DE102020209482A1 - Method for calibration, device for supplying a calibration gas to a vacuum, calibration substance, system for forming a vacuum environment and projection exposure system - Google Patents

Abstract

The invention relates to a method for calibrating a residual gas analysis method for determining a residual gas in a vacuum in a working chamber (3). A composition of a residual gas is characterized by a residual gas spectrum using the residual gas analysis method. According to the invention, the vacuum in the working chamber (3) is supplied with a calibration gas (4) which has a molecular mass occurrence which at least approximately includes an expected molecular mass occurrence of the residual gas, and from the calibration gas supplied to the working chamber (3). (4) a calibration residual gas spectrum (15) is determined.

Description

The invention relates to a method for calibrating a residual gas analysis method for a vacuum in a working chamber, according to which a composition of a residual gas is characterized by a residual gas spectrum using the residual gas analysis method.

The invention also relates to a device for supplying a calibration gas according to the preamble of claim 20.

The invention also relates to a calibration substance according to claim 35.

The invention also relates to a system for forming a vacuum environment according to the preamble of claim 35.

The invention also relates to a projection exposure system according to claim 38.

It is known from the general state of the art that operating different types of systems and carrying out different types of processes in a vacuum can be advantageous. When the vacuum is formed in a working chamber, gas, for example atmospheric air, is removed from the working chamber by means of vacuum devices, as a result of which a vacuum is formed. The absence of gaseous substances in the working chamber prevents, for example, a reaction of the gaseous substances with the materials processed in the working chamber as part of the method.

Optical devices are designed in such a way that they shape and guide light, for example, by means of optical elements. If the light is used to form an optical image, the quality of the optical image can be improved by the optical device being in a vacuum. This is due to the fact that the presence of gases in a region of the optical device degrades the quality of the optical image in that the gases tend to have density fluctuations, which in turn lead to fluctuations in a local refractive index. Fluctuations in a refractive index in turn lead to locally different refraction of the light guided and shaped in the optical device. This can degrade the fidelity of the image. Furthermore, light, in particular EUV (Extreme Ultra Violet) light, can be absorbed by gases. This can also degrade the fidelity of the image.

Projection exposure systems known from the prior art represent optical devices within the meaning of the invention. Projection exposure systems form an optical image of a reticle object in an imaging plane by means of light, in particular DUV (Deep Ultra Violet) light, particularly EUV (Extreme Ultra Violet). ) light, off. Intensity differences in the imaging plane cause a local change in a material located in the imaging plane. In particular, curing of a lacquer can be brought about by a light intensity in the imaging plane.

The presence of a vacuum in a region of the optical device means that dust particles or dirt particles floating in a gas can be reliably removed from the working chamber by a pump device due to buoyancy. Furthermore, due to the removal of the gas present in the working chamber and the resulting loss of buoyancy force, the dust or dirt particles remain on the ground and are thus prevented from settling on optical elements. This is particularly advantageous because dirt and/or dust particles that are on an optical element lead to a deterioration in the quality of the optical image. When using high-energy DUV light and/or high-energy EUV light, the presence of an absorbing dirt particle on an optical element can also lead to a strong local temperature increase, which can go as far as damaging the optical element.

A vacuum also prevents the presence of air, on which in particular EUV light can be absorbed. Absorption of the EUV light in the air can, for example, lead to a deterioration in the quality of the optical imaging by the optical system.

Accordingly, a projection exposure system benefits in particular from operation in a vacuum, since both increased imaging quality and a lower tendency to react with gaseous substances and a lower probability of contamination can be achieved. Operating projection exposure systems in a vacuum is known from the prior art.

Components of a projection exposure system, in particular optical elements and/or mirrors, in particular lenses, have at least some substances, for example adhesives and/or processing aids from previous processing, which can tend to outgas in a vacuum. This includes outgassing a desorption of molecules from an outgassable substance into a gas phase. Together with molecules of the atmospheric air, which have not yet been removed from the working chamber by the pumping devices, these molecules form a so-called residual gas.

Outgassing of the substances capable of outgassing also leads to the presence of molecular species, which in turn can lead to contamination and/or impairment of the vacuum and thus of the optical imaging quality.

An analysis of the residual gas or a residual gas analysis can provide information about the composition of the residual gas and in particular information about the outgassing behavior of the outgassable substances of the projection exposure system.

In this way, for example, an aging behavior and/or a production error and/or a degree of contamination of the projection exposure system can be determined. In particular, EUV projection exposure systems should be regularly characterized in terms of molecular cleanliness during a construction phase and after assembly has been completed.

From the DE 10 2019 203 412 A1 a method for automated process control in machining processes is known. In this case, for a large number of machining processes, a number of process data and at least one characterization parameter of the machining result are recorded for one machining process in each case. The data is used to train a machine learning algorithm.

In order to clean the working chamber and/or the projection exposure system, it is known from the prior art to carry out a thermal desorption process. In this case, a residual gas analysis serves to check the quality of the cleaning.

As a method for analyzing the residual gas or as a residual gas analysis method, mass spectrometry is known from the prior art in order to determine the mass-resolved residual outgassing after a defined time. Here, the molecular components of the residual gas are plotted in a mass spectrum according to their molecular masses and the frequency of their occurrence in the residual gas. An intensity of a spectral value indicates the relative occurrence of a molecular species of a specific mass in an overall ensemble of the residual gas.

Methods for mass determination, such as quadrupole residual gas analysis, are known from the prior art, in which essentially a ratio between the molecular mass of a molecule and its charge is determined after ionization. In rare cases, this can lead to so-called double ionization, which changes the relationship between the molecular mass of a molecule and its charge compared to single ionization. If the molecular mass is determined from the ratio between the molecular mass of a molecule and its charge, a single ionization is usually assumed, but in the case of a double ionization, an incorrectly determined mass results.

Since such incorrectly determined masses are an exception, the general case of single ionization and thus correct mass determination is assumed below. For easier understanding, the molecular mass of a molecule is discussed below and not the relationship between the molecular mass of a molecule and its charge. Within the scope of the invention, double ionizations or multiple ionizations are to be treated as single ionizations, in particular insofar as a large part of the molecules examined has the same degree of ionization.

However, the disclosure of the invention should also be understood as applying to a determination of a relationship between the molecular mass of a molecule and its charge.

By comparing the relative intensities of the individual components of the residual gas, a kind of footprint of the residual gas can be created and characterized. A change in the mass spectrum can indicate a change in the outgassing behavior of the outgassable substances of the projection exposure system and thus, for example, the failure of an individual component. Thus, a comparability of the outgassing rate determination by different residual gas analysis systems is crucial for ensuring the cleanliness of EUV components and thus the service life of the entire EUV optics.

However, different mass spectrometric analysis methods are differently sensitive to molecules of different masses. This is disadvantageous if, for example, a footprint of a residual gas is to be compared with a footprint of a residual gas that has been characterized using a different analysis method.

In order to enable a comparison, the respective residual gas analysis methods must be calibrated.

The comparability between systems of different sizes, geometries, self-degassing and/or suction power is a major challenge.

It is known from the prior art that a residual gas analysis method can be calibrated by supplying gases to the working chamber through a membrane or capillary which have a defined composition of different types of molecules of different types of molecular masses. The relative intensities that the residual gas analysis method gives for the residual gas can then be compared to the actual relative proportions of the respective species of the respective molecular mass. Correction factors for the respective molecular masses can then be introduced to bring the intensities determined by the analysis method into agreement with the actual relative abundances of the individual species. A reproducible ratio of the outgassing of dedicated mass ranges in the mass spectrum is of particular importance here.

It is also known that instead of a gas, solid substances can also be introduced into the vacuum, which have a defined desorption behavior of molecules in the gas phase. However, the desorption behavior of the substances introduced into the vacuum known from practice is subject to a dynamic change over time, which is why the result of a calibration depends on the dwell time of the solid substance in the working chamber.

A disadvantage of the prior art is that the known methods for calibrating the residual gas analysis methods do not cover the entire relevant range of molecular masses and/or do not allow reproducible calibration.

The object of the present invention is to provide a method for calibrating a residual gas analysis method which avoids the disadvantage of the prior art and in particular enables a reproducible calibration.

According to the invention, this object is achieved by a method having the features specified in claim 1.

The invention is also based on the object of providing a device for supplying a calibration gas which avoids the disadvantages of the prior art, in particular enabling a reproducible supply of a calibration gas of defined composition to a vacuum.

According to the invention, this object is achieved by a device having the features specified in claim 20.

The invention is also based on the object of making available a suitable calibration gas for a device for supplying a calibration gas to a vacuum.

According to the invention, this object is achieved by a calibration substance according to claim 35.

The invention is also based on the object of creating a system for forming a vacuum environment which avoids the disadvantages of the prior art, in particular enabling a reliable and comparable analysis of a residual gas in the working chamber.

According to the invention, this object is achieved by a system having the features specified in claim 36.

The invention is also based on the object of creating a projection exposure system which avoids the disadvantages of the prior art and, in particular, enables reliable operation.

According to the invention, this object is achieved by a projection exposure system having the features specified in claim 38.

The method according to the invention relates to a calibration of a residual gas analysis method for determining a residual gas in a vacuum in a working chamber, through which a composition of a residual gas is characterized by a residual gas spectrum using the residual gas analysis method. According to the invention, it is provided that a calibration gas is supplied to the vacuum in the working chamber, which calibration gas has a molecular mass occurrence that at least approximately includes at least an expected molecular mass occurrence of the residual gas. Furthermore, a residual calibration gas spectrum is determined from the calibration gas supplied to the working chamber.

A specific molecular mass occurrence of the residual gas is to be expected for the residual gas. What mass occurrence of the residual gas is to be expected can be known, for example, from empirical values or can be derived from the materials used.

