JPH0246724A - Processing of metal thin film - Google Patents

Abstract

PURPOSE:To prevent a readhesion of a reaction product from causing by a method wherein a metal thin film and a high-frequency power applying electrode are connected to each other and the metal thin film is used as the high-frequency power applying electrode at the time of reactive ion etching. CONSTITUTION:A direct-coupled cover 6 is formed of a conductor, a metal thin film 1' and a high-frequency power applying electrode 3 are arranged in such a way that they are electrically continued to each other and the film 1' is contrived in such a way that a high-frequency power is directly applied to the film 1' itself. As a result, the film 1' is directly turned into the electrode, whereby a dielectric substance on a side where a plasma sheath exists and a dielectric substance on the side opposite to the above side holding the metal thin film surface between the dielectric substances are completely shielded electrostatically and the combination of a high-frequency power at the part of a supporting substrate 2', at which the high-frequency power has been hitherto generated, and the combination of a high-frequency power at parts, at which insulator rings 5 are arranged, become equivalent to each other. As a result, the etching rates in both parts become equal to each other.

Description

[Detailed Description of the Invention] [Summary] The purpose of this invention is to provide a reactive ion etching method that does not cause re-deposition of reaction products with respect to a method for producing fine patterns of metal thin films, and to reduce uneven film thickness. In a method of patterning a metal thin film deposited through an insulator by reactive ion etching, the metal thin film is connected to a high frequency power application electrode to apply high frequency power to the metal thin film during reactive/ion etching. Configured for use as an electrode.

[Industrial application field]

The present invention relates to a metal thin film processing method, and particularly to a method for producing fine patterns such as X-ray masks.

In the X-ray exposure technology required as a means to transfer and form fine circuit patterns in the VLSI manufacturing process, precision processing of metal thin films deposited through insulators with non-uniform film thickness is required. is necessary. As the degree of integration of VLSIs increases, the design rules for circuit patterns become smaller and smaller, making it important to perform pattern processing with higher precision.

[Conventional technology]

In order to explain a method of processing a metal thin film which becomes an absorber of an X-ray mask using conventional RIE (reactive ion etching), FIG. 3 shows a block diagram of a conventional apparatus. The X-ray absorber is formed of a metal thin film such as Ta, and
It is supported by an X-ray mask support substrate 2 made of BN or SiC or the like with a thickness of approximately 4 μm, and a ceramic insulator ring 5 is further bonded thereto. A mask material pattern 10 is formed on the surface of the X-ray absorber 1, and the pattern is transferred to the XwA absorber 1 by reactive ion etching. In the figure, 3 is a high-frequency power application electrode, 4 is a ground electrode, 7 is an outer wall of the reaction chamber, and 8 is a ground electrode.
9 is an etching gas inlet, 9 is a vacuum exhaust system, and 11 is a high frequency power source.

In the above configuration, the X-ray mask support substrate 2 is in an electrically floating state, and the coupling state of high-frequency power is different between the portion where only the X-ray mask support substrate 2 is provided and the portion where the insulator ring 5 is arranged. As a result, the etching speed of the metal thin film of the X-ray absorber 1 differs. For example, gold 1%
R the Ta of the m film with a mixed gas of C12 and CCl4.
In the case of IE, this difference in etching speed promotes redeposition of reaction products.In the RIE mechanism, there is a coexistence of physical sputter etching due to ion bombardment as well as chemical reaction of ions. The influence of the latter is significant. Even if a reaction actually occurs, there are few factors that can repel it with ions, and reaction products tend to accumulate in areas where there is less ion bombardment (lower temperature).

The portions a and a' on the boundary of the insulator ring 5 in FIG.
As mentioned above, since the bonding state of the high-frequency power is different, the impact of ions is small (the temperature is low), and the X-ray mask support substrate 2
Even if etching of the upper Ta layer is completed, the boundary between the X-ray mask support substrate 2 and the portion where the insulator ring 5 is arranged is not exposed to RIE.
reaction products are redeposited. Here, in the case of etching Ta, it is known that tantalum chloride having a relatively low vapor pressure is generated and redeposited on the portions of the X-ray mask support substrate 2 where the temperature is relatively low. This reaction product is hard and difficult to remove once deposited, and may itself be a defect as a mask. Further, the adhesion thickness of the reaction product may be several micrometers, which also hinders accurate placement of the X-ray mask and the object to be exposed in close proximity during X-ray exposure. As a result, a problem has arisen in that the yield of X-ray masks is reduced.

Conventional responses to such reaction products are as follows:
■It was.

■Mechanically scrape and wash.

In this case, since the X-ray mask support substrate 2 is close to an extremely thin portion where only the X-ray mask support substrate 2 exists, there is a risk of damage, which is difficult.

■ Areas where reaction products may re-deposit (a, a)
Design the mask pattern so as not to etch the ' part).

There is a problem that the degree of freedom in mask design is lost, which limits the measures that can be taken.

[Problem to be solved by the invention]

An object of the present invention is to provide a reactive ion etching method that does not cause the re-deposition of reaction products, which is the conventional problem.

