JP2010199310A - Plasma etching method - Google Patents

Abstract

An object of the present invention is to provide a plasma etching method capable of suppressing abnormal discharge of plasma.
Plasma discharge for introducing a first gas, which is less likely to excite plasma than a second gas described later, into a chamber having a flat first electrode and a second electrode facing each other in parallel. Simultaneously with or immediately after the preparation step and the plasma discharge preparation step, a second gas for plasma excitation is introduced into the chamber 10, and the plasma is discharged between the discharge surfaces of the first electrode 11 and the second electrode 12 via the second gas. Including a plasma discharge starting step for discharging, and an etching step for treating the substrate between the first and second electrodes by introducing an etching gas after the plasma discharging starting step or cleaning the inside of the chamber 10. A plasma etching method.
[Selection] Figure 1

Description

  The present invention relates to a plasma etching method using a plasma processing apparatus.

Conventionally, plasma processing apparatuses are used in the manufacture of semiconductor devices, liquid crystal display devices, thin film solar cells, and the like.
As shown in FIG. 4, the plasma processing apparatus introduces a reactive gas into a chamber 10 in which a pair of a cathode electrode 11 and an anode electrode 12 is provided, and controls the pressure provided in an exhaust system 20 of the chamber 10. A substrate supported by the cathode electrode 11 or the anode electrode 11 (not shown) by adjusting the gas pressure in the chamber 10 by the controller 21 and applying a high voltage between the electrodes 11 and 12 to generate plasma. A semiconductor film can be formed thereon using a CVD process, or the surface of a semiconductor substrate (not shown) can be etched (see, for example, Patent Document 1).
4 exemplifies a plasma CVD apparatus, reference numeral 13 is an electrode support member, E is a high-frequency power source, 30 is a power supply cable, 31 is a power terminal, 22 is a vacuum pump, 23 is an exhaust pipe, 40 is a grounding member, 50 denotes a gas supply pipe, 51 denotes a valve, 52 denotes a film forming source gas supply source, 53 denotes a cleaning gas supply source, and 54 denotes an argon gas supply source.

In a CVD process using a plasma CVD apparatus, a film-like or powdery deposit (product) which is originally unnecessary adheres to the discharge surface of the cathode electrode 11, and such a deposit is deposited in the semiconductor film during the CVD process. If it is mixed in, the rate of non-defective products and quality defects will be caused.
Therefore, after the CVD process, the inside of the chamber 10 is cleaned to remove deposits. For example, dry cleaning is performed by introducing a fluorine-based gas such as C ₂ F ₆ , CF ₄ , SF ₆ , or NF ₃ into the chamber 10 from the cleaning gas supply source 53 and converting the cleaning gas into plasma.

FIG. 5 shows a time chart of a conventional plasma cleaning method.
As shown in FIGS. 4 and 5, in the conventional plasma cleaning method, in order to make the cleaning gas made of a fluorine-based compound into plasma, first, only argon (for example, from the argon gas supply source 54 into the chamber 10) , 15 SLM) A plasma is ignited between the electrodes in the introduced state, and then an actual cleaning process is performed.
In the actual cleaning process, the cleaning gas is introduced into the chamber up to, for example, 10 SLM at a flow rate that continuously increases for a predetermined time (for example, 80 seconds), and the input power is applied for a predetermined time (for example, 100 seconds). For example, it is continuously increased to 10 kW.

JP 2007-207925 A

However, as shown in FIG. 4, when the plasma is ignited between the electrodes while only argon (for example, 15 SLM) is introduced into the chamber 10, not only plasma discharge occurs between the cathode electrode 11 and the anode electrode 12 but also plasma discharge occurs. An abnormal discharge that spreads to the periphery between the electrodes that originally does not require plasma discharge occurs. In FIG. 4, a region surrounded by a dotted line represents a plasma region P.
As a result, the power supply cable 30, the power terminal portion 31, the ground member 40, the gas supply pipe 50, the electrode support member 13, and other members connected to the cathode electrode 11 and the anode electrode 12 are damaged by plasma discharge, There arises a problem that the quality of an object to be processed processed by the damaged plasma processing apparatus is caused.
This problem also applies to the plasma etching apparatus.

