A Subsurface Constant Value Calibration Standard Sample

Abstract

The present invention relates to a sub-surface fixed-value calibration standard template, belonging to the field of optical metrology detection technology. The invention solves the problem that a relevant metrology system has not yet been established for sub-surface defect detection metrology and calibration. The invention comprises a transparent film, a fixed-value calibration structure and an auxiliary positioning structure, wherein the fixed-value calibration structure and the auxiliary positioning structure are arranged on the lower side of the transparent film, and the fixed-value calibration structure is located on the inner side of the auxiliary positioning structure. The present invention achieves the purpose of truly simulating the actual state of the sub-surface measured structure by using a fixed-value calibration structure and uniformly coating a transparent film on its surface; the present invention uses a variety of structures to evaluate instrument performance indicators and conduct calibration traceability, which is highly targeted.

Description

Technical Field

[0001] The invention relates to a sub-surface fixed-value calibration standard sample plate, belonging to the technical field of optical metrology detection. Background Art

[0002] High-performance optical components are the core components of modern high-power laser systems and large optical equipment. In order to ensure their processing quality and service reliability, they need to be inspected for surface and sub-surface defects.

[0003] Existing subsurface defect nondestructive testing technologies mainly include: laser modulation scattering technology, total internal reflection microscopy technology, optical coherence tomography technology, high-frequency scanning acoustic microscopy technology, X-ray microscopy imaging technology, and confocal microscopy imaging technology. Among them, confocal microscopy measurement technology has the characteristics of high measurement resolution, strong axial tomography ability, and the ability to measure complex sample structures compared to other technologies. It has relative advantages, but there are still problems such as the inability to guarantee the accuracy of subsurface measurements and difficulty in tracing the values.

[0004] Due to the difference between sub-surface measurement and surface measurement, the accuracy of sub-surface structure measurement and calibration using conventional surface structure standard templates cannot be guaranteed. At the same time, according to public literature, my country and the ISO International Organization for Standardization have not yet established a relevant metrology system for sub-surface defect detection metrology and calibration. Therefore, how to provide a standard template suitable for evaluating the axial positioning accuracy, lateral resolution and measurement sensitivity of sub-surface structure samples when measuring sub-surface structure samples with confocal microscopes is an urgent problem to be solved by technicians in this field.

[0005] Therefore, it is urgent to propose a sub-surface fixed value calibration standard sample to solve the above technical problems. Summary of the invention

[0006] The purpose of the present invention is to solve the problem that a relevant metrology system has not yet been established for sub-surface defect detection metrology and calibration, and to provide a sub-surface fixed value calibration standard template. A brief overview of the present invention is given below to provide a basic understanding of certain aspects of the present invention. It should be understood that this overview is not an exhaustive overview of the present invention. It is not intended to determine the key or important parts of the present invention, nor is it intended to limit the scope of the present invention.

[0007] The technical solution of the present invention:

[0008] A sub-surface fixed value calibration standard template comprises a transparent film, a fixed value calibration structure and an auxiliary positioning structure. The fixed value calibration structure and the auxiliary positioning structure are arranged on the lower side of the transparent film, and the fixed value calibration structure is located inside the auxiliary positioning structure.

[0009] Preferably, the fixed value calibration structure and the auxiliary positioning structure are prepared by photolithography on a fused quartz substrate, and a transparent film with a thickness of H is coated on the surface of the fixed value calibration structure and the auxiliary positioning structure and then cured.

[0010] Preferably, the difference between the refractive index of the transparent film and the refractive index of the fused silica substrate is greater than 1.

[0011] Preferably, the fixed value calibration structure comprises a step structure, a line pair structure and a point structure, and the step structure, the line pair structure and the point structure are arranged in sequence along the horizontal direction.

[0012] Preferably, the step structure includes a plurality of three-step structures, which are arranged equidistantly in the horizontal direction, and the heights of the three steps are H1, H2, and H3, respectively, and H>H3>H2>H1;

[0013] The line pair structure includes a plurality of line pairs arranged vertically, each group of line pairs includes two identical lines, the line width L is the same as the line spacing width D, the plurality of line pairs are arranged in the horizontal direction, the line width in the line pairs increases from left to right, and the spacing between adjacent line pairs increases from left to right;

[0014] The dot structure includes a plurality of circular dot structures arranged in a linear array, the diameters d of the vertical circular dot structures are the same, and the diameters d of the horizontal circular dot structures increase in sequence.

