JP2002353491A - Semiconductor light-receiving element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor light-receiving element that can prevent unwanted stray light from entering a light-receiving element for detecting signal light, and can reduce the mixture of an output signal due to signal light and a signal due to the unwanted stray light. SOLUTION: In the semiconductor light-receiving element, at least one step section is formed on the main surface of a semiconductor substrate via a slope, and a first light-receiving element for detecting signal light is formed on the optical axis of the signal light, on the bottom surface at the step section.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light receiving element used for optical information processing, optical measurement, optical communication, and the like.

[0002]

2. Description of the Related Art In the field of optical devices such as optical information processing, optical measurement, and optical communication, signal light is generally detected by a light receiving element, and a photocurrent from the light receiving element is used as a detection signal. FIG. 7 schematically shows an optical pickup device as an example of a system using a conventional light receiving element for signal light detection. In FIG. 7, 1 is a semiconductor substrate, 4 is a P-type diffusion region, 5 is a PN junction, and 6 is (first)
A light receiving element, 7 is a photocurrent, 8 is a signal light, 9 is an optical axis of the signal light, 10 is a stray light, 19 is a semiconductor laser element, 20 is a laser light, 21, 23, and 26 are lenses, 22 is a half mirror, and 24 Is an optical disk.

The operation of the optical pickup device shown in FIG. 7 will be briefly described. Laser light 20 emitted from a semiconductor laser element 19 is divided into a half mirror 22 and a lens 2.
The information is condensed and irradiated on the optical disc 24 via 3 and the information recorded on the optical disc 24 is detected. Then, the laser beam 20 reflected again from the optical disk 24 is
3. After passing through the half mirror 22, the light enters the (first) light receiving element 6 via the lens 26 and is detected as an optical signal. In the (first) light receiving element 6 shown in FIG. 7, the cross-sectional structure is such that the P-type diffusion region 4 is formed in the N-type semiconductor substrate 1.
And a PN junction 5 is formed to function as a light receiving element.

The (first) light reflected from the optical disk 24
The signal light 8 incident from the surface of the light receiving element 6 generates a carrier of an electron-hole pair in the semiconductor crystal, and the carrier is extracted as a photocurrent 7 to be used as a detection signal. The light incident on the light receiving element surface is
Light is incident to a depth determined by the wavelength of light, the semiconductor impurity concentration, the reflectivity of the semiconductor surface, and the like, and electron-hole pair carriers are generated everywhere up to the incident depth.

[0005]

However, the above-mentioned conventional configuration has the following problems. In the optical pickup device configured as shown in FIG. 7, the laser beam 20 emitted from the semiconductor laser
4, the laser light 20 is not reflected on the (first) light receiving element 6 as the signal light 8 but is entirely incident on the (first) light receiving element 6.
In the various processes until the light enters the light receiving element 6), reflected light is generated on the surface of the optical component or the like, and the reflected light is irregularly reflected at various other places. For this reason, unnecessary light other than the signal light 8 called the stray light 10 is flying in various directions in the optical pickup device.

As shown in FIG. 7, a conventional light receiving element has a P near the surface of a semiconductor substrate 1 having a function as a light receiving element.
Since the N-junction 5 is formed, the stray light 10 flying in various directions has a shape and a position where it is easy to enter. When the unnecessary stray light 10 is incident on the (first) light receiving element 6, an unnecessary photocurrent is generated, and although the photocurrent only from the signal light 8 is originally desired to be used as the detection signal, it is unnecessary for the detection signal. The signals due to the stray light 10 will be mixed. If an unnecessary signal due to such stray light 10 is included in the detection signal, an optical pickup device that uses the light detection signal as a servo signal and a read signal for recording information on the optical disk may cause a servo malfunction, erroneous reading of the optical disk recording information, and the like. It becomes a factor.

[0007] Such stray light, which is a source of unnecessary photocurrent, is found in various optical device devices other than the above-described optical pickup device, and may adversely affect optical signal detection.

