HK1094501B - Method and device for producing extreme ultraviolet radiation or soft x-ray radiation - Google Patents

Abstract

The device for generating extreme ultraviolet (EUV) or soft X-ray radiation comprises a laser source (12) for producing a laser radiation (11) which is focused to intensities beyond 106 W/cm² onto a target to produce a plasma and electrodes mounted on an electrically insulating block (6) and located around the path of the plasma produced by the laser source (12). The electrodes are combined with a device for producing a rapid electric discharge in the plasma with a characteristic time constant which is less than the time constant of the laser produced plasma expansion time.

Description

Method and device for producing extreme ultraviolet radiation or soft X-ray radiation

Technical Field

The present invention relates to a method and a device for generating extreme ultraviolet radiation (EUV) or soft X-ray radiation.

Preferred fields of application of the invention include applications requiring the use of soft X-ray light in the spectral range of 1-20nm (i.e. EUV light). The most prominent application is EUV projection lithography with an operating wavelength of 13.5nm, where a compact, high power, cost-effective and reliable light source needs to be used. Another field of application comprises X-ray analysis methods-such as photoelectron spectroscopy, or fluorescence X-ray analysis-which make use of the spectral range of soft X-ray radiation and can be carried out on a laboratory scale. Furthermore, the method and the device can be used to characterize X-ray optics or X-ray detectors and ultimately as a light source for EUV microscopes in the spectral range of the so-called water window (water window) for in vivo observation of biological tissue.

Background

The use of plasma as an EUV light source and soft and hard X-ray sources is well known. Almost independently of the method of generating the plasma, the plasma emitted must be sufficiently hot (i.e., > 150,000K) and dense (i.e., > 10K)¹⁷Electron/cm³) To emit X-ray and/or EUV radiation.

Various different techniques for generating EUV radiation are known to fulfill the above conditions. These techniques can be divided into discharge-based or laser-based plasma source concepts.

For so-called gas discharge plasma (GDPP) generating sources, a pulsed discharge generates a "spark-like" plasma, wherein a current of about 5 to 100kA flows through the plasma for a time of about 10 nanoseconds to about microseconds. For increasing the conversion to EUV by additional heating and compression, a so-called pinch effect may facilitate this process. Different discharge plasma concepts differ in electrode geometry, voltage-pressure range, plasma dynamics, ignition strategy and electrical generator. Various examples of these discharge plasmas are known, such as dense plasma focus Z-pinch (Z-ping) discharges, capillary discharges, and hollow cathode triggered pinches. Different versions of these discharge plasma concepts are disclosed in U.S. patent documents 6,389,106, 6,064,072 and WO 99/34395.

For so-called Laser Produced Plasma (LPP), a laser beam is focused to a certain density (> 10)¹⁹Atom/cm³) The substance (most commonly referred to as the target). If the intensity exceeds about 10¹⁰W/cm²EUV or even X-ray radiation is emitted from almost any substance. The concept of generating plasma using a target subjected to laser irradiation has been disclosed in WO patent documents No. 02/085080, No. 02/32197, No. 01/30122 and U.S. patent No. 5,577,092.

For the current state of the art of source concepts with maximum conversion efficiencies between 0.5 and 2%, to obtain sufficient EUV power (80-120W) for industrial applications such as EUV lithography, an excitation power of typically 50.000W) to 100.000W has to be coupled into the radiation plasma. Depending on the source concept, this would translate into EUR radiation that produces 300W to over 1,000W directly at the source point. For the existing source concepts LPP and GDPP, there are several factors that make it difficult to meet these required EUV power levels:

1. for the LPP concept, it is limited by two factors: first, it is expected that the cost of a laser having about 10kW of power will far exceed the budget defined by economic production costs. Second, the electrical power required to drive the laser (typically about 1MW) and the cooling required will likely exceed acceptable levels in the semiconductor factory.

