Apparatus for adjusting discharge performance in a laser chamber

Abstract

To provide laser-generated light sources such as those used in integrated circuit photolithographic manufacturing processes.SOLUTION: Disclosed is a laser discharge chamber in which the useful lifetime is extended by local electrical tuning using one or a combination of design of the chamber internal geometry, placement and distribution of components such as electrodes, current returns and capacitors within the chamber, and selective electrical isolation of portions of the components.SELECTED DRAWING: Figure 4A

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Application No. 62 / 666,310, filed May 3, 2018, and U.S. Application No. 62 / 618,168, filed January 17, 2018, each of which is incorporated by reference in its entirety.

[0002] FIELD OF THE INVENTION

[0002] The subject matter disclosed herein relates to laser-generated light sources such as those used in integrated circuit photolithography manufacturing processes. [Background technology]

[0003]

[0003] Excimer lasers are used to generate light in the deep ultraviolet (DUV) portion of the spectrum. For example, DUV excimer laser chambers generate 193 nm laser light using a pulsed capacitive discharge in an Ar-F2 gas mixture. Electrodes are typically made of alloys such as brass, which inevitably fluorinate and erode during discharge, shortening the chamber's lifespan. One approach to extending the useful life of discharge chamber modules is to fabricate the anode from a material that does not exhibit wear. Information about materials suitable for use as anode materials can be found, for example, in U.S. Patent No. 7,301,980, issued November 27, 2007, and U.S. Patent No. 6,690,706, issued February 10, 2004. Both patents are assigned to the assignee of the present application and are incorporated herein by reference in their entirety. While material selection can extend the lifespan of electrodes and, therefore, chambers, there remains a need to further extend these lifespans. In this regard, see U.S. Patent No. 8,446,928, issued May 21, 2013, and U.S. Patent No. 9,246,298, issued January 26, 2016, both of which are assigned to the assignee of the present application and are incorporated herein by reference in their entirety. Summary of the Invention

[0004] The following presents a simplified summary of one or more embodiments in order to provide a basic understanding of the invention. This summary is not an extensive overview of all possible embodiments, and is not intended to identify key or critical elements of all embodiments or to delineate the scope of any or all embodiments. Its sole purpose is to present some concepts of one or more embodiments in a simplified form as a prelude to the more detailed description that is presented later.

[0005]

[0005] According to one aspect, an apparatus is disclosed comprising: a discharge chamber; a first electrode disposed within the discharge chamber; a second electrode disposed within the discharge chamber for creating an electrode gap having a height extending in a first direction between the first electrode and the second electrode and a length extending in a second direction transverse to the first direction between the first electrode and the second electrode; and a plurality of conductive elements electrically connected to the second electrode, each extending substantially in a first direction that is transverse to the electrode gap, the plurality of conductive elements being arranged in a row extending in the second direction, the plurality of conductive elements comprising a first pair of adjacent conductive elements spaced apart in the second direction by a first spacing and a second pair of adjacent conductive elements spaced apart in the second direction by a second spacing that is greater than the first spacing.

[0006] Some of the plurality of conductive elements may be arranged substantially symmetrically about a centerline of the length of the electrode gap. The plurality of conductive elements may include a first plurality of conductive elements and a second plurality of conductive elements electrically connected to the second electrode, each of the second plurality of conductive elements extending substantially in a first direction transverse to the electrode gap on an opposite side of the electrode gap from the first plurality of conductive elements, and the second plurality of conductive elements arranged in a second row extending in the second direction, the second plurality of conductive elements including a third pair of adjacent conductive elements spaced apart in the second direction by a first spacing and a fourth pair of adjacent conductive elements spaced apart in the second direction by a second spacing. Some of the first plurality of conductive elements may be arranged substantially symmetrically about a centerline of the length of the electrode gap, and some of the second plurality of conductive elements may be arranged substantially symmetrically about a midpoint of the length of the electrode gap. The first pair of adjacent conductive elements may be arranged across the electrode gap from the first pair of adjacent conductive elements. The length of the first row and the length of the second row may be substantially coextensive with the length of the electrode gap.

[0007] The lateral ends of the second electrode may be electrically isolated. For example, the lateral ends of the second electrode may be electrically isolated from the walls of the discharge chamber, or there may be a mechanical linkage mechanically coupled to the second electrode and arranged to move the second electrode, and the mechanical linkage may include an insulating element arranged to electrically isolate the second electrode.

[0008]

[0008] According to another aspect, an apparatus is disclosed that includes: a discharge chamber; a first electrode disposed within the discharge chamber, the first electrode having a first electrode length extending in a first direction; a second electrode disposed within the discharge chamber, the second electrode having a second electrode length extending in the first direction and arranged in a spaced apart relationship relative to the first electrode so as to define an electrode gap between the first electrode and the second electrode; a first plurality of capacitors electrically connected to the first electrode and arranged in a first row extending in the first direction; and a second plurality of capacitors electrically connected to the first electrode and arranged in a second row extending in the first direction parallel to the first row, wherein the number of capacitors in the first plurality is the same as the number of capacitors in the second plurality.

[0009] Some of the capacitors of the first plurality of capacitors may be arranged substantially symmetrically about a centerline of the length of the electrode gap, and some of the capacitors of the second plurality of capacitors may also be arranged substantially symmetrically about a centerline of the length of the electrode gap.

[0010] According to another aspect, an apparatus is disclosed that includes: a discharge chamber; a first electrode disposed within the discharge chamber, the first electrode having a first electrode length extending in a first direction; a second electrode disposed within the discharge chamber, the second electrode having a second electrode length extending in the first direction and arranged in a spaced-apart relationship relative to the first electrode to define an electrode gap between the first electrode and the second electrode; and a plurality of capacitive elements electrically connected to the first electrode and arranged in a first row extending in the first direction, at least one of the plurality of capacitive elements having a different capacitance value than at least one other of the plurality of capacitive elements. At least one of the capacitive elements may comprise a pair of capacitors connected in parallel.

