Droplet generation system and generation device for EUV light

Abstract

The invention belongs to the technical field of extreme ultraviolet lithography machines, and discloses a liquid drop generation system and a generation device for EUV light. The device comprises a liquid drop generating device and a focused ultrasonic wave device, and the liquid drop generating device is used for outputting metal liquid drops; and the focused ultrasonic device is arranged above the liquid drop generating device and used for focusing ultrasonic waves and transmitting the ultrasonic waves to the position above the output metal liquid drops, so that the liquid drop generating device outputs the monodisperse metal liquid drops with the controllable size, distance, frequency and movement speed. The liquid drop generation system can gather ultrasonic energy above liquid drops to realize ultrasonic perturbation and improve the energy conversion efficiency at the same time.

Description

Technical Field

[0001] The present invention relates to the technical field of extreme ultraviolet lithography machines, and in particular to a droplet generating system and a generating device for EUV light. Background Art

[0002] As lithography technology rapidly develops towards more sophisticated manufacturing, semiconductor production processes have been able to produce semiconductor devices with increasingly fine feature sizes. At present, in the next generation of semiconductor production needs, it is expected to achieve a more finely processed feature size, that is, micro-processing of 70nm to 45nm, and even a micro-processing feature size of 32nm or less. Therefore, in order to meet the demand for micro-processing with a feature size of 32nm or less, exposure equipment also needs to be further improved, including the need to successfully manufacture a system that produces extreme ultraviolet light (EUV) with a wavelength of about 13.5nm and an optical system that reduces projection reflections.

[0003] At present, methods for generating EUV light include, but are not necessarily limited to, converting a material having an element (such as xenon, lithium or tin) into a plasma state and emitting a spectrum line in the EUV range. It usually uses a laser-produced plasma (LPP) method, specifically bombarding a tin metal of several tens of microns in size (in the form of droplets, plates, strips, flows or material clusters) with a high-energy pulsed laser to form the required plasma that can radiate EUV. The plasma is usually generated in a sealed container (such as a vacuum chamber) and monitored using various types of metrology equipment.

[0004] Among them, the device for generating droplets (such as tin droplets) usually passes through a cylindrical pipe. Under the action of surface tension, Plateau-Rayleigh instability will occur, and the cylindrical droplets will spontaneously become circular monodisperse droplets. The use of ultrasonic waves to generate perturbations and different air pressures can control the emission frequency, size, spacing and other parameters of the droplets. Therefore, ultrasonic devices are often used to adjust the emission frequency, size, spacing and other parameters of the droplets. The prior art usually includes two designs for ultrasonically controlling droplets. One design is to use an annular piezoelectric ceramic sleeve on the outlet pipe of the droplet generating device to directly apply ultrasonic waves to the tin droplets; but the temperature of the tin droplets exceeds 230°C, which is far higher than the Curie temperature of ordinary piezoelectric ceramics. Therefore, it is necessary to specially develop high-temperature resistant piezoelectric ceramics, which is costly. Another solution is to install a piezoelectric ceramic that vibrates up and down on the top cover of the droplet generating device, and couple the ultrasonic wave to the top of the droplet nozzle through a long rod. However, due to the energy attenuation of the long rod and the fact that the diameter of the long rod is much larger than the diameter of the droplet nozzle, a lot of ultrasonic energy is dissipated, and the piezoelectric ceramic has higher power requirements.

[0005] Therefore, there is an urgent need for a droplet generation system and a device for generating EUV light to solve the above technical problems. Summary of the invention

[0006] One object of the present invention is to provide a droplet generation system that can focus ultrasonic energy on the droplets to achieve ultrasonic perturbations while improving energy conversion efficiency.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] Droplet generation system, comprising:

[0009] A droplet generating device, the droplet generating device is used to output metal droplets;

[0010] A focused ultrasonic device, wherein the focused ultrasonic device is disposed above the droplet generating device, and is used for focusing ultrasonic waves and emitting them above the output metal droplets, so that the droplet generating device can output monodisperse metal droplets with controllable size, spacing, frequency and movement speed.

