TW201603649A - Calibration of photoelectromagnetic sensor in a laser source - Google Patents

Abstract

In a laser-produced plasma (LPP) extreme ultraviolet (EUV) system, laser pulses are used to produce EUV light. To determine the energy of individual laser pulses, a photoelectromagnetic (PEM) detector is calibrated to a power meter using a calibration coefficient. When measuring a unitary laser beam comprising pulses of a single wavelength, the calibration coefficient is calculated based on a burst of the pulses. A combined laser beam has main pulses of a first wavelength alternating with pre-pulses pulses of a second wavelength. To calculate the energy of the main pulses in the combined laser beam, the calibration coefficient calculated for a unitary laser beam of the main pulses is used. To calculate the energy of the pre-pulses in the combined laser beam, a new calibration coefficient is calculated. When the calculated energy values drift beyond a pre-defined threshold, the calibration coefficients are recalculated.

Description

Correction technology of optical electromagnetic sensor in laser source Field of invention

This application is all about laser systems and, more specifically, for correction of optical electromagnetic sensors in a laser source of one of the laser-made plasma (LPP) extreme ultraviolet (EUV) systems. .

Background of the invention

The semiconductor industry continues to develop lithography technology, which is capable of printing smaller integrated circuit sizes. Extreme ultraviolet ("EUV") light (sometimes referred to as soft x-ray) is generally defined as electromagnetic radiation having a wavelength between 10 and 102 nm. EUV lithography is generally considered to include EUV light at wavelengths in the range of 10 to 14 nm, and is used to fabricate extremely fine structures (e.g., fine structures below 32 nm) in a substrate such as a germanium wafer. These systems must be highly reliable and provide cost-effective capacity and a reasonable process margin.

The method for producing EUV light includes, but is not necessarily limited to, converting a material into a plasma state having one or more elements (eg, antimony, lithium, tin, indium, antimony, bismuth, aluminum, etc.) having one or More radiation in the EUV range, etc. In one such method, commonly referred to as laser-made plasma ("LPP"), the desired plasma can be in a LPP EUV source plasma chamber. One of the illumination positions is generated by irradiating a target material with a laser beam, such as a fine droplet, a trickle or a bunch of materials having the desired radiation element.

FIG. 1 illustrates some components of a prior art LPP EUV system 100. A laser source 101, such as a CO ₂ laser, will cause a laser beam 102 that passes through a beam delivery system 103 and passes through a focusing beam 104 or the like (including a lens and a steering mirror). The focusing optic 104 has a main focus 105 at an illumination location within an LPP EUV source plasma chamber 110. A fine drop generator 106 produces a fine droplet 107 or the like of a suitable target material which, when fired at the primary focus 105 by the laser beam 102, produces a plasma which illuminates the EUV light. An elliptical mirror ("collector") 108 focuses the EUV light from the plasma in a focus region 109 (also referred to as an intermediate focus position) for delivering the generated EUV light to, for example, a lithography Scanning system (not shown). The focus area 109 will typically be in a scanner (not shown) containing wafers or the like to be exposed to the EUV light. In some embodiments, there may be a plurality of laser sources 101, and all of their beams converge on the focusing optics 104. An LPP EUV source may use a CO ₂ laser and a zinc selenide (ZnSe) lens with an anti-reflective coating and a transparent aperture of about 6 to 8 inches.

The laser source 101 can be operated in a burst mode in which several light pulses are generated in a burst and there is some amount of time between bursts. The laser source 101 can include a plurality of lasers that produce pulsed laser beams having various properties, such as wavelength and/or pulse length. Within the laser source 101, the beam delivery system 103, and the focusing optics 104, the separate laser beams can be combined, split, or manipulated.

The laser beam 102 reaches the LPP EUV source plasma chamber 110 Previously, the beam 102 would be measured at different points within the laser source 101, the beam delivery system 103, and/or the focusing optics 104. These measurements are obtained using various instruments that measure one or more characteristics of the laser beam 102. In some examples, the laser beam 102 can be measured before it is combined with other generated beams, or after it has been combined. However, such instruments may not directly measure certain properties of the laser beam 102, or may not be corrected in a manner that enables the measurement of the properties of the laser beam 102.

Summary of invention

In accordance with an embodiment, a system includes: an energy monitor in a laser fabricated plasma (LPP) extreme ultraviolet (EUV) system configured to measure a laser beam prior to its inclusion The pulse and the main pulse are separated by a length of time, and the energy monitor comprises: a power meter configured to sense an average power of the series of the laser pulses over a defined period of time, and a light An electromagnetic (PEM) detector is configured to provide a voltage signal indicative of a temporary profile of the first pre-pulse separated from the first main pulse by a length of time during a portion of the defined time period; The calibration module is configured to determine a power of the first main pulse according to a main pulse correction coefficient and a pulse integral of a portion of the voltage signal corresponding to the first main pulse, and according to the average power sum The power of the first main pulse determines a power of the first pre-pulse, and is determined according to the power of the first pre-pulse and an integral of a portion of the voltage signal corresponding to the first pre-pulse a front pulse correction coefficient; and one Pulse energy calculation (SPEC) of the front module can be constructed to pulses provided by the correction coefficient and the detector based PEM One of the portions of the second voltage signal corresponding to the second pre-pulse is pulse-integrated to determine an energy of a second pre-pulse, and the correction coefficient according to the main pulse and the corresponding to the second main pulse One of the two voltage signals is pulse integrated to determine the energy of one of the second main pulses.

The system may further include a re-correction module configured to calculate, according to the second voltage signal provided by the PEM, the energy of the laser beam over a second defined time period, and configured to The calculated laser beam energy is compared to the average power sensed by the power meter over the second defined time period, and the correction module is instructed to update the pre-pulse correction coefficient according to the comparison.

