Substrate processing method and substrate processing apparatus

Abstract

To prevent or at least suppress the collapse of a pattern formed on the surface of a substrate when supercritical drying processing is performed.SOLUTION: A substrate processing method includes: a degassing step of removing a dissolved gas in a processing liquid; a liquid film formation step of forming a liquid film of the processing liquid covering a surface of a substrate, by supplying, onto the surface of the substrate, the processing liquid from which the dissolved gas is removed; a carrying-in step of carrying the substrate having the liquid film formed thereon into a processing vessel; and a supercritical drying step of drying the surface of the substrate by flowing a processing fluid into the processing vessel while maintaining a pressure in the processing vessel, into which the substrate having the liquid film formed thereon is carried, at a pressure allowing the processing fluid to be maintained in a supercritical state, to replace the processing liquid covering the surface of the substrate with the processing fluid, and, then, by vaporizing the processing fluid.SELECTED DRAWING: Figure 4

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a substrate processing method and a substrate processing apparatus.

BACKGROUND ART

[0002] In a manufacturing process of a semiconductor device in which a laminated structure of integrated circuits is formed on the surface of a semiconductor wafer (hereinafter referred to as a wafer) that is a substrate, a processing step of treating the wafer surface using a liquid is performed, such as removing fine dust and natural oxide film on the wafer surface with a cleaning liquid such as a chemical solution.

[0003] A method using a supercritical state processing fluid when removing the liquid remaining on the wafer surface in such a processing step is known. For example, Patent Document 1 discloses a substrate processing apparatus that uses a supercritical fluid to dissolve an organic solvent from above the substrate and dry the wafer.

[0004] In the substrate processing apparatus of Patent Document 1, the surface of the wafer is cleaned with a cleaning liquid such as a chemical solution inside the processing apparatus. An organic solvent as a processing liquid is pooled on the surface of the cleaned wafer. The wafer on which the organic solvent is pooled is transported from the cleaning apparatus to a supercritical processing apparatus, where a drying process of the wafer is performed using the supercritical state processing fluid. By pooling the organic solvent on the surface of the wafer in this manner, the surface of the cleaned wafer is prevented from drying before being subjected to the drying process in the supercritical processing apparatus, and the generation of particles is prevented.

PRIOR ART DOCUMENTS

PATENT DOCUMENTS

[0005]

PATENT DOCUMENT 1

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0006] This disclosure provides a technology that can prevent or at least suppress the collapse of patterns formed on the surface of a substrate during supercritical drying. [Means for solving the problem]

[0007] A substrate processing method according to one embodiment of the present disclosure comprises: a degassing step of removing dissolved gas from a processing liquid; a liquid film forming step of supplying the processing liquid from which the dissolved gas has been removed to the surface of a substrate to form a liquid film of the processing liquid covering the surface of the substrate; a loading step of loading the substrate on which the liquid film has been formed into a processing container; and a supercritical drying step of circulating the processing fluid in the processing container while maintaining the pressure inside the processing container into a pressure at which the processing fluid maintains a supercritical state, thereby replacing the processing liquid covering the surface of the substrate with the processing fluid, and then drying the surface of the substrate by vaporizing the processing fluid. [Effects of the Invention]

[0008] According to the embodiments described above, it is possible to prevent or at least suppress the collapse of patterns formed on the surface of a substrate during supercritical drying. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic cross-sectional view of a substrate processing system according to one embodiment of a substrate processing apparatus. [Figure 2] This is a schematic cross-sectional view showing an example configuration of a single-wafer liquid processing unit included in the substrate processing system shown in Figure 1. [Figure 3] This is a schematic cross-sectional view showing one example of the configuration of a supercritical drying unit included in the substrate processing system shown in Figure 1. [Figure 4] This is a piping diagram illustrating the IPA supply mechanism and the degassing configuration provided therein for supplying IPA used in the single-wafer liquid treatment unit shown in Figure 2. [Figure 5] This is a schematic diagram illustrating the collapse of a pattern due to the formation of air bubbles. [Modes for carrying out the invention]

[0010] A substrate processing system 1 according to one embodiment of the substrate processing apparatus of the present disclosure will be described below with reference to the attached drawings. To simplify the explanation of directions, an XYZ Cartesian coordinate system is set up and displayed in the lower left of Figure 1. The Z direction is the up and down direction, and the positive Z direction is the up direction.

