Surface treatment device, substrate bonding device, surface treatment method, and substrate bonding method

Abstract

The present invention comprises: a chamber (1) that can accommodate a substrate (10); a plasma generation unit (2) that can suction a reactive gas into a plasma generation container (21) disposed on the outer peripheral side of the chamber (1) and generate a plasma of the reactive gas; an unsaturated hydrocarbon gas supply unit (3) that can supply an unsaturated hydrocarbon gas into the chamber (1); an ozone gas supply unit (4) that can supply ozone gas into the chamber (1); and a gas discharge unit (5) that can suction the gas inside the chamber (1) and discharge the suctioned gas to the outer peripheral side of the chamber (1). The plasma generation container (21) supplies an active species generated by the plasma of the reactive gas to the inside of the chamber (1) (downstream side).

Description

Surface treatment equipment, substrate bonding device, surface treatment method, substrate bonding method

[0001] The present invention relates to a surface treatment device, a substrate bonding device, a surface treatment method, and a substrate bonding method, and relates to a technology that can contribute to, for example, making it easier to hydrophilize a substrate as desired and to facilitating bonding, etc., using a plurality of hydrophilized substrates.

[0002] For example, the recent increase in the amount of information transmitted via electronic devices due to the advancement of IoT has led to a growing demand for further advances in semiconductor devices. While technological development for miniaturization and integration of semiconductor devices (Moore's Law) has been progressing, there is now a growing demand for further technological advances (More Than Moore), and one example of this is the development and practical application of three-dimensional integrated circuits (3D-ICs).

[0003] For example, in the case of a three-dimensional laminate formed by stacking and bonding multiple substrates (substrates to be bonded, such as semiconductor substrates) with different design rules and functions, it is said that not only can the integration density of semiconductor devices be increased, but the functions (different functions) possessed by each substrate can be integrated and it can also contribute to reducing wiring distances, resulting in various advantages (new benefits, etc.).

[0004] In joining the substrates (objects to be joined) of three-dimensional laminates, a joining method that does not use adhesives, i.e., a direct joining method, is applied. In recent years, attention has begun to be paid to a mode (hybrid joining) that can simultaneously join electrodes, etc. provided on the joining surface of the substrate.

[0005] Specific examples of direct bonding methods include those that mainly include: (1) a step of forming hydroxyl groups on the surface of a substrate (such as a surface to be bonded that has been planarized in advance as necessary) to make the surface hydrophilic (hereinafter simply referred to as the hydrophilization step); (2) a step of stacking two substrates on which the hydroxyl groups have been formed at the surfaces to be bonded (hereinafter simply referred to as the stacking step); and (3) a step of causing a dehydration condensation reaction of the hydroxyl groups on the surfaces to be bonded in the stacked state, to bond the substrates to each other at the surfaces to be bonded (hereinafter simply referred to as the bonding step).

[0006] In the hydrophilization step, for example, Patent Document 1 discloses a configuration in which the surface of a substrate is subjected to plasma treatment (etching, etc.) in a chamber (vacuum chamber, etc.) to make it hydrophilic. Also, Patent Document 2 discloses a configuration in which the surface of a substrate is subjected to plasma treatment in a chamber to form a reservoir (reservoir indicated by reference numeral 5 in Patent Document 2) for storing moisture, etc., thereby facilitating hydrophilization.

[0007] The plasma treatments described in Patent Documents 1 and 2 involve water treatment using moisture or the like (Patent Document 1 involves treatment using a gas containing moisture, as shown in FIG. 8( e), for example, and Patent Document 2 involves treatment of storing water, as shown in paragraphs

[0017] and

[0018] , for example).

[0008] In addition to the direct bonding method described above, other techniques relating to the substrate itself include surface treatment methods for modifying the surface of the substrate (e.g., Patent Documents 3 to 6), and film formation methods for forming various thin films on the surface of the substrate by a CVD method (chemical vapor deposition) or an ALD method (atomic layer deposition) (e.g., Patent Documents 7 and 8).

[0009] Patent No. 3751872 Patent No. 5955866 Patent No. 4905253 Patent No. 5217951 Patent No. 6052470 Patent No. 6057030 Patent No. 6569831 Patent No. 7056710

[0010] In a configuration in which the surface of a substrate (surface to be treated, surface to be bonded, etc.) is simply plasma-treated in a chamber as in Patent Documents 1 and 2, even if the surface can be made hydrophilic, there is a risk that minute dust particles, etc., are generated in the chamber and adhere to the surface of the substrate due to collision of ions, etc. from the plasma with the inner wall surface of the chamber, etc. Dust particles, etc., adhering to the surface of the substrate in this way can be removed by water treatment or water washing, etc., but it is thought that moisture is likely to remain on the surface.

[0011] For example, when a substrate is used as a bonding target, if the bonding surfaces have dust or moisture remaining thereon, bonding at the bonding surfaces may be difficult. As a specific example, in the case of a bonding process, the remaining moisture as described above may inhibit the dehydration condensation reaction, making it impossible to bond the bonding surfaces as desired.

[0012] The present invention has been made in view of the above-mentioned technical problems, and aims to provide a technology that can contribute to preventing dust and the like from adhering to the surface of a substrate, preventing moisture from remaining on the surface of the substrate, and making it easier to make the surface of the substrate hydrophilic as desired.

[0013] The surface treatment device, substrate bonding device, surface treatment method, and substrate bonding method according to the present invention can contribute to solving the above-mentioned problems.

[0014] First, one aspect of a surface treatment apparatus includes a chamber capable of accommodating a substrate, a container disposed on the outer periphery of the chamber, a plasma generation unit capable of drawing a reactive gas into the container and generating plasma of the reactive gas, an unsaturated hydrocarbon gas supply unit capable of supplying an unsaturated hydrocarbon gas into the chamber, an ozone gas supply unit capable of supplying ozone gas into the chamber, and a gas exhaust unit capable of drawing gas from the chamber and exhausting it to the outer periphery of the chamber. The container is characterized in that it is capable of supplying activated species generated by the plasma of the reactive gas into the chamber.

