Patent ID: 12245409

Various implementations are described below with reference to the drawings. In the description below, specific details are set forth to promote an understanding of the various implementations. Any implementation discussed below may be practiced without the specific details.

DETAILED DESCRIPTION

FIG.1Ais a side cross-sectional block diagram of a system100that includes a light source110and an apparatus130for the light source110.FIG.1Bis a cross-sectional view of the apparatus130along the line1B-1B′ ofFIG.1A. The apparatus130includes a shield135that protects a gasket133from degradation.

The apparatus130receives a conductor151that delivers electrical current to an electrode113ain the light source110. The apparatus130includes an insulator131(shown with dotted shading), the gasket133(shown with crossed-line shading), and the shield135(shown with dark gray shading). The shield135blocks or attenuates a transient or time-varying magnetic field that arises from the delivery of the electrical current. The light source110includes a discharge chamber115that contains a gas mixture119. The gasket133seals the discharge chamber115such that the gas mixture119remains in the discharge chamber115.

The gasket133is any type of sealing mechanism and may be, for example, an O-ring or a C-ring. The gasket133includes a non-metallic material. The non-metallic material is any type of material that is not metallic. For example, the gasket133may be made of a rubber or elastomer material, such as, for example, VITON™, available from DuPont Corporation of Wilmington, Delaware. The gasket133may include other compounds or materials that are introduced into the non-metallic material that forms gasket133during manufacture. For example, the gasket133may be a fluorinated material, such as a fluorinated rubber. Although the gasket133includes a non-metallic material, the gasket133may also include metal. For example, the gasket133may be a material that is generally electrically insulating that is coated with an electrically conductive material. In these implementations, the gasket133may be a rubber gasket that is coated with a thin layer of metal. The non-metallic material in the gasket133is more mechanically flexible than the metals that are typically used for gaskets.

The relative flexibility of the non-metallic material results in the gasket133being more robust and more adaptable when exposed to thermal stress as compared to a metal gasket. However, the non-magnetic material is also more susceptible to plasma damage. The transient magnetic field produced by the delivered electrical current creates an inductive electric field that may form plasma from the gas mixture119. Although a metallic gasket is generally resistant to corrosion from this plasma, the non-metallic material of the gasket133is not as resistant and may be damaged and degraded by exposure to the plasma. If the gasket133fails or degrades, the gas mixture119may leak from the discharge chamber115. The gas mixture119may include components (for example, fluorine) that produce dangerous or otherwise unfavorable conditions in the presence of gases, such as oxygen, that are ordinarily found in the atmosphere. Moreover, even in instances in which the gas mixture119does not include components that cause unfavorable conditions in the presence of gases ordinarily found in the atmosphere, loss of the gas mixture119reduces the performance of the light source110.

The shield135blocks or attenuates the transient magnetic field that arises from conducting electrical current in the conductor151. By blocking or attenuating the transient magnetic field, the shield135protects the gasket133, thereby ensuring safe and efficient operation of the light source110and improving the overall performance of the light source110.

In greater detail, the discharge chamber115encloses the electrode113a, an electrode113b, and the gas mixture119. The gas mixture119includes a gain medium formed from, for example, a noble gas and a halogen gas. The apparatus130includes an electrical insulator131that passes through an opening112in a wall114of the discharge chamber115. The wall114is made of a mechanically robust material. For example, the wall may be made of a mechanically robust metal material, such as, for example, aluminum, aluminum coated with nickel, or aluminum coated with another metallic material; a ruggedized polymer; or a mechanically robust metal material with a ruggedized polymer exterior. The opening112is sealed with the gasket133, which is seated in a groove118. The groove118is a recess, slot, or other open region that accommodates the gasket133. The groove118may be formed in any manner. For example, the groove118may be formed in a metallic interior portion114aof the wall114. In another example, the groove118may be formed from a solid metallic wall that is separate from the interior portion114aand separate from the wall114. At least part of the gasket133is inside the discharge chamber115, and the gasket133surrounds the electrical insulator131. The insulator131is made of any type of electrically insulating material. For example, the insulator131may be made of aluminum oxide (Al2O3).

The electrical insulator131defines a channel132that passes through the electrical insulator131and accommodates a conductor151. The conductor151is electrically connected to a power supply197and to the electrode113a. The electrodes113aand113bare made of an electrically conductive material, such as, for example, a metal or a metal alloy. For example, the electrodes113aand113bmay be made of an alloy of copper and zinc. One of the electrodes113aand113bis an anode and the other of the electrodes113aand113bis a cathode. In the example ofFIG.1A, the electrode113ais the cathode and the electrode113bis the anode. In other implementations, the electrode113ais the anode and the electrode113bis the cathode.

In operational use of the light source110, the power supply197provides a time-varying electrical current to the electrode113avia the conductor151. The electrode113bis held at a constant voltage (for example, the electrode113bmay be grounded). Thus, charging the electrode113acreates a potential difference and an electric field between the electrodes113aand113b.

