Semiconductor device manufacturing: process – Making field effect device having pair of active regions... – Having insulated gate
Reexamination Certificate
2002-11-26
2004-03-02
Niebling, John (Department: 2812)
Semiconductor device manufacturing: process
Making field effect device having pair of active regions...
Having insulated gate
C438S253000, C438S250000, C438S393000, C438S396000
Reexamination Certificate
active
06699748
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of fabricating a capacitor, and more particularly to a method of fabricating a capacitor formed in a re-wiring layer of a semiconductor device or a wiring layer of a printed circuit board or the like.
2. Description of the Background Art
In recent years, a demand for miniaturization of electronic devices has been strong and, accordingly, the size of each of various electronic parts is being reduced. A capacitor is not an exception and a demand for miniaturization of capacitors is also strong.
Conventionally, a capacitor is formed in a re-wiring layer in a semiconductor device. On the other hand, a printed circuit board (PCB) is constructed by mounting a capacitor element on the surface of the board, so that its miniaturization is not sufficient. One of methods of realizing miniaturization of a capacitor is a method of providing a capacitor in a printed wiring board so as to be formed in a re-wiring layer of a semiconductor device.
One of capacitor fabricating methods in the case of forming a capacitor in a printed wiring board is a method of forming a dielectric layer by applying a paste resin containing dielectric particles by printing. Although the method is excellent with respect to the point that the dielectric layer can be formed easily, it also has a problem that it is difficult to form a dielectric layer having a high dielectric constant. The problem is caused by the fact that there is a natural limitation on the viscosity of a material applied by printing. Specifically, in the case of mixing a large amount of dielectric particles into a paste resin material to increase the dielectric constant, the viscosity of the material applied exceeds the limit viscosity of application by printing, and it becomes difficult to form an even dielectric layer. Usually, in the case of using printing to form a fine pattern about 100 &mgr;m square, the maximum amount of dielectric particles which can be contained in a resin paste from the viewpoint of viscosity is about 30 vol % to 40 vol % in volume percentages or 80% by weight in a mass ratio, so that it is difficult to form a dielectric layer having a sufficiently high dielectric constant.
As another example of the method of fabricating a capacitor in the case of providing the capacitor in a printed wiring board, there is a known method of forming a capacitor by, in a manner similar to the case of forming a capacitor in a re-wiring layer of a semiconductor device, depositing an oxide layer of high dielectric constant by CVD (Chemical Vapor Deposition) or the like.
FIGS. 11
to
16
are process drawings showing an example of a method of fabricating a capacitor by using CVD. With reference to the drawings, the conventional method of fabricating a capacitor by using CVD will be described in detail later.
First, a first conductive layer
102
is prepared as shown in FIG.
1
. As the first conductive layer, for example, copper foil or the like is used. On the whole principal surface of first conductive layer
102
, an oxide layer
103
of high dielectric constant is deposited by CVD method. Subsequently, as shown in
FIG. 12
, a second conductive layer
107
is formed on oxide layer
103
of high dielectric constant. In such a manner, a sandwich structure of three layers of conductive layer/oxide layer of high dielectric constant/conductive layer is obtained.
After that, as shown in
FIG. 13
, a resist pattern
108
is formed in a predetermined area on second conductive layer
107
, and etching is performed by using resist pattern
108
as a mask. By the operations, as shown in
FIG. 14
, a capacitor of a desired shape in a desired size is formed. Subsequently, as shown in
FIG. 15
, prepregs
109
are stacked so as to sandwich the capacitor and compression-bonded by hot press, thereby forming insulating layers
106
so as to surround the capacitor as shown in FIG.
16
. The prepregs are sheet members obtained by impregnating glass cloth or the like with epoxy resin or the like.
By the processes, the capacitor can be formed in a printed wiring board and the method largely contributes to miniaturization of an electronic device. However, the fabricating method has the following problems.
First, since CVD method is used to form an oxide layer of high dielectric constant, an expensive CVD system has to be introduced. The CVD system is far more expensive than other fabricating systems used to form a printed wiring board. The introduction of the CVD system extremely increases the manufacturing cost of a printed wiring board.
Second, compression bonding by hot press is necessary to form an insulating layer by using prepregs and the formation positions of the insulating layers may be deviated due to flow of the resin in the prepregs or thermal expansion by heating. The positional deviation deteriorates the yield of products, and causes increase in manufacturing cost.
As a capacitor fabricating method which does not cause such problems, there is a capacitor fabricating method disclosed in Japanese Patent Laying-Open No. 7-92695.
FIGS. 17
to
21
are process drawings showing an example of the capacitor fabricating method disclosed in the publication. With reference to the drawings, the capacitor fabricating method disclosed in the publication will be described in detail later.
First, as shown in
FIG. 17
, a substrate
201
is prepared and a first conductive layer
202
is formed in a predetermined area on substrate
201
. Subsequently, as shown in
FIG. 18
, a positive photosensitive resin is applied on substrate
201
so as to cover first conductive layer
202
, thereby forming a positive photosensitive resin layer
203
a.
As the positive photosensitive resin, polysilane resin is used. To apply the positive photosensitive resin, usually, the spin coat method or the like is used. The resin is applied on the whole surface of substrate
201
.
As shown in
FIG. 19
, a mask
210
having a predetermined pattern is prepared and fixed so that only the positive photosensitive resin in the portion on first conductive layer
202
can be exposed, and positive photosensitive resin layer
203
a
is irradiated with ultraviolet rays. In such a manner, only the positive photosensitive resin on the predetermined area of first conductive layer
202
is exposed, and an exposed positive photosensitive resin layer
203
b
is produced.
Subsequently, as shown in
FIG. 20
, positive photosensitive resin layers
203
a
and
203
b
are immersed in a solution
204
in which dielectric particles
205
are dispersed. At this time, positive photosensitive resin layer
203
a
which is not exposed is hardly impregnated with dielectric particles
205
, whereas exposed positive photosensitive resin layer
203
b
is impregnated with a large amount of dielectric particles
205
. This phenomenon occurs for the reason that a molecular chain in the positive photosensitive resin layer is cut by exposure, and small gaps are created in the positive photosensitive resin layer. As a result, dielectric particles
205
are diffused only in exposed positive photosensitive resin layer
203
b
, so that only this portion functions as a dielectric layer, and the remaining positive photosensitive resin layer
203
a
functions as an insulating layer.
Subsequently, as shown in
FIG. 21
, a second conductive layer
207
is formed on positive photosensitive resin layer
203
b
in which dielectric particles
205
are diffused. By the above operations, a sandwich structure of three layers of first conductive layer
202
/positive photosensitive resin layer
203
b
in which dielectric particles
205
are diffused/second conductive layer
207
is obtained, and a capacitor is fabricated. Simultaneously, an insulating layer is formed by positive photosensitive resin layer
203
a
which is not exposed.
By performing the above processes, the capacitor can be formed in a printed wiring board without using an expensive CVD system, and miniaturization of an electronic device can be realized at low cost. Since the die
Fujioka Hirofumi
Toyoshima Toshiyuki
Kennedy Jennifer M.
Mitsubishi Denki & Kabushiki Kaisha
Niebling John
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