[0015] The reactive gas may contain at least one of oxygen, argon, and nitrogen, and the plasma of the reactive gas may be an inductively coupled plasma.

[0016] The chamber may be provided with a shower head at a position facing the substrate accommodated in the chamber, and the shower head may be provided with a supply flow path for the unsaturated hydrocarbon gas from the unsaturated hydrocarbon gas supply unit and a supply flow path for the ozone gas from the ozone gas supply unit.

[0017] The apparatus may further include a control unit capable of controlling the output energy of the plasma of the reactive gas in the plasma generation unit, the supply flow rate of the unsaturated hydrocarbon gas in the unsaturated hydrocarbon gas supply unit, the supply flow rate of the ozone gas in the ozone gas supply unit, the exhaust flow rate of the gas in the chamber by the gas exhaust unit, and the pressure in the chamber.

[0018] The control unit may also be characterized in that it can control the output energy of the plasma of the reactive gas to be set within a range of 50 W to 200 W, and can control the pressure in the chamber to be set within a range of 0.01 Pa to 100 Pa while the plasma of the reactive gas is being generated.

[0019] The control unit may be capable of controlling the pressure in the chamber to be set to 1000 Pa or less while the unsaturated hydrocarbon gas and the ozone gas are being supplied into the chamber.

[0020] One aspect of the substrate joining apparatus is characterized in that it includes the surface treatment apparatus described above, and the chamber includes support parts that support two of the substrates as objects to be joined within the chamber, and the support parts support each of the substrates with their respective surfaces to be joined facing each other so that they can move toward and away from each other in the opposing directions.

[0021] One aspect of the surface treatment method is a method using the surface treatment device, which includes an activation step of activating the surface of the substrate accommodated in the chamber, and a hydroxyl group formation step of forming hydroxyl groups on the surface of the substrate after the activation step.

[0022] The activation step involves drawing a reactive gas into the container to generate plasma of the reactive gas, and supplying activated species generated by the plasma of the reactive gas into the chamber, thereby activating the surface of the substrate.

[0023] The hydroxyl group forming process is characterized in that the unsaturated hydrocarbon gas and the ozone gas having an ozone concentration of more than 50% by volume are supplied to the surface of the substrate contained in the chamber, thereby exposing the surface of the substrate to OH radicals generated by a radical reaction between the unsaturated hydrocarbon gas and the ozone gas, thereby forming hydroxyl groups on the surface of the substrate.

[0024] In addition, in the activation step, the activation depth of the surface of the substrate by the activated species generated by the plasma of the reactive gas may be within a range of 1 nm to 100 nm.

[0025] One aspect of the substrate bonding method is a method for bonding the substrates as bonding objects using the surface treatment device, and includes an activation step of activating the bonding surfaces of the substrates contained in the chamber, a hydroxyl group formation step of forming hydroxyl groups on the bonding surfaces of the substrates after the activation step, a stacking step of overlapping and stacking the two substrates with the hydroxyl groups formed on their bonding surfaces, and a bonding step of heating each of the stacked substrates to bond the substrates at their bonding surfaces.

[0026] The activation step involves drawing a reactive gas into the container to generate plasma of the reactive gas, and supplying activated species generated by the plasma of the reactive gas into the chamber, thereby activating the surface to be bonded of the substrate.

[0027] In the hydroxyl group formation process, an unsaturated hydrocarbon gas and ozone gas having an ozone concentration of more than 50% by volume are supplied to the surfaces to be joined of the substrates contained in the chamber, thereby exposing the surfaces to OH radicals generated by a radical reaction between the unsaturated hydrocarbon gas and the ozone gas, and forming hydroxyl groups on the surfaces to be joined.

[0028] The bonding step is characterized in that the hydroxyl groups are subjected to a dehydration condensation reaction by the heating.

[0029] In addition, in the activation step, the activation depth of the surface to be bonded of the substrate by the activated species generated by the plasma of the reactive gas may be within a range of 1 nm to 100 nm.

[0030] As described above, the present invention can contribute to preventing dust and the like from adhering to the surface of a substrate, preventing moisture from remaining on the surface of the substrate, and facilitating the desired hydrophilization of the surface of the substrate.

[0031] 1 is a characteristic diagram of ozone gas concentration and OH radical generation efficiency (a diagram in which the ashing rate when the ozone concentration is approximately 100% by volume is set to 1, using the ashing effect of photoresist on a Si wafer as an index). FIG. 2 is a schematic configuration diagram for explaining surface treatment apparatus 1A according to an embodiment (a perspective view of the inside of chamber 1, etc.). FIG. 3 is a schematic configuration diagram for explaining apparatus 1B according to an embodiment (a perspective view of the inside of chamber 1, etc.). FIG. 4 is a schematic configuration diagram for explaining apparatus 1C according to verification example 1 (a perspective view of the inside of chamber 1, etc.).

[0032] The surface treatment apparatus, substrate bonding apparatus, surface treatment method, and substrate bonding method of the embodiments of the present invention are completely different from the configurations (so-called direct plasma type configurations; hereinafter simply referred to as conventional configurations) in which the surfaces of substrates are simply subjected to plasma treatment or water treatment in a chamber, as in, for example, Patent Documents 1 and 2. That is, the present embodiments are configured to activate a substrate accommodated in a chamber by a so-called remote plasma type, and further to form hydroxyl groups on the activated surface.

