Plasma shielding for electrostatic MEMS devices

Abstract

A micro-electro-mechanical system (MEMS) device configured to actuate a first portion relative to a second portion, the MEMS device comprising: a first electrode and a second electrode configured such that, in use, applying a voltage to the first electrode and the second electrode will apply a force to the first portion relative to the second portion; and a first baffle configured to prevent fluid or radiation from entering or transmitting from an environment external to the MEMS device into a space occupied by the first electrode and the second electrode.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to European application 22181489.0 filed on June 28, 2022, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to a micro-electromechanical system (MEMS) device configured to actuate a first part relative to a second part. Background Art

[0004] A lithographic apparatus is a machine configured to apply a desired pattern onto a substrate. A lithographic apparatus may be used, for example, in the manufacture of integrated circuits (ICs). A lithographic apparatus may, for example, project a pattern at a patterning device (e.g., a mask) onto a layer of radiation-sensitive material (resist) provided on a substrate.

[0005] To project a pattern onto a substrate, a lithographic apparatus may use electromagnetic radiation. The wavelength of the radiation determines the minimum size of a feature that can be formed on the substrate. Compared to a lithographic apparatus that may use radiation with a wavelength of 193 nm, for example, a lithographic apparatus that uses extreme ultraviolet (EUV) radiation with a wavelength in the range of 4-20 nm (e.g., 6.7 nm or 13.5 nm) may be used to form smaller features on a substrate.

[0006] As is known, a lithographic apparatus may be provided with one or more mirrors or mirror elements actuated by a micro-electromechanical system (MEMS), such as a piezoelectric or capacitive MEMS system.

[0007] Low pressure gaseous hydrogen is commonly used in lithographic equipment to provide a cleaning effect by removing contaminants (eg, hydrocarbons) from within the lithographic equipment.

[0008] In the presence of EUV radiation, gaseous hydrogen can form a plasma. The plasma can form near a component of a lithographic apparatus (or can form elsewhere and migrate to the vicinity of the component) and can damage or otherwise prevent the component from functioning properly. For example, the plasma can provide a short circuit between electrodes of a capacitive MEMS device, thereby preventing it from actuating. As another example, the plasma ions can react with atoms in the component (e.g., silicon atoms) to produce volatile compounds that can then migrate away from the component (known as "hydrogen-induced outgassing").

[0009] The object of the present invention is to alleviate the above mentioned problems. Summary of the invention

[0010] In a first example described herein, there is a microelectromechanical system (MEMS) device configured to actuate a first portion relative to a second portion, the MEMS device comprising: a first electrode and a second electrode configured such that, in use, application of a voltage to the first electrode and the second electrode causes a force to be applied to the first portion relative to the second portion; and a first baffle configured to prevent fluid or radiation from entering or being transmitted from an environment external to the MEMS device into a space occupied by the first electrode and the second electrode.

[0011] The fluid may be a plasma (e.g., a hydrogen plasma) and / or a gas (e.g., a gaseous hydrogen). Advantageously, the first baffle may prevent the gaseous hydrogen within the space occupied by the first electrode and the second electrode from being exposed to radiation (e.g., EUV radiation) (thereby preventing the formation of a hydrogen plasma). For example, the radiation may be radiation directed to a component of the MEMS device or attached to a component of the MEMS device. The first baffle may also prevent the hydrogen plasma from migrating to the space occupied by the first electrode and the second electrode. Thus, the first baffle may prevent damage that may otherwise be caused by the hydrogen plasma.

[0012] The apparatus may further include a labyrinth seal including: the first baffle, wherein the first baffle is coupled to the first portion; and a second baffle, wherein the second baffle is coupled to the second portion.

[0013] Advantageously, the labyrinth seal may prevent hydrogen plasma (or any other fluid that may damage the MEMS device) from entering the space occupied by the first electrode and the second electrode, thereby protecting the MEMS device from damage caused by hydrogen plasma. The labyrinth seal may include silicone.

[0014] The first part may comprise the first electrode; the second part may comprise the second electrode; and in use the force applied to the first part relative to the second part may be caused by a Coulomb force due to the voltage.

[0015] The MEMS device may be an electrostatic MEMS device, and advantageously, the electrostatic MEMS device may be protected from damage caused by hydrogen plasma. Alternatively, the electrostatic MEMS device may be referred to as a capacitive MEMS device. Alternatively, the Coulomb force may be referred to as an electrostatic force.

[0016] The piezoelectric member may be disposed between the first electrode and the second electrode, and the force applied to the first portion relative to the second portion may be due to deformation of the piezoelectric member due to the voltage.

[0017] The MEMS device may be a piezoelectric MEMS device, and advantageously, the piezoelectric MEMS device may be protected from damage caused by hydrogen plasma.

[0018] The first baffle may be electrically grounded.

[0019] The second baffle may be electrically grounded.

[0020] The first portion may further include a reflector, such that when the force is applied to the first portion relative to the second portion, the reflector is caused to move.

[0021] Advantageously, the position of the mirror may be adjusted by operation of a MEMS device, providing a deformable mirror that is robust to damage from the hydrogen plasma.

[0022] The first portion and the first baffle may be integrally formed, and the second portion and the second baffle may be integrally formed.

[0023] The first baffle may be substantially opaque to electromagnetic radiation.

[0024] The second baffle may be substantially opaque to electromagnetic radiation.

[0025] The electromagnetic radiation may be EUV radiation or DUV radiation.

[0026] In a second example described herein, there is a micro-mirror array comprising a plurality of the devices of the first example.

[0027] In a third example described herein, there is a programmable illuminator comprising the micro-mirror array according to the second example for conditioning a radiation beam.

[0028] The programmable illuminator may also include a displacement control feedback system configured to determine the position of each mirror in the micro-mirror array and adjust a voltage applied to an associated electrostatic or piezoelectric actuator based on the determined position and based on a predetermined target position of the mirror.

[0029] In a fourth example described herein, there is a lithographic device arranged to project a pattern from a pattern forming device onto a substrate, the lithographic device comprising a programmable illuminator according to the third example, the programmable illuminator being used to adjust a radiation beam for illuminating the pattern forming device and / or for adjusting a radiation beam for measuring a target structure on the substrate.

[0030] In a fifth example described herein, there is an inspection and / or metrology apparatus comprising a programmable illuminator according to the third example for conditioning a radiation beam for measuring a target structure on a substrate.

[0031] For example, a micromirror array in a programmable illuminator can be used to control or adjust the spectrum and / or spatial distribution of a light or radiation beam used by an inspection and / or metrology device to measure a target structure (e.g., a mark) on a substrate in order to determine the position of the target structure for alignment purposes and / or to perform overlay measurements.

[0032] In a sixth example described herein, there is a method of constructing the device of the first example, the method comprising: providing a substrate; forming a first part and a second part; forming a first electrode and a second electrode, the first electrode and the second electrode being configured such that, in use, applying a voltage to the first electrode and the second electrode will cause a force to be applied to the first part relative to the second part; and forming a first baffle, the first baffle being configured to prevent fluid or radiation from entering or transmitting from an environment external to the MEMS device into a space occupied by the first electrode and the second electrode.

