Substrate processing method and substrate processing system

Abstract

Provided is a substrate processing method for processing a substrate, the method including: grinding a surface of the substrate; supplying, to the surface of the substrate after the grinding, a first cleaning liquid for dissolving at least a portion of a metal bonded to the surface; and supplying, in a scanning manner, a second cleaning liquid over the entire surface of the substrate on which at least a portion of the metal bonded to the surface is dissolved.

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 grinding the surface of a substrate obtained by slicing a semiconductor ingot, supplying an etching liquid to the surface of the ground substrate to etch the surface, and supplying a cleaning liquid to the surface of the etched substrate to remove metal adhering to the surface.

[0003] International Publication No. 2023 / 026909

[0004] The technology according to the present disclosure appropriately cleans the substrate surface after grinding.

[0005] One aspect of the present disclosure is a substrate processing method for processing a substrate, comprising: grinding a surface of the substrate; supplying a first cleaning liquid to the ground surface of the substrate, the first cleaning liquid dissolving at least a portion of metal adhering to the surface; and scanningly supplying a second cleaning liquid to the entire surface of the substrate, from which at least a portion of the metal adhering to the surface has been dissolved.

[0006] According to the present disclosure, the surface of the substrate can be properly cleaned after grinding.

[0007] FIG. 1 is a plan view showing an outline of the configuration of a wafer processing system according to the present embodiment; FIG. 2 is a side view showing an outline of the configuration of an etching apparatus; FIG. 3 is a flow diagram showing an outline of main steps of wafer processing; FIG. 4 is an explanatory diagram showing an outline of an etching process; FIG. 5 is a flow diagram showing an outline of main steps of a cleaning process; FIG. 6 is an explanatory diagram showing an outline of main steps of a cleaning process according to a modified example; FIG. 7 is an explanatory diagram showing an outline of a rinsing process; FIG. 8 is a graph explaining the amount of metal adhesion according to a comparative example and an example; and FIG. 9 is an explanatory diagram showing the state of metal adhesion in wafer processing according to an embodiment.

[0008] In the manufacturing process of semiconductor devices, a disk-shaped silicon wafer (hereinafter simply referred to as a "wafer") obtained by cutting a single crystal silicon ingot with a wire saw or the like is planarized by surface grinding or lapping, and then the front surface is etched by spin etching. In the spin etching process, which is one example of etching, a mixed acid containing hydrofluoric acid, nitric acid, phosphoric acid, and water is used as an etching solution.

[0009] Here, the surface grinding of the wafer W is performed, for example, while the wafer is held by a chuck. The chuck contains metal components, and the metal may adhere to the surface of the wafer after grinding. As described above, even if an attempt is made to etch the surface of the wafer W using an etching solution that is a mixed acid, the metal adhering to the surface of the wafer after grinding may not be completely removed. If metal remains on the surface of the wafer W, the quality of the wafer W will deteriorate. To address this issue, Patent Document 1 discloses a method of removing metal remaining on the surface of the wafer W by supplying a cleaning solution to the surface of the wafer W.

[0010] As a result of extensive research, the present inventors have found that there is room for improvement in terms of more appropriately removing metal adhering to the surface of a ground wafer.

[0011] The technology disclosed herein appropriately cleans the substrate surface after grinding. 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.

[0012] 1, the wafer processing system 1 has a configuration in which a loading / unloading station 10 and a processing station 11 are integrally connected. The loading / unloading station 10 loads / unloads a cassette C, which can accommodate a plurality of wafers W, between the loading / unloading station 10 and the outside. The processing station 11 is equipped with various processing devices that perform desired processing on the wafers W.

[0013] The carry-in / out station 10 is provided with a cassette mounting table 20. In the illustrated example, the cassette mounting table 20 is configured to be able to mount a plurality of cassettes C, for example, two cassettes C, in a line in the Y-axis direction.

[0014] For example, three processing blocks G1 to G3 are provided in the processing station 11. The first processing block G1, the second processing block G2, and the third processing block G3 are arranged in this order from the negative side of the X axis (the side of the loading / unloading station 10) to the positive side.

[0015] The first processing block G1 is provided with reversing devices 30 and 31, a thickness measuring device 40, etching devices 50 and 51 as liquid processing devices, and a wafer transport device 60. The etching device 50 corresponds to the first liquid processing device in this disclosure, and the etching device 51 corresponds to the second liquid processing device in this disclosure. The reversing device 30 and the etching device 50 are arranged side by side in this order from the negative side to the positive side of the X axis. The reversing devices 30 and 31 and the thickness measuring device 40 are stacked in this order, for example, vertically from the bottom up. The etching devices 50 and 51 are stacked in this order, for example, vertically from the bottom up. The wafer transport device 60 is arranged on the positive side of the Y axis from the etching devices 50 and 51. Note that the number and arrangement of the reversing devices 30 and 31, the thickness measuring devices 40, the etching devices 50 and 51, and the wafer transport device 60 are not limited to these.

[0016] The reversing devices 30 and 31 vertically reverse the first surface Wa and the second surface Wb of the wafer W. The reversing devices 30 and 31 may have any configuration.

[0017] In one example, the thickness measurement device 40 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. The calculation unit may further calculate the flatness of the wafer W (total thickness variation (TTV)). The calculation of the thickness distribution and flatness of the wafer W may be performed by the control device 150 (described later) instead of the calculation unit. In other words, a calculation unit (not shown) may be provided in the control device 150 (described later). The configuration of the thickness measurement device 40 is not limited to this and may be configured arbitrarily.

[0018] The etching devices 50 and 51 etch silicon (Si) from the first surface Wa or the second surface Wb after grinding by the processing device 110 described below. The etching devices 50 and 51 also clean the first surface Wa or the second surface Wb after etching with a cleaning solution (post-cleaning, described below) to remove metal adhering to the first surface Wa or the second surface Wb. The detailed configuration of the etching devices 50 and 51 will be described later.

