Substrate processing method and substrate processing apparatus

Abstract

To provide a substrate processing method and a substrate processing device which can surely suppress pattern collapse.SOLUTION: A fixed amount of IPA is supplied to a substrate W after washing treatment from a treatment liquid nozzle 30. A liquid surface level of the IPA is gradually lowered by pre-drying, and when the liquid surface of the IPA coincides with the upper end of a pillar of a pattern formed on the substrate W, the surface of the substrate W is irradiated with flash light from a flash lamp FL, and residual IPA is instantaneously evaporated. Due to irradiation with the flash light having extremely short irradiation time and high intensity, drying time required for removing a treatment liquid from the surface of the substrate W after capillary force acts on a pattern is shorter than collapse time required until the pattern collapses after the capillary force acts on the pattern. Even when the pattern has a large aspect ratio, pattern collapse can be surely suppressed.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a substrate processing method and a substrate processing apparatus for drying a substrate on which a fine pattern is formed. Substrates to be processed include, for example, semiconductor substrates, substrates for liquid crystal display devices, substrates for flat panel displays (FPDs), substrates for optical disks, substrates for magnetic disks, or substrates for solar cells.

Background Art

[0002] Conventionally, in the manufacturing process of semiconductor devices, various processing processes such as cleaning, film formation, and heat treatment are performed on a semiconductor substrate (hereinafter simply referred to as "substrate"). One of such processing processes is a drying process for drying a wet substrate that has been subjected to wet cleaning or the like.

[0003] In addition, with the recent progress of miniaturization, nano-structure patterns with a large aspect ratio may be formed on the substrate. In the drying process, there is a problem that such nano-structures with a large aspect ratio collapse. It has been found that the main cause of the collapse of nano-structures in the drying process is the capillary force acting on the nano-structures during the process of the liquid adhering to the substrate drying. The most common measure against this problem is to use a liquid with a low surface tension as the processing liquid during drying, and typically IPA (isopropyl alcohol) is used. Since the capillary force depends on the surface tension of the liquid, by using a liquid with a low surface tension such as IPA as the processing liquid during drying, it is possible to reduce the capillary force acting on the nano-structure pattern and suppress pattern collapse.

[0004] On the other hand, Patent Document 1 discloses a technique for preventing pattern collapse by irradiating flash light from a flash lamp onto a substrate after a cleaning process to instantaneously evaporate moisture.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2007-19158 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, even when using liquids with low surface tension, such as IPA, the surface tension cannot be reduced to zero, thus limiting the reduction of capillary forces acting on the pattern. Furthermore, even when drying is performed by flash irradiation, it is difficult to adequately prevent pattern collapse, especially in next-generation nanostructure patterns with aspect ratios exceeding 15.

[0007] This invention has been made in view of the above problems, and aims to provide a substrate processing method and a substrate processing apparatus that can reliably suppress pattern collapse. [Means for solving the problem]

[0008] To solve the above problems, the invention of claim 1 provides a substrate processing method for drying a substrate on which a pattern is formed, comprising: a supply step of supplying a processing liquid to the surface of the substrate; and a light irradiation step of irradiating the surface of the substrate with light to heat the surface and evaporate the processing liquid, wherein in the light irradiation step, the drying time required from when capillary force begins to act on the pattern until the pattern collapses is shorter than the collapse time required from when capillary force begins to act on the pattern until the pattern collapses. In the light irradiation step, flash light is irradiated onto the surface of the substrate from a flash lamp, and in the light irradiation step, the energy of the irradiated flash light is adjusted according to the pillar spacing between adjacent pillars in the pattern. It is characterized by the following:

[0009] Furthermore, the invention of claim 2 is a substrate processing method according to the invention of claim 1, The flash lamp emits a flash of light when the liquid level of the processing solution coincides with the upper end of the pillar. It is characterized by the following:

[0010] Furthermore, the invention of claim 3 is, 1 In the substrate processing method according to the invention, The charging voltage is determined based on a conversion table that shows the correlation between the charging voltage of the capacitor in the power supply unit that supplies power to the flash lamp and the pillar spacing. It is characterized by the following:

[0011] Furthermore, the invention of claim 4 is, 1 In the substrate processing method according to the invention, the light irradiation step is characterized in that the energy of the irradiated flash light is increased as the distance between the pillars becomes narrower.

[0012] Furthermore, the invention of claim 5 is, 1 A substrate processing method according to any of claims 4, characterized in that the light irradiation step involves irradiating with flash light that cuts out light with a wavelength of 400 nm or less.

[0014] Furthermore, claims 6 The invention is as follows: 5 A substrate processing method according to any of the inventions, characterized in that the processing solution is isopropyl alcohol.

