Apparatus and method for acoustic control in a laser chamber

Abstract

This device generates laser radiation from an electrical discharge within a gap. Within the discharge chamber, the discharge reflects acoustic waves from the internal surfaces of the chamber. The gap is angled relative to the surfaces of the chamber's internal structures, so that the acoustic waves reflected by these surfaces do not reflect back to their origin, thus not interfering with the laser's operation, especially at high repetition rates.

Description

Technical Field

[0001] (Cross - Reference to Related Applications)

[0001] This application claims priority to U.S. Application No. 63 / 455,054, filed on March 28, 2023, entitled "LASER CHAMBER HAVING DISCHARGE GAP WITH ACOUSTIC CONTROL", which is hereby incorporated by reference in its entirety.

[0002]

[0002] The disclosed subject matter relates to a laser discharge chamber where the discharge in the discharge region generates laser radiation and also generates acoustic disturbances that can be undesirably retro - reflected into the discharge region.

Background Art

[0003]

[0003] Photolithography is a process used when semiconductor circuit elements are patterned on a substrate such as a silicon wafer. A photolithography radiation source provides deep ultraviolet (DUV) light (wavelengths in the range of about 100 nanometers (nm) to about 400 nm) to expose the photoresist on the wafer. Often, the radiation source is a laser source and the radiation is a pulsed laser beam. The radiation beam passes through a reticle or mask following a beam delivery unit and is then projected onto a silicon wafer coated with photoresist. In this way, the chip design is patterned on the photoresist and then etched and cleaned.

[0004]

[0004] In many systems that generate (such as a laser generator) or employ (such as a photolithography system) a laser beam, there is an optical train that includes one or more optical components (mirrors, gratings, prisms, optical switches, filters, etc.). The optical components in the optical train can reflect, process, filter, modify, focus, expand, etc., the laser beam, either wholly or in part, to obtain one or more desired laser beam outputs.

[0005]

[0005] In such systems, the laser beam is generated by generating a discharge in the discharge (inter-electrode) region of one or more laser discharge chambers. One of the challenges in designing and using these systems is that the discharge used to generate the laser radiation also generates strong acoustic waves within the discharge region, causing gas density modulation as it propagates within the laser discharge chamber. Surfaces within the laser discharge chamber can reflect these acoustic waves back into the discharge region, which can adversely affect the performance of the laser. In particular, these reflected waves can consequently cause round-trip time-of-flight resonance depending on the pulse delay or discharge repetition rate.

[0006]

[0006] In this situation, the need for the subject matter of this disclosure arises. [Overview of the project]

[0007]

[0007] In the following, one or more embodiments of the present invention are briefly outlined in order to deepen the basic understanding of the present invention. This outline is not intended to comprehensively review all conceivable embodiments, nor does it identify any particular element of any embodiment as important or critically important, nor does it limit the scope of some or all embodiments. The sole purpose of this outline is to briefly present some concepts related to one or more embodiments as a prerequisite for the more detailed descriptions that will follow.

[0008]

[0008] According to one aspect of one embodiment, a discharge chamber is disclosed comprising a chamber wall extending in a first direction, a first electrode having a first electrode discharge surface, and a second electrode having a second electrode discharge surface, wherein the first electrode discharge surface and the second electrode discharge surface define a discharge gap, the first and second electrodes are configured to induce a plasma discharge within the discharge gap, the first and second electrode discharge surfaces extend parallel to each other in a second direction at a certain angle with respect to the first direction, the first electrode has a top surface parallel to the chamber wall, and therefore the first electrode has a wedge-shaped cross section between the first electrode discharge surface and the top surface.

[0009]

[0009] The first electrode may be a cathode, and its top surface may be attached to the chamber wall. The discharge chamber further comprises an electrode support, which is mechanically coupled to the second electrode and positioned to support the second electrode within the discharge chamber, the magnitude of which is selected to prevent acoustic waves originating from the origin region in the discharge gap during a discharge in the discharge gap from being reflected back to the origin region by the electrode support during the next discharge. The magnitude of the angle may range from 0.5 degrees to 10 degrees.

[0010]

[0010] The discharge chamber further comprises an electrode support mechanically coupled to the second electrode and positioned to support the second electrode within the discharge chamber, with at least a portion of the electrode support located within a distance D from the discharge gap. The distance D may be less than 2 inches.

[0011]

[0011] The discharge chamber may further comprise a pre-onizer extending parallel to the chamber wall and positioned laterally close to the first electrode, with at least a portion of the pre-onizer positioned within a distance D from the discharge gap. The distance D may be less than 2 inches.

