JP2009241164A - Semiconductor sensor apparatus and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-sized and lightweight semiconductor sensor apparatus and a manufacturing method therefor, capable of attaining high resistance to cap cracking and resin cracking and resistance to hole clogging of a holed cap by reducing stress generated by molding resin which a MEMS assembly receives and stabilizing characteristics of the semiconductor sensor apparatus. <P>SOLUTION: By exposing a chip top surface of an upper cap of the MEMS assembly, making the top surface flush with a resin surface or recessing the top surface to reduce the stress generated by the molding resin which the MEMS assembly receives and stabilize the characteristics of the semiconductor sensor apparatus, the small-sized and light-weight semiconductor sensor apparatus capable of attaining high resistance to cap cracking and resin cracking and resistance to hole clogging of a holed cap can be achieved. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to MEMS (Micro-Electro-Mechanical System).
The present invention relates to a semiconductor sensor device having a chip and a manufacturing technique thereof, and more particularly to a semiconductor sensor device having a MEMS chip having a movable part and a technique effective when applied to the manufacturing thereof.

By combining semiconductor manufacturing process technology with machining technology and material technology,
The MEMS technology for realizing a system having a three-dimensional microstructure on a semiconductor substrate can be applied to a very wide range of fields. In particular, these semiconductor sensor devices used for automobiles, airplanes, portable terminal devices, toys and the like are attracting attention in the field of detecting physical quantities such as acceleration, angular velocity, and pressure.

These semiconductor sensor devices are characterized by having movable parts formed by MEMS technology. A physical quantity value such as acceleration, angular velocity, pressure, and the like is obtained by detecting the amount of movement of the movable part by a resistance change or capacitance change of the piezoresistive element and processing the data. Patent Documents 1 to 3 disclose acceleration sensor devices, Patent Documents 4 to 6 disclose angular velocity sensor devices, and Patent Documents 7 to 8 disclose pressure sensor devices.

JP 2006-133123 A JP-A-8-233851 JP-A-11-160348 JP 2006-175554 A JP 2003-194545 A Special table 2005-524077 JP 2004-132947 A JP-A-10-098201

The structure of the acceleration sensor disclosed in Patent Document 1 will be briefly described with reference to FIG. The semiconductor sensor device will be described using an acceleration sensor device unless otherwise specified. In addition, since the structure and configuration of the semiconductor sensor chip used in the semiconductor sensor device conforms to Patent Documents 1 to 8, detailed description may be omitted. FIG. 3a) shows an exploded perspective view of the triaxial acceleration sensor. In the triaxial acceleration sensor 30, the sensor chip 20 and the IC restriction plate 25 are fixed to a case 32 with an adhesive such as resin at a predetermined interval. Chip terminal 2 of sensor chip 20
Reference numeral 1 denotes a wire 34 connected to an IC regulating plate terminal 38, and the IC regulating plate terminal 38 is connected to a case terminal 35 via a wire 34 ′, and a sensor signal is taken out from an external terminal 36. A case lid 33 is fixed to the case 32 with an adhesive and sealed. FIG. 3b) is a kk ′ cross section of FIG. 3a). FIG. 3c) is a plan view of the sensor chip 20 as viewed from the top surface of the sensor. The sensor chip 20 includes a beam portion 22 that forms a pair with a square support frame portion 24 and a weight portion 23, and the weight portion 23 is held at the center of the support frame portion 24 by two pairs of beam portions 22. A piezoresistive element is formed in the beam portion 22, an X-axis piezo 26 and a Z-axis piezo 28 are provided for a pair of beams, and a Y-axis is provided for the other pair of beams.
A shaft piezo 27 is formed. A sensor chip terminal 21 is formed on the support frame portion 24. Illustration of wiring between the sensor chip terminal 21 and the piezoresistive element of each axis is omitted.

In the triaxial acceleration sensor 30 shown in FIG. 3, the case 32 and the case lid 33 are made of ceramic such as alumina. Since the case 32 and the case lid 33 are made of ceramic, there is a limit to reducing the wall thickness, and it is difficult not only to reduce the size but also to reduce the weight. Since the metal case terminal 35 and the external terminal 36 are formed in the ceramic case 32 and these are connected within the ceramic, the case 32 is expensive, and it is difficult to realize an inexpensive acceleration sensor as long as the ceramic case is used. The case 32 and the case lid 33 are bonded and sealed with an adhesive resin 39. Since the resin is used, there is a problem that the air density decreases due to changes in the surrounding environment.

Patent Document 9 describes a method for increasing the airtightness. As shown in FIG. 4a), a MEMS substrate 81 in which a large number of MEMS chips are formed and a cap substrate 82 in which a large number of cap chips are bonded are joined together, and the movable part of the MEMS chip is sealed with upper and lower cap chips.
An S assembly substrate 88 is obtained. Since packaging is performed at the time of the substrate, WLP (Wafer L
evel Package). The separation part 90 indicated by the alternate long and short dash line of the MEMS assembly substrate 88 is cut with a diamond grindstone to obtain the MEMS assembly 80 shown in FIG. 4B).
The part to be sealed is limited to the movable part of the MEMS chip, in other words, by shortening the total joint length, it is easy to ensure airtightness. As shown in FIG. 4 c), the MEMS assembly 80 is bonded to the inner bottom portion of the case 83, and the case lid 84 is bonded to the upper side portion of the case 83 to obtain the semiconductor sensor device 85. However, if the MEMS assembly 80 is put in a case as shown in FIG. A semiconductor sensor device 86 in which the MEMS assembly 80 is covered with a resin 87 by applying a semiconductor resin sealing technique as disclosed in Patent Document 10 has begun to be put into practical use. FIG. 4d) shows an example of resin sealing. MEMS
By reducing the thickness of the mold resin 87 so that the assembly 80, the wiring 89, etc. do not directly touch the outside air, it is possible to reduce the size and weight. Further, unlike the semiconductor sensor device 85 of FIG. 4c), it is possible to reduce the manufacturing cost because the case bonding work or the like is not necessary.

