JP2017228787A - Plasma etching method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma etching method capable of suppressing accumulation of reaction products on a side wall of an etching pattern.SOLUTION: A plasma etching method for plasma-etching a sample includes: a first magnetic film; a second magnetic film arranged above the first magnetic film, a metal oxide film arranged between the first magnetic field and the second magnetic field; a second metal film arranged above the second magnetic film and serving as an upper electrode; and a first metal film arranged below the first magnetic film and serving as a lower electrode. The plasma etching method comprises: a first step of etching the first magnetic film, the metal oxide film, and the second magnetic film using carbon monoxide gas; and a second step of etching the sample using mixed gas of hydrogen gas and inert gas after the first step. The first metal film contains tantalum.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a plasma etching method for plasma etching a magnetic film used in a magnetoresistive memory or the like.

With an increase in the amount of information in recent years, electronic devices are required to reduce power consumption. A semiconductor memory used in an electronic device is also required to be a non-volatile memory that can operate at high speed and can keep information without supplying power. From these demands, the application of magnetoresistive memory (MRAM, hereinafter referred to as MRAM) is expected as a non-volatile memory that operates at low power consumption and at high speed.

In manufacturing MRAM, a mask generated by lithography is used to dry a magnetic film containing at least one of iron (Fe), cobalt (Co), and nickel (Ni) ferromagnetic metals formed on a substrate. A technique for fine processing by etching is required. The technology for finely processing a magnetic film by dry etching is increasing in demand for processing a magnetic head using a magnetic material.

As a method for dry etching of the magnetic film, there are a method using ion beam etching and a method using plasma etching. In particular, plasma etching is widely used in the manufacture of semiconductor devices, and is excellent in mass productivity because a large-diameter substrate can be processed uniformly. However, when the magnetic film is finely processed by plasma etching using a halogen-based gas such as fluorine (F), chlorine (Cl), or bromine (Br) that has been conventionally used, the halogen compound of the magnetic film Since the vapor pressure is low, microfabrication is difficult. Further, since corrosion occurs when the halogen compound deposited on the magnetic film comes into contact with moisture in the atmosphere, it is necessary to carry out a separate anticorrosion treatment.

As a method for solving the above problems, Patent Document 1 discloses a dry etching method for processing a magnetic material while suppressing dissociation of carbon monoxide in plasma. This method utilizes the generation of metal carbonyl having a high vapor pressure, and is suitable for processing a magnetic film because it does not cause corrosion or the like.

JP 2004-356179 A

However, in etching using carbon monoxide (CO) gas containing oxygen atoms (O) as a component, deposition of reaction products on the etching pattern side walls and flat portions increases after etching as shown in FIG. This reaction product is mainly composed of the metal used for the film to be etched. When this reaction product is deposited on the side wall of the etching pattern, there is a possibility that the magnetization free layer and the magnetization fixed layer are electrically short-circuited.

  The MRAM is based on the principle that data is read by detecting a current flowing between the magnetization free layer and the magnetization fixed layer through the tunnel barrier layer, so that the magnetization free layer and the magnetization fixed layer are electrically short-circuited to cause a magnetization direction. Regardless, data cannot be read if current flows. Therefore, it is necessary to prevent the reaction product from being deposited on the sidewall of the etching pattern and electrically shorting the magnetization free layer and the magnetization fixed layer.

  Further, even if the etching gas component does not contain carbon atoms (C) or oxygen atoms (O), if oxygen atoms (O) are contained in the parts exposed to plasma in the vacuum vessel, Oxygen atoms (O) are mixed in. Therefore, a reaction product containing a metal oxide as a main component is generated on the side wall of the etching pattern as in the etching using carbon monoxide (CO) gas.

  For this reason, this invention provides the plasma etching method which can suppress the deposition to the etching pattern side wall of a reaction product.

The present invention includes a first magnetic film, a second magnetic film disposed above the first magnetic film, and a metal disposed between the first magnetic film and the second magnetic film. A sample having an oxide film, a second metal film disposed above the second magnetic film and serving as an upper electrode, and a first metal film disposed below the first magnetic film and serving as a lower electrode In the plasma etching method for plasma etching, a first step of etching the first magnetic film, the metal oxide film, and the second magnetic film using carbon monoxide gas, and after the first step, And a second step of etching the sample using a mixed gas of hydrogen gas and inert gas, wherein the first metal film is a film containing tantalum.

