Etching method and etching apparatus

Abstract

To provide an etching method and an etching device capable of etching Si or SiN with good surface roughness.SOLUTION: An etching method for etching Si or SiN existing on a substrate includes applying radical oxidation treatment to the substrate having Si or SiN to form an oxide film on the surface of Si or SiN, performing chemical treatment of the oxide film with gas, and removing a reaction product produced by the chemical treatment, and repeatedly executes forming the oxide film, performing chemical treatment, and removing the reaction product.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an etching method and an etching apparatus. [Background technology]

[0002] In the manufacturing process of semiconductor devices, there is a process of etching and slimming silicon (Si) or silicon nitride (SiN). Wet etching is often used in such etching processes. For example, Patent Document 1 describes a method of etching polysilicon by wet etching. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 9-260361 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides an etching method and an etching apparatus that can etch Si or SiN with improved surface roughness. [Means for solving the problem]

[0005] An etching method according to one embodiment of the present disclosure is an etching method for etching Si or SiN present on a substrate, the etching method comprising: performing a radical oxidation process on a substrate having Si or SiN to form an oxide film on a surface of the Si or SiN; performing a chemical process using a gas on the oxide film; and removing a reaction product formed by the chemical process, wherein the steps of forming the oxide film, performing the chemical process, and removing the reaction product are repeated multiple times. The radical oxidation treatment is performed by oxygen-containing plasma generated by an oxygen-containing gas, and the oxygen-containing gas is O 2 The substrate has a recess in a side surface thereof in which the Si or SiN is present, and the radical oxidation treatment includes controlling the distribution of the thickness of the oxide film in the depth direction of the recess by adjusting at least one of the pressure and the ratio of the F-containing gas in the oxygen-containing gas. [Effects of the Invention]

[0006] According to the present disclosure, an etching method and an etching apparatus are provided that can etch Si or SiN while improving surface roughness. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a flowchart illustrating an example of an etching method according to an embodiment. [Figure 2] 10 is a flowchart illustrating another example of an etching method according to an embodiment. [Figure 3] 1 is a cross-sectional view showing an example of a structure of a substrate to which an etching method according to an embodiment is applied; [Figure 4] FIG. 4 is a diagram showing a state in which the poly-Si film that becomes the channel in the structure of FIG. 3 has been etched. [Figure 5] 10 is a cross-sectional view showing another example of the structure of a substrate to which the etching method of the embodiment is applied. FIG. [Figure 6] FIG. 6 is a cross-sectional view showing a state in which the SiN film of the ONON stacked structure portion in the structure of FIG. 5 has been recess-etched. [Figure 7] FIG. 4 is a diagram showing the relationship between the number of cycles of Top, Mid, and Btm and the amount of Si etching when the conditions of the radical oxidation step are changed in the structure of FIG. 3 and the radical oxidation step and the oxide removal step are repeated. [Figure 8] FIG. 1 is a diagram showing a presumed mechanism by which top-bottom loading can be controlled by the pressure during radical oxidation treatment and the ratio of NF3 gas, which is an F-containing gas. [Figure 9] 1 is a partial cross-sectional plan view schematically illustrating an example of a processing system used in an etching method according to an embodiment. [Figure 10] 10 is a cross-sectional view schematically illustrating an example of a process module that is installed in the processing system of FIG. 9 and functions as an etching apparatus that performs the etching method of one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments will be described with reference to the accompanying drawings.

[0009] <Etching method> FIG. 1 is a flowchart illustrating an example of an etching method according to an embodiment. The etching method according to this embodiment etches Si or SiN present on a substrate. First, a radical oxidation process is performed on a substrate having Si or SiN to be etched, to form an oxide film on the surface of the Si or SiN (step ST1). Next, a chemical process using a gas is performed on the oxide film (step ST2). Next, a reaction product formed by the chemical process in step ST2 is removed (step ST3). These steps ST1 to ST3 are repeated multiple times. As a result, a desired amount of Si or SiN present on the substrate is etched.

