NL2008468A - Lithographic apparatus and device manufacturing method. - Google Patents

Description

LITHOGRAPHIC APPARATUS AND DEVICE MANUFACTURING METHOD

FIELD

[0001] The present invention relates to a lithographic apparatus and a method for manufacturing a device.

BACKGROUND

[0002] A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In such a case, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g. including part of, one, or several dies) on a substrate (e.g. a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Conventional lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at once, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the “scanning”-direction) while synchronously scanning the substrate parallel or anti-parallel to this direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.

[0003] To assure a good positioning of the substrate it may be necessary to put a measurement system to measure an operational parameter in the apparatus as close as possible to the substrate. It may be necessary to easily replace the substrate table itself in the lithographic apparatus.

SUMMARY

[0004] It is desirable to provide an improved lithographic apparatus.

[0005] According to an embodiment of the invention, there is provided a lithographic apparatus comprising: an illumination system configured to condition a radiation beam; a support constructed to support a patterning device, the patterning device being capable of imparting the radiation beam with a pattern in its cross-section to form a patterned radiation beam; a substrate table constructed to hold a substrate; a measurement system to measure an operational parameter in the apparatus; and, a projection system configured to project the patterned radiation beam onto a target portion of the substrate, wherein the apparatus is provided with a substrate chuck to clamp the substrate table and at least a portion of the measurement system is provided to the substrate table.

[0006] According to a further embodiment there is provided an apparatus comprising: a substrate table constructed to hold a substrate; and, a measurement system to measure an operational parameter in the apparatus; wherein the apparatus is provided with a substrate chuck to clamp the substrate table and at least a portion of the measurement system is provided to the substrate table.

[0007] According to an embodiment of the invention, there is provided a device manufacturing method comprising: transferring a pattern from a patterning device onto a substrate; moving a substrate chuck clamping a substrate table for holding a substrate; and, measuring an operational parameter of the apparatus with a measurement system being at least partially provided to the substrate table.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

[0009] Figure 1 depicts a lithographic apparatus according to an embodiment of the invention;

[0010] Figure 2 depicts a portion of the apparatus of Figure 1 according to an embodiment of the invention;

[0011] Figure 3 depicts a portion of the apparatus of Figure 1 according to a further embodiment of the invention;

[0012] Figure 4 depicts a portion of the apparatus of Figure 1 according to a further embodiment of the invention; and,

[0013] Figure 5 depicts a portion of the apparatus of Figure 4.

DETAILED DESCRIPTION

[0014] Figure 1 schematically depicts a lithographic apparatus according to one embodiment of the invention. The apparatus includes an illumination system (illuminator) IL configured to condition a radiation beam B (e.g. UY radiation or any other suitable radiation), a patterning device support or mask support structure (e.g. a mask table) MT constructed to support a patterning device (e.g. a mask) MA and connected to a first positioning device PM configured to accurately position the patterning device in accordance with certain parameters. The apparatus also includes a substrate table (e.g. a wafer table) WT or "substrate support" constructed to hold a substrate (e.g. a resist-coated wafer) W and moveable by a second positioning device PW configured to accurately position the substrate in accordance with certain parameters. The apparatus further includes a projection system (e.g. a refractive projection lens system) PS configured to project a pattern imparted to the radiation beam B by patterning device MA onto a target portion C (e.g. including one or more dies) of the substrate W.

[0015] The illumination system may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic or other types of optical components, or any combination thereof, to direct, shape, or control radiation.

[0016] The patterning device support holds the patterning device in a manner that depends on the orientation of the patterning device, the design of the lithographic apparatus, and other conditions, such as for example whether or not the patterning device is held in a vacuum environment. The patterning device support can use mechanical, vacuum, electrostatic or other clamping techniques to hold the patterning device. The patterning device support may be a frame or a table, for example, which may be fixed or movable as required. The patterning device support may ensure that the patterning device is at a desired position, for example with respect to the projection system. Any use of the terms “reticle” or “mask” herein may be considered synonymous with the more general term “patterning device.”

[0017] The term “patterning device” used herein should be broadly interpreted as referring to any device that can be used to impart a radiation beam with a pattern in its cross-section so as to create a pattern in a target portion of the substrate. It should be noted that the pattern imparted to the radiation beam may not exactly correspond to the desired pattern in the target portion of the substrate, for example if the pattern includes phase-shifting features or so called assist features. Generally, the pattern imparted to the radiation beam will correspond to a particular functional layer in a device being created in the target portion, such as an integrated circuit.

