Substrate treatment apparatus

Abstract

To provide a substrate treatment apparatus that can improve the removal rate of contaminants.SOLUTION: The substrate treatment apparatus according to an embodiment includes: a mounting table that can rotate a substrate formed of silicon or silicon oxide; a cooling unit that can supply a cooling gas to a space between the mounting table and the substrate: a first liquid supply unit that can supply a first liquid to a surface of the substrate opposite to the mounting table side; a third liquid supply unit that can supply an alkaline third liquid having a surface tension smaller than that of the first liquid to the surface of the substrate; and a control unit. The control unit executes supplying the third liquid to the surface of the substrate, and supplying the cooling gas to the space between the mounting table and the substrate; and after having supplied the third liquid, executes forming a liquid film by supplying the first liquid toward the surface of the substrate, and a freezing step of freezing at least one part of the liquid film existing on the surface of the substrate.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] FIELD An embodiment of the present invention relates to a substrate processing apparatus. [Background technology]

[0002] Freeze cleaning has been proposed as a method for removing contaminants such as particles adhering to the surface of substrates such as imprint templates, photolithography masks, and semiconductor wafers.

[0003] In freeze cleaning, for example, when pure water is used as the cleaning liquid, pure water and cooling gas are first supplied to the surface of a rotating substrate. Next, the supply of pure water is stopped, and some of the supplied pure water is discharged to form a water film on the surface of the substrate. The water film is frozen by the cooling gas supplied to the substrate. As the water film freezes to form an ice film, contaminants such as particles are captured by the ice film and separated from the substrate surface. Next, pure water is supplied to the ice film to melt it, and the contaminants are removed from the substrate surface along with the pure water. This improves the contaminant removal rate.

[0004] Here, because the contaminants are in the form of a film, they may be adsorbed onto the surface of the substrate. Furthermore, the surface of the substrate or the contaminants may be ultra-hydrophobic, or both the surface of the substrate and the contaminants may be ultra-hydrophobic. In these cases, the liquid to be frozen may not be able to penetrate between the substrate and the contaminants. If the liquid to be frozen cannot penetrate between the substrate and the contaminants, the effect of separating the contaminants from the surface of the substrate due to the volume expansion caused by the liquid freezing may not be achieved. As a result, the removal rate may be reduced.

[0005] Therefore, there has been a demand for the development of a substrate processing apparatus that can improve the rate of removal of contaminants. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2018-026436 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a substrate processing apparatus capable of improving the rate of removal of contaminants. [Means for solving the problem]

[0008] The substrate processing apparatus according to the embodiment includes a mounting table capable of rotating a substrate, a cooling unit capable of supplying a cooling gas to the space between the mounting table and the substrate, a first liquid supply unit capable of supplying a first liquid to the surface of the substrate opposite the mounting table, a third liquid supply unit capable of supplying an alkaline third liquid having a surface tension lower than that of the first liquid to the surface of the substrate, and a control unit that controls the rotation of the substrate, the supply of the cooling gas, the supply of the first liquid, and the supply of the third liquid. the control unit controls the supply of the cooling gas, the supply of the first liquid, and the supply of the third liquid, thereby supplying the third liquid to the surface of the substrate and supplying the cooling gas to a space between the stage and the substrate; a liquid film forming step, after the pre-rinsing step, of supplying the first liquid toward the surface of the substrate to form a liquid film; a supercooling step of bringing the liquid film on the surface of the substrate into a supercooled state; and a freezing step of freezing at least a portion of the liquid film on the surface of the substrate. Execute. [Effects of the Invention]

[0009] According to an embodiment of the present invention, a substrate processing apparatus capable of improving the rate of removal of contaminants is provided. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic view illustrating a substrate processing apparatus according to an embodiment of the present invention; [Figure 2]FIG. 2 is a schematic view illustrating a control unit of the substrate processing apparatus according to the present embodiment. [Figure 3] 4 is a timing chart illustrating the operation of the substrate processing apparatus. [Figure 4] 10 is a graph illustrating the temperature change of a liquid supplied to a substrate in a freeze cleaning process. [Figure 5] 10 is a flowchart showing a case where the freeze cleaning process is performed multiple times. [Figure 6] 10 is a flowchart illustrating the operation of the control unit when the freeze cleaning process is performed multiple times. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments will be illustrated with reference to the drawings. In the drawings, like components are designated by like reference numerals and detailed descriptions thereof will be omitted where appropriate. The substrate 100 exemplified below may be, for example, a semiconductor wafer, an imprint template, a photolithography mask, or a plate-like body used in MEMS (Micro Electro Mechanical Systems). The substrate 100 may have a patterned uneven portion formed on its surface, or may be a substrate before the uneven portion is formed (for example, a so-called bulk substrate). However, the use of the substrate processing apparatus 1 is not limited to the substrate 100 illustrated as an example.

[0012] In the following, an example will be described in which the substrate 100 is a photolithography mask. When the substrate 100 is a photolithography mask, the planar shape of the substrate 100 can be a substantially rectangular shape.

[0013] FIG. 1 is a schematic view illustrating a substrate processing apparatus 1 according to the present embodiment. FIG. 2 is a schematic view illustrating the control unit 9 of the substrate processing apparatus 1 according to this embodiment. 1, the substrate processing apparatus 1 includes a mounting unit 2, a cooling unit 3, a first liquid supply unit 4, a second liquid supply unit 5, a third liquid supply unit 15, a housing 6, a blower 7, a control unit 9, and an exhaust unit 11. As shown in Fig. 2, the control unit 9 includes a mechanism control unit 9a, a setting unit 9b, and a storage unit 9c.

