JP2014190875A - Dynamic quantity measurement instrument and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a junction structure which detects strain occurring in a measurement object, with high sensitivity even under a high temperature and allows accurate sensor output even when applied with long-tern strain, by optimizing a junction between a sensor chip having a strain detection part on a semiconductor substrate and abase substrate.SOLUTION: A dynamic quantity measurement instrument includes: a sensor chip having, on a semiconductor substrate, a strain detection part for detecting expansion/contraction in an in-plane direction; a base substrate; and a wiring part for drawing a wire from an electrode of the sensor chip to the outside. A sensor chip rear surface opposite to a surface on which the strain detection part is provided and a front surface of the base substrate are joined via a layer of an intermetallic compound and a metal layer having a high melting point.

Description

  The present invention relates to a mounting structure of a semiconductor mechanical quantity measuring device and a manufacturing method thereof.

  As a method for measuring the deformation (strain) of a measurement object, a technique using a metal foil strain gauge utilizing the fact that the resistance value of the metal foil changes due to strain is known. By attaching this strain gauge to the object to be measured, the length of the metal foil is changed following the strain of the object to be measured, and the resistance value of the metal foil that changes as a result can be detected to enable strain measurement of the object to be measured. Technology. Up to now, there are strain gauges using Cu-Ni alloy foils and Ni-Cr alloy foils, etc. In addition to ensuring and stabilizing strain gauge attachment (sticking), it is also moisture and impact resistant. High protector strain gauges have also been proposed.

  However, since these have high power consumption, there is a problem that the battery is consumed quickly. Therefore, in order to reduce power consumption, a semiconductor dynamic quantity measuring device in which a strain sensitive resistor is formed on silicon has been proposed.

  As a structure of this semiconductor strain gauge (semiconductor dynamic quantity measuring device), it has a flexible thin film provided with a plurality of electrodes, and a semiconductor substrate on which a plurality of electric elements are formed. A structure of a semiconductor strain gauge, which is attached to the semiconductor substrate and in which the plurality of electrodes and the plurality of electric elements are electrically connected, is disclosed in Japanese Patent Application Laid-Open No. 2001-264188 ( Patent Document 1) proposes.

  Japanese Patent Laid-Open No. 2001-272287 (Patent Document 2) has a strain detection element constituted by a silicon chip and a pedestal that transmits the strain to be detected to the strain detection element, and the pedestal has a thermal expansion coefficient of silicon. There is disclosed a strain detection sensor formed of a material that falls within a range of ± 50% of the thermal expansion coefficient of the above, and the strain detection element is formed by heating and fixing a glass-based fixing material.

JP 2001-264188 A JP 2001-272287 A

There are mainly two important items as performance required for a semiconductor dynamic quantity measuring apparatus.
The first important item is to correctly transmit the strain generated in the object to be measured to the strain detector of the semiconductor chip (hereinafter referred to as sensor chip) when performing strain measurement. That is, the accuracy and sensitivity when detecting the strain generated in the object to be measured are important.

  The second important item is that the sensor chip shows the same detection value even when the same amount of strain is generated in the object to be measured for a long time. That is, the stability of the sensor output value is important. This item becomes a more difficult problem when the object to be measured is used at a high temperature. As an application of a mechanical quantity measuring device such as strain and pressure, it may be used for, for example, operation control of automobiles and monitoring of important infrastructure in addition to general household goods. In this case, it is necessary to assume a usage range from about −50 ° C. at a low temperature to about 150 ° C. at a high temperature.

  Usually, the sensor chip has fine wiring or the like on its surface, but the main material is silicon, and the object to be measured is joined using a joining material such as solder. This bonding needs to be performed at a temperature lower than the heat resistance temperature of the sensor chip. As general solder, Sn-3 wt% Ag-0.5 wt% Cu solder having a melting point of about 217 ° C, Pb-5 wt% Sn solder having a melting point of about 310 ° C, and the like are known. In the Sn-3wt% Ag-0.5wt% Cu solder, the temperature is close to the melting point in the usage environment near 100 ° C to 150 ° C, the yield stress of the solder becomes small, the solder softens, and there is a concern that the sensitivity may be lowered. In an environment where strain is applied at a high temperature, creep deformation of the bonding layer occurs, and fluctuation in sensor output becomes a problem. Pb-5wt% Ag solder containing a lot of lead has a higher melting point than Sn-based solder, but it is a soft material, so there is still concern about sensitivity reduction and sensor output accuracy reduction due to creep deformation.

  Therefore, in order to ensure the stability of the sensor output in a high-temperature environment, it is conceivable to bond the sensor chip and the object to be measured using a bonding material having a very high melting point. The temperature cannot be exceeded. In addition, when bonding at a high temperature, the difference in thermal expansion coefficient between silicon, which is the main material of the sensor chip, and the object to be measured increases the probability that the silicon chip will crack, and there is a concern that the yield during manufacturing will be reduced.

