Substrate processing apparatus and substrate processing method

Abstract

[Problem] To provide technology for efficiently enhancing the cleanliness of a processing liquid in a circulation system. [Solution] A substrate processing apparatus comprising: a tank for storing a processing liquid; a circulation line connected to the tank; a pump which is provided in the circulation line and drives the processing liquid so that the processing liquid circulates in a circulation circuit constituted by the tank and the circulation line; a heater for heating the processing liquid flowing in the circulation line; a first filter for filtering the processing liquid flowing in the circulation line; a processing unit for processing a substrate by using the processing liquid supplied from the circulation line; a filter line for removing a portion of the processing liquid circulating in the circulation circuit from the circulation circuit, and for causing the removed processing liquid to flow and return to the circulation circuit; a cooler which is provided in the filter line and cools the processing liquid flowing in the filter line; and at least one second filter which is provided on the downstream side of the cooler in the filter line, and which filters the processing liquid that has been cooled by the cooler before said processing liquid is returned to the circulation circuit.

Description

Technical Field

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

Background Art

[0002] In the manufacture of semiconductor devices, liquid processing using a processing liquid (chemical solution, rinse liquid, etc.) is performed on a substrate such as a semiconductor wafer. Before drying the liquid-processed substrate, the rinse liquid on the surface of the substrate is replaced with IPA (isopropyl alcohol). Thereafter, spin-drying treatment or supercritical drying treatment is performed on the substrate. The cleanliness of the IPA covering the substrate surface immediately before drying has a great influence on the amount of particles after drying.

[0003] Patent Document 1 discloses a processing liquid supply source (processing liquid supply mechanism) improved to improve the cleanliness of IPA. The processing liquid supply source has a storage tank for storing IPA, a first circulation line connected to the storage tank, and a first filter provided in the first circulation line. IPA is supplied to a plurality of processing units via a plurality of supply lines branched from the first circulation line. The processing liquid supply source further has a second circulation line branched from the first circulation line at a branch point on the first circulation line, and a second filter provided in the second circulation line. The second circulation line returns IPA to the tank.

[0004] The flow path length of the second circulation line is shorter than that of the first circulation line. The flow rate of IPA flowing into the second circulation line is smaller than the flow rate of IPA flowing into the first circulation line on the downstream side of the branch point. The amount of filtration per unit time in the second filter is smaller than the amount of filtration per unit time in the first filter. Therefore, the second filter can capture contaminants that cannot be captured by the first filter, and as a result, the cleanliness of IPA in the circulation system can be increased.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] International Publication No. 2022 / 009661 [Overview of the project]

[0006] This disclosure provides a technology for efficiently improving the cleanliness of a treatment liquid within a circulating system.

[0007] According to one embodiment of the present disclosure, a substrate processing apparatus is provided, comprising: a tank for storing a processing liquid; a circulation line connected to the tank; a pump provided in the circulation line for driving the processing liquid to circulate within a circulation circuit formed by the tank and the circulation line; a heater provided in the circulation line for heating the processing liquid flowing through the circulation line; a first filter provided in the circulation line for filtering the processing liquid flowing through the circulation line; a processing unit for processing a substrate using the processing liquid supplied from the circulation line; a filtration line for taking out a portion of the processing liquid circulating within the circulation circuit and returning the taken processing liquid to the circulation circuit; a cooler provided in the filtration line for cooling the processing liquid flowing through the filtration line; and at least one second filter provided downstream of the cooler in the filtration line for filtering the processing liquid cooled by the cooler before it is returned to the circulation circuit.

[0008] According to this disclosure, the cleanliness of IPA within the circulating system can be efficiently increased. [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] Figure 1 is a schematic longitudinal cross-sectional view showing the configuration of the processing unit included in the substrate processing system. [Figure 3] Figure 2 is a piping diagram showing the configuration of the processing liquid supply source (processing liquid supply mechanism) that supplies IPA as the processing liquid to the processing liquid supply section of the processing unit shown in Figure 2. [Figure 4] This is a schematic diagram that shows the same configuration as the embodiment in Figure 3, which serves as a reference for explaining the modified embodiment. [Figure 5] This is a schematic diagram showing the first modified embodiment. [Figure 6] This is a schematic diagram showing a second modified embodiment. [Figure 7] This is a schematic diagram showing a third modified embodiment. [Figure 8] This is a schematic diagram showing a fourth modified embodiment. [Figure 9] This is a schematic diagram showing a modified version of the condenser. [Figure 10] This is a graph used to explain the experimental results. [Modes for carrying out the invention]

[0010] Preferred and non-limiting embodiments will be described below with reference to the attached drawings.

[0011] [Overview of the PCB Processing System] The schematic configuration of the substrate processing system 1 (an example of a liquid processing apparatus) according to the embodiment will be described with reference to Figure 1. Figure 1 is a diagram showing the schematic configuration of the substrate processing system 1 according to the embodiment. In the following, in order to clarify the positional relationships, the X, Y, and Z axes are defined as being orthogonal to each other, and the positive direction of the Z axis is defined as the vertically upward direction.

[0012] As shown in Figure 1, the substrate processing system 1 comprises an input / output station 2 and a processing station 3. The input / output station 2 and the processing station 3 are located adjacent to each other.

[0013] The loading / unloading station 2 comprises a carrier mounting section 11 and a transport section 12. Multiple carriers C, each capable of accommodating multiple substrates, or in this embodiment, semiconductor wafers W (hereinafter referred to as wafers W), in a horizontal position, are mounted on the carrier mounting section 11.

[0014] The transfer unit 12 is provided adjacent to the carrier placement unit 11 and includes a substrate transfer device 13 and a delivery unit 14 inside. The substrate transfer device 13 includes a wafer holding mechanism for holding the wafer W. Further, the substrate transfer device 13 is capable of moving in the horizontal and vertical directions and turning about a vertical axis, and transfers the wafer W between the carrier C and the delivery unit 14 using the wafer holding mechanism.

