JP2012099686A - Light source forming method, exposure method, and device manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an illumination light source reproducing a target illumination light source shape accurately.SOLUTION: A light source forming method comprises the steps of: linking a plurality of mirror elements SE(k=1 to K) to a necessary number N of lens elements FL(n=1 to N) (a plurality of corresponding groups a to f thereto) to form a target illumination light source shape Ψin a plurality of lens elements FLat every unit number (N, for example), in order of light intensity Φreflected by each mirror element; exchanging at least each one mirror element from mirror elements SElinked to respective two lens elements in the necessary number N of lens elements FL(n=1 to N) so as to average sum of light intensities Φwith respect to the mirror elements SElinked to respective two lens elements. Consequently, an illumination light source reproducing a target illumination light source shape can be formed.

Description

  The present invention relates to a light source forming method, an exposure method, and a device manufacturing method, and in particular, light that passes through each of a plurality of optical elements constituting a spatial light modulator is applied to a plurality of sections in a predetermined plane in an illumination optical path. A light source forming method for forming an illumination light source on the predetermined surface by selectively distributing, an exposure method for exposing an object with illumination light from the illumination light source formed by the light source setting method, and a device manufacturing method using the exposure method .

With the miniaturization of device patterns, high resolution is required for projection exposure apparatuses such as so-called steppers or so-called scanning steppers (also referred to as scanners) used for manufacturing semiconductor elements and the like. The resolution R is expressed by the Rayleigh equation, that is, R = k ₁ (λ / NA). Here, λ is the wavelength of the light source (illumination light), NA is the numerical aperture of the projection optical system, and k ₁ is a process factor determined by the resolution and / or process controllability of the resist.

  Conventionally, resolution has been improved by shortening the wavelength λ of illumination light and increasing the numerical aperture of projection optical systems (higher NA). However, the shortening of the exposure wavelength is accompanied by difficulties in the development of light sources and glass materials, for example, and the increase in NA results in a decrease in the depth of focus (DOF) of the projection optical system, thereby improving the imaging performance (imaging characteristics). In order to make it worse, it is not possible to push the increase in NA.

In recent years, an exposure apparatus employing a local immersion exposure technique has been put into practical use to achieve a high NA. However, in an immersion exposure apparatus, the wavelength λ of illumination light is naturally shortened. There is a limit to NA conversion, and Low ₁ has become indispensable.

Under such a background, in order to provide an optical imaging solution that can be mass-produced with a low k ₁ value, for example, a modified illumination realized by a spatial light modulator (SLM) as disclosed in Patent Document 1 or the like Technology is drawing attention.

US Patent Application Publication No. 2009/0097094

  According to the first aspect of the present invention, the light passing through each of the plurality of optical elements constituting the spatial light modulator is selectively distributed to a plurality of sections in a predetermined plane in the illumination optical path, whereby the predetermined A light source forming method for forming an illumination light source for forming a pattern on an object on a surface, wherein at least some of the plurality of optical elements are in the order of light intensity through each of the plurality of optical elements, Associating with a predetermined number of sections according to a predetermined criterion; between two sections of the predetermined number of sections with which at least one of the plurality of optical elements is associated with each other A method of forming a light source is provided that includes exchanging at least each one of the optical elements.

  This makes it possible to form an illumination light source that accurately reproduces the target light source shape in a short time.

  According to the 2nd aspect of this invention, the exposure method which exposes an object with the illumination light from the illumination light source formed by the light source formation method of this invention, and forms a pattern on the said object is provided.

  According to this, it becomes possible to form a pattern on an object with high accuracy.

  According to a third aspect of the present invention, a pattern is formed on an object using the exposure method of the present invention; the object on which the pattern is formed is developed, and a mask having a shape corresponding to the pattern A device manufacturing method is provided that includes: forming a layer on the surface of the object; and processing the surface of the object through the mask layer.

It is a figure which shows schematically the structure of the exposure apparatus which concerns on one Embodiment. It is a figure which shows the structure of the spatial light modulation unit of FIG. It is a figure for demonstrating an example of the luminance distribution measuring device which measures a pupil luminance distribution. 4A and 4B are respectively a two-dimensional intensity distribution and a one-dimensional distribution (in order of intensity on each mirror element) of a light beam irradiated on a plurality of mirror elements of the spatial light modulator. It is a figure which shows an example. FIG. 5A and FIG. 5B respectively show the target illumination light source shape and the luminance formed on the entrance surface of the fly-eye lens substantially the same as the target illumination light source shape formed on the illumination pupil plane. It is a figure which shows an example of 1-dimensional distribution (in order of the brightness | luminance on each lens element). 6A to 6G show combinations of mirror elements that guide reflected light (a plurality of reflected lights) that gives each lens element to which the target luminance is given an intensity (total intensity) equal to the target luminance. It is a figure for demonstrating the solution to obtain | require. FIG. 7A is a diagram showing an example of the target of the shape (pupil luminance distribution) of the tripolar illumination light source, and FIG. 7B is a one-dimensional distribution of luminance on the corresponding lens element (luminance on each lens element). FIG. 7C is a diagram for explaining a solution for obtaining a combination of mirror elements. FIG. 8A is a diagram showing an example of the target shape of the multipolar illumination light source (pupil luminance distribution), and FIG. 8B is a one-dimensional distribution of luminance on the corresponding lens element (luminance on each lens element). FIG. 8C is a diagram for explaining a solution for obtaining a combination of mirror elements. FIG. 9A is a diagram showing an example of a target one-dimensional distribution (in order of luminance on each lens element) of the shape (pupil luminance distribution) of the modified illumination light source, and FIG. 9B is a reflection on the mirror element. FIG. 9C to FIG. 9H are diagrams for explaining a solution for obtaining a combination of mirror elements, showing an example of a one-dimensional distribution of light beams (order of intensity on each mirror element) It is.

  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. As will be described later, in the present embodiment, a projection optical system PL is provided. In the following description, a reticle and wafer are arranged in a direction perpendicular to the Z-axis direction parallel to the optical axis AX of the projection optical system PL and in a plane perpendicular to the Z-axis direction. And the direction perpendicular to the Z and Y axes is the X axis direction, and the rotation (tilt) directions around the X, Y, and Z axes are θx, θy, And the θz direction will be described.

  The exposure apparatus 100 includes an illumination system IOP, a reticle stage RST that holds a reticle R, a projection unit PU that projects a pattern image formed on the reticle R onto a wafer W coated with a sensitive agent (resist), and a wafer W. A wafer stage WST to be held and a control system for these are provided.

  The illumination system IOP includes a light source 1, a beam expander 2, a beam splitter BS1, a spatial light modulation unit 3, a relay optical system 4, a beam splitter BS2, which are sequentially arranged on the optical path of the light beam LB emitted from the light source 1. And an illumination optical system including a fly-eye lens 5 as an optical integrator, a condenser optical system 6, an illumination field stop (reticle blind) 7, an imaging optical system 8, a bending mirror 9, and the like.

  As an example of the light source 1, an ArF excimer laser (output wavelength 193 nm) is used. For example, the light beam LB emitted from the light source 1 has a rectangular cross-sectional shape that is long in the X-axis direction.

  The beam expander 2 includes a concave lens 2a and a convex lens 2b. The concave lens 2a has a negative refractive power, and the convex lens 2b has a positive refractive power.

  A beam splitter BS1 is disposed behind the optical path of the light beam LB with respect to the beam expander 2. The beam splitter BS1 transmits most of the light beam LB and reflects the rest. On the reflected light path of the light beam LB, a beam shape detection unit D1 including an image sensor such as a CCD is disposed. The beam shape detection unit D1 receives the light beam LB from the beam splitter BS1 and detects the intensity distribution (including the positional deviation of the light beam LB) of the light beam LB toward the spatial light modulation unit 3. The detection result of the beam shape detection unit D1 is sent to the main controller 20.

  The spatial light modulation unit 3 includes a so-called K prism (hereinafter simply referred to as a prism) 3P and a reflective spatial light modulator (SLM) 3S disposed on the upper surface (+ Z side surface) of the prism 3P. And. The prism 3P is made of optical glass such as fluorite or quartz glass.

  As shown in an enlarged view in FIG. 2, on the lower surface of the prism 3P, that is, on the side opposite to the spatial light modulator 3S, an incident surface (−Y side surface) and an exit surface (+ Y) parallel to the XZ plane in FIG. V-shaped surfaces (surfaces recessed in a wedge shape) made of surfaces PS1 and PS2 that intersect each other at 60 degrees and intersect each other at 120 degrees are formed. The back surfaces of the surfaces PS1 and PS2 (inner surfaces of the prism 3P) function as reflecting surfaces R1 and R2, respectively.

