JP2012033922A - Exposure apparatus, and method for manufacturing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct imaging characteristics of a projection optical system.SOLUTION: Illumination light emitted from an illumination system via a first reticle is radiated to a second reticle, which is reflective, by a first image-formation optical system, and the illumination light via the second reticle R2 is radiated to a wafer by a second image-formation optical system. Then a regulator changes a reflection distribution by the second reticle R2 within an irradiation region IA R2 by driving the second reticle R2 relative to the irradiation region IA R2 (illumination light) on the basis of the measurement information of position measurement sensors 63, 64.

Description

  The present invention relates to an exposure apparatus and a device manufacturing method, and more particularly to an exposure apparatus used in a lithography process for manufacturing an electronic device (microdevice) and a device manufacturing method using the exposure apparatus.

  Conventionally, in a lithography process for manufacturing electronic devices (microdevices) such as semiconductor elements (integrated circuits, etc.), liquid crystal display elements, etc., a step-and-repeat type projection exposure apparatus (so-called stepper) or a step-and-scan type Projection exposure apparatuses (so-called scanning steppers (also called scanners)) are mainly used.

  As semiconductor devices are highly integrated, the patterns are gradually miniaturized. To cope with the miniaturization of patterns, the exposure wavelength is shortened and the numerical aperture of the projection optical system is increased (high NA). Etc.) have been attempted. For example, the exposure wavelength is shortened to 193 nm of an ArF excimer laser, and the numerical aperture exceeds 1 in the case of a so-called immersion exposure apparatus. However, the demand for higher integration of semiconductor elements does not stop, and along with this, the exposure apparatus is required to further improve the resolution, and now it is finer than the resolution limit of the projection exposure apparatus. It has been demanded that a simple pattern image can be formed on a substrate (wafer). As a possible countermeasure for this, a so-called double patterning method or the like has recently been performed.

  Further, the projection exposure apparatus is required to have high throughput as well as high resolution. For this reason, high-energy illumination light is used, and thermal expansion of the reticle (or mask) or lens elements constituting the projection optical system associated with the use of the exposure apparatus has become a problem.

  Conventionally, as a countermeasure against thermal expansion of the reticle, a method of cooling the reticle, for example, a method of blowing temperature-controlled air (gas) (see, for example, Patent Document 1) has been proposed. Further, as a countermeasure against thermal expansion of the projection optical system (lens elements constituting the projection optical system, etc.), a change in the optical characteristics of the projection optical system is estimated by calculation from the amount of irradiation energy to the projection optical system and the like, It has been practiced to maintain and improve the image formation state of the projected image of the pattern by driving the lens element of the projection optical system (see, for example, Patent Document 2).

  However, in order to correct the change in the imaging state of the projection image of the pattern caused by thermal expansion of the reticle (or mask) that changes over time due to the use of the exposure apparatus or the lens elements constituting the projection optical system, etc. The conventional projection exposure apparatus has a limit.

JP 2010-80855 A US Patent Application Publication No. 2008/0218714

  According to a first aspect of the present invention, there is provided an exposure apparatus that irradiates an energy beam to expose an object and forms a pattern on the object, wherein the pattern disposed on the optical path of the energy beam is formed. A first optical system configured to irradiate a reflective second mask with the energy beam through the first mask and form an image of the pattern on the second mask; and the energy through the second mask. A second optical system that irradiates the object with a beam and forms an image of the pattern image through the second mask on the object, and the second mask on the image plane of the first optical system. Of the second mask and the second mask holding device, which moves in a direction substantially parallel to the first axis substantially along the image plane of the first optical system, and the second mask and the second mask holding device. Position meter that measures at least one position information And systems based on the measurement information from the position measurement system, and a control device for driving said second mask via said second mask holding device, an exposure apparatus equipped with is provided.

  According to this, the second mask is driven by the control device via the second mask holding device based on the measurement information from the position measurement system. Thereby, the reflection surface shape (reflection distribution by the second mask) of the second mask in the energy beam irradiation region is changed, and the image of the pattern of the first mask imaged on the second mask by the first optical system. It is possible to correct the imaging state of the image (re-imaged image) formed on the object by the second imaging optical system.

  Here, the reflection distribution is a superordinate concept such as a bidirectional reflectance distribution that represents a reflection state of light on the reflection surface. The bidirectional reflectance distribution is a bidirectional reflectance distribution function that is one of the reflection models of light, that is, how much light is incident in each direction when light is incident on a certain point on the reflecting surface. A function specific to the reflection point that represents whether the light is reflected can be expressed using a function. In this specification, the term “reflection distribution” is used in this sense.

  According to a second aspect of the present invention, there is provided a device manufacturing method including forming a pattern on the object by the exposure apparatus of the present invention and developing the object on which the pattern is formed. The

It is a figure which shows schematically the structure of the exposure apparatus which concerns on one Embodiment. FIG. 2A is a diagram schematically showing the configuration of the second reticle stage apparatus, and FIG. 2B is a diagram for explaining the deformation of the second reticle. It is a figure for demonstrating an example of arrangement | positioning of the surface position measurement sensors 61 and 62 and the measurement point of a position measurement sensor. FIG. 2 is a block diagram showing an input / output relationship of a main controller that mainly constitutes a control system of the exposure apparatus of FIG. 1. It is a figure for demonstrating an example of arrangement | positioning of the measurement point of the surface position measurement sensors 61 and 62 and a position measurement sensor based on a modification. It is a figure for demonstrating the modification of a 2nd reticle stage.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 schematically shows a configuration of an exposure apparatus 100 according to an embodiment. The exposure apparatus 100 is a step-and-scan projection exposure apparatus, a so-called scanner. In the following, the left-right direction in the drawing in FIG. 1, which is the scanning direction in which the first reticle R1 (and second reticle R2) and the wafer W are relatively scanned, is the Y-axis direction, and the orthogonal direction to the drawing is X-axis. Direction, the direction perpendicular to the X axis and the Y axis (up and down direction in the drawing) is the Z axis direction, and the rotation (tilt) directions around the X axis, Y axis, and Z axis are the θx, θy, and θz directions, respectively. Give an explanation.

