Excimer laser preionization electron measuring device and measuring method thereof

Abstract

The invention provides an excimer laser preionization electron density measuring method and device, and the method comprises the steps: turning off the power supply between a preionization unit and a main discharge electrode, and carrying out the preionization of environment gas in an area between the main discharge electrodes through the preionization unit, so as to form initial electrons; then forming an electric field for driving the initial electrons to directionally drift towards the main discharge electrodes in an area between the main discharge electrodes by using the electron density measurement unit; and finally, acquiring an electric signal variation generated by the main discharge electrode during initial electron directional drift by using an electron density measurement unit, and further calculating the electron density of the initial electrons. The electronic density of the initial electrons generated in the pre-ionization process can be directly calculated, errors caused by power loss when the electronic density is calculated through power in the prior art are avoided, and the pre-ionization effect can be reflected more accurately.

Description

Technical Field

[0001] This application relates to the technical field of excimer lasers, and in particular, to a device and method for measuring pre-ionization electrons of an excimer laser. Background Art

[0002] An excimer laser is a high-power pulsed laser with a mixture of rare gases and halogen gases as the working medium, and is widely used in fields such as semiconductor lithography, medical surgery, and material processing. Excimer lasers usually use a high-voltage pulsed power supply for excitation. However, since their working gases are usually in a high-pressure state (several atmospheres), direct discharge is likely to form non-uniform filamentary discharge, resulting in uneven energy distribution and affecting the quality and efficiency of laser output. To solve this problem, the prior art has introduced pre-ionization technology, that is, before the step of main discharge under the excitation of a high-voltage pulsed power supply, a sufficient number of seed electrons are pre-generated in the discharge space, so as to form spatially overlapping streamers during the main discharge process, that is, to generate uniform glow discharge, thereby improving the laser gain and output stability of the excimer laser.

[0003] The existing pre-ionization technologies usually share a high-voltage pulsed power supply with the main discharge electrodes, and generate ultraviolet radiation through discharge in the initial stage of the high voltage pulse, and then form initial electrons in the discharge region. Currently, the mainstream ultraviolet pre-ionization technologies mainly adopt two structural forms: pre-ionization needle array structure and corona pre-ionization rod structure, and these structures are usually symmetrically arranged on both sides of the main discharge. However, there is a significant technical defect in the existing pre-ionization technologies: that is, neither the pre-ionization needle array structure nor the corona pre-ionization rod structure has an effective means for directly measuring the density of seed electrons generated during the pre-ionization process. This technical gap makes it difficult for researchers to accurately evaluate the actual effect of pre-ionization, and even more impossible to achieve quantitative prediction of the pre-ionization effect.

[0004] Therefore, how to provide a device and a corresponding measurement method that can accurately measure the pre-ionization electron density has become a key technical problem to be solved urgently in this field. Summary of the Invention

[0005] This application aims to solve at least one of the technical problems in the related technologies to some extent.

[0006] To achieve the above object, the first aspect embodiment of this application proposes a method for measuring the pre-ionization electron density of an excimer laser, which is applied to the discharge cavity of the excimer laser. The discharge cavity is provided with main discharge electrodes, and a pre-ionization unit and an electron density measurement unit respectively electrically connected to the negative plate of the main discharge electrodes. The measurement method includes:

[0007] Drive the power supply between the pre-ionization unit and the main discharge electrode to turn off.

[0008] Drive the pre-ionization unit to conduct, so as to pre-ionize the ambient gas in the area between the main discharge electrodes and form initial electrons.

[0009] Drive the electron density measurement unit to conduct, so as to form an electric field in the area between the main discharge electrodes to drive the initial electrons to drift directionally towards the main discharge electrodes.

[0010] Use the electron density measurement unit to obtain the change amount of the electric signal generated by the directional drift of the initial electrons on the main discharge electrode, and calculate the electron density of the initial electrons based on the change amount of the electric signal.

[0011] Optionally, before the step of driving the electron density measurement unit to conduct, it further includes testing the supply voltage of the electron density measurement unit to form an electric field with a preset intensity threshold in the area between the main discharge electrodes.