[0014] The mounting unit 2 has a mounting table 2a, a rotation shaft 2b, and a drive unit 2c. The mounting table 2a is rotatably provided inside the housing 6. The mounting table 2a is plate-shaped. One main surface of the mounting table 2a is provided with a plurality of support portions 2a1 that support the substrate 100. When the substrate 100 is supported by the plurality of support portions 2a1, the surface 100b of the substrate 100 (the surface on which the uneven portion is formed) is oriented away from the mounting table 2a.

[0015] The plurality of supporting portions 2a1 come into contact with the edges of the rear surface 100a of the substrate 100. The portions of the supporting portions 2a1 that come into contact with the edges of the rear surface 100a of the substrate 100 can be tapered or inclined.

[0016] Furthermore, a hole 2aa is provided in the center of the mounting table 2a, penetrating the mounting table 2a in the thickness direction.

[0017] One end of the rotating shaft 2b is fitted into a hole 2aa in the mounting table 2a. The other end of the rotating shaft 2b is provided outside the housing 6. The rotating shaft 2b is connected to a driving unit 2c outside the housing 6.

[0018] The rotating shaft 2b is cylindrical. An air outlet 2b1 is provided at the end of the rotating shaft 2b on the side of the mounting table 2a. The air outlet 2b1 opens to the surface of the mounting table 2a on which the multiple support members 2a1 are provided. The end of the opening side of the air outlet 2b1 is connected to the inner wall of the hole 2aa. The opening of the air outlet 2b1 faces the back surface 100a of the substrate 100 placed on the mounting table 2a.

[0019] Although the example in which the blowing portion 2b1 is provided at the tip of the rotating shaft 2b has been described, the blowing portion 2b1 can also be provided at the tip of a cooling nozzle 3d (described later). Also, the hole 2aa of the mounting table 2a can be used as the blowing portion 2b1.

[0020] A cooling nozzle 3d is attached to the end of the rotating shaft 2b opposite to the mounting table 2a side. A rotating shaft seal (not shown) is provided between the cooling nozzle 3d and the end of the rotating shaft 2b opposite to the mounting table 2a side. Therefore, the end of the rotating shaft 2b opposite to the mounting table 2a side is sealed airtight.

[0021] The driving unit 2c is provided outside the housing 6. The driving unit 2c is connected to the rotation shaft 2b. The driving unit 2c may include a rotating device such as a motor. The rotational force of the driving unit 2c is transmitted to the mounting table 2a via the rotation shaft 2b. Therefore, the driving unit 2c can rotate the mounting table 2a, and ultimately the substrate 100 mounted on the mounting table 2a.

[0022] Furthermore, the driving unit 2c can not only start and stop rotation, but also change the number of rotations (rotation speed). The driving unit 2c can be equipped with a control motor such as a servo motor, for example.

[0023] The cooling unit 3 supplies a cooling gas 3a1 to the space between the mounting table 2a and the rear surface 100a of the substrate 100. The cooling unit 3 includes a coolant unit 3a, a filter 3b, a flow rate control unit 3c, and a cooling nozzle 3d.

[0024] The coolant unit 3a stores the coolant and generates the cooling gas 3a1. The coolant is a liquefied version of the cooling gas 3a1. There are no particular limitations on the cooling gas 3a1, as long as it is a gas that does not easily react with the material of the substrate 100. The cooling gas 3a1 can be, for example, an inert gas such as nitrogen gas, helium gas, or argon gas.

[0025] The coolant unit 3a includes a tank for storing the coolant and an evaporation unit for evaporating the coolant stored in the tank. The tank is provided with a cooling device for maintaining the temperature of the coolant. The evaporation unit raises the temperature of the coolant to generate a cooling gas 3a1 from the coolant. The evaporation unit can use, for example, the outside air temperature or heating with a heat medium. The temperature of the cooling gas 3a1 can be any temperature below the freezing point of the liquid 101, and can be, for example, -170°C.

[0026] Although the example has been described in which the coolant unit 3a generates the cooling gas 3a1 by vaporizing the coolant stored in the tank, it is also possible to cool nitrogen gas or the like using a chiller or the like to generate the cooling gas 3a1. In this way, the coolant unit can be simplified.

[0027] The filter 3b is connected to the coolant unit 3a via a pipe. The filter 3b prevents contaminants such as particles contained in the coolant from flowing out to the substrate 100 side.

[0028] The flow rate control unit 3c is connected to the filter 3b via a pipe. The flow rate control unit 3c controls the flow rate of the cooling gas 3a1. The flow rate control unit 3c may be, for example, a mass flow controller (MFC). Alternatively, the flow rate control unit 3c may indirectly control the flow rate of the cooling gas 3a1 by controlling the supply pressure of the cooling gas 3a1. In this case, the flow rate control unit 3c may be, for example, an auto pressure controller (APC).

