Patent Application
20230205101
The present invention relates to the technical fields of metrology and/or lithography, in particular to the avoiding of particles and/or dirt on the object during such processes. In further embodiments, the invention relates to measurement systems, in particular measurement systems which emit a measurement beam.
A lithographic apparatus is a machine constructed to apply a desired pattern onto a substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). A lithographic apparatus may, for example, project a pattern (also often referred to as “design layout” or “design”) of a patterning device (e.g., a mask) onto a layer of radiation-sensitive material (resist) provided on an object e.g., on a substrate e.g., a wafer. A metrology tool is for example suitable for measuring properties of the object to which a pattern has been applied, e.g. overlay or critical dimension. An inspection apparatus is for example suitable for inspecting a pattern which has been applied to an object e.g. to a substrate, e.g. to a wafer.
As semiconductor manufacturing processes continue to advance, the dimensions of circuit elements have continually been reduced while the amount of functional elements, such as transistors, per device has been steadily increasing over decades, following a trend commonly referred to as ‘Moore's law’. To keep up with Moore's law the semiconductor industry is chasing technologies that enable to create increasingly smaller features. To project a pattern on a substrate a lithographic apparatus may use electromagnetic radiation. The wavelength of this radiation determines the minimum size of features which are patterned on the substrate. Typical wavelengths currently in use are 365 nm (i-line), 248 nm, 193 nm and 13.5 nm. A lithographic apparatus, which uses extreme ultraviolet (EUV) radiation, having a wavelength within a range of 4 nm to 20 nm, for example 6.7 nm or 13.5 nm, may be used to form smaller features on a substrate than a lithographic apparatus which uses, for example, radiation with a wavelength of 193 nm.
During a metrology process or during a lithographic process, the object may be arranged on an object support, e.g. while measurements are made with the metrology tool, or while the pattern is projected onto the substrate, or while an inspection tool is inspecting the substrate. During these processes, it is preferred that no particles or dirt is present on the object, as such particles and/or dirt may results in inaccuracies in the process.
US20070071889A1, which is incorporated herein by reference, discloses a lithographic apparatus and method for conditioning an interior space of a device manufacturing apparatus. A measurement system comprising an interferometer is used to determine the position of the substrate support. It is known to provide gas showers which emit preconditioned gas at least along the optical path. In US20070071889A1, two gas showers are provided on opposite sides of an apparatus component.
It is an object of the invention to provide an improvement of the prior art or at least an alternative. In particular, it is an object of the invention to reduce the particles or dirt on an object during a metrology process or lithographic process.
This object is achieved with an apparatus for use in a metrology process or a lithographic process, the apparatus comprising: an object support module adapted to hold an object; a first gas shower arranged on a first side of the object support module and adapted to emit a gas with a first velocity in a first gas direction which is a horizontal direction to cause a net gas flow in the apparatus to be a substantially horizontal gas flow in the first gas direction at least above the object support module.
In accordance with the invention, a horizontal gas flow above the object support module is present during operational use. As such, particles and/or dirt that are present on the object are removed by the gas flow. In addition, particles and/or dirt present in the apparatus are prevented from ending up on the object.
In an embodiment, the object support module is moveable at least in a two-dimensional plane, and the apparatus further comprises a first measurement system for determining a position of the object support module in at least a first direction in the two-dimensional plane. The first measurement system is adapted to emit a first measurement beam along an optical path to the object support module. The net gas flow further covers at least a part of the optical path of the first measurement beam. The two-dimensional plane may e.g. be a substantially horizontal plane. Advantageously, the properties of the gas through which first measurement beam travels can be known and/or predetermined, thereby improving accuracy of the determined position of the object support module.
In an embodiment, the apparatus further comprises a gas guiding element adapted to guide the gas on a second side of the object support module, wherein the second side is facing away from the first side. Advantageously, the net gas flow in the apparatus is guided as desired on the second side of the object support module.
In an embodiment, the apparatus further comprises a second gas shower adapted to emit gas with a second velocity in a second gas direction towards a second side of the object support module, wherein the second side is facing away from the first side. Advantageously, the second gas shower ensures that the net gas flow in the apparatus is as desired.
