Substrate processing method and substrate processing apparatus

Abstract

This substrate processing method comprises: preparing an aqueous solution containing hydrofluoric acid, nitric acid, and phosphoric acid in a liquid preparation unit; supplying the aqueous solution from the liquid preparation unit to a processing unit; etching a substrate by supplying the aqueous solution to the substrate by means of the processing unit; and returning the aqueous solution supplied to the substrate back to the liquid preparation unit from the processing unit. The substrate processing method comprises: measuring a difference in etching amount at the center of a surface of the substrate between a first substrate and a second substrate different from the first substrate during operation of the processing unit, and storing the difference in a storage unit in association with a blending ratio of the aqueous solution; and preparing the aqueous solution at a blending ratio such that the difference in etching amount between the first substrate and the second substrate during operation of the processing unit is equal to or less than a threshold value.

Description

Substrate processing method and substrate processing apparatus

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

[0002] The substrate processing method described in Patent Document 1 includes a step of grinding the substrate surface and a step of removing a damaged layer formed on the substrate surface by grinding. The step of removing the damaged layer includes a step of supplying a processing liquid to the substrate surface. The processing liquid is, for example, an aqueous solution containing hydrofluoric acid and nitric acid.

[0003] Japanese Patent Application Publication No. 2018-147908

[0004] One aspect of the present disclosure provides a technique for stabilizing the shape of an etching profile on a substrate surface using an aqueous solution containing hydrofluoric acid, nitric acid, and phosphoric acid.

[0005] A substrate processing method according to one aspect of the present disclosure includes preparing an aqueous solution containing hydrofluoric acid, nitric acid, and phosphoric acid in a solution preparation unit, supplying the aqueous solution from the solution preparation unit to a processing unit, etching the substrate by supplying the aqueous solution to the substrate by the processing unit, and returning the aqueous solution supplied to the substrate from the processing unit to the solution preparation unit. The substrate processing method includes measuring a difference in etching amount at the center of a surface of a first substrate and a second substrate different from the first substrate while the processing unit is operating, linking the difference to a compounding ratio of the aqueous solution and storing the result in a memory unit, and preparing the aqueous solution with a compounding ratio such that the difference in etching amount between the first substrate and the second substrate is equal to or less than a threshold while the processing unit is operating.

[0006] According to one aspect of the present disclosure, it is possible to stabilize the shape of an etching profile on a substrate surface using an aqueous solution containing hydrofluoric acid, nitric acid, and phosphoric acid.

[0007] FIG. 1 is a plan view showing a substrate processing apparatus according to an embodiment. FIG. 2 is a flowchart showing a substrate processing method according to an embodiment. FIG. 3 is a cross-sectional view showing an example of an etching apparatus. FIG. 4 is a diagram showing an example of a liquid circuit for an etching liquid. FIG. 5 is a diagram showing an example of an etching profile of a substrate surface processed by the etching apparatus. FIG. 6 is a diagram showing an example of the relationship between the etching profile of a substrate surface and the number of substrates processed during operation of the etching apparatus. FIG. 7 is a diagram showing an example of the relationship between the etching profile of the surface of the first substrate and the etching stop time after the operation of the etching apparatus is stopped. FIG. 8 is a diagram showing another example of the relationship between the etching profile of the surface of a substrate and the number of substrates processed during operation of the etching apparatus. FIG. 9 is a diagram showing another example of the relationship between the etching profile of the surface of the first substrate and the etching stop time after the operation of the etching apparatus is stopped.

[0008] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each drawing, the same or corresponding components are denoted by the same reference numerals, and their description may be omitted. In this specification, the X-axis, Y-axis, and Z-axis directions are perpendicular to each other. The X-axis and Y-axis directions are horizontal directions, and the Z-axis direction is vertical.

[0009] A substrate processing apparatus 1 according to one embodiment will be described with reference to Fig. 1 . The substrate processing apparatus 1 processes a substrate W. The substrate W includes, for example, a semiconductor wafer such as a silicon wafer. The substrate W may include multiple devices formed on the semiconductor wafer. The devices include, for example, electronic circuits. The substrate W may also be a laminated substrate formed by stacking multiple semiconductor wafers. A laminated substrate is obtained by bonding multiple semiconductor wafers together.

[0010] The substrate processing apparatus 1 includes a loading / unloading station 10, a processing station 20, and a control circuit 90. The loading / unloading station 10 and the processing station 20 are arranged in this order from the negative side of the X axis to the positive side of the X axis.

[0011] The loading / unloading station 10 includes a mounting table 11. Cassettes C1 and C2 are placed on the mounting table 11. Cassette C1 stores substrates W before processing. Cassette C2 stores substrates W after processing. The number of cassettes C1 and C2 is not particularly limited. A cassette not shown may store substrates W that have become defective during processing.

[0012] The loading / unloading station 10 includes a first transfer region 12 and a first transfer device 13. The first transfer region 12 is adjacent to the mounting table 11 and a transition device 21, which will be described later. The first transfer device 13 transfers the substrate W between a plurality of devices adjacent to the first transfer region 12. The first transfer device 13 includes a transfer arm that holds the substrate W and a drive unit that moves or rotates the transfer arm. The transfer arm is capable of moving horizontally (in both the X-axis and Y-axis directions) and vertically, and of rotating about a vertical axis. Multiple transfer arms may be provided.

[0013] The processing station 20 includes a transition device 21, a second transfer region 22, a second transfer device 23, a grinding device 24, a cleaning device 25, an etching device 26, and a measuring device 27. The arrangement and number of devices constituting the processing station 20 are not limited to those shown in FIG.