An object of the present invention is to solve the above-mentioned conventional problems and to provide a light receiving element for reducing unnecessary stray light from being incident on a light receiving element for detecting signal light. .

[0009]

In order to achieve the above object, a first semiconductor light receiving element of the present invention has at least one step (recess) formed on a principal surface of a semiconductor substrate via a slope. A first light receiving element for detecting the signal light is formed on the optical axis of the signal light on the bottom surface of the step portion.

As described above, the light receiving element for detecting the signal light for detecting the signal light is formed on the bottom of the stepped portion at a position deeper than the surface of the semiconductor substrate, so that the light receiving element is conventionally formed near the surface of the semiconductor substrate. The stray light that is likely to be incident on the light receiving element for signal light detection is less likely to be incident on the light receiving element for signal light detection, and it is possible to reduce the possibility that the signal due to unnecessary stray light is mixed with the detection signal of the signal light. .

Further, a second semiconductor light receiving element according to the present invention comprises:
At least one step (recess) is formed on the main surface of the semiconductor substrate via a slope, and a first light receiving element for detecting the signal light is provided on the optical axis of the signal light on the bottom of the step. A second light receiving element not intended to detect the signal light is formed on the slope of the stepped portion which is formed and is not on the optical axis of the signal light.

As described above, in addition to the first light receiving element for detecting signal light formed on the bottom surface of the step, the second light receiving element not intended for detecting the signal light is also formed on the slope of the step. Unnecessary carriers generated by the stray light incident on the surface of the semiconductor substrate are absorbed by the second light receiving element and output as an output signal different from a detection signal from the first light receiving element, so that the first light receiving element It is possible to further reduce mixing of a signal due to unnecessary stray light with a detection signal of the signal light from the camera.

Further, in the semiconductor light receiving element of the present invention, the bottom surface of the step portion is provided at a position deeper than a maximum depth at which carriers generated by light vertically incident from the main surface of the semiconductor substrate are diffused. It is characterized by.

Thus, it is possible to minimize the influence of the signal light exerted by the carrier due to the stray light on the output signal.

Further, in the semiconductor light receiving element of the present invention, light from the first light receiving element and the second light receiving element is provided on the same semiconductor substrate as the first light receiving element and the second light receiving element. At least one circuit for detecting a current as a signal is formed.

As described above, by forming a light receiving element and a circuit section for inputting a photocurrent signal from the light receiving element on the same semiconductor substrate in the vicinity, the photocurrent signal is input to a signal processing circuit such as an amplifier circuit. By this time, it becomes difficult for noise to ride, and the signal noise level can be reduced.

Further, in the semiconductor light receiving device of the present invention, a second step portion is further formed on the same semiconductor substrate surface as the step portion on which the light receiving element is formed, and the second step portion has a bottom surface portion. The semiconductor laser device is provided. The slope forming the second step is
The light emitted from the semiconductor laser element is used as a mirror for reflecting the light, and the light emitted from the semiconductor laser element is used as a light source.

As described above, by arranging the semiconductor laser element and the first light receiving element for detecting signal light on the same semiconductor substrate, the light source as signal light, the light receiving element, the signal amplifying circuit and the like can be modularized. It becomes possible.

Further, the optical system of the present invention comprises the above-mentioned semiconductor light receiving element and at least one kind of optical component selected from an optical disk, an optical lens, an optical member for converting light into a wavefront, a reflecting mirror, a prism and a semiconductor laser element. Are arranged.

As described above, by arranging optical components such as lenses on a semiconductor substrate in which a light receiving element and a circuit forming portion are formed on the same substrate and a semiconductor laser element, an optical pickup device can be easily obtained. Thus, a portion for detecting signal light can be formed, and information on signal light can be stably detected even in a situation where stray light or the like is likely to occur.