[0010] This will be explained in detail below. The radical oxidation process in step ST1 generates an oxygen-containing plasma, and oxygen radicals (O radicals) in the oxygen-containing plasma react with a substrate placed in a processing chamber to form an oxide film (SiO2 film) on the surface of Si or SiN. In this process, remote plasma is preferably used so that mainly O radicals in the oxygen-containing plasma can be supplied to the substrate. Remote plasma generates plasma of an oxygen-containing gas in a plasma generation space separate from the processing space where the substrate is placed, and transports the plasma to the processing space. Oxygen ions (O2 ions) in the oxygen-containing plasma are easily deactivated during transport, and mainly O radicals are supplied to the processing space. By mainly reacting with the O radicals on the substrate, ion damage to the substrate can be reduced. The plasma source is not particularly limited, and inductively coupled plasma, microwave plasma, etc. can be used.

[0011] The oxygen-containing gas used to generate the oxygen-containing plasma may be O2 gas alone, or a mixture of O2 gas with at least one of H2 gas, fluorine (F)-containing gas, and rare gas. Examples of F-containing gases that can be used include NF3 gas, SF6 gas, and F2 gas. Among these, NF3 gas is preferred. The rare gas is not particularly limited, but Ar gas is preferred. Adding H2 gas can enhance the oxidizing ability. Adding an F-containing gas generates F radicals, which etch oxide films and Si. The ratio of F-containing gas to O2 gas is preferably 0.5 to 5%. The ratio of H2 gas to H2 gas is preferably 0 to 80%. The ratio of H2 gas to (O2 gas + H2 gas) is preferably 0 to 80%. The addition of a rare gas can stabilize the plasma.

[0012] The pressure during step ST1 is preferably 25 to 500 mTorr (3.33 to 66.7 Pa). The substrate temperature is preferably 15 to 120° C. The time for step ST1 is preferably in the range of 60 to 180 seconds. The flow rates of each gas are set appropriately depending on the apparatus.

[0013] In the step ST2 of performing a chemical treatment with gas on the oxide film, the chemical treatment with gas may be a chemical treatment using a treatment gas containing an F-containing gas. This treatment causes the oxide film to react with the treatment gas to generate a compound that can be removed by heating or the like.

[0014] The F-containing gas contained in the processing gas may be hydrogen fluoride (HF) gas, and gases other than the F-containing gas may be HO gas and reducing gas. The reducing gas may be ammonia (NH) gas or an amine-based gas. By reacting the F-containing gas with the HO gas or reducing gas and the oxide film, a compound that can be removed relatively easily can be produced.

[0015] Among these, the use of HF gas as the fluorine-containing gas and NH3 gas as the reducing gas is preferred. Using HF gas and NH3 gas, a chemical oxide removal (COR) process, which has been known as an oxide removal process, can be performed. In the COR process, HF gas and NH3 gas are adsorbed onto the surface of the oxide film, and then react with the oxide film to produce ammonium silicofluoride (AFS), an ammonium fluoride-based compound.

[0016] In such a COR treatment, the pressure is preferably in the range of 6.66 to 400 Pa (50 to 3000 mTorr), more preferably 13.3 to 266.6 Pa (100 to 2000 mTorr), and the substrate temperature is preferably in the range of 0 to 120°C, more preferably 20 to 100°C.

[0017] Step ST2 can be performed in the same processing vessel as step ST1, which can increase throughput. Of course, these steps may also be performed in separate processing vessels.

[0018] The process of removing the reaction products in step ST3 is performed by supplying an inert gas into the process vessel while evacuating the process vessel with the substrate at the desired temperature. This process can be performed in the same process vessel as the gas-based chemical treatment in step ST2, or in a separate process vessel. In either case, the substrate temperature can be set appropriately and may be the same as or different from that of step ST2. However, if step ST3 is performed in the same process vessel as step ST2, throughput can be increased by performing the substrate temperature at the same temperature as step ST2. If step ST3 is performed in a separate process vessel from step ST2, the process vessel may be heated to, for example, 190 to 300°C to promote removal of the reaction products. Alternatively, as shown in FIG. 2, steps ST2 and ST3 may be repeated. In particular, when performing COR treatment on SiN, there is a risk of SiN being etched by HF / NH3 gas. Therefore, it is preferable to repeat steps ST2 and ST3 in a short period of time to prevent SiN from being etched by the incubation time. When steps ST2 and ST3 are repeated, they may be performed in the same processing vessel or in separate processing vessels.