The various molecular masses occurring in the calibration gas which is supplied to the vacuum, ie the molecular mass occurrence of the calibration gas, and preferably also the types of molecules occurring in the calibration gas are at least partially known. The relative frequency with which molecules of a certain mass occur in the calibration gas, and thus the mass frequency, does not necessarily have to be known. However, the mass frequency is at least reproducible, but preferably known. Thus, the molecular composition of the calibration gas from individual molecules is at least reproducible, but preferably known.

In a residual gas spectrum, mass abundance is the independent variable plotted on an abscissa axis, while mass abundance is a dependent variable plotted on an ordinate axis.

Within the scope of the invention, the mass frequency of the calibration gas can deviate significantly from an expected and/or actual mass frequency of the residual gas. It is sufficient if a mass frequency of the calibration gas is sufficiently high in the range of the expected mass occurrence of the residual gas in order to be able to determine the calibration residual gas spectrum with sufficient statistical certainty, preferably with less than 10 percent statistical error.

However, the calibration gas is preferably also adapted at least approximately to the expected mass frequency of the residual gas with regard to the actual mass frequency.

Of course, the calibration gas can also have individual atoms instead of molecules, such as in the case of noble gases. The disclosure of the invention is to be understood accordingly. For better comprehensibility, a repeated reference to atoms was omitted.

The method according to the invention for calibrating a residual gas analysis method has the advantage that the calibration gas used allows the residual gas analysis method to be calibrated over an at least approximately or approximately complete relevant range of molecular masses. The range of molecular masses that is relevant is that of a residual gas that typically occurs in the vacuum of the working chamber. This can include, for example, components from sealing materials of the working chamber and/or processing aids. The method according to the invention for calibration, by which in particular relevant (mass) spectral ranges can be calibrated, offers the advantage that the occurrence of expected residual gases can be detected particularly well and their composition can be determined particularly reliably. In this way, particularly reliable information can be obtained, for example with regard to a state of a device located in the working chamber, in particular a projection exposure system, and/or the state of the working chamber.

Since, in particular, molecules with large molecular masses are to be expected in residual gases, it is particularly advantageous to use a calibration gas which includes high molecular masses, for example more than 100 atomic mass units.

The feature that the calibration gas has a molecular mass occurrence that comprises at least an expected molecular mass occurrence of the residual gas is to be understood in such a way that the molecular mass occurrence of the calibration gas has at least or at least the expected molecular mass occurrence of the residual gas. It is entirely possible within the scope of the invention for the calibration gas to also include other molecular mass occurrences. However, the molecular mass occurrence of the calibration gas is preferably at least essentially matched to the expected molecular mass occurrence of the residual gas, i.e. the molecular mass occurrence of the calibration gas contains only small other mass occurrences beyond the expected molecular mass occurrence of the residual gas. Such a solution has proven to be particularly suitable. However, as stated above, it is also possible for the calibration gas to have mass occurrences other than the mass occurrences of the residual gas, but the mass occurrence of the calibration gas is preferably selected in such a way that the other molecular mass occurrences make up less than 50% of the total molecular mass occurrence of the Calibration gas accounts for preferably less than 30%, most preferably less than 10%.

The feature that the molecular mass occurrence of the calibration gas at least approximately includes at least an expected molecular mass occurrence of the residual gas is to be understood in such a way that at least the significant parts of the expected molecular mass occurrence of the residual gas are preferably encompassed by the molecular mass occurrence of the calibration gas covers the molecular mass occurrence of the calibration gas little at least 90% of the expected molecular mass occurrence of the residual gas.

The residual gas analysis method is advantageously used here to determine the residual gas after it has been calibrated according to the invention.

The above as well as the following description of the method according to the invention is to be understood in such a way that it is suitable in particular for lithography methods, in particular for projection exposure systems, in particular for DUV and EUV projection exposure systems. The invention is therefore also illustrated using a projection exposure system. However, the invention is not limited to projection exposure systems. The method according to the invention is basically suitable for calibrating any residual gas analysis method for determining a residual gas in a vacuum of a working chamber and is not limited to projection exposure systems. A large number of systems and methods are known from the prior art, in which it is advantageous if the residual gas analysis method for determining a residual gas is calibrated in a vacuum with the solution according to the invention. This applies in particular to working chambers in which optical elements, in particular mirrors, are arranged or accommodated.

The method according to the invention and also the device according to the invention presented below and the system according to the invention are particularly suitable for use in which it is provided that a so-called ultra-high vacuum is produced in the working chamber or ultra-high vacuum conditions are present.

In an advantageous development of the method according to the invention, it can be provided that an empty residual gas spectrum of a vacuum in the working chamber is determined.

The calibration residual gas spectrum is generally made up of a contribution from the calibration gas and an unavoidable contribution from the vacuum of the working chamber to the residual gas, which also occurs without the presence of a calibration gas.

The empty residual gas spectrum can be determined using the residual gas analysis method, whereby no calibration gas is supplied to the working chamber. The contribution of the vacuum of the working chamber without the presence of the calibration gas is therefore advantageously quantified by determining the empty residual gas spectrum.

According to the invention, the empty residual gas spectrum is preferably determined before the calibration gas is supplied to the working chamber.

Furthermore, an empty chamber pressure which prevails in the working chamber before, immediately before and/or during and/or immediately after the determination of the empty residual gas spectrum can be determined.

In an advantageous development of the method according to the invention, it can be provided that a standard spectrum for the residual gas analysis method is determined by determining a difference spectrum between the calibration residual gas spectrum and the empty residual gas spectrum.

In order to more accurately determine the contribution of the calibration gas to the calibration residual gas spectrum, the blank residual gas spectrum is subtracted from the calibration residual gas spectrum, thereby determining the standard spectrum. The standard spectrum therefore has the advantageous property that it has been corrected for the contribution of the empty vacuum of the working chamber. The standard spectrum shows an advantageous better comparability with other standard spectra, since empty residual gas spectra can differ for different working chambers and different vacuums.

In an advantageous development of the method according to the invention, it can be provided that the differential spectrum is normalized to a base value.

In order to further improve the comparability of standard spectra, it can be provided that the standard spectrum results from the difference spectrum by normalizing the difference spectrum to a base value. A normalization of the difference spectrum is advantageous in that the absolute amplitudes of the spectral contributions of the individual molecular species of the calibration gas in the difference spectrum are dependent, for example, on a standard pressure and/or an actually measured chamber pressure and/or the empty chamber pressure. The chamber pressure is the pressure that results after the calibration gas has been fed into the vacuum of the working chamber, for example from a pressure measurement.

The base value used for normalization can preferably be calculated by subtracting the empty chamber pressure from the chamber pressure and dividing the resulting difference or the resulting effective pressure by the standard pressure, for example a set target chamber pressure and/or another pressure value will. Will the standard pressure in a range of chamber pressure selected, the base values with a value of approximately 1 result at low empty chamber pressures.

The more calibration gas that is supplied to the working chamber, the higher the chamber pressure and the higher the absolute amplitudes of the differential spectrum. Since the amplitudes of the difference spectrum correlate closely with the chamber pressure, the difference spectra can be compared by dividing the amplitudes of the difference spectrum by the base value. This is because the baseline correlates closely with chamber pressure due to the way it is calculated.

The standard spectrum calculated in this way is suitable for being compared with other standard spectra or standardized reference spectra which were determined both in other working chambers and with other base values - but using the same method as the standard spectrum.

It can also be advantageous that a standard spectrum for the residual gas analysis method is determined by determining a difference spectrum between the calibration residual gas spectrum and the empty residual gas spectrum and normalizing the difference spectrum to its entire integral spectral mass, i.e. the value of the integral over the entire mass spectrum. Since the integral spectral mass of the difference spectrum is directly dependent on the occurrence of the residual gas or the calibration gas and the working chamber, the difference spectrum can also be normalized to the integral spectral mass of the difference spectrum instead of to the base value in order to make a comparison between standard spectra. In particular, the difference spectrum can be divided by the integral spectral mass of the difference spectrum in order to obtain a standard spectrum. In this way, the numerical values of the amplitudes of the standard spectrum result directly as relative proportions of the respective species with the respective molecular mass in the entire standard spectrum.

In an advantageous development of the method according to the invention, it can be provided that the standard spectrum of the residual gas analysis method is compared, preferably divided, with a reference standard spectrum of a reference residual gas analysis method that was created with the same calibration gas.

In order to determine the relative spectral sensitivity of the residual gas analysis method, it is advantageous if the standard spectrum of the residual gas analysis method is compared with other standard spectra. In particular, a comparison with a reference standard spectrum of a reference residual gas analysis method is advantageous. Provision can thus be made for a single residual gas analysis method, for example mass spectrometry, to be regarded as a standard method with which all other standard spectra to be determined from other residual gas analysis methods are compared. If, for example, a determined standard spectrum shows higher amplitudes in a spectral range of 120 to 140 atomic mass units than the reference standard spectrum, which was determined using the reference residual gas analysis method using the same calibration gas, it can be assumed that the spectral sensitivity of the residual gas analysis method examined in the spectral range of 120 to 140 molecular mass units is higher than that of the reference residual gas analysis method.

Furthermore, it can advantageously be provided that a structure factor is determined from the standard spectrum and/or from parts of the standard spectrum, for example in characteristic ranges, which compares the amplitudes of the standard spectrum with one another and which can be used to compare standard spectra with one another.

If the standard spectrum and the reference standard spectrum are divided by one another, this results in a diagram for the spectral sensitivity of the residual gas analysis method compared to the reference residual gas analysis method, with the numerical values above one signaling a higher spectral sensitivity of the residual gas analysis method compared to the reference residual gas analysis method and Numerical values less than one indicate a lower relative spectral sensitivity of the residual gas analysis method compared to the reference residual gas analysis method.

