JPH10341042A - Method for bonding semiconductor substrates through minute area - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance bonding strength even if the electric coupling area is small by decreasing the residual stress through a method for applying a pressing force while observing an I-V characteristic chart under a state where the electric coupling faces and bonding parts face each other, respectively. SOLUTION: Substrates 1, 2 are disposed oppositely each other and heat treated while being applied with a load in a pressure reduced hydrogen gas flow. Consequently, bonding members 10, 11 abutting each other are bonded gradually through plastic deformation due to creep phenomenon proceeding with time. Plastic deformation proceeds until electric bonding faces 3, 4 are brought into contact with each other and bonded tightly. During plastic deformation, I-V characteristic chart presented on a curve tracer can be observed. Application of load is interrupted when a best I-V characteristic chart is presented on the curve tracer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adhesive bonding method for bonding and electrical bonding in a small area between substrates of the same or different materials at a low temperature.

[0002]

2. Description of the Related Art Conventionally, as a method of directly joining different kinds of semiconductors to each other for manufacturing a light emitting device, there is a method applied in Applied Physics No. 63
Vol. 1 (Hiroshi Wada, Ken Kamijo, p. 53, 1994), InP / GaAs and InP /
Bonding of the combination of Si, after cleaning the non-bonded surface,
It is obtained by placing a weight on a substrate and performing a heat treatment at 700 ° C. for 30 minutes in a hydrogen atmosphere.

[0003] Appl. Phys. Lett. (Lincaln La
b. As described in ZLLian, 56 (8), 19, Feb. 1990, p. 737), bonding of the InP / GaAs combination cleans the surface to be bonded and then the graphite / quartz reactor. In a hydrogen atmosphere at 750 ° C.

[0004]

However, in the above-mentioned conventional example, since the bonding is performed at a high temperature of about 700 ° C. and the substrates are bonded to each other, there are the following disadvantages.

[0005] 1. In the case of joining different kinds of semiconductors having different coefficients of thermal expansion, a phenomenon occurs in which the joined substrate warps during cooling to room temperature after joining at a high temperature or after cooling. That is, a residual stress occurs.

[0006] 2. Since bonding is a combination of electrical bonding and mechanical bonding strength (bonding strength for preventing peeling), reducing the bonding area decreases bonding strength. For this reason, the decrease in the bonding strength
It becomes a factor of peeling at the joining portion during the process, and it is difficult to reduce the joining area.

The present invention solves the above-mentioned drawbacks of the conventional method and provides a bonding method having a high bonding strength with a small residual stress and a small electric coupling area.

[0008]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and have reached the present invention. That is,
The present invention includes the following inventions and the following embodiments.

(A) In a method for obtaining electrical bonding (hereinafter referred to as “electrical coupling”) in a microscopic region between semiconductor substrates made of the same or different materials, a method is used in which an adhesive bonding region that produces electrical coupling and a bonding force are reduced. (1) a process of forming an insulating film in the bonding region; and (b) forming a bonding region formed of an adhesive element to be applied and closely bonding while observing an IV characteristic diagram with a curve tracer. 2) forming an adhesive element for providing a bonding force on the insulating film;
(3) a step of forming one or a plurality of small point-like scratches in a portion of the minute region that becomes an electrical coupling surface of the tightly-bonded region; and (4) a step of forming the tightly-bonded region in the minute region. And (5) an IV characteristic diagram showing the process of forming the minute point-like scratches into etch pits by anisotropic etching using an etchant, and And (6) aligning the adhesive elements and the tightly-bonded regions on the same or different material substrate so that they face each other, and pressing the same or different material substrate. In the step of applying pressure and (7) the step of applying the pressing force, the IV characteristic generated by the electric coupling on the electric coupling surface is used to observe the state of the electric coupling with a curve tracer. Homogeneous or composed of characteristic diagram observation process Adhesion bonding method between the semiconductor substrate and performing at a low temperature of the electrical coupling between the different material substrate to a room temperature to 250 ° C..

[0010] (b) the semiconductor substrate, Si, I _n P,
At least one selected from GaAs and GaN,
Alternatively, the method according to (a), wherein the semiconductor substrate is made of a compound semiconductor formed on the semiconductor substrate.