[0029] The temperature of cooling gas 3a1 generated from the coolant in coolant unit 3a is approximately a predetermined temperature. Therefore, by controlling the flow rate of cooling gas 3a1 using flow rate control unit 3c, the temperature of substrate 100, and therefore the temperature of liquid 101 on surface 100b of substrate 100, can be controlled. In this case, by controlling the flow rate of cooling gas 3a1 using flow rate control unit 3c, it is possible to bring liquid 101 into a supercooled state in the supercooling step described below.

[0030] The cooling nozzle 3d is cylindrical. One end of the cooling nozzle 3d is connected to the flow rate control unit 3c. The other end of the cooling nozzle 3d is provided inside the rotating shaft 2b. The other end of the cooling nozzle 3d is located near the end of the blowing unit 2b1 opposite to the mounting table 2a side (opening side).

[0031] Cooling nozzle 3d supplies cooling gas 3a1, the flow rate of which is controlled by flow rate control unit 3c, to substrate 100. Cooling gas 3a1 emitted from cooling nozzle 3d is supplied directly to rear surface 100a of substrate 100 via blowout portion 2b1.

[0032] The first liquid supply unit 4 supplies the liquid 101 to the surface 100b of the substrate 100. As will be described later, the liquid 101 is preferably a liquid that does not easily react with the material of the substrate 100 and that increases in volume when frozen. The liquid 101 is preferably, for example, water (e.g., pure water or ultrapure water) or a liquid containing water as its main component.

[0033] The liquid containing water as a main component may be, for example, a mixture of water and alcohol, a mixture of water and an acidic solution, or a mixture of water and an alkaline solution. If a mixture of water and alcohol is used, the surface tension can be reduced, making it easier to supply liquid 101 into the fine irregularities formed on surface 100b of substrate 100.

[0034] A mixture of water and an acidic solution can dissolve contaminants such as particles and resist residues adhering to the surface of the substrate 100. For example, a mixture of water and sulfuric acid can dissolve contaminants made of resist or metal.

[0035] However, if there are too many components other than water, it becomes difficult to utilize the physical force that accompanies the increase in volume, which may result in a decrease in the rate of contaminant removal. Therefore, it is preferable that the concentration of components other than water be 5 wt% or more and 30 wt% or less.

[0036] The first liquid supply unit 4 has a liquid storage unit 4a, a supply unit 4b, a flow rate control unit 4c, and a liquid nozzle 4d. The liquid storage unit 4a, the supply unit 4b, and the flow rate control unit 4c are provided outside the housing 6.

[0037] The liquid storage portion 4a stores the above-mentioned liquid 101. The liquid 101 is stored in the liquid storage portion 4a at a temperature higher than the freezing point. The liquid 101 is stored at room temperature (20° C.), for example. The supply unit 4b is connected to the liquid storage unit 4a via a pipe. The supply unit 4b supplies the liquid 101 stored in the liquid storage unit 4a toward the liquid nozzle 4d. The supply unit 4b may be, for example, a pump that is resistant to the liquid 101. Although the example shows the case where the supply unit 4b is a pump, the supply unit 4b is not limited to a pump. For example, the supply unit 4b may supply gas into the liquid storage unit 4a and pressure-feed the liquid 101 stored in the liquid storage unit 4a.

[0038] The flow rate control unit 4c is connected to the supply unit 4b via a pipe. The flow rate control unit 4c controls the flow rate of the liquid 101 supplied by the supply unit 4b. The flow rate control unit 4c can be, for example, a flow rate control valve. The flow rate control unit 4c can also start and stop the supply of the liquid 101.

[0039] The liquid nozzle 4d is provided inside the housing 6. The liquid nozzle 4d is cylindrical. One end of the liquid nozzle 4d is connected to the flow rate control unit 4c via a pipe. The liquid nozzle 4d is also connected to a drive unit (not shown). Therefore, the liquid nozzle 4d moves between approximately the center of the surface 100b of the substrate 100 and approximately the outer periphery of the substrate 100. The other end of the liquid nozzle 4d (the outlet for the liquid 101) faces the surface 100b of the substrate 100 placed on the mounting table 2a. Therefore, when the drive unit (not shown) moves the liquid nozzle 4d to approximately the center of the surface 100b of the substrate 100, the liquid 101 ejected from the liquid nozzle 4d is supplied to the surface 100b of the substrate 100.

[0040] Liquid 101 ejected from liquid nozzle 4d spreads from approximately the center of surface 100b of substrate 100, and a liquid film having a substantially constant thickness is formed on surface 100b of substrate 100. Note that, hereinafter, the film of liquid 101 formed on surface 100b of substrate 100 will be referred to as a liquid film.

[0041] The second liquid supply unit 5 supplies a liquid 102 (which corresponds to an example of the second liquid) to the surface 100b of the substrate 100. The second liquid supply unit 5 has a liquid storage unit 5a, a supply unit 5b, a flow rate control unit 5c, and a liquid nozzle 4d.

[0042] The liquid 102 can be used in the thawing step described below. Therefore, there are no particular limitations on the liquid 102, as long as it is unlikely to react with the material of the substrate 100 and is unlikely to remain on the surface 100b of the substrate 100 in the drying step described below. The liquid 102 can be, for example, water (e.g., pure water or ultrapure water), a mixture of water and alcohol, or the like.

[0043] The configuration of the second liquid supply unit 5 can be, for example, the same as the configuration of the first liquid supply unit 4. For example, the liquid storage unit 5a can be the same as the liquid storage unit 4a described above. The supply unit 5b can be the same as the supply unit 4b described above. The flow rate control unit 5c can be the same as the flow rate control unit 4c described above.