[0033] The method may further include forming a second baffle. The method may further include electrically grounding the first baffle and / or the second baffle. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which:

[0035] Figure 1A A lithography system including a lithography apparatus and a radiation source is depicted;

[0036] Figure 1B Describes known inspection and / or measurement equipment;

[0037] Figure 1C Describes the use Figure 1B Programmable illuminators for inspection and / or metrology equipment;

[0038] Figure 2 depicts a cross-sectional view of an example of a piezoelectric micromirror system;

[0039] Figure 3 depicts a cross-sectional view of an example of an electrostatic micromirror system;

[0040] Figure 4 depicts a perspective view of an example of a piezoelectric micromirror system;

[0041] Figure 5depicts a cross-sectional view of an example of an electrostatic micromirror system including a labyrinth seal;

[0042] Figure 6 depicts a cross-sectional view of an example of a piezoelectric micromirror system including a labyrinth seal;

[0043] Figure 7 A method of forming a micro-mirror array from a plurality of wafers is described; and

[0044] Figure 8 An alternative method of forming a micromirror array including a HF vapor etching step is depicted. DETAILED DESCRIPTION

[0045] Figure 1A A lithographic system is shown comprising a radiation source SO and a lithographic apparatus LA. The radiation source SO is configured to generate an EUV radiation beam B and to provide the EUV radiation beam B to the lithographic apparatus LA. The lithographic apparatus LA comprises an illumination system IL, a support structure MT configured to support a patterning device MA (e.g. a mask), a projection system PS, and a substrate table WT configured to support a substrate W.

[0046] The illumination system IL is configured to condition the EUV radiation beam B before it is incident on the patterning device MA. Thereby, the illumination system IL may comprise a faceted field mirror arrangement 10 and a faceted pupil mirror arrangement 11. The faceted field mirror arrangement 10 and the faceted pupil mirror arrangement 11 together provide a desired cross-sectional shape and a desired intensity distribution for the EUV radiation beam B. The illumination system IL may comprise other mirrors or arrangements in addition to or in place of the faceted field mirror arrangement 10 and the faceted pupil mirror arrangement 11.

[0047] After this conditioning, the EUV radiation beam B interacts with the pattern forming device MA. As a result of this interaction, a patterned EUV radiation beam B' is generated. The projection system PS is configured to project the patterned EUV radiation beam B' onto the substrate W. To this end, the projection system PS may include a plurality of mirrors 13, 14, which are configured to project the patterned EUV radiation beam B' onto the substrate W held by the substrate table WT. The projection system PS may apply a reduction factor to the patterned EUV radiation beam B', thereby forming an image having features that are smaller than corresponding features on the pattern forming device MA. For example, a reduction factor of 4 or 8 may be applied. Although in Figure 1A The projection system PS is shown in FIG. 2 with only two mirrors 13 , 14 , but the projection system PS may comprise a different number of mirrors (eg six or eight mirrors).

[0048] The substrate W may include a previously formed pattern. In this case, the lithographic apparatus LA aligns an image formed by the patterned EUV radiation beam B′ with a pattern previously formed on the substrate W.

[0049] A relative vacuum, i.e., a small amount of gas (e.g., hydrogen) at a pressure well below atmospheric pressure, may be provided in the lithographic apparatus (e.g., the radiation source SO in the illumination system IL and / or the projection system PS). Hydrogen may be provided by an inlet and removed from an outlet (not shown). The hydrogen may provide a cleaning effect (i.e., by removing contaminants from optical surfaces), and a flow of hydrogen from the inlet toward the outlet may remove contaminants from within the lithographic apparatus.

[0050] The hydrogen gas may be exposed to an (unpatterned or patterned) EUV radiation beam B, B'. The EUV radiation beam B, B' may provide sufficient energy to ionize atoms in the hydrogen gas, and thus, when exposed to the EUV radiation beam B, B', the hydrogen gas may be irradiated with sufficient energy to generate a hydrogen plasma. For example, by an electric field within the lithography apparatus, ions in the hydrogen plasma (e.g., H + , H 2+ or H 3+ ) can be accelerated (thereby increasing the energy of the ions).

[0051] Ions in the hydrogen plasma may interact with the lithographic apparatus and components therein. For example, the hydrogen plasma may be generated in a region near a component (where the region near the component is exposed to EUV radiation), and / or the hydrogen plasma may be generated in a region remote from the component and subsequently migrate to the vicinity of the component. There may be a variety of interaction mechanisms (between ions in the hydrogen plasma and components of the lithographic apparatus LA), each of which may cause damage to the component.

[0052] In a first example of an interaction mechanism, electrostatic discharge can damage or prevent normal operation of a component. For example, (under normal operating conditions) a voltage may be applied across two electrodes of a microelectromechanical system (MEMS) device to provide a force for actuating a first portion of the MEMS device relative to a second portion of the MEMS device. The presence of hydrogen plasma in the region near or between the two electrodes may cause current to flow between the two electrodes, thereby preventing the application of sufficient voltage to actuate the MEMS device.

[0053] In a second example of an interaction mechanism, where plasma ions interact with a component (through elastic collisions or other means), the momentum and kinetic energy of one or more atoms in the component may increase. The increase in atomic kinetic energy may cause the atoms to break free of their chemical bonds and "sputter."

[0054] In a third example of an interaction mechanism, ions (i.e., free radicals) in the hydrogen plasma may chemically react with the component to form volatile compounds. As an example, the solder joint may include tin or zinc, and the tin or zinc may chemically react with the hydrogen plasma to form tin hydride or zinc hydride, respectively. As another example, the component may include silicone, and the silicone may chemically react with the hydrogen plasma to form silane (SiH4). The volatile compound (e.g., tin hydride, zinc hydride, or silane) may evaporate (or sublime), and the component (e.g., solder joint) may be substantially degraded. The third example of the interaction mechanism may also be referred to as "hydrogen-induced degassing". Some volatile compounds generated in the hydrogen-induced degassing may cause further damage to other components of the lithography system. For example, tin hydride or zinc hydride may migrate to an optical surface (e.g., a reflective mirror surface of a mirror such as the faceted field mirror device 10 and the faceted pupil mirror device 11), and the material (i.e., tin or zinc) may be deposited on the optical surface, causing irreversible contamination.

[0055] Although three exemplary interaction mechanisms have been described, it will be apparent to those skilled in the art that the apparatus and methods taught herein may be used or adapted to mitigate or prevent damage (e.g., to the lithography apparatus LA or other equipment) that may occur due to other interaction mechanisms (between the hydrogen plasma and the components) or due to other causes of damage (i.e., other than the hydrogen plasma).

[0056] The radiation source SO may be a laser produced plasma (LPP) source, a discharge produced plasma (DPP) source, a free electron laser (FEL) or any other radiation source capable of generating EUV radiation.

