Substrate Processing Equipment

Abstract

To provide a substrate processing apparatus capable of suppressing the collapse of uneven portions and shortening a processing time.SOLUTION: A substrate processing apparatus according to an embodiment includes a mounting table on which a substrate can be rotated, a cooling unit capable of supplying a cooling gas to a space between the mounting table and the substrate, a liquid supply unit capable of supplying liquid to a surface of the substrate opposite to the mounting table, and a controller that controls rotation of the substrate, a flow rate of the cooling gas, and supply of the liquid. The liquid contains water and a solute that increases dislocation density of ice crystals. The controller causes the liquid on the surface of the substrate to become in a supercooled state, freezes the liquid in the supercooled state to generate a frozen film, and lowers a temperature of the frozen film to cause cracks.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] 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 surfaces 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, first, pure water and a cooling gas are supplied to the surface of a rotating substrate. Next, the supply of pure water is stopped, and a part 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. When the water film freezes to form a frozen film, contaminants such as particles are captured by the frozen film and separated from the surface of the substrate. Next, pure water is supplied to the frozen film to melt it, and the contaminants are removed from the surface of the substrate together with the pure water.

[0004] The freeze cleaning method can effectively remove contaminants adhering to the surface of the substrate. Furthermore, if the supply of cooling gas is continued after the frozen film is formed, the temperature of the frozen film may decrease, causing cracks in the frozen film. If cracks occur in the frozen film, the removal rate of contaminants can be further increased.

[0005] However, the surface of the substrate may have a pattern of unevenness. In recent years, the unevenness has become finer. Therefore, if cracks occur in the frozen film, the impact force caused by the cracks may cause the unevenness to collapse. Furthermore, if it takes a long time for cracks to appear after the frozen film is formed, the processing time will be longer accordingly. Therefore, there has been a demand for the development of a substrate processing apparatus that can prevent the collapse of the uneven portions even when cracks are generated in the frozen film, and can shorten the processing time. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2018-026436 A 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 suppressing collapse of uneven portions and shortening processing time. [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 a space between the mounting table and the substrate; a liquid supply unit capable of supplying liquid to a surface of the substrate opposite to the mounting table; a controller for controlling the rotation of the substrate, the flow rate of the cooling gas, and the supply of the liquid; Equipped with The liquid includes water and a solute that increases the dislocation density of ice crystals; the solute is an acid or alkali at a concentration of 100 ppm or less; The controller causes the liquid on the surface of the substrate to be in a supercooled state, freezes the supercooled liquid to generate a frozen film, and lowers the temperature of the frozen film to cause cracks to occur in the frozen film. Effect of the Invention

[0009] According to an embodiment of the present invention, a substrate processing apparatus capable of suppressing collapse of uneven portions and shortening processing time is provided. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic diagram illustrating a substrate processing apparatus according to an embodiment of the present invention; [Diagram 2] 4 is a timing chart illustrating the operation of the substrate processing apparatus. [Diagram 3] 11 is a graph illustrating the change in temperature of liquid supplied to a substrate. [Figure 4] 1A and 1B are schematic diagrams illustrating the mechanism of contaminant separation. [Diagram 5] 1 is a graph illustrating the relationship between solute concentration and time to crack onset. [Figure 6] 1 is a graph illustrating the relationship between solute concentration and time to crack onset. [Figure 7] 1 is a graph illustrating the relationship between the thickness of the liquid film and the number of repetitions of the freeze cleaning process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and detailed description thereof will be omitted as 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). Incidentally, a pattern of unevenness may or may not be formed on the surface of the substrate 100. A substrate without unevenness may be, for example, a substrate before unevenness is formed (for example, a so-called bulk substrate).

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

[0013] FIG. 1 is a schematic view illustrating a substrate processing apparatus 1 according to the present embodiment. As shown in FIG. 1, the substrate processing apparatus 1 includes a mounting section 2, a cooling section 3, a first liquid supply section 4, a second liquid supply section 5, a housing 6, a blower section 7, a detection section 8, an exhaust section 9, and a controller 10.

[0014] The mounting unit 2 has, for example, a mounting table 2a, a rotating shaft 2b, and a driving unit 2c. The mounting table 2a is rotatably provided inside the housing 6. The mounting table 2a has a plate shape. One main surface of the mounting table 2a is provided with a plurality of support parts 2a1 for supporting the substrate 100. When the substrate 100 is supported by the plurality of support parts 2a1, the surface 100b (the surface to be cleaned) of the substrate 100 faces away from the mounting table 2a.

[0015] The edges (edges) of the rear surface 100a of the substrate 100 come into contact with the plurality of supporting portions 2a1. 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. If the portions of the supporting portions 2a1 that come into contact with the edges of the rear surface 100a of the substrate 100 are tapered, the supporting portions 2a1 can come into point contact with the edges of the rear surface 100a of the substrate 100. If the portions of the supporting portions 2a1 that come into contact with the edges of the rear surface 100a of the substrate 100 are inclined, the supporting portions 2a1 can come into line contact with the edges of the rear surface 100a of the substrate 100. If the supporting portions 2a1 come into point or line contact with the edges of the rear surface 100a of the substrate 100, the occurrence of dirt, damage, and the like on the substrate 100 can be suppressed.

[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 of 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 parts 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] The blowing part 2b1 has a shape in which the cross-sectional area increases toward the mounting table 2a side (opening side). Therefore, the cross-sectional area of ​​the hole inside the blowing part 2b1 increases toward the mounting table 2a side (opening side). Although the blowing part 2b1 is provided at the tip of the rotating shaft 2b as an example, the blowing part 2b1 can also be provided at the tip of a cooling nozzle 3d, which will be described later. Also, the hole 2aa of the mounting table 2a can be used as the blowing part 2b1.

[0020] By providing the blowing portion 2b1, the discharged cooling gas 3a1 can be supplied to a wider area of ​​the rear surface 100a of the substrate 100. In addition, the discharge speed of the cooling gas 3a1 can be reduced. This makes it possible to prevent the substrate 100 from being partially cooled or to prevent the cooling speed of the substrate 100 from becoming too fast. As a result, it becomes easier to cause the liquid 101 to be in a supercooled state, which will be described later. In addition, the liquid 101 can be in a supercooled state in a wider area of ​​the front surface 100b of the substrate 100. This makes it possible to improve the removal rate of contaminants.

[0021] 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 end of the rotating shaft 2b opposite to the mounting table 2a side and the cooling nozzle 3d. Therefore, the end of the rotating shaft 2b opposite to the mounting table 2a side is sealed so as to be airtight.

[0022] The driving unit 2c is provided outside the housing 6. The driving unit 2c is connected to the rotating shaft 2b. The driving unit 2c may have a rotating device such as a motor. The rotational force of the driving unit 2c is transmitted to the mounting table 2a via the rotating shaft 2b. Therefore, the driving unit 2c can rotate the mounting table 2a, and thus the substrate 100 mounted on the mounting table 2a.