[0011] As shown in Figure 1, the substrate processing system 1 includes a control device 100. The control device 100 is a computer and includes an arithmetic processing unit 101 and a storage unit 102. The storage unit 102 stores programs (including processing recipes) that control various processes executed in the substrate processing system 1. The arithmetic processing unit 101 controls the operation of each component of the substrate processing system 1, which will be described later, by reading and executing the programs stored in the storage unit 102, thereby executing a series of processes described later. The control device 100 may also include a user interface such as a keyboard, touch panel, or display. The above programs may have been recorded on a storage medium readable by the computer and installed from that storage medium to the storage unit 102 of the control device 100. Examples of storage mediums readable by the computer include hard disks (HDs), flexible disks (FDs), compact disks (CDs), magnetic optical disks (MOs), and memory cards.

[0012] The substrate processing system 1 comprises an input / output section (input / output station) 2 and a processing section (processing station) 6.

[0013] The loading / unloading section 2 comprises a container placement section 21 and a first transport section 22. Multiple substrate transport containers C (e.g., FOUPs) can be placed on the container placement section 21. Multiple substrates W (e.g., semiconductor wafers) are housed in each substrate transport container C in a horizontal position with vertical spacing between them.

[0014] The first transport unit 22 is provided adjacent to the container placement unit 21. Inside the first transport unit 22 are a first substrate transport robot (first substrate transport mechanism) 23 and a transfer unit (transfer unit) 24. The first substrate transport robot 23 is equipped with a substrate holding mechanism as an end effector for holding the substrate W. The first substrate transport robot 23 is capable of moving horizontally and vertically, as well as rotating about a vertical axis. The first substrate transport robot 23 transports the substrate W between the substrate transport container C on the container placement unit 21 and the transfer unit 24.

[0015] The processing unit 6 is located adjacent to the first transport unit 22. The processing unit 6 includes one or more single-wafer liquid processing units 61, one or more supercritical drying units 62 for supercritical drying of the substrates W processed by the single-wafer liquid processing units 61, and a second substrate transport robot (second substrate transport mechanism) 63. In one embodiment, multiple single-wafer liquid processing units 61 and multiple supercritical drying units 62 may be stacked vertically at the positions shown in Figure 1.

[0016] The second substrate transfer robot 63 is equipped with an end effector that is movable by a multi-axis drive mechanism 631 that is movable in the X and Y directions, can be raised and lowered in the Z direction, and can rotate around a vertical axis. The end effector is, for example, a fork-shaped substrate holder 632 that can hold a single substrate in a horizontal position. The second substrate transfer robot 63 (particularly its end effector) can transfer substrates between the transfer unit 24, the single-wafer liquid processing unit 61, and the supercritical drying unit 62 by moving within the transfer space 64. While being transported by the second substrate transfer robot 63, the substrate W is always maintained in a horizontal position.

[0017] A nitrogen gas supply unit 65 for discharging nitrogen gas into the transfer space 64 is provided. The nitrogen gas supply unit 65 is supplied with nitrogen gas from, for example, a nitrogen gas supply source provided as factory utility gas. In order to facilitate nitrogen gas purging in the transfer space 64, an exhaust unit 66 for discharging the atmosphere in the transfer space 64 may be provided. From the viewpoint of improving purge efficiency, it is preferable that the nitrogen gas supply unit 65 and the exhaust unit 66 are provided at positions separated from each other. The nitrogen gas supply unit 65 schematically shown in Figure 1 is provided on the ceiling wall of the rectangular parallelepiped-shaped transfer space 64 Rete Alternatively, in this case, the nitrogen gas supply unit 65 forms a downflow of nitrogen gas in the transfer space 64. Alternatively, the nitrogen gas supply unit 65 may be provided on the side wall of the transfer space 64, and in this case, the nitrogen gas supply unit 65 is arranged in the transfer space 64 to form a side flow of nitrogen gas.

[0018] A partition wall 67 is provided between the transfer space 64 of the processing unit 6 and the delivery unit 24, and a door (not shown) with appropriate airtightness is provided on this partition wall 67. This unillustrated door is opened only when the substrate W passes therethrough. With this configuration, it is possible to prevent wasteful consumption of nitrogen gas due to leakage of nitrogen gas from the transfer space 64 to the first transfer unit 22, and it is also possible to prevent leakage of nitrogen gas from the transfer space 64 to the surrounding environment of the substrate processing system 1.

