JP2022094914A - Etching method and etching device - Google Patents

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

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

In the process of manufacturing a semiconductor device, there is a step of etching silicon (Si) or silicon nitride (SiN) for slimming. Wet etching is often used in etching in such a process. For example, Patent Document 1 describes a method of etching polysilicon by wet etching.

Japanese Unexamined Patent Publication No. 9-260361

The present disclosure provides an etching method and an etching apparatus capable of etching Si or SiN with good surface roughness.

The etching method according to one aspect of the present disclosure is an etching method for etching Si or SiN existing on a substrate, in which a substrate having Si or SiN is subjected to radical oxidation treatment, and an oxide film is applied to the surface of Si or SiN. To produce the oxide film, to perform a chemical treatment with a gas on the oxide film, and to remove the reaction product produced by the chemical treatment. And the chemical treatment and the removal of the reaction product are repeated a plurality of times.

According to the present disclosure, there are provided an etching method and an etching apparatus capable of etching Si or SiN with good surface roughness.

It is a flowchart which shows an example of the etching method which concerns on one Embodiment. It is a flowchart which shows the other example of the etching method which concerns on one Embodiment. It is sectional drawing which shows an example of the structure of the substrate to which the etching method of one Embodiment is applied. It is a figure which shows the state which etched the poly-Si film which becomes a channel in the structure of FIG. It is sectional drawing which shows the other example of the structure of the substrate to which the etching method of one Embodiment is applied. FIG. 5 is a cross-sectional view showing a state in which the SiN film of the ONON laminated structure portion is recess-etched in the structure of FIG. FIG. 3 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. It is a figure which shows the estimation mechanism that the top-bottom loading can be controlled by the pressure at the time of radical oxidation treatment, and the ratio of NF3 gas which is F _- containing gas. It is a partial sectional plan view schematically showing an example of the processing system used for the etching method of one Embodiment. 9 is a cross-sectional view schematically showing an example of a process module mounted on the processing system of FIG. 9 and functioning as an etching apparatus for carrying out the etching method of one embodiment.

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

<Etching method>
FIG. 1 is a flowchart showing an example of an etching method according to an embodiment.
The etching method according to the present embodiment etches Si or SiN existing on the substrate. First, a substrate having Si or SiN, which is an etching target portion, is subjected to radical oxidation treatment to form an oxide film on the surface of Si or SiN (step ST1). Next, the oxide film is chemically treated with gas (step ST2). The reaction product produced by the chemical treatment of step ST2 is then removed (step ST3). These steps ST1 to ST3 are repeated a plurality of times. As a result, Si or SiN present on the substrate is etched in a desired amount.

Hereinafter, it will be described in detail.
The radical oxidation treatment in step ST1 generates oxygen-containing plasma, causes oxygen radicals (O radicals) in the oxygen-containing plasma to act on the substrate housed in the treatment container, and causes an oxide film (O-radical) on the surface of Si or SiN. SiO ₂ film) is formed. At this time, it is preferable to use a remote plasma so that mainly O radicals in the oxygen-containing plasma can be supplied to the substrate. The remote plasma generates a plasma of oxygen-containing gas in a plasma generation space separate from the processing space in which the substrate is arranged, and transports the plasma to the processing space. Oxygen ions (O ₂ ions) in the oxygen-containing plasma are easily deactivated during transportation, and mainly O radicals are supplied to the treatment space. Ion damage to the substrate can be reduced by the action of O radicals mainly on the substrate. The plasma source is not particularly limited, and inductively coupled plasma, microwave plasma, or the like can be used.

Further, the oxygen-containing gas for generating the oxygen-containing plasma used at this time may be O ₂ gas alone, or at least O ₂ gas, H ₂ gas, fluorine (F) -containing gas, and rare gas. It may be a mixed gas with one kind. As the F-containing gas, NF ₃ gas, SF ₆ gas, F ₂ gas and the like can be used. Of these, NF ₃ gas is suitable. The rare gas is not particularly limited, but Ar gas is preferable. Oxidation capacity can be enhanced by adding H ₂ gas. F radicals are generated by adding the F-containing gas, and the oxide film and Si are etched by the F radicals. The ratio of the F-containing gas is preferably 0.5 to 5% for the F-containing gas / _O2 gas. The H ₂ gas is preferably H ₂ gas / (O ₂ gas + H ₂ gas) at 0 to 80%. Further, the plasma can be stabilized by adding a rare gas.

