JP2616460B2 - Semiconductor device and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device having a wiring of aluminum or the like and a method of manufacturing the same, and more particularly to a wiring suitable for miniaturization and a method of forming the wiring.

[0002]

2. Description of the Related Art When forming a wiring by patterning a metal thin film such as aluminum by dry etching such as RIE (Reactive Ion Etching), an impurity ion is implanted into a metal thin film to be processed in advance. Is known to rise. This is because the bonding energy between metals is reduced by ion implantation, and the metal thin film is easily etched.

Several techniques have been proposed for forming wirings utilizing this feature of metal films. 3 (a) to 3 (c)
3A to 3C are cross-sectional views in the order of steps showing a method for forming a wiring proposed in Japanese Patent Application Laid-Open No. Sho 59-100357. First, FIG.
1A, an aluminum film 33 is provided on a silicon substrate 31 via a silicon oxide film 32, and a photoresist film 36 for forming wiring is formed thereon. next,
For example, ions of boron 35 are implanted to damage the aluminum film 33 in a portion not covered by the photoresist film.

[0004] Next, as shown in FIG. 3 (b), the aluminum film 33 is exposed to a plasma 39 atmosphere and the aluminum film 33 is selectively etched to form an aluminum wiring 37. Thereafter, when the photoresist film 36 is removed, a semiconductor device having the target aluminum wiring 37 is obtained as shown in FIG.

FIGS. 4A to 4D show Japanese Patent Application Laid-Open No. 63-18 / 1988.
4A to 4C are cross-sectional views in a process order showing a method of forming a wiring proposed in Japanese Patent No. 1447; In this conventional example, as shown in FIG. 4A, after an aluminum film 43 is formed on a silicon substrate 41 via a silicon oxide film 42, for example, boron 45 is ion-implanted over the entire surface. Next, as shown in FIG. 4B, a photoresist film 46 for forming a wiring is formed, and as shown in FIG. 4C, an aluminum wiring 47 is formed by exposing to a plasma 49. After that, the photoresist film 4
By peeling off 6, a semiconductor device having aluminum wiring 47 is obtained.

In recent years, the miniaturization of wiring has been rapidly advanced, and the era of half micron (0.5 μm) to quarter micron (0.25 μm) is approaching. In the patterning of such a miniaturized structure, the microloading effect due to the density of the pattern becomes remarkable, and processing with high in-plane uniformity becomes difficult. This microloading effect is caused by the fact that ions and radicals for dry etching hardly reach the bottom in a narrow opening compared to a wide opening.

In the conventional method shown in FIG. 3 and FIG. 4, although the etching selectivity of aluminum to a resist or an oxide film is increased by ion implantation of aluminum, there is no effect of suppressing the microloading effect. Therefore, when the pattern is miniaturized and coarse and dense patterns are mixed in the plane, an etching failure occurs. That is, as shown in FIG.
If the etching is continued until the base is completely exposed in the narrow groove B, the pattern becomes thin in the wide groove B, and conversely, when the etching is completed when the patterning in the wide groove A is completed, the pattern becomes narrow. An etching residue occurs in the groove B (FIG. 5B).

Incidentally, since the selectivity of the photoresist to aluminum for etching is not high, a photoresist having a thickness twice or more the thickness of the aluminum film is usually formed and etched. Therefore, when the wiring pattern is miniaturized and its aspect ratio is deteriorated, the aspect ratio of the photoresist is further deteriorated. Since the increase in the aspect ratio of the photoresist is a major cause of the microloading effect, it is necessary to improve the mask aspect ratio by using an etching resistant mask (hard mask) other than the photoresist as the etching mask. Proposed.

FIGS. 6 (a) to 6 (d) are cross-sectional views in the order of steps showing a method of manufacturing the same, which is disclosed by Aoki et al. In Japanese Journal of Abride Physics (Jpn.J. Volume 30 L4376
Page. In this method, first, as shown in FIG.
An aluminum film 53 is formed thereon via a silicon oxide film 52, and a silicon oxide film 52a serving as a mask material is formed thereon.
Is deposited. Then, a photoresist film 56 having a wiring pattern is provided thereon.

Next, as shown in FIG. 6B, using the photoresist film 56 as a mask, the silicon oxide film 52a is patterned by a dry method using a plasma 59 to form an oxide film mask 52b [FIG. Reference].
Next, as shown in FIG. 6C, the aluminum film 53 is patterned by a dry method using the plasma 59 using the formed oxide film mask 52b as a mask.
An aluminum wiring 57 is formed as shown in FIG. According to this method, it is possible to increase the number of ions or the like incident on the etched surface from an oblique direction, so that the microloading effect can be suppressed.