[0011] Optionally, the above-mentioned focused ultrasonic device comprises:

[0012] A signal generator, the signal generator is used to output ultrasonic waves of a preset waveform;

[0013] A power amplifier, the power amplifier is electrically connected to the signal generator to adjust the intensity of the ultrasonic wave;

[0014] A focused ultrasonic transducer, the focused ultrasonic transducer is electrically connected to the power amplifier, and the focused ultrasonic transducer is used to receive ultrasonic waves of a preset waveform and preset intensity and focus and transmit them above the output metal droplets.

[0015] Optionally, the focused ultrasonic transducer comprises a focusing spherical cap piezoelectric ceramic piece to focus and transmit ultrasonic waves.

[0016] Optionally, the above-mentioned focused ultrasonic device also includes a conical rod, which is arranged in the above-mentioned droplet generating device. The above-mentioned conical rod includes a large end and a small end. The large end is connected to the above-mentioned focused ultrasonic transducer, and the small end is arranged above the above-mentioned output metal droplets. The above-mentioned conical rod is used to conduct the above-mentioned focused ultrasonic waves.

[0017] Optionally, the position of the small end of the tapered rod is adjustable to adjust the focusing position of the ultrasound emitted by the focused ultrasound device.

[0018] Optionally, a coupling agent is provided between the large end of the tapered rod and the focused ultrasonic transducer to connect and transmit the focused ultrasonic wave.

[0019] Optionally, an arc-shaped fixed cover is further provided above the droplet generating device, the focused ultrasonic transducer is fixedly connected to the arc-shaped fixed cover, and the portion of the conical rod close to the large end is arranged in the arc-shaped fixed cover and connected to the focused ultrasonic transducer.

[0020] Optionally, the diameter of the focused ultrasonic device is D, 1mm≤D≤200mm, and the frequency of the focused ultrasonic device is F, 20kHz≤F≤20MHz.

[0021] Optionally, the above-mentioned focused ultrasonic device generates focused ultrasonic waves in the following ways: unit lens focused ultrasound, multi-element facet geometric focused ultrasound, single annular self-focused ultrasound and phased array ultrasound.

[0022] Another object of the present invention is to provide a device for generating EUV light, comprising the droplet generation system described in any of the above schemes, which can focus ultrasonic energy on the metal droplets to achieve ultrasonic perturbation and improve energy conversion efficiency.

[0023] Beneficial effects of the present invention:

[0024] The present invention provides a droplet generation system and a generating device for EUV light. By arranging focused ultrasound, the ultrasound emitted above the output metal droplet is focused ultrasound, which improves the transmission efficiency of ultrasound, improves the energy consumption problem of ultrasound, realizes impact perturbation in both vertical and radial directions, improves the spatial accuracy of ultrasound drive, reduces the power of ultrasound drive, and improves energy conversion efficiency. Moreover, they are all commonly used structures, do not need to develop high-cost structures, and reduce the cost of use. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic structural diagram of a droplet generating structure of an ultrasonic control method in the prior art provided by the present invention;

[0026] Figure 2 It is a structural schematic diagram of another droplet generating structure of ultrasonic control method in the prior art provided by the present invention;

[0027] Figure 3 is a schematic structural diagram of a droplet generation system provided in a specific embodiment of the present invention;

[0028] Figure 4 is a working schematic diagram of a droplet generating system provided in a specific embodiment of the present invention;

[0029] Figure 5 is a comparison diagram of tapered rods of different sizes and focused ultrasonic transducers of a droplet generation system provided in a specific embodiment of the present invention;

[0030] Figure 6 It is a comparison diagram of metal droplets under different ultrasonic conditions of the droplet generation system provided by a specific embodiment of the present invention.

[0031] In the figure:

[0032] 1', droplet generating structure; 2', annular ultrasonic transducer; 3', stacked ultrasonic transducer; 4', vibrating rod;

[0033] 101. Liquid metal; 102. Metal droplets;

[0034] 10. droplet generating device; 11. droplet generator; 111. output pipeline; 12. heater;

[0035] 20. Focused ultrasonic device; 201. Focused ultrasonic envelope; 21. Signal generator; 22. Power amplifier; 23. Focused ultrasonic transducer; 24. Conical rod; 241. Large end; 242. Small end; 25. Coupling agent;

[0036] 30. Arc-shaped fixed cover. DETAILED DESCRIPTION

[0037] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0038] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0039] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0040] In the description of this embodiment, the terms "upper", "lower", "left", "right", etc., and the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of description and simplified operation, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used to distinguish in the description and have no special meaning.

