JPH0613357A - Method of etching of semiconductor device - Google Patents

Abstract

PURPOSE:To provide an etching method without deposition of a member to be etched onto a resist side wall upon etching of a dielectric thin film, a high dielectric film, and electrodes thereof by, after processing with ion milling, performing isotropic etching with argon plasma. CONSTITUTION:A photoresist 101 is first applied with rotation on a Pt film 102 formed on a silicon substrate 103(a). A 2mum square pattern is exposed to light and developed (b). Then, anisotropic etching is performed with ion milling for about 7 minutes to completely remove a member to be etched. Thereupon, the member 104 is redeposited on the side wall of the resist (c). Further, 1m Torr. 500W isotropic argon plasma etching is performed for 10 minutes. Herein, argon ions 105 collide the substrate and the resist side all simultaneously, so that the substance to be etched is prevented from being redeposited on the resist side all (d). Hereby, a configuration without deposition on the side wall is ensured after exfoliation of the resist.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for etching a semiconductor device, and more particularly to a method for etching a ferroelectric thin film, a high dielectric constant film and its electrode using ion milling.

[0002]

2. Description of the Related Art For example, in a ferroelectric memory, Pt is a material effective as an electrode of a capacitor section. However, since Pt is chemically very stable, a material that can be used for reactive etching using a chemical reaction in the etching process is aqua regia (HN) in wet etching.
O3: HCl = 1: 3), CF in dry etching
4, although there is a halogen-based gas such as CL2, the former has poor controllability and melts the photoresist, and the latter has a problem that the etching speed is extremely slow because the vapor pressure of the halide of Pt is low. , Practically difficult. Further, in these isotropic etchings, as shown in FIG. 3, during the etching, lateral etching called undercut proceeds, which adversely affects the step conversion difference and the shape reproducibility.

Therefore, conventionally, an ion milling apparatus has been used in which accelerated argon ions collide with an object to be etched, and the object to be etched is sputtered to perform physical and anisotropic etching.

However, in the etching by the ion milling device, there is almost no selection ratio, and
Since the etched object is not volatilized, a part thereof adheres to the side wall of the resist as shown in FIG. Since the deposits on the sidewalls are not dissolved or stripped even after the resist stripping step and remain in a wall shape (FIG. 5), the coverage thereof becomes very small in the subsequent step of forming the interlayer insulating film, and wiring on the interlayer insulating film is reduced. In the step of forming the layer, it may cause disconnection or short circuit of the wiring.

Therefore, conventionally, after exposure and development of the resist, 1
The resist is reflowed by baking at a temperature of 30 ° C to 200 ° C, and the taper angle of the resist is adjusted by thinning the resist film thickness so that the resist does not have a vertical side wall. However, this causes a problem that the size conversion difference between the resist size and the etching size becomes large.

[0006]

SUMMARY OF THE INVENTION The present invention is intended to solve such a problem. The object of the present invention is to prevent the adherend from adhering to the side wall of the resist, and to obtain good dimensional conversion difference and shape reproducibility. An etching method is provided.

[0007]

[Means for Solving the Problems] In order to solve such a problem, there are the following two methods.

First of all, after treating with ion milling,
This is a method of isotropic etching with argon plasma.
This is once etched by ion milling and then again to remove the generated side wall deposits.
This is a method of etching with argon plasma, which is closer to isotropic etching than the ion milling. Here, in the argon plasma etching, not only the side wall deposits but also the substrate are etched. Therefore, it is important to set the respective etching times in consideration of the relationship between the etching rates of the ion milling etching and the argon plasma etching. Is.

Secondly, after treatment with ion milling,
This is a method of isotropic etching with plasma of argon and a halogen-based reactive gas. This is also to remove the side wall deposits generated by ion milling afterwards like the first method, and volatilizes the object to be etched by using plasma of argon and a halogen-based reactive gas, and It is intended to prevent reattachment of the object to be etched.

[0010]

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

First, as shown in FIG. 1A, a Pt film (film thickness of about 1500 Å) formed on a silicon substrate is spin-coated with a photoresist to a film thickness of about 1 micron. A 2 μm square pattern is exposed and developed (FIG. 1B). Then, anisotropic etching is performed by ion milling for about 7 minutes to completely remove the object to be etched. At this time, the object to be etched is redeposited on the side wall of the resist and has a shape as shown in FIG.