  This invention is made | formed in view of such a subject, and it aims at providing the plasma etching method which can suppress the abnormal discharge of plasma.

  Thus, according to the present invention, the plasma that introduces the first gas that is less likely to excite the plasma than the second gas, which will be described later, into the chamber that has the flat first electrode and the second electrode facing each other in parallel. Simultaneously or immediately after the discharge preparation step and the plasma discharge preparation step, a second gas for plasma excitation is introduced into the chamber, and plasma discharge is performed between the discharge surfaces of the first electrode and the second electrode via the second gas. Plasma etching including a plasma discharge starting step and an etching step of treating the substrate placed between the first and second electrodes by introducing an etching gas after the plasma discharge starting step or cleaning the inside of the chamber A method is provided.

In the plasma etching method of the present invention, before the plasma discharge start step, the first gas that is less likely to excite the plasma than the second gas is introduced into the chamber, so that the first and second electrodes in the chamber are surrounded. The first gas is present in advance. Thereafter, when plasma discharge is performed between the first electrode and the second electrode via the second gas, the plasma region is expanded to the periphery of the first and second electrodes by the first gas around the first and second electrodes. It is suppressed.
That is, in the conventional plasma etching method, when the plasma discharge is performed between the first electrode and the second electrode via the second gas, the plasma region extends to the periphery of the first and second electrodes, and the first and second electrodes The power supply cable and its power terminal, grounding member, gas supply pipe, electrode support member and other members connected to the power supply cable were damaged or damaged by plasma discharge, but the present invention prevents such problems. Can do.
In addition, the plasma etching method of the present invention includes a flat plate-like first electrode and a second electrode facing each other in parallel in the chamber, and can form or etch a substrate between the electrodes in a plasma state. The plasma processing apparatus can be applied to the existing plasma processing apparatus without modification.

It is a schematic block diagram of the plasma processing apparatus which can apply the plasma etching method of this invention. It is a figure which shows the time chart of the plasma etching method of this invention. It is a schematic block diagram of another plasma processing apparatus which can apply the plasma etching method of this invention. It is a schematic block diagram of the conventional plasma processing apparatus. It is a figure which shows the time chart of the conventional plasma cleaning method.

  In the plasma etching method of the present invention, plasma that introduces a first gas that is more difficult to excite plasma than a second gas described later into a chamber having a flat plate-like first electrode and a second electrode facing each other in parallel. Simultaneously or immediately after the discharge preparation step and the plasma discharge preparation step, a second gas for plasma excitation is introduced into the chamber, and plasma discharge is performed between the discharge surfaces of the first electrode and the second electrode via the second gas. Including a plasma discharge starting step, and an etching step of treating the substrate installed between the first and second electrodes by introducing an etching gas after the plasma discharge starting step or cleaning the inside of the chamber. Features.

That is, as described above, this plasma etching method introduces the first gas in the plasma discharge start process by introducing the first gas that is less likely to excite the plasma than the second gas into the chamber in the plasma discharge preparation process. Plasma discharge around the electrode is suppressed, and members around the first and second electrodes are prevented from being damaged by the plasma discharge.
Hereinafter, “between the first and second electrodes” may be abbreviated as “between the electrodes”, and “the circumference between the first and second electrodes” may be abbreviated as “the circumference between the electrodes”.

Examples of the second gas used in this plasma etching method include an inert gas generally used as a plasma excitation gas in a plasma processing apparatus, such as helium gas, neon gas, argon gas, nitrogen, oxygen, and the like.
The first gas is not particularly limited as long as it is a gas that is more difficult to be excited by plasma than the second gas, and examples thereof include fluorine-based gas and chlorine-based gas. Among these, stability and versatility are mentioned. From the viewpoint, a fluorine-based gas is preferable. Furthermore, it is preferable that the first gas is the same gas as the etching gas in order to simplify the structure of the gas supply unit of the plasma processing apparatus and reduce the types of gas used.

