Design of multiple off-axis illumination beams for wafer alignment sensor

Abstract

A new method of producing an alignment system of an off-axis illumination beam by using a glass sheet is described. A pair of glass sheets is inserted into an alignment system to produce a pair of off-axis illumination beams. The off-axis illumination beam passes through the aperture stop. A transmissive optical device having a plurality of total reflection mirrors reflects a beam toward an objective lens. Thereafter, the objective lens focuses the beam onto an alignment mark on the substrate. The diffracted beam is then detected and analyzed to determine alignment of the substrate. The compactness of the glass sheet alignment system significantly reduces the footprint of the optical system.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Application No. 63 / 355,220, filed on June 24, 2022, and the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to an alignment system which may be used, for example, in a lithographic apparatus. Background Art

[0004] A lithographic apparatus is a machine that applies a desired pattern to a target portion of a substrate. A lithographic apparatus can be used, for example, to manufacture an integrated circuit (IC). In this case, a pattern forming device (which may alternatively be referred to as a mask or reticle) can be used to generate a circuit pattern corresponding to an individual layer of the IC, and the pattern can be imaged onto a target portion (e.g., including a portion of a die, one or several dies) on a substrate (e.g., a silicon wafer) having a layer of a radiation-sensitive material (resist). In general, a single substrate will contain a network of adjacent target portions that are continuously exposed. Known lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing the entire pattern to the target portion in one exposure; and so-called scanners, in which each target portion is irradiated by scanning the substrate synchronously in parallel or antiparallel to the direction while scanning the pattern through a beam in a given direction (the "scanning" direction). A pattern can also be transferred from a pattern forming device to a substrate by imprinting the pattern onto the substrate. Another lithographic system is an interference lithographic system, in which there is no pattern forming device, but the beam is split into two beams, and the two beams are interfered at the target portion of the substrate by using a reflection system. The interference causes a line to be formed at a target portion of the substrate.

[0005] During a lithographic operation, different processing steps may require the formation of different layers in sequence on a substrate. Thus, the substrate may need to be positioned with a high degree of accuracy relative to an existing pattern formed thereon. Typically, alignment marks, which may include diffraction gratings, are placed on the substrate to be aligned and positioned with reference to a second object. The lithographic apparatus may use an alignment system for detecting the position of the alignment marks and for aligning the substrate using the alignment marks to ensure accurate exposure from the mask.

[0006] Alignment systems typically have their own illumination systems that can be used to illuminate alignment marks during alignment measurements. Determining alignment typically includes determining the position of an alignment mark (or marks) and / or other targets in a layer of a semiconductor device structure. Alignment is typically determined by illuminating the alignment marks with radiation and comparing the characteristics of radiation of different diffraction orders reflected from the alignment marks. Similar techniques are used to measure overlay and / or other parameters. Current alignment sensors have a single measurement illumination spot projected onto a substrate (e.g., a wafer). A single illumination spot is used for measurement, phase and intensity detection of multiple alignment parameters. Current sensors measure measurement marks serially. Therefore, the number of measured marks on a given substrate is limited by throughput considerations.

[0007] Alignment can be performed using off-axis illumination beams. When the illumination beams are not perpendicular to the substrate, they are considered off-axis illumination beams. Off-axis illumination beams are in contrast to on-axis illumination beams, which originate from the center of the optical axis that is perpendicular to the substrate. Off-axis illumination facilitates detection of finer pitch alignment marks using existing objective systems. As a result, the process window can be increased for the customer. Summary of the invention

[0008] A novel system and method for generating off-axis illumination beams is disclosed. Off-axis illumination using a glass plate design can save space within the optical system if compared to grating-based off-axis illumination. Using glass plate illumination can generate collinear beams of different wavelengths, as opposed to the dispersed spectrum of light used for grating-based illumination. The glass plate can be fine-tuned to better control the off-axis illumination beam.

[0009] According to one embodiment, an alignment illumination system includes an illumination source; at least one pair of glass plates; a transmissive optical device having at least one reflector, the transmissive optical device being configured to reflect radiation received from the glass plates; and an objective lens, the objective lens being configured to focus light from the transmissive optical device toward an object to be illuminated. Each glass plate has a plurality of spot reflectors capable of reflecting or partially reflecting and transmitting an illumination beam from the illumination source.

[0010] In one embodiment, the optical system reflects and refracts the illumination beam to produce pairs of off-axis illumination beams. In one embodiment, the off-axis illumination beams in each pair are in phase with each other.

[0011] In one embodiment, the optical path difference of the off-axis illumination beams in each pair can be controlled by tilting one glass sheet in each pair relative to the other glass sheet using a glass sheet drive motor.

[0012] In one embodiment, the off-axis illumination beam has small color separation or co-linearity for different wavelengths. In one embodiment, the illumination angles of all colors of the off-axis illumination beam are the same.

[0013] In one embodiment, the spectral content of the off-axis illumination beam or the on-axis illumination beam can be controlled by adding a thin film coating to the spot mirror.

[0014] In one embodiment, the off-axis illumination beam is polarized by adding a thin film coating to the spot mirror. In one embodiment, the off-axis illumination beam is unpolarized.

[0015] In one embodiment, an aperture plate positioned between the glass plate and the transmission optics blocks unwanted radiation. In one embodiment, the aperture plate blocks the on-axis illumination beam while allowing the off-axis illumination beam to pass through. In one embodiment, the aperture plate blocks the off-axis illumination beam while allowing the on-axis illumination beam to pass through. In one embodiment, the aperture plate allows both the on-axis illumination beam and the off-axis illumination beam to pass through.

[0016] In one embodiment, the plurality of spot mirrors comprises metal or dielectric or a combination thereof.

[0017] In one embodiment, the at least one pair of glass sheets comprises exactly two glass sheets. In one embodiment, the two glass sheets produce a pair of off-axis illumination beams.

[0018] In one embodiment, the at least one pair of glass sheets includes four glass sheets to produce two pairs of off-axis illumination beams.

[0019] In one embodiment, the alignment system measures the alignment of the object.The alignment illumination system and the adjustable aperture stop may be inserted into the alignment system to generate a pair of off-axis illumination beams.

[0020] According to one embodiment, an alignment system includes an illumination source; at least one pair of glass plates; an aperture stop; a transmissive optical device having at least one mirror, the transmissive optical device configured to reflect radiation received from the glass plates; an objective lens configured to focus light from the transmissive optical device toward an object to be illuminated; a stage for holding the object; and an interferometer configured to measure marks on the object. Each glass plate has a plurality of spot mirrors capable of reflecting or partially reflecting and transmitting an illumination beam from the illumination source.

[0021] According to one embodiment, a method for alignment using an alignment illumination system includes: illuminating an illumination beam from an illumination source; using at least one pair of glass plates to reflect the illumination beam from the illumination source; using a transmissive optical device having at least one reflector to reflect radiation received from the glass plates; and using an objective lens to focus light from the transmissive optical device toward an object to be illuminated. Each glass plate has a plurality of spot reflectors.

