Bonding method, structure, and bonding system

Abstract

To provide a bonding method, structure, and bonding system, capable of firmly bonding two objects to be bonded together while sufficiently reducing electrical resistance of bonding parts formed from metal.SOLUTION: A bonding method includes: an argon treatment step of performing argon treatment to a first bonding part and a second bonding part of a substrate; a nitrogen treatment step of performing exposure to nitrogen plasma or irradiation with a nitrogen beam on the first bonding part and the second bonding part; a nitrogen radical treatment step of performing irradiation with nitrogen radicals on the first bonding part and the second bonding part; a hydrophilic treatment step of making water molecules adhere to the first bonding part and the second bonding part; a temporary bonding step of temporarily bonding together two objects to be bonded; and a heat treatment step of keeping the two objects to be bonded at a previously set specified temperature for a specified time to bond first bonding parts together and bond second bonding parts together.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a bonding method, a structure, and a bonding system.

Background Art

[0002] A substrate bonding method has been proposed in which two substrates are bonded by combining reactive ion etching and radical irradiation on the bonding surfaces of two substrates to be bonded (see, for example, Patent Document 1). This substrate bonding method is a method of generating hydroxyl groups (OH groups) on the bonding surfaces of two substrates, bringing the bonding surfaces of the two substrates into contact with each other and applying pressure to form hydrogen bonds between the bonding surfaces to bond the two substrates together. In this substrate bonding method, after performing reactive ion etching by exposing the bonding surfaces of the two substrates to be bonded to oxygen plasma, nitrogen radicals are irradiated onto the bonding surfaces of the two substrates. Then, the two substrates are bonded by bringing the bonding surfaces of the two substrates into contact with each other and applying pressure.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the substrate bonding method described in Patent Document 1, when bonding two substrates having a first bonding portion formed of metal and a second bonding portion formed of an insulator, due to the influence of the oxide film formed on the surface of the first bonding portion, there is a possibility that the electrical resistance in the mutually bonded first bonding portion does not sufficiently decrease.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a joining method, a structure, and a joining system capable of firmly joining two objects to be joined while sufficiently reducing the electrical resistance of a joint formed of a metal.

Means for Solving the Problems

[0006] To achieve the above object, a joining method according to the present invention is a joining method for joining two objects to be joined having a first joint formed of a metal and a second joint formed of an insulator, an argon treatment step of performing an argon treatment on at least one of the first joint and the second joint of the two objects to be joined, a nitrogen treatment step of exposing the first joint and the second joint to nitrogen plasma or irradiating them with a nitrogen beam after the argon treatment step, a nitrogen radical treatment step of irradiating the first joint and the second joint with nitrogen radicals after the nitrogen treatment step, a hydrophilization treatment step of attaching water molecules to the first joint and the second joint after the nitrogen radical treatment step, a temporary joining step of temporarily joining the two objects to be joined after the hydrophilization treatment step, a heat treatment step of joining the first joints and the second joints by maintaining the two objects to be joined at a preset specified temperature for a specified time after the temporary joining step.

[0007] A structure according to the present invention viewed from another aspect is a structure including two base materials joined via a first joint formed of a metal and a second joint formed of an insulator, at least one of the two base materials has no oxide film intervening at the joint interface between the first joints and an amorphous region is formed.

[0008] A joining system according to the present invention viewed from another aspect is A bonding system for bonding two workpieces having a first joint formed of metal and a second joint formed of an insulator, after performing argon treatment on at least one of the first joint and the second joint of the two workpieces, attaching water molecules to the first joint and the second joint, and then temporarily bonding the two workpieces to each other, the two workpieces are maintained at a preset specified temperature for a specified time, thereby bonding the first joints to each other and the second joints to each other.

Advantages of the Invention

[0009] According to the present invention, after performing argon treatment on at least one of the first joint and the second joint of the two workpieces, nitrogen treatment is performed on the first joint and the second joint, and then water molecules are attached to the first joint and the second joint. Then, after temporarily bonding the two workpieces to each other, the two workpieces are maintained at a preset specified temperature for a specified time, thereby bonding the first joints to each other and the second joints to each other. As a result, while sufficiently reducing the electrical resistance of the joint formed of metal, the two workpieces can be firmly bonded to each other.

Brief Description of the Drawings

[0010]

Figure 1

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Embodiments for Carrying Out the Invention

[0011] Hereinafter, a bonding system according to an embodiment of the present invention will be described with reference to the drawings.

[0012] In the bonding system according to this embodiment, in a chamber under reduced pressure, after performing activation treatment and hydrophilic treatment on the bonding surfaces of two objects to be bonded, the two objects to be bonded are brought into contact with each other and then heated to bond the two objects to be bonded. The two objects to be bonded each have a first bonding portion formed of metal and a second bonding portion formed of an insulator. In the activation treatment, an argon treatment step of performing argon treatment on at least one of the first bonding portion and the second bonding portion of the two objects to be bonded, a nitrogen treatment step of exposing the first bonding portion and the second bonding portion to nitrogen plasma or irradiating them with a nitrogen beam, and after the nitrogen treatment step, a nitrogen radical treatment step of irradiating the first bonding portion and the second bonding portion with nitrogen radicals are performed to activate the bonding surfaces of the two objects to be bonded. In the "argon treatment step", at least one of the first bonding portion and the second bonding portion of the two objects to be bonded is exposed to argon plasma or irradiated with an argon beam.

[0013] As shown in FIG. 1, the bonding system according to this embodiment includes an introduction port 961, a take-out port 962, a first transfer device 930, a cleaning device 940, an outer shape alignment device 800, a reversing device 950, an activation treatment device 600, a bonding device 100, a second transfer device 920, a control unit 700, and a load lock chamber 910. A water gas supply unit 960 for supplying water gas into the load lock chamber 910 is connected to the load lock chamber 910. The control unit 700 controls the first transfer device 930, the cleaning device 940, the outer shape alignment device 800, the reversing device 950, the activation treatment device 600, the bonding device 100, the second transfer device 920, and the water gas supply unit 960. HEPA (High Efficiency Particulate Air) filters (not shown) are installed in the first transfer device 930, the cleaning device 940, and the outer shape alignment device 800. As a result, the inside of these devices is an atmospheric pressure environment with extremely few particles. On the other hand, the inside of the reversing device 950, the activation treatment device 600, and the bonding device 100 is a reduced pressure atmosphere.

