Substrate processing method and substrate processing apparatus

Abstract

A method for treating a substrate according to one embodiment is for cleaning a substrate having a patterned Si film and for removing an oxide present on the Si film, and comprises: a cleaning step in which a cleaning fluid comprising hydrofluoric acid and water is supplied to the substrate while the substrate is being rotated, thereby removing the oxide: and a mixing step in which the cleaning fluid is mixed with an organic solvent which is miscible with water and has a lower surface tension than water. The mixing step is conducted when the cleaning step is being conducted and after the lapse of a predetermined time period from initiation of the cleaning step.

Description

[Technical Field]

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

[0002] In the manufacturing process of a semiconductor device, a cleaning process is performed to remove oxides from the surface of a Si film on which a pattern is formed. This cleaning process includes, for example, a cleaning step using DHF to remove oxides, a rinsing step using a rinsing liquid to remove the DHF used in the cleaning step and reaction products, a solvent substitution step to replace the rinsing liquid with a low surface tension solvent such as IPA, and a drying step to remove the solvent from the substrate and dry it (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 9-38595 Summary of the Invention

[0004] The present disclosure provides a technique that can suppress particles generated when cleaning a substrate having a patterned Si film.

[0005] According to one embodiment of the present disclosure, there is provided a substrate processing method for cleaning a substrate having a Si film on which a pattern is formed, the substrate processing method comprising: a cleaning step of supplying a cleaning solution containing hydrofluoric acid and water to the substrate while rotating the substrate to remove the oxide; and a mixing step of mixing an organic solvent that is miscible with water and has a surface tension lower than that of water with the cleaning solution, the mixing step being performed during the cleaning step and after a predetermined time has elapsed since the start of the cleaning step.

[0006] According to the above-described embodiment of the present disclosure, it is possible to suppress particles that are generated when cleaning a substrate having a Si film on which a pattern is formed. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic cross-sectional view of a substrate processing system according to an embodiment of the substrate processing apparatus. [Figure 2] 2 is a schematic vertical cross-sectional view showing an example of the configuration of a processing unit included in the substrate processing system of FIG. 1. FIG. [Figure 3] FIG. 1 is a diagram showing an example of the configuration of a processing liquid supply mechanism that enables one type of processing liquid selected from multiple types of processing liquid to be ejected from one nozzle alone or a mixture of two or more types of processing liquid in a processing unit. [Figure 4] 3 is a diagram showing an example of the configuration of a processing liquid supply source that supplies processing liquid to a processing liquid supply mechanism; [Figure 5A] 1A to 1C are views for explaining a first embodiment of a substrate processing method. [Figure 5B] 1A to 1C are views for explaining a first embodiment of a substrate processing method. [Figure 5C] 1A to 1C are views for explaining a first embodiment of a substrate processing method. [Figure 5D] 1A to 1C are views for explaining a first embodiment of a substrate processing method. [Figure 5E] 1A to 1C are views for explaining a first embodiment of a substrate processing method. [Figure 5F] 1A to 1C are views for explaining a first embodiment of a substrate processing method. [Figure 5G] 1A to 1C are views for explaining a first embodiment of a substrate processing method. [Figure 6A] 10A to 10C are views for explaining a second embodiment of the substrate processing method. [Figure 6B] 10A to 10C are views for explaining a second embodiment of the substrate processing method. [Figure 6C] 10A to 10C are views for explaining a second embodiment of the substrate processing method. [Figure 6D]10A to 10C are views for explaining a second embodiment of the substrate processing method. [Figure 6E] 10A to 10C are views for explaining a second embodiment of the substrate processing method. [Figure 6F] 10A to 10C are views for explaining a second embodiment of the substrate processing method. [Figure 6G] 1A to 1C are views for explaining a first embodiment of a substrate processing method. [Figure 7A] 10A to 10C are views for explaining a second embodiment of the substrate processing method. [Figure 7B] 10A to 10C are views for explaining a second embodiment of the substrate processing method. [Figure 7C] 10A to 10C are views for explaining a second embodiment of the substrate processing method. [Figure 7D] 10A to 10C are views for explaining a second embodiment of the substrate processing method. [Figure 7E] 10A to 10C are views for explaining a second embodiment of the substrate processing method. [Figure 8] FIG. 1 is a diagram for explaining the concept of the amount of IPA added in relation to surface tension. [Figure 9] 1 is a schematic cross-sectional view showing a structure of a substrate to be processed by a substrate processing method. DETAILED DESCRIPTION OF THE INVENTION

[0008] An embodiment of a substrate processing apparatus will be described with reference to the accompanying drawings.

[0009] 1 is a diagram showing a schematic configuration of a substrate processing system according to this embodiment. In the following, to clarify the positional relationship, mutually orthogonal X-axis, Y-axis, and Z-axis are defined, and the positive direction of the Z-axis is defined as the vertically upward direction.

[0010] 1, the substrate processing system 1 includes a loading / unloading station 2 and a processing station 3. The loading / unloading station 2 and the processing station 3 are provided adjacent to each other.

[0011] The loading / unloading station 2 includes a carrier placement section 11 and a transport section 12. On the carrier placement section 11, a plurality of carriers C are placed, each of which accommodates a plurality of substrates, in this embodiment, substrates W such as semiconductor wafers, in a horizontal state.

