Glass bonding method for semiconductor chip, method for manufacturing pressure sensor, and bonding apparatus

Abstract

When glass bonding a semiconductor chip to an object to be bonded, the temperature of a chip heater is controlled to be lower than the heat resistance temperature of the semiconductor chip, and the semiconductor chip is heated by the chip heater. The temperature of the substrate heater is controlled to be higher than the temperature of the chip heater and the softening point of the low-melting-point glass, and the bonded object is heated by the substrate heater. It is preferable that at least a portion of the surface of the chip heater, which is in contact with the surface of the semiconductor chip, is configured from a material having a linear expansion coefficient that is 1 / 2 to 2 times the linear expansion coefficient of the semiconductor chip. As a result, provided are a method capable of achieving more reliable glass bonding and prevention of damage to a semiconductor chip due to heating, and a bonding apparatus capable of implementing the method.

Description

Technical Field

[0001] The present invention relates to a glass bonding method for a semiconductor chip, a manufacturing method for a pressure sensor, and a bonding device. Background Art

[0002] It is known that there is a type of pressure sensor that uses a strain sensor composed of a semiconductor chip to measure the strain of a diaphragm that is deformed according to changes in the pressure of a fluid. The pressure sensor is required to measure the pressure of various types of fluids such as corrosive gases. Therefore, for the components constituting the pressure sensor, such as the diaphragm that is in direct contact with the fluid, stainless steel with excellent corrosion resistance is mostly used. In this case, there is the following problem: if the difference in thermal expansion coefficient between the material constituting the strain sensor and the material constituting the diaphragm is large, the strain sensor cannot be well bonded to the diaphragm, or errors are easily generated in the measurement of strain due to the generation of thermal stress associated with temperature changes.

[0003] In view of the above-mentioned problem, for example, in Patent Document 1, there is described an invention of a pressure sensor in which, when a strain detection element composed of a semiconductor chip and a base are bonded using a bonding layer composed of low-melting-point glass, the bonding layer is made into a multilayer structure composed of three materials having different thermal expansion coefficients, thereby alleviating the generation of thermal stress. In addition, for example, in Patent Document 2 applied for by the present inventor, there is described an invention of a pressure sensor in which a strain sensor is bonded to a beam that is linked to a diaphragm and is composed of a material having a thermal expansion coefficient close to that of the strain sensor, thereby alleviating the generation of thermal stress.

[0004] Furthermore, there is known a bonding device that can heat the workpiece for a short time while pressing the workpiece toward the substrate to perform solder bonding. For example, Patent Document 3 describes the invention of a bonding device that monitors the temperature of a heater that presses the workpiece using a temperature sensor and flows a large pulse current through the heater after phase control, thereby performing solder bonding in a short time.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2017-211338

[0008] Patent Document 2: International Publication No. 2016 / 056555

[0009] Patent Document 3: Japanese Patent Application Laid-Open No. 11-54904 Summary of the invention

[0010] Problem that the invention aims to solve

[0011] In the pressure sensor described in Patent Document 1, a bonding layer having a multilayer structure is used for bonding between the strain sensor and the diaphragm. Therefore, there is a problem that the formation of the bonding layer takes time and / or cost, or multiple temperature settings are required during bonding, which complicates the manufacturing process. In the pressure sensor described in Patent Document 2, there is a problem that the temperature of the strain sensor is likely to rise when the beam and the strain sensor are heated and bonded using solder or low-melting-point glass, which may have an adverse effect on the operation of the strain sensor.

[0012] It is considered to apply the heating method in the bonding device for solder bonding described in Patent Document 3 to the glass bonding of the semiconductor chip as the object of the present invention. However, since the softening point of glass is higher than the melting point of solder, even if the heating time is shortened by passing a pulsed current through the heater, it is impossible to solve the problem that the temperature of the strain sensor is likely to rise due to the softening of the glass.

[0013] The present invention is completed in view of the above-mentioned problems, and its purpose is to provide a glass bonding method and a bonding device capable of implementing the method. When using glass bonding to manufacture a pressure sensor, the glass bonding method can heat the temperature of the bonding layer to a temperature higher than the softening point of the glass, and at the same time can avoid the temperature of the strain sensor in contact with the bonding layer from exceeding the heat resistance temperature.

[0014] Solutions for solving problems

[0015] In one embodiment, the present invention is an invention of a glass bonding method for semiconductor chips. The method can be implemented by sequentially executing the following steps.

[0016] First step S1: A bonding layer made of low-melting-point glass is provided on a predetermined surface of an object to be bonded, that is, a substrate bonding surface.

[0017] Second step S2: The object to be bonded is placed on the substrate heater so that the surface of the object to be bonded, which is the surface on the opposite side to the substrate to be bonded surface, that is, the substrate heated surface, contacts the surface of the substrate heater.

[0018] Third step S3: placing a semiconductor chip on the surface of the bonding layer.

[0019] Fourth step S4: The surface of the chip heater is brought into contact with the chip heated surface, which is the surface of the semiconductor chip opposite to the chip bonded surface that contacts the bonding layer.

[0020] Step 5 S5: forming a clamping state, in which the semiconductor chip, the bonding layer and the object to be bonded are clamped by the chip heater and the substrate heater in a first direction, and the first direction is a stacking direction of the semiconductor chip, the bonding layer and the object to be bonded.

[0021] Step 6 S6: While maintaining the clamping state, the temperature of the chip heater is controlled to a first temperature while the semiconductor chip is heated by the chip heater, and the temperature of the substrate heater is controlled to a second temperature while the bonded object is heated by the substrate heater, wherein the first temperature is a specified temperature lower than the heat resistance temperature of the semiconductor chip, and the second temperature is a specified temperature higher than the temperature of the chip heater and the softening point of the low-melting-point glass.

[0022] Seventh step S7: While maintaining the clamping state, the temperature of the chip heater and the temperature of the substrate heater are lowered to cool the low melting point glass constituting the bonding layer.

[0023] Eighth step S8: The clamping state is released, and the bonded body formed by bonding the semiconductor chip glass to the bonded object is taken out.

[0024] By applying the method of the present invention using two heating units consisting of a chip heater and a substrate heater, the temperature of the bonding layer can be heated to a temperature higher than the softening point of the low melting point glass without the temperature of the semiconductor chip exceeding the heat resistance temperature.

[0025] In a preferred embodiment, at least the portion of the surface of the chip heater that contacts the heated surface of the chip is formed of a material having a linear expansion coefficient that is greater than 1 / 2 and less than 2 times the linear expansion coefficient of the semiconductor chip. In this embodiment, it is difficult to cause a displacement caused by the difference in thermal expansion coefficient between the chip heater and the semiconductor chip during the pressurized bonding process, so damage to the semiconductor chip can be suppressed, and a more reliable bonding can be performed. In other embodiments, the present invention is an invention of a method for manufacturing a pressure sensor and an invention of a bonding device.

[0026] Effects of the Invention

[0027] According to the present invention, compared with the conventional glass bonding method using a single heating unit, it is possible to avoid damage to the semiconductor chip caused by heat and bond the semiconductor chip to the object to be bonded more reliably. Thus, the manufacturing yield of the pressure sensor is improved and the reliability is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a flow chart showing the glass bonding method of the semiconductor chip according to the present invention.

[0029] Figure 2It is a schematic cross-sectional view showing changes in the positional relationship of each member accompanying the progress of the semiconductor chip glass bonding method of the present invention.

[0030] Figure 3 This is a schematic cross-sectional view showing an example of the bonding apparatus of the present invention including a substrate heater including a heat generating portion and a heat adapter.

[0031] Figure 4 It is a schematic cross-sectional view showing an example of the auxiliary heating unit of the present invention.

[0032] Figure 5 It is a schematic perspective view showing an example of the auxiliary heating unit of the present invention.

[0033] Figure 6 1 is a flow chart showing a method for manufacturing a pressure sensor according to the present invention.

[0034] Figure 7 It is a schematic cross-sectional view showing an example of the bonding device of the present invention.

