JP7348019B2 - Etching method and etching device - Google Patents

Description

The present invention relates to an etching method and an etching apparatus.

Etching is being performed on the surface to be processed where the silicon film and silicon oxide film are exposed. In etching the object to be processed, a mixed gas containing ozone gas, anhydrous hydrogen fluoride gas, and ultrapure water vapor is used. In the mixed gas, the selectivity ratio of the silicon oxide film to the silicon film is adjusted by changing the composition of ozone gas, anhydrous hydrogen fluoride gas, and ultrapure water vapor (see, for example, Patent Document 1).

Japanese Patent Application Publication No. 9-190999

By the way, in the above-mentioned etching method, it is necessary to prepare three types of gases: ozone gas, anhydrous hydrogen fluoride gas, and ultrapure water vapor, and each time the selectivity ratio of the silicon oxide film to the silicon film is changed, Since it is necessary to change the flow rate of each gas, complicated processing is required to adjust the selection ratio. Therefore, there is a need for an etching method that can more easily adjust the selectivity between a silicon film and a silicon oxide film.

SUMMARY OF THE INVENTION An object of the present invention is to provide an etching method and an etching apparatus that enable easier adjustment of the selectivity ratio of a silicon oxide film to a silicon film.

An etching method for solving the above problem is an etching method that etches a surface to be processed that includes a silicon film and a silicon oxide film. Supplying an etchant containing fluorine atoms and hydrogen atoms to the surface to be treated, causing the surface to be treated and the etchant to react to generate a reaction product, and the reaction product generating volatilizable energy. and volatilizing the reaction product by applying the reaction product to the reaction product. Two sets of generating the reaction product and volatilizing the reaction product are arranged such that generating the reaction product and volatilizing the reaction product are performed alternately. Repeat more than once. To generate the reaction product, the supply of the etchant to the surface to be processed is terminated during a period in which the amount of etching of the silicon film is saturated and the amount of etching of the silicon oxide film is monotonically increasing.

An etching apparatus for solving the above problem is an etching apparatus that etches a surface to be processed that includes a silicon film and a silicon oxide film. an etchant supply unit that generates an etchant containing fluorine atoms and hydrogen atoms and supplies the etchant to the surface to be treated; and a reaction product generated by the reaction between the surface to be treated and the etchant; an energy supply unit that provides energy that allows the product to volatilize. The etchant supply unit and the energy supply unit supply the etchant and the energy to the surface to be processed alternately and the same number of times, two or more times, and the etchant supply unit supplies the silicon film to the surface to be processed. The supply of the etchant to the surface to be processed is terminated during a period in which the etching amount of the silicon oxide film is saturated and the etching amount of the silicon oxide film is monotonically increasing.

According to each of the above configurations, the supply of etching to the surface to be processed is terminated during a period in which the etching amount of the silicon film is saturated and the etching amount of the silicon oxide film is monotonically increasing. Therefore, the longer the time for supplying the etchant to the surface to be processed, the greater the ratio of the amount of etching of the silicon oxide film to the amount of etching of the silicon film. On the other hand, the shorter the time period for supplying the etchant to the surface to be processed, the smaller the ratio of the amount of etching of the silicon oxide film to the amount of etching of the silicon film. In this way, according to each of the above configurations, it is possible to adjust the selectivity ratio of the silicon oxide film to the silicon film depending on the time point at which the supply of etchant to the surface to be processed is ended. Therefore, it is easier to adjust the selection ratio of the silicon oxide film to the silicon film.

In the etching method, generating the reaction product includes making the etching amount of the silicon oxide film larger than the etching amount of the silicon film at the time when the etching amount of the silicon film is saturated. But that's fine.

According to the above configuration, the longer the time for supplying the etchant to the surface to be processed, the greater the selectivity ratio of the silicon oxide film to the silicon film can be increased within a range greater than 1.

