Joining method

Abstract

To enable efficient use of laser light in a bonding technology using laser light.SOLUTION: A joining method includes a lamination step and a bonding step. In the lamination step, a first object to be bonded and a second object to be bonded are stacked such that a heat absorbing layer and a bonding material layer are sandwiched between their bonding surfaces. In the bonding step, the first object to be bonded and the second object to be bonded are bonded by the bonding material layer by irradiating an endothermic layer with a laser beam and thereby heating the bonding material layer using the heat absorbed by the endothermic layer from the laser beam.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a bonding technique using laser light.

Background Art

[0002] As one of the manufacturing techniques for semiconductor devices (such as MEMS), there is a technique for bonding two wafers by utilizing the eutectic reaction of two kinds of metals. In this technique, a metal layer containing one of the two kinds of metals that cause the eutectic reaction as a main component and a metal layer containing the other metal as a main component are respectively formed on the bonding surfaces of the two wafers. Further, as a combination of the two kinds of metals that cause the eutectic reaction, for example, a combination of aluminum (Al) and germanium (Ge) is used. Then, by causing a eutectic reaction at the contact portion of those metal layers, the two wafers are bonded.

[0003] Such a bonding technique is used, for example, to seal sensors (such as gyro sensors, biosensors, etc.) and waveguides in a device. On the other hand, in order to cause the above-mentioned eutectic reaction, it is necessary to heat the contact portion of the two metal layers to the temperature at which the eutectic reaction occurs. Conventionally, in order to achieve this, while sandwiching the two wafers to bring the two metal layers into contact, the entire two wafers together with the sensor to be sealed were heated (for example, see Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] [[ID=]] However, with the conventional bonding technology described above, the sensor being sealed also gets heated, which posed a risk of heat damage to the sensor. Therefore, the sensors that could be sealed within the device were limited to those with high heat resistance. Furthermore, heating the bonding site (to the temperature at which the eutectic reaction occurs) required a long time, and after bonding, it was necessary to gradually relieve the thermal stress on the wafer, requiring a long cooling time as well. This resulted in the problem of a long time required for each bonding process.

[0006] Another problem was that if the two metals mentioned above had different coefficients of thermal expansion, strain could occur at the joint between the two metal layers during heating and cooling. Therefore, in the conventional joining techniques described above, in order to suppress such strain, it was necessary to select two metals with similar coefficients of thermal expansion, which severely limited the freedom of selection.

[0007] Therefore, in recent years, a technique has been proposed to perform localized heating targeting the contact area of ​​two metal layers using laser light (see Patent Document 2). Specifically, two wafers are sandwiched between a quartz plate that is transparent to laser light and another component (such as a chuck), and in that state, laser light is irradiated onto the contact area of ​​the two metal layers through the quartz plate.

[0008] This laser-based bonding technology reduces thermal impact on the sensor because the contact area between the two metal layers is heated locally. As a result, it becomes possible to encapsulate sensors with low heat resistance within the device. Furthermore, because the bonding area between the two metal layers can be heated intensively with laser light, the temperature of the bonding area can be rapidly raised to the temperature at which a eutectic reaction occurs, thereby shortening the time required for the bonding process.

[0009] Furthermore, even if the two metals mentioned above have different coefficients of thermal expansion, and strain occurs during heating or cooling, this strain will only occur in the localized area irradiated by the laser light, resulting in a significantly smaller strain. Consequently, the impact of this strain on the joint between the two metal layers will be minimal. Therefore, when selecting the two metals, it becomes possible to choose those with different coefficients of thermal expansion, increasing the degree of selection flexibility.

[0010] On the other hand, metals that undergo eutectic reactions often have relatively high reflectivity and transmittance, making it difficult to efficiently absorb laser light. Among such metals, germanium (Ge) absorbs laser light relatively well, but even then, its reflectivity is about 35% and transmittance is about 30%, meaning it can only absorb about 35% of the irradiated laser light. For this reason, technologies that use laser light to induce eutectic reactions have had problems such as difficulty in efficiently heating the target metal layer and the potential for reflected or transmitted laser light to adversely affect sensors and other devices.