[0035] Figure 8 It is a schematic diagram showing an example of the shape of the chip heater of the present invention.

[0036] Fig. 9 This is a graph showing an example of a heating temperature curve of the heater of the present invention. DETAILED DESCRIPTION

[0037] Hereinafter, the mode for implementing the present invention will be described in detail. The following description and drawings show examples of the mode for implementing the present invention, and the mode for implementing the present invention is not limited to the mode shown in the following description and drawings.

[0038] <First embodiment>

[0039] In the first embodiment, the present invention is an invention of a method for bonding a semiconductor chip glass to an object to be bonded. Figure 1 is a flow chart showing this method. Figure 1 As shown, the method includes eight steps S1 to S8. Unless otherwise specified, each step can be executed after the execution of the previous step is completed. Therefore, the eight steps are preferably executed in principle in the order described below. Figure 2 It means according to Figure 1 The flowchart shown is a schematic cross-sectional view showing changes in the positional relationship of each member accompanying the progress of the semiconductor chip glass bonding method of the present invention.

[0040] The first step S1 is as follows: Figure 2 As shown in (a) of the example, on a predetermined surface of the object to be bonded 4, that is, the substrate to be bonded surface ( Figure 2The step of providing a bonding layer 3 composed of low-melting-point glass (on the upper surface of the bonding object 4). The bonded object 4 refers to a component to which a semiconductor chip is to be bonded using the method of the present invention. As a specific example of the bonded object 4, for example, a diaphragm constituting a pressure sensor or a beam linked to the diaphragm can be cited. The bonding layer 3 in the present invention is a layered adhesive provided on the surface of the bonded object 4, and is composed of low-melting-point glass. Low-melting-point glass has higher insulation properties than solder, and therefore has the effect of preventing electrical noise from the bonded object 4 from being transmitted to the semiconductor chip. In addition, low-melting-point glass is also superior to solder in the long-term stability of bonding.

[0041] The low-melting-point glass constituting the bonding layer 3 in the present invention refers to a glass-based material developed mainly as a sealant or adhesive when assembling devices and has a softening point of approximately 400°C or less. As the low-melting-point glass used in the present invention, for example, low-melting-point glasses such as bismuth-based (main components: Bi2O3, ZnO), lead-based (main components: SiO2, B2O3, PbO) and vanadium-based (main components: TeO2, V2O5) can be cited, but are not limited to them. The bonding layer 3 in the present invention may be composed of only one type of low-melting-point glass, or may have a structure in which layers composed of two or more types of low-melting-point glasses are overlapped.

[0042] The purpose of providing the bonding layer 3 in the first step S1 is to place the bonding layer between the semiconductor chip and the object to be bonded 4 to bond the two. The position of providing the bonding layer 3 on the surface of the object to be bonded 4, the shape of the bonding layer 3 and the thickness of the bonding layer 3 can be appropriately determined according to the above-mentioned purpose. As a specific means for providing the bonding layer 3, for example, a method can be adopted in which a glass paste prepared by mixing the above-mentioned low-melting-point glass with an organic binder (also referred to as an "organic carrier") composed of an organic solvent and a resin is provided at a predetermined position of the object to be bonded 4 by screen printing. By heating the object to be bonded 4 coated with the glass paste by this method to remove the organic solvent and firing it, it is possible to prepare an object to be bonded 4 having a bonding layer 3 composed of a low-melting-point glass on the surface.

[0043] The next step S2 is as follows Figure 2 As shown in (b) of the example, the surface of the object to be bonded 4 on the opposite side of the substrate to be bonded surface ( Figure 2The step of placing the object to be bonded 4 on the substrate heater 6 in such a manner that the substrate (i.e., the heated surface of the substrate) contacts the surface of the substrate heater 6. The substrate heater 6 is a heater used for the purpose of heating the object to be bonded 4. The substrate heater 6 is provided with a temperature sensor for measuring its own temperature, and the substrate heater 6 can be heated to a predetermined temperature by a temperature control unit not shown. The "substrate" of the substrate heater 6 is a term named after the object to be bonded 4, on which the semiconductor chip is mounted, as a substrate.

[0044] In addition, the substrate heater 6 itself can be configured such that the surface of the substrate heater 6 in contact with the object 4 to be bonded is along the heated surface of the substrate of the object 4 to be bonded, so that the substrate heater 6 is in direct contact with the object 4 to heat the object 4 to be bonded. Alternatively, the substrate heater 6 can be configured using a portion of the substrate heater 6 having a heating element, namely a heating portion, and a portion located between the object 4 to be bonded and the heating portion, namely a thermal adapter, so that the object 4 to be bonded is heated by conducting heat from the heating portion to the object 4 via the thermal adapter. In this case, the thermal adapter can be configured such that the surface of the thermal adapter in contact with the heating portion is along the shape of the heating portion, and the thermal adapter can be configured such that the surface of the thermal adapter in contact with the object to be bonded is along the shape of the heated surface of the substrate. According to this structure, by replacing the thermal adapter according to the shape of the heated surface of the substrate, one substrate heater (the heating portion) can be used to heat a variety of objects 4 to be bonded.

[0045] Figure 3 2 is a schematic cross-sectional view showing an example of a bonding device of the present invention including a substrate heater composed of a heat generating portion and a heat adapter as described above. Figure 3 In the illustrated bonding device 1, the substrate heater 6 is composed of a portion having a heating element (not shown), namely a heating portion 6h, and a portion located between the beam 4a as the bonded object 4 and the heating portion 6h, namely a heat adapter 6a. The surface of the heat adapter 6a in contact with the heating portion 6h is configured to be along the shape of the heating portion 6h, and the surface of the heat adapter 6a in contact with the bonded object 4 is configured to be along the shape of the substrate heated surface. As a result, the bonded object 4 can be heated by conducting heat from the heating portion 6h to the bonded object 4 via the heat adapter 6a. In addition, when heating the bonded object 4 having a different shape of the substrate heated surface, by replacing it with a heat adapter 6a that matches the shape of the substrate heated surface of the bonded object 4, the bonded object 4 can be heated without replacing the heating portion 6h.

[0046] When the object to be bonded 4 is placed on the substrate heater 6 in the second step S2, the surface of the object to be bonded 4, which is the surface on the opposite side of the substrate bonded surface, that is, the surface on the side where the bonding layer is not provided, is brought into contact with the surface of the substrate heater 6. By doing so, the substrate heated surface is in direct contact with the surface of the substrate heater 6, and thus it is convenient to apply pressure to the object to be bonded 4 from the substrate heater 6 in the subsequent fifth step S5 and to heat the object to be bonded 4 by the substrate heater 6 in the sixth step S6. In addition, the bonding layer 3 provided in the first step S1 is exposed to the surface of the object to be bonded 4 placed on the surface of the substrate heater 6, and thus it is possible to easily bring the semiconductor chip into contact with the surface of the bonding layer 3 in the subsequent third step S3. When as Figure 2 When the bonding layer 3 is provided on the upper surface of the object 4 as illustrated, it is preferable because the semiconductor chip can be easily mounted on the surface of the bonding layer 3. In the following description, the case where the bonding layer 3 is provided on the upper surface of the object 4 is described.

[0047] As a specific means for placing the object to be bonded 4 on the substrate heater 6 in the second step S2, a known method such as an operation based on a human hand or an operation based on a robot arm can be adopted. In terms of positioning accuracy and / or production efficiency, the latter method is preferred. More preferably, the robot arm is equipped with a shooting unit such as a CCD camera, and the operation is performed while analyzing and determining the position and / or direction of the object to be bonded placed on the substrate heater based on the image.

[0048] The next step S3 is as follows Figure 2 The step of placing the semiconductor chip 2 on the surface of the bonding layer 3 as illustrated in (c). The purpose of the third step S3 is to accurately place the semiconductor chip 2 in the correct orientation at a predetermined position on the surface of the bonding layer 3 at the position where the semiconductor chip 2 is to be bonded in the first step S1. In the third step S3, the semiconductor chip 2 placed on the surface of the bonding layer 3 has not yet been bonded to the glass of the object 4 to be bonded. Therefore, it is preferred to keep the surface of the bonding layer 3 horizontal and take care not to apply vibration to the semiconductor chip 2 to avoid displacement of the position of the semiconductor chip 2.

