Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – For plural devices
Reexamination Certificate
1999-06-11
2001-07-10
Chaudhuri, Olik (Department: 2814)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
For plural devices
C257S679000, C257S779000, C257S783000, C257S784000, C257S786000
Reexamination Certificate
active
06259158
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a semiconductor device in which various types of semiconductors having external extraction electrodes (pads) with a small pitch are implemented on a substrate such as a card, and a method of manufacturing the semiconductor device.
BACKGROUND ART
The structure of an IC card that is being mass-produced at present is disclosed in “IC card” (edited by Corporation of the Institute of Electronics, Information and Communication Engineering and published by Ohm Co., Ltd. on May 25, 1990, first edition, pp. 33).
FIG. 13
illustrates a cross sectional structure of its representative main portion. As is illustrated in
FIG. 13
, the conventional IC card includes a module substrate
44
having a conductor circuit, an IC chip
43
implemented on the module substrate, pads
42
provided on the IC chip, and bonding wires
41
to which terminals of the module substrate are connected.
FIG. 4
is a plan view illustrating an IC chip in which wires are bonded. In this method using the wires, a semiconductor active area
102
on the IC chip and bonding pads
42
thereon are situated at different regions with each other. A bonding wire head
132
is a portion situated at the head of a bonding wire
41
.
FIG. 5
illustrates a cross section of the bonding portion illustrated in FIG.
4
. The bonding pad
42
, which is formed on an IC chip
44
, is pressed strongly by the bonding wire head
132
at the time of the bonding. The bonding wire
41
is pressed by a mechanical operation, thereby being caused to be connected to the bonding pad. This sometimes results in a destruction of an active element if it exists under the bonding pad. Accordingly, in the prior art, it was impossible to locate the active element.
Also, in the case of an IC chip of 0.3 mm square that is used in, for example, an IC tag, although size of the bonding pad is in the range of 0.1 to 0.15 mm square and the number of the bonding pads is in the range of about 2 to 10, it turns out that an area that the bonding pads occupy on the IC chip becomes considerably large.
Incidentally, the IC chip is about 200 to 400 &mgr;m thick. In this extent of thickness, especially when a main semiconductor material of which the IC chip is composed is a fragile silicon, there existed a fear that the IC chip is cracked if a bending stress is applied thereto. The larger the IC chip gets, the more apparent this tendency becomes. Conventionally, in order to prevent the IC chip from being cracked, it was necessary to select and use a bending-resistant material as a casing material so that no bending stress is applied to the IC chip. In order to solve this problem, an IC card using a flexible IC chip made thin up to about 1&mgr;m is disclosed in JP-A-3-87299. Concerning the IC card disclosed here, however, it has been found that the following problem exists: Since the IC chip thus thinly filmed is located on the surface of the card substrate, the IC chip is torn if the bending stress especially an expansion stress is applied to the card.
As a method for solving problems like this, JP-A-7-99267 discloses a method of embodying a configuration that a thin type IC chip is provided substantially in proximity to the center of the IC card. In this technique, the pads on the IC chip and electrodes provided on the circuit substrate by printing are set so that they are exposed onto the same plane, and then interconnections between the pads on the IC chip and the electrodes on the circuit substrate are formed by printing with the use of a conductive paste, thereby connecting them electrically. The use of the conductive paste makes it unnecessary to execute the process of the wire bonding, which is economical in fabricating the IC card.
It has become obvious, however, that there exists the following problem when the connection with the pads on the IC chip is established by the above-described printing with the use of the conductive paste: That is to say, since a pitch of the pads formed on the existing IC chip is small and falls in the range of 100 to 150 &mgr;m, the wire bonding is capable of establishing the connection, whereas screen printing with the use of a silver paste is not capable of establishing the connection. Namely, this is a problem that, with the use of the existing technique, it is difficult to make the printing accuracy 200 &mgr;m or less. This problem becomes a serious trouble when the IC chip in which the conventional wire bonding is performed is used without any improvements or modifications.
It is an object of the present invention to provide a semiconductor device in which narrowly-pitched pads formed on an IC chip and electrodes provided on a substrate are connected electrically with each other by interconnections formed by printing, and a method of manufacturing the semiconductor device that allows them to be connected under a stable condition.
It is another object of the present invention to provide a highly reliable semiconductor device in which the narrowly-pitched pads formed on the IC chip and the electrodes printed on the substrate are connected electrically with each other, and a low cost method of manufacturing the semiconductor device that accompanies no increase in the number of the processing steps.
DISCLOSURE OF INVENTION
The above-described purposes are accomplished by providing, on the IC chip, a second pad electrically connected to a first pad provided on the IC chip. Since it is possible to provide the second pad in a desired position, it is possible to form, by printing, the respective interconnections for connecting a plurality of second pads with the plurality of electrodes provided on the substrate. Also, matching of positions is performed between the plurality of second pads and the plurality of electrodes provided on the substrate, thereby making it possible to electrically connect the second pads with the electrodes provided on the substrate in a such a manner that they are opposed to each other. Conductive adhesives are provided between the second pads and the electrodes provided on the substrate, thereby making it possible to enhance a reliability of the connection.
Also, the above-described purposes are accomplished by a method of manufacturing a semiconductor device which includes the following steps of: Preparing an IC chip having the plurality of pads, forming a first insulating film having a first aperture onto which the pads are exposed, forming a first metallic film on the substrate having the first insulating film, forming a second insulating film which extends from the first aperture onto the first insulating film and has an aperture in a region becoming the second pads and onto which the first metallic film is exposed, selectively forming a second metallic film on the first metallic film exposed, removing the second insulating film, removing the exposed first metallic film so as to form the second pads including the first metallic film and the second metallic film, and electrically connecting the second pads with the electrodes provided on the insulating substrate.
Incidentally, the second pads are formed in an active area on the IC chip, thereby making it unnecessary to enlarge the chip areas for formation of new pads. This allows the upper surface of the IC chip to be used effectively.
Also, it is possible to fabricate a bump toward the first pad and the second pads in the same processing step. This, accordingly, results in no increase in the fabrication cost of the IC chip.
Also, positions of the plurality of second pads are aligned with those of the plurality of electrodes on the insulating substrate, thereby allowing a face down bonding to be performed toward the insulating substrate of the IC chip. This makes it possible to shorten distances between the second pads and the electrodes and to reduce resistance in the interconnections.
Also, a gold plated film, which is a technique used customarily, is employed as the second metallic film. This makes it possible to enhance a reliability of the second pads.
Also, thickness of the insulating substrate is mad
Chambliss Alonzo
Chaudhuri Olik
Hitachi , Ltd.
Mattingly Stanger & Malur, P.C.
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