Dose control of extreme ultraviolet light source

Abstract

A dose controller is configured to: receive a measurement of extreme ultraviolet (EUV) pulse energy generated by an EUV interaction, the EUV interaction occurring between a target light pulse generated by a target light source and a target in an interaction region; receiving an EUV pulse energy setpoint associated with a desired EUV pulse energy for exposing the substrate; determining an interaction ratio based on the measured EUV pulse energy and the EUV pulse energy setpoint, the interaction ratio defining a percentage of an average number of EUV interactions over a period of time; determining an energy in one or more target light pulses supplied to the interaction region, the determined energy based on a value of the interaction ratio and the measured EUV pulse energy; and providing the determined interaction ratio and the determined energy to the target light source.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. application No. 63 / 401,872, filed on August 29, 2022, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The disclosed subject matter relates to dose control for extreme ultraviolet (EUV) light sources. Background Art

[0004] Extreme ultraviolet (EUV) light (e.g., electromagnetic radiation having a wavelength of 100 nanometers (nm) or less (sometimes also referred to as soft x-rays), including light having a wavelength of, for example, 20 nm or less, 5 to 20 nm, or 13 to 14 nm) can be used in photolithography processes to create extremely small features in a substrate (e.g., a silicon wafer) by initiating polymerization in a resist layer. Methods for generating EUV light include, but are not limited to, changing the physical state of a source material to a plasma state. The source material includes a compound or element whose emission lines are in the EUV range, such as xenon, lithium, or tin. In one method, which is generally referred to as laser produced plasma ("LPP"), the desired plasma is generated by irradiating the source material (e.g., in the form of droplets, streams, or clusters of the source material) with an amplified beam of light, which may be referred to as a drive laser. For this process, the plasma is typically generated in a sealed container, such as a vacuum chamber, and monitored using various types of metrology equipment. Source materials (such as xenon, lithium, or tin) that emit in the EUV range when in a plasma state are generally referred to as target materials because they are targeted and irradiated by the drive laser. Summary of the invention

[0005] In some general aspects, a dose control device for an extreme ultraviolet (EUV) light source includes a dose controller. The dose controller is configured to receive an EUV pulse energy set point associated with a desired EUV pulse energy for exposing a substrate and a measurement of the EUV pulse energy generated from an EUV interaction, the EUV interaction occurring between a target light pulse and a target. The dose controller includes an interaction module and an adjustment module, the interaction module determining an interaction ratio based on the measured EUV pulse energy and providing the interaction ratio to a target light source that generates the target light pulse, the interaction ratio defining a percentage of an average number of EUV interactions over a period of time. The adjustment module is configured to: calculate an adjusted EUV pulse energy set point based on the determined interaction ratio according to the received EUV pulse energy set point; and provide the adjusted EUV pulse energy set point to the target light source controller.

[0006] Implementations may include one or more of the following features. By providing an adjusted EUV pulse energy set point to a target light source controller, dose stability at a substrate receiving EUV pulse energy may be improved. For example, the interaction module may determine an interaction ratio by comparing the measured EUV pulse energy to an EUV pulse energy set point, the EUV pulse energy set point being associated with a desired EUV pulse energy for exposing the substrate. The interaction ratio may be provided to the target light source to cause the target light source to generate target light pulses according to the interaction ratio, such that an average number of EUV interactions corresponds to the interaction ratio.

[0007] The adjustment module may calculate the adjusted EUV pulse energy set point by calculating the adjusted EUV pulse energy set point when the interaction ratio is within an unacceptable range or outside an acceptable range. The interaction ratio may be within the unacceptable range as long as the dose is unstable, and the interaction ratio may be outside the acceptable range as long as the dose is not within a stable range. The adjustment module may determine whether the interaction ratio is within the unacceptable range or outside the acceptable range by analyzing whether the dose stability metric is within a range of a local maximum or within a range of a local minimum. The dose controller may also include a memory configured to store one or more of an unacceptable range and an acceptable range of the interaction ratio. The dose controller may be configured to access the memory.

[0008] The adjustment module may include: an interaction ratio averaging module configured to average the values ​​of the interaction ratio and output the average interaction ratio; and an update module. The update module may be configured to: receive the average interaction ratio; receive an EUV pulse energy set point associated with a desired EUV pulse energy for exposing the substrate; and calculate an adjusted EUV pulse energy set point based on the average interaction ratio.

[0009] The dose controller may include a target light source controller, and the target light source controller may communicate with the adjustment module and the target light source. The dose controller may include an interactive averaging module, the interactive averaging module being configured to: receive the measured EUV pulse energy over a set number of target light pulses; isolate only the target light pulses that interact with the target; and average the values ​​of the measured EUV pulse energy of the isolated target light pulses to produce an average EUV target energy of EUV interaction. The target light source controller may be configured to: receive the average EUV target energy from the interactive averaging module and receive an adjusted EUV pulse energy set point from the adjustment module, and determine the energy in one or more target light pulses supplied to the interaction region of the receiving target based on the average EUV target energy of the EUV interaction and the adjusted EUV pulse energy set point.

[0010] In other general aspects, an apparatus for an extreme ultraviolet (EUV) light source includes a dose controller. The dose controller is configured to: receive a measurement of EUV pulse energy generated from an EUV interaction, the EUV interaction occurring between a target light pulse generated by a target light source and a target in an interaction region; receive an EUV pulse energy set point associated with a desired EUV pulse energy for exposing a substrate; determine an interaction ratio based on the measured EUV pulse energy and the EUV pulse energy set point, the interaction ratio defining a percentage of an average number of EUV interactions over a period of time; determine an energy in one or more target light pulses supplied to the interaction region, the determined energy being based on a value of the interaction ratio and the measured EUV pulse energy; and provide the determined interaction ratio and the determined energy to the target light source.

[0011] Implementations may include one or more of the following features. For example, a dose controller may determine an interaction ratio by comparing the measured EUV pulse energy with an EUV pulse energy set point. The dose controller may provide the determined interaction ratio to a target light source, thereby causing the target light source to generate target light pulses according to the interaction ratio, so that the average number of EUV interactions corresponds to the interaction ratio. The dose controller may determine the energy in one or more target light pulses supplied to the interaction region by comparing the measured EUV pulse energy with the adjusted EUV pulse energy set point. The dose controller may be configured to calculate an adjusted EUV pulse energy set point based on the determined interaction ratio. The dose controller may calculate the adjusted EUV pulse energy set point by calculating the adjusted EUV pulse energy set point when the interaction ratio is within an unacceptable range or outside an acceptable range. The dose controller may calculate the adjusted EUV pulse energy set point by calculating the adjusted EUV pulse energy set point when the dose of the EUV pulse energy at the substrate is unstable or when the dose is not within a stability range. The dose controller may be further configured to: average the values ​​of the interaction ratio and output the average interaction ratio; receive the average interaction ratio; and calculate an adjusted EUV pulse energy set point based on the average interaction ratio.

[0012] The device may further comprise a memory configured to store one or more unacceptable ranges and acceptable ranges of the interaction ratio, and the dose controller may be configured to access the memory.

[0013] The dose controller may be configured to: receive the measured EUV pulse energy over a set number of target light pulses; isolate only the target light pulses that interact with the target; and average the values ​​of the measured EUV pulse energy of the isolated target light pulses to produce an average EUV target energy for EUV interactions. The dose controller may be configured to: determine the energy in one or more target light pulses supplied to the interaction region of the receiving target based on the average EUV target energy for EUV interactions and an adjusted EUV pulse energy set point, the adjusted EUV pulse energy set point being based on the determined interaction ratio.

[0014] In other general aspects, a method of controlling an extreme ultraviolet (EUV) pulse energy dose supplied to a substrate in an EUV light source is described. The method includes: receiving a measurement of EUV pulse energy generated from an EUV interaction, the EUV interaction occurring between a target light pulse and a target; determining an interaction ratio based on the measured EUV pulse energy, the interaction ratio defining a percentage of an average number of EUV interactions over a period of time; providing the interaction ratio to a target light source generating the target light pulse; calculating an adjusted EUV pulse energy set point based on the determined interaction; and improving dose stability at a substrate exposed by the EUV pulse energy based on the adjusted EUV pulse energy set point.

