A method and apparatus for measuring plasma extreme ultraviolet radiation energy and time domain waveforms

Abstract

The application provides a kind of plasma extreme ultraviolet radiation energy and time domain waveform measurement method and device, it is related to semiconductor manufacturing technology field, the method comprises: the wavelength selection processing is carried out to the extreme ultraviolet wave band radiation light, to separate out single wavelength extreme ultraviolet light, and the single wavelength extreme ultraviolet light is converged, to obtain the single wavelength extreme ultraviolet light after convergence;The single wavelength extreme ultraviolet light after convergence is photoelectric conversion processing, corresponding current signal is generated;The current signal is collected and processed, the time domain waveform of the single wavelength extreme ultraviolet light is obtained according to the time domain waveform of the current signal, and the radiation energy of the single wavelength extreme ultraviolet light in 2pi solid angle is calculated according to the integral intensity of the current signal and the measurement solid angle.The application can measure the single wavelength extreme ultraviolet radiation energy and time domain waveform of plasma simultaneously.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing technology, and in particular to a method for measuring plasma extreme ultraviolet radiation energy and time-domain waveform. Background Technology

[0002] In the field of advanced semiconductor manufacturing, extreme ultraviolet (EUV) lithography has become a key technology for the mass production of chips at process nodes of 5 nanometers and below. The EUV lithography machine employs a laser-driven plasma EUV source, which uses a high-power carbon dioxide laser to drive the plasma. A molybdenum / silicon multilayer ellipsoidal mirror with a solid angle of 5.5° collects and transmits the EUV radiation emitted by the plasma, ultimately outputting EUV light with a power greater than 250W and a center wavelength of 13.5nm (2% bandwidth). Besides lithography applications, many metrology and measurement processes in the EUV lithography process also require EUV sources. Furthermore, with the continuous development of lithography technology, advanced lithography technologies based on shorter wavelength EUV sources (e.g., a center wavelength of 6.7nm) have entered the principle verification and technology evaluation stage. Therefore, in the development of EUV lithography and metrology sources, the measurement of the energy and time-domain waveform of single-wavelength EUV radiation from the plasma is crucial.

[0003] Currently, the most common methods for measuring the energy of single-wavelength extreme ultraviolet (EUV) radiation from plasma mainly employ a pair of molybdenum / silicon multilayer film plane mirrors and a photodiode (Chinese Journal of Lasers, 2025, 52(11):1104006). The specific principle involves using a pair of molybdenum / silicon multilayer film mirrors to filter out the 13.5 nm wavelength EUV light from the plasma, then using a photodiode to convert the light signal into a current signal, and finally calculating the EUV radiation energy value using the current signal. In addition, some researchers have used calibrated EUV spectrometers to measure the energy of single-wavelength EUV radiation from plasma (Acta Physica Sinica, 2008, 57(8):5100-5104). However, neither of these methods can measure the time-domain waveform of plasma EUV radiation. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method and apparatus for measuring plasma extreme ultraviolet radiation energy and time-domain waveform, which can simultaneously measure plasma single-wavelength extreme ultraviolet radiation energy and time-domain waveform.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0006] A method for measuring plasma extreme ultraviolet radiation energy and time-domain waveform, the method comprising:

[0007] Step 1: The aperture of the radiation emitted by the plasma extreme ultraviolet light source is limited to determine the measurement solid angle;

[0008] Step 2: Filter the radiation light after aperture limitation to obtain extreme ultraviolet radiation light;

[0009] Step 3: Perform wavelength selection processing on the extreme ultraviolet radiation to separate the extreme ultraviolet light of a single wavelength, and converge the extreme ultraviolet light of the single wavelength to obtain converged extreme ultraviolet light of a single wavelength.

[0010] Step 4: The converged single-wavelength extreme ultraviolet light is subjected to photoelectric conversion to generate a corresponding current signal.

[0011] Step 5: Acquire and process the current signal, obtain the time-domain waveform of the single-wavelength extreme ultraviolet light based on the time-domain waveform of the current signal, and calculate the radiation energy of the single-wavelength extreme ultraviolet light of the plasma within a 2π solid angle based on the integrated intensity of the current signal and the measured solid angle.

[0012] A plasma extreme ultraviolet radiation energy and time-domain waveform measurement device includes:

[0013] Vacuum maintenance module, used to provide and maintain the vacuum environment required for extreme ultraviolet light transmission;

[0014] An aperture limiting module, disposed within the vacuum maintaining module, is used to limit the aperture of the radiation emitted by the plasma extreme ultraviolet light source to determine the measurement solid angle;

[0015] A filtering module, disposed within the vacuum maintaining module, is used to filter the radiation light processed by the aperture limiting module to obtain extreme ultraviolet radiation light.

[0016] A wavelength selection and convergence module is disposed within the vacuum maintenance module, used to perform wavelength selection on the extreme ultraviolet radiation to separate a single wavelength of extreme ultraviolet light, and to converge the single wavelength of extreme ultraviolet light.