In the etching method described above, volatilizing the reaction product may include that the temperature of the surface to be processed is 80° C. or less. According to this configuration, even if the surface to be processed is exposed to the atmosphere immediately after etching, formation of a thermal oxide film on the surface of the silicon film included in the surface to be processed can be suppressed.

In the above etching method, volatilizing the reaction product may include exposing the surface to be processed to plasma. According to this configuration, it is possible to provide energy necessary for volatilizing the reaction product generated on the surface to be processed while suppressing an increase in the temperature of the surface to be processed.

In the etching method, generating the reaction product may include generating the etchant containing fluorine atoms and hydrogen atoms using a gas containing fluorine atoms and a gas containing hydrogen atoms.

According to the above configuration, it is possible to separately prepare a fluorine source and a hydrogen source for generating an etchant. This makes it possible to increase the degree of freedom in selecting the gas to be used for etching the surface to be processed, compared to the case where the fluorine source and the hydrogen source for generating the etchant are embodied in one gas.

FIG. 1 is an apparatus configuration diagram schematically showing the configuration of an etching apparatus according to an embodiment. 7 is a graph showing the relationship between the etching amount of a silicon oxide film and time, and the relationship between the etching amount of a silicon film and time. 5 is a timing chart showing an example of gas supply, microwave supply, and high-frequency power supply in the etching method of one embodiment. FIG.

An embodiment of an etching method and an etching apparatus will be described with reference to FIGS. 1 to 3. Below, the configuration of the etching apparatus, the etching method, and test examples will be explained in order.

[Etching equipment configuration]
The configuration of the etching apparatus will be explained with reference to FIG.
The etching device etches a surface to be processed that includes a silicon film and a silicon oxide film. The etching apparatus includes an etchant supply section and an energy supply section. The etchant supply unit generates an etchant containing fluorine atoms and hydrogen atoms, and supplies the etchant to the surface to be treated. The energy supply unit provides energy that allows the reaction product to volatilize, to the reaction product generated by the reaction between the surface to be treated and the etchant.

The etchant supply unit and the energy supply unit supply etchant and energy to the processing target alternately and the same number of times, two or more times. The etchant supply unit stops supplying the etchant to the surface to be processed during a period in which the amount of etching of the silicon film is saturated and the amount of etching of the silicon oxide film is monotonically increasing. The configuration of the etching apparatus will be described in more detail below with reference to FIG.

As shown in FIG. 1, the etching apparatus 10 includes a vacuum chamber 11 that accommodates a processing target S including a processing target surface Sa. A shower plate 12 is located inside the vacuum chamber 11 and divides the space defined by the vacuum chamber 11 into two. The space defined by the vacuum chamber 11 is divided by the shower plate 12 into a first space 11A and a second space 11B.

A support section 13 that supports the processing target S is located in the second space 11B. The support section 13 is, for example, a stage on which the processing target S is placed. An exhaust section 14 that exhausts the inside of the vacuum chamber 11 is connected to the second space 11B. Since the shower plate 12 has a plurality of through holes that connect the first space 11A and the second space 11B, the exhaust section 14 exhausts both the first space 11A and the second space 11B. When the exhaust section 14 exhausts the inside of the vacuum chamber 11, the fluid inside the vacuum chamber 11 flows in the direction from the first space 11A to the second space 11B. The exhaust section 14 includes, for example, a pump and a valve.

The etching apparatus 10 includes a first gas supply section 15A, a discharge tube 16, and a microwave source 17. The first gas supply unit 15A supplies, for example, ammonia (NH ₃ ) gas, nitrogen (N ₂ ) gas, and nitrogen trifluoride (NF ₃ ) gas to the discharge tube 16. The first gas supply unit 15A includes, for example, a mass flow controller for supplying each gas. For example, the first gas supply unit 15A mixes NH ₃ gas and N ₂ gas, then supplies the mixed gas to the discharge tube 16, and supplies NF ₃ gas to the discharge tube 16 separately from the mixed gas. do.