[0012] The transport section 12 is provided adjacent to the carrier placement section 11 and includes a substrate transport device 13 and a transfer section 14. The substrate transport device 13 includes a substrate holding mechanism that holds the substrate W. The substrate transport device 13 is capable of moving horizontally and vertically and rotating about a vertical axis, and transports the substrate W between the carrier C and the transfer section 14 using the substrate holding mechanism.

[0013] The processing station 3 is provided adjacent to the transport section 12. The processing station 3 includes a transport section 15 and a plurality of processing units 16. The plurality of processing units 16 are provided side by side on both sides of the transport section 15.

[0014] The transport section 15 includes a substrate transport device 17 therein. The substrate transport device 17 includes a substrate holding mechanism that holds the substrate W. The substrate transport device 17 is capable of moving horizontally and vertically and rotating about a vertical axis, and transports the substrate W between the delivery section 14 and the processing unit 16 using the substrate holding mechanism.

[0015] The processing unit 16 performs predetermined substrate processing on the substrate W transported by the substrate transport device 17 .

[0016] 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 that control 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.

[0017] Such a program may be recorded on a computer-readable storage medium and installed from that storage medium into the storage unit 19 of the control device 4. Examples of computer-readable storage media include hard disks (HDs), flexible disks (FDs), compact disks (CDs), magnetic optical disks (MOs), and memory cards.

[0018] In the substrate processing system 1 configured as described above, first, the substrate transport device 13 in the loading / unloading station 2 takes out the substrate W from the carrier C placed on the carrier placement part 11, and places the taken-out substrate W on the transfer part 14. The substrate W placed on the transfer part 14 is then taken out of the transfer part 14 by the substrate transport device 17 in the processing station 3, and carried into the processing unit 16.

[0019] The substrate W carried into the processing unit 16 is processed by the processing unit 16, and then carried out of the processing unit 16 by the substrate transport device 17 and placed on the delivery section 14. Then, the processed substrate W placed on the delivery section 14 is returned by the substrate transport device 13 to the carrier C on the carrier placement section 11.

[0020] Next, the configuration of the processing unit 16 will be described with reference to FIG.

[0021] The processing unit 16 has a chamber 20 that defines a processing space. A fan filter unit (FFU) 70 is provided on the ceiling of the chamber 20. The FFU 70 blows clean gas (e.g., clean air) downward into the chamber 20.

[0022] The processing unit 16 is provided with a spin chuck (substrate holding and rotating mechanism) 30. The spin chuck 30 has a substrate holding portion (chuck portion) 31 that holds the substrate W in a horizontal position, and a rotation drive portion 32 that rotates the substrate holding portion 31 and the substrate W held thereby about a vertical axis. In the illustrated example, the rotation drive portion 32 has an electric motor 32a and a rotation shaft 32b that connects the electric motor 32a and the substrate holding portion 31.

[0023] The substrate holding portion 31 may be a type called a mechanical chuck, which mechanically holds the peripheral portion of the substrate W using a holding member such as a gripping claw, or may be a type called a vacuum chuck, which vacuum-sucks the central portion of the back surface of the substrate W.

[0024] In this embodiment, since the processing liquid is supplied to the center of the back surface during liquid processing, a mechanical chuck-type substrate holding unit 31 is provided. The illustrated substrate holding unit 31 has a disk-shaped base 31a and a plurality of gripping claws 31b provided at intervals in the circumferential direction on the peripheral edge of the base. When the substrate holding unit 31 holds the substrate W with the gripping claws 31b, a gap is formed between the base 31a and the substrate W.

[0025] The processing unit 16 is provided with a processing fluid supply section 40 for supplying various processing fluids required for processing the substrate W to the substrate W.

[0026] The processing fluid supply unit 40 has a plurality of nozzles Ni (four nozzles are shown in FIG. 2) that discharge processing fluid toward the front surface of the substrate W. To distinguish each nozzle Ni, reference symbols N1, N2, N3, N4, ... are used as necessary. The processing fluid supply unit 40 further has at least one nozzle Nb (one in the illustrated example) that discharges processing fluid toward the center of the back surface of the substrate W. The processing fluid supply unit 40 may further have another nozzle (not shown) (which has a similar configuration to nozzle Nb) that supplies an inert gas (e.g., nitrogen gas) to the center of the back surface of the substrate W.

[0027] The nozzles Ni are carried at the tip end of one or more nozzle arms Ai (two nozzle arms are shown in FIG. 2). The nozzle arms Ai are configured so that the nozzles Ni carried by the nozzle arms Ai can be positioned at least at any position (radial position) between a position above the center of the substrate W held by the substrate holder 31 and a position above the peripheral edge of the substrate W. The nozzle arms may be of a type that can rotate about a vertical axis, or may be of a type that can move translationally along a guide rail. To distinguish between the nozzle arms Ai, natural numbers will be assigned to "i", and reference symbols A1, A2, A3, A4, ... will be used as needed.

[0028] Each nozzle Ni is supplied with a processing liquid from a corresponding processing liquid supply mechanism 40i (which forms part of the processing fluid supply unit 40). In this embodiment, the processing liquid used may be DHF (dilute hydrofluoric acid (hydrofluoric acid diluted with water)), IPA (isopropyl alcohol), DIW, or DIW with CO2 (carbon dioxide) gas dissolved therein.