[0044] If the liquid 102 and the liquid 101 are the same, it is possible to omit the second liquid supply unit 5. Furthermore, although the example has been given of a case where the liquid nozzle 4d is used for both purposes, it is also possible to provide a liquid nozzle for ejecting the liquid 101 and a liquid nozzle for ejecting the liquid 102 separately.

[0045] Furthermore, since the liquid 102 is used in the thawing step, the temperature of the liquid 102 can be set to a temperature higher than the freezing point of the liquid 101. The temperature of the liquid 102 can also be set to a temperature that can thaw the frozen liquid 101. The temperature of the liquid 102 can be set to, for example, about room temperature (20°C).

[0046] When the second liquid supply unit 5 is omitted, the first liquid supply unit 4 is used in the thawing step. That is, the liquid 101 is used. In this case, the temperature of the liquid 101 can be set to a temperature at which the frozen liquid 101 can be thawed. The temperature of the liquid 101 can be set to, for example, about room temperature (20°C).

[0047] The third liquid supply unit 15 supplies an alkaline liquid 103 (corresponding to an example of a third liquid) having a surface tension lower than that of pure water to the surface 100b of the substrate 100. The liquid 103 is, for example, an ammonia solution, a low-concentration SC-1 (Standard Clean 1) solution, a choline (CHOLINE) aqueous solution, or a TMAH (Tetramethyl ammonium hydroxide) aqueous solution. Alternatively, the liquid 103 may be a mixture of these solutions with a liquid containing a surfactant or isopropyl alcohol (IPA).

[0048] Third liquid supply unit 15 has liquid storage unit 15a, supply unit 15b, flow rate control unit 15c, and liquid nozzle 15d. The configuration of third liquid supply unit 15 can be similar to the configuration of first liquid supply unit 4, for example, and therefore description thereof will be omitted.

[0049] The housing 6 is box-shaped. A cover 6a is provided inside the housing 6. The cover 6a receives the liquids 101 and 102 that are supplied to the substrate 100 and then discharged to the outside of the substrate 100 as the substrate 100 rotates. The cover 6a is cylindrical. The vicinity of the end of the cover 6a opposite the mounting table 2a (near the upper end of the cover 6a) is bent toward the center of the cover 6a. This makes it easy to capture the liquids 101 and 102 that splash above the substrate 100.

[0050] A partition plate 6b is provided inside the housing 6. The partition plate 6b is provided between the outer surface of the cover 6a and the inner surface of the housing 6.

[0051] A plurality of exhaust ports 6c are provided on the side surface on the bottom side of the housing 6. In the case of the housing 6 illustrated in FIG. 1, two exhaust ports 6c are provided. The used cooling gas 3a1, air 7a, liquid 101, and liquid 102 are discharged to the outside of the housing 6 through the exhaust ports 6c. An exhaust pipe 6c1 is connected to the exhaust ports 6c, and an exhaust unit (pump) 11 that discharges the used cooling gas 3a1 and air 7a is connected to the exhaust pipe 6c1. In addition, an exhaust pipe 6c2 that discharges the liquids 101 and 102 is connected to the exhaust ports 6c.

[0052] The exhaust port 6c is provided below the substrate 100. Therefore, a downflow is created when the cooling gas 3a1 is exhausted from the exhaust port 6c, which prevents particles from flying up.

[0053] The blower 7 is provided on the ceiling surface of the housing 6. The blower 7 can also be provided on the side of the housing 6 as long as it is on the ceiling side. The blower 7 can include a blower such as a fan and a filter. The filter can be, for example, a HEPA filter (High Efficiency Particulate Air Filter).

[0054] The control unit 9 controls the operation of each element provided in the substrate processing apparatus 1. FIG. 2 shows an example of the configuration of the control unit 9. The control unit 9 can be, for example, a computer having a processing element such as a CPU (Central Processing Unit) and a storage unit 9c such as a semiconductor memory. For example, the mechanism control unit 9a and setting unit 9b shown in FIG. 2 can be the processing element, and the storage unit 9c can be the storage element. The storage element can store a control program that controls the operation of each element provided in the substrate processing apparatus 1. The processing element controls the operation of each element provided in the substrate processing apparatus 1 using the control program stored in the storage element, data input by an operator via the input / output screen (device) 8, and the like.

[0055] The control program and data input by the operator are set by the setting unit 9b to an optimum state for storage in the storage unit 9c (storage element), and then stored in the storage element. The setting unit 9b also reconverts data requested to be output by the operator into an optimum state for display on the input / output screen, and displays it on the input / output screen (device) 8.

[0056] For example, the control unit 9 controls the rotation of the substrate 100, the supply of the cooling gas 3a1, the supply of the liquid 101, the supply of the liquid 102, and the supply of the liquid 103 by controlling the operation of each element provided in the substrate processing apparatus 1 from the mechanism control unit 9a based on a control program stored in the memory unit 9c.

[0057] Next, the operation of the substrate processing apparatus 1 will be illustrated. FIG. 3 is a timing chart illustrating the operation of the substrate processing apparatus 1. In FIG. FIG. 4 is a graph illustrating the temperature change of the liquid 101 supplied to the substrate 100 in the freeze cleaning process.