[0019] Depending on the gas species and conditions such as temperature and pressure, steps ST2 and ST3 can be performed simultaneously. For example, by performing the COR treatment at a temperature at which the AFS decomposes, the chemical treatment using gas in step ST2 and the process of removing the reaction product in step ST3 can proceed simultaneously. After all the treatments are completed, a heat treatment for removing residues may be performed in a separate treatment vessel.

[0020] Conventional wet etching of Si involves etching along the grain boundaries or crystal planes of Si, resulting in poor surface roughness. In contrast, this embodiment involves repeatedly forming an oxide film on the Si surface using plasma oxidation and then removing the oxide film using a process that includes a chemical gas treatment. Because radical oxidation is a surface reaction using oxygen radicals, a thin oxide film is formed without relying on the grain boundaries or crystal planes, and then only the oxide film is removed, resulting in good surface roughness. By repeating this process a desired number of times, the desired amount of etching can be achieved with good control.

[0021] We actually etched a poly-Si blanket wafer using the etching method of this embodiment to confirm the surface roughness. Here, a radical oxidation step was performed at 400 to 1250 mTorr, followed by an oxide film removal step including COR treatment and AFS removal treatment, for 4 to 22 cycles, and then measured the average film thickness and surface roughness. Ra was measured as the surface roughness. The average etching depth was 3.61 to 16.49 nm, with Ra values ​​of 0.1656 nm after 4 cycles, 0.1986 nm after 15 cycles, 0.1988 nm after 18 cycles, and 0.2068 nm after 22 cycles. These values ​​are almost equivalent to the initial surface roughness of 0.127 nm, confirming the excellent surface roughness. In contrast, Ra was 0.6 nm after wet etching, nearly three times that of this embodiment.

[0022] The structure of the substrate to which the etching method of the present embodiment is applied is not particularly limited, but may be, for example, a structure used in a 3D-NAND nonvolatile semiconductor device. Figure 3 is a cross-sectional view showing an example of the structure of such a substrate.

[0023] In this example, a semiconductor wafer (wafer) W, which is a substrate, has an ON-ON stacked structure 102 formed by alternately stacking multiple SiO2 films 111 and SiN films 112 on a silicon base 100. The number of stacked SiO2 films 111 and SiN films 112 is actually about 100. An upper structure 110 is provided on the ON-ON stacked structure 102, and a memory hole 103 is formed that penetrates the upper structure 110 and the ON-ON stacked structure 102 in the stacking direction. In the memory hole 103, a multilayered memory film 104 and a Si film 105 that serves as a channel are formed. The Si film 105 is a crystalline Si film. In this example, as shown in FIG. 4, the Si film 105 that serves as the channel is etched to slim it.

[0024] 5 is a cross-sectional view showing another example of the structure of a substrate used in a 3D-NAND nonvolatile semiconductor device. In this example, the wafer W, which is the substrate, similarly has an ONON stacked structure 102 and an upper structure 110, which are formed by alternately stacking multiple SiO2 films 111 and SiN films 112 on a silicon substrate 100. Slits 106 penetrating the upper structure 110 and the ONON stacked structure 102 in the stacking direction are formed. In this example, as shown in FIG. 6, the multiple SiN films 112 of the ONON stacked structure 102 are recess-etched to a depth of about 3 to 5 nm.

[0025] In such a 3D-NAND nonvolatile semiconductor device, the memory holes 103 and slits 106 are very deep. In such deep recesses, when oxidizing the Si or SiN present on the side surfaces of the recesses, top-bottom loading (loading between the opening and the deepest part) can prevent the formation of an oxide film with the desired thickness uniformity in the depth direction. This type of top-bottom loading is not limited to 3D-NAND nonvolatile semiconductor devices, and is a problem when etching the side surfaces of recesses with a depth of 4 μm or more.

[0026] It was found that adjusting the pressure and / or the ratio of the F-containing gas in the oxygen-containing gas during the radical oxidation treatment is an effective method for controlling such top-bottom loading.