  The present invention also provides a first magnetic film, a second magnetic film disposed above the first magnetic film, and disposed between the first magnetic film and the second magnetic film. A metal oxide film, a second metal film disposed above the second magnetic film and serving as an upper electrode, and a first metal film disposed below the first magnetic film and serving as a lower electrode. In a plasma etching method for plasma etching a sample having, an etching step of etching the first magnetic film, the metal oxide film, and the second magnetic film using a carbon monoxide gas, The film is a film containing tantalum, and the etching step includes a first step and a second step performed after the first step, and the bias RF power in the second step is the first step. Less than one step bias RF power

According to the present invention, it is possible to suppress the deposition of the reaction product on the etching pattern side wall.

1 is a schematic cross-sectional view of a plasma etching apparatus according to the present invention. It is sectional structure drawing of the sample 4 which concerns on this invention. It is a figure which shows the etching result of the 2nd metal film. It is a figure which shows the etching result after step 1 of Table 2. FIG. It is a figure which shows the etching result after step 2 of Table 2. FIG. It is a figure which shows the etching result after step 3 of Table 2. FIG. It is a figure which shows the film thickness dependence of the 2nd reaction product 27 in the gas flow rate ratio of the hydrogen gas with respect to the mixed gas of hydrogen gas and argon gas. It is a figure which shows the dependence with respect to the film thickness of the 2nd reaction product 27 of bias RF electric power. It is a figure which shows the etching result by a prior art.

Embodiments according to the present invention will be described below with reference to FIGS.

  FIG. 1 is a diagram for explaining the outline of the configuration of a plasma etching apparatus according to an embodiment of the present invention. The plasma etching apparatus of the present embodiment includes a vacuum vessel 2 that forms a processing chamber, a bell jar 3 made of an insulating material (for example, a nonconductive material such as quartz or ceramics) that closes the upper portion of the vacuum vessel 2, and a vacuum vessel. 2 and a sample stage 5 on which the sample 4 is placed, and the sample 4 is plasma-etched by the plasma 6 generated in the processing chamber.

  The sample stage 5 is formed on the sample holding unit 7 including the sample stage 5. The cover 8 installed inside the vacuum vessel 2 is for the purpose of adhering the reaction product generated by etching the sample 4 to the wall surface in the vacuum vessel 2 and preventing the reaction product from scattering into the vacuum vessel 2. The surface is roughened. In addition, a coil-shaped first antenna 1 a and second antenna 1 b are arranged outside the bell jar 3. The first antenna 1a is arranged above the second antenna 1b. Further, a disc-shaped Faraday shield 9 that is capacitively coupled to the plasma 6 is installed outside the bell jar 3.

  The antennas 1a and 1b and the Faraday shield 9 are connected to the first high-frequency power source 11 via the matching unit 10. A processing gas is supplied to the vacuum vessel 2 from a gas supply source 12. The gas in the vacuum vessel 2 is evacuated to a predetermined pressure by the exhaust device 13. A second high frequency power supply 14 is connected to the sample stage 5. Thereby, ions in the plasma 6 can be drawn onto the sample 4.

Next, FIG. 2 shows a cross-sectional structure of the sample 4 used in this embodiment. The sample 4 has a silicon substrate (not shown) made of silicon, and a first electrode which is a lower electrode made of a silicon oxide film 25 (SiO ₂ ) and a tantalum film (Ta) sequentially from the bottom on the silicon substrate. Metal film 24, antiferromagnetic exchange bias layer 23, ferromagnetic layer 22, nonmagnetic layer 21 made of ruthenium (Ru) film, first magnetic film 20 that is a magnetization fixed layer, magnesium oxide (MgO ) A metal oxide film 19 which is a tunnel barrier layer made of a film, a second magnetic film 18 which is a magnetization free layer, a second metal film 17 which is an upper electrode made of a tantalum (Ta) film, A hard mask 16 patterned with dimensions is laminated.

The hard mask 16 is made of a silicon oxynitride film (SiON), a silicon nitride film (SiN), an oxide film (SiO ₂ ), or the like. Further, the antiferromagnetic exchange bias layer 23 and the ferromagnetic layer 22
A nonmagnetic layer 21 made of a ruthenium (Ru) film, a first magnetic film 20 that is a magnetization fixed layer, a metal oxide film 19 that is a tunnel barrier layer made of a magnesium oxide (MgO) film, and a magnetization free layer The laminated film up to the second magnetic film 18 is a laminated film constituting a magnetic tunnel junction (MTJ, hereinafter referred to as MTJ), and is hereinafter referred to as an MTJ element constituting film 15.