[0057] As is known in the art, one or more mirrors within the lithographic apparatus LA may be provided with a micro-electromechanical system (MEMS) device to allow the mirror to be moved (i.e. tilted so that the angle of incidence between the mirror and the EUV radiation beams B, B' varies). As an example, the illuminator IL (discussed in more detail below) may be a programmable illuminator provided with one or more MEMS devices for actuating the mirror. Furthermore, the mirror may be one of a plurality of mirrors, each of which is actuated by a corresponding MEMS device in a plurality of MEMS devices. In other words, a single mirror may be replaced by a micro-mirror array in which each micro-mirror is actuated by a MEMS device so that each micro-mirror system (of the micro-mirror array) can be moved independently of the other micro-mirror systems in the micro-mirror array. As an example, the faceted field mirror device 10 and the faceted pupil mirror device 11 may include a micro-mirror array. The micro-mirror array may allow correction of aberrations (or other distortions or undesirable optical effects) in the radiation beam reflected by the micro-mirror array. Additionally or alternatively, the micro-mirror array may eliminate the need for additional mirrors elsewhere in the lithographic apparatus (e.g., “focusing” mirrors, i.e., Figure 1A A mirror (not shown) for projecting the EUV radiation beam B after the EUV radiation beam B is reflected by the faceted pupil mirror device 11).

[0058] Each micro-mirror system may include a reflector (having a reflective mirror surface) fixed to a MEMS device. Alternatively, one side of the MEMS device may be provided with a reflector surface. Optionally, the reflective mirror surface may be provided with one or more coatings to improve optical performance. Each MEMS device of the micro-mirror array may be fixed to a common substrate so that each micro-mirror system (in the micro-mirror array) shares a common backing.

[0059] Each MEMS device may include a piezoelectric element and be actuated by the piezoelectric effect. Additionally or alternatively, each MEMS device may include two or more electrodes and may be actuated using an electrostatic force (i.e., a Coulomb force). The micromirrors and MEMS devices may be collectively referred to as a micromirror system, and a micromirror array may include one or more micromirror systems.

[0060] Figure 1B Shown is an inspection and / or metrology device known from US 9,946,167 B2, the entire content of which is incorporated herein by reference. Figure 1B Corresponding to US 9,946,167 B2 Figure 3 a. The inspection and / or metrology equipment is a dark field metrology equipment for measuring, for example, overlay and / or alignment.

[0061] During lithography, it is often desirable to make measurements of the structures created, for example for process control and verification. Various tools are known for making such measurements, including scanning electron microscopes, which are commonly used to measure critical dimensions (CDs), and specialized tools for measuring overlay, alignment accuracy of two layers in a device, and alignment (i.e., position) of alignment marks on a substrate. Various forms of scatterometers have been developed for use in the field of lithography. These devices direct a radiation beam onto a target structure, such as a grating or mark (mark), and measure one or more properties of the scattered radiation, such as the intensity of the scattered radiation as a function of wavelength at a single reflection angle, the intensity at one or more wavelengths as a function of reflection angle, or the polarization as a function of reflection angle—to obtain a "spectrum" from which properties of interest of the target can be determined. Determination of the properties of interest can be performed by various techniques: for example, reconstruction of the target structure by iterative methods such as rigorous coupled wave analysis or the finite element method; library searching; and principal component analysis.

[0062] Figure 1B The dark field metrology apparatus shown in can be a stand-alone device / system or can be incorporated in the lithography apparatus LA as an alignment system and / or an overlay measurement system (not shown). The optical axis with multiple branches in the whole apparatus is represented by the dashed line O. In the apparatus, the light emitted by the radiation source 111 (e.g., a xenon lamp) is directed to the substrate W via a beam splitter 115 through an optical system including lenses 112, 114 and an objective lens 116. These lenses are arranged in a double sequence of a 4F arrangement. Therefore, the angular distribution of the radiation incident on the substrate can be selected by defining the spatial intensity distribution in a plane presenting the spatial spectrum of the substrate plane (referred to herein as the (conjugate) pupil plane). In particular, this can be achieved by inserting an aperture plate 113 of a suitable form between the lenses 112 and 114 in a plane that is a back-projected image of the objective lens pupil plane. In the example shown, the aperture plate 113 has different forms (labeled 113N and 1135), thereby allowing different illumination modes to be selected. The illumination system in this example forms an off-axis illumination mode. In a first illumination mode, aperture plate 113N provides off-axis illumination from a direction designated "North" for ease of description only. In a second illumination mode, aperture plate 1135 is used to provide similar illumination but from an opposite direction labeled "South". Other illumination modes are possible by using different apertures. The remainder of the pupil plane is desirably dark because any unwanted light outside the desired illumination mode will interfere with the desired measurement signal.

[0063] A target structure (not shown) on substrate W (e.g., a grating or mark (mark)) is placed orthogonal to the optical axis O of objective lens 116. An illumination ray incident on the target structure at an angle offset from axis O produces a zeroth order diffraction ray and two first order diffraction rays. Since the hole in plate 113 has a finite width (required to allow a useful amount of light), the incident ray will actually occupy a certain angle range, and the diffracted rays 0 and +1 / -1 will be slightly spread out. Depending on the point spread function of the smaller target, each of the +1st and -1st orders will be further spread over a certain angle range, rather than a single ideal ray. Note that the grating pitch and illumination angle can be designed or adjusted so that the first order rays entering the objective are closely aligned with the central optical axis.

[0064] At least the 0th and +1st orders diffracted by the target on substrate W are collected by objective lens 116 and directed back through beam splitter 115. Both the first illumination mode and the second illumination mode are shown by designating radially opposite apertures labeled North (N) and South (S). When the incident ray comes from the north side of the optical axis, that is, when the first illumination mode is applied by using aperture plate 113N, the +1 diffracted ray labeled +1 (N) enters the beam. Each diffraction order hits a different point on the sensor so that image processing can compare and contrast the various orders. The pupil plane image captured by sensor 119 can be used to focus inspection and / or metrology equipment, and / or normalize intensity measurements of the first order beam. The pupil plane image can also be used for many measurement purposes (such as reconstruction).

[0065] In the second measurement branch, an optical system including lenses 120 and 122 forms an image of a target on a substrate W on a sensor 123 (e.g., a CCD or CMOS sensor). In the second measurement branch, an aperture plate (referred to as a field stop 121) is arranged in a plane conjugate to the pupil plane. When describing the present invention, this plate will be referred to as the "intermediate pupil plane". The field stop 121 is used to block the zero-order diffraction beam so that only the first-order beam of -1 or +1 is passed to form an image of the target on the sensor 123. The image captured by the sensors 119 and 123 is output to an image processor and controller PU, the functions of which will depend on the specific type of measurement being performed. Note that the term "image" used herein is broad. If only one of the -1 order and +1 order is present, an image of such a grating line will not be formed.

[0066] The illumination system of the inspection and / or metrology device includes an illuminator 110. Figure 1B As shown, the illuminator 110 comprises a lens 112 and an aperture plate 113. Further details of the inspection and / or metrology apparatus may be found in US 9,946,167 B2.

[0067] Figure 1CShown for Figure 1B The programmable illuminator 140 of the inspection and / or measurement device. The programmable illuminator 140 can be used Figure 1B An inspection and / or measurement device is provided to replace the illuminator 110. The programmable illuminator 140 includes a micro-mirror array 133 and a low-NA relay 4F system 135 including a pair of lenses. Radiation or light (e.g., a broadband radiation source or a white light source) from a radiation source 130 (not part of the programmable illuminator 140) can be directed to the micro-mirror array 133 via an optional optical fiber 131 and an optional collimating lens system 132. The processing unit PU can control the micro-mirror array 133 so that the micro-mirrors 134 in the micro-mirror array 133 (or more precisely, the mirrors in the micro-mirrors 134) are individually tilted. By independently adjusting the tilt angle of each individual mirror, the spatial distribution of the light output by the low-NA relay system 135 can be controlled, and various illumination modes can be performed as needed without the use of an aperture plate. If the programmable illuminator 140 is used Figure 1B inspection and / or measurement equipment, it is connected to the lens 114, which means that the light output by the low NA relay system 135 is Figure 1B The lens 114 receives it.

