Substrate processing method and substrate processing device

Abstract

[Problem] The problem of this invention is to prevent particle generation while reducing the amount of low surface tension liquid used. [Solution] A substrate processing method includes: a first processing step of supplying a first processing liquid to a rotating substrate surface and covering the substrate surface with a liquid film of the first processing liquid; and a second processing step of supplying a second processing liquid with a surface tension less than that of the first processing liquid to the substrate surface after the first processing step, and replacing the first processing liquid on the substrate surface with the second processing liquid; the second processing step includes: a first stage in which the first processing liquid is further supplied to the substrate surface simultaneously in addition to the second processing liquid; and a second stage in which the first processing liquid is not supplied after the first stage, and the second processing liquid is supplied to the center of the substrate surface; during at least a first period of the first stage, while maintaining the condition that the distance from the center of rotation of the substrate to the attachment point of the first processing liquid, i.e., a first radial distance, is greater than the distance to the attachment point of the second processing liquid, i.e., a second radial distance, on the substrate surface, both the first and second radial distances gradually increase.

Description

[Technical Field]

[0001] The present invention relates to a substrate processing method and a substrate processing apparatus. [Previous Technology]

[0002] In the manufacture of semiconductor devices, while a substrate is held horizontally and rotated around a vertical axis using a rotary chuck, various processing liquids are supplied to the substrate to apply a predetermined liquid treatment. Patent Document 1 describes the following regarding the transition from a cleaning process to a displacement process: In the latter half of the cleaning process, cleaning liquid is supplied to both the center and outer periphery of the substrate. Then, cleaning liquid continues to be supplied to the outer periphery of the substrate, while the supply of cleaning liquid to the center of the substrate is stopped. Simultaneously, IPA (isopropyl alcohol) is supplied to the center of the substrate. Then, while IPA continues to be supplied to the center of the substrate, the supply of cleaning liquid to the outer periphery of the substrate is stopped. [Prior Art Documents]

[0003] [Patent Document 1] Japanese Patent No. 6118758 [Summary of the Invention]

[0004] [The problem that the invention is intended to solve]

[0005] This invention provides a technique to prevent the generation of defects such as particles, while simultaneously reducing the amount of low surface tension liquid used. [Means for Solving the Problem]

[0006] One embodiment of the present invention provides a substrate processing method, comprising: a first processing step of supplying a first processing liquid to the surface of a rotating substrate, thereby covering the surface of the substrate with a liquid film of the first processing liquid; and a second processing step of, after the first processing step, supplying a second processing liquid with a surface tension less than that of the first processing liquid to the surface of the rotating substrate, thereby replacing the first processing liquid on the substrate with the second processing liquid, thereby covering the surface of the substrate with a liquid film of the second processing liquid; the second processing step includes: a first stage of removing... In addition to the second processing liquid, the first processing liquid is simultaneously supplied; and in the second stage, after the first stage, the first processing liquid is not supplied, but the second processing liquid is supplied to the center of the surface of the rotating substrate; during at least a first period of the first stage, while maintaining the condition that the distance from the center of rotation of the substrate to the attachment point of the first processing liquid, i.e., the first radial distance, is greater than the distance from the center of rotation of the substrate to the attachment point of the second processing liquid, i.e., the second radial distance, both the first radial distance and the second radial distance are gradually increased. [Effects of the Invention]

[0007] According to the present invention, the generation of defects such as particles can be prevented, while the amount of low surface tension liquid used can be reduced.

Implementation Method

[0009] Referring to the accompanying drawings, one embodiment of the substrate processing apparatus will be described.

[0010] Figure 1 is a schematic diagram showing the general configuration of the substrate processing system according to this embodiment. In the following description, in order to clarify the positional relationship, the X-axis, Y-axis and Z-axis that are perpendicular to each other are defined, and the positive direction of the Z-axis is the vertical upward direction.

[0011] As shown in Figure 1, the substrate processing system 1 includes an infeed / outfeed station 2 and a processing station 3. The infeed / outfeed station 2 and the processing station 3 are arranged adjacent to each other.

[0012] The infeed / outfeed station 2 includes a carrier placement section 11 and a conveying section 12. A plurality of carriers C are placed on the carrier placement section 11, and the carriers C hold a plurality of substrates W in a horizontal position. In this embodiment, semiconductor wafers are held in a horizontal position.

[0013] The transport unit 12 is provided adjacent to the carrier placement unit 11, and includes a substrate transport device 13 and a transfer unit 14 inside. The substrate transport device 13 has a wafer holding mechanism for holding the substrate W. Furthermore, the substrate transport device 13 can move in both the horizontal and vertical directions, can rotate around the vertical axis, and uses the wafer holding mechanism to transport the substrate W between the carrier C and the transfer unit 14.

[0014] The processing station 3 is installed adjacent to the conveying section 12. The processing station 3 includes the conveying section 15 and a plurality of processing units 16. The plurality of processing units 16 are arranged side by side on both sides of the conveying section 15.

[0015] The transfer unit 15 is equipped with a substrate transfer device 17. The substrate transfer device 17 is equipped with a wafer holding mechanism for holding the substrate W. Furthermore, the substrate transfer device 17 can move in the horizontal and vertical directions, can rotate around the vertical axis, and uses the wafer holding mechanism to transfer the substrate W between the transfer unit 14 and the processing unit 16.

