KR19980050449A - Optical Switches-Fiber Optic Coupling Devices - Google Patents

Abstract

An optical coupling device using a silicon substrate for passively coupling an optical switch device to an optical fiber. In general, optical coupling devices require very precise mechanical alignment of microns between optical elements and instantaneous and robust bonding methods such as laser welding. This conventional optical coupling device is packaged in such a way that each optical element is first packaged into a very complicated mechanical structure and then attached to each other in a separate case, so that the number of parts is complicated and the alignment work is complicated, so the manufacturing cost is very high. It has the disadvantage of being expensive. On the other hand, if the semiconductor process technology used in the manufacture of semiconductor devices is used for the mechanical processing of silicon substrates, it is possible to manufacture highly precise mechanical structures of less than microns that cannot be obtained by mechanical processing, and it is possible to assemble various optical devices and components. What is intended to be used as a substrate for the silicon optical bench (silicon optical bench) technology. The present invention relates to an optical coupling device capable of passively optically coupling an optical switch device and an optical fiber by using a silicon substrate processed by a semiconductor manufacturing process. In order to achieve the above object, flip chip bonding of an optical switch device to a silicon substrate is achieved. And forming a v-groove for alignment and fixation of the solder bump and the optical fiber, and fixing the optical switch device to the substrate by flip-chip bonding the optical switch device on the solder bump, while the optical switch device automatically aligns with the v-groove. Reduce the number of components and assemble by automatically making optical coupling between the optical switch device and the optical fiber by aligning and fixing the optical fiber in the V-groove, and forming an electrical contact that is electrically connectable to the optical switch device. Minimize the size of the optical coupling device by achieving process simplification It intended to make the manufacturing costs low.

Description

Optical Switches-Fiber Optic Coupling Devices

The present invention relates to an optical coupling device for aligning and optically coupling an optical switch device and an optical fiber. In particular, the optical switch device of the present invention is the most basic optical component necessary for the implementation of the optical exchange system is composed of an even number of channels, and the number of optical fibers connected to the input and output side of each channel is connected to the optical signal input to a specific channel The present invention relates to an optical coupling device that switches an input signal to a specific channel on an output side through control of an optical switch device.

In general, the most important problem in the implementation of the optical switch device is to achieve an efficient optical coupling between the optical switch device and the optical fiber while at the same time achieving the miniaturization of the device and the reduction in manufacturing cost.

The optical waveguide of an optical switch device using a semiconductor currently being developed is about 1 to 2 microns, whereas the optical waveguide of the optical fiber is about 10 microns, and there are many inconsistencies in mode sizes between the two devices. This mismatch in mode size is a fundamental cause of lowering the optical coupling efficiency. In order to overcome this problem, the conventional technique uses a tapered fiber with a sharply processed fiber end to increase optical coupling efficiency or a lens between the optical fiber and the optical switch device to increase optical coupling efficiency. I use it. However, in this conventional technique, the distance between the optical switch element and the optical fiber end must be aligned very precisely at a distance of 10 to 20 microns, and the horizontal alignment between the optical switch device and the optical fiber is much more sensitive than this, so that an error of 1 to 2 microns is achieved. Even more than half of the optical coupling efficiency can be lost. Therefore, this conventional technology is a great reason that the time and cost of assembling the optical coupling device is the biggest reason that the optical system does not have an economic advantage over the system implemented by the conventional electronic device. The difficulty of the assembly process and the increase in manufacturing cost are even more severe as the number of channel of the switch element increases and the number of optical fiber pairs increases.

The present invention simplifies the assembly of the optical coupling device by miniaturizing the size of the optical switch-fiber optical coupling device and enabling the optical coupling of the optical switch device and the optical fiber by the manual alignment method, in particular, increasing the number of channels to two or more. The purpose is to provide an optical coupling device that can be easily assembled even if.

In addition, an object of the present invention is to provide an optical coupling device that can reduce the cost by reducing the number of components used for optical coupling of the optical switch device and the optical fiber.

