KR100211043B1 - Optical coupler of optical element and optical fiber - Google Patents

Abstract

The present invention, in the optical coupling device between the optical element and the optical fiber using flip chip bonding and silicon V-groove, solve the reduction of the optical coupling efficiency due to the alignment error occurring in the conventional manual alignment method In order to achieve the best optical coupling efficiency, a wide V-groove in which the optical fiber is located and two optical fiber fixed shafts within the V-groove are pressed with a separate V-groove-depleted silicon cover to press the optical fiber at a predetermined position between the two fixed shafts. Induces slight bending, ie micro-bending, in the optical fiber and adjusts the position of the end of the optical fiber according to the position of the silicon cover to fix the optical fiber at the position where the optical coupling efficiency between the optical element and the optical fiber is maximized. It provides a photocoupling device.

Description

Optical coupling device between fan element and optical fiber

The present invention relates to an optical coupling device between an optical device and an optical fiber using flip chip bonding and silicon V-groove.

In general, in optical coupling of an optical device such as a semiconductor laser and an optical fiber, the optical waveguide of the optical device must be aligned with the core of the optical fiber precisely in order to efficiently transmit the light of the optical device to the optical fiber. In order to achieve this purpose, two optical coupling hinders are mainly used: active alignment using thiocan and laser welding, and passive alignment using silicon V-groove and flip chip bonding.

The passive alignment method using flip chip bonding and silicon V-groove is known as a promising technology that can reduce the size of the optical package and lower the manufacturing cost compared to the active alignment method using thiocan and laser welding.

The conventional optical coupling device will be described with reference to FIGS. 1 (a) to 1 (c). FIG. 1 (a) shows a semiconductor laser and an optical fiber by using a V-grooveed silicon substrate as a conventional technique. A plan view of the optical coupling device for passive coupling of FIG. 1 (b) is a cross-sectional view taken along line AA ′ of FIG. 1 (a), and FIG. 1 (c) is a side view taken along line BB ′ of FIG. 1 (b).

As shown in the drawing, the conventional optical coupling device forms a V-groove 2 by anisotropic etching on the silicon substrate 1 to fix and align the optical fiber 6 therein, and on the same silicon substrate. Self-position resilience of flip chip bonding by flip chip bonding optical devices such as semiconductor lasers 3 by forming flip chip bonding pads 5 at predetermined positions associated with V-grooves and forming solder bumps thereon This is to automatically align the optical fiber and optical elements.

Unlike conventional wire bonding or soldering method, frill chip bonding forms a metal pad 5 on the substrate and the surface of the device to be bonded, and applies solder bumps on one or both metal pads of the substrate or the device to be bonded. Forming the substrate 1 and the device 3 to be bonded to each other in such a manner that the bonding pads 5 face each other so that the solder material is heated and melted so that the substrate and the device are mechanically bonded to each other. to be.

In flip chip bonding, even if the center positions of two solder bumps of the first closely contacted substrate and the device are shifted from each other within a certain range, the positional resilience of moving the device so that the center positions of the two metal pads are matched by the surface tension of the molten solder. This happens.

Therefore, if the V-groove and the solder bumps are formed at the pre-designed position correctly, the optical element 3 and the optical fiber (automatic) may be automatically formed by placing the optical element chip 3 on the silicon substrate 1 with proper precision and flip-chip bonding. 6) can be aligned.

The alignment error may also occur due to many factors in the automatic alignment of the optical soba 3 and the optical fiber 6 using the flip chip bonding and the silicon V-groove.

First, when the V-groove 2 is formed in the silicon substrate 1, the width and depth of the V-groove 2 are shifted from the designed value. This error mainly occurs because the V-groove 2 pattern is out of alignment with the crystal direction of silicon or the V-groove 2 is excessively etched.

The second factor arises from the photolithography process for metal pad 5 and solder bump formation. This is caused by the misalignment of the alignment keys on the photomask and the silicon substrate horizontally and completely, with an error margin of +/- 1.0. From Can occur in a wide range. In particular, this alignment error becomes larger when there are patterns with large vertical differences such as V-grooves 2, solder bumps, stand-offs, etc. on the silicon substrate 1.