[0016] The processing unit 16 performs a predetermined substrate processing on the substrate W transported by the substrate transport device 17.

[0017] Furthermore, the substrate processing system 1 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 a program that controls various processes performed in the substrate processing system 1. The control unit 18 reads and executes the program stored in the storage unit 19 to control the operation of the substrate processing system 1.

[0018] Furthermore, this program may be stored on a computer-readable storage medium, or it may be installed from that storage medium into the storage unit 19 of the control device 4. Examples of computer-readable storage media include hard disks (HD), floppy disks (FD), optical discs (CD), magneto-optical discs (MO), and memory cards.

[0019] In the substrate processing system 1 configured as described above, firstly, the substrate transport device 13 of the delivery station 2 takes out the substrate W from the carrier C placed in the carrier placement section 11 and places the taken-out substrate W in the transfer section 14. The substrate W placed in the transfer section 14 is taken out from the transfer section 14 by the substrate transport device 17 of the processing station 3 and sent to the processing unit 16.

[0020] The substrate W, which is fed into the processing unit 16, is processed by the processing unit 16 and then sent out from the processing unit 16 by the substrate transfer device 17 and placed in the transfer unit 14. Then, the processed substrate W, which is placed in the transfer unit 14, is sent back to the carrier C of the carrier placement unit 11 by the substrate transfer device 13.

[0021] Next, with reference to FIG2, the configuration of the processing unit 16 will be described.

[0022] As shown in FIG2, the processing unit 16 includes: a chamber 20, a substrate holding and rotating mechanism 30, a processing fluid supply unit 40, and a liquid collection cup 60.

[0023] The chamber 20 houses: a substrate holding and rotating mechanism 30, a processing fluid supply unit 40, and a liquid collection cup 60. A fan filter unit (FFU) 21 is installed on the top of the chamber 20. The FFU 21 forms a downward flow within the chamber 20.

[0024] The substrate holding and rotating mechanism 30 includes: a substrate holding portion (suction cup portion) 31 for holding the substrate W in a horizontal position; and a rotation drive portion 32 for rotating the substrate holding portion 31 holding the substrate W about a vertical axis. The substrate holding portion 31 may be in the form of a mechanical chuck that holds the periphery of the substrate W with gripping claws, or it may be in the form of a vacuum suction cup that vacuum-adsorbs the back side of the substrate W. The rotation drive portion 32 is equipped with an electric motor as a driving force generation source, which can rotate the substrate holding portion 31 at any speed.

[0025] The processing fluid supply unit 40 includes: a plurality of processing fluid nozzles and one or more nozzle arms. In the illustrated embodiment, the plurality of processing fluid nozzles includes at least: a chemical liquid / cleaning nozzle 41, a drying liquid nozzle 42, a cleaning nozzle 43, and a gas nozzle 44. The chemical liquid / cleaning nozzle 41 selectively sprays DHF (dilute hydrofluoric acid) as an acidic chemical liquid and DIW (pure water) as a cleaning liquid. The drying liquid nozzle 42 sprays a liquid with the following characteristics (e.g., miscibility), such as IPA (isopropanol): its surface tension is lower than that of the cleaning liquid, its volatility is preferably higher than that of the cleaning liquid, and it is preferably easily displaced by the cleaning liquid. The cleaning nozzle 43 sprays DIW as a cleaning liquid. The gas nozzle 44 sprays a gas with low humidity and low oxygen concentration, such as nitrogen or other drying gases. As a cleaning liquid, in addition to DIW, functional water formed by dissolving trace amounts of electrolyte components in DIW can also be used.

[0026] Each processing fluid nozzle is supplied with processing fluid by a processing fluid supply mechanism (shown schematically as a double circle in Figure 2). The processing fluid supply mechanism, as is well known in the art, may consist of a processing fluid supply source such as a tank or plant facility, a supply line supplying processing fluid from the processing fluid supply source to the processing fluid nozzles, flow regulating devices such as flow meters, on / off valves, and flow control valves installed on the supply line, and auxiliary appliances such as filters and heaters. Each processing fluid supply mechanism can control the shut-off of the discharge of processing fluid to the corresponding processing fluid nozzle and the discharge flow rate of the processing fluid to the corresponding processing fluid nozzle.

[0027] The chemical liquid / cleaning nozzle 41 is connected to a chemical liquid supply mechanism and a cleaning liquid supply mechanism, which serve as a process fluid supply mechanism, thereby allowing the chemical liquid (DHF) or cleaning liquid (DIW) to be selectively sprayed from the chemical liquid / cleaning nozzle 41.

[0028] In the illustrated embodiment, the processing fluid supply unit 40, as one or more nozzle arms, has two nozzle arms, namely a first nozzle arm 51 and a second nozzle arm 52. In the illustrated embodiment, the first nozzle arm 51 and the second nozzle arm 52 swing about a vertically extending axis of rotation via arm drive mechanisms 53 and 54 provided at their respective base ends. A chemical liquid / cleaning nozzle 41 and a drying liquid nozzle 42 are held at the front end of the first nozzle arm 51. A cleaning nozzle 43 and a gas nozzle 44 are held at the front end of the second arm 52.

