(19)
(11)EP 2 758 981 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
17.06.2020 Bulletin 2020/25

(21)Application number: 12766627.9

(22)Date of filing:  19.09.2012
(51)International Patent Classification (IPC): 
G03F 7/20(2006.01)
H01J 37/304(2006.01)
H01J 37/317(2006.01)
G01N 33/00(2006.01)
(86)International application number:
PCT/EP2012/068444
(87)International publication number:
WO 2013/041569 (28.03.2013 Gazette  2013/13)

(54)

METHOD AND APPARATUS FOR PREDICTING A GROWTH RATE OF DEPOSITED CONTAMINANTS

VERFAHREN UND GERÄT ZUR VORHERSAGE DER WACHSTUMSRATE ABGESCHIEDENER VERUNREINIGUNGEN

PROCÉDÉ ET APPAREIL POUR PRÉDIRE LE TAUX DE CROISSSANCE DÛ À LA DÉPOSITION DE CONTAMINANT


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 19.09.2011 US 201161536295 P

(43)Date of publication of application:
30.07.2014 Bulletin 2014/31

(73)Proprietor: ASML Netherlands B.V.
5504 DR Veldhoven (NL)

(72)Inventor:
  • SMITS, Marc
    NL-2641 AK Pijnacker (NL)

(74)Representative: Peters, John Antoine et al
ASML Netherlands BV Corporate Intellectual Property De Run 6501 P.O. Box 324
5500 AH Veldhoven
5500 AH Veldhoven (NL)


(56)References cited: : 
WO-A1-2009/012919
  
  • K. MURAKAMI ET AL: "Contamination study on EUV exposure tools using SAGA light source (SAGA-LS)", PROCEEDINGS OF SPIE, vol. 7636, 11 March 2010 (2010-03-11), pages 76361U-76361U-7, XP055046236, ISSN: 0277-786X, DOI: 10.1117/12.846676
  
Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


Description

BACKGROUND OF THE INVENTION


1. Field of the Invention



[0001] The invention relates to a growth of deposited contaminants in processing systems, and in particular to a method and an apparatus for predicting a growth rate of deposited contaminants resulting from deposition of gaseous contaminants outgassed from a substance undergoing processing by one or more radiation beams. The invention also relates to a lithography system comprising a resist characterization system and a method for determining suitability of a resist for use in a lithography system.

2. Description of the Related Art



[0002] The desire of the semiconductor industry to manufacture ever smaller device structures, for example for use in integrated circuits (ICs), drives the development of lithography systems using very low wavelengths. Examples of such systems include but are not limited to extreme ultraviolet (EUV) lithography systems and charged particle lithography systems which use electron or ion beams to provide a pattern onto a target substrate surface, as may be known from WO2009012919.

[0003] Components within lithography systems are susceptible to contaminants that are progressively deposited on their surfaces during operation of the lithography system. In particular, contaminants may be formed by reaction of molecular fragments that are stuck on surfaces of the system under the influence of radiation within the lithography system. For example, under irradiation with EUV or charged particle beams, gaseous hydrocarbons may form a layer of carbon on exposed surfaces of system components. The result of the deposition of the gaseous compounds on the surfaces of system components is that the reliability and/or operational accuracy of the lithography system decreases with time. Eventually, the lithography system is incapable of operating within preset requirements, and the malfunctioning components need to be cleaned or replaced. However, both cleaning and replacement of components is time-consuming and expensive, and results in a significant increase in downtime of the lithography system.

[0004] A significant source of gaseous hydrocarbons in lithography systems is the resist layer that is placed on top of a substrate surface to be exposed and is subsequently exposed to radiation, e.g. EUV or charged particles, such as electrons. A suitable resist may be selected to limit the contamination in a lithography system caused by molecular fragments ejected from a resist, in particular due to exposure of the resist to radiation beams. However, presently used methods for characterizing resists are labor intensive and time consuming.

[0005] Prior art document WO2009012919 A1 discloses a lithography system comprising a resist characterization system. Partial pressures of contaminating substances are determined based on the measured mass distribution and the residual gas pressure. The contamination potential is determined from the partial pressures.

[0006] K. Murakami et al., Contamination study on EUV exposure tools using SAGA light source (SAGA-LS), Proc. of SPIE, vol. 7636, 11 March 2000, pages 76361U-76361U-7 discloses the development of a contamination growth model.

BRIEF SUMMARY OF THE INVENTION



[0007] It is an object of the present invention to provide a method and an apparatus for characterizing a resist layer for use in a lithography system that can be easily applied in a limited period of time. For this purpose, the invention provides a lithography system according to claim 1, a method for determining suitability of a resist for use in a lithography system according to claim 6, a computer readable medium according to claim 13, a method for predicting a growth rate of deposited contaminants according to claim 14 and an apparatus for predicting a growth rate of deposited contaminants according to claim 15.

[0008] Conventional methods for measuring the effect of deposited contaminants focused on measuring the potential or risk of contamination, rather than computing a growth rate based on the measurements. A computed growth rate can then be compared directly to a maximum growth rate permitted for a particular lithography system. A model to convert a measured outgassing rate to a growth rate of deposited contaminants can be used to enable such a computation of deposited contaminant growth rate.

[0009] Using conventional methods, the outgas spectrum of a resist can show a high outgas rate of low mass molecular fragments, and result in an indication as a "high risk" resist type. However, a computed growth rate of deposited contaminants for this outgas rate may be below the maximum growth rate threshold for a lithography system and the resist may be acceptable for use in the system.

