WO2018036161A1

WO2018036161A1 - Laser structure for grating coupling and packaging method

Info

Publication number: WO2018036161A1
Application number: PCT/CN2017/078721
Authority: WO
Inventors: 宋琼辉; 杜巍; 马洪勇
Original assignee: 武汉光迅科技股份有限公司
Priority date: 2016-08-25
Filing date: 2017-03-30
Publication date: 2018-03-01
Also published as: CN106207743B; CN106207743A

Abstract

A laser element, comprising a substrate (1) and a laser chip (2). The laser chip is provided with an active region (21) for generating and outputting laser light and an electrode for supplying power to the laser chip. The substrate is provided with, at one end, an etching groove (14) at least partially accommodating the laser chip, and a light emitting surface (18) at the other end. The substrate is further provided with an optical waveguide (11) extending between the etching groove and the light emitting surface. The laser chip is arranged in the etching groove of the substrate, and the active region of the laser chip is aligned with the optical waveguide on the substrate. The laser element comprises only two parts, the substrate integrating the optical waveguide and the electrode as well as the laser chip, without any other discrete elements, and is simple in structural design and low in costs. The laser element can be made using a flip chip bonding alignment process to achieve the coupling of laser light paths and the coupling of the laser with a grating coupler of a silicon photonic integrated chip. The use of a passive alignment technology brings high coupling efficiency, and the laser element is suitable for efficient mass production.

Description

Laser structure and packaging method for grating coupling

Technical field

The present invention relates to a laser component for optical fiber communication, and more particularly to a laser structure and a packaging method for grating coupling, and more particularly to a method for coupling a laser light source to a grating coupler in a silicon photonic device, and the present invention belongs to the field of communications.

Background technique

Silicon photonic materials, due to their high integration, high frequency characteristics, low power consumption, and compatibility with existing large-scale integrated circuit processes, have become a hot research topic in the world. Various silicon photonic devices such as high-speed electro-optic modulators and photodetectors And integrated chips have emerged and matured.

Since the silicon material is an indirect semiconductor material, the material itself is difficult to be fabricated into a laser component. Therefore, an external III-IV laser is generally used as a light source, and the input of the light source is realized by epitaxial growth or coupling alignment. The method of epitaxially growing a III-IV laser on a silicon-based material is highly demanding and difficult to implement. Only a few manufacturers in the world have relevant reports, and no fully mature products are sold in the market. Therefore, most manufacturers use a complete laser chip and silicon photonic chip coupling to achieve the coupling of the laser source.

There are two main structures for coupling the silicon photonic device to the light source, one is an end face coupling structure, and the other is a grating coupler structure. The grating coupler is one of the main light source input methods of the silicon optical chip because it is relatively easy to implement in the process. For the light source input of such a grating coupler, Luxtera is involved in the US patent application publication US201414324544A1, and the entire laser light source part is composed of a plurality of discrete parts such as a laser chip, a lens, an isolator, a mirror, and the like. The number of components and the complicated structure make the production efficiency of the assembly process difficult to improve.

Summary of the invention

The technical problem to be solved by the present invention is to provide a laser structure with simple structure and a coupling alignment method thereof, and to provide a fast coupling alignment method of the grating coupler of the laser and the silicon photonic integrated chip.

The technical solution adopted by the invention is:

A laser element comprising a substrate having an active region for generating and outputting laser light and an electrode for supplying power to the laser chip, the substrate having one end open at least partially accommodating the laser chip Etching the groove, the other end of the substrate is provided with a light-emitting surface, the substrate is further provided with an optical waveguide extending between the etching groove and the light-emitting surface; the laser chip is placed on the substrate In the etched trench, an active region of the laser chip is aligned with an optical waveguide on the substrate.

The surface of the laser chip includes an alignment mark on which an alignment mark is disposed, an alignment mark on the laser chip, and an alignment mark on the substrate for determining the laser chip and the The relative positions between the substrates are to facilitate alignment of the two.

a height positioning block is disposed in the etched groove of the substrate, a vertical height difference of the height positioning block from the center of the optical waveguide and a vertical height of a surface of the laser chip from a center of the active area of the laser chip The difference is consistent so that the active area of the laser chip is aligned with the center of the optical waveguide after the laser chip is placed in place in the etched trench of the substrate.

