Tunable optical system

Abstract

Systems and methods for providing variable spot size and variable focus at a substrate are described. A variable focus lens group may be added to the alignment system to allow for adjustment of spot size and focus. The variable focal length lens is a liquid lens that is tunable based on a voltage applied across the lens. The switching voltage changes the water-oil interface in the liquid lens, which in turn changes the direction in which the light passes. For example, switching on a voltage across the lens shifts the light output direction to converge at the focus. As a result, the variable focal length lens provides adjustments to compensate for fixed spot size and focus disadvantages of the prior art. In addition, a variable focal length lens may also be applied to compensate for spot shift and higher order diffraction order.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. application No. 63 / 412,822, filed on October 3, 2022, and the entire contents of that U.S. application are incorporated herein by reference. Technical Field

[0003] The invention relates to a tunable optical system. 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 integrated circuits (ICs). In this case, a pattern forming device, alternatively referred to as a mask or reticle, can be used to generate circuit patterns corresponding to the layers of the IC, and the pattern can be imaged onto a target portion (e.g., including one or several dies, or a portion of a die) on a substrate (e.g., a silicon wafer) having a layer of radiation-sensitive material (resist). In general, a single substrate will contain a network of adjacent target portions that are exposed in succession. 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 parallel to or antiparallel to a given direction (the "scanning" direction) while scanning the pattern through a beam. The pattern can also be transferred from the pattern forming device to the 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 caused to interfere at the target portion of the substrate by using a reflection system. This interference results in the formation of a line on the target portion of the substrate.

[0005] During a lithographic operation, different processing steps may require that different layers be formed sequentially on a substrate. Therefore, the substrate may need to be positioned with high accuracy relative to a previous pattern formed thereon. Typically, alignment marks, which may include, for example, diffraction gratings, are placed on the substrate to be aligned and positioned relative to a second object. For example, a lithographic apparatus may use an alignment system to detect the position of the alignment marks and use the alignment marks to align the substrate to ensure accuracy in subsequent lithographic operations.

[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 location of an alignment mark (or multiple alignment 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 different diffraction orders of radiation 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 to measure multiple alignment parameters, phase and intensity detection. Current sensors measure metrology marks continuously. Therefore, the number of measured marks on a given substrate is limited by production volume considerations.

[0007] Alignment systems typically use a dual self-referencing interferometer (SRI) system to acquire the intensity as a function of the mark position. The phase of these sinusoidal signals is used to determine the alignment position of the mark. Each SRI has its dedicated polarization state, which is prepared using a feed optic that separates the input light into x and y polarizations. These alignment systems are fixed optical systems.

[0008] However, there are several limitations in current alignment systems. The beam spot size of the target mark at the irradiated wafer is fixed. As a result, the size of the alignment mark is limited. For example, alignment failures may occur for relatively thick resist and / or warped wafers. Another common problem is the undetectable ΔR effect, which is the re-weighting of the diffraction beam numerical aperture due to product wafer stacking. In addition, electromechanical elements need to be used within typical optical modules for higher order suppression. Mechatronics uses mechanical elements that cause the generation of vibration and heat and require a lot of power, all of which are undesirable within an alignment system. Summary of the invention

[0009] A novel system and method are disclosed that facilitates variable spot size and variable focus at a substrate for alignment (and / or overlap) determination. A variable focus lens set is provided in the alignment system to allow adjustment of the spot size and focus. The variable focus lens is a liquid lens that is tunable based on a voltage applied across the lens. Switching the voltage changes the curvature of the water-oil interface in the liquid lens, which in turn changes the direction in which light passes. For example, switching on the voltage across the lens shifts the direction of light output to converge at a focal point. Thus, the variable focus lens provides adjustment to compensate for the fixed spot size and focusing shortcomings of the prior art. In addition, the variable focus lens can also be applied to compensate for spot shift and ΔR effects. Moreover, the variable focus lens can be used instead of an electromechanical element to reject higher diffraction orders.

[0010] According to an embodiment, a wafer alignment measurement system includes: an illumination source; a radiation beam output from the illumination source; a first group of variable focus lenses, the first group of variable focus lenses being configured to receive the radiation beam, wherein the first group of variable focus lenses is controllable to control the illumination spot size at the wafer; a second group of variable focus lenses; and a third group of variable focus lenses located in a pupil plane downstream of an objective lens system, wherein the third group of variable focus lenses is controllable to control at least one of spot shift and higher diffraction orders.

[0011] In an embodiment, a first set of variable focus lenses is located in the illumination system.

[0012] In an embodiment, a first variable focus lens is offset from the optical axis of the illumination source output.

[0013] In an embodiment, there are "N" output channels and "N+1" second variable focus lenses, wherein there is one second variable focus lens in each output channel and one second variable focus lens in the objective system.

[0014] In an embodiment, the third group of variable focus lenses is located in the pupil plane.

[0015] In an embodiment, the first, second and third groups of variable focus lenses can be controlled by applying voltages to the first, second and third groups of variable focus lenses.

[0016] According to an embodiment, a wafer alignment measurement system includes an illumination source, a radiation beam output from the illumination source, and at least two variable focus lenses configured to receive the radiation beam, wherein the variable focus lenses are controllable to control an illumination spot size at a wafer.

[0017] In an embodiment, a variable focus lens is located in the illumination system.

[0018] In an embodiment, the variable focus lens is located between the illumination relay lens and the aperture stop in the illumination system.

[0019] In an embodiment, the variable focus lens can be controlled by applying a voltage to the variable focus lens.

[0020] In embodiments, a variable focus lens is offset from the optical axis of the illumination source output.

[0021] According to an embodiment, a wafer alignment measurement system includes an illumination source and at least two variable focus lenses, one variable focus lens located in an output channel and another variable focus lens located in an objective system, wherein the variable focus lenses are controllable to control the height of focus of an output from the objective system.

[0022] In an embodiment, the illumination source output is a radiation beam that is reflected off the wafer.

[0023] In an embodiment, the radiation beam passes through a variable focus lens after reflection from the wafer.

[0024] In an embodiment, there are "N" output channels and "N+1" variable focus lenses, wherein there is one variable focus lens in each output channel and one variable focus lens in the objective system.

[0025] In an embodiment, the variable focus lens can be controlled by applying a voltage to the variable focus lens.

[0026] According to an embodiment, a wafer alignment measurement system includes: an illumination source; a radiation beam output from the illumination source and traveling toward an objective system; and at least two variable focus lenses, wherein the at least two variable focus lenses are located in a pupil plane downstream of the objective system, wherein the variable focus lenses are controllable to control at least one of a spot shift and higher diffraction orders.

[0027] In an embodiment, the variable focus lens is located in the pupil plane.

[0028] In an embodiment, the variable focus lens is located in the pupil plane between the objective system and the output lens.

[0029] In an embodiment, a variable focus lens compensates for spot shift.

[0030] In an embodiment, a variable focus lens compensates for higher diffraction orders.

[0031] In an embodiment, the variable focus lens can be controlled by applying a voltage to the variable focus lens.

[0032] Other features and advantages of the present invention and the structure and operation of various embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Note that the present invention is not limited to the specific embodiments described herein. Such embodiments are presented herein for illustrative purposes only. Additional embodiments will be apparent to those skilled in the relevant art(s) based on the teachings included herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] 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(s) to make and use the invention.

[0034] Figure 1A is a schematic diagram of a reflective lithography apparatus according to an embodiment of the present disclosure.

[0035] Figure 1B is a schematic diagram of a transmissive lithography apparatus according to an embodiment of the present disclosure.

[0036] Figure 1C is a more detailed schematic diagram of a reflective lithography apparatus according to an embodiment of the present disclosure.

[0037] Figure 2A is a schematic diagram of a lithography unit according to an embodiment of the present disclosure.

[0038] Figure 2B is a schematic diagram of an inspection system according to an embodiment of the present disclosure.

[0039] Figure 2C is a schematic diagram of a measurement technique according to an embodiment of the present disclosure.

[0040] Figure 2D is a schematic diagram of the relationship between a radiation illumination spot and a measurement target of an inspection system according to an embodiment of the present disclosure.

[0041] Figure 3 is a schematic diagram of a prior art alignment system according to an embodiment of the present disclosure.

[0042] Figure 4A is a schematic diagram of a variable focal length lens when no voltage is applied according to an embodiment of the present disclosure.

[0043] Figure 4B is a schematic diagram of a variable focal length lens when a non-zero voltage is applied according to an embodiment of the present disclosure.

[0044] Figure 4C is a schematic diagram of an illumination system for an alignment system for a variable spot size according to an embodiment of the present disclosure.

[0045] Figure 4D is a schematic diagram of an alignment system for variable spot size according to an embodiment of the present disclosure.

[0046] Figure 4E is a schematic diagram of radiation beam spot size of a variable focal length lens with a nominal voltage for a variable spot size according to an embodiment of the present disclosure.

[0047] Figure 4Fis a schematic diagram of radiation beam spot size of a variable focus lens with an applied voltage for variable spot size according to an embodiment of the present disclosure.

[0048] Figure 5A is a schematic diagram of an illumination system of an alignment system for beam steering according to an embodiment of the present disclosure.

[0049] Figure 5B is a schematic diagram of an alignment system for beam steering according to an embodiment of the present disclosure.

[0050] Figure 5C is a schematic diagram of the effect of offset of a variable focal length lens for beam steering according to an embodiment of the present disclosure.

[0051] Figure 5D is another schematic diagram of the effect of offset of a variable focal length lens for beam steering according to an embodiment of the present disclosure.

[0052] Figure 5E The formation of an embodiment according to the present disclosure is shown Figure 5B part of the system Figure 5A , Figure 5C and Figure 5D A combined view of the components shown in .

[0053] Fig. 6A is a schematic diagram of an alignment system for variable focusing according to an embodiment of the present disclosure.

[0054] Figure 6B is a schematic diagram of a thick resist substrate and variable focus according to an embodiment of the present disclosure.

[0055] Figure 6C is a schematic diagram of measuring overlap in a variable focus embodiment according to an embodiment of the present disclosure.