Microwave source 17 excites microwaves. The microwave source 17 irradiates the discharge tube 16 supplied with NH ₃ gas, N ₂ gas, and NF ₃ gas with excited microwaves. The microwave source 17 irradiates the discharge tube 16 with microwaves having a frequency of, for example, 20 MHz or 2.45 GHz. As a result, plasma is generated in the discharge tube 16 from the NH ₃ gas, N ₂ gas, and NF ₃ gas. The generated plasma generated in the discharge tube 16 contains active species such as hydrogen radicals (H ^* ), ammonia radicals ( _NH2 ^* ), and fluorine radicals (F ^* ).

When the active species generated in the discharge tube 16 react, an etchant containing fluorine atoms and hydrogen atoms is generated. The etchant containing fluorine atoms and hydrogen atoms is, for example, NF _x H _y . In NF _x H _y , for example, x may be 1 or more and 3 or less, and y may be 1 or more and 4 or less. The etchant generated in the discharge tube 16 is supplied to the first space 11A.

As described above, the exhaust section 14 forms a fluid flow along the direction from the first space 11A to the second space 11B. Therefore, NF _x H _y supplied to the first space 11A is supplied from the first space 11A to the second space 11B through the through hole of the shower plate 12 that connects the first space 11A and the second space 11B. As a result, NF _x H _y is supplied to the processing target S. Note that NF _x H _y is generated not only in the discharge tube 16 but also between the first space 11A and the processing target S.

In this embodiment, the exhaust section 14, the first gas supply section 15A, the discharge tube 16, and the microwave source 17 constitute an etchant supply section. In this manner, the etchant supply unit supplies the etchant to the surface Sa to be processed to generate a reaction product by reacting with the object S to be processed.

The processing target surface Sa is a surface to which the etchant generated by the etchant supply unit is supplied. A silicon film and a silicon oxide film are exposed on the surface Sa to be processed. In the thickness direction of the processing target S, a silicon film may be stacked on a silicon oxide film, or a silicon film may be stacked on a silicon oxide film. In the thickness direction of the processing target S, the surface position of the silicon film and the surface position of the silicon oxide film may be equal to each other or may be different from each other.

The silicon oxide film is formed from silicon oxide (SiO _x ). NF _x H _y supplied to the processing target S reacts with SiO _x . This produces a reaction product that is more volatile than the silicon oxide film. The reaction product is, for example, (NF ₄ ) ₂ SiF ₆ . The silicon film is made of silicon (Si). NF _x H _y supplied to the processing target S reacts with Si. This produces a reaction product that is more volatile than the silicon film.

The etching apparatus 10 further includes a second gas supply section 15B, a high frequency antenna 18, and a high frequency power source 19. The second gas supply unit 15B supplies, for example, rare gas to the first space 11A. The rare gas supplied by the second gas supply section 15B is, for example, argon (Ar) gas.

The high frequency antenna 18 is located outside the vacuum chamber 11. The high frequency antenna 18 has a shape that surrounds the outer surface of the vacuum chamber 11 in the circumferential direction of the vacuum chamber 11 . The high frequency antenna 18 is located on the opposite side of the shower plate 12 from the first space 11A. In other words, the high frequency antenna 18 is located closer to the exhaust section 14 than the shower plate 12 is. The high-frequency antenna 18 is preferably located between the shower plate 12 and a support position where the support section 13 supports the processing target S in the direction in which the first space 11A and the second space 11B are lined up.

High frequency power source 19 is connected to high frequency antenna 18 . High frequency power supply 19 supplies power having a predetermined frequency to high frequency antenna 18 . The high frequency power supply 19 supplies power having a frequency of, for example, 13.56 MHz to the high frequency antenna 18. When the second gas supply unit 15B supplies Ar gas to the first space 11A, Ar gas is also supplied to the second space 11B. When Ar gas is supplied to the second space 11B, the high frequency power supply 19 supplies high frequency power to the high frequency antenna 18, thereby generating plasma from the Ar gas in the second space 11B.