1 is a bird's eye view of an optical switch-optical fiber optical coupling device of the present invention,

2a is a cross-sectional view of an optical switch-optical fiber optical coupling device according to the present invention;

2B is an enlarged cross-sectional view of a portion of FIG. 2A;

3 is a plan view showing the configuration of a silicon substrate according to the present invention;

4 is a bird's eye view showing a method of attaching an optical switch device, an optical fiber array, and an optical fiber cap onto a silicon substrate of the present invention;

Figure 5 is a bird's eye view showing the structure of the optical fiber v groove as another embodiment of the present invention.

* Explanation of symbols for the main parts of the drawings

1,23, 57: silicon substrate 2,45: optical fiber array

3,42: optical switch device 4,40: optical fiber lid

5,25: wire bonding pads 6,29, 44: v-groove

7,28, 46: pedestal 8,22,24,32,48,49: solder bumps

9,11: surface of silicon substrate 10: surface of optical switch device

12: enlarged portion 21: optical switch device attachment position

26, 31: metal pads 27, 47: substrate alignment mark

41: element alignment mark 43: optical waveguide of the optical switch device

51: V groove of the optical fiber lid 52: Element metal pad

53: element contact metal pad 56: wide v-groove

In order to achieve the above object, the optical switch-optical fiber optical coupling device of the present invention has an alignment mark and solder bumps for alignment and fixing of an optical switch device with a v-groove for alignment of optical fibers, and a pedestal for height adjustment of the optical switch device. After forming on the silicon substrate by the semiconductor manufacturing process to be aligned with each other, the optical fiber array and the optical switch device on the silicon substrate is optically coupled in a passive alignment method. Therefore, the optical coupling device of the present invention comprises a substrate having at least one V groove; An optical fiber array seated in the V groove and fixed on the substrate; And an optical switch formed on the substrate and optically coupled to the optical fiber array and electrically connected to the metal pad.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention;

First, Figure 1 is a bird's eye view of the optical switch-optical fiber optical coupling device of the present invention, 1 is a silicon substrate, 2 is an optical fiber array, 3 is an optical switch device, 4 is an optical fiber cap, 5 is a wire bonding pad.

The optical switch-optical fiber optical coupling device of the present invention is an optical fiber lid for fixing a silicon substrate 1 having a V (V) groove and an optical fiber array 2 and an optical fiber array 2 aligned in the grooves on the substrate 1. (4) and the optical bonding device 3 and the wire bonding pad 5 for electrical connection with the outside.

This will be described in detail with reference to FIGS. 2A and 2B and FIGS. 3 to 5.

Figure 2a is a cross-sectional view of an optical switch-optical fiber optical coupling device according to the present invention, Figure 2b is a cross-sectional view showing an enlarged portion of Figure 2a, Figure 3 is a plan view showing the configuration of a silicon substrate according to the present invention, Figure 4 FIG. 5 is a bird's eye view showing a method of attaching an optical switch device, an optical fiber array, and an optical fiber cap on a silicon substrate of the present invention, and FIG. 5 is a bird's eye view showing the structure of an optical fiber v-home as another embodiment of the present invention.

The optical switch-optical fiber optical coupling device of the present invention comprises an optical fiber lid 4 and an optical fiber lid 2 for fixing an optical fiber array 2 and an optical fiber array 2 aligned with a silicon substrate 1 and a v-groove 6 of the substrate. It consists of an optical switch device 3 attached to the solder bump 8 and the pedestal 7 on (1) and a wire bonding pad 5 for electrical connection to the optical switch device 3. The silicon substrate 1 is an optical bench for aligning and fixing an optical switch device and an optical fiber, and the V-groove 6 embeds the optical fiber array 2 under the silicon substrate 1 so as to bury the optical fiber array. It serves to align (2) in the horizontal and vertical directions (x, z and y directions (directions perpendicular to the surface of the substrate)) and to fix the optical fiber array 2 to the substrate 1.

First, a method of attaching the optical switch device 3 in alignment with the optical fiber array 2 attached to the v-groove 6 will be described with reference to FIGS. 1 to 4. The flip-chip bonding method is a method of attaching the front surface of the semiconductor device (the surface where the optical waveguide is formed in the case of the optical switch device) to face the substrate surface. A technique of forming a solder bump made of a low melting point solder material on one surface or one surface thereof, placing a semiconductor device thereon, and heating the same to bond the semiconductor device and the substrate by adhesion between the molten solder material and the metal. In the present invention, the solder bumps 8 are formed on the surface of the silicon substrate 1 as shown in FIGS. 2A and 2B, and the optical switch device 3 is bonded thereon. At this time, the pedestal 7 is used to adjust the height of the optical switch device 3 from the surface 9 of the silicon substrate 1, which is made by plating or depositing a material such as gold having a higher melting point than the solder material. The height is made such that the height of the optical fiber core (or optical waveguide) attached to the v-groove 6 is equal to the height of the optical waveguide of the optical switch device 3 attached to the pedestal 7.