[0049] In this specification, "semiconductor chip" refers to a chip with a semiconductor integrated circuit mounted on the surface of a substrate (silicon substrate) composed of silicon wafers. The semiconductor chip 2 used in the present invention is preferably a semiconductor chip called a so-called bare chip. A bare chip refers to a semiconductor chip that does not have a package and thus exposes the silicon substrate. The bare chip is directly affected by the surrounding environment due to the lack of packaging. Therefore, if a bare chip is used to form a sensor, the sensitivity of the sensor can be improved. On the other hand, the bare chip is also easily affected by electrical noise, so noise needs to be considered when using it.

[0050] As a specific means of operating the semiconductor chip 2 in the third step S3, a known method such as operation based on human hands or operation based on a robot arm can be adopted. In terms of positioning accuracy and / or production efficiency, the latter method is preferred. More preferably, the robot arm is equipped with a shooting unit such as a CCD camera, and the operation is performed while analyzing and determining the position and / or direction of the bonding layer on which the semiconductor chip is placed based on the image.

[0051] The next step S4 is as follows Figure 2 As shown in (d), the surface of the top portion 5a of the chip heater 5 is aligned with the surface of the semiconductor chip 2 that contacts the bonding layer 3, that is, the surface on the opposite side of the chip to be bonded ( Figure 2 The chip heater 5 is a heater used for heating the semiconductor chip 2 and is an independent heating unit separated from the substrate heater 6. Like the substrate heater 6, the chip heater 5 also has a temperature sensor for measuring its own temperature, and the chip heater 5 can be heated to a predetermined temperature by a temperature control unit not shown.

[0052] The chip heater 5 may also be configured to have the functions of vacuum adsorbing the semiconductor chip 2 and releasing the adsorption, and the chip heater 5 may be driven by a robot. In this case, by performing the third step S3 of vacuum adsorbing the semiconductor chip 2 by the chip heater 5 having a robot and placing the semiconductor chip 2 on the surface of the bonding layer 3, the fourth step S4 of bringing the surface of the chip heater 5 into contact with the surface of the semiconductor chip 2 is also performed simultaneously.

[0053] In the fourth step S4, the surface of the chip heater 5 is brought into contact with the surface of the semiconductor chip 2 that is in contact with the bonding layer, that is, the surface on the opposite side of the chip bonding surface, that is, the chip heating surface. By doing so, the chip heating surface is in direct contact with the surface of the chip heater 5, so it is convenient to apply pressure to the semiconductor chip 2 from the chip heater 5 in the subsequent fifth step S5 and to heat the semiconductor chip 2 using the chip heater 5 in the sixth step S6.

[0054] The next fifth step S5 is a step of forming a clamping state, in which the semiconductor chip 2, the bonding layer 3, and the object to be bonded 4 are clamped in the first direction by the chip heater 5 and the substrate heater 6. The first direction is the stacking direction of the semiconductor chip 2, the bonding layer 3, and the object to be bonded 4. In the fifth step S5, the chip heater 5 and the substrate heater 6 are used to sandwich the entire structure formed by the semiconductor chip 2, the bonding layer 3, and the object to be bonded 4 from two directions, and a force is applied in the direction (compression direction) of the overlapping structure (refer to Figure 2Specifically, a driving mechanism is provided in one or both of the chip heater 5 and the substrate heater 6, and pressure is generated by driving in a direction that brings the two closer. As the driving mechanism, a known unit such as a foot pedal or an electric actuator can be used.

[0055] In the fifth step S5, pressure is applied in the direction (stacking direction) in which the semiconductor chip 2, the bonding layer 3 and the object to be bonded 4 overlap. In other words, for the structure formed by the overlapping of the semiconductor chip 2, the bonding layer 3 and the object to be bonded 4, compressive stress is applied in a direction perpendicular to the stacking surface. At this time, if the components are arranged in such a way that the surfaces of the chip heater 5 and the substrate heater 6 to which stress is applied are parallel to the above-mentioned stacking surface, the force transmission efficiency is the highest. On the other hand, if the surfaces of the chip heater 5 and the substrate heater 6 are inclined relative to the above-mentioned stacking surface, there is the possibility, for example, that the distance between the semiconductor chip 2 and the object to be bonded 4 becomes uneven, thereby reducing the insulation between the two, so that the electrical noise from the object to be bonded 4 is easily transmitted to the semiconductor chip 2, or the semiconductor chip 2 cannot be arranged in the correct orientation relative to the object to be bonded 4, so that it is difficult to exert the desired performance of the semiconductor chip 2 (for example, the performance as a strain gauge, etc.).

[0056] The purpose of applying pressure in the fifth step S5 is to flatten the softened low-melting glass while making it flow when the low-melting-point glass constituting the bonding layer 3 is heated to above the softening point in the subsequent sixth step S6, so that the low-melting-point glass is tightly attached to the surfaces of the semiconductor chip 2 and the object to be bonded 4 without gaps, thereby forming a strong bonding layer 3. If the pressure is too small, gaps will remain in the bonding layer 3 and the bonding force will be reduced. If the pressure is too large, the semiconductor chip 2 will be damaged, or the bonding layer 3 will become too thin, making the electrical insulation between the semiconductor chip 2 and the object to be bonded 4 insufficient. The preferred pressure range is greater than 0.25 Newtons per square millimeter and less than 0.65 Newtons per square millimeter. In order to adjust the pressure, for example, a force-applying unit such as a spring can be provided in at least one of the driving mechanisms of the chip heater 5 and the substrate heater 6.

[0057] The next step 6 S6 is the following step: under a state where pressure is applied, that is, while maintaining the above-mentioned clamping state, the temperature of the chip heater 5 is controlled to a first temperature while the semiconductor chip 2 is heated by the chip heater 5, and the temperature of the substrate heater 6 is controlled to a second temperature while the bonded object 4 is heated by the substrate heater 6, wherein the first temperature is a prescribed temperature lower than the heat resistance temperature of the semiconductor chip 2, and the second temperature is a prescribed temperature higher than the temperature of the chip heater 2 and the softening point of the low-melting-point glass.

[0058] As described above, the chip heater 5 and the substrate heater 6 are provided with temperature sensors that measure their own temperatures independently, and the temperature control unit can be used to heat the chip heater 5 and the substrate heater 6 to independently set temperatures. When the method of the present invention is repeatedly performed, the semiconductor chip 2 and the bonded object 4, which are the objects heated by the chip heater 5 and the substrate heater 6, are constantly replaced, so it is difficult to set temperature sensors on these components to measure the temperature. Therefore, as an alternative means, the temperature of the heater itself is measured. By investigating the correlation between the temperature of the heater and the temperature of the object to be heated in advance, the temperature of the object can be estimated to a certain extent.

[0059] In the sixth step S6, the semiconductor chip 2 is heated by the chip heater 5 while the temperature of the chip heater 5 is controlled to be a first temperature lower than the heat resistance temperature of the semiconductor chip 2. The heat resistance temperature of the semiconductor chip 2 slightly varies depending on the type of the semiconductor chip 2, but is generally higher than 400°C and lower than 500°C. More precisely, it is above 425°C and below 475°C. By controlling the temperature of the chip heater 5 that is in direct contact with the surface of the semiconductor chip 2 to a first temperature lower than the heat resistance temperature of the semiconductor chip 2, for example, 400°C, damage to the semiconductor chip 2 caused by heating can be prevented before it occurs.