In accordance with an embodiment, a method includes: using an energy monitor in a laser-made plasma (LPP) extreme ultraviolet (EUV) system to receive a measurement of a laser beam including a pre-pulse and a main pulse a value, the measured value of the laser beam comprising: a series of the laser pulses measured using a power meter, the average power of one of the defined time periods, and a first voltage signal representing a length of time a temporary profile of a first pre-pulse of one of the pre-pulses separated from the first main pulse of the primary pulses, the first voltage signal being provided by a photo-electromagnetic (PEM) detector; corrected by a primary pulse And integrating a coefficient and a portion of the first voltage signal corresponding to the first main pulse to determine a power of the first main pulse; determining the first according to the average power and the power of the first main pulse a power of a pre-pulse; determining a pre-pulse correction coefficient according to the power of the first pre-pulse and an integral of a portion of the first voltage signal corresponding to the first pre-pulse; correcting according to the pre-pulse Coefficient and by the PEM detector For to correspond to a second front One of the portions of the second voltage signal is integrated to determine an energy of the second pre-pulse; and a portion of the second voltage signal corresponding to the second main pulse according to the main pulse correction coefficient One of the integrals determines the energy of one of the second main pulses.

According to an embodiment, a non-transitory computer readable medium having instructions embodied thereon, the instructions being executable by one or more processors to perform the following operations, comprising: a plasma fabricated in a laser (LPP) An extreme ultraviolet (EUV) system uses an energy monitor to receive a measurement of a laser beam comprising a pre-pulse and a main pulse, the measurement of the laser beam comprising: measuring using a power meter The series of laser pulses are averaged over a defined period of time, and a first voltage signal is indicative of the pre-pulses separated from the first main pulse of one of the main pulses by a length of time a temporary profile of one of the first pre-pulses, the first voltage signal being provided by a photoelectromagnetic (PEM) detector; a correction coefficient according to a main pulse and a portion of the first voltage signal corresponding to the first main pulse One of the integrals determines a power of the first main pulse; determining the power of the first pre-pulse according to the average power and the power of the first main pulse; and the power and corresponding according to the first pre-pulse In the first pre-pulse Integrating a portion of the voltage signal to determine a pre-pulse correction coefficient; and determining a pre-pulse correction coefficient and a portion of the second voltage signal corresponding to a second pre-pulse provided by the PEM detector Integrating to determine an energy of the second pre-pulse; and determining an energy of the second main pulse according to the main pulse correction coefficient and an integral of a portion of the second voltage signal corresponding to a second main pulse .

According to an embodiment, a system includes: an energy monitor in a laser source of a laser-made plasma (LPP) extreme ultraviolet (EUV) system, the energy monitor configured to measure the same wavelength And a laser pulse or the like occurring in a burst, the energy monitor includes: a power meter configured to measure the average power of the laser pulses over a defined period of time, and a photoelectromagnetic (PEM) The detector is configured to provide a first voltage signal indicating that the burst of the laser pulses is temporarily profiled over at least one of the defined time periods; a calibration module is configured to be based on the average power and The first voltage signal determines a correction coefficient, wherein the correction coefficient is a ratio of energy of one of the bursts of the laser pulses determined by integrating the average power with one of the first voltage signals; and calculating a single pulse energy The (SPEC) module is configured to determine the laser pulse of the series according to the correction coefficient and a pulse integral of a second voltage signal provided by the PEM detector indicating a temporary profile of the one of the subsequent pulses Follow-up pulse One energy.

The system can further include a recalibration module configured to calculate a second burst of energy according to a third voltage signal representing a second temporary profile of the second burst, and the second burst can be The energy is compared to a second average power sensed by the power meter, and the correction module is instructed to update the correction coefficient according to the comparison.

According to an embodiment, a method includes: using an energy monitor to measure the same wavelength and occurring in a burst in a laser source of a laser-made plasma (LPP) extreme ultraviolet (EUV) system Laser pulse or the like, the measurement comprising: receiving, by a power meter, an average power of one of the laser pulses measured over a defined period of time; and The (PEM) detector receives a first voltage signal indicative of a temporary profile of one of the bursts of the detected laser pulses in at least a portion of the defined time period; and based on the average power and the first voltage signal Determining a correction coefficient, the correction coefficient being a ratio of energy of one of the bursts of the laser pulses determined by the integration of the average power and one of the first voltage signals; and according to the correction coefficient and by the PEM detector One of the second voltage signals representing one of the subsequent pulses is integrated to determine an energy of a subsequent pulse of one of the series of laser pulses.

According to an embodiment, a non-transitory computer readable medium having instructions embodied thereon, the instructions being executable by one or more processors to perform the following operations, comprising: a plasma fabricated in a laser (LPP) An energy monitor in one of the extreme ultraviolet (EUV) systems uses an energy monitor to measure laser pulses or the like that have the same wavelength and occur in a burst, the measurement comprising: receiving by a power meter over a defined The average power of one of the laser pulses measured during the time period and the receipt of a first voltage signal by a photoelectromagnetic (PEM) detector indicating that the first voltage signal is sensed in at least a portion of the defined time period One of the bursting laser pulses is temporarily shaped; a correction coefficient is determined according to the average power and the first voltage signal, and the correction coefficient is determined by integrating the average power with one of the first voltage signals a ratio of energy of one of the laser pulses; and determining the laser pulse of the series based on the correction factor and an integral of a second voltage signal provided by the PEM detector indicating a temporary profile of one of the subsequent pulses An energy of a subsequent pulse.