  In Japanese Patent Application Laid-Open No. 2001-264188 (Patent Document 1), which has been filed so far, it is predicted that it is difficult to use at high temperatures because an organic thin film is used. Japanese Patent Application Laid-Open No. 2001-272287 (Patent Document 2) shows a structure in which a glass-based fixing material is heated and melted and can be expected to be a hard material, but is destroyed by an external force such as an impact. There is a concern about this, and it is considered necessary to restrict the use environment.

  As described above, in the semiconductor mechanical quantity measuring device, performance important as a measuring instrument such as sensitivity and sensor output stability is greatly influenced by the structure of the joint between the sensor chip and the object to be measured. For this reason, in the present invention, the joint between the sensor chip having the strain detection unit on the semiconductor substrate and the object to be measured is optimized, the strain generated in the object to be measured is detected with high sensitivity even in a high temperature environment, and for a long time. It is an object of the present invention to provide a joint structure capable of producing a stable sensor output with little creep deformation even when strain is applied, and a manufacturing method thereof.

  It is another object of the present invention to provide a sensor chip bonding structure that can be manufactured at a high yield, and a method for manufacturing the same, which prevents a chip crack failure when bonding the sensor chip and the object to be measured.

  The present application includes a plurality of means for solving the above-described problems. To give an example, a sensor chip having a strain detection unit for detecting expansion and contraction in the in-plane direction on a semiconductor substrate, an object to be measured, and the sensor chip, A base substrate that supports the sensor chip and transmits the strain of the measurement object to be detected to the sensor chip, and a wiring portion that leads the wiring from the electrode of the sensor chip to the outside. The back surface of the sensor chip opposite to the surface having the strain detector and the base substrate are bonded via a bonding layer in which an intermetallic compound layer and a high melting point metal layer are laminated. A measuring device was constructed.

  In order to solve the above problems, in the present invention, the bonding layer that bonds the back surface of the sensor chip and the surface of the base substrate includes a first intermetallic compound layer, a high melting point metal layer, and a second metal. The mechanical quantity measuring apparatus according to the above-described is characterized in that it has a three-layer structure in which intermetallic compound layers are laminated.

  In order to solve the above problems, in the present invention, in the method for manufacturing a mechanical quantity measuring device, a base substrate is placed in a heating furnace, and a core layer made of a refractory metal is laminated on the base substrate. A sensor chip having a strain detection unit for detecting expansion and contraction in the in-plane direction on the semiconductor substrate is mounted on the composite solder material having a three-layer structure composed of a low melting point surface solder layer. The surface opposite to the surface having the surface is placed on the composite solder material, heated to a temperature equal to or higher than the melting point of the surface solder layer, the molten solder layer is reacted with the metal of the core layer, Heating was continued until the solder sufficiently formed the intermetallic compound.

  According to the present invention, since the sensor chip and the base substrate are bonded via the hard intermetallic compound layer and the high melting point metal layer, the strain generated in the object to be measured is detected with high sensitivity even at a high temperature, In addition, even when a strain is applied for a long period of time, since the creep deformation of the bonding layer is small, a stable and accurate sensor output is possible, and a high-performance semiconductor dynamic quantity measuring device can be provided.

  In addition, it is possible to reduce cracks in the sensor chip when the sensor chip and the base substrate are joined, and it is possible to improve the manufacturing yield.

It is an example of the cross-sectional block diagram of the mechanical quantity measuring apparatus of Example 1 of this invention. It is an example of the plane block diagram of the mechanical quantity measuring apparatus of Example 1 of this invention. It is an example of the cross-sectional block diagram of the composite solder material used for manufacture of the mechanical quantity measuring apparatus of Example 1 of this invention. It is a figure explaining the process which joins a sensor chip and a base substrate in a heating furnace in the manufacturing method of the mechanical quantity measuring device of Example 1 of this invention. It is a figure which shows the example of a cross section by the side of a sensor chip of the joining layer 3 of a sensor chip and a base substrate. It is sectional drawing of Example 1 which joined the mechanical quantity measuring apparatus 100 of Example 1 of this invention, and the to-be-measured object 30. FIG. It is sectional drawing of Example 2 which joined the mechanical quantity measuring apparatus 100 of Example 1 and the to-be-measured object 30 of this invention. It is an example of the cross-sectional block diagram of the composite solder material of the 5 layer structure used for manufacture of the mechanical quantity measuring apparatus of Example 2 of this invention. It is sectional drawing of the junction structure formed when the composite solder material of a 5-layer structure is applied to manufacture of the mechanical quantity measuring apparatus of Example 2 of this invention. It is sectional drawing which shows the 1st example which applied the mechanical quantity measuring apparatus of Example 3 of this invention to the pressure sensor module. It is sectional drawing which shows the 2nd example which applied the mechanical quantity measuring apparatus of Example 3 of this invention to the pressure sensor module.

