JP2610075B2 - Hybrid integrated circuit and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high performance hybrid integrated circuit using GaAs and Si and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, in a hybrid integrated circuit, for example, an opto-electronic integrated circuit in which a semiconductor laser is integrated with a driving transistor, an amplifying transistor, and the like, an optical device such as a semiconductor laser is mounted on a substrate on which a semiconductor laser such as GaAs can be manufactured. There is known a method in which an element and an electronic element such as a transistor are formed at the same time.

As another method, a method of forming a GaAs film on a Si substrate by a method such as molecular beam epitaxy and forming an optical element or the like on the GaAs film has been studied.

[0004]

However, in the above-described method of integrating both the optical element and the electronic element on the GaAs substrate, the GaAs substrate is several times more expensive than the Si substrate, and the process of forming the semiconductor device is difficult. Since it is more complicated than the case of the Si substrate, there are problems such as a low yield and a high-density integration. The GaAs substrate is S
Since the thermal conductivity is several times worse than that of the i-substrate, there is a problem that it is not suitable for integration of a circuit using a large amount of power.

A GaAs film is formed on a Si substrate,
In a method of integrating an optical element on an aAs film and an electronic element on a Si substrate, at present, a GaAs film having very good characteristics has not been obtained because the crystal lattice constants of Si and GaAs are considerably different. In particular, in the case of an optical device, lattice defects at the atomic level adversely affect characteristics, and it is difficult to form an optical device having good characteristics on this GaAs film.

The present invention has been made in view of the above-mentioned problems, and a hybrid integrated circuit capable of integrating optical elements and electronic elements at a high density, having low cost, good yield, and excellent characteristics, and a method of manufacturing the same. The purpose is to provide.

[0007]

SUMMARY OF THE INVENTION The present invention according to claim 1, the side of the surface to be bonded of the GaAs substrate and a Si substrate
Among them, at least one of the surfaces has a silicon oxide film or
A silicon film, wherein the GaAs substrate and the Si substrate are
Direct bonding by hydroxyl groups attached to each bonding surface
That is a hybrid integrated circuit.

According to a fifth aspect of the present invention, there is provided a semiconductor device comprising the steps of providing an active element on a GaAs substrate and a Si substrate;
Of the surfaces of the substrate and the Si substrate to be bonded,
A silicon oxide film or a silicon film on at least one of the surfaces.
Forming the film by the providing step and the step of providing the film
Hydroxyl groups on each joint surface, including at least one
Attaching each of the contacts to which the hydroxyl group has been attached.
The GaAs substrate and the Si-based
Bonding directly to the GaAs substrate;
And the active element provided on the Si substrate.
Electrically connecting the elements to each other .

[0009]

According to the present invention, a GaAs substrate and a GaAs substrate are provided.
At least one of the surfaces on the bonding side of
Having a silicon oxide film or a silicon film on the surface thereof,
The hydroxyl group attached to each bonding surface allows the GaAs group
The plate and the Si substrate are directly bonded.

According to a fifth aspect of the present invention, a GaAs substrate is provided.
And active elements are provided on the Si substrate, and the GaAs substrate and the
And at least one of the surfaces on the bonding side of the Si substrate
A silicon oxide film or a silicon film is provided on one of the surfaces,
Each junction including at least one of the surfaces on which the film is formed
A hydroxyl group is attached to the surface, and the hydroxyl group is attached to the surface.
The GaAs substrate and the S
i substrate, which was directly bonded to the GaAs substrate.
The active element and the active element provided on the Si substrate
And are electrically connected.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a hybrid integrated circuit according to an embodiment of the present invention and a method for manufacturing the same will be described with reference to the drawings.

FIG. 1 is a schematic sectional view showing the structure of a hybrid integrated circuit according to a first embodiment of the present invention. That is, S which constitutes the hybrid integrated circuit
An electronic element 5 such as a transistor is formed on the i-substrate 1, and an optical element 4 such as a semiconductor laser is formed on the GaAs substrate 2. On a predetermined surface of the GaAs substrate 2, a silicon oxide film (or silicon film) 3 is formed, and the silicon oxide film (or silicon film) 3 and the Si substrate 1 are directly bonded. Will be described later). The optical element 4 and the electronic element 5 formed on each substrate are functionally connected by electrical wiring or the like.