In the present invention, in the plasma discharge start step, if at least the second gas is present between the electrodes and at least the first gas is present between the electrodes, the method of introducing the first gas and the second gas into the chamber That is, it is not particularly limited from which position in the chamber the first and second gases are introduced. Therefore, in order to shorten the time, the second gas may be introduced into the chamber together with the first gas in the plasma preparation process.
In addition, after the plasma is ignited between the electrodes, it is preferable to stop the supply of the first gas in order to stabilize the plasma discharge.

As a method for introducing the first gas and the second gas, for example, the first gas is introduced from the inner wall of the chamber to the periphery between the electrodes in the plasma discharge preparation step, and the second gas is directed from the inner wall of the chamber to the electrodes in the plasma discharge start step. A method of ejecting gas can be considered.
When the first gas introduction part and the second gas introduction part are separately provided, the plasma discharge start process is performed simultaneously with or immediately after the plasma discharge preparation process, that is, immediately after or immediately after the introduction of the first gas into the chamber. It is possible to introduce the second gas into the first gas, but the first gas introduction part and the second gas introduction part are separately required.

In order to simplify the structure of the plasma processing apparatus, it is preferable that the second gas introduction part is shared with the etching gas introduction part of the existing plasma processing apparatus. As an existing plasma processing apparatus, an apparatus in which an etching gas introduction part in which a plurality of holes are formed in a matrix is provided on the discharge surface of a first electrode or a second electrode is known.
Therefore, in this plasma etching method, the introduction of the second gas in the plasma discharge start process is performed by ejecting the second gas from the discharge surface of the first electrode or the second electrode. It is preferable in terms of availability.

Furthermore, it is preferable that the first gas is also ejected from the discharge surface of the first electrode or the second electrode because the existing plasma processing apparatus can be used without modification. In this case, a method of introducing a mixed gas of the first gas and the second gas between the electrodes and then introducing the second gas between the electrodes to generate plasma between the electrodes, or first, a predetermined amount between the electrodes. The first gas can be introduced, and then a predetermined amount of the second gas can be introduced between the electrodes to generate plasma between the electrodes.
In both methods, since the first gas existing between the electrodes is pushed around the interelectrode by the second gas introduced later, the plasma discharge between the electrodes hardly spreads around the interelectrode. As a result, it is possible to prevent damage to members arranged around the electrodes due to plasma, which has been a conventional problem. The former method is preferable in that plasma ignition can be performed more quickly than the latter method.

  Further, in the etching process, it is preferable to continuously increase the flow rate of the etching gas from the start to a predetermined time, so that the etching gas is generated between the electrodes until reaching an effective etching gas flow rate for plasma etching. It becomes easy to maintain stable without extinguishing the plasma. Furthermore, in the etching process, it is more preferable to continuously reduce the flow rate of the second gas so that the pressure in the chamber becomes constant from the start to a predetermined time. In this way, the pressure fluctuation in the chamber during the process of introducing the etching gas can be kept small, and the plasma between the electrodes can be more stably maintained.

