JPS63133672A - Semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a semiconductor device equipped with a low-electric-current polycide electrode which is not exfoliated from a substrate by installing a three- layered polycide electrode which is composed of an impurity-doped polysilicon film and tungsten silicide films where the component ratio of silicon to tungsten for one film is more than a prescribed value and that for the other film is lower than the prescribed value. CONSTITUTION:A three-layered polycide electrode 7 installed is composed of an impurity-doped polysilicon film 4 and a first and a second tungsten silicide films 5, 6 which are laminated in succession on the polysilicon film and whose component ratio of silicon to tungsten is more than 2.6 and less than 2.6, respectively. For example, a field oxide film 2 and a gate oxide film 3 are formed on a semiconductor substrate 1; the polisilicon film 4 is then formed and, at the same time, an impurity is doped. Then, the first tungsten silicide film 5 whose component ratio of silicon to tungsten is 2.7 is formed; in succession, the second tungsten silicide film 6 whose component ratio of silicon to tungsten is 2.5 is formed. After that, the layers 6, 5, 4 are removed selectively; a three- layered polycide gate electrode 7 is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor device, and particularly to the structure of a polycide electrode.

(Prior Art) Conventionally, aluminum or activated polysilicon has been used for electrode materials such as gate electrodes, extraction electrodes, and internal wiring contact electrodes of semiconductor devices.
As semiconductor devices have become smaller and more highly integrated, polycide electrodes having a two-layer structure consisting of an activated polysilicon film and a tungsten silicide film have recently come into use.

[Problem that the invention seeks to solve]

One of the characteristics required of electrodes used in semiconductor devices is the electrical resistance of the electrodes themselves. Generally speaking, it is desirable for this electrical resistance to be as low as possible in terms of the operating speed of semiconductor devices, but it is difficult to say that the resistance has been sufficiently reduced with the conventional tungsten-silicide-polycide structure electrodes mentioned above. . This two-layer polycide electrode is usually formed of a dungesten silicide film having a silicon/tungsten composition ratio of about 2.6 to 2.8. Therefore, it is clear that in order to further reduce the electrical resistance value of the electrode, the proportion of silicon in this tungsten silicide film should be reduced. However, if a tungsten silicide film with a silicon/ringsten composition ratio of less than 2.6 is used, the tungsten silicide film will be removed from the base substrate during the heat treatment process after electrode formation! This may cause an undesirable problem in terms of reliability.

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a semiconductor device equipped with a polycide electrode having low electrical resistance without causing a peeling phenomenon from a base substrate.

Means for Solving Problems] According to the present invention, a semiconductor device has an impurity-doped polysilicon film and a silicon/tungsten composition ratio stacked sequentially on the polysilicon film of 2.6 or more and 2.6 or more, respectively. A polycide electrode having a three-layer structure including a first tungsten silicide film and a second tungsten silicide film having a thickness of less than .6 is provided.

That is, according to the present invention, an electrode having a three-layer tungsten silicide/polycide structure in which two types of tungsten silicide films having different silicon/tungsten composition ratios are sequentially formed on the activated silicon layer. is used.

〔Example〕

Since it is believed that the present invention can be better understood by explaining its manufacturing method, the present invention will be described in detail below with reference to manufacturing process diagrams.

FIGS. 1(a) to 1(e) are manufacturing process diagrams when the present invention is applied to the gate electrode of an MO3 field effect transistor. According to the process diagram of this embodiment, there is a first layer on the semiconductor substrate 1.
As shown in FIG. 1(a), a field oxide film 2 and a gate oxide film 3 are first formed by a conventional technique, and then a polysilicon film 4 is formed to a thickness of, for example, 1,500 mm as shown in FIG. 1(b).
The glass layer is formed manually, and the impurity doping and etching removal of the surface glass layer are performed by a conventional thermal diffusion method. Here, as shown in FIG. 1 (C>), the first tungsten silicide film is made of polysilicon using a sputtering apparatus (not shown) equipped with a tungsten silicide target having a silicon/tungsten composition ratio of, for example, 2.7. A sputtering device (not shown) equipped with a second tungsten silicide target having a silicon/tungsten composition ratio of, for example, 2.5 is used to form a second tungsten silicide target on the film 4 to a thickness of, for example, 1,500 yen. tungsten·
For example, if the silicide film 6 has a thickness of 1500, as shown in FIG. 1(d).
They are sequentially layered as shown in FIG. Therefore, if the first and second tungsten silicide films 5 and 6 and the lowermost polysilicon film 4 are selectively removed by photoetching, a three-layer polycide gate electrode 7 as shown in FIG. 1(e) is formed. can be obtained.

