Target provision control device and method in extreme ultraviolet light source

Abstract

The present application relates to a method of tuning a target device (300) for an extreme ultraviolet (EUV) light source, the target device comprising a target generator, a sensor module (130), and a target generator controller (325). The target generator includes a container (115) configured to contain a target material (114) that generates EUV light in a plasma state and a nozzle structure (117) in fluid communication with the container. The target generator defines an opening (119) in the nozzle structure through which target material received from the container is released. The sensor module is configured to detect an aspect associated with the target material released from the opening as the target material travels along a trajectory toward the target space (112), and to generate a one-dimensional signal from the detected aspect. A target generator controller is in communication with the sensor module and the target generator and is configured to modify a characteristic of the target material based on the analysis of the one-dimensional signal.

Description

Divisional Application Instructions

[0001] This application is a divisional application of Chinese patent application No. 202080016586.4, filed on February 7, 2020, entitled “Target Provision Control Apparatus and Method in Extreme Ultraviolet Light Source”. Cross-references to related applications

[0002] This application claims priority to U.S. Application No. 62 / 810,673, filed on February 26, 2019, which is incorporated herein by reference in its entirety. Technical Field

[0003] The disclosed subject matter relates to an apparatus and method for tuning the characteristics of a target transmitted to a target space of a laser-generated plasma extreme ultraviolet light source. Background Technology

[0004] Extreme ultraviolet (EUV) light is electromagnetic radiation with wavelengths of about 50 nm or less (sometimes also called soft X-rays), including light with wavelengths of about 13 nm. EUV light can be used in photolithography processes to create tiny features in substrates such as silicon wafers.

[0005] Methods for generating EUV light include, but are not limited to, converting materials containing elements such as xenon, lithium, or tin into a plasma state within the EUV emission spectrum. In one such method, commonly referred to as laser-generated plasma (“LPP”), the desired plasma can be generated by irradiating a target material, for example, in the form of droplets, plates, strips, streams, or clusters of material, with an amplified beam, which may be called a driving laser. For this process, the plasma is typically generated in a sealed container (e.g., a vacuum chamber) and monitored using various types of measurement equipment. Summary of the Invention

[0006] In some general aspects, a targeting device for an extreme ultraviolet (EUV) light source includes a target generator, a sensor module, and a target generator controller. The target generator includes a container configured to contain target material that generates EUV light when in a plasma state and a nozzle structure in fluid communication with the container. The target generator defines an opening in the nozzle structure adapted to release target material received from the container. The sensor module is configured to detect aspects of the target material released from the opening as the target material travels along a trajectory toward a target space, and to generate a one-dimensional signal from the detected aspects. The target generator controller communicates with the sensor module and the target generator. The target generator controller is configured to modify the properties of the target material based on analysis of the one-dimensional signal.

[0007] The implementation may include one or more of the following features. For example, the nozzle structure may include a capillary defining an opening, and the opening may extend along the longitudinal direction of the capillary. The target generator controller may include an actuator configured to agitate the rate at which target material is released through the opening. The actuator may include a piezoelectric sensor configured to apply pressure to the target material in fluid form within the container, and the target generator controller may be configured to change the signal provided to the piezoelectric sensor to change the pressure applied to the fluid target material, thereby causing a disturbance in the rate at which the target material is released through the opening.

[0008] The target generator controller may include: a control system configured to generate a drive waveform based on analysis of a one-dimensional signal; and an actuator that communicates with the control system and interacts with the target material. The actuator may be configured to modify the properties of the target material according to the drive waveform from the control system. The control system may be programmable and configured to generate periodic drive waveforms. The control system may be configured to modify multiple aspects of the drive waveform, including modifying one or more of the following: one or more frequencies and one or more phases of the drive waveform. The rate at which the drive waveform is modified may be approximately 100-500 different waveforms per second.

[0009] The sensor module may include: one or more photodiodes, each photodiode outputting a voltage signal related to the current generated by the detected light; a phototransistor; a photoresistor; and a photomultiplier tube.

[0010] The target generator controller can be configured not to communicate with any detection module configured to output a two-dimensional signal associated with the formed target.

[0011] Independent of communication with the target generator controller, the sensor module can communicate with the light source controller, which is configured to adjust one or more characteristics of the radiation pulse directed toward the target space.

[0012] The target generator controller can have a sampling rate of at least 5 MHz.

[0013] The sensor module can be configured to detect light generated by the interaction between the target material and a light curtain guided to pass through a trajectory. The sensor module can also be configured to detect aspects relevant to the target material only when triggered solely by the interaction between the target material and the light curtain.

[0014] The sensor module can be configured to detect aspects related to the target material without relying on image processing and / or trigger signals.

[0015] The target generator can be configured to release target material according to a drive waveform provided by a target generator controller. The target material travels along a trajectory, and at least some of the target material in the form of separated mass blocks can coalesce to form a target in the target space.

[0016] The target device may also include a diagnostic system configured to diagnostically interact with the target material traveling along the trajectory before it enters the target space. A sensor module may be positioned to detect aspects relevant to the diagnostic interaction between the target material and the diagnostic system. The diagnostic interaction may occur at a diagnostic distance from the target space, less than twice the distance between adjacent targets formed by the target material traveling along the trajectory, or half the distance between the opening of the nozzle structure and the target space.

[0017] The target generator controller can be configured to set the steady-state characteristics of the target generator after determining the acceptable range of the target material's properties in the target space based on the analysis of a one-dimensional signal. The target generator controller can also communicate with the control unit of the EUV light source and can be configured to notify the control unit once the steady-state characteristics of the target generator are set.

[0018] In other general aspects, a method is used to control target material traveling along a trajectory toward a target space within a chamber toward an extreme ultraviolet (EUV) light source. The method includes emitting the target material through a longitudinal opening defined in a nozzle, the opening being fluidly coupled to a container configured to contain the target material. The target material generates EUV light in a plasma state. The method includes detecting aspects relevant to the target material as it travels along the trajectory toward the target space. The method includes generating a one-dimensional signal from the detected aspects; analyzing the one-dimensional signal; and modifying one or more properties of the emitted target material based on the analysis of the one-dimensional signal.

[0019] The implementation may include one or more of the following features. For example, by releasing a target material in liquid form through an opening, the target material can be launched through an opening defined in a nozzle. Launching the target material through an opening can cause one or more particles of the target material traveling toward a target space to coalesce into one or more targets before reaching the target space.

[0020] One or more properties of the launched target material can be modified by altering parameters related to the vector velocity of the target material released from the nozzle. The parameters related to the vector velocity of the target material released from the nozzle can be modified by altering the drive waveform provided to the actuator in fluid communication with the target material in the container. The drive waveform provided to the actuator in fluid communication with the target material in the container can be modified by generating or agitating pressure waves within the target material in the container.

[0021] One or more properties of the target material to be emitted can be modified by altering one or more properties at a rate of 100-500 Hz.

[0022] Aspects related to the target material can be detected by detecting light generated by the interaction between the target material and the diagnostic probe. Aspects related to the target material can also be detected by detecting light triggered solely by the interaction between the target material and the diagnostic probe. A one-dimensional signal can be generated from detected light by producing a voltage signal from the current generated by the detected light.

[0023] One-dimensional signals can be analyzed by determining one or more motion properties of the target material.

[0024] One or more properties of the target material to be emitted can be modified by altering one or more properties, independent of any analysis associated with the two-dimensional signal, which is related to the target material.

[0025] Aspects related to the target material can be detected independently of image processing. Aspects related to the target material can be detected independently of the trigger signal associated with the radiation pulse directed towards the target space.

[0026] The method may further include determining, based on analysis of a one-dimensional signal, whether one or more properties of the target material are within acceptable limits in the target space, and notifying the control device of the EUV source when it is determined that one or more properties of the target material are within acceptable limits in the target space. The method may also include maintaining one or more properties of the target material within acceptable limits. Determining whether one or more properties of the target material are within acceptable limits in the target space may include determining that the target material agglomerates into a target with an acceptable shape before entering the target space.

[0027] In other general aspects, a method is used to tune a target device for an extreme ultraviolet (EUV) light source. The method includes operating the target device, comprising a nozzle in fluid communication with a container, in a tuning mode. The tuning mode operation includes releasing target material from the nozzle along a trajectory toward a target space, wherein the target material generates EUV light in a plasma state. The tuning operation mode includes regulating the state of the target material released from the nozzle, including regulating one or more properties of the target material. The regulated one or more properties of the target material include one or more of the following: the location and time at which the target material coalesces into a target along the trajectory before entering the target space. The tuning mode operation includes detecting one or more aspects associated with the target material as it travels along the trajectory toward the target space. The one or more aspects are detected in multiple different tuning states. The method includes determining a set of steady-state performance characteristics associated with the target material based on the detected one or more aspects. The method includes, after determining the set of steady-state performance characteristics associated with the target material, then operating the target device in a steady-state mode based on the set of steady-state performance characteristics, and notifying the control device of the EUV light source to operate the target device in steady-state mode.

[0028] The implementation may include one or more of the following features. For example, one or more aspects related to the target material can be detected as the target material travels along a trajectory toward the target space by detecting one or more aspects related to the target material before the target material coalesces into a target.

