A positioning adjustment method and device for a laser light path

Abstract

The application relates to a positioning adjustment method and device of a laser light path, which method comprises the following steps: using a calibration light with a mark to be incident into an optical system of a laser along a light path of the laser; replacing a preselected optical lens in the optical system with a corresponding replacement lens, the refractive index of the replacement lens relative to the calibration light being the same as that of the corresponding optical lens in the optical system relative to laser light of the laser; adjusting the position and angle of a mechanical structure where each replacement lens is located according to the spot characteristics of the calibration light output from the optical system; and restoring the replacement lens into the corresponding optical lens, thereby completing the positioning adjustment of the light path of the laser. The method of the application introduces cross-line standard light and replacement optical lenses, does not need to change any design in the light path, adjusts the position and angle of each optical lens in the optical system of the laser, and improves the output laser quality of the laser.

Description

Technical Field

[0001] This invention relates to the field of laser technology, and in particular to a method and apparatus for positioning and adjusting the optical path of a laser. Background Technology

[0002] Due to their short wavelength and high power, excimer lasers have become the primary light source for large-scale semiconductor integrated circuit lithography, and lithography machines represent the largest industrial application of excimer lasers. With the lithography node approaching 32nm, ArF excimer lithography has become mainstream and is expected to be applied to even lower nodes like 22nm and 16nm. Relatedly, current research on excimer laser technology mainly focuses on excimer laser technology for lithography. As the lithography node decreases, ArF excimer lasers are required to have more stable narrow spectral linewidths, higher output power, higher dose stability, and longer gas lifetimes. Currently, the method used is to repeatedly input the seed light into the gain amplification cavity using ring cavity technology, resulting in a long residence time in the amplification cavity, and the amplification cavity operates in a deeply saturated state. Compared to single-pass amplification technology, this method has advantages in that it is more efficient, has higher energy, more stable output, and a wider output pulse.

[0003] Accurate control of the optical path through the gain region of the gain amplifier cavity determines the success or failure of ring cavity technology. Excimer lasers, a type of gas laser, are generally characterized by their large size, long optical path, high degree of modularity, and reduced coupling between components. These characteristics all contribute to the difficulty of optical path transmission design and adjustment. Furthermore, ensuring that the assembled optical path and optomechanical structure meets the design precision requirements, and how to perform assembly, adjustment, and testing, also present significant challenges. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method and apparatus for positioning and adjusting the optical path of a laser, used to adjust the position and angle of each optical lens in the optical system of a laser to improve the output laser quality.

[0005] One aspect of the present invention provides a method for positioning and adjusting the optical path of a laser, the method comprising:

[0006] S1. Using a marked calibration light, incident on the optical system of the laser along the optical path of the laser;

[0007] S2. Replace the pre-selected optical lens in the optical system with a corresponding replacement lens, wherein the refractive index of the replacement lens relative to the calibration light is the same as the refractive index of the corresponding optical lens in the optical system relative to the laser light of the laser.

[0008] S3. Based on the spot characteristics of the light output from the optical system after the calibration light is replaced, adjust the position and angle of the mechanical structure where each replacement lens is located;

[0009] S4. Restore the replacement lens to the corresponding optical lens to complete the optical path positioning adjustment of the laser.

[0010] The optical system, transmitted along the optical path, includes, in sequence: a first window, a second window, a mirror group, a first beam splitter, a first tunable mirror, a second tunable mirror, a third window, a fourth window, a refracting prism, and a second beam splitter.

[0011] The seed light output from the first tuned mirror is reflected by the second tuned mirror and then sequentially input into the third and fourth windows for amplification. After being refracted by the refracting prism, it is then sequentially input into the fourth and third windows for amplification. The amplified seed light is then output after passing through the second beam splitter.

[0012] Specifically, the replacement lenses include lenses used to replace the first fabric window, the second fabric window, the reflector group, the first beam splitter, the third fabric window, the fourth fabric window, the refractive prism, and the second beam splitter.

[0013] The calibration light is a crosshair standard light, and the calibration light has a preset divergence angle and spot size.

[0014] The calibration light is visible light.

[0015] The laser is a calcium fluoride excimer laser, and the refractive index of the optical lens in the optical system relative to the laser light from the laser is 1.5.