[0029] The nozzle Ai ejects, as the processing liquid, any one of DHF, a mixture of DHF and IPA, DIW, and a mixture of DIW and IPA. An example of the configuration of a processing liquid supply mechanism 40i that supplies the processing liquid to the nozzle Ai is shown in FIG. 3. The processing liquid supply mechanism 40i forms a part of the processing fluid supply unit.

[0030] The processing liquid supply mechanism 40i has a first liquid circulation line 411 that forms part of a supply source 41 (processing liquid supply source) of a first liquid (here, DHF), a second liquid circulation line 421 that forms part of a supply source 42 (processing liquid supply source) of a second liquid (here, DIW), and a third liquid circulation line 431 that forms part of a supply source (processing liquid supply source) 43 of a third liquid (here, IPA). Each of the supply sources 41, 42, and 43 also forms part of the processing fluid supply unit 40. A first liquid branch line 412, a second liquid branch line 422, and a third liquid branch line 432 branch off from the first, second, and third liquid circulation lines 411, 421, and 431, respectively.

[0031] In Figure 3, the component labeled SOV is an on-off valve, the component labeled CPV is a constant pressure valve, and the component labeled FM is a flow meter. In one example, in each branch line (412, 422, 432), an electropneumatic regulator (not shown) controls the pilot pressure of the constant pressure valve CPV based on the deviation between the detected value of the flow meter FM and the target flow rate, thereby controlling the flow rate of the liquid flowing through the branch line to a desired value. By opening and closing the on-off valve SOV of each branch line and controlling the constant pressure valve CPV, one of DHF, DIW, and IPA can be discharged from the nozzle Ni as the processing liquid, either alone or in any mixture ratio of two or more of them.

[0032] For example, for a nozzle Ni that ejects either DIW or a mixture of DIW and IPA as the processing liquid, a processing liquid supply mechanism in which the components related to DHF are removed from the configuration of Figure 3 can be used. Also, for a nozzle Ni that ejects only IPA as the processing liquid, a processing liquid supply mechanism in which the components related to DHF and DIW are removed can be used. These processing liquid supply mechanisms are not shown in the figures.

[0033] An example of the configuration of the processing liquid supply source will be described with reference to FIG. 4. The processing liquid supply source includes a tank and the aforementioned circulation line 411 (or 421, 431) connected to the tank 44. The tank 44 can be supplied with raw material liquids (at least one, e.g., three, of HF, DIW, IPA, etc.) from supply sources 46A, 46B, and 46C (which are typically provided as factory utilities in a semiconductor manufacturing factory). The raw material liquids are raw materials for the processing liquid to be prepared. The circulation line 411 (or 421, 431) is equipped with a pump 45A for forming a circulating flow, a filter 45B for removing particles from the processing liquid, a temperature controller 45C for controlling the temperature of the processing liquid, and the like. When the processing liquid supplied from the processing liquid supply source is CO2 water (DIW with carbon dioxide dissolved), a carbon dioxide gas dissolving module 45D may be provided in the circulation line to dissolve carbon dioxide gas in the DIW flowing through the circulation line. In FIG. DD, the branch lines 412 (or 422, 432) can be branched at the position indicated by reference character P. Each branch line supplies a processing liquid to each processing unit 16 included in the substrate processing system.

[0034] For example, when a mixed liquid of DHF and IPA is discharged from a nozzle, HF, DIW, and IPA may be mixed in a predetermined ratio in the tank shown in Fig. 4. Alternatively, multiple types of liquids (e.g., DHF and IPA) may be mixed in the treatment liquid supply mechanism shown in Fig. 3 immediately before the treatment liquid is discharged from the nozzle.

[0035] A liquid receiving cup 50 is provided around the substrate holder to collect the processing liquid scattered from the rotating substrate W. The processing liquid collected by the liquid receiving cup 50 is discharged to the outside of the processing unit 16 from a drainage port 51 provided in the bottom of the liquid receiving cup 50. An exhaust port 52 is also provided in the bottom of the liquid receiving cup 50, and the inside of the liquid receiving cup 50 is suctioned through the exhaust port 52. Due to this suction, gas above the substrate W is drawn into the liquid receiving cup 50 from between the periphery of the substrate W and the periphery of the upper opening of the liquid receiving cup 50, flows near the periphery of the substrate W, and is then discharged from the liquid receiving cup 50 through the exhaust port 52.

[0036] Next, several embodiments of a substrate processing method will be described.

[0037] The substrate to be processed is a silicon substrate, and a large number of recesses (e.g., trenches) with a high aspect ratio are formed on the surface thereof, with an oxide film (SiOx) formed on the top surface (see FIG. 9). The substrate processing method described below removes the oxide film while preventing particles from remaining at the bottom of the recesses.

[0038] In the following description, functional water or a mixture of functional water and IPA may be used instead of DIW or a mixture of DIW and IPA as the rinsing treatment liquid. Here, "functional water" refers to DIW to which carbon dioxide gas or a trace amount of ammonia has been dissolved to impart properties not possessed by DIW, such as electrical conductivity. Such functional water is often used to prevent electrostatic damage to devices formed on the substrate W or to suppress particle adhesion by controlling the potential (zeta potential) of the substrate surface and particles. Functional water can be supplied to both the front and back surfaces of the substrate. In the embodiments described below, functional water can be, for example, DIW (also called CO2 water) with dissolved carbon dioxide gas.