[0018] The patterning device may be transmissive or reflective. Examples of patterning devices include masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in lithography, and include mask types such as binary, alternating pbase-shift, and attenuated phase-shift, as well as various hybrid mask types. An example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be individually tilted so as to reflect an incoming radiation beam in different directions. The tilted mirrors impart a pattern in a radiation beam which is reflected by the mirror matrix.

[0019] The term “projection system” used herein should be broadly interpreted as encompassing any type of projection system, including refractive, reflective, catadioptric, magnetic, electromagnetic and electrostatic optical systems, or any combination thereof, as appropriate for the exposure radiation being used, 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”.

[0020] As here depicted, the apparatus is of a transmissive type (e.g. employing a transmissive mask). Alternatively, the apparatus may be of a reflective type (e.g. employing a programmable mirror array of a type as referred to above, or employing a reflective mask).

[0021] The lithographic apparatus may be of a type having two (dual stage) or more substrate tables or "substrate supports" (and/or two or more mask tables or "mask supports"). In such “multiple stage” machines the additional tables or supports may be used in parallel, or preparatory steps may be carried out on one or more tables or supports while one or more other tables or supports are being used for exposure.

[0022] The lithographic apparatus may also 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 and the substrate. An immersion liquid may also be applied to other spaces in the lithographic apparatus, for example, between the mask and the projection system. Immersion techniques can be used to increase the numerical aperture of projection systems. The term “immersion” as used herein does not mean that a structure, such as a substrate, must be submerged in liquid, but rather only means that a liquid is located between the projection system and the substrate during exposure.

[0023] Referring to Figure 1, the illuminator IL receives a radiation beam from a radiation source SO. The source and the lithographic apparatus may be separate entities, for example when the source is an excimer laser. In such cases, the source is not considered to form part of the lithographic apparatus and the radiation beam is passed from the source SO to the illuminator IL with the aid of a beam delivery system BD including, for example, suitable directing mirrors and/or a beam expander. In other cases the source may be an integral part of the lithographic apparatus, for example when the source is a mercury lamp. The source SO and the illuminator IL, together with the beam delivery system BD if required, may be referred to as a radiation system.

[0024] The illuminator IL may include an adjuster AD configured to adjust the angular intensity distribution of the radiation beam. Generally, at least the outer and/or inner radial extent (commonly referred to as σ-outer and σ-inner, respectively) of the intensity distribution in a pupil plane of the illuminator can be adjusted. In addition, the illuminator IL may include various other components, such as an integrator IN and a condenser CO. The illuminator may be used to condition the radiation beam, to have a desired uniformity and intensity distribution in its cross-section.

[0025] The radiation beam B is incident on the patterning device (e.g., mask) MA, which is held on the patterning device support (e.g., mask table MT, and is patterned by the patterning device. Having traversed the patterning device (e.g. mask) 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 positioning device PW and position sensor IF (e.g. an interferometric device, linear encoder or capacitive sensor), the substrate table WT can be moved accurately, e.g. so as to position different target portions C in the path of the radiation beam B. Similarly, the first positioning device PM and another position sensor (which is not explicitly depicted in Figure 1) can be used to accurately position the patterning device (e.g. mask) MA with respect to the path of the radiation beam B, e.g. after mechanical retrieval from a mask library, or during a scan. In general, movement of the patterning device support (e.g. mask table) MT may be realized with the aid of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning), which form part of the first positioning device PM. Similarly, movement of the substrate table WT or "substrate support" may be realized using a long-stroke module and a short-stroke module, which form part of the second positioner PW. In the case of a stepper (as opposed to a scanner) the patterning device support (e.g. mask table) MT may be connected to a short-stroke actuator only, or may be fixed. Patterning device (e.g. mask) MA and substrate W may be aligned using patterning device alignment marks Ml, M2 and substrate alignment marks PI, P2. Although the substrate alignment marks as illustrated occupy dedicated target portions, they may be located in spaces between target portions (these are known as scribe-lane alignment marks). Similarly, in situations in which more than one die is provided on the patterning device (e.g. mask) MA, the mask alignment marks may be located between the dies.

[0026] The depicted apparatus could be used in at least one of the following modes:

[0027] 1. In step mode, the patterning device support (e.g. mask table) MT or "mask support" and the substrate table WT or "substrate support" are kept essentially stationary, while an entire pattern imparted to the radiation beam is projected onto a target portion C at one time (i.e. a single static exposure). The substrate table WT or "substrate support" is then shifted in the X and/or Y direction so that a different target portion C can be exposed. In step mode, the maximum size of the exposure field limits the size of the target portion C imaged in a single static exposure.