[0016] The wavelength of the calibration light is 532 nm, the replacement lens is H-K1 glass, and the refractive index of the replacement lens relative to the calibration light is 1.5.

[0017] The replacement lens has the same structure as the corresponding optical lens.

[0018] In another aspect, the present invention provides a positioning and adjustment device for a laser optical path, the device comprising:

[0019] A calibration light source for emitting marked calibration light, which is incident on the optical system of the laser along the optical path of the laser to be calibrated;

[0020] A replacement lens is used to replace a pre-selected optical lens in the optical system, wherein the refractive index of the replacement lens relative to the calibration light is the same as the refractive index of the corresponding optical lens in the optical system relative to the laser light of the laser.

[0021] A receiving device is used to receive the calibration light output from the optical system after the replaced lens, analyze the spot characteristics of the received light, and determine the adjustment information of the position and angle of the mechanical structure where the replacement lens is located.

[0022] The laser optical path positioning and adjustment method and apparatus of the present invention introduces a crosshair standard beam and a replacement optical lens, without requiring any changes to the optical path design. The resulting optical path refraction is consistent with the actual laser operation, and it does not require coupling into other modules; only the optomechanical structure of the optical path transmission is involved, reducing sources of error and simplifying operation. Furthermore, the crosshair standard beam and the replacement optical glass lens are reusable, requiring no destructive replacement. This saves on laser calibration costs. Attached Figure Description

[0023] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0024] Figure 1 This is a flowchart of the laser optical path positioning and adjustment method of the present invention;

[0025] Figure 2 This is a schematic diagram of the optical path of the excimer laser of the present invention;

[0026] Figure 3 This is a schematic diagram of the optical path of the excimer laser of the present invention after the optical lens is replaced by a replacement lens. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0028] This invention provides a method for positioning and adjusting the optical path of a laser, such as... Figure 1 As shown, the method includes:

[0029] S1. Using a marked calibration light, incident on the optical system of the laser along the optical path of the laser;

[0030] S2. Replace the pre-selected optical lens in the optical system with a corresponding replacement lens, wherein the refractive index of the replacement lens relative to the calibration light is the same as the refractive index of the corresponding optical lens in the optical system relative to the laser light of the laser.

[0031] S3. Based on the spot characteristics of the calibration light output from the optical system after the replaced lens, adjust the position and angle of the mechanical structure where each replacement lens is located;

[0032] S4. Restore the replacement lens to the corresponding optical lens to complete the optical path positioning adjustment of the laser.

[0033] In this embodiment, the laser is an excimer laser, such as an ArF excimer laser. At the same time, this method is also applicable to other types of lasers. By adjusting the position and angle of the optical lenses of the resonant cavity and gain cavity of the laser using the above method, the accuracy of the laser and the quality of the output light can be improved. In addition, the replacement lenses of the above method can be reused, reducing costs.

[0034] The following section uses an ArF excimer laser as an example to describe in detail the above-mentioned laser optical path positioning and adjustment method.

[0035] like Figure 2 The diagram shows the optical path of an existing excimer laser. The seed light output from the resonant cavity enters the gain discharge cavity twice, and the two amplified beams are separated by a small angle α. Figure 2 All optical components are positioned by mechanical structures, meaning that the positioning of the mechanical structures affects the baseline and implementation of the optical path design. Therefore, the positioning adjustment method of the embodiment can be used to adjust the excimer laser.

[0036] like Figure 2 As shown, the present invention mainly focuses on adjusting the optical system between the resonant cavity and the gain cavity. The optical system, transmitted along the optical path, includes, in sequence: a first window 101, a second window 102, a mirror group 103, a first beam splitter 104, a first tunable mirror 105, a second tunable mirror 106, a third window 107, a fourth window 108, a refractive prism 109, and a second beam splitter 110.

[0037] The light output from the linewidth selection module of the excimer laser is seeded after passing through the resonant cavity, and then amplified twice before being output, such as... Figure 2As shown, the seed light output from the first tuned mirror 105 is reflected by the second tuned mirror 106 and then sequentially input into the third window 107 and the fourth window 108 for amplification. After being refracted by the refracting prism 109, it is sequentially input into the fourth window 108 and the third window 107 for amplification. The amplified seed light is then output after passing through the second beam splitter 110.

