JPH0537024A - Optical semiconductor device - Google Patents

Abstract

PURPOSE:To improve the accuracy of optical device mounting by bonding two semiconductor wafers with an insulating film in-between and providing one wafer with a trapezoid groove with a depth reaching the insulating film and a V-groove with a width permitting the alignment of optical axes of optical devices. CONSTITUTION:A bonded substrate obtained by bonding two silicon wafers 18a and 18b with an oxide film 21 in-between, is used for a substrate 18 for optical coupling. In this substrate 18 for optical coupling, a trapezoidal groove 20 to mount a semiconductor laser 1 as a semiconductor luminous element and a V-groove 19 perpendicular to the trapezoid groove 20 to mount an optical fiber 2 and spherical lenses 4 are formed. The depths of the trapezoidal groove 20 and V-groove 19 are determined according to the size and shape of individual optical devices so that the center of the optical beam projecting part 8 of the semiconductor laser 1 is in accordance with those of the optical fiber core and the spherical lenses 4. This enables mounting optical devices with accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical semiconductor device in which a plurality of optical devices are mounted on a semiconductor substrate and these are optically coupled.

[0002]

2. Description of the Related Art In optical fiber communication, it is important to make a light beam of a semiconductor light emitting element incident on an optical fiber efficiently in order to achieve a long communication distance and a high SN ratio. However, a simple method of optically coupling and mounting an optical device has not been established yet. In addition, when fixing the optical device, there is a problem in time-dependent stability of the positional relationship of the optical device due to the misalignment of the shaft center during bonding with an adhesive or during welding, and the interposition of several members for fixing. ..

Therefore, in Japanese Patent Application Laid-Open No. 63-161411 and Japanese Patent Application Laid-Open No. 2-22884, FIG.
Alternatively, by mounting the optical device on the optical coupling substrate as shown in (b), a method of omitting the fine movement adjustment of the optical device which requires a long time is adopted. In the figure, 1 is a semiconductor laser, 2 is an optical fiber, 3 is a substrate for optical coupling, 4 is a spherical lens, 5 is a fine metal wire, 6 is an alignment pattern, 7 is an electrode part, 8 is a light beam emitting part, and 9 is. Is a groove-shaped recess, 10 is a peripheral circuit, 11 is a heat sink, and 12 is a package.

At the position where the optical devices are optically coupled and installed on the optical coupling substrate 3, a linear and cross-shaped pattern having a predetermined width determined by the shape and size of each optical device is formed by a photolithography process or the like. A groove-shaped recess 9 having a predetermined depth, which is formed so that the optical axes of the optical devices coincide with each other, is formed by a dicing saw device along the pattern. Then, the optical device is mounted at the intersection of the groove-shaped recess 9 of the optical coupling substrate 3.

The dicing saw device used for forming the groove-shaped recess 9 is a device for cutting a semiconductor substrate on which an integrated circuit or the like is formed into individual chips, and a blade made by embedding diamond powder or the like in a thin metal plate at high speed. Rotate and cut.
In forming the groove-shaped recess 9 by the dicing saw device, it is necessary to replace with a metal plate having a blade width suitable for obtaining a predetermined groove width, or to control the height of the cutting blade so as to have a predetermined depth. Therefore, in order to improve the accuracy of the depth and position of the groove-shaped recess 9, it is necessary to adjust the position of the cutting blade of the dicing saw device with high accuracy, which makes the device large and occupies and maintains a work space. In terms of operation, the cost is high. Further, there is a limit to the position where the groove can be formed.

Therefore, in Japanese Unexamined Patent Publication No. 60-68301, the groove-shaped concave portion of the optical coupling substrate 3 on which the optical device is mounted is provided for each optical device so that the optical axes have the same height as shown in FIG. Along a pattern with a defined width,
The V groove 19 is formed by etching means.
For example, in the case of a silicon substrate having a {100} crystal plane as the surface, when immersed in an etchant having anisotropy, {100}
The V-groove 19 having a desired depth can be easily obtained by defining the groove width for anisotropic etching in which the etching rates of the {111} plane and the {111} plane are different. The optical device is mounted and fixed at the intersection of the V-shaped grooves 19 or the boundary between the two V-shaped grooves 19 having different groove widths, and is further covered by the pressing plate 26.