2. For the GDPP concept, the limiting factors are as follows. The power must be fed into a volume 10, typically about the volume emitting the radiation³In multiple volumes. For a tolerable 1mm³A typical discharge volume of 1cm³. Since the volume limitation is usually achieved by the discharge electrode or by the insulating material, these materials are subject to excessive heating and erosion, since their typical distance from the thermal plasma is only allowed to be in the order of millimeters to centimeters.

Thus, the generation of plasma (LPP) by laser and plasma (GDPP) by gas discharge seems to be incompatible with the latest requirements of industrial applications, in particular the requirements of extreme ultraviolet radiation lithography (EUVL). Therefore, there is an urgent need for a novel technical solution, which seems to be a necessary condition for successfully introducing EUVL following IRTS roadmap (2009) and Intel roadmap (2007).

Disclosure of Invention

It is therefore an object of the present invention to provide a method and a device for remedying the above-mentioned disadvantages of both basic concepts of plasma generation with gas discharge and plasma generation with laser light and in particular to be able to be applied in better economics for EUV lithography in the spectral range of about 13.5nm without requiring a substantial increase in the power of the device for plasma generation, while at the same time providing a high degree of flexibility in adapting the device to the specific requirements of the user.

The disadvantages of the prior art are reduced while the main advantages of these prior art techniques are retained due to the unexpected synergistic effect used in the method and apparatus of the present invention.

The object of the invention is achieved by a method of generating Extreme Ultraviolet (EUV) or soft X-ray radiation, in which method the radiation is generated by means of a radiation sourceGenerating and heating a plasma in a mixed manner by the combination of laser radiation generated by a laser source and an electric discharge generated by the combination of electrodes and means for generating a rapid electric discharge, wherein the laser radiation is present at a level exceeding 10⁶W/cm²Is focused onto a target, wherein the time constant of the expansion time of the laser-generated plasma exceeds the characteristic time constant of the discharge.

The present invention relates to a hybrid method combining the generation and/or heating of a plasma by laser radiation with the generation and/or heating and/or compressing of a plasma by electrical discharge in such a way that the solution combines both concepts in the following way: the advantages of the single solutions are combined while avoiding the disadvantages of these known methods.

The target may be in excess of 10¹⁹Atom/cm³In the form of a gaseous, liquid spray, cluster spray or solid medium, such as a bulk or foil target.

According to a first embodiment, an EUV plasma is first generated by focusing laser radiation in a laser interaction region of a dense target, and then a discharge is induced in the laser interaction region. It is important to note that the discharge will be able to efficiently couple energy into the EUV plasma even when the laser is no longer coupled to the plasma. For this reason, the discharge can be considered as an enhancer of the initial laser-generated plasma, thereby greatly enhancing the production of EUV light using inexpensive electrical power. This concept is called Discharge enhanced laser Produced Plasma (DBLPP).

According to a second embodiment, a more confined EUV light emission is achieved by focusing laser radiation on a target to generate a cold plasma to produce a cold plasma plume, followed by an active trigger of a discharge in the delocalized interaction region of the plasma plume to heat and compress the plasma. This concept is known as Laser Assisted Gas Discharge generated Plasma (LAGDPP).

According to a third embodiment, a conventional discharge configuration is used to generate a high density discharge plasma. However, during the pinching process, the plasma becomes dense enough to locally allow additional laser heating. This procedure allows modifying and/or optimizing the ion population to enhance EUV radiation (e.g., 13.5nm EUV lithography). This third concept is referred to as laser enhanced gas discharge generated plasma (LBGDPP).

From a general point of view, the three hybrid methods DBLPP, LAGDPP and LBGDPP set out above can be distinguished by: (1) the respective effects of the laser and the discharge on the plasma heating in terms of energy and duration of excitation injected into the EUV emitter plasma, (2) the time delay and the front-to-back order of these two complementary heating mechanisms.

