Abstract: The present invention is a method and apparatus for cleaning a chemical vapor deposition (CVD) chamber using cleaning gas energized to a plasma in a gas mixing volume separated by an electrode from a reaction volume of the chamber. In one embodiment, a source of RF power is coupled to a lid of the chamber, while a switch is used to couple a showerhead to ground terminals or the source of RF power.

Abstract: A focus ring heat transfer method improves heat transfer of a focus ring arranged in an outer peripheral portion of a mounting surface of a mounting table adapted to mount a target substrate in a chamber. The method includes steps of: disposing a heat transfer sheet between the focus ring and the mounting table; and vacuum-evacuating the chamber prior to processing the target substrate and then restoring the pressure the inside of the chamber to an atmospheric pressure or a light vacuum pressure. Therefore, air present in a fine gap between the heat transfer sheet and the mounting surface is removed to allow the heat transfer sheet to adhere to the mounting surface.

Abstract: A particle removal apparatus for removing particles from a chamber of a plasma processing apparatus, wherein the chamber is connected to a gas exhaust port and a plasma of a processing gas is generated in the chamber to plasma process a substrate to be processed, includes a particle charging control member for positively charging particles generated within the chamber by positive ions of an ion sheath region formed in a region other than the vicinity of the substrate to be processed, wherein positively charged particles are discharged from the chamber via the gas exhaust port. Therefore, there is no plasma disturbance or metal contamination, and thus can be applied to a practical use.

Abstract: A showerhead electrode assembly of a plasma processing apparatus includes a thermal control plate attached to a showerhead electrode, and a top plate attached to the thermal control plate. At least one thermal bridge is provided between opposed surfaces of the thermal control plate and the top plate to allow electrical and thermal conduction between the thermal control plate and top plate. A lubricating material between the thermal bridge and the top plate minimizes galling of opposed metal surfaces due to differential thermal expansion between the top plate and thermal control plate. A heater supported by the thermal control plate cooperates with the temperature controlled top plate to maintain the showerhead electrode at a desired temperature.

Abstract: An optical monitoring system includes a ring-shaped object suspended by and engaged with a plurality of vertical plunger shafts. Normally, the vertical plunger shafts move upward and downward reciprocally and coherently, but independently, such that the ring-shaped object ascends or descends horizontally. A light transceiver device is affixed to one vertical plunger shaft. A plurality optical reflector elements are affixed to respective other plunger shafts. A light beam emanated from said light transceiver is reflected by the optical reflector elements and is eventually re-directed back to the light transceiver device.

Abstract: A gas distribution plate is formed of a metallic body having a bottom surface with plural gas disperser orifices and an internal gas manifold feeding the orifices. Each one of an array of discrete RF power applicators held in the plate includes (a) an insulating cylindrical housing extending through the plate, a portion of the housing extending outside of the plate through the bottom surface, and (b) a conductive solenoidal coil contained within the housing, a portion of the coil lying within the portion of the housing that extends outside of the plate through the bottom surface.

Abstract: In an electrode for generating a plasma, disposed to face a surface of a substrate to perform a plasma processing on the surface of the substrate, the electrode includes a metal-based composite material formed by impregnating a metal into a base member made of a porous ceramic, and having a joint surface at least facing toward the entire surface of the substrate. The electrode also includes a conductive plate made of a plasma-resistant material melt-bonded by a metal to the joint surface of the metal-based composite material.

Abstract: A plasma processing apparatus suitable for high-speed and high-definition etching is provided. By applying to a wafer chucking electrode 9 a voltage waveform in which an absolute value of high frequency voltage increases with time and switching between a positive voltage and a negative voltage occurs, a rectangular high frequency voltage is caused to be generated in the wafer 10, with the result that the duty ratio of the rectangular high frequency voltage decreases and that the high energy ion ratio in the energy distribution of ions incident on the wafer increases. Therefore, high efficiency and high accuracy etching becomes possible, providing the advantage that the material selection ratio is improved.

Abstract: There is provided a plasma processing apparatus which processes a substrate by generating plasma in a process vessel by supply of radio frequency power from a radio frequency power source to at least one of a pair of vertically opposed electrodes disposed in the process vessel, the apparatus including an impedance varying circuit which is connected to at least one of the pair of electrodes and in which an impedance varying part varying impedance on the electrode side of the plasma generated in the process vessel and a resistor are connected in series.

