Methods for controlling an energy of a pulsed light beam, optical systems, and energy control apparatuses

Abstract

This invention describes a method for controlling the energy of a pulsed light beam. The method includes: generating a plurality of mixed sets of pulses of the light beam from an optical source, each set of beam pulses associated with a different dominant wavelength and a different target energy; receiving a measurement of the energy of a previous pulse of the light beam; determining an energy error, including comparing the measured energy of the previous beam pulse with a specific target energy associated with the specific set of beam pulses if the previous beam pulse is in a particular set of beam pulses; and adjusting at least one component of the optical source to adjust the energy of a subsequent pulse in the particular set of beam pulses based on the determined energy error.

Description

Technical Field

[0001] This invention relates to forming multiple spatial images in a single lithography exposure pass. For example, the techniques discussed below can be used to form three-dimensional semiconductor components. Prior Technology

[0002] Photolithography is a process for patterning semiconductor circuits onto a substrate such as a silicon wafer. Photolithography optics provide deep ultraviolet (DUV) light for exposing photoresist on the wafer. The DUV light used in photolithography is generated by an excimer optics source. Typically, this optics source is a laser source, and the pulsed beam is a pulsed laser beam. The beam passes through a beam delivery unit, a magnifying mask, or a shield, and is then projected onto the fabricated silicon wafer. In this way, the wafer design is patterned onto the photoresist, which is then etched and cleaned, and the process is repeated. Summary of the Invention

[0003] In some general cases, a method for controlling the energy of a pulsed light beam is described. The method includes: generating a plurality of mixed sets of pulses of the light beam from an optical source, each set of beam pulses associated with a different dominant wavelength and a different target energy; receiving a measurement of the energy of a previous pulse of the light beam; determining an energy error, including comparing the measured energy of the previous beam pulse with a specific target energy associated with the specific set of beam pulses if the previous beam pulse is in a particular set of beam pulses; and adjusting at least one component of the optical source to adjust the energy of a subsequent pulse in the particular set of beam pulses based on the determined energy error.

[0004] Implementations may include one or more of the following features. For example, the method may include receiving each dissimilar target energy associated with each set of beam pulses. The method may include classifying whether the previous beam pulse is in the particular set of beam pulses. The method may include determining an adjustment amount for the at least one component of the optical source. The method may include correcting the adjustment amount for the at least one component of the optical source based on whether the previous beam pulse is in the particular set of beam pulses.

[0005] At least one component of the optical source can be adjusted by changing a voltage supplied to an electrode associated with one of the optical oscillators of the optical source.

[0006] In other general embodiments, a system includes: an optical source device and an energy control device communicating with the optical source device. The optical source device includes: an optical oscillator configured to generate a light pulse in response to an excitation signal, the light pulse having a spectral attribute; and a spectral adjustment device configured to control the spectral attribute of the light pulse. The energy control device is configured to: determine a target energy associated with the spectral attribute of the generated light pulse; and determine an adjustment to the excitation signal based at least on the determined target energy, the adjustment causing the optical oscillator to generate one or more subsequent light pulses to take into account a change in the configuration of the spectral adjustment device.

[0007] Implementations may include one or more of the following features. For example, adjustment of the excitation signal may cause adjustment of the energy of one or more subsequently generated optical pulses.

[0008] The target energy associated with the spectral property of the generated light pulse can be previously defined as being associated with the spectral property of the generated light pulse.

[0009] The optical oscillator can be associated with a plurality of transfer functions, each transfer function being associated with a specific configuration of the spectral adjustment device and a specific value of the spectral property. Furthermore, the energy control device can be configured to determine the adjustment of the excitation signal based on the transfer function associated with the specific configuration of the spectral adjustment device used to generate the one or more subsequent light pulses.

[0010] The spectral adjustment device may include at least one prism and a diffraction element configured optically to each other, and each transfer function is associated with a different state of at least one prism.

[0011] The spectral properties of a light pulse can be a center wavelength of that light pulse, and each configuration of the spectral adjustment device can correspond to a specific value of that wavelength.

[0012] The system may further include a measuring device configured to measure the energy of one of the light pulses. The energy control device may be configured to determine an energy error by comparing the target energy with the measured energy, and the determination of the adjustment of the excitation signal may also be based on the energy error.

[0013] The energy control device can be configured to determine the adjustment of the excitation signal that causes the optical oscillator to generate one or more subsequent light pulses associated with the spectral properties of the generated light pulse.

[0014] The energy control device can be configured to receive a communication via a lithography device configured to receive the light pulse to determine the target energy associated with the spectral attribute of the generated light pulse. The communication provides a set of target energies, each of which is associated with a spectral attribute.

[0015] In other general embodiments, an energy control device includes a control module. The control module is configured to receive an energy value of a previous light pulse emitted from an optical source. The control module is configured to perform a comparison, including comparing the received energy value with a first target energy only when the previous light pulse is in a first set of beam pulses associated with a first dominant wavelength; or comparing the received energy value with a second target energy different from the first target energy only when the previous light pulse is in a second set of beam pulses associated with a second dominant wavelength different from the first dominant wavelength. The control module is configured to adjust at least one component of the optical source based on the comparison, thereby adjusting the energy of a subsequent light pulse having the dominant wavelength associated with the previous light pulse.

[0016] Implementations may include one or more of the following features. For example, the control module may include a classification module configured to classify the previous optical pulse into either the first beam pulse set or the second beam pulse set. The control module may include a comparator configured to determine whether the previous optical pulse is in the first beam pulse set or the second beam pulse set, and based on the determination, provide the first target energy or the second target energy. The control module may include a signal module configured to determine the amount of adjustment to be made to the at least one component of the optical source.

[0017] The control module may include a correction module configured to correct the adjustment amount to be made to at least one component of the optical source based on the previous optical pulse in either the first beam pulse set or the second beam pulse set. The correction module may be configured to correct the adjustment amount by applying a filter to the adjustment amount. The filter may include a notch filter that transmits information having a frequency in a first frequency band and substantially blocks information having a frequency outside the first frequency band. The filter may include a Kalman filter. The correction module may be configured to correct the adjustment amount by applying a pre-correction.

[0018] The control module is configured to adjust at least one component of the optical source based on the comparison to adjust the energy of a subsequent optical pulse having the dominant wavelength associated with the previous optical pulse. This may include sending a signal to the optical source to change a voltage supplied to an electrode associated with one of the optical oscillators of the optical source. The control module is configured to receive the energy value of the previous optical pulse, which may include being configured to receive the energy values ​​of a plurality of previous optical pulses emitted from the optical source. The control module may be configured to adjust the at least one component of the optical source based on the comparison to adjust the energy of a plurality of subsequent optical pulses having the dominant wavelength associated with the previous optical pulse. The control module may be configured to maintain the energy of a subsequent optical pulse that does not have the dominant wavelength associated with the previous optical pulse based on the comparison. Simple Explanation of the Diagram

[0019] Figure 1A is a block diagram of an example of an implementation of the optical lithography system.

[0020] Figure 1B is a block diagram of an example implementation of the optical system used in the photolithography system of Figure 1A.

[0021] Figure 1C is a cross-sectional view of an example of a wafer exposed using the photolithography system of Figure 1A.

[0022] Figure 2A is a block diagram of another example of an implementation of the optical lithography system.

[0023] Figure 2B is a block diagram of an example implementation of a spectral feature selection module that can be used in a photolithography system.

[0024] Figure 2C is a block diagram of an example of an implementation of the line narrowing module.

[0025] Figures 3A, 3B, and 3C are plots of data related to pulse generation and / or pulse bursts in an optical source.

[0026] Figure 4 is a block diagram of another example of an implementation of the optical lithography system.

[0027] Figure 5 is a flowchart of an example of a process for forming a three-dimensional semiconductor component.

[0028] Figures 6A and 6B each show examples of the spectrum of a single light pulse.

[0029] Figure 7 shows an example of the average spectrum used for a single exposure pass.

[0030] Figures 8A and 8B show side and top cross-sectional views of an example wafer, respectively.

[0031] Figures 9A and 9B show side and top cross-sectional views of an example of a three-dimensional semiconductor component, respectively.

[0032] Figures 10A and 10B show examples of simulated data.

[0033] Figure 11A is a block diagram of a photolithography system in which the control system includes an energy control module configured to provide an excitation signal to an optical source. The excitation signal is used to control the electrodes in the optical oscillator of the optical source.

[0034] Figure 11B is an illustration of an example of the transfer function TF (optical energy generated by a single optical oscillator that varies with the wavelength of the emitted pulse beam) of an optical oscillator, showing how the optical energy varies with the wavelength of the emitted pulse beam.

[0035] Figure 12 is a block diagram of an embodiment of the energy control module of Figure 11A used with an optical oscillator.

[0036] Figure 13 is a block diagram of an embodiment of a master oscillator that can constitute an optical oscillator.

[0037] Figure 14 is a table showing the correlation between each target energy and each possible dominant wavelength of the beam output from the optical source, including the optical oscillator.

[0038] Figure 15A is a graph showing the target energy set of each of the four dominant wavelengths of a beam output from an optical source including an optical oscillator.

[0039] Figure 15B is a cross-sectional view of an example of a wafer exposed in the photolithography system of Figure 11, wherein the light beam output from the optical source including the optical oscillator is generated at the four main wavelengths provided in Figure 15A.

[0040] Figure 16 is a block diagram of an embodiment of the energy control module of Figure 11A used with an optical oscillator and including a plurality of energy controllers, each energy controller being associated with the dominant wavelength of the light beam output from an optical source including the optical oscillator.

[0041] Figure 17 is a block diagram illustrating an implementation of an energy controller that can be used in any one or more of the energy control modules in Figures 11, 12 and 16.

[0042] Figure 18 is a block diagram illustrating an implementation of an energy controller that can be used in any one or more of the energy control modules in Figures 11, 12 and 16.

[0043] Figure 19A is a block diagram of an embodiment of the energy control module of Figure 11A, which is used with an optical oscillator and includes a pre-feed energy controller.

[0044] Figure 19B is a block diagram of an implementation of the energy controller previously described in Figure 19A.

[0045] Figure 19C is a block diagram of an implementation of the excitation determination module of the pre-feedback energy controller in Figure 19B.

[0046] Figure 20 is a block diagram of an embodiment of the energy control module of Figure 11A, which is used with an optical oscillator and includes a repetitive control energy controller.

[0047] Figure 21 is a flowchart of the program executed by the photolithography system in Figure 11A. Implementation

[0048] This article discusses techniques for forming more than one spatial image, each located on a different plane, in a single lithography pass, and for forming three-dimensional semiconductor components using these spatial images.

[0049] Referring to Figure 1A, the photolithography system 100 includes an optical (or light) source 105 that provides a light beam 160 to a photolithography exposure apparatus 169, which processes a wafer 170 received by a wafer holder or stage 171. The light beam 160 is a pulsed beam comprising light pulses that are time-separated from each other. The photolithography exposure apparatus 169 includes a projection optics system 175 and a measurement system 172, through which the light beam 160 passes before reaching the wafer 170. The measurement system 172 may include, for example, a camera or other device capable of capturing an image of the wafer 170 and / or the light beam 160 at the wafer 170, or an optical detector capable of capturing data describing the characteristics of the light beam 160, such as the intensity of the light beam 160 at the wafer 170 in the xy plane. The photolithography exposure apparatus 169 may be a liquid immersion system or a dry system. The photolithography system 100 may also include a control system 150 to control the light source 105 and / or the photolithography exposure equipment 169.

[0050] Microelectronic features are formed on wafer 170 by, for example, exposing a radiation-sensitive photoresist layer onto wafer 170 using a light beam 160. Referring also to FIG. 1B, the projection optics system 175 includes a slit 176, a mask 174, and a projection objective, which includes a lens 177. The light beam 160 enters the optics system 175 and illuminates the slit 176, with at least some of the beam 160 passing through the slit 176. In the examples of FIG. 1A and FIG. 1B, the slit 176 is rectangular, shaping the light beam 160 into an elongated rectangular beam. A pattern is formed on the mask 174, and the pattern determines which portions of the shaped beam are transmitted through and blocked by the mask 174. The design of the pattern is determined by the specific microelectronic circuit design to be formed on wafer 170.

[0051] The shaped beam interacts with the mask 174. A portion of the shaped beam transmitted through the mask 174 passes through the projection lens 177 (and can be focused by the projection lens 177) and exposes the wafer 170. The portion of the shaped beam transmitted through the mask 174 forms a spatial image in the xy plane on the wafer 170. The spatial image is an intensity pattern formed by the light reaching the wafer 170 after interacting with the mask 174. The spatial image is located on the wafer 170 and extends generally in the xy plane.

[0052] System 100 is capable of forming a plurality of spatial images during a single exposure pass, each of which is located at a different spatial position along the z-axis in wafer 170. Referring also to Figure 1C, which shows a cross-sectional view of wafer 170 in the yz plane, projection optics system 175 forms two spatial images 173a and 173b at different planes along the z-axis during a single exposure pass. As discussed in more detail below, each of spatial images 173a and 173b is formed by light with different dominant wavelengths.

[0053] The position of the spatial image along the z-axis depends on the characteristics of the optical system 175 (including the projection lens 177 and the mask 174) and the wavelength of the light beam 160. The focusing position of the lens 177 depends on the wavelength of the light incident on the lens 177. Therefore, varying or controlling the wavelength of the light beam 160 allows for control over the positioning of the spatial image. By providing pulses of light with different dominant wavelengths during a single exposure pass, multiple (two or more) spatial images, each at a different position along the z-axis, can be formed in a single exposure pass without moving the optical system 175 (or any component of the optical system 175) and the wafer 170 relative to each other along the z-axis.