In addition to using a standard reference residual gas analysis method, provision can also be made for two residual gas analysis methods to be compared directly with one another without taking a standard reference residual gas analysis method into account. Not all residual gas analysis methods that are examined have to be compared with just one single standard reference residual gas analysis method, but can also be compared with each other in pairs.

In an advantageous development of the method according to the invention, it can be provided that the calibration gas consists of an individual gas or is mixed from several individual gases.

It can be provided within the scope of the invention that the calibration gas consists of a single gas which is the molecular according to the invention has mass occurrences. However, it can also be provided that the calibration gas is mixed from several individual gases.

In order to achieve the most homogeneous possible coverage of the complete relevant spectral mass range or mass occurrence and thus to achieve an advantageously high reliability of the calibration method, the calibration gas can be mixed from several individual gases in such a way that the calibration gas has such individual molecular components that the relevant Cover the spectral range or the relevant molecular mass occurrences and which emerge from the several individual gases. The individual gases should advantageously be selected in such a way that in the calibration gas, which is a mixture of the individual gases, all molecular masses in the relevant spectral mass range or the mass occurrence occur in an approximately uniform manner.

In an advantageous development of the method according to the invention, it can be provided that at least one individual gas is formed by outgassing at least one calibration substance, preferably a liquid.

A representation of at least one individual gas by outgassing from at least one calibration substance has the advantage that an outgassing process, which is to be examined anyway by the residual gas analysis method, is simulated. For example, an individual gas that results from outgassing from at least one calibration substance can cover a spectral mass range that can be similar or at least approximately corresponds to the spectral mass range to be expected of the residual gas. In particular, the calibration substance can contain molecules and/or mixtures of molecules which have different outgassing properties and therefore have a characteristic spectral footprint. A form of an expected standard spectrum of the calibration gas can therefore be predetermined by a suitable selection of the calibration substance. In particular, the ratio of the individual molecular components to one another can be predetermined as a material property of the calibration substance itself.

If the calibration substance is a liquid, this has the particular advantage that outgassing does not have to take place through a desorption process of a molecule from a solid-like structure, but through evaporation from a liquid state of aggregation. As a result, a clearly defined energy barrier, which essentially corresponds to the vaporization enthalpy, must be overcome in order to release a molecule from the liquid.

Furthermore, a liquid has the advantage that a change in the calibration substance in a region close to the surface can be prevented by continued desorption of the molecules of the individual gas from the calibration substance by mixing the liquid. In this way, advantageous homogeneous properties of the surface areas of the liquid leading to outgassing can be produced.

It can be provided within the scope of the invention that only one of the individual gases is formed by outgassing at least one calibration substance, preferably a liquid. However, it has turned out to be advantageous that when the calibration gas is mixed from several individual gases, two, a plurality of the individual gases or preferably all individual gases are formed by outgassing at least one calibration substance, preferably a liquid. The calibration substance does not have to be a liquid; each of the individual gases can have its own calibration substance, in particular a liquid, a solid or a gas.

In an advantageous development of the method according to the invention, it can be provided that the calibration gas is supplied to the working chamber by at least one controllable and/or regulatable dosing device.

The dosing device makes it possible, preferably at any time or as required, to regulate and/or control the supply of the calibration gas to the working chamber. For example, a change in the calibration substance over time can be compensated for by controlling the dosing device. In particular, it can be provided that the dosing device can be controlled by means of a dosing setting device without manual intervention, for example electromechanically and on the basis of values stored in the dosing setting device for setting the dosing device.

In an advantageous further development of the method according to the invention, it can be provided that several dosing devices are provided for mixing the calibration gas from several individual gases, in order to supply the individual gases in doses to the vacuum of the working chamber.

The dosing device thus makes it possible to adjust the mixture of the calibration gas individually or as required or to adjust it to the expected molecular mass occurrence of the residual gas in such a way that the calibration gas has a molecular mass occurrence which at least approximately comprises the expected molecular mass occurrence of the residual gas.

The dosing devices for the multiple individual gases also make it possible for a change in the calibration substances from which the individual gases are preferably formed to be compensated for, if necessary, fully automatically. In principle, it is possible for several individual gases to be supplied to the vacuum of the working chamber via a common dosing device. However, it is advantageous if the plurality of individual gases can each be fed to the vacuum of the working chamber in doses via their own dosing device.

In an advantageous development of the method according to the invention, it can be provided that a chamber pressure in the working chamber is adjusted by means of the dosing device.

A chamber pressure prevailing in the working chamber results from the amount of calibration gas that is in the chamber and the empty chamber pressure. Accordingly, the chamber pressure can be adjusted, for example, by regulating the amount of calibration gas in the working chamber. This can advantageously be done by means of a dosing device which regulates the admission of the individual gases or the calibration gas to the working chamber. It should be noted here that ballistic mass transport under vacuum and ultra-high vacuum conditions can be of little relevance and thus entry of the calibration gas into the working chamber depends only to a small extent on the chamber pressure, but particularly on a setting, in particular an opening width, of the dosing device.

The chamber pressure is therefore also a decisive variable in the base value mentioned above. This applies in particular since the chamber pressure, as described, only has a small influence on an output rate of the calibration substance.

In particular, it is advantageous to choose the chamber pressure in such a way that the chamber pressure that was set when creating the calibration residual gas spectrum is significantly, preferably at least one order of magnitude, greater than the chamber pressure that was determined when creating the empty residual gas spectrum, or the empty chamber pressure. This means that the chamber pressure is preferably ten times greater than the empty chamber pressure. As a result, uncertainties when creating the empty residual gas spectrum can be given less weight when determining the standard residual gas spectrum.

In an advantageous development of the method according to the invention, it can be provided that several individual gases are supplied to the vacuum of the working chamber to form the calibration gas in such a way that the pressure in the working chamber is incrementally increased by several dosing devices until the chamber pressure is reached, with each pressure increment being derived from the Feeding one of the several individual gases results.

If the calibration gas that is fed to the vacuum of the working chamber is made up of several individual gases, the individual gases can be fed to the working chamber in such a way that each individual gas makes a certain defined contribution to the chamber pressure. The relative contribution of the individual gases to the chamber pressure thus defines the relative contribution of the individual gases to the standard spectrum to be determined.

In an advantageous development of the method according to the invention, it can be provided that the calibration gas has molecules with a molecular mass of 1 to 1024 atomic mass units, preferably 1 to 512 atomic mass units, more preferably 1 to 200 atomic mass units.

A mass range of 1 to 512 atomic mass units covers an expected mass range, which is to be expected from outgassing from seals and/or adhesives and/or coatings of optical elements and/or other components. In particular, the range from 1 to 200 atomic mass units includes the outgassing that is to be expected as described.

In an advantageous development of the method according to the invention, it can be provided that the calibration gas contains hydrocarbons and/or water, preferably with a molecular mass of 1 to 1024 atomic mass units, more preferably 1 to 512 atomic mass units, and particularly preferably 1 to 200 atomic mass units .

Using hydrocarbons as a calibration gas has the advantage that hydrocarbons and/or molecular classes chemically related to hydrocarbons are also a typical component of outgassing from materials such as seals and/or coatings and/or adhesives and/or cleaning agents and/or cooling lubricants and/or other processing aids , which can be located within the working chamber. A use of hydrocarbons as Calibration gas thus has the advantage that the residual gas is imitated particularly well.

In particular, the calibration substance can be selected from the class of hydrocarbons in such a way that the calibration substance does not show any mass diversity, as can be observed with polymers, for example. As a result, the method according to the invention can be implemented more stably and with a smaller range of fluctuation.

In an advantageous development of the method according to the invention, it can be provided that an integral value of at least one characteristic range of the standard spectrum is determined and compared with a reference integral value of the same characteristic range of the reference standard spectrum.

Depending on the structure and mass composition of the calibration gas used, it can be advantageous if at least one characteristic range of the standard spectrum is compared with the corresponding characteristic range of the reference standard spectrum instead of the entire standard spectrum.

In particular, it can be advantageous to determine an integral value from the characteristic range of the standard spectrum—by integrating the standard spectrum in the characteristic range. This integral value indicates the relative spectral weight of the characteristic range compared to the entire standard spectrum. A spectral sensitivity of the residual gas analysis method examined can be determined for the characteristic range using the integral value by comparing the integral value with the reference integral value of the same characteristic range of the reference standard spectrum. For example, if the integral value of the characteristic range of the standard spectrum is higher than the reference integral value of the same characteristic range of the reference standard spectrum, this can indicate a higher average spectral sensitivity of the residual gas analysis method in the characteristic range compared to the reference residual gas analysis method.

Furthermore, it can advantageously be provided that the structure factor is determined in the at least one characteristic range and is compared with a reference structure factor of the same characteristic range of the reference standard spectrum obtained in the same way.

A comparison of different residual gas analysis methods can thus advantageously be simplified, since only key figures or integral values and/or structure factors between the standard spectrum and the reference standard spectrum are compared with one another.

Such code numbers can be used particularly advantageously in product specifications for, for example, the working chambers examined, or for devices located in the working chambers.

In this context, a reproducible ratio of the outgassing of the calibration substance in dedicated mass ranges in the standard spectrum, which are typically attributed to volatile and/or non-volatile substances, is particularly advantageous.

In an advantageous development of the method according to the invention, it can be provided that the characteristic ranges do not overlap.

In order to determine meaningful integral values, it can be advantageous to avoid an overlapping of the characteristic ranges, since otherwise the same range of the standard spectrum is taken into account in several integral values, which can reduce their meaningfulness.

It can be advantageous if the characteristic ranges adjoin one another directly or without gaps, but without overlapping. This allows a large part of the standard spectrum to be analyzed using integral values without gaps or overlaps in the characteristic ranges.