[0012]

[0012] The magnitude of the angle can be selected to prevent acoustic waves originating from the origin region within the discharge gap during a discharge within the discharge gap from being reflected back to the origin region by the playonizer during the next discharge. The magnitude of the angle can range from 0.5 degrees to 10 degrees.

[0013]

[0013] The discharge chamber may further include an insulator disposed parallel to the chamber wall and positioned laterally close to the first electrode proximal to the discharge gap. The magnitude of the angle may be selected to prevent acoustic waves generated from the origin region in the discharge gap during discharge from being reflected back to the origin region by the insulator during subsequent discharge. The magnitude of the angle may range from 0.5 to 10 degrees.

[0014]

[0014] According to another aspect of one embodiment, a device is disclosed comprising a laser chamber extending in a first direction along the optical axis of the chamber, a first elongated electrode disposed within the laser chamber and having a first electrode discharge surface, and a second elongated electrode disposed within the laser chamber and having a second electrode discharge surface, wherein the first electrode discharge surface and the second electrode discharge surface are spaced apart from each other and extend parallel to each other in a second direction at an angle with respect to the first direction, defining a discharge gap extending in the second direction. At least one acoustic reflector is located near the discharge gap, close to one of the first and second electrodes and extending in the first direction, and the magnitude of the angle is selected to prevent acoustic waves originating from an origin region within the discharge gap during a discharge in the discharge gap from being reflected back to the origin region by the at least one acoustic reflector during the next discharge.

[0015]

[0015] At least one acoustic reflecting surface may comprise the surface of a pre-onizer extending in a first direction and positioned laterally close to the first elongated electrode, with at least a portion of the pre-onizer further positioned within a distance D from the discharge gap. The distance D may be less than 2 inches.

[0016]

[0016] At least one acoustic reflecting surface may include an insulator extending in the first direction and proximal to the discharge gap.

[0017]

[0017] At least one acoustic reflecting surface may comprise an electrode support surface that is arranged to mechanically support the second electrode and extends in a first direction proximal to the discharge gap.

[0018]

[0018] The magnitude of the angle can be in the range of 0.5 to 10 degrees.

[0019]

[0019] Further embodiments, features, and advantages of the subject matter of this disclosure, as well as the structure and operation of various embodiments, will be described in detail below with reference to the accompanying drawings.

[0020]

[0020] The accompanying drawings are incorporated herein and form a part hereof, and illustrate the present invention, and together with the description, further explain the principles of the subject matter disclosed in the present invention and enable those skilled in the art to make and use the subject matter disclosed in the present invention.

Brief Description of the Drawings

[0021] [Figure 1]

[0021] It is a schematic diagram of a general broad concept of a photolithography system at a non - fixed scale. [Figure 2]

[0022] It is a schematic diagram of a general broad concept of an illumination system that may be used in the photolithography system of FIG. 1 at a non - fixed scale. [Figure 3]

[0023] It is a cross - sectional view at a non - fixed scale of a discharge chamber that may be used in the illumination system of FIG. 2. [Figure 4]

[0024] It is a cross - sectional view at a non - fixed scale of a part of the discharge chamber of FIG. 3. [Figure 5]

[0025] It is a perspective view at a non - fixed scale of the arrangement of components in the discharge chamber of FIG. 3. [Figure 6]

[0026] It is a diagram at a non - fixed scale of the arrangement of electrodes in a discharge chamber according to one aspect of one embodiment. [Figure 7]

[0027] It is a diagram at a non - fixed scale of the arrangement and configuration of electrodes in a discharge chamber according to one aspect of one embodiment. [Figure 8]

[0028] It is a diagram at a non - fixed scale of the arrangement of components in a discharge chamber according to one aspect of one embodiment.

[0022]

[0029] Further features and advantages of the present invention, as well as the structure and operation of various embodiments of the present invention, will be described in detail below with reference to the accompanying drawings. The scope of the invention disclosed herein is not limited to the specific embodiments described herein. Such embodiments are presented herein for illustrative purposes only. Those skilled in the art will be able to identify further embodiments based on the teachings presented herein. [Modes for carrying out the invention]

[0023]

[0030] Various embodiments are described with reference to the drawings. Throughout the drawings, the same reference numeral refers to the same element. In the following description, for the sake of clarity, numerous specific details are provided to facilitate a full understanding of one or more embodiments. However, it will be apparent that in some or all cases the embodiments described below can be implemented without employing the specific design details related thereto. In other cases, well-known structures and devices are shown in block diagram form to facilitate the description of one or more embodiments. This summary is not intended to provide an exhaustive overview of all conceivable embodiments, nor is it intended to identify any particular element of any embodiment as important or critical, nor to limit the scope of any or all embodiments.

