Etching method and etching apparatus

Abstract

Provided is an etching method and an etching apparatus capable of etching Si or SiN in a manner that surface roughness is good. An etching method for etching Si or SiN present on a substrate includes the following processes: performing a radical oxidation process on a substrate having Si or SiN to generate an oxide film on the surface of the Si or SiN; performing a chemical process on the oxide film using a gas; and removing a reaction product generated by the chemical process, and the etching method repeatedly performs the process of generating the oxide film, the process of performing the chemical process, and the process of removing the reaction product multiple times.

Description

TECHNICAL FIELD

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

[0002] In a manufacturing process of a semiconductor device, there is a process of etching silicon (Si) or silicon nitride (SiN) to thin it. In etching in such a process, wet etching is mostly used. For example, in Patent Literature 1, a method of etching polysilicon by wet etching is described.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent Application Laid-Open No. 9-260361 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] The present disclosure provides an etching method and an etching apparatus that enable etching of Si or SiN in a manner in which surface roughness is good.

[0008] SOLUTION TO PROBLEM

[0009] An etching method according to one embodiment of the present disclosure is an etching method for etching Si or SiN present in a substrate, the etching method including: performing a radical oxidation process on a substrate having Si or SiN to generate an oxide film on a surface of the Si or SiN; performing a chemical process on the oxide film with a gas; and removing a reaction product generated by the chemical process, wherein the etching method repeatedly performs the process of generating the oxide film, the process of performing the chemical process, and the process of removing the reaction product a plurality of times.

[0010] EFFECT OF THE INVENTION

[0011] According to the present disclosure, an etching method and an etching apparatus that enable etching of Si or SiN in a manner in which surface roughness is good are provided. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is a flowchart showing an example of an etching method according to one embodiment.

[0013] Figure 2 is a flowchart showing another example of an etching method according to one embodiment.

[0014] Figure 3 is a cross-sectional view showing an example of a configuration of a substrate to which an etching method according to one embodiment is applied.

[0015] Figure 4 It means in Figure 3 The diagram shows the state of the poly-Si film etched as the channel in the structure.

[0016] Figure 5 This is a cross-sectional view showing another example of the structure of a substrate to which an etching method of one embodiment is applied.

[0017] Figure 6 It means in Figure 5 A cross-sectional view of the SiN film grooves etched in the ONON stacked structure.

[0018] Figure 7 It means in Figure 3 The graph shows the relationship between the number of cycles of Top, Mid, and Btm and the Si etching amount when the conditions of the free radical oxidation step are varied to repeat the free radical oxidation step and the oxide removal step.

[0019] Figure 8 This is a diagram illustrating the estimation mechanism by which the top-bottom loading effect can be controlled based on the pressure during free radical oxidation treatment and the ratio of NF3 gas containing F.

[0020] Figure 9 This is a partial cross-sectional top view that schematically illustrates an example of a processing system used in an etching method according to one embodiment.

[0021] Figure 10 It is a summary representation of what is carried on Figure 9 A cross-sectional view of an example of a process module in a processing system that functions as an etching apparatus for implementing an etching method in one embodiment.

[0022] Explanation of reference numerals in the attached figures

[0023] 13: Process module (etching device); 15: Stage; 28: Processing container; 37: Separator; 39: Exhaust mechanism; 40: RF antenna; 42: High-frequency power supply; 61: First gas supply section; 62: Second gas supply section; 100: Silicon substrate; 102: ONON stacked structure section; 103: Storage 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. Detailed Implementation

[0024] The implementation method is described below with reference to the accompanying drawings.

[0025] <Etching Method>

[0026] Figure 1is a flowchart showing an example of an etching method according to an embodiment.

[0027] The etching method according to the present embodiment is used to etch Si or SiN present in a substrate. First, a radical oxidation process is performed on a substrate having Si or SiN as an etching target portion, and an oxide film is formed on the surface of the Si or SiN (step ST1). Next, a chemical process is performed on the oxide film using a gas (step ST2). Next, a reaction product generated by the chemical process of step ST2 is removed (step ST3). These steps ST1 to ST3 are repeated multiple times. In this way, the Si or SiN present in the substrate is etched in a desired amount.

[0028] The details are described below.