100‧‧‧LLP EUV system

101‧‧‧Laser source

102‧‧‧Ray beam

103‧‧‧beam conveyor system

104‧‧‧ Focusing light parts

105‧‧‧ main focus

106‧‧‧Drip generator

107‧‧‧fine drops

108‧‧‧ Ellipsoid

109‧‧‧ Focus area

110‧‧‧LPP EUV source plasma chamber

200, 902‧‧‧ energy monitor

202‧‧‧Power meter

204‧‧‧beam splitter

206‧‧‧ reflector

208‧‧‧Photoelectromagnetic detector

300‧‧‧ diagram

302, 402, 602‧‧ ‧ laser bursts

304‧‧‧ burst length

306‧‧‧Scope window

308‧‧‧ burst cycle

310‧‧‧ rising edge

312‧‧‧ spike

314‧‧‧Voltage scale

316‧‧‧ falling edge

400, 500, 600, 700, 800‧‧‧ charts

502, 804‧‧‧ main pulse

702, 802‧‧‧ pre-pulse

900‧‧‧ system

904‧‧‧ Calibration Module

906‧‧‧ single pulse energy calculation module

908‧‧‧Recalibration module

1000‧‧‧ Calculation method

1002~1008, 1102~1106, 1202~1210‧‧‧ steps

1100, 1200‧‧‧ calibration method

1 is a simplified diagram of a portion of an LPP EUV system in accordance with one of the conventional techniques.

2 is a simplified diagram of an energy monitor in accordance with an embodiment.

3 is a diagram of one of the burst modes of a laser source in accordance with an embodiment.

Figure 4 is a graph showing the output of a PEM detector showing a temporary profile of a burst containing a number of main pulses.

Figure 5 is a graph showing the output of a PEM detector showing a temporary profile of a single main pulse.

Figure 6 is a graph showing the output of a PEM detector showing a temporary profile of a burst containing a plurality of pre-pulses.

Figure 7 is a graph showing the output of a PEM detector showing a temporary profile of a single pre-pulse.

Figure 8 is a graph showing the output of a PEM detector showing a temporary profile of a pre-pulse and a main pulse separated by a length of time.

9 is a block diagram of a system for measuring energy of a pulse in accordance with an embodiment.

FIG. 10 is a flow chart showing an example of a method of measuring energy of one pulse according to an embodiment.

11 is a flow chart showing an example of a method of correcting a photoelectromagnetic (PEM) detector using a power meter of a unit laser beam.

Figure 12 is a flow diagram of an example of a method for correcting a PEM detector using a combined power beam of a laser beam.

Detailed description of the preferred embodiment

In an LPP EUV system, the energy of a laser pulse can be calculated at different locations of the laser source, the beam delivery system, and/or the focusing optics. A sensor used to measure a laser beam in an LPP EUV system does not directly measure the energy of one of the laser beams. The sensors include a power meter that provides a measure of the average power of the pulses produced over a defined period of time. The sensors further include a photoelectromagnetic (PEM) detector that outputs a voltage signal based on infrared (IR) light detected over a defined period of time. The voltage signal provides a temporary profile of one of the respective laser pulses. Using the data collected by the sensors, a correction factor is calculated to correct the PEM detector to the power meter. After the correction, the energy of the pulses can be calculated by the voltage signal provided by the PEM detector.

The measured laser beam may comprise pulses of light of the same wavelength, referred to as a unit laser beam. The unit laser beam may comprise a pre-pulse of a first wavelength or a main pulse of a second wavelength, or the like. To determine the energy of a pulse of light in a unit laser beam, the PEM detector is corrected to the power meter by calculating a correction factor for the unit's laser beam. For a unit laser beam, the correction factor is a ratio of one of the measured values received by the power meter to a voltage signal provided by the PEM detector through a burst. After correction, the correction factor and the voltage signal provided by the PEM detector are used to calculate the energy of the pulses in the unit's laser beam.

In the LPP EUV system, when two different wavelengths of unit laser beams are combined, the resulting combined laser beam has a field in that time Separate pulses of alternating wavelengths, etc. In the illustrated embodiment, the pulses in the combined laser beam alternate between the first pulse of the first wavelength and the main pulse of the second wavelength. When calculating the energy of one of the main pulses in the combined laser beam, the correction factor calculated from the unit laser of the main pulse is used. Due to the different effects between the pre-pulses and the main pulses of the optical components in the LPP EUV system in the combined laser beam, a correction factor for the separation of one of the pre-pulses in the combined laser beam is calculated. The correction coefficients of the pre-pulses are determined based on a difference between the power measured by the power meter and the power of the main pulses attributable to the combined laser beam. After the correction, the correction factor and the voltage signal provided by the PEM detector are used to calculate the respective energies of the pre-pulse and the main pulse in the combined laser beam.

2 is a simplified diagram of an energy monitor 200, including a power meter 202 and a PEM detector 208, in accordance with an embodiment. The energy monitor 200 can receive a laser beam 102 from another component within the laser source 101, for example, using a beam splitter. It will be readily apparent to those skilled in the art that prior to reaching the energy monitor 200, the laser beam 102 passes through one or more optical components to retrieve a portion of the laser beam 102 for measurement. . These optical components may include a diamond window, a partial reflector, or a zinc selenide window. An example of a laser seed module that can include the energy monitor 200 is discussed in U.S. Patent Application Publication No. 2013/0321926, which is incorporated herein by reference.

The energy monitor 200 is configured to measure the laser beam 102 at a particular location in the laser source 101, the beam delivery system 103, or the focusing optics 104. In some of the described embodiments, the energy monitor 200 The configuration enables the energy monitor 200 to measure a unit laser beam 102 of a laser pulse (eg, a pre-pulse or a main pulse, etc.) containing light of the same wavelength. The laser pulses of such light are produced by a single source, but can be produced by more than one source in other systems. In other embodiments described, the configuration of the energy monitor 200 enables the energy monitor to measure a combined laser beam 102 produced by two laser sources having different wavelengths. The laser source 101, beam delivery system 103, and the focusing optics 104 can include more than one energy monitor 200.

