Substrate processing apparatus and substrate processing method

Abstract

To reduce the amount of use of etchant in a technique of etching a substrate by using an etchant containing a phosphoric acid aqueous solution.SOLUTION: A substrate processor according to an aspect of the present disclosure includes a substrate processing unit and a control unit. The substrate processing unit performs etching processing on at least one substrate having a silicon nitride film and a silicon oxide film on a surface thereof, by using a processing solution containing a phosphoric acid aqueous solution and a silicate acid compound. The control unit controls each part. The control unit has a concentration control unit. The concentration control unit controls the concentration of the phosphoric acid in the processing solution such that the etching selectivity of the silicon nitride film with respect to the silicon oxide film falls within a predetermined range from the start to the end of the etching processing.SELECTED DRAWING: Figure 9

Description

Technical Field

[0001] The disclosed embodiments relate to a substrate processing apparatus and a substrate processing method.

Background Art

[0002] Conventionally, in a substrate processing system, a technique for selectively etching a silicon nitride film among a silicon nitride film and a silicon oxide film formed on a substrate by using an etching solution containing an aqueous phosphoric acid solution is known (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present disclosure provides a technique capable of reducing the usage amount of an etching solution in a technique for etching a substrate using an etching solution containing an aqueous phosphoric acid solution.

Means for Solving the Problems

[0005] [[ID=4i]] A substrate processing apparatus according to one aspect of the present disclosure includes a substrate processing unit and a control unit. The substrate processing unit etches one or a plurality of substrates having a silicon nitride film and a silicon oxide film formed on the surface with a processing solution containing an aqueous phosphoric acid solution and a silicate compound. The control unit controls each unit. Further, the control unit has a concentration control unit. The concentration control unit controls the phosphoric acid concentration of the processing solution so that the etching selectivity of the silicon nitride film with respect to the silicon oxide film is within a given range from the start to the completion of the etching process.

Effects of the Invention

[0006] According to this disclosure, in a technique for etching a substrate using an etching solution containing an aqueous phosphoric acid solution, the amount of etching solution used can be reduced. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a schematic block diagram showing the configuration of the substrate processing system according to the embodiment. [Figure 2] Figure 2 is a schematic block diagram showing the configuration of the etching apparatus according to the embodiment. [Figure 3] Figure 3 is a block diagram showing the configuration of a control device according to an embodiment. [Figure 4] Figure 4 shows an example of the relationship between silicate concentration and the etching rate of silicon oxide film at multiple phosphoric acid concentrations. [Figure 5] Figure 5 is a schematic diagram showing the upper and lower limits of silicate concentration at multiple phosphate concentrations. [Figure 6] Figure 6 is a schematic diagram showing the relationship between silicate concentration and etching selectivity at multiple phosphoric acid concentrations. [Figure 7] Figure 7 shows an example of the relationship between phosphoric acid concentration and the etching rate of a silicon nitride film. [Figure 8] Figure 8 shows an example of the linear curves representing the changes in silicate compound concentration, phosphoric acid concentration, and etching selectivity ratio calculated by the calculation unit. [Figure 9] Figure 9 shows an example of the time evolution of the phosphoric acid concentration and etching selectivity ratio of the etching solution in the etching process according to the embodiment. [Figure 10] Figure 10 is a flowchart showing an example of the control process steps performed by the substrate processing system according to the embodiment. [Modes for carrying out the invention]

[0008] The embodiments of the substrate processing apparatus and substrate processing method disclosed herein will be described in detail below with reference to the attached drawings. However, the embodiments described below do not limit this disclosure. Furthermore, it should be noted that the drawings are schematic, and the dimensional relationships and ratios of each element may differ from reality. Moreover, there may be differences in dimensional relationships and ratios between drawings.

[0009] Conventionally, in substrate processing systems, a technique is known in which the silicon nitride film is selectively etched from the silicon nitride film and silicon oxide film formed on a substrate by using an etching solution containing an aqueous phosphoric acid solution. In such a conventional technique, for example, multiple substrates can be etched at once by immersing them together in the etching solution stored in a processing tank.

[0010] On the other hand, in the conventional technology described above, it is necessary to constantly supply an etching solution with a low silica concentration (hereinafter also referred to as "silicic acid concentration") to the processing tank in order to keep the concentration of silicate compounds in the etching solution constant. As a result, a problem arose in that the amount of etching solution used in the etching process increased.

[0011] Therefore, there is a need to overcome the aforementioned problems and realize a technology that can reduce the amount of etching solution used in etching substrates using an etching solution containing an aqueous phosphoric acid solution.

[0012] <Configuration of the substrate processing system> First, the configuration of the substrate processing system 1 according to the embodiment will be described with reference to Figure 1. Figure 1 is a schematic block diagram showing the configuration of the substrate processing system 1 according to the embodiment. The substrate processing system 1 is an example of a substrate processing apparatus.

[0013] As shown in Figure 1, the substrate processing system 1 according to this embodiment includes a carrier loading / unloading unit 2, a lot formation unit 3, a lot placement unit 4, a lot transport unit 5, a lot processing unit 6, and a control device 7.

[0014] The carrier loading / unloading unit 2 includes a carrier stage 20, a carrier transport mechanism 21, carrier stocks 22 and 23, and a carrier mounting table 24.

[0015] The carrier stage 20 mounts a plurality of hoops H conveyed from the outside. The hoop H is a container that houses a plurality (for example, 25) of wafers W arranged vertically in a horizontal posture. The carrier transport mechanism 21 transports the hoop H among the carrier stage 20, the carrier stocks 22 and 23, and the carrier mounting table 24.

[0016] From the hoop H placed on the carrier mounting table 24, a plurality of wafers W before being processed are carried out to the lot processing unit 6 by the substrate transport mechanism 30 described later. Also, a plurality of processed wafers W are carried into the hoop H placed on the carrier mounting table 24 from the lot processing unit 6 by the substrate transport mechanism 30.

[0017] The lot forming unit 3 has a substrate transport mechanism 30 and forms a lot. A lot is composed of a plurality (for example, 50) of wafers W that are processed simultaneously by combining the wafers W housed in one or a plurality of hoops H. The plurality of wafers W forming one lot are arranged at a certain interval with their plate surfaces facing each other.

[0018] The substrate transport mechanism 30 transports a plurality of wafers W between the hoop H placed on the carrier mounting table 24 and the lot mounting portion 4.