Next, isotropic argon plasma etching is performed at 1 mTORR and 500 W for 10 minutes. Figure 1
As shown in (d), the argon ions collide with the substrate and the resist side wall at the same time, so that the substance to be etched is not redeposited on the resist side wall. However, the silicon substrate is also etched as an overetch. As a result, after the resist is peeled off, it is possible to obtain a shape having no side wall deposits as shown in FIG.

As a second embodiment, a Pt film (film thickness of about 1) formed on a silicon substrate is used as in the first embodiment.
Film thickness of photoresist is about 1
Spin coating to micron (Fig. 2 (a)), 2μ
After exposing and developing an m-square pattern (Fig. 2
(B)), etching is performed for about 5 minutes using an ion milling device. In the present embodiment, the object to be etched is not completely removed and remains for several hundred angstroms (FIG. 2).
(C)). After that, isotropic argon plasma etching with 1 m TORR and 500 W is performed for about 10 minutes to remove the deposits on the sidewalls and the remaining object to be etched, and after removing the resist, the etching shape without the deposits on the sidewalls as shown in FIG. To get In this example, not only was there no deposit on the side wall, but an etching shape with good dimensional conversion difference and shape reproducibility could be obtained.

The third embodiment is similar to the first embodiment and has a Pt film (film thickness of about 150) formed on a silicon substrate.
A photoresist is spin-coated to a film thickness of about 1 micron (0 angstrom) (FIG. 1A), and a square pattern of 2 μm square is exposed and developed (FIG. 1B). Next, after performing etching for about 7 minutes with an ion milling device (FIG. 1C), etching is performed for about 7 minutes with plasma of argon and a halogen-based reactive gas to remove the deposits on the side wall, and after removing the resist. An etching shape as shown in 1 (e) was obtained.

In the fourth embodiment, similar to the second embodiment, a Pt film (film thickness of about 150) formed on a silicon substrate is used.
0 angstrom) photoresist was spin coated to a film thickness of about 1 micron (FIG. 2 (a)), and a 2 μm square pattern was exposed and developed (FIG. 2 (b)).
Etching is performed for about 5 minutes with an ion milling device. In the present embodiment, as in the second embodiment, the object to be etched is not completely removed and remains for several hundred angstroms (FIG. 2 (c)). After that, etching was performed with plasma of argon and a halogen-based reactive gas for about 7 minutes to remove the deposits on the sidewalls, and after removing the resist, an etching shape as shown in FIG. 2D was obtained.

In the above examples, Pt was used for the proof, but according to the present invention, other reactive materials such as Ti, Au, Pd, other electrode materials, or ferroelectric films such as PbTiO3, PZT, PLZT, etc. are usually used. It can be applied to materials that are difficult to etch.

[0017]

As described above, in the pattern forming method by etching according to the present invention, it was possible to eliminate the re-adhesion of the object to be etched to the side wall of the resist, which was inevitable in the ion milling etching.
As a result, it was possible to eliminate the problem of coverage of the interlayer insulating film due to the residue of the deposits on the side wall, and the disconnection or short circuit of the wiring layer on the interlayer insulating film. In addition, in the second and fourth embodiments, not only the deposits on the side walls but also the etching shape with good dimensional conversion difference and shape reproducibility could be obtained.

[Brief description of drawings]

FIG. 1 is a process explanatory view of first and third embodiments of the present invention.

FIG. 2 is a process explanatory view of second and fourth embodiments of the present invention.

FIG. 3 is a cross-sectional shape diagram after etching in conventional isotropic etching.

FIG. 4 is a cross-sectional shape diagram after etching in conventional ion milling etching.

FIG. 5 is a cross-sectional shape view after resist stripping in conventional ion milling etching.

[Explanation of symbols]

Photoresist: 101, 201,
301, 401 Pt film: 102, 202,
302, 402 Silicon substrate: 103, 203,
303, 403 Reattachment of etching object (Pt): 104, 204,
404 Argon ion: 105

Claims (3)

[Claims] 1. A method for etching a material of a ferroelectric thin film, a high dielectric constant film, and an electrode thereof, comprising a step of treating by ion milling and a step of etching by argon plasma. Method for etching device. 2. A method of etching any one of a ferroelectric thin film, a high dielectric constant film, and an electrode thereof, comprising a step of performing ion milling and a step of etching with plasma of argon and a halogen-based reactive gas. A method for etching a semiconductor device, comprising: 3. The ferroelectric thin film according to claim 1 or 2 is BaTiO3, PZT, PLZT, the high dielectric constant film is SrTiO3, TaO3, and the electrodes are Pt, Pd, Ti, A.
u and a compound thereof are used for etching a semiconductor device.