[0015] Furthermore, claims 7 The invention relates to a substrate drying apparatus for a substrate on which a pattern is formed, comprising: a substrate holding unit for holding the substrate; a processing liquid supply unit for supplying a processing liquid to the surface of the substrate; and a light irradiation unit for evaporating the processing liquid by irradiating the surface of the substrate with light and heating the surface, wherein the drying time required from the start of capillary force acting on the pattern until the processing liquid is removed from the surface of the substrate is shorter than the collapse time required from the start of capillary force acting on the pattern until the pattern collapses. The light irradiation unit has a flash lamp that irradiates the surface of the substrate with flash light, and adjusts the energy of the flash light emitted from the flash lamp according to the pillar spacing between adjacent pillars in the pattern. It is characterized by the following:

[0016] Furthermore, claims 8 The invention is claimed 7 In the substrate processing apparatus according to the invention, The flash lamp emits a flash of light when the liquid level of the processing solution coincides with the upper end of the pillar. It is characterized by the following:

[0017] Furthermore, claims 9 The invention is claimed 7 In the substrate processing apparatus according to the invention, The charging voltage is determined based on a conversion table that shows the correlation between the charging voltage of the capacitor in the power supply unit that supplies power to the flash lamp and the pillar spacing. It is characterized by the following:

[0018] Furthermore, claims10 The invention according to claim 7 relates to a substrate processing apparatus, and is characterized in that the energy of the flash light irradiated from the flash lamp is increased as the pillar interval becomes narrower.

[0019] Also, the invention according to claim 11 relates to a substrate processing apparatus according to any one of the inventions from claim 7 to claim 10 and further includes a filter provided between the light irradiation unit and the substrate holding unit for cutting light having a wavelength of 400 nm or less from the flash light emitted from the flash lamp.

[0021] Also, the invention according to claim 12 relates to a substrate processing apparatus according to any one of the inventions from claim 7 to claim 11 and is characterized in that the processing liquid is isopropyl alcohol.

Advantages of the Invention

[0022] According to the invention of claims 1 to claim 6 , since the drying time required to remove the processing liquid from the surface of the substrate after the capillary force starts to act on the pattern is shorter than the collapse time required for the pattern to collapse after the capillary force starts to act on the pattern, pattern collapse can be reliably suppressed even for a pattern with a large aspect ratio.

[0023] In particular, according to the invention of claim 4, since the energy of the irradiated flash light is increased as the pillar interval becomes narrower, the drying time can be reliably made shorter than the collapse time, and pattern collapse can be more reliably suppressed.

[0024] In particular, according to the invention of claim 5, since flash light from which light having a wavelength of 400 nm or less is cut is irradiated, damage to the substrate can be suppressed.

[0025] Claim 7Claims 12 According to this invention, the drying time required from the start of capillary force acting on the pattern until the treatment liquid is removed from the substrate surface is shorter than the collapse time required from the start of capillary force acting on the pattern until the pattern collapses. Therefore, even patterns with a large aspect ratio can be reliably suppressed.

[0026] In particular, claims 10 According to this invention, the energy of the flash light emitted from the flash lamp is increased as the distance between pillars decreases, so that the drying time can be made shorter than the collapse time, and pattern collapse can be suppressed more reliably.

[0027] In particular, claims 11 According to this invention, a filter is provided between the light irradiation unit and the substrate holding unit, which cuts out light with a wavelength of 400 nm or less from the flash light emitted by the flash lamp, thereby suppressing damage to the substrate. [Brief explanation of the drawing]

[0028] [Figure 1] This is a schematic plan view illustrating the internal layout of a single-wafer cleaning apparatus equipped with the substrate processing apparatus according to the present invention. [Figure 2] This is a side view showing the main components of the substrate processing apparatus according to the present invention. [Figure 3] This is a flowchart showing the processing procedure in the processing unit. [Figure 4] This is a diagram showing a pattern formed on a substrate. [Figure 5] This diagram shows the state of the substrate immediately after IPA was supplied. [Figure 6] This figure shows the state of the substrate when the liquid level of the IPA coincides with the top edge of the pillar. [Figure 7] This diagram shows a situation where there is a difference in the liquid level of the IPA. [Figure 8]This diagram shows the state of pattern collapse. [Figure 9] This figure shows the correlation between drying speed and pattern collapse rate. [Figure 10] This figure shows a conversion table that registers the correlation between pillar spacing and required charging voltage. [Modes for carrying out the invention]

[0029] Embodiments of the present invention will be described in detail below with reference to the drawings. In the following, expressions indicating relative or absolute positional relationships (e.g., "in one direction," "along one direction," "parallel," "orthogonal," "center," "concentric," "coaxial," etc.) shall, unless otherwise specified, not only strictly represent the positional relationship but also represent a state in which there is a relative displacement in terms of angle or distance within a tolerance or a range in which a similar level of function can be obtained. Similarly, expressions indicating equality (e.g., "identical," "equal," "homogeneous," etc.) shall, unless otherwise specified, not only represent a state in which there is a quantitatively strictly equal state but also represent a state in which there is a difference in which a tolerance or a similar level of function can be obtained. Furthermore, expressions indicating shape (e.g., "circular," "square," "cylindrical," etc.) shall, unless otherwise specified, not only strictly represent the geometrically precise shape but also represent a shape within a range in which a similar level of effect can be obtained, and may have, for example, irregularities or chamfers. Additionally, expressions such as "equipped," "possessing," "containing," "having," etc., for a component are not exclusive expressions that exclude the existence of other components. Furthermore, the expression "at least one of A, B, and C" includes "A only," "B only," "C only," "any two of A, B, and C," and "all of A, B, and C."