In the plasma etching method of the present invention, a film is formed on a substrate supported by an anode electrode by performing plasma discharge through a reaction gas between a first electrode as a cathode electrode and a second electrode as an anode electrode. This is an etching method using a plasma deposition apparatus capable of forming a film, and unnecessary deposits in the chamber can be removed by the etching process.
The plasma etching method of the present invention is an etching method using a plasma etching apparatus that performs plasma discharge through a reaction gas between a first electrode as a cathode electrode and a second electrode as an anode electrode. Thus, the surface of the semiconductor substrate supported by the cathode electrode can be etched.
Further, this plasma etching method includes a horizontal plasma processing apparatus in which first and second electrodes are installed in a chamber in a vertical and parallel manner in the vertical direction, and a chamber in which the first and second electrodes are parallel and perpendicular to the left and right. The present invention can be applied to both vertical plasma processing apparatuses installed inside.
Hereinafter, embodiments of the plasma etching method of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a schematic configuration diagram of a plasma processing apparatus to which the plasma etching method of the present invention can be applied. In FIG. 1, the same components as those in FIG. 4 are denoted by the same reference numerals.
In this plasma processing apparatus, a cathode electrode, which is the first electrode 11 connected to the high-frequency power source E, and an anode electrode, which is the second electrode 12 connected to the ground member 40, face each other up and down at the electrode support member 13. Horizontal plasma CVD that is provided in the chamber 10 in parallel and can form a film on a substrate (not shown) supported by the anode electrode by performing plasma discharge between the electrodes via a reaction gas (raw material gas). Device. The distance between the cathode electrode and the anode electrode is determined according to desired film forming conditions.
Hereinafter, the first electrode 11 is referred to as a cathode electrode 11, and the second electrode 12 is referred to as an anode electrode 12.

The cathode electrode 11 has a rectangular shape and is made of stainless steel, aluminum alloy, or the like. The dimension of the cathode electrode 11 is set to an appropriate value according to the dimension of the substrate on which the film is formed, and can be designed with a slightly larger planar size than the anode electrode 12 and the same thickness as the second electrode 12.
The cathode electrode 11 has a hollow inside, and a number of through holes are formed in the plasma discharge surface facing the paired anode electrode 12 by drilling. In this drilling process, it is desirable to perform circular holes with a diameter of 0.1 mm to 2 mm at a pitch of several mm to several cm.
In addition, a gas supply pipe 50 is connected to one end face of the cathode electrode 11, and a gas supply source part G <b> 1 described later is connected to the cathode electrode 11 via the gas introduction part 50. A predetermined gas is supplied from the gas supply source part G to the inside of the cathode electrode 11 and is ejected from a large number of through holes toward the surface of the substrate placed on the anode electrode 12.

The anode electrode 12 is rectangular and has a heater (not shown) inside, and a substrate is installed on the upper surface, and heats the substrate during film formation under plasma discharge. The substrate is generally a silicon substrate or a glass substrate, but is not particularly limited thereto.
The anode electrode 12 is made of a material having conductivity and heat resistance, such as stainless steel, aluminum alloy, and carbon.
The dimension of the anode electrode 12 is determined to an appropriate value in accordance with the dimension of the substrate on which the thin film is formed. For example, the dimensions of the anode electrode 12 are designed to be 1000 to 1500 mm × 600 to 1000 mm with respect to the dimensions of the substrate 900 to 1200 mm × 400 to 900 mm.
The heater built in the anode electrode 12 controls the heating of the anode electrode 12 to room temperature to 300 ° C., and includes, for example, a sealed heating device such as a sheath heater and a sealed temperature sensor such as a thermocouple in an aluminum alloy. A built-in one can be used.
The interelectrode distance between the cathode electrode 11 and the anode electrode 12 thus configured is, for example, about 5 to 50 mm.

  The gas supply source section G1 includes a source gas supply source g3 for supplying a source gas for forming a desired film on the substrate on the anode electrode 12 in the CVD process, a first gas supply source g1 for supplying a first gas, , A second gas supply source g2 for supplying a second gas, and the first gas supply source g1 also serves as a cleaning gas supply source. Then, the upstream end opposite to the downstream end of the gas supply pipe 50 connected to the cathode electrode 11 is branched and connected to each gas supply source, and valves 51 are respectively provided in these branch pipes.

As the source gas, for example, SiH ₄ (monosilane) gas diluted with H ₂ , diborane gas, phosphine gas, methane gas, oxygen, nitrogen or the like is used.
As the first gas that also serves as the cleaning gas, for example, a fluorine-based gas that is less plasma-excited than the second gas, such as C ₂ F ₆ , CF ₄ , SF ₆ , and NF ₃ , is used. In addition, when using 1st gas different from a craning gas, a 1st gas supply source and a cleaning gas supply source are provided separately.
As the second gas for plasma excitation, an inert gas such as helium gas, neon gas, argon gas, nitrogen or oxygen is used.