[0027] Figure 7 shows the relationship between the number of cycles of Top, middle (Mid), bottom (Btm) and the amount of Si etching when the conditions of the radical oxidation step are changed in the structure of Figure 3 and the radical oxidation step and the oxide removal step are repeated. As shown in this figure, in (a) where the radical oxidation step is under high-pressure conditions (160 mTorr), it can be seen that the etching amount is Top-first with a larger amount at Top than at Btm. In (b) where the radical oxidation step is under low-pressure conditions (50 mTorr), it can be seen that the etching amount is uniform etching with almost the same amount at Top and Btm. In (c) where NF3 is added at 4% to O2 gas under low-pressure conditions (50 mTorr) in the radical oxidation step, it can be seen that the etching amount is Btm-first with a larger amount at Btm than at Top.

[0028] From these results, it can be seen that by adjusting the pressure of the radical oxidation step and NF3 / O2, the etching characteristics can be adjusted to Top > Btm, Top = Btm, and Top < Btm. That is, by changing the pressure during the radical oxidation step and / or the ratio of the F-containing gas in the oxygen-containing gas, the etching amount can be adjusted to any of Top > Btm, Top = Btm, and Top < Btm, and it was confirmed that the top-bottom loading can be controlled.

[0029] Next, the estimated mechanism capable of controlling the top-bottom loading in this way will be described. Figure 8 shows the estimated mechanism by which the top-bottom loading can be controlled by the pressure during the radical oxidation treatment and the ratio of the F-containing gas, NF3 gas.

[0030] Under the high-pressure conditions shown in Figure 8(a), the mean free path is short, preventing O radicals from reaching the bottom. O radicals mainly attack the top portion of the Si film 105, resulting in a thicker oxide film 105a at the top, resulting in top-first etching of the Si film 105. Under the low-pressure conditions shown in Figure 8(b), the mean free path is long, allowing O radicals to reach the bottom as well. As a result, O radicals uniformly attack the Si film 105, resulting in a uniform oxide film 105a, resulting in uniform etching of the Si film 105. Figure 8(c) shows high-pressure conditions with the addition of NF3 gas. Under these conditions, the mean free path is short, preventing both O radicals and F radicals from reaching the bottom. O radicals mainly generate oxide film 105a at the top portion of the Si film 105. F radicals etch the oxide film 105a at the top, but their effect is small. As with Figure 8(a), the Si film 105 is etched top-first. (d) shows the conditions under which the pressure is low and NF3 gas is added. Under these conditions, the mean free path is long, and O radicals uniformly attack the Si film 105. On the other hand, F radicals tend to move to the bottom and etch the Si film 105 at the bottom, resulting in Btm-first etching of the Si film 105.

[0031] <Example of a processing system> Next, an example of a processing system used in the etching method of this embodiment will be described below. Fig. 9 is a partial cross-sectional plan view that schematically shows an example of a processing system used in the etching method of this embodiment.

[0032] 9, the processing system 10 includes a loading / unloading section 11 that stores a plurality of substrates W and loads / unloads the substrates W, a transfer module 12 that serves as a transfer chamber that simultaneously transports two substrates W, and a plurality of process modules 13 that process the substrates W loaded from the transfer module 12. The interior of each process module 13 and transfer module 12 is maintained in a vacuum atmosphere.

[0033] In the processing system 10, the substrates W stored in the load / unload section 11 are transported by a transport arm 14 built into a transfer module 12, and one substrate W is placed on each of two stages 15 arranged inside a process module 13. Next, in the processing system 10, each substrate W placed on the stage 15 is processed in the process module 13, and then the processed substrates W are transported to the load / unload section 11 by the transport arm 14.

[0034] The loading / unloading section 11 has a plurality of load ports 17 as loading stages for FOUPs 16, which are containers that hold a plurality of substrates W; a loader module 18 that receives stored substrates W from the FOUPs 16 placed on each load port 17 or transfers substrates W that have been processed in the process module 13 to the FOUPs 16; two load lock modules 19 that temporarily hold substrates W in order to transfer them between the loader module 18 and the transfer module 12; and a cooling storage 20 that cools substrates W that have been subjected to heat processing.