[0014] The first transfer device 930 has an air transfer robot 931 having an arm for gripping substrates 301 and 302, and the second transfer device 920 also has a vacuum transfer robot 921 having an arm for gripping substrates 301 and 302. The cleaning device 940 cleans the transferred substrates 301 and 302 while discharging water toward them. The outer shape alignment device 800 has an edge recognition sensor and a substrate thickness measurement unit, and while rotating the stage 803 on which the substrates 301 and 302 are placed, the edge recognition sensor 810 recognizes the edges of the substrates 301 and 302, and the substrate thickness measurement unit 802 measures the thicknesses of the substrates 301 and 302. The inversion device 950 inverts and holds the front and back of the transferred substrate 302. Then, the vacuum transfer robot 921 can grip the substrate 302 that the inversion device 950 has inverted and held with the front and back reversed.

[0015] The activation processing apparatus 600 performs an activation process for activating the bonding surfaces of the substrates 301 and 302 respectively. The activation processing apparatus 600 may include, for example, particle beam sources 3161 and 3162 as shown in FIG. 2. Here, the particle beam sources 3161 and 3162 are, for example, fast atom beam (FAB) sources, and include a discharge chamber 31601, an electrode 31602 disposed in the discharge chamber 31601, a beam source driving unit (not shown), and a gas supply unit 31604 for supplying argon gas or nitrogen gas into the discharge chamber 31601. The discharge chamber 31601 is formed in a long box shape from a carbon material, and a plurality of radiation ports 31601a for emitting a particle beam containing neutral atoms are provided on its peripheral wall. The beam source driving unit includes a plasma generation unit (not shown) for generating argon gas plasma in the discharge chamber 31601 and a DC power supply (not shown) for applying a DC voltage between the electrode 31602 and the peripheral wall of the discharge chamber 31601. The beam source driving unit applies a DC voltage between the peripheral wall of the discharge chamber 31601 and the electrode 31602 in a state where argon gas or nitrogen plasma is generated in the discharge chamber 31601. At this time, argon ions or nitrogen ions in the plasma are attracted to the peripheral wall of the discharge chamber 31601. At this time, when the argon ions or nitrogen ions heading toward the radiation port 31601a pass through the radiation port 31601a, they receive electrons from the peripheral wall of the discharge chamber 31601 formed of a carbon material at the outer peripheral portion of the radiation port 31601a. Then, these argon ions or nitrogen ions are discharged outside the discharge chamber 31601 as electrically neutral argon and nitrogen. Further, the activation processing apparatus 600 includes a horizontal driving unit 3163 that collectively supports the particle beam sources 3161 and 3162 and moves the particle beam sources 3161 and 3162 in a horizontal direction orthogonal to the facing direction of the substrates 301 and 302. In the activation processing apparatus 600, as shown in FIG. 3, the particle beam sources 3161 and 3162 move as shown by the arrow AR32 while irradiating the bonding surfaces of the substrates 301 and 302 with particle beams respectively. Note that the argon beam and the nitrogen beam are not limited to FAB, and may be ion beams containing argon ions and nitrogen ions.Further, the activation processing apparatus 600 has a nitrogen radical source that irradiates the substrates 301 and 30 with nitrogen radicals.

[0016] Returning to FIG. 1, the water gas supply unit 960 has a water gas generator (not shown). This water gas generator generates water gas by bubbling carrier gases such as argon (Ar), nitrogen (N 2 ), helium (He), and oxygen (O 2 ) into the stored water. The water gas generator is connected to the load lock chamber 910 via a supply valve and a supply pipe. The flow rates of the water gas and the carrier gas introduced into the load lock chamber 910 are adjusted by controlling the opening degree of the supply valve. Note that the water gas supply unit 960 may be configured to accelerate molecules or clusters of water (H 2 O) and irradiate them toward the bonding surfaces of the substrates 301 and 302. Here, the water gas supply unit 960 may be composed of a particle beam source that emits accelerated water (H 2 O) particles. In this case, as the particle beam source, for example, a configuration that generates water gas using an ultrasonic generating element may be used. Alternatively, a mixed gas of a carrier gas generated by the above-described bubbling or ultrasonic vibration and water (H 2 O) may be introduced into the above-described particle beam source to generate a particle beam of water and irradiate the bonding surfaces of the substrates 301 and 302.

[0017] The load lock chamber 910 is provided with a cooling device (not shown) that cools the stage supporting the substrates 301 and 302. For example, when the temperature in the load lock chamber 910 is set to 25° C. and the humidity is set to 50%, the cooling device cools the stage to 18° C., thereby making the humidity in the vicinity of the substrates 301 and 302 placed on the stage about 80%. Thereby, the amount of water gas supplied from the water gas supply unit 960 into the load lock chamber 910 can be reduced.

[0018] The bonding device 100 bonds the substrates 301 and 302 whose bonding surfaces are activated in the activation processing device 600. As shown in FIG. 4, the bonding device 100 includes a chamber 200, a stage 401, a head 402, a stage driving unit 403, a head driving unit 404, workpiece heating units 421 and 422, and a displacement measuring unit 500. In the following description, the ±Z direction in FIG. 4 is appropriately regarded as the vertical direction, and the XY direction is regarded as the horizontal direction for explanation. The chamber 200 is connected to a vacuum pump 201 via an exhaust pipe 202B and an exhaust valve 203B. When the exhaust valve 203B is opened and the vacuum pump 201 is operated, the gas in the chamber 200 is discharged to the outside of the chamber 200 through the exhaust pipe 202B, and the air pressure in the chamber 200 is reduced (depressurized). Further, the air pressure (degree of vacuum) in the chamber 200 can be adjusted by varying the opening and closing amount of the exhaust valve 203B to adjust the exhaust amount.

