JPH08134666A - Dry etching method - Google Patents

Abstract

PURPOSE: To improve the etching shape and to make anisotropic etching possible by setting a material to be etched on a plasma producing AC electrode. CONSTITUTION: In the dry etching using the plasma of a reactive gas, a material 70 such as a silicon single crystal substrate to be etched is set on a plasma producing AC electrode 21. A vacuum chamber 10 is evacuated, and a reactive gas for etching is introduced into the chamber through a gas feed system 30. The flow rate of the reactive gas is independently controlled with a gas flow controller 31. The pressure and current density are set in a specified range to conduct dry etching. The pressure for dry etching is preferably controlled to 1-50Pa. By this method, a layer of insulating material is not formed on the surface of a material to be etched.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching method. More specifically, it relates to a method for effectively and functionally performing dry etching of a metal, an organic material including an inorganic material and a polymer material using plasma, and particularly, a silicon substrate, a silicon semiconductor thin film, a polymer of polyimide or epoxy. A method of dry etching a material.

[0002]

2. Description of the Related Art For etching a substrate material or a thin film material, wet etching using an alkaline solution or an acid is preferred because it is simple and can be etched at high speed. However, the problems of wet etching are the difficulty of handling the liquid, the problem of waste liquid treatment, the contamination of the substrate, and the inability to freely control the etching shape. At present, the controllability of this etching shape is an extremely important issue from the viewpoint of devices and circuit boards that use a base material. Specifically, an anisotropic etching shape is required instead of an isotropic etching shape. On the other hand, the etching method using plasma is easy to handle because it does not contaminate the base material and is dry (dry type), and is widely used. The problem with the plasma etching method is that the etching rate is extremely slow, and anisotropic etching is also difficult. Furthermore, when the material to be etched is placed on the side of the ground electrode and subjected to plasma etching, an insulating material layer is easily formed on the surface of the material to be etched. Therefore, when plasma etching is applied to the circuit board, an insulating material layer is formed on the surface of the metal thin film, and the insulating material layer functions as a resistance, resulting in deterioration of the function. Further, in the case of etching a semiconductor substrate or a thin film, the semiconductor substrate or the thin film may be contaminated, resulting in a significant deterioration in performance. Therefore, in such a case, there is a problem that it is necessary to add a surface cleaning step after the etching process.

[0003]

DISCLOSURE OF THE INVENTION The present invention remarkably improves the etching shape by the conventionally used plasma etching method, and in particular, enables anisotropic etching and high-speed etching, and can be etched. The purpose is to establish an etching method in which an insulating layer is not formed on the material surface.

[0004]

In order to solve the above-mentioned problems, the inventors of the present invention have made earnest studies, and as a result, in dry etching using plasma of a reactive gas, the material to be etched was placed on an AC electrode for generating plasma. By doing so, it has been found that an anisotropic etching shape which is not hitherto obtained at high speed can be obtained, and an insulating material layer is not formed on the surface of the material to be etched. The present invention has been made based on such findings. That is, according to the present invention, in dry etching using plasma of a reactive gas, a material to be etched is placed on an AC electrode for generating AC plasma, and a dry etching pressure is from 1 to 1. The present invention relates to the dry etching method characterized by being 50 Pa, and the dry etching method characterized by using nitrogen trifluoride as a reactive gas. The details will be described below.

Materials to be etched in the present invention include semiconductor thin films and semiconductor materials such as silicon, silicon carbide, silicon nitride, silicon oxide, germanium or germanium alloys; as metal elements; silver, aluminum, copper, magnesium, iron, etc., Further, metal oxides such as tin oxide, indium oxide, tin-indium oxide, titanium oxide, vanadium oxide, nickel oxide, and tungsten oxide; nitrides such as titanium nitride and silicon nitride are used. Further, it may be a polymer material such as an epoxy resin, a polyimide resin, a polyethylene resin or a polypropylene resin.

The AC plasma referred to in the present invention will be specifically described. As a method for generating plasma, specifically, an AC power supply for plasma generation is used, and an AC voltage is applied to electrodes for plasma generation installed in a vacuum chamber to generate plasma. The frequencies used are commercial frequencies of 50 to 60 Hz, high frequencies of 10 kHz to 1000 MHz, and microwaves of 1 GHz or higher. These discharge powers have a power density in the range of 1 mW / cm ² to 100 W / cm ² , and are appropriately selected according to the material to be etched, the reactive gas species, the discharge method and the like.