[0017] A photoelectric conversion module, disposed within the vacuum maintenance module, is used to receive focused extreme ultraviolet light of a single wavelength and convert it into an electric current signal;

[0018] The signal processing module, connected to the photoelectric conversion module, is used to acquire and process the current signal to obtain the time-domain waveform of the single-wavelength extreme ultraviolet light and calculate its radiant energy.

[0019] Furthermore, the vacuum maintenance module includes a vacuum chamber and a vacuum pump assembly connected to the vacuum chamber.

[0020] Furthermore, the aperture limiting module is an aperture stop.

[0021] Furthermore, the filtering module is a filter film.

[0022] Furthermore, the wavelength selection and convergence module is a multilayer curved surface mirror.

[0023] Furthermore, the photoelectric conversion module is a fast photodiode.

[0024] Furthermore, the surface of the multilayer curved mirror is coated with a multilayer film system for reflecting extreme ultraviolet light at a specific center wavelength, wherein the specific center wavelength is selected from 13.5 nm or 6.7 nm.

[0025] Furthermore, the relative spatial positions of the aperture limiting module, the wavelength selection and convergence module, and the photoelectric conversion module satisfy the imaging relationship.

[0026] Furthermore, the vacuum pump assembly comprises a combination of a mechanical pump and a molecular pump.

[0027] The above-described solution of the present invention has at least the following beneficial effects:

[0028] It uses only a single multilayer curved mirror and does not require a diffraction grating and an extreme ultraviolet camera like extreme ultraviolet spectrometers. Because the multilayer curved mirror focuses the single wavelength of extreme ultraviolet light from the plasma onto the fast photodiode, the brightness of the fast photodiode is greatly improved, enabling high-sensitivity measurements. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of the plasma extreme ultraviolet radiation energy and time-domain waveform measurement device of the present invention;

[0030] In the picture:

[0031] 1-Plasma extreme ultraviolet light source; 2-Plasma; 3-Vacuum chamber; 4-Vacuum pump group; 5-Aperture; 6-Filter film; 7-Multilayer curved surface mirror; 8-Fast photodiode; 9-Readout circuit. Detailed Implementation

[0032] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0033] like Figure 1 As shown, an embodiment of the present invention provides a plasma extreme ultraviolet radiation energy and time-domain waveform measurement device, comprising:

[0034] Vacuum maintenance module, used to provide and maintain the vacuum environment required for extreme ultraviolet light transmission;

[0035] An aperture limiting module, disposed within the vacuum maintaining module, is used to limit the aperture of the radiation emitted by the plasma extreme ultraviolet light source 1 to determine the measurement solid angle;

[0036] A filtering module, disposed within the vacuum maintaining module, is used to filter the radiation light processed by the aperture limiting module to obtain extreme ultraviolet radiation light.

[0037] A wavelength selection and convergence module is disposed within the vacuum maintenance module, used to perform wavelength selection on the extreme ultraviolet radiation to separate a single wavelength of extreme ultraviolet light, and to converge the single wavelength of extreme ultraviolet light.

[0038] A photoelectric conversion module, disposed within the vacuum maintenance module, is used to receive focused extreme ultraviolet light of a single wavelength and convert it into an electric current signal;

[0039] The signal processing module, connected to the photoelectric conversion module, is used to acquire and process the current signal to obtain the time-domain waveform of the single-wavelength extreme ultraviolet light and calculate its radiant energy.

[0040] In this embodiment, through the coordination of the wavelength selection and convergence module, the fast photoelectric conversion module, and the signal processing module, while filtering out single-wavelength extreme ultraviolet light, the instantaneous changes of the light signal are captured by a fast photodiode 8 with a rise time of <1 nanosecond. Then, the current signal is converted into a digital waveform through the readout circuit. For the first time, the calculation of single-wavelength extreme ultraviolet radiation energy and the recording of time-domain waveforms are completed simultaneously, providing complete data support for the dynamic characteristic optimization of extreme ultraviolet light sources (such as photolithography light sources and quantitative detection light sources).

[0041] In a preferred embodiment of the present invention, the vacuum maintaining module includes a vacuum chamber 3 and a vacuum pump group 4 connected to the vacuum chamber 3; the aperture limiting module is an aperture stop 5; the filtering module is a filter film 6; the wavelength selection and convergence module is a multilayer curved surface mirror 7; the photoelectric conversion module is a fast photodiode 8; the surface of the multilayer curved surface mirror 7 is coated with a multilayer film system for reflecting extreme ultraviolet light at a specific center wavelength, wherein the specific center wavelength is selected from 13.5 nm or 6.7 nm; the relative spatial positions of the aperture limiting module, the wavelength selection and convergence module, and the photoelectric conversion module satisfy the imaging relationship; the vacuum pump group 4 includes a combination of a mechanical pump and a molecular pump.