Abstract: A plasma processing apparatus having 90% or more of a side wall of an inner wall 101 of a reaction chamber 1 covered with a dielectric 102, and equipped with an earthed conductive member 21a having an area of less than 10% of the side wall area of the inner wall 101 and having a structure to allow direct current from a plasma to flow therein, wherein the DC earth formed of the conductive member 21 is located at a position where floating potential of plasma (or plasma density) is higher than the floating potential of plasma 9 located near a wafer holding electrode 14 where there is relatively large wall chipping.

Abstract: A plasma etching apparatus includes a processing vessel; a lower electrode on which a target substrate is mounted in the processing vessel; an upper electrode disposed in the processing vessel to face the lower electrode in parallel; a processing gas supply unit configured to supply a processing gas into a processing space between the upper and the lower electrode; a first radio frequency power supply unit configured to apply, to the lower electrode, a first radio frequency power for generating plasma of the processing gas; a focus ring covering a top surface peripheral portion of the lower electrode protruding toward a radial outside of the substrate; a DC power supply configured to output a variable DC voltage; and a DC voltage supply network that connects the DC power supply to either one of the focus ring and the upper electrode or both depending on processing conditions of plasma etching.

Abstract: A plasma processing is performed by using a plasma processing apparatus which includes a first electrode and a second electrode disposed relatively movable to the first electrode between which an object to be processed is disposed, and a solid dielectric material disposed to be continuously connected to at least processing starting and final end sides of the object. A process gas is introduced between the first and second electrodes under a state in which the first electrode abuts on entire surfaces of the object and the solid dielectric material, and a voltage is applied between the first and second electrodes to thereby process the object by plasma discharge generated between the first and second electrodes while moving the second electrode relatively to the first electrode and the object.

Abstract: In a film formation chamber, a gas flow to be introduced is rectified in a direction away from the film formation surface of the substrate on which the film is to be formed, so as to exhaust the fine particles generated in the discharge space and the fragmental particles generated by exfoliation of the film from the wall of the vacuum chamber and the discharge electrode, thereby preventing the particles from adhering the film formation surface of the substrate. The fine particles and fragmental particles are sucked and exhausted from a plurality of apertures provided on the entire surface of the discharge electrode to establish a steady state in which the amount of a film deposited on the discharge electrode and the amount of an exfoliating film to be exhausted are equal to each other, thereby allowing continuous film formation without cleaning the discharge electrode over a long period.

Abstract: In a plasma processing method, on a back side of a cathode electrode is provided at least one conductor plate d.c. potentially insulated from the cathode electrode and an opposing electrode, and the cathode electrode and the conductor plate are enclosed with a shielding wall such that a ratio of an inter-electrode coupling capacitance provided by the cathode electrode and the opposing electrode to a coupling capacitance provided by the cathode electrode and a bottom surface of the shielding wall on the back side of the conductor plate is not less than a predetermined value. Thereby, a high-quality, high-speed plasma processing is realized.

Abstract: A plasma processing apparatus for performing a plasma process on a target substrate includes a process container configured to accommodate the target substrate and to reduce pressure therein. A first electrode is disposed within the process container. A supply system is configured to supply a process gas into the process container. An electric field formation system is configured to form an RF electric field within the process container so as to generate plasma of the process gas. A number of protrusions are discretely disposed on a main surface of the first electrode and protrude toward a space where the plasma is generated.

Abstract: The voltage of a wafer on the pedestal of an RF plasma reactor is instantly determined from the applied bias current and the applied bias voltage sampled during plasma processing of the wafer using a pair constants. Prior to plasma processing of the wafer, a determination is made of first and second constants based upon electrical characteristics of a transmission line through which RF power is coupled to the pedestal. During plasma processing of the wafer, the wafer voltage is determined by performing the steps of sampling an RF input current and an RF input voltage at the impedance match circuit; multiplying the RF input voltage by the first constant to produce a first product; multiplying the RF input current by the second constant to produce a second product; and computing a sum of the first and second products.

Abstract: A plasma processing member includes a ceramic base, a plasma generating electrode embedded in the ceramic base, and an electrode power supply member connected to the plasma generating electrode. The impedance of the plasma processing member when plasma is generated using high frequency power at a frequency higher than 13.56 MHz is adjusted to 25? or less.

