JP2012099687A - Light source adjustment method, exposure method, and manufacturing method of device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To adjust the shape of an illumination light source accurately.SOLUTION: Based on a target of the shape of an illumination light source and the shape of a light beam with which the multiple mirror elements of a spatial light modulator are irradiated, combination of the multiple mirror elements and the multiple lens elements of a fly-eye lens is optimized by a main controller, and then an illumination light source (secondary light source) is formed on the pupil surface of an illumination optical system via the multiple mirror elements according to the optimization results (step 206), the shape of that illumination light source is measured (step 208), assumptions are made about the beam (e.g. deviation of axis of the light beam) and the beam shape is estimated using the measurement results under that assumption (step 214), and then the shape of an illumination light source is adjusted based on the estimation results of the beam shape (step 206). Consequently, the beam shape is estimated accurately, and the shape of the illumination light source can be adjusted accurately based on that results.

Description

  The present invention relates to a light source adjustment method, an exposure method, and a device manufacturing method, and in particular, an illumination light source formed on a predetermined surface in an illumination light path by light passing through each of a plurality of optical elements constituting a spatial light modulator. The present invention relates to a light source adjustment method for adjusting a light source, an exposure method for exposing an object with illumination light from an illumination light source adjusted by the light source adjustment 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 circumstances, in order to provide an optical imaging solution that can be mass-produced with a low k ₁ value, for example, an illumination technique realized by a spatial light modulator (SLM) as disclosed in Patent Document 1 or the like Is attracting attention.

US Patent Application Publication No. 2009/0097094

  According to the first aspect of the present invention, the predetermined surface is obtained 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 adjustment method for adjusting an illumination light source formed on the plurality of optical elements and the plurality of optical elements based on a target shape of the illumination light source and a shape of a beam irradiated to the plurality of optical elements Optimizing combinations with compartments and forming the illumination light source through the plurality of optical elements according to the optimization results; measuring the shape of the illumination light source; making assumptions about the beam; A light source adjustment method comprising: estimating the shape of the beam using the measurement result under: adjusting the shape of the illumination light source based on the estimation result of the beam shape It is.

  According to this, it becomes possible to accurately estimate the shape of the beam and to accurately adjust the shape of the illumination light source based on the result.

  According to the second aspect of the present invention, there is provided an exposure method in which an object is exposed by illumination light from the illumination light source having a light source shape adjusted by the light source adjustment method of the present invention to form a pattern on the object. 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. It is a flowchart which shows roughly the process algorithm of the main controller (internal CPU) regarding the setting of the illumination light source shape at the time of initial adjustment (at the time of starting). It is a flowchart which shows roughly the process algorithm of the main controller (internal CPU) regarding the setting process of the illumination light source shape at the time of the lot head etc. during operation of the exposure apparatus. FIG. 6A is a diagram showing an example of the ideal and measurement result of the intensity distribution (light source shape) of the light beam, and FIG. 6B is a diagram showing an example of the ideal of the illumination light source shape and the measurement result. FIG. 7A and FIG. 7B are diagrams for explaining assumptions regarding changes in the light source shape.

  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 microlens elements having 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, illumination on the pattern surface of the reticle R (the first surface of the projection optical system, the object surface) via the projection optical system PL. A reduced image of the pattern in the region (a reduced image of a part of the pattern) is projected onto the exposure region IA on the wafer W (second surface of the projection optical system, image surface) coated with a resist (sensitive agent). .

  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.

  Further, the wafer stage WST is provided with a luminance distribution measuring device 80 for measuring (measuring) 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.

  The drive device 46 is set with an information storage medium (hereinafter referred to as a CD-ROM for convenience) in which a processing program for adjusting the illumination light source shape and the like are stored as will be described later. 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 shape (pupil luminance distribution) setting process using the spatial light modulation unit 3 (spatial light modulator 3S) in the exposure apparatus 100 of the present embodiment will be described.

  FIG. 4 is a flowchart schematically showing a processing algorithm of the main controller 20 (internal CPU) regarding setting of the illumination light source shape at the time of initial adjustment (starting up) of the exposure apparatus 100.

In the first step 202, initial settings relating to the illumination light source are made. Specifically, the main controller 20 includes information on the illumination light source shape (pupil luminance distribution) stored in the storage device 42, the corresponding illumination system IOP, and control information on the mirror element SE of the spatial light modulator 3S, And information on aberrations of the projection optical system PL are read out. Here, the information regarding the illumination light source shape includes a target illumination light source shape (hereinafter, also referred to as a target as appropriate) Ψ ₀ as the target. The target illumination light source shape Ψ ₀ is expressed as a function Ψ ₀ (ξ, η) of two-dimensional coordinates ξ, η in the illumination pupil plane. The control information of the mirror element SE includes mirror characteristic information such as intensity information of reflected light with respect to the angle of the mirror element SE. Main controller 20 activates each component (light source 1, spatial light modulator 3S, etc.) of illumination system IOP according to the basic information.