The pressure in 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 of step ST1 is preferably in the range of 60 to 180 sec. The flow rate of each gas is appropriately set according to the apparatus.

In the step of chemically treating the oxide film of step ST2 with a gas, as the chemical treatment with a gas, a chemical treatment using a treatment gas containing an F-containing gas can be mentioned. By this treatment, the oxide film and the treatment gas are reacted to produce a compound that can be removed by heating or the like.

Examples of the F-containing gas contained in the treatment gas include hydrogen fluoride (HF) gas, and examples of the gas other than the F-containing gas include _H2O gas and reducing gas. Examples of the reducing gas include ammonia (NH ₃ ) gas and amine-based gas. By reacting the F-containing gas with the _H2O gas or the reducing gas with the oxide film, a compound that can be removed relatively easily can be produced.

Among these, those using HF gas as the fluorine-containing gas and _NH3 gas as the reducing gas are preferable. The HF gas and NH ₃ gas can be used to perform a chemical oxide removal treatment (COR), which is conventionally known as an oxide removal treatment. In the COR treatment, HF gas and _NH3 gas are adsorbed on the surface of the oxide film, and these are reacted with the oxide film to produce ammonium fluoride (AFS), which is an ammonium fluoride-based compound.

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

Step ST2 can be performed in the same processing container as step ST1. The throughput can be increased by performing in the same processing container. Of course, these may be performed in separate processing containers.

The step of removing the reaction product in step ST3 is performed by supplying an inert gas into the processing container while exhausting the processing container while keeping the substrate at a desired temperature. This step may be performed in the same processing container as the chemical treatment with gas in step ST2, or may be performed in a separate processing container. In either case, the substrate temperature may be set appropriately and may be the same as or different from step ST2. However, when step ST3 is performed in the same processing container as step ST2, the substrate temperature is set to the same temperature as step ST2. By doing so, the throughput can be increased. When step ST3 is carried out in a treatment container separate from step ST2, it may be heated to, for example, 190 to 300 ° C. to promote the removal of the reaction product. Further, as shown in FIG. 2, step ST2 and step ST3 may be repeated. In particular, when SiN is COR-treated, there is a risk that SiN will be etched by the HF / NH ₃ gas. Therefore, by repeating step ST2 and step ST3 in a short time, etching of SiN using the incubation time It is preferable to prevent. When step ST2 and step ST3 are repeated, they may be performed in the same processing container or in separate processing containers.

Depending on the gas type and conditions such as temperature and pressure, step ST2 and step ST3 can be performed at the same time. For example, by performing the COR treatment at a temperature at which AFS decomposes, the chemical treatment with gas in step ST2 and the step of removing the reaction product in step ST3 can be simultaneously advanced. Further, after all the treatments are completed, a heat treatment for removing the residue may be performed in a separate treatment container.

In the conventional wet etching of Si, the etching progresses along the grain boundaries or crystal planes of Si, so that the roughness of the surface deteriorates. On the other hand, in the present embodiment, the formation of an oxide film on the Si surface by the plasma oxidation treatment and the removal of the oxide film by the treatment including the chemical treatment with gas are repeated. At this time, since the radical oxidation treatment is a surface reaction by oxygen radicals, a thin oxide film is formed regardless of the crystal grain boundary or the crystal plane, and then only the oxide film is removed, so that the surface roughness is good. be. Then, by repeating these a desired number of times, a desired amount of etching can be performed with good controllability.

The poly-Si blanket wafer was actually etched by the etching method of the present embodiment, and the surface roughness was confirmed. Here, after the radical oxidation step was performed at 400 to 1250 mTorr, the cycle of performing the oxide film removal step including the COR treatment and the AFS removal treatment was performed for 4 to 22 cycles, and the average film thickness and the surface roughness were measured. Ra was measured as the surface roughness. As a result, the average etching amount was 3.61 to 16.49 nm, Ra was 0.1656 nm in 4 cycles, 0.1986 nm in 15 cycles, 0.1988 nm in 18 cycles, and 0.2068 nm in 22 cycles. This is almost the same value as the initial surface roughness of 0.127 nm, and it was confirmed that the surface roughness was good. On the other hand, in the case of wet etching, Ra was 0.6 nm, which was almost three times the value in the case of the present embodiment.

