JPH07111969B2 - Method for manufacturing semiconductor device - Google Patents

Description

The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of forming a wiring layer.

(Prior Art) In recent years, the trend toward higher integration has been increasing in semiconductor integrated circuits. With the miniaturization and high integration of elements, the wiring tends to be thin and thin, and the wiring length tends to become long. is there.
On the other hand, the pn junction is also formed to have a shallow depth, and the contact area for electrical connection between the gate electrode, the source diffusion layer, the drain diffusion layer, etc. and the metal wiring layer tends to be reduced. The wiring resistance is increasing.
Such an increase in wiring resistance is a major obstacle to speeding up integrated circuits.

Therefore, recently, a low resistance high melting point metal film or a silicide thereof is selectively formed on the gate electrode or the source / drain diffusion layer by a chemical vapor deposition method (CVD method) to lower the wiring resistance or Attempts have been made to use a refractory metal or its silicide as a wiring layer.

In particular, tungsten (W), molybdenum (Mo) and the like have low resistance and are considered promising as electrodes and wiring.

However, if these refractory metal films are formed in contact with single crystal silicon, polycrystalline silicon, or the like on the substrate, they will react at a high temperature to produce silicide of the refractory metal film.

For example, as shown in FIG. 4 (a), when a tungsten film having a film thickness of 3000 Å is formed on a silicon substrate 401 by a sputtering method, and thereafter, heat treatment is performed at 800 ° C. or more for 3 hours or more, the silicon substrate 401 and the tungsten film 402 are formed. Reacts with each other, as shown in FIG. 4 (b), tungsten disilicide (WS
i ₂ ) Form the film 403.

At this time, the resistance of pure tungsten is about 5 to 10 μΩcm, whereas the resistance of tungsten disilicide is about 70 μΩcm. Thus, silicide has a resistance value of about 10
However, there is a problem in that the resistance of wirings and electrodes increases, and the operating speed of each element decreases.

Further, when forming a silicide, a volume contraction of 20 to 30% occurs, film stress is generated, which is a cause of damage to the lower layer element or peeling of the film, As a result, it has been a major cause of deterioration in reliability of the integrated circuit.

(Problems to be Solved by the Invention) As described above, in the state where the silicon and the refractory metal film are in contact with each other in the wiring portion or the like, the refractory metal is silicified at a high temperature, which increases wiring resistance and film stress There is a problem that the film peels off.

Further, the high-melting-point metal film and the silicon oxide film have a large thermal expansion coefficient, and not only the peeling easily occurs but the adhesion is poor, but the nitride film has a large thermal expansion coefficient,
Poor adhesion. Therefore, when the refractory metal film and the nitride film are formed so as to cover the insulating film from the contact region,
There is a problem that peeling easily occurs on the insulating film.

Furthermore, unless a nitride film is interposed, a silicide is produced. For example, silicide is
It will have a resistance value of about 10 times.

Therefore, a refractory metal film and a nitride film are selectively formed in the contact region to prevent peeling, and the presence of this nitride prevents the formation of silicide, resulting in a contact structure with low resistance and high reliability. Is provided.

That is, the present invention has been made to solve the above problems, a wiring layer including a refractory metal film formed on a substrate including silicon, without completely silicified even in a high temperature process, low The purpose is to form a contact layer of resistance.

[Configuration of Invention] (Means for Solving Problems) Therefore, in the present invention, the silicon layer (or the silicon substrate) is used.
When the refractory metal film is formed thereon, at least part of the layer of the refractory metal film is made of a refractory metal nitride.

That is, according to the present invention, in a method for manufacturing a semiconductor device, which comprises a step of forming a contact on one main surface of a substrate having an insulating film mixed on the surface so as to be connected to the substrate,
A step of selectively forming a refractory metal layer on the surface of the substrate by a CVD method, a step of selectively forming a nitride of refractory metal on the surface of the refractory metal layer, and a wiring metal layer on the upper layer. And a step of forming.

(Operation) In the refractory metal film thus formed, the nitride is not silicified even after the high temperature process, so that the low resistance can be maintained and the good contact property can be maintained.

That is, for example, when forming a contact hole in a silicon oxide film formed on the surface of a silicon substrate and forming a wiring so as to connect to this contact hole, a selected CV
The method is characterized in that a refractory metal film is selectively formed on the substrate surface by the D method, and a refractory metal nitride film is further formed thereon.