The laser beam 102 passes through the energy monitor 200 following a path of light. The laser beam 102 is split by a beam splitter 204 such that a first portion of the laser beam 102 continues along the optical path and the remainder of the laser beam 102 is directed to Reflector 206. The reflector 206 directs the remainder of the laser beam 102 to the power meter 202.

The power meter 202 is configured to measure the average power of the laser beam 102 over a defined period of time. This measurement may contain several bursts across the laser beam 102. In some examples, the measurement can include 5, 10, or 20 bursts across the laser beam 102. The defined time period can be one fraction of a second or a few seconds. In some instances, the defined time period is one second.

Portions of the laser beam 102 that are not directed to the power meter 202 are directed to another beam splitter 204. From the beam splitter 204, a first portion of the laser beam will, for example, be directed to another sensor or other optical component (not shown). The remainder of the laser beam 102 is directed to the PEM detector 208.

The PEM detector 208 provides a voltage signal indicative of a temporary profile of the beam 102. The temporary profile will contain at least a portion of the defined time period spanned by the power meter 202. The temporary profile can include at least one burst across the laser beam 102. To calculate the energy of a pulse in a combined laser beam, the temporary profile will span a pre-pulse and a main pulse.

Although only one PEM detector 208 is shown in FIG. 2, an added PEM detector (not shown) may also be included in the energy monitor 200. Again, the laser beam 102 can be conditioned using, for example, a lens (not shown) or a diffuser set (not shown) prior to being measured by the PEM detector 208. The energy monitor 200 can be enclosed by a housing and attached to one of the apertures of the laser source 101 or enclosed within the laser source 101.

FIG. 9 illustrates a block diagram of a system 900 for measuring energy of a pulse in accordance with an embodiment. The system 900 includes an energy monitor 902, a calibration module 904, a single pulse energy calculation (SPEC) module 906, and a selective recalibration module 908. The system 900 can be implemented in a variety of ways known to those skilled in the art, including, but not limited to, a computer device having a processor that can access a memory to store executable instructions. The computer device can include one or more input and output components, including certain components, for communicating with other computer devices via a network or other communication means. The system 900 includes one or more modules embodied as operational logic or executable code.

The energy monitor 902 is configured to receive information about laser pulses of the laser beam 102. The energy monitor 902 includes, or is electrically conductive, a power meter and a PEM detector. In some instances, the energy The quantity monitor 902 is the energy monitor 200 and includes the power meter 202 and the PEM detector 208. The power meter is configured to measure the average power of the laser pulses over a defined period of time. The defined time period can be, for example, one second. The PEM detector is configured to provide a voltage signal indicative of a temporary profile of one of the laser pulses over at least a portion of the defined time period.

When the energy monitor 200 or 902 is placed in the LPP EUV system 100 to receive a unit laser beam 102, the correction module 904 is configured to be responsive to the power meter (eg, the power meter 202) and The data collected by the PEM detector (e.g., PEM detector 208) determines a correction factor. A correction factor is calculated for each unit of the laser beam. The correction factor is used to calculate the energy of a single pulse (eg, a single main pulse 502 or a single pre-pulse 702) based on the post-collected PEM detector data. The correction coefficient is a ratio determined by the integration of the average power and one of the voltage signals.

To determine the correction factor in a unit of laser beam 102, the burst of pulses is analyzed. 3 is a diagram 300 of a second burst 302 of a laser pulse in accordance with an embodiment. The diagram 300 is a profile of the temporary profile provided by the PEM detector 208, showing a gradual voltage as a function of time (measured in milliseconds (ms)).

Each burst 302 is shown in the diagram 300 as a curve having a rising edge 310, a peak 312, and maintaining a voltage scale 314 below a highest scale for a time before ending with a falling edge 316. length. The burst 302 begins at the rising edge 310 and terminates at the falling edge. When calculating the energy of the burst 302 to calculate a correction factor, as in other locations As an illustration, the PEM detector 208 has a range window 306 that at least includes the burst length 304. The range window 306 can be lengthened to capture the time between the two bursts 302, or shortened to grab only one or two pulses in the burst 302.

A burst period 308 is referred to as a rising edge 310 of a first burst 302 to a rising edge 310 of a second burst 302. The burst period 308 can be determined by a repetition rate or "rep rate" of the bursts 302 representing a number of bursts over a defined period of time (e.g., one second). The burst repetition rate can be expressed as a frequency, such as 5 Hertz (Hz), 10 Hz, or 20 Hz.

4 is a diagram 400 showing the temporary profile of one of the bursts of unit lasers 102 including one of the primary pulses provided by the output of the PEM detector 208. This chart 400 is a practical example of one of the outputs shown in FIG. The unit laser beam 102 is produced by a single laser source. In one embodiment, the main pulses have a wavelength of 10.59 microns. As shown, the burst 402 will last for approximately 3.5 ms and will contain a predetermined number of laser pulses. According to various embodiments, a burst 402 can include a different number of laser pulses depending on the length of the burst. The laser pulses have a width (measured over a length of time) and an amplitude. As part of calculating the correction factor, the correction module 904 can integrate the pulses of the burst 402 over a length of time shown in the graph 400.

6 is a graph 600 output by the PEM detector 208 showing a temporary profile of a burst 602 of a unit laser beam 102 including a pre-pulse. This chart 600 is a practical example of one of the outputs shown in FIG. The unit laser beam 102 is generated by a single laser source, but can be used in other systems. Most laser sources are produced. In one embodiment, the pre-pulses have a wavelength of 10.26 microns. As shown, the burst 602 has a duration of approximately 3.5 ms and includes a predetermined number of laser pulses. According to various embodiments, a burst 602 can include a different number of laser pulses depending on the burst length. The laser pulses have a width (measured over a length of time) and an amplitude. As part of calculating the correction factor, the correction module 904 can integrate the pulses of the burst 602, etc., over a length of time shown in the graph 600.

