JP7130722B2 - Substrate processing equipment - Google Patents

Description

An embodiment of the present invention relates to a substrate processing apparatus.

A freeze cleaning method 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.

In the freeze cleaning method, for example, when pure water is used as the cleaning liquid, first, pure water and cooling gas are supplied to the surface of the rotated substrate. Next, the supply of pure water is stopped and 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 an ice film, contaminants such as particles are trapped in the ice film and separated from the surface of the substrate. Next, pure water is supplied to the ice film to melt the ice film, and contaminants are removed from the surface of the substrate together with the pure water.

The freeze cleaning method can effectively remove contaminants adhering to the surface of the substrate. However, in recent years, it is desired to further increase the removal rate of contaminants.

JP 2018-026436 A

SUMMARY OF THE INVENTION An object of the present invention is to provide a substrate processing apparatus capable of improving the removal rate of contaminants.

A substrate processing apparatus according to an 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 the surface opposite to the side, and a control unit controlling the rotation of the substrate, the flow rate of the cooling gas, and the supply amount of the liquid. The control unit causes the liquid on the surface of the substrate to be in a supercooled state, freezes the liquid in the supercooled state to generate a frozen film, and controls the temperature of the frozen film. and a thawing step of thawing the cracked frozen film is repeated a plurality of times, and the freeze washing step is repeated If the number of times is 20 or more, the amount of liquid supplied is controlled so that the thickness of the liquid film of the liquid on the surface of the substrate is 300 μm or more and 1200 μm or less .

Embodiments of the present invention provide a substrate processing apparatus capable of improving the removal rate of contaminants.

1 is a schematic diagram for illustrating a substrate processing apparatus according to an embodiment; FIG. 4 is a timing chart for illustrating the action of the substrate processing apparatus; 4 is a graph for illustrating temperature changes of liquid supplied to a substrate in a freeze cleaning process; (a) and (b) are schematic diagrams for illustrating the separation mechanism of contaminants. 4 is a graph for illustrating the relationship between the thickness of the liquid film and the number of repetitions of the freeze cleaning process. It is a schematic diagram for illustrating the substrate processing apparatus which concerns on other embodiment.

Hereinafter, embodiments will be illustrated with reference to the drawings. In addition, in each drawing, the same reference numerals are given to the same constituent elements, and detailed description thereof will be omitted as appropriate.
The substrate 100 exemplified below can be, for example, a semiconductor wafer, an imprint template, a photolithography mask, a plate-like body used for MEMS (Micro Electro Mechanical Systems), or the like.
In some cases, the substrate 100 has an uneven portion, which is a pattern, formed on its surface. Substrate) can be suitably used for cleaning. However, the application of the substrate processing apparatus 1 is not limited to cleaning bulk substrates.

Moreover, in the following, as an example, a case where the substrate 100 is a photolithography mask will be described. When the substrate 100 is a mask for photolithography, the planar shape of the substrate 100 can be substantially rectangular.

FIG. 1 is a schematic diagram for illustrating a substrate processing apparatus 1 according to this 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, a control A portion 9 and an exhaust portion 11 are provided.

The mounting section 2 has a mounting table 2a, a rotating shaft 2b, and a driving section 2c.
The mounting table 2 a is rotatably provided inside the housing 6 . The mounting table 2a has a plate shape. A plurality of support portions 2a1 for supporting the substrate 100 are provided on one main surface of the mounting table 2a. When the substrate 100 is supported by the plurality of supporting portions 2a1, the front surface 100b (the surface to be cleaned) of the substrate 100 faces away from the mounting table 2a.

Edges of the rear surface 100a of the substrate 100 are in contact with the plurality of supporting portions 2a1. A portion of the supporting portion 2a1 that contacts the edge of the back surface 100a of the substrate 100 can be a tapered surface or an inclined surface. If the portion of support portion 2a1 that contacts the edge of back surface 100a of substrate 100 is tapered, support portion 2a1 and the edge of back surface 100a of substrate 100 can be brought into point contact. If the portion of support portion 2a1 that contacts the edge of back surface 100a of substrate 100 is an inclined surface, support portion 2a1 and the edge of back surface 100a of substrate 100 can be in line contact. By making point contact or line contact between support portion 2a1 and the edge of back surface 100a of substrate 100, substrate 100 can be prevented from being soiled or damaged.

Further, a hole 2aa is provided in the central portion of the mounting table 2a so as to extend through the mounting table 2a in the thickness direction.

One end of the rotary shaft 2b is fitted into the hole 2aa of the mounting table 2a. The other end of the rotating shaft 2b is provided outside the housing 6. As shown in FIG. The rotating shaft 2b is connected to the driving portion 2c outside the housing 6. As shown in FIG.

The rotating shaft 2b has a cylindrical shape. A blowout portion 2b1 is provided at the end portion of the rotating shaft 2b on the mounting table 2a side. Blow-out portion 2b1 opens to a surface of mounting table 2a on which a plurality of support portions 2a1 are provided. The opening-side end of blowout portion 2b1 is connected to the inner wall of hole 2aa. The opening of the blowout part 2b1 faces the rear surface 100a of the substrate 100 mounted on the mounting table 2a.

The blowout portion 2b1 has a shape in which the cross-sectional area increases toward the mounting table 2a side (opening side). Therefore, the hole inside the blowout part 2b1 has a larger cross-sectional area toward the mounting table 2a side (opening side). In addition, although the case where the blowing part 2b1 is provided at the tip of the rotating shaft 2b is illustrated, the blowing part 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 blowout portion 2b1.

By providing the blowout portion 2b1, the discharged cooling gas 3a1 can be supplied to a wider area of the back surface 100a of the substrate 100. FIG. Also, the discharge speed of the cooling gas 3a1 can be reduced. Therefore, it is possible to prevent the substrate 100 from being partially cooled or the cooling rate of the substrate 100 from becoming too fast. As a result, it becomes easy to cause a supercooled state of the liquid 101, which will be described later. Also, a supercooled state of the liquid 101 can be generated in a wider area of the surface 100b of the substrate 100. FIG. Therefore, the removal rate of contaminants can be improved.

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 on the side opposite to the mounting table 2a side is sealed so as to be airtight.

The drive unit 2c is provided outside the housing 6. As shown in FIG. The driving portion 2c is connected to the rotating shaft 2b. The drive unit 2c can have a rotating device such as a motor. The rotational force of the driving portion 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 the substrate 100 mounted on the mounting table 2a.

Further, the drive unit 2c can change not only the start and stop of rotation, but also the number of rotations (rotational speed). The drive unit 2c can be provided with a control motor such as a servomotor, for example.

