Substrate processing method and substrate processing apparatus

Abstract

To reduce variation in an etching rate for each silicon oxide film in a technique for etching a laminated film including a plurality of silicon oxide films having different film thicknesses.SOLUTION: The substrate processing method includes a step of preparing a substrate and a step of performing etching processing on the substrate. In the step of preparing a substrate, a substrate having a laminated film including a plurality of silicon oxide films having different film thicknesses is prepared. In the step of etching the substrate, the substrate is etched with an etching solution to which hydrochloric acid is added.SELECTED DRAWING: Figure 12

Description

[Technical Field]

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

[0002] BACKGROUND ART Conventionally, a technique is known in which a silicon oxide film formed on a substrate such as a semiconductor wafer is etched with an etching solution containing, for example, hydrofluoric acid (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 8-31794 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a technique for etching a stacked film including a plurality of silicon oxide films with different thicknesses, which can reduce variations in etching rate for each silicon oxide film. [Means for solving the problem]

[0005] A substrate processing method according to one aspect of the present disclosure includes a step of preparing a substrate and a step of etching the substrate. The step of preparing a substrate includes preparing a substrate having a stacked film including multiple silicon oxide films with different thicknesses. The step of etching the substrate includes etching the substrate with an etching solution containing hydrochloric acid. [Effects of the Invention]

[0006] According to the present disclosure, in a technique for etching a stacked film including a plurality of silicon oxide films with different film thicknesses, it is possible to reduce variations in etching rate for each silicon oxide film. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is an explanatory view of a substrate processing according to an embodiment. [Figure 2] FIG. 2 is an explanatory view of the substrate processing according to the embodiment. [Figure 3] FIG. 3 is a graph showing the change in the variation in etching rate for each silicon oxide film when an etching solution containing hydrochloric acid and a metal salt is used. [Figure 4] FIG. 4 is a graph showing the change in the variation in etching rate for each silicon oxide film when an etching solution containing hydrochloric acid and a metal salt is used. [Figure 5] FIG. 5 is a diagram illustrating the formation of water clusters. [Figure 6] FIG. 6 is a diagram for explaining the formation of the spherical structures. [Figure 7] FIG. 7 is a diagram for explaining how the surface potential of a part of the polysilicon film shifts from the negative side to the positive side. [Figure 8] FIG. 8 is a graph showing the change in the variation in etching rate for each silicon oxide film when an etching solution containing a surfactant is used. [Figure 9] FIG. 9 is a graph showing the change in the variation in etching rate for each silicon oxide film when an etching solution containing a surfactant is used. [Figure 10] FIG. 10 is a diagram showing the configuration of a substrate processing apparatus according to an embodiment. [Figure 11] FIG. 11 is a diagram showing the configuration of a treatment tank according to the embodiment. [Figure 12] FIG. 12 is a flowchart showing the procedure of the process executed by the substrate processing apparatus according to the embodiment. [Figure 13] FIG. 13 is a diagram illustrating an example of the configuration of a processing unit according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments (hereinafter referred to as "embodiments") for carrying out the nozzle, substrate processing method, and substrate processing apparatus according to the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited to these embodiments. Furthermore, the embodiments can be appropriately combined within the scope of not causing any contradiction in the processing content. Furthermore, the same components in the following embodiments will be given the same reference numerals, and redundant explanations will be omitted.

[0009] Furthermore, in the following embodiments, expressions such as "constant," "orthogonal," "perpendicular," or "parallel" may be used, but these expressions do not necessarily mean "constant," "orthogonal," "perpendicular," or "parallel" in the strict sense. In other words, the above expressions allow for deviations due to, for example, manufacturing precision, installation precision, etc.

[0010] In addition, for ease of understanding, the drawings referred to below may show an orthogonal coordinate system in which the X-axis, Y-axis, and Z-axis directions are defined as being orthogonal to each other, with the positive Z-axis direction being the vertically upward direction. Also, the direction of rotation around the vertical axis may be referred to as the θ direction.

[0011] <About substrate processing> First, the contents of the substrate processing according to the embodiment will be described with reference to Figures 1 and 2. Figures 1 and 2 are explanatory views of the substrate processing according to the embodiment.

[0012] In the substrate processing according to the embodiment, first, a semiconductor wafer (hereinafter referred to as wafer W) having the structure shown in Fig. 1 is prepared. The wafer W is configured by forming a plurality of silicon oxide films 11 and a plurality of polysilicon films 12 on a silicon substrate 10.

[0013] The plurality of silicon oxide films 11 are formed at intervals in the vertical direction on the silicon substrate 10. The plurality of silicon oxide films 11 have different thicknesses. The thickness of the plurality of silicon oxide films 11 is, for example, 1 nm or more and 30 nm or less.

[0014] The polysilicon film 12 is formed adjacent to each of the plurality of silicon oxide films 11 in the vertical direction. Since the thicknesses of the plurality of silicon oxide films 11 are different, the polysilicon films 12 in contact with each of the plurality of silicon oxide films 11 are formed at different intervals from each other.

[0015] As described above, the wafer W to be processed has a laminated film in which silicon oxide films 11 and polysilicon films 12 are alternately stacked. The wafer W may have a laminated film including at least a plurality of silicon oxide films 11 with different film thicknesses, and the configuration of the laminated film is not particularly limited to the example shown in FIG. 1 . For example, the other film formed adjacent to each of the plurality of silicon oxide films 11 may be, in addition to the polysilicon film 12 described above, a silicon film, a silicon nitride film, a metal-containing film, or the like. That is, the other film may be selected from at least one of a silicon film, a polysilicon film, a silicon nitride film, and a metal-containing film.

