TWI389409B - Method and apparatus for laser control in a two chamber gas discharge laser - Google Patents

Abstract

A laser control system contains an oscillator gas chamber and an amplifier gas chamber. A first voltage input is operatively connected to deliver electrical pulses to a first pair of electrodes within the oscillator gas chamber and a second pair of electrodes within the amplifier gas chamber. An output of the gas chambers is an energy dose calculated by a trapezoidal window. A control circuit connects to the first voltage input for modifying the first voltage input. A feedback control loop communicates an output of the gas chambers to the control circuit for modifying the first voltage input.

Description

Laser control method and device for two-chamber gas discharge laser Field of invention

The main disclosure of the present disclosure relates generally to laser systems and more particularly to laser control systems for one or two chamber gas discharge lasers.

Background of the invention

Figure 1 is a block diagram of a MOPA (Primary Oscillator/Power Amplifier) laser system 10 known in the prior art. The MOPA laser system 10 is used, for example, in the field of integrated circuit printing. In one embodiment of the MOPA laser system 10, a 193 nm ultraviolet laser beam is provided in a lithography machine/scanner 2 such as a stepper or scanner provided by a Japanese Canon or Nikon device or a Dutch ASML device. Enter 埠. The MOPA laser system 10 includes a laser energy control system 4 for controlling the pulse energy and cumulative dose energy output of the system at a pulse repetition rate such as 4,000 Hz or greater. The MOPA laser system 10 provides a very accurate triggering of the discharges in the two chambers that are related to each other by feedback and feedforward control of the pulse and dose energy.

The main components of the laser system 4 are typically mounted below the layer/board 5 on which the scanner 2 is mounted. However, the MOPA laser system 10 includes a beam delivery unit 6 that provides a closed beam path for delivering the laser beam to one of the input ports of the scanner 2. The light source comprises, for example, a seed laser generator, such as a primary oscillator 11, and an amplified laser portion, such as a power amplifier 12, which will be described in more detail below and which may also be, for example, a An oscillator of the Power Loop Oscillator ("PRA"), which will also be described in more detail below. For convenience, the seed laser may be referred to as a MO and the amplification laser may be referred to as a power amplifier or a PA for the purpose of covering the seed laser arrangement and amplifying the laser throughout the application. Other forms of arrangement, such as a power loop amplifier ("PRA") that is actually an oscillator (ie, a power oscillator ("PO"), and which together form a MOPO, and unless explicitly stated, Otherwise these terms are intended to be broadly defined. The light source also includes a pulse stretcher 22.

Each of the main oscillator 11 and the power amplifier/power oscillator 12 includes a discharge chamber 11A, 12A similar to a single chamber printing laser system. These chambers 11A, 12A comprise two electrodes, a laser gas, and a line for circulating air between the electrodes and the water-cooled fin heat exchanger. The main oscillator 11 produces a first laser beam 14A that is amplified, produced by oscillating in the PO/PRA in a PA architecture by passing through the power amplifier 12 or in a PO/PRA architecture. A second laser beam 14B as shown in FIG. The main oscillator 11 includes a resonant cavity formed by an output coupler 11C and a spectral line widening block 11B. The gain medium of the main oscillator 11 is generated between two elongated electrodes included in the main oscillator discharge chamber 11A. The power amplifier 12 is substantially a discharge chamber 12A and, in the preferred embodiment, is nearly identical to the main oscillator discharge chamber 11A that provides a gain medium between the two electrodes, but the power amplifier 12 may not have The cavity is different from a PO/PRA. This MOPA laser system 10 architecture allows the main oscillator 11 to be designed and operated to maximize beam quality parameters such as wavelength stability and very narrow bandwidth; wherein the power amplifier 12 is designed and operated to maximize power output. For this reason, the MOPA laser system 10 exhibits a higher quality and higher power laser source than a single chamber system.