[0038] To calibrate the optical system of an excimer laser, calibration light is incident on the optical system along the original optical path from the position of the linewidth selection module. Some optical lenses in the optical system are replaced with replacement lenses. Then, a calibration light source is incident on the optical system, and the optical system of the excimer laser is corrected by adjusting the position and angle of the replacement lenses.

[0039] In this embodiment, the calibration light uses a marked crosshair standard light. Visible light can also be selected, allowing for direct observation of the light transmission path in a long optical path. Alternatively, marked fluorescence or other materials can be used as calibration light, with the corresponding receiver at the output end of the optical system used to adjust the optical path.

[0040] like Figure 3 The diagram shows the optical path of an excimer laser after the optical lenses have been replaced. The four window lenses, two beam splitter lenses, the mirror group lenses, and the folding prism lenses in the optical path are replaced, specifically: the first window 101 is replaced with the first replacement window 201, the second window 102 is replaced with the second replacement window 202, the mirror group is replaced with the replacement mirror group 203, the first beam splitter 104 is replaced with the first replacement beam splitter 204, the first tunable mirror 105 is replaced with the first replacement tunable mirror 205, the second tunable mirror 106 is replaced with the second replacement tunable mirror 206, the third window 107 is replaced with the third replacement window 207, the fourth window 108 is replaced with the fourth replacement window 208, the refractive prism 109 is replaced with the replacement refractive prism 209, and the second beam splitter 110 is replaced with the second replacement beam splitter 210. The replacement principle mentioned above is that the refractive index of the lens in the original optical path relative to the laser of the excimer laser (@193nm) is consistent with the refractive index of the replacement lens relative to the calibration light (@cross standard laser wavelength), which can ensure the consistency of the optical path offset.

[0041] In one embodiment, if calcium fluoride (CaF2) is used in the original optical path, its refractive index is n193nm = 1.5; and if the crosshair standard light is selected at 532nm, H-K1 optical glass can be used, with a refractive index n532nm = 1.5. According to the law of refraction, for corresponding wavelengths, materials with the same refractive index will have the same optical path in a flat plate lens of the same thickness; similarly, a prism can be considered equivalent to a parallel plate, and this rule also applies.

[0042] After replacing some lenses, the crosshair standard light is introduced along the optical path. The new optical system, composed of the replaced lenses, receives the crosshair standard light at the output light point through a receiving device. Since the crosshair standard light is known, its divergence angle and spot size are known. Therefore, by detecting the positional deviation of the output light spot, the positioning deviation of the mechanical components in the optical path can be calculated, and it can be determined whether it can be compensated by the tuning structure. Thus, by adjusting the position and angle of the mechanical structure where each replaced lens is located, the high precision of the excimer laser's output light can be achieved.

[0043] The above embodiments are only examples of excimer lasers. In actual use, the optical path positioning and adjustment of the optical systems of other types of lasers, such as resonant cavities and gain cavities, can be adjusted accordingly based on the above method. Therefore, the laser optical path positioning and adjustment method of the present invention can be applied to the positioning and adjustment of the optical paths of various lasers.

[0044] In another embodiment of the present invention, a positioning and adjustment device for a laser optical path is provided, the method specifically including:

[0045] A calibration light source for emitting marked calibration light, which is incident on the optical system of the laser along the optical path of the laser to be calibrated;

[0046] A replacement lens is used to replace a pre-selected optical lens in the optical system, wherein the refractive index of the replacement lens relative to the calibration light is the same as the refractive index of the corresponding optical lens in the optical system relative to the laser light of the laser.

[0047] A receiving device is used to receive the calibration light output from the optical system after the replaced lens, analyze the spot characteristics of the received light, and determine the adjustment information of the position and angle of the mechanical structure where the replacement lens is located.

