WO2018219578A1 - Radiation source - Google Patents
Radiation source Download PDFInfo
- Publication number
- WO2018219578A1 WO2018219578A1 PCT/EP2018/061243 EP2018061243W WO2018219578A1 WO 2018219578 A1 WO2018219578 A1 WO 2018219578A1 EP 2018061243 W EP2018061243 W EP 2018061243W WO 2018219578 A1 WO2018219578 A1 WO 2018219578A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- laser beam
- subsidiary
- pulse
- laser
- radiation source
- Prior art date
Links
- 230000005855 radiation Effects 0.000 title claims abstract description 125
- 239000000446 fuel Substances 0.000 claims abstract description 25
- 230000015572 biosynthetic process Effects 0.000 claims abstract description 15
- 230000003287 optical effect Effects 0.000 claims description 47
- 239000000758 substrate Substances 0.000 claims description 24
- 238000007493 shaping process Methods 0.000 claims description 22
- 230000003321 amplification Effects 0.000 claims description 15
- 238000003199 nucleic acid amplification method Methods 0.000 claims description 15
- 238000005286 illumination Methods 0.000 claims description 12
- 238000000059 patterning Methods 0.000 claims description 12
- 238000000034 method Methods 0.000 claims description 7
- NJPPVKZQTLUDBO-UHFFFAOYSA-N novaluron Chemical compound C1=C(Cl)C(OC(F)(F)C(OC(F)(F)F)F)=CC=C1NC(=O)NC(=O)C1=C(F)C=CC=C1F NJPPVKZQTLUDBO-UHFFFAOYSA-N 0.000 claims description 7
- 230000003111 delayed effect Effects 0.000 claims description 3
- 230000001934 delay Effects 0.000 claims 1
- 230000036278 prepulse Effects 0.000 description 10
- 238000002310 reflectometry Methods 0.000 description 10
- 238000000926 separation method Methods 0.000 description 10
- 238000006243 chemical reaction Methods 0.000 description 9
- 230000002123 temporal effect Effects 0.000 description 8
- 239000007789 gas Substances 0.000 description 6
- 238000007689 inspection Methods 0.000 description 6
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 5
- 230000007547 defect Effects 0.000 description 4
- 230000005670 electromagnetic radiation Effects 0.000 description 4
- 238000003384 imaging method Methods 0.000 description 4
- 230000003595 spectral effect Effects 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 3
- 210000001747 pupil Anatomy 0.000 description 3
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 230000015654 memory Effects 0.000 description 2
- 230000006798 recombination Effects 0.000 description 2
- 238000005215 recombination Methods 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 230000004044 response Effects 0.000 description 2
- 238000003860 storage Methods 0.000 description 2
- 239000000956 alloy Substances 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000006870 function Effects 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000004973 liquid crystal related substance Substances 0.000 description 1
- 230000005381 magnetic domain Effects 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 235000012771 pancakes Nutrition 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000000644 propagated effect Effects 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05G—X-RAY TECHNIQUE
- H05G2/00—Apparatus or processes specially adapted for producing X-rays, not involving X-ray tubes, e.g. involving generation of a plasma
- H05G2/001—Production of X-ray radiation generated from plasma
- H05G2/008—Production of X-ray radiation generated from plasma involving an energy-carrying beam in the process of plasma generation
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/005—Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05G—X-RAY TECHNIQUE
- H05G2/00—Apparatus or processes specially adapted for producing X-rays, not involving X-ray tubes, e.g. involving generation of a plasma
- H05G2/001—Production of X-ray radiation generated from plasma
- H05G2/003—Production of X-ray radiation generated from plasma the plasma being generated from a material in a liquid or gas state
- H05G2/005—Production of X-ray radiation generated from plasma the plasma being generated from a material in a liquid or gas state containing a metal as principal radiation generating component
Definitions
- the present invention relates to a radiation source.
- the radiation source maybe an extreme ultraviolet radiation source.
- the extreme ultraviolet radiation source may form part of a lithographic system.
- a lithographic apparatus is a machine constructed to apply a desired pattern onto a substrate.
- a lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs).
- a lithographic apparatus may for example project a pattern from a patterning device (e.g. a mask) onto a layer of radiation-sensitive material (resist) provided on a substrate.
- a patterning device e.g. a mask
- a layer of radiation-sensitive material resist
- the wavelength of radiation used by a lithographic apparatus to project a pattern onto a substrate determines the minimum size of features which can be formed on that substrate.
- a lithographic apparatus which uses extreme ultraviolet (EUV) radiation being electromagnetic radiation having a wavelength within the range 4-20 nm, may be used to form smaller features on a substrate than a conventional lithographic apparatus (which may for example use electromagnetic radiation with a wavelength of 193 nm).