[0011] Therefore, the objective of the present invention is to enable the efficient use of laser light in bonding technology using laser light. [Means for solving the problem]

[0012] The first joining method according to the present invention comprises a lamination step and a joining process step. In the lamination step, a first joining target and a second joining target are stacked such that a heat-absorbing layer and a joining material layer are sandwiched between their joining surfaces. In the joining process step, a laser beam is irradiated onto the heat-absorbing layer, and the heat absorbed by the heat-absorbing layer from the laser beam is used to heat the joining material layer, thereby joining the first joining target and the second joining target with the joining material layer.

[0013] According to the first bonding method described above, even if the bonding material layer mainly contains a material that does not easily absorb laser light, and therefore it is difficult to efficiently heat the bonding material layer by irradiating it with laser light, irradiating the heat-absorbing layer with laser light allows the heat-absorbing layer to efficiently absorb the laser light, thereby indirectly heating the bonding material layer through the heat-absorbing layer.

[0014] A second joining method according to the present invention is a method for joining a first joining target and a second joining target using laser light, comprising a joining material layer formation step, a lamination step, and a joining treatment step. In the joining material layer formation step, a joining material layer mainly composed of titanium (Ti), chromium (Cr), and at least one of their oxides is formed along at least one of the joining surfaces of the first joining target and the second joining surface. In the lamination step, the first joining target and the second joining target are stacked such that the joining material layer is sandwiched between their joining surfaces. In the joining treatment step, the joining material layer is irradiated with laser light and heated thereby, thereby joining the first joining target and the second joining target with the joining material layer.

[0015] According to the second joining method described above, by irradiating the joining material layer with laser light, the joining material layer efficiently absorbs the laser light, thereby enabling the joining surfaces of two objects to be joined together. [Effects of the Invention]

[0016] According to the present invention, it becomes possible to use laser light efficiently in bonding technology using laser light. [Brief explanation of the drawing]

[0017] [Figure 1] This is a conceptual diagram showing an example of a joining device that can be used in the joining method according to the present invention. [Figure 2] This is a conceptual diagram illustrating the objects to be joined in the first embodiment. [Figure 3](A) Cross-sectional view and (B) plan view showing an example of the pattern shape of the metal layer. [Figure 4] It is a flowchart showing the bonding method according to the first embodiment. [Figure 5] It is a conceptual diagram exemplifying a bonding target in the second embodiment.

Embodiments for Carrying Out the Invention

[0018] [1] Bonding device FIG. 1 is a conceptual diagram showing a bonding device that can be used in the bonding method according to the present invention. As shown in FIG. 1, the bonding device is a device that bonds two bonding targets 101 and 102, and includes a chamber mechanism 1, a pressurizing mechanism 2, a laser light source 3, and a control unit 4. Hereinafter, the configuration of each part will be specifically described.

[0019] <Chamber mechanism 1> The chamber mechanism 1 includes a first chamber component 11, a second chamber component 12, a drive unit 13, and an exhaust unit 14.

[0020] The first chamber component 11 and the second chamber component 12 are parts that constitute a sealed space (hereinafter referred to as "chamber 10") for performing the bonding process, and are configured to be able to selectively realize the formation and opening of the chamber 10 by approaching and separating relatively in the vertical direction. More specifically, it is as follows.

[0021] The first chamber component 11 consists of a first cylindrical portion 111 and a stage 112 supported inside the first cylindrical portion 111 without any gaps. The first cylindrical portion 111 is positioned so that its central axis is aligned with the vertical direction, and the stage 112 is horizontally supported by the first cylindrical portion 111. Here, the stage 112 is a stage that is transparent to laser light and is made of, for example, quartz. Two objects to be joined, 101 and 102, are placed on the stage 112 with their joining surfaces 101a and 102a facing each other. In the example in Figure 1, the objects to be joined 101 and 102 are shown placed on the stage 112 with object 101 facing upwards.

