Substrate bonding method and substrate bonding apparatus

Abstract

This substrate bonding method comprises: a plasma treatment step for treating a bonding surface of each substrate with a rare gas plasma, i.e., a rare gas plasma, and treating the bonding surface of each substrate treated with the rare gas plasma with a hydrogen plasma, i.e., a hydrogen plasma, processing the bonding surface of each substrate after hydrogen plasma processing with nitrogen plasma, i.e., nitrogen plasma; and a substrate bonding step of bonding the two substrates by bringing the bonding surfaces of the two substrates into contact with each other such that the copper pads of the two substrates face each other and the insulating films of the two substrates face each other after the plasma processing step.

Description

Technical Field

[0001] The present invention relates to a substrate bonding method and a substrate bonding device for bonding two substrates. Background Art

[0002] Japanese Patent Application Laid-Open No. 2024-6789A discloses a semiconductor device having a first substrate and a second substrate bonded together. Paragraph 0061 of Japanese Patent Application Laid-Open No. 2024-6789A states, "A second substrate 2 having a second connection wiring layer 22 formed thereon is bonded to the first substrate 3. In this state, O of copper oxide (CuO, Cu2O, etc.) is present on the bonding surface X between the first electrode 33 and the second electrode 23."

[0003] At least one embodiment of the present invention provides a substrate bonding method and a substrate bonding apparatus capable of bonding two substrates while removing copper oxide from surfaces of copper pads. Summary of the Invention

[0004] One embodiment of the present invention is a substrate bonding method for bonding two substrates, each having a bonding surface, wherein copper oxide and an insulating film of a copper pad are exposed on the bonding surface, wherein the substrate bonding method comprises: a plasma treatment step, wherein the bonding surface of each substrate is treated with a rare gas plasma, i.e., a rare gas plasma; the bonding surface of each substrate after the rare gas plasma treatment is treated with a hydrogen plasma, i.e., a hydrogen plasma; and the bonding surface of each substrate after the hydrogen plasma treatment is treated with a nitrogen plasma, i.e., a nitrogen plasma; and a substrate bonding step, wherein, after the plasma treatment step, the bonding surfaces of the two substrates are brought into contact with each other in a manner that the copper pads of the two substrates are opposed to each other and the insulating films of the two substrates are opposed to each other, thereby bonding the two substrates.

[0005] In the above-described embodiment, at least one of the following features may be added to the substrate bonding method.

[0006] The plasma treatment step is a step of performing the following steps on each of the two substrates: a rare gas plasma treatment step of treating the bonding surface with a plasma containing the rare gas plasma but not the nitrogen plasma; a nitrogen plasma treatment step of treating the bonding surface with the nitrogen plasma; and a hydrogen plasma treatment step of treating the bonding surface with the hydrogen plasma simultaneously with at least one of the rare gas plasma treatment step and the nitrogen plasma treatment step, or after the rare gas plasma treatment step and before the nitrogen plasma treatment step.

[0007] The plasma treatment process is a process of performing the following process on each of the two substrates: a first plasma treatment process, supplying a first reaction gas into a sealed container accommodating the substrate, and treating the bonding surface with a first plasma generated by the first reaction gas, wherein the first reaction gas contains the rare gas and the hydrogen gas but does not contain the nitrogen gas; and a second plasma treatment process, supplying a second reaction gas into the sealed container, and treating the bonding surface with a second plasma generated by the second reaction gas, wherein the second reaction gas contains the nitrogen gas.

[0008] The substrate bonding method further includes an oxygen contact step of bringing at least one of oxygen in the atmosphere and oxygen in the liquid into contact with the bonding surfaces of the substrates after the plasma treatment step.

[0009] The oxygen contact step includes a cleaning step of cleaning each of the two substrates with a cleaning liquid and drying the substrates after the plasma treatment step and before the substrate bonding step.

[0010] The substrate bonding method further includes a heat treatment step of heating the two bonded substrates to directly bond the copper contained in the copper pad of one of the two substrates to the copper contained in the copper pad of the other of the two substrates.

[0011] The plasma treatment process is a process of processing the bonding surfaces of each of the substrates with the rare gas plasma, the hydrogen plasma and the nitrogen plasma by causing the plasma treatment unit of the substrate bonding device to generate the rare gas plasma, the hydrogen plasma and the nitrogen plasma. The substrate bonding process is a process of bonding the two substrates by causing the bonding surfaces of the two substrates to contact each other in a manner in which the copper pads of the two substrates are opposed to each other and the insulating films of the two substrates are opposed to each other. The heat treatment process is a process of directly bonding the copper contained in the copper pad of one of the two substrates to the copper contained in the copper pad of the other of the two substrates by causing the heat treatment unit of the substrate bonding device to heat the two bonded substrates.

[0012] The plasma treatment process is a process of generating an inductively coupled plasma of at least one of the rare gas, the hydrogen gas, and the nitrogen gas by supplying a high-frequency current to an antenna arranged in a space between an inner plate and an outer plate, wherein the inner plate seals a hole opened on the inner surface of an outer wall of a sealed container accommodating the substrate, and the outer plate seals a hole opened on the outer surface of the outer wall.

[0013] Another embodiment of the present invention is a substrate bonding device for bonding two substrates respectively having bonding surfaces, wherein the bonding surfaces expose copper oxide and insulating films of copper pads, wherein the substrate bonding device comprises: a plasma processing unit for treating the bonding surfaces of each substrate with a rare gas plasma, i.e., a rare gas plasma, treating the bonding surfaces of each substrate after being treated with the rare gas plasma with a hydrogen plasma, i.e., a hydrogen plasma, and treating the bonding surfaces of each substrate after being treated with the hydrogen plasma with a nitrogen plasma, i.e., a nitrogen plasma; and a bonding unit for bonding the two substrates by bringing the bonding surfaces of the two substrates into contact with each other in a manner such that the copper pads of the two substrates are opposed to each other and the insulating films of the two substrates are opposed to each other after the bonding surfaces of each substrate are treated with the rare gas plasma, hydrogen plasma, and nitrogen plasma.

[0014] In the above-described embodiment, at least one of the following features may be added to the above-described substrate bonding apparatus.

[0015] The plasma processing unit performs the following processes on each of the two substrates: a rare gas plasma treatment process, treating the bonding surface with a plasma containing the rare gas plasma but not the nitrogen plasma; a nitrogen plasma treatment process, treating the bonding surface with the nitrogen plasma; and a hydrogen plasma treatment process, treating the bonding surface with the hydrogen plasma simultaneously with at least one of the rare gas plasma treatment process and the nitrogen plasma treatment process, or after the rare gas plasma treatment process and before the nitrogen plasma treatment process.

[0016] The plasma processing unit performs the following processes on each of the two substrates: a first plasma processing process, supplying a first reaction gas into a sealed container containing the substrates, and using a first plasma generated by the first reaction gas to treat the bonding surface, the first reaction gas contains the rare gas and the hydrogen but does not contain the nitrogen; and a second plasma processing process, supplying a second reaction gas into the sealed container, and using a second plasma generated by the second reaction gas to treat the bonding surface, the second reaction gas containing the nitrogen.

[0017] The substrate bonding apparatus further includes an oxygen contact unit, which brings at least one of oxygen in the atmosphere and oxygen in the liquid into contact with the bonding surface of each substrate after the bonding surface of each substrate is treated with the rare gas plasma, the hydrogen plasma, and the nitrogen plasma.

