阅读说明：本技术 极紫外光辐射源装置 (Extreme ultraviolet radiation source device ) 是由 苏彦硕 张俊霖 张汉龙 陈立锐 郑博中 于 2019-06-28 设计创作，主要内容包括：一种极紫外光辐射源装置包含收集器镜、为产生锡滴的靶材滴产生器、可旋转残屑收集元件、为产生感应耦合电浆的一或多个线圈、为提供用于感应耦合电浆的来源气体的气体入口、以及至少包围收集器镜与可旋转残屑收集元件的腔室。配置气体入口与前述一或多个线圈以致感应耦合电浆与收集器镜间隔设置。(An extreme ultraviolet radiation source apparatus comprises a collector mirror, a target droplet generator for generating droplets of tin, a rotatable debris collecting element, one or more coils for generating an inductively coupled plasma, a gas inlet for providing a source gas for the inductively coupled plasma, and a chamber surrounding at least the collector mirror and the rotatable debris collecting element. The gas inlet and the one or more coils are arranged so that the inductively coupled plasma is spaced from the collector mirror.)

1. An euv radiation source apparatus, comprising:

a collector mirror;

a target drop generator for generating a tin drop;

a rotatable debris collection element;

one or more coils for generating an inductively coupled plasma;

a gas inlet for providing a source gas for the inductively coupled plasma; and

a chamber at least enclosing the collector mirror and the rotatable debris collecting element,

wherein the gas inlet and the coil or coils are arranged such that the inductively coupled plasma is spaced from the collector mirror.

Technical Field

Embodiments of the present disclosure relate to a radiation source device, and more particularly, to an extreme ultraviolet radiation source device.

Background

The present disclosure relates to a patterning method for a semiconductor process, and an apparatus for photolithography.

The semiconductor integrated circuit industry has experienced exponential growth. Technological advances in integrated circuit materials and design have resulted in many generations of integrated circuits, with each generation having smaller and more complex circuits than the previous generation. As integrated circuits evolve, the functional density (i.e., the number of interconnect elements per wafer area) generally increases as the geometry (i.e., the smallest feature (or line) that can be created by the process) decreases. Such scaling procedures generally provide benefits by increasing production efficiency and reducing associated costs. This scaling has also increased the complexity of processing and manufacturing integrated circuits.

For example, the need to perform higher resolution lithography processes has grown. One lithography technique is extreme ultraviolet lithography (EUVL). Extreme ultraviolet lithography employs a scanner that uses light in the extreme ultraviolet region, the light having a wavelength of about 1-100 nm. Some euv scanners provide 4x reduction projection printing, similar to some optical scanners, except that euv scanners use reflective rather than refractive optics, i.e., mirrors rather than lenses. One type of extreme ultraviolet light source is a laser-produced plasma (LPP). Laser generated plasma technology generates extreme ultraviolet light rays by focusing a high energy laser beam on a small tin droplet target to form a highly ionized plasma that emits extreme ultraviolet radiation having a maximum emission peak of 13.5 nm. Then, the extreme ultraviolet light is collected by a laser-generated plasma collector mirror and optically reflected toward a lithography target, such as a wafer. Laser produced plasma collector mirrors suffer damage and degradation due to particle, ion, radiation impingement and, most severely, tin deposition.

Disclosure of Invention

According to one aspect of the present disclosure, an extreme ultraviolet radiation source apparatus is characterized by a collector mirror, a target droplet generator for generating tin droplets, a rotatable debris collecting element, one or more coils for generating an inductively coupled plasma, a gas inlet for providing a source gas for the inductively coupled plasma, and a chamber surrounding at least the collector mirror and the rotatable debris collecting element. The gas inlet and the one or more coils are arranged so that the inductively coupled plasma is spaced from the collector mirror.

Drawings

The disclosure is best understood from the following detailed description when read with the accompanying drawing figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale and are used for illustration purposes only. In fact, the dimensions of various features may be arbitrarily increased or reduced for clarity of discussion.

