JP2011200933A - Joining method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a joining method which can achieve the improvement of joining strength and the yield of joining.SOLUTION: The joining method includes: a surface activation step of respectively activating the sides of the surfaces 1a, 2a to form into the joining boundary faces between a first joining object 1 and a second joining object 2 to be joined with the first joining object 1; and a joining step of joining the first joining object 1 and the second joining object 2 after the surface activation step. The joining step includes: an ordinary temperature pressurizing stage of pressurizing the first joining object 1 and the second joining object 2 at ordinary temperature for a first prescribed time; and a heating-pressurizing joining stage of heating and pressurizing the first joining object 1 and the second joining object 2 after the ordinary temperature pressurizing stage, thus performing diffusion joining between the first joining object 1 and the second joining object 2.

Description

  The present invention relates to a joining method for joining objects to be joined.

  In recent years, in order to form a three-dimensional structure of a MEMS (Micro Electro Mechanical Systems) device or a thermal infrared sensor, bonding of bonding objects such as Si wafers or Si wafers and glass wafers has been performed. The objects to be joined are activated by removing the coating that hinders the joining on the surface of the object to be joined using the surface activation method, and the bonds of the atoms on the surface of the object to be joined are directly joined together. Can be joined.

  As a bonding method of this type, for example, in a reduced-pressure atmosphere, each of the surface side serving as a bonding interface between the first bonding target and the second bonding target to be bonded to the first bonding target is an inert gas. A surface activation step that is activated by the ion beam, and a bonding step that bonds the first bonding target and the second bonding target after the surface activation step, the bonding step comprising: There is known a joining method including a step of joining the first joining object and the second joining object without pressure at normal temperature (for example, Non-Patent Document 1). In the above-described joining method, it is also known to perform heat treatment for improving the joining strength between the first joining object and the second joining object after joining.

Thereby, Si wafers, Si wafers, and wafers such as sapphire (Al ₂ O ₃ ), lithium niobate (LiNbO ₃ ), lithium tantalate (LiTaO ₃ ), and gadolinium gallium garnet (Gd ₃ Ga ₅ O ₁₂ ). It is possible to be joined. However, with only the above-described joining method, even if heat treatment is performed, the joining strength between the joining objects may not be sufficient.

  Further, as another bonding method, for example, plasma is applied to each surface side that becomes a bonding interface between a first bonding target that is a glass wafer and a second bonding target that is a Si wafer to be bonded to the first bonding target. A surface activation step that is activated by atomically bonding OH groups by using the bonding, and a bonding that bonds the first bonding target and the second bonding target after the surface activation step. A step of pressurizing the first object to be joined and the second object to be joined at room temperature, and the first object to be joined after the room temperature pressurization step. There is also known a bonding method including a step of anodic bonding an object and the second object to be bonded (for example, Patent Document 1).

  In the bonding method using the above-described anodic bonding, it is also known that heating may be performed at the time of anodic bonding, and the bonding strength can be improved without generating warpage on the objects to be bonded at a lower temperature. It is said that.

However, in the above-described bonding method using anodic bonding, the bonding interface side of the object to be bonded is limited to a material of any one of Si, SiO ₂ and glass, and can be used for manufacturing various MEMS devices. Is not enough.

Hideki Takagi, “Special Feature“ Frontiers of MEMS / NEMS ”Wafer Room Temperature Bonding Technology”, Surface Science Vol.26, No.2, 2005, pp.82-87

JP 2006-248895 A

  By the way, the bonding method using the surface activation method is to apply some bonding force to atoms on the surface of the bonding object when the bonding interface is viewed microscopically. Although the mechanism of joining by the surface activation method seems simple at first glance, it is thought that it is closely related to the material of the joining object and the surface state of the joining object that changes due to the activation. Most of the relationship between the state and bonding strength is still unclear.

  In this type of bonding method, further improvement in bonding strength and bonding yield is required, but the above-described bonding method alone is not sufficient, and further improvement is required.

  The present invention has been made in view of the above reasons, and an object of the present invention is to provide a joining method capable of improving the joining strength and joining yield.

  The bonding method of the present invention includes a surface activation step for activating each surface side that becomes a bonding interface between a first bonding object and a second bonding object to be bonded to the first bonding object; A joining method comprising a joining step of joining the first joining object and the second joining object after the surface activation process, wherein the joining process is performed at a normal temperature for a first predetermined time. During the normal temperature pressurizing step of pressurizing the first bonding target and the second bonding target, and after the normal temperature pressing step, the first bonding target and the second bonding target It is characterized by having a heating / pressurizing bonding step of performing diffusion bonding between the first bonding object and the second bonding object by heating and pressurizing.

  In this bonding method, the first bonding object and the second bonding object include a bonding layer capable of diffusion bonding on at least one of the surfaces, and the bonding layer is made of Au on the outermost surface. It is preferable to have a surface layer.

  In this bonding method, the first bonding object and the second bonding object include a bonding layer capable of diffusion bonding accompanied by a eutectic reaction on at least one of the surfaces, and the heating / pressure bonding. It is preferable to perform eutectic bonding between the first bonding object and the second bonding object by setting the heating temperature in the process to be equal to or higher than the eutectic temperature in the bonding layer.

  In this bonding method, the heating / pressure bonding step includes heating the first bonding object and the second bonding object by heating to a temperature lower than the eutectic temperature for a third predetermined time. It is preferable to have a first heating / pressurizing process for pressurizing and a second heating / pressurizing process for performing the eutectic bonding after the first heating / pressurizing process.

  The bonding method of the present invention can provide a bonding method capable of improving the bonding strength and the bonding yield.

It is process explanatory drawing explaining the process of the joining method of Embodiment 1 using a joining apparatus. It is a schematic cross section of the joining target object joined by the joining method same as the above. It is a timing chart of the heating and pressurization in the joining process of the joining method same as the above. It is explanatory drawing of the dummy wafer which is a laminated body for confirming the joining state in the joining method same as the above. It is explanatory drawing which shows the joining state of the dummy wafer which is the laminated body joined by the joining method same as the above, and the dummy wafer which is the laminated body joined for the comparison. 6 is a schematic cross-sectional view of a bonding object to be bonded by the bonding method of Embodiment 2. FIG. It is a timing chart of the heating and pressurization in the joining process of the joining method same as the above. 10 is a timing chart of heating and pressurization in a joining step of the joining method of Embodiment 3.

(Embodiment 1)
Hereinafter, each process of the joining method of this embodiment is demonstrated using the joining apparatus 10 shown in FIG. 1, and the 1st joining object 1 and 2nd joining object joined with the joining apparatus 10 using FIG. A configuration example of the object 2 will be described. In FIG. 1 and FIG. 2, the same constituent elements are denoted by the same reference numerals.

  The bonding method according to the present embodiment activates the surfaces 1a and 2a, which are bonding interfaces between the first bonding object 1 and the second bonding object 2 to be bonded to the first bonding object 1, respectively. A surface activation step, and a bonding step of bonding the first bonding target 1 and the second bonding target 2 after the surface activation step.

  In particular, the bonding method according to the present embodiment includes a room temperature pressurizing step in which the bonding step pressurizes the first bonding target 1 and the second bonding target 2 at a normal temperature for a first predetermined time. In addition, the first joining object 1 and the second joining object 2 are heated and pressurized after the room temperature pressurization step, so that the first joining object 1 and the second joining object 2 are connected. A heating and pressure bonding process for performing diffusion bonding.

  The joining apparatus 10 shown in FIG. 1 that joins the first joining object 1 and the second joining object 2 by the joining method of the present embodiment includes a chamber 12 that can hermetically seal the inside. I have. The bonding apparatus 10 can evacuate the interior of the chamber 12 from the exhaust pipe 17 connected to the chamber 12 using the vacuum exhaust apparatus 18.

