Substrate processing method and substrate processing system

Abstract

In the present invention, deriving a fixed replenishment amount for replenishing an etching solution includes: using a test etching solution to perform etching on a test etching target of a test substrate, and generating a reusable test etching solution after etching; replenishing the reusable test etching solution with an inert liquid and estimating the total amount of substances in the reusable test etching solution prior to replenishment with the inert liquid on the basis a test replenishment etching solution after replenishment with the inert liquid; using the estimated total amount of substances in the reusable test etching solution to calculate the total replenishment amount by mathematical optimization such that the absolute error is minimized between a target composition concentration for the reusable test etching solution and a composition concentration of the reusable test etching solution after replenishing the reusable test etching solution with the total replenishment amount of a treatment liquid; and deriving the replenishment amount by using the total replenishment amount and an integrated etching amount of the test etching target.

Description

Substrate processing method and substrate processing system

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

[0002] Patent Document 1 discloses a substrate processing method including a grinding step of grinding the surface of a substrate, a measuring step of measuring the thickness of the ground substrate, a condition determination step of determining processing conditions for a wet etching process to be performed on the substrate based on the measured thickness of the substrate, and a step of supplying a processing liquid to the ground substrate and performing the wet etching process based on the determined processing conditions.

[0003] Japanese Patent Application Laid-Open No. 2018-147908

[0004] The technology according to the present disclosure appropriately reuses the etching liquid used when etching an etching target on a substrate.

[0005] One aspect of the present disclosure is a substrate processing method for processing a substrate, the method comprising: supplying an etching liquid containing a plurality of processing liquids to an etching target on a substrate, and etching the etching target; recovering the etching liquid after etching, and performing a recycling process of replenishing a certain amount of the processing liquid to the etching liquid when a replenishment condition is satisfied, thereby generating a recycled etching liquid for etching a subsequent etching target; and deriving the replenishment amount by performing a recycling process of etching a test etching target on a test substrate using a test etching liquid that is not subjected to the recycling process, and replenishing the recycled etching liquid after etching the test etching target. The method includes generating a test etching solution, replenishing the reused test etching solution with an inert liquid, and estimating the total substance amount of the reused test etching solution before replenishing with the inert liquid from the replenishing test etching solution after replenishing with the inert liquid, calculating the total replenishment amount by mathematical optimization using the estimated total substance amount of the reused test etching solution so that an absolute error between a target composition concentration of the reused test etching solution and a composition concentration of the reused test etching solution after replenishing the reused test etching solution with a total replenishment amount of the treatment liquid, is minimized, and deriving the replenishment amount using the total replenishment amount and an integrated etching amount of the test etching target.

[0006] According to the present disclosure, it is possible to appropriately reuse the etching liquid used when etching an etching target on a substrate.

[0007] FIG. 1 is a plan view showing an outline of the configuration of a wafer processing system. FIG. 2 is a side view showing an outline of the configuration of an etching apparatus. FIG. 3 is an explanatory diagram showing how a nozzle moves in a radial direction. FIG. 4 is a schematic diagram showing an outline of the configuration of a recycling apparatus. FIG. 5 is a flow chart showing the main steps of a wafer processing method. FIG. 6 is a flow chart showing the main steps of a method for deriving a fixed replenishment amount of a processing liquid to replenish an etching liquid. FIG. 7 is a conceptual diagram explaining a method for deriving a fixed replenishment amount by distributing a total fixed replenishment amount. FIG. 8 is an explanatory diagram showing the effect of making the composition concentration of a recycled etching liquid constant according to this embodiment. FIG. 9 is an explanatory diagram showing making the silicon oxidation power of the etching liquid constant by reducing the nitric acid concentration in the etching liquid.

[0008] In the manufacturing process of semiconductor devices, the cut surface of a disk-shaped silicon wafer (hereinafter referred to as "wafer") obtained by cutting a single crystal silicon ingot using a wire saw or the like is flattened and further smoothed to make the wafer thickness uniform. The flattening of the cut surface is performed, for example, by surface grinding or lapping. The smoothing of the cut surface is performed, for example, by spin etching, in which an etching solution is supplied from above the cut surface of the wafer while the wafer is rotating.

[0009] The above-mentioned Patent Document 1 discloses that a wet etching process is performed on a ground wafer to remove a damaged layer formed on the surface of the wafer by the grinding process. In the condition determination process described in Patent Document 1, conditions for the wet etching process, such as the operation of a nozzle that supplies a processing liquid, the rotation speed of the wafer, the supply amount of the processing liquid, the supply time of the processing liquid, and the type of the processing liquid, are determined based on the wafer thickness obtained in the measurement process.

[0010] In order to reduce the consumption of etching liquid in an etching process, it is desirable to recover the etching liquid used for one wafer and reuse it for another wafer. However, when the etching liquid is repeatedly reused for etching multiple wafers, the composition and concentration of the etching liquid changes, which may make it difficult to properly control the etching process of the wafers. Therefore, a process for reusing the etching liquid after etching (hereinafter referred to as a "recycling process") is required.

[0011] In this regard, in the method disclosed in Patent Document 1, the wet etching processing conditions are determined based on the thickness of the wafer after grinding, but the reuse of the etching liquid is not taken into consideration, and the reuse process of the etching liquid is not disclosed or suggested.

[0012] In addition, in the past, etching solution reuse was performed by replenishing the etching solution with a processing solution (processing solution contained in the etching solution), but the amount of processing solution replenished was determined based on the empirical knowledge of engineers. As a result, the conditions for the reuse process were not necessarily optimized, and many experiments were required to determine the conditions for the reuse process. Furthermore, because the reuse process relies on the engineer, the conditions for the reuse process may vary, resulting in poor reproducibility. Poor reproducibility may lead to variations in the conditions, for example, when different engineers have different empirical knowledge. Therefore, there is room for improvement in the conventional etching solution reuse process.

[0013] The technology disclosed herein appropriately reuses an etching solution used when etching an etching target on a substrate. Hereinafter, a wafer processing system as a substrate processing system and a wafer processing method as a substrate processing method according to the present embodiment will be described with reference to the drawings. Note that in this specification and the drawings, elements having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0014] In the wafer processing system 1 according to this embodiment, a wafer W serving as a substrate obtained by slicing an ingot is subjected to processing to improve the in-plane thickness uniformity. Hereinafter, the slicing surfaces of the wafer W will be referred to as a first surface Wa and a second surface Wb. The first surface Wa is the surface opposite the second surface Wb. The first surface Wa and the second surface Wb may also be collectively referred to as the surface of the wafer W.

[0015] 1, the wafer processing system 1 has a configuration in which a loading / unloading station 2 and a processing station 3 are integrally connected. In the loading / unloading station 2, for example, a cassette C capable of accommodating a plurality of wafers W is loaded and unloaded between the loading / unloading station 2 and the outside. The processing station 3 is equipped with various processing devices that perform desired processing on the wafers W.

[0016] The loading / unloading station 2 is provided with a cassette mounting table 10 on which a plurality of cassettes C, e.g., three cassettes C, can be mounted. A wafer transfer device 20 is provided adjacent to the cassette mounting table 10 on the negative side of the X-axis. The wafer transfer device 20 is configured to be movable on a transfer path 21 extending in the Y-axis direction. The wafer transfer device 20 also has, for example, two transfer arms 22, 22 that hold and transfer wafers W. Each transfer arm 22 is configured to be movable horizontally, vertically, around a horizontal axis, and around a vertical axis. The configuration of the transfer arms 22 is not limited to this embodiment and may have any configuration. The wafer transfer device 20 is configured to be able to transfer wafers W to the cassettes C on the cassette mounting table 10 and to a transition device 30, which will be described later.