FIG. 1 is a schematic illustration of an EUV lithography system having a laser-generated plasma EUV radiation source constructed in accordance with some embodiments of the present disclosure;

FIG. 2A is a schematic front view of a debris collection mechanism for an EUV radiation source according to some embodiments of the present disclosure;

FIG. 2B is a schematic side view of a debris collection mechanism for an EUV radiation source according to some embodiments of the present disclosure;

FIG. 2C is a partial view of a blade for an EUV radiation source according to some embodiments of the present disclosure;

FIG. 3 is a schematic view of an EUV radiation source according to an embodiment of the present disclosure;

FIG. 4 is a schematic view of an EUV radiation source according to an embodiment of the present disclosure;

FIG. 5 is a schematic view of an EUV radiation source according to an embodiment of the present disclosure;

FIG. 6 is a schematic view of an EUV radiation source according to an embodiment of the present disclosure;

figure 7 is a schematic view of an euv radiation source according to an embodiment of the present disclosure.

[ notation ] to show

100: extreme ultraviolet radiation source/extreme ultraviolet radiation source device

10A, 10B: radio frequency power supply

105: chamber

110: collector mirror

115: target material drop generator

120: drip catcher

130: first buffer gas supply

135: second buffer gas supply

140. 22: gas outlet

15A, 15B: coil

150: residual scrap collecting mechanism

151: frusto-conical support

152: blade

153: first end support

154: second end support

155: downstream cone

160: outlet port

200: exposure machine

20. 21: gas inlet

300: excitation laser source/excitation laser source device

310: laser generator

320: laser guided optics

330: focusing device

A1: optical axis

BF: base layer

DP: target material drop

DP1, DP 2: damper

EUV: extreme ultraviolet radiation

LR 1: laser

LR 2: exciting laser

MF: main layer

PL: plasma

PP1, PP 2: base plate

ZE: excitation zone

Detailed Description

The following disclosure provides many different embodiments, or examples, for implementing different features of a given subject matter. Specific examples of components and arrangements are described below to simplify the present description. These are, of course, merely examples and are not intended to be limiting. For example, in the description, the formation of a first feature over or on a second feature may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact. Moreover, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

Furthermore, terms of spatial relationship, such as "below … (beneath)", "below … (below)", "lower (lower)", "above … (above)", "upper (upper)", or the like, may be used herein for brevity in describing the relationship of one element or feature to another element(s) or feature(s) as depicted in the figures. The spatially relative terms are intended to encompass different orientations of the elements in use or operation in addition to the orientation depicted in the figures. The devices/elements may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. Furthermore, the term "made of … (made of)" may mean "comprising" or "consisting of …".

The present disclosure generally relates to extreme ultraviolet lithography systems and methods. More particularly, it relates to an apparatus and method for reducing contamination on collector mirrors in laser produced plasma euv radiation sources. Collector mirrors, also known as laser produced plasma collector mirrors or extreme ultraviolet light collector mirrors, are important components of laser produced plasma extreme ultraviolet light radiation sources. It collects and reflects extreme ultraviolet radiation and contributes to the overall extreme ultraviolet conversion efficiency. However, it suffers from damage and deterioration due to impact of particles, ions, radiation, and debris deposition. In particular, tin debris is one of the sources of contamination for extreme ultraviolet light collector mirrors. The lifetime of the euv light collector mirror, i.e. the duration of the decay of the reflectivity to half of itself, is one of the most important factors of euv light scanners. The main reason for collector mirror attenuation is residual metal contamination (tin debris) on the collector mirror surface that is inevitable from the extreme ultraviolet light generation process.

One of the objectives of the present disclosure is to reduce debris deposition on the laser produced plasma collector mirror, thereby increasing its usable lifetime. More specifically, the present disclosure is directed to self-destroying metal coatings and buildup on extreme ultraviolet light collector mirrors by using chlorine-based plasma cleaning. The disclosed techniques maintain the collector mirror in a desired state for a longer period of time, thereby reducing the frequency of replacing the collector mirror. In other words, the euv scanner will maintain the highest exposure energy and throughput and require less frequent maintenance, thereby reducing the one week down time required to replace the collector mirror.