As described above, the optical element 4 is formed on the GaAs substrate 2 having excellent optical characteristics such as light emission, and the electronic element 5 such as a transistor is formed on the Si substrate suitable for forming a large-scale integrated circuit. 1, the high-performance optical element 4 and the large-scale integrated electronic element 5 can be integrated and integrated. Further, since the Si substrate 1 has a high thermal conductivity, even if a high-power semiconductor laser is formed on the GaAs substrate 2, it is possible to sufficiently dissipate heat, and therefore, electronic elements such as a power amplifier are integrated. I was able to do it.

Embodiment 2 FIG. 2 is a schematic sectional view showing the structure of a hybrid integrated circuit according to a second embodiment of the present invention. That is, S which constitutes the hybrid integrated circuit
An electronic element 5 such as a transistor is formed on the i-substrate 1. An optical element (light-emitting element) 4 such as a semiconductor laser is provided on a part of the surface of the GaAs substrate 2 facing the Si substrate 1.
Are formed. A silicon oxide film (or silicon film) 3 is formed at a predetermined portion around the optical element 4 on the surface, and the silicon oxide film (or silicon film) 3 is directly bonded to the surface of the Si substrate 1. (The joining method will be described later). Further G
An optical element (light receiving element) 4 ′ such as a photodiode is formed at a portion of the Si substrate 1 facing the optical element 4 formed on the aAs substrate 2, and the optical element (light emitting element) 4 and the optical element (light receiving element) ) 4 'is adapted to be coupled by light. The optical elements 4, 4 'and the electronic element 5 formed on the respective substrates are functionally connected by electric wiring and the aforementioned optical coupling as required.

As described above, the optical element 4 such as a semiconductor laser is formed on the GaAs substrate 2 having excellent optical characteristics such as light emission.
Some of the optical elements 4 ′ and the electronic elements 5 such as transistors, which can obtain high performance, are formed on the Si substrate 1 suitable for forming a large-scale integrated circuit. , 4 ′ and the large-scale integrated electronic device 5. Thereby, the same effect as that of the first embodiment was obtained. In this case, as described above, the large-scale integrated circuit on the Si substrate 1 and the optical element 4 on the GaAs substrate 2
It was also possible to directly transmit signals by light without using electrical wiring. It was also possible to integrate high-speed electronic elements on the GaAs substrate 2 at the same time.

In any of the above embodiments, G
Instead of the silicon oxide film formed on the aAs substrate, an amorphous silicon film or a polycrystalline silicon film may be used.

In the above embodiment, the light emitting element is formed on the GaAs substrate side, the light receiving element is formed on the Si substrate side, and the two substrates are coupled by light. Conversely, the light receiving element is formed on the GaAs substrate side. May be formed, and a light emitting element may be formed on the Si substrate side to perform light coupling.

In the above embodiment, the space is provided between the light emitting element and the light receiving element. However, the present invention is not limited to this. If the light emitted from the light emitting element is incident on the light receiving element. Good.

(Embodiment 3) A method of manufacturing a hybrid integrated circuit according to a third embodiment of the present invention will be described.

First, a series of semiconductor processing processes including a process to be performed at a temperature higher than a heat treatment temperature necessary for strengthening the bonding force, for example, a diffusion process, etc., are performed on predetermined portions of the Si substrate and the GaAs substrate. Electronic devices such as field effect transistors (FETs) and optical devices such as semiconductor lasers were formed. These diffusion processes and the like are usually performed at a high temperature of 1000 ° C. or more.