[0012] Optionally, the electron density measurement unit includes a measurement circuit and a measurement device. The measurement circuit includes a DC power supply DC, a current-limiting resistor R1, a filter capacitor C1, and a diode D1. Wherein, the positive terminal of the DC power supply DC is grounded, the negative terminal of the DC power supply DC is connected to the first end of the current-limiting resistor R1, the second end of the current-limiting resistor R1 is connected to the negative plate of the main discharge electrode and the first end of the filter capacitor C1, the second end of the filter capacitor C1 is connected to the cathode of the diode D1 and the electric signal acquisition terminal, the anode of the diode D1 is connected to the positive plate of the main discharge electrode, and the measurement device is connected to the electric signal acquisition terminal.

[0013] Optionally, the change amount of the electric signal includes obtaining the change amount of the voltage of the main discharge electrode by using a measurement device, and the measurement device includes one of a high-voltage probe or an oscilloscope.

[0014] Optionally, the following relationship is satisfied between the change amount of the voltage of the main discharge electrode and the electron density of the initial electrons:

[0015]

[0016] Wherein, n e is the electron density of the initial electrons, Q is the total electric charge of the initial electrons drifting directionally to the main discharge electrode, e is the electron charge, V is the volume of the discharge area corresponding to the main discharge electrode, ΔU is the change amount of the voltage obtained by the electron density measurement unit, C d is the capacitance of the positive and negative plates of the main discharge electrode, ∈0 is the vacuum permittivity, ∈r is the relative dielectric constant of the medium between the main discharge electrodes, A is the effective area of the positive and negative plates of the main discharge electrodes, and d is the distance between the positive and negative plates of the main discharge electrodes.

[0017] Optionally, the pre-ionization unit includes an excitation circuit and a pre-ionization structure electrically connected to the excitation circuit. The excitation circuit is electrically connected to the pre-ionization structure and the negative plate of the main discharge electrode to provide a negative high-voltage drive for the pre-ionization process of the pre-ionization structure and the discharge process of the main discharge electrode.

[0018] Optionally, the pre-ionization structure includes one of a pre-ionization needle array structure and a corona pre-ionization rod structure; wherein,

[0019] The pre-ionization needle array structure includes a plurality of ionization needles arranged in an array. One end of each ionization needle is connected to the negative plate of the main discharge electrode, and the other end of each ionization needle is connected to the negative high-voltage output terminal of the excitation circuit;

[0020] The corona pre-ionization rod structure includes a plurality of pre-ionization rods, and the negative ends of each pre-ionization rod and the negative plate of the main discharge electrode are commonly connected to the negative high-voltage output terminal of the excitation circuit.

[0021] Optionally, the step of driving the power supply between the pre-ionization unit and the main discharge electrode to be turned off specifically includes:

[0022] In the case where the pre-ionization structure is the pre-ionization needle array structure, driving an isolation unit provided between the negative plate of the main discharge electrode and the ionization needle to isolate the negative plate of the main discharge electrode from the excitation circuit; or,

[0023] In the case where the pre-ionization structure is the corona pre-ionization rod structure, driving an isolation unit provided between the negative plate of the main discharge electrode and the excitation circuit to isolate the negative plate of the main discharge electrode from the excitation circuit.

[0024] Optionally, after the step of calculating the electron density of the initial electrons based on the change amount of the electrical signal, it further includes driving the isolation unit to conduct the power supply between the negative plate of the main discharge electrode and the ionization needle or the negative high-voltage output terminal of the excitation circuit.

[0025] An embodiment of the second aspect of the present application provides a pre-ionization electron density measurement device for an excimer laser, which is applied to the discharge chamber of an excimer laser. The measurement device includes calculating the electron density of the initial electrons by using the measurement method described in any one of the above.