The structure of the substrate to which the etching method of this embodiment is applied is not particularly limited, and examples thereof include structures used in 3D-NAND non-volatile semiconductor devices. FIG. 3 is a cross-sectional view showing an example of the structure of such a substrate.

In this example, the semiconductor wafer (wafer) W, which is a substrate, has an ONON laminated structure portion 102 in which a plurality of SiO ₂ film 111 and SiN film 112 are alternately laminated on a silicon substrate 100. .. The number of layers of the SiO ₂ film 111 and the SiN film 112 is actually about 100 layers. A superstructure 110 is provided on the ONON laminated structure portion 102, and a memory hole 103 penetrating the superstructure 110 and the ONON laminated structure portion 102 in the stacking direction is formed. The memory hole 103 has a multi-layered memory. A film 104 and a Si film 105 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 as a channel is etched and slimmed.

FIG. 5 is a cross-sectional view showing another example of the structure of the substrate used in the 3D-NAND type non-volatile semiconductor device. In this example, the wafer W, which is a substrate, also has an ONON laminated structure portion 102 and a superstructure 110 in which a plurality of SiO ₂ films 111 and SiN films 112 are alternately laminated on a silicon substrate 100. Have. A slit 106 penetrating in the stacking direction is formed in the superstructure 110 and the ONON laminated structure portion 102. In this example, as shown in FIG. 6, a plurality of SiN films 112 of the ONON laminated structure portion 102 are recess-etched by about 3 to 5 nm.

In such a 3D-NAND type non-volatile semiconductor device, the memory hole 103 and the slit 106 are very deep. In such a deep recess, the desired film thickness uniformity in the depth direction is achieved by top-bottom loading (loading between the frontage and the deepest portion) during the oxidation treatment of Si and SiN existing on the side surface of the recess. An oxide film having the above may not be obtained. Such top-bottom loading is not limited to the 3D-NAND type non-volatile semiconductor device, and becomes a problem in etching the side surface portion of the recess having a depth of 4 μm or more.

As a method for controlling such top-bottom loading, it has been found that it is effective to adjust the pressure during the radical oxidation treatment and / or the ratio of the F-containing gas to the oxygen-containing gas.

FIG. 7 shows the number of cycles of Top, middle (Mid), and bottom (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. It is a figure which shows the relationship with. As shown in this figure, it can be seen that in (a) where the radical oxidation step is a high pressure condition (160 mTorr), the etching amount is Top First, which is larger in Top than in Btm. It can be seen that in (b) where the radical oxidation step is a low pressure condition (50 mTorr), the etching amount is substantially the same for Top and Btm, and uniform etching is obtained. It can be seen that when the radical oxidation step is a low pressure condition (50 mTorr) and 4% of NF ₃ is added to the O ₂ gas (c), the etching amount is Btm first, which is larger in Btm than in Top.

From these results, it can be seen that the etching characteristics can be adjusted to Top> Btm, Top = Btm, and Top <Btm by adjusting the pressure of the radical oxidation step and NF ₃ / O ₂ . That is, the etching amount can be adjusted to any of Top> Btm, Top = Btm, and Top <Btm by changing the pressure during the radical oxidation step and / or the ratio of the F-containing gas in the oxygen-containing gas. , It was confirmed that top-bottom loading can be controlled.

Next, an estimation mechanism that can control top-bottom loading in this way will be described. FIG. 8 is a diagram showing an estimation mechanism in 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.

Under the high pressure condition of (a) in FIG. 8, the mean free path is short, so that the O radical is prevented from reaching the bottom. The O radical attacks mainly the Top portion of the Si film 105, the top portion of the generated oxide film 105a becomes thicker, and the etching of the Si film 105 becomes Top first. Further, under the low pressure condition of (b), since the mean free path is long, the O radical also reaches the bottom. Therefore, the O radicals uniformly attack the Si film 105, the generated oxide film 105a has a uniform thickness, and the Si film 105 is uniformly etched. (C) is a condition under _high pressure and the addition of NF3 gas. Under this condition, the mean free path is short, which prevents both O and F radicals from reaching the bottom. The O radical forms an oxide film 105a mainly on the Top portion of the Si film 105. The F radical etches the oxide film 105a of the Top portion, but its action is small, and the etching of the Si film 105 becomes Top first as in (a). (D) is a condition at low pressure and to which NF ₃ gas is added. Under this condition, the mean free path is long, and the O radicals attack the Si film 105 uniformly. On the other hand, the F radical easily moves to the bottom and etches the Si film 105 at the bottom, and as a result, the etching of the Si film 105 becomes Btm first.