- EUV extreme ultraviolet
- LPP laser-produced plasma
- a radiation source comprising a fuel emitter configured to provide droplets of fuel to a plasma formation region, and a laser system configured to supply a laser beam, wherein the laser system comprises a delay line configured to delay a primary portion of the laser beam relative to a subsidiary portion of the laser beam, such that a pulse of the laser beam subsidiary portion is incident at the plasma formation region before a pulse of the laser beam primary portion.
- directing a pulse of the laser beam subsidiary portion onto a fuel droplet before a pulse of the laser beam primary portion increases the conversion efficiency with which
- EUV radiation is generated.
- the pulse of the laser beam subsidiary portion may form a pedestal which precedes the pulse of the laser beam primary portion.
- the pulse of the laser beam subsidiary portion does not temporally overlap with the pulse of the laser beam primary portion.
- the delay line may be configured to delay pulses of the laser beam primary portion by between 100ns and 300ns relative to pulses of the laser beam subsidiary portion.
- Pulses of the subsidiary laser beam portion pulse may have a duration which is between
- the delay line may comprise an optical amplifier.
- the laser system may be configured such that the laser beam primary portion passes forwards and backwards multiple times within the optical amplifier and the laser beam subsidiary portion travels directly through the optical amplifier.
- this provides significantly more amplification of the laser beam primary portion than the laser beam subsidiary portion.
- the optical amplifier may comprise an entrance window an exit window and a series of mirrors, and wherein the laser system is configured such that the laser beam subsidiary portion passes directly from the entrance window to the exit window, whereas the laser beam primary portion passes from the entrance window via the series of mirrors to the exit window.
- the laser beam may be separated into the primary portion and the secondary portion using a laser beam splitting apparatus.
- the laser system may further comprise a pulse shaping device configured to modify pulses of the laser beam subsidiary portion.
- the laser system may further comprise an amplification system configured to amplify the laser beam primary portion and the laser beam subsidiary portion before they are incident at the plasma formation region.
- a lithographic system comprising the radiation source of the first aspect of the invention, and further comprising an illumination system configured to condition a radiation beam received from the radiation source, a support structure constructed to support a patterning device, the patterning device being capable of imparting the radiation beam with a pattern in its cross-section to form a patterned radiation beam, a substrate table constructed to hold a substrate, and a projection system configured to project the patterned radiation beam onto the substrate.
- directing a pulse of the laser beam subsidiary portion onto a fuel droplet before a pulse of the laser beam primary portion increases the conversion efficiency with which EUV radiation is generated. This provides a higher intensity radiation beam, thereby allowing more substrates to be patterned per hour using the lithographic apparatus.
- a laser system configured to supply a laser beam for an EUV radiation source, wherein the laser system comprises a delay line configured to delay a primary portion of the laser beam relative to a subsidiary portion of the laser beam, such that a pulse of the laser beam subsidiary portion is output from the laser system before a pulse of the laser beam primary portion.
- a method of generating EUV radiation comprising using a pulsed laser system to provide a pulsed laser beam primary portion and a pulsed laser beam subsidiary portion, the primary portion being delayed by a delay line relative to the subsidiary portion, and directing the pulsed laser beam primary portion and the pulsed laser beam subsidiary portion onto fuel droplets to generate EUV radiation emitting plasma.
- directing a pulse of the laser beam subsidiary portion onto a fuel droplet before a pulse of the laser beam primary portion increases the conversion efficiency with which EUV radiation is generated.
- pulses of the laser beam subsidiary portion form pedestals which precede pulses of the laser beam primary portion.
- pulses of the laser beam subsidiary portion does not overlap with pulses of the laser beam primary portion.
- the delay line may delay the laser beam primary portion by between 100ns and 300ns relative to the laser beam subsidiary portion.
- Pulses of the subsidiary laser beam portion pulse may have a duration which is between 30ns and 150ns.
- Figure 1 depicts a lithographic system comprising a radiation source and a lithographic apparatus according to an embodiment of the invention
- Figure 2 depicts an embodiment of a laser system which may form part of the radiation source of figure 1 ;
- Figure 3 depicts an alternative embodiment of a laser system which may form part of the radiation source of figure 1.
- FIG. 1 shows a lithographic system including a mirror array according to one embodiment of the invention.
- the lithographic system comprises a radiation source SO and a lithographic apparatus LA.
- the radiation source SO is configured to generate an extreme ultraviolet (EUV) radiation beam B.
- the lithographic apparatus LA comprises an illumination system IL, a support structure MT configured to support a patterning device MA (e.g. a mask), a projection system PS and a substrate table WT configured to support a substrate W.
- the illumination system IL is configured to condition the radiation beam B before it is incident upon the patterning device MA.
- the projection system is configured to project the radiation beam B (now patterned by the mask MA) onto the substrate W.
- the substrate W may include previously formed patterns. Where this is the case, the lithographic apparatus aligns the patterned radiation beam B with a pattern previously formed on the substrate W.
- the radiation source SO, illumination system IL, and projection system PS may all be constructed and arranged such that they can be isolated from the external environment.