The light-emitting surface of the substrate is a reflective surface, and the reflective surface is at an angle of 30 to 50 degrees with the surface of the substrate to change the light-emitting direction of the optical waveguide in a total reflection manner.

The substrate is further provided with an electrode, and the electrode on the substrate is electrically connected to an electrode that supplies power to the laser chip.

A method of coupling a laser chip and a substrate of the laser element, comprising the steps of: Aligning marks are respectively disposed on the surface of the laser chip and the substrate, and determining that when the active area of the laser chip is aligned with the optical waveguide of the substrate, the alignment mark on the surface of the laser chip and the substrate Aligning the relative positional relationship of the marks as a predetermined relative positional relationship; respectively identifying an alignment mark of the surface of the laser chip and an alignment mark on the substrate in an image recognition manner, thereby accurately determining the laser chip and the substrate a relative position, precisely adjusting a position of the laser chip such that an alignment mark of the laser chip and an alignment mark on the substrate satisfy a predetermined mutual positional relationship, thereby locating the laser chip in a horizontal direction of the substrate The optical waveguide on the substrate is aligned; the surface of the laser chip is completely in contact with the height positioning block on the substrate by pressure control of the laser chip, so that the laser chip is vertically oriented The optical waveguides of the substrate are accurately aligned.

A high precision flip chip bonding apparatus is used to image identify the alignment marks on the surface of the laser chip and the substrate, precisely adjust the position of the laser chip, and pressure control the laser chip.

A laser assembly comprising: a silicon photonic integrated chip and a laser element according to claims 1-5, an electrode on a substrate of the laser element electrically connecting an electrode on the silicon photonic integrated chip and the laser element An electrode of the laser chip, the local area where the reflective surface optical waveguide of the substrate is located is aligned with the grating coupler on the silicon photonic integrated chip.

An alignment accuracy error of the reflective region of the optical waveguide and the grating coupler is less than or equal to 5 micrometers, and a pair between an electrode on the substrate and an electrode on the silicon photonic integrated chip and an electrode of the laser chip The quasi-error is less than or equal to 20 microns.

A method for fabricating a laser assembly, comprising the steps of: aligning an electrode on a substrate of the laser element with an electrode on the silicon photonic integrated chip; and causing a reflective surface of the substrate of the laser element to be optically waveguided The local area is aligned with the grating coupler on the silicon photonic integrated chip; An electro-glue realizes electrical connection between an electrode on a substrate of the laser element and an electrode on the silicon photonic integrated chip; a local area where the reflective surface of the substrate of the laser element is located and the silicon photonic integrated chip A matching glue is placed between the grating couplers.

The advantages of the invention are:

1. The laser as a whole comprises only the substrate and the laser chip integrated with the optical waveguide and the electrode, and has no other discrete components, and has simple structure design and low cost.

2. In the packaging process, the high-precision flip-chip bonding alignment process is used to realize the coupling of the laser optical path; the coupling of the laser and the silicon photonic integrated chip grating coupler can be realized by the conventional patch technology. The entire packaging process is passive alignment technology, high coupling efficiency, suitable for high efficiency and mass production.

DRAWINGS

1 is a schematic structural view of a laser provided by the present invention;

2 is a schematic cross-sectional view showing the structure of a laser provided by the present invention;

3 is a schematic structural view of a substrate of a laser provided by the present invention;

4 is a schematic diagram of a coupling structure of a laser and a silicon photonic integrated chip provided by the present invention;

FIG. 5 is a schematic cross-sectional view showing a coupling of a laser and a silicon photonic integrated chip provided by the present invention; FIG.