[0014] The transition device 21 temporarily stores the substrates W. The transition device 21 is provided between the first transport region 12 and the second transport region 22, and relays the substrates W between the first transport device 13 and the second transport device 23.

[0015] The second transfer region 22 is adjacent to the transition device 21, the grinding device 24, the cleaning device 25, the etching device 26, and the measuring device 27. The second transfer device 23 transfers the substrate W between the multiple devices adjacent to the second transfer region 22. The second transfer device 23 has a transfer arm that holds the substrate W and a drive unit that moves or rotates the transfer arm. The transfer arm is capable of moving in the horizontal direction (both in the X-axis direction and the Y-axis direction) and the vertical direction, and of rotating about the vertical axis. Multiple transfer arms may be provided.

[0016] The grinding device 24 grinds the substrate W. This allows the substrate W to be thinned. The grinding device 24 may grind one side of the substrate W, or may grind both sides of the substrate W. When grinding both sides of the substrate W, one side and the opposite side of the substrate W may be ground by separate grinding devices 24. The grinding device 24 grinds the substrate W, for example, by pressing a grinding wheel against the substrate W while rotating the grinding wheel and the substrate W.

[0017] The cleaning device 25 cleans the substrate W. It can remove grinding debris adhering to the substrate W. When the grinding device 24 grinds both sides of the substrate W, the cleaning device 25 cleans both sides of the substrate W. One side and the other side of the substrate W may be cleaned by different cleaning devices 25. The cleaning device 25 scrubs the substrate W with, for example, a brush or a sponge.

[0018] The etching device 26 etches the substrate W by supplying a processing liquid to the substrate W. Damaged layers caused by grinding the substrate W can be removed, and cracks in the substrate W can be suppressed. When the grinding device 24 grinds both surfaces of the substrate W, the etching device 26 etches both surfaces of the substrate W. One surface and the opposite surface of the substrate W may be etched by separate etching devices 26. Details of the etching device 26 will be described later.

[0019] The measuring device 27 measures the etching amount of the substrate W. In this embodiment, the measuring device 27 measures the etching amount over the entire radial direction of the surface of the substrate W, but may also measure the etching amount only at the center of the surface of the substrate W. The measuring device 27 includes, for example, a laser displacement meter. The measuring device 27 may be provided outside the substrate processing apparatus 1 and transmit the measurement results to the substrate processing apparatus 1.

[0020] The control circuit 90 is, for example, a computer, and includes an arithmetic unit 91 such as a CPU (Central Processing Unit), and a storage unit 92 such as a memory. The storage unit 92 stores programs that control various processes executed in the substrate processing apparatus 1. The control circuit 90 controls the operation of the substrate processing apparatus 1 by causing the arithmetic unit 91 to execute the programs stored in the storage unit 92. A lower-level control circuit that controls the operation of each device constituting the substrate processing apparatus 1 may be provided, and a higher-level control circuit that controls multiple lower-level control circuits may be provided. The control circuit 90 may be configured with the lower-level control circuit and the higher-level control circuit.

[0021] The control circuit 90 includes electronic circuits such as a CPU, a field programmable gate array (FPGA), or an application specific integrated circuit (ASIC), and performs the various control operations described in this specification by executing instruction codes stored in a memory or by being a circuit designed for a specific application.

[0022] Next, a substrate processing method according to one embodiment will be described with reference to Figure 2. The substrate processing method includes, for example, steps S101 to S103. Steps S101 to S103 are performed under the control of a control circuit 90.

[0023] First, the first transport device 13 takes the substrate W out of the cassette C1 and transports it to the transition device 21. Next, the second transport device 23 takes the substrate W out of the transition device 21 and transports it to the grinding device 24.

[0024] Next, the grinding device 24 grinds the substrate W (step S101), thereby thinning the substrate W. Thereafter, the second transport device 23 removes the substrate W from the grinding device 24 and transports it to the cleaning device 25.

[0025] Next, the cleaning device 25 cleans the substrate W (step S102), thereby removing grinding debris adhering to the substrate W. Thereafter, the second transport device 23 removes the substrate W from the cleaning device 25 and transports it to the etching device 26.

[0026] Next, the etching device 26 etches the substrate W (step S103). This can remove a damaged layer caused by grinding the substrate W and suppress cracking of the substrate W. Thereafter, the second transport device 23 takes the substrate W out of the etching device 26 and transports it to the transition device 21.

[0027] Finally, the first transport device 13 takes the substrate W out of the transition device 21 and stores it in the cassette C2. The second transport device 23 may transport the substrate W taken out of the etching device 26 to the measuring device 27. The measuring device 27 measures the etching amount of the substrate W. Thereafter, the first transport device 13 may take the substrate W out of the measuring device 27 and store it in the cassette C2.

[0028] The substrate W is unloaded from the substrate processing apparatus 1 while being accommodated in the cassette C2. As described above, the measuring device 27 may be provided outside the substrate processing apparatus 1, and may measure the etching amount of the substrate W outside the substrate processing apparatus 1. The measuring device 27 may transmit the measurement results to the substrate processing apparatus 1.

[0029] The substrate processing method may include step S103. For example, the substrate processing method may include forming a modified layer inside the substrate W with a laser beam and dividing the substrate W starting from the modified layer, instead of grinding the substrate W (step S101). In either case, the substrate W can be thinned.