  Embodiments of the present invention will be described below with reference to the drawings.

In this embodiment, an example of a structure of a joint part between a sensor chip and a base substrate that is a component of a semiconductor mechanical quantity measuring device will be described.
1 and 2 show examples of a cross-sectional structure and a planar structure of the mechanical quantity measuring device 100 of the present embodiment. The sensor chip 1 has a strain detection unit 2 on the main surface 1a, and the sensor chip back surface 1b, which is the surface opposite to the main surface 1a of the sensor chip 1, is connected to the base substrate 4 via the bonding layer 3. . The strain detector 2 is provided near the center of the sensor chip 1, and a Wheatstone bridge circuit composed of four impurity diffusion resistors is formed. Thereby, the amount of strain is detected by changing the resistance value of the impurity diffusion resistance due to the expansion and contraction generated in the planar direction of the sensor chip 1. In this example, the sensor chip 1 is disposed at substantially the center of the base substrate 4, but is not limited to the center.

  A printed circuit board 20 is disposed on the base substrate 4, and the electrode pads 28 on the printed circuit board 20 and the electrode pads 29 of the sensor chip 1 are connected by wire bonding 21 using Au wire or the like.

  Although not shown, in order to protect the surface of the sensor chip 1 of these mechanical quantity measuring devices 100, protect the wire bonding 21 or the like, or prevent an electrical short, at least the surface of the sensor chip 1 and the wire bonding 21 are provided. The portion to be included may be covered with an insulating material or the like. Alternatively, it may be possible to cover the whole with a cap or the like.

  The bonding layer 3 has a structure in which an intermediate layer 5 made of a high melting point metal is centered and sandwiched between intermetallic compound layers 6a and 6b on both sides. That is, the first intermetallic compound layer 6a is formed on the back surface 1b of the sensor chip 1, and the intermediate layer 5 made of a metal having a high melting point is formed on the surface opposite to the sensor chip 1 bonding interface of the intermetallic compound layer 6a. A second intermetallic compound layer 6 b is formed between the intermediate layer 5 and the base substrate 4.

As an example of the material structure of the bonding layer 3, the first intermetallic compound layer 6a is mainly composed of Cu and Sn, and the chemical composition includes Cu ₃ Sn, Cu ₆ Sn ₅ , or other elements. The intermediate layer 5 made of a high melting point metal contains Cu or Cu as a main component and contains other elements. Similar to the first intermetallic compound layer 6a, the second intermetallic compound layer 6b is mainly composed of Cu and Sn and has a chemical composition of Cu ₃ Sn, Cu ₆ Sn ₅ , or other elements. It is comprised by the component containing.

  FIG. 3 shows a cross-sectional configuration of the original composite solder material 7 for forming the bonding layer 3. The composite solder material 7 is composed of three layers: a core layer 8 made of a high melting point metal, and a low melting point surface solder layer 9 laminated on both sides thereof. In the present embodiment, the material of the core layer 8 is Cu, and the surface solder layer 9 laminated on both surfaces thereof is Sn. This surface layer Sn was formed on the Cu core layer 8 by plating.

FIG. 4 is a diagram illustrating a process for joining the sensor chip 1 and the base substrate 4 in the heating furnace in the method for manufacturing the mechanical quantity measuring device 100. That is, a composite solder material 7 composed of a total of three layers of a core layer 8 and a surface solder layer 9 is mounted on the base substrate 4, and then the surface opposite to the main surface 1 a on which the strain detection portion 2 of the sensor chip 1 is provided. 1b is mounted so as to contact the composite solder material 7. These are put in the heating furnace 10 and heated by, for example, a heater 11 or the like.
Along with the heating and heating, the low-melting surface solder layer 9 formed on the surface of the core layer 8 of the composite solder material 7 is melted and bonded to the back surface 1b of the sensor chip 1 and the base substrate 4. At this time, a part of Cu of the core layer 8 melts into the surface solder layer 9, and Cu and Sn of the surface solder layer 9 react to form an intermetallic compound. The thickness of the surface solder layer 9, the heating temperature, By optimizing the time, Sn of the surface solder layer 9 is changed to a CuSn-based intermetallic compound, and a low melting point Sn hardly remains. Two types of intermetallic compounds are known between Cu and Sn. From the descending order of Cu ratio, Cu ₃ Sn and Cu ₆ Sn ₅ have melting points of 640 ° C. and 415 ° C., respectively. Since the melting point of Sn of the original surface solder layer 9 is 232 ° C., it can be said that the surface solder layer 9 has changed to the high melting point intermetallic compound layer 6.