Japanese Patent Laid-Open No. 3-2535 JP-A-10-170380

The manufacturing process of the acceleration sensor using WLP will be briefly described with reference to FIG. The upper cap substrate 41, the MEMS substrate 42, and the lower cap substrate 43 are fixed to each other at the joint 61 to obtain the MEMS assembly substrate 44 [FIG. 5a)]. Since the fixing operation is performed in a vacuum, the movable part of the MEMS substrate 42 is in a vacuum atmosphere. The upper cap substrate 41 and the lower cap substrate 43 are removed to the separation portion 90 by grinding or the like to form the upper cap chip 45 and the lower cap chip 46 [FIG. 5b)]. M
The EMS board | substrate 42 is isolate | separated by cutting etc. in the isolation | separation part 90, and the MEMS assembly 47 is obtained [FIG. 5c)]
. The circuit board 48 and the wiring board 49 are joined [FIG. 5 d)], and the lower cap chip 46 of the MEMS assembly 47 is bonded and fixed on the circuit board 48 [FIG. 5 e)]. The MEMS assembly 47 and the circuit board 48, and the circuit board 48 and the wiring board 49 are electrically connected by wiring 50 [FIG. 5f)]. The acceleration sensor 40 is obtained by molding the circuit board 48, the wiring 50, and the MEMS assembly 47 on the wiring board 49 with the resin 51 [FIG. 5g].

A manufacturing process of a pressure sensor using WLP will be briefly described with reference to FIG. The upper cap substrate 52 with holes, the MEMS substrate 53, and the lower cap substrate 54 are fixed to each other by the joining portion 61 to obtain the MEMS assembly substrate 55 [FIG. 6a)]. Since the fixing operation is performed in a nitrogen gas atmosphere, the movable portion of the MEMS substrate 42 is in a nitrogen gas atmosphere. The upper cap substrate 52 with holes and the lower cap substrate 54 are removed by grinding or the like to the separation portion 90 to form the upper cap chip 57 and the lower cap chip 58 having the through holes 56 [FIG. 6B]. The MEMS substrate 53 is separated by cutting or the like at the separation unit 90 to obtain a MEMS assembly 59 [FIG. 6c)]. The circuit board 48 and the wiring board 49 are joined together [FIG.
d)], the lower cap chip 58 of the MEMS assembly 59 is bonded and fixed on the circuit board 48 [
FIG. 6e)]. The MEMS assembly 59 and the circuit board 48, and the circuit board 48 and the wiring board 49 are connected to the wiring 5.
Electrical connection is made at 0 [Fig. 6f)]. Circuit board 48 and wiring 50 on wiring board 49, MEM
The S assembly 59 is molded with the resin 51 to obtain the pressure sensor 60 [FIG. 6g)].

When many acceleration sensors 40 and pressure sensors 60 are manufactured and inspected, it has been found that the following problems occur. The acceleration sensor 40 has the problems shown in FIGS. 7a) to 7c). In FIG. 7a), when resin molding is performed, a stress 63 as indicated by an arrow is applied to the MEMS assembly 47 and the characteristics of the acceleration sensor change. It is considered that the stress is generated due to a difference in thermal expansion coefficient between the resin 51, the MEMS assembly 47, the circuit board 48, and the wiring board 49. For example, in comparison with the characteristics of the acceleration sensor without resin mold in FIG.
) With resin molding, X-axis and Y-axis sensitivities (output mV / g per unit acceleration)
) Increases 3 to 5 times, and the three axes are not balanced, resulting in a defective product. When the acceleration sensor 40 having no problem with the three-axis balance was disassembled and investigated, a crack 64 as indicated by a broken line was found in the upper cap chip 45 as shown in FIG. 7B). There was a tendency for the cap chip 45 to be thin on the one containing the cap crack 64. When the cap crack 64 enters, the stress may be relaxed by the cap crack and the three axes may be balanced, but the airtightness of the MEMS assembly 47 is broken, so that the piezoresistive element is easily deteriorated and the reliability is lowered. Will do. On the contrary, if the cap chip 45 is thick, the resin 51 on the cap chip becomes thin, and a resin crack 65 as shown in FIG. Most of the starting points of the resin crack 65 are the corners of the upper cap chip 45. The resin crack 65 does not cause hermetic breakage of the MEMS assembly 47, but must be a defective product in terms of appearance. Since the pressure sensor 60 only detects displacement in one direction, there is no problem that the three axes cannot be balanced unlike the acceleration sensor.
The resin enters into the hole, and the hole clogging 66 is defective.

The present invention reduces the stress generated in the mold resin received by the MEMS assembly, stabilizes the characteristics of the semiconductor sensor device, makes it difficult for cap cracks and resin cracks to enter, and prevents clogging of cap chips with holes, It is an object of the present invention to provide a small and light semiconductor sensor device and a manufacturing method thereof.

A semiconductor sensor device according to the present invention includes a MEMS assembly formed of a MEMS chip having a movable part and an upper and lower cap chip that seals at least the movable part of the MEMS chip on a circuit board fixed on a wiring board. Fix the solid bottom cap chip and MEMS
A semiconductor sensor device in which a chip and a circuit board, a circuit board and a wiring board are connected by wiring, and the circuit board, wiring, and MEMS assembly on the wiring board are sealed with a resin member, and the upper surface of the upper cap chip is sealed It is preferable to be exposed from the resin member.