[0021]

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

(Embodiment 1) FIG. 1 is a configuration diagram of a semiconductor light receiving element according to a first embodiment of the present invention. FIG.
, 1 is a semiconductor substrate, 2 is a slope, 3 is a step portion, 4
Is a P-type diffusion region, 5 is a PN junction, 6 is a first light receiving element,
7, a photocurrent; 8, a signal light; 9, an optical axis of the signal light; and 10, a stray light.

In this embodiment, a step 3 is formed on the main surface of the semiconductor substrate 1 via the slope 2, and the signal light 8 is located on the optical axis 9 of the signal light on the bottom surface of the step 3. It is characterized in that a first light receiving element 6 for signal light detection for the purpose of detection is formed.

In the semiconductor light receiving element shown in FIG. 1, stray light 10 which has conventionally been easily incident on the signal light detecting light receiving element formed near the surface of the semiconductor substrate 1 is firstly formed on the bottom surface of the step portion 3. Before the light reaches the light receiving element 6, the light can easily enter the semiconductor substrate 1 from the slope 2 of the stepped portion 3.
It becomes difficult to enter the first light receiving element 6 for detecting the signal light 8.

For this reason, the stray light 10 is less likely to enter the first light receiving element 6 than in the prior art, so that the photocurrent due to the stray light 10 is reduced, and the stray light 1 unnecessary for the detection signal of the signal light 8 is reduced.
It is possible to reduce mixing of signals due to zero.

The step portion 3 as shown in FIG. 1 is formed by, for example, applying an etching mask such as an oxide film on the surface of the N-type silicon semiconductor substrate 1 and performing anisotropic etching with a potassium hydroxide-based etching solution or the like. Can be formed. After the formation of the step portion, the light receiving element can be formed by forming the P-type diffusion region 2 on the bottom surface of the step portion 3.

(Embodiment 2) FIG. 2 is a configuration diagram of a semiconductor light receiving element according to a second embodiment of the present invention. FIG.
, 11 is a carrier due to stray light, and 12 is a stray light 10
Is the maximum depth at which stray light 10 can enter and generate and diffuse carriers when vertically incident on the semiconductor substrate 1, and is the same as that in the configuration diagram according to the first embodiment shown in FIG. Are denoted by the same reference numerals, and detailed description is omitted.

In this embodiment, when the stray light 10 of the wavelength used as a light source is vertically incident from the main surface of the semiconductor substrate 1, the stray light 10 enters and generates and diffuses the carriers 11 at the maximum. The bottom surface of the step portion 3 and the first light receiving element 6 are formed at a position deeper than the depth 12.

As described in the conventional problem, the stray light 10
Various irregular reflections occur in the optical device. Therefore, the stray light 10 naturally enters the semiconductor substrate from the surface of the semiconductor substrate 1 and generates carriers 11.

At this time, the stray light 10 penetrates the deepest into the semiconductor substrate when the stray light 10 is perpendicularly incident on the main surface of the semiconductor substrate 1, and the light wavelength, the semiconductor impurity concentration, the semiconductor surface To a depth determined by the reflectivity of the substrate and generate carriers.

The carriers 11 caused by the stray light 10 incident from the surface of the semiconductor substrate 1 naturally diffuse inside the semiconductor substrate 1 until they are recombined. If the carrier 11 due to the stray light 10 incident from the surface of the semiconductor substrate 1 is absorbed by the first light receiving element 6 and is output as the photocurrent 7, the stray light 1 unnecessary for the detection signal of the signal light 8 is naturally obtained.
The signals due to 0 are mixed, which has an adverse effect on optical signal detection.

In the present embodiment, the carrier 11 generated by the stray light 10 incident from the surface of the semiconductor substrate 1 is located at a position deeper than the maximum depth 12 that can reach the inside of the semiconductor substrate 1 and the bottom of the step portion 3 and the second The formation of the first light receiving element 6 prevents the carrier 11 from reaching the first light receiving element 6 for detecting the signal light 8. Therefore, the influence of the signal light 8 on the output signal due to the carrier 11 due to the stray light 10 can be reduced to the maximum.