In the next step 204, an intensity distribution (also referred to as a beam shape) within the beam cross section of the light beam LB emitted from the light source 1 is measured. The main controller 20 detects the light beam LB reflected by the beam splitter BS1 using the beam shape detector D1. As a result, a measurement result of the beam shape Φ ₀ (denoted as <Φ ₀ >) is obtained. The beam shape Φ ₀ is expressed as a function Φ ₀ (x, y) of the two-dimensional coordinates x, y in the detection surface of the beam shape detection unit D1, for example.

In the next step 206, the illumination light source is set. Based on the control information of the mirror element SE of the spatial light modulator 3S, the main controller 20 causes the light beam LB having the intensity distribution <Φ ₀ > to pass through the illumination pupil via the spatial light modulator 3S, the fly-eye lens 5 and the like. The control parameter of the mirror element SE is determined so that the intensity distribution formed on the surface, that is, the illumination light source shape Ψ, reproduces the target Ψ ₀ . That is, the main controller 20 determines a plurality of mirror elements SE and fly-eye based on the target Ψ ₀ of the shape of the illumination light source and the measurement result <Φ ₀ > of the beam shape Φ ₀ irradiated to the plurality of mirror elements SE. A combination of the lens 5 and a plurality of lens elements is optimized by a predetermined calculation, and the control parameter of the mirror element SE is determined according to the optimization result. The main control device 20 controls the spatial light modulator 3S (such as the inclination of the mirror element SE) according to the determined control parameter, and sets the illumination light source shape to reproduce the target illumination light source shape. Here, what is expressed is that the actual illumination light source shape that is as close as possible to the target illumination light source shape is set based on the target illumination light source shape that is virtual information. This is because an illumination light source shape that substantially matches the illumination light source shape is reproduced. In this specification, the expression of reproduction in this sense is used.

  In the next step 208, the illumination light source shape Ψ is measured. Main controller 20 calibrates the position of luminance distribution measuring instrument 80 prior to measurement. Here, main controller 20 drives wafer stage WST to position luminance distribution measuring instrument 80 mounted on wafer stage WST directly below alignment system AS. After positioning, main controller 20 uses alignment system AS to detect alignment marks (not shown) provided on luminance distribution measuring instrument 80, and the detection results and measurement results of interferometer system 18 at the time of detection are detected. Are used to find the exact position of the luminance distribution measuring instrument 80 on the stage coordinate system. According to the result, main controller 20 drives wafer stage WST to accurately position luminance distribution measuring instrument 80 (opening on cover glass 80a) on optical axis AX. At the same time, main controller 20 measures the surface position and inclination of cover glass 80a using the focus position detection system (60a, 60b), performs focus / leveling control of wafer stage WST, and controls the upper surface of cover glass 80a. Is positioned at the imaging point (image plane).

  When calibration is completed, main controller 20 starts actual measurement of illumination light source shape Ψ. Illumination light IL is emitted from the illumination light source (secondary light source) set in step 206, and is condensed on the image plane via the illumination system IOP and the projection optical system PL as shown in FIG. Thereby, the illumination light IL passes through the opening on the cover glass 80a and is received by the light receiving element in the light receiving unit 80c via the condenser lens 80b. A light receiving element (such as a two-dimensional CCD) detects the light intensity distribution in the cross section of the illumination light IL. Thereby, the measurement result <Ψ> of the illumination light source shape Ψ is obtained. The measurement result <Ψ> is expressed as a function <Ψ (ξ, η)> of two-dimensional coordinates ξ, η in the illumination pupil plane, similarly to the illumination light source shape Ψ.

  The main controller 20 transfers the measurement result <ψ (ξ, η)> of the illumination light source shape Ψ (ξ, η) to, for example, a host computer or server connected via a LAN (not shown). Strictly speaking, since the illumination light source shape (pupil luminance distribution) is measured at discrete points on the pupil plane coordinate system, the measurement result <Ψ (ξ, η)> is expressed as discrete data.

  In the exposure apparatus 100 of the present embodiment, since the illumination light IL is detected via the projection optical system PL, in principle, the measurement result of the illumination light source shape (pupil luminance distribution) is optical in the projection optical system PL. Error is included. However, in the present embodiment, it is assumed that there is no optical error of the projection optical system PL or correction is performed using the information related to the aberration read in step 202 unless otherwise specified.

In the next step 209, the degree of coincidence between the illumination light source shape reproduced in step 206 and the target is evaluated. Specifically, the main controller 20, the deviation from the target [psi ₀ measurement results <[psi>, for example, determine the RMS error, (assumed to have been defined in step 202) the value and the threshold value of the RMS error between Compare the size of.

Then, in the next step 210, it is determined whether or not the evaluation result is good. When the RMS error is smaller than the threshold value and the target illumination light source shape Ψ ₀ is reproduced with sufficient accuracy, that is, when the evaluation result is satisfactory, the processing of this routine (setting of a series of illumination light source shapes and The adjustment process is terminated.

  On the other hand, if the RMS error value is equal to or greater than the threshold value and the evaluation result is not good, the process proceeds to step 212. In the present embodiment, adjustment processing is selected in steps 212 and 213.