[0029] In the illustrated embodiment, the leading ends of the first nozzle arm 51 and the second nozzle arm 52 (i.e., the processing fluid nozzles (41-44) held here) can be traced in roughly the same arc-shaped trajectory when viewed from above. In the illustrated embodiment, the trajectories of the leading ends of the two nozzle arms 51 and 52 both pass directly above the rotation center Wc of the substrate W. In the illustrated embodiment, since the rotation centers (positions of 53 and 54) of the two nozzle arms 51 and 52 are slightly different, the movement trajectories of the leading ends of the two nozzle arms 51 and 52 are not completely consistent, but it is acceptable to consider them to be roughly the same. Furthermore, although the arrangement of the first nozzle arm 51 and the second nozzle arm 52 in FIG2 is different from that in FIG3, this difference is due to the emphasis on the ease of observation of the diagram, and the arrangement in FIG3 is correct.

[0030] The processing unit 16 may further include other nozzle arms. The nozzle arms are not limited to the rotary arm type shown in the figure, but may also be linear motion type that moves along the guide rail. In the case of providing two rotary arm type nozzle arms, two nozzle arms may be provided so that when viewed from above, the front ends of the two nozzle arms trace a point-symmetric movement trajectory relative to the rotation center Wc of the substrate W.

[0031] The liquid collection cup 60 is provided to surround the substrate holding part 31 and collects the processing liquid that splashes from the rotating substrate W. The processing liquid collected by the liquid collection cup 60 is discharged to the outside of the processing unit 16 through the liquid discharge port 61 provided at the bottom of the liquid collection cup 60. At the bottom of the liquid collection cup 60, an exhaust port 62 is provided to draw the liquid inside the liquid collection cup 60.

[0032] Next, a series of steps for liquid processing performed by the processing unit 16 will be described. The following steps are performed under the control of the control device 4. In one embodiment, the process recipe and control program are stored in the storage section 19 of the control device 4. The control device 4 executes the control program to control the operation of each component of the processing unit 16, thereby performing the steps described later.

[0033] In the illustrated embodiment, the nozzles (41-43) for spraying the processing liquid are mounted on the arms 51 and 52 in a manner that sprays the processing liquid directly downwards. Therefore, in the following description, the position of each nozzle (41-43) itself (specifically, the position of the nozzle outlet) and the position of the "attachment point" where the processing liquid sprayed from each nozzle (41-43) reaches the surface of the substrate W refer to the same position. Furthermore, the nozzle for supplying processing gas sprays processing gas obliquely downwards (towards the periphery of the substrate W).

[0034] In the following description, the term "attachment point" refers to the intersection of the center (central axis of the cylinder) of the liquid (liquid column) ejected cylindrically from the nozzles (41-43) and the surface of the substrate W. When the nozzle ejects liquid directly downwards, the position of the nozzle (strictly speaking, the position of the central axis of the nozzle outlet) is the same as the position of the attachment point (in the horizontal direction other than the height direction). Furthermore, the liquid ejected cylindrically from the nozzle spreads across the surface of the substrate W in an impact manner the instant it adheres to the surface of the substrate W. Therefore, even if the attachment point of the liquid ejected from the nozzle is located slightly radially outward from the rotation center Wc of the substrate W, the liquid will still cover the rotation center Wc of the substrate W due to the impact manner as described above. That is, in this case, the liquid ejected from the nozzle will also supply liquid to the center of the substrate (including the area near the rotation center Wc of the substrate).

[0035] For ease of explanation, to define the position of the nozzle itself and the position of the attachment point, the surface of the substrate W is divided into two regions, I and II. As shown in Figure 3, region I is defined as the area closer to the first nozzle arm 51 than the normal N on the rotation center Wc of the nozzle movement trajectory (shown by two arc-shaped arrows) when viewed from above, and region II is defined as the area closer to the second nozzle arm 52 than the normal N when viewed from above. The position of the nozzle (position of the attachment point) is represented by the R value. When the position of the nozzle (position of the attachment point) is in region I, the R value is represented by the radial distance from the rotation center Wc of the substrate W × (+1). When the position of the nozzle (position of the attachment point) is in region II, the R value is represented by the radial distance from the rotation center Wc of the substrate W × (-1).

[0036] From the beginning to the end of the following series of steps, the substrate W continues to rotate without stopping. The rotation speed of the substrate W varies as needed.

[0037] [Chemical Solution Treatment Step] First, DHF, the chemical solution / cleaning nozzle 41 held on the first nozzle arm 51, is sprayed at a predetermined flow rate to adhere to the rotation center Wc (R = 0 mm) of the rotating substrate W. The DHF adhering to the center of the substrate W flows outwards from the periphery of the substrate W due to centrifugal force, so that the entire surface of the substrate W is covered with a DHF liquid film. By maintaining this state for a predetermined time, the surface of the substrate W is treated with the chemical solution.

[0038] [Cleaning Step] Next, the liquid sprayed from the chemical liquid / cleaning nozzle 41 is switched from DHF to DIW. That is, DIW as a cleaning liquid is sprayed from the chemical liquid / cleaning nozzle 41 at a predetermined flow rate so that the DIW adheres to the center of the substrate W.

[0039] Next, while maintaining the attachment point of DHF from the chemical liquid / cleaning nozzle 41 at the rotation center Wc (R=0mm), DIW is also sprayed from the cleaning nozzle 43 held by the second nozzle arm 52 in such a way that DIW is attached to a position slightly away from the rotation center Wc (e.g., R=-42mm).