[0018] The oxygen contact unit includes a cleaning unit that cleans and dries each of the two substrates with a cleaning liquid after the bonding surfaces of the substrates are treated with the rare gas plasma, the hydrogen plasma, and the nitrogen plasma and before the two substrates are bonded.

[0019] The substrate bonding apparatus further includes a heat treatment unit that heats the two bonded substrates to directly bond the copper contained in the copper pad of one of the two substrates to the copper contained in the copper pad of the other of the two substrates.

[0020] The plasma processing unit generates an inductively coupled plasma of at least one of the rare gas, the hydrogen gas, and the nitrogen gas by supplying a high-frequency current to an antenna arranged in a space between an inner plate and an outer plate, wherein the inner plate seals a hole opened on the inner surface of an outer wall of a sealed container accommodating the substrate, and the outer plate seals a hole opened on the outer surface of the outer wall. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram showing two substrates before bonding.

[0022] Figure 2A 、 Figure 2B It is a schematic diagram showing the cross-section of two substrates before and after bonding.

[0023] Figure 3A 、 Figure 3B 、 Figure 3C 、 Figure 3D 、 Figure 3E 、 Figure 3F This is a schematic diagram for explaining an example of the flow from treating a substrate with plasma to heating two bonded substrates.

[0024] Figure 4A 、 Figure 4B 、 Figure 4C 、 Figure 4D 、 Figure 4E 、 Figure 4F This is a schematic diagram for explaining an example of changes that may occur on the surface of a copper pad when a substrate is treated with plasma or heated.

[0025] Figure 5 This is a schematic diagram of a substrate bonding apparatus according to one embodiment.

[0026] Figure 6 It is a schematic diagram showing a vertical cross section of a plasma processing unit. DETAILED DESCRIPTION

[0027] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0028] First, the two substrates W to be bonded will be described. When distinguishing between the two substrates W, they are referred to as a first substrate W1 and a second substrate W2. Lamination and bonding are synonymous.

[0029] Figure 1 It is a schematic diagram showing two substrates W before being joined. The first substrate W1 and the second substrate W2 are flat circular substrates W with the same diameter. The diameters of the first substrate W1 and the second substrate W2 can be 300 mm or other lengths. The first substrate W1 includes: a first joining surface 111 and a first non-joining surface 131 as two circular planes parallel to each other; and an annular first end surface connecting the outer edges of the first joining surface 111 and the first non-joining surface 131 to each other. Similarly, the second substrate W2 includes: a second joining surface 211 and a second non-joining surface 231 as two circular planes parallel to each other; and an annular second end surface connecting the outer edges of the second joining surface 211 and the second non-joining surface 231 to each other. The first substrate W1 and the second substrate W2 are joined in such a manner that the first joining surface 111 and the second joining surface 211 are opposite to each other.

[0030] Figure 2A and Figure 2B Schematic diagram showing cross sections of two substrates W before and after bonding. Figure 2A and Figure 2B A cross section cut along a plane perpendicular to the two substrates W is shown. Figure 2A A cross section of two substrates W before bonding is shown. Figure 2B A cross section of two substrates W after bonding is shown. Figure 2A The cross sections of the two substrates W after polishing to flatten the first bonding surface 111 and the second bonding surface 211 are shown. Figure 2A and Figure 2B The proportions of the elements shown are not necessarily the same as the actual proportions.

[0031] like Figure 2A As shown, the first substrate W1 includes a plurality of circular plate-shaped layers stacked along the thickness direction of the first substrate W1 and a circular plate-shaped first base material 130 supporting the plurality of layers. The plurality of layers include: a circular plate-shaped first device layer 120 formed on the first base material 130; a circular plate-shaped first bonding layer 110 formed on the first device layer 120. Similarly, the second substrate W2 includes: a plurality of circular plate-shaped layers stacked in the thickness direction of the second substrate W2; a circular plate-shaped second base material 230 supporting the plurality of layers. The plurality of layers include: a circular plate-shaped second device layer 220 formed on the second base material 230; and a circular plate-shaped second bonding layer 210 formed on the second device layer 220.

[0032] The first substrate 130 and the second substrate 230 are made of semiconductors such as single crystal silicon. The first substrate 130 can also be made of materials other than semiconductors. The second substrate 230 is also the same. The surface of the first substrate 130 on the side opposite to the first device layer 120 corresponds to the first non-bonding surface 131 (see Figure 1 ). The surface of the first bonding layer 110 on the side opposite to the first device layer 120 corresponds to the first bonding surface 111. Similarly, the surface of the second substrate 230 on the side opposite to the second device layer 220 corresponds to the second non-bonding surface 231 (see Figure 1 The surface of the second bonding layer 210 opposite to the second device layer 220 corresponds to the second bonding surface 211 .

[0033] Semiconductor devices such as transistors and diodes are arranged in the first device layer 120 and the second device layer 220. The first device layer 120 includes: a plurality of first semiconductor devices 121 forming an electronic circuit; and a first insulating film 122 that electrically insulates the plurality of first semiconductor devices 121. Similarly, the second device layer 220 includes: a plurality of second semiconductor devices 221 forming an electronic circuit; and a second insulating film 222 that electrically insulates the plurality of second semiconductor devices 221. The function of the electronic circuit of the first substrate W1 can be the same as or different from that of the electronic circuit of the second substrate W2.

[0034] The first bonding layer 110 includes a plurality of first copper pads 112 electrically connected to the plurality of first semiconductor devices 121 of the first device layer 120, and a first insulating film 113 electrically insulating the plurality of first copper pads 112. Similarly, the second bonding layer 210 includes a plurality of second copper pads 212 electrically connected to the plurality of second semiconductor devices 221 of the second device layer 220, and a second insulating film 213 electrically insulating the plurality of second copper pads 212.

[0035] The first copper pad 112 and the second copper pad 212 are both made of copper (Cu). The first copper pad 112 is electrically insulated from the other first copper pads 112 by the first insulating film 113. Similarly, the second copper pad 212 is electrically insulated from the other second copper pads 212 by the second insulating film 213. The first insulating film 113 is made of silicon oxide (SiO2). The second insulating film 213 is also made of silicon oxide. The first insulating film 113 and the second insulating film 213 can be silicon oxide films made using TEOS (tetraethoxysilane) or other silicon oxide films. The first insulating film 113 and the second insulating film 213 can be made of an insulating material including silicon other than silicon oxide such as silicon nitride (SiN), or other insulating materials.

[0036] The first copper pad 112 and the first insulating film 113 are exposed on the first joint surface 111. In other words, the first copper pad 112 and the first insulating film 113 constitute the first joint surface 111. The first copper pad 112 and the first insulating film 113 may constitute the entire first joint surface 111 or only a portion of the first joint surface 111. Similarly, the second copper pad 212 and the second insulating film 213 are exposed on the second joint surface 211. In other words, the second copper pad 212 and the second insulating film 213 constitute the second joint surface 211. The second copper pad 212 and the second insulating film 213 may constitute the entire second joint surface 211 or only a portion of the second joint surface 211.