Abstract: A plasma-processing apparatus having a high frequency power application electrode in which plasma is generated by supplying VHF power to the high frequency power application electrode. The plasma-processing apparatus has an impedance-matching equipment comprising a capacitive element and an inductive element, which are mutually connected in series. The apparatus is arranged so that the capacitive element and the inductive element of the impedance-matching equipment are symmetrical with respect to the center of the high frequency power application electrode.

Abstract: Positional relationships are established in a process chamber. An upper electrode is configured with a first surface to support a wafer, and an electrode has a second surface. A linear drive is mounted on the base and a linkage connected between the drive and the upper electrode. Linkage adjustment defines a desired orientation between the surfaces. The linear drive and linkage maintain the desired orientation while the assembly moves the upper electrode with the surfaces moving relative to each other. An annular etching region defined between the electrodes enables etching of a wafer edge exclusion region extending along a top and bottom of the wafer. Removable etch defining rings are configured to define unique lengths along each of the top and bottom of the wafer to be etched. Positional relationships of the surfaces enable limiting the etching to those unique lengths of the exclusion region.

Abstract: A flexible polymer or elastomer coated RF return strap to be used in a plasma chamber to protect the RF strap from plasma generated radicals such as fluorine and oxygen radicals, and a method of processing a semiconductor substrate with reduced particle contamination in a plasma processing apparatus. The coated RF strap minimizes particle generation and exhibits lower erosion rates than an uncoated base component. Such a coated member having a flexible coating on a conductive flexible base component provides an RF ground return configured to allow movement of one or more electrodes in an adjustable gap capacitively coupled plasma reactor chamber.

Abstract: Plasma parameters such as plasma ion density, wafer voltage, etch rate and wafer current in the chamber are determined from external measurements on the applied RF bias electrical parameters such as voltage and current. The method includes sensing RF parameters corresponding to an input impedance, an input current and an input voltage at the input of the impedance match element to a transmission line coupled between the bias generator and the wafer pedestal. The method continues by computing a junction admittance of a junction between the transmission line and the electrode within the wafer pedestal from the input impedance, input current and input voltage and from parameters of the transmission line. The method further includes providing shunt electrical quantities of a shunt capacitance between the electrode and a ground plane, and providing load electrical quantities of a load capacitance between the electrode and a wafer on the pedestal.

Abstract: In the plasma processing apparatus of the present invention, a first electrode (21) for connecting a high frequency electric power source (40) in a chamber is arranged to be opposed to a second electrode (5). A substrate (W) to be processed is placed between the electrodes. There is provided a harmonic absorbing member (51) for being able to absorb harmonics of the high frequency electric power source (40) so as to come in contact with a peripheral portion or circumference of a face of the first electrode 21, which is opposite the second electrode (5). The harmonic absorbing member absorbs the reflected harmonic before the harmonic returns to the high frequency electric power source. By absorbing the harmonic in this manner, the standing wave due to the harmonic will be effectively prevented from being generated, and the density of plasma is made even.

Abstract: The present invention provides an arrangement and method for generating a uniform and stable plasma. The arrangement comprises a discharge space (7) between at least a pair of electrodes (1, 2), which electrodes (1, 2) are arranged for providing an electric field and for generating a plasma in the electric field. At least one of the electrodes (1) has a boundary surface (6) with the discharge space (7). The boundary surface is comprised of one or more alternately arranged conductive (4) and insulating regions (5). The invention further relates to an electrode (1) for use in the arrangement described. The invention may, for example, be used in dielectric barrier discharge configurations, or in arrangements for generating plasmas at atmospheric pressures, or for generating plasmas at low temperatures, such as generating atmospheric pressure glow plasmas (APG) for material processing or surface (3) treatment purposes.

Abstract: A CVD apparatus comprising an optical unit detecting the mass of contaminants adhering to an inner surface of a CVD reactor by irradiating an inner surface of the reactor with light having monochromaticity through an optical window provided on an inner wall of the reactor and receiving its reflected light is provided.

Abstract: A system for non-contact cleaning of particulate contamination of surfaces includes one or more sources that create a charge imbalance between a surface and particles that contaminate the surface, and a power supply that creates a pulsed electrical bias on the surface. This imbalance produces an electrostatic force that propels the particles off the surface. The cleaning process can be associated, for example, with microelectronic lithography and manufacturing.