  More specifically, the chamber 12 of the bonding apparatus 10 communicates with the chamber 12 and contains a predetermined introduced gas (for example, inert gas such as Ar gas, oxygen gas, oxygen gas, and nitrogen gas). An introduction pipe (not shown) for introducing a mixed gas or the like is connected. The introduction pipe is provided with a valve (hereinafter referred to as introduction valve) not shown in the middle of the introduction pipe, and the introduction gas into the vacuum chamber 12 is controlled by controlling the opening and closing of the introduction valve. The gas inflow amount can be adjusted. Further, the joining apparatus 10 is connected to an exhaust pipe 17 that communicates with the chamber 12 and exhausts exhaust gas containing the introduced gas and the like inside the chamber 12 (see the black arrow in FIG. 1). The exhaust pipe 17 includes a vacuum exhaust device 18 that opens a valve (hereinafter referred to as an exhaust valve) provided in the exhaust pipe 17 and exhausts the exhaust gas to the outside of the chamber 12 to increase the degree of vacuum. It is connected. Further, the exhaust pipe 17 can adjust the gas outflow amount and the degree of vacuum of the exhaust gas by controlling the opening and closing of the exhaust valve. In other words, the bonding apparatus 10 has a reduced pressure atmosphere in which the degree of vacuum inside the chamber 12 is appropriately adjusted by adjusting the gas inflow amount of the introduced gas and the gas outflow amount of the exhaust gas. be able to.

  The joining apparatus 10 includes a plurality of the introduction pipes for introducing the introduction gas, and controls the opening and closing of the introduction valves provided in the respective introduction pipes by a control signal from a control apparatus (not shown). Also good. As a result, the bonding apparatus 10 can switch the type of introduced gas introduced into the chamber 12 from, for example, Ar gas to nitrogen gas. In addition, the bonding apparatus 10 can also use, for example, a mixed gas in which the mixing ratio of oxygen gas and nitrogen gas is appropriately changed as the introduction gas introduced into the chamber 12.

The vacuum exhaust device 18 of the joining device 10 used in the joining method of the present embodiment is configured by combining a low vacuum exhaust pump such as a rotary pump and a high vacuum exhaust pump such as a turbo molecular pump. . Although depending on the material of the first joining object 1, the material of the second joining object 2, the specifications of the device to be manufactured, etc., the evacuation device 18 evacuates the interior of the chamber 12 to a predetermined degree of vacuum (for example, 1 What is necessary is just to be able to evacuate to a reduced pressure atmosphere of × 10 ⁻⁴ Pa) or less.

  In addition, the joining apparatus 10 includes a first holder (hereinafter referred to as a lower holder) 14 that holds the first joining object 1 below the inside of the chamber 12 (lower side in FIG. 1A). . For example, the lower holder 14 applies a voltage to a dielectric layer (not shown) provided on the surface side of the lower holder 14 from a pair of internal electrodes (not shown) built in the lower holder 14. An electrostatic chuck capable of generating positive and negative charges is provided. In the lower holder 14, the electrostatic chuck can apply a Coulomb force between the dielectric layer and the first object 1 to be held, and the first object 1 can be held by the lower holder 14. The lower holder 14 may include a mechanical holding unit instead of the electrostatic chuck, and hold the first object 1 to the lower holder 14.

  Further, the lower holder 14 is provided with a first heater (hereinafter referred to as a lower heater) 14a for heating the first object 1 held by the lower holder 14 to a predetermined temperature. In addition, what is necessary is just to comprise the lower heater 14a with the heating wire which can heat the 1st joining target object 1, an infrared lamp, etc., for example.

  A bonding apparatus 10 used in the bonding method of the present embodiment includes a surface activation apparatus 13 that activates the surface 1 a side that is a bonding interface of the first bonding target 1 inside the chamber 12. The surface activation device 13 used in the bonding method of the present embodiment is disposed inside the chamber 12 and above the lower holder 14 that holds the first bonding target 1 (upper side in FIG. 1A). The upper electrode 13a is provided. The surface activation device 13 functions as a plasma irradiation device capable of generating plasma by applying a high-frequency voltage between the upper electrode 13a and the lower holder 14 side.

  The bonding apparatus 10 has a reduced pressure atmosphere in which Ar gas is introduced as an introduction gas into the chamber 12, and the plasma generated by the surface activation apparatus 13 is irradiated to the surface 1 a side serving as the bonding interface of the first bonding object 1. Let Thereby, the joining apparatus 10 becomes possible [performing the surface activation process which activates the said surface 1a side of the 1st joining target object 1 (refer Fig.1 (a)). Here, the introduced gas used in the surface activation step is not limited to Ar gas but may be oxygen gas or the like, but is not limited thereto.

  Further, the surface activation device 13 may be any device that can activate the surface 1a side, which is a bonding interface of the first bonding object 1, and is not only a plasma irradiation device that irradiates plasma, but also an ion beam. An ion beam irradiation apparatus or an atomic beam irradiation apparatus that irradiates an atomic beam can be used as appropriate. The surface activation device 13 may appropriately select a plasma irradiation device, an ion beam irradiation device, or an atomic beam irradiation device according to the material of the first bonding target 1 or the specifications of the device to be manufactured.

  Further, the bonding apparatus 10 used in the bonding method of the present embodiment moves the surface activation device 13 inside the chamber 12 and replaces the surface activation device 13 above the inside of the chamber 12 (FIG. 1B). A transport mechanism (not shown) for disposing a second holder (hereinafter referred to as an upper holder 15) capable of holding the second object 2 to be joined. By the transport mechanism, the upper holder 15 can be disposed at a position facing the surface 1 a side of the first object 1 fixed to the lower holder 14. Similar to the lower holder 14, the upper holder 15 is configured to be able to hold the second object 2 to be bonded to the upper holder 15 by an electrostatic chuck. Similarly to the lower holder 14, the upper holder 15 is a second heater (hereinafter referred to as an upper heater) that can heat the second object 2 held by the upper holder 15 to a predetermined temperature. ) 15a. In addition, the 2nd joining target object 2 hold | maintained at the upper holder 15 is transported to the position facing the first joining target object 1 shown in FIG. Similarly to the activation process step of the first bonding target object 1, an activation processing process for activating the surface 2 a side that becomes the bonding interface of the second bonding target object 2 is separately performed.

  Moreover, the joining apparatus 10 used for the joining method of this embodiment moves the push rod 16a provided in the other surface side facing the one surface side of the upper holder 15 holding the 2nd joining target object 2. FIG. It is possible to provide a joining mechanism 16 that can The joining mechanism 16 brings the upper holder 15 holding the second joining object 2 and the lower holder 14 holding the first joining object 1 close to each other or away by moving the push rod 16a. Can be. Note that the joining mechanism 16 not only moves the push rod 16a but also expands and contracts the push rod 16a, so that the upper holder 15 holding the second joining object 2 and the first joining object 1 are held. The lower holder 14 may be brought close to or separated from each other. Moreover, the pressure according to the load to the 1st joining target object 1 and the 2nd joining target object 2 when the upper holder 15 side is press-contacted to the lower holder 14 side is applied to the upper holder 15 of the joining apparatus 10. A pressure detection means (not shown) capable of detection is incorporated.

  Based on the signal from the pressure detection means, a control device (not shown) described later outputs a control signal for controlling the operation of the joining mechanism 16. The joining mechanism 16 feedback-controls the movement of the push rod 16a by a control signal from the control device, so that the lower holder 14 holding the first joining object 1 and the second joining object 2 are The pressurization applied to the held upper holder 15 can be controlled. In other words, the joining apparatus 10 includes a joining mechanism 16 that can control the raising and lowering of the upper holder 15 disposed to face the lower holder 14 (see FIG. 1B).

  After the surface activation step, the bonding apparatus 10 lowers the upper holder 15 holding the second bonding object 2 toward the lower holder 14 holding the first bonding object 1 (FIG. 1C). 1) and pressurizing the first joining object 1 and the second joining object 2 to perform a room temperature pressurizing step for temporary joining (FIG. 1 ( see c)).