[0022] According to one embodiment, a method for alignment using an alignment illumination system includes: illuminating an illumination beam from an illumination source; using at least one pair of glass plates to reflect or partially reflect and transmit the illumination beam from the illumination source; using an aperture stop to filter radiation received from the glass plates; using a transmission optic having at least one mirror to reflect radiation received from the aperture stop; using an objective lens to focus light from the transmission optic toward an object held by a stage to be illuminated; and measuring marks on the object using an interferometer. Each glass plate has a plurality of spot mirrors.

[0023] Other features and advantages of the present invention and the structure and operation of various embodiments of the present invention are described in detail below with reference to the accompanying drawings. Note that the present invention is not limited to the specific embodiments described herein. The embodiments set forth herein are for illustrative purposes only. Based on the teachings contained herein, other embodiments will be apparent to those skilled in the relevant art. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate the present invention and, together with the description, further serve to explain the principles of the invention and enable one skilled in the relevant art to make and use the invention.

[0025] Figure 1 is a schematic illustration of an alignment system using a grating-based illumination structure.

[0026] Figure 2A is a schematic illustration of a reflective lithography apparatus according to an embodiment of the present disclosure.

[0027] Figure 2B is a schematic illustration of a transmissive lithography apparatus according to an embodiment of the present disclosure.

[0028] Figure 2C is a more detailed schematic illustration of a reflective lithography apparatus according to an embodiment of the present disclosure.

[0029] Figure 3A is a schematic illustration of a lithography cell according to one embodiment of the present disclosure.

[0030] Figure 3B is a schematic illustration of an inspection system according to one embodiment of the present disclosure.

[0031] Figure 3C is a schematic diagram of a measurement technique according to an embodiment of the present disclosure.

[0032] Figure 3D is a schematic diagram of the relationship between a radiation irradiation spot and a measurement target of an inspection system according to an embodiment of the present disclosure.

[0033] Figure 4 is a schematic illustration of an alignment system according to one embodiment of the present disclosure.

[0034] Figure 5 is a schematic illustration of an optical system of an alignment system with a pair of off-axis illumination beams according to one embodiment of the present disclosure.

[0035] Figure 6 is a top view of an optical system of an alignment system with two pairs of off-axis illumination beams according to one embodiment of the present disclosure.

[0036] Figure 7 is a side view of an optical system of an alignment system with two pairs of off-axis illumination beams according to one embodiment of the present disclosure.

[0037] Figure 8 is a rotated view of an optical system of an alignment system with two pairs of off-axis illumination beams according to one embodiment of the present disclosure. DETAILED DESCRIPTION

[0038] Figure 1 An alignment system 100 is shown that uses a grating structure 109 to generate an off-axis illumination beam. The alignment system 100 may include an illumination system 112, a grating structure 109, a lens 110, a mirror 111, an objective lens 117, a stage 122 movable along a direction 124, an image rotation interferometer 126, a detector 128, and a signal analyzer 130. The illumination system 112 generates a radiation beam 113 that impinges on the grating structure 109. The gratings of the grating structure 109 diffract the radiation beam 113 into wide-angle rays. Subsequently, the lens 110 focuses the radiation beam 113 onto the mirror 111. The mirror 111 can be configured to direct the radiation beam 113 onto the substrate 120 for illuminating the alignment mark 118.

[0039] The radiation beam 113 is then reflected from the alignment mark 118 to become a diffracted radiation beam 119 which is directed to an image rotation interferometer 126 along an alignment axis 121. Thereafter, a signal 127 is passed to a detector 128 to detect the position of the substrate 120. The signal 129 is then received by a signal analyzer 130 to determine the position of the stage 122 and to correlate the position of the stage 122 with the position of the center of symmetry of the alignment mark 118.

[0040] The problem with such grating structure alignment systems is that the radiation beam covers a large space because the grating structure diffracts the radiation beam into wide angles of light. Retaining all beams including colored light at different angles requires a large volume dedicated to the transmitted light. As a result, the grating alignment system is both bulky and cumbersome.

[0041] and Figure 1In contrast to the system shown, the present alignment system uses a glass plate to generate off-axis illumination beams. Only two beams need to be used, which is significantly smaller than a grating. Reducing the amount of beams from a wide beam for grating alignment to only two beams in glass plate alignment can save a lot of space within the optical system. As a result, the footprint of the optical system can be greatly reduced. In addition, other advantages of using a glass plate for alignment include that all wavelengths are collinear, as opposed to the dispersed spectrum of light used for grating alignment. The glass plate can be fine-tuned to better control the off-axis illumination beam. Another benefit of off-axis alignment using a glass plate is efficiency. Only the required number of off-axis illumination beams is generated, while grating-based illumination may typically have additional diffraction orders that must be blocked or otherwise removed from the system.

[0042] However, before describing these embodiments in more detail, it is instructive to provide an example environment in which embodiments of the invention may be implemented.

[0043] Example Reflective and Transmissive Lithography Systems

[0044] Figure 2A and Figure 2B is a schematic illustration of a lithographic apparatus 200 and a lithographic apparatus 200' in which or for which embodiments of the present disclosure may be implemented. The lithographic apparatus 200 and the lithographic apparatus 200' each include the following: an illumination system (illuminator) IL configured to condition a radiation beam B (e.g., deep ultraviolet or extreme ultraviolet radiation); a support structure (e.g., a mask stage) MT configured to support a pattern forming device (e.g., a mask, a reticle, or a dynamic pattern forming device) MA and connected to a first positioner PM configured to accurately position the pattern forming device MA; and a substrate stage (e.g., a wafer stage) WT configured to hold a substrate (e.g., a wafer coated with a resist) W and connected to a second positioner PW configured to accurately position the substrate W. The lithographic apparatus 200 and 200' further has a projection system PS configured to project a pattern imparted to the radiation beam B by the patterning device MA onto a target portion (e.g., comprising one or more dies) C of the substrate W. In the lithographic apparatus 200, the patterning device MA and the projection system PS are reflective. In the lithographic apparatus 200', the patterning device MA and the projection system PS are transmissive.

[0045] The illumination system IL may include various types of optical components for directing, shaping or controlling the radiation beam B, such as refractive, reflective, catadioptric, magnetic, electromagnetic, electrostatic or other types of optical components, or any combination thereof.

[0046] The support structure MT holds the patterning device MA in a manner that depends on the orientation of the patterning device MA relative to a reference frame, the design of at least one of the lithographic devices 200 and 200', and other conditions, such as whether or not to hold the patterning device MA in a vacuum environment. The support structure MT may use mechanical, vacuum, electrostatic or other clamping techniques to hold the patterning device MA. The support structure MT may be, for example, a frame or a table that may be fixed or movable as desired. By using sensors, the support structure MT may ensure that the patterning device MA is in a desired position, for example relative to the projection system PS.

[0047] The term “patterning device” MA should be broadly interpreted as referring to any equipment that can be used to impart a pattern in the cross-section of a radiation beam B so as to create a pattern in a target portion C of a substrate W. The pattern imparted to the radiation beam B may correspond to a specific functional layer in a device to be created in the target portion C to form an integrated circuit.

[0048] The pattern forming device MA can be a transmissive device (e.g. Figure 2B lithographic apparatus 200') or reflective (as in Figure 2A 200). Examples of pattern forming devices MA include reticles, masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in lithography and include mask types such as binary, alternating phase shift, and attenuated phase shift, as well as various hybrid mask types. An example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be individually tilted to reflect an incoming radiation beam in different directions. The tilted mirrors impart a pattern in the radiation beam B that is reflected by the matrix of small mirrors.