<Plasma Etching Method of Embodiment 1>
In a CVD process in which a film is formed on a substrate using this plasma CVD apparatus, an originally unnecessary film-like or powdery deposit adheres mainly to the discharge surface of the cathode electrode 11 in the chamber 10. Examples of the deposited film include a silicon oxide film, a silicon nitride film, and a silicon oxynitride film, and these can be removed with a fluorine-based etching gas.
In the plasma etching method of the present invention for removing this deposit, as shown in the time chart of FIG. 2, the plasma preparation step, the plasma discharge start step, and the etching step are performed in this order. In the embodiment, the etching process is a cleaning process.
Hereinafter, this plasma etching method will be described with reference to FIGS.

In the plasma preparation step, the first gas supply source g1 is used as the fluorine-based gas as the first gas in the chamber 10 evacuated by the exhaust system 20 from the start t ₀ to t ₁ (for example, 1 to 100 seconds). NF ₃ gas is introduced at a constant flow rate of 10 SLM. At this time, the NF ₃ gas is supplied into the cathode electrode 11 through the gas supply pipe 50, and the NF ₃ gas is ejected between the electrodes through a plurality of holes provided in the discharge surface of the cathode electrode 11. On the other hand, in the plasma preparation process, Ar gas as an inert gas that is the second gas is not introduced into the chamber 10 from the second gas supply source g2.

In the plasma discharge start process, the introduction of NF ₃ gas between the electrodes is stopped until the next cleaning process, and Ar gas is introduced between the electrodes at a constant flow rate of 50 SLM. At this time, for example, after elapse of the start t _{1 to} t ₂ (for example, 1 to 100 seconds), high frequency power of 1 kW, for example, as plasma ignition power from the high frequency power source E is applied to the cathode electrode 11 between t ₂ and t ₃ (for example, 1 ˜100 seconds), and a plasma is ignited between the electrodes to generate glow discharge plasma.

In this plasma starting process, only Ar gas is introduced between the electrodes between t ₁ and t ₂ (adjustment stage) before plasma ignition, so that the plasma is excited more than the Ar gas existing between the electrodes. Difficult NF ₃ gas is pushed by the Ar gas for plasma excitation and moves to the periphery between the electrodes. Immediately thereafter, plasma ignition is performed between the electrodes via Ar gas, so that plasma discharge can be easily generated.
Further, as shown by a plasma region P surrounded by a dotted line in FIG. 1, the presence of NF ₃ gas around the electrodes suppresses the spread of the generated plasma discharge to the periphery between the electrodes (abnormal discharge). Is done. This prevents members such as the power supply cable 30, the power terminal portion 31, the grounding member 50, and the electrode support member 13 around the electrodes from being damaged by abnormal discharge.

In the cleaning process, while maintaining plasma discharge, an NF ₃ .Ar mixed gas of NF ₃ gas as the cleaning gas from the first gas supply source g1 and Ar gas from the second gas supply source g2 is interposed between the electrodes. be introduced.
At this time, the flow rate of NF ₃ gas, the flow rate of Ar gas, the power value, the pressure in the chamber, etc. can be freely adjusted if the desired cleaning process can be performed without extinguishing the plasma discharge generated between the electrodes. it can.
In order to make it difficult to extinguish the plasma discharge generated between the electrodes, it is preferable to gradually increase the NF ₃ gas and gradually increase the high-frequency power in the cleaning process.

Specifically, as shown in FIG. 2, the flow rate of NF ₃ gas continuously increases from 0 SLM to 10 SLM, for example, between the start t _{3 and} t ₄ (for example, 80 seconds), and between the start t _{3 and} t ₅ ( For example, power is continuously supplied from the high frequency power source E to the cathode electrode 11 from 1 kW to a cleaning processing power value of, for example, 10 kW for 100 seconds. In addition, extinction of plasma discharge can be effectively prevented by making the increase time of the high frequency power slightly longer than the increase time of the NF ₃ gas.