[0015] Preferably: H1=20μm, H2=40μm, H3=60μm, the period of the step structure is W=60μm; the line width L and the line spacing width D can be selected in the range of 200nm~1000nm; the dot structure diameter d can be selected in the range of 100nm~500nm; the etching depth of the line pair structure and the dot structure is in the range of 100nm~200nm.

[0016] Preferably: the auxiliary positioning structure includes a first auxiliary positioning structure and a second auxiliary positioning structure, the first auxiliary positioning structure is arranged at the inner center of the second auxiliary positioning structure, and the fixed value calibration structure is arranged at the inner center of the first auxiliary positioning structure, the first auxiliary positioning structure and the second auxiliary positioning structure both have a rectangular frame structure and an equilateral triangle structure, the long side of the rectangular frame structure is arranged in the horizontal direction, one side of the equilateral triangle is located on the short side of the rectangular frame structure, and the midpoint of one side of the equilateral triangle coincides with the midpoint of the rectangular frame structure.

[0017] The present invention has the following beneficial effects:

[0018] The present invention achieves the purpose of truly simulating the actual state of the sub-surface structure being measured by calibrating the structure with a fixed value and uniformly coating the transparent film on the surface thereof;

[0019] The present invention uses a variety of structures to evaluate instrument performance indicators and conduct calibration traceability, which is highly targeted; uses step structures of different heights to evaluate axial positioning accuracy; uses line pair structures of different widths to evaluate lateral resolution, and uses point structures of different diameters to evaluate measurement sensitivity, thereby providing a guarantee for the accuracy of the value of optical confocal microscopy measurement of sub-surface structure geometric parameters;

[0020] The present invention directly prepares a fixed-value calibration structure on a fused quartz substrate, wherein the design of the three-step structure can better evaluate the axial positioning accuracy of optical confocal microscopy measurement and the sub-surface measurement depth accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the structure of a sub-surface fixed value calibration standard sample;

[0022] Figure 2 It is a structural diagram of a fixed value calibration structure;

[0023] Figure 3 It is a structural cross-sectional view of the stepped structure.

[0024] In the figure: 1-step structure, 2-line pair structure, 3-point structure, 4-first auxiliary positioning structure, 5-second auxiliary positioning structure, 6-horizontal axis, 7-fused quartz substrate, 8-transparent film. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is described below by the specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0026] For the convenience of description, if the words "up", "down", "left" and "right" appear in the present invention, they only indicate that they are consistent with the up, down, left and right directions of the drawings themselves, and do not limit the structure. They are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or component must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0027] Terminology explanation section: The terms "install", "connect", "connect", "fixed" and the like in the present invention should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integrated connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be an internal connection between two elements, or an interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0028] Specific implementation method 1: Combination Figure 1-3 The present embodiment is described. A sub-surface fixed-value calibration standard template of the present embodiment includes a transparent film, a fixed-value calibration structure and an auxiliary positioning structure. The fixed-value calibration structure and the auxiliary positioning structure are arranged on the lower side of the transparent film, and the fixed-value calibration structure is located on the inner side of the auxiliary positioning structure. The present invention directly prepares the fixed-value calibration structure by photolithography (dry etching) on ​​a fused quartz substrate, and uses step structures of different heights, line pair structures of different widths, and point structures of different diameters to evaluate and trace the calibration of instrument indicators such as axial positioning accuracy, lateral resolution, and measurement sensitivity.

[0029] Specific implementation method 2: Combination Figure 1-3 The present embodiment is described as a sub-surface fixed value calibration standard template. The fixed value calibration structure and the auxiliary positioning structure are prepared by photolithography (dry etching) on ​​a fused quartz substrate 7. The surfaces of the fixed value calibration structure and the auxiliary positioning structure are coated with a transparent film 8 with a maximum thickness of H and cured. The upper side of the transparent film is flat, which truly simulates the actual state of the sub-surface structure being measured.

[0030] Specific implementation method three: Combination Figure 1-3 The present embodiment is described as a sub-surface constant value calibration standard sample of the present embodiment, wherein the refractive index of the material selected for the transparent film differs from the refractive index of the fused quartz substrate by more than 1.