[0029] The radical oxidation process of step ST1 generates an oxygen-containing plasma, and oxygen radicals (O radicals) in the oxygen-containing plasma are made to act on a substrate housed in a processing container, and an oxide film (SiO2 film) is formed on the surface of the Si or SiN. At this time, a remote plasma is preferably used so that O radicals are mainly supplied to the substrate from the oxygen-containing plasma. The remote plasma generates a plasma of an oxygen-containing gas in a plasma generation space outside a processing space where the substrate is disposed, and the plasma is carried to the processing space. Oxygen ions (O2 ions) in the oxygen-containing plasma are easily deactivated during the carrying, and O radicals are mainly supplied to the processing space. Since O radicals mainly act on the substrate, ion damage to the substrate can be reduced. The plasma source is not particularly limited, and an inductively coupled plasma, a microwave plasma, or the like can be used.

[0030] In addition, the oxygen-containing gas used at this time to generate the oxygen-containing plasma can be only O2 gas, or a mixed gas of at least one of H2 gas, a fluorine (F)-containing gas, and a rare gas, and O2 gas. As the F-containing gas, NF3 gas, SF6 gas, F2 gas, or the like can be used. Of these, NF3 gas is preferable. The rare gas is not particularly limited, but Ar gas is preferable. By adding H2 gas, the oxidation ability can be improved. By adding the F-containing gas, F radicals are generated, and the oxide film and Si are etched by the F radicals. As for the proportion of the F-containing gas, it is preferable that the F-containing gas / O2 gas be 0.5 to 5%. As for the H2 gas, it is preferable that the H2 gas / (O2 gas + H2 gas) be 0 to 80%. In addition, by adding the rare gas, the plasma can be stabilized.

[0031] The pressure at step ST1 is preferably 25 to 500 mTorr (3.33 to 66.7 Pa). The substrate temperature is preferably 15 to 120°C. In addition, the time of step ST1 is preferably in the range of 60 to 180 seconds. The flow rates of the respective gases can be appropriately set according to the apparatus.

[0032] In the treatment of the oxide film with a gas in step ST2, as the chemical treatment with a gas, chemical treatment with a treatment gas containing an F-containing gas can be given. By this treatment, the oxide film is caused to react with the treatment gas to generate a compound that can be removed by heating or the like.

[0033] As the F-containing gas contained in the treatment gas, hydrogen fluoride (HF) gas or the like can be given, and as a gas other than the F-containing gas, H2O gas and a reducing gas can be given. As the reducing gas, ammonia (NH3) gas, amine gas can be given. By causing the F-containing gas and the H2O gas or the reducing gas to react with the oxide film, a compound that can be removed relatively easily can be generated.

[0034] Among them, it is preferable to use HF gas as the fluorine-containing gas and NH3 gas as the reducing gas. By the HF gas and the NH3 gas, chemical oxide removal treatment (COR) known as oxide removal treatment since old days can be performed. In the COR treatment, the HF gas and the NH3 gas are caused to adsorb to the surface of the oxide film to cause them to react with the oxide film to generate ammonium fluosilicate (AFS) as an ammonium fluoride compound.

[0035] In such a COR treatment, the pressure is preferably in the range of 6.66 to 400 Pa (50 to 3000 mTorr), and more preferably in the range of 13.3 to 266.6 Pa (100 to 2000 mTorr). In addition, the substrate temperature at this time is preferably in the range of 0 to 120°C, and more preferably in the range of 20 to 100°C.

[0036] Step ST2 can be performed in the same treatment vessel as that of step ST1. By performing in the same treatment vessel, productivity can be improved. Of course, it can also be performed in a different treatment vessel.

[0037] The removal of reaction products in step ST3 is performed by supplying an inactive gas into the processing container while venting the container, thus bringing the substrate to the desired temperature. This process can be carried out in the same processing container as the chemical treatment using gas in step ST2, or in a different processing container. As long as the substrate temperature is appropriately set in any case, the temperature can be the same as or different from that in step ST2. However, performing step ST3 in the same processing container as in step ST2, by setting the substrate temperature to the same level as in step ST2, can improve productivity. When performing step ST3 in a processing container other than the processing container of step ST2, the substrate temperature can be heated, for example, to 190–300°C to promote the removal of reaction products. Alternatively, it can be performed as follows... Figure 2 Repeat steps ST2 and ST3 as shown. Especially in the case of COR treatment of SiN, since there is a risk of SiN being etched by HF / NH3 gas, it is preferable to use the incubation time to prevent SiN etching by repeating steps ST2 and ST3 for a short period of time. When repeating steps ST2 and ST3, it can be carried out either in the same processing container or in different processing containers.