[0017] In the loading / unloading station 2 , a transition device 30 for transferring the wafer W to and from the processing station 3 is provided adjacent to the wafer transfer device 20 on the negative side of the X axis of the wafer transfer device 20 .

[0018] For example, three processing blocks G1 to G3 are provided in the processing station 3. The first processing block G1, the second processing block G2, and the third processing block G3 are arranged in this order from the positive side of the X axis (the loading / unloading station 2 side) to the negative side.

[0019] The first processing block G1 is provided with an etching device 40, a thickness measuring device 41, a reversing device 42, and a wafer transfer device 50. The etching device 40, the thickness measuring device 41, and the reversing device 42 are arranged in a stacked configuration. Note that the number and arrangement of the etching device 40, the thickness measuring device 41, and the reversing device 42 are not limited to this.

[0020] The etching device 40 etches silicon (Si) on the first surface Wa or the second surface Wb after grinding by the processing device 80. In order to improve the throughput of wafer processing, a plurality of etching devices 40 may be provided. The detailed configuration of the etching device 40 will be described later.

[0021] In one example, the thickness measurement device 41 includes a measurement unit (not shown) and a calculation unit (not shown). The measurement unit includes a sensor that measures the thickness of the wafer W after etching at multiple points. The calculation unit acquires the thickness distribution of the wafer W from the measurement results (thickness of the wafer W) obtained by the measurement unit, and further calculates the flatness (TTV: Total Thickness Variation) of the wafer W. Note that the calculation of the thickness distribution and flatness of the wafer W may be performed by the control device 110 described below instead of the calculation unit. In other words, a calculation unit (not shown) may be provided in the control device 110 described below. Note that the configuration of the thickness measurement device 41 is not limited to this and may be configured arbitrarily.

[0022] The reversing device 42 vertically reverses the first surface Wa and the second surface Wb of the wafer W. The reversing device 42 may have any configuration.

[0023] The wafer transfer device 50 is disposed on the negative side of the transition device 30 in the X-axis direction. The wafer transfer device 50 has, for example, two transfer arms 51, 51 that hold and transfer a wafer W. Each transfer arm 51 is configured to be movable horizontally, vertically, around a horizontal axis, and around a vertical axis. The wafer transfer device 50 is configured to be able to transfer the wafer W to the transition device 30, the etching device 40, the thickness measurement device 41, the inversion device 42, the cleaning device 60 (described later), the thickness measurement device 61 (described later), the buffer device 62 (described later), and the inversion device 63 (described later).

[0024] The second processing block G2 is provided with a cleaning device 60, a thickness measuring device 61, a buffer device 62, an inverting device 63, and a wafer transfer device 70. The cleaning device 60, the thickness measuring device 61, the buffer device 62, and the inverting device 63 are arranged in a stacked configuration. Note that the number and arrangement of the cleaning devices 60, the thickness measuring devices 61, the buffer device 62, and the inverting device 63 are not limited to this.

[0025] The cleaning device 60 cleans at least the first surface Wa or the second surface Wb after grinding in the processing device 80 described below. For example, a brush is brought into contact with the first surface Wa or the second surface Wb to clean the first surface Wa or the second surface Wb. Note that a pressurized cleaning liquid may be used to clean the wafer W.

[0026] In one example, the thickness measuring device 61 includes a measuring unit (not shown) and a calculating unit (not shown). The measuring unit includes a sensor that measures the thickness of the wafer W after grinding at multiple points. The calculating unit acquires the thickness distribution of the wafer W from the measurement results (thickness of the wafer W) by the measuring unit, and further calculates the flatness (TTV) of the wafer W. Note that the calculation of the thickness distribution and flatness of the wafer W may be performed by the control device 110 described below instead of the calculating unit. In other words, a calculating unit (not shown) may be provided in the control device 110 described below. Note that the configuration of the thickness measuring device 61 is not limited to this and may be configured arbitrarily.

[0027] The buffer device 62 temporarily holds unprocessed wafers W that are transferred from the first processing block G1 to the second processing block G2. The configuration of the buffer device 62 is arbitrary. The buffer device 62 may also include an alignment mechanism (not shown) that adjusts the center position of the wafer W relative to chucks 83 a, 83 b (described later) and / or the horizontal orientation of the wafer W.

[0028] The reversing device 63 vertically reverses the first surface Wa and the second surface Wb of the wafer W. The reversing device 63 may have any configuration.

[0029] The wafer transfer device 70 is disposed, for example, on the Y-axis positive side of the cleaning device 60, the thickness measurement device 61, the buffer device 62, and the inversion device 63. The wafer transfer device 70 has, for example, two transfer arms 71, 71 that suction-hold and transport the wafer W using a suction-holding surface (not shown). Each transfer arm 71 is supported by an articulated arm member 72 and is configured to be movable horizontally, vertically, around a horizontal axis, and around a vertical axis. The wafer transfer device 70 is configured to be able to transport the wafer W to the etching device 40, the thickness measurement device 41, the inversion device 42, the cleaning device 60, the thickness measurement device 61, the buffer device 62, the inversion device 63, and a processing device 80, which will be described later.

[0030] The third processing block G3 is provided with a processing device 80. The processing device 80 grinds the first surface Wa or the second surface Wb of the wafer W to flatten and smooth it.

[0031] The processing device 80 has a rotary table 81. The rotary table 81 is configured to be rotatable about a vertical rotation center line 82 by a rotation mechanism (not shown). Four chucks for suction-holding the wafer W are provided on the rotary table 81. Of the four chucks, two first chucks 83a are chucks used for grinding at a first processing position B1. These two first chucks 83a are arranged in positions symmetrical with respect to a point across the rotation center line 82. The remaining two second chucks 83b are chucks used for grinding at a second processing position B2. These two second chucks 83b are also arranged in positions symmetrical with respect to a point across the rotation center line 82. That is, the first chucks 83a and the second chucks 83b are arranged alternately in the circumferential direction.

[0032] The four chucks 83a, 83b can be moved to the delivery positions A1-A2 and the processing positions B1-B2 by the rotation of the rotary table 81. Furthermore, each of the four chucks 83a, 83b is configured to be rotatable around a vertical axis by a rotation mechanism (not shown).

[0033] The first transfer position A1 is a position on the X-axis positive side and the Y-axis positive side of the turntable 81, where the wafer W is transferred to the first chuck 83a when the first surface Wa is ground. The second transfer position A2 is a position on the X-axis positive side and the Y-axis negative side of the turntable 81, where the wafer W is transferred to the second chuck 83b when the second surface Wb is ground.

[0034] The first processing position B1 is a position on the X-axis negative side and the Y-axis negative side of the rotary table 81, and a first grinding unit 90 is disposed thereat. The first grinding unit 90 has a grinding section 91 equipped with an annular, rotatable grinding wheel (not shown). The grinding section 91 is configured to be movable in the vertical direction along a support 92. As an example, the first grinding unit 90 grinds the first surface Wa or the second surface Wb of the wafer W held by the first chuck 83a.

[0035] The second processing position B2 is a position on the negative X-axis side and the positive Y-axis side of the rotary table 81, and a second grinding unit 100 is disposed thereat. The second grinding unit 100 has a grinding section 101 equipped with an annular, rotatable grinding wheel (not shown). The grinding section 101 is configured to be movable in the vertical direction along a support 102. As an example, the second grinding unit 100 grinds the second surface Wb or the first surface Wa of the wafer W held by the second chuck 83b.

[0036] A thickness measuring device (not shown) for measuring the thickness of the wafer W after grinding may be provided at the transfer positions A1, A2 or the processing positions B1, B2.