[0010] Conventional methods measuring outgas rate and comparing to a threshold level of out gassing may be suitable for lithography systems using optical elements such as mirrors and glass lenses which may be affected by very low levels of deposited contaminants. In charged particle lithography and inspection systems, the lenses are formed by apertures through which charged particle beams pass, and deposited contaminants generally only become a problem when the apertures dimensions are significantly reduced by deposits forming in the apertures. The growth rate of the deposits is more significant in charged particle systems for properly determining the suitability of a resist for use in the system.

[0011] Further aspects of the invention are described in the appended claims and in the following description of embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS



[0012] Various aspects of the invention will be further explained with reference to embodiments shown in the drawings wherein:

FIG. 1 shows a simplified schematic drawing of a lithography system according to an embodiment of the invention;

FIG. 2 schematically shows an embodiment of an apparatus for measuring a resist outgassing mass spectrum;

FIG. 3 shows a flow chart of a method of qualifying the suitability of a resist for use in a lithography system according to an embodiment of the invention;

FIG. 4 schematically shows an embodiment of an apparatus that may be used for forming a growth radiation induced deposition growth rate model;

FIG. 5a shows an exemplary camera image made in the apparatus of FIG. 4;

FIG. 5b shows an exemplary result of a mass spectrum measurement made within the apparatus of FIG. 4;

FIG. 5c schematically shows curves representing the growth rate as a function of contaminant partial pressure for different current densities; and

FIG. 6 schematically shows an embodiment of an apparatus for determining a lithography system geometry factor.


DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS



[0013] The following is a description of various embodiments of the invention, given by way of example only and with reference to the figures. The figures are not drawn to scale and merely intended for illustrative purposes.

[0014] Certain embodiments of the invention will be described with reference to a charged particle lithography system, in particular an electron beam lithography system. As a result, deposition of carbon is assumed to result from the use of electron beams, and the formation of such carbon layer under the influence of an electron beam will be referred to as electron beam induced deposition (EBID). The skilled person will understand that such carbon layers may also develop under the influence of other types of radiation, such as ion beam radiation and EUV-radiation.

[0015] Throughout the specification reference is made to a "resist". This expression should be understood to relate to a material that is sensitive to radiation, such as the types of materials commonly used in lithography systems for patterning a substrate such as a silicon wafer. The resist may be a positive resist in which the portion of the resist that is exposed to the radiation becomes soluble in a further development process. Alternatively, the resist may be a negative resist in which the resist portion exposed to radiation becomes insoluble in a further development process. A resist is generally applied in the form of a thin layer on top of the substrate to be exposed to transfer the pattern that is exposed onto it to the substrate on which it resides.

[0016] Throughout the specification reference is made to "resist outgassing". This expression refers to radiation (e.g. EUV, charged particle, etc.) induced release of gaseous compounds and/or molecular fragments by a resist.

[0017] FIG. 1 shows a simplified schematic drawing of a lithography system 10 that may be used in embodiments of the invention. The lithography system 10 comprises a radiation projection system 20 for projecting radiation onto a substrate, such as a wafer, to be processed. The radiation projection system 20 may include a beamlet generator 21 for generating a plurality of beamlets, a beamlet modulator 22 for patterning the beamlets to form modulated beamlets, and a beamlet projector 23 for projecting the modulated beamlets onto a surface of a target. The components within the radiation projection system 20 are typically arranged in a column and are usually referred to as the electron-optical column or optical column, but may also be simply referred to as the "column". The radiation projection system 20 may be arranged to project any kind of suitable radiation, for example the system 20 may project of charged particle beams, optical beams, or other types of beams.

[0018] The lithography system 10 further comprises a substrate transport system 30 for loading a substrate and positioning the substrate to be processed in the path of the charged particle beams. The system 10 may then further comprise a control system 40 for controlling the substrate transport system 30 to move the substrate with respect to the radiation projection system 20. The control system 40 may base the movement on position information obtained by measurements within the radiation projection system 20, for example by the use of interferometry.

[0019] The lithography system further comprises a resist characterization system 50. The resist characterization system 50 is arranged for determining whether or not a specific type of resist can be exposed by radiation within the lithography system 10. The resist characterization system 50 may be coupled to the substrate transport system 30, for example via a load lock unit 60. The load lock unit 60 may then transfer a substrate, such as a wafer, provided with a resist layer to the lithographic apparatus for lithographic exposure.

[0020] FIG. 2 schematically shows an embodiment of a resist characterization system 50. The resist characterization system 50 is arranged for measuring mass distribution of "outgassing" from the resist, i.e. gases emitted by the resist, particularly when exposed to a radiation beam. The apparatus 51 comprises a chamber 51 which may be pumped down to lower the pressure in the chamber using a pump system 52 known in the art. The apparatus 51 comprises a radiation source 53 for generating one or more radiation beams 54, a substrate 56 provided with a resist layer 57 on the surface, and a measurement device 59.

[0021] The resist layer 57 is exposed to the radiation beam(s) 54, and gaseous compounds originating from the resist layer 57 are measured with measurement device 59. The measurement device 59 may be a residual gas analyzer, for example a Microvision Residual Gas Analyzer of MKS Instruments. The measurement device 59 provides a resist outgas mass distribution. This results in a measured "fingerprint" of the resist layer 57 which may be used to predict the growth rate of outgassing contaminant deposition in the lithography system, as will be discussed in more detail with reference to FIG. 3.

[0022] FIG. 3 shows a flow chart of a method of qualifying the suitability of a resist for use in a lithography system according to an embodiment of the invention. The method will be described with reference to the resist characterization system 50 depicted in FIG. 2, although the method may be used in a different systems as well.

[0023] First, in action 101, the resist to be qualified is provided to the resist characterization system 50. The resist may be presented on a sample, for example a substrate such as a wafer. Alternatively, the resist may be put on a sample already present in the resist characterization system 50.

