JP2005317970A - Lithographic apparatus and device manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithographic apparatus and a method for projecting a patterned beam onto a substrate, using a microlens array system capable of adjusting the magnification. <P>SOLUTION: The beam patterned by an array 1 of individually controllable elements is projected onto a target portion of the substrate 2 by a projection system. The projection system comprise beam expanders 7, 8 for expanding the beam from a pupil, and an array of lenses 11 extending in transverse direction relative to the beam such that each lens of the array focuses a respective portion of the projection beam onto a respective part of the target portion of the substrate. The position of at least one of the lens components, for example a field lens of the beam expander or the lens array, is adjusted to adjust the magnification of the projection system. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  This application is a continuation-in-part of US patent application Ser. No. 10 / 835,601 filed Apr. 30, 2004, which is hereby incorporated by reference in its entirety.

  The present invention generally relates to lithographic apparatus and device manufacturing methods.

  A lithographic apparatus is a machine that applies a desired pattern onto a target portion of a substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs), flat panel displays and other devices involving fine structures. In conventional lithographic apparatus, a patterning apparatus, also referred to as a mask or a reticle, can be used to generate a circuit pattern corresponding to an individual layer of the IC (or other device). This pattern can be imaged onto a target portion (eg, part of one or more dies) of a substrate (eg, a silicon wafer or glass plate) having a layer of radiation sensitive material (eg, resist). Instead of a mask, the patterning device can include an array of individually controllable elements that generate a circuit pattern.

  In general, a single substrate will contain a network of adjacent target portions that are successively exposed. A known lithographic apparatus scans a pattern of a projection beam in a given direction (eg a “scan” direction), a stepper that irradiates each target portion by exposing the entire pattern to one target portion at a time, There are scanners that simultaneously irradiate each target portion by synchronously scanning the substrate parallel or non-parallel to this direction. In general, a single substrate will contain a network of adjacent target portions that are successively exposed. A known lithographic apparatus scans a pattern of a projection beam, a so-called stepper, which irradiates each target portion by exposing the entire pattern to one target portion at a time in a given direction (the “scan” direction), There are so-called scanners that simultaneously irradiate each target portion by synchronously scanning the substrate in parallel or non-parallel to this direction.

  It should be understood that it is essential that the patterned beam be directed onto an appropriate target portion of the substrate surface, whether the lithographic apparatus operates in step mode or scan mode. . In many situations, a multilayer structure is built on the substrate surface as a result of a series of lithographic processing steps. These continuous layers formed on the substrate must be precisely aligned with each other. Therefore, great care is taken that the position of the substrate relative to the beam projection system is known accurately and the pattern magnification on the substrate surface is strictly controlled. In general, it is desirable to obtain a fixed magnification, but it is desirable to be able to adjust the magnification in some situations, such as when a small distortion of the substrate is indicated by measurement between successive processing steps. This is especially true when processing very large substrates where a very small percentage of substrate distortion can lead to significant displacement in terms of the quality and reliability of the manufactured device.

  In a microlens array (MLA) system, an array of lenses is arranged so that each lens projects a corresponding light spot onto the substrate. The patterned beam is projected onto the microlens array through a beam expander. The beam expander is designed to produce a substantially parallel radiation beam that is directed towards the substrate. The microlens array is located between the beam expander and the substrate. Each lens of the microlens array focuses a respective portion of this parallel beam onto a corresponding respective portion of the target portion of the substrate. The microlens array thus images an array of pixels onto the substrate, resulting in a series of radiation spots projected onto the substrate.

  The pitch of the spot is directly related to the pitch of the lenses in the microlens array. To date, magnification adjustment by displacement of the microlens array or field lens has not been used. The inability to adjust the magnification of the microlens array system is seen as a serious drawback of such a system.

  Accordingly, there is a need for a system and method that can provide magnification adjustment of a microlens array using appropriate lens displacement.

  According to one embodiment of the present invention, an illumination system for supplying a radiation projection beam, a patterning system that serves to impart a pattern to a cross section of the projection beam, a substrate table for supporting the substrate, A lithographic apparatus is provided that includes a projection system for projecting a patterned beam onto a target portion of a substrate. The projection system defines a pupil between the patterning system and the substrate table. The projection system includes a series of lens components located between the pupil and the substrate table. The lens component is a beam expander for expanding the beam from the pupil and an array of lenses extending in a direction transverse to the beam, each lens of the array being a respective part of the projection beam. And a lens array extending to focus onto a corresponding respective portion of the target portion of the substrate. The position of at least one of the lens components can be adjusted relative to the pupil to adjust the magnification of the projection system.

  According to another embodiment of the present invention, a device manufacturing method is provided. The method includes providing a substrate, providing a radiation projection beam using an illumination system, applying a pattern to a cross section of the projection beam using a patterning system, and defining a pupil. And projecting the patterned radiation beam onto a target portion of the substrate by a projection system that includes a series of lens components located between the pupil and the substrate table. The lens component is a beam expander for expanding the beam from the pupil and an array of lenses extending transversely to the beam, each lens of the array corresponding to a target portion of the substrate And a lens array extending to focus on each portion of the lens. The method further adjusts the magnification of the projection system by adjusting the position of at least one of the lens components relative to the pupil.