In an advantageous development of the method according to the invention, it can be provided that a first characteristic range comprises molecular masses between 1 and 34 to 54, preferably between 1 and 44, atomic mass units.

In the preferred range, the first characteristic range thus includes in particular the molecular mass of water, which is 18 atomic mass units, as well as other relatively light molecular species. In comparison with a reference integral value, the integral value of the first characteristic range thus reflects how sensitive the examined residual gas analysis method is, in particular with regard to water, in comparison to the reference residual gas analysis method. This can be advantageous to ensure that the residual gas analysis method is able to reliably detect, for example, water leaks in cooling structures that can run inside the working chamber and are water-cooled, and neither overestimates nor underestimates the occurrence of water molecules in the working chamber.

The first characteristic range is preferably designed in such a way that it comprises molecular masses between 1 and 44 atomic mass units. However, it can also be provided that the first characteristic range is molecular weights between 1 and 34 or between 1 and 54 atomic mass units, the upper value of the atomic mass units comprised can also be between 34 or 54 atomic mass units.

In an advantageous development of the method according to the invention, it can be provided that a second characteristic range comprises molecular masses between 35 to 55 and 90 to 110, preferably between 45 and 100, atomic mass units.

The second characteristic range, which preferably comprises molecular masses between 45 and 100 atomic mass units, thus comprises the range from, for example, light hydrocarbons, for example alkanes, up to a chain length of 7 carbon atoms. Constituents of a residual gas that are to be expected in the second characteristic range are, for example, volatile solvents from adhesives and/or seals within the working chamber. An integral value to be determined from the second characteristic range therefore indicates, in comparison with the reference integral value, a spectral sensitivity of the residual gas analysis method compared to the reference residual gas analysis method, which advantageously allows an assessment of the extent to which the residual gas analysis method under investigation is sufficiently sensitive to the occurrence of solvents in a vacuum of the working chamber.

The second characteristic range preferably includes molecular masses between 45 and 100 atomic mass units. Instead of the lower value of the atomic mass units, it can also be provided that the second characteristic range starts at 35 or 55 atomic mass units or a value between these two amounts. Instead of the upper value of the second characteristic range, which is preferably 100 atomic mass units, a value of 90 or 110 atomic mass units can also be provided as the upper limit value, or any value between these two amounts.

The second characteristic range preferably follows the first characteristic range without overlapping, preferably without a gap. This means that the lower value of the second characteristic range is higher by the amount 1 than the upper value of the first characteristic range.

In an advantageous development of the method according to the invention, it can be provided that a third characteristic range comprises molecular masses between 91 to 111 and 190 to 210, preferably between 101 and 200, atomic mass units.

The third characteristic range here preferably includes molecular masses between 101 and 200 atomic mass units and thus, for example, alkanes with a chain length of up to 14 carbon atoms. Such heavy hydrocarbons can, for example, be components of coatings and/or adhesives and/or greasy dirt that is located within the working chamber. An integral value of the third characteristic range thus indicates the sensitivity of the residual gas analysis method to the presence of heavy molecules, for example heavy hydrocarbons, within the working chamber. This applies in particular in comparison to a reference integral value which maps the same characteristic range and which was determined using the reference residual gas analysis method.

The third characteristic range preferably includes molecular masses between 101 and 200 atomic mass units. Instead of the lower value of the atomic mass units, it can also be provided that the third characteristic range starts at 91 or 111 atomic mass units or a value between these two amounts. Instead of the upper value of the third characteristic range, which is preferably 200 atomic mass units, a value of 190 or 210 atomic mass units can also be provided as the upper limit value, or any value between these two amounts.

The third characteristic range preferably follows the second characteristic range without overlapping, preferably without a gap. This means that the lower value of the third characteristic range is higher by the amount 1 than the upper value of the second characteristic range.

According to the invention, it can be provided that the third characteristic range is followed by a fourth characteristic range, in which all values that were mentioned with regard to the third characteristic range are each increased by the amount 100. Accordingly, a fifth characteristic range can also follow the fourth characteristic range, in which, in turn, the values of the fourth characteristic range are each increased by the amount 100.

In an advantageous development of the method according to the invention, it can be provided that the residual gas analysis method is mass spectrometry and/or X-ray photoelectron spectroscopy.

Established methods for creating mass spectra, for example by means of gas chromatography, are, for example, mass spectrometry and X-ray photon spectroscopy, or XPS, and also nuclear magnetic resonance spectroscopy. Using these methods as a residual gas analysis method has the advantage that established structures and systems can be used, which means that a residual gas analysis method can be implemented in a particularly economical and time-saving manner.

The method according to the invention is particularly suitable for calibrating a residual gas analysis method for determining a residual gas in a vacuum in a working chamber which is set up to accommodate a projection exposure system, in particular a DUV or EUV projection exposure system, and/or parts and/or modules of the projection exposure system. Especially in the case of projection exposure systems and in particular in the case of EUV projection exposure systems, it is advantageous if the residual gas spectrum can be determined in a sufficiently reproducible and temporally stable manner. This also makes it possible to compare projection exposure systems of different sizes, geometries, inherent outgassing and/or suction power. The comparability of the outgassing rate can be decisive for the reliability of the cleanliness of EUV projection exposure system components and thus the service life of the entire EUV optics of the projection exposure system. A characterization of the projection exposure systems both in the construction phase as well as after complete installation with regard to molecular cleanliness is important for this. It is advantageous if such a characterization is carried out regularly.

It is particularly advantageous to carry out the calibration of the residual gas analysis method in a working chamber state in which there is no projection exposure system and/or no parts of a projection exposure system in the working chamber. As a result, contamination of the projection exposure system and/or the parts with calibration gas can be avoided. It is particularly advantageous to carry out the calibration before the projection exposure system is introduced into the working chamber.

The invention further relates to a device for supplying a calibration gas to a vacuum according to claim 20.

The device according to the invention for supplying a calibration gas to a vacuum in a working chamber for calibrating a residual gas analysis device for determining a residual gas spectrum of the vacuum in the working chamber provides that the calibration gas consists of an individual gas or the device mixes the calibration gas from several individual gases. Furthermore, the device has at least one container for accommodating at least one calibration substance, which provides an individual gas, and at least one dosing device for dosing the individual gas in the container, and at least one supply line from the container to the working chamber.

The device according to the invention serves to calibrate the residual gas analysis device. For this purpose, the device according to the invention has at least one container for receiving at least one calibration substance. Due to outgassing from the calibration substance, there is also an individual gas in the container, which can be supplied to the working chamber by means of the dosing device via a supply line. With a suitable choice of the calibration substance and a suitable setting of the dosing device, a calibration gas can be supplied to the working chamber, which is composed of molecular species that are distributed in a spectral mass range or have a molecular mass occurrence that has a large overlap with the expected spectral Having a mass range or a molecular mass occurrence of an expected residual gas.

The feed line from the container to the working chamber serves to feed the individual gas to the working chamber.

According to the invention, it can be provided that the device feeds an individual gas, which forms the calibration gas, to the vacuum in the working chamber. According to the invention it can also be provided that the device supplies several individual gases to the vacuum in the working chamber, which together form the calibration gas in the vacuum, ie the calibration gas is mixed from several individual gases. Insofar as the calibration gas is mixed from a plurality of individual gases, it is advantageous if a plurality of containers are provided to each hold at least one calibration substance which makes a respective individual gas available. It is also advantageous in this case if at least one dosing device is provided for each individual gas for dosing the individual gas in the container, which is made available by the calibration substance, in order to supply the corresponding individual gas to the working chamber in doses.

It is advantageous if a container and a dosing device are provided for each individual gas. However, it is also possible for a dosing device to be used for dosing two or more individual gases.

The device according to the invention is particularly suitable for processing steps of the carry out the method according to the invention or to be used in the context of the method according to the invention.

In an advantageous development of the device according to the invention, it can be provided that the at least one supply line is connected to the working chamber in a vacuum-tight manner.

As a result, a deterioration in the vacuum conditions and in particular a penetration of gases from the environment into the vacuum in the working chamber can be avoided.

In an advantageous development of the device according to the invention, it can be provided that the device is set up to determine a calibration residual gas spectrum from the calibration gas supplied to the working chamber and/or the device has an interface, preferably connected to the residual gas analysis device, for receiving the data of a calibration residual gas spectrum.

With such a design of the device, the device has access to the calibration residual gas spectrum that was created using the device according to the invention.

The interface for receiving the data of a calibration residual gas spectrum, which is preferably transmitted by the residual gas analysis device, can in particular be a wired or wireless interface.

In an advantageous development of the device according to the invention, it can be provided that a chamber pressure in the working chamber can be adjusted by means of the at least one dosing device.

If the chamber pressure in the working chamber results from the setting of the at least one dosing device, the amount of calibration gas present in the working chamber can advantageously be determined by means of the dosing device, since the amount of calibration gas in the working chamber is strictly correlated with the chamber pressure. The absolute occurrence of the molecular components of the calibration gas in the residual gas can thus be adjusted via the dosing device and read off or determined via the chamber pressure.

Provision can advantageously be made for the at least one dosing device to be formed from a plurality of sub-dosing devices. In particular, it can be provided that the at least one dosing device is formed from a control dosing device and a shut-off dosing device, which are connected in series. A defined volume flow of the individual gas from the container into the working chamber can be set by the control metering device, for example by setting an opening cross section of the control metering device. This opening cross-section can be retained and the volume flow of the individual gas can be switched off or on by the shut-off dosing device in the form of a binary dosing device.

Such a system has the advantage that the reproducibility is advantageously improved by the control dosing device remaining in its setting, since the same setting of the control dosing device can be used in each case when creating a plurality of calibration residual gas spectra.