[0024]

[0031] The systems described herein may offer advantages in a wide range of applications and embodiments. One such application in semiconductor photolithography is given as a specific, non-limiting example for the sake of clarity. Figure 1 shows a photolithography system 100 including an illumination system 105. As will be described in more detail below, the illumination system 105 includes a light source that generates a pulsed light beam 110 and directs it to a photolithography exposure apparatus 115, such as a scanner, which patterns microelectronic functions onto a wafer 120. The wafer 120 is placed on a wafer table 125 configured to hold the wafer 120 and connected to a positioner 130 configured to precisely position the wafer 120 according to specific parameters.

[0025]

[0032] The pulsed light beam 110 may have wavelengths in the DUV region, for example, 248 nanometers (nm) or 193 nm. The scanner 115 includes an optical arrangement 135 having, for example, one or more condenser lenses, a mask, and an objective lens arrangement. The mask is movable along one or more directions along the optical axis of the pulsed light beam 110 or in a plane perpendicular to the optical axis. The objective lens arrangement includes a projection lens, enabling the transfer of an image from the mask to the photoresist on the wafer 120. The illumination system 105 adjusts the angular range of the pulsed light beam 110 striking the mask. The illumination system 105 also homogenizes (uniformizes) the intensity distribution of the pulsed light beam 110 across the entire mask.

[0026]

[0033] Among other functions, the scanner 115 may include a lithography controller 140 that controls how layers are printed on the wafer 120. The lithography controller 140 may include a memory that stores information such as a process recipe, which determines beam parameters, including the exposure length on the wafer 120, based on, for example, the mask used and other factors affecting exposure. During lithography, pulse bursts of pulsed light beam 110 illuminate the same area of ​​the wafer 120 to build up the illumination dose.

[0027]

[0034] The photolithography system 100 preferably also includes a control system 145. Generally, the control system 145 includes one or more of the following: digital electronic circuit elements, computer hardware, firmware, and software. The control system 145 can be centralized or partially or completely distributed throughout the photolithography system 100.

[0028]

[0035] Figure 2 shows a pulsed laser source that generates a pulsed laser beam as an optical beam 110, as an example of an illumination system 105. Although Figure 2 shows a two-chamber laser system as a non-limiting example, it will be understood that the principles described herein are equally applicable to a single-chamber laser system or a laser system having two or more chambers. A gas discharge laser system may include, for example, a solid or gas discharge master oscillator ("MO") seed laser system 200, an amplification stage, such as a power ring amplifier ("PRA") stage 205, a relay optical system 210, and a laser system output subsystem 215. The seed system 200 may include, for example, an MO chamber 220 containing a pair of electrodes 222 and 224.

[0029]

[0036] The MO seed laser system 200 may also include a master oscillator output coupler ("MO OC") 230, which may include a partial reflection mirror that forms an MO discharge chamber 220 with an oscillator cavity defined by a reflection grating (not shown) in a line narrowbanding module ("LNM") 235 that oscillates to form seed laser output pulses. The MO seed laser system 200 may also include a line-centered analysis module ("LAM") 240. The MO wavefront engineering box ("WEB") 245 may function to redirect the output of the MO seed laser system 200 toward the amplification stage 205 and may include, for example, a multiprism beam expander (not shown) and an optical delay path (not shown). The beam paths passing through the LNM 235, MO discharge chamber 220, MO OC 230, and LAM 240 define the optical axes 237 of each of these components.

[0030]

[0037] The amplification stage 205 may include, for example, a PRA discharge chamber 250, which may also be an oscillator formed by a seed beam incidence and output coupling optical system (not shown), which may be incorporated into, for example, a PRA web 255. The beam may be re-induced by a beam inverter ("BR") 260 through a gain medium in the PRA discharge chamber 250. The PRA web 255 may incorporate a partial reflection input / output coupler (not shown), a maximum reflection mirror for the nominal operating wavelength (e.g., about 193 nm for an ArF system), and one or more prisms. The PRA discharge chamber 250 may also include a pair of electrodes 252 and 254.

