JP2010062433A - Method and apparatus for etching silicon-containing film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To etch a silicon-containing film at a high rate without any residue while suppressing etching of a base film. <P>SOLUTION: A processing gas containing a fluorine-based reactive component is brought into contact with an object to be processed 90 to etch the silicon-containing film 93 on the base film 92. The fluorine-based reactive component is produced by passing a fluorine-based material gas containing a fluorine material (CF<SB>4</SB>) through a plasma space 43 of substantially atmospheric pressure. The content of the fluorine-based material in the fluorine-based material gas is changed by a material content regulating unit 37 in accordance with the progress of the etching. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method and apparatus for etching a silicon-containing film containing silicon atoms such as amorphous silicon and silicon oxide.

The silicon oxide film can be etched by a processing gas containing a fluorine-based reaction gas such as hydrogen fluoride. A silicon film made of substantially silicon atoms such as amorphous silicon can be etched by a processing gas in which a fluorine-based reaction gas such as hydrogen fluoride and an oxidizing reaction gas such as ozone are mixed.
For example, Patent Documents 1 and 2 describe that silicon on a wafer surface is oxidized with ozone to form silicon oxide (Equation 1) and then etched using hydrofluoric acid. The hydrofluoric acid is evaporated by a hydrofluoric acid vapor generator and led to the wafer surface.
Patent Document 3, HF, and COF _2, etc. generated by causing a pressure near atmospheric pressure discharge fluoric gas such as CF _4, is reacted with water which had been mixed with CF ₄ or the like for further COF ₂ It is described that silicon oxide is etched (formula 3) by HF obtained in this manner (formula 2).
Si + 2O ₃ → SiO ₂ + 2O ₂ (Formula 1)
COF ₂ + H ₂ O → CO ₂ + 2HF (Formula 2)
SiO ₂ + 4HF + H ₂ O → SiF ₄ + 3H ₂ O (Formula 3)
Patent Document 4 describes that HF is obtained from humidified CF ₄ by atmospheric pressure plasma discharge (formula 4), O ₃ is added thereto, and silicon oxide is etched.
CF ₄ + 2H ₂ O → 4HF + CO ₂ (Formula 4)
Patent Document 5 describes that CF ₄ and O ₂ are discharged at atmospheric pressure to obtain radicals, which are led from a plasma space to a substrate at a temperature of 20 ° C. or 100 ° C. to etch single crystal silicon.
Patent Document 6 describes that humidified CF ₄ or dry CF ₄ is discharged at atmospheric pressure, and crystalline silicon is etched at a substrate temperature of 90 ° C.
In Patent Document 7, in etching of silicon in a low-pressure chamber, overetching is performed after substituting an etching gas component with a gas species having a high selection ratio with respect to the base at the same time or just before the base film is exposed. A method is described.
JP 2003-264160 A JP 2004-55753 A JP 2000-58508 A JP 2002-270575 A Japanese Patent Laid-Open No. 04-358076 JP 2000-164559 A JP 2002-343798 A

In etching a silicon-containing film such as amorphous silicon or silicon oxide, water added to a fluorine-based raw material for generating a fluorine-based reaction component (see Equation 4) or water generated by an etching reaction (see Equation 3) It adheres to the surface of the silicon-containing film and condenses. The etching reaction is inhibited where there is a condensed water layer. Therefore, the entire silicon-containing film cannot be etched uniformly, and a part of the silicon-containing film tends to remain in spots.
Although it may be possible to remove the moisture by performing a drying process every time moisture adheres to the surface of the silicon-containing film, the processing time becomes long and is not practical. It is also conceivable to reduce the amount of water added to the fluorine-based raw material at the end of etching. However, this will reduce the etching rate.
When the over-etching is sufficiently performed, the silicon-containing film remaining in a spot shape can be removed by etching, but the base film is etched more than necessary.
Depending on the composition of the underlying film, it can be considered that the greater the moisture content, the greater the selectivity of the silicon-containing film to the underlying film.

In order to solve the above problems, the present invention provides a method for etching an object to be processed in which a silicon-containing film is laminated on a base film.
A treatment gas containing a fluorine-based reaction component generated by passing a fluorine-based raw material gas containing a fluorine-based raw material and added with H ₂ O through a plasma space near atmospheric pressure is brought into contact with the object to be processed, and the fluorine-based raw material gas The content rate of the fluorine-type raw material in it is changed according to progress of etching.
In a stage where the base film is not affected, the content of the fluorine-based material is preferably set so that the etching rate of the silicon-containing film is good as long as the fluorine-based material is not wasted. Thereby, processing time can be shortened and raw material cost can be held down. At the stage of affecting the base film, the content of the fluorine-based material in the fluorine-based material gas may be set so that the etching selectivity of the silicon-containing film to the base film is increased. Thereby, the etching of the base film can be suppressed, and the silicon-containing film can be prevented from remaining in the form of spots.

Examples of the silicon-containing material constituting the silicon-containing film include silicon (Si), silicon oxide (SiO ₂ ), silicon carbide (SiC), and silicon oxide carbide (SiOC). Silicon (Si) may be amorphous silicon, polycrystalline silicon, or single crystal silicon. When the silicon-containing film is silicon (Si), it is preferable that the processing gas further includes an oxidizing reaction component. As a result, silicon can be oxidized (see Equation 1) and then etched in the same manner as silicon oxide (see Equation 3). Examples of the oxidizing reaction component include O ₃ , O radical, O ₂ , and preferably O ₃ . Silicon carbide (SiC) and silicon oxide carbide (SiOC) can be converted into silicon (Si) by heating and then etched in the same manner as silicon (see Equations 1 and 3).

The underlying film only needs to be composed of a component different from the silicon-containing film to be etched, and may be a silicon-containing material. When the silicon-containing film to be etched is silicon (Si), the base film is, for example, silicon oxide (SiO ₂ ), silicon nitride (SiN), or the like. When the silicon-containing film to be etched is silicon oxide (SiO ₂ ), the base film is, for example, silicon nitride (SiN). When the silicon-containing film to be etched is silicon carbide (SiC) or silicon oxide carbide (SiOC), the base film is, for example, silicon nitride (SiN), silicon oxide (SiO ₂ ), or the like.

The content is preferably changed stepwise as etching progresses. Thereby, control of a content rate can be made easy. “Stepwise” means that the change in content is discontinuous or stepped.
The content may be changed continuously as etching progresses.

The content is preferably increased as etching progresses.
Thereby, at the stage where the base film is not affected, waste of the fluorine-based raw material can be eliminated in a range where the etching rate is good. At the stage of etching, by increasing the content of the fluorine-based raw material, H ₂ O reacts more with the fluorine-based raw material in the plasma, increasing the amount of HF generated, and reducing the amount of H ₂ O. It can be reduced. The increase in HF works to increase the etching rate of silicon. The decrease in H ₂ O acts in the direction of decreasing the etching rate of silicon. Therefore, the etching rate of the silicon-containing film is not much different from that before the subtraction of the etching rate. On the other hand, when the base film is made of silicon nitride or the like, the etching rate of the base film decreases as H ₂ O decreases. Therefore, the selection ratio of the silicon-containing film to the base film can be increased. Thereby, while maintaining the etching rate of the silicon-containing film satisfactorily, over-etching of the base film can be suppressed, and the occurrence of spotted residues of the silicon-containing film can be reliably prevented.

The content is preferably increased stepwise as etching progresses. Thereby, control of a content rate can be made easy.
The content may be gradually increased as etching progresses.

  Depending on the composition of the underlying film, the content may be reduced stepwise or continuously in order to increase the selectivity of the silicon-containing film to the underlying film as etching proceeds.