Next, after forming a protective film on the Si portion and the GaAs portion on which various elements are formed, other exposed S
The surfaces of the i portion and the GaAs portion were extremely cleaned. Specifically, the surface layer of the GaAs substrate was removed by etching with hydrogen peroxide and an ammonia-based etchant. Also Si
The substrate surface was cleaned with a hydrofluoric acid-based etchant. At that time, only the necessary portion of the protective film was removed. After that, a silicon oxide film was formed on the GaAs substrate by a chemical vapor deposition method or the like. The thickness is about 0.1 to 3 μm, and it is easy to control the thickness and the uniformity of the thickness. Further, the surface of the silicon oxide film was cleaned with buffered hydrofluoric acid. At that time, only the necessary portion of the protective film was removed.

Thereafter, the surface of the silicon oxide film is sufficiently washed with pure water, and the silicon oxide film of the GaAs substrate is uniformly superposed on the exposed portion of the Si substrate.
Direct bonding was easily obtained by the hydroxyl group adsorbed on the i-substrate surface. Although sufficient bonding strength can be obtained as it is, further heat treatment at a temperature of 100 ° C. to 700 ° C. in this state further strengthens the bonding. Here, when the heat treatment temperature is high, there is a difference between the coefficient of thermal expansion of the GaAs substrate and the coefficient of thermal expansion of the Si substrate, so that some restrictions are imposed on the shape, dimensions, and the like. As the thickness of the substrate to be bonded becomes thinner and the area becomes smaller, the bonding strength can be improved without peeling or breakage.

Next, various processes to be processed at a temperature equal to or lower than the heat treatment temperature for strengthening the bonding strength, for example, electrode formation and the like were performed to form a wiring pattern. Aminium or gold was used for the wiring. As a result, a hybrid integrated circuit having the structure shown in Example 2 was obtained. The effect of the heat treatment for strengthening the bonding is, for example, at 200 ° C., the bonding strength is increased several times even if the temperature is maintained for only about 1 hour, and several tens kg / cm 2.
Was obtained. When the temperature is raised to 700 degrees C or more,
Since arsenic escapes from the surface of the GaAs substrate, the characteristics of the surface are greatly degraded and a predetermined performance as an optical element cannot be obtained.

If the above-described bonding between the Si substrate 1 and the silicon oxide film (or silicon film) 3 is performed using an adhesive such as a general resin, the semiconductor after bonding is preferably used in view of heat resistance and chemical resistance. Although there is a problem that the process cannot be performed, the use of the method of the present embodiment solves such a problem because the Si substrate and the GaAs substrate are directly bonded.

Further, when bonding is performed using an adhesive such as a resin, it is difficult to control the thickness of the adhesive with high precision, so that the parallelism of the substrate after bonding is deteriorated, and the accuracy of photolithography is deteriorated. Such problems have also been resolved.
In addition, the direct connection has better heat conduction, so that it can be applied to a circuit with large power consumption.

The mechanism of the direct bonding described above is as follows. The surface of the silicon film or silicon oxide film is subjected to an appropriate surface treatment and then immersed in pure water, so that hydroxyl groups adhere to the surface and both surfaces to be bonded are bonded. It is considered that the bonding is carried out by the hydroxyl group attached to the. After that, when heat treatment is performed, it is considered that bonding is strengthened by mutual diffusion.

(Embodiment 4) A method of manufacturing a hybrid integrated circuit according to a fourth embodiment of the present invention will be described.

In the same manner as in Example 3, the Si substrate and the G
After an electronic element or an optical element is formed at a predetermined position on the aAs substrate, a protective film is formed, and the surface is cleaned. Then, an amorphous silicon film is formed on the GaAs substrate serving as a bonding surface by plasma CVD or the like. Formed. The film thickness of the amorphous silicon to be formed is about 0.1 to 3 μm, almost the same as in the third embodiment. After that, as in Example 3, the amorphous silicon film and the surface of the Si substrate were extremely cleaned. The specific method is almost the same as that of the third embodiment. The surface of the amorphous silicon film was cleaned with a buffered hydrofluoric acid-based etchant. Thereafter, the surface of the amorphous silicon film and the surface of the Si substrate were sufficiently washed with pure water and immediately superimposed uniformly, so that the bonding was easily obtained by the hydroxyl groups adsorbed on the surface of the amorphous silicon film.

