JP2008277779A - Atmosphere exchange method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an atmosphere exchange method of reducing the adhesion of particles to a substrate in a vacuum chamber. <P>SOLUTION: There is provided a method for exchanging atmosphere of the vacuum chamber for a processor for processing a substrate in a vacuum environment. The method includes a process for holding the substrate; with a holding unit laid within the vacuum chamber and a process for exchanging the atmosphere of the vacuum room by means of discharging or supplying air. In the process for exchanging the atmosphere of the vacuum chamber, pressure in the vacuum chamber is retained to be not lower than 10 Pa and not higher than 10,000 Pa of the pressure of the vacuum chamber for 10 or higher and 600 or lower seconds with the temperature made adjustment to lower temperature than that of the substrate in a dust collection unit that is laid within the vacuum chamber. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an atmosphere replacement method.

  Conventionally, load lock chambers for receiving a substrate from a substrate storage unit arranged in an atmospheric pressure environment and carrying it into a processing chamber for processing in a vacuum environment, or receiving a processed substrate from a processing chamber and carrying it out to a substrate storage unit have been known. It has been. The processing chamber in this case is an EUV (Extreme Ultraviolet) exposure apparatus or a plasma processing apparatus.

  The load lock chamber has a function of replacing the atmosphere of the internal space between an atmospheric pressure environment and a vacuum environment. Specifically, when the substrate is carried into the processing chamber, the atmosphere is changed from the atmospheric pressure environment to the vacuum environment (evacuation process), and when the substrate is carried out to the substrate storage unit, the atmosphere is changed from the vacuum environment to the atmospheric pressure environment. Replace atmosphere (supply process). The load lock chamber is connected to the processing chamber via a gate valve and has a substrate transfer mechanism.

  However, since particles generated from the gate valve and the substrate transport mechanism are rolled up during supply and exhaust, a means for reducing or preventing the adhesion of the particles to the substrate is required. In view of this, a method has been proposed in which particle adhesion to the substrate is reduced by utilizing thermophoretic force. In this method, as described in Patent Document 1, the holding unit that holds the substrate is heated to a temperature higher than the ambient temperature, and particles are collected by a low-temperature particle collector that is maintained at a temperature lower than the ambient temperature. To do.

  The principle of thermophoretic force is that when there is a temperature gradient in the gas surrounding the particle, the particle is given a larger kinetic energy than the gas molecule on the cold side, and the particle is transferred from the object on the hot side to the cold side. To move to. The thermophoretic force Fx is given by the following equation obtained by modifying the thermophoretic coefficient equation described in Non-Patent Document 1.

However, Formula 1 assumes that the particles are spherical and the fluid is an ideal gas. Here, Dp is the particle diameter, T is the gas temperature, μ is the viscosity coefficient, ρ is the gas density, Kn is the Knudsen number 2λ / Dp, and λ is the mean free path of the gas η / {0.499P (8M / πRT ^1/2 }, M is the molecular weight, R is the gas constant, and K is k / kp. Further, k is the thermal conductivity of the gas only by the energy of parallel movement, kp is the thermal conductivity of the particle, Cs is 1.17, Ct = 2.18, Cm = 1.14, and ΔT / Δx is the temperature gradient. .
Special registration 2886521 Co-authored by Kikuo Okuyama, Hiroaki Masuda, and Seiji Morooka, “New System Chemical Engineering, Fine Particle Engineering”, published by Ohmsha, May 1992, P106-107

  However, since the size of the load lock chamber is restricted by the gate opening size (W360 mm × H80 mm) defined by the unified standard of the semiconductor industry, it cannot be made as small as the outer shape of the substrate. Therefore, the thermophoretic force in the vicinity of the substrate holding part has to depend on the shape of the load lock chamber, and there is a problem that the thermophoretic force cannot be utilized to the maximum extent.

  The present invention relates to an atmosphere replacement method for reducing particles from adhering to a substrate in a vacuum chamber. In the present invention, the “vacuum chamber” is a device that in principle requires a depressurized state, such as an exposure chamber of an EUV exposure apparatus, and a depressurized state that is temporarily maintained, such as a load lock chamber of a substrate transfer apparatus. Means a device.

  An atmosphere replacement method according to one aspect of the present invention is a method for replacing an atmosphere in a vacuum chamber of a processing apparatus for processing a substrate in a vacuum environment, and the substrate is held by a holding unit installed in the vacuum chamber. And a step of replacing the atmosphere in the vacuum chamber by exhaust or supply, and in the step of replacing the atmosphere in the vacuum chamber, the temperature of the dust collection unit installed in the vacuum chamber is the temperature of the substrate. The pressure in the vacuum chamber is maintained in the range of 10 Pa to 10000 Pa for 10 seconds to 600 seconds in a state adjusted to a lower temperature.

