dry etching are performed to form openings for forming the first and second V-grooves. Portions 71 and 72 are formed. In FIG. 25A, the formation region of the nitride film 70 is represented by hatching.
[0082]
Subsequently, as shown in FIGS. 26A and 26B, the first V-groove 61 and the second V-groove are formed through the openings 71 and 72 by alkali anisotropic etching using KOH or TMAH. 62 is formed simultaneously. In this way, an optical fiber fixing V-groove 61 is formed on the Si substrate 60, and an optical path changing V-groove 62 having a narrower width than the optical fiber fixing V-groove 61 is formed on the extension line of the V-groove 61. It is formed by the same process so that both grooves do not contact. At this time, the etching depth of the first V-groove 61 is set such that the core is located below the upper surface of the V-groove 61 when the optical fiber 66 is fixed (see FIG. 23). Further, the second V-groove 62 is disposed so as not to contact in the extending direction of the first V-groove 61, and the depth thereof is deeper than the height of the core of the optical fiber 66 to be fixed, and It is shallower than the V-groove 61 (see FIG. 23).
[0083]
As an example of the size of the openings 71 and 72 for forming such a groove, the first opening 71 has a width of 200 μm and a length of 1000 μm, and the second opening 72 has a width. Is 100 μm and the length is 200 μm.
[0084]
Next, as shown in FIGS. 27 (a) and 27 (b), convex portions (portions indicated by reference numeral 73 in FIG. 26) remaining between the first V-groove 61 and the second V-groove 62, and both sides thereof. The region including the side wall is cut by dicing to form a fiber stopper groove 63 that is deeper than the first V groove 61 and whose side wall is perpendicular to the upper surface of the Si substrate 60. Thereafter, a reflection film 64 for changing the optical path is formed on the side surface of the second V-groove 62 by Ti / Au vapor deposition, photolithography and etching. In this way, Si carriers are formed.
[0085]
Subsequently, as shown in FIGS. 22 and 23, the optical fiber 66 is fixed to the first V-groove 61, and the surface irradiation type light receiving element 65 is flip-chip mounted to form an optical receiving module.
[0086]
22 and 23, the front-side illumination type light-receiving element is used, but a back-side illumination type light-receiving element may be used.
Further, regarding the V groove (V groove formed in the Si substrate) in each of the embodiments described so far, silicon may remain in the valley portion of the V groove. In short, the V-groove for fixing the optical fiber may be in contact with the optical fiber at least on the tapered surface of the side wall (including the case where it contacts at the edge portions P1 and P2 in the shallow V-groove as shown in FIG. 28). With respect to the V-groove for optical path conversion, an optical path may be formed in the groove.
[Brief description of the drawings]
FIG. 1 is a plan view of an optical receiver module according to a first embodiment.
FIG. 2 is a longitudinal sectional view taken along line AA in FIG.
FIG. 3 is a view taken in the direction of arrow B in FIG.
FIG. 4 is a view taken in the direction of arrow C in FIG.
FIG. 5 is a schematic cross-sectional view showing a specific configuration example of a back-side illuminated light receiving element.
FIG. 6 is a circuit configuration diagram of an OEIC.
FIG. 7 is a view for explaining a manufacturing process of the optical receiver module.
FIG. 8 is a view for explaining a manufacturing process of the optical receiving module.
FIG. 9 is a view for explaining a manufacturing process of the optical receiving module;
FIG. 10 is a view for explaining a manufacturing process of the optical receiving module.
FIG. 11 is a cross-sectional view of an optical receiver module in an application example.
FIG. 12 is a cross-sectional view of an optical receiver module in an application example.
FIG. 13 is a side view of an optical receiver module in an application example.
FIG. 14 is a plan view of an optical receiver module according to a second embodiment.
FIG. 15 is a view for explaining a manufacturing process of the optical receiving module;
FIG. 16 is a view for explaining a manufacturing process of the optical receiving module;
FIG. 17 is a view for explaining a manufacturing process of the optical receiving module;
FIG. 18 is a view for explaining a manufacturing process of the optical receiving module;
FIG. 19 is a view for explaining a manufacturing process of the optical receiving module;
FIG. 20 is a view for explaining a manufacturing process of the optical receiving module;
FIG. 21 is a view for explaining a manufacturing process of the optical receiving module;
FIG. 22 is a plan view of an optical receiver module according to the third embodiment.
23 is a cross-sectional view taken along line DD in FIG.
FIG. 24 is a perspective view of a Si carrier.
FIG. 25 is a view for explaining a manufacturing process of the optical receiving module;
FIG. 26 is a view for explaining a manufacturing process of the optical receiving module;
FIG. 27 is a view for explaining a manufacturing process of the optical receiving module;
FIG. 28 is a cross-sectional view for explaining the relationship between a V-groove and an optical fiber.
FIG. 29 is a cross-sectional view of an optical receiver module for explaining a conventional technique.
FIG. 30 is a cross-sectional view of an optical receiver module for explaining a conventional technique.
FIG. 31 is a cross-sectional view of an optical receiver module for explaining a conventional technique.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... 1st Si substrate, 2 ... 2nd Si substrate, 3 ... Backside illumination type light receiving element, 4 ... Optical fiber, 5 ... Reflective film, 6 ... Pad, 7 ... Wiring, 8 ... Recessed part, 9 ... V groove, DESCRIPTION OF SYMBOLS 10 ... V-groove, 31 ... V-groove, 32 ... V-groove, 33 ... Fiber stopper groove | channel, 41 ... 1st Si substrate, 42 ... 2nd Si substrate, 43 ... Back surface irradiation type light receiving element, 44 ... Optical fiber, 45 ... Reflective film, 46 ... Pad, 47 ... Wiring, 48 ... Recess, 49 ... V groove, 50 ... Pad, 51 ... Pad, 52 ... Solder bump, 60 ... Si substrate, 61 ... V groove, 62 ... V groove, 63 ... Fiber stopper groove, 64 ... Reflective film, 65 ... Light receiving element, 66 ... Optical fiber.