  It is desirable to apply an Au layer, an Ag layer, or the like to the back surface 1b of the sensor chip 1 by plating, vapor deposition, sputtering, or the like so that the surface solder layer 9 of the composite solder material 7 can be easily connected. These surface Au, Ag layers and the like are generally thin and melt into the solder at the time of connection, and the Ni layer (not shown) formed thereunder and the surface solder layer 9 are joined.

Here, by controlling the atmosphere inside the heating furnace 10, oxidation of the surface solder layer 9 of the composite solder material 7 at a high temperature can be suppressed, and good bonding can be obtained. For example, N _2, argon, helium and the like are effective for the atmosphere, but in addition thereto, reducing hydrogen, a mixture thereof, or an organic acid such as formic acid may be used. In addition, an organic substance such as a flux capable of reducing a surface oxide such as Sn may be used. Further, in order to improve the bonding quality such as parallelism of the sensor chip 1 with the base substrate 4, position control, securing a desired bonding height, and void reduction, a bonding correction jig 12 such as a weight 16 or a guide may be used. It is also effective to reduce the voids by applying a vacuum. By performing such a device, a better bonding layer 3 can be obtained.

In the heating furnace 10, in order to sufficiently convert Sn of the surface solder layer 9 into an intermetallic compound, for example, it is heated at a temperature of about 200 ° C. to 400 ° C. for several minutes to several hours, and joined as described above. FIG. 5 shows an example of a cross section of the bonding layer 3 between the sensor chip 1 and the base substrate 4 on the sensor chip 1 side. In this example, since the Ti, Ni, Au layer is previously applied to the surface of the back surface 1b of the sensor chip 1, it reacts with Sn of the surface solder layer 9 of the composite solder material 7 and can be joined. . On the Cu of the core layer 5, a Cu ₃ Sn layer 13 and a Cu ₆ Sn ₅ layer 14 are formed in order. This confirms that the intermetallic compound layer 6b on the base substrate side also shows a similar configuration.

Next, effects obtained by forming the intermetallic compound layer 6 including the Cu ₃ Sn layer 13 and the Cu ₆ Sn ₅ layer 14 will be described. The Cu ₃ Sn layer 13 and the Cu ₆ Sn ₅ layer 14 are intermetallic compounds, and have a Young's modulus at room temperature of about 80 GPa or more, a yield strength of about 1800 MPa, and a micro Knoop hardness of 70 or more. The melting point of the Cu ₆ Sn ₅ layer 14 is 415 ° C., and the melting point of the Cu ₃ Sn layer 13 is 640 ° C. In general, material deformation at a high temperature is greatly influenced by the ratio between the use environment temperature and the melting point. For this reason, a high melting point means a high resistance to deformation such as creep at high temperatures. Therefore, in this example, the sensor sensitivity is high by having the intermetallic compound layer 6 including the Cu ₃ Sn layer 13 and the Cu ₆ Sn ₅ layer 14 which are already hard materials at room temperature, and the temperature is 100 ° C. to 150 ° C. Even under a use environment at a high temperature in the vicinity, creep deformation in the intermetallic compound layer 6 is small, and a stable sensor output can be exhibited over a long period of time.

  Compared to the conventional Sn-based solder with a melting point of 220 ° C to 230 ° C, the Sn-based solder has a Young's modulus of approximately 50 GPa or less at room temperature, a yield strength of approximately 50 MPa or less, and a Micronoop hardness of approximately 7. Yes, softer than the intermetallic compound layer 6 described above. The melting point is also around 220 ° C. to 230 ° C., and the usage environment of 100 ° C. to 150 ° C. is a temperature close to the melting point for this Sn-based solder and is easily deformed. Therefore, in the above high temperature use environment of 100 ° C. to 150 ° C., the Sn solder layer is likely to be creep-deformed, and the solder layer relaxes the strain generated in the object to be measured. This leads to fluctuations in the sensor output value.

From the above, in joining using the composite solder material 7 of the present embodiment, Sn having a melting point of 232 ° C. was used for the surface solder layer 9, so that a normal soldering apparatus was used within the heat-resistant temperature of the sensor chip 1. The sensor chip 1 used can be bonded to the base substrate 4. However, the bonding layer 3 is compounded and increased in hardness during the subsequent cooling process or by once again performing high-temperature treatment after cooling. High melting point can also be achieved. Therefore, it can be said that it is suitable as a joining method of a high-precision mechanical quantity measuring device that requires a joining structure that is hard and hardly deforms. Conversely, it is conceivable to bond using Cu ₃ Sn and Cu ₆ Sn ₅ from the beginning, but heating above these melting points is required, a special bonding device that can handle higher temperatures is required, and sensor chip 1 There is also a concern about the heat resistance of the chip, and there is a concern about chip cracking defects.