In an embodiment, the second gas direction comprises a vertical component, e.g. a downward component. Advantageously, the gas flow on the second side may be directed vertically, e.g. downward, e.g. towards an exhaust.
In an embodiment, the first velocity is greater than the second velocity, preferably at least five times greater, more preferably at least ten times greater, e.g. at least twenty times greater. Advantageously, the net gas flow is primarily determined by the first gas shower, at least above the object support module.
In an embodiment, the second velocity is between 0.01 m/s-1 m/s, preferably between 0.05 m/s-0.5 m/s, more preferably 0.05-0.2 m/s, e.g. 0.1 m/s. It has been found that these velocities result in an advantageous net gas flow.
In an embodiment, the first velocity is between 0.5-5 m/s, preferably between 1-4 m/s, e.g. 2.5 m/s. It has been found that these velocities ensure an advantageous net gas flow above the object support module and/or covering the first measurement beam.
In an embodiment, the first velocity is such that a velocity of the net gas flow is at least 1 m/s along the optical path of the first measurement beam and/or above the object support module. It has been found that these velocities ensure an advantageous net gas flow above the object support module and/or covering the first measurement beam.
In an embodiment, the first gas shower is adapted to emit gas in a direction oriented at an acute angle relative to a horizontal part of the optical path of the first measurement beam. Optionally, the first gas shower is also adapted to emit gas in a direction oriented at an acute angle relative to a horizontal part of an optical path of a second measurement beam. It has been found that an improved coverage of the optical path can be achieved.
In an embodiment, the first gas shower is adapted to emit gas in a direction oriented parallel to a horizontal direction of the optical path of the first measurement beam. It has been found that an improved coverage of the optical path can be achieved.
In an embodiment, the apparatus further comprises a gas filter arranged at an outlet of the first gas shower, wherein the gas filter is adapted to filter and equalize the gas before the gas is emitted by the first gas shower. Advantageously, only a single component is required for filtering and equalizing.
In an embodiment, the optical path of the first measurement beam comprises a vertical part and a horizontal part, wherein the apparatus comprises an optical element adapted to direct the first measurement beam from the vertical part to the horizontal part. Advantageously, the position of the object support module can be determined from the distance travelled by the first measurement beam in the horizontal part. Optionally, the optical element is a beam splitter.
In an embodiment, the first measurement system comprises an interferometer. Advantageously, the measurement with the interferometer is accurate using the first gas shower.
In an embodiment, the first measurement system is adapted to emit a second measurement beam along a second optical path to the object support module for determining a position of the object support module in a second direction in the two-dimensional plane. Advantageously, the position of the object support module can be determined. The two-dimensional plane may e.g. be a substantially horizontal plane.
In an embodiment, the apparatus further comprises a second object support module adapted to hold a second object, wherein the first gas shower is adapted to cause the net gas flow in the apparatus to be a substantially horizontal gas flow in the first gas direction at least above the second object support module. Advantageously, particles and/or dirt are removed from the second object or prevented from ending up on the second object.
The invention further relates to an apparatus for use in a metrology process or a lithographic process, the apparatus comprising an object support module and optionally a vertical measurement system. Said apparatus may optionally be combined with the apparatus according to the invention as explained above.
In an embodiment, the object support module comprises an object table adapted to hold the object, a long stroke module supporting the object table, a first positioner adapted to move the object table relative to the long stroke module, and a second positioner adapted to move both the object table and the long stroke module. Advantageously, the object can be positioned accurately.
In an embodiment, the apparatus further comprises: a measurement frame, wherein the object support module is adapted to move relative to the measurement frame; and a vertical measurement system for determining a position of the object support module in a substantially vertical direction. The vertical measurement system comprises: at least one contactless sensor arranged on the object support module; and a conductive element for detecting the contactless sensor, wherein the conductive element is arranged on the measurement frame. Advantageously, the position in vertical direction can be determined with a relatively simple vertical measurement system.
In an embodiment, the at least one contactless sensor is arranged on the object table. Advantageously, the position of the object can be derived accurately.
