JPH09293690A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method, which makes a selective deposition of an amorphous film possible in a contact hole by a self-alignment process, realizes a contact structure having a low contact resistance and high barrier properties and makes the manufacturing of a semiconductor device having high-speed operating characteristics and a single structure possible. SOLUTION: An insulating film 12, such as an Si oxide film, is formed on the surface of an Si substrate 11 and after a contact hole 13 is openly provided locally in this film 12, a Ti thin film 14 is evenly deposited on the entire surface of the film 12 including this contact hole 13 in a thickness of 10nm or thinner and moreover, the substrate 11 is heated to 450 to 550 deg.C to form an amorphous Ti Six film 15 only on an exposed part of the Si oxide film in the hole 13 and this film 15 is formed into a thin barrier film. An Al film 16 is formed on the barrier film to form the barrier film into a pad.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a method of forming a contact structure using a metal nitride barrier layer in a method of manufacturing a semiconductor device.

[0002]

2. Description of the Related Art With the recent integration of devices, the importance of wiring technology for connecting elements is increasing. Particularly for wiring contacts, it is an urgent task to reduce resistance while maintaining reliability. In conventional contact structures, Al, W, etc. are often used as the main constituent metals, but when these metals and Si of the substrate are closely joined, heat treatment causes interfacial diffusion or silicidation reaction, A high resistance layer is formed at the interface, or the reaction layer breaks through a shallow junction to generate a leak current. In order to prevent this, a barrier layer having a high reaction suppressing force and a low resistance is required, and a barrier layer made of a refractory metal such as Ti or W or a compound thereof has been used.

In particular, various techniques have been proposed in which a metal nitride film having a thin silicidation layer near the interface is used as a barrier by thermally nitriding a refractory metal on Si. For example, JP-A-2-235372 and JP-A-4
-112529 publication. FIG. 4 is a sectional view showing an example thereof, in which a SiO ₂ film 42 is formed as an insulating film on a Si substrate 41, and a contact hole 43 formed in the insulating film 42 is filled with a refractory metal such as Ti or W. A barrier film 44 made of metal nitride is formed, and Al as the main metal is formed on the barrier film 44.
And a metal 45 such as W is formed.

However, the barrier film having such a structure generally has a polycrystalline structure and has a grain boundary which serves as a high-speed diffusion path, and therefore, the barrier property is not sufficient. Therefore, in order to obtain a sufficient barrier property, a film thickness sufficiently thicker than the crystal grain size is required, and contact resistance increases. Further, if this grain boundary is buried by oxidation to enhance the barrier property (1985
September 47th, Upright Physics Letters, 47th
Volume, 471 pages; Applied Physics Letters, vol.47, p471,
(1985), Japanese Unexamined Patent Publication (Kokai) No. 5-267211), the introduction of impurities such as oxygen increases the specific resistance of the material itself, which also increases the contact resistance. Further, in the case of a polycrystalline barrier film, the barrier film is directly S-coated in order to prevent damage on the surface of the Si substrate due to the formation of the barrier film.
Since it cannot be formed on the i substrate, good electrical characteristics cannot be obtained.

From this point of view, it is desirable to make the crystal grains small, and a technique of using an amorphous film or a microcrystalline film as a barrier film obtained by sputtering in a nitrogen atmosphere has been proposed (1989, Applied Surface).・ Science, Volumes 41 and 42, 207
Page; Applied Surface Science, vol, 41/42, p207 (1989).

[0006]

However, when the amorphous film or the fine crystal grain film is formed by the sputtering method, the self-alignment process for selectively forming the barrier film in the contact opening cannot be realized. In particular, there is a problem that the barrier film cannot be formed in the contact hole, which makes it difficult to apply to a fine and highly integrated semiconductor device.

An object of the present invention is to enable selective deposition of an amorphous film in a contact hole by a self-alignment process, to realize a contact structure having a low contact resistance and a high barrier property, a high-speed operation characteristic and a simple operation. It is an object of the present invention to provide a manufacturing method capable of manufacturing a semiconductor device having a structure.