[0049] The term "projection system" PS may include any type of projection system, including refractive, reflective, catadioptric, magnetic, electromagnetic and electrostatic optical systems, or any combination thereof, depending on the exposure radiation being used or other factors such as the use of an immersion liquid or the use of a vacuum on the substrate W. A vacuum environment may be used for EUV or electron beam radiation, since other gases may absorb excess radiation or electrons. A vacuum environment may therefore be provided to the entire beam path with the aid of vacuum walls and a vacuum pump.

[0050] The lithographic apparatus 200 and / or lithographic apparatus 200' may be of a type having two (dual stage) or more substrate tables WT (and / or two or more mask tables). In such "multi-stage" machines, additional substrate tables WT may be used in parallel, or preparatory steps may be performed on one or more tables while one or more other substrate tables WT are being used for exposure. In some cases, the additional tables may not be substrate tables WT.

[0051] refer to Figure 2A and Figure 2B , the illuminator IL receives a radiation beam from a radiation source SO. For example, when the source SO is an excimer laser, the source SO and the lithographic apparatus 200, 200' may be separate physical entities. In this case, the source SO is not considered to form part of the lithographic apparatus 200 or 200', and the radiation beam B is delivered to the lithographic apparatus 200 or 200' by means of a beam delivery system BD (in the case of a laser beam) comprising, for example, suitable directional mirrors and / or a beam expander. Figure 2B In the embodiment of the present invention, the source SO is transferred from the source SO to the illuminator IL. In other cases, for example, when the source SO is a mercury lamp, the source SO may be an integral part of the lithographic apparatus 200, 200'. If desired, the source SO and the illuminator IL and the beam delivery system BD may be referred to as a radiation system.

[0052] The illuminator IL may comprise an adjuster AD (at Figure 2B In general, at least the outer radial extent and / or the inner radial extent (commonly referred to as "σ-outer" and "σ-inner", respectively) of the intensity distribution in a pupil plane of the illuminator can be adjusted. In addition, the illuminator IL may include various other components (in Figure 2B In the embodiment of the present invention, an integrator IN and a condenser CO are provided, such as an illuminator IL. The illuminator IL can be used to condition the radiation beam B to have a desired uniformity and intensity distribution in its cross-section.

[0053] refer to Figure 2A, the radiation beam B is incident on a patterning device (e.g., a mask) MA held on a support structure (e.g., a mask table) MT, and is patterned by the patterning device MA. In the lithographic apparatus 200, the radiation beam B is reflected from the patterning device (e.g., a mask) MA. After reflecting from the patterning device (e.g., a mask) MA, the radiation beam B passes through a projection system PS, which focuses the radiation beam B onto a target portion C of a substrate W. With the aid of a second positioner PW and a position sensor IF2 (e.g., an interferometric measurement device, a linear encoder, or a capacitive sensor), the substrate table WT can be accurately moved (e.g., in order to position a different target portion C in the path of the radiation beam B). Similarly, a first positioner PM and a further position sensor IF1 can be used to accurately position the patterning device (e.g., a mask) MA relative to the path of the radiation beam B. The patterning device (e.g., a mask) MA and the substrate W can be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2.

[0054] refer to Figure 2B , the radiation beam B is incident on a patterning device (e.g., mask MA) held on a support structure (e.g., mask table MT) and is patterned by the patterning device. After traversing the mask MA, the radiation beam B passes through a projection system PS, which focuses the beam onto a target portion C of the substrate W. The projection system has a pupil PPU conjugate to an illumination system pupil IPU. Portions of the radiation emanate from the intensity distribution at the illumination system pupil IPU and traverse the mask pattern without being affected by diffraction at the mask pattern, and produce an image of the intensity distribution at the illumination system pupil IPU.

[0055] With the help of a second positioner PW and a position sensor IF (e.g. an interferometric device, a linear encoder or a capacitive sensor), the substrate table WT can be accurately moved (e.g. to position a different target portion C in the path of the radiation beam B). Similarly, the first positioner PM and another position sensor ( Figure 2B ) can be used to accurately position the mask MA relative to the path of the radiation beam B (eg, after mechanical retrieval from a mask library or during scanning).

[0056] In general, movement of the mask table MT may be achieved with the aid of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning), which form part of the first positioner PM. Similarly, movement of the substrate table WT may be achieved using a long-stroke module and a short-stroke module, which form part of the second positioner PW. In the case of a stepper (as opposed to a scanner), the mask table MT may be connected only to a short-stroke actuator or may be fixed. Mask MA and substrate W may be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2. Although the substrate alignment marks (as illustrated) occupy dedicated target portions, they may be located in spaces between target portions (referred to as scribe alignment marks). Similarly, in the case where more than one die is provided on the mask MA, the mask alignment marks may be located between the dies.

[0057] The mask table MT and the patterning device MA may be in a vacuum chamber, wherein a vacuum robot IVR may be used to move the patterning device, such as a mask, into and out of the vacuum chamber. Alternatively, when the mask table MT and the patterning device MA are outside the vacuum chamber, a non-vacuum robot similar to the vacuum robot IVR may be used for various transport operations. Both the vacuum robot and the non-vacuum robot need to be calibrated in order to smoothly transfer any payload (e.g., a mask) to the fixed kinematic support of the transfer station.

[0058] The lithographic apparatus 200 and 200' may be used in at least one of the following modes:

[0059] 1. In step mode, the support structure (e.g. mask table) MT and the substrate table WT are kept substantially stationary while the entire pattern imparted to the radiation beam B is simultaneously projected onto a target portion C (i.e. a single static exposure). The substrate table WT is then shifted in the X-direction and / or Y-direction so that a different target portion C can be exposed.

[0060] 2. In scan mode, the support structure (e.g. mask table) MT and substrate table WT are scanned synchronously (i.e. single dynamic exposure) while a pattern imparted to the radiation beam B is projected onto a target portion C. The speed and direction of the substrate table WT relative to the support structure (e.g. mask table) MT may be determined by the (de-)magnification and image reversal characteristics of the projection system PS.

[0061] 3. In another mode, the support structure (e.g. mask table) MT holding the programmable patterning device is held substantially stationary, and the substrate table WT is moved or scanned while a pattern imparting B to the radiation beam is projected onto a target portion C. The radiation source SO may be pulsed and the programmable patterning device updated as required after each movement of the substrate table WT or between successive radiation pulses during a scan. This mode of operation may be readily applied to maskless lithography utilizing a programmable patterning device such as a programmable mirror array.

[0062] Combinations and / or variations of the described modes of use or entirely different modes of use may also be employed.

[0063] In some embodiments, the lithographic apparatus 200 includes an extreme ultraviolet (EUV) source configured to generate an EUV radiation beam for EUV lithography. Generally, the EUV source is configured in a radiation system, and a corresponding illumination system is configured to condition the EUV radiation beam of the EUV source.

