Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2001-03-12
2003-08-12
Smith, Matthew (Department: 2825)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S106000, C438S118000, C438S464000, C438S611000, C438S612000, C438S615000
Reexamination Certificate
active
06605523
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a method for manufacturing semiconductor devices, and particularly relates to mounting semiconductor chips on tape substrates.
2. Description of Related Art
In the field of semiconductor devices, TCP (Tape Carrier package) is well-known as a type of package with bear chips mounted. This involves a semiconductor chip being mounted on a film tape carrier
30
shown in FIG.
4
. The film tape carrier
30
is normally formed by applying copper foil on a polyimide resin film, forming a circuit thereupon, and then applying Sn plating or Au plating, and is formed as a long article before being worked as a semiconductor device. Leads are formed of inner leads
20
connected to bumps formed of Au or the like on electrode pads on the semiconductor chip, and outer leads
36
formed integrally with the inner leads
20
and extended for external connections.
The following is a description of a TCP manufacturing method using gang bonding wherein all bumps and inner leads are simultaneously connected. First, on a stage not shown in the drawings, a semiconductor chip is positioned at a location surrounded by device holes
32
, and positioning is performed so that each of the bumps on the semiconductor device and the inner leads to be connected thereto are properly connected. This positioning is performed using two of the bumps and inner leads on a diagonal line, out of the bumps and inner leads at the four corners. Next, as shown in FIG.
5
(A), A heating tool
50
heated to around 500° C. beforehand is lowered to the positioned bumps of the semiconductor chip
40
and the inner leads
20
. The heating tool
50
lowered on the inner leads
20
applies pressure so as to press the bumps and inner leads
20
against the stage.
Further, in the event that the bumps are formed of Au, for example, an Au/Sn eutectic alloy
46
shown in FIG.
5
(B) is formed of the Sn plating of the inner leads
20
and the Au, due to the heat applied from the heating tool. Following connection of the bumps and the inner leads
20
by this eutectic alloy
46
, a resin of epoxy or the like is applied by dropping or printing and then hardened (not shown) in order to avoid mechanical stress and ensure humidity resistance, thereby completing mounting of the semiconductor chip
40
onto the film tape carrier
30
. After the semiconductor chip is mounted, the film tape carrier
30
is punched, thereby removing the unnecessary portions of the film tape carrier
30
. The above steps complete the TCP.
SUMMARY OF THE INVENTION
In the event of connecting the bumps of the semiconductor chip and the inner leads using a heating tool as described above, there have been the following problems in actual practice.
That is, there is a difference between the linear expansions coefficients of the semiconductor chip and the film of the film tape carrier. As described above, the film of the film tape carrier is formed of polyimide, so the linear expansions coefficient of the film is greater, and the pitch of the inner leads becomes longer. Accordingly, in the event that the bumps and inner leads are formed with the same pitch at the stage before thermocompression bonding thereof with the heading tool, there will be difference in the pitch of these by the time that the heating tool comes into contact with the inner leads.
Accordingly, as shown in
FIG. 6
, even in the event that part of the bumps and inner leads are correctly connected as with the bump
10
C and the inner lead
20
C, there is positional shifting between the two at other places. In extreme cases, the shifting may be to the extent that proper connecting is difficult, as with the bump
10
D and the inner lead
20
D. This shifting occurs due to the heat of the heating tool as described above, and thus can be avoided by increasing the descending speed of the heating tool immediately before thermocompression bonding. However, increasing the descending speed of the heating tool leads to applying shock to the semiconductor chip which causes damage, thereby lowering the reliability of the manufactured semiconductor device.
Accordingly, it is an object of the present invention to provide a method for manufacturing a semiconductor device wherein both bumps of the semiconductor chip and leads on the tape substrate can be accurately connected at the time of performing thermocompression bonding of the two using a heating tool.
According to an exemplary embodiment of the present invention, a manufacturing method for a semiconductor device, wherein a semiconductor chip is mounted on a tape substrate, includes a step for causing leads formed on the tape substrate and bumps formed on an active face of the semiconductor chip to face one another; and a step for lowering a heating tool and bringing this into contact with the leads, and performing thermocompression bonding of the leads and the bumps.
In this exemplary embodiment, the lowering speed of the heating tool is changed up to coming into contact with the leads.
With this exemplary embodiment of the present invention thus configured, changing the lowering speed of the heating tool allows the time of contact between the leads and heating tool to be controlled, thereby suppressing stretching of the tape substrate due to heating to a minimum.
Also, with the above semiconductor device, the lowering speed of the heating tool has been made to decrease as the leads are approached.
With this exemplary embodiment of the present invention thus configured, the lowering speed of the heating tool is set to be relative to fast at first, thereby reducing the time of contact between the leads and the heating tool, so that stretching of the tape substrate due to heating can be suppressed to a minimum, and also the lowering speed of the heating tool has been made to decrease as the leads are approached, so as to not apply shock at the time of the leads coming into contact with the semiconductor chip to a degree of damaging the semiconductor chip.
Also, the speed of the heating tool may decrease to approximately 5 mm/second immediately before coming into contact with the leads.
Further, the heating tool is preferably lowered from above the leads at a speed of around 50 mm/second for example, and at the point of descending to a height of 0.1 to 0.5 mm from the leads, the subsequent descending speed is changed to around 5 mm/second.
Also, the tape substrate which is used may have the pitch of the leads set 0.01 to 0.03% shorter than the pitch of the bumps.
With this exemplary embodiment of the present invention thus configured, the difference in the linear expansions coefficients of the tape substrate and the semiconductor chip has been taken into consideration, in the event of using polyimide tape substrates in particular, and accordingly the pitch of the leads has been set 0.01 to 0.03% shorter than the pitch of the bumps, so the pitch of the leads and bumps can be made equal immediately prior to the thermocompression bonding.
Also, the temperature of the heating tool may be set to approximately 520° C., and thermocompression bonding of the bumps and the leads is performed.
With this exemplary embodiment of the present invention thus configured, the temperature of the heating tool is a temperature minimally necessary for suitably forming the eutectic alloy between the bumps and leads, thereby suppressing stretching of the tape substrate.
Also, according to another exemplary embodiment of the present invention, a semiconductor device manufacturing method for bonding a tape substrate, upon which leads are formed, and a semiconductor chip, upon which bumps are formed, on an active face thereof includes at least a step for preparing the tape substrate such that the pitch width of the leads has been set beforehand so as to be equal to a value obtained by multiplying the pitch of the bumps by the ratio of the linear expansion coefficient of the semiconductor chip as to the linear expansion coefficient of the tape substrate at the heating temperature of thermocompression bonding of
Keshavan Belur V.
Oliff & Berridg,e PLC
Seiko Epson Corporation
Smith Matthew
LandOfFree
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