[0041] At present, the droplet generation system often uses ultrasonic emission to control the output size, dimension, spacing, frequency and movement speed of the metal droplets 102. There are two ultrasonic control methods in the prior art, such as Figure 1 As shown, the first ultrasonic control method of droplets is to place an annular ultrasonic transducer 2' on the outlet pipe of the droplet generating structure 1' to emit ultrasonic waves to the outlet pipe to generate perturbations in the vertical direction to affect the liquid metal 101, thereby achieving control over the output size, dimension, spacing, frequency and movement speed of the metal droplets 102. However, the temperature when the metal melts into the metal droplets 102 is relatively high, and the piezoelectric ceramics in the annular ultrasonic transducer 2' also need to be high-temperature resistant ceramics, which are costly and have a high damage rate, making them inconvenient for long-term use. Figure 2 As shown, the second ultrasonic control method of droplets is to set a stacked ultrasonic transducer 3' above the droplet generator 11 structure, and output the ultrasonic waves emitted by the piezoelectric ceramics that vibrate up and down to the top of the outlet pipe through the vibration rod 4', so as to perturb the liquid metal 101 in the vertical direction, thereby achieving the output size, size, spacing, frequency and movement speed control of the metal droplets 102. However, the transmission of ultrasonic waves through the vibration rod 4' will lead to energy attenuation and dissipation, which requires piezoelectric ceramics with higher power to achieve, which undoubtedly increases the difficulty of design.

[0042] Please refer to Figure 3 The present embodiment provides a droplet generating system, which includes a droplet generating device 10 and a focused ultrasonic device 20. The droplet generating device 10 is used to output metal droplets 102; the focused ultrasonic device 20 is arranged above the droplet generating device 10, and the focused ultrasonic device 20 is used to focus and emit ultrasonic waves above the output metal droplets 102, so that the droplet generating device 10 outputs monodisperse metal droplets 102 with controllable size, dimension, spacing, frequency and movement speed.

[0043] The droplet generating system in this embodiment is provided with a focused ultrasonic device 20, so that the ultrasonic wave emitted to the output metal droplet 102 is a focused ultrasonic wave, which improves the transmission efficiency of the ultrasonic wave, improves the energy consumption problem of the ultrasonic wave, realizes impact perturbation in both vertical and radial directions, improves the spatial accuracy of ultrasonic drive, reduces the power of ultrasonic drive, and improves the energy conversion efficiency. Moreover, they are all commonly used structures, and there is no need to develop high-cost structures, thereby reducing the cost of use.

[0044] In this embodiment, the droplet generating device 10 includes a droplet generator 11, an output pipeline 111, solid metal and a heater 12. The output pipeline 111 is arranged below the droplet generator 11 to realize the outflow of liquid metal 101. The solid metal is arranged in the droplet generator 11. The heater 12 is arranged on the periphery of the droplet generator 11 to heat the solid metal to melt it to form liquid metal 101, and output it from the output pipeline 111 to form metal droplets 102.

[0045] Of course, the droplet generating device 10 also includes other structures to realize the output of the droplet generator 11 to the liquid metal 101, which is a conventional structure in the art and will not be described in detail here.

[0046] Please refer to Figures 3 to 5 In this embodiment, the focused ultrasonic device 20 includes a signal generator 21, a power amplifier 22 and a focused ultrasonic transducer 23. The signal generator 21 is used to output ultrasonic waves of a preset waveform; the power amplifier 22 is electrically connected to the signal generator 21 to adjust the intensity of the ultrasonic waves; the focused ultrasonic transducer 23 is electrically connected to the power amplifier 22, and the focused ultrasonic transducer 23 is used to receive ultrasonic waves of a preset waveform and preset intensity and focus and emit them above the output metal droplets 102. The waveform, pulse frequency and modulation state of the output ultrasonic waves are adjusted by the signal generator 21, the intensity of the output ultrasonic waves is adjusted by the power amplifier 22, and the ultrasonic waves are focused and output above the output metal droplets 102 by the focused ultrasonic transducer 23, thereby realizing precise control of the size, spacing, frequency and movement speed of the monodispersed metal droplets 102.