  Further objects and other features of the present invention will become apparent from the preferred embodiments described below with reference to the accompanying drawings.

  ADVANTAGE OF THE INVENTION According to this invention, it can reduce that the particle | grains which float in a vacuum chamber adhere to a board | substrate.

  Hereinafter, a processing apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings. In this embodiment, an EUV exposure apparatus is used as a processing apparatus for processing a substrate in a vacuum environment, but the processing apparatus of the present invention is not limited to this.

  FIG. 1 is a schematic sectional view of an exposure apparatus according to the first embodiment. In FIG. 1, 1 is an excitation laser, which uses a YAG solid-state laser or the like. The excitation laser 1 emits light by irradiating a laser beam toward a point where a light source material serving as a light emitting point of a light source is gasified, liquefied or atomized gas, and plasma source excitation is performed on the light source material atoms. Reference numeral 2 denotes a light source emitting portion of the exposure light source, and the inside has a structure maintained in a vacuum, and 2A denotes a light emission point of the exposure light source. A light source mirror 2B is arranged as a hemispherical mirror centered on the light emitting point 2A in order to collect and reflect all spherical light from the light emitting point 2A in the light emitting direction. The luminescent point 2A is ejected with liquefied Xe, liquefied Xe spray or Xe gas as a luminescent element by a nozzle (not shown) and irradiated with light from the excitation laser 1.

  Reference numeral 3 denotes an exposure chamber (processing chamber) connected to the light source light emitting unit 2. The exposure chamber 3 is maintained in a vacuum environment by an exhaust unit (vacuum pump) 4A (that is, configured to be depressurized). Thus, the exposure chamber 3 is a vacuum chamber capable of maintaining a vacuum pressure suitable for EUV exposure. Reference numeral 5 denotes an illumination optical system that introduces and molds exposure light from the light source light emitting unit 2, and is configured by mirrors 5A to 5D to homogenize and shape the exposure light. Reference numeral 6 denotes a reticle stage, and a reticle (original) 6A, which is a reflection original of an exposure pattern, is electrostatically held by a movable portion on the reticle stage.

  Reference numeral 7 denotes a projection optical system for reducing and projecting the exposure pattern reflected from the reticle 6A. The exposure pattern reflected by the reticle 6A is sequentially reflected on the mirrors 7A to 7E and finally reduced onto the wafer 8A at a specified reduction ratio. Project. Reference numeral 8 denotes a wafer stage. In order to position a wafer 8A, which is a Si substrate for exposing a reticle pattern, at an exposure position, six axes in each of the XYZ axial directions, tilts around the X and Y axes, and rotational directions around the Z axis. Positioning is controlled so that it can be driven.

  A support 9 supports the reticle stage 6 against the floor. A support 10 supports the projection optical system 7 with respect to the floor. A support 11 supports the wafer stage 8 with respect to the floor. In addition, a control unit (not shown) is provided between the reticle stage 6 and the projection optical system 7, and the relative position between the projection optical system 7 and the wafer stage 8 is measured and continuously maintained. The supports 9 to 11 are provided with mounts (not shown) that insulate vibrations from the floor.

  Reference numeral 16 denotes a wafer stocker that temporarily stores the wafer 8A transferred by the atmospheric wafer transfer unit 17A inside the apparatus. The wafer stocker 16 stores a plurality of wafers 8A. The wafer 8A to be exposed is selected from the wafer stocker 16, and is transferred to the holding unit 18 installed in the vacuum chamber (inside the load lock chamber 26). Reference numeral 19 denotes a shield (dust collecting unit) that surrounds the periphery of the wafer 8A. A gate valve 20D connects the space where the wafer stocker 16 is located and the load lock chamber 26, and opens and closes when the load lock chamber 26 is at atmospheric pressure. 20E is also a gate valve that connects the load lock chamber 26 and the exposure chamber 3, and opens and closes when the load lock chamber 26 is in a vacuum state. A wafer transfer unit 17B capable of vacuum transfer of the wafer 8A transfers the wafer 8A from the holding unit 18 to a wafer mechanical pre-alignment temperature controller (not shown) in the exposure chamber (processing chamber). The wafer mechanical pre-alignment temperature controller performs feed coarse adjustment in the rotation direction of the wafer 8A, and simultaneously adjusts the wafer temperature to the reference temperature of the exposure apparatus. The wafer transfer unit 17B sends the wafer 8A, which has been aligned and temperature-controlled by the wafer mechanical pre-alignment temperature controller, to the wafer stage 8.