[0023] Furthermore, the driving unit 2c can change not only the start and stop of rotation but also the number of rotations (rotation speed). In this case, the driving unit 2c can be equipped with a control motor such as a servo motor.

[0024] The cooling unit 3 supplies a cooling gas 3a1 to a space between the mounting table 2a and the rear surface 100a of the substrate 100. The cooling unit 3 includes, for example, a cooling liquid unit 3a, a filter 3b, a flow rate control unit 3c, and a cooling nozzle 3d. The cooling liquid unit 3a, the filter 3b, and the flow rate control unit 3c are provided outside the housing 6.

[0025] The cooling liquid section 3a stores the cooling liquid and generates the cooling gas 3a1. The cooling liquid is a liquefied 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.

[0026] In this case, if a gas with a high specific heat is used, the cooling time of the substrate 100 can be shortened. For example, if helium gas is used, the cooling time of the substrate 100 can be shortened. Also, if nitrogen gas is used, the processing cost of the substrate 100 can be reduced.

[0027] The cooling liquid section 3a has a tank for storing the cooling liquid and an evaporation section for evaporating the cooling liquid stored in the tank. The tank is provided with a cooling device for maintaining the temperature of the cooling liquid. The evaporation section increases the temperature of the cooling liquid to generate the cooling gas 3a1 from the cooling liquid. The evaporation section can use, for example, the outside air temperature or heating with a heat medium. The temperature of the cooling gas 3a1 may be any temperature below the freezing point of the liquid 101, and can be, for example, −170° C.

[0028] Although the cooling liquid unit 3a generates the cooling gas 3a1 by vaporizing the cooling liquid stored in the tank, the cooling gas 3a1 can also be obtained by cooling nitrogen gas or the like using a chiller, etc. In this way, the cooling liquid unit 3a can be simplified.

[0029] The filter 3b is connected to the cooling liquid section 3a via a pipe. The filter 3b prevents contaminants such as particles contained in the cooling liquid from flowing out to the substrate 100 side.

[0030] 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). 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).

[0031] The temperature of the cooling gas 3a1 generated from the cooling liquid in the cooling liquid section 3a is approximately a predetermined temperature. Therefore, by controlling the flow rate of the cooling gas 3a1 with the flow rate control section 3c, the temperature of the substrate 100, and therefore the temperature of the liquid 101 on the surface 100b of the substrate 100, can be controlled. In this case, by controlling the flow rate of the cooling gas 3a1 with the flow rate control section 3c, the liquid 101 can be brought into a supercooled state in the supercooling step described below.

[0032] The cooling nozzle 3d has a cylindrical shape. 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).

[0033] 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 blowing unit 2b1.

[0034] The first liquid supply unit 4 supplies liquid 101 to the surface 100b of the substrate 100. In a freezing process (solid-liquid phase) described below, when the liquid 101 turns into a solid, its volume changes, generating a pressure wave. It is believed that this pressure wave separates contaminants adhering to the surface 100b of the substrate 100. Therefore, the liquid 101 is not particularly limited as long as it is unlikely to react with the material of the substrate 100.

[0035] However, if liquid 101 is a liquid whose volume increases when frozen, it is possible to separate contaminants adhering to the surface of substrate 100 by utilizing the physical force caused by the increase in volume. For this reason, liquid 101 is preferably a liquid that does not easily react with the material of substrate 100 and whose volume increases when frozen. For example, liquid 101 can be a liquid whose main component is water (e.g., pure water or ultrapure water).

[0036] The liquid mainly composed of water may contain, for example, water and a solute that increases the rearrangement density of ice crystals. The solute that increases the rearrangement density of ice crystals may be, for example, an alkali such as ammonia or an acid such as hydrochloric acid. The solute is not particularly limited as long as it can increase the dislocation density of ice crystals. In this case, the solute may be a liquid, a gas, or a solid.

[0037] Furthermore, the liquid 101 containing water as a main component may further contain, for example, alcohol. If the liquid 101 contains alcohol, the surface tension can be reduced, making it easier to supply the liquid 101 into the fine irregularities formed on the surface 100b of the substrate 100.

[0038] Furthermore, a gas can be dissolved in the liquid 101. The gas can be, for example, carbon dioxide gas, ozone gas, hydrogen gas, or the like. If carbon dioxide gas is dissolved in the liquid 101, the electrical conductivity of the liquid 101 can be increased, and therefore, static elimination and prevention of charging of the substrate 100 can be performed. If ozone gas is dissolved in the liquid 101, organic contaminants can be dissolved.

[0039] The first liquid supply unit 4 has, for example, a liquid storage unit 4a, a supply unit 4b, a flow rate control unit 4c, a liquid storage unit 14a, a supply unit 14b, a flow rate control unit 14c, and a liquid nozzle 4d. The liquid storage unit 4a, the supply unit 4b, the flow rate control unit 4c, the liquid storage unit 14a, the supply unit 14b, and the flow rate control unit 14c are provided outside the housing 6.

[0040] The first supply unit can be capable of supplying water (for example, pure water or ultrapure water) to the surface 100b of the substrate 100. The first supply unit has, for example, a liquid storage unit 4a, a supply unit 4b, and a flow rate control unit 4c. The liquid storage section 4a stores, for example, water. The water is stored in the liquid storage section 4a at a temperature higher than the freezing point. For example, water at room temperature (20° C.) is stored in the liquid storage section 4a.

[0041] The supply unit 4b may be, for example, a pump. The suction side of the supply unit 4b is connected to the liquid storage unit 4a via a pipe. The supply unit 4b supplies the water stored in the liquid storage unit 4a toward the liquid nozzle 4d. Although 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 pump the water stored in the liquid storage unit 4a.

[0042] The flow rate control unit 4c can be, for example, a flow rate control valve. The inlet side of the flow rate control unit 4c is connected to the outlet side of the supply unit 4b via a pipe. The outlet side of the flow rate control unit 4c is connected to the inlet side of the liquid nozzle 4d via a pipe. The flow rate control unit 4c controls the flow rate of the water supplied by the supply unit 4b. The flow rate control unit 4c can also start and stop the supply of water.

[0043] The second supply unit can supply a solute to the water supplied by the supply unit of the first supply unit. The second supply unit has, for example, a liquid storage unit 14a, a supply unit 14b, and a flow rate control unit 14c. The liquid storage section 14a stores a solute that increases the dislocation density of ice crystals. In this case, the solute is stored in the liquid storage section 14a in a liquid state. For example, the liquid storage section 14a stores an alkaline solution such as ammonia water or an acidic solution such as hydrochloric acid.