[0030] Next, an example of an etching apparatus 26 will be described with reference to Figure 3. The etching apparatus 26 is an example of a processing section. The processing section supplies a processing liquid L to the substrates W. In this embodiment, the processing section is of a single-wafer type that processes substrates W one by one, but it may also be of a batch type that processes multiple substrates W simultaneously. A single-wafer type processing section will be described below.

[0031] The etching device 26 includes, for example, a processing vessel 31 , a substrate holder 34 , a substrate rotation unit 35 , a nozzle 36 , a nozzle movement unit 37 , a cup 38 , a drain pipe 39 , and an exhaust pipe 40 .

[0032] The processing vessel 31 accommodates a substrate holder 34 and the like. A gate 32 and a gate valve 33 for opening and closing the gate 32 are provided on the sidewall of the processing vessel 31. The substrate W is loaded into the processing vessel 31 through the gate 32 by the second transfer device 23 (see FIG. 1 ). Next, the substrate W is processed with the processing liquid L inside the processing vessel 31. Thereafter, the substrate W is unloaded from the processing vessel 31 through the gate 32 by the second transfer device 23.

[0033] The substrate holder 34 is provided inside the processing vessel 31 and holds the substrate W horizontally. The substrate holder 34 has, for example, claws 34a that hold the outer periphery of the substrate W. A plurality of claws 34a are provided at equal intervals in the circumferential direction of the substrate W. Although not shown, the substrate holder 34 may vacuum-suck the lower surface of the substrate W.

[0034] The substrate rotating unit 35 rotates the substrate holding unit 34, thereby rotating the substrate W together with the substrate holding unit 34. The substrate rotating unit 35 includes a motor and the like.

[0035] The nozzle 36 supplies the processing liquid L to the substrate W. The nozzle 36 supplies the processing liquid L to, for example, the rotating substrate W. The processing liquid L includes, for example, an etching liquid and a rinse liquid. The etching liquid is a mixture of hydrofluoric acid (HF) and nitric acid (HNO ３ ) and phosphoric acid (H ３ P.O. ４ The rinsing liquid is a pure water such as DIW (deionized water). The nozzle 36 supplies the etching liquid and the rinsing liquid to the substrate W in this order. The etching liquid and the rinsing liquid may be supplied by separate nozzles 36. The nozzle 36 is connected to a supply unit 60, which will be described later.

[0036] The nozzle moving unit 37 moves the nozzle 36 in the horizontal direction. The nozzle moving unit 37 moves the nozzle 36, for example, in the radial direction of the substrate W. The nozzle moving unit 37 includes, for example, an arm 37 a that holds the nozzle 36 and a drive unit 37 b that rotates the arm 37 a.

[0037] The cup 38 surrounds the outer periphery of the substrate W held by the substrate holder 34 and collects the processing liquid L that splashes from the outer periphery of the substrate W.

[0038] The drain pipe 39 and the exhaust pipe 40 are provided at the bottom of the cup 38. The drain pipe 39 discharges the processing liquid L that has accumulated inside the cup 38. The drain pipe 39 is connected to a recovery unit 70, which will be described later. The exhaust pipe 40 discharges gas that has accumulated inside the cup 38.

[0039] Next, an example of a liquid circuit for the etching liquid LA will be described with reference to Fig. 4. As shown in Fig. 4, the substrate processing apparatus 1 includes a liquid preparation unit 50, a supply unit 60, and a recovery unit 70. The liquid preparation unit 50 prepares the etching liquid LA. The supply unit 60 supplies the etching liquid LA from the liquid preparation unit 50 to the etching apparatus 26. The recovery unit 70 returns the etching liquid LA from the etching apparatus 26 to the liquid preparation unit 50. The substrate processing apparatus 1 reuses the etching liquid LA. This allows for a reduction in the amount of etching liquid LA that is discarded.

[0040] The liquid preparation unit 50 includes a storage unit 51. The storage unit 51 is, for example, a storage tank, and stores the etching solution LA. The liquid preparation unit 50 also includes a circulation line 52, a pump 53, a filter 54, and a flow meter 55. The circulation line 52 extracts the etching solution LA from the storage unit 51 and returns it to the storage unit 51. By circulating the etching solution LA, the component concentrations can be made uniform.

[0041] A pump 53, a filter 54, and a flow meter 55 are provided in the circulation line 52. The pump 53 pumps out the etching solution LA. The filter 54 collects foreign matter in the etching solution LA. The flow meter 55 detects the flow rate of the etching solution LA. A control circuit 90 controls the pump 53 to maintain a constant output.

[0042] A thermometer and a heater (not shown) may be provided along the circulation line 52. The thermometer detects the temperature of the etching solution LA. The heater heats the etching solution LA. The control circuit 90 controls the heater so that the detected value of the thermometer becomes the set value.

[0043] The solution preparation unit 50 includes a hydrofluoric acid supply unit 56. The hydrofluoric acid supply unit 56 supplies hydrofluoric acid to the storage unit 51. The hydrofluoric acid supply unit 56 includes a supply line 56a connecting a hydrofluoric acid supply source to the storage unit 51, and an adjustment unit 56b that adjusts the amount of hydrofluoric acid supplied. The adjustment unit 56b includes, for example, an open / close valve and a metering tank. The metering tank measures the amount of hydrofluoric acid supplied at one time. The metering tank is provided with a metering meter. The adjustment unit 56b may include a flow meter and a flow rate controller instead of the metering tank.