[0030] Figure 1 is a schematic plan view illustrating the internal layout of a single-wafer cleaning apparatus 100 equipped with the substrate processing apparatus according to the present invention. The single-wafer cleaning apparatus 100 is a device that sequentially cleans substrates W one by one. The substrates W to be processed are silicon disc-shaped semiconductor substrates. In Figure 1 and subsequent figures, the dimensions and number of parts are exaggerated or simplified as necessary for ease of understanding.

[0031] The single-wafer cleaning apparatus 100 performs a surface cleaning treatment on the substrate W by discharging a chemical solution and a rinsing solution onto the substrate W, and then performs a drying treatment on the substrate W. The chemical solutions include, for example, a solution for etching or a solution for removing particles, and specifically, SC-1 solution (a mixed solution of ammonium hydroxide, hydrogen peroxide, and pure water), SC-2 solution (a mixed solution of hydrochloric acid, hydrogen peroxide, and pure water), buffered hydrofluoric acid (BHF), or dilute hydrofluoric acid (DHF) are used. Pure water is typically used as the rinsing solution. In the following description, the chemical solution, rinsing solution, and organic solvents are collectively referred to as "treatment solution".

[0032] The single-wafer washing device 100 comprises a plurality of processing units 1,101, a load port LP, an indexer robot 102, a main transport robot 103, and a control unit 90.

[0033] A carrier C containing multiple substrates W to be processed by the single-wafer washing device 100 is placed on the load port LP. Carrier C containing unprocessed substrates W is transported by an automated guided vehicle (AGV, OHT, etc.) and placed on the load port LP. Carrier C containing processed substrates W is also removed from the load port LP by an automated guided vehicle.

[0034] Carrier C is typically a front-opening unified pod (FOUP) that houses substrates W in a sealed space. Carrier C holds multiple substrates W in a horizontal orientation (the orientation in which the normal to the main surface of the substrate W is aligned with the vertical direction) in a vertical stack at regular intervals using multiple holding shelves formed inside. The maximum number of substrates that can be housed in carrier C is 25 or 50. In addition to FOUP, carrier C may also take the form of an SMIF (Standard Mechanical Interface) pod or an open cassette (OC) that exposes the stored substrates W to the outside air.

[0035] The indexer robot 102 is configured to slide, rotate, and move its hand, which holds the substrate W, forward and backward. The indexer robot 102 transports the substrate W between the carrier C and the main transport robot 103. The indexer robot 102 takes the unprocessed substrate W from the carrier C and passes it to the main transport robot 103. The indexer robot 102 also receives the processed substrate W from the main transport robot 103 and stores it in the carrier C.

[0036] The main transport robot 103 is configured to perform rotational, lifting, and forward / backward movements of the arm that holds the substrate W. The main transport robot 103 carries the substrate W received from the indexer robot 102 into either processing unit 1 or processing unit 101. The main transport robot 103 also passes the substrate W that has been discharged from either processing unit 1 or processing unit 101 back to the indexer robot 102. The main transport robot 103 may also transport the substrate W between processing unit 1 and processing unit 101. For example, the main transport robot 103 carries the substrate W that has been discharged from processing unit 101 into processing unit 1.

[0037] Processing unit 101 performs a cleaning process on one substrate W. Processing unit 1 performs a drying process on one substrate W. The single-wafer cleaning apparatus 100 of this embodiment is equipped with a total of 12 processing units 101 or processing units 1. Specifically, four towers, each consisting of three processing units (processing unit 101 or processing unit 1) stacked vertically, are arranged to surround the main transport robot 103. In Figure 1, one of the three stacked processing units is schematically shown, with one processing unit 1 and three processing units 101 arranged to surround the main transport robot 103. Note that the number of processing units in the single-wafer cleaning apparatus 100 is not limited to 12 and may be changed as appropriate.

[0038] Next, the processing unit 1 mounted on the single-wafer washing device 100 will be described. The processing unit 1, which is a substrate processing apparatus according to the present invention, performs a drying process on the substrate W after the washing process. Figure 2 is a side view showing the main components of the processing unit 1. The processing unit 1 mainly comprises a processing chamber 10, a rotating holding unit 20, a processing liquid nozzle 30, a light irradiation unit 50, and a control unit 90.