[0026] The method and measuring device for measuring the pre-ionization electron density of an excimer laser provided by this application have at least the following beneficial effects:

[0027] This application provides a method and measuring device for measuring the pre-ionization electron density of an excimer laser, including turning off the power supply between the pre-ionization unit and the main discharge electrode, and then using the pre-ionization unit to pre-ionize the ambient gas in the area between the main discharge electrodes to form initial electrons; then using the electron density measuring unit to form an electric field in the area between the main discharge electrodes to drive the initial electrons to drift directionally towards the main discharge electrodes; finally, using the electron density measuring unit to obtain the change amount of the electric signal generated by the directional drift of the initial electrons on the main discharge electrodes, and then calculating the electron density of the initial electrons. This application can directly calculate the electron density of the initial electrons generated during the pre-ionization process, avoiding the error caused by power loss when calculating the electron density in the prior art, and can more accurately reflect the pre-ionization effect.

[0028] Additional aspects and advantages of this application will be given in part in the following description, will become apparent in part from the following description, or will be understood through the practice of this application. Description of the Drawings

[0029] The above-mentioned and / or additional aspects and advantages of this application will become apparent and easy to understand from the following description of the embodiments in conjunction with the drawings, where:

[0030] Figure 1 It is a schematic flowchart of a method for measuring the pre-ionization electron density of an excimer laser shown according to an embodiment of this application.

[0031] Figure 2 It is a schematic electrical connection diagram of a method for measuring the pre-ionization electron density of an excimer laser shown according to an embodiment of this application.

[0032] Figure 3 It is a schematic electrical connection diagram of another method for measuring the pre-ionization electron density of an excimer laser shown according to an embodiment of this application. Detailed Description of the Embodiments

[0033] The embodiments of this application will be described in detail below. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions from beginning to end. The embodiments described below with reference to the drawings are exemplary and are intended to explain this application and should not be construed as a limitation of this application.

[0034] Before the main discharge electrode in the high-pressure discharge chamber of an excimer laser discharges, the main purpose of pre-ionization is to generate a large number of initial electrons (or seed electrons or pre-ionization electrons) in the ambient gas by external means. These initial electrons will form an electron avalanche under the strong electric field of the main discharge electrode. When the number of initial electrons is large enough, the electron avalanches overlap spatially, making the discharge region between the main discharge electrodes exhibit uniform glow discharge rather than filamentary discharge. Research shows that glow discharge is more conducive to the formation of population inversion in the laser medium, thereby improving laser gain and output efficiency.

[0035] However, during the pre-ionization process of existing excimer lasers, the number of seed electrons provided by the pre-ionization process usually cannot be directly quantitatively measured. It can only be indirectly evaluated through discharge uniformity and laser output characteristics, or by measuring the voltage and current during the pre-ionization process and calculating the pre-ionization power through integration to indirectly estimate the number of initial electrons. However, the power consumed during the pre-ionization process will not be completely converted into initial electrons, and some energy will also be dissipated in the form of heat or others, resulting in a deviation in the estimated value of the number of initial electrons and ultimately affecting the control of laser gain and output efficiency.

[0036] Based on the above problems, the present application provides a device and method for measuring the pre-ionization electron density of an excimer laser. By forming an electric field at both ends of the main discharge electrode to drive the initial electrons to move towards the main discharge electrode, and successively calculating the total charge and electron density of the initial electrons generated during the pre-ionization process based on the detected voltage change towards the main discharge electrode. Compared with the prior art, the present application can directly calculate the electron density of the initial electrons generated during the pre-ionization process, avoiding the error caused by power loss when calculating the electron density through power, and being able to more accurately reflect the pre-ionization effect.

[0037] According to the first aspect of the present application, as Figures 1 to 3 shown, a method for measuring the pre-ionization electron density of an excimer laser is provided. This measurement method is applied to the discharge chamber of an excimer laser and is used to measure and calculate the electron density of the initial electrons generated during the pre-ionization process in the discharge chamber of the excimer laser. Among them, the discharge chamber is provided with a main discharge electrode, as well as a pre-ionization unit and an electron density measurement unit respectively electrically connected to the negative plate of the main discharge electrode. The measurement method specifically includes the following steps:

[0038] First, execute step S1 to turn off the power supply between the pre-ionization unit and the main discharge electrode.

