Electrostatic clamp for use in lithography

Abstract

A lithographic apparatus having an electrostatic clamp system includes: a plurality of electrodes configured to apply an electrostatic clamping force to a component; a power source connected to the plurality of electrodes; and a controller configured to control potentials applied to the plurality of electrodes to alternate between a first mode in which an average potential of the plurality of electrodes is a first potential, and a second mode in which an average potential of the plurality of electrodes is a second potential in synchronization with generation of a radiation pulse in the lithographic apparatus. And in the second mode, the average potential of the plurality of electrodes is a second potential; and the first potential is more positive than the second potential.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to European application 23168046.3, filed on 14 April 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to a lithography apparatus having an electrostatic clamping system, a method for controlling an electrostatic clamp for holding components in the lithography apparatus, a method for manufacturing a device, and a computer program comprising instructions, when executed by a control system of the lithography apparatus, to cause the lithography apparatus to execute instructions for controlling the electrostatic clamp for holding components in the lithography apparatus, and the method for manufacturing a device comprising controlling the electrostatic clamp for holding components in the lithography apparatus. Background Technology

[0004] A photolithography apparatus is a machine that applies a desired pattern onto a substrate (typically onto a target portion of the substrate). Photolithography apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In that case, a patterning apparatus (which is alternatively referred to as a mask or photomask) can be used to generate a circuit pattern to be formed on a single layer of the IC. This pattern can be transferred onto a target portion (e.g., a portion including a die, a die, or several dies) on a substrate (e.g., a silicon wafer). Pattern transfer is typically performed by imaging onto a layer of radiation-sensitive material (resist) disposed on the substrate. Typically, a single substrate will comprise a network of adjacent target portions patterned sequentially.

[0005] Photolithography is widely considered one of the key steps in the manufacture of ICs and other devices and / or structures. However, as the size of features manufactured using photolithography becomes smaller and smaller, photolithography is becoming an even more critical factor in enabling the manufacture of smaller ICs or other devices and / or structures.

[0006] The theoretical estimate of the limit of pattern printing can be given by the Rayleigh resolution criterion as shown in equation (1):

[0007] (1)

[0008] Where λ is the wavelength of the radiation used, NA is the numerical aperture of the projection system used to print the pattern, k1 is a process-dependent adjustment factor, also known as the Rayleigh constant, and CD is the feature size (or critical size) of the printed feature. As can be seen from equation (1), the minimum printable size of the feature can be reduced in three ways: by shortening the exposure wavelength λ, by increasing the numerical aperture NA, or by decreasing the value of k1.

[0009] To shorten exposure wavelengths and thus reduce the minimum printable size, extreme ultraviolet (EUV) radiation sources have been proposed. EUV radiation is electromagnetic radiation with wavelengths in the range of 10 nm to 20 nm (e.g., in the range of 13 nm to 14 nm). It has been further proposed that EUV radiation with wavelengths less than 10 nm (e.g., in the range of 5 nm to 10 nm, such as 6.7 nm or 6.8 nm) can be used. Such radiation is referred to as extreme ultraviolet radiation or soft X-ray radiation. Possible sources include, for example, laser-generated plasma sources, discharge plasma sources, or sources based on synchrotron radiation provided by an electron storage ring.

[0010] Once EUV radiation has been generated, it is guided by multiple mirrors through a photolithography device to the patterned surface of a patterning apparatus, which imparts the desired pattern to the EUV radiation.

[0011] During the operation of a photolithography apparatus, a high-voltage electrostatic chuck can be used to hold the patterning apparatus. The environment surrounding the patterning apparatus and the electrostatic chuck can be maintained at a low voltage. This environment can be non-conductive. Therefore, charge can accumulate on the dielectric or ungrounded surface of the patterned surface of the patterning apparatus, such as the patterning surface.

[0012] Due to the photoelectric effect, EUV radiation incident on a patterned surface can cause electrons to escape from the patterned surface and enter the environment surrounding the patterning apparatus. This can make the patterned surface positively charged. EUV radiation can excite hydrogen molecules within the environment surrounding the patterning apparatus to form a plasma. Electrons emitted from the patterned surface can also contribute to this plasma. The free negative charge in the plasma can make contaminant particles in the environment surrounding the patterning apparatus negatively charged. Negatively charged contaminant particles can be attracted to the positively charged patterned surface. Therefore, contaminant particles may be deposited on the patterned surface. Contaminant particles deposited on the patterned surface may absorb and / or scatter EUV radiation incident on the patterned surface. Therefore, contaminant particles may cause defects in the pattern projected onto the substrate, potentially leading to defects in the substrate.

[0013] EUV radiation can be generated in pulses. During the period between pulses, the patterned surface can be discharged by free negative charges in the plasma (i.e., become less positively charged).

[0014] When the coating is positioned in front of the patterning apparatus, both the patterning apparatus and the coating can become positively charged through EUV radiation. During the period between pulses, the negative charge in the plasma can cause the coating to become less positively or less negatively charged. The patterned surface may not discharge through the negative charge, thus remaining positively charged. Therefore, an electric field can exist between the negatively charged coating and the positively charged patterned surface. This electric field may induce electrostatic discharge that could potentially rupture the coating. Summary of the Invention

[0015] The objective of this invention is to provide a lithography apparatus with an electrostatic clamping system and a method for controlling the electrostatic clamps in the lithography apparatus to solve or improve the aforementioned problems. Specifically, the objective of this invention is to provide a lithography apparatus with an electrostatic clamping system and a method for controlling the electrostatic clamps in the lithography apparatus to reduce defects in the patterned surface of the patterning apparatus and lower the risk of film breakage.

[0016] According to the present invention, a photolithography apparatus having an electrostatic clamping system is provided, comprising: a plurality of electrodes configured to apply an electrostatic clamping force to a component; a power supply connected to the plurality of electrodes; and a controller configured to control the potential applied to the plurality of electrodes to alternate between a first mode and a second mode in synchronization with the generation of radiation pulses in the photolithography apparatus, wherein: in the first mode, the average potential of the plurality of electrodes is a first potential; and in the second mode, the average potential of the plurality of electrodes is a second potential; and the first potential is more positive than the second potential.

[0017] Also according to the present invention, a method for controlling an electrostatic clamp for holding a component in a photolithography apparatus is provided, the method comprising: applying a clamping force to the component using a plurality of electrodes positioned in the electrostatic clamp; controlling the potentials applied to the plurality of electrodes such that the average potential of the plurality of electrodes alternates between a first potential and a second potential, wherein: the first potential is more positive than the second potential; and the alternation between the first potential and the second potential is synchronized with the generation of a radiation pulse in the photolithography apparatus. Attached Figure Description

[0018] Embodiments of the invention will now be described by way of example only with reference to the accompanying illustrative drawings, in which corresponding reference numerals indicate corresponding parts.

[0019] Figure 1 A schematic depiction of a photolithography apparatus.

[0020] Figure 2 A more detailed view of the lithography equipment is schematically depicted.

[0021] Figure 3 The schematic depiction may be an electrostatic clamp, a part of the photolithography apparatus according to the present invention, and a pattern forming apparatus.

[0022] Figure 4 A graph depicting the potential (V) of the first surface of the pattern forming apparatus during the time it takes for two EUV radiation pulses to be generated by the photolithography device.

[0023] Figure 5 The schematic depiction includes an electrostatic clamp, which may be part of the photolithography apparatus according to the present invention, and a pattern forming apparatus covered by a film.

[0024] Figure 6A A graph depicting the potential (V) of the first surface of the patterning apparatus and the potential of the film during and after the generation of EUV radiation pulses by the photolithography equipment.

[0025] Figure 6B A graph depicting the charge (Q) on the first surface of the patterning apparatus and the charge on the film during and after the generation of EUV radiation pulses by the photolithography device.

[0026] Figure 7A and Figure 7B The depiction may be a schematic representation of the electrostatic fixture and the pattern forming apparatus covered by the film in part of the photolithography apparatus according to the present invention.

[0027] Figure 8A Plot a graph showing how the EUV radiation intensity (I) changes over time for a given number of EUV radiation pulses.

[0028] Figure 8B Plot a graph showing the change of the average potential (V) of multiple electrodes in an electrostatic fixture over time for a given number of EUV radiation pulses.

[0029] Figure 8C Plot the changes in potential (V) applied to the first set of electrodes and the potential (V) applied to the second set of electrodes over time for a certain number of EUV radiation pulses.

[0030] The features shown in the multiple figures are not necessarily drawn to scale, and the sizes and / or arrangements depicted are not limiting. It will be understood that each figure includes optional features that may not be essential to the invention. Furthermore, not all features of the device are depicted in each of the multiple figures, and the multiple figures may only show some of the components relevant to describing a particular feature. Detailed Implementation

[0031] Figure 1A lithography apparatus 100 including a radiation source SO is schematically depicted according to an embodiment of the present invention. The lithography apparatus 100 includes:

[0032] - Irradiation system (or irradiator) IL, the irradiation system being configured to modulate the radiation beam B (e.g., EUV radiation).

[0033] - A support structure (e.g., a mask stage) MT, which is configured to support a pattern forming apparatus (e.g., a mask or a mask plate) MA and is connected to a first positioner PM configured to accurately position the pattern forming apparatus;

[0034] - A substrate stage (e.g., a wafer stage) WT, the substrate stage being configured to hold a substrate (e.g., a wafer coated with resist) W, and connected to a second positioner PW configured to accurately position the substrate; and

[0035] - A projection system (e.g., a reflective projection system) PS, which is configured to project a pattern, given to a radiation beam B by a pattern forming apparatus MA, onto a target portion C (e.g., comprising one or more dies) of a substrate W.