[0054] In the example of Figure 1A, light passing through the mask 174 is focused onto the focal plane by the projection lens 177. The focal plane of the projection lens 177 is located between the projection lens 177 and the wafer stage 171, and the positioning of the focal plane along the z-axis depends on the properties of the optical system 175 and the wavelength of the light beam 160. Spatial images 173a and 173b are formed by light of different wavelengths, and therefore, spatial images 173a and 173b are located at different positions in the wafer 170. Spatial images 173a and 173b are separated from each other by a separation distance 179 along the z-axis. The separation distance 179 depends on the difference between the wavelength of the light forming spatial image 173a and the wavelength of the light forming spatial image 173b.

[0055] The wafer stage 171 and the mask 174 (or other parts of the optical system 175) move relatively relative to each other in the x, y, and z directions during scanning for routine performance corrections and operations. For example, the movement can be used to achieve basic leveling, compensation for lens distortion, and compensation for stage positioning errors. This relative movement is referred to as incidental operational movement. However, in the system of FIG. 1A, the separation distance 179 is not formed by the relative movement of the wafer stage 171 and the optical system 175. Instead, the separation distance 179 is formed by controlling the dominant wavelength in the pulses passing through the mask 174 during exposure passes. Therefore, unlike some prior systems, the separation distance 179 is not generated solely by moving the optical system 175 and the wafer 170 relative to each other along the z direction. Furthermore, spatial images 173a and 173b are both presented on the wafer 170 during the same exposure pass. In other words, system 100 does not need to form spatial image 173a in the first exposure pass and spatial image 173b in the second subsequent exposure pass.

[0056] Light from the first spatial image 173a interacts with the wafer at portion 178a, and light from the second spatial image 173b interacts with the wafer at portion 178b. These interactions can form electronic features or other physical properties on the wafer 170, such as openings or holes. Since spatial images 173a and 173b are located on different planes along the z-axis, they can be used to form three-dimensional features on the wafer 170. For example, spatial image 173a can be used to form a peripheral region, and spatial image 173b can be used to form channels, trenches, or recesses located at different positions along the z-axis. Therefore, the techniques discussed herein can be used to form three-dimensional semiconductor devices, such as three-dimensional NAND flash memory devices.

[0057] Before discussing additional details related to the formation of multiple spatial images in a single exposure pass, exemplary implementations of the light source 105 and the photolithography system 100 are discussed with respect to Figures 2A to 2C, Figures 3A to 3C and Figure 4.

[0058] Referring to Figure 2A, a block diagram of the photolithography system 200 is shown. System 200 is an example of an implementation of system 100 (Figure 1A). For example, in the photolithography system 200, optical source 205 is used as optical source 105 (Figure 1A). Optical source 205 generates a pulsed beam 260 provided to photolithography exposure apparatus 169. Optical source 205 may be, for example, an excimer optical source that outputs the pulsed beam 260 (which may be a laser beam). As the pulsed beam 260 enters photolithography exposure apparatus 169, it is guided through projection optics system 175 and projected onto wafer 170. In this way, one or more microelectronic features are patterned onto photoresist on wafer 170, and the wafer is developed and cleaned before subsequent processing steps, and this process is repeated. The photolithography system 200 also includes a control system 250, which, in the example of FIG2A, is connected to the components of the optical source 205 and to the photolithography exposure apparatus 169 to control various operations of the system 200. The control system 250 is an example of an implementation of the control system 250 of FIG1A.

[0059] In the example shown in Figure 2A, the optical source 205 is a two-stage laser system that includes a master oscillator (MO) 212 that provides a seed beam 224 to a power amplifier (PA) 230. The MO 212 and PA 230 can be considered as subsystems of the optical source 205, or as part of the optical source 205. The power amplifier 230 receives and amplifies the seed beam 224 from the master oscillator 212 to generate a beam 260 for use in the lithography exposure apparatus 169. For example, the master oscillator 212 can emit pulsed seed beams with a seed pulse energy of approximately 1 millijoule (mJ) per pulse, and these seed pulses can be amplified by the power amplifier 230 to approximately 10 to 15 mJ.

[0060] The master oscillator 212 includes a discharge chamber 214 housing two elongated electrodes 217, a gain medium 219 serving as a gas mixture, and a fan for circulating the gas between the electrodes 217. A resonator is formed between a line-narrowing module 216 on one side of the discharge chamber 214 and an output coupler 218 on the second side of the discharge chamber 214. The line-narrowing module 216 may include diffraction optics, such as a grating for finely tuning the spectral output of the discharge chamber 214. Figures 2B and 2C provide additional details regarding the line-narrowing module 216.

[0061] Figure 2B is a block diagram of an example embodiment of a spectral feature selection module 258 including one or more examples of linen narrowing modules 216. The spectral feature selection module 258 is coupled to light propagating in the optical source 205. In some embodiments (such as shown in Figure 2B), the spectral feature selection module 258 receives light in the chamber 214 of the master oscillator 212 to allow fine tuning of spectral features such as wavelength and bandwidth within the master oscillator 212.

[0062] The spectral feature selection module 258 may include a control module, such as a spectral feature control module 254 comprising any combination of firmware and software in the form of an electronic device. The control module 254 is connected to one or more actuation systems, such as spectral feature actuation systems 255_1 to 255_n. Each of the actuation systems 255_1 to 255_n may include one or more actuators connected to respective optical features 256_1 to 256_n of the optical system 257. The optical features 256_1 to 256_n are configured to adjust specific characteristics of the generated beam 260, thereby adjusting the spectral features of the beam 260. The control module 254 receives control signals from the control system 250, the control signals including specific commands to operate or control one or more of the actuation systems 255_1 to 255_n. Actuation systems 255_1 to 255_n can be selected and designed to operate together, i.e., in series, or actuation systems 255_1 to 255_n can be configured to operate individually. Furthermore, each actuation system 255_1 to 255_n can be optimized to respond to specific types of disturbances.

[0063] Each optical feature 256_1 to 256_n is optically coupled to a beam 260 generated by optical source 105. Optical system 257 can be implemented as a line narrowing module 216C as shown in FIG2C. The line narrowing module includes dispersive optical elements (such as reflection grating 291) and refractive optical elements (such as prisms 292, 293, 294, 295) as optical features 256_1 to 256_n. One or more of prisms 292, 293, 294, 295 may be rotatable. An example of this line narrowing module can be found in U.S. Application No. 12 / 605,306, filed October 23, 2009, entitled "SYSTEM METHOD AN APPARATUS FOR SELECTING AND CONTROLLING LIGHT SOURCE BANDWIDTH" ('306 application), and granted March 27, 2012, as U.S. Patent No. 8,144,739, the contents of which are incorporated herein by reference as if they were fully described. In '306 application, a line narrowing module is described, comprising a beam expander (including one or more prisms 292, 293, 294, 295) and a dispersive element, such as a grating 291. Figure 2C does not show the actuation systems for the actuable optical features such as grating 291 and for one or more of prisms 292, 293, 294, 295.

[0064] Each of the actuators in the actuation systems 255_1 to 255_n is a mechanical device for moving or controlling the respective optical features 256_1 to 256_n of the optical system 257. The actuator receives energy from the module 254 and converts that energy into some kind of motion imparted to the optical features 256_1 to 256_n of the optical system 257. For example, in '306 application, actuation systems are described such as force devices (applying force to the grating region) and a rotating stage for adjusting one or more of the prisms of the beam expander. Actuation systems 255_1 to 255_n may include, for example, motors such as stepper motors, valves, pressure-controlled devices, piezoelectric devices, linear motors, hydraulic actuators, and / or voice coils.

[0065] Returning to Figure 2A, the master oscillator 212 also includes a line center analysis module 220 that receives the output beam from the output coupler 218, and a beam coupling optical system 222 that corrects the size or shape of the output beam as needed to form a seed beam 224. The line center analysis module 220 is a measurement system that can be used to measure or monitor the wavelength of the seed beam 224. The line center analysis module 220 can be placed in other locations within the optical source 205, or it can be placed at the output end of the optical source 205.

[0066] The gas mixture used in the discharge chamber 214 can be any gas suitable for generating a beam at the wavelength and bandwidth required for the application. For the excimer source, in addition to helium and / or neon as buffer gases, the gas mixture may contain an inert gas (rare gas) such as argon or krypton, a halogen such as fluorine or chlorine, and trace amounts of xenon. Specific examples of gas mixtures include argon fluoride (ArF) which emits light at a wavelength of about 193 nm, krypton fluoride (KrF) which emits light at a wavelength of about 248 nm, or xenon chloride (XeCl) which emits light at a wavelength of about 351 nm. By applying a voltage to the elongated electrode 217, the excimer gain medium (gas mixture) is pumped with short (e.g., nanosecond) current pulses during high-voltage discharge.

[0067] The power amplifier 230 includes a beam coupling optics system 232 that receives a seed beam 224 from an auto-oscillator 212 and guides the beam through a discharge chamber 240 and to a beam steering optics element 248. The beam steering optics element 248 corrects or alters the direction of the seed beam 224 so that it is sent back to the discharge chamber 240. The discharge chamber 240 includes a pair of elongated electrodes 241, a gain medium 219 for the mixed gas, and a fan for circulating the mixed gas between the electrodes 241.

[0068] The output beam 260 is guided through a bandwidth analysis module 262, where various parameters of the beam 260 (such as bandwidth or wavelength) can be measured. The output beam 260 can also be guided through a beam preparation system 263. The beam preparation system 263 may include, for example, a pulse stretcher, in which each pulse of the output beam 260 is stretched in time (e.g., in an optical delay unit) to adjust the performance properties of the beam illuminating the lithography exposure apparatus 169. The beam preparation system 263 may also include other components capable of acting on the beam 260, such as reflective and / or refractive optical elements (such as lenses and mirrors), filters, and optical diaphragms (including automatic shutters).

[0069] The photolithography system 200 also includes a control system 250. In the embodiment shown in FIG. 2A, the control system 250 is connected to various components of the optical source 205. For example, the control system 250 can control when the optical source 205 emits light pulses or bursts of light pulses including one or more light pulses by sending one or more signals to the optical source 205. The control system 250 is also connected to the photolithography exposure apparatus 169. Therefore, the control system 250 can also control various states of the photolithography exposure apparatus 169. For example, the control system 250 can control the exposure of the wafer 170, and can therefore be used to control how electronic features are printed on the wafer 170. In some embodiments, the control system 250 can control the scanning of the wafer 170 by controlling the movement of the slit 176 in the xy plane (FIG. 1B). In addition, the control system 250 can exchange data with the metrology system 172 and / or the optical system 175.

[0070] The lithography apparatus 169 may also include, for example, temperature control devices (such as air conditioning and / or heating devices), and / or power supplies for various electrical components. The control system 250 may also control these components. In some embodiments, the control system 250 is implemented as including more than one sub-control system, and at least one sub-control system (lithography controller) is dedicated to controlling the state of the lithography apparatus 169. In these embodiments, the control system 250 may be used as an alternative to or supplement to using a lithography controller to control the state of the lithography apparatus 169.

[0071] The control system 250 includes an electronic processor 251, electronic storage 252, and an I / O interface 253. The electronic processor 251 includes one or more processors suitable for executing computer programs, such as general-purpose or special-purpose microprocessors, and one or more processors of any type of digital computer. Typically, the electronic processor receives instructions and data from read-only memory, random access memory, or both. The electronic processor 251 can be any type of electronic processor.

[0072] Electronic storage 252 may be volatile memory such as RAM, or non-volatile memory. In some embodiments, electronic storage 252 includes both non-volatile and volatile portions or components. Electronic storage 252 may store data and information for the operation of control system 250, components of control system 250, and / or systems controlled by control system 250. Information may be stored in, for example, a lookup table or database. For example, electronic storage 252 may store data indicating the values ​​of different attributes of indicator beam 260 under different operating conditions and performance scenarios.

[0073] Furthermore, the electronic storage 252 can store different formulas or processing programs 259 indicating the parameters of the beam 260 during use. For example, the electronic storage 252 can store a formula indicating the wavelength of each pulse in the beam 260 in a specific exposure pass. The formula can indicate different wavelengths for different exposure passes. The wavelength control techniques discussed below can be applied on a pulse-by-pulse basis. In other words, the wavelength content can be controlled for each individual pulse in an exposure pass to facilitate the formation of a spatial image at a desired location along the z-axis.

[0074] Electronic storage 252 may also store instructions (possibly as computer programs) that, when executed, enable processor 251 to communicate with components in control system 250, optical system 205, and / or lithography equipment 169.

[0075] I / O interface 253 is any kind of electronic interface that allows control system 250 to receive data and signals from an operator, optical system 205, lithography equipment 169, any component or system within optical system 205 and / or lithography equipment 169, and / or an automated program running on another electronic device, and / or to provide data and signals to such entities. For example, I / O interface 253 may include one or more of a visual display, a keyboard, and a communication interface.

[0076] Beam 260 (and beam 160) are pulsed beams and may include one or more pulse bursts that are temporally separated from each other. Each burst may include one or more optical pulses. In some embodiments, a burst includes hundreds of pulses, such as 100 to 400 pulses. Figures 3A to 3C provide an overview of the generation of pulses and bursts in optical source 205. Figure 3A shows the amplitude of wafer exposure signal 300 over time, Figure 3B shows the amplitude of gate signal 315 over time, and Figure 3C shows the amplitude of trigger signal over time.