  The process of unloading the wafer 8A from the exposure chamber 3 is the reverse of the loading procedure.

  Reference numeral 27 denotes an SMIF pod which is a mini-environment used for transporting a reticle cassette in a device factory. A reticle cassette 31 is held in the SMIF pod. When the SMIF pod is opened and closed by the SMIF indexer 34, the reticle cassette 31 is drawn into the exposure apparatus and can be transported by the reticle transport unit 14A. Reference numeral 24 denotes a load lock chamber for converting the reticle cassette 31 from an air atmosphere to a vacuum atmosphere, and includes a cassette holding unit 28 therein.

  A gate valve 20A connects the space where the reticle cassette 31 exists and the load lock chamber 24. The gate valve 20A opens and closes when the load lock chamber 24 is at atmospheric pressure. This is a gate opening / closing mechanism for carrying the reticle 6A from the SMIF indexer 34 to the holding unit of the load lock chamber 24. 20B is also a gate valve and opens and closes when the load lock chamber 24 is in a vacuum state. 20C is also a gate valve, which opens and closes only when the reticle 6A is conveyed to the exposure chamber 3.

  Reference numeral 12 denotes a reticle stocker that temporarily stores the reticle 6A in the reticle cassette 31 from the outside of the apparatus. The reticle 6A is stored in multiple stages according to different patterns and different exposure conditions.

  A reticle transport unit 14 </ b> A transports the reticle cassette 31 from the load lock chamber 24 to the reticle stocker 12. The reticle transport unit 14B is arranged in the reticle transport chamber 13, selects a reticle to be used from the reticle stocker 12, and transports the reticle cassette 31 to a cover opening mechanism 13A that separates the cassette upper cover and the cassette lower dish. The reticle transport unit 14B transports the cassette lower pan in a state separated by the lid opening mechanism 13A to the reticle alignment scope 15 provided at the end of the reticle stage 6. Thereby, the alignment on the reticle 6A is finely moved in the XYZ axis rotation direction with respect to the alignment mark 15A provided on the casing of the projection optical system 7.

  The aligned reticle 6A is chucked directly onto the reticle stage 6 from the cassette lower plate. At this time, at least one of raising of the cassette support part or lowering of the reticle stage is performed so that the relative positions of the cassette support part of the alignment part and the reticle stage 6 are brought close to each other. At that time, the tilt adjustment of the reticle 6A and the reticle stage 6 is also performed. After the reticle 6A is delivered to the reticle stage 6, the empty cassette lower pan is pulled back to the lid opening mechanism 13A by the reticle transport unit 14B, and is stored in the reticle stocker 12 after the lid is closed.

  FIG. 2 is a schematic cross-sectional view of the load lock chamber 26, and shows a state in which the shield 19 as a dust collection unit is moved downward by the drive unit 21, and the shield 19 surrounds the surface of the wafer 8A. The drive unit 21 has a function of bringing at least one of the holding unit 18 and the shield 19 closer to the other after the temperature control units 22A and 22B adjust the temperature of the surface of the shield 19 facing the wafer 8A.

  By moving the shield 19, it is possible to create a narrow space in which the distance between the wafer surface and the shield 19 is 0.5 cm or less, so that the temperature gradient in the space near the wafer surface is larger than that in the conventional vacuum chamber. be able to.

  The load lock chamber 26 is partitioned from the exposure chamber 3 by a gate valve 20E. The pressure detection unit 32 detects that the load lock chamber is evacuated, opens the gate valve 20E, and loads the wafer 8A into the exposure chamber 3. Or carry out. The load lock chamber 26 is configured so that the internal space can be exhausted or depressurized by the exhaust unit 4B, and the internal space can be supplied or pressurized by the air supply unit 29. As described above, the load lock chamber 26 replaces the atmosphere of the internal space between the vacuum environment and the atmospheric pressure environment.

  A flow rate variable valve 33 </ b> A for adjusting the exhaust flow rate and the supply air flow rate is installed in the pipe 23 between the exhaust unit 4 </ b> B and the exhaust port of the load lock chamber 26. The pipe 23 between the air supply unit 29 and the air supply port of the load lock chamber 26 is provided with a variable flow rate valve 33B for adjusting the exhaust flow rate and the air supply flow rate. The flow rate of the gas flowing through the pipe 23 can be arbitrarily changed by the control unit 30 that controls the pressure detection unit 32 and the exhaust / supply / supply unit.