[0042] In this embodiment, each module is fixed in the vacuum chamber 3 (made of stainless steel to avoid gas adsorption affecting the vacuum level) according to the light propagation path. The aperture 5 (a perforated stainless steel sheet) is fixed on the initial propagation path of the radiation light from the plasma extreme ultraviolet light source 1. The filter film 6 (made of pure zirconium, purity ≥99.9999%, thickness 200nm, supported by a stainless steel ring) is fixed behind the aperture 5. The multilayer curved reflector 7 (with a quartz substrate and mounted on a three-dimensional adjustable lens frame) is fixed behind the filter film 6. The photosensitive surface of the fast photodiode 8 (photosensitive surface 1mm×1mm, rise time ≤700 picoseconds, such as the AXUVHS5 type) is aligned. The focal point of the multilayer curved mirror 7, and the relative spatial positions of the aperture 5, the multilayer curved mirror 7, and the fast photodiode 8 strictly satisfy the imaging relationship (i.e., the distance from the plasma 2 to the multilayer curved mirror 7 and the distance from the multilayer curved mirror 7 to the fast photodiode 8 match the radius of curvature of the multilayer curved mirror 7 to ensure that the light can be effectively focused); finally, the readout circuit 9 (FPGA circuit) is electrically connected to the fast photodiode 8 through wires, and the vacuum pump group 4 (a combination of mechanical pump and molecular pump, such as Edwards' STPiS2207 turbo dry pump and 35i magnetic levitation molecular pump) is connected to the vacuum chamber 3 through pipes.

[0043] In this embodiment, vacuum pump group 4 is started. First, the mechanical pump (turbine dry pump) is turned on to pre-evacuate the vacuum chamber 3. After the vacuum level in the chamber drops below 20 Pa, the molecular pump (magnetic levitation molecular pump) is turned on to perform fine evacuation, and finally the vacuum level in the vacuum chamber 3 is maintained at 10 Pa. -3 Below Pa, this vacuum level can completely prevent the atmosphere (oxygen, nitrogen) from absorbing extreme ultraviolet light, ensuring lossless transmission of optical signals from plasma 2 to fast photodiode 8.

[0044] In this embodiment, when the plasma extreme ultraviolet light source 1 is activated, plasma 2 is generated internally (e.g., a carbon dioxide pulsed laser bombarding a 30μm tin droplet, or an Nd:YAG laser bombarding a 20μm gadolinium sphere). Plasma 2 emits a broad spectrum of radiation, including extreme ultraviolet light. At this time, an aperture 5 (4mm in diameter, 375mm in a straight line from plasma 2) located at the front of the propagation path restricts the radiation, allowing only the radiation passing through the aperture to continue propagating. The range of radiation passing through the aperture corresponds to a fixed measurement solid angle, providing an angular reference for subsequent calculation of the radiation energy within a 2π solid angle.

[0045] In this embodiment, the radiation light, after being limited by the aperture, continues to propagate to the filter film 6. The pure zirconium filter film 6 has band-selective transmission characteristics, allowing only extreme ultraviolet (EUV) radiation light (such as the 13.5nm or 6.7nm band) to pass through, completely blocking non-UV radiation light such as visible light and infrared light, avoiding stray light interference with subsequent wavelength selection and signal detection, and ensuring that the light signal entering the next stage is only EUV light. The EUV radiation light is incident on the multilayer curved mirror 7, and the multilayer film system on the surface of the multilayer curved mirror 7 (selected according to the target wavelength) plays a dual role of wavelength-selective reflection and light convergence.

[0046] If the target wavelength is 13.5nm (the core wavelength of current extreme ultraviolet lithography mass production process), the surface of the multilayer curved reflector 7 is coated with 50 layers of alternating molybdenum / silicon multilayer film (each layer is only a few nanometers thick), reflecting only 13.5nm (2% bandwidth) extreme ultraviolet light while blocking other wavelengths of extreme ultraviolet light; if the target wavelength is 6.7nm (a candidate wavelength for next-generation advanced lithography), the surface of the multilayer curved reflector 7 is coated with 200 layers of alternating B4C / La multilayer film, reflecting only 6.7nm (2% bandwidth) extreme ultraviolet light; since the multilayer curved reflector 7 is curved (such as a spherical reflector with a curvature radius of 250mm) and its position has been calibrated by a three-dimensional adjustment frame, the reflected single-wavelength extreme ultraviolet light will be precisely focused onto the photosensitive surface of the fast photodiode 8, improving the light energy density of the photosensitive surface.

[0047] The converged single-wavelength extreme ultraviolet light irradiates the photosensitive surface of the fast photodiode 8. Based on the photoelectric effect, the fast photodiode 8 directly converts the light signal into a corresponding current signal. Since its rise time is ≤1 nanosecond (e.g., 700 picoseconds), it can capture the instantaneous intensity change of extreme ultraviolet light in real time, ensuring that the time domain characteristics of the current signal are completely consistent with the original light signal.

[0048] The readout circuit 9 (FPGA circuit) acquires the current signal output by the fast photodiode 8 in real time and performs two core processing steps:

[0049] The acquired current signal is converted into a digital signal. The time-domain waveform of this digital signal is the time-domain waveform of a single wavelength extreme ultraviolet light, which can directly reflect the dynamic characteristics of the extreme ultraviolet light, such as pulse duration and peak intensity. The current integral intensity is obtained by integrating the current signal. Combined with the measurement solid angle determined by the aperture 5, the total radiation energy of the plasma 2 within the 2π solid angle of a single wavelength extreme ultraviolet light can be calculated by proportional conversion, thus realizing energy quantification.