[0064] Figure 2C The lithographic apparatus 200 is shown in more detail and includes a source collector device SO, an illumination system IL, and a projection system PS. The source collector device 50 is constructed and arranged so that a vacuum environment can be maintained in the closed structure 220 of the source collector device 50. An EUV radiation emitting plasma 210 can be formed by a plasma source generated by a discharge. EUV radiation can be generated by a gas or vapor (e.g., Xe gas, Li vapor, or Sn vapor), wherein a thermal plasma 210 is generated to emit radiation in the EUV range of the electromagnetic spectrum. For example, the thermal plasma 210 is generated by a discharge that causes a plasma that is at least partially ionized. In order to effectively generate radiation, a partial pressure of 10Pa of, for example, Xe, Li, Sn vapor, or any other suitable gas or vapor may be required. In one embodiment, a plasma of stimulated tin (Sn) is provided to generate EUV radiation.

[0065] The radiation emitted by the hot plasma 210 is transferred from the source chamber 211 to the collector chamber 212 via an optional gas barrier or contaminant trap 230 (also referred to as a contaminant barrier or fin trap in some cases), which is located in or behind an opening in the source chamber 211. The contaminant trap 230 may include a channel structure. The contaminant trap 230 may also include a gas barrier or a combination of a gas barrier and a channel structure. The contaminant trap or contaminant barrier 230 also indicated herein includes at least a channel structure as known in the art.

[0066] The collector chamber 212 may include a radiation collector CO, which may be a so-called grazing incidence collector. The radiation collector CO has an upstream radiation collector side 251 and a downstream radiation collector side 252. Radiation traversing the collector CO may be reflected from the grating spectral filter 240 to be focused at a virtual source point IF. The virtual source point IF is often referred to as an intermediate focus, and the source collector arrangement is arranged so that the intermediate focus IF is located at or near the opening 219 in the enclosed structure 220. The virtual source point IF is an image of the radiation emitting plasma 210. The grating spectral filter 240 is particularly useful for suppressing infrared (IR) radiation.

[0067] The radiation then traverses an illumination system IL which may include a faceted field mirror arrangement 222 and a faceted pupil mirror arrangement 224 which are arranged to provide a desired angular distribution of the radiation beam 221 at the patterning device MA and a desired uniformity of radiation intensity at the patterning device MA. When the radiation beam 221 is reflected at the patterning device MA held by the support structure MT, a patterned beam 226 is formed and the patterned beam 226 is imaged by the projection system PS via reflective elements 228, 230 onto a substrate W held by a wafer stage or substrate table WT.

[0068] Typically, more elements than shown may be present in the illumination optics unit IL and the projection system PS. Depending on the type of lithographic apparatus, a grating spectral filter 240 may optionally be present. Furthermore, more mirrors may be present than shown in the figures, for example, more than 100 mirrors may be present in the projection system PS. Figure 2C The reflective elements shown have from 1 to 6 additional reflective elements.

[0069] like Figure 2C As illustrated, the collector optics CO is depicted as a nested collector with grazing incidence reflectors 253, 254 and 255, just as an example of a collector (or collector mirror). The grazing incidence reflectors 253, 254 and 255 are arranged axisymmetrically around the optical axis O, and this type of collector optics CO is preferably used in conjunction with a discharge produced plasma source (commonly referred to as a DPP source).

[0070] Example Lithography Cell

[0071] Figure 3AA lithography unit 300, sometimes also referred to as a lithocell or cluster, is shown. The lithography apparatus 200 or 200' may form part of the lithography unit 300. The lithography unit 300 may also include devices for performing pre-exposure processes and post-exposure processes on a substrate. Traditionally, these devices include a spin coater SC for depositing a resist layer, a developer DE for developing the exposed resist, a cooling plate CH, and a baking plate BK. A substrate handler or robot RO picks up substrates from input / output ports I / O1, I / O2, moves them between different processing devices, and then delivers them to the loading and unloading area LB of the lithography apparatus. These devices, which are generally collectively referred to as tracks, are under the control of a track control unit TCU, which itself is controlled by a supervisory control system SCS, which also controls the lithography apparatus via a lithography control unit LACU. Therefore, different devices can be operated to maximize production volume and processing efficiency.

[0072] Alignment System Embodiments

[0073] One or more targets are specifically provided on the substrate to achieve alignment. Typically, the targets are specially designed and may include periodic structures. For example, the target on the substrate may include one or more 1D periodic structures (e.g., geometric features such as gratings), which are printed so that after development, the periodic structural features are formed by solid resist lines. As another example, the target may include one or more 2-D periodic structures (e.g., gratings), which are printed so that after development, the one or more periodic structures are formed by solid resist columns or vias in the resist. The bars, columns or vias may alternatively be etched into the substrate (e.g., etched into one or more layers on the substrate).

[0074] Figure 3B An example alignment system 10 is depicted that can be used to detect alignment as well as overlay and / or perform other metrology operations. The example alignment system 10 includes a radiation or illumination source 2 that projects or otherwise illuminates radiation onto a substrate W (e.g., which may typically include metrology marks). The redirected radiation is passed to a sensor such as a spectrometer detector 4 and / or other sensor that measures the spectrum (intensity as a function of wavelength) of the specularly reflected radiation and / or diffracted radiation, such as, for example Figure 3C The sensor may generate an alignment signal that transmits alignment data indicating the properties of the reflected radiation. Based on this data, one or more processors PRO ( Figure 3C ) or by other operations to reconstruct the structure or profile that produces the detected spectrum.

[0075] As in Figure 2A and Figure 2B As in the lithographic apparatus 200 and 200', one or more substrate tables may be provided to hold a substrate W during measurement operations. The one or more substrate tables may be similar in form to Figure 2A and Figure 2B The substrate table WT of the inspection system 10 is similar or identical. In examples where the inspection system 10 is integrated with the lithographic apparatus, they may even be the same substrate table. Coarse and fine locators may be provided and configured to accurately position the substrate relative to the measuring optical system. For example, various sensors and actuators are provided to obtain the position of a target portion of interest (e.g., a measurement mark) of the structure and place it under the objective lens. Typically, many measurements are made on the target portion of the structure at different positions across the substrate W. The substrate support may be moved in the X-direction and the Y-direction to obtain different targets, and the substrate support may be moved in the Z-direction to obtain the desired position of the target portion relative to the focus of the optical system. When, for example, in practice the optical system can remain substantially stationary (typically in the X-direction and the Y-direction, but also possibly in the Z-direction) and the substrate moves, it is convenient to think about and describe the operation as if the objective lens was brought to different positions relative to the substrate. Assuming that the relative position of substrate and optical system is correct, in principle it does not matter which one is moving, or if both are moving, or a combination of parts of the optical system that are moving (e.g. in Z and / or tilt direction) where the rest of the optical system is stationary and the substrate is moving (e.g. in X and Y direction, but optionally also in Z and / or tilt direction).

[0076] For a typical alignment measurement, the target (portion) 30 on the substrate W may be a 1-D grating that is printed such that after development, the bars are formed of solid resist lines (e.g., which may be covered by a deposited layer) and / or other materials. Alternatively, the target 30 may be a 2-D grating that is printed such that after development, the grating is formed of solid resist pillars and / or other features in the resist.

