TW202400821A - Laser discharge apparatus and method of forming a protective layer on an electrode in the laser discharge chamber - Google Patents

Abstract

Disclosed is an apparatus and method for creating a protective layer on at least one electrode in a laser chamber in which a layer-forming gas is added to the laser chamber and then the electrode is used to generate a plasma in the laser chamber causing formation of the protective layer.

Description

Laser discharge equipment and method of forming protective layer on electrode in laser discharge chamber

The subject matter disclosed herein relates to laser-generated light sources, such as those used in integrated circuit photolithography manufacturing processes.

In laser discharge chambers such as ArF power ring amplifier excimer discharge chambers ("PRA") or KrF excimer discharge chambers, electrode erosion imposes considerable limitations on the service life of the chamber module. One measure to extend the service life of KrF excimer discharge chamber modules involves making the anodes from wear-resistant materials. Information on materials suitable for use as anode materials may 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 assigned The assignees of this application are hereby incorporated by reference in their entirety.

Fluorine-containing plasma is highly aggressive to metals and can therefore cause electrode corrosion and erosion during operation of the chamber. For example, the nucleation and growth of localized zones of corrosion products that accumulate on the surface of the anode can occur. This results in non-uniformity of discharge between the electrode and the downstream arc. Erosion causes both an increase in the width of the discharge gap and a broadening of the discharge. These phenomena result in lower energy density of the discharge, which in turn necessitates an increase in the voltage difference across the electrodes required to maintain energy output. In addition, discharge broadening reduces the clearance rate of the gas flow, resulting in increased arcing downstream, resulting in energy dropout and resulting dose errors. Once the dose error rate increases above a predetermined threshold, the chamber is considered to have reached the end of its useful life and must be replaced.

One or more metal oxide layers or metal oxynitride layers may serve as a protective layer for the surface of the electrode. For example, the formation of CuO or ZnO can prevent fluorination of electrode materials such as brass. The same is true for the formation of metal oxynitrides, which have excellent compressive strength, flexural strength, fracture toughness, Knoop hardness and shear modulus, and have extremely high fluorination resistance. Having such a layer improves the life of the electrode. However, techniques for forming metal oxides on electrodes currently involve heating the electrodes in an oxygen bath in a furnace. These techniques warp, shrink, and otherwise deform the electrodes. In addition, it usually results in the entire electrode being covered by a protective layer, which is disadvantageous since these methods are not performed on site and if the entire electrode is coated, it is still difficult, if not impossible, to install the coated electrode in the chamber.

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 contemplated embodiments and is intended to neither identify key or critical elements of all embodiments nor 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.

According to one aspect of the embodiments, a laser cavity having an electrode configured to expose the electrode to a layer-forming gas while generating a plasma in the laser cavity to grow on the electrode is disclosed A protective metal oxide layer or metal oxynitride layer. Therefore, the layers grow in the chamber (ie, in situ) during the plasma discharge. This provides better spatial control of the layers without deforming the electrodes.

Other embodiments, features, and advantages of the present invention, as well as the structure and operation of various embodiments, are described in detail below with reference to the accompanying drawings.

Various embodiments are now described with reference to the drawings, wherein like reference numbers are used to refer to like elements throughout. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more embodiments. It will be apparent, however, that in some or all circumstances, any of the embodiments described below may be practiced without the specific design details described below. In other instances, well-known structures and devices are shown in block diagram form in order to facilitate description of one or more embodiments. A simplified summary of one or more embodiments is presented below in order to provide a basic understanding of the embodiments. This summary is not an extensive overview of all contemplated embodiments and is intended to neither identify key or critical elements of all embodiments nor delineate the scope of any or all embodiments.

Figure 1 shows a photolithography system 100 including an illumination system 105. As described more fully below, the illumination system 105 includes a light source that generates a pulsed beam 110 and directs it to a photolithography exposure device or scanner 115 that patterns the microelectronic features. on the wafer 120. Wafer 120 is placed on wafer stage 125, which is constructed to hold wafer 120 and connected to a positioner configured to accurately position wafer 120 according to certain parameters.