[0044] The liquid preparation unit 50 includes a nitric acid supply unit 57. The nitric acid supply unit 57 supplies nitric acid to the storage unit 51. The nitric acid supply unit 57 includes a supply line 57a connecting a nitric acid supply source to the storage unit 51, and an adjustment unit 57b that adjusts the amount of nitric acid supplied. The adjustment unit 57b includes, for example, an open / close valve and a metering tank. The metering tank measures the amount of nitric acid to be supplied at one time. The metering tank is provided with a metering meter. The adjustment unit 57b may include a flow meter and a flow rate controller instead of the metering tank.

[0045] The solution preparation unit 50 includes a phosphoric acid supply unit 58. The phosphoric acid supply unit 58 supplies phosphoric acid to the storage unit 51. The phosphoric acid supply unit 58 includes a supply line 58a connecting a phosphoric acid supply source to the storage unit 51, and an adjustment unit 58b that adjusts the amount of phosphoric acid supplied. The adjustment unit 58b includes, for example, an on-off valve and a metering tank. The metering tank measures the amount of phosphoric acid to be supplied in one go. The metering tank is provided with a metering meter. The adjustment unit 58b may include a flow meter and a flow rate controller instead of the metering tank.

[0046] The etching solution LA is reused. As the number of processed substrates W increases, hydrofluoric acid and nitric acid are consumed by reacting with the substrates W. Therefore, the liquid preparation unit 50 replenishes predetermined amounts of hydrofluoric acid, nitric acid, and phosphoric acid to the reservoir 51 based on the number of processed substrates W or the cumulative discharge amount of the etching solution LA from the nozzle 36. Note that although phosphoric acid does not react with the substrates W and is not consumed, the recovery rate of the etching solution LA is not 100%, so the liquid preparation unit 50 replenishes phosphoric acid in addition to hydrofluoric acid and nitric acid. This allows the concentrations of each component of the etching solution LA to be maintained at set values.

[0047] The liquid preparation unit 50 includes a pure water supply unit 59. The pure water supply unit 59 supplies pure water to the storage unit 51. The pure water supply unit 59 includes a supply line 59a connecting a pure water supply source to the storage unit 51, and an adjustment unit 59b that adjusts the amount of pure water supplied. The adjustment unit 59b includes, for example, an on-off valve and a metering tank. The metering tank measures the amount of water to be supplied at one time. The metering tank is provided with a metering meter. The adjustment unit 59b may include a flow meter and a flow rate controller instead of the metering tank.

[0048] The supply unit 60 includes, for example, a supply line 61, a flow meter 62, a flow rate controller 63, and an on-off valve 64. The supply line 61 connects the solution preparation unit 50 and the etching device 26. For example, the supply line 61 connects the circulation line 52 of the solution preparation unit 50 and the nozzle 36 of the etching device 26 (see FIG. 3 ).

[0049] A flow meter 62, a flow rate controller 63, and an on-off valve 64 are provided in the supply line 61. The flow meter 62 detects the flow rate of the etching liquid LA. The flow rate controller 63 controls the flow rate of the etching liquid LA. A control circuit 90 controls the flow rate controller 63 so that the detected value of the flow meter 62 becomes a set value. The on-off valve 64 opens and closes the flow path of the supply line 61.

[0050] A supply unit 60 is provided for each etching apparatus 26. Accordingly, a supply line 61 is provided for each etching apparatus 26. Although not shown, a plurality of supply lines 61 may connect a plurality of etching apparatuses 26 to one liquid preparation unit 50. The liquid preparation unit 50 may collectively prepare the etching solution LA to be used in a plurality of etching apparatuses 26.

[0051] The recovery unit 70 has a recovery line 71. The recovery line 71 connects the etching device 26 and the solution preparation unit 50. For example, the recovery line 71 connects the drain pipe 39 (see FIG. 3 ) of the etching device 26 and the storage unit 51 of the solution preparation unit 50. A filter 72 may be provided midway along the recovery line 71. The filter 72 collects foreign matter in the etching solution LA.

[0052] The waste unit 75 wastes the etching liquid LA stored in the storage unit 51. The etching liquid LA is disposed of periodically, and is disposed of appropriately, for example, according to the time elapsed since replacement of the etching liquid LA or the number of processed substrates W. The waste unit 75 has a discharge line 75a connected to the storage unit 51 and an opening / closing valve 75b that opens and closes the flow path of the discharge line 75a.

[0053] The etching device 26 repeatedly etches the substrate W. As described above, the etching solution LA is a mixture of hydrofluoric acid (HF) and nitric acid (HNO ３ ) and phosphoric acid (H ３ P.O. ４ The aqueous solution contains nitric acid (HNO ３ ) and coexisting nitrous acid (HNO ２ ) HNO ２ When the substrate W is a silicon wafer, etching of the silicon wafer is considered to proceed according to the following chemical reaction formulas (1) and (2): (1) Si + 4HNO ２ →SiO ２ +4NO+2H ２ O (2) SiO ２ +6HF→H ２ SiF ６ +2H ２ O In addition, phosphoric acid (H ３ P.O. ４ ) is a component that adjusts the viscosity of the etching solution LA. The higher the proportion of phosphoric acid, the higher the viscosity of the etching solution LA.

[0054] As the number of processed substrates W increases, the color of the etching solution LA changes from colorless to reddish brown. The reason why the color of the etching solution LA changes is that NO, which is a product of the above chemical reaction formula (1), is oxidized according to the following chemical reaction formula (3), for example, to produce NO ２ It is presumed that this is because NO is generated. ２ is reddish brown. (3) 2NO + O ２ →2NO ２ .

