Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J49/00—Particle spectrometers or separator tubes
  • H01J49/02—Details
  • H01J49/10—Ion sources; Ion guns
  • H01J49/105—Ion sources; Ion guns using high-frequency excitation, e.g. microwave excitation, Inductively Coupled Plasma [ICP]
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J49/00—Particle spectrometers or separator tubes
  • H01J49/0027—Methods for using particle spectrometers
  • H01J49/0031—Step by step routines describing the use of the apparatus
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J49/00—Particle spectrometers or separator tubes
  • H01J49/02—Details
  • H01J49/24—Vacuum systems, e.g. maintaining desired pressures
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J49/00—Particle spectrometers or separator tubes
  • H01J49/26—Mass spectrometers or separator tubes
  • H01J49/34—Dynamic spectrometers
  • H01J49/40—Time-of-flight spectrometers

Definitions

• the present invention relates to a method and apparatus for measurement by glow discharge spectrometry of a solid sample comprising at least one layer of organic or polymeric material.
• GDS Glow Discharge Spectrometry
• a glow discharge spectrometer generally comprises a plasma reactor, also called a discharge lamp, comprising a vacuum chamber.
• a sample to be analyzed is generally arranged to close the vacuum chamber.
• the sample to be analyzed is exposed to an etching plasma that performs surface ablation.
• plasma provides, through various physicochemical mechanisms, the excitation and ionization of eroded species.
• the plasma reactor forms a source of ionized and / or excited species.
• the monitoring of the species present in the plasma thus makes it possible to measure the elementary chemical composition, molecular and possibly the speciation of the chemical form of the detected elements.
• the vacuum chamber of the plasma source is connected via an opening to a mass spectrometer for the detection of ionized species and / or respectively via an optical window to an optical spectrometer for the analysis of excited species .
• Plasma analysis versus ablation time can be used to determine the depth-resolved sample composition when erosion occurs by uniformly digging the sample, ie when the crater ablation has a flat bottom and flanks perpendicular to the bottom.
• the glow discharge spectrometry can thus make it possible to obtain the profile of the chemical composition of thick or thin-layer materials as a function of the erosion depth (from a few tens of nanometers to a few tens of microns thick) with a resolution nanometric in the most favorable cases.
• glow discharge spectrometry now allows the analysis of semiconductor materials and insulators through the use of radio sources - frequency (RF).
• DC direct current
• RF radio sources - frequency
• Glow discharge spectrometers give good results especially for samples on conductive or semiconductor substrates (eg silicon), which allow good coupling of the electric field in the plasma and rapid erosion (typically of the order of one micron per minute).
• conductive or semiconductor substrates eg silicon
• the erosion is generally much slower (the erosion rate is at least 100 times lower than for conductive or semi-conductive layers).
• conductive and the plasma can produce a heating of the sample which can lead to the damage thereof.
• the sides of the erosion crater are in this case generally not perpendicular to the crater bottom, which affects the resolution in depth.
• a Grimm source type plasma reactor is generally used.
• the carrier gas injected into the reactor to form the plasma is generally a pure noble gas.
• Argon is the most common rare gas in glow discharge mass spectrometry for several reasons: argon ions are effective ablation agents and argon plasma energy levels are sufficient to ionize the majority of elements of the periodic table. In addition, argon has a simple spectrum that does not disturb spectrometric measurements.
• rare gases such as argon or argon can also be used to increase the rate of erosion and / or ionization efficiencies.
• Various gas mixtures have also been experimented for various applications of glow discharge spectrometry (with optical detection or mass detection).
• Hartenstein et al. J. Anal., At. Spectrom., 1999, 14, pp. 1039-1048
• the mixture of argon and helium makes it possible to increase the intensity of certain atomic emission lines and it is mentioned that the mixture of helium and argon increases the ionization efficiency during the analysis of glasses.