[0019] The stage 401 and the head 402 are arranged to face each other in the Z direction within the chamber 200. The stage 401 supports the substrate 301 on its upper surface, and the head 402 supports the substrate 302 on its lower surface. Note that the upper surface of the stage 401 and the lower surface of the head 402 may be subjected to rough machining in consideration of the case where the contact surfaces of the substrates 301 and 302 with the stage 401 and the head 402 are mirror surfaces and are difficult to peel off from the stage 401 and the head 402. The stage 401 and the head 402 each have a holding mechanism (not shown) for holding the substrates 301 and 302. The holding mechanism is composed of an electrostatic chuck or a vacuum chuck.

[0020] The stage driving unit 403 can move the stage 401 in the XY directions and rotate it around the Z axis. The head driving unit 404 moves the head 402 up and down (see the arrow AR1 in FIG. 3). The head driving unit 404 brings the head 402 closer to the stage 401 by moving the head 402 downward. Also, the head driving unit 404 moves the head 402 away from the stage 401 by moving the head 402 upward. When the head driving unit 404 applies a driving force in the direction of bringing the head 402 closer to the stage 401 to the head 402 while the substrates 301 and 302 are in contact with each other, the substrate 302 is pressed against the substrate 301. Further, the head driving unit 404 is provided with a pressure sensor 408 that measures the driving force applied by the head driving unit 404 in the direction of bringing the head 402 closer to the stage 401 to the head 402. From the measured value of the pressure sensor 408, the pressure acting on the bonding surface of the substrates 301 and 302 when the substrate 302 is pressed against the substrate 301 by the head driving unit 404 can be detected. The pressure sensor 408 is composed of, for example, a load cell.

[0021] The bonded object heating units 421 and 422 are composed of, for example, electric heaters. The bonded object heating units 421 and 422 heat the substrates 301 and 302 by transferring heat to the substrates 301 and 302 supported by the stage 401 and the head 402. Also, by adjusting the calorific value of the bonded object heating units 421 and 422, the temperature of the substrates 301 and 302 and their bonding surfaces can be adjusted.

[0022] The misalignment measurement unit 500 measures the horizontal misalignment amount of the substrate 301 with respect to the substrate 302 by recognizing the positions of the alignment marks provided on each of the substrates 301 and 302. The misalignment measurement unit 500 recognizes the alignment marks of the substrates 301 and 302 using light (e.g., infrared light) that passes through the substrates 301 and 302, for example. Based on the misalignment amount measured by the misalignment measurement unit 500, the stage drive unit 403 performs an alignment operation (alignment operation) between the substrates 301 and 302 by moving or rotating the stage 401 in the horizontal direction. The measurement of the misalignment amount by the misalignment measurement unit 500 and the alignment operation of the stage drive unit 403 are both executed under the control of the control unit 700.

[0023] Based on the measurement signals input from the pressure sensor 408, the misalignment measurement unit 500, etc., the control unit 700 outputs control signals to the stage drive unit 403, the head drive unit 404, the bonded object heating units 421 and 422, the activation processing device 600, the vacuum transfer robot 921, the atmospheric transfer robot 931, the water gas supply unit 960, etc., to control them.

[0024] Here, the operation flow of the entire bonding system according to the present embodiment will be described from when the substrates 301 and 302 are introduced into the bonding system until they are bonded and taken out of the bonding system. The substrates 301 and 302 are first placed at the introduction port 961. On the bonding surfaces of the substrates 301 and 302, a first bonding portion formed of a metal and a second bonding portion formed of an insulator are exposed. The first bonding portion is formed of a metal such as Cu. The second bonding portion is formed of an insulator such as silicon oxide (SiO 2 ), alumina (Al 2 O 3 ), etc. And the surface of the first bonding portion and the surface of the second bonding portion are exposed within the same bonding surface of the substrates 301 and 302.

[0025] Next, the substrates 301 and 302 are transported from the introduction port 961 to the cleaning device 940 by the atmospheric transfer robot 931 of the first transfer device 930, and cleaning is performed in the cleaning device 940 to remove foreign substances present on the substrates 301 and 302. Subsequently, the substrates 301 and 302 are transported from the cleaning device 940 to the outer shape alignment device 800 by the atmospheric transfer robot 931, and the outer shape alignment and the measurement of the substrate thickness are performed in the outer shape alignment device 800. Thereafter, the substrates 301 and 302 are transported into the load lock chamber 910 opened to the atmosphere by the atmospheric transfer robot 931. Then, when the degree of vacuum in the load lock chamber 910 becomes the same as the degree of vacuum in the second transfer device 920 by discharging the gas present in the load lock chamber 910, the substrates 301 and 302 are transported to the activation processing device 600 by the vacuum transfer robot 921 of the second transfer device 920.

[0026] Thereafter, the substrates 301 and 302 are transported to the activation processing device 600, and a hydrophilic treatment is performed on the bonding surfaces of the substrates 301 and 302 respectively. The hydrophilic-treated substrates 301 and 302 are transported again into the load lock chamber 910 by the vacuum transfer robot 921. Then, water gas is supplied from the water gas supply unit 960 to the load lock chamber 910, and the bonding surfaces of the substrates 301 and 302 are exposed to the water gas. As a result, more OH groups are generated on the bonding surfaces of the substrates 301 and 302. Next, the substrate 301 is transported to the bonding device 100 by the vacuum transfer robot 921. On the other hand, the substrate 302 is transported to the inversion device 950 by the vacuum transfer robot 921 and is inverted in the inversion device 950. Subsequently, the substrate 302 is transported to the bonding device 100 by the vacuum transfer robot 921.

[0027] Thereafter, substrates 301 and 302 are joined to each other in the joining apparatus 100. The joined substrates 301 and 302 are conveyed back to the load lock chamber 910 by the vacuum transfer robot 921. Thereafter, when the load lock chamber 910 is opened to the atmosphere, the joined substrates 301 and 302 are conveyed from the load lock chamber 910 to the take-out port 962 by the atmosphere transfer robot 931. The above is the flow of the operation of the entire joining system according to the present embodiment.

[0028] Next, a joining method executed by the joining system according to the present embodiment will be described with reference to FIG. 5. Note that FIG. 4 shows the flow of processing from when the substrates 301 and 302 are conveyed into the load lock chamber 910 until they are joined to each other.

