JPH09162161A - Formation of metal pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the accuracy of a pattern by depositing oxide on the surface of a metal film and improving the touch with etching liquid. SOLUTION: A metal film 2a is formed on a TFT glass substrate 1 and coated with photoresist to form a photoresist wiring pattern 3a. The substrate where the metal film 2a is composed of chromium or a chromium alloy is then exposed to O2 plasma ashing atmosphere thus forming a modified hydrophilic layer. Subsequently, chromium is etched with etching liquid at the part not covered with the resist pattern 3a, 3b thus producing a metal pattern in which insufficient etching is eliminated perfectly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a metal pattern, and more particularly to a method for manufacturing a metal pattern such as a metal wiring and a metal light shielding film of a thin film transistor liquid crystal display device.

[0002]

2. Description of the Related Art A conventional method of forming a metal wiring by a wet process will be described by taking a thin film transistor (hereinafter referred to as "TFT") substrate used in a liquid crystal display device as an example. In the TFT, a metal pattern is used for electric wiring, a light-shielding film, etc., and a schematic view of a method for forming the metal pattern is shown in FIG. FIG. 3 is a sectional view showing a conventional etching method.
(A) is up to metal film sputtering, (b) is up to PR patterning, (c) is a wet etching step, and (d) is at the time of completion of metal pattern formation.

First, as shown in FIG. 3 (a), a desired metal material is sputtered or vapor-deposited on a glass substrate 1 to form a few tens.
A metal film 2a having a thickness of about 0 nm is formed. Next, FIG.
As shown in, apply a photoresist on this metal film,
A pattern mask prepared in advance is exposed and transferred, and then developed with an alkaline aqueous solution to form a desired photoresist wiring pattern 3a.

Next, as shown in FIG. 3 (c), the etching solution 4 is brought into contact with the substrate by a method such as a shower, and a portion where the metal film is not required, that is, a portion which is not covered with the photoresist wiring pattern 3a. To remove. However,
At this time, the air bubbles 5 are generated due to the hydrophobic property of the photoresist and the metal film to be etched, and the metal film thereunder is not sufficiently contacted with the etching solution, so that FIG.
The metal pattern residual defect 2c as shown in FIG.

In the TFT manufacturing process, wet etching has a higher throughput than dry etching, a lower manufacturing cost, a high etching selection ratio with various films constituting the TFT other than the film to be etched, and a small damage to the substrate. There are merits such as. Especially,
Wet etching is a fundamental technology for a TFT manufacturing process that does not require pattern accuracy as compared with a semiconductor manufacturing process.

In order to solve this pattern remaining defect, methods such as liquid circulation, shower, and substrate swinging are taken, but this is not a method for fundamentally solving the poor liquid contact, and therefore a large margin is required. Therefore, it is difficult to avoid problems such as reduction in throughput, non-uniformity of pattern line width in a large-area substrate, and elimination of defects.

Further, in order to solve this problem, a method is known in which a resist pattern is treated with a surface modifying solution such as cerium ammonium nitrate to improve its hydrophilicity (Japanese Patent Laid-Open No. 2-73633). . However, with this method, the metal portion is not modified, and a sufficient improvement in etching property is not observed. As a method for improving the hydrophilicity of a metal film, a method of forming a copper oxide film on the surface by heating copper is known (JP-A-3-2600).
No. 74). However, the purpose of this method is to improve the adhesion between the resist and copper, and if the surface layer of the resist is modified, the throughput, the heat resistance of the resist,
There is a problem in terms of the uniformity of the modification effect on the substrate.

[0008]

The problem of the above-mentioned prior art is that when the metal pattern becomes as fine as several microns, even if only the metal surface to be etched or only the resist surface is made hydrophilic, the etching solution and the metal film are A pattern defect may occur due to the contact failure. The reason is that even if only the metal is hydrophilized, if the hydrophobic resist is present in the vicinity, the etching solution is repelled, and the hydrophilic metal film cannot be partially contacted with the etching solution, resulting in pattern abnormality.

Further, even if only the resist is made hydrophilic, if it is a hydrophobic metal, the etching solution is repelled and a pattern defect occurs. The present invention improves the contact with the etching liquid over the entire surface of the sample by modifying both the metal film to be etched and the surface of the resist pattern from hydrophobic to hydrophilic, and eliminates the occurrence of etching defects. With the goal.

[0010]

According to the present invention, a photoresist is applied to the surface of a metal film, exposed and developed using a pattern mask to form a desired resist pattern, and then the metal film is ashed by O ₂ plasma ashing. An oxide film is formed on the surface where there is no resist pattern, and at the same time, the surface of the resist pattern is made hydrophilic, and then the metal film is etched with an etching solution for the metal film. is there.

