JP2941824B2 - Metal wiring pattern forming method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for forming a metal wiring pattern.

INDUSTRIAL APPLICABILITY The present invention can be generally applied to a device having an aluminum-based metal wiring (hereinafter sometimes simply referred to as "metal wiring" as appropriate), and can be used for forming a metal wiring pattern of a micro device, for example, a wiring of a semiconductor device. Alternatively, the present invention can be used for forming a metal wiring pattern using etching when manufacturing a magnetic thin film or the like of a magnetic head.

[Summary of the Invention]

The present invention provides a metal wiring pattern forming method in which a metal film formed on a substrate having a step is processed into a metal wiring pattern using a photoresist pattern formed by exposing a photoresist. Therefore, the metal film formed on the substrate has a step reflecting the step of the substrate, and a silicon oxide thin film is formed on such a metal film, and this is patterned by a photoresist. By patterning the metal film using the obtained silicon oxide thin film pattern as a mask,
Even when the shape of the resist pattern is deteriorated by the light reflected by the metal film, the effect is not affected on the formation of the metal wiring pattern, thereby enabling the formation of the metal wiring pattern with high precision.

[Conventional technology and its problems]

Conventionally, for example, to form a metal wiring pattern on an electronic component such as a semiconductor device, a resist pattern having a shape corresponding to the pattern is formed on a metal wiring to be a desired wiring pattern, and the resist pattern is masked. Wiring turns are obtained by the etching described above. However, in the case where the metal wiring is highly reflective such as aluminum, a resist is formed on the metal wiring, and when a resist is exposed, only a predetermined resist region is exposed using a predetermined mask. However, the light transmitted through the resist is reflected and scattered on the metal wiring, and as a result, a region other than the portion to be exposed is also exposed, whereby the resist pattern may not have a predetermined shape.

When resist patterning is performed on a light-reflective material as described above, there is a problem that halation deteriorates the resist shape.

When aluminum is etched in a state where the resist shape is deteriorated due to halation, for example, aluminum is etched by RIE, the etching rate ratio between the resist and aluminum is relatively small (selectivity ratio is 2-3).
Degree), the thin portion of the resist is etched down to aluminum, and a good-shaped aluminum wiring cannot be obtained.

In order to solve the above problems, conventionally, various techniques for reducing the reflectance are employed.

First, as a conventional technique, there is a means for adding a dye for absorbing an exposure wavelength to a resist. This is a technique in which exposure light is absorbed by a resist itself and reflection from a highly reflective material is suppressed. However, in this method, when the absorption is increased, the resist shape is significantly deteriorated, the resolution is reduced, and the sensitivity is also deteriorated. Conversely, if the absorption is reduced, a sufficient antireflection effect cannot be obtained.

Second, there is a means for coating an organic antireflection film on a highly reflective material. In this method, a highly reflective material is coated with an organic antireflection film, for example, an organic antireflection film commercially available as ARC or SWK (both are registered trade names) to prevent reflection. However, if this means is used, for example, on a substrate having a large step, and the antireflection film is to be formed on a highly reflective material having a step,
Since it is difficult to coat the anti-reflection film with a constant film thickness, the projections are particularly thin, and a sufficient anti-reflection effect cannot be obtained.

In addition, the material is expensive, the solvent is special, and a dedicated coating device is required. Furthermore, there is a problem that temperature characteristics are severe, controllability is difficult, and handling is difficult.

Third, there is a means for depositing an inorganic antireflection film on a highly reflective material. As an inorganic antireflection film, for example,
Sputter Si, a (amorphous) -Si, a metal thin film such as Ti-N or the like can be used. (For example, see JP-A-61-171131 for a conventional technique using a-Si). According to this means, it is possible to deposit the inorganic antireflection film with a substantially constant thickness at the step portion, and the antireflection effect is high. However, depending on the material, it becomes an ultra-thin film,
It is difficult to control the film thickness. In the case of Si-based thin films,
When formed on aluminum, there is a problem that it reacts with aluminum to increase the Si concentration in aluminum. There is also a problem that the process becomes complicated.

As described above, in the conventional techniques, both the technique of including a dye in a resist and the technique of reducing the reflectance of a highly reflective material by using an antireflection film have problems. And cannot always achieve high-precision wiring patterning.

An object of the present invention is to provide a method for forming a metal wiring pattern capable of forming a wiring pattern with high precision without using the means for reducing the reflectance by solving the above-mentioned problems of the prior art. .

