JP2697081B2 - Semiconductor light receiving device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] Regarding a semiconductor light receiving device, there is provided a semiconductor light receiving device having sensitivity to infrared rays, particularly infrared rays in a long wavelength band of 8 to 14 μm, and having a large number of pixels using a GaAs superlattice. For the purpose of providing, a groove including a sub-plane having an inclination of a predetermined angle with respect to a main plane perpendicular to a predetermined crystal axis direction of the semiconductor substrate,
Alternatively, a hole is provided and a superlattice is provided at least on the sub-plane.

[Industrial applications]

The present invention relates to a semiconductor light receiving device, and more particularly to infrared light, particularly 8 to 14 light receiving devices.
The present invention relates to a semiconductor light receiving device having sensitivity to infrared rays in a long wavelength band of μm and having a large number of pixels using a GaAs superlattice.

2. Description of the Related Art Along with recent advances in semiconductor processing technology, a light receiving device having a large number of pixels based on a silicon (Si) charge transfer device (CCD) has been developed as a semiconductor light receiving device for imaging visible light. It can also be used as a light-receiving device for imaging the infrared region.
In a Schottky junction type charge transfer device using Si as a material and a Schottky junction between the Si and a metal such as platinum, a light receiving device with multiple pixels has been developed. But
This Si Schottky junction type light receiving device is sensitive only to infrared rays in the 3 to 5 μm band, is sensitive to long wavelength infrared rays in the 8 to 14 μm band, and is a two-dimensional light receiving device with multiple pixels. There is a request.

In addition, the one-dimensional light receiving device mounted on a satellite has sensitivity to infrared rays in the 8 to 14 μm band for the purpose of resource exploration,
There is a demand for an infrared light receiving device having a long dimension of about 2000 to 4000 pixels.

[Conventional technology]

As a conventional infrared light receiving device, materials having sensitivity to infrared rays in the 8 to 14 μm band include extrinsic Si in which gallium (Ga) or magnesium (Mg) is added to Si at a high concentration, lead / tin / tellurium (PbSnTe). , And mercury / cadmium / tellurium (Hg _1-x Cd _x Te). Among them, an infrared light receiving device using Hg _1-x Cd _x Te as an infrared detecting material has the highest performance.

However, even if an attempt is made to obtain a multi-pixel light receiving device with high sensitivity at a wavelength of 8 to 14 μm using the above Hg _1-x Cd _x Te, an optical system such as a lens for condensing light on the light receiving device is required. Due to the diffraction limit described above, the size of one pixel cannot be made smaller than the wavelength of infrared light to be detected, so that it is not possible to reduce the size of one pixel and achieve high integration like a semiconductor memory device.

For this reason, in particular, in the infrared light receiving device in the 10 μm band, the element size needs to be increased to about 10 μm × 10 μm, and the area of the semiconductor wafer on which the element is formed must be increased with the increase in the number of pixels. It is necessary to increase the yield by securing the number of elements formed per wafer. However, the above-mentioned Hg _1-x Cd _x Te crystal has difficulty in obtaining a large-area crystal.

In general, a charge transfer device that processes signals obtained by the light receiving device is formed using a Si substrate as a material. When this light receiving device and the signal processing device are integrated, the material of the substrate that forms each device is Since the thermal expansion coefficient is different, the thermal strain generated between the substrates due to the liquid nitrogen temperature using the light receiving device and the temperature cycle between the greenhouse is different. Therefore, it is desirable that the light receiving device and the signal processing device are formed using the same substrate. .

Conventionally, as a light receiving device satisfying such requirements, as shown in FIG. 12, a GaAs layer doped with a high concentration of impurities is formed on a GaAs substrate 1 having side edges cut at a predetermined angle in an oblique direction. 2 and then the contact layer 2
A light receiving portion is formed by stacking several tens of aluminum / gallium / arsenic (Al _x Ga _1-x As) superlattices 3 on the light receiving portion, and the contact layer 4 is provided thereon, and electrodes are provided on the contact layers 2 and 4. Is formed, and an arrow A is formed from the obliquely processed side end 1A of the substrate 1.
A semiconductor light-receiving device that detects infrared light incident from different directions is described in the literature (ELECTRONICS LETTERS 9th June 1988 Vol.24 No.12
P747). The energy of the infrared ray incident from the side end 1A of the substrate 1 causes Al _x G
An incident infrared ray is detected by detecting electrons that have transitioned between subbands formed in the superlattice 3 of a _1-x As.