[0022] The second chamber component 12 consists of a second cylindrical portion 121 positioned above the first cylindrical portion 111 and coaxially with the first cylindrical portion 111, and a top plate 122 that closes the upper end of the second cylindrical portion 121. The upper end of the first cylindrical portion 111 and the lower end of the second cylindrical portion 121 are in contact without any gaps, thereby forming a chamber 10 between the stage 112 and the top plate 122.

[0023] The drive unit 13 is the part that moves at least one of the first chamber component 11 and the second chamber component 12 in the vertical direction, thereby bringing them relatively closer together and further apart.

[0024] The exhaust section 14 is the part that reduces the internal pressure of the chamber 10 until the chamber 10 (specifically, the space between the diaphragm 21 and the stage 112, which will be described later) becomes a vacuum. A pressure adjustment device such as a vacuum pump is used in the exhaust section 14. The chamber mechanism 1 may further include a gas supply section that supplies a processing gas (such as argon (Ar) gas) into the chamber 10.

[0025] <Pressurization mechanism 2> The pressurizing mechanism 2 is a mechanism that applies pressure to the joining targets 101 and 102 from the side opposite to the stage 112. In this embodiment, the pressurizing mechanism 2 consists of a diaphragm 21 and a drive unit 22 that operates the diaphragm 21, and applies pressure to the back surface 101b of joining target 101, which is located on the side opposite to the stage 112 of the two joining targets 101 and 102. More specifically, it is as follows.

[0026] The diaphragm 21 is supported without gaps inside the second cylindrical portion 121 so that it can contact the back surface 101b of the object to be joined 101 when the chamber 10 is formed.

[0027] The drive unit 22 operates the diaphragm 21 by transmitting pressure to the diaphragm 21 using the transmission medium 221. More specifically, the transmission medium 221 is filled between the diaphragm 21 and the top plate 122 within the second chamber component 12, and the drive unit 22 operates the diaphragm 21 via the transmission medium 221 by changing the pressure applied to the transmission medium 221. Here, the transmission medium 221 may be a liquid or a gas.

[0028] <Laser light source 3> The laser light source 3 is the part that emits laser light and is positioned below the stage 112, which is transparent to laser light. The laser light source 3 can also irradiate the joining targets 101 and 102 on the stage 112 with laser light through the stage 112, and scan the laser light in a horizontal plane along the pattern shape of the intervening layer, such as the metal layer 201, which will be described later. Furthermore, the laser light source 3 can focus the laser light at the joining point between joining targets 101 and 102.

[0029] <Control Unit 4> The control unit 4 consists of processing units such as a CPU (Central Processing Unit) and a microcomputer, and controls various operating parts of the bonding device (chamber mechanism 1, pressurization mechanism 2, laser light source 3, etc.). Specifically, it is as follows:

[0030] During the joining process, the control unit 4 forms the chamber 10 by bringing the first chamber component 11 and the second chamber component 12 close together and joining them while the two objects to be joined 101 and 102 are placed on the stage 112. The control unit 4 then controls the exhaust unit 14 to reduce the internal pressure of the chamber 10 (specifically, the space between the diaphragm 21 and the stage 112 within the chamber 10) until a vacuum is achieved. The control unit 4 also supplies a processing gas (such as argon (Ar) gas) into the chamber 10 as needed.

[0031] Subsequently, the control unit 4 controls the pressurizing mechanism 2 to apply pressure to the back surface 101b of the object to be joined 101 using the diaphragm 21.

