JP5288555B2 - Inductively coupled plasma processing apparatus and plasma etching method - Google Patents

Description

  The present invention relates to an inductively coupled plasma processing apparatus that performs various plasma processes such as etching and ashing on a substrate.

  In recent years, in order to manufacture a high-speed and low-power consumption device, an SOI substrate in which single crystal Si is formed on SiO 2 that is an insulating film may be used instead of the Si substrate. However, in the SOI substrate, when the Si layer is etched by plasma etching, lateral etching called “notch” (or “notching”) occurs at the boundary between the Si layer and the SiO 2 layer, and the vertical shape However, there is a problem that it cannot be processed (see FIG. 10). The notch is more prominent when a fine pattern having a narrow aspect ratio and a very large aspect ratio is formed in the Si layer.

Notches are thought to occur for the following reasons.
When plasma is generated above the lower electrode disposed in the processing chamber of the plasma processing apparatus and high frequency power is applied to the lower electrode, a potential difference is generated between the plasma and the lower electrode, and an ion sheath electric field in a direction perpendicular to the lower electrode is generated. Arise. Then, positive ions in the plasma are accelerated toward the surface of the SOI substrate by the ion sheath electric field, and the Si layer is etched.

  On the other hand, since electrons in the plasma are not accelerated by the ion sheath electric field, they do not have directionality and enter the fine pattern of the Si layer and collide with the side walls. At this time, when the Si layer is etched, positive ions incident on the bottom surface of the fine pattern and electrons colliding with the side wall of the fine pattern are recombined and neutralized in the Si layer. Is preserved. However, when the etching progresses and reaches the insulating SiO2 layer, the positive ions incident on the bottom surface of the fine pattern are not neutralized with the electrons colliding with the side wall of the fine pattern, and the bottom surface of the fine pattern is positively charged up. Therefore, the trajectory of positive ions incident on the bottom surface of the fine pattern is bent by repulsion due to the positive charges accumulated on the bottom surface of the fine pattern. Therefore, lateral etching occurs at the boundary between the Si layer and the SiO 2 layer, and a notch having a notch shape is generated.

  The problem of notches is not particularly problematic as long as the intervals between the masks provided on the surface of the SOI substrate (intervals between the portions to be etched) are the same. This is because all the parts to be etched are etched at substantially the same speed and reach the SiO 2 layer. However, in a normal device manufacturing process, etched portions with various intervals are mixed on the surface of the SOI substrate, and the etching rate differs for each etched portion. Since it is necessary to continue the etching process until the etched portion having a slow etching rate (usually, the etched portion having a narrow mask interval) reaches the SiO 2 layer, the etched portion having the SiO 2 layer already formed (usually the mask interval is Overetching occurs in a wide portion to be etched), and a notch is generated.

In order to prevent the occurrence of notches, several methods have been proposed in the past. For example, Patent Document 1 describes a method in which a high frequency power applied to a lower electrode is pulsed so that a part of electrons incident on the fine pattern is drawn into the bottom surface of the fine pattern and neutralized with ions. .
Further, as a method for creating a fine pattern with a narrow portion to be etched and a very large aspect ratio, a method of performing etching while forming a fluorine-based polymer film on the side wall is often used. In such a method, in order to draw electrons into the deep bottom surface of the fine pattern, low frequency power is used as power applied to the lower electrode (Patent Document 2), or high frequency power is pulsed (Patent Documents 2 and 3). It has been proposed to modulate high-frequency power (Patent Document 4), or pulse high-frequency power and further modulate low-frequency power (Patent Document 5). However, none of these methods has achieved a sufficient effect.

Japanese Patent Laid-Open No. 06-061182 Special Table 2002-529913 Japanese Unexamined Patent Publication No. 08-250479 Special table 2007-509506 Special Table 2003-515925

  The problem to be solved by the present invention is to provide an inductively coupled plasma processing apparatus capable of preventing the generation of notches as much as possible when etching a fine pattern on a processing substrate.