[0028] 2. In scan mode, the patterning device support (e.g. mask table) MT or "mask support" and the substrate table WT or "substrate support" are scanned synchronously while a pattern imparted to the radiation beam is projected onto a target portion C (i.e. a single dynamic exposure). The velocity and direction of the substrate table WT or "substrate support" relative to the mask table MT or "mask support" may be determined by the (de-)magnification and image reversal characteristics of the projection system PS. In scan mode, the maximum size of the exposure field limits the width (in the non-scanning direction) of the target portion in a single dynamic exposure, whereas the length of the scanning motion determines the height (in the scanning direction) of the target portion.

[0029] 3. In another mode, the patterning device support (e.g. mask table) MT or "mask support" is kept essentially stationary holding a programmable patterning device, and the substrate table WT or "substrate support" is moved or scanned while a pattern imparted to the radiation beam is projected onto a target portion C. In this mode, generally a pulsed radiation source is employed and the programmable patterning device is updated as required after each movement of the substrate table WT or "substrate support" or in between successive radiation pulses during a scan. This mode of operation can be readily applied to maskless lithography that utilizes programmable patterning device, such as a programmable mirror array of a type as referred to above.

[0030] Combinations and/or variations on the above described modes of use or entirely different modes of use may also be employed.

[0031] Figure 2 depicts a portion of the lithographic apparatus of Figure 1. The substrate table WT holds a substrate W and the substrate table WT is provided with a measurement system e.g. position measurement system PMS. In the embodiment of Figure 2, the measurement system is an optical measurement system. The position measurement system PMS may be an optical encoder system which may be used to determine an operational parameter of the apparatus e.g. a position of the substrate table WT with respect to a reference pattern e.g. a grating. The substrate table WT may be provided with other measurement systems, for example it may be provided with a radiation sensor TMS configured to measure an operational parameter of the apparatus. The radiation sensor may be an example of an optical measurement system. The radiation sensor IMS may be an image sensor or a lens interferometer system. The image sensor may measure as the operational parameter a position of an aerial image created by the patterning device, irradiated by the illumination system, which image is projected via the projection system on the radiation sensor IMS. The position of the aerial image may be used to determine alignment of the substrate marks PI, P2 on the substrate W with respect to the alignment marks Ml, M2 of the pattern on the patterning device MA. The lens interferometer system may measure wave front aberrations across a full image field of the projection system PL (in Figure 1) as an operational parameter of the apparatus.

[0032] The substrate table WT may be clamped on a substrate chuck CW. Multiple kinematic interfaces KI may be used to clamp the substrate table WT to the substrate chuck CW. The multiple kinematic interfaces KI are stiff in a direction of the arrow while being flexible in directions perpendicular thereto. Using kinematic interfaces KI may preserve the integrity of the substrate table WT. The position of the substrate table WT in a direction substantially perpendicular to the main surface of the substrate table may be over determined by the multiple (four are shown) kinematic interfaces KI having stiffness in the perpendicular direction. The flexible mode shapes from the substrate table WT in a direction substantially perpendicular to the main surface may be suppressed in this way. The substrate table WT and the substrate chuck CW may be made from the same material, for example SiSiC, SiC, Zerodur (R) or Cordierite. Making both the substrate table WT and the substrate chuck CW from the same material may be favorable from manufacturability and dynamic point of view. The apparatus is provided with a short stroke actuator to exert a force over a relatively short range between the substrate chuck WT and a long stroke carrier LSC moveable over a relatively long range. The substrate chuck WT and the long stroke carrier LSC may also be made form the same material, for example SiSiC, SiC, Zerodur (R) or Cordierite. This may be favorable from manufacturability and dynamic point of view. The long stroke carrier LSC is moveable by a long stroke actuator which exerts a force between the long stoke carrier LSC and a portion of the apparatus over a relatively long range.

[0033] According to an embodiment of the invention, the active components AC of the measurement system may be provided to the substrate chuck CW while the passive components PC of the measurement system may be provided to the substrate table WT (see Figure 3). The passive components PC may comprise one or more of lenses, gratings, coatings, mirrors and or fibers. For example if the measurement system (e.g. optical encoder) is a position measurement system PMS, the passive components PC may comprise a grating, a comercube mirror or a lens. If the measurement system is a radiation sensor for example an image sensor or a lens interferometer system the passive components may comprise lenses, gratings, coatings, mirrors and or fibers as well. The active components AC of the measurement system may be provided to the substrate chuck CW. The active components AC may comprise one or more of radiation sources and radiation sensors. The active components AC may be electrically connected to other parts of the apparatus. A benefit of this arrangement may be that the passive components do not need a connection with the outside word so that there may not be a dynamic shortcut to the substrate table WT. The passive components in this arrangement also may not dissipate heat to the substrate table WT. The active components that need to connect to the rest of the apparatus and may dissipate heat may not influence the substrate table because they are located in the substrate chuck CW.