(C) The method for tightly bonding semiconductor substrates according to (a), wherein the tightly-bonded region where the electrical connection is made is made up of one or a plurality of V-shaped grooves.

(D) The bonding elements in the bonding area are bonded to each other at a low temperature of room temperature to 250 ° C. by the pressing force to obtain a bonding force between the substrates of the same or different materials. Bonding method between semiconductor substrates.

(E) The method according to (a), wherein the adhesive element is made of a material having plastic deformability.

(F) The method according to (e), wherein the material having plastic deformation is a metal material.

(G) The metal material is Al, Au, In,
The method of (f), wherein the semiconductor substrate is at least one of Ga, Sn, Cu, Ti, Zn, and Pb.

(H) The method according to (a), wherein the insulating film is at least one selected from a Si oxide film, a Si nitride film, and an Al oxide film.

(I) The method according to (a), wherein the adhesive element is convex, spherical or hemispherical.

(J) The method for tightly bonding semiconductor substrates according to (a), wherein the tightly bonded region (electrically connected portion) is sealed by applying the pressing force.

(K) The tightly-bonded region (electrically-coupled portion) is sealed in an atmosphere by applying the pressure in an atmosphere substantially free of oxygen. a) The method for tightly bonding between semiconductor substrates described in a).

(1) The close contact between the semiconductor substrates according to (k), wherein the substantially oxygen-free atmosphere is in a vacuum, under reduced pressure, or in a reduced or inert gas under reduced pressure. legal.

(M) The contact bonding method according to (1), wherein the reducing gas or the inert gas is hydrogen gas, argon gas, nitrogen gas or a mixture thereof.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to achieve the above object, a first invention according to the present application provides a bonding force between substrates only by bonding materials having plastic deformability, and a bonding force between semiconductors by the bonding force. Are brought into close contact with each other to provide electrical coupling between the semiconductors. During the plastic deformation of the material in the joining process of the materials having the plastic deformation, that is, during the electrical coupling process between the semiconductors, the best electrical characteristics are observed while observing the IV characteristic diagram between the semiconductors. The joining process is terminated when the joining occurs.

In the above means, first, a tightly-bonded region for forming an electrical connection between semiconductors and a bonding region comprising an adhesive element for providing a bonding force are provided on one semiconductor substrate, and the same is applied to the other semiconductor substrate. In addition, a region where the semiconductors are electrically coupled to each other and a region where a bonding force is applied are provided. Then, the two substrates are positioned so that the tightly bonded region and the bonding region formed of the adhesive element face each other, and thereafter, a load is applied to both the substrates from both sides.

The application of the load causes the joining region to undergo plastic deformation while joining at the same time, and the tightly joined region approaches the distance on the order of atoms and starts to produce electrical coupling. At this time, the application of the load is stopped when the best IV characteristic occurs while observing the IV characteristic between the two substrates.

Since the semiconductor material does not undergo plastic deformation at a low temperature, by applying the load, first, the material having the plastic deformation ability in the joining region starts plastic deformation, and when the load is further increased, Adhesion occurs between the semiconductors. While the adhesion between the semiconductors is in progress, the bonding is completed when the best IV characteristic occurs. That is, by stopping the application of the load, it is not necessary to apply an excessive compressive stress to the electrical coupling portion of the semiconductor substrate, and the electrical coupling portion is protected. When the applied load is removed at this time, the bonding region maintains a state of being bonded, and the semiconductors maintain a state of being tightly bonded. That is, the semiconductor device is configured to bear a compressive force in the tightly bonded region and a tensile force in the bonded region. Therefore, it is not necessary for the semiconductors at the electrical coupling points to have a bonding force with each other, and it is only necessary to perform electrical coupling by close contact. Therefore, the electrical coupling area can be made extremely small.

When a heating process is performed in the process after the joining process, the electrical connection is prevented from peeling off due to the generation of a positive pressure in the space of the tightly-bonded region caused by the Boyle-Charles law. The joining is desirably performed in a reduced-pressure gas atmosphere.

Further, by forming one or a plurality of etch pits by anisotropic etching in the tightly bonded region of one semiconductor substrate, the electrical coupling area can be reduced, and the electrical coupling area can be reduced. Can be increased. When forming the etch pit,
By forming a small point-like scratch at a place where the etch pit is required, the etch pit can be formed by subsequent etching. Then, the size of the etch pit can be controlled by controlling the etching time.

According to the above-mentioned method, it is possible to electrically connect a similar or different semiconductor substrate with each other in a very small area at the time of bonding, thereby increasing the current density at the electrical connection point when the same current value is applied. It becomes possible.

In the present invention, the meaning of electrical coupling in a small area is not particularly limited numerically. However, in the method of the present invention, the electrical connection portion is about 5 μm or less in diameter, and the method of the present invention has a submicron diameter. The bonding in the bonding area can be sufficiently performed.

The substrates to be bonded in the present invention are the same or different types of substrates that need to be electrically bonded to each other, and are most typically semiconductor substrates. The semiconductor substrate is a commonly used well-known substrate and is not particularly limited.
_n P, GaAs, at least one selected from GaN, or AlAs these semiconductor substrates, GaA
A compound semiconductor formed of GaAs, GaInAsP, or the like is used.

The insulating film formed in the bonding region is not particularly limited as long as it is an insulating film usually used for manufacturing a semiconductor.
For example, a Si oxide film, an Al oxide film, and a Si nitride film are exemplified.

The adhesive element formed on the insulating film in the method of the present invention can be used as long as it is made of a material having a plastic deformability, and is preferably a metal material, and particularly preferably the metal material is Al, Au, In. , Ga, Sn, Cu, Ti,
At least one of Zn and Pb or a mixture thereof is used. Also, a resin such as polyimide can be used.

The temperature at which the adhesive element is pressed is 20 ° C. to 250 ° C.
° C, preferably 20 to 60 ° C, and does not require high-temperature bonding unlike conventional methods. Bonding can be performed with a sufficiently large area so that bonding can be easily performed and no residual stress is generated. Therefore, the desired shape can be maintained.

Further, the pressing of the adhesive element is preferably performed in an atmosphere substantially free of oxygen, thereby sealing the tightly-bonded region (electrically connecting portion) in the atmosphere. The atmosphere is preferably in vacuum, under reduced pressure, or in reduced pressure reducing gas or inert gas, and examples of the reducing gas or inert gas include hydrogen gas, argon gas, nitrogen gas or a mixture thereof. . As a result, it is possible to prevent the electrical connection from changing over time.

When the adhesive element is pressed, it is possible to observe while observing the IV characteristics, so that it is possible to electrically and necessaryly join the elements, and to join without applying excessive compressive stress to the electrical joint. It becomes possible to protect.

[0036]

【Example】

(First Embodiment) FIGS. 1 and 2 best illustrate the features of the present invention. In FIG. 1, reference numeral 1 denotes a substrate for close bonding, 2 denotes a substrate for close bonding, and 3 denotes a substrate. 1
An electrical coupling surface (a tight coupling region) composed of a convex portion in
Reference numeral 4 denotes an electrical coupling surface (close contact region) formed of a flat portion of the substrate 2, reference numeral 6 denotes a bonding portion for bonding to the opposing substrate 2, and reference numeral 7 denotes a bonding portion for bonding to the opposing substrate 1. , 8 is an insulating film for electrically insulating, 9 is an insulating film for electrically insulating, 10 is a bonding member on the insulating film 8, 11 is a bonding member on the insulating film 9, and 12 is a close bonding region. 13 is an electrode on the substrate 1 for observing the IV characteristic diagram, 14 is an electrode on the substrate 2 for observing the IV characteristic diagram, and 15 is an electrode 13 and a curve tracer. 3 is a lead for electrically connecting the electrode 14 and the curve tracer, and FIG.
No. 17 indicates I in a state where the substrates 1 and 2 are not electrically coupled.
-V diagram, 18 in FIG. 4 is an IV characteristic diagram in a state where the substrates 1 and 2 are electrically coupled. Next, in the above configuration,
An InP (p-type) wafer is used as one bonding substrate 1, and a concave-shaped bonding portion 6 is formed by RIE (reactive ion etching) using a resist mask. Then, an insulating film 8 made of a Si oxide film is formed on the bonding portion 6 by using a photolithographic process (not shown) using a resist film. A
1 is formed by a photolithography process (not shown), the resist film is removed with a solvent, and the substrate 1 is washed. An InP (n-type) wafer is used as the other bonding substrate 9, and a photolithography process (not shown) using a resist film as an insulating film 9 made of a Si oxide film on the bonding portion 7 as shown in FIG. 1 is used. And a bonding member 11 made of Al on the insulating film 9.
Is formed by using a photolithography process (not shown), the resist film is removed with a solvent, and the substrate 2 is washed.