  In this way, each time the wafer 8A before / after processing is taken in and out of the load lock chamber 26, air supply and exhaust are repeated. For this reason, there is a possibility that particles such as fluorine fine particles generated from the gate valve in the load lock chamber 26 and silver plating fine particles generated from the wafer transfer mechanism are wound up in the process of exhaust / air supply and adhere to the wafer 8A. Therefore, it is important to reduce the fine particles adhering to the wafer 8A in the process of exhausting / supplying air from the load lock chamber 26.

In the holding unit 18 that holds the wafer 8A, all members including the support pins 18A are temperature-controlled at the first temperature (23 ° C.) by the first temperature adjustment unit 22A. This temperature is the same as the temperature of the wafer 8A carried by the holding unit 18. In the present embodiment, the entire surface of the holding unit 18 is uniformly temperature-controlled by circulating a heat medium inside the holding unit 18. The shield 19 for protecting the wafer surface from the particles is temperature-controlled at the second temperature (13 ° C.) by the second temperature control unit 22B on the surface facing the wafer surface. The second temperature on the surface of the shield 19 is adjusted to be 10 ° C. lower than the first temperature. Thus, the temperature control units 22A and 22B can adjust the temperature of the surface of the shield 19 facing the wafer 8A to a temperature lower than the temperature of the wafer 8A. Accordingly, the shield 19 operates as a dust collecting unit having a dust collecting portion. FIG. 3 is a graph showing the thermophoretic force and gravity acting on the fluorine fine particles when the temperature gradient is 10 [K / cm]. The axis is the force [m / s ² ], and the horizontal axis is the pressure [Pa] of the load lock chamber 26. The thermophoretic force curve is obtained by considering the temperature jump of the gas temperature and the solid temperature in Equation 1. From FIG. 3, it is understood that the force acting on the fine particles is maximized at a pressure in the range of 10 Pa to 10,000 Pa.

  In this embodiment, the pressure of the load lock chamber 26 is controlled while the temperature of the shield 19 is controlled and the position is controlled so that the temperature gradient of the space becomes 10 K / cm or more.

FIG. 4 is a graph showing the velocity of fine fluorine particles having a diameter of 0.1 to 1.5 μm floating in the vicinity of the wafer 8A in the load lock chamber 26. The vertical axis represents the velocity of the fine particles [m / s], and the horizontal axis. Is the pressure [Pa] of the load lock chamber 26. The speed is expressed with the direction of gravity as positive. Further, the velocity V ₁ of the fine particles floating near the wafer surface is indicated by a solid line, and the velocity V ₂ of the fine particles floating near the wafer rear surface is indicated by a one-dot chain line. The velocity of fine particles floating near the surface can be expressed by the following equation.

  The thermophoretic velocity can be expressed by the following equation.

Here, the thermophoretic coefficient _Kth is given by the following equation.

  ν is the kinematic viscosity of the gas, α is the specific heat ratio, and is given by the gas heat conduction ratio / particle heat conduction ratio. The average deposition rate on the wafer 8A in the laminar flow field is given by the following equation.

Here, D is a diffusion coefficient and is given by C _C kT / (3πμD _p ). L is the diameter of the wafer, u ₀ is the average velocity of the air current in sufficient distance from the wafer 8A, S _c is given by [nu / D Schmitt number. k is the Boltzmann factor, _{v g} is the gravitational settling velocity ^{_{= D p 2 ρ p gC C}} / (18μ), ρ p is the density of particles, g is the gravitational acceleration, _{C C} is ₁ + K n by the correction factor of Cunningham [1.25 + 0 .4exp (−1.1 / K _n )].

  Expressions 2 to 4 are disclosed in “Renewed Silicon Wafer Surface Cleaning Technology”, published by Realize Science and Technology Center, May 2000, P72-74, supervised by Hattori.

FIG. 5 is a flowchart of wafer processing according to the first embodiment. FIG. 6A is a graph showing an exhaust process of the load lock chamber 26 according to the first embodiment. The vertical axis represents the pressure [Pa] of the load lock chamber 26 and the horizontal axis represents the exhaust time [second]. FIG. 6B is a graph showing the air supply process of the load lock chamber 26 according to the first embodiment. The vertical axis represents the pressure [Pa] of the load lock chamber 26 and the horizontal axis represents the air supply time [second]. 6A and 6B, “E ± XX” on the vertical axis represents “× 10 ^{± XX} ”.

