JP2004031377A - Optical semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-sized optical semiconductor device which can maintain the wavelength of an optical signal emitted from an optical semiconductor element constant. <P>SOLUTION: An optical semiconductor device has an optical semiconductor element 4 laid at the bottom surface of inside of a vessel 1 via an electron-cooling element 2; and a wiring substrate 9, one end part of which is laid on a holding member that is located at one part of the inside or inside of the vessel 1, the other end part of which is laid near the optical semiconductor element 4 of the upper surface of the electron-cooling element 2, and where a wiring conductor 9b is formed to transmit a driving signal input into the optical semiconductor element 4. The wiring substrate 9 has the wiring conductor 9b on the upper surface of an insulating substrate 9a and a grounding conductor layer 9c comprising of an underlying conductor layer formed at nearly all the surface of the lower surface, and a main conductor layer which is formed at one end part and at a region of other end part of the underlying conductor layer. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical semiconductor device used in an optical communication field or the like and containing an optical semiconductor element such as a semiconductor laser (LD).
[0002]
[Prior art]
2A and 2B are cross-sectional views of a conventional optical semiconductor device. In FIG. 2, 1 is a container made of ceramics or the like, 1a is an input terminal joined to the outer surface of the container 1, 2 is an electronic cooling element such as a Peltier element mounted on the bottom surface in the container 1, and 3 is an electronic cooling element A mounting substrate 2 is mounted on the upper surface of the optical semiconductor device 4, an optical semiconductor element 4, a submount 5 on which the optical semiconductor element 4 is mounted, a lens 6 for condensing light emitted from the optical semiconductor element 4, and a lens 6 Is a temperature detector (temperature sensor) for detecting the temperature of the electronic cooling element 2, and 9 is a wiring board for electrically connecting the input terminal 1a and the optical semiconductor element 4.
[0003]
FIGS. 3A and 3B show a top view and a bottom view of the wiring board 9, respectively. In FIG. 3, 19a is an insulating substrate made of ceramics or the like, 19b is a wiring conductor formed on one main surface of the insulating substrate 19a and formed of a line conductor for impedance matching, and 19c is formed on the entire other main surface of the insulating substrate 19a. The formed ground conductor layer. This wiring board 9 has a microstrip line structure, and is a structure that allows high-frequency signals to propagate well.
[0004]
The optical semiconductor element 4 such as an LD used in the optical semiconductor device has a characteristic that the wavelength of an optical signal emitted from the optical semiconductor element 4 changes when the temperature of the optical semiconductor element 4 changes. Therefore, in order to stabilize the wavelength of the optical signal emitted from the optical semiconductor element 4 as much as possible, the optical semiconductor device is configured to keep the temperature of the optical semiconductor element 4 constant.
[0005]
That is, the temperature of the optical semiconductor element 4 changes due to self-heating during driving, the temperature of the external environment of the optical semiconductor device, and the heat of the wiring board 9 for transmitting the high-frequency signal for driving to the optical semiconductor element 4. I do. The electronic cooling device 2 and the temperature detector 8 are provided inside the optical semiconductor device so that the temperature of the optical semiconductor device 4 does not change. When the temperature detector 8 detects a temperature different from the set temperature, the detection signal is fed back to the driving device of the electronic cooling element 2 connected to the outside of the optical semiconductor device, and the driving device detects the detected temperature of the temperature detector 8. Is driven until the temperature reaches the set temperature. As a result, the mounting substrate 3 and the optical semiconductor element 4 mounted via the submount 5 are maintained at a constant temperature.
[0006]
[Problems to be solved by the invention]
However, the conventional optical semiconductor device using the wiring board 9 has the following problems. That is, the wiring board 9 has one end joined to the inner surface of the container 1 and the other end joined to the mounting substrate 3 whose temperature is kept constant by the electronic cooling element 2. The heat further moved toward the container 1 flows back to the mounting substrate 3 through the wiring substrate 9. Due to the influence of the backflowing heat, the temperature of the optical semiconductor element 4 cannot be controlled stably, and as a result, there has been a problem that the wavelength of the optical signal emitted from the optical semiconductor element 4 is not stable.
[0007]
As one configuration for solving this problem, there has been proposed a configuration in which the wiring board 9 is lengthened to increase the thermal resistance thereof, and the backflow of heat from the container 1 to the mounting substrate 3 is suppressed (Japanese Patent Laid-Open No. Hei 9 (1997)). -223847). However, this configuration has a problem that the optical semiconductor device cannot be miniaturized because the wiring substrate 9 is long.
[0008]
Accordingly, the present invention has been completed in view of the above problems, and an object of the present invention is to provide a small-sized optical semiconductor device capable of maintaining a constant wavelength of an optical signal emitted from an optical semiconductor element. is there.