[0068] In order to control the spectral distribution of the light output by the low NA relay system 135, at least a portion of the reflector may include a grating (not shown) located on top of the reflector surface. The grating may be the same for all reflectors, or different gratings may be used, for example gratings with different pitches. By appropriate control of the micro-mirror array 133, the light output by the low NA relay system 135 includes a single wavelength or a single (narrow) wavelength range. However, the micro-mirror array 133 may also be controlled so that the light output by the low NA relay system 135 includes multiple different wavelengths or multiple different (narrow) wavelength ranges. The grating may be patterned on the reflector surface in a photolithographic manner. Each reflector with a grating will diffract light of different wavelengths in different directions according to the associated grating equation. A portion of the diffracted light is captured by the low NA relay system 135 and forms an image. By adjusting the angle of each reflector independently, the light distribution at the output end can be controlled spatially and spectrally because (a) certain diffraction orders will be captured by the low NA relay system 135, while (one or more) other diffraction orders will not be captured. Such spatial and spectral light distribution can be advantageously used, for example, to illuminate and measure overlaid target structures on a substrate, or to measure the position of alignment marks on a substrate.In this document, the terms target structure, target, mark, marking and grating are synonyms for each other where the context permits.

[0069] The spectral bandwidth of the diffracted beam that can be captured by the low NA relay system 135 is dλ=P×NA, where P is the pitch of the grating and NA is the numerical aperture of the low NA relay system 135. In the case of P=500nm and NA=0.02, the spectral bandwidth is 10nm, which means that the diffraction order of the grating includes a wavelength range or band of 10nm.

[0070] The spatial resolution of the low NA relay system 135 is approximately λ / NA. At λ=850 nm and NA=0.02, the spatial resolution is 42.5 microns. If the size of the mirror is larger than 42.5 microns, each mirror can be resolved. A reasonable size for the mirror is 100 microns x 100 microns.

[0071] By rotating / tilting the mirrors around their respective axes, different central wavelength bands can be directed into the low NA relay system 135. The rotation range of each mirror required for operation in the visible wavelength range should be approximately Δλ / 2P, where Δλ=400nm for the operating wavelength range of 450nm-850nm. This means that each mirror must be able to rotate 0.4 radians.

[0072] Figure 2 A cross-sectional view of a simplified example of a piezoelectric micro-mirror system 200 (i.e., a system including a micro-mirror actuated by a MEMS device using the piezoelectric effect) is shown. The piezoelectric mirror system 200 includes a first portion 201 including a mirror 220 having a reflective mirror surface 222. The side of the mirror 220 opposite the reflective mirror surface 222 is fixed to a first end of a central post 230. The central post 230 is typically fixed to a point approximately centered on the side of the mirror 220 opposite the reflective mirror surface 222. The second end of the central post 230 is fixed to a second portion 202 including a substrate 250.

[0073] The central column 230 is resilient so that when a force is applied to the reflector 220, the central column 230 can be deformed, thereby allowing the position of the reflector 220 to move. In other words, the central column 230 can act as a universal joint, thereby allowing the reflector 220 to tilt. The central column 230 can be a biasing member so that when the force is no longer applied, the reflector 220 is driven to a neutral resting position. Although the central column 230 is depicted as a single column, the central column 230 can include multiple resilient members that together act as a universal joint, thereby allowing tilting in the first direction and the second direction without (or minimizing) movement in the third direction.

[0074] The piezoelectric micro-mirror system 200 also includes one or more piezoelectric actuators 240. Each piezoelectric actuator includes one or more layers of piezoelectric material 242 and two or more electrodes 244. Figure 2 In the example of , each piezoelectric actuator includes a single layer of piezoelectric material 242 disposed (i.e., sandwiched) between two electrodes 244. In other examples, each piezoelectric actuator may be provided with multiple layers of piezoelectric material 242 and multiple electrodes 244, with each layer of piezoelectric material 244 disposed between two electrodes 244. When a voltage provided by the electrodes 244 is applied, the piezoelectric material 242 deforms (due to the piezoelectric effect), thereby applying a force to the component to which the piezoelectric actuator 240 is fixed.

[0075] Each piezoelectric actuator 240 can be fixed to the mirror 220 at a first end and fixed to the substrate 250 at a second end. Alternatively, as can be seen by the exemplary piezoelectric micro-mirror system 200, each piezoelectric actuator 240 can be fixed to a component that is fixed (directly or indirectly) to the mirror 220 or to the substrate 250. In the exemplary piezoelectric micro-mirror system 200, each piezoelectric actuator 240 is fixed to a corresponding elastic member 260 (such that the layer of piezoelectric material 242 is aligned with the elastic member 260, as shown in FIG. Figure 2 20 ). Although the piezoelectric actuator 240 is fixed to the first face of the elastic member 260 (i.e., the face opposite to the substrate 202), the piezoelectric actuator 202 may be fixed to the second face of the elastic member 260 (i.e., the face opposite to the reflector 220) instead. A plurality of first posts 224 extend away from the reflector 220 (i.e., toward the substrate 250), and a plurality of second posts 252 extend away from the substrate 250 (i.e., toward the reflector 220). Each first post 224 and each second post 252 may be shorter than the central post 230. A first end of each elastic member 260 is fixed to a corresponding first post 224 (among the plurality of first posts 224), and a second end of each elastic member 260 is fixed to a corresponding second post 252 (among the plurality of second posts 252).

[0076] The piezoelectric micro-mirror system 200 may include any number of piezoelectric actuators 240. The piezoelectric actuators 240 may cooperate in pairs (i.e., on opposite sides of the piezoelectric mirror system 200), so the piezoelectric micro-mirror system 200 may include an even number of piezoelectric actuators, such as two or four. Advantageously, providing the piezoelectric micro-mirror system 200 with at least four piezoelectric actuators allows the first portion 201 including the mirror 220 to be tilted about two different axes.

[0077] As described above, under the application of voltage, the piezoelectric actuator 240 can be deformed by applying a force to the first column 224 and the second column 252. By operating the piezoelectric actuator 240, the angle of the reflector 220 can be changed. A single piezoelectric actuator 240 can be operated, or alternatively, a plurality of piezoelectric actuators 240 can be operated in coordination. For example, by cooperatively operating the piezoelectric actuators 240 on opposite sides of the piezoelectric micro-mirror system 200 (i.e., applying a first voltage to a first piezoelectric actuator that deforms in a first direction, and applying a second voltage that is equal to but opposite to the first voltage to a second piezoelectric actuator that deforms in a second direction), the angle of the reflector 220 (and the reflective mirror surface 222) can be changed. In other words, the reflector 220 can be tilted from a first position to a second position. The first position can be a neutral position, or alternatively, the first position can be an intermediate position (i.e., a position achieved by operating at least one piezoelectric actuator 240).

[0078] After the voltage is stopped (and no force is applied), the central column 230 can drive the mirror 220 to the first position. Additionally or alternatively, an opposite voltage can be applied to each piezoelectric actuator for a sufficient period of time to return the mirror 220 to the first position.