[0029] One or more aspects related to the target material can be detected as the target material travels along a trajectory toward the target space by detecting one or more aspects related to the target formed by the coalesced target material.

[0030] One or more properties of the target material released from the nozzle can be adjusted by regulating one or more of these properties at a rate of approximately 100-500 Hz. Attached Figure Description

[0031] Figure 1A It is a block diagram of a target device including a target generator configured to form a target flow pointing toward a target space of extreme ultraviolet (EUV) light source;

[0032] Figure 1B This is a schematic diagram of an example of a jet formed by a target generator, which splits into sub-targets traveling toward the target space and coalescing targets traveling toward the target space;

[0033] Figure 2 It shows from Figure 1A A schematic diagram of the coalescing phase of sub-targets traveling from the target generator into the target space;

[0034] Figure 3yes Figure 1A A block diagram illustrating the implementation of the target device;

[0035] Figure 4 It is shown Figure 1A A block diagram illustrating the implementation of the operation of the actuator of the target device (or 3);

[0036] Figure 5 yes Figure 3 A block diagram illustrating the implementation of the control system for the target device;

[0037] Figure 6A yes Figure 3 A schematic diagram illustrating the implementation of the actuation device of the target device;

[0038] Figure 6B yes Figure 3 A schematic diagram illustrating the implementation of the actuation device of the target device;

[0039] Figure 7 yes Figure 1A Or, the target device of 3 is incorporated into the block diagram of the realization of an extreme ultraviolet (EUV) light source that provides EUV light to the output device;

[0040] Figure 8A It shows the target and the result. Figure 7 A schematic diagram illustrating the implementation of diagnostic interactions between one or more diagnostic probes generated by an EUV light source diagnostic system;

[0041] Figure 8B It shows the target and the result. Figure 7 A schematic diagram illustrating the implementation of diagnostic interactions between one or more diagnostic probes generated by an EUV light source diagnostic system;

[0042] Figure 9 It is by Figure 1A , 3 Or, a flowchart of the process performed by the target device of 7 to control the movement of the target material toward the target space;

[0043] Figures 10A-10C From Figure 1A , 3 The control system of target device 7 provides a diagram of the implementation of the drive waveform of the actuator;

[0044] Figure 11A From Figure 1A , 3 An example of a graph of the output signal generated by the sensor module of the target device 7, including a diagram of the diagnostic interaction with the target material that generates the output signal;

[0045] Figure 11B From Figure 1A , 3An example of a diagram of the output signal generated by the sensor module of the target device 7, including a diagram of the diagnostic interaction with the target material including the sub-target that generates the output signal;

[0046] Figure 11C It shows from Figure 1A , 3 Several examples of graphs showing the output signal generated by the sensor module of the target device (or 7), including illustrations of the diagnostic interaction with the target material that generates the output signal. Figure 11C The output signal in is in response to Figure 10C It is generated by the driving waveform;

[0047] Figure 12 It is provided Figure 1A , 3 A schematic diagram of the realization of the frequency component of the drive waveform generated by the actuator of or 7, and the target material generated by the drive waveform is shown;

[0048] Figure 13 It is by Figure 1A , 3 Or the target device of 7 performs tuning in such as Figure 7 A flowchart of the process of using the target device in EUV light sources, such as EUV light sources; and

[0049] Figure 14 From Figure 7 A block diagram illustrating the implementation of an EUV light source output device that receives EUV light. Detailed Implementation

[0050] refer to Figure 1A The target device 100 includes a target generator 105 configured to form a flow 110 of a target 111 directed toward a target space 112 containing an extreme ultraviolet (EUV) light source. The target 111 is formed from a target material 114 that generates EUV light in a plasma state. The target space 112 is, for example, the location where the target 111 is converted to a plasma state.

[0051] The target generator 105 includes a container 115 defining a hollow interior configured to contain target material 114. The target generator 105 includes a nozzle structure 117 having an opening (or orifice) 119 in fluid communication with the interior of the container 115. The interior of the container 115 can be maintained at a pressure P greater than the pressure outside the opening 119. The target material 114, in a fluid state, flows from the interior of the container 115 under pressure P (and other possible forces, such as gravity) and through the opening 119 to form a flow 110. The trajectories of the target material 114 and the targets 111 formed by the target material 114 generally extend along the -X direction, although the trajectories of the target material 114 and the targets 111 may include components along a plane perpendicular to the -X direction (i.e., Y and Z components).

[0052] The target material 114 may exit the opening 119 as a jet of target material or as a stream of sub-targets. During steady-state operation of the EUV light source, it is desirable for the target material 114 to arrive at the target space 112 in the form of a defined target 111 with specific dimensions and geometry. For example, as Figure 1B As shown, a jet 121 of target material 114 is released from opening 119, and the jet 121 eventually splits into sub-targets 122 traveling toward target space 112. The phenomenon that causes the jet 121 to split into sub-targets 122 is called Rayleigh Plateau instability. At a location along the trajectory and at a distance Dc before reaching target space 112, these sub-targets 122 coalesce (combine) to form a larger, defined target 111 of a specific size and geometry or shape that reaches target space 112.

[0053] The properties of the target material (including the location Dc where sub-targets 122 coalesce to form target 111, the stability of the formed target 111, and the size and geometry of the formed target 111) can be controlled by controlling aspects related to the pressure P applied to the target material 114. The location Dc where sub-targets 122 coalesce to form target 111, the stability of the formed target 111, and the size and geometry of the formed target 111 can be adjusted or controlled during the tuning mode operation of the target device 100, which occurs before the steady-state mode operation of the EUV source. After the tuning mode is completed, the target device 100 can notify the EUV source and begin operation in steady-state mode (if appropriate). This adjustment and control ensures that the target 111 is formed and stabilized before the target material 114 reaches the target space 112, and that the formed target 111 has the desired size and geometry for effective EUV light generation. Even during steady-state operation, the target device 100 can continue to adjust and control the properties of the target material 114.

[0054] As an example, the jet 121 of target material eventually splits into sub-targets 122, and this can occur naturally (as described above, this is a Rayleigh Plateau instability). The natural splitting of the jet 121 emanating from the opening 119 produces sub-targets 122 at a specific rate, which is at least partially related to the average (or mean) vector velocity of the target material 114 through the opening 119 and the lateral extent (e.g., diameter) of the opening 119. This natural splitting of the jet 121 can occur without modulating the pressure P of the target material 114, because the jet 121 itself is unstable, and this instability begins with the presence of several small perturbations (noise spectrum) within the jet 121. These small perturbations are always at least partially due to, for example, friction between the nozzle structure 117 and the target material 114, and thermal gradients within the jet 121. The noise spectrum is broadband and includes many different frequency components. In some cases, influenced by the geometry of the nozzle structure 117 and the tin-based target material 114, a typical natural splitting frequency can be around 3 MHz. The target device 100 is configured to operate according to a drive waveform (such as the one referenced below). Figure 3 Various parameters of the driving waveform 326 discussed are used to modulate or adjust the pressure P, thereby allowing greater control over the splitting of the jet 121 from the nozzle structure 117. By modulating or adjusting the pressure P (where splitting occurs naturally) with an amplitude greater than the disturbance in the noise spectrum, the exit vector velocity of the target material 114 at the opening 119 is modulated, and the splitting parameters of the jet 121 are controlled. For example, the amplitude of the controlled modulation of the pressure P can be at least an order of magnitude larger than the disturbance in the noise spectrum.

[0055] In order to regulate and control the properties of the target material 114 released from the opening 119 and to ensure that all sub-target materials 122 agglomerate into target 111 before reaching target space 112, the target material device 100 includes a target generator controller 125 and a sensor module 130. The target generator controller generates different driving waveforms to change the way the target material 114 is emitted from the opening 119 and also changes the behavior of the target material 114 as it travels along the trajectory. The sensor module senses or detects the actual behavior of the target material 114 in response to the different driving waveforms generated by the target generator controller 125.

[0056] Sensor module 130 is positioned relative to flow 110. Sensor module 130 is configured to detect one or more aspects related to target material 114 that has been released from opening 119 as the target material 114 travels along a trajectory toward target space 112. Thus, depending on when and where the target material 114 splits (due to Rayleigh Plateau instability) and subsequently coalesces along the trajectory, sensor module 130 can be configured to detect aspects related to one or more of jet 121, sub-target 122, and target 111.

[0057] Target generator controller 125 communicates with target generator 105 and sensor module 130. During tuned mode operation (where the EUV light source is in standby mode and not operating to generate EUV light), target generator controller 125 modifies parameters associated with how target generator 105 operates to detect properties of target material 114 released from opening 119 (such as the location Dc where sub-targets 122 coalesce to form target 111, the stability of the formed target 111, and the size and geometry of the formed target 111). During this detection period (where parameters associated with target generator 105 are modified to alter the properties of the target material), target generator controller 125 analyzes how the properties of target material 114 change. Target generator 125 analyzes output signal 132 from sensor module 130, which is configured to detect aspects of target material 114 modified during detection. The target generator controller 125 adjusts (tunes) the properties of the target material 114 and / or target 111 transmitted to the target space 112 based on the analysis of the output signal 132.