[0035] The loader module 18 is a rectangular housing whose interior is under atmospheric pressure, with multiple load ports 17 arranged side by side on one side that forms the longer side of the rectangle. The loader module 18 also has a transport arm (not shown) inside that is movable in the longitudinal direction of the rectangle. The transport arm loads substrates W from FOUPs 16 placed on each load port 17 into the load lock module 19, or unloads substrates W from the load lock module 19 to each FOUP 16.

[0036] Each load lock module 19 temporarily holds a substrate W housed in a FOUP 16 placed on each load port 17, which is in an atmospheric pressure atmosphere, in order to transfer the substrate W to a process module 13, the interior of which is in a vacuum atmosphere. Each load lock module 19 has a buffer plate 21 that holds two substrates W. Each load lock module 19 also has a gate valve 22a for ensuring airtightness with respect to the loader module 18, and a gate valve 22b for ensuring airtightness with respect to the transfer module 12. Furthermore, a gas introduction system and a gas exhaust system (not shown) are connected to the load lock module 19 by piping, and the interior can be switched between an atmospheric pressure atmosphere and a vacuum atmosphere.

[0037] The transfer module 12 loads unprocessed substrates W from the load / unload section 11 into the process module 13, and loads processed substrates W from the process module 13 back to the load / unload section 11. The transfer module 12 is made of a rectangular housing with a vacuum atmosphere inside, and includes two transport arms 14 that hold and move two substrates W, a rotary table 23 that rotatably supports each transport arm 14, a rotary table 24 on which the rotary table 23 is mounted, and guide rails 25 that guide the rotary table 24 so that it can move in the longitudinal direction of the transfer module 12. The transfer module 12 is also connected to the load lock module 19 of the load / unload section 11 and each process module 13 via a gate valve 22b and further via each gate valve 26, which will be described later. In the transfer module 12, the transport arm 14 transports two substrates W from the load lock module 19 to each process module 13, and then transports the two processed substrates W from each process module 13 to another process module 13 or the load lock module 19.

[0038] In the processing system 10, each process module 13 is for etching Si or SiN, which is an etching target portion. The process module 13 may collectively perform the above steps ST1 to ST3, or may include one process module that performs steps ST1 and ST2 and another process module that performs step ST3.

[0039] The processing system 10 has a control unit 27. The control unit 27 has a main control unit having a CPU that controls the operation of each component of the processing system 10, as well as input devices (keyboard, mouse, etc.), output devices (printer, etc.), display devices (display, etc.), and storage devices (storage media). The main control unit of the control unit 27 causes the processing system 10 to perform a predetermined operation based on a processing recipe stored in, for example, a storage medium built into the storage device or a storage medium set in the storage device.

[0040] <Etching equipment> Next, a description will be given of an example of the process module 13 that functions as an etching apparatus for performing the etching method of the present embodiment and is installed in the processing system 10. Fig. 10 is a cross-sectional view that schematically shows an example of the process module 13 that functions as an etching apparatus in the processing system of Fig. 9.

[0041] 10, the process module 13 functioning as an etching apparatus includes a sealed processing vessel 28 that accommodates a substrate W. The processing vessel 28 is made of, for example, aluminum or an aluminum alloy, and has an open upper end that is closed by a lid 29 that serves as a ceiling. A loading / unloading port 30 for the substrate W is provided in a sidewall 28a of the processing vessel 28, and the loading / unloading port 30 can be opened and closed by the gate valve 26 described above.

[0042] As described above, two stages 15 (only one of which is shown) are disposed at the bottom of the interior of the processing vessel 28, each of which horizontally supports one substrate W. The stage 15 is generally cylindrical and includes a mounting plate 34 on which the substrate W is directly mounted and a base block 35 that supports the mounting plate 34. A temperature control mechanism 36 for controlling the temperature of the substrate W is provided within the mounting plate 34. The temperature control mechanism 36 includes, for example, a conduit (not shown) through which a temperature control medium circulates, and controls the temperature of the substrate W by heat exchange between the temperature control medium flowing within the conduit and the substrate W. When the controlled temperature is high, the temperature control mechanism 36 may be a heater, or both a conduit through which the temperature control medium circulates and a heater may be provided. The stage 15 also has multiple lifting pins (not shown) that can be raised and lowered relative to the upper surface of the mounting plate 34 and are used to load and unload the substrate W into and from the processing vessel 28.