[0029] First, the second transfer device 920 of the joining system conveys the substrate 301 (302) to the activation processing device 600 by the vacuum transfer robot 921, and holds the substrate 301 (302) conveyed in the activation processing device 600 on the stage 610 (step S1).

[0030] Next, the activation processing device 600 of the joining system executes an activation processing step of activating the joining surface of the substrate 301 (302) (step S2).

[0031] Subsequently, the second transfer device 920 of the joining system conveys the substrate 301 (302) from the activation processing device 600 to the load lock chamber 910 by the vacuum transfer robot 921, and holds the conveyed substrate 301 (302) on the stage in the load lock chamber 910 (step S3).

[0032] Thereafter, the water gas supply unit 960 of the joining system introduces water gas from the water gas generator into the load lock chamber 910 to expose the substrate 301 (302) to water gas (H 2 O), thereby performing a water gas exposure step of supplying water to the joining surfaces of the substrates 301 and 302 (step S4). This water gas exposure step corresponds to a hydrophilic treatment step of generating OH groups on the joining surface by supplying moisture to the joining surface of the substrate 301 (302).

[0033] Next, the second transfer device 920 of the bonding system transfers the substrate 301(302) from the load lock chamber 910 to the bonding device 100 by the vacuum transfer robot 921, and the bonding device 100 holds the transferred substrate 301(302) on the stage 401 (head 402) (step S5). Here, in the case of the substrate 302 held by the head 402 of the bonding system, first, the substrate 302 is transferred from the load lock chamber 910 to the inversion device 950, and the inversion device 950 is controlled to invert the front and back of the substrate 302. Then, the bonding system transfers the substrate 302 inverted by the inversion device 950 to the bonding device 100 by the vacuum transfer robot 921. As a result, the substrate 301 is held on the stage 401 and the substrate 302 is held on the head 402.

[0034] Subsequently, the bonding device 100 moves the substrate 302 in the direction in which the substrates 301 and 302 approach each other from the state where the substrates 301 and 302 are separated from each other, and brings the bonding surfaces of the substrates 301 and 302 into contact with each other (step S6). Here, the bonding device 100 first brings the head 402 supporting the substrate 302 closer to the stage 401 supporting the substrate 301 to bring both substrates 301 and 302 closer. Next, in the state where both substrates 301 and 302 are close to each other, the bonding device 100 executes an alignment operation of both substrates 301 and 302 based on the misalignment amount measured by the misalignment measurement unit 500. Subsequently, the bonding device 100 brings the head 402 closer to the stage 401 again to bring the two substrates 301 and 302 into contact with each other.

[0035] Thereafter, the bonding device 100 executes a bonding process for bonding the substrates 301 and 302 (step S7). Here, the bonding device 100 bonds the two substrates 301 and 302 by applying pressure to the two substrates 301 and 302 whose bonding surfaces are in contact with each other. At this time, the bonding surfaces of the substrates 301 and 302 are covered with OH groups or water molecules. Thereby, by bringing the bonding surfaces of the substrates 301 and 302 into contact with each other, the substrates 301 and 302 are temporarily bonded by hydrogen bonds between OH groups or between water molecules.

[0036] Next, the bonding apparatus 100 performs a heat treatment step of maintaining the substrates 301 and 302 bonded to each other via the first bonding portion and the second bonding portion at a preset specified temperature for a specified time (step S8). Here, it is preferable that the bonding apparatus 100 sets the specified temperature to 100°C or higher and 300°C or lower, and the specified time to 1 hour or longer and 8 hours or shorter. Thereby, most of the water molecules and hydrogen generated when the OH groups present on the bonding surfaces of the substrates 301 and 302 shift from hydrogen bonds to covalent bonds, or the water molecules and hydrogen remaining on the bonding surfaces of the substrates 301 and 302 even in a vacuum, escape to the outside of the bonding interface of the substrates 301 and 302, and it is considered that strong covalent bonds are formed between the bonding surfaces. At this time, in the process of water molecules and hydrogen escaping from the bonding interface of the temporarily bonded substrates 301 and 302, the bonding surfaces of the substrates 301 and 302 come into contact with each other even in portions that were not in contact during temporary bonding, and it is considered that the bonding interface substantially expands and the bonding area increases.

[0037] Here, the activation treatment step executed by the aforementioned activation treatment apparatus 600 will be described in detail with reference to FIG. 6. First, the activation treatment apparatus 600 performs an argon treatment of irradiating the bonding surfaces of the substrates 301 and 302 with an argon beam to remove the oxide film on the surface of the first bonding portion, and then performs an argon treatment step of amorphizing the surface of the first bonding portion (step S21). Here, the thickness from the surface of the first bonding portion of the amorphized portion in the first bonding portion is preferably 1 nm or more and 1 μm or less.

[0038] Next, after the activation treatment apparatus 600 stops irradiating the argon beam, it evacuates the Ar gas in the chamber 612. Thereafter, a nitrogen treatment step of irradiating the bonding surfaces of the substrates 301 and 302 with a nitrogen beam is performed on the activation treatment apparatus 600 (step S22).

[0039] Subsequently, the activation treatment apparatus 600 is N with respect to the bonding surfaces of the substrates 301 and 302 2A nitrogen radical treatment step of irradiating radicals is performed (step S23). Thereafter, the process of step S3 in FIG. 5 described above is executed.

[0040] In addition, in the activation treatment according to this embodiment, the processes of steps S22 and S23 described above may be omitted. That is, in the activation treatment, only the process of step S21 may be performed.

[0041] As described above, in the bonding system according to this embodiment, by irradiating the first bonding portions and the second bonding portions of the substrates 301 and 302 with an argon beam, the oxide film formed on the surface of the first bonding portion is removed and then amorphized. Thereafter, the first bonding portion and the second bonding portion are irradiated with a nitrogen beam, and then a radical treatment of irradiating the first bonding portion and the second bonding portion with nitrogen radicals is performed. Thereby, while sufficiently reducing the electrical resistance of the first bonding portion formed of metal, the two substrates 301 and 302 can be firmly bonded to each other.

