JPH03101275A - Light amplifying integrated circuit - Google Patents

Abstract

PURPOSE:To enhance conversion efficiency and enable production to be performed easily by forming a light-emitting element and a photodetector on a semiconductor substrate and by forming a semiconductor by direct junction. CONSTITUTION:An insulating film 2 is formed on a silicon substrate 1, the insulating film 2 and a semiconductor substrate 3 are joined by direct junction, an insulating film 36 is further formed on the semiconductor substrate 3, the insulation film 36 and a semiconductor substrate 4 are directly joined by direct junction, a photodetector element is formed on the semiconductor substrate 3, a light-emitting element is formed on the semiconductor substrate 4, or inversely a light-emitting element is formed on the semiconductor substrate 3, a photodetector is formed on the semiconductor substrate 4, and a transistor 6 which amplifies electrical signal converted by the photodetector and a transistor 6 which drives the light-emitting element are formed on the silicon substrate 1, the semiconductor substrate 3, or the semiconductor substrate 4. Thus, use of the semiconductor substrate achieves an improved crystallinity of semiconductor and enhances light/electron conversion efficiency of light-emitting element or photodetector which are formed on that semiconductor.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an optical amplification integrated circuit in which a silicon substrate and a compound semiconductor layer plate are directly bonded via an insulating film, and optical elements such as light emitting elements are formed on the compound semiconductor substrate.

[Prior art]

Conventionally, optical/electronic integrated circuits include light-emitting integrated circuits in which a light-emitting element such as a semiconductor laser and a drive circuit such as a power transistor are formed on a semi-insulating gallium arsenide substrate, and a light-receiving integrated circuit such as a photodiode on a semi-insulating gallium arsenide substrate. 2. Description of the Related Art A light-receiving integrated circuit including an element and an amplifier circuit such as a high-frequency transistor is known.

[Question B that the invention attempts to solve]

In the field of optical communications, it is necessary to amplify optical signals, but when amplifying the optical signals, the optical signals are usually converted into electrical signals, and after amplifying the electrical signals, The procedure is to convert it into an optical signal. To form a circuit that performs such optical amplification, it is common to form a hybrid of the above-mentioned light-emitting integrated circuit and light-receiving integrated circuit. They are parallel. Therefore, it is expected to develop a vertical-type optoelectronic integrated circuit that is composed of an I-chip that has an optical signal amplification function and has a light receiving element and a light emitting element arranged along the direction of propagation of light, that is, a three-dimensional circuit. There is. SUMMARY OF THE INVENTION An object of the present invention is to provide a vertical optical amplification integrated circuit that has high performance and is easy to manufacture.

[Means to solve the problem]

The present invention includes a silicon substrate in which a window is formed that is open toward the incident direction of light incident perpendicularly to the substrate plane, and an insulating film formed on the main surface of the silicon substrate on the opposite side to the light incident side. A light-receiving element that converts an optical signal into an electrical signal or a light-emitting element that converts an electrical signal into an optical signal is formed at a position that is directly bonded to an insulating film formed on a silicon substrate and faces a window formed on the silicon substrate. The first semiconductor substrate is directly bonded to an insulating film formed on the main surface of the first semiconductor substrate, and when a light receiving element is formed on the first semiconductor substrate, an electrical signal is converted into an optical signal. A silicon substrate, on which a light emitting element for converting light signals is formed, and a second semiconductor substrate on which a light receiving element for converting optical signals into electrical signals is formed when the light emitting elements are formed on the first semiconductor substrate; The present invention is characterized in that a transistor element is formed on the first semiconductor substrate or the second semiconductor substrate to amplify the electrical signal output from the light receiving element and output the amplified signal to the light emitting element.