Example 1 is suitable for reducing fluorine fine particles having a diameter of 1.0 μm. As shown in FIG. 4, the pressure of 3.0E + 04 to 5.0E + 04 Pa is such that the moving speed of the fluorine fine particles having a diameter of 1.0 μm floating in the load lock chamber 26 is maximized in the direction opposite to the wafer 8A. At this time, the time required to move the distance of 0.05 mm from the wafer 8A to the shield 19 is 27 seconds. Accordingly, by maintaining the pressure state of 3.0E + 04 to 5.0E + 04 Pa for 27 seconds or more, the fluorine fine particles having a diameter of 1.0 μm floating between the wafer surface and the shield 19 collide with the shield 19 at least once. Due to this collision, the fine particles adhere to the shield 19, so that the adhesion of the fine particles to the wafer surface can be reduced. For this reason, in this embodiment, the pressure of 3.0E-4 to 5.0E-4 Pa is set as the first pressure, and the microphoresis adheres to the wafer 8A using the thermophoretic force generated in this pressure range. Reduced. In the present embodiment, the fine particles are explained by using fluorine fine particles having a specific gravity of 2130 kg / m ³ as a representative. However, the present embodiment can be applied to other fine particles having different specific gravity.

  In FIG. 5, S100 is a resist coating process, and the wafer 8A after the coating process is transported to the exposure apparatus. In step S101, the wafer 8A is loaded onto the wafer stocker 16 of the exposure apparatus.

  S102 is a step of adjusting the temperature of the holding unit 18 to a temperature of 24 ° C. which is about 1 ° C. lower than the wafer 8A carried into the holding unit 18 from the wafer stocker 16 and adjusting the temperature of the shield 19 to 4 ° C. Holding the wafer at a temperature lower than that of the wafer 8A has an effect of preventing fine particles from adhering to the wafer 8A due to thermophoretic force. In S103, the temperature sensor (not shown) detects that the temperature control of the holding unit 18 and the shield 19 has been completed, and determines. When the temperature adjustment is completed, the process proceeds to the next step. If the temperature adjustment has not been completed, the process returns to the previous step S102.

  S104 is a step of opening the gate valve 20D and transporting and holding the wafer 8A to the holding unit 18 before the load lock chamber 26 is exhausted, that is, in a state of atmospheric pressure. After the transfer of the wafer 8A, the gate valve 20E is closed. When the load lock chamber 26 is at atmospheric pressure, fine particles having a diameter of 1.0 μm or less do not drop by gravity, but are suspended by airflow and Brownian motion. Fine particles larger than 1.0 μm in diameter move in the direction of gravity and adhere to the wafer 8A. However, since the wafer 8A in the load lock chamber 26 is surrounded by the shield 19, the probability of attachment to the wafer 8A is reduced.

  When the density of the fine particles floating in the space between the shield 19 and the wafer 8A is the same as the density of the fine particles floating in other spaces, the larger the volume ratio of the vicinity of the wafer 8A inside the shield and the volume outside the shield is, the larger the ratio is. The effect is increased. In this embodiment, the volume ratio is about 0.003. Therefore, when 1000 particles move in the direction of gravity in the load lock chamber, only 3 particles adhere to the wafer 8A, so the number of particles attached to the wafer 8A is reduced.

  S <b> 105 is a step of moving the shield 19 toward the holding unit 18. The shield 19 is brought close to the wafer 8A to surround the whole. The entire wafer 8A is surrounded by a very small space of about 0.5 cm between the surface of the shield 19 and the wafer 8A. At this time, the shield 19 is intentionally provided with a clearance designed to have a conductance that allows exhaust / air supply simultaneously with the load lock chamber 26. Therefore, exhaust / air supply inside the shield 19 can be performed simultaneously with the entire load lock chamber 26. In this embodiment, the temperature of the shield 19 is controlled and the position is controlled so that the temperature gradient in the space between the shield 19 and the wafer 8A is 40 [K / cm].

  S106 is a first exhaust process. Exhaust is performed by the exhaust unit 4B until the pressure in the load lock chamber 26 reaches 5.0E + 04 Pa from the atmospheric pressure state. When the conventional load lock chamber 26 is depressurized, fine particles having a diameter of 1.0 μm or less begin to move in the direction of gravity. However, in the load lock chamber 26 according to this embodiment, fine particles having a diameter of 1.0 μm or less move in the direction of the shield 19, not in the gravity direction, due to the thermophoretic force. Further, as shown in the graph of FIG. 4, fine particles having a diameter of 1.5 μm or more cannot move in the direction of the shield 19 because the gravity exceeds the thermophoretic force.

  S107 is a second exhaust process. As shown in FIG. 6 (a), the pressure in the load lock chamber 26 is reduced to 5.0E + 04 to 3.0E + 04Pa at a constant exhaust speed, so that the first pressure is maintained for the minimum time during which the effect of thermophoresis can be obtained. maintain. In this embodiment, in order to lower the exhaust speed than in the first exhaust process, the opening degree of the flow rate variable valve 33A is controlled to be small when the pressure in the load lock chamber 26 reaches 5.0E + 04 Pa. Part of the fine particles colliding with the shield 19 adheres to the shield 19 due to the adhesion force caused by van der Waals force.