Claims (8)

A first Si substrate having a recess formed on the surface;
A second Si substrate bonded to a recess forming surface of the first Si substrate, and having a V-groove extending obliquely at a tip thereof on a surface facing the first Si substrate;
An optical fiber sandwiched between the V-groove of the second Si substrate and the surface of the first Si substrate;
A reflective film formed on the oblique surface at the tip of the V-groove of the second Si substrate and converting the optical path of the received light from the optical fiber in the vertical direction;
Flip-chip mounted on a bottom surface of the recess, and a back irradiation type light-receiving element for receiving the light received from the reflective film,
A V-groove for holding an optical fiber is formed in the recess forming surface of the first Si substrate, and the tip of the V-groove of the first Si substrate is an oblique surface,
The optical receiver module , wherein the tip of the optical fiber is in contact with the inclined surface of the tip of the V groove of the first Si substrate . The optical receiver module according to claim 1,
The light receiving module , wherein the light receiving element is a transistor . The optical receiver module according to claim 1 or 2 ,
An optical receiver module, wherein the light receiving element is an IC composed of a transistor and a high frequency matching circuit . The optical receiver module according to claim 2 or 3 ,
A light receiving module, wherein a coplanar line is used as the wiring of the light receiving element . In the optical receiver module according to any one of claims 1 to 4,
The light receiving module, wherein the light receiving element is formed on a semiconductor substrate having a band gap wavelength shorter than a wavelength of received light . In the optical receiver module according to any one of claims 1 to 5,
The light receiving module, wherein the light receiving element is formed on an InP substrate . In the optical receiver module according to any one of claims 1 to 6 ,
A wiring electrically connected to the light receiving element is formed on the Si substrate on the side where the light receiving element is mounted, and an electrode pad is provided at an end of the wiring opposite to the light receiving element. Optical receiver module. A method for manufacturing an optical receiver module, wherein an optical path of received light from an optical fiber is converted in a vertical direction by an oblique surface at a tip of a V groove formed on a Si substrate, and the received light is received by a light receiving element,
A V-groove for holding an optical fiber having a slanted surface at the tip is formed in the first Si substrate, a recess for arranging the light receiving element is formed on an extension line in the extending direction of the V-groove, and the inside of the recess Forming a pad and an electrical wiring for mounting a back-side illuminated light receiving element on the substrate, and further mounting a back-side illuminated light receiving element on the pad to form a first Si carrier;
Forming a V-groove for holding an optical fiber in the second Si substrate, and forming a second Si carrier by forming a reflection film for optical path conversion on the oblique surface at the tip of the V-groove;
The first Si carrier and the second Si carrier are bonded to each other while the tip of the optical fiber is in contact with the inclined surface of the tip of the V groove formed on the first Si carrier, and the optical fiber is sandwiched between the V grooves of both carriers. Fixing with
A method for manufacturing an optical receiver module , comprising:

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