• Hartenstein et al. The addition of helium to argon does not make it possible to achieve the maximum etching rate obtained with a pure argon plasma, whether for a glass type sample. or metal.
• Oxygen may be present in a glow discharge spectrometer, either as an impurity in the carrier noble gas, or as a by-product of the etching of oxygen-containing materials, or as a component of a gaseous mixture forming the carrier gas.
• the presence of oxygen in a glow discharge spectrometer is generally considered as an impurity generating parasitic lines, which are superimposed on the desired lines of the sample, such as for example the OH lines.
• A. Bogaerts ("Effects of oxygen addition to argon glow discharges: A hybrid Monte Carlo-fluid modeling investigation") concerns a theoretical modeling of the effects of the addition of a molecular hydrogen gas H 2 , nitrogen N 2 or oxygen 0 2 to argon in a glow discharge spectrometry apparatus with DC source (dc-GDS). According to this publication, the addition of 0.05 to 5% oxygen produces a decrease in the density of Arm * type metastable excited species and a reduction in the density of eroded atoms, even at low oxygen concentrations.
• the reduction of the etching rate in the presence of gaseous oxygen is attributed to the formation of an oxide layer on the cathode of the glow discharge spectrometer, which is also accompanied by a reduction in the intensity of the emission lines.
• the analysis of organic samples by glow discharge spectrometry poses various problems.
• the erosion rate is several microns / minute for samples of the metal type while it is generally less than 20 nm / minute for samples or organic layers. This low rate of erosion makes it very difficult to analyze samples or thick organic films.
• the poor uniformity of etching obtained on organic samples does not allow a deep resolution to analyze surfaces or thin layers buried under a layer of thick organic material (several microns to several tens of microns thick). .
• the patent document FR2965355 describes a method of measurement by glow discharge spectrometry adapted for an organic solid sample or polymer.
• a radio-frequency type glow discharge is applied to a gaseous mixture comprising at least one rare gas and gaseous oxygen, the concentration of gaseous oxygen being between 1% and 10% by weight of the gaseous mixture and measuring by means of an optical spectrometer at least one signal representative of an excited species of said plasma and / or respectively, by means of a mass spectrometer at least one signal representative of an ionized species.
• One of the aims of the invention is to propose a method and an apparatus for the analysis of organic or polymeric solid samples (or containing polymer or organic layers) by glow discharge spectrometry allowing both to etch a sample having a thickness ranging from a few nanometers to about a hundred microns, with excellent etching uniformity, while increasing the signal-to-noise ratio of the detected signals.
• Another object of the invention is to improve the quality of measurements by glow discharge spectrometry to allow a more precise analysis of the elemental and / or molecular chemical composition of a solid sample comprising at least one layer of polymer or organic material .
• the present invention aims to overcome the drawbacks of the prior art and more particularly relates to a measurement method by glow discharge spectrometry of the elemental and / or molecular chemical composition of a solid sample comprising at least one polymer or organic layer.
• the method comprises the following steps: the sample is disposed so as to close a vacuum chamber of a plasma reactor, the plasma reactor forming an ion source for a mass spectrometer, the sample forming one of the electrodes of the glow discharge plasma reactor ,
• a gaseous mixture comprising at least one rare gas and gaseous oxygen is injected into the vacuum chamber, the concentration of gaseous oxygen being between 0.1% and 15% by weight of the gaseous mixture, and the electrodes of the reactor are applied to an electrical discharge adapted to generate a glow discharge plasma so as to expose the solid sample to said plasma;
• At least one signal representative of an ionized species of negative charge is selected and measured by means of the mass spectrometer.
• the method makes it possible to etch a sample, for example a polymer or an organic sample, with a high etching rate, typically between 100 nanometers / minute and 1 micron / minute, with a flat-bottomed etching crater.
• This method makes it possible, on the one hand, to detect and measure different ionized species than usually measured positive charge ionized species or excited species measured by optical emission spectrometry.
