JPH07297480A - Optical semiconductor device - Google Patents

Abstract

PURPOSE:To provide an optical semiconductor device capacitor element with no in its structure. CONSTITUTION:An N-type semiconductor substrate 12 has a flat part 18 and slant parts 14, 16, and an insulating layer 20 are formed on the upper surface. A P-type region 26 for constituting an optical detector is formed on the slant part 14. A P<+> type region 27 of high concentration is formed in a part of the P-type region 26. An electrode 28 which is directly in contact with the P<+> region 27 is formed. The N-type semiconductor substrate 12, the P-type region 27, the P<+> region 27, and the electrode 28 constitute an optical detector. A semiconductor laser element 32 which emits light against the slant part 14 is formed on the insulating layer 20 of a flat part 18, via an electrode 30 for element mounting. A metal film 22 which partly reflects light is formed on the insulating layer 20 of the slant part 14. The metal film 22 is directly in contact with an N<+> region 24 of high concentration which is formed in a part of the flat part 18 of the N-type semiconductor substrate 12, via a contact hole 25.

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 used for optical recording, optical communication, optical measurement and the like.

[0002]

2. Description of the Related Art An example of a conventional optical semiconductor device is Japanese Patent Publication No. Sho 61.
No. 6558. The structure is shown in FIG. As shown in FIG. 4, a V groove 103 is formed in the n-type semiconductor submount substrate 102. An insulating layer 104 is formed on the submount substrate 102 on the left side of the V groove 103, and a semiconductor laser element 106 is mounted thereon. A p-type layer 108 and a p-side electrode 110 are provided on the submount substrate 102 on the right side of the V groove 103. The insulating layer 11 is formed on the slope on the right side of the V groove 103.
2 and a metal layer 114 for reflecting laser light are provided. An n-side electrode 116 is provided on the lower surface of the submount substrate 102.
Is provided. This structure is a copper heat sink 11
It is installed on top of 8.

The light emitted from the semiconductor laser element 106 is incident on the metal layer 114 formed on the slope of the V groove 103, and a part thereof is reflected there to travel upward. The rest passes through the metal layer 114 and the insulating layer 112 and enters the p-type layer 108. As a result, a current is generated according to the intensity of the incident light on the p-type layer 108. Current is p-side electrode 110 and n-side electrode 1
The intensity of light that is extracted through 16 and enters the p-type layer 108 is obtained based on the current value. With this configuration, a compact optical semiconductor device having a function of monitoring the output of the light source without disturbing the oscillation mode of the light source is realized.

[0004]

However, this configuration has the following problems. As can be seen from FIG. 4, the metal layer 114 includes the insulating layer 112 and the submount substrate 1
It is formed on 02. Moreover, the metal layer 114 and the submount substrate 102 are insulated from each other. In FIG. 4, the lower end of the metal layer 114 is in contact with the submount substrate 102. However, as is well known, a mere junction between a metal and a semiconductor exhibits a rectifying action, so that the electric charges existing in the metal layer 114 are subordinate to each other. It cannot flow freely to the mount substrate 102. Thus, the metal layer 114 and the submount substrate 1
02 is substantially insulated. Therefore, the metal layer 11
4 and the submount substrate 102 form a capacitive element equivalent to a parallel plate capacitor. This capacitive element deteriorates the accuracy of photodetection that captures a weak signal as a parasitic capacitance, or causes the accumulated charge to be discharged at once due to some cause to destroy the semiconductor light source. Therefore, it is desirable that such a capacitive element does not exist in the structure. An object of the present invention is to provide an optical semiconductor device having no capacitive element inside a structure.

[0005]

An optical semiconductor device according to the present invention includes a semiconductor substrate having a flat portion and an inclined surface portion having an inclined surface with respect to the flat portion, and a photodetector formed on the inclined surface portion. An insulating layer that covers the photodetector, a light emitting element that is disposed on a flat portion that emits light toward the slope, and an insulating layer that covers the photodetector. The semiconductor substrate is formed through ohmic contact. And a metal film that is electrically connected to the metal film and reflects the light emitted from the light emitting element.