[0038] Furthermore, depending on the gas type, temperature / pressure, and other conditions, steps ST2 and ST3 can be performed simultaneously. For example, by performing COR treatment at the AFS decomposition temperature, the chemical treatment using the gas in step ST2 and the removal of reaction products in step ST3 can proceed simultaneously. Additionally, after all treatments are completed, heating treatment for residue removal can be performed in different treatment containers.

[0039] In conventional wet etching of Si, etching proceeds along the grain boundaries or crystal planes of Si, resulting in poor surface roughness. In contrast, in this embodiment, the process of forming an oxide film on the Si surface through plasma oxidation and then removing the oxide film through a chemical process involving gas is repeated. Here, the free radical oxidation process is a surface reaction carried out by oxygen free radicals, thus forming a thin oxide film independently of grain boundaries or crystal planes. This oxide film is then removed, resulting in good surface roughness. Furthermore, by repeating these processes a desired number of times, the desired amount of etching can be etched with good control.

[0040] In fact, etching of a poly-Si blank wafer was performed by the etching method of the present embodiment, and surface roughness was confirmed. Here, after the radical oxidation step was performed at 400 to 1250 mTorr, the cycle for 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. As the surface roughness, Ra was measured. As a result, the average etching amount was 3.61 to 16.49 nm, Ra was 0.1656 nm by 4 cycles, 0.1986 nm by 15 cycles, 0.1988 nm by 18 cycles, and 0.2068 nm by 22 cycles. It was confirmed that this was a value approximately equivalent to 0.127 nm, which was the surface roughness as the initial value, and was a good surface roughness. In contrast, in the case of wet etching, Ra was 0.6 nm, which was a value approximately 3 times larger than in the case of the present embodiment.

[0041] The structure of the substrate to which the etching method of the present embodiment is applied is not particularly limited, and for example, a structure for a 3D-NAND type nonvolatile semiconductor device can be given. Figure 3 is a cross-sectional view showing an example of the structure of such a substrate.

[0042] In the present example, a semiconductor wafer (wafer) W as a substrate has an ONON layer stack structure portion 102 obtained by alternately stacking a SiO2 film 111 and a SiN film 112 a plurality of times on a silicon base 100. The number of layers of the SiO2 film 111 and the SiN film 112 is actually about 100 layers. An upper structure 110 is provided on the ONON layer stack structure portion 102, and a memory hole 103 that penetrates in the stacking direction of the upper structure 110 and the ONON layer stack structure portion 102 is formed, and a memory film 104 of a multilayer structure and a Si film 105 as a channel are formed in the memory hole 103. The Si film 105 is a crystalline Si film. In the present example, as shown in Figure 4 , the Si film 105 as a channel is etched to be thinned.

[0043] Figure 5 is a cross-sectional view showing another example of the structure of a substrate used in a 3D-NAND type nonvolatile semiconductor device. In the present example, a wafer W as a substrate similarly has an ONON layer stack structure portion 102 obtained by alternately stacking a SiO2 film 111 and a SiN film 112 a plurality of times on a silicon base 100, and an upper structure 110. A slit 106 that penetrates in the stacking direction is formed in the upper structure 110 and the ONON layer stack structure portion 102. In the present example, as shown in Figure 6 , groove etching of about 3 to 5 nm is performed on a plurality of SiN films 112 of the ONON layer stack structure portion 102.

[0044] In such a 3D-NAND type nonvolatile semiconductor device, the storage hole 103, the slit 106 is very deep. Like this, when the oxidation treatment of Si, SiN existing on the side surface of the recess is performed in the deep recess, due to the top-bottom loading effect (the loading effect between the front surface width and the deepest portion), sometimes an oxide film having a desired film thickness uniformity in the depth direction cannot be obtained. Such a top-bottom loading effect is not limited to the 3D-NAND type nonvolatile semiconductor device, but is a problem in etching of the side surface portion of the recess having a depth of 4 μm or more.