[0036] An irradiation system IL may include various types of optical components for guiding, shaping, or controlling radiation, such as refractive, reflective, magnetic, electromagnetic, electrostatic, or other types of optical components, or any combination thereof.

[0037] The support structure MT holds the patterning apparatus MA in a manner dependent on the orientation of the patterning apparatus, the design of the lithography equipment, and other conditions such as whether the patterning apparatus is held in a vacuum environment. The support structure MT can use mechanical, vacuum, electrostatic, or other clamping techniques to hold the patterning apparatus MA. The support structure MT can be, for example, a frame or stage that is fixed or movable as needed. The support structure MT ensures that the patterning apparatus MA is, for example, in the desired position relative to the projection system PS.

[0038] The term "patterning apparatus" should be interpreted broadly as any apparatus that can be used to impart a pattern to the radiation beam B in a cross section in order to generate a pattern in a target portion C of the substrate W. The pattern imparted to the radiation beam B may correspond to a specific functional layer in a device (such as an integrated circuit) produced in the target portion C.

[0039] Examples of patterning apparatuses include masks, programmable mirror arrays, and programmable liquid crystal display (LCD) panels. Masks are well known in photolithography and include mask types such as binary, alternating phase-shift, and attenuation phase-shift masks, as well as various hybrid mask types. Examples of programmable mirror arrays use a matrix arrangement of small mirrors, each of which can be individually tilted to reflect an incident radiation beam in different directions. The tilted mirrors impart a pattern to the radiation beam reflected by the mirror matrix.

[0040] Similar to the illumination system (IL), the projection system (PS) can include various types of optical components suitable for the exposure radiation used or for other factors such as the use of a vacuum, including refractive, reflective, magnetic, electromagnetic, electrostatic, or other types of optical components, or any combination thereof. It may be desirable to use a vacuum for EUV radiation because other gases may absorb excessive radiation. Therefore, a vacuum environment can be provided throughout the beam path by means of vacuum walls and vacuum pumps.

[0041] As depicted here, the lithography apparatus 100 is of the reflective type (e.g., using a reflective mask).

[0042] The lithography apparatus 100 may be of the type having two (dual-platform) or more substrate stages WT (and / or two or more support structures MT). In such a "multi-platform" lithography apparatus, additional substrate stages WT (and / or additional support structures MT) may be used in parallel, or preparatory steps may be performed on one or more substrate stages WT (and / or one or more support structures MT) while one or more other substrate stages WT (and / or one or more other support structures MT) are used for exposure.

[0043] refer to Figure 1 The irradiation system IL receives an extreme ultraviolet (EUV) radiation beam from a radiation source SO. The radiation source SO can be a laser-generated plasma (LPP) source, a discharge-generated plasma (DPP) source, a free-electron laser (FEL), or any other radiation source capable of generating EUV radiation. Methods for generating EUV light include, but are not limited to, converting a material having at least one element (e.g., xenon, lithium, or tin) into a plasma state using one or more emission spectral lines in the EUV range. In laser-generated plasma (“LPP”), the desired plasma can be generated by irradiating a fuel (such as droplets, streams, or clusters of material having the desired spectral emission element) with a laser beam. The radiation source SO can include a laser ( Figure 1(Not shown) This is part of an EUV radiation system in which the laser is used to provide a laser beam for exciting the fuel. The resulting plasma emits output radiation, such as EUV radiation, which is collected using a radiation collector disposed in the radiation source SO. For example, when a CO2 laser is used to provide the laser beam for fuel excitation, the laser and the radiation source SO can be separate entities.

[0044] In this case, the laser is not considered part of the lithography apparatus 100, and the radiation beam B is transmitted from the laser to the radiation source SO by means of a beam delivery system including, for example, suitable directional mirrors and / or beam expanders. In other cases, for example, when the source is a discharge-generated plasma EUV generator (often referred to as a DPP source), the source can be part of the radiation source SO.

[0045] The illumination system IL may include adjusters for adjusting the angular intensity distribution of the radiation beam. Typically, at least the outer radial range and / or inner radial range (often referred to as σ-outer and σ-inner, respectively) of the intensity distribution in the pupil plane of the illumination system IL can be adjusted. Additionally, the illumination system IL may include various other components, such as faceted field mirror assemblies and faceted pupil mirror assemblies. The illumination system IL can be used to adjust the radiation beam B to have a desired uniformity and intensity distribution in its cross-section.

[0046] A radiation beam B is incident on a patterning apparatus (e.g., a mask) MA held on a support structure (e.g., a mask stage) MT and patterned by the patterning apparatus MA. After reflection from the patterning apparatus (e.g., the mask) MA, the radiation beam B passes through a projection system PS, which focuses the radiation beam B onto a target portion C of the substrate W. The substrate stage WT can be accurately moved, for example, to position different target portions C within the path of the radiation beam B, by means of a second locator PW and a position sensor PS2 (e.g., an interferometer, a linear encoder, or a capacitive sensor). Similarly, a first locator PM and another position sensor PS1 can be used to accurately position the patterning apparatus (e.g., the mask) MA relative to the path of the radiation beam B. The patterning apparatus (e.g., the mask) MA and the substrate W can be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2.

[0047] The controller 500 controls the overall operation of the lithography apparatus 100, and in particular performs the operational processes described further below. The controller 500 may be embodied as a suitably programmed general-purpose computer, including a central processing unit, volatile and non-volatile storage devices, one or more input and output devices such as a keyboard and screen, one or more network connections, and one or more interfaces to various components of the lithography apparatus 100. It will be understood that a one-to-one relationship between the control computer and the lithography apparatus 100 is not necessary. In embodiments of the invention, one computer may control multiple lithography apparatuses 100. In embodiments of the invention, multiple networked computers may be used to control one lithography apparatus 100. The controller 500 may also be configured to control one or more associated process devices and substrate transport devices of a lithography unit or lithography cluster, which the lithography apparatus 100 forms part of said lithography unit or lithography cluster. The controller 500 may also be configured as subordinate to a management control system of the lithography unit or lithography cluster and / or the overall control system of the wafer fab.

[0048] Figure 2 A lithography apparatus 100 is shown in more detail, comprising a radiation source SO, an irradiation system IL, and a projection system PS. The radiation source SO is configured to generate an EUV radiation beam B and supply the EUV radiation beam B to the lithography apparatus LA. The lithography apparatus LA includes the irradiation system IL, a support structure MT configured to support a pattern forming apparatus MA (e.g., a mask), the projection system PS, and a substrate stage WT configured to support a substrate W.

[0049] The irradiation system IL is configured to adjust the EUV radiation beam B before it is incident on the pattern forming apparatus MA. Additionally, the irradiation system IL may include a faceted field mirror assembly 10 and a faceted pupil mirror assembly 11. The faceted field mirror assembly 10 and the faceted pupil mirror assembly 11 together provide the EUV radiation beam B with a desired cross-sectional shape and a desired intensity distribution. Besides, or in place of, the faceted field mirror assembly 10 and the faceted pupil mirror assembly 11, the irradiation system IL may include other mirrors or devices.

[0050] After such adjustment, the EUV radiation beam B interacts with the patterning apparatus MA. Due to this interaction, a patterned EUV radiation beam B' is generated. A projection system PS is configured to project the patterned EUV radiation beam B' onto a substrate W. For this purpose, the projection system PS may include a plurality of mirrors 13, 14 configured to project the patterned EUV radiation beam B' onto the substrate W held by the substrate stage WT. The projection system PS may apply a reduction factor to the patterned EUV radiation beam B', thus forming an image with features smaller than those on the corresponding features of the patterning apparatus MA. For example, a reduction factor of 4 or 8 may be applied. Although the projection system PS is illustrated as having only... Figure 1 The two mirrors 13 and 14 are in the projection system, but the projection system PS may include a different number of mirrors (e.g., six or eight mirrors).

[0051] The substrate W may include a previously formed pattern. In such a case, the photolithography apparatus LA aligns the image formed by the patterned EUV radiation beam B' with the pattern previously formed on the substrate W.

[0052] A relative vacuum, i.e., a small amount of gas (e.g., hydrogen) at a pressure sufficiently below atmospheric pressure, can be provided in the radiation source SO, the irradiation system IL, and / or the projection system PS.

[0053] The radiation source SO can be a laser-generated plasma (LPP) source, a discharge-generated plasma (DPP) source, a free-electron laser (FEL) source, or any other radiation source capable of generating EUV radiation.

[0054] Figure 3 A cross-section of a portion of a support structure MT, which may be a part of a lithography apparatus according to the present invention, is schematically depicted. The cross-section extends in a vertical plane (i.e., parallel to the z-direction). A portion of the support structure MT may be a radially outward portion of the support structure MT. That is, the support structure MT may continue radially inward (e.g., Figure 3 (As depicted in the image, in the rightward direction). During the photolithography operation, the support structure MT holds the pattern forming apparatus MA. According to the present invention, the support structure MT is an electrostatic clamp 100. The electrostatic clamp 100 can be considered as part of the photolithography apparatus or as part of a device separate from the photolithography apparatus.