[0019] The lot mounting portion 4 has a lot transport table 40 and temporarily mounts (waits) the lot transported between the lot forming unit 3 and the lot processing unit 6 by the lot transport unit 5. The lot transport table 40 has a loading side mounting table 41 that mounts the lot before being processed formed in the lot forming unit 3 and an unloading side mounting table 42 that mounts the lot processed in the lot processing unit 6. On the loading side mounting table 41 and the unloading side mounting table 42, a plurality of wafers W for one lot are mounted side by side in a standing posture.

[0020] The lot transport unit 5 has a lot transport mechanism 50 that transports lots between the lot placement unit 4 and the lot processing unit 6, and within the lot processing unit 6. The lot transport mechanism 50 has a rail 51, a movable body 52, and a substrate holder 53.

[0021] The rail 51 is arranged along the X-axis direction, spanning the lot mounting section 4 and the lot processing section 6. The movable body 52 is configured to move along the rail 51 while holding multiple wafers W. The substrate holder 53 is positioned on the movable body 52 and holds multiple wafers W arranged front to back in an upright position.

[0022] The lot processing unit 6 performs etching, cleaning, drying, and other processes on multiple wafers W in one lot all at once. The lot processing unit 6 has two etching processing units 60, a cleaning processing unit 70, a cleaning processing unit 80, and a drying processing unit 90, all arranged along the rail 51.

[0023] The etching apparatus 60 performs etching on multiple wafers W in one lot at once. The cleaning apparatus 70 performs cleaning on multiple wafers W in one lot at once. The cleaning apparatus 80 performs cleaning on the substrate holder 53. The drying apparatus 90 performs drying on multiple wafers W in one lot at once. Note that the number of etching apparatuses 60, cleaning apparatuses 70, cleaning apparatuses 80 and drying apparatuses 90 is not limited to the example in Figure 1.

[0024] The etching apparatus 60 comprises an etching tank 61, a rinsing tank 62, and substrate lifting mechanisms 63 and 64.

[0025] The processing tank 61 is capable of accommodating one lot of wafers W arranged in an upright position, and stores the etching solution (hereinafter also referred to as "etching solution"). Details of the processing tank 61 will be described later.

[0026] A processing solution (such as deionized water) for rinsing is stored in the processing tank 62. Multiple wafers W that form a lot are held in an upright position, arranged front to back, in the substrate lifting mechanisms 63 and 64.

[0027] The etching apparatus 60 holds the lot transported by the lot transport unit 5 with the substrate lifting mechanism 63 and immerses it in the etching solution L in the processing tank 61 to perform the etching process. The etching process is carried out for, for example, about 1 to 3 hours.

[0028] The etched lot in the processing tank 61 is transported to the processing tank 62 by the lot transport unit 5. The etching apparatus 60 then holds the transported lot with the substrate lifting mechanism 64 and performs rinsing by immersing it in the rinsing solution in the processing tank 62. The lot that has been rinsed in the processing tank 62 is transported to the processing tank 71 of the cleaning apparatus 70 by the lot transport unit 5.

[0029] The cleaning apparatus 70 comprises a cleaning treatment tank 71, a rinsing treatment tank 72, and substrate lifting mechanisms 73 and 74. The cleaning treatment tank 71 stores a cleaning chemical solution (hereinafter also referred to as "cleaning chemical solution"). The cleaning chemical solution is, for example, SC1 (a mixture of ammonia, hydrogen peroxide, and water).

[0030] A rinsing treatment tank 72 stores a rinsing treatment solution (such as deionized water). Multiple wafers W for one lot are held in an upright position, arranged front to back, in the substrate lifting mechanisms 73 and 74.

[0031] The cleaning apparatus 70 holds the lot transported by the lot transport unit 5 with the substrate lifting mechanism 73 and performs the cleaning process by immersing it in the cleaning solution in the processing tank 71.

[0032] The lot that has been washed in the processing tank 71 is transported to the processing tank 72 by the lot transport unit 5. The washing processing device 70 then holds the transported lot with the substrate lifting mechanism 74 and performs rinsing by immersing it in the rinsing solution in the processing tank 72. The lot that has been rinsed in the processing tank 72 is transported to the processing tank 91 of the drying processing device 90 by the lot transport unit 5.

[0033] The drying apparatus 90 comprises a processing tank 91 and a substrate lifting mechanism 92. A processing gas for drying is supplied to the processing tank 91. Multiple wafers W for one lot are held in an upright position, arranged front to back, in the substrate lifting mechanism 92.

[0034] The drying apparatus 90 holds the lots transported by the lot transport unit 5 with the substrate lifting mechanism 92 and performs drying using a drying gas supplied into the processing tank 91. The lots that have been dried in the processing tank 91 are transported to the lot placement unit 4 by the lot transport unit 5.

[0035] The cleaning apparatus 80 supplies a cleaning solution to the substrate holder 53 of the lot transport mechanism 50, and further supplies a drying gas to perform the cleaning process on the substrate holder 53.

[0036] The control device 7 controls the operation of each part of the substrate processing system 1 (carrier loading / unloading unit 2, lot formation unit 3, lot placement unit 4, lot transport unit 5, lot processing unit 6, etc.). The control device 7 controls the operation of each part of the substrate processing system 1 based on signals from switches, various sensors, etc.

[0037] The control device 7 includes a microcomputer with a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), input / output ports, and various circuits. The control device 7 controls the operation of the board processing system 1 by, for example, reading and executing a program stored in the memory unit 8 (see Figure 3). Details of the control device 7 will be described later.

[0038] <Configuration of etching apparatus> Next, the configuration of the etching apparatus 60 that performs the etching process on the wafer W will be described with reference to Figure 2. Figure 2 is a schematic block diagram showing the configuration of the etching apparatus 60 according to the embodiment.

[0039] The etching apparatus 60 comprises an etching solution supply unit 100, a DIW supply unit 105, and a substrate processing unit 110. The etching solution supply unit 100 supplies the etching solution L to the substrate processing unit 110. The etching solution L is an example of a processing solution.

[0040] The etching solution supply unit 100 includes an etching solution supply source 101, an etching solution supply path 102, and a flow rate regulator 103.

[0041] The etching solution supply source 101 is, for example, a tank for storing the etching solution L. The etching solution L according to this embodiment contains an aqueous solution of phosphoric acid (H3PO4). In this disclosure, the aqueous solution of phosphoric acid is also simply referred to as "phosphoric acid." Furthermore, the etching solution L according to this embodiment may also contain a silicate compound (hereinafter also simply referred to as "silicic acid").