As described above, the reason why the infrared rays are made to be incident on each layer of the superlattice 3 in the oblique direction is that the light is normally incident on the plane of the superlattice layer in parallel, but the conversion efficiency is the best. When the light is made incident in parallel, the light receiving area cannot be increased because the superlattice layer is extremely thin, about 1 μm or less, and the incidence efficiency is poor.

Therefore, when the light is incident on the superlattice surface at a predetermined angle in consideration of the refractive index and the like of the superlattice surface, the transition efficiency of electrons between subbands is maximized and the conversion efficiency is maximized. I have.

In addition, as shown in FIG. 13, the above-mentioned Al _x Ga _1-x As is formed on a GaAs substrate 1 processed into a triangular prism shape like a prism.
Are formed in the form of an array, and infrared rays are incident from the processing surface of the substrate in the oblique direction from 1B, and an array of semiconductor light receiving elements for detecting the infrared rays is formed. Device 7 is also proposed in the above-mentioned document.

[Problems to be solved by the invention]

However, in the one-dimensional light receiving device 7 having the structure described above, for example, light condensed by using the condensing lens 8 is introduced into the light receiving units 3A, 3B,... Formed by a plurality of superlattices arranged in an array. For this reason, it is difficult to make all the focal points of the light coincide with the positions of the respective light receiving sections, and there is a problem that a high-resolution image cannot be obtained. A three-dimensional light receiving device cannot be obtained.

Further, as described above, it is desirable to form the infrared detecting device and the signal processing device for processing a signal obtained by the detecting device on the same substrate, but such an Al _x Ga _1-x As super lattice is provided. At present, a light receiving device in which a signal processing device is integrally provided on a GaAs substrate has not been proposed.

The present invention has been made in view of the above, and provides a two-dimensional high-sensitivity infrared light receiving device using the superlattice, and a semiconductor provided with a signal processing device on the same substrate on which the light receiving device is formed. It is intended to provide a light receiving device.

[Means for solving the problem]

The semiconductor light receiving device of the present invention has a groove or a hole formed by a sub-plane having a predetermined angle with respect to a main plane perpendicular to a predetermined crystal axis direction of the semiconductor substrate, and the sub-plane has a groove or a hole formed on the sub-plane. It is configured to have a light receiving portion composed of a superlattice provided by being stacked substantially parallel to a plane.

(Operation)

A groove or a hole composed of a sub-plane having a predetermined angle with respect to a main plane perpendicular to a predetermined crystal axis direction of the semiconductor substrate is formed, and laminated on the sub-plane in a direction substantially parallel to the sub-plane. Since the light receiving portion composed of the provided superlattice is provided, even if the incident light is perpendicularly incident on the main plane, the light is incident on the superlattice serving as the light receiving portion at a predetermined angle, so that a semiconductor having high photoelectric conversion efficiency is provided. A light receiving device can be obtained.

In addition, the photosensitive portion of the superlattice formed on the main plane of the semiconductor substrate is patterned to selectively remove the superlattice on the periphery of the main plane of the semiconductor substrate. When the processing circuit is formed, the signal processing circuit and the light receiving unit can be formed on the same substrate, so that the temperature cycle of the operating temperature and the non-operating temperature of the semiconductor light receiving device may cause thermal distortion. It is possible to obtain a high-performance semiconductor light receiving device that does not generate any light.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a sectional view of the semiconductor light receiving device according to the first embodiment of the present invention.

As shown in the figure, a quadrangular pyramid-shaped hole 14 having a (111) plane as a sub-plane or a V-shaped groove having a (110) plane as a sub-plane by etching a GaAs substrate 11 whose main plane 12 is a (001) plane. 14
Is formed on the substrate including the holes or the grooves 14, and N ⁺ GaAs doped with N-type impurities at a high concentration of about 10 ¹⁸ atoms / cm ^3.
A contact layer 21 made of a layer is formed.
A superlattice 15 of undoped Al _x Ga _1-x As is formed on 21,
A contact layer 22 is further formed thereon, and an electrode 23 such as gold is formed on the contact layer 22 to form a light receiving device.

To form the semiconductor light receiving device of the first embodiment, the third
As shown in FIG. 1A, an SiO ₂ film 24 having a predetermined pattern is formed on the GaAs substrate 11 by vapor deposition or sputtering.

Then, using the SiO ₂ film 24 as a mask, phosphoric acid (H ₃ PO
₄ ) Etching is performed using an etching solution of hydrogen peroxide (H ₂ O ₂ ) and water (H ₂ O). By doing this, the main plane
A quadrangular pyramid-shaped hole 14 having a sub-plane 13 of a (111) plane at 54.7 degrees with respect to 12 is formed two-dimensionally.