FIG.1Cis a plot of an example of the potential difference between the electrodes113aand113bover a charge cycle that produces a single pulse of light of a pulsed output light beam116. Between times t0and t1, no current is provided to the electrode113a, and the voltage difference between the electrodes113aand113bis 0 volts (V). Between time t1and time t2, the power supply197supplies a large amount of electrical current (for example, hundreds or thousands of amperes) to the electrode113a. The electrical charge on the electrode113aaccumulates, and the voltage difference between the electrode113aand the electrode113bchanges from 0 V to V1. When the voltage difference reaches V1 at time t2, the electric field between the electrodes113aand113bis sufficient to cause population inversion in the gain medium of the gas mixture119, and a pulse of light is produced. The power supply197stops supplying electrical current, and the voltage differential between the electrodes113aand113bdecreases from V1 to 0 V, and is 0V again at time t3. The potential difference between the electrode113aand113bremains at 0V between time t3and time t4. Repeating the charge cycle produces another pulse of light. By repeating the charge cycle many, pulses of light separated from each other in time are formed and the pulsed light beam116is generated

The electric charge on the electrode113acreates a capacitive electric field between the electrode113aand the metallic interior portion114aof the wall114chamber115, as shown by Equation 1 (which is one of Maxwell's equations):
∇·{right arrow over (E)}=ρ/ε0Equation (1),
where E represents the electric field, p is the total charge per unit volume on the electrode113a, and ε0is the permittivity of free space. In addition to the capacitive electric field, an inductive electric field arises from the delivery of the electrical current to the electrode113avia the conductor151. During a charge cycle, electrical current flows in the conductor151for only a very small amount of time. For example, in the charge cycle shown inFIG.1C, electrical current only flows in the conductor151between the times t1and t2. The amount of time between the times t1and t2is relatively small (for example, a few nanoseconds or tens of nanoseconds). During the rest of the charge cycle, electrical current does not flow in the conductor151. Thus, the electrical current is not constant throughout the charge cycle and is a time-varying electrical current. The electrical current therefore produces a time-varying magnetic field.

The time-varying magnetic field produces an inductive electric field, as shown in Equation 2 (which is another one of Maxwell's equations):

∇×E→=-∂B→∂t,Equation⁢(2)
where E represents the electric field and B represents the magnetic field. Furthermore, the curl of the magnetic field found in Equation (2) is related to the electric field as shown in Equation 3 (which is another one of Maxwell's equations):

∇×B→=μ0⁢J→+1c2⁢∂E→∂t,Equation⁢(3)
where μ0is the permeability of free space, c is the speed of light, J is the total current per unit area, and E is the electric field. For example, if 1000 amperes (A) of current is provided to the electrode113aover a few nanoseconds, the electric field produced will be hundreds to thousands of volts (V) per meter (m), and the magnetic field at the gasket133will be about 500 Gauss (G). The inductive electric field (which is caused by the transient magnetic field) may cause the gas mixture119to ionize or form plasma, which may damage the gasket133.

The material in which the groove118is formed is a mechanically robust material (such as aluminum) that does not completely shield the gasket133from the time-varying magnetic field or does not shield the gasket133from the time-varying magnetic field at all. On the other hand, the apparatus130includes the shield135, which surrounds the conductor151and suppresses or eliminates the time-varying magnetic field. By suppressing or eliminating the time-varying magnetic field, the shield135also reduces or eliminates the inductive electric field and reduces or eliminates the production of plasma that may damage the gasket133.

The shield135is made of any type of material that is capable of providing magnetic shielding. For example, the shield135may be made of a high-permeability metal. Permeability (μ) is a measure of a material's resistance to the formation of a magnetic field or the degree of magnetization that the material obtains in response to an applied magnetic field. The shield135may be made of a metal material with a relatively small skin depth. Skin depth is the depth at which an incident electromagnetic wave has been reduced by 1/e. Materials with high permeability also tend to have a small skin depth. Using a material with a small skin depth for the shield135reduces the size of the shield. Examples of materials that may be used for the shield include, for example, Mu-metal (which is an alloy of nickel and iron), an alloy made of cobalt and iron, an alloy made of silicon and iron, pure iron, steel 410, permalloy, and Metglas 2714A (annealed).

Moreover, the shield135is an element that is made of a material that is not necessarily as mechanically robust as the material in which the groove118is formed. Many materials that have a high permeability and offer the most magnetic shielding are not mechanically robust and would not be suitable for use as the groove118or the wall114. Accordingly, the shield135allows the groove118and the wall114to be made of a mechanically robust material while also providing magnetic shielding to the gasket133.

Although the shield135is an element that is in addition to the groove118and is made of a different material than material in which the groove118is formed, the shield135may take a variety of forms. For example, the shield135may be a separate structure that is formed as a three-dimensional object and then seated into the groove118during assembly of the light source110or during an upgrade or retro-fit of the light source110.FIGS.2D and3Cshow examples of such a three-dimensional object. In other implementations, the material of the shield135is coated onto a portion of the groove118that is between the gasket133and the insulator131.

Moreover, the groove118may take other forms, and the shield135may be placed in a configuration other than shown inFIG.1A. For example, the shield135may be outside of the groove118but still between the conductor151and the gasket133.FIG.1Dshows an example of such a configuration. Furthermore, the light source110may lack the groove118. In these implementations, the gasket133may be bonded to the interior portion114adirectly without being seated in a groove such as the groove118.FIG.4is an example of such an implementation.

