JPH0730208A - Semiconductor device - Google Patents

Abstract

PURPOSE:To provide a semiconductor device which has at least one light emitting element or light receiving element on the semiconductor substrate and allows highly sensitive detection by removing stray light component. CONSTITUTION:An insulated semiconductor island 15 is formed on the semiconductor substrate 1 of a semiconductor device which has at least one light emitting element 2 or a light receiving element 3 on the semiconductor substrate 1. On the semiconductor island, either the light emitting element 2 or the light receiving element 3 is formed, and the semiconductor island 15 is covered with a light shielding part 10 formed of a material which has a larger light absorption coefficient for the emission wavelength of the light emitting element 2 than that of the semiconductor substrate 1 (for example, metals 4 such as W and Al). Thus, a semiconductor is provided with a structure which optically isolates the light emitting element from the light receiving element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device in which a light emitting element and a light receiving element are integrated on a semiconductor substrate, and more particularly to a structure for optically separating the light emitting element and the light receiving element.

[0002]

2. Description of the Related Art As a conventional semiconductor device, for example, "II-II-Journal of Quantum" is used.
Electronics (IEEE Journal of Quntum Electroni
cs, QE-16, pp1044-1047, 1980) ”. FIG. 8 is a perspective view of the above device. In FIG. 8, 2 is a light emitting portion (for example, a semiconductor laser), and 3 is a light receiving portion (for example, a photodiode). In the device as shown in FIG. 8, when the light emission of the light emitting element is spontaneous emission, light is emitted in all directions. Even in the case of stimulated emission, the confinement of light in the lateral direction is not perfect, so that light is emitted in directions other than the desired direction. Further, since the light is emitted to both sides in the vertical direction, the forming direction is limited when integrating a plurality of lasers. The emitted light affects the light receiving element for the following reasons. That is, when the emission wavelength of this light emitting element is longer than the basic absorption edge of the semiconductor substrate,
Since the semiconductor substrate becomes transparent to the light, the light from the light emitting element reaches the light receiving element with almost no absorption. Since the sensitivity region of the light receiving element normally includes the light emission wavelength of the light emitting element, the light receiving element operates with the above-mentioned direct incident light.

[0003]

When the purpose of the light receiving element is to directly monitor the light of the light emitting element as in the example shown in FIG. 8, it is not necessary to optically separate the two. In a reflective sensor or the like that irradiates an object with light from a light emitting element and detects the reflected light, it is desired to reduce the influence of direct light from the light emitting element as much as possible. However, conventionally, it was difficult to sufficiently remove the influence of direct light. As described above, in the conventional semiconductor device in which the light emitting element and the light receiving element are integrated, since the light emitting element and the light receiving element are not structured to be optically separated from each other, there are many stray light components and highly sensitive detection is possible. There was a problem that it was impossible.

The present invention has been made in order to solve the problems of the prior art as described above, and an object of the present invention is to provide a semiconductor device capable of detecting with high sensitivity by removing stray light components.

[0005]

In order to achieve the above object, the present invention is constructed as described in the claims. That is, in the invention described in claim 1, a semiconductor island electrically insulated from other portions by a dielectric film, and a substance having a light absorption coefficient at a light emission wavelength of a light emitting element larger than that of the semiconductor substrate, A light-shielding portion having a shape that covers at least one surface of the semiconductor island is formed on the semiconductor substrate, and only one of the light emitting element and the light receiving element is formed on one semiconductor island. . In the invention according to claim 2, the light shielding portion is also insulated from other portions by the dielectric film.

