JP2841386B2 - Semiconductor device and manufacturing method thereof - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and in particular, to a silicidation junction,
The present invention relates to an electrode having a silicide layer, a structure of metal silicide used for a wiring portion, and a method of manufacturing the same.

2. Description of the Related Art As the density of a semiconductor integrated circuit increases, the size of a MOS transistor, which is a component, is reduced. In such a device, not only the lateral direction, that is, the area, but also the depth direction is reduced. Otherwise, normal transistor operation cannot be maintained. Further, in order to facilitate flattening along with the reduction in the horizontal direction, it is necessary to reduce the thickness of the wiring.

In order to solve the above problems, a method of forming a junction and an electrode using a low-resistance high-melting-point metal silicide layer by a high-concentration impurity diffusion layer in a silicon substrate and a polycrystalline silicon layer has recently attracted attention. . For example, as a conventional technique (silicidation junction method) for forming a silicidation junction layer in the source and drain regions of a MOS transistor in a self-aligned manner, Ii. E. E. E. Transaction of Electron Devices ED-31 (19
1984) 1329 to 1334 (IE ³ , Trans.Electron (Device
s, ED-31 (1984) pp 1329-1334).

An outline of the structure of a conventional silicidation junction will be described with reference to the schematic cross-sectional view of FIG. As shown in FIG. 4, a titanium silicide layer 52 formed in a self-aligned manner on a silicon substrate 51 is connected to a conductor wiring via a selective opening 54 of an insulating film 53.
It is formed between 55 and a high-concentration impurity diffusion layer (n ⁺ or p ⁺ layer) 56 to form a so-called silicidation junction structure.

In the above-mentioned conventional silicidation junction structure, the high concentration impurity diffusion layer 56
Of the sheet resistance is realized.

However, at present, at the time of self-aligned formation of a titanium silicide film, even if good film quality with a uniform film thickness is obtained by performing interface mixing by ion implantation, the titanium silicide Coagulated during the subsequent heat treatment at a relatively high temperature and for a long time (900 ° C. or more, 30 minutes or more), causing surface roughening and cracking, and there was a problem that the silicon substrate was exposed at the cracked portion of silicide. . This will be described with reference to the conceptual cross-sectional view of FIG. As shown in FIG. 5A, the titanium silicide layer formed on the silicon substrate 61 is agglomerated by performing a heat treatment at 900 ° C. for 30 minutes, and as shown in FIG. The silicon substrate 61 is transformed into the island-shaped silicide layer 63, and the silicon substrate 61 of the high-resistance layer is exposed between the island-shaped silicide layers 63. In the integrated circuit process, this high-temperature heat treatment is necessary after the formation of the titanium silicide film, for example, by heat treatment for activating implanted impurities or flattening and reflowing the interlayer insulating film. Such problems are also shown in Journal of Applied Physics (1986), pp. 243 to 245 (JAP (1986), pp. 243 to 245) as experimental results. This problem causes not only the deterioration of the shape but also an electrical increase in sheet resistance and an increase in junction leakage, thereby losing the effectiveness of the silicidation junction.

In view of the above, an object of the present invention is to form a high heat-resistant silicide layer which is free from surface roughening and cracking of the silicide layer and does not deteriorate electrical characteristics even by heat treatment after formation of a silicide junction.

Means for Solving the Problems The present invention has a melting point at a grain boundary of polycrystalline metal silicide,
A semiconductor device comprising an electrode or a wiring made of a thin film mainly composed of a metal silicide containing an element or an element compound higher than the melting point of the metal silicide.

According to the present invention, when a silicide film formed in advance is grown as a polycrystalline film by a heat treatment, the elements contained in the silicide film, for example, carbon and nitrogen are, for example, metal carbide and metal nitride. As a result, these precipitates are deposited at crystal grain boundaries in the film, and these precipitates suppress secondary growth (coalescing of crystal grains) of the silicide film, whereby surface roughness and cracks of the silicide film can be prevented.

