JPH0536628A - Semiconductor device and manufacturing method thereof - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide a semiconductor device having a tungsten-embedded electrode structure which is excellent in ohmic contact with a substrate without lowering the yield and a manufacturing method thereof. [Structure] A semiconductor device of the present invention comprises a gate electrode 5 on a substrate 2.
A MOS type in which a smooth coat film 7 is formed on the main surface on which the impurity region 6 is formed, an electrode opening 12 is formed in the smooth coat film 7, and a tungsten buried electrode 8 is formed in the electrode opening 12. In the semiconductor device, the tungsten silicide film 11 is formed on the bottom of the electrode opening 12. [Effect] Since the tungsten silicide film is formed at the bottom of the electrode opening, an abnormal reaction does not occur at the time of forming the tungsten electrode, and a good ohmic contact electrode can be obtained. Become.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a MOS type semiconductor device and a method of manufacturing the same, and more particularly to a structure of a tungsten buried electrode in a MOS type semiconductor device and a method of manufacturing the same.

[0002]

2. Description of the Related Art FIG. 9 is a diagram showing the structure of a selective tungsten-embedded electrode of a MOS semiconductor device. In the figure, 2 is a silicon substrate, 3 is an element isolation film, 9 is a gate oxide film, 5 is a gate electrode, 4 is a framed oxide film, 6 is an impurity region, 7 is an oxide film (smooth coat film), and 8 is It is a tungsten film.

This selective tungsten-embedded electrode is formed by utilizing the difference in the number of adsorbed molecules between the oxide film of tungsten hexafluoride (WF ₆ ) gas and the silicon substrate, and is formed on the silicon substrate 2 or the gate electrode. Tungsten film 8 only on the electrode opening (contact hole) on
Is what grows.

[0004]

However, the grown tungsten film 8 has extremely low adhesion to the underlying silicon substrate 2 and is peeled off during film formation, which cannot be put to practical use.

When the reaction temperature is raised to improve the adhesion, an abnormal reaction with the silicon substrate called encroachment 15 occurs as shown in the figure, or on the oxide film 7. However, there is a problem that the yield is reduced due to the deposition of the tungsten film 8.

On the other hand, as shown in FIG. 10, when a tungsten film is grown unselectively, a peeling prevention film (such as a titanium nitride film or a titanium tungsten film) is formed as a base layer before forming the tungsten film 8. Adhesion film)
13 is required, but since the peeling prevention film 13 is formed by the sputtering method, it can be deposited with a sufficient film thickness on the bottom of the electrode opening (contact hole) having a diameter of 1.0 μm or less. Therefore, there is a drawback that ohmic contact with the P-type silicon substrate is not sufficient.

The present invention has been made in view of the above points, and provides a semiconductor device having a tungsten-embedded electrode structure in which the yield is not lowered and the ohmic contact with the substrate is good, and a manufacturing method thereof. The purpose is to do.

[0008]

In order to achieve the above-mentioned object, the present invention is constructed as follows.

That is, in the semiconductor device of the present invention, the smooth coat film is formed on the main surface of the substrate on which the gate electrode and the impurity region are formed, and the smooth coat film is formed with the electrode opening portion. In a MOS type semiconductor device in which a tungsten-embedded electrode is formed, a tungsten silicide film is formed at the bottom of the electrode opening.

The semiconductor device manufacturing method of the present invention is
A step of forming a gate electrode on the substrate, a step of forming an impurity region on the substrate, a step of depositing a tungsten film and then performing a heat treatment to turn tungsten in the impurity region and the gate electrode portion into tungsten silicide, and a step of removing unreacted tungsten A step of removing, a step of forming a smooth coat film over the entire main surface to flatten it, a step of forming an electrode opening in the smooth coat film, and a step of forming an embedded tungsten electrode in the electrode opening. Is included.

[0011]

According to the above structure, since the tungsten silicide film is formed at the bottom of the electrode opening (contact hole), the tungsten hexafluoride (WF ₆ ) gas is applied to the substrate when forming the tungsten electrode. Since it does not come into direct contact with, it is possible to obtain an excellent ohmic contact electrode without causing an abnormal reaction.

[0012]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a cross-sectional view of a semiconductor device according to an embodiment of the present invention, in which parts corresponding to the above-mentioned conventional example are designated by the same reference numerals.

This embodiment is a MOS type semiconductor device having a selective tungsten embedded electrode. In this semiconductor device 1, an oxide film 3 for element isolation, a gate electrode 5 having a framed oxide film 4, and an impurity region 6 are formed on a silicon substrate 2, and a smooth coat film formed thereon is further formed. The tungsten film 8 for the buried electrode is selectively grown in the electrode opening (contact hole) 12 of the (oxide film) 7. Incidentally, 9 is a gate oxide film, and 10 is an aluminum wiring. The above configuration is basically the same as the conventional example of FIG.

In the semiconductor device 1 of this embodiment, the tungsten silicide film 11 is formed on the gate electrode 5 and the impurity region 6 at the bottom of the electrode opening 12 of the smooth coat film 7.

A method of manufacturing the semiconductor device 1 having such a structure will be described with reference to the process diagrams of FIGS.

