A split-amplitude collimated flat-top beam laser interference lithography system

Abstract

The present invention discloses a split amplitude collimated flat-top beam laser interference lithography system, which belongs to the field of micro-nano structure technology, and includes a laser, a first reflector, a first half-wave plate, a polarization beam splitter, a second half-wave plate, a second reflector, a third reflector, a fourth reflector, a fifth reflector, a sixth reflector, a fringe locking system, a laser beam shaping system and an interference system. The present invention adopts the above-mentioned split amplitude collimated flat-top beam laser interference lithography system, and the light beam forms a large-area, uniformly distributed collimated flat-top beam after passing through the optical system, which can realize high-performance grating manufacturing with strong duty cycle uniformity and meet the high-precision nano grating processing requirements.

Description

Technical Field

[0001] The invention relates to the technical field of micro-nano structures, and in particular to an amplitude-divided collimated flat-top beam laser interference lithography system. Background Art

[0002] As a micro-nano optical element with a periodic unit structure, grating plays a vital role in the fields of optical precision instruments, optical precision measurement, laser pulse compression, etc. High-end applications require grating devices to have high diffraction efficiency, small wave aberration, and low stray light in the full aperture range. Therefore, it is crucial to manufacture uniform gratings with high structural profiles over a large area.

[0003] Laser interference lithography technology uses dual-beam interference exposure to produce periodic micro-nano structures. It has significant advantages such as no mask, high precision, high production efficiency, and low cost, and is currently the mainstream technology for manufacturing large-area gratings. However, since the energy profile of the fundamental mode beam emitted by the laser is Gaussian (Gaussian beam), using it for exposure has problems such as uneven exposure dose distribution and poor uniformity of grating duty cycle over a large area. The existing technology uses the method of cutting the spot after laser beam expansion to improve the uniformity of energy distribution in the exposure area, which produces a huge energy loss and leads to low laser energy utilization.

[0004] At the same time, current laser interference lithography systems mainly have two optical path structures: wavefront division type and amplitude division type. Existing collimated flat-top beam interference lithography systems are all wavefront division types, which cannot provide fringe locking functions through technologies such as acousto-optic modulators (AOMs) or piezoelectric actuators, are difficult to resist the influence of environmental factors, and cannot meet the manufacturing requirements of high-performance gratings. The flat-top optical elements used in existing amplitude-divided flat-top beam interference lithography systems are all focusing beam shapers, which can only obtain a flat-top beam at a specific position and have extremely large wave aberrations, which cannot meet the performance requirements of high duty cycle uniformity and low diffraction wavefront errors of high-performance gratings.

[0005] Therefore, it is urgent to provide a collimated flat-top beam laser interference lithography system with high duty cycle uniformity, low diffraction wavefront error and high energy utilization. Summary of the invention

[0006] The purpose of the present invention is to provide an amplitude-split collimated flat-top beam laser interference lithography system, which can shape a Gaussian beam into a collimated flat-top beam with uniform energy distribution under an amplitude-split optical configuration, thereby solving the problem that both energy utilization and grating duty cycle uniformity cannot be achieved in existing laser interference lithography technology.

[0007] To achieve the above-mentioned object, the present invention provides an amplitude-divided collimated flat-top beam laser interference lithography system, comprising a laser, a first reflector, a first half-wave plate, a polarization beam splitter, a second half-wave plate, a second reflector, a third reflector, a fourth reflector, a fifth reflector, a sixth reflector, a fringe locking system, a laser beam shaping system and an interference system;

[0008] The optical path structure of the laser interference lithography system is as follows:

[0009] The light emitted by the laser passes through the first reflector, the first half-wave plate, and the polarization beam splitter prism in sequence, and is split into transmitted P polarized light and reflected S polarized light by the polarization beam splitter prism;

[0010] The transmitted P-polarized light is adjusted to S-polarized light through the second half-wave plate, and then passes through the second reflector, the third reflector, the fringe locking system, the laser beam shaping system and the interference system in sequence;

[0011] The reflected S-polarized light passes through the fourth reflector, the fifth reflector, the sixth reflector, the fringe locking system, the laser beam shaping system and the interference system in sequence.

[0012] Preferably, the fringe locking system comprises an acousto-optic modulator and a control circuit.