  The reflecting surface R1 reflects the light parallel to the Y axis that is transmitted from the beam expander 2 through the beam splitter BS1 and perpendicularly incident on the incident surface of the prism 3P in the direction of the spatial light modulator 3S. The reflected light beam LB reaches the spatial light modulator 3S via the upper surface of the prism 3P, and is reflected toward the reflection surface R2 by the spatial light modulator 3S as will be described later. The reflecting surface R2 of the prism 3P reflects the light that has arrived from the spatial light modulator 3S via the upper surface of the prism 3P and emits it to the relay optical system 4 side.

  The spatial light modulator 3S is a reflective spatial light modulator. The spatial light modulator means an element that processes, displays, and erases spatial information such as an image or patterned data by two-dimensionally controlling the amplitude, phase, or traveling direction of incident light. As the spatial light modulator 3S of the present embodiment, a movable multi-mirror array having a large number of minute mirror elements SE arranged on a two-dimensional (XY) plane is used. The spatial light modulator 3S includes a large number of mirror elements. In FIG. 2, only the mirror elements SEa, SEb, SEc, and SEd are shown. The spatial light modulator 3S continuously tilts (rotates) a large number of mirror elements SE and the large number of mirror elements SE within a predetermined range around two orthogonal axes (for example, the X axis and the Y axis) in the XY plane. And the same number of driving units. The drive unit includes, for example, a support column that supports the center of the back surface (the surface on the + Z side, that is, the surface opposite to the reflection surface) of the mirror element SE, a substrate on which the support column is fixed, and four electrodes provided on the substrate. And four electrodes (not shown) provided on the back surface of the mirror element SE so as to face the electrodes. The detailed configuration of the spatial light modulator similar to the spatial light modulator 3S is disclosed in, for example, US Patent Application Publication No. 2009/0097094.

  Returning to FIG. 1, a beam splitter BS2 is disposed behind the optical path of the relay optical system 4, and a fly-eye lens 5 is disposed on the transmitted optical path of the beam splitter BS2. The fly-eye lens 5 is a set of a large number of minute lens elements having a positive refractive power arranged densely in the direction perpendicular to the light beam LB. As will be described later, the fly-eye lens 5 divides the incident light beam into wavefronts, and forms a secondary light source (substantially surface light source) composed of the same number of light source images as the lens elements on the rear focal plane. In this embodiment, it is assumed that a cylindrical micro fly's eye lens disclosed in, for example, US Pat. No. 6,913,373 is adopted as the fly eye lens 5.

  According to the illumination system IOP of the present embodiment, the light beam LB emitted from the light source 1 is incident on the beam expander 2 and passes through the beam expander 2 so that its cross section is enlarged, and a predetermined rectangular cross section is formed. It is shaped into a light beam. The light beam LB shaped by the beam expander 2 passes through the beam splitter BS1 and enters the spatial light modulation unit 3.

  For example, as shown in FIG. 2, four parallel light beams L1 to L4 aligned in the Z-axis direction in the light beam LB enter the inside from the incident surface of the prism 3P and are spatially modulated by the reflecting surface R1. Reflected parallel to each other toward the container 3S. The light beams L1 to L4 are incident on the reflecting surfaces of different mirror elements SEa, SEb, SEc, and SEd arranged in the Y-axis direction among the plurality of mirror elements SE. Here, the mirror elements SEa, SEb, SEc, and SEd are independently tilted by respective driving units (not shown). For this reason, the light rays L1 to L4 are reflected toward the reflecting surface R2 in different directions. Then, the light beams L1 to L4 (light beam LB) are reflected by the reflecting surface R2 and emitted to the outside of the prism 3P. Here, the air-converted optical path lengths of the light beams L1 to L4 from the −Y side surface (incident surface) to the + Y side surface (outgoing surface) of the prism 3P correspond to the air-converted optical path length when the prism 3P is not provided. Is set equal to Here, the air-converted optical path length is an optical path length L / n obtained by converting an optical path length (L) of light in the medium (refractive index n) into an optical path length in the air (refractive index 1).

  Light rays L1 to L4 (light beam LB) emitted to the outside of the prism 3P are aligned in parallel to the Y axis via the relay optical system 4 and pass through the beam splitter BS2 disposed behind the relay optical system 4. Is incident on the fly-eye lens 5. Then, each of the light beams L1 to L4 is incident on one of a large number of lens elements of the fly-eye lens 5, whereby the light beam LB is divided (wavefront division). Thereby, a secondary light source (surface light source, that is, an illumination light source) composed of a plurality of light source images is formed on the rear focal plane LPP of the fly-eye lens 5 that coincides with the pupil plane (illumination pupil plane) of the illumination optical system. .

  FIG. 2 schematically shows light intensity distributions SP1 to SP4 corresponding to the light beams L1 to L4 on the rear focal plane LPP of the fly-eye lens 5. Thus, in this embodiment, the light intensity distribution (also referred to as luminance distribution or illumination light source shape) of the secondary light source (illumination light source) is freely set by the spatial light modulator 3S. The spatial light modulator is not limited to the reflective active spatial light modulator described above, and a transmissive or reflective diffractive optical element as an inactive spatial light modulator can also be used. When such an inactive spatial light modulator is used, the relay optical system 4 can be configured to include, for example, an afocal lens and a zoom lens, and at least a part of the optical members (lens, The light intensity distribution of the secondary light source (illumination light source) can be variably set by controlling the position and / or orientation of the prism member or the like. Further, as a diffractive optical element, for example, Japanese Patent Application Laid-Open No. 2001-217188 and US Pat. No. 6,671,035 corresponding thereto, or Japanese Patent Application Laid-Open No. 2006-005319 and US Pat. No. 7, corresponding thereto. As disclosed in Japanese Patent No. 265,816, etc., the light intensity distribution of the secondary light source (illumination light source) may be variably set by controlling the position of the diffractive optical element having a plurality of sections. Further, in addition to the above-mentioned active or inactive spatial light modulator, a movable illumination aperture disclosed in, for example, Japanese Patent Laid-Open No. 2000-58441 and US Pat. No. 6,452,662 corresponding thereto. The light intensity distribution of the secondary light source (illumination light source) may be variably set using a diaphragm.

  In the present embodiment, the secondary light source formed by the fly-eye lens 5 is used as the illumination light source, and the reticle R held on the reticle stage RST described later is Koehler illuminated. Therefore, the surface on which the secondary light source is formed is a conjugate surface with respect to the surface of the aperture stop 41 (aperture stop surface) of the projection optical system PL, and is called a pupil plane (illumination pupil plane) of the illumination optical system. Further, the irradiated surface (the surface on which the reticle R is disposed or the surface on which the wafer W is disposed) is an optical Fourier transform surface with respect to the illumination pupil plane. When the number of wavefront divisions by the fly-eye lens 5 is relatively large, the overall light intensity distribution formed on the entrance surface of the fly-eye lens 5 and the overall light intensity distribution (pupil intensity distribution) of the entire secondary light source. ) And a high correlation. For this reason, the light intensity distribution on the incident surface of the fly-eye lens 5 and the surface optically conjugate with the incident surface is also referred to as the light intensity distribution (luminance distribution or illumination light source shape) of the secondary light source (illumination light source). it can.

  An illumination pupil distribution measurement unit D2 is disposed on the reflected light path of the beam splitter BS2. The illumination pupil distribution measurement unit D2 includes a CCD imaging unit having an imaging surface disposed at a position optically conjugate with the incident surface of the fly-eye lens 5, and a light intensity distribution formed on the incident surface of the fly-eye lens 5. (Luminance distribution or illumination light source shape) is monitored. That is, the illumination pupil distribution measurement unit D2 has a function of measuring the pupil intensity distribution on the illumination pupil or a surface optically conjugate with the illumination pupil. The measurement result of the illumination pupil distribution measurement unit D2 is supplied to the main controller 20. For the detailed configuration and operation of the illumination pupil distribution measurement unit D2, reference can be made to, for example, US Patent Application Publication No. 2008/0030707.