[Means for solving the problem]

In order to solve the above problems, a method for forming a metal wiring pattern according to the present invention includes the steps of: forming a metal wiring pattern by using a photoresist pattern formed by exposing a photoresist to an aluminum-based metal film formed on a substrate having a step; In the method for forming a metal wiring pattern, the metal film formed on the substrate has a step height reflecting the step of the substrate, and at the time of the exposure, from the metal film having the step In order to prevent the shape of the photoresist pattern from being deteriorated by the reflected light, a silicon oxide thin film and a photoresist film are formed on the metal film, and the thickness of the metal film is set to a, Assuming that the thickness is b, the thickness ratio is a = (5-10) × b, and the silicon oxide thin film is formed by a deposition method. A resist pattern is formed, by etching the oxide film of the silicon photoresist pattern as a mask, then the configuration by etching the metal film an oxide thin film pattern of the silicon as a mask to form a metal wiring pattern.

The configuration of the present invention will be described below with reference to FIG. 1 showing an embodiment of the present invention, which will be described in detail later.

In the present invention, as shown in FIG.
The aluminum-based metal film 1 formed on a substrate 10 having a step like the above and having a step reflecting the step of the substrate 10 is formed by exposing the metal film 1 to a photoresist. In the case of processing into a metal wiring pattern using a pattern, the following configuration is employed in order to prevent the shape of the photoresist pattern from being deteriorated by light reflected from the metal film 1 having such a step at the time of exposure. That is, a silicon oxide thin film 2 is formed on the metal film 1 as shown in FIG. 2B, and a photoresist film 3 is formed as shown in FIG. After exposure and development, a photoresist pattern 31 is formed (see FIG. 3E). In this case, the thickness of the aluminum-based metal film 1 is a, and the thickness of the silicon oxide thin film 2 is b.
Then, it is assumed that the film thickness ratio satisfies a = (5-10) × b, and the silicon oxide thin film 2 is formed by a deposition method. Further, the silicon oxide thin film 2 is etched using the photoresist pattern 31 as a mask, and FIG.
Then, using the silicon oxide thin film pattern 21 as a mask, the metal film 1 is etched to obtain a metal wiring pattern 11 as shown in FIG.

[Action]

As described above, in the present invention, a silicon oxide thin film formed on an aluminum-based metal film is patterned by a photoresist, and the aluminum-based metal film is patterned using the obtained oxide thin-film pattern as a mask. Unlike patterning using a mask as a mask, even if the shape of the resist deteriorates due to the reaction from the aluminum-based metal film, the metal wiring pattern can be formed without being affected by the resist shape, and therefore, the precision is good. An aluminum-based metal wiring pattern can be formed. Further, in the present invention, since the oxide thin film is formed by using a deposition method such as a CVD method, a good film quality can be easily obtained by a conventional apparatus.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to FIG. However, needless to say, the present invention is not limited by the following examples.

In this embodiment, the present invention is applied to a photolithography step of a semiconductor device manufacturing process, and more specifically, is applied to a case where an aluminum wiring pattern is obtained in a predetermined shape on a substrate with high accuracy. .

In this embodiment, first, as shown in FIG. 1A, a metal film 1 is formed from aluminum as an aluminum-based metal film on a substrate 10 as a base. For this formation, means such as deposition such as sputtering or CVD can be used as appropriate. Note that the substrate 10 of the present embodiment is a semiconductor substrate such as a Si substrate, for example, and is a substrate having a step as shown particularly in the present embodiment. The substrate having such a step has a poor film thickness controllability even when an anti-reflection film is formed on the metal wiring formed thereon, and a sufficient effect cannot be obtained. The aluminum wiring may be pure Al or an Al-Si alloy containing silicon (for example, containing Si-1%).

Next, as shown in FIG. 1B, an SiO ₂ film is formed on the metal wiring 1 as the silicon oxide thin film 2. In this embodiment, the thin film 2 can be formed by a plasma CVD method.

Here, assuming that the thickness of the metal wiring 1 is a and the thickness of the thin film 2 is b, the thickness ratio is a = (5-10) × b. This is because when RIE is performed on aluminum, the selectivity between SiO ₂ and Al is S
Since iO ₂ / Al = about 5 to 10, the thickness b of the thin film 2 made of SiO ₂ is appropriately set to a value obtained by dividing the thickness a of the metal wiring made of aluminum by this selectivity. . Therefore, for example, when the film thickness a of the metal wiring 1 is 1.
When the thickness is 0 μm, the thickness b of SiO _{2 as} the thin film 2 is set to 1.0 μm / (5 to 10) = 2000 to 1000 °.

Next, a photoresist film 3 is formed, as shown in FIG.

