JPH07201849A - Method for forming metal wiring - Google Patents

Abstract

PURPOSE:To prevent a metal wiring from being oxidized by forming an oxidation preventing film in at least the side wall of a metal wiring after removing the oxidation preventing and a halogenated metal distribution region to make it feasible to perform metal-wiring work with high fineness and at high density. CONSTITUTION:(a) A silicon nitride film 3 is formed in the whole surface of an SiO2 lower-part insulating layer in the surface of a silicon substrate 1 and (b) next, a copper film 4 is formed in the whole surface for wiring use. (c) After a silicon nitride film 5 for an oxidation preventing film is formed on the copper film 4 again, (e) an SiO2 film 6 is formed. After that, linelike SiO2 mask 7 is formed. (f) Next, bromine ions which are halogen ions, are implanted into the copper film 4. (g) The silicon nitride film 5 and a copper bromide distribution region 8 are removed with a solution of benzene or the like. (h) A silicon nitride film 9 is deposited on the copper film 4 of a wiring and the silicon nitride film 5 covering it. Thereby, the copper wiring is protected from oxidation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a wiring made of a metal such as gold, copper, iron, nickel or platinum.

[0002]

2. Description of the Related Art In integrated circuits, it is desired that metal wiring such as aluminum be formed thin and long and have a lower line resistance. Therefore, for example, copper, which has a lower specific resistance than aluminum and exhibits less migration, has been used as a metal wiring material.

As a technique for forming copper wiring, a metallized substrate dry etching method (Japanese Patent Publication No. 63-47788) is known. In this method, the copper film on the substrate is halogenated to form copper halide, which is irradiated with a laser beam to cause the metal halide reaction to proceed anisotropically to convert the copper halide into NH ₄ OH.
The solution is removed to form copper wiring. In a copper etching process using a similar halogenated substance (Japanese Patent Laid-Open No. 4-159718),
A pattern mask is provided on the copper film, and an anisotropic halogenation reaction is caused in the non-mask portion by high-intensity photoexcitation to form copper halide or vaporize it, and the remaining copper halide is removed with an appropriate solvent. Then, copper wiring is formed.

[0004]

However, in the above-mentioned conventional method for forming metal wiring, the high-power excimer laser light irradiation device and the high-intensity HW of 1000 watts are used, respectively.
Special equipment such as a reactor equipped with a g / Xe lamp is required. Further, the copper wiring is also oxidized by a substance containing oxygen adjacent thereto, and the specific resistance of the copper wiring increases.

The object of the present invention was made in view of the above problems, and a metal wiring forming method capable of performing high-definition and high-density metal wiring processing without requiring a special device and preventing oxidation of the metal wiring. To provide.

[0006]

A method of forming a metal wiring according to the present invention comprises a step of forming an antioxidant film on a wiring metal film provided on a surface of a substrate, and the antioxidant film on the antioxidant film. A step of forming a mask that partially exposes, and a step of ion-implanting halogen ions into the metal film through the exposed portion of the antioxidant film to form a metal halide distribution region made of a metal halide, A step of bringing a two-component etching agent comprising a solvent and a halogen salt into contact with the exposed portion of the antioxidant film to remove the antioxidant film and the metal halide distribution region, and after cleaning and drying the substrate, at least the antioxidant film is removed. Forming on the sidewall of the metal wiring.

[0007]

According to the present invention, a metal halide distribution region with high dimensional accuracy can be formed by ion implantation of halogen ions into a metal film, and this can be anisotropically etched with a two-component etching agent. High-definition and high-density metal wiring can be processed, and oxidation of the metal wiring can be prevented.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a substrate and each layer formed thereon in the process of forming metal wiring according to this embodiment. First, a substrate in which a lower insulating layer 2 of SiO ₂ is formed on the surface of a silicon substrate 1 on which a predetermined diffusion layer is formed is prepared,
A silicon nitride film 3 is formed on the entire surface of the SiO ₂ lower insulating layer 2 to have a film thickness of 700 Å by, for example, a sputtering method or an active sputtering method (FIG. 1A). Here, the silicon nitride film 3 is used as an antioxidant film.