[0060] In the sixth step S6, the substrate heater 6 is used to heat the object 4 to be bonded while controlling the temperature of the substrate heater 6 to a second temperature higher than the temperature of the chip heater 5 and the softening point of the low-melting glass. The softening point of the low-melting glass slightly varies depending on the type of low-melting glass, but is generally higher than 400°C and lower than 450°C. As described above, the temperature of the chip heater 5 is controlled to a first temperature lower than the heat-resistant temperature of the semiconductor chip 2, and the first temperature is often lower than the softening point of the low-melting glass. Therefore, if the temperature of the substrate heater 6 is made the same as the temperature of the chip heater 5, it may not be possible to soften the low-melting glass constituting the bonding layer 3. Therefore, in the present invention, the temperature of the substrate heater 6 is controlled to a second temperature higher than the temperature of the chip heater 5 (i.e., the first temperature) and the softening point of the low-melting glass, so that the low-melting glass is reliably softened and glass bonding is achieved. Such temperature control is achieved by the method of the present invention in which the temperatures of the chip heater 5 and the substrate heater 6 are independently controlled.

[0061] In principle, the sixth step S6 is performed under pressure, that is, while maintaining the clamping state. This is because, as described above, if pressure is not applied in advance from the chip heater 5 and the substrate heater 6 to make the surface of the heater close to the object, the heat of the heater cannot be efficiently transferred to the object. In addition, if pressure is not applied in advance at the moment when the low-melting point glass begins to soften due to heating, an ideal bonding layer 3 tightly filled with low-melting point glass cannot be formed. Needless to say, by continuously applying pressure during the heating step, the glass bonding of the present invention can be achieved. However, in the present invention, it is allowed to start the pressurizing step (the fifth step S5) and the heating step (the sixth step S6) substantially at the same time for the purpose of, for example, improving production efficiency.

[0062] In the sixth step S6, it is preferred that after the semiconductor chip 2 is heated to a predetermined temperature by the chip heater 5 and the bonded object 4 is heated to a predetermined temperature by the substrate heater 6, their temperatures are maintained for a certain period of time. This is because it takes time for heat diffusion for the temperature of the entire bonding layer to reach a temperature above the softening point. The semiconductor chip 2 heated by the chip heater 5 and the bonded object 4 heated by the substrate heater 6 are bonded by a bonding layer 3 having a thickness of about 30 μm. When the temperature (second temperature) of the substrate heater 6 is controlled to be higher than the temperature (first temperature) of the chip heater 5 and maintained, heat is transferred from the bonded object 4 heated to a high temperature to the semiconductor chip 2 through the thinner bonding layer 3, and the temperature of the semiconductor chip 2 may exceed the heat-resistant temperature. In order to prevent such an undesirable situation, for example, the following method is effective: adjusting the holding temperature (first temperature) of the chip heater 5 and the holding temperature (second temperature) of the substrate heater 6 or shortening the holding time of the temperature, and ending the sixth step S6 before the temperature of the semiconductor chip 2 reaches the heat-resistant temperature due to the heat of the substrate heater 6.

[0063] The next step 7 S7 is the following step: while maintaining the pressure, that is, while maintaining the clamping state, the temperature of the chip heater 5 and the temperature of the substrate heater 6 are lowered to cool the low-melting-point glass constituting the bonding layer 3. If the bonding layer 3 composed of the low-melting-point glass softens in the previous step 6 S6, the low-melting-point glass penetrates into the gap between the semiconductor chip 2 and the object to be bonded 4 due to the pressure, forming a thinner bonding layer 3. If the low-melting-point glass is cooled while maintaining the pressure in the step 7 S7, the bonding layer 3 changes to a hard glass state while being in close contact with the surface of the semiconductor chip 2 and the surface of the object to be bonded 4, thereby achieving a strong glass bond.

[0064] If the speed of lowering the temperature of the chip heater 5 and the substrate heater 6 in step 7 S7 is too slow, the semiconductor chip 2 may be damaged by heat or the production efficiency may be reduced. In addition, if the speed is too fast, cracks may sometimes occur in the bonding layer 3. The preferred cooling rate range is 50°C per minute or more and 150°C per minute or less. The temperature of the chip heater 5 and the substrate heater 6 can be lowered to room temperature at a constant cooling rate, the power supply of the heater can be cut off after reaching a certain temperature, or the power supply of the heater can be cut off after reaching a certain temperature and maintaining the temperature for a certain period of time.

[0065] The next final step 8 S8 is a step of releasing the pressure, that is, releasing the clamping state and taking out the bonded body formed by glass bonding the semiconductor chip 2 to the bonded object 4. Since a strong bonding layer has been formed in the previous step 7 S7, the bonding between the semiconductor chip 2 and the bonded object 4 will not peel off even if the pressure is released in the 8th step S8. In order to release the pressure, the above-mentioned driving mechanism is activated to drive one or both of the chip heater 5 and the substrate heater 6 in a direction away from each other. In addition, in order to take out the bonded body, for example, the method of using a robot arm to vacuum adsorb the surface of the semiconductor chip 2 and move the bonded body as described in the 2nd step S2 can be adopted.

[0066] By implementing the method of the present invention described above, it is possible to use a low-melting-point glass having a softening point higher than the heat-resistant temperature of the semiconductor chip for the bonding layer and bond the semiconductor chip glass to the object to be bonded. As shown in step 6 S6, since the temperature of the chip heater is controlled to be lower than the heat-resistant temperature of the semiconductor chip while the semiconductor chip is heated by the chip heater, the temperature of the semiconductor chip will not exceed its heat-resistant temperature. In addition, since the temperature of the substrate heater is controlled to be higher than the temperature of the chip heater and the softening point of the low-melting-point glass while the object to be bonded is heated by the substrate heater, the low-melting-point glass can be softened to complete the glass bonding.

[0067] In a preferred embodiment of the present invention, at least the portion of the surface of the chip heater that contacts the heated surface of the chip is formed by a material having a linear expansion coefficient that is more than 1 / 2 and less than 2 times the linear expansion coefficient of the semiconductor chip. In the method of the present invention, the surface of the chip heater is brought into contact with the surface of the semiconductor chip that is not in contact with the bonding layer (i.e., the heated surface of the chip) (the fourth step S4), pressure is applied by the chip heater and the substrate heater (the fifth step S5), the semiconductor chip is heated by the chip heater, and the bonded object is heated by the substrate heater (the sixth step S6). In addition, the temperature of the chip heater and the substrate heater is lowered and pressure is continuously applied until the glass bonding is completed (the seventh step S7). In the case where the surface of the chip heater and the surface of the semiconductor chip are heated and cooled in a state where they are in close contact due to pressure, sometimes the surfaces of each other rub against each other due to the difference in thermal expansion coefficient between the material constituting the surface of the chip heater and the material constituting the surface of the semiconductor chip. In the case of high pressure, scratches will be generated on the surface of the semiconductor chip due to the friction, which may affect the operation of the semiconductor chip.

[0068] Therefore, in a preferred embodiment, at least the portion of the surface of the chip heater that contacts the heated surface of the chip is formed of a material having a linear expansion coefficient that is not less than 1 / 2 and not more than 2 times the linear expansion coefficient of the semiconductor chip. According to such a structure, since the ratio of the linear expansion coefficients of the materials constituting the surfaces that rub against each other is not less than 1 / 2 and not more than 2 times, the length of the scratches caused by the difference in thermal expansion coefficients is limited, and the risk of serious damage to the semiconductor chip can be reduced.

[0069] In a preferred embodiment of the present invention, the arithmetic mean roughness Ra of at least the surface of the chip heater that contacts the heated surface of the chip is set to 0.80 μm or less. In this preferred embodiment, even if mutual friction occurs due to the difference in thermal expansion coefficient between the chip heater and the semiconductor chip, the surface of the chip heater, which is one of the surfaces of mutual friction, is formed smoothly, so that scratches can be suppressed. Thus, the risk of serious damage to the semiconductor chip can be reduced.