[0077] The bars, pillars, vias, and / or other features may be etched into or onto a substrate (e.g., etched into one or more layers on a substrate), deposited on a substrate, covered by a deposited layer, and / or have other properties. The target (portion) 30 (e.g., bars, pillars, vias, etc.) is sensitive to process changes during the patterning process (e.g., optical aberrations in a lithographic projection device such as a projection system, focus changes, dose changes, etc.), such that process changes manifest as changes in the target 30. Thus, the measured data from the target 30 may be used to determine adjustments to one or more manufacturing processes in the manufacturing process and / or may be used as a basis for making actual adjustments.

[0078] For example, the measured data from target 30 may indicate the overlay of a layer of a semiconductor device. The measured data from target 30 may be used (e.g., by one or more processors PRO and / or other processors) to determine one or more semiconductor device manufacturing process parameters based on the overlay, and to determine adjustments to the semiconductor device manufacturing apparatus based on the determined one or more semiconductor device manufacturing process parameters. In some embodiments, this may include, for example, stage position adjustments, or this may include determining adjustments to mask design, measurement target design, semiconductor device design, intensity of radiation, incident angle of radiation, wavelength of radiation, pupil size and / or shape, resist material, and / or other process parameters.

[0079] Figure 3D A plan view of a typical target (eg, measurement mark) 30 is shown and Figure 5 The range of a typical radiation illumination spot S in a system of FIG. 30 is a periodic structure (e.g., a grating) that is larger than the width (e.g., diameter) of the illumination spot S in one embodiment in order to obtain a diffraction spectrum that is not disturbed by surrounding structures. The width of the spot S may be smaller than the width and length of the target. In other words, the target is 'underfilled' by the illumination, and the diffraction signal is substantially free of any signal from product features, etc., external to the target itself. For example, the illumination arrangement may be configured to provide illumination of uniform intensity across the back focal plane of the objective. Alternatively, the illumination may be constrained to an on-axis direction or an off-axis direction, for example by including an aperture in the illumination path.

[0080] Figure 4 A schematic diagram of a cross-section of an alignment system 400 according to one embodiment is illustrated, which alignment system 400 can be implemented as part of or otherwise combined with a lithographic apparatus 200 or 200' and / or other lithographic apparatus. In an example of this embodiment, the alignment system 400 can be configured to align a substrate (e.g., a semiconductor wafer, substrate W, etc. described above) relative to a pattern forming device (e.g., the pattern forming device MA described above). The alignment system 400 can also be configured to detect the position of an alignment mark on the substrate, and use the detected position of the alignment mark to align the substrate relative to the pattern forming device or other components of the lithographic apparatus 100 or 100'. Such alignment of the substrate can ensure accurate exposure of one or more patterns on the substrate.

[0081] According to one embodiment, the alignment system 400 may include an illumination source 412, an optical system 414, an objective lens 417, an image rotation interferometer 426, a detector 428, and a signal analyzer 430. The illumination source 412 may be configured to provide an electromagnetic narrowband radiation beam 413 having a first polarization state, such as a linear polarization state. In one example, the narrowband radiation beam 413 may be within a wavelength spectrum between about 500 nm and about 900 nm. In another example, the narrowband radiation beam 413 includes a discrete narrow passband within a wavelength spectrum between about 500 nm and about 900 nm. In yet another example, the radiation beam 413 may be monochromatic, for example, provided by a monochromatic light source, such as a laser light source in the illumination source 412. A polychromatic light source, such as an LED, may also be used in the illumination source 412 to provide the polychromatic radiation beam 413.

[0082] The optical system 414 may be configured to receive the radiation beam 413. In one example of this embodiment, the optical system may also be configured to direct the radiation beam 413 onto the substrate 420, such as Figure 4 The optical system 414 may include a transmissive optical device having at least one mirror configured to direct the radiation beam 413 toward an alignment mark 418 located on the substrate 420. The optical system 414 may also include an optical device that generates additional illumination beams split or replicated from the radiation beam 413 and directs them toward the alignment mark 418.

[0083] The substrate 420 can be placed on a stage 422 that is movable along a direction 424. The radiation beam 413 can be configured to illuminate an alignment mark 418 located on the substrate 420. In an example of this embodiment, the alignment mark 418 can be coated with a radiation-sensitive film. In another example, the alignment mark 418 can have a 180° symmetry. That is, when the alignment mark 418 is rotated 180° around an axis of symmetry perpendicular to the plane of the alignment mark 418, the rotated alignment mark 418 may be substantially the same as the non-rotated alignment mark 418.

[0084] like Figure 4 As shown, according to one embodiment, objective lens 417 may be configured to direct diffracted radiation beam 419 toward image rotation interferometer 426. Objective lens 417 may include any suitable number of optical elements suitable for directing diffracted radiation beam 419. In an example embodiment, diffracted radiation beam 419 may be at least a portion of radiation beam 413 diffracted from alignment mark 418. It should be noted that although in Figure 4414, but the present disclosure is not limited thereto. The optical system 414 may be substantially transparent to the diffracted radiation beam 419 and may allow the diffracted radiation beam 419 to pass through without substantially changing the properties of the diffracted radiation beam 419. It should also be noted that although the objective lens 417 is shown as directing the radiation beam 419 toward the image rotation interferometer 426, the present disclosure is not limited thereto. Other optical arrangements may be used to obtain similar results for detecting diffraction signals from the alignment mark 418.

[0085] In some embodiments, the image rotation interferometer 426 may include any suitable set of optical elements, for example, a combination of prisms that may be configured to form two images of the alignment mark 418 based on the received diffracted radiation beam 419. It should be appreciated that high quality images need not be formed, but rather features of the alignment mark 418 should be resolved. The image rotation interferometer 426 may also be configured to rotate one of the two images by 180° relative to the other of the two images, and to interferometrically recombine the rotated image and the unrotated image.

[0086] When the alignment axis 421 of the alignment system 400 passes through the center of symmetry of the alignment mark 418 (not shown), the detector 428 can be configured to receive the recombined image and detect interference as a result of the recombined image. According to an example embodiment, such interference may be due to the alignment mark 418 being 180° symmetrical and the recombined image constructively or destructively interfering. Based on the detected interference, the detector 428 can also be configured to determine the position of the center of symmetry of the alignment mark 418, and therefore detect the position of the substrate 420. According to an example, the alignment axis 421 can be aligned with a light beam that is perpendicular to the substrate 420 and passes through the center of the image rotation interferometer 426.

[0087] In some embodiments, signal analyzer 430 may be configured to receive signal 429 including information of the determined center of symmetry. Signal analyzer 430 may also be configured to determine the position of stage 422 and to correlate the position of stage 422 with the position of the center of symmetry of alignment mark 418. In this way, the position of alignment mark 418, and therefore the position of substrate 420, may be accurately known with reference to stage 422. Alternatively, signal analyzer 430 may be configured to determine the position of alignment system 400 or any other reference element, such that the center of symmetry of alignment mark 418 may be known with reference to alignment system 400 or any other reference element.

[0088] Optical system embodiment

[0089] Figure 5FIG. 5 is a schematic diagram of a cross-section of an optical system 514 according to one embodiment. The optical system 514 may represent Figure 4 The illumination beam 513 may be similar to the one described above with respect to Figure 4 The discussed radiation beam 413 is similar. Because the illumination beam 513 travels along the optical axis 510, it is an on-axis illumination beam.