[0037] The wafer processing system 1 described above is provided with at least one controller 110. The controller 110 processes computer-executable instructions that cause the wafer processing system 1 to perform the various steps described in this disclosure. The controller 110 may be configured to control each element of the wafer processing system 1 to perform the various steps described herein. In one embodiment, some or all of the controller 110 may be included in the wafer processing system 1. The controller 110 may include a processing unit, a storage unit, and a communication interface. The controller 110 is implemented, for example, by a computer. The processing unit may be configured to read from the storage unit a program that provides logic or routines that enable various control operations to be performed, and to execute the read program to perform various control operations. This program may be stored in the storage unit in advance or may be acquired via a medium when needed. The acquired program is stored in the storage unit and read from the storage unit by the processing unit for execution. The medium may be various computer-readable storage media or a communication line connected to the communication interface. The storage medium may be temporary or non-temporary. The processing unit may be a CPU (Central Processing Unit) or one or more circuits. The storage unit may include a RAM (Random Access Memory), a ROM (Read Only Memory), a HDD (Hard Disk Drive), an SSD (Solid State Drive), or a combination thereof. The communication interface may communicate with the wafer processing system 1 via a communication line such as a LAN (Local Area Network).

[0038] Next, the configuration of the etching apparatus 40 will be described.

[0039] 2, the etching apparatus 40 has a wafer holding unit 200 that holds a wafer W. The wafer holding unit 200 holds the outer edge of the wafer W at multiple points, three points in this embodiment. The configuration of the wafer holding unit 200 is not limited to the example shown in the figure; for example, the wafer holding unit 200 may include a chuck (not shown) that suction-holds the wafer W from below. The wafer holding unit 200 is configured to be rotatable about a vertical rotation center line 200a by a rotation mechanism 201, thereby allowing the wafer W held on the wafer holding unit 200 to rotate.

[0040] A cup 210 is provided around the wafer holding part 200. The cup 210 is provided so as to surround the wafer holding part 200 and collects the etching solution E as described below. A drain line 211 for discharging the collected etching solution E is connected to the cup 210. Note that, although the cup 210 does not move up and down in this embodiment, it may be configured so as to be able to move up and down using a lifting mechanism (not shown). Furthermore, a plurality of drain lines 211 may be provided, and a switching mechanism (not shown) may be used to switch between collecting and discharging the post-etching etching solution E and the rinse solution. The rinse solution is used to clean the wafer W after etching. In such a case, in addition to the nozzle 220 for supplying the etching solution described below, a nozzle for supplying the rinse solution (not shown) is provided, and the etching solution E and the rinse solution are reused.

[0041] A nozzle 220 is provided above the wafer holding part 200. The nozzle 220 supplies the etching liquid E to the first surface Wa or the second surface Wb of the wafer W held by the wafer holding part 200. A liquid supply line 221 that supplies the etching liquid E to the nozzle 220 is connected to the nozzle 220. The nozzle 220 is configured to be movable in the horizontal and vertical directions by a movement mechanism 222. In one example, the nozzle 220 is configured to be capable of reciprocating movement (scan movement) or swiveling along a rotation center line 200a of the wafer holding part 200, i.e., above the center of the wafer W as shown in FIG. 3 .

[0042] The etching solution E contains hydrofluoric acid (HF), nitric acid (HNO ３ ) and phosphoric acid (H ３ P.O. ４ ) is included. In one example, the etching solution E contains hydrofluoric acid, nitric acid, phosphoric acid, and water as processing solutions, i.e., a mixture of multiple processing solutions. The etching target may be, for example, amorphous silicon. The etching target of this embodiment can also be applied to the processing of wafers that are not processed by the processing device 80. For example, if a film is formed on the first surface Wa or the second surface Wb, the film is also the etching target.

[0043] In this embodiment, the etching liquid E is reused in the etching process of the wafers W. That is, for example, the etching liquid E used in etching the second side Wb of one wafer W is recovered and reused in etching the first side Wa of the wafer W. Also, for example, the etching liquid E used in etching the first side Wa of one wafer W is recovered and reused in etching the second side Wb of the next wafer W. For this reason, as shown in FIG. 2 , the etching apparatus 40 is provided with a recycling apparatus 300 that performs a process to recover and reuse the etching liquid E used in the etching process. The drain line 211 and the liquid supply line 221 are connected to the recycling apparatus 300.

[0044] As shown in FIG. 4 , the recycling apparatus 300 has a tank 310 that stores etching solution E therein. A source line 320 is connected to the tank 310, and the source line 320 is connected to a source tank 321. A hydrofluoric acid supply source 322, a nitric acid supply source 323, a phosphoric acid supply source 324, and a water supply source 325 are connected to the source tank 321. Hydrofluoric acid, nitric acid, phosphoric acid, and water are supplied to the source tank 321 from the hydrofluoric acid supply source 322, the nitric acid supply source 323, the phosphoric acid supply source 324, and the water supply source 325. Inside the source tank 321, these hydrofluoric acid, nitric acid, phosphoric acid, and water are mixed to generate an aqueous solution (mixed solution) of the processing solution. The source tank 321 adds the processing solution to the etching solution E in the tank 310.

[0045] Valves 326, 327, 328, and 329 for controlling the supply of hydrofluoric acid, nitric acid, phosphoric acid, and water are provided between the hydrofluoric acid supply source 322, the nitric acid supply source 323, the phosphoric acid supply source 324, and the water supply source 325 and the source tank 321, respectively. The amounts of hydrofluoric acid, nitric acid, phosphoric acid, and water supplied are adjusted to adjust the composition and concentration of the mixed solution of the processing liquid supplied from the source tank 321 to the tank 310, thereby adjusting the composition and concentration of the etching solution E in the tank 310. The composition and concentration of the etching solution E are the concentrations of the components in the etching solution E. In this embodiment, the concentrations are expressed in mass percent.

[0046] The drain line 211 is connected to the tank 310. A recovery tank 330 and a valve 331 are provided in this order on the drain line 211 from the etching apparatus 40 side. The recovery tank 330 stores therein the etching liquid E recovered from the cup 210 of the etching apparatus 40. The valve 331 controls the supply of the etching liquid E to the tank 310. The etching liquid E recovered from the cup 210 flows into the tank 310 through this drain line 211.

[0047] The tank 310 is connected to the liquid supply line 221. A pump 340, a filter 341, a heater 342, and a flow meter 343 are provided on the liquid supply line 221 in this order from the tank 310 side. The pump 340 sends the etching solution E from the tank 310 to the nozzle 220 of the etching device 40. The heater 342 adjusts the temperature of the etching solution E to a temperature suitable for the etching process, for example, 25°C. The filter 341 removes impurities from the etching solution E. The flow meter 343 measures the flow rate of the etching solution E supplied to the nozzle 220. The etching solution E, the composition and concentration of which has been adjusted in the tank 310, is supplied to the nozzle 220 through this liquid supply line 221.

[0048] A circulation line 350 is connected between the tank 310 and the nozzle 220 side (downstream side) of the flow meter 343 in the liquid supply line 221. An electromagnetic valve 351 and a concentration meter 352 are provided in this order from the liquid supply line 221 side in the circulation line 350. The circulation line 350 circulates the etching solution E, the composition and concentration of which has been adjusted in the tank 310, from the liquid supply line 221 to the tank 310. The electromagnetic valve 351 controls the flow of the etching solution E in the circulation line 350, and controls the etching solution E to flow in the circulation line 350 when the concentration meter 352 measures the composition and concentration of the etching solution E. The concentration meter 352 measures the composition and concentration of the etching solution E, and detects the concentration of each component contained in the etching solution E, such as hydrofluoric acid, nitric acid, phosphoric acid, water, and hexafluorosilicic acid (H ２ SiF ６ In other words, in the circulation line 350, a concentration meter 352 is used to check whether the composition and concentration of the etching solution E adjusted in the tank 310 are appropriate. Note that hexafluorosilicic acid is a by-product that is generated when the wafer W is etched.