[0055] The etching profile of the substrate surface will be described with reference to Figure 5. The etching profile refers to the variation in the amount of etching depending on the distance from the center of the substrate surface. The etching profile is shown in a graph in which the horizontal axis represents the distance from the center of the substrate surface and the vertical axis represents the amount of etching. In Figure 5, the horizontal axis represents the distance from the center of the substrate surface, the vertical axis represents the amount of etching, and the solid line L1 represents the etching profile. The solid line L1 can be broken down into a dashed line L2 derived from the nitrous acid concentration distribution and a dashed line L3 derived from the flow rate distribution.

[0056] As shown by the solid line L1 in Fig. 5, within a certain range from the center of the substrate surface, the etching amount increases as the distance from the center of the substrate surface increases. This is thought to be because, after the etching solution LA is supplied to the center of the substrate surface, in the process of wetting and spreading radially outward on the substrate surface due to centrifugal force, in addition to the reaction represented by the above chemical reaction formula (1), the reaction represented by the following chemical reaction formula (4) progresses, increasing the concentration of nitrous acid. (4) 2NO + HNO ３ +H ２ O → 3HNO ２ .

[0057] As is clear from chemical reaction formula (1), for example, 4 moles of HNO ２ is consumed, 4 moles of NO are produced, and as is clear from chemical reaction formula (4), 6 moles of HNO are produced by consuming 4 moles of NO. ２ Therefore, the greater the distance from the center of the substrate surface, the higher the concentration of nitrous acid. The higher the concentration of nitrous acid, the more easily the reaction of chemical reaction formula (1) proceeds. Therefore, the higher the concentration of nitrous acid, the faster the etching rate and the greater the etching amount.

[0058] However, when the nitrous acid concentration becomes sufficiently high, the increase in etching rate accompanying the increase in nitrous acid concentration slows down. Therefore, when the distance from the center of the substrate surface exceeds a certain level, the etching amount becomes governed by the flow rate distribution. The flow rate changes depending on the distance from the center of the substrate surface. Basically, the greater the distance from the center of the substrate surface, the greater the centrifugal force and the faster the flow rate. The faster the flow rate, the thinner the liquid film and the smaller the etching amount.

[0059] The etching profile shown in Figure 5 is an example. The etching profile can be adjusted by the rotation speed of the substrate W, etc. The higher the rotation speed of the substrate W, the faster the flow rate. Therefore, the flow rate distribution can be changed by the rotation speed of the substrate W, and the etching profile can be changed. The target etching profile only needs to be set so that the final substrate surface is flat, and can be set in accordance with the height distribution of the substrate surface after grinding.

[0060] 6 shows an example of the relationship between the etching profile of the substrate surface and the number of substrates W processed during operation of the etching apparatus 26. In FIG. 6, the phosphoric acid concentration in the etching solution LA is the conventional set value M1. Conventionally, as shown in FIG. 6, as the number of processed substrates increases, the amount of etching at the center of the substrate surface sometimes increases. This is thought to be because the reaction of the above chemical reaction formula (4) progresses as the number of processed substrates W increases, resulting in an increase in the nitrite concentration in the etching solution LA. The etching solution LA with an increased nitrite concentration accumulates in the reservoir 51.

[0061] The etching solution LA is supplied from the reservoir 51 to the nozzle 36, and then supplied from the nozzle 36 to the center of the substrate surface, whereupon it spreads radially outwardly across the substrate surface due to centrifugal force. If the nitrite concentration of the etching solution LA is high when it is dropped onto the center of the substrate surface, the amount of etching at the center of the substrate surface is large. Therefore, in the past, as the number of processed substrates W increased, the amount of etching at the center of the substrate surface sometimes increased, as shown in FIG.

[0062] 7 shows an example of the relationship between the etching profile of the surface of the first substrate after the operation of the etching apparatus 26 is stopped and the etching stop time ΔT. The etching stop time ΔT is the time during which the operation of the etching apparatus 26 is stopped, i.e., the time during which the etching apparatus 26 temporarily stops etching the substrate W. Hereinafter, the first substrate W after the operation is stopped may be referred to as the first substrate after the operation is restarted. In FIG. 7, the phosphoric acid concentration in the etching solution LA is the conventional set value M1, as in FIG. 6.

[0063] Conventionally, as shown in Figure 7, as the etching stop time ΔT becomes longer, the etching amount at the center of the first substrate surface after restarting operation becomes smaller than the etching amount at the periphery. This is thought to be because the longer the etching stop time ΔT, the more the reaction of the following chemical reaction formula (5) progresses, and the decomposition of nitrous acid progresses. (5) 3HNO ２ →HNO ３ +H ２ O+2NO.

[0064] Chemical reaction formula (5) is the reverse reaction of chemical reaction formula (4). Which of the two chemical reaction formulas (4) and (5) is dominant depends, for example, on whether or not the etching solution LA is in contact with the substrate W. When the etching solution LA is in contact with the substrate W, the reaction of chemical reaction formula (1) proceeds due to the presence of Si, and NO, which is the reactant of chemical reaction formula (4), is produced, so the reaction of chemical reaction formula (4) proceeds. On the other hand, when the etching solution LA is not in contact with the substrate W, the reaction of chemical reaction formula (1) does not proceed due to the absence of Si, and the reaction of chemical reaction formula (5) proceeds instead of chemical reaction formula (4).