Abstract: An apparatus, which performs a plasma process on a target substrate by using plasma, includes first and second electrodes in a process chamber to oppose each other. An RF field, which turns a process gas into plasma by excitation, is formed between the first and second electrodes. An RF power supply, which supplies RF power, is connected to the first or second electrode through a matching circuit. The matching circuit automatically performs input impedance matching relative to the RF power. A variable impedance setting section is connected to a predetermined member, which is electrically coupled with the plasma, through an interconnection. The impedance setting section sets a backward-direction impedance against an RF component input to the predetermined member from the plasma. A controller supplies a control signal concerning a preset value of the backward-direction impedance to the impedance setting section.

Abstract: A plasma processing system for processing a substrate is disclosed. The plasma processing system includes a process chamber within which a plasma is both ignited and sustained for processing. The plasma processing system further includes an electrode disposed at the lower end of the process chamber. The electrode is configured for generating an electric field inside the process chamber. The plasma processing system also includes a component for controlling an impedance between the electrode and the plasma. The impedance is arranged to affect the electric field to improve processing uniformity across the surface of the substrate.

Abstract: A plasma treatment apparatus for thin-film deposition includes a reactor chamber; a pair of parallel-plate electrodes disposed inside the chamber; and a radio-frequency power supply system used for transmitting radio-frequency power to one of the parallel-plate electrodes via multiple supply points provided on the one of the parallel-electrodes. The radio-frequency power supply system includes a radio-frequency transmission unit which includes an inlet transmission path and multiple branches branched off from the inlet transmission path multiple times. Each branch is connected to the supply point and has a substantially equal characteristic impedance value.

Abstract: A plasma processing apparatus includes a processing container for receiving a substrate to be processed and processing the substrate by a plasma of a processing gas, a substrate mounting table, installed in the processing container, for mounting the substrate thereon, and a gas supplying unit for supplying the processing gas into the processing container. Here, the substrate mounting table includes a mounting table main body formed of an insulator component. Here, an electrode is embedded inside the mounting table main body, a high frequency power supply for supplying a high frequency power is connected to the electrode, and one or more exposed electrodes are installed to be exposed toward the outside of the mounting table main body and electrically connected to the electrode in the mounting table main body.

Abstract: A plasma processing apparatus includes a process container configured to have a vacuum atmosphere therein. An upper electrode is disposed to face a target substrate placed within the process container. An electric feeder includes a first cylindrical conductive member continuously connected to the upper electrode in an annular direction. The electric feeder is configured to supply a first RF output from a first RF power supply to the upper electrode.

Abstract: A plasma generation electrode capable of subjecting predetermined components contained in a fluid to be treated to their respective reaction treatments with plasmas having different intensities optimized on a reaction basis, by passing merely once the fluid to be treated, is provided. In the plasma generation electrode, a unit electrode is composed of a tabular ceramic material serving as a dielectric material and an electrically conductive film disposed in the inside of the ceramic material, a plurality of unit electrodes are layered at a constant spacing, the distance between the electrically conductive films disposed in the unit electrodes adjacent to each other is varied partly or the dielectric constant of the ceramic material constituting the unit electrode is varied partly, and plasmas having different intensities can be generated partly in the spaces.

Abstract: An RF power supplier is provided, that enables multiple-frequency RF power. The system uses N RF signal generators, combines the RF signals, amplify the combined signals, and then separates the amplified signal. The output of the system is then a multiple-frequency RF power. Optionally, the frequencies are switchable, so that one may select which frequencies the system outputs.

Abstract: The present invention is a method and apparatus for cleaning a chemical vapor deposition (CVD) chamber using cleaning gas energized to a plasma in a gas mixing volume separated by an electrode from a reaction volume of the chamber. In one embodiment, a source of RF power is coupled to a lid of the chamber, while a switch is used to couple a showerhead to ground terminals or the source of RF power.

Abstract: A plasma processing apparatus includes a process container configured to have a vacuum atmosphere therein. A first upper electrode is disposed to have a ring shape and to face a target substrate placed within the process container. A second upper electrode is disposed radially inside the first upper electrode and electrically insulated therefrom. A first electric feeder is configured to supply a first RF output from a first RF power supply to the first upper electrode at a first power value. A second electric feeder branches from the first electric feeder and is configured to supply the first RF output from the first RF power supply to the second upper electrode at a second power value smaller than the first power value.