  The light beam LB from the secondary light source illuminates the illumination field stop 7 in a superimposed manner via the condenser optical system 6. In this way, the illumination field stop 7 is formed with a rectangular illumination field corresponding to the shape and focal length of the rectangular minute refracting surface, which is the wavefront division unit of the fly-eye lens 5. The light beam LB that passes through the rectangular opening (light transmission portion) of the illumination field stop 7 receives the light condensing action of the imaging optical system 8 and then superimposes the reticle R on which a predetermined pattern is formed. Illuminate. That is, the light beam LB from the secondary light source is collected by the condenser optical system 6, and further, the illumination field stop 7, the imaging optical system 8, the folding mirror 9, etc. (from the condenser optical system 6 to the folding mirror 9). Are collectively emitted from the illumination system IOP via the light transmission optical system 10 and irradiated onto the reticle R as illumination light IL as shown in FIG. In this case, by shaping the light beam LB (illumination light IL) by the illumination field stop 7, a part of the pattern surface (illumination area IAR) of the reticle R is illuminated.

  Reticle stage RST is arranged below (−Z side) illumination system IOP. On reticle stage RST, reticle R is fixed, for example, by vacuum suction. The reticle stage RST can be finely driven in a horizontal plane (XY plane) by a reticle stage drive system (not shown) including a linear motor, for example, and can be driven within a predetermined stroke range in the scanning direction (Y-axis direction). It has become.

  Position information of the reticle stage RST in the XY plane (including rotation information in the θz direction) is transferred to a movable mirror 12 (or an end surface of the reticle stage RST) by a reticle laser interferometer (hereinafter referred to as “reticle interferometer”) 14. For example, it is always detected with a resolution of about 0.25 nm through the formed reflection surface. Measurement information of reticle interferometer 14 is supplied to main controller 20.

  Projection optical system PL is arranged below reticle stage RST (−Z side). As the projection optical system PL, for example, a refractive optical system including a plurality of optical elements (lens elements) arranged along the optical axis AX is used. The projection optical system PL is, for example, both-side telecentric and has a predetermined projection magnification (for example, 1/4 times, 1/5 times, or 1/8 times). Therefore, as described above, when the reticle R is illuminated by the illumination light IL from the illumination system IOP, the pattern surface of the reticle R (the first surface of the projection optical system, the object surface) is projected via the projection optical system PL. A reduced image of the pattern in the illumination area (a reduced image of a part of the pattern) is projected onto the exposure area IA on the wafer W (second surface of the projection optical system, image surface) coated with a resist (sensitizing agent). The

  Among a plurality of lens elements constituting the projection optical system PL, a plurality of lens elements (not shown) on the object plane side (reticle R side) are controlled by an imaging performance correction controller 48 under the main controller 20. For example, it is a movable lens that can be driven in the Z-axis direction, which is the optical axis direction of the projection optical system PL, and in the tilt direction with respect to the XY plane (that is, the θx and θy directions). Further, an aperture stop 41 capable of continuously changing the numerical aperture (NA) within a predetermined range is provided in the vicinity of the pupil plane of the projection optical system PL. As the aperture stop 41, for example, a so-called iris stop is used. The aperture stop 41 is controlled by the main controller 20 via the imaging performance correction controller 48.

  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 including a linear motor and the like, and in Z-axis direction, θx direction, θy direction, and θz direction. It is driven minutely. On wafer stage WST, wafer W is held by vacuum suction or the like via a wafer holder (not shown).

  Position information (including rotation information (yaw amount (rotation amount in θz direction), pitching amount (rotation amount in θx direction) and rolling amount (rotation amount in θy direction)) of wafer stage WST in the XY plane) is a laser. An interferometer system (hereinafter abbreviated as “interferometer system”) 18 always detects with a resolution of about 0.25 nm, for example, via a movable mirror 16 (or a reflecting surface formed on the end surface of wafer stage WST). The The measurement result of the interferometer system 18 is supplied to the main controller 20.

  Further, the position and the inclination of the surface of the wafer W in the Z-axis direction are such that an imaging light beam for forming images of many pinholes or slits toward the imaging surface of the projection optical system PL with respect to the optical axis AX. It is measured by a focal position detection system having an irradiation system 60a that irradiates from an oblique direction and a light receiving system 60b that receives a reflected light beam of the imaging light beam on the surface of the wafer W. As the focal position detection system (60a, 60b), one having the same configuration as the oblique incidence type multipoint focal position detection system disclosed in, for example, US Pat. No. 5,448,332 is used.

  On the wafer stage WST, a reference plate FP whose surface is flush with the surface of the wafer W is fixed. On the surface of the reference plate FP, a reference mark used for baseline measurement of the alignment system AS, a pair of reference marks detected by a reticle alignment system described later, and the like are formed.

  In addition, the wafer stage WST is provided with a luminance distribution measuring device 80 that measures (measures) the pupil luminance distribution on-body. As shown in FIG. 3, the luminance distribution measuring instrument 80 includes a cover glass 80a, a condenser lens 80b, a light receiving unit 80c, and the like.

  The upper surface of cover glass 80a is set equal to the image plane position of projection optical system PL, that is, the plane position of wafer W placed on wafer stage WST. Here, on the upper surface, a light shielding film having a circular opening (pinhole) in the center is formed by vapor deposition of a metal such as chromium. This light shielding film blocks unnecessary light from entering the light receiving unit 80c when measuring the pupil luminance distribution. The cover glass 80a (pinhole) and the light receiving unit 80c are disposed at the front and rear focal positions of the condenser lens 80b, respectively. That is, the light receiving surface of the light receiving unit 80c is arranged at a position optically conjugate with the position of the aperture stop 41 of the projection optical system PL (that is, the pupil plane of the projection optical system PL and the pupil plane of the illumination system IOP). The light receiving unit 80c includes a light receiving element including a two-dimensional CCD and the like, and an electric circuit such as a charge transfer control circuit. The measurement data from the light receiving unit 80c is sent to the main controller 20.

  In the luminance distribution measuring instrument 80 having the above-described configuration, a part of the illumination light IL emitted from the projection optical system PL passes through the pinhole of the cover glass 80a, is condensed by the condenser lens 80b, and is collected by the light receiving unit 80c. Incident on the light receiving surface. Here, the intensity distribution of the illumination light IL at the aperture stop 41 of the projection optical system PL is reproduced on the light receiving surface of the light receiving unit 80c. That is, the intensity distribution on the aperture stop 41 of the illumination light IL passing through the pinhole of the cover glass 80a is measured by the light receiving unit 80c. Here, since the position of the aperture stop 41 is optically conjugate with the positions of the pupil plane of the projection optical system PL and the pupil plane of the illumination system IOP, measuring the intensity distribution of the illumination light IL measures the pupil luminance distribution. Is equivalent to

  An alignment mark (not shown) having a known positional relationship with the pinhole is provided on the upper surface of the cover glass 80a. The alignment mark is used to calibrate the position of the pinhole on the stage coordinate system, that is, the position of the luminance distribution measuring instrument 80.

  By moving the wafer stage WST (that is, the luminance distribution measuring device 80) in the XY two-dimensional directions and performing the above-described measurement, the pupil luminance distribution regarding a plurality of points on the irradiated surface (second surface) is measured. The measurement of the pupil luminance distribution will be further described later.

  Returning to FIG. 1, an alignment system AS for detecting an alignment mark and a reference mark formed on the wafer W is provided on the side surface of the lens barrel 40 of the projection unit PU. As the alignment system AS, for example, an image processing method in which a mark is illuminated and detected by broadband light such as a halogen lamp and the position of the mark is measured by performing image processing on the detected mark image (image). An FIA (Field Image Alignment) system, which is a kind of imaging type alignment sensor, is used.

  Although not shown in the exposure apparatus 100, TTR (Through The Reticle) alignment using light having an exposure wavelength disclosed in, for example, US Pat. No. 5,646,413 is provided above the reticle stage RST. A pair of reticle alignment systems comprising the system is provided. A detection signal of the reticle alignment system is supplied to main controller 20.

  The control system is mainly configured by a main controller 20 in FIG. The main controller 20 is composed of a so-called workstation (or microcomputer) composed of a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), etc. Control all over. The main controller 20 includes, for example, a storage device 42 including a hard disk, an input device 45 including a pointing device such as a keyboard and a mouse, a display device 44 such as a CRT display (or liquid crystal display), and a CD (compact disc). , A drive unit 46 of an information storage medium such as a DVD (digital versatile disc), MO (magneto-optical disc) or FD (flexible disc) is externally connected.

