Substrate processing method and substrate processing system

Abstract

A substrate processing method for processing a substrate, the method comprising: a step for grinding the surface of the substrate; a step for etching the surface by supplying an etching liquid to the surface of the substrate after the grinding; and a step for removing a metal adhering to the surface by supplying a cleaning liquid to the surface of the substrate after the etching. A substrate processing system for processing a substrate, the system comprising: a grinding unit for grinding the surface of the substrate; an etching liquid supply unit for etching the surface by supplying an etching liquid to the surface of the substrate after the grinding; and a cleaning liquid supply unit for removing a metal adhering to the surface by supplying a cleaning liquid to the surface of the substrate after the etching.

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a method for manufacturing a semiconductor wafer, which includes a step of planarizing at least the front surface of a wafer obtained by slicing a semiconductor ingot, and a step of etching the front surface of the planarized wafer by spin etching. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-135464 Summary of the Invention [Problem to be solved by the invention]

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

[0005] One aspect of the present disclosure is a substrate processing method for processing a substrate, the method comprising: grinding a surface of the substrate while holding the substrate on a porous chuck containing metal; and supplying an etching solution to the surface of the substrate after grinding; the thickness distribution of the substrate The method includes etching to make the surface uniform, and applying a cleaning liquid to the surface of the substrate after etching to remove metal adhering to the surface. [Effects of the Invention]

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

[0007]

Figure 1

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Figure 3

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Figure 8

[0008] In the manufacturing process of semiconductor devices, the cut surface of a disk-shaped silicon wafer (hereinafter simply 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 at least the front surface of a wafer obtained by slicing a semiconductor ingot is flattened by surface grinding or lapping, and then the front surface is etched by spin etching. In addition, the spin etching process disclosed in Patent Document 1 uses a mixed acid as an etching solution.

[0010] Here, the surface grinding of the wafer is performed, for example, while the wafer is held by a chuck. The chuck contains a metal component, and the metal may adhere to the surface of the wafer after grinding.

[0011] Also, in the etching of the wafer surface, it is preferable to reduce the etching amount from the viewpoint of improving throughput. For example, if the etching rate is increased in an attempt to improve throughput, the uniformity of etching deteriorates, and as a result, the performance of the product decreases. Further, from the viewpoint of reducing the consumption of the etching solution, it is also preferable to reduce the etching amount.

[0012] When reducing the etching amount as described above, even if the surface of the wafer is etched with an etching solution that is a mixed acid, the metal adhering to the surface of the wafer after grinding may not be completely removed. And if metal remains on the surface of the wafer, the performance of the product will decrease. Therefore, there is room for improvement in the conventional etching process.

[0013] The technology according to the present disclosure appropriately cleans the surface of the substrate after grinding. Hereinafter, a wafer processing system as a substrate processing system according to the present embodiment and a wafer processing method as a substrate processing method will be described with reference to the drawings. In this specification and the drawings, elements having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

[0014] As shown in FIG. 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 is, for example, where a cassette C capable of accommodating a plurality of wafers W is loaded / unloaded with the outside. The processing station 11 is equipped with various processing apparatuses for performing desired processing on the wafer W.

[0015] The loading / unloading 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, for example, two cassettes C in a row in the Y-axis direction.

[0016] The processing station 11 is provided with, for example, three processing blocks G1 to G3. The first processing block G1, the second processing block G2, and the third processing block G3 are arranged in this order from the negative X-axis side (the side of the loading / unloading station 10) to the positive direction side.

[0017] The first processing block G1 is provided with an inversion device 30, 31, a thickness measurement device 40, etching devices 50, 51 as liquid processing devices, and a wafer transfer device 60. The etching device 50 corresponds to the first liquid processing device in the present disclosure, and the etching device 51 corresponds to the second liquid processing device in the present disclosure. The inversion device 30 and the etching device 50 are arranged in this order from the negative X-axis side to the positive direction side. The inversion devices 30, 31 and the thickness measurement device 40 are provided, for example, stacked in this order from the lower stage in the vertical direction. The etching devices 50, 51 are provided, for example, stacked in this order from the lower stage in the vertical direction. The wafer transfer device 60 is arranged on the positive Y-axis side of the etching devices 50, 51. Note that the number and arrangement of the inversion devices 30, 31, the thickness measurement device 40, the etching devices 50, 51, and the wafer transfer device 60 are not limited to this.

[0018] The inversion devices 30, 31 invert the first surface Wa and the second surface Wb of the wafer W in the vertical direction. The configuration of the inversion devices 30, 31 is arbitrary.

[0019] The thickness measurement device 40 includes, in one example, 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 a plurality of points. The calculation unit obtains the thickness distribution of the wafer W from the measurement results (the thickness of the wafer W) by the measurement unit. Note that the calculation unit may further calculate the flatness (TTV: Total Thickness Variation) of the wafer W. Further, the calculation of the thickness distribution and flatness of such a wafer W may be performed by a 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. Note that the configuration of the thickness measurement device 40 is not limited to this and can be arbitrarily configured.