Abstract: A vacuum vessel and at least two electrodes define an internal process space. At least one power supply is connectable with the electrodes. A substrate holder holds a substrate to be treated in the internal process space. At least one of the electrodes has along a first cross section a concave profile and has along a second cross section a convex profile, the first cross section being parallel to the second cross section. Gas is provided to the space through a gas inlet. Power is provided to the electrodes and the substrate is treated.

Abstract: A processing device in which maintenance can be easily carried out and a burden on a worker can be reduced, and a method of maintaining the device are provided. An upper electrode unit 106 structuring a ceiling portion of a processing chamber 102 of an etching device 100 is structured from a lower assembly 128 at a processing chamber 102 side including an upper electrode 130, and an upper assembly 128 at a power supply side including an electro-body 144. A lock mechanism 156 is released, and after the upper assembly 126 is independently raised and removed by a lift mechanism 164, maintenance of the upper assembly 126 and/or the lower assembly 128 is carried out. The lock mechanism 156 is locked, and after the upper and lower assemblies 126, 128 are integrally raised and removed by the lift mechanism 164, maintenance of an interior of the processing chamber 102 is carried out.

Abstract: An electrode assembly for a plasma reaction chamber used in semiconductor substrate processing. The assembly includes an upper electrode, a backing member attachable to an upper surface of the upper electrode, and an outer ring. The outer ring surrounds an outer surface of the backing member and is located above the upper surface of the upper electrode.

Abstract: Static neutralization of a charged object is provided by generating, in an ionizing cell or module, an ion cloud having a mix of positively and negatively charged ions, and reshaping the ion cloud by redistributing the ions into two regions of opposite polarity by using a second voltage. The second voltage creates an electrical field, which is preferably located in the vicinity of the ion cloud. The redistribution of the ions increases the effective range in which available ions may be displaced or directed towards the charged object. The electrical field redistributes ions that form the ion cloud. Ion redistribution within the ion cloud occurs because ions having a polarity corresponding to the polarity of the second voltage are repelled from the electrical field, and ions having a polarity opposite from that of the electrical field are attracted to electrical field.

Abstract: A plasma probe assembly for use in a plasma processing chamber is provided. A semiconductor probe element with a probe surface at a first end of the semiconductor probe element is provided. An electrical connector is electrically connected to the semiconductor probe element. An electrically insulating sleeve surrounds at least part of the probe element. An adjustment device is connected to the semiconductor probe so that the probe surface is coplanar with an interior chamber surface of the plasma processing chamber.

Abstract: In a plasma treating apparatus for carrying out a plasma treatment by setting a plate-shaped work to be an object, an electrode member 46 to abut on a lower surface of the work is constituted by soldering a plate-shaped suction member 45 having a plurality of through holes 45a formed thereon and a cooling plate 44, and a sprayed film 65 obtained by spraying alumina is formed on an upper surface of the suction member 45, and furthermore, an edge of a hole portion 45d in which the through holes 45a are formed is covered with the sprayed film 65. Consequently, it is possible to reduce a consumption of the electrode member due to sputtering to prolong a lifetime, thereby decreasing a component consuming cost and preventing an inner part of the apparatus from being contaminated by a scattered substance.

Abstract: In a plasma processing apparatus for conducting plasma process on a semiconductor wafer 5, a lower electrode 3 provided with an electrode member 46 is disposed in a bottom part 40c of a chamber container 40 which is a main body of a vacuum chamber 2, and an upper electrode 4 provided with a projected face which is projected downward from its lower face inward of its outer edge portion 51a lower than a lower face of the outer edge portion is disposed above the lower electrode 3 so as to move up and down. The upper electrode 4 is moved downward toward the lower electrode 3 to bring the outer edge portion 51a into contact with an annular hermetically sealing face 40d which is formed at an intermediate level HL in a side wall part 40a of the chamber container 40, whereby a hermetically sealed process space 2a is formed between the lower electrode 3 and the upper electrode 4.