[0011]

[0011] According to another aspect, an apparatus is disclosed that includes: a discharge chamber; a first electrode disposed within the discharge chamber, the first electrode having a first electrode length extending in a first direction; a second electrode disposed within the discharge chamber, the second electrode having a second electrode length extending in the first direction and arranged in a spaced apart relationship relative to the first electrode to define an electrode gap between the first electrode and the second electrode; a first number X of capacitors in a first row electrically connected to the first electrode and arranged in the first row in a first row direction substantially parallel to the first electrode length; and a second number Y of capacitors in a second row electrically connected to the first electrode and arranged in the second row in a second row direction substantially parallel to the first electrode length, wherein X and Y are at least 4 and X is less than Y; and a capacitance value of a first capacitor in the second row and a capacitance value of a last capacitor in the second row are equal to each other and less than the capacitance values ​​of the remaining capacitors in the second row.

[0012]

[0012] According to another aspect, there is provided a discharge chamber, a first electrode disposed within the discharge chamber, a second electrode disposed within the discharge chamber, the second electrode for creating an electrode gap having a height extending in a first direction between the first electrode and the second electrode and a length extending in a second direction transverse to the first direction between the first electrode and the second electrode, a first plurality of conductive elements electrically connected to the second electrode and each extending substantially in a first direction that is transverse to the electrode gap, the first plurality of conductive elements being arranged in a row extending in the second direction and comprising a first pair of adjacent conductive elements spaced apart in the second direction by a first spacing and a second pair of adjacent conductive elements spaced apart in the second direction by a second spacing that is greater than the first spacing, and a second plurality of conductive elements electrically connected to the second electrode and each extending substantially in a first direction that is transverse to the electrode gap. An apparatus is disclosed that includes: a second plurality of conductive elements extending substantially in a first direction, transverse to the electrode gap, opposite the first element, the second plurality of conductive elements arranged in a second row extending in the second direction and including a third pair of adjacent conductive elements spaced apart in the second direction by a first spacing and a fourth pair of adjacent conductive elements spaced apart in the second direction by a second spacing; a first plurality of capacitors electrically connected to the first electrode and arranged in the first row extending in the first direction; and a second plurality of capacitors electrically connected to the first electrode and arranged in a second row extending in the first direction parallel to the first row, wherein at least one of the capacitors in the second plurality of capacitors has a different capacitance value than at least one other capacitor in the second plurality of capacitors.

[0013]

[0013] The first pair of adjacent conductive elements may be positioned across the electrode gap from the third pair of adjacent conductive elements. The length of the first row and the length of the second row may be substantially coextensive with the length of the electrode gap. Some conductive elements of the first plurality of conductive elements may be positioned substantially symmetrically about a centerline of the length of the electrode gap. Some conductive elements of the first plurality of conductive elements may be positioned substantially symmetrically about a centerline of the length of the electrode gap, and some conductive elements of the second plurality of conductive elements may be positioned substantially symmetrically about a midpoint of the length of the electrode gap. Some capacitors of the first plurality of capacitors may be positioned substantially symmetrically about a centerline of the length of the electrode gap. Some capacitors of the second plurality of capacitors may also be positioned substantially symmetrically about a centerline of the length of the electrode gap.

[0014] Further embodiments, features, and advantages of the present invention, as well as the structure and operation of the various embodiments, are described in detail below with reference to the accompanying drawings. [Brief explanation of the drawings]

[0015]

[0015] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate, by way of example and not by way of limitation, methods and systems of embodiments of the present invention. Together with the detailed description, the drawings further serve to explain the principles of the methods and systems presented herein and to enable one skilled in the art to make and use the methods and systems. In the drawings, like reference numbers indicate identical or functionally similar elements.

[0016] [Figure 1]

[0016] A schematic diagram of the overall broad concept of a photolithography system according to one aspect of the disclosed subject matter is shown, not to scale. [Figure 2]

[0017] 1 shows a schematic diagram, not to scale, of the overall broad concept of a lighting system according to one aspect of the disclosed subject matter. [Figure 3]

[0018] 1 is a diagrammatic cross-section, not to scale, of a discharge chamber for an excimer laser in accordance with an aspect of the disclosed subject matter. [Figure 4A]

[0019] FIG. 2 is a perspective view of an arrangement of electrical components in a discharge chamber. [Figure 4B]

[0020] FIG. 10 is a plan view of a layout pattern of capacitors in a discharge chamber. [Figure 5A]

[0021] FIG. 2 is an end view of an arrangement of electrical components in a discharge chamber. [Figure 5B]

[0022] FIG. 2 is a side view of an arrangement of electrical components in a discharge chamber. [Figure 6A]

[0023] FIG. 2 is a perspective view of a current return used in a discharge chamber. [Figure 6B]

[0024] FIG. 1 is a perspective view of a current return incorporating aspects of an embodiment disclosed herein; [Figure 7A]

[0025] FIG. 1 is a top view of a layout pattern of capacitors in a discharge chamber incorporating aspects of the embodiments disclosed herein. [Figure 7B]

[0025] Top View

[0025] FIG. 1 is a top view of a layout pattern of capacitors in a discharge chamber incorporating aspects of the embodiments disclosed herein. [Figure 7C]

[0025] FIG. 1 is a top view of a layout pattern of capacitors in a discharge chamber incorporating aspects of the embodiments disclosed herein. [Figure 8A]

[0026] FIG. 1 is a perspective view of an arrangement of electrical components in a discharge chamber incorporating aspects of the embodiments disclosed herein. [Figure 8B]