[0006]

As described above, in the present invention, only one of the light emitting element and the light receiving element is formed on the insulated semiconductor island, and the semiconductor island has the light absorption coefficient at the emission wavelength of the light emitting element. Larger substances (eg W or A
It is covered with a light-shielding part made of metal such as 1). Therefore, the direct light from the light emitting element is not absorbed or reflected by the light shielding portion and does not reach the light receiving element, which enables highly sensitive detection. When the emission wavelength of the light emitting element is shorter than the basic absorption edge of the semiconductor substrate, the light of the light emitting element is absorbed by the semiconductor substrate, so there is little fear that the light from the light emitting element directly reaches the light receiving element. However, when light is absorbed by the semiconductor substrate, there is a possibility that a photocurrent is induced in the semiconductor substrate, and this photocurrent becomes noise of the light receiving element, which substantially lowers the sensitivity. However, if the light shielding portion is covered with the dielectric film and insulated as described in claim 2, the photocurrent generated in the light shielding portion becomes heat in the light shielding portion even when the light emitting element is formed in the semiconductor island. Disappears and does not affect the light receiving element. If the light receiving element is formed on a semiconductor island,
The semiconductor island is electrically isolated from other parts by the dielectric film,
Since it is not affected by the photocurrent, the light shielding portion does not necessarily have to be covered with the dielectric film. If the metal of the light shielding portion is grounded, a better performance can be obtained.

[0007]

FIG. 1 is a diagram showing a first embodiment of the present invention.
(A) is a sectional view and (b) is a plan view. In FIG. 1, a p-type silicon substrate 1 has a light emitting portion 2, a light receiving portion 3,
The light shielding portion 10 is formed. The light emitting portion 2 is formed on the compound semiconductor thin film 9 formed on the semiconductor island 15 having a triangular prism shape (having a triangular cross section). The compound semiconductor thin film 9 may be formed by heteroepitaxial growth, or the “applied physics” may be used.
Letters (Applied Physics Letters 56 (24), 11 June1
990, pp2419-2421) ". Note that FIG. 1 shows an example in which a light emitting diode is used as the light emitting unit 2. Further, the light receiving section 3 is composed of a photodiode, and has an n-type cathode region 5 and a p-type anode region 6 formed therein. Further, in the light-shielding portion 10, the diamond-shaped groove as shown in FIG. 1 is filled with the metal 4, and the outer periphery is covered with the dielectric film 13. The method of forming the groove as described above is described in detail, for example, in Japanese Patent Application Laid-Open No. 1-124673. The metal 4 to be filled is W or A.
l or the like is suitable and is formed by the CVD method. Such a metal is a substance having a larger light absorption coefficient at the emission wavelength of the light emitting element than the silicon substrate 1. It is not necessary to completely fill the inside of the groove, and there is no problem even if there is a cavity in the center. Further, 7 is a metal electrode for wiring, and 8 is an interlayer insulating film. The metal electrode 7 on the light shielding portion 10 also shields the light from above the silicon substrate 1. In the case of forming the semiconductor island 15 having the triangular prism shape as described above, the main plane of the semiconductor substrate is the {100} plane, the shape of the semiconductor island is the triangular prism, and the side surfaces thereof are the {111} plane and the {111} plane. }
It is formed by three planes, a plane and a {111} plane. Then, at least the {111} plane, that is, the portion facing the inside of the semiconductor substrate is formed so as to be covered with the light shielding unit 10.

Next, the operation will be described. Of the light emitted from the light emitting portion 2, the light to the upper portion proceeds as it is, but the light emitted to the lower portion and the lateral direction is reflected or absorbed by the light shielding portion 10 and the metal electrode 7 on the upper portion thereof. The reflected light is
Almost no light reaches the light receiving portion 3 because it is reflected again or emitted to the upper portion. Further, the semiconductor island 15 is the dielectric film 1
Since it is electrically separated from the substrate 1 by 3, the photocurrent generated in the semiconductor island 15 does not affect the light receiving element. Further, the light shielding part 10 and the metal electrode 7 on the upper part thereof also function as a reflector, and effectively guide the light upward in the substrate.

Next, FIG. 2 is a sectional view of a second embodiment of the present invention. In this embodiment, contrary to FIG.
5 is provided with the light receiving portion 3. Even when the light receiving element is formed in the semiconductor island 15 and the light emitting element is provided outside as described above, the light emitting element and the light receiving element can be optically separated as in FIG.

Further, when the light receiving element is formed on the semiconductor island as described above, the semiconductor island is electrically insulated from other portions by the dielectric film and is not affected by the photocurrent. Need not be covered with a dielectric film.