<Example of processing system>
Next, an example of the processing system used in the etching method of the present embodiment will be described. FIG. 9 is a partial cross-sectional plan view schematically showing an example of the processing system used in the etching method of the present embodiment.

As shown in FIG. 9, the processing system 10 includes an carry-in / out unit 11 that stores a plurality of boards W and carries in / out the boards W, and a transfer module 12 as a transfer chamber that simultaneously carries two boards W. A plurality of process modules 13 for processing the substrate W carried in from the transfer module 12 are provided. The inside of each process module 13 and transfer module 12 is maintained in a vacuum atmosphere.

In the processing system 10, the substrate W stored in the loading / unloading section 11 is conveyed by the transfer arm 14 built in the transfer module 12, and one substrate is transferred to each of the two stages 15 arranged inside the process module 13. Place W. Next, in the processing system 10, each substrate W mounted on the stage 15 is processed by the process module 13, and then the processed substrate W is carried out to the loading / unloading section 11 by the transport arm 14.

The loading / unloading unit 11 receives or receives the stored board W from the plurality of load ports 17 as a mounting table of the FOUP 16 which is a container for accommodating the plurality of boards W, and the stored board W from the FOUP 16 mounted on each load port 17. A loader module 18 that delivers the substrate W processed by the process module 13 to the FOUP 16, and two load lock modules that temporarily hold the substrate W to transfer the substrate W between the loader module 18 and the transfer module 12. It has 19 and a cooling storage 20 for cooling the heat-treated substrate W.

The loader module 18 has a rectangular housing having an atmospheric pressure atmosphere inside, and a plurality of load ports 17 are arranged side by side on one side surface constituting the long side of the rectangle. Further, the loader module 18 has a transfer arm (not shown) that can be moved in the longitudinal direction of the rectangle inside. The transfer arm carries the substrate W into the load lock module 19 from the FOUP 16 mounted on each load port 17, or carries out the substrate W from the load lock module 19 to each FOUP 16.

Each load lock module 19 temporarily holds the substrate W because the substrate W housed in the FOUP 16 mounted on each load port 17 in the atmospheric pressure atmosphere is handed over to the process module 13 having a vacuum atmosphere inside. Each load lock module 19 has a buffer plate 21 that holds two substrates W. Further, each load lock module 19 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. Further, a gas introduction system and a gas exhaust system (not shown) are connected to the load lock module 19 by pipes, and the inside can be switched between an atmospheric pressure atmosphere and a vacuum atmosphere.

The transfer module 12 carries in the unprocessed substrate W from the carry-in / out section 11 to the process module 13, and carries out the processed board W from the process module 13 to the carry-in / out section 11. The transfer module 12 is composed of a rectangular housing having a vacuum atmosphere inside, and has two transfer arms 14 that hold and move two substrates W, a rotary table 23 that rotatably supports each transfer arm 14, and rotation. It includes a rotary mounting table 24 on which the table 23 is mounted, and a guide rail 25 that guides the rotary mounting table 24 so as to be movable in the longitudinal direction of the transfer module 12. Further, the transfer module 12 is connected to the load lock module 19 of the carry-in / out section 11 and each process module 13 via the gate valve 22b and each gate valve 26 described later. In the transfer module 12, the transfer arm 14 transfers two boards W from the load lock module 19 to each process module 13, and transfers the two processed boards W from each process module 13 to another process module 13. And carry it out to the load lock module 19.

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 separately include a process module for performing steps ST1 and ST2 and a process module 13 for performing step ST3.