An inductively coupled plasma processing apparatus according to the present invention, which has been made to solve the above problems,
a) a processing chamber;
b) a lower electrode disposed in the processing chamber and on which a processing substrate is placed;
c) gas introduction means for introducing a reactive gas into the processing chamber;
d) an inductive coupling coil disposed outside the processing chamber and generating plasma by exciting a reactive gas in the processing chamber;
e) an oxygen gas introduction pipe for introducing oxygen gas into the processing chamber, and an apparatus for plasma processing a processing substrate with the plasma,
The substrate is a SOI substrate which have a structure in which conductive layers are formed on the insulating layer,
A first high-frequency power source that oscillates high-frequency power having a first frequency of 10 to 800 kHz;
A second high frequency power source that oscillates high frequency power of a second frequency of 10 to 60 MHz higher than the first frequency;
High-frequency power application means for applying, to the lower electrode, superimposed high-frequency power obtained by superimposing high-frequency power oscillated from the second high-frequency power source on high-frequency power oscillated from the first high-frequency power source;
A film forming step of forming an insulating thin film on the side and bottom surfaces of the fine pattern of the processing substrate; and an etching step of removing the insulating thin film formed on the bottom surface of the fine pattern of the processing substrate and etching the conductive layer. Etching means that repeats alternately, and
The etching step includes a first etching step for removing the insulating thin film and a second etching step for etching the insulating layer, and the high-frequency power application means applies the superimposed high-frequency power to the lower portion in the first etching step. Applying to the electrode.

  In the inductively coupled plasma processing apparatus of the present invention, a high frequency power is applied to an inductively coupled coil provided outside the processing chamber, thereby exciting the gas in the processing chamber through the dielectric. For example, the processing chamber is made of aluminum, a plate-like dielectric (quartz plate) is disposed above the processing chamber, and an inductive coupling coil is placed on the dielectric, and the dielectric is cylindrical. And the structure which has arrange | positioned the inductive coupling coil so that the exterior of a dielectric material may be mentioned. In the cylindrical dielectric, it is preferable that the Faraday shield and the dielectric are integrally formed from the viewpoint of excellent spatter prevention and cooling performance.

The substrate processed by the inductively coupled plasma processing apparatus of the present invention is particularly preferably a substrate having a structure in which a conductive layer is formed on an insulating layer. For example, an SOI substrate in which single crystal Si is formed on SiO2 that is an insulating layer can be given. Further, a mask having an opening is provided on the Si surface so that a plurality of portions to be etched are formed. The substrate is placed on a lower electrode disposed in a processing chamber, and a region to be etched is plasma-processed to form a fine pattern.
The lower electrode is preferably capable of adjusting the distance between the plasma generation region and the lower electrode in that the incident amount of ions can be adjusted. For example, the lower electrode may be configured to be movable up and down.

  In the plasma processing apparatus of the present invention, plasma is generated in the processing chamber using an inductive coupling coil provided outside the processing chamber, so that high-density plasma is generated even under a high vacuum as compared with a parallel plate type plasma processing apparatus. be able to. For this reason, it is suitable as a plasma processing apparatus that generates high-density plasma while alternately repeating the film forming process and the etching process to perform an etching process with a high aspect ratio. An example of a gas used in the film forming process is C4F8. An example of the gas used in the etching process is SF6.

  The film forming process is a process of protecting the side surface and the bottom surface of the fine pattern with an insulating CF film in order to perform high aspect ratio etching on the SOI substrate. Although the thickness of the CF-type film on the side surface of the fine pattern varies depending on the depth of the fine pattern, it is about 10 nm to 1 μm, and electrons flow through the CF-type film to the Si layer. For this reason, it is not necessary to consider the influence of charging by electrons.

  The etching process preferably includes at least a first etching process for removing the film (CF film) at the bottom of the fine pattern covered in the film forming process and a second etching process for etching the Si layer. When all the bottoms of the fine pattern are in the Si layer, the charge-up of the bottom of the fine pattern is hardly a problem. Therefore, in the first etching process, the high frequency power applied to the lower electrode is either superposition high frequency power or normal high frequency power. But you can. In the second etching step, it is not essential to apply superposed high-frequency power or normal high-frequency power to the lower electrode, and etching of the Si layer at the bottom of the fine pattern proceeds.

  When any one of the fine pattern bottoms reaches the SiO2 layer or just before the SiO2 layer, the superimposed high-frequency power is applied to the lower electrode. At least in the first etching process, superimposed high frequency power is applied to the lower electrode in order to remove the CF-based film at the bottom of the fine pattern without being charged up with ions. In the second etching step, it is not essential to apply high-frequency power to the lower electrode. Etching does not proceed at the bottom of the fine pattern that has already reached the SiO 2 layer, and etching proceeds at the bottom of the fine pattern that has not yet reached the SiO 2 layer. To do. Further, it is preferable to apply pulsed superimposed high frequency power to the lower electrode in terms of higher notch prevention effect.