[0024] Then, in action 102, the resist is exposed by a radiation beam or beams. The radiation beam may comprises a plurality of beamlets. Preferably, the type of radiation used for the exposure corresponds to the type of radiation used in the lithography system in which the resist is to be used. Due to the radiation exposure, molecular fragments are released from the resist. The measurement device 59 measures the mass distribution of these molecular fragments in action 103.

[0025] The measurement results are then used to predict a growth rate of deposition in the lithography system in action 104. The prediction is based on the measurement results obtained in action 103. Additionally, a model 110 is used. The model is based on earlier measurements of radiation induced deposition caused by known molecular components, preferably using different radiation intensities. Further details with respect to the model 110 will be discussed with reference to FIGS. 4 and 5a-5c.

[0026] Preferably, the prediction of the growth rate is also based on a geometry factor 120 of the lithography system. The geometry factor is representative of the influence of the specific lithography system or type of lithography system on the growth rate of radiation induced deposition. The geometry factor may thus be different for different types of lithography systems. Further details with respect to obtaining a geometry factor of a lithography system will be discussed with reference to FIG. 6.

[0027] Finally, in action 105, the predicted growth rate of deposition in the lithography system is compared to a predetermined threshold growth rate value. Preferably, the predetermined threshold growth rate value corresponds to the maximum allowable growth rate in view of desired uptime requirements of the lithography system. If the predicted growth rate exceeds the predetermined threshold growth rate value, the resist is considered unsuitable for use in the lithography system, and thus rejected. If on the other hand, the predicted growth rate is below such predetermined threshold growth rate, the resist is considered suitable for use in the specific type of lithography system, and thus accepted.

[0028] This method of qualifying the suitability of a resist for use in a lithography system is relatively easy to perform and provides quick results without incurring high costs.

[0029] Embodiments of the method, or portions thereof, may be executed by a processor. The processor may be arranged to execute a computer program. Such computer program may be stored on a computer readable medium that can be loaded into a computer system comprising the processor.

[0030] Methods for qualifying the suitability of a resist for use in a lithography system are not limited to predicting contaminant growth rate due to exposure to radiation beams, but can also be used applied without or before exposure, to measure outgassing of contaminants due to elevated temperature and other factors and the resulting contaminant growth, these methods do not form part of the present invention.

[0031] The requirements for a resist may vary per type of lithography. For example, in EUV lithography, molecular fragments of elements and/or molecules that are difficult to remove by cleaning methods, such as molecules comprising and/or consisting of silicon, phosphor and sulphur, play a substantially equally important role as hydrocarbons. If a layer of only a few nanometers of non-cleanable residue is left on a mirror surface after cleaning, the quality of the optical properties of the mirror, in particular its reflectivity, is still reduced significantly. On the other hand, in the case of charged particle beam lithography, such as electron beam lithography, such "non-cleanable" molecules and/or elements play a less important role, since during the lifetime of an electron optical element, a much thicker layer of non-cleanable residue is acceptable. It has been found that transmission loss starts to play a role for a layer of residue with a thickness greater than 100 nm.

[0032] Furthermore, the surface properties of optical components in an EUV lithography system are very different from the surface properties of optical components in a charged particle beam lithography system. Generally, some molecular fragments that are not cleanable in an EUV lithography system may actually be removable in a charged particle beam lithography system.

[0033] FIG. 4 schematically shows an embodiment of an apparatus 200 that may be used for forming a radiation-induced deposition growth rate model for use in the procedure of FIG. 3. The apparatus 200 comprises a chamber 201 suitable for containing a vacuum, and which can be pumped down using a pump system 202, preferably provided with a controllable opening, for example comprising a valve 214. The chamber includes a controllable inlet 215, for example by means of a suitable valve, for allowing predetermined gaseous compounds into the chamber 201. The apparatus 200 further includes a radiation source 203, a sample holder 204 for positioning a sample 205 in the path of the radiation beam(s), a radiation conversion element 207, a camera 209 and a measurement device 210.

[0034] In the shown embodiment, the radiation source 203 is an electron source arranged for generating an electron beam in the direction of the sample 205, in FIG. 3 schematically denoted by the arrow 220. The sample 205 may take the form of an aperture plate, i.e. a plate provided with a plurality of through holes, such as used in a charged particle lithography system. This may be an aperture array or beam stop plate such as used in a charged particle beam lithography system, or may be a plate specially constructed for the test apparatus. The presence of the aperture plate results in creation of a plurality of electron beamlets, the pattern of which corresponds to the pattern of the apertures in the plate. The plurality of electron beamlets is schematically denoted by the dashed arrow 222. The remainder of the electron beam is blocked by the sample plate.

[0035] The camera 209 is provided with a radiation conversion element 207 arranged for using energy obtained by the impact of electrons onto the conversion element 207 to create and emit photons. An example of such conversion element 207 would be a YAG (Yttrium-Aluminum-Garnet) scintillator. The plurality of electron beamlets formed by the aperture plate impinge on the conversion element 207 and form a plurality of light spots with a pattern corresponding to the pattern of electron beamlets. The light spots are then registered by the camera 209.

[0036] The use of an aperture plate allows the registration of radiation induced deposition in-line without the need to remove the sample 205 for further analysis. Consequently, the amount as well as the growth rate of the radiation induced deposition can be monitored over longer consecutive periods of time. Monitoring the radiation induced deposition parameters with the camera 209 allows for direct feedback. Furthermore, there is no need for characterization after the measurement, although such post characterization may be performed for checking purposes.

[0037] The controllable inlet 215 is arranged to enable a controlled entry of predetermined gaseous compounds, such as molecular fragments. The measurement device 210 is arranged for measuring the mass of contaminants being formed due to the interaction between the electron beam/beamlets and the predetermined gaseous compounds. The measurement device 210 may be a mass spectrometer, for example a Microvision Residual Gas Analyzer of MKS Instruments.