[0077] The control system 250 can be configured to send the wafer exposure signal 300 to the optical source 205 to control the optical source 205 to generate a light beam 260. In the example shown in Figure 3A, the wafer exposure signal 300 has a high bit value 305 (e.g., 1) during time period 307, during which the optical source 205 generates bursts of light pulses. The wafer exposure signal 300 also has a low bit value 310 (e.g., 0) when the wafer 170 is not exposed.

[0078] Referring to Figure 3B, beam 260 is a pulsed beam, and beam 260 includes bursts of pulses. Control system 250 also controls the duration and frequency of the pulse bursts by sending a gate signal 315 to optical source 205. Gate signal 315 has a high bit value 320 (e.g., 1) during a pulse burst and a low bit value 325 (e.g., 0) during the time interval between consecutive bursts. In the illustrated example, the duration when gate signal 315 has a high bit value is also the duration of burst 316. These bursts are temporally separated by burst intervals. During the burst interval, lithography apparatus 169 can position the next die on wafer 170 for exposure.

[0079] Referring to Figure 3C, the control system 250 also uses a trigger signal 330 to control the repetition rate of the pulse within each burst. The trigger signal 330 includes a trigger 340, one of which is provided to the optical source 205 to cause the optical source 205 to generate light pulses. Each time a pulse is generated, the control system 250 can send the trigger 340 to the source 205. Therefore, the repetition rate (the time between two consecutive pulses) of the pulses generated by the optical source 205 can be set by the trigger signal 330.

[0080] As discussed above, when the gain medium 219 is pumped by applying a voltage to electrode 217, the gain medium 219 emits light. When the voltage is applied to electrode 217 in a pulsed manner, the light emitted from the medium 219 is also pulsed. Therefore, the repetition rate of the pulsed beam 260 is determined by the rate at which the voltage is applied to electrode 217, wherein each application of voltage generates one light pulse. The light pulse propagates through the gain medium 219 and exits the chamber 214, passing through the output coupler 218. Thus, a pulse train is generated by periodically and repeatedly applying voltage to electrode 217. Trigger signal 330 can be used, for example, to control the application of voltage to electrode 217 and the repetition rate of the pulses, which, for most applications, can range from about 500 to 6,000 Hz. In some embodiments, the repetition frequency can be greater than 6,000 Hz, and can be, for example, 12,000 Hz or greater.

[0081] Signals from control system 250 can also be used to control electrodes 217 and 241 within master oscillator 212 and power amplifier 230, respectively, to control the individual pulse energies of master oscillator 212 and power amplifier 230, and thus control the energy of beam 260. A delay may exist between the signal provided to electrode 217 and the signal provided to electrode 241. The amount of delay can affect properties of beam 260, such as the amount of coherence in the pulsed beam 260.

[0082] The pulsed beam 260 may have an average output power in the range of tens of watts, for example, from about 50 W to about 130 W. The irradiance of the beam 260 at the output end (i.e., the average power per unit area) may range from 60 W / cm² to 90 W / cm².

[0083] Referring also to Figure 4, wafer 170 is irradiated by beam 260. The lithography apparatus 169 includes an optical system 175 (Figures 1A and 1B). In the example of Figure 4, the optical system 175 (not shown) includes an illuminator system 429, which includes an objective lens configuration 432. The objective lens configuration 432 includes a projection lens 177 (Figure 1B) and enables image transmission from the mask 174 to the photoresist on wafer 170. The illuminator system 429 adjusts the range of the angle at which the beam 260 illuminates the mask 174. The illuminator system 429 can also homogenize the intensity distribution of the beam 260 in the xy plane across the mask 174 (making the intensity distribution uniform).

[0084] In some embodiments, an immersion medium may be supplied to cover wafer 170. The immersion medium may be a liquid used in liquid immersion lithography (such as water). In other embodiments where the lithography is a dry system, the immersion medium may be a gas, such as dry nitrogen, dry air, or clean air. In other embodiments, wafer 170 may be exposed in a pressure-controlled environment (such as a vacuum or partial vacuum).

[0085] During an exposure pass, a plurality of N pulses of beam 260 irradiate the same area of ​​wafer 170. N can be any integer greater than one. The number N of pulses of beam 110 irradiating the same area can be referred to as the exposure window or exposure pass 400. The size of window 400 can be controlled by slit 176. For example, slit 176 may include a plurality of movable blades such that the blades form an aperture in one configuration and close the aperture in another configuration. The size of window 400 can also be controlled by configuring the blades of slit 176 to form an aperture of a specific size.

[0086] The N pulses also determine the illumination dose used for each exposure pass. The illumination dose is the amount of optical energy delivered to the wafer during an exposure pass. Therefore, the properties of the N pulses, such as the optical energy in each pulse, determine the illumination dose. Furthermore, and as discussed in more detail below, the N pulses can also be used to determine the amount of light in each of the spatial images 173a and 173b. Specifically, the formulation may specify that a certain number of the N pulses have a first dominant wavelength forming spatial image 173a, and a certain number of pulses have a second dominant wavelength forming spatial image 173b.

[0087] Additionally, slit 176 and / or mask 174 can move in the scanning direction in the xy plane, such that only a portion of wafer 170 is exposed at a given time or during a specific exposure scan (or exposure pass). The size of the area on wafer 170 exposed by beam 160 is determined by the distance between blades in the non-scanning direction and the length (distance) of the scan in the scanning direction. In some embodiments, the value of N is in the tens, for example from 10 to 100 pulses. In other embodiments, the value of N is greater than 100 pulses, for example from 100 to 500 pulses. The exposure field 479 of wafer 170 is the physical area of ​​wafer 170 exposed in a scan of the exposure slit or window within the lithography apparatus 169.

[0088] The wafer stage 171, mask 174, and objective lens configuration 432 are fixed to an associated actuation system, thereby forming a scanning configuration. In the scanning configuration, one or more of the mask 174, objective lens configuration 432, and wafer 170 (via stage 171) can move relative to each other in the xy plane. However, apart from the incidental relative operative movement between the wafer stage 171, mask 174, and objective lens configuration 432, these components do not move relative to each other along the z-axis during an exposure pass or exposure cycle.

[0089] Referring to Figure 5, a flowchart of process 500 is shown. Process 500 is an example of a process for forming a three-dimensional semiconductor component or a part thereof. Process 500 can be performed using photolithography system 100 or 200. Process 500 is discussed with respect to system 200 shown in Figure 2A. Process 500 is also discussed with respect to Figures 6A through 10B.

[0090] The beam 260 is guided toward the mask 174 (510). The beam 260 is a pulsed beam comprising a plurality of pulses, each of which is temporally separated from each other, as shown in Figure 3C. Figures 6A and 6B show examples of the spectrum of a single pulse that is part of the beam 260. Other pulses in the beam 260 may have different spectra.

[0091] Referring to Figure 6A, the spectrum 601A of the optical pulse 600A is shown. The optical pulse 600A has a non-zero intensity within a wavelength band. This wavelength band can also be referred to as the bandwidth of the pulse 600A.

[0092] The information shown in Figure 6A is the instantaneous spectrum 601A (or emission spectrum) of pulse 600A. Spectrum 601A contains information about how the optical energy or power of the pulse of beam 260 is distributed across different wavelengths (or frequencies). Spectrum 601A is depicted graphically, in which spectral intensity is plotted according to wavelength or optical frequency (not necessarily with absolute calibration). Spectrum 601A can be referred to as the spectral shape or intensity spectrum of the pulse of beam 260. Pulse 600A has a dominant wavelength 602A, which is the peak intensity in the example of Figure 6A. Although the pulse of beam 260 and the spatial image formed by the pulse of beam 260 refer to the dominant wavelength of the pulse, the pulse includes wavelengths other than the dominant wavelength, and the pulse has a finite bandwidth, which can be characterized by a metric. For example, the full width of the spectrum (called FWXM) at the fraction (X) of the maximum peak intensity of the shape of spectrum 601A can be used to characterize the beam bandwidth. As another example, the width of a spectrum containing the fraction (Y) of the integrated spectral intensity (called EY) can be used to characterize the beam bandwidth.

[0093] Pulse 600A is shown as an example of a pulse that may be present in beam 260. When pulse 600A is used to expose a portion of wafer 120, the light in the pulse forms a spatial image. The position of the spatial image in the z-direction (Figs. 1C and 4) is determined by the value of the dominant wavelength 602A. Different pulses in beam 260 may have different dominant wavelengths. For example, to produce two spatial images during a single exposure pass, some pulses in beam 260 have one dominant wavelength (first dominant wavelength), and other pulses in beam 260 have another dominant wavelength (second dominant wavelength). The first and second dominant wavelengths are different wavelengths. The wavelength difference between the first and second dominant wavelengths can be called spectral separation. For example, spectral separation can be from 200 femtometers (fm) to 50 picometers (pm). Although the wavelengths of the various pulses in beam 260 may be different, the spectral shape of the pulses may be the same.

[0094] The light source 205 can dither or switch the dominant wavelength between the first and second dominant wavelengths on an inter-pulse basis, such that each pulse has a different dominant wavelength than the pulses that immediately precede or follow it in time. In these embodiments, assuming that all pulses in the beam 260 have the same intensity, the first and second dominant wavelengths are distributed at different positions in the z-direction in this manner to produce two spatial images with the same intensity.

[0095] In some embodiments, a portion of the pulse (e.g., 33%) has a first dominant wavelength, and the remaining portion (67% in this example) has a second dominant wavelength. In these embodiments, assuming all pulses in beam 260 have the same intensity, the two spatial images are formed with different intensities. The spatial image formed by the pulse with the first dominant wavelength has approximately half the intensity of the spatial image formed by the pulse with the second dominant wavelength. In this way, the dose delivered to a specific location in wafer 170 along the z-axis can be controlled by controlling portions of N pulses having each of the first and second dominant wavelengths.

[0096] A pulse portion having a specific dominant wavelength for an exposure pass can be specified in a recipe file 259 stored in electronic storage 252. Recipe 259 specifies the ratio of various dominant wavelengths used for exposure passes. Recipe 259 can also specify the ratio of other exposure passes, so that different ratios can be used for other exposure passes, and the spatial image can be adjusted or controlled on a field-by-field basis.

[0097] Referring to Figure 6B, the spectrum 601B of pulse 600B is shown. Pulse 600B is another example of a pulse of beam 260. The spectrum 601B of pulse 600B has a different shape than spectrum 601A. Specifically, spectrum 601B has two peaks corresponding to the two dominant wavelengths 602B_1 and 602B_2 of pulse 600B. Pulse 600B is a part of beam 260. When pulse 600B is used to expose a portion of wafer 120, the light in the pulse forms two spatial images at different positions along the z-axis on the wafer. The positions of the spatial images are determined by the wavelengths of the dominant wavelengths 602B_1 and 602B_2.

[0098] The pulses shown in Figures 6A and 6B can be formed by any hardware capable of forming such pulses. For example, a pulse train of pulses (such as pulse 600A) can be formed using a line narrowing module similar to the line narrowing module 216C of Figure 2C. The wavelength of the light diffracted by the grating 291 depends on the angle of the light incident on the grating. A mechanism for changing the incident angle of the light interacting with the grating 291 can be used with this line narrowing module to generate a pulse train of N pulses for exposure passes, wherein at least one of the N pulses has a dominant wavelength different from the dominant wavelength of another of the N pulses. For example, one of the prisms 292, 293, 294, and 295 can be rotated to change the angle of the light incident on the grating 291 on a pulse-by-pulse basis. In some embodiments, the line narrowing module includes a mirror that is located in the path of the beam 260 and is movable to change the angle of the light incident on the grating 291. For example, an example of this implementation is described in U.S. Patent No. 6,192,064, entitled "NARROW BAND LASER WITH FINE WAVELENGTH CONTROL," issued on February 20, 2001.

[0099] Pulses, such as pulse 600B (Figure 6B), can be formed using a line-narrowing module similar to the line-narrowing module 216C of Figure 2C. For example, a stimulated optical element (such as an acousto-optic modulator) can be placed in the path of beam 260 within the line-narrowing module 216C. The acousto-optic modulator deflects the incident light at an angle depending on the frequency of the acoustic wave used to excite the modulator. The acousto-optic modulator includes a material, such as glass or quartz, that allows acoustic waves to propagate, and a transducer coupled to that material. The transducer vibrates in response to an excitation signal, and the vibration generates acoustic waves in the material. The acoustic waves form a moving plane of expansion and compression that changes the refractive index of the material. Thus, the acoustic waves act as a diffraction grating, causing the incident light to simultaneously diffract and exit the material at several different angles. Light from two or more orders can be allowed to reach grating 291, and the light in each of the various diffraction orders has a different angle of incidence on grating 291. In this way, a single pulse comprising two or more dominant wavelengths can be formed. For example, U.S. Patent No. 7,154,928, entitled "LASER OUTPUT BEAM WAVEFRONT SPLITTER FOR BANDWIDTH SPECTRUM CONTROL," issued on December 26, 2006, describes an example of a line narrowing module including an acousto-optic modulator.

[0100] During a single exposure pass, a set of light pulses is directed toward wafer 170 through mask 174 (520). As discussed above, N light pulses can be provided to wafer 170 during the exposure pass. The N light pulses can be consecutive light pulses in beam 260. The exposed portion of wafer 170 sees the average of the spectra of each of the N pulses during the exposure pass. Therefore, if a portion of the N pulses has a first dominant wavelength and the remaining N pulses have a second dominant wavelength, the average spectrum at wafer 170 will be a spectrum including peaks at the first dominant wavelength and peaks at the second dominant wavelength. Similarly, if all or some of the individual pulses of the N pulses have more than one dominant wavelength, those dominant wavelengths can form peaks in the average spectrum. Figure 7 shows an example of an average spectrum 701 at wafer 170. The average spectrum 701 includes a first dominant wavelength 702_1 and a second dominant wavelength 702_2. In the example of Figure 7, the first dominant wavelength 702_1 and the second dominant wavelength 702_2 are separated by a spectral separation 703 of approximately 500 fm. However, other combinations are also possible. The spectral separation 703 makes the first dominant wavelength 702_1 and the second dominant wavelength 702_2 distinct, and the average spectrum 701 includes a spectral region 704 with very low to no intensity between wavelengths 702_1 and 702_2.