(Means for Solving the Problems) The present invention provides an improved reactive ion etching method based on basic considerations regarding the mechanism of the reactive ion etching method.

FIG. 1 is an explanatory diagram of the principle of the present invention, in which the same parts as in FIG. 3 are designated by the same reference numerals.

is a metal thin film, 2° is a support substrate, 3 is a high frequency power application electrode, 4 is a ground electrode, 5 is an insulator ring, and 6 is a direct connection cover.
7 is an outer wall of the reaction chamber, 8 is an etching gas inlet, 9 is a vacuum exhaust system, and 10 is a mask material pattern.

Here, the direct connection cover 6 is formed of a conductor, and is arranged so that the metal thin film 1° and the high-frequency power application electrode 3 are electrically connected, so that the high-frequency power is directly applied to the metal thin film 1'' itself. Take structure.

[Effect]

As a result, 1° of the metal thin film becomes a direct electrode, and
The dielectric material on the opposite side of the plasma sheath across the metal thin film surface is completely electrostatically shielded, and the part where the supporting substrate 2'' is conventionally formed and the part where the insulator ring 5 is placed are completely shielded from static electricity. The coupling of high frequency power with becomes equivalent, resulting in
The etching speed of the image area becomes equal.

〔Example〕

FIG. 2 is a block diagram of one embodiment of the present invention, and in the figure, the first
Components that are the same as those shown in FIGS. 3 and 3 are designated by the same symbols. Ta is used as the X-ray mask absorber of No. 1, and a mixed gas of chlorine ((1!t) and carbon tetrachloride (CCj!4) is used as the etching gas. The direct-coupling cover 6 is formed of a metal conductor, It is configured to be in contact with the periphery of Ta of the X-ray absorber 1, and conduction is established between the high-frequency power application electrode 3 and the X-ray absorber 1. 12 is a carbon tetrachloride cylinder, 13 is a chlorine gas cylinder, 14 is a gas introduction line;
15 is a reaction chamber gas pressure regulating valve.

A resist or something similar is formed on the surface of the X-ray absorber as an RIE mask material pattern 1O,
The pattern of the mask material is transferred to Ta of the X-ray absorber 1.

As an example of etching conditions, the following range is suitable.

Etching gas volume mixing ratio: C1*/(C1+CCea)~0.4~0.
8 Gas Pressure Crab 0, ITorr ~ 0, 2Torr High Frequency Discharge Power Density: 0, 08 W'/c+m" ~ 0, 30 W/
am! If the etching gas mixture ratio is smaller than the above value, carbon adhesion will be noticeable and etching will not proceed; if it is larger, the anisotropy will be lost and the cross-sectional shape of the pattern will become inversely tapered, resulting in Causes dimensional variations.

Whether the gas pressure is higher or lower than the above value, the selectivity of Ta etching with respect to the mask material decreases. Further, if the high-frequency power discharge power density is smaller than the specified value, etching will not proceed, and if it is larger, the X-ray mask support substrate 2 will be damaged.

By using the above-mentioned etching conditions, a difference in the etching speed of the Ta film formed on the X-ray mask support substrate 2 can be created between the portion where only the XyI mask support substrate 2 is located and the portion where the insulator ring 5 is arranged. This makes it possible to perform etching at a constant speed.

In the above, an embodiment of the present invention has been shown for manufacturing an X-ray mask having a Ta X-ray absorber, but the present invention is not limited to this. This method can be applied to reactive ion etching of deposited metal ML, for example, a metal thin film deposited on a silicon wafer with an insulating film interposed therebetween, or a metal FIN deposited on a glass wafer.

〔Effect of the invention〕

As explained above, the present invention improves the uniformity of the etching rate, eliminates the generation of residue at the boundaries of uneven film thickness, and contributes to improving the manufacturing yield of extremely precise patterns such as X-ray masks. It's a big thing to do.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the principle of the present invention, FIG. 2 is a configuration diagram of an embodiment of the present invention, FIG. 3 is a block diagram of a conventional device. 1" is a metal thin film ■ is an X-ray absorber 2' is the support substrate 2 is the X-ray mask support board 3 is a high frequency power application electrode 4 is the ground electrode 5 is an insulator ring 6 is a direct cover 7 is the outer wall of the reaction chamber 8 is the etching gas inlet 9 is vacuum exhaust system 10 is resist pattern 13 is a chlorine gas cylinder 14 is the gas introduction line 15 is the reaction chamber gas pressure regulating valve

Claims (1)

[Claims] 1. In a method of patterning a metal thin film deposited via an insulator having a non-uniform thickness by reactive ion etching, the metal thin film and a high-frequency power applying electrode are connected to each other. A method for processing a metal thin film, characterized in that the metal thin film is used as a high-frequency power application electrode during reactive ion etching. 2. The metal thin film processing method according to claim 1, wherein the metal thin film is an X-ray absorber formed on an X-ray mask support substrate, and the X-ray mask support substrate is reinforced with a ring-shaped insulator. A metal thin film processing method characterized by: