Etching method and substrate processing apparatus

Abstract

An etching method capable of improving the verticality of etching of a boron film or a boron-containing film. The etching method includes: a step of preparing a substrate on which a boron film or a boron-containing film is formed; a step of supplying a processing gas, the processing gas containing chlorine gas, a fluorine-containing gas, and a hydrogen-containing gas; and a step of etching the boron film or the boron-containing film through the plasma of the processing gas via a mask.

Description

Technical Field

[0001] The present disclosure relates to an etching method and a substrate processing apparatus. Background Art

[0002] For example, Patent Document 1 proposes an etching method in which, at a substrate to be processed having a silicon portion, a silicon nitride film, and a silicon oxide film, the silicon portion is selectively etched with respect to the silicon nitride film and the silicon oxide film, and in which a fluorine-containing gas and an inert gas are supplied to the substrate to be processed in an excited state to etch the silicon portion.

[0003] <Prior Art Documents>

[0004] <Patent Documents>

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2018-32664 Summary of the Invention

[0006] <Problems to be Solved by the Invention>

[0007] The present disclosure provides a technique capable of improving the perpendicularity of etching of a boron film or a boron-containing film.

[0008] <Means for Solving the Problems>

[0009] According to one embodiment of the present disclosure, there is provided an etching method including: a step of preparing a substrate on which a boron film or a boron-containing film is formed; a step of supplying a processing gas containing chlorine gas, a fluorine-containing gas, and a hydrogen-containing gas; and a step of etching the boron film or the boron-containing film through a plasma of the processing gas via a mask.

[0010] <Effects of the Invention>

[0011] According to one aspect, it is possible to improve the perpendicularity of etching of a boron film or a boron-containing film. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a cross-sectional schematic view showing an example of a substrate processing apparatus according to one embodiment.

[0013] Figure 2 is a diagram showing an example of etching of a boron-containing film performed by a conventional etching method.

[0014] Figure 3 is a diagram showing an example of etching of a boron-containing film performed by an etching method according to one embodiment.

[0015] Figure 4It is a diagram showing an example of etching a boron-containing film by an etching method according to an embodiment.

[0016] Figure 5 It is a flowchart showing an example of an etching method according to an embodiment. Detailed Embodiments

[0017] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each drawing, the same reference numerals are given to the same components, and repeated descriptions may be omitted.

[0018] [Substrate Processing Apparatus]

[0019] Use Figure 1 The substrate processing apparatus 1 according to an embodiment will be described. Figure 1 It is a cross-sectional schematic diagram showing an example of the substrate processing apparatus 1 according to an embodiment.

[0020] The substrate processing apparatus 1 includes a chamber 10. The chamber 10 provides an internal space 10s therein. The chamber 10 includes a chamber body 12. The chamber body 12 has a substantially cylindrical shape. The chamber body 12 is formed of, for example, aluminum. A corrosion-resistant film is provided on the inner wall surface of the chamber body 12. This film may be a ceramic such as alumina or yttria.

[0021] A passage 12p is formed in the side wall of the chamber body 12. The substrate W is transported between the internal space 10s and the outside of the chamber 10 through the passage 12p. The passage 12p is opened and closed by a gate valve 12g provided along the side wall of the chamber body 12.

[0022] A support portion 13 is provided on the bottom of the chamber body 12. The support portion 13 is formed of an insulating material. The support portion 13 has a substantially cylindrical shape. The support portion 13 extends upward from the bottom of the chamber body 12 in the internal space 10s. The support portion 13 has a mounting table 14 at the upper part. The mounting table 14 is configured to support the substrate W in the internal space 10s.

[0023] The mounting table 14 has a base 18 and an electrostatic chuck 20. The mounting table 14 may further have an electrode plate 16. The electrode plate 16 is formed of a conductor such as aluminum and has a substantially disc shape. The base 18 is provided on the electrode plate 16. The base 18 is formed of a conductor such as aluminum and has a substantially disc shape. The base 18 is electrically connected to the electrode plate 16.