  Next, the reason why the intermediate layer 5 is provided in the bonding layer 3 between the sensor chip 1 and the base substrate 4 will be described.

First, the problem of manufacturing restrictions will be described.
In order to join the sensor chip 1 and the base substrate 4 with only the intermetallic compound layer without the intermediate layer 5, the Cu layer and the Sn layer are formed on the back surface 1 b of the sensor chip 1 or the surface of the base substrate 4. Set them aside. However, in this method, considering the holding time at a high temperature so that Cu and Sn form an intermetallic compound so that the Sn layer does not remain, the Sn layer cannot be made too thick. The thickness of the bonding layer between the sensor chip 1 and the base substrate 4 is reduced. For this reason, if the difference between the thermal expansion coefficients of the materials constituting the sensor chip 1 and the base substrate 4 is large, the bonding layer is thin, so that the stress applied to the bonding layer also increases, and chip cracking or the like may occur. Even when chip cracking does not occur, a large stress is generated in the thin intermetallic compound layer, and there is a concern that the bonding layer 3 may be destroyed if voids or the like are generated during manufacturing. Therefore, from the viewpoint of manufacturing, in a structure in which only thin intermetallic compound layers are joined, there is a concern that chip cracking may occur depending on the substrate material. In particular, when a sensor chip is directly bonded to the object to be measured without using the base substrate, it is difficult to optimize the physical properties of the object to be measured.

  The necessity of the intermediate layer 5 will be described from the viewpoint of sensor characteristics and reliability. By having the intermediate layer 5 made of a refractory metal such as Cu, a metal such as Cu has a higher Young's modulus (about 100 GPa or more) and a higher yield stress than ordinary solder materials. There is little concern about creep. In addition, since the melting point is high, creep deformation in the intermediate layer 5 hardly poses a problem even if the use environment temperature is around 100 ° C. to 150 ° C. Therefore, in the bonding layer 3 of the present invention, by forming the hard intermetallic compound layer 6, the strain generated in the object to be measured is transmitted with good sensitivity because the intermetallic compound layer 6 hardly deforms, and the intermediate layer 5. Since it is composed of a metal layer having a high melting point and a high Young's modulus, it can cope with a strain load mainly by elastic deformation and hardly creep. As a result, creep deformation can be prevented in the entire bonding layer 3, and a stable sensor output and high sensitivity can be obtained even at a high temperature in the vicinity of 100 ° C to 150 ° C.

  The thickness of the intermediate layer 5 such as a Cu layer is preferably 5 μm or more in order to suppress creep deformation of the entire bonding layer 3 even in terms of preventing cracking of the intermetallic compound layer and the sensor chip 1 and measuring maximum allowable strain. Also, from the viewpoint of handling the composite solder material 7 at the time of manufacture, the intermediate layer 5 is desirably 5 μm or more as described above. On the other hand, if the intermediate layer 5 is too thick, there is a concern that the strain generated in the object to be measured is not transmitted to the sensor chip 1, and the intermediate layer such as Cu is used from the upper limit of the thickness at which the maximum strain to be detected is transmitted. The thickness of 5 is desirably about 500 μm or less.

  The thickness of the surface solder layer 9 is preferably at least 2 μm because it is difficult to ensure wetting if it is too thin. Further, in order to proceed with sufficient compounding, if the surface solder layer 9 is thick, a long-time treatment is required, so about 30 μm or less is desirable.

  From the above, the shape of the portion related to the bonding layer of this embodiment is such that the sensor chip 1 is about 1 to 5 mm square, the thickness is about 50 to 400 μm, and the bonding layer 3 has a maximum thickness of 500 to 600 μm. The base substrate 4 has a thickness of about 0.1 to 10 mm.

  In the joining structure of this embodiment, which is an example, the core layer 8 is made of Cu having a thickness of 40 μm, the surface solder layer 9 is made of a composite solder material 7 made of Sn having a thickness of 15 μm, and the sensor chip 1 having a 2 mm square and a thickness of 100 μm is formed on the surface. This is a structure in which a base substrate is joined by a 1 mm thick SUS substrate to which 3 μm Ni and 0.1 μm Au are applied.