[0079] Additionally or alternatively, as described above, each MEMS device may include two or more electrodes, and each MEMS device may be actuated using electrostatic force. In other words, each micro-mirror may be an electrostatic micro-mirror system (i.e., a system including micro-mirrors actuated by a MEMS device using electrostatic force). Since the force used to actuate the MEMS device of the electrostatic micro-mirror system may use capacitance, the electrostatic micro-mirror system may also be referred to as a capacitive micro-mirror system. Figure 3 A cross-sectional view of a simplified exemplary electrostatic micro-mirror system 300 (ie, a system including micro-mirrors actuated by a MEMS device using an electrostatic effect) is shown.

[0080] Similar to the piezoelectric mirror system 200, the electrostatic micro-mirror system 300 includes a first portion 301 including a mirror 320 having a reflective mirror surface 322. The side of the mirror 320 opposite the reflective mirror surface 322 is fixed to a first end of a central post 330. The central post 330 is generally fixed to a point approximately centered on the side of the mirror 320 opposite the reflective mirror surface 322. The second end of the central post 330 is fixed to a second portion 302 including a substrate 350.

[0081] The central post 330 is resilient so that when a force is applied to the reflector 320, the post 330 can deform, thereby allowing the position of the reflector 320 to move. In other words, the central post 330 can act as a universal joint, thereby allowing the reflector 320 to move. The central post 330 can be a biasing member so that when the force is no longer applied, the reflector 320 is driven to a neutral resting position.

[0082] The electrostatic micro-mirror system 300 also includes one or more first electrodes 341 and one or more second electrodes 342. Each first electrode 341 can be fixed to the reflector 320 (or formed integrally with the reflector 320), and each second electrode 342 can be fixed to the substrate 350 (or formed integrally with the substrate 350). Each first electrode 341 can be offset relative to the corresponding second electrode 342, for example, axially offset (i.e., not axially aligned), radially offset, or azimuthally offset. Additionally or alternatively, each electrode (i.e., the first electrode 341 and / or the second electrode 342) can be a comb electrode (i.e., an electrode including a plurality of teeth), and each tooth of the first electrode 341 can be axially offset relative to the corresponding tooth of the second electrode 342.

[0083] The electrostatic micro-mirror system 300 may include any number of electrostatic actuators 340. By operating the electrostatic actuators 340, the angle of the mirror 320 may be changed. A single electrostatic actuator 340 may be operated, or alternatively, the electrostatic actuators 340 may be operated cooperatively in pairs (i.e., on opposite sides of the electrostatic mirror system 300). Thus, the electrostatic micro-mirror system 300 may include an even number of electrostatic actuators 340, such as two or four. Advantageously, providing the electrostatic micro-mirror system 300 with at least four piezoelectric-electrostatic actuators (i.e., two pairs of piezoelectric-electrostatic actuators 341, 342) allows the first portion 301 including the mirror 320 to be tilted about two different axes.

[0084] In the case where a voltage is applied between the first electrode 341 and the corresponding second electrode 342, an electrostatic force (i.e., a Coulomb force) can be applied between the first electrode 342 and the second electrode 341. In an example where the electrostatic actuator 340 operates in cooperation, a voltage can be applied between the first electrode 341 and the second electrode 342 on opposite sides of the electrostatic micro-mirror system 300, and the angle of the mirror 320 (and the reflective mirror surface 322) can be changed. In other words, the mirror 320 can be tilted from a first position to a second position.

[0085] After the voltage is stopped (and the force is no longer applied), the central column 330 can drive the mirror 320 to the first position. Additionally or alternatively, opposite voltages can be applied to each of the first electrode 341 and the second electrode 342 for a sufficient period of time to return the mirror 320 to the first position.

[0086] For simplicity, the piezoelectric micro-mirror system 300 and the electrostatic micro-mirror system 400 are depicted as having a small number of electrodes 244, 341, 342. As will be clear to those skilled in the art, each of the electrodes 244, 341, 342 may be one of a corresponding plurality of electrodes (i.e., the first electrode 341 may be one of a plurality of first electrodes).

[0087] Figure 4 A perspective view of a piezoelectric micro-mirror system 400 is depicted. Similar to the piezoelectric micro-mirror system 200, the piezoelectric micro-mirror system 400 includes a first portion 401 having a mirror 420 with a reflective mirror surface 422. A first end of a central post 430 is fixed to the side of the mirror 420 opposite the reflective mirror surface 422. Four actuators 440 ( Figure 4 The piezoelectric micro-mirror system 400 is fixed to one side of the elastic member 460 (blurred in the figure), and each elastic member 460 is fixed to one of the four first pillars 424. The piezoelectric micro-mirror system 400 also includes a heat sink 470 having a groove 472. For simplicity, other components of the piezoelectric micro-mirror system 400 are not shown.

[0088] The micro-mirror system (i.e., the piezoelectric micro-mirror system 200, 400 or the electrostatic micro-mirror system 300) may also include an electronic device configured to determine the position of the reflector 320. For example, the electrostatic micro-mirror system 300 may also include one or more third electrodes and one or more fourth electrodes. Each third electrode may be fixed to the reflector 320 (or formed integrally with the reflector 320), and each fourth electrode may be fixed to the substrate 350 (or formed integrally with the substrate 350). The third electrode and the fourth electrode may be arranged closer to the central column 330 than the first electrode 341 and the second electrode 342. Advantageously, positioning the first electrode 341 and the second electrode 342 in this manner may increase the torque applied to the reflector 320. The electrical property (e.g., capacitance) between the third electrode 343 and the corresponding fourth electrode 344 may be measured, and the measured electrical property may be used to determine the distance between the third electrode 343 and the corresponding fourth electrode 344. In this way, the angle of the reflector may be determined. It will be clear to those skilled in the art that the electronics configured to determine the position of the mirror may alternatively or additionally comprise piezoelectric electronics material.

[0089] The micro-mirror system 200, 300, 400 may also include a controller configured to control the electronic devices included in the micro-mirror system. For example, the controller may receive an input indicating the desired tilt or inclination of the mirror, and the controller may determine the voltage applied to each electrode to achieve the desired tilt or inclination of the mirror. The controller may use a negative feedback system (using a known position of the mirror determined by the electronic device for determining the position of the mirror) to achieve the desired tilt or inclination of the mirror.

[0090] The micro-mirror systems 200 , 300 , 400 may also include a voltage source and electrical components so that a separate voltage may be provided to each electrode (ie, each of the first electrode 341 , the second electrode 342 , the third electrode 343 , and the fourth electrode 344 ).

[0091] The first part 201, 301, 401 (including the mirror 220, 320, 420) and / or the second part 202, 302, 402 (including the substrate 250, 350) of the micro-mirror system 200, 300, 400 may be electrically grounded. In other words, the first part 201, 301, 401 and / or the second part 202, 302, 402 may be connected (directly, or indirectly, i.e., via another connection) to a ground connection or a charge receiver.

[0092] like Figure 4 As can be shown, the micro-mirror system 400 can also include a heat sink 470. The heat sink can include a plurality of fins (or other components) to increase the surface area to volume ratio, thereby helping to dissipate or radiate thermal energy. For example, the heat sink 470 includes a plurality of grooves 472 extending to the surface of the heat sink 470. Alternatively, the heat sink 470 can be referred to as a heat spreader.