The processing system 10 has a control unit 27. The control unit 27 includes a main control unit having a CPU that controls the operation of each component of the processing system 10, an input device (keyboard, mouse, etc.), an output device (printer, etc.), a display device (display, etc.), and a storage device. Has (storage medium). The main control unit of the control unit 27 causes the processing system 10 to execute a predetermined operation based on, for example, a processing recipe stored in a storage medium built in the storage device or a storage medium set in the storage device.

<Etching equipment>
Next, an example of the process module 13 mounted on the processing system 10 and functioning as an etching apparatus for carrying out the etching method of the present embodiment will be described. FIG. 10 is a cross-sectional view schematically showing an example of a process module 13 that functions as an etching apparatus in the processing system of FIG.

As shown in FIG. 10, the process module 13 functioning as an etching apparatus includes a processing container 28 having a closed structure for accommodating the substrate W. The processing container 28 is made of, for example, aluminum or an aluminum alloy, the upper end thereof is open, and the upper end of the processing container 28 is closed by a lid 29 serving as a ceiling portion. A carry-out port 30 for the substrate W is provided on the side wall portion 28a of the processing container 28, and the carry-out port 30 can be opened and closed by the gate valve 26 described above.

Further, as described above, two stages 15 (only one of which is shown) on which one substrate W is placed in a horizontal state are arranged on the bottom of the inside of the processing container 28. The stage 15 has a substantially columnar shape and has 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 inside the mounting plate 34. The temperature control mechanism 36 has, for example, a pipeline (not shown) in which the temperature control medium circulates, and the temperature of the substrate W is controlled by exchanging heat between the temperature control medium flowing in the pipeline and the substrate W. conduct. When the control temperature is high, the temperature control mechanism 36 may be a heater, or both a pipeline through which the temperature control medium circulates and a heater may be provided. Further, the stage 15 is provided with a plurality of elevating pins (not shown) used for carrying the substrate W into and out of the processing container 28 so as to be retractable with respect to the upper surface of the mounting plate 34.

The inside of the processing container 28 is partitioned 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 that suppresses the permeation of ions in the plasma from the plasma generation space P to the processing space S when the inductively coupled plasma is generated in the plasma generation space P. The plasma generation space P is a space in which plasma is generated, and the processing space S is a space in which the substrate W is etched by radical treatment. A first gas supply unit 61 and a second gas supply unit 62 are provided outside the processing container 28.

The first gas supply unit 61 supplies O ₂ gas, H ₂ gas, NF ₃ gas which is a fluorine-containing gas, and a rare gas (for example, Ar gas) to the plasma generation space P. These gases are plasmatized in the plasma generation space P. Although the noble gas functions as a plasma generating gas, it also functions as a pressure adjusting gas, a purge gas, and the like.

The second gas supply unit 62 puts a processing gas used for chemical treatment, for example, HF gas and _NH3 gas as described above, and a rare gas used as a pressure regulating gas, a purge gas, a diluting gas, or the like into the processing space S. Supply.

An exhaust mechanism 39 is connected to the bottom of the processing container 28. The exhaust mechanism 39 has a vacuum pump and exhausts the inside of the processing space S.

Below the partition plate 37, a heat shield plate 48 is provided so as to face the substrate W. The heat shield plate 48 is for suppressing the heat from affecting the radical distribution in the processing space S because heat is accumulated in the partition plate 37 by repeating the plasma generation in the plasma generation space P. be. The heat shield plate 48 is formed larger than the partition plate 37, and the flange portion 48a constituting the peripheral edge portion is embedded in the side wall portion 28a of the processing container 28. A cooling mechanism 50, for example, a refrigerant flow path, a chiller, or a Pelche element is embedded in the flange portion 48a.

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

When a process module that performs only heat treatment is provided, a process module having the above configuration excluding the plasma generation mechanism and the partition plate is used.

When the etching method according to the above embodiment is carried out by the processing system 10, first, the substrate W having the structure shown in FIG. 3, for example, is taken out from the FOUP 16 by the transfer arm of the loader module 18, and the load lock is performed. Carry it into module 19. After the load lock module 19 is evacuated, the substrate W in the load lock module 19 is carried into the process module 13 functioning as an etching device by the transfer arm 14 of the transfer module 12.