[0045] As a method of controlling such a top-bottom loading effect, it was found that adjusting the pressure at the time of the radical oxidation treatment and / or the ratio of the F-containing gas in the oxygen-containing gas is effective.

[0046] Figure 7 is a graph showing the relationship between the number of cycles of Top (top), middle (Mid), and bottom (Btm) and the Si etching amount in the case where the conditions of the radical oxidation step are changed to repeat the radical oxidation step and the oxide removal step in the configuration of Figure 3 As shown in this graph, in (a) where the radical oxidation step is a high pressure condition (160 mTorr), it is found that it becomes Top first in which the etching amount is larger in Top than in Btm. In (b) where the radical oxidation step is a low pressure condition (50 mTorr), it is found that it becomes uniform etching in which the etching amount is almost the same in Top and in Btm. In (c) where the radical oxidation step is a low pressure condition (50 mTorr) and 4% of NF3 is added to the O2 gas, it is found that it becomes Btm first in which the etching amount is larger in Btm than in Top.

[0047] From these results, it is found 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, it is confirmed that by changing the pressure at the time of 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 one of Top > Btm, Top = Btm, and Top < Btm, and thus the top-bottom loading effect can be controlled.

[0048] Next, an estimation mechanism by which the top-bottom loading effect can be controlled like this will be described. Figure 8 is a graph showing an estimation mechanism by which the top-bottom loading effect can be controlled by the pressure at the time of the radical oxidation treatment and the ratio of the NF3 gas as the F-containing gas.

[0049] In Figure 8under the high pressure condition of (a), the average free path is short, so the O radicals are prevented from reaching the bottom. The O radicals mainly hit the Top portion of the Si film 105, and the Top portion of the generated oxide film 105a is thick, so the etching of the Si film 105 is fast at the Top. In addition, under the low pressure condition of (b), the average free path is long, so the O radicals also reach the bottom. Therefore, the O radicals hit the Si film 105 uniformly, the generated oxide film 105a is of uniform thickness, and the Si film 105 is etched uniformly. (c) is a condition of high pressure with the addition of NF3gas. Under this condition, the average free path is short, so the O radicals and F radicals are prevented from reaching the bottom. The O radicals mainly generate the oxide film 105a at the Top portion of the Si film 105. The F radicals etch the oxide film 105a at the Top portion, but the effect is small, and as in (a), the etching of the Si film 105 is fast at the Top. (d) is a condition of low pressure with the addition of NF3gas. Under this condition, the average free path is long, and the O radicals hit the Si film 105 uniformly. On the other hand, the F radicals easily move to the bottom, and etch the Si film 105 at the bottom, as a result, the etching of the Si film 105 is fast at the Btm.

[0050] <Example of processing system>

[0051] Next, an example of a processing system used in the etching method of the present embodiment will be described. Figure 9 is a partial cross-sectional plan view schematically showing an example of a processing system used in the etching method of the present embodiment.

[0052] As shown in Figure 9 , the processing system 10 is provided with: a load lock chamber 11 for storing a plurality of substrates W and performing loading and unloading of the substrates W; a transfer module 12 as a transfer chamber for simultaneously transferring two substrates W; and a plurality of process modules 13 for performing processing on the substrates W transferred from the transfer module 12. The inside of each process module 13 and the transfer module 12 is maintained as a vacuum atmosphere.

[0053] In the processing system 10, the substrates W stored in the load lock chamber 11 are transferred by a transfer arm 14 built in the transfer module 12, and one substrate W is placed on each of two placement tables 15 provided in the inside of the process module 13. Then, in the processing system 10, after processing is performed on each substrate W placed on the placement table 15 by the process module 13, the processed substrates W are transferred to the load lock chamber 11 by the transfer arm 14.

[0054] The load / unload section 11 has a plurality of load ports 17 as placement stages of containers, i.e., FOUPs 16, which accommodate a plurality of substrates W; a load module 18 that receives substrates W stored from the FOUPs 16 placed on the respective load ports 17 or that delivers substrates W on which processing has been performed by the process module 13 to the FOUPs 16; two load interlocks 19 that temporarily hold substrates W in order to transfer the substrates W between the load module 18 and the transfer module 12; and a cooling storage 20 for cooling substrates W on which heating processing has been performed.