In an embodiment, the at least one contactless sensor is arranged on the long stroke module. Advantageously, less components are arranged on the object table.
In an embodiment, the at least one contactless sensor is a capacitive sensor or an eddy current sensor. It has been found that there are relatively simple sensors with sufficient accuracy.
In an embodiment, the vertical measurement system comprises at least three contactless sensors, wherein the vertical measurement system is adapted to determine a position of the object support module in the vertical direction, a rotation of the object support module around a first horizontal axis, and a rotation of the object support module around a second horizontal axis. Advantageously, the position of the object support module can be determined in three degrees of freedom.
In an embodiment of either of the apparatuses according to the invention, the apparatus is a metrology tool comprising an optics system configured to generate an optical measurement beam and emit the optical measurement beam on the object arranged on the object support module. Advantageously, less particles and/or dirt are present, resulting in less disturbance of the optical measurement beam.
In an embodiment of either of the apparatuses according to the invention, the apparatus is an inspection tool comprising an optics system configured to generate an inspection beam and emit the inspection beam on the object arranged on the object support module. Advantageously, less particles and/or dirt are present, resulting in less disturbance of the inspection beam.
In an embodiment of either of the apparatuses according to the invention, the object comprises a substrate, wherein the apparatus further comprises a mask support for holding a patterning device having a pattern, and projection system for projecting the pattern onto the substrate when the object is arranged on the object support module. Advantageously, less particles and/or dirt are present, resulting in more accurate projection of the pattern.
Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which:
In the present document, the terms “radiation” and “beam” are used to encompass all types of electromagnetic radiation, including ultraviolet radiation (e.g. with a wavelength of 365, 248, 193, 157 or 126 nm) and EUV (extreme ultra-violet radiation, e.g. having a wavelength in the range of about 5-100 nm).
The term “reticle”, “mask” or “patterning device” as employed in this text may be broadly interpreted as referring to a generic patterning device that can be used to endow an incoming radiation beam with a patterned cross-section, corresponding to a pattern that is to be created in a target portion of the substrate. The term “light valve” can also be used in this context. Besides the classic mask (transmissive or reflective, binary, phase-shifting, hybrid, etc.), examples of other such patterning devices include a programmable mirror array and a programmable LCD array.
In operation, the illumination system IL receives a radiation beam from a radiation source SO, e.g. via a beam delivery system BD. The illumination system IL may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic, and/or other types of optical components, or any combination thereof, for directing, shaping, and/or controlling radiation. The illuminator IL may be used to condition the radiation beam B to have a desired spatial and angular intensity distribution in its cross section at a plane of the patterning device MA.
The term “projection system” PS used herein should be broadly interpreted as encompassing various types of projection system, including refractive, reflective, catadioptric, anamorphic, magnetic, electromagnetic and/or electrostatic optical systems, or any combination thereof, as appropriate for the exposure radiation being used, and/or for other factors such as the use of an immersion liquid or the use of a vacuum. Any use of the term “projection lens” herein may be considered as synonymous with the more general term “projection system” PS.
The lithographic apparatus LA may be of a type wherein at least a portion of the substrate may be covered by a liquid having a relatively high refractive index, e.g., water, so as to fill a space between the projection system PS and the substrate W—which is also referred to as immersion lithography. More information on immersion techniques is given in U.S. Pat. No. 6,952,253, which is incorporated herein by reference.
The lithographic apparatus LA may also be of a type having two or more substrate supports WT (also named “dual stage”). In such “multiple stage” machine, the substrate supports WT may be used in parallel, and/or steps in preparation of a subsequent exposure of the substrate W may be carried out on the substrate W located on one of the substrate support WT while another substrate W on the other substrate support WT is being used for exposing a pattern on the other substrate W.
In addition to the substrate support WT, the lithographic apparatus LA may comprise a measurement stage. The measurement stage is arranged to hold a sensor and/or a cleaning device. The sensor may be arranged to measure a property of the projection system PS or a property of the radiation beam B. The measurement stage may hold multiple sensors. The cleaning device may be arranged to clean part of the lithographic apparatus, for example a part of the projection system PS or a part of a system that provides the immersion liquid. The measurement stage may move beneath the projection system PS when the substrate support WT is away from the projection system PS.