The antiferromagnetic exchange bias layer 23 is composed of platinum (Pt), manganese (M
n), an alloy containing palladium (Pd), iridium (Ir), and a laminated film.
The ferromagnetic layer 22, the first magnetic film 20, and the second magnetic film 18 are made of cobalt (Co), iron (
It is formed from an alloy film containing at least two types of Fe) and nickel (Ni).

First, an etching method for the second metal film 17 will be described. As shown in Table 1, tetrafluoromethane (CF ₄ ) using a hard mask 16 patterned to a predetermined size as a mask.
The second metal film 17 is etched using a mixed gas of gas and argon (Ar) gas. Here, the source RF power is high-frequency power supplied from the first high-frequency power supply 11 to the antennas 1a and 1b, and the bias RF power is supplied from the second high-frequency power supply 14 to the sample stage 5. This is high-frequency power.

When the second metal film 17 is etched using a mixed gas of chlorine (Cl ₂ ) gas and tetrafluoromethane (CF ₄ ) gas, residual chlorine components adhere to the surface of the sample 4 and moisture in the atmosphere (H ₂ There is a problem that corrosion occurs due to reaction with O), and the necessity of a separate anticorrosion treatment arises. Further, the MTJ element constituting film 15 is etched with a mixed gas containing ammonia (NH ₃ ) gas, but the remaining chlorine molecules (Cl ₂ ) react with hydrogen atoms (H) of the ammonia (NH ₃ ) gas to cause chloride. Hydrogen (HCl) is formed, and there arises a problem that corrosion occurs in peripheral parts of the vacuum vessel 2 and the gas supply source 12. For this reason, the second metal film 17 and the MTJ element constituent film 15 cannot be processed in the same vacuum vessel 2.

On the other hand, in the plasma etching of the present invention, tetrafluoromethane (CF ₄ ) gas and argon (
By using a mixed gas of Ar) gas, even if the second metal film 17 and the MTJ element constituent film 15 are etched in the same vacuum vessel 2, corrosion does not occur, and a vertical shape is obtained as shown in FIG. 3. I was able to get it. Moreover, since the remaining film thickness of the hard mask 16 after the etching of the second metal film 17 affects the etching shape of the MTJ element constituent film 15 to be performed thereafter, the etching of the MTJ element constituent film 15 is taken into consideration. Must be optimized.

  In this embodiment, when the MTJ element constituent film 15 is etched when the residual film thickness of the hard mask 16 is about 70% of the initial hard mask thickness, the MTJ element constituent film 15 is being etched. The generated reaction product did not scatter and adhered to the side wall of the etching pattern, and a desired etching shape could not be obtained. Conversely, when the MTJ element constituent film 15 is etched with the remaining film thickness of the hard mask 16 being about 10%, the second metal film 17 may disappear during the etching of the MTJ element constituent film 15. .

  For this reason, in this embodiment, in order to obtain a desired etching shape after the MTJ element constituent film 15 is etched, the thickness of the remaining film of the hard mask 16 is set to 30% to 40% of the initial hard mask thickness. It is necessary to control so that it becomes%. Therefore, the etching conditions in Table 1 are such that the gas ratio is adjusted and the bias RF power is adjusted so that the etching shape of the second metal film 17 becomes an optimum shape for the subsequent etching of the MTJ element constituent film 15. And the processing time are adjusted.

Next, etching of the MTJ element constituent film 15 will be described. First, as shown in Step 1 of Table 2, a mixed gas of 85 ml / min ammonia (NH ₃ ) gas and 15 ml / min carbon monoxide (CO) gas was used, the processing pressure was 0.3 Pa, and the source RF power was The second magnetic film 18, the metal oxide film 19, the first magnetic film 20, and the nonmagnetic layer with the second metal film 17 as a mask under etching conditions of 2400 W, bias RF power of 1000 W, and processing time of 120 seconds. 21, the ferromagnetic layer 22, and the antiferromagnetic exchange bias layer 23 were etched. Although the MTJ element constituting film 15 is a multilayer film, the second magnetic film 18, the metal oxide film 19, the first magnetic film 20, the nonmagnetic layer 21, the ferromagnetic layer 22, and the antiferromagnetic exchange bias layer 23 are used. Since each layer of was thin, it was etched in a lump.