  The exposure apparatus 100 includes an illumination system IOP, a first reticle stage RST1 that holds the first reticle R1 and moves in a plane parallel to the XY plane, a projection unit PU that includes a projection optical system PL having an intermediate imaging plane, Second reticle stage RST2 that holds two reticles R2 and moves substantially along the intermediate image plane of projection optical system PL, wafer stage WST that holds wafers W and moves in the XY plane, and controls thereof System. Here, the first reticle R1 is a transmissive reticle, and the second reticle R2 is a reflective reticle.

  The illumination system IOP includes a light source and an illumination optical system, is set (restricted) by a field stop (also referred to as a masking blade or a reticle blind) disposed therein, and is a rectangle that extends in the X-axis direction on the first reticle R1. Illumination light (exposure light) IL is irradiated onto the (or arc-shaped) illumination area IAR1, and the first reticle R1 on which the circuit pattern is formed is illuminated with uniform illuminance. The configuration of the illumination system IOP is disclosed in, for example, US Patent Application Publication No. 2003/0025890. Here, as an example, ArF excimer laser light (wavelength 193 nm) is used as the illumination light IL.

  The first reticle stage RST1 is disposed below (−Z side) the illumination system IOP. On the first reticle stage RST1, a first reticle R1 having a circuit pattern or the like formed on its pattern surface (lower surface in FIG. 1) is placed. The first reticle R1 is fixed on the first reticle stage RST1 by, for example, vacuum suction.

  The first reticle stage RST1 can be finely driven in a horizontal plane (XY plane) by a first reticle stage drive system 11 (not shown in FIG. 1, refer to FIG. 4) including a linear motor, for example, and also in a scanning direction ( It can be driven within a predetermined stroke range in the Y-axis direction which is the left-right direction in FIG. Position information (including rotation information in the θz direction) of the first reticle stage RST1 in the XY plane is transferred by a reticle laser interferometer (hereinafter referred to as “first reticle interferometer”) 14 to the movable mirror 12 (or the first reticle). For example, it is always detected with a resolution of about 0.25 nm via a reflecting surface formed on the end face of the stage RST1. The measurement information of the first reticle interferometer 14 is supplied to the main controller 120 (not shown in FIG. 1, refer to FIG. 4). Based on the measurement information from first reticle interferometer 14, main controller 120 transmits first reticle stage RST <b> 1 position in the Y-axis direction (and position in the X-axis direction) via first reticle stage drive system 11, and (rotation in the θz direction) is controlled.

  Projection unit PU is arranged below (−Z side) first reticle stage RST1. The projection unit PU includes a housing 40, a plurality of optical elements (lenses, mirrors, etc.) held in the housing 40, and a reflective second reticle R2 (reflection surface thereof) held by the second reticle stage RST2. ). The plurality of optical elements irradiate the second reticle R2 with the illumination light IL via the first reticle R1, and connect the pattern image formed on the first reticle R1 to the reflecting surface (pattern surface) of the second reticle R2. The illumination light IL from the reflecting surface of the first imaging optical system PL1 to be imaged and the second reticle R2 is irradiated onto the wafer W, and an image of the pattern formed on the first reticle R1 on the wafer W and the second reticle R2 And a second imaging optical system PL2 that forms a composite image with the pattern image formed on the wafer W. The first imaging optical system PL1 is a refracting optical system with the same magnification or substantially the same magnification (magnification slightly larger than 1). The second imaging optical system PL2 is a reduction system having a projection magnification smaller than 1. In this embodiment, the first imaging optical system PL1, the second reticle R2, and the second imaging optical system PL2 are used as a whole to reduce the telecentric reduction system (projection magnification is, for example, 1/4 or 1/5). A projection optical system PL composed of a catadioptric system is configured. In this case, the reflecting surface of the second reticle R2 is disposed on the imaging surface of the first imaging optical system PL1, which is an intermediate imaging surface of the projection optical system PL.

  In addition, a pupil plane of the projection optical system PL is provided on a part (upper end) of the second imaging optical system PL2, and a compensation optical system 42 having a variable Z position and surface shape of the reflection surface is provided on the pupil plane. ing.

  For this reason, when the illumination area IAR1 on the first reticle R1 is illuminated by the illumination light IL, the illumination light IL transmitted through the first reticle R1 is irradiated to the second reticle R2 via the first imaging optical system PL1. In the illumination area IAR2 on the reflecting surface of the second reticle R2, an equal-magnification image or a minute enlarged image of the pattern of the first reticle R1 is formed. The illumination light IL is reflected by the reflecting surface of the second reticle R2, and is irradiated onto the wafer W whose surface is coated with a resist (sensitive agent) via the second imaging optical system PL2 including the compensation optical system 42, and the illumination area A reduced image of a part of the pattern of the first reticle R1 (a circuit pattern in the illumination area IAR1) via the reflecting surface of the second reticle R2 is exposed to an area (hereinafter referred to as an exposure area) IA on the wafer W conjugate with IAR1. ,It is formed. Here, in the case where a pattern is formed on the second reticle R2, a composition obtained by combining the pattern image of the second reticle R2 in the illumination area IAR2 and the image of the pattern of the first reticle R1 in the illumination area IAR1. An image is formed on the wafer W. Hereinafter, unless otherwise specified, it is assumed that the reflective surface of the second reticle R2 is a reflective surface on which no pattern is formed.

  Then, by synchronous driving of the first reticle stage RST1 and the wafer stage WST, the first reticle R1 is relatively moved in the scanning direction (Y-axis direction) with respect to the illumination area IAR1 (illumination light IL), and at the same time, the exposure area IA ( By moving the wafer W relative to the illumination light IL) in the scanning direction (Y-axis direction), one shot area (partition area) on the wafer W is scanned and exposed, and the first reticle R1 is exposed in the shot area. The pattern is transferred. In FIG. 1, symbol ILL schematically indicates the principal ray of the illumination light IL inside the projection optical system PL.

