JP3371055B2 - Dry etching method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention masks Nb, Ta, Mo refractory metal materials mainly used in thin film devices such as semiconductors and liquid crystals with a resist mask such as an organic photoresist to form plasma. The present invention relates to a dry etching method of etching with a selected etching gas.

[0002]

BACKGROUND OF THE INVENTION In recent years, refractory metal materials such as Nb, Ta and Mo have been mainly used as wiring materials in thin film devices such as semiconductors and liquid crystals. For processing these materials, a dry etching method is used in which these materials are masked with an organic photoresist and unnecessary unmasked portions are etched and removed with an etching gas converted into plasma. .

First, a dry etching apparatus used for dry etching a refractory metal material will be described with reference to FIG.

In FIG. 3, the dry etching apparatus is
An upper electrode 11 and a lower electrode 12 are arranged in a vacuum chamber 10, and the lower electrode 12 is kept at a constant temperature by a water circulation type temperature control means 13. A high frequency power source 15 is connected to the lower electrode 12 through an impedance matching circuit 14, and a high frequency voltage from the high frequency power source 15 is applied between the both electrodes to generate a plasma 16 in the vacuum chamber 10. The etching target 19 placed on the lower electrode 12 is dry-etched by the generated plasma 16. High-frequency power source 1
5 may be a pulse power supply.

An etching gas is introduced into the vacuum chamber 10 through a mass flow controller 17,
The pressure in the vacuum chamber 10 is appropriately maintained by the action of the exhaust system 18.

Next, a conventional example of the dry etching method will be described.

In the conventional dry etching method, N is used.
In the case of dry etching a refractory metal material such as b, Ta or Mo, Nb is used by using an etching gas simple substance containing fluorine such as SF ₆ or SF ₄ or a mixed etching gas containing oxygen added thereto. , Ta, Mo, etc. are generated and dry etching is performed.

Recently, as described in Japanese Patent Publication No. 2-55508, C 1 F and ClF are used as etching gas.
There are some that attempt to improve the etching rate by using ₃ and ClF ₅ .

[0009]

However, in the structure of the above-mentioned conventional example, since the fluorine radicals cause the etching to proceed in the same direction, there is a problem that the anisotropic etching for dry etching in the desired direction cannot be obtained. is there.

Further, the conventional etching gas has a problem that it has a large etching action on the organic photoresist and the selection ratio of the refractory metal to the organic photoresist is low.

Further, ClF ₃ gas and the like have a higher activity than Cl ₂ gas and require careful handling.
There is a problem that it is expensive.

An object of the present invention is to provide a dry etching method which solves the problems of the above conventional example.

[0013]

In order to solve the above-mentioned problems, the present invention supplies an etching gas into a vacuum chamber whose pressure is reduced by a vacuum pump so that the upper and lower chambers installed in the vacuum chamber. A high-frequency voltage or a pulse voltage is applied between the electrodes to turn the etching gas into plasma, and the etching target is made of a refractory metal material and is placed in the vacuum chamber with a resist mask. In the dry etching method of etching, the etching gas is CH.
Mixed gas der of F ₃ gas and Cl ₂ gas is, the mixture gas
The mixing ratio of Cl ₂ gas is 40% or more in volume%.
70% or less, the etching target is Nb, T
It is characterized by being either a or Mo.

The dry etching method of the present invention is preferably applied to the case where the resist mask is an organic photoresist in order to solve the above problems.

As described above, according to the present invention, by using a mixed gas of CHF ₃ gas and Cl ₂ gas having the above mixing ratio as an etching gas, F and Cl in CHF ₃ gas can be improved.
By the Cl ₂ gas, Nb, Ta, NbF halogenating the refractory metal _{M o X, TaF X, MoF} X, N
BCl _x , TaCl _x , MoCl _x, etc. are generated to remove Nb, Ta, Mo at a high speed, and at the same time, CHF ₃ produces an organic polymer to form C, H, F, etc. on the surface of the resist mask. Forming an organic polymer protective film. This organic polymer protective film protects the resist mask and the side surface of the etched recess of the object to be etched, which are covered by the organic polymer protective film, from etching removal (FIG.
reference).

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the dry etching method of the present invention will be described with reference to FIGS.

The dry etching apparatus used in the present embodiment is the one shown in FIG. 3, but the description thereof has been already given and will be omitted. As an etching gas, C
A mixed gas of HF ₃ gas and Cl ₂ gas is used, and Nb (high melting point metal material) masked with an organic photoresist is selected as an object to be etched.

The mixed etching gas of CHF ₃ gas and Cl ₂ gas is (1) F in CHF ₃ and C in Cl ₂ gas.
(2) Since CHF ₃ gas contains C and H, the organic polymer containing C, H, and F decomposed and generated from CHF ₃ is used because the CHF ₃ gas contains C and H. Adheres to the resist mask surface or refractory metal material (Nb) surface to form a protective film.
Has two effects.

FIG. 1 shows the relationship between the mixing ratio of CHF ₃ gas and Cl ₂ gas, the etching rate for Nb, and the Nb-to-organic photoresist selection ratio. In FIG. 1, the mixing ratio is volume%, and the selection ratio of Nb to organic photoresist = (etching rate of Nb) / (etching rate of organic photoresist).