The substrate 1 and the substrate 2 prepared in the above process are opposed to each other as shown in FIG. 1, and then heat-treated in a hydrogen stream under reduced pressure while applying a load as shown in FIG. By applying a load during the heat treatment, the joining member 10 and the joining member 11 move from the butted state to each other, while plastic deformation progresses due to a creep phenomenon over time,
Gradually joining. Eventually, the plastic deformation proceeds until the electrical joint surfaces 3 and 4 come into contact with each other and come into close contact with each other. During the plastic deformation, an IV characteristic diagram projected on a curve tracer as shown in FIGS. 3 and 4 can be observed. During the observation, when the electric coupling surface 3 and the electric coupling surface 4 are not in contact with each other, the IV characteristic diagram is shown in FIG.
On the other hand, when the plastic deformation proceeds and the electric coupling surfaces 3 and 4 come into contact with each other and come into close contact with each other, IV
The characteristic diagram is as shown in FIG. During the observation, the application of the load is stopped when the IV characteristic diagram showing the best characteristics is displayed on the curve tracer.

There is a possibility that the close bonding region of the minute region where the electrical coupling occurs may be broken by applying a load (stress) more than necessary, or the contact may become insufficient due to the insufficient load applied. In the present invention, since the load is applied while observing the IV characteristics, the application can be performed with a minimum necessary.

From the above series of processes, it is possible to firmly join the substrate 1 and the substrate 2 via the joining members 10 and 11, and to obtain an electrical connection having good IV characteristics in the close joining region. It became.

After the substrate 1 and the substrate 2 are adhered to each other by the above-mentioned method, even when various processes are performed, that is, when the adhered substrate is subjected to thinning polishing, immersion in a solvent, and ultrasonic cleaning, the IV is maintained. There was no change in the characteristics, and no change occurred in the tightly joined portion by the IR (infrared camera) camera.

After the device was manufactured by the above method, a voltage was applied between the substrate 1 and the substrate 2 and the current was gradually increased, and light emission was observed.

When the joining process by applying the load is performed in an atmosphere, for example, in a vacuum, under a reduced pressure,
It may be carried out in a reduced pressure Ar gas or nitrogen gas, etc., and the electrical connection can be sealed in the atmosphere, and good results were obtained.

In this embodiment, the insulating film is made of S
Although the i-oxide film is used, it is also possible to use an Al oxide film or a Si nitride film instead, and the intention of the present invention does not change at all.

Furthermore, in this embodiment, a pn junction between InPs was obtained, but a material other than InP, for example, S
It is also possible to perform bonding (electrical coupling) by combining i, InP, GaAs, and GaN or a combination of different materials of these materials, and the intention of the present invention does not change at all.

(Second Embodiment) FIGS. 5 and 6 are drawings showing the features of the present invention best, wherein 1 is a substrate for close bonding, 2 is a substrate for close bonding, and 3
Is an electric coupling surface (tightly bonded region) formed of a convex portion on the substrate 1, 4 is an electric coupling surface (closely bonded region) formed of a flat portion on the substrate 2, and 5 is anisotropic etching formed in the tightly bonded region. Etch pits, 6 are bonding portions for bonding to the opposing substrate 2, 7 are bonding portions for bonding to the opposing substrate 1, 8 is an insulating film for electrically insulating, and 9 is an electrical film. Insulating film for electrical insulation,
Reference numeral 10 denotes a bonding member on the insulating film 8, 11 denotes a bonding member on the insulating film 9, 12 denotes a space in a close bonding region, 13 denotes an electrode on the substrate 1 for observing an IV characteristic diagram, and 14 denotes an electrode. An electrode on the substrate 2 for observing an IV characteristic diagram;
A lead wire for electrically coupling 3 to the curve tracer, 16 is a lead wire for electrically coupling the electrode 14 to the curve tracer, and 17 is an I- in a state where the substrates 1 and 2 are not electrically coupled. A V diagram 18 is an IV characteristic diagram in a state where the substrates 1 and 2 are electrically coupled.