FIG. 1 is a schematic and diagrammatic view of an EUV lithography system. The euv lithography system includes an euv radiation source device 100 for generating euv light, an exposure tool 200, such as a scanner, and an excitation laser source device 300. In some embodiments, as shown in fig. 1, the euv radiation source apparatus 100 and the exposure tool 200 are installed on the main layer MF of the clean room, and the excitation laser source apparatus 300 is installed in the base layer BF below the main layer. The euv radiation source device 100 and the exposure tool 200 are disposed on the base plates PP1 and PP2 via dampers DP1 and DP2, respectively. The euv radiation source device 100 and the exposure tool 200 are coupled to each other through a coupling mechanism, which may include a focusing unit.

The lithography system is an extreme ultraviolet lithography system designed to expose a photoresist layer with extreme ultraviolet light (or extreme ultraviolet radiation). The photoresist layer is a material sensitive to extreme ultraviolet light. The euv lithography system uses an euv radiation source apparatus 100 to generate euv light, e.g., having a wavelength in the range of about 1nm to about 100 nm. In a particular example, the EUV radiation source 100 generates EUV light having a center wavelength of about 13.5 nm. In the present embodiment, the EUV radiation source 100 uses a laser-generated plasma mechanism to generate EUV radiation.

The exposure tool 200 includes a plurality of reflective optical components such as convex/concave/planar mirrors, a mask holding mechanism including a mask table, and a wafer holding mechanism. EUV radiation generated by EUV radiation source 100 is directed to a mask fixed on a mask table using reflective optics. In some embodiments, the mask table includes an electrostatic chuck (e-chuck) to hold the mask. Because the gas molecules absorb extreme ultraviolet light, the lithography system for extreme ultraviolet lithography patterning is maintained in a vacuum or low pressure environment to avoid loss of extreme ultraviolet light intensity.

In the present disclosure, the terms "mask", "photomask", and "reticle" are used interchangeably. In the present embodiment, the mask is a reflective mask. One exemplary structure of the mask includes a substrate having a suitable material, such as a low thermal expansion material or fused quartz. In many instances, this material comprises titania doped silica, or other suitable materials with low thermal expansion. The mask includes a plurality of reflective Multilayers (MLs) deposited on the substrate. The multilayer includes a plurality of film pairs, such as molybdenum-silicon film pairs (e.g., a molybdenum layer above or below a silicon layer in each film pair). Alternatively, the multilayer may comprise a molybdenum-beryllium film pair, or other suitable material configured to be highly reflective of extreme ultraviolet light rays. The mask may further include a capping layer, such as ruthenium, disposed on the plurality of layers to provide protection. The mask also includes an absorber layer, such as a tantalum boron nitride layer, deposited over the multilayer. The absorber layer is patterned to define an integrated circuit layer. Alternatively, another reflective layer may be deposited over the multiple layers and patterned to define an integrated circuit layer, thereby forming an extreme ultraviolet light phase shift mask.

The exposure tool 200 includes a projection optics module for imaging a pattern of a mask onto a semiconductor substrate that is fixed to the substrate stage of the exposure tool 200 and has a photoresist coated thereon. Projection optics typically include reflective optics. The extreme ultraviolet radiation (extreme ultraviolet light rays) directed from the mask carries an image of the pattern defined on the mask and is collected by the projection optics, thereby forming an image on the photoresist.

In the present embodiment, the semiconductor substrate is a semiconductor wafer, such as a silicon wafer or other types of wafers to be patterned. In this embodiment, the semiconductor substrate is coated with a photoresist layer sensitive to extreme ultraviolet light. A number of elements including those described above are integrated together and are operable to perform a lithographic exposure process.

The lithography system may further comprise or be integrated with (or coupled to) other modules.

As shown in FIG. 1, EUV radiation source 100 includes a droplet generator 115 and a laser-generated plasma collector mirror 110 enclosed by chamber 105. The droplet generator 115 generates a plurality of target droplets DP. In some embodiments, target drop DP is a tin drop. In some embodiments, each tin droplet has a diameter of about 30 microns. In some embodiments, the tin droplets DP are generated at a rate of about 50 droplets per millisecond (50kHz) and are introduced into the excitation zone ZE at a velocity of about 70 meters per second. Other materials may also be used for the target droplets, such as tin containing liquid materials, e.g. eutectic alloys containing tin or lithium.

The excitation laser LR2 generated by the excitation laser source device 300 is a pulsed laser. In some embodiments, the excitation laser includes a pre-laser and a main laser. The preheat laser pulse is used to heat (or preheat) the target droplet to produce a low density target plume (plume), which is then heated (or reheated) by the main laser pulse to produce increased euv light emission.