By sealing the movable parts of the MEMS chip such as the acceleration sensor and the gyro sensor with the upper and lower cap chips, the structure in which the output value is hardly affected by the atmosphere and pressure can be obtained. For example, the capacitance C of the capacitance element that detects the capacitance is represented by C = ε ₀ εS / d. Here, ε ₀ is the dielectric constant of vacuum, ε is the dielectric constant of the gas in the MEMS assembly, S is the electrode area, and d is the electrode spacing. Since the capacitance varies depending on the dielectric constant, that is, atmosphere (gas) and pressure (degree of vacuum) in the MEMS assembly, it is preferable to hermetically seal the MEMS assembly. Further, in a resistance element that outputs current or voltage, the resistance value of the resistance element is easily affected by moisture and temperature in the atmosphere. Therefore, it is preferable to hermetically seal in order to reduce the influence of moisture or the like mixed in the MEMS assembly on the measurement value.

The pressure sensor needs to hermetically seal the MEMS chip and the lower cap chip in order to detect deformation of the movable part of the MEMS chip due to a change in external pressure. For example, the movable part of the MEMS chip is formed in a diaphragm shape, and the MEMS chip, the lower cap chip, and the space part are hermetically sealed with an inert gas of vacuum or atmospheric pressure. Along with the pressure change in the external environment, the diaphragm is deformed and the resistance value of the piezoresistive element formed in the diaphragm changes, and the pressure value can be detected by converting the change in resistance value into current or voltage. If the MEMS chip and the lower cap chip are not hermetically sealed, the pressure in the space portion also changes in accordance with a change in the external pressure, so that the diaphragm does not deform and the pressure cannot be detected.

By exposing the upper surface of the upper cap chip without forming the resin of the mold on the upper surface of the upper cap chip of the MEMS assembly, the characteristics of the semiconductor sensor device due to the stress of the resin can be stabilized. The upper surface of the upper cap chip refers to the rear surface of the surface of the upper cap chip that is bonded to the MEMS substrate. By exposing the upper surface of the upper cap chip, the stress due to the resin can be greatly reduced, and the characteristics can be stabilized. Although the same effect can be obtained by exposing the entire upper cap chip, it is preferable to expose only the upper surface because there is a higher risk of the upper cap chip being damaged by an external force by being caught during handling. By eliminating the resin on the top surface of the upper cap chip, the thickness of the semiconductor sensor device can be reduced by the thickness of the resin. Alternatively, it is possible to increase the thickness of the upper cap chip by the resin thickness and improve the mechanical strength. By increasing the thickness of the upper cap chip, the number of grinding steps from the upper cap substrate to the upper cap chip can be reduced, and the grinding tolerance of the upper cap chip thickness can be relaxed.

Silicon is preferably used for the upper and lower cap substrates, and single crystal silicon that is particularly easy to be finely processed is preferable. The MEMS substrate is manufactured by applying semiconductor technology such as film formation, etching, and patterning to single crystal silicon. By producing the cap chip with the same material as the MEMS substrate, the linear thermal expansion coefficient can be adjusted. By combining the linear thermal expansion coefficients, the bonding portion between the MEMS substrate and the cap substrate is not easily broken even when the MEMS substrate and the cap substrate are bonded to each other or a temperature change applied in another manufacturing process. If the cap chip has a simple shape such as a flat plate, glass, polycrystalline silicon, ceramic, etc., which are substantially the same as the linear thermal expansion coefficient of the MEMS substrate, can be used. The cap substrate is provided so as to sandwich the MEMS substrate from above and below, and the material of the upper and lower cap substrates can be changed. For example, the upper cap substrate may be single crystal silicon and the lower cap substrate may be ceramic.

The bonding between the MEMS substrate and the cap substrate is not high temperature resistant because the detection elements, wiring, electrode pads, etc. on the MEMS substrate are not resistant to high temperatures, so anodic bonding or low melting point material bonding (low melting point metal bonding or eutectic crystal) It is preferable to use any method of bonding, low melting glass bonding, resin bonding, etc.), diffusion bonding, and surface activated bonding. The bonding between the MEMS substrate and the cap substrate is more preferably a low melting point material bonding. After aligning the MEMS substrate and the cap substrate, pressurization and heating are performed for bonding. The gap generated by the undulation between the MEMS substrate and the cap substrate is filled with the low-melting-point material, so that the airtightness can be improved. For this reason, since it is not necessary to apply a large pressure to force the substrate to swell, the risk of damaging the cap substrate or the like is reduced. In order to keep the space in the MEMS assembly substrate in a vacuum (under reduced pressure) or to fill and hermetically dry nitrogen or an inert gas, it is preferable that bonding can be performed in a vacuum (depressurized) atmosphere or in a dry nitrogen or inert gas atmosphere. .

For thinning and individualizing the cap substrate of the MEMS assembly substrate, grinding using a diamond grindstone or wet etching can be used. When wet etching is performed, it is necessary to perform processing for protecting the wiring portion and the electrode portion of the MEMS substrate from the etching solution. The MEMS substrate is preferably cut with a diamond grindstone. Cutting can also be performed using a laser.

The circuit board is bonded onto the wiring board, and the MEMS assembly is bonded onto the circuit board using a resin adhesive or a resin film. The MEMS assembly and the circuit board, and the electrodes of the circuit board and the wiring board can be performed by ultrasonic welding or solder welding using a metal thin wire (wire). Instead of the connection by the fine metal wire, the connection by the solder ball or the ball bond can be used. However, it is preferable from the viewpoint of the environment that the solder is a lead-free material.

When a force such as acceleration, angular velocity, or pressure is applied to the MEMS assembly from the outside, it is converted into a physical quantity such as current, voltage, capacitance, etc., by a piezoresistive element or a capacitance element formed on the movable part, and then output. To do. Since the change in the output physical quantity is minute, an element (amplifying circuit or the like) that amplifies the output is formed on the circuit board. Further, when the element is affected by temperature, it is preferable to mount a temperature correction circuit or the like. The wiring board is a printed circuit or a lead frame. In this application,
Although the circuit board and the wiring board are described as being separately manufactured and assembled, the present invention is not limited to this. The circuit board and the wiring board may be formed integrally, or the stacking order of the circuit board and the wiring board may be reversed.