  In step 212, it is determined whether or not the illumination light source shape adjustment process is selected for the first time. In this case, since this is the first time, the determination in step 212 is affirmed, and the routine proceeds to step 214.

In step 214, the beam shape Φ ₀ is estimated (calculation processing). Here, the beam shape Φ ₀ has already been measured in step 204. However, the beam shape detection unit D1 does not detect the light beam LB itself incident on the mirror element SE of the spatial light modulator 3S. For this reason, there is a possibility that an accurate measurement result <Φ ₀ > may not be obtained due to an optical axis shift generated in the spatial light modulation unit 3 (prism 3P) or a detection error of the beam shape detection unit D1. Therefore, in the selection of the first adjustment process, main controller 20 preferentially selects the beam shape Φ ₀ in order to perform the estimation (calculation process) first.

When the beam shape estimation is completed, the process returns to step 206. The main control device 20 uses the beam shape estimation result (represented as << Φ ₀ >>), and the illumination light source shape Ψ formed by the light beam LB having the intensity distribution << Φ ₀ >> reproduces the target Ψ ₀ . Similarly, the control parameters of the mirror element SE are redetermined. The main controller 20 controls the spatial light modulator 3S (such as the tilt of the mirror element SE) according to the determined control parameter, and resets the illumination light source shape to reproduce the target illumination light source shape.

  On the other hand, in the case of selecting the second and subsequent adjustment processes, the determination in step 212 is negative and the process proceeds to step 213. In step 213, it is determined whether or not the selection of the adjustment process is less than the m-th time. If the selection of the adjustment process is less than the m-th time (usually, m is set to 3, 4, 5, etc.), the determination in step 213 is affirmed and the process proceeds to step 216. The basis for setting m times will be described later.

  In step 216, estimation (calculation processing) of mirror characteristics, that is, the intensity of reflected light with respect to the angle of the mirror element SE of the spatial light modulator 3S is performed. Here, the mirror characteristics are already set in step 202. However, since the performance as set is not always obtained, it is necessary to estimate the mirror characteristics.

When the estimation of the mirror characteristics is completed, the process returns to step 206 as before, and the main controller 20 uses the estimation result of the mirror characteristics to change the illumination light source shape in order to reproduce the illumination light source shape. Reset it. That is, the main controller 20, the illumination light source using an estimated result of the mirror characteristic, the intensity distribution "[Phi _0" is formed by a light beam LB having a ( _{"Φ 0"} is <[Phi _0> If not obtained) The control parameter of the mirror element SE is redetermined so that the shape Ψ reproduces the target Ψ ₀ , and the spatial light modulator 3S (the inclination of the mirror element SE, etc.) is controlled according to the determined control parameter.

  Since the estimation of the mirror characteristics requires a shorter processing time than the optimization of the setting of the illumination light source, which will be described later, in the selection of the adjustment process, the main controller 20 selects the optimum illumination light source setting after the estimation of the beam shape. It is decided to select it prioritizing. Further, when the estimation of the mirror characteristic is selected, the illumination light source shape is reset using the estimation result of the mirror characteristic each time, so it is meaningful to repeat the estimation of the mirror characteristic several times. For this reason, the above m is set to 3, 4, 5, etc.

  On the other hand, if the adjustment process is selected for the m-th time and the determination in step 213 is negative, the process proceeds to step 218 to optimize the setting of the illumination light source.

Here, the repetition cycle of the adjustment process, at step 206, the beam shape [Phi ₀ measurement results <[Phi _0> or estimation result "[Phi _0", or based on an initial set or estimated mirror characteristics, illumination source shape Ψ is reproduced. The judgment in step 213 is denied because the illumination light source shape is repeatedly reset based on the results of the beam shape estimation and (m-2 times) mirror characteristic estimation, respectively. This is a case where the shape did not sufficiently match the target, that is, the target illumination light source shape Ψ ₀ was not reproduced with sufficient accuracy. Therefore, in this case, it is unlikely that the target illumination light source shape Ψ ₀ will be reproduced with sufficient accuracy even if the same processing is repeated any more. In this case, it is more important to reproduce the target illumination light source shape Ψ ₀ even if time is required for adjustment because it is a process at the time of initial setting.

Therefore, in step 218, the main controller 20, the illumination source shape [psi (measurement results obtained in step 208 <Ψ>) is reproduced, so as to coincide with the target [psi _0, the control parameters of the mirror elements SE fine By adjusting, the setting of the illumination light source is optimized. That is, the main controller 20 controls the spatial light modulator 3S (such as the inclination of the mirror element SE) according to the optimized control parameter, and reproduces the illumination light source shape.

  Usually, in this step 218, fine adjustments such as the inclination of the plurality of mirror elements SE of the spatial light modulator 3S are repeated over time, and are sequentially performed. Therefore, when the processing of step 218 is completed and the processing returns to step 208 In step 209 and 210, the evaluation result becomes good, and the process ends.

  However, if the determination in step 210 is negative again, the same processing as described above is repeated until the determination in step 210 is affirmed.