[0058] 3 and 4 show the case where the substrate 100 is a 6025 quartz (Qz) substrate (152 mm×152 mm×6.35 mm), the liquid 101 is pure water, and the liquid 103 is an ammonia solution.

[0059] First, the substrate 100 is carried into the housing 6 through a carry-in / out port (not shown) of the housing 6. The carried-in substrate 100 is placed and supported on the multiple supports 2a1 of the mounting table 2a.

[0060] After the substrate 100 is supported on the mounting table 2a, a freeze-cleaning process is performed, which includes a preliminary process, a preliminary rinsing process, a liquid film formation process, a cooling process (supercooling process + freezing process), a thawing process, and a drying process, as shown in Figures 3 and 4.

[0061] First, a preliminary step is performed as shown in FIGS. 3 and 4. In the preliminary step, the control unit 9 controls the drive unit (not shown) to move the liquid nozzle 4d to approximately the center of the front surface 100b of the substrate 100. The control unit 9 controls the supply unit 4b and the flow rate control unit 4c to supply the liquid 101 at a predetermined flow rate to the front surface 100b of the substrate 100. The control unit 9 also controls the flow rate control unit 3c to supply the cooling gas 3a1 at a predetermined flow rate to the rear surface 100a of the substrate 100. The control unit 9 also controls the drive unit 2c to rotate the substrate 100 at a second rotation speed. In the preliminary step, the liquid nozzle 15d waits near the outer periphery of the substrate 100.

[0062] Here, when the atmosphere inside the housing 6 is cooled by the supply of cooling gas 3a1 by the cooling unit 3, frost containing dust in the atmosphere may adhere to the substrate 100, causing contamination. In the preliminary step, the liquid 101 is continuously supplied to the surface 100b of the substrate 100, so that the substrate 100 can be uniformly cooled while preventing frost from adhering to the surface 100b of the substrate 100.

[0063] For example, in the example shown in FIG. 3, the rotation speed of the substrate 100 can be set as a second rotation speed, for example, at about 50 rpm to 500 rpm. The flow rate of the liquid 101 can be set at about 0.1 L / min to 1.0 L / min. The flow rate of the cooling gas 3a1 can be set at about 40 NL / min to 200 NL / min. The process time of the preliminary process can be set at about 1800 seconds. The process time of the preliminary process can be set at any time so that the in-plane temperature of the substrate 100 becomes approximately uniform, and can be determined in advance by conducting experiments or simulations.

[0064] The temperature of the liquid film in the preliminary step is approximately the same as the temperature of the supplied liquid 101 because the liquid 101 is in a flowing state. For example, if the temperature of the supplied liquid 101 is about room temperature (20°C), the temperature of the liquid film will be about room temperature (20°C).

[0065] After supplying liquid 101 for a predetermined time, control unit 9 executes a pre-rinse step. Control unit 9 controls supply unit 4b and flow rate control unit 4c to stop the supply of liquid 101, and controls supply unit 15b and flow rate control unit 15c to supply alkaline liquid 103, which has a lower surface tension than liquid 101, from liquid nozzle 15d to surface 100b of substrate 100. In this case, control unit 9 controls a drive unit (not shown) to move liquid nozzle 4d to the vicinity of the outer periphery of substrate 100, and to move liquid nozzle 15d to a position facing approximately the center of surface 100b of substrate 100.

[0066] Next, the liquid film forming step is performed as shown in Figures 3 and 4. In the liquid film forming step, the supply of liquid 103 that was supplied in the pre-rinse step is stopped. Then, since the rotation of substrate 100 is maintained, liquid 103 on surface 100b of substrate 100 is drained. Note that not all of liquid 103 on surface 100b of substrate 100 is drained. Liquid 103 is left to the extent that it covers surface 100b of substrate 100. After the pre-rinse step, control unit 9 controls the drive unit (not shown) to move liquid nozzle 15d to the vicinity of the outer periphery of substrate 100 and liquid nozzle 4d to a position facing approximately the center of surface 100b of substrate 100. Then, the liquid film forming step is performed. Then, the rotation speed of substrate 100 is reduced to a first rotation speed that is slower than the second rotation speed.

[0067] The first rotation speed may be any rotation speed that can suppress variations in the thickness of the liquid film due to centrifugal force, and may be in the range of 0 to 50 rpm, for example. After the rotation speed of the substrate 100 is set to the first rotation speed, a predetermined amount of liquid 101 is supplied to the substrate 100 to form a liquid film. The flow rate of the cooling gas 3a1 is maintained.

[0068] The thickness of the liquid film formed in the liquid film formation step (the thickness of the liquid film when the supercooling step is performed) can be about 200 μm to 1300 μm. For example, the control unit 9 controls the supply amount of the liquid 101 so that the thickness of the liquid film on the surface 100b of the substrate 100 is about 200 μm to 1300 μm.

[0069] Next, a cooling process (supercooling process + freezing process) is carried out as shown in Figures 3 and 4. In this embodiment, the period of the cooling process from when the liquid film made of liquid 101 becomes supercooled to before freezing begins is called the "supercooling process," and the period from when freezing of the supercooled liquid film begins to before freezing is completely completed is called the "freezing process."

[0070] First, in the supercooling step, the temperature of the liquid film on the substrate 100 is further reduced below the temperature of the liquid film in the liquid film forming step by the cooling gas 3a1 continuously supplied to the rear surface 100a of the substrate 100, resulting in a supercooled state.