[0015] Implementations may include one or more of the following features. For example, the dose stability at the substrate may be improved by adjusting the energy in one or more target light pulses supplied to an interaction region of a receiving target based on an adjusted EUV pulse energy set point and a measured EUV pulse energy. The method may include receiving the measured EUV pulse energy over a set number of target light pulses; isolating only the target light pulses that interact with the target; and averaging the values ​​of the measured EUV pulse energy of the isolated target light pulses to produce an average EUV pulse energy of the EUV interaction. By comparing the average EUV pulse energy of the EUV interaction with the adjusted EUV pulse energy set point, the energy in one or more target light pulses supplied to the interaction region may be adjusted.

[0016] The interaction ratio can be determined by comparing the measured EUV pulse energy to an EUV pulse energy set point, which is associated with a desired EUV pulse energy for exposing the substrate. The interaction ratio can be provided to a target light source to cause the target light source to generate target light pulses according to the interaction ratio, such that an average number of EUV interactions corresponds to the interaction ratio.

[0017] By calculating the adjusted EUV pulse energy set point when the interaction ratio is within an unacceptable range or outside an acceptable range, the adjusted EUV pulse energy set point can be calculated based on the determined interaction ratio. The interaction ratio can be within the unacceptable range as long as the dose is unstable, and the interaction ratio can be outside the acceptable range as long as the dose is not within a stable range. The method may also include: determining whether the interaction ratio is within the unacceptable range or outside the acceptable range includes analyzing whether the dose stability metric is within a range of local maxima or within a range of local minima. The method may include storing one or more of the unacceptable range and the acceptable range of the interaction ratio. The method may include averaging the values ​​of the interaction ratio and outputting the average interaction ratio. By calculating the adjusted EUV pulse energy set point based on the average interaction ratio, the adjusted EUV pulse energy set point can be calculated. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a block diagram of a dose control device for an extreme ultraviolet (EUV) light source, the device generating an EUV radiation pulse for each EUV interaction and supplying the EUV radiation pulse to a substrate, the dose control device including an EUV dose controller;

[0019] Figure 2 showing a set of graphs superimposed on each other, including a graph of a dose stability metric providing an indication of dose stability at a substrate versus a power reduction request, a power reduction request being a request to reduce the power of EUV radiation supplied to the substrate, and a graph of an interaction ratio defining a percentage by which an average number of EUV interactions varies over time, versus the power reduction request;

[0020] Figure 3 yes Figure 1 A block diagram of the implementation of an EUV dose controller and a dose control device;

[0021] Figure 4 It is shown Figure 2 The table of the best and worst interaction ratios in , which is configured to be stored in Figure 3 In the memory of the EUV dose controller;

[0022] Figure 5 Is Figure 1 or Figure 3 A flow chart of a process performed by an EUV dose controller;

[0023] Figure 6 Is Figure 1 or Figure 3 A flow chart of a process performed by an EUV dose controller to improve dose stability at a substrate;

[0024] Figure 7 Is Figure 1 or Figure 3 A flow chart of a process performed by an EUV dose controller for determining an indication of EUV energy in a light pulse of EUV radiation supplied to a substrate;

[0025] Figure 8 Is Figure 1 or Figure 3 A flow chart of a process performed by an EUV dose controller for calculating an adjusted EUV pulse energy set point;

[0026] Fig. 9 shows a set of graphs superimposed on each other, including Figure 2 The two figures, and when Figure 1 or Figure 3 EUV dose controller according to Figure 5-Figure 8 a plot of a dose stability metric versus a power reduction request and a plot of an interaction ratio versus a power reduction request during operation of a process;

[0027] Other features and advantages of various implementations, as well as the structure and operation of various objects, will be described in detail below with reference to the accompanying drawings. It should be noted that the teachings included herein are not limited to the specific implementations described herein. Such implementations are presented herein only for illustrative purposes. Based on the teachings included herein, other implementations will be apparent to those skilled in the relevant art. DETAILED DESCRIPTION

[0028] refer to Figure 1 , the dose control apparatus 100 is configured for an extreme ultraviolet (EUV) light source 150 that supplies EUV radiation 151 in the form of light pulses, each light pulse having a wavelength in the EUV range, to a lithographic exposure apparatus 152. The lithographic exposure apparatus 152 processes a substrate 153 (e.g., a wafer) with the EUV radiation 151. The dose control apparatus 100 operates "online," meaning that it operates during and while the lithographic exposure apparatus 152 processes the substrate 153 with the EUV radiation 151, without interrupting the process.

[0029] The dose control device 100 includes an EUV dose controller 105. The EUV dose controller 105 is configured to control and stabilize the dose of EUV radiation 151 (in the form of light pulses) delivered to the substrate 153 during an exposure pass. The dose is the amount of light energy delivered to the substrate 153 by the light pulses of EUV radiation 151 during the exposure pass. During the exposure pass, multiple light pulses of EUV radiation 151 illuminate the same area of ​​the substrate 153. The number of light pulses of EUV radiation 151 that illuminate the same area of ​​the substrate 153 can be referred to as an exposure pass. In some implementations, the exposure pass can correspond to tens of light pulses in the EUV radiation 151. In other implementations, the exposure pass can correspond to hundreds of light pulses of EUV radiation 151.

[0030] In order to control and stabilize the dose delivered in the light pulses of EUV radiation 151, the EUV dose controller 105 receives information 106 related to the EUV radiation 151, which is generated by the metrology equipment 154. For example, the information 106 may include a measurement of EUV energy in the light pulses of EUV radiation 151. In addition, the EUV dose controller 105 receives an EUV energy set point 107 associated with a desired EUV pulse energy of the light pulses of EUV radiation 151 that expose the substrate 153. For example, the EUV energy set point 107 may be a desired EUV energy for the lithography exposure equipment 152.

[0031] The EUV dose controller 105 provides instructions 108, 109 to the EUV light source 150 to make one or more adjustments related to how to generate EUV radiation 151, these instructions 108, 109 are based on the received information 106 and the EUV energy set point 107. In order to understand these instructions 108, 109, a brief description of the operation of the EUV light source 150 is provided below. EUV radiation 151 is generated or created from EUV interaction occurring in an interaction region 160 within an interior 161 of a container 162. In the EUV interaction, a target material (such as tin) having emission lines in the EUV range within a target 155 is converted to a "plasma state" or "plasma" 156. The target 155 is generated by a target generator 164, which also delivers the target 155 to the interaction region 160 in the form of a target stream. The conversion of the target 155 to the plasma 156 releases radiation in the emission spectrum of the material of the target 155, and the emission spectrum includes EUV radiation 157. At least some of the EUV radiation 157 is collected (by EUV radiation collector 158) and output from EUV light source 150 as EUV radiation 151. In one technique, EUV interaction occurs by illuminating target 155 at interaction region 160 with target light pulses 159p of target beam 159. Target beam 159 is generated by target light source 163. Figure 1 In the depiction of FIG. 1 , EUV interaction occurs only in the interaction region 160 between the target 155 (not specifically shown) and the target light pulse 159p (not specifically shown), and the plasma 156 has been generated, and the plasma has emitted EUV radiation 157 in the form of light pulses. Because the target light beam 159 is in the form of pulses, and the target 155 is individually formed, the EUV interaction occurs at different times according to the repetition rate of the target light pulse 159p interacting with the target 155. Therefore, the light pulses of EUV radiation 157 (and the collected EUV radiation 151) are generated at different times according to the same repetition rate.

[0032] To control the dose of light pulses within the EUV radiation 151, the EUV dose controller 105 provides instructions 108 to the target light source 163. The instructions 108 adjust the energy or power (which is the energy delivered) provided to the target light source 163, which adjusts the energy at which the target light source 163 operates. By adjusting the energy or power to the target light source 163, the energy (and power) in each target light pulse 159p in the target beam 159 can be adjusted within a range of possible values. Adjusting the energy in a target light pulse 159p that interacts with a target 155 in the interaction region 160 adjusts the power of a light pulse of EUV radiation 157 generated from the interaction between the target 155 and the target light pulse 159p. This is because the power within a light pulse of EUV radiation 157 depends, at least in part, on the power of the target light pulse 159p within a range of possible powers. Typically, higher power target light pulses 159p convert more target 155 into plasma 156 , while lower power target light pulses 159p convert less target 155 into plasma 156 , and the amount of plasma 156 produced directly affects the amount of EUV radiation 157 produced by the plasma 156 .