In operation, the radiation beam B is incident on the patterning device, e.g. mask, MA which is held on the mask support MT, and is patterned by the pattern (design layout) present on patterning device MA. Having traversed the patterning device MA, the radiation beam B passes through the projection system PS, which focuses the beam onto a target portion C of the substrate W. With the aid of the second positioner PW and a position measurement system IF, the substrate support WT can be moved accurately, e.g., so as to position different target portions C in the path of the radiation beam B at a focused and aligned position. Similarly, the first positioner PM and possibly another position sensor (which is not explicitly depicted in
To clarify the invention, a Cartesian coordinate system is used. The Cartesian coordinate system has three axis, i.e., an x-axis, a y-axis and a z-axis. Each of the three axis is orthogonal to the other two axis. A rotation around the x-axis is referred to as an Rx-rotation. A rotation around the y-axis is referred to as an Ry-rotation. A rotation around about the z-axis is referred to as an Rz-rotation. The x-axis and the y-axis define a horizontal plane, whereas the z-axis is in a vertical direction. The Cartesian coordinate system is not limiting the invention and is used for clarification only. Instead, another coordinate system, such as a cylindrical coordinate system, may be used to clarify the invention. The orientation of the Cartesian coordinate system may be different, for example, such that the z-axis has a component along the horizontal plane.
The second positioner PW is arranged to accelerate the substrate support WT by providing a driving force between the substrate support WT and the balance mass BM. The driving force accelerates the substrate support WT in a desired direction. Due to the conservation of momentum, the driving force is also applied to the balance mass BM with equal magnitude, but at a direction opposite to the desired direction. Typically, the mass of the balance mass BM is significantly larger than the masses of the moving part of the second positioner PW and the substrate support WT.
In an embodiment, the second positioner PW is supported by the balance mass BM. For example, wherein the second positioner PW comprises a planar motor to levitate the substrate support WT above the balance mass BM. In another embodiment, the second positioner PW is supported by the base frame BF. For example, wherein the second positioner PW comprises a linear motor and wherein the second positioner PW comprises a bearing, like a gas bearing, to levitate the substrate support WT above the base frame BF.
The position measurement system PMS may comprise any type of sensor that is suitable to determine a position of the substrate support WT. The position measurement system PMS may comprise any type of sensor that is suitable to determine a position of the mask support MT. The sensor may be an optical sensor such as an interferometer or an encoder. The position measurement system PMS may comprise a combined system of an interferometer and an encoder. The sensor may be another type of sensor, such as a magnetic sensor. a capacitive sensor or an inductive sensor. The position measurement system PMS may determine the position relative to a reference, for example the metrology frame MF or the projection system PS. The position measurement system PMS may determine the position of the substrate table WT and/or the mask support MT by measuring the position or by measuring a time derivative of the position, such as velocity or acceleration.
The position measurement system PMS may comprise an encoder system. An encoder system is known from for example, United States patent application US2007/0058173A1, filed on Sep. 7, 2006, hereby incorporated by reference. The encoder system comprises an encoder head, a grating and a sensor. The encoder system may receive a primary radiation beam and a secondary radiation beam. Both the primary radiation beam as well as the secondary radiation beam originate from the same radiation beam, i.e., the original radiation beam. At least one of the primary radiation beam and the secondary radiation beam is created by diffracting the original radiation beam with the grating. If both the primary radiation beam and the secondary radiation beam are created by diffracting the original radiation beam with the grating, the primary radiation beam needs to have a different diffraction order than the secondary radiation beam. Different diffraction orders are, for example,+1st order, −1st order, +2nd order and −2nd order. The encoder system optically combines the primary radiation beam and the secondary radiation beam into a combined radiation beam. A sensor in the encoder head determines a phase or phase difference of the combined radiation beam. The sensor generates a signal based on the phase or phase difference. The signal is representative of a position of the encoder head relative to the grating. One of the encoder head and the grating may be arranged on the substrate structure WT. The other of the encoder head and the grating may be arranged on the metrology frame MF or the base frame BF. For example, a plurality of encoder heads are arranged on the metrology frame MF, whereas a grating is arranged on a top surface of the substrate support WT. In another example, a grating is arranged on a bottom surface of the substrate support WT, and an encoder head is arranged below the substrate support WT.