  In addition, oxygen gas is preferably introduced into the treatment chamber in both the etching process and the film formation process. By doing so, it is possible to prevent precipitation of by-products such as sulfur and carbon generated in the processing chamber.

  In the inductively coupled plasma processing apparatus of the present invention, by applying superimposed high frequency power to the lower electrode, ions can be drawn into the fine pattern when the fine pattern is etched on the processing substrate, thereby preventing the occurrence of notches. be able to.

1 is an overall schematic configuration diagram of an inductively coupled plasma processing apparatus according to an embodiment of the present invention. The figure which shows the gas introduction path | route and gas discharge path | route of a process chamber. The figure which shows an example of the standard waveform of superposition high frequency electric power. The figure which shows an example of the waveform of superposition high frequency electric power. The figure which shows the shape of the notch which arises in the bottom part of a fine pattern when etching an SOI substrate. The table | surface which shows the incision distance of the horizontal direction of a notch.

  An inductively coupled plasma processing apparatus according to an embodiment of the present invention will be described with reference to the drawings. As shown in FIGS. 1 and 2, the plasma processing apparatus 1 of the present embodiment is provided with a processing chamber 2 and an inductive coupling coil 4 provided in the upper portion of the processing chamber 2 for generating plasma in the processing chamber 2. And. A lower electrode 6 is provided in the processing chamber 2.

The lower electrode 6 is provided with an electrostatic chuck 8, and a processing substrate such as an SOI substrate placed on the lower electrode 6 is attracted and held by the electrostatic chuck 8.
A refrigerant circulation pipe 10 is disposed in the lower electrode 6. A heat transfer gas supply pipe 12 that supplies heat transfer gas to the electrostatic chuck 8 is disposed in the lower electrode 6. The processing substrate disposed on the lower electrode 6 is maintained at a predetermined temperature (for example, 25 ° C.) by the refrigerant circulating through the refrigerant circulation pipe 10 and the heat transfer gas (for example, helium gas) supplied through the heat transfer gas supply pipe 12. The

An etching gas (for example, SF6), a film forming gas (C4F8), and an oxygen gas are respectively introduced into the processing chamber 2 through gas introduction pipes 14, 16, and 18. Mass flow controllers 141 and 161 and three-way valves 142 and 162 are provided in the introduction pipes 14 and 16 for the etching gas and the film forming gas. The oxygen gas introduction pipe 18 is provided with a mass flow controller 181 and a three-way valve 182. The processing chamber 2 is provided with a load lock chamber 20. Pipes 24, 26 and 27 connected to the exhaust pipe 22 of the load lock chamber 20 are connected to the three-way valves 142, 162 and 182 of the gas introduction pipes 14, 16 and 18. Such a piping system is illustrated in FIG. 15 of JP-A-60-50923.
Further, a vacuum pump 30 and a vacuum pump 31 are provided in the exhaust pipe 28 of the processing chamber 2 and the exhaust pipe 22 of the load lock chamber 20, respectively. The inside of the processing chamber 2 is maintained in a predetermined reduced pressure atmosphere by the vacuum pump 30. The inside of the load lock chamber 20 is maintained in a predetermined reduced pressure atmosphere by the vacuum pump 31, and gas that has not been introduced into the processing chamber 2 is discharged by the three-way valve 142 or 162.

  A cylindrical dielectric 32, a Faraday shield 34 integrally formed on the outer peripheral surface of the dielectric 32, and an inductive coupling coil 4 wound around the outer periphery of the Faraday shield 34 are disposed at the upper portion of the processing chamber 2. Yes. A high frequency power supply 38 is connected to the inductive coupling coil 4 via a matching unit (matching box) 37. The Faraday shield 34 is provided with a cut so that the Faraday shield 34 does not go around the outer periphery of the dielectric 32. As a result, a current opposite to the current flowing through the inductive coupling coil 4 does not flow through the Faraday shield 34.