In the above, the case where the core layer 8 is Cu and the surface solder layer 9 is Sn as an example of the composite solder material 7 is not limited to this as long as the same effect can be obtained. In the present invention, the high melting point metal layer is considered a temperature range of 500 ° C. or more, for example, the core layer is a Cu-based alloy, Fe-based alloy, Ni-based alloy, Al-based alloy, SUS, W, Mo 42 alloy, Invar, etc. can be applied.
In addition to Sn, the surface solder layer 9 is SnAg, SnIn, SnCu, SnZn, SnBi, SnSb, AuSn, or ternary or quaternary solder with other elements added thereto. Can also be used.

  In this embodiment, as a method of manufacturing the composite solder material 7 shown in FIG. 3, the Sn surface solder layer 9 is formed on the Cu core layer 8 by plating, but in addition, the core layer 8 and the surface solder layer 9 are obtained. It is also possible to manufacture by clad rolling with the Cu material and the Sn material overlapped. Alternatively, a dipping method may be employed in which Sn is deposited by dipping a Cu foil in a Sn solder solution that is heated and melted. Alternatively, the solder layer may be formed by supplying a paste-like solder mixed with solder powder and an organic material by a printing method and heating, and then washing if necessary. Alternatively, a method such as vapor deposition or sputtering may be used.

  The composition and thickness of the surface solder layer 9 can be changed on both sides of the core layer 8. For example, the surface solder layer 9 on the side in contact with the sensor chip 1 is made thick, and the surface solder layer 9 on the side in contact with the opposite base substrate 4 is made thin. In the above example, in the normal process, the base substrate 4, the composite solder material 7, and the sensor chip 1 are often laminated and heated in this order, but the solder on the core layer 8 is below the core layer 8 due to the influence of gravity and the like. Even when heated to the same solder layer and heated at the same temperature, compounding may be insufficient with the solder on the lower side of the core layer 8, and thus, on both sides of the core layer 8 of the composite solder material 7. If the thickness of the surface solder layer 9 is changed, optimization of the finished thickness and control of compounding become easy.

  Further, the surface solder layer 9 usually has an oxide film on the surface, and there is a concern that the wettability may be lowered due to the presence of the oxide film depending on the atmosphere and process during bonding. Therefore, a protective layer for preventing oxidation of the surface solder layer 9 may be provided on the outermost surface in order to improve the bonding quality. For example, an Au layer, an Ag layer, a Cu layer, or a two-layer protective layer of these Ag layers / Au layers, etc., the thickness of the entire protective layer is sufficient to be several μm or less. Au, Ag, Cu, etc. are formed by vapor deposition, plating, clad method, etc. Further, since the protective layer is thin and easily dissolved in the solder, it does not cause problems such as melting into the solder during bonding and remaining protective layer. In the case of the Cu protective layer, Cu itself oxidizes, but the Cu oxide film is more easily reduced than the Sn oxide film, and particularly good bonding can be achieved by using hydrogen, formic acid, etc. Is also stable. Cost is also advantageous.

  The core layer 8 below the surface solder layer 9 may be flat, but a dimple or the like may be used, or a core layer that has been roughened to increase the roughness may be used. In addition, a core layer 8 in which small-diameter openings are provided at several locations, at random, or at an equal pitch may be used. As a result, the surface area of the core idea is increased, and the effect of shortening the production by promoting the compounding can be expected. In addition, even if low melting point Sn or the like remains, the remaining low melting point Sn layer is easily dispersed by the surface step of the core layer 8 so that creep deformation hardly occurs. In addition, the adhesion can be improved, and the stabilization effect can be expected by improving the bonding strength.

  In this example, the main material of the sensor chip is silicon. However, the present invention is not limited to this, and SiC or the like may be used. If the temperature sensing unit is also formed on the same chip, the output value can be temperature-corrected with high accuracy.

In FIG. 6, sectional drawing of the example which joined the mechanical quantity measuring apparatus 100 of this invention and the to-be-measured object 30 is shown. In this configuration, the back surface of the base substrate 4 and the device under test 13 are fixed at several places with screws 18.
FIG. 7 shows an example in which the mechanical quantity measuring device 100 of the present invention and the object to be measured 30 are joined by the adhesive 19. By connecting in this way, it becomes possible to detect the strain of the object to be measured with high sensitivity.
In addition to the methods shown in FIGS. 6 and 7, a method using welding, a method using heat due to friction, or the like may be used.

  Further, in Example 1, the sensor chip 1 is bonded to the base substrate 4 and these are connected to the object to be measured 30, but the sensor chip 1 is measured using the bonding layer 3 of the present invention without using the base substrate. It is also possible to join to 30.