Referring toFIG.1D, a system100D is shown. The system100D includes a light source110D. The light source110D includes a discharge chamber115D, which is similar to the discharge chamber115(FIG.1A), except the discharge chamber115D includes a first portion114eand a second portion114d. The electrodes113aand113bare inside chamber115, in the second portion114d. The discharge chamber115D includes a surface114bthat extends generally in the X-Z plane between the first portion114eand the second portion114d. First portion114emay be, for example, a plate or block of metal, such as aluminum. In the implementation shown inFIG.1D, the gasket133is in a groove118D. The groove118D is an open region surrounded by a wall that extends in the Y direction from the surface114b. The groove118D accommodates the gasket133in the open region. The shield135is not in the open region of the groove118D. However, the shield135is between the gasket133and the conductor132, and the shield135also surrounds the insulator131. Thus, regardless of the position of the shield135relative to the groove118D, the shield135blocks or attenuates magnetic fields that may be generated during use of the optical source110D.

Other implementations of the groove118and the groove118D are possible, and the configurations shown inFIGS.1A,1D, and4are provided as examples. For example, the shield135may be placed in the groove118D, or the groove118D may be coated with the material used for the shield135.

FIG.2Ais a perspective view of an apparatus230. The apparatus230is an example of an implementation of the apparatus130(FIGS.1A and1B). The apparatus230may be used with the light source110or with a DUV light source such as shown inFIG.5A or6.FIG.2Bis a cross-sectional view of the apparatus230in the Y-Z plane.FIG.2Cis a cross-sectional view of the apparatus230taken along the line2C-2C′ ofFIG.2B.

The apparatus230includes an electrical insulator231(shown with dotted shading inFIGS.2B and2C), a gasket233(shown with crossed-line shading inFIGS.2B and2C), and a shield235(shown with solid gray shading inFIGS.2B and2C). The electrical insulator231includes a base portion236aand a stem portion236bthat extends in the Y direction from the base portion236a. The stem portion236bis substantially cylindrical in shape. The stem portion236bincludes an outer wall237aand an inner wall237b. The inner wall273bdefines a channel232that passes through the electrical insulator231. In operational use, the channel232receives an electrical conductor, such as the electrical conductor151(FIG.1A). In the example ofFIGS.2A-2C, the channel232has a circular cross-section in the X-Z plane.

The base portion236ais annular and extends generally in the X-Z plane. The base portion236aincludes a first side238aand a second side238bopposite the first side238a. Referring also toFIG.2D, which is a perspective view of the shield235, the shield235includes a cylindrically shaped sidewall239that extends in the Y direction from a first end240ato a second end240b. The sidewall239includes an inner wall241that defines a passageway243. The passageway243has an extent245in the Y direction. When the apparatus230is assembled (as shown inFIGS.2A-2C), the inner wall241of the shield235surrounds the outer wall237aof the stem portion236b, and the end240arests on the first side238aof the base portion236a.

The shield235is made of a material that inhibits or blocks magnetic fields. For example, the shield235may be made of a magnetic or ferrous metal such as a mu-metal, iron, or an iron alloy. The sidewall239of the shield235has a thickness244. The thickness244is the radial distance between the inner wall241and an outer wall242. The thickness244is at least equal to the skin depth of the material of the shield235. In some implementations, the extent245of the shield is at least twice the diameter of the passageway243.

The apparatus230also includes the gasket233. The gasket233may be made of a rubber or elastomer material. The gasket233has an annular shape and may be, for example, an O-ring or a C-ring. The gasket233rests on the first side238aof the base portion236a. The shield235is between the gasket233and the stem portion236b. The gasket233has an extent246in the Y direction. In the example shown inFIG.2C, the shield235is concentric with the channel232and is also concentric with the stem portion236b. Furthermore, the gasket233has an annular shape and is concentric with the channel232, the stem portion236b, and the shield235.

In operational use, the apparatus230is installed in a light source such as shown inFIG.1A. The gasket233acts as a seal and the shield235protects the gasket233from plasma and/or electromagnetic fields created during operation of the light source. In the example shown inFIG.2A, the extent246of the gasket233is smaller than the extent245of the shield. Such a configuration allows the shield235to more fully extinguish or block magnetic fields. However, other implementations are possible. For example, the extent245of the shield235may be equal to the extent246or less than the extent246. Moreover, although a shield235with a greater extent245may eliminate a greater portion of the magnetic field produced during operational use, the extent245of the shield235is limited such that the shield235does not come into contact with metallic objects that carry electrical current or does not come close enough to such metallic objects to present a risk of arcing.

FIG.3Ais a cross-sectional view of an apparatus330and an electrode313a. The apparatus330is another example implementation of the apparatus130(FIG.1A). The apparatus330may be used with the light source110(FIG.1A) or with another light source, such as those shown inFIGS.5A and6.

The apparatus330includes an insulator331(shown with dotted shading), a gasket333(shown with crossed-lined shading), and a shield335(shown in solid dark gray shading) between the insulator331and the gasket333. The insulator331includes a base portion336a, a stem portion336bthat extends in the Y direction from the base portion336a, and a side portion336cthat extends in the −Y direction from the base portion336a. Referring also toFIG.3B, which shows the insulator331in the X-Z plane, the base portion336ahas an annular shape in the X-Z plane.