[0031] Specific implementation method four: Combination Figure 1-3 The present embodiment is described. The present embodiment is a sub-surface fixed value calibration standard template. The fixed value calibration structure includes a step structure 1, a line pair structure 2 and a point structure 3. The step structure 1, the line pair structure 2 and the point structure 3 are arranged in sequence along the horizontal direction, and there is a distance between the step structure 1, the line pair structure 2 and the point structure 3. The sub-surface fixed value calibration standard template uses a variety of structures to evaluate instrument performance indicators and perform calibration traceability, and is highly targeted.

[0032] Specific implementation method five: Combination Figure 1-3The present embodiment is described. The present embodiment is a sub-surface fixed value calibration standard sample. The step structure 1 includes a plurality of three-step structures. The plurality of three-step structures are arranged equidistantly in the horizontal direction. The heights of the three steps are H1, H2, and H3, respectively. H>H3>H2>H1. The step structures of different heights are used to evaluate the axial positioning accuracy.

[0033] The line pair structure 2 includes a plurality of line pairs arranged vertically, each group of line pairs includes two identical lines, the line width L is the same as the line spacing width D, and the plurality of line pairs are arranged in the horizontal direction, the line width in the line pairs increases from left to right, and the spacing between adjacent line pairs increases from left to right; the horizontal resolution is evaluated using line pair structures of different widths;

[0034] The dot structure 3 includes a plurality of circular dot structures arranged in a linear array, wherein the diameters d of the vertical circular dot structures are the same, and the diameters d of the horizontal circular dot structures increase successively; the dot structures with different diameters are used to evaluate the measurement sensitivity, thereby providing a guarantee for the accuracy of the optical confocal microscopy measurement of the geometric parameters of the sub-surface structure.

[0035] Specific implementation method six: Combination Figure 1-3 To illustrate the present embodiment, a sub-surface constant value calibration standard template is provided in the present embodiment, wherein H1=20μm, H2=40μm, H3=60μm, the period of the step structure is W=60μm; the line width L and the line spacing width D can be selected in the range of 200nm~1000nm; the dot structure diameter d can be selected in the range of 100nm~500nm; the etching depth of the line pair structure and the dot structure is in the range of 100nm~200nm.

[0036] Specific implementation method seven: Combination Figure 1-3The present embodiment is described. The present embodiment is a sub-surface fixed value calibration standard template. The auxiliary positioning structure includes a first auxiliary positioning structure 4 and a second auxiliary positioning structure 5. The first auxiliary positioning structure 4 is arranged at the inner center of the second auxiliary positioning structure 5. The fixed value calibration structure is arranged at the inner center of the first auxiliary positioning structure 4. The first auxiliary positioning structure 4 and the second auxiliary positioning structure 5 both have a rectangular frame structure and an equilateral triangle structure. The long side of the rectangular frame structure is arranged in the horizontal direction. One side of the equilateral triangle is located on the short side of the rectangular frame structure. The midpoint of one side of the equilateral triangle coincides with the midpoint of the rectangular frame structure. One vertex of the equilateral triangle is located on the horizontal axis 6 of the fixed value calibration structure. The existence of the auxiliary positioning structure is helpful to quickly determine the position of the fixed value calibration structure area under objective lenses with different fields of view. Different from the previous design structure (such as: the publication number is CN115372368A, the name of the invention is a sub-surface multi-parameter nano standard template and its preparation method), the length and width of the rectangular frame structure in the first auxiliary positioning structure 4 are more than twice the rectangular frame in the second auxiliary positioning structure 5. At the same time, the size of the rectangular frame structure in the second auxiliary positioning structure 5 is more than twice the overall size of the fixed value calibration structure area, which takes into account the rapid initial positioning of the fixed value calibration structure area under objective lenses with different fields of view, and avoids the problem of difficulty in quickly finding the calibration structure area due to the small field of view under a high-power objective lens.

[0037] Embodiment 1:

[0038] A subsurface fixed value calibration standard template includes a fixed value calibration structure under a transparent film and an auxiliary positioning structure, wherein the fixed value calibration structure includes three types of structures, namely, a step structure 1, a line pair structure 2, and a point structure 3, and the auxiliary positioning structure includes a first auxiliary positioning structure 4 and a second auxiliary positioning structure 5 formed of a rectangular frame and an equilateral triangle structure;

[0039] The fixed value calibration structure and the auxiliary positioning structure are prepared by photolithography (dry etching) on ​​a fused quartz substrate, and a transparent film with a thickness of H=100 μm is uniformly coated on the surface of the structure and cured. The refractive index of the material selected for the transparent film is greater than 1 different from that of the fused quartz substrate, such as a photoresist film;