[0033] Specifically, it comprises a chamber capable of accommodating a substrate, a plasma generation unit having a container (hereinafter simply referred to as a plasma generation container) arranged on the outer periphery of the chamber and capable of drawing a reactive gas into the plasma generation container to generate plasma of the reactive gas, an unsaturated hydrocarbon gas supply unit capable of supplying an unsaturated hydrocarbon gas into the chamber, an ozone gas supply unit capable of supplying ozone gas into the chamber, and a gas discharge unit capable of drawing in gas from within the chamber and discharging it to the outer periphery of the chamber.

[0034] The plasma generating vessel is characterized in that it is possible to supply activated species generated by plasma of reactive gas (hereinafter simply referred to as plasma-derived activated species) into the chamber (i.e., downstream side).

[0035] According to this embodiment, damage caused by plasma to the inner wall surface of the chamber and the surface of the substrate can be prevented (the generation of minute dust particles and the like can be prevented), and moisture and the like can also be prevented from remaining on the surface of the substrate.

[0036] Furthermore, plasma-derived active species generated in the plasma generating section on the outer periphery of the chamber can be exposed to the surface of the substrate inside the chamber, making it possible to increase and activate dangling bonds on the surface.

[0037] Furthermore, the surface of the substrate in the chamber (the surface activated by the plasma-derived active species) can be exposed to OH radicals generated by the radical reaction between the unsaturated hydrocarbon gas and the ozone gas, and hydroxyl groups can be formed on the surface of the substrate (for example, a molecular layer of hydroxyl groups can be formed). This method of forming hydroxyl groups on the surface of the substrate can prevent moisture from remaining on the surface of the substrate.

[0038] Therefore, it is easy to make the surface of the substrate hydrophilic as desired. Furthermore, when a plurality of hydrophilic substrates are to be bonded, it is easy to bond the substrates at their bonding surfaces as desired.

[0039] As described above, this embodiment may be configured to activate a substrate accommodated in a chamber using plasma-derived active species via a remote plasma method and further form hydroxyl groups on the activated surface. That is, common technical knowledge from various fields (e.g., direct bonding, plasma, chambers, ozone gas, unsaturated hydrocarbon gas, radical reaction, surface treatment, etc.) may be appropriately applied, and design modifications may be made as necessary by appropriately referring to prior art documents, etc., as shown in the examples below. Note that in the examples below, detailed descriptions may be omitted as appropriate, for example, by using the same reference numerals to refer to overlapping content.

[0040] Reference Examples Relating to Radical Reactions For example, Patent Documents 3 and 4 disclose techniques for removing resist adhering to the surface of a substrate (a target for surface treatment) by utilizing active species (oxidizing species) such as OH radicals generated by a radical reaction between an unsaturated hydrocarbon gas and ozone gas. This resist removal technique utilizes the properties of ozone, namely, the ease with which ozone reacts with carbon double bonds in unsaturated hydrocarbons, without the need for, for example, thermal energy (heating) or UV irradiation.

[0041] The resist removal technology utilizing the above-mentioned radical reaction is highly effective in removing organic substances such as photoresist, and has been put to practical use for, for example, ashing photoresist and removing organic substances from surfaces without causing thermal damage or plasma damage.

[0042] In the radical reaction, first, the carbon double bond is cleaved by the ozone molecule, and the unstable methylene peroxide generated as a result of this reaction acts as an intermediate and undergoes further fission reactions, generating carbon dioxide, water, OH radicals, formic acid, etc. An example of this radical reaction can be shown in the characteristic diagram of ozone gas concentration and OH radical generation efficiency, as shown in Figure 1.

[0043] 1, when the concentration of ozone gas is low (for example, 50% by volume or less), the efficiency of generating OH radicals is also low, and the OH radicals are easily consumed in intermediate reactions. In other words, it can be seen that the number of multi-stage reaction paths in which the generation of OH radicals is amplified is reduced, making it difficult to perform the desired surface treatment. On the other hand, when the concentration of ozone gas is high, OH radicals are generated at high concentrations, and it can be seen that a large amount of OH radicals are easily generated even during the multi-stage reaction process.

[0044] Furthermore, conventional ozone gas generators (for example, general discharge-type ozonizers) were only able to supply ozone gas at low concentrations (for example, a maximum ozone concentration of approximately 23% by volume). However, in recent years, devices that can safely generate ozone gas at high concentrations (for example, the Pure Ozone Generator manufactured by Meidensha) have emerged, and various surface treatment technologies that apply radical reactions have begun to be investigated.

[0045] For example, Patent Documents 5 and 6 disclose a technique for modifying the surface of a substrate by oxidizing the surface using OH radicals and then forming hydrophilic groups mainly composed of hydroxyl groups (a molecular layer of hydrophilic groups). This modification technique is said to be able to modify the surface of the substrate without physically damaging the substrate.

[0046] Specifically, Patent Documents 5 and 6 disclose a method of supplying an unsaturated hydrocarbon gas and an ozone gas into a chamber to cause a radical reaction near the surface of a substrate in the chamber, and modifying the surface of the substrate with OH radicals and the like generated by the radical reaction. Also disclosed are configurations in which an unsaturated hydrocarbon gas and an ozone gas are supplied by a shower head (reference numeral 9 in Patent Document 5, reference numeral 10 or 15 in Patent Document 6) provided in a position facing the substrate in the chamber, thereby enabling the surface of the substrate to be efficiently exposed to OH radicals.

[0047] This showerhead has an unsaturated hydrocarbon gas supply channel and an ozone gas supply channel that are separated from each other (disconnected) inside the showerhead. The surface of the showerhead facing the substrate is provided with a plurality of ejection holes that communicate with the unsaturated hydrocarbon gas supply channel and a plurality of ejection holes that communicate with the ozone gas supply channel.

[0048] By using such a showerhead, radical reactions between the unsaturated hydrocarbon gas and the ozone gas can be easily caused near the surface of the substrate inside the chamber.

[0049] According to the configuration using the above-described radical reaction, it is possible to form hydroxyl groups on the surface of the substrate (modify the surface with hydroxyl groups) and make the surface hydrophilic, without performing water treatment as in the conventional configuration. It is also possible to prevent moisture from remaining on the surface of the substrate.