[0044] The supply unit 14b may be, for example, a pump having resistance to the solute. The suction side of the supply unit 14b is connected to the liquid storage unit 14a via a pipe. The supply unit 14b supplies the solute stored in the liquid storage unit 14a toward the liquid nozzle 4d. Although the supply unit 14b is a pump, the supply unit 14b is not limited to a pump. For example, the supply unit 14b may supply gas into the liquid storage unit 14a to pump the solute stored in the liquid storage unit 14a.

[0045] The flow rate control unit 14c can be, for example, a flow rate control valve. The inlet side of the flow rate control unit 14c is connected to the outlet side of the supply unit 14b via a pipe. The outlet side of the flow rate control unit 14c is connected to the pipe between the flow rate control unit 4c and the liquid nozzle 4d described above. The flow rate control unit 14c controls the flow rate of the solute supplied by the supply unit 14b. The flow rate control unit 14c can also start and stop the supply of the solute. Furthermore, the liquid storage unit 14a, the supply unit 14b, and the flow rate control unit 14c may be, for example, a device for discharging a fixed amount of liquid, such as a dispenser.

[0046] The liquid nozzle 4d is provided inside the housing 6. The liquid nozzle 4d has a cylindrical shape. The discharge side of the liquid nozzle 4d faces the front surface 100b of the substrate 100 placed on the placement table 2a.

[0047] Water, the flow rate of which is controlled by flow rate control unit 4c, and a solute, the flow rate of which is controlled by flow rate control unit 14c, are mixed inside a pipe connected to the inlet side of liquid nozzle 4d to generate liquid 101. The generated liquid 101 flows into liquid nozzle 4d and is supplied from liquid nozzle 4d to surface 100b of substrate 100.

[0048] Furthermore, the discharge side (discharge port of liquid 101) of liquid nozzle 4d is located approximately at the center of surface 100b of substrate 100. Liquid 101 discharged 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 the liquid film.

[0049] In the above, the liquid 101 to be supplied to the substrate 100 is successively generated on the inlet side of the liquid nozzle 4d, but the liquid 101 generated in advance can also be stored in the liquid storage unit 4a. In this way, the liquid storage unit 14a, the supply unit 14b, and the flow rate control unit 14c can be omitted, and the configuration of the substrate processing apparatus 1 can be simplified.

[0050] However, as described later, the concentration of the solute can be used to control cracking, for example, to control the timing at which cracks occur or to prevent cracks from occurring in the frozen film. If the liquid 101 supplied to the substrate 100 is successively generated on the inlet side of the liquid nozzle 4d, it becomes easy to control the concentration of the solute. This makes it easy to control the timing at which cracks occur or to prevent cracks from occurring in the frozen film. Details regarding the solute concentration and crack control will be described later.

[0051] The above-described first liquid supply unit 4 is for the case where the solute is a liquid. When the solute is a gas, a cylinder or the like that stores high-pressure gas may be provided instead of the liquid storage unit 14a and the supply unit 14b. A gas-liquid mixer or the like may also be provided on the inlet side of the liquid nozzle 4d.

[0052] When the solute is a solid, a hopper that stores a powdered solute and a feeder that supplies the powdered solute may be provided instead of the liquid storage unit 14a and the supply unit 14b. A solid-liquid mixer may also be provided on the inlet side of the liquid nozzle 4d.

[0053] If the solute is liquid, it is easy to mix with water, and therefore the concentration of the solute can be easily controlled. Therefore, if the solute is liquid, the configuration of the substrate processing apparatus 1 can be simplified and cracks occurring in the frozen film can be easily controlled.

[0054] The second liquid supply unit 5 supplies liquid 102 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.

[0055] The liquid 102 can be used in the thawing step described below. Therefore, the liquid 102 is not particularly limited 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) or a mixture of water and alcohol.

[0056] The liquid storage unit 5a may be the same as the liquid storage unit 4a described above. The supply unit 5b may be the same as the supply unit 4b described above. The flow rate control unit 5c may be the same as the flow rate control unit 4c described above.

[0057] When the liquid 102 is water, the second liquid supply unit 5 can be omitted. In this case, water is supplied by the liquid storage unit 4a, the supply unit 4b, and the flow rate control unit 4c, and the supply of solute by the liquid storage unit 14a, the supply unit 14b, and the flow rate control unit 14c is not required.

[0058] Moreover, although the liquid nozzle 4d is used for both purposes, a liquid nozzle for ejecting the liquid 101 and a liquid nozzle for ejecting the liquid 102 may be provided separately.

[0059] The temperature of liquid 102 can be set to a temperature higher than the freezing point of liquid 101. The temperature of liquid 102 can also be set to a temperature capable of thawing frozen liquid 101. The temperature of liquid 102 can be set to, for example, about room temperature (20° C.).

[0060] When the second liquid supply unit 5 is omitted, the first liquid supply unit 4 is used in the thawing step. That is, the water used to generate the liquid 101 is supplied to the frozen liquid 101. The temperature of the water used to generate the liquid 101 can be set to a temperature at which the frozen liquid 101 can be thawed. The temperature of the water used to generate the liquid 101 can be, for example, about room temperature (20°C).

[0061] The housing 6 is box-shaped. A cover 6a is provided inside the housing 6. The cover 6a receives the liquids 101, 102 that are supplied to the substrate 100 and are 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 on the opposite side to the mounting table 2a (the vicinity of 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, 102 that splash above the substrate 100.

[0062] Furthermore, 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.

[0063] 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, and liquids 101 and 102 are exhausted to the outside of the housing 6 from the exhaust ports 6c.

[0064] The exhaust unit 9 is connected to the exhaust port 6c via an exhaust pipe 6c1. The exhaust unit 9 exhausts the used cooling gas 3a1 and air 7a to the outside of the housing 6. The exhaust unit 9 can be, for example, a pump or a blower. The used liquids 101 and 102 are exhausted to the outside of the housing 6 via an exhaust pipe 6c2 connected to the exhaust pipe 6c1.

[0065] The exhaust port 6c is provided below the substrate 100. Therefore, a downflow is created by exhausting the cooling gas 3a1 from the exhaust port 6c. As a result, it is possible to prevent particles from flying up.

[0066] In a plan view, the multiple exhaust ports 6c are provided symmetrically with respect to the center of the housing 6. In this manner, the exhaust direction of the cooling gas 3a1 is symmetric with respect to the center of the housing 6. If the exhaust direction of the cooling gas 3a1 is symmetric, the cooling gas 3a1 can be smoothly exhausted.

[0067] The blower 7 is provided on the ceiling surface of the housing 6. The blower 7 can also be provided on the side surface of the housing 6, so 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).