  As described above, in the setting process of the illumination light source shape (pupil luminance distribution) according to the flowchart of FIG. 4, an appropriate adjustment process is selected according to the priority determined in advance according to how many times the adjustment process is selected. Therefore, it is possible to initialize the shape of the illumination light source efficiently and accurately.

FIG. 5 shows a flowchart schematically showing a processing algorithm of the main controller 20 (internal CPU) regarding the setting processing of the illumination light source shape during operation of the exposure apparatus 100, particularly at the time of idling and at the beginning of the lot. Yes. As a precondition, it is assumed that the above-described illumination light source shape setting process is performed when the exposure apparatus 100 is activated (at the time of initial adjustment). That is, it is assumed that the illumination light source shape has been set in step 206, the initial setting for the illumination light source in step 202 has been performed, and the target illumination light source shape Ψ ₀ , mirror characteristic information, and the like have been acquired.

In the first step 302, the beam shape is adjusted in order to reproduce the target illumination light source shape Ψ ₀ .

In the next step 304, the intensity distribution (beam shape) in the beam cross section of the light beam LB emitted from the light source 1 is measured as in step 204 described above. Specifically, main controller 20 detects light beam LB reflected by beam splitter BS1 using beam shape detector D1. From this result, a measurement result <Φ ₀ > of the beam shape Φ ₀ is obtained.

  In the next step 306, the illumination light source shape Ψ is measured. Here, since the setting process at the time of starting up the exposure apparatus 100 (at the time of initial adjustment) requires accuracy, the luminance distribution measuring instrument 80 is used for measuring the illumination light source shape. In the setting process during the operation of the exposure apparatus 100, since the apparatus needs to be recovered in a short time, the illumination pupil distribution measurement unit D2 provided in the illumination system IOP is used. Main controller 20 detects illumination light IL reflected by beam splitter BS2 using illumination pupil distribution measurement unit D2. From this result, a measurement result <ψ> of the illumination light source shape ψ is obtained. The measurement result <Ψ> is transferred to the host computer or server connected to the main controller 20 via a LAN (not shown), for example.

In the next step 308, the degree of coincidence between the illumination light source shape and the target is evaluated. Specifically, main controller 20 obtains a deviation of measurement result <Ψ> measured in step 306 from target Ψ ₀ , for example, an RMS error, and calculates the RMS error value and threshold (when exposure apparatus 100 is activated). Compared with the size of the specified setting process).

Then, in the next step 310, it is determined whether or not the evaluation result is good. When the RMS error is smaller than the threshold value and the target illumination light source shape Ψ ₀ is reproduced with sufficient accuracy, that is, when the evaluation result is satisfactory, the processing of this routine (setting of a series of illumination light source shapes and The adjustment process is terminated.

  On the other hand, if the RMS error value is equal to or greater than the threshold value and the evaluation result is not good, the process proceeds to step 312. In the present embodiment, adjustment processing is selected in steps 312, 314, and 318.

In step 312, it is determined whether or not the illumination light source shape adjustment process is selected for the first time. In this case, since this is the first time, the determination in step 312 is affirmed and the process returns to step 302. Here, for example, the presence or absence of an abnormality in the beam shape is determined using the measurement result <Φ ₀ > measured in step 304 described above, and the process may return to step 302 only when an abnormality in the beam shape is detected. Here, when the adjustment process is selected for the first time, the process returns to step 302 unconditionally and the beam shape is adjusted. That is, in the first adjustment process, the beam shape adjustment is selected with priority over others.

The detection of the abnormality of the beam shape can be performed as follows as an example. That is, main controller 20 compares, for example, measurement result <Φ ₀ > with the beam shape measured in the setting process at the time of activation of exposure apparatus 100. For example, when the optical axis of the light beam LB is deviated, the distribution of the measurement result <Φ ₀ > is shifted, or the integral value thereof is reduced, so that an abnormality in the beam shape is detected.

  On the other hand, in the case of selecting the second and subsequent adjustment processes, the determination in step 312 is negative and the process proceeds to step 314. In step 314, it is determined whether or not the selection of the adjustment process is less than the nth time. If the selection of the adjustment process is less than the nth time (usually, n is set to 3, 4, 5, etc.), the determination in step 314 is affirmed and the process proceeds to step 316. The basis for setting n times will be described later.

In step 316, the setting of the illumination light source is optimized. In step 316, main controller 20 determines, based on the measurement result <ψ> of illumination light source shape Ψ obtained in step 306, the measurement result <Φ ₀ > of beam shape Φ ₀ , the initially set mirror characteristics, and the like. The control parameter of the mirror element SE is finely adjusted so that the illumination light source shape Ψ matches the target Ψ ₀ . Thereby, the setting of the illumination light source is optimized. However, the optimization of the setting of the illumination light source in step 316 is a highly accurate processing algorithm in a short processing time, unlike the processing in step 218 described above. Therefore, in the selection of the adjustment process, the main control device 20 is selected with priority over the beam shape adjustment. In addition, the optimization of the setting of the illumination light source in step 316 is meaningful to be repeated several times because the illumination light source shape is reset. For this reason, the above-mentioned n is set to 3, 4, 5, etc.