[0101] For example, based on the average spectrum, two or more spatial images are formed at wafer 170, the first image being based on a first dominant wavelength and the second image being based on a second dominant wavelength (530). Continuing with the example of average spectrum 701, and also referring to FIG8A, two spatial images 873a and 873b are formed in a single exposure pass based on N pulses. The N pulses include a first set of pulses having a first dominant wavelength 702_1 and a second set of pulses having a second dominant wavelength 702_2. For example, these pulses are single-peak pulses as shown in FIG6A. The pulses having the first dominant wavelength 702_1 form the first spatial image 873a, and the pulses having the second dominant wavelength 702_2 form the second spatial image 873b. Spatial image 873a is formed at a first plane 878a, and spatial image 873b is formed at a second plane 878b. Planes 878a and 878b are perpendicular to the propagation direction of the beam 260 at wafer 170. Planes 878a and 878b are separated by a separation distance of 879 along the z-direction.

[0102] For an average spectrum with a single dominant wavelength, the separation distance 879 is greater than the depth of focus of the lithography apparatus 169. The depth of focus can be defined as the range of focus along the z-direction for a dose value (the amount of optical energy supplied to the wafer), at which a feature size is provided within an acceptable range for the feature size of the process applied to wafer 170. Process 500 can increase the depth of focus of the lithography apparatus 169 by providing more than one distinct spatial image at wafer 170 during a single exposure pass. This is because multiple spatial images can expose the wafer at different locations in the z-direction, with features within an acceptable range for feature size. In other words, process 500 can provide a greater range of depth of focus to the lithography apparatus 169 during a single exposure pass. As discussed above, the operator of the lithography apparatus 169 can control different parameters of the exposure process via recipe file 259. In some embodiments, the operator of the lithography exposure apparatus 169 can receive information from a simulation program, such as Tachyon Source-Mask Optimization (SMO) from Brion (ASML), and this information can be used to program or otherwise specify parameters of the recipe file 259. For example, the operator of the lithography exposure apparatus 169 can know that an upcoming batch does not require as much depth of focus as previous exposure batches. In this example, the operator can specify the depth of focus and dose variation of the simulation program, and the simulation program returns the value of spectral separation 703 to achieve the desired parameters. The operator can then program the recipe file 259 via the I / O interface 253 to specify the value of spectral separation 703 for the upcoming batch. In some embodiments, the operator can use the simulation to determine whether a particular exposure pass requires a greater depth of focus (e.g., possibly by exposing the wafer 170 with multiple spatial images at dissimilar planes). Where a greater depth of focus is not required to form a specific portion of a semiconductor component, a structured recipe file 259 can be created such that, for example, the exposure passes used to form that specific portion of the semiconductor component have an average spectrum including a single dominant wavelength.

[0103] Furthermore, the operator and / or simulator can receive information about the formed three-dimensional component, such as that measured by the measurement system 172 or by another sensor. For example, the measurement system 172 can provide data related to the sidewall angles of the formed 3D semiconductor component, and this data can be used to format parameters in the formula file 259 for subsequent exposure passes.

[0104] Figure 8B shows a spatial image 873a in the xy-plane at plane 878a (see page in Figure 8A). Spatial images 873a and 873b are generally two-dimensional intensity patterns formed in the xy-plane. The nature of the intensity pattern depends on the characteristics of the mask 174. The first plane 878a and the second plane 878b are portions of wafer 170. As illustrated in Figure 8B, the first plane 878a may only be a small portion of the entire wafer 170.

[0105] The value of the separation distance 879 depends on the spectral separation 703 and on the properties of the optical system 275. For example, the value of the separation distance 879 may depend on the focal length, aberrations, and other properties of the lens and other optical elements in the optical system 275. For a scanner lens with chromatic aberration C, the separation distance 879 can be determined from Equation 1: Equation (1), Where ΔD is the separation distance 879 in nanometers (nm), C is the chromatic aberration (defined as the distance the focal plane moves in the propagation direction in response to a change in wavelength, which is a known property of the projection lens 177), and Δλ is the spectral separation 873 in picometers. For a lens 177 with a value of C = 500 nm / pm, the spectral separation 873 can be approximately 10 fm to achieve a focusing separation distance 875 of 5000 nm (5 µm).

[0106] Furthermore, for a specific type of exposure equipment 169, different dominant wavelengths may be required to achieve the desired separation distance 879 due to variations in the manufacturing and installation process and / or modifications made by the end user. As discussed above, the recipe or program control program 259 can be stored on the electronic storage 252 of the control system 250. The recipe 259 can be modified or programmed to be customized for a specific exposure equipment or a type of exposure equipment. The recipe 259 can be programmed during the manufacture of the lithography system 200, and / or the recipe 259 can be programmed by the end user or other operators familiar with the performance of the system 200 via, for example, the I / O interface 253.

[0107] Formulation 259 may also specify different separation distances 879 for different exposure passes used to expose different areas of wafer 170. Alternatively, formulation 259 may specify the separation distance 879 on a batch or layer basis or on a wafer basis. A batch or layer is a group of wafers processed by the same exposure equipment under the same nominal conditions. Formulation 259 also allows specifying other parameters related to spatial images 873a, 873b, such as the dose provided by each image. For example, formulation 259 may specify the ratio of the number of pulses in N pulses having a first dominant wavelength 702_1 to the number of pulses having a second dominant wavelength 702_2. These other parameters may also be specified on a field, batch (or layer) and / or wafer basis.

[0108] Furthermore, formulation 259 can specify that some layers are not exposed by the first dominant wavelength 702_1 and the second dominant wavelength 702_2, but instead by pulse exposure having a spectrum including a single dominant wavelength. For example, this spectrum can be used when a planar semiconductor device is to be formed rather than a three-dimensional semiconductor device. I / O interface 253 allows end users and / or manufacturers to program or generate formulations to specify the number of dominant wavelengths, including, for example, scenarios where a single dominant wavelength is used for a specific layer or batch.

[0109] Furthermore, while the example above discusses an average spectrum 701 with two dominant wavelengths, in other examples, the average spectrum 701 may have more than two dominant wavelengths (e.g., three, four, or five dominant wavelengths), each of which is separated by spectral separation and by regions such as region 704 from the nearest other dominant wavelength. I / O interface 253 allows end users and / or manufacturers to program or generate recipes to specify these parameters.

[0110] A three-dimensional (3D) semiconductor component (540) is formed. Figure 9A shows a cross-sectional view of an example of a 3D semiconductor component 995. Figure 9B shows a wafer 170 and component 995 in the xy plane at a first plane 878a. The 3D semiconductor component 995 can be a complete component or a part of a larger component. The 3D semiconductor component 995 can be any type of semiconductor component having features not entirely formed at one z-position in the wafer 170. For example, the 3D semiconductor component can be a device including a recess or opening extending along the z-axis. The 3D semiconductor component can be used in any type of electronic application. For example, the 3D semiconductor component can be all or part of a 3D NAND flash memory component. A 3D NAND flash memory is a memory in which memory cells are stacked in layers along the z-axis.

[0111] In the example of Figure 9A, the 3D semiconductor component 995 includes a recess 996 formed in a periphery 999. The recess 996 includes a bottom surface 997 and a sidewall 998, the sidewall 998 extending generally along the z-axis between the periphery 999 and the bottom surface 997. The bottom surface 997 is formed by photoresist at a plane 878b exposed by light in the second spatial image 873b (Figure 8A). Features on the periphery 999 are formed using light in the first spatial image 873a (Figure 8A).

[0112] Process 500 may also produce a sidewall angle 992 that is equal to or closer to 90° than sidewall angles that may be produced by other processes. Sidewall angle 992 is the angle between the bottom surface 997 and the sidewall 998. If the sidewall 998 extends in the xz plane and the bottom surface extends in the xy plane, then the sidewall angle 992 is 90°, and in this example it can be considered vertical. A sidewall angle closer to vertical is desirable because, for example, it allows for more defined features in 3D semiconductor components. Process 500 achieves a sidewall angle 992 that is equal to or close to 90° because the positions of the first spatial image 873a and the second spatial image 873b (the first plane 878a and the second plane 878b, respectively) are separate images at different parts of the wafer 170. Creating a separate spatial image in a single exposure pass allows for improvements in the quality of each element in the image, resulting in more vertically oriented and defined features compared to features created by a single spatial image of lower quality.

[0113] Figures 10A and 10B are examples of simulation data related to process 500. Figure 10A shows three plots 1001, 1002, and 1003 of the spatial image intensity and mask positioning along the y-axis (Figure 9A). Each of plots 1001, 1002, and 1003 represents the intensity and mask positioning for a spatial image. In Figure 10A, plot 1001 represents a simulation of the average spectrum of two spatial images formed during a single exposure pass, as discussed above with respect to Figure 5. Plot 1002 represents a simulation of the wafer stage tilted according to ASML's EFESE technique, a procedure used to increase depth of focus to facilitate the printing of three-dimensional features (such as vias and holes) on the wafer. In EFESE, the wafer stage is tilted at an angle to scan the spatial image through the focal point during wafer exposure. EFESE generally produces a greater depth of focus. In Figure 10A, only plot 1002 represents data simulated using EFESE technology. The remaining data shown in Figure 10A do not employ EFESE technology. Plot 1003 represents data simulated from dose-based optimal focus.

[0114] The varying spatial image intensity, as shown in Figure 10A with the mask positioning, illustrates that forming two or more spatial images in a single exposure pass can produce contrast similar to that of a tilted wafer stage. Greater contrast indicates a greater likelihood of properly forming three-dimensional features at different locations along the z-axis (Figure 8A).

[0115] Figure 10B shows three plots 1004, 1005, and 1006 illustrating the critical size varying with the focus position of three different spatial images, each spatial image averaged across exposure passes. In Figure 10B, plot 10004 represents data from a simulation that forms a single spatial image without applying EFESE technology. Plot 1005 represents data from a simulation that applies EFESE technology. As shown, EFESE technology increases the depth of focus compared to a simulation without EFESE because the critical size value remains constant at a greater distance from zero focus. Plot 1005 represents data from a simulation that produces two spatial images in a single exposure pass without applying EFESE technology. The depth of focus in a simulation without EFESE using multiple spatial images is equal to or better than that of EFESE technology. Therefore, process 500 can be used to achieve a greater depth of focus in a single exposure pass without relying on techniques such as EFESE.

[0116] Referring to Figure 11A, an embodiment 1150 of the control system 250 is shown as part of a photolithography system 1100. The control system 1150 includes a processor 251, electronic storage 252, and an I / O interface 253, which are configured together to interface with a spectral feature selection module 258 within the optical source 1105 to adjust the spectral characteristics of a pulsed beam 1160 output from the optical source 1105. Furthermore, the control system 1150 includes an energy control module 1161E configured to provide an excitation signal 1168E to the optical source 1105 for controlling electrodes within a master oscillator (such as master oscillator 212 in Figure 2A) of the optical source 1105. The energy control module 1161E can also be configured to provide the excitation signal to one or more other oscillators within the optical source 1105. The control system 1150 can be used with any type of optical source 1105. The control system 1150 can be used with an optical source 1105 that includes a single optical oscillator. The control system 1150 can also be used with a multi-stage optical source 1105 (such as optical source 205 of FIG2A) that includes one or more optical oscillators and one or more power amplifiers.

[0117] Optical source 1105 provides pulsed beam 1160 to lithography exposure apparatus 1169. Energy control device 1160E is formed by energy control module 1161E and optical detection system 1145E. Optical detection system 1145E is configured to sense light (such as pulsed beam 1160) and generate energy attribute signal 1146E. Optical detection system 1145E is any type of optical sensor or detector capable of measuring the optical energy in pulsed beam 1160 and generating energy attribute signal 1146E based on this measurement. Energy attribute signal 1146E includes information about the energy in one or more pulses of beam 1160. Energy attribute may be, for example, the optical energy of an optical pulse in pulsed beam 1160 or an energy error associated with an optical pulse in pulsed beam 1160.

[0118] The energy control module 1161E generates an excitation signal 1168E or causes the excitation signal 1168E to be generated by a separation device (such as a source supply 1197E), which is configured to amplify the signal and apply a voltage to one or more electrodes 217, as shown in Figure 2A. When the excitation signal 1168E is applied to one or more optical oscillators in the optical source 1105, the optical oscillator generates an optical pulse. The excitation signal 1168E and the pulse in the beam 1160 are time-varying signals. In the following discussion, individual instances of the excitation signal 1168E, the pulse, and the energy attribute signal 1146E can be indexed by k, where k is an integer number. For example, the kth instance of the excitation signal 1168E (excitation signal 1168E(k)) generates pulse k of the beam 1160. The energy control module 1161E receives an example of energy attribute signal 1146E and generates an excitation signal 1168E for each pulse in the beam 1160.