[0058] The output signal 132 from sensor module 130 can be sampled or received at target generator controller 125 at a rate of at least 5 MHz (or at least 20 MHz) (referred to as the sampling rate). Furthermore, target generator controller 125 can measure the system response (i.e., how the target material 114 behaves as it travels along the trajectory) between multiple (e.g., 100-500) different drive waveforms per second (e.g., 100-500 Hz), where each setting tracks the target material 114 (which can be target 111 or pre-agglomerated sub-targets 122) for 50 cycles. In this example, 50 × 100 Hz = 5000 Hz, which is approximately 1000 times the information obtained from a conventional detector outputting a two-dimensional signal. More advanced detectors that output two-dimensional signals at higher frame rates (such as cameras outputting at frame rates higher than 5 Hz) can have a more limited region of interest. Because target material 114 and sub-target 122 tend to be more dispersed over a larger area (e.g., on the order of mm) than target 111, a more limited region of interest in such a two-dimensional sensor means that smaller formations of target material 114 (such as sub-target 122) may go undetected.

[0059] Furthermore, the target generator controller 125 can determine a set of performance characteristics (referred to as "optimal mode performance characteristics") associated with the target generator 105, which produce optimal or improved characteristics for targets 111 transmitted to the target space 112. For example, the optimal mode performance characteristics associated with the target generator 105 may include characteristics that reduce (or eliminate) the number of sub-targets 122 that fail to coalesce into targets 111 before reaching the target space 112. Once the optimal mode performance characteristics are determined, the target generator controller 125 can lock those optimal mode performance characteristics in place and operate the target generator 105 to maintain these optimal mode performance characteristics, at least until further indication or until other factors cause a change in the optimal or improved characteristics. These optimal mode performance characteristics can be used during steady-state operation.

[0060] The target generator controller 125 can perform this tuning quickly, thereby ensuring that the downtime of the EUV light source during tuning is as short as possible. The target generator controller 125 is able to perform rapid tuning because it relies on the output signal 132 from the sensor module 130, which is a one-dimensional signal, and because the output signal 132 from the sensor module 130 is directly connected to the target generator controller 125. A one-dimensional signal is a signal that contains information in only a single dimension or direction. Therefore, a voltage-to-time or current-to-time signal contains information about the magnitude (voltage or current) that changes over time. In contrast, a two-dimensional signal contains two-dimensional information. For example, an image is a two-dimensional signal because it contains information about two coordinates of the sensor along a plane.

[0061] Therefore, the control loop is short and direct. In various implementations, the target generator controller 125 does not share the output signal 132 with other control systems of the EUV light source. Furthermore, the amount of signal processing required by the target generator controller 125 is reduced because one-dimensional signals (which are easier to analyze than multi-dimensional signals or data such as two-dimensional image data or video data) are the primary or only information analyzed in the control loop. For example, the sensor module 130 detects a one-dimensional aspect or characteristic of the target material released from the opening 119.

[0062] As an example, sensor module 130 can detect the intensity of light interacting with the target material. In some implementations, sensor module 130 includes one or more photodiodes, each outputting a voltage signal related to the current generated from the detected light. In other implementations, sensor module 130 may include one or more phototransistors, photoresistors, or photomultiplier tubes, each configured to output a one-dimensional signal 132 for analysis. Sensor module 130 is configured with a sampling rate that enables the detection of multiple aspects of the target material 114 for each instance traveling along a trajectory toward target space 112. Furthermore, sensor module 130 is configured to detect the size of instances of target material 114 as small as 5 μm; this means that even particles as small as 5 μm (such as sub-target 122) will appear in the signal detected at sensor module 130.

[0063] Furthermore, in various implementations, the target generator controller 125 performs this rapid tuning without relying on image processing (or any processing of the two-dimensional signal) or on an external trigger signal. The external trigger signal is a signal other than the output signal 132 that is analyzed by the target generator controller 125. Therefore, the target generator controller 125 triggers the analysis based solely on the information in the output signal 132.

[0064] Typically, the target 111 approaching the target space 112 can be approximately spherical, with a diameter of about 15-40 μm or about 27 μm. Furthermore, the vector velocity of the target 111 approaching the target space 112 can be between 40-180 meters per second (m / s) or up to 500 m / s. The spatial spacing between the targets 111 approaching the target space 112 can be between about 1 mm and 3 mm, and in some implementations about 1.4 mm. The approach speed of the target 111 to the target space 112 can be on the order of tens of kilohertz (kHz), for example, between 20-240 kHz, or 20-160 kHz, or 20-70 kHz. A single target 111 approaching the target space 112 can consist of multiple sub-targets 122. For example, tens or hundreds of sub-targets 122 can coalesce to form a single target 111 approaching the target space 112. Depending on the velocity at which target 111 approaches target space 112, the size of target 111, and the pressure P applied to target material 114, a single target 111 reaching target space 112 can consist of approximately 50-300 smaller sub-targets 122. For example, in order for sub-targets 122 to successfully coalesce into target 111, a rate of approximately 50 kHz (at target space 112), where each target 111 has a diameter of approximately 30 μm, and a pressure P of approximately 28 MPa is applied, each target 111 is formed from approximately 100 coalesced sub-targets 122.

[0065] In some implementations, such as Figure 1B As shown, the nozzle structure 117 includes a capillary 118 that extends generally along a longitudinal direction (i.e., parallel to the X direction) and defines an opening 119. The opening 119 is located at one end of the capillary 118. The capillary 118 may be made of glass in the form of, for example, fused silica, borosilicate, aluminosilicate, or quartz. The target material 114 in the container 115 is in a flowable form. For example, in an implementation where the target material 114 comprises a metal (e.g., tin) that is solid at room temperature, the metal is heated to a temperature at or above its melting point and held at that temperature, causing the target material to become liquid. The target material 114 flows through the capillary 118 and is ejected through the opening 119. The Laplace pressure is the pressure difference between the inside and outside of the curved surface forming the boundary between the gas region and the liquid region. The pressure difference is caused by the surface tension of the interface between the liquid and the gas. When the pressure P is greater than the Laplace pressure, the target material 114 exits the opening 119 as a continuous jet 121.

[0066] As an example, see reference Figure 2Due to the Rayleigh Plateau instability, smaller sub-targets 122-0 can be formed by the jet 121. In this example, nine smaller sub-targets 122-0 are shown as being dispersed along the trajectory at time t0 and generally moving towards the target space 112 in the -X direction. At time t1, after time t0, the group consisting of three smaller sub-targets 122-0 has coalesced into three intermediate sub-targets 122-1, and this coalescing occurs as the smaller sub-targets 122-0 move along the trajectory (thus the intermediate sub-targets 122-1 are farther along the -X direction than their respective smaller sub-targets 122-0). At time t2, after time t1, these three intermediate sub-targets 122-1 have coalesced into a single target 111. Many smaller sub-targets 122-0 can coalesce into intermediate sub-targets 122-1, not just three. Furthermore, the smaller sub-target 122-0 can coalesce in a single event (instead of forming the intermediate sub-target 122-1) to form target 111. The sensor module 130 is arranged relative to the trajectory such that it can sense or detect aspects related to the target material 114 as the target material 114 travels along the trajectory toward the spaced target 114. Therefore, the sensor module 130 can detect any coalescing phase of the sub-target (including phases prior to coalescing) or aspects related to target 111.

[0067] refer to Figure 3 In one implementation, the target device 300 includes a target generator controller 325. In this implementation, the target generator controller 325 includes an actuator 335 configured to agitate the rate at which the target material 114 is released through the opening 119. The target generator controller 325 includes a control system 340 in communication with the actuator 335. The control system 340 is configured to provide a drive signal (e.g., a drive waveform 326) to the actuator 335 to control how pressure P is applied to the fluid target material 114. A signal acquisition device 349 records a one-dimensional output signal 132 from the sensor module 130. The signal acquisition device 349 prepares the output signal 132 for use by the control system 340. The signal acquisition device 349 may include an oscilloscope or analog-to-digital converter that captures the one-dimensional output signal 132 from the sensor module 130 and prepares it for use by the control system 340. In other implementations, the signal acquisition device 349 can be integrated with the sensor module 130, so that the output signal 132 from the sensor module 130 is ready for use by the control system 340.

[0068] The drive signal 326 provided to the actuator 335 is a drive waveform 326, which is periodic in time. The control system 340 is programmable, meaning that the control system 340 is configured to be provided with coded instructions for automatically performing tasks to generate the drive waveform 326 for the actuator 335.

[0069] The target generator controller 325 may also include other processing components, which may be separate components or integrated into the control system 340.

[0070] The control system 340 can also change one or more properties of the drive waveform 326 provided to the actuator 335 to agitate or modulate the pressure P applied to the target material 114, wherein the drive waveform 326 modulates or changes the rate at which the target material 114 is released through the opening 119. In this way, the actuator 335 is configured to modify the characteristics of the target material 114 output from the opening 119 according to the drive waveform 326 from the control system 340.