[0039] [First embodiment] A first embodiment of a substrate processing method will be described below with reference to Figures 5A to 5G. In the following description, different processing liquids are ejected from the same nozzle N1, but this is possible as is clear from the previous description with reference to Figure 3. Note that the nozzle ejecting DHF and the mixture of DHF and IPA and the nozzle ejecting DIW and the mixture of DIW and IPA may be different nozzles.

[0040] <Step 1> DHF washing While the substrate W is being rotated at a rotational speed of 1500 rpm, DHF is discharged from nozzle N1 of arm A1 toward the surface of the substrate at a flow rate of, for example, 1.5 L / min or more (e.g., 2 L / min) (see FIG. 5A). The point at which the DHF lands on the substrate surface is, for example, 15 mm away from the center of rotation of the substrate W. The DHF flows and spreads toward the periphery of the substrate W due to centrifugal force, thereby covering the surface of the substrate with a liquid film of DHF. DHF is also discharged from nozzle Nb toward the center of the back surface of the substrate W at a flow rate of, for example, 1 L / min. This DHF also covers the back surface of the substrate with a liquid film of DHF. The oxide film formed on the top surface of the substrate is removed (etched) by the DHF.

[0041] Furthermore, even if the landing point of the processing liquid ejected from the nozzle N1 on the surface of the substrate W is somewhat distant from the center of rotation of the substrate, there will be no problem of liquid running out at the center of rotation of the substrate (the surface of the substrate being exposed to the atmosphere due to the liquid running out), as long as the center of rotation of the substrate W is covered by the processing liquid that spreads due to the force of the landing. If the processing liquid is ejected from the nozzle at a sufficiently high ejection flow rate, it is guaranteed that the center of rotation of the substrate W will be reliably covered by the processing liquid that spreads due to the force of the landing. This also applies to the subsequent processes.

[0042] <Step 2> DHF + IPA cleaning When the removal of the oxide film is almost completed in step 1, the process moves to step 2. The timing when the removal of the oxide film is almost completed can be determined, for example, by experiment.

[0043] In step 2, instead of DHF, a mixed liquid of DHF and IPA is supplied from nozzle N1 to the front and back surfaces of substrate W, and DHF continues to be supplied from nozzle Nb (see FIG. 5B). In other words, at this time, a mixing process is performed in which DHF and IPA are mixed in the processing liquid supply mechanism 40i for nozzle N1. The rotation speed of substrate W and the position of nozzle N1 may be the same as in step 1. The discharge flow rate of the mixed liquid from nozzle N1 may be, for example, 1 L / min. The IPA content in the mixed liquid is preferably 5 vol% or more, but here it is set to, for example, 10 vol%. This ensures that the mixed liquid reaches the bottom of the recesses of the pattern.

[0044] When a mixture of DHF and IPA is used as the processing liquid, the etch rate of the oxide film is lower than when only DHF is used as the processing liquid. In other words, if a mixture of DHF and IPA is used from the beginning, the time required to remove the oxide film increases, reducing the throughput of the device. For this reason, only DHF is used as the processing liquid at the beginning of the liquid processing. Because the oxide film to be removed is formed only on the outermost surface of the substrate W, there is no particular problem even if the processing liquid does not reach the bottom of the recess in step 1.

[0045] <Step 3> DIW + IPA rinse After performing step 2 for a predetermined time, a mixed solution of DIW (or CO2 water) and IPA is discharged from nozzle N1 as a rinse liquid onto the front surface of the substrate at a flow rate of, for example, 1.5 L / min or more, and DIW (or CO2 water) is discharged from nozzle Nb as a rinse liquid onto the back surface of the substrate at a flow rate of, for example, 1.5 L / min or more (see FIG. 5C). The rotation speed of the substrate W may be 1500 rpm, the same as in step 1. Nozzle N1 is positioned directly above the center of rotation of the substrate W so that the landing point of the mixed solution on the front surface of the substrate W coincides with the center of rotation of the substrate. The IPA content in the mixed solution is preferably 5 vol% or more, but here it is set to, for example, 10 vol%. This ensures that the mixed solution reaches the bottom of the recesses in the pattern.

[0046] In step 3, the processing liquid and reaction by-products used in steps 1 and 2 are washed off the substrate with a rinse liquid. A mixture of DIW (or CO2 water) and IPA is supplied to the surface of the substrate W as a rinse liquid, ensuring that the mixture reaches the bottom of the recesses in the pattern. This ensures that the rinse reaches the bottom of the recesses in the pattern.

[0047] <Step 4> 2-nozzle DIW rinse After executing step 3 for a predetermined time, DIW (which may be CO2 water) is discharged onto the surface of the substrate as a rinse liquid from nozzle N1 of arm A1 at a flow rate of, for example, 1.5 L / min. Simultaneously, nozzle N2 of arm A2, which was in the standby position, is moved to above the center of the substrate W, and DIW (which may be CO2 water) is also discharged onto the surface of the substrate as a rinse liquid from nozzle N2 at a flow rate of, for example, 1.5 L / min (see FIG. 5D). The standby position of the nozzle is a position outside the liquid receiving cup 50 in a plan view. At this time, the landing points of the DIW discharged from nozzles N1 and N2 on the surface of the substrate W are positioned as close to the center of rotation of the substrate W as possible without causing collision between arms A1 and A2. For example, landing point P1 of the DIW discharged from nozzle N1 is located 20 mm away from the center of rotation of the substrate W, and landing point P2 of the DIW discharged from nozzle N2 is located 25 mm away from the center of rotation of the substrate W. However, the liquid landing points P1 and P2 are on opposite sides of the center of rotation of the substrate W. The rotation speed of the substrate W may be 1500 rpm, the same as in step 1.