The correction coefficients for the unit laser beam 102 are calculated in the same way for the unit beam containing the main pulse and the unit beam containing the pre-pulse. First, the correction module 904 determines the energy of the burst of the laser pulse from the average power. The energy produced by the defined time period over which the power is measured is determined: E _total = P _measured * T _period where E _{total is} the energy of the electrical beam 102 over the defined period of time, P _measured by The power measurement taken by the power meter 202, T _period is the defined time period (eg, 1 second) of the power meter 202. From E _total , the amount of energy in a burst is calculated using the burst repetition rate: Where E _burst is the energy of a burst, E _total is the energy of the unit's laser beam 102 over the defined period of time (eg, one second), and f _{burst is} the burst repetition rate.

To determine the correction factor K _p , the following formula will be used: K _p ʃ V dt = E _burst Where K _{p is} the correction coefficient, and V is the voltage signal received by the PEM detector 208, so the integral ʃ V dt is the area under the voltage signal curve provided by the PEM detector 208 over the length of the burst. And E _{burst is} the energy of one of the bursts determined by the average power data received by the power meter 202. The correction coefficient K _p has a unit of W/V.

The SPEC module 906 is configured to calculate the energy of a single pulse using the correction coefficients calculated by the correction module 904. The SPEC module 906 receives the voltage data from the PEM detector 208, which includes a temporary profile of a single pulse (e.g., a single main pulse 502 or a single pre-pulse 702) in a unit laser beam.

FIG. 5 is a graph 500 output by the PEM detector 208 showing the temporary profile of one of the single main pulses 502 in the unit laser beam 102. The single main pulse 502 can be one of the pulses in the burst 402 or can be one of a subsequent burst. The single main pulse 502 is reduced by the grabber of the range window 306 of the PEM detector 208. The main pulse 502 has an amplitude and a width (measured in length of time). The SPEC module 906 can integrate the main pulse 502 as part of calculating the energy of the pulse 502.

FIG. 7 is a graph 700 of a PEM detector output showing a single pre-pulse 702 in the unit laser beam 102. The single pre-pulse 702 is a grabber by reducing the length of time that the PEM detector 208 measures the laser beam 102. The front pulse 702 has an amplitude and a width (for a long time) Degree meter). The SPEC module 906 can integrate the pre-pulse 702 as part of calculating the energy of the pre-pulse 702.

Using the temporary profile of a single pulse, the energy of the single pulse is calculated according to the formula: E _pulse = K _p ʃ V dt where E _pulse is the energy of the pulse and K _p is the pulse for the pulse wavelength being measured a correction factor, and V is a voltage signal received by the PEM detector that represents a temporary profile of one of the measured pulses, such that the integral ʃ Vdt is the voltage provided by the PEM detector 208 over the length of the pulse. The area under the signal curve.

The selective recalibration module 908 is configured to determine whether to recalibrate the PEM detector 208. These correction factors may lose accuracy after prolonged, for example, due to instrumental deviation, aging of the device, or degradation of the laser splitter receiving the laser beam. In a unit laser beam, when a subsequent laser burst is generated (e.g., burst 402 or burst 602), the recalibration module 908 is configured to compare the measured value of the power meter 202 to one. The power of the laser beam 102 is calculated using the information provided by the PEM detector 208. As mentioned earlier, this comparison is made using a one second time period. As will be readily apparent to those skilled in the art, other time periods can be used, such as a burst length 304 or a burst period 308, or a number of burst periods.

To calculate the power of the pulses of the laser beam 102 over a one second period, the energy of the pulses after a burst (e.g., burst 402 or 602) is determined using the correction factor: E _burst = K _p ʃ V dt where K _p is the correction coefficient, and V is the voltage signal received by the PEM detector 208 , so the integral ʃ V dt is the voltage signal curve provided by the PEM detector 208 over the length of time of the burst The area underneath, and E _burst is one of the calculated energy. The sum of the laser pulse energies is used to determine the total energy of the laser beam 102 over the time period: E _total = Σ E _burst where E _burst is a burst of energy and E _total is the defined time period ( For example, one second of the laser beam 102 is calculated as energy, and Σ E _burst is the sum of the laser pulse energies over the defined time period. To determine the power of the pulses, the total energy is divided by the time period (eg, one second) Where E _total is the energy _calculated by the laser beam 102 over the defined time period, P _{calculated is a} power value calculated by the voltage signal received by the PEM detector 208, and T _period is the defined time period (for example, one second).

To determine whether the correction module 904 is instructed to recalculate the correction factor, the recalibration module 908 can calculate a difference between the calculated power and the measured power. This difference can be expressed in %. To determine whether to recalibrate, the recalibration module 908 can compare the difference to a threshold. In some examples, if the two power values differ by more than 15%, the recalibration module 908 instructs the correction module 904 to recalculate the correction coefficient. According to this In comparison, the recalibration manager 908 can instruct the correction module 904 to update the correction coefficient by recalculating the correction coefficient upon subsequent bursts of one of the pulses of the laser beam 102.

When the energy monitor 200 or 902 is placed in the LPP EUV system 100 to receive a combined laser beam 102, the system 900 of FIG. 9 is further configured to determine a correction factor for determining a combined laser beam. The energy of one of the pre-pulses in 102. The energy monitor 902 is disposed in the LPP EUV system 100 to measure a combined laser beam 102.

To calculate the correction coefficients for the pre-pulses in a combined laser beam 102, the correction module 904 uses a different computational group than that used when correcting a unit laser beam. These calculations use the correction coefficients calculated for the unit laser beam 102 of the main pulses to determine a portion of the power that can be attributed to the main pulses as measured by the power meter 202, using the power. The remainder of the decision is made to determine the correction factor for the pre-pulses in the combined laser beam.