[0071] refer to Figure 4 The block diagram illustrates how the actuator 335 affects the change of the target material 114 released through the opening 119. The actuator 335 of the target generator controller 325 induces a displacement 450 in the volume 452 of the target material 114 according to a drive waveform 326 from the control system 340. The volume 452 in which the displacement occurs can be within a container 115 or a nozzle structure 117. This displacement 450 of the volume 452 occurs in response to the physical movement of the actuator 335. Because the target material 114 in a fluid state (such as a liquid) is incompressible, the physical movement of the actuator 335 can be periodic (according to a periodic drive waveform 326), and therefore the displacement 450 can also be periodic. The displacement 450 in the volume 452 induces a pressure wave 454 in the volume 452. The pressure wave 454 is the disturbance (periodic displacement 450) propagating within the target material 114, which is a local pressure P. L The changing wave. The pressure wave 454 in the target material 114 of volume 452 causes a disturbance 456 in the vector velocity of the fluid jet 121 leaving the opening 119 of the nozzle structure 117. The fluid jet 121 splits into sub-targets 122 with different vector velocities, and these differences in vector velocities lead to eventual coalescence 458 into target 111.

[0072] For example, the drive waveform 326 provided to the actuation device 335 is a voltage signal comprising multiple components of different frequencies, and this voltage signal is applied to the actuator 436 within the actuation device 335. In response to the application of the voltage signal, the actuator 436 within the actuation device 335 vibrates at multiple different frequencies.

[0073] As a basic example, the drive waveform 326 may include at least a first frequency component associated with a first frequency and a second frequency component associated with a second frequency. The first frequency is a frequency lower than the second frequency. Vibrating the actuator 436 at the second frequency causes the fluid jet 121 to split into relatively small targets (sub-targets 122) of desired size and velocity. The first frequency is used to modulate the vector velocity of the sub-targets 122 in the flow and promote coalescence between the sub-targets 122, thereby forming larger targets 111, each of which is formed by a plurality of relatively smaller sub-targets 122. Therefore, the rate or frequency at which the targets 111 reach the target space 112 corresponds to the first frequency of the drive waveform 326. In any given set of sub-targets 122, each sub-target 122 travels at a different vector velocity (see...). Figure 2 Sub-targets 122 with higher vector velocities can coalesce with sub-targets 122 with lower vector velocities to form larger coalesced targets 111 constituting flow 110. These larger targets 111 are further separated from the uncoalesced sub-targets 122. After coalescence, the targets 111 in flow 110 are approximately spherical and have a size of about 10-40 μm.

[0074] The second frequency can be on the order of megahertz (MHz). For example, the second frequency can be close to the Rayleigh frequency, which is the frequency that causes Rayleigh Plateau instability and causes jet 121 to split into sub-targets 122. The first frequency (lower) can be on the order of kilohertz (kHz) (e.g., 20-70 kHz or 50 kHz). The first frequency can be used to modulate the vector velocity of sub-targets 122 along the trajectory, or it can be used to determine the generation rate of sub-targets 122. Modulating the pressure in volume 452 at a frequency much lower than the Rayleigh frequency results in the formation of groups of sub-targets 122, each group comprising sub-targets 122 with different vector velocities, thereby causing coalescence.

[0075] More than two frequencies can be used in the drive waveform 326. Introducing additional spectral components of the modulating signal allows for better control and a more efficient coalescing process. Typically, these additional frequencies are higher harmonics of the desired frequency of target 111 and are selected within a range between a first frequency (frequency in the kHz range) and a second frequency (frequency in the MHz range). For example, the drive waveform 326 can consist of several deliberately selected sine waves that are consistent in phase and amplitude, or a periodic waveform containing high-frequency harmonics with the desired target frequency (“first frequency”), such as a pulse wave, sawtooth wave, or sine wave.

[0076] Target material 114 (including sub-target 122 and target 111) is controlled by a periodic drive waveform 326, therefore the timestamp output from sensor module 130 matches the drive waveform 326. The output signal 132 from sensor module 130 includes amplitude peaks corresponding to individual instances of target material 114 (the moments when an aspect associated with target material 114 is detected at sensor module 130), for example, as... Figure 11A-11C As shown. The duration of each peak in the output signal 132 is determined based on characteristics related to the aspects detected by the sensor module 130. Therefore, if the sensor module 130 detects diagnostic light (such as diagnostic light 770) from the interaction between one or more diagnostic probes 769 and the target material 114, each peak in the output signal 132 corresponds to this interaction, and the duration of the peak is determined by the duration of the interaction between the target material 114 and the diagnostic probe 769. In some implementations where the target probe 769 is a beam of light having a range along the X-axis, this duration may correspond to approximately 1 μs. To achieve sufficient resolution in the output signal 132 to accurately detect the target material 114, the sampling rate of the sensor module 13 can be on the order of several MHz, for example, greater than or equal to approximately 1 MHz, greater than or equal to approximately 10 MHz, or greater than or equal to approximately 20 MHz.

[0077] refer to Figure 5 In some implementations, the control system 340 includes a signal processing module 541 configured to receive an output signal 542 from a signal acquisition device 349, wherein the output signal 542 is a voltage signal related to the current generated by light detected at a photodetector in the sensor module 130. Typically, the signal processing module 541 analyzes the output signal 542 from the signal acquisition device 349. For example, the signal processing module 541 may analyze a set of timestamps corresponding to the interaction between the target material 114 and the diagnostic beam as the target material 114 travels along the trajectory toward the target space 112, determine whether the amplitude of the output signal 542 is greater than a threshold, determine the size (such as area) of the output signal 542 that is greater than the threshold, and / or examine the start and end times of the output signal 542 crossing the threshold, as referenced below. Figure 11A and 11B Discussed.

[0078] The signal processing module 541 can determine whether the output signal 542 is stable, and whether and when coalescence occurs, and can determine how the target material 114 behaves as it travels along the trajectory. The signal processing module 541 also knows which drive waveform 326 supplied to the actuator 335 causes the output signal 542 currently being analyzed. Therefore, the signal processing module 541 can determine how to modify the drive waveform 326 supplied to the actuator 335 to improve the properties of the target material 114. For example, the signal processing module 541 can determine how to modify one or more phases and amplitudes of the drive waveform 326.

[0079] The control system 340 also includes an actuation module 543 that communicates with the actuation device 335. If the signal processing module 541 determines that the drive waveform 326 needs adjustment (based on analysis), it sends an appropriate signal to the actuation module 543. The actuation module 543 may be located within the control system 340 (e.g., Figure 5 (as shown), or it can be integrated into the actuator 335.

[0080] The control system 340 may also include or have access to one or more programmable processors 544, and one or more computer program products 545 tangibly embodied in a machine-readable storage device for execution by the programmable processors. The one or more programmable processors may each execute instruction programs to perform a desired function by manipulating input data and generating appropriate output. Typically, the processor receives instructions and data from memory 546. Memory 546 may be read-only memory and / or random access memory. Suitable storage devices for tangibly embodying computer program instructions and data include all forms of non-volatile memory, such as semiconductor storage devices like EPROM, EEPROM, and flash memory devices; disks, such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM disks. Any of the above may be supplemented or incorporated therein by a specially designed ASIC (Application-Specific Integrated Circuit).

[0081] Modules within the control system 340 (such as signal processing module 541 and actuation module 543) may each include their own digital electronic circuitry, computer hardware, firmware and software, as well as dedicated memory, input and output devices, programmable processors, and computer program products. Similarly, any one or more of modules 541 and 543 may access and use memory 546, one or more input devices 547 (such as keyboards, touchscreens, microphones, mice, handheld input devices, etc.), one or more output devices 548 (such as speakers and displays), one or more programmable processors 544, and one or more computer program products 545.

[0082] Although the control system 340 is shown as a separate and complete unit, each of its components and modules can be a separate unit. Furthermore, the target generator controller 325 (or control system 340) may include other components such as dedicated memory, input / output devices, processors, and computer program products. Figure 3 and Figure 5 Not shown. For example, the target generator controller 325 may also interface with an EUV light source. As described above, after the tuning mode is completed, the target device 100 (via the target generator controller 325) may notify the EUV light source and begin operation in steady-state mode (if appropriate).

[0083] Actuation device 335 may include any suitable actuation mechanism capable of modulating or agitating the pressure P of the target material 114 in container 115. In some implementations of the target generator controller 625A, such as... Figure 6A As shown, the actuation device 335 is an actuator 636A included in a cavity or space 616A and mechanically coupled to the target material 114 via a membrane 637A. The membrane 637A is mechanically coupled to the actuator 636A and also to a wall 638A. The wall 638A partially defines the cavity 616A on one side and partially defines an auxiliary fluid chamber 615A that is fluidly coupled to the target material 114 in the container 115. The auxiliary fluid chamber 615A is fluidly coupled to an opening 119 of the nozzle structure 117. Any change in the position of the membrane 637A will produce a corresponding change in the pressure P applied to the target material 114 in the auxiliary fluid chamber 615A, and this will produce a pressure change applied to the target material 114 flowing through the nozzle structure 117 and out of the opening 119. The actuator 636A may be fixed (e.g., by clamping, gluing, welding, or brazing) to the wall of the container 115 or to the sidewall that partially defines the cavity 616A. Actuator 636A can be configured to expand or contract along the X-axis to cause film 637A to move along the X-axis. Actuator 636A can be any suitable mechanism capable of changing the position of film 637A. For example, actuator 636A can be a piezoelectric actuator comprising a piezoelectric material exhibiting an inverse piezoelectric effect, such that the piezoelectric material elongates, bends, contracts, expands, and / or otherwise changes shape when an electric field is applied (from control system 340). In implementations where actuator 636A is a piezoelectric actuator, actuator 636A may comprise a piezoelectric ceramic material, such as lead zirconate titanate (PZT) or other similar materials. In some implementations, actuator 636A can be a single piezoelectric actuator (e.g., a single piezoelectric sheet or monolayer material exhibiting an inverse piezoelectric effect), two piezoelectric actuators, or a multilayer piezoelectric assembly. In some implementations, actuator 636A is formed from a monolayer piezoelectric material deposited directly onto film 637A.