[0016] Further, the wafer W has grooves 15 formed therein for allowing an etching solution to penetrate therein and etch the deposited silicon oxide film 11.

[0017] In the substrate processing according to the embodiment, an etching process using an etching solution is performed to selectively etch the silicon oxide film 11. As a result, as shown in Fig. 2, the end face of the silicon oxide film 11 facing the trench 15 is set back in the width direction of the trench 15 from the end face of the polysilicon film 12 facing the trench 15, and the upper and lower surfaces of the end of the polysilicon film 12 are exposed.

[0018] Here, the greater the difference in film thickness between the silicon oxide films 11 in the stacked film, the greater the variation in etching rate for each silicon oxide film 11. Specifically, a silicon oxide film 11 with a smaller film thickness is more difficult to etch than a silicon oxide film 11 with a larger film thickness.

[0019] In response to this, the inventors of the present application have found that etching the wafer W using an etching solution containing at least one of hydrochloric acid, a metal salt, and a surfactant can suppress variations in the etching rate for each silicon oxide film 11. Figures 3 and 4 are graphs showing changes in the variations in the etching rate for each silicon oxide film 11 when an etching solution containing hydrochloric acid (HCl) and a metal salt (NaCl or CaCl2) is used.

[0020] The processing conditions for the experimental results shown in FIGS. 3 and 4 are as follows: Number of silicon oxide layers in the laminate: 3 Silicon oxide film thickness: 15nm, 30nm, 7.5nm from the bottom Processing steps: Immersion in etching solution (etching process), then immersion in DIW (deionized water) (rinsing process), then drying process using dry gas Etching solution: Hydrofluoric acid (HF) aqueous solution Additives added to the etching solution: hydrochloric acid (HCl) and metal salts (NaCl or CaCl2)

[0021] 3 and 4, the vertical axis indicates the etching rate ratio (ER ratio), which is an index value for determining changes in the variation in etching rate for each silicon oxide film 11. The etching rate ratio is the ratio of the etching rate of the silicon oxide film 11 with the smallest thickness to the etching rate of the silicon oxide film 11 with the largest thickness among the multiple stacked silicon oxide films. The closer the etching rate ratio is to 1, the smaller the variation in etching rate for each silicon oxide film 11 becomes.

[0022] In the graphs shown in Figures 3 and 4, "w / o Additives" indicates the etching rate ratio of the laminated film when an etching solution without added hydrochloric acid and metal salts is used. "HCl" indicates the etching rate ratio of the laminated film when an etching solution with added hydrochloric acid (HCl) is used. "NaCl" indicates the etching rate ratio of the laminated film when an etching solution with added NaCl as a metal salt is used. "CaCl2" indicates the etching rate ratio of the laminated film when an etching solution with added CaCl2 as a metal salt is used. Note that Figure 3 shows the experimental results when the concentrations of hydrochloric acid and metal salts in the etching solution are each 0.05 wt%, and Figure 4 shows the experimental results when the concentrations of hydrochloric acid and metal salts in the etching solution are each 0.5 wt%.

[0023] As shown in FIGS. 3 and 4, the etching rate ratio when an etching solution containing NaCl as a metal salt is used is higher than the etching rate ratio when an etching solution containing no hydrochloric acid or metal salt is used. Also, as shown in FIG. 4, the etching rate ratio when an etching solution containing CaCl as a metal salt is used is higher than the etching rate ratio when an etching solution containing no hydrochloric acid or metal salt is used. Also, as shown in FIG. 4, the etching rate ratio when an etching solution containing hydrochloric acid (HCl) is used is higher than the etching rate ratio when an etching solution containing no hydrochloric acid or metal salt is used. Thus, the experimental results shown in FIGS. 3 and 4 demonstrate that etching the wafers W using an etching solution containing NaCl as a metal salt reduces the variation in the etching rate for each silicon oxide film 11. Also, the experimental results shown in FIG. 4 demonstrate that etching the wafers W using an etching solution containing CaCl as a metal salt reduces the variation in the etching rate for each silicon oxide film 11. Furthermore, from the experimental results shown in FIG. 4, it can be seen that by performing the etching process on the wafer W using an etching solution containing hydrochloric acid (HCl), the variation in etching rate for each silicon oxide film 11 can be suppressed.

[0024] The experimental results can be considered, for example, as follows. That is, the etching mechanism of the silicon oxide film 11 proceeds as follows. First, as shown in chemical reaction formula (1), silicon oxide (SiO2) reacts with hydrofluoric acid (HF) contained in the etching solution and dissolves in the etching solution. In other words, the silicon oxide film 11 is etched.

[0025] SiO2+6HF→H2SiF6+2H2O ··· (1)

[0026] In addition, in the etching solution, the reactions shown in chemical reaction formulas (2) and (3) occur, generating hydrogen difluoride ions (HF2 - ) occurs.

[0027] HF⇔H + +F - (2) HF+F - ⇔HF2 - (3)

[0028] The hydrogen difluoride ions (HF2 - ) functions as an etchant for silicon oxide (SiO2), further promoting the reaction shown in chemical reaction formula (1) above.

[0029] In this way, the etching of the silicon oxide film 11 is carried out by the reaction between silicon oxide (SiO2) and hydrofluoric acid (HF) to form hydrogen difluoride ions (HF2 - Therefore, in order for the etching of the silicon oxide film 11 to proceed, hydrogen difluoride ions (HF2 - ) reaches the silicon oxide film 11.