[0050] This invention overcomes the limitations of existing technologies (such as the molybdenum / silicon planar mirror method and extreme ultraviolet spectrometers) that can only measure energy, and for the first time simultaneously acquires the radiation energy and dynamic temporal characteristics of a single wavelength of extreme ultraviolet light. The multilayer curved mirror 7 focuses the light signal and improves the brightness of the photosensitive surface, solving the problem of weak extreme ultraviolet light signals. The vacuum environment avoids light absorption, and the filter film and the multilayer curved mirror 7 ensure signal purity. The three together guarantee measurement sensitivity and data accuracy. Only one multilayer curved mirror 7 is used to complete wavelength selection and light focusing, eliminating the need for complex components such as diffraction gratings and extreme ultraviolet cameras. The vacuum pump group automatically controls the vacuum, and the readout circuit outputs results in real time, reducing equipment costs and operational difficulty. By changing the multilayer film system (molybdenum / silicon corresponds to 13.5nm, B4C / La corresponds to 6.7nm) and adjusting the position of the aperture and the multilayer curved mirror 7, it can be adapted to different plasma light sources such as tin / gadolinium.

[0051] Before performing any of the following steps, the preliminary operations of device assembly and vacuum environment construction must be completed: Connect the plasma extreme ultraviolet light source 1 (which can generate plasma 2 internally, such as by bombarding tin droplets, gadolinium spheres, or other targets with a carbon dioxide pulsed laser or an Nd:YAG pulsed laser) to the stainless steel vacuum chamber 3 via a flange. Start the vacuum pump group 4 (composed of a mechanical pump such as the Edwards STPiS2207 turbo dry pump and a molecular pump such as the 35i magnetic levitation molecular pump). First, start the mechanical pump to pre-evacuate the vacuum chamber 3. After the vacuum level in the chamber drops below 20 Pa, start the molecular pump for fine evacuation, and finally maintain the vacuum level in the vacuum chamber 3 at 10 Pa. -3 Below Pa, to prevent atmospheric gases such as oxygen and nitrogen from absorbing extreme ultraviolet light, ensuring lossless transmission of optical signals.

[0052] A method for measuring plasma extreme ultraviolet radiation energy and time-domain waveform, the method comprising:

[0053] Step 1 involves aperture confinement of the radiation emitted by the plasma extreme ultraviolet light source to determine the measurement solid angle, specifically including:

[0054] Inside the vacuum chamber 3, an aperture limiting component, aperture 5, is fixedly installed on the initial propagation path of the radiation emitted by the plasma extreme ultraviolet light source 1. Aperture 5 is a rigid, fixed perforated stainless steel sheet with a small hole diameter of 4 mm, and the straight-line distance between aperture 5 and plasma 2 is adjusted to 375 mm. When the plasma extreme ultraviolet light source 1 is activated, high-temperature, high-density plasma 2 is generated inside the light source (such as plasma generated by a carbon dioxide pulsed laser bombarding a 30-micrometer diameter tin droplet, or plasma generated by an Nd:YAG pulsed laser bombarding a 20-micrometer diameter solid gadolinium sphere). Plasma 2 emits a broad spectrum of radiation, including extreme ultraviolet, visible, and infrared light. When this radiation propagates to aperture 5, it can only continue to propagate into the subsequent optical path through the 4-millimeter small hole on aperture 5. Radiation that does not pass through the small hole is blocked by aperture 5. The range of radiation passing through the small hole of aperture 5 corresponds to a fixed spatial angle, which is the measurement solid angle for this measurement, providing a clear angular reference for subsequent calculations of the plasma's radiation energy within a 2π solid angle.

[0055] Step 2 involves filtering the emitted light after aperture confinement to obtain extreme ultraviolet (EUV) radiation, specifically including:

[0056] Inside the vacuum chamber 3, a filter membrane 6 is fixedly installed on the path of radiation light propagation behind the aperture 5. The filter membrane 6 is made of pure zirconium material with a purity of ≥99.9999% and a thickness of 200 nanometers. Its outermost edge is provided with a stainless steel ring to support the pure zirconium membrane and rigidly connect the filter membrane 6 to the vacuum chamber 3, ensuring that the filter membrane 6 is stable and does not shift in the vacuum environment.

[0057] The radiation light (including extreme ultraviolet light, visible light, infrared light, etc.) that has passed through the aperture limitation in step 1 continues to propagate to the filter film 6. The filter film 6, made of pure zirconium material, has band selective transmission characteristics, allowing only extreme ultraviolet radiation light to pass through, while completely blocking non-extreme ultraviolet radiation light such as visible light and infrared light. This separates pure extreme ultraviolet radiation light from the broad spectrum of radiation light, avoiding interference from stray light in the non-extreme ultraviolet band in the subsequent measurement process.

