Metal post manufacturing method

Details Metal post manufacturing method Metal post manufacturing method

2002-04-15

2004-02-24

Lebentritt, Michael S. (Department: 2824)

Semiconductor device manufacturing: process

Including control responsive to sensed condition

Interconnecting plural devices on semiconductor substrate

C438S106000, C438S121000, C438S126000, C438S614000

Reexamination Certificate

active

06696305

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATION
This application claims the priority benefit of Taiwan application Ser. no. 91101024, filed Jan. 23, 2002.
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a metal post manufacturing method. More particularly, the present invention relates to a metal post manufacturing method that involves the conduction of a transient electric arc welding using a conductive electrode. The metal posts serve as via plugs on a ceramic circuit board, a soft or hard plastic circuit board, a glass substrate or a silicon wafer.
2. Description of Related Art
Due to rapid progress in the electronic industry, electronic products continue to shrink in size and increase is functional capacity. In chip packaging area, ball grid array (BGA) and chip scale (CS) packages are developed through market's demand for miniaturization and highly integrated packages. In the manufacturing of printed circuit boards, a multi-layered structure is introduced to reduce area occupation of electronic circuits. To connect various circuit layers within the substrate of a ball grid array package or a chip scale package, a multi-layered printed circuit board or a wafer, conductive via plugs are often formed. Hence, dimensions of minor circuits and plugs within the substrate layer will largely affect the packing density of a package and the level of integration of a printed circuit board and a wafer.
FIGS. 1 through 9
are schematic cross-sectional views showing the progression of steps for forming a conventional build-up substrate board. As shown in
FIG. 1
, an insulating core layer
100
having a conductive layer
102
on each side of the core layer
100
is provided. In general, the conductive layers
102
are copper layers.
As shown in
FIG. 2
, a plurality of through holes
104
are formed in the insulating core layer
100
by laser drilling or mechanical drilling. A conductive layer
106
is formed on the sidewalls of the through holes
104
as well as the two surfaces of the insulating core layer
102
. The conductive layer
106
is also a copper layer. The conductive layer
106
is formed, for example, by forming a seeding layer before conducting an electroplating operation.
As shown in
FIGS. 3 and 4
, a hole-filling operation is carried out. An insulating material
108
is deposited into the through holes
104
. The purpose of filling the through hole
104
is to prevent the intrusion of any moisture. Any moisture that gets into the through hole
104
may expand in the presence of heat to form popcorn-like bubbles. Thereafter, any insulating material
108
above the insulating core layer
100
is ground down to a suitable roughness level.
As show in
FIG. 5
, a conductive layer
110
is formed over the second surface of the insulating core layer
100
globally. The conductive layer
110
covers the exposed insulating material
108
above the insulating core layer
100
. The conductive layer
110
is formed, for example, by forming a seeding layer before conducting an electroplating operation.
As shown in
FIG. 6
, the conductive layer
110
on each side of the core layer
100
is patterned by coating a photoresist layer, conducting photo-exposure, developing the photoresist, etching the conductive layer
110
and removing the photoresist layer.
As shown in
FIG. 7
, a dielectric layer
112
is formed over each side of the insulating core layer
100
. The dielectric layer
112
has a plurality of openings
114
. Each opening
114
exposes a portion of the conductive layer
110
.
As shown in
FIG. 8
, a conductive layer
116
is formed over the dielectric layers
112
, the sidewalls of the openings
114
, and the exposed conductive layer
110
. The conductive layer
116
is formed, for example, by forming a seeding layer before conducting an electroplating operation.
As shown in
FIG. 9
, conductive material is deposited into the openings
114
to form a plurality of via plugs
118
. The conductive layer
116
is patterned by coating a photoresist layer, conducting photo-exposure, developing the photoresist, etching the conductive layer
116
and removing the photoresist layer.
In the conventional build-up substrate manufacturing method, the conductive layers
110
are electrically connected through a plug formed by a plating through-hole (PTH) process. The conductive layer
110
and the conductive layer
116
are electrically connected through a via plug
118
. In other words, to produce the build-up substrate, holes must be drilled to form the through holes
104
, electroplating must be conducted to form the conductive layers (
106
,
110
and
116
) and insulating material
108
must be deposited to fill the through holes. Hence, the conventional fabrication method is both time consuming and complicated.
Moreover, as the level of integration increases and the size of through holes
104
reduces to a diameter of 100 &mgr;m or less, the conventional method no longer can provide a suitable means of fabrication.
SUMMARY OF THE INVENTION
Accordingly, one object of the present invention is to provide a metal post manufacturing method capable of producing via plugs having a dimension ranging from 1 to 200 &mgr;m. The metal post manufacturing method according to this invention is able to replace the conventional plating through-hole (PTH) process.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides a metal post manufacturing method. A fixture having an array of wire guide heads thereon is provided. Each wire guide head contains a conductive wire. A substrate receiving the metal posts is put under the wire guide heads of the fixture. The wire guide heads utilize the production of a transient electric arc to generate the energy necessary for transforming one end of the conductive wire into a dangling block of material having a teardrop shape underneath the guide head. Simultaneously, the entire fixture moves and pulls the array of wire guide heads down to form a plurality of metal posts over the substrate.
In this invention, the conductive wire is made from a material such as aluminum, gold, silver, copper, platinum, zinc or lead-tin alloy. Alternatively, the conductive wire may contain a core material enclosed by one or more conductive material layers such as a copper layer enclosing a lead-tin core, a lead-tin layer enclosing a copper core or a tin or a silver layer enclosing an alloy steel core. In addition, the conductive wire may have a diameter ranging between 1 to 200 &mgr;m.
In this invention, the wire guide heads move towards the substrate so that the teardrop shaped block of conductive material may attach to the substrate. Thereafter, the wire guide heads are pulled in the opposite direction away from the substrate so that height level of the metal post can be properly set. Height level of the metal posts may be modified according to the specification. To form a metal post having a height over the dielectric layer about 1 to 10 &mgr;m, a teardrop shaped block of conductive material is repeatedly formed over the one already attached. In addition, dimension of the metal posts can be controlled by choosing conductive wires with the optimum diameter, from smaller than 50 &mgr;m, between 50 to 100 &mgr;m, between 100 to 200 &mgr;m to 200 &mgr;m and beyond.
The metal post manufacturing method according to this invention may also be applied to the fabrication of a printed circuit board, the substrate (carrier) of a package or a wafer.
This invention also provides a method of forming a build-up substrate board. A carrier having a first conductive layer thereon is provided. The aforementioned metal post manufacturing method is applied to form a plurality of first metal posts over the first conductive layer. A first dielectric layer is formed over the first conductive layer. The first dielectric layer encloses the first metal posts but the upper ends of the first metal posts are exposed. A second conductive layer is formed over the first dielectri

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