[0050] Furthermore, although energy from radical reactions (chemical reaction energy) may act within the chamber, it is possible to avoid the action of energy from plasma processing or the like (energy that may cause plasma damage) as in conventional configurations.

[0051] In addition, when the activity of the surface of the substrate is low (when there are few dangling bonds), it may be difficult to form a sufficient number of hydroxyl groups on the surface of the substrate simply by causing a radical reaction between the unsaturated hydrocarbon gas and the ozone gas near the surface of the substrate, and the substrate may not be rendered hydrophilic as desired.

[0052] On the other hand, in the present embodiment, even if the activity of the surface of the substrate is low, the surface of the substrate can be activated by plasma-derived active species using the remote plasma method, and it becomes easy to form a sufficient number of hydroxyl groups on the activated surface, making it easy to make the surface hydrophilic as desired.

[0053] <Example> <Configuration Example of Surface Treatment Apparatus> An example of the schematic configuration of a surface treatment apparatus 1A according to an example will be described with reference to Fig. 2. This surface treatment apparatus 1A mainly comprises a chamber 1 capable of accommodating a substrate 10, a plasma generation unit 2 having a plasma generation vessel 21 arranged on the outer periphery of the chamber 1, an unsaturated hydrocarbon gas supply unit 3 capable of supplying an unsaturated hydrocarbon gas into the chamber 1, an ozone gas supply unit 4 capable of supplying ozone gas into the chamber 1, and a gas exhaust unit 5 capable of sucking in gas from the chamber 1 and exhausting it to the outer periphery of the chamber 1.

[0054] In the case of the chamber 1 shown in the figure, a support part 6 is provided that can support a substrate 10 accommodated in the chamber 1 on a support stand 61. Furthermore, a shower head 7 is provided on the upper side of the chamber 1 so as to face a surface to be processed (or a surface to be bonded) 11 of the substrate 10 supported by the support part 6.

[0055] The plasma generating unit 2 in the figure is configured to be able to generate inductively coupled plasma. A plasma generating vessel 21 is provided with an intake pipe 22 for drawing a reactive gas into the plasma generating vessel 21. The intake pipe 22 is provided with an intake valve 23 that can adjust the intake flow rate of the reactive gas by opening and closing the intake pipe 22, for example. Furthermore, on the chamber 1 side (i.e., downstream side) of the plasma generating vessel 21, a supply pipe 24 is provided that can supply gases and the like within the plasma generating vessel 21 (gases remaining after plasma generation of the reactive gas and plasma-derived active species) into the chamber 1.

[0056] On the outer periphery of the plasma generating vessel 21, there is provided an electrode portion 25 (for example, an electrode portion extending in a coil shape along the outer periphery of the plasma generating vessel 21) for generating plasma within the plasma generating vessel 21, and a power source 26 capable of applying high-frequency power to the electrode portion 25.

[0057] The unsaturated hydrocarbon gas supply unit 3 includes a supply pipe 31 for supplying the unsaturated hydrocarbon gas, and an intake valve 32 that can adjust the supply flow rate of the unsaturated hydrocarbon gas by opening and closing the supply pipe 31, for example.

[0058] In the case of the unsaturated hydrocarbon gas supply unit 3 shown in the figure, a supply pipe 31 is connected to a shower head 7, and the unsaturated hydrocarbon gas can be supplied into the chamber 1 via an unsaturated hydrocarbon gas supply passage (not shown) in the shower head 7 and a jet port 73.

[0059] The ozone gas supply unit 4 includes a supply pipe 41 for supplying ozone gas, and an intake valve 42 that can adjust the supply flow rate of the ozone gas by opening and closing the supply pipe 41, for example.

[0060] In the case of the ozone gas supply unit 4 shown in the figure, a supply pipe 41 is connected to a shower head 7, and the unsaturated hydrocarbon gas can be supplied into the chamber 1 via an ozone gas supply flow path (a flow path not connected to the unsaturated hydrocarbon gas supply flow path; not shown) in the shower head 7 and a jet port 74.

[0061] The gas exhaust unit 5 includes an exhaust pipe 51 for sucking in gas from within the chamber 1 and exhausting it to the outer periphery of the chamber 1, an exhaust valve 52 that can adjust the exhaust flow rate of gas from within the chamber 1 by opening and closing the exhaust pipe 51, and a vacuum pump (such as an ozone-resistant dry pump) 53 that generates suction force to suck in the gas from within the chamber 1.

[0062] In the case of such a gas exhaust section 5, for example, the suction force of the vacuum pump 53 can be controlled to maintain a reduced pressure state inside the chamber 1 (a state in which the internal pressure is lower than atmospheric pressure), and the gas inside the chamber 1 can be sucked in and exhausted to the outer periphery of the chamber 1.

[0063] Each of the components of the surface treatment device 1A shown above can be configured to be appropriately controlled by a control unit not shown in the figure, for example, the plasma generation unit 2, the unsaturated hydrocarbon gas supply unit 3, the ozone gas supply unit 4, and the gas exhaust unit 5 can be configured to be appropriately controlled.

[0064] For example, in the plasma generating unit 2, the magnitude of the plasma output energy of the reactive gas and the supply flow rate of the plasma-derived active species supplied into the chamber 1 can be appropriately controlled via the intake valve 23, the power supply 26, etc. The supply flow rate of the plasma-derived active species can be controlled, for example, by appropriately using a flow meter or the like in the plasma generating vessel 21, or the pressure can be controlled by appropriately using a pressure gauge or the like.

