JPS5919323A - Method for etching - Google Patents

Abstract

PURPOSE:To enhance dry-etching-resisting property by a method wherein, after a resist pattern has been formed on the material to be etched, the above is post- baked by performing a heat treatment under vacuum, and then an etching is performed on the material to be etched using the resist pattern as a mask. CONSTITUTION:A film 21 to be etched such as Al and the like is provided on a substrate 20, and a resist pattern 22 is provided thereon. A pattern 22 contains abundant residual solvent and moisture 23. Then, the above is post-baked by performing a heat treatment under vacuum, and residual solvent and moisture 23 are removed. Subsequently, a dry-etching is performed on the film 21 to be etched using the resist pattern 22 as a mask.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for post-baking a resist used in the manufacture of semiconductor devices, and particularly to a processing method for improving dry etching resistance.

With the increasing density and miniaturization of semiconductor devices, the conventional wet etching method has been replaced by a dry etching method using plasma. Although the dry etching method has many advantages over the wet etching method, it also has many disadvantages. For example, resists used as masks (mainly organic photoresists) contain accelerated ions.

Since the film is considerably thinned by electrons, thin parts of the film may not function adequately as a mask. Although it is possible to increase the thickness of the resist film in advance, it is difficult to pattern the thick resist with a fine pattern yi with good reproducibility.

The etching resistance of a resist decreases mainly due to film thinning, and film thinning is thought to be mainly caused by temperature rise due to heat during plasma and etching reactions, and physical sputtering by ions and electron particles. .

Therefore, it has been proposed to efficiently cool semiconductor wafers. The method for cooling the wafer is that the area in contact with the wafer holder changes due to warpage of the wafer, etc.1-
It is difficult to obtain reproducibility, and means such as electrostatic chucks and mechanical crimping are required.

Furthermore, electrostatic chucks and mechanical pressure bonding are not preferred methods because they may damage the sea urchin or deteriorate the device characteristics.

The present invention has been made to address the above-described thinning of the resist film during dry etching, and an object of the present invention is to provide a post-bake treatment method after development that improves dry etching resistance.

Post-baking of the photoresist after forming a normal photoresist pattern is carried out at about 15° C. under N2 gas for a few minutes to a few minutes. The purpose of this heat treatment is to react and crosslink the photosensitive groups through a thermal reaction. However, since this treatment is performed under normal pressure, the solvent and water contained in the resist are not sufficiently removed.

The inventor conducted the following experiment to confirm this phenomenon. That is, a (-) resist is applied and post-baked under normal pressure, and then the ueno-- is placed in an etching chamber and evacuated to a vacuum. (b) A wafer without resist coating is placed in an etching chamber and evacuated to vacuum. (C)
Evacuate the area without placing anything on it.

(d) The wafer coated with resist and post-baked under vacuum is placed in an etching chamber and evacuated to vacuum. 0
There are four conditions. 20mT for these four cases
We compared the exhaust time with orr i.

The results are shown in Table 1.

The results shown in Table 1 indicate that outgassing from the resist occurs when only post-baking at normal pressure is performed.

In the actual dry etching process, the wafer is coated with a six-page etchant and exposed to vacuum, so there is outgas such as moisture or solvent before and during etching, and when these outgases evaporate, the resist It is thought that the quality of the resist is degraded by creating spaces within the resist.

These outgases are expected to have a subtle effect on the etching reaction.

Next, the inventor conducted an experiment on the etching resistance of the resist due to the difference in the amount of outgas from the resist. The resist used was post-baked under normal pressure. The object to be etched is aluminum containing 2% Si (hereinafter referred to as A).
fi alloy) using carbon tetrachloride (hereinafter abbreviated as CC14) as an etching gas, Q1W/cd
Etching was carried out in the same manner using the electric power of Note that the resist is positive type and has a thickness of 11 tm. As condition 1, the wafer was left under a high vacuum (5.times.1 O@-5 Torr) for 1 hour and then etched, and as condition 2, etching was started immediately after reaching the high vacuum, and the results shown in Table 2 were obtained.

6 b-f Regarding the wafer etched under condition 1 in Table 2, the resist film was greatly reduced, and the resist was gone at the top of the step and at the edge of the pattern, and a part of the An alloy was etched.

From this experiment, it was found that by leaving the resist under high vacuum for a long time as shown in Condition 1 in Table 2, outgas from the slightly hardened resist after post-baking was generated, resulting in a large number of fine particles inside the resist. It is presumed that a large space is formed, and that the etching resistance of the resist No. 9 is reduced due to this.

Furthermore, in order to improve etching reproducibility and automate etching, there are currently many devices that have load-lock chambers that are in a reduced pressure state before and after the etching chamber (for example, Nikki Anelva ILD-4002 Tokuda 7 Page f' TRI E-303, etc.) However, with these devices, there is a risk that the etching performance of one side of the resist may change between the first batch and the last batch.

The manner in which a VC space in the resist is generated due to outgas from the resist will be schematically illustrated below. FIG. 1 is an explanatory diagram of the case where the resist pattern is left on a post-baked resist pattern under normal pressure, where 1o is the substrate, 11 is the film to be etched, and 1
2 is a resist, 13 is a solvent and moisture in the resist, and 14 is a space created when the solvent and moisture 13 escape.

FIG. 1(a) shows the state of the resist 12 after post-baking under normal pressure, and a large amount of solvent or water 13 remains in the resist. Figure 1 03) shows the state after the resist has been left under vacuum for a while.
The solvent or moisture near the surface expands and evaporates, deforming the resist and forming a space 14, as shown in FIG.
In C), most of the solvent/water 13 in the resist is vaporized and many spaces 14 are created.