[0013] Preferably, the laser beam shaping system includes a beam expansion optical system and a flat-top optical system.

[0014] Preferably, the beam expanding optical system comprises a first beam expanding lens, a first collimating lens, a second beam expanding lens and a second collimating lens;

[0015] The optical path structure of the beam expansion optical system is as follows:

[0016] The two beams of light respectively pass through the first beam expander, the first collimator, the flat-top optical system, the second beam expander and the second collimator in sequence.

[0017] Preferably, the first beam expander and the second beam expander have lenses of different specifications, and the first collimator and the second collimator have lenses of different specifications.

[0018] Preferably, the flat-top optical system comprises a flat-top optical element.

[0019] Preferably, the interference system comprises a workbench, on which a substrate coated with photoresist is arranged.

[0020] Preferably, the first beam expander and the first collimator expand the incident light beam to a size that meets the beam radius requirements of the flat-top optical element; the second beam expander and the second collimator expand the shaped flat-top beam to a size that meets the grating manufacturing area requirements.

[0021] Therefore, the present invention adopts the above-mentioned split amplitude collimated flat-top beam laser interference lithography system, which has the following beneficial effects:

[0022] (1) Using the stripe locking system can improve system stability;

[0023] (2) Using flat-top optical elements to shape the beam can improve the utilization rate of laser energy and realize the manufacture of large-area, high-precision gratings;

[0024] (3) After passing through the optical system, the light beam forms a collimated flat-top beam with a large area and uniform energy distribution, which can realize high-performance grating manufacturing with strong duty cycle uniformity and meet the needs of high-precision nano-grating processing;

[0025] (4) This system can be used to perform high-precision laser interference lithography and manufacture high-precision gratings with high duty cycle uniformity.

[0026] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A schematic diagram of the duty cycle of manufacturing gratings for non-uniform beams and flat-top beams of the present invention;

[0028] Figure 2 It is a schematic diagram of the structure of the amplitude-divided collimated flat-top beam laser interference lithography system of the present invention;

[0029] Figure 3 for Figure 2 Interference fringe intensity distribution diagram at A in the middle;

[0030] Figure 4 It is a schematic diagram of the structure of the beam expansion and shaping optical system of the present invention;

[0031] Figure 5 for Figure 4 The energy distribution of the beam is experimentally measured at B in the middle;

[0032] Figure 6 for Figure 4 The energy distribution of the beam was experimentally measured at C in the middle;

[0033] Figure 7 for Figure 4 The beam energy distribution is experimentally measured at D in the middle;

[0034] Figure 8 for Figure 4 The energy distribution of the beam is experimentally measured at E in the middle;

[0035] Fig. 9The typical structure diagram of the grating at the center, waist and edge of the grating sample manufactured by the laser interference lithography system based on the present invention measured by a scanning electron microscope;

[0036] Reference numerals

[0037] 1. Laser; 2. First reflector; 3. First half-wave plate; 4. Polarization beam splitter; 5. Second half-wave plate; 6. Second reflector; 7. Third reflector; 8. Fourth reflector; 9. Fifth reflector; 10. Sixth reflector; 11. Acousto-optic modulator; 12. First beam expander; 13. First collimator; 14. Flat-top optical element; 15. Second beam expander; 16. Second collimator; 17. Workbench; 18. Laser beam shaping system. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0039] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0040] Example

[0041] like Figure 1-8 As shown, the present invention provides an amplitude-divided collimated flat-top beam laser interference lithography system, comprising a laser 1, a first reflector 2, a first half-wave plate 3, a polarization beam splitter prism 4, a second half-wave plate 5, a second reflector 6, a third reflector 7, a fourth reflector 8, a fifth reflector 9, a sixth reflector 10, a fringe locking system, a laser beam shaping system 18 and an interference system. The wavelength of the laser beam output by the laser 1 is within the existing photoresist sensitive spectrum range.

[0042] The optical path structure of the system is as follows: the light emitted by the laser 1 passes through the first reflector 2, the first half-wave plate 3, and the polarization splitter prism 4 in sequence, and is divided into transmitted P polarized light and reflected S polarized light by the polarization splitter prism 4; the transmitted P polarized light is adjusted to S polarization through the second half-wave plate 5, and then passes through the second reflector 6, the third reflector 7, the fringe locking system, the laser beam shaping system 18 and the interference system in sequence; the reflected light passes through the fourth reflector 8, the fifth reflector 9, the sixth reflector 10, the fringe locking system, the laser beam shaping system 18 and the interference system in sequence.