[0065] A specific example is to control the supply flow rate of plasma-derived active species so that the surface 11 to be treated can be activated to a desired activation depth (e.g., an activation depth measurable by FT-IR, XPS, or the like) in the activation step S1 described below, depending on the type of substrate 1 to be treated and the state of the surface 11 to be treated (such as surface roughness and the thickness of a native oxide film). More specifically, the activation depth of the surface 11 to be treated by the plasma-derived active species can be controlled to be about several nm to several hundred nm (e.g., about 1 nm to 100 nm).

[0066] By activating the treated surface 11 in this manner, it becomes easier to achieve the desired hydrophilicity in the hydroxyl group formation step S2 described below, and it also becomes possible to bond as desired through the lamination step S3 and bonding step S4 described below.

[0067] In the unsaturated hydrocarbon gas supply unit 3, the supply flow rate of the unsaturated hydrocarbon gas is controlled so as to be appropriately set via an intake valve 32 or the like, and in the ozone gas supply unit 4, the supply flow rate of the ozone gas is controlled so as to be appropriately set via an intake valve 42 or the like.

[0068] The gas exhaust unit 5 controls the exhaust flow rate of gas in the chamber 1 and the reduced pressure state in the chamber 1 via an exhaust valve 52, a vacuum pump 53, and the like.

[0069] The reduced pressure state in chamber 1 can be adjusted as appropriate within a range that allows the desired hydrophilization of treatment surface 11 of substrate 10 while each gas is being supplied from, for example, plasma generating unit 2, unsaturated hydrocarbon gas supply unit 3, and ozone gas supply unit 4. For example, the reduced pressure state in chamber 1 can be adjusted by appropriately controlling the opening of exhaust valve 52 and appropriately operating vacuum pump 53.

[0070] As a specific example, while the gas (gas containing plasma-derived activated species) is being supplied from the plasma generating unit 2, the inside of the chamber 1 is kept at 10 －２ The pressure may be reduced to a range of several Pa to several hundred Pa (for example, approximately 0.01 Pa to 100 Pa).

[0071] While each gas is being supplied from the unsaturated hydrocarbon gas supply unit 3 and the ozone gas supply unit 4, the pressure is adjusted to several thousand Pa or less (for example, about 1000 Pa or less), preferably several hundred Pa or less, and more preferably several tens of Pa or less (for example, about 50 Pa or less).

[0072] <Example of Hydrophilizing the Substrate 10 by the Surface Treatment Device 1A> When the treatment surface 11 of the substrate 10 is hydrophilized by the surface treatment device 1A, for example, an activation step S1 and a hydroxyl group formation step S2 as shown below are performed in this order.

[0073] First, in the activation step S1, while a reactive gas is being drawn into the plasma generating vessel 21, high-frequency power from the power source 26 is applied to the electrode portion 25 to generate plasma of the reactive gas within the plasma generating vessel 21, thereby generating plasma-derived active species. The plasma-derived active species thus generated are then supplied into the chamber 1, thereby exposing the treatment surface 11 of the substrate 10 to the plasma-derived active species and activating it.

[0074] Next, in the hydroxyl group formation step S2, an unsaturated hydrocarbon gas from the unsaturated hydrocarbon gas supply unit 3 and ozone gas from the ozone gas supply unit 4 are supplied to the surface 11 to be treated of the substrate 10 in the chamber 1. This causes a radical reaction between the unsaturated hydrocarbon gas and the ozone gas near the surface 11 to be treated of the substrate 10, and OH radicals generated by the radical reaction are exposed to the surface 11 to be treated, forming hydroxyl groups on the surface 11 to be treated.

[0075] <Example of Bonding of Hydrophilized Substrate 10> When the substrate 10 is to be bonded, the treated surface 11 that has been made hydrophilic by performing the activation step S1 and the hydroxyl group formation step S2 as described above is used as the bonding surface, and bonding can be performed, for example, by sequentially performing the lamination step S3 and bonding step S4 as shown below.

[0076] First, in the lamination step S3, two substrates 10 on which hydroxyl groups have been formed through the activation step S1 and the hydroxyl group formation step S2 are stacked (temporarily bonded) on top of each other on the treatment surface 11. It is preferable that the substrates 10 in this stacked state are pressed against each other on the treatment surface 11 (for example, pressed against each other at 1 MPa or more) to ensure sufficient adhesion.

[0077] In the bonding step S4, the substrates 10 that have been stacked in the stacking step S3 are heated to cause a dehydration condensation reaction of the hydroxyl groups, thereby bonding the substrates 10 together at their treatment surfaces 11.

[0078] <Example of Support Structure for Substrate 10> In the activation step S1, the hydroxyl group formation step S2, the lamination step S3, and the bonding step S4 (hereinafter collectively referred to as steps S1 to S4 as appropriate), the substrate 10 may be appropriately supported by a support portion 6, but the support structure of the support portion 6 is not particularly limited. For example, a support structure may be used in which a plurality of substrates 10 are supported within the chamber 1, thereby making it possible to simultaneously perform steps S1 to S4 on each of the substrates 10.

[0079] Also, as in the apparatus 1B shown in FIG. 3, for example, a plurality of substrates 10 housed in a chamber 1 may be supported so as to be freely movable, or each of the substrates 10 may be pressurized or heated.

[0080] 3, the apparatus 1B includes a support unit 6B capable of supporting two substrates 10a, 10b in the chamber 1. The support unit 6B includes a pair of support bases 61a, 61b that are arranged facing each other and support the two substrates 10a, 10b, respectively, a pair of support arms 62a, 62b that support the outer peripheries of the support bases 61a, 61b so that the support bases 61a, 61b can move toward and away from each other in the facing direction (hereinafter simply referred to as the facing direction), and a rotation shaft 63 that supports the support arms 62a, 62b rotatably along the facing direction.

[0081] The support unit 6B configured in this manner can rotate the support arms 62a, 62b about the rotation shaft 63 by, for example, an operating unit (not shown) on the outer periphery of the chamber 1, and can move the support bases 61a, 61b toward and away from each other in opposing directions. The support bases 61a, 61b are also provided with heating units (not shown) capable of heating the substrates 10a, 10b supported on the support bases 61a, 61b, respectively.