[0019] The wafer transfer device 60 has, for example, two transfer arms 61 that hold and transfer the wafer W. Each transfer arm 61 is configured to be movable horizontally, vertically, around a horizontal axis, and around a vertical axis. The wafer transfer device 60 is configured to be able to transfer the wafer W to the cassette C on the cassette mounting table 20, the inverting devices 30 and 31, the thickness measuring device 40, the etching devices 50 and 51, the buffer device 70 (described later), the cleaning device 80 (described later), and the inverting device 90 (described later).

[0020] The second processing block G2 is provided with a buffer apparatus 70, a cleaning apparatus 80, an inverting apparatus 90, and a wafer transfer apparatus 100. The buffer apparatus 70, the cleaning apparatus 80, and the inverting apparatus 90 are stacked vertically in this order from the bottom up. The wafer transfer apparatus 100 is disposed on the negative Y-axis side of the buffer apparatus 70, the cleaning apparatus 80, and the inverting apparatus 90. Note that the number and arrangement of the buffer apparatus 70, the cleaning apparatus 80, the inverting apparatus 90, and the wafer transfer apparatus 100 are not limited to this.

[0021] The buffer device 70 temporarily holds unprocessed wafers W that are transferred from the first processing block G1 to the second processing block G2. The buffer device 70 may have any configuration.

[0022] The cleaning device 80 cleans (pre-cleaning, described later) the first surface Wa or the second surface Wb after grinding by the processing device 110 described later. For example, a brush is brought into contact with the first surface Wa or the second surface Wb to scrub the first surface Wa or the second surface Wb. Note that a pressurized cleaning liquid may be used for pre-cleaning the first surface Wa or the second surface Wb. Furthermore, the cleaning device 80 may be configured to be able to simultaneously clean the first surface Wa and the second surface Wb when pre-cleaning the wafer W.

[0023] The reversing device 90 reverses the first surface Wa and the second surface Wb of the wafer W in the vertical direction, similar to the reversing devices 30 and 31. The reversing device 90 may have any configuration.

[0024] The wafer transfer device 100 has, for example, two transfer arms 101 that hold and transfer a wafer W. Each transfer arm 101 is configured to be movable horizontally, vertically, around a horizontal axis, and around a vertical axis. The wafer transfer device 100 is configured to be able to transfer the wafer W to the etching devices 50 and 51, the buffer device 70, the cleaning device 80, the inversion device 90, and a processing device 110, which will be described later.

[0025] The third processing block G3 is provided with a processing device 110. Note that the number and arrangement of the processing devices 110 are not limited to this.

[0026] The processing apparatus 110 has a rotary table 111. The rotary table 111 is configured to be rotatable about a vertical rotation center line 112 by a rotation mechanism (not shown). Four chucks 113 are provided on the rotary table 111 to suction-hold the wafer W. Of the four chucks 113, two first chucks 113a are used to grind the first surface Wa and suction-hold the second surface Wb. These two first chucks 113a are arranged in point-symmetric positions across the rotation center line 112. The remaining two second chucks 113b are used to grind the second surface Wb and suction-hold the first surface Wa. These two second chucks 113b are also arranged in point-symmetric positions across the rotation center line 112. That is, the first chucks 113a and the second chucks 113b are arranged alternately in the circumferential direction. It should be noted that, for example, a porous chuck is used as the chuck 113. The porous chuck of the chuck 113 contains, for example, a metal such as alumina.

[0027] The four chucks 113 can be moved to the delivery positions A1 to A2 and the processing positions B1 to B2 by the rotation of the rotary table 111. Furthermore, each of the four chucks 113 is configured to be rotatable around a vertical axis by a rotation mechanism (not shown).

[0028] The first transfer position A1 is a position on the negative X-axis side and the positive Y-axis side of the turntable 111, where the wafer W is transferred to the first chuck 113a when the first surface Wa is ground. The second transfer position A2 is a position on the negative X-axis side and the negative Y-axis side of the turntable 111, where the wafer W is transferred to the second chuck 113b when the second surface Wb is ground.

[0029] A thickness measuring unit 120 is provided at each of the transfer positions A1 and A2 to measure the thickness of the wafer W after grinding. In one example, the thickness measuring unit 120 includes a measuring unit (not shown) and a calculating unit (not shown). The measuring unit includes a non-contact sensor that measures the thickness of the wafer W at multiple points. The calculating unit 122 acquires the thickness distribution of the wafer W from the measurement results (thickness of the wafer W) by the measuring unit 121, and further calculates the flatness of the wafer W. The thickness distribution and flatness of the wafer W may be calculated by the control device 150 (described later) instead of the calculation. In other words, a calculating unit (not shown) may be provided in the control device 150 (described later). The thickness measuring unit 120 may also be provided at each of the processing positions B1 and B2.

[0030] The first processing position B1 is located on the X-axis positive side and the Y-axis negative side of the rotary table 111, and a first grinding unit 130 serving as a grinding unit is disposed therein. The second processing position B2 is located on the X-axis positive side and the Y-axis positive side of the rotary table 111, and a second grinding unit 140 serving as a grinding unit is disposed therein.

[0031] The first grinding unit 130 grinds the first surface Wa of the wafer W held by the first chuck 113a. The first grinding unit 130 has a first grinding part 131 equipped with a rotatable annular grinding wheel (not shown). The first grinding part 131 is configured to be movable in the vertical direction along a support 132.

[0032] The second grinding unit 140 grinds the second surface Wb of the wafer W held by the second chuck 113b. The second grinding unit 140 has a configuration similar to that of the first grinding unit 130. That is, the second grinding unit 140 has a second grinding part 141 and a support 142.