In many embodiments, the preheat laser pulse has a spot size of about 100 microns or less, and the main laser pulse has a spot size of about 200 and 300 microns.

Laser pulse LR2 is generated by excitation laser source 300. The excitation laser source 300 may include a laser generator 310, laser guide optics 320, and a focusing device 330. In some embodiments, laser generator 310 comprises a laser source of carbon dioxide or neodymium-doped yttrium aluminum garnet (Nd: YAG). Laser light LR1 generated by laser generator 310 is guided by laser guide optics 320 and focused by focusing device 330 into excitation laser light LR2 before being directed into euv radiation source 100.

Laser LR2 is directed through a window (or lens) into excitation zone ZE. The window is made of a suitable material that is substantially transparent to the laser beam. The generation of the pulsed laser is synchronized with the generation of the target droplets. The pre-pulse heats and converts the target droplets into a low density target plume as the target droplets pass through the excitation zone. The delay between the pre-pulse and the main laser is controlled to cause the target plume to form and expand to the desired size and geometry. When the main pulse heats the target plume, a high temperature plasma is generated. The plasma emitter ultraviolet radiation EUV is collected by collector mirror 110. The collector mirror 110 further reflects and focuses the euv radiation for use in a lithography exposure process. In some embodiments, the droplet catcher 120 is mounted opposite the target droplet generator 115. The droplet catcher 120 is used to catch excess target droplets. For example, some target droplets may be purposefully skipped by the laser pulse.

Collector mirror 110 is designed with appropriate coating materials and shapes to function as a mirror for extreme ultraviolet collection, reflection and focusing, for example. In some embodiments, the collector mirror 110 is designed to have an elliptical geometry. In some embodiments, the collector mirror 110 is coated with a material similar to the reflective multilayer of the euv light shield. In some examples, the coating material of the collector mirror 110 comprises multiple layers (e.g., a plurality of molybdenum/silicon film pairs) and may further comprise a capping layer (e.g., ruthenium) coated on the multiple layers to substantially reflect extreme ultraviolet light rays. In some embodiments, the collector mirror 110 may further comprise a grating structure designed to effectively scatter the laser beam directed to the collector mirror 110. For example, a silicon nitride layer is coated on the collector mirror 110 and patterned to have a grating pattern.

In such euv radiation source devices, the plasma created by the application of the laser generates physical debris, such as droplets of ions, gases and molecules, and the required euv radiation. It is necessary to prevent material build-up on the collector mirror 110 and also to prevent physical debris from leaving the chamber 105 and entering the exposure tool 200.

As shown in fig. 1, in the present embodiment, the buffer gas is supplied from the first buffer gas supply 130 and through the aperture of the collector mirror 110, wherein the pulsed laser light is delivered to the tin droplets through the aperture of the collector mirror 110. In some embodiments, the buffer gas is hydrogen, helium, argon, nitrogen, or another inert gas. In certain embodiments, hydrogen radicals generated by ionization of the buffer gas are made available for cleaning purposes using hydrogen gas. The buffer gas may also be provided via one or more second buffer gas supplies 135 towards the collector mirror 110 and/or around the edge of the collector mirror 110. In addition, the chamber 105 includes one or more gas outlets 140 so that buffer gas may be exhausted out of the chamber 105.

Hydrogen has a low absorption of euv radiation. The hydrogen gas reaching the coated surface of the collector mirror 110 chemically reacts with the metal droplets to form a mixture, such as a metal mixture. When tin is used as the droplets, stannane (SnH) is formed₄) Which is a gaseous by-product of the extreme ultraviolet light generation process. The gaseous stannane is then vented via outlet 140. However, it is difficult to evacuate all of the gaseous stannane from the chamber and to prevent the stannane from entering the exposure tool 200.

To capture stannane or other debris, one or more debris collection mechanisms 150 are used in the chamber 105.

