JPS61135156A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve high-frequency characteristics by inserting a metallic film 4, the formation free energy of an oxide of which is smaller than or approximately the same as that of an silicon oxide, between a tungsten film or a molybdenum film and a natural oxide film 3 consisting of silicon. CONSTITUTION:An silicon dioxide film 11 is formed on the surface of a P type silicon single crystal substrate 10, a film 12 is shaped, and a polycrystalline silicon film 13 is deposited and the polycrystalline silicon 13 at a desired position is etched. An N type impurity region 15 is formed, a titanium film 16 and a tungsten film 17 are shaped, and natural oxide films 18 are reduced and titanium silicide films 19 and tungsten silicide films 20 are formed in succession in direct contacting sections among the natural oxide films 18 and silicon and the titanium film 16. The tungsten film 17 and the titanium film 16 in a section not reacted are removed, an aluminum film is deposited, and the aluminum film except a desired position is removed and a source wiring and a gate wiring are shaped. Accordingly, tungsten silicide has small resistivity, and the resistance of an silicon impurity diffusion layer is increased, thus obtaining a semiconductor device having extremely excellent high-frequency characteristics and high reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a fine and high-performance semiconductor device in which the resistance of an impurity diffusion layer is reduced by using a silicided high-melting point metal, and a method for manufacturing the same.

[Background of the invention]

Regarding lowering the resistance of an impurity diffusion layer using a silicide of a high melting point metal, as described in Japanese Patent Application Laid-open No. 186341/1983, it has been reported that a silicide of a high melting point metal is coated on an impurity diffusion layer by sputtering or the like. is formed. This method does not cause stress in the silicon substrate, is less likely to cause crystal defects, has excellent chemical resistance, and has excellent properties such as being able to form a silicide with a uniform thickness. However, with the above method, it is not possible to form a silicide of a high melting point metal on the impurity diffusion layer in a self-aligned manner.Therefore, it is necessary to use photolithography to process the silicide film of a high melting point metal. This has hindered the miniaturization of semiconductor devices.

In addition, in the case where a silicide of a refractory metal is formed on an impurity diffusion layer in a self-aligned manner to lower the resistance of the impurity diffusion layer, what kind of silicide of a refractory metal is formed and how is it formed? This point has not been sufficiently discussed so far.

When tungsten silicide and molybdenum silicide are formed on a silicon substrate, the stress within the film is lower than that of silicides of other high-melting point metals, and crystal defects are less likely to occur in the silicon substrate. This is because the difference between the coefficient of thermal expansion of molybdenum and the coefficient of thermal expansion of silicon is relatively small. Additionally, tungsten silicide and molybdenum silicide are extremely advantageous in the manufacture of silicon and semiconductor devices because they are not etched by hydrofluoric acid, which is often used in the silicon semiconductor industry.

However, it is difficult to form a silicide of a high melting point metal with a uniform thickness by the reaction between silicon and a high melting point metal.

It is more preferable to use titanium, tantalum, niobium, hafnium, and zirconium as the high melting point metal than to use tungsten or molybdenum as the high melting point metal.
This is due to the formation mechanism of silicide in the high melting point metal due to the reaction between silicon and the high melting point metal. The reason for this is as follows: Before the formation of silicide, the interface between silicon and high melting point metal.

There is a natural silicon oxide film formed on the silicon surface before the high melting point metal is deposited. In order to form a silicide of a high melting point metal, it is necessary to destroy the natural oxide film of silicon and bring the silicon and the high melting point metal into direct contact. When tungsten and molybdenum are selected as high-melting point metals, the free energy of forming oxides of these metals is greater than the free energy of forming silicon oxide, so in order to destroy the natural oxide film of silicon, it is necessary to heat It is necessary to use a certain variation. However, when the natural oxide film is destroyed using thermal fluctuations, it is locally destroyed in areas where the silicon natural oxide film is weak, such as areas where the film thickness is thin.
In this part, the reaction of producing a silicide of the high melting point metal occurs locally, and as a result, the film thickness of the produced silicide of the high melting point metal becomes uneven, resulting in a rough surface. Regarding this.

Japanase J, Appl, Phys.
(1983)■, Nagas in L57-L59
“A 5elf-Aligned M” by awa et al.
The document titled ``O-5ilicide Formation'' discusses how to destroy the natural oxide film of silicon and form a uniform silicide of the high melting point metal by performing ion implantation after depositing the high melting point metal.However, According to this method, the crystallinity of the silicon substrate below the high melting point metal deteriorates.

This deterioration remains even after the silicide of the high melting point metal is formed, reducing the reliability of the semiconductor device.

On the other hand, when titanium, tantalum, niobium, hafnium, and zirconium are used as high-melting point metals, is the free energy of oxide formation of these metals comparable to the free energy of formation of silicon oxide?

Also, since it is small, it is possible to reduce and eliminate the natural oxide film of silicon. Therefore, uniform silicide formation of high melting point metal is relatively easily achieved.

As mentioned above, a high melting point metal silicide suitable for application to silicon semiconductor devices in all respects has not been found so far.