[0032] Here, the diaphragm 21 can flexibly change shape according to the shape of the back surface 101b of the object to be joined 101 when pressure is applied to the back surface 101b, so it can adhere closely to the back surface 101b of the object to be joined 101 and apply uniform pressure, which can deform the object to be joined 101 (including elastic deformation). In addition, the diaphragm 21 can continue to apply uniform pressure to the back surface 101b by following the shape change of the back surface 101b of the object to be joined 101 that accompanies the deformation of the object to be joined 101. Therefore, by applying uniform pressure to the back surface 101b of the object to be joined 101 with the diaphragm 21, even if the pressure is relatively small, it is possible to deform the object to be joined 101 so that the intervening layer (metal layer 201, etc.) is sandwiched between the two objects to be joined 101 and 102 without any gaps, and maintain that state. Furthermore, by reducing the pressure required for joining, the required strength of the stage 112 (the strength to withstand the pressure during joining) also decreases accordingly, and as a result, it becomes possible to make the thickness of the stage 112 relatively small.

[0033] After the pressurization mechanism 2 applies pressure to the back surface 101b of the object to be joined 101, the control unit 4 maintains this state and controls the laser light source 3 to irradiate the joining area between the objects to be joined 101 and 102 via the stage 112. The control unit 4 also scans the laser beam in the horizontal plane along the pattern shape of the intervening layer (metal layer 201, etc.). As a result, the joining surfaces 101a and 102a of the two objects to be joined 101 and 102 are joined together over their entire areas.

[0034] Furthermore, in the bonding device described above, the diaphragm 21 may have a suction surface that attracts the back surface 101b of the object to be bonded 101 (i.e., it may have a function of chucking the object to be bonded 101). The bonding device may also further include an alignment mechanism for adjusting the positional relationship between the object to be bonded 101 held (attracted) by the diaphragm 21 and the object to be bonded 102 placed on the stage 112. As an example, the alignment mechanism can adjust the positional relationship between the object to be bonded 101 held (attracted) by the diaphragm 21 and the object to be bonded 102 placed on the stage 112 by adjusting the position of at least one of the first chamber component 11 and the second chamber component 12 in the horizontal plane.

[0035] In the bonding apparatus described above, the pressurizing mechanism 2 is not limited to one composed of a diaphragm 21, but may be appropriately changed to another mechanism capable of applying pressure to the back surface 101b of the object to be bonded 101. Furthermore, the positional relationship between the stage 112 and the pressurizing mechanism 2 (diaphragm 21) may be appropriately changed to an inverted positional relationship, and the positions of other parts (such as the laser light source 3) may also be appropriately changed accordingly.

[0036] In the bonding apparatus described above, when the object to be bonded 102 is placed on the stage 112, the object to be bonded 102 comes into surface contact with the mounting surface of the stage 112 (the surface on which the object to be bonded 102 is placed). If the object to be bonded 102 is mainly composed of a material with a different refractive index than the material constituting the stage 112 (for example, if the stage 112 is a quartz plate and the object to be bonded 102 is a silicon (Si) wafer), the laser light is more likely to be reflected at the interface between the stage 112 and the object to be bonded 102. Therefore, in order to prevent such reflection of laser light, an anti-reflective film may be formed on the mounting surface of the stage 112.

[0037] Similarly, on the back surface of the stage 112 (the surface opposite to the mounting surface, which is in contact with the air outside the chamber 10), the laser light is reflected due to the difference in refractive index between the stage 112 and the air. Therefore, to prevent such reflection of the laser light, an anti-reflective coating may be formed on the back surface of the stage 112.

[0038] [2] Items to be joined and joining methods [2-1] First Embodiment [2-1-1] Items to be joined Figure 2 is a conceptual diagram showing an example of two joining targets 101 and 102 that can be joined by the joining apparatus described above. The joining targets 101 and 102 are, for example, semiconductor wafers and glass plates, and a heat-absorbing layer 200 and metal layers 201 and 202 (joining material layers) for joining the joining surfaces 101a and 102a are formed on their joining surfaces 101a and 102a as follows.

[0039] A heat-absorbing layer 200 is formed along the joining surface 101a of the object to be joined 101 (heat-absorbing layer formation step), and a metal layer 201 is further formed along the surface of the heat-absorbing layer 200 (joining material layer formation step). Also, a metal layer 202 is formed along the joining surface 102a of the object to be joined 102 (joining material layer formation step). In relation to the "first object to be joined" and "second object to be joined" described in the claims, the object to be joined 101 corresponds to the "first object to be joined," and the object to be joined 102 corresponds to the "second object to be joined."