During the plasma etching in Step 1 of Table 2, on the surface of the sample 4, sputtering with a mixed gas of ammonia (NH ₃ ) gas and carbon monoxide (CO) gas and generation of metal carbonyl by carbon monoxide molecules (CO) occur simultaneously. ing. FIG. 4 shows a cross section of the etched shape after Step 1 treatment in Table 2. At this time, as shown in FIG. 4, the first reaction product 26 is attached to the side walls of the second metal film 17 and the MTJ element constituting film 15.

The plasma etching in Step 1 of Table 2 has a greater contribution to sputtering by a mixed gas of ammonia (NH ₃ ) gas and carbon monoxide (CO) gas than metal carbonyl generation by carbon monoxide molecules (CO). One reaction product 26 is considered that the metal contained in the MTJ element constituting film 15 cannot be converted to metal carbonyl and is deposited on the side wall of the etching pattern.

Next, in step 2 of Table 2, the etching residue and the first reaction product in step 1 are removed. Step 2 of Table 2 reduced the bias RF power from 1000 W to 450 W relative to Step 1 and increased the processing time from 120 seconds to 180 seconds. By reducing the bias RF power, the sputtering of the mixed gas of ammonia (NH ₃ ) gas and carbon monoxide (CO) gas can be reduced, and the generation of metal carbonyl by carbon monoxide molecules (CO) is promoted. Yes.

  Thus, by reducing the sputtering and promoting the generation of metal carbonyl by carbon monoxide molecules (CO), the selectivity between the second metal film 17 and the first metal film 24 that is a tantalum (Ta) film is increased. As a result, the first reaction product 26 could be removed while suppressing the consumption of the second metal film 17 and the first metal film 24. FIG. 5 shows a cross section of the etched shape after step 2 in Table 2. As shown in FIG. 5, the first reaction product 26 could be removed, but a second reaction product 27 different from the first reaction product 26 was deposited on the etching pattern side wall and the flat portion.

  Since this second reaction product could not be removed under the etching conditions in Step 2, it is considered that no metal capable of generating metal carbonyl was contained. Further, the first metal film 24, which is a tantalum (Ta) film, exposed after the MTJ element constituent film 15 is etched cannot form metal carbonyl, so that a mixture of carbon monoxide (CO) gas and ammonia (NH3) gas is mixed. It is non-volatile in the reaction with gas.

Furthermore, when tantalum (Ta) is scattered due to the sputtering effect, the scattered tantalum (Ta
) Reacts with oxygen atoms (O) in the plasma to form tantalum oxide (TaxOy), which is deposited on the sidewall of the etching pattern. From these facts, it is considered that the second reaction product 27 is generally made of tantalum oxide (TaxOy).

  Tantalum oxide (TaxOy) is an insulator. However, as in this embodiment, tantalum (Ta) released into the atmosphere in the vacuum vessel 2 by sputtering is oxidized, and tantalum oxide (TaxOy). When the film is deposited on the sidewall of the etching pattern, the formed tantalum oxide (TaxOy) thin film has many structural defects. For this reason, the formed tantalum oxide (TaxOy) thin film does not necessarily have sufficient insulation. Therefore, when the second reaction product 27 is deposited on the etching pattern, particularly on the side wall of the MTJ element constituting film 15, an electrical short can occur between the second magnetic film 18 and the first magnetic film 20. There is sex.

Therefore, in order to remove the second reaction product 27, plasma etching using a mixed gas of hydrogen (H ₂ ) gas and argon (Ar) gas was performed as shown in Step 3 of Table 2. . Note that the plasma between step 2 and step 3 in Table 2 continued from step 2 to step 3 without interruption. As shown in FIG. 6, the second reaction product 27 could be removed by performing the process of step 3. This is considered as follows.

The tantalum oxide (TaxOy) that is the main component of the second reaction product 27 is reduced by the hydrogen atoms (H) contained in the plasma by the mixed gas of hydrogen (H ₂ ) gas and argon (Ar) gas, Tantalum (Ta) and water molecules (H ₂ O) are generated and water molecules (H ₂ O) are exhausted. On the other hand, tantalum (Ta) generated by the reduction reaction of hydrogen atoms (H) to tantalum oxide (TaxOy) is sputtered by argon atoms (Ar) in the plasma and exhausted while being scattered in the vacuum vessel 2. . Therefore, it is considered that the second reaction product 27 can be removed by etching with a mixed gas of hydrogen (H ₂ ) gas and argon (Ar) gas.