[0068] The blower 7 supplies air 7a (outside air) to the space between the partition plate 6b and the ceiling of the housing 6. Therefore, the pressure in the space between the partition plate 6b and the ceiling of the housing 6 becomes higher than the external pressure. As a result, it becomes easier to guide the air 7a supplied by the blower 7 to the exhaust port 6c. In addition, it is possible to prevent contaminants such as particles from entering the inside of the housing 6 from the exhaust port 6c.

[0069] Moreover, the blower 7 supplies air 7a at room temperature to the surface 100b of the substrate 100. Therefore, the blower 7 can also change the temperature of the liquids 101, 102 on the substrate 100 by controlling the amount of air 7a supplied. For example, the blower 7 can control the supercooled state of the liquid 101 in a supercooling step described below, promote thawing of the liquid 101 in a thawing step, and promote drying of the liquid 102 in a drying step.

[0070] The detection unit 8 is provided in the space between the partition plate 6b and the ceiling of the housing 6. The detection unit 8 detects the temperature of the liquid film or the frozen film formed by freezing the liquid 101. In this case, the detection unit 8 can be, for example, a radiation thermometer, a thermoviewer, a thermocouple, or a resistance temperature detector. The detection unit 8 may also detect the thickness of the liquid film or the surface position of the frozen film. In this case, the detection unit 8 can be, for example, a laser displacement meter or an ultrasonic displacement meter. The detection unit 8 may also be, for example, an image sensor that detects the surface state of the liquid film or the surface state of the frozen film.

[0071] The detected temperature, thickness, and surface state of the liquid film can be used to control the supercooled state of the liquid 101 in the supercooling step described below. Note that controlling the supercooled state means controlling the temperature change curve of the liquid 101 in the supercooled state to prevent the liquid 101 from freezing due to rapid cooling, that is, to maintain the supercooled state.

[0072] Furthermore, the detected temperature, thickness, and surface state of the frozen film can be used to detect the "occurrence of cracks" in the freezing process (solid phase) described below. For example, if the detection unit 8 detects the temperature, the "occurrence of cracks" can be indirectly detected from the temperature of the frozen film in the freezing process (solid phase) described below. If the detection unit 8 detects the thickness, the "occurrence of cracks" can be detected from a change in the surface position of the frozen film in the freezing process (solid phase) described below. If the detection unit 8 detects the surface state, the "occurrence of cracks" can be detected from the surface state of the frozen film in the freezing process (solid phase) described below.

[0073] The controller 10 controls the operation of each element provided in the substrate processing apparatus 1. The controller 10 has, for example, a calculation unit such as a CPU (Central Processing Unit) and a storage unit such as a semiconductor memory. The controller 10 is, for example, a computer. The storage unit can store a control program that controls the operation of each element provided in the substrate processing apparatus 1. The calculation unit controls the operation of each element provided in the substrate processing apparatus 1 using the control program stored in the storage unit, data input by an operator, data from the detection unit 8, etc.

[0074] For example, the cooling rate of the liquid 101 is correlated with the thickness of the liquid film. For example, the thinner the liquid film, the faster the cooling rate of the liquid 101. Conversely, the thicker the liquid film, the slower the cooling rate of the liquid 101. Therefore, the controller 10 can control the flow rate of the cooling gas 3a1 and, in turn, the cooling rate of the liquid 101 based on the thickness of the liquid 101 (thickness of the liquid film) detected by the detection unit 8. Note that the control of the temperature and cooling rate of the liquid 101 is performed when controlling the supercooled state of the liquid 101 in the supercooling step described later. Therefore, when controlling the supercooled state of the liquid 101, the controller 10 can control, for example, at least one of the rotation of the substrate 100, the flow rate of the cooling gas 3a1, and the supply amount of the liquid 101.

[0075] For example, the controller 10 causes the liquid 101 on the surface 100b of the substrate 100 to be in a supercooled state, freezes the supercooled liquid 101 to generate a frozen film, and reduces the temperature of the frozen film to cause cracks in the frozen film. At this time, the controller 10 can control the concentration of the solute, and therefore the cracks, by controlling, for example, at least one of the flow rate control unit 4c and the flow rate control unit 14c.

[0076] Next, the operation of the substrate processing apparatus 1 will be illustrated. FIG. 2 is a timing chart illustrating the operation of the substrate processing apparatus 1. As shown in FIG. FIG. 3 is a graph for illustrating the temperature change of the liquid 101 supplied to the substrate 100. In FIG. 2 and 3 show the case where the substrate 100 is a 6025 quartz (Qz) substrate (152 mm×152 mm×6.35 mm) and the liquid 101 is pure water with added ammonia.

[0077] First, the substrate 100 is carried into the housing 6 through an entrance / exit (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.

[0078] After the substrate 100 is supported on the mounting table 2a, a freeze-cleaning process including a preliminary process, a liquid film forming process, a cooling process, a thawing process, and a drying process is performed as shown in FIGS.

[0079] First, a preliminary process is performed as shown in Figures 2 and 3. In the preliminary process, the controller 10 controls the supply unit 4b, the flow control unit 4c, the supply unit 14b, and the flow control unit 14c to supply the liquid 101 at a predetermined flow rate to the front surface 100b of the substrate 100. The controller 10 also controls the flow control unit 3c to supply the cooling gas 3a1 at a predetermined flow rate to the rear surface 100a of the substrate 100. The controller 10 also controls the drive unit 2c to rotate the substrate 100 at a third rotation speed.

[0080] 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, which may cause 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.

[0081] 2, the third rotation speed of the substrate 100 is, for example, about 50 rpm to 500 rpm. The flow rate of the liquid 101 is about 0.1 L / min to 1.0 L / min. The flow rate of the cooling gas 3a1 is about 40 NL / min to 200 NL / min. The process time of the preliminary process is about 1800 seconds. The process time of the preliminary process may be any time that allows the in-plane temperature of the substrate 100 to become substantially uniform, and can be obtained in advance by performing experiments or simulations.

[0082] Also, the supply of solute from the liquid storage unit 14a may be stopped from the start of the preliminary process to 60 to 120 seconds before the end of the preliminary process. That is, water may be supplied to the surface 100b of the substrate 100 during the above period. This is because, in the preliminary process, if the purpose is only to prevent frost from adhering to the surface 101b of the substrate 100, it is not essential to supply the liquid 101 in which water and the solute are mixed. The aforementioned 60 to 120 seconds is the time required to replace the liquid 101 consisting of only water on the surface 100b of the substrate 100 with the liquid 101 in which water and the solute are mixed. In this case, the last 60 to 120 seconds of the preliminary process is a replacement process in which the liquid 101 is replaced with the liquid 101 in which water and the solute are mixed. In this way, the amount of solute used can be reduced. The replacement process may be performed as a series of processes together with the liquid film formation process described later.

[0083] 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, when the temperature of the supplied liquid 101 is approximately room temperature (20° C.), the temperature of the liquid film is approximately room temperature (20° C.).