[0058] Step 3 involves performing wavelength selection processing on the extreme ultraviolet (EUV) radiation to separate single-wavelength EUV light, and then converging the single-wavelength EUV light to obtain converged single-wavelength EUV light. Specifically, this includes:

[0059] Inside the vacuum chamber 3, a multilayer curved reflector 7, a wavelength selection and converging component, is installed on the extreme ultraviolet (EUV) radiation propagation path behind the filter film 6. The substrate material of the multilayer curved reflector 7 is quartz, and its surface is coated with a multilayer film system for reflecting EUV light of a specific center wavelength. It is mounted on a three-dimensional adjustable lens mounting bracket, and the spatial position of the multilayer curved reflector 7 can be adjusted by adjusting the mounting bracket. At the same time, it is necessary to ensure that the relative spatial positions of the aperture 5, the multilayer curved reflector 7, and the subsequent fast photodiode 8 satisfy the imaging relationship. That is, the straight-line distance from the plasma 2 to the multilayer curved reflector 7 and the straight-line distance from the multilayer curved reflector 7 to the fast photodiode 8 must match the radius of curvature of the multilayer curved reflector 7 (e.g., 250 mm).

[0060] Wavelength selection and light convergence process:

[0061] If the target measurement wavelength is 13.5nm (the core wavelength of the current extreme ultraviolet lithography mass production process, with a bandwidth of 2%), the surface of the multilayer curved reflector 7 is coated with 50 layers of molybdenum / silicon alternating multilayer films (each layer is only a few nanometers thick). When the extreme ultraviolet radiation obtained in step 2 is incident on the multilayer curved reflector 7, the multilayer curved reflector 7 only reflects the extreme ultraviolet light with a wavelength of 13.5nm, while blocking extreme ultraviolet light of other wavelengths, thus achieving the separation of a single wavelength (13.5nm) of extreme ultraviolet light. Subsequently, since the multilayer curved reflector 7 has a curved structure, the separated 13.5nm extreme ultraviolet light is focused by the multilayer curved reflector 7 and propagates towards the photosensitive surface of the fast photodiode 8.

[0062] If the target measurement wavelength is 6.7 nm (a candidate wavelength for next-generation advanced lithography technology, with a bandwidth of 2%), the surface of the multilayer curved mirror 7 is coated with 200 layers of alternating B4C / La multilayer films (each layer is only a few nanometers thick). When extreme ultraviolet (EUV) radiation is incident on the multilayer curved mirror 7, the multilayer curved mirror 7 only reflects EUV light with a wavelength of 6.7 nm, blocking EUV light of other wavelengths, thus completing the separation of a single wavelength (6.7 nm) of EUV light; then, the 6.7 nm EUV light is focused by the curved structure and propagated toward the photosensitive surface of the fast photodiode 8; finally, through the above process, focused EUV light of a single target wavelength is obtained.

[0063] Step 4 involves photoelectric conversion of the converged single-wavelength extreme ultraviolet light to generate a corresponding current signal, specifically including:

[0064] The AXUVHS5 type extreme ultraviolet fast photodiode 8 is used as the photoelectric conversion component. Its photosensitive area size is 1mm×1mm and its rise time is 700 picoseconds, ensuring that it can respond in real time to the instantaneous intensity change of a single wavelength of extreme ultraviolet light.

[0065] The fast photodiode 8 is fixed on the three-dimensional adjustment lens mounting bracket and placed in the vicinity of the focal point of the multilayer curved reflector 7 in the vacuum chamber 3. By adjusting the X-axis, Y-axis and Z-axis displacement of the three-dimensional adjustment bracket, the center of the photosensitive surface of the fast photodiode 8 is made to coincide with the converging optical path axis of the multilayer curved reflector 7 until the photosensitive surface can completely receive the converged single wavelength extreme ultraviolet light (through pre-test verification: when extreme ultraviolet light is incident, the initial current signal strength output by the fast photodiode 8 is stable and there is no obvious fluctuation).

[0066] A shielded wire is used to electrically connect the signal output terminal of the fast photodiode 8 to the signal input terminal of the readout circuit 9 (FPGA circuit). The outer layer of the shielded wire is wrapped with a metal shielding layer to isolate the influence of external electromagnetic interference and weak internal electromagnetic noise on the subsequent current signal transmission of the vacuum chamber 3.

[0067] In step 3, the converged single-wavelength extreme ultraviolet light (13.5nm or 6.7nm) is incident perpendicularly onto the photosensitive surface of the fast photodiode 8. The semiconductor material on the surface of the photosensitive surface (adapted to the extreme ultraviolet light response characteristics) absorbs the extreme ultraviolet photon energy and is excited to generate photogenerated electron-hole pairs.

[0068] A forward bias voltage is applied to the fast photodiode 8 through an external circuit. Under the action of the bias electric field, photogenerated electrons move towards the positive electrode and photogenerated holes move towards the negative electrode, forming a continuous analog current signal. The intensity of this initial current signal changes synchronously with the instantaneous intensity of the incident extreme ultraviolet light. However, due to factors such as the collision of residual trace gas in the vacuum chamber 3 and the dark current of the fast photodiode 8 itself, the initial current signal is mixed with discrete noise spikes (manifested as a sudden increase or decrease in local current value, which does not conform to the true intensity change law of extreme ultraviolet light).