[0055] The load module 18 includes a rectangular housing that is an atmospheric pressure atmosphere inside, and a plurality of load ports 17 are provided side by side on one side face constituting the long side of the rectangle. Also, the load module 18 has a conveyance arm (not shown) inside that is movable along the length direction of the rectangle. The conveyance arm carries in substrates W from the FOUPs 16 placed on the respective load ports 17 to the load interlocks 19 or carries out substrates W from the load interlocks 19 to the respective FOUPs 16.

[0056] Each load interlock 19 temporarily holds substrates W accommodated in the FOUPs 16 placed on the respective load ports 17 of the atmospheric pressure atmosphere in order to deliver the substrates W to the process module 13 that is a vacuum atmosphere inside. Each load interlock 19 has a buffer plate 21 that holds two substrates W. In addition, each load interlock 19 has a gate valve 22a for ensuring airtightness with respect to the load module 18 and a gate valve 22b for ensuring airtightness with respect to the transfer module 12. Also, the load interlock 19 is connected by piping to a gas introduction system and a gas exhaust system, not shown, in the load interlock 19, so that the inside of the load interlock 19 can be switched between the atmospheric pressure atmosphere and the vacuum atmosphere.

[0057] The transfer module 12 transfers the unprocessed substrates W from the load lock module 19 to the process modules 13 and transfers the processed substrates W from the process modules 13 to the load lock module 19. The transfer module 12 includes a rectangular housing having a vacuum atmosphere inside, and includes two transfer arms 14 for holding two substrates W and moving them, a rotary table 23 rotatably supporting each of the transfer arms 14, a rotary stage 24 on which the rotary table 23 is mounted, and a guide rail 25 that guides the rotary stage 24 so as to be movable in the length direction of the transfer module 12. In addition, the transfer module 12 is connected to the load lock module 19 and each of the process modules 13 via the gate valve 22b and each of the gate valves 26 described later. In the transfer module 12, the transfer arms 14 transfer two substrates W from the load lock module 19 to each of the process modules 13, and transfer the two substrates W on which processing has been performed from each of the process modules 13 to the other process modules 13 and the load lock module 19.

[0058] In the processing system 10, each of the process modules 13 is used to perform etching of Si or SiN as the etching target portion. The process modules 13 can collectively perform the steps ST1 to ST3 described above, or can include a process module that performs the step ST1 and the step ST2 and a process module that performs the step ST3, respectively.

[0059] The processing system 10 has a control section 27. The control section 27 has a main control section having a CPU that controls the operation of each of the components 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 (storage medium). The main control section of the control section 27 causes the processing system 10 to perform a prescribed operation, for example, based on a processing recipe stored in the storage medium built in the storage device or the storage medium mounted in the storage device.

[0060] <etching apparatus>

[0061] Next, an example of the process module 13 mounted on the processing system 10 described above and functioning as an etching apparatus that performs the etching method of the present embodiment will be described. Figure 10 is a cross-sectional view schematically showing an example of the process module 13 functioning as an etching apparatus in the processing system 10 described above. Figure 9 is a cross-sectional view schematically showing an example of the process module 13 functioning as an etching apparatus in the processing system 10 described above.

[0062] As shown in FIG. 1, the processing system 10 includes a load lock module 19, a transfer module 12, and a plurality of process modules 13. Figure 10As shown, the process module 13 functioning as an etching apparatus has a processing container 28 of airtight construction that houses the substrate W. The processing container 28 is composed of, for example, aluminum or an aluminum alloy, and has an open upper end, and the upper end of the processing container 28 is closed by a lid 29 as a top portion. A substrate W carrying-in / out port 30 is provided in a side wall portion 28a of the processing container 28, and the substrate W carrying-in / out port 30 is opened and closed by the gate valve 26 described above.

[0063] In addition, as described above, two substrate W placement stages 15 (only one is shown) are arranged in the bottom portion of the inside of the processing container 28, each of which places one substrate W in a horizontal state. The placement stage 15 is in a substantially cylindrical shape, and has a placement plate 34 that directly places the substrate W, and a base block 35 that supports the placement plate 34. A temperature adjustment mechanism 36 that adjusts the temperature of the substrate W is provided in the inside of the placement plate 34. The temperature adjustment mechanism 36 has, for example, a pipe (not shown) through which a temperature adjustment medium circulates, and adjusts the temperature of the substrate W by heat exchange between the temperature adjustment medium flowing in the pipe and the substrate W. In the case of controlling the temperature to be high, the temperature adjustment mechanism 36 can be either a heater or both the pipe through which the temperature adjustment medium circulates and the heater. In addition, the placement stage 15 is provided with a plurality of lift pins (not shown) used when the substrate W is carried in and out of the inside of the processing container 28 in a manner that the lift pins can protrude from and sink into the upper surface of the placement plate 34.