[0040] DIW continues to be sprayed from the chemical liquid / cleaning nozzle 41 and the cleaning nozzle 43, while simultaneously moving the first nozzle arm 51 and the second nozzle arm 52 to move the attachment point of the DIW from the chemical liquid / cleaning nozzle 41 to a position slightly away from the rotation center Wc (e.g., R = +42 mm), and simultaneously moving the attachment point of the DIW from the cleaning nozzle 43 to the rotation center Wc (R = 0 mm). Thereafter, spraying DIW from the chemical liquid / cleaning nozzle 41 is stopped.

[0041] Furthermore, when DIW is sprayed simultaneously from both the chemical liquid / cleaning nozzle 41 and the cleaning nozzle 43, the spray flow rate of each nozzle is preferably less than the spray flow rate of each nozzle when DIW is sprayed from only one of the chemical liquid / cleaning nozzle 41 and the cleaning nozzle 43. If the two nozzles are brought close together and liquid is supplied to the surface of the substrate W at a larger flow rate at the same time, there is a risk of liquid splashing due to mutual interference between the liquids.

[0042] In the above cleaning step, the DIW adhering to the center (or near the center) of the substrate W flows outwards from the periphery of the substrate W due to centrifugal force, so that the entire surface of the substrate W is covered by the DIW liquid film. Along with this, the DHF and reaction products remaining on the surface of the substrate W are washed away by the DIW.

[0043] Furthermore, in the above embodiment, during the cleaning step, the nozzle for spraying the cleaning fluid is changed from the chemical liquid / cleaning nozzle 41 to the cleaning nozzle 43. The reason for this is that the chemical liquid / cleaning nozzle 41 and the drying liquid nozzle 42 are held by the same nozzle arm. For example, if the drying liquid nozzle 42 is held by another nozzle arm (e.g., a third nozzle arm), then the above change operation is not necessary, and it is fine if only the chemical liquid / cleaning nozzle 41 is used to spray the cleaning fluid.

[0044] [IPA Replacement Step] Next, the IPA replacement step for replacing the DIW on the surface of the substrate W (including the recesses of the pattern) with IPA will be described. The IPA replacement step will also be described with reference to Figures 4 and 5.

[0045] Figure 4 shows the movement of the drying liquid nozzle 42 (held by the first nozzle arm 51) and the cleaning nozzle 43 (held by the second nozzle arm 52) as observed from the direction of arrow A in Figure 3. The left side of Figure 4 corresponds to region I (positive R value), and the right side of Figure 4 corresponds to region II (negative R value). In Figure 4, nozzles other than nozzles 42 and 43 are not shown for the sake of simplicity.

[0046] In the graph of Figure 5, the upper section shows the rotational speed of the substrate W, the middle section shows the flow rate of IPA from the drying liquid nozzle 42 (thin solid line) and the flow rate of DIW from the cleaning nozzle 43 (thick solid line), and the lower section shows the distance (thin solid line) from the center of rotation Wc of the attachment point of IPA from the drying liquid nozzle 42 on the surface of the substrate W of the substrate W of the attachment point of DIW from the center of rotation Wc of the substrate W of the attachment point of the cleaning nozzle 43 (thick solid line). In the lower section, the absolute value of the aforementioned R value is shown (regardless of whether the attachment point of the liquid from the nozzles 42 and 43 is located in region I or II). In the graph of Figure 5, the horizontal axis represents the elapsed time from the start time of the IPA replacement step, in seconds.

[0047] When the cleaning nozzle 43 sprays DIW towards the rotation center Wc of the substrate W for a predetermined time, and the cleaning step ends, the drying liquid nozzle 42 is brought closer to the cleaning nozzle 43 while maintaining the position of the cleaning nozzle 43 and the DIW spraying state. At this time, the R value of the drying liquid nozzle 42 is, for example, -42 mm, and the R value of the cleaning nozzle 43 is 0 mm. Furthermore, from the later stage of the cleaning step until this time point, DIW is continuously sprayed from the cleaning nozzle 43 at a large spray flow rate (for example, 1500 ml / min) (refer to Figure 4(A) and Figure 5, where the elapsed time is 0 seconds). During the later stage of the cleaning step, while DIW is being sprayed from the cleaning nozzle 43, it is acceptable to bring the drying liquid nozzle 42 closer to the cleaning nozzle 43.

[0048] Next, the drying liquid nozzle 42 and the cleaning nozzle 43 are moved simultaneously (preferably at the same moving speed, for example, about 22 mm / sec) in the negative direction, so that the drying liquid nozzle 42 is moved directly above the rotation center of the substrate W (the position with R value of 0 mm), and the cleaning nozzle 43 is moved to a position slightly away from the rotation center of the substrate W (for example, the position with R value of -43 mm) (refer to Figures 4 (B), (C) and 5 for a period of 0 seconds to 2 seconds).

[0049] During this movement, when the distance from the attachment point of the IPA from the drying liquid nozzle 42 to the rotation center Wc and the distance from the attachment point of the DIW from the cleaning nozzle 43 to the rotation center Wc become approximately equal (for example, when the R value of the attachment point of the IPA is +22mm and the R value of the attachment point of the DIW is -20mm), the DIW spray flow rate from the cleaning nozzle 43 decreases from the first DIW spray flow rate (for example, 1500ml / min) to a second DIW spray flow rate (for example, 1000ml / min) which is less than the first DIW spray flow rate, and IPA begins to be sprayed from the drying liquid nozzle 42 at the first IPA spray flow rate (for example, 30ml / min) (refer to the time points in Figures 4(B) and 5 where the elapsed time is 1 second).

