JPH08274079A - Plasma ashing of resist film - Google Patents

Abstract

PURPOSE: To provide an ashing process wherein plasma less damages a resist, in carrying out a thin film dry etching process and a subsequent plasma ashing process using the same cathode-coupled dry etching system. CONSTITUTION: A metal thin film 12 deposited on an insulation substrate 11 is patterned in a predetermined pattern using a resist pattern 13 formed on the metal thin film 12 in a dry etching system. Then, plasma ashing is performed on the resist in the dry etching system for resist stripping. The dry etching system is a system having a parallel plate electrode structure. The insulation substrate 11 is set on the cathode side of a plasma discharge electrode, and the RF power density for plasma ashing is set to 0.087-0.174W/cm<2> . Thus, damage to the resist in plasma ashing is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a plasma for removing a resist film used for patterning after patterning a thin film deposited on a substrate by dry etching when manufacturing a semiconductor device such as a thin film transistor. Regarding the ashing method.

[0002]

2. Description of the Related Art When a thin film deposited on a substrate is patterned using the resist formed by photolithography as a mask (resist pattern) to obtain a desired pattern, the resist is etched and then the resist is removed. A wet type resist stripping method is mainly used in which the resist is stripped of unnecessary resist by treating it with a soluble stripping solution.

In the above-mentioned wet type resist stripping method, there is no problem if a wet etching technique using a liquid chemical is used in patterning a thin film, but in the case where the thin film patterning is a dry etching technique using gas plasma. In some cases, the resist could not be stripped sufficiently when the resist was subsequently removed by a wet type stripping solution. This is because the resist pattern is exposed to plasma during dry etching, so that the resist surface is denatured and the resist does not peel off from the thin film surface even when treated with a stripping solution.

In order to solve the above-mentioned problems, plasma ashing utilizing oxygen plasma is used to separate a bond between constituent atoms or molecules of the resist by a large number of particles (electrons, ions, etc.) which are turned into plasma. A method for removing the deteriorated layer has been proposed (see Japanese Patent Laid-Open No. 62-271435). On the other hand, since this ashing process can be performed with the same device configuration as the dry etching process for patterning a thin film, the dry etching process and the ashing process for the thin film are continuously performed by the same dry etching device from the viewpoint of shortening the manufacturing process. It is desirable to have a method of implementation.

[0005]

In the method as described above, when the thin film deposited on the substrate is etched, the installation position of the substrate is determined by the type of the dry etching device. In the case of a cathode-coupled dry etching apparatus in which the substrate to be etched is installed on the cathode side of the plasma discharge electrode, the substrate to be etched is installed on the cathode side of the plasma discharge electrode even during the ashing step.

However, when this cathode-coupled dry etching apparatus is used, accelerated ions collide with the resist film on the substrate to be etched during discharge, so that physical damage to the resist film is large. . In such a case, there is a possibility that the resist cannot be completely peeled off even if the plasma ashing process is performed thereafter. When such a resist peeling defect occurs in a contact portion of a wiring, for example, it causes a contact defect between wirings, which causes a problem of reducing the manufacturing yield of semiconductor devices. The dry etching apparatus and the ashing step for a thin film were not continuously performed by using the dry etching apparatus described in the above (only the ashing step was performed by the anode couple type dry etching apparatus).

The present invention has been made in view of the above circumstances, and in the case where the dry etching process for a thin film and the subsequent plasma ashing process are performed in the same cathode couple type dry etching apparatus, the resist is less damaged by plasma. It is intended to provide an ashing process.

[0008]

In order to achieve the above-mentioned object, the present invention, after patterning a thin film deposited on a substrate into a desired pattern with a resist formed on the thin film by a dry etching apparatus, In the method of plasma ashing the resist in the dry etching apparatus for resist stripping, an apparatus having a parallel plate electrode structure is used as the dry etching apparatus, the substrate is installed on the cathode side of the plasma discharge electrode, and plasma ashing is performed. RF power density of 0.087-0.174W / cm
It is characterized by setting ² .

[0009]

According to the present invention, the damage of the resist is reduced by setting the RF power density of the plasma ashing to 0.087 to 0.174 W / cm ^2, and the substrate to be etched is placed on the cathode side of the plasma discharge electrode. In the etching apparatus, even when the plasma ashing process of the resist is continuously performed with the dry etching process of the thin film, the ashing process in which the resist peeling defect is unlikely to occur can be performed.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the method of the present invention will be described with reference to the drawings. FIG. 1 illustrates a case of forming a gate electrode of a thin film transistor. First, a metal thin film 12 (Ta film in this embodiment) for forming a gate electrode is formed on an insulating substrate 11 such as glass by sputtering or the like. To form a desired resist pattern 1 by photolithography.
3 is formed (FIG. 1A).