The stem portion336bincludes an outer wall337aand an inner wall337b. The inner wall337bdefines a channel332. The outer wall337aincludes ridges354that encircle the stem portion336bin the X-Z plane. The ridges354increase the surface distance of the outer wall337aof the stem portion336bin the Y direction as compared to an implementation that lacks the ridges354. The increase in surface distance or surface path provides better electrical insulation and impedes surface tracking. Surface tracking refers to the formation of a continuous conducting paths across the surface of the insulator331due to surface erosion that may occur due to exposure to high voltages.

The side portion336cextends from the base portion336ain the −Y direction and provides insulation between ends317aand317bof the electrode313aand the interior walls of a discharge chamber (such as the chamber115ofFIG.1A) that encloses the electrode313a. The side portion336cmay have any shape in the X-Z plane. For example, the side portion336cmay have a circular shape, an elliptical shape, or a rectangular shape. The electrode313aand side portion336cmay have the same shape in the X-Z plane, with the side portion336cbeing large enough to surround the electrode313a.

FIG.3Cis a perspective view of the shield335. The shield335includes a cylindrically shaped sidewall339that extends in the Y direction from a first end340ato a second end340b, and a flange348that extends radially outward from the first end340ain the X-Z plane. The sidewall339has a thickness344. The flange348surrounds the first end340a. In the example ofFIGS.3A and3C, the flange348is a circle in the X-Z plane. The flange348has an extent in the Y direction, and the extent may be equal to or greater than the skin depth of the material used for the shield335. The shield335is made of any type of material that suppresses or blocks magnetic fields. For example, the shield335may be made of a mu-metal or an iron alloy.

When the apparatus330is assembled (such as shown inFIG.3A), the flange348is between a first side338aof the base portion336aof the insulator331and the gasket333. The sidewall339of the shield335is between an outer wall337aof the stem portion336band the gasket333. The flange348may increase the amount of magnetic field that the shield335is able to block.

FIG.4is a side cross-sectional view of a discharge chamber415and an apparatus430. The discharge chamber415includes a housing414that encloses an electrode413aand an electrode413b. The housing414also contains a gas mixture419that includes a gain medium. The electrode413amay be a cathode, and the electrode413bmay be an anode. The discharge chamber415includes a housing414that has a metallic inner wall414a, i.e. wall414ais formed of an electrically conductive material.

The apparatus430includes an insulator431(shown with dotted shading). The insulator431includes a base portion436athat extends in the X-Z plane between the electrode413aand a top414bof the inner wall414a. The insulator431also includes a plurality of stem portions436b_1,436b_2,436b_3that extend from the base portion436ain the Y direction. The stem portions436b_1,436b_2,436b_3pass through respective openings412_1,412_2,412_3in the top414b. The gaskets433_1,433_2,433_3surround the respective stem portions436b_1,436b_2,436b_3. The gaskets433_1,433_2,433_3seal the openings412_1,412_2,412_3, respectively.

The gaskets433_1and433_3(shown with crossed-line shading) include a material that is not generally electrically conductive, such as rubber. The gasket433_2is made of a metal material. The stem portion436b_1is surrounded by a shield435_1, and the stem portion436b_3is surrounded by a shield435_3. The shields435_1and435_3are shown with dark gray shading. Each of the stem portions436b_1to436b_3defines a channel that surrounds a respective electrical conductor451_1,451_2,451_3. Each of the electrical conductors451_1,451_2,451_3is electrically connected to the electrode413a.

In operational use, the electrical conductors451_1,451_2,451_3deliver short pulses of electrical charge (for example, 1-100 nanoseconds) to the electrode413arepeatedly over time to repeatedly excite the gain medium in the gas mixture419and to produce a pulsed light beam. The delivery of electrical charge causes the temperature of the housing414; the insulator431; the gaskets433_1,433_2,433_3; and the electrodes413a,413bto change. These elements are made of different materials and have different thermal characteristics and experience different amounts of thermal expansion. In various embodiments, the center portion of the chamber415experiences the least amount of thermal expansion. The relatively low amount of thermal expansion in the center portion of the chamber415allows the gasket433_2to be a metal material.

The amount of thermal expansion may be greater at either end of the chamber415, and the gaskets433_1and433_3include a non-metallic material, such as, for example, rubber, that does not experience a high amount of thermal expansion. However, the gaskets433_1and433_3may be damaged by plasma and thus each of the gaskets433_1and433_3is protected by the respective shield435_1and435_3. The shields435_1and435_3are made of a material with a high permittivity. The shields435_1and435_3may be similar to the shield235or the shield335in shape.

FIGS.5A and6show examples of deep ultraviolet (DUV) optical systems with which the apparatuses130,230,330, or430may be used.FIGS.5A and6are illustrated with the apparatus130, but may use any of the apparatuses230,330, and430. Referring toFIGS.5A and5B, a system500includes a light-generation module510that provides an exposure beam (or output light beam)516to a scanner apparatus580. A control system550is also coupled to the light-generation module510and to various components associated with the light-generation module510.