[0039] It can be understood that the pre-ionization unit generally includes an excitation circuit and a pre-ionization structure electrically connected to the excitation circuit. The excitation circuit is electrically connected to the pre-ionization structure and the negative plate of the main discharge electrode to provide a negative high-voltage drive for pre-ionizing the pre-ionization structure and discharging the main discharge electrode. By driving the power supply between the pre-ionization unit and the main discharge electrode to be turned off, the excitation circuit can independently supply power for the pre-ionization process of the pre-ionization structure, rather than for the discharge process of the main discharge electrode. Thus, initial electrons are formed in the region between the main discharge electrodes, and an electric field is formed between the main discharge electrodes for the subsequent electron density measurement unit, providing conditions for driving the initial electrons to drift directionally towards the main discharge electrode.

[0040] As an example, step S1 can specifically be that the driving isolation unit switches the electrical connection state between the negative plate of the main discharge electrode and the excitation circuit from the conducting state to the off state. The isolation unit can be an insulating sheath that is disposed around the periphery of the negative plate of the main discharge electrode and is used to block the electrical connection state between the negative plate of the main discharge electrode and the excitation circuit, or it can be a switch control device that blocks the electrical connection state between the negative plate of the main discharge electrode and the excitation circuit. The insulating sheath includes, but is not limited to, one of an insulating rubber sleeve or an insulating ceramic sheath. At the same time, the isolation unit can be directly disposed between the negative plate of the main discharge electrode and the excitation circuit, or it can be disposed between the negative plate of the main discharge electrode and the pre-ionization structure. The present application does not limit the structural form and setting of the isolation unit, and can be flexibly set according to the electrical connection state between the negative plate of the main discharge electrode and the pre-ionization structure.

[0041] As an example, the pre-ionization structure can include, but is not limited to, any one of a pre-ionization needle array structure or a corona pre-ionization rod structure.

[0042] As Figure 2 shown, the pre-ionization needle array structure is usually used in medium and low repetition rate excimer lasers in the range of dozens of Hz to hundreds of Hz, and includes a plurality of ionization needles arranged in a fixed interval array. Each ionization needle is composed of an upper contact electrode, a ceramic block, and a J-shaped metal plate. The upper end of the upper contact electrode is connected to the negative high-voltage output terminal of the excitation circuit. The upper end of the upper contact electrode is connected to the lower end of the J-shaped metal plate through the ceramic block. The upper end of the J-shaped metal plate is connected to the negative plate of the main discharge electrode, such that the excitation circuit is equivalent to being connected in series with the negative plate of the main discharge electrode through the ionization needle (after breakdown along the ceramic block). The isolation unit is configured as an insulating sheath disposed around the periphery of the negative plate of the main discharge electrode to cut off the power supply between the negative plate of the main discharge electrode and the ionization needle before the pre-ionization process.

[0043] As Figure 3As shown, the corona pre-ionization rod structure is usually used in kHz-level high-repetition-rate excimer lasers, including a pre-ionization rod. Each pre-ionization rod consists of a grounded metal rod, a ceramic sleeve, and a 3 / 4 circular metal tube. The ceramic sleeve isolates the grounded metal rod from the 3 / 4 circular metal tube. Among them, the 3 / 4 circular metal tube, as the negative end of the pre-ionization rod and the negative plate of the main discharge electrode, is connected to the negative high-voltage output terminal of the excitation circuit together, which is equivalent to connecting the negative plate of the main discharge electrode and the pre-ionization rod in parallel. The grounded metal rod is connected to the positive plate of the main discharge electrode and grounded, and the isolation unit is configured as a switch control device arranged between the negative plate of the main discharge electrode and the negative high-voltage output terminal of the excitation circuit to cut off the power supply between the negative plate of the main discharge electrode and the negative high-voltage output terminal of the excitation circuit before the pre-ionization process.