  Displace at least one lens component of the beam expander relative to the pupil and the lens array, or displace the lens array relative to the pupil and the beam expander, or the lens array and the beam expander. Both of the at least one lens component can be displaced relative to the pupil.

  Other embodiments, features and advantages of the present invention, as well as the structure and operation of various embodiments of the present invention, are described in detail below with reference to the accompanying drawings.

  The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate the invention and, together with the description, explain the principles of the invention and enable those skilled in the art to make and use the invention. It serves to make it possible.

  Next, the present invention will be described with reference to the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements.

Overview and Terminology In one embodiment of the present invention using a microlens array imaging system, the field lens of the beam expander of the illumination system (the field lens can be composed of two or more separate lenses). The function makes the projection system telecentric by ensuring that all components of the light beam between the field lens and the microlens array are parallel and perpendicular to the microlens array. There is to do. However, although the light beam between the field lens and the microlens array can be substantially parallel, absolute parallelism cannot be achieved.

  Thus, if the projection system has some degree of non-telecentricity, according to one embodiment of the present invention, one or more of the lens components located between the pupil and the substrate table By displacing the components, small scale magnification adjustments can be achieved without unduly degrading focusing.

  In one embodiment, the projection system defines a pupil. As used herein, the term “pupil” refers to the plane where the radiation of the projection beams exiting the patterning system from different positions of the patterning system at the same angle relative to the axis of the projection beam perpendicular to the patterning system. Point to.

  For example, in accordance with one embodiment of the present invention, assume a microlens imaging system in which the field lens is initially placed so that a perfectly parallel radiation beam is produced between the field lens and the lens array. Further assume that the light reaching the field lens is divergent light. When the field lens is displaced away from the microlens array, a slightly diverging projection beam is obtained, and when the field lens is displaced toward the microlens array, a slightly convergent projection beam is obtained. However, if the field lens is a relatively weak lens, the displacement required to change the magnification of the projection system to compensate for substrate distortion (typically on the order of ppm) is projected onto the substrate surface. This can be accomplished without unacceptable effects on beam focusing. The change in focus due to the displacement of the microlens array toward or away from the substrate is a first order effect, and the resulting change in magnification is a second order effect, but still useful magnification adjustments are made. can do.

  In this example, the field lens can be constructed from a single lens or two or more lenses. Each field lens can be simply translated in a direction toward or away from the microlens array, or the field lens can be tilted so that a difference in magnification occurs on the surface of the substrate to be exposed. it can. Similarly, the microlens array can be translated and / or tilted.

  As used herein, the term “array of individually controllable elements” is used to impart a pattern to the cross-section of the incident projection beam so that the desired pattern can be formed on the target portion of the substrate. It should be interpreted broadly to refer to a device that can be used. The terms “light valve” and “spatial light modulator” (SLM) can also be used in this context. An example of such a patterning device will be discussed later.

  The programmable mirror array includes a matrix-addressable surface having a viscoelastic control layer and a reflective surface. The basic principle of such an apparatus is, for example, that an addressed region of the reflective surface reflects incident light as diffracted light, and an unaddressed region reflects incident light as non-diffracted light. A suitable spatial filter can be used to remove non-diffracted light from the reflected beam, leaving only the diffracted light to reach the substrate. In this way, the beam is given a pattern according to the addressing pattern of the matrix addressable surface.

  As an alternative embodiment, it should be understood that the filter can remove diffracted light, leaving undiffracted light to reach the substrate. An array of diffractive optical microelectromechanical system (MEMS) devices can also be used in a corresponding manner. Each diffractive optical MEMS device can include a plurality of reflective ribbons that can be deformed relative to one another to form a grating that reflects incident light as diffracted light.

  Another alternative embodiment is a programmable mirror that uses a matrix arrangement of small mirrors, each of which can be individually tilted about an axis by applying an appropriate local electric field or by using piezoelectric actuation means. Including arrays. Again, the mirror can be matrix addressed, and the addressed mirror reflects the incident radiation beam in a different direction than the non-addressed mirror. In this way, the reflected beam is given a pattern according to the addressing pattern of the matrix addressable mirror. The required matrix addressing can be performed using suitable electronic means.

  In either example described above, the array of individually controllable elements can comprise one or more programmable mirror arrays. Detailed information on the mirror array described here can be found in, for example, US Pat. Nos. 5,296,891 and 5,523,193, which are incorporated herein by reference in their entirety, and PCT patent application WO 98/38597 and It can be obtained from WO 98/33096.

  A programmable LCD array can also be used. An example of such a structure is disclosed in US Pat. No. 5,229,872, which is incorporated herein by reference in its entirety.

  For example, when using image structure pre-bias, optical proximity correction image structure, phase variation techniques and multiple exposure techniques, the pattern “displayed” on the array of individually controllable elements is It should also be understood that the pattern that is ultimately transferred onto the substrate can be very different. Similarly, the pattern ultimately produced on the substrate may not match the pattern that is instantaneously formed on the array of individually controllable elements. This means that the pattern on the array of individually controllable elements and / or during a given period or a given number of exposures during which the final pattern formed on each part of the substrate is constructed. This can happen in arrangements where the relative position of the substrate changes.