However, in the above-mentioned method, it is impossible to obtain a groove having a flat bottom surface and a precise depth suitable for mounting an optical device such as a semiconductor light emitting element or a light receiving element having a flat adhesive surface. A groove with a flat {100} face as the bottom is
Etching is stopped in the middle of formation of the V-shaped groove by anisotropic etching to obtain a trapezoidal groove. Since the depth of the trapezoidal groove depends on the time when etching is stopped, it is difficult to form the depth accurately and with good reproducibility. Therefore, an optical device having a flat adhesive surface has a problem that it is difficult to stably install the optical device by aligning the optical axes.

[0008]

As described above, it is necessary to form the depth of a trapezoidal groove for mounting an optical device such as a semiconductor light emitting element or a light receiving element having a flat adhesive surface accurately and with good reproducibility. However, this is a factor that reduces the positional accuracy of the optical device mounted on the optical coupling substrate.

The present invention has been made in consideration of the above circumstances, and it is an object of the present invention to form a trapezoidal groove accurately and with good reproducibility, and to mount all optical devices with high accuracy and simplicity. Another object of the present invention is to provide an optical semiconductor device which can be performed at any time and which is also reliable over time.

[0010]

In order to achieve the above object, the present invention adopts the following configuration.

That is, according to the present invention, a trapezoidal groove and a V-shaped groove are formed on a semiconductor substrate.
In an optical semiconductor device in which a groove is formed and an optical device is installed in each groove, an adhesive substrate in which two semiconductor wafers are bonded via an insulating film is used as a semiconductor substrate, and the depth at which one wafer reaches the insulating film is reached. In addition to the trapezoidal groove, the V groove having a groove width set so that the heights of the optical axes of the respective optical devices coincide with each other is provided.

Further, according to the present invention, when a plurality of optical devices are mounted on the same substrate, an adhesive substrate formed by joining the surfaces of a plurality of semiconductor wafers having a predetermined thickness and smooth surfaces to each other is used as an optical coupling substrate. V groove and trapezoidal groove having a groove width determined for each optical device so that the heights of the optical axes coincide with each other are formed at predetermined positions on the substrate in a linear or cross shape, and
It is characterized in that optical devices are respectively mounted in the groove and the trapezoidal groove to perform optical coupling. In the present invention, a plurality of optical devices are mounted on an adhesive substrate formed by bonding a plurality of semiconductor wafers via an etching stop layer such as an insulating film (oxide film). A V-groove or a trapezoidal groove having a predetermined groove width and having a linear or cross pattern is formed on the surface of the substrate by a photolithography technique and an etching technique. The pattern and groove shape are appropriately selected according to each optical device so as to be optically coupled and installed. Further, the trapezoidal groove is a groove having a flat bottom surface which exposes the etching stop layer of the semiconductor wafer bonding portion. Then, each optical device is attached to the V-shaped groove or the trapezoidal intersection, or to the boundary between two V-shaped grooves or trapezoidal grooves having different groove widths.

[0013]

In the present invention, the trapezoidal groove in which the optical device is installed is formed by using a normal mask aligning process, so that the horizontal position can be accurately defined. Further, since a plurality of wafers are bonded via the etching stop layer such as an oxide film, etching of the trapezoidal groove automatically stops at the oxide film. Therefore, if the thickness of the wafer is accurately polished, it becomes easy to accurately and flatly etch the depth of the trapezoidal groove. On the other hand, the V groove having a depth that does not reach the etching stop layer can be etched to a predetermined depth by defining the groove width. Then, by utilizing these recesses, it becomes possible to mount the optical device at an accurate position in both the horizontal and vertical directions. Further, the V groove is formed by appropriately selecting a single-line or cross-shaped pattern according to each optical device, and mounting is performed without requiring a member for fixing, so that the positional relationship of the optical device can be changed with time. It is stable.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