[0027] FIG. 1 is a top view of a layout pattern of capacitors in a discharge chamber incorporating aspects of the embodiments disclosed herein. [Figure 9]

[0028] FIG. 1 is a perspective view of an array of electrodes and electrode support structures incorporating aspects of the embodiments disclosed herein; [Figure 10A]

[0029] FIG. 1 is a partial cutaway side view of a system for connecting an electrode to an electrode support incorporating aspects of the embodiments disclosed herein. [Figure 10B]

[0029] A partially cutaway side view of a system for connecting an electrode to an electrode support incorporating aspects of the embodiments disclosed herein. [Figure 10C]

[0029] A partially cutaway side view of a system for connecting an electrode to an electrode support incorporating aspects of the embodiments disclosed herein. [Figure 11A]

[0030] FIG. 1 is a partial cutaway side view of an electrode placement system incorporating aspects of the embodiments disclosed herein. [Figure 11B] FIG. 1 is a partial cutaway side view of an electrode placement system incorporating aspects of the embodiments disclosed herein. DETAILED DESCRIPTION OF THE INVENTION

[0017]

[0031] Various embodiments will now be described with reference to the drawings. Like reference numerals are used to refer to like elements throughout the drawings. In the following description, for purposes of explanation, numerous specific details are set forth in order to facilitate a thorough understanding of one or more embodiments. However, it will be apparent that in some or all cases, any of the embodiments described below can be practiced without employing the specific design details described below. In some instances, well-known structures and devices are shown in block diagram form to facilitate describing one or more embodiments. The following presents a simplified summary of one or more embodiments in order to provide a basic understanding of these embodiments. This summary is not an extensive overview of all contemplated embodiments, nor is it intended to identify key or critical elements of all embodiments, nor to delineate the scope of any or all embodiments.

[0018]

[0032] 1, photolithography system 100 includes an illumination system 105. As described in more detail below, illumination system 105 includes a light source that generates and directs a pulsed light beam 110 to a photolithography exposure tool or scanner 115 that patterns microelectronic features on a wafer 120. Wafer 120 is placed on a wafer table 125. The wafer table is constructed to hold wafer 120 and is connected to a positioner configured to precisely position wafer 120 according to certain parameters.

[0019]

[0033] The photolithography system 100 uses a light beam 110 having a wavelength in the deep ultraviolet (DUV) range, e.g., 248 nanometers (nm) or 193 nm. The wavelength of the light beam 110 determines the minimum size of microelectronic features that can be patterned on the wafer 120; lower wavelengths result in smaller minimum feature sizes. When the wavelength of the light beam 110 is 248 nm or 193 nm, the minimum size of the microelectronic features can be, for example, 50 nm or less. The bandwidth of the light beam 110 may be the actual instantaneous bandwidth of its optical spectrum (or emission spectrum), which contains information about how the optical energy of the light beam 110 is distributed across different wavelengths. The scanner 115 includes an optical arrangement, e.g., one or more focusing lenses, a mask, and an objective lens arrangement. The mask is movable along one or more directions, such as along the optical axis of the light beam 110 or in a plane perpendicular to the optical axis. The objective lens arrangement includes a projection lens and allows image transfer from the mask to occur onto the photoresist on the wafer 120. The illumination system 105 adjusts the range of angles at which the light beam 110 is incident on the mask and also homogenizes the intensity distribution of the light beam 110 across the mask.

[0020]

[0034] The scanner 115 may include, among other features, a lithography controller 130, air conditioning devices, and power supplies for various electrical components. The lithography controller 130 controls how layers are printed on the wafer 120. The lithography controller 130 includes memory that stores information such as a process recipe. The process program or recipe determines the length of exposure of the wafer 120 based on, for example, the mask used, as well as other factors that affect the exposure. During lithography, multiple pulses of the light beam 110 may illuminate the same area of ​​the wafer 120 to constitute a dose.

[0021]

[0035] Photolithography system 100 also preferably includes a control system 135. Generally, control system 135 includes one or more of digital electronic circuitry, computer hardware, firmware, and software. Control system 135 also includes memory, which may be read-only memory and / or random-access memory. Storage devices suitable for tangibly embodying computer program instructions and data include all forms of non-volatile memory, including, for example, semiconductor memory devices such as EPROM, EEPROM, and flash memory devices, magnetic disks such as internal hard disks and removable disks, magneto-optical disks, and CD-ROM disks.

[0022]

[0036] Control system 135 may also include one or more input devices (such as a keyboard, touch screen, microphone, mouse, handheld input device, etc.) and one or more output devices (such as a speaker or monitor). Control system 135 also includes one or more programmable processors and one or more computer program products tangibly embodied in a machine-readable storage device for execution by the one or more programmable processors. The one or more programmable processors may each execute a program of instructions to perform a desired function by operating on input data and generating appropriate output. Generally, a processor receives instructions and data from a memory. Any of the foregoing may be supplemented by, or incorporated in, specially designed ASICs (application-specific integrated circuits). Control system 135 may be centralized, or partially or fully distributed throughout photolithography system 100.

[0023]

[0037] Referring to Figure 2, exemplary illumination system 105 is a pulsed laser source that generates a pulsed laser beam as light beam 110. Figure 2 illustrates, in block diagram form, an exemplary gas discharge laser system according to one embodiment of certain aspects of the disclosed subject matter. The gas discharge laser system may include, for example, a solid-state or gas discharge seed laser system 140, an amplification stage, such as a power ring amplifier ("PRA") stage 145, relay optics 150, and a laser system output subsystem 160. Seed system 140 may include, for example, a master oscillator ("MO") chamber 165.