- a gas at a pressure below atmospheric pressure e.g. hydrogen
- a vacuum may be provided in illumination system IL and/or the projection system PS.
- a small amount of gas (e.g. hydrogen) at a pressure well below atmospheric pressure may be provided in the illumination system IL and/or the projection system PS.
- the radiation source SO shown in Figure 1 is of a type which may be referred to as a laser produced plasma (LPP) source.
- the radiation source comprises a laser system 2, which may be referred to as a main pulse laser system.
- the radiation source may optionally comprise an additional laser system 1.
- the additional laser system may be referred to as a pre-pulse laser system 1.
- Laser beams 2, 3 from the laser systems 1, 2 are combined using beam combination optics 5 (e.g. a dichroic mirror) and then deposit energy into a fuel, such as tin (Sn) which is provided from a fuel emitter 6.
- tin is referred to in the following description, any suitable fuel may be used.
- the fuel may for example be in liquid form, and may for example be a metal or alloy.
- the fuel emitter 6 may comprise a nozzle configured to direct tin, e.g. in the form of droplets, along a trajectory towards a plasma formation region 7.
- the laser beam 2 is incident upon the tin at the plasma formation region 7.
- the deposition of laser energy into the tin creates a plasma 8 at the plasma formation region 7.
- Radiation, including EUV radiation, is emitted from the plasma 8 during de-excitation and recombination of ions of the plasma.
- the EUV radiation is collected and focused by a near-normal incidence radiation collector 9 (sometimes referred to more generally as a normal-incidence radiation collector).
- the collector 9 may have a multilayer structure which is arranged to reflect EUV radiation (e.g. EUV radiation having a desired wavelength such as 13.5 nm).
- EUV radiation e.g. EUV radiation having a desired wavelength such as 13.5 nm.
- the collector 9 may have an ellipsoidal configuration, having two focal points. A first focal point may be at the plasma formation region 7, and a second focal point may be at an intermediate focus 10, as discussed below.
- the laser systems 1, 2 may be remote from other parts of the radiation source SO. Where this is the case, the laser beams 3, 4 may be passed from the laser systems 1, 2 to the radiation source SO with the aid of a beam delivery system (not shown) comprising, for example, suitable directing mirrors and/or a beam expander, and/or other optics.
- a beam delivery system (not shown) comprising, for example, suitable directing mirrors and/or a beam expander, and/or other optics.
- the pre-pulse laser system 1 and the main pulse laser system 2 taken together may be referred to as a combined laser system CS.
- Radiation that is reflected by the collector 9 forms a radiation beam B.
- the radiation beam B is focused at point 10 to form an image of the plasma formation region 7, which acts as a virtual radiation source for the illumination system IL.
- the point 10 at which the radiation beam B is focused may be referred to as the intermediate focus.
- the radiation source SO is arranged such that the intermediate focus 10 is located at, or near to, an opening 11 in an enclosing structure 12 of the radiation source.
- the radiation beam B passes from the radiation source SO into the illumination system IL, which is configured to condition the radiation beam.
- the illumination system IL includes a faceted field mirror device 13 and may include a faceted pupil mirror device 14.
- the faceted field mirror device 10 is a mirror array made up of individually controllable mirrors. A mirror of the array together with an associated actuator and sensing apparatus may be referred to as a mirror assembly.
- a controller CT controls the orientations of the mirrors (as is described further below).
- the faceted field mirror device 13 and faceted pupil mirror device 14 together provide the radiation beam B with a desired cross-sectional shape and a desired angular intensity distribution.
- the radiation beam B passes from the illumination system IL and is incident upon the patterning device MA held by the support structure MT.
- the patterning device MA reflects and patterns the radiation beam B.
- the illumination system IL may include other mirrors or devices in addition to or instead of the faceted field mirror device 13 and faceted pupil mirror device 14.
- the projection system PS comprises a plurality of mirrors 15, 16 which are configured to project the radiation beam B onto a substrate W held by the substrate table WT.
- the projection system PS may apply a reduction factor to the radiation beam, forming an image with features that are smaller than corresponding features on the patterning device MA. A reduction factor of 4 may for example be applied.
- the projection system PS has two mirrors 15, 16 in Figure 1, the projection system may include any number of mirrors (e.g. six mirrors).
- the radiation source SO shown in Figure 1 may include components which are not illustrated.
- a spectral filter may be provided in the radiation source.
- the spectral filter may be configured to receive the electromagnetic radiation produced by the plasma and separate the EUV radiation from radiation other than EUV, for example, from infrared radiation.
- the spectral filter may be a transmissive filter that is substantially transmissive for EUV radiation but substantially blocking for other wavelengths of radiation such as infrared radiation.
- the spectral filter may be a reflective filter that reflects incident EUV radiation into a specific direction and non-EUV radiation into other directions.
- the pre-pulse laser system 1 may be configured to provide pulses of radiation which, when incident upon fuel droplets, condition the fuel droplets but do not generate significant amounts of EUV radiation emitting plasma. These pulses, which may be referred to as pre-pulses, may for example modify the shape of the fuel droplets to a pancake shape and/or may ablate some material from the fuel droplets.