[0038] The measurement device 210 is communicatively connected to a processor 211. The processor 211 is also communicatively connected to the camera 209. The processor 211 may be further communicatively connected to a memory 213. The memory 213 and the processor 211 may be part of a single computer system, but they may also be located at different locations. The processor is arranged to perform calculations that enable the formation of a model. More details regarding this model formation will be explained with reference to FIGS. 5a-5c.

[0039] FIG. 5a shows an exemplary camera image made in the apparatus of FIG. 4. The image shows a plurality of spots, which location corresponds to the location of the apertures in the aperture plate. The size of the spots varies as a result of radiation induced deposition clogging the apertures in the sample 205. The camera 209 is arranged to register the total transmission of (part of) the aperture plate 205. Due to the clogging of the apertures by contaminants (e.g. EBIDs), the transmission of beams through the sample aperture plate will decrease over time as the deposited contaminants build up and reduce the diameter of the apertures. By measuring the transmission loss of the aperture plate over time, the growth rate of the radiation induced deposition may be calculated.

[0040] FIG. 5b shows an exemplary result of a mass spectrum measurement with the measurement device 210, in this particular case a residual gas analyzer (RGA). In this example, the assumption is made that particles with a mass of 45 and higher play a role in radiation induced deposition. On the basis of the mass spectrum measured with the measurement device 210 a partial pressure can be derived by summation. The use of such summation is relatively easy and particularly suitable for use with lithography systems that are less sensitive to non-cleanable molecular fragments, such as charged particle lithography systems. FIG. 5c schematically shows curves representing the growth rate as a function of contaminant partial pressure for different current densities. In this specific example, curves I, II and III correspond to electron beam current densities 1 A/m2, 30 A/m2, and 45 A/m2 respectively. The model is formed on the basis of growth rate curves, such as curves I, II and III. The forming of the model may be executed by a processor, such as processor 211 in FIG. 4. The processor may be arranged to execute a computer program. Such computer program may comprise elements that allow for performing a method of forming the model. The computer program may be stored on a computer readable medium that can be loaded into a computer system comprising the processor.

[0041] FIG. 6 schematically shows an embodiment of an apparatus 300 for determining a lithography system geometry factor. The apparatus 300 comprises a chamber 301 which can be pumped down using a pump system 302. The apparatus 300 comprises a radiation source 303 for generating one or more radiation beams 320, a sample holder for positioning a sample 305 in the path of the radiation beam(s), a tape 307 that can be moved in a direction substantially perpendicular to the radiation emitted by the radiation source and a measurement device 310.

[0042] The tape 307 is provided with a resist layer 308 (shown only on a portion of the tape, although it may be applied to an entire surface of the tape), preferably a resist of which mass spectrum measurements are taken to develop the model. The resist layer 308 is to be exposed in a way that mimics the exposure in a specific type of lithography system. For this reason, the tape 307 is continuously transported such that the radiation dose applied to the resist substantially corresponds to the dose such resist would receive in the type of lithography system under investigation. For transportation, the tape may be transferred, for example by means of two spools 312a, 312b as shown in FIG. 6. However, alternative methods for transferring the tape 307 are possible as well. To reduce thermal influences that will not take place within the lithographic system under investigation, the tape 307 may be suitably cooled by means of a cooling element 314.

[0043] Additionally, the sample 305 preferably corresponds to the most critical element in the lithography system under investigation, and its size and shape, as well as its position with respect to the resist, are preferably substantially identical to the size, shape and position of such element within the lithography apparatus under investigation.

[0044] In the shown example, the apparatus 300 is arranged for mimicking a multi-beamlet electron beam lithography apparatus. Therefore, the sample 305 takes the form of an aperture array. The actual exposure parameters may now be mimicked by choosing a suitable beam energy and a suitable transport speed of the tape 307 by rotating the spools 312a, 312b at a suitable rotation speed.

[0045] By mimicking the energy of the radiation impinging on the resist in combination with the geometry of the most vulnerable portion of the lithographic system under investigation, a reliable measurement of the resist outgassing may be obtained. The outgassing may be measured with the measurement device 310. After an exposure period that corresponds to a large number of wafer exposures in the lithography system under investigation, for example about 1000 or more, the sample 305 is removed from the apparatus 300 and the amount of radiation induced deposition is measured.

[0046] The apparatus 300 thus provides information on the influence of the geometry of the lithographic apparatus under investigation on the growth rate of radiation induced deposition, and is therefore referred to as the geometry factor. The geometry facture may improve the quality of the prediction of the radiation induced deposition growth rate in the lithography system. The geometry factor may be calculated using a processor communicatively coupled to the measurement device 310, for example the processor 211 depicted in FIG. 4.

[0047] The use of an apparatus 300 for determining a lithography system geometry factor is particularly useful for lithography system designs in which the final projection of the radiation onto the resist outgassing source, i.e. the substrate to be exposed, is executed by a lens system with a lens that is placed in very close proximity of the resist outgassing source. In terms of vacuum conductance, such projection system is extremely complex to model, and it is virtually impossible to obtain the actual pressure at locations within the projection system in a theoretical way. The apparatus 300 then enables determination of such pressures experimentally.

[0048] The invention has been described by reference to certain embodiments discussed above. It will be recognized that these embodiments are susceptible to various modifications and alternative forms well known to those of skill in the art without departing from the scope of the invention. Accordingly, although specific embodiments have been described, these are examples only and are not limiting upon the scope of the invention, which is defined in the accompanying claims.


