Etching method and plasma etching apparatus

Abstract

This invention provides an etching method and a plasma etching apparatus capable of efficiently supplying etchant to the bottom of an etched shape and increasing the etching rate. The etching method of this invention includes: step (a), providing a silicon-containing substrate to a support stage; step (b), etching the substrate using plasma generated from a first gas containing fluorine gas to form an etched shape having a bottom; step (c), generating plasma from a second gas containing hydrogen fluoride (HF) gas to selectively form a condensed or solidified layer of HF at the bottom of the etched shape; and step (d), supplying bias power to the support stage and etching the bottom using the generated plasma, wherein in steps (c) to (d), the temperature of the substrate is maintained below 0°C.

Description

Technical Field

[0001] This invention relates to etching methods and plasma etching apparatus. Background Technology

[0002] Patent Document 1 discloses a plasma etching technique for forming high aspect ratio recesses in a silicon oxide film, which is the film to be etched. In this technique, the silicon oxide film is etched by generating a plasma containing a fluorine-containing gas such as fluorocarbon gas or hydrofluorocarbon gas, and hydrogen. In high aspect ratio structures such as contact holes of memory devices, the aspect ratio increases as etching progresses, and the amount of etchant supplied decreases.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2016-122774 Summary of the Invention

[0006] The technical problem that the invention aims to solve

[0007] This invention provides a technique for efficiently supplying etchant to the bottom of an etched shape (recess) to improve the etching rate.

[0008] Means for solving technical problems

[0009] According to one aspect of the present invention, an etching method is provided, comprising: step (a) providing a silicon-containing substrate to a support stage; step (b) etching the substrate using plasma generated from a first gas containing a fluorine-containing gas to form an etched shape having a bottom; step (c) generating plasma from a second gas containing hydrogen fluoride (HF) gas to selectively form a condensed or solidified layer of HF at the bottom of the etched shape; and step (d) supplying bias electrical power to the support stage to etch the bottom using the generated plasma, wherein in steps (c) to (d), the temperature of the substrate is maintained below 0°C.

[0010] Invention Effects

[0011] By employing one aspect of the present invention, etchant can be supplied to the bottom of the etched shape with high efficiency, thereby increasing the etching rate. Attached Figure Description

[0012] Figure 1 This is a diagram illustrating an etching method in one embodiment.

[0013] Figure 2 This is a diagram illustrating the process of a second etching in one embodiment.

[0014] Figure 3 This is a diagram used to illustrate the etching process of the film being etched.

[0015] Figure 4 This is a diagram used to illustrate the etching process of the film being etched.

[0016] Figure 5 This is a cross-sectional schematic diagram illustrating an example of a plasma etching apparatus according to one embodiment.

[0017] Explanation of reference numerals in the attached figures

[0018] 1. Chamber, 2. Plasma, 3. Upper electrode, 4. Lower electrode, 5. Electrostatic chuck, 6, 7. RF source, 8. Gas source, 9. Exhaust device, 10. Plasma etching device, 20. Mask, 21. Etched object film, 22. Condensation layer / solidification layer, 80. Control unit, W. Substrate, ST. Support stage. Detailed Implementation

[0019] In one exemplary embodiment, a method for etching a film is provided. The method includes: step (a), providing a silicon-containing substrate to a support stage; step (b), etching the substrate using plasma generated from a first gas containing a fluorine-containing gas to form an etched shape having a bottom; step (c), generating plasma from a second gas containing hydrogen fluoride (HF) gas to selectively form a condensed or solidified layer of HF at the bottom of the etched shape; and step (d), supplying bias power to the support stage and etching the bottom using the generated plasma, wherein in steps (c) to (d), the temperature of the substrate is maintained below 0°C. This embodiment allows for efficient supply of etchant to the bottom of the etched shape, increasing the etching rate.

[0020] In one exemplary embodiment, steps (c) and (d) can be performed repeatedly. Furthermore, in one exemplary embodiment, steps (c) and (d) can be performed simultaneously.

[0021] In one exemplary embodiment, steps (c) and (d) may be performed when the opening size of the etched shape is less than 200 nm and the aspect ratio is greater than 20.