Next, the principle of the alignment of the optical fiber by the v-groove 6 will be described in detail. The v-groove 6 is formed by anisotropic etching of silicon single crystal. Anisotropic etching is an etching with a large difference in the etch rate according to the crystal direction of the single crystal.In the present invention, anisotropic etching is performed in which the etching rate of the silicon {100} plane is several ten times larger than that of the {111} crystal plane. Anisotropic etching of a rectangular pattern arranged parallel to the 110 crystal direction on the surface of the silicon wafer finally yields an etching pattern in the form of a v-groove. The v-groove formed in this way has a great advantage that its width and depth can be precisely controlled with an error of less than 1 micron, which is the basic principle of automatically aligning the optical fiber array to the optical switch device in the present invention. Therefore, in the present invention, the position and width of the V-groove etching pattern are designed in advance in connection with the position and width of the flip chip bonded optical switch device and are parallel to the 110 crystal direction of the silicon wafer using photolithography technology of the semiconductor manufacturing process. The horizontal position (x and z direction) of the optical fiber and the height of the optical fiber core are formed by forming a V-groove etching pattern and then etching it with an anisotropic etching solution such as KOH to form the V-groove and embedding the optical fiber thereon. (y direction) is in the preplanned position.

Next, the silicon substrate 23 according to the present invention will be described with reference to FIGS. 3 and 4 by the V-groove 29, the solder bumps 22, 24, and 32, the substrate alignment mark 27, the pedestal 28, and the metal pad. 26 and 31, wire bonding pads 25, and the like, which will be described in more detail with reference to the following figures, the v-grooves 29 are formed by the number of channels on both sides of the attachment position 21 of the optical switch device. The distance between the centers of the v-grooves 29 is made equal to the distance of the optical waveguide 43 of the optical switch device. In addition, since the end of the v-groove 29 has an inclined side surface, the end of the optical fiber cannot reach the end of the v-groove 29. Therefore, the optical switch device 42 is partially overlapped with the v-groove.

Solder bumps 22, 24, and 32 are used to flip chip bond the optical switch device 42 and the optical fiber cap 40 to the silicon substrate 23. Among them, the solder bumps 32 and the like between the two pedestals 28 are for the electrical connection between the optical switch device 42 and the substrate 23. In other words, the solder bumps 32 are bonded to the metal pads 53 formed on the surface of the optical switch device 42 to be mechanically and electrically connected to the solder bumps 24 through the metal pads 31. It is again connected to the wire bonding pad 25 located outside the attachment position 21 of the optical switch device to form an electrical connection from the optical switch device 42. The silicon substrate 23 then has a pedestal 28 and a substrate alignment mark 27 to enable the optical switch device 42 to be aligned and attached to the silicon substrate 23. First, the substrate alignment mark 27 mutually crosses the optical waveguide 43 on the front surface of the optical switch and the V groove 29 on the silicon substrate 23 when the optical switch device 42 is flip-chip bonded to the silicon substrate 23. For this purpose, an element alignment mark 41 corresponding to the substrate is present on the surface of the optical switch device. The pedestal 28 is then used to align the height of the optical waveguide 43 of the optical switch device attached to the substrate surface with the height of the core of the optical fiber 2 attached to the v-groove as described above. Solder bumps 22 located around the V-groove 29 are for attaching the optical fiber 45 to the V-groove and attaching the optical fiber cap 40 to the chip groove by flip chip bonding. The optical fiber 45 may be attached by application of epoxy or the like without a lid. However, in this case, it is preferable to use the optical fiber cap 40 to prevent the change of the position of the optical fiber during the hardening process of the epoxy. The optical fiber cap 40 may be attached by epoxy or the like without flip chip bonding. In this case, solder bumps 22 for flip chip bonding of the optical fiber cap 40 are not necessary.