[0056] Fig.6D is another schematic diagram of measuring overlap in a variable focus embodiment according to an embodiment of the present disclosure.

[0057] Fig. 7A is a schematic diagram of an alignment system for spot shift and higher order suppression according to an embodiment of the present disclosure.

[0058] Figure 7B is a schematic diagram of calibrating beam size in a spot shifting embodiment according to an embodiment of the present disclosure.

[0059] Figure 7C is another schematic diagram of calibrating beam size in a spot shifting embodiment according to an embodiment of the present disclosure.

[0060] Fig.7Dis another schematic diagram of calibrating beam size in a spot shifting embodiment according to an embodiment of the present disclosure.

[0061] Fig. 7E is a schematic diagram of shifting higher diffraction orders in a higher order suppression embodiment according to an embodiment of the present disclosure.

[0062] Figure 8 A wafer alignment measurement method according to an embodiment is shown.

[0063] Fig. 9 is a block diagram of an exemplary computer system according to an embodiment. DETAILED DESCRIPTION

[0064] For semiconductor manufacturing and / or for other applications, a self-reference interferometer (SRI) can be used in an alignment system to obtain the intensity of reflected radiation according to the position of an alignment mark on a substrate (e.g., a wafer). The phase of these signals is used to determine the alignment position of the mark. However, there are limitations to the SRI method. The beam spot size of the alignment mark on the irradiated substrate is fixed, so that, for example, thick resist and / or warped substrates (e.g., wafers) may inadvertently cause alignment failures. Moreover, with the SRI method, although electromechanical elements are often used in an optical module (OM) for higher-order suppression, these electromechanical elements may cause vibrations that cause inaccurate measurements and / or other problems. In some embodiments, the optical module is composed of a plurality of passive optical components and active optical components, which are used to direct illumination such as light to the wafer under investigation. The optical module also collects diffracted light from the mark on the wafer and directs the light to a multiplexer and an optical detector. For example, the optical module can illuminate a target on the wafer by directing light from a light source to the target, and collect a return signal. The return signal can be sent to a detection electronic device to calculate the target position on the wafer.

[0065] The present system and method provide solutions to these and other problems that allow for variable spot sizes and smaller alignment marks, among other advantages. The present system and method also improves the performance of thick stack measurements and allows for non-mechanical scanning within the OM. As described below, to provide a variable spot size, a set of liquid lenses are utilized in place of the typical input fiber assembly fixed lenses to provide a focus-free function. A voltage applied to two variable focus lenses provides an increased focal length. In another embodiment, two variable focus lenses are used to maintain the numerical aperture to account for thick stacks and maintain the spot size at different focal points.

[0066] As a brief introduction, the following description relates to semiconductor device manufacturing and patterning processes. The following paragraphs also describe several components of systems and / or methods for semiconductor device measurement. For example, these systems and methods can be used to measure alignment, overlay, etc. during semiconductor device manufacturing, or for other operations.

[0067] Exemplary Reflective and Transmissive Lithography Systems

[0068] Figure 1A and Figure 1B is a schematic diagram of a lithographic apparatus 100 and a lithographic apparatus 100', in which or for which embodiments of the present disclosure may be implemented. The lithographic apparatus 100 and the lithographic apparatus 100' respectively 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 100 and 100' 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 100, the patterning device MA and the projection system PS are reflective. In the lithographic apparatus 100', the patterning device MA and the projection system PS are transmissive.

[0069] 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.

[0070] The support structure MT holds the patterning device MA in a manner that depends on the orientation of the patterning device MA relative to the reference frame, the design of at least one of the lithographic apparatuses 100 and 100', and other conditions, such as whether the patterning device MA is held 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 table, which 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.

[0071] The term “patterning device” MA should be broadly interpreted as referring to any device that can be used to impart a pattern to the radiation beam B in its cross-section, such as for producing a pattern in a target portion C of the substrate W. The pattern imparted to the radiation beam B may correspond to a specific functional layer in a device being created in the target portion C to form an integrated circuit.

[0072] The pattern forming device MA may be a transmissive type (e.g. Figure 1B lithographic apparatus 100) or a reflective type (such as in Figure 1A 100). 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. Examples of programmable mirror arrays employ a matrix arrangement of small mirrors, each of which can be individually tilted to reflect an incident radiation beam in different directions. The tilted mirrors impart a pattern in the radiation beam B, which is reflected by the matrix of small mirrors.

[0073] The term "projection system" PS may cover any type of projection system, including refractive, reflective, catadioptric, magnetic, electromagnetic and electrostatic optical systems or any combination thereof, as appropriate for the exposure radiation 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, as other gases may absorb too much radiation or electrons. Therefore, a vacuum environment may be provided to the entire beam path by means of vacuum walls and a vacuum pump.

[0074] The lithographic apparatus 100 and / or lithographic apparatus 100' may be of a type having two (dual stage) or more substrate tables WT (and / or two or more mask tables). In such a "multi-stage" machine, additional substrate tables WT may be used in parallel, or exposure may be performed using one or more other substrate tables WT while preparatory steps are performed on one or more tables. In some cases, the additional tables may not be substrate tables WT.

[0075] refer to Figure 1A and Figure 1B , 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 100, 100' may be separate physical entities. In this case, the source SO is not considered to form part of the lithographic apparatus 100 or 100', and the radiation beam B is delivered to the lithographic apparatus 100 or 100' by means of a beam delivery system BD (in Figure 1BThe beam is delivered from the source SO to the illuminator IL, the beam delivery system BD comprising, for example, suitable guide mirrors and / or a beam expander. 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 100, 100'. If desired, the source SO and the illuminator IL together with the beam delivery system BD may be referred to as a radiation system.

[0076] The illuminator IL may comprise an adjuster AD (at Figure 1B In general, at least the outer and / or 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. Furthermore, the illuminator IL may include various other components ( Figure 1B ), such as an integrator IN and a condenser CO. The illuminator IL can be used to condition the radiation beam B to have a desired uniformity and intensity distribution in its cross-section.

[0077] refer to Figure 1A , 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 100, the radiation beam B is reflected from the patterning device (e.g., a mask) MA. After reflection 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 device, a linear encoder, or a capacitive sensor), the substrate table WT can be accurately moved (e.g., so as 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.

[0078] refer to Figure 1B , the radiation beam B is incident on a patterning device (e.g., mask MA), which is held on a support structure (e.g., mask table MT), and is patterned by the patterning device. After passing through 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 the illumination system pupil IPU. A portion of the radiation emanates from the intensity distribution at the illumination system pupil IPU and passes through the mask pattern without being affected by diffraction at the mask pattern, and produces an image of the intensity distribution at the illumination system pupil IPU.

[0079] 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. in order to position a different target portion C in the path of the radiation beam B). Similarly, the first positioner PM and another position sensor (in Figure 1B ) 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).

[0080] Typically, 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 shown) occupy dedicated target portions, the substrate alignment marks may be located in the space between target portions (referred to as scribe lane alignment marks). Similarly, where more than one die is provided on the mask MA, the mask alignment marks may be located between the dies.

[0081] The mask table MT and the patterning device MA may be in a vacuum chamber, wherein an in-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, an out-of-vacuum robot may be used for various transport operations, similar to the in-vacuum robot IVR. Both the in-vacuum robot and the out-of-vacuum robot need to be calibrated to smoothly transfer any payload (e.g., a mask) to the fixed kinematic mount of the transfer station.

[0082] The lithographic apparatus 100 and 100' may be used in at least one of the following modes:

[0083] 1. In step mode, the support structure (e.g. mask table) MT and the substrate table WT remain substantially stationary while the entire pattern imparted to the radiation beam B is projected once onto a target portion C (i.e. a single static exposure). The substrate table WT is then moved in the X and / or Y direction so that a different target portion C can be exposed.

[0084] 2. In scan mode, the support structure (e.g. mask table) MT and substrate table WT are scanned synchronously while a pattern imparted to the radiation beam B is projected onto a target portion C (i.e. a single dynamic exposure). The speed and direction of the substrate table WT relative to the support structure (e.g. mask table) MT may be determined by the (or less) magnification and image flip characteristics of the projection system PS.

[0085] 3. In another mode, the support structure (e.g., mask table) MT is kept substantially stationary to hold the programmable patterning device, and the substrate table WT is moved or scanned as a pattern imparted to the radiation beam B is projected onto a target portion C. A pulsed radiation source SO may be employed, and the programmable patterning device is updated as required after each movement of the substrate table WT or between successive radiation pulses during a scan. This mode of operation can be readily applied to maskless lithography utilizing a programmable patterning device, such as a programmable mirror array.

[0086] Combinations and / or variations of the described modes of use or entirely different modes of use may also be employed.

[0087] In some embodiments, the lithographic apparatus 100 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.

[0088] Figure 1C The lithographic apparatus 100 is shown in more detail, including a source collector device SO, an illumination system IL and a projection system PS. The source collector device SO is constructed and arranged so that a vacuum environment can be maintained in an enclosure 120 of the source collector device SO. The EUV radiation emitting plasma 110 can be formed by a plasma source generated by a discharge. EUV radiation can be generated by a gas or vapor, such as Xe gas, Li vapor or Sn vapor, wherein a thermal plasma 110 is generated to emit radiation in the EUV range of the electromagnetic spectrum. For example, the thermal plasma 110 is generated by a discharge causing a plasma that is at least partially ionized. A partial pressure of Xe, Li, Sn vapor, or any other suitable gas or vapor, such as 10 Pa, may be required to effectively generate radiation. In an embodiment, an excited tin (Sn) plasma is provided to generate EUV radiation.

[0089] The radiation emitted by the hot plasma 110 is transferred from the source chamber 111 to the collector chamber 112 via an optional gas barrier or contaminant trap 113 (also referred to as a contaminant barrier or foil trap in some cases), which is located in or behind an opening in the source chamber 111. The contaminant trap 113 may include a channel structure. The contaminant trap 113 may also include a gas barrier or a combination of a gas barrier and a channel structure. The contaminant trap 113 further indicated herein includes at least a channel structure, as known in the art.