A thermosetting resin such as an epoxy resin, a silicone resin, or a phenol resin can be used for resin sealing of the MEMS assembly and the circuit board, wiring board, and wire. As a molding method, a potting method using a liquid resin or a transfer molding method using a powder resin can be used. Set the MEMS assembly, circuit board, wiring board, and wire integrated in the mold, inject the thermosetting resin material into the mold, then heat and pressurize to cure the resin Thus, a semiconductor sensor device sealed with resin can be obtained.

A semiconductor sensor device of the present invention includes a MEMS chip formed of a MEMS chip having a movable part, a lower cap chip that seals at least the lower side of the movable part of the MEMS chip, and an upper cap chip that covers the upper side of the movable part. , MEMS on circuit board fixed on wiring board
A semiconductor sensor device in which a lower cap chip of an assembly is fixed, a MEMS chip and a circuit board, a circuit board and a wiring board are connected by wiring, and the circuit board and wiring on the wiring board are sealed with a resin member. The upper cap chip preferably has at least one through hole in the thickness direction of the upper cap chip, and the upper surface of the upper cap chip is preferably exposed from the sealing resin member.

Like a pressure sensor, the MEMS chip and the lower cap chip need to be hermetically sealed in order to detect a change in the external pressure as the amount of deformation of the movable part of the MEMS chip. Between the MEMS chip and the upper cap chip, it is necessary to provide a through hole in the upper cap so that an external pressure change is transmitted to the movable part (diaphragm). From the viewpoint of measurement principle, the upper cap chip may be omitted, but it serves as a protective cover for protecting the movable part that is easily damaged during the manufacture of the pressure sensor. In addition, the upper cap in which the through hole is formed also serves to prevent the diaphragm from being damaged by attenuating the pressure wave by attenuating the pressure wave when there is a sudden change in the external pressure.

By exposing the top surface of the upper cap chip when a MEMS assembly, a circuit board, a wiring board, or a wire-installed product is resin-molded, the upper cap chip can be structured to be hardly affected by the temperature deformation of the resin. . When the upper cap chip is deformed, stress is applied to the MEMS chip, which affects the movement of the movable part of the sensor.

It is also possible to use the upper cap substrate in which the through hole is formed or use the upper cap substrate in which the hole not penetrating is provided and form the through hole when the upper cap substrate is ground and thinned. The through hole may have a cylindrical shape, a truncated cone shape, a polygonal column shape, a polygonal truncated cone shape, or an irregular shape. The size, number and arrangement of the through holes can also be selected.

In the semiconductor sensor device of the present invention, it is preferable that the MEMS chip can detect at least one physical quantity of acceleration, angular velocity, and pressure.

The MEMS chip is an acceleration sensor, a gyro sensor, a pressure sensor, or the like that detects physical quantities such as acceleration, angular velocity, and pressure. When acceleration, angular velocity, pressure, or the like is applied to the MEMS chip from the outside, it is converted into a physical quantity such as a current, voltage, capacitance, or the like by a resistance element or a capacitance element formed on the movable part of the MEMS chip and output.

In the case of a structure in which a MEMS chip element or wiring is formed on the upper cap chip side having a through hole, there is a risk of corrosion due to moisture or gas in the air, so cover the element or wiring with a protective film. It is preferable to keep. As a material for the protective film, silicon oxide or silicon nitride used in a semiconductor process or a MEMS process can be used. Although silicon oxide and silicon nitride may be used alone, when silicon nitride is used, it is preferable to form silicon oxide on the base of silicon nitride. If silicon nitride is directly formed on the wiring, charge injection occurs in the wiring film, and there is a risk of affecting the characteristics of the MEMS chip. It is preferable to insert a silicon oxide film in which charges are difficult to be injected between the wiring and the silicon nitride.

In the semiconductor sensor device of the present invention, it is preferable that the exposed surface of the upper cap chip is the same as or recessed with the surface of the sealing resin member formed on the upper cap chip side.

If the upper cap chip upper surface is more convex than the surface of the sealing resin member, there is a risk that the upper cap chip may be caught and damaged when the semiconductor sensor device is handled. In order to avoid being damaged by being caught, it is preferable that the upper surface of the upper cap chip is the same or recessed from the surface of the sealing resin member. When a part of the wiring comes out from the upper surface of the upper cap chip, the upper surface of the upper cap chip is exposed, and the wiring can be surely resin-molded by making the surrounding resin surface convex.

When installing the MEMS assembly and circuit board, wiring board, and wiring assembly in a mold,
By bringing the mold and the upper cap chip upper surface in contact and performing transfer molding,
Resin molding can be performed so that the upper surface of the upper cap chip is exposed from the resin. Instead of pressing directly against the mold, a resin member adhesion preventing jig may be inserted between the mold and the upper cap chip. By changing the mold or the resin member adhesion preventing jig, the upper surface of the upper cap chip can be made to be the same as or recessed from the resin surface. When the same surface is used, after the resin molding, the resin can be ground with a grindstone to expose the upper surface of the upper cap chip. This is an effective method for exposing the upper surface of the upper cap chip having a through hole. By grinding the upper cap chip having a hole not penetrating at the same time as the resin to form a through hole, it is possible to eliminate a clogging defect in which the mold resin enters the through hole.

The manufacturing method of the semiconductor sensor device of the present invention includes a step of forming a MEMS substrate and a cap substrate, a step of fixing an upper and lower cap substrate to at least a movable part of the MEMS substrate, a step of forming the cap substrate into a cap chip, and cutting the MEMS substrate. Forming a MEMS assembly to form a MEMS assembly, fixing a circuit board on the wiring board, fixing a lower cap chip surface of the MEMS assembly on the circuit board, wiring board and circuit board, circuit board and MEMS Wiring the assembly, circuit board and wiring on the wiring board, sealing the MEMS assembly with a resin member, grinding the upper cap side of the MEMS assembly and sealing resin member surface and upper cap chip surface Preferably, the method includes a step of exposing the upper surface of the upper cap chip to the same surface.