[0070] In a preferred embodiment of the present invention, a bonding layer is provided on the bonding surface of the substrate of the object to be bonded in such a manner that the semiconductor chip is included in the bonding layer in the projection diagram when projected along the stacking direction of the semiconductor chip, the bonding layer and the object to be bonded, i.e., the first direction. In the case where the planar shape of the bonding layer composed of low-melting-point glass provided on the surface of the object to be bonded in the first step S1 is the same shape as the shape of the projection surface of the semiconductor chip (i.e., the outline of the semiconductor chip and the outline of the bonding layer overlap in the projection diagram when projected along the first direction), the end of the semiconductor chip may protrude from the bonding layer only due to a slight positional offset when the semiconductor chip is placed on the surface of the bonding layer in the third step S3. In that case, a portion of the surface of the semiconductor chip that is not in close contact with the bonding layer will be generated locally, so that a firm glass bonding cannot be achieved. In addition, even if the semiconductor chip is placed in the correct position in the third step S3, there is a case where the stress caused by the shrinkage associated with the cooling of the low-melting-point glass in the seventh step S7 is concentrated on the corner of the semiconductor chip. In such a case, it is possible that the bonding layer will peel off from the stress-concentrated portion.

[0071] However, in the above preferred embodiment, since the semiconductor chip is included in the bonding layer in the projection image when projected along the first direction, even if a slight positional shift occurs when the semiconductor chip is placed in the third step S3, the end of the semiconductor chip does not protrude from the bonding layer. In addition, since the bonding layer is formed to the outside of the corner of the semiconductor chip, stress concentration at the corner can be alleviated. Through these effects, the semiconductor chip can be more reliably glass bonded.

[0072] In a preferred embodiment of the present invention, the size and shape of the portion of the surface of the chip heater that contacts the heated surface of the chip are set in a manner that avoids the first area, and the first area is a specified area of ​​the heated surface of the chip. As a specific example of such a first area, for example, an area on the heated surface of the chip provided with a bump or an area provided with a component having a heat resistance temperature lower than the first temperature can be cited. The bump of a semiconductor chip refers to a structure that functions as an electrode that exchanges electrical signals with the semiconductor chip, and a plurality of bumps are usually provided on the peripheral portion of the surface of the semiconductor chip. Since the bump portion protrudes from the surface of the semiconductor chip, if the surface of the chip heater contacts the bump, it is impossible to make the surface of the chip heater and the surface of the semiconductor chip (the heated surface of the chip) in close contact in the fourth step S4, and the heating efficiency decreases. In addition, the bump may be damaged due to pressure. In addition, as a specific example of a component having a heat resistance temperature lower than the first temperature, for example, a sensor element such as a strain gauge can be cited.

[0073] In the above preferred embodiment, the size and shape of the portion of the chip heater surface that contacts the chip heated surface are set to avoid the first area which is a predetermined area of ​​the chip heated surface, thereby eliminating the above inconvenience.

[0074] In addition, the object to be bonded is usually larger in shape than the semiconductor chip and has a larger heat capacity. In particular, when there is a portion of the object to be bonded that is thicker than other portions, the portion has a tendency that the temperature is not easy to rise even if it is heated by the substrate heater. Even if the object to be bonded is heated while the temperature of the substrate heater is controlled to a second temperature that is higher than the temperature of the chip heater (first temperature) and the softening point of the low-melting-point glass in step 6 S6, if there is a portion that is not easy to be heated, there is a possibility that the temperature of the entire object to be bonded does not rise, and as a result, the temperature of the bonding layer does not exceed the softening point of the low-melting-point glass and the glass bonding cannot be completed.

[0075] Therefore, in a preferred embodiment of the present invention, the object to be bonded has a thick-walled portion, which is a portion having a thickness greater than that of other portions of the object to be bonded. For the thick-walled portion, the substrate heater further includes an auxiliary heating unit, which is configured to contact a surface of the thick-walled portion that is neither a substrate bonding surface of the object to be bonded nor a substrate heating surface. The auxiliary heating unit can be realized, for example, by extending a portion of a member constituting the substrate heater in a manner that clamps or surrounds the thick-walled portion of the object to be bonded. Alternatively, it can also be realized by adding a heating element around the thick-walled portion.

[0076] Figure 4 : is a schematic cross-sectional view showing an example of the auxiliary heating unit of the present invention. Figure 5 It is a schematic perspective view showing an example of the auxiliary heating unit of the present invention. Figure 4 and Figure 5 The beam 4a as the object to be bonded 4 shown as an example has a thick wall portion 4b, which is a portion having a thickness greater than that of other portions of the beam 4a. The thick wall portion 4b has a heat capacity greater than that of other portions, and is therefore less likely to be heated than other portions. Therefore, as described above, when only the heated surface of the substrate of the object to be bonded 4 is heated by the substrate heater 6, there is a possibility that the temperature of the entire object to be bonded 4 does not rise, and as a result, the temperature of the bonding layer 3 does not exceed the softening point of the low-melting-point glass, and the glass bonding cannot be completed.

[0077] Therefore, in this preferred embodiment, the substrate heater further includes an auxiliary heating unit for the thick-walled portion, and the auxiliary heating unit is configured to contact a surface of the thick-walled portion that is neither the substrate bonding surface of the bonded object 4 nor the substrate heating surface. Figure 4 and Figure 5 The illustrated substrate heater 6 is Figure 3 The substrate heater 6 shown in the example is similarly composed of a heating portion 6h having a heating element and a heat adapter 6a located between the object 4 and the heating portion 6h. Figure 4 and Figure 5 In the illustrated substrate heater 6, as in Figure 4 As shown in the portion 6s surrounded by the thick dashed line in FIG. 1 , the heat adapter 6a is partially configured to surround the outer peripheral surface of the thick wall portion 4b of the object 4 to be bonded and to be in contact with it. As a result, the heating efficiency of the thick wall portion 4b of the object 4 to be bonded is improved, and the above-mentioned disadvantages can be eliminated. That is, in Figure 4 The portion 6s surrounded by the thick dotted line constitutes an auxiliary heating unit.

[0078] <Second embodiment>

[0079] In the second embodiment, the present invention is an invention of a method for manufacturing a pressure sensor, including the glass bonding method of the semiconductor chip of the first embodiment of the present invention. However, in the second embodiment, the object to be bonded is composed of a diaphragm deformed by pressure or a beam linked to the diaphragm, and the semiconductor chip includes a strain gauge. Figure 6 is a flow chart showing this method. Figure 6 As shown in the figure, the method includes eight steps. The first step S1' and the third step S3' are steps unique to the manufacturing method of the pressure sensor. The remaining second step S2 and the fourth step S4 to the eighth step S8 are steps common to the glass bonding method of the semiconductor chip of the first embodiment. The following description will focus on the first step S1' and the third step S3' unique to the second embodiment.

[0080] The first step S1' is a step of providing a bonding layer composed of low-melting-point glass on the surface of a bonded object composed of a diaphragm deformed by pressure or a beam linked to the diaphragm. The diaphragm in the pressure sensor refers to a thin plate-like component that elastically deforms according to changes in the pressure of the fluid to be measured. Usually, the diaphragm is made of corrosion-resistant stainless steel or the like, and the elastically deformed portion is, for example, configured in the shape of a flat circular plate. One of the surfaces of the diaphragm defines a part of a closed space filled with fluid, and the other surface faces a vacuum or atmospheric pressure environment. The diaphragm itself has a restoring force. When the pressure of the fluid is high, the diaphragm elastically deforms in a manner of expanding toward the vacuum or atmospheric pressure environment. If the pressure of the fluid returns to its original size, the diaphragm returns to a flat shape.

[0081] The beam that is linked to the diaphragm, for example, as can be seen in the pressure sensor described in the above-mentioned Patent Document 2, refers to a member that is made of a material having a thermal expansion coefficient close to that of a strain sensor formed of a semiconductor chip, and is joined to the diaphragm in a manner that follows the movement of the diaphragm that is elastically deformed according to changes in the pressure of the fluid. In the case where the strain sensor is not directly joined to the diaphragm but is joined to the beam that is linked to the diaphragm, since the diaphragm and the beam are independent members, a material having a thermal expansion coefficient close to that of the strain sensor can be selected as the material constituting the beam. As a result, the thermal expansion coefficients of the strain sensor and the beam as the object to be joined can be made close, so that the above-mentioned problem caused by the difference in thermal expansion coefficients between the strain sensor and the object to be joined can be solved. The joining portion where the diaphragm is joined to the beam is formed, for example, by welding.

