Laser amplification device and method

Abstract

The present invention provides a laser amplification device and method, including a reflection cavity and a radio frequency electric field focuser, wherein the reflection cavity is filled with luminescent gas; at least a portion of the reflection cavity is located within the energy focusing range of the radio frequency electric field focuser; and a slit is provided on the outer wall of the reflection cavity for the laser to pass through. The beneficial effects of the present invention are: using a high-reflection annular reflection cavity to replace the traditional linear resonant cavity solves the problem of no suitable transmission window in the deep ultraviolet region, so that the deep ultraviolet laser can be amplified through multiple reflection resonances; the laser reflection path can be accurately controlled by adjusting the incident angle of the incident laser or the size of the slit, so as to achieve high quality factor adjustment of the laser, and the adjustment range is much larger than that of the traditional laser resonant cavity.

Description

Technical Field

[0001] The present invention relates to the field of laser technology, and in particular to a laser amplification device and method. Background Art

[0002] Currently, there are three main solutions for realizing extreme ultraviolet lithography (EUV) light sources: synchrotron radiation source; laser plasma EUV light source; discharge plasma EUV light source.

[0003] Synchrotron radiation source is a new type of artificial light source developed based on high-energy electron ring accelerator. Synchrotron radiation source X-ray source is the brightest X-ray source at present, with advantages such as large output energy, strong stability, good linearity, and clean light source. However, this kind of X-ray source requires the construction of electron linear accelerator and electron storage ring at a cost of 15 to 20 million US dollars. It is expensive, has harsh working conditions, and complex experimental operations, which is not suitable for large-scale industrial production.

[0004] The principle of EUV light generation by laser plasma EUV light source is to irradiate high-energy laser on target materials including xenon or tin, and obtain high-energy ionized plasma through excitation. In recent years, due to the higher energy conversion efficiency of CO2 lasers, and the advantages of low cost and good beam quality, people have gradually transferred the driving laser from 1.06μm Nd:YAG laser to 10.6μm CO2 laser. CO2 laser mainly generates high-temperature dense plasma by bombarding high-density targets (Xe, Sn, Li) with high-power CO2 lasers, thereby exciting extreme ultraviolet radiation with a wavelength of 13.5nm. Although the critical density of CO2 lasers is very low, which ensures that they have less self-absorption, the low density also affects the generation of EUV light.

[0005] Discharge plasma EUV light source technology is to add pulsed high voltage to the discharge gas to generate plasma and release extreme ultraviolet light. It directly converts electrical energy into plasma energy, which can improve the energy conversion efficiency. The device is relatively simple, with low investment and operating costs, and easy operation and maintenance. However, due to the ablation of the tube wall and the electrode, the discharge plasma light source produces a lot of debris, which can easily cause pollution to the EUV optical collection system. At the same time, during the high repetition rate gas discharge process, a large amount of heat will be deposited on the electrode and the capillary wall, affecting the life of the capillary electrode. Summary of the invention

[0006] The technical problem to be solved by the present invention is how to amplify laser efficiently and conveniently.

[0007] In order to solve the above technical problems, the present invention discloses a laser amplification device, and the technical solution of the present invention is implemented as follows:

[0008] A laser amplification device comprises a reflection cavity and a radio frequency electric field focuser, wherein the reflection cavity is filled with luminous gas; at least a part of the reflection cavity is located within the energy focusing range of the radio frequency electric field focuser; and the reflection cavity is provided with a slit for laser to pass through.

[0009] Preferably, the reflection cavity is an annular reflection cavity, a protrusion is provided on the outer side of the reflection cavity, the protrusion is communicated with the reflection cavity, and the radio frequency electric field focuser is opposite to the protrusion.

[0010] Preferably, the reflective cavity structure is an annular tube structure.

[0011] Preferably, the laser amplifying device further comprises a window plate for sealing the slit, and the laser can pass through the window plate.

[0012] Preferably, the slit is an adjustable slit.

[0013] Preferably, the slit width can be adjusted within the range of 10 μm to 1 mm.

[0014] Preferably, the number of the protrusions is more than one, and the number of the RF electric field focusers is the same as the number of the protrusions; the laser amplification device also includes a bracket, the RF electric field focuser is fixed on the bracket, opposite to the protrusion, and the bracket is placed around the outside of the reflection cavity.

[0015] Preferably, the reflective cavity is provided with an air inlet and an air outlet.

[0016] Also disclosed is a laser amplification method, which utilizes the laser amplification device to amplify the seed laser.

[0017] Preferably, the laser amplification method can change the laser amplification factor by adjusting the incident angle of the seed laser or the field intensity of the radio frequency electric field focuser.

