Joining method and joining apparatus

Abstract

To provide a technology that can suppress oxidation of substrate-to-substrate joining surfaces.SOLUTION: A joining method includes the steps for: preparing a first substrate and a second substrate having on the surfaces a first region where an insulating film is exposed and a second region where a conductive film is exposed; applying an ionic liquid to at least one of the surfaces of the first substrate and the second substrate; and joining the surface of the first substrate to the surface of the second substrate via the ionic liquid.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a bonding method and a bonding apparatus.

Background Art

[0002] A technique for bonding substrates having an insulating film and a conductive film formed on their surfaces is known (see, for example, Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present disclosure provides a technique capable of suppressing oxidation of the bonding surface between substrates.

Means for Solving the Problems

[0005] A bonding method according to an aspect of the present disclosure includes a step of preparing a first substrate and a second substrate having a first region where an insulating film is exposed and a second region where a conductive film is exposed on a surface thereof, a step of applying an ionic liquid to at least one of the surfaces of the first substrate and the second substrate, and a step of bonding the surface of the first substrate and the surface of the second substrate through the ionic liquid. death , The aforementioned preparation step includes a step of treating the surface of the first substrate and the surface of the second substrate by chemical mechanical polishing. .

Effects of the Invention

[0006] According to the present disclosure, oxidation of the bonding surface between substrates can be suppressed.

Brief Description of the Drawings

[0007] [Figure 1] Figure 1 is a flowchart showing a joining method according to an embodiment. [Figure 2] Figure 2 is a cross-sectional view showing a joining method according to an embodiment. [Figure 3] Figure 3 is a cross-sectional view showing a joining method according to an embodiment. [Figure 4] Figure 4 is a cross-sectional view showing a joining method according to an embodiment. [Figure 5] Figure 5 is a cross-sectional view showing a joining method according to an embodiment. [Figure 6] Figure 6 is a cross-sectional view showing a joining method according to an embodiment. [Figure 7] Figure 7 is a cross-sectional view showing a joining method according to an embodiment. [Figure 8] Figure 8 is a cross-sectional view showing a joining device according to an embodiment. [Figure 9] Figure 9 is a longitudinal cross-sectional view showing a joining device according to an embodiment. [Modes for carrying out the invention]

[0008] Hereinafter, exemplary embodiments of the present disclosure, not limited to those described herein, will be described with reference to the attached drawings. In all attached drawings, identical or corresponding members or components are denoted by the same or corresponding reference numerals, and redundant descriptions are omitted.

[0009] [Bonding of circuit boards] In recent years, along with the miniaturization and three-dimensionalization of VLSI (Very Large-Scale Integration), 3D stacking technology, which directly bonds electronic circuit elements formed on different substrates separately to create a single electronic circuit element, has attracted attention. In particular, hybrid bonding, in which the insulating film and conductive film of one substrate are simultaneously bonded to the insulating film and conductive film of the other substrate, is important for further increasing the speed and reducing the power consumption of VLSI. The conductive film is, for example, an electrode pad and is used for input and output of electrical signals.

[0010] In hybrid bonding, two substrates with different allowable thermal budgets (for example, the vertical three-dimensional stacked formation of an N-channel (Nch) transistor circuit section and a P-channel (Pch) transistor circuit section of a C-FET (Complementary - Field Effect Transistor) fabricated on a Si substrate, or different substrates such as a Si substrate and a Ge or III-V substrate) can be bonded together after forming electronic circuit elements to form one element. In hybrid bonding, since there is no need for signal communication between low-impedance input / output circuits formed on different substrates, the signal transmission between electronic circuit elements formed on the substrates can be significantly accelerated.

[0011] Hereinafter, regarding hybrid bonding, a bonding method capable of suppressing oxidation of the bonding surface between substrates will be described.

[0012] 〔Bonding Method〕 Referring to FIGS. 1 to 7, the bonding method according to the embodiment will be described. As shown in FIG. 1, the bonding method according to the embodiment has steps S1 to S3. Steps S1 to S3 are carried out in this order.