[0015] The processing station 3 is provided adjacent to the transfer unit 12. The processing station 3 includes a transfer unit 15 and a plurality of processing units 16. The plurality of processing units 16 are arranged side by side on both sides of the transfer unit 15.

[0016] The transfer unit 15 includes a substrate transfer device 17 inside. The substrate transfer device 17 includes a wafer holding mechanism for holding the wafer W. Further, the substrate transfer device 17 is capable of moving in the horizontal and vertical directions and turning about a vertical axis, and transfers the wafer W between the delivery unit 14 and the processing unit 16 using the wafer holding mechanism.

[0017] The processing unit 16 performs substrate processing on the wafer W transferred by the substrate transfer device 17. The processing unit 16 holds the transferred wafer and performs substrate processing on the held wafer. The processing unit 16 supplies a processing liquid to the held wafer and performs substrate processing.

[0018] The processing liquid is a CF-based cleaning liquid for processing the wafer W such as HFC (HydroFluoroCarbon), or a cleaning liquid for cleaning residues of the wafer W such as DHF (Diluted HydroFluoric acid). Further, the processing liquid is a rinsing liquid such as DIW (DeIonized Water) or a replacement liquid such as IPA (IsoPropyl Alcohol).

[0019] The substrate processing system 1 also includes a control device 4. The control device 4 is, for example, a computer and includes a control unit 18 and a storage unit 19. The storage unit 19 stores programs for controlling various processes executed in the substrate processing system 1. The control unit 18 controls the operation of the substrate processing system 1 by reading and executing the programs stored in the storage unit 19.

[0020] Note that such programs may be recorded on a computer-readable storage medium and installed from the storage medium into the storage unit 19 of the control device 4. Examples of computer-readable storage media include hard disks (HD), flexible disks (FD), compact disks (CD), magneto-optical disks (MO), memory cards, and the like.

[0021] In the substrate processing system 1 configured as described above, first, the substrate transfer device 13 of the loading / unloading station 2 takes out the wafer W from the carrier C placed on the carrier placement unit 11 and places the taken-out wafer W on the delivery unit 14. The wafer W placed on the delivery unit 14 is taken out from the delivery unit 14 by the substrate transfer device 17 of the processing station 3 and carried into the processing unit 16.

[0022] 処理ユニット16へ搬入されたウエハWは、処理ユニット16によって基板処理された後、基板搬送装置17によって処理ユニット16から搬出されて、受渡部14に載置される。そして、受渡部14に載置された処理済のウエハWは、基板搬送装置13によってキャリア載置部11のキャリアCへ戻される。 The wafer W carried into the processing unit 16 is subjected to substrate processing by the processing unit 16, then carried out from the processing unit 16 by the substrate transfer device 17, and placed on the delivery unit 14. Then, the processed wafer W placed on the delivery unit 14 is returned to the carrier C of the carrier placement unit 11 by the substrate transfer device 13.

[0023] [Overview of the Processing Unit] Next, the overview of the processing unit 16 will be described with reference to FIG. 2. FIG. 2 is a schematic diagram showing the configuration of the processing unit 16 according to the embodiment. The processing unit 16 includes a chamber 20, a substrate holding mechanism 30, a processing liquid supply unit 40, and a recovery cup 50.

[0024] Chamber 20 houses a substrate holding mechanism 30, a processing liquid supply unit 40, and a recovery cup 50. An FFU (Fan Filter Unit) 21 is provided on the ceiling of chamber 20. The FFU 21 creates a downflow within chamber 20.

[0025] The substrate holding mechanism 30 comprises a holding portion 31, a support column portion 32, and a drive unit 33. The holding portion 31 holds the wafer W horizontally. The support column portion 32 is a member that extends in the vertical direction, with its base end rotatably supported by the drive unit 33, and its tip supporting the holding portion 31 horizontally. The drive unit 33 rotates the support column portion 32 around a vertical axis.

[0026] The substrate holding mechanism 30 rotates the support column 32 using the drive unit 33, thereby rotating the holding portion 31 supported by the support column 32. As a result, the wafer W held in the holding portion 31 rotates.

[0027] The processing liquid supply unit 40 supplies processing liquid to the wafer W. The processing liquid supply unit 40 is connected to the processing liquid supply mechanism (also called the "processing liquid supply source") 70. The processing liquid supply unit 40 is equipped with multiple nozzles. For example, the multiple nozzles are provided corresponding to each processing liquid. Each nozzle discharges the processing liquid supplied from each processing liquid supply mechanism 70 onto the wafer W.

[0028] The collection cup 50 is positioned to surround the holding unit 31 and collects the processing liquid scattered from the wafer W as the holding unit 31 rotates. A drain port 51 is formed at the bottom of the collection cup 50, and the processing liquid collected by the collection cup 50 is discharged to the outside of the processing unit 16 through this drain port 51. An exhaust port 52 is also formed at the bottom of the collection cup 50 to discharge the gas supplied from the FFU 21 to the outside of the processing unit 16.

[0029] [Configuration of IPA supply mechanism] Next, the configuration of the IPA supply mechanism (hereinafter referred to as "IPA supply mechanism 70") among the processing liquid supply mechanisms 70 will be described with reference to Figure 3. The other processing liquid supply mechanisms may have the same or nearly the same configuration as the IPA supply mechanism 70, or they may have other configurations that are well known in the field of semiconductor manufacturing equipment (especially liquid processing equipment).

[0030] Figure 3 shows an example in which the IPA supply mechanism 70 supplies IPA to two processing liquid supply units 40 (specifically, for example, IPA supply nozzles provided in each of the two processing units 16), but it is not limited to this. The IPA supply mechanism 70 may supply IPA to three or more processing liquid supply units 40, or it may supply IPA to just one processing liquid supply unit 40.