[0048] The device in this embodiment can realize the laser optical path positioning and adjustment method of the above embodiment, and its structure is as follows: Figure 3As shown, the calibration light emitted by the calibration light source is used to emit light that replaces the incident optical system of the laser. The replacement lens includes a first replacement window 201, a second replacement window 202, a replacement mirror group 203, a first replacement beam splitter 204, a first replacement tunable mirror 205, a second replacement tunable mirror 206, a third replacement window 207, a fourth replacement window 208, a replacement refractive prism 209, and a second replacement beam splitter 210. After replacing the corresponding lens in the corresponding optical system, the output light is received and analyzed by a receiving device to determine the adjustment information of the position and angle of the mechanical structure where the replacement lens is located. This allows for adjustment of the mechanical structure where the replacement lens is located, and then restoration to the original lens, thereby achieving adjustment of the laser's optical path.

[0049] exist Figure 3 In the illustrated embodiment, the receiving device is a computer monitoring device used to analyze the received light spot. Other receiving devices that can receive the output light and perform corresponding analysis on the light are also applicable to the device of the present invention, and will not be described in detail here.

[0050] The laser optical path positioning and adjustment method and apparatus of the present invention introduces a crosshair standard beam and a replacement optical lens, without requiring any changes to the optical path design. The resulting optical path refraction is consistent with the actual laser operation, and it does not require coupling into other modules; only the optomechanical structure of the optical path transmission is involved, reducing sources of error and simplifying operation. Furthermore, the crosshair standard beam and the replacement optical glass lens are reusable, requiring no destructive replacement. This saves on laser calibration costs.

[0051] It is understood that the present invention has been described through some embodiments, and those skilled in the art can make various changes or equivalent substitutions to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. A method for positioning and adjusting the optical path of a laser, characterized in that, The method includes: S1. Using a marked calibration light, incident on the optical system of the laser along the optical path of the laser; S2. Replace the pre-selected optical lens in the optical system with a corresponding replacement lens, wherein the refractive index of the replacement lens relative to the calibration light is the same as the refractive index of the corresponding optical lens in the optical system relative to the laser light of the laser. S3. Based on the spot characteristics of the light output from the optical system after the calibration light is replaced, adjust the position and angle of the mechanical structure where each replacement lens is located; S4. Restore the replacement lens to the corresponding optical lens to complete the optical path positioning adjustment of the laser.

2. The method as described in claim 1, characterized in that, The optical system, transmitted along the optical path, includes, in sequence: a first window, a second window, a mirror group, a first beam splitter, a first tunable mirror, a second tunable mirror, a third window, a fourth window, a refracting prism, and a second beam splitter.

3. The method as described in claim 2, characterized in that, The seed light output from the first tunable mirror is reflected by the second tunable mirror and then sequentially input into the third and fourth windows for amplification. After being refracted by the refracting prism, it is then sequentially input into the fourth and third windows for amplification. The amplified seed light is then output after passing through the second beam splitter.

4. The method as described in claim 2, characterized in that, The replacement lenses specifically include lenses used to replace the first fabric window, the second fabric window, the reflector group, the first beam splitter, the third fabric window, the fourth fabric window, the refractive prism, and the second beam splitter.

5. The method as described in claim 1, characterized in that, The calibration light is a crosshair standard light, and the calibration light has a preset divergence angle and spot size.

6. The method as described in claim 1, characterized in that, The calibration light is visible light.

7. The method as described in claim 1, characterized in that, The laser is a calcium fluoride excimer laser, and the refractive index of the optical lens in the optical system relative to the laser light from the laser is 1.

5.

8. The method as described in claim 7, characterized in that, The wavelength of the calibration light is 532 nm, the material of the replacement lens is H-K1 glass, and the refractive index of the replacement lens relative to the calibration light is 1.

5.

9. The method as described in claim 1, characterized in that, The replacement lens has the same structure as the corresponding optical lens.

10. A positioning and adjustment device for a laser optical path, characterized in that, The device includes: A calibration light source for emitting marked calibration light, which is incident on the optical system of the laser along the optical path of the laser to be calibrated; A replacement lens is used to replace a pre-selected optical lens in the optical system, wherein the refractive index of the replacement lens relative to the calibration light is the same as the refractive index of the corresponding optical lens in the optical system relative to the laser light of the laser. A receiving device is used to receive the calibration light output from the optical system after the replaced lens, analyze the spot characteristics of the received light, and determine the adjustment information of the position and angle of the mechanical structure where the replacement lens is located.

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