The third cause of the alignment error is due to the incomplete position resilience of flip chip bonding. Generally, the size of an optical device chip such as a semiconductor laser 3 varies from one hundred to one. Only a dozen diameters It is difficult to form a lot of phosphorus solder bumps.

Therefore, due to incomplete position resilience resulting from the limited number of solder bumps, A degree of alignment error occurs.

In addition, the misalignment factor may include a deviation in the diameter of the optical fiber 6 or a deviation from the origin of the optical fiber core 7.

Therefore, in the conventional manual alignment technique using flip chip bonding, it is extremely difficult to recover the alignment error between the V-groove pattern and the solder bump for flip chip bonding during the flip chip bonding process of the optical device. Despite the inherent benefits of the system, it is actually a big factor in that it cannot have economic advantages over active alignment.

The present invention takes advantage of the passive alignment method using V-groove and flip chip bonding, and actively aligns the optical fiber within the alignment error range generated during flip chip bonding, thereby reducing the problem of optical coupling efficiency due to the alignment error. It is an object of the present invention to provide an optical coupling device that can be easily solved.

Figure 1 (a) is a plan view of an optical coupling device for passive coupling between a semiconductor laser and an optical fiber using a V-grooveed silicon substrate as a prior art.

Fig. 1 (b) is a cross-sectional view taken along the line A-A 'in Fig. 1 (a).

FIG. 1 (c) is a side view taken along the line B-B 'of FIG. 1 (b).

2 (a) shows the micro-bending of the optical fiber by the two optical fiber fixing shaft and the V-groove in the silicon groove of the silicon substrate according to the present invention and can adjust the position of the optical fiber end according to the position of the cover Top view of the optical coupling device between the optical element and the optical fiber with the active alignment function added.

FIG. 2 (b) is a cross-sectional view taken along the line C-C 'in FIG. 2 (a).

FIG. 2 (c) is a side view taken along the line D-D 'of FIG. 2 (b).

FIG. 2 (d) is a side view taken along the line E-E 'of FIG. 2 (b).

FIG. 2 (e) is a side view taken along the line F-F 'of FIG. 2 (b).

3 (a) to 3 (d) show the micro-bending of the optical fiber by the two optical fiber fixing shafts and the V-grooved silicon sheath in the V-groove according to the present invention and according to the position of the sheath. A cross-sectional view of the manufacturing process sequence to optically couple the optical element and the optical fiber at the optimum position by adjusting the position.

* Explanation of symbols for main parts of the drawings

1,11 silicon substrate 2,12 V-groove

313: optical device chip 4,14: optical waveguide of the optical device chip

5,15: flip chip bonding pad 6,16: optical fiber

7,17: fiber core 18,20: fiber fixed shaft

19,21: V-groove 22: Silicone cover

23: V-groove in silicone cover 24: Adhesive

The present invention provides an optical coupling device for connecting an optical element and an optical fiber, comprising: a substrate; Two protruding portions having a predetermined depth and width and protruding from the V-shaped groove formed in the substrate and having a predetermined height in the V-shaped groove but having a height lower than the height of the substrate and a width smaller than the width of the V-shaped groove; And a cover positioned between the protrusions to press down the optical fiber by the height of the protrusion to face both ends of the optical fiber.

The present invention also provides a method for connecting an optical element and an optical fiber, the method comprising: providing a substrate; Forming an etch mask having a predetermined full width but forming an etch mask pattern having a narrow line width at two positions spaced apart from each other by a predetermined distance; Anisotropically etching the substrate using the etch mask to form a V-shaped groove having two protrusions inside the groove, and forcing the optical fiber into the V-shaped groove so as to span the two protrusions; And mounting a cover positioned between the two protrusions to cover the optical fiber.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

First, the optical coupling device of the present invention forms a micro-bending on the optical fiber by the two optical fiber fixed axis and the V-groove silicon cover in the V-groove of the silicon substrate, the optical fiber according to the position of the cover It adds an active alignment that allows you to adjust the position of the tip.