6 is a schematic structural view of a silicon photonic integrated chip provided by the present invention;

Figure 7 is a schematic view showing the optical path of the laser provided by the present invention;

Marked in the figure:

1: substrate 2: laser chip

3: gold wire bonding wire 4: silicon photonic integrated chip

5: Gold Tin Solder 6: Conductive adhesive

7: Matching glue 11: Optical waveguide

12, 13: Electrode 14: etching groove

15: alignment mark 16: height positioning block

17: Coupling surface 18: Reflecting surface

21: laser chip active area 41: grating coupler

42,43: Electrode on silicon photonic chip

detailed description

The present invention will be further described in detail below in conjunction with the drawings and embodiments.

The structure of the laser provided by the present invention is as shown in FIG. 1-3, which includes two parts of the substrate 1 and the laser chip 2; wherein the substrate 1 includes the optical waveguide 11, the electrode 12 and the electrode 13, the etching groove 14, and the alignment The mark 15, the height positioning block 16 (not shown in FIG. 1), the coupling surface 17, and the reflecting surface 18, one end of the substrate 1 is provided with an etching groove 14 at least partially accommodating the laser chip 2, and the other end of the substrate 1 is provided with a reflection The surface 18 (ie, the light-emitting surface) extends between the etching groove 14 and the reflecting surface 18, and the reflecting surface 18 is used to change the light-emitting direction of the optical waveguide 11 in a total reflection manner; the laser chip 2 has a laser beam generated and outputted. The active region 21 and the electrodes (anode and cathode) that power the laser chip 2, the surface of the laser chip 2 contains alignment marks. The laser chip 2 is placed in an etched trench 14 of the substrate 1 with the active region 21 of the laser chip aligned with the optical waveguide 11 on the substrate.

The structural cross section of the laser provided by the invention is as shown in FIG. 2. In order to achieve precise alignment of the active region of the laser chip 2 and the optical waveguide 11 on the substrate 1, the alignment mark is designed in the etching groove 14 on the substrate 1. 15 and a height positioning block 16, wherein the vertical height difference of the height positioning block 16 from the center of the optical waveguide 11 coincides with the vertical height difference of the surface of the laser chip 2 from the center of the active area 21 of the laser chip 2, so that the laser chip 2 is on the substrate 1 After the etched trench 14 is placed in place, the laser chip 2 is active The region 21 is aligned with the center of the optical waveguide 11. The alignment mark 15 may be disposed on the substrate 1 at any position that facilitates determining the relative positional relationship between the substrate 1 and the laser chip 2.

The present invention also provides a method of aligning the laser chip 2 with the rapid coupling of the optical waveguide 11 of the substrate 1. By using a high-precision flip-chip bonding apparatus, the alignment of the laser chip 2 can be separately identified by automatic or manual image recognition. Marking and alignment marks 15 on the substrate 1 to accurately determine the relative positional relationship between the laser chip 2 and the substrate 1, precisely adjusting the position of the laser chip 2 by a high-precision flip-chip bonding apparatus, and aligning the alignment of the laser chip 2 and The alignment marks 15 on the substrate 1 satisfy a predetermined mutual positional relationship, thereby aligning the laser chip 2 with the optical waveguide 11 on the substrate 1 in the horizontal direction of the substrate 1; the pressure supplied to the laser chip 2 by the flip-chip bonding apparatus Control is such that the surface of the laser chip 2 is in full contact with the height positioning block 16 on the substrate 1, so that the laser chip 2 is accurately aligned with the optical waveguide 11 of the substrate 1 in the vertical direction, as shown in FIG. Here, the precision alignment requires that the alignment precision error of the laser chip 2 and the optical waveguide 11 is 1 μm or less.

The left end of the electrode 13 on the substrate 1 is located on the bottom surface of the etching groove 14 and is in contact with the electrode of the upper surface of the laser chip 2 (ie, the surface falling into the etching groove 14 and facing the substrate 1). Gold-tin solder 5 is required to be plated, as shown in Figure 3. In the flip-chip bonding process, the gold-tin solder is heated and melted, and the electrodes 13 on the substrate 1 and the electrodes on the upper surface of the laser chip 2 are electrically connected to each other to achieve electrical connection, as shown in FIG. The electrodes on the back side of the laser chip 2 (ie, the lower surface, facing away from the substrate 1) can be electrically connected by means of gold wire bonding, that is, the back electrode of the laser chip 2 and the electrode 12 of the substrate 1 are realized by the gold wire bonding wire 3. Electrical connection, as shown in Figure 1. When both the cathode and the anode of the laser chip 2 are on the upper surface of the laser chip 2, the

electrodes

12, 13 on the substrate 1 are located on the bottom surface of the etching groove 14, respectively, and the cathode and the anode of the laser chip 2 are connected by gold tin solder 5.