[0043] The laser light emitted from the laser 1 is reflected by the first reflector 2, enters the first half-wave plate 3, and then enters the polarization beam splitter prism 4, and is divided into two beams of light with mutually perpendicular vibration directions. One beam is the transmitted P polarized light, which passes through the polarization beam splitter prism 4 without changing the direction of the optical path; the other beam is the reflected S polarized light, which is emitted in a direction perpendicular to the original optical path. By rotating the first half-wave plate 3, the energy ratio of the two beams of light separated by the polarization beam splitter prism 4 can be adjusted.

[0044] The system can change the incident light angle by adjusting the reflector, thereby changing the period of the prepared grating, and the uniformity of the beam energy does not change.

[0045] The P light transmitted by the polarization beam splitter 4 passes through the second half-wave plate 5 and is adjusted by the half-wave plate to maintain the same polarization direction as the S light reflected by the polarization beam splitter 4. The two beams of light are mutually coherent and are adjusted by the second reflector 6, the third reflector 7, the fourth reflector 8, the fifth reflector 9, and the sixth reflector 10 respectively.

[0046] The fringe locking system includes an acousto-optic modulator 11 and a control circuit, and Figure 2 The two AOMs 11 in the circuit are exactly the same. The control circuit includes a photodetector, a reference grating, an A / D conversion data acquisition card, a host computer, a digital IO card and an AOM driver. The fringe locking system uses a photodetector to detect the moiré fringe disturbance generated by the equal periodic reference grating, amplifies the measurement signal and inputs it to the host computer through the A / D conversion data acquisition card. The host computer processes the input data in real time, analyzes and extracts the noise signal, sets the AOM compensation signal frequency difference based on the noise characteristics, and converts it into a binary digital signal, which is transmitted to the AOM driver through the digital IO card to achieve fringe locking of the interference fringe. The phase-locked beam then enters the laser beam shaping system 18.

[0047] The laser beam shaping system 18 includes a beam expander and a flat-top optical system. The optical path structure of the laser beam shaping system 18 is as follows: the two beams of light pass through the first beam expander 12, the first collimator 13, the flat-top optical system, the second beam expander 15, and the second collimator 16 in sequence.

[0048] The beam expansion optical system comprises a first beam expander 12, a first collimator 13, a second beam expander 15 and a second collimator 16. The optical path structure of the beam expansion optical system is as follows: both beams of light pass through the first beam expander 12, the first collimator 13, the flat-top optical system, the second beam expander 15 and the second collimator 16 in sequence.

[0049] The flat-top optical system includes a flat-top optical element 14. The energy non-uniformity of the output beam of the typical flat-top optical element 14 based on cascaded aspheric surfaces can be less than 5%, and the transmittance is greater than 95%. The rated incident Gaussian beam size of the flat-top optical element 14 is a spot diameter of 6 mm, at which point the energy uniformity of the output beam of the flat-top optical element 14 reaches the highest level.

[0050] The light beam is first expanded by the first beam expander 12 to a size that meets the beam radius requirements of the flat-top optical element 14, and then collimated by the first collimator 13 to form parallel light of a spot size that meets the requirements of the flat-top optical element 14. At this time, the parallel light is still a Gaussian beam. The light beam enters the flat-top optical element 14, is shaped by the flat-top beam shaper, and then is emitted to form a flat-top beam with a uniform energy distribution. It is then expanded and collimated by the second beam expander 15 and the second collimator 16 to form a collimated flat-top beam with a large area and uniform energy distribution. The expanded collimated flat-top beam meets the size requirements of the grating manufacturing area. The first beam expander 12 and the second beam expander 15 use different lens specifications; the first collimator 13 and the second collimator 16 use different lens specifications.

[0051] The wavelength of the light beam output by the laser 1 is 413.1nm, and the beam diameter is 1.3mm. After passing through the first beam expander 12 and the first collimator 13, the beam is expanded and collimated to 6mm, meeting the requirements of the flat-top optical element 14. When emitted from the flat-top optical element 14, the beam diameter is 6mm, and after passing through the second beam expander 15 and the second collimator 16, the beam is expanded and collimated to a parallel flat-top beam of 30mm.