[0065] During the etching stop time ΔT, the etching device 26 temporarily stops etching the substrate W, and the etching solution LA does not come into contact with the substrate W. Therefore, the longer the etching stop time ΔT, the more the reaction of chemical reaction formula (5) progresses, and the more the decomposition of nitrous acid progresses. As a result, the nitrous acid concentration of the etching solution LA decreases. The etching solution LA with a reduced nitrous acid concentration accumulates in the reservoir 51.

[0066] The etching solution LA with a reduced nitrite concentration is supplied from the reservoir 51 to the nozzle 36, and then supplied from the nozzle 36 to the center of the substrate surface, whereupon it spreads radially outwardly around the substrate surface due to centrifugal force. If the nitrite concentration of the etching solution LA is low at the center of the substrate surface, the amount of etching is small. Therefore, as shown in Figure 7, it has been considered that, in the past, the longer the etching stop time ΔT, the smaller the amount of etching at the center of the first substrate surface after operation is resumed.

[0067] During the shutdown of the etching apparatus 26, the supply unit 60 temporarily stops supplying the etching liquid LA from the storage unit 51 to the etching apparatus 26. The open / close valve 64 of the supply unit 60 temporarily closes the flow path of the supply line 61. However, during the shutdown of the etching apparatus 26, the pump 53 of the liquid preparation unit 50 does not stop, and the circulation line 52 continues to extract the etching liquid LA from the storage unit 51 and return it to the storage unit 51. By circulating the etching liquid LA, the component concentrations can be made uniform.

[0068] During the shutdown of the etching device 26, the following chemical reaction (6) occurs: ２ The color of the etching solution LA gradually decreases, and the color returns from reddish brown to colorless. (6) 2NO ２ +H ２ O → HNO ３ +HNO ２ .

[0069] After the operation of the etching apparatus 26 is stopped, when the first transport device 13 and the second transport device 23 resume transporting the substrates W, the etching apparatus 26 resumes etching the substrates W. The etching stop time ΔT varies depending on the processing plan for the substrates W. Conventionally, the shape of the etching profile of the first substrate W after restarting operation may vary depending on the etching stop time ΔT.

[0070] The inventors of the present application have investigated stabilizing the shape of the etching profile by increasing the phosphoric acid concentration of the etching solution LA. If the phosphoric acid concentration of the etching solution LA is high, the viscosity of the etching solution LA increases, and the etching solution LA stays at the center of the substrate surface for a longer period of time. Therefore, even if the nitrite concentration of the etching solution LA is low when it is dropped onto the center of the substrate surface, the nitrite concentration will be sufficiently high due to the reaction of chemical reaction formula (4). As a result, it is believed that the shape of the etching profile can be stabilized.

[0071] FIG. 8 shows an example of the relationship between the etching profile of the substrate surface and the number of substrates W processed during operation of the etching apparatus 26. In FIG. 8, the phosphoric acid concentration in the etching solution LA is M2 (M2>M1), which is higher than the conventional set value M1. As shown in FIG. 8, as the number of substrates W processed increases, the components contributing to etching are consumed, and the etching amount decreases across the entire substrate surface. However, the shape of the etching profile remains constant, and the flatness of the substrate surface remains constant. Furthermore, when the phosphoric acid concentration is M2 (M2>M1), the variation in the etching amount at the center of the substrate surface is smaller than when the phosphoric acid concentration is M1.

[0072] 9 shows an example of the relationship between the etching profile of the surface of the first substrate after the etching apparatus is shut down and the etching stop time. In FIG. 9, the phosphoric acid concentration in the etching solution LA is M2 (M2>M1), which is higher than the conventional set value M1. As shown in FIG. 9, the nitrite concentration decreases as the etching stop time ΔT increases, and therefore the etching amount decreases over the entire substrate surface. However, the shape of the etching profile remains constant, and the flatness of the substrate surface remains constant.

[0073] As described above, if the concentration of phosphoric acid in the etching solution LA is high, the shape of the etching profile becomes stable. However, the compounding ratio of the etching solution LA at which the shape of the etching profile becomes stable also depends on etching conditions other than the compounding ratio (e.g., the rotation speed of the substrate W). Therefore, in this embodiment, an experiment is performed with etching conditions other than the compounding ratio fixed, and the compounding ratio is determined based on the experimental results.

[0074] Specifically, for example, the control circuit 90 performs a first control to measure the difference in the etching amount at the center of the substrate surface between a first substrate (substrate A) and a second substrate (substrate B) different from the first substrate while the etching apparatus 26 is in operation, and stores the difference in the etching amount in the memory unit 92 in association with the compounding ratio of the etching solution LA. The control circuit 90 performs the first control described above for each compounding ratio of the etching solution LA. Multiple compounding ratios of the etching solution LA are prepared. The measuring device 27 measures the etching amount. The measuring device 27 is an example of a measuring unit. B may be greater than A. A is preferably 1, but is not limited to 1. The difference between B and A is preferably 100 or more, more preferably 200 or more. The difference between B and A is preferably 1800 or less, more preferably 1200 or less, and even more preferably 600 or less.

[0075] The control circuit 90 controls the preparation of the etching solution LA at a compounding ratio such that the difference in etching amount between substrates A and B is equal to or less than a threshold value while the etching device 26 is in operation. By etching the substrates W using the prepared etching solution LA, it is possible to prevent the shape of the etching profile on the substrate surface from changing as the number of processed substrates W increases while the etching device 26 is in operation.