Next, for example, _N2 gas is introduced into the processing container 28 as the pressure adjusting gas from the second gas supply unit 62, and the pressure in the processing container 28 is set to, for example, 1000 to 2000 mTorr (133.3 to 266.6 Pa). At the same time, the substrate W is held for a predetermined time, for example, 120 seconds on the stage 15 whose temperature is controlled to 80 to 120 ° C. by the temperature control mechanism 36, and the wafer temperature is stabilized at the predetermined temperature.

Next, after purging the inside of the processing container 28, the pressure inside the processing container 28 is preferably 50 to 300 mTorr (6.67 to 40 Pa) to generate oxygen-containing plasma and perform radical oxidation treatment.

When performing the radical oxidation treatment, first, the 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 an oxygen-containing plasma which is an inductively coupled plasma. Generate. At this time, the oxygen-containing gas may be O ₂ gas alone, or H ₂ gas or F-containing gas may be added to the O ₂ gas. Further, a rare gas such as Ar gas may be further supplied.

Next, the plasma of the oxygen-containing gas generated in the plasma generation space P is conveyed to the processing space S via the partition plate 37. At this time, O ₂ ions are deactivated at the partition plate 37, and mainly O radicals in the plasma are selectively introduced into the processing space S. The O radical oxidizes the surface portion of Si or SiN of the substrate W to form an oxide film. Since the treatment at this time is mainly composed of O radicals, the ion damage to the substrate W is small.

At this time, the gas flow rate is preferably O ₂ gas flow rate: 50 to 200 sccm. When supplying H ₂ gas, F-containing gas, and noble gas (Ar gas), it is preferably 200 sccm or less, 3 to 10 sccm, and 30 to 200 sccm, respectively. Further, the plasma generation power is preferably 400 to 800 W.

After the oxygen-containing plasma treatment as described above, the inside of the treatment container 28 is purged, and the oxide film is chemically treated with gas. At this time, the pressure in the processing container 28 was preferably in the range of 100 to 1500 mTorr (13.3 to 200 Pa), and the temperature of the stage 15 (substrate W) was maintained at a temperature of 80 to 120 ° C. by the temperature control mechanism 36. After that, the processing gas containing the F-containing gas, for example, HF gas and NH ₃ gas, is supplied from the second gas supply unit 62 to the processing space S of the processing container 28. As a result, the treatment gas reacts with the oxide film to produce a reaction product that is easily decomposed. For example, HF gas and _NH3 gas are adsorbed on the substrate W and react with the oxide film to produce AFS, which is an ammonium fluoride-based compound.

When HF gas and NH ₃ gas are used, the gas flow rate is preferably HF gas flow rate: 50 to 100 sccm, NH ₃ gas flow rate: 300 to 400 sccm, and inert gas (Ar gas) flow rate: 200 to 400 sccm.

After the above chemical treatment, the inside of the treatment container 28 is purged to remove the reaction product, for example, AFS which is an ammonium fluoride compound. To remove AFS, the temperature of the stage 15 (board W) is maintained at a temperature of 80 to 120 ° C. by the temperature control mechanism 36, and the inert gas is supplied into the processing container 28 while exhausting the processing container 28. Sublimate AFS. This sublimation process may be performed in a processing container of a separate device.

The above radical oxidation treatment, chemical treatment with gas, and heat removal treatment of the reaction product are repeated a plurality of times to etch Si or SiN to a desired thickness. Since the radical oxidation treatment is performed in this way to form an oxide film, and then the chemical treatment with gas and the removal treatment of the reaction product are performed, it is possible to etch Si or SiN with good surface roughness, and control. The sex is also good.

<Other applications>
Although the embodiments have been described above, the embodiments disclosed this time should be considered to be exemplary in all respects and not restrictive. The above embodiments may be omitted, replaced or modified in various forms without departing from the scope of the appended claims and their gist.

For example, the device of the above embodiment is merely an example, and devices having various configurations can be used. Further, although the case where a semiconductor wafer is used as the substrate to be processed is shown, the case is not limited to the semiconductor wafer, but the FPD (flat panel display) substrate represented by the substrate for LCD (liquid crystal display) and other substrates such as ceramic substrates are shown. May be.

