JPH0567800A - Optical semiconductor device - Google Patents

Abstract

PURPOSE:To improve high S/N ratio and to improve rapid response properties by preventing light incidence excepting a photo detecting region. CONSTITUTION:It is premised that a semiconductor device is provided with a photo detector chip F which consists of an N-type semiconductor silicon substrate 1 of low resistance, an N-type semiconductor region 2 of high resistance formed on the N-type semiconductor silicon substrate 1 and a photodetecting region 3 which is formed inside the N-type semiconductor region 2 and consists of a P-type semiconductor region. A coating material 9 which consists of non-transparent resin is formed in a periphery of the photo detecting region 3 to realize a structure without light incidence from a part excepting the photo detecting region 3. Noise element due to diffusion current element and inside irregular reflection light, etc., is eliminated and high S/N ratio and good rapid response properties are realized.

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 provided with a light receiving element chip, and more particularly to a measure for reducing diffusion current.

[0002]

2. Description of the Related Art In recent years, in the field of optical semiconductor devices, particularly in the field of light receiving elements, there has been a demand for devices having higher-speed response than ever before. In particular, in the light receiving element for optical communication, the demand for high-speed response, high S / N ratio, low cost, etc. to various wavelengths of the light emitting element is increasing,
There is an increasing need for a light receiving element that can meet these demands.

On the other hand, the wavelength of the light emitted from the light emitting element is 78
0nm semiconductor laser, 880nm, 830
The light from these light sources becomes incident light of the light receiving element through each optical system. Therefore, the size and shape of the light incident on the light receiving element are determined by the optical system, and the shape of the light receiving region is also determined based on this.

Therefore, FIG. 3 is an example of a concrete optical system, and shows an optical system in which the light from the light emitting element 10 is incident on the light receiving element 13 sealed by the metal type through the fiber 12. .. That is, the light from the light emitting element 10 is once condensed by the lens system 11, enters the fiber 12, propagates through the fiber 12, and then the light emitted from the fiber 12 enters the light receiving element 13.

[0005]

However, in the above-mentioned light-receiving element 13, the light-receiving element 13 is actually used in a state in which a reverse bias is applied to the PN junction, and light is emitted from the area other than the light-receiving area on the chip surface. May be incident. Alternatively, light may enter from the side surface of the light receiving element chip.

That is, the light emitted from the fiber 12 spreads wider than the diameter of the fiber 12, and its size increases as the distance from the output end of the fiber 12 increases. Specifically, FIG. 4 shows a state in which the light emitted from the output end of the fiber 12 enters the light receiving element 13. Due to the light 15 emitted from the fiber 12 and spread, the incident light is applied to a region other than the light receiving region 16 or is reflected by the inner surface of the metal cap 17, and the reflected light is received.
8 side surfaces are illuminated.

The light incident on the semiconductor region other than the light receiving region 16 forms electron-hole pairs, becomes a diffusion current, and is taken out as a photocurrent. This diffusion current is much slower than the drift current generated in the depletion layer from the time when light is incident until it becomes a photocurrent, resulting in a high-speed response time and a reduction in high S / N ratio. There was a problem.

The present invention has been made in view of the above problems, and prevents light from entering from a region other than the light receiving region, thereby lowering the high S / N ratio due to unnecessary photocurrent and reducing the fast response time. The purpose is to prevent the decrease.

[0009]

Means for Solving the Problems In order to achieve the above-mentioned object, the means taken by the present invention is to completely block the light incident from other than the light receiving area.

Specifically, the means taken by the invention according to claim 1 is as follows. First, a low resistance semiconductor substrate, a high resistance semiconductor region of the same conductivity type formed on the low resistance semiconductor substrate, and the high resistance. It is premised on an optical semiconductor device including a light receiving element chip formed in the semiconductor region and having a light receiving region made of a semiconductor region of a conductivity type different from that of the high resistance semiconductor region.

Further, a covering material made of a non-transparent resin is formed around the light receiving region to have another structure.

The means taken by the invention according to claim 2 is, similarly to the invention according to claim 1, first of all, a low resistance semiconductor substrate and a same conductivity type formed on the low resistance semiconductor substrate. It is premised on an optical semiconductor device including a high resistance semiconductor region and a light receiving element chip formed in the high resistance semiconductor region and having a light receiving region formed of a semiconductor region of a conductivity type different from that of the high resistance semiconductor region. ..

Then, at least a concave recessed portion deeper than the thickness of the light receiving element chip is formed, and the light receiving element chip is mounted in the recessed portion.

[0014]

With the above construction, in the invention according to the first aspect, the area other than the light receiving area is optically completely shielded by sealing the periphery of the light receiving area with the covering material of the non-transmissive resin. If the non-transmissive resin coating material is used for sealing, not only the light-receiving region on the front surface but also the side surface of the light-receiving element chip is sealed at the same time. In this state, for example,
The device is created by resealing with a metal case.

As a result, light does not enter the light-receiving element chip from areas other than the light-receiving area, and the influence of ambient light, which is the majority of the diffused current component, can be minimized no matter how the optical system changes. Therefore, the high S / N ratio and the high-speed response are excellent.

Further, according to the second aspect of the invention, since the light receiving element chip is mounted in the concave recess, incident light from the side surface of the light receiving element chip is blocked.

As a result, like the invention according to claim 1,
The effect of ambient light will be minimized, and high S /
The N ratio and the high-speed response are excellent. Further, when the final package is formed and sealed with resin, or when incident light is incident only from the front surface of the light receiving region, it is not necessary to seal even the side surfaces with resin. On the other hand, if a similar resin is used, a double mold is formed, and the molding of the package becomes extremely difficult, which can be prevented.