The silicon-containing film should be etched by relatively reducing the content of the period (hereinafter referred to as the “first etching step”) for etching most (or almost the whole) of the silicon-containing film to be etched. It is preferable to relatively increase the content of the portion of the portion that remains after the first etching step (hereinafter referred to as “second etching step”).
Thus, when the base film is made of silicon nitride or the like, most of the portion to be etched of the silicon-containing film can be etched at a good etching rate and without wasting the fluorine raw material. Then, the silicon-containing film of the remaining silicon-containing film and the base film can be selectively etched and removed while maintaining a good etching rate, and the etching of the base film can be reliably suppressed. In addition, it is possible to reliably prevent spotted residues of the silicon-containing film.

The fluorine source gas in the first etching step further includes a carrier, and the molar ratio of the fluorine source to the carrier is preferably fluorine source: carrier = 3: 97 to 97: 3, and the fluorine source: The carrier is more preferably 5:95 to 30:70.
Preferably, the fluorine-based source gas in the second etching step further includes or does not include a carrier, and the molar ratio of the fluorine-based material to the carrier is fluorine-based material: carrier = 5: 95 to 100: 0. It is more preferable that the system raw material: carrier = 75: 25 to 100: 0.
Thereby, while maintaining the etching rate of the silicon-containing film satisfactorily, the etching of the base film can be surely suppressed, and the formation of spotted residues of the silicon-containing film can be reliably prevented.

The content rate may be increased stepwise in the first etching step, and the content rate in the second etching step may be higher than the final level of the first etching step.
As a result, over-etching of the underlying film can be more reliably suppressed, and the occurrence of spotted residues in the silicon-containing film can be reliably prevented.

The present invention provides an apparatus for etching an object to be processed in which a silicon-containing film is laminated on a base film.
A processing gas supply system that supplies a processing gas containing a fluorine-based reaction component to the object to be processed, the processing gas supply system,
A plasma generator that forms a plasma space near atmospheric pressure;
A raw material supply line for introducing a fluorine-based raw material gas containing a fluorine-based raw material to be the fluorine-based reaction component and added with H ₂ O into the plasma space;
A raw material content adjusting unit that changes the content of the fluorine-based raw material in the fluorine-based raw material gas of the raw material supply line according to the progress of etching;
Other features.
According to this feature, the amount of H ₂ O in the raw material gas decomposed by the atmospheric pressure plasma can be adjusted by adjusting the content rate. Therefore, the content of H ₂ O in the processing gas can be adjusted, and thus the amount of H ₂ O on the surface of the object to be processed can be adjusted. Thus, the etching rate of the silicon-containing film can be adjusted to be good at a stage that does not affect the base film. Therefore, the processing time can be shortened. At the stage of affecting the base film, the silicon-containing film can be adjusted to have a good selectivity with respect to the base film. Therefore, etching of the base film can be suppressed, and the occurrence of spotted residues in the silicon-containing film can be reliably prevented.
It is preferable that the raw material content adjusting unit changes the content in stages as etching progresses. As a result, the control of the raw material content adjusting unit can be facilitated.
The raw material content adjusting unit may continuously change the content as etching progresses.

The raw material content adjusting unit preferably increases the content as etching progresses.
As a result, at a stage where the base film is not affected, the content of the fluorine raw material can be relatively lowered in a range where the etching rate is good, and waste of the fluorine-based raw material can be eliminated. In the advanced stage etching, by increasing the content of the fluorine-based material, in a plasma is more reactive of H _{2 O} and fluorine-based material, while maintaining the etching rate of the silicon-containing film, of H 2 _O The amount can be reduced. Therefore, when the base film is made of silicon nitride or the like, the selectivity of the silicon-containing film to the base film can be increased. Thereby, while maintaining the etching rate of the silicon-containing film satisfactorily, over-etching of the base film can be suppressed, and the occurrence of spotted residues of the silicon-containing film can be reliably prevented.

The raw material content adjusting unit preferably increases the content stepwise as the etching proceeds. As a result, the control of the raw material content adjusting unit can be facilitated.
The raw material content adjusting unit may continuously increase the content as the etching progresses.

  Depending on the composition of the underlayer, etc., in order to increase the selection ratio of the silicon-containing layer to the underlayer as the etching progresses, the raw material content adjustment unit may lower the content stepwise or continuously. .

The raw material content adjusting unit lowers the content rate until most of the portion to be etched of the silicon-containing film is etched, and when etching the remaining silicon-containing film, the content rate is relatively It is preferable to make it high.
As a result, most of the silicon-containing film to be etched can be etched at a good etching rate and without wasting the fluorine raw material. Thereafter, when the remaining silicon-containing film is etched, the etching rate of the silicon-containing film can be maintained satisfactorily, and when the base film is made of silicon nitride or the like, the selectivity with respect to the base film can be increased. Therefore, it is possible to reliably suppress the etching of the base film and to reliably prevent spotted residues of the silicon-containing film.

It is preferable that the raw material supply line mixes a fluorine-based material and a carrier to generate the fluorine-based material gas. It is preferable that the raw material content adjusting unit adjusts the mixing ratio of the fluorine-based raw material and the carrier. Thereby, the content rate of a fluorine-type raw material can be adjusted reliably.
It is preferable to keep the flow rate of the fluorine-based source gas constant and to change the mixing ratio of the fluorine-based source and the carrier.

The present invention provides an apparatus for etching an object to be processed in which a silicon-containing film is laminated on a base film.
A plurality of processing gas supply systems for blowing out a processing gas containing a fluorine-based reaction component;
A switching means for selectively switching a processing gas supply system in which a processing gas is sprayed onto the object to be processed according to the progress of etching;
Each processing gas supply system,
A plasma generator that forms a plasma space near atmospheric pressure;
A raw material supply line for introducing a fluorine-based raw material gas containing a fluorine-based raw material to be the fluorine-based reaction component and added with H ₂ O into the plasma space;
Another feature is that the fluorine source contents in the fluorine source gases of at least two of the plurality of process gas supply systems are different from each other.
According to this feature, the content of the fluorine-based raw material before the plasma treatment of the processing gas sprayed on the object to be processed can be adjusted by selecting the processing gas supply system. The amount by which the H ₂ O in the raw material gas is decomposed by the atmospheric pressure plasma can be adjusted by the difference in content. Therefore, the content of H ₂ O in the processing gas can be adjusted. As a result, the amount of H ₂ O on the surface of the workpiece can be adjusted. Thus, the etching rate of the silicon-containing film can be adjusted to be good at a stage that does not affect the base film. Therefore, the processing time can be shortened. At the stage of affecting the base film, the silicon-containing film can be adjusted to have a good selectivity with respect to the base film. Therefore, etching of the base film can be suppressed, and the occurrence of spotted residues in the silicon-containing film can be reliably prevented.

It is preferable that the switching unit selects a processing gas supply system having a relatively high content rate as etching progresses.
As a result, at a stage that does not affect the underlying film, a processing gas of a processing gas supply system having a relatively low content of the fluorine-based raw material is sprayed on the object to be processed, and the waste of the fluorine-based raw material is eliminated in a range where the etching rate is good. be able to. At the stage where etching has progressed, the amount of H ₂ O of the processing gas sprayed onto the object to be processed can be reduced by switching the processing gas supply system. Therefore, when the base film is made of silicon nitride or the like, the selectivity of the silicon-containing film to the base film can be increased while maintaining the etching rate of the silicon-containing film. As a result, overetching of the underlying film can be suppressed, and the occurrence of spotted residues in the silicon-containing film can be reliably prevented.

When the switching means selects a processing gas supply system having a relatively low content rate until most of the portion to be etched of the silicon-containing film is etched, and the remaining silicon-containing film is etched, It is preferable to select a processing gas supply system having a relatively high rate.
As a result, when the base film is made of silicon nitride or the like, most of the portion to be etched of the silicon-containing film can be etched at a good etching rate and without waste of the fluorine raw material, and then the remaining silicon When etching the containing film, the selectivity to the base film can be increased while maintaining a good etching rate of the silicon-containing film, etching of the base film can be reliably suppressed, and spotted residues of the silicon-containing film are formed. Can be surely prevented.

  The switching means may select a processing gas supply system having a relatively low content as the etching proceeds.