[0031]

[0038] The Bandwidth Analysis Module ("BAM") 265 may receive the pulsed output laser beam from the PRA discharge chamber 250 and may extract a portion of the beam for measurement purposes, for example, to measure the output bandwidth and pulse energy. The pulsed laser output beam then passes through the PRA web 255 and is sent to the Optical Pulse Stretcher ("OPuS") 270 and the Combined Automatic Shutter Measurement Module ("CASMM") 275, which in this case may also be the location of the pulse energy meter. One purpose of the OPuS 270 is, for example, to convert a single output laser pulse into a pulse train. Secondary pulses generated from the original single output pulse can be delayed relative to each other. By distributing the original laser pulse energy into a secondary pulse train, the effective pulse length of the laser can be increased while simultaneously reducing the peak pulse intensity. Therefore, the OPuS 270 may be configured to receive the laser beam from the PRA web 255 and direct its output to the CASMM 275.

[0032]

[0039] The beam paths through BR260, PA discharge chamber 250, and BAM265 define the optical axes 267 of each of these components.

[0033]

[0040] The PRA discharge chamber 250 and the MO discharge chamber 220 are configured as chambers that induce a laser gas discharge in the laser gas so that the discharge between the electrodes causes a population inversion of high-energy molecules or excimers, such as ArF, KrF, F2, XeF, and / or XeCl, and produces relatively broadband radiation that can be linewidthed to a relatively very narrow bandwidth and center wavelength selected in LNM235.

[0034]

[0041] Next, moving to Figure 3, a laser discharge chamber 300 is shown, which can function as, for example, a PRA discharge chamber 250 or an MO discharge chamber 220. The chamber 300 consists of, for example, an upper chamber body 305 and a lower chamber body 310, which are connected to each other by appropriate means, for example, bolting, thereby defining the interior of the chamber 315. The upper chamber body 305 and the lower chamber body 310 also define the vertical walls 320 inside the chamber, and the lower chamber body 310 defines the horizontal bottom wall 325 inside the chamber.

[0035]

[0042] In this specification, including the claims, terms such as “up,” “down,” “upper,” “lower,” “top,” “bottom,” “summit,” “bottom,” “vertical,” and “horizontal” mean only relative orientations unless otherwise indicated or made clear from the context, and not any absolute orientation such as orientation relative to gravity.

[0036]

[0043] Alternatively, for example, a gas discharge system comprising two elongated opposing electrodes, namely a cathode 330 and an anode 335, is included inside the chamber 315, defining an elongated gas discharge gap or region 340 between them. In response to a sufficient voltage applied to the cathode 330 and anode 335, a discharge occurs in the gas discharge region 340, resulting in the generation of radiation with a characteristic central wavelength or nearby, which is optically guided along the optical axis of the output laser light pulse, which is roughly aligned with the longitudinal optical axis of the laser discharge chamber 300 along the X-axis (outside the plane of the figure), as shown in the inset.

[0037]

[0044] Furthermore, an anode support bar 345, for example, may be installed inside the chamber interior 315. The anode 335 may be electrically connected to the upper chamber body 305 via multiple current returns, and the upper chamber body 305, together with the lower chamber body 310, is maintained at a common voltage, such as the ground voltage.

[0038]

[0045] The cathode 330 may be connected to the discharge high-voltage feed via the assembly 350, for example, by a high-voltage feedthrough 355 passing through the main insulator 360. The main insulator 360 may keep the cathode 330 electrically isolated from the upper chamber body 305. Also, a preionizer 365, which may be, for example, a preionizer tube, may be installed inside the chamber 315, for example, in close proximity to the cathode 330. The preionizer 365 may be configured as an elongated, hollow dielectric (e.g., ceramic) tube surrounding the electrode. Further details regarding the preionizer are described in U.S. Patent No. 7,542,502, filed June 2, 2009, entitled "Thermal-expansion Tolerant, Preionizer Electrode for a Gas Discharge Laser".

[0039]

[0046] All patent applications, patents, and publications cited herein are incorporated herein by reference in their entirety, except for definitions, subject matter disclaimers, and denials, and unless the incorporated material conflicts with the disclosure expressly made herein. In case of any conflict, the language of this disclosure shall prevail.

[0040]

[0047] Furthermore, a gas circulation system comprising a gas circulation fan 370 may be installed inside the chamber 315, which may be, for example, a generally cylindrical cross-flow fan 370. The fan 370 functions to move the gas inside the chamber 315 in a generally circular manner, as shown in the cross-sectional view of Figure 3, removing gas containing ionized particles and debris and depleting F2 from the discharge area 340 during continuous gas discharge, and thus replenishing the discharge area 340 with fresh gas before the next gas discharge. The gas circulation system may also include a plurality of heat exchangers 375 in a generally circular gas flow path to remove heat added to the gas, for example, by the discharge and the operation of the fan 370.