[0042] In the etching solution L according to this embodiment, the silicate compound can be added, for example, by a solution in which colloidal silicon is dispersed.

[0043] The etching solution supply path 102 connects the etching solution supply source 101 and the outer tank 112 of the processing tank 61, supplying the etching solution L from the etching solution supply source 101 to the outer tank 112.

[0044] The flow regulator 103 is located in the etching solution supply passage 102 and adjusts the flow rate of the etching solution L supplied to the outer tank 112. The flow regulator 103 includes an on-off valve, a flow control valve, and a flow meter.

[0045] The DIW supply unit 105 supplies DIW (Deionized Water) to the substrate processing unit 110. This allows the concentration of the phosphoric acid aqueous solution in the etching solution L stored in the processing tank 61 (hereinafter also referred to as "phosphoric acid concentration") to be adjusted.

[0046] The DIW supply unit 105 includes a DIW supply source 106, a DIW supply path 107, and a flow regulator 108.

[0047] The DIW supply source 106 is, for example, a tank for storing DIW. The DIW supply path 107 connects the DIW supply source 106 to the outer tank 112 of the processing tank 61, and supplies DIW from the DIW supply source 106 to the outer tank 112.

[0048] The flow regulator 108 is located in the DIW supply path 107 and adjusts the flow rate of DIW supplied to the outer tank 112. The flow regulator 108 includes an on-off valve, a flow control valve, and a flow meter, etc.

[0049] The substrate processing unit 110 immerses the wafer W in the etching solution L supplied from the etching solution supply unit 100 and performs an etching process on the wafer W. The wafer W is an example of a substrate. In this embodiment, for example, the silicon nitride film can be selectively etched from among the silicon nitride film and silicon oxide film formed on the wafer W.

[0050] The substrate processing unit 110 comprises a processing tank 61, a substrate lifting mechanism 63, an etching solution circulation unit 120, and a gas supply unit 140. The processing tank 61 has an inner tank 111 and an outer tank 112.

[0051] The inner tank 111 is a tank for immersing the wafer W in the etching solution L, and contains the etching solution L for immersion. The inner tank 111 has an opening 111a at its top, and the etching solution L is stored up to the vicinity of the opening 111a.

[0052] In the inner tank 111, multiple wafers W are immersed in etching solution L using a substrate lifting mechanism 63, and the wafers W are subjected to etching. The substrate lifting mechanism 63 is configured to be able to move up and down and holds multiple wafers W in a vertical position, arranged front to back.

[0053] The outer tank 112 is positioned outside the inner tank 111 so as to surround it on all four sides in a plan view, and receives the etching solution L flowing out from the opening 111a of the inner tank 111. As shown in Figure 2, the liquid level in the outer tank 112 is maintained lower than the liquid level in the inner tank 111.

[0054] The etching solution circulation unit 120 circulates the etching solution L between the inner tank 111 and the outer tank 112. The etching solution circulation unit 120 includes a circulation path 121, a pump 122, a heater 123, a filter 124, a concentration sensor 125, and a plurality (three in the figure) of processing solution nozzles 126.

[0055] The circulation path 121 connects the outer tank 112 and the inner tank 111. One end of the circulation path 121 is connected to the bottom of the outer tank 112, and the other end of the circulation path 121 is connected to the processing liquid nozzle 126 located inside the inner tank 111. The circulation path 121 contains, in order from the outer tank 112 side, a pump 122, a heater 123, a filter 124, and a concentration sensor 125.

[0056] Pump 122 forms a circulating flow of etching solution L, which is sent from the outer tank 112 through the circulation path 121 to the inner tank 111. The etching solution L also overflows from the opening 111a of the inner tank 111 and flows back into the outer tank 112. In this way, a circulating flow of etching solution L is formed within the substrate processing unit 110. That is, this circulating flow is formed in the outer tank 112, the circulation path 121, and the inner tank 111.

[0057] The heater 123 adjusts the temperature of the etching solution L circulating through the circulation path 121. The filter 124 filters the etching solution L circulating through the circulation path 121. The concentration sensor 125 measures the phosphoric acid concentration in the etching solution L circulating through the circulation path 121, thereby determining the phosphoric acid concentration of the etching solution L stored in the processing tank 61. The signal generated by the concentration sensor 125 is transmitted to the control unit 9.

[0058] The processing liquid nozzle 126 discharges the etching liquid L circulating in the circulation path 121 upward inside the inner tank 111, forming an upward flow inside the inner tank 111.

[0059] The gas supply unit 140 supplies inert gas (for example, nitrogen gas) to the bottom of the inner tank 111 where the etching solution L is stored and to the bottom of the outer tank 112, respectively. As a result, bubbles of inert gas are discharged to the bottom of the inner tank 111 and the bottom of the outer tank 112.

[0060] The gas supply unit 140 includes a gas supply source 141, a gas supply passage 142, a flow regulator 143, a plurality of gas nozzles 144, a gas supply passage 145, a flow regulator 146, and a plurality of gas nozzles 147.

[0061] The gas supply line 142 connects the gas supply source 141 to the multiple gas nozzles 144 and supplies inert gas from the gas supply source 141 to the multiple gas nozzles 144.

[0062] The flow regulator 143 is located in the gas supply passage 142 and adjusts the amount of inert gas supplied to the multiple gas nozzles 144. The flow regulator 143 includes an on-off valve, a flow control valve, and a flow meter, among other things.

[0063] Multiple gas nozzles 144 are arranged in multiple rows (six rows in the figure) below the wafer W and processing liquid nozzle 126 in the inner tank 111. The multiple gas nozzles 144 discharge inert gas bubbles upward into the etching liquid L stored in the inner tank 111, forming an upward flow inside the inner tank 111.

[0064] The gas supply line 145 connects the gas supply source 141 to the multiple gas nozzles 147 and supplies inert gas from the gas supply source 141 to the multiple gas nozzles 147.

[0065] The flow regulator 146 is located in the gas supply path 145 and adjusts the amount of inert gas supplied to the multiple gas nozzles 147. The flow regulator 146 includes an on-off valve, a flow control valve, and a flow meter, among other things.