As noted above, the amplifier portion can be assembled, such as by two beam paths of the discharge region of the discharge chamber of the amplifier or oscillations in the chamber containing the discharge chamber of the amplifier, as shown in FIG. The beam oscillates within the cavity of the main oscillator chamber 11A between the LNP 11B containing the MO 11 and the output coupler 11C (having a 30% reflection coefficient), and is severely lined as it passes through the LNP 10C. Reduced. The wavelength of the laser beam from one of the output couplers 11C is measured by a line center analysis module 7. The spectrally broadened seed beam is reflected downward by a mirror in the MO wavelength processing block (MO WEB) 24 and is slightly skewed at an angle via the PA wavelength processing block (PA WEB) 26. (relative to the electrode direction) is reflected horizontally to the amplifier chamber 12. At the rear end of the amplifier, a beam commutator 28 reflects the beam back horizontally in line with the direction of the electrode to oscillate a second time through the PA chamber 12 or in the PO/PRA chamber. The bandwidth of one of the lasers from the discharge chamber 12A is measured by a spectral analysis module 9, although the bandwidth of the laser can be replaced with a bandwidth analysis module.

The laser system output beam pulse 14B is passed from the PA/PO chamber 12A to a beam splitter 16. The beam splitter 16 reflects approximately 60% of the power amplifier output beam 14B into a delay path generated by the four focusing mirrors 20A, 20B, 20C, and 20D. The 40% transmitted portion of each pulse of beam 14B becomes the first peak of one of the widened pulses corresponding to one of the output beam pulses 14C. The output beam 14C is directed by beam splitter 16 to focus the reflected portion to mirror 20A of point 22. The beam is then unrolled and reflected from mirror 20B, which converts the unfolded beam into a parallel beam and directs it to mirror 20C which again focuses the beam at point 22. The beam is then redirected into a parallel beam by a mirror 20D like the mirror 20B and directed back to the beam splitter 16, wherein 60% of the first reflected light is preferably associated with the output beam 14C The first transmitted portion of the pulse is uniformly reflected to become a majority of a second peak in the output beam pulse of the laser system. 40% of the reflected beam is transmitted to beam splitter 16 and accurately along the path of the first reflected beam that produces additional small peaks in the widened pulse. The result is the completed output beam 14C, which extends from 20 ns to approximately 70 ns over the pulse length. A beam delivery unit (BDU) transmits the output beam 14C. The BDU can include two beam pointing mirrors 40A, 40B, one or both of which can be controlled to provide tilt and offset correction for varying beam directions.

In accordance with this prior art, FIG. 2 is an illustration of one of the energy control block diagrams 50 for the MOPA/MOPO laser system of FIG. Figure 2 illustrates various control elements that control one of the voltages 52 of the MOPA laser system 10. The energy control block diagram 50 includes a static control 54 that provides a voltage that is desired to achieve a substantially determined one of the energy targets 56 (if there are no other effects to account for). A feed forward block 58 provides a voltage adjustment based on a trigger interval 60. Trigger interval 60 can be used to calculate the repetition rate, number of shots, and duty cycle that affect the "voltage input - energy output" relationship. This voltage adjustment is calculated as a function of this value. An energy servo 62 adjusts the voltage input 52 based on the calculated voltage error of one of the previous emissions. A jitter cancel 66 adjusts the voltage to cancel the energy change caused by a time jitter 68. Finally, an energy jitter 70 provides a periodic signal to the voltage input 52 that is used to estimate the effect of voltage on MO energy, output energy, and MOPA time. These five voltage signals are added together to produce the voltage input 52. When the laser is fired, energy 72 is measured. The energy target is subtracted from the measured energy to produce an energy error signal 74 that is scaled by dV/dE (the laser's estimate of the derivative of the energy with respect to the energy 76). The resulting voltage error 64 is used to drive an adaptive algorithm 78 that adjusts some of the voltage signals in a manner that minimizes energy error, dose error, energy sigma, or some combination thereof.

The MOPA laser system 10 shown in Figure 1 is an improvement of the single chamber system that provides greater beam control, beam power and stability than the single chamber system. However, solving the system's pitch disturbances and further sharpening time and energy control can significantly improve the operation.

Summary of invention

Some aspects of embodiments of the present disclosure provide a system and method for controlling a laser system. Briefly, in terms of architecture, one level of a possible embodiment of the system can be implemented as follows. The system includes an oscillator gas chamber and an amplifier gas chamber. A first voltage input is operatively coupled to deliver an electrical pulse to a first pair of electrodes within the oscillator gas chamber and a second pair of electrodes within the amplifier gas chamber. One of the gas chamber outputs is an energy dose calculated from a trapezoidal window. A control circuit is coupled to the first voltage input for modifying the first voltage input. A feedback control loop passes the output of one of the gas chambers to a control circuit for modifying the first voltage input.