[0041]

[0048] The gas circulation system may also have a plurality of curved baffles 380 and flow guide vanes 385, which may function to form a generally circular gas flow path from the discharge region 340 to the heat exchanger 375 and ultimately to the intake of the fan 370, and from the output of the fan 370 back to the discharge region 340. The upper chamber body 305 may also have an attached metal fluoride trap 390 that is in fluid communication with the inside of the chamber 315.

[0042]

[0049] Figure 4 is a schematic diagram further illustrating how the electrodes and adjacent components are positioned within the gas discharge laser chamber. As shown in Figure 4, the anode 335 and cathode 330 are arranged opposite each other, with the elongated cathode discharge surface 332 facing the elongated discharge anode surface 337. The anode 335 is mounted on an anode support bar 345. The gas discharge region 340, which is the space defined between the elongated cathode discharge surface 332 and the elongated anode discharge surface 337, typically has a height of about 0.5 inches (in the Y-axis direction). In one example, the respective lengths L of the anode 335 and cathode 330 (see Figure 5) may range, for example, from about 20 to 30 inches. As mentioned above, the width of the discharge region and the length of the electrodes may be varied to suit the needs of a particular application. Figure 4 also shows a plyonizer 365.

[0043]

[0050] Figure 5 is a perspective view showing an example of the arrangement of components within the laser discharge chamber 300. As can be seen from Figure 5, the elongated cathode discharge surface 332 of the cathode 330 faces the elongated anode discharge surface 337 of the anode 335 through a gap that defines the discharge region 340. When a discharge occurs in the discharge region 340, the radiation generated by the discharge propagates in the direction indicated by the arrow 400. The optical axis 410 of the laser discharge chamber 300 is also shown. As shown in the figure, the optical axis 410 can be considered to extend parallel to the X-axis of the right-handed Cartesian coordinate system. The elongated cathode 330, the elongated anode 335, and the gap that defines the discharge region 340 all extend parallel to the optical axis 410. Figure 5 also shows a pre-onizer 365 extending parallel to the optical axis 410. In Figure 5, the main insulator 360 extending parallel to the optical axis 410 is shown by a dashed line (in phantom). Figure 5 also shows an anode support bar 345 extending parallel to the optical axis 410.

[0044]

[0051] As mentioned above, the discharge occurring in the discharge region 340 generates acoustic waves inside the discharge chamber 300. The acoustic waves generated by the discharge propagate outward from the discharge region 340, are reflected off the inner surface of the laser discharge chamber 300, and then return to the discharge region, where they distort the laser beam generated by subsequent pulses.

[0045]

[0052] The amount of distortion generally depends on the relationship between the pulse repetition rate and the time-flight distance of the acoustic wave traveling at the speed of sound from the discharge region to the reflective surface within the laser discharge chamber and then returning. At high repetition rates, for example in the range of 5.8 kHz to 6 kHz, the reflective surface closer to the discharge region 340 dominates the resonant acoustic distortion effect. This includes the surfaces above and below the discharge region, such as the pre-onizer, main insulator, and anode support bar facing the discharge region.

[0046]

[0053] To address the distortion of this high repetition rate, according to one embodiment, the cathode discharge surface and the anode discharge surface are both parallel to each other longitudinally but are oriented to be inclined with respect to the optical axis of the laser discharge chamber, which is defined by optical elements at each end of the discharge chamber that establish the resonant laser cavity. Thus, the erosion rate may be constant along the length of the electrode, but the discharge surface is no longer parallel to structures (e.g., main insulator, pre-onizer, and anode support bar) proximal to the discharge region that may cause reflection. The inclination of the cathode discharge surface can be physically machined within the cathode such that one end of the cathode is higher (longer in the y-dimension) than the other end.