[0066] The multiple gas nozzles 147 are arranged in multiple rows (two rows in the figure) along the four sides of the inner tank 111 in a plan view, for example, at the bottom of the outer tank 112. The multiple gas nozzles 147 discharge inert gas bubbles upward into the etching solution L stored in the outer tank 112, for example, forming an upward flow inside the outer tank 112.

[0067] The etching apparatus 60 according to this embodiment can supply a fast-flowing etching solution L into the gaps between multiple wafers W positioned side by side in the inner tank 111 by discharging inert gas bubbles from multiple gas nozzles 144. Therefore, according to this embodiment, multiple wafers W can be etched efficiently and uniformly.

[0068] Furthermore, the etching apparatus 60 according to this embodiment can promote the evaporation of the etching solution L stored in the inner tank 111 by discharging inert gas bubbles from a plurality of gas nozzles 144.

[0069] Furthermore, the etching apparatus 60 according to this embodiment can promote the evaporation of the etching solution L stored in the outer tank 112 by discharging inert gas bubbles from a plurality of gas nozzles 147.

[0070] <Embodiment> Next, the details of the etching process according to the embodiment will be described with reference to Figures 3 to 9. Figure 3 is a block diagram showing the configuration of the control device 7 according to the embodiment. As shown in Figure 3, the control device 7 comprises a storage unit 8 and a control unit 9.

[0071] Furthermore, the control device 7 may also have various functional units that are known to be present in computers, in addition to the functional units shown in Figure 3, such as various input devices and audio output devices.

[0072] The memory unit 8 is implemented by, for example, semiconductor memory elements such as RAM and flash memory, or storage devices such as hard disks and optical discs. The memory unit 8 has an etching information storage unit 8a. The memory unit 8 also stores information used for processing in the control unit 9.

[0073] The etching information storage unit 8a stores various data showing the relationship between the phosphoric acid concentration and silicate concentration of the etching solution L, and the etching rates of silicon oxide and silicon nitride films in etching solutions L with these concentrations. Details of the data stored in this etching information storage unit 8a will be explained with reference to Figures 4 to 7.

[0074] Figure 4 shows an example of the relationship between silicate concentration and the etching rate of the silicon oxide film at multiple phosphoric acid concentrations. As shown in Figure 4, in the etching process according to the embodiment, at all phosphoric acid concentrations, the lower the silicate concentration of the etching solution L, the higher the etching rate of the silicon oxide film.

[0075] In other words, in the etching process according to the embodiment, at all phosphoric acid concentrations, the etching rate of the silicon oxide film gradually decreases as the silicate concentration of the etching solution L increases, and when it exceeds a certain threshold, the etching rate becomes negative.

[0076] Thus, a negative etching rate for the silicon oxide film indicates that the silicon oxide film on wafer W is not etched during the etching process, but rather that a silicon oxide film is deposited.

[0077] Furthermore, in the etching process according to the embodiment, as the phosphoric acid concentration of the etching solution L increases, the rate at which the etching rate decreases in response to the increase in silicate concentration gradually slows down, and the threshold silicate concentration at which the etching rate becomes negative gradually increases.

[0078] Based on the measurement results shown in Figure 4, the control unit 9 (see Figure 3) can calculate the data shown in Figure 5. Figure 5 shows the upper and lower limits of silicate concentration at multiple phosphoric acid concentrations.

[0079] As shown in Figure 5, in the etching process according to this embodiment, there are upper and lower limits to the silicate concentration at each phosphoric acid concentration in the etching solution L. The lower limit of the silicate concentration corresponds, for example, to the case where the etching rate of the silicon oxide film is a given positive value, as shown in the results in Figure 4.

[0080] If the etching rate of the silicon oxide film exceeds a given positive value, the etching selectivity ratio of the silicon nitride film to the silicon oxide film cannot be maintained at the desired ratio (for example, 900:1 or 1900:1), making it difficult to perform the desired etching process.

[0081] Therefore, in the etching process according to this embodiment, a lower limit of the silicate concentration is set for each phosphoric acid concentration.

[0082] Furthermore, the upper limit of the silicate concentration corresponds, for example, to the case where the etching rate of the silicon oxide film is less than zero, as shown in the results in Figure 4. When the etching rate of the silicon oxide film is negative, the silicon oxide film is deposited on the wafer W during the etching process, making it difficult to perform the desired etching process.

[0083] Therefore, in the etching process according to this embodiment, an upper limit of the silicate concentration is set for each phosphoric acid concentration.

[0084] As shown in Figure 5, in the etching process according to this embodiment, as the phosphoric acid concentration of the etching solution L increases, the margin between the lower and upper limits of the silicate concentration (hereinafter also referred to as the "regrowth margin") gradually widens.

[0085] This indicates that, in the etching process according to the embodiment, the permissible range of silicate concentration gradually widens as the phosphoric acid concentration of the etching solution L increases.

[0086] Figure 6 is a schematic diagram showing the relationship between silicate concentration and etching selectivity at multiple phosphoric acid concentrations. In subsequent figures, the "etching selectivity value" refers to the etching rate of the silicon nitride film when the etching rate of the silicon oxide film is set to 1.

[0087] As shown in Figure 6, in the etching process according to the embodiment, at all phosphoric acid concentrations, the etching selectivity ratio gradually increases as the silicate concentration of the etching solution L increases.

[0088] Furthermore, in the etching process according to the embodiment, as the phosphoric acid concentration of the etching solution L increases, the rate at which the etching rate increases in relation to the increase in silicate concentration gradually slows down.

[0089] As a result, as shown in Figure 6, in the etching process according to this embodiment, the silicate concentration at which the desired etching selectivity ratio is obtained gradually increases as the phosphoric acid concentration of the etching solution L increases.

[0090] Figure 7 shows an example of the relationship between phosphoric acid concentration and the etching rate of the silicon nitride film. As shown in Figure 7, in the etching process according to this embodiment, as the phosphoric acid concentration of the etching solution L increases, the etching rate of the silicon nitride film gradually decreases.

[0091] This indicates that, in the etching process according to the embodiment, as the phosphoric acid concentration of the etching solution L increases, the processing time required to complete the desired etching process also increases.

[0092] The data shown in Figures 4 to 7 can be obtained, for example, by measuring the etching rates of silicon oxide films and silicon nitride films in multiple types of etching solutions L having multiple phosphoric acid concentrations and multiple silicate concentrations, respectively. The various data obtained are then stored in advance in the etching information storage unit 8a of the storage unit 8.