  An imaging characteristic correction controller 41 (not shown in FIG. 1, refer to FIG. 4) is connected to the compensation optical system. The imaging characteristic correction controller 41 adjusts the formation state of the image projected on the wafer W by changing the Z position and the surface shape of the reflection surface of the compensation optical system 42 that reflects the illumination light IL. Here, the shape (surface position) of the reflection surface of the compensation optical system 42 is measured by, for example, an encoder that measures the driving amount of an actuator (not shown) that changes the surface position, or a sensor that measures the shape of the reflection surface. The measurement result is transmitted to the imaging characteristic correction controller 41. The imaging characteristic correction controller 41 controls the adaptive optical system 42 in accordance with an instruction from the main control device 120 regarding correction of the distortion of the projected image. In the present embodiment, the imaging characteristic correction controller 41 and the compensation optical system 42 adjust the formation state of the image projected on the wafer W or maintain it satisfactorily, so that the optical characteristics of the projection optical system PL, for example, An imaging characteristic correction device that adjusts various aberrations (imaging characteristics) such as spherical aberration (aberration at the imaging position), coma aberration (aberration at magnification), astigmatism, curvature of field, distortion (distortion), etc. It is configured. The imaging characteristic correction apparatus may include a configuration in which some lens elements are slightly driven in the Z-axis direction (direction parallel to the optical axis AXp) and tilted with respect to the XY plane by an actuator such as a piezo element. Of course, in this case, the actuator may be controlled by the imaging characteristic correction controller 41.

  FIG. 2A schematically shows the configuration of the second reticle stage RST2 that holds the second reticle R2.

  The second reticle stage RST2 includes a main body portion 52, a table portion 54, and a plurality of actuators 51. The main body 52 is supported on the reticle base RB2. The main body 52 is a box-shaped member having a rectangular bottom with an upper surface opened. The table portion 54 is a kind of pin chuck type reticle holder, and a large number of pins P are formed on the upper surface thereof by etching. The second reticle R2 is vacuum-sucked by the table portion 54 and supported by a large number of pins P with the reflecting surface RP2 facing the + Z direction. The table portion 54 is formed of a flexible material or a material that deforms (bends) when a force is applied and has elasticity. The table portion 54 is disposed in the main body portion 52, connected to the peripheral wall of the main body portion 52 via a plurality of (four in this embodiment) support members 53, and is supported substantially parallel to the bottom portion. The plurality of actuators 51 include, for example, piezo elements, and are two-dimensionally arranged inside the main body 52, that is, in the space between the bottom and the table portion 54, and apply a force in the + Z direction to the lower surface of the table portion 54. . Here, by independently controlling each of the plurality of actuators 51 to create a distribution of force applied to the lower surface of the table portion 54, the table portion 54 is supported by the peripheral wall of the main body portion 52 via the support member 53. Small deformation with respect to a point.

  Here, by slightly deforming the table portion 54 using a plurality of actuators 51, for example, as shown in FIG. 2B, a strong force (see the black arrow) is applied to the center of the lower surface of the table portion 54. The reflecting surface RP2 of the second reticle R2 can be minutely deformed by applying a weak force (see the white arrow) to deform the table portion 54. Since the illumination light IL is irradiated into the illumination area IAR2 on the reflection surface RP2, the reflection distribution (for example, bidirectional reflectance distribution) of the illumination light IL by the second reticle R2 changes, and the second reticle R2 is a kind of Functions as an adaptive optical system. The closer the actuators 51 are arranged, the more freely the reflecting surface RP2 can be deformed.

  The second reticle stage RST2 is a moving magnet type plane composed of a coil unit (stator) 50A in the reticle base RB2 and a magnet unit (movable element) 50B provided at the bottom of the second reticle stage RST2. It is driven in the XY plane by a motor. That is, the second reticle stage drive system 50 (see FIG. 4) that drives the second reticle stage RST2 is configured by the planar motor (50A, 50B). Second reticle stage drive system 50 is controlled by main controller 120.

  The planar motor is not limited to the moving magnet type, and may be a moving coil type. In any case, the planar motor does not need to be a magnetic levitation method, and an air levitation method can be used. When an air levitation type planar motor is employed, the upper surface of the reticle base RB2 serving as the guide surface needs to be processed so as to have a high flatness.

In the exposure apparatus 100 of the present embodiment, as shown in FIG. 2A, the first imaging optical system PL1 has a lower end (exit end) sandwiching the optical path of the illumination light IL on the ± Y side, respectively. Surface position measuring sensors 61 and 62 for measuring the position (surface position) in the Z-axis direction of the reflecting surface RP2 of the two reticle R2 are provided. Each of the surface position measuring sensors 61 and 62 irradiates a plurality of points on the reflecting surface RP2 of the second reticle R2 with a plurality of measuring lights. Here, as shown in FIG. 3, the plurality of measurement lights are orthogonal to the scanning direction (Y-axis direction) on the + Y side and the −Y side of the illumination area IAR2 on the reflection surface RP2 illuminated by the illumination light IL. Irradiation is performed on lines 61 ₀ and 62 ₀ (strictly, a plurality of points on the lines 61 ₀ and 62 ₀ ) extending in the non-scanning direction (X-axis direction). Surface position measurement sensors 61 and 62, by receiving the reflected light from the reflecting surface RP2, measures the line ₆₁ 0, 62 ₀ over in the surface shape of the reflection surface RP2 of the second reticle R2 (surface position distribution) . The surface position measurement sensors 61 and 62 may be sensors of any configuration as long as they can irradiate the measurement light on the lines 61 ₀ and 62 ₀ (strictly, a plurality of points on the lines 61 ₀ and 62 ₀ ). For example, a multipoint focus position detection system disclosed in, for example, US Pat. No. 5,448,332 can be used as a surface position measurement sensor. Measurement information from the surface position measurement sensors 61 and 62 is supplied to the main controller 120 (see FIG. 4).