[0049] In this case, the etching solution E recovered in the cup 210 is discharged to the recycling device 300 via the drain line 211. In the recycling device 300, one or more of hydrofluoric acid, nitric acid, and phosphoric acid are added to the etching solution E from a hydrofluoric acid supply source 322, a nitric acid supply source 323, and a phosphoric acid supply source 324, thereby adjusting the composition and concentration of the etching solution E. In addition, the temperature of the etching solution E is adjusted by a heater 342. Then, the etching solution E adjusted to a composition and temperature suitable for the etching process is supplied to the nozzle 220 via the liquid supply line 221. By recycling the etching solution E in this way, the amount of etching solution E used can be reduced, thereby reducing costs.

[0050] Next, a description will be given of wafer processing performed using the wafer processing system 1 configured as described above. In this embodiment, a wafer W is cut from an ingot using a wire saw or the like and lapped, and then processed to improve the in-plane thickness uniformity.

[0051] First, a cassette C containing a plurality of wafers W is placed on the cassette mounting table 10 of the carry-in / out station 2. The wafers W are stored in the cassette C with their first surfaces Wa facing upward and their second surfaces Wb facing downward. Next, the wafers W in the cassette C are removed by the wafer transfer device 20 and transferred to the transition device 30. The wafers W transferred to the transition device 30 are then transferred to the buffer device 62 by the wafer transfer device 50. In the buffer device 62, the center position of the wafers W relative to the chucks 83a, 83b and / or the horizontal orientation of the wafers W may be adjusted.

[0052] Next, the wafer W is transferred to the processing device 80 by the wafer transfer device 70 and transferred to the first chuck 83a at the first transfer position A1. The second surface Wb of the wafer W is held by suction on the first chuck 83a.

[0053] Next, the rotary table 81 is rotated to move the wafer W to the first processing position B1, and the first surface Wa of the wafer W is then ground by the first grinding unit 90 (S1 in FIG. 5).

[0054] Next, the rotary table 81 is rotated to move the wafer W to the first transfer position A1. At the first transfer position A1, the first surface Wa of the wafer W after grinding may be cleaned by a cleaning unit (not shown).

[0055] Next, the wafer W is transferred by the wafer transfer device 70 to the cleaning device 60. In the cleaning device 60, the first surface Wa and the second surface Wb of the wafer W are cleaned (S2 in FIG. 5).

[0056] Next, the wafer W is transferred to the reversing device 63 by the wafer transfer device 70. In the reversing device 63, the first surface Wa and the second surface Wb of the wafer W are reversed upside down (S3 in FIG. 5). That is, the wafer W is reversed so that the first surface Wa faces downward and the second surface Wb faces upward.

[0057] Next, the wafer W is transferred to the processing device 80 by the wafer transfer device 70 and transferred to the second chuck 83b at the second transfer position A2. The first surface Wa of the wafer W is held by suction on the second chuck 83b.

[0058] Next, the rotary table 81 is rotated to move the wafer W to the second processing position B2, and the second surface Wb of the wafer W is then ground by the second grinding unit 100 (S4 in FIG. 5).

[0059] Next, the rotary table 81 is rotated to move the wafer W to the second transfer position A2. At the second transfer position A2, the second surface Wb of the wafer W after grinding may be cleaned by a cleaning unit (not shown).

[0060] Next, the wafer W is transferred by the wafer transfer device 70 to the cleaning device 60. In the cleaning device 60, the second surface Wb and the first surface Wa of the wafer W are cleaned (S5 in FIG. 5).

[0061] Next, the wafer W is transferred to the thickness measuring device 61 by the wafer transfer device 70 or the wafer transfer device 50. The thickness measuring device 61 measures the thickness of the wafer W at multiple points after grinding both the first surface Wa and the second surface Wb to obtain the thickness distribution of the wafer W after grinding, and further calculates the flatness of the wafer W (S6 in FIG. 5). The calculated thickness distribution and flatness of the wafer W are output to, for example, the control device 110. Note that if the processing device 80 is provided with a thickness measuring device, the thickness of the wafer W after grinding may be measured by the thickness measuring device of the processing device 80.

[0062] The control device 110 determines optimal etching conditions for the second surface Wb, optimizing the etching amount distribution (etching profile) in the etching process of the second surface Wb, from the output thickness distribution and flatness of the wafer W (S7 in FIG. 5). Note that the etching amount is the amount of the wafer W removed by etching, and the etching amount distribution is the distribution of the etching amount within the wafer surface. The method of determining the optimal etching conditions for the second surface Wb in the control device 110 is arbitrary, and for example, the method disclosed in International Publication No. 2023 / 068066 may be used.

[0063] Next, the wafer W is transferred by the wafer transfer device 50 to the etching device 40. In the etching device 40, the second surface Wb of the wafer W is etched with the etching solution E under the optimal etching conditions determined in S7 (S8 in FIG. 5). In S8, by etching the second surface Wb under the optimal etching conditions, the etching amount distribution is optimized and the second surface Wb is formed into a target shape.

[0064] The etching of the second surface Wb in S8 may be performed under predetermined etching conditions, in which case S6 and S7 of this embodiment are omitted.

[0065] The etching solution E used in etching the second surface Wb in S8 is collected in the recycling device 300 and recycled (S9 in FIG. 5). The method of recycling the etching solution E in the recycling device 300 will be described later.

[0066] Next, the wafer W is transferred to the reversing device 42 by the wafer transfer device 50. In the reversing device 42, the first surface Wa and the second surface Wb of the wafer W are reversed upside down (S10 in FIG. 5). That is, the wafer W is reversed so that the first surface Wa faces upward and the second surface Wb faces downward.

[0067] Next, the wafer W is transferred by the wafer transfer device 50 to the thickness measurement device 41. The thickness measurement device 41 measures the thickness of the wafer W at multiple points to obtain the thickness distribution of the wafer W after grinding, and further calculates the flatness of the wafer W (S11 in FIG. 5). The calculated thickness distribution and flatness of the wafer W are output to, for example, the control device 110.

[0068] The control device 110 determines optimal etching conditions for the first surface Wa, which optimize the etching amount distribution in the etching process on the first surface Wa, from the thickness distribution and flatness of the output wafer W (S12 in FIG. 5). The method for determining the optimal etching conditions for the first surface Wa in the control device 110 is also arbitrary, and similar to S7, the method disclosed in WO 2023 / 068066, for example, may be used.

[0069] Next, the wafer W is transferred by the wafer transfer device 50 to the etching device 40. In the etching device 40, the first surface Wa of the wafer W is etched with the etching solution E under the optimal etching conditions determined in S12 (S13 in FIG. 5). In S13, the first surface Wa is etched under the optimal etching conditions to optimize the etching amount distribution and process the first surface Wa into a target shape. In addition, the etching solution E used in etching the first surface Wa in S13 is, for example, the etching solution E that was reused in S9.

[0070] The etching solution E used in etching the first surface Wa in S13 is collected in the recycling device 300 and recycled (S14 in FIG. 5). The method of recycling the etching solution E in the recycling device 300 will be described later.

[0071] Next, the wafer W is transferred by the wafer transfer device 50 to the thickness measurement device 41. The thickness measurement device 41 measures the thickness of the wafer W after etching at multiple points on both the first surface Wa and the second surface Wb, thereby obtaining the thickness distribution of the wafer W after grinding (S15 in FIG. 5). The flatness of the wafer W may also be calculated. The calculated thickness distribution of the wafer W is output to, for example, the control device 110, and is used, for example, in processing another wafer W to be processed next in the wafer processing system 1. Note that when the thickness of the wafer W after grinding is measured by the thickness measurement device of the processing device 80, the thickness of the wafer W after etching may also be measured in the thickness measurement device 61.