[0055] The pattern forming apparatus MA to be held by the electrostatic clamp 100 may include a first surface 110 and a second surface 111. The first surface 110 and the second surface 111 may be substantially parallel. The first surface 110 may be a patterned surface and includes a patterned region. The patterned region may be configured to impart a pattern to be projected onto the substrate W. The patterned region may be configured to reflect a radiation beam such that the reflected radiation beam is a patterned radiation beam. The second surface 111 is opposite to the first surface 110.

[0056] Both the electrostatic fixture 100 and the patterning apparatus MA can be housed within a patterning apparatus environment 90. The patterning apparatus environment 90 can be isolated from the external environment surrounding the lithography equipment and / or other components within the lithography equipment, thereby substantially preventing gaseous and contaminant particles from entering the patterning apparatus environment 90. The patterning apparatus environment 90 can be partially evacuated. That is, the pressure within the patterning apparatus environment 90 can be lower than the ambient pressure. This is to limit the attenuation of EUV radiation as it travels through the patterning apparatus environment 90. Even if the pressure within the patterning apparatus 90 is lower than the ambient pressure, the patterning apparatus environment 90 is not a complete vacuum, and therefore gaseous particles are still present within the patterning apparatus environment 90.

[0057] The electrostatic clamp 100 may include a clamping surface 102. When the pattern forming apparatus MA is clamped to the electrostatic clamp 100, the clamping surface 102 may face the second surface 111 of the pattern forming apparatus MA. When the pattern forming apparatus MA is clamped to the electrostatic clamp 100, the first surface 110 of the pattern forming apparatus MA may face away from the clamping surface 102. The clamping surface 102 may be substantially flat. The electrostatic clamp 100 may be configured such that when the pattern forming apparatus MA is clamped to the electrostatic clamp 100, the clamping surface 102 of the electrostatic clamp 100 is substantially parallel to the second surface 111 of the pattern forming apparatus MA.

[0058] The electrostatic clamp 100 may include a plurality of electrodes 104A to 104D. The plurality of electrodes 104A to 104D may be embedded within the body of the electrostatic clamp 100. For example, the plurality of electrodes 104A to 104D may be embedded below the clamping surface 102 of the electrostatic clamp 100. Each of the plurality of electrodes 104A to 104D may be connected to a power supply such that a potential can be applied to each of the plurality of electrodes 104A to 104D.

[0059] The electrostatic clamp 100 may include a plurality of protrusions 106. These protrusions may protrude from the clamping surface 102 of the electrostatic clamp 100. The electrostatic clamp 100 may be configured such that the distal ends of the plurality of protrusions 106 (i.e., the ends furthest from the clamping surface 102 of the electrostatic clamp 100) form flat surfaces. When the pattern forming apparatus MA is clamped to the electrostatic clamp 100, the second surface 111 of the pattern forming apparatus MA may contact the distal ends of the plurality of protrusions 106. Therefore, the clamping surface 102 of the electrostatic clamp 100 and the electrodes 104A to 104D, which may be embedded below the clamping surface 102 of the electrostatic clamp, may be separated from the second surface 111 of the pattern forming apparatus MA.

[0060] The clamping surface 102 of the electrostatic clamp 100 and the plurality of electrodes 104A to 104D that can be embedded below the clamping surface 102 of the electrostatic clamp 100 can also be separated from the second surface 111 of the pattern forming apparatus MA by the dielectric coating 105.

[0061] Each of the plurality of electrodes 104A to 104D may have a rectangular shape. However, this is not necessary for the present invention, and the shape of the plurality of electrodes 104A to 104D is not particularly limited. The plurality of electrodes 104A to 104D may be uniformly distributed on the clamping surface 102 of the electrostatic clamp 100. However, the specific arrangement of the plurality of electrodes 104A to 104D on the clamping surface 102 of the electrostatic clamp is not particularly limited. Figure 3 As depicted, four electrodes 104A to 104D are present in the radially outward portion of the electrostatic clamp 100. However, the number of electrodes 104A to 104D in the electrostatic clamp is not particularly limited and can be any number, such as 2, 3, 4, 5, 10, 20 or more.

[0062] The pattern forming apparatus MA, held by the electrostatic jig 100, may have a first conductive coating 112 on a first surface 110 and a second conductive coating 113 on a second surface 111. The first conductive coating 112 and the second conductive coating 113 may respectively cover a large portion of the first surface 110 and the second surface 111. The first conductive coating 112 and the second conductive coating 113 may be substantially electrically isolated. That is, the first conductive coating 112 may be electrically isolated from the second conductive coating 113, and each of the first conductive coating 112 and the second conductive coating 113 may be substantially electrically isolated from other components within the photolithography apparatus. Therefore, charge may accumulate on the first surface 110 and the second surface 111.

[0063] Each of the plurality of electrodes 104A to 104D can be connected to a power source (not shown) so that a potential can be applied to each of the plurality of electrodes 104A to 104D. The controllers 104A to 104D can control the potential applied to each of the plurality of electrodes 104A to 104D.

[0064] The plurality of electrodes 104A to 104D may include a first group of electrodes 104A, 104C and a second group of electrodes 104B, 104D. The first group of electrodes 104A, 104C may be connected to one or more first voltage sources and the second group of electrodes 104B, 104D may be connected to one or more second voltage sources. The potential applied to the first group of electrodes 104A, 104C may be different from the potential applied to the second group of electrodes 104B, 104D. For example, the potential applied to the second group of electrodes 104B, 104D may have a similar magnitude to the potential applied to the first group of electrodes 104A, 104C, but have the opposite polarity to the potential applied to the first group of electrodes 104A, 104C.

[0065] Each of the first set of electrodes 104A, 104C and the second set of electrodes 104B, 104D can be uniformly arranged on the clamping surface 102 of the clamping device 100. For example, the first set of electrodes 104A, 104C and the second set of electrodes 104B, 104D can be arranged in a two-dimensional checkerboard pattern. In the checkerboard arrangement, electrodes 104A to 104D can alternate between the first set of electrodes 104A, 104C and the second set of electrodes 104B, 104D along a first direction and a second direction, wherein the first direction and the second direction are perpendicular to each other and lie in the plane of the clamping surface 102.

[0066] When a potential is applied to the plurality of electrodes 104A to 104D, a high electric field is formed between the plurality of electrodes 104A to 104D and the patterning apparatus MA, thereby causing the patterning apparatus MA to be attracted to the plurality of electrodes 104A to 104D. Specifically, the potential applied to the plurality of electrodes 104A to 104D causes charge separation within the second conductive coating 113. The displacement of charges within the second conductive coating 113 means that an attractive force can be formed between the plurality of electrodes 104A to 104D and the second conductive coating 113. Therefore, the electrostatic clamp 100 can apply a clamping force to the patterning apparatus MA.

[0067] The potential applied to the plurality of electrodes 104A to 104D can be large enough to overcome the gravity applied to the patterning apparatus MA by the clamping force applied by the electrostatic clamp. The required potential can depend on the mass of the patterning apparatus MA and the quality of the first conductive coating 112 and the second conductive coating 113. The magnitude of the potential applied to the plurality of electrodes 104A to 104D can be approximately several kV. For example, the magnitude of the potential applied to the plurality of electrodes 104A to 104D can be greater than 100 V, preferably greater than 300 V, and more preferably greater than 1 kV. The magnitude of the potential applied to the plurality of electrodes 104A to 104D can be less than 100 kV, preferably less than 50 kV, and more preferably less than 25 kV.

[0068] A shielding blade 120 can be disposed within the photolithography apparatus and adjacent to the first surface 110 of the patterning apparatus MA. For example, the shielding blade 120 can be configured such that it is displaced from the first surface 110 in the z-direction. When the surface film 131 is disposed in front of the patterning apparatus MA, the shielding blade 120 can be configured such that it is displaced from the first surface 110 in the z-direction. The shielding blade 120 can be configured to selectively shield the patterning apparatus MA from radiation beam irradiation during exposure. The photolithography apparatus can be configured such that the shielding blade 120 is movable in a horizontal plane to provide different levels of shielding for the patterning apparatus MA.

[0069] Contaminant particles may be present in the patterning apparatus environment 90. Even if the patterning apparatus environment 90 is separated from the external environment and / or other components within the lithography apparatus, it is still possible for some contaminant particles to enter the patterning apparatus environment 90 from the external environment and / or other parts of the lithography apparatus. Furthermore, contaminant particles can be generated within the patterning apparatus environment 90 by mechanisms such as abrasion, which occurs when there is relative movement between contact surfaces.

[0070] The lithography equipment can be an EUV lithography equipment. That is, the lithography equipment can be configured to project an EUV radiation beam onto a substrate W. During exposure, the EUV radiation beam can be incident on a patterned area of ​​a first surface 110 of a patterning apparatus MA. This can cause electrons to be released from the first surface 110 due to the photoelectric effect. Therefore, the first surface 110 can become positively charged.