[0024] The electrostatic chuck 20 is provided on the base 18. A substrate W is placed on the upper surface of the electrostatic chuck 20. The electrostatic chuck 20 has a main body and an electrode. The main body of the electrostatic chuck 20 has a substantially disc-shaped form and is formed of a dielectric. The electrode of the electrostatic chuck 20 is a film-like electrode and is provided inside the main body of the electrostatic chuck 20. The electrode of the electrostatic chuck 20 is connected to a DC power supply 20p via a switch 20s. When a voltage from the DC power supply 20p is applied to the electrode of the electrostatic chuck 20, an electrostatic attraction force is generated between the electrostatic chuck 20 and the substrate W. By this electrostatic attraction force, the substrate W is held on the electrostatic chuck 20.

[0025] On the peripheral portion of the base 18, an edge ring 25 is arranged so as to surround the edge of the substrate W. The edge ring 25 is also referred to as a focusing ring. The edge ring 25 is used to improve the in-plane uniformity of the plasma processing for the substrate W. The edge ring 25 can be formed of silicon, silicon carbide, quartz, or the like.

[0026] A flow path 18f is provided inside the base 18. A heat exchange medium (refrigerant, heat medium) for temperature adjustment is supplied to the flow path 18f via a pipe 22a from a cooler unit (not shown) provided outside the chamber 10. The heat exchange medium supplied to the flow path 18f returns to the cooler unit via a pipe 22b. By the heat exchange between the heat exchange medium and the base 18, the temperature of the substrate W placed on the electrostatic chuck 20 is adjusted.

[0027] A gas supply line 24 is provided in the substrate processing apparatus 1. The gas supply line 24 supplies a heat transfer gas (e.g., He gas) from a heat transfer gas supply mechanism between the upper surface of the electrostatic chuck 20 and the back surface of the substrate W.

[0028] The substrate processing apparatus 1 further includes an upper electrode 30. The upper electrode 30 is provided above the mounting table 14 so as to face the mounting table 14. The upper electrode 30 is supported by a member 32 at the upper part of the chamber main body 12. The member 32 is formed of an insulating material. The upper electrode 30 and the member 32 close the upper opening of the chamber main body 12.

[0029] The upper electrode 30 may include a top plate 34 and a support body 36. The lower surface of the top plate 34 is the lower surface on the side of the internal space 10s and demarcates the internal space 10s. The top plate 34 can be formed of a low-resistance conductor or semiconductor that generates less Joule heat. The top plate 34 has a plurality of gas discharge holes 34a penetrating the top plate 34 in the thickness direction of the top plate 34.

[0030] The support body 36 supports the top plate 34 in a detachable manner. The support body 36 is formed of a conductive material such as aluminum. A gas diffusion chamber 36a is provided inside the support body 36. The support body 36 has a plurality of gas holes 36b extending downward from the gas diffusion chamber 36a. The plurality of gas holes 36b communicate with the plurality of gas discharge holes 34a respectively. A gas introduction port 36c is formed in the support body 36. The gas introduction port 36c is connected to the gas diffusion chamber 36a. A gas supply pipe 38 is connected to the gas introduction port 36c.

[0031] A valve unit 42, a flow rate controller unit 44, and a gas source unit 40 are connected to the gas supply pipe 38. The gas source unit 40, the valve unit 42, and the flow rate controller unit 44 constitute a gas supply section. The gas source unit 40 includes a plurality of gas sources. The valve unit 42 includes a plurality of on-off valves. The flow rate controller unit 44 includes a plurality of flow rate controllers. Each of the plurality of flow rate controllers in the flow rate controller unit 44 is a mass flow controller or a pressure-controlled flow rate controller. Each of the plurality of gas sources in the gas source unit 40 is connected to the gas supply pipe 38 via the corresponding on-off valve of the valve unit 42 and the corresponding flow rate controller of the flow rate controller unit 44.

