JPS59169179A - Semiconductor integrated circuit device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a semiconductor integrated circuit device, and more particularly to the structure of a gate electrode and a gate insulating film of an insulated gate field effect transistor constituting a semiconductor integrated circuit device.

[Background technology]

Insulated gate field effect transistor (hereinafter referred to as MI 5F)
It is known to use a two-layer film consisting of a polycrystalline silicon layer and a molybdenum silicide layer thereon, instead of the conventional polycrystalline silicon layer, as a gate electrode for an ET (ET). According to such a MISFET, the advantages of the conventional silicon gate MISFET can be maintained,
Furthermore, higher speeds can be achieved due to the reduction in wiring resistance.

However, as molybdenum MO has a large active energy and is highly reactive, the inventor's studies have revealed that there is a problem that the electrical characteristics of the device become unstable. Although the resistance is much lower than that of the polycrystalline silicon layer, it becomes a hindrance when trying to achieve even higher speeds.

[Purpose of the invention]

An object of the present invention is to provide a conductor device comprising a MISFET that is suitable for increasing the speed of the device and has a stable gate electrode structure.

The objects and novel features of the present invention and its pond will become apparent from the description of the present specification and the accompanying drawings.

[Summary of the invention]

A brief overview of typical inventions disclosed in this application is as follows.

In other words, MISFET game)! By making the pole a two-layer structure of a tantalum silicide (TaSi2) layer and a polycrystalline silicon layer, and the gate insulating film a two-layer structure of a silicon nitride (Si3N4) film and a silicon oxide (S + 02) film, the characteristics can be improved. It constitutes a stable MISFET and also achieves high speed.

〔Example〕

Embodiments of the invention will be described with reference to FIGS. 1 to 4.

As shown in FIG. 1, a field silicon oxide film 2 is formed on selective regions of the surface of a p-type silicon substrate 1 using a well-known selective oxidation method.
A thin gate silicon oxide film 3 is formed on the surface of the active region, a thin silicon nitride film 4 is formed thereon by, for example, CVD (chemical vapor deposition technology), and then a polysilicon film is formed on the entire surface. 5 is formed by CVD method,
Thereafter, an impurity such as phosphorus is diffused to form the polysilicon 5 into a low resistance material. Next, a tantalum silicide film 6 is formed on the entire surface by, for example, sputtering.

Then, as shown in FIG. 2, the tantalum silicide, polysilicon, and silicon nitride films are sequentially etched using photolithography to form a gate electrode pattern and, if necessary, a wiring turn. Next, arsenic all over the surface.
Impurity ions such as phosphorus are implanted into the silicon substrate.
After forming the ion implantation layer 14 in the active region of the surface and the part not covered with the gate electrode, as shown in FIG.
After forming a phosphosilicate glass film (PSG film) 7 by method D, heat treatment is performed to activate the ion-implanted impurities and form an N-type source layer 8 and a drain layer 9.

Next, as shown in FIG. 4, contact holes 10.degree. 11 and contact holes 12 for multilayer wiring are formed in the source and drain by photolithography.

Then, an aluminum film is formed on the entire surface by, for example, sputtering, and each electrode pattern 13a, 13b, 13c is formed by photolithography.

The MISFET formed as described above is
As the upper layer 6 of il, instead of molybdenum silicide,
Since tantalum silicide is used, electrically stable characteristics are obtained; in other words, since molybdenum is active and highly reactive, it is not stable even after the gate electrode is formed. Additionally, since molybdenum oxide is extremely unstable (sublimable), it is difficult to obtain a stable gate electrode during the manufacturing process, whereas tantalum has low reactivity and its oxide is also extremely difficult to obtain. Since tantalum is a stable substance, it is easy to obtain a very stable gate electrode, and since tantalum has a resistance value of 11 times lower than that of molybdenum, the resistance of the gate wiring can be further reduced. Although it depends on the amount of silicon contained in the tantalum silicide layer, the resistance of the gate wiring can be reduced to about 1/2 of that when a molybdenum silicide layer is used.

On the other hand, the problems peculiar to the use of tantalum Ta as an electrode material have been solved by using a silicon nitride film for the gate insulating film. It was found that during annealing to activate the 14-layer structure, tantalum diffuses through the polycrystalline silicon layer and reaches the gate insulating film, which deteriorates the breakdown voltage when the gate insulating film is made of a 5in2 film. . Furthermore, it has been found that the cause of this is that tantalum has a property of containing 5iOz as a ring element, so that the gate 5I02 film becomes ring element.

In order to eliminate the cause of defects caused by tantalum, we form a silicon nitride film that has a higher ability to prevent heavy metal diffusion than a silicon oxide film, and prevents metal from reaching the silicon oxide film due to diffusion. A silicon oxide film with good adhesion to the silicon substrate is formed to stabilize the interface. (1) Stable tantalum silicide with low reactivity is used! Since it is used as part of the pole, an electrically stable element can be obtained.

(2) As the gate insulating film, a silicon nitride film is formed on top of the silicon oxide film, which is more stable and has a higher ability to prevent the diffusion of this metal, so even if tantalum silicide is used as the gate electrode, it can be removed by high-temperature heat treatment. It is possible to prevent the tantalum in the gate material from diffusing into the silicon oxide film, thereby preventing the gate breakdown voltage from deteriorating.

(3) Since the gate electrode has a two-layer structure of the tantalum silicide layer as the upper layer and the polysilicon layer as the lower layer, the interface between the gate electrode and the gate insulating film does not deteriorate.

(4) Since the gate insulating film has a two-layer structure of an electrified silicon film as an upper layer and a silicon oxide film as a lower layer, the interface between the silicon substrate and the insulating film is stable.

(51) The speed can be further increased than when molybdenum is used as the gate electrode material.

Although the invention made by the inventor has been specifically explained based on the examples above, the present invention is not limited to the above-mentioned examples and can be modified without departing from the gist thereof. Needless to say (.0) For example, it is also possible to use a tantalum layer instead of the tantalum silicide layer.

[Brief explanation of the drawing]

1, 2, 3, and 4 are cross-sectional views showing a conductor integrated circuit device according to the present invention in the order of its manufacturing process. DESCRIPTION OF SYMBOLS 1... P-type silicon wafer, 2... Field oxide film, 3... Gate oxide silicon, 4... Silicon nitride, 5... Polysilicon, 6... Tantalum silicide, 7... Phosphorus Silicate glass film, 8... Source layer, 9... Drain layer, 10... Source upper contact hole, 11... Ton-in upper contact hole, 12... Multi-wiring contact hole, 13a+13b, 13c. ...Aluminum TM.

Claims (1)

[Claims] 1. A semiconductor substrate, a gate insulating film consisting of a silicon oxide film formed on the surface of this substrate and a silicon nitride film formed thereon, a polycrystalline silicon layer formed on this gate insulating film, and its 1. A semiconductor integrated circuit device comprising an insulated gate field effect transistor having a gate electrode comprising a tantalum silicide layer formed thereon.