[0064] The inside of the processing container 28 is divided into an upper plasma generation space P and a lower processing space S by a partition plate 37. The partition plate 37 functions as a so-called ion trap that suppresses the penetration of ions in the 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 in which plasma is generated, and the processing space S is a space in which the substrate W is subjected to etching by radical processing. A first gas supply portion 61 and a second gas supply portion 62 are provided outside the processing container 28.

[0065] The first gas supply portion 61 supplies O2 gas, H2 gas, NF3 gas as a fluorine-containing gas, and a rare gas (for example, Ar gas) to the plasma generation space P. These gases are plasma-ized in the plasma generation space P. In addition, the rare gas functions as a plasma generation gas, but can also function as a pressure adjustment gas, a purge gas, or the like.

[0066] The second gas supply portion 62 supplies, as a processing gas for chemical processing, for example, the HF gas and the NH3 gas described above, and a rare gas used as a pressure adjustment gas, a purge gas, or a dilution gas, or the like, to the processing space S.

[0067] An exhaust mechanism 39 is connected to the bottom of the processing container 28. The exhaust mechanism 39 has a vacuum pump to exhaust the interior of the processing space S.

[0068] A heat insulation plate 48 is disposed below the partition plate 37 and facing the substrate W. The heat insulation plate 48 is used to suppress the heat accumulation in the partition plate 37 due to plasma generation in the repeated plasma generation space P, so as to prevent this heat from affecting the distribution of free radicals in the processing space S. The heat insulation plate 48 is formed to be larger than the partition plate 37, and the flange portion 48a constituting its periphery is embedded in the side wall portion 28a of the processing container 28. In addition, a cooling mechanism 50, such as a refrigerant flow path, a cooler, or a Peltier element, is embedded in the flange portion 48a.

[0069] The cover 29, which serves as the top of the processing container 28, is formed, for example, from a circular quartz plate and is configured as a dielectric window. A ring-shaped RF antenna 40 is formed on the cover 29 for generating inductively coupled plasma in the plasma generation space P of the processing container 28. The RF antenna 40 is connected to a high-frequency power supply 42 via a matching device 41. The high-frequency power supply 42 outputs high-frequency power at a specified frequency (e.g., 13.56 MHz or higher) suitable for generating plasma through inductively coupled high-frequency discharge at a specified output value. The matching device 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 side (RF antenna 40, plasma).

[0070] Furthermore, in the case of setting up a process module that only performs heating treatment, a structure is used in which the plasma generation mechanism and the partition plate are removed from the process module described above.

[0071] In implementing the etching method described in the above embodiment using the processing system 10, firstly, the FOUP 16 is removed by the conveying arm of the loading module 18, for example, a material having... Figure 3 The substrate W with the structure shown is moved into the loading interlock module 19. After the loading interlock module 19 is evacuated, the substrate W in the loading interlock module 19 is moved into the process module 13, which functions as an etching apparatus, by the transfer arm 14 of the transfer module 12.

[0072] Next, N2 gas, which is used as a pressure regulating gas, is introduced into the processing container 28 from the second gas supply unit 62, so that the pressure in the processing container 28 becomes, for example, 1000 to 2000 mTorr (133.3 to 266.6 Pa), and the substrate W is held on the mounting stage 15, which is conditioned to 80 to 120°C by the temperature control mechanism 36, for a predetermined time, for example, 120 seconds, so that the wafer temperature is stabilized to the predetermined temperature.

[0073] Next, after purging the processing container 28, the pressure in the processing container 28 is preferably set to 50 to 300 mTorr (6.67 to 40 Pa), and an oxygen-containing plasma is generated to perform radical oxidation processing.

[0074] When performing radical oxidation processing, first, an oxygen-containing gas is supplied from the first gas supply portion 61 to the plasma generation space P, and high-frequency power is supplied to the RF antenna 40 to generate an oxygen-containing plasma as an inductively coupled plasma. At this time, as the oxygen-containing gas, it can be only O2 gas, or H2 gas or an F-containing gas can be added to the O2 gas. In addition, a rare gas such as Ar gas can also be supplied.