[0037] like Figure 2B As shown, the first bonding surface 111 of the first substrate W1 and the second bonding surface 211 of the second substrate W2 overlap with a plurality of first copper pads 112 and a plurality of second copper pads 212 facing each other, and a first insulating film 113 and a second insulating film 213 facing each other. The first and second substrates W1 and W2 are then heated. This electrically connects one second copper pad 212 to one first copper pad 112, and the first semiconductor device 121 and the second semiconductor device 221 are electrically connected via the first and second copper pads 112 and 212.

[0038] Next, an example of a flow from processing the substrate W with plasma to heating the two bonded substrates W will be described.

[0039] Figures 3A to 3F It is a schematic diagram for explaining the same example. Figures 4A to 4D This is a schematic diagram for explaining an example of changes that may occur on the surface of the copper pads 112 and 212 when the substrate W is processed by plasma. Figures 4E to 4F This is a schematic diagram for explaining an example of changes that may occur on the surfaces of the copper pads 112 and 212 when the substrate W is heated.

[0040] When the first substrate W1 and the second substrate W2 are bonded, the first substrate W1 and the second substrate W2 are treated with plasma. Figure 3A As shown, the first substrate W1 is carried into the sealed container 12 and is supported by the substrate holder 11 disposed in the sealed container 12 . Figure 3A An example is shown in which the substrate holder 11 horizontally supports the first substrate W1 in the sealed container 12 in a state in which the first bonding surface 111 of the first substrate W1 faces upward.

[0041] The first substrate W1 is supported by the substrate holder 11. After the door 12d of the sealed container 12 is closed, the gas in the sealed container 12 is exhausted to reduce the gas pressure in the sealed container 12 to a value lower than the atmospheric pressure. Then, the first plasma treatment process is performed, that is, the first bonding surface 111 of the first substrate W1 is treated with the first plasma P1 generated by the first reaction gas. Specifically, when the gas pressure in the sealed container 12 is lower than the atmospheric pressure, the first reaction gas, that is, a mixed gas of argon and hydrogen, is supplied into the sealed container 12, and then the plasma source 14 ionizes the first reaction gas in the sealed container 12. As a result, the first reaction gas in the sealed container 12 is changed into the first plasma P1, that is, argon plasma and hydrogen plasma, and the first bonding surface 111 of the first substrate W1 is exposed to the first plasma P1.

[0042] The plasma generated in the first plasma treatment process can be either an inductively coupled plasma or a plasma other than an inductively coupled plasma, such as a capacitively coupled plasma or a surface wave plasma. This is also true for the second plasma treatment process and the third plasma treatment process described later. In the case of treating the first substrate W1 and the second substrate W2 with an inductively coupled plasma, an inductively coupled plasma can be generated from the reaction gas in the sealed container 12 by supplying a high-frequency current to at least one antenna arranged in the sealed container 12 or to at least one antenna arranged in the space within the outer wall 12w of the sealed container 12 (see Figure 6 ).

[0043] As described above, the first bonding surface 111 of the first substrate W1 is composed of the first copper pad 112 and the first insulating film 113. Figure 4A As shown, the surface of first copper pad 112, which is part of first joint surface 111, is composed of copper oxide, such as copper (I) oxide (cuprous oxide: Cu2O) or copper (II) oxide (copper oxide: CuO). In other words, the surface of first copper pad 112 is terminated with oxygen atoms. The surface of second copper pad 212 is also terminated with oxygen atoms. This is because the copper atoms constituting the surfaces of first and second copper pads 112 and 212 are oxidized by oxygen in the air or in liquid.

[0044] like Figure 4B As shown, argon plasma, which is an example of a rare gas (Group 18 element), removes oxygen atoms from the copper oxide constituting the surface of the first copper pad 112, and converts at least one of Cu2O and CuO into Cu. Figure 4CAs shown, hydrogen atoms (strictly speaking, hydrogen radicals or excited hydrogen atoms; the same applies hereinafter) contained in the hydrogen plasma bond with the copper constituting the surface of the first copper pad 112, forming Cu-H bonds on the surface of the first copper pad 112. In other words, the surface of the first copper pad 112 is terminated with hydrogen atoms. As a result, oxygen atoms exposed on the surface of the first copper pad 112 are replaced with hydrogen atoms.

[0045] After the oxygen atoms exposed on the first bonding surface 111 of the first substrate W1 are replaced with hydrogen atoms, a second plasma treatment process is performed, that is, the first bonding surface 111 of the first substrate W1 is treated with a second plasma P2 generated by a second reaction gas. Specifically, Figure 3B As shown, with the gas pressure in the sealed container 12 lower than atmospheric pressure, after a second reaction gas, i.e., a mixed gas of argon, hydrogen, and nitrogen, is supplied into the sealed container 12, the plasma source 14 is operated to ionize the second reaction gas in the sealed container 12. As a result, the second reaction gas in the sealed container 12 is converted into a second plasma P2, i.e., argon plasma, hydrogen plasma, and nitrogen plasma, and the first bonding surface 111 of the first substrate W1 is exposed to the second plasma P2.

[0046] When supplying the second reactant gas into the sealed container 12, the supply of the second reactant gas can be started after all the first reactant gas has been exhausted from the sealed container 12, or the supply of the second reactant gas can be started while some of the first reactant gas remains in the sealed container 12. In the above example, since the first reactant gas is a mixture of argon and hydrogen, and the second reactant gas is a mixture of argon, hydrogen, and nitrogen, nitrogen can be supplied into the sealed container 12 to mix with the remaining argon and hydrogen in the sealed container 12. The supply of the second reactant gas can be started while the plasma source 14 is ionizing the first reactant gas in the sealed container 12, or the supply of the second reactant gas can be started after the plasma source 14 stops ionizing the first reactant gas.

[0047] As described above, the oxygen atoms exposed on the first bonding surface 111 of the first substrate W1 are replaced by hydrogen atoms. Figure 4D As shown, the nitrogen plasma replaces the hydrogen atoms exposed on the surface of the first copper pad 112 with nitrogen atoms, forming Cu-N bonds on the surface of the first copper pad 112. If the hydrogen atoms are just replaced by nitrogen atoms (if the nitrogen atoms are in a highly active state), at least one of the hydrogen atoms cut off from the first copper pad 112 and the like and the hydrogen atoms contained in the hydrogen plasma will bond with the nitrogen atoms already bonded to the copper atoms. Figure 4D As shown, Cu-NH2 bonds are formed on the surface of the first copper pad 112. In other words, the surface of the first copper pad 112 is terminated with amino groups (NH2).

[0048] After the surface of the first copper pad 112 is amino-terminated, the plasma source 14 stops ionizing the second reaction gas in the sealed container 12. Thus, the generation of argon plasma, hydrogen plasma, and nitrogen plasma stops. Then, while supplying an inert gas (nitrogen, argon, etc.) into the sealed container 12, the exhaust of gas from the sealed container 12 is stopped. Thus, the second reaction gas or second plasma P1 in the sealed container 12 is exhausted, and the gas pressure in the sealed container 12 rises to atmospheric pressure or close to atmospheric pressure. Then, the door 12d of the sealed container 12 is opened, and the first substrate W1 is unloaded from the sealed container 12.