[0022] In one exemplary embodiment, the substrate temperature may be set to below -40°C after step (a).

[0023] In one exemplary embodiment, the bottom may be etched using a plasma of a second gas or a plasma of a rare gas in step (d).

[0024] In one exemplary embodiment, bias power may be supplied to introduce ions from the plasma to the bottom, causing the condensate or solidified layer formed at the bottom to react with the bottom, thereby enabling etching.

[0025] In one exemplary embodiment, a method for etching a film is provided. The method includes: a step of providing a silicon-containing substrate to a support stage within a chamber; a setting step of setting the temperature of the substrate to below 0°C; a supply step of supplying a mixed gas containing hydrogen fluoride (HF) gas at a volumetric flow rate ratio of at least 30% relative to the total flow rate of the process gas into the chamber; and an etching step of supplying radio-frequency power for plasma generation, using the plasma generated from the mixed gas to etch the substrate. During the supply and etching steps, the temperature of the substrate is maintained below 0°C. This embodiment improves the etching rate.

[0026] In one exemplary embodiment, the substrate temperature may be set to below -40°C in the setting process, and the substrate temperature may be maintained below 0°C in the supply process and the etching process.

[0027] In one exemplary embodiment, the silicon-containing substrate may comprise a silicon oxide film or a silicon nitride film.

[0028] In one exemplary embodiment, the silicon-containing substrate may comprise a laminate of a silicon oxide film and a silicon nitride film.

[0029] In one exemplary embodiment, the silicon-containing substrate may comprise a laminate of a silicon oxide film and a polycrystalline silicon film.

[0030] In one exemplary embodiment, a plasma etching apparatus is provided, comprising: a chamber; a support stage disposed within the chamber for supporting a substrate; a plasma generation unit for generating plasma within the chamber; and a control unit. The control unit of the plasma etching apparatus is capable of performing: step (a) receiving a silicon-containing substrate and supporting it on the support stage; step (b) etching the substrate using plasma generated from a first gas containing fluorine gas to form an etched shape having a bottom; step (c) generating plasma from a second gas containing hydrogen fluoride (HF) gas to selectively form a condensed or solidified layer of HF at the bottom of the etched shape; and step (d) supplying bias electrical power to the support stage to etch the bottom using the generated plasma, wherein the temperature of the substrate is maintained below 0°C during steps (c) to (d).

[0031] Hereinafter, the embodiments for carrying out the present invention will be described with reference to the accompanying drawings. In the drawings, the same reference numerals are used to label the same components, and repeated descriptions are omitted.

[0032] In the following description, from Figure 5 The electrical power supplied to the plasma etching apparatus by one of the two high-frequency power sources (RF power sources) is also called HF power. Figure 5 The electrical power supplied by the other of the two high-frequency power supplies to the lower electrode within the plasma etching apparatus is also called the LF power (or bias power). The HF power is primarily a high-frequency power used for plasma generation, which helps in generating plasma. The LF power is primarily a high-frequency power used for biasing, which helps introduce ions into the substrate W. Here, the substrate W to be processed is a wafer with a diameter of 300 mm. The temperature of the substrate W can be controlled by measuring the surface temperature of the substrate W using a temperature sensor attached to the surface of the substrate W via an adhesive such as silicone. Furthermore, in this specification, mixed gas refers to a gas (etching gas) obtained by mixing two or more gases.

[0033] In this embodiment, refer to Figure 1 This describes the method MT for etching a substrate. In the following description, except as otherwise provided... Figure 1 In addition, refer to Figure 5 Furthermore, the following explanation will use the application of method MT to substrate W using plasma etching apparatus 10 as an example. Method MT includes steps S1 to S5. Step S5 includes at least... Figure 2 The processes S51 to S53.