The position information of the second reticle R2 is measured by the position measurement sensors 63 and 64 shown in FIG. The position measurement sensors 63 and 64 are respectively provided at both ends in the X-axis direction (one side and the other side of the optical path of the illumination light IL) of the lower end (exit end) of the first imaging optical system PL1. As the position measurement sensors 63 and 64, for example, a diffraction interference type encoder head can be adopted. Corresponding to the position measurement sensors 63 and 64, as shown in FIG. 3, the scales S3 and S4 extend in the Y-axis direction on the ± X side of the illumination area IAR2 of the reflection surface RP2 on the second reticle R2, respectively. It is touched. On the surfaces of the scales S3 and S4, a reflective two-dimensional diffraction grating having the periodic direction in the X-axis direction and the Y-axis direction is formed. Position measuring sensors 63 and 64, respectively, the measuring light, the point 63 ₀ on the scale S3, S4, is irradiated to the point 64 _0. Here, the Y position of the point 63 _0, the point 64 ₀ is equal to Y position of the center of the illumination area IAR2. The position measurement sensors 63 and 64 receive the reflected light from the scales S3 and S4, respectively, and measure the X, Y, and Z positions of the second reticle R2 at the points 63 ₀ and 64 ₀ .

  Measurement information from the position measurement sensors 63 and 64 is supplied to the main controller 120 (see FIG. 4). The main controller 120 determines the position of the second reticle R2 (and the second reticle stage RST2) in the XY plane (including the yawing amount (rotation amount θz in the θz direction)) from the measurement information of the position measurement sensors 63 and 64. And the Z position of the second reticle R2 and the rolling amount (rotation amount θy in the θy direction) are measured. Note that the pitching amount (rotation amount θx in the θx direction) of the second reticle stage RST2 is measured using a second reticle interferometer 65 described later. The main controller 120 drives (position control) the second reticle stage RST2 via the second reticle stage drive system 50 based on the measurement information.

  The configuration of the position measurement sensors 63 and 64 is not limited to a configuration including only a single sensor capable of measuring the XYZ position, but a plurality of sensors, for example, one sensor capable of measuring the XY position and the Z position. A configuration combining one sensor capable of measurement, a configuration combining one sensor capable of measuring the XZ position and one sensor capable of measuring the YZ position, one sensor capable of measuring the X position, and A configuration in which one sensor capable of measuring the Y position and one sensor capable of measuring the Z position can be employed.

  In the present embodiment, as shown in FIG. 4, an interferometer system (differentiated from the first reticle interferometer 14 and called a second reticle interferometer) 65 is provided independently of the position measurement sensors 63 and 64. . Main controller 120 uses second reticle interferometer 65 to move second reticle stage RST2 through a movable mirror (reflecting surface (not shown) formed on the end surface) provided on second reticle stage RST2. The positions in the X axis, Y axis, and θz directions, and at least the pitching amount θx are measured.

  Based on the measurement information from position measurement sensors 63 and 64 (or second reticle interferometer 65), main controller 120 drives surface of second surface stage RST2 in the Y-axis direction from surface position measurement sensors 61 and 62. The measurement information of the surface position of the reflective surface RP2 and the measurement information of the Y position from the corresponding position measurement sensors 63 and 64 (or the second reticle interferometer 65) are stored in the memory in association with each other. The main controller 120 then determines the surface shape (surface position) of the reflection surface RP2 of the second reticle R2 based on the measurement information of the surface position of the reflection surface RP2 stored in the memory and the measurement information of the corresponding Y position. Distribution). Based on the obtained surface position distribution, main controller 120 controls a plurality of actuators 51 to slightly deform reflective surface RP2 of second reticle R2 to form a desired reflective surface (corresponding reflective distribution). Set. At this time, main controller 120 considers the rolling amount of second reticle R2 measured by position measurement sensors 63 and 64 and the pitching amount of second reticle stage RST2 measured by second reticle interferometer 65. A plurality of actuators 51 are controlled.

In the exposure apparatus 100 of this embodiment, as shown in FIG. 2A, a purge cover 80 is provided at the lower end (exit end) of the first imaging optical system PL1 of the housing 40 of the projection unit. Yes. Purge cover 80 is a rectangular cylindrical portion 82 ₁ elongated in the X-axis direction in a plan view, the flange portion 82 ₂ provided at the upper end of the cylindrical portion 82 _1, + Y direction from the lower end of the cylindrical portion 82 ₁ And a pair of plate portions 82 ₃ and 82 ₄ respectively extending in the −Y direction.

Flange portion 82 _2, its upper surface is fixed to the lower surface of the housing 40. The cylindrical portion 82 ₁ surrounds the irradiation area of illumination light IL emitted from the first imaging optical system PL1. X-axis direction length of the cylindrical portion 82 ₁ is set to the length of the distance and the same degree in the X-axis direction of the second main body portion 52 of the reticle stage RST2.

Plate portion 82 ₃ is a parallel plate-shaped portion to the XY plane extending from the lower end of the cylindrical portion 82 ₁ of the + Y side on the + Y side. The lower surface of the plate portion 82 _3, thin plate-shaped proximity cooling device 110A is fixed. The lower surface of the proximity cooling device 110A is positioned slightly higher than the upper end surface of the second reticle R2 (substantially coincides with the upper end surface of the main body 52).

Plate portion 82 ₄ is a parallel plate-shaped portion to the XY plane extending toward the -Y side from the lower end of the cylindrical portion 82 ₁ of the -Y side. The lower surface of the plate portion 82 _4, thin plate-shaped proximity cooling device 110B is fixed. The lower surface of the proximity cooling device 110B is located on the same XY plane as the lower surface of the proximity cooling device 110A.

  A predetermined clearance, for example, several μm to several mm, is provided between the lower surface of the proximity cooling device 110A and the upper end surface of the second reticle R2, and between the lower surface of the proximity cooling device 110B and the upper end surface of the second reticle R2. A clearance of 3 mm at the maximum is formed.

The length of the proximity cooling devices 110A, 110B of the X-axis direction is the cylindrical portion 82 ₁ of the X-axis direction length and set equal to or slightly shorter. Also, the proximity cooling device 110A has its Y axis so that its lower surface can at least partially face the second reticle R2 regardless of its position within the movement range of the second reticle stage RST2 in the Y axis direction. The direction length and installation position are set. Similarly, the proximity cooling device 110B has its Y surface so that its lower surface can at least partially face the second reticle R2 regardless of its position within the movement range of the second reticle stage RST2 in the Y-axis direction. The axial length and installation position are set.