[0008]

According to a manufacturing method of the present invention, a barrier film formed between a silicon substrate and a contact metal is uniformly deposited with a refractory metal thin film on the silicon substrate, and then a substrate temperature is set. Is kept at 450 to 550 ° C., and is exposed to a reactive nitrogen-containing gas to form a thin barrier layer of amorphous or microcrystalline state composed of a refractory metal, silicon, and nitrogen. For example, as a preferred mode of the present invention, an insulating film such as silicon oxide is formed on the surface of a silicon substrate, a contact hole is locally formed in this insulating film, and then a refractory metal thin film is formed on the entire surface including the contact hole. Is uniformly deposited, and the substrate is further heated to 450 to 550 ° C. to form an amorphous layer composed of the refractory metal and silicon only in the exposed silicon portion in the contact hole, and unreacted metal on the insulating film is removed. After being removed by chemical etching, it is exposed to a reactive nitrogen-containing gas to form an amorphous or microcrystalline thin barrier layer composed of the refractory metal, silicon and nitrogen.

Here, the refractory metal thin film is made of Ti, Zr,
It is preferable to form Hf to a thickness of 10 nm or less. Further, in the step of exposing to a reactive nitrogen-containing gas, radical nitrogen beam irradiation or irradiation with a highly reactive nitrogen compound gas such as hydrazine or ammonia is adopted.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Next, a first embodiment of the present invention will be described with reference to FIG. First, as shown in FIG.
An insulating film 12 made of SiO ₂ is formed on the surface of the (100) Si substrate 11, and the insulating film 12 is selectively etched to form a contact hole 13 at a required position.
Then, a polycrystalline Ti film 14 having a thickness of 4 nm is deposited using an electron beam gun in a high vacuum.

Next, as shown in FIG. 1B, the deposited polycrystalline Ti film 14 is heated at 500 ° C. for 5 minutes,
The polycrystalline Ti film 14 in the region in contact with the Si substrate 11 is
i Amorphous film 15 is modified. This is RHEED
(Reflection high-speed electron diffraction) The pattern becomes a halo, and XPS
Since the Si peak intensity of (X-ray photoelectron spectroscopy) significantly increases, it can be confirmed that the surface layer is an amorphous layer of TiSi _x . When the heating temperature is 600 ° C. or higher, crystallization of silicide starts rapidly and an amorphous film cannot be obtained. When the heating temperature is 400 ° C. or lower, interdiffusion between metal and silicon takes time. Therefore, it is found that the range of 450 to 550 ° C. is desirable. It was

Then, as shown in FIG. 1C, a radical nitrogen source is used while maintaining the temperature of the Si substrate to about 1 × 1.
A radical nitrogen beam with a flux of 0 ^-5 Torr is supplied to the substrate surface for 5 minutes. As a result, the Ti amorphous film 15 was found to have Ti, Si,
The film is modified into a uniform film containing N in almost equal amounts to form a barrier film. The barrier film 15 observed by a cross-sectional TEM (transmission electron microscope) is a uniform film having a very steep interface and a thickness of 5 nm, and has an amorphous structure composed of very fine particles having a diameter of 1 nm or less. . Also,
Since the RHEED pattern remains a halo even when the substrate temperature is raised to 800 ° C., the amorphous structure of this film is extremely stable, and the amorphous TiSi _x has a thickness of 65%.
This is in marked contrast to the easy phase transition to a polycrystalline structure near 0 ° C.

Then, as shown in FIG. 1D, an Al film 16 is deposited to a thickness of 50 nm on the Ti amorphous film 15,
This Al film 16 is etched together with the polycrystalline Ti film 14 into a desired pattern to form a contact wiring. In this wiring structure, heat treatment (55
Even if the temperature is 0 ° C. for 60 minutes, the barrier film 15 maintains a flatness although the film thickness is slightly reduced, and is suppressed to a level equal to or less than the thickness of the interfacial diffusion barrier film.

As described above, when Ti reacts with silicon, it becomes a metastable amorphous silicide state at a temperature lower than the crystallization temperature. If nitriding is performed at this stage, the amorphous state is stabilized and a dense and uniform barrier film can be formed. Since this film has a high barrier property, the film thickness can be significantly reduced as compared with the conventional one, and the contact resistance can be reduced. In addition, since a damaged layer due to sputtering or the like does not remain at the interface, good bonding can be realized.