[0030] As the etching of the silicon oxide film 11 progresses, the reactions shown in chemical reaction formulas (2) and (3) progress in the etching solution, and hydrogen ions (H + ) increases. Hydrogen ions (H + ) cannot exist stably in the etching solution and combines with water molecules (i.e., becomes hydrated) to form oxonium ions (HO + ) is the oxonium ion (HO + ) are attracted to the surface of the polysilicon film 12 because the polysilicon film 12 in contact with the silicon oxide film 11 is negatively charged. +5, the polysilicon films 12 bond with water molecules (i.e., are hydrated) on the surface of the polysilicon film 12 to form water clusters 16p in which a plurality of water molecules are arranged in a plane. FIG. 5 is a diagram for explaining the formation of water clusters. The water clusters 16p are formed more densely as the intervals between the polysilicon films 12 in contact with the silicon oxide film 11 become narrower, in other words, as the thickness of the silicon oxide film 11 becomes smaller.

[0031] Therefore, when the thickness of the silicon oxide film 11 is small, the hydrogen difluoride ions (HF2 - ) may be prevented from reaching the silicon oxide film 11. As a result, the etching rate of the silicon oxide film 11 having a small thickness becomes smaller than the etching rate of the silicon oxide film 11 having a large thickness. As a result, the etching rate of each silicon oxide film 11 varies.

[0032] On the other hand, when an etching solution containing a metal salt (e.g., NaCl) is used, the metal salt in the etching solution is ionized to form metal ions (e.g., Na + ) and anions (e.g., Cl - ) is generated. Anions (e.g., Cl) generated from metal salts in the etching solution - ) destroys the hydration structure (i.e., bonds between water molecules) of the water clusters 16p on the surface of the polysilicon film 12. In addition, metal ions (e.g., Na + ) bond with water molecules (i.e., are hydrated) on the surface of the polysilicon film 12 to form spherical structures 16s in which a plurality of water molecules are arranged in a spherical shape, as shown in FIG. 6. FIG. 6 is a diagram for explaining the formation of the spherical structures. When the spherical structures 16s are formed on the surface of the polysilicon film 12, hydrogen difluoride ions (HF2 - ) can pass through, and hydrogen difluoride ions (HF2 -) is not prevented from reaching the silicon oxide film 11. As a result, it is considered that the variation in etching rate for each silicon oxide film 11 is reduced compared to when an etching solution to which no metal salt is added is used.

[0033] Furthermore, when an etching solution containing hydrochloric acid is used, the pH of the etching solution becomes more acidic (for example, pH less than 1), which makes it easier for the surface potential of a portion of the polysilicon film 12 to shift from negative to positive, as shown in FIG. 7. FIG. 7 is a diagram for explaining how the surface potential of a portion of the polysilicon film shifts from negative to positive. When the surface potential of a portion of the polysilicon film 12 shifts from negative to positive, oxonium ions (HO + ) repel each other, making it difficult for the water clusters 16p to be formed. Therefore, even if the thickness of the silicon oxide film 11 is small, hydrogen difluoride ions (HF2 - ) can pass through, and hydrogen difluoride ions (HF2 - ) is not prevented from reaching the silicon oxide film 11. As a result, it is considered that the variation in etching rate for each silicon oxide film 11 is reduced, similar to the case where an etching solution containing a metal salt is used.

[0034] 8 and 9 are graphs showing the change in the variation in etching rate for each silicon oxide film 11 when an etching solution containing a surfactant (OACl, OTMACl, or SDBS) is used.

[0035] The processing conditions for the experimental results shown in FIGS. 8 and 9 are the same as those for the experimental results shown in FIGS. 3 and 4, except for the following points. Surfactants added to the etching solution: n-octylamine hydrochloride (OACl), n-octyltrimethylammonium chloride (OTMACl), or sodium dodecylbenzenesulfonate (SDBS)

[0036] 8 and 9, the vertical axis indicates the etching rate ratio (ER ratio), which is an index value for determining changes in the variation in the etching rate for each silicon oxide film 11. The etching rate ratio is the ratio of the etching rate of the silicon oxide film 11 with the smallest thickness to the etching rate of the silicon oxide film 11 with the largest thickness among the multiple stacked silicon oxide films. The closer the etching rate ratio is to 1, the smaller the variation in the etching rate for each silicon oxide film 11 becomes.

[0037] In the graphs shown in FIGS. 8 and 9, "w / o Additives" indicates the etching rate ratio of the laminated film when an etching solution without surfactant was used. "OACl" indicates the etching rate ratio of the laminated film when an etching solution with OACl added as a surfactant was used. "OTMACl" indicates the etching rate ratio of the laminated film when an etching solution with OTMACl added as a surfactant was used. "SDBS" indicates the etching rate ratio of the laminated film when an etching solution with SDBS added as a surfactant was used. Note that FIG. 8 shows the experimental results when the surfactant concentration in the etching solution was 0.05 wt%, and FIG. 9 shows the experimental results when the surfactant concentration in the etching solution was 0.5 wt%.

[0038] As shown in FIGS. 8 and 9 , the etching rate ratio when an etching solution containing OTMACl as a surfactant is used is higher than the etching rate ratio when an etching solution containing no surfactant is used. Also, as shown in FIG. 9 , the etching rate ratio when an etching solution containing OACl or SDBS as a surfactant is used is higher than the etching rate ratio when an etching solution containing no surfactant is used. Thus, the experimental results shown in FIGS. 8 and 9 indicate that etching the wafer W using an etching solution containing OTMACl as a surfactant can reduce the variation in the etching rate for each silicon oxide film 11. Also, the experimental results shown in FIG. 9 indicate that etching the wafer W using an etching solution containing OACl or SDBS as a surfactant can reduce the variation in the etching rate for each silicon oxide film 11.