[0119] The amount of optical energy generated in response to the application of excitation signal 1168E (i.e., the energy in the pulse of beam 1160) depends on the characteristics of excitation signal 1168E. For example, excitation signal 1168E may be a voltage pulse train, and the characteristics of excitation signal 1168E may include the amplitude and / or duration of the voltage pulses. Energy control module 1161E determines excitation signal 1168E or its characteristics. In the following discussion, energy control module 1161E and its various embodiments are described as generating or determining excitation signal 1168E. However, in some embodiments, energy control module 1161E (or any of its various embodiments) generates the characteristics of signal 1168E provided to source supplier 1197E based on characteristics of signal 1168E. For example, excitation signal 1168E may be a high-voltage signal generated by source supplier 1197E.

[0120] An energy control module 1161E is implemented to achieve spectrally characteristic-dependent (e.g., wavelength-dependent) dose or energy control at the lithography exposure apparatus 1169. Specifically, the energy control module 1161E allows the dose and / or energy of the current pulse in the beam 1160 to be changed relative to previous and adjacent pulses in the beam 1160. This change can be performed for each pulse of the beam 1160, such that the energy changes with each pulse of the beam 1160. By modifying and correcting the excitation signal 1168E provided to the optical source 1105, the energy control module 1161E is configured to provide inter-pulse control of the dose and / or energy of pulses in the beam 1160.

[0121] It may be necessary to generate different energies for each pulse in a manner that depends on the wavelength selected for different pulses. In this way, it may be desirable for the dose and / or energy values ​​of the pulses to depend on the pulse wavelength (or other spectral characteristics or only the number or duration of pulses). For example, referring to Figure 7, it may be necessary to generate a first set of pulses with a first dominant wavelength 702_1 at a first target energy Etarget1, and a second set of pulses with a second dominant wavelength 702_2 at a second target energy Etarget2, which is different from the first target energy Etarget1. In this way, the dose and / or energy of the pulses of beam 1160 can be optimized at each spatial image 873a, 873b in the field.

[0122] As discussed above with reference to Figures 2A to 2C, the optical source 1105 includes a spectral feature selection module 258, which is coupled to the light propagating in the optical source 1105 to enable fine tuning of spectral features, such as the wavelength and bandwidth within the master oscillator 212. In multifocal imaging, the spectral feature selection module 258 can change its configuration by each pulse or by each nth pulse, where n is an integer greater than 1. The optical oscillator 212 is associated with a plurality of transfer functions, each transfer function being associated with a specific configuration of the spectral feature selection module 258, and each transfer function being related to the efficiency characteristics of that configuration. The specific transfer function correlates the characteristics of the excitation signal 1168E with the amount of optical output (within pulse beams 224 or 260) generated by the optical oscillator 212 in that specific configuration. Referring to a specific example of FIG2A, the transfer function of a specific configuration of optical oscillator 212 (and a specific configuration of spectral feature selection module 258) relates the amount of voltage applied to electrode 217 in chamber 214 to the optical energy generated by the gain medium within chamber 214.

[0123] Referring to Figure 11B, the transfer function TF (the optical energy generated by a single optical oscillator 212 that varies with the provided excitation energy) varies with the wavelength of the emitted pulsed beam. Figure 11B includes: a transfer function TF(1), which is the efficiency of the optical oscillator 212 when the center or dominant wavelength of the pulse is the first wavelength (λp1); and a transfer function TF(2), which is the efficiency of the optical oscillator 212 when the center or dominant wavelength of the pulse is the second wavelength (λp2). The transfer functions TF(1) and TF(2) correlate the voltage V applied to the excitation mechanism of the optical oscillator 212 with the optical energy of the pulse of the beam 1160 generated by the optical oscillator 212. Both transfer functions TF(1) and TF(2) are locally close to linear, but have different slopes and different y-intercepts. The pulse energy (Epulse) depends on the transfer function TF, as follows: Epulse = TF × [HVSetPoint - OffsetV] + OffsetE + noise, where HVSetPoint is the discharge voltage setpoint, OffsetV is the voltage offset applied to the excitation mechanism of the optical oscillator 212, and OffsetE is the energy offset.

[0124] In one example, the optical oscillator 212 alternates between generating optical pulses at a first dominant wavelength (λp1) and optical pulses at a second dominant wavelength (λp2) to generate a pulsed beam 1160 having spectral peaks at both the first and second dominant wavelengths. In this manner, the optical pulses at the first dominant wavelength (λp1) are typically mixed with (and in some embodiments, interleaved with) the optical pulses at the second dominant wavelength (λp2).

[0125] System 1160 attempts to maintain a first target energy Etarget1 for an optical pulse at a first dominant wavelength (λp1) and a second target energy Etarget2 for an optical pulse at a second dominant wavelength (λp2). For example, the k-th pulse has energy E1 and a dominant wavelength of λp2. After the k-th pulse is generated, the optical elements in the spectral feature selection module 258 are actuated such that the dominant wavelength of the (k+1)-th pulse is λp2. Therefore, system 1160 determines the voltage applicable to the optical oscillator 212 for generating the (k+1)-th pulse based on an estimate of the transfer function TF(2), which is an accurate representation of the efficiency of the configuration of the optical oscillator 212 when it is configured to generate a pulse with a dominant wavelength of the second dominant wavelength (λp2).

[0126] The energy control module 1161E can be configured to determine the excitation signal 1168E based on a transfer function associated with a specific configuration of the spectral feature selection module 258 used to generate subsequent light pulses. For example, the spectral feature selection module 258 includes at least one prism, and each transfer function can be associated with a different location of the at least one prism.

[0127] Whenever the energy of the current pulse changes relative to previous and neighboring pulses, energy interference due to differences in the transfer function and imperfect estimations associated with each state of the spectral feature selection module 258 of optical source 1105 occur. Furthermore, undesirable oscillations in the energy of the pulses of beam 1160 can be attributed to coupling between the energy and wavelength of the pulses of beam 1160. Without any type of correction mechanism that quickly accounts for such energy interference, the dose and / or energy of the pulses of beam 1160 may be erroneous or suboptimal, further contributing to errors at wafer 170. The energy control module 1161E uses a correction module and a modeling module to correct or adjust the excitation signal 1168E. This modeling module estimates the transfer function of each state of the spectral feature selection module 258 so that the energy control module 1161E can remove or reduce energy interference. Furthermore, the energy control module 1161E performs this control on an inter-pulse basis to account for errors occurring in each pulse condition.

[0128] Referring to Figure 12, an embodiment 1261E of the energy control module 1161E is shown for use with an optical oscillator 1212E. The energy control module 1261E is configured to be implemented as part of a control system 1150 or 250. The optical oscillator 1212E may be one of two or more optical oscillators in a multi-stage optical source (such as optical source 205 in Figure 2A). The output of the optical oscillator 1212E is a pulsed beam, such as seed beam 224 or output beam 260 (Figure 2A). In some embodiments, there may be separate energy control modules 1261E configured for each optical oscillator in the multi-stage optical source. For example, a first energy control module 1261E may be configured for a master oscillator 212, while a second energy control module 1261E may be configured for a power amplifier 230 (see Figure 2A). In other embodiments, a single energy control module 1261E can be configured for both the master oscillator 212 and the power amplifier 230 (see Figure 2A).

[0129] The energy control module 1261E includes a comparator 1263E and an energy controller 1262E. The energy control module 1261E also includes a target energy generator 1270E. The comparator 1263E receives an energy attribute signal 1246E from the optical detection system 1145E and a target energy Etarget 1271E from the target energy generator 1270E. The comparator 1263E performs comparison functions, such as subtraction to determine the error signal 1266E. The energy controller 1262E includes one or more modules configured to determine an excitation signal 1268E, corresponding to the reference excitation signal 1168E in Figure 11A. The excitation signal 1268E takes into account the error signal 1266E and also considers changes in the transfer function of the optical oscillator 1212E, as discussed below.

[0130] Referring to Figure 13, a more detailed view of the master oscillator 212 is shown. Two elongated electrodes 217 comprise a cathode 217-a and an anode 217-b contained within a discharge chamber 214. The potential difference between the cathode 217-a and the anode 217-b creates an electric field in the gaseous gain medium 219. This potential difference is generated by controlling a source supply 1197E to apply a voltage to the cathode 217-a and / or the anode 217-b. In this example, the source supply 1197E is controlled by an excitation signal 1168E. The excitation signal 1168E includes information sufficient to cause the source supply 1197E to generate a voltage signal 1168Ev and to apply this voltage signal 1168Ev to the master oscillator 212 according to a trigger signal 330 (Figure 3C). The voltage signal 1168Ev has an amplitude specified by the excitation signal 1168E. Source supply 1197E applies a voltage signal 1168Ev to apply a voltage of a specific amplitude to cathode 217-a and / or anode 217-b, such that the electric field is sufficient to induce population inversion and provide energy to gain medium 219 to generate pulses of beam 224 by stimulated emission. This potential difference is repeatedly generated to form pulse trains, which are emitted as beam 224 and thus as beam 260 (Figure 2A).

[0131] Referring again to 12, comparator 1263E implements a comparison function such as subtraction. Comparator 1263E receives energy attribute signal 1246E from optical detection system 1145E and the value of target energy Etarget 1271E from target energy generator 1270E. Energy attribute signal 1246E includes an indication of the amount of optical energy in pulse k-1, where pulse k-1 is the pulse immediately preceding pulse k.

[0132] The target energy Etarget 1271E is the target or desired optical energy value of a subset of optical pulses in beam 1160. The target energy Etarget 1271E is a predefined optical energy associated with the acceptable or optimal performance of the photolithography system 1100. The value of Etarget 1271E can be stored in electronic storage 252 or another location within the optical source 1105, and is ready for use by comparator 1263E when needed. In some embodiments, the value of Etarget 1271E can be indicated by the photolithography exposure device 1169 (as shown by arrow 1165). As discussed above, the energy control module 1161E is implemented to achieve spectrally characteristic-dependent dose or energy control at the photolithography exposure device 1169. In order to implement wavelength-dependent dose or energy control, the target energy generator 1270E provides or determines the target energy Etarget 1271E, which is associated with the spectral properties (such as the dominant wavelength λp) of the pulse of the beam 1160 generated by the optical oscillator 1212E.

[0133] For example, Figure 14 shows a table showing the correlation between each target energy Etarget 1271E_i and each possible dominant wavelength λp 1402_i in the pulse set of beam 1160, where i is an integer greater than 1 and has a maximum value of M. This table can be stored in optical source 1105 or lithography device 1169 and accessed by target energy generator 1270E after the pulse of beam 1160 is generated.

[0134] As another example, Figure 15A shows a graph of the target energy Etarget 1571E relative to four principal wavelengths 1502, each of which is associated with a set of beam pulses. Therefore, principal wavelength 1502a is associated with target energy Etarget 1571Ea; principal wavelength 1502b is associated with target energy Etarget 1571Eb; principal wavelength 1502c is associated with target energy Etarget 1571Ec; and principal wavelength 1502d is associated with target energy Etarget 1571Ed. In this example, as shown in Figure 15B, four distinct spatial images 1573a, 1573b, 1573c, and 1573d are formed at wafer 170 during the same exposure pass. Each spatial image 1573a, 1573b, 1573c, and 1573d is formed along the z-axis at separate and distinct planes 1578a, 1578b, 1578c, and 1578d. The position of the planes depends on the dominant wavelength 1502. Thus, for example, spatial image 1573a is formed at plane 1578a, and its position along the z-axis depends on the dominant wavelength 1502a. Therefore, each spatial image 1573a, 1573b, 1573c, and 1573d is associated with separate distinct energies 1571Ea, 1571Eb, 1571Ec, and 1571Ed. In Figure 15B, each phase energy 1571Ea, 1571Eb, 1571Ec, 1571Ed is represented by different brightness levels within the respective spatial images 1573a, 1573b, 1573c, 1573d.

[0135] Referring again to Figure 12, in order to determine the target energy Etarget 1271E associated with the dominant wavelength of pulse k-1 of beam 1160, the target energy generator 1270E can access information or data from optical source 1105 regarding the dominant wavelength of pulse k-1. For example, if energy attribute signal 1246E is associated with pulse k-1, the target energy generator 1270E can output the target energy Etarget 1271E associated with the dominant wavelength of pulse k-1. As another example, the target energy generator 1270E can output the target energy Etarget 1271E based on the number of pulses or an index. For example, referring to Figures 15A and 15B, if pulse k-1 has a dominant wavelength 1502c (corresponding to the pulse set specified by c), the target energy generator 1270E determines the target energy Etarget 1271E for pulse k-1 to be 1571Ec. On the other hand, if pulse k-1 has a dominant wavelength of 1502a (corresponding to the set of pulses specified by a), then the target energy generator 1270E determines that the target energy Etarget 1271E for pulse k-1 is 1571Ea.

[0136] Furthermore, an indication of the value of Etarget 1271E and / or the amount of optical energy in the energy attribute signal 1246E may be processed prior to being received by the comparator 1246E. For example, if the value of Etarget 1271E is in energy (Joules) and the indication of the amount of optical energy in the energy attribute signal 1246E is in power (watts), the indication can be previously converted to energy (Joule) units at comparator 1263E . The comparator 1263E determines the energy error 1266E associated with the pulse k-1 of the beam 1160. The energy error 1266E corresponds to the difference between the amount of energy in the pulse k-1 and the Etarget 1271E .

[0137] The energy error 1266E is provided to the energy controller 1272E, which judges the incentive signal 1268E. The characteristics of the incentive signal 1268E are based on the energy error 1266E (which in turn is based on an indication of the amount of energy in the energy attribute signal 1246E). Furthermore, the energy controller 1272E corrects the excitation signal 1268E to account for changes in the transfer function of the optical oscillator 1212E . The transfer function varies due to the spectral properties (wavelengths) of the pulses in beam 1160 being intentionally not all identical. For example, the central or dominant wavelength of each pulse can be changed on a pulse-by-pulse basis before the pulse is generated, thereby changing the configuration of the spectral feature selection module 258 . The dominant wavelength may alternate between a complex number of values ​​to form a pulse beam 1160 with a spectral peak at each principal wavelength, wherein any two peaks are separated from each other by a spectral distance that is the difference between the dominant wavelengths of the two peaks. At wavelengths between two adjacent dominant wavelengths, very little or no light is present in the pulsed beam.