[0011]

However, in the conventional technique using the above-described hard mask, the following problems occur when the miniaturization is further advanced. First, even if the aspect ratio of the mask is improved, the aspect ratio of the wiring remains the same. Therefore, when the aspect ratio of the wiring is further increased, the microloading effect becomes significant again. Second, with the miniaturization of the device size, it is necessary to improve the resistance of the aluminum wiring to electromigration and stress migration. Therefore, a laminated wiring structure in which titanium, titanium nitride, tungsten, or the like is laminated on aluminum is used. However, when this laminated wiring is adopted, it is difficult to increase the etching selectivity between each layer of the wiring and the hard mask (SiO ₂ ), and it is difficult to cope with the hard mask. Becomes The present invention has been made in view of this point, and an object of the present invention is to provide a wiring structure capable of suppressing a microloading effect without relying on a hard mask, and a method of forming the same.

[0012]

According to the present invention, in order to attain the above object, according to the present invention, a metal film constituting a wiring contains an impurity in a region where a wiring pattern is dense and an impurity in a region where a wiring pattern is coarse. And a semiconductor device characterized by containing no.

Further, according to the present invention, (1) a step of forming a metal film on the entire surface of an interlayer insulating film on a semiconductor substrate;
(2) a step of forming a photoresist mask having an opening in a region where the wiring pattern is dense; and (3) an impurity is implanted by ion implantation to selectively introduce the impurity into the metal film below the opening. (4) stripping the photoresist film for ion implantation and forming a new photoresist mask for wiring formation; and (5) forming the metal film via the photoresist mask for wiring formation. Forming a wiring by processing the substrate by a dry etching method.

[0014]

According to the present invention, since the ion implantation is performed in advance in the region where the wiring pattern of the metal film is dense, the binding energy of the metal in that region is reduced.
As a result, the etching rate increases, so that the microloading effect caused by the coarse and dense pattern can be suppressed, and uniform etching can be performed.

Also, when a film of titanium or the like is formed on the aluminum film as a measure against migration, the crystal structure of the film is disturbed and the etching rate is increased. Similarly, the microloading effect can be suppressed.

[0016]

Next, embodiments of the present invention will be described with reference to the drawings. [First Embodiment] FIGS. 1A to 1C show a first embodiment of the present invention.
FIG. 5 is a cross-sectional view of a semiconductor chip shown in the order of steps for describing the example. First, as shown in FIG. 1A, a silicon oxide film 12 having a thickness of about 500 nm is formed on a silicon substrate 11 by a thermal oxidation method or a vapor phase growth method, and is formed thereon by an ion deposition method or a sputtering method. About 1μ thick
An aluminum film 13 having a thickness of m is formed. Next, a photoresist is applied on the aluminum film 13 to a thickness of about 1 μm, and exposure and development are performed to form a photoresist film 14 having an opening in a region where a wiring pattern is dense.

Next, as shown in FIG. 1 (b), phosphorus 1 is ion-implanted using the photoresist film 14 as a mask.
5 at an acceleration energy of 45 keV and a dose of 1 × 1
Inject at 0 ¹⁶ / cm ² . Note that the dose amount and energy of the implanted ions may be set to optimal values according to the degree of the density difference of the wiring and the thickness of the aluminum film. Further, the ion implantation may be divided into a plurality of times, and the ions may be implanted with different energies so that the entire film thickness is uniformly doped with impurities. After the ion implantation, the photoresist film 14 is peeled off.
After coating to a film thickness of μm, exposure and development,
As shown in FIG. 5, a photoresist film 16 for forming a wiring is formed.

Next, as shown in FIG. 1D, using the photoresist film 16 as a mask, for example, microwave power: 300 mA, RF power: 150 by dry etching.
W, pressure: 2 mTorr, chlorine gas flow rate: 30 sccm
To form an aluminum wiring 17. After forming the aluminum wiring 17, the photoresist film 1 is formed.
6 is peeled off, and a heat treatment (so-called hydrogen alloy) is performed in a hydrogen atmosphere at, for example, 450 ° C. for 30 minutes to diffuse impurities in the aluminum film.

As described above, according to the present embodiment, by implanting impurities into a region where the pattern of the aluminum film is dense, the etching rate in that region can be increased, and the microloading effect due to the density of the pattern can be suppressed. can do.

By diffusing the impurities implanted into the aluminum film, an alloy of the diffused impurities and aluminum is formed at the grain boundaries or the impurities are precipitated at the grain boundaries, so that the film surface is hardened. The cured film has increased mechanical strength and increased resistance to composition fluctuations, and thus has improved electromigration and stress migration resistance.

It has been confirmed that by devising the aluminum wiring structure, there is no problem in electromigration / stress migration resistance up to the 0.3 μm level, and there is no problem even if there is a region where impurities are not diffused. (Yoshikawa et al. IEEE Transaction on Electron Device (TRAN
SACTION ON ELECTRON DEVIC
ES) 1993, 40 volumes, No. 2, 296 pages).