The manufacturing method of the semiconductor sensor device of the present invention includes a step of forming a MEMS substrate and a cap substrate, a step of fixing an upper and lower cap substrate to at least a movable part of the MEMS substrate, a step of forming the cap substrate into a cap chip, and cutting the MEMS substrate. Forming a MEMS assembly to form a MEMS assembly, fixing a circuit board on the wiring board, fixing a lower cap chip surface of the MEMS assembly on the circuit board, wiring board and circuit board, circuit board and MEMS It is preferable to have a step of wiring the assembly, a step of sealing the MEMS assembly in which the resin member adhesion preventing jig is pressed against the upper surface of the circuit board and wiring on the wiring substrate and the upper cap chip, with the resin member.

By exposing the upper surface of the upper cap chip and making it the same as the resin surface, it is possible to reduce the stress generated by the mold resin received by the MEMS assembly and stabilize the characteristics of the semiconductor sensor device. It was possible to provide a small and lightweight semiconductor sensor device that is difficult to enter and that clogging of the cap chip with holes hardly occurs.

Hereinafter, the present invention will be described in detail based on examples with reference to the drawings. In order to make the explanation easy to understand, the same reference numerals are used for the same parts and parts.

A semiconductor sensor device according to a first embodiment of the present invention will be described with reference to FIG. The description of the semiconductor sensor device of the present application uses an acceleration sensor and a pressure sensor, and the semiconductor sensor device, the acceleration sensor, and the pressure sensor are used synonymously. The process from the production of the MEMS assembly substrate to the MEMS assembly and the circuit board and wiring of the wiring board of the acceleration sensor of FIG. 1 is the same as the production process and method shown in FIGS. 5a) to 5g). The process for removing the resin on the upper surface of the upper cap chip later is different. A detailed description of the steps performed up to FIG. 1 will be given with reference to FIGS.

The MEMS substrate 42 shown in FIG. 3 is manufactured by an SOI (Silicon On Insul) having a silicon oxide layer of about several μm and a silicon layer of about 6 μm on a silicon plate having a thickness of about 400 μm.
ator) wafers were used. As shown in FIG. 3, a photoresist pattern was formed in the shape of the piezoresistive elements 26 to 28 on the surface on the silicon layer side. Boron 1-3 in the silicon layer
x10 ¹⁸ atoms / cm ^{3 is} implanted to form piezoresistive elements 26 to 28, and wiring (not shown) and sensor chip terminals 21 connected to the piezoresistive elements 26 to 28 are formed using a metal sputtering and dry etching apparatus. did. The silicon layer and the silicon plate were processed using a photolithography and dry etching apparatus to form a beam portion 22 formed in the silicon layer, and a weight portion 23 and a support frame portion 24 formed from the silicon layer to the silicon plate. . The silicon oxide layer functions as an etching stopper during dry etching of silicon. Since only silicon is dry etched, the silicon plate is dry etched but the silicon oxide layer remains. After dry etching, the silicon oxide layer was removed by wet etching by dipping in an aqueous solution of hydrofluoric acid and ammonium fluoride. The dry etching was carried out in a plasma introducing SF6, oxygen mixed gas and C ₄ F ₈ gas are alternately. A MEMS substrate 42 having a large number of acceleration sensor chips 20 formed on one wafer was produced. On the upper and lower surfaces of the MEMS substrate 42, bonding portions 61 formed with a bonding material to be bonded to the cap substrate were provided. Junction 61
In this example, a laminated film of Au—Sn alloy as a bonding material was formed by electroplating to a thickness of 5 μm. Junction 6
The width of 1 was set to 60 μm so as to be hermetically sealed.

After the piezoresistive elements 26 to 28, the wiring, and the sensor chip terminal 21 are formed, silicon nitride is formed on them by CVD (Chemical Vapor Deposition).
. After stacking 2 μm, the silicon nitride on the sensor chip terminal 21 was removed by photolithography and etching. Next, after opening the sensor chip terminal 21 and the joint 61 with a photoresist, a laminated film was formed in the order of Cr 0.1 μm-Ni 0.4 μm-Au 0.5 μm by metal sputtering. Next, the photoresist and the metal film other than the sensor chip terminal 21 and the joint 61 were removed, and the portion exposed to the grinding fluid was protected with a protective film. In this example, the cap chip was separated into individual pieces by grinding, so the protective film may be omitted, but when the individualization is performed by wet etching or the piezoresistive element is exposed to the atmosphere. It is better not to omit the pressure sensor.

The upper cap substrate 41 and the lower cap substrate 43 are made of silicon having a thickness of 400 μm. The cap substrate is ground up to the separation portion 90 indicated by the alternate long and short dash line to be separated into individual pieces to obtain cap chips 45 and 46. Deep groove for dividing into 250 μm, shallow groove covering the movable part of the MEMS chip is 20 μm
m formed by wet etching.

The MEMS substrate 42 having a thickness of about 410 μm and the upper and lower cap substrates 41 and 43 having a thickness of about 400 μm were held under reduced pressure while being adjusted to a predetermined position. A pressure of about 10 kN was applied to the upper and lower cap substrates and heated at about 300 ° C. for about 1 minute to obtain a MEMS assembly substrate 44. Since the MEMS substrate and the cap substrate have a thickness of about 400 μm, the MEMS substrate and the cap substrate have sufficient mechanical strength, and there was no problem of cracking or cracking during pressure bonding.