[0071] EUV radiation within the pattern forming apparatus environment 90 can also cause contaminant particles to become negatively charged. This is likely because the presence of EUV radiation within the pattern forming apparatus environment 90 causes the formation of plasma from gas molecules within the pattern forming apparatus environment 90. Plasma can form in the pattern forming apparatus environment 90 because photons within the EUV radiation beam ionize hydrogen molecules, thereby generating free electrons. In the example using 13.5 nm EUV radiation, each photon can have an energy of approximately 92 eV, where the ionization energy of molecular hydrogen is approximately 15 eV. Therefore, the generated free electrons can have sufficient energy (e.g., >75 eV) and range to generate secondary plasma relatively far from the initial ionization event. Electrons released in this way (i.e., with an energy of approximately 75 eV) can ionize another, two, or even three hydrogen molecules. Therefore, even if primary plasma is generated only at the EUV photon incident point, secondary plasma can still be generated throughout the clamping environment 90, for example, near the pattern forming apparatus MA. Furthermore, electrons emitted from the first surface 110 due to the photoelectric effect can contribute to the plasma within the patterning apparatus environment 90. Electrons can also be emitted from other surfaces incident with EUV radiation. The grounded surface incident with EUV radiation can continue to supply electrons to the plasma throughout the entire period of generating the EUV radiation pulse. Free electrons within the plasma can be absorbed by contaminant particles, causing those particles to become negatively charged.

[0072] Since the first surface 110 becomes positively charged and the contaminant particle P becomes negatively charged, an electrostatic attraction can be applied between the first surface 110 and the contaminant particle. This can cause the contaminant particle to accelerate toward the first surface 110. Therefore, contaminant particles within the photolithography apparatus can be deposited onto the first surface 110. The contaminant particles deposited on the first surface 110 can absorb and / or scatter EUV radiation incident on the patterned area of ​​the first surface 110. Therefore, the contaminant particles may cause defects in the pattern projected onto the substrate W, which can result in defects in the substrate W.

[0073] In EUV lithography systems, EUV radiation can be generated in pulses. That is, there are periods where EUV radiation is generated and periods where it is not. EUV radiation pulses are typically generated at a fast frequency. This frequency can be, for example, about 50 kHz, about 60 kHz, or about 100 kHz. During a typical EUV pulse cycle (e.g., a cycle that begins when the first EUV radiation pulse is generated and immediately ends before the generation of the next EUV radiation pulse), EUV radiation pulses can be generated only for a short amount of time. For example, EUV radiation pulses can be generated within about 1% of the time of a typical EUV pulse cycle.

[0074] Figure 4 Plot on the same axis: (1) a graph of EUV intensity (I) as a function of time (solid line), and (2) a graph of the potential (V) of the first surface 110 of the pattern forming device MA as a function of time (t) (dashed line). Figure 4 The time period for generating two EUV radiation pulses by the photolithography apparatus is described. The described scenario could be one where the surface film 131 is not positioned in front of the first surface 110 of the patterning apparatus MA. As explained above, after the EUV radiation pulse begins, the EUV radiation incident on the first surface 110 can cause electrons to be emitted from the first surface 110, resulting in the first surface 110 becoming positively charged. This results in the first surface 110 carrying a positive potential. After the EUV pulse ends, the first surface 110 can be discharged. That is, the amount of positive charge on the first surface 110 can be reduced. This can make the first surface 110 approximately neutral. The discharge of the patterned surface 40 can be caused by free negative charges in the plasma formed within the patterning apparatus environment 90. This means that during the EUV photolithography process, the first surface 110 can cycle frequently between being positively charged and substantially neutral.

[0075] During exposure, the second surface 111 may not become positively charged because it is not exposed to EUV radiation. Instead, the second surface 111 may become negatively charged due to the free negative charge of the plasma within the patterning apparatus environment 90.

[0076] Figure 5 The schematic depiction includes an electrostatic clamp 100, which may be part of a lithography apparatus according to the invention, and a pattern forming apparatus covered by a film 131. The film 131 may be positioned opposite a first surface 110. For example, the film 131 may be positioned such that it is displaced from the first surface 110 in the z-direction. The film may be a film assembly configured to protect the pattern forming apparatus MA from contaminant particles within the pattern forming apparatus environment 90. To minimize absorption of EUV radiation, the film is very thin and therefore very easily damaged. The film 131 may be supported by a film frame 132. The film 131 may be stretched across the film frame 132. The film 131 may be substantially electrically isolated. That is, the film 131 may be substantially electrically isolated from the pattern forming apparatus MA and substantially electrically isolated from other components within the lithography apparatus. Therefore, electrostatic charges may accumulate on the film 131.

[0077] When the film 131 is disposed in front of the first surface 110, a field may be formed between the film 131 and the first surface 110 due to the difference in charge-discharge rate between the film 131 and the first surface 110. Figure 6AA graph depicting the change of potential (V) (indicated by dashed lines) of the first surface 110 (indicated by solid lines) and the potential (V) of the film 131 (indicated by solid lines) of the pattern forming apparatus MA over time (t). Figure 6B A graph depicting the change of charge (Q) (indicated by dashed lines) on the first surface 110 of the pattern forming apparatus MA and the charge (Q) (indicated by solid lines) on the film 131 over time (t). The charge can be measured in nanocoulombs (nC). Figure 6A and Figure 6B The time period depicted includes the time during which the EUV radiation pulse is generated by the lithography equipment, and the time after the EUV radiation pulse is generated by the lithography equipment. The time can be measured in µs.

[0078] During the time following the generation of an EUV radiation pulse using a photolithography device, the positively charged first surface 110 can attract free negative charges within the plasma. As these free negative charges are attracted to the first surface 110, they can settle onto the surface film 131. Therefore, the charge on the surface film 131 can become more negative. For example, as... Figure 6B As depicted, the amount of positive charge on the film 131 can be reduced and then becomes negative (although it does not necessarily have to have a negative potential relative to the clamp). At the same time, the film 131 can substantially prevent free negative charges from reaching the first surface 110. Therefore, the first surface 110 can remain positively charged.

[0079] During the period following an EUV radiation pulse, the fact that the first surface 110 carries a positive charge and the film 131 carries a negative charge may cause an electric field to exist between the first surface 110 and the film 131. Because the first surface 110 and the film 131 are very close and a field exists between them, electrostatic discharge (ESD) may occur. The probability of ESD increases with increasing electric field strength. ESD can cause a large current to flow through the film 131. This can cause damage to the film 131. For example, in the case where the film 131 comprises a thin metal film, a large current flowing through the film 131 can cause the thin metal film to rupture.

[0080] The rupture of the film 131 can also be caused by other mechanisms. For example, an electric field between the first surface 110 and other components near the patterning apparatus MA may cause a discharge from the patterning apparatus to the other components. The current and heat generated by this discharge can cause the film to rupture.

[0081] The potentials applied to the multiple electrodes 104A to 104D can be controlled, so that the average potential of the multiple electrodes 104A to 104D can be varied. That is, the potentials applied to the multiple electrodes 104A to 104D can be controlled, so that the average potential of the multiple electrodes can be positive, negative, or neutral.

[0082] exist Figure 3 In the electrostatic clamp 100 depicted, a plurality of electrodes 104A to 104D can be divided into a first group of electrodes 104A and 104C and a second group of electrodes 104B and 104D. The potential applied to the first group of electrodes 104A and 104C can have a magnitude substantially equal to that applied to the second group of electrodes 104B and 104D, but has the opposite polarity to the potential applied to the second group of electrodes 104B and 104D. The number of electrodes in the first group of electrodes 104A and 104C can be substantially the same as the number of electrodes in the second group of electrodes 104B and 104D. Therefore, the average potential of the plurality of electrodes 104A to 104D can be approximately 0V.

[0083] Figure 7A and Figure 7B The depiction may be a schematic representation of the electrostatic clamp 100 and the pattern forming apparatus MA of the photolithography apparatus according to the present invention. Figure 7A and Figure 7B In this process, the first surface 110 of the pattern forming apparatus MA is covered by a film 131. However, this is not necessary for the present invention, or for the operation of the electrostatic clamp 100 in the first and second modes, the operation of the electrostatic clamp 100 in the first and second modes will now be described.

[0084] exist Figure 7A In the electrostatic clamp 100 depicted, the magnitude of the positive potential applied to the first set of electrodes 104A and 104C can be greater than the magnitude of the negative potential applied to the second set of electrodes 104B and 104D. If the number of electrodes in the first set of electrodes 104A and 104C is substantially equal to the number of electrodes in the second set of electrodes 104B and 104D, then the average potential of the plurality of electrodes 104A to 104D can be positive.

[0085] exist Figure 7B In the electrostatic clamp 100 depicted, the magnitude of the positive potential applied to the first set of electrodes 104A and 104C can be less than the magnitude of the negative potential applied to the second set of electrodes 104B and 104D. If the number of electrodes in the first set of electrodes 104A and 104C is substantially equal to the number of electrodes in the second set of electrodes 104B and 104D, then the average potential of the plurality of electrodes 104A to 104D can be negative.

[0086] Typically, the magnitude and polarity of the average potential of the multiple electrodes 104A to 104D can be controlled by adjusting the difference between the magnitude of the potential applied to the first set of electrodes 104A and 104C and the magnitude of the potential applied to the second set of electrodes 104B and 104D.

[0087] This method is not limited to the aforementioned techniques for controlling multiple electrodes 104A to 104D to have a positive or negative average potential. Alternatively, the first group of electrodes 104A and 104C can be negative, and the second group of electrodes 104B and 104D can be positive. Furthermore, more than two groups of electrodes 104A to 104D can exist. For example, three, four, five, or more groups of electrodes 104A to 104D can exist. The electrostatic clamp 100 can be configured such that different potentials can be applied to each group of electrodes 104A to 104D. That is, the potential applied to each group of electrodes can be independently controlled. Further alternatively, each electrode 104A to 104D can be independently controlled such that different potentials can be applied to each electrode 104A to 104D. As those skilled in the art will appreciate, there are various methods for controlling the multiple electrodes 104A to 104D to make the average potential of the multiple electrodes 104A to 104D positive or negative.

