JP2006248895A - Bonding method, device produced by this method, and bonding device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bonding method which comprises sticking OH groups on the bonding surfaces of both objects to be bonded by atomically coupling the OH groups by utilizing plasma and then subjecting the both objects to be bonded to anode bonding; and a bonding device. <P>SOLUTION: After sticking OH groups on the bonding surfaces of an upper wafer 7 comprising glass and a lower wafer 8 comprising Si by atomically coupling the OH groups by utilizing plasma, anode bonding is performed. Thereby, the bonding strength can be enhanced at a lower temperature. After temporary bonding by hydrophilizing treatment, the final anode bonding is performed. Thus, the production efficiency is enhanced and objects to be bonded are mutually bonded in a three-layer structure without causing warp. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a technique for bonding a plurality of objects such as wafers by anodic bonding.

  Conventionally, in wafer bonding of Si and glass, a method of applying anodic bonding by applying a voltage with the glass side as a cathode in a state where both wafers are in contact and heating to a high temperature of about 400 ° C. to 500 ° C. is known. Yes. In the conventional method, after cleaning the wafer, it is transported in the air to perform anodic bonding, and thus organic substances are unavoidably adhered to the bonding surface. As shown in FIG. 5, the strength is as weak as 3 MPa at 200 ° C. Therefore, the strength is increased to about 9 MPa by high temperature heating at about 400 ° C. That is, in conventional anodic bonding, high-temperature heating must be used in combination.

Further, in the room temperature bonding method shown in Patent Document 1, an example is shown in which metals are etched with an Ar ion beam and bonded at room temperature in a state where the bonding surface is surface-activated. However, this method removes organic matter and oxide film on the bonding surface, thereby creating a bonding surface electrically activated by metal dangling bonds and bonding it by atomic force. Glass or SiO ₂ that is an oxide cannot be firmly bonded.

  In addition, as shown in Patent Document 2, when plasma processing is performed with objects to be bonded facing each other, one of the objects to be bonded always becomes a plasma electrode, and the ion particles of the reaction gas are accelerated so that the object on the plasma electrode side is accelerated. Collide with joints. Therefore, it is suitable for physical etching to remove the organic layer on the bonding surface, but is not suitable for chemical treatment such as attaching OH groups to the bonding surface because the ion collision force is too strong.

  As an application in which anodic bonding is often used, a method of sealing a high-frequency device or a MEMS device from one side or both sides as shown in FIG. 8 is often used.

JP 54-124853 A JP 2003-318217 A

  In the conventional anodic bonding method, at least some organic substances are redeposited on the bonding surfaces, and at the time of anodic bonding, at least some organic substance layers are sandwiched at the bonding interface. Originally, if the glass is heated to about 200 ° C. where it is softened, it should be able to be strongly bonded by anodic bonding by voltage application. However, since the organic layer is attached, the organic matter is decomposed by heating at a high temperature of about 400 ° C. to 500 ° C. From this, it can be seen that the bonding strength is increased for the first time. In addition, since there was no joining in a vacuum, there was a problem of air void biting. In addition, the conventional method requires several hours for anodic bonding, so that the production efficiency is poor. In addition, if the objects to be joined are temporarily joined using an adhesive or the like, foreign matter is bitten between Si and glass, so that anodic bonding cannot be performed. In particular, MEMS devices that are aligned and bonded with high accuracy have to be produced with low efficiency.

In addition, in the room temperature bonding method shown in Patent Document 1, since an organic substance and an oxide film on the bonding surface are removed to create a bonding surface that is electrically activated to a metal or semiconductor and bonding is performed by atomic force, Si other than metal is used. Semiconductors, especially oxide glass and SiO ₂ cannot be bonded firmly. Also, because it is at room temperature, it is not softened, so it creates a part with insufficient joint strength to leave gaps and residual stress that can not be joined due to dust consisting of fine particles and waviness of the flatness of the joining surface. Become. Therefore, it is necessary to remove the residual stress by annealing for several hours even at a low temperature. Further, in order to fill and bond these gaps, it is necessary to press the objects to be joined together at a high pressure to bring the undulations and gaps of the bonding interface into close contact, and it is necessary to use a considerable high pressure of 300 MPa or more.

  Further, as shown in Patent Document 2, when the object to be bonded is arranged oppositely and plasma treatment is performed, one of the objects to be bonded always becomes a plasma electrode, and the ion particles of the reaction gas are accelerated and collide with the object to be bonded. Therefore, it is suitable for physical etching to remove the organic material layer, but is not suitable for surface activation by chemical treatment such as attaching OH groups to the bonding surface because the ion collision force is too strong. As described above, there is no method that satisfies both cleaning and adsorption.

  In addition, as shown in FIG. 8, in the method of sealing a high-frequency device or a MEMS device from one side or both sides, an example of a material that is commonly used is glass anodic bonding on one side or both sides of Si. It becomes a structure to stop. However, even in the three-piece structure, since the glass is anodically bonded in order from one side of the device, the difference in the linear expansion coefficient between Si and glass causes the heating during anodic bonding as shown in FIG. The warp will occur and the worst will occur.

  Accordingly, an object of the present invention is to provide a bonding method and a bonding apparatus for anodic bonding of the two objects to be bonded after bonding OH groups atomically to the bonding surfaces of the objects to be bonded by using plasma. There is to do. Further, OH groups are atomically bonded to the bonding surfaces of the objects to be bonded by atomic bonding to temporarily bond the both objects to be bonded, and then anodic bonding the objects to be bonded and perform the main bonding. A bonding method and a bonding apparatus are provided.

  The means of both the joining method and the joining apparatus according to the present invention for solving the above-mentioned problems will be described collectively below.

In order to solve the above-mentioned problems, the present invention, after bonding OH groups atomically using plasma on the bonding surfaces of the objects to be bonded, which are either Si, SiO ₂ or glass, It consists of the joining method which anodic-joins both to-be-joined objects (Claim 1).

In addition, the present invention provides a plasma processing unit that attaches OH groups by atomically bonding to a bonding surface between objects to be bonded that are any one of Si, SiO ₂ , and glass by using plasma, and the plasma processing unit And an anodic bonding means for anodic bonding the objects to be bonded with OH groups attached to the bonding surface.

In the present invention, after joining both the objects to be bonded, the plasma is used to attach and bond the OH groups to the bonding surfaces of the objects to be bonded which are any one of Si, SiO ₂ and glass. And a joining method in which the two objects to be joined are subjected to anodic bonding to perform main bonding (Claim 2).

In addition, the present invention provides a plasma processing unit that attaches OH groups by atomically bonding to a bonding surface between objects to be bonded that are any one of Si, SiO ₂ , and glass by using plasma, and the plasma processing unit Temporary bonding means for temporarily bonding the two bonded objects having OH groups attached to the bonding surface, and main bonding means for performing main bonding by applying a voltage to the temporary bonded both bonded objects and heating them. And an anodic bonding means having the above structure (claim 13).

  An anodic bonding is a method in which a voltage is applied between both objects to be contacted, the bonding interface is brought into close contact by an electrostatic force between materials mixed with an element that decomposes into movable ions by the voltage application, and heated at least. This is a method in which one material is softened and adhered and covalently bonded. The hydrophilization treatment by plasma refers to a treatment that facilitates bonding by making an activated state by bonding OH groups atomically to the bonding interface by using plasma.

There are the following two concepts in the bonding principle by surface activation by plasma. First, in materials such as metals, surface organics and oxides are removed by etching to generate dangling bonds of active metal atoms on the surface, and the other dangling bonds are joined together. Let _Second , in the case of an oxide containing Si, glass, SiO ₂ , or ceramic, the bonding surface is activated with OH groups and bonded with the other OH groups by hydrophilization treatment with oxygen or nitrogen plasma. Let In the case of plasma, there is atmospheric pressure plasma that can be processed under atmospheric pressure in addition to low-pressure plasma and can be easily handled. The feature of the present invention is that, in accordance with the bonding principle by the second hydrophilization treatment, OH groups are atomically bonded and attached to the joint surface using plasma, and after hydrophilic treatment, anodic bonding is performed at a lower temperature. And, it is to increase the bonding strength, and after the temporary bonding by the hydrophilization treatment, the main bonding is performed by the anodic bonding in which the process or the apparatus is separated, thereby improving the production efficiency and having a three-layer structure in which warpage does not occur. It is in a place that enables joining.