[0047]

[0054] An arrangement incorporating these features is shown in Figure 6. In Figure 6, the laser discharge chamber 600 comprises a first electrode 630 and a second electrode 635. The first electrode 630 may be configured to function as a cathode. The second electrode 635 may be configured to function as an anode. As shown in the figure, the discharge surface 632 of the first electrode 630 is positioned at an angle θ (rotation around the Z axis, with respect to the horizontal XZ plane, and therefore also referred to as a perpendicular angle herein) with respect to a line parallel to the optical axis 410 of the discharge chamber 600. The discharge surface 637 of the second electrode 635 is also positioned at an angle θ with respect to a line parallel to the optical axis 410 of the discharge chamber 600. Thus, the discharge surface 632 of the first electrode 630 and the discharge surface 637 of the second electrode 635 are parallel to each other. The discharge region 640 between the discharge surface 632 of the first electrode 630 and the discharge surface 637 of the second electrode 635 is at the same angle θ with respect to a line parallel to the optical axis 410.

[0048]

[0055] In other words, the orientation of the discharge region 640 is substantially rotated counterclockwise or clockwise by an angle θ with respect to the orientation parallel to the optical axis 410. This means that the discharge region 640 is at the same angle θ with respect to the acoustic wave reflecting surfaces proximal to the discharge region 640, such as the main insulator, the pre-onizer, and the anode support bar, which are positioned parallel to the optical axis 410. Therefore, when acoustic waves generated from a discharge within the discharge region 640 collide with these surfaces, they tend to be reflected to a return sub-region well away from the originating sub-region, rather than returning directly to the sub-region of the discharge region 640 where the acoustic waves originated, resulting in a lower likelihood of generating time-of-flight resonances that would interfere with subsequent discharges within the discharge region 640. In this specification, including in the claims, the term “proximal” means within 2 inches from the discharge region 640. Generally, it is the surface in this range of the discharge region 640 that contributes most significantly to time-of-flight resonances at high repetition rates.

[0049]

[0056] The magnitude of the angle θ can be selected such that it is small enough not to introduce significant deviations or obstructions to the optical path through the laser discharge chamber 600, and large enough so that acoustic waves reflected from the proximal surface are not directly reflected back to the discharge region where the acoustic waves originated within the time required to interfere with the next discharge. Generally, the angle θ is in the range of approximately 0.5° to approximately 10°.

[0050]

[0057] Figure 7 shows an arrangement in which the first electrode 630 (e.g., cathode) is directly attached to the upper chamber wall 617 of the laser discharge chamber 600. Therefore, the first electrode has a roughly wedge-shaped cross-section in the XY plane, i.e., between the upper chamber wall 617 and the first electrode discharge surface 632, and the inclined bottom surface of the wedge forms the first electrode discharge surface 632 which forms an angle θ with a line parallel to the optical axis 410.

[0051]

[0058] Figure 8 also shows the arrangement in which the first electrode 630 is directly attached to the upper wall 617 of the laser discharge chamber 600, having a roughly wedge-shaped cross-section in the XY plane. Figure 8 also shows several components having acoustic reflectors proximal to the discharge region 640, which, without the acoustic reflectors, would reflect acoustic waves back to their source region in the discharge region 640 between the first electrode discharge surface 632 and the second electrode discharge surface 637. These elements include the main insulator 360 (light gray shading), the plyonizer 365 (shown by dashed lines as it is covered by the main insulator 360), and the second electrode (anode) support bar 645. Figure 8 also shows the distance D between at least a portion of the plyonizer 365 and the inter-electrode discharge gap 640. This distance D varies along the length of the first electrode 630, but it will be understood that in some embodiments, the distance D is generally less than 2 inches along the entire length of the plyonizer 365. In fact, the vertical (Y-axis) distance between the discharge gap and the playonizer 365 varies as a function of the longitudinal (along the X-axis) region of measurement. In the illustrated example, this function is linear and decreases as the distance along the X-axis increases. At least a portion of the second electrode support bar 645 is also generally within the distance D of the inter-electrode discharge gap 640.

[0052]

[0059] Some of the above explanation is from the perspective of a functional block diagram, where some functions are assigned to some blocks, and other functions are assigned to other blocks. The division and assignment between blocks are arbitrary, and it should be understood that different divisions and assignments are possible, as long as the overall function is performed as described above.

[0053]

[0060] The above description includes examples of several embodiments. Of course, it is impossible to describe every conceivable combination of components or methodologies for the purpose of illustrating these embodiments, but those skilled in the art will understand that many more combinations and permutations of elements of various embodiments are possible based on this disclosure. Accordingly, the embodiments described are intended to represent and disclose all changes, modifications, and variations that fall within the spirit and scope of the appended claims.