[0031] The IPA supply mechanism 70 includes a tank 71, a treatment liquid replenishment section 72, a drain line 73, a circulation line 74, a filtration line 75, a supply line 76, and a return line 77.

[0032] Tank 71 stores IPA. The treatment liquid replenishment unit 72 supplies new IPA to Tank 71 when replacing the IPA in Tank 71 or when the amount of IPA in Tank 71 falls below a predetermined amount. The drainage line 73 discharges the IPA from Tank 71 to the outside when replacing the IPA in Tank 71.

[0033] The circulation line 74 is equipped with, in order from the side closest to the tank 71 (upstream side), a pump 80, a heater (inline heater) 81, a temperature sensor 82, a first filter 83, a flow meter 84, and a back pressure valve 85.

[0034] Pump 80 pumps IPA through the circulation line 74, thereby creating a circulating flow of IPA that flows from tank 71 to circulation line 74, through circulation line 74, and then returns to tank 71. In other words, a circulation circuit is formed by tank 71 and circulation line 74, and IPA circulates through this circuit.

[0035] The amount of heat generated by the electric heater 81 is controlled, for example, by the control device 4 (see Figure 1), so that the temperature of the IPA flowing through the circulation line 74, as detected by the temperature sensor 82, reaches a predetermined temperature. This maintains the temperature of the IPA flowing through the circulation line 74 at a predetermined temperature (for example, around 50°C to 70°C).

[0036] The flow meter 84 measures and monitors the flow rate of IPA flowing through the circulation line 74.

[0037] Multiple supply lines 76 (the same number as the processing units 16) are connected to the region of the circulation line 74 upstream of the back pressure valve 85. IPA extracted from the circulation line 74 via the supply lines 76 is supplied to the processing liquid supply section 40 of the processing unit 16 (specifically, the nozzle for discharging IPA).

[0038] The back pressure valve 85 plays a role in stably maintaining the pressure upstream of the back pressure valve 85 (i.e., the pressure in the area where the supply line 76 of the circulation line 74 is connected) at a predetermined value. This allows for stable control of the flow rate of IPA into each supply line 76.

[0039] In the processing unit 16, for example, the wafer W is subjected to chemical treatment, followed by a rinsing treatment. After the rinsing treatment, IPA is supplied to the wafer W via the processing liquid supply unit 40, thereby replacing the rinsing liquid (e.g., DIW (pure water)) on the wafer W with IPA. Subsequently, the wafer W is subjected to a spin drying treatment. Alternatively, the wafer W, on which a liquid film of IPA has formed on its surface, is transported from the processing unit 16 to a supercritical drying unit (not shown) and subjected to supercritical drying. Regardless of the type of drying treatment applied, the cleanliness of the IPA supplied immediately before drying the wafer W is extremely important in improving the cleanliness of the wafer W after drying.

[0040] When the final drying of the wafer W is performed by a supercritical drying unit, some of the processing units 16 shown in Figure 1 become liquid processing units, and some of the others become supercritical drying units. The supercritical drying unit supplies a supercritical fluid (e.g., supercritical CO2) into a supercritical chamber, replaces the IPA liquid film on the wafer W with this supercritical fluid, and then dries the wafer W by bringing the pressure inside the supercritical chamber to atmospheric pressure. The configuration and operation of the supercritical drying unit are well known in the technical field of semiconductor device manufacturing, so a detailed explanation is omitted.

[0041] The supply line 76 is equipped with a flow meter 100, a constant pressure valve 101, a filter 102, and an on / off valve 103.

[0042] The control device 4 adjusts the set pressure of the constant pressure valve 101 based on the deviation of the actual IPA flow rate detected by the flow meter 100 from the target flow rate, thereby controlling the flow rate of IPA discharged from the processing liquid supply unit 40 (IPA discharge nozzle) to match the target flow rate. In other words, in this case, the constant pressure valve 101 acts as a flow rate control valve.

[0043] At a branching point 79 set in the supply line 76 between the filter 102 and the on-off valve 103, the aforementioned return line 77 branches off from the supply line 76. Each return line 77 is provided with an on-off valve 110.

[0044] The multiple return lines 77 merge downstream of the on-off valve 110 to form a single return line (which, for convenience of explanation, will also be called the "main return line 78"). The downstream end of the main return line 78 is connected to the tank 71. The main return line 78 is equipped with a temperature sensor 111 for measuring the temperature of the IPA flowing through it. If the IPA supply mechanism 70 has only one return line 77, it goes without saying that the downstream end of that single return line 77 is connected to the tank 71.

[0045] By switching the on / off valve 103 of the supply line 76 and the on / off valve 110 of the branch line 77, it is possible to switch between a first state in which IPA flowing into the supply line 76 is supplied to the substrate W from the processing liquid supply unit 40 (on / off valve 110 is closed, on / off valve 103 is open) and a second state in which IPA flowing into the supply line 76 is returned to the tank 71 through the return line 77 (on / off valve 110 is open, on / off valve 103 is closed).

[0046] During normal operation of the substrate processing system 1 (here, meaning when processing is carried out in each processing unit 16 according to a predetermined processing schedule), temperature-controlled IPA is constantly circulating in the circulation line 74, and the on-off valves 110 and 103 are in either the first or second state. In other words, when IPA is not being supplied to the wafer W from the processing liquid supply unit (IPA nozzle) 40, the IPA that flows from the circulation line 74 into the supply line 76 returns to the tank 71 through the return line 77 and the main return line 78. This suppresses the temperature drop in the piping of the supply line 76.

[0047] At a branching point 86 set in the circulation line 74, the filtration line 75 branches off from the circulation line 74. In the embodiment shown in Figure 3, the downstream end of the filtration line 75 is directly connected to the tank 71.