According to this embodiment, the polycide gate electrode 7 has a tungsten silicide film with a silicon/tungsten composition ratio of 2.6 or more, which has a film quality that is difficult to peel off during a heat treatment process, as an underlying layer, and a film composition ratio with a low electrical resistance value. Since the tungsten silicide film with a particle diameter of less than 2.6 is formed as an upper layer, it can share the advantages of both, and has both stability against heat treatment and low electrical resistance characteristics. That is, according to experiments, the film thickness ratio of the polysilicon film 4 and the first and second tungsten silicide films 5 and 6 was set to 4, respectively.
:2:2, it is proven that the electrical resistance can be reduced by about 20 to 30% compared to the conventional structure electrode of the same shape and size.

FIGS. 2(a) to 2(c) show the gate wiring connection and source of an MO3 field effect transistor according to the present invention.

This is a diagram showing a manufacturing process when the electrode is taken out from the train region. According to this embodiment, as in the previous embodiment, a field oxide film 12 and a gate oxide film 13 are first formed on a semiconductor substrate 11, and then a gate electrode 14, source and drain diffusion layers 15 and 16, and an interlayer passivation film 17 are formed. , contact holes 18 are formed, respectively. [See Figure 2 (a>)] Then, as detailed in the previous example,
One impurity-doped polysilicon film, a first tungsten silicide film 20, and a second tungsten silicide film 21 are formed, respectively. [Figure 2 (
b) see]. If the first and second tungsten silicide films 20 and 21 and the polysilicon film 19 are selectively removed by photoetching, the gate electrode 14 and the source and drain regions 15 and 16 will be etched as shown in FIG. 2(c). Polycide electrodes for wiring 22 and 23.
24 respectively. Since the wiring polycide electrode of this embodiment is formed from a laminated film of two tungsten silicide films having different composition ratios, it has both stability against heat treatment and low electrical resistance characteristics.

〔Effect of the invention〕

As explained in detail above, according to the present invention, an electrode made of tungsten silicide polycide in a semiconductor device is made of a laminated film of two tungsten silicide films each having different properties such as heat treatment resistance and low resistance characteristics. Since the electrode is formed in a three-layer structure, it has the effect of reducing the electrical resistance of the electrode by at least 20 to 30% and preventing peeling from the underlying substrate, significantly improving the reliability of semiconductor devices. You can force it.

[Brief explanation of the drawing]

Figures 1 (a) to (e) are manufacturing process diagrams in which the present invention is applied to the gate electrodes of MO3 field effect transistors, and Figures 2 (a) to (c) are manufacturing process diagrams in which the present invention is applied to the gate electrodes of MO8 field effect transistors. FIG. 3 is a manufacturing process diagram when the gate wiring connection and the lead-out electrodes from the source and drain regions are performed. 1.11... semiconductor substrate, 2. ]2...Field oxide film, 3.13...Day 1 ~ Oxide film, 4, one...
・Polysilicon film containing impurities, 5.20...first tungsten silicide film, 6,21...second tungsten silicide film, 7...3-layer structure (according to the present invention) Polycide gate electrode, 22°23.2
4... (according to the present invention) polycide electrode for wiring with a three-layer structure. Agent Patent Attorney Uchihara Oto (Okonomata-de (ku) (b) (C) Figure 1 (d) Section f 4-space passivation length /2 contact hole ((
:;I-) Kaya Figure 2 (C) Figure 2

Claims (1)

[Claims] A three-layer structure consisting of an impurity-doped polysilicon film and first and second tungsten silicide films having a silicon/tungsten composition ratio of 2.6 or more and less than 2.6, which are sequentially laminated on the polysilicon film. A semiconductor device comprising a polycide electrode.