(Embodiment 3) FIG. 3 is a configuration diagram of a semiconductor light receiving device according to a third embodiment of the present invention. FIG.
In the figure, 13 is a second light receiving element, 14 is a photocurrent from the second light receiving element, 15 is a P-type diffusion region, which is located at the same position as in the configuration diagram according to the second embodiment shown in FIG. Are denoted by the same reference numerals, and detailed description is omitted.

In this embodiment, like the first semiconductor photodetector of the present invention, a step portion 3 is formed on the main surface of a semiconductor substrate 1 with a slope 2 interposed therebetween, and a signal surface is provided on the bottom surface of the step portion 3. A first light receiving element 6 for signal light detection is formed on the optical axis 9 of the light and intended to detect the signal light 8, and further, a slope located at a position not on the optical axis 9 of the signal light. 2, a second light receiving element 13 not intended to detect the signal light 8
Is formed.

As described in the second embodiment, the stray light 10 also enters the semiconductor substrate from the surface of the semiconductor substrate 1,
A carrier 11 is generated. In the present embodiment, the stray light 10 is generated by being incident from the surface of the semiconductor substrate 1,
In order to eliminate the influence of the carrier 11 on the first light receiving element 6, the second light receiving element 13 is formed on the slope 2 of the step 3 at a position not on the optical axis 9 of the signal light, and the semiconductor substrate 1 is formed. 1 due to stray light 10 floating and diffusing near the surface of
1 is absorbed by the second light receiving element 13. Carrier 11 due to stray light 10 absorbed by second light receiving element 13
Is externally output as a photocurrent 14 from the second light receiving element 13 and is distinguished from a detection signal by the photocurrent 7 from the first light receiving element 6. Similarly, the carrier generated by the stray light 10 incident from the slope 2 is also absorbed by the second light receiving element 13, so that the influence on the first light receiving element 6 can be reduced.

For this reason, it is possible to further reduce the mixing of the signal due to the unnecessary stray light 10 with the detection signal of the signal light 8 from the first light receiving element 6.

The light receiving element structure shown in the third embodiment is as follows.
Before forming the step portion 3 for forming the first light receiving element 6, a P-type diffusion region 15 for forming the second light receiving element 13 is embedded in the surface of the semiconductor substrate 1, and thereafter,
It can be formed by performing etching to form the step portion 3.

(Embodiment 4) FIG. 4 is a configuration diagram of a semiconductor light receiving device according to a fourth embodiment of the present invention. FIG.
In the figure, reference numeral 16 denotes a circuit forming portion, and the same portions as those in the configuration diagram according to the third embodiment shown in FIG.

In this embodiment, the photocurrents 7 and 14 from the first light-receiving element 6 and the second light-receiving element 13, respectively.
And a circuit for detecting the input signal, and a circuit forming section 1 having functions such as an amplifier circuit and an arithmetic circuit.
6 is formed on the same semiconductor substrate 1.

As described above, by forming a light receiving element and a circuit section for inputting a photocurrent signal from the light receiving element on the same semiconductor substrate 1, the photocurrent signal is input to a signal processing circuit such as an amplifier circuit. There is an advantage that noise becomes difficult to be taken by the time, and the signal noise level can be reduced. Further, the cost can be reduced as compared with the case where the light receiving element chip and the circuit chip as the external circuit are individually formed and combined.

(Embodiment 5) FIG. 5 is a configuration diagram of a semiconductor light receiving device according to a fifth embodiment of the present invention. FIG.
In FIG. 5, 17 is a second step portion, 18 is a slope, 19 is a semiconductor laser device, 20 is a laser beam, and FIG.
The same parts as those in the configuration diagram according to the fourth embodiment shown in FIG.

In this embodiment, a second step 17 is formed separately from the step 3 for forming the first light receiving element 6, and a semiconductor laser device is formed on the bottom of the second step 17. The laser light 20 emitted from the semiconductor laser element 19 is reflected by the slope 18 in a direction perpendicular to the semiconductor substrate 1.