[0020] The etching devices 50 and 51 etch silicon (Si) on 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 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.

[0021] The wafer transfer device 60 has, for example, two transfer arms 61 that hold and transfer a 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).

[0022] 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.

[0023] 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.

[0024] The cleaning device 80 cleans 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 and clean the first surface Wa or the second surface Wb. Note that, for cleaning the first surface Wa or the second surface Wb, a pressurized cleaning liquid may be used. Further, the cleaning device 80 may be configured to be able to clean the first surface Wa and the second surface Wb simultaneously when cleaning the wafer W.

[0025] Similar to the inversion devices 30 and 31, the inversion device 90 inverts the first surface Wa and the second surface Wb of the wafer W in the vertical direction. The configuration of the inversion device 90 is arbitrary.

[0026] The wafer transfer device 100 holds and transfers the wafer W and, for example, has two transfer arms 101. Each transfer arm 101 is configured to be movable in the horizontal direction, the vertical direction, around the horizontal axis, and around the vertical axis. Then, 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 the processing device 110 described later.

[0027] The processing device 110 is provided in the third processing block G3. Note that the number and arrangement of the processing devices 110 are not limited to this.

[0028] The processing device 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). On the rotary table 111, four chucks 113 for sucking and holding the wafer W are provided. Among the four chucks 113, two first chucks 113a are chucks used for grinding the first surface Wa and suck and hold the second surface Wb. These two first chucks 113a are arranged at positions that are point-symmetrical with respect to the rotation center line 112. The remaining two second chucks 113b are chucks used for grinding the second surface Wb and suck and hold the first surface Wa. These two second chucks 113b are also arranged at positions that are point-symmetrical with respect to the rotation center line 112. That is, the first chucks 113a and the second chucks 113b are alternately arranged in the circumferential direction. Note that, for example, a porous chuck is used for the chuck 113. Further, the porous chuck of the chuck 113 contains a metal such as alumina, for example.

[0029] The four chucks 113 are movable to the delivery positions A1 to A2 and the processing positions B1 to B2 when the rotary table 111 rotates. Further, each of the four chucks 113 is configured to be rotatable about a vertical axis by a rotation mechanism (not shown).

[0030] The first delivery position A1 is a position on the negative X-axis side and the positive Y-axis side of the rotary table 111, and the wafer W is delivered to the first chuck 113a when grinding the first surface Wa. The second delivery position A2 is a position on the negative X-axis side and the negative Y-axis side of the rotary table 111, and the wafer W is delivered to the second chuck 113b when grinding the second surface Wb.

[0031] A thickness measuring unit 120 is provided at each of the delivery positions A1 and A2 to measure the thickness of the wafer W after grinding. The thickness measuring unit 120 includes, for example, 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.

[0032] The first processing position B1 is a position on the X-axis positive side and the Y-axis negative side of the rotary table 111, where a first grinding unit 130 serving as a grinding unit is disposed. The second processing position B2 is a position on the X-axis positive side and the Y-axis positive side of the rotary table 111, where a second grinding unit 140 serving as a grinding unit is disposed.

[0033] 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.

[0034] 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.

[0035] The above wafer processing system 1 is provided with a control device 150. The control device 150 is a computer including, for example, a CPU, a memory, etc., and has a program storage unit (not shown). The program storage unit stores a program for controlling the processing of the wafer W in the wafer processing system 1. Note that the above program may be recorded on a computer-readable storage medium H and installed from the storage medium H into the control device 150. Further, the storage medium H may be temporary or non-temporary.

[0036] Next, the detailed configurations of the above-described etching devices 50 and 51 will be described. In the following description, the configuration of the etching device 50 will be described, but the configuration of the etching device 51 is the same.

[0037] As shown in FIG. 2, the etching device 50 has a wafer holding unit 200 as a substrate holding unit that holds the wafer W. The wafer holding unit 200 holds the outer edge portion of the wafer W at a plurality of points, three points in this embodiment. Note that the configuration of the wafer holding unit 200 is not limited to the illustrated example. For example, the wafer holding unit 200 may include a chuck (not shown) that adsorbs and holds the wafer W from below. The wafer holding unit 200 is configured to be rotatable about a vertical axis by a rotation mechanism 201, and thus the wafer W held on the wafer holding unit 200 is configured to be rotatable.

[0038] An inner cup 210 and an outer cup 220 are provided around the wafer holding unit 200. The inner cup 210 is provided so as to surround the wafer holding unit 200 and collects the etching solution as will be described later. A drain line 211 for discharging the collected etching solution is connected to the inner cup 210. Further, the inner cup 210 is configured to be movable up and down by a lifting mechanism 212.