The photolithography system 100 uses a beam 110 with a wavelength in the deep ultraviolet (DUV) range, such as a wavelength of 248 nanometers (nm) or 193 nm. The minimum size of microelectronic features that can be patterned on wafer 120 depends on the wavelength of beam 110, with shorter wavelengths resulting in smaller minimum feature sizes. When the wavelength of the beam 110 is 248 nm or 193 nm, the minimum size of the microelectronic features may be, for example, 50 nm or less, although other light wavelengths and other minimum feature sizes may be generated according to other embodiments. The bandwidth of beam 110 may be the actual instantaneous bandwidth of its spectrum (or emission spectrum), which contains information about how the light energy of beam 110 is distributed across different wavelengths. Photolithographic exposure equipment or scanner 115 includes an optical arrangement having, for example, one or more condenser lenses, masks, and objective lens arrangements. The mask may move along one or more directions, such as along the optical axis of the beam 110 or in a plane perpendicular to the optical axis. The objective configuration includes a projection lens and enables image transfer from the photoresist masked onto the wafer 120 . The lighting system 105 adjusts the range of angles at which the light beam 110 irradiates the mask. The illumination system 105 also homogenizes the intensity distribution of the beam 110 across the mask (uniformes the intensity distribution of the beam 110 across the mask).

Scanner 115 may include a lithography controller 130, air conditioning, and power supplies for various electrical components, among other features. Lithography controller 130 controls the manner in which layers are printed on wafer 120 . Lithography controller 130 includes memory that stores information such as process recipes. The process sequence or recipe determines the length of exposure of wafer 120 based on, for example, the mask used and other factors that affect exposure. During lithography, multiple pulses of light beam 110 illuminate the same area of wafer 120 to achieve an illumination dose.

Photolithography system 100 may also suitably include a control system 135. Generally speaking, the control system 135 includes one or more of digital electronic circuit systems, computer hardware, firmware, and software. The 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 (by way of 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.

Control system 135 may also include one or more input devices (such as keyboards, touch screens, microphones, mice, handheld input devices, etc.) and one or more output devices (such as speakers or monitors). The 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. One or more programmable processors can each execute a program of instructions to perform a desired function by operating on input data and producing appropriate output. Typically, a processor receives instructions and data from memory. Any of the foregoing may be supplemented by or incorporated into a specially designed ASIC (Application Special Integrated Circuit). The control system 135 may be centralized or partially or entirely distributed throughout the photolithography system 100 .

Referring to FIG. 2 , exemplary illumination system 105 is a pulsed laser source that generates a pulsed laser beam as beam 110 . Figure 2 illustratively and in a block diagram shows a gas discharge laser system according to an 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 145, such as a power ring amplifier ("PRA") stage, relay optics 150, and laser system output subsystem 160 . Seed system 140 may include, for example, a master oscillator (“MO”) cavity 165.

The seed laser system 140 may also include a master oscillator output coupler ("MO OC") 175, which may include a partially reflective mirror that is coupled to a reflective grating (not shown) in a line narrowing module ("LNM") 170 ) together form an oscillator cavity in which the seed laser 140 oscillates to form a seed laser output pulse, that is, a master oscillator (“MO”). The system may also include a line center analysis module ("LAM") 180. The LAM 180 can include an etalon spectrometer for fine wavelength measurements as well as a coarser resolution grating spectrometer. MO wavefront engineering box ("WEB") 185 may be used to redirect the output of MO seed laser system 140 to amplification stage 145, and may include, for example, an amplifier with, for example, a multi-channel beam expander (not shown). beams and coherence busting, for example in the form of optical delay paths (not shown).

The magnification stage 145 may include, for example, the PRA laser cavity 200, which may also be an oscillator formed, for example, from seed beam injection and outcoupling optics (not shown), which may be incorporated into the PRA WEB 210 and may be redirected back by beam diverter 220 via the gain medium in chamber 200 . PRA WEB 210 may incorporate a partially reflective input/output coupler (not shown) and a maximum reflective mirror for the nominal operating wavelength (e.g., approximately 193 nm for an ArF system), and one or more mirrors.