[0013] In step S1, a first substrate 10 and a second substrate 20 are prepared.

[0014] As shown in FIG. 2, the first substrate 10 has an arithmetic unit 11 and a wiring layer 12.

[0015] The arithmetic unit 11 is formed including a part of a base substrate 13. The arithmetic unit 11 includes semiconductor devices such as transistors, for example. The base substrate 13 is a semiconductor wafer, for example.

[0016] The wiring layer 12 is, for example, a multilayer wiring. The wiring layer 12 includes a wiring 14, an electrode pad 15, a first insulating film 16, and a second insulating film 17. The wiring 14 is provided in multiple layers. The wiring 14 is formed of, for example, copper (Cu). The wiring 14 is electrically connected to the arithmetic unit 11. The electrode pad 15 is provided on the wiring 14 at the position farthest from the underlying substrate 13. The electrode pad 15 is electrically connected to the wiring 14. The electrode pad 15 is electrically connected to the arithmetic unit 11 via the wiring 14. The upper surface of the electrode pad 15 is exposed. The electrode pad 15 is formed of, for example, Cu. The first insulating film 16 is, for example, an interlayer insulating film that fills the space between the wirings 14. The interlayer insulating film is preferably a low dielectric constant (Low-k) film. The interlayer insulating film is not particularly limited, and examples thereof include a SiO film, a SiN film, a SiOC film, a SiON film, or a SiOCN film. The SiO film means a film containing silicon (Si) and oxygen (O). The atomic ratio of Si to O in the SiO film is not limited to 1:1. The same applies to the SiN film, the SiOC film, the SiON film, and the SiOCN film. The second insulating film 17 is provided on the first insulating film 16. The upper surface of the second insulating film 17 is exposed. The upper surface of the second insulating film 17 is flush with, for example, the upper surface of the electrode pad 15. The second insulating film 17 may be, for example, an insulating film excluding an oxide film. In this case, when the ionic liquid is applied to the surface of the first substrate 10 in step S2, it is possible to suppress dissolution and alteration in the ionic liquid. The second insulating film 17 is, for example, a SiC film.

[0017] The wiring layer 12 may further have a barrier film, for example, between the wiring 14 and the first insulating film 16. The wiring layer 12 may further have a barrier film, for example, between the electrode pad 15 and the first insulating film 16. The barrier film suppresses the diffusion of metal from the wiring 14 and the electrode pad 15 to the first insulating film 16. The barrier film is not particularly limited, and examples thereof include a TaN film and a TiN film. The TaN film means a film containing tantalum (Ta) and nitrogen (N). The atomic ratio of Ta to N in the TaN film is not limited to 1:1. The same applies to the TiN film.

[0018] Thus, the first substrate 10 has a first region A11 on its surface 10a where the second insulating film 17 is exposed, and a second region A12 where the electrode pad 15 is exposed. The second insulating film 17 is an example of an insulating film, and the electrode pad 15 is an example of a conductive film.

[0019] The second substrate 20 has substantially the same configuration as, for example, the first substrate 10. As shown in Figure 3, the second substrate 20 has a calculation unit 21 and a wiring layer 22.

[0020] The calculation unit 21 is formed including a portion of the base substrate 23.

[0021] The wiring layer 22 is, for example, a multilayer wiring. The wiring layer 22 has wiring 24, an electrode pad 25, a first insulating film 26, and a second insulating film 27. The electrode pad 25 is formed from, for example, the same material as the electrode pad 15. In this case, even if the electrode pad 15 and the electrode pad 25 come into contact via the ionic liquid in step S3, dissimilar metal contact corrosion (galvanic corrosion) does not occur.

[0022] Thus, the second substrate 20 has a first region A21 on its surface 20a where the second insulating film 27 is exposed, and a second region A22 on its surface where the electrode pad 25 is exposed. The second insulating film 27 is an example of an insulating film, and the electrode pad 25 is an example of a conductive film.