[0048] <Step 5> Transition from 2-nozzle DIW rinse to 1-nozzle DIW rinse Next, the nozzle N1 of the arm A1 is moved to the peripheral edge of the substrate W while still discharging DIW (which may be CO2 water), and then the discharging of DIW from the nozzle N1 is stopped and the nozzle N1 is moved to a standby position (scan-out of the nozzle N1). Once the nozzle N1 starts moving toward the peripheral edge of the substrate W, the nozzle N2 of the arm A2 is moved so that the landing point of the DIW (which may be CO2 water) from the nozzle N2 on the surface of the substrate W coincides with the center of rotation of the substrate, and the discharge flow rate of the DIW from the nozzle N2 is increased to 2.0 L / min. This transition occurs from rinsing with DIW discharged from two nozzles to rinsing with DIW discharged from a single nozzle (see FIG. 5E).

[0049] In step 5, DIW is discharged from nozzle Nb to the center of the rear surface of the substrate at a discharge flow rate of 1.0 L / min.

[0050] <Step 6> Transition from DIW rinse to IPA replacement for one nozzle After performing the single-nozzle DIW rinse in step 4 for a predetermined time, nozzle N3 of arm A1, which was in its standby position, is moved to a position directly above the center of rotation of the substrate W. Then, IPA is ejected from nozzle N3 at a flow rate of, for example, 75 mL / min. The rotation speed of the substrate W is then reduced, for example, from 1500 rpm to 1000 rpm. The IPA may be at room temperature. Just before nozzle N3 reaches a position directly above the center of rotation of the substrate W, nozzle N2 of arm A2 begins to move toward the periphery of the substrate W while continuing to eject DIW to avoid a collision between arms A1 and A2. Once nozzle N2 reaches the periphery of the substrate W, the ejection of DIW from nozzle N1 is stopped, and nozzle N2 is moved to its standby position (nozzle N2 scan-out) (see Figure 5F). After nozzle N2 scan-out begins, the rotation speed of the substrate W is reduced, for example, from 1000 rpm to 700 rpm.

[0051] <Step 7> IPA replacement By continuing to discharge IPA from the nozzle N3 of the arm A1 for a predetermined time under the conditions described in step 5, the DIW on the surface of the substrate W (including the inside of the recess) is replaced with IPA (see FIG. 5G).

[0052] <Step 8> Drying Thereafter, the IPA on the substrate W is removed to dry the substrate W. Specifically, the substrate can be dried by, for example, the following known drying method.

[0053] (Drying method 1) The discharge of IPA from nozzle N3 is stopped, and the rotation speed of the substrate W is increased to, for example, about 1500 rpm. As a result, a dry core (a region not wetted with IPA) is formed in the center of the substrate W, and this gradually spreads radially outward, thereby drying the substrate. Drying may be promoted by spraying an inert gas such as nitrogen gas into the dry core at the boundary between the dry core and the region outside the dry core that is wetted with IPA.

[0054] (Drying method 2) The substrate may be dried using a known sublimation drying technique. The procedure for sublimation drying is generally as follows: At the end of step 7, the IPA covering the surface of the substrate is replaced with a sublimable substance dissolved in a solvent. The solvent of the sublimable substance is then evaporated to solidify the sublimable substance, and the substrate is then heated to sublimate the sublimable substance.

[0055] (Drying method 3) The substrate may be dried using a known supercritical drying technique. The supercritical drying procedure is generally as follows: While continuing to eject IPA from the nozzle N3, the rotation speed of the substrate W is reduced to an extremely low speed, forming a puddle of IPA on the surface of the substrate. The substrate with the IPA puddle formed is then loaded into a supercritical drying apparatus. In the supercritical chamber of the supercritical drying apparatus, the IPA is replaced with a supercritical fluid (e.g., supercritical CO2). The supercritical chamber is then returned to room temperature and pressure, causing the supercritical CO2 to vaporize and be removed from the substrate.

[0056] [Second embodiment] A second embodiment of the substrate processing method will be described below with reference to Figures 6A to 6G. As is clear from Figures 6A to 6C (which are the same as Figures 5A to 5C), in the second embodiment, the DHF cleaning in step 1, the DHF+IPA cleaning in step 2, and the DIW+IPA rinse in step 3 are performed under the same conditions as in the first embodiment. A duplicated description of steps 1 to 3 in the second embodiment will be omitted.

[0057] After steps 1 to 3 are completed, steps 4 to 6 are performed. Steps 4 to 6 of the second embodiment differ from steps 4 to 6 of the first embodiment only in that the processing liquid discharged from nozzles N1 and N2 onto the surface of the substrate W is a mixture of DIW and IPA (see FIGS. 6D to 6F). The IPA content in the mixture used in steps 4 to 6 is preferably 5 vol% or more, but here it is set to, for example, 10 vol%. This ensures that the mixture reaches the bottom of the recesses in the pattern, allowing for more efficient removal of particle-causing substances near the bottom of the recesses.

[0058] Steps 7 (see FIG. 6G) to 8 (not shown) are performed after steps 4 to 6 are completed. Steps 7 to 8 of the second embodiment are performed under the same conditions as steps 7 to 8 of the first embodiment.