[0138] A calibrated excitation signal 1268E is applied to the optical oscillator 1212E to correct for changes in the efficiency of the optical oscillator 1212E . By calibrating the excitation signal 1268 E , the energy control module 1261 E causes the pulse energy of a particular dominant wavelength in the pulse beam 1160 to be in or within the acceptable range of the target energy 1271E associated with that particular dominant wavelength.

[0139] Referring to Figure 16, an embodiment 1661E of the energy control module 1161E is shown for use with an optical oscillator 1212E. In this embodiment, the energy control module 1661E includes a plurality of energy controllers 1672E, one energy controller for each dominant wavelength λp. In this embodiment, two energy controllers 1672E_1 and 1672E_2 are shown, one energy controller for each of the two dominant wavelengths, such that the optical oscillator 1212E generates pulses having a first dominant wavelength λp1 at a first target energy 1671E_1 and a second dominant wavelength λp2 at a second target energy 1671E_2. In other embodiments, the energy control module 1661E may include more than two energy controllers 1672E, as many as there are dominant wavelengths in the beam 1160. Each of the energy controllers 1672E may have any suitable design or operation. Furthermore, any one of the energy controllers 1672E within the energy control module 1661E may have a different design or operation than the other energy controllers 1672E within the energy control module 1661E.

[0140] The energy control module 1661E includes a set of comparators 1663E, one comparator for each energy controller 1672E. In the illustrated embodiment, a first comparator 1663E_1 is associated with a first energy controller 1672E_1, and a second comparator 1663E_2 is associated with a second energy controller 1672E_2. The energy control module 1661E also includes a target energy generator 1670E that generates a target energy Etarget for each dominant wavelength λp. Therefore, in this embodiment, the target energy generator 1670E generates a first target energy Etarget 1671E_1 for a first dominant wavelength λp1, which is provided to the first comparator 1663E_1, and generates a second target energy Etarget 1671E_2 for a second dominant wavelength λp2, which is provided to the second comparator 1663E_1.

[0141] The energy control module 1661E includes switches 1646Es configured to determine where to send the energy attribute signal 1646E. Specifically, if the current pulse has a first dominant wavelength λp1, the switches 1646Es provide the energy attribute signal 1646E to a first comparator 1663E_1, and if the current pulse has a second dominant wavelength λp2, the switches 1646Es provide the energy attribute signal 1646E to a second comparator 1663E_2. In other embodiments, instead of the switches at the optical detection system 1145E, individual switches may be implemented at comparators 1663E_1 and 1663E_2.

[0142] The energy controller (such as energy controller 1272E configured to operate on all dominant wavelengths λp, or energy controllers 1672E_1, 1672E_2, each configured to operate on a single dominant wavelength λp) can have any suitable design or operation. Several embodiments suitable for the energy controller will now be discussed with reference to Figures 17 through 20. Any of these energy controllers can be implemented as any one of energy controllers 1272E, 1672E_1, or 1672E_2. Furthermore, the operation of multiple energy controllers may be combined into a single energy controller among energy controllers 1272E, 1672E_1, and 1672E_2.

[0143] Referring to Figure 17, the energy controller implementation 1772E uses a notch filter. The energy controller 1772E includes a delay module 1767E, an excitation determination module 1762E, and a correction module 1764E. The delay module 1767E receives an energy error 1766E from a comparator 1763E, which can be any of comparators 1263E, 1663E_1, or 1663E_2. The delay module 1767E introduces a time delay into the energy error 1766E to ensure proper causality; such that actions taken by the energy controller 1772E are not applied to the received measurement pulse (from the energy attribute signal 1246E). When the delay module 1767E is presented as a discrete block, its function can be implemented within the optical detection system 1145E or the excitation determination module 1762E.

[0144] The energy error 1766E is provided to the incentive judgment module 1762E, which judges the incentive signal 1768Ep. The characteristics of the incentive signal 1768Ep are based on the energy error 1766E , which in turn is based on an indication of the amount of energy in the energy attribute signals 1246E , 1646E . Thus, for example, the incentive decision module 1762E may determine how much to adjust the voltage of the electrode of the oscillator 1212E to offset the error in the energy of the beam output by the self-oscillator 1212E .

[0145] The incentive signal 1768Ep is provided to the calibration module 1764E. The calibration module 1764E judges the calibrated incentive signal 1768E based on the incentive signal 1768Ep. Specifically, the calibration module 1764E corrects the excitation signal 1768Ep to account for changes in the transfer function of the optical oscillator 1212E . The transfer function varies due to the spectral properties of the pulses in beam 1160 being intentionally not all identical. For example, the central or dominant wavelength λp of each pulse may be changed on a pulse-by-pulse basis prior to generating a pulse, thereby changing the configuration of the spectral feature selection module 258 . The dominant wavelength may alternate between a complex number of values ​​to form a pulse beam 1160 with a spectral peak at each principal wavelength, wherein any two peaks are separated from each other by a spectral distance that is the difference between the dominant wavelengths of the two peaks. At wavelengths between two adjacent dominant wavelengths, very little or no light is present in the pulsed beam.

[0146] The calibration module 1764E implements a filter (such as a notch filter) that judges the calibrated incentive signal 1768E based on at least each of the following: transfer function TF(k), k-th pulse when the kth pulse is generated by optical oscillator 1212E Energy error 1766E for the rush, cumulative energy error for the k-th pulse, one or more values ​​of a previous excitation signal for a pulse having the same dominant wavelength as the k-th pulse and one or more tuning parameters or gains related to the energy and / or dose error. Broadly speaking, the notch filter rejects signals with frequencies in the band and transmits signals with frequencies outside the band. The notch filter is configured to reject energy interference that can be attributed to using light pulses of different configurations (different transfer functions) from the optical oscillator 1212E . The notch filter can be expressed by the following equation: Equation (2), Where k is the integer number of pulses indexed, Vsp is the calibrated excitation signal 1768E, and specifically, Vsp(k+1) is the calibrated excitation signal 1768E for pulse k+1, GN is KH / KE, where KH is the tuning parameter of the gain related to dose error, KE is the tuning parameter or gain related to energy error, and Vservo is the voltage command calculated according to the following equation (3): Equation (3), Where e(k) is the energy error 1766E of the kth pulse, D(k) is the cumulative energy error or dose error of the kth pulse, and dEdV(k) is the transfer function when the optical oscillator 1212E generates the kth pulse.

[0147] A calibrated excitation signal 1768E is applied to the optical oscillator 1212E to correct for variations in the efficiency of the optical oscillator 1212E. Using the calibrated excitation signal 1268E, the energy control module 1261E ensures that the pulse energy of a specific dominant wavelength in the pulse beam 1160 is within or within an acceptable range of a target energy (such as Etarget 1271E, or Etarget 1671E_1, Etarget 1671E_2) associated with that specific dominant wavelength.

[0148] Referring to Figure 18, the energy controller implementation 1872E uses a Kalman filter that employs linear quadratic estimation. The energy controller 1872E includes a delay module 1867E that receives error signals from a comparator 1863E, which can be any of comparators 1263E, 1663E_1, or 1663E_2. As discussed above, the delay module 1867E introduces a time delay into the energy error 1866E to ensure proper causality; such that actions taken by the energy controller 1872E are not applied to the received measurement pulse (from the energy attribute signal 1246E). When the delay module 1867E is presented as a discrete block, its function can be implemented within the optical detection system 1145E or another component of the energy controller 1872E. The energy controller 1872E includes an excitation determination module 1862E, a correction module 1864E, and a second comparator 1869E.

[0149] Similar to excitation determination module 1762E, excitation determination module 1862E determines the excitation signal 1868Ep based on the energy error 1866E output by self-delay module 1867E. Specifically, excitation determination module 1862E includes a set of transfer function models, each of which is associated with a separate state of optical oscillator 1212E. Specifically, each transfer function TF of optical oscillator 1212E is associated with a specific configuration of spectral feature selection module 258 that generates different dominant wavelengths λp, and each transfer function TF is related to the efficiency characteristics of that configuration. Excitation determination module 1862E selects the model M(TF) associated with the transfer function TF of optical oscillator 1212E that generates the k-th pulse in order to calculate the excitation signal 1868Ep. In equation form, this can be expressed as follows: Equation (4), Where k is an integer greater than or equal to 1 representing the number of pulses of beam 1160, Chk is the state of the optical oscillator 1212E that generates the k-th pulse in beam 1160, and dedv(Chk) is the model M(TF) of the transfer function modeling the optical oscillator 1212E that generates the k-th pulse. V* and E* are determined as part of the modeling. V(k+1) is the excitation signal 1868Ep determined for the k+1 pulse.

[0150] The correction module 1864E is implemented as a Karman filter, which efficiently rejects inter-pulse energy interference with a known period. The Karman filter 1864E uses the energy error 1866E from comparator 1863E and the excitation signal 1868Ep from excitation determination module 1862E to determine the output signal 1864Eo. The output signal 1864Eo is then provided to a second comparator 1869E. The second comparator 1869E determines the corrected excitation signal 1868E based on the output signal 1864Eo and the excitation signal 1868Ep.

[0151] The output signal 1864Eo of the Karman filter 1864E is based on a factor directly related to the energy error 1866E of the k-th pulse, a model M(TF) associated with the period of the configuration change of the spectral feature selection module 258, and the excitation signal 1868E applied to generate the k-th pulse. The output signal 1864Eo of the Karman filter 1864E also takes into account the gain and tuning parameters of the Karman filter 1864E.

[0152] The output signal 1864Eo of the Karman filter can be expressed by the following equation: Equation (5), Where A = -1, and KXpost(k) is an estimate of the output of the Karman filter 1864E for the k-th pulse, given by: Equation (6) is: KXpost(k) = KXpred(k) + K_K(k) * Ke(k). Where K_K is the gain of the 1864E Karman filter, given as follows: Equation (7), And Ke(k) is given by the following: Equation (8), Where error(k) is the energy error 1866E of the kth pulse, dedv(M(TF)) is the model associated with the optical oscillator 1212E used to generate the kth pulse in the beam 1160, and HVcommand(k) is the excitation signal applied to generate the kth pulse.

[0153] K_S(k) is given by K_S(k) = KPpred(k) + R, where R is the tuning parameter. Furthermore, KPpred(k) is the covariance of KXpred(k). KPpred(k) can also be considered as the confidence level for determining the gain K_K of the Karman filter 1864E. Therefore, if KPpred(k) is 0, then K_K = 0, which means that we are extremely confident in the model prediction and will not need the output from the optical detection system 1145E. On the other hand, if KPpred(k) is extremely large compared to the noise R in the optical detection system 1145E, then K_K = 1, which means that we can trust only the optical detection system 1145E. KPpred(k+1) is given by: KPpred(k+1) = A * KPpost(k) * A′ + Q Equation (9), Where A = -1, Q are the tuning parameters of the 1864E Kármán filter, and KPpost(k) is given by the following: Equation (10), Where C is the tuning parameter of the 1864E Karman filter and can be equal to 1 in this embodiment, and R is the tuning parameter.

[0154] The second comparator 1869E determines the calibrated excitation signal 1868E as follows: HVSP(k) = HVCommand(k) + HVDefault - KXpred(k), Equation (11), Wherein HVSP(k) is the calibrated excitation signal 1868E, HVCommand(k) is the uncalibrated excitation signal 1868Ep determined by the excitation determination module 1862E for the k-th pulse, HVDefault is the parameter of the nominal excitation signal for estimating the transfer function TF of the optical oscillator 1212E for the k-th pulse, and KXpred(k) is the output signal 1864Eo of the Karman filter 1864E for the k-th pulse. The value of HVDefault can be stored in electronic memory and retrieved by the energy controller 1872E when needed. The value of HVDefault can be a voltage value, and can be, for example, greater than 100 volts.

[0155] Referring to Figure 19A, the energy control module 1161E, in its implementation 1961E, employs a pre-programming method to reject or reduce inter-pulse energy interference or variations attributable to intentionally altering the configuration of the spectral feature selection module 258 associated with the optical oscillator 1212E, thereby changing the spectral properties of the beam 1160 generated by the optical oscillator 1212E. The energy control module 1961E relies on a set of estimated EvsV(λp), each estimate having a relationship between the input (excitation signal or V) to the optical oscillator 1212E and the output (energy E of the beam 1160) from the optical oscillator 1212E for each dominant wavelength λp. The energy control module 1961E includes a target energy generator 1970E (which operates similarly to the target energy generator 1270E), a comparator 1963E, and an energy controller 1972E.

[0156] Referring to Figures 19B and 19C, details of the energy controller 1972E are shown. The energy controller 1972E includes a delay module 1967E and an excitation determination module 1962E. The output of the delay module 1967E is the energy error 1966E output from the comparator 1963E. The energy error 1966E corresponds to a measure of the difference between the energy attribute signal 1946E (which is the energy in the previous pulse, see Figure 19A) and the energy target 1971E. The excitation determination module 1962E determines the calibrated excitation signal 1968E and provides the calibrated excitation signal 1968E to the optical oscillator 1212E.