  As described above, in this embodiment, the purge cover 80, the proximity cooling devices 110A and 110B, and the second reticle R2 form a substantially airtight space 181. In this space 181, for example, clean dry air (CDA) is supplied as a purge gas from a supply port (not shown) and exhausted to the outside through an exhaust port (not shown). That is, the internal gas (air) in the space 181 is purged with CDA. CDA has an extremely small ratio of water vapor, which is a haze generation reaction acceleration substance of a reticle (mask), compared to normal air. The space 181 is a substantially airtight purge chamber. Hereinafter, this space is referred to as a purge space 181.

  The proximity cooling devices 110 </ b> A and 110 </ b> B are cooled by heat exchange with a refrigerant passing through the inside of a cooling pipe (not shown). The temperatures of the proximity cooling devices 110A and 110B are monitored by a temperature sensor (not shown), and the temperature signal is transmitted to the temperature controller 28 (see FIG. 4) so as to be controlled to a target value. The temperature control of the proximity cooling devices 110A and 110B can be achieved by changing the temperature of the refrigerant. A semiconductor Peltier element (not shown) is installed between the proximity cooling devices 110A and 110B and the refrigerant, and a current flowing therethrough is changed. This can also be achieved by actively controlling the amount of heat transfer. In the latter case, there is an advantage that the temperature control response of the proximity cooling devices 110A and 110B is accelerated. In the present embodiment, the proximity cooling devices 110A and 110B cool the second reticle R2 and the second reticle stage RST2 in a non-contact manner. That is, the second reticle R2 (and the second reticle stage RST2) is cooled by, for example, radiant heat transfer by the proximity cooling devices 110A and 110B.

  Returning to FIG. 1, wafer stage WST is driven on stage base 22 with a predetermined stroke in the X-axis direction and Y-axis direction by stage drive system 24 (not shown in FIG. 1, see FIG. 4) including a linear motor and the like. At the same time, it is finely driven in the Z-axis direction, θx direction, θy direction, and θz direction. On wafer stage WST, wafer W is held by vacuum suction or the like via a wafer holder (not shown). Wafer stage WST is not limited to a single 6-degree-of-freedom drive stage, and may be configured by a plurality of stages that can drive wafer W with 6 degrees of freedom by combining the drive directions of the respective stages.

  Position information of wafer stage WST in the XY plane (including rotation information (yaw amount (rotation amount θz in θz direction), pitching amount (rotation amount θx in θx direction), rolling amount (rotation amount θy in θy direction))) Is reflected by a laser interferometer system (hereinafter abbreviated as “interferometer system”) 18 through a movable mirror 16 (reflection surface formed on the end surface of wafer stage WST) with a resolution of, for example, about 0.25 nm. Always detected. Measurement information of the interferometer system 18 is supplied to the main controller 120 (see FIG. 4). Main controller 120 controls the position (including rotation in the θz direction) of wafer stage WST in the XY plane via stage drive system 24 in accordance with the measurement information from interferometer system 18.

  Further, the position and inclination of the surface of the wafer W in the Z-axis direction are determined by, for example, a focus sensor AF (see FIG. 5) comprising an oblique incidence type multi-point focus position detection system disclosed in US Pat. No. 5,448,332. 1 (not shown, see FIG. 4). The measurement information of the focus sensor AF is also supplied to the main controller 120 (see FIG. 4).

  On the side surface of the second imaging optical system PL2 of the projection unit PU, a wafer alignment system (hereinafter referred to as an alignment system) AS that detects an alignment mark or the like formed on the wafer W is provided. As an example of the alignment system AS, an FIA (Field Image Alignment) system, which is a kind of image processing type imaging alignment sensor, is used.

  In the exposure apparatus 100, a TTR (Through The Reticle) alignment system using light having an exposure wavelength disclosed in, for example, US Pat. No. 5,646,413 is also provided above the first reticle stage RST1. A pair of reticle alignment systems 13 (not shown in FIG. 1, refer to FIG. 4) is provided. The detection signal of the reticle alignment system 13 is supplied to the main controller 120 (see FIG. 4).

  FIG. 4 is a block diagram showing the input / output relationship of the main controller 120 that mainly constitutes the control system of the exposure apparatus 100 of the present embodiment. The main controller 120 includes a so-called microcomputer (or workstation) comprising a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), etc., and controls the entire apparatus. Control.

  Next, the operation of the exposure apparatus 100 of the present embodiment configured as described above will be briefly described.

  Prior to exposure, the first reticle R1 is loaded onto the first reticle stage RST1 by a reticle loader (not shown). At the same time, the second reticle R2 corresponding to the first reticle R1 is loaded on the second reticle stage RST2. Further, a wafer W on which a sensitive layer (resist layer) is formed by a coater / developer (not shown) provided in the exposure apparatus 100 is transferred to a wafer holder (not shown) of wafer stage WST by a wafer loader (not shown). Loaded on top.

  Thereafter, like the normal scanner, the main controller 120 uses the pair of reticle alignment systems 13, a reference mark plate (not shown) on the wafer stage WST, the alignment system AS, and the like to perform the reticle alignment and alignment system AS. Baseline measurement is performed. Subsequent to these preparation operations, the main controller 120 executes wafer alignment (alignment measurement) such as so-called multi-shot EGA within a shot.

  The reticle alignment and the baseline measurement of the alignment system AS are disclosed in detail in, for example, US Pat. No. 5,646,413, and the subsequent in-shot multipoint EGA is disclosed in, for example, US Pat. , 876,946 and the like.

  Based on the in-shot multipoint EGA, an array coordinate of shot areas on the wafer and a deformation amount (magnification, rotation, orthogonality) including the magnification of each shot area are obtained.