[0088] In a photolithography apparatus, some components, such as the shielding blade 120, can be grounded. That is, some components, such as the shielding blade 120, can be at a potential of approximately 0 V. Other relatively large conductive components at ground potential can be present near the electrostatic jig 100 and the patterning apparatus MA. When the average potential of the plurality of electrodes 104A to 104D is not 0 V, an electric field can be established between the electrostatic jig 100 and / or other grounded components within the photolithography apparatus. For example, an electric field can be established between the electrostatic jig 100 and the shielding blade 120. Therefore, when the average potential of the plurality of electrodes in the electrostatic jig is not 0 V, a capacitive potential can be induced in the first conductive coating 112 on the first surface 110 of the patterning apparatus MA, and a capacitive potential can be induced in the second conductive coating 113 on the second surface 111 of the patterning apparatus MA.

[0089] When the first conductive coating 112 and the second conductive coating 113 are in a substantially uncharged state, the potential induced in the first conductive coating 112 and the second conductive coating 113 can have the same polarity as the average potential of the plurality of electrodes 104A to 104D. That is, if the average potential of the plurality of electrodes 104A to 104D is negative, the potential induced in the first conductive coating 112 and the second conductive coating 113 can be negative. If the average potential of the plurality of electrodes 104A to 104D is positive, the potential induced in the first conductive coating 112 and the second conductive coating 113 can be positive. If the average potential of the plurality of electrodes 104A to 104D is approximately 0 V, the electrostatic clamp 100 may not induce a potential in the first conductive coating 112 or the second conductive coating 113. Generally, if the first conductive coating 112 and the second conductive coating 113 are in a substantially uncharged state, the potential induced in the first conductive coating 112 and the second conductive coating 113 can be controlled by controlling the average potential of the plurality of electrodes 104A to 104D.

[0090] In this context, the average potential of the plurality of electrodes 104A to 104D can be an average value calculated (i.e., weighted by the potentials) taking into account the capacitively induced potentials in the first conductive coating 112 and the second conductive coating 113. The capacitively induced potentials of the electrodes in the first conductive coating 112 and the second conductive coating 113 can be proportional to the surface area of ​​the electrodes and the permittivity of the region between the electrodes and the first conductive coating 112 and the second conductive coating 113, and inversely proportional to the distance between the electrodes and the first conductive coating 112 and the second conductive coating 113. When the plurality of electrodes 104A to 104D are disposed in a plane parallel to the first conductive coating 112 and the second conductive coating 113 (i.e., the distance between the plurality of electrodes 104A to 104D and the first conductive coating 112 and the second conductive coating 113 is substantially uniform) and the permittivity is uniform throughout the region between the plurality of electrodes 104A to 104D and the first conductive coating 112 and the second conductive coating 113, the contribution of the electrodes to the average potential can depend on the potential of the electrodes and the surface area of ​​the electrodes. Therefore, the average potential of the multiple electrodes 104A to 104D can be a weighted average of the surface areas of each of the multiple electrodes.

[0091] Although the capacitive induction of potentials in the first conductive coating 112 and the second conductive coating 113 has been described with reference to the shielding blade 120, this is not essential to the present invention. That is, if the shielding blade 120 is not present, the electrostatic fixture may be able to capacitively induce potentials in the first conductive coating 112 and the second conductive coating 113 of the pattern forming apparatus MA. In some embodiments, other components of the lithography apparatus may perform the function of the shielding blade 120 described above.

[0092] In this paper, the potentials applied to multiple electrodes can be controlled such that the average potentials of the multiple electrodes 104A to 104D alternate between a first mode and a second mode. In the first mode, the potentials applied to the multiple electrodes 104A to 104D can make the average potential of the multiple electrodes 104A to 104D a first potential. In the second mode, the potentials applied to the multiple electrodes 104A to 104D can make the average potential of the multiple electrodes 104A to 104D a second potential. The state in which the average potentials of the multiple electrodes 104A to 104D alternate between the first potential and the second potential can be referred to as an exposure state.

[0093] Furthermore, the first potential can be more positive than the second potential. For example, if the second potential is negative, the first potential can also be negative, but with a smaller value than the second potential, or the first potential can be positive. If the second potential is positive, the first potential can be positive and have a larger value than the second potential. The difference between the first and second potentials can be greater than 10 V, preferably greater than 50 V, and more preferably greater than 75 V. The difference between the first and second potentials can be less than 1000 V, preferably less than 700 V, and more preferably less than 500 V. For example, the first potential can be approximately 100 V and the second potential can be approximately -100 V. Alternatively, the first potential can be approximately -5 V and the second potential can be approximately -100 V.

[0094] During exposure, the alternation of the average potential of multiple electrodes 104A to 104D between the first potential and the second potential can be synchronized with the generation of radiation pulses in the lithography equipment.

[0095] During an exposure cycle, the period in which radiation pulses are generated can be referred to as an on cycle, and the period in which no radiation pulses are generated can be referred to as an off cycle. The lithography apparatus can operate in a first mode during the on cycle or for most of the on cycle (i.e., where the average potential of the plurality of electrodes 104A to 104D is a first potential). The lithography apparatus can operate in a second mode during the off cycle or for most of the off cycle (i.e., where the average potential of the plurality of electrodes 104A to 104D is a second potential).

[0096] In the context of this invention, "synchronization" can mean that the generation of radiation pulses and the alternation between the first and second modes occur at the same frequency with a stable phase relationship. However, it may not necessarily mean that the switching from the first mode to the second mode (or vice versa) occurs simultaneously with the termination (or start) of the radiation pulses in the lithography apparatus.

[0097] For example, the transition from the second mode to the first mode can begin before the start time of the radiation pulse (i.e., before the time the radiation pulse is initiated). This can be advantageous when there is a delay between the start time of the transition from the second mode to the first mode and the time when the first mode is achieved (i.e., the time when the average potential of the multiple electrodes 104A to 104D becomes the first potential). That is, this can be advantageous when the transition of the average potential of the multiple electrodes 104A to 104D from the second potential to the first potential involves a rise time. By starting the switch from the second mode to the first mode before the start of the radiation pulse, it can be ensured that the average potential of the multiple electrodes 104A to 104D is the first potential at the start time of the radiation pulse. Furthermore, the transition from the first mode to the second mode can begin after the end time of the radiation pulse (i.e., after the time the radiation pulse terminates). This ensures that the electrostatic clamp 100 operates in the first mode throughout the entire opening cycle.

[0098] The frequency at which the electrostatic clamp 100 performs the entire cycle in the exposure state can be the same as the frequency of EUV radiation. For example, the electrostatic clamp can alternate between a first mode and a second mode at frequencies greater than 19 kHz, preferably greater than 49 kHz, more preferably greater than 59 kHz, and even more preferably greater than 99 kHz.

[0099] The second potential can be negative. Therefore, if the second surface 111 of the patterning apparatus MA is substantially uncharged, a negative potential can be induced in the second surface 111 of the patterning apparatus MA during the shutdown cycle. By inducing a negative potential in the second surface 111 of the patterning apparatus MA during the shutdown cycle, negative charges from the plasma generated by EUV radiation within the patterning environment 90 can be repelled from the second surface 111 of the patterning apparatus MA. Therefore, the degree to which the second surface 111 of the patterning apparatus MA becomes negatively charged can be reduced. Furthermore, if the first surface 110 of the patterning apparatus MA is substantially uncharged, a negative potential can be induced in the first surface 110 of the patterning apparatus MA during the shutdown cycle. By inducing a negative potential in the first surface 110 of the patterning apparatus MA during the shutdown cycle, contaminant particles within the patterning apparatus environment that have become negatively charged due to the negative charge in the plasma can be repelled from the first surface 110. Therefore, defects caused by the deposition of contaminant particles on the first surface 110 can be reduced.

[0100] By changing the average potential of the multiple electrodes 104A to 104D to a first potential (which is more positive than the second potential, i.e., although the first potential is negative, it has a smaller magnitude, or it is positive), the potential induced in the first surface 110 becomes less negative. This means that the extent to which light emission occurs from the first surface 110 when EUV radiation is incident on it can be reduced.

[0101] The first potential can be positive. If the first potential is positive and the first conductive coating 112 and the second conductive coating 113 are not significantly negatively charged, a positive potential can be induced in the first conductive coating 112 and the second conductive coating 113 (i.e., at the first surface 110 and the second surface 111 of the patterning apparatus MA). That is, the electrostatic clamp can be configured such that a positive potential is induced in the first surface 110 and the second surface 111 during the on-cycle and a negative potential is induced in the first surface 110 and the second surface 111 during the off-cycle. By inducing a positive potential in the first surface 110 during the on-cycle, the emission of electrons from the first surface 110 can be reduced. Therefore, the first surface can become positively charged to a lesser extent and can contribute fewer electrons to the plasma in the image processing device environment 90.