As shown in fig. 1, one or more debris collection mechanisms 150 are disposed along optical axis a1 between excitation zone ZE of euv radiation source 100 and outlet port 160. Fig. 2A is a front view of the debris collecting mechanism 150, and fig. 2B is a side view of the debris collecting mechanism 150. Fig. 2C is a partial view of the debris collection mechanism 150. The debris collecting mechanism 150 comprises a frusto-conical support frame 151, a first end support 153 and a second end support 154, which operably support a plurality of vanes 152 (rotatable debris collecting elements) that rotate within the housing. The first end support 153 has a larger diameter than the second end support 154. By rotating the blades 152 to sweep away slow tin atoms and/or stannane, the debris collection mechanism 150 can be used to prevent tin vapor from coating the surfaces of the collector mirror 110 and/or other components/portions within the chamber 105. In some embodiments, a downstream cone 155 is disposed between the debris collection mechanism 150 and the outlet port 160.

Such vanes 152 project radially inwardly from the frustoconical cage 151. The vanes 152 are thin, long flat plates. In some embodiments, each blade has a triangular or trapezoidal trapezoid shape in plan view. Such vanes 152 are aligned with their longitudinal axes parallel to the optical axis a1 such that they result in the smallest possible cross-sectional area for EUV radiation. The vane 152 projects toward the optic axis a1, but does not extend to the optic axis. In some embodiments, the central core of the debris collection mechanism 150 is hollow. The debris collection mechanism 150 is rotated by a drive unit comprising one or more motors, one or more belts and/or one or more transmissions, or any rotating mechanism. In some embodiments, blade 152 is heated by a heater at 100 ℃ to 400 ℃.

As mentioned above, contamination of tin debris on the collector mirror, blades and/or other parts of the euv radiation source is a major cause of euv scanner exposure energy loss and throughput degradation. Collector mirror lifetime is maintained for, for example, about 3 months, and then it is usually necessary to take one week or more of downtime to replace the collector mirror with a new collector mirror, thereby maintaining high exposure energy and throughput.

In some embodiments, hydrogen radicals resulting from the extreme ultraviolet light exposure are used to etch tin debris by forming stannane. However, stannane is thermodynamically unstable and causes tin to redeposit on the collector mirror or other parts of the euv radiation source. In addition, the production of hydrogen radicals affects the generation of extreme ultraviolet light with more tin debris.

In this embodiment, metal contamination is removed by using inductively coupled plasma to generate halogen radicals, such as chlorine radicals, to remove tin debris and/or to prevent tin debris from depositing on the collector mirror or other portions of the euv radiation source. In some embodiments, gas injection with adjustable gas flow and gas species for different species of radical/ion generation may be used. In some embodiments, a halogen-containing gas is used. In certain embodiments, a chlorine-containing gas is used to generate chlorine radicals/ions that can remove tin by etching through the formation of tin tetrachloride. The chlorine-containing gas may be chlorine gas or CH_xCl_y(x + y ═ 4, and y is not zero), silicon tetrachloride or dichlorosilane. In some embodiments, argon, helium, xenon and/or the like are also suppliedOne or more carrier gases for hydrogen. In addition, in some embodiments, the distribution of plasma locations is adjustable to control the spatial distribution of the tin etch. In some embodiments, multiple circuits providing inductively coupled plasma sources are used to adjust the current ratio between the different circuits and to change the plasma profile, which dominates the spatial etch rate. In some embodiments, the source gas for providing the inductively coupled plasma comprises one or more of helium, argon, xenon, chlorine, hydrogen, oxygen, silane, and silicon tetrachloride.

In other embodiments, a silicon-containing gas and/or a zirconium-containing gas is used to form a passivated coating layer of zirconium dioxide and/or silicon dioxide on portions within the laser chamber. In some embodiments, zirconium tetra-tert-butoxide (Zr (OC (CH)₃)₃)₄) As the zirconium source gas and using silicomethane as the silicon source gas. The oxygen source gas may be oxygen. One or more carrier gases including argon, helium, xenon, and/or hydrogen are also provided in some embodiments.