[0054]

[0061] Furthermore, where the term "includes" is used in either the detailed description or the claims, it is intended to be comprehensive, similar to how the term "comprising" is interpreted when used as a conjunction in the claims. Also, while elements of the described aspects and / or embodiments may be described or claimed in the singular, plural forms are also assumed unless explicitly stated to be limited to the singular. Furthermore, unless otherwise stated, all or part of any aspect and / or embodiment may be used in conjunction with all or part of any other aspect and / or embodiment.

[0055]

[0062] The aspects and embodiments of this disclosure can be further described by the following clauses. 1. A chamber wall extending in the first direction, A first electrode having a first electrode discharge surface, A second electrode having a second electrode discharge surface, A discharge chamber equipped with, The first electrode discharge surface and the second electrode discharge surface define a discharge gap, and the first and second electrodes are configured to induce a plasma discharge within the discharge gap. The first and second electrode discharge surfaces extend parallel to each other in a second direction at a certain angle with respect to the first direction. The first electrode has a top surface parallel to the chamber wall, and therefore the first electrode has a wedge-shaped cross-section between the first electrode discharge surface and the top surface. Discharge chamber. 2. The discharge chamber according to Clause 1, wherein the first electrode is a cathode and its top surface is attached to the chamber wall. 3. The discharge chamber according to Clause 1, further comprising an electrode support mechanically coupled to the second electrode and positioned to support the second electrode within the discharge chamber, wherein the magnitude of the angle is selected to prevent acoustic waves originating from an originating region within the discharge gap during a discharge within the discharge gap from being reflected back to the originating region by the electrode support during the next discharge. 4. A discharge chamber as described in Clause 3, wherein the angle is in the range of 0.5 to 10 degrees. 5. The discharge chamber according to Clause 1, further comprising an electrode support mechanically coupled to a second electrode and positioned to support the second electrode within the discharge chamber, wherein at least a portion of the electrode support is located within a distance D from the discharge gap. 6. A discharge chamber as described in Clause 5, where the distance D is less than 2 inches. 7. The discharge chamber according to Clause 1, further comprising a pre-onizer extending parallel to the chamber wall and positioned laterally close to the first electrode, wherein at least a portion of the pre-onizer is positioned within a distance D from the discharge gap. 8. A discharge chamber as described in Clause 7, where the distance D is less than 2 inches. 9. The discharge chamber according to Clause 7, wherein the magnitude of the angle is selected to prevent acoustic waves originating from the origin region within the discharge gap during a discharge within the discharge gap from being reflected back to the origin region by the pre-onizer during the next discharge. 10. A discharge chamber as described in Clause 9, wherein the angle is in the range of 0.5 to 10 degrees. 11. The discharge chamber according to Clause 1, further comprising an insulator disposed parallel to the chamber wall and positioned laterally close to the first electrode proximal to the discharge gap. 12. The discharge chamber according to Clause 11, wherein the magnitude of the angle is selected to prevent acoustic waves originating from an originating region within the discharge gap during a discharge within the discharge gap from being reflected back to the originating region by the insulator during the next discharge. 13. A discharge chamber as described in Clause 12, wherein the magnitude of the angle is in the range of 0.5 degrees to 10 degrees. 14. A laser chamber extending along the optical axis of the chamber in the first direction, A first elongated electrode, which is disposed within the laser chamber and has a first electrode discharge surface, A second elongated electrode, which is disposed within the laser chamber and has a second electrode discharge surface, A device equipped with, The first electrode discharge surface and the second electrode discharge surface are arranged with a gap between them, extending parallel to each other in the second direction at a certain angle with respect to the first direction, defining a discharge gap extending in the second direction. At least one acoustic reflecting surface is positioned near the discharge gap and extends in a first direction in close proximity to one of the first and second electrodes. An apparatus in which the magnitude of the angle is selected to prevent acoustic waves originating from an originating region within a discharge gap during a discharge within the discharge gap from being reflected back to the originating region by at least one acoustic reflecting surface during the next discharge. 15. The apparatus according to Clause 14, comprising the surface of a pre-onizer having at least one acoustic reflective surface extending in a first direction and disposed in close lateral proximity to a first elongated electrode, wherein at least a portion of the pre-onizer is further disposed within a distance D from the discharge gap. 16. The apparatus described in Clause 15, where the distance D is less than 2 inches. 17. The apparatus according to Clause 14, wherein at least one acoustic reflecting surface extends in a first direction and comprises an insulator proximal to the discharge gap. 18. The apparatus according to Clause 14, comprising an electrode support surface, wherein at least one acoustic reflective surface is arranged to mechanically support a second electrode and extends in a first direction proximal to the discharge gap. 19. The apparatus described in Clause 14, wherein the magnitude of the angle is in the range of 0.5 degrees to 10 degrees.