[0042] By the way, in the bonding of substrates 301 and 302 through the first and second joints formed of conventional Cu, first, substrates 301 and 302 in which the first joint is recessed more than the second joint are generated by polishing with CMP. These substrates 301 and 302 have, for example, a first joint pb1 and a second joint pb2 as shown in FIG. 7(A). In this case, when temporarily bonding substrates 301 and 302 together, the bonding wave advances between the second joints pb2. That is, the bonding wave hardly advances between the first joints pb1 formed of Cu, and naturally advances on the surface of the second joints pb2 formed of an insulator without pressing substrates 301 and 302. In addition, for example, as shown in FIG. 7(B), when the first joint pb21 protrudes more than the second joint pb22, substrates 301 and 302 are bonded through the first joint pb21. Therefore, in order to advance the bonding wave, it is necessary to have a structure in which the first joint pb1 is recessed more than the second joint pb2 as shown in FIG. 7(A). Since the bonding wave can be advanced, it is preferable because substrates 301 and 302 can be temporarily bonded by advancing the bonding wave from their central portions without pressure, thereby improving the bonding accuracy. When substrates 301 and 302 are bonded under pressure, the bonding accuracy over the entire surfaces of substrates 301 and 302 decreases due to the influence of distortion generated in substrates 301 and 302, but substrates 301 and 302 may be bonded under pressure. Further, the depth from the surface of the second joint pb2 to the surface of the first joint pb1 may be set to a depth such that the first joints pb1 expand and come into contact with each other in the heat treatment process. Note that the depth from the surface of the second joint pb2 to the surface of the first joint pb1 may be a depth at which the first joint pb1 and the second joint pb2 can be made flush by CMP with respect to substrates 301 and 302.

[0043] Next, with water molecules attached to the surfaces of the first joint and the second joint, in an atmospheric environment, the second joints of the substrates 301 and 302 are brought into contact with each other to temporarily join the substrates 301 and 302. Then, by performing heat treatment on the substrates 301 and 302 at a temperature of about 350°C, the second joints are permanently joined to each other, and the first joints are thermally expanded to bring the first joints into contact with each other, and the Cu forming the first joints is diffused to join the first joints to each other. However, in this method, since moisture exists between the first joints to be joined to each other, the oxide film present at the interface between the first joints increases during the heat treatment. Therefore, Cu is diffused at a high temperature of 350°C in the heat treatment to remove the oxide film at the interface between the first joints. This method could not cope with the joining of the substrates 301 and 302 including devices with an allowable temperature of 300°C or lower.

[0044] On the other hand, as a method of joining joints formed of a metal such as Cu, after removing the oxide film formed on the joint surface by an Ar beam or the like, in an atmosphere with a relatively high degree of vacuum, with no moisture intervening between the joints to be joined to each other, there is an ultra-high vacuum direct bonding method in which the joints are brought into contact with each other to directly bond the joints. However, in the case of the substrates 301 and 302 having a so-called hybrid joint surface where the first joint formed of a metal and the second joint formed of an insulator such as an oxide, nitride, or carbide composed of an ionic crystal are exposed, it is necessary to simultaneously bond both the first joints and the second joints by the same process. Then, in the aforementioned ultra-high vacuum direct bonding method, although the first joints formed of a metal can be joined, the second joints formed of an insulator cannot be joined. Also, in the joining of the second joints formed of an insulator, joining by the aforementioned ultra-high vacuum direct bonding method is not possible, and hydrophilic bonding with an OH group intervening is required. Therefore, for the second joint, N 2 RIE treatment and N 2By continuously performing radical treatment, an unstable ON group is generated on the second joint portion, and then, before the ON group disappears, it is brought into contact with water molecules present in the atmosphere to generate OH groups on the surface of the second joint portion. Then, the second joint portions having OH groups generated on their surfaces are brought into contact with each other to hydrophilically bond the second joint portions to each other. In this hydrophilic bonding, strong bonding can be achieved by performing heat treatment at a low temperature of 100°C or higher and 200°C or lower. However, the direct bonding method in ultra-high vacuum between the first joint portions and the hydrophilic bonding between the second joint portions cannot be simply combined.

[0045] Therefore, in the present embodiment, the oxide film formed on the surface of the first joint portion is removed by Ar treatment using Ar plasma or an Ar particle beam, and a porous region is formed in the vicinity of the surface of the second joint portion. As shown in FIG. 8(A), by irradiating the surface of the first joint portion pb1 with an Ar particle beam, the natural oxide film Lox formed in the vicinity of the surface of the first joint portion pb1 is removed, and as shown in FIG. 8(B), an amorphous region Lam is formed in the vicinity of the surface of the second joint portion pb1. Further, as shown in FIG. 8(C), by irradiating the surface of the second joint portion pb2 with an Ar particle beam, as shown in FIG. 8(D), a porous region Lpo is formed in a region reaching a depth corresponding to the energy of the Ar particle beam from the surface of the second joint portion pb2. As a result, it has been discovered that water molecules can be accumulated in the porous region Lpo in the vicinity of the surface of the second joint portion. Further, if the substrates 301 and 302 are bonded to each other in a vacuum, the water molecules attached to the surfaces of the substrates 301 and 302 are removed, no moisture is present at the interface between the first joint portions, and it has been discovered that it is possible to bond the second joint portions to each other with the water molecules accumulated in the porous regions in the vicinity of their surfaces interposed therebetween.

[0046] However, for the hydrophilic bonding between the second joints, after the activation treatment for activating the substrates 301 and 302, a step of attaching water molecules to the surfaces of the substrates 301 and 302 is required. In this step of attaching water molecules, water molecules also adhere to the surface of the first joint. On the other hand, in the Ar treatment of the present embodiment, an amorphous region is further formed after removing the oxide film on the surface of the first joint. Then, it was discovered that the oxide film formed by the attachment of water molecules on the amorphous region on the surface of the first joint diffuses and disappears by heat treatment at a relatively low temperature compared to a relatively strong oxide film with high crystallinity. Based on these findings, it has been possible to realize two opposing joints: the bonding by the ultra-high vacuum direct bonding method without the intervention of moisture and the hydrophilic bonding with the intervention of moisture. That is, in the present embodiment, after the Ar treatment, nitrogen gas treatment is performed, and then nitrogen radical treatment is performed.