The position measurement system PMS may comprise an interferometer system. An interferometer system is known from, for example, United States patent U.S. Pat. No. 6,020,964, filed on Jul. 13, 1998, hereby incorporated by reference. The interferometer system may comprise a beam splitter, a mirror, a reference mirror and a sensor. A beam of radiation is split by the beam splitter into a reference beam and a measurement beam. The measurement beam propagates to the mirror and is reflected by the mirror back to the beam splitter. The reference beam propagates to the reference mirror and is reflected by the reference mirror back to the beam splitter. At the beam splitter, the measurement beam and the reference beam are combined into a combined radiation beam. The combined radiation beam is incident on the sensor. The sensor determines a phase or a frequency of the combined radiation beam. The sensor generates a signal based on the phase or the frequency. The signal is representative of a displacement of the mirror. In an embodiment, the mirror is connected to the substrate support WT. The reference mirror may be connected to the metrology frame MF. In an embodiment, the measurement beam and the reference beam are combined into a combined radiation beam by an additional optical component instead of the beam splitter.
The first positioner PM may comprise a long-stroke module and a short-stroke module. The short-stroke module is arranged to move the mask support MT relative to the long-stroke module with a high accuracy over a small range of movement. The long-stroke module is arranged to move the short-stroke module relative to the projection system PS with a relatively low accuracy over a large range of movement. With the combination of the long-stroke module and the short-stroke module, the first positioner PM is able to move the mask support MT relative to the projection system PS with a high accuracy over a large range of movement. Similarly, the second positioner PW may comprise a long-stroke module and a short-stroke module. The short-stroke module is arranged to move the substrate support WT relative to the long-stroke module with a high accuracy over a small range of movement. The long-stroke module is arranged to move the short-stroke module relative to the projection system PS with a relatively low accuracy over a large range of movement. With the combination of the long-stroke module and the short-stroke module, the second positioner PW is able to move the substrate support WT relative to the projection system PS with a high accuracy over a large range of movement.
The first positioner PM and the second positioner PW each are provided with an actuator to move respectively the mask support MT and the substrate support WT. The actuator may be a linear actuator to provide a driving force along a single axis, for example the y-axis. Multiple linear actuators may be applied to provide driving forces along multiple axis. The actuator may be a planar actuator to provide a driving force along multiple axis. For example, the planar actuator may be arranged to move the substrate support WT in 6 degrees of freedom. The actuator may be an electro-magnetic actuator comprising at least one coil and at least one magnet. The actuator is arranged to move the at least one coil relative to the at least one magnet by applying an electrical current to the at least one coil. The actuator may be a moving-magnet type actuator, which has the at least one magnet coupled to the substrate support WT respectively to the mask support MT. The actuator may be a moving-coil type actuator which has the at least one coil coupled to the substrate support WT respectively to the mask support MT. The actuator may be a voice-coil actuator, a reluctance actuator, a Lorentz-actuator or a piezo-actuator, or any other suitable actuator.
The lithographic apparatus LA comprises a position control system PCS as schematically depicted in
After the pattern is projected onto the substrate W, a metrology tool may be used to measure properties of the substrate, e.g. overlay or critical dimension. The present invention may be applied to such a metrology tool. In other embodiments, the present invention can be applied to a lithography apparatus or an inspection tool.