Further, by changing the shape of the opening 25 of the mask of the SiO ₂ film 24 and changing the composition of the etching solution to perform etching, a V-shape having a sub-plane that forms an angle of 45 degrees with the main plane 12 is formed. The groove 14 can be formed one-dimensionally.

Next, after the SiO ₂ film 24 is removed, as shown in FIG. 3 (b), on the substrate 11 including the holes or the grooves 14, a high pressure of about 10 ¹⁸ atoms / cm ^{3 is formed} by using a molecular beam epitaxial growth method or the like. After forming a contact layer 21 doped with an N-type impurity at a concentration, and further forming several tens of non-doped Al _x Ga _1-x As superlattices 15,
Further, a contact layer 22 is formed thereon.

Next, as shown in FIG. 3 (c), the superlattice 15 and the contact layer 22 thereon are etched in a predetermined pattern in a state where the contact layer 21 on the main plane 12 is partially left. An electrode 23 is formed on the layers 21 and 22 to form a semiconductor light receiving device.

FIG. 4 is a sectional view of a semiconductor light receiving device according to a second embodiment of the present invention.

As shown in the figure, a quadrangular pyramid-shaped hole or a V-shaped groove 14 having the (111) plane as the sub-plane 13 is formed in the GaAs substrate 11 having the (001) plane as the main plane 12 by etching. A contact layer 21 made of an N ⁺ GaAs layer doped with a high concentration of N-type impurities is formed on the substrate including the groove 14, and a non-doped Al _x Ga _{1 -x} As superlattice layer is formed on the contact layer 21. Several tens of layers 15 are formed in layers, and a contact layer 22 is further formed thereon.
Is formed thereon, and a transmission layer 31 made of GaAs that transmits infrared rays is formed thereon using a molecular beam epitaxial growth method, and then flattened using a bias sputtering method to be buried and formed thereon. A reflection layer 32 made of gold or germanium that reflects the infrared rays is formed, and an electrode 23 is formed on the contact layer 21 and the reflection layer 32 to form a light receiving device.

In this way, the infrared light transmitted along the direction of arrow A from the bottom of the GaAs substrate that transmits the infrared light is introduced into the superlattice 15, and a part of the incident infrared light transmitted through the superlattice becomes
Further, since the light passes through the transmission layer 31 and strikes the reflection layer 32 and re-enters the superlattice 15, a light-receiving device with higher sensitivity than in the first embodiment can be obtained.

To form the semiconductor light receiving device of the second embodiment, the fifth
As shown in FIG. 1A, an SiO ₂ film 24 having a predetermined pattern is formed on the GaAs substrate 11 by vapor deposition.

Further, using the SiO ₂ film 24 as a mask, etching is performed using an etchant of phosphoric acid (H ₃ PO ₄ ), hydrogen peroxide (H ₂ O ₂ ), and water (H ₂ O). In this way, the main plane 12
A quadrangular pyramid-shaped hole 14 including the sub-plane 13 of the 54.7 degree (111) plane is formed two-dimensionally.

Further, when the etching is performed by changing the pattern of the opening of the SiO ₂ film 24 and changing the ratio of the components constituting the etching solution, the angle (11
A V-shaped one-dimensional groove 14 having a sub-plane 13 of the 0) plane is formed.

Next, as shown in FIG. 5 (b), a hole is formed on the substrate including the groove 14 by a molecular beam epitaxial growth method or the like.
After forming a contact layer 21 doped with an N-type impurity at a high concentration of about ¹⁸ atoms / cm ³ , further forming several tens of non-doped Al _x Ga _1-x As superlattices 15, and further forming a contact layer 22. After forming, an infrared transmitting layer made of GaAs is formed on the contact layer 22.
31 is formed thick.

Next, as shown in FIG. 5 (c), the surface of the transmission layer 31 is flattened using a bias sputtering method so as to be parallel to the main plane 12, and then the superlattice layer 15 laminated on the substrate 11 is processed. After partially removing the contact layer 22 and the light-receiving device, a reflective layer 32 of a gold-germanium alloy is formed.

FIG. 6 (a) shows a third embodiment of the semiconductor light receiving device of the present invention.
And an equivalent circuit diagram thereof is shown in FIG. 6 (b).

In the present embodiment, the reflection layer 32 of the light receiving device of the second embodiment is formed of a conductor layer such as a gold-germanium alloy, and an insulating film 41 made of a SiO ₂ film is provided thereon. A conductor layer made of a gold-germanium alloy is provided on an insulating film 41, and the insulating film 41 has an integral capacity.