[0039] The outer cup 220 is provided so as to surround the wafer holding part 200 on the outside of the inner cup 210, and collects the rinse liquid or the cleaning liquid as described later. A drain line 221 for discharging the collected rinse liquid or cleaning liquid is connected to the outer cup 220. Although the outer cup 220 does not move up and down in the present embodiment, it may be configured to be movable up and down by a lifting mechanism (not shown).

[0040] Above the wafer holding part 200, an etching liquid nozzle 230 as an etching liquid supply part, a rinse liquid nozzle 231, and a cleaning liquid nozzle 232 as a cleaning liquid supply part are provided. The etching liquid nozzle 230 and the rinse liquid nozzle 231 are provided integrally and are configured to be movable in the horizontal direction and the vertical direction by a moving mechanism 233. Also, the cleaning liquid nozzle 232 is configured to be movable in the horizontal direction and the vertical direction by a moving mechanism 234. Note that the number of moving mechanisms for moving these liquid nozzles is not limited to this. For example, the etching liquid nozzle 230, the rinse liquid nozzle 231, and the cleaning liquid nozzle 232 may be provided integrally, and there may be one moving mechanism. Also, the etching liquid nozzle 230, the rinse liquid nozzle 231, and the cleaning liquid nozzle 232 may be provided separately, and there may be three moving mechanisms.

[0041] The etching liquid nozzle 230 supplies the etching liquid to the first surface Wa or the second surface Wb of the wafer W held by the wafer holding part 200, and etches the first surface Wa or the second surface Wb. The etching liquid contains hydrofluoric acid (HF), nitric acid (HNO3), and phosphoric acid (H3PO4). In one example, the etching liquid E is an aqueous solution containing hydrofluoric acid, nitric acid, phosphoric acid, and water.

[0042] In the present embodiment, the etching liquid is reused for etching a plurality of wafers W. That is, the etching liquid used for one wafer W is recovered and reused for etching the next wafer W. For this reason, an etching liquid recycling part 240 is provided in the etching apparatus 50.

[0043] The etching solution recycling unit 240 is connected to the drainage line 211. Also, a supply line 241 is connected to the etching solution recycling unit 240, and the supply line 241 is connected to the etching solution nozzle 230. A valve 242 for controlling the supply of the etching solution is provided in the supply line 241. Further, a concentration meter 243 for measuring the concentration of the etching solution is provided in the supply line 241. The concentration meter 243 can measure the concentration of each component contained in the etching solution, such as hydrofluoric acid, nitric acid, phosphoric acid, etc.

[0044] The etching solution recycling unit 240 has, for example, a tank for storing the etching solution inside. 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 recycling unit 240. The hydrofluoric acid supply source 244, the nitric acid supply source 245, and the phosphoric acid supply source 246 each store hydrofluoric acid, nitric acid, and phosphoric acid inside, and supply the hydrofluoric acid, nitric acid, and phosphoric acid to the etching solution inside the etching solution recycling unit 240. Valves 247, 248, and 249 for controlling the supply of hydrofluoric acid, nitric acid, and phosphoric acid are provided between the hydrofluoric acid supply source 244, the nitric acid supply source 245, the phosphoric acid supply source 246 and the etching solution recycling unit 240, respectively.

[0045] In such a case, the etching solution recovered by the inner cup 210 is discharged to the etching solution recycling unit 240 via the drainage line 211. In the etching solution recycling unit 240, the composition ratio of the etching solution is adjusted by supplying any one or a plurality of hydrofluoric acid, nitric acid, and phosphoric acid from the hydrofluoric acid supply source 244, the nitric acid supply source 245, and the phosphoric acid supply source 246 to the etching solution. Then, the etching solution with the adjusted composition ratio is supplied to the etching solution nozzle 230 via the supply line 241. By reusing the etching solution in this way, the amount of etching solution used can be reduced and the cost can be reduced.

[0046] 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. 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. The rinse liquid supply source 251 stores the rinse liquid therein. A valve 252 is provided in the liquid supply line 250 to control the supply of the rinse liquid. The rinse liquid may be, for example, pure water.

[0047] The cleaning liquid nozzle 232 supplies a cleaning liquid to the first surface Wa or the second surface Wb of the wafer W held by the wafer holder 200, and removes metal adhering to the first surface Wa or the second surface Wb. A two-fluid nozzle is used as the cleaning liquid nozzle 232.

[0048] A liquid supply line 260 is connected to the cleaning liquid nozzle 232, and the liquid supply line 260 is connected to a cleaning liquid supply source 261. The cleaning liquid supply source 261 stores a cleaning liquid therein. A valve 262 that controls the supply of the cleaning liquid is provided on the liquid supply line 260. Note that the cleaning liquid used is a liquid that can remove metal from the first surface Wa or the second surface Wb of the wafer W, such as hydrofluoric acid or a mixture of hydrofluoric acid and hydrogen peroxide (FPM).