Some aspects of the disclosed landmarks can also be viewed as providing a method for controlling a laser system. In this regard, an embodiment of such a method can be summarized in particular as the step of operatively transmitting a first voltage input as an electrical pulse to a first pair of electrodes within an oscillator gas chamber. And a second pair of electrodes in an amplifier gas chamber; calculating an energy dose of one of the gas chambers through a trapezoidal window; modifying the first voltage input through a control circuit; and transmitting through a feedback control loop One of the gas chamber outputs is passed to the control circuit to modify the first voltage input.

Other systems, methods, features and advantages of the present invention will be or become apparent to those skilled in the art. It is intended that all such other systems, methods, features and advantages are included within the scope of the disclosure, and are covered by the appended claims.

Simple illustration

Many aspects of the invention can be better understood in conjunction with the following figures. The elements in the figures are not necessarily drawn to scale, and the emphasis is on the principles of the disclosure. Moreover, in the drawings, like reference numerals refer to the

Figure 1 is a block diagram of a MOPA/MOPRA laser system.

Figure 2 is an illustration of an energy control block diagram for one of the MOPA/MOPRA laser systems of Figure 1.

Figure 3 is a diagram showing a graph of a trapezoidal window of different repetition rates in accordance with a first exemplary embodiment of the present disclosure.

Figure 4 is a diagram showing a plot of the frequency response of the dose operators of the windows illustrated in Figure 3, in accordance with a first exemplary embodiment of the present disclosure.

Figure 5 is an illustration of one of the energy control block diagrams of the MOPA/MOPRA laser system of Figure 1 in accordance with a first exemplary embodiment of the present disclosure.

Figure 6 is a flow chart illustrating one method of providing a laser control system of Figure 5 in accordance with the first exemplary embodiment of the present disclosure.

Detailed description of the preferred embodiment

The elements of the present disclosure are based on the recognition that although square windows have been previously used for energy dose calculations, some advantages can be realized by employing windows of varying shapes. In accordance with a first exemplary embodiment of the present disclosure, FIG. 3 is an illustration of a graph of a trapezoidal window showing varying repetition rates. In accordance with the level of the first exemplary embodiment of the present disclosure, FIG. 4 is an illustration of a frequency response graph for the dose operator of the window illustrated in FIG. Note that although there is a set of zeros that vary with varying window widths, there is a clear zero presence for all windows at 20% and 40% sampling rates. These zeros correspond to zeros of the five pulse moving averages. A trapezoidal window can be displayed as a convolution of a rectangular window having a size equal to the window size and less than the trailing edge and a five-pulse rectangular window.

In accordance with a first exemplary embodiment of the present disclosure, FIG. 5 is an illustration of an energy control block diagram 150 for the MOPA/MOPRA laser system 10 of FIG. Figure 5 illustrates various control elements that control one of the voltage inputs 152 of the MOPA/MOPARA laser system 10. The energy control block diagram 150 includes a static control 154 that provides a voltage that is desired to achieve a substantially determined one of the energy targets 156 (if there are no other effects to account for). One of the goals of one of the static controls 154 is to cause the energy controller to respond to changes in the energy target 156. If a user adjusts an energy target, the first voltage input 152 for the first shot should be estimated to satisfy the new energy set point. The static control 154 can provide the following voltage signals:

Where E _ref is approximately set to a nominal energy of the laser system 10 and V _ref is the voltage required to emit the laser at E _ref .

Feed forward block 158 provides a voltage adjustment based on a trigger interval 160. The trigger interval 160 is used to estimate the repetition rate, number of shots, and duty cycle that affect the "voltage input - energy output" relationship. This voltage adjustment for the trigger interval 160 is calculated as a function of this value. More specifically, the voltage signal provided by the feedforward block 158 can be given by V = f ₀ (D) + f ₁ (R, n), where D is the duty cycle, R is the repetition rate and n is the number of shots . It should be noted that the feedforward voltage has two items. One f ₀ depends on the duty cycle and/or the burst interval, and the other f ₁ depends on the number of shots and the repetition rate. By design, f ₁ is always zero at the first shot of each burst. Therefore, f ₀ alone determines the feed voltage for the first transmission of the burst. The purpose of this item is to adjust the change in performance of the laser, which generally lasts throughout the burst. Description of the f ₁ Transient any shape. This law assumes that the duty cycle or inter-cluster spacing effect for all emissions in a burst, only shifts the energy to the number of shots up or down by the same amount. The shape of this energy transient is assumed to depend only on the repetition rate. The f ₁ (R, n) function compensates for the shape of the energy transient.