[0084] Next, a liquid film forming step is performed as shown in Fig. 2 and Fig. 3. In the liquid film forming step, the controller 10 controls the drive unit 2c to rotate the substrate 100 at a second rotation speed. The second rotation speed is a rotation speed at which the thickness of the liquid film is such that a high removal rate can be obtained. The second rotation speed is, for example, 50 rpm to 100 rpm. In other words, the controller 10 rotates the substrate 100 at a rotation speed that is the same as or lower than the rotation speed in the preliminary step.

[0085] 2, the supply of liquid 101 that was supplied in the preliminary step is stopped, and substrate 100 is rotated at the second rotation speed until the predetermined thickness is reached. Whether the predetermined thickness is reached may be confirmed by measuring the thickness of the liquid film using detection unit 8. The thickness of the liquid film may be measured by detection unit 8, and the time required for the liquid film to reach the predetermined thickness may be calculated in advance from the measured thickness, and the second rotation speed may be maintained for the time required for the liquid film to reach the predetermined thickness.

[0086] Thereafter, the rotation speed of the substrate 100 is set to a first rotation speed. The first rotation speed is a rotation speed at which the liquid film of the liquid 101 supplied onto the substrate 100 is maintained at a uniform thickness. 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, for example, about 0 rpm to 50 rpm.

[0087] The flow rate of the cooling gas 3a1 in the liquid film forming step is set to be the same as the flow rate of the cooling gas 3a1 in the preliminary step. As described above, in the preliminary step, the in-plane temperature of the substrate 100 is made substantially uniform. By maintaining the flow rate of the cooling gas 3a1 in the liquid film forming step to be the same as in the preliminary step, the in-plane temperature of the substrate 100 can be maintained in a substantially uniform state.

[0088] Also, when it is desired to make the thickness of the liquid film thicker, the rotation speed can be changed from the third rotation speed to the first rotation speed without changing to the second rotation speed. In this case, it is preferable that the first rotation speed is close to 0 rpm. In particular, if the rotation of the substrate 100 is stopped, it is possible to further suppress the variation in thickness of the liquid film caused by the centrifugal force. The first rotation speed may be set from the preliminary step onward. The third rotation speed may be slower than the first rotation speed.

[0089] Furthermore, when moving from the preliminary step to the liquid film forming step, the liquid 101 supplied in the preliminary step may be discharged by rotating the substrate 100 at high speed. In this case, after discharging the liquid 101, the rotation speed of the substrate 100 may be set to a rotation speed (50 rpm) or less at which a liquid film of uniform thickness is maintained, or after the rotation of the substrate 100 is stopped, a predetermined amount of liquid 101 may be supplied to the substrate 100. In this way, a liquid film having a predetermined thickness can be easily formed.

[0090] As described later, the thickness of the liquid film formed in the liquid film formation process (the thickness of the liquid film when the cooling process is performed) can be about 300 μm to 1300 μm. For example, the controller 10 controls the supply amount of the liquid 101 and the rotation speed of the substrate 100 to make the thickness of the liquid film on the surface 100b of the substrate 100 about 300 μm to 1300 μm. The thickness of the liquid film will be described in detail later.

[0091] Next, the cooling process is performed as shown in FIG. 2 and FIG. 3. In the present embodiment, the period before the liquid 101 in the supercooled state starts to freeze is called the "supercooling process", the period after the liquid 101 in the supercooled state starts to freeze until the freezing is completely completed is called the "freezing process (solid-liquid phase)", and the period before the frozen liquid 101 is further cooled to cause cracks is called the "freezing process (solid phase)". In the supercooling process, only the liquid 101 exists on the surface 100b of the substrate 100. In the freezing process (solid-liquid phase), the liquid 101 and the liquid 101 frozen are present on the surface 100b of the substrate 100. In the freezing process (solid phase), only the liquid 101 frozen is present on the surface 100b of the substrate 100. The solid-liquid phase means a state in which the liquid 101 and the liquid 101 frozen are present throughout. In addition, the state in which only the liquid 101 is frozen is called a frozen film 101a.

[0092] First, in the supercooling step, the temperature of the liquid film on the substrate 100 is further lowered 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.

[0093] Here, if the cooling speed of the liquid 101 becomes too fast, the liquid 101 will not reach a supercooled state and will soon freeze. Therefore, the controller 10 controls at least one of the rotation speed of the substrate 100, the flow rate of the cooling gas 3a1, and the supply amount of the liquid 101, so that the liquid 101 on the surface 100b of the substrate 100 reaches a supercooled state.

[0094] The control conditions under which liquid 101 becomes supercooled are affected by the size of substrate 100, the viscosity of liquid 101, the specific heat of cooling gas 3a1, etc. Therefore, it is preferable to appropriately determine the control conditions under which liquid 101 becomes supercooled by conducting experiments or simulations.

[0095] In the supercooled state, freezing of the liquid 101 begins due to, for example, the temperature of the liquid film, the presence of contaminants such as particles or air bubbles, vibration, etc. For example, in the presence of contaminants such as particles, freezing of the liquid 101 begins when the temperature T of the liquid 101 falls to -35°C or higher and -20°C or lower. Freezing of the liquid 101 can also be started by applying vibration to the liquid 101, for example by varying the rotation of the substrate 100.

[0096] When the supercooled liquid 101 starts freezing, the process transitions from the supercooling process to the freezing process (solid-liquid phase). In the freezing process (solid-liquid phase), the liquid 101 and the frozen liquid 101 are present on the surface 100b of the substrate 100 as a whole. As described above, in the supercooled liquid 101, a certain percentage of the starting points of freezing start become contaminants. It is considered that the contaminants attached to the surface 100b of the substrate 100 are separated because the contaminants become the starting points of freezing start, pressure waves are generated due to the volume change when the liquid 101 changes to a solid, and physical forces are generated due to the increase in volume. Therefore, the contaminants attached to the surface 100b of the substrate 100 can be separated by the pressure waves and physical forces generated when a part of the liquid 101 freezes.

[0097] When the liquid film on the surface 100b of the substrate 100 is completely frozen, the process transitions from the freezing step (solid-liquid phase) to the freezing step (solid phase). In the freezing step (solid phase), the temperature of the frozen film 101a on the surface 100b of the substrate 100 further drops. Here, the liquid 101 mainly contains water. Therefore, when the liquid film on the surface 100b of the substrate 100 is completely frozen to form the frozen film 101a, and the temperature of the frozen film 101a further drops, the volume of the frozen film 101a shrinks and stress is generated in the frozen film 101a.

[0098] In this case, for example, when the temperature of the frozen film 101a becomes −50° C. or lower, cracks occur in the frozen film 101a. When cracks occur in the frozen film 101a, the contaminants 103 adhering to the surface 100b of the substrate 100 are separated from the surface 100b of the substrate 100. The mechanism by which the contaminants 103 are separated from the surface 100b of the substrate 100 is not necessarily clear, but can be considered as follows.