[0049] Furthermore, an air supply line 263 is connected to the cleaning liquid nozzle 232, and the air supply line 263 is connected to a gas supply source 264. The gas supply source 264 stores therein a gas, for example, nitrogen gas which is an inert gas. The air supply line 263 is provided with a valve 265 which controls the supply of gas.

[0050] In the cleaning liquid nozzle 232, the cleaning liquid from the liquid supply line 260 and the gas from the gas supply line 263 are mixed and sprayed onto the first surface Wa or the second surface Wb of the wafer W. By spraying the cleaning liquid in this manner, metals are removed not only chemically by the cleaning liquid but also by the physical collision force of the cleaning liquid.

[0051] Next, the wafer processing performed using the wafer processing system 1 configured as described above will be explained. In the present embodiment, a process for improving the in-plane thickness uniformity is performed on the wafer W cut out from an ingot by a wire saw or the like and lapped.

[0052] First, a cassette C containing a plurality of wafers W is placed on the cassette mounting table 20 of the loading / unloading station 10. In the cassette C, the wafers W are stored with the first surface Wa facing upward and the second surface Wb facing downward. Next, the wafer W in the cassette C is taken out by the wafer transfer device 60 and transferred to the buffer device 70.

[0053] Next, the wafer W is transferred to the processing device 110 by the wafer transfer device 100 and delivered to the first chuck 113a at the first delivery position A1. At the first chuck 113a, the second surface Wb of the wafer W is sucked and held.

[0054] Next, the rotary table 111 is rotated to move the wafer W to the first processing position B1. Then, the first surface Wa of the wafer W is ground by the first grinding unit 130 (step S1 in FIG. 3).

[0055] Next, the rotary table 111 is rotated to move the wafer W to the first delivery position A1. At the first delivery position A1, the first surface Wa of the ground wafer W may be cleaned by a cleaning unit (not shown).

[0056] Also, at the delivery position A1, the thickness of the wafer W after grinding by the first grinding unit 130 is measured by the thickness measurement unit 120 (step S2 in FIG. 3).

[0057] As described above, the thickness measurement unit 120 measures the thickness of the wafer W after grinding at multiple points to obtain the thickness distribution of the wafer W on its 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.

[0058] Next, the wafer W is transferred to the cleaning apparatus 80 by the wafer transfer apparatus 100. In the cleaning apparatus 80, the first surface Wa of the wafer W is cleaned (step S3 in FIG. 3).

[0059] 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.

[0060] 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.

[0061] Next, the rotary table 111 is rotated to move the wafer W to the second processing position B2. Then, the second surface Wb of the wafer W is ground by the second grinding unit 140 (step S5 in FIG. 3).

[0062] 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).

[0063] Also, at the delivery position A2, the thickness measuring unit 120 measures the thickness of the wafer W after grinding by the second grinding unit 140 (step S6 in FIG. 3). In step S6, the same process as in step S2 is performed. That is, the thickness measuring unit 120 acquires the thickness distribution of the wafer W after grinding 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 the second grinding unit 140 and the surface of the second chuck 113b when grinding the next wafer W is adjusted.

[0064] Next, the wafer W is transferred to the cleaning apparatus 80 by the wafer transfer apparatus 100. In the cleaning apparatus 80, the second surface Wb of the wafer W is cleaned (step S7 in FIG. 3).

[0065] Next, the wafer W is transferred to the etching apparatus 50 by the wafer transfer device 60. In the etching apparatus 50, the first face Wa of the wafer W is held by the wafer holder 200 with the second face Wb facing upward, as shown in FIG. 4(a). 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 face Wb. Then, the etching liquid E is supplied to the entire surface of the second face Wb, and the entire surface of the second face Wb is etched (step S8 in FIG. 3).

[0066] 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 etching time can be shortened, improving the throughput of wafer processing. Also, the amount of etching solution used in etching can be reduced.

[0067] Also, the etching solution E used in step S8 is recovered in the inner cup 210 and discharged to the etching solution recycling unit 240 through the drainage line 211. Then, the etching solution E is supplied from the etching solution recycling unit 240 to the etching solution nozzle 230 through the liquid supply line 241 and reused for etching the next wafer W.

[0068] Next, as shown in FIG. 4(b), the cleaning solution nozzle 232 is moved above the central portion of the wafer W. Also, the inner cup 210 is lowered so that the outer cup 220 is disposed to surround the wafer holding portion 200. Then, while rotating the wafer W, the cleaning solution nozzle 232 is moved between above the central portion and above the outer peripheral portion of the wafer W, and the cleaning solution C is supplied from the cleaning solution nozzle 232 to the second surface Wb. Then, the cleaning solution C is supplied to the entire surface of the second surface Wb, and the entire surface of the second surface Wb is cleaned (step S9 in FIG. 3). Note that the cleaning solution C used in step S9 is recovered in the outer cup 220 and discharged from the drainage line 221.