It can also be advantageous that the dosing device, or the dosing adjustment device that adjusts the dosing device, includes a control device which sets the control dosing unit as a function of a current chamber pressure in such a way that the current chamber pressure as the actual chamber pressure is at least approximately the same as a desired chamber pressure or a desired chamber pressure. For this purpose it is of particular advantage if the working chamber has a pressure measuring device which can transmit information about the actual chamber pressure to the control device. The control device is designed such that a difference between the actual chamber pressure and the target chamber pressure can be determined and the dosing device can be controlled, for example, as a function of this differential pressure.

If the device according to the invention mixes the calibration gas from several individual gases and several dosing devices are provided for this purpose, it can be provided that the control device controls the several dosing devices in such a way that the desired chamber pressure, i. H. the target chamber pressure, is adjusted accordingly and the calibration gas in the chamber is mixed in the desired mixing ratio from the individual gases.

Furthermore, the above-mentioned vacuum-tight feed line can ensure that a pressure prevailing in the working chamber after the calibration gas has been introduced, or the chamber pressure, results almost exclusively from the presence of the calibration gas in the working chamber, with an influence of unwanted foreign substances on the chamber pressure can be minimized.

In an advantageous development of the device according to the invention, it can be provided that a computing device is provided that is set up to determine a standard spectrum by subtracting an empty residual gas spectrum from a calibration residual gas spectrum and by a base value, which is preferably derived from a difference between the chamber pressure and an empty chamber pressure, which is divided by a standard pressure.

The empty chamber pressure is the pressure that prevails in the working chamber immediately before and/or during and/or immediately after the determination of the empty residual gas spectrum.

In this case, the standard pressure is, for example, the set target chamber pressure and/or another pressure value. The standard pressure can in particular be between 10 ^-7 and 10 ^-6 mbar, preferably 5*10 ^-7 mbar.

The standard spectrum can advantageously be determined by a computing device in that an empty residual gas spectrum, which was preferably determined by the residual gas analysis device from the residual gas of the vacuum in the working chamber, is subtracted from the calibration residual gas spectrum of the vacuum in the working chamber into which the calibration gas is introduced, and by the base value is divided. The empty residual gas spectrum, the calibration residual gas spectrum as well as the chamber pressure and the empty chamber pressure and the standard pressure can be stored in the computing device and the associated computing operations can be carried out. In this way, the processes required for determining the standard spectrum can advantageously be implemented centrally in a computing device. The computing device can be part of the device according to the invention or it can be provided that the computing device is part of the residual gas analysis device. This is advantageous in that the residual gas analysis device generally has computer-like devices which then communicate with the device according to the invention, if necessary.

Provision can advantageously be made for the computing device to have at least one stored standard spectrum, for example a reference standard spectrum.

In an advantageous development of the device according to the invention, it can be provided that a reference computing device is provided in order to compare the standard spectrum with standard spectra of other residual gas analysis devices and/or a reference standard spectrum of a reference residual gas analysis device.

A reference computing device offers the advantage that a comparison of the standard spectrum with other residual gas analysis devices and/or a reference standard spectrum of a reference residual gas analysis device is made possible. It can be particularly advantageous if reference standard spectra are stored or stored in the reference computing device, as a result of which a comparison can advantageously take place quickly. In particular, it can be provided that the reference computing device is part of the computing device or part of the device according to the invention or part of the residual gas analysis device. It is also advantageous if the reference computing device is designed in such a way that all operations that are necessary to carry out a comparison between the standard spectrum and the reference standard spectrum can be carried out.

In particular, it can be provided that both the computing device and the reference computing device are designed as a computer-like program on a central computing device.

If the reference computing device is not physically part of the device according to the invention, it can be provided that the reference computing device communicates with the device according to the invention, for example as part of the residual gas analysis device, so that the device according to the invention also has the corresponding data.

In an advantageous further development of the device according to the invention, it can be provided that the at least one calibration substance is a liquid and the individual gas is outgassed from the calibration substance.

A calibrating substance in the form of a liquid has the advantage that the calibrating substance can be introduced particularly easily into the container of the device and outgassing of the individual gas escaping from the liquid can take place in a particularly defined manner and with particularly constant molecular compositions.

Another advantage of a liquid or alternatively a solid calibration substance is the higher mass density in a solid or a liquid compared to a gas. Accordingly, the container that holds the calibration substance can be smaller. A comparable number of molecules in a gaseous calibration substance as, for example, in a liquid calibration substance stanz, can only be introduced into the container if the gaseous calibration substance is either compressed, which can lead to liquefaction, or the container is enlarged in such a way that it is able to accommodate the corresponding amount of gaseous calibration substance.

Insofar as the device according to the invention is designed to mix the calibration gas from a plurality of individual gases, it can be provided that the containers each have a liquid, solid or gaseous calibration substance. A majority, particularly preferably all, of the containers preferably have a liquid calibration substance.

In an advantageous development of the device according to the invention, it can be provided that the at least one calibration substance is a liquid hydrocarbon and/or a mixture of liquid hydrocarbons and the individual gas is outgassed from the calibration substance.

It can be provided that one, a plurality or all of the individual gases are outgassed from a corresponding calibration substance.

A mixture of individual gases that form the calibration gas can be achieved particularly easily by mixing individual gases that have outgassed from calibration substances. It can be provided that in each container there is precisely one calibrating substance that is preferably pure in terms of its molecular composition, or that at least one container contains a mixture of calibrating substances. A mixture of calibration substances can be produced particularly efficiently and reliably in a defined composition and with defined outgassing behavior by mixing liquid calibration substances.

Designing the device such that a molecularly pure calibrating substance is introduced into each container has the advantage that the properties of the calibrating substance are particularly homogeneous on a surface capable of outgassing, since segregation of the calibrating substance is made more difficult due to its molecular purity.

Hydrocarbons have the advantage that hydrocarbons can exist as liquids over a wide range of molecular masses. As a result, a calibration gas can be made available which has molecular components in a very wide range of molecular masses.

In an advantageous development of the device according to the invention, it can be provided that the at least one calibration substance is a gas.

A gas as a calibration substance has the advantage that a calibration gas with particularly clear molecular properties can be produced by dispensing with an outgassing process.

In an advantageous development of the device according to the invention, it can be provided that the at least one calibration substance is a solid and the individual gas is outgassed from the calibration substance.

If the calibration gas is mixed from several individual gases, it can be provided that the individual gases are each outgassed from a calibration substance, which is a liquid or a solid, or the calibration substance is a gas. However, it is also possible to use a liquid calibration substance for one or more individual gases and/or to use a solid as the calibration substance for one or more individual gases and/or to provide that the calibration substance is a gas for one or more individual gases.

In an advantageous development of the device according to the invention, it can be provided that the at least one calibration substance has molecules with a molecular mass of 1 to 1000 atomic mass units, preferably 1 to 200 atomic mass units

In an advantageous development of the device according to the invention, it can be provided that the at least one calibration substance has hydrocarbons and/or water, preferably with a molecular mass of 1 to 1000 atomic mass units, particularly preferably 1 to 200 atomic mass units.

In an advantageous development of the device according to the invention, it can be provided that the calibration gas is chemically inert.

If the calibration gas is not willing to react or is chemically inert, this has the advantage that the spectral mass composition of the calibration gas is not changed by chemical reactions. In particular, a shift in the mass spectrum in the direction of higher molecular masses due to the formation of chemical bonds between the molecules of the calibration gas is reduced as a result.

Another advantage of a chemically inert calibration gas is that the molecules of the calibration gases do not form any chemical compounds with substances that are in the vacuum of the working chamber. If this were the case, the calibration gas would act as a kind of dirt, which should actually be minimized by applying the vacuum to the working chamber. Furthermore, a chemical reaction of the calibration gas falsifies the chamber pressure, for example, since the chamber pressure depends on the number of molecules present in the working chamber and the volume available for the molecules, but not on the molecular mass of the molecules. A reaction of two light molecules to form a heavy molecule would therefore lead to a reduction in chamber pressure.

In an advantageous development of the device according to the invention, it can be provided that the at least one individual gas has at least approximately exclusively molecules from the calibration substance and fragments thereof.

A single gas, which preferably consists only of the molecules of the calibration substance and their fragments, has the advantage that a large spectral mass range can be covered with a single molecularly homogeneous calibration substance, since the molecules of the calibration substance can break down into defined fragments and the ratio of the occurrence of the Fragments to each other can be very defined. Since the fragments appear as discrete peaks in the mass spectrum with atomic mass resolution, which have a very defined distance from each other, for example when a carbon atom is split off, such an individual gas forms a characteristic footprint in the standard spectrum, which scans the relevant spectral range in defined steps.

In an advantageous development of the device according to the invention, it can be provided that the working chamber is set up to accommodate a projection exposure system for semiconductor lithography with an illumination system with a radiation source and an optical system which has at least one optical element.

The device according to the invention is particularly suitable for supplying a calibration gas to a working chamber into which a projection exposure system can be introduced. The residual gas spectrum to be expected has a defined characteristic that depends on the components of the projection exposure system. The calibration gas can then be adjusted accordingly. As a result, the residual gas spectrum can be determined particularly reliably. It is particularly advantageous to carry out the calibration of the residual gas analysis method in a working chamber state in which there is no projection exposure system and/or parts of a projection exposure system in the working chamber. As a result, contamination of the projection exposure system and/or the parts with calibration gas can be avoided. It is particularly advantageous to carry out the calibration before the projection exposure system is introduced into the working chamber.

Especially with projection exposure systems, in particular with DUV and EUV projection exposure systems, it is of particular advantage if the residual gas spectrum can be determined reproducibly and stably over time, in particular to create a comparability between systems of different sizes, geometry, inherent outgassing and/or suction power. Determining the residual gas spectrum can be essential for ensuring the cleanliness of components of projection exposure systems, in particular EUV projection exposure systems, in particular their optics, and can also influence the service life of the entire projection exposure system.