[0157] Figure 19C is a block diagram of the excitation determination module 1962E. The excitation determination module 1962E may include a feedback controller FC. In some embodiments, the feedback controller FC is a proportional-integral-derivative (PID) controller that receives the error signal 1966E and generates an output applied to one of the selected transfer functions downstream (as discussed below). For example, a PID controller includes a proportional term, an integral term, and a derivative term. Although a PID controller is discussed, any feedback controller can be used as the feedback controller FC.

[0158] The excitation determination module 1962E includes a transfer function selector 1974E, which selects a transfer function TF(1), TF(2), ..., TF(N). Each of the transfer functions TF(1), TF(2), ..., TF(N) is an estimated transfer function for an optical oscillator 1212E with a specific dominant wavelength λp, and each of the transfer functions TF(1), TF(2), ..., TF(N) is associated with a specific configuration (Figure 13) of the spectral feature selection module 258. The spectral feature selection module 258 has N different configurations, each of which is associated with a different spectral parameter (e.g., center or dominant wavelength or bandwidth) of the output beam 1160. N is an integer greater than one that indexes all possible configurations of the spectral feature selection module 258 relevant to a specific application. Each of the N configurations of the spectral feature selection module 258 is associated with a specific transfer function TF(1), TF(2), ..., TF(N) of the optical oscillator 1212E. For example, the index value of N associated with a specific transfer function TF(1), TF(2), ..., TF(N) can be stored in a lookup table or database by defining the data of the transfer function TF and the center or dominant wavelength λp generated by that configuration of the spectral feature selection module 258. The transfer functions TF(1), TF(2), ..., TF(N) can be stored on the electronic storage 252 and can be accessed by the energy control module 1961E. The transfer functions TF(1), TF(2), ..., TF(N) can be associated with the N configurations by the manufacturer, or can be provided by the operator of the system 1100, or can be estimated and updated online using the history of the input (discharge voltage) and output (measured energy).

[0159] The transfer function selector 1974E determines which of the transfer functions TF(1), TF(2), ..., TF(N) is associated with the configuration of the k-th pulse of the output beam 1160 emitted from the optical oscillator 1212E. The transfer function selector 1974E can select from the transfer functions TF(1), TF(2), ..., TF(N) by implementing a remainder function that returns the remainder of a division operation of k by M, where M is an integer representing the number of N configurations of the spectral feature selection module 258 that alternate or cycle between generating optical pulses and k-index the number of pulses. Therefore, M is two, N, or any number greater than 2 and less than or equal to N. If the transfer function selector 1974E implements a remainder function and M=2, then the transfer function selector 1974E returns 0 for pulses with an even k-index number and 1 for pulses with an odd k-index number. In these embodiments, when the transfer function selector 1974E returns 0, the transfer function TF(1) is selected, and when the transfer function selector 1974E returns 1, the transfer function TF(2) is selected.

[0160] In another example, the center or dominant wavelength λp of the optical pulses generated by the optical oscillator 1212E varies pulse by pulse according to a predetermined formula. For example, the optical oscillator 1212E and the spectral feature selection module 258 can be controlled such that the dominant wavelength λp cycles sequentially among four predetermined dominant wavelengths (such as those shown in Figures 15A and 15B). Thus, the transfer function selector 1974E selects the transfer function TF(2) for the second and sixth pulses, and the transfer function TF(3) for the third and seventh pulses, and so on.

[0161] Error signal 1966E is provided to the selected transfer function TF (via transfer function selector 1974E), and the output of the selected transfer function TF is provided to gain 1984E and then to integrator 1985E. Pre-compensation correction signal 1967E is provided to integrator 1985E and is based on the EvsV curve selected based on the dominant wavelength of the next pulse of beam 1160. Pre-compensation correction signal 1967E removes, reduces, or rejects energy interference. Signal 1967E corrects for the energy difference caused by changes in the configuration of spectral feature selection module 258 and changes in Etarget during operation of optical oscillator 1212E, and determines the corrected excitation signal 1968E. The corrected excitation signal 1968E (V(k+1)) is determined based on the following equation: Equation (12), Where k is an integer greater than or equal to 1 and represents the number of pulses in the beam output by the optical oscillator 1212E, λk is the wavelength of the k-th pulse generated by the optical oscillator 1212E, E is the energy value, V is the voltage value, and TF(λk) is one of the transfer functions TF(1), TF(2), ..., TF(N) of the optical oscillator 1212E that generates the wavelength in the k-th pulse. V* and E* are the filtered versions, which are the moving averages of the original voltage and energy values, respectively.

[0162] Referring to Figure 20, embodiment 2061E of the energy control module 1161E uses a repetitive control method that relies on the energy supplied to invert or eliminate arbitrary repetitive interference (displayed as a pattern in the energy attribute signal 2046E). This repetitive interference is attributed to the intentional alteration of the configuration of the spectral feature selection module 258 associated with the optical oscillator 1212E, in order to change the spectral properties of the light beam 1160 generated by the optical oscillator 1212E. The energy control module 2061E includes a target energy generator 2070E (which operates similarly to the target energy generator 1270E), a comparator 2063E, and an energy controller 2072E.

[0163] To reverse or eliminate arbitrary repetitive interference, the energy controller 2072E requires deductive knowledge of the properties of the arbitrary repetitive interference to model the interference and batch-modify the excitation signal 2068E (i.e., modify a set number of future pulses). The energy controller 2072E may include a deductive module 2072ED, configured to acquire this deductive knowledge by, for example, measuring interference on each burst of the pulse, and then using this information to generate a model of the interference. The energy controller 2072E may also include a correction module 2072EC, configured to modify the excitation signal 2068E based on the interference model.

[0164] The energy controller 2072E relies heavily on direct observation of such disturbances; therefore, it is important to incorporate deductive knowledge about the disturbances, including how they change or alter. For example, if it is known that the disturbances change significantly with the repetition rate of the pulses of beam 1160, it may be useful to ensure that the deductive module takes this dependency into account.

[0165] In some implementations, the deduction module 2072ED within the energy controller 2072E can acquire energy attribute signals 2046E over a period of time, for example, a set number of pulses (referred to as an interference period) in a burst of beam 1160. The deduction module 2072ED then compares each of these energy attribute signals 2046E with a target energy Etarget 2071E to generate an energy error (which is a part of the energy signal 2066E) for each pulse in the interference period. The deduction module 2072ED can calculate how much of this energy error has been estimated to have been removed by other feedback controllers within the energy controller 2072E and add it back to the measured energy error to obtain a total error. Other feedback controllers may include those discussed herein. The remainder is the amount of energy error that other feedback controllers would not remove or could not remove, and that the energy deduction module 2072ED would remove. For each pulse during the interference cycle, the deductive module 2072ED updates the magnitude of the interference and (alternatively) a flag, and the error is passed through an integrator (within the deductive module 2072ED) with a gain of less than one to obtain the interference shape to be reversed. Each pulse in the interference cycle is processed independently, and it is assumed that there is no correlation between the pulses. On the next interference cycle, the correction module 2072EC adds the latest interference shape to the excitation signal 2068E. This technique is repeated for each interference cycle, and this technique leads to the training of the pre-trained control.

[0166] Referring to Figure 21, procedure 2100 is executed by photolithography system 1100. Procedure 2100 determines a calibrated input signal (excitation signal 1168E) for application to optical source 1105, and specifically to optical oscillator 1212E. Procedure 2100 is implemented at least in part by control system 1150, which includes energy control module 1161E. Control system 1150 and / or portions thereof (such as energy control module 1161E) may be implemented as part of optical source 1105, as part of photolithography exposure apparatus 1169, or separately from (but in communication with) both optical source 1105 and / or photolithography exposure apparatus 1169.

[0167] A plurality of pulse sets (2105) are generated for the beam 1160. Specifically, the optical source 1105 generates the beam 1160 such that each pulse in the beam 1160 is associated with a different dominant wavelength λp, and may also be associated with a different target energy Etarget. The different dominant wavelength λp is determined based on the configuration of the spectral feature selection module 258.

[0168] Next, the energy of the previous pulse of the receiving beam 1160 is measured (2110). For example, the control system 1150 (and specifically, the energy control module 1161E) receives the energy attribute signal 1146E for the k-th pulse (which can be regarded as the previous pulse) from the detection system 1145E.

[0169] Determine the energy error of the previous pulse (2115). For example, referring to Figure 12, the error signal 1266E is output from comparator 1263E, or referring to Figure 16, the error signal 1666E_1 is output from comparator 1663E_1. If the k-th pulse has a dominant wavelength λp2, the comparator (such as 1263E or 1663E_2) compares the measured energy of the previous beam pulse (determined from the energy attribute signal 1146E) with the second target energy Etarget2, because the second target energy Etarget2 is associated with the second pulse set. On the other hand, if the k-th pulse has a dominant wavelength λp1, the comparator (such as 1263E or 1663E_1) compares the measured energy of the previous beam pulse (determined from the energy attribute signal 1146E) with the first target energy Etarget1, because the first target energy Etarget1 is associated with the first pulse set.

[0170] At least one component of optical source 1105 is adjusted to adjust the energy (2120) of subsequent pulses of beam 1160 based on a judgment error (2115). The adjusted subsequent pulse has the same dominant wavelength as the previous pulse. Thus, for example, if spectral feature selection module 258 is configured to alternate between generating pulses with a first dominant wavelength λp1 and generating pulses with a second dominant wavelength λp2 (as shown in Figures 7 and 8A), and the previous pulse (which is the k-th pulse) has the first dominant wavelength λp1, then the k+2x pulse (where x is a positive integer) is adjusted because the k+2x pulse also has the first dominant wavelength λp1.

[0171] Specifically, a calibrated excitation signal 1168E is applied to an optical oscillator 1212E. For example, the voltages of electrodes 217-a and 217-b are adjusted based on this calibrated excitation signal 1168E.

[0172] The embodiments may be further described using the following terms: 1. A method for controlling the energy of a pulsed light beam, the method comprising: This generates multiple sets of mixed pulses from an optical source, each set of pulses associated with a different dominant wavelength and a different target energy; Measurement of the energy of the preceding pulse of the received beam; Determining energy error includes, if the previous beam pulse is in a specific beam pulse set, comparing the measured energy of the previous beam pulse with the specific target energy associated with that specific beam pulse set; and Adjust at least one component of the optical source to adjust the energy of subsequent pulses in a specific beam pulse set based on a determined energy error. 2. The method of clause 1 further comprises receiving each dissimilar target energy associated with each set of beam pulses. 3. The method of clause 1 further includes classifying whether the previous beam pulse is in a particular set of beam pulses. 4. The method of clause 1 further includes determining the amount of adjustment to at least one component of the optical source. 5. The method of Clause 1, further comprising adjusting at least one component of the optical source based on whether the previous beam pulse is in a particular set of beam pulses. 6. The method of clause 1, wherein adjusting at least one component of the optical source comprises changing the voltage supplied to an electrode associated with an optical oscillator of the optical source. 7. A system comprising: Optical source device, comprising: An optical oscillator configured to generate light pulses in response to an excitation signal, the light pulses having spectral properties; and A spectral adjustment device, configured to control the spectral properties of light pulses; and An energy control device that communicates with an optical source device is configured to: Determine the target energy associated with the spectral properties of the generated light pulse; and The adjustment of the excitation signal is determined at least based on the determined target energy, and the adjustment causes the optical oscillator to generate one or more subsequent optical pulses to take into account changes in the configuration of the spectral adjustment device. 8. The system as described in clause 7, wherein adjustment of the excitation signal causes adjustment of the energy of one or more subsequently generated optical pulses. 9. The system of clause 7, wherein the target energy associated with the spectral properties of the generated light pulse was previously defined as being associated with the spectral properties of the generated light pulse. 10. The system of clause 7, wherein the optical oscillator is associated with a plurality of transfer functions, each transfer function being associated with a specific configuration of the spectral adjustment device and a specific value of the spectral properties; and the energy control device is configured to determine the adjustment of the excitation signal based on the transfer functions associated with the specific configuration of the spectral adjustment device used to generate one or more subsequent light pulses. 11. The system of clause 7, wherein the spectral adjustment device comprises at least one prism and a diffraction element configured optically in communication with each other, and each transfer function is associated with a different state of at least one prism. 12. The system of clause 7, wherein the spectral properties of the light pulse are the center wavelength of the light pulse, and each configuration of the spectral adjustment device corresponds to a specific value of the wavelength. 13. The system of clause 7 further includes a measuring device configured to measure the energy of an optical pulse. 14. The system of clause 13, wherein the energy control device is configured to determine the energy error by comparing the target energy with the measured energy, and the determination of the adjustment of the excitation signal is also based on the energy error. 15. The system of clause 7, wherein the energy control device is configured to determine, by determining the adjustment of the excitation signal to cause the optical oscillator to generate one or more subsequent optical pulses associated with the spectral properties of the generated optical pulses. 16. The system of clause 7, wherein the energy control device is configured to receive communication via a lithography device configured to receive light pulses to determine a target energy associated with the spectral properties of the generated light pulses, the communication providing a set of target energies, each of which is associated with a spectral property. 17. An energy control device, comprising: The control module is configured as follows: The energy value of the previous light pulse received from the optical source; Performing comparisons includes: The received energy value is compared with the first target energy only when the previous optical pulse is in the first beam pulse set associated with the first dominant wavelength; or The received energy value is compared with the second target energy, which is different from the first target energy, only when the previous optical pulse is in a set of second beam pulses associated with a second dominant wavelength different from the first dominant wavelength; and At least one component of the optical source is adjusted based on comparison, thereby adjusting the energy of the subsequent optical pulse having a dominant wavelength associated with the previous optical pulse. 18. An energy control device as described in clause 17, wherein the control module includes a category module configured to classify previous optical pulses in a first set of beam pulses or a second set of beam pulses. 19. An energy control device as described in clause 17, wherein the control module includes a comparator configured to determine whether a previous optical pulse is in a first set of beam pulses or a second set of beam pulses, and to provide a first target energy or a second target energy based on the determination. 20. The energy control device of clause 17, wherein the control module includes a signal module configured to determine the amount of adjustment to be made to at least one component of the optical source. 21. The energy control device of clause 17, wherein the control module includes a correction module configured to correct an adjustment amount to be made to at least one component of the optical source based on a previous optical pulse in a first beam pulse set or a second beam pulse set. 22. The energy control device as described in clause 21, wherein the correction module is configured to correct the adjustment amount by applying a filter to the adjustment amount. 23. The energy control device of clause 22, wherein the filter includes a notch filter that transmits information having a frequency in a first frequency band and substantially blocks information having a frequency outside the first frequency band. 24. Energy control equipment as described in clause 22, wherein the filter includes a Karman filter. 25. An energy control device as described in clause 21, wherein a calibration module is configured to calibrate an adjustment amount by applying a pre-compensated calibration to the adjustment amount. 26. An energy control device as described in clause 17, wherein a control module is configured to adjust at least one component of an optical source based on comparison to adjust the energy of a subsequent optical pulse having a dominant wavelength associated with a previous optical pulse, including sending a signal to the optical source to change the voltage supplied to an electrode associated with an optical oscillator of the optical source. 27. An energy control device as described in clause 17, wherein the energy value of a previous optical pulse is configured to receive the energy value of a plurality of previous optical pulses emitted from an optical source. 28. An energy control device as described in clause 17, wherein a control module is configured to adjust at least one component of an optical source based on comparison, thereby adjusting the energy of a plurality of subsequent optical pulses having a dominant wavelength associated with a previous optical pulse. 29. An energy control device as described in clause 17, wherein the control module is configured to maintain the energy of subsequent optical pulses that do not have a dominant wavelength associated with the previous optical pulse based on comparison.