[0009]
[Means for Solving the Problems]
The optical semiconductor device of the present invention has an optical semiconductor element mounted on a bottom surface in a container via an electronic cooling element, and one end mounted on a part of an inner surface of the container or a supporting member disposed on the inner surface. And a wiring board on which the other end is placed near the optical semiconductor element on the upper surface of the electronic cooling element, and on which a wiring conductor for transmitting a drive signal input to the optical semiconductor element is formed. In the optical semiconductor device, the wiring substrate is formed such that the wiring conductor is formed on an upper surface of an insulating substrate, and a base conductor layer formed substantially over the entire lower surface and a portion of the one end and the other end of the base conductor layer. A ground conductor layer including the formed main conductor layer is formed.
[0010]
In the optical semiconductor device of the present invention, the wiring substrate has a wiring conductor formed on the upper surface of the insulating substrate, and a base conductor layer formed on substantially the entire lower surface, and portions of the one end and the other end of the base conductor layer. Since the ground conductor layer consisting of the main conductor layer formed on the wiring conductor is formed, the wiring conductor can have a microstrip line structure, so that when the wiring conductor transmits a high-frequency signal as a drive signal, High-frequency signals can be transmitted well. In addition, since the main conductor layer made of gold or the like that easily conducts heat is not formed at the center of the ground conductor layer, the heat transfer path is cut off at the center of the ground conductor layer to increase the thermal resistance of the wiring board. Can be. As a result, the amount of heat transmitted from the container to the electronic cooling element via the wiring board can significantly reduce the component passing through the ground conductor layer. Therefore, the temperature control of the optical semiconductor element can be stably performed, the wavelength of the optical signal emitted from the optical semiconductor element is kept constant, and optical communication with high accuracy is possible.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
The optical semiconductor device of the present invention will be described below in detail. The overall basic structure of the optical semiconductor device of the present invention is the same as that of a conventional optical semiconductor device, and is as shown in FIGS. 2 (a) and 2 (b). That is, 1 is a substantially rectangular parallelepiped container made of ceramics such as alumina (Al ₂ O ₃ ) ceramic, resin, metal or the like, and 1a is an input terminal brazed to a metallized layer formed on the outer surface of the container 1 or the like. .
[0012]
Reference numeral 2 denotes an electronic cooling element such as a Peltier element mounted on the bottom surface of the container 1, and reference numeral 3 denotes a mounting substrate installed on the upper surface of the electronic cooling element 2. The mounting substrate 3 is made of a copper-tungsten alloy (Cu-W) or the like. Further, 4 is an optical semiconductor element such as an LD or PD, 5 is a submount made of ceramics or resin such as alumina (Al ₂ O ₃ ) ceramic on which the optical semiconductor element 4 is mounted, and 6 is an output of the optical semiconductor element 4. 7 is a lens holding member for holding the lens 6, 8 is a temperature detector (temperature sensor) for detecting the temperature of the electronic cooling element 2, 9 is the input terminal 1a and the optical semiconductor element 4 Is a wiring board for electrically connecting. The temperature detector 8 is a thermistor formed of metal oxide, silicon, or the like.
[0013]
1A and 1B are a top view and a bottom view of a wiring board 9 in the optical semiconductor device of the present invention. In FIG. 1, 9a is an insulating substrate made of ceramics such as alumina (Al ₂ O ₃ ) ceramics, 9b is a wiring conductor made of a line conductor or the like for impedance matching, 9c is a ground conductor, and 9d is a ground conductor layer. The central portion 9e of the ground conductor layer 9c, in which an adhesion metal layer and a diffusion prevention layer are sequentially laminated, is a ground conductor layer 9c in which a main conductor layer is laminated at one end and the other end of the diffusion prevention layer. It is the end of.
[0014]
The underlying conductor layer may be composed of only the adhesion metal layer, or may be composed of the adhesion metal layer and the diffusion preventing layer. Hereinafter, a case in which the underlying conductor layer includes the adhesion metal layer and the diffusion preventing layer will be described.
[0015]
The optical semiconductor device of the present invention includes an optical semiconductor element 4 mounted on the bottom surface of the container 1 via the electronic cooling element 2, and a support member disposed on a part of the inner surface of the container 1 or an inner surface of the container 1. A wiring board 9 on which the other end is mounted near the optical semiconductor element 4 on the upper surface of the electronic cooling element 2 and on which a wiring conductor 9b for transmitting a drive signal input to the optical semiconductor element 4 is formed. The wiring substrate 9 includes a wiring conductor 9b formed on the upper surface of the insulating substrate 9a, a base conductor layer formed on substantially the entire lower surface, and one end and the other end of the base conductor layer. And a ground conductor layer 9c composed of the main conductor layer.