Cooling unit 3 supplies cooling gas 3a1 to the space between mounting table 2a and back surface 100a of substrate 100 . The cooling unit 3 has a coolant unit 3a, a filter 3b, a flow control unit 3c, and a cooling nozzle 3d. Coolant section 3 a , filter 3 b , and flow control section 3 c are provided outside housing 6 .

The coolant unit 3a stores the coolant and generates the coolant gas 3a1. The cooling liquid is obtained by liquefying the cooling gas 3a1. The cooling gas 3 a 1 is not particularly limited as long as it is a gas that does not readily 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.

In this case, the cooling time of the substrate 100 can be shortened by using a gas with a high specific heat. 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.

The cooling liquid unit 3a has a tank that stores the cooling liquid and a vaporization unit that vaporizes the cooling liquid contained in the tank. The tank is provided with a cooling device for maintaining the temperature of the coolant. The evaporator raises the temperature of the cooling liquid to generate cooling gas 3a1 from the cooling liquid. For example, the vaporization section can use the temperature of the outside air or heat with a heat medium. The temperature of the cooling gas 3a1 may be any temperature below the freezing point of the liquid 101, and may be -170° C., for example.
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 be obtained by cooling nitrogen gas or the like with a chiller or the like. . In this way, the coolant section can be simplified.

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 coolant from flowing out to the substrate 100 side.

The flow controller 3c is connected to the filter 3b via piping. The flow controller 3c controls the flow rate of the cooling gas 3a1. The flow controller 3c can be, for example, an MFC (Mass Flow Controller). Further, the flow 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 control unit 3c can be, for example, an APC (Auto Pressure Controller).

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

The cooling nozzle 3d has a cylindrical shape. One end of the cooling nozzle 3d is connected to the flow controller 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 positioned near the end opposite to the mounting table 2a side (opening side) of the blowout portion 2b1.

The cooling nozzle 3d supplies the substrate 100 with the cooling gas 3a1 whose flow rate is controlled by the flow control unit 3c. Cooling gas 3a1 discharged from cooling nozzle 3d is directly supplied to rear surface 100a of substrate 100 via blowing portion 2b1.

The first liquid supply section 4 supplies the liquid 101 to the surface 100 b of the substrate 100 . In the freezing step (solid-liquid phase), which will be described later, when the liquid 101 changes to a solid, the volume changes and pressure waves are generated. 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 hardly reacts with the material of the substrate 100 . The liquid 101 in the supercooled state also has the property that a change in density due to non-uniform temperature of the liquid film, the presence of contaminants such as particles, vibration, and the like are the starting point of freezing. In other words, some percentage of starting points of freezing also have the property of becoming contaminants.

If the liquid 101 is a liquid whose volume increases when frozen, it is conceivable that contaminants adhering to the surface of the substrate 100 can be separated using the physical force that accompanies the increase in volume. Therefore, 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. For example, the liquid 101 can be water (eg, pure water, ultrapure water, etc.), or a liquid containing water as its main component.

The liquid containing water as a main component can be, for example, a mixture of water and alcohol, a mixture of water and an acid solution, a mixture of water and an alkali solution, or the like.
Since the surface tension can be lowered by using a mixture of water and alcohol, it becomes easy to supply the liquid 101 inside the fine irregularities formed on the surface 100 b of the substrate 100 .

A mixed solution of water and an acid 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 such as resist and metal.
A mixed solution of water and an alkaline solution can lower the zeta potential, so that contaminants separated from the surface 100b of the substrate 100 can be prevented from reattaching to the surface 100b of the substrate 100.

However, if there are too many components other than water, it becomes difficult to utilize the physical force that accompanies the increase in volume, so there is a risk that the contaminant removal rate will decrease. Therefore, the concentration of components other than water is preferably 5 wt % or more and 30 wt % or less.

Further, gas can be dissolved in the liquid 101 . The gas can be, for example, carbon dioxide gas, ozone gas, hydrogen gas, or the like. Dissolving carbon dioxide gas in the liquid 101 can increase the electrical conductivity of the liquid 101, so that the substrate 100 can be neutralized and prevented from being charged. By dissolving ozone gas in the liquid 101, contaminants made of organic matter can be dissolved.

The first liquid supply section 4 has a liquid storage section 4a, a supply section 4b, a flow control section 4c, and a liquid nozzle 4d. The liquid storage section 4a, the supply section 4b, and the flow control section 4c are provided outside the housing 6. As shown in FIG.

The liquid storage portion 4a stores the liquid 101 described above. The liquid 101 is stored in the liquid storage portion 4a at a temperature higher than its freezing point. The liquid 101 is stored at room temperature (20° C.), for example.
The supply portion 4b is connected to the liquid storage portion 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 can be, for example, a pump that is resistant to the liquid 101, or the like. In addition, although the case where the supply part 4b was a pump was illustrated, the supply part 4b is not necessarily limited to a pump. For example, the supply unit 4b may supply gas to the inside of the liquid storage unit 4a to pump the liquid 101 stored in the liquid storage unit 4a.

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

The liquid nozzle 4 d is provided inside the housing 6 . The liquid nozzle 4d has a cylindrical shape. One end of the liquid nozzle 4d is connected to the flow controller 4c via a pipe. The other end of the liquid nozzle 4d faces the surface 100b of the substrate 100 mounted on the mounting table 2a. Therefore, the liquid 101 ejected from the liquid nozzle 4 d is supplied to the surface 100 b of the substrate 100 .

Also, the other end of the liquid nozzle 4 d (ejection port for the liquid 101 ) is positioned substantially at the center of the surface 100 b of the substrate 100 . The liquid 101 ejected from the liquid nozzle 4 d spreads from substantially the center of the surface 100 b of the substrate 100 to form a liquid film having a substantially constant thickness on the surface 100 b of the substrate 100 . Note that the film of the liquid 101 formed on the surface 100b of the substrate 100 is hereinafter referred to as a liquid film.

The second liquid supply section 5 supplies the liquid 102 to the surface 100b of the substrate 100 . The second liquid supply section 5 has a liquid storage section 5a, a supply section 5b, a flow control section 5c, and a liquid nozzle 4d.

Liquid 102 can be used in the thawing process described below. Therefore, the liquid 102 is not particularly limited as long as it hardly reacts with the material of the substrate 100 and does not easily remain on the surface 100b of the substrate 100 in the drying process described below. The liquid 102 can be, for example, water (eg, pure water, ultrapure water, etc.), a mixture of water and alcohol, or the like.

The liquid storage portion 5a can be the same as the liquid storage portion 4a described above. The supply unit 5b can be similar to the supply unit 4b described above. The flow control unit 5c can be the same as the flow control unit 4c described above.