The insulating substrate 11 on which the resist pattern 13 is formed is arranged on the cathode electrode side of a dry etching apparatus having a parallel plate electrode structure, and a fluorine-based gas (for example, SF gas) is used.
Dry etching using ₆ gases (Fig. 1
(B)). At this time, oxygen gas is mixed with SF ₆ which is an etching gas. The etching rates of the resist pattern 13 and the metal thin film (Ta) 12 during the dry etching change depending on the mixing ratio of SF6 and oxygen gas. When the oxygen gas is increased, the etching rate of the resist pattern 13 increases. With the increase of the etching rate of the resist pattern 13, the resist pattern 13a which is initially formed by photolithography is reduced in size during the dry etching, and the pattern section of the metal thin film pattern 12 'after etching is reduced. A slope is formed at the angle. At the same time, the quality of the resist changes (resist quality change portion 13b) due to plasma damage during dry etching (FIG. 1C).

Next, in the same dry etching apparatus, in order to remove the resist pattern 13, plasma ashing is performed using oxygen gas (gas is switched). At this time, by performing the ashing under the condition that the plasma damage to the resist pattern 13 does not occur, the resist-altered portion 13c is generated only in the surface layer of the resist pattern 13 (FIG. 1).
(D)). For example, the ashing conditions for suppressing plasma damage are: oxygen flow rate: 100 SCCM, pressure: 11 P
a, RF power density: 0.087 to 0.174 W / cm ² ,
Ashing time: 2 min.

Subsequently, the resist pattern 13 is removed by an organic resist stripping solution (FIG. 1 (e)). In this process, since the resist pattern 13a which is not deteriorated is soluble in the resist stripping solution, the resist deteriorated portions 13b and 13c are also lifted off and the metal thin film pattern 12 '(gate electrode) having no resist residue is removed. It can be obtained (FIG. 1 (f)).

The inventors of the present invention have examined conditions under which the resist pattern 13 is not damaged in the plasma ashing method of the above embodiment.
As shown in the graph, the damage of the resist pattern 13 depends on the etching rate of the resist. If the RF power density is 0.217 W / cm ² or more, the damage of the resist film is large, and the RF power density is 0.087 to 0.174
It was confirmed that W / cm ² was preferable. The lower limit of the RF power density is set to 0.087 W / cm ² in order to secure the energy required to exert the ashing effect.

That is, when the RF power density during plasma ashing is 0.217 W / cm ² or more, FIG.
As shown in (d), the entire resist pattern 13 is damaged and becomes a resist-altered portion 13c, and even if it is subsequently treated with an organic resist stripping solution (FIG. 3 (e)), A part of the altered resist altered portion 13c cannot be removed, resulting in resist peeling failure (FIG. 3 (f)). FIG. 3 shows a comparative example in which the dry etching step and the ashing step are performed in the same etching apparatus as in FIG. 2, and the etching apparatus is a cathode coupling type apparatus. ) To (f) correspond to the processes of (a) to (f) in FIG. 3A to 3C are shown in FIG.
It is exactly the same as (a) to (c), and in the drawing, the same members as those in FIG. 2 are denoted by the same reference numerals.

In the above embodiment, oxygen gas was used for plasma ashing, but CF ₄ , SF ₆ was used as oxygen gas.
The same effect can be obtained when a proper amount of such gas is mixed. Further, although the metal thin film is used as the thin film to be etched in this embodiment, it can be applied to a thin film made of a semiconductor or an insulator.

[0017]

According to the method of the present invention, by using an ashing process in which resist peeling failure does not occur after dry etching of a thin film, a resist plasma is formed in an etching apparatus in which a substrate to be etched is installed on the cathode side of a plasma discharge electrode. By making it possible to perform the ashing process continuously with the dry etching process of the thin film, the manufacturing process can be shortened, and the yield in the manufacturing method of a semiconductor device or the like using the thin film can be improved.

[Brief description of drawings]

1A to 1F are process cross-sectional explanatory views of a method for ashing a resist film according to the method of the present invention.

FIG. 2 is a graph showing the RF power density dependency of a resist etching rate.

3A to 3F are process cross-sectional explanatory views showing a comparative example of the ashing method of the resist film.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 ... Insulating substrate, 12 ... Metal thin film, 12 '... Metal thin film pattern (gate electrode), 13, 13a ... Resist pattern, 13b ... Resist altered portion (those caused by dry etching), 13c ... Resist altered portion (plasma) (Caused by ashing)

Claims (1)

[Claims] 1. A thin film deposited on a substrate is patterned with a resist formed on the thin film into a desired pattern by a dry etching apparatus, and then the resist is removed in the dry etching apparatus to remove the resist. In the plasma ashing method, an apparatus having a parallel plate electrode structure is used as the dry etching apparatus, the substrate is placed on the cathode side of the plasma discharge electrode, and the RF power density of the plasma ashing is 0.087 to 0.
A method of plasma ashing a resist film, characterized in that the resist film is 174 W / cm ² .