Claims

1. A lithography system (10) comprising:

- a radiation projection system (20) for projecting radiation onto a substrate (56);

- a substrate transport system (30) for loading and positioning the substrate to be processed in the path of the projected radiation;

- a control system (40) for controlling the substrate transport system to move the substrate; and

- a resist characterization system (50) arranged for determining whether a specific type of resist is suitable to be exposed by radiation within the lithography system.

wherein the resist characterization system (50) is arranged for:

- exposing the resist (57) on a surface of the substrate with one or more radiation beams (54);

- measuring a mass distribution of molecular fragments emitted from the resist;

- using a growth rate model (110), based on earlier measurements of radiation induced deposition caused by known molecular fragments for different partial pressures;

- predicting a growth rate of deposited molecular fragments on the basis of the growth rate model of molecular fragments and the measured mass distribution of molecular fragments, and the deriving of a partial pressure on the basis of the measured mass distribution of molecular fragments; and

- comparing the predicted growth rate with a predetermined threshold growth rate, the threshold growth rate being related to a maximum allowable growth rate in the lithography system.


 
2. The system of claim 1, wherein the radiation takes the form of one or more charged particle beamlets, and wherein the earlier measurements of radiation induced deposition are performed for different current densities of the one or more charged particle beamlets.
 
3. The system of any one of the preceding claims, wherein the radiation projection system (20) comprises a beamlet generator (21) for generating a plurality of beamlets, a beamlet modulator (22) for patterning the beamlets to form modulated beamlets, and a beamlet projector (23) for projecting the modulated beamlets onto the surface of the substrate.
 
4. The system of any one of the preceding claims, wherein the resist characterization system (50) is coupled to the substrate transport system (30) for transferring the substrate to the lithographic system for lithographic exposure.
 
5. The system of any one of the preceding claims, wherein the resist characterization system (50) comprises a chamber (51), a pump system (52) arranged for pumping down the chamber to lower the pressure in the chamber; a radiation source (53) for generating the one or more radiation beams (54), the substrate (56) provided with a resist layer (57) on the surface, and a measurement device (59), comprising a residual gas analyzer.
 
6. A method for determining suitability of a resist for use in a lithography system (10), the method comprising:

- providing a substrate (56) having the resist (57) on a surface of the substrate;

- exposing the resist with one or more radiation beams (54);

- measuring a mass distribution of molecular fragments emitted from the resist;

- predicting a growth rate of deposited molecular fragments on the basis of a growth rate model of molecular fragments and the measured mass distribution of molecular fragments,
and the deriving of a partial pressure on the basis of the measured mass distribution of molecular fragments, the model based on earlier measurements of radiation induced deposition caused by known molecular fragments for different partial pressures; and

- comparing the predicted growth rate with a predetermined threshold growth rate, the threshold growth rate being related to a maximum allowable growth rate in the lithography system.


 
7. The method of claim 6, wherein the radiation takes the form of one or more charged particle beamlets, and wherein the earlier measurements of radiation induced deposition are performed for different current densities of the one or more charged particle beamlets.
 
8. The method of any one of claims 6-7, wherein predicting the growth rate of deposited molecular fragments is further based on a geometry factor, the geometry factor being representative of the influence of one or more properties of the lithography system.
 
9. The method of claim 8, wherein the geometry factor is representative of the influence of the geometry of the lithography system on the growth rate of the deposition.
 
10. The method of any one of claims 6-9, wherein the model includes growth rates for a plurality of different molecular fragments.
 
11. The method of any one of claims 6-10, wherein the model includes growth rates for different intensities of the radiation beam.
 
12. The method of any one of claims 6-11, wherein deriving the partial pressure comprises summation using the measured mass distribution of the molecular fragments.
 
13. A computer readable medium for performing, when executed by a processor, the method of determining suitability of a resist for use in a lithography system according to any one of claims 6-12.
 
14. A method for predicting a growth rate of deposited contaminants resulting from deposition of gaseous contaminants outgassed from a substance undergoing processing by one or more radiation beams, the method comprising:

- exposing the substance with the one or more radiation beams;

- measuring a mass distribution of molecules and molecular fragments of the contaminants emitted from the substance;

- predicting a growth rate of deposited molecules and molecular fragments of the contaminants on the basis of a growth rate model and the measured mass distribution of molecular fragments, and the deriving of a partial pressure on the basis of the measured mass distribution of molecular fragments, the model being based on earlier measurements of radiation induced deposition caused by known molecular fragments for different partial pressures; and

- comparing the predicted growth rate with a predetermined threshold growth rate, the threshold growth rate being related to a maximum allowable growth rate in a lithography system.


 
15. An apparatus for predicting a growth rate of deposited contaminants resulting from deposition of gaseous contaminants outgassed from a substance undergoing processing by one or more radiation beams, the apparatus comprising:

- a chamber (51);

- a pump system (52) arranged for pumping down the chamber to lower the pressure in the chamber;

- a radiation source (53) for generating the one or more radiation beams (54);

- a substrate (56) provided with the substance (57) on a surface of the substrate;

- a measurement device (59) for measuring a mass distribution of molecular fragments of the gaseous contaminants outgassed from a substance; and

- a processor configured to predict a growth rate of the deposited contaminants on the basis of a growth rate model of molecular fragments and the measured mass distribution of molecular fragments, and the deriving of a partial pressure on the basis of the measured mass distribution of molecular fragments, the model being based on earlier measurements of radiation induced deposition caused by known molecular fragments for different partial pressures.