Next, FIG. 3 is a sectional view of a third embodiment of the present invention. This embodiment is an example in which the MOSFET 22 is integrated together. In this case, the cathode region 5 of the light emitting portion 2 is electrically isolated by the epitaxial layer 21 and the isolation region 11 so that the potential of each electrode of the diode can be independently determined.
In the MOSFET 22, 12 is a source / drain region and 14 is a gate electrode.

Next, FIG. 4 is a sectional view of a fourth embodiment of the present invention. In this embodiment, the semiconductor island 15 has a pentagonal cross section. A method for forming such a groove is described in detail in, for example, Japanese Patent Application Laid-Open No. 1-206970. When forming the pentagonal semiconductor island 15 as described above, the main plane of the semiconductor substrate is the {100} plane, the shape of the semiconductor island is the pentagonal prism, and the side surface thereof is parallel to the main plane. It is formed by five {111} planes and two {110} planes. Then, at least the {111} plane and the {110} plane of the semiconductor island, that is, the portion facing the inside of the semiconductor substrate is formed so as to be covered with the light shielding portion 10.

Next, FIG. 5 is a sectional view of a fifth embodiment of the present invention. This embodiment is an example in which a groove for forming the semiconductor island 15 is formed by isotropic etching.
In this case, as shown in the drawing, the groove has a circular cross-sectional shape. A method of manufacturing such a groove is described in, for example, “Extended Abstruct of 5th Interna- tional Workshop on Future Electron Devices”.
tional Workshop onFuture Electron Devices, 1988, p
p155-) ”.

Next, FIG. 6 is a sectional view of a sixth embodiment of the present invention. This embodiment is an example in which the present invention is applied to a reflection type photo sensor. In FIG. 6, the silicon substrate 1
Is housed in a package 16, and a window 19 for transmitting light is provided on the upper lid of the package 16.
A part of the light emitted from the light emitting unit 2 provided in the semiconductor island 15 is collimated by the lens 20, passes through the window 19, and then reaches the slit 18 provided outside. When incident on the opening of the slit 18, the light reaches the reflection plate 17 and is reflected. The light reflected by the reflection plate 17 passes through the window 19 again and enters the light receiving unit 3. When the light hits other than the opening of the slit 18, the light is not reflected and does not enter the light receiving unit 3. The position and displacement of the slit 18 are detected based on this difference. Note that FIG.
In this device, a plurality of light receiving elements are arranged in the light receiving section 3 at different positions, and even a slight displacement of the slit can be detected by the output signal of each light receiving element. Further, a light shielding portion 10 is provided around the light emitting portion 2, but the metal 4 of the light shielding portion 10 is connected to the metal electrode 7 so that the light is not applied to the portions other than the light emitting portion 2 and the light receiving portion 3. It has become.

Next, FIG. 7 is a diagram of a seventh embodiment of the present invention, in which (a) is a perspective view and (b) is a side view. This embodiment is a radar that measures the distance to the reflection plate 17 by the time required for the light emitted from the light emitting unit 2 including a semiconductor laser or the like to be reflected by the reflection plate 17 and return to the light receiving unit 3. It is an example in which the present invention is applied to. Since the light of one light emitting element is weak, in this embodiment, the light emitting unit 2
A large number of light emitting elements are provided in the
It is configured to be radiated toward. Further, the light receiving portion 3 is formed inside the semiconductor island surrounded by the light shielding portion 10. In FIG. 7, the light from the light emitting unit 2 spreads radially and is reflected by the reflection plate 17 to further spread and return. However, for the sake of illustration, the distance between the substrate 1 and the reflection plate 17 is small. Because it is narrow, the spread of the luminous flux is exaggerated.

In the above description, an example using a silicon substrate has been described, but another semiconductor substrate such as GaAs may be used. In that case, it is not necessary to use heteroepitaxial or bonding, and all elements may be formed on the same substrate. Further, even when a silicon substrate is used, when a structure emitting light like porous silicon is formed, both the light emitting element and the light receiving element may be formed on the silicon substrate.