The net gas flow is the resulting gas flow in the apparatus 100. In
In an embodiment, the object support module 110 is moveable at least in a two-dimensional plane d1, d2, which optionally is a substantially horizontal plane d1,d2. The apparatus 100 further comprises a first measurement system 102 for determining a position of the object support module 110 in at least a first direction d1 in the two-dimensional plane d1, d2. The first measurement system 102 is adapted to emit a first measurement beam 104 along an optical path 104a, 104b to the object support module 110, wherein the net gas flow further covers at least a part of the optical path 104a, 104b of the first measurement beam 104. In this embodiment, the first measurement beam 104 thus travels through and is being conditioned by gas that has been emitted by the first gas shower 120, as is illustrated in
In an embodiment, the apparatus 100 further comprises a gas guiding element 171, which is visible in
In an embodiment, the apparatus 100 further comprises a second gas shower 130. The second gas shower 130 is adapted to emit gas with a second velocity in a second gas direction towards a second side 112 of the object support module 110, wherein the second side 112 is facing away from the first side 111. In
In an embodiment, the second gas direction comprises a vertical component. This may be advantageous to direct the net gas flow towards the first exhaust 140, e.g. when the first exhaust 140 is arranged at a lower level than the second gas shower 130 and/or the object support module 110. The second gas shower 130 is optionally arranged at a higher level than the object support module 110 and/or the fist gas shower 120, as is shown in
In an embodiment, the first velocity is greater than the second velocity, preferably at least five times greater, more preferably at least ten times greater, e.g. at least twenty times greater. Since the first gas shower 120 emits gas at a greater velocity than the second gas shower 130, the net gas flow is primarily determined by the first gas shower 120, at least above the object support module 110.
In an embodiment, the second velocity is between 0.01 m/s-1 m/s, preferably between 0.05 m/s-0.5 m/s, more preferably 0.05-0.2 m/s, e.g. 0.1 m/s. It has been found that this is sufficient to ensure that the net gas flow is as desired, in the shown example towards the first exhaust 140.
In an embodiment, the first velocity is between 0.5-5 m/s, preferably between 1-4 m/s, e.g. 2.5 m/s. In an embodiment, the first velocity is such that a velocity of the net gas flow is at least 1 m/s along the optical path 104a, 104b of the first measurement beam 104 and/or above the object support module 110. It has been found that in these embodiments the first velocity is sufficient to ensure that no particles and/or dirt end up on the object 101, and/or to ensure that the properties of the gas through which the first measurement beam 104 travels are determined by the gas emitted by the first gas shower 120.
In an embodiment, the first measurement system 102 comprises an interferometer 106. For example, the interferometer 106 may be adapted to determine the position of the object support module 110 and/or the object 101 based on a distance travelled by the first measurement beam 104. For example, the optical element 105 may be a beam splitter or the first measurement system 102 may comprise a beam splitter on another location. The beam splitter is arranged to split the first measurement beam 104 in two sub-beams, of which one is directed towards the object support module 110. The first measurement system 102 may be adapted to determine the position of the object support module 110 based on a phase-difference between the two sub-beams. The first measurement beam 104 may e.g. be directed by a reflective surface 113 that is arranged on the first side 111 of the object support module 110. In the shown embodiment, the first measurement beam 104 is directed back to the interferometer 106, wherein the interferometer 106 comprises a detector. It is also possible that the detector is arranged on a different position in the apparatus 100, wherein the first measurement beam 104 is directed towards said detector by the reflective surface 113.
In an embodiment, the first gas shower 120 is adapted to emit the gas towards at least a part of the second optical path. In this embodiment, the second measurement beam 108 travels at least partly through the gas emitted by the first gas shower 120, of which the properties may be predetermined and/or known. The accuracy of the determination of the position of the object support module 110 in the second direction d2 can as such be improved. As can be seen in
In an embodiment, the apparatus 100 further comprises a process tool 160, which may e.g. be adapted to be arranged substantially above the object 101 in operational use. For example, the process tool 160 may be used to perform the metrology process of lithographic process to which the object 101 is subjected. The object support module 110 may e.g. be used to position the object 101 below the process tool 160. The process tool 160 may e.g. be adapted to emit a radiation beam 161 onto the object 101, as is illustrated in
In an embodiment, the apparatus 100 is a metrology tool, comprising an optics system configured to generate an optical measurement beam 161 and emit the optical measurement beam 161 on the object 101 arranged on the object support module 110. For example, the metrology tool may be used to make overlay and/or critical dimension measurements of an object 101 that has been subjected to a lithographic process. In this embodiment, the optics system may e.g. be arranged in the process tool 160 and/or the optical measurement beam 161 may be directed through the process tool 160.
