Excimer laser stable output device based on energy attenuator

Abstract

The invention discloses an excimer laser stable output device based on an energy attenuator. The excimer laser stable output device comprises an excimer laser, the adjustable energy attenuator, a 45-degree placed partial reflector, an energy monitor, a deposition cavity and a target material. The excimer laser generates pulse laser output; the energy attenuator is used for adjusting laser output energy to a target set value; a 45-degree partial reflector is placed for light splitting; the energy monitor is used for monitoring the actual energy of the laser beam on line and feeding back the current energy state; the laser focusing optical system is used for focusing the adjusted laser beam to the surface of the target material to form the required light spot size and energy density; the deposition cavity is used for performing pulse laser deposition under a controlled vacuum atmosphere condition to form a thin film; the target material is used for generating laser ablation under laser irradiation and generating plasma plume; the substrate or the metal base band is used for receiving plasma plume and growing a thin film.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of laser, and particularly relates to a kind of stable output device of excimer laser based on energy attenuator. BACKGROUND

[0002] Pulse laser deposition (PLD) is a widely used technique for preparing high-quality thin film materials, which usually uses an excimer laser (such as KrF, 248 nm) as an excitation source. In a PLD system, to ensure the stability of the laser energy density on the target surface, the laser is often operated in a "constant energy mode" or a "constant pressure mode" to ensure the consistency of thin film growth.

[0003] In the "constant energy mode", the system detects the output energy of a single pulse in real time and automatically adjusts the discharge voltage to maintain constant energy output; while in the "constant pressure mode", a constant discharge voltage is set to maintain approximately stable laser output. Both of these two modes have their own advantages and disadvantages in practical use, but they all cannot avoid a core problem - as the service life of the laser extends, its output efficiency decreases, and a higher voltage is needed to maintain the same energy. The change in voltage leads to changes in the morphology, size and energy distribution of the laser spot, which in turn affects the shape and energy density of the focused spot, and affects the deposition quality and reproducibility.

[0004] Studies have shown that energy instability can cause changes in the plasma plume, which in turn causes uneven film thickness, composition deviation and decreased crystalline quality. Although conventional methods such as aperture are used to stabilize the spot boundary, their correction ability is limited when the energy distribution changes.

[0005] During the use of an excimer laser, especially under long-time or high-frequency operation, the stability of its laser output decreases. In order to maintain the set energy, the discharge voltage needs to be gradually increased, which will inevitably change the shape and distribution of the laser beam.

[0006] Small changes in laser energy and energy density can lead to inconsistencies in the target evaporation process, causing fluctuations in thin film performance and seriously affecting the repeatability and controllability of PLD preparation.

[0007] Although some systems use apertures or apertures to limit the spot range, the problem of uneven lateral energy distribution of the laser still exists, and this method cannot fundamentally solve the problem. At present, there is a lack of a stable control means that can maintain consistent target energy density and spot regardless of the influence of laser aging. SUMMARY

[0008] To solve the above technical problems, the application provides a kind of stable output device of excimer laser based on energy attenuator, and the specific technical scheme is as follows:

[0009] An energy attenuator-based excimer laser stable output device, comprising: an excimer laser, an adjustable energy attenuator, a 45° partial mirror, an energy monitor, a mirror, a focusing lens, a deposition cavity, a target material, a plume, and a substrate or metal base strip;

[0010] The excimer laser is used to generate pulsed laser output in a constant voltage mode.

[0011] The adjustable energy attenuator is used to adjust the laser output energy to a target set value to compensate for the attenuation of the excimer laser output energy.

[0012] The 45° partial mirror is used to split the output transmission light and reflection light, and the transmission light acts on the energy monitor for laser energy measurement.

[0013] The energy monitor is used to monitor the actual energy of the laser beam online and feedback the current energy state.

[0014] The mirror and the focusing lens constitute a laser focusing optical system, which is used to focus the adjusted laser beam to the surface of the target material to form a required spot size and energy density.

[0015] The deposition cavity is used to perform pulsed laser deposition to form a thin film under a controlled vacuum atmosphere.

[0016] The target material is used to generate laser ablation and produce a plasma plume under laser irradiation.

[0017] The substrate or metal base strip is used to receive the plasma plume and grow a thin film.

[0018] The present application has the following beneficial effects:

[0019] Improve the stability of laser energy: through external attenuation compensation mechanism, no longer rely on dynamic voltage adjustment after laser aging, effectively reduce the laser energy drift.