The relationship of the f ₁ (R, n) function with the repetition rate and the number of shots is maintained in a table. A simple integrator is used to accommodate the bins. Previously, the zones were initialized to zero, requiring several bursts before the laser control correctly reverses the transient at the repetition rate. Instead of initializing these regions with zeros, the feedforward region can be initialized with the value of the trained region that is closest in frequency. Initializing the regions with one of the correct values close to the shape of the energy transient allows the laser control to be faster and with greater accuracy to reverse the transient at the repetition rate.

An energy servo 162 adjusts the voltage input 152 based on a calculated voltage error 164 of one of the previous transmissions within the same burst. This adjustment from the energy servo 162 can be calculated in at least one pair of different modules. First, IISquared feedback is a reciprocal law known to those skilled in the art. This feedback law returns a voltage proportional to the integral of the voltage error (integral gain) and another voltage proportional to the voltage error integral quadratic (I square gain). Several sets of gains are provided: soft; hard; and MO. When the goal is to minimize the energy error of the emission, the soft gain is used in the operational mode. Soft gain is selected to minimize energy error. Hard gain is used in dose and sigma mode. The purpose of hard gain is to minimize the dose (integration of the energy error) and tend to be larger than the soft gain. This MO gain is used in the MO energy control mode and is also intended to minimize energy errors.

Another alternative to IISquared feedback is dose feedback. As with the IISquared controller with hard gain, the dose feedback controller is designed to minimize the dose. However, it utilizes a control law that provides better performance through a non-rectangular dose window (eg, a trapezoidal dose window). The dose feedback is controlled by a size parameter and a gain vector. The dose feedback controller can only be used in dose and sigma mode and a linear quadratic regulator can be applied to minimize the sum of the sum of the energy dose and the energy error 172. Using this linear quadratic regulator instead of 100% integral feedback has been shown in the test to reduce the energy dose error by approximately 25%.

As shown in FIG. 5, the result of the laser system 4 is that the voltage input 152 is converted to energy (estimated by the energy measurement 172) via a static gain. In addition, a set of interference is added to the energy signal. Thus the state of the system can be equated with the interference dynamics and dose operator. The energy servo 162 can be directed to provide voltage regulation in response to the behavior of the doser. The energy dose feedback can be calculated from a state feedback vector K and an inner product of a vector xd characterizing the state of the dose operator.

Vdose=-K xd

Where K is calculated as one of the linear quadratic regulators that minimizes the sum of the square of the energy error and the square of the energy dose error.

A jitter cancellation 166 adjusts the voltage to cancel the energy change caused by a time jitter 168. One of the eliminations of this by-product is to estimate the derivative of the voltage with respect to MOPA/MOPRA time at a fixed energy to calculate MopaOPpoint 180 (the operating point u of the MOPA laser system, which is defined as a u= at a constant energy) 1/E*dV/dt, where E is a laser energy, V is the voltage and t is the MOPA time, one of the difference between the emission time between the MO and the PA chamber. For some aspects of time control, the local slope of the time vs. energy curve is needed. This information is obtained by applying a jitter signal to the different times required by the MO and PA rectifier triggers. Because time is coupled to energy, this jitter signal produces a matched jitter in energy. The jitter cancellation algorithm adaptively finds a voltage signal that, when used in the laser, accurately eliminates the energy jitter produced by the time jitter signal. Therefore, this time jitter no longer occurs in the energy signal and therefore has no effect on the energy sigma or energy dose.

One of the by-products of the cancellation algorithm is the derivative of the voltage with respect to time at a fixed energy. This by-product is the time jitter used to confirm the slope information at the first location. A parameter dMpopdMopa (the derivative of the difference between the MO and PA chamber emission time of the MopaOpPoint) used in the laser control system for gas control can be used to cancel the jitter almost immediately in response to changes in the MOPA time ( The difference between the MO and PA chamber emission time). If the parameter is canceled (off), a "large" change in MOPA/MOPRA time, MopaOpPoint 180 ("Mpop") will jump to a new value and then the next thousands of shots will move to a different Value. Some of these time jitter signals will percolate into energy during the time when the MopaOpPoint 180 estimates positive convergence. If the above gas control parameters are correctly set, a "large" (1-2 ns) change in MOPA/MOPRA time, a MopaOpPoint 180 should jump to a new value and then remain at the new value with little drift. .