With this configuration, it is possible to prevent the formation of silicide and form a contact wiring with low resistance.

Further, by selectively forming the W-WN film only in the contact region without forming the W-WN film (that is, the refractory metal and the nitride of the refractory metal) on the insulating film, the W-WN film is formed.
-The poor adhesion between the WN film and the insulating film eliminates the disadvantage that peeling easily occurs, and it becomes possible to form a contact with a long life.

Desirably, if the refractory metal layer is formed with a silicide over the entire thickness in a subsequent thermal process, a region to be silicided is defined in the subsequent process, and the resistance value does not vary.

Further, by forming a three-layer structure of the first refractory metal layer selectively formed on the substrate surface, the refractory metal nitride layer, and the second refractory metal layer, a more stable structure can be obtained. Thus, it is possible to form a low resistance wiring layer.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

Example 1 FIGS. 1A to 1D are views showing a process of forming a wiring layer on a silicon substrate 101 in which a predetermined element region (not shown) is formed.

First, as shown in FIG. 1A, a tungsten nitride (WN) film 102 having a film thickness of 1000 Å is formed on a silicon substrate 101 by a sputtering method. The sputtering is performed in a nitrogen atmosphere using tungsten as a target.

Next, as shown in FIG. 1B, a tungsten film 103 having a film thickness of 3000 Å is formed by a sputtering method.

As described above, when the semiconductor device on which the wiring layer including the tungsten nitride film 102 and the tungsten film 103 is formed is subjected to heat treatment at 950 ° C. for 300 minutes in an argon atmosphere, formation of tungsten silicide is observed. The surface resistance is 0.5 Ω / square, which is about one-tenth of the case where tungsten silicide is formed.

Further, as shown in FIG. 1C, heat treatment is performed for 60 minutes in an ammonia atmosphere at 800 ° C. to form a tungsten nitride film 104 on the surface of the tungsten film 103.

Subsequently, as shown in FIG. 1D, a polycrystalline silicon film 105 having a film thickness of about 5000 Å is formed on the upper layer by the CVD method.

For semiconductor devices in which each layer is formed in this manner, 10
Although heat treatment was performed for 60 minutes in an oxygen atmosphere at 00 ° C., no silicide was found at the interface between the tungsten nitride film 104 and the polycrystalline silicon film 105, and the polycrystalline silicon film 105 and the silicon substrate 101 were not separated from each other. Electrical continuity was confirmed.

Thus, according to the method of the first embodiment of the present invention, while maintaining good electrical contact with the silicon substrate and the polycrystalline silicon film even after the high temperature step of 1000 ° C.,
A low resistance tungsten film can be maintained.

Example 2 Next, LDD (L ightly D oped D rain and source)
A method of forming the contact layer and the wiring layer on the MOSFET having the structure will be described.

First, as shown in FIG. 2A, a field oxide film (insulating film) 202 for element isolation is formed on a p-type silicon substrate 201 made of (100) oriented single crystal silicon and having a specific resistance of 8 Ωcm to form an element formation region. After the formation, a gate electrode 204 composed of a highly-doped phosphorus-doped polycrystalline silicon layer is formed on the thin gate oxide film 203 formed in this region. Then, using the gate electrode 204 and the field oxide film 202 as a mask, phosphorus (P ⁺ ) ions are implanted by an ion implantation method at an acceleration voltage of 40 keV and an implantation amount of 1 × 10 ¹⁴ / cm ² to form shallow source / drain regions. The n ⁻ diffusion layers 205a and 205b are formed.

After that, as shown in FIG. 2B, hydrogen combustion oxidation is performed by heating to 750 ° C., and an oxide film (insulating film) 206 is formed on the surface of the gate electrode 204 and the shallow diffusion layer of the source / drain regions.
To form. Here, by performing hydrogen combustion oxidation at a low temperature of 750 ° C., the dependency of the oxidation rate on the impurity concentration can be increased, and a thicker oxide film is formed on the gate electrode than on the source / drain regions. (The thickness of the oxide film is 600Å on the gate electrode and 1 on the source / drain regions.
It was 00Å. Subsequently, as shown in FIG. 2C, the source / drain regions are exposed by reactive ion etching using a Freon-based gas or wet etching using a dilute solution of hydrofluoric acid. The oxide film 206 is etched up to this point, and then arsenic (As ⁺ ) ions are implanted by an ion implantation method at an acceleration voltage of 50 keV and an implantation dose of 1 × 10 ¹⁶ / cm ² to form deep n ⁺ diffusion layers in the source / drain regions. 207a and 207b are formed.