FIG. 10 shows the bonding principle by the hydrophilization treatment. As shown in FIG. 10A, OH groups are attached to the Si surface by a hydrophilization treatment using oxygen plasma or the like. Next, as shown in FIG. 10B, both objects to be joined are brought into contact and temporarily joined by hydrogen bonding. Subsequently, as shown in FIG. 10C, H ₂ O is released by heating to obtain a strong covalent bond of Si—O—Si. The method of joining by hydrophilization by plasma treatment is simple and effective for oxide joining including Si, glass, SiO ₂ and ceramics.

  In this way, OH groups are generated on the surfaces, and hydrogen bonding is performed with the OH groups on both surfaces, whereby temporary bonding can be performed. Heating for a few hours is necessary for strong main joining, but if it is temporary joining, it is completed instantaneously. Further, even in the joining with sealing as shown in FIG. 8, the temporary joining subjected to the hydrophilic treatment is accompanied with water at the interface, and thus the sealing performance is excellent. In general, oxygen plasma or nitrogen plasma is used for the hydrophilic treatment, and bonding is possible even by atmospheric pressure plasma. Although it is difficult to determine the conditions as it is to join firmly, if the temporary bonding level is sufficient, the bonding by the hydrophilization treatment is relatively easy and suitable for temporary bonding.

As described in the conventional method, the surface activation method by etching with Ar ions is a method that can be bonded at a low temperature. However, an organically activated surface of a metal is created by removing organic substances and oxide film on the surface to form atoms. Since bonding is performed by an interstitial force, strong main bonding is difficult in the bonding of semiconductors other than metals and particularly oxides, and is suitable for temporary bonding. Moreover, it is easy to form covalent bonds such as Si-O by temporary bonding at room temperature and main bonding by anodic bonding to non-metal semiconductors such as Si, especially SiO ₂ , glass and ceramics containing oxides. Therefore, the hydrophilic treatment method of the present invention is suitable. Further, the room-temperature bonding requires a high vacuum state of 10 ⁻⁸ Torr even in the bonding between Si, but the plasma processing method is preferable because it can be easily handled at a vacuum degree of about 10 ⁻² Torr. A particularly suitable combination is preferable because a combination of Si and glass facilitates covalent bonding such as Si—O by the main bonding by anodic bonding and increases the bonding strength. Moreover, since it is suitable also for joining by hydrophilic treatment, it is suitable.

  Further, a bonding method may be employed in which the bonding surfaces have a surface shape in which the bonding surfaces are in close contact with each other, one or more particles are on the bonding surface, and anodic bonding is performed. Further, the joining surface may have a shape in which the joining surfaces are in close contact with each other, and one or more particles are on the joining surface, and a joining apparatus that performs anodic joining may be used.

As described above, even if fine particles are sandwiched, if anodic bonding is used, bonding can be performed without gaps by softening of glass by heating or adhesion by electrostatic force. In other words, after the hydrophilic treatment of the objects to be bonded, even if the objects to be bonded are overlapped with each other, even if minute particles (voids) are sandwiched between the bonded surfaces, the objects to be bonded are heated by the anodic bonding. Since the bonding surfaces are attracted to each other by the electrostatic force and the bonding surfaces are in close contact with each other, the objects to be bonded can be bonded together without any gap. At this time, voids can be completely eliminated by bonding at a low temperature, which cannot be achieved by conventional anodic bonding. That is, it is possible to join objects to be joined which are any one of Si, SiO ₂ and glass at a low temperature while preventing generation of voids. Further, it comprises a method of anodic bonding with a pressing force of 300 Mpa or less during the main bonding. In addition, it comprises a joining device for anodic joining, comprising a pressurizing means for pressurizing with a pressing force of 300 Mpa or less during the main joining. In the above-mentioned room temperature bonding, since the material is not softened, a pressure of 300 Mpa or more is required. However, it is possible to bond at 300 Mpa or less, for example, 100 Mpa by heating by anodic bonding and electrostatic force.

  The environment for performing surface activation and anodic bonding is not particularly limited, and includes the present invention regardless of whether it is in a vacuum or in the atmosphere. The present invention also includes a state where the surface activation device is separated from the bonding device.

  Moreover, this invention consists of the joining method of Claim 2 which isolate | separates a process or an apparatus and performs this joining by the said anodic bonding after the said temporary joining under normal temperature (Claim 3).

  Moreover, this invention consists of the joining apparatus of Claim 13 with which the said temporary joining means and the said main joining means are each provided in the independent space (Claim 14).

  The normal temperature refers to bonding at a temperature of 150 ° C. or lower, which allows bonding at a lower temperature, while typical solder capable of metal bonding at a low temperature can be bonded at 183 ° C., and is preferably room temperature. Conventional bonding methods that use an adhesive or diffusion bonding by high-temperature heating are known. The adhesive can be temporarily bonded, but cannot be used for bonding a fine structure such as MEMS or electrical bonding such as a semiconductor. In addition, there are many disadvantages such as weak adhesive strength, gas release, and moisture absorption. In addition, since the diffusion method is at a high temperature, there still remains a problem of heat resistance of the material and a problem that warpage occurs due to a difference in linear expansion coefficient between the dissimilar materials or the worst cracking occurs.

However, these problems can be solved if it is possible to directly bond a surface-activated material that has been hydrophilized by plasma at room temperature. However, because it is at room temperature, it can be easily used for temporary bonding because it does not increase the bonding strength unless residual stress and strain due to surface roughness and waviness of mass-produced materials are removed. Originally, it is necessary to anneal for several hours to increase the bonding strength, and if this is performed in one process or apparatus, the mass production efficiency decreases. Therefore, the mass production efficiency can be improved by separating the temporary joining step bonded at room temperature and the main joining step by heating, and performing them with a separate apparatus. As described above, the surface activation treatment is a treatment including removal of deposits by etching and a hydrophilic treatment, and Si, glass, SiO ₂ and ceramic are particularly suitable for the hydrophilic treatment.

  Moreover, this invention consists of the joining method of Claim 3 which balances the process of the said some main joining with respect to the number 1 of the processes of the said temporary joining (Claim 4).

  Moreover, this invention consists of a joining apparatus of Claim 14 with which the said anodic joining means has several said main joining means with respect to the number 1 of the said temporary joining means (Claim 15).

  The mass production efficiency can be further improved by taking a line balance with a plurality of main bonding apparatuses with respect to a single temporary bonding apparatus or process. For example, if it takes 10 minutes for temporary bonding and 1 hour for main bonding, it is possible to bond one apparatus every 10 minutes by arranging six main bonding apparatuses on the temporary bonding apparatus 1. In terms of cost, it is overwhelmingly possible to arrange one temporary joining device and six main joining devices that are simply heated by applying a voltage rather than arranging six temporary book integrated devices.

  Moreover, this invention consists of the joining method in any one of Claim 2 thru | or 4 which performs the said temporary joining in air | atmosphere in the pressure reduction chamber by which pressure reduction or gas substitution was carried out (Claim 5).

  Furthermore, the present invention includes a decompression chamber in which the temporary joining means is disposed, performs the temporary joining in the decompression chamber that has been decompressed or replaced with gas, and performs the final joining in the atmosphere. 15. The joining device according to any one of 15 (claim 16).

  In a device in which the inside is sealed with a vacuum or an inert gas as shown in FIG. 8, if temporary bonding is performed in a reduced pressure atmosphere or a gas replacement atmosphere in a reduced pressure chamber, Because it is sealed with, air does not enter. In particular, when bonding is performed by a hydrophilization treatment, water is present at the interface, so that the sealing effect is also high. Therefore, this joining can be performed in the atmosphere, and cost reduction and efficiency improvement are achieved.

  In addition, if the plasma is depressurized or atmospheric pressure plasma, it can be handled with a degree of vacuum that is easier than other energy waves, and costs can be reduced. Moreover, if it is atmospheric pressure plasma, it can be handled more easily. However, some bonding materials cannot be bonded without low-pressure plasma treatment, which is advantageous for bonding.

  Further, the present invention provides the method according to any one of claims 1 to 4, wherein the OH groups are bonded atomically to the bonding surface before bonding, and then the two objects to be bonded are anodic bonded without being exposed to the atmosphere. It consists of a joining method (claim 6).

  In the present invention, the plasma processing means and the anodic bonding means are each provided in a decompression chamber, and OH groups are atomically bonded to the bonding surface by the plasma processing means and then exposed to the atmosphere. The joining apparatus according to any one of claims 13 to 15, wherein the two objects to be joined are subjected to anodic bonding without being performed (claim 17).