Note that if the liquid 102 and the liquid 101 are the same, the second liquid supply section 5 can be omitted. Moreover, although the case where the liquid nozzle 4d is also used has been exemplified, the liquid nozzle for ejecting the liquid 101 and the liquid nozzle for ejecting the liquid 102 can be provided separately.

Also, the temperature of the liquid 102 can be higher than the freezing point of the liquid 101 . Also, the temperature of the liquid 102 can be set to a temperature at which the frozen liquid 101 can be thawed. The temperature of the liquid 102 can be, for example, normal temperature (20° C.).

If the second liquid supply section 5 is omitted, the first liquid supply section 4 is used in the thawing step. That is, the liquid 101 is used. The temperature of the liquid 101 can also be a temperature at which the frozen liquid 101 can be thawed. The temperature of the liquid 101 can be, for example, normal temperature (20° C.).

The housing 6 has a box shape. A cover 6 a is provided inside the housing 6 . The cover 6a receives the liquids 101 and 102 supplied to the substrate 100 and discharged to the outside of the substrate 100 as the substrate 100 rotates. The cover 6a has a tubular shape. The vicinity of the end of the cover 6a opposite to the mounting table 2a side (the vicinity of the upper end of the cover 6a) is bent toward the center of the cover 6a. Therefore, the liquids 101 and 102 splashing above the substrate 100 can be easily captured.

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

A plurality of outlets 6c are provided on the side surface of the housing 6 on the bottom side. In the case of the housing 6 illustrated in FIG. 1, two discharge 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 from the discharge port 6c. An exhaust pipe 6c1 is connected to the exhaust port 6c, and an exhaust section (pump) 11 for exhausting the used cooling gas 3a1 and air 7a is connected to the exhaust pipe 6c1. A discharge pipe 6c2 for discharging the liquids 101 and 102 is connected to the discharge port 6c.

The outlet 6 c is provided below the substrate 100 . Therefore, the cooling gas 3a1 is discharged from the discharge port 6c to create a downflow flow. As a result, it is possible to prevent the particles from soaring.

In a plan view, the plurality of discharge ports 6c are provided symmetrically with respect to the center of the housing 6. As shown in FIG. By doing so, the exhaust direction of the cooling gas 3a1 becomes symmetrical with respect to the center of the housing 6. FIG. If the cooling gas 3a1 is discharged symmetrically, the cooling gas 3a1 can be discharged smoothly.

The air blower 7 is provided on the ceiling surface of the housing 6 . Note that the air blower 7 can also be provided on the side surface of the housing 6 as long as it is on the ceiling side. The blower section 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).

The air blower 7 supplies air 7 a (outside air) to the space between the partition plate 6 b 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 easy to guide the air 7a supplied by the air blower 7 to the discharge port 6c. In addition, it is possible to prevent contaminants such as particles from entering the housing 6 through the outlet 6c.

Further, the air blower 7 supplies room temperature air 7a to the front surface 100b of the substrate 100 . Therefore, the air blower 7 can change the temperature of the liquids 101 and 102 on the substrate 100 by controlling the supply amount of the air 7a. Therefore, the air blower 7 can control the supercooled state of the liquid 101 in the supercooling process described later, accelerate the thawing of the liquid 101 in the thawing process, and accelerate the drying of the liquid 102 in the drying process. can.

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

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 process described later. 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. to ensure that it is maintained.

Further, the detected temperature, thickness, and surface state of the frozen film can be used to detect "occurrence of cracks" in the freezing step (solid phase), which will be described later. For example, when the detection unit 8 detects temperature, it is possible to indirectly detect "occurrence of cracks" from the temperature of the frozen film in the freezing step (solid phase), which will be described later. When the detector 8 detects the thickness, it is possible to detect "occurrence of cracks" from changes in the surface position of the frozen film in the freezing step (solid phase) described later. When the detection unit 8 detects the surface state, it is possible to detect "occurrence of cracks" from the surface state of the frozen film in the freezing step (solid phase) described later.

The control unit 9 controls the operation of each element provided in the substrate processing apparatus 1 . The control unit 9 can have, for example, an arithmetic element such as a CPU (Central Processing Unit) and a storage element such as a semiconductor memory. The control unit 9 can be, for example, a computer. The memory element can store a control program for controlling the operation of each element provided in the substrate processing apparatus 1 . The arithmetic element controls the operation of each element provided in the substrate processing apparatus 1 using the control program stored in the memory element, data input by the operator, data from the detection unit 8, and the like.

For example, the cooling rate of the liquid 101 has a correlation with the thickness of the liquid film. For example, the thinner the liquid film is, the faster the liquid 101 is cooled. Conversely, as the thickness of the liquid film increases, the cooling rate of the liquid 101 decreases. Therefore, the controller 9 can control the flow rate of the cooling gas 3 a 1 and thus the cooling rate of the liquid 101 based on the thickness of the liquid 101 (thickness of the liquid film) detected by the detector 8 . The temperature and cooling rate of the liquid 101 are controlled when controlling the supercooled state of the liquid 101 in the supercooling process described later. Therefore, for example, the control unit 9 can control the rotation of the substrate 100, the flow rate of the cooling gas 3a1, and the supply amount of the liquid 101. FIG.

For example, the control unit 9 causes the liquid 101 on the surface 100b of the substrate 100 to enter a supercooled state, freezes the supercooled liquid 101 to generate a frozen film, and controls the temperature of the frozen film. to crack the frozen film.

Next, the operation of the substrate processing apparatus 1 will be illustrated.
FIG. 2 is a timing chart for illustrating the action of the substrate processing apparatus 1. FIG.
FIG. 3 is a graph for illustrating temperature changes of the liquid 101 supplied to the substrate 100 in the freeze cleaning process.

2 and 3, the substrate 100 is a 6025 quartz (Qz) substrate (152 mm×152 mm×6.35 mm) and the liquid 101 is pure water.

First, the substrate 100 is loaded into the housing 6 through a loading/unloading port (not shown) of the housing 6 . The loaded substrate 100 is placed and supported on the plurality of supporting portions 2a1 of the placing table 2a.

After the substrate 100 is supported on the mounting table 2a, as shown in FIG. 2, a freezing cleaning process including a preliminary process, a liquid film forming process, a cooling process, a thawing process, and a drying process is performed.

First, preliminary steps are performed as shown in FIGS. In the preliminary process, the control unit 9 controls the supply unit 4b and the flow control unit 4c to supply the surface 100b of the substrate 100 with the liquid 101 at a predetermined flow rate. Further, the control unit 9 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. FIG. Further, the control unit 9 controls the driving unit 2c to rotate the substrate 100 at the third rotation speed.