  Therefore, main controller 120 deforms the shape of the reflecting surface of compensation optical system 42 of projection optical system PL via imaging characteristic correction controller 41, and drives the lens element as necessary. Further, main controller 120 sets the reflection surface shape of second reticle R2 corresponding to the pattern of first reticle R1, thereby initially correcting the formation state (distortion and the like) of the projected image. Specifically, main controller 120 drives second reticle stage RST2 in the Y-axis direction, measures surface position measurement information on reflecting surface RP2 from surface position measurement sensors 61 and 62, and second reticle interferometer. Based on the measurement information of the Y position of the second reticle stage RST2 from 65, the surface shape (Z position (surface position) distribution) of the reflection surface RP2 of the second reticle R2 is obtained. Based on the obtained surface position distribution (surface shape), the plurality of actuators 51 of the second reticle stage driving system 50 (planar motors (50A, 50B)) are individually driven to reflect the reflecting surface RP2 of the second reticle R2. Is slightly deformed to set the shape of the reflecting surface RP2 to an optimum shape for forming the pattern image of the first reticle R1.

  Main controller 120 determines wafer stage WST as a wafer based on the alignment coordinates of the shot area on wafer W obtained by alignment measurement (multi-point EGA in a shot) and the baseline of alignment system AS previously measured. The stepping operation for moving to the scanning start position of each shot region on W and the scanning exposure operation for synchronously moving the first reticle stage RST1 and wafer stage WST at a speed ratio according to the projection magnification of the projection optical system PL are repeated. Thus, the image of the pattern of the first reticle R1 is transferred to all shot areas on the wafer W.

  During the exposure operation of the step-and-scan method, the main controller 120 drives the second reticle stage RST2 in the −Y direction or the + Y direction based on the measurement information from the position measurement sensors 63 and 64. The surface shape (corresponding reflection distribution) of the reflecting surface of the second reticle R2 in the region corresponding to the illumination region IAR2 is changed. At the same time (or instead of this), main controller 120 is based on measurement information from surface position measurement sensors 61 and 62 obtained when second reticle stage RST2 is driven in the −Y direction or the + Y direction. The plurality of actuators 51 may be controlled. Thereby, the surface shape (reflection distribution) of the reflecting surface RP2 of the second reticle R2 in the region corresponding to the illumination region IAR2 is partially changed. By irradiating the illumination light IL onto the reflection surface RP2 whose surface shape (reflection distribution) is partially changed, the formation state (for example, distortion) of the projection image is corrected. Therefore, main controller 120 considers the thermal expansion of first reticle R1 caused by the absorption of illumination light IL as the number of exposed shot areas increases (the deformation of the pattern image due to the thermal expansion is reduced). As described above, the surface shape (reflection distribution) of the region of the reflection surface RP2 of the second reticle R2 may be partially changed.

  Alternatively, main controller 120 considers the thermal expansion of first reticle R1 caused by absorption of illumination light IL as the number of exposed shot areas increases while second reticle R2 is stationary (thermal The surface shape (reflection distribution) of the reflective surface RP2 of the second reticle R2 corresponding to the illumination region IAR2 is partially controlled by controlling the plurality of actuators 51 so that the deformation of the pattern image due to expansion is reduced). It is also possible to change to. In any case, measurement information from the position measurement sensors 63 and 64 is used when changing the surface shape (corresponding reflection distribution) of the reflection surface of the second reticle R2 in the region corresponding to the illumination region IAR2.

  Further, when the exposure process is repeated for a plurality of wafers, main controller 120 appropriately measures the distortion of the projected image using an aerial image measuring device (not shown) or the like at predetermined intervals. Based on the above, the imaging characteristics of the projection optical system PL may be corrected via the imaging characteristic correction controller 41 and the plurality of actuators 51. As a result, it is possible to reduce deterioration in imaging performance due to thermal expansion of the first reticle R1 and thermal expansion of the lens element.

  As described above, according to the exposure apparatus 100 of the present embodiment, the main controller 120 drives the second reticle R2 via the second reticle stage RST2 based on the measurement information from the position measurement sensors 63 and 64. Is done. Thereby, the reflecting surface shape (reflection distribution by the second reticle) of the second reticle R2 in the irradiation region of the illumination light IL via the first reticle R1 is changed, and the first imaging optical system is formed on the second reticle R2. Correcting the imaging state (for example, distortion) of the image of the pattern of the first reticle R1 formed by PL1 formed on the object (re-imaged) by the second imaging optical system PL2. It becomes possible. Therefore, according to the exposure apparatus 100, the pattern image of the first reticle R1 is accurately formed on each of the plurality of shot regions on the wafer W through the projection optical system PL by the step-and-scan exposure. It becomes possible.

In the above embodiment, the position measurement sensors 63 and 64 measure the X, Y, and Z positions of the second reticle R2 at the same measurement point. However, the present invention is not limited to this, and the X, Y, and Z positions are measured. Any of the measurement points may be different from other measurement points. For example, in the example shown in FIG. 5, the scales S3 and S4 are extended in the Y-axis direction on the ± X side of the second reticle R2 on the table portion 54 of the second reticle stage RST2. In this configuration, the position measurement sensor 63, 64 as in the above embodiment, the measuring light, the point 63 ₀ respectively on the second reticle R2, is irradiated to the point 64 _0. The points 63 ₀ and 64 ₀ are defined at the same positions as the points 63 ₀ and 64 ₀ (see FIG. 3) in the above embodiment. The position measurement sensors 63 and 64 receive the reflected light from the second reticle R2, and measure the Z position of the second reticle stage RST2 at the points 63 ₀ and 64 ₀ . These pieces of measurement information are supplied to the main controller 120, and the main controller 120 determines the Z position (including the rolling amount θy) of the second reticle R2.

In addition, the position measurement sensors 63 and 64 irradiate the points 63 ₁ and 64 ₁ on the scales S3 and S4 with different measurement lights, respectively. The Y positions of the points 63 ₁ and 64 ₁ are equal to the Y position of the center of the illumination area IAR2. The position measurement sensors 63 and 64 receive the reflected light from the scales S3 and S4, respectively, and measure the X position and the Y position of the second reticle stage RST2 at the points 63 ₁ and 64 ₁ . These pieces of measurement information are supplied to the main controller 120, and the main controller 120 determines the position (including the yawing amount θz) of the second reticle stage RST2 in the XY plane.