  The joining apparatus 10 maintains the pressurization (see the white arrow in FIG. 1D) between the first joining object 1 and the second joining object 2 after the room temperature pressurization step. The first joining object 1 and the second joining object 2 are heated by the lower heater 14a and the upper heater 15a. Thereby, the joining apparatus 10 can perform the heating and pressurizing joining process which performs the diffusion joining used as the main joining between the 1st joining target object 1 and the 2nd joining target object 2 (FIG. 1 ( see d)).

  The joining apparatus 10 includes the introduction valve provided in the introduction pipe for introducing a predetermined introduction gas into the chamber 12, the exhaust valve for exhausting the inside of the chamber 12 to a predetermined degree of vacuum, and the vacuum exhaust apparatus 18. , A control device (not shown) comprising a computer on which a program for controlling the operation of the surface activation device 13, the transport mechanism, the lower heater 14a, the upper heater 15a, the joining mechanism 16 for moving the push rod 16a, and the like is mounted. ).

  Moreover, the joining apparatus 10 aligns the positions of the first joining object 1 and the second joining object 2 prior to the joining process of the first joining object 1 and the second joining object 2. You may let them. In this case, the joining apparatus 10 includes an alignment device (not shown) that aligns the first joining object 1 and the second joining object 2 inside the chamber 12, for example, the first joining object. What is necessary is just to attach | subject a different alignment mark to the corners by the side of the surface 1a and 2a of the thing 1 and the 2nd joining target object 2, respectively. Even if a positional shift caused by thermal expansion of the first bonding target object 1 or the second bonding target object 2 occurs during the surface activation step, the bonding apparatus 10 causes the alignment apparatus to perform the first bonding target 1. And the second joining object 2 can be recognized, and the first joining object 1 and the second joining object 2 can be aligned and joined with high accuracy.

  The bonding apparatus 10 may have a structure of a bonding apparatus that performs the surface activation process and the bonding process in separate chambers. When the surface activation step and the bonding step are performed in separate chambers, the bonding apparatus connects the respective chambers with a transfer chamber (not shown) that can be in a reduced pressure atmosphere, and the first bonding object 1 or It is good also as a structure which conveys the 2nd joining target object 2 by a conveyance means (not shown).

  Next, the joining object joined by the joining method of this embodiment is demonstrated using FIG.

The first object 1 shown in FIG. 2A to be bonded by the bonding method of this embodiment uses a wafer 11 made of Si. The first bonding object 1 includes a bonding layer 3 on the surface 1a side of the first bonding object 1 that is a bonding interface between the first bonding object 1 and the second bonding object 2. The bonding layer 3 was formed on the insulating layer 31 made of SiO ₂ formed on the wafer 11 made of Si, the intermediate layer 32 made of Ti formed on the insulating layer 31, and the intermediate layer 32. And a surface layer 33 made of Au as the outermost surface. The intermediate layer 32 can improve the adhesion between the insulating layer 31 made of SiO ₂ and the surface layer 33 made of Au.

Insulating layer 31 formed on the wafer 11 may be a thermal oxide film such as SiO _2, may be such as SiO ₂ or _Si 3 _{N 4} which is deposited by various CVD methods. The intermediate layer 32 formed on the insulating layer 31 and the surface layer 33 formed on the intermediate layer 32 can be appropriately formed by a vapor deposition method or a sputtering method. The bonding layer 3 may be formed in a predetermined shape using a lithography technique and an etching technique, or may be provided on the entire surface 1 a of the first bonding target 1. In the bonding method of the present embodiment, the surface layer 33 made of an Au film having a thickness of about 0.2 μm is formed on the surface 1a side of the first object 1 by vapor deposition. The thickness of the surface layer 33 is not limited to the above-described film thickness, and may be set as appropriate depending on the material of the surface layer 33 and the like.

The first bonding object 1 to be bonded by the bonding method of the present embodiment is appropriately provided with a bonding layer 3 on the surface 1a of the first bonding object 1 in order to perform bonding appropriately. The bonding layer 3 is not necessarily provided as long as the form of diffusion bonding can be performed. In addition, the bonding layer 3 is not necessarily formed in a plurality of layers serving as the insulating layer 31, the intermediate layer 32, and the surface layer 33, and may be configured as a single layer. As the material of the bonding layer 3, for example, a metal material such as Au, Cu, Al, or Pt can be used. The material of the bonding layer 3 may be an alloy. Further, when the surface 1 a of the first object 1 is provided with an insulating layer 31 such as SiO ₂ , the bonding layer 3 is an intermediate layer that improves the adhesion between the surface layer 33 made of Au and the insulating layer 31. 32 may be provided as appropriate. Further, the bonding layer 3 may appropriately include an intermediate layer 32 as a barrier layer that prevents unnecessary metal material from diffusing between the surface layer 33 and the first bonding target 1. As the material of the intermediate layer 32, a metal material such as Ti, Cr, Pt, or Mo can be used.

Further, the first bonding target 1 is not limited to the wafer 11 made of Si, but may be another material. As a material of the first object 1, for example, glass, sapphire, lithium niobate, lithium tantalate, gadolinium gallium garnet, or the like can be used. Further, in the material of the first object 1 to be bonded, an insulating layer 31 such as a SiO ₂ layer may be formed. Furthermore, the shape of the first bonding target 1 is not limited to a wafer shape, and may be a chip shape. That is, the first bonding object 1 may use chips that are various functional devices.

Moreover, the 2nd joining target object 2 shown to Fig.2 (a) joined by the joining method of this embodiment is comprised with the wafer 21 which consists of Si similarly to the 1st joining target object 1. FIG. The second bonding object 2 includes a bonding layer 4 on the surface 2a side of the second bonding object 2 that is a bonding interface between the second bonding object 2 and the first bonding object 1. The bonding layer 4 was formed on the insulating layer 41 made of SiO ₂ formed on the wafer 21 made of Si, the intermediate layer 42 made of Ti formed on the surface of the insulating layer 41, and the surface of the intermediate layer 42. And a surface layer 43 made of Au serving as the outermost surface. In the bonding method of the present embodiment, a surface layer 33 made of an Au film having a thickness of about 0.2 μm is formed on the surface 2a side of the second object 1 by vapor deposition.

  In addition, as long as the above-mentioned diffusion bonding can be performed, the second bonding object 2 and the bonding layer 4 can use an appropriate configuration, film thickness, and material similarly to the first bonding object 1 and the bonding layer 3. . Therefore, the second bonding object 2 is not limited to the wafer 21 made of Si, but may be made of various materials or chips that are various functional devices. Similarly, the bonding layer 4 can be made of various materials and shapes.

  Here, the diffusion bonding in the bonding method of the present embodiment means that the surface 1a side of the first bonding target 1 and the surface 2a side of the second bonding target 2 are brought into close contact with each other, and the first bonding target 1 And a second bonding object 2 under a temperature condition equal to or lower than the melting point, pressurizing to the extent that plastic deformation does not occur as much as possible, and joining using the diffusion of atoms generated at the bonding interface. In addition, in the joining interface, the plastic deformation which reduces that the unjoined area | region (void) which is not joined to the surface 1a side of the 1st joining target object 1 and the surface 2a side of the 2nd joining target object 2 reduces arises. It may be generated.

  Therefore, the diffusion bonding is performed by temporarily melting and liquefying the solid phase diffusion bonding in which the bonding interface for performing the diffusion bonding is bonded in a solid state and the metal inserted into the bonding interface when performing the diffusion bonding. And liquid phase diffusion bonding in which diffusion is used for isothermal solidification. In the bonding method of this embodiment, the bonding is widely interpreted, and the direct bonding of Au—Au in which Au and Au are bonded is also included in the diffusion bonding.