Here, if the atmosphere in the housing 6 is cooled by the supply of the cooling gas 3a1 by the cooling unit 3, frost containing dust in the atmosphere may adhere to the substrate 100 and cause contamination. Since the liquid 101 is continuously supplied to the surface 100b of the substrate 100 in the preparatory step, the substrate 100 can be uniformly cooled and frost can be prevented from adhering to the surface 100b of the substrate 100. FIG.

For example, in the case illustrated in FIG. 2, the rotation speed of the substrate 100 can be, for example, about 50 rpm to 500 rpm as the third rotation speed. Also, the flow rate of the liquid 101 can be about 0.1 L/min to 1.0 L/min. Also, the flow rate of the cooling gas 3a1 can be about 40 NL/min to 200 NL/min. Moreover, the process time of the preliminary process can be set to about 1800 seconds. It should be noted that the process time of the preparatory process may be any time during which the in-plane temperature of the substrate 100 becomes substantially uniform, and can be obtained by performing experiments or simulations in advance.

The temperature of the liquid film in the preliminary step is almost 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 normal temperature (20° C.), the temperature of the liquid film is about normal temperature (20° C.).

Next, as shown in FIGS. 2 and 3, a liquid film forming step is performed. When the liquid film forming step is performed, the number of rotations (second number of rotations) is set such that the liquid film has a thickness (predetermined thickness) at which a high removal rate can be obtained. The second rotation speed is, for example, 50 rpm to 100 rpm. In other words, the controller 9 rotates the substrate 100 at the same number of rotations as in the preliminary process or at a number of rotations smaller than that in the preliminary process. Then, as illustrated in FIG. 2, the supply of the liquid 101 that has been supplied in the preliminary step is stopped, and the substrate 100 is rotated at the second rotation speed until the substrate 100 reaches a predetermined thickness. It may be confirmed by measuring the thickness of the liquid film with the detection unit 8 whether or not the predetermined thickness has been reached. The thickness of the liquid film may be measured by the detection unit 8 to calculate in advance the time required for the liquid film to reach a predetermined thickness, and the second rotation speed may be maintained during the time required for the predetermined thickness. Thereafter, the number of rotations of the substrate 100 is set to a number of rotations (first number of rotations) at which the liquid film of the liquid 101 supplied from the supply unit 4b onto the substrate 100 is maintained to have a uniform thickness. The first rotational speed may be any rotational speed that can suppress variations in the thickness of the liquid film due to centrifugal force, and may be, for example, 0 rpm to 50 rpm or less. During the liquid film forming process, the flow rate of the cooling gas 3a1 is maintained at the same supply rate as in the preliminary process. As described above, the in-plane temperature of the substrate 100 is made substantially uniform in the preliminary process. In the liquid film forming process, the flow rate of the cooling gas 3a1 is maintained at the same supply amount as in the preliminary process, so that the substrate 100 can be maintained in a state in which the in-plane temperature is substantially uniform.
Moreover, when it is desired to increase the predetermined thickness, the number of rotations can be changed from the third number of rotations to the first number of rotations instead of the second number of rotations. Moreover, in this case, it is preferable that the first rotation speed be a rotation speed close to 0 rpm. In particular, if the rotation of the substrate 100 is stopped, it is possible to further suppress variations in the thickness of the liquid film due to centrifugal force.
In addition, it is good also as a 1st rotation speed from a preliminary process. Also, the third rotation speed may be a rotation speed slower than the first rotation speed.

Further, when shifting from the preliminary process to the liquid film forming process, the liquid 101 supplied during the preliminary process may be discharged by rotating the substrate 100 at high speed. In this case, after the liquid 101 is discharged, the rotation speed of the substrate 100 is set to a rotation speed (50 rpm) or less at which a liquid film having a uniform thickness is maintained, or after the rotation of the substrate 100 is stopped, a predetermined amount of liquid is applied. 101 may be supplied to the substrate 100 . By doing so, a liquid film having a predetermined thickness can be easily formed.

As will be described later, the thickness of the liquid film formed in the liquid film forming process (thickness of the liquid film during the cooling process) can be about 300 μm to 1300 μm. For example, the controller 9 controls the supply amount of the liquid 101 and the number of revolutions of the substrate 100 to set the thickness of the liquid film on the surface 100b of the substrate 100 to approximately 300 μm to 1300 μm.
The details of the thickness of the liquid film will be described later.

A cooling step is then performed as shown in FIGS. In the present embodiment, in the cooling process, the period before the supercooled liquid 101 starts to freeze is referred to as the "supercooling process", and the supercooled liquid 101 starts to freeze and freezes. The period before complete completion is called the "freezing process (solid-liquid phase)", and the period until 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. FIG. In the freezing step (solid-liquid phase), the liquid 101 and the frozen liquid 101 exist on the surface 100b of the substrate 100 . In the freezing step (solid phase), only the frozen liquid 101 exists on the surface 100 b of the substrate 100 . Note that the solid-liquid phase means a state in which the liquid 101 and the frozen liquid 101 exist entirely. A state in which only the liquid 101 is frozen is called a frozen film 101a.

First, in the supercooling step, the cooling gas 3a1 continuously supplied to the back surface 100a of the substrate 100 causes the temperature of the liquid film on the substrate 100 to drop further below the temperature of the liquid film in the liquid film forming step. state.

Here, if the cooling rate of the liquid 101 is too high, the liquid 101 will not be in a supercooled state and will freeze immediately. Therefore, the control unit 9 controls at least one of the number of rotations of the substrate 100, the flow rate of the cooling gas 3a1, and the amount of supply of the liquid 101, so that the liquid 101 on the surface 100b of the substrate 100 becomes supercooled. make it

The control conditions for the supercooled state of the liquid 101 are affected by the size of the substrate 100, the viscosity of the liquid 101, the specific heat of the cooling gas 3a1, and the like. Therefore, it is preferable to appropriately determine the control conditions under which the liquid 101 is in the supercooled state through experiments and simulations.

In the supercooled state, freezing of the liquid 101 starts due to, for example, the temperature of the liquid film, the presence of contaminants such as particles and air bubbles, vibration, and the like. For example, when contaminants such as particles are present, the liquid 101 starts to freeze when the temperature T of the liquid 101 becomes -35°C or higher and -20°C or lower. Further, by vibrating the liquid 101 by, for example, changing the rotation of the substrate 100, freezing of the liquid 101 can be started.