[0039] The processing chamber 10 is a hollow housing. A rotating holding unit 20 and a processing liquid nozzle 30, etc., are provided inside the processing chamber 10. During substrate processing, the processing chamber 10 houses the substrate W to be processed.

[0040] The processing chamber 10 is provided with an entrance / exit (not shown). This entrance / exit is opened and closed by a shutter. With the entrance / exit open, the main transport robot 103 loads and unloads the substrates W into and out of the processing chamber 10. The entrance / exit is closed while the substrates W are being processed.

[0041] The rotating holding unit 20 includes a spin chuck 22 and a spin motor 25. The spin chuck 22 is a substrate holding unit that holds the substrate W in a horizontal position. In this embodiment, the spin chuck 22 is a vacuum suction type chuck. The spin chuck 22 holds the central part of the lower surface of the substrate W by suction. Note that the spin chuck 22 may be other types of chucks, such as a clamping type mechanical chuck.

[0042] The spin chuck 22 has a disc shape with a diameter smaller than the diameter of the substrate W. When the lower surface of the substrate W is held by the spin chuck 22, the peripheral edge of the substrate W protrudes outward beyond the outer edge of the spin chuck 22.

[0043] The spin chuck 22 is connected to the spin motor 25 via the spin shaft 27. That is, the upper end of the spin shaft 27 of the spin motor 25 is connected to the center of the lower surface of the spin chuck 22. When the spin motor 25 rotates the spin shaft 27 while the substrate W is held in contact with the spin chuck 22, the substrate W and the spin chuck 22 rotate in the horizontal plane around the rotation axis A1 which is aligned vertically.

[0044] A cup 40 is provided to surround the spin chuck 22. The cup 40 has a cylindrical shape, and the upper part of the cup 40 is sloped so that it approaches the spin chuck 22 as it goes upwards. However, the inner diameter of the upper part of the cup 40 is larger than the diameter of the substrate W. The upper end of the cup 40 is higher than the height of the substrate W held by the spin chuck 22. Therefore, liquid scattered by centrifugal force from the substrate W rotated by the spin motor 25 is caught and collected by the cup 40. The liquid collected by the cup 40 is discharged from a drain pipe 45 provided at the bottom of the cup 40. The cup 40 may also have a multi-stage structure with multiple collection ports for different purposes.

[0045] The processing liquid nozzle 30 is attached to the tip of a horizontally extending rod-shaped nozzle arm 31. The nozzle arm 31 is supported by an arm support shaft 32 that extends vertically. The arm support shaft 32 is connected to a nozzle drive unit 33. The nozzle drive unit 33 rotates the arm support shaft 32 around a rotation axis A2 along the vertical direction. When the nozzle drive unit 33 rotates the arm support shaft 32, the nozzle arm 31 performs a pivoting motion, and the processing liquid nozzle 30 moves along an arc trajectory between a standby position outside the cup 40 and a processing position above the substrate W held by the spin chuck 22.

[0046] Furthermore, the nozzle drive unit 33 moves the arm support shaft 32 and the nozzle arm 31 up and down. As a result, the processing liquid nozzle 30 also moves up and down along the vertical direction.

[0047] The processing liquid is supplied to the processing liquid nozzle 30 from a processing liquid supply source (not shown). The processing liquid nozzle 30 discharges the supplied processing liquid downwards. By discharging the processing liquid at a processing position above the substrate W, the processing liquid is supplied to the surface of the substrate W. In this embodiment, the processing liquid nozzle 30 supplies IPA (isopropyl alcohol) as the processing liquid to the substrate W.

[0048] The light irradiation unit 50 is positioned above the processing chamber 10. The light irradiation unit 50 comprises a light source consisting of multiple xenon flash lamps FL and a reflector 52 provided to cover the top of the light source. The light irradiation unit 50 may also be provided above the processing chamber 10 in a lamp housing separate from the processing chamber 10.

[0049] Each of the multiple flash lamps FL is a rod-shaped lamp with a long cylindrical shape, and they are arranged in a planar manner such that their longitudinal directions are parallel to each other along the main surface of the substrate W held by the rotating holding part 20 (i.e., along the horizontal direction). Therefore, the plane formed by the arrangement of the flash lamps FL is also a horizontal plane.

[0050] A xenon flash lamp FL comprises a cylindrical glass tube (discharge tube) containing xenon gas, with an anode and cathode connected to capacitors at both ends, and a trigger electrode attached to the outer surface of the glass tube. Since xenon gas is an electrically insulating material, electricity does not flow through the glass tube under normal conditions, even if charge is stored in the capacitor. However, when a high voltage is applied to the trigger electrode to break the insulation, the electricity stored in the capacitor flows instantaneously through the glass tube, and light is emitted due to the excitation of xenon atoms or molecules at that time. In such a xenon flash lamp FL, the electrostatic energy previously stored in the capacitor is converted into extremely short light pulses of 0.1 milliseconds to 100 milliseconds, giving it the characteristic of being able to emit extremely strong light compared to halogen lamps, etc. In other words, a flash lamp FL emits flash light with an irradiation time of 0.1 milliseconds to 100 milliseconds.