A bandwidth analysis module ("BAM") 230 at the output of the amplification stage 145 can receive the pulsed output laser beam from the amplification stage and intercept it for metrology purposes, such as to measure the output bandwidth and pulse energy. part of the beam. The pulsed laser output beam then passes through the optical pulse stretcher ("OPuS") 240 and the output combined automatic shutter metrology module ("CASMM") 250, which can also be the location of the pulse energy meter. One purpose of OPuS 240 may be, for example, to convert a single output laser pulse into a pulse train. Secondary pulses generated from the original single output pulse may be delayed relative to each other. By distributing the original laser pulse energy into secondary pulse trains, the effective pulse length of the laser can be extended while the peak pulse intensity is reduced. OPuS 240 can therefore receive the laser beam from PRA WEB 210 via BAM 230 and direct the output of OPuS 240 to CASMM 250.

As is known in the art, PRA laser cavity 200 and MO 165 are configured as a chamber in which a discharge between electrodes can cause a discharge of the laser gas in the laser gas to produce a population of inverted high energy molecules, including For example, Ar, Kr, and/or Xe, thereby producing relatively broad-band radiation that can be line-narrowed to a relatively very narrow bandwidth and center wavelength selected in line-narrowing module (“LNM”) 170 .

The configuration of such a chamber 300 is shown in Figure 3, which is a highly stylized cross-sectional view of a discharge chamber. Chamber 300 includes an upper electrode 310 that acts as a cathode, and a lower electrode 320 that acts as an anode. One or both of lower electrode 320 and upper electrode 310 may be integrally contained within the pressure envelope of chamber 300 bounded by chamber walls 305, or one of the electrodes may not be so contained. The laser gas discharge occurs between these two electrodes in the gap A. Also shown in Figure 3 is an upper insulator 315 and a lower insulator 325. The lower electrode 320 is electrically connected to the wall 305 of the chamber 300 . For safety reasons, the chamber wall 305 and the lower electrode 320 need to be maintained at ground potential. In the embodiment shown in FIG. 3 , the upper electrode 310 is driven by the voltage supplier 340 at a negative voltage relative to the lower electrode 320 .

As mentioned, a voltage supply 340 is also shown in FIG. 3 that establishes a voltage gradient across cathode 310 and anode 320. Although the sign of the polarity of the output of voltage supply 340 is shown (-), it should be understood that this is a relative and not an absolute polarity, that is, relative to the polarity of lower electrode 320 which will generally be in contact with the body of chamber 300 electrical contact and must be maintained at ground (0) potential. The upper electrode (cathode 310) is charged to a large (approximately 20 kV) negative voltage.

The electrodes in chamber 300 are known to corrode. The erosion may be the result of a fluorination reaction with the electrode material according to embodiments using ArF or KrF, for example, or the erosion may be attributed to any of a variety of other erosion mechanisms. According to one aspect of the embodiment, a layer-forming gas is introduced into the chamber 300 and a plasma is subsequently ejected in the chamber 300 to facilitate formation of a protective layer on the electrode. This is shown in Figure 4. In Figure 4, there is a gas inlet 400 that introduces layer forming gas into the chamber 300. The gas inlet 400 is in fluid communication with a valve 410 operated under the control of a control unit 430 to selectively connect the gas inlet 400 to at least one source 420 of layer forming gas. Once the partial pressure of the layer-forming gas in chamber 300 has reached a desired value, the plasma is ejected in chamber 300 by establishing an appropriate voltage difference between electrodes 310, 320. After a predetermined time interval, the voltage difference is removed and the layer forming gas is evacuated, but a protective layer 510 has been formed on the electrodes 310, 320, as shown in Figure 5.

Plasmas can be used to aid the growth of metal oxides, metal nitrides and metal oxynitrides on surfaces. The discharge chamber is essentially a plasma source, so under the right conditions, a protective layer can be grown in situ. For example, a layer-forming gas containing oxygen and/or nitrogen may be introduced into the chamber. The chamber will then operate in a manner similar to the way it is normally operated to function as a laser cavity. The plasma will form a protective layer together with oxygen and/or nitrogen.