[0018] The beneficial effects of implementing the present invention are:

[0019] 1. The high-reflection annular reflective cavity is used to replace the traditional linear resonant cavity, which solves the problem of no suitable transparent window in the deep ultraviolet region, so that the deep ultraviolet laser can be amplified through multiple reflection resonances;

[0020] 2. The laser reflection path can be precisely controlled by adjusting the incident angle of the incident laser or the size of the slit, thereby achieving high quality factor adjustment of the laser, and the adjustment range is much larger than that of the traditional laser resonant cavity. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only one embodiment of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 is a schematic structural diagram of a laser amplification device in one embodiment;

[0023] Figure 2 is a schematic diagram of the structure of a reflection cavity in one embodiment;

[0024] Figure 3 is another structural schematic diagram of a laser amplification device in one embodiment;

[0025] Figure 4 is another structural schematic diagram of a laser amplification device in an embodiment;

[0026] Figure 5 FIG. 1 is a schematic diagram of the structure of a bracket and a reflective cavity in one embodiment.

[0027] In the above drawings, the figure numbers represent:

[0028] 1-reflection cavity, 11-protrusion, 2-RF electric field focuser, 3-laser reflection path, 4-support. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] In a specific embodiment, Figure 1 , Figure 2 A laser amplification device comprises a reflection cavity 1 and a radio frequency electric field focuser 2, wherein the reflection cavity 1 is filled with a luminescent gas; at least a portion of the reflection cavity 1 is located within the energy focusing range of the radio frequency electric field focuser 2; and the reflection cavity 1 is provided with a slit for laser passage.

[0031] Using the deep ultraviolet laser generated by high-order harmonics as a seed, adjusting the incident angle of the laser so that it enters the reflection cavity 1 from the slit, and is reflected in the reflection cavity 1, the radio frequency electric field focuser 2 is coupled with the reflection cavity 1, and the energy is coupled to the annular reflection cavity 1, and the luminous gas is stimulated to be converted into plasma. The incident laser absorbs energy when passing through the plasma area, and the laser is enhanced and amplified. By adjusting the incident angle of the laser, its reflection path is controlled, and the high quality factor of the laser can be adjusted (i.e., Q-switching); the slit is opened on the reflection cavity 1, and the laser can be shot into the reflection cavity 1 for reflection. The position where the slit is opened can be the outside of the reflection cavity 1 or the inside of the reflection cavity 1, and the technicians in this field can choose according to different needs. The specific structure of the radio frequency electric field focuser 2 can refer to the documents CN205752100U, CN206225324U, CN106469641A, CN106992110A, and CN206595228U.

[0032] There is a one-to-one correspondence between the luminescent gas described in the present disclosure and the wavelength of the incident laser. The incident seed laser is usually a pulsed light of 30fs-3ps with a pulse frequency of 1KHz-80MHz; the luminescent gas is usually a single gas such as He, Ne, Ar, Kr, Xe, etc. Taking Kr gas as an example, when using a 780nm pump, the generated seed laser can be 20.8nm, 30.5nm, 37.0nm, etc., and Kr gas should be excited to the 13th order, 19th order and 23rd order respectively. The selection of gas types is within the common sense of those skilled in the art. Of course, it can also be a combination of the aforementioned types of gases, or a combination of these gases with other gases, or only composed of other types of gases, without special restrictions here.

[0033] The laser amplification device disclosed in the present invention uses a high-reflection annular reflective cavity to replace the traditional linear resonant cavity, which solves the problem of no suitable transmission window in the deep ultraviolet region, so that the deep ultraviolet laser can be amplified through multiple reflection resonances. However, the present invention can also be used not only for deep ultraviolet laser amplification, but also for extreme ultraviolet laser or laser amplification in other frequency bands.

[0034] In a preferred embodiment, the reflection cavity 1 is an annular reflection cavity, a protrusion 11 is provided on the outer side of the reflection cavity 1, the protrusion 11 is connected to the reflection cavity 1, and the radio frequency electric field focuser 2 is opposite to the protrusion 11.

[0035] The protrusion 11 is also filled with luminescent gas. The protrusion 11 is provided so that the luminescent gas in the reflection cavity 1 can be better coupled with the radio frequency electric field focuser.

[0036] In a preferred embodiment, Figure 2 The cavity structure of the reflection cavity 1 is a ring tube structure.

[0037] The reflection cavity 1 of the annular tube structure can better control the reflection path of the laser, and the annular surface is curved and smooth, so that the laser can be continuously reflected on the surface with less loss.

[0038] In a preferred embodiment, the laser amplification device further comprises a window plate for sealing the slit, and the laser can pass through the window plate.

[0039] In a preferred embodiment, the slit is an adjustable slit.

[0040] In a preferred embodiment, the slit width can be adjusted within the range of 10 μm to 1 mm.