8 is a temporary profile 800 of a voltage signal output by a PEM detector 208 comprising a combined pulse of a pre-pulse and a main pulse separated by a length of time. The combined laser beam 102 is generated by combining the unit laser beams 102 into a single laser beam. Therefore, in one burst of the combined laser beam 102, the pre-pulse of the burst 602, etc., and the burst The main pulse of 402 alternates in turn. As shown in Figure 8, a pre-pulse 802 will be in the first 15 microseconds than a main pulse 804. The laser pulses have a width (measured over a length of time) and an amplitude. The correction module 904 and the SPEC module 906 can be separated from the main pulse 804 as long as the length of time shown in the chart 800. The pre-pulse 802 is integrated. The integral is used to determine a correction factor for calculating the energy of the pre-pulse and to calculate the energy of a subsequent pre-pulse in a combined laser beam.

The correction module 904 calculates the power of the main pulse of the combined beam according to a voltage signal provided by the PEM detector 208 indicating a portion of the temporary profile of the main pulse in the combined pulse. Using this temporary profile, the energy of the main pulse is calculated according to the following formula: E _{main pulse} = K _mp ʃ V dt where E _{main pulse is} the energy of the main pulse and K _mp is calculated for the unit laser beam a correction factor of the main pulse of 102, and V is a voltage signal received by the PEM detector that represents a temporary profile of one of the measured main pulses, such that the integral ʃ V dt is the length of time through the main pulse The PEM detector 208 provides the area under the voltage signal curve.

The average power of the combined pulses is measured by the power meter 202 over the defined period of time (e.g., one second). Depending on the energy of the main pulse, the power attributable to the main pulses over the defined time period is calculated as: Wherein E _{main pulse is} the energy of the _{main pulse} , P _{main pulse} is the calculated power of the main pulse, T _period is the defined time period used by the power meter 202, and Σ E _{main pulses} is the power meter 202 The sum of the energies of the main pulses that occur during the defined time period. To determine that the power measured by the power meter 202 can be attributed to the portion of the _pre-pulse , the correction module 904 determines the difference: P _pre-pulse = P _measured - P _{main pulse} where P _pre-pulse The portion of the power measured by the power meter over the defined period of time that can be attributed to the pulse before the combined pulse, P _measured is the power of the combined pulse _measured by the power meter 202, and P _{main pulse} The calculated power for these main pulses.

Using the power attributable to the pre-pulses, the energy attributable to the pre-pulses will be determined as follows: Wherein E _pre-pulse is the total energy of the _pre-pulses of the defined time period used by the power meter 202, and P _pre-pulse is the power measured by the power meter over the defined time period. The portion of the pulse that is attributed to the combined pulse, T _period is the defined period of time (e.g., one second) of the power meter 202.

To determine the correction factor for the previous pulse in the combined laser beam, the following formula is used: Where K _pp is the correction factor of the previous pulse in the combined laser beam, and V is the voltage signal received by the PEM detector 208, such that the integral ʃ V dt is at least a portion of the defined time period The PEM detector 208 provides the area under the voltage signal curve, and E _pre-pulse is the total energy of the pulse prior to the defined time period used by the power meter 202. The correction coefficient K _pp has a unit of W/V.

When the correction factor of the pre-pulse in the combined laser beam is determined, the SPEC module 906 receives the voltage data from the PEM detector 208, which includes a pair of pre-pulses and main pulses of a combined laser beam. One of the temporary profiles. The SPEC module 906 can determine the energy of a subsequent _pre-pulse using the following formula: E _pre-pulse = K _pp ʃ V dt where E _pre-pulse is the energy of the single prepulse, and K _pp is used for the combined thunder a correction factor for the pulse of the pre-pulse in the beam 102, and V is the voltage signal received by the PEM detector 208 that represents a temporary profile of one of the measured pre-pulses, such that the integral ʃ V dt is the The length of the pre-pulse is the area under the voltage signal curve provided by the PEM detector 208.

The selective recalibration module 908 is more capable of determining whether the power meter 202 is to be used to recalibrate the PEM detector 208 for the prepulse in the combined laser beam 102, as previously described. For the combined laser beam, the recalibration module 908 determines the pulse power corresponding to the power meter 202 by adding the pulse energy in the combined laser beam for a defined period of time. The recalibration module 908 will calculate one of the powers calculated from the sum as compared to the power measured by the power meter 202, as previously described.

10 is a flow diagram of an exemplary method 1000 for calculating the energy of a pulse, in accordance with an embodiment. The method 1000 can be performed by the system 900.

At an operation 1002, a PEM detector is calibrated for a first laser beam using a power meter. The first laser can cause a main pulse or a prepulse in a unit laser beam. As described above, FIG. 11 is a method of using a power meter to correct a PEM detector to determine a pulse in a unit laser beam. One of the energies is an example flow chart of method 1100. The method 1100 can be performed as part of operation 1002, for example, by the energy monitor 200 or 900 of the system 900 and the correction module 904.

At an operation 1102, a power measurement is received by the power meter (e.g., power meter 202). The power measurement represents the average power of the pulse of the unit laser beam 102 over a period of time.

At an operation 1104, a voltage signal over a length of time is received by a PEM detector (e.g., PEM detector 208). The voltage signal is a temporary profile of one of the bursts of one of the unit laser beams 102. The length of time experienced by the data collected by the PEM detector 208 is at least one burst of the power meter 202 during the time period.

At an operation 1106, the correction factor for the laser beam 102 is calculated. This correction factor is calculated as described in relation to the correction mold 904. The correction factor can be calculated by the correction module 904.

If the energy monitor 200 is measuring a unit laser beam, the method 1000 skips operation 1004 and proceeds to an operation 1006. In this operation 1006, the energy of a pulse is calculated. The energy of the pulse will be calculated, for example, as described elsewhere with respect to the SPEC module 906. In some examples, the SPEC module 906 performs the operation 1006.