[0090] The collector chamber 112 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 151 and a downstream radiation collector side 152. Radiation passing through the collector CO may be reflected from the grating spectral filter 140 to be focused in a virtual source point IF. The virtual source point IF is often referred to as an intermediate focus, and the source collector device is arranged so that the intermediate focus IF is located at or near an opening 119 in the enclosure structure 120. The virtual source point IF is an image of the radiation emitting plasma 110. The grating spectral filter 140 is particularly useful for suppressing infrared (IR) radiation.

[0091] The radiation then passes through an illumination system IL which may include a faceted field mirror arrangement 122 and a faceted pupil mirror arrangement 124 arranged to provide a desired angular distribution of the radiation beam 121 at the patterning device MA and a desired uniformity of radiation intensity at the patterning device MA. When the radiation beam 121 is reflected at the patterning device MA held by the support structure MT, a patterned beam 126 is formed and the patterned beam 126 is imaged by the projection system PS via reflective elements 128, 130 onto a substrate W held by a wafer stage or substrate table WT.

[0092] 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 140 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 1C The reflective elements shown are as many as 1 to 6 additional reflective elements.

[0093] like Figure 1C As shown, the collector optics CO is depicted as a nested collector with grazing incidence reflectors 153, 154 and 155, just as an example of a collector (or collector mirror). The grazing incidence reflectors 153, 154 and 155 are arranged axially symmetrically around the optical axis O, and this type of collector optics CO is preferably used in combination with a discharge produced plasma source (commonly referred to as a DPP source).

[0094] Exemplary Lithography Cell

[0095] Figure 2A A lithography unit 200 is shown, sometimes also referred to as a lithography cell or cluster. The lithography apparatus 100 or 100' may form part of the lithography unit 200. The lithography unit 200 may also include equipment for performing pre-exposure and post-exposure processes on a substrate. Conventionally, these equipment include a spin coater SC for depositing a resist layer, a developer DE for developing the exposed resist, a chill 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 equipment, and then transfers them to a feed station LB of the lithography apparatus. These devices, often collectively referred to as track or coating and developing systems, are under the control of a track or coating and developing system control unit TCU, which itself is controlled by a monitoring system SCS, which also controls the lithography apparatus via a lithography control unit LACU. Therefore, different equipment can be operated to maximize production volume and processing efficiency.

[0096] The manufacturing facility in which the lithography cell 200 is located also typically includes a metrology system that measures the substrate W that has been processed in the lithography cell or other objects in the lithography cell. Figure 1A , Figure 1B , Figure 1C ). The metrology system may be, for example, part of a lithographic cell, or it may be part of a lithographic apparatus. One or more measurement parameters may include, for example, alignment between successive layers formed in or on a patterned substrate, overlay, critical dimensions (CD) of features formed in or on a patterned substrate (e.g., critical line width), focus or focus error of an optical lithography step, dose or dose error of an optical lithography step, optical aberration of an optical lithography step, etc. The measurements are often performed on one or more dedicated metrology targets provided on the substrate. The measurements may be performed after resist development but before etching, after etching, after deposition, and / or at other times.

[0097] There are various techniques for measuring structures formed during the patterning process, including the use of scanning electron microscopes, image-based measurement tools, and / or various specialized tools. A fast and non-invasive form of a specialized metrology tool is a metrology tool in which a radiation beam is directed onto a target on the surface of a substrate and the properties of the scattered (diffraction / reflection) beam are measured. By evaluating one or more characteristics of the radiation scattered by the substrate, one or more characteristics of the substrate can be determined. Traditionally, this can be referred to as diffraction-based metrology. Applications of such diffraction-based metrology include measurement of alignment, overlay, and the like. For example, alignment and / or overlay can be measured by comparing multiple portions of the diffraction spectrum (e.g., comparing different diffraction orders in the diffraction spectrum of a periodic grating).

[0098] Thus, in a device manufacturing process (e.g., a patterning process or a lithography process), a substrate or other object may be subjected to various types of measurements during or after the process. The measurements may determine whether a particular substrate is defective, may establish adjustments to the process and equipment used in the process (e.g., aligning two layers on a substrate or aligning a patterning device to a substrate), may measure the performance of the process and equipment, or may be used for other purposes. Examples of measurements include optical imaging (e.g., optical microscopy), non-imaging optical measurements (e.g., diffraction-based measurements, such as ASML YieldStar metrology tools, ASML SMASH metrology systems), mechanical measurements (e.g., profilometry using a stylus, atomic force microscopy (AFM)), and / or non-optical imaging (e.g., scanning electron microscopy (SEM)).

[0099] The measurement results may be provided directly or indirectly to the monitoring system SCS. If an error is detected, adjustments may be made to the exposure of subsequent substrates (especially if the check can be performed quickly and rapidly enough so that one or more other substrates of the batch are still to be exposed) and / or to the subsequent exposure of the exposed substrate. Furthermore, already exposed substrates may be stripped and reprocessed to increase yield, or discarded to avoid further processing on substrates that are known to be defective. In the event that only some target portions of the substrate are faulty, further exposures may be performed only on those target portions that meet the specifications. Other manufacturing process adjustments are contemplated.

[0100] The metrology system may be used to determine one or more characteristics of a substrate structure, and in particular, how one or more characteristics vary between different substrate structures, or between different layers of the same substrate structure. The metrology system may be integrated into the lithographic apparatus 100 or 100' or the lithographic apparatus 200, or may be a stand-alone device.

[0101] Alignment System Embodiments

[0102] One or more targets may be 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 1-D periodic structures (e.g., geometric features such as gratings) that 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) that 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 optionally be etched into the substrate (e.g., etched into one or more layers on the substrate).

[0103] Figure 2B An exemplary alignment system 10 is depicted that can be used to detect alignment and overlay and / or perform other metrology operations. It 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, which measures the spectrum (intensity as a function of wavelength) of the specularly reflected and / or diffracted radiation, such as, for example, at Figure 2C The sensor may generate an alignment signal conveying alignment data indicative of the characteristics of the reflected radiation. From this data, the structure or profile that produced the detected spectrum may be reconstructed by one or more processors PRO (a general example of such a structure or profile is shown in Figure 2C ), or reconstructed by other operations.

[0104] As in Figure 1A and Figure 1B In the lithographic apparatus 100 and 100' of the present invention, one or more substrate tables may be provided to hold a substrate W during a measurement operation. The one or more substrate tables may be similar in form to Figure 1A and Figure 1BThe substrate table WT of the inspection system 10 is similar or identical to that of the substrate table WT. In examples where the inspection system 10 is integrated with a lithographic apparatus, they may even be the same substrate table. Coarse and fine positioners 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 acquire the position of a target portion of interest of a structure (e.g. a metrology mark) and to bring the target portion to an appropriate position under the objective lens. Typically, many measurements will be made of the target portion of the structure at different positions across the substrate W. The substrate support may be moved in the X and Y directions to acquire different targets, and in the Z direction to acquire the desired position of the target portion relative to the focus of the optical system. When, for example, in practice the optical system may remain substantially stationary (typically in the X and Y directions, but possibly also in the Z direction) and the substrate moves, it is convenient to think of and describe the operation as if the objective lens is 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 of the substrate and the optical system is moving, or if both are moving, or a combination of a part of the optical system is moving (e.g. in Z and / or tilt direction) while the rest of the optical system is stationary and the substrate is moving (e.g. in X and Y directions, but optionally in Z and / or tilt direction).

[0105] 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 (which may be covered by a deposited layer, for example) 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.

[0106] The bars, pillars, vias, and / or other features may be etched into or onto the substrate (e.g., etched into one or more layers on the substrate), deposited on the substrate, covered by a deposited layer, and / or have other characteristics. The target (portion) 30 (e.g., bars, pillars, vias, etc.) is sensitive to process variations in the patterning process (e.g., optical aberrations in a lithographic projection apparatus such as in the projection system, focus variations, dose variations, etc.), such that process variations manifest themselves in variations in the target 30. Thus, measurement data from the target 30 may be used to determine adjustments to one or more manufacturing processes, and / or used as a basis for making actual adjustments.

[0107] For example, the measurement data from the target 30 may indicate an overlap of layers of the semiconductor device. The measurement data from the 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 overlap, and to determine adjustments to the semiconductor device manufacturing apparatus based on the one or more determined semiconductor device manufacturing process parameters. In some embodiments, for example, this may include a stage position adjustment, 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.

[0108] Figure 2D A plan view of a typical target (e.g., a measurement mark) 30 and the extent of a typical radiation illumination spot S are shown. Typically, in order to obtain a diffraction spectrum without interference from surrounding structures, in an embodiment, the target 30 is a periodic structure (e.g., a grating) that is larger than the width (e.g., diameter) of the illumination spot S. 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 limited to on-axis or off-axis directions, for example by including an aperture in the illumination path.

[0109] Prior art alignment systems

[0110] Figure 3 A schematic diagram of an alignment system 300 of the prior art according to an embodiment is shown, which alignment system 300 can be implemented as a part of or otherwise combined with a lithographic apparatus 100 or 100' and / or other lithographic apparatus. In an example of this embodiment, the alignment system 300 can be configured to align a substrate (e.g., a semiconductor wafer, the above-mentioned substrate W, etc.) relative to a pattern forming device (e.g., the above-mentioned pattern forming device MA). The alignment system 300 can be further 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.

[0111] According to an embodiment, the alignment system 300 may include an illumination source 305, an input optical fiber 307, an illumination system 310, a spot reflector 320, an objective lens 330, a self-referencing interferometer (SRI) 340, polarization beam splitters 341a and 341b, and an output system 350. The optical module 399 of the system 300 may include any optical components in or along the radiation path for guiding or controlling the radiation in the system 300. The illumination source 305 may be configured to provide an electromagnetic narrowband radiation beam 306 having a first polarization state (e.g., a linear polarization state). In an example, the narrowband radiation beam 306 may be within a spectrum of wavelengths between about 500nm and about 900nm. In another example, the narrowband radiation beam 306 includes discrete narrow bands within a spectrum of wavelengths between about 500nm and about 900nm. In yet another example, the radiation beam 306 may be monochromatic, for example, provided by a monochromatic light source (such as a laser light source in the illumination source 305). A polychromatic light source (eg, an LED) may also be used in the illumination source 305 to provide the polychromatic radiation beam 306 .