[0051] Furthermore, the reflector 52 is positioned above the multiple flash lamps FL so as to cover them all. The basic function of the reflector 52 is to reflect the flash light emitted from the multiple flash lamps FL downwards. The reflector 52 is made of an aluminum alloy plate, and its surface (the side facing the flash lamps FL) is roughened by blasting.

[0052] Each of the multiple flash lamps FL is supplied with power from the power supply unit 60. The power supply unit 60 includes a capacitor, a coil, etc. The power supply unit 60 applies a preset voltage to the capacitor to store charge, and when flash light is emitted, it supplies the electricity stored in the capacitor to the flash lamp FL.

[0053] The energy of the flash light emitted from the flash lamp FL is determined by the energy stored in the capacitor of the power supply unit 60. When a capacitor with capacitance C is charged with a charging voltage V, the energy stored in the capacitor is CV. 2 The result is / 2. Since capacitance C is a constant inherent to the capacitor, the energy stored in the capacitor can be adjusted by the charging voltage V. Alternatively, an IGBT (insulated gate bipolar transistor) may be provided in the power supply unit 60, and the waveform of the current flowing through the flash lamp FL may be defined by the IGBT to adjust the illumination time of the flash lamp FL.

[0054] An optical filter 70 is provided between the light irradiation unit 50 and the rotation holding unit 20. The optical filter 70 cuts out ultraviolet light with a wavelength of 400 nm or less from the flash light emitted by the flash lamp FL.

[0055] The control unit 90 controls various operating mechanisms provided in the single-wafer washing device 100. The control unit 90 also controls the operation of the processing unit 1. The hardware configuration of the control unit 90 is similar to that of a general computer. Specifically, the control unit 90 includes a CPU, which is a circuit that performs various calculations; a ROM, which is a read-only memory that stores basic programs; a RAM, which is a read-write memory that stores various information; and a storage unit 91 (for example, a magnetic disk or SSD) that stores control software and data. The control unit 90 is electrically connected to the spin motor 25 and nozzle drive unit 33 of the rotating holding unit 20, and controls their operation.

[0056] The memory unit 91 of the control unit 90 stores a conversion table 93. The conversion table 93 registers the correlation between the pillar spacing in the pattern formed on the substrate W and the charging voltage applied to the flash lamp FL. The control unit 90 controls the power supply unit 60 to charge the capacitor with the charging voltage V determined from the conversion table 93. Further details on the control using the conversion table 93 will be described later.

[0057] Next, the processing operation of the processing unit 1 mounted on the single-wafer washing device 100 will be described. Figure 3 is a flowchart showing the processing procedure in the processing unit 1. In this embodiment, a nanostructure pattern is formed on the substrate W to be processed.

[0058] Figure 4 shows a pattern formed on a substrate W. The base portion 81 of the substrate W is a flat, disc-shaped silicon component. Numerous elongated cylindrical pillars 85 are erected on the surface of the base portion 81 of the substrate W, forming a nanostructure pattern. In this embodiment, for example, the diameter d of the cylindrical pillars 85 is 30 nm, and the height h is 600 nm. That is, the aspect ratio of the nanostructure pattern is 20. Also, for example, the pillar spacing p between adjacent pillars 85 is 60 nm. A substrate W on which such a nanostructure pattern, with multiple pillars 85 erected, is formed is brought into a single-wafer washing apparatus 100 for processing.

[0059] Returning to Figure 3, prior to processing in processing unit 1, the substrate W is cleaned by processing unit 101 (step S1). First, the indexer robot 102 takes one unprocessed substrate W from the carrier C of the load port LP and passes it to the main transport robot 103, which then transports the received substrate W into processing unit 101. Processing unit 101 performs surface cleaning on the substrate W. Specifically, after supplying a chemical solution to the surface of the rotating substrate W to remove particles, pure water is supplied to the surface of the substrate W for rinsing. After the cleaning process using the processing solution is completed, the substrate W is unloaded from processing unit 101 by the main transport robot 103 and transported into processing unit 1. Since the processing solution is still attached to the substrate W immediately after the cleaning process, processing unit 1 performs a drying process on the substrate W. In addition, processing unit 101 may rotate the substrate W at high speed after the cleaning process to perform a complete drying, but even in this case, it is not possible to completely remove moisture from the substrate W, so a drying process using processing unit 1 is necessary.

[0060] The main transport robot 103 carries the washed substrate W into the processing chamber 10 and holds it in the spin chuck 22 (step S2). The spin chuck 22 holds the substrate W in a horizontal position by suction on the center of the lower surface of the transported substrate W.