[0023] Step S1 may include flattening the surface 10a of the first substrate 10 and the surface 20a of the second substrate 20 by chemical mechanical polishing (CMP). In this case, when joining the surface 10a of the first substrate 10 and the surface 20a of the second substrate 20 in step S3, the generation of voids caused by the step difference between the exposed surfaces of the electrode pads 15, 25 and the exposed surfaces of the second insulating films 17, 27 can be suppressed. Step S1 may also include cleaning the surfaces 10a, 20a with a cleaning solution after flattening them.

[0024] In step S2, as shown in Figure 4, an ionic liquid is applied to the surface 10a of the first substrate 10. This covers the surface 10a of the first substrate 10 with a liquid film 18 of the ionic liquid, thereby preventing oxidation of the exposed surface of the electrode pad 15.

[0025] Step S2 may include, for example, gelling or solidifying the liquid film 18 applied to the surface 10a of the first substrate 10. In this case, the applied ionic liquid can react with the material constituting the electrode pad 15, preventing the exposed surface of the electrode pad 15 from melting. For example, the liquid film 18 can be gelled or solidified by heating an ionic liquid that becomes a gel or solid at a first temperature to a second temperature to liquefy it, and then applying it to the first substrate 10 held at the first temperature. The first temperature may be, for example, room temperature. The second temperature is a temperature higher than the first temperature and is not particularly limited as long as it is a temperature at which the ionic liquid can be liquefied.

[0026] The ionic liquid may contain, for example, a material that dissolves oxide films. In this case, by applying the ionic liquid to the surface 10a of the first substrate 10, oxide films such as native oxide films that may form on the exposed surface of the electrode pad 15 can be removed.

[0027] The ionic liquid may contain, for example, an oxoacid structure with 6 or more carbon atoms. When the number of carbon atoms is 6 or more, the ionic liquid exhibits low viscosity at relatively low temperatures, allowing it to be coated onto the first substrate 10 at relatively low temperatures. Preferably, the number of carbon atoms is 8 or more. In this case, the ionic liquid can be easily coated onto the first substrate 10 at low temperatures. The oxoacid structure may be present in at least one of a cation and an anion. Examples of oxoacid structures include carboxylate anions with 6 or more carbon atoms. Examples of carboxylate anions with 6 or more carbon atoms include decanoate anions (C9H 19 COO -) is preferred. When the ionic liquid contains a carboxylic acid anion with 6 or more carbon atoms, various cations can be used. Examples of cations include phosphate cations and sulfate cations. Trihexyltetradecylphosphonium decanoate (THTDP-DcO) is preferred as the ionic liquid.

[0028] In step S2, as shown in Figure 5, an ionic liquid is applied to the surface 20a of the second substrate 20, similar to the first substrate 10. This covers the surface 20a of the second substrate 20 with a liquid film 28 of the ionic liquid, thereby preventing oxidation of the exposed surface of the electrode pad 25.

[0029] In step S2, for example, the ionic liquid may be applied only to the surface 10a of the first substrate 10, or only to the surface 20a of the second substrate 20. In step S2, for example, the ionic liquid may be applied to at least one of the surfaces 10a, 20a of the first substrate 10 and the second substrate 20.

[0030] In step S3, the surface 10a of the first substrate 10 and the surface 20a of the second substrate 20 are joined via the liquid films 18 and 28.

[0031] First, as shown in Figure 6, the surface 10a of the first substrate 10 and the surface 20a of the second substrate 20 are held facing each other, and the first substrate 10 and the second substrate 20 are aligned. Alignment includes, for example, aligning the electrode pad 15 and the electrode pad 25. Alignment also includes, for example, aligning the second insulating film 17 and the second insulating film 27.

