JPH03190223A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent generation of a junction leakage current and to reduce a contact resistance by forming an opening in an insulating film on a semiconductor substrate, so sequentially forming a tungsten film and a copper alloy film including metal for forming a reaction preventive film as to cover the substrate exposed in the bottom of the opening, and then heat treating it. CONSTITUTION:A field insulating film 2 made of SiO is formed on a substrate 1, and an electrode contact window 3 is formed in the film 2. Then, a W film 5 is formed in the window 3, a copper alloy file containing metal except tungsten is formed as an electrode.wiring layer 6, and then annealed. A barrier layer is formed in a 2-layer structure of a conventional W layer and a diffused barrier layer containing W of high barrier effect by the heat treatment, and the contact of the substrate 1 and the electrode.wiring is silicified. Thus, an ohmic contact having low contact resistance is obtained, mutual diffusion of the wiring 8 and a field oxide film SiO2 at the sidewall of the window 3 can be prevented to prevent pn junction leakage current.

Description

[Detailed Description of the Invention] [Summary] Regarding a method for manufacturing a semiconductor device in which a barrier metal is formed in a contact window between a semiconductor substrate and an electrode/wiring, the interconnection between a wiring made of copper or a copper alloy and Si, 5i02 is To provide a method for manufacturing a semiconductor device in which a reaction prevention film having a two-layer structure with a high barrier effect to prevent diffusion is formed easily and with good coverage, thereby preventing the occurrence of junction leakage current and obtaining low contact resistance. In a semiconductor device having an electrode/wiring layer made of a copper alloy, a step of forming an insulating film having an opening on a semiconductor substrate;
forming a tungsten film so as to cover at least the semiconductor substrate exposed at the bottom of the opening; reacting with the tungsten film on the tungsten film to connect at least one of the semiconductor substrate or the insulating film to the electrode/wiring; forming a copper alloy film containing a metal constituting a reaction prevention film that prevents reaction with the tungsten layer; forming a reaction prevention film formed by reacting the tungsten film with the metal; and a step of performing heat treatment to react with the film to form a reaction layer, or in such a structure, heat treatment in a nitrogen-containing gas atmosphere. The method is characterized in that it includes a step of forming a nitride film containing the metal on the copper alloy film by performing the above steps.

[Industrial application field]

The present invention relates to a method for manufacturing a semiconductor device in which a barrier metal is formed within a contact window between a semiconductor substrate and an electrode/wiring.

In recent years, LSI (Large 5cale
Along with the demand for higher integration in semiconductor devices, interconnections have become finer, and electromigration of electrodes and interconnections in the submicron region has become a problem. Therefore, a wiring material with high electromigration resistance is required. Electrodes and wiring made of copper (CU) or copper alloys have electromigration resistance that is two orders of magnitude higher than conventional aluminum (AI) wiring, and their electrical resistance is about 1/2 as low, making them suitable for electrodes in next-generation semiconductor devices.・It is seen as promising as a wiring material. However, when the process used to form conventional aluminum wiring is used to form copper wiring, the heat treatment during the process causes the Cu in the wiring to mix with silicon (Si) in the semiconductor substrate and silicon dioxide (SiOz) in the field oxide film. There is a concern that the Cu or Cu alloy reacts easily and the pn junction is destroyed due to interdiffusion between the Cu or Cu alloy, the Si substrate, and the field oxide film 5in2. Cu absorbs holes in the diffusion layer of the silicon substrate.
Since it becomes a nucleus for the generation of electron pairs, it becomes a cause of junction leakage current and deteriorates the device characteristics. Another problem is that copper is easily oxidized. Therefore, a method of forming electrodes and wiring made of copper or copper alloy without causing such disadvantages has been desired.

[Conventional technology]

Therefore, when copper or copper alloy is used as a wiring material, a reaction prevention film such as tungsten (W) is formed between the wiring and the substrate to prevent mutual diffusion between the copper or copper alloy and the silicon substrate and field oxide film 5i02. That is, a barrier layer is interposed, and a titanium (Ti) film or the like is formed at the contact interface between the wiring and the silicon semiconductor substrate to reduce the contact resistance.

[Problem to be solved by the invention]

However, when W is used as the barrier layer, it is difficult to obtain a sufficient barrier effect between the wiring material steel or copper alloy, the substrate St, and the field oxide film 5i02. Because, W
The film is formed within the electrode contact window using a sputtering method, and in particular W is deposited on the side wall of the electrode contact window.
The film becomes thin, and when interdiffusion between copper and the field oxide film Sio2 occurs, electrodes and interconnects pass from this thinly formed sidewall W film through the field oxide film and are electrically connected to the substrate. In other words, junction leakage current occurs, degrading device characteristics. For this reason, a method has been adopted in which a TiN film and then a W film are sequentially formed as a reaction prevention film to improve barrier properties. However, this method had the drawback of increasing the number of steps. In particular, when the TiN film is formed by sputtering, the step coverage becomes poor. Furthermore, since each layer is formed by sputtering, the step coverage gradually deteriorates due to the shadowing effect, so there still remains the problem that junction leakage current from the side walls of the contact window cannot be prevented.