The operation of the light receiving device will be described. As shown in FIG. 6 (b), a voltage is applied between the formed conductive reflective layer 32 and the conductor layer 42 formed in this embodiment to apply the insulating film 41. The electric charge is accumulated in the capacitor 43 formed by the above. Further, the voltage between the conductor layer 42 and the reflection layer 32 is measured at the stage where the application of the voltage is stopped and left for a predetermined time. Then, by introducing infrared rays into the superlattice 15 during the discharge time, the resistance of the superlattice fluctuates, and the superlattice becomes a photoconductive layer. To detect infrared rays.

In this way, the capacitance is charged and discharged by the photoconductivity of the infrared light introduced into the superlattice, whereby an integration effect is generated in the capacitance and a semiconductor light receiving device with an improved S / N ratio can be obtained.

FIG. 7 shows a fourth embodiment of the semiconductor light receiving device of the present invention.

This embodiment is different from the first, second and third embodiments in that a plurality of sub-planes 13 are regularly arranged in the main plane 12 described above.
The point is that the superlattice 15 is provided on the main and sub planes.

By doing so, the area of the light receiving area formed by the superlattice 15 is increased, and a detection device with higher sensitivity than the first, second and third embodiments can be obtained.

FIG. 8 (a) shows a fifth embodiment of the semiconductor light receiving device of the present invention.
8 (b). In the present embodiment, the eighth
As shown in FIG. 8A and FIG. 8B, a main plane 12 of the substrate 11 and a sub-plane inclined at a predetermined angle with respect to the main plane.
13 is formed by etching, a hole 14 including the sub-plane 13,
Alternatively, after providing the groove 14, a superlattice 15 is provided on the entire surface of the substrate, and after selectively removing only the superlattice on the peripheral portion of the substrate, the superlattice 15 formed on the groove 14 is removed. Separation is performed at a predetermined pitch, and etching is performed so that the superlattice remains only on the hole 14, and the electrode 23 is provided on the exposed flat main plane 12. In this way, an array-shaped one-dimensional light receiving device in which elements are separated can be obtained.

FIG. 9 shows a sixth embodiment of the semiconductor light receiving device of the present invention.

As shown in the figure, a hole 14 having a predetermined angle sub-plane 13 with respect to the main plane of the substrate is provided two-dimensionally on the GaAs substrate 11, and a superlattice 15 is selectively provided on the hole 14 to provide a light receiving portion. Provide. A source region of a switching element 51 made of a Schottky junction type MES FET (Metal Semiconductor FET) is provided so as to be connected to the superlattice corresponding to the superlattice 15 of each light receiving unit.

Further, by providing signal circuits such as a shift register 52 connected to the gate electrode of the switching element 51 and a multiplexer 53 connected to the drain region of the switching element 51 around the substrate, the signal from each light receiving section 15 is shifted. A line address type two-dimensional image pickup device capable of scanning with the register 52, converting the signal into a time series signal with the multiplexer 53, and processing the signal is obtained.

The configuration of the seventh embodiment of the semiconductor light receiving device of the present invention is
FIG. 10A shows an equivalent circuit diagram of this embodiment in FIG. As shown in FIGS. 10 (a) and 10 (b), the light receiving element 61 shown in the third embodiment is formed on a GaAs substrate.
Are arranged two-dimensionally at a predetermined pitch, and a Schottky junction type MES corresponding to the superlattice of each light receiving portion of the light receiving element 61 is provided.
Switching element composed of FET (Metal Semiconductor)
51 source regions are provided to connect to the superlattice.

Further, a signal processing circuit such as a shift register 52 connected to the gate electrode of the switching element 51 and a multiplexer 53 connected to the drain region of the switching element 51 are provided on the periphery of the substrate. Then, the light receiving element 61 at a predetermined position is set by the shift register 52, and a voltage is applied to the switching element 51 corresponding to the light receiving element 61 to accumulate charges in the capacitance 43 of the light receiving element. Then, the application of the voltage to the switching element 51 is stopped, and the charge is discharged from the capacitor 43. When the infrared light enters the light receiving element at the predetermined position, the value of the resistance 44 of the superlattice changes, so that the voltage fluctuation of the switching element discharged for a predetermined time is read by a multiplexer 53 to detect the incident infrared light. The result is a two-dimensional imaging device.

 An eighth embodiment of the present invention is shown in FIG.