In the present invention, the metal film in the method for producing a metal pattern is chromium or an alloy containing chromium as a main component, aluminum or an alloy containing aluminum as a main component, molybdenum or an alloy containing molybdenum as a main component,
It is characterized by being any one of tungsten, an alloy containing tungsten as a main component, tantalum, an alloy containing tantalum as a main component, titanium, and an alloy containing titanium as a main component. Regarding the composition of the alloy, for example, Al-40 wt% Cr, Al-2 wt% Ti, Al
-2wt% Mo, Al-2wt% Ta, Al-2wt%
W, Al-2 wt% Zr, Al-2 wt% V, Al-2
wt% Nd, Al-1 wt% Si-0.5 wt% Cu,
Al-0.05 wt% Ti-0.05 wt% B, Al-
0.05wt% Zr-0.05wt% W, Al-0.0
5wt% Cr-0.05wt% Ti-0.05wt%
B, Mo-2 wt% Ta, Mo-2 wt% W, Mo-2
Examples include wt% Mg, W-2 wt% Ta, W-2 wt% Mo, and Ta-2 wt% W.

[0012]

In the present invention, after forming a resist pattern on the metal film, an oxide film is formed on the surface of the metal film by O ₂ plasma ashing, and at the same time, the surface of the resist pattern is made hydrophilic, and then an etching solution for the metal film is used. The method is characterized in that the metal film is etched, and a metal oxide film is formed on the surface of the portion of the metal film not covered with the resist pattern, that is, the portion removed by etching, by performing the O ₂ plasma ashing treatment. .
The metal film becomes more hydrophilic by being oxidized, and the liquid contact at the time of etching is improved.

Further, the surface of the resist pattern is also oxidized by O ₂ plasma ashing, and the heat at that time causes the surface layer to be smoothly denatured and modified to be hydrophilic. Therefore, even when a fine pattern is formed, the etching liquid is sufficiently spread to the details of the pattern, and no pattern defect occurs. As the metal film, as shown in FIG. 2, chromium, molybdenum, aluminum, tantalum, tungsten, titanium, or an alloy containing them as a main component is effectively hydrophilized by O ₂ plasma ashing.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The steps of the method for producing a metal pattern of the present invention, the metal film and the etching solution will be described with reference to FIGS.

[0015]

Embodiment 1 FIG. 1 shows a first embodiment of the present invention.
Details will be described with reference to (a) to (c). First, similarly to FIG. 3 shown in the above-mentioned conventional technique, as shown in FIG. 1A, a desired metal material is sputtered or vapor-deposited on the TFT glass substrate 1 to form a metal film 2a. Further, FIG.
As shown in (b), a photoresist is applied on this metal film, a pattern mask prepared in advance is exposed and transferred, and then developed with an alkaline aqueous solution to obtain a structure in which a desired photoresist wiring pattern 3a is formed.

In this embodiment, the metal film 2a is chromium or an alloy containing chromium as a main component, and is formed to a thickness of about 200 nm by the sputtering method. The substrate in this state is exposed to the atmosphere of O ₂ plasma ashing. O ₂ plasma ashing acts on a polymer such as a resist to promote vaporization due to oxidation and depolymerization on the resist surface layer due to a chemical reaction between atomic oxygen O generated in O ₂ plasma and a polymer resin. Therefore, an oxide film is grown on the surface of the metal film by the same chemical reaction.

O ₂ plasma ashing treatment is performed for 60 seconds under the conditions of a pressure of 40 pa, an RF output of 800 W, and an O ₂ flow rate of 200 sccm to obtain the structure of FIG. 1 showing the present invention. The metal oxide thin film 2b, in this case, the chromium oxide film is formed very thinly only on the portion of the surface of the chromium film which is not covered with the photoresist pattern 3a. Further, the surface portion of the photoresist pattern 3a is also oxidized by O ₂ plasma ashing, and the surface is smoothly altered by the heat at that time, so that the hydrophilically modified layer 3b is formed. After that, for example, an etching solution containing cerium ammonium nitrate and nitric acid as main components is used to etch the chrome in a portion not covered with the resist patterns 3a and 3b. Finally, the resist is removed to form a chrome wiring having a desired pattern shape. To get

In the method of the above embodiment, the chromium oxide thin film 2b is formed on the surface of the chromium film, and the resist surface layer 3b hydrophilized by O ₂ plasma ashing is formed on the resist surface. The liquid contact between the etching liquid and the chromium film is improved, and highly accurate pattern formation without etching defects can be performed. Further, since the chromium wiring formed by the present invention is masked by the resist pattern during O ₂ ashing, an unnecessary oxide film is not formed more than the naturally formed oxide film.

[0019]

Second Embodiment The second embodiment is the same as the first embodiment except that aluminum or an alloy containing aluminum as the main component is used as the metal to be sputtered first, and phosphoric acid is used as the etching solution. And to use an aqueous solution containing nitric acid as a main component. By forming hydrophilic aluminum oxide on the surface by O ₂ ashing and modifying it, a highly accurate pattern without etching defects can be obtained as in the first embodiment.