As shown, with respect to Figure 4, a trapezoidal window is used, with clear zeros appearing for 20% to 40% of the sampling rate for all windows (where the leading and trailing edges of the trapezoidal window are 5 pulses). The amplitude of a jitter is typically set low to reduce the energy jitter, but the low amplitude delays the calculation of the derivative of the energy dose to the voltage estimate. If the jitter moves below zero of one of the trapezoidal windows, the amplitude can be increased with a reduced negative impact.

Mpop compensation 182 adjusts this voltage input 152 to compensate for MOPA time variations. This adjustment is primarily a change in the stabilizing energy over a DtMopaTarget of more than about 1 nanosecond. If a laser operates with Bandwidth Control Enable (ASC) and is currently operating away from resonance to keep the bandwidth constant, the control system reduces the delay between the MO and PA flip-flops. At this time, MopaOpPoint will be a low and negative value because DtMopaTarget is a value of several nanoseconds below the highest efficiency. Next, the scanner 2 converts the repetition rate into a repetition rate that depends on a bandwidth resonance. The bandwidth rises and the bandwidth controller boosts DtMopaTarget by a few nanoseconds to compensate. This brings the laser closer to the highest efficiency and energy in a step-by-step manner. The step of energy change will affect the energy dose until the energy server has a chance to compensate.

At the same time, the MopaOpPoint Compensation 182 mitigates this effect. With the same value dMpopDMopa used to adjust the jitter cancellation for the Mopa time variation, it is possible to calculate the amount of voltage that would be required to vary with a given Mopa time variation. When the Mopa time changes rapidly, the MopaOpPoint compensation 182 can predict what voltage change is needed and provide an appropriate voltage signal to the voltage input 152 without any waiting for an energy error 174 to occur. The MopaOpPoint Compensation 182 can be described as:

V=Eu ² /2k

Where E is the laser energy, u is MopaOpPoint, and k is the derivative of dMpopDMopa or MopaOpPoint with respect to the Mopa time (the difference in emission time between the MO and the PA chamber).

An interference prediction 184 predicts the voltage input 152 based on one of the voltage errors, assuming that the interference affecting the energy is a DC offset plus some tones. The tones are at a frequency that is a multiple of the MO and PA/PO fan speeds. This predicted voltage error is subtracted from the voltage input 152, thereby eliminating the effects due to DC offset or fan blade passage.

Finally, an energy jitter 170 provides a periodic signal applied to the voltage input 152 for calculating the effect of voltage on MO energy, output energy, and MOPA time. The periodic signal from the energy jitter 170 is n long and can be described by this equation:

V[k]=Acos(2πn _d k/n) k=0,...,n-1

Where A is the jitter amplitude and n _d is the number of cosine periods in one complete period of the jitter.

The jitter signal is delayed by a fixed number of transmissions at the beginning of each burst. This delay is provided such that the jitter fails to combine with the beginning of the burst effect to push the laser 4 out of specification. In order to prevent other signals at or near the jitter frequency from interfering with the derivative estimate, the phase of the jitter signal can be randomized, and randomization is performed by randomly starting the jitter by the value k in the above equation. For the windows shown in Figure 3, the jitter frequency is one-fifth of the repetition rate (each trapezoidal window advances 5 times behind). This is the critical frequency of a laser using a trapezoidal window to calculate the dose. For a window with four pulse leading and trailing edges, 20% of the repetition rate is within one of the zeros of the dose operator. Therefore, jitter at this frequency will have no effect on the dose.

These voltage signals are added together to produce the voltage input 152. This energy is measured 172 when the laser is fired. The energy target is subtracted from the measured energy to produce an energy error signal 174 that is scaled by dV/dE (the voltage estimate 176 of the voltage derivative of the energy). The resulting voltage error 164 is used to drive an adaptation algorithm 178 that adjusts some of the voltage signals in a manner that minimizes energy error, dose error, or energy sigma or a combination thereof.

In accordance with this first exemplary embodiment of the disclosed subject matter, FIG. 6 is a flow chart diagram 200 illustrating one method of providing the laser control system 150 of FIG. It should be noted that any flow descriptions or blocks in the flowcharts should be understood to represent modules, program fragments, partial codes or steps including one or more instructions for implementing particular logical functions in the flow, and alternative implementations The aspects are included within the scope of the disclosure, wherein the functions may be performed in an order that is not in the order shown or discussed. The artisans who expose the landmarks understand.

