Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – For plural devices
Reexamination Certificate
1998-08-07
2001-11-06
Chaudhuri, Olik (Department: 2814)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
For plural devices
C257S778000, C257S780000
Reexamination Certificate
active
06313529
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application is based upon and claims the benefit of priority of prior Japanese Patent Application No. H.9-214574 filed on Aug. 8, 1997, the contents of which are incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device provided with a semiconductor sensor chip including a structural member which is displaced in accordance with physical quantity applied thereto in order to detect the physical quantity such as acceleration and yaw rate, and a manufacturing method thereof.
2. Description of Related Art
For example, an electrostatic capacity type semiconductor acceleration sensor is provided with a beam structure which is displaced in response to an acceleration applied thereto. A sensor chip provided with a sensing portion including the beam structure is manufactured by use of a surface micro machining technique applied to semiconductor materials. Because the semiconductor acceleration sensor as described above is easily miniaturized and has good consistency with a semiconductor manufacturing process, the sensing portion and a sensor circuit for carrying out control of the sensing portion and processing of sensor outputs are formed together in a common semiconductor chip.
As a form of a package to house such a semiconductor acceleration sensor, a resin-molded package is most suitable to reduce the cost of production. However, when the resin-molded package is adopted, it is necessary to protect the beam structure having a small mechanical strength from pressure of molding resin. For this reason, conventionally, a protecting cap is provided on the semiconductor chip so as to cover the sensing portion and the sensor circuit.
In recent years, an acceleration sensor utilized in an air-bag system or a suspension control system of a vehicle is required to achieve miniaturization and low manufacturing cost. However, in a conventional arrangement in which the sensing portion and the sensor circuit stand in a single plane on the common semiconductor chip and the protecting cap is provided thereabove, it is difficult to meet the requirement of miniaturization and low cost. That is, in a conventional semiconductor acceleration sensor, not only the chip size thereof is two-dimensionally enlarged but also it is necessary to provide the protecting cap separately. Therefore, miniaturization of the sensor is very difficult. Further, because the chip size is two-dimensionally enlarged, the number of sensor chips taken from a single wafer is reduced. Furthermore, because the sensing portion and the sensor circuit are formed on the common chip, the number of steps in manufacturing process performed to the common chip is increased and a yield factor of the sensor chip is thereby decreased. As a result, the manufacturing cost of the sensor chip rises. This tendency becomes significant as a degree of integration and an area of the sensor circuit becomes large.
Also, as disclosed in Japanese Patent Application Laid-Open No. H.6-347475, there is a semiconductor sensor in which a sensor chip is disposed on a glass substrate and a protecting cover formed from a silicon plate provided with a signal processing circuit and a concave portion for housing the sensor chip is placed to cover the sensor chip. Due to such a structure, the semiconductor sensor can withstand molding resin.
However, in such a semiconductor sensor as well, because the sensor chip and the signal processing circuit are two-dimensionally arranged and the protecting cover is separately provided, the size thereof is enlarged in two-dimension. As a result, it is difficult to achieve miniaturization of the sensor as a whole. Further, because the glass substrate and the protecting cover (silicon plate) are bonded by anodic junction, a condition of air tightness may be insufficient. Furthermore, because a pulling-out electrode from the signal processing circuit is physically contacted with a pulling-out electrode from the glass substrate to connect them each other, contact resistance between the pulling-out electrodes may be increased. As a result, the reliability of operation of the sensor is low.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a semiconductor device in which, even though a sensing portion including a structural member which is displaced in accordance with physical quantity applied thereto and a processing circuit for an output from the sensing portion are integrally provided, miniaturization and low cost thereof can be achieved and the reliability of operation thereof can be enhanced and to provide a manufacturing method thereof.
According to the present invention, one face of a sensor chip constituted by a semiconductor substrate on which a sensing portion is formed is connected to a circuit chip on which a processing circuit for an output from the sensing portion is formed via bump electrodes to electrically connect the sensing portion and the processing circuit. Further, in this connected state, a sealing member is interposed between the sensor chip and the circuit chip so that the sensing portion is located in an air-tight space formed by the sealing member.
As a result, the sensor chip and the circuit chip are arranged in the so-called COC (chip on chip) structure. Therefore, the size of the semiconductor device is prevented from enlarging in two-dimension. Further, the sensor chip functions as a conventional protecting cap. Consequently, the size of the semiconductor device can be miniaturized as a whole.
Also, since the chip sizes of the sensor chip and the circuit chip can be made small, the number of chips obtained from a single wafer can be increased. Further, since the sensor chip and the circuit chip are formed separately to each other, the number of steps in manufacturing process performed with respect to each of chips can be reduced and the yield factor of each chip can be enhanced. Accordingly, the manufacturing cost of the semiconductor device can be decreased. Furthermore, because the air-tight space containing the sensing portion is formed by the sealing member, even when a resin-molded package of low cost is used to house the semiconductor device, the sensing portion does not receive adverse influences from the molding resin. In view of this aspect also, the reduction of the manufacturing cost can be promoted.
Electrical connection between the sensor chip and the circuit chip can be reliably ensured by the bump electrodes. Further, the sealing member can prevent liquid from invading into the air-tight space in which the sensing portion is located. Therefore, the reliability of operation in the semiconductor device can be enhanced.
The semiconductor device according to the present invention can be manufactured by a method as described below. First, in an electrode forming step, bump electrodes are formed on either one of a surface of the sensor chip on which the sensing portion is formed and a surface of the circuit chip, and electrode pads to be bonded to the bump electrodes are formed on the other thereof. In a sealing member forming step, in order to form the air-tight space containing the sensing portion, the sealing member of a rectangular frame shape is formed on either one of the surface of the sensor chip on which the sensing portion is formed and the surface of the circuit chip, a joining pad of the same frame shape to be bonded to the sealing member is formed on the other thereof.
Thereafter, in a connecting step, the bump electrodes are bonded to the electrode pads and the sealing member is bonded to the joining pad. As a result, the sensor chip is connected on the circuit chip, and the air-tight space containing the sensing portion is formed by the sealing member of the rectangular frame shape interposed between the sensor chip and the circuit chip.
REFERENCES:
patent: 3591839 (1971-07-01), Evans
patent: 3657610 (1972-04-01), Yamamoto et al.
patent: 4129042 (1978-12-01), Rosvold
patent: 4891984 (1990-01-01), Fujii et al.
patent: 5006487 (1991-0
Akita Shigeyuki
Yoshihara Shinji
Chaudhuri Olik
Denso Corporation
Doan Theresa T.
Pillsbury & Winthrop LLP
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