[Second Embodiment] Next, a second embodiment of the present invention will be described with reference to FIG. FIG.
(D) is sectional drawing of the semiconductor chip shown in order of the process for demonstrating the 2nd Example of this invention. First, FIG.
As shown in (a), a silicon oxide film 22 having a thickness of about 500 nm is formed on a silicon substrate 21 by a thermal oxidation method or a vapor phase growth method, and a silicon oxide film 22 having a thickness of 0.1 nm is formed thereon by an ion deposition method or a sputtering method. A 9 μm aluminum film 23 is formed, and a 0.1 μm thick aluminum film 23 is further formed thereon by sputtering.
An m-thick titanium nitride (TiN) film 28 is formed. Then
A photoresist is applied on the titanium nitride film 28 to a thickness of 1 μm, and is exposed and developed to form a photoresist film 24 having an opening in a region where the wiring pattern is dense.

Next, as shown in FIG. 2B, arsenic 25 is ion-implanted using the photoresist film 24 as a mask.
For example, at an acceleration energy of 70 keV and a dose of 1 × 10
Inject at ¹⁶ / cm ² . Next, as shown in FIG. 2C, after ion implantation, the photoresist film 24 is peeled off, and a 2.5 μm-thick photoresist film 26 for wiring formation is newly formed on the titanium nitride film. .

Next, as shown in FIG. 2D, for example, microwave power: 300 mA, RF power: 150 by dry etching using the photoresist film 26 as a mask.
W, pressure: 2 mTorr, chlorine gas flow rate: 30 sccm
To form an aluminum wiring 27 having a coating of a titanium nitride film 28. Thereafter, the photoresist film 26 is peeled off, and a hydrogen alloy is applied at, for example, 450 ° C. for 30 minutes to diffuse impurities in the wiring.

As described above, according to the present embodiment, even when a wiring coated with a film for preventing electro / stress migration, which is difficult to cope with in the conventional example shown in FIG. By implanting an impurity into a dense region, the etching rate in that region can be increased, and the microloading effect due to the dense and dense pattern can be suppressed.

[0026]

As described above, in the method of manufacturing a semiconductor device according to the present invention, a dense wiring region of a wiring forming metal film is doped with impurities in advance and then patterned. Therefore, it is possible to increase only the etching rate in a proper wiring region, thereby suppressing a microloading effect and forming a highly accurate and highly reliable wiring.

The effect of accelerating the etching rate by ion implantation can be similarly expected for a high-melting point metal film or a high-melting point metal compound film other than the aluminum film.
Even in the case of forming wiring with a coating for electromigration and stress migration, which was difficult to deal with in the conventional example, impurities are ion-implanted into the area where the wiring pattern is dense, and the etching rate in that area is reduced. By selectively increasing the number, it is possible to easily cope with the problem.

Further, according to the present invention, in a metal film in which an impurity is diffused, an impurity alloy is formed at a grain boundary or an impurity precipitates at the grain boundary and the film surface is hardened. As a result, it is possible to improve the mechanical strength and the resistance to the composition fluctuation, thereby improving the resistance to electromigration and stress migration.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a manufacturing method according to a first embodiment of the present invention in the order of steps.

FIG. 2 is a sectional view showing a manufacturing method according to a second embodiment of the present invention in the order of steps.

FIG. 3 is a cross-sectional view in a process order for explaining a conventional method of manufacturing a semiconductor device in which an etching rate is improved by ion implantation.

FIG. 4 is a cross-sectional view in a process order for explaining a method of manufacturing a conventional semiconductor device in which an etching rate is improved by ion implantation.

FIG. 5 is a cross-sectional view for explaining a microloading effect.

FIG. 6 is a sectional view in order of process for explaining a manufacturing method of a conventional example.

[Explanation of symbols]

11, 21, 31, 41, 51 Silicon substrate 12, 22, 32, 42, 52, 52a Silicon oxide film 52b Oxide film mask 13, 23, 33, 43, 53 Aluminum film 14, 24 Photoresist film 15 Phosphorus 25 Arsenic 35, 45 Boron 16, 26, 36, 46, 56 Photoresist film 17, 27, 37, 47, 57 Aluminum wiring 28 Titanium nitride film 39, 49, 59 Plasma

Claims (4)

(57) [Claims] 1. A semiconductor device having a wiring of a metal film, wherein the metal film contains impurities in a region where a wiring pattern is dense, and does not contain impurities in a region where the wiring pattern is rough. apparatus. 2. The method according to claim 1, wherein said impurity is phosphorus (P) or arsenic (A).
2. The semiconductor device according to claim 1, wherein s) is satisfied. 3. The semiconductor device according to claim 1, wherein the metal film is a metal film mainly composed of aluminum or a film coated with a high melting point metal or a high melting point metal compound. 4. A step of: (1) forming a metal film on an interlayer insulating film on a semiconductor substrate; and (2) forming a photoresist mask having an opening in a region where a wiring pattern is dense on the metal film. (3) implanting impurities by ion implantation to selectively introduce impurities into the metal film below the openings; and (4) stripping the photoresist film for ion implantation and newly Forming a photoresist mask for forming a wiring; and (5) forming a wiring by processing the metal film by a dry etching method through the photoresist mask for forming a wiring. A method for manufacturing a semiconductor device.