[0052] The interference system includes a workbench 17, on which a substrate coated with photoresist is placed. The two beams of collimated flat-top light emitted by the second collimator 16 form interference on the workbench 17. The two incident lights perform interference exposure on the photoresist coated on the substrate, thereby producing a grating with a large area and high duty cycle uniformity. Fig. 9 The grating has good structural consistency in the three annular regions, indicating that the grating prepared by this system has high duty cycle uniformity.

[0053] Table 1 shows the grating duty cycle measured at five points evenly taken at the center, waist and edge of the experimentally prepared grating sample. From the results in Table 1, it can be obtained that the maximum deviation of the grating duty cycle manufactured by the method provided by the present invention is less than ±3%.

[0054] Table 1 Grating duty cycle

[0055]

[0056] Therefore, the present invention adopts the above-mentioned amplitude-divided collimated flat-top beam laser interference lithography system, which takes into account the characteristics of high energy utilization, high grating duty cycle uniformity, low grating diffraction wavefront error and fringe locking, and has advantages in high-performance grating manufacturing.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A split amplitude collimated flat-top beam laser interference lithography system, characterized in that: It includes a laser, a first reflector, a first half-wave plate, a polarization beam splitter, a second half-wave plate, a second reflector, a third reflector, a fourth reflector, a fifth reflector, a sixth reflector, a fringe locking system, a laser beam shaping system and an interference system; The optical path structure of the laser interference lithography system is as follows: The light emitted by the laser passes through the first reflector, the first half-wave plate, and the polarization beam splitter prism in sequence, and is split into transmitted P polarized light and reflected S polarized light by the polarization beam splitter prism; The transmitted P-polarized light is adjusted to S-polarized light through the second half-wave plate, and then passes through the second reflector, the third reflector, the fringe locking system, the laser beam shaping system and the interference system in sequence; The reflected S-polarized light passes through the fourth reflector, the fifth reflector, the sixth reflector, the fringe locking system, the laser beam shaping system and the interference system in sequence; The fringe locking system includes an acousto-optic modulator and a control circuit, wherein the control circuit includes a photodetector, a reference grating, an A / D conversion data acquisition card, a host computer, a digital IO card and an acousto-optic modulator driver; The fringe locking system uses a photoelectric detector to detect the moiré fringe disturbance generated by the equal-periodic reference grating, amplifies the measurement signal and inputs it to the host computer through an A / D conversion data acquisition card, and the host computer processes the input data in real time, analyzes and extracts the noise signal, sets the acousto-optic modulator to compensate for the signal frequency difference based on the noise characteristics, and converts it into a binary digital signal, which is transmitted to the acousto-optic modulator driver through a digital IO card to achieve fringe locking of the interference fringe; The laser beam shaping system comprises a beam expansion optical system and a flat-top optical system; the flat-top optical system comprises a flat-top optical element.

2. The amplitude-divided collimated flat-top beam laser interference lithography system according to claim 1, characterized in that: The beam expansion optical system comprises a first beam expander, a first collimator, a second beam expander and a second collimator; The optical path structure of the beam expansion optical system is as follows: The two beams of light respectively pass through the first beam expander, the first collimator, the flat-top optical system, the second beam expander and the second collimator in sequence.

3. The amplitude-divided collimated flat-top beam laser interference lithography system according to claim 2, characterized in that: The specifications of the lenses used in the first beam expander and the second beam expander are different, and the specifications of the lenses used in the first collimator and the second collimator are different.

4. The amplitude-divided collimated flat-top beam laser interference lithography system according to claim 1, characterized in that: The flat-top optical system includes a flat-top optical element.

5. The amplitude-divided collimated flat-top beam laser interference lithography system according to claim 1, characterized in that: The interference system comprises a workbench on which a substrate coated with photoresist is arranged.

6. The amplitude-divided collimated flat-top beam laser interference lithography system according to claim 2, characterized in that: The first beam expander and the first collimator expand the incident light beam to a size that meets the beam radius requirements of the flat-top optical element; the second beam expander and the second collimator expand the shaped flat-top beam to a size that meets the grating manufacturing area requirements.

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