The invention further relates to a calibration substance according to claim 35.

The calibration substance according to the invention is particularly suitable for use in the device according to the invention and thereby enables reliable calibration.

The calibration substance can preferably be in the form of a liquid calibration substance; alternatively, it is also possible for the calibration substance to be a solid or a gas.

The invention further relates to a system for forming a vacuum environment according to claim 36.

The system according to the invention for forming a vacuum environment has a working chamber, a vacuum device for generating a vacuum in the working chamber, a pressure measuring device for determining a chamber pressure in the working chamber and a residual gas analysis device for determining a residual gas spectrum of a residual gas in the vacuum. According to the invention, a device according to one of claims 20 to 34 is provided in order to calibrate the residual gas analysis device for determining a residual gas spectrum in the vacuum.

In the system according to the invention, the device can be used to calibrate the residual gas analysis device in such a way that the residual gas spectrum rum of the residual gas in the vacuum of the working chamber can be determined particularly reliably and reproducibly. Such a system also offers the advantage that different types of devices and devices can be arranged within the working chamber, the cleanliness and operating condition of which can be determined by the residual gas analysis device.

The device for feeding the calibration gas into the working chamber of the system can preferably be designed in the manner already described above with regard to the device.

In an advantageous further development of the system, it can be provided that the working chamber is designed to accommodate at least part of a projection exposure system.

In particular, it can be provided that the working chamber is designed to accommodate parts and/or modules of a projection exposure system.

The working chamber can be provided to accommodate individual components, sub-components, fastening means, processing aids and/or components, in particular optical elements, very particularly preferably mirrors. With the method according to the invention, the said components can be qualified particularly reliably with regard to a potential for outgassing of a residual gas, for example before delivery.

Such a working chamber also represents an advantageous working space for a lithographic-optical process to be carried out with the projection exposure system, for example. The optical process which can be carried out in the working chamber according to the invention benefits in particular from the residual gas spectrum which can be determined particularly reliably within the scope of the working chamber according to the invention.

The projection exposure system is preferably an EUV projection exposure system. All optics, in particular all mirrors of the EUV projection exposure system, are preferably arranged in the working chamber. It is particularly preferred if the entire projection exposure system, in particular an EUV projection exposure system, is arranged in the working chamber.

It is advantageous if the residual gas analysis method is calibrated before parts of the projection exposure system or the projection exposure system are brought into the working chamber.

The invention also relates to a projection exposure system according to claim 38.

The projection exposure system according to the invention for semiconductor lithography has an illumination system with a radiation source and an optical system, which has at least one optical element. At least one of the optical elements is arranged in a working chamber having a vacuum. Residual gases in the vacuum in the working chamber are determined by means of a residual gas analysis method which is calibrated using a method according to one of Claims 1 to 19 and/or a device according to one of Claims 20 to 34 is provided in order to have a residual gas analysis device for determining a residual gas spectrum in to calibrate the working chamber.

The projection exposure system according to the invention has the advantage that the operating status of the projection exposure system can be determined reliably and reproducibly using a residual gas analysis method, since the residual gas analysis method can be carried out using a method or a device according to the invention, preferably before the projection exposure system or parts or modules of the projection exposure system are brought into the working chamber, has been calibrated. As a result, the residual gas analysis method is particularly reliable and can determine residual gases in the vacuum in the working chamber in a particularly reliable manner. The composition of the residual gases in the vacuum determined in this way therefore provides particularly reliable information about, for example, a degree of purity and/or aging and/or outgassing from components of the projection exposure system.

Features that have been described in connection with one of the objects of the invention, namely given by the method according to the invention, the device according to the invention, the calibration substance according to the invention, the system according to the invention and the projection exposure system according to the invention, can also be advantageously implemented for the other objects of the invention. Advantages that were mentioned in connection with one of the objects of the invention, namely given by the method according to the invention, the device according to the invention, the calibration substance according to the invention, the system according to the invention and the projection exposure system according to the invention, can also be understood in relation to the other objects of the invention.

In addition, it should be noted that terms such as "comprising", "having" or "with" do not exclude any other features or steps. Furthermore, terms such as "a" or "that" which indicate a singular number of steps or features do not exclude a plurality of features or steps - and vice versa.

Exemplary embodiments of the invention are described in more detail below with reference to the drawing.

The figures each show preferred exemplary embodiments in which individual features of the present invention are shown in combination with one another. Features of an exemplary embodiment can also be implemented separately from the other features of the same exemplary embodiment and can accordingly easily be combined with features of other exemplary embodiments by a person skilled in the art to form further meaningful combinations and sub-combinations.

Elements with the same function are provided with the same reference symbols in the figures.

• 1 eine EUV-Projektionsbelichtungsanlage;
• 2 eine DUV-Projektionsbelichtungsanlage;
• 3 eine prinzipmäßige Darstellung der erfindungsgemäßen Vorrichtung und des erfindungsgemäßen Systems;
• 4 eine prinzipmäßige Darstellung eines Kalibrierrestgasspektrums;
• 5 eine blockdiagrammartige Darstellung des erfindungsgemäßen Verfahrens; und
• 6 eine prinzipmäßige Darstellung eines Normspektrums in einem Spektralbereich von 0 bis 200 atomaren Masseneinheiten.

They show schematically:

• 1 an EUV projection exposure system;
• 2 a DUV projection exposure system;
• 3 a basic representation of the device according to the invention and the system according to the invention;
• 4 a basic representation of a calibration residual gas spectrum;
• 5 a block diagram representation of the method according to the invention; and
• 6 a basic representation of a standard spectrum in a spectral range from 0 to 200 atomic mass units.

1 shows an example of the basic structure of an EUV projection exposure system 400 for semiconductor lithography, for which the invention can preferably be used. In particular, the invention can be applied in that at least one optical element of the projection exposure system is arranged in a vacuum working chamber 3, with residual gases in the vacuum in working chamber 3 being determined by means of a residual gas analysis method which is calibrated with a method and/or a device 1 according to the invention is provided in order to calibrate a residual gas analysis device 2 for determining a residual gas spectrum in the working chamber 3 .

In addition to a radiation source 402 , an illumination system 401 of the projection exposure system 400 has optics 403 for illuminating an object field 404 in an object plane 405 . A reticle 406 which is arranged in the object field 404 and is held by a reticle holder 407 shown schematically is illuminated. Projection optics 408, shown only schematically, are used to image the object field 404 in an image field 409 in an image plane 410. A structure on the reticle 406 is imaged on a light-sensitive layer of a wafer 411 arranged in the area of the image field 409 in the image plane 410, which is wafer holder 412, also shown in part, is held.

The radiation source 402 can emit EUV radiation 413, in particular in the range between 5 nanometers and 30 nanometers, in particular 13.5 nm. To control the radiation path of the EUV radiation 413, optically differently designed and mechanically adjustable optical elements are used. The optical elements of the in 1 The EUV projection exposure system 400 shown is configured as an adjustable mirror in suitable embodiments that are mentioned below only by way of example.

The EUV radiation 413 generated with the radiation source 402 is aligned by means of a collector integrated in the radiation source 402 in such a way that the EUV radiation 413 passes through an intermediate focus in the region of an intermediate focal plane 414 before the EUV radiation 413 impinges on a field facet mirror 415. Downstream of the field facet mirror 415, the EUV radiation 413 is reflected by a pupil facet mirror 416. Field facets of the field facet mirror 415 are imaged in the object field 404 with the aid of the pupil facet mirror 416 and an optical assembly 417 with mirrors 418, 419, 420.

In 2 an exemplary DUV projection exposure system 100 is shown. The projection exposure system 100 has an illumination system 103, a device known as a reticle stage 104 for receiving and precisely positioning a reticle 105, by means of which the later structures on a wafer 102 are determined, a wafer holder 106 for holding, moving and precisely positioning the wafer 102, and an imaging device , namely a projection lens 107, with a plurality of optical elements 108 which are held in a lens housing 140 of the projection lens 107 by means of sockets 109.

The optical elements 108 as individual refractive, diffractive and / or reflective optical elements 108 such. B. lenses, mirrors, prisms, end plates and the like, be formed.

The basic functional principle of the projection exposure system 100 provides that the structures introduced into the reticle 105 are imaged onto the wafer 102 .

The illumination system 103 provides a projection beam 111 in the form of electromagnetic radiation that is required for imaging the reticle 105 onto the wafer 102 . A laser, a plasma source or the like can be used as the source for this radiation. The radiation is shaped in the illumination system 103 via optical elements in such a way that the projection beam 111 has the desired properties in terms of diameter, polarization, shape of the wave front and the like when it strikes the reticle 105 .

An image of the reticle 105 is generated by means of the projection beam 111 and transmitted to the wafer 102 by the projection lens 107 in a correspondingly reduced size. The reticle 105 and the wafer 102 can be moved synchronously, so that areas of the reticle 105 are imaged onto corresponding areas of the wafer 102 practically continuously during a so-called scanning process.

An air gap between the last optical element 108 or the last lens and the wafer 102 can be replaced by a liquid medium which has a refractive index>1. The liquid medium can be, for example, ultrapure water. Such a structure is also referred to as immersion lithography and has an increased photolithographic resolution.

3 shows a device 1 for supplying a calibration gas 4 to a vacuum in a working chamber 3 for calibrating a residual gas analysis device 2 for determining a residual gas spectrum of a vacuum in a working chamber 3.

The device 1 feeds a calibration gas 4 into the vacuum in the working chamber 3 , the calibration gas 4 consisting of a single gas 5 or the device 1 mixing the calibration gas 4 from a plurality of single gases 5 . For this purpose, the device 1 has at least one container 6 for receiving at least one calibration substance 7, which makes an individual gas 5 available. Furthermore, the device 1 has at least one dosing device 8 for dosing the individual gas 5 located in the container 6 and at least one feed line 9 from the container 6 to the working chamber 3 .