[0019] Any single-wafer liquid treatment unit 61 known in the field of semiconductor manufacturing equipment can be used. An example of the configuration of a single-wafer liquid treatment unit 61 that can be used in this embodiment will be briefly described below with reference to Figure 2. The single-wafer liquid treatment unit 61 includes a spin chuck 611 that can hold the substrate W in a horizontal position and rotate it around a vertical axis, and one or more nozzles 612 that discharge treatment liquid onto the substrate W held and rotating by the spin chuck 611. The nozzles 612 are supported on an arm 613 for moving the nozzles 612. The single-wafer liquid treatment unit 61 has a liquid receiving cup 614 for collecting treatment liquid scattered from the rotating substrate W. The liquid receiving cup 614 has a drain port 615 for discharging the collected treatment liquid outside the liquid treatment unit 61 and an exhaust port 616 for discharging the atmosphere inside the liquid receiving cup 614. Clean gas is blown downward from a fan filter unit 618 located on the ceiling of the chamber 617 of the single-wafer liquid treatment unit 61, drawn into the liquid receiving cup 614, and discharged to the exhaust port 616.

[0020] As the fan filter unit 618, one can be used that has the function of selectively discharging clean air and an inert gas, in this case nitrogen gas (N2 gas). In this case, the clean air is the air in the cleanroom where the substrate processing system 1 is installed, filtered by a filter (e.g., ULPA filter) in the fan filter unit 618, and the nitrogen gas is supplied from a nitrogen gas supply source provided as factory power for a semiconductor manufacturing plant. Fan filter units 618 with such functions are well known in the field of semiconductor manufacturing equipment, and a detailed explanation of their structure is omitted.

[0021] As the supercritical drying unit 62, any known unit in the technical field of semiconductor manufacturing apparatuses can be used. A configuration example and operation of the supercritical drying unit 62 that can be used in the present embodiment will be briefly described below with reference to Figure 1 and Figure 3. The supercritical drying unit 62 includes a supercritical chamber 621, and a substrate support tray 622 that can move forward and backward relative to the supercritical chamber 621. Figure 1 depicts the substrate support tray 622 retracted from the supercritical chamber 621, and in this state, the second substrate transfer robot 63 can deliver and receive the substrate W to and from the substrate support tray 622.

[0022] Figure 3 shows a state in which the substrate support tray 622 is accommodated in the supercritical chamber 621. The substrate support tray 622 has a lid 625, and the lid 625 closes the opening of the supercritical chamber 621 via a seal member (not shown), so that a sealed processing space is formed inside the supercritical chamber 621. Reference numeral 623 denotes a supply port 623 for a processing fluid (for example, CO2 (carbon dioxide)), and reference numeral 624 denotes an exhaust port for a fluid (CO2, IPA, etc.).

[0023] In order to set a region 628 (the region where the substrate support tray 622 is located in Figure 1) in the supercritical drying unit 62, where the substrate W is delivered to and received from the substrate support tray 622, to a nitrogen gas atmosphere, nitrogen gas is supplied to the supercritical drying unit 62 supply department 626 can be provided. In order to accelerate the nitrogen gas purge of the region 628, an exhaust unit 627 for exhausting the atmosphere in the region 628 may be provided. From the viewpoint of improving purge efficiency, the nitrogen gas supply unit 626 and the exhaust unit 627 are preferably provided at positions separated from each other.

[0024] Next, with reference to Figure 4, an IPA (isopropyl alcohol) supply mechanism 700 for supplying IPA used in the single-wafer type liquid processing unit 61 and a degassing configuration provided therein will be described.

[0025] The IPA supply mechanism 700 includes a tank 702 for storing IPA and a circulation line 704 connected to the tank 702. The circulation line 704 is equipped with, in order from upstream, a pump 706, a temperature controller 708, a filter 710, a flow meter 712, and a constant pressure valve 714. The pump 706 pressurizes and delivers the IPA, thereby creating a circulating flow of IPA in the circulation line 704. The temperature controller 708 adjusts the temperature of the IPA to a temperature suitable for use in the single-wafer liquid treatment unit 61 to which the IPA is supplied. The filter 710 removes contaminants such as particles from the IPA. The constant pressure valve 714 allows the IPA to flow into the single-wafer liquid treatment unit 61 to which the IPA is supplied at an appropriate pressure.