Three alternative examples of the first exemplary embodiment will now be described separately with respect to Figure 6.

In a first alternative, as indicated by block 202, a first voltage input is operatively transmitted as an electrical pulse to a first pair of electrodes within an oscillator gas chamber and a chamber within an amplifier gas chamber The second pair of electrodes. One of the energy doses of the outputs of the gas chambers is calculated through a trapezoidal window (block 204). The first voltage input is adjusted by a control circuit wherein the frequency response of a dose operator has at least one zero (block 206). At least one of an energy dither and a time dither is initialized below one of the zeros (block 208). An output of one of the gas chambers is passed to the control circuit via a feedback control loop to adjust the first voltage input (block 210).

In a second alternative, as indicated by block 202, a first voltage input is operatively delivered in the form of an electrical pulse to a first pair of electrodes within a gas chamber and a second chamber within an amplifier gas chamber Electrode. One of the energy doses of one of the gas chambers is calculated through a trapezoidal window (block 204). The first voltage input is adjusted by a control circuit, wherein the control circuit adjusts the first voltage input according to V=Eu ² /2k, where E is a laser energy, u is a MopaOpPoint, and k is a MopaOpPoint with respect to the gas chambers The derivative of the difference in emission time between chambers. Block 208 is not used in this alternative. An output of one of the gas chambers is passed to the control circuit via a feedback control loop to adjust the first voltage input (block 210).

In a third alternative, as indicated by block 202, a first voltage input is operatively transmitted as an electrical pulse to a first pair of electrodes within an oscillator gas chamber and a first portion of an amplifier gas chamber Two pairs of electrodes. One of the energy doses of one of the gas chambers is calculated through a trapezoidal window (block 204). The first voltage input is adjusted by a control circuit _{applying a dose} of energy dose to V _dose = -K xd to be added to the first voltage input, wherein K is a state feedback vector, which is estimated to be minimized One of the linear quadratic mediators is a weighted sum of the square of the energy error and the square of an energy dose error, and xd is a vector characterizing one of the states of a dose operator (block 206). Block 208 is not used in this alternative. An output of one of the gas chambers is output through a feedback control loop to the control circuit to adjust the first voltage input (block 210).

It should be emphasized that the above described embodiments of the present invention, and particularly, the "preferred" embodiments are merely possible examples of implementations and are merely intended to provide a clear understanding of the principles of the invention. Many changes and modifications may be made to the above described embodiments of the invention without departing from the spirit and scope of the invention. All such changes and modifications are intended to be included within the scope of the disclosure and the scope of the disclosure.

2. . . Lithography machine/scanner

4. . . Laser energy control system, laser system

5. . . Layer/board

6. . . Beam transfer unit

7. . . Line center analysis module

9. . . Spectral analysis module

10. . . MOPA laser system, MOPA/MOPRA laser system, laser system

11. . . Main oscillator, MO

11A. . . Discharge chamber, main oscillator chamber

11B. . . Line width reduction block

11C. . . Output coupler

12. . . Power amplifier / power oscillator

12A. . . Discharge chamber, amplifier chamber, PA chamber, PA/PO chamber

14A. . . First laser beam

14B. . . Second laser beam, laser system output beam pulse, power amplifier output beam

14C. . . Output beam pulse, output beam

16. . . Beam splitter

20A, 20B, 20C, 20D. . . Focusing mirror

twenty two. . . Pulse stretcher, point

twenty four. . . MO wavelength processing block (MO WEB)

26. . . PA wavelength processing block (PA WEB)

28. . . Beam commutator

40A, 40B. . . Beam pointing mirror

50. . . Energy control block diagram

52. . . Voltage and voltage input

72. . . energy

74. . . Energy error signal

150. . . Energy control block diagram, laser control system

152. . . Voltage input

54,154. . . Static control

56, 156. . . Energy target

58,158. . . Feed forward block

60,160. . . Trigger interval

62, 162. . . Energy servo

64,164. . . Voltage error

66, 166. . . Jitter cancellation

68,168. . . Time jitter

70, 170. . . Energy jitter

172. . . Energy measurement, energy error

174. . . Energy error signal

76, 176. . . Laser estimation

78, 178. . . Adaptive algorithm

180. . . MopaOpPoint (MOPA operating point)

182. . . MopaOpPoint compensation, Mpop compensation

184. . . Interference prediction

200. . . flow chart

202, 204, 206, 208, 210. . . Square

Figure 1 is a block diagram of a MOPA/MOPRA laser system.