A second embodiment of the present invention will be described with reference to FIG. First, as shown in FIG. 2A, an insulating film 22 made of SiO ₂ having a thickness of 300 nm is formed on the surface of the (100) plane n-Si substrate 21, and a part of the insulating film 22 has a diameter of 10 μm.
The contact hole 23 is opened. Then, a polycrystalline Ti film 24 having a thickness of 10 nm is deposited on the entire surface by a sputtering method, and by heating at 500 ° C. for 5 minutes, only the Ti film 24 in the contact hole 23 is amorphous TiSi _x 25.
Reform to.

Then, as shown in FIG. 2B, the unreacted Ti film 24 is removed by once taking it out from the high vacuum tank and immersing it in an etching solution containing hydrochloric acid as a main component for 1 minute. It is again introduced into a high vacuum to perform radical nitrogen beam irradiation. Line analysis of this sample surface by AES (Auger electron spectroscopy)
Since each element of Ti, Si, N, and O is observed on the bottom surface of the contact hole 23, and only Si, N, and O are observed on the surface of the insulating film 22, the contact as shown in FIG. Conductive amorphous TiS only on the bottom surface of the hole 23
It can be confirmed that the iN film 26 is formed and the SiN film 27 is formed on the surface of the insulating film 22. In doing so,
As shown in FIG. 2D, an Al film 28 having a thickness of 200 nm is formed, and A is formed in the contact hole by a lithography process.
l pads are formed.

When the diode characteristics of the Schottky junction thus manufactured are evaluated by the IV method, a curve close to an ideal with a barrier height of 0.55 eV can be obtained. This indicates that the damaged layer on the surface of the substrate introduced by the sputtering process is eaten by silicidation, and an interface with few defects is obtained. The barrier height is half the bandgap of Si (1.1 eV), and when an ohmic contact is used, it is expected that a sufficiently low contact resistance will be obtained for both n-type and p-type substrates. It is considered to be effective for forming a (complementary-MOS) element.

During the deposition of the Ti film 24 of this embodiment and the subsequent heat treatment, the amorphous TiSix 25 is formed only on the exposed portion of the Si substrate, and the amorphous TiSi _x 25 is formed on the exposed portion of the insulating film 22 by T.
Since the interface reaction with i is slow, the unreacted Ti film 24 remains. In the etching solution mainly composed of hydrochloric acid, because the rate of dissolution of metal Ti unreacted much faster than that of the amorphous TiSi _X, only unreacted Ti film 24 after chemically removed, and the nitriding process By S
Amorphous TiS is selectively formed only on the exposed portion of the i substrate 21.
The iN barrier film 26 can be formed, and the barrier film can be formed only in the contact hole.

[0019]

EXAMPLE FIG. 3 is a diagram showing an example in which a contact structure manufactured by the method of the present invention was evaluated. Here, the Kelvin method test pattern is formed to measure the contact resistance. First, as shown in FIG. 3A, a (100) plane p-Si substrate (resistivity: 10 to 20Ω) is used.
cm, 4 inch φ) 31 and a thickness of 0.5 on the surface
A field oxide film 32 of μm is formed, and the field oxide film 3 in the contact region is formed by a normal photolithography technique.
2 is removed and a contact hole 33 is opened. Although not shown, a protective thermal oxide film of 20 nm was grown in the contact hole 33, and then As ions were implanted into the Si substrate 31. The driving conditions are
The dose amount is 5 × 10 ¹⁵ cm ⁻² and the energy is 80 KeV. After performing activation annealing at 900 ° C. for 30 minutes in a nitrogen atmosphere, the protective thermal oxide film in the contact hole 33 is removed from the substrate in buffered hydrofluoric acid (pH˜4).

Then, as shown in FIG.
The substrate 31 was introduced into the vacuum layer, and a Ti thin film having a thickness of 10 nm was deposited on the entire Si substrate 31 by the sputtering method.
The sputtered vacuum layer has an A of 1 × 10 ⁻⁵ Torr or less.
After heating the substrate at 500 ° C. for 5 minutes as an r atmosphere, the substrate is subsequently irradiated with a radical nitrogen beam with a flux intensity of 1 × 10 ⁻⁴ Torr. At this stage, an amorphous TiSiN film 34 is formed on the surface of the Si substrate 31 in the contact hole 33, and a TiN film 35 is formed on the surface of the field oxide film 32.

Then, as shown in FIG. 3C, the temperature of the Si substrate is lowered to 150 ° C. or lower, and the thickness of the Si substrate is reduced to 0.6 in the same vacuum chamber.
A μm Al film 36 is deposited. Next, for this substrate,
The Al film 36 and the underlying TiN film 35 are etched by a lithographic process using Cl ₂ as a reaction gas,
Form the contact pads in the desired shape.