[0034] Figure 4 depicts another embodiment of the invention. The active components AC of the measurement system may be provided to the long stroke carrier LSC while the passive components PC of the measurement systems may be provided to the substrate table WT and/or the substrate chuck CW. In this embodiment there is even no physical connection for providing electricity, light or control data to the substrate chuck VC necessary. The substrate chuck VC and/or the substrate table WT is therefore dynamically isolated from the rest of the apparatus which is beneficial because there may be less vibrations of the substrate table WT. The left part of Figure 4 discloses that no passive components PC are provided to the substrate table WT. The right part of Figure 4 discloses that passive components are provided to the substrate table WT and to the substrate chuck CW. It must be understood that the configuration on the right part of Figure 4 may also be applied to the complete substrate table, wafer chuck and long stroke carrier LSC. The other way around the configuration of the right part of Figure 4 may also be provided to the complete substrate table, wafer chuck and long stroke carrier LSC.

[0035] The substrate table WT may be provided with protrusions PR on both sides of the substrate table WT. The substrate W may be clamped with a vacuum on the protrusions PR and at the same time the substrate table WT may be clamped on the substrate chuck VC with a vacuum too. The protrusions between the substrate table and the substrate chuck CW allow a vacuum to be created between the substrate table WT and the substrate chuck CW. The vacuum creates a normal force pressing the substrate table WT against the substrate chuck CW, the friction between the protrusion and the substrate table WT makes that the substrate table WT follows the substrate chuck CW. By releasing the vacuum the substrate table is easily replaceable.

[0036] Alternatively, the vacuum clamp on one/or both sides of the substrate table WT may be replaced by an electrostatic clamp, this may be beneficial if the substrate table is used in a vacuum environment .e.g. a lithographic apparatus using extreme ultraviolet. Optionally, the substrate table WT may be provided with a fastening portion BT comprising for example a bolt or a screw to fasten the substrate table WT to the substrate chuck CW. Alternatively, the vacuum clamp and the protrusions PR may be replaced completely by one or more bolts or screws keeping the substrate table WT fixed on the substrate chuck CW. Compared to a vacuum clamp the bolts or screws provide for a very rigid connection. Replacing the substrate table WT from the substrate chuck CW may however be easier when a vacuum or electrostatic clamp may be used.

[0037] Figure 5 discloses a position measurement system PMS for use in an embodiment of the invention according to Figure 4. The position measurement system PMS is provided with an active portion mounted on the long stroke carrier LSC and comprising a laser or an light emitting diode to provide a measurement beam MB. The measurement beam may be diffracted by the reference grating RGR mounted on a reference frame. The diffracted beam may be directed to the substrate grating WTR which diffracts the beam to a comer cube mirror CM which reflects the beam back in the same direction as where it came from and the beam may traverse through the substrate table grating WTR and the reference grating RGR back to the active portion AC of the position measurement system PMS which is provided with a radiation sensitive sensor, for example a CCD or photo diode to measure a position of the reference grating RGR with respect to the reference grating of the substrate table RWT. The sensor may be connected to an electrical output or an optical fiber output for providing the measured position to a controller of the lithographic apparatus.

[0038] The measurement system may be a capacitive measurement system comprising passive components e.g. a capacitive element such as a capacitive coating or metal plate on the substrate table and an active component such as a capacitive sensor on the substrate chuck or the long stroke carrier. Capacitive sensors may be good absolute sensor which can measure a position without the need of a long calibration step.

[0039] Although specific reference may be made in this text to the use of lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein may have other applications, such as the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat-panel displays, liquid-crystal displays (LCDs), thin-film magnetic heads, etc. The skilled artisan will appreciate that, in the context of such alternative applications, any use of the terms “wafer” or “die” herein may be considered as synonymous with the more general terms “substrate” or “target portion", respectively. The substrate referred to herein may be processed, before or after exposure, in for example a track (a tool that typically applies a layer of resist to a substrate and develops the exposed resist), a metrology tool and/or an inspection tool. Where applicable, the disclosure herein may be applied to such and other substrate processing tools. Further, the substrate may be processed more than once, for example in order to create a multi-layer IC, so that the term substrate used herein may also refer to a substrate that already contains multiple processed layers.