[0093] Returning to the explanation of Figure 3, the control unit 9 is realized by, for example, a CPU, MPU (Micro Processing Unit), GPU (Graphics Processing Unit), etc., executing the program stored in the memory unit 8 using RAM as the working area.

[0094] Furthermore, the control unit 9 may be implemented using an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array).

[0095] The control unit 9 comprises an acquisition unit 9a, a calculation unit 9b, a determination unit 9c, a concentration control unit 9d, and a setting unit 9e, and realizes or executes the functions and operations of the control processing described below. Note that the internal configuration of the control unit 9 is not limited to the configuration shown in Figure 3, and other configurations are also acceptable as long as they perform the control processing described later.

[0096] The acquisition unit 9a acquires the formation status of silicon nitride and silicon oxide films on multiple wafers W that are scheduled to undergo etching. The acquisition unit 9a acquires the formation status of silicon nitride and silicon oxide films on multiple wafers W that are scheduled to undergo etching, for example, based on the lot ID of hoop H (see Figure 1).

[0097] The lot ID of this hoop H is stored in advance, for example, in the memory unit 8 or an external memory device (not shown).

[0098] For example, the acquisition unit 9a acquires information about the formation state of silicon nitride and silicon oxide films on multiple wafers W, such as the film thickness and number of layers of silicon nitride and silicon oxide films formed on multiple wafers W. The acquisition unit 9a also acquires, for example, the number of wafers W that are scheduled to undergo etching next, based on the lot ID of the hoop H.

[0099] The calculation unit 9b performs various calculation processes. Details of these calculation processes will be explained with reference to Figure 8. Figure 8 shows an example of the linear graph L1 showing the concentration transition of silicate compounds, the linear graph L2 showing the concentration transition of phosphoric acid, and the curve L3 showing the transition of etching selectivity, all calculated by the calculation unit 9b.

[0100] The calculation unit 9b calculates the time evolution of the silicate concentration during the etching process of the multiple wafers W, as shown in Figure 8(a), based on the formation state of the silicon nitride film and silicon oxide film on the multiple wafers W acquired by the acquisition unit 9a.

[0101] In the etching process according to this embodiment, as shown in Figure 8(a), the time course of the silicate concentration during the etching process of multiple wafers W gradually increases. This is because the silicon oxide film gradually dissolves from the entire multiple wafers W.

[0102] Furthermore, as shown in Figure 8(b), the calculation unit 9b calculates a linear curve L2 of phosphoric acid concentration changes such that the phosphoric acid concentration of the etching solution L is maintained at the concentration at that time.

[0103] Furthermore, the calculation unit 9b calculates the time course of the etching selectivity ratio when the silicate concentration and phosphoric acid concentration of the etching solution L change according to the values ​​shown on the concentration change lines L1 and L2.

[0104] For example, the calculation unit 9b calculates the time evolution of the etching selectivity ratio based on the concentration evolution lines L1 and L2 and the data shown in Figure 6, etc. As a result, the time evolution of the etching selectivity ratio is calculated as a evolution curve L3, as shown in Figure 8(c). This evolution curve L3 of the etching selectivity ratio gradually increases as the etching process progresses.

[0105] Returning to the explanation of Figure 3, the determination unit 9c determines whether or not an etching process is possible such that the etching selectivity ratio falls within a given range from the start to the completion of the etching process.

[0106] Specifically, the determination unit 9c determines whether the time progression of the etching selectivity ratio, shown by the etching selectivity ratio transition curve L3 (see Figure 8) calculated as described above, is maintained within a given range of etching selectivity ratios (for example, 900-1100 or 1900-2100).

[0107] The concentration control unit 9d controls the phosphoric acid concentration of the etching solution L so that the etching selectivity ratio is within a given range from the start to the completion of the etching process.

[0108] For example, if the concentration control unit 9d determines that the time progression of the etching selectivity ratio is within a given range, it controls the phosphoric acid concentration of the etching solution L along the phosphoric acid concentration progression line L2 (see Figure 8) from the start to the completion of the etching process.

[0109] In this case, if the phosphoric acid concentration of the etching solution L falls below the concentration transition line L2, the concentration control unit 9d operates the gas supply unit 140 to promote the evaporation of the etching solution L. On the other hand, if the phosphoric acid concentration of the etching solution L rises above the concentration transition line L2, the concentration control unit 9d operates the DIW supply unit 105 to decrease the phosphoric acid concentration of the etching solution L.

[0110] As a result, even when the silicate concentration of the etching solution L gradually increases during the etching process of multiple wafers W, the etching process can be carried out within the desired range of etching selectivity without replenishing the etching solution L with new solution.

[0111] Therefore, according to the embodiment, in a technique for etching a wafer W using an etching solution L containing phosphoric acid, the amount of etching solution L used can be reduced.

[0112] In addition, in this embodiment, when the concentration control unit 9d performs etching on multiple wafers W based on the phosphoric acid concentration transition line L2, it is preferable to control the phosphoric acid concentration of the etching solution L based on the measurement results of the concentration sensor 125 (see Figure 2).

[0113] This allows for accurate tracing of the phosphoric acid concentration transition line L2 during the etching process, enabling accurate etching of multiple wafers W.

[0114] The etching time from start to finish in a single etching process is determined, for example, based on the phosphoric acid concentration of the etching solution L at the start of the etching process and the etching rate of the silicon nitride film shown in Figure 7.

[0115] Returning to the explanation of Figure 3, the setting unit 9e sets a new phosphoric acid concentration for the etching solution L when the determination unit 9c determines that etching is not possible in which the etching selectivity ratio is within a given range from the start to the completion of the etching process.

[0116] The new phosphoric acid concentration is higher than the current phosphoric acid concentration and is such that the etching selectivity ratio remains within a given range from the start to the completion of the etching process. The setting unit 9e also adjusts the phosphoric acid concentration of the etching solution L stored in the processing tank 61 to the newly set phosphoric acid concentration value.

[0117] Thus, in this embodiment, even if the etching selectivity exceeds the upper limit A2 (see Figure 9), and the next etching process cannot be carried out within the given etching selectivity range, the next etching process can be carried out by setting a new phosphoric acid concentration.

[0118] In other words, in this embodiment, even if the etching selectivity ratio exceeds the upper limit A2 and the next etching process cannot be carried out as is, it becomes unnecessary to replace the etching solution L in the processing tank 61, thus reducing the amount of etching solution L used.