A superimposed high frequency power supply device 40 is connected to the lower electrode 6. The superposition high frequency power supply device 40 applies superposition high frequency power to the lower electrode 6, and includes a first high frequency power source 42 that oscillates a high frequency power of a first frequency, and a high frequency power of a second frequency higher than the first frequency. And a second high frequency power supply 44 that oscillates. In the following description, the high frequency power oscillated by the first high frequency power supply 42 is referred to as “low frequency power”.
The first and second high frequency power sources 42 and 44 can oscillate high frequency power at a predetermined interval (pulse) in accordance with the output signal of the pulse signal device 46. The first high frequency power source 42 is connected to the lower electrode 6 via a matching unit 48, a filter 50, and an adder 51. The second high frequency power supply 44 is connected to the adder 51 through a matching unit 52. As a result, the superimposed high frequency power obtained by superimposing the high frequency power from the second high frequency power supply 44 on the low frequency power from the first high frequency power supply 42 is applied to the lower electrode 6.
The driving of the mass flow controllers 141, 161, 181, valves 142, 162, 182, pulse signal machine 46, adder 51, vacuum pump 30 and the like is controlled by a control device (not shown).

Next, a process for forming a fine pattern by etching the Si layer of the SOI substrate using the inductively coupled plasma processing apparatus 1 will be described. The SOI substrate is obtained by forming single crystal Si on an insulating SiO 2 layer.
First, prior to the start of the etching process, the inside of the processing chamber 2 is maintained at a predetermined reduced pressure atmosphere, for example, 20 mTorr by the vacuum pump 30.
In this state, the etching process is started, and SF 6 as an etching gas is introduced into the processing chamber 2 from the etching gas supply source through the gas introduction pipe 14. Further, oxygen gas is introduced into the processing chamber 2 from the oxygen gas supply source through the gas introduction pipe 18.
In the etching step, the outlet position of the three-way valve 162 is adjusted so that the film forming gas supplied from the film forming gas supply source to the gas introduction pipe 14 is discharged to the exhaust pipe 22 of the load lock chamber 20. .
For example, high frequency power of 13.56 MHz is applied to the inductive coupling coil 4. As a result, the SF 6 in the processing chamber 2 enters a plasma state, and the Si layer is etched.

After the etching process is performed for a predetermined time, a film forming process is performed next.
In the film forming process, the three-way valve 142 of the etching gas introduction pipe 14 is switched, and SF 6 is discharged to the exhaust pipe 22 of the load lock chamber 20. At the same time, the three-way valve 162 of the film forming gas introduction pipe 16 is switched, and the film forming gas C4F8 is introduced into the processing chamber 2. Further, oxygen gas is introduced into the processing chamber 2 from the oxygen gas supply source through the gas introduction pipe 18. Note that, in synchronization with the introduction of the film forming gas, the residual gas from the etching process is discharged from the processing chamber 2.
As a result, the film forming gas is turned into plasma by the inductive coupling coil 4, and the CF-based polymer that functions as a protective film is polymerized on the side wall and bottom surface of the fine pattern.

The etching process and the film forming process are repeated alternately until the fine pattern reaches the boundary between the Si layer and the SiO 2 layer of the SOI substrate.
The oxygen gas continuously introduced into the processing chamber 2 during the etching process and the film forming process has a function of removing the protective film formed on the bottom surface of the fine pattern in the film forming process. Oxygen gas also contributes to the removal of sulfur and carbon. Therefore, by introducing oxygen gas, the protective film on the bottom surface of the fine pattern can be quickly removed and etched in the vertical direction in the etching process performed after the film forming process.

  The etching process performed after the film forming process includes a first etching process for strongly drawing ions into the fine pattern and removing the protective film on the bottom surface, and a second etching process for etching the Si layer. Divided.

  In the first etching step, the superimposed high frequency power is applied to the lower electrode 6 from the superimposed high frequency power supply device 40. On the other hand, in the second etching process, the application of the superimposed high frequency power to the lower electrode 6 is stopped. In the film forming process, it is not necessary to draw ions contributing to etching (SF6 ions) into the bottom surface of the fine pattern. Therefore, the superimposed high frequency power may not be applied to the lower electrode 6.

Next, a method for applying superimposed high frequency power to the lower electrode 6 will be described.
For example, a low frequency power of 400 kHz sine wave is output from the first high frequency power source 42 and introduced into the filter via a matching unit. The low frequency power component of the superimposed high frequency power plays a role of drawing electrons vertically into the fine pattern. The sine wave frequency of the low frequency power is preferably 10 to 800 kHz. When the frequency of the low frequency power is out of this range, the effect of drawing electrons tends to be reduced. The electrons drawn here are derived from electrons generated in the plasma and electrons generated by a high-frequency power component included in the superimposed high-frequency power. That is, since the superimposed high frequency power includes a high frequency power component, it is possible to generate electrons efficiently and sufficiently.