[0024]

[0038] The seed laser system 140 may also include a master oscillator output coupler ("MO OC") 175. The master oscillator output coupler may comprise a partially reflective mirror, which, together with a reflective grating (not shown) in the line narrowing module ("LNM") 170, forms an oscillator cavity. The seed laser 140 oscillates within this oscillator cavity to form seed laser output pulses, i.e., forming the master oscillator ("MO"). The system may also include a line center analysis module ("LAM") 180. The LAM 180 may include an etalon spectrometer for fine wavelength measurement and a grating spectrometer for coarser resolution. The MO wavefront engineering box ("WEB") 185 may serve to redirect the output of the MO seed laser system 140 toward the amplification stage 145 and may include beam expansion, for example, via a multi-prism beam expander (not shown), and coherence destruction, for example, in the form of an optical delay path (not shown).

[0025]

[0039] The amplification stage 145 includes a PRA lasing chamber 200, which may be, for example, an oscillator, formed by, for example, seed beam input and output coupling optics (not shown) that may be incorporated into a PRA WEB 210 and redirected by a beam reverser 220 back through a gain medium within the chamber 200. The PRA WEB 210 may incorporate partially reflective input / output couplers (not shown), a maximum reflective mirror for the nominal operating wavelength (e.g., around 193 nm for an ArF system), and one or more prisms.

[0026]

[0040] A bandwidth analysis module ("BAM") 230 at the output of the amplifier stage 145 receives the pulsed output laser light beam from the amplifier stage and may pick off a portion of the light beam for metrology purposes, such as measuring the output bandwidth and pulse energy. The pulsed laser output light beam then passes through an optical pulse stretcher ("OPuS") 240 and an output complex autoshutter metrology module ("CASMM") 250, which may also be the location of a pulse energy meter. One purpose of the OPuS 240 may be, for example, to convert a single output laser pulse into a pulse train. Secondary pulses created from the original single output pulse may be delayed relative to each other. By distributing the original laser pulse energy into a train of secondary pulses, the effective pulse length of the laser may be extended while the peak pulse intensity may be reduced. Thus, the OPuS 240 may receive the laser beam from the PRA WEB 210 via the BAM 230, and the output of the OPuS 240 may be directed to the CASMM 250.

[0027]

[0041] The PRA lasing chamber 200 and MO 165 are configured as chambers in which an electrical discharge between electrodes may cause a lasing gas discharge in a lasing gas, creating a population inversion of energetic molecules, including, for example, argon, krypton, xenon, and / or fluorine, to produce relatively broadband radiation that may be line-narrowed to a relatively very narrow bandwidth and center wavelength selected in LNM 170, as is known in the art. Such a chamber 300 configuration is shown in FIG. 3, which is a highly stylized cross-sectional view of the discharge chamber. Chamber 300 includes an upper electrode 310, which acts as a cathode, and a lower electrode 320, which acts as an anode. Either or both of the lower electrode 320 and the upper electrode 310 may be completely contained within the pressure envelope of chamber 300 defined by chamber walls 305, or one of the electrodes may not be so contained. A lasing gas discharge occurs between these two electrodes in a gap having a width A. Also shown in Figure 3 are an upper insulator 315 and a lower insulator 325. The lower electrode 320 is electrically connected to the wall 305 of the chamber 300 by tab 306. The lower electrode 320 is therefore electrically connected to the upper half of the chamber 300. For safety reasons, it is desirable to maintain the chamber wall 305, and therefore the lower electrode 320, at ground potential. In the embodiment shown in Figure 3, the upper electrode 310 is driven by a voltage source 340 at a negative voltage relative to the lower electrode 320.

[0028]

[0042] When acting as an anode, as shown in FIG. 3 , the lower electrode 320 is beneficially made of a material that does not exhibit wear, but actually grows an erosion-resistant coating 330 (also called a “reef”) that maintains the surface of the lower electrode 320 in substantially the same position as when the lower electrode 320 was new. Alternatively, the electrode may be coated with an erosion-resistant coating. The dimensions of the coating 330 are exaggerated in FIG. 3 for illustrative purposes. Alternatively, the extendable anode 320 moves vertically upward to compensate for erosion losses from the anode 320. The grown coating 330 does not form on the upper electrode 310 when it acts as a cathode, so that the upper electrode 310 erodes during laser firing. Note that the upper electrode 310 has a small bump 312. In current chambers, this erosion leads to both an increase in the discharge gap dimension A and a spreading of the discharge, especially when the bump 312 is completely eroded by vertical erosion of the electrode 310.

[0029]

[0043] 3 also shows a voltage source 340 that generates pulses to induce a discharge in the discharge gap between the cathode 310 and the anode 320. While a (-) symbol is shown for the polarity of the output of the voltage source 340, it will be understood that this is a relative, rather than an absolute, polarity, i.e., relative to the polarity of the bottom electrode 320, which is generally in electrical contact with ground (0) potential through the current return 350 and tab 306. The current return 350 may be enclosed within the chamber 300, as described below. The top electrode (cathode 310) is charged to a large (-20 kV) negative voltage.

[0030]

[0044] One component of the power supply 340, not shown in FIG. 3, is a bank of capacitors that generate the pulses that cause the discharge. The capacitors that generate the pulses that cause the discharge are located adjacent to the cathode 310. This is illustrated in FIG. 4A, where a row of capacitors 360 is located above half the length of the cathode 310. Although not shown in FIG. 4A, another row of capacitors 360 is located above the other half of the length of the cathode 310. This is illustrated in FIG. 4B. Also shown in FIGS. 4A and 4B is a row of feedthrough assemblies 370 that transfer power from the exterior to the interior of the chamber 300. Thus, the total design peak capacitance is achieved by two rows of parallel capacitors 360 that are asymmetrically laid out. Note that both the cathode 310 and the anode 320 are illustrated in FIG. 4A as having rectangular cross sections. This is merely to make the illustration easier to understand. Those skilled in the art will recognize that these electrodes may generally each have any one of a number of shapes. Capacitor 360 is secured within socket 365. Figure 4B illustrates socket 365 empty.