[0112] The illumination system 310 may be configured to receive the radiation beam 306. In the example of this embodiment, the illumination system 310 may be further configured to direct the radiation beam 306 onto the substrate W. The illumination system 310 may include an illumination relay lens 312, a fixed lens input fiber assembly (IFA) 311, and an aperture stop 313. The illumination system 310 may also include an optical device that generates an additional illumination beam that is separated or replicated from the radiation beam 306 and directs the additional illumination beam toward an alignment mark (not shown) on the substrate W.

[0113] The substrate W may be mounted on a table WT movable in one direction (see Figure 1A , Figure 1B and Figure 1C ). The radiation beam 306 may be configured to illuminate an alignment mark located on the substrate W. In an example of this embodiment, the alignment mark may be coated with a radiation sensitive film. In another example, the alignment mark may have a symmetry of 180°. That is, when the alignment mark is rotated 180° around an axis of symmetry perpendicular to the plane of the alignment mark, the rotated alignment mark may be substantially the same as the unrotated alignment mark.

[0114] like Figure 3As shown in FIG. 3 , according to an embodiment, the objective lens 330 may be configured to direct the diffracted radiation beam 335 toward the self-referencing interferometer 340. The objective lens 330 may include any suitable number of optical elements suitable for directing the diffracted radiation beam 335. The objective lens 330 may also include a field stop 331. In an exemplary embodiment, the diffracted radiation beam 335 may be at least a portion of the radiation beam 306 diffracted from the alignment mark. The spot mirror 320 may be substantially transparent to the diffracted radiation beam 335 and may allow the diffracted radiation beam 335 to pass through the spot mirror 320 without substantially changing the characteristics of the diffracted radiation beam 335. It should also be noted that even though the objective lens 330 is shown as directing the radiation beam 335 toward the self-referencing interferometer 340, the present disclosure is not limited thereto. Other optical arrangements may be used to obtain similar results of detecting diffraction signals from alignment marks.

[0115] In some embodiments, the self-referencing interferometer 340 may include any suitable set of optical elements, such as a combination of a prism, a half-wave plate, and a compensator, that may be configured to form two images of the alignment mark based on the received diffracted radiation beam 335. It should be understood that although high quality images need not be formed, the features of the alignment mark should be resolved, and the self-referencing interferometer 340 may be further configured to rotate one of the two images by 180° relative to the other of the two images, and interferometrically reconstruct the rotated image and the unrotated image.

[0116] After passing through the self-referencing interferometer 340, the diffracted radiation beam 335 is incident on polarizing beam splitters 341a and 341b. Polarizing beam splitters 341a and 341b redirect the diffracted radiation beam 335 to an output system 350. A first output channel 351a includes an output lens 352a and an output field stop 353a for passing the diffracted radiation beam 335 to a detector (not shown) for measuring the sum of the y-components of the beam. A second output channel 351b includes an output lens 352b and an output field stop 353b and a second detector (not shown) for measuring the difference of the y-components of the beam. A third output channel 351c includes an output lens 352c and an output field stop 353c and a third detector (not shown) for measuring the sum of the x-components of the beam. A fourth output channel 351d includes an output lens 352d and an output field stop 353d and a fourth detector (not shown) for measuring the difference of the x-components of the beam.

[0117] The above detector can be configured to receive the recombined image and detect interference caused by the recombined image when the alignment axis of the alignment system 300 passes through the symmetry center of the alignment mark (not shown). According to an exemplary embodiment, this interference may be due to the alignment mark being 180° symmetrical and the recombined image interfering constructively or destructively. Based on the detected interference, the detector can be further configured to determine the position of the symmetry center of the alignment mark and thus detect the position of the substrate W. According to an example, the alignment axis can be aligned with a light beam that is perpendicular to the substrate 420 and passes through the center of the self-referencing interferometer 340.

[0118] Variable focal length lens

[0119] FIG. 4A to FIG. 4B 4 shows a schematic diagram of a variable focal length lens 420. The lens 420 is shown as "off" ( Figure 4A ) configuration and "on" ( Figure 4B ) is configured as described below. The variable focus lens 420 is a liquid lens including water 404 and oil 405 and forming a water-oil interface 406, wherein an interface film 427 forms a seal between the water 404 and the oil 405. Figure 4A and Figure 4B Other components of lens 420 are also shown, including an optical window 421 configured to transmit light beam 403 (and / or other radiation), a metal structural component 423, and a lens 420 that is configured to transmit light beam 403 (and / or other radiation). Figure 4B ) provides an electrostatic pressure of 425.

[0120] The focal length of lens 420 may be fine-tuned and modified by applying a specified voltage 408 to lens 420 . Figure 4A The water-oil interface 406 is shown when no voltage is applied (“off”). Because the lens 420 is connected to the ground 407, Figure 4A The applied voltage is not shown in FIG. In one example, in the absence of a voltage, the water 404 and the oil 405 naturally form a slightly concave curvature at the interface 406, so that the incident light beam 403 parallel to the optical axis OA diverges slightly when leaving the variable focus lens 420. As another example, Figure 4B The water-oil interface 406 is shown when a non-zero voltage 408 is applied ("on"). The applied voltage 408 in the liquid lens 420 generates an electrostatic pressure 425 at or near the edge 429, resulting in a buildup of positive charge (see Figure 4B As a result, the negative charge within water 404 (see Figure 4B The “-” symbol marked in FIG. 4 is attracted to the positive charge. Therefore, the water 404 moves to the edge 429 of the lens 420, which displaces the oil 405 into the center 431 of the lens 420. Figure 4BIt is shown that the curvature of the interface 406 has now become convex, converging the incident light beam 403 to a focus 433 on the optical axis OA.

[0121] The variable focal length lens 420 can replace (as described below) the input fiber assembly of a typical prior art alignment system (e.g., the system 300 described above). Compared to typical prior art alignment systems, the variable focal length lens 420 described herein provides a fast response (e.g., on the order of milliseconds), has a compact design, low heat dissipation at the lens, low power consumption of approximately 1 mW (+ / - 20%), and allows tunability of the functionality of the optical module 399, among other advantages.

[0122] Variable spot size alignment system

[0123] Figure 4C Variable focal length lenses 401 and 402 are shown incorporated into an illumination system 410 (eg, each lens is similar and / or identical to focal length lens 420 described above). Illumination system 410 may be as follows: Figure 4D A portion of a variable spot size alignment system 400 is shown. Figure 4D As shown, Figure 3 The irradiation system 310 comprises Figure 4C In one embodiment, the variable spot size alignment system 400 (eg Figure 4D ) using Figure 3 The remainder of the components of the alignment system 300. Figure 4C In the illumination system 410, the variable focal length lenses 401 and 402 of the illumination system are replaced Figure 3 The alignment system 400 may be configured to include a fixed lens IFA 311 of the illumination system 310. By removing the IFA 311 and inserting lenses 401 and 402, the alignment system 400 may achieve a variable spot size at the substrate W.

[0124] According to an embodiment, the illumination system 410 (eg Figure 4C and Figure 4D The illumination system 410 is configured to receive the radiation beam 306 from the input optical fiber 307, for example, along an optical axis AX (the optical axis AX can be similar and / or the same as the optical axis OA described above). The illumination system 410 includes a fixed lens, such as an illumination relay lens 312, which receives the radiation beam 306 before the radiation is passed to the first variable focus lens 401 and then to the second variable focus lens 402 before reaching the aperture stop 313.

[0125] The set of variable focal length lenses is usually used in pairs (in this case, a pair of variable focal length lenses 401 and 402) to manipulate the focal length. However, a set of variable focal length lenses is not limited to two lenses.

[0126] In one embodiment, a nominal amount of voltage is applied to the variable focal length lenses 401 and 402 to achieve a curvature of the film(s) 435, 437 (similar and / or identical to the film 427 described above). When an increasing voltage is applied, in one embodiment, an increased focal length is achieved and the spot size of the radiation on the substrate changes. The configuration may be such that a negative voltage is applied to achieve a decreased focal length (and a different spot size of the radiation on the substrate). If desired, the polarity of the voltage to achieve a different curvature to increase or decrease the focal length may be flipped.

[0127] Figure 4D Shown by Figure 4C The illumination system 410 shown replaces the Figure 3 4. By replacing the input fiber assembly (IFA) 311 with an illumination system 410 including variable focal length lenses 401 and 402, a variable spot size on the substrate W can be achieved. The spot size on the substrate W can be enlarged or reduced by applying different voltages to the lenses 401, 402. Depending on the size of the alignment mark, the spot size can be enlarged or reduced. By using the above voltages to change the spot size of the radiation on the substrate to match the size of the alignment (or other measurement) mark, alignment marks of various sizes can be more easily measured.

[0128] exist Figure 4E and Figure 4F The change in size of the light spot 491 is shown in FIG. Figure 4E A schematic diagram showing the size of the spot 491 of the radiation beam 306 when a nominal voltage is applied to the variable focal length lenses 401 and 402. Upon exiting the input fiber 307, the radiation beam 306 expands in size 481 until the radiation beam 306 reaches the illumination relay lens 312. The illumination relay lens 312 changes the incident beam into a parallel radiation beam 483. With the nominal voltage applied to each of the variable focal length lenses 401 and 402, the water-oil interface 406 (see Figure 4A and Figure 4B ) There is no curvature in the lens 401. As a result, the parallel radiation beam 306 remains the same when leaving each lens 401 and 402. The parallel radiation beam 306 then travels through the aperture stop 313 and the spot 491 has a diameter D1.

[0129] Figure 4F Schematic diagram showing the size of the spot 491 of the radiation beam 306 when a voltage is applied to the variable focus lenses 401 and 402. Figure 4E, upon exiting the input fiber 307, the radiation beam 306 expands in size 481 until the radiation beam 306 reaches the illumination relay lens 312. The illumination relay lens 312 changes the incident beam into a parallel radiation beam 483. By applying a voltage to each of the variable focus lenses 401 and 402, at the water-oil interface 406 (see Figure 4A and Figure 4B ). As a result, the increased focal length of lenses 401 and 402 increases 489 the size of the parallel radiation beam 306 as it leaves the second lens 402. Finally, the magnified radiation beam 306 travels through the aperture stop 313 and the spot 491 has an enlarged diameter D2.