[0044] Then, step S2 is executed to drive the pre-ionization unit to conduct, so as to pre-ionize the ambient gas in the area between the main discharge electrodes and form initial electrons.

[0045] It can be understood that the excitation circuit is usually connected in series with a capacitor Cn, a magnetic switch, and a peaking capacitor Cp. Among them, the first end of the magnetic switch is connected to the negative voltage end of the negative high-voltage power supply, the second end is connected to the negative end of the pre-ionization structure and the first end of the peaking capacitor, and the second end of the peaking capacitor is connected to the positive plate of the main discharge electrode. The magnetic switch is used to drive and switch the on-off state of the power supply between the negative high-voltage power supply and the pre-ionization structure, and the peaking capacitor Cp is used to steepen the negative high-voltage pulse during the charge and discharge process.

[0046] Thus, when the magnetic switch is in the on state, the power supply between the negative high-voltage power supply and the pre-ionization structure is turned on, and the pre-ionization structure pre-ionizes the ambient gas in the area between the main discharge electrodes and forms initial electrons.

[0047] Next, step S3 is executed to drive the electron density measurement unit to conduct, so as to form an electric field that drives the initial electrons to drift directionally towards the main discharge electrode in the area between the main discharge electrodes;

[0048] It can be understood that the electron density measurement unit may include a measurement circuit. The measurement circuit includes a DC power supply DC, a current-limiting resistor R1, a filter capacitor C1, and a diode D1. Among them, the positive end of the DC power supply DC is grounded, the negative voltage end of the DC power supply DC is connected to the first end of the current-limiting resistor R1, the second end of the current-limiting resistor R1 is connected to the negative plate of the main discharge electrode and the first end of the filter capacitor C1, the second end of the filter capacitor C1 is connected to the cathode of the diode D1 and the electrical signal acquisition end, and the anode of the diode D1 is connected to the positive plate of the main discharge electrode.

[0049] Since the negative voltage terminal of the DC power supply DC is connected to the negative electrode plate of the main discharge electrode through the current-limiting resistor R1, and the positive electrode plate of the main discharge electrode is grounded, when the electron density measurement unit is turned on, the DC power supply DC can form an electric field in the region between the main discharge electrodes to drive the initial electrons to drift directionally towards the main discharge electrode. The supply voltage range of the DC power supply DC is between -3 kV / cm and -5 kV / cm (adjusted according to the distance d between the main discharge electrodes and the air pressure p). The supply voltage of the DC power supply DC needs to be strong enough to drive the charge drift, but must be lower than the DC breakdown threshold of the main discharge electrode. The current-limiting resistor R1 is used to limit the current in the measurement circuit, protect the DC power supply DC and subsequent measurement devices, and avoid overcurrent damage when the main discharge electrode is accidentally broken down. The resistance value of the current-limiting resistor R1 needs to balance current limitation and signal sensitivity to ensure the safety of the circuit and the measurability of the voltage at the electrical signal acquisition end. The filter capacitor C1 is used to filter out high-frequency noise in the measurement circuit (such as pulse interference of pre-ionization) and stabilize the voltage signal at the electrical signal acquisition end. The capacitance value of the filter capacitor C1 (such as 1 nF) needs to match the time constant of the measurement circuit, and the cut-off frequency is lower than the signal frequency band (such as <1 MHz). The one-way conduction type of the diode D1 can prevent the forward current of the main discharge electrode from flowing reversely into the electrical signal acquisition end of the measurement circuit, thereby protecting the measurement device. The diode D1 is selected as a high-voltage fast-recovery diode (such as reverse breakdown voltage >10 kV) to avoid signal delay or leakage current influence.

[0050] Further, the measurement circuit may further include a current-limiting resistor R2 and a current-limiting resistor R3. Among them, the current-limiting resistor R2 is serially arranged between the filter capacitor C1 and the current-limiting resistor R1, and the current-limiting resistor R3 is arranged in parallel at both ends of the diode D1.