[0033] As described above, the target light source 163 operates within a possible power range required by the lithographic exposure apparatus 152. At various times during operation, the lithographic exposure apparatus 152 may require such a low dose that simply adjusting the power at which the target light source 163 operates (via instructions 108) is insufficient to reduce the power of the light pulses of EUV radiation 157 to provide such a low concentration. This is because the target light source 163 operates within a possible power range and cannot operate at a power outside of (e.g., below) the range. Because of this limitation, the EUV dose controller 105 also provides instructions 109 to the target light source 163 due to the possible power range at which the target light source 163 operates. The instructions 109 relate to an interaction ratio, also known as a hit / miss ratio. The interaction ratio defines a percentage of the average number of EUV interactions over a period of time. As described above, EUV interactions occur by irradiating the target 155 with a target light pulse 159p of the target beam 159 at the interaction region 160. Therefore, when the target light pulse 159p "hit" the target 155 in the interaction region 160, a "hit" corresponds to an EUV interaction. On the other hand, a "miss" corresponds to a situation where the target light pulse 159p misses the target 155 in the interactive area 160. The interactive ratio is the ratio of the number of hits to the number of misses in a period of time. The instructions 109 adjust the interactive ratio by instructing the target light source 163 to adjust the number of targets 155 illuminated with the target light pulse 159p in the interactive area 160 in a period of time. For example, the instructions 109 may instruct the target light source 163 to adjust the pointing of the target light beam 159 so that a certain percentage of the target light pulses 159p miss the corresponding targets 155 in the interactive area 160. As another example, the instructions 109 may instruct the target light source 163 to adjust the timing of generating the target light pulses 159p so that some of the target light pulses 159p arrive at the interactive area 150 at a time when the target 155 is not in the interactive area 160, and therefore these specific target light pulses 159p will miss the target 155.

[0034] Therefore, when the lithographic exposure device 152 requests a specific dose, the EUV dose controller 105 is able to adjust either or both of the instructions 108 and 109. A specific desired dose Dr is obtained by a specific energy value Ei (instruction 108) and a specific interaction ratio value IRk (instruction 109). However, the same specific desired dose Dr can be obtained with a completely different energy value Ei' (instruction 108) and a completely different interaction ratio value IRk' (instruction 109). For example, for a specific desired dose Dr, if the energy value Ei' is higher than the energy value Ei, the interaction ratio value IRk' will be lower than the interaction ratio value IRk to maintain the same specific desired dose Dr. Therefore, the EUV dose controller 105 can force the interaction ratio value (instruction 109) to change by changing the energy value (instruction 108), as described below.

[0035] refer to Figure 2 , a graph 270 showing a dose stability metric 272 versus a power reduction request 274. The power reduction request 274 is an amount of reduction in the power of the EUV radiation 151 supplied to the substrate 153. The power reduction request may be indicated from the lithography exposure apparatus 152. The lithography exposure apparatus 152 expects the EUV dose controller 105 to operate at a relatively large power reduction request 274, such as from 10% to 70%, which is Figure 2 range shown. Thus, a 10% power reduction request indicates a request to reduce the power of the EUV radiation 151 by 10% relative to the maximum power, and a 70% power reduction request indicates a request to reduce the power of the EUV radiation 151 by 70% relative to the maximum power. The dose stability metric 272 is an indication of the stability of the dose, which, as described above, is the amount of light energy delivered from a light pulse of the EUV radiation 151 to the substrate 153 during an exposure pass. In this particular example, an improvement in dose stability is indicated by a decrease in the dose stability metric 272, while a deterioration in dose stability is indicated by an increase in the dose stability metric 272. The dose stability metric 272 may be a measurement of a property associated with the amount of light energy delivered from the EUV radiation 151 to the substrate 153. The dose stability metric 272 may be reported by the lithography exposure apparatus 152.

[0036] Superimposed on the graph 270 is a graph 276 of an interaction ratio 278 versus a power reduction request 274. In this example, the interaction ratio 278 is given as a percentage of interaction over time, so an interaction ratio 278 of 80% corresponds to 80% of the target light pulses 159p hitting the corresponding target 155 in the interaction region 160, and an interaction ratio 278 of 50% corresponds to 50% of the target light pulses 159p hitting the corresponding target 155 in the interaction region 160. In this example, the maximum interaction ratio 278 is approximately 90%. A minimum power reduction request (power reduction request) 274 of 10% corresponds to a request to reduce the power of the EUV radiation 151 by 10% relative to the maximum power. At this minimum power reduction request 274, the interaction ratio 278 is at a maximum of 90%, and the interaction ratio 278 remains at this maximum until the power reduction request 274 reaches approximately 30%.

[0037] While the power reduction request 274 remains below 30%, the EUV dose controller 105 sends instructions 108 to the target light source 163 to reduce the energy of the target light pulses 159p interacting with the target 155 in the interaction region 160 ( Figure 1). As described above, by reducing the energy of the target light pulse 159p interacting with the target 155, the dose (i.e., the amount of light energy delivered to the substrate 153 from the light pulse in the EUV radiation 151) is reduced. For example, if the power reduction request 274 is 10%, the instructions 108 may indicate that the energy of the target light pulse 159p should be reduced by 10%. Furthermore, as long as the power reduction request 274 remains below 30%, the EUV dose controller 105 can control the dose using only the instructions 108 to reduce the energy of the target light pulse 159p.

[0038] At a power reduction request 274 of 30% and above, the EUV dose controller 105 sends an instruction 109 to the target light source 163 to reduce the interaction ratio 278 from a maximum value (90% in this example). By reducing the interaction ratio 278 from its maximum value, the power in the light pulses of the EUV radiation 151 can be reduced by an amount greater than 30% relative to the maximum power. As shown in graph 276, as the power reduction request 274 increases to above 30%, the interaction ratio 278 decreases (e.g., in a standard linear manner). For example, at a power reduction request 274 of approximately 40% (a request to reduce the power of the EUV radiation 151 by 40% relative to the maximum power), the interaction ratio 278 is approximately 80%, which means that 80% of the target light pulses 159p hit their corresponding targets 155 in the interaction region 160. At approximately 70% power reduction request 274 (a request to reduce the power of EUV radiation 151 by 70% relative to the maximum power), interaction ratio 278 is approximately 40%, meaning that 40% of target light pulses 159p hit their respective targets 155 in interaction region 160 .

[0039] As described above, the EUV dose controller 105 can be instructed by the lithographic exposure device 152 to reduce the power of the EUV radiation 151 supplied to the substrate 153 according to the power reduction request 274. The 10% power reduction request indicates a request to reduce the power of the EUV radiation 151 by 10% relative to the maximum power. As the power reduction request increases above 10% to a maximum value of 70% (in this example), the interaction ratio 278 decreases and the dose stability metric 272 changes. Generally, in this particular example, when the metric 272 is low, the dose stability is within an acceptable range. On the other hand, when the metric 272 is close to a local maximum (or peak), the dose stability is within an unacceptable range. As can be seen from Figures 270 and 276, certain values ​​of the interaction ratio 278 are better for dose stability (and are considered acceptable).

[0040] The values ​​of the interaction ratio 278 that are optimal (and acceptable and desirable) for dose stability are those values ​​of the interaction ratio 278 for which the dose stability metric 272 is at a local minimum. In particular, an interaction ratio 278 of 80% ( Figure 2 ) corresponds to a dose stability metric 272 at a local minimum D1 (approximately 2.0). An interaction ratio 278 of 60% ( Figure 2 IR2 in FIG. 2 ) corresponds to a dose stability metric 272 at a local minimum D2 (approximately 2.6). An interaction ratio 278 of 40% ( Figure 2 IR3 in FIG. 2 ) corresponds to the dose stability metric 272 at the local minimum D3 (approximately 3.2). Therefore, the interaction ratios 278 IR1, IR2, and IR3 are optimal for dose stability.