[0031]

[0045] Also not shown in Figure 3 is a "rib cage"-like structure for the current return 350. This is shown in Figures 4A and 6A. A conventional current return 350 is made from evenly spaced, equally sized, metallic current return wires 355, as shown. The wires 355 are connected to a plate 357 below the anode 320. The wires 355 are also connected to a current bus 358. Figure 4A also shows one of the tabs 306 that electrically connect the end of the bottom electrode 320 to the wall 305 of the chamber 300.

[0032]

[0046] Although not shown in FIG. 4A , another row of wires is connected to the opposite side of plate 357, and these wires are connected to a current bus. Each wire 355 in one row is arranged symmetrically with its counterpart in the other row, so that the wires 355 form pairs, with each pair surrounding a segment of cathode 310, the discharge region, and the anode 320. This is illustrated in the schematic cross section of FIG. 5A . A high-voltage supply 375 provides voltage from capacitor 360 to cathode 310. When a discharge 318 occurs in the discharge gap between cathode 310 and anode 320, current from the discharge 318 flows through anode 320, plate 357, return wire 355, and current bus 358 to ground. Each pair of return wires 355 brackets region D of cathode 310, anode 320, and discharge region 318. Tab 306 is not visible in Figure 5A, but is visible in Figure 5B. Figure 6A also illustrates the physical arrangement of plate 357, return wire 355, and current bus 358.

[0033]

[0047] Generally, in conventional designs, the longitudinal extent of the current return 350 is independent of the length of the actual discharge 318. The longitudinal extent of the current return 350 may be longer or shorter than the length of the actual discharge. For example, as shown in FIG. 5B, some pairs of wires 355 are located beyond both longitudinal ends of the discharge 318. In conventional designs, the area D (shown in FIG. 5A) bounded by opposing pairs of current return wires 355 (one member in one row, the corresponding member in the other row) is the same along the length of the anode 320. Also, in conventional designs, the distance (pitch) between adjacent current return wires 355 in the same row is the same along the length of the anode 320, and the distance is arbitrarily selected as a constant without adjustment or optimization. The discharge is approximately 55 cm long, 13.5 mm high, and 3 mm wide.

[0034]

[0048] In short, in conventional designs, the chamber's internal geometry is not electrically tuned to local levels. Elements such as peaking capacitors and current paths are designed so that their integral values ​​enable basic overall chamber performance, but component selection and placement are not locally optimized. Existing technologies also include peaking capacitor (Cpk) layouts that are not electrically tuned for optimal discharge performance. Specifically, there may be an empty socket on one side of the chamber (empty socket 365 in Figure 4B).

[0035]

[0049] In this new embodiment, the current returns are adjustable by three categories of design variables: longitudinal extent and average spacing, local current return spacing, and bounded area.

[0036]

[0050] Considering these in turn, with respect to longitudinal extent and average spacing, the longitudinal extent of wire 355 may be selected to optimize discharge, as illustrated in Figures 5B and 6B. Increasing or decreasing the length of the current return area for the discharge will change the local discharge current at both ends. There is an optimal current return area length for optimal local discharge.

[0037]

[0051] With respect to local current return spacing, the local spacing between particular current returns may be selected such that some wires 355 are separated by gaps with a wider spacing B and others are separated by gaps with a narrower spacing C, where B is not equal to C, without the remaining wires 355 all having the same spacing. Varying the width of the spacing changes the local discharge current.

[0038]

[0052] With respect to bounded regions, in FIG. 5A , region D is bounded by a current path including wire 355, anode 320, discharge 318, cathode 310, high-voltage supply 375, and capacitor 360. Region D, which encompasses the electrical return path, can be locally adjusted or "tuned" to affect the local discharge 318. For example, current return wire 355 may be moved closer to or farther away from discharge 318, as shown by dashed wires 355a and 355b in FIG. 5A , thus changing region D. While this is illustrated with respect to the right side of FIG. 5A , it will be understood that a similar reconfiguration could be made for the left side. The size of D affects the local discharge current; thus, the local current can be finely tuned with the variation of D.

[0039]

[0053] For capacitors, symmetry in their physical arrangement promotes improved discharge, especially end-of-life behavior. Therefore, capacitors are advantageously arranged to allow for symmetric capacitance distribution. This can be achieved by using capacitors with customized values ​​and by strategically placing capacitors and depletions to locally tailor capacitance to achieve locally optimized discharge.

[0040]

[0054] In comparison with the design illustrated in FIG. 4B, FIGS. 7A, 7B, and 7C illustrate other possible geometries. FIG. 7A shows a symmetrical arrangement of a first row 380 of capacitors 360 and a second row 382 of capacitors 362, each row having the same number of capacitors (14 in the illustrated example, but other numbers may be used), with the capacitor values ​​selected to achieve a desired total capacitance. Capacitors 360 and 362 may all have the same value, in which case the capacitance of the array would be symmetrically distributed about the longitudinal axis 318a and the transverse axis 318b of the discharge region 318. An array with a different capacitance distribution can also be achieved by using capacitors 360 with a different capacitance than capacitors 362, resulting in an array in which the capacitance is asymmetrically distributed about the longitudinal axis 318a and symmetrically distributed about the transverse axis 318b of the discharge region 318.

[0041]

[0055] The arrangement is symmetrical about the discharge area 318. Figure 7B shows an arrangement with a symmetrical arrangement in which two columns of capacitors are used, each with the same number of capacitors, and the capacitor values ​​are selected so that the total capacitance is the desired design value. However, in the arrangement of Figure 7B, fewer capacitors are used, each with a higher value, so that the same total capacitance can be achieved. And, in the arrangement of Figure 7B, there are fewer capacitors beyond the discharge area 318.