  In this context, reference is made in this context in particular to the use of a lithographic apparatus in IC manufacturing, but the lithographic apparatus described herein may be used in other applications such as DNA chips, MEMS, MOEMS, integrated optics, magnetic domain memory. It should be understood that it has the manufacture of inductive and sensing pattern flat panel displays, thin film magnetic heads and the like. In the context of such alternative applications, those skilled in the art will appreciate that the terms “wafer” or “die” as used herein can be considered synonymous with the more general terms “substrate” or “target portion”, respectively. I want to be understood. The substrate referred to herein can be processed before or after exposure, for example, with a track (typically a tool that applies a layer of resist to the substrate and develops the exposed resist) or a measurement or inspection tool. In some cases, the disclosure herein can be applied to such and other substrate processing tools. Further, a substrate can be processed more than once, for example to create a multi-layer IC, so the term substrate as used herein can also refer to a substrate that already contains multiple processed layers.

  As used herein, the terms “radiation” and “beam” include ultraviolet (UV) radiation (eg, wavelengths 365, 248, 193, 157 or 126 nm), extreme ultraviolet (EUV) radiation (eg, wavelengths 5-20 nm), and Includes all types of electromagnetic radiation, including particle beams such as ion beams and electron beams.

  The term “projection system” as used herein is appropriate with respect to other elements such as exposure radiation used, or use of immersion liquid, use of vacuum, including refractive optics, reflective optics, and catadioptric optics. It should be broadly interpreted as encompassing various types of projection systems. Any use of the term “lens” herein may be considered as synonymous with the more general term “projection system”.

  The illumination system also includes various types of optical components, including refractive, reflective and catadioptric optical components that direct, shape and control the radiation projection beam, which are collectively referred to below. Or it may be called a "lens" independently.

  The lithographic apparatus may be of a type having two (eg, dual stage) or three or more substrate tables (and / or two or more mask tables). In such a “multi-stage” apparatus, these additional tables can be used concurrently in parallel, or one or more other tables while using one or more tables for exposure. Preparatory steps can be performed on the table.

  The lithographic apparatus can also be a type of apparatus in which the substrate is immersed in a liquid (eg, water) having a relatively high refractive index to fill a space between the last element of the projection system and the substrate. It is also possible to use immersion liquid in other spaces of the lithographic apparatus, for example in the space between the mask and the first element of the projection system. Immersion techniques are well known in the art for increasing the numerical aperture of projection systems.

  The apparatus further includes a fluid treatment cell that allows interaction between the fluid and the irradiated portion of the substrate (eg, selectively deposits chemicals on the substrate or selectively modifies the surface structure of the substrate). Can be provided.

Lithographic Projection Apparatus FIG. 1 schematically depicts a lithographic projection apparatus 100 according to one embodiment of the invention. The apparatus 100 includes at least a radiation system 102, an array 104 of individually controllable elements, an object table 106 (eg, a substrate table), and a projection system (“lens”) 108.

  The radiation system 102 can be used to provide a radiation (eg, UV radiation) projection beam 110 and in this particular case further includes a radiation source 112.

  An array of individually controllable elements 104 (eg, a programmable mirror array) can be used to impart a pattern to the projection beam 110. The position of the array of individually controllable elements 104 can generally be fixed relative to the projection system 108. However, in an alternative device, the array of individually controllable elements 104 can be connected to a positioning device (not shown) for accurately positioning the array 104 relative to the projection system. As shown, individually controllable elements 104 are reflective (eg, having a reflective array of individually controllable elements).

  The object table 106 can include a substrate holder (not specifically shown) for holding a substrate 114 (eg, a resist-coated silicon wafer or glass substrate), with respect to the projection system 108. The substrate 114 can be connected to a positioning device 116 for accurate placement.

Projection system 108 (eg, a quartz and / or CaF ₂ lens system, or a catadioptric system that includes a lens element made from the material, or a mirror system) receives a patterned beam received from beam splitter 118. It can be used to project onto a target portion 120 (eg, one or more dies) of the substrate 114. Projection system 108 can project an image of array of individually controllable elements 104 onto substrate 114. Alternatively, the projection system 108 can project an image of a secondary source on which the elements of the array of individually controllable elements 104 act as shutters. Projection system 108 can further include a microlens array (MLA) for forming a secondary source and projecting microspots onto substrate 114.

  A radiation source 112 (eg, an excimer laser) can produce a radiation beam 122. The beam 122 is supplied to an illumination system (illuminator) 124, either directly or after passing through an adjustment device 126, such as a beam expander 126, for example. The illuminator 124 may comprise an adjustment device 128 that sets the radially outward and / or radially inward extent (commonly referred to as σ inner and σ outer) of the intensity distribution of the radiation beam 122. In addition, the lighting device 124 generally includes various other components, such as an integrator 130 and a capacitor 132. In this way, the projection beam 110 incident on the array of individually controllable elements 104 has the desired cross-sectional uniformity and cross-sectional intensity distribution.