[0069] Here, when grinding the first surface Wa of the wafer W in step S1, the second surface Wb is sucked and held by the first chuck 113a. At this time, since the first chuck 113a, which is a porous chuck, contains metal, metal may adhere to the second surface Wb. Also, when etching the second surface Wb with the etching solution E in step S8, since the etching amount is as small as 5 μm or less, the metal adhering to the second surface Wb may not be completely removed by such etching.

[0070] Therefore, in step S9, the cleaning solution C is supplied to the second surface Wb to remove the metal adhering to the second surface Wb. Specifically, the metal is lifted off and removed from the second surface Wb by the cleaning solution C. In addition, since the cleaning solution nozzle 232 is a two-fluid nozzle that injects the cleaning solution C onto the second surface Wb, the metal is also removed by the physical impact force of the cleaning solution C.

[0071] In step S9, the cleaning liquid nozzle 232 is moved between above the center and above the outer periphery of the wafer W while supplying the cleaning liquid C to the second surface Wb from the cleaning liquid nozzle 232, so that the cleaning liquid C is supplied to the entire surface of the second surface Wb. Furthermore, the physical collision force of the cleaning liquid C described above also affects the entire surface of the second surface Wb. Therefore, metal can be removed from the second surface Wb.

[0072] Next, as shown in FIG. 4(c), 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. Then, the rinse liquid R is diffused to the outer periphery by 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 is collected in the outer cup 220 and discharged from the drain line 221. It is also desirable to supply the rinse liquid R between steps S8 and S9.

[0073] 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.

[0074] 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.

[0075] 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 being rotated, the etching solution nozzle 230 is moved between above the center and above the outer periphery of the wafer W, and the etching solution E is supplied from the etching solution nozzle 230 to the first surface Wa. As a result, the etching solution E is 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). Note that this etching of the first surface Wa is similar to the etching of the second surface Wb in step S8, and the etching amount is, for example, 5 μm or less.

[0076] Next, in the etching device 51, while rotating the wafer W, the cleaning liquid nozzle 232 is moved between above the center and above the outer periphery of the wafer W, and the cleaning liquid C is supplied from the cleaning liquid nozzle 232 to the first surface Wa. This cleans the first surface Wa, and metal adhering to the first surface Wa is removed (step S13 in FIG. 3). Note that this cleaning of the first surface Wa is similar to the cleaning of the second surface Wb in step S9 above.

[0077] Next, in the etching apparatus 51, while rotating the wafer W, a 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 the above-mentioned step S10. It is also desirable to supply the rinse liquid R between steps S12 and S13.

[0078] 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).

[0079] In step S15, as described above, the thickness of the wafer W is measured at a plurality of points to obtain the thickness distribution of the wafer W after etching. The obtained thickness distribution of the wafer W is output to, for example, the control device 150. Based on the thickness distribution of the wafer W, the control device 150 then adjusts the composition ratio of the etching solution E used for the wafer W to be etched next (step S16 in FIG. 3). The method for adjusting the composition ratio of the etching solution E will be described later.

[0080] On the other hand, the wafer W whose thickness distribution has been measured by the thickness measuring device 40 is transported by the wafer transport device 60 to the cassette C on the cassette mounting table 20. In this way, a series of wafer processes in the wafer processing system 1 are completed. Note that polishing may be performed outside the wafer processing system 1 on the wafer W that has been subjected to the desired process in the wafer processing system 1.

[0081] According to the above embodiment, in steps S9 and S13, since the surface of the wafer W is cleaned using the cleaning liquid C, the metal attached to the surface of the wafer W can be removed. Moreover, since the cleaning liquid C is sprayed onto the surface of the wafer W from the cleaning liquid nozzle 232 which is a two-fluid nozzle, in addition to the chemical metal removal ability of the cleaning liquid C, the physical metal removal ability due to the impact force of the cleaning liquid C is also exerted, and the metal can be removed efficiently. As a result, it becomes possible to maintain the product performance of the wafer W.

[0082] Note that when the chemical metal removal ability of the cleaning liquid C is sufficient, a normal nozzle instead of a two-fluid nozzle may be used for the cleaning liquid nozzle 232. In such a case, the cleaning liquid C may be supplied from the cleaning liquid nozzle 232 to the central portion of the wafer W, and the cleaning liquid C may be diffused to the outer peripheral portion by centrifugal force. In this modified example, although the metal removal ability is inferior compared to the above embodiment, the cleaning liquid nozzle 232 becomes inexpensive, and the cost can be reduced.

