Active solid-state devices (e.g. – transistors – solid-state diode – Encapsulated – With specified encapsulant
Reexamination Certificate
1999-03-16
2001-07-03
Williams, Alexander O. (Department: 2826)
Active solid-state devices (e.g., transistors, solid-state diode
Encapsulated
With specified encapsulant
C257S790000, C257S666000, C257S783000, C257S788000, C257S787000, C257S698000, C257S729000, C257S687000, C257S414000, C257S467000, C257S468000, C257S469000, C257S774000, C257S676000, C361S704000
Reexamination Certificate
active
06255741
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of Japanese Patent Applications No. 10-67276, filed on Mar. 17, 1998, and No. 11-66948 filed on Mar. 12, 1999, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a semiconductor device including a semiconductor chip covered with a protective sheet, and a method of manufacturing the same.
2. Description of the Related Art
Conventionally, a semiconductor physical quantity sensor such as a semiconductor acceleration sensor or a semiconductor pressure sensor includes a movable part formed on a silicon chip. Such a sensor outputs an electrical signal corresponding to a physical quantity such as acceleration or pressure, according to a displacement of the movable part.
For instance, JP-A-9-211022 discloses an acceleration sensor including a beam structure that is formed on a silicon substrate as a movable part and is displaced upon receiving an acceleration, a. movable electrode disposed on the beam structure, and a fixed electrode formed on the silicon substrate to face the movable electrode. The accelerating sensor detects acceleration based on a change in distance between the movable electrode and the fixed electrode.
This kind of semiconductor device usually includes a protective cap for covering and protecting the movable part. As disclosed in JP-A-6-347475, a glass substrate, which is bonded to a semiconductor wafer by anode coupling, can be used as the protective cap. In this case, however, the glass substrate is liable to form gaps at the bonding portion with the semiconductor wafer due to surface roughness of its bonding interface. Therefore, when dicing cut is carried out, grinding water easily enters into the semiconductor device through the gaps to cause various problems. For instance, the water may disturb the movement of the movable part due to surface tension thereof.
On the other hand, JP-A-9-27466 discloses not a glass substrate but an UV-hardening sheet as a protective cap. When the UV-hardening sheet is used as the protective cap, the problem such that grinding water enters into the semiconductor device during the dicing cut does not occur. However, the UV-hardening sheet is deformed at a temperature of approximately 8° C. to 90° C. Because of this, the UV-hardening sheet must be detached from the semiconductor device when subsequent steps such as a wire bonding step necessitating a temperature higher than that are carried out. This results in an increase in a number of manufacturing steps.
Further, there is a both-surface exposed type structure including a beam structure (movable part) as a sensing part that is exposed on both surfaces of a chip. In such a structure, when the chip is mounted on a lead frame by adhesive, or is fixed to a package by adhesive, the adhesive is liable to contact the sensing part to disturb the movement of the movable part. When the both-surface exposed type sensor chip is molded with resin, the resin easily contacts the movable part. Even when the sensor chip is fixed to the lead frame or the package, the resin can contact the movable part by passing through a gap at the bonding portion of the chip.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above problems. An object of the present invention is to provide a semiconductor chip covered with a protective cap and capable of being manufactured at low cost with a small number of manufacturing steps. Another object of the present invention is to prevent adhesive and molding resin from adhering a movable part of a semiconductor chip during a manufacturing process.
According to the present invention, a main side protective resin sheet having an opening is bonded to a semiconductor chip to expose a pad on the semiconductor chip from the opening, through a main side heat resisting adhesive. The pad is connected to a wire. The main side protective resin sheet and the main side heat resisting adhesive have first and second heat resisting temperatures that are higher than a first temperature capable of fixing the wire to the pad by bonding. Because the main side protective resin sheet is bonded to the semiconductor chip by the heat resisting adhesive, grinding water does not invade through the bonding portion during dicing-cut. Because the first and second heat resisting temperatures are higher than the temperature capable of fixing the wire to the pad by bonding, the wire bonding can be carried out to the semiconductor chip without removing the main side protective resin sheet, resulting in decreased number of manufacturing steps.
The first and second heat resisting temperatures of the main side protective resin sheet and the main side heat resisting adhesive are higher than a temperature capable of fixing the semiconductor chip to a lead frame. Therefore, the semiconductor chip can be fixed to the lead frame without removing the protective resin sheet. The first and second heat resisting temperatures are higher than a temperature capable of molding the semiconductor chip with resin. Therefore, the semiconductor chip can be molded with resin without removing the protective resin sheet.
The first and second heat resisting temperatures are higher than a temperature capable of fixing the semiconductor chip to a package. Therefore, the semiconductor chip can be fixed to the package together with the protective resin sheet. Preferably, the main side protective resin sheet is made of polyimide, and the main side heat resisting adhesive includes a silicone adhesive.
When the semiconductor structure is exposed at both surfaces of the semiconductor chip, a back side protective resin sheet is further bonded to the semiconductor chip to cover the semiconductor structure on an opposite side of the main side protective resin sheet. The back side protective resin sheet can be bonded to the semiconductor chip by a back side heat resisting adhesive. Preferably, the back side protective resin sheet is made of polyimide and the back side heat resisting adhesive includes a silicone adhesive as well.
The back side protective resin sheet is resistible to the temperatures capable of bonding the wire to the pad, fixing the semiconductor chip to the lead frame, molding the semiconductor chip with resin, and fixing the semiconductor chip to the package, as well as the main side protective sheet and the main side heat resisting adhesive. That is, the main side and back side protective resin sheets are not thermally deformed at the temperatures described above. This allows the resin sheets to remain on the semiconductor chip during the manufacturing steps described above. Even when the semiconductor structure is exposed on the both surfaces of the semiconductor chip, because the semiconductor structure is covered by the main side and back side protective sheets, the adhesive and resin does not contact the semiconductor structure during the manufacturing steps. Further, the invasion of grinding water during dicing-cut can be prevented.
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Atsumi Kinya
Fujii Tetsuo
Inomata Sumitomo
Sakai Minekazu
Shimoyama Yasuki
Denso Corporation
Pillsbury & Winthrop LLP
Williams Alexander O.
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