[0076] If the etching solution LA is prepared at a compounding ratio that makes the difference in etching amount between the Ath substrate and the Bth substrate less than a threshold value while the etching apparatus 26 is in operation, it is possible to prevent the shape of the etching profile of the first substrate W after operation is resumed from changing depending on the etching stop time ΔT. However, the control circuit 90 may perform the second control described below in order to actively eliminate the influence of the etching stop time ΔT on the etching profile.

[0077] The control circuit 90 performs second control by measuring the difference in the etching amount at the center of the surface of the first substrate after the operation of the etching apparatus 26 is resumed between a first time (time C) when the operation of the etching apparatus 26 is stopped and a second time (time D) different from the first time, and storing the difference in the etching amount in a memory unit in association with the compounding ratio of the etching liquid LA. The control circuit 90 performs the second control described above for each compounding ratio of the etching liquid LA. Multiple compounding ratios of the etching liquid LA are prepared. The measuring device 27 measures the etching amount. D may be greater than C. C is preferably 0, but is not limited to 0. The difference between D and C is preferably 1 hour (1 h) or more, more preferably 2 hours (2 h) or more. The difference between D and C is preferably 18 hours (18 h) or less, more preferably 10 hours (10 h) or less. It is preferable to etch 100 or more substrates W before the operation of the etching apparatus 26 is stopped.

[0078] The control circuit 90 controls the preparation of the etching solution LA at a compounding ratio such that the difference in etching amount between operation downtimes C and D is equal to or less than a threshold value. By etching the substrate W using the prepared etching solution LA, it is possible to prevent the shape of the etching profile of the first substrate W after operation is resumed from changing depending on the etching downtime ΔT.

[0079] If the etching solution LA is prepared at a compounding ratio such that the difference in etching amount between the operation shutdown times C and D is equal to or less than a threshold value, it is possible to prevent the shape of the etching profile of the substrates W from changing depending on the number of processed substrates W during operation of the etching apparatus 26. However, the control circuit 90 may perform the first control described above in order to actively eliminate the influence of the number of processed substrates W on the etching profile.

[0080] 4, the substrate processing apparatus 1 may include a concentration sensor S1 that measures the phosphoric acid concentration of the etching solution LA. In FIG. 4, the concentration sensor S1 is provided in the circulation line 52, but may also be provided in the reservoir 51. The installation position of the concentration sensor S1 is not particularly limited.

[0081] The control circuit 90 controls the supply of phosphoric acid to the etching solution LA so that the measurement value of the concentration sensor S1 becomes equal to or greater than the lower limit. When the measurement value of the concentration sensor S1 falls below the lower limit, the control circuit 90 activates the phosphoric acid supply unit 58. The lower limit is set in advance by experiment or the like so that the shape of the etching profile is stabilized.

[0082] When the measurement value of the concentration sensor S1 exceeds the upper limit, the control circuit 90 may stop the phosphoric acid supply unit 58. This, for example, can prevent unnecessary replenishment of phosphoric acid. Furthermore, excessive decreases in the hydrofluoric acid concentration and nitric acid concentration of the etching solution LA due to the replenishment of phosphoric acid can be suppressed, and excessive decreases in the etching rate can be suppressed. The upper limit is set based on the lower limit.

[0083] 4, the substrate processing apparatus 1 may include a viscosity sensor S2 that measures the viscosity of the etching solution LA. In FIG. 4, the viscosity sensor S2 is provided in the circulation line 52, but may be provided in the reservoir 51. The installation position of the viscosity sensor S2 is not particularly limited.

[0084] The control circuit 90 controls the supply of phosphoric acid to the etching solution LA so that the measurement value of the viscosity sensor S2 is equal to or greater than the lower limit. When the measurement value of the viscosity sensor S2 falls below the lower limit, the control circuit 90 activates the phosphoric acid supply unit 58. The lower limit is set in advance by experiment or the like so that the shape of the etching profile is stabilized.

[0085] When the measurement value of the viscosity sensor S2 exceeds the upper limit, the control circuit 90 may stop the phosphoric acid supply unit 58. This, for example, can prevent unnecessary replenishment of phosphoric acid. Furthermore, excessive decreases in the hydrofluoric acid concentration and nitric acid concentration of the etching solution LA due to the replenishment of phosphoric acid can be suppressed, and excessive decreases in the etching rate can be suppressed. The upper limit is set based on the lower limit.

[0086] The control circuit 90 may monitor the measurement value of the flow meter 55 while performing control to maintain the output of the pump 53 constant. If the output of the pump 53 is constant, the flow rate of the etching liquid LA decreases as the viscosity of the etching liquid LA increases. Therefore, the control circuit 90 may perform control to replenish phosphoric acid to the etching liquid LA so that the measurement value of the flow meter 55 is equal to or less than the upper limit. If the measurement value of the flow meter 55 is equal to or less than the upper limit, the viscosity of the etching liquid LA becomes equal to or greater than the lower limit.

[0087] When the measurement value of the flow meter 55 falls below the first lower limit, the control circuit 90 may stop the phosphoric acid supply unit 58. This, for example, can stop the unnecessary supply of phosphoric acid. Furthermore, excessive decreases in the hydrofluoric acid concentration and nitric acid concentration of the etching solution LA due to the supply of phosphoric acid can be suppressed, and excessive decreases in the etching rate can be suppressed. The first lower limit is set based on the upper limit.

[0088] The control circuit 90 may perform control to notify an abnormality when the measurement value of the flow meter 55 falls below a second lower limit. The control circuit 90 performs control to notify an abnormality by controlling an image display device, a warning light, a buzzer, etc. The second lower limit is a value lower than the first lower limit.

