Assembly and adjustment device for pulse broadening unit

Abstract

This application discloses an assembly and adjustment device for a pulse broadening unit, comprising: a visible light source device, a pulse broadening unit, a phase delay element, a linear polarizer, and a reticle; the pulse broadening unit includes a beam splitter and a mirror assembly; the output beam from the visible light source device is incident on the beam splitter; the beam splitter splits the received output beam into a first reflected beam and a transmitted beam; the first reflected beam, after passing through a reflective lens assembly, is incident on the exit surface of the beam splitter, and after being reflected by the exit surface, it illuminates the reticle together with the transmitted beam; the linear polarizer is disposed in the optical path from which the transmitted beam exits, and the angle between its transmission direction and the polarization direction of the transmitted beam transmitted from the beam splitter satisfies the following condition: eliminating part of the energy of the transmitted beam; the phase delay element is disposed in the optical path before the first reflected beam is incident on the exit surface of the beam splitter, and is used to rotate the polarization direction of the first reflected beam by the same angle.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical technology, in particular to a kind of pulse stretcher unit's installation and adjustment device. BACKGROUND

[0002] ArF excimer laser is widely used in integrated circuit manufacturing field.Excimer laser needs to rely on gas high-voltage discharge to generate deep ultraviolet laser radiation, and the laser pulse width generated by discharge cavity is about 10ns due to the limitation of glow discharge time.In order to ensure that the light source realizes good transmission after energy method process, reduce the light-induced damage of various optical elements in subsequent transmission process, and improve the service life of optical elements, laser pulse stretcher device is needed to expand laser pulse from time domain, reduce laser irradiation peak power density.The principle of pulse stretcher unit to realize pulse expansion is multi-mirror mutual coupling imaging laser delay mechanism.Pulse stretcher unit contains multiple mirrors.At present, the pulse stretcher unit equipped for excimer laser used in immersion lithography machine generally needs 12 mirrors or even more.The mirrors need to be accurately installed to the specified position to form an accurate delay optical path, so that the laser beams can accurately coincide when reaching the outlet of pulse stretcher unit.

[0003] The installation and adjustment of pulse stretcher unit equipped for excimer laser is very difficult.The main reasons for the difficulty are as follows:1, the mirrors of pulse stretcher unit equipped for excimer laser are coated with high-reflectivity film for 193nm waveband, and the reflectivity of visible light waveband is between 4-10%.If the commonly used visible light waveband installation and adjustment instrument (such as visible light collimator) is directly used for installation and adjustment, the intensity of light beam directly transmitted from beam splitter will be much stronger than that of light beam output after passing through mirror, so the commonly used visible light waveband installation and adjustment instrument (such as visible light collimator) cannot be used for installation and adjustment.2, the number of mirrors of pulse stretcher unit equipped for excimer laser is large, and the optical path is long, which leads to high positioning accuracy requirement for mirrors, and the position of mirror cannot be directly determined by the accuracy of mechanical processing.

[0004] The commonly used method for installation and adjustment of pulse stretcher unit equipped for current excimer laser is to use deep ultraviolet collimator and deep ultraviolet autocollimator for installation and adjustment, but there is no commercial product for deep ultraviolet collimator and deep ultraviolet autocollimator, which has great research and development difficulty and high research and development cost. SUMMARY

[0005] The present application provides a kind of pulse stretcher unit installation and adjustment device to solve the problem of difficult installation and adjustment of pulse stretcher unit equipped for excimer laser in prior art.

[0006] The present application provides a kind of pulse stretcher unit installation and adjustment device, which comprises a visible light source device, a pulse stretcher unit, a phase delay element, a linear polarizer and a reticle.