[0061] After the substrate W is held in the spin chuck 22, the processing liquid nozzle 30 moves from a standby position outside the cup 40 to a processing position above the substrate W. The rotation of the substrate W by the spin motor 25 is also started. Subsequently, the processing liquid nozzle 30 supplies the processing liquid to the surface of the substrate W (step S3). In this embodiment, the processing liquid nozzle 30 supplies IPA (isopropyl alcohol) as the processing liquid. The processing liquid nozzle 30 moves 1 cm 2 20 μl of IPA is supplied to the surface of the substrate W. The surface tension of IPA is lower than that of water, and the water adhering to the substrate W is replaced by IPA when it is supplied. After supplying the predetermined amount of IPA, the processing liquid nozzle 30 returns from the processing position to the standby position.

[0062] Figure 5 shows the state of the substrate W immediately after IPA is supplied. Immediately after IPA is supplied, the liquid level of the IPA is higher than the upper end of the pillar 85. That is, the entirety of multiple pillars 85 is submerged in the IPA. In this state, where the entirety of multiple pillars 85 is submerged in the IPA, no meniscus is formed between adjacent pillars 85, and therefore no capillary force is generated. Consequently, there is no stress acting on the multiple pillars 85, and the pillars 85 do not deform and collapse. Furthermore, even during the cleaning process in the processing unit 101, the entirety of the pillars 85 remains submerged in the processing liquid, so there is no risk of pattern collapse.

[0063] As the substrate W to which IPA is supplied rotates, the IPA is spread thinly and coated over the entire surface of the substrate W. In addition, due to the centrifugal force accompanying the rotation of the substrate W, a portion of the IPA above the upper end of the pillar 85 is scattered from the substrate W. This causes the substrate W to undergo pre-drying (step S4). Pre-drying is the removal of a portion of the IPA above the upper end of the pillar 85. In this embodiment, pre-drying is performed by the scattering of IPA due to the rotation of the substrate W and the evaporation of IPA. The period for pre-drying is at the latest as long as the liquid level of the IPA is above the upper end of the pillar 85. As for pre-heating, for example, hot air may be blown onto the substrate W to promote the evaporation of IPA. Alternatively, pre-drying may be performed by evaporating the IPA by natural drying alone.

[0064] Pre-drying causes the IPA liquid level to gradually decrease, until it eventually reaches the upper end of the pillar 85. Figure 6 shows the state of the substrate W when the IPA liquid level reaches the upper end of the pillar 85. A meniscus forms between adjacent pillars 85 when the IPA liquid level drops to a height that matches the upper end of the pillar 85. Once a meniscus is formed, capillary forces act on the pillars 85 on both sides of the meniscus.

[0065] In this embodiment, when the liquid level of the IPA coincides with the upper end of the pillar 85, the flash lamp FL irradiates the surface of the substrate W with flash light (step S5). By irradiating the substrate W with a flash light that is extremely short in duration (0.1 milliseconds to 100 millisends, 5 milliseconds in this embodiment) and of high intensity, the surface of the substrate W is instantaneously heated, and a very large amount of thermal energy is imparted to the IPA remaining on the surface. By instantaneously providing thermal energy exceeding the amount of heat required to evaporate the IPA remaining on the surface of the substrate W, the IPA evaporates in an instant and the substrate W is dried. In other words, by evaporating the IPA faster than the pattern collapses due to capillary force, the substrate W can be dried without the pattern collapsing. When irradiating with flash light, the processing liquid nozzle 30 is positioned in a standby position outside the cup 40, and the rotation of the substrate W is stopped.

[0066] After the drying process of the substrate W is completed, the main transport robot 103 removes the substrate W from the processing chamber 10 (step S6). Then, the substrate W is passed from the main transport robot 103 to the indexer robot 102 and returned to the carrier C.

[0067] In this embodiment, when the liquid level of the IPA coincides with the upper end of the pillar 85 and capillary force due to the meniscus begins to act on the pattern, a flash of light is irradiated to instantaneously evaporate any remaining IPA. If a flash of light is not irradiated, after the liquid level of the IPA coincides with the upper end of the pillar 85, the movement of the liquid level due to interaction caused by capillary force becomes dominant. As a result, as shown in Figure 7, a difference in liquid level occurs between the pillars 85. Ideally, the liquid level should be uniform even after the liquid level of the IPA coincides with the upper end of the pillar 85, but this does not happen, and a difference in liquid level always occurs.

[0068] If the liquid level is uniform, the capillary forces acting on each pillar 85 from the surroundings will also be uniform, and the pillars 85 will not deform. However, if there is a difference in the liquid level as shown in Figure 7, the balance of the capillary forces acting on each pillar 85 will be disrupted, and the pillars 85 will deform. When the degree of deformation of the pillars 85 becomes large, as shown in Figure 8, the pillars 85 will come into contact with the adjacent pillars 85, leading to the collapse of the pattern.