[0083] Also, when the physical metal removal ability of the cleaning liquid C is sufficient, instead of hydrofluoric acid, FPM, etc., for example, pure water may be used as the cleaning liquid C. Also in this modified example, compared with the above-described embodiment, the metal removal ability is inferior, but the cleaning liquid C becomes inexpensive and the cost can be reduced.

[0084] Next, a method for adjusting the composition ratio of the etching liquid E in the step S16 will be described.

[0085] In the present embodiment, when etching the wafer W in steps S8 and S12, the etching liquid E is reused for a plurality of wafers W. In such a case, as investigated by the present inventors, in etching, the composition ratio of the etching liquid E changes due to the reaction between the wafer W (silicon) and the etching liquid E (mixed acid). Then, when the present inventors investigated the change over time of the etching liquid E, the results shown in FIG. 5 were obtained. In FIG. 5, the dotted line shows the radial distribution of the etching amount of the wafer W when the etching liquid E in the initial state is used. The solid line shows the radial distribution of the etching amount of the wafer W when the etching liquid E after etching a predetermined number of wafers W is used. As shown in FIG. 5, when the etching liquid E is repeatedly reused, the etching amount decreases as a whole. Also, the etching amount at the center of the wafer W is less than the etching amount at the outer peripheral portion, and the etching profile in the wafer radial direction changes. As a result, the process performance of the etching becomes unstable.

[0086] When the etching solution E is repeatedly reused, the hydrofluoric acid in the etching solution E is consumed. Then, as the concentration of hydrofluoric acid decreases, the etching amount decreases due to the reuse of the etching solution E. Therefore, when the inventors tried to add hydrofluoric acid to the etching solution E, the results shown in FIG. 6 were obtained. In FIG. 6, the dotted line shows the radial distribution of the etching amount of the wafer W when the wafer W is etched using the etching solution E without adding hydrofluoric acid to the reused etching solution E. The solid line shows the radial distribution of the etching amount of the wafer W when hydrofluoric acid is added to the reused etching solution E and the wafer W is etched using the etching solution E. As shown in FIG. 6, when hydrofluoric acid is added to the etching solution E, the overall etching amount of the wafer W increases. However, the etching profile is not improved, and the etching amount at the center of the wafer W remains less than that at the outer peripheral portion.

[0087] Further, when the inventors tried to add hydrofluoric acid and nitric acid to the etching solution E, the results shown in FIG. 7 were obtained. In FIG. 7, the dotted line shows the radial distribution of the etching amount of the wafer W when the wafer W is etched using the etching solution E without adding either hydrofluoric acid or nitric acid to the reused etching solution E. The solid line shows the radial distribution of the etching amount of the wafer W when hydrofluoric acid and nitric acid are added to the reused etching solution E and the wafer W is etched using the etching solution E. As shown in FIG. 7, when hydrofluoric acid and nitric acid are added to the etching solution E, the overall etching amount of the wafer W increases. However, still the etching profile is not improved, and the etching amount at the center of the wafer W remains less than that at the outer peripheral portion.

[0088] In order to increase the overall etching amount, it is preferable to add nitric acid in addition to hydrofluoric acid. In the etching of wafer W, hydrofluoric acid and nitric acid contribute chemically, and the process of etching with hydrofluoric acid and oxidizing with nitric acid is repeated. Therefore, when the etching solution E is repeatedly reused, both hydrofluoric acid and nitric acid in the etching solution E are consumed. However, since the concentration of nitric acid is higher than that of hydrofluoric acid, even if the concentration of nitric acid decreases, the decrease in the concentration of hydrofluoric acid has a greater impact on etching. For this reason, adding hydrofluoric acid to the etching solution E directly contributes to an increase in the etching amount. However, from a long-term perspective, it is preferable to add nitric acid in addition to hydrofluoric acid in order to maintain the concentration balance of hydrofluoric acid and nitric acid in the etching solution E.

[0089] Here, phosphoric acid in the etching solution E does not contribute chemically to the etching of wafer W and is not consumed by the etching. However, when wafer W is etched, water is generated as a by-product. For this reason, the concentration of phosphoric acid relatively decreases. And when the concentration of phosphoric acid decreases, the viscosity of the etching solution E decreases, so that the etching solution E at the center of the rotating wafer W during etching tends to diffuse to the outer periphery. More specifically, when the viscosity of the etching solution E is lower than the centrifugal force caused by the rotation of the wafer W small In this case, the etching solution E tends to diffuse to the outer periphery. For this reason, the etching amount at the center of the wafer W becomes less than the etching amount at the outer periphery.