Etching the surface with plasma, removing deposits, and performing hydrophilic treatment with plasma without exposing to the atmosphere with the new surface of the substrate exposed, allows hydrophilic treatment without an organic layer. Subsequently, both objects to be bonded are brought into contact, voltage is applied, and anodic bonding is performed by heating, so that there is no adhesion of organic substances, and basically the bonding force is due to voltage application, and covalent bonding such as Si-O is performed. Is called. Therefore, there is no peeling from the organic material layer after bonding due to hydrogen bonding force and strength after annealing, so that annealing at a low temperature is sufficient to release H ₂ O after hydrogen bonding without diffusion. Bonding strength can be obtained. When one side is glass, the heating may be a temperature necessary to soften the glass and follow the other-side object to be joined without any gap, and about 200 ° C. is sufficient. Further, if the flatness and flatness of the objects to be joined are obtained, it is not necessary to soften them, and the joining strength increases accordingly even at room temperature.

  Further, in the present invention, the plasma is a low pressure plasma, and after the OH group is atomically bonded to the bonding surface by using the low pressure plasma and attached, the two objects to be bonded are continuously formed in the same chamber. The bonding method according to any one of claims 1 to 4, wherein the contact is made in a vacuum (claim 7).

  The plasma processing means and the anodic bonding means have a reduced pressure chamber disposed therein, and the plasma by the plasma processing means is a reduced pressure plasma, and OH groups are atomized on the bonding surface using the reduced pressure plasma. The bonding apparatus according to any one of claims 13 to 15, wherein the objects to be bonded are brought into contact with each other in vacuum continuously in the decompression chamber after being bonded together and attached (claim 18).

  Although it is possible to divide and handle the chamber for hydrophilization treatment and anodic bonding with plasma, for example, both objects to be bonded are held opposite to the upper and lower electrodes in the same chamber, and after the hydrophilization treatment, plasma is continuously applied. By switching the power source to the anodic bonding power source, the same electrode can be used as it is, and only one chamber is required, leading to compactness and cost reduction. Moreover, it is not necessary to draw a high vacuum compared to other energy waves. Further, since the bonding is in a vacuum, it is possible to prevent biting of the void.

  It is also possible to divide and handle the plasma processing and bonding chambers. However, as shown in FIGS. 1 and 11, both objects to be bonded are held opposite to the upper and lower electrodes in the same chamber, and the plasma processing is performed. After that, the temporary bonding is continuously performed, so that one chamber is sufficient, which leads to compactness and cost reduction. Further, since the temporary bonding is in a vacuum, it is possible to prevent biting of voids. Further, the plasma is formed by using an alternating power source. Further, the plasma comprises a joining device using an alternating power source. By using an alternating power source, positive ions and negative electrons are alternately applied to the surface of the object to be joined, so that they are neutralized and less damaged such as charge-up than other energy waves. Therefore, it is suitable for semiconductors and devices.

  The plasma may be a method and apparatus using an alternating power source. By using an alternating power source, positive ions and negative electrons are alternately applied to the surface of the object to be joined, so that they are neutralized and less damaged such as charge-up than other energy waves. Therefore, it is suitable for semiconductors and devices.

  Moreover, this invention consists of the joining method in any one of Claim 1 thru | or 7 which heats both said to-be-joined objects at 200 degrees C or less at the time of joining or after joining (Claim 8).

  Moreover, this invention consists of the joining apparatus in any one of Claim 12 thru | or 18 which heats both said to-be-joined objects at 200 degrees C or less at the time of joining or after joining (Claim 19).

  Also in the heating means, the means for heating to 400 ° C. or more is difficult because a special heater needs to be selected. As shown in FIG. 5, in the conventional method of anodic bonding of glass and Si after carrying in the atmosphere, there is only a bonding strength of 3 MPa at 200 ° C. even when bonded in vacuum, and the strength of 9 MPa is finally raised to a high temperature of 400 ° C. I was able to get it. This is because the organic matter adheres to the air during transportation and includes a joining surface including the organic material layer, so that the joining strength does not increase, and the joining strength is increased only after the organic matter is decomposed by raising the temperature to 400 ° C.

  However, what was subsequently anodic bonded in vacuum without being exposed to the atmosphere after dry cleaning by Ar etching in vacuum has a bonding strength of 6 MPa even at room temperature, 10 MPa at 200 ° C. and conventional heating at 400 ° C. A sufficient bonding strength equal to or higher than that was obtained. Incidentally, when the bonding strength in a high vacuum after Ar ion beam treatment is measured, it can be seen that the bonding strength does not increase more than the conventional method even if heated at room temperature at 5 MPa and 400 ° C. The bonding strength here may be nearly double the strength depending on the measurement method and is used as comparative data although it is relatively low strength data. Moreover, although mentioned later for details, also in the hydrophilization processing method in FIG. 6, the favorable joining result in 200 degrees C or less is obtained.

Further, in the present invention, when bonding OH groups atomically to the bonding surfaces, gas containing H ₂ O or H, OH groups is mixed, and then both the objects to be bonded are brought into contact with each other. Or a joining method according to any one of claims 8 to 9 (claim 9).

The present invention also includes water gas generating means, and when OH groups are atomically bonded to the bonding surfaces to be attached, a gas containing H ₂ O or H, OH groups is mixed, and then both the bonded surfaces are bonded. The bonding apparatus according to any one of claims 12 to 19 which contacts an object (claim 20).

A gas containing H ₂ O or H and OH groups is also called water gas. Normally, when treated with oxygen plasma and transported in the atmosphere, the atmosphere contains moisture, so OH groups are formed naturally, but in order to avoid the adhesion of impurities and organic substances, it is exposed to the atmosphere in a vacuum. In the case where the process proceeds to the temporary joining without any problem, there may be a case where water is insufficient and OH groups are not sufficiently formed. Therefore, it is effective to supply a gas containing H ₂ O or H, OH groups during the oxygen plasma treatment or before the joining after the treatment. Although the water gas can be supplied as it is, it is more effective because it is activated by mixing the water gas into oxygen or by performing plasma treatment using the water gas as a reaction gas continuously after the oxygen plasma treatment.

  The present invention is also a bonding method in which three or more objects to be bonded are stacked and bonded, and objects to be bonded having the same linear expansion coefficient and having different linear expansion coefficients are sandwiched from both sides. It consists of the joining method in any one of Claims (Claim 10).

  Further, the present invention is a joining apparatus that sandwiches joints having different linear expansion coefficients from both sides with joints having the same linear expansion coefficient, and stacks and joins three or more joints by voltage application means. 21. From the joining device according to claim 12, wherein a voltage is simultaneously applied from the sandwiched workpieces having different linear expansion coefficients toward an outer workpiece having the same linear expansion coefficient. (Claim 21).

  As shown in FIG. 8, in a high-frequency device and a MEMS device, there are a method of sealing one side (FIG. 8A) and a method of sealing both sides (FIG. 9B). As shown in FIG. 4, in the method of sealing one side, warpage occurs due to the difference in linear expansion coefficient between the two materials. On the other hand, as shown in FIG. 9 (b), if the object to be joined having the same linear expansion coefficient is sandwiched from both sides and heated after being sandwiched from both sides, the opposing forces from both sides cancel each other. No warpage will occur.

  However, in the conventional method, the only way to increase the bonding accuracy is to heat and bond one by one. This is clamped with a jig in order to temporarily fix without using an adhesive, but there is a problem that the position is shifted or there is no space for clamping. Therefore, if the method of temporary bonding at room temperature by surface activation is used, as shown in FIG. 9B, three or more members are sandwiched between materials having the same linear expansion coefficient on both sides, thereby obtaining positional accuracy and After joining, it can be joined with high accuracy without warping by heating and performing the main joining. Of course, it is possible to increase the production efficiency by arranging a plurality of main joining devices with respect to the temporary joining device.

  Further, in the present invention, the hydrophilic treatment by the plasma is performed by etching the both objects to be bonded with the plasma having a strong ion collision force in the first half of the hydrophilic treatment, and the colliding ion molecules are surface molecules of the both objects to be bonded. After physical treatment to replace or adhere to the surface, the ion collision force is weakened in the latter half of the hydrophilization treatment without exposure to the atmosphere, and the both radicals are activated by active radicals or active ions of the plasma having a weak ion collision force. The surface of the object to be bonded may be chemically treated.

  The present invention further includes a reduced pressure plasma processing means for switching an ion collision force against an object to be bonded. The reduced pressure plasma processing means performs the hydrophilic treatment by the plasma, and the both objects to be bonded are ion-impacted in the first half of the hydrophilic treatment. In the latter half of the hydrophilization treatment, the physical ions are etched by the strong plasma and replaced with or attached to the surface molecules of the objects to be bonded without being exposed to the atmosphere. Alternatively, the ion collision force may be weakened by a low-pressure plasma treatment means, and the surfaces of both the objects to be bonded may be chemically treated with active radicals or active ions of plasma having a weak ion collision force.