[0032] In the substrate processing apparatus 1, a shielding member 46 is detachably provided along the inner wall surface of the chamber body 12 and the outer periphery of the support portion 13. The shielding member 46 is used to prevent reaction by-products from adhering to the chamber body 12. The shielding member 46 is formed, for example, by forming a corrosion-resistant film on the surface of a base material made of aluminum. The corrosion-resistant film can be formed of a ceramic such as yttrium oxide.

[0033] A baffle 48 is provided between the support body 13 and the side wall of the chamber body 12. The baffle 48 is formed, for example, by forming a corrosion-resistant film (such as a film of yttrium oxide) on the surface of a base material made of aluminum. A plurality of through holes are formed in the baffle 48. An exhaust port 12e is provided below the baffle 48 and at the bottom of the chamber body 12. An exhaust device 50 is connected to the exhaust port 12e via an exhaust pipe 52. The exhaust device 50 includes a pressure regulating valve and a vacuum pump such as a turbomolecular pump.

[0034] The substrate processing apparatus 1 further includes a first high-frequency power supply 62 and a second high-frequency power supply 64. The first high-frequency power supply 62 is a power supply that generates first high-frequency power (hereinafter also referred to as "HF power" or "HF power"). The first high-frequency power has a frequency suitable for plasma generation. The frequency of the first high-frequency power is, for example, a frequency in the range of 27 MHz to 100 MHz. The first high-frequency power supply 62 is connected to the susceptor 18 via a matcher 66 and an electrode plate 16. The matcher 66 has a circuit for matching the output impedance of the first high-frequency power supply 62 with the impedance on the load side (the susceptor 18 side). It should be noted that the first high-frequency power supply 62 can be connected to the upper electrode 30 via the matcher 66. The first high-frequency power supply 62 constitutes an example of a plasma generation unit.

[0035] The second high-frequency power supply 64 is a power supply that generates second high-frequency power (hereinafter also referred to as "LF power" or "LF power"). The frequency of the second high-frequency power is lower than the frequency of the first high-frequency power. When the second high-frequency power is used together with the first high-frequency power, the second high-frequency power is used as high-frequency power for a bias voltage for attracting ions to the substrate W. The frequency of the second high-frequency power is, for example, a frequency in the range of 400 kHz to 13.56 MHz. The second high-frequency power supply 64 is connected to the susceptor 18 via a matcher 68 and an electrode plate 16. The matcher 68 has a circuit for matching the output impedance of the second high-frequency power supply 64 with the impedance on the load side (the susceptor 18 side).

[0036] It should be noted that the second high-frequency power can be used without using the first high-frequency power, that is, plasma can be generated using only a single high-frequency power. In this case, the frequency of the second high-frequency power can be a frequency greater than 13.56 MHz, for example, it can be 40 MHz. In addition, in this case, the substrate processing apparatus 1 may not include the first high-frequency power supply 62 and the matcher 66. The second high-frequency power supply 64 constitutes an example of a plasma generation unit.

[0037] In the substrate processing apparatus 1, gas is supplied from the gas supply unit to the internal space 10s to generate plasma. In addition, by supplying the first high-frequency power and / or the second high-frequency power, a high-frequency electric field is generated between the upper electrode 30 and the susceptor 18. The plasma is generated by the generated high-frequency electric field.

[0038] The substrate processing apparatus 1 includes a power supply 70. The power supply 70 is connected to the upper electrode 30. The power supply 70 applies a voltage for attracting positive ions existing in the internal space 10s to the top plate 34 to the upper electrode 30.