Figure 2 is an illustration of an energy control block diagram for one of the MOPA/MOPRA laser systems of Figure 1.

Figure 3 is a diagram showing a graph of a trapezoidal window of different repetition rates in accordance with a first exemplary embodiment of the present disclosure.

Figure 4 is a diagram showing a plot of the frequency response of the dose operators of the windows illustrated in Figure 3, in accordance with a first exemplary embodiment of the present disclosure.

Figure 5 is an illustration of one of the energy control block diagrams of the MOPA/MOPRA laser system of Figure 1 in accordance with a first exemplary embodiment of the present disclosure.

Figure 6 is a flow chart illustrating one method of providing a laser control system of Figure 5 in accordance with the first exemplary embodiment of the present disclosure.

2. . . Lithography machine/scanner

4. . . Laser energy control system, laser system

5. . . Layer/board

6. . . Beam transfer unit

7. . . Line center analysis module

9. . . Spectral analysis module

10. . . MOPA laser system, MOPA/MOPRA laser system, laser system

11. . . Main oscillator, MO

11A. . . Discharge chamber, main oscillator chamber

11B. . . Line width reduction block

11C. . . Output coupler

12. . . Power amplifier / power oscillator

12A. . . Discharge chamber, amplifier chamber, PA chamber, PA/PO chamber

14A. . . First laser beam

14B. . . Second laser beam, laser system output beam pulse, power amplifier output beam

14C. . . Output beam pulse, output beam

16. . . Beam splitter

20A, 20B, 20C, 20D. . . Focusing mirror

twenty two. . . Pulse stretcher, point

twenty four. . . MO wavelength processing block (MO WEB)

26. . . PA wavelength processing block (PA WEB)

28. . . Beam commutator

40A, 40B. . . Beam pointing mirror

Claims (27)