[0130] Currently, existing alignment systems (e.g. Figure 3 The system 300 shown in FIG. 3 can achieve an illumination spot size as small as about 30 μm to measure an alignment mark of 30 μm × 80 μm. However, by using an alignment system with a variable spot size Figure 4C The illumination system 410 can achieve a variable spot size that can be fine-tuned to a range of 10 μm to 40 μm or less to measure alignment marks as small as 10 μm×10 μm or less.

[0131] Beam Steering Alignment System

[0132] Figure 5A A schematic diagram of an illumination system 510 of a beam steering alignment system is shown. The illumination system 510 includes a relay lens 312 (e.g., Figure 4C 312 is similar and / or the same as the relay lens 312 shown in FIG. 1 ), a first variable focal length lens 501 and a second variable focal length lens 502 (similar to the relay lens 312 shown in FIG. 1 ). Figure 4C lenses 401 and 402 are similar and / or identical) and aperture stop 313 (similar to Figure 4C 313 as shown). Figure 5A As shown, the illumination system 510 can be configured to receive the radiation beam 306 from the optical fiber 307. The illumination system 510 includes an illumination relay lens 312 that receives the radiation beam 306, a first variable focal length lens 501, a second variable focal length lens 502, and an aperture stop 313. The second variable focal length lens 502 is offset 503 from the first variable focal length lens 501 and the optical axis AX.

[0133] Figure 5B A beam steering alignment system 500 is shown including an illumination system 510. Figure 5B middle, Figure 3 The illumination system 310 shown consists of Figure 5A In one embodiment, the beam steering alignment system 500 (eg, Figure 5BAs shown) using Figure 3 The remaining components of the alignment system 300.

[0134] FIG. 5C to FIG. 5D A schematic diagram showing the effect of the variable focus lens 502 being offset from the optical axis AX. Figure 5C It is shown that when the variable focal length lens 502 does not deviate from the optical axis AX, the illumination spot 333 on the substrate W coincides with the optical axis AX. Figure 5D 3. It is shown that when the variable focus lens 502 is offset from the optical axis AX, the illumination spot 333 on the substrate W also becomes offset from the optical axis AX. The offset from the optical axis AX of the variable focus lens 502 directs the radiation beam 306 to reflect off the spot reflector 320 at a different angle, which in turn results in the illumination spot 333 being offset from the optical axis AX, as shown in FIG. Figure 5D For example, a beam steering angle of 1.8 mrad tilt results in a scan length of ±24 μm.

[0135] By offsetting the variable focus lens 502 from the optical axis AX, the beam can be offset laterally at the substrate W. In beam steering, the substrate W is stationary and the lens 502 is moved, which in turn changes the beam 306. The beam can be steered in the x and / or y direction. Beam steering can be used to compensate for lateral scan offsets due to the substrate table WT (substrate table WT shown and described above). Because beam steering is easier to perform than accelerating and decelerating the substrate table WT, beam steering can be used to measure alignment. Therefore, beam steering can be used to perform alignment diagnostics. In addition, beam steering allows non-mechanical scanning within the optical module 399 (see Figure 5B ).

[0136] For the sake of clarity, Figure 5E Show Figure 5A , Figure 5C and Figure 5D A combined view 591 of the elements shown in FIG. 59, which form Figure 5B is part of a larger alignment system 500. For example, Figure 5E Tunable lenses 501 and 502 are shown, wherein lens 502 is offset from optical axis AX and lens 501. When lens 502 is not offset from optical axis AX, illumination spot 333 on substrate W coincides with optical axis AX. When variable focal length lens 502 is offset from optical axis AX, illumination spot 333 on substrate W also becomes offset from optical axis AX. The offset of variable focal length lens 502 relative to optical axis AX causes radiation beam 306 to reflect off spot reflector 320 at different angles, which in turn results in illumination spot 333 offset from optical axis AX.

[0137] For non-mechanical beam scanning of optical modules for alignment marks, Figure 5EThe design shown in ensures that the beam steering will still fall within the spot mirror 320. The current spot size and spot mirror size ensure that the 0th order blocking is maintained. Even if the beam 306 deviates from the optical axis AX when incident on the substrate W, the 0th order of the diffracted radiation beam 335 is still blocked by the spot mirror 320. As a result, because the 0th order beam has been blocked, dark field measurement is still possible. In addition, regular and angled raster scanning can be achieved without using mechanical elements. In addition, there is a combined bidirectional angled scanning. In turn, the lateral scanning offset is compensated.

[0138] In other embodiments, for more marks, beam steering may be used in combination with a high bandwidth detector and a constant high speed substrate stage WT to account for the Doppler shift of different marks. Furthermore, an additional coherent illumination spot may be generated at the substrate W and beam steering provided above the original beam spot. The alignment position may be achieved as a function of the beam steering angle. Alternatively, the direct beam may be placed directly onto the detector.

[0139] Variable focus (or variable focus) alignment system

[0140] Fig. 6A Schematic diagram of a variable focus alignment system 600 is shown. The variable focus alignment system 600 is similar to the 3D image alignment system 600 except that the input fiber assembly (IFA) 311 is removed and a first variable focus lens 601 is added to the objective lens 330 and second variable focus lenses 602a to 602d are added to the output channels 351a to 351d, respectively. Figure 3 The alignment system 300 is the same as in FIG.

[0141] According to an embodiment, the first variable focus lens 601 is located in the objective lens 330. Second variable focus lenses 602a, 602b, 602c and 602d are located in the output channels 351a, 351b, 351c and 351d, respectively. As a result, each output channel radiation beam will travel through a pair of variable focus lenses, which is the first variable focus lens 601 and one of the second variable focus lenses 602a to 602d of the output channel. These variable focus lenses are located in the collection path of the sensor. Therefore, when there are "N" output channels, there are "N+1" variable focus lenses in the alignment system. Fig. 6A In the example of , there are 4 (N) output channels and 5 (N+1) variable focus lenses. There is a first variable focus lens 601 in the objective lens 330, and there are four second variable focus lenses 602a to 602d in the output channels 351a to 351d, for a total of five variable focus lenses.

[0142] By having a first variable focus lens 601 in the objective 330 and second variable focus lenses 602a to 602d in the output channels 351a to 351d, respectively, the focus of the radiation beam at the substrate W can be changed. Changing the focus allows measurements to be made at alignment marks positioned at different z levels. Thus, the alignment system 600 has the ability to align on warped substrates or thick resist layers and perform overlay. Furthermore, the variable focus for through-stack measurements allows thick stack measurements within the alignment sensor and diffraction-based overlay.

[0143] For example, Figure 6B The zoom alignment system 600 is shown. Fig. 6A ) is a schematic diagram of a thick resist substrate W in FIG. The substrate W includes an alignment mark 610 located below a resist layer 611. Despite the thickness of the multiple layers of resist 611, the alignment mark 610 layer below remains in focus. By focusing the variable focal length lenses 601 and 602a to 602d (such as Fig. 6A By applying a voltage (as shown), the focus of the radiation beam 306 can be changed so that the radiation beam 306 is focused at the level of the alignment mark 610. In some embodiments, the zoom alignment system 600 can be used to align a thick 3D NAND stack with thick resist and warped wafers.

[0144] FIG. 6C to FIG. 6D Schematic diagram of measuring the overlap (eg, offset "d") of alignment marks 610a and 610b in a variable focus alignment system. Figure 6C In , the top alignment mark 610a (grating) can be measured by focusing the radiation beam 306 at the surface of the alignment mark 610a. Fig.6D In the embodiment of the present invention, the bottom alignment mark 610b (grating) can be measured by focusing the radiation beam 306 at the surface of the alignment mark 610b. As a result, the offset "d" between the alignment mark gratings can be determined. For example, variable focus can be applied in a Z-Star system with diffraction gratings located at different z levels.

[0145] Variable focus alignment system 600 ( Fig. 6A ) can maintain the same marking pitch range. The numerical aperture pitch is between 0.118 and 0.7. The variable focus allows for typical thick stacks in the order of millimeters. In addition, Figure 4C The use of variable focal length lenses 401 and 402 at the IFA in can be used with variable focus to maintain the spot size at different focal points. Overlap capability in the zoom alignment system 600 is achieved by using multiple z-level alignment signals. In addition, variable focus can be used in the alignment system 600 to provide an adjustable working distance at commercially proven aperture sizes. Variable focus can also be deployed in the YieldStar for overlay measurements.

[0146] Spot shift and high-order suppression alignment system

[0147] Fig. 7A A schematic diagram of an alignment system 700 for spot shifting and higher order suppression is shown. The alignment system 700 is similar to the alignment system 700 except that the input fiber assembly (IFA) 311 is removed and a first variable focus lens 701 and a second variable focus lens 702 are added in the pupil plane. Figure 3 The alignment system 300 is the same as in FIG.

[0148] According to an embodiment, a first variable focal length lens 701 and a second variable focal length lens 702 (each similar and / or identical to lens 420 described above) are located in a pupil plane downstream of the objective lens 330 and upstream of the self-referencing interferometer 340. Positioning the variable focal length lenses 701 and 702 at the pupil plane provides spot shift calibration and higher order suppression. For example, by applying different voltages to the variable focal length lenses 701 and 702, a spot shift of the calibrated diffracted radiation beam 335 may be achieved.

[0149] FIG. 7B to FIG. 7D A schematic diagram of calibrating the light spot shift using variable focal length lenses 701 and 702 is shown. Figure 7B 330. The spot shift of the diffracted radiation beam 335 for the variable focal length lenses 701 and 702 with nominal voltage is shown. The diffracted radiation beam 335 reflects off the alignment mark on the substrate W. As the light rays become parallel, the diffracted radiation beam 335 expands until the diffracted radiation beam 335 reaches the objective lens 330. With the nominal voltage applied to each of the variable focal length lenses 701 and 702, there is no curvature in the water-oil interface 406 (see Figure 4A and Figure 4B ). As a result, the parallel diffracted radiation beam 335 remains the same when leaving each lens 701 and 702. Thereafter, the beam 335 travels to the self-referencing interferometer 340.