• the method makes it possible to measure signals having a signal intensity and / or a signal-to-noise ratio that are much greater than the signals representative of positively charged ionised species or optical emission signals, under the same plasma and for the same sample.
• the rare gas mixture gas is selected from argon, neon, krypton, helium or a mixture of said noble gases.
• the solid sample comprises a stack of organic or polymeric layers.
• the mass spectrometer being of the time-of-flight spectrometer type, at least one signal representative of an ionized species of negative charge is measured as a function of the respective flight time of said ionized species.
• the sample to be measured comprises a stack of layers and the oxygen concentration of the gaseous mixture is modified during exposure to the glow discharge plasma as a function of the layer of the stack exposed to said plasma.
• a pulsed radio-frequency or radio-frequency electric discharge is applied.
• said method comprises the simultaneous application of a radio-frequency electric field or pulsed radio frequency and an axial or transverse magnetic field with respect to an axis of the glow discharge plasma reactor.
• said method further comprises a calibration step according to which: placing a reference sample having a known composition in the vacuum chamber of the glow discharge plasma reactor, the reference sample forming one of the electrodes of the plasma reactor;
• a gaseous mixture comprising at least one rare gas and gaseous oxygen is injected into the vacuum chamber, the concentration of gaseous oxygen being between 0.1% and 15% by weight of the gaseous mixture, the electrodes of the reactor are applied to plasma, an electrical discharge adapted to generate a glow discharge plasma, so as to expose said reference sample to said plasma;
• At least one signal representative of an ionised species of negative charge of said plasma is measured by mass spectrometry
• the measurement is calibrated by mass spectrometry of said ionized negative charge species relative to the known composition of said reference sample.
• the method comprises another step in which another signal representative of another ionised species of positive charge is selected and measured by means of another mass spectrometer.
• the invention also relates to a glow discharge spectrometry apparatus for the analysis of a solid sample, preferably comprising at least one organic or polymeric layer, said spectrometric apparatus comprising a glow discharge plasma reactor comprising a vacuum chamber connected to a fluidic plasma gas injection circuit, the glow discharge plasma reactor having an electrical circuit adapted to apply an electrical discharge, preferably radio frequency or pulsed radio frequency, between the solid sample to be analyzed and a electrode in the presence of said plasma gas so as to generate a glow discharge plasma, a mass spectrometer connected to the vacuum chamber of the glow discharge plasma reactor so as to extract ionized species from said glow discharge plasma, the spectrometer mass comprising a mass analyzer adapted for analysis r said ionized species and a detector adapted to detect said ionized species analyzed.
• a glow discharge plasma reactor comprising a vacuum chamber connected to a fluidic plasma gas injection circuit, the glow discharge plasma reactor having an electrical circuit adapted to apply an electrical discharge, preferably radio frequency or pulsed radio frequency, between the solid
• the fluidic gas injection circuit is adapted to inject into the vacuum chamber of the glow discharge plasma reactor a gaseous mixture comprising oxygen gas and at least one rare gas, the oxygen concentration. gaseous being between 0.1% and 15% by weight of the gaseous mixture, so as to expose the solid sample to the glow discharge plasma formed by glow discharge of said oxygenated gas mixture, and the mass spectrometer is arranged and adapted to detect and measure at the least one signal representative of an ionized species of negative charge.
• the electrical circuit is adapted to apply a pulsed radio frequency or radio-frequency electric discharge.
• the mass spectrometer comprises a time-of-flight mass analyzer.
• the glow discharge spectrometry apparatus further comprises another mass spectrometer connected to the vacuum chamber of the glow discharge plasma reactor so as to extract other ionized species from said discharge plasma. wherein said other mass spectrometer is arranged and adapted to detect and measure at least one other signal representative of another ionized species of positive charge.
• the glow discharge spectrometry apparatus makes it possible to simultaneously measure negatively charged ions and other positively charged ions.
• the invention advantageously makes it possible to analyze the elementary chemical composition of materials or stacks of thin or thick layers, this analysis being resolvable in depth.