Next, resist patterning is performed. That is, as shown in FIG. 1D, the resist 3 is exposed using a mask 4 having a predetermined mask pattern. At this time, since the metal wiring 1 serving as the base of the thin film 3 is made of highly reflective aluminum, the exposure light is partially scattered as indicated by arrows in the drawing, and is abbreviated as shown in FIG. 1 (d). , Resist 3
May be overexposed due to halation.

When the exposed resist 3 is developed,
As shown in FIG. 1 (e), for example, the resist pattern 31 has a poor shape such that the upper part of the trapezoid is chipped.

Next, the SiO ₂ , which is the thin film 2, is RIE by using the resist pattern 31 whose shape has been deteriorated due to the halation from the aluminum that is the metal wiring 1 as a mask. Thus, a structure having the thin film pattern 21 is obtained as shown in FIG. Since the etching selectivity between the resist and the SiO ₂ is usually 5 to 10, the thickness of the resist pattern 31 is sufficient if the thickness of the resist pattern 31 is 500 ° for 2000 ° of SiO ₂ . In this example, the resist 3 was formed at about 200 to 400 ° and good results were obtained.

Further, the metal wiring 1 made of aluminum is etched by RIE using the thin film pattern 21 of SiO ₂ having a thickness of 1000 to 2000 ° as a mask. Thus, the structure shown in FIG. 1 (g) is obtained. At this time, although the drawing shows a state in which the resist pattern 31 remains, this may be eliminated. In any case, the metal wiring 1 is etched with good shape by the thin film pattern 21, and the metal wiring pattern 11 with good precision and good shape is obtained.

After removing the remaining resist pattern 31, FIG. 1 (h)
To get the structure.

In the prior art, aluminum was directly etched with a poorly-shaped resist pattern 31, so aluminum as a metal wiring reflects the shape of the resist pattern,
It has become a poorly shaped wiring pattern,
As in the present invention, when the silicon oxide thin film 2 is interposed and the patterning of the metal wiring 1 is performed by the pattern 21 of the thin film, the metal wiring pattern 11 having a good shape can be obtained regardless of the shape of the resist pattern 31. can get.

As described above, when the present invention is applied, even if the shape of the resist pattern 31 is deteriorated by halation, the aluminum-based metal film 1 can be etched without deterioration of the shape, and a good aluminum-based metal wiring pattern 11 can be obtained.

In particular, in this embodiment, if a resist of about 500 ° remains, the Si forming the thin film 2 using the resist pattern 31 as a mask.
Since aluminum can be etched by etching O ₂ and using the obtained thin film pattern 21 of SiO ₂ as a mask, the influence of halation of aluminum can be eliminated.

In the conventional etching of aluminum using only a resist as a mask, when the resist shape is deteriorated by halation, the selectivity of resist / Al is 2-3 and 1.0 μm.
If the resist thickness does not remain in the range of about 4,000 to 5,000 mm with respect to aluminum, a favorable aluminum wiring pattern cannot be formed at the time of etching, and the effect of this embodiment on this is clear.

As described above, according to the present invention, despite the fact that the metal film 1 is an aluminum-based metal film which is a highly reflective material, the influence of halation is removed in the resist patterning on the metal film 1, and the aluminum-based metal film is formed in a favorable shape. A metal wiring pattern can be formed.

〔The invention's effect〕

As described above, according to the present invention, even when the metal wiring is made of a highly reflective material, there is an effect that a metal wiring pattern with good shape accuracy can be obtained by an easy process.

[Brief description of the drawings]

1A to 1H are sectional views showing an embodiment of the present invention in the order of steps. DESCRIPTION OF SYMBOLS 1 ... Metal film, 2 ... Silicon oxide or nitride thin film, 3 ... Photoresist, 11 ... Metal wiring pattern,
21 ... silicon oxide or nitride pattern, 31 ...
Photoresist pattern.

Claims (1)

(57) [Claims] 1. A method of forming a metal wiring pattern, comprising processing an aluminum-based metal film formed on a substrate having a step into a metal wiring pattern using a photoresist pattern formed by exposing a photoresist, The metal film formed on the substrate has a step reflecting the step of the substrate, and at the time of the exposure, the shape of the photoresist pattern is deteriorated by light reflected from the metal film having the step. In order to prevent this, a silicon oxide thin film and a photoresist film are formed on the metal film, and when the thickness of the metal film is a and the thickness of the oxide thin film is b, a = (5 to 10 X), and the silicon oxide thin film is formed by a deposition method. After exposure, a photoresist pattern is formed. The oxide thin film of the silicon is etched as a mask, and then a metal wiring pattern forming method of forming an etching to the metal interconnection pattern the metal film an oxide thin film pattern as a mask of the silicon.