  On the other hand, if the adjustment process is selected for the nth time and the determination in step 314 is negative, the process proceeds to step 318 to determine whether or not the estimation of the beam shape and / or the estimation of the mirror characteristic is selected. To do. The estimation of the beam shape (step 214) and the estimation of the mirror characteristic (step 216) have already been performed at least once when the exposure apparatus 100 is started. Therefore, only when the other adjustment processing (in this case, (n-2) iterations of optimization of the setting of the illumination light source in step 316) is performed, the evaluation result in step 310 is not satisfactory. The estimation and / or the estimation of the mirror characteristic is selected.

  If the determination in step 318 is negative, the process proceeds to step 320. In step 320, the beam shape estimation similar to step 214 described above and / or the mirror characteristic estimation similar to step 216 are performed. When the beam shape estimation and / or mirror characteristic estimation ends, the process proceeds to step 322.

In step 322, the illumination light source is reset using the estimation result of the beam shape and / or the mirror characteristic. Specifically, the main controller 20 uses the above estimation result to re-set the control parameters of the mirror element SE so that the illumination light source shape Ψ reproduces the target Ψ ₀ , as in step 206 described above. decide. Then, main controller 20 controls spatial light modulator 3S (such as the inclination of mirror element SE) according to the determined control parameter, and reproduces the illumination light source shape.

  On the other hand, if the determination in step 318 described above is affirmative, that is, if the estimation of the beam shape and / or the mirror characteristic has already been selected, all the processes that can be performed without stopping the exposure apparatus have been selected. Therefore, in order to select maintenance as the last option, the process proceeds to step 324 to notify the operator of the necessity of maintenance of the spatial light modulator 3S of the spatial light modulation unit 3. As an example, this notification is performed by displaying “SLM maintenance is required” on the display screen of the display device 44 and by emitting the same content by voice from a speaker (not shown). After the notification, the process proceeds to step 326 and waits for an instruction to restart (restart). Since the maintenance of the spatial light modulator 3S is performed with the exposure apparatus 100 stopped, a long processing time is required. Therefore, the main control device 20 selects the last when the desired light source shape is still not obtained as a result of all other processing.

  The exposure apparatus 100 is temporarily stopped by the operator who has received the notification by the above display and sound, and the mirror element SE of the spatial light modulator 3S is inspected. After the inspection is completed, the operator instructs the restart of the exposure apparatus 100. Thereby, the determination in step 326 is affirmed, and the routine proceeds to step 328.

  In step 328, after restarting, calibration of the mirror characteristics and resetting of the illumination light source are performed. Specifically, main controller 20 restarts exposure apparatus 100, calibrates the characteristics of mirror element SE, and controls mirror element SE in the same manner as step 206 based on the result of the calibration. Determine the parameters. The main controller 20 controls the spatial light modulator 3S (such as the inclination of the mirror element SE) according to the determined control parameter, and reproduces the illumination light source shape.

  After the process of step 328 is completed, the process returns to step 306, and thereafter, the above-described process is repeated until the determination in step 310 is affirmed.

  As described above, in the setting process of the illumination light source shape (pupil luminance distribution) according to the flowchart of FIG. 5, an adjustment method that can be accurately adjusted in a short time is preferentially selected, so that the exposure apparatus 100 is in operation. However, the illumination light source can be adjusted efficiently with almost no decrease in throughput.

  Next, the beam shape estimation processing in steps 214 and 320 will be described including its estimation principle.

FIG. 6A schematically shows an example of the measurement result <Φ ₀ > of the beam shape Φ ₀ measured in step 204. As a measurement result <Φ ₀ >, a step function distribution is obtained with respect to the two-dimensional coordinates x, y in the detection surface of the beam shape detection unit D1 (FIG. 6A shows the one-dimensional coordinates x). Distribution is shown). In step 206, based on the measurement result <Φ ₀ > and the control information of the mirror element SE of the spatial light modulator 3S, the illumination light source shape Ψ sets the target Ψ ₀ schematically shown in FIG. 6B, for example. The control parameter of the mirror element SE is determined so as to reproduce.

However, as described above, in step 204, the light beam LB itself incident on the mirror element SE of the spatial light modulator 3S is not detected. For this reason, the measurement result <Φ ₀ > may not be accurate. Here, when the actual beam shape Φ ₀ deviates from the measurement result <Φ ₀ >, for example, as shown in FIG. 6A, the spatial light modulator 3S is based on the measurement result <Φ ₀ >. Since the target Ψ ₀ is set to be reproduced, as a result, as shown in FIG. 6B, the illumination light source shape Ψ deviated from the target Ψ ₀ is reproduced. Assuming such a situation, the beam shape estimation process is prepared as an adjustment process selected with the highest priority.