- the main pulse laser system 2 may be configured to provide pulses of radiation which, when incident upon fuel droplets, convert the fuel droplets into EUV radiation emitting plasma. These pulses of radiation may be referred to as main pulses.
- the main pulses of radiation may have significantly more energy than the pre-pulses of radiation.
- the main pulses of radiation may have a longer wavelength than the pre-pulses of radiation.
- the main pulses of radiation may be infrared, and may have a wavelength of around 10 microns (e.g. 10.6 microns). Alternatively, the main pulses of radiation may have a shorter infrared wavelength, e.g. around 1 micron.
- the pre-pulses of radiation may also be infrared, and may also have a wavelength of around 10 microns (e.g. 10.3 microns). Alternatively, the pre-pulses of radiation may have a shorter infrared wavelength, for example around 1 micron.
- the pre-pulses of radiation may have a wavelength in a range of around 1 micron to around 10 microns.
- the main pulse laser system 2 comprises a laser 20 configured to emit a pulsed laser beam 4, which may be referred to as the main beam of radiation.
- the laser 20 may for example be a CO 2 laser.
- the laser beam 4 passes through optics 22 (e.g. a polarizer, beam condition optics, etc) and is then incident upon a first partial reflector 24.
- the first partial reflector 24 may for example have a reflectivity of around 10% or less.
- the first partial reflector 24 may for example have a reflectivity of around 1% or more.
- the majority of the laser beam 4, which may be referred to as a primary portion 4a passes through the first partial reflector 24 and enters a delay line 26.
- the delay line may comprise mirrors 25 arranged to reflect the laser beam primary portion 4a back and forth until it has travelled a desired distance (e.g. tens of meters e.g. between 30 and 100 meters). On leaving the delay line 26 the primary portion of the laser beam 4a travels to a second partial reflector 32.
- a desired distance e.g. tens of meters e.g. between 30 and 100 meters.
- the pulse shaping device 30 is configured to modify pulses of the subsidiary portion of the laser beam 4b.
- the pulse shaping device 30 may for example be an electro-optic modulator (EOM).
- EOM electro-optic modulator
- the pulse shaping device 30 may for example remove an unwanted sharp peak at the beginning of a pulse of the subsidiary portion of the laser beam 4b. This may provide a flatter pulse shape, which may be desirable for a pedestal pulse.
- Other forms of pulse shaping may be applied by the pulse shaping device 30.
- the pulse shaping device 30 may for example be used to shorten pulses of the subsidiary portion of the laser beam 4b.
- the pulse shaping device 30 may also attenuate pulses of the subsidiary portion 4b.
- the pulse shaping device 30 may be an acousto-optic modulator (AOM).
- AOM acousto-optic modulator
- the AOM may be used to attenuate pulses of the subsidiary portion of the laser beam 4b.
- the AOM might not have a sufficiently fast response to remove a peak from the beginning of a pulse or to shorten a pulse.
- the subsidiary portion of the laser beam 4b is reflected by another reflector
- the pulse shaping device 30 may be omitted.
- the second partial reflector 32 may for example have a reflectivity of around 10% or less.
- the second partial reflector 32 may for example have a reflectivity of around 1% or more.
- the second partial reflector 32 may have the same reflectivity as the first partial reflector 24 (this may provide maximum transmission of the primary portion of the laser beam 4a).
- the delayed primary portion of the laser beam 4a is incident upon the partial reflector 32 and the undelayed subsidiary portion 4b of the laser beam is also incident upon the partial reflector 32. Since the second partial reflector 32 has a low reflectivity, most of the primary portion of the laser beam 4a is transmitted by the second partial reflector 32.
- the primary portion of the laser beam 4a then travels to an amplification system 34.
- the amplification system 34 may for example be a series of optical amplifiers.
- a reflected part of the primary portion of the laser beam 4a is incident upon a beam dump 36.
- Most of the subsidiary portion of the laser beam 4b is transmitted by the second partial reflector 32 and is incident upon the beam dump 36.
- a reflected part, e.g. around 10% or less, of the subsidiary portion of the laser beam 4b travels to the amplification system.
- part of the primary portion 4a and part of the subsidiary portion 4b of the laser beam are recombined at the second partial reflector 32 and travel together through the amplification system 34.
- the primary portion 4a and the subsidiary portion 4b of the laser beam travel together to the plasma formation region 7 (see figure 1).
- the primary portion of the laser beam 4a will have a power of 81% of the initial power of the laser beam 4 and the subsidiary portion 4b will have a power of 1 % of the initial power of the laser beam. Hence, 18% of the laser beam will be incident upon the beam dump 36. In other embodiments the relative proportions of the powers may be different.
- the subsidiary portion 4b of the laser beam will have a power which is significantly lower than the primary portion 4a of the laser beam.