[0026] Multiple branching points 715 are set in the circulation line 704, and at each branching point 715, a branch supply line 716 branches off from the circulation line 704. The downstream end of each branch supply line 716 is connected to a nozzle 612 for IPA supply of the corresponding single-wafer liquid treatment unit 61. The branch supply line 716 is equipped with, in order from upstream, a dissolved gas monitor 718, a constant pressure valve 720, an on-off valve 722, and a dissolved gas filter (e.g., a hollow fiber membrane filter) 724. At branching point 728 set in the branch supply line 716, a branch return line 730 branches off from the branch supply line 716. An on-off valve 732 is equipped in the branch return line 730. Multiple branch return lines 730 merge to form a single return line 734, and the downstream end of the return line 734 is connected to a tank 702.

[0027] The deaeration line 742 branches off from the branching point 740 set in the circulation line 704. The deaeration line 742 is sequentially equipped with an inline megasonic 744, an inline dissolved gas monitor (dissolved gas sensor) 746, a constant pressure valve 748, and a hollow fiber membrane filter 750, starting from the upstream side. The downstream end of the deaeration line 742 is connected to the tank 702.

[0028] The inline megasonic 744 generates cavitation bubbles by applying high-power ultrasound to the IPA flowing through the degassing line 742. The inline dissolved gas monitor (dissolved gas sensor) 746 measures the concentration of gases contained in the IPA flowing through the degassing line 742, particularly gases harmful to the treatment described later, such as oxygen and carbon dioxide. The constant pressure valve 748 adjusts the flow rate of the IPA flowing through the degassing line 742.

[0029] When the outside of the hollow fiber membrane of the hollow fiber membrane filter 750 is reduced in pressure and IPA is flowed through the hollow fiber membrane, the bubbles contained in the IPA (these are cavitation bubbles generated by the inline megasonic 744) and dissolved gases contained in the IPA pass through the walls of the hollow fiber membrane and exit to the outside of the hollow fiber membrane. This reduces the amount of bubbles and dissolved gases in the IPA. Degassing is also possible with the hollow fiber membrane filter 750 alone. However, in this degassing line 742, the gas in the IPA is converted into bubbles by the inline megasonic 744 upstream of the hollow fiber membrane filter 750, making it possible to further improve the efficiency of dissolved gas removal compared to degassing with the hollow fiber membrane filter 750 alone. The IPA from which the dissolved gases have been removed is returned to the tank 702.

[0030] In the embodiment shown in Figure 4, the inline degassing mechanism is composed of two inline devices: an inline megasonic 744 and a hollow fiber membrane filter 750. As mentioned above, degassing can also be performed using only the hollow fiber membrane filter 750, so it is also possible to configure the inline degassing mechanism using only the hollow fiber membrane filter 750. An inline degassing mechanism is a mechanism that is installed in a line (a liquid flow path such as a pipe) and can degas a liquid while the liquid is flowing through the mechanism (without stopping the liquid flow).

[0031] IPA is supplied to tank 702 from IPA supply source 760 via IPA supply line 762. An on-off valve 764 is installed in the IPA supply line 762. In most cases, the IPA supply source 760 is provided as factory power for the semiconductor manufacturing plant where the substrate processing system 1 is installed. A drain line 766 is connected to tank 702, and an on-off valve 768 is installed in the drain line 766.

[0032] In the first configuration example of the IPA supply mechanism 700, a supply source 780 of inert gas, in this case nitrogen gas, is connected to the tank 702 via a gas supply line 782. An on / off valve 784 is connected to the gas supply line 782. In many cases, the nitrogen gas supply source 780 is also supplied as factory power. A heater 790 is also provided in the tank 702. Furthermore, a cooler 726 is interposed downstream of the filter 724 of the branch supply line 716. The components described in this paragraph are depicted with dashed or dotted lines.

[0033] In the second configuration example of the IPA supply mechanism 700, a vacuum pump (pressure reducing device) 770 is connected to the tank 702 via a pressure reducing line 772. An on-off valve 774 and a vacuum filter 776 are interposed in the pressure reducing line 772. A drain line 778 is connected to the pressure reducing line 772.

[0034] The only difference between the first and second configuration examples is the part described above; all other components are common to both.