  With respect to FIG. 1, it should be noted that the radiation source 112 can be housed within the housing of the lithographic projection apparatus 100 (eg, as is often the case when the radiation source 112 is a mercury lamp). In an alternative embodiment, the radiation source 112 can be arranged separately from the lithographic projection apparatus 100. In this case, the radiation beam 122 will be directed into the device 100 (eg with the aid of a suitable guiding mirror). This latter scenario is often used when the radiation source 112 is an excimer laser. It should be understood that both of these scenarios are contemplated within the scope of the present invention.

  The beam 110 then enters the array 104 of individually controllable elements after being guided using the beam splitter 118. After being reflected by the array of individually controllable elements 104, the beam 110 passes through the projection system 108, which focuses the beam 110 onto the target portion 120 of the substrate 114.

  Another target portion 120 is placed in the path of the beam 110 using the positioning device 116 (and optionally an interferometer measurement device 134 on the base plate 136 that receives the interferometer beam 138 via the beam splitter 140). As described above, the substrate table 106 can be accurately moved. If a positioner for the individually controllable element array 104 is used, this can be used to accurately position the array 104 of individually controllable elements relative to the path of the beam 110, for example during scanning. It can be corrected. Movement of the object table 106 is generally accomplished using a long stroke module (rough positioning) and a short stroke module (fine positioning) not explicitly shown in FIG. A similar system can be used to position the array 104 of individually controllable elements. Alternatively / additionally, the projection beam 110 may be moved in order to fix the position of the object table 106 and / or the array of individually controllable elements 104 and obtain the required relative movement.

  In an alternative configuration of this embodiment, the substrate table 106 is fixed and the substrate 114 is moved on the substrate table 106. In this case, the substrate table 106 has a number of openings in its flat upper surface, through which gas is provided that provides a gas cushion that can support the substrate 114. This is conventionally called an air support device. The substrate 114 is moved over the substrate table 106 using one or more actuators (not shown) that have the ability to accurately position the substrate 114 relative to the path of the beam 110. Alternatively, the substrate 114 can be moved on the substrate table 106 by selectively starting / stopping gas release through the openings.

  In the present description, the lithographic apparatus 100 according to the present invention will be described as an apparatus for exposing a resist on a substrate, but the present invention is not limited to this method of use. It should be understood that the apparatus 100 can also be used to project the projection beam 110 provided with.

  The illustrated apparatus 100 can be used in four preferred modes:

  1. Step mode: The entire pattern on the array of individually controllable elements 104 is projected onto the surface of one target portion 120 at a time (ie, with one static exposure). The substrate table 106 is then moved to another position in the x and / or y direction to illuminate another target portion 120 with the patterned projection beam 110.

  2. Scan mode: Essentially the same as step mode, except that a given target portion 120 is not exposed in a single static exposure. Instead, the array of individually controllable elements 104 can be moved at a velocity v in a predetermined direction (so-called “scan direction”, eg the y direction), so that the projection beam 110 is individually controllable elements. Scan the array 104. At the same time, the substrate table 106 is synchronously moved at a speed V = Mv in the same direction or in the opposite direction. Here, M is the magnification of the projection system 108. In this way, a relatively large target portion 120 can be exposed without sacrificing resolution.

  3. Pulse mode: The array 104 of individually controllable elements is essentially fixed and the entire pattern is projected onto one target portion 120 of the substrate 114 using the pulsed radiation system 102. The substrate table 106 is moved at an essentially constant speed so that the patterned projection beam 110 scans a line across the substrate 106. Between pulses of the radiation system 102, the pattern on the array of individually controllable elements 104 is updated as needed so that a continuous target portion 120 at the required location on the substrate 114 is exposed. The timing of the pulse is adjusted. As a result, the projection beam 110 provided with the pattern can scan the substrate 114 to expose the complete pattern on the strip of the substrate 114. This process is repeated until the entire substrate 114 is exposed line by line.

  4). Continuous scan mode: essentially the same as pulsed mode, but with a substantially constant radiation system 102 and when the patterned projection beam 110 scans and exposes the substrate 114 The difference is that the pattern on the array 104 of individually controllable elements is updated.

  Combinations and / or variations on the above described modes of use or entirely different modes of use may also be employed.

  FIG. 2 shows the embodiment of the present invention shown in FIG. 1 in detail. The array of individually controllable elements 104 in FIG. 1 corresponds to the array 1 in FIG. 2, and the substrate 114 in FIG. 1 corresponds to the substrate 2 in FIG.

  In the embodiment shown in FIG. 2, a radiation beam (not shown) is reflected by the beam splitter 3 towards the array 1 through a series of lenses 4, 5 and 6. The light is then reflected by the array 1, passes through the lenses 6, 5 and 4 and then passes through the beam splitter 3. Light exiting the beam splitter 3 passes through a beam expander defined by lenses 7, 8, 9 and 10 and a microlens array 11, which in turn passes a series of light spots onto the substrate 2. Focus on top. Lenses 7 and 8 expand the beam exiting beam splitter 3. Lenses 9 and 10 serve as field lenses and produce a substantially parallel beam in the microlens array 11. This creates a nominally telecentric optical system. The lenses 9, 10 and 11 are supported in the frames 12, 13 and 14 and the positions of the frames 12, 13 and 14 are adjustable, so that small displacements of the lenses 9, 10 and 11 are controlled in a controlled manner. Can be achieved. In the case shown in FIG. 2, the pupil is defined in a plane with the lens 7.