The feed line 9 from the container 6 to the working chamber 3 is connected to the working chamber 3 in a vacuum-tight manner.

Insofar as the calibration gas 4 consists of a single gas, it can be sufficient in the exemplary embodiment if a container 6 and a dosing device 8 are provided. Insofar as it is provided that the calibration gas 4, as in the embodiment in 3 shown, mixes from several individual gases 5, a separate container 6 for receiving at least one calibration substance 7 and a separate dosing device 8 are preferably provided for each of the individual gases 5.

It can also be provided that a dosing device 8 is provided for dosing two or more individual gases 5 .

In the exemplary embodiment, three containers 6 are provided for receiving at least one calibration substance 7, each of which makes an individual gas 5 available. However, the invention is not limited to this.

The working chamber 3 also includes a vacuum device 10 for generating a vacuum and a pressure measuring device 11 for determining a chamber pressure.

The device 1 is set up here to determine a calibration residual gas spectrum 15 from the calibration gas 4 supplied to the working chamber 3 . Alternatively or additionally, the device 1 can have an interface (not shown), preferably connected to the residual gas analysis device 2 , for receiving the calibration residual gas spectrum 15 .

In the exemplary embodiment, the chamber pressure in the working chamber 3 can be adjusted by means of the dosing device 8 . In the exemplary embodiment shown, the dosing devices 8 each include a control dosing device 12 for controlling the introduction of the individual gas 5 into the working chamber 3 and a downstream shut-off dosing device 13 to open or close a connection between the supply line 9 and the container 6.

Furthermore, a computing device (not shown) is provided in the exemplary embodiment in order to determine a standard spectrum 14 by subtracting an empty residual gas spectrum from a calibration residual gas spectrum 15 and by using a base value, which preferably results from a difference between the chamber pressure and an empty chamber pressure, which is determined by a standard pressure is divided.

The empty chamber pressure is the pressure which prevails in the working chamber 3 immediately before and/or during and/or immediately after the determination of the empty residual gas spectrum.

In this case, the standard pressure is, for example, a set target chamber pressure and/or another pressure value.

The empty residual gas spectrum, ie the spectrum that is in the vacuum of the working chamber 3 before the calibration gas 4 is introduced, is preferably determined before the calibration gas 4 is introduced into the working chamber 3 .

Furthermore, a reference computing device (not shown) is provided in the present exemplary embodiment in order to compare the standard spectrum 14 with standard spectra of other residual gas analysis devices and/or a reference standard spectrum of a reference residual gas analysis device.

The arithmetic unit not shown or the reference arithmetic unit not shown can be designed as parts of the residual gas analysis device 2 and/or as parts of the device 1 and possibly communicate with one another in order to exchange data or the determined spectra. Suitable wireless or wired interfaces can be provided for this purpose. This is not shown in more detail in the exemplary embodiment.

in the in 3 In the exemplary embodiment shown, the at least one calibration substance 7 used in the device 1 is a liquid hydrocarbon and the individual gas 5, which is in the gas phase above the liquid calibration substance 7 in the container 6, has outgassed from the calibration substance 7. Alternatively it can be provided that the calibration substance 7 is another liquid and/or a mixture of liquid hydrocarbons.

In the 3 The individual gases 5 identified by the reference number 7 are represented as basic molecules which are in a gas phase above the liquid calibration substance 7 .

It can also be provided that the calibration substance 7 is a solid.

Likewise, it can alternatively be provided that the at least one calibration substance 7 is a gas.

Insofar as the calibration gas 4 is composed of several individual gases 5, as shown in the exemplary embodiment, it can be provided that the calibration substances 7, from which the individual gas 5 outgass, are each in an identical aggregate state. However, it is also possible for calibration substances to be arranged in the containers 6 whose state of aggregation is not identical.

In principle, it is also possible in the exemplary embodiment for a container 6 to contain a plurality of calibration substances 7, preferably, but not necessarily, in the same state of aggregation. This means that an individual gas 5 can also outgas from a number of calibration substances 7 in the container 6 .

In the present exemplary embodiment, the calibration substances 7 have hydrocarbons with a molecular mass of 1 to 200 atomic mass units.

The hydrocarbons in the individual gases 5 are chemically inert under the conditions prevailing in the working chamber 3 and consequently form a chemically inert calibration gas 4 .

In particular, the calibration gas 4 consists of the individual gases 5, which at least approximately exclusively contain hydrocarbon molecules of the same type from the calibration substance 7, as well as fragments of the hydrocarbon molecules from the calibration substance 7.

Not shown but it is provided that the working chamber 3 is set up to accommodate a projection exposure system for semiconductor lithography with an illumination system 103, 401 with a radiation source 402 and an optical system 107, 403, 408, which at least one optical element 108, 415, 416, 418, 419, 420.

The working chamber 3, the vacuum device 10 for generating a vacuum in the working chamber 3, the pressure measuring device 11 for determining the chamber pressure and/or the empty chamber pressure in the working chamber 3 and the residual gas analysis device 2 for determining a residual gas spectrum of a residual gas in the vacuum represent a system for training a vacuum environment.

4 shows a basic representation of a calibration residual gas spectrum 15. In this case, an intensity is plotted on a vertical y-axis and a molecular mass in atomic mass units is plotted on a horizontal x-axis.

The calibration residual gas spectrum 15 shows individual gas peaks 15a which result from the contributions of the individual gases 5 to the calibration residual gas spectrum 15 . The individual gases 5 are indicated by the symbols representing the individual gases 5 above the individual gas peaks 15a 3 shown. Individual gases 5 produce within a defined pressure Area of the chamber pressure specific peaks in the calibration residual gas spectrum 15 with a characteristic position and intensity.

5 shows a block diagram representation of a possible sequence of the method according to the invention.

A method for calibrating a residual gas analysis method for determining a residual gas in a vacuum of the working chamber 3, according to which a composition of the residual gas is characterized by a residual gas spectrum using the residual gas analysis method, can be described with the help of the 3 Implement device 1 shown particularly advantageous.

In the method, a calibration gas 4 is supplied to the vacuum in the working chamber 3, which has a molecular mass occurrence that at least approximately includes an expected molecular mass occurrence of the residual gas. Furthermore, a residual calibration gas spectrum 15 is determined from the calibration gas 4 supplied to the working chamber 3 .

For this purpose, in a first block 16, an empty residual gas spectrum of a vacuum in the working chamber 3 and preferably an empty chamber pressure are determined.

In a second block 17 , at least one individual gas 5 is supplied to the vacuum of the working chamber 3 by means of the dosing devices 8 until a stable chamber pressure is reached, which is preferably ten times greater than the empty chamber pressure from the block 16 .

A calibration residual gas spectrum 15 is determined in a third block 18 .

In a fourth block 19, a difference spectrum between the calibration residual gas spectrum 15 and the empty residual gas spectrum is determined.

In a fifth block 20, the difference spectrum is standardized to a base value, from which the standard spectrum 14 results. In the exemplary embodiment, the base value is preferably calculated from the stable chamber pressure reached at the end of block 17, from which the empty chamber pressure is subtracted, by dividing the difference between the chamber pressure and the empty chamber pressure by the standard pressure.

In a sixth block 21, a relative spectral sensitivity of the residual gas analysis method is determined from the standard spectrum 14 by comparing the standard spectrum 14 with a reference standard spectrum, which was determined using a reference residual gas analysis method that was created with the same calibration gas 4. Provision can also be made for only individual spectral ranges of the standard spectrum 14 to be compared with corresponding spectral ranges of the reference standard spectrum in order to determine the relative spectral sensitivity.

In particular, provision can be made for the standard spectrum 14 and the reference standard spectrum to be divided by one another.

In the present exemplary embodiment, the calibration gas 4 is mixed from a plurality of individual gases 5 for an advantageously homogeneous distribution of the molecular components of the calibration gas 4 .

In the present exemplary embodiment, the three individual gases 5 are supplied to the vacuum of the working chamber 3 in such a way that the pressure in the working chamber 3 is incrementally increased by the multiple metering devices 8 until the desired chamber pressure is reached. Each pressure increment results from the supply of one of the several individual gases 8 by means of the metering devices 8.

It is particularly advantageous to design the blocks in the in 5 presented chronological order.

6 shows a basic representation of a standard spectrum 14 which was determined using a residual gas analysis method which was calibrated using the method according to the invention.

That in the 6 The standard spectrum 14 shown has a first characteristic range 22 which includes molecular masses between 1 and 44 atomic mass units.

The standard spectrum 14 shown also includes a second characteristic range 23, which includes molecular masses between 45 and 100 atomic mass units.

The standard spectrum 14 shown also has a third characteristic range 24 which includes molecular masses between 101 and 200 atomic mass units.

The first identification region 22 includes water as well as relatively light molecular species.

The second characteristic range 23 includes so-called light hydrocarbons or LHCs. The third characteristic range 24 thus includes molecular weights of so-called heavy hydrocarbons or HHCs.

In the present exemplary embodiment, integral values are determined from the first characteristic range 22, the second characteristic range 23 and the third characteristic range 24, which are compared with reference integral values of the same characteristic ranges of a reference standard spectrum.

Alternatively and/or additionally, structure factors can also be determined in the characteristic ranges, which are compared with reference structure factors of the same characteristic ranges of a reference standard spectrum.

In the present exemplary embodiment, the residual gas analysis method is mass spectrometry. Alternatively it can be provided that the residual gas analysis method is an X-ray photoelectron spectroscopy.

The present exemplary embodiment is to be understood in such a way that it discloses both the method according to the invention and the device according to the invention, the system according to the invention and an exemplary projection exposure system as well as the use of a suitable calibration substance.