[0041] The values ​​of the interaction ratio 278 that are worst for dose stability (and unacceptable) are those values ​​of the interaction ratio 278 for which the dose stability metric 272 is at a local maximum. In particular, approximately 90% of the interaction ratios 278 ( Figure 2 The dose stability metric 272 corresponds to the local maximum D4 (approximately 3.1) at the local maximum. The interaction ratio 278 ( Figure 2 An interaction ratio 278 (represented by IR5 in FIG. 1 ) corresponds to a dose stability metric 272 at a local maximum D5 (approximately 2.8). An interaction ratio 278 (represented by IR6) of approximately 50% corresponds to a dose stability metric 272 at a local maximum D6 (approximately 5.8). Therefore, interaction ratios IR4, IR5, and IR6 are the worst for dose stability.

[0042] The EUV dose controller 105 is designed to distinguish between worst and best interaction ratios 278, and by making this distinction, improves the stability of the dose, thereby improving the stability of the amount of light energy delivered from the EUV radiation 151 to the substrate 153. Specifically, the EUV dose controller 105 is configured to calculate adjustments to the EUV energy set point 107 (which, as described above, is associated with the desired EUV pulse energy of the light pulses of the EUV radiation 151 that expose the substrate 153) based on knowledge of the worst and best interaction ratios 278, and this adjusted EUV energy set point is used to control the target light source 163 via instructions 108. The EUV dose controller 105 thus converges to an operating point (interaction ratio 278) that is favorable to dose stability. Figure 2, the EUV dose controller 105 converges on the interaction ratios 278 IR1, IR2, and IR3. The EUV dose controller 105 detects when the operation of the target light source 163 is approaching one of the worst or unacceptable interaction ratios 278 IR4, IR5, or IR6, and switches or moves to an achievable good interaction ratio 278 IR1, IR2, or IR3, thereby maintaining or improving the dose stability at the substrate 153. The EUV dose controller 105 adjusts the value of the instructions 108 (based on the knowledge of the worst and best interaction ratios 278) to be able to modify the value of the instructions 109 to avoid the worst and unacceptable interaction ratios while still controlling the light pulse dose within the EUV radiation 151 according to the requirements of the lithographic exposure equipment 152. As discussed next, the EUV dose controller 105 is able to perform these tasks because it has been redesigned to enable communication between a first task module and a second task module within the EUV dose controller 105. The first task module determines the energy or power in the target light pulse 159p, and provides the instructions 108 with the determined energy or power to the target light source 163. The second task module determines an interaction ratio 278 and provides the instruction 109 with the determined interaction ratio 278 to the target light source 163 .

[0043] Figure 2 An example of a set of unacceptable interaction ratios 278 IR4, IR5, IR6 and a set of acceptable interaction ratios 278 IR1, IR2, IR3 is shown. The values ​​of the unacceptable interaction ratios 278 and the acceptable interaction ratios 278 can be related to Figure 2 In addition, there may be fewer than three or more than three unacceptable interaction ratios 278 (or acceptable interaction ratios 278). In addition, for different EUV light sources 150 and / or different lithography exposure equipment 152, the actual values ​​of the unacceptable interaction ratios 278 and the acceptable interaction ratios 278 and the shapes of the graphs 270 and 276 may be different.

[0044] refer to Figure 3 , an implementation 305 of the EUV dose controller 105 is shown in the EUV dose device 300. The EUV dose controller 305 is configured to receive a measurement of the EUV pulse energy 106 resulting from an EUV interaction, wherein the EUV interaction occurs between the target light pulse 159p and the target 155, such as Figure 1 The EUV dose controller 305 is configured to receive an EUV pulse energy set point 107, which is associated with a desired EUV pulse energy for exposing the substrate 153, such as Figure 1 shown.

[0045] The EUV dose controller 305 includes an interaction module 310 and an adjustment module 320. The adjustment module 320 communicates with the interaction module 310 and the target light source controller 315. The EUV dose controller 305 may also include an interaction averaging module 325 that receives a measurement of the EUV pulse energy 106. The interaction averaging module 325 communicates with the target light source controller 315 and sends the average EUV target energy of the EUV interaction 326 to the target light source controller 315. Importantly, the target light source controller 315 (first task module) has a communication path with the interaction module 310 (second task module). Although not required, the adjustment module 320 may also include a substructure for dividing the operation tasks. For example, the adjustment module 320 may include an interaction ratio averaging module 322 and an update module 324 that communicates with the interaction ratio averaging module 322. The interaction ratio averaging module 322 receives the interaction ratio 328 from the interaction module 310 and outputs the average interaction ratio 328AV. Update module 324 receives the average interaction ratio 328AV and EUV pulse energy setpoint 107 from lithographic exposure apparatus 152. In other implementations, interaction ratio averaging module 322 may receive measurement 106 of EUV energy in light pulses of EUV radiation 151 instead of receiving interaction ratio 328 from interaction module 310.

[0046] The EUV dose controller 305 also includes a memory 311 that is accessible by one or more modules within the EUV dose controller 305, such as the interaction module 310, the adjustment module 320, or the target light source controller 315. The memory 311 is configured to store information that can be accessed and / or used by one or more modules to facilitate or implement the operation of the EUV dose controller 305. Such stored information can be information or data output from each of these modules, information received from the metrology device 154, the EUV energy set point 107, or the measurement 106 of EUV energy in the light pulses of EUV radiation 151. The memory 311 can be a read-only memory and / or a random access memory, and can provide a storage device suitable for tangibly embodying computer program instructions and data.

[0047] The memory 311 may be configured to store one or more unacceptable ranges of the interaction ratio 328 and one or more acceptable ranges of the interaction ratio 328. For example, referring again to Figure 2 and Figure 4 , the memory 311 may store a table 475 (e.g., a lookup table) of the best interaction ratios 328B and the worst interaction ratios 328W. In the table 475, the ratios 328B and 328W are given as percentages. In this example, only five interaction ratios IR are listed because this refers to Figure 2 However, in other examples, there may be fewer or more than five interaction ratios for the IR to be considered the best or worst.

[0048] The EUV dose controller 305 may also include one or more input and / or output devices 312 (such as a keyboard, a touch-enabled device, an audio input device as input and audio or video for output), and one or more processors 313. The EUV dose controller 305 may include other modules not described. Communication between any of the modules 310, 320, 315, 325 and the memory 311 may be through a direct or physical connection (e.g., wired) or a wireless connection, so that information can be freely transferred between any module of the EUV dose controller 305, the memory 311, and other components of the EUV dose device 300.

[0049] Although the EUV dose controller 305 is represented as a box in which all its components appear to be located in the same location, the EUV dose controller 305 may also be composed of components (such as modules 310, 320, 315, 325) that are physically remote from each other. Each of the modules 310, 320, 315, 325 may be or include a dedicated processing system for receiving data and analyzing data, or one or more of the modules 310, 32, 315, 325 may be combined into a single processing system. Each of the modules 310, 320, 315, 325 may include or have access to one or more programmable processors 313, and may execute a program of instructions to perform a desired function by operating on input data and generating appropriate outputs. The modules 310, 320, 315, 325 may be implemented in any of digital electronic circuitry, computer hardware, firmware, or software.

[0050] The interaction module 310 is configured to determine an interaction ratio 328 and to provide the EUV light source 150 ( Figure 1 ) provides instructions 309 including the determined interaction ratio 328 to the target light source 163 within the . The interaction module 310 makes this determination based on the measured EUV pulse energy 106. For example, the interaction module 310 may compare the measured EUV pulse energy 106 to the EUV energy set point 107, and if the measured EUV pulse energy 106 is not close enough to the EUV energy set point 107, the interaction module 310 determines how to adjust the interaction ratio 328.

[0051] The EUV dose controller 305 may also include an input module 314 configured to receive input signals. For example, the measured EUV pulse energy 106 and the EUV energy set point 107 may initially be received by the input module 314. As described above, the input module 314 may forward each input signal to appropriate other modules within the EUV dose controller 305.

[0052] refer to Figure 5, process 540 is performed by the EUV dose controller 105 or 305. Initially, the EUV dose controller 105 / 305 receives a measurement 106 of EUV energy in a light pulse of EUV radiation 151 (541). As described above, the EUV radiation 151 is generated from an EUV interaction between a target light pulse 159p in the interaction region 160 and the target 155. Referring to the EUV dose controller 305, the interaction module 310 receives the measurement 106. Next, the EUV dose controller 105 / 305 determines an interaction ratio 328 (542) based on the EUV pulse energy measurement 106, and provides the determined interaction ratio 328 to the target light source 163 (543). As described above, the interaction ratio 328 defines a percentage of the average number of EUV interactions over a period of time. For example, referring to the EUV dose controller 305, the interaction module 310 determines the interaction ratio 328 (542) and supplies the interaction ratio 328 to the target light source 163 (543). In this way, the target light source 163 generates the target light pulses 159 p according to the interaction ratio 328 , so that the average number of EUV interactions corresponds to the supplied interaction ratio 328 .