When the supercooled liquid 101 starts to freeze, the supercooling process shifts to the freezing process (solid-liquid phase). In the freezing step (solid-liquid phase), the liquid 101 and the frozen liquid 101 exist entirely on the surface 100b of the substrate 100 . As described above, the liquid 101 in the supercooled state has the property that some percentage of the starting points of freezing become contaminants. Contaminants adhering to the surface 100b of the substrate 100 are considered to be separated due to this property, the pressure wave accompanying the volume change when the liquid 101 changes to solid, the physical force accompanying the volume increase, and the like. there is Therefore, the contaminants adhering to the surface 100b of the substrate 100 can be separated by a pressure wave, physical force, or the like generated when part of the liquid 101 freezes.

When the liquid film on the surface 100b of the substrate 100 is completely frozen, the freezing step (solid-liquid phase) transitions 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 is further lowered. Here, the liquid 101 mainly contains water. Therefore, the liquid film on the surface 100b of the substrate 100 is completely frozen to form a frozen film 101a, and when the temperature of the frozen film 101a further decreases, the volume of the frozen film 101a is reduced and stress is generated in the frozen film 101a. .

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 the frozen film 101a cracks, the contaminants 103 adhering to the surface 100b of the substrate 100 are separated from the surface 100b of the substrate 100. FIG. Although the mechanism by which the contaminant 103 is separated from the surface 100b of the substrate 100 is not necessarily clear, it can be considered as follows.

FIGS. 4A and 4B are schematic diagrams for illustrating the separation mechanism of contaminants 103. FIG.
As shown in FIG. 4A, when the temperature of the frozen film 101a decreases in the freezing step (solid phase), a stress F corresponding to the difference between the thermal expansion coefficient of the frozen film 101a and the thermal expansion coefficient of the substrate 100 is applied. occurs.

Then, as shown in FIG. 4(b), when the temperature of the frozen film 101a further drops (for example, below −50° C.), the frozen film 101a cannot withstand the increased stress F, and cracks occur in the frozen film 101a. . In this case, since the coefficient of thermal expansion of the frozen film 101a mainly composed of water is generally larger than the coefficient of thermal expansion of the substrate 100, the frozen film 101a faces outward as shown in FIG. It deforms into a convex shape and cracks occur.

Since the contaminants 103 are taken into the frozen film 101a, when the frozen film 101a is deformed convexly (when cracks occur), as shown in FIG. 103 is separated from surface 100b of substrate 100 .

Further, according to the knowledge obtained by the present inventors, it has been found that increasing the thickness of the liquid film during the supercooling process improves the removal rate of the contaminants 103 in the freezing process (solid phase). This is probably because increasing the thickness of the liquid film increased the stress F, and the bending of the frozen film 101a when deformed convexly toward the outside increased. In this case, if the removal rate of the contaminants 103 is improved in the freezing step (solid phase), the number of executions can be reduced when the freezing cleaning step is repeated multiple times. Therefore, it is possible to shorten the time required for the freeze cleaning operation, and thereby improve productivity.

FIG. 5 is a graph for illustrating the relationship between the thickness of the liquid film and the number of repetitions of the freeze cleaning process. The number of times in the figure is the number of repetitions of the freeze cleaning process. Also, the target removal rate of contaminants on the substrate 100 was set to 90%. The target removal rate (predetermined removal rate) may be set such that the yield in cleaning the substrate 100 is an allowable value. Also, the first rotational speed was set to 0 rpm in order to eliminate the influence of centrifugal force. Therefore, the thickness with which the liquid film can be uniformly formed on the surface 100b of the substrate 100 was 300 μm.

As can be seen from FIG. 5, 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 when performing the supercooling process. . Further, 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 thickness of the liquid film to 600 μm or more. Further, 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 thickness of the liquid film to 1000 μm or more.

By the way, since the thickness of the liquid film is affected by the surface tension of the liquid 101 and the like, it can be increased up to about 1300 μm. However, if the thickness is increased to about 1300 μm, part of the liquid film may spill from the substrate 100 even at a rotational speed of 50 rpm or less. Therefore, the maximum thickness of the liquid film can be about 1200 μm. Therefore, the thickness of the liquid film when performing the supercooling step is preferably 300 μm or more and 1200 μm or less when the number of repetitions is 20 or more, and is 600 μm or more and 1200 μm or less when the number of repetitions is 10 or more. more preferably.

If the thickness of the liquid film is set to 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 freezing cleaning step 20 times. When forming a liquid film having a thickness within the above range, if the number of revolutions is set to 50 rpm or less, the liquid 101 is not shaken off by centrifugal force, and the liquid film can be easily formed. Also, if the thickness of the liquid film is set to 600 μm or more and 1200 μm or less, the number of times of execution can be reduced to 10 times or more and less than 20 times. Therefore, it is possible to shorten the time required for the freeze cleaning operation, and thereby improve productivity. To further reduce the number of executions to 5 or more and less than 10, it is preferable to set the thickness to 1000 μm or more and 1200 μm or less.
Note that the number of execution times of the freeze cleaning process is input by the operator via an input/output screen (not shown). Alternatively, the substrate processing apparatus 1 may read a mark such as a bar code or QR code (registered trademark) attached to a case for housing the substrate.

The results shown in FIG. 5 are data obtained when thawing was performed at about -50° C., at which cracks occur. According to the knowledge obtained by the present inventors, it was found that when cooling is continued even when cracks occur in the frozen film 101a, the removal rate exceeds 90% when the freeze cleaning step is performed once. That is, if the processing time of the freezing step (solid phase) is set long, a high removal rate can be obtained even in one freezing step. Furthermore, it was also found that when the processing time of the freezing step (solid phase) is set long, a high removal rate can be obtained regardless of the thickness of the liquid film.
It is not clear about the mechanism why the removal rate is improved regardless of the thickness of the liquid film by setting the processing time of the freezing step (solid phase) long. However, by performing the freezing step (solid phase) for a predetermined time or longer, a high removal rate can be obtained even in a single freezing step.

Next, after cracking occurs in the frozen film 101a, a thawing process is performed as shown in FIGS. The generation of cracks can be detected by the detector 8 . For example, when the detection unit 8 detects the temperature, in the freezing step (solid phase), the temperature of the frozen film 101a (for example, −50° C. or less) indirectly detects the “occurrence of cracks”. be able to. When the detection unit 8 detects the thickness, it is possible to detect "occurrence of cracks" from changes in the surface position of the frozen film 101a in the freezing step (solid phase). When the detection unit 8 is an image sensor, it is possible to detect "occurrence of cracks" by image processing in the freezing step (solid phase).