[0041] The size of the slit is related to the input laser power. When the input power is large, the slit needs to be opened larger, and when the input power is small, the slit can be opened smaller. For example, when the input laser power is 0.01mW, the size of the slit is generally in the range of 10μm-0.1mm, when the input seed laser power is 0.1mW, the size of the slit is generally in the range of 0.1mm-0.3mm, when the input seed laser power is 0.2mW, the size of the slit is generally in the range of 0.2mm-0.6mm, when the input seed laser power is 1.0mW, the size of the slit is generally in the range of 0.4mm-1.0mm, and technicians in this field can adjust it according to actual conditions.

[0042] In a preferred embodiment, the number of the protrusions 11 is more than one, and the number of the RF electric field focusers 2 is the same as the number of the protrusions; the laser amplification device also includes a bracket 4, the RF electric field focuser 2 is fixed on the bracket, opposite to the protrusion 11, and the bracket 4 is placed around the outside of the reflection cavity 1.

[0043] The number of protrusions 11 and the number of RF electric field focusers 2 are the same. When the number of protrusions 11 is more than two, the protrusions 11 are evenly distributed on the outside of the reflection cavity 1, and the distances between adjacent protrusions 11 are the same; each RF electric field focuser 2 corresponds to a protrusion 11. The more RF electric field focusers 2 there are, the better the laser enhancement effect. Technical personnel in this field can make a selection according to actual needs.

[0044] In a preferred embodiment, the reflective cavity 1 is provided with an air inlet and an air outlet.

[0045] For lasers with wavelengths below 110nm, it is necessary to open an air inlet and an air outlet on the reflection cavity 1, and the luminescent gas needs to be continuously injected during operation; for lasers with wavelengths above 110nm, the reflection cavity 1 should be a sealed structure to seal the luminescent gas inside.

[0046] In yet another specific embodiment, a laser amplification method is disclosed, which uses the laser amplification device to amplify the seed laser.

[0047] In a preferred embodiment, the laser amplification method can change the laser amplification factor by adjusting the incident angle of the seed laser or the field intensity of the radio frequency electric field focuser 2 .

[0048] The amplification factor is mainly determined by the incident angle of the laser, the field strength of the RF electric field focuser, and the reflectivity of the reflection cavity. Generally, the larger the incident angle, the better (greater than 60 degrees), the higher the field strength of the focuser, the better, and the larger the reflectivity of the reflection cavity surface, the better. The theoretically estimated amplification factor can reach 10 to 1000 times. During use, the amplification factor of the laser can be changed by adjusting the incident angle of the seed laser or the field strength of the RF electric field focuser.

[0049] At present, there are few mechanisms for generating extreme ultraviolet laser amplification, mainly using a higher-power pump laser to heat the luminescent gas to produce plasma. In terms of volume, this pump laser is very large, consumes kilowatts of power, is as big as a small refrigerator, is expensive, costs about 500,000 to 1.5 million, and has a service life of about 10,000 hours. The present invention uses solid-state RF focusing technology, uses a low-voltage DC solid-state RF source, can be powered by a lithium battery, is slightly smaller than an A5 notebook, has a service life of more than 20,000 hours, and consumes about 250 watts.

[0050] The various embodiments listed above can be combined with each other for implementation without contradiction. Those skilled in the art can combine the drawings and the explanation of the embodiments above as a basis for combining the technical features in different embodiments.

[0051] It should be pointed out that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A laser amplification device, characterized in that: Including reflection cavity and radio frequency electric field focuser, The reflection cavity is filled with luminous gas; At least a portion of the reflection cavity is located within the energy focusing range of the radio frequency electric field focuser; The reflection cavity is provided with a slit for the laser to pass through; The reflection cavity is an annular reflection cavity, a protrusion is provided on the outer side of the reflection cavity, the protrusion is connected to the reflection cavity, and the radio frequency electric field focuser is opposite to the protrusion, and the distances between adjacent protrusions are the same.

2. The laser amplification device according to claim 1, characterized in that: The cavity structure of the reflection cavity is an annular tube structure.

3. The laser amplification device according to claim 1, characterized in that: The invention also comprises a window sheet for sealing the slit, and the laser can pass through the window sheet.

4. The laser amplification device according to claim 1, characterized in that: The slit is an adjustable slit.

5. The laser amplification device according to claim 4, characterized in that: The width of the slit can be adjusted within the range of 10 μm to 1 mm.

6. The laser amplification device according to claim 1, characterized in that: The number of the protrusions is more than one, and the number of the radio frequency electric field focusers is the same as the number of the protrusions; The laser amplifying device further comprises a bracket, the radio frequency electric field focuser is fixed on the bracket, opposite to the protrusion, and the bracket is placed around the outside of the reflection cavity.

7. The laser amplification device according to claim 1, characterized in that: The reflection cavity is provided with an air inlet and an air outlet.

8. A laser amplification method, characterized in that: The seed laser is amplified using the laser amplification device as described in any one of claims 1 to 7.

9. The laser amplification method according to claim 8, characterized in that: The laser amplification factor is changed by adjusting the incident angle of the seed laser or the field intensity of the radio frequency electric field focuser.

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