[0053] The interaction ratio 328 can be adjusted whenever the dose required by the lithographic exposure apparatus 152 is so low that simply adjusting the operating power of the target light source 163 (via the instructions 108) is insufficient to reduce the power of the light pulses of EUV radiation 151 supplied to the substrate 153. To determine the interaction ratio 328 (542), in some implementations, the interaction module 310 compares the EUV pulse energy measurement 106 to an EUV energy set point 107 that is associated with a desired EUV pulse energy for the light pulses of EUV radiation 151 that expose the substrate 153. For example, if the interaction module 310 determines that the difference Δ between the EUV pulse energy measurement 106 and the EUV energy set point 107 is IR is greater than a predetermined threshold, the value of the interaction ratio 328 may be reduced by the difference Δ IR , thereby reducing the number of EUV interactions within the interaction region 160. On the other hand, if the interaction module 310 determines the difference Δ IR If the interaction ratio 328 is less than or equal to a predetermined threshold, the value of the interaction ratio 328 may be maintained.

[0054] As mentioned above Figure 3 As described above, some values ​​of the interaction ratio 328 have a much worse effect on dose stability, while some values ​​of the interaction ratio 328 have a much better effect on dose stability. Therefore, the EUV dose controller 105 / 305 also calculates an adjusted EUV pulse energy set point (544) based on the interaction ratio 328 determined at 542. For example, referring to Figure 3, the adjustment module 320 can calculate an adjusted EUV pulse energy set point 307A based on the determined interaction ratio 328. Based on the calculated adjusted EUV pulse energy set point 307A, the received EUV pulse energy 151 ( Figure 1 )'s dose stability at substrate 153 is improved (545).

[0055] refer to Figure 6 , process 645 may be performed to improve dose stability at substrate 153 ( Figure 5 545 in). Process 645 may be performed by target light source controller 315. Target light source controller 315 receives adjusted EUV pulse energy set point 307A from adjustment module 320 (630). Target light source controller 315 also receives an indication of EUV energy in a light pulse of EUV radiation 151 (631). Target light source controller 315 compares the EUV energy indication to adjusted EUV pulse energy set point 307A (632). For example, target light source controller 315 may determine a difference Δ between the EUV energy indication and the adjusted EUV pulse energy set point 307A. E Is it greater than a predetermined threshold (632). E If the difference Δ is greater than a predetermined threshold (632), the target light source controller 315 may adjust the energy in one or more target light pulses 159p supplied to the interaction zone 160 (633). E If the energy in the one or more target light pulses 159p is less than or equal to the predetermined threshold (632), the target light source controller 315 may maintain the energy in the one or more target light pulses 159p supplied to the interaction area 160 (634). The target light source controller 315 sends an instruction 108 including the energy in the one or more target light pulses 159p (from step 633 or step 634) to the target light source 163 (635).

[0056] In some implementations, the indication of EUV energy in the light pulse of EUV radiation 151 received at 631 may directly correspond to the measurement 106 of EUV energy in the light pulse of EUV radiation 151. In other implementations, reference Figure 7, an indication of EUV energy in a light pulse of EUV radiation 151 can be determined based on the measurement 106 according to process 731. Process 731 can be performed by the interactive averaging module 325. The interactive averaging module 325 receives the measurement 106 of EUV energy in light pulses of EUV radiation 151 over a set number of target light pulses 159p (736). The interactive averaging module 325 isolates only the target light pulses 159p that interact with the target 155 in the interaction region 160 (737). The interactive averaging module 325 averages the values ​​of the measured EUV pulse energies 106 of the isolated target light pulses 159p to produce an average EUV target energy of the EUV interactions 326 (738).

[0057] Reference again Figure 5 As described above, the EUV dose controller 105 / 305 calculates the adjusted EUV pulse energy set point 307A based on the interaction ratio 328 at 544 and provides the adjusted EUV pulse energy set point 307A to the target light source controller 315. In some implementations, reference Figure 8 , the adjustment module 320 is configured to calculate the adjusted EUV pulse energy set point 307A according to the process 844. The interaction ratio averaging module 322 receives the interaction ratio 328 from the interaction module 310 (846). The interaction ratio averaging module 322 averages the values ​​of the interaction ratio 328 over a period of time and outputs an average interaction ratio 328AV (847). The update module 324 receives the average interaction ratio 328AV and also receives the EUV pulse energy set point 107, which is associated with the desired EUV pulse energy for exposing the substrate 153 ( Figure 1 and Figure 3 )(848). The update module 324 calculates the adjusted EUV pulse energy set point 307A based on the average interaction ratio 328AV and the EUV pulse energy set point 107 (849). By detecting the average interaction ratio 328AV, the update module 324 is able to detect or predict when the interaction ratio 328 is approaching one of the worst (or unacceptable) interaction ratios (e.g., Figure 2 In order to detect or predict when the interaction ratio 328 is approaching one of the worst (or unacceptable) interaction ratios, the update module 324 can access data in the lookup table 475 stored in the memory 311. The update module 324 calculates the adjusted EUV pulse energy set point 307A (via the instructions 308) in a manner that forces the target light source controller 315 to change the energy value provided to the target light source 163. By doing so, the EUV dose controller 305 is able to avoid sending pulses with unacceptable interaction ratios (such as Figure 2 Instruction 309 (ratio 278IR4, IR5 or IR6).

[0058] In some implementations, the interaction ratio 328 is predicted to be within an unacceptable range, such as within a range of intolerable interaction ratios (e.g., Figure 2 The update module 324 can calculate the adjusted EUV pulse energy set point 307A based on the ratio 278 IR4, IR5 or IR6 in the EUV radiation 151. As described above, as long as the dose delivered to the substrate 153 in the light pulses of the EUV radiation 151 is unstable, the interaction ratio 328 is in an unacceptable range. In other implementations, by predicting that the interaction ratio 328 will be outside the acceptable range, for example, outside the range of acceptable ratios (such as Figure 2 IR1, IR2, and IR3), the update module 324 can calculate the adjusted EUV pulse energy set point 307A. As described above, as long as the dose delivered to the substrate 153 in the light pulse of EUV radiation 151 is not within the stability range, the interaction ratio 328 is outside the acceptable range. In addition, the update module 324 is configured to access the interaction ratio associated with the unacceptable range and the interaction ratio associated with the acceptable range from the memory 311. As described above, the interaction ratio 278 that is best for dose stability is those values ​​of the dose stability metric 272 that are at a local minimum (at Figure 2 ), while the worst interaction ratios 278 for dose stability are those values ​​where the dose stability metric 272 is at a local maximum (in Figure 2 ). However, in other implementations of the dose stability metric 272, this may be reversed such that the best interaction ratios 278 for dose stability are those values ​​for which the dose stability metric 274 is at a local maximum, and the worst interaction ratios 278 for dose stability are those values ​​for which the dose stability metric 272 is at a local minimum.

[0059] refer to Fig. 9 , a graph 270 of a dose stability metric 272 versus a power reduction request 274 and a graph 276 of an interaction ratio 278 versus a power reduction request 274 are shown. These are Figure 2 The figure depicted in . Fig. 9Also shown in FIG. 970A is a graph of the dose stability metric 272 versus the power reduction request 274 and a graph 976A of the interaction ratio 278 versus the power reduction request 274 when the EUV dose controller 105 / 305 operates according to the processes 540, 645, 731, and 844 to distinguish between the worst and best interaction ratios. By using the new value of the EUV energy set point 307A, the EUV dose controller 105 / 305 drives the dose control from the unacceptable interaction ratios IR4, IR5, and IR6 to one of the acceptable and preferred interaction ratios IR1, IR2, or IR3. The value of the dose stability metric 272 in FIG. 970A is driven from the peak values ​​of D4, D5, and D6 (in FIG. 270) to the values ​​D4', D5', and D6' at the corresponding next adjacent acceptable interaction ratios (IR1, IR2, and IR3). Additionally, FIG. 976A illustrates how the interaction ratio 278 (and instructions 109 / 309) may be adjusted indirectly by adjusting the energy provided to the target light source 163 (instructions 108 / 308).