On the other hand, the Ar gas may be continuously fixed at a constant flow rate of 50 SLM (indicated by a solid line in FIG. 2), or the increase in the continuous flow rate of the NF ₃ gas is offset to keep the chamber pressure constant. As shown, the flow rate may be continuously reduced to 0 SLM between t ₃ and t ₄ (indicated by a one-dot chain line in FIG. 2).
In the latter case, the pressure fluctuation in the chamber 10 during the process of introducing the cleaning gas (NF ₃ gas) can be suppressed to be small, which is effective in preventing the disappearance of plasma between the electrodes. In the former case as well, the pressure fluctuation in the chamber 10 can be reduced by adjusting the exhaust system 20.

Thereafter, the flow rate of NF ₃ gas and the flow rate of Ar gas are fixed to a constant value after t ₄ , and the high frequency power is fixed to a constant value after t ₅ , so that the discharge surface of the cathode electrode 11 in the chamber 10 is mainly used. The deposit adhering to is removed by plasma etching using NF ₃ gas and cleaned.
In this cleaning process, since the ratio of the NF ₃ gas that is difficult to be excited by plasma existing in the chamber 10 is higher than that at the start of discharge, the cleaning is performed without the plasma region P extending to the periphery between the electrodes.

(Embodiment 2)
FIG. 3 is a schematic configuration diagram of another plasma processing apparatus to which the plasma etching method of the present invention can be applied. In FIG. 3, the same components as those in FIGS. 1 and 4 are denoted by the same reference numerals.
In this plasma processing apparatus, a cathode electrode 11 connected to a high-frequency power source E and an anode electrode 12 connected to a grounding member 40 are provided in the chamber 10 so as to be opposed to each other in the vertical direction by an electrode support member 13. This is a horizontal plasma etching apparatus capable of etching the surface of the semiconductor substrate S supported by the cathode electrode 11 by performing plasma discharge between the electrodes via an etching gas. The distance between the cathode electrode 11 and the anode electrode 12 is determined according to desired etching conditions and is, for example, about 5 to 50 mm.

  In this plasma etching apparatus, the cathode electrode 11 is disposed below the anode electrode 12, the cathode electrode 11 has a built-in heater, and a plurality of holes for ejecting gas are formed on the discharge surface of the anode electrode 12. Unlike the plasma CVD apparatus of the first embodiment, the other points are the same except that the gas supply pipe 50 is connected to the anode electrode 12 and the gas supply source unit G2 does not have a source gas supply source. It is the composition. As this plasma etching apparatus, an existing apparatus can be used.

When etching the surface of the semiconductor substrate S on the cathode electrode 11 with this plasma etching apparatus, conventionally, an inert gas for plasma excitation is first introduced between the electrodes in order to ignite plasma between the electrodes. The plasma discharge spread to the periphery between the electrodes, and the members disposed around the electrodes were damaged.
The plasma etching method according to the first embodiment described above can also solve such a conventional problem that has also occurred due to the etching process in the plasma etching apparatus. However, since the interelectrode distance between the cathode electrode 11 and the anode electrode 12 is different between the plasma CVD apparatus and the plasma etching apparatus, the flow rates of various gases, input power, chamber pressure, and the like may be different.

<Plasma Etching Method of Embodiment 2>
When etching the surface of the semiconductor substrate using this plasma etching apparatus, as shown in the time chart of FIG. 2 similar to the first embodiment, the plasma preparation process, the plasma discharge start process, and the etching process are performed in this order.
Hereinafter, this plasma etching method will be described with reference to FIGS.

In the plasma preparation step, the first gas supply source g1 is used as the fluorine-based gas as the first gas in the chamber 10 evacuated by the exhaust system 20 from the start t ₀ to t ₁ (for example, 1 to 100 seconds). NF ₃ gas is introduced at a constant flow rate of 10 SLM. At this time, the NF ₃ gas is supplied into the anode electrode 12 through the gas supply pipe 50, and the NF ₃ gas is ejected between the electrodes through a plurality of holes provided in the discharge surface of the anode electrode 12. On the other hand, in the plasma preparation process, Ar gas as an inert gas that is the second gas is not introduced into the chamber 10 from the second gas supply source g2.