By exposing the processing target S to the plasma generated from Ar gas, energy for volatilizing the reaction product is given to the reaction product on the processing target surface Sa. In this embodiment, the exhaust section 14, the second gas supply section 15B, the high frequency antenna 18, and the high frequency power supply 19 constitute an energy supply section.

The energy supply unit is capable of applying energy to the processing object S to heat the processing object to a temperature lower than the temperature at which silicon and oxygen forming the surface of the processing object S after etching react in the atmosphere. . It is preferable that the energy supply unit provides the processing object S with energy to heat the processing object S to a temperature of 80° C. or lower.

The amount of energy that the energy supply section gives to the processing object S, in other words, the temperature of the processing object S, tends to increase as the amount of power supplied to the high frequency antenna 18 increases, for example. It tends to increase as the time that power is supplied to 18 increases. Therefore, the amount of energy that the energy supply unit gives to the processing target S can be controlled by the amount of power supplied to the high-frequency antenna 18 and the time during which the power is supplied to the high-frequency antenna 18.

[Etching method]
The etching method will be explained with reference to FIGS. 2 and 3.
The etching method is a method for etching the processing target surface Sa including a silicon film and a silicon oxide film. The etching method includes producing a reaction product and volatilizing the reaction product. In generating a reaction product, an etchant containing fluorine atoms and hydrogen atoms is supplied to the surface Sa to be processed, and the surface Sa to be processed and the etchant are reacted to generate a reaction product. In volatilizing the reaction product, the reaction product is volatilized by providing the reaction product with energy that allows the reaction product to volatilize.

The etching method includes two sets of generating a reaction product and volatilizing the reaction product so that generating the reaction product and volatilizing the reaction product are performed alternately. Repeat more than once. To generate the reaction product, the supply of the etchant to the surface Sa to be processed is terminated during a period in which the amount of etching of the silicon film is saturated and the amount of etching of the silicon oxide film is monotonically increasing.

According to the etching method, the supply of etching to the surface Sa to be processed is terminated during a period in which the etching amount of the silicon film is saturated and the etching amount of the silicon oxide film is monotonically increasing. Therefore, the longer the time for supplying the etchant to the surface Sa to be processed, the greater the ratio of the amount of etching of the silicon oxide film to the amount of etching of the silicon film. On the other hand, the shorter the time for supplying the etchant to the surface Sa to be processed, the smaller the ratio of the amount of etching of the silicon oxide film to the amount of etching of the silicon film. In this way, according to the etching method, the selection ratio of the silicon oxide film to the silicon film can be adjusted depending on the point in time when the supply of the etchant to the surface Sa to be processed is ended. Therefore, it is easier to adjust the selection ratio of the silicon oxide film to the silicon film. The etching method will be described in more detail below with reference to the drawings.

FIG. 2 is a graph showing changes over time in the etching amount of a silicon film and the etching amount of a silicon oxide film when an etchant containing fluorine atoms and hydrogen atoms is used.
Note that the trends in the etching amount of the silicon film and the etching amount of the silicon oxide film shown in FIG. 2 are observed when the etching of the processing target S is performed under the following conditions. In addition, the etching amount of the silicon film and the etching amount of the silicon oxide film shown in FIG. 2 are obtained when a polycrystalline silicon film and a silicon oxide film each having a predetermined thickness and size are placed in the same etching apparatus. This is the amount of etching obtained when these films were etched.

・Fluorine-containing gas NF ₃
・Flow rate of fluorine-containing gas: 100 sccm or more and 5000 sccm or less ・Hydrogen-containing gas NH ₃
・Flow rate of hydrogen-containing gas: 10 sccm or more and 100 sccm or less ・Microwave frequency: 2.45 GHz
・Output of microwave source 17 2000W or more and 6000W or less ・Pressure in vacuum chamber 11 100Pa or more and 1300Pa or less

As shown in FIG. 2, the etching amount of the silicon film increases rapidly from the time when the supply of etchant to the surface Sa to be processed is started until 3 seconds after the start of the supply of etchant. It also increases between seconds and five seconds later. However, the etching rate from 3 seconds after starting the etchant supply is higher than the etching rate from 3 seconds to 5 seconds after starting the etchant supply. Then, from 5 seconds to 10 seconds after the start of etchant supply, the etching amount of the silicon film is maintained at approximately 0.4 nm. In other words, the etching rate from 5 seconds to 10 seconds after the start of etchant supply is approximately "0".