[0069] The readout circuit 9 sets the sampling frequency according to the rule that the sampling frequency is not less than twice the highest frequency of a single wavelength extreme ultraviolet light signal (to satisfy the Nyquist sampling theorem and ensure no signal aliasing). For example, when adapting to a 13.5nm extreme ultraviolet light pulse signal, the sampling frequency is set to 1GHz.

[0070] The readout circuit 9 samples the initial current signal in real time, converting the continuous analog current signal into discrete digital current signal data points. Each data point contains two sets of information: the horizontal axis parameter is the sampling time (denoted as X, in picoseconds), and the vertical axis parameter is the current value at the corresponding sampling time (denoted as Y, in microamps), forming an ordered set of data points {(X1, Y1), (X2, Y2), ..., (Xn, Yn)}, where X1 < X2 < ... < Xn (corresponding to the time series of the extreme ultraviolet light signal).

[0071] Using sampling time X as the horizontal axis and current value Y as the vertical axis, the above discrete data point set is mapped in a two-dimensional rectangular coordinate system to form a visual data point distribution map. In this map, the effective signal points (corresponding to the actual intensity change of extreme ultraviolet light) show a continuous fluctuation trend, while the noise points (discrete spikes) deviate from this trend.

[0072] Based on the time-domain characteristics of extreme ultraviolet light signals (pulsed radiation with rising, peak, and falling edges), three initial convex hull vertices are selected from the data point set:

[0073] Vertex A is the data point with the smallest X value (corresponding to the initial sampling time of the extreme ultraviolet light signal, i.e., the starting point of the pulse rising edge); Vertex C is the data point with the largest X value (corresponding to the final sampling time of the extreme ultraviolet light signal, i.e., the ending point of the pulse falling edge); Vertex B is the data point with the largest Y value (corresponding to the peak time of the extreme ultraviolet light signal, i.e., the sampling point with the highest pulse intensity); the above three vertices constitute the core contour line segments AB and BC of the initial convex hull.

[0074] The triangle construction and area feature judgment rules are as follows: For each point P(Xp, Yp) to be judged in the data point set other than A, B, and C, the adjacent vertices of the initial convex hull are sequentially taken (such as A and B, B and C) to form triangles with point P (such as △APB, △BPC); the spatial position of point P is determined by the numerical feature of the triangle area.

[0075] If the area of ​​the triangle is 0, it means that point P is located on the line segment formed by adjacent vertices (such as AB, BC), and is a valid signal point; if the area of ​​the triangle is positive, it means that point P is located inside the line segment (i.e., within the convex hull area), and is a valid signal point; if the area of ​​the triangle is negative, it means that point P is located outside the line segment (i.e., outside the convex hull area), and is a noise point (because this point deviates from the true intensity variation trend of extreme ultraviolet light).

[0076] If the point P to be judged is a valid signal point and is located outside the initial convex hull segment (with a positive area and exceeding the current convex hull contour), then point P is added to the convex hull vertex set, and the convex hull contour is updated (e.g., line segment AB is updated to AP and PB); this operation is repeated until all data points have been judged, and finally the smallest convex polygon that encloses all valid signal points (i.e., the optimized convex hull) is formed.

[0077] Remove all noise points identified as being located outside the convex hull from the data point set, and retain the valid signal points located inside the convex hull or on the boundary of the convex hull, forming the optimized data point set {(X1', Y1'), (X2', Y2'), ..., (Xm', Ym')} (m≤n).

[0078] The readout circuit 9 smooths the optimized data point set and restores the discrete effective signal points into a continuous analog current signal through linear interpolation. This signal is the pure current signal after noise removal, and its time-domain waveform (including the slope of the rising edge of the pulse, the peak position, the slope of the falling edge, and the pulse duration) is completely consistent with the time-domain waveform of the single-wavelength extreme ultraviolet light incident in step 3.

[0079] The purified current signal, optimized by the convex hull algorithm and the triangle area algorithm, is transmitted in real time to the signal processing unit of the readout circuit 9 through a shielded wire.

[0080] Step 5 involves acquiring and processing the current signal, obtaining the time-domain waveform of the single-wavelength extreme ultraviolet light based on the time-domain waveform of the current signal, and calculating the radiant energy of the single-wavelength extreme ultraviolet light within a 2π solid angle of the plasma based on the integrated intensity of the current signal and the measured solid angle. Specifically, this includes:

[0081] The signal processing unit readout circuit 9 (using FPGA circuitry) is electrically connected to the fast photodiode 8 via wires to ensure that the readout circuit 9 can receive the current signal output by the fast photodiode 8 in real time.