[0082] The purpose of providing the bonding layer in the first step S1' is to place the bonding layer between the semiconductor chip and the diaphragm or beam to bond the two, as in the case of the first step S1 in the first embodiment. The position of the bonding layer on the surface of the diaphragm or beam, the shape of the bonding layer and the thickness of the bonding layer can be appropriately determined according to the above purpose. As a specific means for providing the bonding layer, for example, a method can be adopted in which a glass paste prepared by mixing low-melting-point glass with an organic binder (organic carrier) containing an organic solvent and a resin is provided at a predetermined position of the diaphragm or beam by screen printing, as in the case of the first step S1. By heating the diaphragm or beam coated with the glass paste by this method to remove the organic solvent and firing, a diaphragm or beam having a bonding layer composed of low-melting-point glass on the surface can be prepared.

[0083] The third step S3' is a step of placing a semiconductor chip including a strain gauge on the surface of the bonding layer. The purpose of the third step S3' is to accurately place the semiconductor chip including the strain gauge in a correct orientation at a predetermined position on the surface of the bonding layer provided on the surface of the diaphragm or the beam in the first step S1'. In order to manufacture the pressure sensor in the second embodiment, the semiconductor chip placed on the surface of the bonding layer must be a semiconductor chip including a strain gauge. By bonding such a semiconductor chip to the surface of the diaphragm or the beam, the strain of the diaphragm or the beam linked to the diaphragm can be measured to obtain the pressure of the fluid acting on the diaphragm.

[0084] In this specification, a "strain gauge" refers to a sensor for measuring the strain of an object. As the strain gauge in the second embodiment, a known strain gauge such as a metal strain gauge that utilizes the change in resistance of a metal foil or a semiconductor strain gauge that utilizes the piezoresistive effect of a semiconductor can be used. Such a strain gauge can be installed as a part of a semiconductor integrated circuit during the process of manufacturing a semiconductor chip. For a semiconductor chip including a strain gauge, in addition to the strain gauge, an amplifier circuit, a control circuit, and / or a temperature sensor can also be mounted.

[0085] The processes of the second step S2 and the fourth step S4 to the eighth step S8 after the third step S3' are common to the steps in the first embodiment, and therefore, the description thereof is omitted here. However, in the case of using the above-mentioned beam as the object to be bonded, if the diaphragm is bonded to the beam when performing the processes of the fourth step S4 to the eighth step S8, it may be difficult to apply pressure and / or heat to the beam. Therefore, in this case, it is preferred to implement the second embodiment using the beam before being bonded to the diaphragm. In addition, the bonded body formed by bonding the semiconductor chip glass including the strain gauge to the object to be bonded, which is the product after completing all the steps included in the second embodiment, is an intermediate product for manufacturing a pressure sensor, and is not yet completed as a pressure sensor. The pressure sensor is completed by connecting the required peripheral equipment such as the diaphragm, the flexible printed wiring substrate, and the power supply to the bonded body.

[0086] By implementing the method of the present invention described above, a low-melting-point glass having a softening point higher than the heat-resistant temperature of the semiconductor chip including the strain gauge can be used for the bonding layer to bond the semiconductor chip glass to the diaphragm or the beam linked to the diaphragm. In addition, the intermediate product obtained by this method can be used to manufacture a finished product of the pressure sensor. As described above, the bonding layer composed of low-melting-point glass has higher insulation than, for example, solder, and thus can prevent unexpected electrical noise from being transmitted to the semiconductor chip via the diaphragm or via the diaphragm and the beam, thereby improving the reliability of the operation of the pressure sensor. In addition, low-melting-point glass is also superior to solder in the long-term stability of bonding, so the life of the pressure sensor is prolonged.

[0087] In a preferred embodiment of the present invention, the size and shape of the portion of the chip heater surface that contacts the heated surface of the chip are set in a manner that avoids the area where the strain gauge is provided. Usually, the strain gauge is mostly provided in the center of the semiconductor chip. If the portion of the chip heater surface that contacts the semiconductor chip overlaps with the position where the strain gauge is provided, the heat from the chip heater is easily transferred to the strain gauge. In that case, due to the interaction between the heat transferred from the substrate heater to the strain gauge via the bonded object, the temperature of the strain gauge may exceed the heat resistance temperature.

[0088] In this preferred embodiment, since the surface of the chip heater is formed in a manner avoiding the region where the strain gauge is provided, heat from the chip heater is not easily transferred to the strain gauge. Therefore, it is possible to more reliably prevent the strain gauge from being heated to a temperature exceeding the heat-resistant temperature. As a specific shape of the surface of the chip heater, for example, it is preferably set to a ring shape in which the central portion is hollowed in a manner avoiding the strain gauge provided in the central portion of the semiconductor chip.

[0089] <Third Embodiment>

[0090] In the third embodiment, the present invention is an invention of a bonding device for bonding a semiconductor chip glass to a bonded object having a bonding layer composed of a low-melting-point glass on a predetermined surface, i.e., a substrate bonded surface. The bonding device of the present invention has the same overall structure as the bonding device for solder bonding described in Patent Document 3. The bonding device can be roughly divided into a portion for bonding the glass and a power supply for supplying a controlled current to a heater. Figure 7 This is a diagram schematically showing only the main parts of the structure of the glass bonding part. Figure 7 The structure of the bonding device of the present invention will be described.

[0091] The bonding device 1 of the present invention is provided with a chip heater 5 capable of adsorbing and heating a semiconductor chip 2. The chip heater 5 has the functions of adsorbing the semiconductor chip 2, applying pressure to the semiconductor chip 2, and heating the semiconductor chip 2. The chip heater 5 is capable of adsorbing the semiconductor chip 2, transporting the semiconductor chip 2 to a position where the bonding layer 3 is provided by a position adjustment unit described later, and then accurately placing the semiconductor chip 2 at the position. The adsorption of the semiconductor chip 2 by the chip heater 5 can be achieved, for example, by vacuum adsorption. Specifically, for example, by providing a cavity at the top portion 5a of the chip heater 5 that contacts the semiconductor chip 2 and exhausting the air present in the cavity portion by a vacuum pump, the semiconductor chip 2 can be vacuum adsorbed to the chip heater 5. In addition, by stopping the exhaust based on the vacuum pump, the adsorption can be released and the semiconductor chip 2 can be separated from the chip heater 5. In addition, the cavity for adsorption can also serve as a cavity provided on the surface of the chip heater in order to avoid the specified area, i.e., the first area, of the heated surface of the chip as described above.

[0092] The chip heater 5 includes a heating resistor and can heat the semiconductor chip 2 by supplying current to the heating resistor. Figure 7 In the illustrated chip heater 5, the arms extending in the left-right direction are composed of a heating resistor as a whole, and heat is generated by flowing current in the left-right direction. The top end portion 5a of the chip heater 5 combined with the arms has a ring shape, and the top end portion 5a contacts the chip heating surface of the semiconductor chip 2 to transfer heat to the chip bonding surface.

[0093] The bonding apparatus 1 of the present invention includes a substrate heater 6 capable of placing and heating a bonded object 4. The substrate heater 6 is an independent heating mechanism different from the chip heater 5. The bonded object 4 having a bonding layer 3 on its surface is placed on the substrate heater 6 to heat the bonded object 4. The substrate heater 6 includes a heating resistor and can heat the bonded object 4 by supplying current to the heating resistor.