A contact is formed on the element region thus formed.

First, after removing the oxide film on the gate electrode, by selective CVD as shown in FIG. 2D, on the deep n ⁺ diffusion layers 207a and 207b in the source / drain regions and on the gate electrode 204.
A first tungsten film 208 having a film thickness of 500 Å is formed on each of them.

Then, the surface of the first tungsten film 208 is nitrided in an ammonia gas atmosphere at 550 ° C.
The film thickness of 09 is about 300Å. (FIG. 2 (e)) Further, as shown in FIG. 2 (f), a second tungsten film 210 having a film thickness of 1000Å is formed again on the tungsten nitride film 209 by the selective CVD method.

In this way, a low-resistance contact layer is formed on the source / drain regions and the gate electrode, and then a normal MOSFET manufacturing process, that is, deposition of a silicon oxide film,
Even after a high temperature (950 ° C.) process in which the PSG or BPSG film is deposited and flattened to flatten the PSG or BPSG film, the first tungsten 208 that is in direct contact with the source / drain regions and the gate electrode is As shown in FIG. 2 (g), a tungsten silicide film 208 'is formed, but the second tungsten film 210 on the tungsten nitride film is scarcely silicided.

Therefore, the contact resistance to the gate electrode and the source / drain-in region is one-tenth to one-fifth that of the conventional MOSFET in which the tungsten nitride film is not interposed, and the operating speed of the MOSFET is dramatically increased. improves.

By the way, the refractory metal film and the silicon oxide film have large thermal expansion coefficients, and peeling is apt to occur, resulting in poor adhesion. Further, the nitride film has large thermal expansion coefficients far apart, resulting in poor adhesion. Therefore, when the refractory metal film and the nitride film are formed so as to extend from the contact region to the insulating film, there is a problem that peeling easily occurs from the insulating film.
However, according to such a method, the W-WN film can be selectively formed only in the contact region without forming the W-WN film on the insulating film, and the adhesion between the W-WN film and the insulating film can be improved. It is possible to form a contact with a long life by eliminating the disadvantage that peeling is likely to occur due to poor contact resistance.

Further, the reduction of the contact resistance to the gate electrode can alleviate the restrictions on the circuit design of the integrated circuit, and the integrated circuit can be miniaturized.

Further, as in the conventional case, when the tungsten film is simply formed on the gate electrode and the source / drain regions (second
Since the tungsten film is silicified after the subsequent high temperature step (corresponding to FIG. 7D), the high temperature step cannot be performed to maintain the low resistance. Therefore, it becomes impossible to melt PSG or BPSG, and it becomes difficult to flatten the surface, so that the reliability of the wiring pattern formed in the upper layer is significantly reduced. On the other hand, according to the method of the present invention, as described above, the low resistance can be maintained even after the high temperature process, so that it is possible to form a highly reliable upper layer wiring pattern.

Example 3 Further, since the contact resistance can be reduced, Example 2
As a modified example of FIG. 2, after the MOSFET is formed in the same manner until the formation of the element region shown in FIGS. 2A to 2C, the third region is formed.
As shown in FIG. 3A, prior to the formation of the first tungsten film, the tungsten nitride film, and the second tungsten film as the wiring layer, the silicon oxide film 3 with a film thickness of 5000 Å is formed by the CVD method.
After depositing 01, contact holes h are formed on the source / drain regions and the gate electrode by photolithography. That is, after forming the contact holes, similarly to the second embodiment, the first tungsten film 302, the tungsten nitride film 303, and the second tungsten film 304 are sequentially formed by the sputtering method and patterned to form the wiring layer.

