JPH06140353A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To reduce contact resistance by forming a natural oxide film through a reaction with the dissolved oxygen in a washing water thereby to prevent the occurrence of silicon nodule. CONSTITUTION:A wafer having a contact hole formed therein is pre-etched, and dipped for washing in a washing bath filled with a washing water. During this, oxygen (O2) is supplied to the washing water to cause an extremely thin natural oxide film 16 to be formed within the contact hole by the dissolved oxygen. Subsequently an electrode 17 is formed by deposition of Al-Si and photo etching.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device having a miniaturized contact hole in which generation of silicon nodules is suppressed.

[0002]

2. Description of the Related Art In the field of IC, LSI, etc., 1 to 2% by weight of silicon (S
Aluminum silicon containing (i) (Al-Si)
Is often used. However, with the miniaturization of devices, the miniaturization of contact holes for making electrical connection between wiring and diffusion regions has progressed, and at present 2.0 mm × 2.0.
A size of mm or less is required. When miniaturization progresses to this point, as shown in FIG. 6, silicon in the Al-Si electrode (1) epitaxially grows in the contact hole to form a silicon nodule (2), and the grown silicon nodule makes contact. There is a drawback that the contact resistance increases because the surface is blocked. Particularly in semiconductor integrated circuits, the P-type diffusion region is often set to a lower impurity concentration, so that the contact resistance of the P-type diffusion region becomes more problematic than that of the N-type.

Therefore, for example, Japanese Unexamined Patent Publication No. 01-312868.
As described in the publication, a silicon metal surface is covered by interposing a barrier metal such as Mo-Si or W-Si between the aluminum electrode (1) and the substrate (3). It is a common practice to prevent the generation of jules.

[0004]

However, the use of a barrier metal requires a facility (sputtering device, etc.) dedicated to the barrier metal, and the process becomes complicated due to poor selectivity with respect to silicon, resulting in high cost. There was a flaw.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional drawbacks. After the contact hole is formed and the natural oxide film in the contact hole is removed with buffer hydrofluoric acid. The present invention provides a method of manufacturing a semiconductor device, which can suppress silicon nodules at low cost by cleaning with cleaning water supplied with oxygen.

[0006]

According to the present invention, by cleaning with cleaning water supplied with oxygen, the dissolved oxygen and silicon cause the surface of the silicon in the contact hole to become extremely thin (2 to 10).
Å) A new native oxide film (16) is formed. This natural oxide film (16) has a property of being extremely thin and very brittle, unlike an oxide film bonded to oxygen in the air such as being left standing, steam, dry and the like. Therefore, by covering the silicon crystal surface, generation of silicon nodules can be prevented, and at the same time, alloying of aluminum with aluminum in the alloying step can be prevented.

[0007]

An embodiment of the present invention will be described in detail below with reference to the drawings. First, referring to FIG. 2, the surface of a substrate (10) having a large number of P-type or N-type diffusion regions formed for forming circuit elements is covered with a silicon oxide film (11), and a normal photoresist using a photoresist is used. Contact hole (12) in silicon oxide film (11) by etching process
To form. The P-type or N-type diffusion region is exposed in the contact hole (12). The substrate (10) may be an epitaxial layer such as BIP-IC.

The etching of the silicon oxide film is performed by a hydrofluoric acid buffer solution (buffer-hydrofluoric acid) or reactive ion etching (RIE). In the actual process, the substrate is washed with water and dried after etching, and exposed to air until the next process is performed. Therefore, several tens of liters of natural oxide film is formed on the silicon surface in the contact hole (12), and if it is left as it is, it will become an obstacle to the ohmic contact. Perform a pre-etch. The pre-etching is performed by etching with a hydrofluoric acid buffer solution for several tens of seconds, and then washing with water and drying are performed again.

At the time of washing with water in the above pre-etching, oxygen (O ₂ ) which is the feature of the present invention is supplied. That is, as shown in FIG.
A plurality of wafers (1
When immersing 3) in the washing tank (15) filled with the washing water (14) to perform washing with water, oxygen is supplied into the washing water (14) from a cylinder (not shown). The cleaning water (14) is pure water, and the liquid temperature and pressure of the cleaning water (14) are values determined according to the air temperature and atmospheric pressure in the clean room. Under this condition, the dissolved oxygen in the wash water (14) should be saturated,
Oxygen is always supplied in excess.