[0020] Maintain the consistency of the spot shape: avoid the asymmetry of the spot caused by the change of laser distribution under high voltage, and ensure the consistency of the PLD process and the quality of the thin film.

[0021] Improve the repeatability and controllability: even if the performance of the laser decreases during the experiment, the energy density on the surface of the target material can be kept constant by adjusting the attenuator.

[0022] Prolong the service life of the laser: reduce the frequent increase of voltage to maintain the output, and reduce the aging speed of the laser.

[0023] The system is simple to implement: it can be realized by using existing optical elements, which is low in cost, strong in universality, and convenient for upgrading in existing PLD systems. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a schematic diagram of an optical path;

[0025] Figure 2 is a schematic diagram of an energy attenuator.

[0026] In the figure, the reference signs are:

[0027] Excimer laser 1, energy attenuator 2, 45° placed partial reflector 3, energy monitor 4, reflector 5, focusing lens 6, deposition cavity 7, target material 8, plume 9, substrate or metal base 10. DETAILED DESCRIPTION

[0028] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application. In addition, the technical features involved in the various embodiments of the present application described below can be combined with each other as long as they do not conflict with each other. In order to achieve the above-mentioned objectives, the technical solutions adopted by the present application are as follows.

[0029] The present application proposes an excimer laser stable output device based on an energy attenuator, as shown in Figure 1 which comprises: an excimer laser 1, an adjustable energy attenuator 2, a 45° placed partial reflector 3, an energy monitor 4, a reflector 5, a focusing lens 6, a deposition cavity 7, a target material 8, a plume 9, and a substrate or metal base 10. The 45° placed partial reflector 3, for example, has a reflectivity of 95% and a transmittance of 5%, and the transmitted light is used for energy detection.

[0030] The excimer laser 1 is used to generate pulsed laser output in a constant voltage mode;

[0031] The adjustable energy attenuator 2 is used to adjust the laser output energy to a target set value to compensate for the attenuation of the output energy of the excimer laser 1; preferably a rotating filter, an adjustable angle metal mesh attenuator, etc.

[0032] The 45° placed partial reflector 3 is used for light splitting, for example, with a reflectivity of 95% and a transmittance of 5%, and the transmitted light is used for laser energy measurement by the energy monitor 4;

[0033] The energy monitor 4 is used to monitor the actual energy of the laser beam online and feedback the current energy state; preferably a laser energy meter;

[0034] The reflector 5 and the focusing lens 6 constitute a laser focusing optical system, which is used to focus the adjusted laser beam to the surface of the target material 8 to form a desired spot size and energy density; preferably a lens and a reflector;

[0035] Deposition chamber 7 for thin film formation by pulsed laser deposition under controlled vacuum atmosphere conditions;

[0036] Target 8 for laser ablation under laser irradiation and generation of plasma plume 9;

[0037] Substrate or metal base strip 10 for receiving the plasma plume and growing the thin film.

[0038] The excimer laser 1 operates in constant voltage mode to avoid the impact of energy drift on the laser spot morphology.

[0039] The adjustable energy attenuator 2 and the energy monitor 4 form a closed-loop control system, which can automatically adjust the attenuation intensity according to the feedback signal of the energy monitor 4, and realize the dynamic stable output of laser energy.

[0040] The 45° placed partial reflector 3 can split light, and a small amount of transmitted light is used for energy detection.

[0041] The energy attenuator 2 drives the rotating filter or adjusts the angle of the grid attenuator through the motor, has precise step control ability, and the control precision is better than 0.5%.

[0042] The laser focusing optical system includes an adjustable angle reflector and multiple focal length lenses, which are used to accurately adjust the laser incidence angle and spot size, and adapt to different deposition requirements.

[0043] The target 8 is a REBCO high-temperature superconducting target material, which is used in the preparation process of superconducting coated conductor thin films.

[0044] The energy monitor 4 is located after the 45° placed partial reflector 3, receives the transmitted light, and can reflect the actual energy of the laser incident on the target surface.

[0045] The deposition chamber 7 is equipped with replaceable windows, a target table and a rotating sample table, which is suitable for multi-target alternating deposition process.

[0046] The adjustment parameters of the energy attenuator 2 are associated with the use time of the excimer laser 1 for calibration, and the energy can be calibrated by preset parameters when starting.

[0047] The excimer laser 1, energy attenuator 2, energy monitor 4 and laser focusing optical system are integrated through a software control platform to realize graphical interface control, data recording and automatic compensation adjustment.