[0007] The pulse stretching unit comprises a beam splitting element and a mirror group;

[0008] The output light beam output by the visible light source device is incident on the beam splitting element; the beam splitting element divides the received output light beam into a first reflected light beam and a transmitted light beam; the first reflected light beam is incident on the exit surface of the beam splitting element after passing through the reflection lens group, and after being reflected by the exit surface, it is irradiated together with the transmitted light beam to the reticle;

[0009] The linear polarizer is arranged in the light path of the transmitted light beam, and the included angle between the light transmission direction of the linear polarizer and the polarization direction of the transmitted light beam transmitted from the beam splitting element satisfies the following condition: eliminating part of the energy of the transmitted light beam;

[0010] The phase retardation element is arranged in the light path before the first reflected light beam is incident on the exit surface of the beam splitting element, and is used to rotate the polarization direction of the first reflected light beam by the same angle as the included angle.

[0011] As an embodiment, the visible light source device is arranged on the cavity of the pulse stretching unit, and the cavity is a mechanical reference; the output light beam of the visible light source device is concentric with the entrance light path of the pulse stretching unit.

[0012] As an embodiment, the visible light source device is a laser, and the wavelength of the output light beam of the laser is in the visible light wavelength range.

[0013] As an embodiment, the polarization direction of the laser is horizontal.

[0014] As an embodiment, the laser is a 532nm laser.

[0015] As an embodiment, the included angle between the light transmission direction and the polarization direction of the transmitted light beam transmitted from the beam splitting element is 90 degrees, and the phase retardation element is a half-wave plate.

[0016] As an embodiment, the mirror group comprises four mirrors: a first mirror, a second mirror, a third mirror, and a fourth mirror; and the phase retardation element is arranged between the beam splitting element and the first mirror.

[0017] The first reflected light beam is incident on the exit surface of the beam splitting element after passing through the reflection lens group, and after being reflected by the exit surface, it is irradiated together with the transmitted light beam to the reticle, comprising:

[0018] The first reflected light beam is incident to the first mirror through the phase delay element, is reflected by the first mirror, the second mirror and the third mirror in sequence, and is incident to the fourth mirror; the second reflected light beam formed by the reflection of the fourth mirror is reflected by the exit surface of the beam splitting element to form a third reflected light beam; and the third reflected light beam and the transmitted light beam are incident to the reticle together.

[0019] As an implementation form, the number of mirrors included in the mirror group is even.

[0020] As an implementation form, the mirror is a spherical mirror.

[0021] As an implementation form, the reticle is a ground glass reticle, and the pattern is a chessboard pattern.

[0022] Compared with the prior art, the application has the following advantages:

[0023] The application provides an adjusting device of a pulse stretching unit, which comprises a visible light source device, a pulse stretching unit, a phase delay element, a linear polarizer and a reticle; the pulse stretching unit comprises a beam splitting element and a mirror group; the output light beam output by the visible light source device is incident to the beam splitting element; the beam splitting element divides the received output light beam into a first reflected light beam and a transmitted light beam; the first reflected light beam is incident to the exit surface of the beam splitting element after passing through the mirror group, is reflected by the exit surface, and is incident to the reticle together with the transmitted light beam; the linear polarizer is arranged in the light path of the transmitted light beam, and the included angle between the light transmission direction of the linear polarizer and the polarization direction of the transmitted light beam transmitted from the beam splitting element satisfies the following condition: the part of the energy of the transmitted light beam can be eliminated; the phase delay element is arranged in the light path before the first reflected light beam is incident to the exit surface of the beam splitting element, and is used for rotating the polarization direction of the first reflected light beam by the same angle as the included angle.

[0024] The pulse expansion unit adjusting device provided by the application can solve the problem that the pulse expansion unit equipped by the excimer laser has low reflectivity to the light emitted by the visible light source device (for example, an auxiliary laser), and the light brightness of the two light spots at the outlet of the pulse expansion unit is too different. By using the polarization characteristics of the light, the angle between the transmission direction of the polarizer and the polarization direction of the transmission light beam transmitted from the beam splitting element can eliminate part of the energy of the transmission light beam, so that the linear polarizer is used to attenuate the transmission light beam with higher brightness, and the phase delay element is arranged in the light path before the first reflected light beam is incident on the exit surface of the beam splitting element, so as to rotate the polarization direction of the first reflected light beam by the same angle as the aforementioned angle, thereby realizing that the reflected light beam is not attenuated, and the brightness values of the two light beams reaching the reticle are close, so that the visible light source device (for example, an auxiliary laser) can be used to adjust the pulse expansion unit. The problem of difficult adjustment of the pulse expansion unit equipped by the excimer laser in the prior art is solved. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 FIG. 1 is a schematic diagram of a pulse expansion unit adjusting device provided by the application.