A laser control system comprising: an oscillator gas chamber; an amplifier gas chamber; a first voltage input operatively coupled to deliver an electrical pulse to a first pair of the oscillator gas chamber An electrode and a second pair of electrodes in the gas chamber of the amplifier; one of the gas chamber outputs is an energy dose calculated through a trapezoidal window; and is coupled to the first voltage input for adjusting the first voltage input a control circuit, wherein a frequency response of a dose operator has at least one zero; is arranged to initialize at least one of energy jitter and one time jitter at one of the zeros; and to place one of the gas chambers The output is passed to one of the control circuits for adjusting the first voltage input to feedback the control loop. The laser control system of claim 1, wherein the control circuit adjusts the first voltage input according to the equation V=Eu ² /2k, where E is a laser energy, u is a MopaOpPoint, and k is a MopaOpPoint The derivative of the difference in emission time between the gas chambers. The laser control system of claim 1, wherein the at least one of energy jitter and one time jitter further comprises initializing one of the energy jitters at one of the zeros. The laser control system of claim 3, wherein the periodic signal from the energy jitter is n transmission lengths, has an amplitude A, and satisfies V[k]=Acos(2πn _d k/n) Where k is equal to 0 to n-1 and n _d is the number of cosine periods in one complete period of the jitter. The laser control system of claim 1, wherein the at least one time jitter of an energy jitter and a time jitter is arranged to be initialized at one of the zeros. The laser control system of claim 1, wherein the control circuit further comprises an energy dose feedback circuit calculated according to V _dose = -K xd, wherein K is calculated to minimize the square of the energy error and One of the squares of the energy dose error is weighted by one of the linear quadratic mediators to solve the state feedback vector, and xd is a vector characterizing one of the states of a dose operator. The laser control system of claim 1, wherein the control circuit further comprises a function of energy transients, wherein the plurality of repetition rate regions are initialized to a non-zero value. The laser control system of claim 7, wherein the repetition rate zone is initialized to a value of the trained zone having a similar repetition rate. The laser system of claim 1, wherein the control circuit further comprises a linear quadratic regulator that returns a state of a filter that approximates one of the dose operators. A laser control system comprising: an oscillator gas chamber; an amplifier gas chamber; a first voltage input operatively coupled to deliver an electrical pulse to a first pair of the oscillator gas chamber An electrode and a second pair of electrodes in the gas chamber of the amplifier; one of the gas chamber outputs is an energy dose calculated through a trapezoidal window; and is coupled to the first voltage input for adjusting the first voltage input a control circuit, wherein the control circuit adjusts the first voltage input according to the equation V=Eu ² /2k, where E is a laser energy, u is a MopaOpPoint, and k is a launch time of the MopaOpPoint between the gas chambers a derivative of the difference; and passing the output of one of the gas chambers to one of the control circuits for adjusting the first voltage input to feedback the control loop. The laser control system of claim 10, wherein the first voltage input further comprises inputting from one of the energy target calculations Where E _ref is approximately set to one of the nominal energies of the laser system, and V _ref is the approximate voltage required to emit the laser at E _ref . The laser control system of claim 10, wherein one of the dose operators has a frequency response having at least one zero, and the control circuit further comprises an energy jitter initialized at one of the zeros. The laser control system of claim 12, wherein the periodic signal from the energy jitter is n transmission lengths, has an amplitude A and satisfies V[k]=Acos(2πn _d k/n) Where k is 0 to n-1 and n _d is the number of cosine periods in one complete period of the jitter. A laser control system according to claim 10, wherein one of the dose operators has a frequency response having at least one zero, and a time jitter is combined to initialize at one of the zeros. The laser control system of claim 10, wherein the control circuit further comprises an energy dose feedback circuit calculated according to V _dose = -K xd, wherein K is to minimize the square of the energy error and A weighted sum of the squares of the energy dose error is a state feedback vector calculated by one of the linear quadratic regulators, and xd is a vector characterizing one of the states of an energy operator. The laser control system of claim 10, wherein the control circuit further comprises a function of energy transients, wherein the plurality of repetition rate regions are initialized to a non-zero value. The laser control system of claim 16, wherein the repetition rate zone is initialized to a value of the trained zone having a similar repetition rate. The laser control system of claim 10, wherein the control circuit further comprises a linear quadratic regulator for feeding back a state of one of the filters of one of the dose operators. A laser control system comprising: an oscillator gas chamber; an amplifier gas chamber; a first voltage input operatively coupled to deliver an electrical pulse to a first pair of the oscillator gas chamber An electrode and a second pair of electrodes in the gas chamber of the amplifier; one of the gas chamber outputs is an energy dose calculated through a trapezoidal window; and is coupled to the first voltage input for adjusting the first voltage input a control circuit, the control circuit further comprising an energy dose feedback circuit calculated according to Vdose=-K xd, wherein K is a linear quadratic adjustment that minimizes a weighted sum of a square of the energy error and a square of the energy dose error a state feedback vector calculated by one of the solutions, and xd is a vector characterizing one of the states of an energy operator; and passing one of the gas chamber outputs to adjust the first voltage input One of the control circuits returns the control loop. The laser control system of claim 19, wherein the control circuit adjusts the first voltage input according to the equation V=Eu ² /2k, where E is a laser energy, u is a MopaOpPoint, and k is a MopaOpPoint The derivative of the difference in emission time between the gas chambers. The laser control system of claim 19, wherein one of the dose operators has a frequency response having at least one zero, and the control circuit further comprises initializing one of the energy jitters at the one of the zeros. The laser control system according to claim 21, wherein one of the periodic signals from the energy jitter is n transmission lengths, has an amplitude A, and satisfies V[k]=Acos(2πn _d k/n), Where k is 0 to n-1, and n _d is the number of cosine periods in one complete period of the jitter. The laser control system of claim 19, wherein one of the dose operators has a frequency response having at least one zero, and a time jitter is combined to initialize at one of the zeros. The laser control system of claim 19, wherein the first voltage input further comprises inputting one of an energy target calculation V= Where E _ref is approximately set to one of the nominal energies of the laser system and V _ref is the approximate energy required to emit the laser at E _ref . The laser control system of claim 19, further comprising a function of energy transients, wherein the plurality of repetition rate regions are initialized to a non-zero value. The laser control system of claim 25, wherein the repetition rate zone is initialized to a value of the trained zone having a similar repetition rate. The laser control system of claim 19, wherein the control circuit further comprises the linear quadratic regulator to feedback a state of one of the filters of the one of the dose operators.