[0090] Therefore, the inventors tried adding hydrofluoric acid, nitric acid, and phosphoric acid to the etching solution E, and obtained the results shown in FIG. 8. In FIG. 8, the dotted line indicates the radial distribution of the etching amount of the wafer W when the wafer W is etched using the etching solution E to be reused without adding any of hydrofluoric acid, nitric acid, and phosphoric acid. The solid line indicates the radial distribution of the etching amount of the wafer W when the wafer W is etched using the etching solution E to be reused with hydrofluoric acid, nitric acid, and phosphoric acid added. As shown in FIG. 8, when hydrofluoric acid, nitric acid, and phosphoric acid are added to the etching solution E, the overall etching amount of the wafer W increases. Furthermore, the etching amount at the center of the wafer W increases, and the etching profile is also improved.

[0091] If only phosphoric acid is added to the etching solution E, the concentration of hydrofluoric acid will be relatively lowered, resulting in a decrease in the overall etching amount. For this reason, when phosphoric acid is added to improve the etching profile, it is preferable to also add hydrofluoric acid.

[0092] Furthermore, the component added to the etching solution E to improve the etching profile is not limited to phosphoric acid. Any component that does not contribute to etching of the wafer W and improves the viscosity of the etching solution E can be added to the etching solution E.

[0093] As a result of the above-mentioned intensive investigations, the present inventors have come to the following findings. To increase the overall etching amount, add hydrofluoric acid to the etching solution. If the etching amount is to be increased overall, it is preferable to add more nitric acid. To improve the etching profile, add phosphoric acid to the etching solution. To improve the etching profile, it is preferable to add more hydrofluoric acid.

[0094] Based on the above findings, when adjusting the composition ratio of the etching solution E in step S16, the following controls (1) to (3) are performed. (1) In the thickness distribution of the wafer W measured in step S15, when the thickness of the wafer W is overall large (when the etching amount is small), hydrofluoric acid is added to the etching solution E. At this time, it is preferable to further add nitric acid. Note that when the thickness of the wafer W is overall large, for example, it means that the thickness of the wafer W measured in step S15 is overall large compared to the target thickness of the wafer W after etching. (2) In the thickness distribution of the wafer W measured in step S15, when the thickness of the central portion of the wafer W is larger than the thickness of the outer peripheral portion (when the etching amount of the central portion of the wafer W is smaller than the etching amount of the outer peripheral portion), phosphoric acid is added to the etching solution E. At this time, it is preferable to further add hydrofluoric acid. (3) In the thickness distribution of the wafer W measured in step S15, when the thickness of the wafer W is overall large and the thickness of the central portion of the wafer W is larger than the thickness of the outer peripheral portion, hydrofluoric acid and phosphoric acid are added to the etching solution E. At this time, it is preferable to further add nitric acid.

[0095] Note that the method for determining the addition amounts of hydrofluoric acid, nitric acid, and phosphoric acid added to the etching solution E in the above (1) to (3) is arbitrary. For example, hydrofluoric acid, nitric acid, and phosphoric acid may be added in predetermined amounts, and after using the etching solution E, the thickness distribution of the wafer W may be measured to determine the addition amounts of the hydrofluoric acid, nitric acid, and phosphoric acid. Or for example, based on the measurement results measured by the concentration meter 243, the addition amounts of hydrofluoric acid, nitric acid, and phosphoric acid may be determined.

[0096] Then, the etching solution E whose composition ratio has been adjusted by performing the above (1) to (3) is supplied from the etching solution recycling unit 240 to the etching solution nozzle 230 via the liquid supply line 241 and reused for the next etching.

[0097] Note that the adjustment of the composition ratio of the etching solution E by the above (1) to (3) may be performed for each wafer W, or may be performed for a plurality, for example, for each lot (25 pieces).

[0098] According to the above embodiment, based on the thickness distribution of the wafer W after etching measured in step S15, in step S16, any one or more of hydrofluoric acid, nitric acid, and phosphoric acid can be selected and added to the etching solution E, and the composition ratio of the etching solution E can be appropriately adjusted. Therefore, when etching a plurality of wafers W, even when the etching solution E is reused, in-plane uniform etching can be performed on the wafer W using the etching solution E with the adjusted composition ratio, and the surface shape of the wafer W after etching can be appropriately controlled.

[0099] The embodiments disclosed this time should be considered as illustrative in all respects and not restrictive. The above embodiments may be omitted, substituted, or changed in various forms without departing from the scope and gist of the appended claims.

Explanation of Reference Numerals

[0100] 1 Wafer processing system 50 Etching apparatus 51 Etching apparatus 110 Processing apparatus 130 First grinding unit 140 Second grinding unit 230 Etching solution nozzle 232 Cleaning solution nozzle W Wafer

Claims

1. A substrate processing method for processing a substrate, comprising: grinding the surface of the substrate while holding the substrate on a porous chuck containing metal; supplying an etching solution to the surface of the substrate after grinding to etch the substrate to make the thickness distribution uniform; supplying a cleaning solution to the surface of the substrate after etching to remove the metal adhering to the surface.