[0042]

[0056] The arrangement of Figure 7C features one row of capacitors 360 and one row of capacitors 362, with capacitors 364 at either end of the row of capacitors 362 having a capacitance that is different from the capacitance of the other capacitors 362 in the row. The arrangement of Figure 7C is not symmetrical across the longitudinal axis 318a of the discharge region 318, but is symmetrical along the longitudinal axis 318a. The arrangement of Figure 7C provides the ability to tailor the capacitance by using fewer capacitors or by using some capacitors with a first capacitance and some capacitors with a second capacitance that is different from the first capacitance.

[0043]

[0057] Furthermore, two capacitors with identical individual capacitances, when connected in series, will exhibit half the capacitance of each individual capacitor. Therefore, the symmetry of the design of FIG. 4B, which uses a total of 27 identical capacitors to achieve the desired total capacitance, can be improved by using two pairs of series-connected capacitors to achieve the same value as a single conventional capacitor. Such an arrangement is shown in FIGS. 8A and 8B. This results in a group of 30 capacitors (26 capacitors 360 in parallel and two pairs of series capacitors 400 also in parallel with the other 26) that matches the total capacitance of 27 capacitors. This group of 30 can then be laid out symmetrically, with the two pairs of series-stacked capacitors 400 located symmetrically along the length of the discharge 318.

[0044]

[0058] Those skilled in the art will understand that the capacitance distribution, as defined by, for example, capacitor location, stacked capacitor location, air gaps, or capacitors of different values, can be manipulated and tailored for best discharge performance, and that the possible variations are not limited by the specific examples provided above.

[0045]

[0059] Also shown in FIG. 9 , the lower electrode 320 is supported by tabs 306 secured to the chamber 300 by fasteners 308, for example. See U.S. Patent No. 7,995,637, issued August 9, 2011, which is assigned to the assignee of the present application and incorporated herein by reference in its entirety. Similarly, FIG. 10A illustrates the lower electrode 320 having tabs 306 connected to a support element 316 by fasteners 308, for example, threaded bolts. Also shown are additional hardware, such as washers 309 and threaded nuts 314, that may be necessary or convenient for securing the tabs 306 to the support element 316. The support element 316 is connected to the chamber 300. Generally, the tabs 306 and fasteners 308 are made of materials that establish a conductive path from the end of the lower electrode 320 to the chamber 300. However, it may be advantageous to electrically insulate the end of the lower electrode 320 from the chamber 300. In this regard, see U.S. Patent Application Publication No. 2007 / 0071058, published March 9, 2007, which is assigned to the assignee of the present application and is incorporated herein by reference in its entirety, and which proposes eliminating anode support and chamber wall current paths to promote reefing, which current paths may also be eliminated as a means to spatially tailor the chamber interior.

[0046]

[0060] For example, as shown in FIG. 10B, the mechanical connection between the tab 306 and the support element 316 may be supplemented by an insert that electrically insulates the tab 306 from the support element 316. FIG. 10B shows an insert consisting of an upper insert portion 322 and a lower insert portion 324 that cooperate to isolate the tab 306 from the support element 316. FIG. 10C shows an arrangement in which the tab 306 is made of an insulating material, such as a plastic or ceramic material. The plastic material may be polytetrafluoroethylene. The fastener 308 may also be made of an insulating material, and an insulating layer may be placed between the tab 306 and the support element 316.

[0047]

[0061] In some arrangements, the end of the electrode 320 is connected to a mechanical linkage system that changes the vertical position of the electrode 320. See U.S. Patent No. 8,526,481, issued September 3, 2013, and U.S. Patent No. 8,446,928, issued May 21, 2013. Both patents are assigned to the assignee of the present application and are incorporated herein by reference in their entireties. Such a system is shown in FIG. 11A. In this system, a lever 510, moved by an actuator 520, raises and lowers an electrode support rod 500 that supports the electrode 320. These components are also typically made of a material that provides a conductive path from the end of the electrode 320 to the wall of the chamber 300. However, if it is desired that the end of the electrode 320 be electrically isolated from the wall of the chamber 320, this path can be interrupted by, for example, inserting an insulator 530 between the lever 510 and the actuator 520.

[0048]

[0062] Also, the need for any mechanical or electrical connections at the ends of electrode 320 can be avoided by modifying other components in the system to provide physical support for electrode 320. Such physical support would otherwise be provided by mechanically fastening end tabs to the electrode. For example, referring again to FIG. 6A , current return 350 could be made physically strong enough to provide sufficient support for an electrode disposed on plate 357 so that the use of tabs could be avoided. As with other measures, this would eliminate the short current return path through tab 306.

[0049]

[0063] Thus, disclosed herein is a laser discharge chamber whose useful life is extended by localized electrical conditioning using any one or combination of strategies including design of the chamber's internal geometry, placement and distribution of components within the chamber, such as electrodes, current returns, and capacitors, and selective electrical isolation of some of the components.

[0050]

[0064] The above description includes examples of multiple embodiments. Of course, it is not possible to describe every conceivable combination of components or methods for purposes of describing the above-described embodiments, and those skilled in the art will recognize that many other combinations and permutations of various embodiments are possible. Accordingly, the described embodiments are intended to embrace all such modifications, alterations, and variations that fall within the spirit and scope of the appended claims. Furthermore, to the extent the term "includes" is used in the detailed description or claims, such term is intended to be inclusive, similar to the interpretation of the term "comprising" when used as a transitional term in the claims. Furthermore, although elements of described aspects and / or embodiments may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated. Furthermore, unless otherwise stated, all or a portion of any aspect and / or embodiment may be utilized with all or a portion of any other aspect and / or embodiment.