[0026] Figure 2 FIG. 2 is a schematic diagram of a reticle pattern provided by the first embodiment of the application. DETAILED DESCRIPTION

[0027] In the following description, many specific details are set forth in order to provide a thorough understanding of the application. However, the application can be practiced without the specific details, and the skilled person can make similar generalizations without departing from the scope of the application, so the application is not limited to the specific implementation disclosed below.

[0028] The first embodiment of the application provides a pulse expansion unit adjusting device, as shown in Figure 1 .

[0029] The pulse expansion unit adjusting device comprises a visible light source device 1-1, a pulse expansion unit, a phase delay element 1-3, a linear polarizer 1-4, and a reticle 1-5.

[0030] The pulse expansion unit comprises a beam splitting element 1-2-1 and a mirror group 1-2-2.

[0031] The visible light source device 1-1 is arranged on the cavity of the pulse expansion unit, and the cavity is a mechanical reference; the output light beam of the visible light source device is concentric with the entrance light path of the pulse expansion unit.

[0032] The output light beam output by the visible light source device 1-1 is incident to the beam splitting element 1-2-1; the beam splitting element 1-2-1 divides the received output light beam into a first reflected light beam and a transmitted light beam; the first reflected light beam is incident to the exit surface of the beam splitting element 1-2-1 after passing through the reflection lens group, and after being reflected by the exit surface, the first reflected light beam and the transmitted light beam together irradiate the reticle 1-5;

[0033] The linear polarizer 1-4 is arranged in the light path of the transmitted light beam, and the included angle between the light transmission direction of the linear polarizer and the polarization direction of the transmitted light beam transmitted from the beam splitting element satisfies the following condition: eliminating part of the energy of the transmitted light beam;

[0034] The phase delay element 1-3 is arranged in the light path before the first reflected light beam is incident to the exit surface of the beam splitting element 1-2-1, and is used to rotate the polarization direction of the first reflected light beam by the same angle as the aforementioned included angle.

[0035] The working principle of the adjusting device of the pulse stretching unit provided by the first embodiment of the present application is described as follows: the output light beam output by the visible light source device 1-1 is incident to the beam splitting element 1-2-1; the beam splitting element 1-2-1 divides the received output light beam into a first reflected light beam and a transmitted light beam; the transmitted light beam reaches the linear polarizer 1-4, and since the included angle between the light transmission direction of the linear polarizer and the polarization direction of the transmitted light beam transmitted from the beam splitting element can eliminate part of the energy of the transmitted light beam, the transmitted light beam eliminates part of the energy after passing through the linear polarizer; the phase delay element 1-3 after the beam splitting element 1-2-1 rotates the polarization direction of the first reflected light beam reflected by the beam splitting mirror by an angle, and the angle is the angle of the included angle between the light transmission direction of the linear polarizer and the polarization direction of the transmitted light beam transmitted from the beam splitting element, so that the energy of the reflected light beam is not attenuated after passing through the linear polarizer; since the transmitted light beam eliminates part of the energy after passing through the linear polarizer, and the energy of the reflected light beam is not attenuated after passing through the linear polarizer, the brightness values of the two light beams reaching the reticle are close, so that the visible light source device (for example, an auxiliary laser) can be used to adjust the pulse stretching unit.

[0036] Since the pulse stretching unit is currently adjusted by using a deep ultraviolet collimator and a deep ultraviolet autocollimator, there is no commercially available product for the deep ultraviolet collimator and the deep ultraviolet autocollimator, the research and development is difficult, and the research and development cost is high. In practical applications, an auxiliary visible light source device (for example, an auxiliary laser) can be considered for adjustment, but the optical power of the light reaching the pulse stretching unit outlet of the excimer laser equipped with a beam splitting mirror is much larger than the optical power of the light reflected by the beam splitting mirror and reaching the pulse stretching unit outlet of the excimer laser equipped with a reflection mirror. The brightness values of the two light spots at the pulse stretching unit outlet of the excimer laser are too different, which exceeds the observation range of the human eye, and adjustment cannot be performed. Therefore, the visible light source device cannot be directly used in the adjustment of the pulse stretching unit of the excimer laser.