  In the above embodiment, the configuration in which the second reticle R2 held on the second reticle stage RST2 is deformed by the plurality of actuators 51 arranged in the second reticle stage RST2 has been described. However, the present invention is not limited to this, and the second reticle stage drive system 50 is configured by a magnetic levitation type planar motor, and the planar motor is driven by the second reticle stage RST2 and the shape of the reflecting surface of the second reticle R2 is deformed. It may be used also as an actuator for the above.

  FIG. 6 shows an example of the configuration of the second reticle stage RST2 'according to the modification. In this modification, the second reticle stage RST2 ′ is a kind of pin chuck type reticle holder, like the above-described table portion 54, and a large number of pins P are formed on the upper surface thereof by etching. . The second reticle stage RST2 'is made of a flexible material or a material that deforms (bends) when a force is applied and has elasticity.

  Second reticle stage RST2 'is arranged on reticle base RB2. On the bottom of the second reticle stage RST2 ', a plurality of permanent magnets constituting the magnet unit 50B are arranged in a matrix in the XY two-dimensional direction. Corresponding to the magnet unit 50B, a plurality of coils constituting the coil unit 50A are arranged in a matrix in the XY two-dimensional direction inside the reticle base. However, in this modification, the plurality of coils include a Z drive coil in addition to the X drive coil and the Y drive coil. The plurality of coils constituting the coil unit 50A may include an XZ drive coil and a YZ drive coil.

  In the present embodiment, a magnetic levitation method capable of driving the second reticle stage RST2 in the X axis, Y axis, Z axis, θx, θy, and θz directions with six degrees of freedom by the magnet unit 50B and the coil unit 50A. The planar motor is configured. That is, the second reticle stage drive system for driving the second reticle stage RST2 'is configured by the magnetic levitation type planar motor (50A, 50B). The second reticle stage drive system is controlled by main controller 120. For example, main controller 120 individually controls the amount of current supplied to a plurality of coils included in stator 50A, and for example, at the center of the lower surface of second reticle stage RST2 ′ as shown in FIG. The second reticle stage RST2 ′ is deformed by applying a strong force (see black arrow) and a weak force (see white arrow) around it to deform the second reticle stage RST2 ′. The reflecting surface RP2 is slightly deformed.

In the above embodiment, the substantially entire lower surface of the pair of the plate portion ₈₂ 3, 82 ₄ of the purge cover 80, near cooling devices 110A, 110B are assumed to be fixed to face. However, not limited thereto, the plate portion 82 _3, 82 ₄ may be used magnitude proximity cooling device facing the portion of each of the lower surface. In this case, the remaining portion of each of the lower surface of the plate portion 82 _3, 82 _4, to fix the separate member, in the proximity cooling device and its other members, near the cooling device 110A of the above embodiments, and 110B What is necessary is just to comprise the block of the same area and the same height. In this way, the airtightness of the purge space 181 can be ensured to the same extent as in the above embodiment.

  In the exposure apparatus 100 of the above-described embodiment, a purge space is formed above the first reticle R1 using the purge cover 80 and the proximity cooling devices 110A and 110B described above and the same purge cover and proximity cooling device. In addition, it is desirable to cool the first reticle R1.

  In the above embodiment, the case where the position of the first reticle stage RST1 is measured by the first reticle interferometer 14 and the position of the wafer stage WST is measured by the interferometer system 18 is illustrated. However, the present invention is not limited to this, and an encoder (an encoder system composed of a plurality of encoders) may be used instead of or together with the first reticle interferometer 14. Similarly, an encoder (an encoder system composed of a plurality of encoders) may be used instead of or together with the interferometer system 18.

  In the above-described embodiment, the case where the exposure apparatus is a dry type that exposes the wafer W without using liquid (water) has been described. However, the present invention is not limited to this. For example, International Publication No. 99/49504, Europe As disclosed in Patent Application Publication No. 1,420,298, International Publication No. 2004/055803, U.S. Patent No. 6,952,253, etc., between the projection optical system and the wafer. The above-described embodiment can also be applied to an exposure apparatus that forms an immersion space including an optical path of illumination light and exposes the wafer with illumination light through the projection optical system and the liquid in the immersion space. Further, the above embodiment can be applied to an immersion exposure apparatus disclosed in, for example, US Patent Application Publication No. 2008/0088843.

  In the above-described embodiment, the case where the exposure apparatus is a scanning exposure apparatus such as a step-and-scan method has been described. However, the present invention is not limited thereto, and the above-described embodiment is applied to a stationary exposure apparatus such as a stepper. Also good. In addition, as disclosed in, for example, US Pat. No. 6,590,634, US Pat. No. 5,969,441, US Pat. No. 6,208,407, a plurality of wafers. The above-described embodiment can also be applied to a multi-stage type exposure apparatus including a stage. Further, as disclosed in, for example, International Publication No. 2005/0774014, an exposure apparatus provided with a measurement stage including a measurement member (for example, a reference mark and / or a sensor) separately from the wafer stage is also described above. The embodiment can be applied.

The light source is not limited to the ArF excimer laser, and pulses such as a KrF excimer laser (output wavelength 248 nm), F ₂ laser (output wavelength 157 nm), Ar ₂ laser (output wavelength 126 nm), Kr ₂ laser (output wavelength 146 nm), etc. It is also possible to use a laser light source, an ultrahigh pressure mercury lamp that emits bright lines such as g-line (wavelength 436 nm), i-line (wavelength 365 nm), and the like. A harmonic generator of a YAG laser or the like can also be used. In addition, as disclosed in, for example, US Pat. No. 7,023,610, a single wavelength laser beam in an infrared region or a visible region oscillated from a DFB semiconductor laser or a fiber laser is used as vacuum ultraviolet light. For example, a harmonic that is amplified by a fiber amplifier doped with erbium (or both erbium and ytterbium) and wavelength-converted into ultraviolet light using a nonlinear optical crystal may be used.

  Further, as disclosed in, for example, US Pat. No. 6,611,316, two reticle patterns are synthesized on a wafer via a projection optical system, and 1 on the wafer by one scan exposure. The above embodiment can also be applied to an exposure apparatus that performs double exposure of two shot areas almost simultaneously.