 


Ansprüche

1. Ein Lithographiesystem (10), das Folgendes beinhaltet:

- ein Strahlungsprojektionssystem (20) zum Projizieren von Strahlung auf ein Substrat (56);

- ein Substrattransportsystem (30) zum Laden und Positionieren des zu verarbeitenden Substrats in dem Weg der projizierten Strahlung;

- ein Steuersystem (40) zum Steuern des Substrattransportsystems, um das Substrat zu bewegen; und

- ein Photolackcharakterisierungssystem (50), das eingerichtet ist, um zu bestimmen, ob eine spezifische Art von Photolack zur Belichtung durch Strahlung innerhalb des Lithographiesystems geeignet ist,

wobei das Photolackcharakterisierungssystem (50) für Folgendes eingerichtet ist:

- Belichten des Photolacks (57) auf einer Oberfläche des Substrats mit einem oder mehreren Strahlungsstrahlen (54);

- Messen einer Massenverteilung von dem Photolack emittierter molekularer Fragmente;

- Verwenden eines Wachtumsratenmodells (110) auf der Basis früherer Messungen strahlungsinduzierter, durch bekannte molekulare Fragmente bewirkter Abscheidung für unterschiedliche Teildrücke;

- Vorhersagen einer Wachstumsrate abgeschiedener molekularer Fragmente auf der Basis des Wachstumsratenmodells molekularer Fragmente und der gemessenen Massenverteilung molekularer Fragmente und des Ableitens eines Teildrucks auf der Basis der gemessenen Massenverteilung molekularer Fragmente; und

- Vergleichen der vorhergesagten Wachstumsrate mit einer vorgegebenen Schwellenwert-Wachstumsrate, wobei die Schwellenwert-Wachstumsrate mit einer maximalen erlaubten Wachstumsrate in dem Lithographiesystem in Beziehung steht.


 
2. System gemäß Anspruch 1, wobei die Strahlung die Form eines oder mehrerer Ladungsträgerteilstrahlen annimmt und wobei die früheren Messungen strahlungsinduzierter Abscheidung für unterschiedliche Stromdichten des einen oder der mehreren Ladungsträgerteilstrahlen durchgeführt werden.
 
3. System gemäß einem der vorhergehenden Ansprüche, wobei das Strahlungsprojektionssystem (20) einen Teilstrahlerzeuger (21) zum Erzeugen einer Vielzahl von Teilstrahlen, einen Teilstrahlmodulator (22) zum Versehen der Teilstrahlen mit einem Muster, um modulierte Teilstrahlen zu bilden, und einen Teilstrahlprojektor (23) zum Projizieren der modulierten Teilstrahlen auf die Oberfläche des Substrats beinhaltet.
 
4. System gemäß einem der vorhergehenden Ansprüche, wobei das Photolackcharakterisierungssystem (50) mit dem Substrattransportsystem (30) gekoppelt ist, um das Substrat zur lithographischen Belichtung an das lithographische System zu transferieren.
 
5. System gemäß einem der vorhergehenden Ansprüche, wobei das Photolackcharakterisierungssystem (50) eine Kammer (51), ein Pumpsystem (52), das eingerichtet ist, um die Kammer zum Absenken des Drucks in der Kammer abzupumpen, eine Strahlungsquelle (53) zum Erzeugen des einen oder der mehreren Strahlungsstrahlen (54), das auf der Oberfläche mit einer Photolackschicht (57) versehene Substrat (56) und eine Messvorrichtung (59), die einen Restgasanalysator beinhaltet, beinhaltet.
 
6. Ein Verfahren zum Bestimmen der Eignung eines Photolacks zur Verwendung in einem Lithographiesystem (10), wobei das Verfahren Folgendes beinhaltet:

- Bereitstellen eines Substrats (56), das auf einer Oberfläche des Substrats den Photolack (57) aufweist;

- Belichten des Photolacks mit einem oder mehreren Strahlungsstrahlen (54);

- Messen einer Massenverteilung von dem Photolack emittierter molekularer Fragmente;

- Vorhersagen einer Wachstumsrate abgeschiedener molekularer Fragmente auf der Basis eines Wachstumsratenmodells molekularer Fragmente und der gemessenen Massenverteilung molekularer Fragmente und des Ableitens eines Teildrucks auf der Basis der gemessenen Massenverteilung molekularer Fragmente, wobei das Modell auf früheren Messungen strahlungsinduzierter, durch bekannte molekulare Fragmente bewirkter Abscheidung für unterschiedliche Teildrücke basiert; und

- Vergleichen der vorhergesagten Wachstumsrate mit einer vorgegebenen Schwellenwert-Wachstumsrate, wobei die Schwellenwert-Wachstumsrate mit einer maximalen erlaubten Wachstumsrate in dem Lithographiesystem in Beziehung steht.


 
7. Verfahren gemäß Anspruch 6, wobei die Strahlung die Form eines oder mehrerer Ladungsträgerteilstrahlen annimmt und wobei die früheren Messungen strahlungsinduzierter Abscheidung für unterschiedliche Stromdichten des einen oder der mehreren Ladungsträgerteilstrahlen durchgeführt werden.
 
8. Verfahren gemäß einem der Ansprüche 6-7, wobei das Vorhersagen der Wachstumsrate abgeschiedener molekularer Fragmente ferner auf einem Geometriefaktor basiert, wobei der Geometriefaktor den Einfluss einer oder mehrerer Eigenschaften des Lithographiesystems darstellt.
 
9. Verfahren gemäß Anspruch 8, wobei der Geometriefaktor den Einfluss der Geometrie des Lithographiesystems auf die Wachstumsrate der Abscheidung darstellt.
 
10. Verfahren gemäß einem der Ansprüche 6-9, wobei das Modell Wachstumsraten für eine Vielzahl unterschiedlicher molekularer Fragmente umfasst.
 
11. Verfahren gemäß einem der Ansprüche 6-10, wobei das Modell Wachstumsraten für unterschiedliche Intensitäten des Strahlungsstrahls umfasst.
 