  Displacement actuators (not shown) are attached to the frames 12, 13 and 14, and are used to adjust the positions of the lenses 9, 10 and 11. These actuators are used to adjust the height and / or tilt of these lenses. This actuator can be, but is not limited to, for example, an electromechanical, electromagnetic, thermal, piezoelectric actuator, or can operate in any way convenient to accurately control the position of the lens. As will be described later, an actuator drive mechanism (not shown) receives displacement control information from the control system. The amount of lens displacement is measured and controlled using a feedback control arrangement (not shown). In addition, an algorithm is used that relates the position of the lens to the magnification. As will be explained later, this algorithm can be modeled by simulation or experiment.

Exemplary Array of Individually Controllable Elements Referring now to FIGS. 3-7, details of the array 1 of individually controllable elements are shown. Array 1 includes an array of spatial light modulators (FIG. 3). General features of spatial light modulators are described, for example, in US Pat. No. 5,311,360, which is hereby incorporated by reference in its entirety.

  In the embodiment shown in FIG. 3, the spatial light modulator comprises an array of 8 × 8 elements that can be individually controlled by a drive mechanism defined in region 15 of array 1. Of course, in alternate embodiments, much larger arrays are used, such as 512 × 512 or 1024 × 1024 arrays. Each element of the array 1 includes an elongated series of displaceable members 16 (FIG. 4). The displaceable member 16 can be controlled by a sample and hold circuit 17 located adjacent to the displaceable member 16 (FIG. 5).

  In the embodiment shown in FIGS. 4 and 5, each element corresponds to one pixel of the pattern imparted to the projection beam directed onto the array. The displaceable member 16 typically takes a coplanar configuration, thereby defining a mirror. This is illustrated in FIG. 6, where arrow 18 represents incident light and arrow 19 represents reflected light.

  FIG. 7 illustrates a method according to one embodiment of the present invention in which the displaceable member 16 is moved to a desired position when a bias voltage is applied to each element. In this state, the incident light indicated by arrow 20 is not simply reflected, but diffracted as indicated by arrow 21. Such diffracted light does not return the optical system toward the substrate 2 to be exposed. In this way, a desired pattern can be imparted to the light beam delivered to the lenses 7, 8, 9, 10 and 11 of FIG.

Exemplary Microlens Array FIG. 8 shows the structure of a microlens array according to one embodiment of the present invention. The illustrated structure corresponds to, for example, the component 11 in FIG. The microlens array essentially includes a large number of very small lenses, each lens focusing one pixel of light onto the substrate 2.

  FIG. 9 schematically shows a matrix of points according to an embodiment of the invention projected onto the substrate 2.

  Referring to FIGS. 8 and 9, indicated by the dashed line 22 tilted with respect to the direction indicated by the line 23 parallel to the scanning direction of the optical system, eg the direction 24 in which the substrate 2 is displaced under the microlens array. The optical system is arranged so that the matrix of points is aligned in the direction. Therefore, a desired exposure pattern can be constructed on the substrate by appropriate control of individual pixels when the substrate is displaced in the direction of arrow 24 under the microlens array.

Exemplary Configuration for Changing the Projection Beam Using a Field Lens FIG. 10 schematically illustrates a substrate 2 positioned under a microlens array 11 according to one embodiment of the present invention. In this embodiment, the field lens 25 has one lens. It should be understood that a field lens can include one lens as shown in FIG. 10, two lenses as shown in FIG. 2, or three or more lenses. However, in any of these embodiments, the purpose of the field lens is to produce a substantially parallel projection beam. In this embodiment, a projection beam 26 is shown. The projection beam 26 irradiates each individual lens element 27 of the microlens array 11. Any number of elements 27 can be used based on the desired application, of which only three are shown.

  The microlens array 11 extends perpendicular to the beam 26, i.e. horizontally on the surface of the substrate 2 to be exposed. The distance between the microlens array 11 and the substrate 2 is the distance at which the respective pixels of the array 104 (FIG. 1) or the array 1 (FIG. 2) are focused on the surface of the substrate 2. The main optical axis 28 of the projection system is parallel to the line 29 of each lens 27 (the line 29 indicates the direction in which light is guided from each lens 27 of the microlens array 11 toward the substrate 2). In this figure, the projection system defines a pupil corresponding to the plane in which the illustrated radiation intersects the axis 28 above the field lens 25.

  FIG. 11 is a schematic top view of array 11 showing a 3 × 3 lens array when the embodiment of FIG. 10 is used. The circumference of one lens is indicated by a circle 30, the outer periphery of the illumination beam projected onto the lens is indicated by a circle 31, and the position of the image spot focused by the lens on the underlying substrate is indicated by a circle 32. ing. In this embodiment, the circles 30, 31 and 32 are concentric circles. The magnification is a function of the spacing between the image spots on the substrate, which in this embodiment is equal to the spacing of the lenses in the array 11.