The light-generation module510includes an optical oscillator512. The optical oscillator512generates the output light beam516. The optical oscillator512includes a discharge chamber515, which encloses a cathode513-aand an anode513-b. The discharge chamber515also contains a gaseous gain medium519(shown with light dotted shading inFIG.5A). A potential difference between the cathode513-aand the anode513-bforms an electric field in the gaseous gain medium519. The potential difference is generated by controlling a power supply597to provide electrical current to the cathode513-a. The electric field provides energy to the gain medium519sufficient to cause a population inversion and to enable generation of a pulse of light via stimulated emission. Repeated creation of such a potential difference forms a train of pulses, which are emitted as the light beam516. The repetition rate of the pulsed light beam516is determined by the rate at which voltage is applied to the electrodes513-aand513-b. The repetition rate of the pulses may range, for example, between about 500 and 6,000 Hz. In some implementations, the repetition rate may be greater than 6,000 Hz, and may be, for example, 12,000 Hz or greater. Each pulse emitted from the optical oscillator512may have a pulse energy of, for example, approximately 1 milliJoule (mJ).

The gaseous gain medium519may be any gas suitable for producing a light beam at the wavelength, energy, and bandwidth required for the application. The gaseous gain medium519may include more than one type of gas, and the various gases are referred to as gas components. For an excimer source, the gaseous gain medium519may contain a noble gas (rare gas) such as, for example, argon or krypton; or a halogen, such as, for example, fluorine or chlorine. In implementations in which a halogen is the gain medium, the gain medium also includes traces of xenon apart from a buffer gas, such as helium.

The gaseous gain medium519may be a gain medium that emits light in the deep ultraviolet (DUV) range. DUV light may include wavelengths from, for example, about 100 nanometers (nm) to about 400 nm. Specific examples of the gaseous gain medium519include argon fluoride (ArF), which emits light at a wavelength of about 193 nm, krypton fluoride (KrF), which emits light at a wavelength of about 248 nm, or xenon chloride (XeCl), which emits light at a wavelength of about 351 nm.

A resonator is formed between a spectral adjustment apparatus595on one side of the discharge chamber515and an output coupler596on a second side of the discharge chamber515. The spectral adjustment apparatus595may include a diffractive optic such as, for example, a grating and/or a prism, that finely tunes the spectral output of the discharge chamber515. The diffractive optic may be reflective or refractive. In some implementations, the spectral adjustment apparatus595includes a plurality of diffractive optical elements. For example, the spectral adjustment apparatus595may include four prisms, some of which are configured to control a center wavelength of the light beam516and others of which are configured to control a spectral bandwidth of the light beam516.

The spectral properties of the light beam516may be adjusted in other ways. For example, the spectral properties, such as the spectral bandwidth and center wavelength, of the light beam516may be adjusted by controlling a pressure and/or gas concentration of the gaseous gain medium of the chamber515. For implementations in which the light-generation module510is an excimer source, the spectral properties (for example, the spectral bandwidth or the center wavelength) of the light beam516may be adjusted by controlling the pressure and/or concentration of, for example, fluorine, chlorine, argon, krypton, xenon, and/or helium in the chamber515.

The pressure and/or concentration of the gaseous gain medium519is controllable with a gas supply system590. The gas supply system590is fluidly coupled to an interior of the discharge chamber515via a fluid conduit589. The fluid conduit589is any conduit that is capable of transporting a gas or other fluid with no or minimal loss of the fluid. For example, the fluid conduit589may be a pipe that is made of or coated with a material that does not react with the fluid or fluids transported in the fluid conduit589. The gas supply system590includes a chamber591that contains and/or is configured to receive a supply of the gas or gasses used in the gain medium519. The gas supply system590also includes devices (such as pumps, valves, and/or fluid switches) that enable the gas supply system590to remove gas from or inject gas into the discharge chamber515. The gas supply system590is coupled to the control system250.

The optical oscillator512also includes a spectral analysis apparatus598. The spectral analysis apparatus598is a measurement system that may be used to measure or monitor the wavelength of the light beam516. In the example shown inFIG.5A, the spectral analysis apparatus598receives light from the output coupler596.

The light-generation module510may include other components and systems. For example, the light-generation module510may include a beam preparation system599. The beam preparation system599may include a pulse stretcher that stretches each pulse that interacts with the pulse stretcher in time. The beam preparation system also may include other components that are able to act upon light such as, for example, reflective and/or refractive optical elements (such as, for example, lenses and mirrors), and/or filters. In the example shown, the beam preparation system599is positioned in the path of the exposure beam516. However, the beam preparation system599may be placed at other locations within the system500.

The system500also includes the scanner apparatus580. The scanner apparatus580exposes a wafer582with a shaped exposure beam516A. The shaped exposure beam516A is formed by passing the exposure beam516through a projection optical system581. The scanner apparatus580may be a liquid immersion system or a dry system. The scanner apparatus580includes a projection optical system581through which the exposure beam516passes prior to reaching the wafer582, and a sensor system or metrology system570. The wafer582is held or received on a wafer holder583. The scanner apparatus580also may include, for example, temperature control devices (such as air conditioning devices and/or heating devices), and/or power supplies for the various electrical components.