In order to increase the optical coupling efficiency, a wide V-groove in which the optical fiber is located and two optical fiber fixed shafts in the V-groove are separated, and a separate V-groove silicon cover is used to press the optical fiber at a predetermined position between the two fixed shafts. It is an optical coupling device that finds a position where the optical coupling efficiency between the optical element and the optical fiber is maximized by inducing a slight bending, that is, micro bending and thereby adjusting the position of the optical fiber end according to the position of the silicon cover.

That is, when the optical fiber is in close contact with the V-groove, the optical element 13 has the width of the V-groove 12 etched from the silicon substrate 11 as shown in FIGS. 2 (a) to 2 (e). The optical waveguide 14 and the core 17 of the optical fiber 16 are etched more than twice as wide as the alignment error caused in the flip chip bonding process, rather than the width of the core 17 which is exactly aligned.

The V-grooves (hereinafter, referred to as optical fiber fixed shafts or fixed sides) 19, 21 having a narrower width than the V-grooves are etched at predetermined points on the left and right sides of the V-grooves at predetermined points. At this time, the widths of the V-grooves 19 and 21 in the optical fiber fixed shafts 18 and 20 are the optical waveguides of the optical element 13 when the optical fiber 16 is in close contact with the V-grooves 19 and 21 in the fixed shaft. 14) and the core 17 of the optical fiber 16 to have a wider width than the degree of alignment error caused by the flip chip bonding process than the width that is exactly aligned.

On the silicon substrate having such a structure, flip chip bonding pads 15 are formed at predetermined positions associated with the V-grooves, and solder bumps are formed thereon to form the optical device chips 13 therein. After flip chip bonding, when the optical fiber 16 is inserted into the V-groove 12 of the silicon substrate, the optical fiber is only in contact with the narrowly etched V-groove portions, that is, the two fixed shaft V-grooves 19 and 21. It is not in contact with other parts of the wide V-groove 12, and the position of the core 17 at the end of the optical fiber is the optical waveguide 14 of the optical element chip 13 even when the maximum alignment error occurs in the flip chip bonding process. It is located lower than the part.

Then, when the optical fiber is covered at the midpoint between the two fixed shafts by using the separately manufactured V-groove-shaped silicon cover 22, the optical fiber is formed by the two fixed shafts 18 and 20 and the silicon cover 22 and the second (b) As shown in the diagram, micro bending occurs up and down, thus increasing the position of the optical fiber end side of the optical element.

The height of the fiber ends depends on the relative position of the cover in the z-axis direction with respect to the two fixed axes, and the change in the position of the cover in the x-axis will induce a change in the position of the fiber ends in the x-axis. .

On the other hand, by applying a current to the optical element 13 to emit light from the optical waveguide 14, it is possible to monitor the optical output coupled to the optical fiber core 17 at the other end of the optical fiber.

In this state, when the silicon cover 22 is moved to the x-axis and the z-axis in the above-described manner, the position of the ends of the optical fiber 16 moves on the x-axis and the y-axis, so that the light emitted from the optical element 13 The optical coupling efficiency to the optical fiber core 17 is changed to fix the optical fiber 16 to the silicon substrate 11 at a position where the optical coupling efficiency is optimal.

2 (c) to 2 (e) show side views of the optical coupling core 17 and the optical waveguide 14 of the optical device chip 13 as side views of the respective optical coupling devices. FIG. 2 (c) is a side view of the end of the optical fiber and shows the state in which the optical fiber core 17 and the optical waveguide 14 of the optical device chip are correctly aligned. FIG. The lower part of the optical fiber is in contact with the etching surface of the V-groove 19 in the fixed shaft 18, the second (e) is a side view of the cover 22, the upper part of the optical fiber is silicon The state in contact with the etching surface of the cover V-groove 23 is shown.

The manufacturing method of the optical coupling device according to the present invention will be described with reference to FIGS. 3 (a) to 3 (d) as follows.

First, a silicon substrate 11 having a V-groove of the above structure as shown in FIG. 3 (a) is fabricated. In order to etch the V-groove having the two fixed axes 18 and 20 on the silicon substrate 11, the pattern of the silicon nitride film as the etch mask may be narrowed at the fixed axis portion as shown in FIG. 2 (a). .