[Effect]

The mechanical strength of the optical amplification integrated circuit of the present invention is mainly maintained by the silicon substrate. Light is incident perpendicularly to the substrate plane from a window formed perpendicularly to the substrate plane of the silicon substrate. Further, a first semiconductor substrate 81 made of GaAs or the like is directly bonded to an insulating film formed on the main surface of the silicon substrate on the side opposite to the light incident side. A light receiving element such as a photodiode or a light emitting element such as a semiconductor laser that converts an optical signal into an electrical signal is formed in a portion of the first semiconductor substrate facing the window formed in the silicon substrate. When a light-receiving element is formed on the first semiconductor substrate, light enters the light-receiving element through a window in the silicon substrate, and the light-receiving element converts the optical signal into an electrical signal. Furthermore, if a light emitting element is formed, light is output from the light emitting element through the window of the silicon substrate. Further, a second semiconductor substrate made of S+, GaAs, etc. is directly bonded to the insulating film formed on the main surface of the first semiconductor substrate. A light emitting element such as a semiconductor laser or a light receiving element such as a photodiode is formed on the second semiconductor substrate. When a light emitting element is formed on the second semiconductor substrate, an electrical signal is input to the light emitting element and converted into an optical signal, and the optical signal is output from the light emitting element. Furthermore, if a light receiving element is formed on the second semiconductor substrate, an optical signal is incident on the light receiving element, changed into an electrical signal, and output. An amplifier element such as a transistor formed on a silicon substrate, a first semiconductor substrate, or a second semiconductor substrate is connected between the light receiving element and the light emitting element, and the light receiving element performs conversion. The generated electrical signal is amplified by the amplification element, and then input to the light emitting element and converted into an optical signal.