  In the storage device 42, information on the illumination light source shape (pupil luminance distribution) in which the imaging state of the projection image projected onto the wafer W by the projection optical system PL is optimum (for example, aberration or line width is within an allowable range), The control information of the illumination system IOP corresponding to this, in particular, the mirror element SE of the spatial light modulator 3S, the information on the aberration of the projection optical system PL, and the like are stored.

  In the drive device 46, an information storage medium (hereinafter, referred to as an information storage medium) that stores a program for setting an illumination light source (both allocation of mirror elements to lens elements and replacement of the allocated mirror elements), which will be described later, is stored. In the description, CD-ROM is set for convenience. Note that these programs may be installed in the storage device 42. Main controller 20 reads these programs onto the memory as appropriate.

  In the exposure apparatus 100, as in a normal scanner, after performing preparatory work such as wafer exchange, reticle exchange, reticle alignment, baseline measurement of the alignment system AS, and wafer alignment (such as EGA), exposure in a step-and-scan manner is performed. Operation is performed. Detailed description is omitted.

  Next, an illumination light source setting (formation) and resetting (adjustment) process using the spatial light modulation unit 3 (spatial light modulator 3S) in the exposure apparatus 100 of the present embodiment will be described.

  As described above, in the illumination system IOP provided in the exposure apparatus 100, the light beam LB from the light source 1 is irradiated onto a part of the plurality of mirror elements SE included in the spatial light modulator 3S, and a part of the plurality of mirror elements SE is irradiated. The light beam LB is reflected by each of the mirror elements SE. And each of these reflected light (for example, light rays L1-L4) is guide | induced to either of the many lens elements which comprise the fly eye lens 5 (refer FIG. 2). Thus, the light beam LB is divided (wavefront division), and an illumination light source including a plurality of light source images is formed on the rear focal plane LPP of the fly-eye lens 5, that is, the illumination pupil plane.

Here, the number of mirror elements SE of the spatial light modulator 3S is, for example, 640 × 168 (≈1 × 10 ⁵ ), and the number of lens elements of the fly-eye lens 5 is, for example, 128 ² (≈1. 6 × 10 ⁴ ). Therefore, 1 × 10 ⁵ rays reflected by the individual mirror elements SE are appropriately combined and guided to a 1.6 × 10 ⁴ lens element, in other words, 1.6 × 10 ⁴ constituted by the lens element. An illumination light source (secondary light source) is formed (set) by appropriately superimposing 1 × 10 ⁵ rays on the bright spot. Further, the illumination light source is adjusted (reset) by adjusting the superposition of the set light rays.

  Examples of the setting (formation) and resetting (adjustment) processing (basic) of the illumination light source will be described with reference to FIGS. 4 (A) to 5 (F).

FIG. 4A shows an example of the intensity distribution Φ ₀ of the light beam LB reflected on the mirror element SE _k (k = 1 to K (K is the total number of mirror elements)) of the spatial light modulator 3S. Has been. In this example, a light beam LB having a Gaussian spot-like intensity distribution Φ ₀ is shown.

The intensity distribution Φ ₀ is measured by the main controller 20 using the beam shape detection unit D1. However, since the surface of each mirror element SE _k is sufficiently small with respect to the cross section of the light beam LB, the light beam LB is received by a plurality of mirror elements SE _k , and the intensity distribution Φ ₀ is on the mirror element SE _k . Can be expressed as a set of intensities Φ _0k of the light beam LB. For convenience of explanation, it is assumed that each mirror element SE _k is assigned an index k (= 1 to K) in order of the intensity Φ _0k (Φ ₀₁ ≧ Φ ₀₂ ≧ Φ ₀₃ ≧...).

In FIG. 4B, the intensity of the light beam LB reflected by each mirror element SE _k , that is, Φ _0k is shown with the index k (= 1 to K) as the horizontal axis.

FIG. 5A shows the incident surface of the fly-eye lens 5 that is substantially the same as the target illumination light source shape (target of the luminance distribution) formed on the rear focal plane LPP (illumination pupil plane) of the fly-eye lens 5. The target illumination light source shape (luminance distribution target) Ψ ₀ formed above is shown. This target illumination light source shape (hereinafter also referred to as a target as appropriate) Ψ ₀ has a luminance distribution in which the luminance is non-zero inside the circular pole and the luminance is zero outside.

The target Ψ ₀ is read from the storage device 42 by the main controller 20 prior to the setting and resetting process of the illumination light source. However, since the target illumination light source shape [psi ₀ incident surface of each lens element FL _n (exit surface) is sufficiently small, the target [psi ₀ is represented as a set of the target brightness [psi _0n on each lens element FL _n can do. For convenience of description, each lens element FL _n has an index n (= 1 to Nf (Nf is the total number of lens elements FL _n )) in the order of target luminance Ψ _0n (Ψ ₀₁ ≧ Ψ ₀₂ ≧ Ψ ₀₃ ≧...). ).

In FIG. 5B, the target luminance Ψ _0n on the incident surface (or exit surface) of each lens element FL _n is shown with the horizontal axis as an index n (= 1 to Nf).

The target illumination light source shape shown in FIG. 5B is obtained by appropriately superimposing the reflected light of intensity Φ _0k reflected by each of the mirror elements SE _k (k = 1 to K) shown in FIG. (Target of luminance distribution) Ψ _0n (n = 1 to Nf) is formed. This is to obtain a combination of mirror elements SE _k that guides reflected light (a plurality of reflected lights) that gives an intensity (total intensity) equal to Ψ _0n to each lens element FL _n given the target brightness Ψ _0n. It is none other than.

For example, the number of lens elements required to form the target Ψ ₀ shown in FIG. 5A (the number of lens elements where the target luminance Ψ _0n ≠ 0 is equal to the number of black spots in the figure) is As shown in FIG. 5B, it is assumed that N (<total number of lens elements Nf). For the mirror elements SE _k of the total number (or indeed the total number of available mirror elements) K, there up to N ^K Street combination of mirror elements SE _k described above, the optimum one from among the huge number of combinations Must find a combination. For this reason, in this embodiment, the solution which calculates | requires optimal combination efficiently in a short time is employ | adopted.

Here, the basic principle of this solution will be described assuming that K = 42 and N = 6 as an example. FIG. _6A shows the intensity Φ _{0k of the} light beam LB reflected by each of the mirror elements SE _k (k = 1 to 42).

First, as shown in FIG. 6 (A), mirror elements SE _k (k = 1 to 42) are arranged in the order of the intensity Φ _0k , in units equal to the required number N = 6 of lens elements. Assign to groups (a, b, c, d, e, f). As a result, as shown in FIG. 6B, the first six mirror elements SE _{1 to} SE ₆ are sequentially allocated to the groups a to f. Here, as an example, the number of units is 6, which matches the required number N = 6, but is not limited to this, and the number of units may be 1, for example.

In FIG. 6B and other figures, each of the mirror elements SE _k (k = 1 to 42) uses a rectangle having a length proportional to the corresponding intensity Φ _0k (see FIG. _6A ). It is expressed. The number in each rectangle corresponds to the index of the mirror element SE _k .

Next, the groups a to f are switched in the order of the sum of the intensities Φ _0k for the mirror elements SE _k distributed to the respective groups. Here, since each of the mirror elements SE _k (k = 1 to 6) is allocated to the groups a to f in the order of their intensities Φ _{0 k} , the groups a to f are not replaced.

Next, the next six mirror elements SE _k (k = 7 to 12) are grouped into groups a to f in the reverse order (in the order of decreasing intensity Φ _0k ) as shown in FIG. Distribute. In this case, the mirror element SE ₇ is assigned to the group f (intensity Φ ₀₆ ) having the smallest sum of the intensity Φ _0k for the distributed mirror element SE _k , and the sum e of the intensity Φ _0k is followed by the small group e. Mirror element SE ₈ is assigned to (intensity Φ ₀₅ ), the sum of intensity Φ _0k is assigned to group e, then mirror element SE ₉ is assigned to small group d (intensity Φ ₀₄ ), and the sum of intensity Φ _0k is assigned to group d. , The mirror element SE ₁₀ is assigned to the small group c (intensity Φ ₀₃ ), the sum of the intensity Φ _0k is assigned to the group c, the mirror element SE ₁₁ is assigned to the small group b (intensity Φ ₀₂ ), and the intensity Φ _0k is summed. Is small after group b (the sum of the intensities Φ _0k is the largest), and the group a (intensity Φ ₀₁ ) is assigned the mirror element SE ₁₂ You can

Next, the groups a to f are switched in the order of the sum of the intensities Φ _0k for the mirror elements SE _k distributed to the respective groups. Here, as is clear from FIG. 6C, the sum of the intensity Φ _0k is increased in the order of the groups a to f, so that the groups a to f are not replaced (see FIG. 6D). .