Next, in the above configuration, an InP (p-type) wafer is used as one of the bonding substrates 1, and a concave-shaped bonding portion 6 is formed by RIE (reactive ion etching) using a resist mask. As a result, an electric coupling surface 3 consisting of a convex portion is produced. Thereafter, an insulating film 8 consisting of a Si oxide film is formed on the joining portion 6 by using a photolithography process (not shown) using a resist film. Then, a bonding member 10 made of Al is formed on the insulating film 8 by using a photolithography process (not shown). Thereafter, the resist film is removed with a solvent, and the substrate 1 is washed.

As shown in FIG. 5, an InP (n-type) wafer is used as the other substrate 9 for bonding, and S
An insulating film 9 made of an i-oxide film is formed by a photolithographic process (not shown) using a resist film, and a bonding member 11 made of Al is formed on the insulating film 9 by a photolithographic process (not shown). A film is formed, and then a diamond needle is gently pressed into the tightly bonded region (electrical connection surface 4) from above the resist film, and then immersed in an etchant to form an etch pit 5 by anisotropic etching. To form In this case, since the etch pit is easily generated at the scratched portion, the etch pit can be formed at an arbitrary position. Thereafter, the resist film was removed with a solvent,
Then, the substrate 2 is washed.

The substrate 1 and the substrate 2 prepared by the above process are opposed to each other as shown in FIG. 1, and then subjected to a heat treatment (2) in a hydrogen stream under reduced pressure while applying a load as shown in FIG.
00 ° C). By applying a load during the heat treatment, the joining member 10 and the joining member 11 gradually join from the butted state while plastic deformation progresses due to a creep phenomenon over time. Eventually, the plastic deformation proceeds until the electrical joint surfaces 3 and 4 come into contact with each other and come into close contact with each other. During the plastic deformation, the I- which is projected on a curve tracer as shown in FIGS.
A V characteristic diagram can be observed. During the observation, when the electric coupling surface 3 and the electric coupling surface 4 are not in contact with each other, the IV characteristic diagram is as shown in FIG. 3, while the plastic deformation progresses and the electric coupling surface 3 4 and FIG. 4 come into contact with each other, and the IV characteristic diagram is as shown in FIG. During the observation, the application of the load is stopped when the IV characteristic diagram showing the best characteristics is displayed on the curve tracer. From the above series of processes, the substrate 1 and the substrate 2 are firmly joined via the joining members 10 and 11, and the electric connection having good IV characteristics is formed on the minute electric connection surface in the close connection region. It has become possible.

After the substrate 1 and the substrate 2 are adhered to each other by the above-described method, even when various processes are performed, that is, when the adhered substrate is subjected to thinning polishing, immersion in a solvent, and ultrasonic cleaning, the IV is maintained. No change occurred in the characteristics, and no change occurred in the tightly joined portion by the IR (infrared camera) camera.

After the device was manufactured by the above-described method, a voltage was applied between the substrate 1 and the substrate 2 and the current was gradually increased, and light emission was observed.

In this embodiment, A is used as the joining member.
1 is used, but any other material having plastic deformability may be used. For example, Au, Ga, Cu, Ti, Zn, P
Even with b and Sn, the same effect as that of the Al is produced.

In this embodiment, the bonding process by applying the load was performed at a low temperature (a temperature of 250 ° C. or less) during the heat treatment. However, good results were obtained when the bonding was performed at room temperature.

[0053]

As described above, according to the present invention,
After cleaning the electrical coupling surface and the junction formed on the substrate,
By applying a pressing force while observing (observing) the IV characteristic diagram in a state where the electric coupling surfaces are opposed to each other and the joints are opposed to each other, a good electric connection between the electric coupling surfaces is obtained. Bonding and obtaining mechanical strength for bonding between joints (to prevent peeling) enable close bonding between substrates and minimizing the electrical coupling area by making etch pits It is a method to Electrical coupling at room temperature or low temperature is possible,
In addition, it is possible to obtain a sufficient bonding strength (strength for preventing peeling) between the bonding portions. 2. Since a sufficient bonding strength can be obtained only by the bonding portions, it is possible to minimize the bonding area of the electrical coupling surface as much as possible. 3. Since the pressing force is applied while observing the IV characteristic diagram, good electrical coupling can be obtained without applying the pressing force more than necessary.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a light emitting device structure before a close bonding according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a light emitting device structure using a contact bonding method according to a first embodiment of the present invention.