[0049] Similar to the first bonding surface 111 of the first substrate W1, the first plasma treatment process and the second plasma treatment process are also performed on the second bonding surface 211 of the second substrate W2. Specifically, the second bonding surface 211 of the second substrate W2 is treated with argon plasma and hydrogen plasma as the first plasma P1, and then the second bonding surface 211 of the second substrate W2 is treated with argon plasma, hydrogen plasma, and nitrogen plasma as the second plasma P2. As a result, the surface of the second copper pad 212 is amino-terminated. Then, the second reaction gas and the second plasma P2 in the sealed container 12 are discharged, and the gas pressure in the sealed container 12 is raised to atmospheric pressure or close to atmospheric pressure. Then, the door 12d of the sealed container 12 is opened, and the second substrate W2 is unloaded from the sealed container 12.

[0050] If the first bonding surface 111 of the first substrate W1 is sequentially treated with the first plasma P1 and the second plasma P2, the surface of the first insulating film 113, which is part of the first bonding surface 111, is also sequentially treated with the first plasma P1 and the second plasma P2. Similarly, if the second bonding surface 211 of the second substrate W2 is sequentially treated with the first plasma P1 and the second plasma P2, the surface of the second insulating film 213, which is part of the second bonding surface 211, is also sequentially treated with the first plasma P1 and the second plasma P2. Both the first insulating film 113 and the second insulating film 213 are made of silicon oxide. The oxygen atoms contained in the silicon oxide are replaced with amino groups. As a result, the surfaces of the first insulating film 113 and the second insulating film 213 are terminated with amino groups.

[0051] If the first substrate W1 is unloaded from the sealed container 12, air comes into contact with the first bonding surface 111 of the first substrate W1. Similarly, if the second substrate W2 is unloaded from the sealed container 12, air comes into contact with the second bonding surface 211 of the second substrate W2. Therefore, oxygen in the air comes into contact with the surface of the first copper pad 112. Since the surface of the first copper pad 112 is amino-terminated, even if air comes into contact with the first bonding surface 111 of the first substrate W1, the copper atoms constituting the surface of the first copper pad 112 will not turn into copper oxide. The copper atoms constituting the surface of the second copper pad 212 will not turn into copper oxide. Therefore, even if air comes into contact with the first bonding surface 111 of the first substrate W1 and the second bonding surface 211 of the second substrate W2, the state in which the surface of the first copper pad 112 and the surface of the second copper pad 212 are amino-terminated can be maintained.

[0052] Although not shown in the figure, the first substrate W1 includes at least one alignment mark, which is a reference when adjusting the alignment of the first substrate W1 and the second substrate W2. The same applies to the second substrate W2. After the first substrate W1 and the second substrate W2 are treated with plasma generated by the first reaction gas and the second reaction gas, respectively, Figure 3D As shown, with the first bonding surface 111 of the first substrate W1 and the second bonding surface 211 of the second substrate W2 spaced apart and facing each other, an alignment confirmation step is performed to confirm the alignment of the magnitude and direction of the offset between the first and second substrates W1, W2. Then, an alignment adjustment step is performed to reduce the offset between the first and second substrates W1, W2 by relatively moving the first and second substrates W1, W2 based on the confirmed alignment. Figure 3D An example is shown of confirming and adjusting the alignment of the first substrate W1 and the second substrate W2 based on an image generated by a camera 34, wherein the camera 34 captures a first mask M1 and a second mask M2 respectively provided on a first chuck 31A holding the first substrate W1 and a second chuck 31B holding the second substrate W2.

[0053] After the second plasma treatment process is performed and before the alignment confirmation process is performed, Figure 3C As shown, a cleaning process can be performed, that is, each of the first substrate W1 and the second substrate W2 is cleaned with a cleaning liquid such as pure water and then dried. In this way, particles (such as copper particles) generated during the plasma treatment of the first substrate W1 and the second substrate W2 can be removed from the first substrate W1 and the second substrate W2. Furthermore, even if oxygen in the air or oxygen in the cleaning liquid comes into contact with the first bonding surface 111 of the first substrate W1 and the second bonding surface 211 of the second substrate W2, the amino-terminated state of the surfaces of the first copper pad 112 and the second copper pad 212 can be maintained as described above.

[0054] After adjusting the alignment of the first substrate W1 and the second substrate W2, as shown in FIG. Figure 3E As shown, the substrate bonding process of bonding the first substrate W1 and the second substrate W2 is performed by directly contacting the first bonding surface 111 of the first substrate W1 and the second bonding surface 211 of the second substrate W2 under atmospheric pressure. Figure 3F As shown, a heat treatment process is performed to heat the bonded first substrate W1 and second substrate W2. Figure 3F This example shows a case where a plurality of first substrates W1 and second substrates W2 are heated simultaneously. This heating is also called annealing.

[0055] If the first and second substrates W1 and W2 are brought into contact after being heated, the first copper pads 112 and second copper pads 212 of the first and second substrates W1 and W2 may be separated before being heated. In this case, heating the first and second substrates W1 and W2 causes the first and second copper pads 112 and 212 to expand and come into contact with each other. As a result, the first and second substrates W1 and W2 are heated while the first and second copper pads 112 and 212 are in contact with each other.

[0056] like Figure 4E As shown, the surface of the first copper pad 112 is terminated with amino groups, and the surface of the second copper pad 212 is terminated with amino groups. If the first substrate W1 and the second substrate W2 are heated while the first copper pad 112 and the second copper pad 212 are in contact with each other, the two amino groups are separated from the surfaces of the first copper pad 112 and the second copper pad 212. As a result, a reaction of "Cu-NH2+Cu-NH2→Cu-Cu+N2+2H2" ("-" represents a bond between two atoms) occurs, as shown in FIG. Figure 4F As shown, the copper atoms forming the surface of the first copper pad 112 are directly bonded to the copper atoms forming the surface of the second copper pad 212. As shown in the chemical reaction formula, the two amino groups are separated and become one nitrogen molecule (gas) and two hydrogen molecules (gas). These nitrogen and hydrogen molecules are then expelled from between the first substrate W1 and the second substrate W2 or absorbed by the first insulating film 113 or the second insulating film 213.

[0057] It is generally believed that amino groups bonded to copper atoms will be detached at a temperature above 200°C. Therefore, in the heat treatment process, it is sufficient to heat the first substrate W1 and the second substrate W2 at a temperature above 200°C. Specifically, the first substrate W1 and the second substrate W2 can be heated at a temperature above 200°C and below 350°C, or at a temperature above 200°C and below 250°C. In the case where there is only one nitrogen atom bonded to one copper atom instead of an amino group, when the first substrate W1 and the second substrate W2 are heated at a temperature higher than the temperature at which the amino group detaches, the nitrogen atom detaches. Therefore, compared with the case of detaching the nitrogen atom, the case of detaching the amino group can reduce the heating temperature of the first substrate W1 and the second substrate W2.

[0058] On the other hand, if the first substrate W1 and the second substrate W2 are heated while the first insulating film 113 and the second insulating film 213 are in contact with each other, four hydrogen atoms are detached from the two amino groups, that is, four hydrogen atoms are detached from one amino group constituting the surface of the first insulating film 113 and one amino group constituting the surface of the second insulating film 213. As a result, the reaction of "Si-NH2+Si-NH2→Si-NNN-Si+2H2" ("-" represents a bond between two atoms) occurs, and the silicon atoms constituting the surface of the first insulating film 113 and the silicon atoms constituting the surface of the second insulating film 213 are combined via two nitrogen atoms. As shown in the chemical reaction formula, the four hydrogen atoms that have detached become two hydrogen molecules (gas). Such hydrogen molecules are discharged from between the first substrate W1 and the second substrate W2, or are absorbed by the first insulating film 113 or the second insulating film 213.