[0039] The substrate processing apparatus 1 may further include a control unit 80. The control unit 80 may be a computer having a processor, a storage unit such as a memory, an input device, a display device, an input / output interface for signals, etc. The control unit 80 controls each unit of the substrate processing apparatus 1. In the control unit 80, an operator can perform operations such as inputting commands using the input device to manage the substrate processing apparatus 1. In addition, in the control unit 80, the operating state of the substrate processing apparatus 1 can be visually displayed through the display device. Furthermore, a control program and process data are stored in the storage unit. The control program is executed by the processor to perform various processes in the substrate processing apparatus 1. The processor executes the control program and controls each unit of the substrate processing apparatus 1 according to the process data.

[0040] [Conventional etching method]

[0041] Next, refer to Figure 2 An example of the result when the boron-containing film is etched by a conventional etching method using the substrate processing apparatus 1 having this structure will be described. Then, refer to Figure 3 An example of the result when the boron-containing film is etched by an etching method according to an embodiment using the substrate processing apparatus 1 will be described.

[0042] In the conventional etching method and the etching method according to an embodiment described later, as Figure 2 (a) shows, etching is performed on a substrate on which a boron-containing film 110 is formed on a base film 100 and a mask 120 is formed thereon. The base film 100 may be formed of a silicon-containing film such as a silicon oxide film (SiO2) or a silicon nitride film (SiN). The boron-containing film 110 is an example of an etching target film. The etching target film may be a boron film instead of the boron-containing film 110. In this example, although the boron-containing film 110 is a silicon film doped with boron, it is not limited thereto. In this example, although the mask 120 is a silicon oxide film, it is not limited thereto and may also be a silicon-containing film such as a silicon nitride film. Although a pattern having a hole H when viewed from the upper surface is formed in the mask 120, it is not limited thereto and a pattern of a groove may also be formed.

[0043] The boron-containing film 110 is etched through the mask 120 until the base layer 100 is exposed, and a hole H (deep hole) is formed in the boron-containing film 110 by etching. The diameter of the opening of the hole H formed on the upper surface of the boron-containing film 110 is referred to as "TOP CD". The aspect ratio is the ratio of the TOP CD of the boron-containing film 110 to the thickness of the boron-containing film 110 (= thickness of the boron-containing film 110 / TOP CD), and is 20 to 30 or more in this example.

[0044] The process conditions of the conventional etching method are as follows.

[0045] <Process conditions>

[0046]

[0047] It should be noted that before the step of etching the boron-containing film 110 under the above process conditions, a step of removing the native oxide film is performed. The step of removing the native oxide film is carried out by supplying nitrogen trifluoride (NF3) gas and oxygen (O2) gas into the chamber 10 for about 5 seconds. Thereby, the native oxide film on the substrate can be removed.

[0048] After the step of removing the native oxide film, the control unit 80 controls each unit of the substrate processing apparatus 1 according to the above process conditions. The control unit 80 controls the pressure in the chamber 10 to 30 mT, controls the temperature of the electrostatic chuck 20 to 120 °C, supplies chlorine gas into the chamber 10, and applies HF power and LF power to the stage 14. Regarding the application of HF power and LF power, LF power and HF power are applied in sequence in such a manner that the pulse frequency is 2.0 kHz. Specifically, LF power is applied with a duty ratio of 13%, and during this period, HF power is stopped (OFF). Then, HF power is applied with a duty ratio of 50%, and during this period, LF power is stopped. Then, during the remaining 37% of the time, LF power and HF power are stopped. This pulsed power application is repeated at a frequency of 2.0 kHz.

[0049] As a result, the shape of the hole H formed by the conventional etching method is as shown in Figure 2 (b) and Figure 2 (c). In the conventional etching method, as shown in Figure 2 (b), the etched shape of the hole H formed in the boron-containing film 110 tapers toward the top of the hole H, and the longitudinal cross-sectional shape of the hole H is conical (Problem 1).

[0050] In addition, as shown in Figure 2 (c), when the mask selection ratio during etching the hole H in the boron film 110 is insufficient, the mask 120 sometimes disappears before the bottom of the hole H reaches the base film 100 (Problem 2).