[0035] Next, the operation of the IPA supply mechanism 700 in the first configuration example described above will be explained. Nitrogen gas is supplied from the nitrogen gas supply source 780 to the tank 702, creating a nitrogen gas atmosphere inside the tank 702. This suppresses the dissolution of oxygen and carbon dioxide gas into the IPA. In addition, when a predetermined amount of IPA is supplied from the IPA supply source 760 to the tank 702 and the tank 702 is filled with IPA, the pump 706 is activated, and the heater 790 attached to the tank 702 is also activated. This brings the IPA in the tank 702 to its boiling point less thanThe IPA is heated to an appropriate temperature (for example, about 70°C), and the heated IPA circulates through the circulation line 704. The temperature controller 708 also heats the IPA flowing through the circulation line 704, maintaining the IPA at an appropriate temperature. Heating the IPA reduces the solubility of the gas in the IPA, making it more difficult for the gas to dissolve in the IPA in the tank, and some of the gas that was already dissolved in the IPA detaches from it.

[0036] A portion of the IPA flowing through the circulation line 704 flows into the degassing line 742, where it is degassed by the inline megasonic 744 and the hollow fiber membrane filter 750 according to the mechanism described above, and returned to the tank 702. At this time, the IPA is also heated, which increases the degassing efficiency.

[0037] The IPA flowing through the circulation line 704 flows into at least some of the multiple branch supply lines 716 (for example, those corresponding to the single-wafer liquid processing unit 61 whose processing start time is approaching), and instead of going to the nozzle 612, it flows into the corresponding branch return line 730, and is then returned to the tank 702 via the return line 734.

[0038] If the above conditions persist for a while and at least the following conditions are met, the control device 100 determines that it is OK to supply IPA to the substrate W in the single-wafer liquid treatment unit 61 (IPA supply ready state). - The dissolved gas monitor 746 on the degassing line 742 indicates that the gas concentration in the IPA (e.g., oxygen gas concentration and / or carbon dioxide gas concentration) is below a predetermined threshold. - The dissolved gas monitor 718 corresponding to the single-wafer liquid processing unit 61, whose processing start time is approaching, has determined that the gas concentration in the IPA (e.g., oxygen gas concentration and / or carbon dioxide gas concentration) has fallen below a predetermined threshold. Other conditions include ensuring that the temperature of the IPA circulating in the circulation line 704 is within a predetermined temperature range. A temperature sensor can be installed in the tank 702 or in a suitable line connected to the tank to check the temperature of the IPA.

[0039] Preferably, after it is confirmed that the IPA supply is ready, the processing of one substrate W is started in the single-wafer liquid processing unit 61. When supplying IPA to the substrate W, the cooler 726 is activated, the on-off valve 732 is closed and the on-off valve 722 is opened. As a result, the IPA, whose temperature has been lowered to a predetermined temperature (for example, room temperature to about 30°C) by the cooler 726, is supplied to the substrate W from the IPA discharge nozzle 612.

[0040] Next, the operation of the IPA supply mechanism 700 in the second configuration example described above will be explained. Similar to the first configuration example, IPA is supplied from the IPA supply source 760 to the tank 702, and when a predetermined amount of IPA has accumulated in the tank 702, the inside of the tank 702 is depressurized by the vacuum pump 770 so that the condition that "the internal pressure (absolute pressure, not gauge pressure) of the tank 702 is greater than the vapor pressure of the IPA" is met. Furthermore, the pump 706 is activated. Since the inside of the tank 702 is depressurized, some of the gas dissolved in the IPA is released from the IPA. Similar to the first configuration example, the IPA circulates through the circulation line 704, and some of the IPA flowing through the circulation line 704 flows into the degassing line 742, where it is degassed by the in-line megasonic 744 and hollow fiber membrane filter 750 installed in the degassing line 742.

[0041] Furthermore, similar to the first configuration example, the IPA flowing through the circulation line 704 flows into at least some of the multiple branch supply lines 716 (for example, those corresponding to the single-wafer liquid processing unit 61 whose processing start time is approaching), and instead of going to the nozzle 612, it flows into the corresponding branch return line 730, and is then returned to the tank 702 via the return line 734. At this time, the dissolved gas concentration is monitored by the dissolved gas monitor 746 of the degassing line 742 and the dissolved gas monitor 718 of the branch supply line 716 in the same manner as in the first configuration example, and once it is confirmed that the IPA is ready to be supplied, the single-wafer liquid processing unit 61 is permitted to start processing one substrate W. In the second configuration example, unlike the first configuration example, the IPA in the tank 702 is not heated and the IPA in the branch supply line 716 is not cooled.