Embodiment FIG. 1 is a schematic view showing the structure of a titanium silicide film according to an embodiment of the present invention.

FIG. 1 (a) is a schematic cross-sectional view of the present silicide film, and FIG. 1 (b) is an enlarged view of a main part 10 of FIG. 1 (a). First, a description will be given with reference to FIG. The silicide film 12 formed on the silicon substrate 11 has polycrystalline grains 13 of silicide.
And impurities having a melting point higher than the melting point of the silicide film 12 existing at the grain boundaries 14.

Next, the impurities present in the grain boundaries 14 will be described with reference to FIG. In the grain boundaries 14 between the polycrystalline grains 13 of silicide, carbon 15, titanium nitride 16, and titanium carbide 17 are mixed to form a precipitate layer.

Next, a method for forming the titanium silicide layer 12 will be described with reference to FIG. Here, a formation method by a silicidation reaction method will be described as an example. As shown in FIG. 2A, a titanium thin film 22 containing carbon or nitrogen is placed on a silicon substrate 21 in an atmosphere containing carbon or nitrogen.
To form This titanium thin film containing carbon or nitrogen
22 can be easily formed by a sputter deposition method of a titanium thin film in an atmosphere containing a trace amount of carbon or nitrogen. For example, a titanium thin film containing 0.1% carbon can be formed under sputtering conditions in which an argon gas is a main component and a methane gas having a partial pressure of 1/100 is introduced into a sputtering apparatus having a titanium target. In addition, similarly, argon gas is the main component,
Under sputtering conditions in which 1/100 nitrogen gas was introduced, 0.05%
A titanium thin film containing nitrogen can be formed. After the titanium thin film 22 containing a trace amount of carbon or nitrogen is formed by the above-described method, heat treatment is performed at a temperature equal to or higher than the silicidation temperature, that is, 600 ° C., for example, in nitrogen gas for 1 minute to 60 minutes. As shown in FIG. 2B, a titanium silicide layer 24 in which carbon, titanium carbide or titanium nitride is deposited on a silicon substrate 21 at a crystal grain boundary 23 with a trace amount of carbon or nitrogen can be formed.

Even if the titanium silicide film formed by this method is heat-treated in an inert gas at 900 ° C. for 60 minutes, as shown in FIG. 2C, the secondary growth of the titanium silicide layer 24 (crystal grains 24a Is suppressed by a deposited layer (see FIG. 1 (b)) of carbon, titanium nitride, titanium carbide or the like deposited on the crystal grain boundary 23, and the surface and morphology of the silicide layer 24 are not deformed and the surface and the morphology are smooth. Was. In order to suppress such secondary growth, the melting point of the layer deposited on the grain boundary 23 is high (titanium nitride 2930 ° C., titanium carbide 3140 ° C., carbon 3510 ° C.). This is because each layer is stable without secondary growth even in the heat treatment. It is generally said that the temperature at which secondary growth occurs is about 0.6 times the melting point of the substance.

Next, the effects of the present invention will be described with respect to the data of the embodiment. At temperatures up to 1100 ° C, which is higher than the heat treatment temperature used in practical semiconductor processes, nitrogen-free titanium and titanium containing 0.05% nitrogen are deposited on a silicon substrate to a thickness of 35%.
Table 1 shows the results of measuring the sheet resistance by heat-treating the sample formed in nm in an argon gas atmosphere.