[0033] The wafer processing system 1 described above is provided with at least one controller 150. The controller 150 processes computer-executable instructions that cause the wafer processing system 1 to perform the various steps described in this disclosure. The controller 150 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 150 may be included in the wafer processing system 1. The controller 150 may include a processing unit, a storage unit, and a communication interface. The controller 150 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 H or a communication line connected to the communication interface. The storage medium H may be temporary or non-temporary. The processing unit may be a CPU (Central Processing Unit). 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).

[0034] Next, a detailed description will be given of the configuration of the above-mentioned etching apparatuses 50 and 51. In the following description, the configuration of the etching apparatus 50 will be described, but the configuration of the etching apparatus 51 is also the same.

[0035] 2, the etching apparatus 50 has a wafer holding unit 200 as a substrate holding unit 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, and 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 around a vertical axis by a rotation mechanism 201, thereby allowing the wafer W held on the wafer holding unit 200 to rotate.

[0036] An inner cup 210 and an outer cup 220 are provided around the wafer holding part 200. The inner cup 210 is provided to surround the wafer holding part 200 and collects the etching liquid as described below. A drain line 211 that discharges the collected etching liquid is connected to the inner cup 210. The inner cup 210 is configured to be able to move up and down by an elevating mechanism 212.

[0037] The outer cup 220 is provided outside the inner cup 210 so as to surround the wafer holding part 200, and collects the rinse liquid or cleaning liquid as described below. A drain line 221 for discharging the collected rinse liquid or cleaning liquid is connected to the outer cup 220. Note that, although the outer cup 220 does not move up and down in this embodiment, it may be configured to be able to move up and down by a lifting mechanism (not shown).

[0038] Above the wafer holding part 200, an etching solution nozzle 230 and a rinse solution nozzle 231 are provided as etching solution supply parts, and a liquid film forming nozzle 232 and a spray nozzle 233 are provided as cleaning solution supply parts. The etching solution nozzle 230 and the rinse solution nozzle 231 are provided integrally and are configured to be movable in the horizontal and vertical directions by a movement mechanism 234. The liquid film forming nozzle 232 and the spray nozzle 233 are provided integrally and are configured to be movable in the horizontal and vertical directions by a movement mechanism 235. The number of movement mechanisms for moving these liquid nozzles is not limited to this. For example, the etching solution nozzle 230, the rinse solution nozzle 231, the liquid film forming nozzle 232, and the spray nozzle 233 may be provided integrally and one movement mechanism may be used. Alternatively, the etching solution nozzle 230, the rinse solution nozzle 231, the liquid film forming nozzle 232, and the spray nozzle 233 may be provided separately and four movement mechanisms may be used.

[0039] The etching liquid nozzle 230 supplies an etching liquid to the first surface Wa or the second surface Wb of the wafer W held by the wafer holder 200, thereby etching the first surface Wa or the second surface Wb of the wafer W. The etching liquid may be hydrofluoric acid (HF), nitric acid (HNO ３ ), and phosphoric acid (H ３ P.O. ４ In one example, the etching solution E is an aqueous solution containing hydrofluoric acid, nitric acid, phosphoric acid, and water.

[0040] In this embodiment, the etching device 50 is provided with an etching liquid supply tank 240 .

[0041] A liquid supply line 241 is connected to the etching liquid supply tank 240, and the liquid supply line 241 is connected to the etching liquid nozzle 230. A valve 242 that controls the supply of the etching liquid is provided on the liquid supply line 241. In addition, a concentration meter 243 that measures the concentration of the etching liquid is provided on the liquid supply line 241. The concentration meter 243 can measure the concentration of each component contained in the etching liquid, such as hydrofluoric acid, nitric acid, phosphoric acid, etc.

[0042] A hydrofluoric acid supply source 244, a nitric acid supply source 245, and a phosphoric acid supply source 246 are connected to the etching solution supply tank 240. Valves 247, 248, and 249 for controlling the supply of hydrofluoric acid, nitric acid, and phosphoric acid are provided between the etching solution supply tank 240 and the hydrofluoric acid supply source 244, the nitric acid supply source 245, and the phosphoric acid supply source 246, respectively.

[0043] The etching liquid collected in the inner cup 210 may be discharged to the etching liquid supply tank 240 via the drain line 211 and reused.

[0044] The rinse liquid nozzle 231 supplies a rinse liquid to the first surface Wa or the second surface Wb of the wafer W held by the wafer holder 200, thereby rinsing the first surface Wa or the second surface Wb after etching. A liquid supply line 250 is connected to the rinse liquid nozzle 231, and the liquid supply line 250 is connected to a rinse liquid supply source 251. A valve 252 that controls the supply of the rinse liquid is provided on the liquid supply line 250. The rinse liquid may be, for example, pure water.

[0045] The liquid film forming nozzle 232, which serves as a cleaning liquid supply unit, supplies a first cleaning liquid C1 to the first surface Wa or the second surface Wb of the wafer W held in the wafer holding unit 200, and forms a liquid film of the first cleaning liquid C1 on the first surface Wa or the second surface Wb.

[0046] A first cleaning liquid supply line 260 is connected to the liquid film forming nozzle 232, and the first cleaning liquid supply line 260 is connected to a first cleaning liquid supply source 261. A valve 262 that controls the supply of the first cleaning liquid C1 is provided on the first cleaning liquid supply line 260. Note that the first cleaning liquid C1 is a chemical liquid that dissolves metal from the first surface Wa or the second surface Wb of the wafer W, and examples of the chemical liquid that can be used include hydrofluoric acid, a mixture of hydrofluoric acid and hydrogen peroxide (FPM), or a mixture of hydrochloric acid and hydrogen peroxide (HPM).

[0047] 2, the liquid film forming nozzle 232 is provided so that its tip is inclined in the radial direction of the wafer W so as to face away from the injection nozzle 233. In addition, a control mechanism 263 is provided to the liquid film forming nozzle 232. The control mechanism 263 is configured to be controllable so as to adjust the landing position on the wafer W of the first cleaning liquid C1 supplied from the liquid film forming nozzle 232.