[0034] In process S1, such as Figure 5 As shown, a substrate W containing the film to be etched is supported within chamber 1 by a support stage ST. The support stage ST includes an electrostatic chuck 5, which can hold the substrate W using electrostatic force. The film to be etched is a silicon-containing film. The silicon-containing film includes a silicon oxide film (SiO2) or a silicon nitride film (SiN). The silicon-containing film may also include silicon-containing films other than silicon oxide films. The silicon-containing film may include two or more types of silicon-containing films. The two or more types of silicon-containing films may include a laminate of silicon oxide film and polysilicon film, or a laminate of silicon oxide film and silicon nitride film. In this embodiment, an example of etching a silicon oxide film as the film to be etched is described. For example, etching with an aspect ratio of 20 or higher for 3D-NAND or DRAM can be used.

[0035] The substrate W may also have a mask with openings in the etchable film. The mask can be formed from various films capable of achieving a selectivity ratio with the silicon-containing film that is the etchable film. The mask can be a carbon-containing film. An example of a carbon-containing film includes photoresist or amorphous carbon. The mask can also be a silicon-containing film, for example, a polycrystalline silicon mask.

[0036] Etching can utilize gases containing fluorine. These gases can be fluorocarbons such as CF4, C2F6, C4F6, and C4F8; hydrofluorocarbons such as CH3F, CH2F2, and CHF3; gases such as SF6 and NF6; hydrogen fluoride (HF); or combinations of one or more of these. The fluorine-containing gas may also contain hydrogen-containing gases. These hydrogen-containing gases can be H2, CH4, etc. Furthermore, in addition to these gases, rare gases such as Ar may also be present. The plasma generated from fluorine-containing gases or fluorine and hydrogen-containing gases has light fluoride and hydrogen ions, thus minimizing damage to the mask. Therefore, a high mask selectivity ratio can be obtained. In one example, when the aspect ratio is a specified value (e.g., 20) or higher, a mixture of hydrogen fluoride gases can be used as the etching gas. The hydrogen fluoride gas in the mixture can contain hydrogen fluoride gas at a volumetric flow rate of 30% or more relative to the total flow rate of the mixed gas (processing gas). In this example, the aspect ratios A1 to A3 are calculated without including the mask. Alternatively, as follows... Figure 4 As shown in A1 to A3, the aspect ratio is calculated using a mask. It is sufficient to determine the aspect ratio of the condensate or solidified layer of hydrogen fluoride that can be formed (described later).

[0037] The mask on the silicon-containing film can be a metal-containing mask. The metal-containing mask can be formed of materials such as tungsten (W), titanium (Ti), molybdenum (Mo), ruthenium (Ru), hafnium (Hf), or aluminum (Al).

[0038] Next, in step S2, the temperature of the substrate is controlled to be below 0°C. For example, the temperature of the substrate (the temperature of the support stage ST) is set to below -40°C before etching begins (here, the temperature of the substrate before etching begins is approximately the same as the temperature of the support stage ST before etching begins). By keeping the substrate temperature below 0°C, and in one example below -40°C, the supply of etchant to the bottom of the etched shape can be promoted, increasing the etching rate. Alternatively, the substrate temperature can be set to below -70°C before etching begins. The support stage ST can be cooled using a cooler, or the substrate temperature can be adjusted by circulating a refrigerant such as liquid nitrogen or Freon in the support stage ST. Considering the heat input generated by the plasma, the temperature of the refrigerant circulating in the support stage ST during etching is set to a temperature 10°C to 50°C lower than the target temperature of the substrate. In one example, a refrigerant at -120°C to -40°C is supplied to the flow path 18 in the support stage ST. In addition, the target temperature of the substrate is preset to any temperature below 0°C. In addition to supplying refrigerant to the support platform ST, heat transfer gas can also be supplied from the heat transfer gas piping 19 of the support platform ST to the space between the front side of the electrostatic chuck 5 and the back side of the substrate W held thereon. Heat conduction can be controlled by controlling the pressure of the heat transfer gas supplied between the front side of the electrostatic chuck 5 and the back side of the substrate W, thereby regulating the temperature of the substrate. An inert gas can be used as the heat transfer gas. In one example, a rare gas, such as helium, can be used. Thus, the temperature of the substrate W can be controlled to below 0°C.