It can be said that the etching amount of the silicon film is saturated when the etching rate after the etching amount of the silicon film reaches a specific amount is maintained at less than 1/100 of the etching rate of the silicon oxide film. In the example shown in FIG. 2, it is recognized that the etching amount of the silicon film is saturated after 5 seconds after starting the supply of the etchant.

On the other hand, the amount of etching of the silicon oxide film is approximately proportional to the elapsed time from the time when the supply of etchant is started. That is, the etching rate of the silicon oxide film is approximately constant from the time when the supply of etchant is started. Further, the amount of etching of the silicon oxide film monotonically increases from the time when the supply of etchant is started.

In this way, the amount of etching of the silicon film becomes saturated after a predetermined period of time has elapsed since the start of supply of etchant, while the amount of etching of silicon oxide film monotonically increases. Therefore, as the length from the time when the etchant supply starts to the time when the etchant supply is stopped, that is, the period during which reaction products are generated, increases, the ratio of the amount of etching of the silicon oxide film to the amount of etching of the silicon film increases. It is possible to increase the In other words, by changing the period from the start to the end of etchant supply, it is possible to change the ratio of the amount of etching of the silicon oxide film to the amount of etching of the silicon film.

Furthermore, 5 seconds after the start of etchant supply, the amount of etching of the silicon oxide film is greater than the amount of etching of the silicon film. That is, in the example shown in FIG. 2, at the time when the amount of etching of the silicon film is saturated, the amount of etching of the silicon oxide film is larger than the amount of etching of the silicon film. Therefore, the longer the time for supplying the etchant to the surface Sa to be processed, the greater the selectivity ratio of the silicon oxide film to the silicon film can be increased within a range greater than 1.

FIG. 3 is a timing chart for explaining the etching method. FIG. 3 shows the supply of NH ₃ gas, N ₂ gas, and NF ₃ gas by the first gas supply unit 15A, the microwave irradiation by the microwave source 17, the supply of Ar gas by the second gas supply unit 15B, and , an example of the timing in each of the supply of high frequency power by the high frequency power supply 19 is shown.

As shown in FIG. 3, at timing T1, supply of NH ₃ gas, N ₂ gas, and NF ₃ gas to the discharge tube 16 is started. Next, at timing T2, irradiation of the discharge tube 16 with microwaves is started. The period between timing T1 and timing T2 is a period until the pressure inside the discharge tube 16 becomes almost constant, and after the pressure inside the discharge tube 16 becomes stable, the microwave is irradiated to the discharge tube 16. be done. As a result, at timing T2, supply of etchant to the silicon oxide film and generation of reaction products are started. Note that, as described above, the etchant is, for example, NF _x H _y , and the reaction product is, for example, (NF ₄ ) ₂ SiF ₆ .

In this manner, in this embodiment, an etchant containing fluorine atoms and hydrogen atoms is generated using a gas containing fluorine atoms and a gas containing hydrogen atoms. Therefore, it is possible to separately prepare a fluorine source and a hydrogen source for generating an etchant. As a result, it is possible to increase the degree of freedom in selecting the gas used for etching the surface Sa to be processed, compared to the case where the fluorine source and the hydrogen source for generating the etchant are embodied in one gas.

At timing T3, irradiation of the microwave to the discharge tube 16 is stopped. Etchant for generating reaction products is generated approximately during the period from timing T2 to timing T3. Therefore, the period from timing T2 to timing T3 is set according to the ratio of the etching amount of the silicon film to the etching amount of the silicon oxide film on the processing target surface Sa. Next, at timing T4, the supply of NH ₃ gas, N ₂ gas, and NF ₃ gas to the discharge tube 16 is stopped.