[0084] In the implementation of actuator 636A as a piezoelectric actuator including piezoelectric material, the piezoelectric material can have any suitable shape, and this shape can depend on the shape of membrane 637A. For example, the piezoelectric material can be in the shape of a disk, square, rectangular, cylindrical, tubular, or ring. In the implementation of actuator 636A as a piezoelectric actuator, the configuration of the piezoelectric material can be selected based on how the piezoelectric actuator is mounted within cavity 616A.

[0085] Although not shown, electrodes can be placed near the piezoelectric material to apply an electric field to it, and modulation of the electric field results in mechanical modulation of the piezoelectric material. The electric field generated by the electrodes can be controlled by a signal from the control system 340.

[0086] In other implementations of the target generator controller 625B, such as Figure 6B As shown, the actuation device 335 includes an actuator 636B that interacts with the nozzle structure 117. For example, the sidewall 637B of the capillary 118 is mechanically coupled to the actuator 636B. The actuator 636B may be, for example, a piezoelectric actuator that expands and contracts in response to an applied voltage signal from the control system 340, thereby causing deformation of the sidewall 637B. By deforming the sidewall 637B, a pressure wave is formed in the target material 114, and the pressure of the target material 114 is modulated. The actuator 636B may be an annulus having an opening that receives the capillary 118, and the actuator 636B may be fixed or attached to the sidewall 637B. For example, the actuator 636B may be bonded to the sidewall 637B.

[0087] refer to Figure 7 The implementation of the target device 700 is incorporated into the EUV light source 760, which provides EUV light 778 to the output device 780, which may be a photolithography device. The EUV light source 760 includes a vacuum chamber 761 defining the target space 112.

[0088] EUV light source 760 includes an EUV light collector 762 arranged relative to a target space 112, a light source 763 that generates one or more radiation pulses 767 directed toward the target space 112, a diagnostic system 764 arranged relative to a target material 114 traveling toward the target space 112, a detection module 765 arranged relative to the target material 114 traveling toward the target space 112, and a control device 766 that communicates with the light source 763, the diagnostic system 764, the detection module 765, the output device 780, and the sensor module 130.

[0089] Typically, each target 111 is composed of target material 114 (provided from target device 700), and target material 114 emits EUV light 768 upon conversion to plasma. Each target 111 is at least partially or substantially converted to plasma through its interaction with radiation pulses 767 generated by light source 763, such interaction occurring within target space 112. Each target 111 is a target mixture comprising target material 114 and optional impurities such as non-target particles. Target material 114 is a substance capable of being converted to a plasma state having an emission line in the EUV range. Target 111 can be, for example, a drop of liquid or molten metal, a portion of a liquid stream, solid particles or clusters, solid particles contained within a droplet, a foam of target material, or solid particles contained in a portion of a liquid stream. Target material 114 can include, for example, water, tin, lithium, xenon, or any material having an emission spectral line in the EUV range upon conversion to a plasma state. For example, target material 114 can be elemental tin, which can be used as pure tin (Sn); as tin compounds, such as SnBr4, SnBr2, SnH4; as tin alloys, such as tin-gallium alloys, tin-indium alloys, tin-indium-gallium alloys, or any combination of these alloys. In the absence of impurities, each target 111 comprises only target material 114. The discussion provided herein is an example in which each target 111 is a droplet made of a molten metal such as tin. However, each target 111 can take other forms.

[0090] Light source 763 generates one or more radiation pulses 767 that are typically guided to target space 112 in a direction perpendicular to the X-axis. Light source 763 includes one or more light sources that generate one or more radiation pulses 767, a beam transmission system including an optical steering assembly that alters the direction or angle of the radiation pulse beams 767, and a focusing assembly that focuses the radiation pulse beams 767 onto target space 112. Exemplary optical steering assemblies include optical elements, such as lenses and mirrors, which deflect or guide the radiation pulse beams 767 as needed through refraction or reflection. Light source 763 may include an actuation system communicating with control device 766, and the actuation system can be used to control or move various characteristic light sources 763, including the beam transmission system, focusing assembly, and light sources.

[0091] Light source 763 includes at least one gain medium and an energy source for exciting the gain medium to generate a radiation pulse beam 767. The radiation pulse beam 767 constitutes a plurality of optical pulses that are time-separated from each other. In other implementations, the beam output from light source 763 may be a continuous wave (CW) beam. Light source 764 may be, for example, a solid-state laser (e.g., a 1070 nm and 50 W Nd:YAG laser, an erbium-doped fiber (Er:glass) laser, or a neodymium-doped YAG (Nd:YAG) laser).

[0092] EUV light collector 762 collects as much EUV light 768 as possible emitted from the plasma and redirects the EUV light 768 as the collected EUV light 778 to the output device 780. The light collector 762 may be a reflective optical device, such as a curved mirror capable of reflecting light with EUV wavelengths (i.e., EUV light 768) to form the generated EUV light 778.

[0093] A diagnostic system 764 is arranged relative to a target material 114 traveling toward a target space 112. The diagnostic system 764 is configured to generate one or more diagnostic probes 769 that diagnostically interact with the target 111 traveling along a trajectory before entering the target space 112. In some implementations, the diagnostic system 764 generates one or more diagnostic beams as one or more diagnostic probes 769. Each diagnostic beam is guided to a trajectory TR such that diagnostic light 770 is generated when the target 111 passes through the diagnostic beam. In some implementations, the diagnostic beam has a center wavelength in the near-infrared region. For example, the generated diagnostic light 770 may be a portion of the diagnostic beam reflected, scattered, or passing through the target 111.

[0094] Also refer to Figure 8A Diagnostic interactions between target 111 and one or more diagnostic probes 769 can occur at a diagnostic distance dp away from target space 112. During tuned-mode operation (i.e., before steady-state operation of EUV light source 760), the diagnostic distance dp can be less than twice the spacing between adjacent targets 111 formed by target material 114 traveling along the trajectory. For example, sensor module 130 can detect diagnostic light 770 due to interactions between target 111 and diagnostic probes 769 during or after the preceding target 111p has entered target space 112.

[0095] In other implementations, such as Figure 8B As shown, the diagnostic interaction between the target material 114 (which may be sub-target 122 and / or target 111) and one or more diagnostic probes 769 can be closer to the opening 119 of the nozzle structure 117. For example, the diagnostic distance dp is located approximately halfway between the opening 119 of the nozzle structure 117 and the target space 112. In these implementations, the sensor module 130 is arranged to detect at a distance from the target space 112 that is greater than... Figure 8A The diagnostic light 770 is generated at a relatively larger distance, as shown. This arrangement of the sensor module 130 and the diagnostic probe 769 is suitable for use during steady-state operation of the EUV light source 760.

[0096] During tuning (before steady-state operation of the EUV light source 760), if the position Dc of the sub-target 122 coalescing to form target 111 is reduced to about or less than the diagnostic distance dp from target space 112, diagnostic interaction can occur between the sub-target 122 and one or more diagnostic probes 769.

[0097] In this implementation, sensor module 130 is configured to detect diagnostic light 770, which is an aspect related to target material 114. Specifically, diagnostic light 770 is generated by the interaction between diagnostic probe 769 and target material 114 (which may be in the form of sub-target 122 or target 111) as target material 114 travels toward target space 112. Output signal 132 from sensor module 130 is provided to target generator controller 125, as described above. Furthermore, sensor module 130 is configured to detect diagnostic light 770 only when triggered by diagnostic light 770 and without any other external triggering. Sensor module 130 is configured to detect aspects related to target material 114 (diagnostic light 770 in this example) without relying on image processing.

[0098] Depending on the arrangement of the diagnostic system 764 and sensor module 130 relative to the target space 112, during steady-state operation of the EUV light source 760, a second output signal 732-2 from sensor module 130 can be provided (independently and separately from the one provided to the target generator controller 125) to control device 766 for other types of processing. The second output signal 732-2 is identical to output signal 132, except that it follows a different and separate path from the path from sensor module 130 to control device 766. For example, control device 766 can analyze the second output signal 732-2 from sensor module 130 to estimate one or more properties of target 111 (such as arrival, motion, velocity (magnitude), velocity vector, and acceleration). Control device 766 may include a light source control module configured to determine how to adjust light source 763 to adjust one or more characteristics (such as timing and direction) of radiation pulses 767 directed towards target space 112 based on the output from sensor module 130.