Further, in the present invention, when the light-shielding portion is formed around the light emitting element, the shape thereof serves as a reflector, so that the substantial light output of the light emitting element can be greatly improved. In addition, there is an advantage that a high heat dissipation effect can be obtained by forming the light shielding portion with a metal having a higher thermal conductivity than that of the semiconductor.

[0018]

As described above, according to the present invention, a semiconductor island insulated from the other is formed on a semiconductor substrate, and only one of a light emitting element and a light receiving element is formed on one semiconductor island. In addition, since the semiconductor island is covered with the light shielding portion, direct light from the light emitting element is not absorbed or reflected by the light shielding portion and does not reach the light receiving element, which enables highly sensitive detection. When the light shielding portion is covered with the dielectric film and insulated as described in claim 2, the photocurrent generated in the light shielding portion disappears as heat in the light shielding portion and affects the light receiving element. Is eliminated, so that it is possible to obtain an effect that detection with higher sensitivity becomes possible.

[Brief description of drawings]

FIG. 1 is a first embodiment of the present invention, in which (a) is a sectional view and (b) is a plan view.

FIG. 2 is a sectional view of a second embodiment of the present invention.

FIG. 3 is a sectional view of a third embodiment of the present invention.

FIG. 4 is a sectional view of a fourth embodiment of the present invention.

FIG. 5 is a sectional view of a fifth embodiment of the present invention.

FIG. 6 is a sectional view of a sixth embodiment of the present invention.

FIG. 7 is a seventh embodiment of the present invention, (a) is a perspective view, (b) is a side view.

FIG. 8 is a perspective view of an example of a conventional device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Silicon substrate 12 ... Source / drain region 2 ... Light emitting part 13 ... Dielectric film 3 ... Light receiving part 14 ... Gate electrode 4 ... Metal 15 ... Semiconductor island 5 ... Cathode region 16 ... Package 6 ... Anode region 17 ... Reflector 7 ... Wiring metal electrode 18 ... Slit 8 ... Interlayer insulating film 19 ... Window 9 ... Compound semiconductor thin film 20 ... Lens 10 ... Light shielding part 21 ... Epitaxial layer 11 ... Isolation region 22 ... MOSF
ET area

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location H01L 31/12 E 7210-4M H 7210-4M // H01L 31/10

Claims (4)

[Claims] 1. A semiconductor device having at least one light emitting element and at least one light receiving element formed on a semiconductor substrate, the semiconductor being formed on the semiconductor substrate and electrically insulated from other portions by a dielectric film. One of the semiconductor islands, and a light-shielding portion formed of a substance having a light absorption coefficient at the emission wavelength of the light-emitting element that is larger than that of the semiconductor substrate and having a shape covering at least one surface of the semiconductor islands. A semiconductor device, wherein only one of the light emitting element and the light receiving element is formed in the semiconductor device. 2. The semiconductor device according to claim 1, wherein the light shielding portion is made of a material having a light absorption coefficient at a light emission wavelength of the light emitting element that is larger than that of the semiconductor substrate, and covers at least one surface of the semiconductor island. And a semiconductor device electrically insulated from other portions of the semiconductor substrate by a dielectric film. 3. The main surface of the semiconductor substrate is a {100} surface, the shape of the semiconductor island is a triangular prism, and the side surfaces thereof are three surfaces of the main surface, the {111} surface and the {111} surface. And at least the {111} plane of the semiconductor island is covered with a light shielding portion made of a substance having a light absorption coefficient at the emission wavelength of the light emitting element that is larger than that of the semiconductor substrate. The semiconductor device according to claim 1 or 2. 4. The main plane of the semiconductor substrate is a {100} plane, the shape of the semiconductor island is a pentagonal prism, and the side surfaces thereof are the main plane, two {111} planes and two {110} planes. And at least the {111} plane and the {110} plane of the semiconductor island are light-shielding portions made of a substance having a light absorption coefficient at the emission wavelength of the light-emitting element that is larger than that of the semiconductor substrate. The semiconductor device according to claim 1, wherein the semiconductor device is covered.