As described above, by disposing the semiconductor laser element 19 and the first light receiving element 6 for detecting the signal light 9 on the same semiconductor substrate 1, a light source as signal light, a light receiving element,
The signal amplification circuit and the like can be made into a module, which has advantages such as cost reduction and simplification of alignment of optical components.

In order to emit the laser beam from the semiconductor laser device 19 in the direction perpendicular to the semiconductor substrate 1 as described above, the inclined surface 18 must be at 45 ° to the main surface of the semiconductor substrate 1.
A structure having a slight inclination is required. Such a substrate structure uses a (100) plane silicon semiconductor substrate having an off angle of 5 ° to 15 ° around the <110> direction as an axis of the semiconductor substrate 1, and using an etching mask such as an oxide film to form water. This is because a step having a (111) plane as a slope is formed by performing anisotropic etching with a potassium oxide-based etchant or the like. In this case, the slope 18 having an angle of 39 ° to 49 ° with respect to the main surface of the semiconductor substrate 1 can be formed. Further, in order to efficiently reflect the laser beam 20 on the slope 18,
A high-reflectance coating film (for example, A
u about 3000 °) is formed, and the reflectance is 99% or more. Further, by forming the solder plating on the bottom surface of the second step portion 17, the solder and the Au electrode of the semiconductor laser element 19 can be fused by heat, and the semiconductor laser element 19 can be fixed.

(Embodiment 6) FIG. 6 is a configuration diagram of a semiconductor light receiving device according to a sixth embodiment of the present invention. FIG.
, 23, and 26 are lenses, 22 is a half mirror, 24 is an optical disk, and 25 is a mirror, and the same reference numerals are given to the same portions as those in the other configuration diagrams according to the fifth embodiment shown in FIG. Therefore, detailed description is omitted.

In this embodiment, the lenses 21, 23, 26, the half mirror 22,
It is characterized in that at least one optical component such as an optical disk 24 and a mirror 25 is arranged.

As in this embodiment, the semiconductor substrate 1 in which the light receiving element 6 and the circuit forming portion 16 are formed on the same substrate and the semiconductor laser element 19 are integrated, and the semiconductor substrate 1 is provided on the signal light 8 incident side. By arranging optical components such as the lens 21, it is possible to easily form a portion for detecting signal light, such as an optical pickup device, and to stably transmit information on signal light even in a situation where stray light or the like is likely to occur. Can be detected.

In the above description of the embodiment of the present invention, a description has been given of a case where a P-type diffusion region is buried in an N-type silicon semiconductor substrate to form a PN junction and function as a semiconductor light receiving element. , The present invention relates to N
The invention is not limited to the type silicon semiconductor substrate, but is effective for all devices having a function as a light receiving element formed on a P type silicon semiconductor substrate, a compound semiconductor substrate, and the like. It was done.

In the embodiment of the present invention, for the sake of simplicity, a first light receiving element for detecting a signal light and a step portion for constituting the first light receiving element are shown in FIG. However, the present invention is also applicable to a case where a plurality of steps are formed and a light receiving element is formed in each of the steps.
As an embodiment in which a plurality of steps and a light receiving element are formed as described above, there is an optical system in which a detection signal light is divided into two or more signal lights by a diffraction element or the like.

The wavelength of the signal light is not particularly limited, but the present invention is applicable to a case where the wavelength is limited to a specific wavelength.

Further, the first light receiving element, the second light receiving element, the circuit forming section, and the semiconductor laser element are simply arranged on the semiconductor substrate.
In particular, the present invention is not limited to this, and may be in any positional relationship.

[0052]

As described above, in the semiconductor light receiving device of the present invention, a step is formed on the main surface of the semiconductor substrate through the slope, and the signal light is placed on the optical axis of the signal light on the bottom surface of the step. Since the first light receiving element for detecting the light is formed, the stray light that has been easily incident on the light receiving element for signal light detection formed near the surface of the semiconductor substrate in the past is converted to the signal light detection for signal light. It is possible to make it difficult to enter the first light receiving element.