For both GDPP and LPP concepts, the elemental composition of the target is typically chosen to best match the emitted spectral distribution to the application requirements. For the particular case of EUVL, the broadband emitter xenon is generally considered one of the most suitable materials because (1) it exhibits one of the highest conversion efficiencies in the spectral range of interest, (2) it is chemically neutral, and (3) it is well heated by the laser due to its high Z value. However, other emitters have also been investigated in GDPP or LPP concepts, such as oxygen, lithium, tin, copper or iodine.

The current pulse applied by the electrodes in the presence of plasma is provided by a rapid discharge of the stored energy of the capacitor.

The current pulse applied by the electrodes in the presence of plasma is selected to have a period in the range of 1 to 3 nanoseconds.

Preferably, the current pulses applied by the electrodes in the presence of plasma are selected to have an amplitude in the range of 2-3 digit kiloamperes.

The current pulses applied by the electrodes in the presence of plasma are switched in a defined temporal relationship to the ignition of the laser pulses generated by the laser source.

The temperature of the generated plasma is in the 6-digit kelvin range (i.e., 100,000-400,000K).

The plasma is generated at a gas pressure selected in the range below 10 Pa.

The plasma emits radiation with a wavelength shorter than 50 nm.

The object of the invention is further achieved by a device for generating Extreme Ultraviolet (EUV) or soft X-ray radiation, comprising: a laser source for generating a laser radiation having a laser power in excess of 10⁶W/cm²Is focused on a target to generate plasma; electrodes arranged around the path of the laser source generated plasma, said electrodes being combined with means for generating a rapid discharge in the plasma, wherein the characteristic time constant of the discharge is smaller than the time constant of the expansion time of the laser generated plasma (preferably about 200ns or less).

The means for generating a rapid discharge may comprise means for storing electrical energy, such as a capacitor bank or a pulse compressor.

If a capacitor bank is used, the electrodes may be connected directly to the capacitor bank to produce a fast discharge.

Alternatively, the electrodes may be connected to the capacitor bank by a power on-off switch which is switched on by a logic control element to generate the rapid discharge.

The discharge time of the electrodes exceeds 100ns and 200ns, but the laser pulse duration of the laser pulse generated by the laser source is several nanoseconds and does not exceed 60 ns.

According to a particularly preferred embodiment of the invention in combination with the first embodiment (DBLPP), the device comprises a nozzle for injecting cold-jet targets, such as micro-liquid jet targets, spray targets, cluster targets or a erupting gas target, into a joint vacuum chamber provided with at least one electrically insulating block for accommodating the electrode around a laser interaction region of the target.

The electrically insulating mass exhibits high thermal conductivity and is preferably cooled at low temperatures, thereby enabling the elimination of thermal loads resulting from absorption of both unused in-band and out-of-band radiation.

The electrically insulating block may further serve as a thermal shield for a cryogenic target injector pinch, star pinch, or capillary discharge configuration.

According to a first embodiment, the device comprises a laser source for generating a laser radiation of more than 10%⁶W/cm²Is focused on a dense target to generate a plasma.

According to a second embodiment, the laser beam generated by the laser source irradiates a solid block target, a solid foil target, a liquid target, a spray target, a cluster target or a eruptive gas target to generate a cold plasma plume, the discharge electrode is arranged in the path of the plasma plume with the laser interaction region, the electrode helps to heat and compress the plasma to generate more confined EUV radiation.

In this case, the apparatus may include a pulse generator connected to the electrodes, the pulse generator triggering a discharge when the plasma plume enters the space between the electrodes.

According to a third embodiment, the apparatus comprises: a plurality of discharge electrodes disposed near a sputtering target to generate a high density plasma using a conventional discharge configuration of a GDPP on a plasma path; a laser source that irradiates the plasma in a manner that maintains EUV radiation emission; and a triggering means for triggering a laser pulse when the pinching process makes the plasma dense enough to allow additional laser heating.

The device may further comprise a second vacuum chamber connected to the first vacuum chamber via an aperture to receive unused target material downstream of the EUV light emitting region.

