Microstructure array optical element multi-dimensional information measuring device based on digital holographic system and measuring method thereof

Abstract

The invention discloses a micro-structure array optical element multi-dimensional information measuring device and method based on a digital holographic system. The device comprises a laser, a collimating and beam expanding module, two beam splitting prisms, a rectangular prism, an axially movable lens, a reference mirror, a piezoelectric displacement driver and a camera. The beam expanding and collimating module is arranged to be of a Galileo structure, efficient transmission of light energy is achieved, object light only passes through the system once through the right-angle prism, the wavefront aberration problem introduced by secondary diffraction is avoided, the position of the lens capable of moving axially is adjusted, and the light energy transmission efficiency is improved. Focusing light spot characteristic analysis and light field spectrum characteristic evaluation of the microstructure array optical element are achieved, the position of the reference mirror is moved to enable object light to interfere with reference light, and three-dimensional shape measurement of the microstructure array optical element is achieved. The method has the advantages of high precision, wide applicability, strong compatibility and the like.

Description

Technical Field

[0001] The present invention belongs to the field of optical engineering technology, and specifically relates to a multi-dimensional information comprehensive measurement device for microstructure array optical elements based on digital holography technology, integrating three-dimensional morphology measurement, focused light spot characteristic analysis and light field spectrum characteristic evaluation. Background Art

[0002] In the field of deep ultraviolet lithography, microstructure array optical elements achieve precise control of the propagation path of nanoscale light waves with their sophisticated structural design and excellent optical performance. This control capability not only ensures the high accuracy of the lithography process, but also significantly improves the transmission efficiency and stability of deep ultraviolet light within complex systems. In order to meet the growing demand for refinement and miniaturization in the field of integrated circuit manufacturing, the manufacturing process of such components must meet nanometer-level precision standards. In view of this, it is particularly important to perform multi-dimensional, high-precision measurements on microstructure array optical elements.

[0003] The three-dimensional morphological characteristics of microstructure array optical elements, including parameters such as their height, width, depth, and microstructure spacing, are key factors in determining the propagation path of light waves and have a significant impact on the ability and efficiency of regulating light waves. Although interferometry technology is currently widely used as the main characterization method to reveal three-dimensional morphology, when dealing with microstructures with complex morphological characteristics, this technology faces the challenge of accurate analysis due to the overly dense interference fringes. At the same time, the focusing ability of microstructure array optical elements is a key indicator to measure their optical performance. This type of element divides the complete wavefront into multiple local areas and uses each sub-lens to focus the light waves in the corresponding local area. By accurately detecting the distribution of these focal points, the overall and local focusing efficiency of microstructure array optical elements can be comprehensively evaluated. In addition, observing the spectral characteristics of light waves modulated by microstructure array optical elements on the back focal plane of the lens is an indispensable and important basis for guiding its processing process. By accurately capturing and analyzing the response and distribution of light waves in different frequency domains, possible wavefront aberrations can be identified and optimized, which is crucial to ensure that the processing accuracy and optical element performance meet the design requirements. Currently, there is no technology that can simultaneously integrate the three-dimensional morphology, focusing ability and spectral characteristics of microstructure array optical elements. Therefore, it is urgent to develop a multi-dimensional integrated characterization method. Summary of the invention

[0004] In order to overcome the shortcomings of the above-mentioned prior art, the present invention provides a multi-dimensional information measurement device and a measurement method of a microstructure array optical element based on a digital holographic system, which is used to perform three-dimensional morphology measurement, focus spot characteristic analysis, and light field spectrum characteristic evaluation on the microstructure array optical element. The analysis problem caused by the overly dense interference fringes is solved, and the in-depth analysis of the focus spot and light field spectrum characteristics is realized, so as to comprehensively and accurately evaluate the optical performance of the element, and provide key data support for processing optimization and manufacturing.

[0005] The technical solution of the present invention is:

[0006] A device for measuring multi-dimensional information of microstructure array optical elements based on a digital holographic system, which is characterized by comprising:

[0007] Laser, used to emit laser light source;

[0008] The beam expansion and collimation module is set behind the laser and is used to adjust the laser light source to an ideal plane wavefront;

[0009] A right-angle prism, arranged behind the microstructure array optical element, for changing the optical path direction of the object light;

[0010] A movable lens, disposed behind the right-angle prism, for adjusting the focal length of the object light;

[0011] A reference mirror, disposed on a reference light path of the first beam splitter prism, for reflecting the reference light to the second beam splitter prism;

[0012] A second beam splitter prism is disposed behind the movable lens and is used to combine the object light and the reference light and direct them to the camera;

[0013] Camera, used to record the light field information of the object light;

[0014] The invention also comprises an adjustment mechanism for adjusting the axial position of the movable lens, so that the camera can respectively record the spectrum distribution of the object light, the focused light spot or the light field information on the plane conjugate with the focal plane of the microstructure array optical element.