In Example 1, the composite solder material 7 has an example of a three-layer structure of the core layer 8 and the surface solder layer 9, but a five-layer structure in which the base layer 23 is inserted between the core layer 8 and the surface solder layer 9. An example of the composite solder material 22 is shown in FIG.
This is because it is necessary for the metal of the core layer 8 to be dissolved and diffused to the surface solder layer 9 at a certain rate in order to form an intermetallic compound within a working time that can be put to practical use to some extent. This is a limitation in material selection. Therefore, by adopting such a five-layer structure 22, the surface solder layer 9 and the base layer 23 are selected from Sn-based solder, Cu, Ni, Ag, or Au, which is easily formed into an intermetallic compound, and the core layer 8 is An appropriate metal material can be selected from the viewpoint of thermal expansion coefficient, Young's modulus, material cost, and the like.

  For example, a material such as 42 alloy has a merit that its thermal expansion coefficient is low, although dissolution in the surface solder layer 9 is slow. Therefore, by using 42 alloy as the core layer 8, Cu as the underlayer 23, and Sn layer on the surface, the underlayer 23 and the surface solder layer 9 can be made into an intermetallic compound within a certain working time in the joining process. The melting point and strength can be increased. At the same time, the presence of the 42 alloy used for the core layer 8 makes it possible to optimize the deformation behavior and reliability of the entire bonding layer.

  FIG. 9 shows a bonding structure formed when this composite solder material 22 is applied to the manufacture of a mechanical quantity measuring device. A bonding layer 24 is formed between the sensor chip 1 and the base substrate 4, and this is an intermediate layer. 25, and an unreacted portion 26 of the underlayer 23 and an intermetallic compound layer 27 above and below it. By adopting such a structure, it is possible to share the roles of the part that controls the bonding and the part that controls the performance of the sensor module, and it is possible to provide a mechanical quantity measuring device that excels in both sensor sensitivity and long-term reliability.

  In addition to this, it is also possible to provide the surface solder layer 9 after forming the base layer 23 only on one side of the core layer 8 and to provide only the surface solder layer 9 on the other side of the core layer 8.

An example in which the mechanical quantity measuring device of the present invention is applied to a pressure sensor module is shown in FIG.
A pressure sensor module 400 whose sectional view is shown in FIG. 10 includes a container 54 including a cylindrical portion 52 provided with a hollow hole 51 inside and a lid portion 53 that closes an upper portion of the hollow hole 51 in the cylindrical portion 52. . Further, a region of a diaphragm 56 is formed in the lid portion 53 at the upper part of the hollow hole 51, and the sensor chip 1 includes the intermetallic compound layer of the present invention and a high melting point metal layer. A sensor module 57 attached to the base substrate 4 via the bonding layer 3 is attached to the surface opposite to the hollow hole 51 of the diaphragm 56 portion. A printed circuit board 20 is attached via wire bonding 21 in order to output a strain detection amount from the sensor chip 1. Further, a case 58 and a connector (not shown) are attached to the periphery in order to protect these sensor module 57 portions and output measurement values.

  The base substrate 4 is made of, for example, a CIC substrate, Mo, 42 Alloy, SUS, Al, ceramic, or the like, and a SUS material or the like is applied to the cylindrical portion 52, the diaphragm 56 portion, or the like. The case 58 is made of resin or the like, but may be made of a metal material if it does not have heat resistance.

  The diaphragm 56 and the base substrate 4 are joined using welding, brazing material, screw fixing, caulking, heat due to friction, or the like. Further, when the volume of the pressure sensor module 400 is limited and cannot be stored, the printed board 20 uses a flexible board or a springy thing such as a connector or a probe pin to extract a signal. It is also possible.

  In the pressure sensor module 400, the joint portion 55 is connected to, for example, a hydraulic piping of an automobile. Therefore, the sensor chip 1 connected to the base substrate 4 bonded to the diaphragm 56 via the bonding layer 3 of the present invention is distorted via the diaphragm 56 according to the change of the hydraulic pressure, so that the change of the pressure is an electric signal. Convert to and measure.

  In manufacturing the pressure sensor module 400, the sensor module 57 in which the sensor chip 1 is attached to the base substrate 4 using the bonding layer 3 may be separately prepared and then attached to the lid portion 53. A process of attaching the sensor chip 1 after attaching the substrate 4 first may be used.

  A pressure sensor module 500 structure in which the sensor chip 1 is directly joined to the diaphragm 56 without using the base substrate 4 is also possible. An example of this is shown in FIG. 11, in which the sensor chip 1 is directly bonded to the diaphragm 56 using the bonding layer 3 having the intermetallic compound layer of the present invention and a high melting point metal layer. The diaphragm 56 is distorted in accordance with the change in hydraulic pressure, and the amount of distortion is detected by the strain detector 2 of the sensor chip 1 to convert the change in pressure into an electrical signal. When the base substrate 4 is not used as in this example, a surface treatment layer that can ensure the wetting of the solder layer may be required on the surface of the diaphragm 56 opposite to the hollow hole 51.