- the power of the subsidiary portion 4b may for example be less than 5% of the power of the primary portion 4a, and may for example be less than 1% of the power of the primary portion.
- a delay between the subsidiary pulse and the primary pulse is determined by an optical path length of the delay line 26. For example, if the delay line 26 has an optical path length of around 30m then the subsidiary pulse will precede the primary pulse by around 100 ns.
- the optical path length of the delay line 26 may be selected or may be adjustable to provide a desired temporal separation between the subsidiary pulse and the primary pulse.
- the optical path length of the delay line 26 may be adjustable (e.g. by modifying a separation between reflectors of the delay line).
- the temporal separation may for example be between 100ns and 300ns.
- the temporal separation between two pulses may for example be measured as the temporal separation between centres of the two pulses (which may be halfway between ends of the pulses), or may be measured as the temporal separation between leading edges of the two pulses.
- the temporal separation is therefore a result of rearranging in the time-dimension different temporal portions of the laser beam.
- the duration of the subsidiary pulse may be significantly less than the separation between the subsidiary pulse and the primary pulse. Where this is the case the subsidiary pulse may be separated from the primary pulse. In an embodiment, the duration of the subsidiary pulse may be similar to or longer than the separation between the subsidiary pulse and the primary pulse. Where this is the case the subsidiary pulse may merge with the primary pulse. In such a situation the subsidiary pulse may be referred to as a pedestal.
- the primary pulse may for example have a duration which is between 30ns and 150ns.
- the subsidiary pulse may for example have a duration which is between 30ns and 150ns.
- the primary pulse and the subsidiary pulse may have the same duration. Measurements of pulse duration may refer to the full width at half-maximum of the pulse. A significant proportion of the pulse may extend beyond this duration.
- the subsidiary pulse and the primary pulse may each have a duration of 75ns and may have a temporal separation of 100ns (as applied by the delay line 26). Although the full width at half-maximum points of the subsidiary pulse and primary pulse will not meet each other, the subsidiary and primary pulse will still overlap with each other because a significant proportion of the pulses extends beyond the full width half-maximum duration.
- the subsidiary pulse may still be considered to form a pedestal. The same applies to other delay line lengths and other pulse durations.
- FIG. 3 An alternative embodiment of the main laser system 2 is depicted in figure 3.
- an optical amplifier 40 acts as a delay line.
- the optical amplifier 40 is depicted schematically in cross section viewed from one side and, in addition, the ends of the optical amplifier are also schematically depicted.
- the optical amplifier 40 comprises an annular chamber 42 filled with gas which is excited using for example a radio frequency voltage applied across the annular chamber 42. A laser beam passing through the gas receives energy from the excited gas and is thereby amplified.
- An entrance window 44 and an exit window 46 are provided at opposite ends 43, 45 of the annular chamber 42.
- Mirrors 48 are also provided at the opposite ends 43, 45 of the annular chamber 42.
- the mirrors 48 are oriented to cause an incident laser beam to reflect from one mirror at one of the ends 43, 45 to a next mirror at the other one of the ends 43, 45 along an optical path which travels backwards and forwards between ends 43, 45 of the annular chamber 42 and at the same time progresses around the annular chamber 42.
- the optical amplifier 40 may for example be a Tru-Coax optical amplifier, available from Trumpf of Stuttgart, Germany.
- a laser beam primary portion 4a to be amplified enters the optical amplifier 40 via the entrance window 44, is reflected by the mirrors 48 and travels around the annular chamber 42 whilst at the same time being amplified.
- the amplified laser beam primary portion 4a then leaves via the exit window 46.
- a subsidiary portion of the laser beam 4b (indicated by a dashed line) which does not require significant amplification also passes through the optical amplifier 40.
- the subsidiary portion of the laser beam 4b passes directly from the entrance window 44 to the exit window 46 and is not reflected by the mirrors 48 around the annular chamber 42.
- the subsidiary portion of the laser beam 4b thus only receives a small amount of amplification from the gas in the annular chamber, and travels over a much shorter distance within the annular chamber 42 than the laser beam primary portion 4a.
- an acousto-optic modulator (AOM) 50 is used to separate the subsidiary portion of the laser beam 4b such that it is non- coaxial with respect to the laser beam primary portion 4a when it enters the optical amplifier 40.
- the acousto-optic modulator 50 diffracts the incident laser beam 4 to form a zeroth order and a first order.
- the first order beam is the laser beam primary portion 4a.
- the laser beam primary portion 4a passes through a first partial reflector 52 and then enters the optical amplifier 40. Part of the laser beam primary portion 4a is reflected by the partial reflector 52 and is incident upon a beam dump 56.
- the first order beam is the subsidiary portion of the laser beam 4b.
- the first order beam is incident upon a reflector 54.
- the reflector 54 may have a reflectivity of 100% or may be a partial reflector, for example with a reflectivity of around 50% or more. If the reflector 54 is a partial reflector, then the portion of the subsidiary portion of the laser beam which passes through the reflector 54 is incident upon a second beam dump 57.