The present invention uses wiring made of copper or copper alloy and Si, 5in.
Provided is a method for manufacturing a semiconductor device in which a reaction prevention film having a two-layer structure with a high barrier effect is easily formed with good coverage to prevent a reaction with 2, thereby preventing the occurrence of junction leakage current and obtaining low contact resistance. The purpose is to

[Means to solve the problem]

In a semiconductor device having an electrode/wiring layer made of a copper alloy, the present invention includes a step of forming an insulating film having an opening on a semiconductor substrate, and a step of forming an insulating film with tungsten to cover at least the semiconductor substrate exposed at the bottom of the opening. a step of forming a film, and a metal forming a reaction prevention film on the tungsten film that reacts with the tungsten film to prevent reaction between the semiconductor substrate or at least one of the insulating films and the electrode/wiring layer. A process of forming a copper alloy film, forming a reaction prevention film formed by the reaction between the tungsten film and the metal, and heat treatment to form a reaction layer formed by the reaction between the semiconductor substrate and the tungsten film. The method is characterized in that it includes a step of performing the method. Alternatively, in such a structure, the method may include a step of forming a nitride film containing the metal on the copper alloy film by performing heat treatment in a gas atmosphere containing nitrogen.

In other words, the diffusion of copper or copper alloy into Si or SiO□ is prevented by heat-treating the barrier layer to create a two-layer structure consisting of a conventional W layer and a diffusion barrier layer containing W, which has a higher barrier effect. are doing. At the same time, through the heat treatment, a silicide layer is created in the contact area between the substrate and the electrode/wiring to reduce contact resistance, and a protective film is formed on the electrode/wiring to prevent oxidation.

(Function) According to the present invention, the barrier layer that prevents reactions between the substrate and the electrodes/wirings is made into a two-layer structure using heat treatment, so the manufacturing process can be simplified compared to forming each layer separately. Since a two-layer barrier layer with good step coverage can be formed to a certain thickness on the side wall of the contact window by heat treatment, it is possible to form a barrier layer with a constant thickness of two layers on the side wall of the contact window, which has been a problem in the past.
Mutual diffusion between the wiring and the field oxide film 5iOz can be prevented, and pn junction leakage current can be prevented from occurring. Furthermore, since this heat treatment simultaneously silicides the contact portion between the semiconductor substrate and the electrode/wiring, ohmic contact with low contact resistance can be obtained. Further, if this heat treatment is performed in a nitrogen-containing atmosphere and a nitride film is simultaneously formed on the surface, oxidation of the electrodes and wiring can be prevented.

〔Example〕

FIG. 1 is a sectional view of a main part of a semiconductor device for explaining one embodiment of the present invention. This will be explained below with reference to this figure. FIG. 1(a) shows the state before heat treatment. First, as a semiconductor substrate 1, for example, a p-type St substrate with 5
An O7 field insulating film 2 made of iO2 and having a thickness of, for example, about 4,000 layers is formed by thermal oxidation. Next, the field insulating film 2 is selectively dry etched using a conventional photolithography technique to form an electrode contact window 3. It is assumed that impurity diffusion regions forming part of active elements and passive elements have already been formed in the Si substrate 1.
Symbol 4 indicates an impurity diffusion region that requires ohmic contact. Next, a 0W film 5 having a thickness of, for example, about 1000 layers is formed using a sputtering method, and then a copper alloy film containing a metal other than tungsten, such as Cu-titanium (Ti), is formed as an electrode/wiring M6 using a sputtering method.
The alloy is formed to a thickness of, for example, 5000. In this case, the composition of the Cu-Ti alloy is such that Ti is 10% of Cu.
[% by weight]. At this time, other metals than Ti may be used as the metal other than tungsten. for example,
Molybdenum (MO) is listed. Thereafter, annealing is performed at 600° C. for 130 minutes in a nitrogen atmosphere. FIG. 1(b) shows this situation. By this heat treatment, C
Ti diffused from the u-Ti alloy film 6 to the interface reacts with the W film 5, forming a diffusion barrier layer T with a higher barrier effect than Wli5.
i W 7 is formed with a thickness of 700-800 people. In this process, Ti contained in the Cu--Ti alloy IA6 is consumed and the Cu--Ti alloy film 6 turns into a nearly pure Cu film 8.