Using an # 2000 diamond grindstone, the upper and lower cap substrates 41 and 42 were ground to the separating portion 90 indicated by the alternate long and short dash line. The upper cap substrate was ground by about 200 μm to form an upper cap chip 45 having a thickness of about 200 μm. The lower cap substrate 46 was ground by about 300 μm to form a lower cap chip 46 having a thickness of about 100 μm. The thickness of the upper cap chip is 100 μm from the lower cap chip.
By increasing the thickness, the mechanical strength could be secured even when the upper surface of the upper cap chip was exposed from the resin member. 3-5 (L / min) on diamond grinding wheel and MEMS assembly substrate during grinding
An amount of grinding fluid was applied. The surface roughness of the cap chip was Ra ≦ 200 nm. The surface roughness Ra was measured according to JISB0601. A MEMS grindstone was used in the same manner as the grinding, and the MEMS substrate was cut at the separation part 90 indicated by a one-dot chain line to obtain a MEMS assembly 47.

A circuit board 48 for performing amplification of signals from the acceleration sensor chip, temperature correction, and the like was fixed on a wiring board 49 having a thickness of 100 μm with a die attach film. MEM on circuit board 48
The lower cap chip 46 of the S assembly 47 was fixed with a die attach film. A bare gold wire 50 having a diameter of 25 μm was connected between the MEMS assembly 47, the circuit board 48, and the wiring board 49 with an ultrasonic bonder.

An epoxy resin 51 was molded from the structure in which the MEMS assembly 47, the circuit board 44, and the wiring board 49 were assembled using a transfer molding method. By molding at 175 ° C,
The structure was completely sealed in an epoxy resin 51 to obtain an acceleration sensor 40 having the resin 51 on the upper surface of the upper cap chip. The steps so far are in accordance with the steps of FIGS. 5a) to 5g). Thereafter, the epoxy resin 51 on the opposite surface of the wiring board 49 was ground using a GC600 grindstone until the upper cap chip 45 was exposed to obtain the acceleration sensor 1 shown in FIG.
Since the grinding process was performed, the exposed surface of the resin 51 on the upper cap chip side and the upper cap chip are the same surface.

2a) and 2b) are sectional views of other embodiments of the semiconductor sensor device of the present invention.
The semiconductor sensor device is the same acceleration sensor as that of the first embodiment, and is the same from FIG. 5a) to FIG. 5f). In the first embodiment, the structure in which the MEMS assembly 47, the circuit board 44, and the wiring board 49 are assembled is completely molded in the epoxy resin 51. However, in this embodiment, a resin member adhesion preventing jig is used at the time of molding. Use an epoxy resin 51 on the top surface of the upper cap chip.
Is not molded. In a state where a resin member adhesion preventing jig (not shown) is pressed onto the upper cap chip 45 in FIG. 2A), an epoxy resin 51 is molded using a transfer molding method. After molding, the resin member adhesion preventing jig was removed, and the upper surface of the upper cap chip 45 was exposed. When a part of the wiring 50 is located above the upper surface of the upper cap chip, an effective structure is obtained. In the method in which the upper cap chip is exposed by grinding after molding as in the first embodiment, the wiring is also ground. Therefore, it is essential that the wiring is positioned below the upper surface of the upper cap chip. In FIG. 2b), a part of the surface of the mold resin is the same as the upper surface of the upper cap chip. Since the upper surface of the upper cap chip in FIGS. 2a) and 2b) is recessed from the resin surface, the risk of damage by hitting the upper cap chip with other objects could be reduced.

FIG. 2c) shows a cross-sectional view of another embodiment of the semiconductor sensor device of the present invention. The semiconductor sensor device is a pressure sensor 2. The process from the manufacturing of the MEMS assembly board to the wiring of the MEMS assembly, the circuit board, and the wiring board of the pressure sensor of FIG. 2c) is shown in FIGS. 6a) to 6g).
The manufacturing process and method are the same as those described above, except that the process of removing the resin on the upper surface of the upper cap chip after resin molding is different. A detailed description of the steps performed up to FIG. 2c) will be made with reference to FIG.

For manufacturing the MEMS substrate 53 shown in FIG. 6, an SOI wafer having a silicon plate having a thickness of about 400 μm and a silicon oxide layer having a thickness of several μm and a silicon layer having a thickness of about 6 μm was used. As shown in FIG. 6, a photoresist pattern was formed in the shape of the piezoresistive element 68 on the surface on the silicon layer side. Boron is implanted into the silicon layer 1 to ³ × 10 ¹⁸ atoms / cm ³ , and the piezoresistive element 68
The wiring (not shown) and the sensor chip terminal connected to the piezoresistive element 68 were formed using a metal sputtering and dry etching apparatus. The silicon layer and the silicon plate were processed using photolithography and a dry etching apparatus, and the diaphragm 67 was formed. The silicon oxide layer functions as an etching stopper during dry etching of silicon. Since only silicon is dry etched, the silicon plate is dry etched but the silicon oxide layer remains. After dry etching, the silicon oxide layer was removed by wet etching by dipping in an aqueous solution of hydrofluoric acid and ammonium fluoride. Dry etching was performed in plasma in which SF ₆ , an oxygen mixed gas, and a C ₄ F ₈ gas were alternately introduced. A MEMS substrate 53 having a large number of pressure sensor chips formed on one wafer was produced. On the upper and lower surfaces of the MEMS substrate 53, bonding portions 61 formed with a bonding material to be bonded to the cap substrate were provided. Junction 6
In 1, a laminated film of Au—Sn alloy as a bonding material was formed by electroplating to a thickness of 5 μm. The width of the joint portion 61 was set to 60 μm so as to be hermetically sealed.

The upper cap substrate 52 with holes and the lower cap substrate 54 were made of silicon having a thickness of 400 μm. The cap substrate is ground up to the separation portion 90 indicated by the alternate long and short dash line and separated into cap pieces 57 and 5.
Get 8. A deep groove for separating into individual pieces was 250 μm, a shallow groove having a depth of 20 μm covering the movable part of the MEMS chip, and a hole having a depth of about 200 μm was formed in the shallow groove by wet etching. When the upper cap substrate 52 with holes is ground to the separation portion 90 indicated by the alternate long and short dash line, the hole provided in the shallow groove portion penetrates to become the through hole 56.