  In the latter half of the plasma treatment, the hydrophilic treatment is successfully performed by performing the plasma treatment by reducing the ion collision force in the latter half of the plasma treatment. In normal plasma treatment, impurities are removed by physical treatment, OH groups are added to the surface by chemical treatment, and nitrogen is substituted. However, the chemical treatment of the surface has a strong ion impact force. Therefore, it is difficult to remove and uniformly chemically treat the surface.

  Therefore, in the latter half of the plasma treatment, there are many ions and radicals that are not accelerated by weakening the ion collision force and performing the plasma treatment, so the chemical reaction is promoted and the chemical treatment is uniformly performed on the bonding surface, and the surface activation treatment is performed. Can do. Therefore, it is possible to increase the bonding strength at a low temperature and to facilitate temporary bonding. Further, the latter half of the plasma treatment is not necessarily half in time and has a meaning not related to time. Further, the first half and the second half of the plasma treatment may be spaced apart from each other, but it is preferable in terms of chemical treatment to be continuous.

In the present invention, the physical treatment may be performed with Ar or CF ₄ plasma.

  In the present invention, the chemical treatment may be performed with oxygen or nitrogen plasma.

In the present invention, the physical treatment may be performed with Ar or CF ₄ plasma.

  In the present invention, the chemical treatment may be performed with oxygen or nitrogen plasma.

Etching the surface with plasma, removing deposits, and exposing to the atmosphere with the new surface of the substrate exposed, followed by hydrophilic treatment with oxygen plasma allows hydrophilic treatment without an organic layer. Therefore, there is no peeling from the organic material layer after bonding due to hydrogen bonding force and strength after annealing, so that annealing at a low temperature is sufficient to release H ₂ O after hydrogen bonding without diffusion. Bonding strength can be obtained. As shown in FIG. 6, in the conventional method of joining by oxygen plasma treatment after air conveyance, the joining strength at room temperature is 3 MPa, and the joining strength is 200 ° C., 6 MPa, and 400 ° C., 9 MPa. This is because organic matter adheres to the air during transportation and includes a joining surface including an organic material layer, so that the joining strength does not increase and the strength is increased only by diffusion. The physical treatment refers to a phenomenon in which the surface layer is etched, a phenomenon in which ion molecules collide with the surface layer, and a phenomenon in which the surface molecules are replaced or a phenomenon in which they adhere to the surface. For example, Ar ion is an action of etching an adhesion layer by Ar plasma, and indicates that oxygen ion replaces or adheres to a surface layer in oxygen plasma. Chemical treatment refers to a phenomenon in which a surface layer is treated by a chemical reaction with active radicals or active ions with weak ion collision force.

However, after being dry-cleaned by Ar etching in vacuum and subsequently subjected to a hydrophilic treatment with oxygen plasma without exposure to the atmosphere, the bonding strength is 5 MPa even at room temperature, and a sufficient bonding strength of 8 MPa is obtained at 200 ° C. I was able to. Incidentally, when the bonding strength in a high vacuum after the Ar ion beam treatment was measured, it was found that the bonding strength did not increase more than the conventional method as it was even when heated at room temperature at 5 MPa and 400 ° C. The use of Ar, which is inactive as the plasma used in the physical treatment, is not affected by any material, and the atomic weight is large, so that the etching power is high and suitable. In addition, when the object to be bonded is Si, SiO ₂ , glass, or ceramic, it is preferable to use CF ₄ as a plasma reaction gas because a more efficient material can be etched. As the plasma used in the chemical treatment, use of oxygen is preferable because OH groups are easily attached. Even when nitrogen is used, OH groups can be similarly attached.

  Note that a bonding method and a bonding apparatus that include plasma processing means for switching the ion collision force, weaken the ion collision force in the latter half of the plasma processing, and promote chemical treatment may be used.

  The process of hydrophilization treatment by plasma treatment is performed by reducing the ion collision force in the latter half of the plasma treatment, thereby removing impurities by physical treatment and attaching OH groups to the surface by chemical treatment. Although they are arranged or replaced with nitrogen or the like, even if the surface is chemically treated, it is removed because of the strong ion collision force, and it is difficult to chemically treat the surface uniformly.

  Therefore, in the latter half of the plasma treatment, there are many ions and radicals that are not accelerated by weakening the ion collision force and performing the plasma treatment, so the chemical reaction is promoted and the chemical treatment is uniformly performed on the bonding surface, and the surface activation treatment is performed. Can do. Therefore, the bonding strength can be increased at a low temperature. The low temperature is preferable because the conventional method requires 400 ° C. or higher and can be bonded within 400 ° C., which is lower than that.

  In addition, the joining method and joining apparatus whose said joining temperature is 200 degrees C or less may be sufficient. As shown in FIG. 6, bonding at 200 ° C. is possible. Further, the latter half of the plasma treatment is not necessarily half in time and has a meaning not related to time. Further, the first half and the second half of the plasma treatment may be spaced apart from each other, but it is preferable in terms of chemical treatment to be continuous. In particular, the physical treatment is etching for removing impurities as a pretreatment for attaching OH groups. Here, in the step of attaching OH groups, by changing ion collision force, oxygen is attached by physical treatment. The purpose of this is to enhance the OH group adhesion by chemical treatment, and to efficiently attach the OH group.

  Further, the plasma processing means for switching the ion collision force is a low-pressure plasma, and the plasma electrode is arranged so that it can be switched between two parts, that is, the object holding electrode and the counter electrode, and the power source is connected to the object holding electrode side. A bonding method and a bonding apparatus may be used in which plasma processing is performed by applying plasma, and then power is applied to the counter electrode side to weaken ion collision force and plasma processing is performed to promote chemical processing.

  On the plasma electrode side, an electric field is created and ions collide by acceleration, so the ion collision force increases. On the surface facing the electrode, ions do not accelerate and collision is low, but there are many ions and radicals that are not accelerated. Therefore, the chemical reaction is accelerated. The plasma electrode is arranged so that it can be switched between two parts, a workpiece holding electrode and a counter surface electrode, plasma processing is performed by applying power to the workpiece holding electrode side, and then the power source is switched to the counter surface electrode side to perform ion treatment. By performing plasma treatment with weak collision force, impurities are removed and there are many ions and radicals that are not accelerated by weakening ion collision force, so the chemical reaction is promoted and the surface of the junction is uniformly activated. be able to. Therefore, the bonding strength can be increased at a low temperature.

  FIG. 6 shows the difference between the temperature and the bonding strength when the plasma power source is applied only to the conventional object-holding electrode and when the object-holding electrode and the counter electrode are switched. The conventional method required 400 ° C. to obtain sufficient strength, but in this method, sufficient bonding strength could be obtained from room temperature within 400 ° C. to within 200 ° C. In addition, the counter electrode may be arranged opposite to the parallel plate type, but the same effect can be obtained if it is arranged around other than the electrode. In order to avoid re-deposition of the electrode material due to sputter etching, the side surface is preferable to the facing surface. The term “opposite surface electrode” as used herein includes the placement of electrodes in the surrounding area.

  Further, the plasma processing means for switching the ion collision force is a low-pressure plasma, and comprises an RF plasma power source capable of adjusting Vdc, and the Vdc value is changed in the latter half of the plasma processing to weaken the ion collision force and promote chemical treatment. It may be a bonding method and a bonding apparatus for performing plasma treatment.

  On the plasma electrode side, an electric field is created, but the speed at which ions collide depends on the Vdc value. For example, + oxygen ions are accelerated as the Vdc value is-and the ion collision force increases. As they approach 0, the velocity decreases, the ion collision force decreases, and there are many ions and radicals that are not accelerated. Is promoted. The plasma treatment is performed with the Vdc value increased to the-side, and then the adsorption process is performed by bringing the Vdc value close to 0, and in the latter half of the plasma treatment, the plasma treatment with weakened ion collision force is performed to remove impurities. In addition, since there are many ions and radicals that are not accelerated by weakening the ion collision force, the chemical reaction is promoted and the surface of the bonding surface can be uniformly activated. Therefore, the bonding strength can be increased at a low temperature. The result similar to FIG. 6 was obtained for the joining result.

  In addition, the plasma processing means for switching the ion collision force is a low-pressure plasma and comprises a pulse wave plasma power source whose pulse width can be adjusted. The pulse width is changed in the latter half of the plasma processing to weaken the ion collision force and perform chemical treatment. A bonding method and a bonding apparatus that perform plasma treatment to be promoted may be used.

  On the plasma electrode side, an electric field is created, but by adjusting the pulse width, the interval between the + ion collision-electric field time and the collision weakens-the electric field weak time can be adjusted. -Increasing the time of the electric field increases + ion collision,-Reducing the electric field time decreases + ion collision.