[0090] In this example of an embodiment, optical system 514 may include a pair of glass plates 550, aperture plate 552, and transmission optics 553. Glass plates 550 each have a plurality of spot mirrors 560 for reflecting and refracting illumination beam 513. As a result, illumination beam 513 is incident on glass plates 550 to produce a pair of illumination beams 515. Illumination beam 515 is an off-axis illumination beam, and downstream of glass plates 550 is aperture plate 552, which selectively blocks unwanted radiation. Figure 5 513 and the off-axis illumination beam 515 are retained. Downstream of the aperture plate 552 is the transmission optics 553. The transmission optics 553 includes a plurality of mirrors 563. Each mirror 563 is associated with an illumination beam. The mirrors 563 reflect the on-axis illumination beam 513 and the off-axis illumination beam 515 toward the objective lens 417. The objective lens 417 can be configured to focus the illumination beams 513 and 515 onto the substrate 420. The illumination beams 513 and 515 converge on the alignment mark 418 of the substrate 420, as shown in FIG. Figure 4 shown.

[0091] Figures 6 to 8 A schematic diagram of a cross-section of an optical system 614 is illustrated according to one embodiment. Figure 6 is a top view of the optical system 614, Figure 7 is a side view, Figure 8 is a rotated view of optical system 614. Optical system 614 may represent Figure 4 An example embodiment of the optical system 414 is shown. The illumination beam 613 can be the same as described above with respect to Figure 4 The discussed radiation beam 413 is similar. Because the illumination beam 613 travels along the optical axis 610, it is an on-axis illumination beam.

[0092] In one example of this embodiment, the optical system 614 may include a first pair of glass plates 650, a second pair of glass plates 651, an aperture plate 652, and a transmission optical device 653. The glass plates 650 and 651 each have a plurality of spot mirrors 660 and 661, respectively, for reflecting and refracting the radiation beam 613. As a result, the illumination beam 613 is incident on the first pair of glass plates 650 to produce a first pair of illumination beams 615, such as Figure 6 and Figure 8 Clearly shown. Figure 7Only the first illumination beam 615 is shown because, according to this view, the second illumination beam 615 is located below and covered by the first illumination beam 615 (the first illumination beam 615 also covers the illumination beam 613). In addition, the illumination beam 613 is then incident on the second pair of glass plates 651 to produce a second pair of illumination beams 616, as shown in FIG. Figure 7 and Figure 8 Clearly shown. Similar to the above, Figure 6 Only the first illumination beam 616 is shown. Illumination beams 615 and 616 are off-axis illumination beams. Downstream of glass plates 650 and 651 is an aperture plate 652 that selectively blocks unwanted radiation. Figures 6 to 8 The diagram shows a situation in which the on-axis illumination beam 613 and the off-axis illumination beams 615 and 616 are retained. Downstream of the aperture plate 652 is the transmission optics 653. The transmission optics 653 includes a plurality of mirrors 663. Each mirror 663 is associated with an illumination beam. The mirrors 663 reflect the on-axis illumination beam 613 and the off-axis illumination beams 615 and 616 toward the objective lens 417, as shown in FIG. Figure 7 and Figure 8 Objective lens 417 may be configured to focus illumination beams 613, 615, and 616 onto substrate 420, as shown. Figure 7 and Figure 8 As shown. Illumination beams 613, 615 and 616 converge on alignment mark 418 of substrate 420, as shown. Figure 4 shown.

[0093] Although the above embodiments have one or two pairs of off-axis illumination beams, the system is not limited thereto. More than two pairs of off-axis illumination beams may be generated.

[0094] Glass plates 550, 650 and 651 are each a pair of glass plates. Each pair of glass plates 550, 650 and 651 receives illumination beams 513 and 613 to generate off-axis illumination beam pairs 515, 615 and 616, respectively. Additional glass plate pairs can be inserted into the optical path to generate additional off-axis illumination beam pairs. In addition, one of the glass plates in the pair can be slightly tilted relative to the other glass plate to change the characteristics of the off-axis illumination beam. The glass plates can be tilted using a glass plate drive motor (not shown). As a result, the optical path difference between the beam pairs, the amount of light and the power can be controlled.

[0095] The plurality of spot reflectors 560, 660 and 661 are partially reflective spot reflectors or fully reflective spot reflectors. A partially reflective spot reflector refracts some of the radiation beam while reflecting the rest of the beam. On the other hand, a fully reflective spot reflector reflects the entire beam. Each spot reflector is a discrete area of ​​a reflective coating on the glass plate. The reflective coating comprises a metal or a dielectric or a combination thereof.

[0096] Aperture plates 552 and 652 are located between glass plates 550, 650 and 651 and transmissive optics 553 and 653. Aperture plates 552 and 652 block unwanted radiation while allowing certain illumination beams to pass through and reach alignment mark 418. Aperture plates 552 and 652 can be moved into and out of the path of the illumination beam using an aperture plate drive motor (not shown). In a first configuration, aperture plates 552 and 652 block on-axis illumination beams 513 and 613 while allowing off-axis illumination beams 515, 615 and 616 to pass through. In a second configuration, aperture plates 552 and 652 block off-axis illumination beams 515, 615 and 616 while allowing on-axis illumination beams 513 and 613 to pass through. In a third configuration, aperture plates 552 and 652 allow on-axis illumination beams 513 and 613 and off-axis illumination beams 515, 615 and 616 to pass through.

[0097] Transmission optics 553 and 653 include a plurality of mirrors 563. Mirrors 563 may be fully reflective. The number of mirrors in the transmission optics is equal to the number of illumination beams. Transmission optics 553 and 653 reflect each of the beams toward objective lens 417.

[0098] Below are additional details of the off-axis illumination beam pairs. The off-axis illumination beam pairs 515, 615, and 616 are in phase with each other and have matching optical paths. Moreover, by tilting one glass plate 550, 650, and 651 in each pair relative to the other glass plate, the optical path difference between the beams 515, 615, and 616 in each pair can be fine-tuned. Additionally, the off-axis illumination beams can be polarized or non-polarized. This can be achieved by adding a thin film coating to the spot reflectors 560, 660, and 661. Alternatively, a polarizer (not shown) in the optical path can change the off-axis illumination beam to polarized or non-polarized. Since the off-axis illumination beams are generated by the glass plates (as opposed to the grating structure), the off-axis illumination beams can have less color separation for different wavelengths, or be made completely achromatic, or collinear. In other words, the off-axis illumination beams are all the same color, rather than the color spectrum of the grating structure. As a result, the illumination angles of all colors of the off-axis illumination beams are the same. In addition, the spectral composition of the off-axis illumination beams can be controlled by adding a thin film coating. Thin film coatings will alter the power intensity of the off-axis illumination beam.

[0099] In some embodiments, optical systems 514 and 614 may be inserted into Figure 4 The alignment system 400 in FIG. 5 is similar to the alignment system 400 in FIG. 5. As a result, the optical systems 514 and 614 are backward compatible and can be used to upgrade the existing alignment system.

[0100] The embodiments may also be described using the following terms.

[0101] 1. An alignment and illumination system, comprising:

[0102] Irradiation source;

[0103] at least one pair of glass sheets, wherein each glass sheet has a plurality of spot mirrors capable of reflecting or partially reflecting and transmitting an illumination beam from the illumination source;

[0104] a transmissive optic having at least one mirror configured to reflect radiation received from the glass sheet; and

[0105] An objective lens is configured to focus light from the transmission optics toward an object to be illuminated.