[0047] Note that the amorphous region formed in the Ar treatment diffuses and disappears by performing heat treatment at a temperature of 100°C or higher and 300°C or lower (preferably 100°C or higher and 200°C or lower) for 2 hours or more and 8 hours or less as long as the thickness is 1 nm or more and 1 μm or less (preferably 15 nm or less).

[0048] As described above, the embodiments of the present invention have been explained, but the present invention is not limited to the configurations of the foregoing embodiments. For example, the activation treatment apparatus 600 may perform an argon treatment step by exposing the first joints and the second joints of the substrates 301 and 302 to Ar plasma. In this case, as shown in FIG. 9, the activation treatment apparatus 600 may have a stage 610, a chamber 612, a trap plate 614, a waveguide 615, a magnetron 616, and a high-frequency power supply 617. Further, the activation treatment apparatus 600 has an N 2 gas supply unit (nitrogen gas supply unit) 620A and an Ar gas supply unit (argon gas supply unit) 620B. N 2 The gas supply unit 620A is N 2It may have a gas storage section 621A, a supply valve 622A, and a supply pipe 623A. The Ar gas supply section 620B has an Ar gas storage section 621B, a supply valve 622B, and a supply pipe 623B. Substrates 301 and 302 are placed on the stage 610. The chamber 612 is connected to a waveguide 615 through a glass window 613. The chamber 612 is connected to a vacuum pump 201 through an exhaust pipe 202A and an exhaust valve 203A. When the exhaust valve 203A is opened and the vacuum pump 201 is operated, the gas in the chamber 612 is discharged outside the chamber 612 through the exhaust pipe 202A, and the air pressure in the chamber 612 is reduced (depressurized).

[0049] The microwave generated by the magnetron 616 is introduced into the chamber 612 through the waveguide 615. As the magnetron 616, for example, one that generates microwaves with a frequency of 2.45 GHz can be adopted. And, when N 2 gas is introduced and microwaves are introduced from the waveguide 615, a plasma PLM is formed in the vicinity of the glass window 613 in the chamber 612. The trap plate 614 traps the ions contained in the plasma PLM and allows only radicals to flow down to the stage 610. The magnetron 616 and N 2 the gas supply section 620A and the trap plate 614 generate a plasma PLM in the chamber 612 and supply N 2 radicals in the plasma to the bonding surfaces of the substrates 301 and 302 supported on the stage 610, thus constituting a plasma generation source. Here, the activation processing apparatus 600 has been described as having a configuration including a magnetron 616 and a waveguide 615, but it is not limited thereto. Instead, a configuration including a flat electrode provided on the glass window 613 and a high-frequency power source electrically connected to the flat electrode may be used. In this case, as the high-frequency power source, for example, one that applies a 27 MHz high-frequency bias can be adopted.

[0050] The high-frequency power supply (bias application unit) 617 applies a high-frequency bias to the substrates 301 and 302 supported by the stage 610. As this high-frequency power supply 617, for example, one that generates a high-frequency bias of 13.56 MHz can be adopted. In this way, by applying a high-frequency bias to the substrates 301 and 302 with the high-frequency power supply 617, a sheath region is generated where ions having kinetic energy repeatedly collide with the substrates 301 and 302 near the bonding surfaces of the substrates 301 and 302. Then, the bonding surfaces of the substrates 301 and 302 are etched by the ions having kinetic energy present in this sheath region.

[0051] Also, in the embodiment, for example, the activation processing apparatus 600 may perform a nitrogen treatment step by exposing the first and second bonding portions of the substrates 301 and 302 to nitrogen plasma.

[0052] In the embodiment, the activation processing apparatus may be configured to generate N 2 radicals by ICP (Inductively Coupled Plasma). For example, as shown in FIG. 10, the activation processing apparatus 2600 includes a stage 610, a chamber 2612, a solenoid coil 2616, and a high-frequency power supply 617. In FIG. 10, the same components as those in the modification example shown in FIG. 9 are denoted by the same reference numerals as in FIG. 9. N 2 The N gas storage unit 621A is connected to the chamber 2612 via a supply valve 622A and a supply pipe 623A. Also, the Ar gas storage unit 621B is also connected to the chamber 2612 via a supply valve 622B and a supply pipe 623B. Further, the chamber 2612 is connected to a vacuum pump 201 via an exhaust pipe 202A and an exhaust valve 203A.

[0053] A high-frequency current of, for example, 27.12 MHz is supplied to the solenoid coil 2616. Then, N 2When a high-frequency current flows through the solenoid coil 2616 with gas introduced, a high-density plasma PLM is formed in the chamber 2612. Here, the ions in the plasma PLM are trapped by the magnetic field generated by the solenoid coil 2616, and only the radicals in the plasma PLM flow downward to the stage 610.

[0054] According to this configuration, a plasma PLM with a higher density than the plasma PLM that can be generated by the activation processing apparatus 600 according to the embodiment can be formed in the chamber 2612. Therefore, N 2 In radical treatment, N supplied to the bonding surfaces of the substrates 301 and 302 2 The supply amount of radicals per unit time can be increased, so N 2 The amount of radicals increases, which is more effective for improving the bonding strength of the substrates 301 and 302.

[0055] Also, in the embodiment, an example was described in which after the substrates 301 and 302 are cleaned in the cleaning apparatus 940, the activation treatment of the bonding surfaces of the substrates 301 and 302 is performed in the activation processing apparatus 600, and then the bonding process of the substrates 301 and 302 is performed in the bonding apparatus 100. However, the order of cleaning, hydrophilic treatment, and bonding of the substrates 301 and 302 is not limited to this. For example, after the hydrophilic treatment of the bonding surfaces of the substrates 301 and 302 is performed, the substrates 301 and 302 may be cleaned, and then the bonding process of the substrates 301 and 302 may be performed.