[0042] Next, the processing flow of substrate W in the substrate processing system 1 will be explained. The first substrate transport robot of the loading / unloading section 2. 23 Next, the substrate W is removed from the substrate transport container C placed on the container placement section 21, and the removed substrate W is placed on the transfer unit 24. Then, the substrate W is removed from the transfer unit 24 by the second substrate transport robot 63 of the processing unit 6 and transported to the single-wafer liquid processing unit 61.

[0043] The substrate W, which has been loaded into the single-wafer liquid processing unit 61, is held in a horizontal position by a spin chuck 611. Next, the substrate W is rotated around its vertical axis by the spin chuck 611. In this state, various processing liquids necessary for processing are sequentially supplied to the substrate W from one or more nozzles 612 assigned to each processing liquid, thereby performing liquid processing on the substrate W. An example of liquid processing is described below. First, a pre-wetting process is performed by supplying a pre-wetting liquid to the substrate W. Next, a chemical processing process (wet etching or chemical cleaning) is performed by supplying a chemical solution to the substrate W. Next, a rinsing process is performed by supplying a rinsing liquid (e.g., DIW (pure water)) to the substrate W. The chemical processing process and the rinsing process may be performed multiple times each.

[0044] In one embodiment, for example, the following steps are performed on a single substrate W. Process 1: Pre-wetting process using DIW (DIW). Step 2: DHF etching process Step 3: DIW Rinse Process Step 4: SC1 cleaning process Step 5: DIW Rinse Process In steps 1 to 5 described above, DHF (dilute hydrofluoric acid) and SC1 are supplied from different nozzles 612. DIW may be supplied from a nozzle 612 specifically for DIW supply, or, for example, from a nozzle 612 used for DHF supply.

[0045] In step 2 described above, SiO2 (silicon oxide) is removed by DHF etching, and vertically extending columnar bodies made of Si (silicon) are formed at roughly equal pitches. Similar columnar bodies are shown in Figure 5. In one exemplary embodiment, the substrate W is dried by the supercritical drying treatment described later while preventing the collapse of the Si columnar bodies.

[0046] After the final rinsing step (for example, step 5 above), IPA is supplied to the substrate W from the IPA discharge nozzle 612 while the substrate W continues to rotate, and the rinsing liquid on the surface of the substrate W (including the surface of the recesses in the pattern) is replaced with IPA (IPA replacement step). Then, while the supply of IPA from the nozzle continues, the rotation speed of the substrate is reduced to an extremely low speed to adjust the thickness of the IPA, and then the supply of IPA is stopped and the rotation of the substrate W is stopped. As a result, the surface of the substrate W is covered with an IPA liquid film (IPA paddle) of the desired thickness (IPA paddle formation step). In this single-wafer liquid processing unit 61, the IPA supplied to the substrate W in the IPA replacement step and the IPA paddle formation step is the IPA that has undergone the degassing treatment described above.

[0047] To prevent oxygen and carbon dioxide from dissolving back into the degassed IPA, it is preferable to create an inert gas atmosphere, such as a nitrogen gas atmosphere, in the chamber of the single-wafer liquid treatment unit 61. For this purpose, nitrogen gas is supplied from a fan filter unit 618 equipped with a nitrogen gas discharge function. Since nitrogen gas has a lower solubility in IPA compared to oxygen gas and carbon dioxide gas, creating a nitrogen gas atmosphere around the substrate W to which the IPA is attached can suppress the dissolution of gas into the IPA.

[0048] The atmosphere inside the chamber of the single-wafer liquid treatment unit 61 is preferably a nitrogen gas atmosphere, at least for the duration that a substrate W with IPA on its surface is inside the chamber. Therefore, for example, it is preferable that the atmosphere inside the chamber is a nitrogen gas atmosphere at the latest when the discharge of IPA is started. When no substrate W is present inside the chamber, and when no IPA is adhering to the surface of a substrate inside the chamber, the atmosphere inside the chamber may be a clean air atmosphere with the composition of normal air.