[0102] The magnitude of the positive first potential is such that the positive potential induced at the first surface 110 of the pattern forming apparatus is sufficient to prevent the emission of electrons via the photoelectric effect. That is, the magnitude of the positive first potential is such that the positive potential induced at the first surface 110 is greater than the stopping potential (V). stop The maximum kinetic energy of the electron emitted via light emission is given by equation (2), where h is Planck's constant (4.14 × 10⁻⁶). -15 (eVs), f is the radiation frequency, and φ is the work function of the material (i.e., the minimum energy required to induce the emission of electrons from the surface). The work function is a property of the material of the surface that emits electrons.

[0103] (2)

[0104] When the energy supplied to the electrons through the electric field induced by the positive potential at the first surface 110 is greater than the maximum possible kinetic energy of the emitted electrons, light emission cannot occur. Therefore, the stopping potential can be defined as in equation (3).

[0105] (3)

[0106] In EUV lithography, the wavelength of radiation can be approximately 13.5 nm. Therefore, the photon energy of photons within the EUV radiation beam can be approximately 92 eV. The work function of the first surface 110 can depend on the material forming the first surface 110. Typically, the work function can be between 2 eV and 7 eV. If the work function is 7 eV or less, the potential induced on the first surface 110 is preferably approximately 85 V or greater to substantially suppress light emission. If the work function is 2 eV or less, the potential induced on the first surface 110 is preferably approximately 90 V or greater to substantially suppress light emission. To ensure substantially suppressing light emission regardless of the work function of the material, the potential induced on the first surface 110 is preferably approximately 92 V or greater. To ensure substantially suppressing light emission regardless of the inaccuracy of the electrostatic fixture 100, the potential induced on the first surface is preferably approximately 99 V or greater. The first potential can be less than 2,000 V, preferably less than 1,000 V, and more preferably less than 500 V. This is to ensure that the time required for the electrostatic clamp 100 to switch from the first mode to the second mode (and vice versa) is not excessive. This ensures that the electrostatic clamp 100 can alternate between the first mode and the second mode (and vice versa) at the frequency at which radiation pulses are generated in the lithography equipment.

[0107] The means of alternating between the first and second modes and synchronizing with the generation of radiation pulses by the lithography apparatus are not particularly limited. In an embodiment, the signal responsible for initiating the radiation pulse can also be sent to the electrostatic fixture 100, allowing the electrostatic fixture 100 to be controlled to switch from the second mode to the first mode simultaneously with the initiation of the radiation pulse. Similarly, the signal responsible for terminating the radiation pulse can also be sent to the electrostatic fixture 100, allowing the electrostatic fixture 100 to be controlled to switch from the first mode to the second mode simultaneously with the termination of the radiation pulse. Alternatively, the electrostatic fixture 100 can determine when to generate a radiation pulse using a sensor (not shown) within the electrostatic fixture 100 itself or a sensor within an electrostatic fixture system including the electrostatic fixture. An example of this is described in more detail below. Further alternatively, the generation of the radiation pulse and the alternation between the first and second modes can occur independently. In such a case, the generation of the radiation pulse and the alternation between the first and second modes can occur synchronously because they begin at the same predetermined time and continue at the same predetermined frequency.

[0108] Figures 8A to 8C An example is given of the generation of radiation pulses and the synchronization of the alternation between the first and second modes.

[0109] Figure 8A Plot a graph showing how the EUV radiation intensity (I) changes with time (t) for a given number of EUV radiation pulses. Figures 8A to 8C The duration described includes three radiation pulses. Specifically, the first radiation pulse has a start time of t=t1 and an end time of t=t2, the second radiation pulse has a start time of t=t3 and an end time of t=t4, and the third radiation pulse has a start time of t=t5 and an end time of t=t6. The entire cycle of radiation pulses can be considered as from t1 to t3.

[0110] Figure 8B Plot a graph showing the average potential (V) of the multiple electrodes 104A to 104D in the electrostatic clamp 100 as a function of time (t) for three radiation pulses. (See figure) Figure 8B As depicted, prior to the start time (t1) of the first radiation pulse, the average potential of the plurality of electrodes 104A to 104D is the second potential (V2). As described above, the second potential is negative. Immediately before the start time of the first radiation pulse (t=t1), the electrostatic clamp 100 begins to switch from the second mode to the first mode. During the relatively short switching phase, the average potential of the plurality of electrodes is increased. By the start time (t1) of the first radiation pulse, the average potential of the plurality of electrodes 104A to 104D may have reached the first potential (V1). During the time period in which the radiation pulse is generated (i.e., from t=t1 to t=t2), the average potential of the plurality of electrodes 104A to 104D is the first potential (V1). At or immediately after the end time of the radiation pulse (t2), the electrostatic clamp 100 begins to switch from the first mode to the second mode. During a relatively short switching phase, the average potential of the multiple electrodes 104A to 104D can be reduced until the average potential of the multiple electrodes 104A to 104D is the second potential (V2). The cycle can then be repeated. The entire cycle alternating between the first and second modes can be considered as running from t=t1 to t=t3.

[0111] Figure 8C An exemplary method is described that can control the average potential of multiple electrodes 104A to 104D. Figure 8C A graph is plotted showing the change in potential (V) applied to the first set of electrodes 104A and 104C and the second set of electrodes 104B and 104D over time (t) for a certain number of EUV radiation pulses. The number of electrodes in the first set of electrodes 104A and 104C can be substantially the same as the number of electrodes in the second set of electrodes 104B and 104D. Therefore, the average potential of the multiple electrodes 104A to 104D is the average of the potentials applied to the first set of electrodes 104A and 104C and the potentials applied to the second set of electrodes 104B and 104D.

[0112] like Figure 8CAs can be seen, the potential applied to the first set of electrodes 104A and 104C remains positive throughout the three pulse cycles. The potential applied to the second set of electrodes 104B and 104D remains negative throughout the three pulse cycles. Before the start time of the first radiation pulse (t=t1), V=V A2 A potential is applied to the first set of electrodes 104A and 104C, and V = V B2 A potential is applied to the second set of electrodes 104B and 104D. V B2 The value is greater than V A2 The magnitude of the potential. Therefore, the average potential of the multiple electrodes 104A to 104D is negative, such as... Figure 8B As depicted in [the text]. During the time period in which the radiation pulse is generated (i.e., from t=t1 to t=t2), V=V A1 A potential is applied to the first set of electrodes 104A and 104C, and V = V B1 A potential is applied to the second set of electrodes 104B and 104D. In order to obtain V A2 Move to V A1 The potential applied to the first set of electrodes 104A and 104C increases, and in order to increase the potential from V B2 Move to V B1 The potential applied to the second set of electrodes 104B and 104D increases (i.e., the magnitude of the negative potential applied to the second set of electrodes becomes smaller). During the time period in which the radiation pulse is generated (i.e., from t=t1 to t=t2), V A1 The value is greater than V B1 The magnitude of the potential is such that the average potential of the multiple electrodes 104A to 104D is positive.

[0113] The manner in which potentials are applied to the first set of electrodes 104A, 104C and the second set of electrodes 104B, 104D is not essential to this invention. Alternatively, the potential applied to one of the first set of electrodes 104A, 104C or the second set of electrodes 104B, 104D can be constant. For example, the potential applied to the first set of electrodes 104A, 104C can remain constant. In such a case, the potential applied to the second set of electrodes 104B, 104D can vary depending on the generation of radiation pulses in the photolithography apparatus. B1 With V B2 Alternating between them, such as Figure 8C As described in the text, in this case, if V B2 The value of V is greater than the value of the constant potential applied to the first set of electrodes 104A and 104C and V B1 If the magnitude of the potential is less than the magnitude of the constant potential applied to the first set of electrodes 104B and 104D, then the average potential of the multiple electrodes 104A to 104D can alternate between negative and positive, such as... Figure 8B As depicted in the diagram. As will be understood, other possible methods may be employed to apply a potential to the first and second groups of electrodes 104A to 104D in order to generate... Figure 8B The pattern depicts the average potential of multiple electrodes 104A to 104D.

[0114] By reducing or suppressing the emission of electrons from the first surface 110 of the patterning apparatus MA when a radiation pulse is incident on it, the first surface 110 becomes positively charged to a lesser extent, or may become completely non-positively charged. This means that the potential of the first surface 110 can be rapidly reduced when the average potential of the plurality of electrodes 104A to 104D becomes negative (i.e., when the electrostatic clamp 100 switches to the second mode). This is because the discharge of the first surface 110 caused by the plasma within the patterning apparatus environment 90 needs to be low-level, or not at all. Therefore, the average potential of the first surface 110 decreases over time. This means that negatively charged contaminant particles can be attracted to the first surface 110 to a lesser extent. Therefore, fewer contaminant particles can be deposited on the first surface 110. This can mean that the pattern projected onto the substrate includes fewer defects, and thus the defect rate of the substrate can be improved. By ensuring that the electrostatic clamp 100 operates in the first mode throughout the entire on-cycle, emission due to the photoelectric effect can be reduced or prevented throughout the on-cycle.

[0115] Furthermore, suppressing the emission of electrons from the first surface 110 of the patterning apparatus MA can reduce the plasma density in the patterning apparatus environment 90. The presence of plasma in the patterning apparatus environment 90 causes particles to be released from the surface. The presence of plasma within the patterning apparatus environment 90 can also be responsible for making contaminant particles negatively charged. Therefore, by reducing the plasma density within the patterning apparatus environment 90, the defect degree of the first surface 110 can be further improved.