2 and 3 illustrate the case where the liquid 101 and the liquid 102 are the same liquid. Therefore, the liquid 101 is indicated in FIGS. 2 and 3 . In the thawing process, the control unit 9 controls the supply unit 4b and the flow control unit 4c to supply the surface 100b of the substrate 100 with the liquid 101 at a predetermined flow rate. When the liquid 101 and the liquid 102 are different, the control unit 9 controls the supply unit 5b and the flow rate control unit 5c to supply the liquid 102 at a predetermined flow rate to the surface 100b of the substrate 100. FIG.

Further, the control unit 9 controls the flow rate control unit 3c to stop the supply of the cooling gas 3a1. Further, the control unit 9 controls the drive unit 2c to increase the rotation speed of the substrate 100 to the fourth rotation speed. The fourth rotation speed can be, for example, approximately 200 rpm to 700 rpm.
If the substrate 100 rotates faster, the liquid 101 and the frozen liquid 101 can be shaken off by centrifugal force. Therefore, the liquid 101 and the frozen liquid 101 can be discharged from the surface 100 b 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 liquid 101 and the frozen liquid 101. FIG.

The amount of liquid 101 or liquid 102 supplied is not particularly limited as long as it can be thawed. Further, the fourth rotation speed of the substrate 100 is not particularly limited as long as the liquid 101, the frozen liquid 101, and the contaminants 103 can be discharged.

Next, a drying process is performed as shown in FIGS. In the drying process, the control unit 9 controls the supply unit 4b and the flow control unit 4c to stop the supply of the liquid 101. FIG. When the liquid 101 and the liquid 102 are different liquids, the control unit 9 controls the supply unit 5b and the flow rate control unit 5c to stop the supply of the liquid 102. FIG.

Further, the control unit 9 controls the driving unit 2c to increase the rotation speed of the substrate 100 to a fifth rotation speed higher than the fourth rotation speed. The faster the substrate 100 rotates, the faster the substrate 100 can be dried. Note that the fifth number of rotations of the substrate 100 is not particularly limited as long as the substrate can be dried.
The substrate 100 that has undergone freeze cleaning is carried out of the housing 6 through a loading/unloading port (not shown) of the housing 6 .
By doing so, one freeze cleaning step can be performed.

In addition, as described above, the freeze cleaning process is performed multiple times. Therefore, if the next freeze cleaning process is carried out, the supply of the cooling gas 3a1 is maintained even in the thawing process. By doing so, the same state as in the preliminary process can be generated. Therefore, the preparatory step and the drying step in the subsequent freeze washing step can be omitted.

Therefore, when the freeze cleaning process is repeated a plurality of times, the freeze cleaning process includes a supercooling process in which the liquid 101 on the surface 101b of the substrate 100 is in a supercooled state, and a process in which the liquid 101 and the liquid 101 are frozen. and a freezing step (solid-liquid phase) in which the liquid 101 is completely frozen to form the frozen film 101a, and the temperature of the frozen film 101a is lowered to generate cracks in the frozen film 101a (solid-liquid phase). ) and a thawing step.

In the substrate processing apparatus 1 according to the present embodiment, in the freezing step (solid-liquid phase), in addition to the properties of the liquid in a supercooled state in which freezing starts from contaminants, the liquid 101 changes to a solid state. The contaminants 103 adhering to the surface of the substrate 100 are separated by pressure waves accompanying volume changes, physical forces accompanying volume increases, and the like.
Furthermore, in the freezing step (solid phase), cracks are generated in the frozen film 101a, so that the frozen film 101a in which the contaminants 103 are taken in deforms convexly toward the outside. Separate the adhering contaminants 103 .
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). Therefore, the removal rate of the contaminants 103 can be improved.

Further, in the substrate processing apparatus 1 according to the present embodiment, in the cooling step, the rotation speed is set to the first rotation speed that can suppress variations in the thickness of the liquid film due to centrifugal force. In the cooling process, when the second number of rotations is maintained to provide a predetermined thickness, the centrifugal force due to the second number of rotations is applied to the liquid 101 on the surface 100 b of the substrate 100 . Centrifugal force increases with distance from the center of rotation. Therefore, the liquid 101 collects on the outer edge of the substrate 100 . At this time, forces such as the viscosity and surface tension of the liquid 101 act on the liquid 101 on the outer edge of the substrate 100, so the thickness of the liquid film on the outer edge of the substrate 100 increases. That is, the thickness of the liquid film in the central portion of the substrate 100 becomes relatively thin.

As described above, increasing the thickness of the liquid film during the supercooling step improves the removal rate of the contaminants 103 in the freezing step (solid phase). In other words, in the cooling process, if the second number of rotations is maintained at which the predetermined thickness is achieved, the removal rate of the central portion of the substrate 100 may decrease.

In addition, in the present embodiment, the cooling gas 3a1 is supplied from the blowing part 2b1 in the central portion of the mounting table 2a. Therefore, the temperature of the outer edge of the substrate 100 is higher than the temperature of the central portion of the substrate 100 . As described above, in the cooling step, when the second rotational speed is maintained, the thickness of the liquid film on the outer edge of the substrate 100 increases. Therefore, the liquid film on the outer edge of the substrate 100, which is thicker than the liquid film on the central portion of the substrate 100, must be cooled in a state inferior to the central portion of the substrate 100 in terms of cooling efficiency. Therefore, the liquid film on the outer edge of the substrate 100 has a lower cooling rate than the central portion of the substrate 100 . In other words, the occurrence of cracks at the outer edge of the substrate 100 is delayed.

The freezing step (solid phase) ends when cracks are confirmed to occur on all surfaces of the substrate 100 . Therefore, if the freezing step (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 step (solid phase) becomes long.

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 will be long, and there is a possibility that the expected removal rate cannot be obtained. Therefore, in the cooling step, it is preferable to set the number of revolutions to the first speed that can suppress variations in the thickness of the liquid film due to the centrifugal force.

Further, when the rotation of the substrate 100 is stopped (at 0 rpm), the thickness of the liquid film in the central portion of the substrate 100 becomes thicker than the thickness of the liquid film in the outer edge of the substrate 100 . The liquid film thickness gradient is opposite to the substrate 100 temperature gradient described above. That is, the cooling rate is constant between the central portion and the outer edge portion of the substrate 100 . If the cooling rate is constant between the central portion and the outer edge portion of the substrate 100, cracks will occur at the central portion and the outer edge portion of the substrate 100 at the same time. can do. Therefore, it is preferable to stop the rotation of the substrate 100 (0 rpm).

Further, when the number of repetitions of the freeze cleaning process is set to 20 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 while improving the productivity. can be effectively improved to 90% or more. In addition, when the number of repetitions of the freeze washing process is 5 or more, if the thickness of the liquid film is 1000 μm or more and 1200 μm or less, the removal rate of the contaminants 103 can be increased to 90% or more while improving productivity. can be substantially improved.