Nb etching rate (nm / min) in FIG.
And the Nb to organic photoresist selection ratio, the following can be understood.

1. CHF ₃ gas alone does not have an action of etching Nb, but when Cl ₂ gas is added, etching progresses, the etching rate increases as the mixing ratio of Cl ₂ gas increases, and the mixing ratio of Cl ₂ gas becomes 5
The increase rate of the etching rate decreases from around 0%.

2. CHF ₃ Nb to organic photoresist selectivity ratio in gas alone is 0, Cl ₂ the selected ratio and the addition of gas is increased, but the selection ratio increases with increasing mixing ratio of Cl ₂ gas, Cl ₂ gas The selection ratio starts to decrease when the mixing ratio of is about 50%.

Next, in the above 1.2. What can be estimated by the above will be described based on FIG.

In FIG. 2, 1 is a substrate, 2 is a high melting point metal material of Nb, 3 is a surface of the high melting point metal material of Nb 2 before etching, and 4 is an organic photoresist.

Cl in the Cl ₂ gas is NbCl _x
As the F radicals in the CHF ₃ gas are halogenated and removed as NbF _x in the Nb (high melting point metal material) 2, at the same time, the organic polymer containing C, H and F decomposed and produced from CHF ₃ is used as an organic photoresist. 4 surface and Nb
It adheres to the surface of (high melting point metal material) 2 to form an organic polymer protective film 5.

The organic polymer protective film 5 adheres to and protects the top surface and side surfaces of the organic photoresist 4, and at the same time, the recess side surfaces of Nb (high melting point metal material) 2 are etched to form recesses. Adhere to. The organic polymer protective film 5 is scarcely formed on the bottom surface of the recess due to the removal effect during dry etching.

On the other hand, as shown in FIG. 1, since the mixed etching gas has a different action tendency depending on its mixing ratio,
Desired dry etching can be performed by selecting the mixing ratio according to the purpose.

For example, as shown in FIG. 1, when the Cl ₂ gas mixture ratio is around 50%, the Nb etching rate is large and the Nb-to-organic photoresist selection ratio is large. About 10 times, the etching progresses concentratedly on the portion of Nb (high melting point metal material) 2 to be etched, and high-speed etching can be performed. In this case, the optimum ratio of Cl ₂ gas mixing ratio Ru 40% to 70% der.

The organic polymer protective film 5 adheres to and protects the top surface and the side surfaces of the organic photoresist 4, so that it has been conventionally dry-etched with an etching gas and is considered to have low reliability. The photoresist 4 can be used with high reliability.

Further, it is considered that the organic polymer protective film 5 adheres not only to the side surface of the concave portion of Nb (high melting point metal material) 2 which is a concave portion by etching but also to the bottom surface thereof.
As for the bottom surface, since they face each other at right angles to the direction of the applied high voltage, the etching action is strong and the organic polymer protective film 5 is hardly formed. As shown in FIG.
b Etching rate can be obtained. On the other hand, with respect to the etching on the side surface, since it is parallel to the direction of the applied high voltage, the etching action is weak and the protective effect of the organic polymer protective film 5 is recognized, so that the lateral etching can be suppressed. Therefore, it is possible to perform anisotropic etching by mainly etching the bottom surface of Nb (high-melting-point metal material) 2 that has been etched to form a recess, with less etching on the side surface of the recess.

Although the organic photoresist is used as the resist mask in the present embodiment, the same result can be obtained with other resist masks.

[0032]

According to the dry etching method of the present invention, it is possible to selectively perform high-speed dry etching with different directions by concentrating on the portion of the refractory metal material to be etched.

[Brief description of drawings]

FIG. 1 is a diagram showing an Nb etching rate and a Nb-to-organic photoresist selection ratio with respect to a Cl ₂ gas mixture ratio in a mixed gas of CHF ₃ gas and Cl ₂ gas in an embodiment of a dry etching method of the present invention. is there.

FIG. 2 is a schematic diagram showing a dry etching reaction mechanism in one embodiment of the dry etching method of the present invention.

FIG. 3 is a schematic diagram showing a configuration of a dry etching apparatus.

[Explanation of symbols]

1 substrate 2 High melting point metal material 3 Surface of refractory metal material before etching 4 Organic photoresist 5 Organic polymer protective film 10 vacuum chamber 11 Upper electrode 12 Lower electrode 13 Water circulation type temperature control means 14 Impedance matching circuit 15 High frequency power supply 16 plasma 17 Mass Flow Controller 18 Exhaust system

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 21/3065 C23F 4/00 H01L 21/3213

Claims (2)

(57) [Claims] 1. An etching gas is supplied into a vacuum chamber whose pressure is reduced by a vacuum pump, and a high frequency voltage or a pulse voltage is applied between upper and lower electrodes installed in the vacuum chamber to plasma the etching gas. Turned into
In the dry etching method of etching an object to be etched of a refractory metal material provided with a resist mask in the vacuum chamber with the plasmaized etching gas, the etching gas is CHF ₃
Ri mixed gas der between the gas and the Cl ₂ gas, a mixed gas thereof
The mixing ratio of Cl ₂ gas in volume% is 40% or more 70
% Or less, and the etching target is Nb, Ta, M
The dry etching method which is characterized in that either o. 2. The resist mask is an organic photoresist
The dry etching method according to a claim 1.