[0099] 4(a) and (b) are schematic diagrams for illustrating the separation mechanism of the contaminant 103. FIG. As shown in FIG. 4(a), when the temperature of the frozen film 101a decreases in the freezing step (solid phase), a stress F according to the difference between the thermal expansion coefficient of the frozen film 101a and the thermal expansion coefficient of the substrate 100 is generated.

[0100] 4(b), when the temperature of the frozen film 101a drops further (for example, to −50° C. or lower), the frozen film 101a cracks because it cannot withstand the increased stress F. In this case, since the thermal expansion coefficient of the frozen film 101a, which is mainly composed of water, is generally greater than that of the substrate 100, the frozen film 101a deforms in a convex shape toward the outside, causing cracks, as shown in FIG.

[0101] Since the frozen film 101a contains contaminants 103, when the frozen film 101a deforms into a convex shape toward the outside (when a crack occurs), the contaminants 103 are separated from the surface 100b of the substrate 100, as shown in Figure 4(b).

[0102] Next, the control of cracks will be described. As described above, cracks occur when the frozen film 101a can no longer withstand the increased stress F caused by a drop in the temperature of the frozen film 101a. Therefore, an impact force occurs when cracks occur. In recent years, the patterns (uneven portions) formed on the surface 100b of the substrate 100 have become finer. Therefore, there is a risk that the patterns (uneven portions) will collapse due to the impact force when cracks occur. Furthermore, if it takes a long time for cracks to occur after the formation of the frozen film 101a, the processing time will be longer accordingly.

[0103] As a result of investigations, the present inventors have found that cracking can be controlled by adding a solute that increases the dislocation density of ice crystals to water and changing the concentration of the solute. 5 and 6 are graphs illustrating the relationship between solute concentration and time to crack initiation. The horizontal axis in Figures 5 and 6 is the concentration of the solute. The vertical axis is the relative value (%) when the time until cracks occur when no solute is added (0 ppm) is set to "100." Therefore, the larger the relative value (%), the longer the time until cracks occur. Moreover, Fig. 5 shows the case where ammonia is used as the solute, and Fig. 6 shows the case where hydrochloric acid is used as the solute.

[0104] As can be seen from Figures 5 and 6, when the concentration of the solute is greater than 0 ppm and less than or equal to 100 ppm, the time until cracks occur can be shortened whether an alkali such as ammonia or an acid such as hydrochloric acid is used as the solute.

[0105] As mentioned above, cracks occur when the frozen film 101a can no longer withstand the increased stress F caused by a drop in the temperature of the frozen film 101a. Adding a solute increases the dislocation density of the ice crystals that are the starting points for fracture. If the dislocation density of the ice crystals increases, cracks will occur at a smaller stress F. Therefore, as shown in Figures 5 and 6, the time until cracks occur is shortened. If the time until cracks occur is shortened, the processing time (the time required for one freeze-cleaning process) can be shortened.

[0106] Furthermore, if cracks occur at a smaller stress F, the impact force generated when the cracks occur will be smaller, making it possible to suppress the collapse of the pattern (unevenness).

[0107] Even if cracks occur at a smaller stress F, the separation mechanism of the contaminants 103 described in Figures 4(a) and 4(b) remains unchanged. In addition, there is no change in the relationship between the thickness of the liquid film and the number of repetitions of the freeze cleaning process, which will be described later in Figure 7. Therefore, by adding a solute that increases the dislocation density of ice crystals to water and keeping the concentration of the solute within a predetermined range, it is possible to prevent the pattern (uneven portion) from collapsing, shorten the processing time, and improve the removal rate of the contaminants 103.

[0108] In addition, as can be seen from Figures 5 and 6, if the concentration of the solute is set to a certain value or higher, the occurrence of cracks can be prevented. If cracks do not occur, the impact force described above does not occur, and the collapse of the pattern (unevenness) can be significantly reduced.

[0109] The controller 10 controls at least one of the flow rate control units 4c and 14c depending on the rigidity of the pattern (concave and recessed portion) and the like, thereby controlling the concentration of the solute and, in turn, controlling cracks.

[0110] For example, for a pattern with low rigidity (unevenness), the concentration of the solute is set to more than 0 ppm and not more than 100 ppm, so that cracks are generated at a smaller stress F, thereby reducing the impact force. Furthermore, for a pattern with even lower rigidity (unevenness), the concentration of the solute is set to, for example, 10,000 ppm or more, so that cracks are not generated, thereby eliminating the generation of impact force.

[0111] Furthermore, according to the findings of the present inventors, it has been found that increasing the thickness of the liquid film during the supercooling step improves the removal rate of the contaminants 103 during the freezing step (solid phase). This is probably because increasing the thickness of the liquid film increases the bending of the frozen film 101a when it deforms into a convex shape toward the outside. In this case, if the removal rate of the contaminants 103 during the freezing step (solid phase) improves, the number of times the freeze cleaning step is repeated can be reduced. This makes it possible to shorten the time required for the freeze cleaning operation and thereby improve productivity.

[0112] FIG. 7 is a graph illustrating the relationship between the thickness of the liquid film and the number of repetitions of the freeze cleaning process. The number in the figure indicates the number of repetitions of the freeze cleaning process. The target removal rate of contaminants on the substrate 100 was set to 90%. The target removal rate (predetermined removal rate) may be set so that the yield in cleaning the substrate 100 is an acceptable value. In order to eliminate the influence of centrifugal force, the first rotation speed was set to 0 rpm. As a result, the thickness of the uniform liquid film formed on the surface 100b of the substrate 100 was 300 μm.

[0113] 7, when the number of repetitions is 20 or more, the removal rate of the contaminants 103 can be improved to 90% or more by setting the liquid film thickness to 300 μm or more during the supercooling step. When the number of repetitions is 10 or more, the removal rate of the contaminants 103 can be improved to 90% or more by setting the liquid film thickness to 600 μm or more. When the number of repetitions is 5 or more, the removal rate of the contaminants 103 can be improved to 90% or more by setting the liquid film thickness to 1000 μm or more.

[0114] Incidentally, the thickness of the liquid film is influenced by the surface tension of the liquid 101 and the like, and can be made as thick as about 1300 μm. However, if the thickness of the liquid film is made as thick as about 1300 μm, there is a risk that part of the liquid 101 will spill out of the substrate 100 even at a rotation speed of 50 rpm or less. Therefore, the maximum thickness of the liquid film can be made as thick as about 1200 μm. For example, the thickness of the liquid film during the supercooling step is preferably 300 μm or more and 1200 μm or less when the number of repetitions is 20 or more, and more preferably 600 μm or more and 1200 μm or less when the number of repetitions is 10 or more.