[0048] The control mechanism 263 according to this embodiment is a flow rate control mechanism. In this embodiment, the landing position is adjusted by the control device 150 controlling the flow rate of the first cleaning liquid C1 supplied from the liquid film forming nozzle 232 in the control mechanism 263. That is, when the flow rate is increased, the flow velocity of the first cleaning liquid C1 discharged from the liquid film forming nozzle 232 increases. When the flow velocity is higher, the supplied first cleaning liquid C1 follows a trajectory closer to the inclination direction of the liquid film forming nozzle 232 than to the direction of gravity until it lands on the wafer W. In this case, the first cleaning liquid C1 lands at a position closer to the intersection of the inclination direction of the liquid film forming nozzle 232 and the surface of the wafer W. Conversely, when the flow velocity is lower, the supplied first cleaning liquid C1 follows a trajectory closer to the direction of gravity than to the inclination direction of the liquid film forming nozzle 232 until it lands on the wafer W. In this case, the first cleaning liquid C1 lands at a position closer to the position where the direction directly below the liquid film forming nozzle 232 intersects with the surface of the wafer W. As a result, by supplying the first cleaning liquid at a predetermined flow rate corresponding to the position of the liquid film forming nozzle, the landing position can be adjusted, and the liquid can be controlled to land near the center of the wafer W. The relationship between the position of the liquid film forming nozzle 232, the flow rate, and the landing position may be obtained and stored in advance by experiment or simulation, and read out during control.

[0049] The liquid film forming nozzle 232 forms a liquid film of the first cleaning liquid C1 to cover the first surface Wa or the second surface Wb of the wafer W, thereby dissolving at least a portion of the metal adhering to the first surface Wa or the second surface Wb.

[0050] The spray nozzle 233, which serves as a cleaning liquid supply unit, supplies a second cleaning liquid C2 to the first surface Wa or the second surface Wb of the wafer W held in the wafer holding unit 200, thereby removing metal adhering to the first surface Wa or the second surface Wb.

[0051] A second cleaning liquid supply line 270 is connected to the spray nozzle 233, and the second cleaning liquid supply line 270 is connected to a second cleaning liquid supply source 271. The second cleaning liquid supply line 270 is provided with a valve 272 that controls the supply of the second cleaning liquid C2. The second cleaning liquid C2 is a liquid that can remove metal by the physical impact force when supplied from the spray nozzle 233. In one embodiment, the second cleaning liquid C2 is a chemical liquid that dissolves metal from the first surface Wa or the second surface Wb of the wafer W, such as hydrofluoric acid, a mixture of hydrofluoric acid and hydrogen peroxide (FPM), or a mixture of hydrochloric acid and hydrogen peroxide (HPM). In one embodiment, the second cleaning liquid C2 is the same liquid as the first cleaning liquid C1. In another embodiment, the second cleaning liquid C2 is pure water.

[0052] An air supply line 273 is connected to the injection nozzle 233, and the air supply line 273 is connected to a gas supply source 274. The gas supply source 274 supplies, for example, nitrogen gas, which is an inert gas. The air supply line 273 is provided with a valve 275 that controls the supply of gas.

[0053] In the spray nozzle 233, the second cleaning liquid C2 from the second cleaning liquid supply line 270 and the gas from the gas supply line 273 are mixed and sprayed onto the first surface Wa or the second surface Wb of the wafer W. By spraying the second cleaning liquid C2 in this manner, metals are also removed by the physical collision force of the second cleaning liquid C2. In addition, if the second cleaning liquid C2 is configured to be able to chemically remove metals like the first cleaning liquid C1, the metals are also removed by dissolution as a chemical action of the second cleaning liquid C2.

[0054] The first cleaning liquid C1 and the second cleaning liquid C2 may be the same cleaning liquid. In such a modification, instead of providing the first cleaning liquid supply source 261 and the second cleaning liquid supply source 271 separately, a common supply source for supplying the same cleaning liquid may be provided. Also, the first cleaning liquid supply line 260 and the second cleaning liquid supply line 270 may be partially shared.

[0055] In addition, in one embodiment, when the liquid film forming nozzle 232 and the injection nozzle 233 are provided separately, the moving mechanism 235 may be provided only for the injection nozzle 233. In this case, the liquid film forming nozzle 232 may be provided directly above the center of the wafer W, and its tip may be provided so as to point directly downward without being inclined.

[0056] Furthermore, the control mechanism 263 is not limited to a flow rate control mechanism, and may be any mechanism capable of controlling the adjustment of the landing position of the first cleaning liquid C1 supplied from the liquid film forming nozzle 232 on the wafer W. The control mechanism 263 according to one modification is a mechanism for vertically moving the tip position of the liquid film forming nozzle 232 that supplies the first cleaning liquid C1. In this modification, when the tip position is moved to a higher position, the first cleaning liquid C1 lands at a position closer to the inclination direction and further away from directly below the liquid film forming nozzle 232. When the tip position is moved to a lower position, the first cleaning liquid C1 lands at a position closer to directly below the liquid film forming nozzle 232. Furthermore, the control mechanism 263 according to another modification is a variable throttle valve provided in the liquid film forming nozzle 232, and is a mechanism for changing only the flow rate.

[0057] 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.

[0058] First, a cassette C containing a plurality of wafers W is placed on the cassette mounting table 20 of the loading / unloading station 10. 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 wafer transfer device 60 removes the wafers W from the cassette C and transfers them to the buffer device 70.

[0059] Next, the wafer W is transferred to the processing device 110 by the wafer transfer device 100 and transferred to the first chuck 113a at the first transfer position A1. The second surface Wb of the wafer W is held by suction on the first chuck 113a.

[0060] Next, the rotary table 111 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 130 (step S1 in FIG. 3).

[0061] Next, the turntable 111 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).