[0173] Other embodiments are within the scope of the patent application.

[0174] 100: Light and Shadow System 105: Optical source 150: Control System 160: Beam 169: Photolithography equipment 170: Wafer 171: Wafer Stage 172: System of Weights and Measures 173a: Spatial Imagery 173b: Spatial Imagery 174: Mask 175: Projection Optical System 176: Slit 177: Lens 178a: Part 178b: Partial 179: Separation distance 200: Photolithography System 205: Optical Source 212: Master Oscillator 214: Discharge Chamber 216: Line narrowing module 216C: Line Narrowing Module 217: Electrode 217-a: Cathode 217-b: Anode 218: Output Coupler 219: Gain Medium 220: Line Center Analysis Module 222: Beam-coupled optical system 224: Seed Beam 230: Power Amplifier 232: Beam-coupled optical system 240: Discharge Chamber 241: Electrode 248: Beam steering optics 250: Control System 251: Electronic Processor 252: Electronic storage device 253:I / O interface 254: Spectral Feature Control Module 255_1~255_n: Spectral Characteristic Actuation System 256_1~256_n: Optical characteristics 257: Optical System 258: Spectral Feature Selection Module 259: Formula File 260: Beam 262: Bandwidth Analysis Module 263: Beam Preparation System 291: Reflection Grating 292: Prism 293: Prism 294: Prism 295: Prism 300: Wafer Exposure Signal 305: High value 307: Time Period 310: Low value 315: Gate signal 316: Breaking News 320: High value 325: Low value 330: Trigger signal 340: Trigger 400: Window 429: Lighting System 432: Objective lens configuration 479: Exposure Field 500: Process 510: Operation 520: Operation 530: Operation 540: Operation 600A: Pulse 600B: Pulse 601A: Spectrum 601B: Spectrum 602A: Main Wavelength 602B_1: Dominant Wavelength 602B_2: Dominant Wavelength 701: Average Spectrum 702_1: First dominant wavelength 702_2: Second dominant wavelength 703: Spectral Separation 704: Spectral Region 873: Spectral Separation 873a: Space Imagery 873b: Space Imagery 875: Focusing Separation Distance 878a: Plane 878b: Plane 879: Separation distance 992: Side wall angle 995: 3D Semiconductor Components 996: concave part 997: Bottom 998: Sidewall 999: Surrounding Area 1001: Plotting 1002: Plotting 1003: Plotting 1004: Plotting 1005: Plotting 1006::Graphics 1100: Photomicrography System 1105: Optical Source 1145E: Optical Detection System 1146E: Energy Attribute Signal 1150: Control System 1160: Pulse Beam 1160E: Energy Control Equipment 1161E: Energy Control Module 1165: Arrow 1168E: Excitation signal 1168Ev: Voltage signal 1169: Photolithography equipment 1197E: Power Supply 1212E: Optical Oscillator 1246E: Energy Attribute Signal 1261E: Energy Control Module 1263E: Comparator 1266E: Error signal 1268E: Excitation signal 1270E: Target Energy Generator 1271E: Target Energy 1271E_i: Target energy 1272E: Energy Controller 1402_i: Dominant wavelength 1502: Dominant Wavelength 1502a: Main wavelength 1502b: Main wavelength 1502c: Dominant Wavelength 1502d: Dominant Wavelength 1571E: Target Energy 1571Ea: Target Energy 1571Eb: Target Energy 1571Ec: Target Energy 1571Ed: Target Energy 1573a: Spatial Imagery 1573b: Spatial Imagery 1573c: Spatial Imagery 1573d: Spatial Imagery 1578a: Plane 1578b: Plane 1578c: Plane 1578d: Plane 1646E: Energy Attribute Signal 1646Es: Switcher 1661E: Energy Control Module 1663E: Comparator 1663E_1: First comparator 1663E_2: Second comparator 1666E_1: Error signal 1670E: Target Energy Generator 1671E_1: First target energy 1671E_2: Second target energy 1672E: Energy Controller 1672E_1: Energy Controller 1672E_2: Energy Controller 1762E: Excitation Determination Module 1763E: Comparator 1764E: Calibration Module 1766E: Energy Error 1767E: Delay Module 1768E: Corrected excitation signal 1768Ep: Excitation Signal 1772E: Energy Controller 1862E: Excitation Determination Module 1863E: Comparator 1864E: Calibration Module 1864Eo: Output signal 1866E: Energy Error 1867E: Delay Module 1868E: Corrected excitation signal 1868Ep: Excitation Signal 1869E: Second Comparator 1872E: Energy Controller 1946E: Energy Attribute Signal 1961E: Energy Control Module 1962E: Excitation Determination Module 1963E: Comparator 1966E: Energy Error 1967E: Delay Module / Pre-compensation Correction Signal 1968E: Corrected excitation signal 1970E: Target Energy Generator 1971E: Energy Target 1972E: Energy Controller 1974E: Transfer Function Selector 1984E: Gain 1985E: Integrator 2046E: Energy Attribute Signal 2061E: Energy Control Module 2063E: Comparator 2066E: Energy Signal 2068E: Excitation signal 2070E: Target Energy Generator 2071E: Target Energy 2072E: Energy Controller 2072EC: Calibration Module 2072ED: Deduction Module 2100: Program 2105: Operation 2110: Operation 2115: Operation 2120: Operation Epulse: Pulse energy Etarget: Target energy Etarget1: First target energy Etarget2: Second target energy EvsV(λp): Estimation FC: Feedback Controller TF(1): Transfer function TF(2): Transfer function TF(N): Transfer function λp: dominant wavelength λp1: First dominant wavelength λp2: Second dominant wavelength

Claims

1. A method for controlling the energy of a pulsed light beam, the method comprising: generating a plurality of intermingled sets of pulses of the light beam from an optical source, each set of light beam pulses being associated with a distinct primary wavelength and a distinct target energy; receiving a measurement of the energy of a previous pulse of the light beam; determining an energy error, including comparing the measured energy of the previous light beam pulse with a distinct target energy associated with the distinct set of light beam pulses if the previous light beam pulse is in a particular set of light beam pulses; and adjusting at least one component of the optical source to adjust the energy of a subsequent pulse in the particular set of light beam pulses based on the determined energy error, wherein adjusting at least one component of the optical source comprises changing a voltage supplied to an electrode associated with an optical oscillator of the optical source.

2. The method of claim 1, further comprising receiving each dissimilar target energy associated with each set of beam pulses.

3. The method of claim 1, further comprising classifying whether the previous beam pulse is in the particular set of beam pulses.

4. The method of claim 1, further comprising determining the adjustment amount of the at least one component of the optical source.

5. The method of claim 1, further comprising adjusting the amount of adjustment of at least one component of the optical source based on whether the previous beam pulse is in the particular set of beam pulses.

6. An optical system comprising: an optical source device including: an optical oscillator configured to generate a light pulse in response to an excitation signal, the light pulse having a spectral property; a spectral adjustment device configured to control the spectral property of the light pulse; and an energy control device in communication with the optical source device, the energy control device being configured to: determine a target energy associated with the spectral property of the generated light pulse; and determine an adjustment to the excitation signal based at least on the determined target energy, the adjustment causing the optical oscillator to generate one or more subsequent light pulses to take into account a change in the configuration of the spectral adjustment device.

7. The optical system of claim 6, wherein the adjustment of the excitation signal causes an adjustment of the energy of the one or more subsequently generated optical pulses.

8. The optical system of claim 6, wherein the target energy associated with the spectral property of the generated light pulse was previously defined as being associated with the spectral property of the generated light pulse.

9. The optical system of claim 6, wherein the optical oscillator is associated with a plurality of transfer functions, each transfer function being associated with a specific configuration of the spectral adjustment device and a specific value of the spectral attribute; and the energy control device is configured to determine the adjustment of the excitation signal based on the transfer function associated with the specific configuration of the spectral adjustment device for generating the one or more subsequent optical pulses.

10. The optical system of claim 6, wherein the spectral adjustment device comprises at least one prism and a diffraction element configured optically in communication with each other, and each transfer function is associated with a different state of the at least one prism.

11. The optical system of claim 6, wherein the spectral attribute of an optical pulse is a center wavelength of the optical pulse, and each configuration of the spectral adjustment device corresponds to a specific value of the wavelength.

12. The optical system of claim 6, further comprising a measuring device configured to measure the energy of one of the optical pulses.

13. The optical system of claim 12, wherein the energy control device is configured to determine an energy error by comparing the target energy with the measured energy, and the determination of the adjustment of the excitation signal is also based on the energy error.

14. The optical system of claim 6, wherein the energy control device is configured to determine the adjustment of the excitation signal that causes the optical oscillator to generate one or more subsequent optical pulses associated with the spectral properties of the generated optical pulse by determining the adjustment of the excitation signal that causes the optical oscillator to generate one or more subsequent optical pulses.

15. The optical system of claim 6, wherein the energy control device is configured to receive a communication via a lithography device configured to receive the light pulse to determine the target energy associated with the spectral attribute of the generated light pulse, the communication providing a set of target energies, each target energy in the set being associated with a spectral attribute.

16. An energy control device comprising: a control module configured to: receive an energy value of a previous light pulse emitted from an optical source; and perform a comparison, comprising: The received energy value is compared with a first target energy only when the previous optical pulse is in a first set of beam pulses associated with a first dominant wavelength; or the received energy value is compared with a second target energy different from the first target energy only when the previous optical pulse is in a second set of beam pulses associated with a second dominant wavelength different from the first dominant wavelength; and at least one component of the optical source is adjusted based on the comparison to adjust the energy of a subsequent optical pulse having the dominant wavelength associated with the previous optical pulse, wherein the control module is configured to adjust at least one component of the optical source based on the comparison to adjust the energy of the subsequent optical pulse having the dominant wavelength associated with the previous optical pulse, comprising: the control module being configured to send a signal to the optical source to change a voltage supplied to an electrode associated with an optical oscillator of the optical source.

17. The energy control device of claim 16, wherein the control module includes a category module configured to classify the previous optical pulse in the first set of beam pulses or in the second set of beam pulses.

18. The energy control device of claim 16, wherein the control module includes a comparator configured to determine whether the previous optical pulse is in the first set of beam pulses or the second set of beam pulses, and to provide the first target energy or the second target energy based on the determination.

19. The energy control device of claim 16, wherein the control module includes a signal module configured to determine the amount of adjustment to be made to the at least one component of the optical source.

20. The energy control device of claim 16, wherein the control module includes a correction module configured to correct the amount of adjustment to be made to the at least one component of the optical source based on the previous optical pulse in the first beam pulse set or the second beam pulse set.

21. The energy control device of claim 20, wherein the correction module is configured to correct the adjustment amount by applying a filter to the adjustment amount.

22. The energy control device of claim 21, wherein the filter includes a notch filter that transmits information having a frequency in a first frequency band and substantially blocks information having a frequency outside the first frequency band.

23. The energy control device of claim 21, wherein the filter includes a Karman filter.

24. The energy control device of claim 20, wherein the correction module is configured to correct the adjustment amount by applying a pre-compensated correction to the adjustment amount.

25. The energy control device of claim 16, wherein the energy value of the previous optical pulse is configured to receive the energy value of a plurality of previous optical pulses emitted from the optical source.

26. The energy control device of claim 16, wherein the control module is configured to adjust at least one component of the optical source based on the comparison, thereby adjusting the energy of a plurality of subsequent optical pulses having the dominant wavelength associated with the previous optical pulse.

27. The energy control device of claim 16, wherein the control module is configured to maintain the energy of a subsequent optical pulse that does not have the dominant wavelength associated with the previous optical pulse based on the comparison.

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