1A and 1B are schematic views of an optical semiconductor device according to an embodiment of the present invention. FIG. 1A is a perspective view and FIG. 1B is a sectional view. The optical coupling substrate on which the optical device is mounted is an adhesive substrate 18 in which a silicon wafer 18a having a SiO ₂ film (insulating film) 21 formed on the surface thereof by thermal oxidation or the like and another silicon wafer 18b are directly bonded to each other. To use. The direct bonding technology is a technology that has come to be used in the manufacturing process of IGBT (Insulated Gate Bipolar Transistor) and power with high withstand voltage. First, OH groups are formed on the smooth surface of two semiconductor wafers, Contact the surfaces of. The OH groups of the respective wafers are hydrogen-bonded to each other to bring the two wafers into close contact with each other, and the heat treatment causes a dehydration condensation reaction and movement of oxygen atoms. As a result, the atoms that make up the wafer are bound together,
The semiconductor wafer is directly bonded to form an adhesive substrate. The silicon wafer of the adhesive substrate has a (100) crystal plane as a surface, and a V groove having an angle of 70.6 ° can be obtained by an anisotropic etchant such as a KOH solution or hydrazine.

The optical coupling substrate 18 has a trapezoidal groove portion 20 for mounting the semiconductor laser 1 as a semiconductor light emitting element.
Then, a V-shaped groove 19 for installing the optical fiber 2 and the spherical lens 4 perpendicularly intersecting the trapezoidal groove 20 is formed. The semiconductor laser 1 is installed in a single trapezoidal groove 20 having an alignment pattern 6 provided in the vicinity thereof. The ball lens 4 is stably installed in the V-shaped groove 19 having a cross shape. Further, the optical fiber 2 has a single V
It is installed in the groove 19. The depths of the trapezoidal groove 20 and the V-shaped groove 19 are determined according to the size and shape of each optical device so that the light beam emitting portion 8 of the semiconductor laser 1 and the core of the optical fiber 2 and the central portion of the spherical lens 4 coincide with each other. It is determined accordingly.

As described above, after the individual optical devices are installed in the groove portions 19 and 20 of the optical coupling substrate 18, they are fixed with an adhesive, or they have the same shape as the V groove 19 of the substrate 18 but the groove width is small and similar. The pressing plate (not shown) having the V-groove is capped and fixed.

Next, the manufacturing process of the optical coupling substrate used in the above embodiment will be described. First, as shown in FIG. 2A, Si is formed on one silicon wafer surface of the adhesive substrate 18.
After forming the O ₂ film 21, a resist 22 is applied on the entire surface. Then, after a desired pattern is formed on the resist by a photolithography process, the SiO ₂ film 21 is selectively etched to transfer the pattern to the SiO ₂ film 21.

Then, by immersing in an anisotropic etchant such as KOH solution or hydrazine for a predetermined time, V corresponding to the width of the pattern as shown in FIG. 2B is formed.
A groove 19 and a trapezoidal groove 20 are obtained. The V-shaped groove 19 has a shape formed when it does not reach the bonded portion of the semiconductor wafer, and the trapezoidal groove 20 is formed by automatically stopping the etching of the recessed portion by the etching stop layer such as the oxide film 21 of the bonded portion. .. If the thickness of the silicon wafer 18a is accurately polished, the depth of the trapezoidal groove 20 can be accurately determined. After that, the SiO ₂ film 21 used as a mask is removed with ammonium fluoride or the like to obtain an optical coupling substrate.

FIG. 3 is a schematic diagram showing how the apparatus of this embodiment is installed in a package. The optical coupling substrate 18 is provided with a trapezoidal groove 23 that serves as a positioning when the optical coupling substrate 18 is installed in the package 12. Specifically, precisely polish the thickness of the wafer,
The optical coupling substrate 18 is provided with a trapezoidal groove 23 for alignment, which is etched to have a precise depth and a flat bottom surface. The optical coupling substrate 18 is mounted on the package 1 so that the bottom surface of the alignment trapezoidal groove 23 and the alignment portion 27 of the package 12 are aligned with each other.
When installed in position 2, the positional relationship between the optical axis of the optical device mounted on the optical coupling substrate 18 and the package 12 is accurately determined.