[0032] Next, as shown in Figure 7, the first substrate 10 and the second substrate 20 are heated to a temperature at which the liquid films 18 and 28 liquefy, and the surfaces 10a of the first substrate 10 and 20a of the second substrate 20 are brought close together and pressed together. This causes the surfaces 10a of the first substrate 10 and 20a of the second substrate 20 to be in close contact. At this time, the liquefied ionic liquids of the liquid films 18 and 28 dissolve the electrode pads 15 and 25. As a result, metal-metal and metal-carbon-metal bonds are formed through the ionic liquids, and the contact resistance between electrode pad 15 and electrode pad 25 is reduced. In addition, when the surfaces 10a of the first substrate 10 and 20a of the second substrate 20 are joined, the ionic liquid on the joining surfaces of the first substrate 10 and 20 is pushed out and removed. Therefore, it is not necessary to remove the liquid films 18 and 28 before joining the surface 10a of the first substrate 10 and the surface 20a of the second substrate 20. Also, for example, if the electrode pad 15 and the electrode pad 25 are formed from the same material, galvanic corrosion will not occur even if the electrode pad 15 and the electrode pad 25 come into contact via the ionic liquid. For example, when THTDP-DcO is used as the ionic liquid, it is preferable to heat the first substrate 10 and the second substrate 20 to 230°C to 240°C in step S3.

[0033] In step S3, for example, the first substrate 10 and the second substrate 20 may be pressed together, and then the first substrate 10 and the second substrate 20 may be heated to a temperature at which the liquid films 18 and 28 liquefy.

[0034] In step S3, the surface 10a of the first substrate 10 and the surface 20a of the second substrate 20 may be joined via the liquid films 18 and 28 under a vacuum atmosphere. In this case, the surfaces of the electrode pads 15 and 25 do not come into contact with oxidizing gases or moisture, thus suppressing oxidative corrosion. Since ionic liquids do not easily volatilize even under a vacuum atmosphere and high-temperature environments, the liquid films 18 and 28 do not disappear before the surface 10a of the first substrate 10 and the surface 20a of the second substrate 20 are joined.

[0035] As described above, according to the bonding method of the embodiment, an ionic liquid is applied to at least one bonding surface of the first substrate 10 and the second substrate 20, and then the surface 10a of the first substrate 10 and the surface 20a of the second substrate 20 are bonded via the ionic liquid. This allows the first substrate 10 and the second substrate 20 to be bonded while the bonding surface between the first substrate 10 and the second substrate 20 is protected by the ionic liquid. Therefore, oxidation of the bonding surface between the first substrate 10 and the second substrate 20 can be suppressed.

[0036] According to the bonding method of the embodiment, when bonding the surface 10a of the first substrate 10 and the surface 20a of the second substrate 20, the ionic liquid on the bonding surface of the first substrate 10 and the second substrate 20 is pushed out and removed. Therefore, it is not necessary to remove the liquid film 18,28 of the ionic liquid before bonding the surface 10a of the first substrate 10 and the surface 20a of the second substrate 20.

[0037] According to the bonding method of this embodiment, the surface 10a of the first substrate 10 and the surface 20a of the second substrate 20 are bonded together via liquid films 18 and 28 under a vacuum atmosphere. Therefore, the surfaces of the electrode pads 15 and 25 do not come into contact with oxidizing gases or moisture, thus suppressing oxidative corrosion. Since the ionic liquid does not easily volatilize even under a vacuum atmosphere and high-temperature environments, the liquid films 18 and 28 do not disappear before the surface 10a of the first substrate 10 and the surface 20a of the second substrate 20 are bonded together. Therefore, degassing from the liquid films 18 and 28 is less likely to occur when the first substrate 10 and the second substrate 20 are pressed together. Furthermore, since the pressed surfaces can be kept under vacuum in a high-temperature environment, a very strong adhesion force can be obtained.

[0038] According to the bonding method of the embodiment, when bonding the surface 10a of the first substrate 10 and the surface 20a of the second substrate 20, the ionic liquid dissolves the electrode pads 15 and 25. As a result, metal-metal bonds and metal-carbon-metal bonds are formed through the ionic liquid, and the contact resistance between electrode pad 15 and electrode pad 25 is reduced.

