JPS61133646A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain highly reliable ohmic contact, by forming a high-melting- point metal on the surface of a substrate, which is exposed in a contact window, and forming a barrier metal and a wiring layer. CONSTITUTION:As ions are implanted in a P type silicon substrate, and an N<+> type silicon diffused layer 2 is formed. Then, a silicon oxide film 4 is deposited on the surface. Thereafter, a contact window 3 is formed. Then, a tungsten film 5 as a high-melting-point metal film is formed on the layer 2. Thereafter a titanium nitride film 6 as a barrier metal is formed. Then, an aluminum film 7 as a contact electrode and a wiring layer is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for manufacturing a semiconductor device, and particularly to a method for manufacturing a semiconductor device, and in particular, a method for manufacturing a semiconductor device using a highly reliable microstructure between a diffusion layer region formed on a semiconductor substrate and a wiring layer. The present invention relates to a method of forming a contact electrode of an area.

[Technical background of the invention and its problems]

In the field of semiconductor devices, since the 1970s, the trend towards higher integration has been particularly strong, and ultra-large scale integrated circuits (
The technology has advanced to the point where systems such as computers can now be constructed on a single semiconductor chip.

Incidentally, higher speed and higher integration of integrated circuits are achieved by miniaturization of elements. For example, in MO8 integrated circuits, as devices become smaller, the area of contact areas for electrical connections between polycrystalline silicon gate electrodes, source diffusion layers, drain diffusion layers, etc. and metal wiring layers is reduced. At the same time, it becomes necessary to form the PN junction to have a shallow depth.

However, as the contact surface lines become smaller or PN junctions are formed shallower, even when aluminum-silicon alloy is used as the wiring material, contact resistance increases due to the precipitation of excess silicon contained in aluminum and Problems such as destruction of PN junctions become apparent. Especially in the case of VLSI, a few millimeter square siri lunch 21
Since there are more than 1 million contacts per person,
Such deterioration of connection characteristics leads to a decrease in the reliability of elements, and is a major obstacle to increasing the speed and integration of integrated circuits.

For example, as shown in FIG. 5, the depth of the PN junction formed by implanting arsenic (As) ions into a P-type silicon (8i) substrate 21 is 0.1μ. When an aluminum (A1) electrode 5 is formed with respect to the silicon diffusion layer η through a contact window drilled in the insulating film n, silicon and aluminum are formed between the N+ type silicon diffusion layer n and the aluminum electrode 5. The PN junction may be short-circuited due to an interfacial reaction based on the interaction.

As a technique for solving this problem, there is a method of forming a barrier metal in order to prevent the above-mentioned interfacial reaction from occurring between the N+ type silicon diffusion layer n and the aluminum electrode 5. is attracting attention.

In this method, for example, as shown in FIG. 6, after forming an insulating layer portion having a contact window U at a position corresponding to an N+ type silicon diffusion layer B formed in a P type silicon substrate 21, Prior to forming the aluminum layer as the contact electrode 5, a titanium nitride film is formed as a barrier metal over the entire surface by sputtering, but this method also has the following drawbacks. .

In other words, when a barrier metal is formed by a normal sputtering method, the film thickness of the barrier metal around the contact window row is thinner at the flat parts, and the strain due to film stress of the barrier metal is concentrated in these parts. Cracks are likely to occur in the film. In this way, despite the formation of the barrier metal, the barrier effect disappears, and the aluminum layer reacts with the N+ type silicon diffusion layer, causing N+ type silicon to dissolve into the aluminum layer, as shown in Figure 7. Aluminum sometimes penetrated into the release path of silicon atoms in a wedge shape. This is called penetration of the diffusion layer, and is a cause of bond failure.

Furthermore, when forming the barrier metal by sputtering, a natural oxide film of silicon is formed on the surface of the diffusion layer, resulting in an increase in contact resistance. In order to solve this problem, a technique has been proposed in which a cleaning process of the silicon natural oxide film is performed by sputter etching using argon ions, etc. prior to the formation of the barrier metal. However, there still remain problems such as contamination of devices within the system.

In this way, with the method of forming barrier metals by sputtering, there are many problems in realizing contact electrodes with sufficiently low contact resistance and high reliability as devices, making it difficult to put them into practical use. there were.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and it is possible to connect a wiring layer and a semiconductor layer (diffusion layer) without deteriorating the bonding characteristics even for a substrate having a fine and shallow semiconductor layer (diffusion layer). The purpose is to form a low-resistance and highly reliable ohmic contact between the two.

[Summary of the invention]

Therefore, in the method of the present invention, after forming a contact window on an insulating film formed on the surface of a substrate having a semiconductor layer such as a diffusion layer, first, a vapor phase epitaxy method is used to remove the substrate exposed within the contact window. A high melting point metal is selectively formed on the surface, and then a barrier metal and a wiring layer are sequentially formed.