[0049] Once processing in the single-wafer liquid treatment unit 61 is complete, the end effector (substrate holder) of the second substrate transfer robot 63 enters the single-wafer liquid treatment unit 61, removes the substrate W with IPA paddles formed on its surface from the spin chuck 611, and transfers it to the supercritical drying unit 62. The transfer space 64 through which the substrate W passes during transfer from the single-wafer liquid treatment unit 61 to the supercritical drying unit 62 is adjusted to an inert gas (in this case, nitrogen gas) atmosphere. Therefore, even when the substrate W passes through the transfer space 64, it is possible to prevent oxygen and carbon dioxide from the air from dissolving again into the IPA on the substrate W.

[0050] The second substrate transfer robot 63 places the substrate W, which has been brought into the supercritical drying unit 62, onto the substrate support tray 622 of the supercritical drying unit 62. Next, the substrate support tray 622 is housed inside the supercritical chamber 621, and a lid 625, which is integrated with the substrate support tray 622, seals the supercritical chamber 621. The inside of the housing of the supercritical drying unit 62 (inside region 628) is also in an inert gas (in this case, nitrogen gas) atmosphere. Therefore, it is possible to prevent oxygen and carbon dioxide from the air from dissolving again into the IPA on the substrate W between the time the substrate W is brought into the supercritical drying unit 62 and when it is housed inside the supercritical chamber 621 while placed on the substrate support tray 622.

[0051] Once the substrate W is placed inside the supercritical chamber 621, a supercritical drying process is performed. First, a processing fluid (e.g., CO2) is supplied into the supercritical chamber 621 from a supercritical fluid supply source (not shown) via a supply port 623, thereby filling the supercritical chamber 621 with CO2 while increasing the pressure inside the chamber (pressurization process). In addition, before the supercritical chamber 621 is pressurized, CO2 may also be supplied through another supply port (not shown) that opens toward the lower surface of the substrate support tray 622.

[0052] Once the pressure inside the supercritical chamber 621 reaches the supercritical state guarantee pressure (the pressure at which CO2 alone and the CO2-IPA mixture are guaranteed to maintain a supercritical state), a flow process is performed. In the flow process, CO2 supplied from the supply port 623 flows over the IPA paddle along the surface of the substrate W and is discharged from the exhaust port 624 (see arrow in the figure). By continuing this process, the IPA on the surface of the substrate W is replaced by CO2. Once the IPA has been replaced by supercritical CO2, the exhaust port 624 side is connected to an atmospheric pressure space, returning the supercritical chamber 621 to atmospheric pressure. This vaporizes the supercritical CO2 on the surface of the substrate W, drying the surface of the substrate W (discharge process). In this way, the substrate W can be dried while preventing the collapse of the pattern formed on the surface of the substrate W.

[0053] As soon as the substrate support tray 622, on which the substrate W is placed, enters the supercritical chamber 621 (which is maintained at a relatively high temperature (e.g., about 80°C)), the temperature of the IPA on the substrate W rises. Consequently, dissolved gases in the IPA vaporize, and bubbles are formed in the IPA. When a fine and high aspect ratio pattern is formed on the surface of the substrate W, especially when thin, tall, vertically extending columnar sections are spaced apart and grooves are formed between the columnar sections, if large bubbles (see, for example, symbol B in Figure 5) form in the IPA within the grooves, the force generated by the expansion of the bubbles can damage the columnar sections, potentially causing the pattern to collapse. In this embodiment, since degassed IPA is used, bubbles are less likely to form, and therefore pattern collapse due to the above mechanism is less likely to occur.

[0054] Furthermore, since the space where the substrate W with the IPA paddles may be located is under a nitrogen gas atmosphere, it is possible to suppress the increase in the amount of dissolved IPA gas during transport. As a result, pattern collapse due to the above mechanism becomes less likely to occur.

[0055] Here, the "nitrogen gas atmosphere" mentioned above does not necessarily have to be an atmosphere with a nitrogen gas concentration of 100%; it may be an appropriate value in which the nitrogen gas concentration in the atmosphere is higher than the nitrogen gas concentration in the air.

[0056] After the supercritical drying process is complete, the dried substrate W is removed from the supercritical drying unit 62 by the second substrate transfer robot 63 and transported to the transfer unit 24. Next, the first substrate transfer robot 23 removes the substrate W from the transfer unit 24 and places it back into the original substrate transfer container C located on the container placement section 21.