[0059] If the first and second substrates W1, W2 are heated while their first bonding surface 111 and second bonding surface 211 are in direct contact, the aforementioned reaction occurs across the entire interface between the first and second substrates W1, W2. This improves the bonding strength between the first and second substrates W1, W2. Furthermore, because the two copper atoms are directly bonded at the interface between the first and second copper pads 112 and 212, electrical resistance is reduced compared to a situation where copper oxide is located between the two copper atoms.

[0060] In the aforementioned example, the first reaction gas is a mixture of argon and hydrogen, and the second reaction gas is a mixture of argon, hydrogen, and nitrogen. However, the compositions of the first and second reaction gases are not limited thereto as long as the terminal oxygen atoms can be substituted with amino groups. The number of times the first bonding surface 111 of the first substrate W1 and the second bonding surface 211 of the second substrate W2 are treated with plasma (the number of plasma treatment steps) can be one or three times.

[0061] For example, in the aforementioned example, the second plasma treatment step may be omitted, and the first bonding surface 111 of the first substrate W1 and the second bonding surface 211 of the second substrate W2 may be treated with plasma of argon, hydrogen, and nitrogen.

[0062] In the above example, the first reaction gas may be a mixture of argon and hydrogen, and the second reaction gas may be nitrogen. Alternatively, the first reaction gas may be argon, and the second reaction gas may be argon, hydrogen, and nitrogen.

[0063] In the above example, after the first plasma treatment step and the second plasma treatment step have been performed and before the heat treatment step, a third plasma treatment step may be performed to treat the first bonding surface 111 of the first substrate W1 or the second bonding surface 211 of the second substrate W2 using a third plasma generated from a third reaction gas. In this case, the first reaction gas may be argon, the second reaction gas may be hydrogen, or a mixture of hydrogen and argon, and the third reaction gas may be nitrogen, a mixture of hydrogen and nitrogen, or a mixture of argon, hydrogen, and nitrogen.

[0064] Next, the substrate bonding apparatus 1 that performs the above-mentioned steps will be described.

[0065] Figure 5 It is a schematic diagram of a substrate bonding apparatus 1 according to one embodiment. Figure 6 It is a schematic diagram showing a vertical cross section of the plasma processing unit 2a.

[0066] The substrate bonding apparatus 1 is an apparatus for bonding two disc-shaped substrates W such as semiconductor wafers. Figure 5 As shown, a substrate bonding apparatus 1 comprises: a plurality of load ports LP, each housing a carrier CA accommodating a plurality of substrates W, such as a FOUP (Front-Opening Unified Pod); a plurality of processing units 2 for processing the substrates W transferred from the load ports LP; a transport system TS for transporting the substrates W between the load ports LP and the processing units 2; and an outer wall 1a forming a sealed space accommodating the processing units 2 and the transport system TS. The substrate bonding apparatus 1 further comprises a control unit 3 for controlling the substrate bonding apparatus 1.

[0067] Figure 5The example shown has three load ports LP. The three load ports LP include: a first load port LP1, which receives a carrier CA containing a first substrate W1; a second load port LP2, which receives a carrier CA containing a second substrate W2; and a third load port LP3, which receives a carrier CA containing a first substrate W1 and a second substrate W2 that have been bonded. The first and second load ports LP1 and LP2 serve as loading ports for carriers CA containing substrates W to be bonded by the substrate bonding apparatus 1. The third load port LP3 serves as an unloading port for carriers CA containing two substrates W that have been bonded by the substrate bonding apparatus 1.

[0068] The transport system TS transports the substrate W from the first load port LP1 and the second load port LP2 to the plurality of processing units 2, and transports the substrate W from the plurality of processing units 2 to the third load port LP3. The transport system TS also transports the substrate W between the plurality of processing units 2. The transport system TS may include at least one transport robot TR. Figure 5 One or more substrates W are transported in a horizontal posture along the transport path TP indicated by the bold line.

[0069] The transport robot TR includes at least one hand TH that holds a single substrate W in a horizontal posture. The transport robot TR moves along the transport path TP while holding the substrate W horizontally with the hand TH. Figure 5 An example is shown in which the transfer path TP extends from the first load port LP1 and the second load port LP2 to the plurality of processing units 2 and returns from the plurality of processing units 2 to the third load port LP3.

[0070] The plurality of processing units 2 include a plasma processing unit 2a, a cleaning unit 2b, a bonding unit 2c, and a heat treatment unit 2d. Figure 5 The example in which two plasma processing units 2a and two cleaning units 2b are provided is shown. Unless otherwise specified, the bonding unit 2c described in this specification bonds the substrates W under atmospheric pressure.

[0071] The plasma processing unit 2a performs the aforementioned plasma processing steps, including the first, second, and third plasma processing steps. The cleaning unit 2b cleans the substrate W with a cleaning solution such as pure water and then dries the substrate W. The bonding unit 2c bonds two substrates W by bringing them into contact. The thermal processing unit 2d performs the aforementioned thermal processing steps.

[0072] The plasma processing unit 2a, cleaning unit 2b, and bonding unit 2c are single-substrate units that process substrates W one by one (however, in the bonding unit 2c, a set of first and second substrates W1, W2 is considered a single substrate W). The thermal processing unit 2d can be a single-substrate unit that processes bonded substrates W one by one, or a batch unit that processes multiple bonded substrates W at once. A bonded substrate W is a set of bonded first and second substrates W1, W2.

[0073] The cleaning unit 2b includes: a rotary chuck 21, which holds a substrate W horizontally while rotating the substrate W around a vertical line passing through the center of the substrate W; a chamber 22, which accommodates the substrate W held by the rotary chuck 21; and a cleaning liquid nozzle 23, which sprays cleaning liquid onto the substrate W held by the rotary chuck 21.

[0074] The joining unit 2c includes a first chuck 31A that holds a first substrate W1, a second chuck 31B that holds a second substrate W2, and a chamber 32 that accommodates the first and second substrates W1, W2 held by the first and second chucks 31A, 31B. The first chuck 31A includes a first mask M1, and the second chuck 31B includes a second mask M2. The first and second masks M1, M2 are made of a material that transmits visible light, such as glass. The joining unit 2c also includes at least one actuator 33 that moves the first and second chucks 31A, 31B relative to each other, and a camera 34 that confirms the alignment of the first and second substrates W1, W2 by imaging the first and second masks M1, M2. The positional relationship between the first and second masks M1 and M2 can be detected by cameras (not shown) or determined by positioning members (such as positioning pins) provided on the first and second masks M1, M2.

[0075] At least one actuator 33 of the bonding unit 2c adjusts the alignment of the first and second substrates W1 and W2 by relatively moving the first and second chucks 31A and 31B. The at least one actuator 33 also bonds the first and second substrates W1 and W2 by relatively moving the first and second chucks 31A and 31B. An actuator is a device that converts driving energy, such as electrical energy, fluid energy, magnetic energy, thermal energy, or chemical energy, into mechanical work, i.e., the movement of an object. Actuators include electric motors (rotary motors), linear motors, air cylinders, and other devices.