[0040] Here, metal layer 201 is a bonding material layer mainly containing one of the two metals that undergo a eutectic reaction, and metal layer 202 is a bonding material layer mainly containing the other metal. Examples of combinations of the two metals include aluminum (Al) and germanium (Ge), copper (Cu) and tin (Sn), silver (Ag) and tin (Sn), and indium (In) and tin (Sn).

[0041] On the other hand, many of the metals that undergo eutectic reactions have difficulty efficiently absorbing laser light. For example, metals such as aluminum (Al), silver (Ag), and gold (Au) have high reflectivity, making it difficult to efficiently absorb laser light. Also, germanium (Ge) is a metal that transmits some light (transmittance of about 30%), so if germanium (Ge) is used as the main component in either metal layer 201 or 202, and the thickness of that metal layer is on the order of the wavelength of light, then light interference will occur within the metal layer, thereby inhibiting the absorption of laser light. For this reason, variations in the thickness of the metal layer (for example, a film thickness variation of about ±10%) will cause variations in the laser light absorption efficiency in that metal layer, and consequently, variations in the bonding state. For these reasons, the technology of generating a eutectic reaction using laser light had problems such as difficulty in efficiently heating the target metal layers 201 and 202, and the possibility that reflected or transmitted laser light could adversely affect the sensor 103 and other components.

[0042] Therefore, in this embodiment, the heat-absorbing layer 200 described above is formed to enable efficient use of laser light. Specifically, the heat-absorbing layer 200 is a layer mainly composed of a material that absorbs laser light more easily than the metals constituting the metal layers 201 and 202. More specifically, the heat-absorbing layer 200 is a layer mainly composed of titanium (Ti), chromium (Cr), and at least one of their oxides. Here, titanium (Ti) and chromium (Cr) have higher reflectivity than germanium (Ge), but they are materials that transmit almost no light, which is the cause of the interference phenomenon described above, and can stably absorb about 40% of the irradiated laser light as heat. The material constituting the heat-absorbing layer 200 is not limited to titanium (Ti), chromium (Cr), and their oxides, but can be any various material that absorbs laser light more easily than the metals constituting the metal layers 201 and 202. For example, such a material can be a resin in which a heat-absorbing material such as carbon is dispersed.

[0043] With such a heat-absorbing layer 200, even if the metal layers 201 and 202 mainly consist of metals that do not easily absorb laser light, and therefore it is difficult to efficiently heat the metal layers 201 and 202 by irradiating them with laser light, irradiating the heat-absorbing layer 200 with laser light makes it possible to efficiently absorb the laser light into the heat-absorbing layer 200, thereby indirectly heating the metal layers 201 and 202 through the heat-absorbing layer 200.

[0044] Although not particularly limited, the various layers described above are formed by vacuum deposition (including sputtering and vapor deposition) or coating of various materials onto the bonding surfaces 101a and 102a.

[0045] Figure 2 schematically shows a case where a metal layer 201 is formed over the entire area of ​​the bonding surface 101a and a metal layer 202 is formed over the entire area of ​​the bonding surface 102a. However, in the actual manufacturing process of semiconductor devices (such as MEMS), the metal layers 201 and 202 are patterned into various shapes depending on the shape and application of the device. In this case, the heat-absorbing layer 200 may also be patterned into the same shape as the metal layer 201. Figures 3(A) and (B) are cross-sectional and plan views showing examples of the pattern shapes of the metal layers 201 and 202. Note that Figure 3(B) is a plan view of only the metal layer 202 of the metal layers 201 and 202. In this example, the metal layers 201 and 202 are formed in a rectangular frame shape that surrounds each sensor 103 so that each sensor 103 can be sealed inside the device. The heat-absorbing layer 200 is also formed in the same shape as the metal layer 201. Furthermore, the pattern shapes of metal layers 201 and 202 are not limited to a rectangular frame shape, but can be appropriately changed depending on the shape and application of the device.