12. Verfahren gemäß einem der Ansprüche 6-11, wobei das Ableiten des Teildrucks eine Summierung unter Verwendung der gemessenen Massenverteilung der molekularen Fragmente beinhaltet.
 
13. Ein computerlesbares Medium zum Durchführen, wenn durch einen Prozessor ausgeführt, des Verfahrens des Bestimmens der Eignung eines Photolacks zur Verwendung in einem Lithographiesystem gemäß einem der Ansprüche 6-12.
 
14. Ein Verfahren zum Vorhersagen einer Wachstumsrate abgeschiedener Verunreinigungen, die aus der Abscheidung gasförmiger Verunreinigungen resultieren, welche von einer eine Verarbeitung durch einen oder mehrere Strahlungsstrahlen durchlaufenden Substanz ausgegast werden, wobei das Verfahren Folgendes beinhaltet:

- Belichten der Substanz mit dem einen oder den mehreren Strahlungsstrahlen;

- Messen einer Massenverteilung von Molekülen und molekularen Fragmenten der von der Substanz emittierten Verunreinigungen;

- Vorhersagen einer Wachstumsrate abgeschiedener Moleküle und molekularer Fragmente der Verunreinigungen auf der Basis eines Wachstumsratenmodells und der gemessenen Massenverteilung molekularer Fragmente und des Ableitens eines Teildrucks auf der Basis der gemessenen Massenverteilung molekularer Fragmente, wobei das Modell auf früheren Messungen strahlungsinduzierter, durch bekannte molekulare Fragmente bewirkter Abscheidung für unterschiedliche Teildrücke basiert; und

- Vergleichen der vorhergesagten Wachstumsrate mit einer vorgegebenen Schwellenwert-Wachstumsrate, wobei die Schwellenwert-Wachstumsrate mit einer maximalen erlaubten Wachstumsrate in einem Lithographiesystem in Beziehung steht.


 
15. Ein Gerät zum Vorhersagen einer Wachstumsrate abgeschiedener Verunreinigungen, die aus der Abscheidung gasförmiger Verunreinigungen resultieren, welche von einer eine Verarbeitung durch einen oder mehrere Strahlungsstrahlen durchlaufenden Substanz ausgegast werden, wobei das Gerät Folgendes beinhaltet:

- eine Kammer (51);

- ein Pumpsystem (52), das eingerichtet ist, um die Kammer zum Absenken des Drucks in der Kammer abzupumpen;

- eine Strahlungsquelle (53) zum Erzeugen des einen oder der mehreren Strahlungsstrahlen (54);

- ein Substrat (56), das auf einer Oberfläche des Substrats mit der Substanz (57) versehen ist;

- eine Messvorrichtung (59) zum Messen einer Massenverteilung molekularer Fragmente der gasförmigen Verunreinigungen, die von einer Substanz ausgegast werden; und

- einen Prozessor, der zum Vorhersagen einer Wachstumsrate der abgeschiedenen Verunreinigungen auf der Basis eines Wachstumsratenmodells molekularer Fragmente und der gemessenen Massenverteilung molekularer Fragmente und des Ableitens eines Teildrucks auf der Basis der gemessenen Massenverteilung molekularer Fragmente konfiguriert ist, wobei das Modell auf früheren Messungen strahlungsinduzierter, durch bekannte molekulare Fragmente bewirkter Abscheidung für unterschiedliche Teildrücke basiert.


 


Revendications

1. Un système de lithographie (10) comprenant :

- un système de projection de rayonnement (20) pour projeter un rayonnement sur un substrat (56) ;

- un système de transport de substrat (30) pour charger et positionner le substrat devant être traité dans la trajectoire du rayonnement projeté ;

- un système de commande (40) pour commander le système de transport de substrat afin de déplacer le substrat ; et

- un système de caractérisation de réserve (50) agencé pour déterminer si un type spécifique de réserve peut convenir pour une exposition par rayonnement au sein du système de lithographie,

dans lequel le système de caractérisation de réserve (50) est agencé pour :

- l'exposition de la réserve (57) sur une surface du substrat avec un ou plusieurs faisceaux de rayonnement (54) ;

- le mesurage d'une distribution des masses de fragments moléculaires émis depuis la réserve ;

- l'utilisation d'un modèle de taux de croissance (110), basé sur des mesures antérieures de dépôt induit par rayonnement causé par des fragments moléculaires connus pour différentes pressions partielles ;

- la prédiction d'un taux de croissance de fragments moléculaires déposés sur la base du modèle de taux de croissance de fragments moléculaires et de la distribution des masses de fragments moléculaires mesurée, et de la dérivation d'une pression partielle sur la base de la distribution des masses de fragments moléculaires mesurée ; et

- la comparaison du taux de croissance prédit avec un taux de croissance seuil prédéterminé, le taux de croissance seuil étant relatif à un taux de croissance admissible maximal dans le système de lithographie.


 
2. Le système de la revendication 1, dans lequel le rayonnement prend la forme d'un ou de plusieurs mini-faisceaux de particules chargées électriquement, et dans lequel les mesures antérieures de dépôt induit par rayonnement sont réalisées pour différentes densités de courant des un ou plusieurs mini-faisceaux de particules chargées électriquement.
 
3. Le système de n'importe laquelle des revendications précédentes, dans lequel le système de projection de rayonnement (20) comprend un générateur de mini-faisceaux (21) pour générer une pluralité de mini-faisceaux, un modulateur de mini-faisceaux (22) pour conformer les mini-faisceaux selon un motif afin de former des mini-faisceaux modulés, et un projecteur de mini-faisceaux (23) pour projeter les mini-faisceaux modulés sur la surface du substrat.
 