Figure 3 shows a schematic view of a vacuum chamber of an euv light radiation source according to an embodiment of the present disclosure. As shown in FIG. 3, one or more additional inductively coupled plasma circuits are provided on or around the vessel boundary of the downstream cone 155 to generate the plasma PL. In this configuration, since the plasma PL is generated at a position away from the collector mirror 110, it is possible to prevent the plasma PL from damaging the collector mirror. In some embodiments, the plasma PL does not directly etch tin debris deposited on the collector mirror 110. In some embodiments, chlorine-containing gas is introduced from gas inlet 20. The source gas is introduced from a location near the extreme ultraviolet light outlet port 160 (see fig. 1). By controlling the flow of one or more source gases through one or more fluid controllers, it is possible to control the location at which the plasma PL is generated. In some embodiments, the plasma PL contacts the downstream cone 155, while in other embodiments the plasma PL does not contact the downstream cone 155.

In some embodiments, two rf power supplies 10A and 10B are provided, which provide ac power (ac current) to the coils 15A and 15B, respectively. The rf power supplies 10A and 10B can independently control the current/power to the coils 15A and 15B. In some embodiments, the phases of the ac currents supplied by the two rf power supplies 10A and 10B are 180 degrees apart from each other. By controlling the current values and/or phase of one or more RF power sources, it is possible to control the location at which the plasma PL is generated. In other embodiments, the phases of the alternating currents are the same. In some embodiments, only one rf power supply is provided, while in other embodiments three or more rf power supplies having different current phases or the same phase are provided. In some embodiments, the frequency of the RF power source is 13.56MHz, while in other embodiments the frequency is 2.45 GHz.

Figure 4 shows a schematic view of a chamber of an euv radiation source according to another embodiment of the present disclosure. As shown in FIG. 4, one or more inductively coupled plasma circuits are provided on or around the perimeter of the container of debris collection mechanism 150 to generate plasma PL. In this configuration, since the plasma PL is generated at a position away from the collector mirror 110, it is possible to prevent the plasma PL from damaging the collector mirror. In some embodiments, chlorine-containing gas is introduced from gas inlet 21. The source gas is introduced from a location between the debris collection mechanism 150 and the collector mirror 110 and is exhausted from a location between the debris collection mechanism 150 and the downstream cone 155 (gas outlet 22) and/or a location near the extreme ultraviolet light outlet port 160. Therefore, the plasma PL generated with the source gas flows from the collector mirror side to the downstream cone side, whereby it is possible to prevent the collector mirror 110 from being damaged by the plasma PL. By controlling the flow of one or more source gases through one or more fluid controllers, it is possible to control the location at which the plasma PL is generated. In some embodiments, the plasma PL contacts the debris collection mechanism 150, while in other embodiments the plasma PL does not contact the debris collection mechanism 150.

In some embodiments, two rf power supplies 10A and 10B are provided, which provide ac power (ac current) to the coils 15A and 15B, respectively. In some embodiments, the phases of the ac currents supplied by the two rf power supplies 10A and 10B are 180 degrees apart from each other. By controlling the current values and/or phase of one or more RF power sources, it is possible to control the location at which the plasma PL is generated. In other embodiments, the phases of the alternating currents are the same. In some embodiments, only one rf power supply is provided, while in other embodiments three or more rf power supplies having different current phases or the same phase are provided.

Figure 5 shows a schematic view of a chamber of an euv radiation source according to another embodiment of the present disclosure. As shown in FIG. 5, one or more inductively coupled plasma circuits are provided on or around the collector mirror 110 to generate the plasma PL. In this configuration, the generation of the plasma PL is controlled such that the plasma PL is generated at a location sufficiently far from the collector mirror 110 to prevent the plasma PL from damaging the collector mirror. In some embodiments, the plasma PL (light emitting section) does not contact the collector mirror 110. In other embodiments, a distance between the plasma PL and the collector mirror 110 that is longer than the size of the plasma emission region is provided, since the radicals are active even after leaving the plasma PL.

In some embodiments, chlorine-containing gas is introduced from gas inlet 21. The source gas is introduced from a location between the debris collection mechanism 150 and the collector mirror 110 and is exhausted from a location between the debris collection mechanism 150 and the downstream cone 155 (gas outlet 22) and/or a location near the extreme ultraviolet light outlet port 160. Therefore, the plasma PL generated with the source gas flows from the collector mirror side to the downstream cone side, so it is possible to prevent the plasma PL from damaging the collector mirror 110. By controlling the flow of one or more source gases through one or more fluid controllers, it is possible to control the location at which the plasma PL is generated. In some embodiments, the plasma PL contacts the debris collection mechanism 150, while in other embodiments the plasma PL does not contact the debris collection mechanism 150.