[0093] The reflective mirror surface of the reflector can have any suitable shape. For example, although the reflective mirror surface 422 is Figure 4 250, 350 is depicted as having a square shape, but other shapes (e.g., circular, triangular, or hexagonal) are also possible. Advantageously, a mosaic shape (or a combination of micro-mirror systems with different shapes) can be used to provide a micro-mirror array with a substantially continuous reflector surface. The shape of the substrate 250, 350 can be the same as the shape of the reflector 220, 320.

[0094] When configured as a micro-mirror array, the reflective mirror surface 222, 322, 422 of each micro-mirror system 200, 300, 400 may be a portion of a larger reflective mirror surface. For example, the micro-mirror array may include a flexible continuous material (including a reflective surface), and the continuous material may be fixed to an actuator of each micro-mirror system 200, 300, 400. By actuating the actuator in each micro-mirror system 200, 300, 400 of the micro-mirror array, the position of the flexible continuous material may be adjusted, thereby providing the effect of changing the reflective surface.

[0095] In use, in the lithographic apparatus LA, as described above, a micro-mirror system (such as micro-mirror systems 200, 300, 400) may be damaged by hydrogen plasma. Gaseous hydrogen may migrate to the space occupied by an electrode (i.e., electrode 244, first electrode 341, or second electrode 342) or other sensitive electronic devices, and in the space occupied by the electrode, the gaseous hydrogen may be exposed to EUV radiation, thereby generating hydrogen plasma. Additionally or alternatively, hydrogen plasma may be generated elsewhere in the lithographic apparatus LA and migrate to the space occupied by the electrode. The hydrogen plasma may cause damage, for example, due to hydrogen-induced degassing in the micro-mirror system including silicone.

[0096] Figure 5 A cross-sectional view of an exemplary electrostatic micro-mirror system 500 is shown that is substantially the same as the electrostatic micro-mirror system 300 (similar components are also given similar reference numerals, such as Figure 3 The center column 530 is marked as 330).

[0097] like Figure 5 As shown, the electrostatic micro-mirror system 500 may include a first baffle 561. The first baffle 561 is provided as a part of the first part 501, but alternatively, the first baffle 561 may be provided as a part of the second part 502. The first baffle 561 may be coupled to the first part 501 (including the reflector 520), and optionally, the first baffle 561 may be integrally formed with the first part 502. In other words, the first baffle 561 and the first part 501 may be part of a single structure. As an example, the first baffle 561 and the first part 501 may include silicone. Alternatively, the first baffle 561 may be formed separately from the first part 501.

[0098] Advantageously, the first baffle 561 can prevent fluid (e.g., gaseous hydrogen or hydrogen plasma) from entering the space occupied by the first electrode 541 and the second electrode 542. Additionally or alternatively, the first baffle 561 can prevent radiation (e.g., EUV radiation beam B) from being transmitted from the environment external to the MEMS device into the space occupied by the first electrode 541 and the second electrode 542. Thus, the first baffle 561 can reduce or prevent damage caused by hydrogen plasma.

[0099] In an example where the electrostatic mirror system 500 further includes an electronic device configured to determine the position of the mirror, the space occupied by the first electrode 541 and the second electrode 542 may also include a space occupied by the electronic device configured to determine the position of the mirror. Thus, the first baffle 561 may reduce or prevent damage to the electronic device configured to determine the position of the mirror caused by the hydrogen plasma.

[0100] Optionally, the electrostatic micro-mirror system 500 may further include a second baffle 562. In other words, the electrostatic micro-mirror 500 may include a labyrinth seal 560 including a first baffle 561 and a second baffle 562. The second baffle 562 is shown as being coupled to the second portion 502 (but more generally, coupled to one of the first portion 501 and the second portion 502 that is not coupled to the first baffle), and optionally, the second baffle 561 may be integrally formed with the second portion 502. The second baffle 562 may be offset relative to the first baffle 561 (i.e., not aligned with the same axis). That is, the central axis of the first baffle 561 is not aligned with the central axis of the second baffle 562.

[0101] Advantageously, the labyrinth seal 560 can also reduce or prevent damage caused by hydrogen plasma. Advantageously, if the gap (between the first baffle 561 and the second baffle 562) is small enough, the first baffle 561 and the second baffle 562 can allow charged elements of the plasma to recombine.

[0102] The first baffle 561 and the second baffle 562 may each be substantially opaque to radiation. For example, the first baffle 561 and the second baffle 562 may have a low transmittance to EUV radiation.

[0103] Each of the first baffle 561 and the second baffle 562 may define a continuous closed loop, i.e., in an example where the first baffle 561 is disposed on an outer edge of the first portion 501, the first baffle 561 may form an outer circumference around the first portion 501 without any gaps. In this manner, the first baffle 561 and the second baffle 562 provide a labyrinth seal 560 around the electrostatic micro-mirror system 500, so that there are no gaps through which plasma can enter or radiation can be transmitted.

[0104] The first baffle 561 and the second baffle 562 can each be sufficiently long (i.e., in the size or dimension of the faces extending away from the first portion 501 and the second portion 502, respectively) to ensure that there is overlap between the end of the first baffle 561 and the end of the second baffle 562. Figure 5 561 and the second baffle 562 are depicted as being substantially the same length, but each of the first baffle 561 and the second baffle 562 may have a different length (and width). As described above, the first baffle 561 and the second baffle 562 may not be aligned (i.e., the first baffle 561 may be axially aligned with the second baffle 562, and each of the first baffle 561 and the second baffle 562 may be disposed at a different distance from the common axis). In other words, when disposed as part of the micro-mirror system 500, a portion of the first baffle 561 surrounds a portion of the second baffle 562. In other words, the first baffle 561 and the second baffle 562 may be symmetrical (i.e., the same shape but different proportions) relative to the center of the reflector 520. The spacing (between the first baffle 561 and the second baffle 562) is such that there is sufficient clearance to allow the first portion 501 to move while still preventing fluid from entering.

[0105] For a typical micro-mirror system 500, the reflector 520 may be 1000×1000×1000µm, and the central column 530 may be a cylinder with a radius of about 5µm and a length of about 100-150µm. The length of each of the first electrode 541 and the second electrode 542 may be 50µm. In such a reflector, each baffle (i.e., the first baffle 561 and the second baffle 562) may be (approximately) 1-2µm in width and (approximately) 60-70µm in length.

[0106] Each of the baffles 561 , 562 may be rigid, or alternatively, may be resilient. Advantageously, the rigid baffles 561 , 562 may provide “end stops”, ie, limits to the allowed movement of the mirror 520 .

[0107] Each of the first baffle 561 and the second baffle 562 may be electrically grounded. For example, the first baffle 561 and the first portion 501 may be integrally formed of the same material, and the first portion 501 may be electrically grounded (by connecting the first portion 501 to a ground connection or otherwise grounded). Likewise, the second baffle 562 and the second portion 502 may be integrally formed of the same material, and the second portion 502 may be electrically grounded. The first baffle 561 and the second baffle 562 may be electrically connected in other ways so that the voltage of the first baffle 561 is maintained at the voltage of the second baffles 561, 562. Grounding the first baffle 561 and the second baffle 562 may advantageously conduct ion currents and / or photocurrents generated when ions and / or photons are blocked, respectively, thereby preventing charge accumulation.