[0051] Problem 1 will be further described in detail. The mask 120 formed of the silicon oxide film is difficult to be etched by chlorine gas. In addition, as shown in Figure 2 (b), the reaction by-products 130 generated during etching the boron-containing film 110 are likely to adhere to the side walls of the mask 120 which is a silicon oxide film. In the case of etching the boron-containing film 110 using a single gas of chlorine, BCl x O y and SiCl x O y are deposited on the mask 120. Therefore, as shown in Figure 2As shown in (b), the TOP CD of the hole H formed in the boron-containing film 110 (the TOP CD of the hole H formed by a conventional etching method is denoted as "TOP CD1") is reduced due to the reaction by-product 130. It should be noted that the diameter of the bottom surface of the hole H formed in the boron-containing film 110 is referred to as "BTM CD", and the BTM CD formed in the boron-containing film 110 by a conventional etching method is denoted as "BTM CD1".

[0052] On the other hand, the boron-containing film 110 is easily etched by chlorine gas, and, as Figure 2 shown in (b), the reaction by-product 130 generated during etching hardly adheres to the side wall of the boron-containing film 110 directly below the mask 120. It is considered that the reason is that the bonding between the reaction by-product 130 and the silicon oxide film serving as the mask 120 plays a major role, while the bonding between the reaction by-product 130 and the boron-containing film 110 does not play a major role.

[0053] For the above reasons, since it is difficult to form the reaction by-product 130 as a protective film on the side surface of the boron-containing film 110 directly below the mask 120, the etching in the direction of the side surface of the boron-containing film 110 directly below the mask 120 is promoted. Therefore, as Figure 2 shown in (b), the side surface of the boron-containing film 110 directly below the mask 120 is etched, and a bowing shape in which the hole H bulges outward is generated.

[0054] In this regard, in order to widen the TOP CD1 of the hole H formed in the boron-containing film 110, it is considered to add a gas of fluorine (F) or the like to chlorine gas. In this case, although the TOP CD1 of the boron-containing film 110 is widened, the mask 120 made of a silicon oxide film is etched, the pattern of the mask 120 is deformed, and the mask selectivity is reduced.

[0055] The reason is, for example, that since the chemical reactivity of the boron-containing film 110 is low, the BTM CD1 of the hole H formed in the boron-containing film 110 is difficult to widen when chlorine gas is used. In this regard, it is speculated that when a gas with higher reactivity such as a gas of fluorine or the like is added to chlorine gas and used, although the chemical reaction of the boron-containing film 110 is promoted, the mask 120 is even etched, causing the mask 120 to be deformed.

[0056] Therefore, in the etching method according to an embodiment described below, the above problems are solved by adding a specific gas to chlorine gas and performing etching. Hereinafter, the etching method according to an embodiment will be described.

[0057] [Etching Method According to an Embodiment]

[0058] Referring to Figure 3The shape of the holes H formed in the boron-containing film by the etching method according to one embodiment using the substrate processing apparatus 1 will be described. Figure 3 (a) is the same as Figure 2 (b) and is a diagram showing an example of the result when the substrate of Figure 2 (a) is etched by a conventional etching method as a comparative example. Figure 3 (b) is a diagram showing an example of the result when the substrate of Figure 2 (a) is etched by the etching method according to one embodiment.

[0059] Except for the gas species of the processing gas, the process conditions of the etching method according to the present embodiment are the same as those of the conventional etching method. The gas species are as follows.

[0060] <Process conditions>

[0061] Gas species: Chlorine (Cl2) 150 sccm, Nitrogen trifluoride (NF3) 10 sccm, Hydrogen (H2) 40 sccm, Silicon tetrachloride (SiCl4) 5 sccm, Oxygen (O2) 10 sccm

[0062] Among the processing gases, nitrogen trifluoride gas is an example of a fluorine-containing gas, and the fluorine-containing gas is not limited thereto and may also be carbon tetrafluoride (CF4) gas. In addition, hydrogen gas is an example of a hydrogen-containing gas, and the hydrogen-containing gas is not limited thereto and may also be hydrogen bromide (HBr) gas. In addition, silicon tetrachloride gas is an example of a silicon-containing gas, and the silicon-containing gas is not limited thereto and may also be silicon tetrafluoride (SiF4) gas. In addition, oxygen gas is an example of an oxygen-containing gas, and the oxygen-containing gas is not limited thereto and may also be carbon dioxide (CO2) gas or carbonyl sulfide (COS) gas.