Next, a method of assembling the optical switch device 42 and the optical fiber array 45 to the silicon substrate 23 configured as described above will be described. The optical switch device 42 is formed on the silicon substrate 50 using flip chip bonding equipment. For this purpose, the optical switch device 42 is soldered in a state where the substrate alignment mark 47 formed on the substrate 50 and the element alignment mark 41 formed on the surface of the optical switch device 42 are aligned with each other. The element metal pad 52 and the element contact metal pad 53 of the optical switch device 42 by heating the substrate while being placed on the bump 48 and brought into close contact with the pedestal 46 with the optical switch device 42 at an appropriate pressure. ) Is bonded to the solder bumps 48 on the substrate 50.

Next, the optical fiber array 45 is fixed to the V-groove 44 on the substrate to which the optical switch device 42 is attached. Since the optical switch device always uses two or more strands of optical fiber arrays, the optical fiber is made into an array in advance. It can also be used. In this case, since the distance between the optical fibers is most easily equal to the outer diameter of the optical fiber, it is preferable that the interval between the V-grooves 44 is the same. A feature of the present invention is that it is very easy to align the optical fiber array 45 to the v-groove 44. That is, the optical fiber array 45 is properly aligned with the v-groove 44 on one side of the optical switch device 42, and then the end of the optical fiber is brought into contact with one side wall of the optical switch device 3, 42 or spaced at an appropriate distance. Next, the v-groove 51 of the cap 40 for fixing the optical fiber is aligned and pressed so that the optical fiber array 45 is automatically brought into close contact with the v-groove 44 to be aligned with the v-groove 44. In the same manner, the optical fiber array 45 is attached to the other side of the optical switch device, the optical fiber cap 40 is attached, and then the optical fiber cap 40 is fixed. The bonding may be performed by heating. Alternatively, when bonding with epoxy, an appropriate amount of epoxy is applied to the place where the lid on the substrate is placed before the optical fiber lid 40 is placed, and then appropriately heated and bonded according to the type of epoxy.

Next, FIG. 5 is another type of optical fiber alignment v-groove usable in the present invention, the width of which is wide at the end of the silicon substrate 57 for the purpose of preventing cutting and reducing stress of the optical fiber attached to the v-groove. It is characterized by the use of a wide v groove 56.

Accordingly, the present invention is not only capable of automatically optically coupling the optical switch device and the optical fiber array by flip-chip bonding the optical switch device on a silicon substrate and aligning the optical fiber array with the v-groove, but also the components necessary for manufacturing the optical coupling device. The small number and the simple assembly process can reduce the size of the optical switch-optical fiber optical coupling device and reduce the manufacturing cost.

As described above, according to the optical switch-optical fiber coupling device of the present invention, it is possible to drastically reduce the volume of the optical switch-optical fiber optical coupling device, simplify the assembly process and bring about a reduction in the number of parts. Optical switch-optic fiber optical coupling device is very effective in greatly reducing the price.

Claims (9)

A substrate on which at least one V groove is formed; An optical fiber array seated in the V groove and fixed on the substrate; And an optical switch formed on the substrate, the optical switch being optically coupled to the optical fiber array and electrically connected to the metal pad. The optical coupling device according to claim 1, wherein said substrate is made of a silicon wafer. The optical coupling device according to claim 1, wherein the optical coupling device optically couples the optical fiber and the optical switch to the device. The optical coupling device of claim 1, wherein the optical coupling device further comprises a lid attached to fix and protect the optical fiber seated on the substrate. The optical coupling device according to claim 1 or 2, wherein the substrate further comprises an alignment mark (27) capable of bonding at the correct position of the optical switch device. The optical coupling device according to claim 1, wherein the optical defect device further comprises a pedestal for adjusting a height of the optical switch bonded. The optical switch-optical fiber optical coupling device according to claim 2, wherein the crystal direction of the silicon substrate 1 is (100). The optical switch-optical fiber optical coupling device according to claim 1, wherein the spacing of the V grooves is equal to that of two directly bonded fiber optic cores. The optical coupling device of claim 1, wherein the optical coupling device further comprises a groove formed at an end of the substrate and extending to the V groove and having a width wider than the width of the V groove on a line.