[0108] The labyrinth seal 560 may include other baffles. In other words, the first baffle 561 may be one of a plurality of first baffles, and / or the second baffle 562 may be one of a plurality of second baffles. The other baffles may advantageously further reduce damage caused by hydrogen plasma.

[0109] The labyrinth seal 560 may be provided on other micro-mirror systems. Figure 6 FIG. 6 is a cross-sectional view of an example piezoelectric micro-mirror system 600. Figure 2 The piezoelectric micro-mirror system 200 shown is substantially the same. Figure 6 Similar components in FIG. 6 are given similar reference numerals. The piezoelectric micro-mirror system 600 further includes a labyrinth seal 660, which includes a first baffle 661 and a second baffle 662. Alternatively or additionally, the micro-mirror system 500, 600 including the labyrinth seal 560, 660 may be disposed in an inspection and / or measurement device (e.g., Figure 1B dark field equipment shown).

[0110] Although example micromirror systems (e.g., micromirror systems 200, 300, 400, 500, 600) are described herein, it will be clear to those skilled in the art that baffles (e.g., 561, 562, 661, 662) and / or labyrinth seals (e.g., 560, 660) may be provided on other MEMS devices. Features of the example micromirror systems that have been described have been described for exemplary purposes, and these features should not be construed as essential features of the present invention. Furthermore, although MEMS devices have been discussed with respect to example applications of lithographic apparatus, these applications are for example purposes, and it will be clear to those skilled in the art that MEMS devices may be used for other applications.

[0111] The labyrinth seals 560, 660 and / or baffles 561, 562, 661, 662 can be manufactured using standard techniques for manufacturing micro-mirror systems known to those skilled in the art (for example, by providing a plurality of silicon wafers, forming elements of the micro-mirror array in the wafers, and then bonding the wafers to each other), and the labyrinth seals 560, 660 and / or baffles 561, 562, 661, 662 can be manufactured by adjusting the method accordingly.

[0112] As a first example of a known method for manufacturing a micromirror system comprising comb electrodes and a heat spreader, Figure 7 A schematic diagram of five silicon wafers bonded together to form a micro-mirror array is shown. The five wafers include a wafer 700 for forming a mirror 701, a wafer 702 for forming an upper spring element 703 and optionally a flexible connector 704 for forming a heat spreader, a wafer 705 for forming a comb 706 of a comb (i.e., electrostatic) actuator and for forming a lower spring element 707, a wafer 708 as an interposer wafer for providing electrical connection to the micro-mirror array and also for forming a substrate 709 supporting the micro-mirror array, and a wafer 710 for providing electrical connection to the interposer wafer 708.

[0113] The method of forming a micro-mirror array may include the following steps:

[0114] a. Provide a first wafer 702 ("upper spring wafer"), which may be a SOI wafer with a 1um thick highly doped silicon film. The upper spring 703 pattern is formed in the wafer, and optionally also in the flexible connector 704 of the heat spreader.

[0115] b. Provide a second wafer 705 ("comb wafer"), and form a comb element 706 in the second wafer 705. The comb wafer may include two SOI wafers bonded together, one SOI wafer having a thin (e.g., 1 um) highly doped silicon film, and the other SOI wafer having a thicker (e.g., 30 um) highly doped silicon layer. Alternatively, the comb wafer 705 may include an SOI wafer having a thin (e.g., 1 um thick) highly doped silicon film, and a highly doped silicon layer (e.g., 30 um thick) deposited thereon. Wafer 705 is patterned to form the comb element 706 of the comb actuator.

[0116] c. Bonding the first wafer 702 to the second wafer 705 to connect the upper spring element 703 to the comb actuator. The bonding step may include melt bonding in the presence of a cavity. After bonding, the handle wafer of the second wafer 705 may be removed, followed by via patterning, metal filling and patterning or CMP, and photolithography and etching to form the lower spring element 707.

[0117] d. Provide a third wafer 708 ("interposer wafer"), which may be a SOI wafer having a 100 um thick silicon film. Pattern the third wafer 708 to form cavities.

[0118] e. Bonding the third wafer 708 to the first wafer 702 and the second wafer 705 to connect the comb actuator to the substrate 709. The bonding step may include melt bonding in the presence of a cavity. After bonding, the handle wafer of the third wafer 708 may be removed, followed by via etching through the silicon and oxide of the third wafer 704, oxide liner deposition, and then further via etching through the silicon and oxide in the second wafer 702, TSV copper filling and CMP, and forming a redistribution layer (RDL) pattern on the non-bonded side of the interposer wafer 708.

[0119] f. Forming connections to the heat sink and sensing element. The steps of forming connections to the heat sink and sensing element may include removing the handle wafer of the first wafer 702, then patterning and etching through-holes through the highly doped silicon film of the first wafer 702, metal filling and patterning, depositing and patterning bonding metal, and removing the oxide diaphragm on top of the highly doped silicon film of the first wafer 702.

[0120] g. Providing a fourth wafer 700 ("mirror wafer"). The mirror wafer 700 may be a SOI wafer with a 250um thick silicon film. Providing the mirror wafer 700 may include: depositing bonding material and patterning, forming a protrusion of a capacitor top plate as a sensing element, depositing a hard mask and patterning, providing a resist mask and etching silicon (e.g., 100um etching and over-etching), removing the resist mask and further etching silicon (e.g., 150um), and removing the hard mask.

[0121] h. Bonding the mirror wafer 700 to the wafer stack comprising the first wafer 702, the second wafer 705 and the third wafer 708 to form pillars connecting the mirrors to the substrate 709. The bonding may comprise eutectic bonding.

[0122] i. Bump pads are formed on the third wafer 708 and etched to release the posts supporting the mirrors 701 .

[0123] j. Providing a fifth wafer 710 (“electronic device wafer”). Providing the fifth wafer 710 may include providing HV components, analog components, and digital CMOS components in the electronic device wafer, forming TSVs (eg, 5,000 to 10,000 connections), and forming bump balls for connecting to the interposer wafer 708.

[0124] k. Attach the electronics wafer 710 to the interposer wafer 708 using the solder bumps on the respective wafers 708 and 710 .

[0125] 1. Removing the handle wafer of the mirror wafer 700 to release the mirrors 701, and then cutting (eg, laser cutting) to complete the micro-mirror array.

[0126] As a second example of a known method of manufacturing a micro-mirror system including a comb electrode and a heat spreader, Figure 8 A schematic diagram of an alternative method of forming a micro-mirror array comprising only three wafers bonded together is shown. The three wafers include a mirror wafer 810 for forming a mirror 801, an intermediate wafer 802 for forming spring elements 803, combs 804 of a comb actuator, and a substrate 805 supporting the micro-mirror array, and an electronics wafer 806 for providing electrical connections 807 to the micro-mirror array.