[0099] The detection module 765 is arranged relative to the target material 114 traveling toward the target space 112. The detection module 765 can detect two-dimensional aspects related to the target material 114 and also outputs a two-dimensional signal related to the target material 114. The output signal 771 from the detection module 765 is sent to the control device 766. The target generator controller 125 does not use the output signal 771 from the detection module 765 in its analysis. Therefore, in various implementations, the target generator controller 125 does not communicate with any detection module (such as the detection module 765) that outputs the two-dimensional output signal 771, and does not depend on such a two-dimensional output signal.

[0100] The target generator controller 125 communicates with the control device 766. Therefore, once the acceptable performance range of the target material 114 at the target space 112 is determined based on the analysis of the one-dimensional output signal 132, the target generator controller 125 sets the steady-state characteristics of the target generator 105. The target generator controller 125 can then notify the control device 766 so that the control device 766 can begin operating the EUV light source 760 in steady-state mode to generate EUV light 778 for the output device 780.

[0101] refer to Figure 9 The target device 100 executes process 980 to control the movement of the target material 114 toward the target space 112. In some implementations, process 980 is executed during tuned mode operation and before the use of the EUV light source 760 in steady-state mode operation. During tuned mode operation, the EUV light source 760 does not produce EUV light 778 for use by the output device 780, and the target device 100 performs operations to determine a set of steady-state performance characteristics associated with the target material 114.

[0102] In other implementations, process 980 is executed when the EUV source 760 operates in steady-state mode and thus generates EUV light 778 for use by the output device 780. During steady-state mode operation, the target device 100 performs operations to maintain a set of steady-state performance characteristics associated with the target material 114. In such an implementation, the sensor module 130 (and diagnostic system 764) may be positioned closer to the nozzle structure 117 to ensure that the information acquired by the target generator controller 125 has sufficient time to act on the target material 114 before it reaches the target space 112.

[0103] Process 980 includes launching target material 114 (981) through an opening 119 defined in nozzle structure 117. Target material 114 is launched (981) according to a drive waveform 326 provided from control system 340 to actuator 335. Examples 1026A and 1026B of drive waveform 326 are respectively... Figure 10A and10B As shown in the diagram. The drive waveform 326 is an amplitude (such as voltage) provided to the actuator 335 as a function of time (in arbitrary units). The drive waveform 1026A consists of a sine wave of a second frequency plus a square wave of a first frequency less than the second frequency. The drive waveform 1026B consists of a sine wave of a second frequency plus another sine wave of a first frequency less than the second frequency.

[0104] Figure 10C A set of examples of drive waveform 326 are shown: 1026C-1, 1026C-2, 1026C-2, 1026C-4, and 1026C-5. Figure 10C Each of the driving waveforms 1026C-1, 1026C-2, 1026C-2, 1026C-4, and 1026C-5 shown includes a square wave (second frequency component) with a second frequency plus a sine wave (first frequency component) with a first frequency lower than the second frequency. Specifically, the second frequency is approximately ten times the first frequency. For example, the first frequency could be approximately 50 kHz and the second frequency could be approximately 500 kHz. The phase between the first frequency component (sine wave) and the second frequency component (square wave) varies in each driving waveform 1026C-1, 1026C-2, 1026C-2, 1026C-4, and 1026C-5, and this phase variation affects the position of subtarget 122 relative to target 111 in the flow pointing towards target space 112. The effect of this variation is... Figure 11C This is shown more clearly in the text.

[0105] Refer again Figure 9Process 980 includes detecting one or more aspects (982) related to the target material 114 traveling along the trajectory toward the target space 112, and generating a one-dimensional signal (983) from the detected aspects. Sensor module 130 is arranged to detect one or more aspects related to the target material 114. Furthermore, as described above, the position Dc of the sub-target 122 coalescing to form target 111 depends on the drive waveform 326 provided to actuator 335. Therefore, for some drive waveforms 326 (or for certain spectral parameters of drive waveform 326), sensor module 130 detects one or more aspects related to the coalesced target 111. For other drive waveforms 326 (or for certain spectral parameters of drive waveform 326), sensor module 130 detects one or more aspects related to the sub-target 122 (which may be sub-target 122-0 or 122-1, or any sub-target that has not fully coalesced into target 111). Specifically, if process 980 is performed during tuned mode operation (before steady-state operation of the EUV source 760), the drive waveform 326 is adjusted to cause the coalescence position Dc to be adjusted within a possible range. Then, during tuned mode operation, the sensor module 130 detects aspects related to sub-target 122 and target 111.

[0106] For example, sensor module 130 can detect diagnostic light 770 generated as the target material 114 (such as sub-target 122 or target 111) travels toward target space 112 due to the interaction between the target material 114 and one or more diagnostic probes 769. The output signal 132 from sensor module 130 is a one-dimensional signal, such as a measure of the intensity of the diagnostic light 770 as a function of time. Examples 1132A and 1132B of the one-dimensional output signal 132 are respectively... Figure 11A and 11B As shown in the image.

[0107] Output signal 1132A shows the intensity of diagnostic light 770 reflected or scattered from coalescing targets 111-A1, 111-A2, and 111-A3 when the coalescing targets interact with the diagnostic probe 769. In this example, output signal 1132A shows three peaks at times tA1, tA2, and tA3. The peaks at times tA1, tA2, and tA3 correspond to increases in the intensity of diagnostic light 770 reflected from coalescing targets 111-A1, 111-A2, and 111-A3, respectively. In this example, the drive waveform 326 provided to the actuator 335 is configured to ensure that sub-target 122 coalesces before reaching the diagnostic probe 769 (therefore, Dc is greater than dp).

[0108] Output signal 1132B shows the intensity of diagnostic light 770 reflected or scattered from coalescing targets 111-B1, 111-B2, 111-B3 and sub-targets 122-B4 and 122-B5. Output signal 1132B exhibits larger peaks at times tB2, tB2, and tB3, corresponding to increases in the intensity of diagnostic light 770 reflected from the respective coalescing targets 111-B1, 111-B2, and 111-B3. Output signal 1132B exhibits smaller peaks at times tB4 and tB5, corresponding to increases in the intensity of diagnostic light 770 reflected from the respective sub-targets 122-B4 and 122-B5. The peaks at times tB4 and tB5 have lower intensities than the peaks at times tB1, tB2, and tB3 because sub-targets 122-B4 and 122-B5 have relatively small surface areas that interact with the diagnostic probe 769.

[0109] In other implementations, refer to Figure 11C The sensor module 130 outputs a set of one-dimensional output signals 1132C-1, 1132C-2, 1132C-3, 1132C-4, and 1132C-5. In these implementations, each of the output signals 1132C-1, 1132C-2, 1132C-3, 1132C-4, and 1132C-5 corresponds to, respectively, as shown in the figure. Figure 10C The driving waveforms shown are 1026C-1, 1026C-2, 1026C-4, and 1026C-5. Output signals 1132C-1 and 1132C-5 display a set of peaks with a first amplitude, each peak corresponding to the fully coalesced target 111 (as illustrated in the schematic diagram of streams 1110C1 and 5). Output signals 1132C-2, 1132C-3, and 1132C-4 display a set of peaks with a primary amplitude and a set of peaks with a secondary amplitude smaller than the primary amplitude, respectively. The peaks with the primary amplitude correspond to the fully coalesced target 111, while the peaks with the secondary amplitude correspond to the sub-target 122. Furthermore, the positions of the peaks with the secondary amplitude are shifted in each of the output signals 1132C-2, 1132C-3, and 1132C-4, indicating that the position of the sub-target 122 is shifted relative to the target 111. For example, output signal 1132C-2 can be generated from stream 1110C2; output signal 1132C-3 can be generated from stream 1110C3; and output signal 1132C-4 can be generated from stream 1110C4.

[0110] Sensor module 130 (or signal acquisition device 349) sends output signal 132 to control system 340, which determines the value of the timestamp corresponding to the intensity peak in output signal 132. For example, control system 340 determines timestamps tA1, tA2, tA3 from output signal 1132A or timestamps tB1-tB5 from output signal 1132B.

[0111] Process 980 includes analyzing a one-dimensional signal (984). The shape of the output signal 132 is related to the amount or intensity of the diagnostic light 770 illuminating the detector of the sensor module 130. Therefore, the control system 340 can convert the output signal 132 into a set of values ​​corresponding to the maximum intensity of the detected light. For example, the signal processing module 541 in the control system 340 can digitally timestamp each individual voltage peak of the output signal 132. The value of each maximum intensity can be digitally timestamped and then used to determine one or more movement characteristics of the target 111. The signal processing module 541 can select the position of the timestamps (such as timestamps tA1, tA2, tA3 in the output signal 1132A) to approximately correspond to the center position of the corresponding peak. For example, in some implementations, signal processing module 541 may be configured to low-pass filter the transient peak signal from the detector in sensor module 130 (which may be a photodiode). Signal processing module 541 may determine the derivative of the time-filtered signal and use the zero-crossing of the derivative to estimate the center position of the peak, and then select that position as a timestamp (such as timestamps tA1, tA2, tA3). In other implementations, signal processing module 541 may select the midpoint of the half-maximum intersection as the position of each timestamp. The shape of the transient peak signal may vary depending on the shape of target 111 (e.g., target 111 may experience shape oscillations as it travels along its trajectory), therefore, signal processing module 541 may be sensitive to the shape of the centroid, but in some implementations, it may not be the shape of the transient peak signal.