Drawings

For purposes of illustration, the present invention will now be described with reference to the accompanying schematic drawings, which show preferred embodiments, and in which:

FIG. 1A is a schematic representation of a specific embodiment of the present invention, in which a cold droplet spray target is used to ignite and confine the discharge by a laser-generated plasma,

FIG. 1B is a schematic view of the particular embodiment shown in FIG. 1A, but with another type of ejection target (micro-fluid ejection),

FIG. 2 is a schematic side view of the embodiment of FIG. 1A, showing the laser beam focused on an interaction region and the resulting useful EUV radiation injected into a large region, an

FIG. 3 is a schematic diagram of a particular embodiment of a laser assisted discharge source (LAGGDPP) according to the present invention.

Detailed Description

The above-mentioned disadvantages of generating an X-ray source by a laser generation scheme or by a discharge generation scheme only are avoided according to the present invention by utilizing a specific synergistic combination of the laser generation scheme concept and the discharge generation scheme concept, which may include various mixed source embodiments.

Fig. 1A, 1B and 2 relate to a first embodiment, which may be referred to as a discharge enhanced laser produced plasma source (DBLPP).

According to a first embodiment of the invention, an apparatus for generating Extreme Ultraviolet (EUV) or soft X-ray radiation comprises: a laser source for generating a laser radiation having a laser power in excess of 10⁶W/cm²Is focused on a dense target to generate plasma; an electrode arranged around the path of the plasma generated by the laser source, said electrode being combined with means for generating a rapid discharge in the plasma, the characteristic time constant of the discharge being smaller than the time constant of the expansion time (in the case of a DBPLL device) of the laser-generated plasma.

The invention in this preferred form operates in the following manner: a cold (i.e., liquid or solid) sputtering target, a spray target, a cluster target, or a propellant gas target 1 is injected through a nozzle or other similar apparatus 2 into a vacuum chamber 3 that serves as an interaction chamber. The laser interaction region 4 on the target is surrounded by electrodes 5, which electrodes 5 are fixed by some electrically insulating mass 6 and constitute a discharge cell. The electrodes are arranged in a Z pinch, hollow cathode pinch, star pinch, or capillary discharge configuration. Electrically insulating mass 6 is preferably cryogenically cooled and exhibits high thermal conductivity, thereby eliminating the thermal load created by absorbing both the unused in-band and out-of-band radiation. The mass 6 also acts as a thermal shield for a possible cryogenic target injector. The sputter target enters a second vacuum chamber 7 which is connected to the source chamber 3 via an aperture 8. The impact of the laser on the interaction zone 4 on the target 1 generates a plasma (either emitting EUV radiation or not), which triggers the discharge (which means that the discharge power supply does not necessarily need an own triggering unit). Useful EUV light can be collected in a large cone whose axis of symmetry is perpendicular to the plane of the drawing of fig. 1A and directed to the reader. This large cone 10 can be seen in fig. 2, fig. 2 being a side view of fig. 1A, showing a laser beam 11 generated by a laser source 21 and focused on the interaction region 4, and showing the useful EUV radiation generated, which is incident to the right into a large cone 10.

Fig. 1A further shows pumping means 9 of the first and second vacuum containers 3, 7. Preferably, the gas pressure in the chambers 3, 7 is chosen in the range below 10 Pa.

In the presence of plasma in the interaction zone 4, the current pulse flowing from the electrode 5 is provided by a rapid discharge of energy stored in a capacitive manner.

The rapid discharge may be generated by an electrode system 5 directly connected to a capacitor bank (not shown). Alternatively, the rapid discharge can be achieved by a power on-off switch that is switched on by a logic control element and connected between the electrode 5 and the capacitor bank.

The voltage applied to the electrodes 5 is higher than the ignition voltage of the gas discharge at the pressure in question.

The current pulses supplied by the electrodes 5 are switched in a defined temporal relationship with the ignition of the laser pulses.

The time constant of the LPP expansion time is greater than the characteristic time constant of the discharge.