[0082] In the apparatus 1B, substrates 10a and 10b can be used as the bonding targets, and steps S1 to S4 can be performed as appropriate. First, when performing the activation step S1, as shown in FIG. 3, two substrates 10a and 10b are supported on support stages 61a and 61b so that the surfaces to be treated (bonded surfaces) 11, which are the side surfaces of each substrate, face each other but are spaced apart. In this supported state (hereinafter simply referred to as the "substrate supported state"), a reactive gas is introduced into the plasma generating vessel 21, and high-frequency power from the power source 26 is applied to the electrode unit 25 to generate plasma of the reactive gas within the plasma generating vessel 21, thereby generating plasma-derived active species. The plasma-derived active species thus generated are then supplied into the chamber 1, whereby the surfaces to be treated 11 of the substrates 10a and 10b are exposed to the plasma-derived active species and activated.

[0083] Next, when the hydroxyl group forming step S2 is performed, with the substrates supported, an unsaturated hydrocarbon gas and ozone gas are supplied from the unsaturated hydrocarbon gas supply unit 3 and the ozone gas supply unit 4, respectively. As a result, a radical reaction occurs near the treatment surface 11 of each of the substrates 10 a, 10 b, and hydroxyl groups are formed on the treatment surface 11.

[0084] Thereafter, in the stacking step S3, the support unit 6B is operated to move the support bases 61a, 61b closer to each other in the opposing direction, thereby overlapping and stacking the treatment surfaces 11 of the substrates 10a, 10b and pressing them together. Then, in the bonding step S4, the substrates 10a, 10b in the stacked (pressure-welded) state are heated by the heating unit, causing a dehydration condensation reaction of the hydroxyl groups, and the substrates 10a, 10b are bonded at their treatment surfaces 11.

[0085] Therefore, with the above-described apparatus 1B, steps S1 to S4 can be performed on the substrates 10a and 10b in a so-called in-situ manner within the same chamber 1. That is, the apparatus 1B not only hydrophilizes the treatment surfaces 11 of the substrates 10a and 10b, but can also be used as an apparatus for bonding the substrates 10a and 10b together (substrate bonding apparatus).

[0086] For example, in the case of the surface treatment apparatus 1A, after the activation step S1 and the hydroxyl group formation step S2 are performed in the chamber 1, the substrate 10 is removed from the chamber 1 and the lamination step S3 and the bonding step S4 are performed, but in this case, it is thought that a considerable amount of moisture may remain on the treated surface 11 of the substrate 10. On the other hand, according to the apparatus 1B, since the steps S1 to S4 can be performed in-situ as described above, it is easier to prevent moisture from remaining on the treated surface 11.

[0087] <Examples of reactive gas, unsaturated hydrocarbon gas, and ozone gas> Various types of reactive gas can be used as long as it can generate plasma of the reactive gas in the activation step S1, thereby generating plasma-derived active species and activating the treatment surface 11 of the substrate 10. Specific examples of reactive gases include gases containing components such as oxygen, argon, and nitrogen, as well as mixed gases containing a plurality of such components.

[0088] The unsaturated hydrocarbon gas and the ozone gas may be any gas that can cause a radical reaction in the hydroxyl group forming step S2 and form hydroxyl groups on the surface 11 to be treated, and various modes are applicable.

[0089] Specific examples of unsaturated hydrocarbon gases include ethylene, propylene, acetylene, butadiene, benzene, toluene, o-xylene, styrene, α-butylene, etc. Specific examples of ozone gas include ozone gas having an ozone concentration of more than 50% by volume, and more preferably ozone gas having a high concentration (e.g., 80% by volume or more, or 90% by volume or more).

[0090] <Example of substrate 10> The substrate 10 can be one that can activate the treatment surface 11 through an activation step S1 and a hydroxyl group formation step S2 to form hydroxyl groups, and when the substrate 10 is to be bonded, it is possible to apply one that can be bonded through the activation step S1 and the hydroxyl group formation step S2 followed by a lamination step S3 and a bonding step S4. Although not particularly limited, if necessary, the treatment surface 11 can be planarized in advance (for example, planarized by CMP or the like so as to have a surface roughness that is sufficiently small at the atomic level).

[0091] Furthermore, since the hydroxyl group formation step S2 and the bonding step S4 can each be performed at a relatively low temperature, for example, when the base 10 is a substrate or a film, it is not limited to a substrate with relatively high heat resistance such as a silicon substrate, but may also be a substrate formed of a synthetic resin with relatively low heat resistance.

[0092] Examples include various substrates used in MEMS, semiconductors, FPDs, etc., such as silicon substrates, glass substrates, GaN substrates, SiC substrates, and diamond substrates, as well as metal substrates, film-like substrates, and silicon oxide films (SiO ２ The substrate may be of the same or different type and may be selected and applied from these substrates.

[0093] When the base 10 is made of a resin, examples of the resin include polyester resin, aramid resin, olefin resin, polypropylene, PPS (polyphenylene sulfide), PET (polyethylene terephthalate), and the like.

[0094] Other examples include those made from PE (polyethylene), PEN (polyethylene naphthalate), POM (polyoxymethylene or acetal resin), PEEK (polyether ether ketone), ABS resin (acrylonitrile, butadiene, styrene copolymer synthetic resin), PA (polyamide), PFA (tetrafluoroethylene, perfluoroalkoxyethylene copolymer), PI (polyimide), PVD (polyvinyl dichloride), acrylic resin, etc.

[0095] Verification Example 1 After the substrate 10 was hydrophilized using the surface treatment device 1A under any of the conditions (1) to (4) described below, the water contact angle (°) of the treated surface 11 of the substrate 10 was observed, and the results are shown in Table 1 described below.