  It is preferable that the process gas flow rates of the raw material supply lines of the plurality of process gas supply systems are substantially equal to each other. It is preferable that each raw material supply line mixes a fluorine-based raw material and a carrier to generate the fluorine-based raw material gas. Thereby, the content rates of the fluorine-based raw materials can be different from each other while the processing gas flow rates of the at least two processing gas supply systems are substantially equal to each other.

Examples of the fluorine-based raw material include perfluorocarbon (PFC), hydrofluorocarbon (HFC), SF ₆ , NF ₃ , and XeF ₂ . Examples of the PFC include CF ₄ , C ₂ F ₆ , C ₃ F ₆ , C ₃ F _{8 and the} like. Examples of the HFC include CHF ₃ , C ₂ H ₂ F ₂ , and CH ₃ F.
An OH-containing compound may be used in place of H ₂ O. Examples of the OH group-containing compound include hydrogen peroxide water and alcohol.
Examples of the carrier include noble gases such as Ar and He, and N _{2 and the} like.
Examples of the fluorine-based reaction component include HF, COF _{2 and the} like.

When the silicon-containing material is silicon, silicon carbide, silicon oxycarbide, or the like, it is preferable that the processing gas supply system supplies a processing gas containing a fluorine-based reaction component and an oxidizing reaction component to the object to be processed. . Thereby, the silicon-containing material can be oxidized with an oxidizing reaction component (Equation 1), and then etched with a fluorine-based reaction component (Equation 3).
When the silicon-containing material is silicon carbide, silicon oxide carbide, or the like, it is preferable to further include a heating unit. By heating the object to be processed with a heating means, silicon carbide, silicon oxide silicon carbide, or the like can be siliconized, and then etched in the same manner as when the silicon-containing material is silicon.
When the silicon-containing material is silicon, silicon carbide, silicon oxycarbide, or the like, the oxygen-based source gas in which the source supply line becomes the fluorine-based source gas and an oxidizing reaction component (O ₃ , O radical, etc.) It is preferable to introduce at least a fluorine source gas into the plasma space.
Examples of the oxygen-based source gas include O ₂ , NO, NO ₂ , N ₂ O and the like, preferably O ₂ .
The raw material supply line may be configured to mix and introduce the fluorine-based source gas and the oxygen-based source gas into the plasma space.
The oxidizing reaction component may be obtained by converting the oxygen-based source gas into plasma, excitation activation, or ozonization on a line different from the source supply line. In that case, the fluorine-based reaction component from the raw material supply line and the oxidizing reaction component from the other line may be mixed and supplied to the object to be processed, or supplied to the object to be processed from separate outlets. You may decide to do it.

The vicinity of atmospheric pressure refers to a range of 1.013 × 10 ^{4 to} 50.663 × 10 ⁴ Pa, and 1.333 × 10 ^{4 to} 10.664 considering the ease of pressure adjustment and the simplification of the apparatus configuration. × 10 ⁴ Pa is preferable, and 9.331 × 10 ^{4 to} 10.9797 × 10 ⁴ Pa is more preferable.

  According to the present invention, the silicon-containing film can be etched without residue and at a high rate, and etching of the base film can be suppressed.

Embodiments of the present invention will be described below.
First Embodiment The present invention is applied to etching a silicon-containing film formed on an object to be processed.
FIG. 2A shows an example of the workpiece 90 before etching. The object 90 to be processed includes, for example, glass for flat panel display as a substrate 91, a base film 92 is formed on the glass substrate 91, and a silicon-containing film 93 to be etched is laminated on the base film 92. The base film 92 is made of, for example, silicon nitride (SiNx). The silicon-containing film 93 to be etched is made of, for example, amorphous silicon (a-Si). Although illustration is omitted, a portion of the silicon-containing film 93 to be processed 90 that is not to be etched is covered with a mask such as a resist. A portion of the silicon-containing film 93 that is not masked becomes a portion to be etched.

  FIG. 1 shows an example of an etching apparatus 1 used for etching the silicon-containing film 93. The etching apparatus 1 includes a processing gas supply system 10 and a support unit 20. The workpiece 90 is supported by the support unit 20. The support part 20 is composed of a stage, for example. A heating unit 21 is provided inside the support unit 20. The workpiece 90 can be heated by the heating unit 21.

The processing gas supply system 10 includes a raw material supply line 30 and a plasma generation unit 40. A fluorine-based gas supply unit 31 is provided at the upstream end of the raw material supply line 30. The fluorine-based gas supply unit 31 includes a fluorine-based raw material supply unit 35 and a carrier supply unit 36. The fluorine-based material supply unit 35 stores fluorine-based materials. Examples of the fluorine-based raw material include CF ₄ , CHF ₃ , C ₂ F ₆ , C ₃ F ₈ , SF ₆ , NF ₃ , and XeF ₂ . Here, CF ₄ is used as the fluorine-based material. The carrier supply unit 36 stores a carrier (diluted gas). Examples of the carrier include Ar, He, N _{2 and the} like. Here, Ar is used as the carrier. CF ₄ from the fluorine-based material supply unit 35 is diluted by Ar from the carrier supply unit 36 and is sent to the line 30 as a fluorine-based material gas. Alternatively, the amount of Ar supplied from the carrier supply unit 36 may become zero, and CF ₄ from the fluorine-based material supply unit 35 may be sent to the line 30 as it is as a fluorine-based material gas (CF ₄ 100% gas). .

The fluorine-based gas supply unit 31 is further provided with a fluorine-based raw material content rate adjusting unit 37. The raw material content rate adjusting unit 37 includes, for example, a mass flow controller, a flow rate control valve, and the like, and adjusts the mixing ratio of CF ₄ and Ar, that is, the content rate of the fluorine raw material in the fluorine-based source gas (CF ₄ + Ar). The flow rate ratio of CF ₄ and Ar is adjusted, for example, in the range of CF ₄ : Ar = 3: 97 to 100: 0. Even if the flow rate ratio of CF ₄ and Ar is changed, the flow rate of the fluorine-based source gas (CF ₄ + Ar) is adjusted to be always constant.

An addition unit 32 is connected to the raw material supply line 30. The addition unit 32 is configured by a humidifier that stores liquid water (H ₂ O), vaporizes the liquid water, and adds it to the fluorine-based source gas (CF ₄ + Ar) in the source supply line 30. ing. As a method of addition, a part of the fluorine-based raw material gas flowing through the raw material supply line 30 is diverted to the addition unit 32, and this diverted gas is brought into contact with the liquid surface of the addition unit 32 to vaporize water into the diversion gas. Alternatively, the diverted gas may be bubbled in the water of the addition unit 32 to vaporize the water. Water may be vaporized by heating with a heater and supplied to the raw material supply line 30.

An oxygen-based raw material supply unit 34 is connected downstream from the addition unit 32 of the raw material supply line 30. The raw material supply unit 34 supplies an oxygen-based raw material gas to the raw material supply line 30. Thereby, the fluorine-based source gas and the oxygen-based source gas are mixed in the source supply line 30. Examples of the oxygen-based raw material include O ₂ , NO, NO ₂ , and N ₂ O. Here, O ₂ is used as the oxygen-based source gas. The connection point of the oxygen-based material supply unit 34 to the material supply line 30 may be upstream of the addition unit 32.

The downstream end of the raw material supply line 30 extends to the plasma generation unit 40.
The plasma generation unit 40 has a pair of electrodes 41 and 41 facing each other. A solid dielectric layer (not shown) is provided on the facing surface of at least one of the electrodes 41. One of these electrodes 41, 41 is connected to a power source 42, and the other is electrically grounded. By supplying voltage from the power source 42, the space 43 between the electrodes 41 and 41 becomes a plasma space near atmospheric pressure. A raw material supply line 30 is connected to the upstream end of the plasma space 43. At the downstream end of the plasma space 43, an ejection portion 49 made of a nozzle is provided. The ejection part 49 faces the workpiece 90 on the support part 20. The ejection part 49 may be relatively moved (scanned) with respect to the support part 20 so as to reciprocate between both ends of the support part 20.