[0048] The filtration line 75 includes, in order from upstream, a cooler 90, a temperature sensor 91, a flow control valve 92, at least one second filter 93, and a flow meter 94. Although not shown in the figures, an on / off valve may be provided, for example, near the upstream end of the circulation line 74 (upstream of the cooler 90) to isolate the filtration line 75 from the circulation line 74. The arrangement order of the devices 90, 91, 92, 93, and 94 is not limited to this, as long as the IPA is cooled by the cooler 90 and then passes through the second filter 93.

[0049] The cooler 90 cools the IPA passing through it. The cooler 90 has, for example, a refrigerant tank 90a for storing a refrigerant CM, such as water, and a heat exchanger 90b immersed in the refrigerant stored in the refrigerant tank 90a, as schematically shown in Figure 3. The heat exchanger 90b is made of, for example, a spirally wound stainless steel tube. The inner surface of the stainless steel tube that is in contact with the IPA flowing inside the stainless steel tube is coated with a resin to prevent metal ions from leaching from the inner surface into the IPA.

[0050] It is also possible to construct the heat exchange section 90b of the cooler 90 from a resin material (resin tube). However, resin materials have poor thermal conductivity and generally are permeable to moisture. Therefore, if water is used as the refrigerant in the refrigerant tank 90a, water may mix with the IPA, potentially worsening the particle level during wafer drying. For this reason, it is preferable that the heat exchange section 90b be formed from a metal material.

[0051] In one embodiment, refrigerant CM supplied from the refrigerant supply mechanism 90c is supplied into the refrigerant tank 90a via a supply port provided at the bottom of the refrigerant tank 90a, and discharged from the refrigerant tank 90a via a discharge port provided at the top of the refrigerant tank 90a. As the refrigerant CM flows through the refrigerant tank 90a in this manner, heat exchange takes place in the heat exchange section 90b between the refrigerant CM and the heated (for example, 50-70°C) IPA, thereby cooling the IPA to a desired temperature. The refrigerant supply mechanism 90c is supplied with refrigerant from a suitable refrigerant supply source (for example, a DIW supply source provided as factory power).

[0052] To adjust the cooling capacity of the cooler 90, the refrigerant supply mechanism 90c may include equipment (e.g., a refrigerant cooling device, a flow control valve for adjusting the refrigerant flow rate, etc.) that adjusts at least one of the temperature and flow rate of the refrigerant CM supplied from the refrigerant supply mechanism 90c to the refrigerant tank 90a.

[0053] The flow control valve 92 installed in the filtration line 75 can be a type of valve with a flow rate adjustment function, such as a needle valve with a variable opening degree or a constant pressure valve with a variable set pressure. The mechanism of flow control using a constant pressure valve is the same as the mechanism of flow control using a constant pressure valve 101 in the supply line 76.

[0054] The flow meter 94 measures the flow rate of IPA flowing through the filtration line 75. Based on the deviation between the actual IPA flow rate measured by the flow meter 94 and the target IPA flow rate, the control device 4 can adjust the flow rate of IPA flowing through the filtration line 75 by adjusting the settings of the flow control valve 92 (set opening of the needle valve, set pressure of the constant pressure valve), for example. The adjustment of the IPA flow rate can be determined by considering the cooling capacity of the cooler 90 and the filtration capacity of the second filter 93, etc. (details will be described later).

[0055] In the embodiment shown in Figure 3, three second filters 93 (filter modules) are provided in parallel as "at least one second filter," and these three second filters 93 form one filter set. By arranging the second filters 93 in parallel, it is possible to keep the IPA flow rate through one filter module 93 low while increasing the total IPA flow rate through the filter set.

[0056] Next, we will describe the filters included in the IPA supply mechanism 70.

[0057] IPA heated to, for example, 50°C to 70°C passes through the first filter 83 provided in the circulation line 74. In order to enable the simultaneous supply of IPA to multiple supply lines 76 corresponding to multiple processing units 16, it is necessary to set the flow rate of IPA circulating in the circulation line 74 to a relatively high value (for example, about 5 L / min).

[0058] When relatively high-temperature IPA is flowed through the circulation line 74, materials forming the wetted parts of equipment such as filters and heaters leach into the IPA. It is difficult to remove such leached contaminants to a level that meets the most stringent standards required in modern processes using only the first filter 83. The reasons for this include the following: - Substances that are completely dissolved in IPA pass through the filter. - Substances that are not completely dissolved in IPA (e.g., gel-like substances) will deform and pass through the filter media even if they come into contact with it under high flow rate and high differential pressure conditions. Also, even if contaminants are initially captured by the filter media, they can detach from the filter media under high flow rate and high differential pressure conditions. - Filters can capture pollutants not only through physical filtration (capture of particles by sieving) but also through adsorption (adsorption by van der Waals forces or hydrogen bonding), however, their adsorption capacity decreases at high temperatures.

[0059] If IPA containing contaminants is supplied to wafer W without being removed, it will degrade particle performance.

[0060] The second filter 93, located in the filtration line 75, is provided to remove contaminants that cannot be removed by the first filter 83 for the reasons mentioned above. As previously stated, the filter removes contaminants not only through physical filtration but also through adsorption. Adsorption allows for the capture of contaminants that are smaller than the mesh size of the filter media or that can pass through the mesh due to deformation. To ensure sufficient adsorption, it is effective to lower the temperature of the liquid (IPA) passing through the filter or to reduce the flow rate of the liquid passing through the filter.

[0061] Considering the above, a portion of the IPA flowing through the circulation line 74 at a temperature of approximately 50°C to 70°C is introduced into the filtration line 75. In the filtration line 75, the IPA is first cooled to a temperature of, for example, 40°C or lower by the cooler 90, and then the cooled IPA is passed through the second filter 93. By cooling the IPA, at least a portion of the contaminants completely dissolved in the IPA precipitates, and the deformability of the gel-like contaminants (organic matter) in the IPA is reduced. Furthermore, cooling the IPA can improve the adsorption effect of the filter (second filter 93) (desorption from the filter element is suppressed). In this state, by passing the IPA through the second filter 93, contaminants that cannot be removed by the first filter 83 can be efficiently removed by the second filter 93.