[0106] 2. The alignment illumination system of clause 1, wherein the glass plate reflects and refracts the illumination beam to produce a pair of off-axis illumination beams.

[0107] 3. The alignment illumination system of clause 2, wherein the off-axis illumination beams in each pair are in phase with each other.

[0108] 4. The aligned illumination system of clause 2, wherein the optical path difference of the off-axis illumination beams in each pair can be controlled by tilting one glass sheet of the pair relative to the other glass sheet using a glass sheet drive motor.

[0109] 5. The alignment illumination system of clause 2, wherein the off-axis illumination beams have small color separation or are co-linear for different wavelengths.

[0110] 6. The alignment illumination system of clause 2, wherein the illumination angles for all colors of the off-axis illumination beam are the same.

[0111] 7. The alignment illumination system of clause 2, wherein the spectral content of the off-axis illumination beam or the on-axis illumination beam can be controlled by adding a thin film coating to the spot mirror.

[0112] 8. The alignment illumination system of clause 2, wherein the off-axis illumination beam is polarized by adding a thin film coating to the spot mirror.

[0113] 9. The alignment illumination system of clause 2, wherein the off-axis illumination beam is unpolarized.

[0114] 10. The alignment illumination system of clause 1, wherein an aperture plate located between the glass plate and the transmissive optics blocks unwanted radiation.

[0115] 11. The alignment illumination system of clause 10, wherein the aperture plate blocks an on-axis illumination beam and allows an off-axis illumination beam to pass through.

[0116] 12. The alignment illumination system of clause 10, wherein the aperture plate blocks off-axis illumination beams while allowing on-axis illumination beams to pass through.

[0117] 13. The alignment illumination system of clause 10, wherein the aperture plate allows an on-axis illumination beam and an off-axis illumination beam to pass through.

[0118] 14. The alignment illumination system of clause 1, wherein the plurality of spot reflectors comprise metal or dielectric or a combination thereof.

[0119] 15. The alignment illumination system of clause 1, wherein the at least one pair of glass sheets comprises exactly two glass sheets.

[0120] 16. The alignment illumination system of clause 15, wherein the two glass plates produce a pair of off-axis illumination beams.

[0121] 17. The aligned illumination system of clause 1, wherein the at least one pair of glass plates comprises four glass plates to produce two pairs of off-axis illumination beams.

[0122] 18. An alignment system for measuring the alignment of an object, wherein the alignment illumination system and the adjustable aperture stop according to clause 1 can be inserted into the alignment system to produce a pair of off-axis illumination beams.

[0123] 19. An alignment system comprising:

[0124] Irradiation source;

[0125] at least one pair of glass sheets, wherein each glass sheet has a plurality of spot mirrors capable of reflecting or partially reflecting and transmitting an illumination beam from the illumination source;

[0126] Aperture diaphragm;

[0127] a transmissive optic having at least one reflector configured to reflect radiation received from the glass sheet;

[0128] an objective lens configured to focus light from the transmission optics toward an object to be illuminated;

[0129] a stage for holding the object to be irradiated; and

[0130] An interferometer is configured to measure the markings on the object.

[0131] 20. A method for alignment using an alignment illumination system, comprising:

[0132] irradiating an irradiation beam from an irradiation source;

[0133] using at least one pair of glass plates to reflect or partially reflect and transmit the illumination beam from the illumination source, wherein each glass plate has a plurality of spot mirrors;

[0134] reflecting radiation received from the glass sheet using transmissive optics having at least one reflector; and

[0135] An objective lens is used to focus the light from the transmission optics towards an object to be illuminated.

[0136] 21. The method of clause 20, wherein the glass sheet reflects and refracts the illumination beam to produce a pair of off-axis illumination beams.

[0137] 22. A method according to clause 21, wherein the off-axis illumination beams in each pair are in phase with each other.

[0138] 23. The method of clause 21, wherein the optical path difference of the off-axis illumination beams in each pair is controllable by tilting one glass sheet of the pair relative to the other glass sheet using a glass sheet drive motor.

[0139] 24. The method of clause 21, wherein the off-axis illumination beams have a small color separation or are co-linear for different wavelengths.

[0140] 25. The method of clause 21, wherein the illumination angles for all colors of the off-axis illumination beam are the same.

[0141] 26. The method of clause 21, wherein the spectral content of the off-axis illumination beam or the on-axis illumination beam can be controlled by adding a thin film coating to the spot mirror.

[0142] 27. The method of clause 21, wherein the off-axis illumination beam is polarized by adding a thin film coating to the spot mirror.

[0143] 28. The method of clause 21, wherein the off-axis illumination beam is unpolarized.

[0144] 29. The method of clause 20, wherein an aperture plate positioned between the glass plate and the transmissive optic blocks unwanted radiation.

[0145] 30. The method of clause 29, wherein the aperture plate blocks an on-axis illumination beam while allowing an off-axis illumination beam to pass through.

[0146] 31. The method of clause 29, wherein the aperture plate blocks off-axis illumination beams while allowing on-axis illumination beams to pass through.

[0147] 32. The method of clause 29, wherein the aperture plate allows both an on-axis illumination beam and an off-axis illumination beam to pass through.

[0148] 33. The method of clause 20, wherein the plurality of spot mirrors comprises a metal or a dielectric or a combination thereof.

[0149] 34. The method of clause 20, wherein the at least one pair of glass sheets comprises exactly two glass sheets.

[0150] 35. The method of clause 34, wherein the two glass plates produce a pair of off-axis illumination beams.

[0151] 36. The method of clause 20, wherein the at least one pair of glass sheets comprises four glass sheets to produce two pairs of off-axis illumination beams.

[0152] 37. A method for measuring the alignment of an object using an alignment system, wherein the alignment illumination system and the adjustable aperture stop according to clause 20 can be inserted into the alignment system to produce a pair of off-axis illumination beams.

[0153] 38. A method for alignment using an alignment illumination system, comprising:

[0154] irradiating an irradiation beam from an irradiation source;

[0155] using at least one pair of glass plates to reflect or partially reflect and transmit the illumination beam from the illumination source, wherein each glass plate has a plurality of spot mirrors;

[0156] filtering radiation received from the glass sheet using an aperture stop;

[0157] reflecting radiation received from the aperture stop using a transmission optic having at least one mirror;

[0158] using an objective lens to focus light from the transmission optics toward an object to be illuminated held by a stage; and

[0159] An interferometer is used to measure the markings on the object.

[0160] This specification discloses one or more embodiments incorporating features of the present invention. The one or more disclosed embodiments merely illustrate the present invention. The scope of the present invention is not limited to the one or more disclosed embodiments. The present invention is defined by the appended claims.

[0161] The one or more embodiments described and references in the specification to "one embodiment," "an embodiment," "an example embodiment," etc. indicate that the one or more embodiments described may include a particular feature, structure, or characteristic, but not every embodiment necessarily includes the particular feature, structure, or characteristic. Moreover, these phrases do not necessarily refer to the same embodiment. In addition, when a particular feature, structure, or characteristic is described in conjunction with an embodiment, it should be understood that it is within the knowledge of a technician in the field to implement such features, structures, or characteristics in conjunction with other embodiments, whether or not explicitly described.