[0039] Next, in step S3, the substrate W is etched. This etching in step S3 is referred to as the "first etching." In step S3, a fluorine-containing gas can be supplied to the chamber from the gas source 8 as the etching gas, and a high-frequency electrical power of 27MHz to 100MHz for plasma generation can be supplied from the RF source 6 to the upper electrode 3 to generate plasma from the etching gas. In another example, the high-frequency electrical power for plasma generation can also be supplied from the RF source 6 to the support stage ST (lower electrode). In one example, the magnitude of the high-frequency electrical power supplied from the RF source 6 can be 0.1kW to 5kW. Alternatively, a bias electrical power of 200kHz to 13.56MHz can be supplied from the RF source 7 to the support stage ST (lower electrode) for etching. The magnitude of the bias electrical power can be 5kW or more. It is not limited to high-frequency electrical power; voltage pulses can also be used. In one example, a direct current (DC) voltage pulse can be applied. The fluorine-containing gas supplied to the chamber in step S3 is an example of the "first gas."

[0040] As the etching gas, a fluorocarbon gas (e.g., CF4) can be used. A hydrogen-containing gas (e.g., H2) can also be supplied. Furthermore, rare gases can be added. When the film to be etched contains a silicon nitride film, a fluorocarbon or hydrofluorocarbon gas (e.g., CHF3) can be used as the etching gas. The high-frequency electrical power used for plasma generation is not limited to a continuous wave; it can also be a pulsed wave with a specified duty cycle (defined by on-time / (on-time + off-time)). The duty cycle can be varied during etching. In step S3, the substrate W is etched using plasma generated from a gas containing fluorine-containing gas to form an etched shape with a bottom. Thus, as... Figure 3 As shown in (a), ions and free radicals in the plasma act through mask 20 to etch the target film 21. Figure 3 Examples of etched shapes include holes H and line shapes. In the first etching, in one example, the etching is approximately to a depth A1 with an aspect ratio of about 20.

[0041] Next, in step S4, it is determined whether the opening size of the etched shape is less than or equal to a specified value and the aspect ratio is greater than or equal to a specified value. For example, it is determined whether the opening size of the etched shape is less than or equal to 200 nm and the aspect ratio is greater than or equal to 20. Here, the specified aspect ratio is simply that it can be formed at the bottom of the recess. Figure 3 The value of the hydrogen fluoride condensate or solidified layer 22 in (b) is sufficient. In one embodiment, the aspect ratio (opening size, etc.) can be measured using an optical mechanism located inside or outside the cavity.

[0042] If the opening size of the etched shape is larger than a predetermined value (e.g., 200 nm), or the aspect ratio is smaller than a predetermined value (e.g., aspect ratio 20), the process returns to step S3 to continue the first etching. Conversely, if the opening size of the etched shape is less than or equal to a predetermined value (e.g., 200 nm) and the aspect ratio is greater than or equal to a predetermined value (e.g., aspect ratio 20), the process proceeds to step S5. Alternatively, in step S4, instead of the above determination, it can be determined whether a predetermined time has elapsed since the start of the first etching. In this case, if the predetermined time has elapsed, the process returns to step S3 to continue the first etching. Conversely, if the predetermined time has elapsed, the process proceeds to step S5.

[0043] In step S5, etching continues on the substrate W. This etching in step S5 is referred to as the "second etching." The first and second etchings are consecutive etchings of the same etchable film. In another example, the second etching can be performed after the first etching, or other processes can be performed between the first and second etchings. In step S5, an etching gas containing hydrogen fluoride (HF) is supplied to the chamber from the gas source 8. If the gas used in step S3 contains hydrogen fluoride, the etching gas supplied in step S5 can be the same gas as the fluoride-containing gas supplied in step S3. When the same gas is used, gas switching is not required in step S5, improving productivity. The etching gas containing hydrogen fluoride supplied to the chamber in step S5 is an example of a "second gas."