  In this example, the time for moving the 1.0 μm fluorine fine particles to the shield 19 0.5 cm above was set to 40 seconds. That is, the pressure is reduced to 5.0E + 04 to 3.0E + 04 Pa in 40 seconds to collect fine particles. It is preferable to change the time according to the specific gravity of the fine particles which are the most problematic in the processing step of the wafer 8A.

  S108 is a third exhaust process. The vacuum is exhausted from 5.0E + 04 to 3.0E + 04 Pa, which is the first pressure, to 1.0E-04 Pa, which is the second pressure. S 109 is a step of moving the shield 19 in the direction opposite to the holding unit 18. The shield 19 is retracted to an appropriate position so that the wafer 8A can be transferred by the transfer unit 17B.

  In general, in the second exhaust process, the temperature of the shield 19 installed in the load lock chamber is lower than the temperature of the substrate in a state where the pressure in the range of 10 Pa to 10,000 Pa is maintained for 10 seconds to 600 seconds. Adjusting to the temperature is sufficient. The reason why the pressure is in the range of 10 Pa or more and 10,000 Pa or less is that the thermophoretic force obtained from FIG. 3 is the maximum or 98% of the maximum value. The reason why “10 seconds or more” is set is that 10 seconds is the shortest time required for the fluorine fine particles having a diameter of 1.0 μm to move to the shield 19. The condition at this time is that the distance between the wafer 8A and the shield 19 is 0.2 cm, and the temperature gradient of the space between the shield 19 and the wafer 8A is 100 [K / cm]. The reason why “600 seconds or less” is set is that 600 seconds is the longest time required for the fluorine fine particles having a diameter of 1.0 μm to move to the shield 19. The condition at this time is that the distance between the wafer 8A and the shield 19 is 1.0 cm, and the temperature gradient in the space between the shield 19 and the wafer 8A is 10 [K / cm]. Further, in FIG. 6A, the exhaust speed in the second exhaust process is monotonously decreasing, but this inclination does not matter. In FIG. 6A, the exhaust speed of the second exhaust process has a slope different from that of the first exhaust process and the third exhaust process, but the first to third exhaust processes decrease monotonously. May be. This also applies to Examples 2 and 3, which will be described later with reference to FIGS. 7 (a) and 8 (a).

  S110 is a vacuum transfer process. After the load lock chamber 26 is evacuated, that is, in a state of the second pressure, the gate valve 20E is opened, and the wafer 8A is transferred to the exposure chamber 3 by the transfer unit 17B. After the transfer, the gate valve 20E is closed. In this step, since there are almost no fine particles floating in the load lock chamber 26, the possibility of adhering to the wafer 8A is low even if it is transported.

  S111 is an exposure process. Since S112 is the same as S102, description thereof is omitted. In step S113, the temperature of the holding unit 18 is adjusted to 22 ° C., which is about 1 ° C. lower than the wafer carried into the holding unit 18 from the exposure chamber 3, and the temperature of the shield 19 is adjusted to 12 ° C. S114 is a vacuum transfer process. The gate valve 20E is opened while the load lock chamber 26 is at the second pressure, and the wafer 8A is transferred to the holding unit 18 of the load lock chamber 26 by the transfer unit 17B. After the transfer, the gate valve 20E is closed.

  S115 is a step of moving the shield 19 in the direction of the holding unit 18, and since it is the same as S105, description thereof is omitted. S116 is a first air supply process. In the first air supply process, air is supplied until the pressure in the load lock chamber 26 is changed from the second pressure 1E−04 Pa to 3.0E + 04 Pa which is the first pressure.

  S117 is a second air supply process. Air is supplied until the pressure in the load lock chamber 26 reaches 5.0E + 04 Pa. Although the fine particles wound up in the load lock chamber in the first air supply process fall, the thermophoretic force acts in the vicinity of the wafer 8A and moves to the shield 19 to reduce adhesion to the wafer 8A. In this example, the time for moving the 1.0 μm fine fluorine particles to the shield 19 0.5 cm above was set to 40 seconds as in S107.

  S118 is a third air supply process. Air is supplied until the pressure in the load lock chamber 26 reaches atmospheric pressure. In this step, the fine particles wound up in the first and second air supply steps are floating. Since the wafer 8A is surrounded by the shield 19, adhesion of fine particles to the wafer 8A can be reduced. S 119 is a process of transferring the wafer 8 A in the load lock chamber 26 to the wafer stocker 16 in the atmosphere. S120 is a resist coating process.