[0046] [2-1-2] Joining method Next, a joining method for joining the above-mentioned joining targets 101 and 102 (see Figure 2) using laser light will be described. Figure 4 is a flowchart showing the joining method according to the first embodiment. The joining method of this embodiment includes a lamination process and a joining process performed using the joining apparatus described above. The lamination process and the joining process will be described in detail below. The joining method of this embodiment may further include at least one of the following: a heat-absorbing layer formation process for forming the heat-absorbing layer 200 described above, and a metal layer formation process for forming the metal layers 201 and 202 described above.

[0047] In the lamination process, the objects to be joined 101 and 102 are stacked such that the heat-absorbing layer 200, the metal layer 201, and the metal layer 202 are sandwiched between their joining surfaces 101a and 102a. Specifically, the objects to be joined 101 and 102 are placed on the stage 112 of the joining apparatus in such a state (see Figure 1).

[0048] In the joining process, the heat-absorbing layer 200 is irradiated with laser light, and the heat absorbed by the heat-absorbing layer 200 from the laser light is used to heat the metal layers 201 and 202. Then, the joining surfaces 101a and 102a of the two objects to be joined, 101a and 102a, are joined by using the eutectic reaction between the two metals that occurs as a result of such heating to bond the metal layers 201 and 202.

[0049] Specifically, the control unit 4 of the joining device forms a chamber 10 by bringing the first chamber component 11 and the second chamber component 12 close together and joining them while the two objects to be joined 101 and 102 are placed on the stage 112. The control unit 4 then controls the exhaust unit 14 to reduce the internal pressure of the chamber 10 until a vacuum is achieved inside the chamber 10. Subsequently, the control unit 4 applies pressure to the back surface 101b of the object to be joined 101 with the diaphragm 21 by controlling the pressurizing mechanism 2. Then, while maintaining the applied pressure, the control unit 4 irradiates the heat-absorbing layer 200 with laser light by controlling the laser light source 3 through the stage 112. The control unit 4 also heats the metal layers 201 and 202 over the entire area of ​​the objects to be joined 101 and 102 via the heat-absorbing layer 200 by scanning the laser light in a horizontal plane along the pattern shape of the intervening layer (metal layer 201, etc.). Then, by utilizing the resulting eutectic reaction to bond the metal layers 201 and 202, the bonding surfaces 101a and 102a of the two objects to be joined, 101 and 102, are joined together.

[0050] With this joining method, as described above, the heat-absorbing layer 200 efficiently absorbs the laser light, thereby indirectly heating the metal layers 201 and 202 through the heat-absorbing layer 200, thus enabling joining using laser light efficiently.

[0051] [2-1-3] Variant <First variation> The joining method described above is not limited to joining using a eutectic reaction (eutectic joining), but is also effective when joining two joining targets 101 and 102 with at least one joining material layer, such as joining using materials with high reflectivity or high light transmittance, soldering, or welding, because the heat-absorbing layer 200 can be used to heat the joining material layer. In this case, during the joining material layer formation step, the joining material layer can be formed along at least one of the surface of the heat-absorbing layer 200 and the joining surface 102a of the joining target 102.

[0052] <Second variation> In the bonding method described above, if it is desired to further increase the heat absorption efficiency of the heat absorption layer 200, the surface of the heat absorption layer 200 may be subjected to a treatment to increase its surface roughness, such as chemical treatment or blasting, before the lamination process (surface treatment process).

[0053] <Third variation> In the joining method described above, if at least one of the objects to be joined, 101 and 102, contains a material with high thermal conductivity as its main component, the heat generated by the absorption of laser light by the heat-absorbing layer 200 may diffuse to the objects to be joined, potentially hindering efficient heating of the metal layers 201 and 202.