[0040] Although specific reference may have been made above to the use of embodiments of the invention in the context of optical lithography, it will be appreciated that the invention may be used in other applications, for example imprint lithography, and where the context allows, is not limited to optical lithography. In imprint lithography a topography in a patterning device defines the pattern created on a substrate. The topography of the patterning device may be pressed into a layer of resist supplied to the substrate whereupon the resist is cured by applying electromagnetic radiation, heat, pressure or a combination thereof. The patterning device is moved out of the resist leaving a pattern in it after the resist is cured.

[0041] The terms “radiation” and “beam” used herein encompass all types of electromagnetic radiation, including ultraviolet (UV) radiation (e.g. having a wavelength of or about 365, 248, 193, 157 or 126 nm) and extreme ultra-violet (EUV) radiation (e.g. having a wavelength in the range of 5-20 nm), as well as particle beams, such as ion beams or electron beams.

[0042] The term “lens”, where the context allows, may refer to any one or combination of various types of optical components, including refractive, reflective, magnetic, electromagnetic and electrostatic optical components.

[0043] While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. For example, the invention may take the form of a computer program containing one or more sequences of machine-readable instructions describing a method as disclosed above, or a data storage medium (e.g. semiconductor memory, magnetic or optical disk) having such a computer program stored therein.

[0044] 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 clauses set out below. Other aspects of the invention are set out as in the following numbered clauses: 1 A lithographic apparatus comprising: an illumination system configured to condition a radiation beam; a support constructed configured to support a patterning device, the patterning device being capable of imparting the radiation beam with a pattern in its cross-section to form a patterned radiation beam; a substrate table constructed to hold a substrate; a measurement system configured to measure an operational parameter of the apparatus; a projection system configured to project the patterned radiation beam onto a target portion of the substrate, and a substrate chuck configured to clamp the substrate table, wherein at least a portion of the measurement system is provided to the substrate table.

2. The lithographic apparatus according to clause 1, comprising a short stroke actuator configured to exert a force over a relatively short range between the substrate chuck and a long stroke carrier moveable over a relatively long range.

3. The lithographic apparatus according to clause 2, wherein the long stroke carrier is moveable by a long stroke actuator which is configured to exert a force between the long stoke carrier and a portion of the apparatus over a relatively long range.

4. The lithographic apparatus according to any of the preceding clauses, wherein the substrate chuck and the substrate table are made from the same material.

5. The lithographic apparatus according to any of the preceding clauses, wherein the substrate chuck and the substrate table are made from SiSiC.

6. The lithographic apparatus according to any of the preceding clauses, wherein the portion of the measurement system which is provided to the substrate table comprises passive components of the measurement system.

7. The lithographic apparatus according to clause 6, wherein the passive components comprise one or more of lenses, capacitive elements, gratings, coatings, mirrors and fibers.

8. The lithographic apparatus according to any of the preceding clauses, wherein active components of the measurement system are provided to the substrate chuck.

9. The lithographic apparatus according to clause 8, wherein the active components comprise one or more of radiation sensors, capacitive sensors and illumination sources.

10. The lithographic apparatus according to any of the preceding clauses, wherein the operational parameter in the apparatus is a position of the substrate table and the measurement system is an optical measurement system provided with an incremental encoder measurement system comprising a grid plate and an encoder head.

11. The lithographic apparatus according to any of the preceding clauses, wherein the measurement system is an optical measurement system comprising a sensor configured to receive radiation from the illumination system via the projection system and the patterning device.

12. The lithographic apparatus according to any of the preceding clauses, wherein the operational parameter is the alignment position of a pattern of the patterning device with respect to the measurement system.

13. The lithographic apparatus according to any of the preceding clauses, wherein the operational parameter is an operational parameter of the illumination system and/or the projection system.

14. An apparatus comprising: a substrate table constructed to hold a substrate; and, a measurement system configured to measure an operational parameter of the apparatus; wherein the apparatus is provided with a substrate chuck to clamp the substrate table and at least a portion of the measurement system is provided to the substrate table.

15. A device manufacturing method comprising: transferring a pattern from a patterning device onto a substrate; moving a substrate chuck that clamps a substrate table, the substrate table configured to hold a substrate; and, measuring an operational parameter of the apparatus with a measurement system that is at least partially provided to the substrate table.

Claims (1)

A lithography device comprising: an exposure device adapted to provide a radiation beam; a carrier constructed to support a patterning device, the patterning device being able to apply a pattern in a section of the radiation beam to form a patterned radiation beam; a substrate table constructed to support a substrate; and a projection device adapted to project the patterned radiation beam onto a target area of the substrate, characterized in that the substrate table is adapted to position the target area of the substrate in a focal plane of the projection device.