[0062] At the transfer position A1, the thickness measuring unit 120 measures the thickness of the wafer W after grinding by the first grinding unit 130 (step S2 in FIG. 3).

[0063] As described above, the thickness measuring unit 120 measures the thickness of the wafer W after grinding at multiple points to obtain the thickness distribution of the wafer W on the first surface Wa after grinding, and further calculates the flatness of the wafer W. The calculated thickness distribution and flatness of the wafer W are output to, for example, the control device 150 and used for grinding another wafer W to be held by the first chuck 113a next (to be ground by the first grinding unit 130). Specifically, based on the obtained thickness distribution and flatness of the wafer W, the relative tilt between the surface of the grinding stone and the surface of the first chuck 113a when grinding the next wafer W is adjusted so as to improve the thickness distribution and flatness of the next wafer W after grinding by the first grinding unit 130.

[0064] Next, the wafer W is transferred by the wafer transfer device 100 to the cleaning device 80. In the cleaning device 80, the first surface Wa of the wafer W is pre-cleaned (step S3 in FIG. 3). Note that the cleaning of the first surface Wa or the second surface Wb after grinding and before etching in S3 and S7 described later is referred to as "pre-cleaning."

[0065] Next, the wafer W is transferred to the reversing device 90 by the wafer transfer device 100. In the reversing device 90, the first surface Wa and the second surface Wb of the wafer W are reversed upside down (step S4 in FIG. 3). That is, the wafer W is reversed so that the first surface Wa faces downward and the second surface Wb faces upward.

[0066] Next, the wafer W is transferred to the processing device 110 by the wafer transfer device 100 and transferred to the second chuck 113b at the second transfer position A2. The first surface Wa of the wafer W is held by suction on the second chuck 113b.

[0067] Next, the rotary table 111 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 140 (step S5 in FIG. 3).

[0068] Next, the turntable 111 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).

[0069] Also, at transfer position A2, thickness measurement unit 120 measures the thickness of the wafer W after grinding by second grinding unit 140 (step S6 in FIG. 3). In step S6, the same process as step S2 is performed. That is, thickness measurement unit 120 acquires the thickness distribution of the wafer W after grinding of the second surface Wb, and further calculates the flatness of the wafer W. Then, based on the calculated thickness distribution and flatness of the wafer W, the relative inclination between the surface of the grinding stone of second grinding unit 140 and the surface of second chuck 113b when grinding the next wafer W is adjusted.

[0070] Next, the wafer W is transferred by the wafer transfer device 100 to the cleaning device 80. In the cleaning device 80, the second surface Wb of the wafer W is pre-cleaned (step S7 in FIG. 3).

[0071] Next, the wafer W is transferred to the etching apparatus 50 by the wafer transfer device 60. In the etching apparatus 50, the first surface Wa of the wafer W is held by the wafer holder 200 with the second surface Wb facing upward, as shown in FIG. 4 . At this time, the inner cup 210 is raised and disposed so as to surround the periphery of the wafer holder 200. Next, the etching liquid nozzle 230 is moved above the center of the wafer W. Then, while rotating the wafer W, the etching liquid nozzle 230 is moved between above the center and above the outer periphery of the wafer W, and etching liquid E is supplied from the etching liquid nozzle 230 to the second surface Wb. This causes the etching liquid E to be supplied to the entire surface of the second surface Wb, and the entire surface of the second surface Wb is etched (step S8 in FIG. 3 ).

[0072] The etching of the second surface Wb in step S8 is performed to prevent distortion of the wafer after grinding and to improve the uniformity of the wafer thickness. The etching amount of the second surface Wb in step S8 is, for example, 5 μm or less. When the etching amount is small, the time required for etching can be shortened, thereby improving the throughput of wafer processing. In addition, the amount of etching solution used in etching can be reduced.

[0073] In one embodiment, the etching liquid E used in step S8 is collected in the inner cup 210 and discharged to the etching liquid supply tank 240 via the drain line 211. Then, the etching liquid E is supplied from the etching liquid supply tank 240 to the etching liquid nozzle 230 via the liquid supply line 241 and reused for etching the next wafer W.

[0074] In one embodiment, a rinsing step (not shown) is performed after S8 and before S9. As shown in FIG. 8 , the rinse liquid nozzle 231 is moved above the center of the wafer W. At this time, the inner cup 210 is lowered, and the outer cup 220 is positioned to surround the wafer holder 200. Then, while the wafer W is being rotated, the rinse liquid R is supplied from the rinse liquid nozzle 231 to the center of the second surface Wb. Then, centrifugal force causes the rinse liquid R to spread to the outer periphery, rinsing the entire surface of the second surface Wb. The rinse liquid R used in step S10 may be collected in the outer cup 220 and discharged through the drain line 221. Then, the wafer W continues to rotate with the supply of the rinse liquid R from the rinse liquid nozzle 231 stopped. Then, the second surface Wb is dried.

[0075] Next, the post-etched second surface Wb is post-cleaned (step S9 in FIG. 3 ). Note that the cleaning of the second surface Wb or the first surface Wa after etching in S9 and S13 described later is referred to as “post-cleaning.” When the first surface Wa of the wafer W is ground in step S1, the second surface Wb is suction-held by the first chuck 113a. Since the first chuck 113a, which is a porous chuck, contains metal, metal may adhere to the second surface Wb. Therefore, the post-cleaning in S9 (S13) removes such metal. As shown in FIGS. 5 and 6 , post-cleaning is performed by supplying a first cleaning liquid C1 from the liquid film forming nozzle 232 and a second cleaning liquid C2 from the spray nozzle 233.