【Example】

The present invention will be described below based on a specific example. FIG. 1 is a diagram showing the manufacturing process of an optical amplification integrated circuit according to an embodiment of the present invention. As shown in FIG. 1, a diffusion layer of a power transistor to be formed in FIG. 1 (d>) was formed in advance on a silicon substrate 1 as shown in FIG. Thermal oxidation was performed at 1100° C. in an atmosphere to form an insulating film 2 made of Stew and having a thickness of about 1 mm.At this time, the surface of the insulating film 2 was polished to increase the bonding strength with the silicon substrate to be bonded. The smoothness may be increased by doing so.Next, impurities were diffused on the bonding surface 32 side of the first semiconductor substrate 3 made of Si to form a two-layer 31 made of P-type Si.Next, The bonding surface 32 of the first semiconductor substrate 3 and the surface of the insulating film 2 formed on the silicon substrate 1 are cleaned with 0.degree. Next, the bonding surface 32 of the first semiconductor substrate 3 and the surface of the insulating film 2 formed on the silicon substrate 1 were bonded, and the bonding surface 32 of the first semiconductor substrate 3 was bonded to the surface of the insulating film 2 formed on the silicon substrate 1, and the temperature was increased to 1100 to 1200 in an inert gas such as oxygen or nitrogen, or in vacuum.
It was heated in the range of 0.degree. C. and left for 1 hour. Through this step, the hydroxyl groups formed on the bonding surface 32 of the first semiconductor substrate 3 and the surface of the insulating WI2 formed on the silicon substrate 1 cause a dehydration condensation reaction to form Si and S10. are strongly chemically bonded. In this embodiment, no voltage is applied during bonding, but a voltage may be applied between the silicon substrate 1 and the first semiconductor substrate 3. Next, as shown in FIG. 1(b), the first semiconductor substrate 3 is polished and made into a thin film, and then the diffusion layer and the eight layers 34.2 of the high frequency transistor formed in FIG. 1(d) are formed. A diffusion layer of layer 31 was formed, and a photodiode consisting of two layers 31 and eight layers 34 was formed. Then, a one-thick insulating film 36 made of Stew was formed on the main surface 33 of the first semiconductor substrate 3 by heating it to about 1100° C. in an oxygen atmosphere. At this time, the surface of the insulating film 36 may be polished to increase its smoothness in order to increase the bonding strength with the compound semiconductor to be bonded. Although the insulating film at the bonding interface in FIGS. 1(a) and 1(b) is a thermal oxide film, it may be an oxide film deposited by CVD or the like. Further, the diffusion layer of each transistor and the diffusion layer of the photodiode may be formed by ion implantation from above the thermal oxide film which is the junction interface. Thereafter, as shown in FIG. 1(C), a GaAs
The bonding surface 40 of the second semiconductor substrate 4 made of s and the surface of the insulating film 36 of the first semiconductor substrate 3 are coated with H, O, -H, SOl.
were washed with water to form hydroxyl groups on their surfaces and activate them. Next, the bonding surface 40 of the second semiconductor substrate 4 and the surface of the insulating film 36 of the first semiconductor substrate 3 were subjected to hydrophilic treatment by anodic oxidation. After that, those surfaces are joined and approximately 350 ~
It was heated in a range of 600°C and left for 1 hour. Through this step, the hydroxyl groups formed on the bonding surface 40 of the second semiconductor substrate 4 and the surface of the insulating film 36 formed on the first semiconductor substrate 3 cause a dehydration condensation reaction to form GaAs and 5iO-
are strongly chemically bonded. At this time, a voltage may be applied to bond them. In this way, the second semiconductor substrate 4 and the insulating film 36 were bonded together by direct bonding. Thereafter, unnecessary portions of the second semiconductor substrate 4 were removed by etching. Next, a high frequency transistor 5 was formed in a portion of the first semiconductor substrate 3 where a diffusion layer was previously formed. Next, a portion of the first semiconductor substrate 3 where no element was formed was removed by etching to expose a portion of the silicon substrate 1 on which a diffusion layer had been formed in advance. Next, a power transistor 6 was formed on the exposed portion of the silicon substrate 1. Thereafter, an electrical wiring layer 51 made of aluminum was formed so that the electrical signal converted by the photodiode 35 was amplified by the high frequency transistor 5. Further, an electric wiring layer 52 made of aluminum was formed so that the electric signal amplified by the high frequency transistor 5 was further amplified in power by the power transistor 6 to drive the semiconductor laser 42. Thereafter, a protective film 53 was formed except for only the light emitting surface 42a of the semiconductor laser 42. Next, the entire upper part of the silicon substrate 1 was protected with photoresist or the like, and the window 7 was formed by etching from the bottom surface 11 of the silicon substrate 1 by masking the portion other than the portion corresponding to the window 7. Thereafter, aluminum was deposited on the side wall 71 of the window 7 to form a light guide section. The optical amplification integrated circuit 8 thus produced is packaged as shown in FIG. That is, the optical amplification integrated circuit 8 is bonded onto the base 90 in which the communication hole 91 is formed so that the communication hole 94 and the central axis of the window 7 of the silicon substrate 1 of the optical amplification integrated circuit 8 coincide. An input optical fiber 92 is connected to the communication hole 91. Further, a case 93 is joined to the base 90, and a communication hole 94 is formed in the upper part of the case 93, and an optical fiber 95 for output is connected to the communication hole 93. Power for signal amplification is input through bins 96 and 97 protruding from the base 90. In the optical amplification integrated circuit 8 created in this way, the window 7
Light is incident from the photodiode 35 formed on the first semiconductor substrate 3, and the optical signal is converted into an electrical signal by the photodiode 35 formed on the first semiconductor substrate 3. Then, the electrical signal is transmitted to the first semiconductor substrate 3.
is amplified by a high frequency transistor 5 formed in