• the invention will find a particularly advantageous application in the analysis of polymeric or organic solid materials of small thickness and / or thin layer and / or thick layer, up to several tens of microns thick in a limited time to a few minutes or a few tens of minutes.
• the invention makes it possible to analyze stacks of different polymer materials and to differentiate these materials as a function of the engraving depth.
• the method and system of the invention make it possible to analyze buried interface layers under an upper layer several tens of microns thick.
• the present invention also relates to the features which will emerge in the course of the description which follows and which will have to be considered individually or in all their technically possible combinations.
• FIG. 1 shows schematically a glow discharge spectrometry apparatus equipped with a gas mixing system
• FIG. 2 shows schematically in exploded view a multilayer sample
• FIG. 3 schematically represents a sectional view of a glow discharge plasma reactor coupled to a mass spectrometer
• FIG. 4 schematically represents a glow discharge spectrometry apparatus coupled to a time-of-flight mass spectrometer
• FIG. 5 schematically represents an exploded view of a multilayer sample
• FIG. 6 illustrates an example of a time-of-flight mass spectrometer measurement of an organic sample, the mass spectrometer being configured in negative mode;
• FIG. 7 illustrates an example of a time-of-flight mass spectrometer measurement of an organic sample similar to that of FIG. 5, the mass spectrometer being configured in a positive mode.
• FIG. 1 diagrammatically shows a glow discharge spectrometry apparatus 1 equipped with a plasma discharge carrier gas supply system.
• the glow discharge spectrometry apparatus 1 comprises a plasma reactor 2, generally of Grimm lamp type, in the form of a tube, within which the plasma is confined.
• the gas pumping system is not shown in the diagram of Figure 1.
• a solid sample is exposed to the glow discharge plasma.
• the sample 10 forms one of the electrodes of the plasma reactor 2.
• the glow discharge spectrometry apparatus 1 comprises a spectrometer 4, which is here a mass spectrometer (MS), for the analysis of the species ionized plasma.
• MS mass spectrometer
• a mass spectrometer measures elements and compounds according to their mass-to-charge ratio m / z. Compared to optical spectrometry, which is simpler, mass spectrometry generally allows for better sensitivity.
• the mass spectrometer is for example of the type of time-of-flight mass spectrometer (TOF-MS for Time Of Flight Mass Spectrometer).
• TOF-MS Time Of Flight Mass Spectrometer
• a time-of-flight mass spectrometer can record an entire mass spectrum in a nearly continuous manner (a complete spectrum every 30 microseconds), which allows continuous monitoring of all the species according to the etching depth in the sample.
• the measurement dynamics of the detector makes it possible to measure both the elements and components forming the matrix of the sample, the majority elements, but also elements present in the state of traces.
• mass spectrometry makes it possible to analyze the presence of isotopic markers used, for example, to detect the presence and diffusion of certain species in a material, for example for the study of corrosion.
• a carrier gas supply line 5 connects one or more gas sources to the vacuum chamber of the reactor 2.
• the gas supply line 5 is divided into two lines. 5a and 5b respectively connected to a first gas source 6 and a second gas source 7.
• the first gas source 6 is for example a bottle comprising a mixture of argon and oxygen (for example at 4% by weight). in gaseous oxygen).
• the second gas source 7 is a bottle of pure argon.
• a first flowmeter 8a makes it possible to adjust the flow of gas on the line 5a from the first gas source 6 and directed towards the gas supply line 5 of the plasma reactor 2.
• a second flowmeter 8b makes it possible to adjust the gas flow on the line 5b from the second gas source 7 and directed to the gas supply line 5 of the plasma reactor 2.
• a controller 9 adjusts the controls of the flow meters 8a and 8b so as to obtain the desired concentration of the gaseous mixture injected via line 5 into the vacuum chamber of the plasma reactor.
• the addition of oxygen gas to the plasma gas has positive effects (see patent document FR2965355).