[0150] Figure 7C 335 is shown with a medium voltage applied to lenses 701 and 702. The diffracted radiation beam 335 reflects off the alignment mark on the substrate W. As the light rays become parallel, the diffracted radiation beam 335 expands until the diffracted radiation beam 335 reaches the objective lens 330. With the medium voltage applied, a curvature is formed at the interface 406 (see Figure 4A and Figure 4B ). As a result, the diffracted radiation beam 335 has been shifted to a smaller spot size when leaving the second lens 702. Thereafter, the beam 335 is incident on the self-referencing interferometer 340.

[0151] Fig.7D335 using lenses 701 and 702 with high voltage. In addition to the degree of applied voltage, Fig.7D Similar to Figure 7C Due to the use of higher voltages, interface 406 (see Figure 4A and Figure 4B ) has a sharper curvature. As a result, the diffracted radiation beam 335 has shifted to an even smaller spot size when leaving the second lens 702.

[0152] By positioning the afocal lens system (lenses 701 and 702) in the pupil plane (see Fig. 7A ), pupil measurement compensation can be performed. Pupil measurement can be used to resolve product crosstalk. Product crosstalk is the signal that leaks from the surrounding structure of the target mark to the detection system. When the spot size changes (such as in Figure 4C Crosstalk occurs in the alignment system 400 of FIG. 4 and yet the aperture field stop (e.g., aperture stop 313) remains the same as the illumination field stop. If the alignment mark is not underfilled, signal leakage from adjacent structures to the alignment diffraction grating on substrate W will be captured. In other words, increasing the spot size will illuminate not only the alignment mark but also the surrounding structures adjacent to the alignment grating. However, using spot shift calibration in pupil metrology, product crosstalk can be mitigated.

[0153] In addition, the spot shift can be used to compensate for the ΔR effect. The ΔR effect is a re-weighting of the diffracted beam NA due to product wafer stacking. Since there is no clear pupil measurement that can help measure the shift of the spot in the pupil, the ΔR effect will be undetectable. The ΔR effect may occur when the diffracted radiation beam 335 from the substrate W is shifted due to stacking on the alignment mark. The ΔR effect can be compensated by calibrating the changes in the wavefront sample due to stacking changes. The calibration can be performed by generating a return signal as a function of the spot shift. The curve can be compared to a calibration curve measured for the same target mark pitch on the benchmark. The tunable system facilitates spot shift. Therefore, pupil measurement allows stacking measurements and facilitates smaller marks (for example, as described above with respect to FIG. 7B to FIG. 7D described).

[0154] Second, variable focus lenses 701 and 702 are inserted into the pupil plane (see Fig. 7A The positions of 701 and 702 in the figure produce higher order suppression. Fig. 7E A voltage is shown applied to the variable focus lenses 701 and 702 in the pupil plane to suppress higher diffraction orders.The diffracted radiation beam 335 reflects off the surface of the substrate W and splits into diffracted beam spots. Fig. 7E1 and 3 order diffraction beam spots are shown. Objective lens 330 receives the beam spot and transmits the beam spot to variable focal length lenses 701 and 702. A voltage is applied to lenses 701 and 702 at interface 406 (see Figure 4A and Figure 4B ) which pushes the beam spot radially outward away from the optical axis (not shown). Upon exiting the second lens 702, the 3rd order diffraction beam radially outward, so that the 3rd order diffraction beam diameter is outside the clear aperture of the lens 336. As a result, the +3 and -3 diffraction order beam spots are filtered out and do not pass through the lens 336. On the other hand, the +1 and -1 diffraction order beams, although pushed outward, remain within the aperture of the lens 336 and thus pass through.

[0155] The tunable beam shift as a function of the mark pitch allows higher orders to be suppressed within the optical module (e.g., the Nth higher order (N>1) can be suppressed). Fig. 7E In the case of , it is desirable to remove the 3rd order diffraction beam; otherwise, the 3rd order diffraction beam will contaminate the signal. Therefore, the higher diffraction orders of the mark pitch can be filtered out. The higher diffraction order contributions from the mark cannot be separated using a single pixel detector (e.g., I+total=I+1+I+2+I+3...). In existing systems, only the total dc signal, I+total and I-total, can be measured. The algorithm for correcting alignment position errors requires knowledge of a pair of diffraction orders (such as +1 and -1, +2 and -2, etc.). Removing the higher order signals and calculating the alignment position based only on the detected orders results in higher accuracy and less noise in the o / p position.

[0156] Alignment System 700 ( Fig. 7A ) is a non-electromechanical alternative to suppressing unwanted orders. Instead of using electromechanical elements to remove higher diffraction orders, variable focus lenses 701 and 702 can be applied. As a result, alignment system 700 can be improved by using variable focus lenses 701 and 702 instead of electromechanical elements.

[0157] Multiple Alignment System Embodiments That Can Be Used Together

[0158] FIG. 4A to FIG. 7E One or more of the components and / or systems shown may be in Figure 3 In other words, for example, the alignment system 300 can be adjusted to include Figure 4A and Figure 5A The illumination systems 410 and 510 are respectively in the objective lens 330 Fig. 6A The first variable focal length lens 601 and the output channels 351a to 351d Fig. 6A The second variable focal length lenses 602a to 602d, and the Fig. 7AVariable focal length lenses 701 and 702. This results in three sets of variable focal length lenses positioned in alignment system 300. In this embodiment, the variable focal length lenses in alignment system 300 can be positioned on optical axis AX, such as Figure 4C 401 and 402 in, or may be positioned offset from the optical axis AX, such as Figure 5A 502 of them.

[0159] Furthermore, the two embodiments may be used together. For example, Figure 4C The irradiation system 410 and Fig. 6A The variable focal length lenses 601 and 602a to 602d can be used together Figure 3 Alignment system 300. Alternatively, Figure 5A The irradiation system 510 and Fig. 7A The variable focal length lenses 701 and 702 can be used together. It goes without saying that any combination of the embodiments can be used together in the alignment system 300. The above-mentioned benefits and advantages exist in this embodiment.

[0160] Figure 8 An alignment method 800 is shown. In some embodiments, for example, the method 800 is performed as part of an alignment sensing operation in a semiconductor device manufacturing process. In some embodiments, one or more operations of the method 800 can be performed in or by a system described herein (including a computer system (e.g., such as a computer system)). Fig. 9 In some embodiments, the method 800 includes: generating (802) a radiation beam output with an illumination source; receiving (804) the radiation beam with a first set of variable focus lenses; controlling (806) the first set of variable focus lenses to change the illumination spot size at the wafer; positioning (808) a second set of variable focus lenses, one of which is located in the output channel and another of which is located in the objective system; controlling (810) the second set of variable focus lenses to change the height of the focus of the output from the objective system; positioning (812) a third set of variable focus lenses in a pupil plane downstream of the objective system; controlling (814) the third set of variable focus lenses to change at least one of the spot shift and higher diffraction orders and / or other operations.

[0161] The operation of method 800 is intended to be illustrative. In some embodiments, method 800 may be completed with one or more additional operations not described and / or without one or more operations discussed. For example, in some embodiments, method 800 may include additional operations, which include determining adjustments to the semiconductor device manufacturing process. In some embodiments, method 800 includes determining one or more semiconductor device manufacturing process parameters. One or more semiconductor device manufacturing process parameters may be determined based on alignment values ​​and / or other information indicated by measurement signals and / or other similar systems. One or more parameters may include parameters of radiation (radiation for measurement), overlap values, alignment values, measurement inspection positions on layers of semiconductor device structures, radiation beam tracks across targets, and / or other parameters. In some embodiments, process parameters may be broadly interpreted as including platform positions, mask designs, measurement target designs, semiconductor device designs, radiation intensity (for exposure resists, etc.), radiation incident angles (for exposure resists, etc.), radiation wavelengths (for exposure resists, etc.), pupil sizes and / or shapes, resist materials, and / or other parameters.

[0162] In some embodiments, method 800 includes determining a process adjustment based on one or more determined semiconductor device manufacturing process parameters, adjusting semiconductor device manufacturing equipment and / or other operations based on the determined adjustment. For example, if the determined alignment measurement is not within process tolerance, the out-of-tolerance measurement may be caused by one or more manufacturing processes, and the process parameters of the one or more manufacturing processes have drifted and / or otherwise changed so that the process no longer produces acceptable devices (e.g., the measurement may violate a threshold of acceptability). One or more new or adjusted process parameters may be determined based on the measurement determination. The new or adjusted process parameters may be configured to cause the manufacturing process to produce acceptable devices again.

[0163] For example, a new or adjusted process parameter may cause a previously unacceptable measurement to be adjusted back into an acceptable range. The new or adjusted process parameter may be compared to the existing parameters for a given process. For example, if there is a difference, then the difference may be used to determine an adjustment to the equipment used to produce the device (e.g., parameter "x" should be increased / decreased / changed so that parameter "x" matches a new or adjusted version of parameter "x" determined as part of method 800). In some embodiments, method 800 may include electronically adjusting the equipment (e.g., based on the determined process parameter). Electronically adjusting the equipment may include, for example, sending an electronic signal and / or other communication to the equipment, which results in a change in the device. Electronic adjustments may include, for example, changing settings on the equipment and / or other adjustments.

[0164] Additionally, the operation of method 800 is Figure 8 The order shown and described herein is not intended to be limiting.

[0165] In some embodiments, one or more portions of method 800 may be implemented in and / or controlled by one or more processing devices (e.g., a digital processor, an analog processor, a digital circuit designed to process information, an analog circuit designed to process information, a state machine, and / or other mechanisms for electronically processing information). The one or more processing devices may include one or more devices that perform some or all of the operations of method 800 in response to instructions stored electronically on an electronic storage medium. The one or more processing devices may include one or more devices configured by hardware, firmware, and / or software to be specifically designed to perform one or more operations of method 800 (e.g., see below with respect to Fig. 9 for discussion).