[0039] The results of this experiment can be considered, for example, as follows. That is, when an etching solution containing a surfactant is used, the surfactant in the etching solution destroys the hydration structure (i.e., the bonds between water molecules) of the water clusters 16p (see FIG. 5) on the surface of the polysilicon film 12. When the hydration structure of the water clusters 16p on the surface of the polysilicon film 12 is destroyed, hydrogen difluoride ions (HF2 - ) can pass through, and hydrogen difluoride ions (HF2 - ) is not prevented from reaching the silicon oxide film 11. As a result, it is considered that the variation in etching rate for each silicon oxide film 11 is reduced compared to when an etching solution containing no surfactant is used.

[0040] Therefore, based on the results shown in FIGS. 3, 4, 8, and 9, in the substrate processing according to the embodiment, the silicon oxide film 11 is etched using an etching solution containing at least one of hydrochloric acid, a metal salt, and a surfactant.

[0041] The etching solution according to the embodiment is a chemical solution containing hydrofluoric acid, and the concentration of hydrofluoric acid in the etching solution is, for example, 0.1 wt % to 50 wt %.

[0042] The metal salt added to the etching solution may be, for example, an alkali metal halide or an alkaline earth metal halide. The alkali metal halide may be, for example, the aforementioned NaCl. The alkali metal halide may also contain at least one of Li, Na, K, Rb, and Cs. The alkaline earth metal halide may be, for example, the aforementioned CaCl2. The alkaline earth metal halide may also contain at least one of Mg, Ca, Sr, and Ba.

[0043] Furthermore, the concentrations of hydrochloric acid and metal salt in the etching solution are preferably 0.5 wt % or more and 5 wt % or less. As a result, as is clear from the experimental results shown in Figures 3 and 4, it is possible to reduce variations in the etching rate for each silicon oxide film 11 regardless of the type of metal salt. Furthermore, by keeping the concentration of metal salt in the etching solution at 5 wt % or less, it is possible to suppress contamination of the wafer W by metal.

[0044] Furthermore, the concentration of hydrochloric acid before it is added to the etching solution is preferably, for example, 35 wt % or more and 37 wt % or less.

[0045] The surfactant added to the etching solution may be, for example, a cationic surfactant or an anionic surfactant. The cationic surfactant may be, for example, the aforementioned n-octylamine hydrochloride (OACl) or n-octyltrimethylammonium chloride (OTMACl). The anionic surfactant may be, for example, the aforementioned sodium dodecylbenzenesulfonate (SDBS).

[0046] Furthermore, the concentration of the surfactant in the etching solution is preferably 0.5 wt % or more and 5 wt % or less. As a result, it is possible to reduce the variation in the etching rate for each silicon oxide film 11, regardless of the type of surfactant, as is clear from the experimental results shown in Figures 8 and 9. Furthermore, by setting the concentration of the surfactant in the etching solution to 5 wt % or less, it is possible to prevent organic matter (contaminants) removed by the surfactant from remaining on the surface of the wafer W.

[0047] [Configuration of substrate processing equipment] Next, the configuration of a substrate processing apparatus for performing the above-described substrate processing will be described with reference to Fig. 10. Fig. 10 is a diagram showing the configuration of a substrate processing apparatus according to an embodiment.

[0048] As shown in FIG. 10, the substrate processing apparatus 1 according to the embodiment includes a carrier loading / unloading section 2, a lot forming section 3, a lot placing section 4, a lot transport section 5, a lot processing section 6, and a control section .

[0049] The carrier loading / unloading section 2 includes a carrier stage 20, a carrier transport mechanism 21, carrier stocks 22 and 23, and a carrier placement table 24.

[0050] A plurality of carriers 9 transported from outside are placed on the carrier stage 20. The carrier 9 is a container that accommodates a plurality of (e.g., 25) semiconductor wafers (hereinafter referred to as wafers W) arranged one above the other in a horizontal position. A carrier transport mechanism 21 transports the carriers 9 between the carrier stage 20, carrier stocks 22 and 23, and a carrier mounting table 24.

[0051] A plurality of wafers W before processing are transferred from the carrier 9 placed on the carrier mounting table 24 to the lot processing section 6 by the substrate transfer mechanism 30 described later. Furthermore, a plurality of processed wafers W are transferred from the lot processing section 6 to the carrier 9 placed on the carrier mounting table 24 by the substrate transfer mechanism 30.

[0052] The lot formation unit 3 has a substrate transfer mechanism 30 and forms lots. A lot is made up of a plurality of (e.g., 50) wafers W that are combined and processed simultaneously, each of which is accommodated in one or more carriers 9. The plurality of wafers W that form one lot are arranged at a fixed interval with their plate surfaces facing each other.

[0053] The substrate transfer mechanism 30 transfers a plurality of wafers W between the carrier 9 placed on the carrier placement table 24 and the lot placement unit 4.

[0054] The lot placement unit 4 has a lot transfer table 40 on which lots transferred by the lot transfer unit 5 between the lot formation unit 3 and the lot processing unit 6 are temporarily placed (on standby). The lot transfer table 40 has an entrance lot placement table 41 on which lots formed in the lot formation unit 3 before being processed are placed, and an exit lot placement table 42 on which lots processed in the lot processing unit 6 are placed. A plurality of wafers W for one lot are placed in an upright position, lined up front and back, on the entrance lot placement table 41 and the exit lot placement table 42.