13 Process module (etching device)
15 Stage 28 Processing container 37 Partition plate 39 Exhaust mechanism 40 RF antenna 42 High frequency power supply 61 First gas supply part 62 Second gas supply part 100 Silicon substrate 102 ONON laminated structure part 103 Memory hole (recess)
105 Si film (channel)
105a oxide film 106; slit (recess)
111 SiO ₂ film 112 SiN film P Plasma generation space S Processing space W Substrate

Claims (17)

It is an etching method that etches Si or SiN existing on the substrate.
Radical oxidation treatment is applied to the substrate having Si or SiN to form an oxide film on the surface of Si or SiN.
Chemical treatment of the oxide film with gas and
To remove the reaction product produced by the chemical treatment,
Have,
An etching method in which the formation of the oxide film, the chemical treatment, and the removal of the reaction product are repeated a plurality of times. The etching method according to claim 1, wherein the chemical treatment and the removal of the reaction product are repeated a plurality of times. The etching method according to claim 1 or 2, wherein the formation of the oxide film and the chemical treatment are carried out in the same processing container. The etching method according to claim 1 or 2, wherein the chemical treatment and the removal of the reaction product are carried out in the same treatment container. The etching method according to claim 1 or 2, wherein the formation of the oxide film, the chemical treatment, and the removal of the reaction product are carried out in the same processing container. The etching method according to any one of claims 1 to 3, wherein the chemical treatment and the removal of the reaction product are carried out in separate treatment containers. The etching method according to any one of claims 1 to 6, wherein the radical oxidation treatment generates an oxygen-containing plasma from an oxygen-containing gas and causes mainly oxygen radicals to act in the oxygen-containing plasma. The etching method according to claim 7, wherein the oxygen-containing gas is O ₂ gas alone or a mixed gas of O ₂ gas and at least one of H ₂ gas, F-containing gas, and a rare gas. The etching method according to claim 8, wherein the F-containing gas is NF ₃ gas. Claim 7 to claim 7, wherein the oxygen-containing plasma is generated by remote plasma in a plasma generation space separate from the processing space in which the substrate is arranged, and supplies oxygen radicals in the oxygen-containing plasma to the substrate. 9. The etching method according to any one of 9. The substrate has a recess having a depth of 4 μm or more, and the Si or SiN is present on the side surface of the recess, and loading between the frontage and the deepest portion of the recess during the radical oxidation treatment. The etching method according to any one of claims 8 to 10, wherein the pressure and / or the ratio of the F-containing gas to the oxygen-containing gas is adjusted so as to control. The etching method according to any one of claims 1 to 11, wherein the chemical treatment with the gas is performed with a treatment gas containing a fluorine-containing gas. The etching method according to claim 12, wherein the treatment gas containing the fluorine-containing gas includes a fluorine-containing gas and an _H2O gas or a reducing gas. The etching method according to claim 12 or 13, wherein the treatment gas containing the fluorine-containing gas contains HF gas as the fluorine-containing gas and NH ₃ gas as the reducing gas. The etching method according to claim 14, wherein the reaction product is an ammonium fluoride-based compound produced after the chemical treatment. An etching device that etches Si or SiN existing on a substrate.
A processing container for accommodating the substrate and
A mounting table on which the substrate provided in the processing container is placed, and
A first gas supply mechanism for supplying oxygen-containing gas into the processing container,
A radical oxidation mechanism that generates oxygen-containing plasma from the oxygen-containing gas and radically oxidizes it mainly with oxygen radicals 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 container,
The temperature control mechanism that controls the temperature of the stand described above and
An exhaust mechanism that evacuates the inside of the processing container and
Control unit and
Have,
The control unit
Radical oxidation treatment is applied to the substrate having Si or SiN to form an oxide film on the surface of Si or SiN.
Chemical treatment of the oxide film with gas and
To remove the reaction product produced by the chemical treatment,
Control the radical oxidation mechanism, the first gas supply mechanism, the second gas supply mechanism, the temperature control mechanism, and the exhaust mechanism so that
An etching apparatus that controls the formation of the oxide film, the chemical treatment, and the removal of the reaction product a plurality of times. The processing container further has a partition portion for partitioning the upper plasma generation space and the lower treatment space, and the radical oxidation mechanism generates the oxygen-containing plasma in the plasma generation space and oxygen passed through the partition portion. The etching apparatus according to claim 16, wherein the substrate is subjected to radical oxidation treatment by radicals.

Images