[0096] The substrate 10 was a silicon wafer having a thermal oxide film formed on one end face thereof, and the surface of the thermal oxide film (a surface having a water contact angle of 54° before hydrophilization) was used as the treated surface 11. The activation step S1 was performed using nitrogen gas as the reactive gas, with the output energy of the plasma of the reactive gas set to 150 W, the pressure inside the plasma generating vessel 21 set to 200 Pa, the pressure inside the chamber 1 (treatment pressure) set to 10 Pa, and the treatment time set to 8 minutes.

[0097] The hydroxyl group forming step S2 was carried out by using an unsaturated hydrocarbon gas, ethylene gas as an ozone gas, and high-concentration ozone gas (ozone concentration of 80% by volume or more), with the supply flow rate of the unsaturated hydrocarbon gas set to 40 sccm, the supply flow rate of the ozone gas set to 200 sccm, the pressure in chamber 1 (processing pressure) set to 40 Pa, and the processing time set to 1 minute.

[0098] Condition (1): Hydrophilization is achieved by performing only the activation step S1 (hydroxyl group forming step S2 is omitted). Condition (2): Hydrophilization is achieved by performing only the hydroxyl group forming step S2 (activation step S1 is omitted). Condition (3): Hydrophilization is achieved by performing both the activation step S1 and the hydroxyl group forming step S2. Condition (4): Hydrophilization is achieved by performing a conventional water treatment after the activation step S1 (hydroxyl group forming step S2 is omitted).

[0099]

[0100] As shown in Table 1, the treated surface 11 of the substrate 10 hydrophilized under condition (1) had a small water contact angle compared to when the surface was hydrophilized under condition (2). It is believed that under condition (1), the activation step S1 caused the formation of dangling bonds and surface nitridation on the treated surface 11, which reacted with moisture in the atmosphere to hydrophilize the surface. Under condition (2), the OH radicals in the hydroxyl group formation step S2 caused considerable modification of dangling bonds that were presumably present on the treated surface 11 with hydroxyl groups and removal of organic contamination. However, compared to the case of condition (1), the hydrophilization was insufficient.

[0101] On the other hand, in the case of condition (3), the treated surface 11 activated by the activation step S1 (the treated surface 11 with dangling bonds generated by the activation step S1 and surface nitridation) is modified with hydroxyl groups by OH radicals in the hydroxyl group formation step S2, and it is thought that sufficient hydrophilization is achieved without using moisture in the atmosphere.

[0102] <Verification Example 2> Next, two substrates 10 hydrophilized according to any one of the conditions (1) to (4) were prepared for each of the conditions (1) to (4), and the two substrates 10 were bonded through the lamination step S3 and the bonding step S4 to measure the bonding strength (J / m ２ ) were observed, and the results are shown in Table 2.

[0103]

[0104] As shown in Table 2, the substrate 10 hydrophilized under condition (3) achieved the highest bonding strength compared to the substrates hydrophilized under conditions (1), (2), and (4). In the case of condition (3), it is believed that the hydroxyl group modification by OH radicals in the hydroxyl group formation step S2 was effectively performed on the treated surface 11 activated by the activation step S1. In the case of condition (4), it is believed that excess moisture remained on the treated surface 11 due to the water treatment after the activation step S1, inhibiting bonding at the treated surface 11 and resulting in low bonding strength.

[0105] <Verification Example 3> Next, in the apparatus 1C having the conventional configuration shown in FIG. 4, the substrate 10 was hydrophilized in the same manner as in Verification Example 1 by applying any one of the conditions (5) to (8) described below, and then the bonding strength (J / m ２ The results are shown in Table 3 below.

[0106] The apparatus 1C of FIG. 4 has the same configuration as the surface treatment apparatus 1A, but in place of the plasma generating unit 2, a direct plasma type plasma generating unit 2C is used.

[0107] In this plasma generating unit 2C, an intake pipe 22 for intake of a reactive gas is connected to the shower head 7, and the reactive gas can be supplied into the chamber 1 via a reactive gas supply flow path (a flow path not connected to the unsaturated hydrocarbon gas supply flow path and the ozone gas supply flow path; not shown) in the shower head 7 and a jet port 75. In addition, the support table 61 is used as an electrode, and high-frequency power from the power source 26 can be applied to both the support table 61 and the shower head 7.

[0108] In the apparatus 1C, an activation step S11, which will be described later, was first performed, followed by a hydroxyl group formation step S2, a lamination step S3, and a bonding step S4. In this activation step S11, high-frequency power from the power source 26 was applied to both the support table 61 and the showerhead 7 while a reactive gas was supplied into the chamber 1. This generated plasma of the reactive gas in the chamber 1, which in turn generated plasma-derived activated species that were exposed to and activated the treatment surface 11 of the substrate 10.

[0109] The activation step S11 was performed using nitrogen gas as the reactive gas, with the plasma output energy of the reactive gas set to 375 W, the pressure in the chamber 1 (processing pressure) set to 500 Pa, and the processing time set to 30 seconds.

[0110] Condition (5): Hydrophilization is achieved by performing only the activation step S11 (hydroxyl group forming step S2 is omitted). Condition (6): Hydrophilization is achieved by performing only the hydroxyl group forming step S2 (activation step S11 is omitted). Condition (7): Hydrophilization is achieved by performing both the activation step S11 and the hydroxyl group forming step S2. Condition (8): Hydrophilization is achieved by performing a conventional water treatment after the activation step S11 (hydroxyl group forming step S2 is omitted).

[0111]

[0112] As shown in Table 3, the substrate 10 hydrophilized under conditions (5) to (8) tended to have lower bonding strength than the substrate 10 hydrophilized under conditions (1) to (4). In the cases of conditions (5) to (8), ions and the like from the plasma generated in the activation step S11 collided (etched, etc.) with the inner wall surface of the chamber 1, the shower head 7, etc., generating minute dust particles and the like within the chamber 1, which adhered to the treated surface 11 of the substrate 10 and inhibited the desired bonding.