[0076] Figure 5 This figure shows an example of a batch-type heat treatment unit 2d. Regardless of whether the heat treatment unit 2d is a single-sheet type or a batch-type heat treatment unit 2d, the heat treatment unit 2d includes a substrate holder 41 for holding two bonded substrates W, a heat treatment furnace 42 for accommodating the two substrates W held by the substrate holder 41, and a heater 43 for increasing the temperature within the heat treatment furnace 42.

[0077] like Figure 6 As shown, the plasma processing unit 2a includes a substrate holder 11 that supports a first substrate W1 or a second substrate W2; a sealed container 12 that accommodates the first substrate W1 or the second substrate W2 supported by the substrate holder 11. The plasma processing unit 2a also includes an exhaust pipe 13d that guides gas exhausted from the sealed container 12; a gas supply pipe 13s that guides gases such as reactant gases to be supplied to the sealed container 12; and a plasma source 14 that generates plasma from the reactant gases within the sealed container 12. The sealed container 12 includes an outer wall 12w that defines an interior space for accommodating the first substrate W1 or the second substrate W2, and a door 12d that opens and closes an opening. The outer wall 12w defines an interior space for accommodating the first substrate W1 or the second substrate W2, and an opening for allowing the first substrate W1 or the second substrate W2 to enter and exit the interior space.

[0078] Figure 6 FIG. 1 shows an example in which the plasma source 14 generates inductively coupled plasma. The plasma source 14 includes at least one antenna 15 corresponding to a coil and a high-frequency power supply 16 for supplying a high-frequency current to the at least one antenna 15 . Figure 6 An example is shown in which two antennas 15 are arranged in two spaces within outer wall 12w. In this example, antennas 15 are arranged in the space between inner plate 17, which closes a hole opened on the inner surface of outer wall 12w, and outer plate 18, which closes a hole opened on the outer surface of outer wall 12w.

[0079] When the air pressure in the space between inner plate 17 and outer plate 18 drops to a value below atmospheric pressure, high-frequency power supply 16 supplies a high-frequency current to antenna 15. This high-frequency current, supplied to antenna 15, generates an induced electric field within sealed container 12, ionizing the reactant gas within. This generates plasma. Embedded antenna 15, located within outer wall 12w of sealed container 12, is electrically insulated from the plasma by inner plate 17, which acts as a dielectric.

[0080] Figure 6 The U-shaped antenna 15 is shown as an example in which it is arranged in a vertical plane with an upwardly opened posture. The U-shaped antenna 15 includes two parallel portions that are parallel or substantially parallel to each other and a connecting portion ( Figure 6The connecting portion of the antenna 15 is arranged in the space inside the outer wall 12w. The area of ​​the space inside the antenna 15 is equivalent to the area of ​​the antenna 15. The area of ​​the antenna 15 is smaller than the area of ​​the first bonding surface 111 of the first substrate W. The inductance of the antenna 15 decreases as the area of ​​the antenna 15 decreases. The area of ​​the antenna 15 may also be greater than or equal to the area of ​​the first bonding surface 111. The antenna 15 can be maintained in a horizontal position. The antenna 15 can be arranged inside or outside the sealed container 12. The number of turns of the coiled antenna 15 may be greater than or equal to 1.

[0081] Control device 3 (refer to Figure 5 ) controls the electrical and electronic equipment of the substrate bonding apparatus 1. The control apparatus 3 includes: a processor 3a for processing information such as the execution of a processing program; and a memory 3b for storing information such as the program to be executed by the processor 3a. The control apparatus 3 controls the substrate bonding apparatus 1 to carry out the transport and processing of the substrate W. In other words, the control apparatus 3 is programmed to carry out the transport and processing of the substrate W. The control apparatus 3 controls the substrate bonding apparatus 1, thereby referring to Figures 1 to 4F While performing the various steps from the plasma treatment step to the heat treatment step described above, the processor 3a may be any one of a CPU (central processing unit), an MPU (microprocessing unit), a GPU (graphics processing unit), or a DSP (digital signal processor), or a combination thereof. Alternatively, the processor 3a may include an FPGA (field-programmable gate array) or an ASIC (application-specific integrated circuit).

[0082] Next, the effects of this embodiment will be described.

[0083] In this embodiment, the copper oxide exposed on the copper pads 112 and 212 and the bonding surfaces 111 and 211 of the insulating films 113 and 213 are treated using rare gas plasma (rare gas plasma), hydrogen plasma (hydrogen plasma), and nitrogen plasma (nitrogen plasma). Argon is an example of a rare gas (Group 18 element). The rare gas plasma removes oxygen atoms from the copper oxide on the copper pads 112 and 212, converting the copper oxide into copper atoms. The hydrogen plasma causes the hydrogen atoms to bond with the copper atoms on the copper pads 112 and 212. The nitrogen plasma replaces the hydrogen atoms bonded to the copper atoms on the copper pads 112 and 212 with nitrogen atoms, and causes the nitrogen atoms to bond with the copper atoms. After bonding with the copper atoms, due to the high activity of the nitrogen atoms, hydrogen atoms separated from the copper atoms, and other hydrogen atoms on the bonding surfaces 111 and 211, bond with the nitrogen atoms. As a result, amino groups bond with the copper atoms, and the surfaces of the copper pads 112 and 212 are terminated with amino groups.

[0084] After the bonding surfaces 111 and 211 of each substrate W are treated with plasma, the bonding surfaces 111 and 211 of the two substrates W are brought into contact. As a result, the copper pads 112 and 212 of the two substrates W face each other, and the insulating films 113 and 213 of the two substrates W face each other. As described above, the surfaces of the copper pads 112 and 212 are terminated with amino groups. Therefore, two amino groups are located between two copper atoms. When the two bonded substrates W are heated, the amino groups are detached from the interface between the two copper pads 112 and 212, and the copper atoms of the two copper pads 112 and 212 directly bond to each other. Therefore, compared to a case where copper oxide is present at the interface between the two bonded copper pads 112 and 212, the resistance of the interface can be reduced.

[0085] In this embodiment, the bonding surfaces 111 and 211 of each substrate W are treated with a plasma containing a rare gas plasma but not a nitrogen plasma. Subsequently, the bonding surfaces 111 and 211 of each substrate W are treated with a nitrogen plasma. The treatment of the bonding surfaces 111 and 211 with hydrogen plasma, i.e., the hydrogen plasma treatment, can be performed either before or simultaneously with the treatment of the bonding surfaces 111 and 211 with nitrogen plasma, i.e., the nitrogen plasma treatment. In the former case, the hydrogen plasma treatment can be performed simultaneously with the treatment of the bonding surfaces 111 and 211 with a rare gas plasma, i.e., the rare gas plasma treatment.

[0086] Before removing oxygen atoms from the copper oxide, if the bonding surfaces 111 and 211 of the substrates W are treated with a plasma containing a rare gas plasma and nitrogen plasma, but not hydrogen plasma, the nitrogen atoms may stabilize in a state of being bound to copper atoms after the oxygen atoms are removed from the copper oxide. In other words, copper nitride (Cu3N) may form on the surfaces of the copper pads 112 and 212. After the nitrogen and copper atoms are stabilized, even if the bonding surfaces 111 and 211 of the substrates W are treated with hydrogen plasma, the nitrogen atoms will not or will hardly convert into amino groups. Furthermore, compared to the case where amino groups are removed, the nitrogen atoms contained in the copper nitride will not be removed from the interface between the two copper pads 112 and 212 unless the two substrates W are heated at high temperatures.