In some embodiments, two rf power supplies 10A and 10B are provided, which provide ac power (ac current) to the coils 15A and 15B, respectively. In some embodiments, the phases of the ac currents supplied by the two rf power supplies 10A and 10B are 180 degrees apart from each other. By controlling the current values and/or phase of one or more RF power sources, it is possible to control the location at which the plasma PL is generated. In other embodiments, the phases of the alternating currents are the same. In some embodiments, only one rf power supply is provided, while in other embodiments three or more rf power supplies having different current phases or the same phase are provided.

FIGS. 6 and 7 illustrate embodiments of the present disclosureSchematic representation of the chamber of the euv light radiation source of other embodiments. The configuration of fig. 6 is a combination of the three configurations explained in accordance with fig. 3 to 5. In some embodiments, two of the configurations of fig. 3-5 are combined. In one embodiment, the configurations of fig. 3 and 4 are combined, as shown in fig. 7. By adjusting the relative signal strength of the RF power source, such as phase and/or gas flow, it is possible to adjust the position of the plasma (the strongest plasma position). When combined with the configurations of fig. 3-5, two rf power supplies 10A and 10B are applied to the coils 15A and 15B of fig. 3-5 in some embodiments, while respective rf power supplies 10A and 10B are applied to the respective coils 15A and 15B of fig. 3-5 in other embodiments. In some embodiments, when the pressure is below about 1.0 x 10^-6The etching rate of tin by chlorine plasma is higher than about 600 nm/min.

In the foregoing embodiment, the plasma PL is generated to remove tin debris. In other embodiments, a passivation layer is formed on portions within the vacuum chamber of the euv light radiation source. For example, by using zirconium-containing and/or silicon-containing gases, it is possible to deposit zirconium dioxide and/or silicon dioxide on portions within the vacuum chamber, such as collector mirrors and/or vanes.

In the exposure mode where extreme ultraviolet light rays are generated by laser pulses, stannane is generated by the reaction between tin and hydrogen or hydrogen radicals. In this exposure mode, when a chlorine-containing gas is introduced and a plasma containing chlorine radicals is generated, tin tetrachloride is also generated. By draining stannane and tin tetrachloride from the chamber, it is possible to reduce the generation of tin debris within the chamber. Since the thermal decomposition temperature of tin tetrachloride is higher than 1250K, tin tetrachloride is more stable than stannane (decomposition temperature is 300K-500K). Thus, by increasing the amount of tin tetrachloride, it is possible to avoid redeposition of tin on parts within the chamber.

By generating a plasma containing chlorine radicals in an idle mode in which extreme ultraviolet light is not generated (and thus tin by-products are not generated), tin debris or tin by-products deposited on portions within the chamber may be removed by forming tin tetrachloride. By draining stannane and tin tetrachloride from the chamber, it is possible to reduce the generation of tin debris within the chamber.

In other embodiments, the source gas is changed from the chlorine-containing gas to the zirconium-containing gas and/or the silicon-containing gas after the plasma for removing the tin debris is generated and the tin debris is removed in the idle mode. Thus, a passivation layer consisting of zirconium dioxide and/or silicon dioxide is formed on the partially cleaned surface in the vacuum chamber of the euv light radiation source. In some embodiments, the deposition of the passivation layer and the etching of the plasma are repeated.

In an embodiment of the present disclosure, tin debris caused during extreme ultraviolet light generation is removed using a plasma of an inductively coupled plasma generated from a chlorine-containing gas. Since tin tetrachloride has a higher decomposition temperature than stannane, it is possible to more effectively remove tin debris from the vacuum chamber of the euv radiation source. In other embodiments, a passivation layer may be formed on portions of the vacuum chamber of the UV radiation source by using zirconium-containing gas and/or silicon-containing gas to prevent deposition of tin debris and/or to facilitate removal of deposited tin debris. It is thus possible to extend the lifetime of the collector mirror and to reduce the frequency of replacing a used collector mirror with a new, clean collector mirror.

It is to be understood that not necessarily all advantages will be discussed herein, that no particular advantage is required in all embodiments or examples, and that other embodiments or examples may provide different advantages.

