Three-dimentional shape measurement system and correlative measurement method using interferometer and atomic force microscope

Abstract

The present disclosure relates to a three-dimensional shape measurement system and measurement method using an interferometer and an AFM. In particular, the present invention relates to, as a three-dimensional shape measurement device of a measurement object through an interferometer and an AFM, a three-dimensional shape measurement system using the interferometer and an AFM including: an interference unit that measures a shape of a measurement object (2); and an AFM unit (200) that measures the measurement object, has an active cantilever beam (150) moved through a 3-axis piezo actuator, and measures the boundary of a specific area of the measurement object (2).

Description

[0001] THREE-DIMENTIONAL SHAPE MEASUREMENT SYSTEM AND CORRELATIVE MEASUREMENT METHOD USING INTERFEROMETER AND ATOMIC FORCE MICROSCOPE

[0002] BACKGROUND

[0003] Related Applications

[0004] This application claims the priorities of German Patent Application No. DE 10 2024 107 059.5 and Korean Patent Application No. 10-2024-0034321, both filed on 12 March 2024, the contents of which are incorporated by reference.

[0005] Technical Field

[0006] The present disclosure relates to a three-dimensional shape measurement system and measurement method using an interferometer, for example a phase shifting interferometer, and an atomic force microscope (AFM).

[0007] Related Art

[0008] Known methods for measuring the microscopic surface shape of precision parts and features include a stylus-based measurement method, scanning electron microscope (SEM) measurement method, scanning probe microscope, phase shifting interferometry (PSI), whitelight scanning interferometry, a confocal scanning microscope measurement method, etc.

[0009] These known methods measure geometric features on a two-dimensional plane, such as circles, lines, angles, and line widths, or inspect patterns for defects, foreign objects, asymmetries, etc. The known methods are primarily based on probe systems including an optical microscope, illumination, and an imaging device, typically a CCD camera, and utilize image-processing techniques.

[0010] Among these methods, white-light scanning interferometry, phase shifting interferometry (PSI) , spectral interferometry, confocal microscopy and digital holography are gaining traction as non-contact and non-destructive methods that are widely applied to three- dimensional measurement of microscopic shapes, including semiconductor pattern measurement, surface roughness measurement of soft materials, Ball Grid Array (BGA) ball measurement, laser marking pattern measurement, via hole measurement, etc.

[0011] Although these two methods are based on different measurement principles, the methods can be implemented in the same optical and measurement system, except that the two methods use multi -wavelength and monochromatic wavelength. Therefore, these two methods can be used together in commercially available measurement systems. These two measurement methods use optical interference signals that appear bright and dark depending on the optical path difference between two lights when the two lights originate simultaneously from a reference point and measurement point, travel along different optical paths and then merge.

[0012] As a prior art related to such white-light scanning interferometry (WSI), Korean Patent No. 10-0598572 (July 07, 2006) discloses white-light scanning interferometry for measuring the thickness of a transparent thin film layer or obtaining information about the surface shape of the thin film layer during the process of applying the transparent thin film layer onto the surface of an opaque metal layer in the semiconductor and liquid crystal display (LCD) manufacturing process.

[0013] The measurement principle behind this white-light scanning interferometry is to use the short coherence length which is characteristic of white light due to the wide distribution of frequencies in white light. In particular, the white-light scanning Interferometry uses the principle that an interference signal occurs only when the reference light and measurement light (separated by a beamsplitter, which is an optical splitter) undergo substantially the same optical path difference.

[0014] The interference signals are observed at measurement points within a measurement area during moving of the measurement object in the direction of the optical axis of the interferometer with a micro-gap of several nanometres between the surface of the measurement object and the objective of the interferometer. The short interference signal occurs at a point at which the same optical path difference as that of a reference mirror occurs at the measurement point. By calculating the occurrence positions of these interference signals at a plurality of measurement points within the measurement area, information about the three-dimensional shape of the surface of the measurement area can be acquired. This acquired information enables the measurement of the surface shape of the thin film layer.

[0015] A phase shifting imaging interferometer that combines a phase shifting technique and ellipsometry was proposed in Carre, P. Installation et utilisation du comparateur photoelectrique et interferentiel du Bureau International des Poids et Mesures.

[0016] Metrologia 1966, 2, 13, for measuring the 2D thickness profile of thin films. This imageprocessing technique has been developed to enhance the precision of the interferometer.