At timing T4, supply of Ar gas to the first space 11A is also started. At timing T4, the supply of etchant to the first space 11A is stopped and the supply of Ar gas is started at the same time. Therefore, the pressure within the vacuum chamber 11 is less likely to fluctuate compared to a case where stopping the supply of etchant and starting supply of Ar gas are performed at different timings.

At timing T5, supply of high frequency power to the high frequency antenna 18 is started. The period between timing T4 and timing T5 is a period until the pressure in the vacuum chamber 11 becomes almost constant, and after the pressure in the vacuum chamber 11 becomes stable, high frequency power is supplied to the high frequency antenna 18. be done. Further, the period between timing T4 and timing T5 is a period in which gas containing fluorine atoms, such as an etchant, supplied into the vacuum chamber 11 is exhausted to the outside of the vacuum chamber 11 using Ar gas. As a result, the gas containing fluorine atoms is exhausted to the outside of the vacuum chamber 11 before high frequency power is supplied to the high frequency antenna 18, thereby suppressing the generation of plasma from the gas containing fluorine atoms. Active species containing fluorine contained in the plasma, such as radicals containing fluorine and ions containing fluorine, may corrode a part of the processing target S. According to this embodiment, since plasma is generated after the gas containing fluorine atoms is exhausted, corrosion of the processing target S can be suppressed.

Next, at timing T6, the supply of high frequency power to the high frequency antenna 18 is stopped. The period from timing T5 to timing T6 is a period in which the reaction products are exposed to plasma and energy for volatilizing the reaction products is given to the reaction products. Therefore, the period from timing T5 to timing T6 can be set depending on the amount of reaction products generated on the processing target S, for example. At timing T7, the supply of Ar gas to the first space 11A is stopped.

In the period from timing T5 to timing T6, it is preferable that the temperature of the object to be processed is 80° C. or lower. Thereby, even if the processing target surface Sa is exposed to the atmosphere immediately after etching, formation of a thermal oxide film on the surface of the silicon film included in the processing target surface Sa is suppressed. In this embodiment, by exposing the processing target S to plasma, reaction products generated on the processing target surface Sa are volatilized. Therefore, it is possible to provide the reaction products generated on the processing target surface Sa with the energy necessary for the reaction products to volatilize while suppressing the temperature of the processing target surface Sa from increasing.

In addition, since reaction products are removed by exposing the surface Sa to be processed to plasma, the delay from the start of plasma generation, that is, from timing T5 to the start of removal of reaction products, is short. . On the other hand, when the reaction product is heated together with the surface to be processed Sa, the temperature of the surface to be processed Sa to which the reaction product has adhered reaches the target temperature for removing the reaction product. A predetermined amount of time is required. In this respect, according to the present embodiment, the period from the start of supply of energy to the reaction product until the start of removal of the reaction product can be shortened.

In this embodiment, the period from timing T1 to timing T4 is a process of generating a reaction product, and the period from timing T4 to timing T7 is a process of volatilizing the reaction product. In the etching method, it is possible to adjust the period from timing T1 to timing T4 depending on the desired selectivity between the silicon film and the silicon oxide film. In addition, in the etching method, the number of times of repeating the step of generating a reaction product and the step of volatilizing the reaction product is set to two or more times depending on the desired amount of etching of the silicon film and the silicon oxide film. It is possible to set the number of times.

[Test example]
[Test Example 1]
A first silicon substrate made of polycrystalline silicon and a second silicon substrate on which a silicon oxide film was formed were prepared. Then, the first silicon substrate and the second silicon substrate were placed in an etching apparatus, and each silicon substrate was etched under the following conditions.