A method of etching the silicon-containing film 93 of the workpiece 90 using the etching apparatus 1 having the above configuration will be described.
The etching process is divided into a first etching process from the initial stage to the middle stage (before reaching the final stage) of etching and a second etching process performed at the final stage of etching.

[First etching step]
In the first etching step, the fluorine-based gas supply unit 31 mixes CF ₄ from the fluorine-based material supply unit 35 and Ar from the carrier supply unit 36 to obtain a fluorine-based material gas (CF ₄ + Ar). Hereinafter, the fluorine-based source gas in the first etching step is appropriately referred to as “first fluorine-based source gas”. The content rate adjusting unit 37 adjusts the content rate of the fluorine source material (CF ₄ ) in the first fluorine source gas (CF ₄ + Ar). Specifically, the mixing ratio (molar ratio) of CF ₄ and Ar of the first fluorine-based source gas is preferably set to CF ₄ : Ar = 3: 97 to 97: 3, and CF ₄ : Ar = More preferably, the ratio is 5:95 to 30:70. By making the amount of the fluorine-based raw material (CF ₄ ) not more than necessary, waste of the fluorine-based raw material can be suppressed.

The fluorine-based source gas (CF ₄ + Ar) obtained in the fluorine-based gas supply unit 31 is sent to the source supply line 30. A predetermined amount of water (H ₂ O) is added to the fluorine-based source gas by the addition unit 32. The amount of water added is increased as much as possible without causing condensation. Preferably, the fluorine-based source gas contains water having a dew point temperature of 10 to 50 ° C. The dew point temperature of the fluorine-based source gas is preferably lower than the ambient temperature or the temperature of the workpiece 90. Thereby, dew condensation can be prevented in the piping constituting the raw material supply line 30 and on the surface of the workpiece 90. When the object 90 is not heated by the heating unit 21 and is brought to room temperature, it is preferable that the dew point of the fluorine-based source gas is 15 to 20 ° C.

The oxygen-based material gas (O ₂ ) from the oxygen-based material supply unit 34 is mixed with the fluorine-based material gas (CF ₄ + Ar + H ₂ O) after adding water to generate a mixed material gas. The volume mixing ratio of the fluorine-based source gas and the oxygen-based source gas is preferably fluorine-based source gas: oxygen-based source gas = 1: 9 to 9: 1, and fluorine-based source gas: oxygen-based source gas = 1: 2-2. : 1 is more preferable. Since the volume ratio of water is sufficiently small with respect to the fluorine-based source gas and the oxygen-based source gas, the volume ratio between the fluorine-based source gas and the oxygen-based source gas before adding water and the fluorine after adding water The volume ratio of the system material gas and the oxygen system material gas is almost the same.

The mixed raw material gas (CF ₄ + Ar + O ₂ + H ₂ O) is introduced into the interelectrode space 43 from the downstream end of the raw material supply line 30.
At the same time, a voltage is supplied from the power source 42 to the electrode 41, and plasma near atmospheric pressure is generated in the interelectrode space 43. Thereby, the mixed gas is turned into plasma (including decomposition, excitation, activation, radicalization, ionization, etc.), and a processing gas containing a fluorine-based reaction component and an oxidizing reaction component is generated. Hereinafter, the processing gas in the first etching step is appropriately referred to as “first processing gas”. The first processing gas is a recipe that can etch silicon at a high rate and suppress waste of CF ₄ . Examples of the fluorine-based reaction component include HF, COF _{2 and the} like. These fluorine-based reaction components are mainly produced by the decomposition of CF ₄ and H ₂ O. Examples of the oxidizing reaction component include O ₃ and O radicals. These oxidizing reaction components are mainly produced using O ₂ as a raw material.

The first processing gas is ejected from the plasma generation unit 40 and sprayed onto the workpiece 90 on the support unit 20. As a result, the oxidizing reaction component in the first processing gas comes into contact with the silicon-containing film 93 made of amorphous silicon, and an oxidation reaction of silicon occurs to generate silicon oxide (Formula 1). A fluorine-based reaction component comes into contact with this silicon oxide (formula 3), and volatile SiF ₄ is generated. Thus, the silicon-containing film 93 is etched at a good etching rate.

The first processing gas also contains a component of the mixed raw material gas that has not been decomposed in the plasma space 43, and thus also contains water. A part of this water reacts with the fluorine-based reaction component COF ₂ to generate HF (Equation 2) and contributes to the etching of silicon. A part of the remaining water adheres to the surface of the workpiece 90 and condenses. Further, water is generated by the etching reaction (formula 3) by HF, and a part of this water adheres to the surface of the workpiece 90 and condenses. Thereby, a condensed layer of water is formed on the surface of the workpiece 90. Etching of silicon is facilitated by a condensed layer of moderately thick water. On the other hand, the condensed layer of water sometimes becomes thicker than necessary at the surface of the workpiece 90. The etching reaction is hindered where the condensed layer is thick. Therefore, as shown in FIGS. 2B and 2C, the surface of the workpiece 90 just before the etching reaches the final stage, the portion where the base film 92 is exposed, and the silicon-containing film 93 to be etched. Can still be left. The remaining silicon-containing film 93 is referred to as a remaining film 93a. The remaining film 93a has a spotted shape (a mottled shape).

[Second etching step]
As shown in FIGS. 2B and 2C, when the etching progresses and a part of the base film 92 is exposed or just before it is exposed, the first etching process is switched to the second etching process.

In the second etching step, the fluorine-based material content rate adjusting unit 37 changes the content rate of CF _{4 in} the fluorine-based material gas (CF ₄ + Ar) to a size different from the content rate in the first etching step. Other processing conditions are preferably the same as those in the first etching step.

More specifically, in the fluorine-based gas supply unit 31, CF ₄ from the fluorine-based material supply unit 35 and Ar from the carrier supply unit 36 are mixed to obtain a fluorine-based material gas (CF ₄ + Ar). Hereinafter, the fluorine-based source gas in the second etching step is appropriately referred to as “second fluorine-based source gas”. The CF ₄ content in the second fluorine-based source gas (CF ₄ + Ar) is set higher than the CF ₄ content of the first fluorine-based source gas by the content rate adjusting unit 37. Specifically, the mixing ratio (molar ratio) of CF ₄ and Ar of the second fluorine-based raw material gas is preferably set to CF ₄ : Ar = 5: 95 to 100: 0, and CF ₄ : Ar = More preferably, the ratio is 75:25 to 100: 0.

The total flow rate of CF ₄ and Ar (fluorine-based source gas flow rate) is the same as that in the first etching step. Therefore, the Ar flow rate in the second etching process is reduced by the amount of increase in the CF ₄ flow rate than in the first etching process.

Water (H ₂ O) in the addition section 32 is added to the second fluorine-based source gas (CF ₄ + Ar). The amount of water added is the same as in the first etching step.

The oxygen-based source gas (O ₂ ) from the oxygen-based source supply unit 34 is mixed with the second fluorine-based source gas after adding water to obtain a mixed source gas (CF ₄ + Ar + O ₂ + H ₂ O). The volume mixing ratio of the fluorine-based source gas and the oxygen-based source gas is the same as that in the first etching step. This mixed raw material gas is introduced into the plasma space 43 to be turned into plasma. As a result, a processing gas containing a fluorine-based reaction component such as HF or COF ₂ and an oxidizing reaction component such as O ₃ or O radical is generated. Hereinafter, the processing gas in the second etching step is appropriately referred to as “second processing gas”.