Next, the next unit number N (= 6) mirror elements SE _k (k = 13 to 18) are grouped in the reverse order (in ascending order of intensity Φ _0k ) as shown in FIG. 6 (E). Sorted into a to f. For example, the mirror elements _{SE 13} to the smallest group f of the sum of the intensities [Phi _0k (intensity Φ ₀₆ + Φ ₀₇₎ is mirror elements _{SE 18} is the largest group a sum of intensity [Phi _0k (intensity Φ ₀₁ + Φ ₀₁₂₎ is Sorted.

Next, the groups a to f are switched in the order of the sum of the intensities Φ _0k for the mirror elements SE _k distributed to the respective groups. Here, since the sum of the intensities Φ _0k is large in the order of the groups a, f, b, e, c, and d, as shown in FIG. _6F , the order in which the sum of the intensities Φ _0k is large (a, f, The groups a to f are switched in the order of b, e, c, and d).

Thereafter, with respect to the remaining mirror elements SE _k (k = 19 to 42), similarly to the above, allocation to the groups a to f and replacement of the groups a to f are repeated for each unit. As a result, finally, as shown in FIG. 6G, the seven mirror elements SE _k are assigned to each of the groups a to f so that the sum of the intensities Φ _0k is approximately uniform.

  When the inventor performed the above-described simulation of mirror element distribution in the case of the number of lens elements (necessary number) N = 3724, 8645, and 14451 of the fly-eye lens of the illumination light source, The error (uniformity of the sum of the strengths) with respect to the whole of the maximum value and the minimum value of the sum of the strength and the strength was 28, 0.1%, 12, 0.4%, and 7,1.8%, respectively. . Here, the degree of superimposition is the number of mirror elements for one lens element, and is 7 in the above example. The calculation time was the same (0.047 seconds) in all cases. From this, it can be seen that the higher the degree of superposition, the higher the accuracy.

  The accuracy of uniformity achieved by the above-described method (the difference between the maximum value and the minimum value of the sums of the intensities of the groups a to f) is the intensity of the mirror element that is finally distributed. In the above-described method, since the mirror elements are arranged in the descending order of the strength, the strength by the mirror element finally distributed is minimized, and a highly accurate uniformity can be realized.

Further, an appropriate number of mirror elements SE _k distributed to the groups a to f are exchanged to make the sum of the intensity Φ _0k of the mirror elements SE _k distributed to each group uniform. As an example, the appropriate number is two.

For example, two mirror elements are selected from the mirror elements distributed to the group b (see FIG. _6G ) having the largest sum of the intensity Φ _{0k, and} the group e having the smallest sum (see FIG. 6G) is selected. Two mirror elements are selected from among the mirror elements distributed in (), and each of the two mirror elements is exchanged.

Here, by switching, as the strength [Phi _0k sum _Σ k∈e Φ _0k for strength [Phi _0k sum _Σ k∈b Φ _0k and group e for the group b is equalized (averaged) , Select each two mirror elements. Here, the symbols Σ _kεb and _Σkεe mean the sum of the mirror elements SE _k assigned to the groups b and e, respectively. That is, one-half of the difference between the sum between the intensity of the group b and _{e (Σ k∈b Φ 0k -Σ k∈e} Φ 0k) / 2 ≒ appropriate to give _{Φ 0kb1 + Φ 0kb2 -Φ 0ke1 -Φ} 0ke2 Each two mirror elements SE _kb1 , SE _kb2 and SE _ke1 , SE _ke2 are selected.

  Similar mirror elements are exchanged between other groups, for example, between groups f and c and between groups a and d.

Further, the groups a to f after the replacement of each two mirror elements are rearranged in the order of the sum of the intensities Φ _0k for the mirror elements SE _k assigned to the groups a to f, and the same mirror element replacement as above is further performed once or more ( Multiple times).

As a result, the sum of the intensity Φ _0k for the distributed mirror element SE _k is further uniformed, and the target illumination light source shape Ψ ₀ is obtained.

  The inventor conducted the simulation of the replacement of each of the two mirror elements and the rearrangement of the groups described above. When the superposition degree 12) and 14451 (superposition degree 7) were performed, the error (intensity) with respect to the whole of the maximum value and the minimum value of the sum of the intensities when the replacement was performed five times. The uniformity of the sum was 0.0003%, 0.017%, and 0.19%, respectively.

The appropriate number is not limited to 2, but may be 1 or 3, for example. The higher the appropriate number, the higher the uniformity. However, a long processing time is required. Further, instead of exchanging the two groups among the groups a to f described above, an appropriate number (at least one each) of mirror elements SE _k allocated to the two groups is exchanged. You can go.

  In the above description, the replacement of mirror elements is limited by the number of times, but the following method may be used.

First, the mirror elements are switched between the ends of the groups a to f rearranged by the sum of the strengths, that is, the group having the largest sum of the strengths Φ _0k and the group having the smallest sum. Next, the groups a to f are switched in the order of the sum of the intensity Φ _0k . This mirror element replacement and group replacement are repeated.

  In this method, when the mirror element is exchanged, the maximum group and the minimum group are always selected as the targets. Therefore, as long as an appropriate pair for exchange (corresponding to half of the difference between the maximum and minimum) is found, the accuracy continues to improve. If no suitable set is found, exit the group. That is, the accuracy of the combination can be specified.

  It should be noted that the group a and the group d in FIG. 6 (G) originally have the same sum of strengths, so there is a high possibility that an appropriate pair for replacement is not found. It can be shortened.

  Next, with reference to FIGS. 7A to 8C, an example of illumination light source setting (formation) and resetting (adjustment) processing for multipolar illumination will be described.

FIG. 7A shows an example of the target Ψ ₀ of the shape (luminance distribution) of the tripolar illumination light source. The target Ψ ₀ is discretely expressed as a set of target brightness Ψ _0n on each lens element FL _n , as before. For convenience of explanation, it is assumed that the index n is attached to the lens element FL _n in the order of the target luminance Ψ _0n (Ψ ₀₁ ≧ Ψ ₀₂ ≧ Ψ ₀₃ ≧...).

In FIG. 7B, the target luminance Ψ _0n is shown with the horizontal axis as an index n (= 1 to Nf). In this example, the target luminance for the lens elements FL _n constituting the poles a, b, and c shown in FIG. 7A is strong in order (Ψ _0a > Ψ _0b > Ψ _0c ), and each pole is configured. The number of lens elements FLn is N _a , N _b , and N _c in this order.

As shown in FIG. 7 (C), the mirror elements _SE k (k = _1~K), intensity Φ in the order of _0k, for each unit number N, poles a, b, respectively c _{n a, n b,} n distributes _c pieces each. Here, n _a + n _b + n _c = N. Here, the numbers n _a , n _b and n _{c to be} distributed are the required numbers N _a , N _b and N _{c of} the lens elements FL _n constituting the poles a, b and _c and the target luminances Ψ _0a , Ψ _0b and Ψ _0c. (N _a : n _b : n _c = N _a Ψ _0a : N _b Ψ _0b : N _c Ψ _0c ).

In the above distribution, the unit number N is the total number of mirror elements SE _k (or the actual number of mirror elements that can be actually used) multiplied by an integer (or an integer multiple thereof) that approximates the inverse of the required setting accuracy of the illumination light source. The total number is a number that is K or less. For example, when a setting accuracy of 0.1% is required, N satisfying a product 1000N ≦ K with a number 1000 (or an integer multiple thereof) approximating the reciprocal of the setting accuracy, for example, N = 100 is selected. . Further, the unit number N may be twice the reciprocal of the setting accuracy (in this case, the unit number N is K or less). For example (when strictly speaking) N = 400 is selected when a setting accuracy of 0.5% is required. By unit number N increases, the number n _a of mirror elements which are distributed to each _pole, n _b, n _c becomes large, each pole a, b, accuracy allocation to c improved. Further, when selecting a mirror element to be distributed to each of the poles a, b, and c from the unit number N, there is a risk that bias may occur if the elements are allocated in order of n _a , n _b , and nc in _descending order of strength. Therefore, random extraction may be performed. This makes it possible to efficiently set an illumination light source shape having a substantially uniform luminance distribution for each pole. Of course, as long as the number N of units is K or less, any integer of 1 or more can be selected. For each of the poles a, b, and c, the number of combinations of mirror elements SE _k and the frequency of combination (the number of mirror elements SE _k assigned to one of the lens elements constituting each pole) are appropriately determined. Therefore, high setting accuracy can be obtained.