  In the bonding method of the present embodiment, the bonding interface between the first bonding object 1 and the second bonding object 2 is such that the bonding layer 3 of the first bonding object 1 and the second bonding object 2 described above. In addition to Au—Au bonded using the bonding layer 4, diffusion bonding such as Cu—Cu, Al—Al, Cu—Si, Pt—Si or the like can be performed.

  Accordingly, in the bonding method of the present embodiment, for example, as a bonding object, the material of the first bonding object 1 is Si, and the material of the second bonding object 2 is sapphire, lithium niobate, lithium tantalate. Also, it is possible to obtain a sufficient bonding strength even with different materials such as gadolinium gallium garnet.

  Similarly, the first bonding target 1 shown in FIG. 2B is composed of a wafer 11 made of Si. The first bonding object 1 includes a bonding layer 3 on the surface 1a side of the first bonding object 1 that is a bonding interface between the first bonding object 1 and the second bonding object 2. The bonding layer 3 includes an intermediate layer 32 made of Ti formed on the wafer 11 made of Si, and a surface layer 33 made of Au formed on the intermediate layer 32.

  Moreover, the 2nd joining target object 2 shown in FIG.2 (b) is comprised by the wafer 21 which consists of Si. The second bonding object 2 includes a bonding layer 4 on the surface 2a side of the second bonding object 2 that is a bonding interface between the second bonding object 2 and the first bonding object 1. The bonding layer 4 includes an intermediate layer 42 made of Ti formed on the surface of the wafer 21 made of Si, and a surface layer 43 made of Au formed on the surface of the intermediate layer 42.

  In the joining method of the present embodiment, the first joining object 1 shown in FIGS. 2A and 2B and the second joining are performed in the same joining process using the joining apparatus 10 in FIG. Au—Au diffusion bonding can be performed with the object 2.

  Hereinafter, each process of joining the 1st joined object 1 and the 2nd joined object 2 with joining device 10 which mentioned the joining method of this embodiment mentioned above is explained in order.

  In the joining apparatus 10 shown in FIG. 1 used in the joining method of the present embodiment, first, the lower holder 14 provided with the first joining object 1 below the chamber 12 (lower side of FIG. 1B). The chamber 12 is placed in a state where the second object 2 is placed on the upper holder 15 provided above the chamber 12 (upper side in FIG. 1 (b)) and held in a vertically opposed position. Closed (not shown).

  Subsequently, the joining apparatus 10 opens the exhaust valve of the exhaust pipe 17 with the introduction valve of the introduction pipe communicating with the interior of the chamber 12 closed, and exhausts the interior of the chamber 12 by the vacuum exhaust apparatus 18. Thus, the degree of vacuum inside the chamber 12 is increased.

  Next, the bonding apparatus 10 opens the introduction valve, and introduces an introduction gas (for example, Ar gas) from the introduction pipe into the chamber 12. The joining device 10 adjusts the exhaust amount exhausted from the exhaust pipe 17 and the introduction amount of the introduced gas introduced from the introduction pipe, thereby maintaining the degree of vacuum inside the chamber 12 constant. A reduced-pressure atmosphere of gas is used.

  Thereafter, a degassing process for removing gas components such as unnecessary moisture adsorbed on the first joining object 1 and the second joining object 2 before joining is suitably performed. The degassing process may be performed by heating the first joining object 1 and the second joining object 2 before joining with the lower heater 14 a of the lower holder 14 and the upper heater 15 a of the upper holder 15. The joining apparatus 10 is an unnecessary gas adsorbed on the first joining object 1 and the second joining object 2 before joining by heating the first joining object 1 and the second joining object 2. Release (desorb) components. The bonding apparatus 10 can appropriately remove unnecessary gas components by exhausting the gas components from the exhaust pipe 17 to the outside of the chamber 12.

  Here, the degassing treatment is performed at an appropriate temperature (for example, 100) in order to maintain the cleanliness of the surfaces 1a and 2a serving as the bonding interface between the first bonding target 1 and the second bonding target 2, for example. (° C. or higher). The heating time in the degassing process may be appropriately set in the range of about 2 to 10 minutes from the viewpoint of in-plane temperature uniformity, reproducibility, etc., but is not particularly limited. Moreover, what is necessary is just to set the temperature of the said degassing process suitably in the range in which the 1st joining target object 1 and the 2nd joining target object 2 do not receive a heat damage.

  Next, the bonding apparatus 10 moves the upper holder 15 by the transport mechanism, and moves the upper part of the surface activation apparatus 13 above the first bonding object 1 held by the lower holder 14 below the chamber 12. The electrode 13a is disposed (see FIG. 1A).

  In the bonding method of the present embodiment, after performing a degassing process (not shown), the chamber 12 of the bonding apparatus 10 is evacuated while introducing Ar gas as an introduction gas, whereby the inside of the chamber 12 has a predetermined degree of vacuum. A reduced pressure atmosphere (for example, about several Pa) is maintained. Subsequently, the bonding apparatus 10 generates plasma by applying a high-frequency AC voltage between the upper electrode 13a of the surface activation apparatus 13 and the lower holder 14 side. The surface activation device 13 of the bonding apparatus 10 irradiates the plasma on the surface 1a side of the first bonding target 1 held by the lower holder 14 for a predetermined time (for example, 60 seconds). Thereby, the surface activation apparatus 13 of the joining apparatus 10 can perform the surface activation process which activates the surface 1a side of the 1st joining target object 1 with a plasma.

  The bonding apparatus 10 activates the surface 2a side of the second bonding object 2 separately by plasma with a surface activation apparatus (not shown) in the same manner as the activation to the first bonding object 1 described above. The surface activation process is performed.

  The surface 1a side of the first bonding object 1 and the surface 2a side of the second bonding object 2 are usually covered with a film made of an oxide or an organic substance in the atmosphere. Therefore, the surface 1a side of the first bonding target 1 and the surface 2a side of the second bonding target 2 are in a state where the composition and chemical bond are different from the inner side. When the surface 1a side of the first bonding object 1 and the surface 2a side of the second bonding object 2 are bonded, the above-described coating film forms the first bonding object 1 and the second bonding object 2. It is thought that this is a factor that hinders the bonding with.

  In the bonding method of the present embodiment, the surface activation step may remove the coating film formed on the surface 1a side of the first bonding target 1 or the surface 2a side of the second bonding target 2. it can. In the surface activation step, the bonding partner is formed on the surface 1a side of the first bonding target 1 or the surface 2a side of the second bonding target 2 with a part of the bond where the exposed atoms form a chemical bond. It can be lost. Therefore, the surface 1a side of the 1st joining target object 1 and the surface 2a side of the 2nd joining target object 2 can make high the reactivity at the time of joining.

  That is, in the joining object illustrated in FIG. 2, the surface layer 33 provided on the surface 1a side of the first joining object 1 and the surface layer 43 provided on the surface 2a side of the second joining object 2 are provided. Will be activated.

  In the surface activation step, plasma is generated not only in a reduced pressure atmosphere but also at atmospheric pressure to activate the surface 1a side of the first object 1 or the surface 2a side of the second object 2. However, it is preferably performed in a reduced pressure atmosphere.

  When the surface activation step is performed in a reduced-pressure atmosphere, the surface activation step can further increase the reactivity as compared with the surface activation step performed at atmospheric pressure. That is, when the surface activation process is performed in a reduced pressure atmosphere, the surface activation process is performed by exhausting the exhaust gas from the exhaust pipe 17 while introducing the introduction gas from the introduction pipe. In a reduced pressure atmosphere. Therefore, the bonding apparatus 10 removes the coating film formed on the surface 1a side of the first bonding object 1 and the surface 2a side of the second bonding object 2, and removes the components of the coating from the chamber 12 outside. Can be efficiently exhausted. As a result, the bonding apparatus 10 is contaminated again by combining the surface 1a side of the first bonding object 1 and the surface 2a side of the second bonding object 2 with the components of the coating film removed in the surface activation step. It can be suppressed.