Next, a process similar to that of the third embodiment is performed, if necessary, so that an optical device formed on a GaAs substrate and an electronic device formed on a Si substrate are integrally integrated. The circuit can be manufactured, and the same effect as that of the third embodiment is obtained. The bonding strength in this case is
The value was 2 to 5 times that obtained when the silicon oxide film was used.

(Embodiment 5) A method of manufacturing a hybrid integrated circuit according to a fifth embodiment of the present invention will be described.

In the same manner as in Example 3 or 4, an electronic element or an optical element is formed at a predetermined position on the Si substrate and the GaAs substrate, and then a protective film is formed, and the surface is cleaned. A silicon oxide film or an amorphous silicon film was formed on a GaAs substrate. Then, as in Example 3 or 4, the silicon oxide film or the amorphous silicon film and the surface of the Si substrate were extremely cleaned. The specific method is described in Example 3 or 4.
Is almost the same as The surface of the silicon oxide film or the amorphous silicon film was cleaned with a buffered hydrofluoric acid-based etchant. Thereafter, the surface of the silicon oxide film or the amorphous silicon film and the surface of the Si substrate were sufficiently washed with pure water, and the surfaces to be joined were overlapped.

After drying, a high DC voltage was applied to the silicon oxide film portion or the silicon film portion while heating both substrates. As a result, an electrostatic force was applied, and a strong direct bonding was obtained. Next, a process similar to that of the third embodiment is performed, if necessary, to manufacture a hybrid integrated circuit in which the optical device formed on the GaAs substrate and the electronic device formed on the Si substrate are integrated. Became possible, and the same effect as in Example 3 was obtained. The bonding strength in this case was even stronger than that obtained by simply heat-treating.

At this time, a silicon oxide film or a silicon oxide film used for bonding is provided by using a semiconductor substrate for the Si substrate and the GaAs substrate or providing a low resistance portion on a part of the substrate so that a high voltage is applied to the film of the bonding portion. A high voltage could be effectively applied to the amorphous silicon film. In this case, the silicon oxide film originally has a high resistance, but in the case of an amorphous silicon film, it is desirable to make the resistance as high as possible.

The applied voltage is suitably from 50 to 1000 V for a film thickness of 1 micron. When the voltage is high, it is better to apply the voltage in a pulsed manner.

(Embodiment 6) A method of manufacturing a hybrid integrated circuit according to a sixth embodiment of the present invention will be described.

In the same manner as in Example 3, the Si substrate and the G
After forming an electronic element or an optical element at a predetermined position on the aAs substrate, forming a protective film and cleaning the surface, a polycrystalline silicon film is formed on the GaAs substrate serving as a bonding surface by plasma CVD or the like. Formed. The thickness of the polycrystalline silicon to be formed is about 0.1 to 3 μm, almost the same as in the third embodiment. Then, as in Example 3, the polycrystalline silicon film and the surface of the Si substrate were extremely cleaned. The specific method is almost the same as that of the third embodiment. The surface of the polycrystalline silicon film was cleaned with a buffered hydrofluoric acid-based etchant. Thereafter, the surface of the polycrystalline silicon film and the surface of the Si substrate were sufficiently washed with pure water and immediately superimposed uniformly, so that the bonding was easily obtained by the hydroxyl groups adsorbed on the surface of the polycrystalline silicon film. Next, a process similar to that of the third embodiment is performed, if necessary, to manufacture a hybrid integrated circuit in which the optical device formed on the GaAs substrate and the electronic device formed on the Si substrate are integrated. Became possible, and the same effect as in Example 3 was obtained.

In each of the above embodiments of the method of manufacturing a hybrid integrated circuit, the example of the structure of the second embodiment has been described. However, in order to obtain the structure of the first embodiment, in each of the embodiments of each manufacturing method, A silicon oxide film or a silicon film is simply referred to as G
This was realized by forming it on the back surface of the aAs substrate.
In this case, the connection between the optical element and the like on the GaAs substrate and the electronic element and the like on the Si substrate was made by an external wire or by forming a via hole in the GaAs substrate.