[0044] In another example, when hydrogen fluoride gas is present in step S3, the flow rate of hydrogen fluoride gas supplied in step S5 can be greater than that supplied in step S3. The mixed gas supplied in step S5 can contain different gases than the gas supplied in step S3. Furthermore, when hydrogen fluoride gas is present in step S3, the flow rate ratio of hydrogen fluoride gas supplied in step S5 relative to other gases in the mixed gas can be higher than the flow rate ratio of hydrogen fluoride gas supplied in step S3 relative to other gases. Therefore, even with a higher aspect ratio, sufficient hydrogen fluoride can be supplied to the bottom of the etched shape.

[0045] Regarding other processing conditions in step S5, for example, high-frequency electrical power of 27MHz to 100MHz for plasma generation can be supplied from the RF source 6 to the upper electrode 3 to generate plasma from the etching gas. Alternatively, high-frequency electrical power for plasma generation can be supplied from the RF source 6 to the support stage ST (the lower electrode in one example). The etching gas can be a mixture of two or more gases containing hydrogen fluoride (HF). The mixed gas can be supplied to the chamber 1 separately and mixed within the chamber 1, or it can be mixed before being supplied to the chamber 1. In one example, the frequency of the high-frequency electrical power supplied from the RF source 6 can be 0.1kW to 5kW. In addition, a bias power of 200kHz to 13.56MHz is supplied from the RF source 7 to the support stage ST to promote etching. The magnitude of the bias power can be 5kW or more. The bias power is not limited to high-frequency electrical power and can also be a voltage pulse such as a DC pulse.

[0046] The gas supplied in step S5 may contain at least one of the following, in addition to hydrogen fluoride gas: a fluorocarbon gas, a hydrofluorocarbon gas, and other halogen-containing gases. Examples of fluorocarbon gases include CF4, C3F8, C4F6, C4F8, and C5F8. Examples of hydrofluorocarbon gases include CH3F, CH2F2, and CHF3. Other halogen-containing gases may include Cl2 and / or HBr. SF6 and / or NF3 may also be included. The fluorocarbon gas or hydrofluorocarbon gas can protect the mask.

[0047] The etching gas used in step S5 may also contain hydrogen-containing gas (H2 gas in one example). Additionally, rare gases may be included. When the film to be etched contains a silicon nitride film, fluorocarbon or hydrofluorocarbon gases (e.g., CHF3) may be used as the etching gas. The high-frequency electrical power used for plasma generation is not limited to continuous waves; it can also be a pulsed wave with a specified duty cycle. The duty cycle can be varied during etching.

[0048] Process S5 includes at least the following: Figure 2 The processes S51 to S53 are shown. In process S51, the substrate W is etched using plasma generated from a mixed gas containing hydrogen fluoride gas, and a condensed or solidified layer of hydrogen fluoride is selectively formed at the bottom of the etched shape.

[0049] In the case of etched shapes with an opening size less than a specified size and an aspect ratio greater than a specified size, in one example, where the opening size is less than 200 nm and the aspect ratio is greater than 20, the pressure at the bottom becomes higher than that in the gas phase due to the influence of etching byproducts evaporating from the bottom. Therefore, hydrogen fluoride easily condenses or solidifies. Furthermore, in the case of condensation, capillary condensation occurs, and hydrogen fluoride selectively adsorbs at the bottom. Even in the case of no condensation, due to the polarization of hydrogen fluoride molecules, cohesive forces arise between individual hydrogen fluoride molecules, thus hydrogen fluoride selectively adsorbs at the bottom where the surface energy is lowest.

[0050] During etching, although the temperature of the substrate rises due to the heat input from the plasma, the temperature can be controlled by adjusting the pressure of the heat transfer gas supplied between the back side of the substrate and the front side of the support stage, and the temperature of the substrate is maintained below 0°C during etching. That is, in the process of supplying etching gas containing hydrogen fluoride gas into the chamber 1, and in the process of supplying high-frequency electrical power for plasma generation, and etching the substrate W using plasma generated from the etching gas, the temperature of the substrate is maintained below 0°C.