[0037] Compared with the prior art, the first embodiment of this application addresses the problems of low reflectivity of light emitted by visible light source devices (e.g., auxiliary lasers) in the pulse stretching unit equipped with an excimer laser and excessive brightness difference between the two light spots at the exit of the pulse stretching unit. By utilizing the polarization characteristics of light, the polarizer is set such that the angle between the transmission direction and the polarization direction of the transmitted beam transmitted from the beam splitter satisfies the condition of eliminating part of the energy of the transmitted beam. This achieves attenuation of the brighter transmitted beam using a linear polarizer. At the same time, a phase delay element is placed in the optical path before the first reflected beam is incident on the exit surface of the beam splitter to rotate the polarization direction of the first reflected beam by the same angle as the aforementioned angle. This achieves no attenuation of the reflected beam, making the brightness values ​​of the two beams reaching the reticle close. Thus, the pulse stretching unit can be assembled and adjusted using a visible light source device (e.g., auxiliary laser).

[0038] In one implementation, the visible light source device can be a laser, and the wavelength of the laser's output beam is within the visible light band. The polarization direction of the laser can be horizontal.

[0039] The laser can be a 532nm laser, or a laser of other wavelengths can be selected.

[0040] In one implementation, the angle between the light transmission direction and the polarization direction of the transmitted beam transmitted from the beam splitter is 90 degrees, and the phase delay element is a half-wave plate.

[0041] It should be noted that the angle between the transmission direction of the linear polarizer and the polarization direction of the transmitted beam from the beam splitter can also be other angles, as long as it can achieve the goal of eliminating part of the transmitted beam's energy and ensuring that the energies of the two beams (transmitted beam and reflected beam) reaching the reticle are close. The phase delay element can also be a single element or a combination of elements capable of rotating the polarization direction of the first reflected beam by a certain angle (the degree measure of the angle between the transmission direction of the linear polarizer and the polarization direction of the transmitted beam from the beam splitter).

[0042] In one implementation, the mirror assembly includes an even number of mirrors. For example, the mirror assembly may include 4 or 6 mirrors.

[0043] As one implementation method, the reflector can be a spherical reflector.

[0044] In one implementation, the mirror assembly includes four mirrors: a first mirror, a second mirror, a third mirror, and a fourth mirror; a phase delay element is disposed between the beam splitter and the first mirror.

[0045] The first reflected beam, after passing through the reflecting lens group, enters the exit surface of the beam splitter element. After being reflected by the exit surface, it, along with the transmitted beam, illuminates the reticle, including:

[0046] The first reflected beam is incident on the first reflecting mirror after passing through the phase delay element, and is then reflected by the first, second, and third reflecting mirrors before being incident on the fourth reflecting mirror. The second reflected beam formed by the reflection of the fourth reflecting mirror is reflected by the exit surface of the beam splitter to form the third reflected beam. The third reflected beam and the transmitted beam together illuminate the reticle.

[0047] like Figure 1 As shown, the reflector group includes four reflectors: a first reflector 1-2-2-1, a second reflector 1-2-2-2, a third reflector 1-2-2-3, and a fourth reflector 1-2-2-4; a phase delay element 1-3 is disposed between the beam splitter element 1-2-1 and the first reflector 1-2-2-1; the first reflected beam passes through the phase delay element 1-3 and is incident on the first reflector, and is reflected sequentially by the first reflector 1-2-2-1, the second reflector 1-2-2-2, and the third reflector 1-2-2-3 before being incident on the fourth reflector 1-2-2-4; the second reflected beam formed by the reflection of the fourth reflector 1-2-2-4 is reflected by the exit surface of the beam splitter element 1-2-1 to form a third reflected beam; the third reflected beam and the transmitted beam together illuminate the reticle 1-5.

