JPH0212873A - Semiconductor device - Google Patents

Abstract

PURPOSE:To prevent the generation of a contact failure in a gate electrode by a method wherein barrier metal films are respectively interposed between diffused layers and wiring metal films at the contact parts of the diffused layers and no barrier metal film is interposed between the gate electrode and a wiring metal film at the contact part of the gate electrode. CONSTITUTION:In a semiconductor device constituted in such a way that the device is provided with a gate electrode 5 formed of a poly Si film and wiring metal (Al) films 8 are respectively connected to the electrode 5 and diffused layers 4 which are used as source and drain layers, barrier metal films 7 are respectively interposed between the layers 4 and the metal films 8 at the contact parts of the layers 4 and no barrier metal film is interposed between the electrode 5 and the metal film 8 at the contact part of the electrode 5. For example, titanium nitride films 7 are respectively interposed only at the contact parts of diffused layers 4. Thereby, the generation of an alloy spike in the layers 4 is prevented and/on the other hand, the contact of a dissimilar metal in the gate electrode is avoided to prevent the generation of a weak current, the formation of a current path in case the electrode is exposed to a liquid is prevented to prevent the corrosion of the metal and the generation of a contact failure in the gate electrode can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a structure of a junction between a wiring metal and an element, and particularly to a semiconductor device having a barrier metal at the junction.

[Conventional technology]

As semiconductor devices become denser and faster, it becomes essential to reduce element dimensions, and the dimensions of contact holes for connecting interconnect metals and elements also tend to become smaller. By the way, in conventional semiconductor devices, aluminum doped with silicon is used as a wiring metal.

For example, in FIG. 3, a field oxide film 2 and a gate oxide film 3 are formed on a silicon substrate 1, and a diffusion layer 4 as a source/drain is formed under the gate oxide film 3. This figure shows a MOS (MOS) run lister on which a gate electrode 5 made of polysilicon is formed. Then, after forming an interlayer insulating film 6 such as PSG on this, a contact hole is formed on the diffusion layer 4 and the gate electrode 5, and aluminum doped with silicon is connected as a wiring metal 8 through this contact hole. The structure is taken.

That is, if the aluminum 8 as the wiring metal is not doped with silicon, interdiffusion of silicon and aluminum will occur at the contact area M between the diffusion layer 4 and the aluminum 8, as shown in the area A in FIG. This causes so-called alloy spiking, which destroys the bond.

However, when aluminum doped with silicon is used, silicon precipitation becomes a problem.

In particular, when silicon is deposited inside a fine contact hole, the inside of the contact hole is filled with extremely high-resistance silicon, increasing the contact resistance and deteriorating the characteristics.

Therefore, in the past, as shown in FIG. 4, an attempt was made to solve the above-mentioned problem by interposing a barrier metal 7 such as titanium nitride below the aluminum 8 of the contact hole to prevent mutual diffusion with the diffusion layer. being done.

[Problems to be Solved by the Invention] As described above, in the configuration using the barrier metal, the barrier metal 7 is interposed between not only the diffusion layer but also the gate electrode 5 and the wiring metal 8, and the contact portion is connected to the wiring metal. It has a two-layer structure with barrier metal. Therefore, two types of metals having different work functions come into contact with each other, a contact electromotive force is generated between them, and a weak current constantly flows.

Such a weak current flows into the silicon substrate 1 through the diffusion layer 4 at the contact portion of the diffusion N4, and no particular problem occurs. However, since the gate electrode 5 is normally floating, there is no path for current to flow, and if a process such as washing with water is carried out in this state, the contact portion of the gate electrode 5 will be exposed to current in water, as shown in section B in Figure 4. A passage will be formed. For this reason, there is a problem in that the metal with a larger ionization tendency is ionized and dissolved into the water, and this portion is corroded, resulting in poor contact in the gate electrode 5.

SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor device that can prevent contact failure in gate electrodes.

[Means to solve the problem]

The semiconductor device of the present invention is a semiconductor device configured such that a wiring metal is connected to a gate electrode formed of polysilicon and a diffusion layer serving as a source/drain, respectively. A barrier metal is interposed between the gate electrode and the wiring metal, and no barrier metal is interposed between the gate electrode and the wiring metal.