[0015] Furthermore, it also includes a shielding mechanism for shielding the reference mirror when measuring the spectrum distribution of the object light to avoid the occurrence of interference.

[0016] Furthermore, it also includes a piezoelectric displacement system connected to the reference mirror, which is used to adjust the position of the reference mirror to change the optical path difference between the reference light and the object light.

[0017] Furthermore, the beam expansion and collimation module adopts a Galilean structure to maintain the effectiveness of light energy transmission and obtain a higher wavefront quality.

[0018] Furthermore, the camera can be located on a plane conjugate to the focal plane of the microstructure array optical element to record the focused light spot.

[0019] Further, the camera can be located at the back focal plane of the movable lens to record the spectral distribution of the object light.

[0020] Furthermore, it also includes a digital image processing module for processing the light field information recorded by the camera to obtain the three-dimensional morphology information of the microstructure array optical element.

[0021] A method for measuring using the above-mentioned device for measuring multi-dimensional information of microstructure array optical elements based on a digital holographic system is characterized in that it comprises the steps of:

[0022] a. Use the collimation and beam expansion module to adjust the laser to an ideal plane wavefront;

[0023] b. The plane wavefront is decomposed into two beams by the first beam splitter prism, one of which is recorded as object light after passing through the microstructure array optical element, and the other is recorded as reference light after being reflected by the reference mirror.

[0024] c. Block the reference mirror, and after the object light passes through the right-angle prism, the axially movable lens and the beam splitter prism, use the camera to record the current light field distribution;

[0025] d. Without blocking the reference mirror, the object light will interfere with the reference light after passing through the right-angle prism, the axially movable lens and the beam-splitting prism, and the current interference fringes will be recorded by the camera.

[0026] When the reference mirror is blocked, the position of the movable lens is adjusted so that the camera is at the rear focal plane of the movable lens, the spectrum distribution of the light field is recorded, and the wavefront characteristics of the microstructure array optical element are analyzed.

[0027] When the reference mirror is blocked, the position of the movable lens is adjusted so that the camera is located at a plane conjugate with the focal plane of the microstructure array optical element, and the focused light spot is recorded to achieve the measurement of the focusing performance of the microstructure array optical element.

[0028] When the reference mirror is not blocked, the reference light and the object light are combined and interfered at the second beam splitter prism. The position of the movable lens is adjusted, the camera is placed at the conjugate full-frame position, and the interference fringe pattern of the object light and the reference light is recorded.

[0029] A piezoelectric displacement system is used to adjust the position of the reference mirror and change the optical path difference between the object light and the reference light. The complex amplitude of the holographic wavefront is obtained by a four-step phase shift method, and the three-dimensional morphology of the microstructure array optical element is obtained by computer simulation of Fresnel reverse diffraction propagation.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The present invention is applicable to the deep ultraviolet band, can achieve efficient transmission of light energy, and avoid the wavefront aberration problem introduced by secondary diffraction.

[0032] (2) The present invention is based on digital holographic technology and the principle of "interference recording and diffraction reproduction" can solve the problem that interference measurement cannot be resolved due to too dense fringes.

[0033] (3) Based on the measurement of light field intensity and amplitude, the present invention adds the measurement dimension of polarization state, which has the advantages of high precision and multi-dimensionality. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of the optical path of the system for measuring the optical spectrum distribution in the present invention.

[0035] Figure 2 This is a spectrum distribution diagram of light after passing through the microstructure array optical element in the present invention.

[0036] Figure 3 Schematic diagram of the optical path of the system for detecting the distribution of the focused light spot in the present invention.

[0037] Figure 4 This is the distribution diagram of the focused light spot after the detection light passes through the microstructure array optical element in the present invention.

[0038] Figure 5 It is a schematic diagram of the structure for measuring the three-dimensional morphology of the microstructure array optical element in the present invention.