[0076] In the post-cleaning, first, as shown in step S101 of FIG. 5 and FIG. 6A, the liquid film forming nozzle 232 and the spray nozzle 233 are moved above the outer periphery of the wafer W. At this time, the inner cup 210 may be lowered, and the outer cup 220 may be positioned so as to surround the periphery of the wafer holder 200. Then, while rotating the wafer W, the first cleaning liquid C1 is first supplied from the liquid film forming nozzle 232. At this time, the flow rate of the first cleaning liquid C1 is controlled so that the first cleaning liquid C1 lands near the center of the wafer W. The first cleaning liquid C1 that has landed near the center of the wafer W is spread toward the outer periphery of the wafer as the wafer rotates. As a result, a liquid film of the first cleaning liquid C1 is formed on the surface of the wafer W.

[0077] Next, as shown in step S102 of FIG. 5 and FIG. 6B , while the supply of the first cleaning liquid C1 from the liquid film forming nozzle 232 continues, the second cleaning liquid C2 is supplied from the spray nozzle 233. The supply of the second cleaning liquid C2 from the spray nozzle 233 in S102 may be started after a desired time has elapsed since the liquid film of the first cleaning liquid C1 is formed on the entire surface of the second side Wb in S101. The time from the formation of the liquid film of the first cleaning liquid C1 until the supply of the second cleaning liquid C2 can be determined in advance experimentally or by simulation as a time such that the amount of metal adhering to the surface of the second side Wb of the wafer W due to post-cleaning becomes less than a desired amount. In one embodiment, when FPM is used as the first cleaning liquid C1, the second cleaning liquid C2 is supplied 10 seconds or more, for example, 15 seconds, after the liquid film of the first cleaning liquid C1 is formed.

[0078] Next, as shown in step S103 of FIG. 5 and FIG. 6( c), while continuing to supply the first cleaning liquid C1 from the liquid film forming nozzle 232 and the second cleaning liquid C2 from the spray nozzle 233, the liquid film forming nozzle 232 and the spray nozzle 233 are moved between above the center and above the outer periphery of the wafer W. Due to the movement of the spray nozzle 233 and the rotation of the wafer W, the second cleaning liquid C2 from the spray nozzle 233 is supplied to the entire surface of the second surface Wb while drawing a spiral on the second surface Wb. This supply of the second cleaning liquid C2 from the spray nozzle 233 to the entire surface of the second surface Wb by the relative movement of the spray nozzle 233 and the wafer W is referred to as "scanning supply." By supplying the second cleaning liquid C2 in a scanning manner, the second cleaning liquid C2 is supplied to the entire surface of the second surface Wb while maintaining the liquid film of the first cleaning liquid C1, and the entire surface of the second surface Wb is cleaned. The first cleaning liquid C1 and the second cleaning liquid C2 used in the post-cleaning may be collected in the outer cup 220 and discharged from the drain line 221.

[0079] Here, the supply control of the first cleaning liquid C1 from the liquid film forming nozzle 232 in S103 will be described. The supply of the first cleaning liquid C1 is controlled by the control mechanism 263 of the liquid film forming nozzle 232 so that the landing position on the wafer W is near the center of the wafer W. The control mechanism 263 in this embodiment is a flow rate control mechanism. When the liquid film forming nozzle 232 is located above a position away from the center of the wafer W, the control mechanism 263 controls the flow rate to be large. On the other hand, when the liquid film forming nozzle 232 is located above a position close to the center of the wafer W, the control mechanism 263 controls the flow rate to be small. By controlling the flow rate, the landing position can be adjusted, and the liquid can be controlled to land near the center of the wafer W. This also makes it possible to supply the second cleaning liquid C2 while maintaining the liquid film of the first cleaning liquid C1.

[0080] In one embodiment, the liquid film forming nozzle 232 and the injection nozzle 233 are provided separately, and the liquid film forming nozzle 232 is provided directly above the center of the wafer W, and its tip is provided so as to point directly downward without being inclined. In addition, the moving mechanism 235 moves only the injection nozzle 233. Supply control in this modified example will be described with reference to FIG.

[0081] 7A, in S101, while the wafer W is being rotated, the first cleaning liquid C1 is first supplied from the liquid film forming nozzle 232. In this modification, the first cleaning liquid C1 supplied from the liquid film forming nozzle 232 lands near the center of the wafer W and is spread toward the outer periphery of the wafer as the wafer rotates. As a result, a liquid film of the first cleaning liquid C1 is formed on the surface of the wafer W.

[0082] In this modification, for example, after the first cleaning liquid C1 is supplied for 15 seconds, next, in S102, as shown in FIG. 7B, the second cleaning liquid C2 is supplied from the spray nozzle 233 while continuing to supply the first cleaning liquid C1 from the liquid film forming nozzle 232. Next, in S103, as shown in FIG. 7C, while continuing to supply the first cleaning liquid C1 from the liquid film forming nozzle 232 and the second cleaning liquid C2 from the spray nozzle 233, only the spray nozzle 233 is moved by the movement mechanism 235, and the second cleaning liquid C2 is supplied in a scanning manner. Note that, as will be described later, if it is considered that the metal M4 has been sufficiently dissolved by the chemical action of the first cleaning liquid C1 in S102 to such an extent that it can be removed by the physical action of the collision of the second cleaning liquid C2 in S103, the supply of the first cleaning liquid C1 may be stopped in S103.

[0083] Next, as shown in FIG. 8 , the rinse liquid nozzle 231 is moved above the center of the wafer W. At this time, the inner cup 210 is lowered, and the outer cup 220 is positioned to surround the periphery of the wafer holder 200. Then, while the wafer W is being rotated, the rinse liquid R is supplied from the rinse liquid nozzle 231 to the center of the second surface Wb. This causes the rinse liquid R to spread to the outer periphery due to centrifugal force, and the entire surface of the second surface Wb is rinsed (step S10 in FIG. 3 ). The rinse liquid R used in step S10 may be collected in the outer cup 220 and discharged through the drain line 221.

[0084] Next, the wafer W continues to rotate while the supply of the rinse liquid R from the rinse liquid nozzle 231 is stopped, thereby drying the second surface Wb.