[0094] The bonding device 1 of the present invention is provided with a temperature measuring unit (not shown) for measuring the temperature of the chip heater 5 and the substrate heater 6 separately. As the temperature measuring unit, for example, a thermocouple or a temperature measuring resistor can be used. By separately providing the temperature measuring unit in the chip heater 5 and the substrate heater 6, the temperature of the chip heater 5 and the substrate heater 6 can be controlled independently of each other using the temperature control unit described later. Figure 7 In the illustrated chip heater 5, for example, it is preferable to provide a temperature measuring unit at a position close to the tip portion 5a having a ring shape. Thus, the temperature of the tip portion 5a of the chip heater 5 heated by power supply can be measured. Figure 7 In the illustrated substrate heater 6, for example, it is preferable to provide a temperature measuring unit at a position close to the position where the object to be bonded 4 is placed. Thereby, the temperature of the substrate heater 6 at the position closest to the object to be bonded 4 can be measured.

[0095] The bonding device 1 of the present invention is provided with a position adjustment unit (not shown) for accurately placing the semiconductor chip 2 adsorbed on the chip heater 5 at a position where the bonding layer 3 is provided on the surface of the object to be bonded 4 (substrate bonding surface). As a specific structure of the position adjustment unit, for example, as described above, a robot arm is preferably used. By mounting a shooting unit such as a CCD camera on the robot arm and analyzing and determining the position and / or direction of the bonding layer 3 based on the image, the semiconductor chip 2 can be accurately placed at the position where the bonding layer 3 is provided.

[0096] The bonding device 1 of the present invention is provided with a pressurizing unit for forming a clamping state, in which the semiconductor chip 2, the bonding layer 3, and the object to be bonded 4 are clamped by the chip heater 5 and the substrate heater 6 in the stacking direction of the semiconductor chip 2, the bonding layer 3, and the object to be bonded 4. As a specific structure of the pressurizing unit, as described above, a driving mechanism can be provided on one or both of the chip heater 5 and the substrate heater 6, and pressure can be applied by driving in a direction that brings the two closer. As the driving mechanism, for example, a known unit such as a foot pedal or an electric actuator can be used.

[0097] The bonding device 1 of the present invention is provided with a temperature control unit that independently controls the temperature of the chip heater 5 and the substrate heater 6. That is, while maintaining the above-mentioned clamping state, the temperature control unit controls the temperature of the chip heater 5 to a predetermined temperature lower than the heat resistance temperature of the semiconductor chip 2, that is, a first temperature, and heats the semiconductor chip 2 using the chip heater 5. At the same time, the temperature control unit controls the temperature of the substrate heater 6 to a predetermined temperature higher than the temperature of the chip heater 5 and the softening point of the low-melting-point glass, that is, a second temperature, and heats the object to be bonded 4 using the substrate heater 6. The temperatures of the chip heater 5 and the substrate heater 6 can be controlled independently of each other using a separately provided temperature measuring unit.

[0098] The temperature control unit preferably maintains the temperature of the chip heater 5 and the temperature of the substrate heater 6 at constant temperatures respectively after the above-mentioned heating is completed. As described above, during this period, the softened low-melting-point glass penetrates into the gap between the semiconductor chip 2 and the object to be bonded 4 due to pressure, forming a thinner bonding layer 3. Next, while maintaining the pressure, the temperature control unit lowers the temperature of the chip heater 5 and the temperature of the substrate heater 6 to cool the low-melting-point glass of the bonding layer 3. As described above, during this period, the bonding layer 3 changes to a hard glass state while being in close contact with the surfaces of the semiconductor chip 2 and the object to be bonded 4, completing a strong glass bond.

[0099] The bonding device 1 of the present invention is provided with a removal unit, which releases the above-mentioned clamping state and removes the bonded body formed by glass bonding of the semiconductor chip 2 to the bonded object 4. As described above, since a strong bonding layer 3 has been formed on the bonded body, the bonding between the semiconductor chip 2 and the bonded object 4 will not be peeled off even if the pressure is released. In order to release the pressure, the above-mentioned driving mechanism is activated to drive one or both of the chip heater 5 and the substrate heater 6 in a direction away from each other. In addition, in order to remove the bonded body, for example, a robot arm can be used to vacuum adsorb the surface of the semiconductor chip 2 while moving the bonded body and placing it on a product placement location.

[0100] By using the bonding device of the present invention described above, it is possible to use a low-melting-point glass having a softening point higher than the heat-resistant temperature of the semiconductor chip for the bonding layer and to bond the semiconductor chip glass to the object to be bonded. Since the temperature of the chip heater is controlled to a first temperature lower than the heat-resistant temperature of the semiconductor chip by the temperature control unit while the semiconductor chip is heated by the chip heater, the temperature of the semiconductor chip does not exceed its heat-resistant temperature. In addition, since the temperature of the substrate heater is similarly controlled to a second temperature higher than the temperature of the chip heater and the softening point of the low-melting-point glass by the temperature control unit while the object to be bonded is heated by the substrate heater, the low-melting-point glass can be softened and the glass bonding can be completed.

[0101] Example

[0102] The embodiment described here is only an example of the embodiment of the present invention, and the embodiment of the present invention is not limited to the embodiment described in the embodiment.

[0103] A raw material of Kovar (registered trademark) obtained by mixing nickel and cobalt with iron was machined to produce a Figure 4 The beam 4a is of the shape shown. The diameter of the beam 4a is about 10 mm. The linear expansion coefficient of Kovar alloy is 5.0×10 -6 K. This value is close to the thermal expansion coefficient of low-melting glass. Next, a bonding layer 3 composed of low-melting glass is applied to the surface of the end of the beam 4a by screen printing, and then the beam 4a is heated to remove the organic solvent and the low-melting glass is fired, thereby preparing a bonded object 4 composed of the beam 4a having a bonding layer 3 composed of low-melting glass on the surface. The shape of the bonding layer 3 is a square with a length and width of 3.0 mm and a thickness of 30 μm to 40 μm. The length and width of the bonding layer 3 is larger than the length and width of 2.5 mm, which is the size of the shape of the projection surface of the semiconductor chip 2.

[0104] Next, the beam 4a is placed as the object 4 to be joined. Figure 7 The substrate heater 6 of the bonding device 1 shown in FIG. Figure 4 and Figure 5 As shown in FIG. 1 , the auxiliary heating unit 6s is provided in such a manner as to contact the outer peripheral surface of the thicker portion of the beam 4a, that is, the thick wall portion 4b. Next, the semiconductor chip 2 including the strain gauge is adsorbed using the chip heater 5, and the semiconductor chip 2 is placed on the surface of the bonding layer 3 provided on the beam 4a as the object to be bonded 4 using a position adjustment unit not shown including a robot arm. In addition, the chip heater 5 for adsorbing the semiconductor chip 2 is made of tungsten carbide. The linear expansion coefficient of tungsten carbide is 5.6×10 -6 / K. This value is the linear expansion coefficient of silicon constituting the semiconductor chip 2, which is 3.0×10 -6 / K is not less than 1 / 2 and not more than 2 times. The arithmetic mean roughness Ra of the surface of the tip portion of the chip heater 5 that contacts the surface of the semiconductor chip 2 (chip heated surface) is 0.80 μm.

[0105] Figure 8It is a schematic diagram showing the positional relationship between the surface of the semiconductor chip 2 on the side that is not in contact with the bonding layer 3 (the chip heated surface) and the shape of the top portion 5a of the chip heater 5 adsorbed on the surface. There is a strain gauge 2a near the center of the semiconductor chip 2. The top portion 5a of the chip heater 5 shown by the oblique lines has an annular shape with a hole in the center, and the area where the strain gauge 2a is provided can be avoided by utilizing the hole. In addition, there is a bump 2b on the peripheral portion of the semiconductor chip 2. The size and shape of the top portion 5a of the chip heater 5 are configured to also avoid the area of ​​the semiconductor chip 2 where the bump 2b is provided.

[0106] Next, the drive mechanism (not shown) linked to the chip heater 5 is operated to drive the chip heater 5 in the direction of the substrate heater 6, and pressure is applied in the stacking direction of the semiconductor chip 2, the bonding layer 3 and the beam 4a to clamp the semiconductor chip 2, the bonding layer 3 and the beam 4a (forming a clamping state). The magnitude of the pressure at the bonding layer 3 at this time is 0.45 Newtons per square millimeter. The magnitude of the pressure is adjusted by a spring provided at the joint portion where the drive mechanism and the chip heater 5 are joined.