[0017] Various methods to be utilized for using phase shift between two beams have been proposed, and numerous phase shifting interferometers have been developed and applied in diverse fields.

[0018] The phase shifting interferometry is a well-established technology for surface characterization that relies on the digitalization of interference data acquired during a controlled phase shift. The phase shift is most often introduced by controlled mechanical oscillation of the interference objective lens. This technique of phase shifting interferometry provides full 3D images with a typical height measurement repeatability of less than 1 nm independent of the field size. Microscopes for the phase shifting interferometry employ a range of specialized interference objective lens for measuring roughness and microscopic form.

[0019] The simplest case of incident illumination occurs when the illuminating light is vertically incident on the surface of the sample. The relationship of the phase shift to the differences in the height due to changes in the surface morphology is given by the following equation:

[0020] K=47t / X

[0021] K corresponds to the rate at which the interference signal oscillates sinusoidally between the reference mirror and the sample surface. If the numerical aperture of the set-up of the phase shifting interferometer and the wavelength is known, then in principle the measurement is self-calibrated by virtue of the measurement principle. This assumes that the refractive index remains the same over the whole sample surface of the sample.

[0022] The AFM relies on a tip-scanning technique to produce very high resolution, 3-D images of sample surfaces. The AFM measures van der Waals forces (which are very small, and typically less than 1 nN) acting between the atomically sharp AFM-tip and the sample surface. These small forces are measured by measuring the motion of a flexible cantilever beam. The force acting on the tip causes a cantilever deflection which is measured by tunnelling, capacitive, piezoresistive or optical detectors. The AFMs based on active cantilever beams can obtain resolution down to the atomic level. Measurements with the AFMs have been performed on a wide variety of surfaces in air, liquid, or vacuum by employing piezoelectric scanners and active cantilever beams fabricated as micro-electro-mechanical systems (MEMS). The MEMS- based force sensing (or probe-based instruments) provide high-quality imaging at high imaging rates by using a sharp AFM-tip positioned at an end of the cantilever beam and by using a low force-load or low tracking force to characterize the surface structure of the sample. In lithographic mode, the AFM-tip is modified to engrave information, for example by fieldemission electrons, to a sample surface.

[0023] Sensing of the deflection of the cantilever beam has been primarily performed through external methods such as optical beam deflection (OBD) systems. The AFM-tip at the free end of the flexible cantilever beam is brought in contact with the sample surface. Features on the sample surface cause the cantilever beam to deflect in the vertical directions as the sample moves under the AFM tip. A laser beam from a diode laser (637 nm) is directed onto the back of the cantilever beam near its free end. The reflected laser beam from the vertex of the cantilever beam is directed onto a quad photodetector. The quad photodetector is a split photodetector with four quadrants and is commonly called a position-sensitive detector or PSD. The differential signal from top photodiodes and bottom photodiodes provides an AFM deflection signal which is a sensitive measure of the vertical deflection of the cantilever beam.

[0024] Another optical method for detecting the deflection of the cantilever is laser interferometry. This approach focuses a laser beam onto the rear of the cantilever rear to directly detect displacement.

[0025] Yet another detection method applies the principle of astigmatism sensing. The principle of astigmatism sensing is used in the optical pickup device of CD / DVD readers for detecting the cantilever deflection. This design mechanism enables the detection of the focus state of the light reflected from the target object via the astigmatism principle using a focus error signal that is proportional to the defocus distance generated in the photodiode.

[0026] Recent advances in nanofabrication technology enables the production of active cantilever probes (also called cantilever beams) with embedded sensors and actuators. The Atomic Force Microscopy (AFM) equipped with active probes provides new capabilities and simplified user operation compared to conventional passive probes without integrated sensor or actuators.

[0027] The sensing of the deflection of the AFM cantilever beam can be implemented by employing piezoresistive or piezoelectric sensing. The publication I. Rangelow et al.: " Review Article: Active scanning probes: A versatile toolkit for fast imaging and emerging nanofabrication ", Journal of Vacuum Science & Technology B 35, 06G101 (2017); DOI: 10.1116 / 1.4992073 provides an active cantilever design for a high-speed atomic force microscope with a more accurate conversion of the control action into a topographic signal.

[0028] Co-Pending PCT Patent Application No. WO 2024 / 089217, MICROMECHANICAL BEAM, nano analytik GmbH relates to a design for high sensitivity active scanning probe using design that enables the scanning probe to be used in an optimal state by setting the bandwidth to be higher.