Then, for each pole a, b, c, in the same procedure as example described above, the target brightness [psi _0a, [psi _0b, each lens element FL _n given the Ψ _0c, Ψ _0a, Ψ _0b , Ψ _0c , an optimum combination of mirror elements SE _k that guides reflected light (a plurality of reflected lights) that gives an intensity (total intensity) equal to Ψ _0c is _obtained .

FIG. 8A shows an example of a target illumination light source shape (luminance distribution target) Ψ ₀ of multipolar illumination employed in the exposure apparatus 100 of the present embodiment. In FIG. 8 (B), the target brightness [psi _0n on each lens element FL _n is shown on the horizontal axis as the index n. In this example, the number of lens elements FL _n constituting the five poles a, b, c, d, and e shown in FIG. 8A is shown in the column of necessary number of MFE in FIG. Thus, 386, 386, 981, 386, 386 (ratio 2: 2: 5: 2: 2), respectively, and the target luminance Ψ _0n for each pole is the ratio 100: 80: 60: 40: 20 ( (See FIG. 8B).

The total number of mirror elements is K = 107000. The mirror element SE _k (k = 1 to K) has 255, 204, 388, and 254 in accordance with the ratio of the product of the number of lens elements FL _n constituting each pole and the target luminance Ψ _0n for each unit number 1000. 102 and 51 are assigned to poles a, b, c, d, and e, respectively. As a result, the mirror elements SE _{k of} 27285, 21825, 41516, 10914, and 5457 are distributed to the poles a, b, c, d, and e, respectively. Note that the number of mirror elements SE _k assigned to one of the lens elements constituting each pole, that is, the frequency of combination is 70, 56, 42, 28,14.

  As a result of experiments conducted by the inventors, it was found that the uniformity of the sum of the strengths within about 0.1% can be obtained in the processing time of about 0.01 seconds with respect to the above example.

  Next, with reference to FIG. 9A to FIG. 9H, an illumination light source setting and resetting (adjustment) process for a more complicated deformed illumination will be described with an example.

FIG. 9A shows an example of a target illumination light source shape (luminance distribution target) Ψ ₀ of modified illumination. The target illumination light source shape Ψ ₀ is discretely expressed as a set of target luminances Ψ _0n on each lens element FL _n as before. For convenience of explanation, it is assumed that the index n is attached to the lens element FL _n in the order of the target luminance Ψ _0n (Ψ ₀₁ ≧ Ψ ₀₂ ≧ Ψ ₀₃ ≧...). In FIG. 9A, the luminance Ψ _0n is shown with the horizontal axis as the index n (= 1 to N).

In FIG. 9B, the intensity Φ _0k of the light beam LB reflected by each mirror element SE _k is shown with the horizontal axis as an index k (= 1 to K). The reflected light of intensity Φ _0k is appropriately overlapped to form a target illumination light source shape (target of luminance distribution) Ψ _0n of modified illumination shown in FIG. 9A.

First, a constant term C _n for each lens element FL _n is obtained using the target Ψ _0n (n = 1 to N). The constant term C _{n specifies the} luminance having the maximum value between the target luminance Ψ _0n and the target luminance Ψ _0n (n = 1 to N), that is, the difference between the target luminance Ψ ₀₁ by the sum of intensity and the sum of luminance. (Ψ ₀₁ −Ψ _0n ) * Σφ / ΣΨ. FIG. 9C shows the constant term C _n with the index n (= 1 to N) as the horizontal axis (that is, in ascending order).

Next, threshold values (Th1 to Th6) as shown in FIG. The threshold values (Th1 to Th6) include the distribution of the constant term C _n (n = 1 to N) (that is, the distribution of the target luminance Ψ _0n (n = 1 to N)) and the reflected light intensity Φ _0k (k = 1 to 1). K) as appropriate. For example, the threshold Th is the sum ΣΦ _0k + C _n of the maximum intensity among the intensities Φ _0n for mirror elements that have not yet been distributed and the constant term C _n and the intensity Φ _0k for mirror elements SE _k that have already been distributed. It can be set as the sum with the minimum intensity.

Next, the mirror elements _SE k (k = _1~K), strength [Phi in the order of _0k, sum _Σ k∈n Φ _0k + C between the intensity [Phi _0k for mirror elements SE _k already distributed and constant term _{C n} Until _n exceeds the first threshold Th1 sufficiently (or well) (or until the average of the sum exceeds the first threshold Th1), the lens elements FL in ascending order from the smallest lens element of the sum Σ _kεn Φ _0k + C _n distribute to _n . Thus, as shown in FIG. 9D, among the first n _a (= 4) mirror elements SE _k (k = 1 to n _a ), the mirror elements SE ₁ and SE ₃ are the lens elements FL _1. The mirror elements SE ₂ and SE ₄ are distributed to the lens element FL ₂ .

For the convenience of explanation, the constant term C _n is introduced, and the mirror element is used by using the sum Σ _k∈n φ _0k + C _n of the constant term C _n and the intensity φ _0k for the already allocated mirror element SE _k. SE _k (k = 1 to K) is allocated to the lens element FL _n (n = 1 to N) as described above, and this is a constant term C _n = Ψ ₀₁ −Ψ _0n. Using the difference Ψ _0n −Σ _k∈n Φ _0k between the luminance Ψ _0n and the sum of the intensities Φ _0k for the already distributed mirror element SE _k , the lens element with the largest difference Ψ _0n −Σ _k∈n Φ _0k in descending order from already distributed was mirror elements SE _k strength [Phi _0k sum sigma _k∈N [Phi _0k for up to well above (well) the first threshold value Th1, the mirror elements SE _k in order of strength [Phi _0k Corresponding to the distribution to each lens element FL _n The

Next, the lens elements FL _n (n = 1 to N) are arranged in ascending order of the intensity Φ _0k and the sum Σ _k∈n Φ _0k + C _n of the distributed mirror element SE _k and the constant term C _n (the difference described above). Rearrange in the order of Ψ _0n −Σ _k∈n Φ _0k ). Here, as can be seen from FIG. 9 (D), the sum Φ ₀₁ + Φ ₀₃ + _{C 1} of the lens element FL ₁ is smaller than the sum Φ ₀₂ + Φ ₀₄ + _{C 2} of the lens element FL _2, further sum [Phi ₀₂ Since + Φ ₀₄ + C ₂ is smaller than the constant term C _n for the other lens elements FL _n (n ≧ 3), the lens elements FL _n are not rearranged.

Next, the mirror elements _SE k (k = _5~K), strength [Phi in the order of _0k, sum _Σ k∈n Φ _0k + _{C n} (or sum sigma _k∈N [Phi _0k strength [Phi _0k) the second threshold value Th2 (Or until the average of the sum exceeds the second threshold Th2) from the smallest lens element of the sum Σ _k∈n Φ _0k + C _n (difference Ψ _0n −Σ _k∈n Φ _0k is the largest) The lens element is distributed to the lens element FL _{n (} in order from the largest lens element to the largest). As a result, as shown in FIG. 9E, the next n _b (= 12) mirror elements SE _k (k = 5 to 16) are distributed to the lens elements FL _{1 to} FL ₆ .

Next, the lens elements FL _n (n = 1 to N) are arranged in ascending order of the intensity Φ _0k and the sum Σ _k∈n Φ _0k + C _n of the distributed mirror element SE _k and the constant term C _n (the difference described above). Rearrange in the order of Ψ _0n −Σ _k∈n Φ _0k ). As a result, the lens elements FL _{1 to} FL ₆ are rearranged as shown in FIG. 9F.

Then, in the same manner as described above, the mirror elements _SE k a (k = 17~K), in order of strength [Phi _0k, sum _Σ k∈n Φ _0k + _{C n} (or intensity [Phi _0k sum _Σ k∈n Φ _0k) Until the third threshold Th3 is significantly exceeded (or until the average of the sum exceeds the third threshold Th3), from the smallest lens element of the sum Σ _k∈n Φ _0k + C _n (difference Ψ _0n −Σ _{k∈ n} Φ _0k is _assigned to the lens element FL _{n (} in order from the largest lens element). As a result, as shown in FIG. 9G, the next n _c (= 35) mirror elements SEk (k = 17 to 51) are distributed to the lens elements FL _{1 to} FL ₁₀ .