・Fluorine-containing gas NF ₃
・Flow rate of fluorine-containing gas 1000sccm
・Hydrogen-containing gas _NH3
・Flow rate of hydrogen-containing gas 50sccm
・Microwave frequency 2.45GHz
・Output of microwave source 17 2500W
・Pressure inside vacuum chamber 11 500Pa
・Etching time 50 seconds

In Test Example 1, it was found that the etching amount of the first silicon substrate was 0.43 nm, and the etching amount of the silicon oxide film was 6.30 nm. Further, in Test Example 1, the selectivity ratio, which is the ratio of the amount of etching of the silicon oxide film to the amount of etching of the first silicon substrate, was found to be 14.6.

[Test Example 2]
In Test Example 1, the etching time, that is, the time for supplying the etchant to each silicon substrate, was changed to 10 seconds, and the step of generating reaction products and the step of volatilizing the reaction products were alternately performed for 5 seconds. Each silicon substrate was etched by the same method as in Test Example 1, except that etching was performed twice.

In Test Example 2, it was found that the etching amount of the first silicon substrate was 2.01 nm, and the etching amount of the silicon oxide film was 5.96 nm. Further, in Test Example 2, the selectivity ratio, which is the ratio of the amount of etching of the silicon oxide film to the amount of etching of the first silicon substrate, was found to be 3.0.

In this way, by changing the point at which the supply of etchant to the processing target is stopped within the period when the amount of etching of the silicon film is saturated and the amount of etching of the silicon oxide film is monotonically increasing, It is possible to adjust the selectivity of the oxide film.

As explained above, according to one embodiment of the etching method and etching apparatus, the effects described below can be obtained.
(1) The selectivity ratio of the silicon oxide film to the silicon film can be adjusted depending on the time point at which the supply of etchant to the surface Sa to be processed is ended. Therefore, it is easier to adjust the selection ratio of the silicon oxide film to the silicon film.

(2) The longer the time for supplying the etchant to the surface Sa to be processed, the greater the selectivity ratio of the silicon oxide film to the silicon film can be increased within a range greater than 1.

(3) Even if the surface to be processed Sa is exposed to the atmosphere immediately after etching, formation of a thermal oxide film on the surface of the silicon film included in the surface to be processed Sa is suppressed.

(4) It is possible to provide the reaction products generated on the processing target surface Sa with the energy necessary for the reaction products to volatilize while suppressing the temperature of the processing target surface Sa from increasing.

(5) It is possible to separately prepare a fluorine source and a hydrogen source for generating an etchant. This makes it possible to increase the degree of freedom in selecting the gas to be used for etching the processing target S, compared to the case where the fluorine source and the hydrogen source for generating the etchant are embodied in one gas.

Note that the embodiment described above can be modified and implemented as follows.
[Energy supply section]
- The energy supply unit may provide the reaction product with energy to volatilize the reaction product by heating the processing target surface Sa to a predetermined temperature. In this case, for example, the etching apparatus 10 can include a heating section that heats the support section 13. Further, the energy supply unit may provide the reaction product with energy to volatilize the reaction product by both exposing the processing target to plasma and heating the processing target.

[ _NF3 gas]
- NF ₃ gas may be supplied to the first space 11A. Thereby, it is possible to generate an etchant containing hydrogen atoms and fluorine atoms from the active species containing hydrogen supplied from the discharge tube 16 to the first space 11A and the molecules in the NF ₃ gas. It is.

[gas]
- The gas containing fluorine atoms may be a gas containing fluorine atoms other than NF ₃ gas, and the gas containing hydrogen may be a gas containing hydrogen atoms other than NH ₃ gas. The gas containing fluorine atoms may be, for example, fluorine (F ₂ ) gas. The gas containing hydrogen atoms may be, for example, hydrogen (H ₂ ) gas.

- Gases used to generate plasma when volatilizing reaction products include rare gases other than Ar gas, such as helium (He) gas, neon (Ne) gas, krypton (Kr) gas, and xenon (Xe). It may be any gas.

[Temperature of processing target]
- When volatilizing the reaction product, the temperature of the surface Sa to be processed may be heated to a temperature higher than 80°C. In this case, for example, the etching apparatus 10 may include a cooling unit that cools the surface Sa to be processed to cool the surface Sa to be processed. This makes it possible to shorten the time from when the reaction products generated on the surface to be processed Sa are volatilized until the temperature of the surface to be processed Sa becomes low enough to suppress the oxidation reaction on the surface to be processed Sa. It is.