[0107] Next, while maintaining the state in which the pressure is applied as described above (i.e., the clamping state), the temperature measuring unit and the temperature control unit provided in the bonding apparatus 1 are used to control the temperature of the chip heater 5 to 400° C., which is lower than the heat resistance temperature of the semiconductor chip 2, i.e., 450° C., and to heat the semiconductor chip 2 by the chip heater 5, and to control the temperature of the substrate heater 6 to 450° C., which is higher than the temperature of the chip heater 5, i.e., 400° C., and the softening point of the low-melting-point glass, and to heat the beam 4a and the auxiliary heating unit 6a by the substrate heater 6. That is, the first temperature is set to 400° C., and the second temperature is set to 450° C. The time required for the temperature rise is 60 seconds.

[0108] Next, the temperature of the chip heater 5 is maintained at the first temperature, i.e., 400°C, and the temperature of the substrate heater 6 is maintained at the second temperature, i.e., 450°C, while heating is continued for 100 seconds. Thereafter, the temperature of the chip heater 5 and the temperature of the substrate heater 6 are lowered to 250°C while maintaining the pressure, thereby cooling the low melting point glass of the bonding layer 3. The time required for this temperature drop is 100 seconds. After further maintaining the temperature at 250°C for 40 seconds, the power supply of the heater is turned off. Fig. 9 The graph shows the time changes of the target temperatures of the chip heater 5 and the substrate heater 6 to be controlled by the temperature control unit during this period.

[0109] Next, the pressure is released (i.e., the clamping state is released), and the semiconductor chip 2 is vacuum-adsorbed by the chip heater 5 to form a bonded body formed by glass bonding to the beam 4a. After that, the bonded body is moved to the product placement position by the position adjustment unit, and the vacuum is released to place it there. The beam 4a of the obtained bonded body is welded to the diaphragm, and electrodes and other auxiliary components are installed to complete the pressure sensor.

[0110] The pressure sensor manufactured by the above method was inspected, and the glass bonding between the semiconductor chip 2 and the beam 4a was strong, and no separation of the bonding was observed. In addition, the operation of the pressure sensor was stable, and no electrical noise was observed in the output signal.

[0111] Description of Reference Numerals

[0112] 1. Bonding device; 2. Semiconductor chip; 2a. Strain gauge; 2b. Bump; 3. Bonding layer; 4. Object to be bonded; 4a. Beam; 4b. Thick-walled portion; 5. Chip heater; 5a. Top portion; 6. Substrate heater; 6h. Heat generating portion; 6a. Heat adapter; 6s. Auxiliary heating unit.

Claims

1. A method for glass bonding of a semiconductor chip, wherein: The glass bonding method comprises: A first step, in which a bonding layer composed of a low-melting-point glass is provided on a predetermined surface of the object to be bonded, i.e., a bonding surface of the substrate; A second step, in which the object to be bonded is placed on the substrate heater in such a manner that a surface of the object to be bonded, which is a surface of the substrate to be heated, opposite to the surface of the substrate to be bonded is in contact with a surface of the substrate heater; A third step, in which the semiconductor chip is placed on the surface of the bonding layer; A fourth step, in which the surface of the chip heater is brought into contact with the surface of the semiconductor chip on the opposite side of the surface in contact with the bonding layer, i.e., the chip heated surface; A fifth step, in which a clamping state is formed, wherein the semiconductor chip, the bonding layer, and the object to be bonded are clamped by the chip heater and the substrate heater in a first direction, the first direction being a stacking direction of the semiconductor chip, the bonding layer, and the object to be bonded; A sixth step, in which the semiconductor chip is heated by the chip heater while the chip heater is controlled to a first temperature, and the object to be bonded is heated by the substrate heater while the substrate heater is controlled to a second temperature while the chip heater is controlled to a first temperature while the clamping state is maintained, wherein the first temperature is a prescribed temperature lower than the heat resistance temperature of the semiconductor chip, and the second temperature is a prescribed temperature higher than the temperature of the chip heater and the softening point of the low-melting-point glass; A seventh step, in which the temperature of the chip heater and the temperature of the substrate heater are lowered while maintaining the clamping state to cool the low-melting-point glass constituting the bonding layer; and In the eighth step, the clamping state is released to take out the bonded body formed by bonding the semiconductor chip glass to the bonded object.

2. The glass bonding method for semiconductor chips according to claim 1, wherein: At least a portion of the surface of the chip heater that contacts the heated surface of the chip is formed of a material having a linear expansion coefficient that is not less than 1 / 2 and not more than 2 times the linear expansion coefficient of the semiconductor chip.

3. The glass bonding method for semiconductor chips according to claim 1, wherein: The arithmetic mean roughness Ra of at least the surface of the chip heater that contacts the heated surface of the chip is set to 0.80 μm or less.

4. The method for glass bonding of a semiconductor chip according to claim 1, wherein: The bonding layer is provided on the bonding surface of the substrate so that the semiconductor chip is included in the bonding layer in a projection view when projected in the first direction.

5. The method for glass bonding of a semiconductor chip according to claim 1, wherein: The size and shape of a portion of the surface of the chip heater that contacts the chip heated surface are set so as to avoid a first region that is a predetermined region of the chip heated surface.

6. The method for glass bonding of a semiconductor chip according to claim 5, wherein: The first region of the semiconductor chip is a region where bumps are disposed or a region where a member having a heat resistance temperature lower than the first temperature is disposed.

7. The method for glass bonding of a semiconductor chip according to claim 1, wherein: The object to be joined has a thick wall portion, which is a portion having a thickness greater than that of other portions of the object to be joined, The substrate heater further includes an auxiliary heating unit for the thick portion, the auxiliary heating unit being configured to be in contact with a surface of the thick portion which is neither the substrate-joined surface of the object to be joined nor the substrate-heated surface.

8. A method for manufacturing a pressure sensor, wherein: The manufacturing method comprises the glass bonding method for a semiconductor chip according to any one of claims 1 to 7, The object to be joined is composed of a diaphragm deformed by pressure or a beam linked to the diaphragm. The semiconductor chip includes a strain gauge.

9. The method for manufacturing a pressure sensor according to claim 8, wherein: The manufacturing method includes the glass bonding method of the semiconductor chip according to claim 6, The first region of the semiconductor chip is a region where the strain gauge is disposed.

10. A bonding device for bonding a semiconductor chip glass to an object to be bonded having a bonding layer made of low-melting-point glass on a predetermined surface, that is, a substrate bonding surface, wherein: The joining device comprises: A chip heater capable of adsorbing and heating the semiconductor chip; a substrate heater capable of placing and heating the object to be bonded; a temperature measuring unit that individually measures the temperature of the chip heater and the temperature of the substrate heater; a position adjustment unit for accurately placing the semiconductor chip adsorbed on the chip heater at a position on the surface of the object to be bonded where the bonding layer is provided; a pressurizing unit that forms a clamped state in which the semiconductor chip, the bonding layer, and the object to be bonded are clamped by the chip heater and the substrate heater in a stacking direction of the semiconductor chip, the bonding layer, and the object to be bonded; a temperature control unit, which controls the temperature of the chip heater to a first temperature while maintaining the clamping state and heats the semiconductor chip with the chip heater, and controls the temperature of the substrate heater to a second temperature while heating the bonded object with the substrate heater, and then, while maintaining the clamping state, lowers the temperature of the chip heater and the temperature of the substrate heater to cool the low-melting-point glass constituting the bonding layer, wherein the first temperature is a prescribed temperature lower than the heat-resistant temperature of the semiconductor chip, and the second temperature is a prescribed temperature higher than the temperature of the chip heater and the softening point of the low-melting-point glass; as well as The taking-out unit releases the clamping state and takes out a bonded body formed by bonding the semiconductor chip glass to the bonded object.

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