The coupling surface 17 of the optical waveguide 11 on the substrate 1 on the side wall of the etching groove 14 is designed to be at an angle of 6 to 10 degrees with the laser emitting end surface of the active region 21 of the laser chip 2, and the purpose thereof is to reduce the laser. The reflection of light between the chip 2 and the coupling end face 17 of the optical waveguide 11 reduces the effect of the reflected light on the power and mode stability of the laser chip 2.

The right end (exit end face) of the substrate 1 is polished to an angle of 30 to 50 degrees with respect to the surface of the substrate 1 (ie, the horizontal plane) to form a reflecting surface for emitting light, the purpose of which is to transmit the laser light through the optical waveguide 11 to the right end of the substrate 1. After the (ejecting end face), total reflection occurs, and is output in a direction perpendicular to the surface of the substrate 1 (i.e., perpendicular to the horizontal plane).

The relative positions of the

electrodes

12, 13 and the waveguide reflection regions on the substrate 1 coincide with the relative positions of the

electrodes

42, 43 and the grating coupler 41 on the silicon photonic integrated chip 4.

Figure 4-5 shows the coupling structure of the laser and silicon photonic integrated chip. The other portion of the laser substrate 1 is bonded to the upper surface of the silicon photonic integrated chip 4 except for the left end region where the laser chip 2 is located. The upper surface of the silicon photonic integrated chip 4 is designed with a grating coupler 41 and

electrodes

42, 43 as shown in FIG.

By the patch technology, the right end portion of the electrode 13 on the laser substrate 1 is aligned with the upper electrode 43 of the silicon photonic integrated chip 4, and the right end portion of the electrode 12 on the laser substrate 1 is aligned with the upper electrode 42 of the silicon photonic integrated chip 4, the laser substrate The local area where the reflective surface waveguide is located is aligned with the grating coupler 41 on the silicon photonic integrated chip 4. Electrical connection is made between the

electrodes

12, 13 on the laser substrate 1 and the silicon photonic integrated chip 4

electrodes

42, 43 using a conductive paste 6, and the matching adhesive 7 is used between the laser substrate 1 and the grating coupler 41 on the silicon photonic integrated chip 4. Reflection of the grating surface. As shown in FIG. 5, the alignment precision of the reflection region of the optical waveguide 11 and the grating coupler 7 is required to be 5 μm or less, and the alignment error between the electrodes is 20 μm or less.

The conductive adhesive 6 and the matching adhesive 7 are all heat-curing adhesives, and the curing temperature is 150-200 degrees, which is lower than the soldering temperature of the gold-tin solder 250-350 degrees, and does not affect the reliability of the laser chip bonding. It does not affect the performance of other regions on the silicon photonic integrated chip 4.

When the laser module constructed in the above manner works, the

electrodes

42 and 43 of the silicon photonic integrated chip 4 are operated. The output driving current is loaded to the cathode and the anode of the laser chip 2 through the conductive paste 6 and the

electrodes

12, 13 on the laser substrate 1, so that the laser chip 2 operates to emit light, and the light emitted from the active region 21 of the laser chip 2 enters the substrate 1. The optical waveguide 11 is transmitted to the right end reflection surface 18 of the substrate 1 and then reflected and outputted from the lower surface of the substrate 1, and finally enters the grating coupler 41 on the silicon photonic integrated chip 4 through the matching glue 7, thereby realizing the light from the laser. The chip 2 outputs the entire process to the input of the silicon photonic integrated chip 4, as shown in FIG.

While the present invention has been described in detail and shown by reference to the specific embodiments of the present invention, Various changes have been made to the details of the fabrication of the laser structure and packaging method. These changes are intended to fall within the scope of protection as claimed in the appended claims.