[0062] The IPA that passes through the second filter 93 contains a relatively large amount of organic matter or aggregates thereof with hydrophilic groups as contaminants. From the viewpoint of efficiently adsorbing such contaminants, it is preferable that the filter material of the second filter 93 be made of a material with hydrophilic groups (specifically, for example, nylon, hydrophilized polyimide, or fluororesin (e.g., hydrophilic PTFE)).

[0063] Furthermore, most commercially available filters capable of adsorbing and removing the aforementioned contaminants (e.g., gel-like substances) have low heat resistance temperatures (e.g., around 40°C). From this perspective, it may be necessary to install a cooler (90) before the second filter 93. In any case, if gel-like substances are the target of removal, the removal efficiency of gel-like substances can be increased by lowering the IPA temperature.

[0064] To increase the efficiency of the second filter 93 in filtering gel-like contaminants, it is preferable to perform filtration under low flow rate and low differential pressure conditions. The flow rate of IPA passing through one second filter 93 is preferably set within the range of, for example, 50 to 500 ml / min (milliliters per minute).

[0065] It is preferable that the flow rate Q2 of IPA flowing through the filtration line 75 is sufficiently smaller than the flow rate Q1 of IPA flowing through the first filter 83 of the circulation line 74 (i.e., the sum of the flow rate of IPA flowing through the circulation line 74 downstream of the branching point 86 and the flow rate of IPA flowing through the filtration line 75). If cooled IPA is constantly returned from the filtration line 75 to the tank 71 at a large flow rate, the power consumption of the heater 81 will increase, and the temperature stability of the IPA in the circulation system and, consequently, the temperature stability of the IPA supplied to the processing unit 16 may be impaired. Note that if multiple (N) second filters 93 are provided in parallel, the flow rate of IPA passing through one second filter 93 is Q2 / N.

[0066] Considering the above, as an example, if the flow rate Q1 is set to 5 L / min (liters per minute), the flow rate Q2 should be set to, for example, 500 ml / min or less. In this case, it has been confirmed that the temperature of the IPA flowing through the filtration line 75 can be stably maintained at, for example, 70°C. Note that the appropriate range for the ratio of Q1 to Q2 will vary depending on various factors such as the capacity of the heater 81 and the target temperature of the IPA flowing through the filtration line 75, so the above values ​​are merely examples.

[0067] The length of the filtration line 75 is preferably shorter than that of the circulation line 74. By shortening the circulation line 74, the frequency of low-temperature filtration for the same volume of IPA can be increased, thereby improving the filtration efficiency.

[0068] The following describes the basic concepts for setting the temperature T1 of the IPA supplied to the processing unit 16 (i.e., the temperature of the IPA heated by the heater 81), the temperature T2 of the IPA after passing through the cooler 90 of the filtration line 75, and the above flow rates Q1 and Q2.

[0069] - The higher the temperature T1, the greater the amount of contaminants that leach into the IPA flowing through the circulation line 74. - The lower the temperature T2, the higher the contaminant capture rate of the second filter 93 when the material passes through the second filter 93. - The greater the temperature difference between temperature T1 and temperature T2 (in other words, the greater the decrease in IPA temperature in the cooler 90), the greater the power consumption of the heater 81, and the less stable the temperature of the entire circulation system (especially the temperature of the IPA supplied from the circulation line 74 to the processing liquid supply section of the processing unit 16). - The lower the flow rate Q2, the higher the contaminant capture rate of the second filter 93 as the fluid passes through the second filter 93. - The higher the flow rate Q2 (or the higher the ratio of flow rate Q2 to flow rate Q1), the greater the power consumption of the heater 81, and the less stable the temperature of the entire circulation system (especially the temperature of the IPA supplied from the circulation line 74 to the processing liquid supply section of the processing unit 16).

[0070] I will now describe specific examples of operations that take the above points into consideration.

[0071] When the temperature T1 is relatively low, around 50-60°C, the amount of contaminants leaching into the IPA is relatively small. In this case, the temperature T2 can be relatively high; for example, it can be set to around 40°C. The flow rate Q2 can also be relatively high.

[0072] When the temperature T1 is relatively high, around 70°C, a relatively large amount of contaminants leach into the IPA. In this case, it is preferable to keep the temperature T2 relatively low in order to sufficiently remove the contaminants. For example, the temperature T2 should be set to 30°C or lower. It is also preferable to keep the flow rate Q2 relatively low.

[0073] A function or table (table) showing suitable temperatures T2 and flow rates Q2 corresponding to a given temperature T1 (or temperature T1 and flow rate Q1) may be stored in the control device 4. In this case, the temperature T2 and flow rate Q2 may be determined based on this function or table, and the operation of the cooler 90 (refrigerant temperature and / or refrigerant flow rate) and / or the opening degree of the flow control valve 92 may be automatically adjusted. The cooler 90 may be operated under constant conditions at all times. In this case, the flow rate Q2 can be changed according to the desired temperature T2. Such control of operating conditions can be performed under the control of the control device 4.