[0051] As a method to maintain the substrate temperature below 0°C, for example, during etching, the pressure of the heat transfer gas supplied between the substrate W and the electrostatic chuck 5 can be controlled, and / or the magnitude of the bias power can be controlled. Thus, after the etched shape reaches a predetermined opening size or less and a predetermined aspect ratio or greater—in one example, after the etched shape reaches an opening size of 200 nm or less and an aspect ratio of 20 or greater—the flow rate of the hydrogen fluoride gas can be adjusted to selectively form a condensed layer of liquid phase or a solidified layer of solid phase at the bottom of the etched shape, resulting from the condensation of hydrogen fluoride. This condensed layer or solidified layer is obtained by preferentially physical adsorbing hydrogen fluoride, which acts as an etchant, at the bottom of the etched shape. Using method MT, even after etching has reached a depth with an aspect ratio of 20 or greater, for example, 20 or greater, the condensed layer or solidified layer can be used to maintain or increase the etching rate.

[0052] Figure 3 (a) indicates the etching (first etching) of hole H at a depth A1 that is less than the specified aspect ratio, for example, less than 20.

[0053] Figure 3 (b) represents the etching (second etching) of the hole H with an etching depth A2 (>A1) greater than the specified aspect ratio. In the second etching, the hole H becomes deeper, and condensation or solidification occurs. Taking advantage of this, the etchant of hydrogen fluoride gas can be supplied to the bottom of the etched shape with high efficiency, and a condensed or solidified layer 22 of hydrogen fluoride can be selectively formed at the bottom of the etched shape.

[0054] In process S51, if the flow rate of hydrogen fluoride gas is too high, it will cause the opening of the etched shape to close, and the etching will stop. Therefore, by controlling the flow rate of hydrogen fluoride gas to a specified level and controlling the temperature of the substrate to below 0°C, a condensation layer or solidification layer is selectively formed at the bottom of the etched shape by utilizing condensation or solidification phenomena, thus promoting etching.

[0055] exist Figure 2 In step S52, which follows step S51, ions from the plasma of the mixed gas generated by supplying bias electrical power to the support stage ST are brought to the bottom of the etched shape. Then, the energy of these ions is used to cause the hydrogen fluoride condensate or solidified layer 22 to react with the etch target film, promoting etching of the etch target film. Thus, as shown... Figure 3 As shown in (b), the etched film 21 is anisotropically etched.

[0056] In particular, in process S52, by applying a bias electrical power to the support stage ST, ions are controlled to reach the condensation layer or solidification layer 22. Thus, by setting (forming) the condensation layer or solidification layer 22, which acts as an etchant, etching can be promoted and the etching rate can be increased.

[0057] In step S53, it is determined whether the etching of the target film has been completed. For example, it can be done as follows: Figure 3 The etching is considered complete when the substrate film 23 of the etched object film 21 is exposed, as shown in (c). For example, whether the substrate film 23 is exposed can be determined using end-point detection technology. However, the method for determining whether etching has ended is not limited to this.

[0058] If etching is determined not to be complete in step S53, return to step S51 and repeat steps S51 and S52. During the repetition of steps S51 and S52, maintain the substrate temperature below 0°C. If etching is determined to be complete in step S53, terminate this method MT.

[0059] In the method MT described above, step S51, which forms the condensation layer or solidified layer 22, and step S52, which involves etching using a mixed gas plasma, are described as separate steps, but they can also be performed simultaneously. Steps S51 and S52 can be repeated. It is not limited to the case where steps S51 and S52 are repeatedly performed sequentially; it also includes the case where the condensation layer or solidified layer 22 is formed while simultaneously undergoing etching using a mixed gas plasma. Performing steps S51 and S52 simultaneously can improve etching productivity.

[0060] The mixed gas containing hydrogen fluoride used in the second etching may contain rare gases. Examples of rare gases include argon and helium. In the second etching, rare gases help promote etching by utilizing ions (e.g., argon ions) in the plasma. That is, in the second etching, bias power is supplied to the support stage ST, introducing ions from the plasma to the bottom of the etched shape. Thus, the energy of the ions can be used to cause the condensate or solidified layer 22 formed at the bottom of the etched shape to react with the bottom of the etched shape, thereby enabling etching. However, it is not only rare gas ions that provide energy to the condensate or solidified layer 22 to promote etching. Various ions from the plasma containing the mixed gas of rare gases are introduced into the substrate W, providing energy to the condensate or solidified layer 22 to enable etching. Furthermore, the gas used in the first etching may also contain rare gases, enabling the stable generation of plasma.