[0071] In a supercooled state, the liquid film begins to freeze due to, for example, the temperature of the liquid film, the presence of contaminants such as particles or bubbles, vibration, etc. For example, in the presence of contaminants such as particles, the liquid film begins to freeze when its temperature T falls to -35°C or higher and -20°C or lower. The liquid film can also begin to freeze by vibrating it, for example by varying the rotation of the substrate 100.

[0072] When the supercooled liquid film starts to freeze, the process shifts from the supercooling process to the freezing process. In the freezing process, at least a portion of the liquid film on the surface 100b of the substrate 100 is frozen. In the freeze cleaning process of this embodiment, the case where the liquid film is completely frozen to become a frozen film 101a will be described.

[0073] Next, a decompression step is performed as shown in FIGS. In the thawing process, the control unit 9 controls the supply unit 4b and the flow rate control unit 4c to supply the liquid 101 at a predetermined flow rate to the surface 100b of the substrate 100. The control unit 9 also controls the flow rate control unit 3c to stop the supply of the cooling gas 3a1. This starts thawing the frozen film 101a, and the frozen film 101a gradually turns into the liquid 101. The control unit 9 also controls the drive unit 2c to increase the rotation speed of the substrate 100 to a third rotation speed, which is faster than the second rotation speed. The faster the rotation of the substrate 100, the centrifugal force can throw off the liquids 101 and 102. This makes it easier to drain the liquid 101 from the surface 100b of the substrate 100. At this time, contaminants separated from the surface 100b of the substrate 100 are also drained together with the liquid 101.

[0074] The supply amount of liquid 101 is not particularly limited as long as it can thaw the liquid 101. The third rotation speed of substrate 100 is not particularly limited as long as it can discharge liquid 101, the frozen liquid 101, and contaminants.

[0075] Next, a drying step is performed as shown in Figures 3 and 4. In the drying step, the control unit 9 controls the supply unit 4b and the flow rate control unit 4c to stop the supply of the liquid 101. The control unit 9 also controls the drive unit 2c to further increase the rotation speed of the substrate 100 to a fourth rotation speed that is faster than the third rotation speed. If the rotation speed of the substrate 100 is increased, the substrate 100 can be dried more quickly. The fourth rotation speed of the substrate 100 is not particularly limited as long as drying is possible.

[0076] After the freeze cleaning, the substrate 100 is carried out of the housing 6 through a carry-in / out port (not shown) of the housing 6 . By doing so, one freeze-cleaning step can be performed.

[0077] However, as described above, if contaminants are adsorbed on the surface 100b of the substrate 100, if the surface 100b of the substrate 100 or the contaminants are highly hydrophobic, or if the surface 100b of the substrate 100 and the contaminants are both highly hydrophobic, the liquid 101 to be frozen may not be able to penetrate between the substrate 100 and the contaminants. If the liquid 101 to be frozen cannot penetrate between the substrate 100 and the contaminants, the effect of the liquid 101 expanding in volume when it freezes may not be achieved, which may result in a decrease in the contaminant removal rate.

[0078] Therefore, the substrate processing apparatus 1 according to this embodiment performs a pre-rinsing step using liquid 103 before performing the liquid film formation step. Because liquid 103 has low surface tension, it spreads even on a superhydrophobic surface. Therefore, liquid 103 can penetrate between the substrate and the contaminants. At this time, the surface tension of the surface 100b of the substrate 100 is reduced by liquid 103. Furthermore, liquid 103 is an alkaline solution. Therefore, if the substrate 100 or the contaminants are made of a material that dissolves in an alkaline solution, liquid 103 etches the surface 100b of the substrate 100 or the contaminants. Therefore, even if the contaminants are adsorbed on the surface 100b of the substrate 100, a gap can be formed between the contaminants and the surface 100b of the substrate 100. Examples of materials that dissolve in alkaline solutions include silicon (Si) and silicon oxide (SiO2).

[0079] After the preliminary rinse step, a liquid film is formed. The surface tension of the surface 100b of the substrate 100 is reduced by the liquid 103. This makes it easier for the liquid 101 to penetrate into the gap between the substrate 100 and the contaminant. The liquid 103 remains in the gap between the substrate 100 and the contaminant. Therefore, the liquid 103 remaining in the gap and the liquid 101 gradually mix. The amount of liquid 101 supplied is greater than the amount of liquid 103 remaining on the surface 100b of the substrate 100. Therefore, the liquid 103 is diluted, and it can be considered that the liquid 103 has been replaced by the liquid 101. In this way, the liquid 101 can penetrate into the gap between the surface 100b of the substrate 100, whose surface tension has been reduced by the liquid 103, and the contaminant. Therefore, whether contaminants are adsorbed on surface 100b of substrate 100, whether surface 100b of substrate 100 or the contaminants are superhydrophobic, or whether surface 100b of substrate 100 and the contaminants are superhydrophobic, the volume expansion caused by freezing of liquid 101 causes the contaminants to separate from surface 100b of substrate 100. As a result, the contaminant removal rate can be improved.

[0080] Here, it is conceivable to supply liquid 103 to surface 100b of substrate 100 in the preliminary step. However, as described above, liquid 103 etches surface 100b of substrate 100. Therefore, by supplying liquid 103 in the preliminary rinse step after supplying liquid 101 in the preliminary step, it is possible to shorten the supply time of liquid 103, which may etch surface 100b of substrate 100. This also reduces the amount of liquid 103 used.