[0055] The lot transport unit 5 has a lot transport mechanism 50, and transports lots between the lot placement unit 4 and the lot processing unit 6 and inside the lot processing unit 6. The lot transport mechanism 50 has rails 51, a moving body 52, and a substrate holder 53.

[0056] Rails 51 are arranged along the X-axis direction across the lot mounting section 4 and the lot processing section 6. Movable body 52 is configured to be able to move along rails 51 while holding a plurality of wafers W. Substrate holders 53 are provided on movable body 52 and hold a plurality of wafers W lined up in front and behind each other in an upright position.

[0057] The lot processing section 6 performs etching, cleaning, drying, etc. on one lot of wafers W. The lot processing section 6 has a plurality of (here, two) etching processing sections 60, a substrate holder cleaning processing section 80, and a drying processing section 90 arranged along a rail 51.

[0058] The etching processing device 60 performs etching processing on one lot of multiple wafers W in a batch. The substrate holder cleaning processing device 80 performs cleaning processing on the substrate holder 53. The drying processing device 90 performs drying processing on one lot of multiple wafers W in a batch. The numbers of etching processing devices 60, substrate holder cleaning processing devices 80, and drying processing devices 90 are not limited to the example in FIG. 10 .

[0059] The etching treatment device 60 includes a treatment tank 61 for etching treatment, a treatment tank 62 for rinsing treatment, and substrate lifting mechanisms 63 and 64.

[0060] The processing tank 61 and the processing tank 62 are each capable of accommodating one lot of wafers W and store an etching liquid therein. The processing tank 61 stores an etching liquid. The processing tank 61 will be described in detail later.

[0061] A processing liquid (deionized water, etc.) for rinsing is stored in the processing bath 62. The substrate lifting mechanisms 63 and 64 hold a plurality of wafers W that form a lot in an upright position, lined up one behind the other.

[0062] The etching processing device 60 holds the lot transported by the lot transport unit 5 with a substrate lifting mechanism 63 and immerses it in the etching liquid in the processing tank 61 to perform an etching process. Furthermore, the etching processing device 60 holds the lot transported to the processing tank 62 by the lot transport unit 5 with a substrate lifting mechanism 64 and immerses it in the rinse liquid in the processing tank 62 to perform a rinse process.

[0063] The drying processing device 90 includes a processing tank 91 and a substrate lifting mechanism 92. A processing gas for drying processing is supplied to the processing tank 91. The substrate lifting mechanism 92 holds a plurality of wafers W for one lot in an upright position, lined up front and rear.

[0064] The drying processing device 90 holds the lot transported by the lot transport unit 5 with a substrate lifting mechanism 92 and performs a drying process using a processing gas for drying process supplied into the processing tank 91. The lot that has been dried in the processing tank 91 is transported to the lot mounting unit 4 by the lot transport unit 5.

[0065] The substrate holder cleaning processing device 80 performs a cleaning process on the substrate holders 53 of the lot transfer mechanism 50 by supplying a cleaning processing liquid to the substrate holders 53 and further supplying a dry gas.

[0066] The control unit 7 controls the operation of each unit (such as the carrier loading / unloading unit 2, the lot formation unit 3, the lot placement unit 4, the lot transport unit 5, and the lot processing unit 6) of the substrate processing apparatus 1. The control unit 7 controls the operation of each unit of the substrate processing apparatus 1 based on signals from switches, various sensors, etc.

[0067] The control unit 7 includes a microcomputer having a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), input / output ports, etc., and various other circuits, and controls the operation of the substrate processing apparatus 1 by reading and executing programs stored in a storage unit (not shown). The control unit 7 has a computer-readable storage medium 8. The storage medium 8 stores the programs for controlling the various processes executed in the substrate processing apparatus 1. The programs may be stored in the computer-readable storage medium 8 or may be installed in the storage medium 8 of the control unit 7 from another storage medium.

[0068] Examples of the computer-readable storage medium 8 include a hard disk (HD), a flexible disk (FD), a compact disk (CD), a magnet optical disk (MO), and a memory card.

[0069] [Configuration of treatment tank] Next, the configuration of a processing tank 61 used in the etching process according to this embodiment will be described with reference to Fig. 11. Fig. 11 is a diagram showing the configuration of the processing tank 61 according to this embodiment.

[0070] As shown in FIG. 11, a processing tank 61 performs an etching process for etching the silicon oxide film 11 formed on the wafers W by immersing one lot of wafers W in an etching solution.

[0071] The processing tank 61 includes an inner tank 100 and an outer tank 110. The processing tank 61 also includes a circulation unit 120 and an etching liquid supply unit .

[0072] The inner tank 100 is open at the top and stores an etching solution therein. A lot (plurality of wafers W) is immersed in the inner tank 100.

[0073] The outer tank 110 is open at the top and is disposed around the upper portion of the inner tank 100. The etching solution that overflows from the inner tank 100 flows into the outer tank 110.

[0074] The circulation unit 120 circulates the etching solution between the inner bath 100 and the outer bath 110. The circulation unit 120 includes a circulation path 121, a nozzle 122, a pump 123, a filter 124, and a temperature adjustment unit 125.

[0075] The circulation path 121 connects the outer tank 110 and the inner tank 100. One end of the circulation path 121 is connected to the outer tank 110, and the other end of the circulation path 121 is connected to a nozzle 122 arranged inside the inner tank 100.

