Semiconductor device, and thin film capacitor

Details Semiconductor device, and thin film capacitor Semiconductor device, and thin film capacitor

2001-07-11

2003-02-25

Nguyen, Tuan H. (Department: 2813)

Semiconductor device manufacturing: process

Making field effect device having pair of active regions...

Having insulated gate

C438S250000, C438S393000

Reexamination Certificate

active

06524905

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device, a method for manufacturing the same, and a thin film capacitor, and in particular, relates to a constitution of a semiconductor device integrated with a thin film capacitor which functions as a decoupling capacitor.
2. Description of the Related Art
When a load is applied very rapidly to a semiconductor integrated circuit device (hereinafter, called an LSI), a voltage drop is observed due to a parasitic resistance and a parasitic inductance present between the power source and ground wirings of the LSI. The voltage drop becomes larger when the parasitic resistance and the parasitic inductance increases, and when the fluctuation time of the load current becomes shorter. The operational frequency has been increased recently from several hundreds of MHz to a level on the order of GHz, and the rising time of the clock has become very short, so that voltage drops have become larger, which causes malfunction of the LSI. In order to reduce such a voltage drop for such reasons, an effective measure is to dispose a capacitor between the power source line of the LSI and the ground wirings of the LSI in parallel. This capacitor disposed in parallel is generally called a decoupling capacitor. When the LSI is temporarily subjected to a voltage drop, the charge accumulated on both electrodes of the capacitor is instantaneously discharged so that the temporal drop of the source voltage can be compensated.
When an ideal state is assumed in which the equivalent series inductance and the equivalent series resistance of the decoupling capacitor is zero, it is possible to discharge the charge instantaneously, and to suppress the voltage fluctuation to zero. In practice, however, since the capacitor has a certain amount of equivalent series inductance and equivalent series resistance, an LC resonance is generated and the capacitor does not work above the resonant frequency. Therefore, as the operational frequency of the LSI increases, it is necessary to reduce the equivalent series inductance of the decoupling capacitor and to shorten the distance between the LSI and the capacitor.
Conventionally, a discrete multilayer ceramic capacitor has been used, because it has a comparatively small equivalent series inductance at a high frequency range. The discrete multilayer ceramic capacitor has a features that its equivalent series resistance and the equivalent series inductance are small when compared with an electrolytic capacitor and in practice, the equivalent series inductance can be reduced to a level of 0.4 nH for a capacitor with a capacitance of 0.01 &mgr;F. Therefore, the voltage drop has been conventionally prevented by disposing a number of multilayer ceramic capacitor around the LSI which performs a high speed operation.
FIG. 13
shows a conventional example, in which a number of multilayer ceramic capacitors
13
functioning as decoupling capacitors are mounted around the LSI chip
12
mounted on a printed circuit board
11
.
Conventional examples, in which decoupling capacitors are disposed at the nearest positions to the LSI, are disclosed in Japanese Unexamined Patent Application, First Publications No. Hei 7-183470 and No. Hei 7-183459. In these conventional examples, the decoupling capacitors are adhered to the upper surface of the LSI using a conductive adhesive.
Accordingly, manufactures of the conventional semiconductor integrated circuits used to provide a plurality of types of LSIs, the operational frequency of each of which was guaranteed, for the convenience of customers' selection, or manufacturers often manufactured LSIs in accordance with customer designs.
When the performance of a capacitor is considered, the resonant frequency of the above-described discrete multilayer ceramic capacitor is at a level of approximately 80 MHz, so that the multilayer ceramic capacitor cannot compensate for the voltage drop of the LSIs which are operated at several hundreds of MHz or on the order of GHz. Furthermore, the decoupling capacitors arranged shown in
FIG. 13
occupy a considerable area of the printed circuit board, so that such arrangement is disadvantageous in reducing the size of the electronic devices.
The method of adhering a capacitor on the surface of an LSI as disclosed in Japanese Unexamined Patent Application, First Publications No. Hei 7-183470 and No. Hei 7-183459 cannot cope with operations in a higher frequency range of more than several hundreds of MHz because of the resistance of the adhesive and contact resistance of the capacitor with the LSI, and because of the presence of an inductance component resulting from the shape of the adhesive.
The fact that the equivalent series inductance of the decoupling capacitor can be decreased by decreasing the thickness of the dielectrics constituting the capacitor has been known. Although the thickness of the dielectric layers in the discrete multilayer ceramic capacitors are generally on the order of a micronmeter, the thickness of the dielectric layers in the thin film capacitor used inside of the LSI is on the order of a nanometer, so that the equivalent series inductance is quite small and the decoupling capacitor is operable in the GHz frequency range.
In particular, when a dielectric film is used such as (Ba, Sr)TiO
3
having a higher dielectric constant than SrTiO
3
which has the high dielectric constant of 300 at room temperature, it is possible to increase the charge stored per a unit area to more than several tens of times than the SiO
2
or Si
3
N
4
. This is because the dielectric constants of the SrTiO
2
or (Ba, Sr)TiO
3
are 300 to 500 or more, while the dielectric constants of SiO
2
and Si
3
N
4
are 3.9 and 7.
An example of forming a decoupling capacitor on an aluminum nitride using a SrTiO
3
film deposited by sputtering as a dielectric material is disclosed in Japanese Unexamined Patent Application, First Publication No. Hei 8-97360. However, in this example, the decoupling capacitor was formed on the printed circuit board for mounting a multi-chip module, so that the deposition temperature for depositing SrTiO
3
is limited. In general, it is known that the dielectric constant becomes high when this type of dielectric material is formed at high temperature. Thus, the dielectric film formed at a limited temperature cannot have a high dielectric constant, which can be provided if the deposition is performed at higher temperature range.
When a manufacturer stores a variety of types of LSI having different operational frequencies in order to meet customer demand, some types of LSI will be stored and will not be ordered and some types will be ordered in excess of what is stored, which incurs high prices for some customers and low profits for the manufacturer. On the other hand, when the manufacturer cooperates in designing an LSI with a customer, if the customer wishes to change the design in the operating frequency or to reduce the price after the design is completed, the manufacturer and the customer will both suffer from delay of delivery and increased cost.
SUMMARY OF THE INVENTION
The present invention is made to solve the above problems and an object of the present invention is to provide a thin film capacitor as a decoupling capacitor having a lower equivalent series inductance than that of the conventional discrete multilayer ceramic capacitor. An object of the present invention is to provide a semiconductor device, which is capable of being operated at a higher operational frequency range, capable of being mounted in a reduced area, and capable of being manufactured at a reduced cost and with a reduced delivery time.
According to the first aspect, a semiconductor device comprises: a plurality of elements formed on a semiconductor substrate; an interlayer insulating film covering the plurality of elements; a plurality of wiring blocks including a power source wire block and a ground wire block connected to the plurality of elements; an uppermost insulating film which covers these wiring bl

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