When the wafer is cleaned with the cleaning water (14) supplied with oxygen in this way, the oxygen dissolved in the pure water reacts with the silicon of the wafer, and the contact hole is extremely exposed as shown in FIG. A thin (1-10Å) native oxide film (16) is formed. This natural oxide film (16) is thinner than the natural oxide film formed during the above-mentioned storage, and moreover, compared with an oxide film combined with oxygen in the air such as air, dry O ₂ and wet O ₂ (steam oxidation). It is very brittle and weak.

Subsequently, Al-Si is deposited by the sputtering method immediately after the pre-etching so that the natural oxide film does not grow. The deposited Al-Si layer is patterned by a normal photoetching technique to form an electrode (17), and an alloying process at about 400 ° C. for several tens of minutes is performed near the final stage of the manufacturing process. In this alloying step, Al-Si of the electrode and the silicon in the contact hole (12) are alloyed to form an ohmic contact as shown in FIG. Since the natural oxide film (16) formed by the reaction with the dissolved oxygen has an extremely thin and brittle property, it does not hinder the eutecticization of Al—Si and silicon. On the other hand, since the natural oxide film (16) is not present at the interface between Al-Si and Si and the silicon crystal plane is not exposed, it is possible to prevent the silicon nodules from epitaxially growing in the contact hole (12). .

FIG. 5 is a diagram comparing the contact resistance and its variation between the conventional method and the present application. The size of the contact hole (12) is 1.6 μ × 1.6 μ, and the conventional method is a normal process using only Al—Si without using a barrier metal. Specifically, the N-type contact is the emitter of the NPN transistor or the source / drain region of the N-channel MOS transistor, and the P-type contact region is the source / drain region of the P-channel MOS transistor. Due to the high impurity concentration and the barrier height, the N-type contact has no great difference in contact resistance and variation. However, the burying of the contact hole due to the silicon nodules that was sometimes seen in the conventional method was not observed. Compared with P-type contacts, the contact resistance was reduced from 86.0Ω to 65.8Ω, a decrease of 20Ω.
The variation (δ / x) in contact resistance is 33.4.
% To 6.6%, a significant improvement. Of course, no burial of the contact hole by the silicon nodules was observed.

As described above, according to the present invention, by suppressing generation of the joule (2) of silicon, good contacts for both P type and N type can be stably obtained without variation.

[0014]

As described above, according to the present invention, it is possible to prevent the epitaxial growth of the silicon nodules (2) by intentionally forming the natural oxide film by the reaction with the dissolved oxygen. Moreover, since the natural oxide film (16) can be easily broken by the Alui process, it has an advantage that good ohmic contact can be obtained with little variation.

Further, since it is a simple method of only supplying oxygen, it has an advantage that it can be carried out at a very low cost as compared with the method using a barrier metal. Furthermore, since oxygen is supplied to the saturated state, there is an advantage that it can be easily carried out by controlling only the processing time. Further, since no special chemical is used, it is harmless, and since oxygen is constantly supplied, the treatment capacity does not deteriorate as compared with the chemical liquid, and thus it has an advantage of further increasing the convenience of treatment.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining the present invention.

FIG. 2 is a first sectional view for explaining the present invention.

FIG. 3 is a second sectional view for explaining the present invention.

FIG. 4 is a third sectional view for explaining the present invention.

FIG. 5 is a diagram for comparing the present invention with a conventional example.

FIG. 6 is a cross-sectional view for explaining a conventional example.

Claims (1)

[Claims] 1. A step of forming a contact hole in an insulating film covering a semiconductor surface, a step of performing wet etching to remove a natural oxide film formed in the contact hole, and a step of washing out the etching solution. A step of washing with water,
A method of manufacturing a semiconductor device, comprising: supplying oxygen into the cleaning water in the water washing step.