Another optical semiconductor device according to the present invention includes a semiconductor substrate having a flat portion and an inclined surface portion having a surface inclined to the surface, a photodetector formed on the inclined surface portion, and a photodetector. An insulating layer that covers, a light emitting element that is arranged on a flat portion that emits light toward the slope, and an insulating layer that covers the photodetector, and is electrically connected to the photodetector. And a metal film that reflects the light emitted from the light emitting element.

[0007]

In the present invention, the metal film is electrically connected to the semiconductor substrate or the photodetector. Therefore, the electric charges existing in the metal film can freely flow to the semiconductor substrate or the photodetector, so that the metal film does not constitute a capacitive element. As a result, an optical semiconductor device having high signal detection sensitivity and high reliability can be realized.

[0008]

EXAMPLE A first example of an optical semiconductor device of the present invention will be described with reference to FIG. The n-type semiconductor substrate 12 has a concave portion formed by anisotropic etching or the like, and has a flat portion 18
And slope portions 14 and 16. An insulating layer 20 is formed on the upper surface of the semiconductor substrate 12 to insulate the semiconductor laser element 32 from the semiconductor substrate 12 and to prevent a short circuit of the pn junction due to the metal film 22.

On the slope 14 of the n-type semiconductor substrate 12, a p-type region 26 for forming a photodetector is formed by ion implantation or the like. A contact hole 29 is formed in the insulating layer by etching by photolithography or the like, and ion implantation is further performed using the insulating layer as a mask to form ap + region 27. This contact hole 29
A metal electrode 28 is provided to cover the insulating layer 20 so as to cover the insulating layer 20. That is, the electrode 28 is electrically connected to the p + region 27 through the contact hole 29 formed in the insulating layer 20. These are the n-type semiconductor substrate 12 and the p-type region 2.
6, p + region 27 and electrode 28 work together to form p-type region 26
It constitutes a photodetector that outputs a signal corresponding to the intensity of the light incident on.

The insulating layer 20 covering the flat portion 18
An electrode 30 for mounting a device is provided on the semiconductor laser device 32, and a semiconductor laser device 32 is provided on the electrode 30 via a solder material not shown.
Are joined so as to emit light toward the slope 14.

Insulating layer 20 covering the slope portion 14
A metal film 22 that reflects a part of the light emitted from the semiconductor laser element 32 is provided on the above. Metal film 2
2 is an electrically conductive high-concentration n + region 24 formed in a part of the flat portion 18 of the n-type semiconductor substrate 12 through a contact hole 25 formed in the insulating layer 20 covering the high-concentration n + region 24. Is in contact with.

The n + region 24 and the p + region 27 are not limited to the ion implantation. For example, when the n-type region is silicon, gold (Au) or aluminum (Al) which easily diffuses into the silicon is used as an electrode or a metal film. It can be provided by using. By covering the contact holes with these metals and then heat treating them at 100 ° C. to 300 ° C., the metal ions diffuse into the n or p type regions, and the high concentration n + regions 24 and p + regions 27 are formed. When formed, ohmic contact is realized.

The light emitted from the semiconductor laser device 26 is incident on the metal film 22 and a part of the light is reflected by the metal film 22.
As shown by the reference numeral 34, it is directed upward and is used for a device (not shown). In addition, part of the metal film 22 and the insulating layer 2
The light passes through 0 and enters the p-type region 26. As described above, the metal film 22 is formed to have a thickness that reflects a part of the light emitted from the semiconductor laser element 26 and transmits a part of the light. The thickness depends on the material, for example, in the case of gold, 100
It can range from 0 to 4000 Angstroms. The light incident on the p-type region 26 causes an external circuit connected to the electrode 28 to generate a current according to its intensity.
Therefore, by examining the current flowing through the electrode 28, the intensity of light incident on the p-type region 26 can be determined. That is, a part of the light emitted toward the other device is directly monitored.