  In the above embodiment, the object on which the pattern is to be formed (the object to be exposed to which the energy beam is irradiated) is not limited to the wafer, but may be another object such as a glass plate, a ceramic substrate, a film member, or a mask blank. good.

  The use of the exposure apparatus is not limited to the exposure apparatus for semiconductor manufacturing, but for example, an exposure apparatus for liquid crystal that transfers a liquid crystal display element pattern to a square glass plate, an organic EL, a thin film magnetic head, an image sensor (CCD, etc.), micromachines, DNA chips and the like can also be widely applied to exposure apparatuses. Further, in order to manufacture reticles or masks used in not only microdevices such as semiconductor elements but also light exposure apparatuses, EUV exposure apparatuses, X-ray exposure apparatuses, electron beam exposure apparatuses, etc., glass substrates or silicon wafers, etc. The above embodiment can also be applied to an exposure apparatus that transfers a circuit pattern.

  An electronic device such as a semiconductor element includes a step of designing a function / performance of the device, a step of manufacturing a reticle based on the design step, a step of manufacturing a wafer from a silicon material, and the exposure apparatus (pattern forming apparatus) of the above-described embodiment. And a lithography step for transferring the mask (reticle) pattern to the wafer by the exposure method, a development step for developing the exposed wafer, and an etching step for removing the exposed member other than the portion where the resist remains by etching, It is manufactured through a resist removal step for removing a resist that has become unnecessary after etching, a device assembly step (including a dicing process, a bonding process, and a packaging process), an inspection step, and the like. In this case, in the lithography step, the exposure method described above is executed using the exposure apparatus of the above embodiment, and a device pattern is formed on the wafer. Therefore, a highly integrated device can be manufactured with high productivity.

  The exposure apparatus of the present invention is suitable for forming a pattern on an object. The device manufacturing method of the present invention is suitable for manufacturing micro devices.

  42 ... Compensating optical system, 50 ... Second reticle stage drive system (planar motor), 51 ... Actuator, 61, 62 ... Surface position measuring sensor, 63, 64 ... Position measuring sensor, 65 ... Second reticle interferometer, 80 ... Purge cover, 100 ... exposure apparatus, 110A, 110B ... proximity cooling device, 120 ... main controller, IL ... illumination light, PL ... projection optical system, PL1 ... first imaging optical system, PL2 ... second imaging optical system , R1 ... first reticle, R2 ... second reticle, RP2 ... reflecting surface, RST1 ... first reticle stage, RST2 ... second reticle stage, W ... wafer.

Claims (13)

An exposure apparatus that irradiates an energy beam to expose an object and forms a pattern on the object,
A second reflective mask is irradiated with the energy beam through a first mask on which a pattern arranged on the optical path of the energy beam is formed, and an image of the pattern is formed on the second mask. 1 optical system,
A second optical system that irradiates the object with the energy beam through the second mask and forms an image of the image of the pattern through the second mask on the object;
Holding the second mask on the imaging plane of the first optical system and holding the second mask moving in a direction substantially parallel to the first axis substantially along the imaging plane of the first optical system; Equipment,
A position measurement system for measuring position information of at least one of the second mask and the second mask holding device;
An exposure apparatus comprising: a control device that drives the second mask via the second mask holding device based on measurement information from the position measurement system.   The first optical system is arranged such that the measurement system can face a measurement surface substantially parallel to an imaging surface of the first optical system provided in at least one of the second mask and the second mask holding device. A head unit that is integrally provided in the system, irradiates the measurement surface with measurement light, and receives return light from the measurement surface, and based on the output of the head unit, the predetermined measurement direction The exposure apparatus according to claim 1, wherein position information of at least one of the second mask and the second mask holding device is measured.   The measurement surface is provided with a diffraction grating having a predetermined direction as a periodic direction, and the head portion receives measurement light from the diffraction grating and is orthogonal to the periodic direction of the diffraction grating and the measurement surface. The exposure apparatus according to claim 2, wherein position information of the measurement object in at least one direction is output. The diffraction grating is a two-dimensional diffraction grating having periodicity in two axial directions orthogonal to each other in the measurement plane;
The head unit outputs position information of at least one of the second mask and the second mask holding device with respect to at least one of a periodic direction of the diffraction grating and a direction orthogonal to the measurement surface. Item 4. The exposure apparatus according to Item 3. The second mask is a reflective mask in which the diffraction grating is formed in a region outside the pattern region,
The second mask holding device changes a surface shape of a holding member that holds the second mask and a holding surface of the second mask of the holding member, and forms the image of the first optical system on the holding member. A holding member drive system that drives along the surface,
The exposure apparatus according to any one of claims 2 to 4, wherein the control device changes a surface shape of a second mask holding surface of the holding member via the holding member drive system.   The said holding member drive system has a drive device which drives the said holding member along the image plane of the said 1st optical system, and a drive mechanism which changes the surface shape of the said 2nd mask holding surface. The exposure apparatus described.   Provided at the lower end of the first imaging optical system, a slight gap is formed on the upper surface of the second mask on one side and the lower end on the other side of the irradiation region of the energy beam in the direction parallel to the first axis. And a cover portion that has a facing portion that is opposed to each other and that makes a space including the irradiation region of the energy beam between the first optical system and the second mask substantially airtight to the outside. The exposure apparatus according to any one of 1 to 6.   The exposure apparatus according to claim 7, wherein at least a part of the facing surface portion of the cover portion is configured by a pair of cooling members arranged on one side and the other side across the irradiation region.   The exposure apparatus according to claim 7 or 8, wherein the space is purged with a purge gas. The first optical system and the second optical system constitute a projection optical system that projects the pattern of the first mask onto the object,
The first optical system has a projection magnification of 1 or slightly larger than 1,
The exposure apparatus according to claim 1, wherein the second optical system has a projection magnification smaller than one.   The exposure apparatus according to claim 1, wherein the projection optical system includes a compensation optical system on a pupil plane thereof.   The exposure apparatus according to claim 1, further comprising a moving member that moves while holding the first mask. Forming a pattern on the object by the exposure apparatus according to claim 1;
Developing the object on which a pattern has been formed.

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