- the reflected portion is incident upon the first partial reflector 52 and travels from that partial reflector to the optical amplifier 40 (with part of the beam passing through the first partial reflector 52 and being incident upon the beam dump 56).
- the first partial reflector 52 may for example have a reflectivity of around 1 %.
- the subsidiary portion of the laser beam 4b may have a power which is less than the power of the laser beam primary portion 4a by a factor of around 100 before it enters the optical amplifier 40.
- the second partial reflector 52 is oriented such that the subsidiary portion of the laser beam 4b is non-coaxial with the laser beam primary portion 4a when they enter the optical amplifier 40.
- the orientation of the partial reflector 52 is such that the subsidiary portion of the laser beam 4b passes through the entrance window 44 but is not incident upon a mirror 48 of the optical amplifier 40. Instead, the subsidiary portion of the laser beam 4b passes out of the exit window 46.
- the laser beam primary portion 4a travels around the annular chamber 42 of the optical amplifier 40 but the subsidiary portion of the laser beam 4b does not.
- the optical amplifier 40 acts as a delay line and, at the same time, amplifies the laser beam primary portion 4a.
- the optical amplifier 40 advantageously provides two functions simultaneously.
- the embodiment depicted in figure 3 may include a pulse shaping device 60 which is configured to modify pulses of the subsidiary portion of the laser beam 4b.
- the pulse shaping device 60 may for example be an electro-optic modulator (EOM).
- EOM electro-optic modulator
- the pulse shaping device 60 may for example remove an unwanted sharp peak at the beginning of a pulse of the subsidiary portion of the laser beam 4b. This may provide a flatter pulse shape, which may be desirable for a pedestal pulse.
- Other forms of pulse shaping may be applied by the pulse shaping device 60.
- the pulse shaping device 60 may for example be used to shorten pulses of the subsidiary portion of the laser beam 4b.
- the pulse shaping device 60 may also attenuate pulses of the subsidiary portion 4b.
- the pulse shaping device 60 may be an acousto-optic modulator (AOM).
- the AOM may be used to attenuate pulses of the subsidiary portion of the laser beam 4b.
- the AOM might not have a sufficiently fast response to remove a peak from the beginning of a pulse or to shorten a pulse.
- the pulse shaping device 60 may be omitted.
- the laser system 1 further comprises an amplification system 62 through which the subsidiary pulse
- the amplification system 62 may for example be a series of optical amplifiers.
- the subsidiary portion of the laser beam 4b is non-collinear with the primary portion of the laser beam 4a when it enters the optical amplifier 40.
- This non- collinearity allows the subsidiary portion of the laser beam 4b to travel directly from the entrance window 44 to the exit window 46 instead of being reflected by mirrors 48 of the optical amplifier 40.
- the subsidiary portion of the laser beam 4b and the primary portion of the laser beam 4a are non-collinear when they enter the optical amplifier 40, they are also non- collinear when they exit the optical amplifier.
- the non-collinear nature of the subsidiary and primary laser beam portions 4a, 4b may be a combination of different spatial positions of the laser beams and different angular orientations of the laser beams (which may be referred to as beam pointing).
- the partial reflector 52 and the reflector 54 may be adjusted to modify the spatial position and the beam pointing of the subsidiary portion of the laser beam 4b relative to the primary portion of the laser beam 4a in order to obtain a desired combination of beam position and beam pointing.
- the subsidiary portion of the laser beam 4b may be incident upon the partial reflector 52 at a different spatial position from the primary portion of the laser beam 4a, and may be pointed such that it subsequently intersects with the primary portion of the laser beam.
- this approach has been used to cause the subsidiary portion of the laser beam 4b to intersect with the primary portion of the laser beam 4a within the amplification system 62.
- the subsidiary portion of the laser beam 4b may intersect with the primary portion of the laser beam 4a at some other position (e.g. at a position where a spatial filter is provided).
- the subsidiary portion of the laser beam 4b may not intersect with the primary portion of the laser beam 4a.
- the spatial position and the beam pointing of the primary portion of the laser beam 4a relative to the subsidiary portion of the laser beam 4b may be adjusted.
- optical amplifier depicted in figure 3 has an entrance window 44 at one end and an exit window 46 at an opposite end, in another embodiment the entrance and exit windows may be at the same end.
- the optical amplifier 40 depicted in figure 3 is annular the optical amplifier may have some other shape.
- the optical amplifier may be cuboid.
- the optical amplifier may for example have an entrance window at one end face and an exit window at an opposite end face.
- the optical amplifier may for example have an entrance window and an exit window at the same end face.
- AOM acousto-optic modulator
- other apparatus may be used to split the laser beam (e.g. a partially reflective mirror).
- any suitable laser beam splitting apparatus may be used to separate the laser beam into the subsidiary portion and the primary portion, e.g. a partially reflective mirror or a modulator.