[0029] There has also been attempts made toward optomechanical disclosed in US Patent US8997258B2 from 31 January 2015, MICROSCOPE PROBE AND METHOD FOR USE OF SAME Vladimir Aksyuk, Kartik Srinivasan, Houxun Miao, Ivo W. Rangelow, Thomas Michels.

[0030] Advances in semiconductor micro / nano-fabrication techniques have enabled embedment of miniaturized sensors in the cantilevers with sizes on the micrometre scale. The latest designs of the cantilevers incorporate multiple piezoresistive elements at the base of the cantilever where the maximum bending stress occurs. Typically, four piezoresistive elements are used to form a full Wheatstone bridge configuration, which improves sensitivity and reduces thermal drift.

[0031] Piezoresistive sensing facilitates embedded measurement of the deflection of the cantilever via resistance measurement, enabling both static and dynamic measurements over a wide bandwidth (from DC to megahertz). The sensitivity is comparable to that of the aforementioned optical methods but is not limited by the diffraction limit and can employ nanometre-scale cantilevers.

[0032] An integrated electrothermal actuator is used for driving the cantilever in ac-mode and is used to produce a frequency of oscillation of the cantilever around its resonance to achieve adequate efficiency. The electrothermal actuator on the cantilever can be used to drive the cantilever in resonance (AC) as well as deflect the cantilever at lower frequencies off-resonance (DC) in state of z-piezoelectric actuator. The electrothermal actuator is used to change the energy from an electrical current to mechanical energy thermally using differences in expansion coefficients of different layers in the electrothermal actuator. An example is given in US Patent No 7,141,808 B2. It would also be possible to use a bimorph actuator, or a bimaterial, which comprises two or more different thermally expanding materials overlayered in a sandwich form. The bimorph actuator is typically used for out-of-plane actuation. As the electrical current passes through the one of the lavers in the cantilever, the temperature of the material in one of the layers increases. This temperature will produce a greater expansion in the material of one of the layers than the expansion in the other one of the layers, because the other one of the layers has a different thermal expansion coefficient. These different thermal expansion coefficients result in out-of-plane deflection of the cantilever.

[0033] With the use of state-of-the-art semiconductor manufacturing technology, the geometric dimension (“footprint”) of the sensing element can be significantly smaller than that of conventional strain gauges when considering the effect of miniaturization. The reduction of the footprint enables specialized probes design for more accurate force measurement.

[0034] The primary requirement for dynamic mode operation is excitation of the cantilever resonance. Some actuation strategies can also allow control over static deflection. The advanced AFM cantilever beams or probes built using combinations of embedded self-sensing and self-actuated methods. Such probes are called active cantilevers. This is discussed in more detail in a review article: Active scanning probes: A versatile toolkit for fast imaging and emerging nanofabrication, Ivo W. Rangelow, Tzvetan Ivanov, Ahmad Ahmad, Marcus Kaestner, Claudia Lenk, Iman S. Bozchalooi, Fangzhou Xia, Kamal Youcef-Toumi, Mathias Holz, and Alexander Reum, Journal of Vacuum Science & Technology B 35, 06G101 (2017); DOI: 10.1116 / 1.4992073.

[0035] The following further relevant prior art documents are known: Korean Patent Publication No. 10-2023-0044421, Korean Patent Publication No. 10-2024-0023166, and Korean Patent No. 10-2601670.

[0036] Summary of the Invention

[0037] The performance of the AFM system (as shown in Fig.l 1) is provided by combination of following features: (i) a high-frequency cantilever, (ii) a fast AFM controller implemented in a high-speed DSP FPGA device, (iii) a high-speed closed-loop scanner, and (iv) a quick approach technique. The cantilever excitation scheme includes high-precision, dedicated DDS generators and low-noise excitation drivers for bridge supply and self-actuation allowing a defined digital control. The analogue part for the read-out signal is specially designed to feature high bandwidth (up to 5 MHz), high gain and extremely low noise (less than 1.59 nV / Hz'A).