• gaseous oxygen to a neutral plasma gas makes it possible to produce at the same time rapid erosion of organic or polymeric materials and a flat-bottom erosion crater in these materials.
• the proportion of gaseous oxygen in the gaseous mixture is preferably between 0.1% and 15% by weight of the gaseous mixture. This proportion is sufficient to obtain a sharp increase in the etching rate of a layer of organic or polymeric material.
• the etching rate of a polymer or organic sample is generally between about 100 nanometers / minute and 1 micron / minute.
• Argon or another rare gas, however, remains the predominant gaseous species in this gaseous mixture.
• the preferred mode and the most used corresponds to the detection and measurement of ionized species of positive charge. Indeed, it is known that argon essentially generates positively charged ions.
• gaseous mixture comprising a strong majority of argon (from 85% to 99.9% by mass, and preferably between 90% and 99% of the mass volume), it is expected that the gaseous mixture also produces a majority of positively charged ions.
• FIG. 2 schematically represents an exploded view of an exemplary sample 10 that it is desired to analyze by glow discharge mass spectrometry.
• the sample 10 comprises a substrate 11, an intermediate layer 12, for example an adhesion layer, a protective layer of the substrate, or interdiffusion elements between the substrate and the other layers.
• the sample 10 may comprise a complex structure, for example a stack of layers 13, 14, 15.
• FIG. 3 schematically represents a sectional view of a glow discharge plasma reactor 2 coupled to a mass spectrometer, according to one embodiment of the invention.
• the glow discharge plasma reactor comprises a vacuum vessel 22.
• a vacuum pump system 25 is connected to the vacuum vessel 22.
• a gas supply line 5 is connected to the enclosure vacuum 22, to allow admission of the gaseous mixture comprising a mixture of gaseous oxygen and neutral gas.
• a tubular electrode 23 is placed inside the plasma reactor. The tubular electrode 23 is for example connected to ground.
• the sample 10 to be analyzed is placed against another electrode 3 connected to a power source.
• a pulsed RF electric source is used which makes it possible to minimize the thermal stresses induced in the sample 10, in particular for fragile materials.
• the vacuum chamber 22 of the glow discharge plasma reactor 2 is coupled to a mass spectrometer 4 which detects ionized species extracted from the plasma.
• the use of a pulsed RF source offers particular advantages because the ionization mechanisms of the species present in the plasma vary during the period of the RF source.
• An electric power supplied by an RF generator is applied to the electrode 3 so as to produce an electrical pulse for a limited time. Measurements are made by mass spectrometry just before the start of the electrical pulse, during the electrical pulse and after stopping this electrical pulse.
• the mass spectrometry signal can be analyzed on different so-called prepeak (prepeak), plateau and post-pulse (afterglow) time zones respectively.
• prepeak prepeak
• plateau plateau
• post-pulse (afterglow) time zones respectively.
• the use of mass spectrometry signals over these three time zones offers original and rich analytical combinations of information not only for fragile materials but for all types of thin film materials and stacks.
• the afterglow time domain is precisely the area of interest for material analysis, especially for polymeric or organic materials.
• glow discharge mass spectrometry positively charged ionized species are conventionally measured.
• the rare gas for example argon
• the rare gas mainly generates ionized species of positive charge.
• this method does not make it possible to increase the ionization efficiencies of the positively charged ionized species and therefore does not make it possible to improve the signal-to-noise ratio of the signals detected by mass spectrometry.
• One aspect of the present invention is based on the selection of negative charge ions and the detection of a mass spectral signal of these negative ions in combination with plasma exposure in the presence of a gaseous mixture of oxygen. and rare gas.
• the mass spectrometer 4 is configured in negative mode, so as to extract only negative charge ions from the glow discharge plasma formed in the presence of a mixture of rare gas and oxygen.