If the protective layer is required to be a metal oxide, the layer forming gas may be, for example, an oxygen-containing gas. Examples of oxygen-containing gases include _O2 , _H2O , _{H2O2 , O3} , nitrous oxide ( _NOx ), and air. If the protective layer is required to be nitride, the layer forming gas may be, for example, a nitrogen-containing gas. Examples of nitrogen-containing gases include N ₂ , NH ₃ , nitrous oxide (NO _x ), and air. If the protective layer is required to be a metal oxynitride, the layer forming gas may be, for example, a gas containing or a mixture of nitrogen and oxygen. Examples of such gases include nitrous oxide ( _NOx ), mixtures of the above-mentioned oxygen-containing gases and nitrogen-containing gases, and air. These gases are examples only, and it will be apparent to one of ordinary skill in the art that other gases may be used.

The concentration/pressure of the layer-forming gas used to form the protective layer may suitably be in the range of about 1 part per million to about 38 kPa, or in the range of about 1 part per million to about 4 kPa. Since the total filling pressure of the chamber is about 380 kPa of the laser gas, this corresponds to a concentration of about one part per million to about 1% of the layer-forming gas.

Under these conditions, plasma may be ejected in chamber 300 by applying a voltage difference in the range of about 17 kV to about 28 Kv, as an example, although other voltage differences may be used.

As shown in Figure 5, electrode 500 may be electrode 310 or 320, which will be formed from a host material such as brass, which is an alloy of copper and zinc. A protective layer 510 will form on the exposed surface of electrode 500 due to exposure to the plasma and layer-forming gases. The composition of protective layer 510 will generally depend on the electrode material and layer-forming gas being used. The oxygen-containing gas can be used to form a protective layer 510 composed of a mixture of CuO or ZnO on the brass electrode. The nitrogen-containing gas can be used to form the copper nitride (Cu3N) or zinc nitride (Zn3N2) protective layer 510 of the brass electrode. Nitrogen- and oxygen-containing gases can be used to form the copper oxynitride (C _x O _y N _z ) or zinc oxynitride (Zn _x O _y N _z ) protective layer 510 of the brass electrode. It will be apparent to those of ordinary skill in the art that other combinations may exist. The thickness of the protective layer 510 generally ranges from about nanometers to about 10 microns.

The thickness of protective layer 510 will generally vary with formation rate and formation time. The rate of formation will depend on the chemistry of layer formation and the characteristics of the plasma.

The protective layer formed on top of the electrode surface due to the in-situ layer reduces erosion of the electrode. In various embodiments, the protective layer formed on top of the electrode surface as a result of in-situ layer formation plays an important role in reducing fluorination reactions with the host material of the electrode. The more dense and uniform the protective layer is, the more it can be expected that the erosion rate will be reduced.

6 is a flow chart describing a process for forming a protective layer in situ on an electrode according to one aspect of the embodiment. In step S10, a layer-forming gas is introduced into the chamber containing the electrodes until a desired partial pressure is reached. In step S20, plasma is ejected by applying voltage to the electrode for a predetermined period of time, so that the layer-forming gas can form a protective layer on the electrode surface. In step S30, the plasma is stopped by removing the voltage. In step S40, the layer-forming gas is evacuated from the chamber. Therefore, a protective layer is formed on the electrode.

These steps can be repeated periodically to re-grow layers. Alternatively, the protective layer can be continuously grown by the controlled introduction of a dilute mixture containing oxygen, nitrogen, or both.

One advantage of the process just described is that layer growth is limited to the discharge region of the electrode where the plasma exists, so the spatial control of layer growth is better. Furthermore, the heating of the electrodes is the same as what the electrodes typically experience during normal operation of the chamber, so the electrodes are less likely to deform. The possibility of repeating the growth cycle at any time also contributes to a longer overall electrode life.

The above description includes examples of various embodiments. Of course, it is not possible to describe every conceivable combination of components or methods for the purpose of describing the foregoing embodiments, but one of ordinary skill in the art will recognize that many other combinations and permutations of the various embodiments are possible. The described embodiments are therefore intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the appended claims. Furthermore, to the extent that the term "comprises" is used in the embodiments or claims, in a manner similar to the way the term "includes" is interpreted when "includes" is used as a transition word in a claim, the term is intended to be Including sexual. Furthermore, although elements of the described aspects and/or embodiments may be described or claimed in the singular, the plural is encompassed unless the singular limitation is expressly stated. Additionally, unless otherwise stated, all or part of any aspect and/or embodiment may be utilized in combination with all or part of any other aspect and/or embodiment.