[0116] With the film 131 positioned in front of the first surface 110, an additional advantage is achieved: the emission of electrons from the first surface 110 of the pattern forming apparatus MA is suppressed when a radiation pulse is incident on the first surface 110. Specifically, because the first surface 110 may not become positively charged, no electric field (such as that between the first surface 110 and the film 131) may be established (e.g., regarding...). Figure 6A and Figure 6B (Described electric field). This means that the risk of rupture of the membrane 131 can be mitigated.

[0117] There is capacitance between several components in a photolithography apparatus. Specifically, the capacitance between the clamping surface 102 and the second surface 111 of the pattern forming apparatus MA can be considered as a variable capacitance, which varies depending on the gap between the clamping surface 102 and the second surface 111.

[0118] In a closed system, no charge can enter or leave the system, and for a given initial charge state, any change in the separation or spacing between the electrostatic fixture 100 and the pattern forming apparatus MA will cause a corresponding change in the variable capacitance. Furthermore, this capacitance change will also cause the potential across the capacitor to change significantly depending on the change in spacing. Specifically, the relationship Q = CV must always be maintained for each capacitor (assuming no charge is injected). Therefore, if the capacitance C is changed and the amount of charge Q included in the capacitor is kept the same, the potential V must change inversely proportional to the changed capacitance C. This can cause a significant potential amplification.

[0119] As explained above, charge can accumulate on the isolation surfaces of the pattern forming apparatus MA (e.g., first surface 110 and second surface 111). Residual charge can remain on the clamped pattern forming apparatus MA once released from the electrostatic clamp 100. As the released pattern forming apparatus MA moves away from the clamp surface, the increased spacing between the clamp surface and the pattern forming apparatus surface can lead to a decrease in capacitance and an amplification of potential. That is, assuming a proportional relationship between charge and potential in a closed system (i.e., Q = CV), any decrease in capacitance (inversely proportional to the spacing between the parallel plates) will cause a proportional increase in potential. Therefore, when the pattern forming apparatus MA separates from the clamp 100, the potential of the pattern forming apparatus may rise sufficiently to cause hydrogen electrical breakdown. Such a discharge can cause damage to the pattern forming apparatus MA, the electrostatic clamp 100, and / or particle generation damage, which may lead to subsequent defects. Therefore, it is preferable that the residual charge on the pattern forming apparatus is minimal or nonexistent before it is released from the electrostatic clamp 100.

[0120] The residual charge that may exist on the pattern forming apparatus before it is released from the electrostatic clamp is a negative electrostatic charge on the second surface 111. This negative electrostatic charge can be caused by free charges in the plasma being attracted to the second surface 111.

[0121] To repel negative charges from the second surface 111, the photolithography apparatus can operate in an alternating state. In the alternating state, the average potential of the multiple electrodes 104A to 104D may not alternate between the first and second potentials. Instead, the average potential of the multiple electrodes can be maintained at a constant negative potential.

[0122] Before removing the pattern forming apparatus MA from the electrostatic chuck, the lithography apparatus can operate in alternating states during a predetermined cycle. For example, the lithography apparatus can operate in alternating states for a predetermined number of pulses before the end of an exposure cycle. By operating to make the average potential of the plurality of electrodes 104A to 104D negative, the second surface 111 of the electrostatic chuck 100 is capacitively charged with a negative potential. Therefore, negative charges are repelled from the second surface 111. Thus, negative charging of the second surface 111 can be prevented during the cycle before unloading the pattern forming apparatus from the electrostatic chuck 100. Therefore, damage to the pattern forming apparatus caused by discharge during the release of the pattern forming apparatus MA from the electrostatic chuck 100 can be avoided. In this context, release refers not only to the time when the clamping force between the electrostatic chuck 100 and the pattern forming apparatus MA is removed, but also to the subsequent cycle in which the electrostatic chuck 100 separates from the pattern forming apparatus MA (i.e., the cycle in which the distance between the electrostatic chuck 100 and the pattern forming apparatus MA increases).

[0123] In the alternating state, the electrostatic clamp can operate constantly in the second mode. That is, in the alternating state, the average potential of the plurality of electrodes 104A to 104D can be the second potential. Alternatively, the magnitude of the average potential of the plurality of electrodes 104A to 104D can be larger in the alternating state than in the second mode. For example, the average potential of the plurality of electrodes can be approximately -5 V in the second mode, and the average potential of the plurality of electrodes 104A to 104D can be approximately -20 V in the alternating state. In the second mode, it is preferable that the magnitude of the (negative) average potential of the plurality of electrodes 104A to 104D is sufficient to reduce to the point that the second surface 111 becomes negatively charged, but it is preferable that the magnitude of the (negative) average potential of the plurality of electrodes 104A to 104D is not so large that positive charges in the pattern forming apparatus environment 90 are attracted to the first surface 110. This will make the first surface 110 positively charged, which will then need to be compensated for by negative charges during the on-cycle. In the alternating state (i.e., during the release period), the accumulation of positive charge on the first surface 110 is less important, and the reduction of charge accumulation on the second surface 111 is more important. Therefore, the magnitude of the average potential of the plurality of electrodes 104A to 104D can be larger in the alternating state than in the second mode.

[0124] By alternating the average potential of the plurality of electrodes 104A to 104D between a first potential (where the first potential is positive) and a second potential (where the second potential is negative) according to the generation of radiation pulses in the photolithography apparatus, each of the benefits of the patterning apparatus MA carrying both positive and negative potentials can be realized. That is, for most of the exposure time, negative charges can be repelled from the second surface 111 and contaminant particles can be repelled from the first surface 110 of the patterning apparatus MA, and the emission of electrons from the first surface 110 of the patterning apparatus MA when the radiation pulse is generated can be reduced or prevented. By reducing or preventing the emission of electrons from the first surface 110 of the patterning apparatus MA when the radiation pulse is generated, the first surface 110 becomes positively charged to a lower extent, which means that contaminant particles are attracted to the first surface 110 to a lower extent. Therefore, the deposition of contaminant particles on the first surface 110 of the patterning apparatus MA can be effectively reduced, and the accumulation of negative charges on the second surface 111 of the patterning apparatus MA can be effectively avoided. Therefore, the defect degree of the substrate can be reduced. At the same time, it can mitigate the risks associated with removing the charged pattern forming apparatus MA from the electrostatic clamp 100.

[0125] In one embodiment, when the pattern forming apparatus MA is clamped to an electrostatic fixture, the second surface 111 of the pattern forming apparatus MA can be connected to a circuit (not shown). The circuit can be connected to the second surface 111 of the pattern forming apparatus via contact portions.

[0126] The circuitry may include a power source such that the second surface 111 can be induced to carry a predetermined potential via a contact portion. During exposure cycles, net charge can accumulate on the second surface 111 of the patterning apparatus MA. This may impair the potential induced on the first surface 110 of the patterning apparatus MA. This can be avoided by providing an electrical connection to the second surface 111, which causes the second surface 111 to carry the desired potential. This can be particularly advantageous when the second surface 111 of the patterning apparatus MA is charged by plasma in the patterning apparatus environment 90 only when a radiation pulse is generated by the lithography equipment.

[0127] Alternatively or additionally, the circuitry connected to the second surface 111 of the patterning apparatus MA may include a sensor. The sensor may be configured to detect the photocurrent induced in the second surface 111 of the patterning apparatus MA. The sensor may be a galvanometer. When the first surface 110 becomes positively charged due to electron emission caused by radiation incident on the first surface 110, a charge mirroring the charge on the first surface 110 may be induced on the second surface 111. Therefore, the sensor in the circuitry connected to the second surface 111 can detect when the first surface 110 is irradiated. That is, the sensor in the circuitry connected to the second surface 111 can detect when a radiation pulse is generated by the lithography apparatus. When detected by the sensor in the circuitry, the alternation between a first mode and a second mode can be controlled based on whether a radiation pulse is being generated in the lithography apparatus. Therefore, a closed system embedded in the electrostatic jig 100 or an electrostatic jig system including the electrostatic jig 100 can control the alternation between the first mode and the second mode based on the generation of a radiation pulse in the lithography apparatus.

[0128] Alternatively or concurrently, the second surface 111 may be electrically connected to the first surface 110. For example, the second surface 111 may be electrically connected to the first surface 110 via one side of the patterning apparatus MA. For example, a conductive material (not shown) may be disposed on one side of the patterning apparatus, the conductive material being in contact with the first conductive coating 112 and the second conductive coating 113.

[0129] The system and method of the present invention can be implemented in current models of electrostatic clamps without any changes to the hardware. Therefore, the system and method can be implemented quickly and easily.

[0130] The photolithography equipment according to the present invention can be used for the manufacture of ICs.

[0131] While specific references can be made to the use of lithography equipment in IC manufacturing within this document, it should be understood that the lithography equipment described herein can have other applications. Possible other applications include manufacturing integrated optical systems, guiding and detecting patterns for magnetic domain memories, flat panel displays, liquid crystal displays (LCDs), thin-film magnetic heads, etc.

[0132] Where circumstances permit, embodiments of the invention may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the invention may also be implemented by 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 means 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, acoustic, or other forms of propagation signals (e.g., carrier waves, infrared signals, digital signals, etc.), etc. Furthermore, firmware, software, routines, and instructions may be described herein as performing certain actions. However, it should be understood that such descriptions are merely for convenience, and such actions are actually caused by a computing device, processor, controller, or other means executing firmware, software, routines, instructions, etc., and such actions can enable actuators or other means to interact with the physical world.