That is, in the method of manufacturing a semiconductor device according to this embodiment, first, as shown in FIG. 2, an element isolation oxide film 3 is selectively formed on a silicon substrate 2, and then, as shown in FIG. As described above, the gate electrode 5 is formed after forming the gate oxide film 9. The gate electrode 5 is usually formed by depositing a polycrystalline silicon film by several thousand angstroms by a low pressure CVD method and patterning it by a photolithography method and an etching method.

Next, as shown in FIG. 4, a framed oxide film 4 is formed on the side wall of the gate electrode 5. This framing step is necessary to prevent high-concentration impurities from overlapping the gate end when the gate length is about 1 μm width or less, and after the oxide film is deposited by the low pressure CVD method. , And is etched back by the reactive ion etching (RIE) method. Further, the high concentration impurity region 6 is formed. The low concentration impurity region is omitted.

Next, as shown in FIG. 5, a tungsten film 11a is formed, and then heat treatment is performed to change the tungsten film 11a on the gate electrode 5 and the silicon substrate 2 into the tungsten silicide 11. At this time, the tungsten film 11a on the framed portion 4 and the element isolation oxide film 3 is not silicided. If the tungsten film 11a is too thick, it reacts with a large amount of silicon and causes crystal defects, so 1000 angstroms or less is suitable.

Next, the unreacted tungsten film 11a is removed by an acid treatment to form a smooth coat film 7 on the entire main surface and flatten it, and then the smooth coat film 7 is formed on the smooth coat film 7 as shown in FIG. The electrode opening 12 is formed.

Further, a tungsten film 8 is selectively grown in the electrode opening 12 to form a buried tungsten electrode as shown in FIG. 7, and an aluminum wiring 10 is further formed to complete the semiconductor device 1 of FIG. obtain.

As described above, during the selective growth of the tungsten film 8, since the tungsten silicide 11 has already been formed, the tungsten hexafluoride (WF ₆ ) gas does not come into direct contact with the silicon substrate 2, so that an abnormal reaction occurs. It does not occur, and the tungsten electrode 8 and the tungsten silicide 11 are well bonded. The passivation process and the like are omitted.

[0023] Figure 8 is another cross-sectional view of the semiconductor device 1 ₀ according to an embodiment the method of the present invention, the parts corresponding to the embodiments described above are denoted by the same reference numerals.

In this embodiment, the tungsten film 8 is not selected.
Before the formation of the tungsten film 8, a titanium nitride film 13 is formed as a peeling prevention film (adhesion film), the tungsten film 8 is formed on the entire surface in a non-selective manner, and the electrode opening portion is formed by etching back. A structure in which the tungsten film 8 is left only inside 12, so-called,
The case using the blanket method is shown.

Also in this embodiment, the titanium nitride film 13 as the exfoliation preventing film and the tungsten silicide 11 are well bonded. The other structure is the same as that of the above-mentioned embodiment.

[0026]

As described above, according to the present invention, since the tungsten silicide film is formed at the bottom of the electrode opening (contact hole), when the embedded tungsten electrode is grown, the gas does not contact the substrate. Since they do not come into direct contact with each other, an abnormal reaction does not occur, and a good ohmic contact electrode can be obtained.

[Brief description of drawings]

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

FIG. 2 is a cross-sectional view showing a state where an element isolation oxide film 3 is selectively formed on a silicon substrate 2.

FIG. 3 is a cross-sectional view showing a state where a gate electrode 5 is formed.

FIG. 4 is a cross-sectional view showing a state where a framed oxide film 4 is formed on a side wall portion of a gate electrode 5.

FIG. 5 is a cross-sectional view showing a state where tungsten silicide 11 is formed.

FIG. 6 is a cross-sectional view showing a state in which an electrode opening 12 is formed in the smooth coat film 7.

FIG. 7 is a sectional view showing a state in which a buried tungsten electrode 8 is formed.

FIG. 8 is a semiconductor device 1 ₀ according to another embodiment method of the present invention.
FIG.

FIG. 9 is a sectional view of a conventional example.

FIG. 10 is a cross-sectional view of another conventional example.

[Explanation of symbols]

1, ₁₀ Semiconductor device 2 Silicon substrate 3 Element isolation film 5 Gate electrode 6 Impurity region 7 Smooth coat film 8 Tungsten film 11 Tungsten silicide 12 Electrode opening

Claims (2)

[Claims] 1. A smooth coat film is formed on a main surface of a substrate on which a gate electrode and an impurity region are formed, an electrode opening is formed in the smooth coat film, and a tungsten buried electrode is formed in the electrode opening. A semiconductor device of the MOS type, wherein a tungsten silicide film is formed on the bottom of the electrode opening. 2. A step of forming a gate electrode on a substrate, a step of forming an impurity region on a substrate, a step of depositing a tungsten film and then performing a heat treatment to convert tungsten in the impurity region and the gate electrode portion into tungsten silicide, A step of removing unreacted tungsten, a step of forming a smooth coat film on the entire main surface to planarize it, a step of providing an electrode opening in the smooth coat film, and a tungsten electrode buried in the electrode opening. And a step of forming a semiconductor device.