[0076] The pump 123, the filter 124, and the temperature adjustment unit 125 are provided in the circulation path 121. The pump 123 sends the etching liquid in the outer bath 110 to the circulation path 121. The filter 124 removes impurities from the etching liquid flowing through the circulation path 121. The temperature adjustment unit 125 is, for example, a heater, and adjusts the temperature of the etching liquid flowing through the circulation path 121 to a temperature suitable for the etching process. The pump 123 and the temperature adjustment unit 125 are controlled by the control unit 7.

[0077] The circulation unit 120 sends the etching liquid from the outer tank 110 into the inner tank 100 via the circulation path 121. The etching liquid sent into the inner tank 100 overflows from the inner tank 100 and flows back into the outer tank 110. In this way, the etching liquid circulates between the inner tank 100 and the outer tank 110.

[0078] The etching liquid supply unit 130 supplies an etching liquid to the processing tank 61. The etching liquid supply unit 130 includes an etching liquid supply source 131, a supply path 132, a valve 133, and a switching unit 134.

[0079] The etching liquid supply source 131 supplies an etching liquid to which at least one of hydrochloric acid, a metal salt, and a surfactant has been added in advance. The supply path 132 is connected to the etching liquid supply source 131 and supplies the etching liquid supplied from the etching liquid supply source 131 to the inner tank 100 or the outer tank 110. The valve 133 is provided in the supply path 132 and opens and closes the supply path 132. The switching unit 134 is provided in the supply path 132 and switches the destination of the etching liquid flowing through the supply path 132 between the inner tank 100 and the outer tank 110.

[0080] The valve 133 and the switching unit 134 are electrically connected to the control unit 7 and controlled by the control unit 7. For example, when storing etching liquid in an empty processing tank 61, the control unit 7 controls the valve 133 and the switching unit 134 to supply new etching liquid from the etching liquid supply source 131 to the inner tank 100. Furthermore, when refilling the processing tank 61 with etching liquid, the control unit 7 controls the valve 133 and the switching unit 134 to supply new etching liquid from the etching liquid supply source 131 to the outer tank 110.

[0081] [Specific operation of the substrate processing apparatus] Next, a specific operation of the substrate processing apparatus 1 according to the embodiment will be described with reference to Fig. 12. Fig. 12 is a flowchart showing the procedure of processing executed by the substrate processing apparatus 1 according to the embodiment. The procedure shown in Fig. 12 is executed under the control of the control unit 7.

[0082] 12, a preparation process is first performed (step S101) in the substrate processing apparatus 1. In the preparation process, a plurality of wafers W each having a stacked film including a plurality of silicon oxide films 11 with different film thicknesses are prepared, as shown in FIG.

[0083] Next, in the substrate processing apparatus 1, an etching process using an etching solution is performed on a plurality of wafers W forming a lot (step S102). In the etching process, the plurality of wafers W are lowered using the substrate lifting mechanism 63, so that the plurality of wafers W are immersed in the etching solution stored in the inner tank 100 of the processing tank 61.

[0084] This etching process is performed until the stacked film formed on the wafer W changes from the initial state shown in Fig. 1 to the stacked surface exposed state shown in Fig. 2. That is, the etching process etches the silicon oxide film 11 in contact with the polysilicon film 12, thereby exposing the stacked surfaces (upper and lower surfaces) of the polysilicon film 12.

[0085] The inventors of the present application have confirmed through experiments that an etching solution containing at least one of hydrochloric acid, a metal salt, and a surfactant reduces variations in the etching rate for each silicon oxide film 11, compared to an etching solution containing no hydrochloric acid, a metal salt, or a surfactant. Therefore, the substrate processing apparatus 1 performs etching using an etching solution containing at least one of hydrochloric acid, a metal salt, and a surfactant. This reduces variations in the etching rate for each silicon oxide film 11.

[0086] Next, a rinse process is performed (step S103) in the substrate processing apparatus 1. In the rinse process, the plurality of wafers W that have been subjected to the etching process are transferred to a processing tank 62 for the rinse process and immersed in a rinse liquid (deionized water or the like) stored in the processing tank 62. This allows the etching liquid to be washed away from the plurality of wafers W.

[0087] Next, a drying process is performed in the substrate processing apparatus 1 (step S104). In the drying process, the plurality of wafers W that have been subjected to the rinsing process are transferred to a processing tank 91 for drying process, and the rinsing liquid adhering to the surfaces of the plurality of wafers W is removed by a processing gas. As a result, the plurality of wafers W are dried.

[0088] Thereafter, the plurality of wafers W that have been dried are accommodated in the carrier 9 placed on the carrier stage 20. This completes the substrate processing for one lot.

[0089] [Variations] The substrate processing according to the embodiment can also be applied to a single-wafer processing unit that processes one wafer W at a time. Fig. 13 is a diagram showing an example of the configuration of a processing unit according to a modified example.

[0090] As shown in FIG. 13, a processing unit 200 according to the modified example includes a chamber 220, a substrate holding mechanism 230, a nozzle 240, and a collection cup 250.

[0091] The chamber 220 accommodates a substrate holding mechanism 230, a nozzle 240, and a collection cup 250. A fan filter unit (FFU) 221 is provided on the ceiling of the chamber 220. The FFU 221 forms a downflow within the chamber 220.

[0092] The substrate holding mechanism 230 includes a holder 231, a support 232, and a drive unit 233. The holder 231 holds the wafer W horizontally. The support 232 is a member extending in the vertical direction, and its base end is rotatably supported by the drive unit 233, with its tip end supporting the holder 231 horizontally. The drive unit 233 rotates the support 232 around a vertical axis. The substrate holding mechanism 230 rotates the support 232 using the drive unit 233, thereby rotating the holder 231 supported by the support 232, and thereby rotating the wafer W held by the holder 231.