  In some situations, it is desirable to adjust the magnification of the optical system to compensate for substrate surface distortion. For example, if the dimensions of the substrate are affected by thermal expansion or contraction, it is desirable to be able to adapt the thermal expansion or contraction by making small adjustments to the magnification of the optical system.

  According to one embodiment of the present invention, by adjusting the position of the field lens 25, adjusting the position of the lens array 11, or adjusting both the position of the field lens 25 and the position of the lens array 11, This can be achieved. Since the field lens 25 is generally a relatively weak lens, a small displacement of the field lens 25 does not cause a primary change in resolution. However, a small displacement of the field lens 25 brings the spots projected by the microlens array 11 closer to each other (when reducing the magnification) or away from each other (when increasing the magnification). Similarly, small movements of the array 11 can adjust the magnification without unduly impairing focusing on the substrate surface.

  FIG. 12 shows the response of the optical system to a small displacement of the field lens 25 in the direction of the microlens array 11. Although the position of the spot projected by the microlens array 11 on the optical axis 28 of the entire system does not change, the line 29 tilts inward toward the optical axis 28 as it approaches the substrate 2.

  FIG. 13 shows the displacement of the circumference 31 of the illumination beamlet and the image spot 32 with respect to the lens circle 30 of the array 11. The position of the image spot 32 is shown superimposed on the position of the corresponding image spot 32 (shown as a white circle) in FIG. This figure shows that the magnification of the optical system is effectively reduced. Although focusing is somewhat impaired, the slope of the line 29 is relatively small and its overall effect is not so great. Thus, by displacing the field lens 25, a small change (about 15 ppm) in the magnification range can be easily achieved.

  14 and 15 show the results of moving the field lens 25 away from the microlens array 11. When the field lens 25 is displaced in this way, the line 29 is inclined outward with respect to the axis 28 toward the substrate 2. 14 and 15 thus show a small increase in the magnification of the entire optical system.

  For ease of explanation, it should be understood that the displacement of line 29 shown in FIGS. 12 and 14 is greatly exaggerated compared to the actual slope of line 29 where the change in magnification is about 15 ppm. The range of magnification change is only a few ppm, or more than 15 ppm, for example 100 ppm.

  Although only one field lens 25 is shown in FIGS. 10-15, it should be understood that more than one field lens can be provided. For example, in FIG. 2 where two field lenses 9 and 10 are provided, the respective lenses can be displaced on the support frames 12 and 13 to achieve an appropriate magnification change.

  In the embodiment shown in FIGS. 12 and 14, the field lens 25 is displaced in a direction parallel to the main optical axis 28. As a result, the change in magnification is uniform over the entire area of the substrate 2. It should be understood that in other embodiments, it may be desirable to implement different magnification adjustments depending on the position on the substrate 2. This is the case, for example, when the magnification adjustment is performed as a result of a temperature gradient on a large substrate similar to the type of substrate used to manufacture large liquid crystal displays.

  FIG. 16 shows two possible positions of the field lens 25 (one shown as a solid line and the other as a dashed line) and the resulting two sets of image spots, according to one embodiment of the present invention. ing. In this embodiment, the field lens 25 can be tilted with respect to the optical axis 28 to reduce the magnification on one side of the array 11 and increase the magnification on the other side of the array 11. The magnification adjustment between the two sides of the array 11 depends on the position on the array 11.

  The effect of moving the field lens 25 and not the lens array 11 is shown in FIGS.

  As shown in FIG. 2, the lens array 11 can also be displaced by displacing the frame 14.

  In one embodiment where the illumination beam between the lens 10 and the lens array 11 is not perfectly parallel, displacing the array 11 in the axial direction results in a magnification that is the same as when the lens 10 is displaced in the axial direction. Change. If the lens array 11 is moved in the axial direction, the focusing is somewhat lost, but if this is considered excessive, this can be compensated by adjusting the position of the substrate 2 in the axial direction. Similarly, when the lens array 11 is tilted to change the tilt of the array 11 with respect to the optical axis, the change in magnification varies depending on the position on the substrate.

  The invention thus makes it possible to carry out a magnification adjustment of a small but potentially very important lithographic apparatus, depending on the microlens array.

Exemplary Operation FIG. 17 is a flow diagram illustrating a magnification control process 1700 according to one embodiment of the invention. In this embodiment, only the field lens is displaced. It should be understood that this method can be performed by one of the above systems or other lithographic systems.

  In step 1702, a desired nominal magnification is calculated to obtain a nominal magnification output 33. The light is then projected through the projection system. The field lens is placed at a predetermined nominal position. In step 1704, the actual magnification is measured to obtain a measured magnification output 34. In one embodiment, this can be done using an alignment sensor. In step 1706, the nominal magnification output 33 and the measured magnification output 34 are compared to obtain a magnification error output 35 representing the change in magnification necessary to achieve the nominal magnification.

  In step 1708, the magnification error output 35 is input into a model of the relationship between magnification and field lens position that has been derived in advance. This step then uses this model to obtain an actuator control output 36 that represents the desired actuator position corresponding to the desired field lens position that, when achieved, results in zero magnification error. The output 36 is input to the field lens position control system 37. The field lens position control system 37 outputs a signal 1710 that is used to displace the field lens 38 to the position indicated by the actuator control output 36. The actual field lens position is measured by the field lens position displacement detection system 39. This system produces an output 40. The output signal 40 is used as a feedback control signal, which is received by the actuator control system 37. Feedback control signal 40 ensures that the actual field lens position matches the desired field lens position represented by output 36.