Other aspects of the invention are set forth in the following numbered items. 1. An apparatus, comprising: a laser chamber; an electrode positioned at least partially within the laser chamber; a source of layer-forming gas connectable to the laser chamber; and a voltage supply, Electrically connected to the electrode and configured to supply voltage to the electrode to generate a plasma on a surface of the electrode in the presence of a layer-forming gas to form a protective layer on the electrode. 2. The equipment of item 1, wherein the layer-forming gas contains an oxygen-containing gas. 3. The equipment of item 2, wherein the oxygen-containing gas contains O ₂ . 4. The equipment of item 2, wherein the oxygen-containing gas contains H ₂ O. 5. The equipment of item 2, wherein the oxygen-containing gas contains H ₂ O ₂ . 6. The equipment of item 2, wherein the oxygen-containing gas contains O ₃ . 7. The equipment of item 2, wherein the oxygen-containing gas contains nitrous oxide. 8. The equipment of item 2, wherein the oxygen-containing gas contains air. 9. The device according to any one of clauses 1 to 8, wherein the protective layer includes a metal oxide. 10. The device according to any one of items 2 to 8, wherein the electrode includes brass and the protective layer includes copper oxide CuO. 11. The device according to any one of clauses 2 to 8, wherein the electrode comprises brass and the protective layer comprises zinc oxide ZnO. 12. The equipment of item 1, wherein the layer-forming gas contains a nitrogen-containing gas. 13. The equipment of item 12, wherein the nitrogen-containing gas contains N ₂ . 14. The equipment of item 12, wherein the nitrogen-containing gas contains NH ₃ . 15. The equipment of item 12, wherein the nitrogen-containing gas contains nitrous oxide. 16. The equipment of item 12, wherein the nitrogen-containing gas contains air. 17. The device according to any one of clauses 12 to 16, wherein the protective layer includes a metal nitride. 18. The device of any one of clauses 12 to 16, wherein the electrode comprises brass and the protective layer comprises copper nitride. 19. The device of any one of clauses 12 to 16, wherein the electrode comprises brass and the protective layer comprises zinc nitride. 20. The equipment of item 1, wherein the layer-forming gas contains a nitrogen-containing and oxygen-containing gas. 21. The equipment of item 20, wherein the nitrogen-containing and oxygen-containing gases include nitrous oxide. 22. The equipment of item 20, wherein the nitrogen-containing and oxygen-containing gases include air. 23. The device according to any one of clauses 20 to 22, wherein the protective layer includes a metal oxynitride. 24. The device of any one of clauses 20 to 22, wherein the electrode comprises brass and the protective layer comprises copper oxynitride. 25. Apparatus according to any one of clauses 20 to 22, wherein the electrode comprises brass, and the protective layer comprises zinc oxynitride. 26. A method of forming a protective layer on an electrode in a laser discharge chamber, the method comprising: adding a layer of forming gas to the laser discharge chamber to achieve a predetermined partial pressure; and using the electrode for a predetermined period The amount of time creates a plasma within the laser discharge chamber. 27. The method of clause 26, wherein the layer-forming gas contains an oxygen-containing gas. 28. The method of clause 27, wherein the oxygen-containing gas contains O ₂ . 29. The method of clause 27, wherein the oxygen-containing gas contains H ₂ O. 30. The method of clause 27, wherein the oxygen-containing gas contains H ₂ O ₂ . 31. The method of clause 27, wherein the oxygen-containing gas contains O ₃ . 32. The method of clause 27, wherein the oxygen-containing gas contains nitrous oxide. 33. The method of clause 27, wherein the oxygen-containing gas contains air. 34. The method of any one of clauses 26 to 33, wherein the protective layer includes a metal oxide. 35. The method of any one of clauses 26 to 33, wherein the electrode includes brass and the protective layer includes copper oxide CuO. 36. The method of any one of clauses 26 to 33, wherein the electrode comprises brass and the protective layer comprises zinc oxide ZnO. 37. The method of clause 26, wherein the layer-forming gas contains a nitrogen-containing gas. 38. The method of clause 37, wherein the nitrogen-containing gas contains N ₂ . 39. The method of clause 37, wherein the nitrogen-containing gas comprises NH ₃ 40. The method of clause 37, wherein the nitrogen-containing gas comprises nitrous oxide. 41. The method of clause 37, wherein the nitrogen-containing gas contains air. 42. The method of any one of clauses 37 to 41, wherein the protective layer includes a metal nitride. 43. The method of any one of clauses 37 to 41, wherein the electrode comprises brass and the protective layer comprises copper nitride. 44. The method of any one of clauses 37 to 41, wherein the electrode comprises brass and the protective layer comprises zinc nitride. 45. The method of clause 26, wherein the layer-forming gas contains a nitrogen-containing and oxygen-containing gas. 46. The method of clause 26, wherein the nitrogen-containing and oxygen-containing gas includes nitrous oxide. 47. The method of item 26, wherein the nitrogen-containing and oxygen-containing gases include air. 48. The method of any one of clauses 45 to 47, wherein the protective layer includes a metal oxynitride. 49. The method of any one of clauses 45 to 47, wherein the electrode comprises brass and the protective layer comprises copper oxynitride. 50. The method of any one of clauses 45 to 47, wherein the electrode comprises brass and the protective layer comprises zinc oxynitride.