[0115] If the thickness of the liquid film is 300 μm or more and 1200 μm or less, the removal rate of the contaminants 103 is improved to 90% or more by repeating the freeze cleaning process 20 times. When forming a liquid film with a thickness in the above range, if the rotation speed is 50 rpm or less, the liquid 101 is not shaken off by centrifugal force, so the liquid film is easily formed. In addition, if the thickness of the liquid film is 600 μm or more and 1200 μm or less, it is possible to reduce the number of times of execution to 10 times or more and less than 20 times. Therefore, it is possible to shorten the time of the freeze cleaning work and thereby improve productivity. To further reduce the number of times of execution to 5 times or more and less than 10 times, it is preferable to set the thickness of the liquid film to 1000 μm or more and 1200 μm or less.

[0116] The number of times the freeze cleaning process is to be performed is input by an operator via an input / output screen (not shown). Alternatively, the substrate processing apparatus 1 may read a mark such as a barcode or a QR code (registered trademark) attached to a case for storing the substrates 100.

[0117] Next, returning to FIG. 2 and FIG. 3, the operation of the substrate processing apparatus 1 will be further described. As shown in Figs. 2 and 3, after cracks occur in the frozen film 101a, the thawing process is performed. The occurrence of cracks can be detected by the detection unit 8. For example, if the detection unit 8 detects temperature, the "occurrence of cracks" can be indirectly detected from the temperature (e.g., -50°C or lower) of the frozen film 101a in the freezing process (solid phase). If the detection unit 8 detects thickness, the "occurrence of cracks" can be detected from a change in the surface position of the frozen film 101a in the freezing process (solid phase). If the detection unit 8 is an image sensor, the "occurrence of cracks" can be detected by image processing in the freezing process (solid phase).

[0118] 2 and 3 show a case where the thawing step is performed using the first liquid supply unit 4. In the thawing step, only water needs to be supplied from the first liquid supply unit 4, but for convenience, in FIGS. 2 and 3, it is described as liquid 101. In the thawing step, the controller 10 controls the supply unit 4b and the flow rate control unit 4c to supply water at a predetermined flow rate to the surface 100b of the substrate 100. In the case where the second liquid supply unit 5 is used in the thawing step, the controller 10 controls the supply unit 5b and the flow rate control unit 5c to supply liquid 102 at a predetermined flow rate to the surface 100b of the substrate 100.

[0119] Furthermore, the controller 10 controls the flow control unit 3c to stop the supply of the cooling gas 3a1. Furthermore, the controller 10 controls the drive unit 2c to increase the rotation speed of the substrate 100 to a fourth rotation speed. The fourth rotation speed is, for example, about 200 rpm to 700 rpm. If the rotation speed of the substrate 100 is increased, the water or liquid 101 used for thawing can be thrown off by centrifugal force. Therefore, the water or liquid 101 used for thawing can be discharged from the surface 100b of the substrate 100. At this time, the contaminants 103 separated from the surface 100b of the substrate 100 are also discharged together with the above.

[0120] The supply amount of water or liquid 102 is not particularly limited as long as thawing can be performed. The fourth rotation speed of substrate 100 is not particularly limited as long as the water used for thawing, the frozen liquid 101, and the contaminants 103 can be discharged.

[0121] Next, a drying process is performed as shown in Figures 2 and 3. In the drying process, the controller 10 controls the supply unit 4b and the flow rate control unit 4c to stop the supply of water used for thawing. When the liquid 102 is used, the controller 10 controls the supply unit 5b and the flow rate control unit 5c to stop the supply of the liquid 102.

[0122] Furthermore, the controller 10 controls the driving unit 2c to increase the rotation speed of the substrate 100 to a fifth rotation speed that is faster than the fourth rotation speed. If the rotation speed of the substrate 100 is increased, the substrate 100 can be dried quickly. The fifth rotation speed of the substrate 100 is not particularly limited as long as the substrate 100 can be dried.

[0123] After the freeze cleaning is completed, the substrate 100 is carried out of the housing 6 through a carry-in / out opening (not shown) of the housing 6 . By carrying out the above steps, one freeze-washing step can be carried out.

[0124] As described above, the freeze cleaning process can be performed multiple times. Therefore, if the next freeze cleaning process is performed, the supply of the cooling gas 3a1 can be maintained even in the thawing process. In this way, the same condition as the preliminary process can be generated, so that the preliminary process in the next freeze cleaning process can be omitted.

[0125] For example, when the freeze cleaning process is repeated multiple times, the freeze cleaning process may include at least a supercooling process in which the liquid 101 on the surface 100b of the substrate 100 is brought into a supercooled state, a freezing process (solid-liquid phase) in which the liquid 101 and frozen versions of the liquid 101 exist, a freezing process (solid phase) in which the liquid 101 is completely frozen to form a frozen film 101a and the temperature of the frozen film 101a is lowered to cause cracks to occur in the frozen film 101a, and a thawing process.

[0126] In the substrate processing apparatus 1 according to this embodiment, in the freezing process (solid-liquid phase), freezing begins with the contaminants as a starting point, and contaminants 103 adhering to the surface of the substrate 100 are separated by pressure waves caused by the change in volume when the liquid 101 turns into a solid, and by physical forces caused by the increase in volume.

[0127] Furthermore, in the freezing step (solid phase), cracks are generated in the frozen film 101a, so that the frozen film 101a containing the contaminants 103 is deformed into a convex shape facing outward. By deforming the frozen film 101a into a convex shape, the contaminants 103 contained in the frozen film 101a are separated from the surface of the substrate 100.

[0128] That is, according to the substrate processing apparatus 1, the contaminants 103 are separated by different mechanisms in the freezing process (solid-liquid phase) and the freezing process (solid phase), and therefore the removal rate of the contaminants 103 can be improved.

[0129] In addition, in the substrate processing apparatus 1 according to the present embodiment, the rotation speed of the substrate 100 in the cooling step is set to a first rotation speed that can suppress the thickness of the liquid film from varying due to centrifugal force. In the cooling step, when the second rotation speed that results in a predetermined thickness is maintained, the centrifugal force due to the second rotation speed is applied to the liquid 101 on the surface 100b of the substrate 100. The centrifugal force becomes larger the farther away from the center of rotation. Therefore, the liquid 101 gathers at the outer edge of the substrate 100. At this time, the viscosity and surface tension of the liquid 101 act on the liquid 101 at the outer edge of the substrate 100, so that the thickness of the liquid film at the outer edge of the substrate 100 becomes thicker. In other words, the thickness of the liquid film at the center of the substrate 100 becomes relatively thinner.

[0130] As described above, if the thickness of the liquid film is increased during the supercooling step, the removal rate of the contaminants 103 during the freezing step (solid phase) is improved. In other words, if the second rotation speed at which the predetermined thickness is obtained is maintained during the cooling step, the removal rate of the central portion of the substrate 100 may decrease.