[0060] Reference again Figure 1 , provides more details about EUV light source 150 and EUV interaction. Target beam 159 can be considered as an amplified beam traveling along a beam path toward interaction region 160. Container 162 can be a vacuum chamber. Figure 1 The path of target 155 is shown in the plane of the page. However, the path of target 155 can enter or leave the plane of the page at any angle relative to the plane of the page. Thus, for example, the path of target 155 can enter or leave the page, such as in a plane that includes the path of target beam 159 and is perpendicular to the plane of the page. As described above, when target light pulse 159p interacts (impacts) with target 155 in interaction region 160, the target material within target 155 is converted into plasma 156, which has emission line elements in the EUV range. The resulting plasma 156 has certain characteristics that depend on the composition of the target material within target 155. These characteristics can include the wavelength of EUV radiation 157 generated by plasma 156 and the type and amount of fragments released from plasma 156.

[0061] The EUV light source 150 also includes a target generator 164 that delivers, controls, and directs the targets 155. Each target 155 can be in the form of a droplet, a liquid stream, a solid particle or cluster, a solid particle included in a droplet, or a solid particle included in a liquid stream. The EUV light source 150 can also include a target catcher (not shown) positioned to receive unused targets and / or some remnants of used targets. Each target 155 includes a target material, such as water, tin, lithium, xenon, or any material that has an emission line in the EUV range when converted to a plasma state. For example, elemental tin can be used as pure tin (Sn); as a tin compound, such as SnBr4 SnBr 2 SnH 4 ; as a tin alloy, such as a tin-gallium alloy, a tin-indium alloy, a tin-gallium alloy, or any combination of these alloys. One or more targets 155 may also include impurities, such as non-target particles. Thus, in the absence of impurities, the target 155 consists only of the target material. The target 155 is delivered by the target generator 164 into the interior 161 of the container 162 and reaches the interaction region 160.

[0062] The target light source 163 may generate a target light beam 159 due to a population inversion within one or more gain media of the target light source 163. In addition, a beam delivery system 165 including a beam transmission system and a focusing assembly may be positioned at the output of the target light source 163 to steer and / or modify the target light beam 159 as desired, and to focus the target light beam 159 into the interaction region 160. The target light beam may be an "amplified beam" that includes one or more of: light from a laser system (target light source 163) that is merely amplified, but not necessarily coherent laser oscillations; and light from a laser system (target light source 162) that is amplified and also coherent laser oscillations. The optical amplifier in the target light source 163 may include a fill gas as a gain medium, the fill gas including CO 2 , and can amplify light having a wavelength between about 9100 and about 11000 nanometers (nm), particularly about 10600 nm, with a gain greater than or equal to 1000. Suitable amplifiers and lasers for target light source 163 may include pulsed laser devices, for example, pulsed gas discharge CO 2 Laser devices that generate radiation at about 9300 nm or about 10600 nm, for example, under DC or RF excitation, operate at relatively high power (e.g., 10 kW or more) and high pulse repetition rate (e.g., 50 kHz or more).

[0063] The EUV radiation collector 158 may be a collector mirror having an aperture that allows the target beam 159 to pass through and reach the interaction region 160. The collector mirror may be, for example, an ellipsoidal mirror having a primary focus at the interaction region 160 and a secondary focus at an intermediate position (also referred to as an intermediate focus) where EUV radiation 151 may be output from the EUV light source 150 and may be input to the lithography exposure apparatus 152.

[0064] The metrology equipment 154 may include one or more radiation detectors that measure one or more parameters of the EUV radiation 151, including but not limited to EUV pulse energy, EUV energy distribution as a function of wavelength, energy within a specific wavelength band, energy outside a specific wavelength band, and angular distribution of EUV intensity and / or average power. For example, the EUV dose controller 105 / 305 uses information from the detectors to control and optimize parameters such as timing and focusing of the target light pulse 159p to properly intercept the target 155 at the correct location and time (within the interaction region 160) to effectively and efficiently generate EUV radiation 151, or to adjust the dose of EUV radiation 151 at the substrate 153 using instructions 108 / 109.

[0065] EUV light source 150 may also include other features not shown.

[0066] The lithographic exposure apparatus 152 processes a substrate 153 received by a wafer holder or stage (not shown). The EUV radiation 151 is a pulsed beam comprising light pulses separated in time from one another. The lithographic exposure apparatus 152 comprises a projection optical system PO through which the EUV radiation 151 passes before reaching the substrate 153. The lithographic exposure apparatus 152 may also comprise a metrology system (not shown), which may comprise, for example, a camera or other device capable of capturing an image of the substrate 153 and / or the EUV radiation 151 at the substrate 153, or an optical detector capable of capturing data describing characteristics of the EUV radiation 151, such as the intensity of the EUV radiation 151 at the substrate 153 in the plane of the substrate 153. The projection optical system PO comprises one or more illumination mirrors to illuminate a reflection pattern or mask. EUV radiation 151 reflected from the pattern or mask is further reflected and reduced by one or more reduction mirrors and irradiates the substrate 153 (or one or more photosensitive layers on the substrate 153, not shown) to allow a patterned structure to be formed in or on the substrate 153.

[0067] The following sections may be used to further describe the implementation.

[0068] 1. A dose control device for an extreme ultraviolet (EUV) light source, the dose control device comprising:

[0069] Dosage controller, comprising:

[0070] an input module configured to receive an EUV pulse energy setpoint associated with a desired EUV pulse energy for exposing a substrate and a measurement of EUV pulse energy resulting from an EUV interaction occurring between a target light pulse and a target;

[0071] an interaction module configured to determine an interaction ratio based on the measured EUV pulse energy and provide the interaction ratio to a target light source generating the target light pulses, the interaction ratio defining a percentage of an average number of EUV interactions over a period of time; and

[0072] The regulation module is configured as follows:

[0073] calculating an adjusted EUV pulse energy setpoint from the received EUV pulse energy setpoint based on the determined interaction ratio; and

[0074] The adjusted EUV pulse energy set point is provided to a target light source controller.

[0075] 2. The dose control device of section 1, wherein the interaction module determines the interaction ratio by comparing the measured EUV pulse energy with the EUV pulse energy set point, the EUV pulse energy set point being associated with the desired EUV pulse energy for exposing the substrate.

[0076] 3. The dose control device according to Section 1, wherein the interaction ratio is provided to the target light source to cause the target light source to generate the target light pulses according to the interaction ratio, so that the average number of EUV interactions corresponds to the interaction ratio.

[0077] 4. The dose control device according to Chapter 1, wherein the adjustment module is configured to calculate the adjusted EUV pulse energy set point, including: when the interaction ratio is within an unacceptable range or outside an acceptable range, the adjustment module calculates the adjusted EUV pulse energy set point.

[0078] 5. The dose control device according to Section 4, wherein the interaction ratio is within the unacceptable range as long as the dose is unstable, and the interaction ratio is outside the acceptable range as long as the dose is not within the stable range.

[0079] 6. The dose control device according to Chapter 5, wherein the adjustment module determines whether the interaction ratio is within the unacceptable range or outside the acceptable range by analyzing whether the dose stability metric is within the range of a local maximum value or within the range of a local minimum value.

[0080] 7. A dose control device according to Chapter 4, wherein the dose controller further comprises a memory configured to store one or more of the unacceptable range and the acceptable range of the interaction ratio, wherein the dose controller is configured to access the memory.

[0081] 8. The dosage control device according to Section 1, wherein the adjustment module comprises:

[0082] an interaction ratio averaging module configured to average the values ​​of the interaction ratios and output an average interaction ratio; and

[0083] An update module is configured to: receive the average interaction ratio; receive an EUV pulse energy set point associated with a desired EUV pulse energy for exposing the substrate; and calculate the adjusted EUV pulse energy set point based on the average interaction ratio.

[0084] 9. The dosage control device according to Chapter 1, wherein the dosage controller includes the target light source controller, wherein the target light source controller communicates with the adjustment module and the target light source.