According to one aspect of the present disclosure, an euv radiation source apparatus includes a collector mirror, a target drop generator for generating tin drops, a rotatable debris collection element, one or more coils for generating an inductively coupled plasma, a gas inlet for providing a source gas for the inductively coupled plasma, and a chamber surrounding at least the collector mirror and the rotatable debris collection element. The gas inlet and the one or more coils are arranged so that the inductively coupled plasma is spaced from the collector mirror. In one or more of the foregoing and following embodiments, the source gas comprises one or more of helium, argon, xenon, chlorine, hydrogen, oxygen, silane, silicon tetrachloride, and dichlorosilane. In one or more of the foregoing and following embodiments, the source gas is a chlorine-containing gas. In one or more of the foregoing and following embodiments, the euv light radiation source apparatus further comprises a downstream cone provided between the rotatable debris collecting element and the euv light outlet port. At least one coil surrounds or covers the downstream cone. In one or more of the foregoing and following embodiments, the source gas is provided from a location between the downstream cone and the extreme ultraviolet light outlet port. In one or more of the foregoing and following embodiments, at least one coil surrounds or covers the rotatable debris collecting element. In one or more of the foregoing and following embodiments, the source gas is provided from a location between the rotatable debris collecting element and the collector mirror. In one or more of the foregoing and following embodiments, the euv light radiation source apparatus further comprises a downstream cone provided between the rotatable debris collecting element and the euv light outlet port. The source gas is discharged from at least one of a location between the rotatable debris collection element and the downstream cone and a location between the downstream cone and the extreme ultraviolet light outlet port. In one or more of the foregoing and following embodiments, the euv light radiation source apparatus further comprises an ac power source for supplying ac power to the one or more coils. In one or more of the foregoing and following embodiments, two or more coils are provided, and the current of each of the two or more coils is independently adjustable. In one or more of the foregoing and following embodiments, a phase of a current flowing into one of the two or more coils is 180 degrees different from a phase of a current flowing into another of the two or more coils. In one or more of the foregoing and following embodiments, the gas inlet for providing the source gas is located at a position between the downstream cone and the extreme ultraviolet light outlet port. In one or more of the foregoing and following embodiments, the gas inlet for providing the source gas is located at a position between the rotatable debris collecting element and the collector mirror. In one or more of the foregoing and following embodiments, a gas outlet port for exhausting the source gas is provided at least one of a location between the rotatable debris collection element and the downstream cone and a location between the downstream cone and the extreme ultraviolet light outlet port.

According to another aspect of the present disclosure, an euv light radiation source apparatus comprises a collector mirror, a target droplet generator for generating tin droplets, a rotatable debris collecting element, one or more coils for generating an inductively coupled plasma, a gas inlet for providing a source gas for the inductively coupled plasma, and a chamber surrounding at least the collector mirror and the rotatable debris collecting element. The source gas includes one or more of a silicon-containing gas and a zirconium-containing gas. In one or more of the foregoing and following embodiments, the source gas comprises zirconium tetra-tert-butoxide. In one or more of the foregoing and following embodiments, at least one coil surrounds or covers the backside of the collector mirror. In one or more of the foregoing and following embodiments, at least one coil surrounds or covers the rotatable debris collecting element. In one or more of the foregoing and following embodiments, the euv light radiation source apparatus further comprises a downstream cone provided between the rotatable debris collecting element and the euv light outlet port. At least one coil surrounds or covers the downstream cone.

In accordance with another aspect of the present disclosure, in a method of cleaning a portion of a chamber of an extreme ultraviolet radiation source, a chlorine-containing gas is supplied into the chamber and an inductively coupled plasma is generated by supplying an alternating current to a coil disposed within the chamber, thereby removing tin debris by forming tin tetrachloride. The collector mirror is not damaged by the inductively coupled plasma generated. In one or more of the foregoing and following embodiments, the inductively coupled plasma is generated during periods when extreme ultraviolet light is not being generated. In one or more of the foregoing and following embodiments, the current to each coil is independently controlled. In one or more of the foregoing and following embodiments, the phase of the current flowing in one of the coils is 180 degrees out of phase with the phase of the current flowing in the other of the coils.

The foregoing outlines features of some embodiments or examples so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments or examples introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.