  In the bonding method of the present embodiment, the bonding apparatus 10 transfers the entire upper holder 15 holding the second bonding target object 2 by the transfer mechanism, which is different from the surface activation process of the first bonding target object 1. At the position, a surface activation step for activating the surface 2a side that becomes the bonding interface of the second bonding object 2 is separately performed. That is, the bonding apparatus 10 performs the surface activation process at a location different from the position where the first bonding target 1 and the second bonding target 2 are arranged to face each other. Thereby, compared with what joins 10 and arranges the 1st joined object 1 and the 2nd joined object 2 facing, and performs the above-mentioned surface activation process, the above-mentioned film of the removed film It is possible to suppress the risk of components flying and adhering to the surface 1a side of the first bonding target 1 or the surface 2a side of the second bonding target 2 facing each other.

  In addition, although there exists a possibility that the component of the said film may adhere again, the joining apparatus 10 performs the said surface activation process in the position where the 1st joining target object 1 and the 2nd joining target object 2 were opposingly arranged. Thereby, the surface activation process of the first bonding target 1 and the second bonding target 2 can be performed at a time to be simplified.

  Subsequently, in the bonding method of the present embodiment, the bonding apparatus 10 performs a bonding process of bringing the first bonding target object 1 and the second bonding target object 2 into contact with each other after the surface activation process. .

  After the surface activation step, the bonding apparatus 10 is held by the upper holder 15 again above the first bonding object 1 held by the lower holder 14 below the chamber 12 by the transport mechanism. Two joining objects 2 are arranged (see FIG. 1B).

  Inside the chamber 12 in a reduced-pressure atmosphere, the joining mechanism 16 moves the push rod 16a of the joining mechanism 16 in a direction in which the upper holder 15 approaches the lower holder 14 (see a white arrow in FIG. 1C). (See FIG. 1C). Thereby, the joining apparatus 10 can apply a load gradually and pressurize between the 1st joining target object 1 and the 2nd joining target object 2 (refer Ia of FIG. 3).

  Here, the bonding apparatus 10 brings the first bonding target portion 1 and the second bonding target object 2 into contact with each other at a normal load for a first predetermined time (for example, 1 hour) (for example, 5000 N). ) To perform a room temperature pressurization process for temporary bonding by maintaining the pressurization (see Ib in FIG. 3). In addition, the load applied by the pressurization in the room temperature pressurization process is appropriately set depending on the material of the first object 1, the material of the second object 2, the specifications of the bonding performance of the device to be manufactured, and the like. That's fine.

  Next, the joining apparatus 10 pressurizes between the first joining object 1 and the second joining object 2 after the room temperature pressurization step (see the white arrow in FIG. 1D). ), The lower heater 14a provided in the lower holder 14 and the upper heater 15a provided in the upper holder 15 are heated. The first object 1 and the second object 2 are gradually heated by the lower heater 14a and the upper heater 15a (see IIa in FIG. 3).

  The joining apparatus 10 maintains the first joining object 1 and the second joining object 2 at a predetermined temperature (for example, 200 ° C.) for a second predetermined time (for example, 1 hour). A heating / pressure bonding process for diffusion bonding to be bonded is performed (see IIb in FIG. 3).

  In addition, it is not necessary to maintain the load given by the pressurization in the heating / pressure joining process at the same load as the room temperature pressurizing process, and the material of the first joining object 1 and the second joining object 2 What is necessary is just to set suitably according to the specification of the joining performance of a material or the device to manufacture.

  Thereafter, the bonding apparatus 10 stops heating the lower heater 14a and the upper heater 15a, and gradually decreases the temperatures of the first bonding object 1 and the second bonding object 2 inside the chamber 12. (See IIc in FIG. 3).

  After the temperature of the first joining object 1 and the second joining object 2 is lowered to room temperature (for example, 30 ° C.), the joining apparatus 10 closes the exhaust valve of the exhaust pipe 17. Further, the bonding apparatus 10 supplies nitrogen gas from the introduction pipe to the inside of the chamber 12 to return the inside of the chamber 12 from the reduced pressure atmosphere to the atmospheric pressure. The joining apparatus 10 releases the electrostatic chucks of the lower holder 14 and the upper holder 15, and then moves the push rod 16 a of the joining mechanism 16 in the direction away from the lower holder 14 by the joining mechanism 16. That is, the joining apparatus 10 can gradually reduce the load applied between the first joining object 1 and the second joining object 2 (see IIIa in FIG. 3).

  Thereby, it becomes possible to take out from the chamber 12 the laminate in which the first object 1 and the second object 2 are bonded.

  Next, the joining state of the laminate in which the first joining object 1 and the second joining object 2 are joined by the joining method of the present embodiment will be described in detail. Here, the bonding state of the laminate bonded by the bonding method of the present embodiment can be confirmed by an ultrasonic microscope image of the dummy wafer 5 which is the laminate illustrated in FIG. 4A shows a plan view of the dummy wafer 5. On the right side of FIG. 4A, an enlarged portion extracted from the center of the dummy wafer 5 as shown by a broken line is shown. FIG. 4B shows an AA cross section in the enlarged portion of the dummy wafer 5.

  The dummy wafer 5 is configured by bonding a pair of wafers having substantially the same outer shape and oriented on the orientation flat surface 5a as a first bonding object 1 and a second bonding object 2, respectively (FIG. 4 ( see a)). Each of the pair of wafers has substantially the same structure as the first bonding target 1 and the second bonding target 2 shown in FIG. 2B, and one wafer is the first bonding target. The difference is that a bonding layer 3 is formed on the surface 1a side of the object 1 by patterning into a pattern to be described later.

  That is, in the dummy wafer 5, the first bonding target 1 of one wafer is formed by the wafer 11 made of Si. In the dummy wafer 5, the second bonding target 2 of the other wafer is formed by a wafer 21 made of Si. In the first object 1, a bonding layer 3 is formed on the surface 1 a side of the first object 1 by vapor deposition. The bonding layer 3 includes an intermediate layer 32 made of Ti formed on the wafer 11 made of Si, and a surface layer 33 made of Au formed on the intermediate layer 32.

  A bonding layer 4 is formed on the second bonding object 2 on the surface 2a side of the second bonding object 2 by vapor deposition. The bonding layer 4 includes an intermediate layer 42 made of Ti formed on the surface of the wafer 21 made of Si, and a surface layer 43 made of Au formed on the surface of the intermediate layer 42.

  Here, the connection layer 3 formed on the surface 1a side of the first bonding target 1 constituting the dummy wafer 5 is patterned into a predetermined shape using a lithography technique and an etching technique. That is, the bonding layer 3 is not formed on the entire surface of the wafer in plan view on one of the wafers constituting the dummy wafer 5, and the bonding layer 3 is not provided depending on the location of the one wafer (see FIG. 4 (b)).

  Specifically, the bonding layer 3 of the first bonding object 1 has line-shaped bonding portions 3a and 3a parallel to the vertical direction (vertical direction in FIG. 4A) and the horizontal direction (FIG. 4A). Are formed by line-like joint portions 3b and 3b parallel to each other. In addition, the bonding layer 3 of the first object to be bonded 1 forms a rectangular bonding portion 3c at the center surrounded by vertical and horizontal line-shaped bonding portions 3a, 3a, 3b, 3b.

  That is, in the dummy wafer 5, a portion where the bonding portions 3 a, 3 b, 3 c of the bonding layer 3 patterned on the first bonding target 1 and the bonding layer 4 of the second bonding target 2 are bonded is bonded. It becomes area | region BR.