[0016]
In the present invention, the other end of the wiring board 9 is placed near the optical semiconductor element 4, but the distance between the other end of the wiring board 9 and the optical semiconductor element 4 is about 10 mm or less. A phenomenon in which heat transferred from the cooling element 2 to the container 1 side flows back through the wiring board 9 to the optical semiconductor element 4 from the mounting substrate 3 is likely to occur. In addition, one end of the wiring board 9 is placed on a part of the inner surface of the container 1 or on a support member arranged on the inner surface. Can be placed on the shelf 1b or a step provided on the inner surface thereof. Further, when placed on a support member disposed on the inner surface of the container 1, a support member having a columnar shape or a prism shape is provided on the bottom surface in contact with the bottom surface near the inner surface of the container 1 or in contact with the inner surface. It can also be placed on
[0017]
The outer shape of the container 1 of the present invention can be various shapes such as a rectangular parallelepiped, a cubic, and a cylindrical shape such as a cylindrical shape, but it is preferable that the inside has a flat bottom surface on which the electronic cooling element 2 can be placed. It is preferable that the container 1 has a configuration in which an upper surface is opened and the opening is closed by a lid after each component is accommodated in the interior, since each component can be easily accommodated.
[0018]
The metallized layer on the outer surface of the container 1 is formed so as to penetrate the inner and outer surfaces of the container 1 by manufacturing the container 1 by a ceramic lamination method, and the metallized layer on the inner surface side of the container 1 is formed by the wiring conductor 9 b of the wiring board 9. Are electrically connected to each other by a bonding wire or the like.
[0019]
In the central portion 9d of the ground conductor layer 9c formed on the lower surface of the wiring board 9 of the present invention, the length of the wiring conductor 9b formed of a line conductor in the line direction is preferably 0.05 to 2.0 mm. If the thickness is less than 0.05 mm, the central portion 9 d for blocking heat transfer is short, so it is difficult to suppress the amount of heat transferred from the container 1 to the electronic cooling element 2 via the wiring board 9. If it exceeds 2.0 mm, the length of the wiring conductor 9b becomes longer, and the impedance characteristics of the microstrip line tend to become unstable.
[0020]
The length of the wiring conductor 9b at the end 9e of the ground conductor layer 9c in the line direction is preferably 0.10 to 1.0 mm. When the thickness is less than 0.10 mm, the bonding strength of the wiring board 9 becomes weak, and the wiring board 9 is easily peeled. If it exceeds 1.0 mm, the end 9e becomes long, and it becomes difficult to suppress the amount of heat transmitted from the container 1 to the electronic cooling element 2 via the wiring board 9.
[0021]
The formation pattern of the ground conductor layer 9c is preferably a substantially square central part 9d and a substantially square end 9e as shown in FIG. 1B, but is not limited to this, and the transmission characteristic of the high-frequency signal is deteriorated at the end 9e. A pattern in which one or a plurality of island-shaped non-formation portions of the main conductor layer may be provided within a range not to cause the deterioration and not to deteriorate the bonding property to the mounting substrate 3. With such a configuration, heat transfer can be suppressed even at the end 9e. Further, the ground conductor layer 9c may be formed to extend on a side surface of the wiring substrate 9b of the insulating substrate 9a substantially parallel to the line direction.
[0022]
The center portion 9d of the ground conductor layer 9c preferably has a thickness of 0.01 to 1.2 μm. If the thickness is less than 0.01 μm, a high-frequency signal is likely to leak from the center portion 9d formed of the adhesion metal layer and the diffusion preventing layer, so that the grounding is performed. Without functioning as a conductor layer, it becomes difficult for the wiring conductor 9b to transmit a high-frequency signal satisfactorily. When the thickness is more than 1.2 μm, the effect of blocking heat is reduced, and is not enough to increase the thermal resistance of the wiring board 9.
[0023]
The insulating substrate 9a forming the wiring substrate 9 is made of an insulating material such as ceramics (sintered body) or resin, for example, an aluminum oxide (Al ₂ O ₃ ) -based sintered body, an aluminum nitride (AlN) -based sintered body, It is made of a silicon (SiC) -based sintered body, a silicon nitride (Si ₃ N ₄ ) -based sintered body, a glass ceramic sintered body, or the like.
[0024]
The wiring conductor 9b and the ground conductor layer 9c are formed by a thin film forming method such as an evaporation method, a sputtering method, a CVD method, and a plating method, and are processed into a predetermined pattern by a photolithography method, an etching method, a lift-off method, or the like.
[0025]
Like the end 9e of the ground conductor layer 9c, the wiring conductor 9b is formed of a three-layer conductor layer in which an adhesion metal layer, a diffusion prevention layer, and a main conductor layer are sequentially laminated. The adhesion metal layer is preferably made of at least one of Ti, Cr, Ta, Nb, Ni—Cr alloy, Ta ₂ N, and the like, in terms of adhesion with the insulating substrate 9a made of ceramics or the like. The thickness of the adhesion metal layer is preferably about 0.01 to 0.2 μm. If it is less than 0.01 μm, it will be difficult to firmly adhere, and if it exceeds 0.2 μm, peeling will easily occur due to internal stress during film formation.