In the plasma discharge start process, the introduction of NF ₃ gas between the electrodes is stopped until the next etching process, and Ar gas is introduced between the electrodes at a constant flow rate of 50 SLM. At this time, for example, after elapse of time t _{1 to} t ₂ (for example, 1 to 100 seconds), high-frequency power of 10 kW, for example, as plasma ignition power from the high-frequency power source E is applied to the cathode electrode 11 between t ₂ and t ₃ (for example, 1 ˜100 seconds), and a plasma is ignited between the electrodes to generate glow discharge plasma. In FIG. 2, the RF power between t ₂ and t ₃ is described as 1 kW, but in the case of the second embodiment, it is 10 kW.

In this plasma starting process, only Ar gas is introduced between the electrodes between t ₁ and t ₂ (adjustment stage) before plasma ignition, so that the plasma is excited more than the Ar gas existing between the electrodes. Difficult NF ₃ gas is pushed by the Ar gas for plasma excitation and moves to the periphery between the electrodes. Immediately thereafter, plasma ignition is performed between the electrodes via Ar gas, so that plasma discharge can be easily generated.
Further, as shown by the plasma region P surrounded by the dotted line in FIG. 3, the presence of NF ₃ gas around the electrodes suppresses the spread of the generated plasma discharge to the periphery between the electrodes (abnormal discharge). Is done. This prevents members such as the power supply cable 30, the power terminal portion 31, the grounding member 50, and the electrode support member 13 around the electrodes from being damaged by abnormal discharge.

In the etching process, an NF ₃ .Ar mixed gas of NF ₃ gas as the etching gas from the first gas supply source g1 and Ar gas from the second gas supply source g2 is maintained between the electrodes while maintaining plasma discharge. be introduced.
At this time, the flow rate of NF ₃ gas, the flow rate of Ar gas, the power value, the pressure in the chamber, etc. can be freely adjusted as long as a desired etching process can be performed without extinguishing the plasma discharge generated between the electrodes. it can.
In order to make it difficult to extinguish the plasma discharge generated between the electrodes, it is preferable to gradually increase the NF ₃ gas and gradually increase the high-frequency power in the etching process.

Specifically, as shown in FIG. 2, the flow rate of NF ₃ gas continuously increases from 0 SLM to 10 SLM, for example, between start t _{3 and} t ₄ (for example, 10 to 1,000 seconds), and start t _{3 to} t _5. In the meantime (for example, for 10 to 1,100 seconds), the electric power is continuously supplied from the high frequency power source E to the cathode electrode 11 from 1 kW to an etching processing power value of, for example, 20 kW. At this time, extinction of the plasma discharge can be effectively prevented by making the increase time of the high frequency power slightly longer than the increase time of the NF ₃ gas. In FIG. 2, the RF power at t ₅ is described as 10 kW, but in the case of the second embodiment, it is 20 kW.

On the other hand, the Ar gas may be continuously fixed at a constant flow rate of 50 SLM (indicated by a solid line in FIG. 2), or the increase in the continuous flow rate of the NF ₃ gas is offset to keep the chamber pressure constant. As shown, the flow rate may be continuously reduced to 0 SLM between t ₃ and t ₄ (indicated by a one-dot chain line in FIG. 2).
In the latter case, the pressure fluctuation in the chamber 10 in the process of introducing the etching gas (NF ₃ gas) can be suppressed to be small, which is effective for preventing the disappearance of plasma between the electrodes. In the former case as well, the pressure fluctuation in the chamber 10 can be reduced by adjusting the exhaust system 20.