Here, the advantage of directly monitoring a part of the light emitted toward another device will be described. As a general method of monitoring the emitted light of the semiconductor laser element, a method of monitoring the light emitted on the opposite side of the emitted light to be used (or the backward emitted light if the light to be used is the forward emitted light of the semiconductor laser element) There is. However, in this method, when a part of the light directed to another device returns to the semiconductor laser element, the amplification state of the light in the semiconductor laser element changes, and the ratio of the emitted light amount of the front and the rear changes. Therefore, the amount of light emitted from the front cannot be correctly monitored. In this embodiment, since a part of the front emission light is directly monitored,
Based on the transmittances of the metal film 22 and the insulating layer 20, it is possible to accurately monitor light traveling to another device.

According to the structure of this embodiment, the metal film 22 is n
The electric charge existing in the metal film 22 that is electrically connected to the semiconductor substrate 12 via the + region 24 can freely flow to the semiconductor substrate 12. Therefore, the metal film 22 and the p-type region 26 which face each other with the insulating layer 20 in between do not form a capacitive element. As a result, the electric charge accumulated for some reason does not flow into the semiconductor laser device 26 having a low withstand voltage and are destroyed. As a result, it is possible to obtain a highly reliable optical semiconductor device capable of correctly monitoring the amount of light emitted from the semiconductor laser element 26.

A modified example of this embodiment is shown in FIG. In the figure, the same components as in the first embodiment are designated by the same reference numerals.
In this modification, the n + region 24 is provided not at the bottom of the metal film 22 but at a distant position. On the insulating layer 20 covering the n + region 24, an electrode 36 is provided which is in electrical contact with the n + region 24 through a contact hole formed in the insulating layer 20. The electrode 36 is connected via the wire 38.
It is electrically connected to the metal film 22. With this configuration, the same effect as that of the first embodiment can be obtained.

A second embodiment of the optical semiconductor device of the present invention is shown in FIG.
Will be explained. In FIG. 3, members equivalent to those in the first embodiment are designated by the same reference numerals, and detailed description of each member will be omitted by referring to the description of the first embodiment.

Here, the difference from the first embodiment will be described with reference to FIG. No n + region is formed in the semiconductor substrate 12, and no contact hole for contacting the metal film 22 and the semiconductor substrate 12 is formed in the insulating layer 20. That is, the metal film 22 and the semiconductor substrate 12 are electrically isolated by the insulating layer 20. Instead, a part of the metal film 22 is located on the electrode 28, and the metal film 22 is electrically connected to the p-type region 26 via the p + region 27.

The metal film 22 is formed so as to have a thickness smaller than the spread of the light emitted from the semiconductor laser element 26 and to completely reflect the light. The thickness depends on the material, and is, for example, 4000 angstroms or more in the case of gold.

In the light emitted from the semiconductor laser element 26, since the metal film 22 is smaller than the spread of the emitted light, only a part near the center is reflected by the metal film 22 and is directed upward as indicated by reference numeral 34. And used for a device not shown. The light outside the metal film 22 passes through the insulating layer 20 and enters the p-type region 26. p-type region 2
The light incident on 6 is transmitted to the external circuit connected to the electrode 28.
A current is generated according to the strength. Therefore, by examining the current flowing through the electrode 28, the intensity of light incident on the p-type region 26 can be determined. That is, a part of the light emitted toward the other device is directly monitored.

In this embodiment, the metal film 22 is composed of the electrodes 28 and p.
Since it conducts to the p-type region 26 via the + region 27,
The metal film 22 and the p-type region 26 which face each other with the insulating layer 20 in between.
Does not form a capacitive element. Therefore, no charges are accumulated around the metal film 22. As a result, it is possible to obtain a highly reliable optical semiconductor device capable of correctly monitoring the amount of light emitted from the semiconductor laser element 26.

Since the device of this embodiment does not have an n + region, there is an advantage that the number of manufacturing steps required for forming the n + region is smaller than that in the first embodiment. The optical semiconductor device of the present invention has been described above based on the embodiments, but the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention.

For example, although the n-type semiconductor substrate is used in all of the above-mentioned embodiments, a p-type semiconductor substrate may be used. In this case, the p-type region for forming the photodetector is n
The function and effect are the same only in the type diffusion region.