[0074] When replacing IPA in use within the processing liquid supply mechanism 70 (tank 71 and lines 74, 75, 76, 77, etc., composed of pipelines) with new (unused) IPA (or when starting up a new substrate processing system 1), the following operations can be performed. That is, the flow rate Q2 may be set to a relatively high first flow rate during the first period, from the start of circulation of the new IPA by the pump 80 and temperature control of the new IPA by the heater 81 until a predetermined time has elapsed, and then the flow rate Q2 may be reduced to a lower second flow rate during the subsequent second period. During the first period, although the filtration efficiency (contaminant capture rate) is relatively low, the filtration volume per unit time can be increased, so the cleanliness of the IPA in the circulation system (e.g., in the tank) can be raised to a first level in a relatively short time. Subsequently, during the second period, although the filtration volume per unit time decreases, filtration with relatively high filtration efficiency becomes possible, so the cleanliness of the IPA in the circulation system can be raised to a second level, which is higher than the first level. This reduces the time required to raise the cleanliness of the IPA in the circulating system to the second level, compared to setting the flow rate Q2 to a lower second flow rate from the beginning. The ability to perform such operations is one of the major advantages of installing a flow control valve 92 in the filtration line 75.

[0075] If metal ions leaching (for example, through the coating) from the stainless steel tubes constituting the heat exchange section 90b of the cooler 90 are a problem, then a filter with metal ion removal capabilities, such as a membrane filter, may be used as the second filter 93. Some membrane filters also have the ability to capture organic matter or aggregates thereof that have hydrophilic groups as described above.

[0076] Furthermore, the filter 102 provided in the supply line 76 can be, for example, smaller than the first filter 83 provided in the circulation line 74, but otherwise having the same specifications as the first filter 83.

[0077] According to the above embodiment, a portion of the IPA flowing through the circulation circuit consisting of the tank 71 and the circulation line 74 is taken out to the filtration line 75, cooled in the filtration line 75, further filtered by the second filter 93, and then returned to the tank 71. Once cooled, the IPA is not mixed with high-temperature IPA until it is filtered by the second filter 93. Therefore, it is possible to remove contaminants (particle-causing substances) that cannot be removed by the first filter 83 installed in the circulation line 74, where IPA flows at high temperature and high flow rate. As a result, the cleanliness of the IPA flowing through the circulation line 74 is also increased, and consequently, the cleanliness of the IPA supplied to the wafer W from the processing liquid supply unit 40 of the processing unit 16 can also be increased.

[0078] Furthermore, by installing multiple second filters 93 in parallel in the filtration line 75, the flow rate of IPA passing through a single second filter 93 can be kept low, thereby more reliably removing contaminants. Note that contaminants also leach from the second filters 93 through which relatively low-temperature IPA passes, and the more second filters 93 there are, the greater the total amount of leached contaminants. However, since some of the leached contaminants are captured by the second filters 93, and the total amount of contaminants captured by the second filters 93 (contaminants contained in the IPA flowing throughout the entire circulation system) also increases with a larger number of second filters 93, a larger number of second filters 93 is preferable. However, considering the current cleanliness requirements for IPA, three second filters 93 are often sufficient.

[0079] The embodiments and modified embodiments described above will be briefly explained below with reference to schematic diagrams in Figures 4 to 8.

[0080] Figure 4 is a simplified representation of the embodiment shown in Figure 3. To facilitate understanding of the drawings, in Figures 4 to 8, the following symbols are also used: tank 71 is labeled "T", pump 80 is labeled "P", heater 81 is labeled "H", first filter 83 is labeled "F1", back pressure valve 85 is labeled "BPV", cooler 90 is labeled "C", flow control valve 92 is labeled "FCV", and second filter 93 is labeled "F2". In addition, in Figures 4 to 8, the labels of some equipment not directly related to the explanation have been omitted.

[0081] Figure 5 shows a first modified embodiment, in which the downstream end of the filtration line 75 is connected to the circulation line 74 rather than directly to the tank T (71). In this case, the filtration line 75 is indirectly connected to the tank 71 via the circulation line 74. The connection position of the filtration line 75 in the circulation line 74 is downstream of the back pressure valve BPV (85) and upstream of the tank T. In this first modified embodiment, the filtration line 75 is the same as in the embodiment of Figure 4 in that it is provided to take a portion of the treated liquid (IPA) circulating in the circulation circuit (tank 71 + circulation line 74) and return the taken treated liquid (IPA) to the circulation circuit (circulation line 74 in the example of Figure 5). The first modified embodiment also provides the same effects as the embodiment of Figure 4.

[0082] Figure 6 shows a second modified embodiment. Here, instead of providing a dedicated filtration line 75, a cooler C and a second filter 93 are provided in the main return line 78 (i.e., the part where multiple return lines 77 merge into a single return line). In this second modified embodiment, the supply line 76 (the part upstream of the branching point 79) and the return line 77 (78) correspond to filtration lines that take a portion of the processed liquid (IPA) circulating within the circulation circuit (tank 71 + circulation line 74) and return the taken processed liquid (IPA) to the circulation circuit (tank 71 in the example of Figure 6).

[0083] Since the flow rate of IPA flowing into the return line 77(78) changes depending on the operating status of the multiple processing units 16, problems may arise if the flow rate of the main return line 78 is freely restricted. For this reason, if it is desired to adjust the flow rate of IPA flowing through the second filter 93, a bypass line (see the dashed line in Figure 6) may be provided that bypasses the cooler C and the second filter 93 and connects the return line 77(78) to the tank, and a valve (not shown) with a flow rate control function may be provided in the return line 77(78) and / or the bypass line. Alternatively, a number of second filters 93 may be provided such that when the flow rate of IPA flowing through the main return line 78 is at its maximum, the flow rate of IPA passing through each second filter 93 is reduced to a level that can achieve the desired filtration performance.

[0084] In this second modified embodiment, as in the embodiment shown in Figure 4, low-temperature filtration of the IPA is performed, allowing for efficient removal of contaminants from the IPA.