[0040] The periodic step structure 1 in the fixed value calibration structure has three different step heights H1 = 20 μm, H2 = 40 μm, H3 = 60 μm, and the period of the step structure is W = 60 μm;

[0041] Each line pair in the line pair structure 2 is a combination of two lines of a specific width L, and the spacing width D between the lines is the same as the width of the line itself; the line widths and line spacing widths of different line pairs are different; the line width L and the line spacing width D can be selected in the range of 200nm to 1000nm;

[0042] In the dot structure 3, the dot structure diameter d of each column is the same, and the dot structure diameters of different columns are different; the dot structure diameter d can be selected in the range of 100nm to 500nm;

[0043] The etching depth of line pair structure and dot structure is in the range of 100nm to 200nm;

[0044] The auxiliary positioning structure includes a rectangular frame structure and an equilateral triangle structure. One side of the equilateral triangle is located on the short side of the rectangular frame structure, and one vertex of the equilateral triangle is located on the horizontal axis of the fixed value calibration structure, which helps to quickly determine the area position of the fixed value calibration structure.

[0045] It should be noted that in the above embodiments, as long as the technical solutions are not contradictory, they can be arranged and combined, and those skilled in the art can exhaust all possibilities based on the mathematical knowledge of arrangement and combination. Therefore, the present invention will no longer describe the technical solutions after arrangement and combination one by one, but it should be understood that the technical solutions after arrangement and combination have been disclosed by the present invention.

[0046] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A subsurface fixed value calibration standard sample, characterized in that: It includes a transparent film, a fixed value calibration structure and an auxiliary positioning structure. The fixed value calibration structure and the auxiliary positioning structure are arranged on the lower side of the transparent film, and the fixed value calibration structure is located inside the auxiliary positioning structure. The fixed value calibration structure comprises a step structure (1), a line pair structure (2) and a point structure (3), wherein the step structure (1), the line pair structure (2) and the point structure (3) are sequentially arranged in a horizontal direction; The auxiliary positioning structure comprises a first auxiliary positioning structure (4) and a second auxiliary positioning structure (5), the first auxiliary positioning structure (4) is arranged at the inner center of the second auxiliary positioning structure (5), and the fixed value calibration structure is arranged at the inner center of the first auxiliary positioning structure (4), the first auxiliary positioning structure (4) and the second auxiliary positioning structure (5) both have a rectangular frame structure and an equilateral triangle structure, the long side of the rectangular frame structure is arranged in the horizontal direction, one side of the equilateral triangle is located on the short side of the rectangular frame structure, and the midpoint of one side of the equilateral triangle coincides with the midpoint of the rectangular frame structure; The length and width of the rectangular frame structure in the first auxiliary positioning structure (4) are more than (2) times the rectangular frame structure in the second auxiliary positioning structure (5), and the size of the rectangular frame structure in the second auxiliary positioning structure (5) is more than (2) times the overall size of the fixed value calibration structure area; The step structure (1) comprises a plurality of three-step structures, which are arranged equidistantly in the horizontal direction, and the heights of the three steps are H1, H2, and H3, respectively, and H>H3>H2>H1; the period of the step structure is W; The line pair structure (2) comprises a plurality of line pairs arranged vertically, each group of line pairs comprises two identical lines, the line width L is the same as the line spacing width D, the plurality of line pairs are arranged in a horizontal direction, the line widths in the line pairs increase from left to right, and the spacings between adjacent line pairs increase from left to right; The dot structure (3) comprises a plurality of circular dot structures arranged in a linear array, wherein the diameters d of the vertical circular dot structures are the same, and the diameters d of the horizontal circular dot structures increase in sequence; The fixed value calibration structure and the auxiliary positioning structure are prepared by photolithography on a fused quartz substrate (7), and a transparent film (8) with a thickness of H is coated on the surface of the fixed value calibration structure and the auxiliary positioning structure and then cured; The difference between the refractive index of the transparent film and the refractive index of the fused silica substrate is greater than 1.

2. A subsurface constant value calibration standard sample according to claim 1, characterized in that: H1=20μm, H2=40μm, H3=60μm, the period of the step structure is W=60μm; the line width L and the line spacing width D can be selected in the range of 200nm~1000nm; the dot structure diameter d can be selected in the range of 100nm~500nm; the etching depth of the line pair structure and the dot structure is in the range of 100nm~200nm.

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