The signal is input to a power transistor 6 formed on a silicon substrate 1. Then, the semiconductor laser 42 formed on the second semiconductor substrate 4 is driven by the power transistor 6, and light is output from its light emitting surface 42a. In addition, in the above embodiment, insulation II! I36 is 5if
t, but 5iOsl! In addition to i, Si and GaAs
A material having a coefficient of thermal expansion intermediate between that of Pyrex and the like may also be used. This substance firmly fixes Si and GaAs. Further, in the above embodiment, the first semiconductor substrate 3 is made of Si, but like the second semiconductor substrate 4, it is made of GaAs.
It may be formed using a compound semiconductor such as. Furthermore, in the above embodiment, the light receiving element was formed on the first semiconductor substrate 3 and the light emitting element was formed on the second semiconductor substrate 4. A light receiving element may be formed on the surface. In this case, as shown in FIG. 2, the light enters the second semiconductor substrate 4 from above and is output downward through the window 7 of the silicon substrate 1. Next, another embodiment will be described with reference to FIG. As in the previous embodiment, an insulator [2] is formed on a silicon substrate 1. A first semiconductor substrate 81 made of Si and a second semiconductor substrate 82 made of GaAs were bonded to the insulating film 2 by direct bonding as described in the previous embodiment. A photodiode 83 is formed on the first semiconductor substrate 81, and a semiconductor laser 84 is formed on the second semiconductor substrate 82. A transistor 85 is formed on the silicon substrate 1 to amplify the electrical signal converted by the photodiode 83 and drive the semiconductor laser 82 . Further, a window 7 is formed in the silicon substrate 1 as in the previous embodiment. In this optical amplification integrated circuit, a photodiode 8 is connected from the top.
The optical signal incident on the photodiode 3 is converted into an electrical signal by the photodiode 83, and the electrical signal is amplified by the transistor 85. The amplified electrical signal is then applied to the semiconductor laser 84 and converted into an optical signal by the semiconductor laser 84. The optical signal is outputted downward through the window 7 of the silicon substrate 1. In this way, the first semiconductor substrate 81 and the second semiconductor substrate 82 on which the light-receiving element or the light-emitting element is formed are disposed on the same plane of the insulating film 2 on the silicon substrate 1, and the insulating film 2 and They may be joined by direct joining. Further, as shown in FIG. 4, windows 7a and 7b are formed on the silicon substrate.
and bonding the second semiconductor substrate 82 on which the semiconductor laser 84 is formed to the insulating film 2 on the window 7a,
The first semiconductor substrate 81 on which the photodiode 83 is formed may be bonded to the insulating film 2 on the window 7b. In this case, light enters the photodiode 83 from below through the window 7b, and enters the semiconductor laser 83 through the window 7a.
It is output downward from 4. Effects of the Invention The present invention forms an insulating film on a silicon substrate, joins the insulating film and a first semiconductor substrate by direct bonding, and further forms an insulating film on the first semiconductor substrate. Then, the insulating film and the second semiconductor substrate are directly bonded to form a light receiving element on the first semiconductor substrate and a light emitting element on the second semiconductor substrate, or conversely, the first semiconductor substrate A light emitting element is formed on the second semiconductor substrate, a light receiving element is formed on the second semiconductor substrate, and an electric signal converted by the light receiving element is amplified to drive the light emitting element on the silicon substrate, the first semiconductor substrate, or the second semiconductor substrate. It forms a transistor that Therefore, since a semiconductor substrate is used, the crystallinity of the semiconductor is better than when an epitaxial growth layer is used, and the light-to-electron conversion efficiency of a light emitting element or a light receiving element formed on the semiconductor can be increased. Furthermore, since the semiconductor is formed by direct bonding, manufacturing is easier than in conventional heteroepitaxial growth. Further, since the light emitting element and the light receiving element are arranged on the optical axis, and the signal amplification circuit is arranged on the silicon substrate or the semiconductor substrate, the entire element can be made compact.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the manufacturing process of an optical amplification integrated circuit according to a specific embodiment of the present invention, FIG. 2 is a sectional view showing the assembly of the optical amplification integrated circuit, and FIGS. FIG. 4 is a sectional view of an optical amplification integrated circuit according to another embodiment. 1. Silicon substrate 2.36 Insulating film 3.81
- First semiconductor substrate 4.82° - Second semiconductor substrate 5...High frequency transistor 6...Power transistor? , 7a, 7b・Window 35
．． 83...Photodiode 42.84...° Semiconductor laser

Claims (1)

[Scope of Claims] A silicon substrate in which a window is formed that is open toward the incident direction of light incident perpendicularly to the substrate plane, and a window formed on the main surface of the silicon substrate on the opposite side to the light incident side. an insulating film, and a light receiving element that is directly bonded to the insulating film formed on the silicon substrate and that converts an optical signal into an electrical signal at a position facing the window formed on the silicon substrate, or converts the electrical signal into an optical signal. A first semiconductor substrate on which a light-emitting element to be converted is formed, an insulating film formed on a main surface of the first semiconductor substrate, and directly bonded to the insulating film formed on the first semiconductor substrate. If a light receiving element is formed on the first semiconductor substrate, a light emitting element that converts an electrical signal into an optical signal is formed, and if a light emitting element is formed on the first semiconductor substrate, a light emitting element is formed. a second semiconductor substrate on which a light receiving element that converts a signal into an electrical signal is formed, and the electrical signal output from the light receiving element is amplified on the silicon substrate, the first semiconductor substrate, or the second semiconductor substrate. and a transistor element that outputs the amplified signal to the light emitting element.