JP2000031129A - Etching method for semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an etched substance from redepositing on resist sidewalls and to reduce critical dimension losses and improve profile reproducibility by effecting argon plasma isotropic etching after a step by an ion milling has been performed. SOLUTION: A photoresist 101 is applied to a Pt film 102 formed on a silicon substrate 103 by means of spin coating. Then, the resultant substrate is subjected to anisotropic etching by an ion milling system for about 7 minutes to thereby remove the film 102 completely therefrom. At this time, redeposits 104 of the etched substance are formed on the sidewalls of the photoresist 101. Then, the resultant substrate is subjected to argon plasma isotropic etching for 10 minutes at 1 m Torr and 500 W. Since argon ions 105 bombard the substrate 103 and the resist sidewalls, the etched substance does not redeposit on the sidewalls. However, the substrate 103 is etched due to overetching. As a result, a profile free of sidewall redeposits 104 can be obtained after the removal of the photoresist.

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 electrodes 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 portion. However, since Pt is chemically very stable, a substance 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 problems such as poor controllability and melting of the photoresist, and the latter has an extremely low etching rate due to the low vapor pressure of the halide of Pt. Difficult in terms of practicality. In addition, in these isotropic etchings, as shown in FIG. 3, during the etching, etching in a lateral direction called an undercut progresses, which adversely affects step conversion difference and shape reproducibility.

[0003] 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 physically and anisotropically etched by sputtering.

However, in the etching by the ion milling apparatus, there is almost no selectivity, and
Since the etched object does not volatilize, a part thereof adheres to the side wall of the resist as shown in FIG. The side wall deposits remain in a wall shape without being dissolved or stripped even after the resist stripping step (FIG. 5), so that the coverage becomes very small in the subsequent step of forming the interlayer insulating film, and wiring is formed on the interlayer insulating film. In the step of forming a layer, the wiring may be disconnected or short-circuited.

Therefore, conventionally, after exposure and development of a 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 reducing the resist film thickness so that the resist does not have vertical side walls. However, this has caused a problem that the size conversion difference between the resist size and the etching size is increased.

[0006]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above-mentioned problems, and has as its object to prevent the object to be etched from adhering to the resist side wall and to provide a good dimensional conversion difference and good shape reproducibility. An etching method is provided.

[0007]

Means for Solving the Problems To solve such a problem, there are the following two methods.

First, after treatment by ion milling,
This is a method of performing isotropic etching with argon plasma.
This is, once etched by ion milling, once 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, since not only the side wall deposits but also the substrate are etched in the argon plasma etching, 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. It is.

Second, after treatment by ion milling,
This is a method of performing isotropic etching with plasma of argon and a halogen-based reactive gas. This also removes the side wall deposits generated by ion milling as in the first method later, and volatilizes the object to be etched by using plasma of argon and a halogen-based reactive gas, thereby forming the above-mentioned resist side wall. This prevents re-adhesion of the object to be etched.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.

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

Next, isotropic argon plasma etching at 1 mTORR, 500 W is performed for 10 minutes. Here, FIG.
As shown in (d), since the argon ions collide with the substrate and the resist side wall at the same time, the substance to be etched does not adhere to the resist side wall. However, the silicon substrate is also etched as an overetch. Thus, after the resist is stripped, a shape free of the side wall deposit can be obtained as shown in FIG.

As a second embodiment, a Pt film (having a film thickness of about 1) formed on a silicon substrate as in the first embodiment is used.
500 Å thick photoresist
Spin coating to a 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 this embodiment, the object to be etched is not completely removed, but remains for several hundred angstroms (FIG. 2).
(C)). Thereafter, isotropic argon plasma etching at 1 mTORR, 500 W is performed for about 10 minutes to remove the adhered material on the side wall and the remaining object to be etched. After the resist is peeled off, the etched shape without the adhered material on the side wall as shown in FIG. Get. In the present embodiment, not only no side wall deposits were found, but also an etched shape with good dimensional conversion difference and shape reproducibility was obtained.

In the third embodiment, as in the first embodiment, a Pt film (having a thickness of about 150
Then, a photoresist is spin-coated so as to have a thickness of about 1 μm (FIG. 1A), and a 2 μm square pattern is exposed and developed (FIG. 1B). Next, after etching is performed for about 7 minutes by an ion milling apparatus (FIG. 1C), etching is performed for about 7 minutes by plasma of argon and a halogen-based reactive gas to remove the deposits on the side walls. An etched shape as shown in FIG. 1 (e) was obtained.

In the fourth embodiment, similarly to the second embodiment, a Pt film (about 150 nm thick) formed on a silicon substrate is used.
(0 angstrom), a photoresist is spin-coated so as to have a film thickness of about 1 micron (FIG. 2A), and a 2 μm square pattern is exposed and developed (FIG. 2B).
Etching is performed for about 5 minutes using an ion milling apparatus. In this embodiment, as in the second embodiment, the object to be etched is not completely removed and remains for about several hundred angstroms (FIG. 2C). Thereafter, etching was performed for about 7 minutes with plasma of argon and a halogen-based reactive gas to remove deposits on the side walls, and after the resist was stripped, an etched shape as shown in FIG. 2D was obtained.

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

[0017]

As described above, in the method of forming a pattern by etching according to the present invention, the re-adhesion of the object to be etched to the resist side wall, which cannot be avoided in the ion milling etching, can be eliminated.
As a result, the problem of coverage of the interlayer insulating film due to the residue of the deposit on the side wall and the occurrence of disconnection and short-circuit of the wiring layer on the interlayer insulating film could be prevented. Further, in the second and fourth embodiments, it was possible to obtain an etched shape having good dimensional conversion difference and shape reproducibility as well as the inside of the side wall deposits.

[Brief description of the 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 a second and a fourth embodiment of the present invention.

FIG. 3 is a cross-sectional view 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 view of the conventional ion milling etching after resist removal.

[Explanation of symbols]

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

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[Procedure amendment]

[Submission date] July 26, 1999 (1999.7.2)
6)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

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[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

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[0007]

Means for Solving the Problems To solve such a problem, the following method can be mentioned.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction contents]

[0008] As a method of etching a semiconductor device of the present invention, the method of etching a semiconductor device having at least one of a ferroelectric thin film, a high dielectric constant film and an electrode thereof is anisotropic to the material. A step of performing isotropic etching and a step of performing isotropic etching on the material after the step of performing anisotropic etching.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Deleted

Claims (3)

[Claims] 1. A method for 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 argon plasma. Equipment etching method. 2. A method for etching any one of a ferroelectric thin film, a high dielectric constant film and its electrode, comprising the steps of ion milling and etching with a 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, wherein BaTiO3, PZT, PLZT, the high dielectric constant film is SrTiO3, TaO3, and the electrodes are Pt, Pd, Ti, A.
u and a compound thereof.