[0072] Thereafter, the wafer W that has undergone all the processing is transferred to the cassette C on the cassette mounting table 10 via the transition device 30. This completes the series of wafer processing in the wafer processing system 1. Note that the wafer W that has undergone processing in the wafer processing system 1 may be polished outside the wafer processing system 1.

[0073] Next, the above-mentioned method for recycling the etching liquid E (S9 and S14 in FIG. 5 ) will be described. Note that the recycling process of the etching liquid E in S9 and the recycling process of the etching liquid E in S14 are the same process. In the following description, the etching of the second surface Wb in S8 and the etching of the first surface Wa in S13 may be collectively referred to as "etching the wafer W."

[0074] The etching solution E used in etching in the etching device 40 is collected in a cup 210 and discharged to the recycling device 300 via a drain line 211. In the recycling device 300, the etching solution E is subjected to a recycling process to generate a recycled etching solution Er. The recycled etching solution Er is supplied to the nozzle 220 via a liquid supply line 221 and is reused as the etching solution E for etching the wafer W.

[0075] In the recycling process in the recycling apparatus 300, first, it is detected whether the replenishment conditions are satisfied. The replenishment conditions are satisfied, for example, when the cumulative supply amount of etching solution E supplied to the wafer W reaches a threshold value after repeatedly etching the wafer W and recovering the etching solution E after etching. The threshold value for the cumulative supply amount is set arbitrarily. Furthermore, although the cumulative supply amount is used as the replenishment condition in this embodiment, the cumulative number of wafer W processed or the cumulative elapsed time may also be used. The cumulative number of processes may be calculated from the cumulative supply amount. For example, when calculating the optimal etching conditions as described above, the supply amount of etching solution E may change for each etching. The cumulative number of processes may be calculated based on this supply amount for each etching.

[0076] When the cumulative supply amount of etching solution E reaches a threshold value and satisfies the replenishment condition, a treatment liquid containing one or more of hydrofluoric acid, nitric acid, and phosphoric acid is replenished to the etching solution E from the hydrofluoric acid supply source 322, the nitric acid supply source 323, and the phosphoric acid supply source 324, thereby adjusting the composition concentration of the etching solution E. When the treatment liquid is replenished to the etching solution E, a fixed amount of the treatment liquid is replenished. This fixed amount of replenishment (hereinafter referred to as the "fixed replenishment amount") is a fixed amount of replenishment determined in advance, for example, by conducting a test, and is the replenishment amount for each treatment liquid (each component). The method for deriving the fixed replenishment amount will be described later.

[0077] Next, in the reuse process, the temperature of the etching solution E is adjusted by the heater 342. Then, the etching solution E adjusted to a composition concentration and temperature suitable for the etching process is supplied to the nozzle 220 via the liquid supply line 221.

[0078] Note that the replenishment condition is not satisfied until the cumulative supply amount of the etching solution E reaches the threshold value, and the processing solution is not replenished to the etching solution E. In this case, in the reuse process, only the temperature of the etching solution E is adjusted by the heater 342.

[0079] Next, a method for deriving the fixed amount of replenishment of the processing liquid to be replenished to the etching liquid E in the above-mentioned recycling process will be described. In this embodiment, the fixed amount of replenishment is derived using a test wafer Wt as a test substrate and a test etching liquid Es. Note that the test wafer Wt before etching and the test etching liquid Es are the same as the wafer W and the etching liquid E before etching, respectively. Furthermore, the test etching target of the test wafer Wt is the silicon of the test wafer Wt, but as described above, the test etching target may be, for example, amorphous silicon, and if a film is formed on the surface of the test wafer Wt, the film also becomes the test etching target.

[0080] In this embodiment, to derive the fixed amount of replenishment, a reuse test etching solution generation process, a test replenishment process, a total fixed amount of replenishment calculation process (mathematical optimization process), and a fixed amount of replenishment derivation process (distribution process) are mainly carried out in sequence.

[0081] First, the composition and concentration of a new test etching solution Es is measured before etching the test wafer Wt (T1 in FIG. 6). In the following description, the new test etching solution Es before etching is referred to as a new test etching solution En. The composition and concentration of the new test etching solution En is measured using, for example, the concentration meter 352 of the recycling apparatus 300.

[0082] Next, the thickness of the test wafer Wt before etching is measured (T2 in FIG. 6). The thickness measurement of the test wafer Wt is performed by, for example, a thickness measurement device 61.

[0083] In this embodiment, T1 and T2 are performed in this order, but the order of T1 and T2 may be reversed, or T1 and T2 may be performed in parallel.

[0084] Next, the surface of the test wafer Wt is repeatedly etched with the test etching solution Es. At this time, the test etching solution Es is reused, but the processing solution replenishment in the reuse process described above is not performed. In other words, the composition and concentration of the test etching solution Es is not adjusted. Then, the test etching solution Es is obtained after repeatedly etching the surface of the set number of test wafers Wt. In the following description, the test etching solution Es after etching the set number of test wafers Wt is referred to as the reused test etching solution Et, and the reused test etching solution Et is generated to derive a fixed amount of replenishment (T3 in FIG. 6 ).

[0085] The set number of etching processes for the test wafers Wt is set arbitrarily, for example, to 100 to 1000. The set number of processing processes may be set, for example, to the number of processing processes at which the composition concentration of the test etching solution Es changes (for example, 100 wafers), or may be set to the planned number of processing processes at which the etching solution E is replaced when processing the wafers W (for example, 1000 wafers).

[0086] In addition, the set number of processes in this embodiment is, in other words, the number of times the surface of the test wafer Wt is etched. For example, as described above, etching may be performed repeatedly on a set number of test wafers Wt, and in such a case, the cumulative etching amount described below is the sum of the etching amounts of each test wafer Wt. Also, for example, etching may be performed repeatedly on one or more test wafers Wt, and the total number of etchings is the set number of times, and in such a case, the cumulative etching amount described below is the sum of the etching amounts of the set number of times.

[0087] Next, the thickness of the etched test wafer Wt is measured (T4 in FIG. 6). The thickness of the test wafer Wt is measured one by one (one by one), that is, the thickness of the test wafer Wt for a set number of processings is measured. The thickness measurement of the test wafer Wt is performed, for example, by the thickness measurement device 41.

[0088] Next, the composition and concentration of the reused test etching solution Et is measured (T5 in FIG. 6). The composition and concentration of the reused test etching solution Et is measured using, for example, the concentration meter 352 of the reuse apparatus 300.

[0089] In this embodiment, T4 and T5 are performed in this order, but the order of T4 and T5 may be reversed, or T4 and T5 may be performed in parallel.

[0090] As described above, in the generation step (T3) of the recycled etching solution Er, the composition concentration (T1) of the new test etching solution En, the thicknesses (T2, T4) of the test wafer Wt before and after etching, and the composition concentration (T5) of the recycled test etching solution Et are obtained before and after the generation step (T3). Note that the integrated etching amount of the test wafer Wt is calculated from the thicknesses (T2, T4) of the test wafer Wt before and after etching, as will be described later.

[0091] Next, an inert chemical, for example, phosphoric acid, is test-replenished to the reused test etching solution Et produced in T3 (T6 in FIG. 6). In T6, the amount of substance of the inert chemical to be test-replenished is determined. When calculating the total quantitative replenishment amount by mathematical optimization in T9, which will be described later, the total amount of substance of the reused test etching solution Et is required. However, since there is no method for directly measuring this total amount of substance, the total amount of substance is estimated by the method of test-replenishment of an inert chemical.