[0075] Next, the plasma of the oxygen-containing gas generated in the plasma generation space P is carried to the processing space S via the partition plate 37. At this time, the O2 ions are deactivated by the partition plate 37, and mainly O radicals in the plasma are selectively introduced into the processing space S. By the O radicals, the surface of Si or SiN of the substrate W is partially oxidized to generate an oxide film. The processing at this time is processing mainly with O radicals, and thus ion damage to the substrate W is small.

[0076] At this time, as for the gas flow rate, it is preferable that the O2 gas flow rate be 50 to 200 seem. In addition, in the case where H2 gas, an F-containing gas, or a rare gas (Ar gas) is supplied, it is preferable that they be 200 seem or less, 3 to 10 seem, and 30 to 200 seem, respectively. In addition, as for the plasma generation power, it is preferable that it be 400 to 800 W.

[0077] After performing the oxygen-containing plasma processing as described above, the processing container 28 is purged, and the oxide film is chemically processed with a gas. At this time, it is preferable that the pressure in the processing container 28 be set to a range of 100 to 1500 mTorr (13.3 to 200 Pa), and the temperature of the stage 15 (substrate W) be maintained at a temperature of 80 to 120°C by the temperature control mechanism 36, and then a processing gas containing an F-containing gas, such as HF gas and NH3 gas, be supplied from the second gas supply portion 62 to the processing space S of the processing container 28. By this, the processing gas reacts with the oxide film and generates a reaction product that is easily decomposed. For example, the HF gas and NH3 gas are adsorbed to the substrate W, and they react with the oxide film to generate AFS as an ammonium fluoride compound.

[0078] As for the gas flow rate in the case where HF gas and NH3 gas are used, it is preferable that the HF gas flow rate be 50 to 100 seem, the NH3 gas flow rate be 300 to 400 seem, and the non-reactive gas (Ar gas) flow rate be 200 to 400 seem.

[0079] After the chemical treatment as above, the inside of the processing container 28 is purged, and a removal treatment of a reaction product, for example, AFS as an ammonium fluoride compound, is performed. The removal of AFS is performed by supplying a non-reactive gas into the processing container 28 while exhausting the processing container 28, in a state where the temperature of the stage 15 (substrate W) is maintained at 80 to 120°C by the temperature adjustment mechanism 36, to sublimate AFS. This sublimation treatment can also be performed in a processing container of a different apparatus.

[0080] The radical oxidation treatment, the chemical treatment using a gas, and the heating removal treatment of a reaction product are repeated a plurality of times to etch Si or SiN to a desired thickness. The radical oxidation treatment is performed to form an oxide film, and then the chemical treatment using a gas and the removal treatment of a reaction product are performed, so that the etching of Si or SiN can be performed with good surface roughness, and the controllability is also good.

[0081] <Other Applications>

[0082] The above describes the embodiments, but it should be considered that the embodiments disclosed this time are illustrative in all respects and are not restrictive. The above-described embodiments can be omitted, substituted, changed in various ways without departing from the scope of the appended claims and the spirit thereof.

[0083] For example, the apparatus of the above-described embodiments is merely illustrative, and an apparatus of various structures can be used. In addition, although a case where a semiconductor wafer is used as a processed substrate is shown, it is not limited to a semiconductor wafer, and can be other substrates such as an FPD (flat panel display) substrate typified by an LCD (liquid crystal display) substrate, a ceramic substrate, and the like.

Claims

1. An etching method for etching Si or SiN present on a substrate, the etching method comprising the following processes: a radical oxidation process is performed on a substrate having Si or SiN to form an oxide film on the surface of the Si or SiN; a chemical process is performed on the oxide film using a gas; and a reaction product generated by the chemical process is removed, wherein the etching method repeatedly performs the process of forming the oxide film, the process of performing the chemical process, and the process of removing the reaction product, in the radical oxidation process, an oxygen-containing plasma is generated from an oxygen-containing gas, and oxygen radicals in the oxygen-containing plasma are made to act, the oxygen-containing gas being H2 gas, a fluorine-containing gas, and a mixed gas of a rare gas and O2 gas, the substrate has a recess having a depth of 4 μm or more, the Si or the SiN is present on the side surface of the recess, and when the radical oxidation process is performed, the pressure and the proportion of the fluorine-containing gas in the oxygen-containing gas are adjusted to control the loading effect between the front surface width and the deepest portion of the recess, the pressure when the radical oxidation process is performed is 50 to 160 mTorr.