Further, in addition to the first light receiving element for detecting the signal light, a stepped slope portion at a position not on the optical axis of the signal light is provided.
Since the second light receiving element not intended to detect signal light is formed, unnecessary carriers generated by stray light incident on the surface of the semiconductor substrate are absorbed by the second light receiving element, and the first light receiving element is used. By outputting the detection signal from the light receiving element as an output signal different from the detection signal, it is possible to reduce mixing of a signal due to unnecessary stray light with the detection signal of the signal light.

Therefore, it can be widely used for optical information processing, optical measurement, optical communication and the like, and its industrial value is great.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a semiconductor light receiving element according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a semiconductor light receiving element according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram of a semiconductor light receiving element according to a third embodiment of the present invention.

FIG. 4 is a configuration diagram of a semiconductor light receiving element according to a fourth embodiment of the present invention.

FIG. 5 is a configuration diagram of a semiconductor light receiving element according to a fifth embodiment of the present invention.

FIG. 6 is a configuration diagram of a semiconductor light receiving element according to a sixth embodiment of the present invention.

FIG. 7 is a configuration diagram of a conventional semiconductor light receiving element.

[Explanation of symbols]

Reference Signs List 1 semiconductor substrate 2 slope 3 stepped portion 4 P-type diffusion region 5 PN junction 6 first light receiving element 7 photocurrent 8 signal light 9 optical axis of signal light 10 stray light 11 carrier due to stray light 12 stray light enters and generates and diffuses carriers Maximum depth that can be performed 13 Second light receiving element 14 Photocurrent from second light receiving element 15 P-type diffusion region 16 Circuit forming part 17 Second stepped part 18 Slope 19 Semiconductor laser element 20 Laser light 21 Lens 22 Half mirror 23 Lens 24 Optical disk 25 Mirror 26 Lens

Continuing on the front page (72) Inventor Tetsuo Chato 1006 Kadoma Kadoma, Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. Reference) 5D119 AA20 BA01 CA10 FA05 FA25 JA07 JA43 KA02 KA23 LB04 LB05 5F049 MA02 MB02 NA04 NB01 NB07 NB08 QA20 RA07 TA20 5F088 AA02 AB03 BA03 BA16 BB10 EA09 EA11 GA07

Claims (6)

[Claims] At least one step portion is formed on a main surface of a semiconductor substrate via a slope, and a first light receiving portion for detecting the signal light is provided on an optical axis of the signal light on the bottom surface of the step portion. A semiconductor light receiving element, wherein the element is formed. 2. A method according to claim 1, wherein at least one step portion is formed on the main surface of the semiconductor substrate via a slope, and a first light receiving portion for detecting the signal light is provided on the optical axis of the signal light on the bottom surface of the step portion. A semiconductor light receiving element, wherein an element is formed and a second light receiving element not intended for detecting the signal light is formed on the slope of the stepped portion which is not on the optical axis of the signal light. 3. The stepped bottom surface is provided at a position deeper than a maximum depth at which carriers generated by light vertically incident from a main surface of a semiconductor substrate are diffused. 4. The semiconductor light receiving element according to claim 1. 4. At least for detecting a photocurrent from the first light receiving element and the second light receiving element as a signal on the same semiconductor substrate as the first light receiving element and the second light receiving element. 4. The semiconductor light receiving device according to claim 1, wherein one circuit is formed. 5. A semiconductor device comprising: a second step portion formed on the same semiconductor substrate surface as the step portion on which the light receiving element is formed; and a semiconductor laser device disposed on the bottom surface of the second step portion. The semiconductor light-receiving element according to claim 1, wherein: 6. The semiconductor light-receiving element and at least one kind of optical component selected from an optical disk, an optical lens, an optical member for converting light into a wavefront, a reflection mirror, a prism, and a semiconductor laser element. Optical system.