The gas flow ratio of hydrogen (H ₂ ) gas to the mixed gas of hydrogen (H ₂ ) gas and argon (Ar) gas and the bias RF power were determined for the following reasons. FIG. 7 is a diagram showing the film thickness dependence of the second reaction product 27 in the gas flow rate ratio of hydrogen (H ₂ ) gas to the mixed gas of hydrogen (H ₂ ) gas and argon (Ar) gas. As can be seen from FIG. 7, hydrogen (
H ₂ ) Gas flow rate is 70 ml / min, Argon (Ar) gas flow rate is 30 ml / min
In this case, the film thickness of the second reaction product 27 was 0 nm.

Therefore, the flow rate of hydrogen (H ₂ ) gas and the flow rate of argon (Ar) gas in Step 3 of Table 2 were set to 70 ml / min and 30 ml / min, respectively. When the flow ratio of hydrogen (H ₂ ) gas to argon (Ar) gas is 1: 1 (the gas flow rate is 50 ml / min each),
There is a possibility that the same effect as in this embodiment may be obtained by adjusting the bias RF power and the etching time.

  Next, FIG. 8 is a diagram showing the dependence of the bias RF power on the film thickness of the second reaction product 27. The film thickness of the deposited second reaction product 27 decreases as the bias RF power increases. However, the second reaction product 27 was not deposited at the bias RF power of 1350 W. For this reason, the bias RF power in Step 3 of Table 2 was set to 1350 W.

In the present invention, the plasma is continued during the transition from step 2 to step 3 in Table 2. When changing the type of gas while continuing the plasma, there is a concern about plasma instability or disappearance of the plasma between steps. Although not occurring in the present embodiment, for these concerns, a gas replacement step is inserted, for example, for about 3 seconds before etching the mixed gas of hydrogen (H ₂ ) gas and argon (Ar) gas. It is possible to take measures.

For example, after etching with a mixed gas of ammonia (NH ₃ ) gas and carbon monoxide (CO) gas, a step of plasma etching with a mixed gas of ammonia (NH ₃ ) gas and argon (Ar) gas is performed as a gas replacement step. Then, plasma etching is performed with a mixed gas of hydrogen (H ₂ ) gas and argon (Ar) gas. At this time, in order to reduce the influence of the gas replacement step on the etched pattern shape after etching, it is desirable to reduce the bias RF power in the gas replacement step (for example, 50 W).

  Further, when the process of step 3 is not performed, the second reaction product deposited on the second metal film 17 has a thickness of 5 nm, and the second reaction product deposited on the side wall of the MTJ element constituting film 15. The film thickness of the second reaction product deposited on the first metal film 24 was 6.6 nm. However, when the process of step 3 was performed, the film was formed on the second metal film 17. The thickness of the deposited second reaction product is 1.5 nm, the presence or absence of the second reaction product deposited on the side wall of the MTJ element constituting film 15, and the second reaction product deposited on the first metal film 24. The film thickness of the reaction product was 0 nm.

  Thus, about the etching pattern shape after an etching, in this invention, the quantity of the reaction product is reduced by etching step 3 of Table 2. FIG. In particular, since there is no deposition of the second reaction product 27 on the side wall of the MTJ element constituting film 15, an electrical short circuit between the second magnetic film 18 and the first magnetic film 20 is prevented, and a good magnetoresistance effect is achieved. Can be obtained. However, when the second reaction product 27 does not cause an electrical short circuit or when the second reaction product 27 can be removed by a manufacturing process other than etching, step 3 in Table 2 is not necessarily required as the present invention. Absent.

As described above, by using the present invention, even after etching using a mixed gas of ammonia (NH ₃ ) gas and carbon monoxide (CO) gas, the metal oxide on the side wall and the flat portion of the etching pattern is a main component. The deposition of reaction products can be reduced.

In Step 1 and Step 2 of Table 2 in this example, a mixed gas of ammonia (NH ₃ ) gas and carbon monoxide (CO) gas was used. However, the present invention generates metal carbonyl. Since the gas can be any gas, a mixed gas containing carbon monoxide (CO) gas may be used. Further, in Step 3 of Table 2 in this embodiment, an example using a mixed gas of hydrogen (H ₂ ) gas and argon (Ar) gas has been described. However, the present invention is not limited to argon gas, but helium gas, An inert gas such as nitrogen gas, xenon gas, or krypton gas may be used.