In an embodiment, the apparatus 100 is an inspection tool comprising an optics system configured to generate an inspection beam 161 and emit the inspection beam 161 on the object 101 arranged on the object support module 110. The inspection tool may e.g. be used to inspect an object 101 that has been subjected to a lithographic process. In this embodiment, the optics system may e.g. be arranged in the process tool 160 and/or the inspection beam 161 may be directed through the process tool 160.
In an embodiment, the object 101 comprises a substrate, wherein the apparatus 100 further comprises a mask support for holding a patterning device having a pattern, and projection system for projecting the pattern onto the substrate when the object 101 is arranged on the object support module 110. The pattern may e.g. be projected onto the substrate by means of the radiation beam 161. For example, the apparatus 100 may be a lithographic apparatus LA as illustrated in
Whereas in the shown embodiment the second support module 210 is provided, it embodiments it is also possible that the object support module 110 comprises a first object table for holding the object 101 and a second object table for holding the second object 201. The first gas shower 120 is adapted to cause the net gas flow in the apparatus 100 to be a substantially horizontal gas flow in the first gas direction at least above the first object table and the second object table.
In an embodiment, the apparatus 100 further comprises a second measurement system 202 for determining a position of the second object support module 210 in at least a fourth direction which is in the two-dimensional plane d1, d2. In the shown embodiment, the fourth direction is parallel to the first direction d1. The second measurement system is adapted to emit a third measurement beam 204 along a third optical path to the second object support module 210. The first gas shower 120 is adapted to cause the net gas flow in the apparatus 100 to cover at least a part of the third optical path of the third measurement beam 204. Optionally, the second measurement system 202 comprises an interferometer 206. Optionally, a third reflective surface 213 is arranged on the second object support module 210 for directing the third measurement beam 204 towards a detector. Optionally, the second measurement system 202 comprises a second interferometer 207 adapted to emit a fourth measurement beam 208 towards the second object support module 210, wherein e.g. a fourth reflective surface 218 is arranged on the second object support module 210 for directing the fourth measurement beam 208 towards a detector.
The gas may be, for example, a conditioned gas, an inert gas, a gas mixture, air, or a different gas. The gas may be ultra clean air of purity class 1, or air of purity class 2 or purity class 3. The temperature of the gas may be relatively stable, for example, stable within 0.10 degrees C. or stable within 0.0010 degrees C. It is known from the prior art how such a thermally stable gas may be provided.
Each of the gas showers 120, 130 may be arranged and configured in various ways. For example, each gas shower 120, 130 may include one or more suitable gas outlet sides to disperse laminar gas flows into the apparatus 100. Each of the outlet sides may be provided, for example, with a porous material, a suitable gas disperser, monofilament cloth, one or more sheets having gas apertures, or a different gas distributor. Each gas shower outlet sides may include one or more layers of one or more materials. The outlet sides may be a wall or wall part of an upstream gas distribution chamber of the respective gas showers, or the outlet sides may be provided in such a wall or a wall part. In the shown embodiment, during use, the gas flows 121, 131 flow substantially perpendicularly from the respective outlet sides. In an embodiment, each gas shower 120, 130, or respective gas outlet side is configured to generate a substantially uniform laminar gas flow from gas that is being supplied to the gas shower during use.
In these embodiments, the second positioner 117 may be used for relatively large movements of the object 101, and the first positioner 116 for smaller movements, which e.g. require more accuracy. The first positioner 116 and/or the second positioner 117 may comprise actuators. Said actuators may e.g. mechanical actuator, piezo-actuators, or contactless actuators, e.g. electromagnetic actuators such as Lorentz-actuators
In an embodiment, the apparatus 100 further comprises a measurement frame 150, wherein the object support module 110 is adapted to move relative to the measurement frame 150. The apparatus 100 further comprises a vertical measurement system for determining a position of the object support module 110 in a substantially vertical direction d3. The vertical measurement system comprises: at least one contactless sensor 301, 401 arranged on the object support module 110; and a conductive element 311, 411 for detecting the contactless sensor 301, 401. The conductive element 311, 411 is arranged on the measurement frame 150.