[0051]

[0065] Other aspects of the invention are set forth in the following numbered clauses: 1. A discharge chamber; a first electrode disposed within the discharge chamber; a second electrode disposed within the discharge chamber for creating an electrode gap having a height extending in a first direction between the first electrode and the second electrode and a length extending in a second direction transverse to the first direction between the first electrode and the second electrode; a plurality of conductive elements electrically connected to the second electrode, each extending substantially in a first direction transverse to the electrode gap, the plurality of conductive elements being arranged in rows extending in the second direction, the plurality of conductive elements including a first pair of adjacent conductive elements spaced apart in the second direction by a first spacing and a second pair of adjacent conductive elements spaced apart in the second direction by a second spacing greater than the first spacing; An apparatus comprising: 2. The apparatus of clause 1, wherein some of the plurality of conductive elements are arranged substantially symmetrically about a centerline of the length of the electrode gap. 3. The device of clause 1, wherein the plurality of conductive elements comprises a first plurality of conductive elements and further comprises a second plurality of conductive elements electrically connected to the second electrode, each of the second plurality of conductive elements extending substantially in a first direction that is transverse to the electrode gap on an opposite side of the electrode gap from the first plurality of conductive elements, the second plurality of conductive elements arranged in a second row extending in the second direction, and comprising a third pair of adjacent conductive elements spaced apart in the second direction by a first interval and a fourth pair of adjacent conductive elements spaced apart in the second direction by a second interval. 4. The apparatus of clause 3, wherein some of the conductive elements of the first plurality of conductive elements are arranged substantially symmetrically about a center line of the length of the electrode gap, and some of the conductive elements of the second plurality of conductive elements are arranged substantially symmetrically about a center point of the length of the electrode gap. 5. The apparatus of clause 2, wherein the first pair of adjacent conductive elements are positioned across an electrode gap from the first pair of adjacent conductive elements. 6. The apparatus of clause 2, wherein the length of the first row and the length of the second row are substantially coextensive with the length of the electrode gap. 7. The apparatus of clause 1, wherein the lateral ends of the second electrode are electrically insulated. 8. The apparatus of clause 7, wherein the discharge chamber comprises a wall, and the lateral ends of the second electrode are electrically insulated from the wall of the discharge chamber. 9. The device of clause 7, further comprising a mechanical linkage mechanically coupled to the second electrode and arranged to move the second electrode, the mechanical linkage comprising an insulating element arranged to electrically isolate the second electrode. 10. The apparatus of clause 1, wherein a plurality of conductive elements electrically connected to the second electrode are arranged to support the second electrode. 11. A discharge chamber; a first electrode disposed within the discharge chamber, the first electrode having a first electrode length extending in a first direction; a second electrode disposed within the discharge chamber, the second electrode having a second electrode length extending in the first direction and arranged in a spaced apart relationship relative to the first electrode so as to define an electrode gap between the first electrode and the second electrode; a first plurality of capacitors electrically connected to the first electrode and arranged in a first row extending in a first direction; a second plurality of capacitors electrically connected to the first electrode and arranged in a second row extending in the first direction parallel to the first row; In an apparatus comprising: The number of capacitors in the first plurality is the same as the number of capacitors in the second plurality. 12. The apparatus of clause 11, wherein some of the capacitors of the first plurality of capacitors are arranged substantially symmetrically about a centerline of the length of the electrode gap. 13. The apparatus of clause 12, wherein some of the capacitors of the second plurality of capacitors are arranged substantially symmetrically about a centerline of the length of the electrode gap. 14. The apparatus of clause 11, wherein the lateral ends of the second electrode are electrically insulated from the walls of the discharge chamber. 15. The apparatus of clause 11, further comprising a plurality of conductive elements electrically connected to the second electrode and arranged to support the second electrode. 16. A discharge chamber; a first electrode disposed within the discharge chamber, the first electrode having a first electrode length extending in a first direction; a second electrode disposed within the discharge chamber, the second electrode having a second electrode length extending in the first direction and arranged in a spaced apart relationship relative to the first electrode so as to define an electrode gap between the first electrode and the second electrode; a plurality of capacitance elements electrically connected to the first electrode and arranged in a first column extending in a first direction, at least one of the plurality of capacitance elements having a capacitance value different from at least one other capacitance element of the plurality of capacitance elements; An apparatus comprising: 17. The apparatus of clause 16, wherein at least one of the capacitive elements comprises a pair of capacitors connected in parallel. 18. A discharge chamber; a first electrode disposed within the discharge chamber, the first electrode having a first electrode length extending in a first direction; a second electrode disposed within the discharge chamber, the second electrode having a second electrode length extending in the first direction and arranged in a spaced apart relationship relative to the first electrode so as to define an electrode gap between the first electrode and the second electrode; a first number X of capacitors in a first row electrically connected to the first electrode and arranged in a first row in a first row direction substantially parallel to the length of the first electrode; a second number Y of capacitors in a second column electrically connected to the first electrode and arranged in a second column in a second column direction substantially parallel to the length of the first electrode; In an apparatus comprising: wherein X and Y are at least 4, X is less than Y, and the capacitance values ​​of the first capacitor in the second string and the last capacitor in the second string are equal to each other and less than the capacitance values ​​of the remaining capacitors in the second string. 19. A discharge chamber; a first electrode disposed within the discharge chamber; a second electrode disposed within the discharge chamber for creating an electrode gap having a height extending in a first direction between the first electrode and the second electrode and a length extending in a second direction transverse to the first direction between the first electrode and the second electrode; a first plurality of conductive elements electrically connected to the second electrode, each of the first plurality of conductive elements extending substantially in a first direction transverse to the electrode gap, the first plurality of conductive elements being arranged in a row extending in the second direction, the first plurality of conductive elements comprising a first pair of adjacent conductive elements spaced apart in the second direction by a first spacing and a second pair of adjacent conductive elements spaced apart in the second direction by a second spacing greater than the first spacing; a second plurality of conductive elements electrically connected to the second electrode, each of the second plurality of conductive elements extending substantially in a first direction transverse to the electrode gap on an opposite side of the electrode gap from the first plurality of conductive elements, the second plurality of conductive elements being arranged in a second row extending in the second direction and including a third pair of adjacent conductive elements spaced apart in the second direction by a first spacing and a fourth pair of adjacent conductive elements spaced apart in the second direction by a second spacing; a first plurality of capacitors electrically connected to the first electrode and arranged in a first row extending in a first direction; a second plurality of capacitors electrically connected to the first electrode and arranged in a second row extending in the first direction parallel to the first row, at least one of the capacitors of the second plurality of capacitors having a capacitance value different from at least one other capacitor of the second plurality of capacitors; An apparatus comprising: 20. The apparatus of clause 19, wherein the first pair of adjacent conductive elements are positioned across an electrode gap from the third pair of adjacent conductive elements. 21. The apparatus of clause 19, wherein the length of the first row and the length of the second row are substantially coextensive with the length of the electrode gap. 22. The apparatus of clause 19, wherein some of the conductive elements of the first plurality of conductive elements are arranged substantially symmetrically about a centerline of the length of the electrode gap. 23. The apparatus of clause 19, wherein some of the conductive elements of the first plurality of conductive elements are arranged substantially symmetrically about a midline of the length of the electrode gap, and some of the conductive elements of the second plurality of conductive elements are arranged substantially symmetrically about a midpoint of the length of the electrode gap. 24. The apparatus of clause 23, wherein some of the capacitors of the first plurality of capacitors are arranged substantially symmetrically about a centerline of the length of the electrode gap. 25. The apparatus of clause 23, wherein some of the capacitors of the second plurality of capacitors are arranged substantially symmetrically about a centerline of the length of the electrode gap. 26. The apparatus of clause 23, wherein some of the capacitors of the first plurality of capacitors are arranged substantially symmetrically about a centerline of the length of the electrode gap. 27. The apparatus of clause 19, wherein some of the capacitors of the second plurality of capacitors are arranged substantially symmetrically about a centerline of the length of the electrode gap. 28. The device of clause 19, wherein the lateral ends of the second electrode are electrically insulated. 29. The apparatus of clause 19, wherein the first and second pluralities of conductive elements are arranged to support a second electrode.