[0085] Next, the wafer W is transferred to the reversing device 31 by the wafer transfer device 60. In the reversing device 31, the first surface Wa and the second surface Wb of the wafer W are reversed upside down (step S11 in FIG. 3). That is, the wafer W is reversed so that the first surface Wa faces upward and the second surface Wb faces downward.

[0086] Next, the wafer W is transferred to the etching apparatus 51 by the wafer transfer device 60. In the etching apparatus 51, the wafer W is held by the wafer holder 200 with the first surface Wa facing upward and the second surface Wb facing upward. Then, while the wafer W is rotated, the etching solution nozzle 230 is moved between above the center and above the periphery of the wafer W, and etching solution E is supplied from the etching solution nozzle 230 to the first surface Wa. The etching solution E is then supplied to the entire surface of the first surface Wa, and the entire surface of the first surface Wa is etched (step S12 in FIG. 3). The etching of the first surface Wa in S12 is performed to reduce distortion of the wafer after grinding and improve the uniformity of the wafer thickness. The etching of the first surface Wa is similar to the etching of the second surface Wb in S8, and the etching amount is, for example, 5 μm or less.

[0087] In one embodiment, a rinsing step (not shown) is performed after S12 and before S13, which is similar to S10.

[0088] Next, the first surface Wa after etching is post-cleaned (step S13 in FIG. 3). Note that this post-cleaning of the first surface Wa is similar to the post-cleaning of the second surface Wb in S9 above, and includes steps S101 to S103 in FIG. 5.

[0089] Next, in the etching apparatus 51, while rotating the wafer W, the rinse liquid R is supplied from the rinse liquid nozzle 231 to the center of the first surface Wa, thereby rinsing the first surface Wa (step S14 in FIG. 3). Note that this rinsing of the first surface Wa is similar to the rinsing of the second surface Wb in step S10.

[0090] Next, the wafer W is transferred by the wafer transfer device 60 to the thickness measuring device 40. The thickness measuring device 40 measures the thickness distribution of the wafer W after etching by the etching device 51 (step S15 in FIG. 3).

[0091] Meanwhile, the wafer W whose thickness distribution has been measured by the thickness measuring device 40 is transferred by the wafer transfer device 60 to the cassette C on the cassette mounting table 20. This completes the series of wafer processing steps in the wafer processing system 1. Note that the wafer W that has been subjected to the desired processing in the wafer processing system 1 may be polished outside the wafer processing system 1.

[0092] The cleaning steps S9 and S13, including S101 to S103, according to this embodiment resulted in a lower amount of various metals adhering to the surface of the wafer W after cleaning using a cleaning liquid sprayed from a single two-fluid nozzle than in the comparative example. Figure 9 shows the amounts of various metals adhering to the surface of the wafer W in an example in which cleaning using S9 (S13) according to this embodiment was performed on the surface of the wafer W after the grinding (S5 or S1), cleaning (S7 or S3), and etching (S8 or S12) steps according to this embodiment were completed, and in a comparative example in which cleaning was performed using a cleaning liquid sprayed from a single two-fluid nozzle. As can be seen from Figure 9, the amounts of various metals adhering to the surface of the wafer W in the example are each less than the amounts of various metals adhering to the surface of the wafer W in the comparative example.

[0093] The effect of the cleaning in S9 (S13) according to this embodiment will be discussed below with reference to FIG. 10 . As shown in FIG. 10( a), various metals M1 to M4 with different adhesion states are believed to exist on the surface of the wafer W after grinding. Metal M1 that is only adhered to the surface of the wafer W can be removed by pre-cleaning (S7 or S3) using a brush (FIG. 10( b)), while shallowly embedded metal M2 can be removed by etching (S8 or S12) (FIG. 10( c)). At the point in time when etching is complete (FIG. 10( c)), in addition to shallowly embedded metal M3, more deeply embedded metal M4 may be present. In response to this, in S101, a liquid film of the first cleaning liquid C1 is formed and maintained in that state for a desired period of time. As a result, it is believed that at least a portion of the metal particles M3 and M4, which remained in contact with the liquid film of the first cleaning liquid C1, were dissolved by the chemical action of the first cleaning liquid C1, becoming smaller metal particles M3' and M4', which were easily detached from the surface of the wafer W ( FIG. 10( d) ). Furthermore, it is believed that the easily detached metal particles M3' and M4' were subsequently removed by the physical action of the second cleaning liquid C2 in S102 and S103. That is, it is believed that the cleaning in the Example removed metal particles M4 that had penetrated more deeply than could have been removed by the cleaning in the Comparative Example, in which cleaning was performed by spraying cleaning liquids from a single two-fluid nozzle. That is, it is believed that the chemical action of the first cleaning liquid C1 sufficiently dissolved the metal particles M4, particularly the more deeply embedded metal particles M4, to the extent that they could be removed by the physical action of the collision of the second cleaning liquid C2 in S102 and S103. From this perspective, if the metal M4 can be dissolved in the first cleaning liquid C1 to the extent that it can be removed solely by the physical action of the second cleaning liquid C2, the second cleaning liquid C2 may be pure water, although from the viewpoint of metal removal, it is preferable to use a chemical solution that dissolves metal as the second cleaning liquid C2.

[0094] According to the above embodiment, in the post-cleaning (S9, S13), the surface of the wafer W is cleaned using the liquid film forming nozzle 232 and the spray nozzle 233, so it is possible to remove metal adhering to the surface of the wafer W. Furthermore, it is possible to reduce the amount of metal adhering to the surface of the wafer W compared to the comparative example in which post-cleaning is performed by spraying the cleaning liquid from a single two-fluid nozzle.

[0095] Furthermore, by reducing the amount of metal compared to the comparative example, the amount of etching can be reduced in the etching (S8 or S12). This is because etching a large thickness of the wafer in the etching (S8 or S12) eliminates the need to remove metal. This improves the throughput of the etching (S8 or S12), improves uniformity, and reduces the amount of chemical solution consumed.