[0051] The current-limiting resistor R2 can further divide the voltage and limit the current, reducing the influence of noise on the signal acquisition end. The resistance value of the current-limiting resistor R2 needs to cooperate with R1 to ensure the rationality of the voltage division ratio. The current-limiting resistor R3 provides a discharge path for the diode D1 to avoid measurement drift caused by charge accumulation. The resistance value of the current-limiting resistor R2 needs to be much larger than the impedance of the measurement circuit to avoid the shunt effect.

[0052] As an example, the output voltage of the DC power supply DC is a negative high voltage of -5 kV, the resistance value of the current-limiting resistor R1 is 40 MΩ, the resistance value of the current-limiting resistor R2 is 100 kΩ, the resistance value of the current-limiting resistor R3 is 1 MΩ, and the capacitance value of the filter capacitor C1 is 1 nF.

[0053] In addition, since in step S1, the power supply between the main discharge electrode and the excitation circuit has been turned off by the isolation unit, the initial electrons (and / or positive charges) will not be interfered by the negative high-voltage power supply during the process of drifting directionally towards the positive electrode plate (and / or positive and negative charges) of the main discharge electrode.

[0054] To avoid the situation where some initial electrons drift out of the area outside the electric field range before the electric field is formed, resulting in errors in subsequent electron density calculations. In some other embodiments, step S3 can be executed first to drive the electron density measurement unit to conduct, so as to form an electric field in the area between the main discharge electrodes to drive the subsequently formed initial electrons to drift directionally towards the main discharge electrodes. Then, step S2 is executed to drive the pre-ionization unit to conduct, so as to pre-ionize the ambient gas in the area between the main discharge electrodes and form initial electrons. Thus, the initial electrons will be driven by the electric field force to drift towards the main discharge electrodes at the first moment of formation, which avoids the initial electrons drifting out of the area outside the electric field and ensures the accuracy of subsequent electron density calculations. That is to say, the present application does not specifically limit the specific execution order of step S2 and step S3. For example, step S2 can be executed first, and then step S3; or step S3 can be executed first, and then step S2; or step S2 and step S3 can be executed simultaneously.

[0055] Finally, S4 is executed to use the electron density measurement unit to obtain the change amount of the electric signal generated by the directional drift of the initial electrons on the main discharge electrodes, and calculate the electron density of the initial electrons based on the change amount of the electric signal.

[0056] It can be understood that the electron density measurement unit should also include a measuring device, and the measuring device is connected to the electric signal acquisition end for monitoring the change amount of the electric signal of the main discharge electrodes.

[0057] Since the electric field can drive the seed electrons (and positive charges) between the main discharge electrodes to drift directionally towards the positive plate (positive charges towards the negative plate) of the main discharge electrodes, when these electrons (or positive charges) are adsorbed onto the positive plate (negative plate) of the main discharge electrodes, it will cause a change in the electric signal of the main discharge electrodes. Thus, by connecting the measuring device to the electric signal acquisition end, the change amount of the electric signal caused by the directional drift of the initial electrons can be directly obtained by the measuring device, and the electron density of the initial electrons can be calculated based on the obtained change amount of the electric signal.

[0058] As an example, the change amount of the electric signal includes obtaining the change amount of the voltage of the main discharge electrodes by using the measuring device. The measuring device includes but is not limited to one of a high-voltage probe or an oscilloscope, and requires a high input impedance to reduce the influence on the measurement circuit. The input impedance of the measuring device ≥ 10 MΩ, and the bandwidth ≥ 200 MHz to capture fast transient electric signals. By adjusting the ratio between the first resistor R1 and the first capacitor C1, the signal-to-noise ratio of the measuring device can be optimized.

[0059] Thus, the relationship between the change amount of the voltage of the main discharge electrodes and the electron density of the initial electrons satisfies:

[0060]

[0061] where n e is the electron density of the initial electrons, Q is the total charge of the initial electrons drifting directionally to the main discharge electrode, e is the electron charge, V is the volume of the discharge region corresponding to the main discharge electrode, ΔU is the voltage change obtained by the electron density measurement unit, C d is the capacitance of the positive and negative plates of the main discharge electrode, ∈0 is the vacuum permittivity, and ∈0 ≈ 8.854×10 -12 F / m, ∈ r is the relative permittivity of the medium between the main discharge electrodes, and ∈ r ≈ 1, A is the effective area of the positive and negative plates of the main discharge electrode, and d is the distance between the positive and negative plates of the main discharge electrode.