Furthermore, the lens elements FL _n (n = 1 to N) are arranged in ascending order of the intensity Φ _0k and the sum Σ _k∈n Φ _0k + C _n of the distributed mirror element SE _k and the constant term C _n (the difference Ψ described above). _{0n -Σ k∈n Φ 0k} is sorted in descending order). As a result, the lens elements FL _{1 to} FL ₁₀ are rearranged as shown in FIG.

Thereafter, sequentially changing the threshold value to the next threshold Th4～Th6, and distribution of mirror elements SE _k similar to that described above, the rearranging of the lens element FL _n, repeated. Thus, the mirror elements SE _k of required number lens element _{FL n (n = 1~N),} ( sum sigma _k∈N [Phi _0k or strength [Phi _0k) the sum _Σ k∈n Φ _0k + _{C n} is the last The distribution is performed so as to approximate the threshold value Th6 and to be substantially uniform.

  As a result of performing a simulation in which the inventors apply the above-described allocation of the mirror elements to the modified illumination to, for example, the multipolar illumination shown in FIGS. 8A and 8B, the processing time is 0.1. It was confirmed that the mirror elements were distributed with a degree of uniformity of about 3 seconds and a uniformity of about 3%.

Furthermore, as before, the mirror elements SE _k distributed to the lens element _FL n (n = _1~N) by replacing appropriate number, the sum _Σ k∈n Φ _0k + _{C n} for each lens element FL _n It can also be made uniform. In the experiments by the inventors, this mirror element replacement allows, for example, a processing time of about 0.1 second and a uniformity of about 0.01 for the multipolar illumination shown in FIGS. 8A and 8B. %, The mirror element SE _k was confirmed to be distributed.

  In the exposure apparatus 100 of the present embodiment, the main controller 20 activates the exposure apparatus 100 to set the above-described illumination light source (both allocation of mirror elements to lens elements and replacement of the allocated mirror elements). Executes at the time of idling. Further, the main control device 20 appropriately replaces the mirror elements allocated to the set illumination light source during the lot processing or the like. Thereby, an illumination light source that reproduces the target illumination light source shape almost accurately is formed, and the shape is always maintained.

As described above in detail, in the exposure apparatus 100 of the present embodiment, the movable multi-mirror array is used as the spatial light modulator 3S, and the fly-eye lens 5 is used as the optical integrator. Then, by selectively distributing the light through each of the plurality of mirror elements SE _k constituting the movable multi-mirror array 3S to the plurality of lens elements FL _n of the fly-eye lens 5 in the illumination optical path, the illumination optical system An illumination light source (secondary light source) is formed on the pupil plane (substantially coincident with the exit-side focal plane of the fly-eye lens 5). Then, a plurality of mirror elements SE _k (at least a part thereof) are determined in accordance with a predetermined criterion as described above with reference to an example in the order of the intensity of light reflected by each of the plurality of mirror elements SE _k. correspondence to the lens element FL _n numbers, between at least one of which two lens elements FL _n predetermined number associated lens element of the plurality of mirror elements SE _k, mirror associated with each At least one mirror element of the elements SE _k is exchanged, and the light intensity sum Φ _0k for the mirror elements SE _k associated with each of the two lens elements FL _n is averaged. This makes it possible to form an illumination light source that accurately reproduces the target light source shape in a short time.

  Further, according to the exposure apparatus 100 of the present embodiment, the pattern of the reticle R is transferred onto the wafer W by irradiating the illumination light IL from the illumination light source having the light source shape formed as described above. This makes it possible to transfer the pattern onto the wafer with high resolution and high accuracy.

In the above embodiment, the movable multi-mirror array is used as the spatial light modulator 3S, the fly-eye lens 5 is used as the optical integrator, and light passes through each of the plurality of mirror elements SE _k constituting the movable multi-mirror array 3S. A case has been described in which is selectively distributed to the plurality of lens elements FL _n of the fly-eye lens 5 in the illumination optical path. That is, in the above embodiment, for the sake of simplification of description, the number and shape of the sections (grids) formed near the entrance surface of the fly-eye lens by the spatial light modulator 3S and the lens element FL _{n of the} fly-eye lens 5 it has been described on the assumption that the shape of the incident surface of the number and the lens element FL _n of match. However, in general, the number (or shape) of the grid and the number (or shape) of the lens elements often do not correspond one-to-one. In such a case, if each grid is provided instead of each lens element FL _n of the fly-eye lens 5 in the above embodiment, the method of the above embodiment is employed as it is to accurately determine the target light source shape. The reproduced illumination light source can be formed in a short time. Here, the number of lens elements of the fly-eye lens (the number of wavefront divisions of the fly-eye lens) may be larger than the number of grids. As described above, when the number of wavefront divisions by the fly-eye lens 5 is relatively large, the overall light intensity distribution formed on the incident surface of the fly-eye lens 5 and the overall light intensity distribution ( Since the pupil intensity distribution shows a high correlation, the method of the above embodiment can be used as it is, and an illumination light source that accurately reproduces the target light source shape can be formed in a short time.

  In addition, the spatial light modulator is not limited to the movable multi-mirror array described above. For example, a transmissive liquid crystal display element, an electrochromic display (ECD), or a transmissive diffraction element installed in the optical path of illumination light from the light source. Transmission type spatial light modulator such as optical element, DMD (Deformable Micro-mirror Device or Digital Micro-mirror Device), reflective liquid crystal display element, electrophoretic display (EPD: ElectroPhoretic Display), electronic paper (or electronic Ink), a reflective spatial light modulator such as a light diffractive light valve, and a reflective diffractive optical element can also be used.

  Further, the optical integrator is not limited to a fly-eye lens, and a diffractive optical element or an internal reflection type optical integrator (typically a rod integrator) may be used. In this case, the condensing lens is arranged so that the front focal position of the relay optical system 4 coincides with the rear focal position of the relay optical system 4 (corresponding to the position of the incident surface of the fly-eye lens 5 of the above embodiment). And the rod type integrator is arranged so that the incident end is positioned at or near the rear focal position of the condenser lens. At this time, the exit end of the rod integrator is the position of the field stop 7. In the case of using a rod type integrator, a position optically conjugate with the position of the aperture stop of the projection optical system PL in the imaging optical system 8 downstream of the rod type integrator can be called an illumination pupil plane. In addition, since a virtual image of the secondary light source of the illumination pupil plane is formed at the position of the entrance surface of the rod integrator, this position and a position optically conjugate with this position are also referred to as the illumination pupil plane. Can do. At this time, a beam splitter BS2 for guiding light to the illumination pupil distribution measurement unit D2 can be disposed between the relay optical system 4 and the condenser lens.

  In the above-described embodiment, the configuration in which the pupil luminance distribution is measured on the wafer surface using the luminance distribution measuring instrument 80 provided on the wafer stage WST is adopted. However, the luminance distribution measuring instrument 80 is placed on the reticle stage RST. It is also possible to employ a configuration in which the pupil luminance distribution is measured on the pattern surface of the reticle. In this case, the measurement result of the pupil luminance distribution does not include the influence of the optical characteristics (for example, aberration) of the projection optical system PL, which is suitable for accurately measuring the pupil luminance distribution.

  In the above embodiment, one spatial light modulation unit (spatial light modulator) is used. However, the present invention is not limited to this, and a plurality of spatial light modulation units (spatial light modulators) can also be used. As an illumination optical system for an exposure apparatus using a plurality of spatial light modulation units, for example, an illumination optical system disclosed in US Patent Application Publication No. 2009/0109417 and US Patent Application Publication No. 2009/0128886 is used. Can be adopted.

  In the above embodiment, the spatial light modulator that independently controls the tilt of the mirror elements arranged two-dimensionally is employed. As such a spatial light modulator, for example, European Patent Application No. 779530 is disclosed. , U.S. Pat. No. 6,900,915, U.S. Pat. No. 7,095,546, and the like.

  It is also possible to employ a spatial light modulator that independently controls the height of the mirror element as the spatial light modulator. As such a spatial light modulator, for example, the spatial light modulator disclosed in US Pat. No. 5,312,513 and US Pat. No. 6,885,493 can be employed. Furthermore, the above-described spatial light modulator can be modified in accordance with the disclosure of, for example, US Pat. No. 6,891,655 or US Patent Application Publication No. 2005/0095749.