  The dummy wafer 5 is formed by bonding the patterned bonding layer 3 of the first bonding target 1 and the bonding layer 4 formed on the entire surface 2 of the second bonding target 2 to perform diffusion bonding of Au—Au. I am doing. Based on a plan view of the dummy wafer 5 observed with an ultrasonic microscope image, it is possible to discriminate between a bonded region of the dummy wafer 5 that is diffusion-bonded by Au—Au and an unbonded region that is not bonded.

  Here, the bonding method of this embodiment is compared with the bonding method for comparison according to the bonding state of the dummy wafer 5 shown in FIG.

  The dummy wafer 5 shown in FIG. 5A illustrates a bonding state in which bonding is performed only by the heating / pressure bonding process described above without performing the room temperature pressing process after the surface activation process described above. In the dummy wafer 5 shown in FIG. 5A, the bonding region BR in the dummy wafer 5 is bonded separately from the non-bonding region formed by the bonding layer 3 patterned on the upper, right, and lower left and right sides of FIG. A non-bonded region (void) 5da appears.

  Further, the dummy wafer 5 shown in FIG. 5B shows a bonded state in which the dummy wafer 5 is bonded only by performing the room temperature pressurization process described above after the surface activation process described above. In the dummy wafer 5 shown in FIG. 5B, it can be seen that the bonding region BR in the dummy wafer 5 has a smaller unbonded region 5db than that in FIG. Thereby, it can be seen that the bonding method of FIG. 5B has better bonding strength and bonding yield than the bonding method of FIG.

  Furthermore, in the dummy wafer 5 of FIG. 5C showing the bonding method of the present embodiment, the unbonded region 5dc of the bonded region BR in the dummy wafer 5 is smaller than that of FIG. 5B. Thereby, it can be seen that the bonding method of the present embodiment has better bonding strength and bonding yield than the bonding method used in FIGS. 5A and 5B.

  The reason why the bonding strength and the bonding yield of the bonding method in this embodiment are excellent is not clear, but can be considered as follows.

  In the bonding method using the surface activation method in which the surface 1a side of the first bonding object 1 and the surface 2a side of the second bonding object 2 are activated and bonded, the state of the surface for bonding (surface Roughness).

  Here, when the heat treatment is performed before the first bonding object 1 and the second bonding object 2 are fixed by bonding, the first bonding object 1 and the second bonding object 2 are used. Due to the thermal expansion, movement occurs in the materials constituting the first bonding object 1 and the second bonding object 2 at the bonding interface. When movement occurs in the materials constituting the first object 1 and the second object 2, the surface 1a side of the first object 1 and the surface 2a side of the second object 2 are moved. Surface roughening and undulation may occur. When surface roughness or undulation occurs on the surface 1a side of the first object 1 and the surface 2a side of the second object 2, the surface 1a side of the first object 1 and the second object It is considered that it is difficult to stably join the surface 2a side of 2.

  Further, when the heat treatment is performed before being fixed by the bonding, the moisture contained in the first bonding target object 1 and the second bonding target object 2 diffuses in the direction of the bonding interface. When there are minute cavities generated by surface roughening or undulation on the surface 1a side of the first object 1 or the surface 2a side of the second object 2, the water stays in the cavity and the first object 1 This becomes a factor that inhibits the joining between the joining object 1 and the second joining object 2. Furthermore, it is speculated that the first bonding object 1 and the second bonding object 2 cause a decrease in bonding strength even when the diffused moisture is vaporized and trapped in the cavity. The

  In the joining method of the present embodiment, temporary joining is performed once in a room temperature pressurizing process in which the first joining object 1 and the second joining object 2 are pressurized at room temperature inside the chamber 12. ing. Further, the bonding method of the present embodiment is a heating / pressure bonding in which heating and pressurization are performed for improving the bonding strength between the first bonding object 1 and the second bonding object 2 after the room temperature pressing process. Diffusion bonding, which is main bonding, is performed in the process.

  Therefore, in the joining method of the present embodiment, in the room temperature pressurizing step for temporarily joining the first joining object 1 and the second joining object 2, the first joining object 1 and the second joining by heat. The expansion of the object 2 and the moisture contained in the first object 1 and the second object 2 are not substantially diffused and desorbed in the direction of the bonding interface. Further, in the heating / pressure bonding process for performing the main bonding in the bonding method of the present embodiment, it is assumed that thermal expansion or the like occurs in the first bonding object 1 or the second bonding object 2 due to the heating and pressurization. In addition, since temporary bonding has already been performed, it is possible to suppress the movement of the material of the first bonding object 1 and the second bonding object 2, the retention of moisture at the bonding interface, the desorption of moisture, and the like. It is thought that it becomes. Note that the cavity is deformed by a heating / pressure bonding process in the bonding process unless an oxide or an impurity as an organic component is present at the bonding interface. Therefore, the cavity is closed, and then diffusion of the material at the bonding interface occurs and bonding can be performed.

  As a result, the joining method according to the present embodiment can stably realize joining with a small unjoined region in the joining between the first joining object 1 and the second joining object 2 finally. It is possible to improve the bonding strength and the bonding yield.

  In the bonding method of the present embodiment, the first bonding object 1 and the second bonding object 2 include bonding layers 3 and 4 capable of diffusion bonding on at least one of the surfaces 1a and 2a, and the bonding layer. 3 and 4 have surface layers 33 and 43 whose outermost surfaces are made of Au.

  By the way, since Au is a relatively soft metal material compared with Cu or the like, its shape is easily deformed by heating and pressurization, and solid-phase diffusion of Au—Au is also likely to occur. Therefore, diffusion bonding can be performed relatively easily by the heating and pressure bonding process described above.

  However, although Au is suitable for solid phase diffusion bonding, it has a large linear expansion coefficient and sometimes contains moisture inside.

  For this reason, the surface layers 33 and 43 made of Au are used between the first bonding target 1 and the second bonding target 2 and the above-mentioned room temperature pressing process is not performed, but only the heating / pressure bonding process is performed. In such a case, there is a risk of being affected by thermal expansion, surface moisture retention or moisture desorption.

  In the bonding method of the present embodiment, after performing the surface activation step, normal temperature heating is performed to pressurize the first bonding target 1 and the second bonding target 2 at a normal temperature for a first predetermined time. A first joining object 1 is obtained by performing a pressure process and heating and pressurizing the first joining object 1 and the second joining object 2 for a second predetermined time after the room temperature pressurizing process. And a pressurizing / heating bonding process for performing diffusion bonding between the first bonding object 2 and the second bonding object 2. In the bonding method of the present embodiment, the above-described room temperature pressurization step and the above-described pressurization / heating bonding step are performed, so that the thermal expansion of the surface layers 33 and 43, moisture retention and moisture desorption at the bonding interface. It is possible to suppress the influence of the above and to realize good bonding.

  In general, when different materials are used for joining the first joining object 1 and the second joining object 2, the temperature of the heat treatment that improves the joining strength due to thermal stress caused by the difference in thermal expansion coefficient. In many cases, sufficient bonding strength tends not to be obtained. That is, if the temperature of the heat treatment is too high, the first bonded object 1 and the second bonded object 2 that are bonded are damaged, and peeling from the bonding interface occurs. Moreover, after joining between the 1st joining target object 1 and the 2nd joining target object 2, there exists a possibility that an internal stress may remain inside the 1st joining target object 1 or the 2nd joining target object 2. is there. However, in the bonding method of the present embodiment, even if the above-described different materials are bonded as the first bonding object 1 and the second bonding object 2, it is possible to suppress the internal stress from remaining at a relatively low temperature. However, it is possible to obtain a sufficient bonding strength.

  By the way, when manufacturing a MEMS device, for example, using the bonding method of this embodiment, for example, an SOI wafer and a Si wafer are bonded at a wafer level using the bonding apparatus 10 of this embodiment shown in FIG. Thus, after forming a wafer level package structure, individual MEMS devices can be formed by a dividing process (dicing process) for dividing the package structure individually.