The synchronization between the laser and the discharge is implicitly controlled by the laser source 12.

The capacitively stored electrical energy is connected to a preferred discharge path having an inductance low such that the discharge time is longer than 100ns and preferably shorter than 200ns (i.e., preferably between 100 and 200 ns).

The described device for generating Extreme Ultraviolet (EUV) or soft X-ray radiation by using a hybrid combination of both laser generation and discharge generation methods is preferred for generating short-wave radiation in the sense that: most of the drive power is inexpensive electrical power and the laser plasma enables the discharge to occur at a higher density and/or more confined than if the discharge was present alone, and the laser plasma enables the discharge to occur at a greater distance from the electrodes to avoid corrosion and to define the thermal load.

Fig. 1B shows only one cold spray target, which can be obtained as specified in the above-mentioned document WO 02/085080.

FIG. 3 shows a second embodiment of the present invention, which is shown in a view similar to FIGS. 1A and 1B. The laser source and the laser beam are thus not shown in fig. 3, but are similar to the laser source 12 and the laser beam 11 in fig. 2.

However, fig. 3 shows: a solid target 104; a laser spot 105 in which a laser beam impinges on the solid target 104 and effects ablation of the target 104; and a delocalized interaction region 106, which constitutes the actual EUV source and in which the discharge occurs from electrode 102.

Electrodes 102 are mounted on electrically insulating block 101, electrically insulating block 101 being similar to block 6 in fig. 1A and 2.

Reference numeral 107 relates to the plasma plume and reference numeral 110 relates to the useful EUV radiation injected into a large cone.

Fig. 3 shows a so-called laser-assisted gas discharge generated plasma (LAGDPP), in which a cold plasma is generated by a laser pulse (region 105). Subsequent discharge via electrode 102, which uses the laser-generated plasma as a discharge channel, heats and compresses the plasma to achieve more efficient and more confined EUV radiation (region 106).

According to a second embodiment of the invention, the apparatus for generating extreme Ultraviolet (UEV) or soft X-ray radiation comprises: a laser that vaporizes a solid or liquid target to produce a cold plasma plume; a plurality of discharge electrodes arranged in the path of the plasma plume; and a pulse generator connected to the electrodes which triggers a discharge when plasma plume enters the space between the electrodes, the discharge helping to heat and compress the plasma for more confined EUV emission.

More generally, in the LAGDPP concept, the present invention uses a laser that vaporizes a solid or liquid target material (e.g., tin or lithium or other material) used as an active material in a gas discharge generated plasma, which may also be supported by one or more buffer gases. As soon as the plasma plume 107 enters the space between the electrodes 101, the discharge is triggered in an active manner. Useful EUV radiation is preferably emitted in a large cone 110. For example, the conversion efficiency of LAGDPP gas discharge plasma with tin reaches more than 1.3% (for discharge plasma, 2% of the in-band EUV radiation is converted into input electrical energy).

In a first embodiment of the invention (DBLPP), the laser generates a high density plasma with a small extended range and uses cheap discharge energy to:

a) the plasma is heated to achieve emission over a longer period of time (thereby producing a greatly increased duty cycle of the EUV source),

b) the plasma is confined for effective emission over a longer period of time.

Furthermore, DBLPP allows:

a) the discharge is initiated in such a way that it has already taken place at high density and in a small volume,

b) the gas discharge is forced to generate plasma at a location remote from the electrodes and other hardware to avoid erosion.

According to a third embodiment of the invention, the apparatus for generating Extreme Ultraviolet (EUV) or soft X-ray radiation comprises: discharge electrodes disposed proximate to a sputtering target similar to those used in conventional GDPP processes to generate a high density plasma in the plasma path using a conventional discharge configuration (e.g., in the form of GDPP); a laser source that irradiates the plasma in a manner that maintains EUV radiation emission; and a triggering means for triggering a laser pulse when the pinch process makes the plasma dense enough to allow for additional laser heating (LBGDPP device case).