[0054] Therefore, in order to prevent such heat diffusion, a heat diffusion prevention layer may be formed on the joint surface of the joining objects 101 and 102 that mainly contain a material with high thermal conductivity (prevention layer formation step). In this case, in the heat absorption layer formation step and the metal layer formation step, the heat absorption layer 200 and the metal layer 202 will be formed on the surface of the heat diffusion prevention layer.

[0055] <Fourth variation> The joining method described above is not limited to the main joining method, in which all contact points of the metal layers 201 and 202 are joined with laser light, but may also be used for temporary joining, in which only a few of the contact points of the metal layers 201 and 202 are joined with laser light. Here, temporary joining is a joining process performed to maintain the positional relationship between the joining targets 101 and 102, which has been adjusted by an alignment mechanism (not shown), so that it does not collapse due to vibrations that occur during transport.

[0056] Furthermore, the joining method described above is not limited to the joining apparatus exemplified in Figure 1; other joining apparatuses may be used as long as they are capable of clamping the objects to be joined 101 and 102 and irradiating the joining area with laser light.

[0057] [2-2] Second Embodiment [2-2-1] Target to be joined Figure 5 is a conceptual diagram showing other examples of two bonding targets 101 and 102 that can be bonded by the bonding apparatus described above. Bonding targets 101 and 102 are, for example, semiconductor wafers or glass plates, and a bonding material layer 203 is formed along either one of their bonding surfaces 101a and 102a (bonding material formation step). Here, the bonding material layer 203 is a layer mainly composed of titanium (Ti), chromium (Cr), and at least one of their oxides. In relation to the "first bonding target" and "second bonding target" described in the claims, bonding target 101 may be understood as the "first bonding target" and bonding target 102 as the "second bonding target," or conversely, bonding target 102 may be understood as the "first bonding target" and bonding target 101 as the "second bonding target." Furthermore, the bonding material layer 203 may be formed on both bonding surfaces 101a and 102a.

[0058] Titanium (Ti), chromium (Cr), and their oxides are metals that readily absorb laser light, as described in the first embodiment. The inventors have found that by forming a bonding material layer 203 using titanium (Ti), chromium (Cr), or their oxides, which possess such properties, the bonding surfaces 101a and 102a of two objects to be bonded 101 and 102 can be bonded together using only the bonding material layer 203, without the need for metal layers 201 and 202 that bond through a eutectic reaction as in the first embodiment.

[0059] Therefore, with the above-described bonding material layer 203, by irradiating the bonding material layer 203 with laser light, the bonding material layer 203 efficiently absorbs the laser light, thereby making it possible to bond the bonding surfaces 101a and 102a of the two objects to be bonded 101 and 102 together.

[0060] [2-2-2] Joining method Next, a joining method for joining the above-mentioned joining targets 101 and 102 (see Figure 5) using laser light will be described. The joining method of this embodiment includes a lamination process and a joining process performed using the joining apparatus described above, similar to the flowchart shown in Figure 4. The lamination process and the joining process will be described in detail below. The joining method of this embodiment may further include a joining material layer formation process for forming the joining material layer 203 described above.

[0061] In the lamination process, the objects to be joined 101 and 102 are stacked such that a bonding material layer 203 is sandwiched between their bonding surfaces 101a and 102a. Specifically, the objects to be joined 101 and 102 are placed on the stage 112 of the bonding apparatus in such a state (see Figure 1).

[0062] In the joining process, a laser beam is irradiated onto the joining material layer 203, causing the joining material layer 203 to absorb the laser beam and heat it. This heating of the joining material layer 203 then joins the joining surfaces 101a and 102a of the two objects to be joined, 101 and 102.

[0063] Specifically, the control unit 4 of the joining device forms a chamber 10 by bringing the first chamber component 11 and the second chamber component 12 close together and joining them while the two objects to be joined 101 and 102 are placed on the stage 112. The control unit 4 then controls the exhaust unit 14 to reduce the internal pressure of the chamber 10 until a vacuum is created inside the chamber 10. Subsequently, the control unit 4 applies pressure to the back surface 101b of the object to be joined 101 using the diaphragm 21 by controlling the pressurizing mechanism 2. Then, while maintaining the applied pressure, the control unit 4 controls the laser light source 3 to irradiate the joining material layer 203 with laser light via the stage 112. The control unit 4 also heats the joining material layer 203 over the entire area of ​​the objects to be joined 101 and 102 by scanning the laser light in a horizontal plane along the pattern shape of the joining material layer 203. Then, by heating the bonding material layer 203, the bonding surfaces 101a and 102a of the two objects to be bonded 101 and 102 are joined together.