[0026]
The diffusion prevention layer is preferably made of at least one of Pt, Pd, Rh, Ni, a Ni—Cr alloy, a Ti—W alloy, and the like, for preventing mutual diffusion between the adhesion metal layer and the main conductor layer. The thickness of the diffusion prevention layer is preferably about 0.05 to 1 μm. If the thickness is less than 0.05 μm, defects such as pinholes are generated and the function as the diffusion prevention layer is hardly achieved. If it exceeds 1 μm, peeling is likely to occur due to internal stress during film formation. When a Ni—Cr alloy is used for the diffusion prevention layer, the adhesion can be ensured, so that the adhesion metal layer can be omitted.
[0027]
Further, the main conductor layer is preferably made of Au, Cu, Ni, Ag or the like having a small electric resistance, and its thickness is preferably about 0.1 to 5 μm. If it is less than 0.1 μm, the electrical resistance tends to increase, and if it exceeds 5 μm, peeling tends to occur due to internal stress during film formation. Further, since Au is a noble metal and expensive, it is preferable to form it as thin as possible from the viewpoint of cost reduction. Since Cu is easily oxidized, it is preferable to cover it with a protective layer composed of a Ni layer and an Au layer.
[0028]
Further, the wiring conductor 9b and the end portion 9e may be formed with the same film configuration, or may be formed with different film configurations.
[0029]
The electrical connection between the wiring conductor 9b and the optical semiconductor element 4 can be made via a bonding wire or a wiring pattern formed on the surface of the mounting substrate 3. The ground conductor layer 9c is grounded by being electrically connected to a metal container 1 or a ground conductor formed on the inner and outer surfaces of the container 1.
[0030]
The present invention is not limited to the above-described embodiment, and various changes may be made without departing from the spirit of the present invention.
[0031]
【The invention's effect】
The optical semiconductor device of the present invention has an optical semiconductor element mounted on the bottom surface of the container via the electronic cooling element, and one end mounted on a support member disposed on a part of or the inner surface of the container. And a wiring board on which the other end is mounted near the optical semiconductor element on the upper surface of the electronic cooling element and on which a wiring conductor for transmitting a drive signal input to the optical semiconductor element is provided. A wiring conductor is formed on the upper surface of the insulating substrate, and a ground conductor layer formed of a base conductor layer formed on substantially the entire lower surface and a main conductor layer formed at one end and the other end of the base conductor layer is formed. By doing so, the wiring conductor can have a microstrip line structure, so that when the wiring conductor transmits a high-frequency signal as a drive signal, the high-frequency signal can be transmitted well. In addition, since the main conductor layer made of gold or the like that easily conducts heat is not formed at the center of the ground conductor layer, the heat transfer path is cut off at the center of the ground conductor layer to increase the thermal resistance of the wiring board. Can be. As a result, the amount of heat transmitted from the container to the electronic cooling element via the wiring board can significantly reduce the component passing through the ground conductor layer. Therefore, the temperature control of the optical semiconductor element can be stably performed, the wavelength of the optical signal emitted from the optical semiconductor element is kept constant, and optical communication with high accuracy is possible.
[Brief description of the drawings]
FIG. 1 shows an example of an embodiment of a wiring board in an optical semiconductor device of the present invention, wherein (a) is a top view of the wiring board and (b) is a bottom view of the wiring board.
2A and 2B show an example of an embodiment of the optical semiconductor device of the present invention, wherein FIG. 2A is a side sectional view of the optical semiconductor device, and FIG. 2B is a front sectional view of the optical semiconductor device.
3A and 3B show an example of a wiring board in a conventional optical semiconductor device, wherein FIG. 3A is a top view of the wiring board, and FIG. 3B is a bottom view of the wiring board.
[Explanation of symbols]
1: container 2: electronic cooling element 4: optical semiconductor element 9: wiring substrate 9a: insulating substrate 9b: wiring conductor 9c: ground conductor layer 9d: central portion 9e of ground conductor layer: end portion of ground conductor layer

Claims (1)

An optical semiconductor element mounted on the bottom surface of the container via an electronic cooling element, and one end of the optical semiconductor element is mounted on a part of the inner surface of the container or a support member disposed on the inner surface, and A wiring board, the other end of which is placed near the optical semiconductor element on the upper surface, and a wiring conductor for transmitting a drive signal input to the optical semiconductor element. The wiring conductor is formed on the upper surface of the insulating substrate, the base conductor layer formed on substantially the entire lower surface, and the main conductor layer formed at the one end and the other end of the base conductor layer An optical semiconductor device, comprising: a ground conductor layer comprising:

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