The electrical characteristics of the contact structure thus manufactured were evaluated by the IV method for a contact size of 1 × 1 μm ² . The average specific resistance value of 100 contacts was 1 × 10 ⁻⁷ Ωcm ² or less, which was a sufficiently low value. Further, the same sample was subjected to a heat treatment at 500 ° C. for 60 minutes in a hydrogen atmosphere, and then the same contact resistance measurement was carried out. As a result, the average specific resistance value hardly increased, and no leak current was observed. 100%
It was a non-defective product rate close to.

In the present invention, as the metal constituting the barrier film, in addition to Ti described above, Zr, Hf, which has an amorphous structure prior to crystallization of silicide, is used.
Other high melting point metals such as The same effect can be obtained even when the main contact metal contains a metal such as Cu, Ag, W, or Mo, an alloy thereof, or a trace amount of another element in addition to Al. In addition to the radical nitrogen beam irradiation, the same effect can be obtained by irradiating a highly reactive nitrogen compound gas such as hydrazine (N ₂ H ₄ ) or ammonia (NH ₃ ) in the nitriding process.

[0024]

As described above, in the manufacturing method of the present invention, the following effects can be obtained. The first effect is that by using the contact structure of the present invention, the operation speed of the semiconductor device can be increased. The reason is that an amorphous thin film having a grain size of 1 nm or less can be obtained, so that the film thickness for ensuring the barrier property can be small, and impurities such as oxygen and carbon that increase the resistance are less likely to be mixed in, resulting in low contact. This is because resistance can be obtained. Second
The effect of is that the device configuration can be simplified. The reason is that the damage caused by sputtering or the like on the substrate does not remain on the interface, and the electrical characteristics of the interface junction with the substrate are excellent, so that the barrier film formed by this process directly on the exposed Si portion of the opening. This is because the process can be performed and a process such as formation of a base silicide layer is unnecessary. The third effect is that the device can be highly integrated. The reason is that since the silicidation reaction is used during the process, the self-alignment process is possible by selective deposition on the contact opening.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of the present invention in the order of steps.

FIG. 2 is a cross-sectional view showing a second embodiment of the present invention in the order of steps.

FIG. 3 is a cross-sectional view showing an example of the present invention in the order of steps.

FIG. 4 is a cross-sectional view illustrating a conventional contact structure.

[Explanation of symbols]

11, 21, 31 Si substrate 12, 22, 32 Insulating film 13, 23, 33 Contact hole 14, 24 Ti film 15, 25 Armophus TiSi _X film 16, 28, 36 Al film 26, 34 Amorphous TiSiN film 27 SiN film 35 TiN film

Claims (4)

[Claims] 1. A method of manufacturing a semiconductor device having a barrier film between a silicon substrate and a contact metal, wherein the barrier film is formed by uniformly depositing a refractory metal thin film on a silicon substrate, and then setting the substrate temperature at 450. Manufacture of a semiconductor device, characterized in that it is exposed to a reactive nitrogen-containing gas while maintaining the temperature at ˜550 ° C. to form a thin barrier layer of amorphous or microcrystalline state composed of the refractory metal, silicon and nitrogen. Method. 2. An insulating film of silicon oxide or the like is formed on the surface of a silicon substrate, a contact hole is locally formed in this insulating film, and then a refractory metal thin film is uniformly deposited on the entire surface including the contact hole. Then, the substrate is 450 to 5
After heating to 50 ° C., an amorphous layer composed of the refractory metal and silicon is formed only on the exposed silicon portion in the contact hole, and the unreacted metal on the insulating film is removed by chemical etching. A method of manufacturing a semiconductor device, comprising forming an amorphous or microcrystalline thin barrier layer composed of the refractory metal, silicon and nitrogen by exposing to a gas containing gas. 3. The method for manufacturing a semiconductor device according to claim 1, wherein the refractory metal thin film is formed of Ti, Zr, and Hf with a thickness of 10 nm or less. 4. The semiconductor device according to claim 1, wherein the step of exposing to a reactive nitrogen-containing gas is radical nitrogen beam irradiation or irradiation of a highly reactive nitrogen compound gas such as hydrazine or ammonia. Production method.