In this embodiment, the tantalum film (Ta) is used for the upper electrode and the lower electrode. However, the present invention may be any metal film or alloy film containing at least a tantalum (Ta) element. Furthermore, although a magnesium oxide (MgO) film is used for the tunnel barrier layer in this embodiment, a metal oxide film exhibiting insulating properties, for example, an aluminum oxide (Al ₂ O ₃ ) film may be used. Further, in the present embodiment, the example of the MTJ element structure in which the magnetization free layer is disposed above the magnetization fixed layer has been described. However, in the present invention, the MTJ element in which the magnetization fixed layer is disposed above the magnetization free layer is described. Structure may be sufficient.

  In addition, the MTJ element structure of this example was a structure provided with a magnetization free layer, a tunnel barrier layer, a magnetization fixed layer, a nonmagnetic layer, a ferromagnetic layer, and an antiferromagnetic exchange bias layer. The MTJ element structure according to the present invention may be a structure including a magnetization free layer, a tunnel barrier layer, and a magnetization fixed layer. Further, with respect to the etching time, a light emission monitoring device may be provided in the vacuum vessel 2 and the etching time of the upper electrode and the MTJ element constituting film 15 may be controlled using the light emission monitoring device.

  Further, in the above-described embodiment, the example using the plasma etching apparatus of the inductively coupled plasma source has been described. However, the present invention is not limited thereto, and the microwave Electrocyclotron Resonance (ECR) plasma etching apparatus, the capacitively coupled plasma source is used. A plasma etching apparatus or a helicon type plasma etching apparatus may be used.

DESCRIPTION OF SYMBOLS 1a 1st antenna 1b 2nd antenna 2 Vacuum vessel 3 Berja 4 Sample 5 Sample stand 6 Plasma 7 Sample holding part 8 Cover 9 Faraday shield 10 Matching device 11 First high frequency power source 12 Gas supply source 13 Exhaust device 14 Second High-frequency power source 15 MTJ element constituent film 16 Hard mask 17 Second metal film 18 Second magnetic film 19 Metal oxide film 20 First magnetic film 21 Nonmagnetic layer 22 Ferromagnetic layer 23 Antiferromagnetic exchange bias layer 24 One metal film 25 Silicon oxide film 26 First reaction product 27 Second reaction product

The present invention includes a first magnetic film, a second magnetic film disposed above the first magnetic film, and a metal disposed between the first magnetic film and the second magnetic film. and oxide film, the second and the second metal film disposed over the magnetic film, plasma etching is plasma etching a sample having a first metal layer disposed below the first magnetic film In the method, a first step of etching the first magnetic film, the metal oxide film, and the second magnetic film using a carbon monoxide gas, and a hydrogen gas and an inert gas after the first step. And a second step of removing a reaction product on the side wall of the etching pattern using the mixed gas, wherein the first metal film is a film containing tantalum.

Claims (8)

A first magnetic film, a second magnetic film disposed above the first magnetic film, a metal oxide film disposed between the first magnetic film and the second magnetic film, In a plasma etching method of plasma etching a sample having a second metal film disposed above the second magnetic film and a first metal film disposed below the first magnetic film,
A first step of etching the first magnetic film, the metal oxide film, and the second magnetic film using carbon monoxide gas;
After the first step, the second step of removing reactive organisms on the etching pattern sidewall using a mixed gas of hydrogen gas and inert gas,
The plasma etching method, wherein the first metal film is a film containing tantalum. The plasma etching method according to claim 1, wherein
The plasma etching method, wherein the second step is performed while supplying high frequency power to a sample stage on which the sample is placed. The plasma etching method according to claim 1, wherein
The first step is performed while supplying a first high-frequency power to a sample stage on which the sample is placed,
The second step is performed while second high frequency power is supplied to the sample stage,
The plasma etching method, wherein the second high frequency power is larger than the first high frequency power. In the plasma etching method according to claim 2 or 3,
The first step includes a first etching step and a second etching step performed after the first etching step,
The high frequency power supplied to the sample stage on which the sample is placed in the second etching step is smaller than the high frequency power supplied to the sample stage on which the sample is placed in the first etching step. A plasma etching method. In the plasma etching method according to any one of claims 2 to 4,
The plasma etching method, wherein a flow rate of the hydrogen gas is larger than a flow rate of the inert gas. In the plasma etching method according to any one of claims 2 to 4,
The first step further uses ammonia gas,
The second metal film is a film containing tantalum,
The plasma etching method, wherein the inert gas is an argon gas. The plasma etching method according to claim 4, wherein
The plasma etching method, wherein a processing time of the second etching step is longer than a processing time of the first etching step. The plasma etching method according to claim 6, wherein
The plasma etching method further comprising the step of etching the second metal film using a mixed gas of tetrafluoromethane gas and argon gas before the first step.

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