[0063] It should be noted that the silicon-containing gas and the oxygen-containing gas may not be included in the processing gas. For example, the processing gas may be a mixed gas of chlorine gas and a fluorine-containing gas and a hydrogen-containing gas, or a gas containing these gases. In addition, the processing gas may be a mixed gas of chlorine gas and a fluorine-containing gas and a hydrogen-containing gas and a silicon-containing gas and an oxygen-containing gas, or a gas containing these gases.

[0064] In the etching method according to the present embodiment, before the step of etching the boron-containing film 110 under the above process conditions, a mixed gas of nitrogen trifluoride (NF3) gas and oxygen (O2) gas may be supplied into the chamber 10 to perform a step of removing the native oxide film.

[0065] (Addition of NF3 / H2 and its effect)

[0066] In Figure 3 the result of the etching method according to one embodiment ofFigure 3 Compared with the result of the conventional etching method in (a), the reaction by-products 130 attached to the mask 120 can be thinned. The reason is that the reaction by-products 130 attached to the mask 120 react with nitrogen trifluoride gas and hydrogen gas due to the addition of nitrogen trifluoride gas and hydrogen gas and are etched, or the reaction by-products 130 react with nitrogen trifluoride gas and hydrogen gas before attaching to the mask 120 and are removed. Therefore, as Figure 3 shown in (b), compared with TOP CD1, the TOP CD of the hole H formed in the boron-containing film 110 (the TOC CD of the hole H formed by the etching method of this embodiment is marked as "TOP CD2") can be controlled wider. It should be noted that the CD at the bottom of the hole H formed by the etching method of this embodiment, that is, the BTM CD is marked as "BTM CD2".

[0067] Thus, in the etching method of this embodiment, it can be controlled that TOP CD2 > TOP CD1, so that the width of the hole H is wider. Since it can be controlled in such a way that TOP CD2 does not become narrower, in the etching of the boron-containing film 110 with chlorine gas, the straightness of the ions injected into the hole H can be ensured, and it is easy to widen the BTM CD2 at the bottom of the hole H. Therefore, it can be controlled that BTM CD2 > BTM CD1, and the etching shape of the hole H formed in the boron-containing film 110 can be made more vertical.

[0068] In addition, it is considered that during etching, the hydrogen (H) of the hydrogen gas contained in the processing gas reacts with the boron (B) in the reaction by-products 130 of BCl x O y generated during the etching of the boron-containing film 110, and becomes a compound such as BH radical and is discharged. Therefore, it is more difficult for the reaction by-products 130 to attach to the side surface of the mask 120 or the side surface of the hole H in the boron-containing film 110. It is considered that this also makes it easier to widen the BTM CD2 of the hole H compared with the BTM CD1 of the hole H formed by the conventional etching method without hydrogen gas in the processing gas.

[0069] It should be noted that as a secondary effect, by scavenging fluorine free radicals (F free radicals), the controllability of nitrogen trifluoride gas can be improved. That is, if only nitrogen trifluoride gas is added to chlorine gas, it is difficult to overcome the problems that the mask 120 of the silicon oxide film is etched and the shape of the mask 120 is deformed. In contrast, in the etching method according to the present embodiment, hydrogen gas is added together with nitrogen trifluoride gas. Thereby, fluorine (F) reacts with hydrogen (H) to become hydrogen fluoride (HF), so that F is consumed. Therefore, by controlling the flow rate of nitrogen trifluoride gas, the amount of reaction by-products 130 attached to the side surface of the mask 120 can be easily controlled.