The individual mirror elements SE _k (k = 1 to K (K is a mirror) with respect to the cross section of the light beam LB reflected on _K mirror elements SE _{k of the} spatial light modulator 3S (K is the total number of mirror elements) The surface of the total number of elements SE)) is sufficiently small. For this reason, since the light beam LB is received by the plurality of mirror elements SE _k , the intensity distribution Φ ₀ (and measurement result <Φ ₀ >) is the intensity Φ _0k of the light beam LB on the mirror element SE _k ( <Φ _0k >). Hereinafter, the intensity Φ _0k is also expressed as a beam shape Φ _0k as appropriate. In addition, the surface (exit surface) of each lens element FL _n (n = 1 to Nf (Nf is the total number of lens elements)) with respect to the illumination light source shape Ψ (and target shape Ψ ₀ , measurement result <Ψ>) is Since it is sufficiently small, the illumination light source shape Ψ (and target shape Ψ ₀ , measurement result <Ψ ₀ >) is expressed as a set of luminance Ψ _n (Ψ _0n , <Ψ _n >) on each lens element FL _n. Can do.

The spatial light modulator 3S has an intensity Φ _0k reflected by the individual mirror elements SE _k (k = 1 to K) on the bright spots of Nf constituted by the lens elements FL _n (n = 1 to Nf). The illumination light source shape Ψ is reproduced by appropriately superimposing the reflected light. That is, in step 206, as represented by the formula, each of the lens elements FL _n to the target luminance [psi _0n is given, the reflected light that gives the total intensity Σ _k w _nk Φ _0k equal to the target luminance [psi _0n Coefficients (combination coefficients) w _nk (n = 1 to Nf, k = 1 to K) representing the combination of guided mirror elements SE _k are obtained.

ここで、個々の組み合わせ係数ｗ_ｎｋ（ｎ＝１〜Ｎｆ，ｋ＝１〜Ｋ）の値は１又は０であり、非零係数の数はＫに等しい（Σ_ｎｋｗ_ｎｋ＝Ｋ）。

Here, the value of each combination coefficient w _nk (n = 1 to Nf, k = 1 to K) is 1 or 0, and the number of non-zero coefficients is equal to K (Σ _nk w _nk = K).

The beam shape Φ _0k (k = 1 to K) is estimated from the measurement result <Ψ _n > of the illumination light source shape Ψ obtained in step 208.

First as a method, as the illumination light source shape [psi _n is sufficiently approximate to the measurement results <[psi _n>, i.e. so that the square error ε to the next illumination source shape [psi _n and measurement result <[psi _n> is minimized The beam shape Φ _0k (k = 1 to K) is estimated.

ここで、誤差逆伝搬法を適用する。すなわち、式（１）中のΦ_０ｋに、ステップ２０４において得られている計測結果〈Φ_０ｋ〉を代入する。式（１）及び式（２）を用いて、次のように、変分Δｗ_ｎｋを求める。

Here, the error back propagation method is applied. That is, [Phi _0k in formula (1), and the measurement results obtained in step 204 is substituted for <Φ _0k>. Using equation (1) and equation (2), the variation Δw _nk is obtained as follows.

ただし、非零要素（ｗ_ｎｋ≠０）のみ考えればよい。係数ηは学習率である。求められた変分Δｗ_ｎｋを加えて、次のように、組み合わせ係数ｗ_ｎｋ（ｎ＝１〜Ｎｆ，ｋ＝１〜Ｋ）を更新する。

However, only non-zero elements (w _nk ≠ 0) need be considered. The coefficient η is a learning rate. The obtained variation Δw _nk is added, and the combination coefficient w _nk (n = 1 to Nf, k = 1 to K) is updated as follows.

さらに、更新された組み合わせ係数ｗ_ｎｋを用いて式（３）から変分Δｗ_ｎｋを求め、式（４）のように組み合わせ係数ｗ_ｎｋを更新する。このようにして変分Δｗ_ｎｋを求めることと、組み合わせ係数ｗ_ｎｋを更新することとを、変分Δｗ_ｎｋが十分小さくなるまで繰り返す。

Further, using the updated combination coefficient w _nk , the variation Δw _nk is obtained from Expression (3), and the combination coefficient w _nk is updated as in Expression (4). Thus, the variation Δw _nk is obtained and the combination coefficient w _nk is updated until the variation Δw _nk is sufficiently small.

Finally, the beam shape (intensity) Φ _0k is estimated by applying the obtained combination coefficient w _nk to Φ _0k (here, the measurement result <Φ _0k > is substituted). Since the non-zero element w _nk (≠ 0) of the combination coefficients corresponds to the beam shape Φ _0k on a one-to-one basis, _obtaining the combination coefficient w _nk is equivalent to _{obtaining the} beam shape Φ _0k. is there.

Note that the value of the learning rate η is appropriately determined according to the degree of convergence of the solution. However, if a large value is selected as the learning rate η, the solution converges faster while the solution oscillation becomes noticeable, or the solution may diverge without converging. In such a case, a so-called friction term μΔw _nk may be added to the right side of Equation (4). For example, the friction coefficient μ = 0.5.