  In general, in the second air supply process, similarly to the second exhaust process, the shield installed in the load lock chamber in a state where the pressure in the range of 10 Pa to 10,000 Pa is maintained for 10 seconds to 600 seconds. It is sufficient to adjust the temperature of 19 to a temperature lower than the temperature of the substrate. The reason for “pressure in the range of 10 Pa or more and 10,000 Pa or less” and “10 seconds or more and 600 seconds or less” is also the same as in the second exhaust process. In addition, in FIG. 6B, the air supply speed in the second air supply process decreases to an increase, but this inclination does not matter. In FIG. 6B, the air supply speed of the second air supply process has a slope different from that of the first air supply process and the third air supply process, but the first to third air supply processes. May increase monotonically. This also applies to Examples 2 and 3 which will be described later with reference to FIGS. 7B and 8B.

  As described above, in the exhaust / supply process of the load lock chamber 26, the thermophoretic force is utilized to the maximum by maintaining the first pressure in the range of 5.0E + 04 to 3.0E + 04Pa for a certain period of time. It is possible to reduce adhesion of fine particles to the surface.

  The present embodiment is different from the first embodiment in that the pressure in the load lock chamber 26 may vary within a certain pressure range in the second exhaust process in S107 and the second air supply process in S117. FIG. 7A is a graph showing an exhaust process of the load lock chamber 26 according to the second embodiment. The vertical axis represents the pressure [Pa] of the load lock chamber 26, and the horizontal axis represents the exhaust time [second]. FIG. 7B is a graph showing the air supply process of the load lock chamber 26 according to the second embodiment. The vertical axis represents the pressure [Pa] of the load lock chamber 26 and the horizontal axis represents the exhaust time [second].

  The second exhaust process of S107 will be described. Exhaust is performed to reduce the pressure in the load lock chamber 26 to 3.0E + 04 to 5.0E + 04 Pa. When the pressure in the load lock chamber 26 reaches 100 Pa, the exhaust valve is closed and the exhaust is temporarily stopped. For this reason, the Brownian motion of the gas acting on the fine particles is reduced, and the relative thermophoretic force can be increased. Although the pressure in the load lock chamber 26 gradually increases due to outgas and leak, since the effect of thermophoretic force is large in this pressure range, adhesion of fine particles can be reduced. In this pressure range, the fine particles inside the shield 19 do not drop by gravity, move toward the shield 19 by the thermophoretic force, and adhere to the shield 19.

  The second air supply process of S117 in the second embodiment will be described. Air is supplied until the pressure in the load lock chamber 26 reaches 100 Pa. When the pressure in the load lock chamber 26 reaches 100 Pa, the flow rate variable valve 33B is closed and the supply of air is temporarily stopped. For this reason, the Brownian motion of the gas acting on the fine particles is reduced, and the relative thermophoretic force can be increased. Therefore, Example 2 can reduce the adhesion of fine particles to the wafer 8A.

  This example is suitable for reducing fluorine fine particles having a diameter of 1.0 μm. This embodiment is different from the first embodiment in that the opening degree of the exhaust valve of the load lock chamber 26 is controlled in the second exhaust process, and the exhaust flow rate is controlled and maintained at 4.0E + 04 Pa. The first pressure in this example is 4.0E + 04 Pa.

  As shown in FIG. 4, when the pressure in the load lock chamber 26 is 4.0E + 04 Pa, the speed in the direction opposite to the gravity becomes maximum. At this time, the time required to move the distance of 0.05 mm from the surface of the wafer 8A to the shield 19 is 215 seconds. Therefore, by maintaining the pressure state of 4.0E + 04 Pa for 215 seconds, the fine particles floating between the wafer surface and the shield 19 collide with the shield 19 at least once. Due to this collision, the fine particles adhere to the shield 19, so that the adhesion of the fine particles to the wafer surface can be reduced.

  The movement time of the fine particles takes 221 seconds when the pressure in the load lock chamber 26 is 3.0E-04 Pa, and 230 seconds when the pressure is 5.0E-04 Pa. This reduces the throughput of the apparatus. Therefore, in this embodiment, the diameter and mass are reduced by reducing the adhesion of fine particles to the wafer 8A by using the thermophoretic force generated in this pressure range with the pressure of 4.0E + 04 Pa as the first pressure. Reduces large particles in a minimum amount of time.