[0039] In the figure: laser 1, beam expansion and collimation module (first lens 2 and second lens 3), first beam splitter prism 4, microstructure array optical element 5, right angle prism 6, movable lens 7, second beam splitter prism 8, camera 9 and reference mirror 10; A is the back focal plane of the movable lens 7, B is the focal plane of the microstructure array optical element, B' is the conjugate focal plane, C is the full-frame of the light beam passing through the microstructure array optical element, and C' is its conjugate full-frame. DETAILED DESCRIPTION

[0040] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The following examples or drawings are used to illustrate the present invention, but do not constitute a limitation of the present invention.

[0041] A multi-dimensional information measurement device based on a digital holographic system includes a laser, a collimating beam expansion module, a beam splitter prism, a right-angle prism, a camera and a plurality of lenses. The measurement method includes the following steps:

[0042] (1) A collimating beam expansion module is used to modulate the wavefront emitted by the laser into an ideal plane wavefront, wherein the collimating beam expansion module is a Galilean structure.

[0043] (2) The light wavefront is decomposed into two beams by the first beam splitter prism. A microstructure array optical element is placed in one beam and is recorded as the object light path. An axially movable reference mirror is placed in the other beam and the light reflected by the reference mirror is recorded as the reference light path.

[0044] (3) Block the reference light, and obtain the light field spectrum on the rear focal plane of the movable lens after the object light diffracted by the microstructure array optical element passes through the right-angle prism. Place the camera at the rear focal plane of the movable lens to record the light field spectrum distribution.

[0045] (4) Block the reference light, and after the object light diffracted by the microstructure array optical element passes through the right-angle prism, adjust the position of the movable lens so that the camera is located at the conjugate focal plane, and record the distribution of the focused light spot.

[0046] (5) After the object light diffracted by the microstructure array optical element passes through the right-angle prism, the object light and the reference light are combined at the second beam splitter prism to cause interference. The position of the movable lens is adjusted so that the camera is located at the conjugate plane of the element's transmitted wavefront and the interference fringes are recorded.

[0047] Embodiment 1:

[0048] like Figure 1 As shown, a laser 1 emits a laser light source, and a beam expansion and collimation module with a Galilean structure is arranged behind the laser 1, wherein the collimation module is composed of a positive lens 2 and a negative lens 3, and its purpose is to maintain the effectiveness of light energy transmission and obtain a higher wavefront quality. A beam splitting prism 4 is arranged behind the beam expansion and collimation module, which is used to decompose the light beam into an object light and a reference light path. A reference mirror 10 is blocked, and a right-angle prism 6 is arranged behind the sample 5, which is used to make the object light pass through the measurement system only once, so as to avoid the wavefront aberration introduced by secondary diffraction. A movable lens 7, a beam splitting prism 8 and a camera 9 are arranged behind the right-angle prism 6. By adjusting the axial position of the movable lens 7, the light wavefront obtained by being reflected by the beam splitting prism 8 and recorded by the camera 9 is a light field spectrum distribution, as shown in FIG. Figure 2 shown.

[0049] Example 2: Figure 3 As shown, the difference between this example and Example 1 is that in Example 1, the axial position of the movable lens 7 is moved so that the camera 9 is located at the rear focal plane of the movable lens 7, that is, the light field spectrum distribution is detected. In this Example 2, the axial position of the movable lens 7 is adjusted so that the camera 9 is located at B', that is, conjugate with the focal plane B of the sample, and the focused light spot is detected, as shown in FIG. Figure 4 shown.

[0050] Example 3: Figure 5As shown, the difference between this example and Example 1 is that in Example 1, the reference mirror 10 is blocked, and there is no interference in the entire optical path. The camera 9 detects the spectral distribution of the light field. In this Example 3, the reference mirror 10 is not blocked, and the light reflected by the reference mirror is recorded as the reference light. The axial position of the movable lens 7 is adjusted so that the camera 9 is located at C', that is, conjugate with the full-frame C of the transmitted light beam. The reference light and the object light interfere when they are combined in the beam-splitting prism 8, and the piezoelectric ceramic driver is used to control the axial position of the reference mirror 10. The three-dimensional morphology information of the sample is obtained by changing the optical path difference between the reference light and the object light, using phase shift demodulation technology and digital image processing technology.

[0051] The multi-dimensional information measuring device based on the digital holographic system of the present invention has the advantages of high precision and non-contact measurement, and can realize accurate measurement and analysis of multi-dimensional information such as microstructure array optical elements. By adjusting the configuration and parameter settings of the device, it can be flexibly applied to different measurement needs.