Here, the number K of the mirror elements SE _k of the spatial light modulator 3S is, for example, 640 × 168 (≈1 × 10 ⁵ ), and the number Nf of the lens elements FL _n of the fly-eye lens 5 is, for example, 128. ² (≈1.6 × 10 ⁴ ). That is, since Nf <K, the beam shape Φ _0k cannot be estimated from the measurement result <Ψ _n > of the illumination light source shape Ψ in the above-described handling. Therefore, assumptions regarding several beams are selectively made.

For example, if it is predicted from the measurement result of the beam shape in step 204 that the light beam is shifted in the plane, the first assumption is that the light beam LB is within the spatial light modulation unit 3 (prism 3P). Consider the case where the optical axis is deviated. In this case, as shown in FIG. 7A, the beam shape Φ _0k is expected to present a distribution whose position is shifted while maintaining the distribution shape of the measurement result <Φ _0k >. Therefore, Φ _0k in equation (1) is expressed as follows.

ここで、係数ｓ_ｋｋ’は分布のシフトを表現し、シフトのない理想的な場合に単位行列ｓ_ｋｋ’＝δ_ｋ,ｋ’である。空間光変調ユニット３の構成より、あるいは経験的に光軸のずれ得る範囲を定め、その範囲に対応する係数ｓ_ｋｋ’のみを上述の誤差逆伝搬法を用いて決定する。範囲に対応しない係数ｓ_ｋｋ’はゼロに固定する。

Here, the coefficient s _{kk ′} represents a shift of the distribution, and in an ideal case without a shift, the unit matrix s _{kk ′} = δ _{k, k ′} . A range in which the optical axis can be shifted is determined from the configuration of the spatial light modulation unit 3 or empirically, and only the coefficient s _{kk ′} corresponding to the range is determined using the error back propagation method described above. The coefficient s _{kk ′} not corresponding to the range is fixed to zero.

For example, when it is predicted that the cross section of the beam has been enlarged or reduced from the measurement result of the beam shape in step 204, as a second assumption, for example, it is assumed that the relative distance between the components of the illumination system IOP has changed. To do. In this case, the beam shape Φ _0k is expected to present an enlarged or reduced distribution while maintaining the distribution shape of the measurement result <Φ _0k >, as shown in FIG. 7B. Even in this case, the beam shape Φ _0k can be expressed as in Expression (5). A range in which the distribution can be expanded / reduced is determined, and only the coefficient s _{kk ′} corresponding to the range is determined using the error back propagation method described above. The coefficient s _{kk ′} not corresponding to the range is fixed to zero.

By imposing these assumptions, the degree of freedom of estimation (maximum K) is substantially limited to Nf or less, and the beam shape Φ _0k can be estimated by the error back propagation method described above.

Finally, the final beam shape Φ _0k is obtained by smoothing the result of the error back propagation method by applying a moving average or the like.

As a second method for estimating the measurement result beam shape [Phi _0k from <Ψ _n>, by weighting the ratio of the illumination light source shape [psi _n and measurement result <[psi _n> to a corresponding combination of the beam shape [Phi _0k, The beam shape Φ _0k can also be estimated. That is, the measurement result <Φ _0k > obtained in step 204 is substituted as the initial condition of the beam shape Φ _0k . Substituting the beam shape Φ _0k into the equation (1), the illumination light source shape Ψ _n is obtained. Then, the ratio <Ψ _n > / Ψ _n is multiplied by all Φ _0k corresponding to the non-zero coefficients among the coefficients w _nk (k = 1 to K) for each n. This process is performed for all n (= 1 to Nf).

Alternatively, the difference between the illumination light source shape [psi _n and measurement result <[psi _n> by adding the corresponding combination of beam shape [Phi _0k, it is also possible to estimate the beam shape [Phi _0k. That is, the measurement result <Φ _0k > obtained in step 204 is substituted as the initial condition of the beam shape Φ _0k . Substituting the beam shape Φ _0k into the equation (1), the illumination light source shape Ψ _n is obtained. Then, the difference (<Ψ _n > −Ψ _n ) / K ′ is added to all Φ _0k corresponding to the non-zero coefficients among the coefficients w _nk (k = 1 to K) for each _n . K ′ is the number of non-zero coefficients w _nk (Σ _k w _nk ) for the index n. This process is performed for all n (= 1 to Nf).

The obtained beam shape Φ _0k is smoothed by applying polynomial fitting, B-spline interpolation, moving average, or the like. Note that the degree of smoothing is appropriately adjusted by appropriately determining the order of the polynomial, the order of interpolation, and the range of the moving average.

The above processing is repeatedly performed on the obtained beam shape Φ _0k until the square error ε between the illumination light source shape Ψ _n and the measurement result <Ψ _n > is equal to or less than a predetermined threshold value.

Note that the measurement result <ψ _n > of the illumination light source shape Ψ is measured using the luminance distribution measuring instrument 80 through the projection optical system PL, particularly in step 208. A gentle distribution is expected for the illumination light source shape Ψ. In such a case, the right side of Equation (2) is convolved using a filter function. As the filter function, for example, since the reflection surface of the mirror element SE _k (k = 1 to K) is rectangular, a Sinc function (Sinc ² (ξ)) can be employed.