[0047] It should be noted that the above-mentioned preset waveforms and preset intensities are design requirement values ​​and can be set according to actual needs and are not specifically limited here.

[0048] Specifically, the focused ultrasonic transducer 23 includes a focusing spherical cap piezoelectric ceramic sheet to focus and transmit ultrasonic waves, thereby achieving focusing of the ultrasonic waves and improving energy conversion efficiency.

[0049] It is understandable that the size of the focusing spherical cap piezoelectric ceramic piece can be adaptively changed according to actual needs to change the focus of ultrasonic focusing, the distribution ratio in the impact direction, etc., so as to produce different focused ultrasonic envelopes 201.

[0050] Furthermore, the focused ultrasonic device 20 further includes a tapered rod 24, which is disposed in the droplet generating device 10. The tapered rod 24 includes a large end 241 and a small end 242, wherein the large end 241 is connected to the focused ultrasonic transducer 23, and the small end 242 is disposed above the output metal droplet 102. The tapered rod 24 is used to conduct the focused ultrasonic wave. The arrangement of the tapered rod 24 forms a focused ultrasonic envelope 201, which realizes the conduction and further focusing of the ultrasonic wave, so that the focused ultrasonic wave can be accurately transmitted to the top of the output metal droplet 102, thereby improving the positioning accuracy and focusing effect of the ultrasonic wave.

[0051] Optionally, the position of the small end 242 of the tapered rod 24 is adjustable to control the focus position of the ultrasound emitted by the focused ultrasound device 20, thereby achieving various forms of ultrasound output to ensure that the range of ultrasound perturbation of the metal droplet 102 meets the requirements.

[0052] It is understandable that the size of the tapered rod 24 can be adjusted according to the size of the focusing spherical cap piezoelectric ceramic piece, the size of the droplet generator 11, and the position of the focus, so as to generate different focused ultrasound envelopes 201.

[0053] Furthermore, a coupling agent 25 is provided between the large end 241 of the conical rod 24 and the focused ultrasonic transducer 23 to connect and transmit the focused ultrasonic wave. The provision of the coupling agent 25 improves the connectivity between the two, thereby reducing the energy loss of the focused ultrasonic wave transmitted to the conical rod 24 and improving the energy conversion efficiency.

[0054] Furthermore, an arc-shaped fixing cover 30 is provided above the droplet generating device 10, the focused ultrasonic transducer 23 is fixedly connected to the arc-shaped fixing cover 30, and the portion of the tapered rod 24 close to the large end 241 is arranged in the arc-shaped fixing cover 30 and connected to the focused ultrasonic transducer 23. The arc-shaped fixing cover 30 can not only fix the tapered rod 24 and the focused ultrasonic transducer 23, but also achieve complete fitting between the tapered rod 24, the coupling agent 25 and the focused spherical cap piezoelectric ceramic sheet, thereby achieving efficient conduction of the focused ultrasonic wave.

[0055] Optionally, the diameter of the focused ultrasonic device 20 is D, 1mm≤D≤200mm, which is the controllable diameter range of the focused ultrasonic device 20 that satisfies the disturbance of the liquid metal 101. Specifically, the larger the diameter of the focused ultrasonic device 20, the more energy of the concentrated ultrasonic wave. Exemplarily, the diameter can be controlled to be 1mm, 5mm, 10mm, 15mm, 20mm.

[0056] Optionally, the frequency of the focused ultrasonic device 20 is F, 20kHz≤F≤20MHz, which is the controllable frequency range of the focused ultrasonic device 20 that satisfies the disturbance of the liquid metal 101. Specifically, the greater the frequency of the focused ultrasonic device 20, the higher the vibration efficiency and energy transfer efficiency. Exemplarily, the frequency can be controlled to be 20kHz, 200kHz, 500kHz, 1MHz, 10MHz, 20MHz.

[0057] Optionally, the focused ultrasound device 20 generates focused ultrasound in the following ways: unit lens focused ultrasound, multi-element facet geometric focused ultrasound, single annular self-focused ultrasound and phased array ultrasound, all of which can achieve the generation of focused ultrasound.