The reaction pressure at the time of plasma generation is appropriately selected from the viewpoint of the etching rate and the anisotropy of the etching processed shape. The reaction pressure is important for satisfying the high speed etching and the anisotropy of the etching processed shape. Is a factor. That is, the reaction pressure is usually 0.01 ~ 300Pa,
Preferably, 0.1-150Pa, more preferably 1-50Pa,
Even more preferably, 1 to 30 Pa is used.

The reactive gas used in the present invention is a mixed gas of an etching compound gas and a supporting gas, and the etching compound gas is a mixed gas of a compound gas containing a fluorine atom and a compound gas containing an oxygen atom. As the compound containing a fluorine atom, fluorine (F ₂ ), a fluorinated carbon compound such as carbon tetrafluoride, nitrogen trifluoride, a halogenated fluorine or the like is used, and in terms of handling, fluorine such as carbon tetrafluoride is preferably used. Carbonated compounds and nitrogen trifluoride are used, and from the viewpoint of etching rate, nitrogen trifluoride is more preferably used. A compound containing an oxygen atom is appropriately added to these compound gases. As the compound containing an oxygen atom, oxygen (O ₂ ) is used in terms of handling, but it is also possible to use a gas that has been ozonized in advance. The concentration of these mixed gases is
The concentration of the compound gas containing fluorine atoms is 0.001 to 10
Used in the range of 0% (volume concentration).

It is preferable to introduce a gas such as hydrogen, helium, argon, neon, xenon, krypton or nitrogen together with the compound gas as a supporting gas. When these supporting gases are used, it is effective to use them in the range of 0.01 to 100% (volume concentration) in the concentration of the compound gas for etching, and it is appropriately selected in consideration of the etching rate and etching shape. It is a thing. A flow rate of these reactive gases in the range of 1 to 1000 cc / min is sufficient.
It is appropriately selected depending on the relationship with the reaction pressure and is not limited in carrying out the present invention.

During etching, the temperature of the material to be etched is appropriately selected. From an industrial point of view, it is 20 ° C. to 500 ° C., but the present invention is effective in that temperature range. There is no hindrance to the practical implementation, and it is not limited.

An apparatus for practicing the present invention is shown in FIG. The apparatus includes a vacuum chamber (10) for generating plasma for dry etching, an AC power source (20) for generating plasma for generating AC voltage, a plasma generating AC electrode (21) for applying AC voltage, and a compound gas for etching. A gas supply system (30) for supplying a reactive gas for etching, which comprises a gas flow rate controller (31) for supplying gas and a gas flow rate controller (32) for supplying supporting gas, a pressure gauge (111), and a pressure regulator (50). ), An evacuation device (60) (which is composed of a turbo molecular pump and a dry pump), a material to be etched (70), a built-in heater capable of heating the material to be etched (70), and is grounded. It consists of a grounding electrode (80) and a heating power supply (81).

[0012]

EXAMPLES One embodiment of the present invention will be described below with reference to examples. Example 1 Using the apparatus of FIG. 1, a silicon single crystal substrate was used as the material to be etched. The substrate is connected to the plasma generating AC electrode (2
After being installed in 1) and evacuating to 10 ⁻⁴ Pa, the reactive gas was introduced into the vacuum chamber through the gas supply system (30) for supplying the reactive gas for etching. CF ₄ and O ₂ were used as etching compound gases. Each flow rate is 5 by independent control using the gas flow controller (31).
cc / min and 25 cc / min. A pressure regulator (50) was used to set the pressure to 150 Pa. For the alternating current, a high frequency of 13.56 MHz was used, and the power density for plasma generation was 0.5 W / cm ² . To evaluate the etching rate and shape, the surface of the silicon single crystal substrate was coated with a copper thin film, and 500 μφ
The hole was prepared and exposed to the plasma for etching for 30 minutes, and then the etching rate was obtained by measuring the step difference of the opening. In addition, the shape anisotropy is obtained by cutting a sample to expose a cross section, and observing the surface with a scanning electron microscope or an optical microscope. The etching rate was evaluated by the ratio of the etching rate in the D direction (ED / ES). In addition, the presence or absence of an insulating layer formed on the substrate surface was evaluated by measuring the resistance of the surface of the copper thin film by the four-point probe method.