[0061] Alternatively, in step S51, a mixed gas containing hydrogen fluoride can be supplied to form a condensate layer or solidified layer 22. In step S52, the gas type can be switched from the mixed gas to a rare gas, and the rare gas can be supplied for etching. Steps S51 and S52 can be repeated. However, the mixed gas can also contain a rare gas, and steps S51 and S52 can be performed using the same gas type.

[0062] [Plasma Etching Device]

[0063] The plasma etching apparatus described above can be used in the MT method. Figure 5 This is a cross-sectional schematic diagram illustrating an example of a plasma etching apparatus 10 according to one embodiment. The plasma etching apparatus 10 provides an example of several plasma generation systems for exciting plasma from a process gas.

[0064] Figure 5 This describes a capacitively coupled plasma (CCP) device capable of forming plasma 2 between chamber 1, upper electrode 3, and support stage ST. The support stage ST has a lower electrode 4 and an electrostatic chuck 5. The substrate W is held on the support stage ST. RF sources 6 and 7 can be coupled to both upper electrode 3 and lower electrode 4, and different RF frequencies can be used. In another example, RF sources 6 and 7 can be coupled to the same electrode. Alternatively, direct current (DC) power can be coupled to the upper electrode. A gas source 8 is connected to chamber 1 to supply process gas to chamber 1. Additionally, an exhaust device 9 is connected to chamber 1 to exhaust gas from the interior of chamber 1. Furthermore, a temperature sensor can be provided to measure the substrate temperature non-contactly.

[0065] Figure 5 The plasma etching apparatus has a control unit 80 including a processor and a memory, which controls the various components of the plasma etching apparatus 10 to perform plasma treatment on the substrate W.

[0066] [Example]

[0067] The following is an example of the processing conditions for each step in the method MT of the implementation embodiment.

[0068] <First Etching ( Figure 1 S3) >

[0069]

[0070] <Second Etching ( Figure 1 S5 in

[0071] The target film is a SiO2 film (aspect ratio of 20 or higher).

[0072] (Condensation layer formation process) Figure 2 S51 in the process) and etching process ( Figure 2 S52 in

[0073]

[0074] As explained above, the etching method of this embodiment can promote etching.

[0075] Furthermore, there are options that do not need to be executed. Figure 1 The cases of steps S3 and S4 are as follows. For example, a substrate W with a recess having a specified aspect ratio can be prepared (step S1), the substrate can be temperature-controlled (step S2), and the second etching step S5 can be performed. The aspect ratio mentioned here can be, for example, Figure 4 As shown, the aspect ratio is calculated based on the opening formed by the mask. Figure 4 The depths A1 to A3 of the recess, including the mask, are shown in the diagram. If the aspect ratio of the mask opening is greater than or equal to the aspect ratio that allows the formation of a condensation layer or a solidified layer, then step S3 can be omitted. The specified aspect ratio refers to the aspect ratio that allows the formation of a condensation layer or a solidified layer in the area to be etched (the bottom of the recess or the surface of the film to be etched). By providing a substrate with a shape having this aspect ratio, steps S3 and S4 can be omitted.

[0076] Furthermore, the embodiments disclosed in this invention also include the methods described in items (A1) and (A2) below.

[0077] (A1) An etching method comprising: step (a) providing a substrate to a support stage, the substrate having a silicon-containing film comprising a silicon oxide film and a mask formed on the silicon-containing film, wherein a recess having a first aspect ratio defined by a bottom and sidewalls is formed in the silicon-containing film and the mask; step (b) supplying a gas containing hydrogen fluoride (HF) to form a condensate layer or solidified layer of HF on the bottom; and step (c) supplying an electrical bias to the support stage and etching the bottom surface using plasma to form a recess having a second aspect ratio higher than the first aspect ratio, the first aspect ratio being a higher aspect ratio than that capable of forming the condensate layer or solidified layer of HF, wherein in steps (b) and (c), the temperature of the substrate is maintained below 0°C.