[0081] Therefore, it is preferable that the time for supplying liquid 101 onto surface 100b of substrate 100 is longer than the time for supplying liquid 103. For example, the time for the preliminary step is set to 300 to 1500 seconds, and the time for the preliminary rinsing step is set to 30 to 180 seconds.

[0082] Furthermore, in the liquid film forming step, the supply of cooling gas 3a1 is maintained. Therefore, if liquid 103 remains on surface 100b of substrate 100, it is possible to prevent frost from forming on the surface of substrate 100, and it is also possible to maintain a substantially uniform in-plane temperature of substrate 100 in the preliminary step.

[0083] However, if too much liquid 103 remains, there is a risk of over-etching the surface 100b of the substrate 100. Therefore, it is preferable that the thickness of the film of the remaining liquid 103 be 10% or less of the thickness of the liquid film formed in the liquid film forming step.

[0084] Note that ammonia solution, low-concentration SC-1 solution, choline solution, and TMAH solution have a higher surface tension than surfactants or IPA. Therefore, these solutions may be mixed with a liquid containing a surfactant or IPA to adjust the surface tension. This can further reduce the surface tension of the surface 100b of the substrate 100. This allows the liquid 101 to more easily penetrate into the gap between the surface 100b of the substrate 100 and the contaminants formed by etching the surface 100b of the substrate 100.

[0085] Alternatively, the liquid 103, such as an ammonia solution, a low-concentration SC-1 solution, a choline aqueous solution, or a TMAH aqueous solution, may be supplied from the liquid nozzle 15d to the surface 100b of the substrate 100, and the liquid 104, such as a liquid containing a surfactant or pure water mixed with IPA, having a surface tension lower than that of the liquid 103, may be supplied from the liquid nozzle 15d alternately.

[0086] In the pre-rinse step, by supplying liquid 104 having a surface tension lower than that of liquid 103, the surface tension of surface 100b of substrate 100 can be reduced to be lower than that of liquid 103. Therefore, by supplying liquid 104 having a surface tension lower than that of liquid 103 between the supplies of liquid 103, the next liquid 103 can more easily penetrate into gaps between surface 100b of substrate 100 and contaminants, which have been formed by etching surface 100b of substrate 100 with liquid 103 previously supplied to surface 100b of substrate 100.

[0087] Alternatively, the liquid film forming step may be performed after supplying liquid 104 having a surface tension lower than that of liquid 103. In this way, liquid 104 having a surface tension lower than that of liquid 103 can reduce the surface tension of surface 100b of substrate 100 more than liquid 103. Therefore, liquid 101 can more easily penetrate into gaps formed by etching surface 100b of substrate 100 between surface 100b of substrate 100 and the contaminants.

[0088] It is preferable that liquid 104, which has a surface tension lower than that of liquid 103, is a neutral liquid. If liquid 104, which has a surface tension lower than that of liquid 103, is neutral, the liquid film formed from liquid 101 will also be neutral. Therefore, in the subsequent process, etching of surface 100b of substrate 100 by the liquid film can be suppressed.

[0089] Furthermore, liquid 103 and liquid 104 having a surface tension lower than that of liquid 103 may be supplied from separate nozzles. For example, liquid 104 having a surface tension lower than that of liquid 103 may be supplied from nozzle 4d. This prevents liquid 103 and liquid 104 having a surface tension lower than that of liquid 103 from mixing in the piping. This makes it possible to reduce the amount of liquid 103 contained in the liquid film formed by liquid 101. This makes it possible to further suppress etching of surface 100b of substrate 100 in the subsequent process.

[0090] The freeze-cleaning step may be performed multiple times. FIG. 5 is a flow chart showing a case where the freeze-cleaning step is carried out multiple times. As shown in FIG. 5, if the next freeze-cleaning step is to be performed, the process may be returned to the preliminary rinsing step after the thawing step.

[0091] The operation of the control unit 9 in this case will be described with reference to FIG. FIG. 6 is a flowchart illustrating the operation of the control unit 9 when the freeze cleaning process is performed multiple times. The number of times the freeze cleaning process is to be repeated is stored in advance in the storage unit 9c by the operator.

[0092] As shown in FIG. 6, first, a preliminary step is performed, followed by a preliminary rinsing step (S001 to S003). After the preliminary rinsing step is performed, the liquid film forming step (S004 to S007) is performed.

[0093] Next, the control unit 9 performs a cooling process. In the cooling process, detection data is acquired from a detection unit (not shown) to determine whether the liquid film has frozen (S008). The detection data may be the temperature of the liquid film, or the thickness or cloudiness of the liquid film. If it is determined that the liquid film has not frozen after a predetermined time has passed, a warning is output and the device is stopped (S008b).

[0094] When the control unit 9 determines that the liquid film has frozen, it then determines whether a predetermined number of repetitions of the freeze cleaning process have been reached (S009). If the next freeze cleaning process is to be performed, the control unit 9 controls the first liquid supply unit 4 to supply the liquid 101 to the surface 100b of the substrate 100 while maintaining the supply of the cooling gas 3a1 even during the thawing process (S009a). This creates the same conditions as the preliminary process. Therefore, as shown in FIG. 5, the preliminary process and drying process can be omitted from the next freeze cleaning process.