- the subsidiary portion of the laser beam 4b may have a power which is 5% or less of the power of the laser beam primary portion 4a, e.g. 1% or less.
- a pulse of the subsidiary portion of the laser beam 4b may have a power of a few mJ whereas a pulse of the laser beam primary portion 4a may have a power of a few hundred mJ (e.g. around 400 mJ).
- the invention may form part of a mask inspection apparatus.
- the mask inspection apparatus may use EUV radiation to illuminate a mask and use an imaging sensor to monitor radiation reflected from the mask. Images received by the imaging sensor are used to determine whether or not defects are present in the mask.
- the mask inspection apparatus may include optics (e.g. mirrors) configured to receive EUV radiation from an EUV radiation source and form it into a radiation beam to be directed at a mask.
- the mask inspection apparatus may further include optics (e.g. mirrors) configured to collect EUV radiation reflected from the mask and form an image of the mask at the imaging sensor.
- the mask inspection apparatus may include a processor configured to analyse the image of the mask at the imaging sensor, and to determine from that analysis whether any defects are present on the mask.
- the processor may further be configured to determine whether a detected mask defect will cause an unacceptable defect in images projected onto a substrate when the mask is used by a lithographic apparatus.
- the invention may form part of a metrology apparatus.
- the metrology apparatus may be used to measure alignment of a projected pattern formed in resist on a substrate relative to a pattern already present on the substrate. This measurement of relative alignment may be referred to as overlay.
- the metrology apparatus may for example be located immediately adjacent to a lithographic apparatus and may be used to measure the overlay before the substrate (and the resist) has been processed.
- Embodiments of the invention may form part of a mask inspection apparatus, a metrology apparatus, or any apparatus that measures or processes an object such as a wafer (or other substrate) or mask (or other patterning device). These apparatus may be generally referred to as lithographic tools. Such a lithographic tool may use vacuum conditions or ambient (non- vacuum) conditions.
- EUV radiation may be considered to encompass electromagnetic radiation having a wavelength within the range of 4-20 nm, for example within the range of 13-14 nm. EUV radiation may have a wavelength of less than 10 nm, for example within the range of 4- 10 nm such as 6.7 nm or 6.8 nm.
- Embodiments of the invention may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the invention may also be implemented as instructions stored on a machine-readable medium, which may be read and executed by one or more processors.
- a machine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device).
- a machine -readable medium may include read only memory (ROM); random access memory (RAM); magnetic disk storage media; optical storage media; flash memory devices; electrical, optical, acoustical or other forms of propagated signals (e.g. carrier waves, infrared signals, digital signals, etc.), and others.
- firmware, software, routines, instructions may be described herein as performing certain actions. However, it should be appreciated that such descriptions are merely for convenience and that such actions in fact result from computing devices, processors, controllers, or other devices executing the firmware, software, routines, instructions, etc.
Landscapes
- Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Engineering & Computer Science (AREA)
- Plasma & Fusion (AREA)
- X-Ray Techniques (AREA)
- Exposure And Positioning Against Photoresist Photosensitive Materials (AREA)
- Lasers (AREA)
- Plasma Technology (AREA)
- Preparing Plates And Mask In Photomechanical Process (AREA)
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2019561890A JP7239491B2 (ja) | 2017-05-30 | 2018-05-03 | 放射源 |
CN201880035555.6A CN110692283B (zh) | 2017-05-30 | 2018-05-03 | 辐射源 |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP17173481.7 | 2017-05-30 | ||
EP17173481 | 2017-05-30 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2018219578A1 true WO2018219578A1 (en) | 2018-12-06 |
Family
ID=58994856
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/EP2018/061243 WO2018219578A1 (en) | 2017-05-30 | 2018-05-03 | Radiation source |
Country Status (4)
Country | Link |
---|---|
JP (1) | JP7239491B2 (ja) |
CN (1) | CN110692283B (ja) |
NL (1) | NL2020864A (ja) |