Claims

1. A device for measuring multidimensional information of microstructure array optical elements based on a digital holographic system, characterized in that: include: Laser, used to emit laser light source; The beam expansion and collimation module is set behind the laser and is used to adjust the laser light source to an ideal plane wavefront; A right-angle prism, arranged behind the microstructure array optical element, for changing the optical path direction of the object light; A movable lens, disposed behind the right-angle prism, for adjusting the focal length of the object light; A reference mirror, disposed on a reference light path of the first beam splitter prism, for reflecting the reference light to the second beam splitter prism; A second beam splitter prism is disposed behind the movable lens and is used to combine the object light and the reference light and direct them to the camera; Camera, used to record the light field information of the object light; The invention also comprises an adjustment mechanism for adjusting the axial position of the movable lens, so that the camera can respectively record the spectrum distribution of the object light, the focused light spot or the light field information on the plane conjugate with the focal plane of the microstructure array optical element.

2. The device for measuring multidimensional information of microstructure array optical elements based on a digital holographic system according to claim 1, characterized in that: The invention also comprises a shielding mechanism, which is used for shielding the reference mirror when measuring the spectrum distribution of the object light, so as to avoid the occurrence of interference phenomenon.

3. The device for measuring multidimensional information of microstructure array optical elements based on a digital holographic system according to claim 1 or 2, characterized in that: It also includes a piezoelectric displacement system connected to the reference mirror and used for adjusting the position of the reference mirror to change the optical path difference between the reference light and the object light.

4. The device for measuring multi-dimensional information of microstructure array optical elements based on a digital holographic system according to claim 1 or 2, characterized in that: The beam expansion and collimation module adopts a Galileo structure to maintain the effectiveness of light energy transmission and obtain a higher wavefront quality.

5. The device for measuring multi-dimensional information of microstructure array optical elements based on a digital holographic system according to claim 1 or 2, characterized in that: The camera can be located in a plane conjugate to the focal plane of the microstructure array optical element to record the focused light spot.

6. The device for measuring multi-dimensional information of microstructure array optical elements based on a digital holographic system according to claim 1 or 2, characterized in that: The camera can be located at the back focal plane of the movable lens to record the spectral distribution of the object light.

7. The device for measuring multi-dimensional information of microstructure array optical elements based on a digital holographic system according to any one of claims 1 to 6, characterized in that: The invention also comprises a digital image processing module for processing the light field information recorded by the camera to obtain the three-dimensional morphology information of the microstructure array optical element.

8. A method for measuring using the device for measuring multi-dimensional information of microstructure array optical elements based on a digital holographic system according to any one of claims 1 to 7, characterized in that: Includes steps: a. Use the collimation and beam expansion module to adjust the laser to an ideal plane wavefront; b. The plane wavefront is decomposed into two beams by the first beam splitter prism, one of which is recorded as object light after passing through the microstructure array optical element, and the other is recorded as reference light after being reflected by the reference mirror. c. Block the reference mirror, and after the object light passes through the right-angle prism, the axially movable lens and the beam splitter prism, use the camera to record the current light field distribution; d. Without blocking the reference mirror, the object light will interfere with the reference light after passing through the right-angle prism, the axially movable lens and the beam-splitting prism, and the current interference fringes will be recorded by the camera.

9. The method according to claim 7, characterized in that: When the reference mirror is blocked, the position of the movable lens is adjusted so that the camera is at the rear focal plane of the movable lens, the spectrum distribution of the light field is recorded, and the wavefront characteristics of the microstructure array optical element are analyzed.

10. The method according to claim 7, characterized in that When the reference mirror is blocked, the position of the movable lens is adjusted so that the camera is located at a plane conjugate with the focal plane of the microstructure array optical element, and the focused light spot is recorded to achieve the measurement of the focusing performance of the microstructure array optical element.

11. The method according to claim 7, characterized in that When the reference mirror is not blocked, the reference light and the object light are combined and interfered at the second beam splitter prism. The position of the movable lens is adjusted, the camera is placed at the conjugate full-frame position, and the interference fringe pattern of the object light and the reference light is recorded.

12. The method according to claim 11, characterized in that A piezoelectric displacement system is used to adjust the position of the reference mirror and change the optical path difference between the object light and the reference light. The complex amplitude of the holographic wavefront is obtained by a four-step phase shift method, and the three-dimensional morphology of the microstructure array optical element is obtained by computer simulation of Fresnel reverse diffraction propagation.

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