[0113] In the case of condition (8), it is possible that dust and the like adhering to the treated surface 11 of the substrate 10 was removed by the water treatment. However, it is thought that excess moisture remained on the treated surface 11 due to the water treatment, which inhibited bonding at the treated surface 11 and reduced the bonding strength.

[0114] Although the present invention has been described in detail above only with respect to the specific examples, it will be apparent to those skilled in the art that various modifications are possible within the scope of the technical concept of the present invention, and it is natural that such modifications fall within the scope of the claims.

[0115] REFERENCE SIGNS LIST 10 (10a, 10b)... Substrate 11... Surface to be treated (surface to be bonded) 1... Chamber 2... Plasma generating section 3... Unsaturated hydrocarbon gas supply section 4... Ozone gas supply section 5... Gas exhaust section 6... Support section

Claims

1. A surface treatment apparatus comprising: a chamber capable of accommodating a substrate; a plasma generation unit having a container arranged on the outer periphery of the chamber and capable of drawing a reactive gas into the container and generating plasma of the reactive gas; an unsaturated hydrocarbon gas supply unit capable of supplying an unsaturated hydrocarbon gas into the chamber; an ozone gas supply unit capable of supplying ozone gas into the chamber; and a gas exhaust unit capable of drawing gas within the chamber and exhausting it to the outer periphery of the chamber, wherein the container is capable of supplying activated species generated by the plasma of the reactive gas into the chamber.

2. The surface treatment apparatus according to claim 1, wherein said reactive gas contains at least one of oxygen, argon, and nitrogen.

3. The surface treatment apparatus according to claim 1, wherein the plasma of the reactive gas is an inductively coupled plasma.

4. The surface treatment apparatus according to claim 1, wherein the chamber is provided with a shower head at a position facing the substrate accommodated in the chamber, and the shower head is provided with: a supply flow path for the unsaturated hydrocarbon gas from the unsaturated hydrocarbon gas supply unit; and a supply flow path for the ozone gas from the ozone gas supply unit.

5. The surface treatment apparatus according to claim 1, further comprising a control unit capable of controlling the output energy of the plasma of the reactive gas in the plasma generation unit, the supply flow rate of the unsaturated hydrocarbon gas in the unsaturated hydrocarbon gas supply unit, the supply flow rate of the ozone gas in the ozone gas supply unit, the exhaust flow rate of the gas in the chamber by the gas exhaust unit, and the pressure in the chamber.

6. The surface treatment apparatus according to claim 5, characterized in that the control unit can control the output energy of the plasma of the reactive gas to be set within a range of 50 W to 200 W, and can control the pressure within the chamber to be set within a range of 0.01 Pa to 100 Pa while the plasma of the reactive gas is being generated.

7. The surface treatment apparatus according to claim 5, characterized in that the control unit can control the pressure in the chamber to be set to 1000 Pa or less while the unsaturated hydrocarbon gas and the ozone gas are being supplied into the chamber.

8. A substrate joining device comprising the surface treatment device according to any one of claims 1 to 7, wherein the chamber comprises support parts for supporting two of the substrates to be joined within the chamber, and the support parts support the substrates so that the surfaces to be joined face each other and can move toward and away from each other in the opposing directions.

9. A method using the surface treatment apparatus of any one of claims 1 to 7, comprising: an activation step of activating the surface of the substrate accommodated in the chamber; and a hydroxyl group formation step of forming hydroxyl groups on the surface of the substrate after the activation step, wherein the activation step comprises drawing a reactive gas into the container to generate plasma of the reactive gas, and supplying active species generated by the plasma of the reactive gas into the chamber, thereby activating the surface of the substrate; and the hydroxyl group formation step comprises supplying the unsaturated hydrocarbon gas and the ozone gas having an ozone concentration of more than 50% by volume, respectively, to the surface of the substrate accommodated in the chamber, thereby exposing the surface of the substrate to OH radicals generated by a radical reaction between the unsaturated hydrocarbon gas and the ozone gas, thereby forming hydroxyl groups on the surface of the substrate.

10. A surface treatment method according to claim 9, wherein in said activation step, the activation depth of the surface of said substrate by the activated species generated by the plasma of said reactive gas is within the range of 1 nm to 100 nm.

11. A method for bonding substrates as objects to be bonded using the surface treatment device according to any one of claims 1 to 7, comprising: an activation step of activating the surfaces to be bonded of the substrates housed in the chamber; a hydroxyl group formation step of forming hydroxyl groups on the surfaces to be bonded of the substrates after the activation step; a stacking step of overlapping and stacking the two substrates on which the hydroxyl groups have been formed, on their surfaces to be bonded; and a bonding step of heating the stacked substrates to bond the substrates on their surfaces to be bonded, wherein the activation step involves drawing a reactive gas into the container to generate plasma of the reactive gas and supplying active species generated by the plasma of the reactive gas into the chamber, thereby activating the surfaces to be bonded of the substrates; and the hydroxyl group formation step involves supplying an unsaturated hydrocarbon gas and ozone gas having an ozone concentration of more than 50% by volume, respectively, to the surfaces to be bonded of the substrates housed in the chamber, thereby exposing the surfaces to be bonded to OH radicals generated by a radical reaction between the unsaturated hydrocarbon gas and the ozone gas, thereby forming hydroxyl groups on the surfaces to be bonded. The substrate bonding method is characterized in that the bonding step causes a dehydration condensation reaction of the hydroxyl groups by heating.

12. A method for bonding substrates according to claim 11, wherein in the activation step, the activation depth of the surfaces of the substrates to be bonded by the activated species generated by the plasma of the reactive gas is within the range of 1 nm to 100 nm.

Images