[0082] The readout circuit 9 continuously and in real-time acquires the pure current signal output by the fast photodiode 8, following the rule that the sampling frequency is not less than twice the highest frequency of the single-wavelength extreme ultraviolet light signal (in accordance with the Nyquist sampling theorem, avoiding waveform distortion caused by signal aliasing). During the acquisition process, the analog-to-digital converter (ADC) module of the readout circuit 9 needs to synchronously record two sets of key information for each sampling point: one is the sampling timestamp (with the time zero point being the starting moment of the rising edge of the extreme ultraviolet light pulse, accurate to the picosecond level), and the other is the current amplitude at the corresponding moment (in microamps, reflecting the intensity of the extreme ultraviolet light at that moment).

[0083] The collected discrete digital signal points containing timestamps and current amplitudes are temporarily stored in the buffer unit of the readout circuit 9. At the same time, the digital signals are pre-processed to remove isolated anomalies caused by transient electromagnetic interference (judgment criteria: the current amplitude of a digital signal point exceeds ±50% of the average current amplitude of its 10 adjacent sampling points, and there is no corresponding extreme ultraviolet light intensity change logic), further ensuring the accuracy of subsequent waveform reconstruction and energy calculation.

[0084] The waveform generation module of the readout circuit 9 uses the sampling timestamp as the horizontal axis (time dimension, unit: picosecond) and the preprocessed current amplitude as the vertical axis (intensity dimension, unit: microamp). It connects discrete digital signal points into a continuous waveform curve using a linear interpolation algorithm. This curve is the time-domain waveform of the single-wavelength extreme ultraviolet light incident on the photosensitive surface of the fast photodiode 8 in step 3. The rising edge of the waveform corresponds to the process of the extreme ultraviolet light intensity rising from the baseline to the peak value, and the slope of the rising edge reflects the rate of increase of the extreme ultraviolet light intensity. The peak point of the waveform corresponds to the moment when the current amplitude is the largest, that is, the moment when the extreme ultraviolet light intensity is the highest. The falling edge of the waveform corresponds to the process of the extreme ultraviolet light intensity falling from the peak value to the baseline, and the slope of the falling edge reflects the rate of decay of the extreme ultraviolet light intensity. The time interval between the two ends of the waveform (from the starting point of the rising edge to the ending point of the falling edge) is the total duration of the extreme ultraviolet light pulse.

[0085] The reconstructed time-domain waveform is displayed in real time on the visualization interface of the readout circuit 9, and simultaneously stored in a standardized data format (such as CSV) to a local storage unit or an external storage device. The stored data must include key characteristic parameters of the waveform: rise time (time from 10% peak current to 90% peak current), peak current value and corresponding time, fall time (time from 90% peak current to 10% peak current), and total pulse duration, providing direct time-domain data support for subsequent dynamic characteristic optimization of the plasma extreme ultraviolet light source 1 (such as adjusting the parameters of the laser bombardment target to optimize the pulse waveform).

[0086] The integration module of the readout circuit 9 performs integration on the preprocessed discrete digital signal to calculate the current integral intensity. The specific operation logic is as follows: the effective radiation period of the extreme ultraviolet light pulse is used as the integration interval. The starting point of this interval is the rising edge start time (the moment when the current amplitude first reaches 10% of the peak current) and the ending point is the falling edge end time (the moment when the current amplitude first falls back to 10% of the peak current). Within this interval, the current amplitudes of all discrete digital signal points are accumulated and summed. The sum obtained is the current integral intensity (unit: microampere-picosecond).

[0087] It should be noted that the current integral intensity is directly proportional to the total radiant energy of a single wavelength of extreme ultraviolet light within the solid angle being measured. Since the photoelectric conversion efficiency of the fast photodiode 8 (the current value converted from a unit energy of extreme ultraviolet light) has been determined through previous calibration experiments (calibration method: using a standard extreme ultraviolet light source with known radiant energy to irradiate the fast photodiode 8, and establishing the correspondence between the current integral intensity and the standard radiant energy), the current integral intensity can be directly used as a quantitative characterization parameter for measuring the radiant energy within the solid angle.

[0088] Based on the structural parameters of aperture 5 (diameter of 4mm) and the straight-line distance between aperture 5 and plasma 2 (375mm) in step 1, the specific angle value Ω1 of the measured solid angle is calculated through geometric relationships. The core logic is as follows: the spatial angle corresponding to the cone formed by plasma 2 as the vertex and the edge of the aperture 5 as the boundary is the measured solid angle Ω1; while the 2π solid angle is the fixed angle value corresponding to the hemispherical spatial region with plasma 2 as the vertex (a known physical quantity, corresponding to the coverage range of the hemispherical space); the proportional calculation module of the readout circuit 9 determines the proportional coefficient k between the 2π solid angle and the measured solid angle based on the above angle value, k=2π / Ω1, which reflects that the 2π solid angle is a multiple of the measured solid angle.