2. The substrate processing method according to claim 1, wherein the substrate is a substrate after lapping.

3. The substrate processing method according to claim 2, wherein the processing of the substrate is a processing for improving the in-plane uniformity of the thickness of the substrate after lapping.

4. A substrate processing method for processing a substrate, comprising: grinding the surface of the substrate while holding the substrate on a porous chuck containing metal; supplying an etching solution to the surface of the substrate after grinding to etch the surface to make it in-plane uniform; supplying a cleaning solution to the surface of the substrate after etching to remove the metal adhering to the surface, wherein the etching solution contains hydrofluoric acid, nitric acid, and phosphoric acid.

5. The substrate processing method according to any one of claims 1 to 4, wherein removing the metal adhering to the surface of the substrate is removing the metal adhering from the porous chuck containing metal.

6. The substrate processing method according to any one of claims 1 to 4, wherein the cleaning solution contains hydrofluoric acid.

7. The substrate processing method according to claim 6, wherein the cleaning solution is a solution in which hydrofluoric acid and hydrogen peroxide are mixed.

8. When removing the metal, the cleaning solution is mixed with a gas in a two-fluid nozzle and sprayed onto the surface of the substrate.

9. In the etching, the etching amount of the surface of the substrate is 5 μm or less.

10. Grinding the surface of the substrate while holding the substrate on the porous chuck containing metal includes grinding the second surface of the substrate while holding the first surface of the substrate on the porous chuck containing metal, and grinding the first surface while holding the second surface on the porous chuck containing metal. Etching the surface of the substrate after grinding by supplying an etching solution to make the surface uniform in-plane, and supplying a cleaning solution to the surface of the substrate after etching to remove the metal adhering to the surface are performed on the first surface and the second surface. The substrate processing method according to any one of claims 1 to 4.

11. The substrate processing method according to claim 10, comprising measuring the thickness of the substrate at a plurality of points after etching the first and second surfaces of the substrate.

12. The substrate processing method according to claim 11, comprising adjusting the composition ratio of the etching solution to be used for the substrate to be etched next based on the thickness distribution of the substrate.

13. A substrate processing system for processing a substrate, A grinding unit for grinding the surface of the substrate while holding the substrate on a porous chuck containing metal, An etching solution supply unit for supplying an etching solution to the surface of the substrate after grinding to etch the substrate to make the thickness distribution uniform, A substrate processing system having a cleaning solution supply unit for supplying a cleaning solution to the surface of the substrate after etching to remove the metal adhering to the surface.

14. The substrate is a substrate after lapping. The substrate processing system according to claim 13.

15. The processing of the substrate is processing for improving the in-plane uniformity of the thickness of the substrate after lapping. The substrate processing system according to claim 14.

16. A substrate processing system for processing a substrate, A grinding unit for grinding the surface of the substrate while holding the substrate on a porous chuck containing metal, An etching solution supply unit for supplying an etching solution to the surface of the substrate after grinding to etch the substrate to make the surface uniform in-plane, A cleaning solution supply unit for supplying a cleaning solution to the surface of the substrate after etching to remove the metal adhering to the surface, and The etching solution contains hydrofluoric acid, nitric acid and phosphoric acid. The substrate processing system.

17. The cleaning solution supply unit removes the metal adhering to the surface of the substrate from the porous chuck containing metal. The substrate processing system according to any one of claims 13 to 16.

18. The cleaning solution contains hydrofluoric acid. The substrate processing system according to any one of claims 13 to 16.

19. The cleaning solution is a solution in which hydrofluoric acid and hydrogen peroxide are mixed. The substrate processing system according to claim 18.

20. The substrate processing system according to any one of claims 13 to 16, wherein the cleaning liquid supply unit has a two-fluid nozzle that mixes and injects the cleaning liquid and gas.

21. having a control device, The control device performs control to make the etching amount on the surface of the substrate 5 μm or less in the etching. The substrate processing system according to any one of claims 13 to 16.

22. an inversion device for inverting the substrate; a plurality of liquid processing devices including the etching liquid supply unit and the cleaning liquid supply unit, The plurality of liquid processing devices are a first liquid processing device for etching to make the first surface of the substrate uniform in-plane; a second liquid processing device for etching to make the second surface of the substrate uniform in-plane after etching the first surface of the substrate by the first liquid processing device and then inverting the substrate by the inversion device. The substrate processing system according to any one of claims 13 to 16.

23. having a thickness measuring device for measuring the thickness of the substrate, The thickness measuring device measures the thickness of the substrate at a plurality of points after etching the second surface of the substrate by the second liquid processing device. The substrate processing system according to claim 22.

24. having a control device, The control device adjusts the composition ratio of the etching liquid used for the substrate to be etched next based on the thickness distribution of the substrate measured by the thickness measuring device. The substrate processing system according to claim 23.

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