[0018]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a schematic sectional view of a light receiving element which is an optical semiconductor device showing a first embodiment of the invention according to claim 1. The light-receiving element chip F of the light-receiving element comprises a low-resistance N-type semiconductor silicon substrate 1, and a high-resistance N-type semiconductor region 2 of the same conductivity type as that of the silicon substrate 1 is formed on the silicon substrate 1 by epitaxial growth. ˜40 μm formed. The specific resistance used was 100 to 300 Ω · cm. Furthermore, in the N-type semiconductor region 2, an impurity boron is doped to form a P-type semiconductor region having a conductivity type different from that of the N-type semiconductor region 2, and the P-type semiconductor region is configured as the light receiving region 3. Has been done. The light receiving area 3 is
The anode electrode portion 4 is connected to the anode electrode portion 4 while having a diameter of 500 μm and alloyed with aluminum.

The light-receiving element chip F thus formed is mounted on the stem 5, and the back surface of the chip and the external extraction pin are short-circuited, and the external extraction pin serves as the cathode terminal 6. The anode electrode portion 4 is connected to an external extraction pin by an Au wire 7, and the external extraction pin serves as an anode terminal 8.

In the light-receiving element chip F, which is a feature of the present invention, the region other than the light-receiving region 3 has a light-shielding structure. That is, the side surface of the light receiving element chip F,
Outside the light receiving area 3 on the front surface (the upper surface in FIG. 1)
A coating material 9 made of an epoxy resin that is impermeable to light is coated so that the light is incident on the light receiving element chip F only from the front surface of the light receiving region 3. And
The light receiving element chip F is coated with the coating material 9 and then 16
It is baked and cured in a constant drying oven at around 0 ° C.

Therefore, for example, of the light emitted from the fiber, the light emitted only from the front of the light receiving region 3 enters the light receiving element chip F. As a result, in the conventional light-receiving element chip, there is photosensitivity in a wide area corresponding to twice the area of the light-receiving area and the reverse voltage 5
While a diffusion current component of about 30% was generated in addition to the drift current component generated in the depletion layer region under the application of V, according to the present invention, the diffusion current is reduced to 10% or less. We were able to. With this effect, the response time can be shortened by 10% or more, and the S / N ratio is improved.

FIG. 2 shows a second embodiment of the invention according to claim 2.

In the present embodiment, the covering material 9 is not formed around the light receiving element chip F used in the first embodiment, and the recessed portion 21 is formed in the Au-plated metal stem 20. is there.

Specifically, the recess 21 is formed to be larger and deeper than the light receiving element chip F (height 300 μm, 1 cm opening), for example, the depth is 300 μm and the diameter is 1.8.
It is formed to cm. The inner peripheral surface of the depression 21 is configured as the cathode electrode portion 22, and the depression 2
A light receiving element chip F is mounted inside the device 1. Other configurations are similar to those of the first embodiment.

Therefore, according to the second embodiment, when the final package is formed and sealed with resin, or when the incident light is incident only from the front surface of the light receiving region 3, the stem 20 can be easily processed. Since the light shielding structure can be formed, there is an advantage that the cost is low.

In the first and second embodiments,
It is needless to say that the peripheral portion of the light receiving region 3 on the surface of the light receiving element chip F may be shielded by two layers of aluminum or the like, and in this case, the high speed response and the S / N ratio can be improved. ..

[0028]

As described above, according to the first aspect of the present invention, by covering the area other than the light receiving area with the light non-transmissive resin coating material, the light is received from the area other than the light receiving area. Since it can be prevented from entering the chip,
No matter how the optical system changes, the influence of ambient light, which is the majority of the diffused current component, can be minimized, so that the high S / N ratio and high-speed response can be excellent. ..

Further, according to the invention of claim 2, the high speed response time and the S / N ratio can be improved similarly to the invention of claim 1, and at the same time, the light shielding can be performed at a low cost by a simple processing technique. Since it can be realized, its practical value is great.

Further, in the inventions according to claims 1 and 2, when the peripheral portion of the light receiving area on the chip surface of the light receiving element chip is shielded by two layers of aluminum or the like, a high response time and S
The / N ratio can be more effectively exhibited.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a light receiving element showing a first embodiment of the present invention.

FIG. 2 is a vertical sectional view of a light receiving element showing a second embodiment of the present invention.

FIG. 3 is a configuration diagram of an optical system using a conventional communication light receiving element.

FIG. 4 is an enlarged cross-sectional view of a conventional light receiving element.

[Explanation of Codes] 1 N-type semiconductor silicon substrate 2 N-type semiconductor region 3 Light-receiving region (P-type semiconductor region) 4 Anode electrode part 5, 20 Stem 6 Cathode terminal 7 Au wire 8 Anode terminal 9 Coating material 21 Cavity part F Light-receiving Element chip

Claims (2)

[Claims] 1. A low resistance semiconductor substrate, a high resistance semiconductor region of the same conductivity type formed on the low resistance semiconductor substrate, and a high resistance semiconductor region formed in the high resistance semiconductor region and different from the high resistance semiconductor region. In an optical semiconductor device including a light-receiving element chip formed of a light-receiving region formed of a conductive type semiconductor region, a light coating characterized in that a non-transparent resin coating material is formed around the light-receiving region. Semiconductor device. 2. A low resistance semiconductor substrate, a high resistance semiconductor region of the same conductivity type formed on the low resistance semiconductor substrate, a high resistance semiconductor region formed in the high resistance semiconductor region, and different from the high resistance semiconductor region. In an optical semiconductor device including a light-receiving element chip formed of a light-receiving region formed of a conductive semiconductor region, a concave depression portion at least deeper than the thickness of the light-receiving element chip is formed, and the light-receiving element chip is mounted in the depression portion. An optical semiconductor device characterized by being processed.