[0069] Therefore, in this embodiment, flash light irradiation is performed so that the IPA evaporates at a rate faster than the rate at which a difference in liquid level occurs due to interaction caused by capillary forces. In other words, by irradiating with a flash light of extremely high intensity for a very short irradiation time, the drying time required from when capillary forces begin to act on the pattern until the treated liquid is removed from the surface of the substrate W is made shorter than the collapse time required from when capillary forces begin to act on the pattern until the pattern collapses. Note that the pattern collapses when a pillar 85 deforms and comes into contact with an adjacent pillar 85.

[0070] In this way, by drying the substrate W at a speed faster than the rate at which differences in liquid level occur due to interactions caused by capillary forces, pattern collapse can be reliably suppressed even in next-generation nanostructure patterns with large aspect ratios.

[0071] Figure 9 shows the correlation between drying speed and pattern collapse rate. In the figure, the "X" marks indicate natural drying of IPA alone, which has the slowest drying speed and the highest pattern collapse rate. The square marks indicate the case where nitrogen gas at room temperature is blown onto the IPA, which has a slightly faster drying speed than natural drying, but the collapse rate is similarly high. On the other hand, the triangle marks indicate the case where normal heating is applied to the IPA, which has a considerably faster drying speed, but the collapse rate remains high. In contrast, the circle marks indicate the case where flash light is irradiated onto the IPA, as in this embodiment, which has an extremely high drying speed and a low pattern collapse rate.

[0072] Furthermore, in this embodiment, the energy of the flash light is adjusted according to the pillar spacing p between adjacent pillars 85 in the pattern. As described above, in this embodiment, the flash light is irradiated such that the drying time required from the start of capillary force acting on the pattern until the processing liquid is removed from the surface of the substrate W is shorter than the collapse time required from the start of capillary force acting on the pattern until the pattern collapses. The collapse time required for the pattern to collapse is the time required from the start of deformation of pillar 85 until it comes into contact with the adjacent pillar 85, and this time decreases as the pillar spacing p decreases. Therefore, the narrower the pillar spacing p becomes, the shorter the drying time must be, and the energy of the irradiated flash light must be increased. Specifically, the narrower the pillar spacing p becomes, the larger the charging voltage V applied to the capacitor of the power supply unit 60 is increased.

[0073] Figure 10 shows a conversion table 93 that registers the correlation between the pillar spacing p and the required charging voltage V. The correlation between the pillar spacing p and the required charging voltage V is determined in advance by experiment or simulation, and the conversion table 93 is created based on this. The created conversion table 93 is stored in the memory unit 91 of the control unit 90 (see Figure 2). As shown in Figure 10, the conversion table 93 registers a correlation in which the required charging voltage V increases as the pillar spacing p becomes narrower.

[0074] The control unit 90 reads the charging voltage V corresponding to the pillar spacing p in the pattern formed on the substrate W from the conversion table 93 and controls the power supply unit 60 to charge the capacitor with that charging voltage V. In this way, flash light of appropriate energy corresponding to the pillar spacing p in the pattern formed on the substrate W is irradiated, making the drying time shorter than the collapse time and reliably suppressing pattern collapse. The pillar spacing p in the pattern can be described, for example, in the processing recipe.

[0075] Furthermore, in this embodiment, an optical filter 70 is provided that cuts out light with a wavelength of 400 nm or less from the flash light. When the light emitted from the flash lamp FL passes through the optical filter 70, light with a wavelength of 400 nm or less is removed from the flash light. Therefore, the surface of the substrate W is irradiated with flash light from which ultraviolet light with a wavelength of 400 nm or less has been removed. Ultraviolet light with a wavelength of 400 nm or less has a significant chemical effect, and by cutting out such light with a wavelength of 400 nm or less from the flash light, it is possible to suppress damage to the pattern from extremely high-intensity flash light.

[0076] While embodiments of the present invention have been described above, various modifications can be made to this invention without departing from its spirit. For example, in the above embodiments, IPA was supplied to the substrate W as the processing liquid, but the invention is not limited to this, and other types of processing liquids may be supplied. For example, pure water may be supplied to the substrate W as the processing liquid from the processing liquid nozzle 30, and then the pure water may be evaporated by irradiating it with flash light. However, since IPA has a lower heat of evaporation and lower surface tension compared to pure water, using IPA as in the above embodiments allows the substrate W to be dried with flash light of lower energy, and the pattern is less likely to collapse.

[0077] Furthermore, in the above embodiment, a flash of light from a flash lamp FL was irradiated onto the substrate W coated with IPA to achieve a drying time shorter than the collapse time. However, instead, laser light may be irradiated onto the surface of the substrate W. Laser light also has an extremely short irradiation time and high intensity. Therefore, even if laser light is irradiated onto the substrate W coated with IPA, the drying time can be made shorter than the collapse time, and pattern collapse can be suppressed.