  On the other hand, high frequency power of 13.56 MHz, for example, is output from the second high frequency power supply 44 and introduced to the output side of the filter via a matching unit. The high frequency power is preferably a sine wave because it is easy to adjust the matching with the low frequency power. The high frequency power component of the superimposed high frequency power plays a role of generating electrons. The sine wave frequency of the high frequency power is preferably 10 to 60 MHz. If the frequency of the high-frequency power deviates from this range, ions are less likely to enter the fine pattern and the etching rate tends to decrease.

  The ratio of the power of the high frequency power component (second high frequency power) to the power of the low frequency power component (high frequency power of the first frequency) of the superimposed high frequency power is preferably 1: 0.5 to 1: 100. If the power ratio is out of this range, the effect of drawing electrons into the fine pattern tends to decrease, or the effect of efficiently generating electrons tends to decrease. FIG. 3 shows an example of superimposed high frequency power in which the ratio of the power of the high frequency power component to the power of the low frequency power component is 1: 0.5.

  In addition, high-frequency power components (such as 13.56 MHz) are once subjected to amplitude modulation at low frequencies, and superimposed high-frequency power is obtained by superimposing low-frequency power components (such as 400 kHz) on this amplitude-modulated high-frequency power. It is also possible. Here, it is preferable that the low frequency which modulates an amplitude to a high frequency electric power component is a frequency lower than a low frequency electric power component. For example, if the low frequency power component is 400 kHz, the frequency for performing amplitude modulation on the high frequency power component is preferably 200 kHz.

  FIG. 4 shows superimposed high-frequency power on which pulsed high-frequency power obtained by applying a pulse signal (pulse ON: 500 μsec, pulse OFF: 1500 μsec) with the same phase to the first high-frequency power supply and the second high-frequency power supply is superimposed. An example of power is shown.

Next, it occurs at the bottom of the fine pattern (the boundary between SiO2 and Si) when the SOI substrate (8 inches) is actually etched using an inductively coupled plasma processing apparatus (RIE-800iPB) manufactured by Samco Corporation. The state of occurrence of a notch was examined.
In this inductively coupled plasma processing apparatus, the processing chamber is made of aluminum, and a plasma generation chamber made of a cylindrical dielectric is provided above the lower electrode. A single winding inductive coupling coil is provided around the dielectric, and a high frequency power source (13.56 MHz) is connected to the inductive coupling coil. Further, the lower electrode is movable in the vertical direction, and the distance between the inductive coupling coil and the lower electrode can be adjusted.
In the SOI substrate, a Si layer having a thickness of 60 μm is laminated on a SiO 2 layer, and a photoresist is provided on the surface of the Si layer. In this photoresist, slits (etched portions) having a width of 3 μm are provided at equal intervals.

[Example 1]
Superimposing a high frequency power (40 W) with a first frequency of 400 kHz oscillated from the first high frequency power supply and a high frequency power (20 W) with a second frequency of 13.56 MHz oscillated from the second high frequency power supply on the lower electrode. The superimposed high frequency power obtained by the above was applied.
Next, SF6 (flow rate 100 sccm) and oxygen gas (flow rate 10 sccm) are introduced into the plasma generation chamber for 4 seconds to perform etching (superimposed high-frequency power is applied to the lower electrode only for the first 2 seconds), and C4F8. Etching was carried out by alternately repeating the steps of forming a film by introducing (flow rate 100 sccm) and oxygen gas (flow rate 10 sccm) into the plasma generation chamber for 2 seconds. In addition to the time required for reaching the SiO2 layer (10 minutes), the etching process was further performed for 5 minutes with the same conditions. After completion of the etching, the shape of the notch formed at the bottom of the fine pattern was observed with an electron microscope to measure the lateral cut distance. Here, the notch distance in the horizontal direction of the notch means the length indicated by the symbol L in FIG.