FIG. 3 is an IV characteristic diagram of a light emitting element before close contact bonding according to first and second embodiments of the present invention.

FIG. 4 is an IV characteristic diagram of the light emitting device after the close bonding according to the first and second embodiments of the present invention.

FIG. 5 is a cross-sectional view of a light emitting device structure before close bonding according to a second embodiment of the present invention.

FIG. 6 is a cross-sectional view of a light emitting device structure using a contact bonding method according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Substrate 3 Electrical coupling surface 4 Electrical coupling surface 5 Etch pit 6 Joining part 7 Joining part 8 Insulating film 9 Insulating film 10 Joining member 11 Joining member 12 Space 13 Electrode 14 Electrode 15 Lead wire 16 Lead wire 17 I -V diagram 18 IV diagram

Claims (13)

[Claims] 1. A method for obtaining electrical bonding (hereinafter referred to as electrical coupling) in a minute region between semiconductor substrates made of the same or different materials. A contact area formed by an adhesive element for the purpose of contact, and a structure in which adhesion is performed while observing an IV characteristic diagram with a curve tracer. The structure includes: (1) a process of forming an insulating film in the joint area; (3) forming an adhesive element for providing a bonding force on the insulating film; and (3) forming one small point-like flaw in a portion of the minute region which is to be an electrical coupling surface of the close coupling region. Or (4) forming the minute point-like flaws in the tightly-bonded area in the minute area into etch pits by anisotropic etching with an etchant; To the bonding surface of the On the surface of the side, I
Forming an electrode for observing a -V characteristic diagram; and (6) aligning the adhesive elements and the tightly-bonded regions on the same or different material substrate so that they face each other, (7) In the process of applying a pressing force between the material substrates, (7) in the process of applying the pressing force, the IV characteristic generated by the electrical coupling on the electrical coupling surface is used to determine the state of the electrical coupling using a curve tracer. A method for closely bonding semiconductor substrates, wherein electrical connection between substrates of the same or different materials is performed at a low temperature from room temperature to 250 ° C. in an IV characteristic diagram observation process for observation. Wherein said semiconductor substrate, Si, I _n P, GaA
2. The method according to claim 1, wherein the semiconductor substrate is at least one selected from the group consisting of s and GaN, or a compound semiconductor formed on these semiconductor substrates. 3. The method according to claim 1, wherein the tightly-bonded region in which the electrical connection is made is formed of a flat or one or a plurality of V-shaped grooves. 4. The bonding elements in the bonding area are bonded to each other at a low temperature of room temperature to 250 ° C. by the pressing force,
2. The method according to claim 1, wherein the bonding strength between the substrates of the same or different materials is obtained. 5. The method according to claim 1, wherein the adhesive element is made of a material having a plastic deformation ability. 6. The method according to claim 5, wherein the material having plastic deformation is a metal material. 7. The method according to claim 1, wherein the metal material is Al, Au, In, Ga,
7. The method according to claim 6, wherein at least one of Sn, Cu, Ti, Zn, and Pb is used. 8. An insulating film comprising a Si oxide film, a Si nitride film, and an Al film.
2. The method according to claim 1, wherein the method is at least one selected from oxide films. 9. The method according to claim 1, wherein the adhesive element is convex, spherical, or hemispherical. 10. The tightly-bonded region (electrically-coupled portion) is sealed by applying the pressing force.
The method for tightly bonding semiconductor substrates according to the above. 11. The tightly-bonded region (electrically-coupled portion) is sealed in the atmosphere by applying the pressure in an atmosphere substantially free of oxygen. 2. The method for tightly bonding semiconductor substrates according to 1. 12. The method according to claim 11, wherein the atmosphere substantially free of oxygen is in a vacuum, under reduced pressure, or in a reduced gas or an inert gas under reduced pressure. . 13. The method according to claim 12, wherein the reducing gas or the inert gas is hydrogen gas, argon gas, nitrogen gas or a mixture thereof.