The metrology system570includes a sensor571. The sensor571may be configured to measure a property of the shaped exposure beam516A such as, for example, bandwidth, energy, pulse duration, and/or wavelength. The sensor571may be, for example, a camera or other device that is able to capture an image of the shaped exposure beam516A at the wafer582, or an energy detector that is able to capture data that describes the amount of optical energy at the wafer582in the x-y plane.

Referring also toFIG.5B, the projection optical system581includes a slit584, a mask585, and a projection objective, which includes a lens system586. The lens system586includes one or more optical elements. The exposure beam516enters the scanner apparatus580and impinges on the slit584, and at least some of the output light beam516passes through the slit584to form the shaped exposure beam516A. In the example ofFIGS.5A and5B, the slit584is rectangular and shapes the exposure beam516into an elongated rectangular shaped light beam, which is the shaped exposure beam516A. The mask585includes a pattern that determines which portions of the shaped light beam are transmitted by the mask585and which are blocked by the mask585. Microelectronic features are formed on the wafer582by exposing a layer of radiation-sensitive photoresist material on the wafer582with the exposure beam516A. The design of the pattern on the mask is determined by the specific microelectronic circuit features that are desired.

The configuration shown inFIG.5Ais an example of a configuration for a DUV system. Other implementations are possible. For example, the light-generation module510may include N instances of the optical oscillator512, where N is an integer number greater than one. In these implementations, each optical oscillator512is configured to emit a respective light beam toward a beam combiner, which forms the exposure beam516.

FIG.6shows another example configuration of a DUV system.FIG.6is a block diagram of a photolithography system600that includes a light-generation module610that produces a pulsed light beam616, which is provided to the scanner apparatus580. The light-generation module610is illustrated with the apparatus130, but may be used with the apparatus230,330, or430. The control system550is coupled to various components of the light-generation module610and the scanner apparatus680to control various operations of the system600.

The light-generation module610is a two-stage laser system that includes a master oscillator (MO)612_1that provides the seed light beam618to a power amplifier (PA)612_2. The PA612_2receives the seed light beam618from the MO612_1and amplifies the seed light beam618to generate the light beam616for use in the scanner apparatus580. For example, in some implementations, the MO612_1may emit a pulsed seed light beam, with seed pulse energies of approximately 1 milliJoule (mJ) per pulse, and these seed pulses may be amplified by the PA612_2to about 6 to 15 mJ, but other energies may be used in other examples.

The MO612_1includes a discharge chamber615_1having two elongated electrodes613a_1and613b_1, a gain medium619_1(shown with light dotted shading inFIG.6) that is a gas mixture, and a fan (not shown) for circulating the gas mixture between the electrodes613a_1,613b_1. A resonator is formed between a line narrowing module695on one side of the discharge chamber615_1and an output coupler696on a second side of the discharge chamber615_1.

The discharge chamber615_1includes a first chamber window663_1and a second chamber window664_1. The first and second chamber windows663_1and664_1are on opposite sides of the discharge chamber615_1. The first and second chamber windows663_1and664_1transmit light in the DUV range and allow DUV light to enter and exit the discharge chamber615_1.

The line narrowing module695may include a diffractive optic such as a grating that finely tunes the spectral output of the discharge chamber615_1. The light-generation module610also includes a line center analysis module668that receives an output light beam from the output coupler696and a beam coupling optical system669. The line center analysis module668is a measurement system that may be used to measure or monitor the wavelength of the seed light beam618. The line center analysis module668may be placed at other locations in the light-generation module610, or it may be placed at the output of the light-generation module610.

The gas mixture that is the gain medium619_1may be any gas suitable for producing a light beam at the wavelength and bandwidth required for the application. For an excimer source, the gas mixture may contain a noble gas (rare gas) such as, for example, argon or krypton, a halogen, such as, for example, fluorine or chlorine and traces of xenon apart from a buffer gas, such as helium. Specific examples of the gas mixture include argon fluoride (ArF), which emits light at a wavelength of about 193 nm, krypton fluoride (KrF), which emits light at a wavelength of about 248 nm, or xenon chloride (XeCl), which emits light at a wavelength of about 351 nm. Thus, the light beams616and618include wavelengths in the DUV range in this implementation. The excimer gain medium (the gas mixture) is pumped with short (for example, nanosecond) current pulses in a high-voltage electric discharge by application of a voltage to the elongated electrodes613a_1,613b_1.

The PA612_2includes a beam coupling optical system669that receives the seed light beam618from the MO612_1and directs the seed light beam618through a discharge chamber615_2, and to a beam turning optical element692, which modifies or changes the direction of the seed light beam618so that it is sent back into the discharge chamber615_2. The beam turning optical element692and the beam coupling optical system669form a circulating and closed loop optical path in which the input into a ring amplifier intersects the output of the ring amplifier at the beam coupling optical system669.

The discharge chamber615_2includes a pair of elongated electrodes613a_2,613b_2, a gain medium619_2(shown with light dotted shading inFIG.6), and a fan (not shown) for circulating the gain medium619_2between the electrodes613a_2,613b_2. The gas mixture that forms the gain medium619_2may be the same as the gas mixture that forms gain medium619_1.