  For example, + oxygen ions are accelerated and the ion collision force is increased as the electric field time is increased, and the velocity is decreased and the ion collision force is decreased as the electric field time is shortened, and many ions and radicals are not accelerated. The chemical reaction is accelerated because it is present. Adjust the pulse width to increase the electric field time to perform plasma treatment, and then reduce the electric field time to perform plasma processing. Since there are many ions and radicals that are not accelerated by removing impurities and weakening the ion collision force in the reduced pressure plasma treatment, the chemical reaction is promoted and the surface of the joint can be uniformly activated. . Therefore, the bonding strength can be increased at a low temperature. The result similar to FIG. 6 was obtained for the joining result.

  Note that a bonding method and a bonding apparatus for bonding a plurality of objects to be bonded to each other in the atmosphere after bonding may be used. In this case, the chemical reaction is promoted by weakening the ion collision force in the latter half of the plasma treatment, and the surface activation treatment can be performed uniformly on the bonding surface. Since the bonding surface has already been subjected to chemical treatment such as OH group or nitrogen substitution, bonding can be performed in the air.

  Furthermore, a bonding method and a surface activation device may be used in which a plurality of objects to be bonded are bonded to each other in a reduced pressure after the processing step. Even if it is once returned to atmospheric pressure and an adsorption layer is attached, it is preferable because the pressure can be reduced in a vacuum chamber and the objects to be bonded are brought into close contact with each other so that air can be bonded by a voiceless without involving the bonding interface. .

  Further, the plasma processing means for switching the ion collision force is a means for switching between the two low-pressure plasma irradiation means, a first plasma irradiation means for performing plasma processing by applying power to the object holding electrode side, and plasma processing In a joining method and a joining apparatus for switching plasma generated in a separate chamber to a second plasma irradiation means for trapping ions and irradiating radicals in the latter half to weaken ion collision force and promote chemical treatment There may be.

  As shown in FIG. 12, in a state where the wafer 503 to be bonded is held on the bonded object holding electrode serving as a plasma power source, first, an RF plasma power source 501 is applied to perform physical processing by ion collision on the bonded object. . Subsequently, more radicals 504 generated by the upper surface wave plasma are irradiated to the down flow through the ion trap plate 502. Since ions 505 are captured by the ion trap plate 502, more radicals 504 can be irradiated, and chemical treatment is further promoted. In FIG. 12, 500 is a surface wave plasma generating means, 506 is a vacuum chamber, 507 is a reactive gas supply port, 508 is an exhaust port, 509 is an object holding electrode, 510 is a microwave power source, and 511 is a surface wave plasma. A generation region 512 is an RF plasma generation region.

  The plasma processing means for switching the ion collision force is a means for switching between the reduced pressure plasma and the atmospheric pressure plasma. After the surface of the object to be bonded is treated with the reduced pressure plasma by increasing the ion collision force, the ion collision is performed with the atmospheric pressure plasma. A bonding method and a bonding apparatus that perform plasma treatment that weakens force and promotes chemical treatment may be used.

  By dividing the plasma treatment into low-pressure plasma and atmospheric pressure plasma, impurities are removed by physical treatment in the low-pressure plasma treatment, OH groups are added to the surface by chemical treatment, and substitution with nitrogen is performed. What has been chemically treated on the surface is removed because of its strong ion collision force, and it is difficult to uniformly chemically treat the surface.

  Therefore, by performing the atmospheric pressure plasma treatment after the reduced pressure plasma treatment, in the atmospheric pressure plasma, since ions cannot be accelerated by an electric field as in vacuum, the ion collision force is weak, and there are many ions and radicals that are not accelerated, so there is a chemical reaction. Is promoted, and the bonding surface can be uniformly subjected to chemical treatment and surface activation treatment can be performed. Therefore, the bonding strength can be increased at a low temperature. The low temperature is preferable because the conventional method requires 400 ° C. or higher and can be bonded within 400 ° C., which is lower than that. In addition, the joining method and surface activation apparatus whose said joining temperature is 200 degrees C or less may be sufficient. As shown in FIG. 6, bonding at 200 ° C. is possible, which is more preferable.

  Note that a bonding method and a bonding apparatus in which the reaction gas is a mixed gas containing oxygen and nitrogen may be used.

  By using a gas containing nitrogen, not only an OH group but also a group containing O and N is generated in a chemical treatment in which the ion collision force is weakened. As a result, Si, O, and N compounds are generated at the interface at the time of bonding, and strong bonding is possible even at room temperature. FIG. 6 shows a comparison between the case of only oxygen reaction gas and the case of reaction gas containing oxygen and nitrogen. In the case of only oxygen, strong bonding is not possible unless it is heated to about 200 ° C. However, when oxygen and nitrogen are mixed, strong bonding is possible even from room temperature to 100 ° C.

  In addition, the joining method and joining apparatus which use different gas or different compound gas for plasma reaction gas in the latter half of plasma processing may be used. By using a different gas or a different gas mixture in the latter half of the plasma treatment, a gas superior in chemical treatment can be preferably used. For example, efficient plasma treatment can be achieved by using Ar gas in the first half of the plasma treatment and oxygen gas in the second half. Further, oxygen gas can be used in the first half and nitrogen gas can be used in the second half. Even if different gases are not used, a mixed gas of Ar and oxygen may be used, and Ar may be mixed in the first half and oxygen in the second half. In addition, when a mixed gas of oxygen and nitrogen is used, it is sufficient to add more oxygen in the first half and more nitrogen in the second half.

  Alternatively, the plasma reaction gas may be a bonding method and a bonding apparatus that use a reaction gas containing oxygen and switch to a reaction gas containing nitrogen during plasma processing with weakened ion collision force.

  In the chemical treatment in which the ion collision force is weakened, by using a gas containing nitrogen, not only OH groups but also groups containing O and N are generated. In addition, since OH groups are somewhat attached even in the first half of the plasma treatment, substitution of OH groups and N is performed during chemical treatment with weakened ion collision force. Chemical treatment means treatment including substitution. As a result, Si, O, and N compounds are generated at the interface at the time of bonding, and strong bonding is possible even at room temperature. In this method, the same good results as in FIG. 6 were obtained.

  In addition, the joining method and surface activation apparatus which join the heating temperature at the time of joining to 100 degrees C or less by a solid layer may be sufficient. Furthermore, the joining method and joining apparatus which join by the heating temperature at the time of joining at normal temperature, and a solid layer may be sufficient.

  If only OH groups are efficiently arranged except for water molecules, bonding can be performed at 100 ° C. or lower. Further, it is preferable to perform a chemical treatment in the latter half of the plasma treatment with a reactive gas containing nitrogen because bonding is possible even at room temperature. In addition, the method and the bonding apparatus described above are bonded after the adsorption step of exposure to a gas containing water molecules or hydrogen under atmospheric pressure after the treatment step and before the bonding step. After the treatment process, exposure to water molecules or gas containing hydrogen under atmospheric pressure makes it easier for the bonding surface to adsorb water molecules and hydrogen than in a low-pressure plasma with less water molecules and hydrogen. OH groups are arranged side by side, making hydrogen bonding easier.

  Further, the present invention is a device produced by the bonding method according to any one of claims 1 to 10, wherein the object to be bonded is a wafer or a chip cut out from the wafer, and OH groups are bonded atomically. Then, the device is made of a device such as a semiconductor device or a MEMS device created by the anodic bonding.

This method is particularly suitable because Si is used as a base material in semiconductors. Further, glass, ceramic, and SiO ₂ that are insulators are frequently used and effective in sealing and bonding between a semiconductor and a package. Specifically, handling and bonding on a wafer, which is a semiconductor manufacturing process, is most effective, but it is also suitable in a chip state after dicing.

  Bonding at a low temperature is possible, and ions are released when heated at a high temperature after ion implantation. Therefore, it is suitable for a semiconductor device that is vulnerable to heat. In a MEMS device in which dissimilar materials are stacked, distortion occurs due to high-temperature heating during conventional bonding, and if one of them is an actuator, a malfunction occurs. However, in this method, since bonding can be performed at a low temperature, distortion due to heat is suppressed, which is preferable. In addition, since pressure sensors and the like are conventionally bonded to glass and Si, distortion due to high-temperature heating during bonding has affected the reliability of the device. In this method, since bonding can be performed at a low temperature, a highly reliable MEMS device without distortion is preferable.

  Further, the present invention is a bonding method for anodic bonding both bonded objects after surface activation treatment is performed on the bonded surfaces of the bonded objects by an energy wave that is an atomic beam, an ion beam, or plasma, The amount of etching by the surface activation treatment is a bonding method in which the amount is 1 nm or more.