The summary of the present invention is summarized as follows. (1) A semiconductor substrate having a flat portion and a sloped portion having a surface inclined to the surface, a photodetector formed on the sloped portion, an insulating layer covering the photodetector, and a flat portion on the flat portion. The light emitting element, which is arranged and emits light toward the slope, and the light emitting element, which is formed on the insulating layer that covers the photodetector and is electrically connected to the semiconductor substrate through ohmic contact, emits the light. An optical semiconductor device comprising: a metal film that reflects light.

The first embodiment (FIGS. 1 and 2) corresponds to this. According to this structure, since the metal film is electrically connected to the semiconductor substrate by ohmic contact, it does not form a capacitive element, and therefore electric charges are not accumulated in the metal film. As a result, a highly sensitive and highly reliable optical semiconductor device can be obtained.

(2) An optical semiconductor device according to the above item (1), wherein the semiconductor substrate has a high concentration impurity region of the same type, and the metal film is electrically connected to the high concentration impurity region. The ohmic contact is realized by electrically connecting the metal film and the semiconductor substrate via the high concentration impurity region.

(3) The optical semiconductor device according to the above item (2), wherein the metal film is in direct contact with the high concentration impurity region. The configuration of FIG. 1 corresponds to this.

(4) An optical semiconductor device according to the item (2), wherein the metal film is electrically connected to the high concentration impurity region through a conductive member. The configuration of FIG. 2 corresponds to this.

(5) A semiconductor substrate having a flat portion and a slope portion having a surface inclined to the surface, a photodetector formed on the slope portion, an insulating layer covering the photodetector, and the flat portion. The light emitting element, which is arranged on the top and emits light toward the slope, and the light emitted from the light emitting element, which is formed on the insulating layer covering the photodetector and is electrically connected to the photodetector. An optical semiconductor device including a metal film that reflects light.

The configuration of the second embodiment (FIG. 3) corresponds to this. Since the metal film is electrically connected to the photodetector, the metal film does not form a capacitive element, and therefore electric charges are not accumulated in the metal film. As a result, a highly sensitive and highly reliable optical semiconductor device can be obtained.

(6) An optical semiconductor device according to the item (5), wherein the metal film is electrically connected to the electrode of the photodetector. (7) The optical semiconductor device according to the item (6), wherein the metal film is in direct contact with the electrode.

(8) In the above item (6), the photodetector includes an impurity region formed on a slope portion of a type different from that of the semiconductor substrate and a high-concentration impurity region of the same type formed in the impurity region. An optical semiconductor device having an electrode of the photodetector electrically contacting the high concentration impurity region.

[0033]

According to the present invention, since the capacitive element does not exist inside the structure, an optical semiconductor device having high signal detection sensitivity and high reliability can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of an optical semiconductor device of the present invention.

FIG. 2 is a sectional view showing a modified example of the first embodiment.

FIG. 3 is a sectional view showing a second embodiment of an optical semiconductor device of the present invention.

FIG. 4 is a cross-sectional view showing a conventional optical semiconductor device.

[Explanation of symbols]

12 ... N-type semiconductor substrate, 14 ... Slope portion, 18 ... Flat portion,
20 ... Insulating layer, 22 ... Metal film, 24 ... N + region, 26 ...
p-type region, 32 ... Semiconductor laser device.

Claims (3)

[Claims] 1. A semiconductor substrate having a flat portion and a slope portion having a surface inclined to the surface, a photodetector formed on the slope portion, an insulating layer covering the photodetector, and a flat portion of the flat portion. The light emitting element, which is disposed above and emits light toward the slope, and the light emitting element, which is formed on the insulating layer that covers the photodetector and is electrically connected to the semiconductor substrate through ohmic contact, An optical semiconductor device comprising: a metal film that reflects emitted light. 2. The optical semiconductor device according to claim 1, wherein the semiconductor substrate has high-concentration impurity regions of the same type, and the metal film is electrically connected to the high-concentration impurity regions. 3. A semiconductor substrate having a flat portion and a slope portion having a surface inclined to the surface, a photodetector formed on the slope portion, an insulating layer covering the photodetector, and a flat portion of the flat portion. Light emitted from the light emitting element, which is formed on the light emitting element that emits light toward the sloped portion arranged above and the insulating layer that covers the photodetector and is electrically connected to the photodetector, is provided. An optical semiconductor device comprising a reflective metal film.