[0078] Furthermore, in the above embodiment, flash light was irradiated when the liquid level of the IPA coincided with the upper end of the pillar 85. However, the surface of the substrate W may be irradiated with flash light before the liquid level of the IPA coincides with the upper end of the pillar 85. That is, the substrate W may be irradiated with flash light when the liquid level of the IPA is higher than the upper end of the pillar 85. From this viewpoint, pre-drying in the above embodiment is not an essential step, and it is possible to irradiate with flash light without pre-drying. However, in this case, the amount of liquid IPA remaining on the surface of the substrate W will be larger, and the amount of heat required to completely evaporate it will be greater than in the above embodiment. Therefore, the energy of the flash light will need to be greater in order to provide more thermal energy than that amount of heat required to evaporate. Accordingly, it is most preferable to irradiate with flash light when the liquid level of the IPA coincides with the upper end of the pillar 85, as in the above embodiment.

[0079] Furthermore, in the above embodiment, the processing unit 101 performed the cleaning process on the substrate W and the processing unit 1 performed the drying process. However, it is also possible to perform both the cleaning and drying processes in a single processing unit. Specifically, for example, the processing unit 1 may be further provided with a cleaning liquid nozzle for discharging the cleaning liquid, so that the cleaning and drying processes of the substrate W are performed continuously within the processing unit 1. [Explanation of symbols]

[0080] 1,101 Processing Units 10 Processing Chambers 20 Rotating holding part 22 Spin Chuck 25 Spin Motors 30 Processing liquid nozzles 33 Nozzle drive unit 40 cups 50 Light-irradiated section 60 Power Supply Units 70 Optical Filters 90 Control Unit 85 Pillar 93 Conversion Table 100-sheet washing machine FL Flash Lamp W board

Claims

1. A substrate processing method for drying a substrate on which a pattern has been formed, A supply step of supplying a processing liquid to the surface of the substrate, A light irradiation step in which the surface of the substrate is irradiated with light and the surface is heated to evaporate the processing liquid, Equipped with, In the light irradiation step, the drying time required from the start of capillary force acting on the pattern until the treatment liquid is removed from the surface of the substrate is shorter than the collapse time required from the start of capillary force acting on the pattern until the pattern collapses. In the light irradiation step, flash light is irradiated onto the surface of the substrate from a flash lamp. A substrate processing method characterized in that, in the light irradiation step, the energy of the flash light irradiated is adjusted according to the pillar spacing between adjacent pillars in the pattern.

2. In the substrate processing method according to claim 1, A substrate processing method characterized in that the flash lamp emits a flash of light when the liquid level of the processing liquid coincides with the upper end of the pillar.

3. In the substrate processing method according to claim 1, A substrate processing method characterized by determining the charging voltage based on a conversion table that shows the correlation between the charging voltage of a capacitor in a power supply unit that supplies power to the flash lamp and the pillar spacing.

4. In the substrate processing method according to claim 1, The substrate processing method is characterized in that, in the light irradiation step, the energy of the irradiated flash light is increased as the distance between the pillars becomes narrower.

5. In the substrate processing method according to claim 1, The substrate processing method is characterized in that the light irradiation step involves irradiating the substrate with flash light that filters out light with a wavelength of 400 nm or less.

6. In the substrate processing method according to claim 1, A substrate treatment method characterized in that the treatment solution is isopropyl alcohol.

7. A substrate processing apparatus for drying a substrate on which a pattern has been formed, A substrate holding portion for holding the substrate, A processing liquid supply unit that supplies processing liquid to the surface of the substrate, A light irradiation unit that irradiates the surface of the substrate with light to heat the surface and evaporate the processing liquid, Equipped with, The drying time required from the start of capillary force acting on the pattern until the treatment liquid is removed from the surface of the substrate is shorter than the collapse time required from the start of capillary force acting on the pattern until the pattern collapses. The light irradiation unit has a flash lamp that irradiates the surface of the substrate with flash light, A substrate processing apparatus characterized by adjusting the energy of the flash light emitted from the flash lamp according to the pillar spacing between adjacent pillars in the pattern.

8. In the substrate processing apparatus according to claim 7, A substrate processing apparatus characterized in that the flash lamp emits a flash of light when the liquid level of the processing liquid coincides with the upper end of the pillar.

9. In the substrate processing apparatus according to claim 7, A substrate processing apparatus characterized by determining the charging voltage based on a conversion table that shows the correlation between the charging voltage of a capacitor in a power supply unit that supplies power to the flash lamp and the pillar spacing.

10. In the substrate processing apparatus according to claim 7, A substrate processing apparatus characterized in that the energy of the flash light emitted from the flash lamp increases as the distance between the pillars becomes narrower.

11. In the substrate processing apparatus according to claim 7, A substrate processing apparatus further comprising a filter provided between the light irradiation unit and the substrate holding unit, which cuts out light with a wavelength of 400 nm or less from the flash light emitted by the flash lamp.

12. In the substrate processing apparatus according to claim 7, The substrate processing apparatus is characterized in that the processing solution is isopropyl alcohol.

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