[0087] As described above, treating the bonding surfaces 111 and 211 of each substrate W with a rare gas plasma, a hydrogen plasma, and a nitrogen plasma increases the probability of hydrogen atoms bonding to copper atoms before nitrogen atoms bond to copper atoms. If hydrogen atoms bond to copper atoms first, the surfaces of the copper pads 112 and 212 can be terminated with amino groups. This prevents or reduces the formation of copper nitride on the surfaces of the copper pads 112 and 212.

[0088] In this embodiment, a first reaction gas containing a rare gas and hydrogen but not nitrogen is supplied to the sealed container 12 that accommodates the substrate W, and a first plasma P1 containing a rare gas and hydrogen but not nitrogen is generated by the first reaction gas. As a result, the oxygen atoms contained in the copper oxide are replaced by hydrogen atoms. Then, a second reaction gas containing at least nitrogen is supplied to the sealed container 12, and a second plasma P2 containing at least nitrogen is generated by the second reaction gas. As a result, amino groups are combined with copper atoms constituting the surface of the copper pads 112 and 212. The second reaction gas can be a gas containing neither a rare gas nor hydrogen (nitrogen), or a gas containing one or both of a rare gas and hydrogen in addition to nitrogen. In the latter case, when copper oxide remains on the surface of the copper pads 112 and 212, the oxygen atoms contained in the copper oxide are replaced by hydrogen atoms, and then the hydrogen atoms are replaced by amino groups.

[0089] The first reaction gas differs from the second reaction gas in that it does not contain nitrogen. Therefore, even if a mixed gas of a rare gas, hydrogen, and nitrogen is not supplied to the sealed container 12, the second reaction gas can be supplied to the sealed container 12 by adding nitrogen to the first reaction gas in the sealed container 12. Therefore, the first reaction gas does not need to be exhausted from the sealed container 12 before the supply of the second reaction gas begins. Furthermore, if nitrogen is added to the first reaction gas in the sealed container 12 while the plasma source 14 ionizes the gas in the sealed container 12, it is possible to continuously switch from the first plasma processing step to the second plasma processing step.

[0090] In this embodiment, oxygen is brought into contact with the bonding surfaces 111 and 211 of the substrates W that have been treated with plasma. Specifically, an oxygen-containing gas such as air is brought into contact with the substrate W, or a liquid containing dissolved oxygen is brought into contact with the substrate W. The transport system TS and the cleaning unit 2b are examples of oxygen contact units. Even if copper oxide is removed from the surfaces of the copper pads 112 and 212, if oxygen atoms or oxygen molecules come into contact with the surfaces of the copper pads 112 and 212, the copper atoms will be oxidized on the surfaces of the copper pads 112 and 212 before the two substrates W are bonded. When the surfaces of the copper pads 112 and 212 are amino-terminated, such oxidation can be prevented or reduced. Therefore, there is no need to bond the two substrates W in a vacuum, nor is there any need to transport each substrate W in a vacuum using the transport robot TR.

[0091] In this embodiment, the bonding surfaces 111 and 211 of the plasma-treated substrates W are cleaned with a cleaning liquid and then dried. Even if oxygen is dissolved in the cleaning liquid, the amino-terminated surfaces of the copper pads 112 and 212 can suppress or prevent oxidation of copper atoms on the surfaces of the copper pads 112 and 212 by the oxygen in the cleaning liquid. Furthermore, the supply of cleaning liquid to the bonding surfaces 111 and 211 of the substrates W can reduce particles generated during plasma treatment of the bonding surfaces 111 and 211 of the substrates W. This can reduce particles remaining at the interface between the two bonded substrates W.

[0092] In this embodiment, the two bonded substrates W are heated. This heating causes amino groups to dissociate from the interface between the two copper pads 112 and 212, allowing the copper atoms of the two copper pads 112 and 212 to directly bond with each other. Consequently, compared to a situation where copper oxide exists at the interface between the two bonded copper pads 112 and 212, the resistance of the interface can be reduced. Furthermore, compared to a situation where copper oxide disappears from the interface between the two copper pads 112 and 212 by heating the two bonded substrates W, the heating temperature of the two substrates W can be lowered.

[0093] In this embodiment, a single substrate bonding apparatus 1 performs both plasma treatment and substrate W bonding. Specifically, the plasma processing unit 2a of the substrate bonding apparatus 1 performs plasma treatment on each of the two substrates W, and then the bonding unit 2c of the substrate bonding apparatus 1 bonds the two substrates W. After bonding the two substrates W, the thermal treatment unit 2d of the substrate bonding apparatus 1 heats the two substrates W. This heating removes amino groups from the interface between the two copper pads 112 and 212. Because the thermal treatment is also performed in the same substrate bonding apparatus 1 in addition to the plasma treatment and substrate W bonding, the period between plasma treatment and thermal treatment can be shortened. Consequently, the amount of amino groups that deteriorate or disappear during this period can be reduced.

[0094] In this embodiment, a high-frequency current is supplied to the antenna 15, generating an induced electric field within the sealed container 12 containing the substrates W. This ionizes the gas within the sealed container 12, generating an inductively coupled plasma of at least one of a rare gas, hydrogen, and nitrogen. This inductively coupled plasma contacts the bonding surfaces 111 and 211 of the substrates W within the sealed container 12, thereby treating the bonding surfaces 111 and 211. Inductively coupled plasma is a high-density plasma with a high density of electrons, ions, and radicals. Therefore, the bonding surfaces 111 and 211 of the substrates W can be uniformly treated.

[0095] The antenna 15 is arranged in the space between the inner plate 17 and the outer plate 18. The inner plate 17 closes the hole opened on the inner surface of the outer wall 12w of the sealed container 12, and the outer plate 18 closes the hole opened on the outer surface of the outer wall 12w of the sealed container 12. The antenna 15 is limited to the size of the space that can be arranged within the outer wall 12w. As a result, the antenna 15 can be miniaturized and the inductance of the antenna 15 can be reduced. If the inductance of the antenna 15 is low, the voltage applied to the antenna 15 when a high-frequency current is supplied to the antenna 15 is reduced, and the damage to the substrate W caused by the plasma is reduced. Therefore, the damage can be reduced and the bonding surfaces 111 and 211 can be uniformly treated with plasma.

[0096] Next, other embodiments will be described.

[0097] The rare gas (Group 18 element) contained in the reaction gas for generating plasma may be a rare gas other than argon, such as helium and neon.

[0098] At least one of the plasma processing unit 2a and the heat treatment unit 2d may be a device separate from the substrate bonding apparatus 1. That is, at least one of the plasma processing unit 2a and the heat treatment unit 2d may be disposed outside the outer wall 1a of the substrate bonding apparatus 1.

[0099] Two or more of the aforementioned structures may be combined. Two or more of the aforementioned steps may also be combined.

[0100] The embodiments of the present invention have been described in detail, but these specific examples are only used to illustrate the technical content of the present invention and should not be limited to interpreting the present invention based on these specific examples. The spirit and scope of the present invention are limited only by the scope of the appended claims.

[0101] This application claims priority based on Japanese Patent Application No. 2024-043677, filed on March 19, 2024, the entire contents of which are incorporated herein by reference.