FIG. 6 is a schematic diagram illustrating a substrate processing apparatus 1a according to another embodiment.
As shown in FIG. 6, the substrate processing apparatus 1a 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, a temperature A detection unit 8a, a gas supply unit 10, an exhaust unit 11, and a control unit 9 are provided.

The temperature detector 8a detects the temperature of the space between the substrate 100 and the mounting table 2a. This temperature is substantially equal to the temperature of the mixed gas (mixed gas of the cooling gas 3a1 and the gas 10d) flowing between the substrate 100 and the mounting table 2a. The temperature detection unit 8a can be, for example, a radiation thermometer, a thermoviewer, a thermocouple, a resistance temperature detector, or the like.

The gas supply unit 10 has a gas storage unit 10a, a flow control unit 10b, and a connection unit 10c.
The gas storage unit 10a stores and supplies the gas 10d. The gas storage unit 10a can be a high-pressure cylinder containing the gas 10d, a factory pipe, or the like.
The flow controller 10b controls the flow rate of the gas 10d. The flow control unit 10b can be, for example, an MFC that directly controls the flow rate of the gas 10d, or an APC that indirectly controls the flow rate of the gas 10d by controlling the pressure.

The connecting portion 10c is connected to the rotating shaft 2b. The connecting portion 10c connects the space between the rotating shaft 2b and the cooling nozzle 3d and the flow control portion 10b. The connecting portion 10c can be, for example, a rotary joint.

The gas 10 d is not particularly limited as long as it is a gas that hardly reacts with the material of the substrate 100 . The gas 10d can be, for example, an inert gas such as nitrogen gas, helium gas, argon gas. In this case, the gas 10d can be the same gas as the cooling gas 3a1. However, the temperature of the gas 10d is higher than the temperature of the cooling gas 3a1. The temperature of the gas 10d can be room temperature, for example.

If the cooling rate of the liquid 101 is too fast, the liquid 101 will not be in a supercooled state and will freeze immediately. That is, it becomes impossible to perform a supercooling process. In this case, the cooling speed of the liquid 101 can be controlled by at least one of the rotation speed of the substrate 100 and the flow rate of the cooling gas 3a1. However, the temperature of the cooling gas 3a1 becomes substantially constant due to the temperature setting in the cooling section that supplies the cooling gas 3a1. Therefore, it may be difficult to reduce the cooling rate of the liquid 101 with the flow rate of the cooling gas 3a1.

Also, if the number of revolutions of the substrate 100 is reduced, the thickness of the liquid film is increased, so that the cooling rate can be reduced. However, since the thickness of the liquid film has a thickness limit that can be maintained by surface tension, it may be difficult to reduce the cooling rate of the liquid 101 at the rotation speed of the substrate 100 .

Therefore, in the present embodiment, the cooling rate of the liquid 101 can be reduced by mixing the cooling gas 3a1 with the gas 10d having a temperature higher than that of the cooling gas 3a1. The cooling rate of the liquid 101 can be controlled by the flow rate of the gas 10d and the cooling gas 3a1, the mixing ratio of the gas 10d and the cooling gas 3a1, the temperature of the gas 10d, and the like.

By mixing the cooling gas 3a1 with the gas 10d having a temperature higher than that of the cooling gas 3a1, the temperature of the gas supplied to the space between the substrate 100 and the mounting table 2a can be adjusted more precisely. Therefore, the cooling temperature of the substrate 100 can be adjusted with higher accuracy. Also, the supercooled state of the liquid 101 can be controlled more easily.

The liquid 101 in a supercooled state has the property of starting to freeze from contaminants, and the volume expansion coefficient due to the phase change becomes a larger value than the liquid 101 frozen without supercooling. The aforementioned properties are correlated with the rate at which liquid becomes solid, and the lower the freezing start temperature, the higher the rate at which freezing starts from contaminants. Further, the volume expansion coefficient due to phase change becomes the highest when the freezing start temperature is in the range of -20°C to -35°C. For these reasons, the freezing start temperature is preferably as low as possible, for example, -20°C or lower.

As described above, by mixing the cooling gas 3a1 with the gas 10d having a temperature higher than that of the cooling gas 3a1, the probability that the liquid 101 in the supercooled state can be cooled to −20° C. or lower can be increased. As a result, a high removal rate can be obtained in the freezing step (solid-liquid phase). In addition, the removal rate up to the freezing step (solid-liquid phase) in each freeze washing step is stabilized. As a result, the removal rate of each substrate 100 is stabilized and the yield is improved. Therefore, the removal rate of contaminants is improved.

In addition, if the gas supply unit 10 is provided, the cooling rate in the freezing step (solid-liquid phase) of the cooling step is adjusted so that the temperature T at the start of freezing is −40° C. or more and −20° C. or less. be able to adjust.

Even if the detection unit 8 detects the temperature of the liquid film and controls the flow rate of the cooling gas 3a1, the temperature of the front surface 100b side of the substrate 100 (the temperature of the liquid film) and the temperature of the back surface 100a side of the substrate 100 and there may be a difference. Therefore, if the flow rate of the cooling gas 3a1 is controlled based only on the temperature of the liquid film detected by the detection unit 8, even if the temperature of the liquid film reaches the appropriate temperature, the temperature of the liquid film and the back surface 100a of the substrate 100 will be , the temperature gradient in the thickness direction of the substrate 100 may increase. When the temperature gradient in the thickness direction of the substrate 100 increases, the density change due to temperature non-uniformity may become the starting point of freezing.

In addition, when the temperature gradient becomes large, variations in density tend to occur, and the change in density due to this variation in density is considered to be the starting point of freezing. Therefore, there is a possibility that the timing of freezing may vary even within the plane of the substrate 100 .

According to the present embodiment, the control unit 9 controls at least one of the flow rate of the gas 10d and the cooling gas 3a1 and the mixing ratio of the gas 10d and the cooling gas 3a1 based on the temperature detected by the temperature detection unit 8a. can do.

Therefore, the controller 9 performs such control in the preliminary process, and after the difference between the temperature detected by the detector 8 and the temperature detected by the temperature detector 8a falls within a predetermined range, the preliminary It is possible to switch from the process to the supercooling process (supply stop of the liquid 101). In this way, freezing can be started in a state in which the temperature gradient in the thickness direction of the substrate 100 is small, so variation in timing of freezing can be suppressed.