In a selective operation 1008, a decision will be made, ie whether The PEM detector is to be recalibrated, for example, with the recalibration module 908. The decision is made by comparing the power calculated by the voltage signal provided by the PEM detector with the power measured by the power meter. If the decision is to be recalibrated, the method 1000 will return to operation 1002, or in some instances, return to operation 1004. If the decision is not to be corrected, the method 1000 will return to operation 1006.

When the laser beam measured by the energy monitor 200 is a combined laser beam, the method 1000 proceeds from the operation 1002 to the operation 1004. The PEM detector is collimated for a combined beam to determine the energy of one of the pre-pulses within the combined beam. A second laser can cause a prepulse or the like in each burst, which, as previously described, is combined with a main pulse or the like in a combined laser beam 102. At operation 1004, the correction coefficients for the pre-pulses in the combined laser beam 102 are determined. The correction coefficients for the pre-pulses in the combined laser beam 102 are determined separately from the previous pulse in the unit laser beam 102 because the optical components of the LPP EUV system 100 are combined in the unit laser beam 102 Thereafter, the relationship between the temporary profile of the pre-pulse and the power measured by the power meter 202 is affected. The correction coefficients of the pre-pulses are determined based on a difference between the power measured by the power meter and the power of the main pulses attributable to the combined laser beam.

12 is a flow diagram of an exemplary method 1200 of using a power meter (eg, power meter 202) to calibrate a PEM detector (eg, PEM detector 208) on a combined laser beam having a pre-pulse and a main pulse, and the like. Figure. The method 1200 is an example of a method of performing the operation 1004 of the method 1000 when the laser beam measured by the energy monitor 200 is a combined laser beam. this method 1200 can be performed, for example, by calibration module 904 of system 900.

At an operation 1202, the voltage data is received from the PEM detector 208 in the energy monitor 200 or 902. The voltage data is a temporary profile of one of the combined laser beams 102, as shown in FIG. The length of time experienced by the data collected by the PEM detector 208 is at least a portion of the time period of the power meter 202.

At an operation 1204, the power attributable to the main pulses will be determined. The power of the main pulses is determined as described in relation to the correction module 904 and the SPEC module 906.

At an operation 1206, the power profile is received by the power meter 202. The power data represents the average power of the combined laser beam 102 over a period of time.

At an operation 1208, the power in the combined laser beam 102 attributable to the pre-pulses may be determined. The power of the pre-pulses is determined as described in relation to the correction module 904 and the SPEC module 906.

At an operation 1210, the correction coefficients for the pre-pulses in the combined laser beam 102 are calculated. The correction factor is calculated as described in relation to the correction module 904.

When the laser beam measured by the energy monitor 200 is a combined laser beam, it proceeds to the operation 1006, and the energy of each of the main pulse and the pre-pulse in the combined laser beam is manipulated as before. Calculated in the manner of 1006. The correction factor of the operation 1002 calculated for the unit beam of the main pulse is used to calculate the energy of one of the main laser pulses in the combined laser beam. To calculate the energy of the previous pulse in the combined laser beam, the correction of operation 1004 The coefficients will be used. When the laser beam measured by the energy monitor 200 is a combined laser beam, the method 1000 can proceed to the selective operation 1008 as previously described.

The disclosed methods and apparatus have been described above with reference to a few embodiments. Other embodiments will be readily apparent to those skilled in the art upon review of this disclosure. Certain aspects of the methods and apparatus may be readily implemented using configurations other than those described in the above embodiments, or in conjunction with elements other than those described above. For example, different algorithms and/or logic circuits, etc., which may be more complex than the above, and possibly different types of laser beam generating systems, etc., may also be used.

Also, it should be appreciated that the methods and apparatus described can be implemented in many ways, including as a method, a device, or a system. The methods described herein can be implemented with program instructions that can instruct a processor to perform the methods, and the instructions are recorded on a non-transitory computer readable storage medium, such as a hard disk drive, soft Discs, such as CD-ROMs or digital versatile discs (DVDs), flash memory, etc., or transmitted to a computer network, where the program instructions are placed on an optical or electronic communication link. Transfer. It should be noted that the order of the various steps of the method described may be varied while remaining within the scope of the disclosure.

It should be understood that the examples provided are for illustrative purposes only and may be extended to other applications and embodiments with different conventions and techniques. While a few embodiments are disclosed, it is not intended to limit the disclosure to the embodiments disclosed. On the contrary, it is intended to cover all such changes, modifications, and equivalents

In the above description, the present invention has been described with reference to the specific embodiments thereof, but those skilled in the art will understand that the invention is not limited thereto. The various features and aspects of the above described invention may be used individually or together. Further, the present invention can be utilized in any number of environments and applications beyond those described herein without departing from the broader spirit and scope of the disclosure. Accordingly, the specification and drawings are to be regarded as It should be understood that such "including", "including" and "having", if used herein, are intended to be interpreted as open-ended terms of technology.