In the second etching step, since the content of CF ₄ is high, H ₂ O reacts with CF ₄ more in the plasma and decomposes. Therefore, the amount of HF generated is increased and the amount of H ₂ O is decreased compared to the first etching step. The increase in HF works to increase the etching rate of silicon. The decrease in H ₂ O acts in the direction of decreasing the etching rate of silicon. Therefore, the etching rate of the film 93 made of silicon is subtracted and is not much different from the first etching step. On the other hand, the etching rate of the underlying silicon nitride film 92 decreases due to the decrease in H ₂ O. The degree of decrease in the etching rate of silicon nitride is greater than the degree of decrease in the etching rate due to the decrease in H ₂ O of silicon. Therefore, the selection ratio of the etching target film 93 to the base film 92 can be increased. As a result, as shown in FIG. 2C, the spot-like residual film 93a can be selectively etched and removed while maintaining a good silicon etching rate, and the overetching amount d of the base film 92 is reduced. it can.

Switching from the first etching step to the second etching step can be easily performed only by changing the content ratio of CF ₄ , and, for example, the response is better than changing the addition rate of water by the addition unit 32.

Next, another embodiment of the present invention will be described. In the following embodiments, the same reference numerals are given to the drawings for the same configurations as those of the above-described embodiments, and the description thereof is omitted.
Second Embodiment As shown in FIG. 3, the processing gas supply system 10 of the second embodiment generates a fluorine-based reaction component and an oxidizing reaction component separately. The oxygen-based raw material supply unit 34 is not connected to the raw material supply line 30 extending from the fluorine-based gas supply unit 31. The material supply line 30 introduces only the fluorine-based material gas (CF ₄ + Ar + H ₂ O) into the plasma generation unit 40. The oxygen-based source gas is not introduced into the plasma generation unit 40.

The oxygen-based raw material supply unit 34 is connected to a plasma generation unit 44 that is different from the plasma generation unit 40.
The plasma generation unit 44 has a pair of electrodes 45 and 45 facing each other. A solid dielectric layer (not shown) is provided on the opposing surface of at least one of the electrodes 45. One of these electrodes 45, 45 is connected to a power source 46, and the other is electrically grounded. By supplying voltage from the power supply 46, the space 47 between the electrodes 45 and 45 becomes a plasma space near atmospheric pressure. An oxygen-based material supply unit 34 is connected to the upstream end of the plasma space 47.

  A fluorine-based ejection path 51 extends from the downstream end of the plasma space 43 of the plasma generation unit 40. An oxygen-based ejection path 52 extends from the downstream end of the plasma space 47 of the plasma generation unit 44. These ejection paths 51 and 52 merge with each other. The common jet part 53 is continued to this merge part. The common ejection part 53 faces the workpiece 90 on the support part 20. The common ejection part 53 may be moved relative to the support part 20 so as to reciprocate between both ends of the support part 20.

  The path from the fluorine-based raw material supply unit 35 and the path from the carrier supply unit 36 are merged via the fluorine-based raw material content rate adjusting unit 37, as in the first embodiment.

In the first etching process of the second embodiment, as in the first etching process of the first embodiment, CF ₄ and Ar are mixed so that the content of CF ₄ is relatively low, and the first fluorine-based raw material is mixed. A gas is obtained, to which water (H ₂ O) is added. Then, the first fluorine-based source gas (CF ₄ + Ar + H ₂ O) after the addition of water is introduced into the plasma space 43 without being mixed with O ₂ to be converted into plasma. Thus, CF ₄ and _{H 2} O is decomposed, first fluorine-based reactive gas containing fluorine-based reactive components, such as HF and COF ₂ is generated. The first fluorine-based reaction gas is led out to the ejection path 51.

At the same time, oxygen-based source gas (for example, O ₂ ) from the oxygen-based source supply unit 34 is introduced into the plasma space 47 of the plasma generation unit 44 to be converted into plasma, and includes an oxidizing reaction component such as O ₃ or O radical. Oxidizing reaction gas is generated. This oxidizing reaction gas is led out from the plasma generation unit 44 to the ejection path 52 and mixed with the first fluorine-based reaction gas from the ejection path 51. A mixed gas of the first fluorine-based reaction gas and the oxidizing reaction gas becomes the first processing gas. The volume mixing ratio of the first fluorine-based reaction gas and the oxidizing reaction gas is preferably the first fluorine-based reaction gas: the oxidizing reaction gas = 1: 9 to 9: 1, and the first fluorine-based reaction gas: the oxidizing reaction gas. = 1: 2 to 2: 1 is more preferable. As a result, a process gas recipe is obtained in which the etching rate of silicon is high and the waste of CF ₄ is suppressed. This processing gas is sprayed from the ejection portion 53 onto the workpiece 90, and most of the portion of the silicon-containing film 93 to be etched is etched to expose a portion of the base film 92.

Subsequently, in the second etching step, as in the second etching step of the first embodiment, CF ₄ and Ar are mixed so that the content of CF ₄ is relatively high, and the second fluorine-based source gas is mixed. To which water (H ₂ O) is added. Then, the second fluorine-based source gas (CF ₄ + Ar + H ₂ O) after the addition of water is introduced into the plasma space 43 without being mixed with O ₂ to be converted into plasma. Thereby, CF ₄ and H ₂ O are decomposed, and a second fluorine-based reaction gas containing a fluorine-based reaction component such as HF and COF ₂ is generated. Since the CF ₄ content of the second fluorine-based source gas is higher than that of the first fluorine-based source gas, more H ₂ O is decomposed and more HF is generated. Therefore, the second fluorine-based reaction gas is The amount of HF is larger than that of the first fluorine-based reaction gas, and the amount of H ₂ O is small. This second fluorine-based reaction gas is led out to the ejection path 51.

In the plasma generation unit 44, an oxidizing reaction gas is generated by converting the oxygen-based source gas (for example, O ₂ ) into plasma following the first etching step. This oxidizing reaction gas is led out to the ejection path 52 and mixed with the second fluorine-based reaction gas from the ejection path 51 to obtain a second processing gas. The volume mixing ratio of the second fluorine-based reaction gas and the oxidizing reaction gas is preferably the second fluorine-based reaction gas: the oxidizing reaction gas = 1: 9 to 9: 1, and the second fluorine-based reaction gas: the oxidizing reaction gas. = 1: 2 to 2: 1 is more preferable. The second processing gas after mixing is sprayed onto the workpiece 90 from the ejection part 53. Since the HF content in the second process gas is high and the water content is low, the remaining film 93a can be selectively etched while maintaining a good etching rate, and the etching of the base film 92 can be suppressed. Furthermore, the spotted residual film 93a of silicon can be reliably removed.

  In the second embodiment, since the fluorine-based source gas and the oxygen-based source gas are converted into plasma by separate plasma generation units 40 and 44, the generation amount of the fluorine-based reaction component and the generation amount of the oxidizing reaction component are sufficiently large. can do. Thereby, the etching rate of the silicon-containing film 93 in each of the first and second etching steps can be increased, and the processing time can be further shortened.

Third Embodiment As shown in FIG. 4, in the third embodiment, an ozonizer 48 is used in place of the plasma generation unit 44 as an oxidizing reaction gas generation device. Oxygen gas (O ₂ ) from the oxygen-based raw material supply unit 34 is introduced into the ozonizer 48 to generate an oxidizing reaction gas containing O ₃ , and this oxidizing reaction gas is led out to the ejection path 52. Yes.
Other configurations and operations are the same as those in the second embodiment.

Fourth Embodiment As shown in FIG. 5, the etching apparatus 1 of the fourth embodiment includes a plurality (two) of processing gas supply systems 10. Each processing gas supply system 10 has substantially the same configuration as the processing gas supply system 10 of the first embodiment (FIG. 1). When distinguishing between the two supply systems 10, each component of the first process gas supply system 10 </ b> A is denoted by the same reference numeral as the corresponding component in the process gas supply system 10 of the first embodiment, Each component of the second process gas supply system 10B is denoted by the same reference numeral as that of the corresponding component in the process gas supply system 10 of the first embodiment.