[0166] Fig. 9 1 is a diagram of an exemplary computer system CS that can be used for one or more operations described herein. The computer system CS includes a bus BS or other communication mechanism for transmitting information, and a processor PRO (or processors) coupled to the bus BS for processing information. Figure 3 The computer system CS further comprises a main memory MM, such as a random access memory (RAM) or other dynamic storage device, coupled to the bus BS, for storing information and instructions to be executed by the processor PRO. The main memory MM can also be used to store temporary variables or other intermediate information during the execution of instructions by the processor PRO. The computer system CS further comprises a read-only memory (ROM) ROM or other static storage device coupled to the bus BS for storing static information and instructions for the processor PRO. A storage device SD, such as a magnetic disk or optical disk, is provided and coupled to the bus BS for storing information and instructions.

[0167] The computer system CS can be connected to a display DS via a bus BS, such as a flat or touch panel display or a cathode ray tube (CRT) for displaying information to a computer user. An input device ID including alphanumeric and other keys is connected to the bus BS for transmitting information and command selections to the processor PRO. Another type of user input device is a cursor control CC, such as a mouse, trackball, or cursor direction keys, for transmitting direction information and command selections to the processor PRO and for controlling cursor movement on the display DS. The input device typically has two degrees of freedom in two axes, such as a first axis (e.g., x) and a second axis (e.g., y), which allows the input device to specify a position in a plane. A touch panel (screen) display can also be used as an input device.

[0168] In some embodiments, all or some of the one or more operations described herein may be performed by the computer system CS in response to the processor PRO executing one or more sequences of one or more instructions included in the main memory MM. Such instructions may be read from another computer-readable medium (such as a storage device SD) into the main memory MM. The execution of the instruction sequence included in the main memory MM causes the processor PRO to perform the process steps (operations) described herein. One or more processors in a multi-processing arrangement may also be used to execute the instruction sequence included in the main memory MM. In some embodiments, a hard-wired circuit may be used in place of a software instruction or in combination with a software instruction. Therefore, the description herein is not limited to any particular combination of hardware circuits and software.

[0169] The term "computer-readable medium" or "machine-readable medium" used herein refers to any medium that participates in providing instructions to the processor PRO for execution. Such a medium can take a variety of forms, including but not limited to non-volatile media, volatile media, and transmission media. Non-volatile media include, for example, optical or magnetic disks, such as storage devices SD. Volatile media include dynamic memory, such as main memory MM. Transmission media include coaxial cables, copper wires, and optical fibers, including wires (the wires include bus BS). Transmission media can also take the form of sound waves or light waves, such as those generated during radio frequency (RF) and infrared (IR) data communications. Computer-readable media can be non-temporary, such as floppy disks, flexible disks, hard disks, magnetic tapes, any other magnetic media, CD-ROMs, DVDs, any other optical media, punch cards, paper tapes, any other physical media with hole patterns, RAMs, PROMs and EPROMs, FLASH-EPROMs, any other memory chips or boxes. Non-temporary computer-readable media can have instructions recorded thereon. Instructions can implement any operation described herein when executed by a computer. Transitory computer readable media may include, for example, carrier waves or other propagated electromagnetic signals.

[0170] Various forms of computer-readable media may involve carrying one or more sequences of one or more instructions to the processor PRO for execution. For example, the instruction may initially be carried on a disk of a remote computer. The remote computer may load the instruction into its dynamic memory and send the instruction via a telephone line using a modem. The modem local to the computer system CS may receive data on the telephone line and convert the data into an infrared signal using an infrared transmitter. An infrared detector connected to the bus BS may receive the data carried in the infrared signal and place the data on the bus BS. The bus BS transfers the data to the main memory MM, from which the processor PRO retrieves and executes the instruction. The instruction received by the main memory MM may optionally be stored on a storage device SD before or after being executed by the processor PRO.

[0171] The computer system CS may also include a communication interface CI connected to the bus BS. The communication interface CI provides a bidirectional data communication connected to a network link NDL connected to a local network LAN. For example, the communication interface CI may be an integrated services digital network (ISDN) card or a modem to provide a data communication connection to a telephone line of a corresponding type. As another example, the communication interface CI may be a local area network (LAN) card to provide a data communication connection to a compatible LAN. A wireless link may also be implemented. In any such implementation, the communication interface CI sends and receives electrical signals, electromagnetic signals or optical signals carrying digital data streams representing various types of information.

[0172] The network link NDL usually provides data communication to other data devices through one or more networks. For example, the network link NDL can provide a connection to the host computer HC through a local network LAN. This can include data communication services provided by the global packet data communication network (now generally referred to as the "Internet" INT). The local network LAN (Internet) can use electrical signals, electromagnetic signals or optical signals that carry digital data streams. The signals through the various networks and the signals on the network data link NDL and the signals through the communication interface CI (the signals carry digital data to and from the computer system CS) are exemplary forms of carrier waves that transmit information.

[0173] The computer system CS can send messages and receive data including program code through (multiple) networks, network data links NDL and communication interfaces CI. In the Internet example, the host computer HC can transmit the requested code of the application program through the Internet INT, the network data link NDL, the local network LAN and the communication interface CI. For example, an application program downloaded in this way can provide all or part of the method described herein. The received code can be executed by the processor PRO when it is received, and / or stored in the storage device SD or other non-volatile storage device for later execution. In this way, the computer system CS can obtain the application code in the form of a carrier wave.

[0174] This specification discloses one or more embodiments incorporating features of the present invention. The disclosed embodiment(s) merely illustrate the present invention. The scope of the present invention is not limited to the disclosed embodiment(s). The present invention is defined by the appended claims.

[0175] Although the described embodiment(s) and references in the specification to "one embodiment," "an embodiment," "an exemplary embodiment," etc. indicate that the described embodiment(s) may include a particular feature, structure, or characteristic, every embodiment may not necessarily include the particular feature, structure, or characteristic. Furthermore, such phrases do not necessarily refer to the same embodiment. Furthermore, 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 those skilled in the art to implement such feature, structure, or characteristic in conjunction with other embodiments, whether or not explicitly described.

[0176] Although specific reference may be made herein 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 term "wafer" or "die" herein may be considered synonymous with the more general term "substrate" or "target portion", respectively. The substrate referred to herein may be processed before or after exposure in, for example, a track or coating development equipment (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, a substrate may be processed more than once, for example to create a multi-layer IC, so that the term "substrate" used herein may also refer to a substrate that already includes multiple processed layers.

[0177] Although specific reference may have 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, such as 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 provided to the substrate, whereby the resist is cured by application of electromagnetic radiation, heat, pressure, or a combination thereof. After the resist is cured, the patterning device is removed from the resist, leaving the pattern in the resist.

[0178] It should be understood that the phraseology or terminology herein is for the purpose of description rather than limitation, so that those skilled in the relevant art(s) will interpret the phraseology or terminology of the specification based on the teachings herein.

[0179] In the embodiments described herein, the terms "lens" and "lens element" as the context allows may refer to any one or combination of various types of optical components, including refractive, reflective, magnetic, electromagnetic, and electrostatic optical components.

[0180] Furthermore, 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 13.5 nm), or hard X-rays operating at wavelengths less than 5 nm, and particle beams, such as ion beams or electron beams. Generally, radiation having wavelengths between about 400 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 wavelengths of about 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 about 100 nm to 200 nm. Deep UV (DUV) generally refers to radiation having a wavelength in the range of 126 nm to 428 nm, and in one embodiment, an excimer laser can produce DUV radiation used within a lithographic apparatus. It should be understood that radiation having a wavelength in the range of, for example, 5 nm to 20 nm refers to radiation having a wavelength band, at least a portion of which is in the range of 5 nm to 20 nm.

[0181] The term "substrate" as used herein generally describes a material upon which subsequent layers of material are added. In embodiments, the substrate itself may be patterned, and the material added on top of the substrate may also be patterned, or may remain unchanged and not patterned.

[0182] As used herein, the term "substantially in contact" generally describes elements or structures that are only slightly separated from each other and in physical contact with 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 actual embodiments of the structures described herein may include misalignment tolerances without departing from the spirit and scope of the present invention.

[0183] As used herein, the term "optically coupled" generally refers to one coupled element being configured to impart light directly or indirectly to another coupled element.

[0184] The term "optical material" as used herein generally refers to a material that allows light or optical energy to propagate therein or therethrough.

[0185] 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.

[0186] It should be understood 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 the inventor(s), and thus are not intended to limit the present invention and the appended claims in any way.

[0187] The present invention has been described above with the aid of functional building blocks that illustrate the implementation of specified functions and their relationships. For ease of description, the boundaries of these functional building blocks have been arbitrarily defined herein. Alternative boundaries may be defined as long as the specified functions and their relationships are appropriately performed.

[0188] Various embodiments of the present system and method are disclosed in the list of subsequently numbered aspects. In the following, additional features, characteristics and exemplary technical solutions of the present disclosure will be described according to the aspects that can be optionally claimed in any combination:

[0189] 1. A wafer alignment measurement system, comprising: an illumination source; a radiation beam output from the illumination source; a first group of variable focus lenses configured to receive the radiation beam, wherein the first group of variable focus lenses is controllable to control the illumination spot size at the wafer; a second group of variable focus lenses, wherein one variable focus lens is located in an output channel and another variable focus lens is located in an objective system, wherein the second group of variable focus lenses is controllable to control the height of the focus of the output from the objective system; and a third group of variable focus lenses located in a pupil plane downstream of the objective system, wherein the third group of variable focus lenses is controllable to control at least one of spot shift and higher diffraction orders.

[0190] 2. The wafer alignment measurement system of clause 1, wherein the first set of variable focus lenses is located in an illumination system.

[0191] 3. A wafer alignment measurement system according to any one of the preceding aspects, wherein a first variable focus lens is offset from an optical axis of the radiation beam.

[0192] 4. A chip alignment measurement system according to any one of the preceding aspects, wherein there are "N" output channels and "N+1" second variable focus lenses, wherein there is a second variable focus lens in each output channel and there is a second variable focus lens in the objective lens system.