[0043] The interior of the processing vessel 28 is divided by a partition plate 37 into an upper plasma generation space P and a lower processing space S. The partition plate 37 functions as a so-called ion trap, which suppresses transmission of ions in plasma from the plasma generation space P to the processing space S when inductively coupled plasma is generated in the plasma generation space P. The plasma generation space P is a space where plasma is generated, and the processing space S is a space where etching is performed on the substrate W by radical processing. A first gas supply unit 61 and a second gas supply unit 62 are provided outside the processing vessel 28.

[0044] The first gas supply unit 61 supplies O gas, H gas, NF gas which is a fluorine-containing gas, and a rare gas (e.g., Ar gas) to the plasma generating space P. These gases are converted into plasma in the plasma generating space P. The rare gas functions as a plasma generating gas, but also functions as a pressure adjusting gas, a purge gas, etc.

[0045] The second gas supply unit 62 supplies to the processing space S processing gases used for chemical processing, such as the above-mentioned HF gas and NH 3 gas, and rare gases used as pressure adjusting gas, purge gas, dilution gas, or the like.

[0046] An exhaust mechanism 39 is connected to the bottom of the processing vessel 28. The exhaust mechanism 39 has a vacuum pump and evacuates the inside of the processing space S.

[0047] A heat shield 48 is provided below the partition plate 37 so as to face the substrate W. The heat shield 48 is provided to prevent heat from accumulating in the partition plate 37 due to repeated plasma generation in the plasma generation space P from affecting the radical distribution in the processing space S. The heat shield 48 is formed larger than the partition plate 37, and a flange portion 48a forming the peripheral edge thereof is embedded in the side wall portion 28a of the processing vessel 28. A cooling mechanism 50, for example, a refrigerant flow path, a chiller, or a Peltier element is embedded in the flange portion 48a.

[0048] The lid 29, which serves as the ceiling of the processing vessel 28, is formed, for example, from a circular quartz plate and configured as a dielectric window. An annular RF antenna 40 for generating inductively coupled plasma in the plasma generation space P of the processing vessel 28 is formed on the lid 29, and the RF antenna 40 is connected to a high-frequency power supply 42 via a matching box 41. The high-frequency power supply 42 outputs high-frequency power at a predetermined output value and a predetermined frequency (e.g., 13.56 MHz or higher) suitable for generating plasma by inductively coupled high-frequency discharge. The matching box 41 has a variable reactance matching circuit (not shown) for matching the impedance on the high-frequency power supply 42 side with the impedance on the load (RF antenna 40 and plasma) side.

[0049] When a process module for carrying out only heat treatment is provided, the process module having the above configuration is used without the plasma generating mechanism and the partition plate.

[0050] When the etching method according to the embodiment is performed using the processing system 10, first, a substrate W having the structure shown in Fig. 3 is removed from the FOUP 16 by the transfer arm of the loader module 18 and loaded into the load lock module 19. After the load lock module 19 is evacuated, the substrate W in the load lock module 19 is loaded into the process module 13, which functions as an etching apparatus, by the transfer arm 14 of the transfer module 12.

[0051] Next, a pressure-regulating gas, such as N2 gas, is introduced into the processing vessel 28 from the second gas supply unit 62, and the pressure inside the processing vessel 28 is adjusted to, for example, 1000 to 2000 mTorr (133.3 to 266.6 Pa). The substrate W is then held for a predetermined time, for example, 120 seconds, on the stage 15, whose temperature is adjusted to 80 to 120°C by the temperature adjustment mechanism 36, to stabilize the wafer temperature at the predetermined temperature.

[0052] Next, after purging the processing vessel 28, the pressure inside the processing vessel 28 is preferably set to 50 to 300 mTorr (6.67 to 40 Pa), and oxygen-containing plasma is generated to perform radical oxidation processing.