• the ionization mechanisms depend on the chemical species and the electrical charge of the ionized species. It is surprisingly observed that, unlike the signals relating to the positively charged ionized species, the mass spectrometry signals relating to the negatively charged ionized species have a high intensity even in pulsed mode in the time zone after the end of the draw ( afterglow in English), when the gaseous mixture comprises oxygen, in particular when analyzing samples comprising an organic or polymeric layer.
• a mass spectrometer makes it possible to measure ionized species, either of negative charge or of positive charge. It is not practically possible to simultaneously measure these two types of species in the same spectrometer.
• the electrodes of a mass spectrometer must be gradually connected to an electrical potential of several hundred to a few thousand volts.
• the polarization change of the electrodes of a mass spectrometer must therefore be carried out progressively.
• a too fast reversal of the polarities of a mass spectrometer can in some cases damage the mass spectrometer. It is therefore not possible to quickly reverse the polarity of the electrodes of a mass spectrometer for the detection of negative ionized species.
• the mass spectrometer is configured for the detection of negative ionized species before starting the glow discharge plasma.
• FIG. 4 schematically represents a glow discharge spectrometry apparatus coupled to a polarized time-of-flight mass spectrometer 4 for detecting and measuring the negatively charged ionized species.
• the glow discharge spectrometry apparatus comprises a glow discharge plasma reactor 2 comprising a vacuum chamber connected to a gas supply line 5.
• a bottle 6 comprising a mixture of oxygen and rare gas, for example argon with 4% by mass oxygen, and another bottle 7 comprising rare gas (argon) are connected to the gas supply line 5.
• the sample 10 is placed in the plasma reactor in contact with a counter -electrode 3.
• a pulsed RF power source 33 is electrically connected to the counter-electrode 3.
• the average applied power is generally between a few watts to a hundred watts, the pressure of the gas mixture is a few torr.
• the time-of-flight mass spectrometer 4 is connected to the vacuum chamber of the plasma reactor so as to extract ionized species of negative charge from the glow discharge plasma and to analyze them on the one hand as a function of their mass ratio on charge and secondly as a function of time.
• the time-of-flight mass spectrometer 4 illustrated in FIG. 4 comprises a valve 40, a skimmer 41, an ion optics system 42, 43, an orthogonal mass spectrometer (48) with its electronics (blower 44). and ion mirror 45), and a detector 46 which typically detects a mass spectrum, for example about every 30 microseconds.
• the time-of-flight mass spectrometer 4 is equipped with a three-stage turbo-molecular pump system 50, 51, 52.
• the time-of-flight mass spectrometer 4 is configured and adapted to extract only negative charge ionized species from the glow discharge plasma formed in the plasma reactor 2, in the presence of a gas mixture of oxygen and rare gas.
• the time-of-flight mass spectrometer 4 makes it possible to analyze the ionized species of negative charge as a function of their mass-to-charge ratio m / z.
• Figure 5 is a schematic perspective view of an exemplary sample 10 that is analyzed by glow discharge mass spectrometry.
• the sample 10 comprises a stack consisting of a substrate 13 of polyethylene, a layer 14 of polyvinylidenechloride approximately 2 microns thick, and a layer 15 of nylon about 10 microns thick.
• FIG. 7 illustrates an example of a pulsed RF time-of-flight mass spectrometer measurement of an organic sample, the time-of-flight mass spectrometer 4 being configured in positive mode and the plasma being carried out in a mixture of oxygen and rare gas, with a proportion of 5% oxygen by volume of the mixture.
• FIG. 7 represents, as a function of the depth of etching D in the sample, the intensity I (in ion intensities) of the signals relating to different ionized species associated respectively with different mass-to-charge ratios m / z.
• Other known methods of analysis make it possible to identify the ionized species detected as a function of their mass-to-charge ratio. More particularly, in FIG. 7, different signals associated respectively with the presence of the following ionized species have been identified: hydrogen nitride (NH 3 + ), sodium (Na + ), and chlorine oxide (CIO + ion).