[0058] This embodiment also provides a device for generating EUV light, which includes the droplet generation system described in any of the above schemes. It has all the beneficial effects of the above droplet generation system, and can achieve EUV light with finer wavelength, thereby achieving finer feature size processing of semiconductor devices.

[0059] Refer to the following Figures 3 to 6 The working process of the droplet generation system in this embodiment is introduced as follows: first, the signal generator 21 is started to output an ultrasonic waveform, which can be adjusted to a sine wave, a square wave, a pulse wave, etc.; in conjunction with the power amplifier 22, a focused ultrasonic wave is output to the liquid metal 101 of the droplet generator 11 through a focused ultrasonic wave generation method, and the generation of monodisperse metal droplets 102 of various sizes, dimensions, spacings, frequencies and movement speeds can be achieved by changing the waveform and the ultrasonic wave output method.

[0060] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, various obvious changes, readjustments and substitutions can be made without departing from the protection scope of the present invention. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A droplet generating system, characterized in that: include: A droplet generating device (10), wherein the droplet generating device (10) is used to output metal droplets (102); A focused ultrasonic device (20), the focused ultrasonic device (20) being arranged above the droplet generating device (10), and the focused ultrasonic device (20) being used to focus ultrasonic waves and emit them above the outputted metal droplets (102), so that the droplet generating device (10) can output monodisperse metal droplets (102) with controllable size, spacing, frequency and movement speed.

2. The droplet generation system according to claim 1, characterized in that: The focused ultrasonic device (20) comprises: A signal generator (21), the signal generator (21) being used to output ultrasonic waves of a preset waveform; A power amplifier (22), the power amplifier (22) being electrically connected to the signal generator (21) to adjust the intensity of the ultrasonic wave; A focused ultrasonic transducer (23), the focused ultrasonic transducer (23) being electrically connected to the power amplifier (22), the focused ultrasonic transducer (23) being used to receive ultrasonic waves of a preset waveform and preset intensity and to focus and emit the ultrasonic waves above the output metal droplet (102).

3. The droplet generation system according to claim 2, characterized in that: The focused ultrasonic transducer (23) comprises a focusing spherical cap piezoelectric ceramic sheet to focus and transmit ultrasonic waves.

4. The droplet generating system according to claim 2, characterized in that: The focused ultrasonic device (20) further comprises a conical rod (24), wherein the conical rod (24) is arranged in the droplet generating device (10), and the conical rod (24) comprises a large end (241) and a small end (242), wherein the large end (241) is connected to the focused ultrasonic transducer (23), and the small end (242) is arranged above the output metal droplet (102), and the conical rod (24) is used to conduct the focused ultrasonic wave.

5. The droplet generation system according to claim 4, characterized in that: The position of the small end (242) of the tapered rod (24) is adjustable to adjust the focus position of the ultrasound emitted by the focused ultrasound device (20).

6. The droplet generation system according to claim 4, characterized in that: A coupling agent (25) is also provided between the large end (241) of the tapered rod (24) and the focused ultrasonic transducer (23) to connect and transmit focused ultrasonic waves.

7. The droplet generation system according to claim 4, characterized in that: An arc-shaped fixed cover (30) is also provided above the droplet generating device (10), the focused ultrasonic transducer (23) is fixedly connected to the arc-shaped fixed cover (30), and the portion of the conical rod (24) close to the large end (241) is arranged in the arc-shaped fixed cover (30) and connected to the focused ultrasonic transducer (23).

8. The droplet generating system according to any one of claims 1 to 7, characterized in that: The diameter of the focused ultrasonic device (20) is D, 1 mm ≤ D ≤ 200 mm, and the frequency of the focused ultrasonic device (20) is F, 20 kHz ≤ F ≤ 20 MHz.

9. The droplet generating system according to any one of claims 1 to 7, characterized in that: The focused ultrasonic device (20) generates focused ultrasonic waves in the following ways: unit lens focused ultrasound, multi-element small plane geometric focused ultrasound, single annular self-focused ultrasound and phased array ultrasound.

10. A device for generating EUV light, characterized in that Comprising a droplet generating system as described in any one of claims 1-9.

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