[0193] 5. The wafer alignment measurement system according to any one of the preceding aspects, wherein the third group of variable focus lenses is located in a pupil plane.

[0194] 6. A wafer alignment measurement system according to any one of the preceding aspects, wherein the first group of variable focus lenses, the second group of variable focus lenses and the third group of variable focus lenses can be controlled by applying voltage to the first group of variable focus lenses, the second group of variable focus lenses and the third group of variable focus lenses.

[0195] 7. A chip alignment measurement system, comprising: an illumination source; a radiation beam output from the illumination source; and at least two variable focus lenses, the at least two variable focus lenses being configured to receive the radiation beam, wherein the variable focus lenses are controllable to control the illumination spot size at the chip.

[0196] 8. The wafer alignment measurement system according to any one of the preceding aspects, wherein the variable focus lens is located in the illumination system.

[0197] 9. The wafer alignment measurement system according to any one of the preceding aspects, wherein the variable focus lens is located between an illumination relay lens and an aperture stop in the illumination system.

[0198] 10. The wafer alignment measurement system according to any one of the preceding aspects, wherein the variable focus lens is controllable by applying a voltage to the variable focus lens.

[0199] 11. A wafer alignment measurement system according to any one of the preceding aspects, wherein a variable focus lens is offset from an optical axis of the radiation beam.

[0200] 12. A wafer alignment measurement system comprising: an illumination source; and at least two variable focus lenses, wherein one variable focus lens is located in an output channel and another variable focus lens is located in an objective system, wherein the variable focus lens is controllable to control the height of the focus of the output from the objective system.

[0201] 13. A wafer alignment measurement system according to any one of the preceding aspects, wherein the output of the illumination source is a radiation beam that is reflected off the wafer.

[0202] 14. The wafer alignment measurement system of any one of the preceding aspects, wherein the radiation beam passes through the variable focus lens after reflecting off the wafer.

[0203] 15. A chip alignment measurement system according to any one of the preceding aspects, wherein there are "N" output channels and "N+1" variable focus lenses, wherein there is one variable focus lens in each output channel and one variable focus lens in the objective lens system.

[0204] 16. The wafer alignment measurement system according to any one of the preceding aspects, wherein the variable focus lens can be controlled by applying a voltage to the variable focus lens.

[0205] 17. A wafer alignment measurement system comprising: an illumination source; a radiation beam output from the illumination source and traveling to an objective system; and at least two variable focus lenses, the at least two variable focus lenses being located in a pupil plane downstream of the objective system, wherein the variable focus lenses are controllable to control at least one of spot shift and higher diffraction orders.

[0206] 18. The wafer alignment measurement system according to any one of the preceding aspects, wherein the variable focus lens is located in a pupil plane.

[0207] 19. The wafer alignment measurement system according to any of the preceding aspects, wherein the variable focus lens is located in the pupil plane between the objective lens system and a self-referencing interferometer.

[0208] 20. The wafer alignment measurement system according to any one of the preceding aspects, wherein the variable focus lens compensates for spot shift.

[0209] 21. The wafer alignment measurement system according to any of the preceding aspects, wherein the variable focus lens compensates for higher diffraction orders.

[0210] 22. The wafer alignment measurement system according to any one of the preceding aspects, wherein the variable focus lens can be controlled by applying a voltage to the variable focus lens.

[0211] 23. A chip alignment measurement method, the method comprising: generating a radiation beam output using an illumination source; receiving the radiation beam using a first group of variable focus lenses; controlling the first group of variable focus lenses to change the illumination spot size at the chip; positioning a second group of variable focus lenses, one of which is located in an output channel and another of which is located in an objective system; controlling the second group of variable focus lenses to change the height of the focus of the output from the objective system; positioning a third group of variable focus lenses in a pupil plane downstream of the objective system; and controlling the third group of variable focus lenses to change at least one of the spot shift and higher diffraction orders.

[0212] 24. The wafer alignment measurement method according to clause 23, wherein the first set of variable focus lenses is located in an illumination system.

[0213] 25. A wafer alignment measurement method according to any one of the preceding aspects, wherein a first variable focus lens is offset from an optical axis of the radiation beam.

[0214] 26. A chip alignment measurement method according to any one of the preceding aspects, wherein there are "N" output channels and "N+1" second variable focal length lenses, wherein there is a second variable focal length lens in each output channel and there is a second variable focal length lens in the objective lens system.

[0215] 27. The wafer alignment measurement method according to any one of the preceding aspects, wherein the third group of variable focus lenses is located in a pupil plane.

[0216] 28. A wafer alignment measurement method according to any one of the preceding aspects, wherein the first group of variable focus lenses, the second group of variable focus lenses and the third group of variable focus lenses can be controlled by applying voltage to the first group of variable focus lenses, the second group of variable focus lenses and the third group of variable focus lenses.

[0217] 29. A wafer alignment measurement method, comprising: generating a radiation beam output from an illumination source; receiving the radiation beam using at least two variable focus lenses; and controlling the variable focus lenses to change the illumination spot size at the wafer.

[0218] 30. The wafer alignment measurement method according to any one of the preceding aspects, wherein the variable focus lens is located in an illumination system.

[0219] 31. The wafer alignment measurement method according to any one of the preceding aspects, wherein the variable focus lens is located between an illumination relay lens and an aperture stop in the illumination system.

[0220] 32. The wafer alignment measurement method according to any one of the preceding aspects, wherein the variable focus lens can be controlled by applying a voltage to the variable focus lens.

[0221] 33. A wafer alignment measurement method according to any one of the preceding aspects, wherein a variable focus lens is offset from the optical axis of the radiation beam.

[0222] 34. A wafer alignment measurement method, the method comprising: an illumination source; and at least two variable focus lenses, one variable focus lens located in an output channel and another variable focus lens located in an objective system, wherein the variable focus lenses are controllable to control the height of focus of the output from the objective system.

[0223] 35. A wafer alignment measurement method according to any one of the preceding aspects, wherein the output of the illumination source is a radiation beam reflected from a wafer.

[0224] 36. A wafer alignment measurement method according to any one of the preceding aspects, wherein the radiation beam passes through the variable focus lens after reflecting off the wafer.

[0225] 37. A chip alignment measurement method according to any one of the preceding aspects, wherein there are "N" output channels and "N+1" variable focus lenses, wherein there is a variable focus lens in each output channel and there is a variable focus lens in the objective lens system.

[0226] 38. The wafer alignment measurement method according to any one of the preceding aspects, wherein the variable focus lens can be controlled by applying a voltage to the variable focus lens.

[0227] 39. A chip alignment measurement method, the method comprising: generating a radiation beam output from an illumination source that travels to an objective system; positioning at least two variable focus lenses in a pupil plane downstream of the objective system; and controlling the variable focus lenses to change at least one of a spot shift and higher diffraction orders.

[0228] 40. The wafer alignment measurement method according to any one of the preceding aspects, wherein the variable focus lens is positioned in a pupil plane.

[0229] 41. A wafer alignment measurement method according to any one of the preceding aspects, wherein the variable focus lens is positioned in the pupil plane between the objective lens system and a self-referencing interferometer.

[0230] 42. The wafer alignment measurement method according to any one of the preceding aspects, wherein the variable focus lens compensates for spot shift.

[0231] 43. The wafer alignment measurement method according to any one of the preceding aspects, wherein the variable focus lens compensates for higher diffraction orders.

[0232] 44. The wafer alignment measurement method according to any one of the preceding aspects, wherein the variable focus lens can be controlled by applying a voltage to the variable focus lens.

[0233] The above description of specific embodiments will fully disclose the general nature of the invention so that others can easily modify and / or adapt such specific embodiments for various applications by applying the knowledge of those skilled in the art without departing from the general concept of the invention and without undue experimentation. Therefore, based on the teachings and guidance set forth herein, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments.

[0234] 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. A wafer alignment measurement system, comprising: Irradiation source; as well as At least two variable focus lenses, one variable focus lens located in the output channel and another variable focus lens located in the objective system, wherein the variable focus lenses are controllable to control the height of focus of the output from the objective system.

2. The wafer alignment measurement system of claim 1, wherein: The output of the illumination source is a radiation beam that is reflected off the wafer.

3. The wafer alignment measurement system of claim 2, wherein: The radiation beam passes through the variable focus lens after reflecting off the wafer.

4. The wafer alignment measurement system of claim 3, wherein: There are "N" output channels and "N+1" variable focus lenses, wherein there is one variable focus lens in each output channel and one variable focus lens in the objective system.

5. The wafer alignment measurement system of claim 3, wherein: The variable focus lens can be controlled by applying a voltage to the variable focus lens.

6. A wafer alignment measurement system comprising: Irradiation source; a radiation beam output from the illumination source and traveling toward the objective system; as well as At least two variable focus lenses are located in a pupil plane downstream of the objective system, wherein the variable focus lenses are controllable to control at least one of spot shift and higher diffraction orders.

7. The wafer alignment measurement system of claim 6, wherein: The variable focus lens is located in the pupil plane.

8. The wafer alignment measurement system of claim 6, wherein: The variable focus lens is located in the pupil plane between the objective system and a self-referencing interferometer.

9. The wafer alignment measurement system of claim 6, wherein: The variable focus lens compensates for spot shift.

10. The wafer alignment measurement system of claim 6, wherein: The variable focus lens compensates for higher diffraction orders.

11. The wafer alignment measurement system of claim 6, wherein: The variable focus lens can be controlled by applying a voltage to the variable focus lens.

12. A wafer alignment measurement method, the method comprising: Irradiation source; as well as At least two variable focus lenses, one variable focus lens located in the output channel and another variable focus lens located in the objective system, wherein the variable focus lenses are controllable to control the height of focus of the output from the objective system.

13. The wafer alignment measurement method according to claim 12, wherein: The output of the illumination source is a radiation beam that is reflected off the wafer.

14. The wafer alignment measurement method according to claim 13, wherein: The radiation beam passes through the variable focus lens after reflecting off the wafer.

15. The wafer alignment measurement method according to claim 14, wherein: There are "N" output channels and "N+1" variable focus lenses, wherein there is one variable focus lens in each output channel and one variable focus lens in the objective system.

Images