[Purpose of the invention]

The present invention provides a semiconductor device with excellent high frequency characteristics by lowering the resistance of an impurity diffusion layer by providing a tungsten silicide film or a molybdenum silicide film with a uniform thickness formed by a reaction between a silicon film and a high-melting point metal film. and its manufacturing method.

[Summary of the invention]

Tungsten silicide films and molybdenum silicide films have excellent properties for manufacturing silicon semiconductor devices, but when producing silicides of these high-melting point metals, the natural oxide film of silicon interposed on the silicon surface Silicide formation of the above-mentioned high melting point metal was suppressed, and formation of a silicide with a uniform film thickness was prevented. However, as shown in Figure 2.

Between the tungsten film or molybdenum film and the natural silicon oxide film 3 covering the silicon film 1, there is a metal film 4 whose free energy of oxide formation is smaller than or comparable to that of silicon oxide. By inserting this, the above problem could be solved as shown below.

When heat treatment is performed, the metal film 4 reduces the silicon natural oxide film 3 before forming tungsten silicide or molybdenum silicide, and as shown in FIG. 3, the natural oxide film 3 disappears and a new metal is formed. An oxide film 5 is formed, but this metal oxide film 5 has a film thickness of 0 to 10 nm, which is extremely non-uniform, and in most areas, the tungsten film or molybdenum film 2 forms a silicon film 1 through the metal film 4. will come into contact with. That is, after the metal film 4 undergoes a silicide production reaction by heat treatment, the silicide reaction of the tungsten film or molybdenum film 2 occurs uniformly, and the tungsten silicide or molybdenum silicide is formed between the metal silicide film 6 of uniform thickness and the tungsten silicide or molybdenum silicide. A film 7 can be formed.

Examples of metals whose free energy of formation of an oxide is smaller than or comparable to that of silicon oxide include titanium, tantalum, niobium, hafnium, zirconium, and compounds thereof.

In addition, the heat resistance temperature of these metals and their silicides is 10
The film thickness of titanium, tantalum, niobium, hafnium, zirconium, or alloys made of these metals is such that all the natural oxide film of silicon is reduced. As long as it is as thick as possible, it is sufficient. If this film is made too thick,
Prior to the formation of tungsten silicide or molybdenum silicide, a thick silicide film of the metal is formed, increasing stress on the silicon substrate. Furthermore, the diffusion constant of silicon element in the silicides of these metals is comparable to or larger than the diffusion constant of silicon element in tungsten silicide or molybdenum silicide, so these metals are in direct contact with silicon covered with a natural oxide film. In parallel with the formation of self-other tungsten or molybdenum silicide in the area where the tungsten silicide is formed, silicide of the metal is also formed around this area, and furthermore, tungsten film or molybdenum Because silicon is supplied into the film, tungsten silicide or molybdenum silicide is eventually formed around the direct contact area between the silicon covered by the natural oxide film and the above metal. This phenomenon is called bridging. However, this is not preferable in terms of manufacturing semiconductor devices.

Considering the above points, it is desirable that the thickness of the metal film made of titanium, tantalum, niobium, hafnium, zirconium, or an alloy of these metals be less than Ions.

A semiconductor device and a method for manufacturing the same according to the present invention.

In a semiconductor device having a silicon semiconductor covered with an insulating film having an opening, a lower metal layer made of at least one metal selected from titanium, tantalum, niobium, hafnium, and zirconium is coated on the silicon semiconductor layer having the opening. a step of depositing an upper metal layer made of tungsten or molybdenum or both on the lower metal layer; and a step of performing heat treatment at 400° C. or higher in vacuum, the silicon semiconductor layer comprising the silicide of the lower metal layer and the silicide of the upper metal layer, and from the back surface of the insulator at the portion in contact with the upper opening. The back surface of the silicide of the lower metal layer is located inside the metal layer.

[Embodiments of the invention]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view showing one embodiment of a semiconductor device according to the present invention, and (a), (b), and (c) are cross-sectional views in the manufacturing process, respectively. In FIG. 1(a), a silicon dioxide film 11, which will serve as an insulating isolation region between elements, is formed at a desired position on the surface of a p-type silicon single crystal substrate IO by ordinary selective oxidation.

Next, a gate oxide film 12 is formed by a thermal oxidation reaction of silicon.
was formed in a 5-on-11 pattern on the exposed surface of the silicon substrate 10. Further, a polycrystalline silicon film 13 was deposited to a thickness of 30 mm by conventional chemical vapor deposition, and the polycrystalline silicon 13 was etched at desired positions by photolithography. Next, a phosphor glass film of 50% was deposited using the usual chemical vapor deposition method.
A portion 12 of the gate oxide film that is not covered with the phosphor glass film 14 and the polycrystalline silicon film 13 is deposited to a thickness of 0 nm and then etched by reactive ion etching.
' was formed. Note that in reactive ion etching, the etching speed in the direction parallel to the surface of the silicon substrate 10 is extremely slow compared to the speed in the perpendicular direction. ' remains. Thereafter, an n-type impurity region 15 was formed by normal ion implantation and heat treatment.