[0039] Incidentally, one example of a conventional hybrid bonding method involves planarizing the bonding surface of the substrates using CMP (Chemical Polymer Processing), then applying benzotriazole (BTA) to the bonding surface to suppress surface oxidation of the conductive film exposed on the bonding surface. In this method, since the substrates are bonded together after the BTA is removed, the bonding between the conductive films is weak, voids are generated at the bonding surface between the conductive films, and connection failures are likely to occur.

[0040] Another example of a conventional hybrid bond involves planarizing the bonding surface of the substrate using CMP (Chemical Manufacturing), then applying a conductive adhesive to the bonding surface, and bonding the conductive films together via the conductive adhesive. In this method, resistance tends to increase due to the conductive adhesive. Also, leakage current tends to flow between adjacent conductive films via the conductive adhesive.

[0041] In contrast, according to the bonding method of the embodiment, the substrates are bonded together via an ionic liquid, resulting in strong adhesion between the conductive films. This suppresses the generation of voids at the bonding surface between the conductive films. Furthermore, according to the bonding method of the embodiment, when the substrates are bonded together, any unnecessary ionic liquid is pushed out from the bonding surface, and the ionic liquid between adjacent conductive films is removed. As a result, leakage current is less likely to flow between adjacent conductive films.

[0042] [Joining equipment] Referring to Figures 8 and 9, a joining apparatus for carrying out the joining method according to the embodiment will be described.

[0043] As shown in Figure 8, the bonding apparatus has a processing container 100 whose interior can be sealed. On the side of the processing container 100 facing the positive X direction, there is an inlet / outlet 101 for transporting the upper substrate WU, the lower substrate WL, and the polymer substrate WT. The inlet / outlet 101 is opened and closed by an opening / closing shutter 102.

[0044] The interior of the processing container 100 is divided into a transport area T1 and a processing area T2 by an inner wall 103. An inlet / outlet 101 is formed on the side of the processing container 100 in the transport area T1. An inlet / outlet 104 for transporting the upper substrate WU, lower substrate WL, and polymer substrate WT is formed in the inner wall 103. The inlet / outlet 104 is opened and closed by a gate valve 105. The gate valve 105 is optional.

[0045] A transition 110 is provided on the positive X-direction side of the transport area T1 for temporarily placing the upper substrate WU, lower substrate WL, and polymer substrate WT. The transition 110 is formed in, for example, two stages, and can simultaneously place any two of the upper substrate WU, lower substrate WL, and polymer substrate WT.

[0046] The transport area T1 is provided with a substrate transporter 112 that is movable along a transport path 111 extending in the X direction. The substrate transporter 112 is also movable in the vertical direction and around the vertical axis, and transports the upper substrate WU, lower substrate WL, and superimposed substrate WT within the transport area T1 or between the transport area T1 and the processing area T2.

[0047] A position adjustment mechanism 120 is provided on the negative X-direction side of the transport area T1 to adjust the horizontal orientation of the upper substrate WU and the lower substrate WL.

[0048] A rail 130 extending along the Y direction is provided on the negative X-direction side of the position adjustment mechanism 120 in the transport area T1. The rail 130 is provided, for example, from the outside of the negative Y-direction side of the position adjustment mechanism 120 to the outside of the positive Y-direction side. Two nozzle arms 131 and 132 are attached to the rail 130, for example.

[0049] A nozzle 133 for discharging ionic liquid is supported on the nozzle arm 131. The nozzle arm 131 is movable on the rail 130 by the nozzle drive unit 134. This allows the nozzle 133 to move from the positive Y-direction side of the position adjustment mechanism 120 to above the upper substrate WU and lower substrate WL held by the position adjustment mechanism 120. The nozzle arm 131 is vertically adjustable by the nozzle drive unit 134, allowing the height of the nozzle 133 to be adjusted. A supply pipe (not shown) for supplying ionic liquid to the nozzle 133 is connected to the nozzle 133. The supply pipe is provided with a heating mechanism such as a heater for heating the ionic liquid flowing inside.