Abstract: First and second electrodes at opposite ends and magnets between the electrodes define an enclosure. Inert gas (e.g. argon) molecules pass into the enclosure through an opening near the first electrode and from the enclosure through an opening near the second electrode. A ring near the first electrode, a plate near the second electrode and the magnets are at a reference potential (e.g. ground). The first electrode is biased at a high voltage by a high alternating voltage to produce a high intensity negative electrical field. The second electrode is biased at a low negative voltage by a low alternating voltage to produce a low intensity negative electrical field. Electrons movable in a helical path in the enclosure near the first electrode ionize inert gas molecules. A wafer having a floating potential and an insulating layer is closely spaced from the second electrode.

Abstract: A system comprises a processing chamber for maintaining a hydrogen plasma at low pressure. The processing chamber has a long, wide, thin geometry to favor deposition of thin-film silicon on sheet substrates over the chamber walls. The sheet substrates are moved through between ends. A pair of opposing radio frequency electrodes above and below the workpieces are electrically driven hard to generate a flat, pancaked plasma cloud in the middle spaces of the processing chamber. A collinear series of gas injector jets pointed slightly up on a silane-jet manifold introduce 100% silane gas at high velocity from the side in order to roll the plasma cloud in a coaxial vortex. A second such silane-jet manifold is placed on the opposite side and pointed slightly down to further help roll the plasma and maintain a narrow band of silane concentration.

Abstract: The present invention is a method and apparatus for cleaning a chemical vapor deposition (CVD) chamber using cleaning gas energized to a plasma in a gas mixing volume separated by an electrode from a reaction volume of the chamber. In one embodiment, a source of RF power is coupled to a lid of the chamber, while a switch is used to couple a showerhead to ground terminals or the source of RF power.

Abstract: The present invention is a method and apparatus for cleaning a chemical vapor deposition (CVD) chamber using cleaning gas energized to a plasma in a gas mixing volume separated by an electrode from a reaction volume of the chamber. In one embodiment, a source of RF power is coupled to a lid of the chamber, while a switch is used to couple a showerhead to ground terminals or the source of RF power.

Abstract: An etching apparatus of the present invention comprises a reaction chamber, a lower electrode placed on the bottom surface of the reaction chamber, an upper electrode placed at the ceiling of the reaction chamber to face the lower electrode, and a focus ring placed on the lower electrode and having a cavity for holding a to-be-processed substrate. The lower surface of the upper electrode is provided, at its middle part, with a recess having a smaller inside diameter than the diameter of the to-be-processed substrate. Thus, in the generation of plasma, the amount of further incident radicals can be reduced in a middle part of the to-be-processed substrate. Therefore, a hole or the like located in the middle part of the to-be-processed substrate can be formed to have a desired shape without having a tapered shape.

Abstract: An apparatus for coating surfaces of a workpiece is configured to establish a pressure gradient within internal passageways through the workpiece, so that the coating within the internal passageways exhibits intended characteristics, such as those relating to smoothness or hardness. The coating apparatus may include any or all of a number of cooperative systems, including a plasma generation system, a manipulable workpiece support system, an ionization excitation system configured to increase ionization within or around the workpiece, a biasing system for applying a selected voltage pattern to the workpiece, and a two-chamber system that enables the plasma generation to take place at a first selected pressure and the deposition to occur at a second selected pressure.

Abstract: A dry etching method includes loading a wafer on a lower electrode having at least two cooling paths. Cooling fluids having different temperatures are supplied to each of the cooling paths of the lower electrode so that the multiple cooling paths are at different temperatures from one another. The wafer is etched during cooling.

Abstract: A hybrid coupled plasma type apparatus includes: a chamber having a gas-injecting unit; an electrostatic chuck in the chamber; an insulating plate over the gas-injecting unit; a high frequency generator; an impedance matching circuit connected to the high frequency generator; first and second antennas connected to the impedance matching circuit in parallel, a power of the high frequency generator being supplied to the first and second antennas; an electrode of a plate shape connected to one of the first and second antennas in serial, the power of the high frequency generator being supplied to the electrode; and a power distributor between the high frequency generator and one of the first and second antennas.

Abstract: An apparatus for adjusting an etching area of a semiconductor wafer includes an adjustable shielding plate. The adjustable shielding plate includes a plurality of shielding members. Each of the plurality of shielding members are movable between a first position configured to shield a portion of a semiconductor wafer from an etching gas and a second position configured to expose an unshielded etching portion of the semiconductor wafer to the etching gas.