[0048] An adjustable energy attenuator 2 is arranged in the optical path to attenuate the laser energy by changing its transmittance or shielding area;

[0049] Combining the energy meter reading, adjust the energy attenuator 2 parameters to obtain the required stable laser energy output; make the laser output to maintain the optimal energy density, the spot shape constant. Energy attenuator 2 can be adjusted manually or by closed-loop control mode automatically; can set the target energy range, the system automatically compensates for energy attenuation. Energy attenuator is installed in the front section of focusing or laser transmission path in the middle, to ensure that the adjustment process will not affect the focusing effect; the material used for energy attenuator needs to be resistant to strong light damage, with high stability and repeatability.

[0050] As Figure 2 shown, the energy attenuator schematic diagram, including two synchronous rotation of the attenuation piece and compensation piece, wherein one surface of the attenuation piece is plated with a special dielectric film, its transmittance changes with the incident angle, by changing the angle can continuously adjust the attenuation of the light beam. Another compensation piece both sides are coated with antireflection film, with the attenuation piece synchronous rotation, accurate offset caused by the angle change of the light beam transverse offset, so as to change the light beam energy at the same time, ensure that the light beam exit position remains stable and unchanged.

[0051] Specific embodiments are as follows:

[0052] 1. A rotating adjustable energy attenuator (filter set) is set at the output end of a KrF laser;

[0053] 2. The laser energy meter is set at 45° behind the partial reflector 1 cm, real-time monitoring of laser pulse energy;

[0054] 3. Set the target energy to 300 mJ, if the initial output of the laser is 450 mJ, through the rotation of the filter attenuation to the target value;

[0055] 4. With the laser output drops (such as to 370 mJ), the system automatically reduces the filter shielding angle, continue to maintain the output at 300 mJ;

[0056] 5. In the process of continuous operation of 40,000 pulses, the target surface energy density fluctuation control in ± 2%.

Claims

1. An excimer laser stable output device based on an energy attenuator, characterized in that: include: Excimer laser, adjustable energy attenuator, 45° placed partial reflector, energy monitor, reflector, focusing lens, deposition chamber, target material, plume, and substrate or metal base tape; Excimer laser for generating pulsed laser output in constant voltage mode; An adjustable energy attenuator is used to adjust the laser output energy to a target set value to compensate for the attenuation of the excimer laser output energy; A partial reflector is placed at 45 degrees to split the output of transmitted light and reflected light. The transmitted light acts on the energy monitor to measure the laser energy. Energy monitor, used to monitor the actual energy of the laser beam online and provide feedback on the current energy status; The reflector and focusing lens constitute the laser focusing optical system, which is used to focus the adjusted laser beam onto the target surface to form the required spot size and energy density; A deposition chamber, used for forming thin films by pulsed laser deposition under controlled vacuum atmosphere conditions; A target material, used for laser ablation and plasma plume generation under laser irradiation; The substrate or metal substrate is used to receive the plasma plume and grow the thin film.

2. The excimer laser stable output device based on an energy attenuator according to claim 1, characterized in that: The excimer laser operates in a constant voltage mode.

3. The excimer laser stable output device based on an energy attenuator according to claim 1, characterized in that: The adjustable energy attenuator and the energy monitor form a closed-loop control system, which can automatically adjust the attenuation intensity according to the feedback signal from the energy monitor to achieve dynamic and stable output of laser energy.

4. The excimer laser stable output device based on an energy attenuator according to claim 1, characterized in that: The energy attenuator is driven by a motor to rotate the filter or adjust the angle of the grid attenuator.

5. The excimer laser stable output device based on an energy attenuator according to claim 1, characterized in that: The laser focusing optical system includes an adjustable angle reflector and multiple groups of focal length lenses, which are used to accurately adjust the laser incident angle and spot size.

6. The excimer laser stable output device based on an energy attenuator according to claim 1, characterized in that: The target material is a REBCO high-temperature superconducting target material.

7. The excimer laser stable output device based on an energy attenuator according to claim 1, characterized in that: A replaceable window, a target stage and a rotating sample stage are arranged in the deposition chamber.

8. The excimer laser stable output device based on an energy attenuator according to claim 1, characterized in that: The partial reflector placed at 45° preferably has a reflectivity of 95% and a transmittance of 5%.

9. The excimer laser stable output device based on an energy attenuator according to claim 1, characterized in that: The energy monitor is preferably a laser energy meter.

10. The excimer laser stable output device based on an energy attenuator according to claim 1, characterized in that: The adjustment parameters of the energy attenuator are correlated and calibrated with the use time of the excimer laser, and energy calibration is performed using preset parameters during startup.

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