[0070] If the reaction by-products 130 attached to the side surface of the mask 120 are completely removed, a protective film of the mask 120 will not be formed, and the shape of the mask 120 may be deformed. In contrast, in the etching method according to the present embodiment, the amount (thickness) of the reaction by-products 130 attached to the side surface of the mask 120 can be controlled. In other words, the TOP CD2 of the boron-containing film 110 can be controlled. Thereby, the BTM CD2 can be controlled, and the perpendicularity of the shape of the hole H can be improved.

[0071] (Addition of SiCl4 / O2 and Its Effects)

[0072] Next, with reference to Figure 4 the functions and effects in the case where silicon tetrachloride gas and oxygen are further included in the processing gas will be described. Figure 4 (a) shows an example of etching in the case where nitrogen trifluoride gas and hydrogen gas are added and silicon tetrachloride gas and oxygen are not added in an etching method according to an embodiment. Figure 4 (b) shows an example of etching in the case where nitrogen trifluoride gas, hydrogen gas, silicon tetrachloride gas, and oxygen are added in an etching method according to an embodiment.

[0073] As Figure 4 (a) shows, when nitrogen trifluoride gas and hydrogen gas are added to chlorine gas and silicon tetrachloride gas and oxygen are not added, the selectivity of the mask 120 may sometimes be insufficient. In contrast, as Figure 4 (b) shows, when nitrogen trifluoride gas, hydrogen gas, silicon tetrachloride gas, and oxygen are added to chlorine gas, the selectivity of the mask 120 can be improved.

[0074] The reason is that by further adding silicon tetrachloride gas and oxygen to chlorine gas, the reaction by-products 130 of SiCl x O y are more likely to selectively attach to the mask 120 with respect to the boron-containing film 110. Therefore, SiClx O y The reaction by - product 130 of y adheres to the upper surface of the mask 120. Meanwhile, on the side surface of the mask 120, fluorine (F) reacts with hydrogen (H) to become hydrogen fluoride (HF), consuming F, so that the amount (thickness) of the reaction by - product 130 adhering to the side surface of the mask 120 can be controlled. In other words, in the etching method according to the present embodiment, by adding silicon tetrachloride gas and oxygen, the balance between the deposition of the reaction by - product 130 on the mask 120 and the etching of the boron - containing film 110 can be precisely controlled. Thereby, the perpendicularity of the hole H can be improved, and at the same time, the selectivity of the mask 120 can be improved.

[0075] In addition, the oxygen that does not participate in the generation of the reaction by - product 130 oxidizes the boron - containing film 110 or is used to generate BCl x O y and SiCl x O y of the reaction by - product 130 and helps to form a protective film on the side wall of the boron - containing film 110. Therefore, the lateral etching of the boron - containing film 110 is suppressed by the protective film of the reaction by - product 130, so that the etching shape of the hole H can be made more perpendicular.

[0076] It should be noted that when supplying the processing gas in the etching method according to the present embodiment, nitrogen trifluoride gas and hydrogen, and both silicon tetrachloride gas and oxygen can be supplied simultaneously. Or, one of the nitrogen trifluoride gas and hydrogen, and silicon tetrachloride gas and oxygen can be supplied first, and then the other gas can be supplied.

[0077] [Flow of the etching method]

[0078] Next, with reference to Figure 5 the flow of the etching method according to one embodiment will be described. Figure 5 is a flowchart showing an example of the etching method according to one embodiment. The etching method according to the present embodiment is controlled by a controller 80 and is executed in a substrate processing apparatus 1.

[0079] When this process starts, a substrate having a boron - containing film 110 formed on a base film 100 and a mask 120 having a silicon oxide film formed thereon is carried into the chamber 10 and placed on the stage 14 for preparation (step S1).