[0089] The readout circuit 9 multiplies the current integral intensity obtained in step 4 by the scaling factor k to obtain the equivalent current integral intensity corresponding to the 2π solid angle. Then, combining this with the previously calibrated photoelectric conversion efficiency of the fast photodiode 8, it converts the equivalent current integral intensity corresponding to the 2π solid angle into the total radiant energy (in joules) of the plasma 2 within a single wavelength of extreme ultraviolet light within the 2π solid angle. The converted radiant energy value within the 2π solid angle is synchronously output to the display interface along with the time-domain waveform reconstructed in step 3, and automatically recorded in the measurement report. Simultaneously, the readout circuit 9 performs a logical verification of the calculation results. If the radiant energy value exceeds the conventional radiant energy range of this type of plasma extreme ultraviolet light source 1 (e.g., the 13.5nm extreme ultraviolet light generated by carbon dioxide laser bombardment of tin droplets, where the radiant energy within the 2π solid angle is typically around 10...), the circuit will detect the radiant energy. -6 ~10 -5 If the measurement is on the order of joules, an early warning signal will be issued, prompting the operator to check whether the solid angle calculation is accurate or whether the photoelectric conversion efficiency calibration is faulty, so as to ensure the reliability of the final measurement result.

[0090] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for measuring plasma extreme ultraviolet radiation energy and time-domain waveform, characterized in that, The method includes: Step 1: The aperture of the radiation emitted by the plasma extreme ultraviolet light source is limited to determine the solid angle of measurement. Inside the vacuum chamber (3), an aperture limiting component aperture (5) is fixedly installed on the initial propagation path of the radiation emitted by the plasma extreme ultraviolet light source (1). The plasma extreme ultraviolet light source (1) is started, and high-temperature and high-density plasma (2) is generated inside the light source. The plasma (2) emits broadband radiation. When the broadband radiation propagates to the aperture (5), it continues to propagate to the subsequent light path through the 4 mm aperture on the aperture (5). The radiation that does not pass through the aperture is blocked by the aperture (5). Step 2: Filter the radiation light after aperture limitation to obtain extreme ultraviolet radiation light; Step 3: Perform wavelength selection processing on the extreme ultraviolet radiation to separate the extreme ultraviolet light of a single wavelength, and converge the extreme ultraviolet light of the single wavelength to obtain converged extreme ultraviolet light of a single wavelength. Step 4: The converged single-wavelength extreme ultraviolet light is subjected to photoelectric conversion to generate a corresponding current signal. Step 5: Acquire and process the current signal, obtain the time-domain waveform of the single-wavelength extreme ultraviolet light based on the time-domain waveform of the current signal, and calculate the radiation energy of the single-wavelength extreme ultraviolet light of the plasma within a 2π solid angle based on the integrated intensity of the current signal and the measured solid angle. Specifically, the plasma extreme ultraviolet radiation energy and time-domain waveform measurement device includes: Vacuum maintenance module, used to provide and maintain the vacuum environment required for extreme ultraviolet light transmission; An aperture limiting module, located within the vacuum maintaining module, is used to limit the aperture of the radiation emitted by the plasma extreme ultraviolet light source (1) to determine the measurement solid angle. A filtering module, disposed within the vacuum maintaining module, is used to filter the radiation light processed by the aperture limiting module to obtain extreme ultraviolet radiation light. A wavelength selection and convergence module is disposed within the vacuum maintenance module and is used to select the wavelength of the extreme ultraviolet radiation to separate a single wavelength of extreme ultraviolet light and to converge the single wavelength of extreme ultraviolet light; the wavelength selection and convergence module is a multilayer curved surface mirror (7). A photoelectric conversion module, disposed within the vacuum maintenance module, is used to receive focused extreme ultraviolet light of a single wavelength and convert it into an electric current signal; The signal processing module, connected to the photoelectric conversion module, is used to acquire and process the current signal to obtain the time-domain waveform of the single-wavelength extreme ultraviolet light and calculate its radiant energy.

2. The method for measuring plasma extreme ultraviolet radiation energy and time-domain waveform according to claim 1, characterized in that, The vacuum maintenance module includes a vacuum chamber (3) and a vacuum pump assembly (4) connected to the vacuum chamber (3).

3. The method for measuring plasma extreme ultraviolet radiation energy and time-domain waveform according to claim 1 or 2, characterized in that, The aperture limiting module is an aperture stop (5).

4. The method for measuring plasma extreme ultraviolet radiation energy and time-domain waveform according to claim 1, characterized in that, The filtering module is a filter film (6).

5. The method for measuring plasma extreme ultraviolet radiation energy and time-domain waveform according to claim 1, characterized in that, The photoelectric conversion module is a fast photodiode (8).

6. The method for measuring plasma extreme ultraviolet radiation energy and time-domain waveform according to claim 5, characterized in that, The surface of the multilayer curved mirror (7) is coated with a multilayer film system for reflecting extreme ultraviolet light at a specific center wavelength, wherein the specific center wavelength is selected from 13.5 nm or 6.7 nm.

7. The method for measuring plasma extreme ultraviolet radiation energy and time-domain waveform according to claim 1, characterized in that, The relative spatial positions of the aperture limiting module, the wavelength selection and convergence module, and the photoelectric conversion module satisfy the imaging relationship.

8. The method for measuring plasma extreme ultraviolet radiation energy and time-domain waveform according to claim 2, characterized in that, The vacuum pump assembly (4) comprises a combination of mechanical pumps and molecular pumps.

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