Next, a copper film 4 is formed on the entire surface of the silicon nitride film 3 as a metal film for wiring with a film thickness of 5000 angstrom (FIG. 1 (b)). Although the copper film 4 is used as the metal film here, a film of gold, silver, copper, iron, nickel, platinum, zinc or the like may be used. Next, a silicon nitride film 5 as an antioxidant film is formed again on the entire surface of the copper film 4 to a film thickness of 150 Å (FIG. 1 (c)). In the above film formation, the films are sequentially formed by the sputtering method or the active sputtering method, but they may be formed by another known method such as CVD.

Next, SiO 2 is formed on the silicon nitride film 5.₂Membrane 6
Is formed over the entire surface to a thickness of 4000 Å (Fig.
1 (d)). Here, by the photolinography method, S
iO₂After the pattern photoresist is formed on the film 6, the etching is performed.
SiO not covered with photoresist by ching process
₂Is removed to form a line-shaped SiO with a width of 1 μm and a pitch of 0.5 μm.
₂A mask 7 is formed (FIG. 1 (e)). After etching process
Pattern photoresist is removed by a resist removal process.
Ku.

Next, using an ion implanter, SiO ₂
A predetermined amount of halogen ions (x), for example, bromine ions are implanted into the copper film 4 through the exposed upper silicon nitride film 5 which is not covered with the mask 7 (FIG. 1 (f)). As a result, the copper film is halogenated to copper bromide, and an accurate copper bromide distribution region 8 is formed by controlling the amount of bromine ions. Although bromine is used as the halogen here, chlorine, fluorine, or iodine may be used.

Next, 2 consisting of an organic solvent and a halogen salt
A silicon nitride film 5 and a copper bromide distribution region 8 with a solution of a component type etching agent such as benzene and cetylpyridium bromide
Are removed (FIG. 1 (g)). Although a solution of benzene and cetylpyridinium bromide is used here, an etching agent composed of acetonitrile and tetraethylammonium bromide or a solution of acetonitrile and trimethylamine hydrochloride may be used. Alcohol, ester as organic solvent
A two-component etching agent composed of ether, nitrile, hydrocarbon, etc., and a halogenated salt of the same kind as the halogen used for injection is used.

In the presence of such a two-component etching agent,
The metal is oxidized by halogen, and this and a halide salt form a complex and are eluted in the organic solvent, so that the dissolution of the metal progresses anisotropically and the copper bromide distribution region 8 can be accurately removed. This is because the etching reaction does not proceed unless the two-component etching agent and halogen are present at the same time. next,
The substrate is washed with a solvent such as benzene and then dried. It is preferable to perform it in a state where it is not exposed to the atmosphere. When the metal is copper, copper halide is not only diluted ammonia water,
It can also be washed off with a suitable solvent such as water or acetone.

Next, the copper film 4 is formed into a wiring having a predetermined pattern.
And the silicon nitride film 5 and SiO ₂ covering it
A silicon nitride film 9 is formed on the entire surface of the mask 7 to a film thickness of 1000.
It deposits in Angstrom (Fig. 1 (h)). Since the antioxidant film is formed at least on the side wall of the metal wiring in this manner, the silicon nitride film 9 is formed on the formed copper wiring 4
Can be protected from oxidation by oxygen and moisture in the atmosphere existing in the vicinity of the.

In the above embodiments, the Cu wiring is shown, but the same effect can be obtained with other alloy wiring. As described above, according to this embodiment, a high-definition and high-density metal wire can be formed. By covering the copper metal wiring layer on all sides with the silicon nitride film as the anti-oxidation film, the oxidation can be prevented and the increase in the resistance of the metal wiring over time can be suppressed.

If ion implantation is used in the formation of metal wiring, the amount of halogen ions implanted can be accurately controlled.
Halogen corrosion is reduced. Ion implantation (ion impl
In the (antation) technique, the target implantation element is ionized, and this is accelerated to an energy of several tens to several hundreds of KeV and is implanted into the film to be implanted.
It can be precisely controlled over a wide range from ppm to about 10%. In the case of the example, bromine was used,
When injecting chlorine ions, for example, the acceleration energy is 5
It is used as a range of 0 KeV to 350 KeV. For example 150
When injected at an acceleration energy of KeV, the chlorine ion dose is 8.5 × 10 ¹⁸ / cm ² . Since this is a technique that uses a physical process that does not go through a thermal equilibrium state, it has the following excellent advantages.