[0056] Furthermore, in the embodiment, in the load lock chamber 910, without opening the load lock chamber 910 to the atmosphere, the bonding surfaces of the substrates 301 and 302 are exposed to water gas (H 2Although the configuration for performing the water supply process of exposing to water gas (H₂O) has been described, the location where the bonding surfaces of the substrates 301 and 302 are exposed to water gas is not limited to the load lock chamber 910. For example, in the activation processing apparatus 600, a configuration in which the bonding surfaces of the substrates 301 and 302 are exposed to water gas may be employed. In this case, the aforementioned water gas generation apparatus may be configured to be connected to the chamber 612 of the activation processing apparatus 600 via a supply valve and a supply pipe. Further, the water supply process may be performed within the chamber 200 of the bonding apparatus 100 or within the chamber of the second transfer apparatus 920. Alternatively, in the substrate bonding method according to the embodiment, after the substrates 301 and 302 are transferred to the load lock chamber 910, the load lock chamber 910 may be opened to the atmosphere to supply moisture to the bonding surfaces of the substrates 301 and 302. In this case, the atmosphere having a predetermined humidity existing outside the load lock chamber 910 is introduced into the load lock chamber 910. And when introducing the atmosphere into the load lock chamber 910, in order to prevent the adhesion of unfavorable impurities (e.g., carbon) in the atmosphere to the bonding surfaces of the substrates 310 and 302, it is preferable that the load lock chamber 910 is configured to introduce the atmosphere into the load lock chamber 910 through a predetermined filter. Then, after the load lock chamber 910 is opened to the atmosphere, the load lock chamber is depressurized again, and then the substrates 301 and 302 may be transferred from the load lock chamber 910 to the bonding apparatus 100. According to this configuration, since it is not necessary to connect the water gas supply unit 960 to the load lock chamber 910, the configuration of the bonding system can be simplified.

[0057] Alternatively, the substrate bonding method may be configured such that after performing the water supply process of exposing the bonding surfaces of the substrates 301 and 302 to water gas without opening the load lock chamber 910 in the load lock chamber 910, the load lock chamber 910 is opened to the atmosphere.

[0058] In the embodiment, the configuration for performing the water supply process of supplying water gas (H₂O) to the bonding surfaces of the substrates 301 and 302 has been described. However, the present invention is not limited thereto. For example, instead of water gas, a gas containing H or OH groups or a gas containing a carbon compound may be supplied to the bonding surfaces of the substrates 301 and 302. 2 O) has been described, but not limited to this. For example, instead of water gas, a gas containing H, OH groups or a gas containing a carbon compound may be supplied to the bonding surfaces of the substrates 301 and 302.

[0059] In the embodiment, an example of performing a heat treatment for heating the substrates 301 and 302 in the bonding apparatus 100 has been described, but the configuration is not limited to performing the heat treatment in the bonding apparatus 100. For example, for example, after performing temporary bonding in the bonding apparatus 100, a heat treatment process may be performed on the substrates 301 and 302 by an annealing furnace (not shown) separate from the bonding apparatus 100.

[0060] In the embodiment, an example of performing the Ar treatment process has been described, but instead, a treatment using an inert gas such as neon, krypton, or xenon, or a non-oxidizing gas such as nitrogen may be performed.

[0061] In the embodiment, an example of performing the nitrogen radical treatment process has been described, but instead, a treatment of irradiating the bonding surfaces of the substrates 301 and 302 with an unsaturated hydrocarbon gas and ozone may be performed. Specifically, a gas exposure process of exposing at least one of the bonding surfaces of the two objects to be bonded to an atmosphere in which an unsaturated hydrocarbon gas and an ozone gas are present may be performed. Examples of the unsaturated hydrocarbon gas include ethylene gas. In this case, together with the gas exposure process, a moisture removal process of removing moisture adhering to at least one of the bonding surfaces may be performed. Note that instead of the nitrogen treatment process and the nitrogen radical treatment process, the gas exposure process may be performed.

[0062] The bonding apparatus according to the present invention is, for example, as shown in FIG. 11, a so-called chip mounter for mounting a chip CP on a substrate WT, and may be a bonding apparatus 4100 including a stage 4031, a bonding unit 4033, a head driving unit 36 for driving a head 4033H, and imaging units 4035a, 4035b, and 4041. The stage 4031 holds the substrate WT in a posture in which the surface WTf of the substrate WT where the chip CP is to be mounted faces vertically downward, that is, in the -Z direction. The bonding unit 33 includes a piezo actuator for adjusting the inclination of the head 4033H, a second disk member 334, and a head 33H that holds the chip CP from vertically below (-Z direction). The head driving unit 36 moves the head 33H holding the chip CP vertically upward (+Z direction) to bring the head 33H closer to the stage 31 and bring the chip CP into contact with the substrate WT.

[0063] In the embodiment, as shown in, for example, FIG. 12(A), the activation processing apparatus 600 has a support portion 5062 that supports the holding frame RI1 in a posture in which one surface side of the sheet TE where the chip CP is attached faces the particle beam source 61 side, that is, in a posture facing vertically downward, and performs an argon processing step of irradiating an Ar particle beam or a nitrogen processing step of irradiating a nitrogen particle beam toward the bonding surface CPf of each chip CP attached to the sheet TE from the particle beam source 61. Here, the activation processing apparatus 600 prepares only one holding frame RI1 for holding the sheet TE to which a plurality of chips CP are attached, and irradiates the chips CP attached to the sheet TE held by the prepared holding frame RI1 with an Ar particle beam and a nitrogen particle beam as shown by an arrow AR535. The activation processing apparatus 600 moves the particle beam source 31601 in the X-axis direction while irradiating the bonding surface CPf of the chip CP with the particle beam, as shown by an arrow AR534 in FIGS. 12(A) and (B), for example. Here, the activation processing apparatus 600 may irradiate the bonding surface CPf of all the chips CP attached to the tape TE with the particle beam while moving the particle beam source 31601 in the +X direction, and then irradiate the bonding surface CPf of the chip CP with the particle beam while moving the particle beam source 61 in the -X direction.

[0064] According to this configuration, since the chip CP attached to the sheet TE is irradiated with an Ar particle beam and a nitrogen particle beam, impurities generated from the chip CP or the sheet TE are blown in a direction away from the chip CP and do not return to the bonding surface CPf side of the chip CP. Therefore, it is effective from the viewpoint of reducing the adhesion of impurities to the bonding surface CPf of the chip CP.