[0062] Furthermore, before the step of driving the electron density measurement unit to conduct, it should also include testing the voltage applied to both ends of the main discharge electrode of the electron density measurement unit to form an electric field with a preset intensity threshold in the region between the main discharge electrodes. That is to say, the electric field intensity should not be too high. An overly high electric field intensity will cause the main discharge electrode to be directly broken down, thus affecting the measurement results. The electric field intensity should not be too low either. An overly low electric field intensity will cause the electric field forces received by the initial electrons and positive charges in the region between the main discharge electrodes to be too low, affecting the drift of the initial electrons or positive charges towards the main discharge electrode, or the initial electrons or positive charges drifting outside the electric field, thus affecting the accuracy of the measurement results.

[0063] It should be noted that the specific method for testing and adjusting the voltage applied to both ends of the main discharge electrode in this application may not be specifically limited, including but not limited to replacing a DC power supply DC with different voltage thresholds, or replacing or adding voltage-dividing resistors with different resistance values in the measurement circuit, etc.

[0064] After step S4, it should also include driving the isolation unit to switch the electrical connection state between the negative plate of the main discharge electrode and the excitation circuit from the off state to the on state, so that the excitation circuit can supply normal power to the main discharge electrode, and then fully ionize the ambient gas in the discharge chamber.

[0065] It should be noted that the measurement method provided in this application may not be specifically limited to the type of excimer laser and its pumping method to which it is adapted. The laser type may include but not be limited to any one of laser types such as solid lasers, gas lasers, and liquid lasers. Similarly, the pumping method of the laser may include but not be limited to any one of pumping methods such as discharge pumping, optical pumping, and chemical pumping.

[0066] According to a second aspect of the present application, there is also provided an excimer laser pre-ionization electron density measurement device, which is applied to the discharge cavity of an excimer laser and calculates the electron density of the initial electrons by using the measurement method described in any one of the above.

[0067] In summary, the present application provides an excimer laser pre-ionization electron density measurement method and its measurement device, including shutting off the power supply between the pre-ionization unit and the main discharge electrode, and then using the ionization unit to pre-ionize the ambient gas in the region between the main discharge electrodes to form initial electrons; then using the electron density measurement unit to form an electric field in the region between the main discharge electrodes to drive the initial electrons to drift directionally towards the main discharge electrodes; and finally using the electron density measurement unit to obtain the change amount of the electric signal generated by the directional drift of the initial electrons on the main discharge electrodes, and then calculating the electron density of the initial electrons. Compared with the prior art, the present application can directly calculate the electron density of the initial electrons generated during the pre-ionization process, avoiding the error caused by power loss when calculating the electron density through power, and can more accurately reflect the pre-ionization effect.

[0068] In the description of the foregoing embodiments, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0069] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present application, "a plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

Claims

1. A method for measuring the pre-ionization electron density of an excimer laser, which is applied to the discharge chamber of the excimer laser, is characterized in that A main discharge electrode is provided in the discharge chamber, and a pre-ionization unit and an electron density measurement unit are respectively electrically connected to the negative plate of the main discharge electrode. The measurement method includes: Drive the power supply between the pre-ionization unit and the main discharge electrode to be turned off; Drive the pre-ionization unit to conduct, so as to pre-ionize the ambient gas in the area between the main discharge electrodes and form initial electrons; Drive the electron density measurement unit to conduct, so as to form an electric field in the area between the main discharge electrodes to drive the initial electrons to drift directionally towards the main discharge electrode; Use the electron density measurement unit to obtain the change in the electrical signal generated by the directional drift of the initial electrons on the main discharge electrode, and calculate the electron density of the initial electrons based on the change in the electrical signal.