[0092] In this embodiment, phosphoric acid is used as the inert chemical solution, but any chemical solution that does not chemically react with the reused test etching solution Et can be selected. If a chemical solution that chemically reacts with the reused test etching solution Et, such as nitric acid, is used for test replenishment, the amount of nitric acid in the reused test etching solution Et will change depending on the amount of nitric acid added for test replenishment, making it impossible to properly estimate the total amount of substance in the reused test etching solution Et before test replenishment. Therefore, an inert chemical solution is used for test replenishment.

[0093] Next, the composition and concentration of the test replenishment etching solution Eu after test replenishment of the reused test etching solution Et with the inert chemical solution is measured (T7 in FIG. 6). The composition and concentration of the test replenishment etching solution Eu is measured using, for example, the concentration meter 352 of the reuse device 300.

[0094] Next, the total amount of substance of the reused test etching solution Et before test replenishment measured at T5, the total amount of substance of the test replenishment etching solution Eu after test replenishment measured at T7, and the amount of substance of the inert chemical solution replenished at T6 are used to estimate (T8 in FIG. 6 ). The total amount of substance of the reused test etching solution Et is the sum of the amounts of substance of each component (hydrofluoric acid, nitric acid, phosphoric acid, water, and hexafluorosilicic acid). The molar fractions calculated by converting the mass % concentrations of each component in the reused test etching solution Et into molar ratios are used as the composition concentrations of the reused test etching solution Et before test replenishment. In the following description, these molar fractions are referred to as "pre-test replenishment molar fractions." Similarly, the molar fractions calculated by converting the mass % concentrations of each component in the test replenishment etching solution Eu into molar ratios are used as the composition concentrations of the test replenishment etching solution Eu after test replenishment. In the following description, these molar fractions are referred to as "post-test replenishment molar fractions."

[0095] In T8, the total amount of substance of the reused test etching solution Et before test replenishment is estimated from the material balance relationship based on the change in the molar fraction before test replenishment and the molar fraction after test replenishment. The material balance relationship equation is arbitrary, but for example, it can be obtained by modifying a balance equation that takes into account how the total amount of substance of the reused test etching solution Et changes when the inert chemical solution is test replenished. By inputting the molar fraction before test replenishment, the molar fraction after test replenishment, and the amount of substance of the inert chemical solution into this material balance relationship equation, the total amount of substance of the reused test etching solution Et before test replenishment is calculated for each component.

[0096] In T8, a representative value of the total amount of substance of the reused test etching solution Et for each component, for example, the average or median, is estimated as the total amount of substance of the reused test etching solution Et before the test replenishment. While the total amount of substance for each component should essentially be the same, in reality, this may not be the case due to various factors. Therefore, a representative value of the total amount of substance for each component is calculated.

[0097] Next, the total quantitative replenishment amount is calculated as the total replenishment amount by mathematical optimization using the compositional concentrations of the new test etching solution En measured in T1, the compositional concentrations of the reused test etching solution Et before the test replenishment measured in T5, and the total amount of substance of the reused test etching solution Et estimated in T8 (T9 in FIG. 6). The total quantitative replenishment amount is the total amount of processing solution to be replenished to the reused test etching solution Et after etching the surfaces of the set number of test wafers Wt, and is the replenishment amount for each processing solution (each component). As described above, in the reuse process of etching solution E, when the replenishment conditions are met, a quantitative replenishment amount of processing solution is replenished to the etching solution E, and the total quantitative replenishment amount is the cumulative amount of these quantitative replenishment amounts.

[0098] In T9, the total quantitative replenishment amount is calculated by mathematical optimization so as to minimize the absolute error between the target composition concentration of the recycled test etching solution Et and the composition concentration of the recycled test etching solution Et after the total quantitative replenishment amount of treatment solution is replenished to the recycled test etching solution Et. As in T8, the molar fraction of the recycled test etching solution Et is calculated and used as the target composition concentration of the recycled test etching solution Et. In the following description, this molar fraction is referred to as the target molar fraction. Furthermore, the molar fraction of the recycled test etching solution Et is also calculated and used as the composition concentration of the recycled test etching solution Et after the total quantitative replenishment amount of treatment solution is replenished. In the following description, this molar fraction is referred to as the molar fraction after the total quantitative replenishment. Therefore, in T9, the absolute error between the target molar fraction and the molar fraction after the total quantitative replenishment is minimized.

[0099] Although the target molar fraction is set arbitrarily, the target composition concentration of the reused test etching solution Et in this embodiment is the composition concentration of the new test etching solution En measured at T1. That is, the target molar fraction is the molar fraction of the new test etching solution En. In this case, the goal is to return the composition concentration of the reused test etching solution Et, which is obtained by replenishing the reused test etching solution Et with a total fixed replenishment amount of processing solution after etching the surfaces of a set number of test wafers Wt, to the composition concentration of the new test etching solution En before etching.

[0100] The total post-quantitative replenishment molar fraction is calculated using the composition concentration (molar fraction) of the recycled test etching solution Et before test replenishment measured in T5 and the total substance amount of the recycled test etching solution Et estimated in T8.

[0101] In T9, an evaluation function relating to the absolute error between the target molar fraction and the molar fraction after total replenishment is set. This evaluation function can be set arbitrarily, but for example, it is a function that calculates the sum of each component by dividing the absolute error between the target molar fraction and the molar fraction after total replenishment by the target molar fraction. The reason for dividing by the target molar fraction is to normalize the absolute error for each component. Then, the total replenishment amount is calculated by mathematical optimization so as to minimize the evaluation function.

[0102] Next, the total quantitative replenishment amount is calculated by dividing the total quantitative replenishment amount using the total quantitative replenishment amount calculated in T9 and the cumulative etching amount of the test wafers Wt calculated from T2 and T4, to derive the quantitative replenishment amount (T10 in FIG. 6). The quantitative replenishment amount is the amount of processing liquid to be replenished to the etching liquid E when the replenishment conditions are met. The quantitative replenishment amount D is divided from the total quantitative replenishment amount C as shown in FIG. 7 and calculated using the following formula (1). Note that the horizontal axis in FIG. 7 indicates the number of test wafers Wt processed, the first vertical axis indicates the cumulative etching amount of the test wafers Wt (solid line in FIG. 7), and the second vertical axis indicates the cumulative replenishment amount of the processing liquid (dotted line in FIG. 7). D=C×(A / B) (1) where, A: cumulative etching amount of the test wafers Wt when the replenishment conditions are met, B: cumulative etching amount of the test wafers Wt after etching the set number of processes, C: total quantitative replenishment amount, D: quantitative replenishment amount

[0103] The cumulative etching amounts A and B of the test wafers Wt are calculated by using the thickness of the test wafers Wt measured at T2 and the thickness of the test wafers Wt measured at T4, and the difference between these values ​​is used as the cumulative etching amount. The cumulative etching amount A is the cumulative etching amount from the first test wafer Wt to ​​the test wafer Wt when the first correction condition is satisfied. Alternatively, the cumulative etching amount A is the cumulative etching amount from the test wafer Wt when the nth correction condition is satisfied to the test wafer Wt when the (n+1)th correction condition is satisfied. Note that the replenishment condition is the same as the replenishment condition in etching the wafers W, and occurs when the cumulative supply amount of the test etching solution Es supplied to the test wafers Wt reaches a threshold value. The cumulative etching amount B is the cumulative etching amount from the first test wafer Wt to ​​the set number of test wafers Wt processed.

[0104] The cumulative supply amount of the test etching solution Es is proportional to the number of test wafers Wt processed, but the cumulative etching amount is in a curved line relative to the number of test wafers Wt processed. The etching amount of the test wafers Wt is proportional to the consumption amount of the test etching solution Es, and the consumption amount of the test etching solution Es is also proportional to the optimal fixed amount of replenishment, so the etching amount and the optimal fixed amount of replenishment are proportional to each other. Therefore, the above formula (1) is established.