[0020]

Third Embodiment Next, a third embodiment will be shown. The third embodiment is the same as the first embodiment except that molybdenum or an alloy containing molybdenum as a main component is used as the metal to be sputtered first, and hydrofluoric acid and nitric acid are mainly used as the etching solution. It is to use an aqueous solution as a component. Also in this case, molybdenum oxide having hydrophilicity is formed on the surface by O ₂ ashing, and a highly accurate pattern without etching defects can be obtained.

[0021]

Fourth Embodiment Next, a fourth embodiment will be shown. This fourth embodiment is the same as the first embodiment, except that tungsten or an alloy containing tungsten as the main component is used as the metal to be initially sputtered, and hydrogen peroxide solution is mainly used as the etching solution. It is to use an aqueous solution as a component.
Also in this case, as in the first embodiment, hydrophilic tungsten oxide is formed on the surface by O ₂ ashing,
A highly accurate pattern without etching defects can be obtained.

[0022]

Fifth Embodiment Next, a fifth embodiment will be shown. This fifth embodiment is the same as the first embodiment, except that tantalum or an alloy containing tantalum as a main component is used as the metal to be sputtered first, and hydrofluoric acid and nitric acid are mainly used as the etching solution. It is to use an aqueous solution as a component. In this case as well, hydrophilic tantalum oxide is formed on the surface by O ₂ ashing, and a highly accurate pattern without etching defects can be obtained.

[0023]

Sixth Embodiment Next, a sixth embodiment will be shown. This sixth embodiment is the same as the first embodiment, except that titanium or an alloy containing titanium as the main component is used as the metal to be sputtered first, and hydrofluoric acid and nitric acid are mainly used as the etching solution. It is to use an aqueous solution as a component. Also in this case, hydrophilic titanium oxide is formed on the surface by O ₂ ashing, and a highly accurate pattern without etching defects can be obtained.

In each of the above embodiments, the above six types of metal materials are shown, but the present invention is not limited to these. Also, the condition for O ₂ ashing is pressure 10
~200pa, RF output 400~2000W, _{O 2} flow rate 100-1000 sccm, process time 30~180se
It does not matter if you change it in the range of c. Further, in view of the purity of various metals, the process conditions before and after ashing, the manufacturing cost, etc., the range may be changed beyond the range shown above.

FIG. 2 shows the experimental result according to the present invention. FIG. 2 is a diagram showing the surface modification effect of O ₂ plasma treatment, in which the horizontal axis represents the O ₂ plasma treatment time (Sec) and the vertical axis represents the contact angle (degree) with water. Pressure 4 on various metal films
The change in the contact angle with water is shown when the treatment is performed under the conditions of 0 pa, RF output of 800 W, and O ₂ flow rate of 200 sccm.

The oxide film is formed so as not to interfere with etching, and the portion remaining as a pattern is covered with the resist pattern during the O ₂ plasma ashing process, so that an unnecessary oxide film is formed. There is no.
Further, the resist surface is also hydrophilized by the two effects of oxidizing the surface by the O ₂ plasma ashing treatment and smoothing the surface by the heat during the treatment, and exposing the substrate in contact with the etching solution. Since the entire surface is made hydrophilic, no defective etching occurs.

[0027]

As described above, according to the present invention,
The wettability between the metal film to be etched and the etching solution is improved, and the effect of being able to completely eliminate the occurrence of etching defects is obtained because the surface of the metal film is oxidized by the O ₂ plasma ashing treatment. A film is formed,
This is because the resist pattern was modified, the entire surface became hydrophilic, and the liquid contact property was improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an etching method according to an embodiment of the present invention.

FIG. 2 is a diagram showing a surface modification effect of O ₂ plasma ashing treatment according to an embodiment of the present invention.

FIG. 3 is a sectional view showing a conventional etching method.

[Explanation of symbols]

1 TFT glass substrate 2a Metal film 2b Metal oxide thin film 2c Metal pattern residual defect 3a Photoresist wiring pattern 3b O ₂ Resist surface layer hydrophilized by plasma ashing 4 Etching solution 5 Bubbles

Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location H01L 29/786 H01L 29/78 627C 21/336

Claims (2)

[Claims] 1. A photoresist is applied to the surface of a metal film,
After exposing and developing using a pattern mask to form a desired resist pattern, an oxide film is formed on a portion of the surface of the metal film where there is no resist pattern by O ₂ plasma ashing, and at the same time, the surface of the resist pattern is made hydrophilic. And then etching the metal film with an etching solution for the metal film. 2. The metal film according to claim 1, wherein chromium or an alloy containing chromium as a main component, aluminum or an alloy containing aluminum as a main component, molybdenum or an alloy containing molybdenum as a main component, or tungsten or a main component containing tungsten. 2. A method for producing a metal pattern, comprising: an alloy containing tantalum, tantalum, an alloy containing tantalum as a main component, titanium, or an alloy containing titanium as a main component.