[0112] Other aspects of the output signal 542 (such as 1132A and 1132B) can be analyzed by the signal processing module 541. (See reference) Figure 11A and 11BThe signal processing module 541 can determine whether the amplitudes of the output signals 1132A and 1132B are greater than the corresponding thresholds ValA and ValB. If the output signals 1132A and 1132B are greater than the thresholds ValA and ValB, respectively, this indicates that the sensor module 130 has sensed the target material 114. The signal processing module 541 can determine the size (e.g., areas ArA and ArB, respectively) of the peak values ​​of the output signals 1132A and 1132B, which have amplitudes greater than the thresholds ValA and ValB. The signal processing module 541 can also view the start and end times (e.g., StA, StB, EndA, EndB) at which the peak values ​​of the output signals 1132A and 1132B intersect with the thresholds ValA and ValB, respectively.

[0113] The control system 340 can analyze the timestamps from the output signal 132 to determine the characteristics of the target material 114 traveling along the trajectory toward the target space 112. During steady-state operation, the analyzed information can be used to determine the time it takes for the target 111 to reach a specific spatial location (such as a region within the target space 112), estimate the velocity (magnitude), velocity vector, or acceleration of the target 111, or estimate the time interval between the arrival of the target 111 at a specific spatial location and the arrival of another target at that specific spatial location.

[0114] The signal processing module 541 can also access other data related to the target 111 or the diagnostic system 764 that can be stored in the memory 546. For example, the memory 546 can store information related to a previous vector velocity associated with the target 111 or a previous target. If the diagnostic system 764 is designed as a dual-beam diagnostic system, the memory 546 can store information related to the spacing between the diagnostic probes, or the memory 546 can store the position of the diagnostic probe 769 interacting with each target 111.

[0115] The signal processing module 541 can use the determined timestamp to determine the velocity (quantity) or vector velocity of the target 111.

[0116] The signal processing module 541 can determine the predicted time when the target 111 will arrive at its position within the target space 112. The signal processing module 541 is able to determine the predicted time when the target 111 arrives at its position within the target space 112 by using the estimated vector velocity and other information stored in the memory 546.

[0117] One or more outputs from signal processing module 541 can be considered as control signals and directed to an actuation system that interfaces with light source 763. The control signals from signal processing module 541 provide instructions to cause the actuation system (interfacing with light source 763) to adjust aspects of light source 763 to regulate one or more of the following: the release timing of one or more radiation pulses 767 and the direction of travel of radiation pulses 767.

[0118] During the tuning operation, the analyzed information can be used to determine whether any peak in the output signal 132 corresponds to sub-target 122 (or incompletely coalesced target 111). For example, the difference in timestamps between sub-target 122 and other adjacent sub-targets 122 or targets 111 should be less than the difference in timestamps between two adjacent targets 111. This is evident from the output signal 1132B. Therefore, the difference tB1-tB2 > tB1-tB4.

[0119] As an example, such as Figure 12 As shown, certain shapes and parameters of the drive waveform 326 can be configured to delay the coalescing of the subtarget 122. One way to do this is to apply a perturbation, such as a sine wave (third frequency) 1226p, over the coalescing signal at a first frequency. By changing the parameters of this perturbation sine wave, such as the phase and amplitude of the perturbation sine wave 1226p, the coalescing can be altered (delayed or accelerated), such that the perturbation sine wave at the third frequency cancels out the coalescing signal at the first frequency. If the perturbation sine wave 1226p at the third frequency has sufficient amplitude, coalescing can be completely prevented, and the subtarget 122 can be detected by the sensor module 130. For example, the perturbation sine wave in the drive waveform 326 can be timed so that the subtarget 122 is emitted in accordance with the maximum vector velocity gradient of the pressure wave 454 (generated by the perturbation sine wave 1226p of the drive waveform 326). By doing so, sub-targets 122 approaching this large vector velocity gradient are less likely to move toward each other (because their vector velocities are not modified by the coalescing signal of the first frequency in the driving waveform 326) and therefore remain uncoalesced at time t1. The information collected about the sub-targets 122 can be used by the signal processing module 541 to optimize or improve coalescence.

[0120] Process 980 includes modifying one or more properties of the target material 114 emitted from opening 119 based on analysis of a one-dimensional signal (985). Thus, when process 980 is performed while the EUV source 760 is operating in steady-state mode, in this step, the control system 340 can modify parameters associated with the drive waveform 326 provided to the actuator 335, and by making such modifications, the behavior of the target material 114 emitted from opening 119 is modified with the aim of maintaining a set of steady-state performance characteristics associated with the target material 114. When process 980 is performed during tuning mode (when the EUV source 760 is in standby mode and not operating in steady-state mode), at 982, the control system 340 modifies parameters (such as wavelength or frequency and phase) associated with the drive waveform 326 provided to the actuator 335 to detect other aspects related to the target material 114. Modification of the target material 114 can be a change in the vector velocity of the target material 114 released from opening 119, such as changing the time or location of coalescence.

[0121] refer to Figure 13 The execution process 1390 is used to tune the target device (such as target device 100 or 700). In discussing process 1390, reference is made to... Figure 7 The target device 700. Initially, the target device 700 operates in tuning mode 1390A, and once tuning mode 1390A is completed, the target device 700 begins to operate in steady-state mode 1390B.

[0122] During tuning mode 1390A, target material 114 is released from nozzle structure 117 along a trajectory toward target space 112 (1391). This has been discussed above with respect to step 981. Next, one or more properties of the target material 114 (released from nozzle structure 117) are adjusted (1392). For example, the position Dc and time at which sub-targets 122 composed of target material 114 coalesce into target 111 can be adjusted in step 1392. This adjustment can occur under the control of control system 340, which modifies the drive waveform 326 provided to actuator 335 (and by modifying the drive waveform 326, the properties of target material 114 are modified).

[0123] Process 1390 then includes detecting one or more aspects related to the target material 114 as the target material travels toward the target space 112 (1393). This has been discussed above with respect to step 982. In particular, because the target device 700 is tuned (1390A) at this stage, this detection 1393 occurs in multiple different adjustment states (set in 1392) to determine a set of steady-state performance characteristics associated with the target material 114 (1394).

[0124] Once the steady-state performance characteristics associated with the target material 114 are determined (1394), the EUV source 760 can begin operating in steady-state mode. Therefore, the target device 700 notifies the EUV source 760 that it is operating in steady-state mode (1395). For example, the target device 700 (via the target generator controller 125) can send a signal to the control device 766, causing the control device 766 to begin operating the EUV source 760 in steady-state mode to generate EUV light 778 for the output device 780. In steady-state mode 1390B, the target device 700 operates in steady-state mode (1396) and continuously queries whether tuning has been requested (1397). If an operator or some external command requests tuning of the target device 700 (1397), the target device 700 can notify the EUV source 760 (if necessary) that steady-state mode 1390B will cease (1398).

[0125] refer to Figure 14 The image illustrates an implementation 1480 of a photolithography apparatus 780. The photolithography apparatus 1480 exposes a substrate (which may be referred to as a wafer) W using an exposure beam B. The photolithography apparatus 1480 includes multiple reflective optical elements R1, R2, R3, a mask M, and a slit S, all housed within a housing 10. The housing 10 is a shell, container, or other structure capable of supporting the reflective optical elements R1, R2, the mask M, and the slit S, and also capable of maintaining a vacuum space within the housing 10.

[0126] EUV light 778 enters the housing 10 and is reflected by the optical element R1 through the slit S toward the mask M. The slit S partially defines the shape of the distributed light used to scan the substrate W in the photolithography process. The dose or the number of photons transmitted to the substrate W depends on the size of the slit S and the scanning speed of the slit S.

[0127] The mask M can also be referred to as a photomask or patterning device. The mask M includes a spatial pattern representing features to be formed in photoresist on a substrate W. EUV light 778 interacts with the mask M. The interaction between the EUV light 778 and the mask M causes the pattern of the mask M to be applied to the EUV light 778 to form an exposure beam B. The exposure beam B passes through a slit S and is guided to the substrate W by optical elements R2 and R3. The interaction between the substrate W and the exposure beam B exposes the pattern of the mask M onto the substrate W, thereby forming photoresist features at the substrate W. The substrate W includes a plurality of portions 20 (e.g., dies). The area of ​​each portion 20 in the YZ plane is smaller than the area of ​​the entire substrate W in the YZ plane. Each portion 20 can be exposed by the exposure beam B to include a copy of the mask M, such that each portion 20 includes electronic features indicated by the pattern on the mask M.

[0128] The lithography equipment 1480 may include a lithography control system 30 that communicates with a control device 766 of the EUV light source 760.