The vertical measurement system allows to determine the position of the object 101 in the vertical direction d1. The use of contactless sensors 301, 401 has been found advantageous, as it is a relatively simple arrangement which does not disturb the object 101 or the metrology process of lithographic process to which the object 101 is subjected. This is in particular an advantage in view of prior art systems which use e.g. interferometer systems to determine the position in the vertical direction. Furthermore, the vertical measurement system as shown in
In the present example, the first gas shower is arranged at the first side of the object support module 110. This is a particular advantage in view of prior art systems that provide gas showers above the object support module 110, because space is provided for arranging the conductive elements 311, 411. Nevertheless, it is explicitly noted that these embodiments of the vertical measurement system may be applied with or without being combined with the first gas shower and/or second gas shower as described herein.
In an embodiment, the at least one contactless sensor 301 is arranged on the object table 114. This ensures that movements of the object table 114 relative to the long stroke module 115 are taken into account when using the vertical measurement system.
In an embodiment, the at least one contactless sensor 401 is arranged on the long stroke module 115. In general, the long stroke module 115 may have more space available to position the at least one contactless sensor.
In an embodiment, the at least one contactless sensor 301, 401 is a capacitive sensor or an eddy current sensor. It has been found that such sensors provide sufficient accuracy, while being relatively simple to implement and without disturbing the metrology process or lithographic process.
In an embodiment, the vertical measurement system comprises at least three contactless sensors 301, 401, wherein the vertical measurement system is adapted to determine a position of the object support module 110 in the vertical direction, a rotation of the object support module 110 around a first horizontal axis, and a rotation of the object support module 110 around a second horizontal axis. Having three contactless sensors 301, 401 allows determining three degrees of freedom. In an embodiment, the vertical measurement system comprises four contactless sensors 301, 401, e.g. each being arranged close to a corner of the object table 114 or long stroke module 115.
It is noted that in embodiments wherein the apparatus 100 comprises a second object support module 210 as e.g. shown in
Further embodiments are disclosed in the subsequent numbered clauses:
1. Apparatus for use in a metrology process or a lithographic process, the apparatus comprising:
Although specific reference may be made in this text to the use of a lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein may have other applications. Possible other 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.
Although specific reference may be made in this text to embodiments of the invention in the context of a lithographic apparatus, embodiments of the invention may be used in other apparatus. Embodiments of the invention may form part of a mask inspection apparatus, a metrology apparatus, or any apparatus that measures or processes an object such as a wafer (or other substrate) or mask (or other patterning device). These apparatus may be generally referred to as lithographic tools. Such a lithographic tool may use vacuum conditions or ambient (non-vacuum) conditions.
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, where the context allows, is not limited to optical lithography and may be used in other applications, for example imprint lithography.
Where the context allows, embodiments of the invention may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the invention may also be implemented as instructions stored on a machine-readable medium, which may be read and executed by one or more processors. A machine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine-readable medium may include read only memory (ROM); random access memory (RAM); magnetic storage media; optical storage media; flash memory devices; electrical, optical, acoustical or other forms of propagated signals (e.g. carrier waves, infrared signals, digital signals, etc.), and others. Further, firmware, software, routines, instructions may be described herein as performing certain actions. However, it should be appreciated that such descriptions are merely for convenience and that such actions in fact result from computing devices, processors, controllers, or other devices executing the firmware, software, routines, instructions, etc. and in doing that may cause actuators or other devices to interact with the physical world.
While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. The descriptions above are intended to be illustrative, not limiting. Thus it will be apparent to one skilled in the art that modifications may be made to the invention as described without departing from the scope of the claims set out below.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20178785.0 | Jun 2020 | EP | regional |
This application claims priority of EP application 20178785.0 which was filed on 8 Jun. 2020, and which is incorporated herein in its entirety by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/064255 | 5/27/2021 | WO |