[Example 2]
Superimposed high-frequency power superimposed on pulsed high-frequency power obtained by applying a pulse signal (pulse ON: 500 μsec, pulse OFF: 1500 μsec) with the same phase to the first high-frequency power supply and the second high-frequency power supply Plasma etching was performed in the same manner as in Example 1 except that the above was applied. After completion of the etching, the shape of the notch formed at the bottom of the fine pattern was observed with an electron microscope to measure the lateral cut distance.

[Comparative Example 1]
Plasma etching was performed in the same manner as in Example 1 except that only the high frequency power (13.56 MHz) oscillated from the second high frequency power source was applied to the lower electrode. After completion of the etching, the shape of the notch formed at the bottom of the fine pattern was observed with an electron microscope, and the lateral cut distance was measured in the same manner as in Example 1.

[Comparative Example 2]
Plasma etching was performed in the same manner as in Example 1 except that only the high frequency power (400 kHz) oscillated from the first high frequency power source was applied to the lower electrode. After completion of the etching, the shape of the notch formed at the bottom of the fine pattern was observed with an electron microscope, and the lateral cut distance was measured in the same manner as in Example 1.

[Comparative Example 3]
Except that pulsed high frequency power obtained by applying a pulse signal (pulse ON: 500 μsec, pulse OFF: 1500 μsec) to the high frequency power source of Comparative Example 1 was applied to the lower electrode in the same manner as in Example 1. Plasma etching was performed. After completion of the etching, the shape of the notch formed at the bottom of the fine pattern was observed with an electron microscope, and the lateral cut distance was measured in the same manner as in Example 1.

FIG. 6 shows the horizontal cut distance measured in Examples 1 and 2 and Comparative Examples 1 to 3.

DESCRIPTION OF SYMBOLS 1 ... Inductively coupled plasma processing apparatus 2 ... Processing chamber 4 ... Inductive coupling coil 6 ... Lower electrode 8 ... Electrostatic chucks 14, 16, 18 ... Gas introduction pipe 40 ... Superposition high frequency electric power supply apparatus 42 ... First high frequency power supply 44 ... First 2 high frequency power supply

Claims (3)

a) a processing chamber;
b) a lower electrode disposed in the processing chamber and on which a processing substrate is placed;
c) gas introduction means for introducing a reactive gas into the processing chamber;
d) an inductive coupling coil disposed outside the processing chamber and generating plasma by exciting a reactive gas in the processing chamber;
e) In an inductively coupled plasma processing apparatus comprising: an oxygen gas introduction pipe for introducing oxygen gas into the processing chamber, wherein the processing substrate is plasma-processed by the plasma;
The substrate is a SOI substrate which have a structure in which conductive layers are formed on the insulating layer,
A first high-frequency power source that oscillates high-frequency power having a first frequency of 10 to 800 kHz;
A second high frequency power source that oscillates high frequency power of a second frequency of 10 to 60 MHz higher than the first frequency;
High-frequency power application means for applying, to the lower electrode, superimposed high-frequency power obtained by superimposing high-frequency power oscillated from the second high-frequency power source on high-frequency power oscillated from the first high-frequency power source;
A film forming step of forming an insulating thin film on the side and bottom surfaces of the fine pattern of the processing substrate; and an etching step of removing the insulating thin film formed on the bottom surface of the fine pattern of the processing substrate and etching the conductive layer. Etching means that repeats alternately, and
The etching step includes a first etching step for removing the insulating thin film and a second etching step for etching the insulating layer, and the high-frequency power application means applies the superimposed high-frequency power to the lower portion in the first etching step. An inductively coupled plasma processing apparatus characterized by being applied to an electrode.   The inductively coupled plasma processing apparatus according to claim 1, wherein a pulse signal is applied to at least one high-frequency power source. A method of plasma etching a processing substrate, which is an SOI substrate mounted on a lower electrode in a processing chamber and having a structure in which a conductive layer is formed on an insulating layer,
A film forming step for forming an insulating thin film on the side and bottom surfaces of the fine pattern of the processing substrate; and an etching step for removing the insulating thin film formed on the bottom surface of the fine pattern on the processing substrate and etching the conductive layer. And
The etching step includes a first etching step for removing the insulating thin film and a second etching step for etching the insulating layer,
In the first etching step, a superimposed high frequency power in which a high frequency power having a first frequency of 10 to 800 kHz and a high frequency power having a second frequency of 10 to 60 MHz higher than the first frequency are applied to the lower electrode. A plasma etching method comprising:

Images