[0078] (A2) An etching method comprising: step (a) providing a substrate to a support stage, the substrate having a silicon-containing film comprising a silicon oxide film and a mask having an opening having a first aspect ratio formed on the silicon-containing film; step (b) supplying hydrogen fluoride (HF) to form a condensed layer or solidified layer of HF on the silicon-containing film; and step (c) supplying an electrical bias to the support stage and etching the silicon-containing film using plasma, the first aspect ratio being a higher aspect ratio than that capable of forming a condensed layer or solidified layer of HF on the silicon-containing film, wherein in steps (b) and (c), the temperature of the substrate is maintained below 0°C.

[0079] (A3) The etching method as described in any one of (A1) and (A2), wherein plasma is formed from HF in the step of forming the condensation layer or solidified layer.

[0080] The etching method and plasma etching apparatus of one embodiment disclosed herein should be considered illustrative rather than limiting in all respects. The above embodiments can be modified and altered in various ways without departing from the appended claims and their spirit. The items described in the above embodiments can be further configured and combined without contradiction.

[0081] As the plasma etching apparatus of the present invention, a capacitively coupled plasma (CCP) type plasma processing apparatus has been illustrated above, but other plasma processing apparatuses can also be used. For example, an inductively coupled plasma (ICP) type plasma processing apparatus, a radial line slot antenna (RLSA) type plasma processing apparatus, an electron cyclotron resonance plasma (ECR) type plasma processing apparatus, and a helicon wave plasma (HWP) type plasma processing apparatus can be used.

Claims

1. An etching method, characterized in that, include: Step (a) involves providing a silicon-containing substrate onto a support platform; Step (b) involves etching the substrate using plasma generated from a first gas containing fluorine gas to form an etched shape with a bottom. Step (c) involves generating plasma from a second gas containing hydrogen fluoride gas, selectively forming a condensed or solidified layer of hydrogen fluoride at the bottom of the etched shape; and In step (d), bias electrical power is supplied to the support stage, and the bottom is etched using the plasma generated from the second gas. In steps (c) to (d), the temperature of the substrate is maintained below 0°C.

2. The etching method as described in claim 1, characterized in that: The process (c) and the process (d) are performed simultaneously.

3. The etching method as described in claim 1 or 2, characterized in that: The steps (c) and (d) are performed when the opening size of the etched shape is less than 200 nm and the aspect ratio is greater than 20.

4. The etching method as described in claim 1 or 2, characterized in that: After step (a), the temperature of the substrate is set to below -40°C.

5. The etching method as described in claim 1 or 2, characterized in that: Ions from the plasma generated from the second gas are introduced to the bottom, causing the condensate or solidified layer formed on the bottom to react with the bottom, thereby enabling etching.

6. The etching method as described in claim 1 or 2, characterized in that: The silicon-containing substrate comprises a silicon oxide film or a silicon nitride film.

7. The etching method as described in claim 1 or 2, characterized in that: The silicon-containing substrate comprises a laminate of silicon oxide film and silicon nitride film.

8. The etching method as described in claim 1 or 2, characterized in that: The silicon-containing substrate comprises a laminate of silicon oxide film and polycrystalline silicon film.

9. A plasma etching apparatus, characterized in that, include: chamber; A support platform for supporting the substrate is disposed within the cavity; A plasma generation unit for generating plasma within the cavity; and Control Department The control unit is capable of performing: Step (a): Accepting a silicon-containing substrate and supporting it on the support platform; Step (b) involves etching the substrate using plasma generated from a first gas containing fluorine gas to form an etched shape with a bottom. Step (c) involves generating plasma from a second gas containing hydrogen fluoride gas, selectively forming a condensed or solidified layer of hydrogen fluoride at the bottom of the etched shape; and In step (d), bias electrical power is supplied to the support stage, and the bottom is etched using the plasma generated from the second gas. In steps (c) to (d), the temperature of the substrate is maintained below 0°C.

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