[Period of supplying etchant]
- The period during which the etchant is supplied to the processing target surface Sa may be the same for multiple times, or the multiple times may include times during which the etchant is supplied for different periods. In either case, the above-mentioned ( It is possible to obtain an effect similar to 1).

[Etching amount]
- At the time when the amount of etching of the silicon oxide film is saturated, the amount of etching of the silicon oxide film may be equal to or less than the amount of etching of the silicon film. Even in this case, the above-mentioned (1 ) can achieve similar effects.

[Etching equipment]
- The etching apparatus 10 may include a first vacuum tank and a second vacuum tank, and the first vacuum tank and the second vacuum tank may be separated by a gate valve. In this case, a step of generating a reaction product is performed in the first vacuum tank, and a step of volatilizing the reaction product is performed in the second vacuum tank. According to such an etching apparatus, for example, even when the reaction product is volatilized by heating the reaction product, the first vacuum chamber is not heated. This prevents speed-limiting.

DESCRIPTION OF SYMBOLS 10... Etching device, 11... Vacuum chamber, 11A... First space, 11B... Second space, 12... Shower plate, 13... Support part, 14... Exhaust part, 15A... First gas supply part, 15B... Second gas Supply unit, 16...discharge tube, 17...microwave source, 18...high frequency antenna, 19...high frequency power supply, S...processing target, Sa...processing target surface.

Claims (6)

An etching method for etching a surface to be processed including a silicon film and a silicon oxide film,
supplying an etchant containing fluorine atoms and hydrogen atoms to the surface to be treated, and causing the surface to be treated and the etchant to react to generate a reaction product;
volatilizing the reaction product by imparting energy to the reaction product that allows the reaction product to volatilize;
Two sets of generating the reaction product and volatilizing the reaction product are arranged such that generating the reaction product and volatilizing the reaction product are performed alternately. Repeat more than once,
Generating the reaction product includes terminating the supply of the etchant to the surface to be processed during a period in which the etching amount of the silicon film is saturated and the etching amount of the silicon oxide film is monotonically increasing;
An etching method, wherein the ratio of the etching amount of the silicon oxide film to the etching amount of the silicon film is changed by changing the period from the start to the end of the supply of the etchant. Generating the reaction product includes that the etching amount of the silicon oxide film is larger than the etching amount of the silicon film at a time when the etching amount of the silicon film is saturated ;
The period from the start to the end of the supply of the etchant is 50 seconds or less
The etching method according to claim 1. The etching method according to claim 1 , wherein volatilizing the reaction product includes keeping the temperature of the surface to be processed at 80° C. or lower. The etching method according to any one of claims 1 to 3, wherein volatilizing the reaction product includes exposing the surface to be processed to plasma. Any one of claims 1 to 4, wherein generating the reaction product includes generating the etchant containing fluorine atoms and hydrogen atoms using a gas containing fluorine atoms and a gas containing hydrogen atoms. The etching method described in item 1. An etching apparatus for etching a surface to be processed including a silicon film and a silicon oxide film,
an etchant supply unit that generates an etchant containing fluorine atoms and hydrogen atoms and supplies the etchant to the surface to be treated;
an energy supply unit that supplies energy that allows the reaction product to volatilize to a reaction product generated by the reaction between the surface to be treated and the etchant;
The etchant supply unit and the energy supply unit supply the etchant and the energy to the surface to be treated alternately and the same number of times, two or more times,
The etchant supply unit stops supplying the etchant to the surface to be processed during a period in which the amount of etching of the silicon film is saturated and the amount of etching of the silicon oxide film is monotonically increasing;
An etching apparatus, wherein the ratio of the etching amount of the silicon oxide film to the etching amount of the silicon film is changed by changing the period from the start to the end of the supply of the etchant.