[0105] By carrying out T1 to T10 as described above, the fixed amount of replenishment of the processing liquid to be replenished to the etching liquid E in the reuse processing is derived.

[0106] Here, in the past, the amount of processing liquid replenished to the etching solution in the reuse process was determined based on the empirical knowledge of engineers. As a result, the conditions for the reuse process were not always optimized, and many experiments were required to determine the conditions for the reuse process. Furthermore, because it was dependent on the engineer, the conditions for the reuse process could vary, resulting in poor reproducibility. As a result, it was difficult to maintain a constant composition concentration of the reused etching solution after the reuse process.

[0107] In contrast, according to the present embodiment, the quantitative replenishment amount of the treatment liquid to be replenished to the etching liquid E in the reuse process can be derived by mathematical optimization so that the composition concentration of the reuse test etching liquid Et becomes the target composition concentration. That is, the optimal solution for the quantitative replenishment amount can be derived. In this case, the quantitative replenishment amount can be derived without relying on the empirical knowledge of engineers as in the past, so that the quantitative replenishment amount can be optimized, the number of experiments required to determine the conditions for the reuse process can be reduced, and reproducibility can be improved. Furthermore, because the quantitative replenishment amount can be optimized, it becomes possible to maintain a constant composition concentration of the reuse etching liquid Er after the reuse process of the etching liquid E.

[0108] Here, the results of experiments conducted by the present inventors to evaluate the effects of this embodiment are shown. Fig. 8( a) is a graph illustrating, as a comparative example, changes in the composition and concentration of the etching solution when the replenishment amount of the processing solution is determined based on the empirical knowledge of engineers, as in the conventional method. Fig. 8( b) is a graph illustrating changes in the composition and concentration of the etching solution E when a fixed amount of the processing solution of this embodiment is replenished. The horizontal axis of Fig. 8 represents the elapsed time of the etching process (from time 0 (zero) to time T), and the vertical axis represents the concentrations of each component (hydrofluoric acid, nitric acid, phosphoric acid, water, hexafluorosilicic acid) in the etching solution E. As shown in Fig. 8, the composition and concentration of the etching solution cannot be kept constant using the conventional method based on the empirical knowledge of engineers. However, according to this embodiment, the composition and concentration of the etching solution E (recycled etching solution Er) can be made approximately constant.

[0109] In the above embodiment, the composition and concentration of the recycled etching solution Er (etching solution E) can be kept constant by optimizing the fixed amount of replenishment of the processing solution to the etching solution E. As a result of extensive research by the present inventors in this regard, it was found that even if the composition and concentration of the recycled etching solution Er is kept constant, when the recycled etching solution Er is repeatedly used as the etching solution E to etch wafers W, the distribution of the amount of etching may change over time as the number of wafers W processed increases. Specifically, it was found that in the etching process using the recycled etching solution Er, the amount of etching at the center of the wafer W increases compared to the etching process using the etching solution E before etching.

[0110] In the etching process of the wafer W, among the components of the etching solution E, nitric acid oxidizes the silicon of the wafer W to form silicon dioxide (SiO ２ In the etching process of the wafer W, the silicon of the wafer W and the etching solution E undergo a chemical reaction to produce nitrogen oxides (NO Ｘ ) is generated, and nitrogen oxides react with water to form nitrous acid (HNO ２ ) occurs.

[0111] 9A, when the etching solution E of this embodiment is reused and the concentration of nitric acid in the reused etching solution Er (etching solution E) is kept constant, the silicon oxidizing power of the nitrous acid increases as the amount of nitrous acid contained in the etching solution E increases, resulting in an increase in the silicon oxidizing power of the etching solution E. Note that the horizontal axis in FIG. 9 represents the number of processed wafers W, the first vertical axis represents the silicon oxidizing power of the etching solution E (solid line in FIG. 9), and the second vertical axis represents the composition concentration of the etching solution E (dotted line in FIG. 9).

[0112] Furthermore, the inventors conducted experiments and found that when the concentration of nitric acid in the etching solution E is increased as the number of processed wafers W increases, the amount of etching at the center of the wafer W increases. Therefore, in light of these findings, it is presumed that when etching a plurality of wafers W using the etching solution E repeatedly, the amount of nitrous acid in the etching solution E increases, and this increase in nitric acid increases the amount of etching at the center of the wafer W.

[0113] 9B, as the number of processed wafers W increases, the concentration of nitric acid in the processing solution replenished to the etching solution E in the reuse processing is reduced, thereby reducing the concentration of nitric acid in the generated reuse etching solution Er. In this case, the silicon oxidizing power of the nitric acid can be reduced, and therefore the silicon oxidizing power of the etching solution E can be kept constant.

[0114] In this embodiment, the concentration of nitric acid in the processing solution is reduced while the fixed replenishment amount of the processing solution to be replenished to the etching solution E in the reuse process is derived by mathematical optimization as in the above embodiment. Specifically, the evaluation function used when calculating the total fixed replenishment amount by mathematical optimization in T9 of the above embodiment is changed to an evaluation function that reduces the concentration of nitric acid. In the following description, the evaluation function that keeps the composition concentration of the etching solution E constant as in the above embodiment is referred to as the first evaluation function, and the evaluation function that reduces the concentration of nitric acid in the etching solution E as in the present embodiment is referred to as the second evaluation function.

[0115] The first evaluation function in the above embodiment is a function that calculates the sum of each component by dividing the absolute error between the target molar fraction and the molar fraction after total fixed replenishment by the target molar fraction, for example.

[0116] The second evaluation function of this embodiment expands the first evaluation function into each component. In this case, in the nitric acid term of the second evaluation function, the total molar fraction of hexafluorosilicic acid after the total replenishment of nitric acid is weighted and added to calculate the total molar fraction. Then, the total replenishment amount is calculated by mathematical optimization so that the absolute error between the target molar fraction of nitric acid and the total molar fraction is minimized. Note that in this embodiment, molar fraction is used, but this molar fraction is calculated from the concentration, and as mentioned above, it is synonymous with concentration.

[0117] Here, since there is a correlation between the concentration (molar fraction) of hexafluorosilicic acid and the concentration (molar fraction) of nitrous acid, an increase in nitrous acid in the etching solution E also increases hexafluorosilicic acid. Therefore, in the second evaluation function, an increase in nitrous acid is regarded as an increase in hexafluorosilicic acid, and the increase in hexafluorosilicic acid is taken into consideration when calculating the above-mentioned combined molar fraction. In other words, the second evaluation function is a function that decreases the concentration of nitric acid as the concentration of nitrous acid increases, and decreases the silicon oxidation power of nitric acid as the silicon oxidation power of nitrous acid increases.

[0118] In the second evaluation function, the weighting factor α of the molar fraction of hexafluorosilicic acid after total replenishment can be set arbitrarily. For example, when α = 5, the total replenishment amount is optimized so that the sum of five times the molar fraction of hexafluorosilicic acid after total replenishment and the molar fraction of nitric acid after total replenishment becomes the target molar fraction of nitric acid. In this case, the replenishment amount of the treatment solution is reduced compared to when α = 1.

[0119] Furthermore, in the constraint conditions of the second evaluation function, the value (fluctuation ratio) obtained by dividing the difference between the target molar fraction of phosphoric acid and the molar fraction after total quantitative replenishment by the target molar fraction of phosphoric acid is set to be equal to or greater than the constraint ratio β. Similarly, the value (fluctuation ratio) obtained by dividing the difference between the target molar fraction of water and the molar fraction after total quantitative replenishment by the target molar fraction of water is set to be equal to or greater than the constraint ratio β. Then, the value (fluctuation ratio) obtained by dividing the combined molar fraction of nitric acid by the target molar fraction of nitric acid is set to be equal to or greater than the constraint ratio 2β. Note that β is a value between 0 (zero) and 1 (inclusive). Under these constraint conditions, the concentration (molar fraction) of phosphoric acid and the concentration (molar fraction) of water in the etching solution E are forcibly increased, and the concentration (molar fraction) of nitric acid is reduced.