[0050] That is, at a time interval of 1 second, the first stage of the IPA replacement step of supplying both IPA and DIW to the substrate W begins. At this time, since IPA is sprayed before the drying liquid nozzle 42 reaches directly above the rotation center Wc of the substrate, it can more reliably prevent the absence of liquid in the area near the rotation center of the substrate W. This effect is advantageous compared to the situation where IPA is not sprayed from the time the cleaning nozzle 43 leaves the position directly above the rotation center Wc of the substrate until the drying liquid nozzle 42 reaches directly above the rotation center Wc of the substrate.

[0051] When the attachment point of the IPA from the drying liquid nozzle 42 is aligned with the rotation center Wc, and the attachment point of the DIW from the cleaning nozzle 43 reaches a position slightly away from the rotation center Wc (e.g., a position with an R value of -42mm), the cleaning nozzle 43 continues to move in the negative direction, while the drying liquid nozzle 42 moves in the opposite direction in the positive direction (refer to the time points of 2 seconds in Figures 4(C) and 5). That is, the cleaning nozzle 43 and the drying liquid nozzle 42 move in opposite directions. Furthermore, while the drying liquid nozzle 42 begins to move from the rotation center Wc towards the periphery in the positive direction, or approximately simultaneously, the rotational speed of the substrate W is reduced (1000rpm → 700rpm). By reducing the rotational speed of the substrate W, the time at which the drying area begins to form near the rotation center Wc on the surface of the substrate W is delayed.

[0052] At this time, the cleaning nozzle 43 and the drying nozzle 42 are moved in opposite directions in such a way that the absolute value of the distance (R value) from the attachment point of the DIW from the cleaning nozzle 43 from the rotation center Wc is always greater than the absolute value of the distance (R value) from the attachment point of the IPA from the drying fluid nozzle 42 from the rotation center Wc. (Refer to Figure 4 (C) to (E) and the lower part of Figure 5 for a period of 2 to 5.3 seconds).

[0053] Furthermore, as shown in the lower part of Figure 4, the moving speed of the cleaning nozzle 43 and the moving speed of the drying liquid nozzle 42 are kept the same, so that the difference between the absolute R value of the DIW attachment point and the absolute R value of the IPA attachment point is kept constant. In this case, the moving speeds of the cleaning nozzle 43 and the drying liquid nozzle 42 can be set in, for example, the range of 20 to 50 mm / sec. Also, while the difference between the absolute R value of the DIW attachment point and the absolute R value of the IPA attachment point also depends on the spray flow rates of the DIW and IPA, it is preferably within the range of approximately 40 mm to 90 mm. If the difference is too large, the liquid splash prevention effect described later may decrease. Furthermore, if the difference is too small, liquid splashing may occur due to collision between the attached DIW and the attached IPA.

[0054] When the cleaning nozzle 43 reaches a position near the periphery of the substrate W (e.g., a position where the R value of the DIW attachment point is -140mm) (see Figure 4(E)), the movement of the cleaning nozzle 43 is stopped, and the ejection of DIW from the cleaning nozzle 43 also stops. At the same time or approximately simultaneously, while continuing to eject IPA from the drying liquid nozzle 42, the drying liquid nozzle 42 is moved to a position directly above the rotation center Wc (R = 0mm). Also, at the same time or approximately simultaneously, when the drying liquid nozzle 42 reaches the position directly above the rotation center Wc, the ejection flow rate of IPA from the drying liquid nozzle 42 is increased to a second ejection flow rate (e.g., 75ml / min) (see Figures 4(E) to (F) and Figure 5, the elapsed time is after 5.3 seconds).

[0055] That is, at a time point of 5.3 seconds, the first stage of the IPA replacement step, which involves supplying both IPA and DIW to the substrate W, ends, and the second stage of the IPA replacement step, which involves supplying only IPA to the substrate W, begins. Thereafter, the second stage of the IPA replacement step ends by continuously supplying IPA to the rotation center Wc of the substrate for a predetermined time.

[0056] Furthermore, in the first stage of the IPA replacement step, an IPA liquid film is formed in the central region of the substrate W, and a mixed liquid film of IPA and DIW is formed in the peripheral region. Strictly speaking, in the state shown in Figure 4(B) (at the point where 1 second has elapsed), the rotation center Wc of the substrate W is only covered by DIW, which "attaches slightly radially outward from the rotation center Wc and then diffuses back to the rotation center Wc in an attached manner," while the area closer to the radially outward side than the IPA attachment point is covered by the mixed liquid of IPA and DIW. Subsequently, as shown in Figures 4(C) to (E), as time passes, the area where the inner IPA liquid film exists becomes wider, and the area where the outer mixed liquid film exists becomes narrower. Then, in the second stage of the IPA replacement step, the entire surface area of ​​the substrate W is covered by the IPA liquid film.

[0057] That is, in the IPA replacement step, if we look at each part of the substrate W surface, firstly, the DIW on that part will be replaced by a mixture of IPA and DIW, and then replaced by IPA.