[Effect]

The above configuration avoids contact between dissimilar metals in the gate electrode to prevent the generation of weak current, prevents the formation of current paths when exposed to liquid, prevents metal corrosion, and prevents contact failure. prevent.

〔Example] Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a sectional view of one embodiment of the present invention.

The MO3I-run lister has a field oxide film 2 and a gate oxide film 3 formed on a silicon i-board 1, and a diffusion N4 as a source and drain formed under this gate oxide film 3.
A gate electrode 5 made of polysilicon is formed on the gate oxide film 3.

Further, a glabellar insulating film 6 such as PSG is formed thereon, and a contact hole is formed above the diffusion layer 4 and the gate electrode 5.

Then, a titanium nitride film 7 is deposited on the entire surface by a 2,000-person sputtering method, and the titanium nitride 7 other than the contact portion of the diffusion layer 4 is removed by ordinary photolithography and dry etching techniques. As a result, the gate electrode 5
The titanium nitride film in the contact hole is also removed, and the barrier metal 7 is formed only in the contact hole of the diffusion layer 4.

Next, 1.0 μm of silicon-doped aluminum 8 is deposited as a wiring metal, and this is etched using photolithography technology to form a predetermined wiring pattern. A transistor is formed.

Therefore, in this configuration, since the barrier metal 7 exists in the contact portion of the diffusion N4, the aluminum 8 and the silicon of the diffusion layer 4 do not interdiffuse with each other, and alloy spikes can be prevented. Further, since the minute current generated by the contact between the barrier metal 7 and the aluminum 8 flows from the diffusion layer 4 to the silicon substrate 1, corrosion of the wiring portion does not occur.

On the other hand, since there is no barrier metal in the contact portion of the gate electrode 5, corrosion of the wiring does not occur. In this case, since there is no barrier metal, mutual diffusion of aluminum and silicon occurs, but even if this mutual diffusion occurs, the device characteristics are not adversely affected and no problem occurs.

FIG. 2 shows a second embodiment of the present invention, and parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and their explanation will be omitted.

In this example, the gate electrode 5 of the MO3I-run lister
A tungsten silicide layer 9 is provided on the upper surface of the structure. This structure has a lower layer resistance than polysilicon alone, so it can also be used as an element interconnect, making it suitable for high density.

Note that this structure can be manufactured by adding a step of depositing 2,000 tungsten silicides onto the polysilicon in the steps of the above embodiment before patterning the polysilicon when forming the gate electrode 5. .

In this embodiment, a different metal is brought into contact with the aluminum 8 at the contact portion of the gate electrode 5, but in this case, the contact portion is not exposed to the liquid, so no current bus is formed in the liquid. Corrosion of wiring metal does not occur.

〔Effect of the invention〕

As explained above, in the present invention, a barrier metal is interposed between the contact part of the diffusion layer and the wiring metal, and a barrier metal is not interposed between the gate electrode and the wiring metal. , while preventing alloy spikes in the diffusion layer, it also prevents the generation of weak current by avoiding contact between different metals in the gate electrode, and prevents the formation of current paths when exposed to liquid, thereby increasing the This has the effect of preventing corrosion and contact failure.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of one embodiment of the present invention, FIG. 2 is a sectional view of another embodiment of the invention, and FIGS. 3 and 4 are sectional views of different conventional structures. 1... Silicon substrate, 2... Field oxide film, 3
...Gate oxide film, 4...Diffusion layer, 5...Gate electrode, 6...Interlayer insulating film, 7...Titanium nitride film (barrier metal) 8...Aluminum, 9... Tungsten silicide. Figure Figure

Claims (1)

[Claims] 1. In a semiconductor device having a gate electrode formed of polysilicon and configured so that wiring metal is connected to the gate electrode and diffusion layers serving as a source and drain, respectively, the wiring metal is connected to the contact portion of the diffusion layer. A semiconductor device characterized in that a barrier metal is interposed between the gate electrode and the wiring metal, and no barrier metal is interposed between the gate electrode and the wiring metal.