Claims

A laser element comprising a substrate and a laser chip, the laser chip having an active region for generating and outputting a laser, and an electrode for supplying power to the laser chip, wherein at least one portion of the substrate is open at least An etched groove of the laser chip, the other end of the substrate is provided with a light-emitting surface, and the substrate is further provided with an optical waveguide extending between the etched groove and the light-emitting surface; the laser chip is placed at In the etched trench of the substrate, an active region of the laser chip is aligned with an optical waveguide on the substrate.
A laser element according to claim 1 wherein: the surface of said laser chip comprises alignment marks, said substrate is provided with alignment marks, alignment marks on said laser chip and said Alignment marks on the substrate are used to determine the relative position between the laser chip and the substrate to facilitate alignment of the two.
A laser element according to any one of claims 1 to 2, wherein a height positioning block is disposed in the etching groove of the substrate, and the height of the height positioning block is from the center of the optical waveguide. The difference from the surface of the laser chip is perpendicular to the vertical height difference of the center of the active area of the laser chip, so that the laser chip is placed in position in the etched groove of the substrate, the laser chip The active region is aligned with the center of the optical waveguide.
A laser element according to any one of claims 1 to 3, wherein the light-emitting surface of the substrate is a reflective surface, and the reflective surface is at an angle of 30 to 50 degrees with respect to the surface of the substrate, thereby The total reflection mode changes the light outgoing direction of the optical waveguide.
A laser element according to any one of claims 1 to 4, wherein the substrate is further provided with an electrode, and an electrode on the substrate is electrically connected to an electrode for supplying power to the laser chip.
A method for coupling a laser chip and a substrate of a laser element according to claims 3-5, comprising the steps of:

Providing an alignment mark on the surface of the laser chip and the substrate, respectively, and determining an alignment mark of the surface of the laser chip when an active area of the laser chip is aligned with an optical waveguide of the substrate The relative positional relationship of the alignment marks on the substrate as a predetermined relative positional relationship;

Identifying an alignment mark on a surface of the laser chip and an alignment mark on the substrate in an image recognition manner, thereby accurately determining a relative position of the laser chip and the substrate, and accurately adjusting a position of the laser chip The alignment mark of the laser chip and the alignment mark on the substrate satisfy a predetermined mutual positional relationship, thereby aligning the laser chip with the optical waveguide on the substrate in a horizontal direction of the substrate;

The surface of the laser chip is brought into full contact with the height locating block on the substrate by pressure control of the laser chip such that the laser chip is accurately aligned with the optical waveguide of the substrate in a vertical direction.
The method of claim 6 wherein the high precision flip chip bonding apparatus is used to image identify the alignment marks on the surface of the laser chip and the substrate, to precisely adjust the position of the laser chip, and to give The laser chip is used for pressure control.
A laser assembly, comprising: a silicon photonic integrated chip and a laser element according to claims 1-5, an electrode on a substrate of the laser element electrically connecting an electrode on the silicon photonic integrated chip and the The electrode of the laser chip of the laser element, the local area where the reflective surface optical waveguide of the substrate is located is aligned with the grating coupler on the silicon photonic integrated chip.
A laser assembly according to claim 8, comprising: an alignment accuracy error of said reflective region of said optical waveguide with said grating coupler of less than or equal to 5 micrometers, said electrode on said substrate and said silicon The alignment error between the electrode on the photonic integrated chip and the electrode of the laser chip is less than or equal to 20 microns.
A method for fabricating a laser assembly according to claim 8 or 9, characterized in that Including the steps:

Aligning an electrode on a substrate of the laser element with an electrode on the silicon photonic integrated chip;

Aligning a local area where the reflective surface optical waveguide of the substrate of the laser element is located with a grating coupler on the silicon photonic integrated chip;

Electrically connecting the electrodes on the substrate of the laser element to the electrodes on the silicon photonic integrated chip using a conductive paste;

A matching glue is disposed between a local area where the reflective surface optical waveguide of the substrate of the laser element is located and a grating coupler on the silicon photonic integrated chip.