[0058] During the IPA replacement step, before the IPA attachment point from the drying liquid nozzle 42 moves away from the rotation center Wc towards the periphery of the substrate W and returns to the rotation center Wc, a dry area should not be formed near the rotation center Wc on the surface of the substrate W. This is because if an undesirable dry area is formed, there is a risk of generating defects such as particles. In actual device applications, under the processing conditions illustrated in Figures 4 and 5, even if the surface of the substrate W is hydrophobic, a dry area will not be formed near the rotation center Wc on the substrate surface, and processing can proceed smoothly; this has been confirmed. Furthermore, when drying occurs near the rotation center Wc, it can be addressed by appropriately combining the following processes: increasing the spray flow rate of the IPA from the drying liquid nozzle 42, decreasing the rotation speed of the substrate W, and shortening the time it takes for the IPA attachment point to move away from the rotation center W and return to the rotation center Wc.

[0059] In the above-described IPA replacement step, the attachment points of the cleaning nozzle 43 and the drying liquid nozzle 42 are moved radially outward in such a way that the distance from the attachment point of the DIW from the cleaning nozzle 43, measured from the rotation center Wc, is always greater than the distance from the attachment point of the IPA from the drying liquid nozzle 42, measured from the rotation center Wc. Therefore, the consumption of IPA can be reduced, and even if the surface of the substrate W is hydrophobic, liquid splashing can be prevented or significantly suppressed. Furthermore, when liquid splashing occurs, there is a risk of contamination of the substrate W due to the backflow of droplets from the liquid collection cup adhering to the substrate W, and the small droplets floating around the substrate W adhering to the substrate W.

[0060] The reasons for achieving the above-mentioned effect will be explained below. When DIW is supplied to the center of the substrate from the self-cleaning nozzle, the self-cleaning nozzle stops dispensing DIW, and IPA is immediately dispensed from the drying liquid nozzle towards the center of the substrate. At this time, before the IPA liquid film diffuses to the periphery of the substrate, there is a risk that the DIW liquid film breaks at the periphery of the substrate W, exposing that periphery to air. This phenomenon is particularly likely to occur when the surface of the substrate W is hydrophobic. By increasing the dispensing flow rate of IPA from the drying liquid nozzle, the IPA liquid film can be rapidly diffused across the entire surface area of ​​the substrate, thus suppressing the occurrence of the above phenomenon. However, this leads to an increase in the amount of expensive IPA used.

[0061] By continuously spraying IPA from the drying liquid nozzle toward the center of the substrate, the adhesion point of the DIW sprayed from the cleaning nozzle gradually approaches the periphery of the substrate, which can prevent the liquid film from breaking off in the outer area of ​​the substrate, and at the same time make the area covered by the IPA liquid film expand toward the periphery of the substrate.

[0062] The inventors discovered through experiments that, while maintaining the adhesion point of the IPA sprayed from the drying liquid nozzle at the center of rotation of the substrate, the adhesion point of the DIW sprayed from the cleaning nozzle gradually approaches the periphery of the substrate W. Specifically, in one experimental example, when the IPA spray flow rate decreased to below a certain critical value (50 ml / min), liquid splashing occurred when the adhesion point of the DIW was closer to the outer edge than a certain radial position (approximately 85 mm from the center of rotation).

[0063] Since the surface tension of IPA is much lower than that of DIW, and the miscibility between IPA and DIW is also higher, the substrate surface with a sufficiently thick IPA liquid film can be considered equivalent to a surface with higher hydrophilicity. The thickness of the liquid film formed on the substrate by IPA, which is sprayed from the drying liquid nozzle and adheres to the center of rotation of the substrate, becomes thinner as it moves radially outward. When DIW sprayed from the cleaning nozzle at a larger flow rate collides with a thinner part of the IPA liquid film, the IPA liquid film is damaged near the point of impact, and the DIW directly collides with the hydrophobic surface, resulting in liquid splashing. Liquid splashing can be prevented by increasing the spray flow rate of IPA from the drying liquid nozzle, but this would also lead to an increase in the amount of expensive IPA used.

[0064] In the above embodiment, the two attachment points are moved radially outward together in such a way that the distance from the DIW attachment point of the cleaning nozzle 43, measured from the rotation center Wc, is always greater than the distance from the IPA attachment point of the drying liquid nozzle 42, measured from the rotation center Wc. Therefore, since the radial position of the DIW attachment point is irrelevant, the thickness of the IPA liquid film at the DIW attachment point is maintained at a sufficiently large thickness, thus preventing liquid splashing.

[0065] 〔Drying Step〕 When the second stage of the IPA replacement step ends (that is, when the IPA replacement step ends), the drying step is performed. First, starting from the state shown in FIG4(F), IPA is continuously sprayed from the drying liquid nozzle 42, and the position of the IPA attachment point is moved in the positive direction from the rotation center Wc of the substrate W toward the periphery. At the same time as the drying liquid nozzle 42 moves, nitrogen gas, which is used as a drying gas, is sprayed from the gas nozzle 44 held by the second nozzle arm 52, and the gas nozzle 44 is also moved toward the periphery of the substrate.

[0066] At this time, the drying liquid nozzle 42 and the gas nozzle 44 are moved in opposite directions to ensure that the position of the IPA adhesion point is always closer to the radially outer side of the collision point between the nitrogen mainstream ejected from the gas nozzle 44 and the surface of the substrate W. In this way, the circular drying area formed at the center of the substrate W gradually expands radially, and eventually the entire surface of the substrate W becomes dry. It is preferable to move the drying liquid nozzle 42 and the gas nozzle 44 so that the mainstream of gas is blown to a position on the surface of the substrate W that is slightly closer to the radially inner side of the boundary between the dried area and the non-dried area (the area where the IPA liquid film exists).