[0059] [Third embodiment] A second embodiment of the substrate processing method will be described below with reference to Figures 7A to 7E. This third embodiment differs from the first and second embodiments described above mainly in that only nozzles N1 and N3 attached to arm A1 are used.

[0060] 7A to 7C, in the third embodiment, the DHF cleaning in step 1, the DHF+IPA cleaning in step 2, and the DIW+IPA rinse in step 3 are performed under the same conditions as in the first embodiment. A duplicated description of steps 1 to 3 in the second embodiment will be omitted.

[0061] Next, step 4 is performed. In step 4 of the third embodiment, while the mixed liquid (DIW+IPA) continues to be discharged from nozzle N1 (at a discharge flow rate of, for example, 1.5 L / min), IPA is also discharged from nozzle N3 at a flow rate of, for example, about 200 mL / min (see FIG. 7D). At this time, nozzles N1 and N3 are positioned so that a liquid landing point P3 of the mixed liquid (e.g., an IPA concentration of 10 vol%) discharged from nozzle N1 on the substrate surface and a liquid landing point P4 of the IPA discharged from nozzle N3 on the substrate surface are located approximately equidistant from the center of rotation of the substrate (preferably, the liquid landing point P4 is slightly closer to the center of rotation of the substrate). The rotation speed of the substrate W may be 1500 rpm, the same as in steps 1 to 3. DIW is also discharged from nozzle Nb toward the center of the back surface of the substrate. The mixed liquid ejected from nozzle N1 and the IPA ejected from nozzle N3 are mixed on the substrate W, and the resulting mixed liquid (also referred to as the "secondary mixed liquid" for distinction (IPA concentration greater than 10 vol%)) covers the entire surface of the substrate W (including the inside of the recesses of the pattern).

[0062] After performing step 4 of the third embodiment for a predetermined time, the process proceeds to step 5. In step 5, the discharge of the mixed liquid (DIW+IPA) from nozzle N1 is stopped, and the discharge of IPA from nozzle N3 (at a discharge flow rate of approximately 200 mL / min) is continued. At this time, the landing point P5 of the IPA from nozzle N3 is aligned with the center of rotation of the substrate (see FIG. 7C). By continuing this state for a predetermined time, the entire surface of the substrate W (including the insides of the recesses of the pattern) will eventually be covered with IPA at a concentration of approximately 100%.

[0063] During the execution of step 4, the concentration of IPA contained in the mixed solution from nozzle N1 may be gradually (continuously or stepwise) increased. For example, the IPA concentration may be set to, for example, 10 vol% at the start of step 4, and increased to, for example, 35 vol% at the end of step 4, which is higher than 20 vol%. By reducing the difference in surface tension between the solution discharged from nozzle N1 and the solution discharged from nozzle N3 in this manner, splashing is reduced and exposure of the substrate surface due to the Marangoni force can be prevented. This reduces the particle level on the substrate W. The gradual increase in the concentration of IPA contained in the mixed solution from nozzle N1 may be performed before the start of step 4 (i.e., in step 3). A similar operation (gradually increasing the concentration of IPA contained in the mixed solution) may be performed during the execution of step 5 of the second embodiment (see FIG. 6E).

[0064] According to the above embodiment, the following advantageous effects can be obtained.

[0065] According to the first to third embodiments, by supplying DHF to the substrate in the initial stage of cleaning (Step 1), cleaning (etching) can be performed efficiently in a short time (e.g., a few seconds). Then, after cleaning has progressed to a certain extent, a mixture of DHF and IPA is supplied to the substrate (Step 2). Because the surface tension of the mixture (DHF+IPA) is lower than that of DHF, the processing liquid (mixture) sufficiently penetrates to the bottom of the recesses in the pattern. Although the mixture containing IPA has a slightly lower oxide etching ability than DHF without IPA, it still has the ability to dissolve dissolved oxide-derived substances, preventing such substances from adhering to the bottom of the recesses and becoming particles. Furthermore, mixing IPA into DHF can improve coverage during the cleaning (etching) process. In other words, mixing IPA reduces the surface tension of the processing liquid (DHF), thereby ensuring the maintenance of a liquid film even at the periphery of the substrate (especially on substrates with hydrophobic surfaces), which is prone to liquid starvation. This allows for highly uniform cleaning from the center to the periphery of the substrate. Furthermore, it is possible to prevent the generation of particles due to exposure of the peripheral edge of the substrate to the atmosphere.

[0066] We will provide additional explanation on the above points.

[0067] <About surface tension> Please refer to Figure 8. The extent to which the surface tension of the processing liquid should be reduced can be calculated based on the following Young's equation. cosθ=(γ S -γ SL ) / γ L θ: Contact angle (deg) gamma S : Surface tension of solid (mN / m) gamma SL : Surface tension of solid-liquid interface (mN / m) gamma L : Surface tension of the liquid (mN / m) "Good wetting" means that the contact angle θ = 0. When the liquid expands dynamically, θ=0, and the wettability S is S=γ S -(γ L +γ SL ) When S≧0, it can be said that the surface is easily wetted. In other words, gamma S ≧γ L +γ SL When this condition holds, the liquid will spontaneously wet the solid surface. In the above equation, γ when the left and right sides are balanced L is defined as the critical surface tension (γc) of the solid (γc can be determined from the Zisman plot). For relatively low surface tension, γ C =γ S It may be treated as such. In other words, the minimum requirements for good wetting are gamma C (=γ S )>γ L Surface tension γ of silicon surface (surface from which oxide has been removed) S is known to be 51.5 mN / m, so the surface tension of the liquid, γ L should be reduced to a value sufficiently smaller than this, for example, at least about 50 mN / m or less. Note that what is described in this paragraph is a basic concept, and the required surface tension γ L can be determined experimentally.