On the other hand, the optical fiber connector 24 having the positioning portion 25 for the package 12 can be formed so that the positional relationship between the optical fiber 14 and the package 12 is accurately determined. Therefore, it is possible to easily couple the optical axis of the optical device and the optical fiber 14 with the package 12 interposed therebetween in a positional relationship having a high optical coupling rate.

As described above, according to this embodiment, as the optical coupling substrate 18, an adhesive substrate in which two silicon wafers 18a and 18b are adhered to each other with the oxide film 21 in between is used. Since the trapezoidal groove 20 is formed by etching until reaching, the trapezoidal groove 20 can be accurately and reproducibly formed by accurately polishing the thickness of the wafer 18a. Therefore, an optical device such as the semiconductor laser 1 having a flat adhesive surface can be mounted on the optical coupling substrate 18 with high positional accuracy.

Since the groove is formed by etching, the position of the groove is not limited and the surface of the substrate can be effectively used. For example, since the cross-shaped groove for mounting the spherical lens 4 can be formed within a required range, the blank portion on the substrate is wider than in the conventional example of FIG. 4A in which the groove-shaped recess is formed by the dicing saw device. .. Therefore, as shown in FIG. 3, it becomes possible to mount a peripheral circuit such as a semiconductor laser drive circuit in the margin portion, which is useful for miniaturization of the module.

The present invention is not limited to the above-described embodiments, and various modifications can be carried out without departing from the scope of the invention. In the embodiment, silicon is used as the semiconductor wafer, but any semiconductor that can be bonded via the insulating film can be used. Further, the insulating film interposed between the semiconductor wafers is not limited to SiO ₂ and may be SiON, Si ₃ N ₄ or the like.

[0025]

As described above in detail, according to the present invention, 2
By using an adhesive substrate in which a plurality of semiconductor wafers are adhered via an insulating film, not only V-shaped grooves but also trapezoidal shaped grooves can be formed with high precision, so that all optical devices can be mounted accurately with ease. The cost can be reduced and the reliability can be improved over time. It is also effective for integrating optical devices and peripheral circuits.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an optical semiconductor device according to an embodiment of the present invention,

FIG. 2 is a perspective view showing a manufacturing process of the optical coupling substrate used in the above embodiment,

FIG. 3 is a perspective view showing an apparatus according to an embodiment and a package in which the apparatus is installed;

FIG. 4 is a schematic configuration diagram showing a conventional optical semiconductor device,

FIG. 5 is a perspective view showing a conventional example using an optical coupling substrate in which a V groove is formed by etching.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Semiconductor laser, 2 ... Optical fiber, 4 ... Spherical lens, 5 ... Metal fine wire, 6 ... Alignment pattern, 7 ... Electrode part, 8 ... Light beam emitting part, 10 ... Peripheral circuit, 12 ... Package, 18a, 18b ... Semiconductor wafer, 18 ... Adhesive substrate, 19 ... V groove, 20 ... Trapezoidal groove, 21 ... SiO ₂ film, 22 ... Resist film, 23 ... Optical coupling substrate and package alignment groove, 24 ... Fiber connector, 25 ... Package And fiber connector alignment part, 27 ... alignment part.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Hamasaki 1 Komukai Toshiba-cho, Kouki-ku, Kawasaki-shi, Kanagawa Stock company Toshiba Research Institute

Claims (1)

Claim: What is claimed is: 1. An adhesive substrate comprising two semiconductor wafers bonded together via an insulating film, one wafer being selectively etched to form a trapezoidal groove and a V groove, and A first optical device installed in a trapezoidal groove of the adhesive substrate; and a second optical device installed in a V groove of the adhesive substrate, wherein the trapezoidal groove is formed to a depth reaching the insulating film. The optical semiconductor device is characterized in that the V groove has a groove width set such that the heights of the optical axes of the first and second optical devices are the same.