  FIG. 8A is a graph showing an exhaust process of the load lock chamber 26 according to the third embodiment. The vertical axis represents the pressure [Pa] of the load lock chamber 26 and the horizontal axis represents time [second]. Including the transfer process of the wafer 8A and the moving process of the shield 19, the atmospheric transfer process, the first exhaust process, the second exhaust process, the third exhaust process, and the vacuum transfer process are shown separately. This embodiment is different from the first embodiment in the second exhaust process.

  Hereinafter, the second exhaust process will be described. When the pressure in the load lock chamber 26 reaches 500 Pa, slow exhaust and slow air supply are performed so that the exhaust gas is switched to slow exhaust and maintained at 500 Pa. The exhaust flow rate of the load lock chamber 26 is controlled by controlling the opening degree of the flow rate variable valve 33 </ b> A installed between the exhaust unit 4 </ b> B and the load lock chamber 26. Further, the air supply flow rate of the load lock chamber 26 is controlled by controlling the opening degree of the flow rate variable valve 33 </ b> B installed between the air supply unit 29 and the load lock chamber 26.

  FIG. 8B is a graph showing an air supply process of the load lock chamber 26 according to the present embodiment. The vertical axis represents the pressure [Pa] of the load lock chamber, and the horizontal axis represents time [second]. Including the transfer process of the wafer 8A and the moving process of the shield 19, the vacuum transfer process, the first supply process, the second supply process, the third supply process, and the atmospheric transfer process are shown separately. The second embodiment is different from the first embodiment in the second air supply process. The load lock chamber 26 is maintained at 500 Pa by the same control as in the second air supply process.

  Since the load lock chamber 26 of the third embodiment can always generate the maximum thermophoretic force, the effect of reducing the adhesion of fine particles is greater than that of the load lock chamber 26 of the first and second embodiments. Therefore, the third embodiment can reduce the adhesion of fine particles to the wafer 8A.

  Although the above-mentioned embodiment is an application example to a semiconductor wafer that is a silicon substrate, the substrate to which the present invention is applied is not limited to a wafer. Further, in the vacuum chamber, thermophoretic force acts on particles floating near the surface of the substrate, and particle adhesion to the substrate surface can be reduced. In this embodiment, the surface of the substrate is arranged in a direction perpendicular to the gravity, but the present invention does not limit the orientation of the substrate.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the gist.

It is a schematic sectional drawing of the exposure apparatus by Example 1 of this invention. It is a schematic sectional drawing of the load lock chamber shown in FIG. It is the graph which showed the thermophoretic force which acts on the fluorine fine particle which floats in the load lock chamber shown in FIG. It is the graph which showed the relationship between the moving speed of a fluorine fine particle, and a pressure. It is a flowchart by Example 1 of the present invention. It is the graph which showed the pressure curve of the load lock chamber by Example 1 of this invention. It is the graph which showed the pressure curve of the load lock chamber by Example 2 of this invention. It is the graph which showed the pressure curve of the load lock chamber by Example 3 of this invention.

Explanation of symbols

3 Exposure chamber (vacuum chamber)
4B Exhaust unit 18 Holding unit 19 Shield 21 Drive unit 22A, 22B Temperature control unit 24 Load lock chamber (vacuum chamber)
29 Air supply unit

Claims (5)

A method for replacing an atmosphere in a vacuum chamber of a processing apparatus for processing a substrate in a vacuum environment,
Holding the substrate with a holding unit installed in the vacuum chamber;
Replacing the atmosphere of the vacuum chamber with exhaust or supply air,
In the step of replacing the atmosphere in the vacuum chamber, the pressure in the vacuum chamber is set to 10 Pa or more and 10,000 Pa or less in a state where the temperature of the dust collection unit installed in the vacuum chamber is adjusted to a temperature lower than the temperature of the substrate. An atmosphere replacement method characterized in that the range is maintained for 10 seconds or more and 600 seconds or less.   The atmosphere replacement method according to claim 1, further comprising a step of bringing one of the substrate and the dust collection unit held by the holding unit closer to the other.   In the approaching step, the substrate and the dust collection unit held by the holding unit so that a temperature gradient in the space between the substrate held by the holding unit and the dust collection unit is 10 K / cm or more. The atmosphere replacement method according to claim 2, wherein one of the units is brought close to the other.   The atmosphere replacement method according to claim 1, wherein the vacuum chamber is a load lock chamber connected to a processing chamber for processing the substrate through a gate valve. A step of processing a substrate in a processing chamber in a vacuum environment;
Replacing the atmosphere of the load lock chamber connected to the processing chamber for processing the substrate through a gate valve using the atmosphere replacement method according to any one of claims 1 to 3;
And a step of moving the substrate between the processing chamber and the load lock chamber via the gate valve.