[Effects of the Invention] That is, after drilling a contact window for the diffusion layer (semiconductor layer) and before forming a barrier metal by sputtering, a vapor phase growth process of a high melting point metal using a metal compound gas is introduced. As a result, a high melting point metal film is selectively deposited only within the contact window formed in the insulating film covering the substrate surface, and the step difference due to the presence of the contact window is alleviated, so the barrier metal film thickness is reduced in the area where the barrier metal film is thinner. The barrier metal is almost completely eliminated, and the barrier metal has an almost uniform thickness, and there is almost no junction breakdown due to penetration of the diffusion layer (semiconductor layer).

In addition, when a high melting point metal film is formed by vapor phase growth, the natural oxide film on the substrate surface is completely removed because it reacts with the semiconductor layer (diffusion layer) and grows the high melting point metal. This makes it possible to realize an ohmic contact with extremely low resistance.

As described above, according to the method of the present invention, it is possible to form a low resistance and extremely reliable ohmic contact to the diffusion layer on a substrate having a fine and shallow diffusion layer.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows the structure of a semiconductor device formed by the method of one embodiment of the present invention, in which a contact is made in a portion corresponding to an N+ type silicon diffusion layer 2 in a P type silicon substrate 1. An insulating film 4 having a window 3 is formed, a tungsten film 5 is formed as a high-melting point metal layer in this contact window 3, a titanium nitride film 6 is formed as a barrier metal on top of this film, and a titanium nitride film 6 is formed as an electrode wiring layer. Aluminum films 7 are sequentially formed.

Next, a method for forming a semiconductor device having such a structure will be explained.

First, as shown in FIG.
N+ type silicon diffusion layer 2 with N junction depth X = 0.1 μm
A silicon oxide film 4 is deposited as an insulating film on the zero surface gold body, and a contact window 3 is bored therein by photolithography or the like. (Etching at this time is performed using reactive ion etching.) Next, as shown in Figure 3, tungsten hexafluoride (WF
6) and argon (Ar) as a high-melting point metal coating by a vapor phase growth method using a mixed gas of argon (Ar).
A film 5 is selectively formed only on the N+ type silicon diffusion layer 2 exposed within the contact window 3. The formation conditions include a substrate temperature of 250 to 450"O, and a pressure in the reactor of 1.times.10@-2 to 760".

The partial pressure of tungsten hexafluoride gas is I x 10-'~5
It is desirable to set it in the range of x10-2. Also, the film thickness is 2
It is desirable to set it as 00-1000;.

After this, a titanium nitride film (TiN) 6 is formed as a barrier metal by sputtering under normal conditions.
It is formed to have a film thickness of 500 to 1000 Å. (FIG. 4) Finally, an aluminum film 7 is formed as a contact electrode and an electrode wiring layer, and the semiconductor device as shown in FIG. 1 is completed.

The contact electrode thus formed is formed on the tungsten film, which is deposited on the N+ type silicon diffusion layer without any natural oxide film remaining, through a titanium nitride film as a barrier metal. ), contact resistance can be kept low. That is, since the growth of the tungsten film progresses through reaction with silicon on the surface of the N+ type silicon diffusion layer, the tungsten film is deposited with the natural oxide film completely removed, and the contact electrode portion is Contact resistance can be suppressed to about several tens of ohms even for microscopic devices with a diameter of 1.0 μm or less.

In addition, when forming a titanium nitride film as a barrier metal by sputtering, the underlying tungsten film is filled into the contact window with a uniform thickness, which reduces the level difference caused by the contact window and makes it more uniform. A titanium nitride film with a thickness of It will be extremely expensive.

In the example, a tungsten film formed by a vapor phase growth method using tungsten hexafluoride as a reactive gas was used as a high melting point film to be formed within the contact window, but a tungsten chloride compound was used as the reactive gas. 6
It is also possible to use a tungsten film formed using other tungsten compounds such as tungsten compounds, etc., or use a gas phase film formed using fluorides, chlorides, etc. of molybdenum (Mo), niobium (Nb), tantalum (Ta), titanium (Ti), etc. A film selected from grown films and the like may be used.

Further, in the embodiment, a titanium nitride film was used as the barrier metal, but it goes without saying that tantalum or hafnium nitride may also be used.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a contact portion of a semiconductor device formed by the method of an embodiment of the present invention, and FIGS. 2 to 4 are
Figures 5 to 7 showing the manufacturing process of the device are diagrams showing conventional examples. 1... Silicon substrate, 2... Silicon diffusion layer, 3.
...Contact window, 4...Silicon oxide film, 5...
Tungsten film, 6... Titanium nitride film, 7... Aluminum film, 21... Silicon substrate, n... Silicon diffusion layer, n... Insulating film, U... Contact window, 5
...Aluminum electrode, 26...Titanium nitride film.

Claims (2)

[Claims] (1) A method for forming an electrode wiring layer electrically connected to the semiconductor layer via a barrier metal layer on an insulating film formed on a substrate having a semiconductor layer, the method comprising: , after the drilling step of forming a contact window in the semiconductor layer, and prior to the step of forming the barrier metal layer and the electrode wiring layer, a high melting point metal is selected in the formed contact window by a vapor phase growth method. 1. A method for manufacturing a semiconductor device, comprising a step of depositing the semiconductor device. (2) The barrier metal layer prevents an interfacial reaction between the semiconductor layer and the electrode wiring layer.
1) A method for manufacturing the semiconductor device described in item 1).