  In various embodiments, a model of the relationship between magnification and field lens position can be derived by simulation or experiment as discussed below.

  In one embodiment, based on the design of the optical projection system, the performance of the projection system can be simulated. This can be done to calculate the non-telecentricity of the system as a function of the position of the field lens relative to the pupil of the projection optics, ie the position of the field lens relative to the beam expander. In this embodiment, the magnification of the projection system at the substrate level can be derived from the non-telecentricity, the lens array geometry, and the position of the lens array relative to the field lens. In this way, a model of the relationship between the field lens position and the lens array position can be obtained. This model is then programmed into the control system, for example as a look-up table. This model is then used as described with reference to FIG. 17 to control the movement of the actuator that adjusts the position of the field lens.

  In other embodiments, experiments can be used rather than simulations. The relationship between the change in field lens position and the resulting change in magnification is measured using a measurement system. This process is repeated to measure a range of positions and a magnification corresponding to the position. A lookup table is obtained from these measurements. This lookup table is programmed into the control system. During operation of the exposure system, this look-up table provides an input to an actuator for moving the field lens along with the magnification error measured by the system. In this way, the magnification error is corrected. To compensate for machine drift, this experiment can be performed periodically and the lookup table can be updated periodically.

  The embodiment of the invention described with reference to FIG. 2 uses a diffractive optics (MEMS) device as an example, but other contrast devices can be used, any variable contrast device or controllable transmission. It should be understood that a mold patterning device can be used to impart an appropriate pattern to the beam projected through the adjustable field lens and the adjustable lens array. Similarly, appropriately designed beam expanders, such as refractive or reflective beam expanders, can be used. All such changes and substitutions are contemplated within the scope of the present invention.

Exemplary Configuration for Changing Projection Beam Using a Field Lens FIGS. 18 and 19 are schematic views of a field lens, microlens and substrate according to one embodiment of the present invention. Reference numerals in FIGS. 18 and 19 correspond to those used in FIG.

  Referring to FIG. 18, the substrate 2 is located above the focal plane of the microlens array 11. This occurs, for example, when the substrate 2 is swollen. In the past, when this occurred, the substrate was moved until it coincided with the focal plane. However, when using a large area substrate, such as a flat panel display substrate, the substrate may not be able to be moved to the focal plane. In this embodiment of the invention, the microlens 11 is moved relative to the substrate 2 to correct this discrepancy.

  Referring to FIG. 19, the microlens array 11 has been moved upward, and as a result, the microlens array 11 is approaching the field lens 25. The focal plane of the microlens array 11 is also moved upward by a corresponding amount so that the substrate 2 is located at the focal plane. In this way, the bulge of the substrate 2 can be corrected by using the microlens array 11.

  It should be understood that each line 29 of the lens 27 is parallel to the main optical axis 28 of the projection system even after movement of the microlens array 11. In other words, the magnification of the system does not change due to the movement of the microlens array 11. In one embodiment, the field lens 25 is arranged with respect to the remaining components of the projection system (see FIG. 2) so that the line 29 is parallel, for example as shown in FIG. 10, before the movement of the microlens array 11. Is done.

  FIG. 20 is a top view of a microlens array according to one embodiment of the present invention. In this embodiment, three actuators 50 are used to actuate the microlens array 11. The actuator 50 is coupled to the periphery of the microlens array 11 and can be operated independently. When raising or lowering the microlens array 11, all three actuators 50 are operated.

  It should be understood that it may be desirable to move one side or corner of the microlens array 11 upward and not move the rest. This can be used, for example, to perform focal plane correction to account for the bulges of the substrate 2 that are only on one side or one corner of the microlens array 11. In this embodiment, one or two actuators 50 are operated according to the required movement of the microlens array 11. In this embodiment, the line 29 of the lens 27 may not be parallel to the main optical axis 28 of the projection system. By adjusting the position of the field lens 25, a part of this deviation can be corrected.

  Although only one projection system is shown in the figure, it should be understood that the lithographic apparatus can comprise several projection systems that are used simultaneously. For example, a lithographic system used to manufacture a flat panel display screen can comprise a plurality of projection systems arranged to cover the entire width of the flat panel display substrate. The optical elements of each projection system can be adjusted independently.

CONCLUSION While various embodiments of the present invention have been described, it should be understood that they have been presented for purposes of illustration and not limitation. It will be apparent to those skilled in the art that various modifications, in form and detail, can be made to these embodiments without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the above-described exemplary embodiments, but is defined only by the claims and their equivalents.