[0095] Therefore, when the freeze-cleaning process is repeated multiple times, the freeze-cleaning process only needs to include at least a pre-rinse process in which an alkaline liquid 103 having a low surface tension is supplied to the surface 100b of the substrate 100, a liquid film formation process in which a liquid film having a predetermined thickness is formed on the surface 100b of the substrate 100, a supercooling process in which the liquid film on the surface 100b of the substrate 100 is brought into a supercooled state, a freezing process in which at least a portion of the liquid film is frozen, and a thawing process in which liquid 102 is supplied to the frozen film 101a on the surface 100b of the substrate 100 to thaw the frozen liquid film.

[0096] This allows the liquid 101 to easily penetrate between the substrate 100 and the contaminants. This improves the contaminant removal rate in one freeze cleaning process. As a result, the number of times the freeze cleaning process is repeated can be reduced, thereby improving the operating rate of the substrate processing apparatus 1. Furthermore, the liquid 103 is an alkaline solution, and therefore can reduce the zeta potential of the substrate 100. Therefore, even if contaminants separated from the surface 100b of the substrate 100 in the thawing step re-adhere to the surface 100b of the substrate 100, the re-adhesion contaminants can be removed from the surface 100b of the substrate 100 by supplying the liquid 103 to the surface 100b of the substrate 100 in the subsequent pre-rinse step. Therefore, when the freeze cleaning process is repeated, it is not necessary to use the liquid 103 in the thawing process. Therefore, it is possible to prevent the substrate 100 from being etched by the liquid 103 in the thawing process. Also, it is possible to remove redeposited contaminants while saving the amount of the liquid 103 used.

[0097] The embodiments have been described above as examples. However, the present invention is not limited to these descriptions. Regarding the above-described embodiment, a person skilled in the art may add, delete or modify components as appropriate. Any design changes, additions, omissions or changes to conditions of processes are also included in this To the extent that it possesses the characteristics of the invention, it is included within the scope of the invention.

[0098] For example, the shape, size, number, arrangement, etc. of each element included in the substrate processing apparatus 1 are merely examples. However, the present invention is not limited to the above and can be changed as appropriate. For example, in the preliminary step, the substrate does not always need to be rotated at the second rotation speed, but can be rotated at the first rotation speed. In this case, just before proceeding to the liquid film forming step, the rotation speed may be set to the second rotation speed or less. The rotation number may be set so that at least a part of the liquid 102 is discharged. Also, if the onset of freezing can be detected, it is not always necessary to carry out the preliminary step. In the thawing process, thawing does not necessarily have to be started on the frozen film 101a. For example, the liquid 101 is thawed from a supercooled state to a partially frozen state (solid-liquid phase state). may be started. [Explanation of symbols]

[0099] 1 substrate processing apparatus, 2 placement unit, 3 cooling unit, 3a1 cooling gas, 4 first liquid supply unit, 5 second liquid supply unit, 6 housing, 8 detection unit, 9 control unit, 15 third liquid supply unit, 100 substrate, 100a back surface, 100b front surface, 101 liquid, 101a frozen film, 102 liquid, 103 liquid

Claims

1. a mounting table capable of rotating a substrate made of silicon or silicon oxide; a cooling unit capable of supplying a cooling gas to a space between the mounting table and the substrate; a first liquid supply unit capable of supplying a first liquid to a surface of the substrate opposite to the mounting table side; a third liquid supply unit capable of supplying an alkaline third liquid having a surface tension lower than that of the first liquid to the surface of the substrate; a control unit that controls the rotation of the substrate, the supply of the cooling gas, the supply of the first liquid, and the supply of the third liquid; Equipped with the control unit controls the supply of the cooling gas, the supply of the first liquid, and the supply of the third liquid, supplying the third liquid to the surface of the substrate and supplying the cooling gas to a space between the stage and the substrate; After supplying the third liquid, supplying the first liquid toward the surface of the substrate to form a liquid film; After the liquid film on the surface of the substrate is brought into a supercooled state, The substrate processing apparatus freezes at least a portion of the liquid film on the surface of the substrate.

2. 2. The substrate processing apparatus according to claim 1, wherein the control unit stops the supply of the third liquid when the first liquid is being supplied, and controls the rotation of the substrate so that the third liquid remains on the surface of the substrate.

3. 3. The substrate processing apparatus according to claim 1, wherein the third liquid is at least one of an ammonia solution, a low-concentration SC-1 solution, a choline solution, and a TMAH solution.

4. 4. The substrate processing apparatus according to claim 3, wherein the third liquid is a liquid containing a surfactant or a mixture of the third liquid with IPA.

5. the third liquid supply unit includes the third liquid and a liquid having a surface tension smaller than that of the third liquid; The control unit A substrate processing apparatus according to any one of claims 1 to 4, wherein before supplying the first liquid toward the surface of the substrate to form a liquid film, the supply of the third liquid and the supply of a liquid having a surface tension lower than that of the third liquid are alternately performed.

6. the first liquid supply unit includes the first liquid and a liquid having a surface tension smaller than that of the third liquid; The control unit A substrate processing apparatus according to any one of claims 1 to 4, wherein before supplying the first liquid toward the surface of the substrate to form a liquid film, the supply of the third liquid and the supply of a liquid having a surface tension lower than that of the third liquid are alternately performed.

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