  The present invention also includes means for applying a voltage and means for heating. After the surface activation treatment is performed on the bonding surfaces of the objects to be bonded by an energy wave that is an atomic beam, an ion beam, or plasma, both the objects are bonded. The bonding apparatus includes an anodic bonding means for performing anodic bonding, and includes a bonding apparatus in which the amount of etching by the surface activation treatment by the energy wave is 1 nm or more.

  It is effective to etch at least 1 nm since the deposits present on the surface of the object to be bonded are deposited to 1 nm or more in several seconds when exposed to the atmosphere even after wet cleaning.

  The effect of the present invention is that the bonding strength can be increased at a lower temperature by anodic bonding after OH groups are atomically bonded and adhered to the bonding surface using plasma and then subjected to hydrophilic treatment. . Further, OH groups are atomically bonded to the bonding surfaces of the objects to be bonded by atomic bonding to temporarily bond the both objects to be bonded, and then anodic bonding the objects to be bonded and perform the main bonding. Thus, the production efficiency can be increased, and the objects to be joined can be joined to each other with a three-layer structure without generating warpage.

  Moreover, all the processing can be performed in one chamber by arranging both objects to be bonded in the same vacuum chamber.

  In this embodiment, there is provided a method and a bonding apparatus in which a wafer to be bonded is surface-activated by plasma and temporarily bonded, and anodic bonding is performed in main bonding in which processes are divided. Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 7 shows a configuration for increasing production efficiency by separating the temporary bonding by surface activation and the main bonding by anodic bonding as an embodiment of the present invention.

  As shown in FIG. 7, the surface of the bonding is activated by a plasma processing apparatus A as an energy wave processing apparatus, a room temperature temporary bonding in a vacuum is performed by a temporary bonding apparatus B, and a heating main bonding in the atmosphere is a main bonding. The production efficiency is improved by balancing a plurality of apparatuses C (three in FIG. 7).

  Further, the plasma processing apparatus A and the temporary bonding apparatus B can be configured by the same apparatus. FIG. 1 shows a wafer bonding apparatus that performs glass bonding and Si wafer temporary bonding or anodic bonding for main bonding according to an embodiment of the present invention in which the plasma processing apparatus A and the temporary bonding apparatus B are the same apparatus. In this embodiment, the glass wafer as the object to be bonded is held on the upper side and the Si wafer is held on the lower side facing up and down, the chamber is closed, and after etching with Ar plasma in a vacuum, the objects to be bonded are brought into contact with each other. Join. In the case of performing up to the main bonding, the apparatus is an apparatus for applying a voltage to perform anodic bonding and, in some cases, softening the glass by heating to increase the bonding area and increase the strength.

  As shown in FIG. 1, the apparatus configuration includes an upper wafer 7 made of glass, a head unit that performs elevation control and pressure control by the Z axis 1, and a lower wafer 8 made of Si. It is divided into a stage part for aligning the wafer. A pressure detection means is incorporated in the Z-axis 1 and feedback control is performed by feeding back to the torque control of the Z-axis servomotor. Separately, the chamber wall 3 that can be moved up and down by an actuator is lowered, vacuumed in a state of being grounded to the chamber base 10 through the fixed packing 5, and plasma treatment is performed by introducing a reactive gas, and the head portion is lowered to both wafers. Is contact-pressurized, switched to an anode power source, and a voltage is applied to perform anodic bonding. The chamber wall 3 is sealed with an O-ring so as to be movable up and down, but it may be received at the thinned shaft or on the outer periphery of the piston. In some cases, the upper electrode 6 and the lower electrode 9 are also provided with a heater and can be heated at the time of bonding.

  FIG. 2 shows an embodiment in which one unit continuously performs plasma processing to main bonding by anodic bonding. The operation will be described in order. The upper wafer 7 made of glass is held by the upper electrode 6 with the chamber wall 3 raised as shown in FIG. Subsequently, the lower wafer 8 made of Si is held on the lower electrode 9. The holding method includes a mechanical chucking method, but an electrostatic chuck method is desirable. Subsequently, as shown in FIG. 2B, the chamber wall 3 is lowered, and the chamber base 10 is grounded via the fixed packing 5. Since the chamber wall 3 is shielded from the atmosphere by the sliding packing 4, the vacuum in the chamber can be increased by opening the discharge valve 14 with the suction valve 13 closed and evacuating the vacuum pump 15. it can.

Next, as shown in FIG. 2 (c), the chamber is filled with a reaction gas composed of Ar. The vacuum pump 15 can be filled with the reaction gas while maintaining a certain degree of vacuum by controlling the discharge amount of the discharge valve 14 and the gas suction amount of the suction valve 13 while operating. As shown in FIGS. 4D and 4E, in this method, first, Ar gas is filled, and plasma is generated by applying an alternating power supply plasma voltage to the lower electrode 9 at a vacuum degree of about 10 ⁻² Torr. Then, the surface of the lower wafer 8 is etched and cleaned by Ar plasma. Subsequently, the same alternating power supply is applied to the upper electrode 6 to etch and clean the upper wafer with Ar plasma. Next, as shown in FIG. 2B, the chamber is evacuated and Ar is discharged. In some cases, vacuuming is performed while heating both electrodes to about 100 ° C., whereby Ar adhering to the surface or being driven into the member is discharged.

  Subsequently, as shown in FIG. 2 (f), the piston-type head 2 is lowered by the Z-axis 1 while the chamber wall 3 and the Z-axis 1 are in contact with the sliding packing 4 in a vacuum, and both wafers are evacuated in the vacuum. An anode power supply voltage is applied between the upper electrode 6 holding the upper wafer 7 made of glass and the lower electrode 9 as a cathode, and a covalent bond such as Si—O is caused at the bonding interface to perform anodic bonding. Let The inside of the chamber is shielded from the external atmosphere by the sliding packing 4 between the chamber wall 3 and the Z-axis 1, and the piston-type head portion can be lowered while being kept in a vacuum. In some cases, the strength is increased by simultaneously heating from 200 ° C. to 400 ° C. with heaters charged in both electrodes.

  Thereafter, as shown in FIG. 2 (h), air is supplied into the chamber and the pressure is returned to atmospheric pressure, the head portion is raised, and both bonded wafers are taken out. In the case of a method of switching between Ar and the atmosphere or two kinds of gases such as nitrogen and oxygen in one chamber, the gas switching valve 16 can select and supply Ar and the atmosphere gas. First, after selecting and filling Ar, the suction valve 13 is closed, the inside of the chamber is evacuated, and Ar is discharged. Then, the gas switching valve 16 switches to atmospheric gas, the suction valve 13 is opened, and the inside of the chamber is opened to the atmosphere. Can be filled and released to the atmosphere when opening the chamber.

  In some cases, bonding may be performed after aligning the positions of both wafers 7 and 8. FIG. 3 shows a method of alignment before evacuation. An upper mark 23 for alignment is attached to the upper wafer 7 at two places, and a lower mark 24 for alignment is attached to the lower wafer 8 at two similar positions. A two-view recognition means 25 is inserted between the wafers 7 and 8, and the upper and lower mark positions are read by the recognition means 25. The two-field recognition means 25 branches the upper and lower mark images by a prism 26 and separates them into an upper mark recognition means 27 and a lower mark recognition means 28 and reads them. The recognizing means 25 is moved by a table having an X axis, a Y axis, and possibly a Z axis, and can read a mark at an arbitrary position. Thereafter, the position of the lower wafer 8 is corrected and moved to the position of the upper wafer 7 by the alignment table 20. After the movement, it is possible to increase the accuracy by inserting the recognizing means 25 with two fields of view and correcting it repeatedly.

  FIG. 4 shows a method that allows alignment even after joining after evacuation. When it is necessary to align both objects to be bonded with high accuracy, it is necessary to perform alignment after the plasma processing step. This is because the object to be bonded and the object to be bonded holding means are displaced due to thermal expansion due to the heat generated by the plasma processing. After the plasma processing, the positions of both objects to be bonded are recognized and aligned by the recognition means. High-precision bonding within a few μm is possible without displacement.

  It is preferable in terms of accuracy that the means for translating and / or rotating the object to be joined for alignment is provided in the vacuum chamber, and an optical system and an image sensor serving as recognition means for recognizing the positions of both objects to be joined are provided in the chamber. A glass window is preferably provided outside the chamber. Many optical systems and image sensors cannot be used in a vacuum, and it is preferable to install them in the external atmosphere in order to maintain accuracy. Further, it is difficult to move the moving means for alignment by a small amount of operation from the outside, and it is preferable to provide the moving means in the chamber in order to obtain high accuracy. In addition, the plasma processing step, the alignment step, and / or the temporary bonding step can be performed in separate chambers and connected as a cluster structure by a conveying means in a vacuum, but the apparatus becomes complicated and expensive.