[0093] The nozzle 240 is disposed above the wafer W held by the holder 231 and supplies various processing liquids to the wafer W.

[0094] The collection cup 250 is disposed to surround the holder 231, and collects the processing liquid scattered from the wafer W due to the rotation of the holder 231. A drainage port 251 is formed in the bottom of the collection cup 250, and the processing liquid collected by the collection cup 250 is discharged from the drainage port 251 to the outside of the processing unit 200. In addition, an exhaust port 252 is formed in the bottom of the collection cup 250, which discharges the gas supplied from the FFU 221 to the outside of the processing unit 200.

[0095] The processing unit 200 further includes an etching liquid supply unit 260 and a rinsing liquid supply unit 270 .

[0096] The etching liquid supply unit 260 includes an etching liquid supply source 261 and a valve 262, and supplies the etching liquid supplied from the etching liquid supply source 261 to the nozzle 240. The rinsing liquid supply unit 270 includes a rinsing liquid supply source 271 and a valve 272, and supplies the rinsing liquid (deionized water, etc.) supplied from the rinsing liquid supply source 271 to the nozzle 240.

[0097] An etching process is first performed in the processing unit 200. In the etching process, the valve 262 is opened for a predetermined time, so that an etching liquid is supplied to the wafer W held by the substrate holding mechanism 230 and rotated.

[0098] Next, a rinsing process is performed in the processing unit 200. In the rinsing process, the valve 272 is opened for a predetermined time, and a rinsing liquid is supplied to the wafer W held and rotated by the substrate holding mechanism 230. Thereafter, a drying process is performed in the processing unit 200. In the drying process, the rotation speed of the wafer W is increased to spin off the rinsing liquid from the wafer W, thereby drying the wafer W. When the drying process is completed, the substrate processing for one wafer W is completed.

[0099] In this way, the substrate processing according to the embodiment can also be applied to a single-wafer processing unit that processes wafers W one by one.

[0100] [Other variations] In the above embodiment, an example has been shown in which the polysilicon film 12 and each of the plurality of silicon oxide films 11 are formed adjacent to each other in the vertical direction in the stacked film formed on the wafer W, but the structure of the stacked film is not limited to this. For example, in the stacked film, each of the plurality of silicon oxide films 11 and another film formed adjacent to each of the plurality of silicon oxide films 11 may be formed adjacent to each other in the horizontal direction.

[0101] In the above embodiment, after the etching process (step S101) of the wafer W is performed using an etching solution containing a metal salt, a removal process may be performed using SC2 (a mixed solution of hydrochloric acid and hydrogen peroxide) to remove the metal salt remaining on the surface of the wafer W. In such a case, it is preferable that the other films formed adjacent to each of the plurality of silicon oxide films 11 are not metal-containing films.

[0102] As described above, the substrate processing method according to the embodiment includes a step of preparing a substrate (e.g., wafer W) and a step of etching the substrate. The substrate preparing step includes preparing a substrate having a stacked film including multiple silicon oxide films (e.g., silicon oxide film 11) with different thicknesses. The substrate etching step includes etching the substrate with an etching solution containing at least one of hydrochloric acid, a metal salt, and a surfactant. Therefore, the substrate processing method according to the embodiment can reduce variations in the etching rate for each silicon oxide film in a technique for etching a stacked film including multiple silicon oxide films with different thicknesses.

[0103] The concentrations of hydrochloric acid and metal salt in the etching solution may be 0.5 wt% or more and 5 wt% or less. This reduces the variation in etching rate for each silicon oxide film, regardless of the type of metal salt. Furthermore, by keeping the concentration of metal salt in the etching solution at 5 wt% or less, contamination of the substrate by metal can be suppressed.

[0104] The concentration of the surfactant in the etching solution may be 0.5 wt% or more and 5 wt% or less. This reduces the variation in etching rate for each silicon oxide film, regardless of the type of surfactant. Furthermore, by keeping the concentration of the surfactant in the etching solution at 5 wt% or less, it is possible to prevent organic matter (contaminants) removed by the surfactant from remaining on the surface of the substrate.

[0105] The substrate processing method according to the embodiment may further include, after the step of etching the substrate, a step of removing metal salts remaining on the surface of the substrate with SC2, thereby suppressing contamination of the substrate with metals.

[0106] The disclosed embodiments should be considered in all respects as illustrative and not restrictive. Indeed, the above-described embodiments may be embodied in various forms. Furthermore, the above-described embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims.