[0050] A nozzle 150 for discharging ionic liquid is supported on the nozzle arm 132. The nozzle arm 132 is movable on the rail 130 by the nozzle drive unit 151. This allows the nozzle 150 to move from the negative Y-direction side of the position adjustment mechanism 120 to above the upper substrate WU and lower substrate WL held by the position adjustment mechanism 120. The nozzle arm 132 is vertically adjustable by the nozzle drive unit 151, allowing the height of the nozzle 150 to be adjusted. A supply pipe (not shown) for supplying ionic liquid to the nozzle 150 is connected to the nozzle 150. The supply pipe is provided with a heating mechanism such as a heater for heating the ionic liquid flowing inside. Only one of the nozzles, 133 or 150, may be provided.

[0051] The processing area T2 is provided with a lower chuck 160 for placing and holding the lower substrate WL on its upper surface, and an upper chuck 161 for suction-holding the upper substrate WU on its lower surface. The lower chuck 160 and the upper chuck 161 are housed in the processing area T2. The upper chuck 161 is provided above the lower chuck 160. The upper chuck 161 is configured to be positioned opposite the lower chuck 160. That is, the lower substrate WL held by the lower chuck 160 and the upper substrate WU held by the upper chuck 161 can be positioned opposite each other.

[0052] Inside the lower chuck 160, there is a suction tube (not shown) that communicates with an electrostatic adsorption electrode (not shown) or a vacuum pump (not shown) which is electrically connected to a DC power supply (not shown). The lower substrate WL is held in place by electrostatic force such as Coulomb force generated on the electrostatic adsorption electrode or by suction from the suction tube.

[0053] A heating mechanism 160a, such as a heater, is provided inside the lower chuck 160. The heating mechanism 160a heats the lower substrate WL, which is held by adsorption to the lower chuck 160.

[0054] Below the lower chuck 160, a chuck drive unit 163 is provided via a shaft 162. The chuck drive unit 163 is configured to raise and lower the lower chuck 160. The chuck drive unit 163 may also be configured to move the lower chuck 160 horizontally. The chuck drive unit 163 may also be configured to rotate the lower chuck 160 around a vertical axis.

[0055] Inside the upper chuck 161, there is a suction tube (not shown) that communicates with an electrostatic adsorption electrode (not shown) or a vacuum pump (not shown) which is electrically connected to a DC power supply (not shown). The upper substrate WU is held in place by electrostatic force such as Coulomb force generated on the electrostatic adsorption electrode or by suction from the suction tube.

[0056] A heating mechanism 161a, such as a heater, is provided inside the upper chuck 161. The heating mechanism 161a heats the upper substrate WU, which is held by adsorption to the upper chuck 161.

[0057] A rail 164 extending along the Y direction is provided above the upper chuck 161. The upper chuck 161 is movable along the rail 164 by a chuck drive unit 165. The chuck drive unit 165 is configured to raise and lower the upper chuck 161. The chuck drive unit 165 may also be configured to rotate the upper chuck 161 around a vertical axis.

[0058] The transport area T1 is provided with a reversal mechanism 170 that moves between the transport area T1 and the processing area T2 and reverses the front and back surfaces of the upper substrate WU. The reversal mechanism 170 has a holding arm 171 that holds the upper substrate WU. A suction pad (not shown) is provided on the holding arm 171 to attract and hold the upper substrate WU horizontally. The holding arm 171 is supported by a drive unit 173. The drive unit 173 is configured to rotate the holding arm 171 around a horizontal axis and to extend and retract the holding arm 171 in the horizontal direction. Below the drive unit 173 is a drive unit 174. The drive unit 174 is configured to rotate the drive unit 173 around a vertical axis and to raise and lower the drive unit 173 in the vertical direction. The drive unit 174 is attached to a rail 175 that extends in the Y direction. The rail 175 extends from the processing area T2 to the transport area T1. The inversion mechanism 170 is movable along the rail 175 between the position adjustment mechanism 120 and the upper chuck 161 by the drive unit 174. The configuration of the inversion mechanism 170 is not limited to this, as long as it can invert the front and back surfaces of the upper substrate WU. The inversion mechanism 170 may be provided, for example, in the processing area T2. Alternatively, the inversion mechanism may be provided on the substrate transport body 112, and another transport mechanism may be provided at the position of the inversion mechanism 170.