  This can be performed continuously in one chamber by using the apparatus configuration as shown in FIG. 1 and the alignment method as shown in FIG. 4, thereby simplifying the apparatus and reducing the cost. Moreover, the deposits can be minimized by carrying out continuously. The upper wafer 7 is provided with two upper marks 23 for alignment, and the lower wafer 8 is provided with two lower marks 24 for alignment. The top and bottom marks are shaped so that they can be recognized in the same field of view even if they overlap. Both wafers after the plasma treatment are brought close to each other, passed through the mark reading transmission part 19 and the glass window 21, and passed through the lower wafer by the IR (infrared) recognition means 22, and the upper and lower alignment marks attached with metal are simultaneously formed. Recognize and read position. If the depth of focus does not match, the IR recognition means 22 may be moved up and down for reading.

The IR recognizing means 22 may be moved by a table having an X axis, a Y axis, and, in some cases, a Z axis so that a mark at an arbitrary position can be read. Thereafter, the position of the lower wafer 8 is corrected and moved to the position of the upper wafer 7 by the alignment table 20. After the movement, it is possible to repeat the correction by the IR recognition unit 22 again to increase the accuracy. The IR recognition method can also be used for bonding Si. In addition, when glass is held down and Si is held up, alignment is possible even with visible light. After the oxygen plasma treatment, water gas is easily used as a bonding method after substituting with a gas containing H ₂ O or H or OH groups, but an H ₂ O molecular beam, hydrogen gas, or the like can also be used.

Etching with Ar plasma is preferable in terms of efficiency, but surface activation treatment with other gases such as nitrogen and oxygen is also possible and is included in the present invention. In particular, in the case of temporary bonding by hydrophilization treatment, oxygen or nitrogen plasma is used, OH groups are arranged on the bonding surface to activate the surface, and both wafers are brought into contact and hydrogen bonded. If heating is used in combination, the strength will increase to eutectic bonding. In addition, this apparatus is used as a temporary bonding apparatus, and after the temporary bonding by surface activation, the main bonding is performed by anodic bonding in which the process or apparatus is separated, thereby improving production efficiency and having a three-layer structure in which warpage does not occur. Bonding can also be possible. If it adds and describes to the said flow, after Ar plasma processing, the operation | movement shown to FIG.2 (c), (d), (e) will carry out oxygen plasma processing of the surface by supplying oxygen gas instead of Ar. . As a method of switching between two gases, Ar and oxygen, in one chamber, the gas switching valve 16 can select and supply Ar and oxygen gas (O ₂ ). First, after selecting and filling Ar, the suction valve 13 is closed and the inside of the chamber is evacuated to discharge Ar, then the gas switching valve 16 is switched to oxygen gas, the suction valve 13 is opened, and the chamber is filled with oxygen gas. Fill with. Further, since the gas switching valve 16 can inhale the atmosphere, it can be released to the atmosphere when the chamber is opened. Next, water gas is supplied, and in some cases, plasma treatment is performed as a reaction gas, and the surface is hydrophilized.

  Subsequently, as shown in FIG. 2 (f), the piston-type head 2 is lowered by the Z-axis 1 while the chamber wall 3 and the Z-axis 1 are in contact with the sliding packing 4 in a vacuum, and both wafers are evacuated in the vacuum. They are brought into contact and temporarily joined by hydrogen bonding force. When used as an apparatus for pre-bonding and main-bonding batch bonding, as shown in FIG. 2 (g), heating is performed while applying a voltage between the electrodes 6 and 9, and anodic bonding is performed. The inside of the chamber is shielded from the external atmosphere by the sliding packing 4 between the chamber wall 3 and the Z-axis 1, and the piston-type head portion can be lowered while being kept in a vacuum. In some cases, the strength is increased by simultaneously heating with heaters charged in both electrodes. Thereafter, as shown in FIG. 2 (h), air is supplied into the chamber to return to the atmospheric pressure, the head portion is raised, and both bonded wafers 7 and 8 are taken out.

  In the configuration in which the mark is read by the IR recognizing means 22, the path of the IR light source in the space between the mark reading transmission part 19, the glass window 21, and the alignment table is not limited to space and glass, but is made of a material that transmits IR light. It only has to be configured. Further, not only the reflected light but also a light source on the opposite side of the IR recognition means 22 may be used as the transmitted light.

  Although it is preferable from the viewpoint of efficiency to clean the wafer on the alternating electrode surface as a plasma processing method, there are cases where the wafer is cleaned by setting the electrode in a place other than the wafer in order to reduce uniformity and damage.

  Next, FIG. 11 shows a temporary bonding apparatus in which the plasma processing is performed at a slid position without performing the wafer processing at the position where the wafer is opposed. This temporary bonding apparatus is configured as shown in FIG. 11, and a head 207 for holding an upper wafer 210 and a stage 208 for holding a lower wafer 209 are arranged in a vacuum chamber 211. The head 207 is a torque-controlled lift drive motor. A Z-axis lifting mechanism 202 to which 201 is connected, a θ-axis mechanism 203 that rotates the Z-axis lifting mechanism 202, and an XY alignment table 206 that moves the head 207 in the XY horizontal direction are provided. By feeding back the applied pressure detected by the pressure detection means 204 to the torque control type lifting drive motor 201, position control and pressure control can be performed while switching. The XY alignment table 206 uses means that can be used even in a vacuum. However, since the Z and θ axis mechanisms are installed outside the vacuum chamber, the head portion and the outside are cut off by the bellows 205 so as to be movable.

  The stage 208 can be slid by the slide moving means 229 between the joining position and the standby position. A high-precision guide and a linear scale for recognizing the position are attached to the slide moving means 229, and the stop position between the joining position and the standby position can be maintained with high precision. This moving means 229 may have any configuration.

  As an object holding means for the head 207 and the stage 208, a mechanical chucking method may be used, but an electrostatic chuck is preferably provided. In addition, a heater for heating is provided and serves as a plasma electrode, and has three functions of holding means, heating means, and plasma generating means.

As the pressure reducing means, a vacuum pump 217 is connected to the exhaust pipe 215, and opening / closing and flow rate adjustment are performed by the exhaust valve 216, so that the degree of vacuum can be adjusted. On the intake side, an intake gas switching valve 220 is connected to the intake pipe 218, and opening / closing and flow rate adjustment are performed by the intake valve 219. As the suction gas, two kinds of plasma reaction gases can be connected, and for example, Ar 221 and oxygen (O ₂ ) 222 can be connected. Moreover, the gas which changed the mixture of the mixed gas can also be connected. The other is connected to the atmosphere 223 for releasing the atmospheric pressure or nitrogen containing water molecules. The degree of vacuum and the reaction gas concentration including the atmospheric pressure can be adjusted to optimum values by adjusting the flow rate including opening and closing of the intake valve 219 and the exhaust valve 216.

  Alignment mark recognizing means comprising an alignment optical system is arranged above the stage standby position and below the head, outside the vacuum chamber 211, as stage side recognizing means 213 and head side recognizing means 212, respectively. These recognition means only need to be at least one stage and one on the head side. If a small object such as a chip is to be recognized, the alignment marks 227 and 228 can read a θ-direction component and two marks in one field of view. By arranging it inside, even one recognition means can read sufficiently. The recognition means is a camera with an optical lens made of, for example, visible light or IR (infrared) light.

  The vacuum chamber 211 is provided with a glass window 214 made of a material that can be transmitted through the optical system of the recognition means, for example, glass. The glass window 214 is transmitted through the vacuum chamber 211 to recognize the alignment marks 227 and 228 of the object to be bonded in the vacuum chamber 211. In the case of fine alignment with high accuracy at the nano level, after rough positioning, visible light, IR (red (red)) is applied to the head side recognition means 212 with the upper wafer 210 and the lower wafer 209 close to about several μm. Outside) By using a dual-purpose recognition means and providing a transmission hole or transmission material at the position of the alignment mark on the stage, the alignment mark on both wafers is recognized simultaneously through the stage from the bottom and again X, Y, θ Can be aligned in the direction.

  By such a temporary bonding apparatus, plasma processing is performed at a position where the upper wafer 210 and the lower wafer 209 are slid to prevent the etched substance from re-adhering to the counter wafer, or the surface facing the wafer can be removed. By using an electrode, it is possible to weaken the etching force and enhance the chemical treatment to facilitate the attachment of OH groups. After the plasma processing, the lower stage slides to a position facing the upper wafer, and a bonding process similar to the above is performed.