2. The measurement method according to claim 1, characterized in that, Before the step of driving the electron density measurement unit to conduct, it also includes testing the supply voltage of the electron density measurement unit to form an electric field with a preset intensity threshold in the area between the main discharge electrodes.

3. The measurement method according to claim 1, characterized in that, The electron density measurement unit includes a measurement circuit and a measurement device. The measurement circuit includes a DC power supply DC, a current limiting resistor R1, a filter capacitor C1, and a diode D1; wherein, the positive terminal of the DC power supply DC is grounded, the negative terminal of the DC power supply DC is connected to the first end of the current limiting resistor R1, the second end of the current limiting resistor R1 is connected to the negative plate of the main discharge electrode and the first end of the filter capacitor C1, the second end of the filter capacitor C1 is connected to the cathode of the diode D1 and a signal acquisition terminal, the anode of the diode D1 is connected to the positive plate of the main discharge electrode, and the measurement device is connected to the signal acquisition terminal.

4. The measurement method according to claim 3, characterized in that The change in the electrical signal includes obtaining the change in the voltage of the main discharge electrode by using a measurement device, and the measurement device includes one of a high voltage probe or an oscilloscope.

5. The measuring method according to claim 4, characterized in that The relationship between the change in the voltage of the main discharge electrode and the electron density of the initial electrons satisfies: where n e is the electron density of the initial electrons, Q is the total electric charge of the initial electrons drifting directionally to the main discharge electrode, e is the electron charge, V is the volume of the discharge region corresponding to the main discharge electrode, ΔU is the voltage change obtained by the electron density measurement unit, C d is the capacitance of the positive and negative plates of the main discharge electrode, ∈0 is the vacuum permittivity, ∈ r is the relative permittivity of the medium between the main discharge electrodes, A is the effective area of the positive and negative plates of the main discharge electrode, and d is the distance between the positive and negative plates of the main discharge electrode.

6. The measurement method according to claim 1, characterized in that, The pre-ionization unit includes an excitation circuit and a pre-ionization structure electrically connected to the excitation circuit. The excitation circuit is electrically connected to the pre-ionization structure and the negative plate of the main discharge electrode to provide a negative high voltage drive for the pre-ionization process of the pre-ionization structure and the discharge process of the main discharge electrode.

7. The measuring method according to claim 6, characterized in that The pre-ionization structure includes one of a pre-ionization needle array structure and a corona pre-ionization rod structure; wherein, The pre-ionization needle array structure includes a plurality of ionization needles arranged in an array. One end of each ionization needle is connected to the negative plate of the main discharge electrode, and the other end of each ionization needle is connected to the negative high voltage output terminal of the excitation circuit; The corona pre-ionization rod structure includes a plurality of pre-ionization rods, and the negative ends of each pre-ionization rod and the negative plate of the main discharge electrode are commonly connected to the negative high voltage output terminal of the excitation circuit.

8. The measurement method according to claim 7, wherein The step of driving the power supply between the pre-ionization unit and the main discharge electrode to be turned off specifically includes: When the pre-ionization structure is the pre-ionization needle array structure, drive the isolation unit disposed between the negative plate of the main discharge electrode and the ionization needle to isolate the negative plate of the main discharge electrode from the excitation circuit; or, When the pre-ionization structure is the corona pre-ionization rod structure, drive the isolation unit disposed between the negative plate of the main discharge electrode and the excitation circuit to isolate the negative plate of the main discharge electrode from the excitation circuit.

9. The measuring method according to claim 8, characterized in that After the step of calculating the electron density of the initial electrons based on the change amount of the electrical signal, it further includes driving the isolation unit to conduct power supply between the negative plate of the main discharge electrode and the ionization needle or the negative high-voltage output end of the excitation circuit.

10. A pre-ionization electron density measurement device for an excimer laser, which is applied to the discharge cavity of the excimer laser, is characterized in that The measuring device includes measuring and calculating the electron density of the initial electrons by using the measuring method according to any one of claims 1 to 9.

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