[0059] An exhaust port 181 is provided on the side of the processing container 100 in the processing area T2. An exhaust passage 182 is connected to the exhaust port 181. A pressure regulating valve 183 and a vacuum pump 184 are sequentially installed in the exhaust passage 182 to allow the processing area T2 to be exhausted.

[0060] [Operation of the joining device] The operation of the bonding apparatus when bonding the upper substrate WU and the lower substrate WL will be described. The lower substrate WL corresponds to the first substrate 10, and the upper substrate WU corresponds to the second substrate 20.

[0061] First, the upper substrate WU is transported to the bonding device. The upper substrate WU is transported to the position adjustment mechanism 120 by the substrate transporter 112 via the transition 110. Next, the nozzle 133 is moved above the center of the upper substrate WU by the nozzle arm 131. Subsequently, while rotating the upper substrate WU, ionic liquid is supplied from the nozzle 133 to the surface of the upper substrate WU. The supplied ionic liquid is diffused onto the surface of the upper substrate WU by centrifugal force, and the ionic liquid is applied to the surface (step S2 in Figure 1). Next, the horizontal orientation of the upper substrate WU is adjusted by the position adjustment mechanism 120.

[0062] Next, the upper substrate WU is transferred from the position adjustment mechanism 120 to the holding arm 171 of the reversing mechanism 170. Subsequently, in the transport area T1, the holding arm 171 is reversed, thereby reversing the front and back surfaces of the upper substrate WU. That is, the front surface of the upper substrate WU is oriented downwards. Next, the reversing mechanism 170 moves towards the upper chuck 161, and the upper substrate WU is transferred from the reversing mechanism 170 to the upper chuck 161. The back surface of the upper substrate WU is held by the upper chuck 161. Subsequently, the upper chuck 161 is moved by the chuck drive unit 165 to a position above the lower chuck 160 and facing the lower chuck 160. The upper substrate WU then waits in the upper chuck 161 until the lower substrate WL, which will be described later, is transported to the bonding device. Note that the reversal of the front and back surfaces of the upper substrate WU may be performed while the reversing mechanism 170 is moving.

[0063] Next, the lower substrate WL is loaded into the bonding apparatus. The lower substrate WL is transported to the position adjustment mechanism 120 by the substrate transporter 112 via the transition 110. Subsequently, the nozzle 133 is moved above the center of the lower substrate WL by the nozzle arm 131. Then, while rotating the lower substrate WL, ionic liquid is supplied from the nozzle 133 to the surface of the lower substrate WL. The supplied ionic liquid is diffused onto the surface of the lower substrate WL by centrifugal force, and the ionic liquid is applied to the surface (step S2 in Figure 1). Subsequently, the horizontal orientation of the lower substrate WL is adjusted by the position adjustment mechanism 120.

[0064] Next, the lower substrate WL is transported to the lower chuck 160 by the substrate transporter 112 and held by the lower chuck 160. At this time, the back surface of the lower substrate WL is held by the lower chuck 160 so that the front surface of the lower substrate WL faces upward. A groove (not shown) that conforms to the shape of the substrate transporter 112 may be formed on the upper surface of the lower chuck 160 to avoid interference between the substrate transporter 112 and the lower chuck 160 when the lower substrate WL is transferred.

[0065] Next, the gate valve 105 closes the inlet / outlet 104, and the vacuum pump 184 evacuates the processing area T2 to reduce the pressure.

[0066] Next, the horizontal position of the lower substrate WL held by the lower chuck 160 and the upper substrate WU held by the upper chuck 161 is adjusted. Specifically, first, for example, a CCD camera is used to image the surfaces of the lower substrate WL and the upper substrate WU. Then, based on the captured images, the upper chuck 161 adjusts the horizontal position of the upper substrate WU so that a predetermined reference point (not shown) on the surface of the lower substrate WL coincides with a reference point (not shown) on the surface of the upper substrate WU. If the lower chuck 160 is movable horizontally by the chuck drive unit 163, the horizontal position of the lower substrate WL may be adjusted by the lower chuck 160. Alternatively, the relative horizontal positions of the lower substrate WL and the upper substrate WU may be adjusted by both the lower chuck 160 and the upper chuck 161.