[0119] Figure 9 shows an example of the time evolution of the phosphoric acid concentration and etching selectivity ratio of the etching solution L in the etching process according to the embodiment.

[0120] As shown in Figure 9, in the etching process according to this embodiment, the etching solution L is replaced in the processing tank 61, and the phosphoric acid concentration of the etching solution L is set to a given initial concentration Ca (for example, about 85 wt% to 90 wt%). At this time, the temperature of the etching solution L is set to, for example, 150°C to 170°C.

[0121] Then, the concentration control unit 9d (see Figure 3) performs the first etching process X1 on the multiple wafers W (see Figure 1) after replacement with fresh solution, based on the linear change L2 of the phosphoric acid concentration. That is, in the first etching process X1, the concentration control unit 9d controls the phosphoric acid concentration so that it remains constant at the initial concentration Ca.

[0122] Then, in the first etching process X1, etching is performed on multiple wafers W such that the transition curve L3 of the etching selectivity ratio falls between a given lower limit A1 (e.g., 900 or 1900) and a given upper limit A2 (e.g., 1100 or 2100).

[0123] On the other hand, in the second etching process X2 that follows, if the phosphoric acid concentration is maintained at the initial concentration Ca from the previous step, the etching selectivity ratio will exceed the upper limit A2.

[0124] Therefore, in the etching process according to this embodiment, the setting unit 9e sets a new phosphoric acid concentration Ca1. As a result, as shown in Figure 6, the etching selectivity ratio decreases even if the etching solution L has the same silicate concentration.

[0125] This new phosphoric acid concentration Ca1 is, for example, the phosphoric acid concentration at which the etching selectivity ratio is lower limit A1 in the etchant solution L at the time the first etching treatment X1 is completed.

[0126] Then, in the second etching process X2, the concentration control unit 9d controls the phosphoric acid concentration so that it becomes constant at the new phosphoric acid concentration Ca1. As a result, in the second etching process X2, the transition curve L3 of the etching selectivity ratio falls between a given lower limit A1 and a given upper limit A2.

[0127] In the subsequent third etching process X3, even if the phosphoric acid concentration is maintained at the previous phosphoric acid concentration Ca1, the etching selectivity ratio does not exceed the upper limit A2. Therefore, in the etching process according to this embodiment, the previous phosphoric acid concentration Ca1 is maintained.

[0128] Then, in the third etching process X3, the concentration control unit 9d controls the phosphoric acid concentration so that it remains constant at the previous phosphoric acid concentration Ca1. As a result, in the third etching process X3, the transition curve L3 of the etching selectivity ratio falls between a given lower limit A1 and a given upper limit A2.

[0129] On the other hand, in the next, fourth etching process X4, if the phosphoric acid concentration is maintained at the previous phosphoric acid concentration Ca1, the etching selectivity ratio will exceed the upper limit A2.

[0130] Therefore, in the etching process according to this embodiment, the setting unit 9e sets a new phosphoric acid concentration Ca2. As a result, as shown in Figure 6, the etching selectivity ratio decreases even if the etching solution L has the same silicate concentration.

[0131] This new phosphoric acid concentration Ca2 is, for example, the phosphoric acid concentration at which the etching selectivity ratio becomes the lower limit A1 in the etchant solution L at the completion of the third etching process X3.

[0132] Then, in the fourth etching process X4, the concentration control unit 9d controls the phosphoric acid concentration so that it becomes constant with the new phosphoric acid concentration Ca2. As a result, in the fourth etching process X4, the transition curve L3 of the etching selectivity ratio falls between a given lower limit A1 and a given upper limit A2.

[0133] Thus, in this embodiment, the same etching solution L can be used to repeatedly perform patch processing on multiple wafers W.

[0134] The concentration control unit 9d then controls the phosphoric acid concentration so that the nth etching process Xn is constant at the upper limit phosphoric acid concentration Cb. In this embodiment, since the etching selectivity ratio exceeds the upper limit A2 in the next etching process, the etching solution L is replaced in the processing tank 61.

[0135] Thus, in this embodiment, even if the silicate concentration of the etching solution L gradually increases during multiple etching processes X1 to Xn, the etching process can be carried out within the desired range of etching selectivity without replenishing the etching solution L with new solution.

[0136] Therefore, according to the embodiment, in a technique for etching a wafer W using an etching solution L containing phosphoric acid, the amount of etching solution L used can be reduced.

[0137] Furthermore, in this embodiment, when the concentration control unit 9d continuously uses the same etching solution L as shown in Figure 9, it is preferable to increase the phosphoric acid concentration of the etching solution L in a stepwise manner so that the etching selectivity ratio is within a predetermined range.

[0138] This allows etching to be performed within the desired etching selectivity range without replenishing the etching solution L, thus reducing the amount of etching solution L used.

[0139] Furthermore, in this embodiment, the gas supply unit 140 may be operated to promote the evaporation of the etching solution L, thereby increasing the phosphoric acid concentration of the etching solution L in a stepwise manner. This allows the phosphoric acid concentration of the etching solution L to be increased in a stepwise manner by a simple means.

[0140] Furthermore, in this embodiment, gas nozzles 147 are provided not only in the inner tank 111 but also in the outer tank 112. This further promotes the evaporation of the etching solution L stored in the processing tank 61, allowing the system to quickly reach a new phosphoric acid concentration when one is set.

[0141] Therefore, according to the embodiment, the throughput of the etching process can be improved.

[0142] Furthermore, in the embodiment, the given etching selectivity range may be an arbitrary range. This allows the etching process of the embodiment to be performed within a range of etching selectivity that suits the user's needs.

[0143] In the embodiments described so far, examples have been shown in which the technology of this disclosure is applied to batch processing in which multiple wafers W are processed at once. However, this disclosure is not limited to such examples. For example, the technology of this disclosure may also be applied to single-wafer processing in which wafers W are etched one by one.

[0144] In this case, for example, a recycling mechanism for reusing the etching solution L used in the etching process is provided in the substrate processing section of the single-wafer processing, and the above technology is applied to such a recycling mechanism.

[0145] Furthermore, in the technology disclosed herein, a silicate concentration sensor is provided separately to measure the silicate concentration of the etching solution L in the processing tank 61, and the phosphoric acid concentration of the etching solution L may be controlled based on the measurement value of this silicate concentration sensor and the regrowth margin data shown in Figure 5.