In each of the above embodiments, no other film was formed on the Si substrate. However, the same direct bonding is possible even if a silicon oxide film or a silicon film is formed on the Si substrate. Met.

In each of the above embodiments, the flatness of the film surface used for bonding is important in any case.
When the conditions are poor and the unevenness of the surface is large, it becomes difficult to join, so that sufficient attention has been required.

In any of the embodiments, first, an electronic device formed on a Si substrate and an optical device formed on a GaAs substrate are integrally integrated. Significantly smaller and lighter.

In each of the embodiments, since a large-scale integrated circuit can be formed on a Si substrate which can be formed with a high yield, and an optical element can be formed on a GaAs substrate which can obtain high performance, the integrated circuit can be integrated using a single substrate. As a result, a higher performance hybrid integrated circuit was obtained with higher yield.

Also, in any of the embodiments, the bonding method is such that the GaAs substrate and the Si substrate are directly bonded by a silicon-based inorganic material having a controlled film thickness, so that the flatness is extremely good and the large scale integration is possible. In addition to enabling submicron photolithography, which is required for, the reliability against heat and vibration has been greatly improved.

[0043]

As is apparent from the above description, the present invention has the advantages that optical elements and electronic elements can be integrated at a high density, low cost, good yield, and good characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a configuration of a hybrid integrated circuit according to a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing a configuration of a hybrid integrated circuit according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Si substrate 2 GaAs substrate 3 Silicon oxide film or silicon film 4 Optical element (light emitting element) 4 'Optical element (light receiving element) 5 Electronic element

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuyoshi Kotara 1006 Kazuma Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. (56) References JP-A-3-262143 (JP, A) JP-A-1 -293664 (JP, A) JP-A-62-217633 (JP, A) OPTICAL AND QUANT UM ELECTRONICS 20 (1988) PP. 441-474 JOURNAL OF LIGHTWAVE AVE TECHNOLOGY. VOL. 8NO. 6 (1990) PP. 846-862

Claims (6)

(57) [Claims] 1. A method for bonding a GaAs substrate and a Si substrate.
Silicon oxide on at least one of the
A GaAs substrate and a Si substrate, each of which has a silicon film or a silicon film .
A hybrid integrated circuit, which is directly joined by the attached hydroxyl group . 2. A method for bonding a GaAs substrate and a Si substrate.
Silicon oxide on at least one of the
A GaAs substrate and a Si substrate, each having a base film or a silicon film.
Treatment to attach acid groups, superposition treatment, and heat treatment
And a direct bonding . 3. The bonding of a GaAs substrate and a Si substrate.
Silicon oxide on at least one of the
A GaAs substrate and a Si substrate, each having a base film or a silicon film.
The process of attaching acid groups, the process of superposition, and the bonding
Heat treatment performed while applying a DC voltage to the surface
A hybrid integrated circuit characterized by being joined . 4. The method according to claim 1 , wherein the temperature ranges from 100 ° C. to 700 ° C.
The hybrid integrated circuit according to claim 2, wherein heat treatment is performed . 5. An active element on a GaAs substrate and a Si substrate
And a table on the bonding side of the GaAs substrate and the Si substrate.
A silicon oxide film or a silicon oxide film is formed on at least one of the surfaces.
Or providing a silicon film, and reducing the surface on which the film is formed by the step of providing the film.
At least a process to attach hydroxyl groups to each joint surface included in one
And joining each of the bonding surfaces to which the hydroxyl groups are attached.
Directly bonding the GaAs substrate and the Si substrate
The active element and the Si provided on the GaAs substrate.
Step of electrically connecting the active element provided on the substrate
Manufacture of hybrid integrated circuit comprising: the degree, the
How . 6. After 100 ° C., a temperature of 100 ° C.
It is noted that a heat treatment process in the temperature range of 700 ° C has been added.
A method for manufacturing a hybrid integrated circuit according to claim 5 .