[0068] According to the literature, the surface tension of water without IPA (DIW) is approximately 72 mN / m, that of water with 5 vol% IPA is approximately 48 mN / m, that of water with 10 vol% IPA is approximately 40 mN / m, and that of water with 15 vol% IPA is approximately 35 mN / m, decreasing in a reciprocal curve. While the surface tension of HF is slightly lower than that of DIW, the surface tension of DHF containing approximately 10 vol% HF is thought to be not much different from that of DIW, and the relationship between the IPA concentration and surface tension in a DHF+IPA mixture is thought to be not much different from the relationship between the IPA concentration and surface tension in a DIW+IPA mixture.

[0069] As described above, since the surface tension of water with an IPA content of 5 vol% is about 48 mN / m, if the mixture (DIW + IPA or DHF + IPA) contains 5 vol% or more of IPA, the mixture will spontaneously spread on the solid surface. That is, the mixture can sufficiently enter into the concave portions of the pattern with a high aspect ratio. Incidentally, when tests were conducted, it was confirmed that by adding 5 vol% of IPA to the treatment liquid (DHF, DIW), the particles were significantly reduced.

[0070] <Regarding the etching rate> According to the tests conducted by the inventor, regarding the etching rate of the oxide film at room temperature, when the case of DHF (without IPA) is about 300 Å / min, it is about 260 Å / min with an IPA content of 5 vol%, about 220 - 230 Å / min with an IPA content of 10 vol%, and about 180 - 190 Å / min with an IPA content of 15 vol%. It has been confirmed that it generally decreases linearly as the IPA content increases. That is, even if about 5 - 10 vol% of IPA is added to DHF, although the etching rate somewhat decreases, the etching ability is not lost. Therefore, in the first to third embodiments, the transition from step 1 to step 2 may be performed at the timing when the oxide is generally removed. That is, as long as the transition from step 1 to step 2 is not performed at an extremely early timing, there is no fear that the processing time (required etching time) will increase at a problematic level.

[0071] <Other effects due to IPA addition> Adding IPA reduces the dielectric constant of water. Therefore, in DHF for example, the deviation of HF is suppressed and the ion amount decreases. As a result, the charging of the Si surface and the fine particles (particle causative substances) in the liquid is suppressed. In an acidic liquid, the sign of the zeta potential of the fine particles (both organic and inorganic substances) on the Si surface and in the liquid becomes reversed, and an attractive force acts between them. However, as described above, the amount of charge decreases due to the addition of IPA, making it difficult for the fine particles to adhere to the Si surface. From this point as well, the amount of particles can be reduced. The same can be said for the vicinity of the bottom of the concave portion of the pattern. Incidentally, the decrease in the etching rate due to the addition of IPA described above can also be explained by the suppression of the deviation of HF in DHF due to the addition of IPA.

[0072] <Effect of rinsing with DIW+IPA mixed solution> Also, according to the above-described first to third embodiments, the rinsing liquid used in the rinse (step 3) performed after cleaning (etching) is a mixed solution of DIW (CO2 water may also be used) and IPA. Therefore, the rinsing liquid sufficiently enters up to the bottom of the concave portion of the pattern, and the concave portion is sufficiently rinsed. Therefore, it is possible to further prevent the adhesion of particle causative substances to the bottom of the concave portion. Also, similar to the cleaning (etching) treatment with the mixed solution (DHF+IPA), since the surface tension of the rinsing liquid decreases, it is possible to surely maintain a liquid film even at the peripheral portion of a substrate where liquid dripping is likely to occur (especially a substrate having a hydrophobic surface). Therefore, it is possible to perform a highly uniform rinsing process from the central portion to the peripheral portion of the substrate. Also, it is possible to prevent the generation of particles due to the exposure of the substrate peripheral portion to the atmosphere.

[0073] Also, according to the above-described second and third embodiments, the processing liquid used in all the steps after step 3 contains IPA. Therefore, in all the steps, the processing liquid can be more surely put into the bottom of the concave portion.

[0074] The particle increment was investigated by processing substrates with different amounts of IPA added. In steps 1 and 2, when no IPA was added to DHF or DIW, the particle increment was approximately 156 (19 nm / Adder Particle Counts), when 5 vol% IPA was added, the particle increment was approximately 117, when 10 vol% IPA was added, the particle increment was approximately 101, and when 15 vol% IPA was added, the particle increment was approximately 78. Furthermore, when IPA was added to the DIW supplied to the substrate surface from step 3 onwards, the particle increment was further reduced to approximately half.

[0075] In the above first to third embodiments, step 1 and step 2 may be executed alternately multiple times.

[0076] In the first to third embodiments, the chemical liquid (cleaning liquid or etching liquid) used in steps 1 and 2 is not limited to HF (DHF), but may be another chemical liquid containing hydrofluoric acid and water, such as a mixed aqueous solution of HF (hydrofluoric acid) and HNO3 (nitric acid), DSP (a mixed aqueous solution of H2SO4 (sulfuric acid), H2O2 (hydrogen peroxide) and HF), BHF ((buffered hydrofluoric acid) a mixed aqueous solution of HF and NHF), FPM (a mixed aqueous solution of HF and H2O2), etc.