[0146] This also allows etching to be performed within the desired range of etching selectivity without replenishing the etching solution L, thus reducing the amount of etching solution L used.

[0147] The substrate processing apparatus (substrate processing system 1) according to the embodiment comprises a substrate processing unit 110 and a control unit 9. The substrate processing unit 110 etches one or more substrates (wafers W) on which silicon nitride films and silicon oxide films are formed on their surfaces with a processing solution (etching solution L) containing an aqueous phosphoric acid solution and a silicate compound. The control unit 9 controls each part. The control unit 9 also has a concentration control unit 9d. The concentration control unit 9d controls the phosphoric acid concentration of the processing solution (etching solution L) from the start to the completion of the etching process so that the etching selectivity ratio of the silicon nitride film to the silicon oxide film is within a given range. This makes it possible to reduce the amount of etching solution L used in a technique for etching wafers W using an etching solution L containing an aqueous phosphoric acid solution.

[0148] Furthermore, the substrate processing apparatus (substrate processing system 1) according to this embodiment further includes a concentration sensor 125 for measuring the phosphoric acid concentration of the processing solution (etching solution L). The concentration control unit 9d controls the phosphoric acid concentration of the processing solution (etching solution L) based on the measurement result of the concentration sensor 125. This enables the etching process of the wafer W to be carried out with high accuracy.

[0149] Furthermore, in the substrate processing apparatus (substrate processing system 1) according to the embodiment, the concentration control unit 9d corrects the phosphoric acid concentration of the processing solution (etching solution L) based on data showing the relationship between the phosphoric acid concentration and the silicate concentration in the processing solution when the etching selectivity ratio is within a given range. This enables the etching process of the wafer W to be carried out with high accuracy.

[0150] Furthermore, in the substrate processing apparatus (substrate processing system 1) according to the embodiment, the given range is an arbitrary range. This allows the etching process of the embodiment to be performed within a range of etching selectivity ratios according to the user's wishes.

[0151] Furthermore, in the substrate processing apparatus (substrate processing system 1) according to the embodiment, when the same processing solution (etching solution L) is used continuously, the concentration control unit 9d maintains the phosphoric acid concentration of the processing solution (etching solution L) at a constant value during a certain etching process. Also, when the same processing solution (etching solution L) is used continuously, the concentration control unit 9d maintains the phosphoric acid concentration of the processing solution (etching solution L) at a constant value above a certain value during etching processes after a certain etching process. This makes it possible to reduce the amount of etching solution L used.

[0152] Furthermore, in the substrate processing apparatus (substrate processing system 1) according to the embodiment, the substrate processing unit 110 includes an inner tank 111, an outer tank 112, and a gas supply unit 140. The inner tank 111 has an opening 111a at its top, stores a processing solution (etching solution L), and immerses multiple substrates (wafers W) in it. The outer tank 112 is located outside the inner tank 111 and receives the processing solution (etching solution L) flowing out from the opening 111a. The gas supply unit 140 supplies inert gas to the bottoms of the inner tank 111 and the outer tank 112. In addition, the concentration control unit 9d controls the amount of inert gas supplied to at least one of the inner tank 111 and the outer tank 112 to increase the phosphoric acid concentration of the processing solution (etching solution L) in a stepwise manner. This makes it possible to increase the phosphoric acid concentration of the etching solution L in a stepwise manner by simple means.

[0153] Furthermore, in the substrate processing apparatus (substrate processing system 1) according to the embodiment, the control unit 9 has a determination unit 9c. The determination unit 9c determines whether or not etching is possible such that the etching selectivity ratio is within a given range from the start to the completion of the etching process. The determination unit 9c makes this determination based on the phosphoric acid concentration and silicate concentration of the processing solution in the inner tank 111 when the etching process is started, and the formation state of silicon nitride film and silicon oxide film on multiple substrates. As a result, even if the next etching process cannot be carried out within a given etching selectivity ratio range, the setting unit 9e can reset the phosphoric acid concentration, making the next etching process possible without problems.

[0154] Furthermore, in the substrate processing apparatus (substrate processing system 1) according to the embodiment, the control unit 9 has a setting unit 9e. The setting unit 9e sets a new phosphoric acid concentration that enables etching processing such that the etching selectivity ratio is within a given range from the start to the completion of the etching processing. The setting unit 9e also sets a new phosphoric acid concentration if the determination unit 9c determines that etching processing such that the etching selectivity ratio is not within a given range is not possible from the start to the completion of the etching processing. This ensures that even if the next etching processing cannot be performed within a given etching selectivity ratio range, the next etching processing can be performed without any problems.

[0155] Furthermore, in the substrate processing apparatus (substrate processing system 1) according to the embodiment, the control unit 9 has an acquisition unit 9a. The acquisition unit 9a acquires the formation state of silicon nitride film and silicon oxide film on multiple substrates (wafers W) based on the lot ID of a hoop H having the number of substrates (wafers W) and the processing recipe for the substrates (wafers W). This enables the etching process of wafers W to be carried out with high accuracy.

[0156] <Control Processing Procedure> Next, the procedure for the control processing according to the embodiment will be explained with reference to Figure 10. Figure 10 is a flowchart showing an example of the procedure for the control processing executed by the substrate processing system 1 according to the embodiment.

[0157] In the control process according to this embodiment, first, the control unit 9 adjusts the phosphoric acid concentration of the etching solution L in the replaced processing tank 61 to an initial value (initial concentration Ca) (see Figure 9) (step S101).

[0158] Next, the control unit 9 acquires wafer information for multiple wafers W housed in hoop H and scheduled to undergo etching, based on the lot ID of hoop H (step S102). In step S102, the number of wafers W scheduled to undergo etching, the formation status of silicon nitride films and silicon oxide films on multiple wafers W, and other information are acquired.

[0159] Next, the control unit 9 calculates a linear contour line L1 of the silicate compound concentration transition in the next etching process based on the acquired wafer information of the wafer W (step S103). Then, the control unit 9 calculates a linear contour line L2 of the phosphoric acid concentration transition in the next etching process based on the calculated linear contour line L1 of the silicate compound concentration transition (step S104).

[0160] Next, the control unit 9 calculates a curve L3 for the etching selectivity ratio in the next etching process based on the calculated straight line L1 for the silicate compound concentration transition and the straight line L2 for the phosphoric acid concentration transition (step S105).