[0129] Other aspects of the invention are set forth in the following numbered clauses. 1. A target device for an extreme ultraviolet (EUV) light source, the target device comprising: A target generator includes a container configured to contain target material that generates EUV light when in a plasma state and a nozzle structure in fluid communication with the container, the target generator defining an opening in the nozzle structure adapted to release the target material received from the container; The sensor module is configured as follows: As the target material travels along a trajectory toward the target space, aspects related to the target material released from the opening are detected, and A one-dimensional signal is generated from the detected aspect; and A target generator controller, communicating with the sensor module and the target generator, is configured to modify the properties of the target material based on analysis of the one-dimensional signal. 2. The target device according to Clause 1, wherein the nozzle structure includes a capillary defining the opening, and the opening extends along the longitudinal direction of the capillary. 3. The target device according to Clause 2, wherein the target generator controller includes an actuation device configured to agitate the rate at which the target material is released through the opening. 4. The target device according to Clause 3, wherein the actuation device includes a piezoelectric sensor configured to apply pressure to a target material in fluid form in the container, and the target generator controller is configured to change the signal provided to the piezoelectric sensor to change the pressure applied to the fluid target material, thereby causing a disturbance in the rate at which the target material is released through the opening. 5. The target device according to Clause 1, wherein the target generator controller comprises: a control system configured to generate a drive waveform based on the analysis of the one-dimensional signal; and an actuation device communicating with the control system and interacting with the target material, wherein the actuation device is configured to modify the properties of the target material according to the drive waveform from the control system. 6. The target device according to Clause 5, wherein the control system is programmable and configured to generate periodic drive waveforms. 7. The target apparatus according to Clause 5, wherein the control system is configured to modify aspects of the drive waveform, including modifying one or more of the following: one or more frequencies of the drive waveform and one or more phases of the drive waveform, and the drive waveform is modified at a rate of approximately 100-500 different waveforms per second. 8. The target device according to Clause 1, wherein the sensor module comprises: One or more photodiodes, each photodiode outputting a voltage signal related to the current generated by the detected light; a phototransistor; a photoresistor; and a photomultiplier tube. 9. The target device according to Clause 1, wherein the target generator controller does not communicate with any detection module configured to output a two-dimensional signal associated with the formed target. 10. The target device according to Clause 1, wherein the sensor module communicates with a light source controller independently of communication with the target generator controller, the light source controller being configured to: adjust one or more characteristics of the radiation pulse directed toward the target space. 11. The target device according to Clause 1, wherein the target generator controller has a sampling rate of at least 5 MHz. 12. The target device according to Clause 1, wherein the sensor module is configured to detect light generated by the interaction between the target material and a light curtain guided to pass through the trajectory. 13. The target device according to Clause 12, wherein the sensor module is configured to detect aspects related to the target material when triggered solely by the interaction between the target material and the light curtain. 14. The target device according to Clause 1, wherein the sensor module is configured to detect aspects related to the target material without relying on image processing and / or trigger signals. 15. The target apparatus according to Clause 1, wherein the target generator is configured to: release target material according to a drive waveform provided by the target generator controller, the target material traveling along the trajectory, and at least some of the target material in the form of a separated mass block coalescing to form the target at the target space. 16. The target device according to Clause 1 further includes a diagnostic system configured to: diagnostically interact with the target material traveling along the trajectory before the target material enters the target space, wherein the sensor module is positioned to detect aspects related to the target material in relation to the diagnostic interaction between the target material and the diagnostic system. 17. The target device according to Clause 16, wherein the diagnostic interaction occurs at a diagnostic distance away from the target space, the diagnostic distance being less than twice the spacing between adjacent targets formed by the target material traveling along the trajectory, or half the distance between the opening of the nozzle structure and the target space. 18. The target device according to Clause 1, wherein the target generator controller is configured to: set the steady-state characteristics of the target generator after determining, based on the analysis of the one-dimensional signal, that the properties of the target material in the target space are within an acceptable range. 19. The target device according to Clause 18, wherein the target generator controller also communicates with the control device of the EUV light source and is configured to notify the control device once the steady-state characteristics of the target generator are set. 20. A method for controlling the movement of target material along a trajectory within a target space in a chamber toward an extreme ultraviolet (EUV) light source, the method comprising: Target material is emitted through a longitudinal opening defined in a nozzle, the opening being fluidly coupled to a container configured to contain the target material, wherein the target material generates EUV light in a plasma state; As the target material travels along the trajectory toward the target space, aspects related to the target material are detected. A one-dimensional signal is generated from the detected aspect; Analyze the one-dimensional signal; and Based on the analysis of the one-dimensional signal, one or more properties of the emitted target material are modified. 21. The method according to Clause 20, wherein firing the target material through the opening defined in the nozzle comprises: releasing the target material in liquid form through the opening. 22. The method according to Clause 21, wherein the emission of target material through the opening causes one or more particles of the target material traveling toward the target space to coalesce into one or more targets before reaching the target space. 23. The method according to Clause 20, wherein modifying one or more properties of the target material being launched comprises: modifying parameters relating to the vector velocity of the target material released from the nozzle. 24. The method according to Clause 23, wherein modifying the parameters related to the vector velocity of the target material released from the nozzle includes: modifying the drive waveform provided to the actuator in fluid communication with the target material in the container. 25. The method according to Clause 24, wherein modifying the drive waveform provided to the actuation device in fluid communication with the target material in the container comprises: generating a pressure wave in the target material in the container. 26. The method according to Clause 20, wherein modifying the one or more properties of the target material to be emitted comprises: modifying the one or more properties at a rate of 100-500 Hz. 27. The method according to Clause 20, wherein detecting the aspect related to the target material comprises: detecting light generated by the interaction between the target material and the diagnostic probe. 28. The method according to Clause 27, wherein detecting the aspect related to the target material comprises: detecting light triggered solely by the interaction between the target material and the diagnostic probe. 29. The method according to Clause 27, wherein generating the one-dimensional signal from the detected light comprises: generating a voltage signal from a current generated from the detected light. 30. The method according to Clause 20, wherein analyzing the one-dimensional signal includes determining one or more motion properties of the target material. 31. The method according to Clause 20, wherein modifying the one or more properties of the target material to be emitted comprises: modifying the one or more properties independently of any analysis relating to a two-dimensional signal, which is related to the target material. 32. The method according to Clause 20, wherein the detection of said aspect related to said target material is independent of image processing. 33. The method according to Clause 20, wherein the detection of the aspect related to the target material is independent of the trigger signal related to the radiation pulse directed toward the target space. 34. The method according to Clause 20 further comprises: determining, based on the analysis of the one-dimensional signal, whether one or more properties of the target material are within acceptable limits in the target space, and when it is determined that the one or more properties of the target material are within acceptable limits in the target space, notifying the control device of the EUV light source. 35. The method according to Clause 34 further includes maintaining one or more properties of the target material within the acceptable range. 36. The method according to Clause 34, wherein determining whether one or more properties of the target material are within acceptable limits in the target space comprises: determining that the target material agglomerates into a target having an acceptable shape before entering the target space. 37. A method for tuning a target device for an extreme ultraviolet (EUV) light source, the method comprising: The target device, which includes a nozzle in fluid communication with a container, is operated in a tuned mode, the tuned mode operation including: The target material is released from the nozzle along a trajectory toward the target space, wherein the target material generates EUV light in a plasma state; Adjusting the state of the target material released from the nozzle includes adjusting one or more properties of the target material, including adjusting one or more of the following: the position and time at which the target material coalesces into a target along the trajectory before entering the target space; 38. The method according to Clause 37, wherein detecting one or more aspects related to the target material as the target material travels along the trajectory toward the target space comprises: detecting one or more aspects related to the target material before the target material coalesces into a target. 39. The method according to Clause 37, wherein detecting one or more aspects related to the target material as the target material travels along the trajectory toward the target space comprises: detecting one or more aspects related to a target formed by the coalesced target material. 40. The method according to Clause 37, wherein adjusting one or more properties of the target material released from the nozzle comprises: adjusting the one or more properties at a rate of about 100-500 Hz.

Claims

1. A method for tuning a target device for an extreme ultraviolet (EUV) light source, the method comprising: The target device, which includes a nozzle in fluid communication with a container, is operated in a tuned mode, the tuned mode operation including: The target material is released from the nozzle along a trajectory toward the target space, wherein the target material generates EUV light in a plasma state; Adjusting the state of the target material released from the nozzle includes adjusting one or more properties of the target material, including adjusting one or more of the following: the position and time at which the target material coalesces into a target along the trajectory before entering the target space; As the target material travels along the trajectory toward the target space, one or more aspects related to the target material are detected, wherein the detection includes detection under multiple different adjustment states; and A set of steady-state performance characteristics associated with the target material are determined based on the detected one or more aspects; After determining the set of steady-state performance characteristics associated with the target material, the target device is then operated in a steady-state mode based on the set of steady-state performance characteristics; and The control device of the EUV light source is notified to operate the target device in steady-state mode.

2. The method of claim 1, wherein detecting one or more aspects related to the target material as the target material travels along the trajectory toward the target space comprises: Detect one or more aspects related to the target material before the target material agglomerates into a target.

3. The method of claim 1, wherein detecting one or more aspects related to the target material as the target material travels along the trajectory toward the target space comprises: Detect one or more aspects related to a target formed by aggregated target material.

4. The method of claim 1, wherein adjusting one or more properties of the target material released from the nozzle comprises: Adjust one or more of the aforementioned characteristics at a rate of approximately 100-500 Hz.

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