[0067] After the above steps, the series of processes for one of the substrates W is completed.

[0068] According to the above embodiment, a liquid film can be maintained on the surface of the substrate W, while preventing liquid splashing.

[0069] In the above embodiment, during the IPA replacement step, after the attachment point of the IPA from the drying liquid nozzle 42 coincides with the rotation center Wc, the moving direction of the drying liquid nozzle 42 is reversed, causing it to move in the positive direction (see Figures 4(C) to (E)), but it is not limited to this. As shown in Figures 6(C) to (E), the drying liquid nozzle 42 can also be moved in the negative direction (i.e., towards region II) in the same way as the cleaning nozzle 43.

[0070] During the IPA replacement step, when both IPA and DIW are sprayed simultaneously, the auxiliary nozzle 70 shown in Figures 7 and 8 can also be used as the nozzle for spraying DIW. In this case, in the processing unit 16, in addition to the configuration shown in Figures 2 and 3, the auxiliary nozzle 70 is further added. Therefore, during general cleaning treatment, the chemical liquid / cleaning nozzle 41 or the cleaning nozzle 43 can be used.

[0071] An auxiliary nozzle 70 may be disposed on the top surface of the liquid collection cup 60, for example, near the top opening of the liquid collection cup 60. The auxiliary nozzle 70 ejects DIW in a manner that roughly follows a parabolic trajectory, as shown in FIG. 7. The auxiliary nozzle 70 may rotate (tilt) as indicated by arrow 71, thereby changing the attachment point (radial position of the attachment point) of the DIW ejected from the auxiliary nozzle 70 on the substrate W. The rotation range of the auxiliary nozzle 70 is set taking into account the rotation direction of the substrate W (arrow ω) so that, when viewed from above, the vector of the DIW ejected from the auxiliary nozzle 70 is roughly along the vector on the attachment point of the DIW that indicates the direction of movement of the substrate W.

[0072] Furthermore, the IPA used in the IPA replacement step has a surface tension much lower than that of DIW, thus effectively suppressing pattern collapse caused by surface tension in the subsequent drying step. IPA not only has a lower surface tension than DIW but also higher volatility and is easily replaced by DIW. Therefore, it is widely used in semiconductor device manufacturing for covering the substrate surface immediately before the drying step. Any liquid with the same characteristics as IPA (especially low surface tension) can be used to replace IPA in the IPA replacement step. In this case, the IPA replacement step is called a liquid replacement step for drying. Furthermore, the drying step is not limited to the drying method described in the above embodiments; for example, a supercritical drying method can also be used.

[0073] Furthermore, in the above embodiment, the replacement step (IPA replacement step) for replacing DIW with IPA is described. However, the technology used in the IPA replacement step can be widely used in steps that replace the first processing liquid covering the substrate surface with a second processing liquid whose surface tension is less than that of the first processing liquid. In this case, when replacing the first processing liquid with the second processing liquid, a liquid film can be maintained on the entire surface of the substrate W, while preventing liquid splashing.

[0074] The embodiments disclosed herein should be considered illustrative rather than restrictive in all respects. Without departing from the scope and spirit of the appended patent application, the above embodiments may be omitted, substituted, or modified in various ways.

[0075] The substrate 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. [Simplified Explanation of the Diagram]

[0008] [Fig. 1] is a cross-sectional view of a substrate processing apparatus according to an embodiment. [Fig. 2] is a longitudinal cross-sectional view showing an example of a processing unit included in the substrate processing apparatus of Fig. 1. [Fig. 3] is a schematic top view showing a portion of the components, such as the liquid receiving cup, nozzle, and nozzle arm, removed from the processing unit of Fig. 2. [Fig. 4] (A) to (F) are schematic side views illustrating an example of the operation of the drying liquid nozzle and the cleaning nozzle in the IPA replacement step. [Fig. 5] is a diagram illustrating an example of the operation of the processing unit in the IPA replacement step. [Fig. 6] (A) to (F) are schematic side views illustrating other examples of the operation of the drying liquid nozzle and the cleaning nozzle in the IPA replacement step. [Fig. 7] is a schematic longitudinal cross-sectional view showing a portion of the components of an embodiment obtained by adding auxiliary nozzles to the processing units of Fig. 2 and Fig. 3. [Fig. 8] is a schematic top view showing a portion of the components of the processing unit of Fig. 7 removed.