[0107] In addition, the following supplementary notes are disclosed regarding the above-described embodiment. (Appendix 1) preparing a substrate having a stacked film including a plurality of silicon oxide films having different thicknesses; Etching the substrate with an etching solution containing hydrochloric acid; A substrate processing method comprising: (Appendix 2) preparing a substrate having a stacked film including a plurality of silicon oxide films having different thicknesses; Etching the substrate with an etching solution containing a metal salt; A substrate processing method comprising: (Appendix 3) preparing a substrate having a stacked film including a plurality of silicon oxide films having different thicknesses; Etching the substrate with an etching solution containing a surfactant; A substrate processing method comprising: (Appendix 4) the stacked film further includes another film formed adjacent to each of the plurality of silicon oxide films, 4. The substrate processing method according to any one of claims 1 to 3, wherein the other film is selected from at least one of a silicon film, a polysilicon film, a silicon nitride film, and a metal-containing film. (Appendix 5) 5. The substrate processing method according to claim 4, wherein in the stacked film, the other film and each of the plurality of silicon oxide films are formed adjacent to each other in a vertical or horizontal direction. (Appendix 6) 6. The substrate processing method according to any one of claims 1 to 5, wherein the thickness of the plurality of silicon oxide films is 1 nm or more and 30 nm or less. (Appendix 7) 7. The substrate processing method according to claim 1, wherein the etching solution contains hydrofluoric acid. (Appendix 8) 8. The substrate processing method according to claim 7, wherein the concentration of the hydrofluoric acid in the etching solution is 0.1 wt % or more and 50 wt % or less. (Appendix 9) 2. The substrate processing method according to claim 1, wherein the concentration of the hydrochloric acid before being added to the etching solution is 35 wt % or more and 37 wt % or less. (Appendix 10) 3. The substrate processing method according to claim 2, wherein the metal salt is an alkali metal halide or an alkaline earth metal halide. (Appendix 11) the alkali metal halide includes at least one of Li, Na, K, Rb, and Cs; 11. The substrate processing method of claim 10, wherein the alkaline earth metal halide includes at least one of Mg, Ca, Sr, and Ba. (Appendix 12) 2. The substrate processing method according to claim 1, wherein the concentration of each of the hydrochloric acid and the metal salt in the etching solution is 0.5 wt % or more and 5 wt % or less. (Appendix 13) 4. The substrate processing method according to claim 3, wherein the surfactant is a cationic surfactant or an anionic surfactant. (Appendix 14) the cationic surfactant is n-octylamine hydrochloride (OACl) or n-octyltrimethylammonium chloride (OTMACl); 14. The substrate processing method according to claim 13, wherein the anionic surfactant is sodium dodecylbenzenesulfonate (SDBS). (Appendix 15) 15. The substrate processing method according to claim 3, wherein the concentration of the surfactant in the etching solution is 0.5 wt % or more and 5 wt % or less. (Appendix 16) The substrate processing method according to claim 2, further comprising the step of removing the metal salt remaining on the surface of the substrate with SC2 after the step of etching the substrate. (Appendix 17) a treatment tank for storing an etching solution containing hydrochloric acid; A control unit that controls each part Equipped with The control unit A substrate having a laminated film including a plurality of silicon oxide films with different thicknesses is immersed in the etching solution stored in the treatment tank, thereby performing an etching treatment on the substrate. Substrate processing equipment. (Appendix 18) a treatment tank for storing an etching solution to which a metal salt has been added; A control unit that controls each part Equipped with The control unit A substrate having a laminated film including a plurality of silicon oxide films with different thicknesses is immersed in the etching solution stored in the treatment tank, thereby performing an etching treatment on the substrate. Substrate processing equipment. (Appendix 19) a processing tank for storing an etching solution containing a surfactant; A control unit that controls each part Equipped with The control unit A substrate having a laminated film including a plurality of silicon oxide films with different thicknesses is immersed in the etching solution stored in the treatment tank, thereby performing an etching treatment on the substrate. Substrate processing equipment. [Explanation of symbols]

[0108] 1. Substrate processing equipment 7 Control Unit 10 Silicon substrate 11 Silicon oxide film 12 Polysilicon film 15 groove 16p Water Cluster 16s spherical structure 60 Etching treatment equipment 61 Treatment tank 100 inner tank 110 Outer tank 120 Circulation section 130 Etching liquid supply unit W wafer

Claims

1. preparing a substrate having a stacked film including a plurality of silicon oxide films having different thicknesses; performing an etching treatment on the substrate with an etching solution containing hydrofluoric acid and having a metal salt added thereto, the metal salt having a concentration of 0.5 wt % or more and 5 wt % or less; Including, the stacked film further includes another film formed adjacent to each of the plurality of silicon oxide films, The substrate processing method, wherein the other film is selected from at least one of a silicon film, a polysilicon film, a silicon nitride film, and a metal-containing film.

2. 2. The substrate processing method according to claim 1, wherein in the stacked film, the other film and each of the plurality of silicon oxide films are formed adjacent to each other in the vertical or horizontal direction.

3. 2. The substrate processing method according to claim 1, wherein the thickness of the plurality of silicon oxide films is 1 nm or more and 30 nm or less.

4. 2. The substrate processing method according to claim 1, wherein the concentration of the hydrofluoric acid in the etching solution is 0.1 wt % or more and 50 wt % or less.

5. 2. The substrate processing method according to claim 1, wherein the metal salt is an alkali metal halide or an alkaline earth metal halide.

6. the alkali metal halide includes at least one of Li, Na, K, Rb, and Cs; 6. The substrate processing method according to claim 5, wherein the alkaline earth metal halide includes at least one of Mg, Ca, Sr, and Ba.

7. 2. The substrate processing method according to claim 1, further comprising the step of removing the metal salt remaining on the surface of the substrate with SC2 after the step of etching the substrate.

8. a treatment tank for storing an etching solution containing hydrofluoric acid and a metal salt added thereto, the metal salt having a concentration of 0.5 wt % or more and 5 wt % or less; A control unit that controls each part Equipped with The control unit immersing a substrate having a stacked film including a plurality of silicon oxide films having different thicknesses in the etching solution stored in the treatment tank, thereby performing an etching treatment on the substrate; the stacked film further includes another film formed adjacent to each of the plurality of silicon oxide films, the other film is selected from at least one of a silicon film, a polysilicon film, a silicon nitride film, and a metal-containing film; Substrate processing equipment.

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