  In the above embodiment, the case where the present invention is applied to the scanning stepper has been described. However, the present invention is not limited to this, and the present invention may be applied to a stationary exposure apparatus such as a stepper. The present invention can also be applied to a step-and-stitch reduction projection exposure apparatus that synthesizes a shot area and a shot area.

  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 present invention can also be applied to a multi-stage type exposure apparatus provided with a stage. Further, as disclosed in, for example, US Pat. No. 7,589,822, an exposure including a measurement stage including a measurement member (for example, a reference mark and / or a sensor) separately from the wafer stage. The present invention can also be applied to an apparatus.

  In the above embodiment, the case where the exposure apparatus 100 is a dry-type exposure apparatus that exposes the wafer W without using liquid (water) has been described. As disclosed in US Pat. No. 1,420,298, WO 2004/055803, US Pat. No. 6,952,253, and the like, an immersion optical path including illumination light path between the projection optical system and the wafer. The present invention can also be applied to an exposure apparatus that forms a space and exposes the wafer with illumination light through the liquid in the projection optical system and the immersion space.

  The projection optical system of the exposure apparatus according to the present invention including the exposure apparatus of the above-described embodiment may be any of a reduction system as well as an equal magnification and an enlargement system, and the projection optical system is not only a refraction system but also a reflection system and Either a catadioptric system may be used, and the projected image may be an inverted image or an erect image.

  In the above embodiment, a so-called polarized illumination method disclosed in US Patent Application Publication No. 2006/0170901 and US Patent Application Publication No. 2007/0146676 can be applied.

The light source of the exposure apparatus is not limited to the ArF excimer laser, but is 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). It is also possible to use a pulse laser light source such as a super high pressure mercury lamp that emits bright lines such as g-line (wavelength 436 nm) and i-line (wavelength 365 nm). 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, International Publication No. 2001/035168, an exposure apparatus (lithography system) that forms line and space patterns on a wafer W by forming interference fringes on the wafer W is provided. The exposure apparatus 110 can be employed.

  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. An exposure apparatus that double exposes two shot areas almost simultaneously can be employed as the exposure apparatus 110.

  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 present invention 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 a device, a step of manufacturing a reticle based on the design step, a step of manufacturing a wafer from a silicon material, the above-described exposure apparatus (pattern forming apparatus), and its Lithography step to transfer the mask (reticle) pattern to the wafer by the exposure method, development step to develop the exposed wafer, etching step to remove the exposed member other than the portion where the resist remains by etching, etching is completed This is manufactured through a resist removal step for removing the resist that is no longer necessary in step 1, 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 that constitutes a part of the lithography system of the above embodiment, and a device pattern is formed on the wafer, so that a highly integrated device is produced. It can be manufactured with good performance.

  As described above, the light source forming method of the present invention is suitable for forming an illumination light source. The exposure method of the present invention is suitable for exposing an object with illumination light from an illumination light source. The device manufacturing method of the present invention is suitable for manufacturing an electronic device such as a semiconductor element or a liquid crystal display element.

DESCRIPTION OF SYMBOLS 1 ... Light source, 2 ... Beam expander, 3S ... Spatial light modulator, 4 ... Relay optical system, 5 ... Fly eye lens, 7 ... Illumination field stop, 20 ... Main controller, 100 ... Exposure apparatus, IOP ... Illumination system , PL ... projection optical system, R ... reticle, W ... wafer, SE k _... mirror element, IL ... illumination light, FL n _... lens element.

Claims (21)

In order to form a pattern on an object on the predetermined surface by selectively distributing light through each of the plurality of optical elements constituting the spatial light modulator to a plurality of sections in the predetermined surface in the illumination optical path A light source forming method for forming the illumination light source of
Associating at least some of the plurality of optical elements with a predetermined number of sections according to a predetermined criterion in order of the intensity of light passing through each of the plurality of optical elements;
At least one optical element among the optical elements associated with each other between two of the predetermined number of sections associated with at least one of the plurality of optical elements. Replacing the light source. In the associating, at least a part of the plurality of optical elements is divided into the number of sections necessary for setting the luminance distribution of the illumination light source for each unit in the order of the intensity of light passing through each of the plurality of optical elements. Map to
The light source forming method according to claim 1, wherein in the replacement, at least each one of the optical elements associated with each of the two sections is replaced.   The light source forming method according to claim 2, wherein the number of units is equal to the required number.   In the associating, the light intensity of the plurality of optical elements in the order of the intensity of light passing through each of the plurality of optical elements in the required number of sections, the light intensity of the already associated optical elements. The light source forming method according to claim 2, wherein the light sources are associated in ascending order of the sum of the intensities from the section having the smallest sum.   In the replacement, assuming that the required number is N, the sum of the light intensities for the optical elements already associated in the N sections is between the i-th and (Ni) -th sections. The light source forming method according to any one of claims 2 to 4, wherein the optical elements are interchanged. Prior to both the mapping and the swapping,
Grouping the plurality of sections into a plurality of first groups according to the luminance distribution of the illumination light source;
Allocating the plurality of optical elements to the plurality of first groups according to a ratio of a product of the number of sections belonging to each grouped first group and the luminance of the corresponding illumination light source. In addition,
The light source formation method according to claim 2, wherein the association and the replacement are performed for each of the plurality of first groups.   In the sorting, the plurality of optical elements are divided into a plurality of second groups by a predetermined number in order of the intensity of light passing through each of the plurality of optical elements, and belong to each of the plurality of second groups. The light source forming method according to claim 6, wherein the predetermined number of optical elements are distributed to the plurality of first groups according to the ratio.   The number of the second group is an integer that is a product of the predetermined number or less than the total number of the plurality of optical elements and approximates the reciprocal of the required setting accuracy of the shape of the illumination light source, or an integer multiple of the integer. The light source forming method according to claim 7, which is a number. In the association, at least a part of the plurality of optical elements is already corresponded among the number of sections necessary for setting the luminance distribution of the illumination light source in the order of the intensity of light passing through each of the plurality of optical elements. The difference between the sum of the light intensities for the attached optical element and the target luminance determined from the luminance distribution is correlated with each section until the sum exceeds a threshold in descending order from the largest section.
2. The light source formation according to claim 1, wherein in the replacement, the optical elements are replaced between two of the required number of sections to which at least one of the plurality of optical elements is associated. Method.   The light source forming method according to claim 9, wherein the changing of the threshold value and the association are repeated.   In the replacement, assuming that the necessary number is N, the difference among the N sections associated with at least one of the plurality of optical elements is between the i-th and (Ni) -th sections. The light source forming method according to claim 9 or 10, wherein the optical elements are interchanged.   In the replacement, each of the two optical elements associated with each of the two sections is associated with each of the optical elements, which gives a difference in the light intensity that approximates one half of the difference between the sums of the light intensities. The light source forming method according to any one of claims 1 to 11, wherein at least each of the optical elements is exchanged between the two sections.   The light source formation method according to any one of claims 1 to 12, wherein in the replacement, each two optical elements of the optical elements associated with each of the two sections are replaced.   The light source formation method according to any one of claims 1 to 13, wherein the replacement is performed for all of the sections associated with at least one of the plurality of optical elements.   The light source forming method according to claim 14, wherein the replacement is repeated a plurality of times. In the vicinity of the predetermined surface, an optical integrator including a plurality of optical elements arranged two-dimensionally is disposed,
The light source forming method according to claim 1, wherein the illumination light source is formed on an emission side of the plurality of optical elements of the optical integrator with light passing through the spatial light modulator. The light passing through the predetermined surface is condensed by a condensing optical system,
Position the incident surface of the internal-reflection optical integrator near the condensing position of the condensing optical system,
The light source forming method according to any one of claims 1 to 15, wherein a virtual image of the illumination light source is formed at a position of the incident surface of the optical integrator with light passing through the spatial light modulator.   An exposure method for exposing an object with illumination light from an illumination light source formed by the light source forming method according to claim 1 to form a pattern on the object.   19. The projection object is illuminated with illumination light from the illumination light source, and light from the illuminated projection object is passed through a projection optical system to form an image of the projection object on the object. Exposure method.   The exposure method according to claim 19, wherein the predetermined surface is a position optically conjugate with a position of an aperture stop of the projection optical system or a vicinity of the conjugate position. Forming a pattern on the object using the exposure method according to any one of claims 18 to 20;
Developing the object on which the pattern is formed, and forming a mask layer having a shape corresponding to the pattern on the surface of the object;
Processing the surface of the object through the mask layer.