However, the use of the device according to the invention, the method according to the invention and the system according to the invention is not restricted to being used for projection exposure systems. The method according to the invention, the device according to the invention and the system according to the invention are suitable for determining the residual gases of different working chambers or systems and materials located therein, the exemplary embodiment is to be understood accordingly.

Reference List

1

contraption

2

Residual gas analysis device

3

working chamber

4

calibration gas

5

single gas

6

container

7

calibration substance

8th

dosing device

9

supply line

10

vacuum device

11

pressure gauge

12

control dosing device

13

shut-off dosing device

14

standard spectrum

15

Calibration residual gas spectrum

15a

single gas peak

16

first block

17

second block

18

third block

19

fourth block

20

Fifth block

21

sixth block

22

First identification area

23

Second identification area

24

Third identification area

100

projection exposure system

102

wafers

103

lighting system

104

reticle stages

105

reticle

106

wafer holder

107

projection lens

108

optical element

109

version

111

projection beam

140

lens body

400

projection exposure system

401

lighting system

402

radiation source

403

optics

404

object field

405

object level

406

reticle

407

reticle holder

408

projection optics

409

image field

410

picture plane

411

wafers

412

wafer holder

413

EUV radiation

414

intermediate focal plane

415

field facet mirror

416

pupil facet mirror

417

optical assembly

418

mirror

419

mirror

420

mirror

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102019203412 A1 [0016]

Claims (38)

Method for calibrating a residual gas analysis method for determining a residual gas in a vacuum in a working chamber (3), according to which a composition of a residual gas is characterized by a residual gas spectrum using the residual gas analysis method, characterized in that a calibration gas (4) is added to the vacuum in the working chamber (3) is supplied, which has a molecular mass occurrence which at least approximately comprises at least an expected molecular mass occurrence of the residual gas, and a calibration residual gas spectrum (15) is determined from the calibration gas (4) supplied to the working chamber (3). procedure after claim 1 , characterized in that an empty residual gas spectrum of the vacuum of the working chamber (3) is determined. Procedure according to one of Claims 1 or 2 , characterized in that a standard spectrum (14) for the residual gas analysis method is determined by determining a differential spectrum between the calibration residual gas spectrum (15) and the empty residual gas spectrum. procedure after claim 3 , characterized in that the differential spectrum is normalized to a base value. procedure after claim 3 or 4 , characterized in that a relative spectral sensitivity of the residual gas analysis method is determined by comparing, preferably dividing, the standard spectrum (14) of the residual gas analysis method with a reference standard spectrum of a reference residual gas analysis method that was created with the same calibration gas (4). Procedure according to one of Claims 1 until 5 , characterized in that the calibration gas (4) consists of an individual gas (5) or is mixed from several individual gases (5). procedure after claim 6 , characterized in that at least one individual gas (5) is formed by outgassing at least one calibration substance (7), preferably a liquid. Procedure according to one of Claims 1 until 7 , characterized in that the calibration gas (4) is supplied to the working chamber (3) by at least one controllable and/or regulatable dosing device (8). procedure after claim 8 , characterized in that for mixing the calibration gas (4) from several individual gases (5) several dosing devices (8) are provided in order to meter the individual gases (5) to the vacuum of the working chamber (3). procedure after claim 8 or 9 , characterized in that a chamber pressure in the working chamber (3) is adjusted by means of the dosing device (8). procedure after claim 10 , characterized in that several individual gases (5) are supplied to the vacuum of the working chamber (3) to form the calibration gas (4) in such a way that the pressure in the working chamber (3) is incrementally increased by several dosing devices (8) until the chamber pressure is reached is, each pressure increment resulting from the supply of one of the several individual gases (5). Procedure according to one of Claims 1 until 11 , characterized in that the calibration gas (4) has molecules with a molecular mass of 1 to 1024 atomic mass units, preferably 1 to 512 atomic mass units, more preferably 1 to 200 atomic mass units. Procedure according to one of Claims 1 until 12 , characterized in that the calibration gas (4) comprises hydrocarbons and/or water, preferably 1 to 1024 atomic mass units, more preferably with a molecular mass of 1 to 512 atomic mass units and particularly preferably 1 to 200 atomic mass units. Procedure according to one of Claims 5 until 13 , characterized in that an integral value of at least one characteristic range (22,23,24) of the standard spectrum (14) is determined and compared with a reference integral value of the same characteristic range (22,23,24) of the reference standard spectrum. procedure after Claim 14 , characterized in that several characteristic ranges (22, 23, 24) are provided and the characteristic ranges (22, 23, 24) do not overlap. procedure after Claim 14 or 15 , characterized in that a first characteristic range (22) comprises molecular masses between 1 and 34 to 54, preferably between 1 and 44, atomic mass units. Procedure according to one of Claims 14 until 16 , characterized in that a second characteristic range (23) molecular weights between 35 to 55 and 90 to 110, preferably between 45 and 100, atomic mass units. Procedure according to one of Claims 14 until 17 , characterized in that a third characteristic range (24) comprises molecular masses between 91 to 111 and 190 to 210, preferably between 101 and 200, atomic mass units. Procedure according to one of Claims 1 until 18 , characterized in that the residual gas analysis method is mass spectrometry and/or X-ray photoelectron spectroscopy. Device (1) for supplying a calibration gas (1) to a vacuum in a working chamber (3) for calibrating a residual gas analysis device (2) for determining a residual gas spectrum of a residual gas in the vacuum, characterized in that the calibration gas (4) consists of a single gas (5 ) or the device (1) mixes the calibration gas (4) from several individual gases (5), the device (1) having at least one container (6) for receiving at least one calibration substance (7) which is an individual gas (5). provides at least one metering device (8) for metering the individual gas (5) located in the container (6), and at least one supply line (9) from the container (6) to the working chamber (3). device after claim 20 , characterized in that the at least one supply line (9) is connected to the working chamber (3) in a vacuum-tight manner. Device (1) after claim 20 or 21 , characterized in that the device (1) is set up to determine a calibration residual gas spectrum (15) from the calibration gas (4) supplied to the working chamber (3) and/or the device (1), preferably with the residual gas analysis device (2) connected, interface for receiving the data of a calibration residual gas spectrum (15). Device (1) according to one of claims 20 until 22 , characterized in that a chamber pressure in the working chamber (3) can be adjusted by means of the at least one dosing device (8). Device (1) after Claim 23 , characterized in that a computing device is provided which is set up to determine a standard spectrum (14) by subtracting an empty residual gas spectrum of the vacuum of the working chamber (3) from the calibration residual gas spectrum (15) before the calibration gas (4) is supplied and is divided by a base value, which preferably results from a difference between the chamber pressure and an empty chamber pressure, which is divided by a standard pressure. Device (1) after Claim 24 , characterized in that a reference computing device is provided in order to compare the standard spectrum (14) with standard spectra of other residual gas analysis devices and/or a reference standard spectrum of a reference residual gas analysis device. Device (1) according to one of claims 20 until 25 , characterized in that the at least one calibration substance (7) is a liquid and the individual gas (5) has outgassed from the calibration substance (7). Device (1) according to one of claims 20 until 26 , characterized in that the at least one calibration substance (7) is a liquid hydrocarbon and/or a mixture of liquid hydrocarbons and the individual gas (5) is outgassed from the calibration substance (7). Device (1) according to one of claims 20 until 26 , characterized in that the at least one calibration substance (7) is a gas. Device (1) according to one of claims 20 until 26 , characterized in that the at least one calibration substance (7) is a solid and the individual gas (5) has outgassed from the calibration substance (7). Device (1) according to one of claims 20 until 29 , characterized in that the at least one calibration substance (7) has molecules with a molecular mass of 1 to 1000 atomic mass units, preferably 1 to 200 atomic mass units. Device (1) according to one of claims 20 until 30 , characterized in that the at least one calibration substance (7) comprises hydrocarbons and/or water with a molecular mass of 1 to 1000 atomic mass units, preferably 1 to 200 atomic mass units. Device (1) according to one of claims 20 until 31 , characterized in that the calibration gas (4) is chemically inert. Device (1) according to one of claims 20 until 32 , characterized in that the at least one individual gas (5) has at least approximately exclusively molecules from the calibration substance (7) and fragments thereof. Device (1) according to one of claims 20 until 33 , characterized in that the working chamber (3) is set up to accommodate a projection exposure system (100, 400) for semiconductor lithography with an illumination system (103, 401) with a radiation source (402) and an optical system (107, 403, 408), which has at least one optical element (415, 416, 418, 419, 420, 108). Calibration substance (7) for use in a device (1) according to one of claims 20 until 34 . System for forming a vacuum environment, having a working chamber (3), a vacuum device (10) for generating a vacuum in the working chamber (3), a pressure measuring device (11) for determining a chamber pressure in the working chamber (3) and a residual gas analysis device (2) for determining a residual gas spectrum of a residual gas in the vacuum, characterized in that a device (1) according to one of claims 20 until 34 is provided in order to calibrate the residual gas analysis device (2) for determining the residual gas spectrum in the vacuum. system after Claim 36 , characterized in that the working chamber (3) is designed to accommodate at least part of a projection exposure system (100.400). Projection exposure system (100, 400) for semiconductor lithography, with an illumination system (103, 401) with a radiation source (402) and an optical system (107, 403, 408) which has at least one optical element (415, 416, 418, 419, 420 , 108), wherein at least one of the optical elements (415, 416, 418, 419, 420, 108) is arranged in a working chamber (3) having a vacuum, residual gases in the vacuum in the working chamber (3) being analyzed using a residual gas analysis method be determined, which with a method according to one of Claims 1 until 19 is calibrated and / or a device (1) according to one of claims 20 until 34 is provided in order to calibrate a residual gas analysis device (2) for determining a residual gas spectrum in the working chamber (3).

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