[0056]

[0063] The above embodiments and examples, as well as other embodiments, are included in the following claims.

Claims

1. A chamber wall extending in the first direction, A first electrode having a first electrode discharge surface, A second electrode having a second electrode discharge surface, A discharge chamber equipped with, The first electrode discharge surface and the second electrode discharge surface define a discharge gap, and the first and second electrodes are configured to induce a plasma discharge within the discharge gap. The first and second electrode discharge surfaces extend parallel to each other in a second direction at a certain angle with respect to the first direction, The first electrode has a top surface parallel to the chamber wall, and therefore the first electrode has a wedge-shaped cross-section between the first electrode discharge surface and the top surface. Discharge chamber.

2. The discharge chamber according to claim 1, wherein the first electrode is a cathode and the top surface is attached to the chamber wall.

3. The discharge chamber according to claim 1, further comprising an electrode support mechanically coupled to the second electrode and positioned to support the second electrode within the discharge chamber, wherein the magnitude of the angle is selected to prevent acoustic waves generated from an originating region within the discharge gap during a discharge within the discharge gap from being reflected back to the originating region by the electrode support during the next discharge.

4. The discharge chamber according to claim 3, wherein the magnitude of the angle is in the range of 0.5 degrees to 10 degrees.

5. The discharge chamber according to claim 1, further comprising an electrode support mechanically coupled to the second electrode and positioned to support the second electrode within the discharge chamber, wherein at least a portion of the electrode support is located within a distance D from the discharge gap.

6. The discharge chamber according to claim 5, wherein the distance D is less than 2 inches.

7. The discharge chamber according to claim 1, further comprising a pre-onizer extending parallel to the chamber wall and disposed in close proximity to the first electrode in the lateral direction, wherein at least a portion of the pre-onizer is disposed within a distance D from the discharge gap.

8. The discharge chamber according to claim 7, wherein the distance D is less than 2 inches.

9. The discharge chamber according to claim 7, wherein the magnitude of the angle is selected to prevent acoustic waves generated from a starting region within the discharge gap during a discharge within the discharge gap from being reflected back to the starting region by the playonizer during the next discharge.

10. The discharge chamber according to claim 9, wherein the magnitude of the angle is in the range of 0.5 degrees to 10 degrees.

11. The discharge chamber according to claim 1, further comprising an insulator disposed parallel to the chamber wall and positioned laterally close to the first electrode proximal to the discharge gap.

12. The discharge chamber according to claim 11, wherein the magnitude of the angle is selected to prevent acoustic waves generated from an originating region within the discharge gap during a discharge within the discharge gap from being reflected back to the originating region by the insulator during the next discharge.

13. The discharge chamber according to claim 12, wherein the magnitude of the angle is in the range of 0.5 degrees to 10 degrees.

14. A laser chamber extending along the optical axis of the chamber in a first direction, A first elongated electrode, having a first electrode discharge surface, is disposed within the laser chamber. A second elongated electrode, having a second electrode discharge surface, is disposed within the laser chamber. A device equipped with, The first electrode discharge surface and the second electrode discharge surface are arranged with a gap between them, extending parallel to each other in the second direction at a certain angle with respect to the first direction, defining a discharge gap extending in the second direction. At least one acoustic reflecting surface is positioned near the discharge gap and extends in the first direction in close proximity to one of the first electrode and the second electrode, The magnitude of the angle is selected to prevent acoustic waves generated from an originating region within the discharge gap during a discharge within the discharge gap from being reflected back to the originating region by the at least one acoustic reflecting surface during the next discharge.

15. The apparatus according to claim 14, wherein the at least one acoustic reflective surface comprises the surface of a preionizer extending in the first direction and disposed in close proximity to the first elongated electrode in the lateral direction, and at least a portion of the preionizer is further disposed within a distance D from the discharge gap.

16. The apparatus according to claim 15, wherein the distance D is less than 2 inches.

17. The apparatus according to claim 14, wherein the at least one acoustic reflecting surface extends in the first direction and comprises an insulator proximal to the discharge gap.

18. The apparatus according to claim 14, wherein the at least one acoustic reflecting surface comprises an electrode support surface that is arranged to mechanically support the second electrode and extends in the first direction proximal to the discharge gap.

19. The apparatus according to claim 14, wherein the magnitude of the angle is in the range of 0.5 degrees to 10 degrees.

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