100:Light lithography system 105:Lighting system 110:Beam 115:Scanner 120:wafer 125:Wafer table 130:Micro shadow controller 135:Control system 140:Seed laser system 145: Magnification stage 150:Relay optics 160: Laser system output subsystem 165:Master oscillator cavity 170: Line narrowing module 175:Master oscillator output coupler 180: Line center analysis module 185:Wavefront engineering box 200:PRA laser cavity 210:PRA WEB 220:Beam commutator 230: Bandwidth analysis module 240: Optical pulse stretcher 250: Output combined automatic sunshade weight and measurement module 300: Chamber 305: Cavity wall 310: Upper electrode 315: Upper insulator 320:Lower electrode 325:Lower insulator 340:Voltage supplier 400:Air inlet 410:Valve 420: Source 430:Control unit 500:Electrode 510:Protective layer A: Gap S10: Steps S20: Steps S30: Steps S40: Steps

The accompanying drawings, which are incorporated in and form a part of this specification, illustrate the methods and systems of embodiments of the invention by way of example and not limitation. The drawings and embodiments together further serve to explain the principles of the methods and systems presented herein and enable those skilled in the relevant art to obtain and use the methods and systems presented herein. In the drawings, the same reference numbers indicate identical or functionally similar elements.

Figure 1 shows a schematic diagram, not to scale, of a general broad concept of a photolithography system in accordance with the disclosed subject matter.

Figure 2 shows a schematic diagram, not to scale, of an overall broad concept of a lighting system in accordance with the disclosed subject matter.

Figure 3 is a diagrammatic cross-section, not to scale, of a discharge cavity of an excimer laser in accordance with aspects of the disclosed subject matter.

Figure 4 is a diagrammatic, not to scale, cross-section of a discharge cavity of an excimer laser in accordance with aspects of the disclosed subject matter.

Figure 5 is a cross-sectional view of an electrode with a protective layer in accordance with aspects of the disclosed subject matter.

6 is a flowchart illustrating a method in accordance with aspects of the disclosed subject matter.

Other features and advantages of the invention, as well as the structure and operation of various embodiments of the invention, are described in detail below with reference to the accompanying drawings. It should be noted that this invention is not limited to the specific embodiments described herein. Such embodiments are presented herein for illustrative purposes only. Additional embodiments will be apparent to those skilled in the relevant art based on the teachings contained herein.

300: Chamber

305: Cavity wall

310: Upper electrode

315: Upper insulator

320:Lower electrode

325:Lower insulator

340:Voltage supplier

Claims (1)

A laser discharge device containing: i. A laser cavity; ii. An electrode positioned at least partially within the laser cavity; iii. A source of layer-forming gas connectable to the laser cavity, wherein the layer-forming gas other than a laser gas is introduced from the source into the laser cavity to achieve a desired A partial pressure is required, and the source is in selective fluid communication with the laser chamber under the control of a control unit; and iv. A voltage supply electrically connected to the electrode and configured to supply voltage to the electrode, The laser cavity is configured to expose the electrode to the layer-forming gas while generating a plasma in the laser cavity to grow a protective layer on the electrode.