[0057] According to the above embodiment, by using degassed IPA as the processing liquid that replaces the supercritical processing fluid during supercritical drying, pattern collapse can be prevented or significantly suppressed. Furthermore, by making the atmosphere of the space in which the substrate with IPA paddles is transported a nitrogen gas atmosphere, pattern collapse can be prevented more reliably or significantly suppressed.

[0058] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The above embodiments may be omitted, replaced, or modified in various ways without departing from the scope and spirit of the appended claims.

[0059] The substrate is not limited to semiconductor wafers, but may be other types of substrates used in the manufacture of semiconductor devices, such as glass substrates or ceramic substrates. Furthermore, in the above embodiment, the atmosphere inside the tank (702) when degassing and the atmosphere in the space where the substrate W with the IPA paddles is located or transported were nitrogen gas atmospheres, but are not limited to this, and may be other inert gas atmospheres (e.g., argon gas).

Claims

1. A degassing process to remove dissolved gases from the processing liquid, A liquid film formation step involves supplying the treatment liquid from which the dissolved gas has been removed to the surface of the substrate to form a liquid film of the treatment liquid covering the surface of the substrate, A loading step involves loading the substrate on which the liquid film has been formed into a processing container, A supercritical drying step is performed in which the pressure inside the processing container into which the substrate on which the liquid film has been formed is introduced is maintained at a pressure that maintains the processing fluid in a supercritical state, the processing fluid is circulated inside the processing container, thereby replacing the processing liquid covering the surface of the substrate with the processing fluid, and then the surface of the substrate is dried by vaporizing the processing fluid. Equipped with, A substrate processing method comprising the degassing step of heating the processing liquid stored in a container to a temperature below the boiling point of the processing liquid while creating an inert gas atmosphere inside the container storing the processing liquid.

2. The substrate processing method according to claim 1, wherein the inert gas is nitrogen gas or argon gas.

3. A degassing step to remove dissolved gas from the processing liquid, A liquid film formation step involves supplying the treatment liquid from which the dissolved gas has been removed to the surface of the substrate to form a liquid film of the treatment liquid covering the surface of the substrate, A loading step involves loading the substrate on which the liquid film has been formed into a processing container, A supercritical drying step is performed in which the pressure inside the processing container into which the substrate on which the liquid film has been formed is introduced is maintained at a pressure that maintains the processing fluid in a supercritical state, the processing fluid is circulated inside the processing container, thereby replacing the processing liquid covering the surface of the substrate with the processing fluid, and then the surface of the substrate is dried by vaporizing the processing fluid. Equipped with, The degassing step includes applying ultrasonic vibrations to the processing liquid to generate bubbles in the processing liquid and removing the bubbles from the processing liquid. A substrate processing method wherein generating bubbles in the processing liquid and removing bubbles from the processing liquid is performed by flowing the processing liquid through a circulation path connected to a container for storing the processing liquid, using an in-line degassing mechanism provided in the circulation path.

4. A degassing step to remove dissolved gas from the processing liquid, A liquid film formation step involves supplying the treatment liquid from which the dissolved gas has been removed to the surface of the substrate to form a liquid film of the treatment liquid covering the surface of the substrate, A loading step involves loading the substrate on which the liquid film has been formed into a processing container, A supercritical drying step is performed in which the pressure inside the processing container into which the substrate on which the liquid film has been formed is introduced is maintained at a pressure that maintains the processing fluid in a supercritical state, the processing fluid is circulated inside the processing container, thereby replacing the processing liquid covering the surface of the substrate with the processing fluid, and then the surface of the substrate is dried by vaporizing the processing fluid. Equipped with, A substrate processing method further comprising, between the completion of the liquid film formation step and the completion of the loading step, changing the atmosphere of the space through which the substrate on which the processing liquid film has been formed passes to an inert gas atmosphere.

5. The substrate processing method according to claim 4, wherein the inert gas is nitrogen gas or argon gas.

6. A substrate processing method according to any one of claims 1 to 5, further comprising a chemical treatment step of applying a chemical solution to the substrate before the liquid film formation step.

7. The substrate processing method according to claim 6, wherein the chemical treatment is an etching treatment.

8. The substrate processing method according to claim 7, wherein the etching process forms a pattern having a plurality of grooves on the substrate.

Images