From this result, during the heat treatment at 530 ° C. to 680 ° C., titanium undergoes a solid phase reaction with the silicon substrate to form titanium silicide, and the resistance value is low. No difference in sheet resistance was observed between the two samples before the heat treatment at 1100 ° C. for 2 seconds, but after the heat treatment at 1100 ° C. for 20 seconds, the sheet resistance of the sample containing nitrogen was 2.5%.
Although there is not much difference between Ω / □ and the heat treatment up to 1100 ° C for 2 seconds, 62Ω after heat treatment at 1100 ° C for 20 seconds for samples containing no nitrogen
/ □, which is 30 times higher sheet resistance. This difference in sheet resistance results from the difference in surface morphology of the titanium silicide film. FIG. 3 shows a planar TEM characteristic diagram of both samples after heat treatment at 1100 ° C. for 20 seconds. FIG. 3 (a) corresponds to a sample containing no nitrogen, and FIG. 3 (b) corresponds to a sample containing nitrogen. In FIG. 3 (a), titanium silicide (TiSi ₂ ) is used.
Are aggregated to form an island-like silicide layer (black portion in the figure), and the silicon substrate (white portion in the diagram) is exposed.
On the other hand, in (b), no aggregation and no exposure of the silicon substrate as in (a) were observed, and the entire surface was formed of titanium silicide (TiSi ₂ ).
And the surface morphology is smooth.

In this embodiment, the metal silicide is titanium silicide. However, the same applies to other materials such as tungsten silicide, cobalt silicide and nickel silicide.

As for the content of the impurity, the resistance value of the formed silicide film is low, and excessive content is not suitable for stabilization, and an appropriate amount is from 10 ^-3 % to 10%.

Although the base substrate of the silicide film has been described using a silicon material, other materials such as a silicon oxide film and a silicon nitride film may be used. Furthermore, when this high heat-resistant silicide film was used as a component of a gate electrode and a silicidation bonding layer in a MOS transistor, good electrical characteristics were obtained even after a heat treatment at 900 ° C. for 30 minutes.
cm or more, and in the latter, a value of 0.5 nA / cm ² or less in junction leakage current was obtained.

As a method of manufacturing this structure, a film was formed by a sputtering method in the above-described embodiment. It is easy to control the content of carbon and nitrogen in the formed film from 10 ^-3 % to 10% by mixing methane gas and nitrogen gas to a certain degree.

In the above embodiment, a silicidation reaction between metal and silicon was used as a method of forming a silicide film. However, it goes without saying that similar results can be obtained by forming a silicide film directly during deposition.

Effects of the Invention As described above, according to the present invention, it is possible to suppress the secondary growth of crystal grains during high-temperature heat treatment of a silicide layer by forming a high melting point precipitation layer at a grain boundary. Therefore, deterioration of the formation of the silicide layer due to the high-temperature heat treatment after the formation of the silicide layer can be prevented, and an electrode having excellent electric characteristics can be formed, and its practical effect is large.

[Brief description of the drawings]

1 (a) and 1 (b) are a cross-sectional view of a silicide thin film structure and an enlarged view in the vicinity of a crystal grain boundary according to an embodiment of the present invention, and FIGS. FIG. 3 (a) and FIG. 3 (b) show 1100
FIG. 4 is a schematic diagram of a silicidation junction of titanium silicide film after heat treatment at 20 ° C. for 20 seconds, FIG. 4 (a) and FIG. 5 (b) show degradation of conventional silicide film by heat treatment. It is a conceptual composition. 11 silicon substrate, 12 silicide layer, 13 polycrystalline grains, 14 grain boundaries, 15 carbon, 16 titanium nitride, 17
...... Titanium carbide.

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Kamimae 1006 Kadoma, Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (56) References JP-A-62-227019 (JP, A) JP-A-63-63 204743 (JP, A) JP-A-58-125824 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01L 21/28-21/288 H01L 29/40-29/43

Claims (2)

(57) [Claims] 1. An electrode or wiring comprising a metal silicide-based thin film containing an element or a compound of an element having a melting point higher than the melting point of the metal silicide at a grain boundary of the polycrystalline metal silicide. A semiconductor device characterized by the above-mentioned. 2. A method for forming a polycrystalline metal silicide thin film, comprising the steps of: adding an element having a melting point higher than the melting point of the metal silicide to a gas phase atmosphere for forming the polycrystalline metal silicide thin film; A method of manufacturing a semiconductor device, comprising forming a thin film in which a compound is precipitated and contained in a crystal grain boundary of the metal silicide.