• the etching depth D in the sample is calibrated by calibration methods known elsewhere. On an axis parallel to the abscissa axis, the layers 13, 14, 15 corresponding to the engraving depth D in the sample are represented.
• the intensity scale of the time-of-flight mass spectrometry signals relative to the positively charged ionized species remains limited to a measurement dynamic of between approximately 10 ⁇ 4 and 1.
• the signals representative of the hydrogen nitride ion (NH 3 + ) and the sodium ion (Na + ) each reach a plateau.
• the mass spectrometry signals relating to the chlorinated ionized species (CIO + ion) are very weak, and almost undetectable because of the same order of magnitude as the signal noise.
• FIG. 6 illustrates an example of a time-of-flight mass spectrometer measurement of an organic sample similar to that of FIG. 5, the mass spectrometer being configured in a negative mode, always in the presence of a gaseous oxygen mixture and rare gas.
• the intensity scale of the time-of-flight mass spectrometry signals relative to the negatively charged ionized species ranges from about 10 ° to about 10 5 .
• the time-of-flight mass spectrometer can detect abundantly ionized species such as C10 " , CI “ , CN “ , CNO " and C 2 H " combined with a gaseous mixture of oxygen.
• the intensity of the signals measured in the negative mode is much higher than that of the signals measured in the positive mode, and the changes in the layers are clearly observed, for an etching depth D of between 0 and approximately 8 microns.
• the nylon layer 15 has essentially representative signals of the nitride ions CN “ and CNO " which are non-halogenated ionized species, whereas during the etching of the chlorinated polyvinyldene layer 14, r an etching depth D between about 8 and 12 microns, there is a sharp increase in signals representative of chlorine ions C10 " and CI " . Finally, during the etching of the polyethylene layer 13, for an etching depth D of between approximately 12 and 25 microns, an increase in the signal representative of the C 2 H " ion is observed and a relative decrease in the signals representative of chlorine ions IOC "and IC" and nitride ions CN “and NOC".
• the signal to noise ratio measurements by spectrometry glow discharge mass is significantly increased in the negative mode as compared to the positive mode.
• This increase in the intensity of Signals measured by mass spectrometry are particularly interesting in the application to a sample comprising at least one layer of organic or polymeric material.
• Measurement by mass spectrometry of negatively charged ionized species makes it possible to analyze different ionized species of positively charged ionized species obtained under the same plasma conditions and with the same sample. It appears that the presence of oxygen in the plasma gas makes it possible to increase the production of ionised species of negative charge in the glow discharge plasma and thus to greatly increase the intensity of the mass spectrometry measurement signals. ionized species of negative charge. Thus, mass spectrometry measurements of ionized species of negative charge are detected which have a signal-to-noise ratio much better than in positive mode.
• the negative mode mass spectrometry combines the advantages of high etching rate, etching with an erosion crater. flat bottom and can be deep (several tens of microns) and obtaining mass spectrometry measurements that have a high intensity, and a significant signal-to-noise ratio, especially in the region of the afterglow of a glow discharge of RF mode pulsed.
• These negative-mode mass spectrometry measurements in the presence of a glow discharge in a mixture of rare gas and oxygen, provide signals of greater intensity than the intensity of positive mass spectrometry signals, including including and surprisingly for the detection of non halogenated ionized species and most particularly for the detection of non halogenated ionized species, such as metal species or organic species (i.e. composed essentially of carbon elements, hydrogen, oxygen and / or nitrogen).
• non halogenated ionized species such as metal species or organic species (i.e. composed essentially of carbon elements, hydrogen, oxygen and / or nitrogen).
• the apparatus and method of the invention are particularly applicable to the analysis of a stack of different polymer layers.
• the apparatus and method of the invention also apply to the analysis of hybrid samples comprising a polymer layer deposited on a metal substrate, or a polymer layer deposited on a glass substrate, or a metal layer deposited on a polymer substrate.

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