Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Die bond
Reexamination Certificate
1999-06-18
2001-09-18
Wilczewski, Mary (Department: 2822)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Die bond
C257S783000, C257S780000, C257S738000
Reexamination Certificate
active
06291895
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device and to a method of fabricating the same. In particular, the present invention relates to a semiconductor device having a package structure of a BGA or a CSP type and to a method of fabricating such a semiconductor device.
2. Description of the Related Art
In recent years, with the increasing demand for small, light and thin electronic apparatuses, smaller, lighter, and thinner semiconductor devices are required. In order to satisfy this demand, semiconductor devices having package structures of the BGA and the CSP types have been developed.
A semiconductor device having a package structure of a BGA or a CSP type comprises a semiconductor chip, an FPC tape such as a TAB tape for mounting the semiconductor chip thereto and solder balls arranged on the TAB tape. The semiconductor chip is fixed to the TAB tape by a die bonding material. The TAB tape has bonding pads and ball pads, the bonding pads and the ball pads being interconnected in the TAB tape by a wiring pattern. The semiconductor chip is connected to the bonding pads of the TAB tape by wires.
The solder balls are arranged on the ball pads of the TAB tape and thus function as external electrodes. As a result, the semiconductor chip and the solder balls are electrically connected to each other by the TAB tape as an interposer. In the case where a semiconductor device of surface mount type having solder balls functioning as external terminals, such as a semiconductor device of BGA or CSP type, is mounted to a motherboard, the semiconductor device is, in general, heated in a solder reflowing equipment having an ambient temperature of about 250° C. to connect the melted solder balls to the electrode pads of the motherboard.
Also, it is conceivable to attach a buffer resin sheet to the TAB tape to reduce the stress arising due to the difference in the coefficient of thermal expansion between the semiconductor chip and the TAB tape, and to apply the die bonding material to the buffer resin sheet to thereby fix the semiconductor chip to the TAB tape.
In the semiconductor device in which the semiconductor chip is fixed on to the TAB tape by the die bonding material and sealed by the sealing resin, moisture is contained in the polyimide constituting the TAB tape, the sealing resin and the die bonding material. Especially, the polyimide making up the TAB tape is a material which easily absorbs moisture. Therefore, when the solder balls are reflowed to mount the semiconductor device to the motherboard, the moisture contained in the TAB tape, the sealing resin and the die bonding material is evaporated with the increase in temperature and the vapor causes cracking and/or bulging of the semiconductor device.
In order to solve this problem, a method has been proposed in which small holes are formed through the TAB tape before the semiconductor chip is mounted to the TAB tape, so that the moisture contained in the semiconductor device may be released through the small holes when the solder balls are reflowed after the semiconductor chip is mounted to the TAB tape. The cracking and bulging of the semiconductor device can be prevented by releasing the moisture contained in the semiconductor device.
However, if small holes are formed in the TAB tape in advance, the die bonding material between the semiconductor chip and the TAB tape may flow and may fill up the holes of the TAB tape at the time of heat treatment during the fabrication process of the semiconductor device, with the probable result that the holes fail to function as vapor escape holes. It is also possible that the die bonding material flows through holes of the TAB tape and contaminates the reverse side of the TAB tape or the jigs or tools to be used. In the case where the buffer resin sheet is attached to the TAB tape, on the other hand, the buffer resin sheet blocks the flow of the die bonding material, but the buffer resin sheet is melted and fills up the holes of the TAB tape, often leading to the failure of the holes to function as vapor escaping holes.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a semiconductor device and a method of fabricating the same which can prevent cracking and bulging of the semiconductor device.
According to the present invention, there is provided a method of fabricating a semiconductor device comprising a semiconductor chip, a tape for mounting the semiconductor chip thereto, an adhesive resin layer interposed between the semiconductor chip and the tape and solder balls arranged on the tape, the method comprising the steps of fixing the semiconductor chip to the tape by the adhesive resin layer, and forming at least one hole in the tape after the step of fixing the semiconductor chip to the tape by the adhesive resin layer.
In this arrangement having at least one hole formed in the tape, the moisture contained in the semiconductor device is released through the at least one hole when the solder balls are reflowed, to thereby prevent cracking and bulging of the semiconductor device. Since the hole is formed after the step of fixing the semiconductor chip to the tape by the adhesive resin layer, the hole is not filled up with the adhesive resin layer which may flow at the time of heat treatment during the semiconductor fabrication process and thus effectively functions as a vapor escape hole.
Preferably, the method further includes the step of attaching the solder balls to the tape. The step of attaching solder balls to the tape is executed after the step of fixing the semiconductor chip to the tape by the adhesive resin layer and before the step of forming the hole.
Preferably, the hole is formed through the tape using a laser beam to such an extent as to reach the adhesive resin layer.
Preferably, the method further comprises the step of sealing the semiconductor chip with a sealing resin.
Preferably, the step of fixing the semiconductor chip to the tape by the adhesive resin layer includes the step of applying a die bonding material to the tape. As an alternative, the step of fixing the semiconductor chip to the tape by the adhesive resin layer includes the step of attaching a buffer material to the tape and the step of applying a die bonding material to the buffer material. As another alternative, the step of fixing the semiconductor chip to the tape by the adhesive resin layer includes the step of connecting the semiconductor chip to the tape by protruding electrodes and the step of filling an under-filling material between the semiconductor chip and the tape.
A semiconductor device according to another aspect of the present invention comprises a semiconductor chip, a tape for mounting the semiconductor chip thereto, an adhesive resin layer interposed between the semiconductor chip and the tape and solder balls arranged on the tape and is characterized in that the tape and the adhesive resin layer have at least one hole extending through the tape and reaching the adhesive resin layer.
In this arrangement, the tape and the adhesive resin layer having at least one hole formed through the tape and reaching the adhesive resin layer are produced according to the method of fabricating the semiconductor device described above and have the same function and effect as the corresponding ones described above. Specifically, when the solder balls are rendered to reflow, the moisture contained in the semiconductor device is released through the hole to thereby prevent cracking and bulging of the semiconductor device. At the same time, the hole is not filled up with the adhesive resin layer which flows at the time of the heat treatment during the semiconductor fabrication process and therefore effectively operates as a vapor escape hole.
Preferably, the semiconductor device comprises a sealing resin for sealing the semiconductor chip, and the adhesive resin layer is made of a die bonding material for fixing the semiconductor chip to the tape. As an alternative, the semiconductor device comprises a sealing resin for
Honna Koji
Kumagaya Yoshikazu
Taniguchi Fumihiko
Armstrong Westerman Hattori McLeland & Naughton LLP
Fujitsu Limited
Wilczewski Mary
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