  In the pressure sensor modules 400 and 500 created as described above, even when the joint portion 3 of the sensor chip 1 is at a high temperature, it is stable with little creep deformation and has high reliability such as a temperature cycle. For this reason, even when used in a high-temperature environment such as measuring the fuel pressure of gasoline in an automobile or the like, the change in pressure can be measured with high sensitivity and stably for a long period of time. Further, in this method, there are few chip cracking defects in the bonding process of the sensor chip 1, and the yield at the time of manufacture is good.

DESCRIPTION OF SYMBOLS 1 Sensor chip 1a Main surface 1b of sensor chip 2 Back surface of sensor chip 2 Strain detector 3 Bonding layer 4 Base substrate 5 Intermediate layers 6, 6a, 6b of bonding layer 7 Intermetallic compound layer 7 Composite solder material 8 Core layer 9 Surface solder layer 10 Heating furnace 11 Heater 12 Bonding correction jig 13 Intermetallic compound layer (Cu ₃ Sn layer)
14 Intermetallic compound layer (Cu ₆ Sn ₅ layer)
16 Weight 18 Screw 19 Adhesive 20 Printed circuit board 21 Wire bonding 22 5-layer composite solder material 23 Underlayer 24 Bonding layer 25 Intermediate layer 26 Unreacted portion of underlayer 27 Intermetallic compound layer 28 Electrode pad 29 Electrode pad 30 DUT 51 Hollow hole 52 Cylinder portion 53 Lid portion 54 Container 55 Joint portion 56 Diaphragm 57 Sensor module 58 Case 100 Mechanical quantity measuring device 400 Pressure sensor module 500 Pressure sensor module

Claims (9)

A sensor chip having a strain detector for detecting expansion and contraction in the in-plane direction on the semiconductor substrate;
A base substrate interposed between the measurement object and the sensor chip to support the sensor chip and transmit the distortion of the measurement object to be detected to the sensor chip;
A wiring portion for leading the wiring from the electrode of the sensor chip to the outside,
The mechanical quantity measurement characterized in that the back surface of the sensor chip opposite to the surface having the strain detection section and the base substrate are bonded via a bonding layer in which an intermetallic compound layer and a high melting point metal layer are laminated. apparatus.   The bonding layer for bonding the back surface of the sensor chip and the base substrate has a three-layer structure in which a first intermetallic compound layer, a high melting point metal layer, and a second intermetallic compound layer are stacked. The mechanical quantity measuring device according to claim 1.   The mechanical quantity measuring device according to claim 1, wherein the intermetallic compound layer contains Cu and Sn, Ni and Sn, Au and Sn, or Ag and Sn as main components.   The metal layer is made of any one of Cu, Cu alloy, Ni, Ni alloy, Al, Al alloy, Fe alloy, SUS, W, Mo, 42 alloy, and Invar. The mechanical quantity measuring device according to claim 1 or 2.   The mechanical quantity measuring device according to claim 1, wherein the metal layer has a thickness in a range of 5 μm to 500 μm. Place the base substrate in the heating furnace,
On top of that, a composite solder material having a three-layer structure composed of a core layer made of a refractory metal and a low-melting surface solder layer laminated on both sides thereof is placed.
Furthermore, a sensor chip having a strain detection unit for detecting expansion and contraction in the in-plane direction on the semiconductor substrate is placed on the surface of the composite solder material opposite to the surface having the strain detection unit,
Heating above the melting point of the surface solder layer, reacting the molten solder layer with the metal of the core layer,
Heating is continued until the solder in the solder layer sufficiently forms an intermetallic compound.   The core layer of the composite solder material is composed of any material of Cu, Cu alloy, Ni, Ni alloy, Al, Al alloy, Fe alloy, SUS, W, Mo, 42 alloy, and Invar. The method of manufacturing a mechanical quantity measuring device according to claim 6, wherein:   The surface solder layer of the composite solder material may be Sn, SnAg solder, SnIn solder, SnCu solder, SnZn solder, SnBi solder, SnSb solder, AuSn solder, or one or two other types thereof. The method for manufacturing a mechanical quantity measuring device according to claim 6, wherein the mechanical quantity measuring device is made of any material of solder added with an element. In place of the composite solder material having a five-layer structure in which a base layer is inserted between the core layer and the surface solder layer of the composite solder material having the three-layer structure,
The surface solder layer and the base layer are composed of materials that are easily intermetallic compounded with each other,
The core layer is configured by selecting a metal material having a sufficiently high Young's modulus to such an extent that creep deformation does not easily occur due to strain generated in the measurement object. A method for manufacturing a mechanical quantity measuring device.

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