[0080] Next, a processing gas containing chlorine gas, fluorine-containing gas, hydrogen-containing gas, silicon-containing gas, and oxygen-containing gas is supplied into the chamber 10 (step S2). Next, LF power and HF power are sequentially applied to the stage 14 with their respective duty cycles (step S3). Thereby, the boron-containing film 110 is etched by the plasma of the generated processing gas (step S4), and this processing is completed. It should be noted that a process of removing the natural oxide film may be performed before step S2.

[0081] As described above, the etching method according to the present embodiment includes: a step of preparing a substrate on which a boron film or a boron-containing film is formed; a step of supplying a processing gas containing chlorine gas, fluorine-containing gas, and hydrogen-containing gas; and a step of etching the boron film or the boron-containing film through the plasma of the processing gas via a mask. By this etching method, the verticality of etching of the boron film or the boron-containing film can be improved.

[0082] In the step of supplying the processing gas, it may contain chlorine gas, fluorine-containing gas, hydrogen-containing gas, silicon-containing gas, and oxygen-containing gas. Thereby, the selectivity of the mask can be improved.

[0083] Although the etched boron film or boron-containing film by the etching method according to the present embodiment can function as a mask for the base film 100, for example, the function of the etched boron film or boron-containing film is not limited thereto.

[0084] It should be considered that the etching method and the substrate processing apparatus according to an embodiment of the present disclosure are exemplary in all aspects and not restrictive. Without departing from the appended claims and their gist, the above embodiment can be modified and improved in various ways. For the contents described in the above multiple embodiments, other structures can also be adopted without contradiction, and combinations can be made without contradiction.

[0085] The substrate processing apparatus of the present disclosure can be applied to any type of apparatus such as an atomic layer deposition (ALD) apparatus, capacitively coupled plasma (CCP), inductively coupled plasma (ICP), radial line slot antenna (RLSA), electron cyclotron resonance plasma (ECR), and helicon wave plasma (HWP).

[0086] In addition, although a plasma processing apparatus has been described as an example of a substrate processing apparatus, the substrate processing apparatus may be any apparatus that etches a substrate, and is not limited to a plasma processing apparatus.

Claims

1. An etching method, comprising: a step of preparing a substrate, on which a boron film or a silicon film doped with boron is formed; a step of supplying a processing gas, the processing gas being composed of chlorine gas, a fluorine-containing gas, a hydrogen-containing gas, a silicon-containing gas, and an oxygen-containing gas; and a step of etching the boron film or the silicon film doped with boron through the plasma of the processing gas via a mask, the hydrogen-containing gas being H2 gas, the fluorine-containing gas being NF3 gas or CF4 gas.

2. The etching method according to claim 1, wherein the mask is a silicon-containing film.

3. The etching method according to claim 1 or 2, wherein high-frequency power for ion attraction and high-frequency power for plasma generation are sequentially applied in a pulsed manner to generate the plasma of the processing gas.

4. The etching method according to claim 1 or 2, wherein the mask is a silicon oxide film.

5. The etching method according to claim 1, wherein the silicon-containing gas is SiCl4 gas or SiF4 gas.

6. The etching method according to claim 1, wherein the oxygen-containing gas is O2 gas, CO2 gas, or COS gas.

7. The etching method according to claim 1, wherein the processing gas contains Cl2 gas, NF3 gas, the H2 gas, SiCl4 gas, and O2 gas.

8. A substrate processing apparatus, comprising a gas supply unit and a control unit, Among them, the control unit performing the following steps: a step of preparing a substrate in a chamber, on which a boron film or a silicon film doped with boron is formed; a step of supplying a processing gas from the gas supply unit to the chamber, the processing gas being composed of chlorine gas, a fluorine-containing gas, a hydrogen-containing gas, a silicon-containing gas, and an oxygen-containing gas; and a step of etching the boron film or the silicon film doped with boron through the plasma of the processing gas via a mask, the hydrogen-containing gas being H2 gas, the fluorine-containing gas being NF3 gas or CF4 gas.

Images