WO (1) | WO2018219578A1 (ja) |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20040264512A1 (en) * | 2003-06-26 | 2004-12-30 | Northrop Grumman Corporation | Laser-produced plasma EUV light source with pre-pulse enhancement |
US20090080476A1 (en) * | 2007-09-20 | 2009-03-26 | Cymer, Inc. | Immersion lithography laser light source with pulse stretcher |
US20160007434A1 (en) * | 2014-07-07 | 2016-01-07 | Asml Netherlands B.V. | Extreme ultraviolet light source |
US20160149368A1 (en) * | 2014-11-26 | 2016-05-26 | Electronics And Telecommunications Research Institute | Pulse width stretcher and chirped pulse amplifier including the same |
Family Cites Families (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH08285901A (ja) * | 1995-04-13 | 1996-11-01 | Nippon Telegr & Teleph Corp <Ntt> | 電圧測定方法及び電圧測定装置 |
US7916388B2 (en) | 2007-12-20 | 2011-03-29 | Cymer, Inc. | Drive laser for EUV light source |
EP2556729A1 (en) * | 2010-04-08 | 2013-02-13 | ASML Netherlands BV | Euv radiation source and euv radiation generation method |
US8462425B2 (en) | 2010-10-18 | 2013-06-11 | Cymer, Inc. | Oscillator-amplifier drive laser with seed protection for an EUV light source |
US9516732B2 (en) * | 2011-09-02 | 2016-12-06 | Asml Netherlands B.V. | Radiation source |
JP6021454B2 (ja) * | 2011-10-05 | 2016-11-09 | ギガフォトン株式会社 | 極端紫外光生成装置および極端紫外光生成方法 |
EP2651196B1 (en) * | 2012-04-13 | 2017-04-12 | Ecole Polytechnique | All optical high energy radiation source |
JP5374724B2 (ja) | 2012-04-18 | 2013-12-25 | ギガフォトン株式会社 | 極端紫外光源装置 |
WO2013174620A1 (en) * | 2012-05-21 | 2013-11-28 | Asml Netherlands B.V. | Radiation source |
US10114157B2 (en) * | 2012-09-20 | 2018-10-30 | Applied Materials, Inc. | Pulse width controller |
JP2013084971A (ja) | 2012-12-03 | 2013-05-09 | Gigaphoton Inc | 極端紫外光源用ドライバレーザ |
CN105573061B (zh) * | 2014-10-16 | 2018-03-06 | 中芯国际集成电路制造(上海)有限公司 | Euv光源和曝光装置 |
-
2018
- 2018-05-03 WO PCT/EP2018/061243 patent/WO2018219578A1/en active Application Filing
- 2018-05-03 JP JP2019561890A patent/JP7239491B2/ja active Active
- 2018-05-03 NL NL2020864A patent/NL2020864A/en unknown
- 2018-05-03 CN CN201880035555.6A patent/CN110692283B/zh active Active
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20040264512A1 (en) * | 2003-06-26 | 2004-12-30 | Northrop Grumman Corporation | Laser-produced plasma EUV light source with pre-pulse enhancement |
US20090080476A1 (en) * | 2007-09-20 | 2009-03-26 | Cymer, Inc. | Immersion lithography laser light source with pulse stretcher |
US20160007434A1 (en) * | 2014-07-07 | 2016-01-07 | Asml Netherlands B.V. | Extreme ultraviolet light source |
US20160149368A1 (en) * | 2014-11-26 | 2016-05-26 | Electronics And Telecommunications Research Institute | Pulse width stretcher and chirped pulse amplifier including the same |
Also Published As
Publication number | Publication date |
---|---|
JP2020521998A (ja) | 2020-07-27 |
NL2020864A (en) | 2018-12-04 |
JP7239491B2 (ja) | 2023-03-14 |
CN110692283B (zh) | 2023-09-19 |
CN110692283A (zh) | 2020-01-14 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US8663881B2 (en) | Radiation source, method of controlling a radiation source, lithographic apparatus, and method for manufacturing a device | |
US11266002B2 (en) | System for monitoring a plasma | |
JP5179522B2 (ja) | レーザデバイス、放射源、及びリソグラフィ投影装置 | |
JP5606498B2 (ja) | 放射源およびリソグラフィ装置 | |
US10222702B2 (en) | Radiation source | |
US20170048958A1 (en) | Stabilizing EUV Light Power in an Extreme Ultraviolet Light Source | |
JP6047573B2 (ja) | 放射源 | |
JP2013524525A (ja) | Euv放射源およびeuv放射生成方法 | |
JP6305426B2 (ja) | Euvリソグラフィ装置用ビーム搬送装置 | |
JP5921548B2 (ja) | リソグラフィ装置、euv放射発生装置、およびデバイス製造方法 | |
US10686290B2 (en) | Radiation source | |
US20140218706A1 (en) | Radiation source and lithographic apparatus | |
JP2010045354A (ja) | 放射源、リソグラフィ装置、およびデバイス製造方法 | |
JP7239491B2 (ja) | 放射源 | |
JP6100882B2 (ja) | リソグラフィ装置、センサ及び方法 | |
WO2020086901A1 (en) | Monitoring light emissions | |
JP6845035B2 (ja) | 極紫外放射源 | |
JP2022539994A (ja) | 光増幅キャビティと共に使用するための測定システム | |
WO2023237313A1 (en) | Multi-wavelength shadowgraphy for an euv radiation source | |
NL2012718A (en) | Radiation systems and associated methods. |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
121 | Ep: the epo has been informed by wipo that ep was designated in this application |
Ref document number: 18722952 Country of ref document: EP Kind code of ref document: A1 |
|
ENP | Entry into the national phase |
Ref document number: 2019561890 Country of ref document: JP Kind code of ref document: A |
|
NENP | Non-entry into the national phase |
Ref country code: DE |
|
122 | Ep: pct application non-entry in european phase |
Ref document number: 18722952 Country of ref document: EP Kind code of ref document: A1 |