Where the processing gas supply systems 10A and 10B are different from the processing gas supply system 10 of the first embodiment (FIG. 1), the fluorine-based raw material content adjusting unit 37 is omitted from the fluorine-based gas supply unit 31. Is a point. Fluorine-based gas supply unit 31, without changing the mixing ratio of CF ₄ and Ar in the course of the etching process, during the entire duration of the process, maintaining the mixture ratio of CF ₄ and Ar constant. And mixing ratio of CF ₄ and Ar fluorine gas supply unit 31A of the first processing gas supply system 10A, the mixing ratio of CF ₄ and Ar fluorine gas supply unit 31B of the second processing gas supply system 10B is different from each other ing.

The mixing ratio of CF ₄ and Ar in the fluorine-based gas supply unit 31A is the same as that in the first etching process of the first embodiment, and the ratio of CF ₄ is relatively small. The mixing ratio of CF ₄ and Ar in the fluorine-based gas supply unit 31B is the same as that in the second etching process of the first embodiment, and the ratio of CF ₄ is relatively large. Accordingly, the first processing gas supply system 10A ejects the first processing gas. The second processing gas supply system 10B ejects the second processing gas.

  A moving means 22 is connected to the support portion 20. Although detailed illustration is omitted, the moving means 22 includes, for example, a drive unit such as a motor and a slide unit that is advanced and retracted by the drive unit, and the support unit 20 is connected to the slide unit. The moving unit 22 causes the support unit 20 to have a first position (solid line in FIG. 5) facing the first processing gas ejection part 49A and a second position (in FIG. 5) facing the second processing gas ejection part 49A. It is moved between the two-dot chain line).

In the first etching step, the support unit 20 is positioned at the first position by the moving means 22. As a result, the processing gas ejected from the first processing gas supply system 10A comes into contact with the workpiece 90, and most of the silicon-containing film 93 is etched. Thereafter, the support unit 20 is moved from the first position to the second position by the moving means 22. Thereby, it is possible to shift from the first etching process to the second etching process with little time. In the second etching step, the processing gas ejected from the second processing gas supply system 10 </ b> B contacts the workpiece 90. The processing gas from the second processing gas supply system 10B has a higher content of the fluorine-based raw material CF ₄ than the first processing gas supply system. Thereby, the residual film 93a can be selectively etched while maintaining a good etching rate, the etching of the base film 92 can be suppressed, and the silicon-like residual film 93a can be reliably removed.
The moving unit 22 constitutes a switching unit that selectively switches between the processing gas supply systems 10 </ b> A and 10 </ b> B through which the processing gas is blown onto the workpiece 90.

  The moving means 22 may be connected to the ejection parts 49A and 49B instead of the support part 20, and instead of moving the support part 20 between the first position and the second position, the ejection part 49A, By moving 49B, the ejection part 49A may be opposed to the support part 20 in the first etching process, and the ejection part 49B may be opposed to the support part 20 in the second etching process.

Fifth Embodiment As shown in FIG. 6, in the fifth embodiment, the workpiece 94 is a continuous sheet. The continuous sheet-like workpiece 94 is fed from the feed roll 23 and taken up by the take-up roll 24. A heating unit 21 is provided on the back side of the workpiece 94 between the rolls 23 and 24.

  An ejection portion 49A of the first processing gas supply system 10A is disposed at a position between the rolls 23 and 24 near the feeding roll 23. An ejection portion 49B of the second processing gas supply system 10B is disposed at a position near the take-up roll 24 between the rolls 23 and 24.

  The workpiece 94 fed out from the feed roll 23 comes into contact with the first processing gas from the first processing gas supply system 10A. Then, it contacts with the second processing gas from the second processing gas supply system 10B. Thereby, it can transfer to a 2nd etching process continuously from a 1st etching process. The feeding roll 23 and the take-up roll 24 function as a workpiece support section that replaces the stage-shaped support section 20. In addition, the feed roll 23 and the take-up roll 24 constitute a switching unit that selectively switches between the processing gas supply systems 10A and 10B in which the processing gas is blown to the workpiece 90.

Sixth Embodiment The change in the content of the fluorine raw material CF ₄ is not limited to two stages, and may be performed in three or more stages. In the first etching step, the CF ₄ content may be changed over two or more stages. In the second etching process, the CF ₄ content may be changed over two or more stages.

FIG. 7 shows an embodiment in which the content ratio of CF ₄ is changed over three stages in the first etching process and the second etching process.
The etching apparatus 1 includes three processing gas supply systems 10. Each processing gas supply system 10 has the same configuration as the processing gas supply systems 10A and 10B of the fourth embodiment (FIG. 5) and the fifth embodiment (FIG. 6). When these three processing gas supply systems 10 are distinguished from each other, the first stage (left side in FIG. 7) of the processing gas supply system 10 and components thereof are marked with X, and the second stage (center in FIG. 7). ) Is attached to the reference numerals of the processing gas supply system 10 and its constituent elements, and Z is attached to the reference numerals of the processing gas supply system 10 and its constituent elements in the third stage (right side in FIG. 7). The first-stage and second-stage process gas supply systems 10X and 10Y become the first process gas supply system for executing the first etching process. The processing gas supply system 10Z at the final stage (third stage) becomes the second processing gas supply system for executing the second etching process.

The CF ₄ content in the first-stage fluorine-based gas supply unit 31X may be approximately the same as that in the first etching process of the first embodiment. That is, preferably CF ₄ : Ar = 3: 97 to 97: 3, and more preferably CF ₄ : Ar = 5: 95 to 30:70.

The content of CF _{4 in} the second stage fluorine-based gas supply unit 31Y is higher than that in the first stage, preferably CF ₄ : Ar = 5: 95 to 100: 0, and more preferably CF ₄ : Ar = 40:60 to 80:20.

The CF ₄ content in the third-stage (final stage) fluorine-based gas supply unit 31Z is preferably higher than that in the second stage, and is approximately the same as that in the second etching process of the first embodiment. That is, preferably CF ₄ : Ar = 5: 95 to 100: 0, and more preferably CF ₄ : Ar = 75: 25 to 100: 0.
Therefore, the CF ₄ content increases stepwise as the downstream processing gas supply system 10 is reached.

The total flow rates of CF ₄ and Ar in the three processing gas supply systems 10 are equal to each other, and the blowing flow rates of the processing gases are substantially equal to each other. Therefore, the Ar flow rate decreases as the processing gas supply system 10 in the subsequent stage is reached. When CF ₄ : Ar = 100: 0 in the final stage, the Ar flow rate is zero.

The ejection parts 49 of the plasma generation parts 40 of the three processing gas supply systems 10 are arranged in a line at intervals. A roller conveyor 25 is installed below the ejection portions 49. The roller conveyor 25 is extended in the arrangement direction of the ejection portions 49. The workpiece 90 is conveyed by the roller conveyor 25 in the order below the first stage ejection part 49X, below the second stage ejection part 49Y, and below the third stage ejection part 49Z.
The roller conveyor 25 constitutes a conveying unit and a supporting unit for the workpiece 90. And the roller conveyor 25 comprises the switching means which selectively switches the process gas supply system 10 with which process gas is sprayed on the to-be-processed object 90. FIG.

[First etching process]
As the workpiece 90 is transported by the roller conveyor 25, it first comes into contact with the processing gas from the first stage processing gas supply system 10X and is etched. The recipe of the first stage processing gas is set so that silicon can be etched at a high rate and waste of CF ₄ is suppressed. In the first-stage etching, the surface of the silicon-containing film 93 becomes rough and becomes uneven. The underlying silicon nitride film 92 is not exposed yet.

Next, the workpiece 90 comes into contact with the processing gas from the second stage processing gas supply system 10Y and is etched. The CF ₄ content in the second stage is higher than that in the first stage. Therefore, H ₂ O is decomposed more than in the first stage, the amount of HF generated increases, and the amount of H ₂ O in the blown gas decreases. Therefore, the selection ratio of the silicon-containing film 93 to the base film 92 can be increased while maintaining a good etching rate of the silicon-containing film 93. Thereby, when the concave portion of the uneven surface of the silicon-containing film 93 reaches the interface with the base film 92, it is possible to suppress the base film 92 from being scraped.