1 depicts a lithographic apparatus according to a first embodiment of the invention. FIG. 2 is a diagram based on one embodiment of the present invention showing FIG. 1 in more detail. 1 is a schematic diagram of an array of spatial light modulators according to one embodiment of the present invention. FIG. FIG. 4 is a perspective view of a displaceable element of the spatial light modulator assembly of FIG. 3. FIG. 4 is a schematic diagram of one element of the spatial light modulator of FIG. 3. FIG. 4 is a diagram illustrating a state of one element of the spatial light modulator illustrated in FIG. 3. FIG. 4 is a diagram illustrating another state of one element of the spatial light modulator illustrated in FIG. 3. 1 is a perspective view of a microlens array according to an embodiment of the present invention. FIG. FIG. 2 is a schematic diagram of an exposure principle according to an embodiment of the present invention that relies on using a microlens array. 1 is a schematic diagram of a field lens, a microlens and a substrate according to one embodiment of the present invention having a nominal magnification configuration. FIG. FIG. 6 is a top view of a microlens array according to an embodiment of the present invention showing the position of image spots projected at nominal magnification. FIG. 11 is a diagram corresponding to FIG. 10 after the field lens is displaced to lower the magnification. FIG. 13 is a top view of the microlens array showing the position of the image spot at a low magnification after the field lens is displaced as shown in FIG. FIG. 11 is a diagram corresponding to FIG. 10 after the field lens is displaced to increase the magnification. FIG. 15 is a top view of the microlens array showing the position of the image spot at a high magnification after the field lens is displaced as shown in FIG. 14. FIG. 6 is a schematic diagram of a field lens, a microlens and a substrate according to one embodiment of the present invention showing the result of changing the tilt of the field lens relative to the microlens array. 3 is a flow diagram representing a magnification measurement / adjustment process according to one embodiment of the present invention. 1 is a schematic view of a field lens, a micro lens, and a substrate according to an embodiment of the present invention. FIG. 1 is a schematic view of a field lens, a micro lens, and a substrate according to an embodiment of the present invention. FIG. 1 is a top view of a microlens array according to one embodiment of the present invention. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Array of individually controllable elements 2 Substrate 3 Beam splitter 4 Lens 5 Lens 6 Lens 7 Lens 8 Lens 9 Lens 10 Lens 11 Microlens array 12 Frame 13 Frame 14 Frame 15 Drive mechanism 16 Displaceable member 17 Sample and Hold circuit 18 Incident light 19 Reflected light 20 Incident light 21 Diffracted light 25 Field lens 26 Projected beam 27 Lens element 28 Main optical axis 29 Lens element line 30 Lens periphery 31 Illumination beam outer periphery 32 Image spot position 100 Lithographic projection apparatus 102 Radiation system 104 Array of individually controllable elements 106 Object table 108 Projection system 110 Projection beam 112 Radiation source 114 Substrate 116 Positioning device 118 Beam splitter 120 Target portion 122 Radiation beam 12 4 Lighting system (lighting device)
126 Adjusting devices (beam expanders, etc.)
128 adjustment device 130 integrator 132 capacitor 134 interferometer measurement device 136 base plate 138 interferometer beam 140 beam splitter

Claims (12)

An illumination system for supplying a radiation projection beam;
A pattern forming system for imparting a pattern to the projection beam;
A substrate table that supports the substrate;
A projection system that projects the patterned beam onto a target portion of the substrate and defines a pupil between the patterning system and the substrate table, the projection system comprising:
A series of lens components positioned between the pupil and the substrate table, the lens components comprising:
A beam expander for expanding the beam provided with the pattern from the pupil;
An array of lenses extending in a direction transverse to the beam provided with the pattern, wherein each lens of the lens array passes a respective portion of the beam provided with the pattern onto the substrate; A lens array extending to focus onto a corresponding respective portion of the target portion, and
A lithographic apparatus, wherein a position of at least one of the lens components can be adjusted relative to the pupil to adjust a focal plane of the projection system.   A lithographic apparatus according to claim 1, further comprising an actuator system for displacing the lens array relative to the pupil and the beam expander.   A lithographic apparatus according to claim 2, wherein the actuator system comprises three or more actuators.   A lithographic apparatus according to claim 3, wherein the actuators are independently operable.   A lithographic apparatus according to claim 1, wherein the beam expander generates a substantially parallel radiation beam between the beam expander itself and the lens array.   A lithographic apparatus according to claim 1, wherein the tilt of the lens array relative to the patterned beam can be adjusted. Applying a pattern to the radiation beam;
Projecting the patterned beam onto a target portion of a substrate using a projection system that defines a pupil and includes a series of lens components positioned between the pupil and the substrate table;
Enlarging the patterned beam from the pupil using a beam expander portion of the lens component and a lens array extending transverse to the patterned beam. Steps,
Using each lens of the lens array to focus a respective portion of the patterned beam onto a corresponding respective portion of the target portion of the substrate;
Adjusting the focal plane of the projection system by adjusting the position of at least one of the lens components relative to the pupil.   8. The method of claim 7, further comprising displacing the lens array with respect to the pupil and the beam expander.   The method of claim 8, wherein the displacement step comprises using three or more actuators.   The method of claim 9, wherein the displacing step further comprises operating the actuator independently.   8. The method of claim 7, further comprising positioning the beam expander such that a substantially parallel radiation beam is generated between the beam expander and the lens array.   The method of claim 7, further comprising adjusting a tilt of the lens array relative to the projection beam.

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