[0067] Next, the chuck drive unit 163 raises the lower chuck 160, bringing the surface of the lower substrate WL held by the lower chuck 160 into contact with the surface of the upper substrate WU held by the upper chuck 161, and pressing them together. The heating mechanism 160a heats the lower substrate WL, and the heating mechanism 161a heats the upper substrate WU. As a result, the upper substrate WU and the lower substrate WL are joined via the ionic liquid, and a polymerized substrate WT is formed (step S3 in Figure 1).

[0068] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The above embodiments may be omitted, replaced, or modified in various ways without departing from the scope and spirit of the appended claims. [Explanation of Symbols]

[0069] 10. First board 10a surface 15 electrode pads 17. Second insulating film 18 Liquid film 20 Second board 20a surface 25 electrode pads 27. Second insulating film 28 Liquid film A11,A21 1st area A12,A22 2nd area

Claims

1. A step of preparing a first substrate and a second substrate having a first region on their surface where an insulating film is exposed and a second region on which a conductive film is exposed, A step of applying an ionic liquid to at least one of the first substrate and the second substrate, A step of joining the surface of the first substrate and the surface of the second substrate via the ionic liquid, It has, The preparation step includes a step of treating the surface of the first substrate and the surface of the second substrate by chemical mechanical polishing. Joining method.

2. A step of preparing a first substrate and a second substrate having a first region on their surface where an insulating film is exposed and a second region on which a conductive film is exposed, A step of applying an ionic liquid to at least one of the first substrate and the second substrate, A step of joining the surface of the first substrate and the surface of the second substrate via the ionic liquid, It has, The coating step includes the step of coating the ionic liquid onto the surface of the first substrate and the surface of the second substrate. Joining method.

3. A step of preparing a first substrate and a second substrate having a first region on their surface where an insulating film is exposed and a second region on which a conductive film is exposed, A step of applying an ionic liquid to at least one of the first substrate and the second substrate, A step of joining the surface of the first substrate and the surface of the second substrate via the ionic liquid, It has, The aforementioned joining process is, A step of pressing the first substrate and the second substrate together, A step of heating the first substrate and the second substrate, including, Joining method.

4. The coating step includes gelling the ionic liquid coated on at least one of the first substrate and the second substrate, The heating step includes liquefying the ionic liquid that has been gelled in the coating step. The joining method according to claim 3.

5. The aforementioned joining process is carried out under a vacuum atmosphere. The joining method according to any one of claims 1 to 3.

6. The conductive film exposed on the surface of the first substrate and the conductive film exposed on the surface of the second substrate are formed from the same material. The joining method according to any one of claims 1 to 3.

7. The aforementioned ionic liquid is THTDP-DcoO. The joining method according to any one of claims 1 to 3.

8. A coating mechanism for coating an ionic liquid onto at least one of a first substrate and a second substrate, each having a first region on its surface where an insulating film is exposed and a second region on its surface where a conductive film is exposed. A first holding portion and a second holding portion that hold the surface of the first substrate and the surface of the second substrate facing each other, A drive mechanism that brings the surface of the first substrate and the surface of the second substrate into close contact by bringing the first holding portion and the second holding portion relatively close together, A heating mechanism for heating the first substrate and the second substrate, which are held in the first and second holding parts, respectively, Equipped with, Bonding equipment.

9. A processing container housing the first holding part and the second holding part, A vacuum pump for exhausting the inside of the processing container, It also has, The joining apparatus according to claim 8.

10. The conductive film exposed on the surface of the first substrate and the conductive film exposed on the surface of the second substrate are formed from the same material. The joining apparatus according to claim 8.

11. The aforementioned ionic liquid is THTDP-DcoO. The joining apparatus according to claim 8.

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