Claims

1. A substrate bonding method comprising bonding two substrates each having a bonding surface, wherein copper oxide of a copper pad and an insulating film are exposed on the bonding surface, wherein: The substrate bonding method comprises: a plasma treatment step of treating the bonding surfaces of the substrates with a rare gas plasma, i.e., a rare gas plasma, treating the bonding surfaces of the substrates after the rare gas plasma treatment with a hydrogen plasma, i.e., a hydrogen plasma, and treating the bonding surfaces of the substrates after the hydrogen plasma treatment with a nitrogen plasma, i.e., a nitrogen plasma; as well as The substrate bonding step is to bond the two substrates by bringing the bonding surfaces of the two substrates into contact with each other so that the copper pads of the two substrates face each other and the insulating films of the two substrates face each other after the plasma treatment step.

2. The substrate bonding method according to claim 1, wherein: The plasma treatment step is a step of performing the following steps on each of the two substrates: a rare gas plasma treatment step of treating the bonding surface with a plasma containing the rare gas plasma but not the nitrogen plasma; a nitrogen plasma treatment step of treating the bonding surface with the nitrogen plasma; and The hydrogen plasma treatment step treats the bonding surface with the hydrogen plasma simultaneously with at least one of the rare gas plasma treatment step and the nitrogen plasma treatment step, or after the rare gas plasma treatment step and before the nitrogen plasma treatment step.

3. The substrate bonding method according to claim 2, wherein: The plasma treatment step is a step of performing the following steps on each of the two substrates: a first plasma treatment step of supplying a first reaction gas into a sealed container containing the substrate and treating the bonding surface with a first plasma generated by the first reaction gas, wherein the first reaction gas contains the rare gas and the hydrogen gas but does not contain the nitrogen gas; and In the second plasma treatment step, a second reaction gas is supplied into the sealed container, and the bonding surface is treated with a second plasma generated by the second reaction gas, wherein the second reaction gas contains the nitrogen gas.

4. The substrate bonding method according to any one of claims 1 to 3, wherein The method further includes an oxygen contact step of bringing at least one of oxygen in the atmosphere and oxygen in the liquid into contact with the bonding surfaces of the substrates after the plasma treatment step.

5. The substrate bonding method according to claim 4, wherein: The oxygen contact step includes a cleaning step of cleaning each of the two substrates with a cleaning liquid and drying the substrates after the plasma treatment step and before the substrate bonding step.

6. The substrate bonding method according to any one of claims 1 to 3, wherein: The method further includes a heat treatment step of heating the two bonded substrates to directly bond the copper contained in the copper pad of one of the two substrates to the copper contained in the copper pad of the other of the two substrates.

7. The substrate bonding method according to claim 6, wherein: The plasma treatment step is a step of causing a plasma processing unit of a substrate bonding apparatus to generate the rare gas plasma, the hydrogen plasma, and the nitrogen plasma, thereby treating the bonding surfaces of the substrates with the rare gas plasma, the hydrogen plasma, and the nitrogen plasma. The substrate bonding step is a step of bonding the two substrates by bringing the bonding surfaces of the two substrates into contact with each other using a bonding unit of the substrate bonding device so that the copper pads of the two substrates face each other and the insulating films of the two substrates face each other, thereby bonding the two substrates. The heat treatment step is a step of directly bonding the copper contained in the copper pad of one of the two substrates to the copper contained in the copper pad of the other of the two substrates by causing the heat treatment unit of the substrate bonding apparatus to heat the two bonded substrates.

8. The substrate bonding method according to any one of claims 1 to 3, wherein The plasma treatment process is a process of generating an inductively coupled plasma of at least one of the rare gas, the hydrogen gas, and the nitrogen gas by supplying a high-frequency current to an antenna arranged in a space between an inner plate and an outer plate, wherein the inner plate seals a hole opened on the inner surface of an outer wall of a sealed container accommodating the substrate, and the outer plate seals a hole opened on the outer surface of the outer wall.

9. A substrate bonding apparatus for bonding two substrates each having a bonding surface where copper oxide and an insulating film of a copper pad are exposed, wherein: The substrate bonding device comprises: a plasma processing unit for treating the bonding surfaces of the substrates with a rare gas plasma, i.e., a rare gas plasma, treating the bonding surfaces of the substrates after the rare gas plasma treatment with a hydrogen plasma, i.e., a hydrogen plasma, and treating the bonding surfaces of the substrates after the hydrogen plasma treatment with a nitrogen plasma, i.e., a nitrogen plasma; A bonding unit, after the bonding surfaces of the two substrates are treated with the rare gas plasma, hydrogen plasma and nitrogen plasma, brings the bonding surfaces of the two substrates into contact with each other in a manner such that the copper pads of the two substrates are opposed to each other and the insulating films of the two substrates are opposed to each other, thereby bonding the two substrates.

10. The substrate bonding apparatus according to claim 9, wherein: The plasma processing unit performs the following steps on each of the two substrates: a rare gas plasma treatment step of treating the bonding surface with a plasma containing the rare gas plasma but not the nitrogen plasma; a nitrogen plasma treatment step of treating the bonding surface with the nitrogen plasma; and The hydrogen plasma treatment step treats the bonding surface with the hydrogen plasma simultaneously with at least one of the rare gas plasma treatment step and the nitrogen plasma treatment step, or after the rare gas plasma treatment step and before the nitrogen plasma treatment step.

11. The substrate bonding apparatus according to claim 10, wherein: The plasma processing unit performs the following steps on each of the two substrates: a first plasma treatment step of supplying a first reaction gas into a sealed container containing the substrate and treating the bonding surface with a first plasma generated by the first reaction gas, wherein the first reaction gas contains the rare gas and the hydrogen gas but does not contain the nitrogen gas; and In the second plasma treatment step, a second reaction gas is supplied into the sealed container, and the bonding surface is treated with a second plasma generated by the second reaction gas, wherein the second reaction gas contains the nitrogen gas.

12. The substrate bonding apparatus according to any one of claims 9 to 11, wherein: The invention further comprises an oxygen contact unit for bringing at least one of oxygen in the atmosphere and oxygen in the liquid into contact with the bonding surface of each substrate after the bonding surface of each substrate is treated with the rare gas plasma, the hydrogen plasma, and the nitrogen plasma.

13. The substrate bonding apparatus according to claim 12, wherein: The oxygen contact unit includes a cleaning unit that cleans and dries each of the two substrates with a cleaning liquid after the bonding surfaces of the substrates are treated with the rare gas plasma, the hydrogen plasma, and the nitrogen plasma and before the two substrates are bonded.

14. The substrate bonding apparatus according to any one of claims 9 to 11, wherein: The invention further comprises a heat treatment unit for directly bonding the copper contained in the copper pad of one of the two substrates to the copper contained in the copper pad of the other of the two substrates by heating the two bonded substrates.

15. The substrate bonding apparatus according to any one of claims 9 to 11, wherein: The plasma processing unit generates an inductively coupled plasma of at least one of the rare gas, the hydrogen gas, and the nitrogen gas by supplying a high-frequency current to an antenna arranged in a space between an inner plate and an outer plate, wherein the inner plate seals a hole opened on the inner surface of an outer wall of a sealed container accommodating the substrate, and the outer plate seals a hole opened on the outer surface of the outer wall.

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