The discharge chamber615_2includes a first chamber window663_2and a second chamber window664_2. The first and second chamber windows663_2and664_2are on opposite sides of the discharge chamber615_2. The first and second chamber windows663_2and664_2transmit light in the DUV range and allow DUV light to enter and exit the discharge chamber615_2.

When the gain medium619_1or619_2is pumped by creating a potential difference between the electrodes613a_1,613b_1or613a_2,613b_2, respectively, the gain medium619_1and/or619_2emits light. The repetition rate of the pulses may range between about 500 and 6,000 Hz for various applications. In some implementations, the repetition rate may be greater than 6,000 Hz, and may be, for example, 12,000 Hz or greater, but other repetition rates may be used in other implementations.

The output light beam616may be directed through a beam preparation system699prior to reaching the scanner apparatus580. The beam preparation system699may include a bandwidth analysis module that measures various parameters (such as the bandwidth or the wavelength) of the beam616. The beam preparation system699also may include a pulse stretcher that stretches each pulse of the output light beam616in time. The beam preparation system699also may include other components that are able to act upon the beam616such as, for example, reflective and/or refractive optical elements (such as, for example, lenses and mirrors), filters, and optical apertures (including automated shutters).

The DUV light-generation module610also includes the gas management system690, which is in fluid communication with an interior678of the DUV light-generation module610.

FIG.7is a flow chart of a process700. The process700is an example of a method of protecting a component in a light source and a method of operating a light source. The process700may be performed using any light source that includes one or more of the apparatuses130,230,330, and430. For example, the process700may be performed with the light source110, the light-generation module510, or the light-generation apparatus610. The process700is discussed with respect to the light source110(FIG.1A).

The shield135is provided between the insulator131and a component to be shielded (710). For example, the component to be shielded may be the gasket133. The shield135is made of a material that inhibits or blocks magnetic fields. The insulator131defines the channel132, which passes through the insulator131.

The electrical conductor151is placed in the channel132(720). The electrical conductor151is electrically connected to the electrode113aand to the power supply197. The electrical conductor151is any type of device or structure that is capable of carrying electrical current. For example, the electrical conductor151may be, a cable or a thick copper wire.

The gas mixture119is provided to an interior of the chamber115. For example, the light source110may be fluidly coupled to a gas supply (such as the gas supply590ofFIG.5A). The electrodes113aand113b, and at least a portion of the insulator131and the gasket133are also in the interior of the chamber115.

The power supply197provides a time-varying current to the conductor151, and the electrode113ais charged (730). The time-varying current produces a time-varying magnetic field, as discussed above. However, the shield135surrounds the conductor151and the insulator131and blocks or attenuates the time-varying magnetic field. As a result, there is no or very little electric field in the vicinity of the gasket133, and the gas mixture119and/or the gain medium in the gas mixture119and the gasket133is not exposed to a plasma of the gas mixture119and/or a plasma of the gain medium.

The implementations can be further described using the following clauses:

1. An apparatus for a light source, the apparatus comprising:

an electrical insulator that defines a channel, the channel configured to receive an electrical conductor;a gasket that surrounds at least a portion of the electrical insulator, the gasket comprising a non-metallic material; anda shield between the channel and the gasket.
2. The apparatus of clause 1, wherein the shield is configured to reduce a magnetic field produced by an electrical current in the electrical conductor.
3. The apparatus of clause 2, wherein the shield is configured to block the magnetic field such that substantially no electric field is present near the gasket.
4. The apparatus of clause 1, wherein the shield comprises a magnetic metal.
5. The apparatus of clause 1, wherein the shield comprises a mu-metal.
6. The apparatus of clause 1, wherein the gasket comprises an elastomer material.
7. The apparatus of clause 1, wherein the electrical insulator comprises a base portion and a stem portion that extends from the base portion, and the channel passes through the stem portion and the base portion.
8. The apparatus of clause 7, wherein the shield surrounds a portion of an outer side of the stem portion.
9. The apparatus of clause 7, wherein the stem portion is a cylinder, the channel passes through the cylinder, and the base portion extends orthogonally from the stem portion.
10. The apparatus of clause 9, wherein the channel is concentric with the cylinder, and the base portion is concentric with the cylinder.
11. The apparatus of clause 1, wherein the electrical insulator is a substantially cylindrical body, and the shield surrounds a portion of an outer side of the cylindrical body.
12. The apparatus of clause 1, wherein the shield comprises a ferrite or an iron alloy.
13. A discharge chamber comprising:a housing;an electrode in the housing;an electrical conductor that passes through the housing and is electrically connected to the electrode;an electrical insulator that surrounds a portion of the electrical conductor;a gasket that surrounds the electrical insulator; anda shield around the electrical insulator, wherein the shield is configured to block or attenuate a magnetic field.
14. The discharge chamber of clause 13, wherein the shield is disposed between the electrical insulator and the gasket.
15. The discharge chamber of clause 13, wherein the gasket comprises an electrically insulating material.
16. The discharge chamber of clause 15, wherein the electrically insulating material comprises an elastomer.
17. The discharge chamber of clause 15, wherein the gasket comprises an O-ring.
18. The discharge chamber of clause 13, wherein the housing comprises an inner wall, and the inner wall comprises an electrically conductive material.
19. The discharge chamber of clause 13, further comprising a second electrode in the housing.
20. The discharge chamber of clause 19, wherein the housing contains a gaseous gain medium.
21. The discharge chamber of clause 20, wherein the gaseous gain medium comprises fluorine.
22. The discharge chamber of clause 21, wherein the gasket comprises a fluorinated material.
23. The discharge chamber of clause 13, wherein the shield is configured to block or attenuate a transient magnetic field produced by a time-varying electrical current that flows in the electrical conductor.
24. The discharge chamber of clause 13, wherein the chamber comprises:N electrical insulators;N gaskets; andN electrical conductors, whereinN is an integer number greater than one,each of the N electrical insulators surrounds one of the electrical conductors, each of the N gaskets surrounds one of the N electrical insulators, andat least one of the N gaskets is entirely metallic.
25. The discharge chamber of clause 13, wherein the discharge chamber is configured for use in a deep ultraviolet (DUV) light source.
26. The discharge chamber of clause 13, wherein the gasket is in a groove, and the shield is between the electrical insulator and the groove.
27. A deep ultraviolet (DUV) light source comprising:a first chamber configured to produce a first pulsed DUV light beam, the first chamber comprising:a first housing;a first electrode assembly in the first housing;a first insulator comprising a first channel configured to receive a first electrical conductor, wherein the first electrical conductor is configured to electrically connect to the first electrode assembly;a first gasket that surrounds a portion of the first insulator; anda first shield that surrounds a portion of the first channel, wherein the first shield is configured to block or attenuate magnetic fields.
28. The DUV light source of clause 27, further comprising a second chamber configured to produce a second pulsed DUV light beam, the second chamber comprising:a second housing;a second electrode assembly in the second housing;a second insulator comprising a second channel configured to receive a second electrical conductor, wherein the second electrical conductor is configured to electrically connect to the second electrode assembly;a second gasket that surrounds a portion of the second insulator; anda second shield that surrounds a portion of the second channel, wherein the first shield is configured to block or attenuate magnetic fields.
29. The DUV light source of clause 28, wherein the first shield is concentric with the first gasket, and the second shield is concentric with the second gasket.
30. The DUV light source of clause 28, wherein the first pulsed light beam comprises a seed light beam, the second chamber is positioned to receive the seed light beam, and the second pulsed light beam is based on the seed light beam.
31. The DUV light source of clause 28, wherein the first pulsed light beam and the second pulsed light beam are emitted toward a common beam combiner.
32. The DUV light source of clause 30, wherein the first gasket and the second gasket comprise an elastomer material.
33. The DUV light source of clause 28, wherein the first electrode assembly comprises a first anode and a first cathode, and the first electrical conductor is configured to electrically connect to the first cathode.
34. The DUV light source of clause 30, whereinthe first electrode assembly comprises a first anode and a first cathode, and the first electrical conductor is configured to electrically connect to the first cathode; andthe second electrode assembly comprises a second anode and a second cathode, and the second electrical conductor is configured to electrically connect to the second cathode.
35. The DUV light source of clause 27, further comprising a power supply external to the first housing, wherein the power supply is configured to electrically connect to the electrical conductor, and, in operational use, the power supply provides a high-voltage excitation pulse to the electrical conductor.
36. The DUV light source of clause 28, wherein the first shield is concentrically disposed between the first gasket and the first insulator and the second shield is disposed concentrically between the second gasket and the first insulator.
37. A method of operating a laser, the method comprising:providing a shield between an insulator and a component, wherein the insulator passes through a wall of a discharge chamber of the laser and the insulator defines a channel;placing an electrical conductor in the channel; andconducting a time-varying current in the electrical conductor to charge an electrode in the discharge chamber of the laser, wherein the shield blocks a magnetic field formed around the electrical conductor such that substantially no electric field is present near the component.
38. The method of clause 37, wherein the component comprises an elastomer gasket.
39. The method of clause 37, further comprising:providing a gaseous gain medium to the discharge chamber, whereinthe component is a gasket configured to seal the chamber and prevent the gaseous gain medium from escaping the chamber; andthe shield blocks a magnetic field formed around the electrical conductor such that substantially no electric field is present near the component and substantially no plasma of the gaseous gain medium is formed at the component.
40. A light source comprising:a discharge chamber;an electrode in the discharge chamber;an electrically insulating structure comprising:a base portion in the discharge chamber, wherein the base portion extends between the electrode and an external wall of the discharge chamber; anda plurality of stem portions extending from the base portion and through the external wall of the discharge chamber, wherein each stem portion comprises a channel that passes through the stem portion and the base portion, and each channel is configured to receive an electrical conductor that electrically connects to the electrode;a plurality of gaskets, wherein each gasket surrounds one of the stem portions, and at least one of the gaskets comprises a non-metallic material that surrounds a respective one of the stem portions; anda shield disposed between each of the at least one non-metallic gaskets and the respective one of the stem portions.
41. The light source of clause 40, wherein the plurality of gaskets comprises at least one metallic gasket, and each of the at least one metallic gaskets surrounds a respective one of the stem portions without a shield between the metallic gasket and the respective one of the stem portions.

These and other implementations are within the scope of the claims.