[0131] In this embodiment, the cooling gas 3a1 is supplied from the blowing portion 2b1 in the center of the mounting table 2a. Therefore, the temperature of the outer edge of the substrate 100 is higher than that of the center of the substrate 100. As described above, if the second rotation speed is maintained in the cooling process, the thickness of the liquid film on the outer edge side of the substrate 100 becomes thicker. Therefore, the thick liquid film on the outer edge side of the substrate 100 is cooled in a state where the cooling efficiency is inferior, so the liquid film on the outer edge side of the substrate 100 is cooled at a slower rate than the center of the substrate 100. In other words, the occurrence of cracks on the outer edge side of the substrate 100 is delayed.

[0132] The freezing process (solid phase) is completed when it is confirmed that cracks have occurred in all regions of the substrate 100. Therefore, if the freezing process (solid phase) is performed in a state in which the thickness of the liquid film varies due to centrifugal force, the processing time of the freezing process (solid phase) will be long.

[0133] In other words, if the freezing step (solid phase) is performed in a state where the thickness of the liquid film varies due to centrifugal force, the processing time may become longer and the expected removal rate may not be obtained. Therefore, in the cooling step, it is preferable to set the rotation speed of the substrate 100 to the first rotation speed that can suppress the variation in the thickness of the liquid film due to centrifugal force.

[0134] Furthermore, when the rotation of the substrate 100 is stopped (0 rpm), the thickness of the liquid film at the center of the substrate 100 becomes thicker than the thickness of the liquid film on the outer edge side of the substrate 100. The gradient of the thickness of the liquid film is opposite to the temperature gradient of the substrate 100 described above. In other words, the cooling rate becomes constant at the center and outer edge of the substrate 100. When the cooling rate becomes constant at the center and outer edge of the substrate 100, cracks will occur simultaneously at the center and outer edge of the substrate 100, so that it is possible to prevent the processing time of the freezing step (solid phase) from becoming longer. Therefore, it is preferable to stop the rotation of the substrate 100 (0 rpm).

[0135] Furthermore, when the freeze cleaning process is repeated 20 times or more, if the thickness of the liquid film during the freeze cleaning process is set to 300 μm or more and 1200 μm or less, the removal rate of the contaminants 103 can be improved to 90% or more while improving productivity. Furthermore, when the freeze cleaning process is repeated 5 times or more, if the thickness of the liquid film is set to 1000 μm or more and 1200 μm or less, the removal rate of the contaminants 103 can be improved to 90% or more while further improving productivity.

[0136] The above are examples of the embodiments. However, the present invention is not limited to these descriptions. Regarding the above-mentioned embodiments, those in the art who have appropriately added or removed components or modified the design, or added or omitted steps or modified conditions, are also included within the scope of the present invention as long as they have the characteristics of the present invention.

[0137] For example, the shape, size, number, arrangement, and the like of each element included in the substrate processing apparatus 1 are not limited to those exemplified, and can be changed as appropriate.

[0138] Also, cooling may be continued under predetermined conditions for a predetermined time from the start time of the freezing process (solid-liquid phase) and the freezing process (solid phase). For example, the temperature can be measured and the start point can be the point at which the temperature rises from a supercooled state, or the point at which the temperature drops from a temperature equilibrium state and becomes completely solidified. In this way, if the start points of the freezing process (solid-liquid phase) and the freezing process (solid phase) can be detected by the detection unit 8, the function of determining the occurrence of cracks can be omitted from the results obtained by analyzing or calculating the data of the detection unit 8. In other words, a simple controller 10 can be made.

[0139] Also, occurrence of cracks may be detected by reflectance. When cracks occur, the frozen film 101a is peeled off from the substrate 100, causing a change in reflectance. This change in reflectance allows it to be determined that the frozen film 101a has been sufficiently peeled off, and thawing can be started. By detecting occurrence of cracks by reflectance, occurrence of cracks that cannot be detected by temperature change can be detected. As a result, the contaminant 103 can be removed more reliably.

[0140] Also, based on the knowledge that cracks occur at temperatures below -50°C, -50°C can be set as the threshold. For example, when the temperature of frozen film 101a falls below -50°C, it may be determined that cracks have occurred and thawing may begin. In this way, a mechanism for measuring reflectance and refractive index and a mechanism for capturing images can be omitted, resulting in a simple configuration. Note that thawing may begin about 0.2 to 2.0 seconds after the threshold is reached.

[0141] Also, the processing surface of the substrate 100 may be imaged, and cracks may be observed from the image. For example, the image may be processed to detect a predetermined crack state (number, area). For example, since cracks appear as white streaks, the image may be binarized to black and white to detect the cracks. Then, when the number or area of ​​the cracks reaches or exceeds a threshold, it may be determined that the frozen film 101a has sufficiently peeled off, and thawing may be started. If the occurrence of cracks is directly detected, the contaminants 103 may be removed more reliably. [Explanation of symbols]

[0142] 1 substrate processing apparatus, 2 placement section, 2a placement table, 3 cooling section, 3a1 cooling gas, 4 first liquid supply section, 6 housing, 8 detection section, 10 controller, 100 substrate, 100a back surface, 100b front surface, 101 liquid, 101a frozen film, 102 liquid, 103 contaminant

Claims

1. A mounting table capable of rotating a substrate; a cooling unit capable of supplying a cooling gas to a space between the mounting table and the substrate; a liquid supply unit capable of supplying liquid to a surface of the substrate opposite to the mounting table; a controller for controlling the rotation of the substrate, the flow rate of the cooling gas, and the supply of the liquid; Equipped with The liquid includes water and a solute that increases the dislocation density of ice crystals; the solute is an acid or alkali at a concentration of 100 ppm or less; The controller causes the liquid on the surface of the substrate to be in a supercooled state, freezes the supercooled liquid to generate a frozen film, and lowers the temperature of the frozen film to cause cracks in the frozen film.

2. the liquid supply unit includes a first supply unit capable of supplying the water and a second supply unit capable of supplying the solute; 2. The substrate processing apparatus of claim 1, wherein the liquid is generated by mixing the water supplied by the first supply unit and the solute supplied by the second supply unit, and the generated liquid is supplied to the surface of the substrate.

3. The substrate processing apparatus according to claim 1 , further comprising a detection unit that detects the crack.

4. Further comprising a controller for controlling the first supply unit and the second supply unit; The first supply unit has a flow rate control unit that controls a flow rate of the water, The second supply unit has a flow rate control unit that controls a flow rate of the solute, 3 . The substrate processing apparatus according to claim 2 , wherein the controller controls at least one of a flow rate control unit of the first supply unit and a flow rate control unit of the second supply unit to control the concentration of the solute.

Images