[Second etching process]
Next, the workpiece 90 comes into contact with the processing gas from the third stage (final stage) processing gas supply system 10Z and is etched. The third stage CF ₄ content is even higher than the second stage (final stage of the first etching step). Therefore, the selection ratio of the silicon-containing film 93 to the base film 92 can be further increased. Thereby, the overetching amount d (FIG. 2D) of the base film 92 can be made sufficiently small, and the spotted residual film 93a of the silicon-containing film can be reliably removed.

The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope obvious to those skilled in the art.
For example, the silicon-containing film 93 to be etched is not limited to amorphous silicon, but may be polysilicon or single crystal silicon.
The silicon-containing film 93 to be etched is not limited to silicon, and may be silicon oxide, silicon carbide, silicon oxide carbide, or the like.
When the silicon-containing film 93 to be etched is silicon oxide, the processing gas does not need to contain an oxidizing reaction component. Therefore, the oxygen-based raw material supply unit 34 can be omitted.
When the silicon-containing film 93 to be etched is silicon carbide or silicon oxide carbide, it can be converted into silicon by a heating operation, and then etched in the same manner as in the above embodiment.

The base film 92 is not limited to silicon nitride, and may be any component different from the silicon-containing film 93 to be etched.
For the silicon-containing film 93 made of silicon such as amorphous silicon, the base film 92 may be silicon oxide.
When the silicon-containing film 93 to be etched is silicon oxide, the base film may be, for example, silicon nitride.
When the silicon-containing film 93 to be etched is silicon carbide or silicon oxide carbide, the base film 92 may be, for example, silicon nitride or silicon oxide.

Depending on the components of the underlying film, the CF ₄ content may be lowered in order to increase the selectivity of silicon to the underlying film as etching proceeds. The CF ₄ content in the second etching step may be lower than that in the first etching step. After decreasing the CF ₄ content, it may be increased. After increasing the CF ₄ content, it may be decreased. The CF ₄ content is not limited to changing stepwise, but may be continuously changed (gradual decrease or increase).

The content rate of CF ₄ may be changed by increasing or decreasing the flow rate of CF ₄ while maintaining the flow rate of Ar constant.

Instead of CF ₄ , other PFCs (perfluorocarbons) such as C ₂ F ₆ , C ₃ F ₆ , and C ₃ F ₈ may be used as the fluorine-based raw material. CHF ₃ , CH ₂ F ₂ , and CH ₃ HFC (hydrofluorocarbon) such as F may be used, and fluorine-containing compounds other than PFC and HFC such as SF ₆ , NF ₃ , and XeF ₂ may be used.
As the carrier (dilution gas), other inert gas such as He, Ne, N ₂ may be used instead of Ar.
As the oxygen-based raw material, oxygen-containing compounds such as NO, NO ₂ , and N ₂ O may be used instead of O ₂ .

Instead of generating the oxidizing reaction component using the plasma generating unit 44 or the ozonizer 48, the oxidizing reaction component itself such as O ₃ is stored in a tank or the like, and the oxidizing reaction component is taken out from the tank to remove fluorine. You may mix with a system reaction component.
In the second embodiment (FIG. 3) and the third embodiment (FIG. 4), the fluorine-based reactive gas and the oxidizing reactive gas are not mixed and blown out from different jetting portions toward the workpiece. Also good.
Instead of water (H ₂ O), an OH group-containing compound may be used. Examples of the OH group-containing compound include hydrogen peroxide water (H ₂ O ₂ ) and alcohols such as ethanol and methanol. However, in the case of hydrogen peroxide, the reactivity is high and it is difficult to stably add it to the gas of the fluorine-based reaction component. In the case of alcohol, the carbon component (C) reacts when it is introduced into the plasma, and an organic polymer is produced. Therefore, it is necessary to decompose and remove it. Therefore, H ₂ O that can be supplied simply and stably is preferable.

  The timing of switching from the first etching process to the second etching process is not limited to the stage where the base film 92 is exposed, and may be set to a stage just before the base film 92 is exposed.

When a plurality of processing gas supply systems 10 are provided and the system 10 facing the workpiece 90 is selectively switched by the switching means, there are two processing gas supply systems 10 (fourth and fifth embodiments (FIGS. 5 and 6). )) Or three (sixth embodiment (FIG. 7)), four or more may be provided.
It is sufficient that CF ₄ content of at least two process gas supply system 10 of the plurality of processing gas supply system 10 are different, all the CF ₄ content of a plurality of processing gas supply system 10 is different by one-stage However, the CF ₄ contents of a part (two or more) of the processing gas supply systems 10 among the plurality (three or more) of the processing gas supply systems 10 may be the same.

In the sixth embodiment (FIG. 7), two processing gas supply systems 10X may be provided side by side, and four processing gas supply systems 10 may be provided in the entire apparatus 1. This structure is suitable when the thickness of the silicon-containing film 93 is large and the amount that can be etched by one processing gas supply system 10X is less than half the thickness of the silicon-containing film 93. That is, by providing two processing gas supply systems 10X, more than half or most of the silicon-containing film 93 can be etched at a good etching rate and while suppressing waste of CF ₄ . Thereafter, etching is performed by increasing the silicon selection ratio in the processing gas supply system 10Y, and then etching is performed by further increasing the silicon selection ratio in the processing gas supply system 10Z.
Depending on the thickness of the silicon-containing film 93, three or more processing gas supply systems 10X may be arranged in parallel.

  A plurality of embodiments may be combined with each other. For example, each processing gas supply system 10 of the fourth to sixth embodiments (FIGS. 5 to 7) is replaced with a fluorine-based reaction component and an oxidizing reaction component in the same manner as the second and third embodiments (FIGS. 3 and 4). May be generated by different routes.

In the first to third embodiments (FIGS. 1 to 4), the raw material content rate adjusting unit 37 may increase (change) the CF ₄ content rate in three steps or more. Then, as in the sixth embodiment, the overetching amount d of the base film 92 can be sufficiently reduced while the etching rate is reliably increased, and the spotted residual film 93a of the silicon-containing film can be reliably removed.
In the first to third embodiments (FIGS. 1 to 4), the raw material content rate adjusting unit 37 may gradually increase the CF ₄ content rate continuously.
Depending on the components of the base film 92 and the like, in the first to third embodiments (FIGS. 1 to 4), the raw material content rate adjusting unit 37 may lower the CF ₄ content rate stepwise or continuously.

  The etching method and the etching apparatus according to the present invention are designed to remove contaminants including silicon adhering to the surface of an object to be processed, and to remove a roughened portion of a silicon wafer or glass, in addition to pattern etching of an object to be processed patterned with a resist. It can also be applied to planarization, roughening of the front or back surface of a silicon wafer or glass.

Examples will be described. The present invention is not limited to this example.
Using the etching apparatus of FIG. 3, the amorphous silicon film was etched in two stages, a first etching process and a second etching process. The base film was silicon nitride, and a sample in which amorphous silicon was laminated on the base film was used.
First, the first etching process was performed.
CF ₄ was used as a fluorine-based raw material. Ar was used as a dilution gas (carrier). CF ₄ was diluted with Ar to obtain a fluorine-based source gas (CF ₄ + Ar). The mixing ratio is as follows.
CF ₄ : Ar = 10: 90

Water was added to the fluorine-based source gas (CF ₄ + Ar) with a commercially available water addition device. The amount of water was controlled so that the dew point temperature was 18 ° C. The fluorine-based source gas (CF ₄ + Ar + H ₂ O) after the addition of water was converted into plasma by the plasma generation unit 40. The plasma discharge conditions are as follows.
Distance between electrodes: 1mm
Voltage between electrodes: 12kV
Power frequency: 40 kHz (pulse wave)
Separately, O ₂ as an oxygen-based source gas was introduced into another plasma generation unit 44 and turned into plasma under atmospheric pressure to obtain an oxidizing reaction gas. The plasma discharge conditions were the same as those of the plasma generator 40.
The fluorine-based reaction gas from the plasma generation unit 40 and the oxidizing reaction gas from the plasma generation unit 44 were mixed to obtain a first processing gas. The volume mixing ratio of the fluorine-based reaction gas and the oxidizing reaction gas was 1: 1.