In the third embodiment of the present inventionExample-in what is known as laser-enhanced gas discharge-generated plasma (LBGDPP), a conventional GDPP is generated which emits EUV radiation. Effectively synchronized with the discharge, the laser is focused on the plasma to sustain EUV emission for a longer time, or to effectively excite a radiation channel, which may help to improve EUV yield. There are three main approaches to this concept, depending on the desired mode of plasma excitation. To extend the plasma emission time, it needs to be at only 10 deg.f⁹-10¹⁰W/cm²Intensity within the range. For opening a new transmission channel, the preferred use is at 10¹²W/cm²Intensity within the range. Over 10¹⁴W/cm²May excite non-linear effects.

In summary, due to the hybrid nature of the DBLPP concept, several synergistic effects occur, in particular:

1. the process starts with a laser-generated plasma emitting 13.5nm EUV light. The laser plasma thus causes a triggering of a discharge that provides cheap electrical energy to maintain the plasma temperature even after the laser pulse has ended. The pinch effect will then confine the plasma for the longest possible EUV emission time (temporal level much larger than the typical laser pulse duration).

2. Due to the pre-formed LPP plasma, GDPP can operate at much longer plasma-electrode distances without significant spatial jitter (as defined by the stability of the laser focus). In addition, DBLPP will maintain the characteristic plasma size of the previous LPP plasma. Finally, since a strongly confined cold laser target is used (GDPP will not be used with a cryogenically cooled target or solid-for this reason, in the LAGDPP concept a laser is used to prepare the target for the subsequent GDPP), the residual gas pressure around the laser focal length and between the discharge electrodes is very low. This situation allows the discharge spark to be accurately generated by the pre-formed laser generated plasma. Thus, the position of the laser focus always defines the path of the spark path. (this is in contrast to previous experiments with laser-triggered discharges-in these experiments the entire chamber was filled with gas-so the laser-triggered discharge followed a random spark path.)

3. The preformed LPP allows confinement by a magnetic field before discharge occurs.

For optimal use of the hybrid source concept, the synchronization between laser and discharge (LAGDPP and LBGDPP) may be actively controlled, or even spontaneously performed (DBLPP). The absolute time jitter of EUV emission is much lower compared to the GDPP concept, since it is controlled in situ by the generation of the laser plasma and not necessarily by some external power supply.

Claims (26)

1. A method for generating Extreme Ultraviolet (EUV) or soft X-ray radiation, wherein a plasma is generated and heated in a hybrid manner by the combination of a laser radiation generated by a laser source with an electric discharge generated by electrodes in combination with means for generating a rapid electric discharge, the laser radiation having a value of more than 10⁶W/cm²Wherein the time constant of the expansion time of the laser-generated plasma exceeds the characteristic time constant of the discharge, wherein the discharge time between the electrodes is between 100ns and 200ns,and the laser pulse duration of the laser pulse generated by the laser source is a few nanoseconds and does not exceed 60 ns.

2. The method of claim 1, wherein the target is one more than 10¹⁹Atom/cm³Gaseous, liquid spray, cluster spray, or solid media.

3. The method of claim 2, wherein an EUV plasma is first formed by focusing the laser radiation in a laser interaction region on the target, and then a discharge is induced in the laser interaction region, thereby promoting the initial laser-generated plasma and enhancing total EUV light production.

4. A method as claimed in claim 1 or 2 wherein a cold plasma is generated from the laser radiation focused on the target to form a cold plasma plume and a discharge is then actively triggered in a delocalised interaction region of the plasma plume to heat and compress the plasma for more confined EUV light emission.

5. The method of claim 1, wherein the current pulse applied by the electrode in the presence of plasma is provided by the rapid discharge of stored energy of the capacitance.

6. The method of claim 1, wherein the current pulse applied by the electrode in the presence of plasma is selected to have a period in a range of 1 to 3 bits of nanoseconds.