It is said that the dry etching resistance of the resist, that is, the amount of resist etched during etching, decreases as the post-baking temperature increases and the post-baking time increases.One of the reasons for this is that This seems to be because residual solvent and moisture in the resist are removed. However, lengthening the post-bake time or raising the temperature is undesirable because it causes deformation of the resist pattern.

In this way, if a large number of spaces 14 as shown in FIG. 1(c) are created, the film loss of the resist 12 during dry etching will be large, and the etched object will have a large amount of space 14 as shown in FIG. 1(d) after etching.
), which creates unevenness and prevents accurate etching. Moreover, when such unevenness occurs, it is difficult to perform uniform etching over the entire semiconductor wafer.

In order to solve the problem of residual solvent and moisture in the resist mentioned above, a method is used to form a hardened layer on the resist surface using CF4 plasma, etc. to prevent the internal solvent and moisture from evaporating. .

The problem with this method is that many irregularities are formed on the altered resist surface, resulting in fine particles of about 1 μ'm! Turns cannot be formed with high precision, and after the altered layer disappears during etching, the resist layer that has not been particularly processed is exposed, making it ineffective.

The present invention is characterized in that after the solvent and water in the resist are removed by post-baking in a vacuum before the resist is hardened, dry etching of the object to be etched is performed on the resist mask. (Resist before heat treatment such as post-bake) U is soft, and even if the solvent and water are removed, the removed areas will be filled with resist from other areas,
There are fewer cracks or spaces, and the etching resistance is improved. Also, because it is exposed to a vacuum,
Even if exposed to vacuum before or during etching, no changes occur.

ti, the present invention improves the etching resistance of the resist pattern by irradiating the resist pattern with energy beams of appropriate intensity such as electron beams, ion beams, or X-rays to promote polymerization before the dry etching process. Furthermore, this method is often carried out in a vacuum, and in this case, it is used in conjunction with the above-mentioned improvement in etching resistance in a vacuum. The reason for the improvement in etching resistance due to energy ray irradiation is as follows. That is, it is known that even a positive type photoresist becomes negative type under appropriate ion beam or electron beam irradiation.

This phenomenon is that the photosensitive group is destroyed by X-rays, electrons or ions and polymerization proceeds. Therefore, by irradiating an already developed resist pattern with X-rays, electrons, or ions to destroy the photosensitive groups and thermally polymerize them, the dry etching resistance of the resist can be improved. It is known that during ion implantation or dry etching, the resist often hardens or changes in quality, improving chemical resistance. That is, the dry etching resistance of the resist can be improved by using electron beams, ion beams, or X-rays with appropriate energy.

Recognizing this fact, the present inventor provides the following dry etching method that improves the etching resistance of the resist.

11 page Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a diagram showing a dry etching process according to an embodiment of the present invention, in which 20 is a substrate, 21 is a film to be etched, such as An, and 22 is an etching mask. For example, in a positive resist pattern, 23 is solvent-based moisture remaining in the resist.

FIG. 2(-) shows a state in which a resist pattern 22 is formed after resist coating. There is a lot of residual solvent/moisture 23 in the resist pattern 22 . 2) shows a state during post-baking in a vacuum according to the method of the present invention. This treatment reduces the amount of residual solvent/moisture 23. The post-bake conditions at this time are a temperature of 100 to 200°C and a degree of vacuum of 1 to 100 mTo.
rr, time is 3-30M. FIG. 2(C) shows a state in which post-baking has been completed. After this, the film to be etched 21'5t is etched by dry etching using the resist pattern 22 as a mask (FIG. 2d).

In this step, moisture, solvent, etc. are removed during the above-mentioned post-bake treatment, and the space 14 as shown in FIG. 1 is not created. Therefore, the etching resistance of the resist is improved, and even if the resist pattern 22 is etched, its film thinning occurs uniformly, and the masking effect is fully exerted.
Accurate dry etching can be performed without creating unevenness as shown in the figure.

In addition, in the present invention, the same effect can be achieved not only by post-bake treatment in vacuum, but also by irradiation with energy rays of about 10 to 300 eV, such as electron beams, ion beams, or X-rays. Both may be used in combination by irradiating the energy rays during the post-baking process below.

Furthermore, the object to be etched in the present invention is not limited to 82, but can also be applied to other objects such as insulating films.As described above, according to the present invention, the dry etching resistance of the resist can be improved. This makes it possible to improve etching controllability and reproducibility, and greatly contributes to uniform and highly accurate 13-page etching in the manufacture of semiconductor devices.

[Brief explanation of drawings]

Figures 1 (=) to (d) are cross-sectional views of the post-bake and etching process according to the conventional method, and Figures 2 (-) to (d)
1 is a cross-sectional view of an etching process according to an embodiment of the present invention. 2o... Axial substrate, 21... Film to be etched, 22... 11 resist pattern. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 3

Claims (3)

[Claims] (1) An etching method characterized in that after a resist pattern is formed on an object to be etched, the resist pattern is post-baked by heat treatment under vacuum, and then the object to be etched is etched using the resist pattern as a mask. . (2) After forming a resist pattern on the object to be etched,
An etching method characterized in that the resist pattern is irradiated with energy rays to promote polymerization, and then the object to be etched is etched using the resist pattern as a mask. (3) After forming resist pattern-1 on the object to be etched,
An etching method characterized in that the resist pattern is irradiated with an energy beam under vacuum and then heat-treated and post-baked, and then the object to be etched is etched using the resist pattern as a mask. 2 vane