  When the energy wave treatment is an ion beam other than plasma or an atomic beam, two beam irradiation devices are attached to the apparatus shown in FIG. 11, and the wafer surface may be individually irradiated obliquely at the slid position. .

  Of course, the above-described temporary bonding apparatus can also be used as a temporary bonding apparatus in which energy wave processing such as plasma is performed by a dedicated apparatus and energy wave processing is excluded.

  Next, the present bonding apparatus will be described. Since the present bonding apparatus is already in the state of being vacuum-sealed or gas-filled in the temporary bonding apparatus, it may be a simple apparatus in which a voltage is applied and heated in the atmosphere. As an anodic bonding apparatus, it is possible to soften the glass by applying voltage and heating to fill the gaps due to the biting of dust, material irregularities and undulations, increasing the bonding area and increasing the strength. By arranging a plurality of such simple joining devices as shown in FIG. 7C, the production efficiency can be increased and the cost can be reduced.

  As shown in FIG. 9 (b), three or more members are sandwiched with materials having the same linear expansion coefficient on both sides to obtain positional accuracy, and are temporarily joined at room temperature, and then heated and fully joined to provide high accuracy without warping. Can be joined.

  In addition, the hydrophilic treatment can be successfully performed by performing the plasma treatment by reducing the etching power in the latter half of the plasma treatment. In normal plasma treatment, impurities are removed by physical treatment, OH groups are added to the surface by chemical treatment, and nitrogen is replaced. However, the etching power is high despite chemical treatment on the surface. It is removed because it is strong, and it is difficult to chemically treat the surface uniformly.

  Therefore, in the latter half of the plasma treatment, there are many ions and radicals that are not accelerated by weakening the etching force and performing the plasma treatment, so the chemical reaction is promoted and the chemical treatment is uniformly performed on the bonding surface, and the surface activation treatment can be performed. it can. Therefore, it is possible to increase the bonding strength at a low temperature and to facilitate temporary bonding. The etching force can be switched by switching the plasma Vdc value, switching the pulse width, or using the wafer and the opposite surface as an electrode.

It is a schematic block diagram of the joining apparatus which concerns on one embodiment of this invention. It is a figure which shows the actual joining process in one embodiment. It is an alignment block diagram in the air | atmosphere using the recognition means of 2 visual fields. It is the alignment block diagram in the vacuum which used IR recognition means. It is a comparison graph after a conventional construction method and Ar plasma processing. It is a comparison graph of joining. It is the figure which comprised the temporary joining apparatus and this joining apparatus efficiently. It is a device figure with sealing. It is a figure which shows the curvature | sledge by heating. It is a figure which shows the joining chemical formula by a hydrophilic treatment. It is a stage slide type temporary joining apparatus figure. It is a schematic block diagram of the apparatus in a modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Z-axis 2 Piston type head 3 Chamber wall 4 Sliding packing 5 Fixed packing 6 Upper electrode 7 Upper wafer 8 Lower wafer 9 Lower electrode 10 Chamber base 11 Inlet 12 Outlet 13 Inlet valve 14 Outlet valve 15 Vacuum pump 16 Gas switching Valve 17 Gas A
18 Gas B
19 Mark reading transmission unit 20 Alignment table 21 Glass window 22 IR recognition means 23 Upper mark 24 Lower mark 25 Two field of view recognition means 26 Prism 27 Upper mark recognition means 28 Lower mark recognition means 100 Glass 101 Silicon 201 Torque controlled lift drive motor 202 Z axis elevating mechanism 203 θ axis rotating mechanism 204 Pressure detecting means 205 Bellows 206 XY alignment table 207 Head 208 Stage 209 Lower wafer 210 Upper wafer 211 Vacuum chamber 212 Head side recognizing means 213 Stage side recognizing means 214 Glass window 215 Exhaust pipe 216 Exhaust valve 217 Vacuum pump 218 Intake pipe 219 Intake valve 220 Intake gas switching valve 221 Ar
222 O ₂
223 Atmosphere 227 Upper alignment mark 228 Lower alignment mark 229 Slide moving means

Claims (21)

A bonding method in which plasma is used to bond OH groups to the bonding surfaces of bonded objects that are either Si, SiO ₂ , or glass, and then anodic bonding the bonded objects. After bonding both the objects to be bonded by temporarily bonding the OH groups to the bonding surfaces of the objects to be bonded which are either Si, SiO ₂ or glass by atomically bonding them using plasma. A joining method in which an object is anodically bonded for main bonding.   The bonding method according to claim 2, wherein after the temporary bonding at room temperature, the process or apparatus is separated and the main bonding by the anodic bonding is performed.   The bonding method according to claim 3, wherein a plurality of the main bonding processes are balanced against the number of the temporary bonding processes.   The bonding method according to claim 2, wherein the temporary bonding is performed in a reduced pressure or gas-reduced reduced pressure chamber, and the main bonding is performed in the atmosphere.   The bonding method according to any one of claims 1 to 4, wherein after bonding OH groups to the bonding surfaces atomically and adhering, the two objects to be bonded are subjected to anodic bonding without exposure to the atmosphere.   The plasma is a low-pressure plasma, and after the OH groups are bonded atomically to the bonding surface by using the low-pressure plasma, the two objects to be bonded are continuously contacted in a vacuum in the same chamber. The joining method according to any one of claims 1 to 4.   The joining method according to claim 1, wherein the objects to be joined are heated at 200 ° C. or less during or after joining. 9. The method according to claim 1, wherein, when OH groups are atomically bonded to the bonding surface and adhered, a gas containing H ₂ O or H or OH groups is mixed, and then both the objects to be bonded are brought into contact with each other. The joining method described in 1.   10. A joining method for joining three or more objects to be joined together, wherein the objects to be joined having the same linear expansion coefficient and having different linear expansion coefficients are sandwiched from both sides. Joining method.   It is a device created by the bonding method according to any one of claims 1 to 10, wherein the object to be bonded is a wafer or a chip cut out from a wafer, and after OH groups are atomically bonded and attached A device such as a semiconductor device or a MEMS device produced by anodic bonding. Plasma processing means for attaching and bonding OH groups atomically to the bonding surfaces of the objects to be bonded which are either Si, SiO ₂ or glass using plasma;
And an anodic bonding means for anodic bonding the objects to be bonded with OH groups attached to the bonding surfaces by the plasma processing means. Plasma processing means for attaching and bonding OH groups atomically to the bonding surfaces of the objects to be bonded which are either Si, SiO ₂ or glass using plasma;
A temporary bonding means for temporarily bonding the two bonded objects having OH groups attached to the bonding surface by the plasma processing means, and applying a voltage to the temporary bonded both bonded objects to heat An anodic bonding means having a main bonding means for bonding.   The joining apparatus according to claim 13, wherein the temporary joining means and the main joining means are provided in independent spaces. The anodic bonding means includes
The joining apparatus according to claim 14, wherein a plurality of the main joining means are provided for the number 1 of the temporary joining means. The temporary joining means includes a decompression chamber disposed therein,
The bonding apparatus according to any one of claims 13 to 15, wherein the temporary bonding is performed in the decompression chamber subjected to reduced pressure or gas replacement, and the main bonding is performed in the atmosphere.   The plasma processing means and the anodic bonding means are each provided in a decompression chamber, and after the OH groups are atomically bonded and attached to the bonding surface by the plasma processing means, the both of them are exposed without being exposed to the atmosphere. The bonding apparatus according to claim 13, wherein an object to be bonded is anodically bonded. A vacuum chamber in which the plasma processing means and the anodic bonding means are disposed;
The plasma generated by the plasma processing means is a low-pressure plasma, and after the OH groups are atomically bonded and attached to the bonding surface using the low-pressure plasma, the two bonded portions are continuously formed in the low-pressure chamber. The bonding apparatus according to claim 13, wherein an object is contacted in a vacuum.   The joining apparatus according to claim 12, wherein both the objects to be joined are heated at 200 ° C. or less during or after joining. Water gas generating means,
20. Either of the objects to be joined is brought into contact with H ₂ O or a gas containing H and OH groups when adhering OH groups to the bonding surfaces by atomic bonding. The joining apparatus as described in. It is a joining device that sandwiches joints having different linear expansion coefficients from both sides with joined objects having the same linear expansion coefficient, and joins three or more joined objects in an overlapping manner,
21. The voltage is applied simultaneously from the sandwiched workpieces having different linear expansion coefficients to the outer workpieces having the same linear expansion coefficient by means of voltage application means. Welding equipment.

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