[0085] Figure 7 shows a third modified embodiment, in which both the upstream and downstream ends of the filtration line 75 are connected to the tank T(71). In other words, in this third modified embodiment, the circulation line 74 and the filtration line 75 each form an independent circulation circuit in portions other than the tank T. In this case, the driving force of the pump P(80) cannot be used to circulate IPA in the filtration line 75. For this reason, an additional pump P2(80) is provided to create a circulating flow of IPA in the filtration line 75. The flow rate of IPA circulating in the filtration line 75 may be adjusted only by changing the operating conditions of the pump P2, or it may be done using a flow rate control device (not shown) provided in the filtration line 75. In the third modified embodiment, it becomes easier to precisely control the flow rate of IPA flowing through the filtration line 75 compared to the other embodiments.

[0086] In this third modified embodiment, as in the embodiment shown in Figure 4, low-temperature filtration of the IPA is performed, allowing for efficient removal of contaminants from the IPA.

[0087] Figure 8 shows a fourth modified embodiment, in which two filtration lines 75 are provided. The equipment (90-94) provided in each filtration line 75 is the same. Preferably, an on-off valve 95 is provided near the upstream end of at least one of the filtration lines 75. By opening and closing this on-off valve 95, it is possible to switch between a state in which IPA flows through both filtration lines 75 simultaneously and a state in which IPA flows through only one filtration line 75. With this configuration, for example, when it is desired to quickly increase the cleanliness of the IPA present in the circulation system, such as when changing the liquid in tank 71, filtration can be performed using both filtration lines 75, and after the cleanliness has stabilized, filtration can be performed using only one of the filtration lines 75.

[0088] As a fifth modified embodiment not shown, the IPA supply mechanism 70 may include two or more of the filtration lines 75 (including those shared with the return line 77(78)) shown in Figure 4 (or Figure 5), Figure 6, and Figure 7.

[0089] In another modified embodiment, two or more coolers 90 may be provided in series or in parallel in a single filtration line 75 (not shown).

[0090] As schematically shown in Figure 9, the refrigerant tank 90a of the cooler 90 may house the second filter 93 so that not only the heat exchange section 90b but also the second filter 93 can be cooled by the refrigerant CM. If water is used as the refrigerant CM, it is preferable that the components immersed in water be made of a metal that does not allow water to pass through, or be covered with a material that does not allow water to pass through. In this case, the arrangement order of the various devices (90-94, etc.) in the filtration line 75 may be changed as long as it does not impair functionality. For example, the flow control valve 92 may be placed upstream of the heat exchange section 90b or downstream of the second filter 93.

[0091] [Examples] The results of tests conducted to confirm the effectiveness of the embodiment are described below. The test was conducted using an IPA supply mechanism 70 with a configuration almost identical to that shown in Figure 3, but with a bypass line connecting the equipment from the cooler 90 to the flow meter 94 to the filtration line 75. A first filter with a nominal filtration accuracy of 5 nm was used, and a second filter 93 with a nominal filtration accuracy of 5 nm was also used.

[0092] New IPA was added to tank 71 and the IPA, temperature-controlled to 70°C, was circulated through circulation line 74. At this time, the bypass line was opened to prevent IPA from passing through the equipment from cooler 90 to flow meter 94. At 1.5 hours, 2.5 hours, 3 hours, 4 hours, and 5 hours from the start of circulation, IPA removed from circulation line 74 was supplied to wafer W from processing liquid supply unit 16 (IPA nozzle), and then the wafer W was spin-dried. After drying, the particle increment (adder particles) with a size of 13.5 nm or larger on the surface of wafer W was examined. At this time, all of the IPA that flowed into filtration line 75 was diverted to the bypass line, and low-temperature filtration was not performed.

[0093] The test results are shown in the graph in Figure 10. As is clear from the left half of this graph, the particle increase decreased with time from the start of circulation, reaching a minimum value after 4 hours and not decreasing further. This is considered to be the limit of filtration by the first filter 83 of the circulation line 74.

[0094] Subsequently, the bypass line of the filtration line 75 was shut off, and the IPA flowing into the filtration line 75 was cooled to 28°C in the cooler 90. After that, the IPA was filtered by passing it through three parallel-connected second filters 93. The flow rate of IPA passing through each second filter 93 was set to 0.12 L / min. The low-temperature IPA filtered by the second filters 93 was returned to the tank 71. In this state, at 0.25 hr, 0.5 hr, 1.5 hr, 2 hr, and 2.5 hr, IPA taken from the circulation line 74 was supplied to the wafer W from the processing liquid supply unit 16 (IPA nozzle), and then the wafer W was spin-dried. Then, the particle increment (adder particle) with a size of 13.5 nm or larger was examined in the same manner as above.

[0095] As is clear from the right half of the graph in Figure 10, the particle increase further decreased with time from the start of low-temperature filtration, reaching its minimum value after 2 hours and not decreasing any further. This is considered to be the limit of filtration by the second filter 93 of filtration line 75.

[0096] The minimum particle increment achieved by filtration with only the first filter 83 was 373, while the minimum particle increment achieved by combining filtration with the first filter 83 and low-temperature filtration with the second filter 93 was 192. In other words, the minimum particle increment was improved by nearly 50%.

[0097] We also conducted several other tests under similar conditions, and in each case, we confirmed that the minimum particle increment could be improved by approximately 40-50%.

[0098] SEM observation of the particles revealed that when filtration with the first filter 83 and low-temperature filtration with the second filter 93 were combined, the amount of particles originating from the gel-like substance was reduced compared to when filtration with the first filter 83 alone was performed.

[0099] 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.

[0100] In the disclosed embodiments, the treatment liquid to be filtered was IPA, but it is not limited to this, and may be an organic solvent used in BEOL (back end of line) (e.g., propylene glycol, ethylene glycol, dimethyl sulfoxide, etc.).