This allows the resistance of the electrode/wiring layer 6 to be lowered. In this reaction, the thickness of the W layer 5 is reduced to about 300 because W is consumed to form TiW. Through this heat treatment, the TiW layer 7 is formed, and at the same time, a reaction between silicon and tungsten progresses on the surface of the silicon substrate 1 within the electrode contact window 3, resulting in tungsten silicide (WSi).
x) Film 9 is formed to reduce contact resistance. In this way, in contact with the substrate 1, the TiW layer 7/W layer 5/WSix1i9 is formed between the Cu layer 8 and the St substrate 1 in a self-aligned manner. In the present invention, the formation of the TiW film 7 and the silicidation (formation of the WSix film 9) are performed simultaneously by annealing, so there is no need to increase the number of manufacturing steps. Furthermore, a reaction prevention film with better coverage can be formed than by forming 2N barrier layers one by one. Further, if this heat treatment is performed in a nitrogen atmosphere, the Cu--Ti alloy film 6 reacts with nitrogen in the atmosphere, and a titanium nitride film (not shown) can be formed on the surface of the Cu--Ti alloy film 6. With this film, copper electrodes and
Oxidation of the wiring layer can be prevented. Note that if there is no need to form a nitride film, the heat treatment may be performed in a vacuum or in an inert gas atmosphere. Finally, the W film 5, TiW film 7, and Cu film 8 are patterned using dry etching technology to form a wiring shape. At this time, patterning may be performed before heat treatment. In the present invention, the semiconductor substrate 1 is not necessarily limited to a silicon substrate, but can be applied to any substrate in which there is a possibility that copper may react with copper or a copper alloy used as an electrode/wiring material and diffuse into the substrate. Ru. In addition, in the present invention, Cu is used as a starting material to form electrodes and wiring made of copper, which has strong electromigration resistance.
The reason for using the -Ti alloy is that Ti easily reacts with W to form a TiW film with a high barrier effect. This is also due to the fact that TiN is easily formed as an anti-oxidation film on the electrode/wiring layer. Therefore, if a layer other than TiW with excellent barrier effect can be formed, the electrode and
The wiring material is not limited to Cu-Ti alloy, of course, C
It is also possible to add other elements to the u-Ti alloy film. The reason why the W layer 5 is adopted as the base of the Cu--Ti layer 6 is that it has good ohmic contact with the impurity diffusion layer 4 and is easy to react with the substrate St to generate WSix. Further, in the present invention, the reaction prevention film 7
Although the WSix film 9 and the surface nitride film are formed simultaneously in one heat treatment, they may be formed separately. For example, first, after forming a reaction prevention film and a WSix film at 600°C, the temperature is slightly raised and heat treatment is performed at 800°C.
A nitride film is formed on the surface. In this way, each film can be formed at the optimum temperature, so that the device characteristics can be expected to be improved.

Note that the present invention can also be applied to multilayer wiring. This is because the nitride film formed by heat treatment in a nitrogen atmosphere serves as a reaction prevention film with the interlayer insulating layer.

〔effect〕

As explained above, according to the present invention, a reaction prevention film having a two-layer structure with good coverage can be formed in a simple process in manufacturing a semiconductor device having electrodes and wiring made of a copper alloy. This contributes to the simplification of the semiconductor device, and also contributes to improving the reliability of the semiconductor device.

Furthermore, it reduces the contact resistance between the substrate and the electrodes/wirings, prevents oxidation of the electrodes/wirings, prevents high resistance due to oxidation, and contributes to speeding up semiconductor devices.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part of a semiconductor device for explaining one embodiment of the present invention. In the figure, semiconductor substrate 2: insulating film 3: electrode contact window 4: impurity diffusion region 5: tungsten (W) layer 6: electrode/wiring layer 7: reaction prevention film 8 electrode/wiring layer after near-annealing 9: semiconductor substrate Reaction layer between and tungsten layer /-57〉
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Claims (1)

[Claims] 1. In a semiconductor device having an electrode/wiring layer made of a copper alloy, a step of forming an insulating film having an opening on a semiconductor substrate and covering at least the semiconductor substrate exposed at the bottom of the opening. A step of forming a tungsten film, and a metal forming a reaction prevention film on the tungsten film that reacts with the tungsten film and prevents reaction between the semiconductor substrate or at least one of the insulating films and the electrode/wiring layer. a step of forming a copper alloy film containing the tungsten film, a reaction prevention film formed by the reaction between the tungsten film and the metal, and a heat treatment to form a reaction layer formed by the reaction between the semiconductor substrate and the tungsten film. A method for manufacturing a semiconductor device, comprising the steps of: 2. The method for manufacturing a semiconductor device according to claim 1, further comprising the step of forming a nitride film containing the metal on the copper alloy film by performing heat treatment in a gas atmosphere containing nitrogen. .