Next, after cleaning the exposed silicon surface using a dilute hydrofluoric acid solution, a titanium film 16 was formed by a lOnm vacuum evaporation method, as shown in FIG. 1(b). In place of the titanium film 16, a tantalum film, a niobium film, a hafnium film, a zirconium film, or a mixture thereof may be used. Note that the n-type impurity diffusion region 15 and the polycrystalline silicon film 13
A natural oxide film 18 of silicon, which was formed before the titanium film 16 was deposited, was present at the interface between the titanium film 16 and the titanium film 16 . A 5ON tungsten film 17 is placed on the titanium film 16.
It was formed to a hazy thickness by a conventional sputter deposition method. A molybdenum film may be used instead of the tungsten film 17.

Next, as shown in Figure 1 (Q), 58
Heat treatment at 0° is performed, and in the areas where the silicon covered with the natural oxide film 18 and the titanium film 16 are in direct contact, the natural oxide film 18 is reduced by the titanium film 16, and the titanium silicide film 19 is reduced.
Then, a tungsten silicide film 20 was sequentially formed. The above heat treatment does not necessarily need to be carried out in a vacuum, and may be carried out in a nitrogen atmosphere, a rare gas atmosphere, a hydrogen atmosphere, an oxygen field, water vapor, or a mixed atmosphere of these gases.The unreacted portion is then removed with hydrogen peroxide. The tungsten film 17 and titanium film 16 were removed. Next, a phosphor glass film 21 is deposited for 500 ns by a conventional chemical vapor deposition method, holes are opened at desired positions by a photolithography method, an aluminum film is deposited by a vacuum evaporation method, and then a desired area is formed by a photolithography method. Source wirings 22, 23 and gate wirings 24 were formed by removing the aluminum film except for these areas.

According to this embodiment, a tungsten silicide film 20 having a uniform thickness is formed in the source and drain n-type impurity diffusion regions 1.
could be formed in a self-aligned manner on the surface of No. 5. As a result of measuring the electrical characteristics, it was found that the sheet resistance of the source and drain impurity diffusion regions 15 could be reduced, and the high frequency characteristics of the device were improved.

Furthermore, since the tungsten silicide film has a uniform thickness and low stress, a bond between the n-type impurity diffusion layer 15 and the P-type silicon substrate with excellent characteristics such as reverse breakdown voltage can be obtained, which improves the reliability of the semiconductor device. I was able to improve my performance.

〔Effect of the invention〕

As described above, a semiconductor device and a method for manufacturing the same according to the present invention include a semiconductor device having a silicon semiconductor covered with an insulator having an opening, and a method for manufacturing the same. , niobium, hafnium, and zirconium; depositing an upper metal layer on the lower metal layer, consisting of tungsten or molybdenum, or both; nitrogen; A step of heat-treating the silicide of the lower metal layer and the silicide of the upper metal layer in an atmosphere of at least one gas selected from hydrogen, oxygen, a rare gas, and water vapor or in a vacuum at a temperature of 400°C or higher. and the back surface of the silicide of the lower metal layer is located inside the silicon semiconductor layer from the back surface of the insulator in contact with the opening.

A tungsten silicide film or a molybdenum silicide film having a uniform thickness can be formed in a self-aligned manner only on the exposed portions of silicon, and since the tungsten silicide or molybdenum silicide has a low resistivity, the resistance of the silicon impurity diffusion layer can be reduced. Therefore, it is possible to obtain a semiconductor device which can be measured, has good high frequency characteristics, and is extremely reliable.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing one embodiment of a semiconductor device according to the present invention, (a), (b), and (c) are cross-sectional views in the manufacturing process, respectively, and FIG. 2 is an explanatory diagram showing an outline of the present invention. , 3rd
The figure is an explanatory diagram showing the state after heat treatment in the above state. 10... Silicon semiconductor layer 11... Silicon dioxide film 12... Gate oxide film 13... Polycrystalline silicon 14... Phosphorus glass film

Claims (3)

[Claims] (1) In a semiconductor device having a silicon semiconductor layer covered with an insulating film having an opening, titanium silicide, tantalum silicide, silicide, etc. that are in contact with the silicon semiconductor layer at the opening and generated by reaction with the silicon semiconductor layer niobium,
a lower silicide layer made of at least one type of silicide selected from hafnium silicide and zirconium silicide; and at least one type of silicide selected from tungsten silicide and molybdenum silicide, which is in contact with the lower silicide layer and is produced by reaction with the silicon semiconductor layer. and an upper silicide layer consisting of an upper silicide layer, the back surface of the lower silicide layer being located inside the silicon semiconductor layer from the back surface of the insulating film in contact with the opening. (2) Titanium,
a step of depositing a lower metal layer made of at least one metal selected from tantalum, niobium, hafnium, and zirconium; a step of depositing an upper metal layer of tungsten or molybdenum or both on the lower metal layer; , 400°C in an atmosphere containing at least one gas among hydrogen, oxygen, rare gas, and water vapor or in vacuum.
A method for manufacturing a semiconductor device, comprising the step of performing the above heat treatment. (3) The method for manufacturing a semiconductor device according to claim 2, wherein the lower metal layer has a thickness of 10 nm or less.