[0048] It should be noted that, for ease of installation and adjustment, the phase delay element can be placed between the beam splitter element 1-2-1 and the first reflector 1-2-2-1. In specific implementation, the phase delay element can also be placed between the first and second reflectors, between the second and third reflectors, between the third and fourth reflectors, or between the fourth reflector and the beam splitter element.

[0049] The reticle can be made of frosted glass with a checkerboard pattern. Reticles made of other materials are also available, and patterns can be designed according to requirements.

[0050] The following describes a specific scheme and basic principle of a pulse broadening unit assembly and adjustment device for an excimer laser. For example... Figure 1As shown. The cavity of the pulse stretching unit equipped with the excimer laser is a mechanical reference. The auxiliary laser used for assembly is a 532nm laser with a polarization ratio of 10000:1. The polarization direction is horizontal. The 532nm laser is mounted on the mechanical reference, and the output beam of the 532nm laser 1-1 is concentric with the entrance optical path of the pulse stretching unit 1-2. A half-wave plate 1-3 is installed after the beam splitter 1-2-1 to rotate the polarization direction of the reflected beam from the beam splitter by 90°. A linear polarizer 1-4 with an extinction ratio of 100000:1 is placed in front of the frosted glass reticle 1-5. The transmission direction of the linear polarizer is perpendicular to the polarization direction of the transmitted beam from the beam splitter, aiming to block most of the transmitted beam from the beam splitter. A frosted glass reticle 1-5 is installed at the exit of the pulse stretching unit. The pattern on the frosted glass reticle is a checkerboard pattern, as shown. Figure 2 As shown. The width of each small square is 1mm.

[0051] In this specific implementation, the optical power of the 532nm laser is 10000mW. The reflectivity of beam splitter 1-2-1 for the 532nm laser is 20%, and the reflector's reflectivity is also 20%. Therefore, the optical power of the transmitted beam through the beam splitter reaching reticle 1-5 is 0.88mW. The optical power of the reflected beam from beam splitter 1-2-1 reaching reticle 1-5 is 0.64mW. It is evident that the optical powers of the two are similar, and their brightness on the reticle is also similar. Adjusting the first, second, third, and fourth reflectors, the beam spot of the beam splitter's reflected light is aligned with the beam spot of the transmitted light, meaning the two beam spots appear to overlap on the reticle. At this point, the pulse broadening unit equipped with the excimer laser has completed its adjustment.

[0052] against Figure 1 The adjustment process for the pulse broadening unit shown in the diagram may include the following steps:

[0053] (1) Mount the 532nm laser 1-1 onto the mechanical reference, and the polarization direction of the output laser is horizontal.

[0054] (2) Install the beam splitter 1-2-1 onto the lens mount and tighten it.

[0055] (3) Install the first reflector 1-2-2-1.

[0056] (4) Install half-wave plates 1-3.

[0057] (5) Turn on the 532nm laser and wait for it to stabilize.

[0058] (6) Adjust the first reflector 1-2-2-1 so that the 532nm laser shines on the center of the first reflector.

[0059] (7) Install the second reflector 1-2-2-2 and adjust the first reflector 1-2-2-1 so that the 532nm laser shines on the center of the second reflector.

[0060] (8) Install the third reflector 1-2-2-3 and adjust the second reflector 1-2-2-2 so that the 532nm laser shines on the center of the third reflector.

[0061] (9) Install the fourth reflector 1-2-2-4 and adjust the third reflector 1-2-2-3 so that the 532nm laser shines on the center of the fourth reflector.

[0062] (10) Install frosted glass reticle 1-5.

[0063] (11) Install linear polarizers 1-4.

[0064] (12) Adjust the linear polarizers 1-4 to make the light spot that passes through the beam splitter and illuminates the frosted glass reticle the weakest.