Claims

1. A substrate processing method comprising: a first processing step of supplying a first processing liquid to the surface of a rotating substrate and covering the surface of the substrate with a liquid film of the first processing liquid; and a second processing step of, after the first processing step, supplying a second processing liquid with a surface tension less than that of the first processing liquid to the surface of the rotating substrate, thereby replacing the first processing liquid on the substrate with the second processing liquid, thereby covering the surface of the substrate with a liquid film of the second processing liquid; the second processing step comprising: a first stage of simultaneously supplying the first processing liquid to the surface of the rotating substrate, in addition to the second processing liquid; and a second stage of supplying the second processing liquid to the center portion of the surface of the rotating substrate without supplying the first processing liquid after the first stage; the first stage comprising a first step and a second step; the first step being supplying the first processing liquid to the surface of the rotating substrate and simultaneously supplying the second processing liquid to the center portion of the surface of the rotating substrate; the second step being... After the initial step, while maintaining the condition that the distance from the center of rotation of the substrate to the attachment point of the first processing liquid, i.e., the first radial distance, on the surface of the substrate is greater than the distance from the center of rotation of the substrate to the attachment point of the second processing liquid, i.e., the second radial distance, and controlling at least one of the supply flow rate of the second processing liquid and the rotation speed of the substrate to maintain the liquid film of the second processing liquid at the center of the surface of the substrate, while gradually increasing both the first radial distance and the second radial distance and simultaneously supplying both the first processing liquid and the second processing liquid to the surface of the rotating substrate; the second stage begins when the attachment point of the first processing liquid reaches the periphery of the surface of the substrate due to the second step and the supply of the first processing liquid to the surface of the rotating substrate is stopped; the second stage includes a third step, in which the second processing liquid is continued to be supplied to the surface of the rotating substrate, and in this state the attachment point of the second processing liquid on the surface of the substrate moves towards the center of the surface of the substrate.

2. The substrate processing method as described in claim 1, wherein, In the second step, the difference between the first radial distance and the second radial distance is maintained within the range of 40mm to 90mm.

3. The substrate processing method as described in claim 1 or 2, wherein, In the second step, the difference between the first radial distance and the second radial distance is maintained at a constant level.

4. The substrate processing method as described in claim 1 or 2, wherein, In the first step, the position of the attachment point of the second treatment liquid, which is also the first position, is consistent with the rotation center of the substrate, or is located near the rotation center of the substrate to the extent that the rotation center of the substrate is covered by the second treatment liquid.

5. The substrate processing method as described in claim 4, wherein, The first processing liquid is continuously supplied to the rotating substrate from the time the first processing step is performed until the second stage of the second processing step begins and the supply stops. At the end of the first processing step, the attachment point of the first processing liquid is aligned with the rotation center of the substrate. Subsequently, in the first step of the second processing step, the attachment point of the first processing liquid is moved away from the rotation center of the substrate, while the attachment point of the second processing liquid is moved towards the rotation center of the substrate.

6. The substrate processing method as described in claim 5, wherein, At least at the end of the first processing step, the position of the attachment point of the first processing liquid on the surface of the substrate is consistent with the rotation center of the substrate, or is located near the rotation center of the substrate to the extent that the rotation center of the substrate is covered by the first processing liquid.

7. The substrate processing method as described in claim 6, wherein, In the first step of the second processing step, the supply flow rate of the first processing liquid is less than the supply flow rate of the first processing liquid in the first processing step.

8. The substrate processing method as described in claim 1 or 2, wherein, In the third step of the second stage of the second processing step, after the attachment point of the second processing liquid on the surface of the substrate is moved to the center of the surface of the substrate, the second processing liquid is continuously supplied to the center of the surface of the substrate.

9. The substrate processing method as described in claim 1 or 2, wherein, In the third step of the second stage of the second processing step, after the attachment point of the second processing liquid on the surface of the substrate is moved to the center of the surface of the substrate, the supply flow rate of the second processing liquid is greater than the supply flow rate of the second processing liquid in the first step of the second stage and in the second step.

10. The substrate processing method as described in claim 1 or 2, wherein, In the first step of the first stage of the second processing step, the attachment point of the second processing liquid is consistent with the rotation center of the substrate, or is located near the rotation center of the substrate to the extent that the rotation center of the substrate is covered by the second processing liquid.

11. The substrate processing method as described in claim 10, wherein, In the third step of the second stage of the second processing step, the attachment point of the second processing liquid is moved toward the center of the surface of the substrate before a dry area not covered by the liquid film is generated near the rotation center of the substrate.

12. The substrate processing method as described in claim 1 or 2, wherein, In the second processing step, the first processing fluid is supplied from the first nozzle held by the first nozzle arm, and the second processing fluid is supplied from the second nozzle held by the second nozzle arm.

13. The substrate processing method as described in claim 1 or 2, wherein, The first treatment liquid is a cleaning liquid, and the second treatment liquid is an organic solvent with a surface tension lower than that of the cleaning liquid.

14. The substrate processing method as described in claim 13, wherein, The cleaning solution is composed of pure water or functional water made by dissolving trace amounts of electrolyte components in pure water.

15. The substrate processing method of claim 1 or 2 further comprises: a chemical liquid treatment step, wherein a chemical liquid is supplied to the surface of the rotating substrate; the first processing step is a cleaning step, wherein the chemical liquid is washed away by supplying a cleaning liquid, which is the first processing liquid, to the substrate that has undergone the chemical liquid treatment step.

16. A substrate processing apparatus comprising: a substrate holding portion for holding a substrate in a horizontal orientation; a rotation drive portion for rotating the substrate holding portion about a vertical axis; at least two nozzles configured to supply processing liquid to the substrate held by the substrate holding portion, to cleaning liquid to the substrate held by the substrate holding portion, to a low surface tension liquid to the substrate held by the substrate holding portion, and to simultaneously supply cleaning liquid and low surface tension liquid to the substrate held by the substrate holding portion; at least one nozzle arm for moving the at least two nozzles; and a control portion for controlling the operation of the substrate processing apparatus to perform the substrate processing method described in any one of claims 1 to 15.

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