[0161] Next, the control unit 9 determines whether the etching selectivity ratio is within a given range in the calculated etching selectivity ratio transition curve L3 (step S106).

[0162] Then, if it is determined that the etching selectivity ratio is within a given range (step S106, Yes), the control unit 9 loads multiple wafers W into the inner tank 111 of the processing tank 61 all at once (step S107). Then, the control unit 9 etches the multiple wafers W all at once in the processing tank 61 (step S108).

[0163] Next, the control unit 9 controls the phosphoric acid concentration of the etching solution L during the etching process based on the phosphoric acid concentration transition line L2 calculated in step S104 (step S109). Then, the control unit 9 removes the multiple wafers W that have been etched from the processing tank 61 (step S110) and returns to the process in step S102.

[0164] On the other hand, if it is determined that the etching selectivity ratio is not within a given range during the process in step S106 (step S106, No), the control unit 9 sets a new phosphoric acid concentration for the etching solution L in the processing tank 61 (step S111).

[0165] Next, the control unit 9 determines whether the newly set phosphoric acid concentration exceeds a given upper limit Cb (step S112). If it is determined that the newly set phosphoric acid concentration does not exceed the given upper limit (step S112, No), the process returns to step S103.

[0166] On the other hand, if it is determined that the phosphoric acid concentration exceeds a given upper limit (step S112, Yes), the etching solution L in the processing tank 61 is replaced with a new solution (step S113), and the series of substrate processing is terminated.

[0167] The substrate processing method according to the embodiment includes an etching step (step S108) and a concentration control step (step S109). The etching step (step S108) involves etching one or more substrates (wafers W) on which silicon nitride films and silicon oxide films are formed on their surfaces with a processing solution (etching solution L) containing phosphoric acid and a silicate compound. The concentration control step (step S109) controls the phosphoric acid concentration of the processing solution (etching solution L) from the start to the completion of the etching process so that the etching selectivity ratio of the silicon nitride film to the silicon oxide film is within a given range. This makes it possible to reduce the amount of etching solution L used in a technique for etching wafers W using an etching solution L containing an aqueous phosphoric acid solution.

[0168] While embodiments of this disclosure have been described above, this disclosure is not limited to the embodiments described above, and various modifications are possible without departing from its spirit.

[0169] The embodiments disclosed herein should be considered in all respects as illustrative and not restrictive. Indeed, the embodiments described above can be embodied in a variety of forms. Furthermore, the embodiments described above may be omitted, replaced, or modified in various ways without departing from the scope and spirit of the appended claims. [Explanation of symbols]

[0170] 1. Substrate Processing System (An Example of a Substrate Processing Device) 7 Control device 8 Memory section 8a Etching Information Storage Unit 9. Control Unit 9a Acquisition part 9b Calculation Unit 9c Judgment part 9d Concentration Control Unit 9e Settings Section 61 Processing tank 110 PCB Processing Unit 111 Inner tank 112 Outer tank 140 Gas Supply Department W wafer (an example of a substrate) L Etching solution (an example of a processing solution)

Claims

1. A substrate processing unit that etches one or more substrates on which a silicon nitride film and a silicon oxide film are formed on the surface with a processing solution containing phosphoric acid and a silicate compound, A control unit that controls each part, Equipped with, The control unit, The system includes a concentration control unit that controls the phosphoric acid concentration of the processing solution based on data showing the relationship between the phosphoric acid concentration and the silicate concentration in the processing solution when the etching selectivity ratio of the silicon nitride film to the silicon oxide film is within a given range, from the start to the completion of the etching process, When the same processing solution is used continuously, the concentration control unit maintains the phosphoric acid concentration of the processing solution at a constant value during a certain etching process, and maintains the phosphoric acid concentration of the processing solution at a value greater than or equal to the aforementioned value during etching processes that occur after that initial etching process. Circuit board processing equipment.

2. The system further comprises a concentration sensor for measuring the phosphate concentration of the processing solution, The concentration control unit controls the phosphate concentration of the processing solution based on the measurement results from the concentration sensor. The substrate processing apparatus according to claim 1.

3. The given range is an arbitrary range. The substrate processing apparatus according to claim 1 or 2.

4. The aforementioned substrate processing unit is An inner tank having an opening at the top, which stores the processing liquid and immerses a plurality of the substrates in it, An outer tank is positioned outside the inner tank and receives the processing liquid flowing out from the opening, A gas supply unit that supplies inert gas to the bottom of the inner tank and the outer tank, It has, The concentration control unit controls the amount of inert gas supplied to at least one of the inner tank and the outer tank, thereby increasing the phosphoric acid concentration of the processing liquid in a stepwise manner. The substrate processing apparatus according to claim 1 or 2.

5. The control unit, The system includes a determination unit that determines whether or not etching is possible from the start to the completion of the etching process such that the etching selectivity ratio falls within a given range, based on the phosphoric acid concentration and silicate concentration of the processing solution in the inner tank when the etching process is started, and the formation state of silicon nitride films and silicon oxide films on the plurality of substrates. The substrate processing apparatus according to claim 4.

6. The control unit, The device has a setting unit that, if the determination unit determines that etching is not possible to perform etching with the etching selectivity within the given range from the start to the completion of the etching process, sets a new phosphoric acid concentration to enable etching with the etching selectivity within the given range from the start to the completion of the etching process. The substrate processing apparatus according to claim 5.

7. The control unit, The unit includes an acquisition unit that acquires the formation state of silicon nitride films and silicon oxide films on multiple substrates based on the lot ID of a hoop having the number of substrates and the processing recipe for the substrates. The substrate processing apparatus according to claim 5.

8. An etching step in which one or more substrates on which a silicon nitride film and a silicon oxide film are formed on their surfaces are etched with a processing solution containing phosphoric acid and a silicate compound, From the start to the completion of the etching process, a concentration control step is performed to control the phosphoric acid concentration of the processing solution based on data showing the relationship between the phosphoric acid concentration and the silicate concentration in the processing solution when the etching selectivity ratio of the silicon nitride film to the silicon oxide film is within a given range, so that the etching selectivity ratio of the silicon nitride film to the silicon oxide film is within a given range. Includes, When the same processing solution is used continuously, the concentration control step maintains the phosphoric acid concentration of the processing solution at a constant value during a certain etching process, and maintains the phosphoric acid concentration of the processing solution at a value greater than or equal to the aforementioned value during etching processes that occur after that etching process. Substrate processing method.

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