As shown in the drawing, the light receiving surface side of the semiconductor light receiving device formed in the first to seventh embodiments is placed on an In metal bump 72 so as to face a cold head 71 cooled using liquid nitrogen or the like.
And so on. Then, an anti-reflection film 73 of ZnS or the like is formed on the back surface of the substrate by vapor deposition or the like, and infrared rays are made incident from the back surface to form a wiring layer 74 formed on the side surface of the cold head 71.
A voltage is applied to the light-receiving device via. In this way, GaAs has a relatively large heat capacity and has a characteristic that heat is difficult to dissipate, but by cooling the substrate with a cold head during this operation, a high-sensitivity light receiving device with less noise can be obtained. .

〔The invention's effect〕

As is clear from the above description, according to the present invention, there is an effect that a high-performance semiconductor light receiving device having a large number of pixels and having high sensitivity to infrared rays, particularly a long wavelength band of 8 to 14 μm, can be obtained.

[Brief description of the drawings]

FIG. 1 is a principle view of a semiconductor light receiving device according to the present invention, FIG. 2 is a sectional view of a first embodiment of the semiconductor light receiving device according to the present invention, and FIGS. FIG. 4 is a cross-sectional view showing a manufacturing process of the light-receiving device according to the embodiment; FIG. 4 is a cross-sectional view of the second embodiment of the semiconductor light-receiving device of the present invention; FIG. 5 (a) to FIG. FIG. 6 (a) is a sectional view of a third embodiment of the device of the present invention, FIG. 6 (b) is an equivalent circuit diagram of the third embodiment, and FIG. FIG. 8 (a) and FIG. 8 (b) are cross-sectional views of a fourth embodiment of the apparatus of the present invention.
FIG. 9 is a perspective view of an embodiment, FIG. 9 is a plan view of a sixth embodiment of the device of the present invention, FIG. 10 (a) is a configuration diagram of a seventh embodiment of the device of the present invention, and FIG. FIG. 11 is an equivalent circuit diagram of the seventh embodiment, FIG. 11 is a cross-sectional view of the eighth embodiment of the device of the present invention, FIG. 12 is a cross-sectional view of the conventional device, and FIG. 13 is a schematic diagram of the conventional device. In the figure, 11 is a semiconductor substrate (GaAs substrate), 12 is a main plane, 13 is a sub-plane, 14 is a groove or a hole, 15 is a super lattice, 21 and 22 are contact layers, 23 is an electrode, and 24 is a SiO ₂ film. , 25 is an opening, 31 is a transmission layer, 32 is a reflection layer, 41 is an insulating film, 42 is a conductor layer, 43 is a capacitor,
44 is a resistor, 51 is a switching element, 52 is a shift register, 53 is a multiplexer, 61 is a light receiving element, 71 is a cold head, 72 is a metal bump, 73 is an antireflection film, and 74 is a wiring layer.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Soichiro Hitoda 1015 Uedanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside Fujitsu Limited (72) Inventor Kazuya Kubo 1015 Kamikodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture (56) References JP-A-1-181480 (JP, A)

Claims (6)

(57) [Claims] 1. A semiconductor device comprising: a groove or a hole formed by a sub-plane having a predetermined angle with respect to a main plane perpendicular to a predetermined crystal axis direction of a semiconductor substrate; A semiconductor light receiving device, comprising: a light receiving portion composed of a superlattice provided by being stacked in parallel. 2. A light to be detected which is buried in a groove or a hole provided with the superlattice, has a surface parallel to a main plane of the semiconductor substrate, and transmits light to be detected. The semiconductor light receiving device according to claim 1, further comprising a reflection layer that reflects light on the transmission layer. 3. An integrated capacitor comprising said reflective layer made of a conductor, an insulating layer formed on said reflective layer, and a conductive layer formed on said insulating layer. A semiconductor light receiving device as described in the above. 4. The semiconductor device according to claim 1, further comprising a plurality of said sub-planes regularly provided in a main plane of said semiconductor substrate.
4. The semiconductor light receiving device according to 2 or 3. 5. The semiconductor device according to claim 1, further comprising a wiring provided on said main plane of said semiconductor substrate, and a peripheral circuit for scanning a signal from said light receiving section and converting it into a time series signal. 5. The semiconductor light receiving device according to 3 or 4. 6. A semiconductor device provided with a superlattice, comprising cooling means provided opposite to the main plane of the semiconductor substrate, wherein light to be detected is introduced from the back surface side of the semiconductor substrate. 6. A semiconductor light receiving device according to claim 2, 3, 4, or 5.