[0089] Although the embodiments of the substrate processing method and substrate processing apparatus according to the present disclosure have been described above, the present disclosure is not limited to the above embodiments. Various changes, modifications, substitutions, additions, deletions, and combinations are possible within the scope of the claims. These naturally fall within the technical scope of the present disclosure.

[0090] This application claims priority based on Japanese Patent Application No. 2023-122279 filed with the Japan Patent Office on July 27, 2023, the entire contents of which are incorporated herein by reference.

[0091] 1 Substrate processing apparatus 26 Etching apparatus (processing section) 50 Liquid preparation section 60 Supply section 70 Recovery section 90 Control circuit

Claims

1. A substrate processing method comprising: preparing an aqueous solution containing hydrofluoric acid, nitric acid, and phosphoric acid in a solution preparation unit; supplying the aqueous solution from the solution preparation unit to a processing unit; etching the substrate by supplying the aqueous solution to the substrate by the processing unit; and returning the aqueous solution supplied to the substrate from the processing unit to the solution preparation unit; measuring a difference in the amount of etching at the center of the surface of a first substrate between a first substrate and a second substrate different from the first substrate while the processing unit is operating, linking the difference to a compounding ratio of the aqueous solution and storing the result in a memory unit; and preparing the aqueous solution with a compounding ratio such that the difference in the amount of etching between the first substrate and the second substrate is equal to or less than a threshold while the processing unit is operating.

2. The substrate processing method according to claim 1, further comprising: measuring a phosphoric acid concentration of said aqueous solution; and replenishing said aqueous solution with phosphoric acid so that the measured phosphoric acid concentration of said aqueous solution becomes equal to or exceeds a lower limit value.

3. The substrate processing method according to claim 1 or 2, further comprising: measuring a viscosity of the aqueous solution; and supplying phosphoric acid to the aqueous solution so that the measured viscosity of the aqueous solution becomes equal to or exceeds a lower limit.

4. A substrate processing method as described in claim 1 or 2, wherein the solution preparation section comprises a storage section for storing the aqueous solution, a circulation line for extracting the aqueous solution from the storage section and returning it to the storage section, a pump provided in the circulation line, and a flow meter provided in the circulation line, and the substrate processing method comprises controlling an output of the pump to a constant value, and supplying phosphoric acid to the aqueous solution so that the measurement value of the flow meter is equal to or lower than an upper limit value.

5. The substrate processing method according to claim 4, further comprising the step of notifying an abnormality when the measurement value of the flow meter falls below a lower limit value.

6. The substrate processing method according to claim 1 or 2, comprising: measuring a difference in the amount of etching at the center of the surface of the first substrate after operation is resumed between a first time when the processing unit is stopped and a second time different from the first time, linking the difference to a compounding ratio of the aqueous solution and storing the result in a memory unit; and preparing the aqueous solution with a compounding ratio such that the difference in the amount of etching between the first time when the processing unit is stopped and the second time is equal to or less than a threshold value.

7. A substrate processing apparatus comprising: a processing section for etching a substrate by supplying an aqueous solution containing hydrofluoric acid, nitric acid, and phosphoric acid to the substrate; a liquid preparation section for preparing the aqueous solution; a supply section for supplying the aqueous solution from the liquid preparation section to the processing section; and a recovery section for returning the aqueous solution from the processing section to the liquid preparation section; a measurement section for measuring a difference in the amount of etching at the center of the surface of a first substrate and a second substrate different from the first substrate while the processing section is in operation; a memory section for storing the difference in the amount of etching measured by the measurement section in association with a compounding ratio of the aqueous solution; and a control circuit for controlling the preparation of the aqueous solution at a compounding ratio such that the difference in the amount of etching between the first substrate and the second substrate is equal to or less than a threshold while the processing section is in operation.

8. The substrate processing apparatus according to claim 7, further comprising a concentration sensor for measuring a phosphoric acid concentration in the aqueous solution, and wherein the control circuit controls the supply of phosphoric acid to the aqueous solution so that the measured value of the phosphoric acid concentration in the aqueous solution becomes equal to or exceeds a lower limit value.

9. A substrate processing apparatus as claimed in claim 7 or 8, further comprising a viscosity sensor for measuring the viscosity of the aqueous solution, and wherein the control circuit controls the supply of phosphoric acid to the aqueous solution so that the measured viscosity of the aqueous solution becomes equal to or exceeds a lower limit value.

10. A substrate processing apparatus as described in claim 7 or 8, wherein the solution preparation unit has a storage section for storing the aqueous solution, a circulation line for extracting the aqueous solution from the storage section and returning it to the storage section, a pump provided in the circulation line, and a flow meter provided in the circulation line, and the control circuit performs control to maintain an output of the pump constant and control to replenish phosphoric acid to the aqueous solution so that the measurement value of the flow meter is equal to or lower than an upper limit value.

11. The substrate processing apparatus according to claim 10, wherein the control circuit performs control to notify an abnormality when the measurement value of the flow meter falls below a lower limit value.

12. A substrate processing apparatus as described in claim 7 or 8, wherein the measurement unit measures a difference in the amount of etching at the center of the surface of the first substrate after operation is resumed between a first time when the processing unit is down and a second time different from the first time, the memory unit stores the difference in the amount of etching measured by the measurement unit in association with a compounding ratio of the aqueous solution, and the control circuit controls the preparation of the aqueous solution at a compounding ratio such that the difference in the amount of etching between the first time when the processing unit is down and the second time is equal to or less than a threshold value.

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