900‧‧‧ system

902‧‧‧Energy monitor

904‧‧‧ Calibration Module

906‧‧‧ single pulse energy calculation module

908‧‧‧Recalibration module

Claims (22)

A system comprising: an energy monitor in a laser-made plasma (LPP) extreme ultraviolet (EUV) system, the energy monitor configured to measure a laser beam comprising a length of time separated The pre-pulse and the main pulse, etc., the energy monitor comprises: a power meter configured to sense an average power of the series of the laser pulses over a defined period of time, and a photoelectromagnetic (PEM) The detector is configured to provide a voltage signal indicative of a temporary profile of the first pre-pulse separated from the first main pulse by the length of time during a portion of the defined time period; a calibration module Determining, according to a main pulse correction coefficient and a pulse integral of a portion of the voltage signal corresponding to the first main pulse, determining a power of the first main pulse, and according to the average power and the first The power of the main pulse determines a power of the first pre-pulse, and determines a pre-pulse correction according to the power of the first pre-pulse and an integral of a portion of the voltage signal corresponding to the first pre-pulse Coefficient; and a single pulse energy The calculation (SPEC) module is configured to determine a second front according to the pre-pulse correction coefficient and one of the second voltage signals provided by the PEM detector corresponding to a pulse integral of a portion of the second pre-pulse One of the pulses of energy, and the pulse corresponding to the main pulse correction coefficient and the second voltage signal corresponding to a portion of the second main pulse Integration determines the energy of one of the second main pulses. The system of claim 1, further comprising a recalibration module configured to calculate an energy of the laser beam over a second defined time period based on the second voltage signal provided by the PEM. The system of claim 2, wherein the recalibration module is further configured to compare the calculated energy of the laser beam to the average power sensed by the power meter over the second defined time period And according to the comparison, the correction module is required to update the pre-pulse correction coefficient. The system of claim 3, wherein the recalibration module is configured to indicate that the correction module is to update the pre-pulse correction coefficient if the comparison exceeds a threshold. The system of claim 1, wherein the correction module is configured to be determined by subtracting the power attributable to the main pulses during the defined time period by the average power over the defined time period The power of the first pre-pulse. A method comprising: using an energy monitor in a laser-made plasma (LPP) extreme ultraviolet (EUV) system to receive a measurement of a laser beam comprising a pre-pulse and a main pulse, the radar The measured value of the beam includes: an average power of the series of the laser pulses measured over a defined period of time using a power meter, and a first voltage signal representing the length of the master with a length of time a temporary profile of the first pre-pulse of one of the pre-pulses separated by one of the first main pulses, the first voltage signal being provided by a photoelectromagnetic (PEM) detector; Determining a power of the first main pulse according to a main pulse correction coefficient and an integral of the first voltage signal corresponding to a portion of the first main pulse; according to the average power and the power of the first main pulse Determining a power of the first pre-pulse; determining a pre-pulse correction coefficient according to the power of the first pre-pulse and the integral of the first voltage signal corresponding to a portion of the first pre-pulse; And a correction coefficient and a second voltage signal provided by the PEM detector corresponding to one of a portion of the second pre-pulse to determine an energy of a second pre-pulse; and the correction coefficient according to the main pulse and the first The two voltage signals are integrated with one of a portion of the second main pulse to determine an energy of a second main pulse. The method of claim 6, further comprising calculating an energy of the laser beam over a second defined time period based on the second voltage signal provided by the PEM. The method of claim 7, further comprising comparing the calculated energy of the laser beam to an average power over the second defined time period, and updating the pre-pulse correction coefficient according to the comparison. The method of claim 8, wherein the pre-pulse correction coefficient is based on the comparison exceeding a threshold. The method of claim 6, wherein determining the power of the first pre-pulse is subtracted from the average power over the defined time period The power of the main pulses can be performed in the time period. A system comprising: an energy monitor in a laser source of a laser-made plasma (LPP) extreme ultraviolet (EUV) system, the energy monitor configured to measure a wavelength and be in a burst a laser pulse or the like occurring in the medium, the energy monitor comprising: a power meter configured to measure an average power of the laser pulses over a defined period of time, and a photoelectromagnetic (PEM) detector structure Forming a temporary profile of the burst capable of providing a first voltage signal indicative of at least a portion of the defined time period; a calibration module configured to be responsive to the average power and The first voltage signal determines a correction coefficient, wherein the correction coefficient is a ratio of the energy of the burst of the laser pulses determined by the average power to an integral of the first voltage signal; and a single pulse energy calculation a (SPEC) module configured to determine the string of the laser pulses based on the correction factor and a pulse integral of a second voltage signal representative of a temporary profile of the subsequent pulse provided by the PEM detector Subsequent pulse An energy. The system of claim 11, further comprising a recalibration module configured to calculate a second burst of energy based on a third voltage signal representing a second temporary profile of the second burst. The system of claim 12, wherein the recalibration module is further configured to compare the energy of the second burst to one of the sensing by the power meter The average power is based on the comparison to indicate that the correction module is to update the correction coefficient. The system of claim 13, wherein the recalibration module is configured to indicate that the correction module is to update the correction coefficient if the comparison exceeds a threshold. The system of claim 11, wherein the laser pulses are primary pulses. The system of claim 11, wherein the laser pulses are pre-pulses. A method comprising: using an energy monitor in a laser source of a laser-made plasma (LPP) extreme ultraviolet (EUV) system to measure laser pulses having the same wavelength and occurring in a burst The measuring comprises: receiving, by a power meter, an average power of the ones of the laser pulses measured over a defined period of time; and receiving a first voltage signal by a photoelectromagnetic (PEM) detector One of the laser pulses sensed during at least a portion of the defined time period is temporarily profiled; a correction coefficient is determined based on the average power and the first voltage signal, the correction coefficient being determined by the average power And a ratio of an energy of one of the laser pulses to an integral of the first voltage signal; and a second voltage signal according to the correction coefficient and a temporary profile of the subsequent pulse provided by the PEM detector One of the integrals determines the energy of one of the subsequent pulses of the string of the laser pulses. The method of claim 17, further comprising calculating a second burst of energy based on a third voltage signal indicative of a temporary profile of the second burst. The method of claim 18, further comprising comparing the energy of the second burst to a second average power sensed by the power meter, and updating the correction coefficient according to the comparison. The method of claim 19, wherein updating the correction coefficient is based on the comparison exceeding a threshold. The method of claim 17, wherein the laser pulses are main pulses. The method of claim 17, wherein the laser pulses are pre-pulses.