Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Reexamination Certificate
1996-11-22
2001-05-15
Paladini, Albert W. (Department: 2841)
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
C257S737000, C257S738000, C257S780000, C438S613000
Reexamination Certificate
active
06232563
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a bump electrode and a method for fabricating the same, and more particularly, to a bump electrode for bonding the substrate to external terminals and a method for fabricating the same.
2. Discussion of the Related Art
A bonding method using a bump has been widely used in packaging of a semiconductor device or the driving device of a liquid crystal display (LCD). The driving device of a LCD is connected to a thin film transistor (TFT) array substrate. A technique of packaging the driving device, in general, has the following variations: (1) the driving device is mounted on a printed circuit board (PCB), and then the PCB and the TFT array substrate are connected to each other, (2) the driving device is mounted on a flexible tape, and the flexible tape and the TFT array substrate are connected to each other, (3) the driving device is directly mounted on the substrate (Chip on Glass; COG).
The bonding method using a bump is mainly used in a direct package technique. In this method, an anisotropic conductive film (ACF) or anisotropic conductive adhesive (ACA) is used to bond a device having the bump to the terminal of an external substrate. These ACF and ACA contain conductive balls which are 5 to 7 &mgr;m large in diameter. When ACF or ACA is coated on a mounting portion of an external substrate and the device having the bump is pressed on the external substrate, the device and substrate are electrically connected to each other through the conductive balls contained in ACF or ACA. However, as the size of semiconductor device becomes smaller, the distance between the bumps formed on the device becomes shorter. Thus, the adjacent bumps can be electrically connected to each other through the conductive balls contained in ACF or ACA. This causes an electrical short in the device.
FIG. 1
is a cross-sectional view of a conventional substrate bump. The conventional bump electrode includes a pad
2
on a semiconductor substrate
1
, on which a driving device is formed. A passivation layer
3
is formed on a portion of the pad
2
and an exposed portion of the substrate
1
. A barrier metal
4
(used for diffusion stop, adhesive and oxidation resistance layer) is formed on an exposed portion of pad
2
and a portion of the passivation layer
3
over the pad
2
. A bump
5
is formed on the barrier metal
4
.
FIG. 2
shows a state in which adjacent bumps
5
are electrically connected to each other through conductive balls
6
contained in an adhesive material
7
when the semiconductor substrate
1
is bonded to a substrate
8
. In the bonding process, an adhesive material
7
, such as ACF or ACA, is coated on the substrate
8
, and then heat and pressure are applied to the semiconductor substrate
1
to thereby bond the substrate
1
to the substrate
8
. Here, according to heat or pressure applied to the bump
5
, the adhesive material
7
flows between the bumps, and gathers the conductive balls in the space between the bumps. In this way, the adjacent bumps can be electrically connected to each other.
The top surface of the bump
5
actually comes into contact with the terminal of the external substrate
9
. However, since the side of the bump
5
is exposed, if the bumps are close enough to each other, the conductive balls contained in the adhesive material may gather between the bumps and electrically connect the adjacent bumps. This causes an undesirable electrical short between the adjacent bumps.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a bump electrode and method for fabricating the same that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a bump electrode and method for fabricating the same, which is suitable for preventing an electrical short in a semiconductor device in the bonding process using bumps.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a bump electrode includes a pad formed on a semiconductor substrate; a passivation layer formed on the semiconductor substrate and a portion of the pad; a barrier metal formed on an exposed portion of the pad; a bump formed on the barrier metal; and an insulating layer formed on the side of the bump.
In another aspect, the present invention provides a method for fabricating a bump electrode including the steps of forming a pad on a semiconductor substrate, forming a passivation layer on the pad and semiconductor substrate, and exposing a portion of the pad; forming a barrier metal on the passivation layer and the exposed portion of the pad; forming a bump only on the barrier metal placed on the pad, the bump being formed of conductive material; forming an insulating layer on the passivation layer and the exposed portion of the pad; and removing a portion of the insulating layer to be left only on the side of the bump, the portion being placed on the bump.
In another aspect, a bump electrode includes a semiconductor substrate, a pad formed on the semiconductor substrate, a passivation layer formed on the semiconductor substrate to expose a portion of the pad, a barrier metal formed on the exposed portion of the pad and a portion of the passivation layer, and a bump formed on the barrier metal, in which the bump consists of first and second bumps, the first bump having an oxide layer formed on its side, the second bump being formed on the first bump.
In a further aspect, the present invention provides a method for fabricating a bump electrode including the steps of forming a pad on a semiconductor substrate, forming a passivation layer on the semiconductor substrate including the pad, and exposing a portion of the pad; forming a barrier metal on the passivation layer and the exposed portion of the pad; forming a photoresist pattern to expose the barrier metal placed on the exposed portion of the pad; forming a first bump using the photoresist pattern, the first bump being formed of a first conductive material; forming a second bump on the first bump using the photoresist pattern, the second bump being formed of a second conductive material; and removing the photoresist pattern, and oxidizing the first bump to form an oxide layer on the side of the first bump.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
REFERENCES:
patent: 4389516 (1983-06-01), Sugio et al.
patent: 5059553 (1991-10-01), Berndlmaier et al.
patent: 5065505 (1991-11-01), Matsubara et al.
patent: 5123986 (1992-06-01), Sugiyama et al.
patent: 5290732 (1994-03-01), Kumar et al.
patent: 5310699 (1994-05-01), Chikawa et al.
patent: 4-196434 (1992-07-01), None
patent: 6-224252 (1994-08-01), None
patent: 6-232211 (1994-08-01), None
Baek Young Sang
Kim Seong Jin
LG Electronics Inc.
Morgan & Lewis & Bockius, LLP
Paladini Albert W.
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