7. The method of claim 1, wherein the current pulse applied by the electrode in the presence of plasma is selected to have an amplitude in the range of one 2 to 3 kiloamperes.

8. The method of claim 1, wherein the current pulse applied by said electrode in the presence of plasma is switched in a prescribed time relationship with said ignition of said laser pulse generated by said laser source, whereby synchronization between a fast discharge and said laser pulse causes said current pulse and said laser pulse to combine and facilitate generation of said plasma.

9. The method of claim 1, wherein the generated plasma has a temperature in the 6-digit kelvin absolute temperature range.

10. The method of claim 1, wherein the plasma is generated at a gas pressure selected in a range below 10 Pa.

11. The method of claim 1, wherein the plasma emits radiation having a wavelength shorter than 50 nm.

12. The method of claim 1, wherein the target is selected from the group consisting of: xenon, tin, copper, lithium, oxygen, iodine.

13. The method of claim 2, wherein the target is a bulk target or a foil target.

14. An apparatus for generating Extreme Ultraviolet (EUV) or soft X-ray radiation, wherein it comprises: a laser source for generating a laser radiation of more than 10⁶W/cm²The intensity of the plasma is focused on a target to form a plasma; electrodes arranged around the path of the plasma formed by the laser source, the electrodes being combined with means for forming a rapid discharge in the plasmaAnd, the rapid discharge has a characteristic time constant that is less than the time constant of the expansion time of the laser-generated plasma, wherein the discharge time between the electrodes is between 100ns and 200ns, and the laser pulse duration of the laser pulse generated by the laser source is a few nanoseconds and does not exceed 60 ns.

15. The apparatus of claim 14, wherein the means for forming a rapid discharge comprises a pulse compressor.

16. The apparatus of claim 14, wherein the means for forming a rapid discharge comprises a capacitor bank.

17. The apparatus of claim 16, wherein the electrode is directly connected to the capacitor bank to form the rapid discharge.

18. The apparatus of claim 16, wherein said electrode is connected to said capacitor bank via a power on-off switch, said power on-off switch being turned on by a logic control element to create said rapid discharge.

19. The apparatus of claim 14, comprising a nozzle for injecting a cold-jet target, a micro-fluid jet target, a droplet-jet target, a cluster-jet target, or a propellant gas target into a jointed vacuum chamber equipped with at least one electrically insulating block to house the electrodes around a laser interaction region of the target.

20. The apparatus of claim 19, wherein the electrically insulating mass is cryogenically cooled and allows for the elimination of thermal loads created by absorption of both in-band and out-of-band radiation that is not used.

21. The apparatus of claim 19 or 20, wherein said electrically insulating mass also serves as a thermal shield for a cryogenic target injector.

22. The apparatus according to claim 19, wherein it further comprises a second vacuum chamber connected to said jointed vacuum chamber via an aperture to receive unused target material downstream of the EUV light emission region (10) generated by said laser interaction region (4).

23. The device of claim 19, wherein the electrodes are arranged in a Z-pinch, hollow cathode pinch, star pinch, or capillary discharge configuration.

24. The apparatus of claim 14, wherein a laser beam formed by the laser source irradiates a solid block, solid foil, liquid, spray, cluster, or erupting gas target to form a cold plasma plume, and the discharge electrode is disposed in a path of the plasma plume with a laser interaction region that facilitates heating and compression of the plasma for more confined EUV emission.

25. The apparatus of claim 24, including a pulse generator connected to said electrodes, said pulse generator triggering an electrical discharge when said plasma plume enters the space between said electrodes.

26. The apparatus of any one of claims 14 to 18, wherein it comprises: discharge electrodes disposed proximate to a sputtering target to form a high density plasma in the path of the plasma using a conventional discharge configuration of a plasma generated by a gas discharge; a laser source that irradiates the plasma in a manner that maintains the EUV radiation emission; and means for triggering the laser pulse when a pinch process makes the plasma dense enough to allow additional laser heating.