[0065] This concludes the introduction of the first embodiment of this application. The pulse stretching unit assembly and adjustment device provided in the first embodiment of this application addresses the problems of low reflectivity of the pulse stretching unit equipped with an excimer laser to the laser from a visible light-assisted laser, and excessive difference in laser brightness at the exit of the pulse stretching unit equipped with an excimer laser. By utilizing the polarization characteristics of light, the polarizer is set such that the angle between the transmission direction and the polarization direction of the transmitted beam transmitted from the beam splitter element is sufficient to eliminate part of the energy of the transmitted beam. This achieves attenuation of the brighter transmitted beam using a linear polarizer. Simultaneously, a phase delay element is placed in the optical path before the first reflected beam is incident on the exit surface of the beam splitter element to rotate the polarization direction of the first reflected beam by the same angle as mentioned above, thereby achieving no attenuation of the reflected beam and making the brightness values ​​of the two beams reaching the reticle similar. Thus, a visible light source device (e.g., an auxiliary laser) can be used to assemble and adjust the pulse stretching unit. Furthermore, using a visible light-assisted laser is less expensive than using a deep ultraviolet collimator; and compared to using a deep ultraviolet collimator, the beam spots of the two beams can be directly adjusted to coincide, resulting in higher precision.

[0066] Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of this application. Therefore, the scope of protection of this application should be determined by the scope defined in the claims of this application.

Claims

1. A tuning device for a pulse stretching unit, characterized in that The application relates to a visible light source device, a pulse broadening unit, a phase delay element, a linear polarizer and a reticle, wherein the visible light source device is arranged on a cavity of the pulse broadening unit, the cavity is a mechanical reference; and an output light beam of the visible light source device is concentric with an entrance light path of the pulse broadening unit. The pulse broadening unit comprises a beam splitting element and a mirror group. The output light beam output by the visible light source device is incident on the beam splitting element. The beam splitting element divides the received output light beam into a first reflected light beam and a transmitted light beam; the first reflected light beam is incident on an exit surface of the beam splitting element after passing through the mirror group, and is reflected by the exit surface to be irradiated to the reticle together with the transmitted light beam. The linear polarizer is arranged in a light path of the transmitted light beam, and an included angle between a light transmission direction of the linear polarizer and a polarization direction of the transmitted light beam transmitted from the beam splitting element satisfies the following condition: eliminating part of the energy of the transmitted light beam. The phase delay element is arranged in a light path before the first reflected light beam is incident on the exit surface of the beam splitting element, and is used for rotating the polarization direction of the first reflected light beam by an angle same as the included angle. The visible light source device is a laser, and a wavelength of the output light beam of the laser is in a visible light wave band range.

2. The alignment device of the pulse stretching unit according to claim 1, characterized in that The polarization direction of the laser is a horizontal direction.

3. The alignment device of a pulse stretching unit according to claim 2, characterized in that The laser is a 532nm laser.

4. The alignment device of the pulse stretching unit according to claim 2, characterized in that The included angle between the light transmission direction and the polarization direction of the transmitted light beam transmitted from the beam splitting element is 90 degrees, and the phase delay element is a half-wave plate.

5. The alignment device of the pulse stretching unit according to claim 1, characterized in that, The mirror group comprises four mirrors: a first mirror, a second mirror, a third mirror and a fourth mirror; and the phase delay element is arranged between the beam splitting element and the first mirror.

6. The alignment device of the pulse stretching unit of claim 1, wherein, The first reflected light beam is incident on the exit surface of the beam splitting element after passing through the mirror group, and is reflected by the exit surface to be irradiated to the reticle together with the transmitted light beam, which comprises the following steps: The first reflected light beam is incident on the first mirror through the phase delay element, is reflected by the first mirror, the second mirror and the third mirror in sequence, and is then incident on the fourth mirror; a second reflected light beam formed by the reflection of the fourth mirror is reflected by the exit surface of the beam splitting element to form a third reflected light beam; and the third reflected light beam is irradiated to the reticle together with the transmitted light beam. The number of the mirrors comprised by the mirror group is even.

7. The alignment device of the pulse stretching unit according to claim 1, characterized in that The mirror is a spherical mirror.

8. The alignment device of a pulse stretching unit according to claim 7, characterized in that The reticle is a ground glass reticle, and the pattern is a chessboard pattern.

9. The alignment device of the pulse stretching unit of claim 1, wherein, ​

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