The upper cap substrate 52 with holes, the MEMS substrate 53, and the lower cap substrate 54 are fixed by the joint 61 to obtain the MEMS assembly substrate 55. The adhering operation was performed in a nitrogen gas atmosphere at 1 atm. A pressure of about 10 kN was applied to the upper and lower cap substrates and heated at about 300 ° C. for about 1 minute to obtain a MEMS assembly substrate 55. Since the MEMS substrate and the cap substrate have a thickness of about 400 μm, the MEMS substrate and the cap substrate have sufficient mechanical strength, and there was no problem of cracking or cracking during pressure bonding.

Using a # 2000 diamond grindstone, upper cap substrate 52 with holes and lower cap substrate 5
3 was ground to the separation portion 90 indicated by the alternate long and short dash line. Upper and lower cap chips 57 and 58 were obtained by grinding the upper cap substrate 52 with holes by about 200 μm and the lower cap substrate 54 by about 300 μm. During grinding, 3 to 5 (L / min) of grinding fluid was applied to the diamond grindstone and the MEMS assembly substrate.
The surface roughness of the cap chip was Ra ≦ 200 nm. Surface roughness Ra is measured by JI
SB0601 was followed. A MEMS grindstone was used in the same manner as the grinding, and the MEMS substrate 53 was cut at the separation portion 90 indicated by a one-dot chain line to obtain a MEMS assembly 59. MEMS assembly MEM
Between the S chip and the lower cap chip is sealed with nitrogen at 1 atm.
There is atmospheric pressure between the tip and the top cap with hole. The thickness of the upper cap chip 57 with a hole is about 100 μm thicker than that of the lower cap chip. By securing the mechanical strength and obtaining the depth of the through hole, the pressure of the movable part is reduced by abrupt pressure change. This is to prevent damage.

A circuit board 48 for amplifying a signal from a pressure sensor chip and correcting the temperature was fixed on a wiring board 49 having a thickness of about 100 μm with a die attach film. MEM on circuit board 48
The lower cap chip 58 of the S assembly 59 was fixed with a die attach film. A bare gold wire 50 having a diameter of 25 μm was connected between the MEMS assembly 59, the circuit board 48, and the wiring board 49 with an ultrasonic bonder.

An epoxy resin 51 was molded from the structure in which the MEMS assembly 59, the circuit board 48, and the wiring board 49 were assembled using a transfer molding method. By molding at 175 ° C,
The structure was completely sealed in an epoxy-based resin 51, and a pressure sensor 60 having the resin 51 on the upper surface of the upper cap chip 57 with a hole was obtained except for the through-hole 56 portion. The process up to this point is shown in FIG.
) To FIG. 6g). Thereafter, the epoxy resin 51 on the opposite surface of the wiring board 49 was ground using a GC600 grindstone until the upper cap chip 57 with a hole was exposed to obtain a pressure sensor shown in FIG. 2c). Since the grinding process is performed, the exposed surface of the resin 51 on the upper cap chip with holes and the upper cap chip with holes is the same surface.

FIG. 2d) shows a cross-sectional view of another embodiment of the semiconductor sensor device of the present invention. The semiconductor sensor device is a pressure sensor 2. In Example 3, the MEMS assembly 59 and the circuit board 48,
The structure in which the wiring board 49 is assembled is completely molded in the epoxy resin 51.
In this embodiment, a resin member adhesion preventing jig is used at the time of molding so that the epoxy resin 51 is not molded on the upper surface of the upper cap chip 57 with holes. In a state where a resin member adhesion preventing jig (not shown) is pressed onto the upper cap chip 57 with holes shown in FIG. 6), an epoxy resin 51 is molded using a transfer molding method. After molding, the resin member adhesion preventing jig was removed to expose the upper surface of the upper cap chip 57.

The sensitivity of each axis of the acceleration sensor 1 in which the upper surface of the upper cap chip manufactured in Examples 1 and 2 was exposed was measured. For comparison, an acceleration sensor 40 in which a mold resin is also formed on the upper surface of a conventional upper cap chip was used. The sensitivity of the X axis and the Y axis was obtained as a ratio with the sensitivity of the Z axis (output mV / g per unit acceleration) being 1. The sensitivity of each axis is the range value and average value of the upper and lower limits of 500 samples. In Example 1, the X axis is 0.9 to 1.2, an average of 1.05, and the Y axis is 0.95 to 1.
15 is 1.03 on average. In Example 2, the X axis is 0.95 to 1.2 and an average of 1.08, and the Y axis is 0.98 to 1.10 and an average of 1.01. The X-axis of the conventional product is 3.5 to 5.1 and an average of 4.3
. The Y axis was 2.5 to 3.2 and the average was 2.8. By exposing the upper surface of the upper cap chip as in Examples 1 and 2, the difference in sensitivity between the X axis and the Z axis can be almost eliminated.
We were able to eliminate defects caused by the imbalance of the three axes.

For the presence or absence of cracks in the cap chip, the acceleration sensors of Examples 1 and 2 were visually inspected with a microscope for actual testing, and the conventional products for comparison were selected indiscriminately from 200 acceleration sensor resins. Removed and inspected. In the acceleration sensors of Examples 1 and 2, there were no cracks in the upper cap chip. In the conventional product, 27 acceleration sensors had cracks, and the defect rate was as high as 13.5%. Resin cracks starting from the end of the upper cap chip were not observed in Examples 1 and 2, and the defect rate was 0%. Since the resin on the upper surface of the upper cap chip in Example 1 was ground, the number of resin cracks was zero, which is considered to be an effect of increasing the thickness of the upper cap chip. By thickening,
The deformation of the upper cap chip was suppressed at the time of resin molding, and it was difficult for resin cracks to occur.
The thickness of the upper cap chip can be increased because the upper surface of the upper cap chip is exposed to reduce the thickness of the acceleration sensor. In the comparative conventional product, a resin crack was confirmed in 1 out of 500 pieces, and the defect rate was 0.2%. By exposing the upper surface of the upper cap chip, not only was the sensitivity balanced, but the occurrence of cracks and resin cracks in the upper cap chip could be suppressed.