  That is, the bonding apparatus 10 is not limited to the case of manufacturing a MEMS device or the like, and is not limited to the case where the bonding apparatus 10 is composed of two types of bonding objects. Can also be manufactured. In this case, the joining apparatus 10 may perform the joining process for joining the joining objects by repeating the surface activation process described above in the present embodiment for each joining object.

  A device manufactured using the bonding method of the present embodiment is not limited to a sensor element such as an acceleration sensor, a gyro sensor, or a thermal infrared sensor, but may be an electronic device such as an integrated circuit device. In addition, since the bonding method of the present embodiment can be used for manufacturing a composite substrate by bonding different types of materials, it can be applied to, for example, manufacturing optical devices and high-frequency devices.

(Embodiment 2)
The joining method of this embodiment is substantially the same as the joining method of Embodiment 1, and diffusion bonding between the first joining object 1 and the second joining object 2 shown in FIG. Instead of bonding by solid phase diffusion bonding of Au, the first bonding target 1 and the second bonding are performed using the first bonding target 1 and the second bonding target 2 shown in FIG. The difference is that diffusion bonding with the object 2 is bonded by eutectic bonding. In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 1, and description is abbreviate | omitted suitably.

  The first bonding object 1 and the second bonding object 2 used in the bonding method of the present embodiment are bonded layers 3 and 4 capable of diffusion bonding with a eutectic reaction on at least one of the surfaces 1a and 2a. It has.

  In the bonding method of this embodiment, the bonding process after the surface activation process is performed at room temperature to pressurize the first bonding object 1 and the second bonding object 2 for a first predetermined time at room temperature. The first bonding object is obtained by heating and pressing the first bonding object 1 and the second bonding object 2 at a temperature equal to or higher than the eutectic temperature in the bonding layers 3 and 4 after the pressing process and the room temperature pressing process. Eutectic bonding is performed between the object 1 and the second object 2.

  More specifically, as a bonding method of the present embodiment, an example in which a first bonding target 1 that is a Si wafer and a second bonding target 2 that is a Si wafer are bonded by eutectic bonding of Au—Si. This will be described based on the configuration of FIG.

A first object 1 shown in FIG. 6A is composed of a wafer 11 made of Si. The first bonding object 1 includes a bonding layer 3 on the surface 1a side of the first bonding object 1 that is a bonding interface between the first bonding object 1 and the second bonding object 2. The bonding layer 3 was formed on the insulating layer 31 made of SiO ₂ formed on the wafer 11 made of Si, the intermediate layer 32 made of Ti formed on the insulating layer 31, and the intermediate layer 32. And a surface layer 33 made of Au.

Moreover, the 2nd joining target object 2 shown to Fig.6 (a) is comprised by the wafer 21 which consists of Si. The second bonding object 2 includes a bonding layer 4 on the surface 2a side of the second bonding object 2 that is a bonding interface between the second bonding object 2 and the first bonding object 1. The bonding layer 4 includes an insulating layer 41 made of SiO ₂ formed on the surface of the wafer 21 made of Si, a semiconductor layer 22 made of Si formed on the surface of the insulating layer 41, and a surface of the semiconductor layer 22. And a surface layer 43 made of Au.

Similarly, the first object 1 shown in FIG. 6B is composed of a wafer 11 made of Si. The first bonding object 1 includes a bonding layer 3 on the surface 1a side of the first bonding object 1 that is a bonding interface between the first bonding object 1 and the second bonding object 2. The bonding layer 3 was formed on the insulating layer 31 made of SiO ₂ formed on the wafer 11 made of Si, the intermediate layer 32 made of Ti formed on the insulating layer 31, and the intermediate layer 32. And a surface layer 33 made of Au.

  Moreover, the 2nd joining target object 2 shown in FIG.6 (b) is comprised by the wafer 21 which consists of Si. The second bonding object 2 includes a bonding layer 4 on the surface 2a side of the second bonding object 2 that is a bonding interface between the second bonding object 2 and the first bonding object 1. The bonding layer 4 is composed only of the surface layer 43 made of Au formed on the surface of the wafer 21 made of Si.

A first bonding target 1 shown in FIG. 6C is composed of a wafer 11 made of Si. The first bonding object 1 includes a bonding layer 3 on the surface 1a side of the first bonding object 1 that is a bonding interface between the first bonding object 1 and the second bonding object 2. The bonding layer 3 was formed on the insulating layer 31 made of SiO ₂ formed on the wafer 11 made of Si, the intermediate layer 32 made of Ti formed on the insulating layer 31, and the intermediate layer 32. And a surface layer 33 made of Au.

  On the other hand, the second bonding target 2 shown in FIG. 6C is composed of a wafer 21 made of Si, and the second bonding target 2 is shown in FIGS. 6A and 6B. The bonding layer 4 as shown is not provided.

  In the joining method of the present embodiment, after performing the same surface activation process as in Embodiment 1, the joining between the first joining object 1 and the second joining object 2 shown in FIG. In accordance with the timing chart shown in FIG. Hereinafter, the joining process of this embodiment will be described in detail with reference to FIG.

  In the joining process of the present embodiment, a load is gradually applied and pressurized between the first joining object 1 and the second joining object 2 (see Ia in FIG. 7).

  Maintaining pressurization with a predetermined load (for example, 5000 N) at a normal temperature for a first predetermined time (for example, 1 hour) by bringing the first bonding target portion 1 and the second bonding target object 2 into contact with each other. A room temperature pressurizing step for temporary bonding is performed (see Ib in FIG. 7).

  Next, after the room temperature pressurization step, the first joining object 1 and the second joining object 2 are heated and gradually heated while maintaining the pressurized load (see IIa in FIG. 7). ).

  The first bonding object 1 and the second bonding object 2 are set to be equal to or higher than the eutectic temperature (for example, 400 ° C.) of the bonding layers 3 and 4 for a second predetermined time (for example, 1 hour). A heating / pressure bonding step is performed in which Si—Au eutectic bonding is performed as diffusion bonding (see IIb in FIG. 7).

  Thereafter, the temperature of the first joining object 1 and the second joining object 2 is gradually lowered (see IIc in FIG. 7).

  After the temperature of the 1st joining target object 1 and the 2nd joining target object 2 falls to normal temperature (for example, 30 ° C), it starts between the 1st joining target object 1 and the 2nd joining target object 2. The load is gradually reduced (see IIIa in FIG. 7).

  Thereby, it becomes possible to perform the joining process in the joining method of this embodiment.

  In the bonding method of the present embodiment, the heating / pressure bonding process shown in FIG. 7B may be further divided into a first heating / pressurizing process and a second heating / pressurizing process. it can. That is, in the first heating / pressurizing process, the first joining object 1 is heated to a temperature (for example, 200 ° C.) lower than the eutectic temperature for a third predetermined time (for example, 1 hour). And the second bonding object 2 are pressurized by a predetermined load (for example, 5000 N), and solid phase diffusion bonding is performed between the first bonding object 1 and the second bonding object 2. Subsequently, in the second heating / pressurizing process, eutectic bonding is performed by pressurizing with a predetermined load (for example, 5000 N) at a temperature equal to or higher than the eutectic temperature (for example, 400 ° C.). You may go. In the bonding method of the present embodiment, the heating / pressure bonding step may be performed by applying different loads to the pressurization in the first heating / pressurization process and the pressurization in the second heating / pressurization process. Good.

  Thereby, the bonding method of the present embodiment can perform the eutectic reaction more uniformly while suppressing the enlargement of the cavities in the stage of solid phase diffusion bonding, and further increase the final bonding strength. It becomes possible.

  Examples of the diffusion bonding performed in the bonding step in the bonding method of the present embodiment include eutectic bonding such as Au—Si, Au—Sn, and Al—Si.