[0120] In T9, the total fixed replenishment amount is calculated by mathematical optimization so as to minimize the second evaluation function under the constraint conditions set as above. Then, in T10, the total fixed replenishment amount calculated in T9 is distributed to derive the fixed replenishment amount.

[0121] According to this embodiment, the concentration of nitric acid in the processing liquid is reduced while a fixed replenishment amount of the processing liquid to be replenished to the etching liquid E in the reuse process is derived by mathematical optimization. Therefore, the silicon oxidation power of the etching liquid E is kept constant, and an increase in the etching amount at the center of the wafer W is suppressed, thereby making the etching amount distribution of the wafer W uniform within the wafer surface. As a result, the surface shape of the wafer W after etching can be made to a target shape. In other words, the surface shape of the wafer W after etching can be appropriately controlled.

[0122] In the above embodiment, the case where the concentration of nitric acid in the processing liquid is reduced when a fixed amount of processing liquid is replenished to the etching liquid E in the reuse process has been described, but the technology of the present disclosure can be applied to cases other than the fixed amount of processing liquid replenishment. That is, even when an arbitrary amount of processing liquid is replenished to the etching liquid E in the reuse process, by reducing the concentration of nitric acid in the processing liquid, the silicon oxidation power of the etching liquid E can be made constant and the etching amount distribution of the wafer W can be made uniform within the wafer surface.

[0123] In the above embodiment, various processes are performed on both the first surface Wa and the second surface Wb of the wafer W. However, the technology of the present disclosure can also be applied to various processes performed on one surface of the wafer W. For example, for an overlapped wafer in which a first wafer and a second wafer are bonded together, the surface of the first wafer is ground to thin it, and the ground surface of the first wafer is then etched to smooth it. The technology of the present disclosure can be applied to etching the ground surface of the first wafer.

[0124] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The above-described embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims. For example, the components of the above-described embodiments may be arbitrarily combined. Such an arbitrary combination naturally provides the functions and effects of each of the components involved in the combination, and also provides other functions and effects that are apparent to those skilled in the art from the description of this specification.

[0125] Furthermore, the effects described herein are merely descriptive or exemplary and are not limiting. In other words, the technology according to the present disclosure may achieve other effects that are apparent to those skilled in the art from the description of this specification, in addition to or in place of the above-described effects.

[0126] REFERENCE SIGNS LIST 1 wafer processing system 40 etching device 110 control device 300 recycling device E etching solution Er recycled etching solution Es test etching solution Et recycled test etching solution Eu test replenishment etching solution W wafer Wt test wafer

Claims

1. A substrate processing method for processing a substrate, comprising: supplying an etching solution containing a plurality of types of processing solutions to an etching target on a substrate, and etching the etching target; recovering the etching solution after etching, and performing a reuse process of replenishing a certain amount of the processing solution to the etching solution when a replenishment condition is satisfied, thereby generating a reused etching solution for etching a subsequent etching target, wherein deriving the replenishment amount comprises: performing an etching process on a test etching target on a test substrate using a test etching solution not subjected to the reuse process, thereby generating a reused test etching solution after etching the test etching target; replenishing the reused test etching solution with an inert liquid, and estimating a total substance amount of the reused test etching solution before replenishing the inert liquid from the test replenishment etching solution after replenishing the inert liquid; and calculating the total substance amount of the reused test etching solution by mathematical optimization using the estimated total substance amount of the reused test etching solution so that an absolute error between a target composition concentration of the reused test etching solution and a composition concentration of the reused test etching solution after replenishing the reused test etching solution with the total replenishment amount of the processing solution is minimized; deriving the replenishment amount using the total replenishment amount and an integrated etching amount of the test etching target.

2. A substrate processing method as described in claim 1, in which the total amount of substance of the reused test etching solution before replenishment of the inert liquid is estimated from a material balance relationship using the composition concentrations of the reused test etching solution before replenishment of the inert liquid, the composition concentrations of the test replenishment etching solution after replenishment of the inert liquid, and the amount of substance of the inert liquid.

3. The substrate processing method of claim 2, further comprising the steps of: calculating a total amount of substance for each component in the reuse test etching solution; and estimating a representative value of the total amount of substance for each component as the total amount of substance of the reuse test etching solution before replenishment with inert liquid.

4. The substrate processing method according to claim 1, wherein the target composition concentration of the reused test etching solution is a composition concentration of the test etching solution before etching the test etching target.

5. The substrate processing method according to claim 1, wherein the compositional concentration of the reused test etching solution is a molar fraction of a component in the reused test etching solution.

6. The substrate processing method of claim 1, wherein the cumulative etching amount of the test etching object is calculated using the compositional concentration of the test etching solution before etching the test etching object and the compositional concentration of the reused test etching solution after etching the test etching object.

7. The substrate processing method according to claim 1, wherein the replenishment condition is based on an accumulated supply amount of the etching liquid supplied to the etching target.

8. A substrate processing system for processing substrates, comprising: an etching device for supplying an etching solution containing a plurality of types of processing liquid to an etching target on a substrate to etch the etching target; a recycling device for recovering the etching solution after etching, and performing a recycling process of refilling the etching solution with a fixed amount of the processing liquid when a replenishment condition is satisfied, thereby generating a recycled etching solution for etching a subsequent etching target; and a control device for deriving the replenishment amount, wherein the control device performs a control for etching a test etching target on a test substrate using a test etching solution not subjected to the recycling process, thereby generating a recycled test etching solution after etching the test etching target; a control for refilling the recycled test etching solution with an inert liquid, and estimating a total substance amount of the recycled test etching solution before the refilling of the inert chemical liquid from the test replenishment etching solution after the refilling of the inert chemical liquid; and a control for calculating the total replenishment amount by mathematical optimization using the estimated total substance amount of the recycled test etching solution so that an absolute error between a target composition concentration of the recycled test etching solution and a composition concentration of the recycled test etching solution after the recycled test etching solution is replenished with a total replenishment amount of the processing liquid is minimized. and deriving the replenishment amount using the total replenishment amount and an integrated etching amount of the test etching target.

9. The substrate processing system of claim 8, wherein the control device executes control to estimate the total amount of substance of the reused test etching solution before replenishment of the inert liquid from a material balance relationship using the composition concentrations of the reused test etching solution before replenishment of the inert liquid, the composition concentrations of the test replenishment etching solution after replenishment of the inert liquid, and the amount of substance of the inert liquid.

10. The substrate processing system of claim 9, wherein the control device calculates a total amount of substance for each component in the reuse test etching solution and performs control to estimate a representative value of the total amount of substance for each component as the total amount of substance of the reuse test etching solution before inert liquid replenishment.

11. The substrate processing system according to claim 8, wherein the target composition concentration of the reused test etching solution is a composition concentration of the test etching solution before etching the test etching target.

12. The substrate processing system of claim 8, wherein the compositional concentration of the reused test etchant is a mole fraction of a component in the reused test etchant.

13. The substrate processing system of claim 8, wherein the control device performs control to calculate an accumulated etching amount of the test etching target using a composition concentration of the test etching solution before etching the test etching target and a composition concentration of the reused test etching solution after etching the test etching target.

14. The substrate processing system according to claim 8, wherein the replenishment condition is based on an accumulated supply amount of the etching liquid supplied to the etching target.

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