[0064] According to this joining method, as described above, the joining material layer 203 efficiently absorbs the laser light, thereby enabling the joining of the two joining targets 101 and 102, and thus achieving joining using laser light efficiently.

[0065] [2-2-3] Variation <Fifth variation> In the joining technology described above, as in the first embodiment, a heat diffusion prevention layer may be formed on the joining surface of the objects to be joined in order to prevent heat diffusion to the objects to be joined (prevention layer formation step).

[0066] <Sixth variation> The joining technique described above, as in the first embodiment, may be used not only for the main joining but also for temporary joining. Furthermore, the joining method described above may use any joining device that is capable of clamping the objects to be joined 101 and 102 and irradiating the joining area with laser light, not limited to the joining device exemplified in Figure 1.

[0067] The above-described embodiments and modifications should be considered in all respects as illustrative and not restrictive. The scope of the present invention is indicated by the claims, rather than by the above-described embodiments and modifications. Furthermore, the scope of the present invention is intended to include all modifications within the meaning and scope equivalent to the claims.

[0068] Furthermore, the embodiments and modifications described above may not limit the subject matter of the invention to the joining method described above, but may also include parts of the processes constituting the joining method (for example, lamination processes and joining processes) or joining equipment used in the joining method. [Explanation of Symbols]

[0069] 1. Chamber mechanism 2. Pressurization mechanism 3. Laser light source 4. Control Unit 10 Chambers 11. First Chamber Component 12 Second Chamber Component 13 Drive unit 14 Exhaust section 21 Diaphragm 22 Drive unit 101, 102 Joining targets 101a, 102a joint surface 101b Back 103 Sensor 111 First cylindrical section 112 stages 121 Second cylindrical section 122 Top plate 200 Endothermic layer 201, 202 Metal layer (bonding material layer) 203 Bonding material layer 221 Communication medium

Claims

1. A lamination process in which the first object to be joined and the second object to be joined are stacked such that a heat-absorbing layer and a joining material layer are sandwiched between their joining surfaces, After the lamination process, a pressurizing step is performed in which pressure is applied to the back surface of the first or second object to be joined using a pressure transmission medium that is a gas or liquid. A bonding process in which, after the pressurization step, laser light is irradiated onto the heat-absorbing layer, and the bonding material layer is heated by utilizing the heat absorbed by the heat-absorbing layer from the laser light, thereby bonding the first and second objects to be bonded together with the bonding material layer, A joining method comprising the following features.

2. The bonding method according to claim 1, wherein the heat-absorbing layer is a layer mainly composed of titanium (Ti), chromium (Cr), and at least one of their oxides.

3. A surface treatment step to increase the surface roughness of the heat-absorbing layer before the lamination process. The joining method according to claim 1 or 2, further comprising the above.

4. A lamination step in which a first object to be joined and a second object to be joined are stacked such that a joining material layer containing at least one of titanium (Ti), chromium (Cr), and their oxides as the main components is sandwiched between their joining surfaces, After the lamination process, a pressurizing step is performed in which pressure is applied to the back surface of the first or second object to be joined using a pressure transmission medium that is a gas or liquid. A bonding process in which, after the pressurizing step, laser light is irradiated onto the bonding material layer, thereby heating the bonding material layer, and the first and second objects to be bonded are bonded together by the bonding material layer. A joining method comprising the following features.

5. The joining method according to any one of claims 1, 2, and 4, wherein a heat diffusion prevention layer is formed on at least one of the joining surfaces of the first and second objects to be joined.

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