[0127] The method of forming a micro-mirror array may include the following steps:

[0128] a. Providing a first wafer 802 ("intermediate wafer"). The providing step may include providing a SOI wafer with a 1um thick highly doped silicon film, depositing oxide, etching anchor trenches, filling the trenches with polysilicon and then performing CMP, patterning the oxide to provide a mask layer for the lower spring element 803, and epitaxially growing a 30um thick silicon layer on the patterned oxide and then performing CMP. The step of providing the intermediate wafer may also include silicon dry reactive ion etching (DRIE) using oxide as a stop layer, filling the etched silicon with oxide, epitaxially growing a 1um thick silicon layer (polysilicon and single crystal) for the upper spring element 803, and etching the silicon layer to form the upper spring element 803. The step of providing the intermediate wafer may also include flipping the wafer, via etching, isolation layer deposition, filling the vias with metal and patterning (e.g., to form 5000 to 10000 connections).

[0129] b. Providing a second wafer 810 ("mirror wafer"). The mirror wafer 810 may be a SOI wafer with a silicon film of 250um. Providing the mirror wafer 810 may include: depositing and patterning a bonding material, forming a protrusion of a capacitor top plate as a sensing element, depositing and patterning a hard mask, providing a resist mask and etching silicon (e.g., 100um etching and over-etching), removing the resist mask and further etching silicon (e.g., 150um), and removing the hard mask.

[0130] c. Bonding the first wafer and the second wafer together. The bonding may include eutectic bonding.

[0131] d. Release the spring elements 803 and combs 804. The release step may include forming bump pads (e.g., 10 to 20 bump pads per mirror), etching vias through the handle wafer of the first wafer to form space for movement of the lower spring elements 803, thereby forming a path for subsequent vapor phase HF etching, and etching the oxide to release the spring elements 803 and combs 804 using vapor phase HF etching.

[0132] e. Providing a third wafer 806 (“electronic device wafer”). Providing the electronic device wafer 806 may include providing HV components, analog components, and digital CMOS components in the electronic device wafer, forming TSVs (eg, 5,000 to 10,000 connections), and forming bump balls for connecting to the intermediate wafer 802.

[0133] f. Attach the electronics wafer 806 to the intermediate wafer 802 using the solder bumps on the respective wafers.

[0134] g. Removing the handle wafer of the mirror wafer 810 to release the mirrors 801, and then cutting (eg, laser cutting) to complete the micro-mirror array.

[0135] Although specific reference is made to the use of EUV radiation and to the lithography apparatus LA comprising the use of EUV radiation, it will be apparent to a person skilled in the art that the labyrinth seal 560, 660 (and apparatus comprising a labyrinth seal, such as the micromirror system 500, 600) may also be advantageously used with other types of radiation (e.g., radiation having a wavelength of 100 nm to 400 nm), or in systems using such other types of radiation.

[0136] The drawings included herein are schematic diagrams, and any ratios between components should not be interpreted as limiting in any way. Figure 5Although the first baffle 561 and the second baffle 562 are depicted as being thinner than the first electrode 541 and the second electrode 542, the first baffle 561 or the second baffle 561 can be any suitable size (for example, the width of the first baffle 561 can be similar to that of the first electrode 541, or can be wider than the first electrode 541).

[0137] 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. Other possible applications include 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.

[0138] Although embodiments of the invention may be specifically mentioned herein in the context of lithographic equipment, embodiments of the invention may be used in other equipment. Embodiments of the invention may form part of a mask inspection and / or metrology equipment, a metrology equipment, or any equipment that measures or processes objects such as wafers (or other substrates) or masks (or other patterning devices). These equipment may generally be referred to as lithographic tools. Such lithographic tools may use vacuum conditions or ambient (non-vacuum) conditions.

[0139] Although specific reference may have been made above to the use of embodiments of the present invention in the context of optical lithography, it will be appreciated that the present invention is not limited to optical lithography and may be used in other applications such as imprint lithography where the context permits.

[0140] Although specific embodiments of the present invention have been described above, it should be understood that the present invention may be practiced in a manner other than that described. The above description is intended to be illustrative rather than restrictive. Therefore, it will be clear to those skilled in the art that modifications may be made to the described invention without departing from the scope of the claims set forth below.

Claims

1. A micro-electromechanical system (MEMS) device (500, 600), the MEMS device being configured to actuate a first portion (501, 601) relative to a second portion (502, 602), the MEMS device comprising: a first electrode (541, 644) and a second electrode (542, 644), the first electrode and the second electrode being configured such that, in use, application of a voltage to the first electrode and the second electrode causes a force to be applied to the first portion relative to the second portion; as well as A first baffle (561, 562, 661, 662) configured to prevent fluid or radiation from entering or transmitting from an environment external to the MEMS device into a space occupied by the first electrode and the second electrode.

2. The device (500, 600) according to claim 1, further comprising a labyrinth seal (560, 660), wherein the labyrinth seal comprises: The first baffle (561, 661), wherein the first baffle is coupled to the first portion (501, 601); as well as A second baffle (562, 662), the second baffle being connected to the second portion (502, 602).

3. The device (500, 600) according to claim 1 or 2, wherein: The first portion (501) includes the first electrode (541); The second portion (502) includes the second electrode (542); and wherein, in use, a force applied to the first portion relative to the second portion is caused by a Coulomb force due to the voltage.

4. The device (600) according to claim 1 or 2, wherein: The piezoelectric component (642) is disposed between the first electrode (644) and the second electrode (644), and The force applied to the first portion (601) relative to the second portion (602) is due to deformation of the piezoelectric member due to the voltage.

5. The device (500, 600) according to any preceding claim, wherein The first baffle (561, 661) is electrically grounded.

6. The device (500, 600) according to claims 2 to 5, wherein: The second baffle (562, 662) is electrically grounded.

7. An apparatus according to any preceding claim, wherein: The first part (501, 601) further comprises a reflector (520, 620), such that when the force is applied to the first part relative to the second part, the reflector is caused to move.

8. The device (500, 600) of any preceding claim, wherein the first portion (501, 601) and the first baffle (561, 661) are integrally formed, and the second portion (502, 602) and the second baffle (562, 662) are integrally formed.

9. The device (500, 600) according to any preceding claim, wherein: The first baffle (561, 661) is substantially opaque to electromagnetic radiation.

10. The device (500, 600) according to any one of claims 2 to 9, wherein: The second baffle is substantially opaque to electromagnetic radiation.

11. A micro-mirror array comprising a plurality of devices (500, 600) according to any preceding claim.

12. A programmable illuminator comprising a micro-mirror array according to claim 11 for conditioning a radiation beam.

13. A lithographic device arranged to project a pattern from a pattern forming device onto a substrate, the lithographic device comprising a programmable illuminator according to claim 12, the programmable illuminator being used to adjust a radiation beam for illuminating the pattern forming device and / or for adjusting a radiation beam for measuring a target structure on the substrate.

14. An inspection and / or metrology apparatus comprising a programmable illuminator according to claim 12 for conditioning a radiation beam for measuring a target structure on a substrate.

15. A method of constructing a device (500, 600) according to any one of claims 1 to 10, the method comprising: providing a substrate; forming a first portion (501, 601) and a second portion (502, 602); forming a first electrode (541, 644) and a second electrode (542, 644), the first electrode and the second electrode being configured such that, in use, application of a voltage to the first electrode and the second electrode will cause a force to be applied to the first portion relative to the second portion; as well as A first baffle (561, 562, 661, 662) is formed, the first baffle being configured to prevent fluid or radiation from entering or transmitting from an environment external to the MEMS device into a space occupied by the first electrode and the second electrode.

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