[0065] When processing the chip CP attached to the sheet TE, it is preferable to perform a gas exposure treatment step of weakening the irradiation intensity of the plasma or the particle beam and exposing it to an atmosphere in which an unsaturated hydrocarbon gas and an ozone gas are present.

[0066] The present invention can be implemented in various embodiments and modifications without departing from the spirit and scope of the present invention in a broad sense. In addition, the above-described embodiments are for explaining the present invention and do not limit the scope of the present invention. That is, the scope of the present invention is indicated by the claims rather than the embodiments. And various modifications made within the scope of the claims and within the scope of the meaning of the invention equivalent thereto are regarded as being within the scope of the present invention.

Industrial Applicability

[0067] The present invention is suitable for the manufacture of, for example, CMOS (Complementary MOS) image sensors, memories, arithmetic elements, and MEMS (Micro Electro Mechanical Systems).

Explanation of Signs

[0068] 100: Bonding device, 200,612,2612: Chamber, 201: Vacuum pump, 202A,202B: Exhaust pipe, 203A,203B: Exhaust valve, 301,302: Substrate, 401,610,803: Stage, 402: Head, 403: Stage drive unit, 404: Head drive unit, 408: Pressure sensor, 421,422: Bonding object heating unit, 500: Position deviation measurement unit, 600,2600: Activation processing device, 613: Glass window, 614: Trap plate, 615: Waveguide, 616: Magnetron, 617: High-frequency power supply, 620A:N 2 Gas supply unit, 620B: Ar gas supply unit, 621A:N 2 Gas storage unit, 621B: Ar gas storage unit, 622A,622B: Supply valve, 623A,623B: Supply pipe, 700: Control unit, 800: Outer shape alignment device, 802: Substrate thickness measurement unit, 810: Edge recognition sensor, 910: Load lock chamber, 920: Second transfer device, 930: First transfer device, 921: Vacuum transfer robot, 931: Atmospheric transfer robot, 940: Cleaning device, 950: Inversion device, 960: Water gas supply unit, 961: Introduction port, 962: Extraction port, 2616: Solenoid coil

Claims

1. A bonding method for bonding two workpieces having a first bonding portion formed of a metal and a second bonding portion formed of an insulator, an argon treatment step of performing argon treatment on at least the first bonding portion and the second bonding portion of one of the two workpieces, a nitrogen treatment step of exposing the first bonding portion and the second bonding portion to nitrogen plasma or irradiating them with a nitrogen beam after the argon treatment step, a nitrogen radical treatment step of irradiating the first bonding portion and the second bonding portion with nitrogen radicals after the nitrogen treatment step, a hydrophilic treatment step of attaching water molecules to the first bonding portion and the second bonding portion after the nitrogen radical treatment step, a temporary bonding step of temporarily bonding the two workpieces together after the hydrophilic treatment step, a heat treatment step of bonding the first bonding portions to each other and the second bonding portions to each other by maintaining the two workpieces at a preset specified temperature for a specified time after the temporary bonding step, including: Bonding method.

2. In the argon treatment step, after removing the oxide film formed on at least the surface of the first bonding portion, the surface of the first bonding portion is amorphized, The bonding method according to claim 1.

3. In the argon treatment step, a porous region is formed in the vicinity of the surface of the second bonding portion, The bonding method according to claim 1 or 2.

4. The thickness of the amorphized portion in the first bonding portion from the surface of the first bonding portion is 1 nm or more and 1 μm or less, The bonding method according to claim 2.

5. The specified temperature is 100°C or more and 300°C or less, The bonding method according to claim 1 or 2.

6. The specified time is 1 hour or more and 8 hours or less, The bonding method according to claim 5.

7. In the argon treatment step, an argon beam is irradiated onto at least the first bonding portion and the second bonding portion of one of the two workpieces, The bonding method according to claim 1 or 2.

8. In the nitrogen treatment step, a nitrogen beam is irradiated onto at least the first bonding portion and the second bonding portion of one of the two workpieces, The bonding method according to claim 1 or 2.

9. The surface of the first bonding portion and the surface of the second bonding portion are exposed within the same bonding surface, The bonding method according to claim 1 or 2.

10. The first joint portion is formed of Cu. The bonding method according to claim 1 or 2.

11. The first joint portion is recessed more than the second joint portion. The bonding method according to claim 1 or 2.

12. A structure including two base materials joined via a first joint portion formed of a metal and a second joint portion formed of an insulator, at least one of the two base materials has an amorphous region formed at a joint interface between the first joint portions without an oxide film intervening therebetween. Structure.

13. A bonding method for bonding two workpieces having a first joint portion formed of a metal and a second joint portion formed of an insulator, an argon treatment step of performing argon treatment on at least one of the first joint portion and the second joint portion of the two workpieces; a hydrophilic treatment step of attaching water molecules to the first joint portion and the second joint portion after the argon treatment step; a temporary bonding step of temporarily bonding the two workpieces together after the hydrophilic treatment step; a heat treatment step of bonding the first joint portions and the second joint portions together by maintaining the two workpieces at a preset specified temperature for a specified time after the temporary bonding step. Bonding method.

14. A bonding method for bonding two workpieces having a first joint portion formed of a metal and a second joint portion formed of an insulator, an argon treatment step of performing argon treatment on at least one of the first joint portion and the second joint portion of the two workpieces; a gas exposure step of exposing a bonding surface of at least one of the two workpieces to an atmosphere in which an unsaturated hydrocarbon gas and an ozone gas are present; a temporary bonding step of temporarily bonding the two workpieces together after the gas exposure step. Bonding method.

15. A bonding system for bonding two workpieces having a first joint portion formed of a metal and a second joint portion formed of an insulator, after performing argon treatment on at least one of the first joint portion and the second joint portion of the two workpieces, water molecules are attached to the first joint portion and the second joint portion, and then the two workpieces are temporarily bonded together, and then the two workpieces are maintained at a preset specified temperature for a specified time to bond the first joint portions and the second joint portions together. Bonding system.

16. After performing argon treatment on at least one of the first and second joint portions of the two objects to be joined, and before attaching water molecules to the first and second joint portions, after exposing the first and second joint portions to nitrogen plasma or irradiating them with a nitrogen beam, irradiate the first and second joint portions with nitrogen radicals. The joining system according to claim 15.

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