Example 2 Etching was performed in the same manner as in Example 1 except that the reaction pressure was 50 Pa.

Example 3 Etching was performed in the same manner as in Example 1 except that the reaction pressure was 25 Pa.

Example 4 In Example 2, the reactive gas was NF ₃ 50 cc / min, O ₂ , 50
Etching was performed in the same manner except that the rate was changed to cc / min.

Example 5 As in Example 1, the apparatus shown in FIG. 1 was used, and a polyimide resin film was used as the material to be etched. The polyimide resin film was placed on a plasma-generating AC electrode and evacuated, and then CF ₄ and O ₂ were used as etching compound gases. Each flow rate is 50cc / min and 50cc /
Minutes The reaction pressure was set to 50 Pa. A high frequency of 13.56 MHz was used, and a power density of plasma generation was 0.3 W / cm ² . The etching rate and shape were evaluated by coating the surface of the polyimide resin film with a copper thin film, forming a hole of 500 μφ, exposing it to the plasma for etching for 30 minutes, and then measuring the step difference in the opening to determine the etching rate. I asked. These are the same as in the first embodiment.

Example 6 In Example 5, the reactive gas was NF ₃ 50 cc / min, O ₂ , 50
Etching was performed in the same manner except that the rate was changed to cc / min.

Example 7 Etching was performed in the same manner as in Example 6 except that the reaction pressure was 30 Pa. Example 8

Etching was carried out in the same manner as in Example 6 except that the power density for plasma generation was 0.5 W / cm ² .

Comparative Examples 1 to 3 In the same manner as in Examples 1 to 3, except that the silicon single crystal substrate as the material to be etched was placed on the ground electrode (80) facing the plasma generating AC electrode. Etched.

Comparative Example 4 In Example 4, the reaction pressure was 350 Pa. The other conditions were the same as those in the example.

Comparative Examples 5 to 7 Similar to Examples 5 to 7, except that the silicon single crystal substrate as the material to be etched was placed on the ground electrode (80) facing the plasma generating AC electrode. Etched.

Comparative Example 8 In Example 8, the reaction pressure was 350 Pa. The other conditions were the same as those in the example. The results of these Examples and Comparative Examples are shown in Tables 1 to 4.

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

[Table 3]

[0027]

[Table 4]

As is apparent from the table, it was found that when the etching method in this embodiment was used, anisotropic etching was obtained at a high speed and that an insulating layer was not formed on the surface of the material to be etched. The dry etching method according to the invention proves to be effective.

[0029]

As is clear from the above Examples and Comparative Examples, it was confirmed that by using the dry etching method of the present invention, an anisotropic etching shape can be obtained at a high speed, and It was confirmed that no insulator layer was formed on the surface of the material to be etched. This is effective for processing semiconductor thin films such as ICs and LSIs, and is very effective for forming a multilayer circuit board. The present invention provides high quality and high quality required in these fields. We can provide technology that enables reliability,
It should be said that this is a very useful invention.

[Brief description of drawings]

FIG. 1 is a diagram of a plasma etching apparatus for carrying out the present invention.

FIG. 2 is a diagram showing a method for evaluating anisotropy in the present invention.

[Explanation of symbols]

 10 vacuum chamber 20 AC power source for plasma generation 21 AC electrode for plasma generation 30 Gas supply system 31 Gas flow rate controller 32 Gas flow rate controller 50 Pressure regulator 60 Vacuum exhaust device 70 Etching material 80 Grounding electrode 81 Heating power source 111 Pressure gauge

Claims (3)

[Claims] 1. A dry etching method, wherein in dry etching using plasma of a reactive gas, a material to be etched is placed on an alternating current electrode for generating alternating current plasma. 2. The pressure for dry etching is 1 to 5
It is 0 Pa, The dry etching method of Claim 1 characterized by the above-mentioned. 3. The dry etching method according to claim 1, wherein nitrogen trifluoride is used as the reactive gas.