Even in such a structure, even after a high temperature process of 800 ° C. or higher, as shown in FIG. 3B, only the first tungsten film in the wiring layer is changed to the tungsten silicide film 302 ′, and the second tungsten film 302 ′ is formed. The tag-stain film is hardly silicified. Therefore, PSG, BP as an interlayer insulating film (not shown) on the wiring layer
Even after undergoing a flattening process such as SG, low resistance can be maintained, and the reliability of the upper wiring can be greatly improved.

In the second and third embodiments, the first tungsten film, the tungsten nitride film, and the second tungsten film have a three-layer structure, but the first tungsten film is omitted and the tungsten nitride film is directly formed. It may be formed, and if done in this way, the tungsten silicide film is almost completely absent. However, in reality, since a slight natural oxide film is formed on the silicon surface, the existence of the first tungsten film causes the interface to be silicified and the natural oxide film disappears, so that the contact resistance is reduced. Alternatively, a two-layer structure in which a tungsten film and a tungsten nitride film are stacked in this order may be used. Further, it goes without saying that it is also effective when laminating another wiring metal such as a metal on the upper layer.

Further, although tungsten is used as the refractory metal in the examples, it is needless to say that other refractory metals such as molybdenum (Mo) and titanium (Ti) may be used without being limited to tungsten. .

In addition, when forming a tungsten nitride film, a method of using tungsten nitride as a target when a sputtering method is used, a method of using tungsten as a target and sputtering in a nitrogen or ammonia atmosphere, a tungsten film is formed by a sputtering method. After that, the method of nitriding this can be applied, and CV
Both the method of nitriding the tungsten film and the method of forming the tungsten nitride film after the tungsten film is formed by the D method are also applicable.

[Effects of the Invention] As described above, according to the method of the present invention, when a contact layer or a wiring layer containing at least a refractory metal is formed in a semiconductor region or the like, a part of the refractory metal film is formed. Since the layer is made of a refractory metal nitride, it is possible to maintain stable and low resistance contact properties and wiring characteristics even when the subsequent process includes a high temperature process.

[Brief description of drawings]

1 (a) to 1 (d) are diagrams showing a process of forming a wiring layer according to the first embodiment of the present invention, and FIGS. 2 (a) to 2 (g) are
FIGS. 3 (a) and 3 (b) are diagrams showing a wiring layer forming process of the second embodiment of the present invention, and FIGS. 4 (a) and 4 (b) are diagrams showing a wiring layer forming process of the third embodiment of the present invention. FIGS. 9A and 9B are diagrams showing a conventional wiring layer forming process. 101: Silicon substrate, 102: Tungsten nitride film, 10
3 ... Tungsten film, 104 ... Tungsten nitride film, 10
5 ... Polycrystalline silicon film, 201 ... Silicon substrate, 202 ...
… Field oxide film, 203 …… Gate oxide film, 204 …… Gate electrode, 205a, 205b …… Shallow n ⁻ diffusion layer, 206 …… Oxide film, 207a, 207b… Deep n ⁺ diffusion layer (source / drain region) ), 208 ... first tungsten film, 209 ... tungsten nitride film, 210 ... second tungsten film, 208 '...
Tungsten silicide, 301 ... Silicon oxide film, 302 ... First tungsten film, 303 ... Tungsten nitride film, 304
...... Second tungsten film, 304 '... Tungsten silicide, h ... Contact hole, 401 ... Silicon substrate, 402 ...
… Tungsten film, 403 …… Tungsten silicide film.

Claims (4)

[Claims] 1. A method of manufacturing a semiconductor device, which comprises a step of forming a contact on a main surface of a substrate having a surface on which a silicon region and an insulating film region coexist, so as to connect to the silicon region by a selective CVD method. A step of selectively forming a refractory metal layer on the surface of the silicon region, a step of selectively forming a refractory metal nitride layer on the surface of the refractory metal layer, and a wiring metal layer on the upper layer. And a step of forming the semiconductor device. 2. The semiconductor device according to claim 1, wherein the refractory metal layer is formed with a film thickness such that silicide is formed over the entire thickness in a subsequent thermal process. Manufacturing method. 3. The method for manufacturing a semiconductor device according to claim 1, wherein a layer made of a refractory metal is formed as the wiring metal layer. 4. The second refractory metal layer is selectively formed as the wiring metal layer on the nitride layer of the refractory metal, according to claim 1 or 2. A method of manufacturing a semiconductor device according to item 1.