2. The etching method according to claim 1, wherein the etching method repeatedly performs the process of performing the chemical process and the process of removing the reaction product.

3. The etching method according to claim 1 or 2, wherein the process of forming the oxide film and the process of performing the chemical process are performed in the same processing vessel.

4. The etching method according to claim 1 or 2, wherein the process of performing the chemical process and the process of removing the reaction product are performed in the same processing vessel.

5. The etching method according to claim 1 or 2, wherein the process of forming the oxide film, the process of performing the chemical process, and the process of removing the reaction product are performed in the same processing vessel.

6. The etching method according to claim 1 or 2, wherein the process of performing the chemical process and the process of removing the reaction product are performed in different processing vessels.

7. The etching method according to claim 1, wherein the fluorine-containing gas is NF3 gas.

8. The etching method according to claim 1, wherein the oxygen radicals in the oxygen-containing plasma are supplied to the substrate by generating the oxygen-containing plasma in a plasma generation space different from a processing space in which the substrate is arranged, by a remote plasma.

9. The etching method according to claim 1 or 2, wherein the chemical process using a gas is performed using a processing gas containing a fluorine-containing gas.

10. The etching method according to claim 9, wherein the processing gas containing a fluorine-containing gas contains a fluorine-containing gas and H2O gas or a reducing gas.

11. The etching method according to claim 10, wherein the processing gas containing a fluorine-containing gas contains HF gas as the fluorine-containing gas and NH3 gas as the reducing gas.

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

13. An etching apparatus for etching Si or SiN present on a substrate, the etching apparatus comprising: a processing vessel that houses a substrate; a stage for placing the substrate disposed in the processing vessel; a first gas supply mechanism that supplies an oxygen-containing gas into the processing vessel; a radical oxidation mechanism that generates an oxygen-containing plasma from the oxygen-containing gas, and performs a radical oxidation treatment by mainly oxygen radicals therein to generate an oxide film on a surface of Si or SiN; a second gas supply mechanism that supplies a gas that chemically treats the oxide film into the processing vessel; a temperature adjustment mechanism that adjusts the temperature of the stage; an exhaust mechanism that performs vacuum exhaust on the processing vessel; and a control section, wherein the control section controls the radical oxidation mechanism, the first gas supply mechanism, the second gas supply mechanism, the temperature adjustment mechanism, and the exhaust mechanism to perform the following processes: performing a radical oxidation treatment on a substrate having Si or SiN to generate an oxide film on a surface of Si or SiN; chemically treating the oxide film with a gas; and removing a reaction product generated by the chemical treatment, and the control section controls to repeatedly the process of generating the oxide film, the process of performing the chemical treatment, and the process of removing the reaction product, the radical oxidation treatment generates an oxygen-containing plasma from an oxygen-containing gas, and mainly oxygen radicals in the oxygen-containing plasma are made to act, the oxygen-containing gas is H2 gas, a fluorine-containing gas, and a mixed gas of a rare gas and O2 gas, the substrate has a recess portion having a depth of 4 μm or more, Si or SiN is present on a side surface of the recess portion, when the radical oxidation treatment is performed, a pressure and a ratio of the fluorine-containing gas in the oxygen-containing gas are adjusted to control a load effect between a front surface width and a deepest portion of the recess portion, and the pressure when the radical oxidation treatment is performed is 50 to 160 mTorr.

14. The etching apparatus according to claim 13, further comprising: a partition portion that divides the processing vessel into an upper plasma generation space and a lower processing space, the radical oxidation mechanism generates the oxygen-containing plasma in the plasma generation space, and performs a radical oxidation treatment on the substrate using oxygen radicals after the partition portion.

15. The etching apparatus according to claim 14, wherein the radical oxidation mechanism generates the oxygen-containing plasma in the plasma generation space, and performs a radical oxidation treatment on the substrate using oxygen radicals after the partition portion. ​ ​ ​ ​ ​ ​ wherein ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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