[0077] In the first to third embodiments, ethanol or ethyl lactate may be used instead of IPA. Like IPA, ethanol and ethyl lactate are miscible with water and have significantly lower surface tension and dielectric constant than water. Therefore, the same effect as that achieved by adding IPA can be obtained.

[0078] In the above embodiment, multiple types of processing liquids are mixed together and then discharged from nozzle Ni (i.e., after a mixing step is performed before discharge from the nozzle). However, this is not limiting, and multiple types of processing liquids may be discharged from multiple nozzles Ni onto the substrate and then mixed on the substrate (performing a mixing step after discharge). Specifically, for example, instead of discharging a mixture of DHF and IPA from one nozzle Ni in step 2, DHF may be supplied from a first nozzle Ni and IPA may be supplied from a second nozzle Ni to the central portion of the substrate, respectively, and DHF and IPA may be mixed on the substrate. In this case, DHF may be supplied from the first nozzle Ni to the central portion of the rotating substrate W (corresponding to step 1), and then IPA may be supplied from the second nozzle Ni to the central portion of the substrate W while DHF continues to be supplied from the first nozzle Ni to the central portion of the substrate W (corresponding to step 2).

[0079] In the above embodiment, the liquid supplied from the nozzle Nb to the center of the rear surface of the substrate does not contain IPA, but it may contain IPA.

[0080] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive, and the above-described embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims.

[0081] The substrate is not limited to a semiconductor wafer, but may be any other type of substrate used in the manufacture of semiconductor devices, such as a glass substrate or a ceramic substrate.

Claims

1. 1. A substrate processing method for cleaning a substrate having a patterned Si film, the method comprising the steps of: a cleaning step of supplying a cleaning solution containing hydrofluoric acid and water to the substrate while rotating the substrate to remove the oxide; a mixing step of mixing an organic solvent that is miscible with water and has a surface tension lower than that of water with the cleaning liquid; Equipped with The substrate processing method, wherein the mixing step is performed during the cleaning step and after a predetermined time has elapsed since the start of the cleaning step.

2. The cleaning solution containing hydrofluoric acid is discharged from a first nozzle onto the rotating substrate, 2. The substrate processing method according to claim 1, wherein the mixing step is a step of mixing the organic solvent into the cleaning liquid before the cleaning liquid is discharged onto the substrate from the first nozzle.

3. The cleaning solution containing hydrofluoric acid is discharged from a first nozzle onto the rotating substrate, 2. The substrate processing method according to claim 1, wherein the mixing step is a step of discharging the organic solvent onto the substrate from a second nozzle different from the first nozzle, and mixing the cleaning liquid and the organic solvent on the substrate.

4. a rinsing step of supplying a rinsing liquid made of water or functional water to the substrate while rotating the substrate after the cleaning step to rinse the surface of the substrate, 2. The substrate processing method according to claim 1, wherein an organic solvent that is miscible with water and has a surface tension lower than that of water is mixed into the rinse liquid during at least a part of the rinsing step.

5. a rinsing step of supplying a rinsing liquid made of water or functional water to the substrate while rotating the substrate after the cleaning step to rinse the surface of the substrate, 3. The substrate processing method according to claim 2, wherein an organic solvent that is miscible with water and has a surface tension lower than that of water is mixed into the rinse liquid during at least a part of the rinsing step.

6. a rinsing step of supplying a rinsing liquid made of water or functional water to the substrate while rotating the substrate after the cleaning step to rinse the surface of the substrate, 4. The substrate processing method according to claim 3, wherein an organic solvent that is miscible with water and has a surface tension lower than that of water is mixed into the rinse liquid during at least a part of the rinsing step.

7. an organic solvent replacement step of, after the rinsing step, supplying the organic solvent to the substrate while rotating the substrate, and replacing the rinsing liquid on the substrate with the supplied organic solvent; 5. The substrate processing method according to claim 4, wherein the concentration of the organic solvent contained in the rinse liquid on the substrate is changed so that the concentration reaches a maximum at the end of the rinse step.

8. 5. The substrate processing method according to claim 4, wherein functional water obtained by dissolving carbon dioxide in pure water is used as the rinse liquid in the rinsing step.

9. 8. The substrate processing method according to claim 7, wherein functional water in which carbon dioxide is dissolved in pure water is used as the rinse liquid in the rinsing step.

10. 2. The substrate processing method according to claim 1, wherein the organic solvent mixed in the cleaning liquid is isopropyl alcohol, ethanol, or ethyl lactate.

11. 5. The substrate processing method according to claim 4, wherein the organic solvent mixed in the rinse liquid is isopropyl alcohol, ethanol, or ethyl lactate.

12. A substrate processing apparatus, a substrate holding and rotating mechanism that holds and rotates the substrate; a processing liquid supply unit that supplies a plurality of types of processing liquid to the substrate being rotated by the substrate holding and rotating mechanism, the plurality of types of processing liquid including at least a cleaning liquid containing hydrofluoric acid and water, a rinse liquid, and an organic solvent that is miscible with water and has a surface tension lower than that of water; a control unit that controls operations of at least the substrate holding and rotating mechanism and the processing liquid supply unit to cause the substrate processing apparatus to perform the substrate processing method according to any one of claims 1 to 11; A substrate processing apparatus comprising:

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