Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2002-09-13
2004-12-14
Gurley, Lynne A. (Department: 2812)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S667000
Reexamination Certificate
active
06831002
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a manufacturing method of a semiconductor device in which wirings, connected electrically to elements such as other electronic components, are provided by electrolytic plating.
BACKGROUND OF THE INVENTION
In case where wirings are provided on a front surface of an insulating protective film by electrolytic plating for the purpose of electrical connection with elements such as other electronic components or wiring substrates, known is a method of providing electrical conductivity by a contact of a cathode (negative electrode) terminal of an electrolytic plating apparatus with a conductive layer as a feeding layer, which is provided on the front surface of the insulating protective film.
As such an electrolytic plating apparatus known is a jet-type electrolytic plating apparatus
100
as shown in FIG.
17
.
In the electrolytic plating apparatus
100
, a plating liquid blows out through a meshed anode terminal (positive electrode)
103
from a spout
102
which is provided at the center of the bottom of a cup
101
. A wafer
110
is supported by a wafer support ring
104
which is provided at the top opening part of the cup
101
. The wafer
110
is provided with a feeding layer, which is provided on the entire front surface where semiconductor elements are formed. Further, on the feeding layer a mask having openings corresponding to parts to be given electrolytic plating. A plurality of cathode terminals
105
, provided to the wafer support ring
104
, are in contact with several points of the outer periphery of the feeding layer of the wafer
110
.
Plating treatment is given by passing a predetermined electric current between the anode electrode
103
and the cathode terminals
105
while applying a plating liquid blown out from the spout
102
to the front surface of the wafer
110
.
However, the plating method using the electrolytic plating apparatus
100
has the following problems.
Problem 1
When a plating liquid flows into a small contact area between the cathode terminal
105
and the feeding layer, a large voltage drop causes an abnormal growth of plating deposit. The powdery abnormal plating deposit falls down and sticks on the front surface of the wafer
110
, which causes a faulty plating such as plating including raised portions.
Problem 2
A larger diameter of the wafer
110
causes a difference in the plating thickness between the circumferential direction and the radial direction. This is because the cathode terminals
105
and the feeding layer come contact with each other at several contact points of the outer periphery of the wafer
110
, which increases a difficulty of the flow of plating current in an area far from the contact points, thereby causing a thin plating.
One measure against the above problem 1 is a technique of Japanese Laid-Open Patent Publication No. 2000-328291 (Tokukai 2000-328291, published on Nov. 28, 2000, hereinafter referred to as “prior art 1”). The prior art 1 discloses arrangement of a wafer support ring
104
and a cathode terminal
105
and a conducting method as shown in FIG.
18
. According to the prior art 1, a wafer
110
(see
FIG. 17
) closely sticks to a packing
106
, having a smaller diameter than that of the wafer
110
, which is provided so as to prevent a plating liquid from flowing into anywhere other than the surface to be plated. The cathode terminal
105
electrically contacts over the substantially entire periphery of the wafer
110
outside the packing
106
, so that the cathode terminal
105
and the plating liquid cannot come into contact with each other.
Another measure against the above problem 1 is a technique of Japanese Laid-Open Patent Publication No. 41697/1992 (Tokukaihei 4-41697, published on Feb. 12, 1992, hereinafter referred to as “prior art 2”). The prior art 2 discloses an arrangement of a cathode terminal (a contact pin for plating)
105
and a conducting method. According to the prior art 2, a tip of a cathode terminal
105
made of metal, which electrically contacts with a feeding layer (base conductive coating film) is surrounded by a flexible insulating cover
107
having a shape of suction cup to prevent the contact with the plating liquid. The cathode terminal
105
is pushed on the wafer (a work to be plated)
110
(see FIG.
17
), and the insulating cover
107
deforms and closely sticks to the wafer
110
, thereby preventing the plating liquid from contacting with the tip of the cathode terminal
105
.
As one measure against the above problem 2, the prior art 1 has an arrangement in which the cathode terminal
105
electrically contacts over the substantially entire periphery of the wafer
110
, whereby the plating current in the feeding layer (base metallic layer) passes uniformly in the circumferential direction. Further, the anode electrode
103
(see
FIG. 17
) is arranged to the umbrella shape high in the center near to the wafer
11
, thereby making the thickness of plating in the radial direction uniform.
Further, as another measure against the above problem 2, the thickness of the feeding layer can be increased so that the plating current can easily pass.
Incidentally, in such an arrangement as the above prior arts 1 and 2 in which the contact of the packing
106
and the insulating cover
107
with the wafer
110
separates the cathode terminal
105
and the plating liquid, involved is a risk of the substantial contact of the cathode terminal
105
and the plating liquid. Therefore, it cannot be said that the arrangement can perfectly prevent the faulty plating caused by the growth of the abnormal plating deposit due to the contact of the plating liquid and the cathode terminal. Accordingly, inevitable are damage to the wafer
110
when the contact occurs and increased costs along with maintenance of the electrolytic plating apparatus
100
including the cathode terminal
105
.
Further, the above prior art 1 has an arrangement in which the cathode terminal
105
electrically contacts over the substantially entire periphery of the feeding layer outside the packing
106
, which is provided to prevent the plating liquid from flowing into anywhere other than the surface to be plated. However, the packing
106
contacts over the substantially entire periphery of the wafer
110
; therefore, an outer part from the packing
106
is not plated. This results in decrease in yield and requires a condition that parts where the packing
106
contacts should be flat.
Further, in the arrangement of the prior art 2 in which the insulating cover
107
is provided around the tip of the cathode terminal
105
to prevent the contact with the plating liquid, it is important to keep the optimal balance in height between the tip of the cathode terminal
105
and the top end part of the insulating cover
107
. Because of a small difference in height between the tip of the cathode terminal
105
and the top end part of the insulating cover
107
, the cathode terminal
105
comes into contact with the wafer
110
before the deformed insulating cover
107
sticks to the wafer
110
. This causes less stickiness of the insulating cover
107
, so that the cathode terminal
105
and the plating liquid comes into contact with each other. Conversely, when the position of the tip of the cathode terminal
105
is too much lower than the insulating cover
107
, the electrical contact of the wafer
110
and the cathode terminal
105
is difficult, which causes a poor conductivity.
Further, in the conducting method of the above prior art 1, the anode electrode
103
has the umbrella shape high in the center near to the wafer
110
to make the thickness of plating in the radial direction uniform, with consideration that the plating current in the radial direction of the wafer
110
is decreased toward the center of the wafer
110
. However, it is necessary to work the meshed anode electrode
103
into an umbrella shape, thereby increasing manufacturing costs. Further, it is necessary to change a suitable shape of the anode electrode
103
and its position, depending
Ishio Toshiya
Iwazaki Yoshihide
Mori Katsunobu
Nakanishi Hiroyuki
Suminoe Shinji
Gurley Lynne A.
Sharp Kabushiki Kaisha
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