[0162] Although specific reference may be made in this text to the use of lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein may have other applications, such as the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat panel displays, liquid crystal displays (LCDs), thin film magnetic heads, etc. Those skilled in the art will appreciate that in the context of such alternative applications, any use of the terms "wafer" or "die" herein may be considered synonymous with the more general terms "substrate" or "target portion", respectively. Before or after exposure, the substrates referred to herein may be processed in, for example, a track (a tool that typically applies a resist layer to a substrate and develops the exposed resist), a metrology tool, and / or an inspection tool. Where applicable, the disclosure herein may be applied to such and other substrate processing tools. In addition, the substrate may be processed more than once, for example, to produce a multi-layer IC, so that the term substrate used herein may also refer to a substrate that already contains multiple processed layers.

[0163] Although specific reference has been made above to the use of embodiments of the invention in the context of optical lithography, it will be appreciated that the invention may be used in other applications, for example, imprint lithography, and that the invention is not limited to optical lithography where the context permits. In imprint lithography, the topography in the patterning device defines the pattern produced on the substrate. The topography of the patterning device may be pressed into a layer of resist supplied to the substrate, whereupon the resist is cured by applying electromagnetic radiation, heat, pressure, or a combination thereof. The patterning device is removed from the resist, leaving a pattern therein after the resist has been cured.

[0164] It should be understood that the phraseology or terminology herein is for the purpose of description rather than limitation, so that the phraseology or terminology of this specification should be interpreted by those skilled in the relevant art based on the teachings herein.

[0165] In the embodiments described herein, where the context permits, the terms "lens" and "lens element" may refer to any one or combination of various types of optical components, including refractive optical components, reflective optical components, magnetic optical components, electromagnetic optical components, and electrostatic optical components.

[0166] In addition, the terms "radiation" and "beam" as used herein encompass all types of electromagnetic radiation, including ultraviolet (UV) radiation (e.g., having a wavelength λ of 365 nm, 248 nm, 193 nm, 157 nm, or 126 nm), extreme ultraviolet (EUV or soft X-ray) radiation (e.g., having a wavelength in the range of 5 nm to 20 nm, such as, for example, 13.5 nm), or hard X-rays operating at less than 5 nm, and particle beams, such as ion beams or electron beams. Generally, radiation having wavelengths between about 400 nm and about 700 nm is considered visible radiation; radiation having wavelengths between about 780 nm and 3000 nm (or greater) is considered IR radiation. UV refers to radiation having a wavelength of approximately 100 nm to 400 nm. In lithography, the term "UV" also applies to wavelengths that can be produced by mercury discharge lamps: G-line 436 nm, H-line 405 nm, and / or I-line 365 nm. Vacuum UV or VUV (i.e., UV absorbed by gases) refers to radiation having a wavelength of approximately 100 nm to 200 nm. Deep UV (DUV) generally refers to radiation having a wavelength range of 126 nm to 428 nm, and in one embodiment, an excimer laser can generate DUV radiation used within a lithographic apparatus. It should be appreciated that radiation having a wavelength range of, for example, 5 nm to 20 nm refers to radiation having a particular wavelength band, at least a portion of which is within the range of 5 nm to 20 nm.

[0167] The term "substrate" as used herein generally describes a material on which subsequent material layers are added. In various embodiments, the substrate itself can be patterned, and the material added on top of it can also be patterned or left without patterning.

[0168] As used herein, the term "substantially in contact" generally describes elements or structures that are in physical contact with each other, with only a slight separation from each other, which is generally caused by misalignment tolerance. It should be understood that the relative spatial descriptions between one or more specific features, structures, or characteristics (e.g., "vertically aligned", "substantially in contact", etc.) used herein are for illustrative purposes only, and that actual implementations of the structures described herein may include misalignment tolerances without departing from the spirit and scope of the present invention.

[0169] As used herein, the term "optically coupled" generally refers to one coupling element being configured to impart light, directly or indirectly, to another coupling element.

[0170] As used herein, the term "optical material" generally refers to a material that allows light or light energy to propagate therein or therethrough.

[0171] While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. This description is not intended to limit the invention.

[0172] It should be appreciated that the Detailed Description section, rather than the Summary and Abstract sections, is intended to be used to interpret the claims. The Summary and Abstract sections may set forth one or more but not all exemplary embodiments of the present invention as contemplated by one or more of the inventors, and thus are not intended to limit the present invention and the appended claims in any way.

[0173] The present invention is described above by means of functional building blocks that illustrate the implementation of specific functions and their relationships. For ease of description, the boundaries of these functional building blocks are arbitrarily defined herein. Alternative boundaries can be defined as long as the specified functions and their relationships are properly performed.

[0174] The above description of the specific embodiments will fully reveal the general nature of the invention so that others can, by applying the knowledge in the art, modify and / or adapt these specific embodiments for various applications at any time without departing from the general concept of the invention without undue experimentation. Therefore, based on the teachings and guidance given herein, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments.

[0175] The breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

Claims

1. An alignment and illumination system, comprising: Irradiation source; at least one pair of glass sheets, wherein each glass sheet has a plurality of spot mirrors capable of reflecting or partially reflecting and transmitting an illumination beam from the illumination source; a transmissive optic having at least one reflector configured to reflect radiation received from the glass sheet; as well as An objective lens is configured to focus light from the transmission optics toward an object to be illuminated.

2. The alignment illumination system of claim 1, wherein the glass plate reflects and refracts the illumination beam to produce a pair of off-axis illumination beams.

3. The alignment illumination system of claim 2, wherein the off-axis illumination beams in each pair are in phase with each other.

4. The alignment illumination system of claim 2, wherein the optical path difference of the off-axis illumination beams in each pair can be controlled by tilting one glass sheet of the pair relative to the other glass sheet using a glass sheet drive motor.

5. The alignment illumination system of claim 2, wherein the off-axis illumination beams have small color separation or are co-linear for different wavelengths.

6. The alignment illumination system of claim 2, wherein the illumination angles for all colors of the off-axis illumination beam are the same.

7. The alignment illumination system of claim 2, wherein the spectral content of the off-axis illumination beam or the on-axis illumination beam can be controlled by adding a thin film coating to the spot mirror.

8. The alignment illumination system of claim 2, wherein the off-axis illumination beam is polarized by adding a thin film coating to the spot mirror.

9. The alignment illumination system of claim 2, wherein the off-axis illumination beam is unpolarized.

10. The alignment illumination system of claim 1, wherein an aperture plate positioned between the glass plate and the transmissive optics blocks unwanted radiation.

11. The alignment illumination system of claim 10, wherein the aperture plate blocks an on-axis illumination beam and allows an off-axis illumination beam to pass through.

12. The alignment illumination system of claim 10, wherein the aperture plate blocks off-axis illumination beams while allowing on-axis illumination beams to pass through.

13. The alignment illumination system of claim 10, wherein the aperture plate allows an on-axis illumination beam and an off-axis illumination beam to pass through.

14. The alignment illumination system of claim 1, wherein the plurality of spot reflectors comprise metal or dielectric or a combination thereof.

15. The alignment illumination system of claim 1, wherein the at least one pair of glass sheets comprises exactly two glass sheets.

Images