[0038] The amplified signal is converted using a fast ADC providing a conversion time in the range of 10 ns - 12 ns with high resolution. The digitized signal is fed to an all-digital fast lock- in amplifier. The output of amplifier is used as feedback for the precise all-digital PI controller for fast Z-regulation. These blocks are implemented in a high-speed DSP FPGA and provide an overall delay less than 5ps (Figure 4). The scanning speed also depends on the X and Y positioning system, which uses high-resolution DDS generators. Three precision DAC channels and low-noise voltage drivers are used to fit the X, Y and Z output signals in a range from 0 to 10V. These modules provide an overall delay less than 25 ps. The high-speed 3D closed-loop scanner is an essential part of the system. It is driven by a low-noise high-voltage amplifier which amplifies the X, Y and Z signals up to 150V. A fast approach motor is controlled by the digital motor driver providing high current and short reaction time. The combined delay of all blocks results in total system delay of less than 40 ps confirmed experimentally. A high-speed Ethernet communication interface build in the controller provide a real-time data sampling and visualization using PC software. Summarizing all delay times of all system ingredients (FPGA, DAC, ADC, Lock-in, Pl-controller) the bandwidth of the system is as high as 200 kHz.

[0039] The phase detection systems set out in this document can be employed as a method of measuring the critical dimensions (CD) of nano-features indirectly, by using the phase variation produced by the repeated x-shift and y-shift of the samples (object) and accurate measuring of the shift of the samples. Thus, the precision of the measurement system depends on the accuracy of the measuring of the x-shift and the y-shift of the samples.

[0040] The phase detection system can be used as an experimental platform for basic research in the field of scale-spanning AFM tip-based and laser-based nanofabrication for subnanometre structuring on large surfaces. The sample stage position is controlled by laser interferometers and deliver high precision metrology with 20 picometer resolution and subnanometre reproducibility. It can be equipped with active cantilever AFM heads as well as with laser stage systems that can measure with nanometre reproducibility and accuracy.

[0041] The phase detection systems can be used as a method of measuring the critical dimensions (CD) of nano-features indirectly, by using the phase variation produced by the repeated x and y shifts of the samples (measurement objects) and accurate measuring of the shift of the samples. Thus, the precision of the measurement system depends on the accuracy of the measuring of the x-shift and the y-shift of the samples.

[0042] The system can be used as a platform for research in the field of scale-spanning AFM tip-based and laser-based nanofabrication for subnanometer structuring on 4-inch surfaces. The laser interferometer based high precision machine has 20 picometer resolution and subnanometer reproducibility. The laser interferometer can be equipped with AFM tips as well as with laser systems that can both write and read, i.e., measure with nanometre reproducibility and accuracy.

[0043] The present disclosure teaches a method and device to overcome conventional problems as described above. According to an aspect of the present disclosure, it aims to provide a three-dimensional shape measurement system and measurement method using an interferometer and an AFM. The object can be inspected by using a phase shifting interferometry imaging mode employed by a scanning probe microscope, and improved 3D images with a general height measurement repeatability of less than 0.3nm can be generated, regardless of the field size.

[0044] In addition, according to a further aspect of the present disclosure, it aims to provide a three-dimensional shape measurement system and measurement method using an interferometer and an AFM. The measurement object can be rapidly and accurately analysed by measuring its shape in a large imaging field with the interference (PSI) unit and calibrating only the areas with high error values caused by the differences of the refractive index coefficients with the AFM unit. According to a further aspect of the present disclosure, it aims to provide a three-dimensional shape measurement system and measurement method using an interferometer and an AFM. The accuracy may be increased by aligning the interference optical axis (in the direction of the light beam) with the measurement point during the AFM measurement and the deflection position of the tip may be accurately measured by an active cantilever with an embedded a piezoresistive detection sensor and a small-scale integrated actuator in the probe without using a high beam deflection system. Nanopositioning may be achieved through 3-axis piezo actuator.

[0045] A first aspect of the present disclosure may be achieved by providing, as a three- dimensional shape measurement device of a measurement object through an interferometer and an AFM, a three-dimensional shape measurement system using the interferometer and an AFM including: an interference unit that measures the surface morphology of the measurement object; and an AFM unit that gets metrological information used for dimensional calibration from the image obtained by the interferometer, has an active cantilever beam moved by a 3- axis piezo actuator, and measures the boundary of a specific area of the measurement object.

[0046] When acquiring an interference signal and an AFM signal using the interferometer, a measurement point of the AFM is controlled by a 3-axis piezo actuator and aligned with an optical axis with a radius of about 500pn of the interferometer.

[0047] The active cantilever beam of the AFM is provided on one side of a scanner on a frame, including: a tip that is provided on the end of a cantilever; an actuator that is embedded in the cantilever and actuated to deform the cantilever so as to cause the tip to press against the measurement point; and a piezoresistance detection sensor that is embedded in the cantilever and measures piezoresistance applied to the measurement object by the tip.