4. Le système de n'importe laquelle des revendications précédentes, dans lequel le système de caractérisation de réserve (50) est couplé au système de transport de substrat (30) pour transférer le substrat au système lithographique pour exposition lithographique.
 
5. Le système de n'importe laquelle des revendications précédentes, dans lequel le système de caractérisation de réserve (50) comprend une chambre (51), un système de pompe (52) agencé pour évacuer par pompage la chambre afin d'abaisser la pression dans la chambre, une source de rayonnement (53) pour générer les un ou plusieurs faisceaux de rayonnement (54), le substrat (56) pourvu d'une couche de réserve (57) sur la surface, et un dispositif de mesure (59), comprenant un analyseur de gaz résiduels.
 
6. Un procédé pour déterminer si une réserve peut convenir pour une utilisation dans un système de lithographie (10), le procédé comprenant :

- la fourniture d'un substrat (56) ayant la réserve (57) sur une surface du substrat ;

- l'exposition de la réserve avec un ou plusieurs faisceaux de rayonnement (54) ;

- le mesurage d'une distribution des masses de fragments moléculaires émis depuis la réserve ;

- la prédiction d'un taux de croissance de fragments moléculaires déposés sur la base d'un modèle de taux de croissance de fragments moléculaires et de la distribution des masses de fragments moléculaires mesurée, et de la dérivation d'une pression partielle sur la base de la distribution des masses de fragments moléculaires mesurée, le modèle étant basé sur des mesures antérieures de dépôt induit par rayonnement causé par des fragments moléculaires connus pour différentes pressions partielles ; et

- la comparaison du taux de croissance prédit avec un taux de croissance seuil prédéterminé, le taux de croissance seuil étant relatif à un taux de croissance admissible maximal dans le système de lithographie.


 
7. Le procédé de la revendication 6, dans lequel le rayonnement prend la forme d'un ou de plusieurs mini-faisceaux de particules chargées électriquement, et dans lequel les mesures antérieures de dépôt induit par rayonnement sont réalisées pour différentes densités de courant des un ou plusieurs mini-faisceaux de particules chargées électriquement.
 
8. Le procédé de n'importe laquelle des revendications 6 à 7, dans lequel la prédiction du taux de croissance de fragments moléculaires déposés est en sus basée sur un facteur de géométrie, le facteur de géométrie étant représentatif de l'influence d'une ou de plusieurs propriétés du système de lithographie.
 
9. Le procédé de la revendication 8, dans lequel le facteur de géométrie est représentatif de l'influence de la géométrie du système de lithographie sur le taux de croissance du dépôt.
 
10. Le procédé de n'importe laquelle des revendications 6 à 9, dans lequel le modèle inclut des taux de croissance pour une pluralité de différents fragments moléculaires.
 
11. Le procédé de n'importe laquelle des revendications 6 à 10, dans lequel le modèle inclut des taux de croissance pour différentes intensités du faisceau de rayonnement.
 
12. Le procédé de n'importe laquelle des revendications 6 à 11, dans lequel la dérivation de la pression partielle comprend une sommation en utilisant la distribution des masses des fragments moléculaires mesurée.
 
13. Un support lisible par ordinateur pour réaliser, lorsqu'exécuté par un processeur, le procédé consistant à déterminer si une réserve peut convenir pour une utilisation dans un système de lithographie selon n'importe laquelle des revendications 6 à 12.
 
14. Un procédé pour la prédiction d'un taux de croissance de contaminants déposés résultant du dépôt de contaminants gazeux dégazés depuis une substance soumise à un traitement par un ou plusieurs faisceaux de rayonnement, le procédé comprenant :

- l'exposition de la substance avec les un ou plusieurs faisceaux de rayonnement ;

- le mesurage d'une distribution des masses de molécules et fragments moléculaires des contaminants émis depuis la substance ;

- la prédiction d'un taux de croissance de molécules et fragments moléculaires déposés des contaminants sur la base d'un modèle de taux de croissance et de la distribution des masses de fragments moléculaires mesurée, et de la dérivation d'une pression partielle sur la base de la distribution des masses de fragments moléculaires mesurée, le modèle étant basé sur des mesures antérieures de dépôt induit par rayonnement causé par des fragments moléculaires connus pour différentes pressions partielles ; et

- la comparaison du taux de croissance prédit avec un taux de croissance seuil prédéterminé, le taux de croissance seuil étant relatif à un taux de croissance admissible maximal dans un système de lithographie.


 
15. Un appareil pour la prédiction d'un taux de croissance de contaminants déposés résultant du dépôt de contaminants gazeux dégazés depuis une substance soumise à un traitement par un ou plusieurs faisceaux de rayonnement, l'appareil comprenant :

- une chambre (51) ;

- un système de pompe (52) agencé pour évacuer par pompage la chambre afin d'abaisser la pression dans la chambre ;

- une source de rayonnement (53) pour générer les un ou plusieurs faisceaux de rayonnement (54) ;

- un substrat (56) pourvu de la substance (57) sur une surface du substrat ;

- un dispositif de mesure (59) pour mesurer une distribution des masses de fragments moléculaires des contaminants gazeux dégazés depuis une substance ; et

- un processeur configuré pour la prédiction d'un taux de croissance des contaminants déposés sur la base d'un modèle de taux de croissance de fragments moléculaires et de la distribution des masses de fragments moléculaires mesurée, et de la dérivation d'une pression partielle sur la base de la distribution des masses de fragments moléculaires mesurée, le modèle étant basé sur des mesures antérieures de dépôt induit par rayonnement causé par des fragments moléculaires connus pour différentes pressions partielles.


 




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Cited references

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Patent documents cited in the description




Non-patent literature cited in the description