(1) The amount and depth of implanted ions can be accurately controlled. Since the ion implantation is performed while measuring the number of ions to be implanted into the substrate or the film, the precision of the implantation amount is extremely high. Regarding the implantation depth, the implantation distribution can be predicted quite accurately if the substrate, the type of ions, and the ion energy are given. (2) Since ions can be implanted at room temperature, a wide range of substances can be used as a mask for selective implantation. In particular, since a photo photoresist can be used, the mask can be protected by leaving the photo photoresist on the SiO ₂ mask 7.

(3) Implanted ions can be doped deep inside the thin film on the surface of the substrate or through the forming layer on the thin film. (4) The lateral spread of implanted ions is small. In ion implantation, high-energy (10 to several hundred keV) ions collide with a solid, and the energy is much larger than the atomic displacement energy in the solid crystal, so that many lattice defects occur in the crystal. For example, when implanting Sb ions into a Si single crystal substrate, the implanted region becomes almost completely amorphous by high-concentration ion implantation of about 10 ¹⁴ / cm ² . Therefore, the reaction between the implanted ions and the implanted side becomes good.

The LSS theory established by Lindhard, Scharff, and Schiott defines a probability density function that gives a distribution probability regarding the stationary position of an incident ion, derives an equation that satisfies it, and then determines an arbitrary order of the distribution. Since a general formula for calculating the moment of is given,
It is known that the ion implantation distribution in the film to be injected, which is represented by the projection range Rp based on the S theory and its variance ΔRp, can be approximated by a Gaussian distribution having an average value Rp and a variance ΔRp. Also, regarding the implantation distribution when the ions are implanted into the multilayer film, for example, when there is not much difference in the ΔRp / Rp ratio of the implanted ions between the two layers of the copper film 4 and the silicon nitride film 5, the ion distribution by each layer It is also known to be required from.

[0020]

According to the method of the present invention, since existing facilities can be used, a precise halogenated metal salt region can be formed by direct introduction of halogen by an ion implantation device without requiring a special device, and Since the halogen non-implanted portion is not etched by the two-component etching agent, complete anisotropic etching can be achieved. Therefore, accurate metal wiring can be formed.

Further, since the halogen is implanted under the structure in which the upper and lower sides of the metal film are sandwiched by the antioxidant films such as the silicon nitride film,
It is possible to prevent oxidation of the metal film during the process. Since the metal wiring obtained after forming the metal layer of copper or the like is covered with the anti-oxidation film on all four sides of the metal wiring, the reliability of the metal wiring with time is improved. Further, unlike the dry etching method, since a three-component etchant mixed with a halogen gas is not used, the chemical solution can be easily managed.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a substrate and respective layers formed thereon in a process of forming a metal wiring according to this embodiment.

[Explanation of symbols]

1 Substrate 2 Lower Insulation Layer 3 Silicon Nitride Film 4 Copper Film 5 Silicon Nitride Film 6 SiO ₂ Film 7 SiO ₂ Mask 8 Copper Bromide Distribution Region 9 Silicon Nitride Film x Halogen Ion

Claims (2)

[Claims] 1. A step of forming an antioxidant film on a wiring metal film provided on a surface of a substrate, and a step of forming a mask on the antioxidant film to partially expose the antioxidant film, A step of implanting halogen ions into the metal film through the exposed portion of the antioxidant film to form a metal halide distribution region composed of a metal halide; and a two-component etching agent composed of a solvent and a halogen salt, A step of contacting the exposed portion of the antioxidant film to remove the antioxidant film and the metal halide distribution region; and a step of forming an antioxidant film on at least the side wall of the metal wiring after cleaning and drying the substrate. And a method for forming a metal wiring. 2. The method for forming a metal wiring according to claim 1, wherein an antioxidant film is formed on the surface of the substrate before the formation of the metal film for wiring.