When the silicon substrate 11 is anisotropically etched using an etching mask having such a shape, the fixed shafts 18 and 20 having a width and a depth smaller than that of the V-groove 12 are formed. In this case, the width of the etched region on the mask is a flip chip bonding process in a region having a fixed axis, than the width in which the optical waveguide 14 of the optical element 13 and the core 17 of the optical fiber 16 are exactly aligned. It is designed to be located further down by the degree of alignment error caused by, and the width of the V-groove 12 outside the fixed axis is etched to be more than twice as wide as the maximum alignment error occurring during flip chip bonding. do.

Subsequently, after attaching the optical device chip 13 to the predetermined position where the flip chip bonding pad 15 is placed on the silicon substrate 11 as shown in FIG. Push it into the groove 12 so that it spans the two fixed shafts 18, 20.

Subsequently, as shown in FIG. 3 (c), when the silicon cover 22 is used to cover the optical fiber 16 at an intermediate point between the two fixed shafts 18 and 20, the optical fiber is divided into two fixed shafts 18. , 20) and the silicon cover 22, the micro-bending occurs up and down as shown in the drawing, the position of the optical fiber end side of the optical element is changed, this position of the optical fiber end is the x-axis of the cover for the two fixed axes And relative position in the z-axis direction. Therefore, while applying a current to the optical element 13 to emit light from the optical waveguide 14, while moving the silicon cover 22 while monitoring the optical output coupled to the optical fiber core 17 at the other end of the optical fiber, the optical fiber ( 16) As the position of the end moves on the x-axis and y-axis, the optical coupling efficiency of the light emitted from the optical device to the optical fiber core is changed, so that the optical coupling efficiency is optimized.

Finally, as shown in FIG. 3 (d), the optimum optical fiber position is found by the V-groove active alignment method, and the optical fiber 16 is fixed on the silicon substrate 11 using the adhesive 24 in the state. .

The present invention solves the problem of the strong coupling of optical coupling efficiency due to alignment error, which is the biggest disadvantage in the optical alignment device of the manual alignment method using the V-groove formed on the silicon substrate and the optical device flip chip bonding. The new structure of the V-groove silicon substrate with the cover and the active alignment in the V-groove can be solved and the optimum optical coupling efficiency can be obtained.

In addition, the active alignment method finds the optimal optical coupling position, which greatly reduces the alignment accuracy required for the silicon substrate fabrication and the optical device chip fabrication process, and also reduces the optical fiber precision, thus improving the overall optical coupling module yield. It also has the effect of reducing manufacturing costs.

Claims (9)

An optical coupling device for connecting an optical element and an optical fiber, comprising: a substrate; A V-shaped groove formed on the substrate with a predetermined depth and width; Two projections protruding in the V-groove with a predetermined height so that the substrate has a height lower than the height and a width narrower than the width of the V-groove; And a cover positioned between the protrusions to press the optical fiber downward by the height of the protrusion to face both ends of the optical fiber upwards. The optical coupling device of claim 1, wherein the substrate is a silicon substrate. The optical coupling device according to claim 2, wherein the width of the uppermost V-groove is wider than the diameter of the optical fiber. 4. The optical coupling device according to claim 3, wherein the uppermost width of the protrusion is wider than the diameter of the optical fiber and narrower than the uppermost width of the V-groove. The optical coupling device according to claim 1, wherein the cover is fixed to be movable on the substrate so that the position of the optical fiber can be adjusted. A method of connecting an optical element and an optical fiber, the method comprising: providing a substrate; Forming an etch mask having a predetermined line width and forming an etch mask pattern having a narrow line width at two positions spaced apart from each other by a predetermined distance; Anisotropically etching the substrate using the etching mask to form a V-shaped groove having two raised portions inside the groove; Pushing the optical fiber into the V-groove to span over two projections; And mounting a cover positioned between the two protrusions to cover the optical fiber. 6. The method of claim 5 wherein the substrate is a silicon substrate. 7. The method of claim 6, wherein the width of the top of the V-shaped groove is formed wider than the diameter of the optical fiber. The method of claim 5, wherein the cover is fixed to be movable on the substrate to enable positioning of the optical fiber.