[0053] When performing the radical oxidation treatment, first, an oxygen-containing gas is supplied from the first gas supply unit 61 to the plasma generation space P, and high-frequency power is supplied to the RF antenna 40 to generate oxygen-containing plasma, which is inductively coupled plasma. At this time, the oxygen-containing gas may be O2 gas alone, or O2 gas may be added with H2 gas or an F-containing gas. Furthermore, a rare gas such as Ar gas may also be supplied.

[0054] Next, the plasma of the oxygen-containing gas generated in the plasma generation space P is transported to the processing space S via the partition plate 37. At this time, the O ions are deactivated by the partition plate 37, and mainly O radicals in the plasma are selectively introduced into the processing space S. These O radicals oxidize the Si or SiN surface portion of the substrate W, producing an oxide film. Since the processing at this time is mainly performed by O radicals, ion damage to the substrate W is small.

[0055] In this case, the gas flow rate is preferably O2 gas flow rate: 50 to 200 sccm. When H2 gas, F-containing gas, and rare gas (Ar gas) are supplied, the flow rates are preferably 200 sccm or less, 3 to 10 sccm, and 30 to 200 sccm, respectively. The plasma generating power is preferably 400 to 800 W.

[0056] After the oxygen-containing plasma process described above, the processing chamber 28 is purged, and the oxide film is subjected to a chemical process using a gas. The pressure within the processing chamber 28 is preferably set to a range of 100 to 1500 mTorr (13.3 to 200 Pa), and the temperature of the stage 15 (substrate W) is maintained at 80 to 120°C by the temperature control mechanism 36. Then, a processing gas containing an F-containing gas, such as HF gas and NH3 gas, is supplied from the second gas supply unit 62 to the processing space S of the processing chamber 28. This causes the processing gas to react with the oxide film, generating reaction products that are easily decomposed. For example, the HF gas and NH3 gas are adsorbed onto the substrate W, and react with the oxide film to generate AFS, an ammonium fluoride-based compound.

[0057] When HF gas and NH3 gas are used, the gas flow rates are preferably HF gas flow rate: 50 to 100 sccm, NH3 gas flow rate: 300 to 400 sccm, and inert gas (Ar gas) flow rate: 200 to 400 sccm.

[0058] After the above chemical treatment, the processing vessel 28 is purged and a process for removing reaction products, such as AFS, which is an ammonium fluoride-based compound, is performed. The AFS is removed by supplying an inert gas into the processing vessel 28 while evacuating the processing vessel 28, while maintaining the temperature of the stage 15 (substrate W) at 80 to 120°C using the temperature control mechanism 36, to sublimate the AFS. This sublimation process may be performed in a processing vessel of a separate device.

[0059] The above radical oxidation process, gas-based chemical treatment, and thermal removal of the reaction products are repeated multiple times to etch Si or SiN to the desired thickness. In this way, radical oxidation is performed to generate an oxide film, and then gas-based chemical treatment and removal of the reaction products are performed, so Si or SiN etching can be performed with good surface roughness and controllability.

[0060] <Other applications> Although the embodiments have been described above, the disclosed embodiments should be considered to be illustrative and not restrictive in all respects. The above embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims.

[0061] For example, the apparatuses in the above embodiments are merely examples, and apparatuses with various configurations can be used. Also, although the case where a semiconductor wafer is used as the substrate to be processed has been described, the substrate is not limited to a semiconductor wafer, and may be other substrates such as an FPD (flat panel display) substrate, typified by an LCD (liquid crystal display) substrate, or a ceramic substrate. [Explanation of symbols]

[0062] 13 Process module (etching equipment) 15 stages 28 Processing vessel 37 Partition 39 Exhaust system 40 RF antenna 42 High frequency power supply 61 First gas supply unit 62 Second gas supply unit 100 Silicon substrate 102 ONON laminated structure 103 Memory hole (recess) 105 Si film (channel) 105a oxide film 106; Slit (recess) 111 SiO2 film 112 SiN film P Plasma generation space S Processing space W substrate