Thereafter, the flow rate of NF ₃ gas and the flow rate of Ar gas are fixed to a constant value after t ₄ , and the high frequency power is fixed to a constant value after t ₅ , and the surface of the semiconductor substrate S on the cathode electrode 11 is NF Etching is performed by plasma etching using ₃ gases.
In this etching process, since the ratio of the NF ₃ gas that is difficult to be excited by plasma existing in the chamber 10 is higher than that at the start of discharge, the etching process is performed without the plasma region P extending to the periphery between the electrodes.

(Other embodiments)
1. In the first and second embodiments, the horizontal plasma processing apparatus in which the first electrode and the second electrode are arranged in parallel and horizontally in the chamber so as to be opposed to each other in the vertical direction is described as an example. The present invention can also be applied to a vertical plasma processing apparatus in which the first and second electrodes are arranged in a parallel and vertical manner in the chamber so as to face the left and right.
2. In the first and second embodiments, the plasma processing apparatus in which a pair of the first electrode and the second electrode is provided in the chamber has been described as an example. However, in the plasma etching method of the present invention, the first and second electrodes are in the chamber. The present invention can also be applied to a multistage plasma processing apparatus provided with a plurality of pairs. In this case, an impedance matching unit that performs impedance matching between the electrode pairs may be connected to the high-frequency power source E.
3. In the etching process of the first and second embodiments, the flow rate of the fluorine-based gas and the high-frequency power value are continuously increased, and the flow rate of the inert gas is continuously decreased. It may be increased or decreased automatically.

  The present invention can be applied to a plasma processing apparatus used in the manufacture of semiconductor devices, liquid crystal display devices, thin film solar cells and the like.

10 Chamber 11 First electrode (cathode electrode)
12 Second electrode (anode electrode)
DESCRIPTION OF SYMBOLS 13 Electrode support member 20 Exhaust system 21 Pressure control controller 22 Vacuum pump 30 Power supply cable 40 Grounding member 50 Gas supply pipe 51 Valve E High frequency power supply G1, G2 Gas supply source part g1 1st gas supply source g2 2nd gas supply source g3 Source gas supply source P Plasma region

Claims (9)

A plasma discharge preparatory step of introducing a first gas that is less likely to excite plasma than a second gas described later into a chamber having a plate-like first electrode and a second electrode facing each other in parallel;
At the same time as or immediately after the plasma discharge preparation step, a plasma discharge start step for introducing a second gas for plasma excitation into the chamber and causing plasma discharge between the discharge surfaces of the first electrode and the second electrode via the second gas; ,
A plasma etching method comprising: an etching step of treating a substrate installed between the first and second electrodes by introducing an etching gas after the plasma discharge start step or cleaning the inside of the chamber .   2. The plasma etching method according to claim 1, wherein the introduction of the second gas in the plasma discharge start step is performed by ejecting the second gas between the electrodes from the discharge surface of the first electrode or the second electrode.   The plasma etching method according to claim 1 or 2, wherein in the etching step, the flow rate of the etching gas is increased continuously or stepwise from the start to a predetermined time.   4. The plasma etching method according to claim 3, wherein in the etching step, the flow rate of the second gas is decreased continuously or stepwise so that the pressure in the chamber becomes constant from the start to a predetermined time.   The plasma etching method according to claim 1, wherein the first gas is a fluorine-based gas and the second gas is an inert gas.   The plasma etching method according to claim 1, wherein the first gas is the same gas as the etching gas. A plasma film forming apparatus capable of forming a film on a substrate supported by an anode electrode by causing plasma discharge through a reaction gas between a first electrode as a cathode electrode and a second electrode as an anode electrode Etching method used,
The plasma etching method according to claim 1, wherein unnecessary deposits in the chamber are removed by an etching process.   The plasma etching method according to claim 1, wherein the deposit includes at least one of silicon oxide, silicon nitride, and silicon oxynitride, and the etching gas includes a fluorine-based gas. An etching method using a plasma etching apparatus that performs plasma discharge between a first electrode as a cathode electrode and a second electrode as an anode electrode through a reactive gas,
The plasma etching method according to claim 1, wherein the surface of the semiconductor substrate supported by the cathode electrode is etched by an etching process.

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