The workpiece 90 was placed on the stage 20, and the plasma ejection part 53 was disposed above it. While the first processing gas was blown out from the plasma ejection portion 53, the ejection portion 53 was moved (scanned) so as to reciprocate from one end to the other end of the workpiece 90. The moving speed was 4 m / min. The one-way movement in the forward direction or the backward direction was set as one scan, the scan was performed 18 times, and the first etching process was completed. At this time, spot-like amorphous silicon 93a having a thickness of 0.1 to 10 μm remained on the surface of the workpiece 90 (see FIGS. 2B and 2C).
The etching rate of the amorphous silicon film in the first etching step was 9.8 nm / scan, and the selectivity of the amorphous silicon film to the silicon nitride film was about 1.3.

Subsequently, a second etching step was performed. The processing conditions were the same as those in the first etching step except for the CF ₄ content of the fluorine-based source gas and the number of scans of the ejection portion 53. The content of CF ₄ in the second etching step was higher than that in the first etching step, and the mixing ratio of CF ₄ and Ar was as follows.
CF ₄ : Ar = 80: 20

The number of scans in the second etching process was four. As a result, the remaining amorphous silicon 93a could be completely removed.
The etching rate of the amorphous silicon film in the second etching step was 10.2 nm / scan, and the selection ratio of the amorphous silicon film to the silicon nitride film was higher than that in the first etching step and was about 2.6. Therefore, it was confirmed that overetching of the underlying silicon nitride film 92 can be reduced while maintaining the etching rate of the amorphous silicon to be etched high.

  The present invention is applicable, for example, to the manufacture of flat panel displays (FPD) and semiconductor wafers.

It is explanatory drawing which shows schematic structure of 1st Embodiment of this invention. (A) is sectional drawing of the to-be-processed object before an etching, (b) is a top view of the to-be-processed object at the time of completion | finish of a 1st etching process, (c) is sectional drawing of (b). (D) is a plan view of the object to be processed at the end of the second etching step. It is explanatory drawing which shows schematic structure of 2nd Embodiment of this invention. It is explanatory drawing which shows schematic structure of 3rd Embodiment of this invention. It is explanatory drawing which shows schematic structure of 4th Embodiment of this invention. It is explanatory drawing which shows schematic structure of 5th Embodiment of this invention. It is explanatory drawing which shows schematic structure of 6th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Etching apparatus 10, 10A, 10B Processing gas supply system 10X, 10Y, 10Z Processing gas supply system 21 Heating part 22 Moving means (switching means)
25 Roller conveyor (switching means)
30 Raw material supply line 31 Fluorine-based material supply unit 32 Addition unit 34 Oxygen-based material supply unit 31 Fluorine-based gas supply unit 35 Fluorine-based material supply unit 36 Carrier supply unit 37 Material content rate adjustment unit 40 Plasma generation unit 43 Plasma space 44 Plasma generating portion 47 Plasma space 48 Ozonizer 49 Ejecting portion 90 Object to be processed 92 Base film 93 Silicon-containing film 93a Residual silicon film 94 Continuous sheet-like object to be processed

Claims (16)

In a method of etching a workpiece in which a silicon-containing film is laminated on a base film,
A treatment gas containing a fluorine-based reaction component generated by passing a fluorine-based material gas containing a fluorine-based material and containing a H ₂ O or OH group-containing compound through a plasma space near atmospheric pressure is brought into contact with the object to be treated; A method for etching a silicon-containing film, wherein the content of the fluorine-based material in the fluorine-based material gas is changed according to the progress of etching.   The etching method according to claim 1, wherein the content rate is increased as etching progresses.   The etching method according to claim 1, wherein the content rate is increased stepwise as etching progresses.   The content rate of a period for etching most of the silicon-containing film to be etched (hereinafter referred to as “first etching step”) is relatively lowered, and the first portion of the silicon-containing film to be etched is 4. The content rate according to claim 1, wherein the content of a period (hereinafter referred to as a “second etching process”) for etching a portion remaining after one etching process is relatively high. Etching method. The fluorine source gas in the first etching step further includes a carrier, and the molar ratio of the fluorine source and the carrier is fluorine source: carrier = 3: 97 to 97: 3,
The fluorine-based source gas in the second etching step further includes or does not include a carrier, and the molar ratio of the fluorine-based material to the carrier is fluorine-based material: carrier = 5: 95 to 100: 0. The etching method according to claim 4. The molar ratio of the fluorine-based material to the carrier of the fluorine-based material gas in the first etching step is fluorine-based material: carrier = 5: 95 to 30:70,
6. The etching according to claim 4, wherein a molar ratio of the fluorine-based material to the carrier in the fluorine-based material gas in the second etching step is fluorine-based material: carrier = 75: 25 to 100: 0. Method.   The content rate in the first etching step is increased stepwise, and the content rate in the second etching step is higher than that in the final step of the first etching step. The etching method according to claim 1. In an apparatus for etching an object to be processed in which a silicon-containing film is laminated on a base film,
A processing gas supply system that supplies a processing gas containing a fluorine-based reaction component to the object to be processed, the processing gas supply system,
A plasma generator that forms a plasma space near atmospheric pressure;
A raw material supply line that introduces into the plasma space a fluorine-based source gas that includes a fluorine-based source material that serves as the fluorine-based reaction component and to which an H ₂ O or OH group-containing compound is added;
A raw material content adjusting unit that changes the content of the fluorine-based raw material in the fluorine-based raw material gas of the raw material supply line according to the progress of etching;
A silicon-containing film etching apparatus comprising:   The etching apparatus according to claim 8, wherein the raw material content adjusting unit increases the content rate as etching progresses.   The etching apparatus according to claim 8 or 9, wherein the raw material content adjusting unit increases the content in a stepwise manner as etching progresses.   The raw material content adjusting unit lowers the content rate until most of the portion to be etched of the silicon-containing film is etched, and when etching the remaining silicon-containing film, the content rate is relatively The etching apparatus according to claim 8, wherein the etching apparatus is made higher. The raw material supply line mixes a fluorine-based raw material and a carrier to generate the fluorine-based raw material gas,
The etching apparatus according to claim 8, wherein the raw material content adjusting unit adjusts a mixing ratio of the fluorine-based raw material and the carrier. In an apparatus for etching an object to be processed in which a silicon-containing film is laminated on a base film,
A plurality of processing gas supply systems for blowing out a processing gas containing a fluorine-based reaction component;
A switching means for selectively switching a processing gas supply system in which a processing gas is sprayed onto the object to be processed according to the progress of etching;
Each processing gas supply system,
A plasma generator that forms a plasma space near atmospheric pressure;
A raw material supply line that introduces into the plasma space a fluorine-based source gas that includes a fluorine-based source material that serves as the fluorine-based reaction component and to which an H ₂ O or OH group-containing compound is added;
The silicon-containing film etching apparatus is characterized in that the fluorine-containing raw material contents in the fluorine-based raw material gases of at least two of the plurality of processing gas supply systems are different from each other.   The etching apparatus according to claim 13, wherein the switching unit selects a processing gas supply system having a relatively high content rate as etching progresses.   When the switching means selects a processing gas supply system having a relatively low content rate until most of the portion to be etched of the silicon-containing film is etched, and the remaining silicon-containing film is etched, The etching apparatus according to claim 13 or 14, wherein a processing gas supply system having a relatively high rate is selected.   The processing gas flow rates of the raw material supply lines of the plurality of processing gas supply systems are substantially equal to each other, and each raw material supply line mixes a fluorine-based material and a carrier to generate the fluorine-based material gas. The etching apparatus according to any one of -15.

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