Claims

1. a first row of capacitors extending along a first direction; a second series of capacitors extending parallel to the first series of capacitors, the second series having a different number of capacitors than the first series of capacitors; a first electrode extending parallel to the first row of capacitors and aligned with a centerline between the first row of capacitors and the second row of capacitors, the first electrode being electrically coupled to the first row of capacitors and the second row of capacitors; A discharge chamber comprising:

2. 10. The discharge chamber of claim 1, wherein the first row of capacitors has two more capacitors than the second row of capacitors.

3. 10. The discharge chamber of claim 1, wherein the first series of capacitors comprises a first capacitance value and a second capacitance value different from the first capacitance value.

4. 2. The discharge chamber of claim 1, wherein two capacitors at opposite ends of the first series of capacitors have a first capacitance value and another capacitor between the opposite ends has a second capacitance value different from the first capacitance value.

5. 5. The discharge chamber of claim 4, wherein each of the other capacitors between the ends of the first series of capacitors has the same capacitance value as each capacitor of the second series of capacitors.

6. 2. The discharge chamber of claim 1, further comprising a second electrode extending parallel to the first electrode, the second electrode being electrically coupled to a first row of conductors and a second row of conductors, the second row of conductors being arranged symmetrically with the first row of conductors about a centerline of the second electrode along the first direction.

7. 7. The discharge chamber of claim 6, further comprising a first conductive bus coupled to each conductor of the first row of conductors, wherein a length of the first conductive bus in the first direction is greater than a length of the conductors of the first row arranged in a spaced-apart relationship in the first direction.

8. 8. The discharge chamber of claim 7, further comprising a second conductive bus arranged symmetrically with the first conductive bus about the center line of the second electrode along the first direction, the second conductive bus being coupled to each conductor of the second row of conductors.

9. a discharge chamber; a first electrode extending along a first direction, the first electrode being coupled to and arranged between a first row of capacitors and a second row of capacitors, the first row of capacitors and the second row of capacitors having at least two conductance values, and the second row of capacitors having a different number of capacitors than the first row of capacitors; a second electrode spaced apart from the first electrode along a second direction transverse to the first direction, the second electrode being coupled to the first column conductors and the second column conductors and arranged between the first column conductors and the second column conductors; A radiation source comprising:

10. 10. The radiation source of claim 9, wherein each conductor in the first column of conductors is coupled to a first conductive bus and to a plate, and each conductor in the second column of conductors is coupled to a second conductive bus and to the plate, and along the first direction, a length of the first conductive bus in the first direction is greater than a length of the conductors in the first column in the first direction and less than a length of the plate in the first direction.

11. 10. The radiation source of claim 9, wherein the capacitors in the first row are arranged symmetrically with the capacitors in the second row about a center line of the first electrode along the first direction.

12. 12. The radiation source of claim 11, wherein a total capacitance value of the capacitors in the first series is different from a total capacitance value of the capacitors in the second series.

13. 10. The radiation source of claim 9, wherein the capacitors in the first row are arranged asymmetrically with respect to the capacitors in the second row about a centerline of the first electrode along the first direction.

14. 10. The radiation source of claim 9, wherein the first row of capacitors has more capacitors than the second row of capacitors.

15. 10. The radiation source of claim 9, wherein the first row of capacitors has two more capacitors than the second row of capacitors.

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