Claims

1. 1. An etching method for etching Si or SiN present on a substrate, comprising: performing a radical oxidation process on a substrate having Si or SiN to form an oxide film on the surface of the Si or SiN; performing a chemical treatment on the oxide film using a gas; removing reaction products produced by the chemical treatment; and repeating the steps of forming the oxide film, performing the chemical treatment, and removing the reaction product multiple times; the radical oxidation treatment is performed by oxygen-containing plasma generated from an oxygen-containing gas; the oxygen-containing gas is a mixed gas of O 2 gas and an F-containing gas; the substrate has a recess on a side surface thereof in which the Si or SiN is present, the radical oxidation treatment includes controlling a thickness distribution of the oxide film in a depth direction of the recess by adjusting at least one of a pressure and a ratio of the F-containing gas in the oxygen-containing gas. Etching method.

2. The etching method according to claim 1 , wherein the steps of performing the chemical treatment and removing the reaction product are repeated multiple times.

3. 3. The etching method according to claim 1, wherein the formation of the oxide film and the chemical treatment are carried out in the same processing chamber.

4. 3. The etching method according to claim 1, wherein the chemical treatment and the removal of the reaction product are carried out in the same processing chamber.

5. 3. The etching method according to claim 1, wherein the steps of forming the oxide film, performing the chemical treatment, and removing the reaction product are carried out in the same processing chamber.

6. 4. The etching method according to claim 1, wherein the chemical treatment and the removal of the reaction product are carried out in separate treatment vessels.

7. The F-containing gas is NF ３ The etching method according to claim 1 , wherein the gas is a gas.

8. 8. The etching method according to claim 1, wherein the oxygen-containing plasma is generated by remote plasma generation in a plasma generation space separate from a processing space in which the substrate is placed.

9. 9. The etching method according to claim 1, wherein the chemical treatment with a gas is performed with a treatment gas containing a fluorine-containing gas.

10. The process gas containing the fluorine-containing gas is a mixture of a fluorine-containing gas and H ２ The etching method according to claim 9 , further comprising O gas or a reducing gas.

11. The process gas containing the fluorine-containing gas contains HF gas as the fluorine-containing gas and NH 3 as the reducing gas. ３ The etching method of claim 10 comprising a gas.

12. The etching method according to claim 11, wherein the reaction product is an ammonium fluoride-based compound produced after the chemical treatment.

13. An etching apparatus for etching Si or SiN present on a substrate, comprising: a processing vessel for accommodating a substrate; a mounting table provided in the processing chamber on which the substrate is placed; a first gas supply mechanism that supplies an oxygen-containing gas into the processing chamber; a radical oxidation mechanism that performs a radical oxidation process using oxygen-containing plasma generated from the oxygen-containing gas to form an oxide film on the surface of Si or SiN; a second gas supply mechanism for supplying a gas for chemically treating the oxide film into the processing chamber; a temperature control mechanism that controls the temperature of the mounting table; an exhaust mechanism that evacuates the processing chamber; A control unit; and The control unit performing a radical oxidation process on a substrate having Si or SiN to form an oxide film on the surface of the Si or SiN; performing a chemical treatment on the oxide film using a gas; removing reaction products produced by the chemical treatment; controlling the radical oxidation mechanism, the first gas supply mechanism, the second gas supply mechanism, the temperature adjustment mechanism, and the exhaust mechanism so that and controlling the steps of forming the oxide film, performing the chemical treatment, and removing the reaction product to be repeated multiple times; the oxygen-containing gas is a mixed gas of O 2 gas and an F-containing gas; the substrate has a recess on a side surface thereof in which the Si or SiN is present, the radical oxidation treatment includes controlling a thickness distribution of the oxide film in a depth direction of the recess by adjusting at least one of a pressure and a ratio of the F-containing gas in the oxygen-containing gas. Etching equipment.

14. 14. The etching apparatus according to claim 13, further comprising a partition that separates the processing vessel into an upper plasma generation space and a lower processing space, wherein the radical oxidation mechanism generates the oxygen-containing plasma in the plasma generation space and passes the oxygen-containing plasma through the partition to perform radical oxidation processing on the substrate.

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