[0096] In the above embodiment, the second cleaning liquid C2 is supplied from the spray nozzle 233 while the supply of the first cleaning liquid C1 from the liquid film forming nozzle 232 continues in S102 and S103, but this is not limiting. In one embodiment, a liquid film of the first cleaning liquid C1 is formed in S101, and then, after the desired time described above has elapsed, the supply of the first cleaning liquid C1 from the liquid film forming nozzle 232 is stopped. Thereafter, the second cleaning liquid C2 is supplied from the spray nozzle 233 in S102. Even in this case, the above-described action and effect of the liquid film of the first cleaning liquid C1 can be obtained, and metal adhering to the surface of the wafer W can be reduced.

[0097] 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, in the present embodiment, an example of a wafer obtained by cutting a disk-shaped silicon wafer from a single crystal silicon ingot using a wire saw or the like and flattening one surface thereof by surface grinding or lapping has been used, but the present invention is not limited to such an example.

[0098] 232 Liquid film forming nozzle 233 Spray nozzle W Wafer C1 First cleaning liquid C2 Second cleaning liquid

Claims

1. A substrate processing method for processing a substrate, comprising: grinding the surface of the substrate; supplying a first cleaning liquid to the surface of the substrate after grinding to dissolve at least a part of the metal adhering to the surface; and scan-supplying a second cleaning liquid to the entire surface of the substrate where at least a part of the metal adhering to the surface has been dissolved.

2. The substrate processing method according to claim 1, wherein the first cleaning liquid is supplied so as to form a liquid film covering the surface of the substrate.

3. The substrate processing method according to claim 2, wherein the supply of the second cleaning liquid is started after a predetermined time has elapsed since the formation of the liquid film of the first cleaning liquid.

4. The substrate processing method according to claim 2, wherein after starting the supply of the first cleaning liquid, the supply of the second cleaning liquid is started, and while continuing the supply of the first cleaning liquid, the second cleaning liquid is supplied.

5. The first cleaning liquid is supplied from a liquid film forming nozzle, and the second cleaning liquid is supplied from an injection nozzle. When removing the metal, while rotating the substrate, the first cleaning liquid is supplied from the liquid film forming nozzle so that the first cleaning liquid lands on the central portion of the substrate, and the second cleaning liquid is supplied from the injection nozzle while moving the injection nozzle between the central portion and the outer peripheral portion of the substrate. The substrate processing method according to any one of claims 1 to 4.

6. The liquid film forming nozzle and the injection nozzle are provided integrally. When removing the metal, in the liquid film forming nozzle that moves integrally with the injection nozzle, the first cleaning liquid is supplied at a predetermined flow rate corresponding to the position of the liquid film forming nozzle. The substrate processing method according to claim 5.

7. The second cleaning liquid is supplied from a two-fluid nozzle configured to mix the second cleaning liquid with a gas and inject it. The substrate processing method according to any one of claims 1 to 4.

8. The injection nozzle is a two-fluid nozzle configured to mix the second cleaning liquid with a gas and inject it. The substrate processing method according to claim 5.

9. Further comprising supplying an etching liquid to the surface of the substrate after grinding to etch the surface, and supplying the first cleaning liquid and the second cleaning liquid to the surface of the substrate after etching. The substrate processing method according to any one of claims 1 to 4.

10. The first cleaning liquid contains hydrofluoric acid. The substrate processing method according to any one of claims 1 to 4.

11. The substrate processing method according to claim 9, wherein the first cleaning liquid is a liquid in which hydrofluoric acid and hydrogen peroxide are mixed.

12. A substrate processing system for processing a substrate, comprising: a grinding unit for grinding the surface of the substrate; a first cleaning liquid supply unit for supplying a first cleaning liquid capable of dissolving at least a part of the metal adhering to the surface of the substrate after grinding so as to form a liquid film covering the surface; and a second cleaning liquid supply unit for scanningly supplying a second cleaning liquid to the entire surface of the substrate.

13. The substrate processing system according to claim 12, further comprising a control unit, wherein when removing the metal, the control unit supplies the first cleaning liquid from the first cleaning liquid supply unit so that the first cleaning liquid lands on the central portion of the substrate while rotating the substrate, and executes control to supply the second cleaning liquid from the second cleaning liquid supply unit while moving the second cleaning liquid supply unit between the central portion and the outer peripheral portion of the substrate.

14. The substrate processing system according to claim 13, wherein the control unit executes control to start supplying the second cleaning liquid after a predetermined time has elapsed since the liquid film of the first cleaning liquid was formed.

15. The substrate processing system according to claim 13, wherein the control unit starts supplying the second cleaning liquid after starting to supply the first cleaning liquid, and executes control to supply the second cleaning liquid while continuing to supply the first cleaning liquid.

16. The first cleaning liquid supply unit and the second cleaning liquid supply unit are integrally provided, and when removing the metal, the control unit executes control to supply the first cleaning liquid at a predetermined flow rate corresponding to the position of the first cleaning liquid supply unit in the first cleaning liquid supply unit that moves integrally with the second cleaning liquid supply unit.

17. The substrate processing system according to claim 13, further comprising an etching liquid supply unit for supplying an etching liquid to the surface of the substrate after grinding to etch the surface, and the control unit executes control to supply the first cleaning liquid and the second cleaning liquid to the surface of the substrate after etching.

18. The substrate processing system according to any one of claims 12 to 17, wherein the second cleaning liquid supply unit is a two-fluid nozzle configured to mix the second cleaning liquid with a gas and spray it.

19. The substrate processing system according to any one of claims 12 to 17, wherein the first cleaning liquid contains hydrofluoric acid.

20. The substrate processing system according to claim 19, wherein the first cleaning liquid is a liquid in which hydrofluoric acid and hydrogen peroxide are mixed.

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