[0085] 10. A dose control device according to Chapter 9, wherein the dose controller includes an interactive averaging module, which is configured to: receive the measured EUV pulse energy on a set number of target light pulses; isolate only the target light pulses that interact with the target; and average the values ​​of the measured EUV pulse energy of the isolated target light pulses to produce an average EUV target energy of EUV interactions.

[0086] 11. A dose control device according to Chapter 10, wherein the target light source controller is configured to: receive the average EUV target energy from the interaction averaging module and receive the adjusted EUV pulse energy set point from the adjustment module, and determine the energy in one or more target light pulses supplied to the interaction area receiving the target based on the average EUV target energy of the EUV interaction and the adjusted EUV pulse energy set point.

[0087] 12. The dose control apparatus of Section 1, wherein providing the adjusted EUV pulse energy set point to the target light source controller improves dose stability at a substrate receiving the EUV pulse energy.

[0088] 13. An apparatus for an extreme ultraviolet (EUV) light source, the apparatus comprising:

[0089] The dosage controller is configured to:

[0090] receiving a measurement of EUV pulse energy resulting from an EUV interaction occurring between a target light pulse generated by a target light source and a target in an interaction region;

[0091] receiving an EUV pulse energy setpoint associated with a desired EUV pulse energy for exposing a substrate;

[0092] determining an interaction ratio based on the measured EUV pulse energy and the EUV pulse energy set point, the interaction ratio defining a percentage of an average number of EUV interactions over a period of time;

[0093] determining an energy in one or more target light pulses supplied to the interaction region, the determined energy being based on the value of the interaction ratio and the measured EUV pulse energy; and

[0094] The determined interaction ratio and the determined energy are provided to the target light source.

[0095] 14. The apparatus of Section 13, wherein the dose controller determines the interaction ratio by comparing the measured EUV pulse energy with the EUV pulse energy set point.

[0096] 15. An apparatus according to section 13, wherein the dose controller provides the determined interaction ratio to the target light source, thereby causing the target light source to generate the target light pulses according to the interaction ratio, so that the average number of EUV interactions corresponds to the interaction ratio.

[0097] 16. The apparatus of Chapter 13, wherein the dose controller determines the energy in one or more target light pulses supplied to the interaction region by comparing the measured EUV pulse energy to an adjusted EUV pulse energy set point.

[0098] 17. The apparatus according to Section 16, wherein the dose controller is configured to calculate the adjusted EUV pulse energy set point based on the determined interaction ratio.

[0099] 18. The apparatus according to Section 17, wherein the dose controller calculates the adjusted EUV pulse energy set point by calculating the adjusted EUV pulse energy set point when the interaction ratio is within an unacceptable range or outside an acceptable range.

[0100] 19. An apparatus according to Chapter 17, wherein the dose controller calculates the adjusted EUV pulse energy set point by calculating the adjusted EUV pulse energy set point when the dose of the EUV pulse energy at the substrate is unstable or when the dose is not within a stability range.

[0101] 20. The device according to Section 16, wherein the dosage controller is further configured to:

[0102] Averaging the values ​​of the interaction ratios and outputting an average interaction ratio;

[0103] receiving the average interaction ratio; and

[0104] An adjusted EUV pulse energy set point is calculated based on the average interaction ratio.

[0105] 21. The device according to Chapter 13 further includes a memory configured to store one or more unacceptable ranges and acceptable ranges of the interaction ratio, wherein the dosage controller is configured to access the memory.

[0106] 22. An apparatus according to Chapter 13, wherein the dose controller is configured to: receive measured EUV pulse energy over a set number of target light pulses; isolate only the target light pulses that interact with the target; and average the values ​​of the measured EUV pulse energy of these isolated target light pulses to produce an average EUV target energy of EUV interactions.

[0107] 23. An apparatus according to section 22, wherein the dose controller is configured to determine the energy in one or more target light pulses supplied to an interaction region receiving the target based on an average EUV target energy of the EUV interaction and an adjusted EUV pulse energy set point, the adjusted EUV pulse energy set point being based on the determined interaction ratio.

[0108] 24. An apparatus according to Chapter 13, wherein the dose controller includes an input module configured to: receive a measurement of the EUV pulse energy generated from the EUV interaction, and receive the EUV pulse energy set point associated with the desired EUV pulse energy for exposing the substrate.

[0109] 25. A method of controlling the dose of extreme ultraviolet (EUV) pulse energy supplied to a substrate in an EUV light source, the method comprising:

[0110] receiving a measurement of EUV pulse energy resulting from an EUV interaction occurring between a target light pulse and a target;

[0111] determining an interaction ratio based on the measured EUV pulse energy, the interaction ratio defining a percentage of an average number of EUV interactions over a period of time;

[0112] providing the interaction ratio to a target light source generating the target light pulse;

[0113] calculating an adjusted EUV pulse energy set point based on the determined interaction; and

[0114] Dose stability at a substrate exposed by the EUV pulse energy is improved based on the adjusted EUV pulse energy set point.

[0115] 26. A method according to Chapter 25, wherein improving the dose stability at the substrate exposed by the EUV pulse energy based on the adjusted EUV pulse energy set point includes: adjusting the energy in one or more target light pulses supplied to an interaction region receiving the target based on the adjusted EUV pulse energy set point and the measured EUV pulse energy.

[0116] 27. The method according to Chapter 26 also includes receiving measured EUV pulse energy over a set number of target light pulses; isolating only the target light pulses that interact with the target; and averaging the values ​​of the measured EUV pulse energy of these isolated target light pulses to produce an average EUV pulse energy of EUV interaction, wherein adjusting the energy in one or more target light pulses supplied to the interaction region includes comparing the average EUV pulse energy of the EUV interaction with the adjusted EUV pulse energy set point.

[0117] 28. The method of Chapter 25, wherein determining the interaction ratio comprises comparing the measured EUV pulse energy to an EUV pulse energy set point associated with a desired EUV pulse energy for exposing the substrate.

[0118] 29. A method according to Chapter 25, wherein the interaction ratio is provided to the target light source to cause the target light source to generate the target light pulses according to the interaction ratio, so that the average number of EUV interactions corresponds to the interaction ratio.

[0119] 30. The method of Chapter 25, wherein calculating the adjusted EUV pulse energy set point based on the determined interaction ratio comprises calculating the adjusted EUV pulse energy set point when the interaction ratio is within an unacceptable range or outside an acceptable range.

[0120] 31. A method according to Chapter 30, wherein as long as the dose is unstable, the interaction ratio is within the unacceptable range, and as long as the dose is not within the stable range, the interaction ratio is outside the acceptable range.

[0121] 32. The method according to Chapter 31 also includes: determining whether the interaction ratio is within the unacceptable range or outside the acceptable range includes analyzing whether the dose stability metric is within the range of a local maximum or within the range of a local minimum.

[0122] 33. The method according to Chapter 30 also includes storing one or more of the unacceptable range and the acceptable range of the interaction ratio.

[0123] 34. The method according to Section 25 further comprises:

[0124] averaging the values ​​of the interaction ratios and outputting an average interaction ratio; and

[0125] Wherein calculating the adjusted EUV pulse energy set point includes calculating the adjusted EUV pulse energy set point based on the average interaction ratio.

[0126] The implementations described above and other implementations are within the scope of the following claims.

Claims

1. A dose control device for an extreme ultraviolet (EUV) light source, the dose control device comprising: Dosage controller, comprising: an input module configured to receive an EUV pulse energy setpoint associated with a desired EUV pulse energy for exposing a substrate and a measurement of EUV pulse energy resulting from an EUV interaction occurring between a target light pulse and a target; an interaction module configured to determine an interaction ratio based on the measured EUV pulse energy and provide the interaction ratio to a target light source generating the target light pulses, the interaction ratio defining a percentage of an average number of EUV interactions over a period of time; and The regulation module is configured as follows: calculating an adjusted EUV pulse energy setpoint from the received EUV pulse energy setpoint based on the determined interaction ratio; and The adjusted EUV pulse energy set point is provided to a target light source controller.

2. The dose control apparatus of claim 1 , wherein the interaction module determines the interaction ratio by comparing the measured EUV pulse energy with the EUV pulse energy set point, the EUV pulse energy set point being associated with the desired EUV pulse energy for exposing the substrate. 3 . The dose control apparatus according to claim 1 , wherein the interaction ratio is provided to the target light source to cause the target light source to generate the target light pulses according to the interaction ratio so that an average number of the EUV interactions corresponds to the interaction ratio.