The flow rate of the gas 10d supplied from the gas supply unit 10 is controlled without controlling the flow rate of the cooling gas 3a1 by the flow control unit 3c (the flow rate of the cooling gas 3a1 is kept constant). It is also possible to control the cooling state. In such a case, the flow control section 3c can be omitted. However, if the flow rate control unit 3c and the gas supply unit 10 are provided, the supercooled state of the liquid 101 can be controlled more easily.
Further, by controlling the amount of air 7a supplied by the air blower 7, the supercooled state of the liquid 101 can be controlled.

Further, the supply of the gas 10d from the gas supply unit 10 may be stopped in the freezing step (solid phase) based on the temperature detected by the detection unit 8. FIG. For example, when the liquid 101 is completely frozen, the temperature of the frozen liquid 101 begins to decrease again because the latent heat does not raise the temperature. By detecting this temperature drop with the temperature detection unit 8, it is determined that the liquid 101 has completely frozen, and the supply of the gas 10d from the gas supply unit 10 may be stopped.
By doing so, the time for the freezing step (solid phase), that is, the time until cracks form, can be shortened.

The embodiments have been illustrated above. However, the invention is not limited to these descriptions. Regarding the above-described embodiments, those in which those skilled in the art appropriately add, delete, or change the design of components, or add, omit, or change the conditions of steps, as long as they have the features of the present invention. are included within the scope of the present invention.

For example, the shape, size, number, arrangement, etc. of each element provided in the substrate processing apparatus 1 are not limited to those illustrated and can be changed as appropriate.

Further, cooling may be continued under predetermined conditions for a predetermined time from the start time of the freezing step (solid-liquid phase) and the freezing step (solid phase). For example, the starting point is the point where the temperature is observed, and the point where the temperature is observed to rise from the supercooled state, or the point where it can be determined that the temperature has decreased from the parallel state to complete solidification.
In this way, if the detection unit 8 can detect the start time of the freezing process (solid-liquid phase) and the freezing process (solid phase), the presence or absence of crack generation can be determined from the results obtained by analyzing or calculating the data of the detection unit 8. The substrate processing apparatus 1 may not have the function of determining the That is, the control section 9 can be simplified.

Alternatively, cracks may be detected based on reflectance. When cracks occur, the frozen film is separated from the substrate, and the reflectance changes. Based on this change in reflectance, it is determined that the ice has sufficiently separated, and thawing begins.
By detecting cracks based on reflectance in this way, cracks that cannot be detected from temperature changes can be reliably detected. As a result, particles can be removed more reliably.

In addition, based on the knowledge that cracks occur when the temperature is -50°C or lower, -50°C is set as a threshold, and when the temperature of the frozen film falls below the threshold, it is assumed that cracks have occurred, and thawing is started. may
By doing so, it is possible to eliminate the need for a mechanism for capturing a reflectance, a refractive index, and an image, thereby simplifying the configuration. Note that decompression may be started after about 0.2 to 2.0 seconds have elapsed since the threshold value was reached.

Alternatively, the processed surface of the substrate 100 may be imaged, and cracks may be observed from the imaged image. For example, a captured image is processed to detect a predetermined crack state (number, area). Since the crack looks like a white streak, the image is binarized in black and white to detect the crack. Then, when the number of cracks or the area of cracks reaches or exceeds a threshold value, it can be determined that the ice has sufficiently separated, and thawing can be started.
By doing so, the generation of cracks is directly detected, so that particles can be removed more reliably.

Reference Signs List 1 substrate processing apparatus 1a substrate processing apparatus 2 mounting section 3 cooling section 3a1 cooling gas 4 first liquid supply section 5 second liquid supply section 6 housing 8 detection section 9 control section 10 gas supply unit, 10d gas, 100 substrate, 100a back surface, 100b front surface, 101 liquid, 101a frozen film, 102 liquid, 103 contaminants

Claims (7)

a mounting table capable of rotating the 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 a liquid to a surface of the substrate opposite to the mounting table;
a control unit that controls the rotation of the substrate, the flow rate of the cooling gas, and the supply amount of the liquid;
with
The control unit
The liquid on the surface of the substrate is supercooled, the liquid in the supercooled state is frozen to form a frozen film, and the temperature of the frozen film is lowered to reduce the temperature of the frozen film. Repeating a freeze cleaning step including at least a cooling step for cracking the frozen film and a thawing step for thawing the cracked frozen film a plurality of times,
If the number of repetitions of the freezing cleaning step is 20 or more, the substrate processing apparatus controls the amount of supply of the liquid so that the thickness of the liquid film of the liquid on the surface of the substrate is 300 μm or more and 1200 μm or less. . If the number of repetitions of the freeze cleaning process is 5 times or more and less than 10 times, the control unit controls the amount of supply of the liquid to reduce the thickness of the liquid film of the liquid on the surface of the substrate to 1000 μm . The substrate processing apparatus according to claim 1 , wherein the thickness is 1200 µm or less. The control unit
The liquid supply unit is controlled to supply the liquid to the surface of the substrate opposite to the mounting table side at a temperature higher than a freezing point, and the cooling unit is controlled to supply the cooling gas to the mounting table of the substrate. After supplying to the side surface, this state is maintained until a predetermined time elapses,
after the predetermined time has elapsed, controlling the mounting table to change the number of rotations to a second number at which the thickness of the liquid film becomes a predetermined thickness;
After changing to the second rotation speed, while controlling the cooling unit to maintain the supply of the cooling gas, the liquid supply unit is controlled to stop the supply of the liquid;
after stopping the supply of the liquid, rotating the substrate at the second rotation speed until the thickness of the liquid film reaches a predetermined thickness;
After the thickness of the liquid film reaches a predetermined thickness, the mounting table is controlled to stop the rotation of the substrate, or the rotation speed is set to the first rotation speed which is slower than the second rotation speed. 3. The substrate processing apparatus according to 1 or 2. 4. The substrate processing apparatus according to any one of claims 1 to 3, further comprising a detection unit for detecting said crack. The detection unit is
sensing the temperature of the liquid overlying the surface of the substrate;
The control unit
5. The substrate processing apparatus according to claim 4, wherein the time at which the liquid film becomes the frozen film is detected from the temperature detected by the detection unit, and the frozen film is thawed after a predetermined time has elapsed. The detection unit is
detecting the temperature of the liquid film overlying the surface of the substrate;
The control unit
storing in advance a temperature at which cracks occur in the frozen film;
5. The substrate processing apparatus according to claim 4, wherein the frozen film is thawed when the temperature detected by the detector reaches a temperature at which the crack occurs. The detection unit is
imaging the surface of the substrate;
The control unit
The number of cracks or the crack area is stored in advance as a threshold,
5. The substrate processing apparatus according to claim 4, wherein the cracks are detected from the image captured by the detection unit, and the frozen film is thawed when the number of cracks or the area of the cracks exceeds the threshold value.

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