If the square error ε between the illumination light source shape Ψ _n (target Ψ _0n ) and the measurement result <Ψ _n > is smaller than a predetermined threshold, it is assumed that the beam shape Φ _0k is measured with sufficient accuracy. The beam shape estimation processing in 214 and 320 may be skipped.

As described above, according to the exposure apparatus 100 of the present embodiment, the main controller 20 controls the illumination light source shape target Ψ ₀ and the light beams irradiated to the plurality of mirror elements SE _k of the spatial light modulator 3S. Based on the shape (beam shape) Φ ₀ , the combination of the plurality of mirror elements SE _k and the plurality of lens elements FL _n of the fly-eye lens 5 is optimized, and through the plurality of mirror elements SE _k according to the optimization result. Then, an illumination light source (secondary light source) is formed on the pupil plane of the illumination optical system (step 206), the shape Ψ of the illumination light source is measured (step 208), an assumption about the beam is made, and the measurement is performed under the assumption. Using the result <Ψ>, the beam shape Φ ₀ is estimated (step 214), and the shape of the illumination light source is adjusted based on the beam shape estimation result (step 206). Here, at the time of estimating the beam shape, at least one of an axial deviation of the light beam, enlargement / reduction of the cross section of the light beam, and a change in intensity of the light beam on the mirror element SE is assumed. Thereby, according to the exposure apparatus 100 of this embodiment, it is possible to accurately estimate the beam shape Φ ₀ and accurately adjust the illumination light source shape Ψ based on the result.

  Further, according to the exposure apparatus 100 of the present embodiment, the reticle R on which a pattern is formed with the illumination light IL from the illumination light source having the light source shape adjusted as described above is illuminated, and the reticle R from the illuminated reticle R is illuminated. The light is passed through the projection optical system PL to form an image of the pattern of the reticle R on the wafer W. As a result, the pattern of the reticle R can be accurately transferred onto the wafer W.

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, the number of sections (grids) formed in the vicinity of the entrance surface of the fly-eye lens by the spatial light modulator 3S and the number of lens elements FL _n of the fly-eye lens 5 are described. The explanation was based on the assumption that However, in general, the number of grids and the number of 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.

  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 elements, DMD (Deformable Micro-mirror Device or Digital Micro-mirror Device), reflective liquid crystal display element, electrophoretic display (EPD), electronic paper (or electronic Ink), a reflective spatial light modulator such as a light diffractive light valve, a reflective diffractive optical element, and the like 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 illumination 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 100 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 100.

  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 adjustment method of the present invention is suitable for adjusting the shape of the 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, 6 ... Condenser optical system, 7 ... Illumination field stop, 8 ... Imaging optical system, 9 ... Folding mirror, 20 ... main controller, 80 ... luminance distribution measuring instrument, 100 ... exposure apparatus, IOP ... illumination system, PL ... projection optical system, PU ... projection unit, R ... reticle, W ... wafer.

Claims (15)

Light source adjustment for adjusting the illumination light source formed on the predetermined surface by selectively distributing the 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 method,
Based on the shape target of the illumination light source and the shape of the beam irradiated on the plurality of optical elements, the combination of the plurality of optical elements and the plurality of sections is optimized, and the plurality of the plurality of optical elements is optimized according to the optimization result. Forming the illumination source via an optical element;
Measuring the shape of the illumination light source;
Making assumptions about the beam and using the measurement results under the assumption to estimate the shape of the beam;
Adjusting the shape of the illumination light source based on the estimation result of the beam shape.   The hypothetical subject includes at least one of an off-axis of the beam, an enlargement or reduction of a cross-section of the beam, and a change in intensity of the beam on the plurality of optical elements. The light source adjustment method of description.   The light source adjustment method according to claim 1, wherein in the estimation, a shape of the beam that minimizes a deviation between the measurement result and the target is estimated.   The light source adjustment method according to claim 3, wherein in the estimation, the intensity of the beam passing through each of the plurality of optical elements is estimated using an error back propagation method.   The light source adjustment method according to claim 4, wherein in the estimation, a parameter for improving the convergence is adjusted according to a degree of convergence of a solution of the error back propagation method.   The light source adjustment method according to claim 3, wherein the estimating includes correcting the intensity of the beam on the plurality of optical elements corresponding to the shift and estimating the shape of the beam.   The light source adjustment method according to claim 1, wherein in the estimation, the target is convolved using a filter function corresponding to a characteristic of the illumination light source.   The light source adjustment method according to claim 1, wherein in the estimation, the estimated shape of the beam is smoothed.   The light source adjustment method according to claim 1, wherein the estimation is performed when a deviation between the measurement result and the target exceeds a threshold value. In the vicinity of the predetermined surface, an optical integrator including a plurality of optical elements arranged two-dimensionally is disposed,
The light source adjustment method according to any one of claims 1 to 9, 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 adjustment method according to any one of claims 1 to 9, 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 in which an object is exposed to illumination light from the illumination light source having the light source shape adjusted by the light source adjustment method according to claim 1 to form a pattern on the object.   13. 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 13, 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 claim 12;
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.

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