  Therefore, examples of materials for the bonding layer 3 formed on the first bonding target 1 and the bonding layer 4 formed on the second bonding target 2 include Au and Au, Au and Si, and Au and Sn. Al, Si, and the like may be appropriately selected and used. When the insulating layer 31 is provided on the bonding layer 3, the adhesion between the insulating layer 31 and the surface layer 33 made of Au is generally low. Therefore, the adhesion with the surface layer 33 may be improved by forming an intermediate layer 32 between the insulating layer 31 and the surface layer 33 made of Au. When the intermediate layer 32 is formed between the surface layer 33 and the wafer 11 made of Si, Au—Si is diffused between the Au of the surface layer 43 and Si on the wafer 11 side through the intermediate layer 32. The intermediate layer 32 preferably has a thickness of, for example, about several tens of nm or less.

  The bonding method in the present embodiment includes a room temperature pressure process and a heating / pressure bonding process in which bonding is performed by eutectic bonding after the room temperature pressure process.

  In joining the first joining object 1 and the second joining object 2, the surfaces 1 a and 2 a which are the joining interfaces of the first joining object 1 and the second joining object 2 are activated. When the heating / pressurizing bonding step of simply heating and pressurizing is performed after the surface activation step, it exists on the surface 1a, 2a side that becomes the bonding interface between the first bonding object 1 and the second bonding object 2. Due to the above-described cavities, uniform bonding cannot be performed, and an unbonded region may be generated at the bonding interface.

  On the other hand, the bonding method according to the present embodiment includes the first bonding object 1 and the first bonding object 1 and the second bonding object 2 before the first bonding object 1 and the second bonding object 2 are bonded by eutectic bonding. Solid phase bonding is performed between the second bonding object 2 and the second bonding object 2 in a room temperature pressure process.

  Therefore, the joining method in the present embodiment can suppress the generation of the new cavity between the first joining object 1 and the second joining object 2 and the enlargement of the cavity. . Moreover, the joining method in this embodiment is the first joining object 1 and the second joining after the first joining object 1 and the second joining object 2 are solid-phase joined by the room temperature pressurization process. By eutectic bonding with the object 2, the material of the bonding layer 3 or the like becomes a liquid phase, the minute cavities are filled, and the bonding strength can be further improved by bonding more uniformly.

  Therefore, the bonding method according to the present embodiment is such that the surface roughness that becomes the bonding interface between the first bonding object 1 and the second bonding object 2 described above is large to some extent, and the surface activation process and heating / pressure bonding are performed. Even when it is difficult to sufficiently reduce the unbonded region only by the solid phase diffusion by the process, it is possible to improve the bonding strength and the bonding yield.

(Embodiment 3)
The bonding method of the present embodiment is substantially the same as the bonding method of the second embodiment, and bonding between the first bonding object 1 and the second bonding object 2 is performed using Au—Si eutectic bonding. Instead, the first bonding object 1 and the second bonding object 2 are bonded using Au—Sn eutectic bonding.

  In the bonding method of this embodiment, a pair of wafers (not shown) are bonded. One of the pair of wafers includes a bonding layer 3 in which the first bonding target 1 is a wafer 11 made of Si, and the wafer 11 is plated with an AuSn alloy. The other wafer has the second bonding object 2 as a wafer 21 made of Si, and has a base layer made of Ni plated on the wafer 21 and a surface layer 43 made of Au formed on the base layer. A bonding layer 4 is provided.

  In the joining method of this embodiment, after performing the same surface activation process as Embodiment 1, between the 1st joining target object 1 and the 2nd joining target object 2 according to the timing chart shown in FIG. Joining is performed by a joining process of heating and pressurizing. Hereinafter, the joining process of this embodiment will be described in detail with reference to FIG.

  In the joining process of the present embodiment, a load is gradually applied and pressurized between the first joining object 1 and the second joining object 2 (see Ia in FIG. 8).

  Maintaining pressurization with a predetermined load (for example, 5000 N) at a normal temperature for a first predetermined time (for example, 1 hour) by bringing the first bonding target portion 1 and the second bonding target object 2 into contact with each other. A room temperature pressurizing step for temporary bonding is performed (see Ib in FIG. 8).

  Next, after the room temperature pressurization step, the first joining object 1 and the second joining object 2 are heated and gradually heated while maintaining the pressurized load (see IIa in FIG. 8). ).

  The first bonding object 1 and the second bonding object 2 are set to be equal to or higher than the eutectic temperature (for example, 300 ° C.) of the bonding layers 3 and 4 for a second predetermined time (for example, 1 hour). A heating / pressure bonding step is performed in which Au—Sn eutectic bonding is performed as diffusion bonding (see IIb in FIG. 8).

  Thereafter, the temperature of the first joining object 1 and the second joining object 2 is gradually lowered (see IIc in FIG. 7).

  Thereafter, the temperatures of the first object 1 and the second object 2 are gradually decreased (see IIc in FIG. 8).

  After the temperature of the 1st joining target object 1 and the 2nd joining target object 2 falls to normal temperature (for example, 30 ° C), it starts between the 1st joining target object 1 and the 2nd joining target object 2. The load is gradually reduced (see IIIa in FIG. 8).

  Thereby, it becomes possible to perform the joining process in the joining method of this embodiment.

  In the bonding method of the present embodiment, the heating / pressure bonding process shown in IIb of FIG. 8 may be further divided into a first heating / pressure process and a second heating / pressure process. it can. That is, in the first heating / pressurizing process, the first bonding object 1 is heated to a temperature (for example, 200 ° C.) lower than the eutectic temperature for a third predetermined time (for example, 1 hour). And the second bonding object 2 are pressurized by a predetermined load (for example, 5000 N), and solid phase diffusion bonding is performed between the first bonding object 1 and the second bonding object 2. Subsequently, in the second heating / pressurizing process, eutectic bonding is performed by pressurizing with a predetermined load (for example, 5000 N) at a temperature equal to or higher than the eutectic temperature (for example, 300 ° C.). You may go. In the bonding method of the present embodiment, the heating / pressure bonding step may be performed by applying different loads to the pressurization in the first heating / pressurization process and the pressurization in the second heating / pressurization process. Good.

  The diffusion bonding performed in the bonding step in the bonding method of the present embodiment is Au—Sn eutectic bonding, and as with the Au—Si eutectic bonding bonded in Embodiment 2, the bonding strength and the bonding yield are improved. Can be achieved.

DESCRIPTION OF SYMBOLS 1 1st joining target object 1a, 2a surface 2 2nd joining target object 3, 4 Joining layer 10 Joining apparatus 43 Surface layer

Claims (4)

A surface activation step of activating each of the surface sides serving as a bonding interface between the first bonding target and the second bonding target to be bonded to the first bonding target; and after the surface activation step, A joining method comprising a joining step of joining the first joining object and the second joining object,
The joining step includes a room temperature pressurizing step of pressurizing the first joining object and the second joining object for a first predetermined time at room temperature, and the first step after the room temperature pressurizing step. Diffusion bonding between the first bonding object and the second bonding object by heating and pressurizing the bonding object and the second bonding object for a second predetermined time. And a heating / pressure bonding step for performing bonding.   The first bonding object and the second bonding object include a bonding layer capable of diffusion bonding on at least one of the surfaces, and the bonding layer has a surface layer whose outermost surface is made of Au. The bonding method according to claim 1, wherein:   The first bonding object and the second bonding object include a bonding layer capable of the diffusion bonding accompanied by a eutectic reaction on at least one of the surfaces, and the heating of the heating / pressure bonding process. The eutectic bonding is performed between the first bonding object and the second bonding object by setting the temperature to be equal to or higher than the eutectic temperature in the bonding layer. Joining method.   The heating / pressurizing joining step is a first step of heating the first joining object and the second joining object by heating to a temperature lower than the eutectic temperature for a third predetermined time. The bonding method according to claim 3, further comprising: a heating / pressurizing process of step 2 and a second heating / pressurizing process of performing the eutectic bonding after the first heating / pressurizing process.

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