[0101] The substrate to be processed is not limited to semiconductor wafers, but may also be other types of substrates used in the manufacture of semiconductor devices, such as glass substrates and ceramic substrates. [Explanation of Symbols]

[0102] 71 tanks 74 Circulation Line 80 pumps 81 Heater 83 First Filter 75;76+77(78) filtration line 90 Cooler 93 Second filter

Claims

1. A tank for storing the processed liquid, A circulation line connected to the aforementioned tank, A pump provided in the circulation line drives the processing liquid so that it circulates within the circulation circuit formed by the tank and the circulation line, A heater provided in the circulation line for heating the processing liquid flowing through the circulation line, A first filter is provided in the circulation line and filters the processing liquid flowing through the circulation line, A processing unit that processes a substrate using the processing liquid supplied from the circulation line, A filtration line is provided to take a portion of the processed liquid circulating within the circulation circuit from the circulation circuit and return the taken processed liquid to the circulation circuit. A cooler provided in the filtration line for cooling the processed liquid flowing through the filtration line, A second filter is provided downstream of the cooler in the filtration line, and filters the processed liquid cooled by the cooler before the processed liquid is returned to the circulation circuit, A substrate processing apparatus equipped with the following:

2. The substrate processing apparatus according to claim 1, wherein the upstream end of the filtration line is connected to the circulation line, and the downstream end of the filtration line is directly connected to the tank or indirectly connected to the tank via the circulation line.

3. The substrate processing apparatus according to claim 1, further comprising a flow control valve provided in the filtration line for adjusting the flow rate of the processing liquid flowing through the filtration line.

4. The substrate processing apparatus according to claim 1, wherein a plurality of the second filters are provided, and these plurality of second filters are interposed in parallel in the filtration line.

5. The substrate processing apparatus according to claim 1, wherein the cooler comprises a metal tube through which the processing liquid flows and a refrigerant container that houses a refrigerant for cooling the metal tube from the outside, and the inner surface of the metal tube is provided with a resin coating to prevent the elution of metal components from the metal tube.

6. The substrate processing apparatus according to claim 1, wherein the processing solution is an organic solvent.

7. The substrate processing apparatus according to claim 1, wherein the second filter is formed of a resin material having an adsorption effect due to hydrophilic groups or an adsorption effect due to van der Waals forces.

8. The substrate processing apparatus according to claim 1, wherein the second filter is a membrane filter having metal removal performance.

9. The substrate processing apparatus according to claim 1, wherein the heater heats the processing liquid to a temperature of 50°C or higher, and the cooler cools the processing liquid to a temperature of 40°C or lower.

10. The substrate processing apparatus according to claim 1, wherein both ends of the filtration line are directly connected to the tank, the processing liquid that flows directly from the tank to the filtration line is returned directly to the tank, and an additional pump is provided, separate from the pump, to circulate the processing liquid in the filtration line.

11. A supply line connected to the circulation line, wherein the processing liquid taken out from the circulation line is supplied to the processing unit via the supply line, A return line connected to the supply line, provided to allow the processing liquid flowing through the circulation line to be returned to the tank without being supplied to the processing unit, Furthermore, The substrate processing apparatus according to claim 1, wherein the return line is provided with the cooler and the at least one second filter, and the series of lines consisting of the supply line and the return line can be used as the filtration line.

12. The substrate processing apparatus according to claim 1, wherein two or more coolers are provided in series or in parallel in the filtration line.

13. The substrate processing apparatus according to claim 1, wherein two or more of the aforementioned filtration lines are provided, and each of these two or more filtration lines is provided with a cooler and a second filter.

14. The substrate processing apparatus according to claim 1, wherein the length of the filtration line is shorter than the length of the circulation line.

15. The substrate processing apparatus according to claim 1, wherein the filtration line is provided with a flow control valve for adjusting the flow rate of the processing liquid that flows through the second filter.

16. The system further comprises at least a control device for controlling the operation of the flow control valve, The substrate processing apparatus according to claim 15, wherein the control device is configured to control the operation of the flow control valve such that the flow rate of the processing liquid flowing through the second filter becomes a first flow rate until the amount of material to be filtered contained in the processing liquid circulating in the circulation circuit decreases to a first amount, and after the amount of material to be filtered decreases to a first amount, the flow rate of the processing liquid flowing through the second filter becomes a second flow rate which is smaller than the first flow rate.

17. The substrate processing apparatus according to claim 1, wherein the processing solution is isopropyl alcohol, propylene glycol, ethylene glycol, or dimethyl sulfoxide.

18. A tank for storing the processed liquid, A circulation line connected to the aforementioned tank, A pump provided in the circulation line drives the processing liquid so that it circulates within the circulation circuit formed by the tank and the circulation line, A heater provided in the circulation line for heating the processing liquid flowing through the circulation line, A first filter is provided in the circulation line and filters the processing liquid flowing through the circulation line, A processing unit that processes a substrate using the processing liquid supplied from the circulation line, A filtration line is provided to take a portion of the processed liquid circulating within the circulation circuit from the circulation circuit and return the taken processed liquid to the circulation circuit. A cooler provided in the filtration line for cooling the processed liquid flowing through the filtration line, A second filter is provided downstream of the cooler in the filtration line, and filters the processed liquid cooled by the cooler before the processed liquid is returned to the circulation circuit, In a substrate processing method performed using a substrate processing apparatus equipped with, The heating device is used to adjust the temperature of the processing liquid to a predetermined temperature, and the first filter is used to filter the processing liquid while circulating the processing liquid within the circulation circuit. While circulating the processing liquid within the circulation circuit, a portion of the processing liquid circulating within the circulation circuit is taken out to the filtration line. The processed liquid extracted into the filtration line is cooled by a cooler, The process liquid cooled by the cooler is filtered by a second filter, The process involves returning the processed liquid filtered by the second filter from the filtration line to the circulation circuit and mixing it with the processed liquid flowing through the circulation circuit. The mixed processing liquid is supplied from the circulation line to the processing unit to perform liquid treatment on the substrate, A substrate processing method comprising the following:

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