4. The dose control device according to claim 1, wherein the adjustment module is configured to calculate the adjusted EUV pulse energy set point comprising: The adjustment module calculates the adjusted EUV pulse energy set point when the interaction ratio is within an unacceptable range or outside an acceptable range. 5 . The dose control apparatus according to claim 4 , wherein the interaction ratio is within the unacceptable range as long as the dose is unstable, and the interaction ratio is outside the acceptable range as long as the dose is not within a stable range. 6 . The dose control device of claim 5 , wherein the adjustment module determines whether the interaction ratio is within the unacceptable range or outside the acceptable range by analyzing whether the dose stability metric is within a range of a local maximum or a range of a local minimum. 7 . The dose control device according to claim 4 , wherein the dose controller further comprises a memory configured to store one or more of the unacceptable range and the acceptable range of the interaction ratio, wherein the dose controller is configured to access the memory.

8. The dosage control device according to claim 1, wherein the adjustment module comprises: an interaction ratio averaging module, configured to average the values ​​of the interaction ratios and output an average interaction ratio; as well as An updating module is configured to: receive the average interaction ratio; An EUV pulse energy setpoint associated with a desired EUV pulse energy for exposing the substrate is received; and the adjusted EUV pulse energy setpoint is calculated based on the average interaction ratio.

9. The dosage control device of claim 1, wherein the dosage controller comprises the target light source controller, wherein the target light source controller communicates with the adjustment module and the target light source.

10. The dose control apparatus of claim 9, wherein the dose controller comprises an interactive averaging module configured to: receive the measured EUV pulse energy over a set number of target light pulses; isolating only target light pulses that interact with the target; And the values ​​of the measured EUV pulse energies of the isolated target light pulses are averaged to produce an average EUV target energy of the EUV interaction.

11. A dose control device according to claim 10, wherein the target light source controller is configured to: receive the average EUV target energy from the interaction averaging module and receive the adjusted EUV pulse energy set point from the adjustment module, and determine the energy in one or more target light pulses supplied to the interaction area receiving the target based on the average EUV target energy of the EUV interaction and the adjusted EUV pulse energy set point.

12. The dose control apparatus of claim 1, wherein providing the adjusted EUV pulse energy set point to the target light source controller improves dose stability at a substrate receiving the EUV pulse energy.

13. An apparatus for an extreme ultraviolet (EUV) light source, the apparatus comprising: The dosage controller is configured to: receiving a measurement of EUV pulse energy resulting from an EUV interaction occurring between a target light pulse generated by a target light source and a target in an interaction region; receiving an EUV pulse energy setpoint associated with a desired EUV pulse energy for exposing a substrate; determining an interaction ratio based on the measured EUV pulse energy and the EUV pulse energy set point, the interaction ratio defining a percentage of an average number of EUV interactions over a period of time; determining an energy in one or more target light pulses supplied to the interaction region, the determined energy being based on the value of the interaction ratio and the measured EUV pulse energy; as well as The determined interaction ratio and the determined energy are provided to the target light source.

14. The apparatus of claim 13, wherein the dose controller determines the interaction ratio by comparing the measured EUV pulse energy with the EUV pulse energy set point.

15. The apparatus of claim 13, wherein the dose controller provides the determined interaction ratio to the target light source, thereby causing the target light source to generate the target light pulses according to the interaction ratio so that an average number of the EUV interactions corresponds to the interaction ratio.

16. The apparatus of claim 13, wherein the dose controller determines energy in one or more target light pulses supplied to the interaction region by comparing the measured EUV pulse energy to an adjusted EUV pulse energy set point. 17 . The apparatus of claim 16 , wherein the dose controller is configured to calculate the adjusted EUV pulse energy set point based on the determined interaction ratio. 18 . The apparatus of claim 17 , wherein the dose controller calculates the adjusted EUV pulse energy set point by calculating the adjusted EUV pulse energy set point when the interaction ratio is within an unacceptable range or outside an acceptable range.

19. The apparatus according to claim 17, wherein the dose controller calculates the adjusted EUV pulse energy set point by calculating the adjusted EUV pulse energy set point when a dose of the EUV pulse energy at the substrate is unstable or when the dose is not within a stability range.

20. The device of claim 16, wherein the dosage controller is further configured to: Averaging the values ​​of the interaction ratios and outputting an average interaction ratio; receiving the average interaction ratio; and An adjusted EUV pulse energy set point is calculated based on the average interaction ratio.

21. The apparatus of claim 13, further comprising a memory configured to store one or more unacceptable ranges and acceptable ranges of the interaction ratio, wherein the dosage controller is configured to access the memory.

22. The apparatus of claim 13, wherein the dose controller is configured to: receive measured EUV pulse energies over a set number of target light pulses; isolate only the target light pulses that interact with the target; and average the values ​​of the measured EUV pulse energies of the isolated target light pulses to produce an average EUV target energy of EUV interactions.

23. The apparatus of claim 22, wherein the dose controller is configured to determine energy in one or more target light pulses supplied to an interaction region receiving the target based on an average EUV target energy of the EUV interactions and an adjusted EUV pulse energy set point, the adjusted EUV pulse energy set point being based on the determined interaction ratio.

24. The apparatus of claim 13, wherein the dose controller comprises an input module configured to receive the measurement of the EUV pulse energy resulting from the EUV interaction and to receive the EUV pulse energy setpoint associated with the desired EUV pulse energy for exposing the substrate.

25. A method of controlling the dose of extreme ultraviolet (EUV) pulse energy supplied to a substrate in an EUV light source, the method comprising: receiving a measurement of EUV pulse energy resulting from an EUV interaction occurring between a target light pulse and a target; determining an interaction ratio based on the measured EUV pulse energy, the interaction ratio defining a percentage of an average number of EUV interactions over a period of time; providing the interaction ratio to a target light source generating the target light pulse; calculating an adjusted EUV pulse energy setpoint based on the determined interaction; as well as Dose stability at a substrate exposed by the EUV pulse energy is improved based on the adjusted EUV pulse energy set point.

26. The method of claim 25, wherein improving dose stability at the substrate exposed by the EUV pulse energy based on the adjusted EUV pulse energy set point comprises: The energy in one or more target light pulses supplied to an interaction region receiving the target is adjusted based on the adjusted EUV pulse energy set point and the measured EUV pulse energy.

27. The method of claim 26, further comprising receiving measured EUV pulse energies over a set number of target light pulses; isolating only target light pulses that interact with the target; and averaging the values ​​of the measured EUV pulse energies of the isolated target light pulses to produce an average EUV pulse energy of EUV interactions, wherein adjusting the energy in one or more target light pulses supplied to the interaction region comprises comparing the average EUV pulse energy of the EUV interactions to the adjusted EUV pulse energy set point.

28. The method of claim 25, wherein determining the interaction ratio comprises: The measured EUV pulse energy is compared to an EUV pulse energy set point that correlates to a desired EUV pulse energy for exposing the substrate.

29. The method of claim 25, wherein the interaction ratio is provided to the target light source to cause the target light source to generate the target light pulses according to the interaction ratio such that an average number of EUV interactions corresponds to the interaction ratio.

30. The method of claim 25, wherein calculating the adjusted EUV pulse energy set point based on the determined interaction ratio comprises: The adjusted EUV pulse energy set point is calculated when the interaction ratio is within an unacceptable range or outside an acceptable range.

31. The method of claim 30, wherein the interaction ratio is within the unacceptable range as long as the dose is unstable, and the interaction ratio is outside the acceptable range as long as the dose is not within a stable range.

32. The method of claim 31 further comprising: Determining whether the interaction ratio is within the unacceptable range or outside the acceptable range includes analyzing whether the dose stability metric is within a range of a local maximum or within a range of a local minimum.

33. The method of claim 30, further comprising storing one or more of the unacceptable range and the acceptable range of the interaction ratio.

34. The method of claim 25, further comprising: Averaging the values ​​of the interaction ratios and outputting an average interaction ratio; as well as Wherein calculating the adjusted EUV pulse energy set point comprises calculating the adjusted EUV pulse energy set point based on the average interaction ratio.

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