[0048] One side of the active cantilever beam projects outwardly from the side of the scanner, and an end portion thereof is tapered downwardly from a main body of the probe.

[0049] The actuator is an electrothermal actuator having a bimorph structure and a resistive heating element, and the piezoresistance detection sensor has a Wheatstone bridge structure comprised of four piezoresistive elements and measures the connection state and contact pressure of the tip.

[0050] The interference unit includes: an illumination optic module that has a light source emitting light; a polarizing beamsplitter that reflects a first polarized wave of the light to a reference mirror and passes a second polarized wave through the measurement object; a quarter-wave plate that polarizes a first polarized reflected light reflected from the reference mirror and reflected by the polarizing beamsplitter, and a second polarized reflected light reflected from the measurement object and passed through the polarized beam beamsplitter; and a polarized camera that located on the back end of the quarter-wave plate, and acquires multiple interferometric images having different polarization states.

[0051] A second aspect of the present disclosure may be achieved by providing, as a three- dimensional shape measurement method of a measurement object through an t interferometer and an AFM, a three-dimensional shape measurement method using an interferometer and an AFM including: Step SI, wherein the shape of the measurement object within the field of view is measured using the interference unit and an interference measurement signal is acquired; Step S2, wherein an active cantilever beam is moved to the boundary of a specific area of the measurement object using a 3-axis actuator of an AFM unit and the boundary of the measurement object is measured; and Step 3, wherein a measurement value for a boundary region is calibrated based on the AFM measurement signal.

[0052] The step S2 may include: Step S21, wherein the probe tip is positioned at a specific measurement point of a boundary region of the specific area through the 3-axis actuator based on the initial position value of the probe tip, and aligning the optical axis of the interferometer with the measurement point; Step S22, wherein an actuator embedded in the cantilever beam is actuated and the tip applies pressure to the measurement point; and Step S23, wherein piezoresistance applied to the measurement point by the tip is measured through a piezoresistance measurement sensor embedded in the cantilever.

[0053] When the actuator is an electrothermal actuator having a bimorph structure and a resistive heating element, in the Step S22, an AC voltage applied to the electrothermal actuator stimulates probe resonance, and then a DC voltage controls a static deflection.

[0054] Yet further, the present disclosure may be characterized in that the Step SI includes steps of emitting light from a light source; passing the light through an illumination optics module and passing the collimated light through a polarizer; reflecting a first polarized wave of the light in a polarizing beamsplitter to be incident on a reference mirror, and passing a second polarized wave to be incident on the measurement object; reflecting a first polarized reflected light reflected onto the reference mirror onto the polarizing beamsplitter, and passing a second polarized reflected light reflected onto the measurement object through the polarized beamsplitter; polarizing the first and second polarized reflected lights by penetrating a quarterwave plate; and interfering the first and second polarized reflected lights polarized in a polarized camera and acquiring multiple interference images having different polarization states.

[0055] According to a three-dimensional shape measurement system and measurement method using an interferometer and an AFM in accordance of an aspect of the present disclosure, shape measurement system and method is capable of inspecting the object by using an interferometry imaging mode employed by a scanning probe microscope and generating improved 3D images with a general height measurement repeatability of less than 0.3nm, regardless of the field size.

[0056] The three-dimensional shape measurement system and measurement method using an interferometer and an AFM is capable of rapidly and accurately analysing the measurement object by measuring with the AFM unit the shape of the measurement object in large field by the interference imaging unit and calibrating only those surfaces of the samples with different refractive index coefficients. The reason for this is that PSI has many error sources. These error sources include phase-shift errors, vibrations, detector non-linearity, stray reflections, quantization errors, frequency instability, and intensity fluctuations. The error sources are challenging when measuring the topology of a surface (i.e. surface morphology) of a measurement object when the material of the measurement object has varying refractive indices. To overcome these limitations, the system and method of the current application combines PSI with AFM and leverages the high imaging resolution of AFM. Unlike PSI, the performance of AFM is independent of the probe material’s refractive index and enables correlative imaging of the topology of the surface of the measurement object. In other words, the system and method enable the determination of the real values of the topology of the measurement object.