Evaluation was made on the clogging of the upper cap chip of the pressure sensor 2 in which the upper surface of the upper cap chip manufactured in Examples 3 and 4 was exposed. For comparison, a pressure sensor 60 in which a mold resin was also formed on the upper surface of a conventional upper cap chip was used. Each 1000 pressure sensors were examined for clogging under a stereomicroscope. The number of clogged holes in the pressure sensors of Examples 3 and 4 was 0, and the defect rate was 0%. In 32 conventional products, clogging was observed at one or more through-holes, and the defect rate was 3.2%.

It is sectional drawing of the 1st Example of this invention. It is sectional drawing of the other Example of this invention. It is a disassembled perspective view and sectional drawing of the conventional acceleration sensor, and the top view of an element. It is sectional drawing of the acceleration sensor using the conventional MEMS assembly board | substrate. It is a figure explaining the manufacturing process of the acceleration sensor using the conventional WLP. It is a figure explaining the manufacturing process of the pressure sensor using the conventional WLP. It is a figure explaining the malfunction point of the semiconductor sensor apparatus using the conventional WLP.

Explanation of symbols

1 Accelerometer,
2 pressure sensor,
20 Acceleration sensor chip,
21 Sensor chip terminal,
22 Beam,
23 weight part,
24 support frame,
25 IC chip,
26 X-axis piezo,
27 Y-axis piezo,
28 Z-axis piezo,
30 3-axis acceleration sensor,
32 cases,
33 lid,
34 wires,
35 Case terminal,
36 External terminal
37 Adhesive,
38 IC regulation plate terminal,
39 Adhesive resin,
40 Accelerometer,
41 Upper cap substrate,
42 MEMS substrate,
43 Lower cap substrate,
44 MEMS assembly substrate,
45 Upper cap tip,
46 Lower cap tip,
47 MEMS assembly,
48 circuit board,
49 Wiring board,
50 wiring,
51 resin,
52 Upper cap substrate with holes,
53 MEMS substrate,
54 Lower cap substrate,
55 MEMS assembly substrate,
56 through holes,
57 Upper cap tip,
58 Lower cap tip,
59 MEMS assembly,
60 pressure sensor,
61 joints,
63 stress,
64 Cap crack,
65 resin cracks,
66 clogged holes
67 Diaphragm,
68 piezoresistive elements,
69 Sensor chip terminal,
80 MEMS assembly,
81 MEMS substrate,
82 Cap substrate,
83 cases,
84 Case lid,
85,86 Semiconductor sensor device,
87 resin,
88 MEMS assembly substrate 89 wiring,
90 Separation part.

Claims (6)

A MEMS assembly formed of a MEMS chip having a movable part and an upper and lower cap chip that seals at least the movable part of the MEMS chip is mounted on a circuit board fixed on the wiring board.
A semiconductor sensor device in which a lower cap chip of an EMS assembly is fixed, a MEMS chip and a circuit board, a circuit board and a wiring board are connected by wiring, and the circuit board and wiring on the wiring board are sealed with a resin member The upper surface of the upper cap chip is exposed from the sealing resin member. A MEMS assembly formed of a MEMS chip having a movable part, a lower cap chip that seals at least the lower side of the movable part of the MEMS chip, and an upper cap chip that covers the upper side of the movable part is fixed on the wiring board. The lower cap chip of the MEMS assembly is fixed on the circuit board, the MEMS chip and the circuit board, the circuit board and the wiring board are connected by wiring, and the circuit board and wiring on the wiring board and the MEMS assembly are sealed with a resin member. The upper cap chip has at least one through hole in the thickness direction of the upper cap chip, and the upper surface of the upper cap chip is exposed from the sealing resin member. Semiconductor sensor device. The semiconductor sensor device according to claim 1, wherein the MEMS chip is capable of detecting at least one physical quantity of acceleration, angular velocity, and pressure. 3. The semiconductor sensor device according to claim 1, wherein an exposed surface of the upper cap chip is the same as or recessed from a surface of the sealing resin member formed on the upper cap chip side. A step of forming a MEMS substrate and a cap substrate, a step of fixing the upper and lower cap substrates to at least a movable part of the MEMS substrate, a step of forming the cap substrate into a cap chip, and MEMS
Cutting the substrate into chips to form a MEMS assembly, fixing the circuit board on the wiring board, fixing the lower cap chip surface of the MEMS assembly on the circuit board, wiring board and circuit board, Wiring the circuit board and the MEMS assembly, the circuit board and wiring on the wiring board, the step of sealing the MEMS assembly with a resin member, and grinding the upper cap side of the MEMS assembly to form a surface of the sealing resin member 3. The method of manufacturing a semiconductor sensor device according to claim 1, further comprising the step of exposing the upper surface of the upper cap chip to the same surface as the upper surface of the upper cap chip surface. A step of forming a MEMS substrate and a cap substrate, a step of fixing the upper and lower cap substrates to at least a movable part of the MEMS substrate, a step of forming the cap substrate into a cap chip, and MEMS
Cutting the substrate into chips to form a MEMS assembly, fixing the circuit board on the wiring board, fixing the lower cap chip surface of the MEMS assembly on the circuit board, wiring board and circuit board, Wiring the circuit board and the MEMS assembly, and having the circuit board and wiring on the wiring board, and sealing the MEMS assembly in which the resin member adhesion preventing tool is pressed against the upper surface of the upper cap chip with the resin member. 3. A method of manufacturing a semiconductor sensor device according to claim 1, wherein the method is a semiconductor sensor device.

Images