[0133] While specific reference may be made herein to embodiments of the invention within the context of photolithography equipment, embodiments of the invention can be used in other equipment. Embodiments of the invention can form part of mask inspection equipment, metrology equipment, or any equipment that measures or processes objects such as wafers (or other substrates) or masks (or other patterning apparatus). These devices are generally referred to as photolithography tools.

[0134] Although specific reference has been made above to the use of embodiments of the invention in the context of optical lithography, it will be understood that the invention is not limited to optical lithography where circumstances permit.

Claims

1. A photolithography apparatus with an electrostatic clamping system, comprising: Multiple electrodes configured to apply an electrostatic clamping force to the component; A power source connected to the plurality of electrodes; as well as A controller configured to control the potentials applied to the plurality of electrodes to alternate between a first mode and a second mode in synchronization with the generation of radiation pulses in the photolithography apparatus, wherein: In the first mode, the average potential of the plurality of electrodes is a first potential; and In the second mode, the average potential of the plurality of electrodes is the second potential; and The first potential is more positive than the second potential.

2. The photolithography apparatus according to claim 1, wherein, The controller is configured to: cause the electrostatic clamp to operate in a first mode during the time when the lithography equipment generates a radiation pulse, and cause the electrostatic clamp to operate in a second mode during the time when the lithography equipment does not generate a radiation pulse.

3. The photolithography apparatus according to any one of the preceding claims, wherein, The controller is configured to switch from the second mode to the first mode before the start time of the radiation pulse, and to switch from the first mode to the second mode after the end time of the radiation pulse.

4. The photolithography apparatus according to any one of the preceding claims, wherein, The second potential is negative.

5. The photolithography apparatus according to any one of the preceding claims, wherein, The first potential is positive.

6. The photolithography apparatus according to claim 5, wherein, The component includes a first surface and a second surface opposite to the first surface, and The photolithography apparatus is configured such that when the electrostatic fixture operates in the first mode, a positive potential is induced on the first surface and the second surface, and when the electrostatic fixture operates in the second mode, a negative potential is induced on the first surface and the second surface.

7. The photolithography apparatus according to claim 5 or 6, wherein, The first potential causes the positive potential induced on the first surface to be equal to or greater than the stopping potential of the material forming the first surface for the wavelength of the radiation pulse generated by the photolithography device.

8. The photolithography apparatus according to any one of claims 5 to 7, wherein, The average potential of the electrode in the first mode is such that the positive potential induced on the first surface is greater than 85 V, preferably greater than 90 V, more preferably greater than 92 V and more preferably greater than 99 V, and less than 2,000 V, preferably less than 1,000 V and more preferably less than 500 V.

9. The photolithography apparatus according to any one of the preceding claims, wherein, The plurality of electrodes includes a first group of electrodes and a second group of electrodes, and in both the first mode and the second mode, a positive potential is applied to the first group of electrodes and a negative potential is applied to the second group of electrodes.

10. The photolithography apparatus according to claim 9, wherein, In the first mode, the magnitude of the potential applied to the first set of electrodes is greater than the magnitude of the potential applied to the second set of electrodes, and in the second mode, the magnitude of the potential applied to the first set of electrodes is less than the magnitude of the potential applied to the second set of electrodes.

11. The photolithography apparatus according to claim 9 or 10, wherein, The first set of electrodes and the second set of electrodes are uniformly distributed on the surface of the electrostatic clamp, and the surface of the electrostatic clamp is configured to face the second surface of the component when the component is clamped to the electrostatic clamp.

12. The photolithography apparatus according to any one of the preceding claims, wherein, When the component is supported by the electrostatic clamp, the plurality of electrodes are separated from the second surface of the component by a dielectric coating and / or a plurality of protrusions, thereby substantially electrically isolating the component.

13. The photolithography apparatus according to any one of the preceding claims, wherein, The controller is configured to cause the electrostatic clamp to alternate between the first mode and the second mode at a frequency greater than 19 kHz, preferably greater than 49 kHz, more preferably greater than 59 kHz, and even more preferably greater than 99 kHz.

14. The lithography apparatus according to any one of the preceding claims further includes a contact portion and a circuit, the contact portion and the circuit being configured such that an electrical connection is formed between the second surface of the component and the circuit when the component is held by the electrostatic clamp.

15. The photolithography apparatus according to claim 14, wherein, The circuit and the contact portion are configured to apply a predetermined potential to the second surface of the component.

16. The photolithography apparatus according to claim 14 or 15, wherein, The circuit includes a sensor configured to detect a current induced on a second surface of the component, enabling it to determine whether the lithography apparatus is generating a radiation pulse.

17. The photolithography apparatus according to any one of the preceding claims, wherein, The controller is configured to alternate between the first mode and the second mode during exposure, and the controller is configured to control the potential applied to the plurality of electrodes such that the average potential is a constant negative potential during the alternation state.

18. The photolithography apparatus according to claim 17, wherein, The lithography apparatus is configured to operate in the alternating states during a predetermined period before the component is released from the electrostatic chuck.

19. The photolithography apparatus according to any one of claim 17 or 18, wherein, The controller is configured to control the potential applied to the plurality of electrodes in the alternating states to operate constantly in the second mode.

20. The photolithography apparatus according to any one of the preceding claims, wherein, The component is a pattern forming apparatus, the first surface is a patterned surface having a patterned area configured to impart a pattern to a radiation pulse generated by the photolithography apparatus, and the second surface is a clamping surface on which an electrostatic clamp applies an attractive force.

21. The lithography apparatus according to any one of the preceding claims further includes a radiation source configured to generate EUV radiation pulses.

22. A method for controlling an electrostatic clamp for holding a component in a photolithography apparatus, the method comprising: A clamping force is applied to the component using multiple electrodes positioned in the electrostatic clamp; The potential applied to the plurality of electrodes is controlled such that the average potential of the plurality of electrodes alternates between a first potential and a second potential, wherein: The first potential is more positive than the second potential; and The alternation between the first potential and the second potential is synchronized with the generation of radiation pulses in the photolithography device.

23. The method according to claim 22, wherein, The average potential of the plurality of electrodes is the first potential during the time when the lithography device generates a radiation pulse, and the average potential of the plurality of electrodes is the second potential during the time when the lithography device does not generate a radiation pulse.

24. The method according to any one of claim 22 or 23, wherein, The switching of the potential from the second potential to the first potential begins before the start time of the radiation pulse, and the switching of the potential from the first potential to the second potential begins after the end time of the radiation pulse.

25. The method according to claim 23 or 24, wherein, The second potential is negative.

26. The method according to any one of claims 22 to 25, wherein, The first potential is positive.

27. The method according to claim 26, wherein, The component includes a first surface and a second surface opposite to the first surface, and a positive potential is induced on the first surface and the second surface when the average potential of the plurality of electrodes is the first potential, and a negative potential is induced on the first surface and the second surface when the average potential of the plurality of electrodes is the second potential.

28. The method according to claim 27, wherein, The first potential causes the positive potential induced on the first surface for the wavelength of the radiation pulse generated by the photolithography device to be greater than the stopping potential of the material forming the first surface.

29. The method according to any one of claims 26 to 28, wherein, The first potential causes the positive potential induced on the first surface to be greater than 85 V, preferably greater than 90 V, more preferably greater than 92 V and more preferably greater than 99 V, and less than 2,000 V, preferably less than 1,000 V and more preferably less than 500 V.

30. The method according to any one of claims 26 to 29, wherein, The plurality of electrodes includes a first group of electrodes and a second group of electrodes, with a positive potential applied to the first group of electrodes and a negative potential applied to the second group of electrodes.

31. The method according to claim 30, wherein, To generate the first potential, the magnitude of the potential applied to the first set of electrodes is greater than the magnitude of the potential applied to the second set of electrodes, and to generate the second potential, the magnitude of the potential applied to the first set of electrodes is less than the magnitude of the potential applied to the second set of electrodes.

32. The method according to any one of claims 23 to 31, wherein, The frequency at which the first potential alternates with the second potential is greater than 19 kHz, preferably greater than 49 kHz, more preferably greater than 59 kHz, and even more preferably greater than 99 kHz.

33. The method according to any one of claims 22 to 32, further comprising applying a predetermined potential to a second surface of the component via a physical connection.

34. The method according to any one of claims 23 to 33, further comprising detecting a current induced on a second surface of the component, determining, based on the detected current, whether a radiation pulse is being generated by the photolithography apparatus, and controlling, based on the determination of whether a radiation pulse is being generated, the alternation of the average potential of the plurality of electrodes between the first potential and the second potential.

35. The method according to any one of claims 23 to 34, further comprising: The potential applied to the plurality of electrodes is controlled such that the average potential of the plurality of electrodes is negative for a predetermined period before the component is released from the electrostatic clamp.

36. The method according to any one of claims 23 to 35, further comprising: The potential applied to the plurality of electrodes is controlled such that the average potential of the plurality of electrodes remains constant at the second potential for a predetermined period before the component is released from the electrostatic clamp.

37. A method of manufacturing a device, comprising the method of controlling an electrostatic clamp for holding a component in a lithography apparatus according to any one of claims 22 to 36.

38. A computer program comprising instructions that, when executed by a control system of a lithography apparatus, cause the lithography apparatus to perform the method according to any one of claims 22 to 37.

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