[0057] The three-dimensional shape measurement system and measurement method using an interferometer and an AFM is capable of increasing the accuracy by aligning the interference optical axis with the measurement point during the AFM measurement, accurately measuring the deflection position of the tip by embedding a piezoresistive or other cantilever deflection sensor, for example but not limited to a laser beam deflection system and an integrated actuator onto the cantilever. A reduction of the effective mass of the cantilever beam allows for an increase in bandwidth and thus also for a higher scan speed.

[0058] The method and system of this document is used, for example, in defect analysis and metrological review on semiconductor wafers, gaining traction for control and metrology, for example in Chemical Mechanical Polishing (CMP), where the “dishing” effect must be carefully monitored.

[0059] The method and system of this document is used for basic research in the field of scalespanning AFM tip-based and laser-based nanofabrication for sub-nanometre structuring on large surfaces. The sample stage position is controlled by laser interferometers and deliver high precision metrology with 20 picometer resolution and sub-nanometre reproducibility. It can be equipped with active cantilever AFM heads as well as with laser stage systems that can measure with nanometre reproducibility and accuracy.

[0060] It will be appreciated that the interferometer set out in this application is a phase shifting interferometer. The invention is, however, not limited to phase shifting interferometer and other types of interferometers can be used, such as but not limited to, white scanning interferometry, spectral interferometry, confocal microscopy and digital holography.

[0061] BRIEF DESCRIPTION OF THE DRAWINGS

[0062] The accompanying drawings of this specification exemplify a preferred embodiment of the present disclosure, the spirit of the present disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, and thus it will be understood that the present disclosure is not limited to only contents illustrated in the accompanying drawings.

[0063] FIG. 1 shows a micrograph and an AFM measurement signal for the measurement object. The Figure shows a PSI image CMP-TSV (true surface vias) (filled with Cu) and an active probe in dishing measurement position of 20pm TSVs fabrication of Cu-filled vias in a thin silicon wafer. In terms of the optical system, an LED light source with a central wavelength of 532 nm and a broad bandwidth of 10 nm was utilized. The system offers a field of view of 60 pm x 60 pm, with a pixel resolution of 100 nm. It should be noted that this image is not correlated or not calibrated with the AFM measurements.

[0064] FIG. 2 shows an interference (PSI) measurement signal for the measurement object with through-silicon vias (TSVs). This image is employed for navigation of the AFM-tip into area of interest.

[0065] FIG. 3 shows a comparative graph of an AFM topology profile obtained with the active cantilever beam and a PSI measurement signal in a specific area (Cu area) of the measurement object.

[0066] FIGs. 4A and 4B show PSI measurement signals in a specific area (Cu area) repeatedly measured by a phase shift interferometer to obtain average values.

[0067] FIG. 5 shows a flowchart of a three-dimensional shape measurement method using a phase shift interferometer and an AFM according to an aspect of the present disclosure,

[0068] FIG. 6 shows a schematic view of an interference set-up unit according to a first aspect of the present disclosure, FIG. 7 shows a schematic view of an interference set-up unit according to a second aspect of the present disclosure,

[0069] FIG. 8 shows a schematic view of an interference set-up unit according to a third aspect of the present disclosure,

[0070] FIG. 9 shows a flowchart of an interference signal measurement method according to a third aspect of the present disclosure.

[0071] FIG. 10 shows a schematic view of a three-dimensional shape measurement system using a phase shift interferometer and an AFM according to an aspect of the present disclosure,

[0072] FIG. 11 shows a schematic view and a partially enlarged view of an AFM unit according to an aspect of the present disclosure, allows for high-speed measurements and minimize wear of the tip positioned at the micromechanical beam, a non-contact mode of operation is used.

[0073] FIG. 12 shows an SEM image of active cantilever which includes small sensing cantilever and actuating part which a secure cantilever (large bandwidth) deflection in vertical direction in state of piezoelectric stack used in conventional scanning probe systems. The design results in a high-bandwidth 550kHz-micro-cantilever with an integrated tip made from silicon, diamond or GaN. The probe may have a force detection bandwidth greater than 45 kHz, apply a force to the sample of less than 2 nN when activated in oscillation mode, compensator in the control -loop and have a step response time of about 150ps.

[0074] FIG. 13 shows a flowchart of a measurement method through an AFM unit according to an aspect of the present disclosure.

[0075] FIG: 14 shows the general set-up of the integrated PSI and AFM. The measurement object (wafer, substrate) is under the PSI-objective and the AFM-Probe (cantilever) is in between the objective and the measurement object (wafer, substrate).

[0076] DETAILED DESCRIPTION OF THE INVENTION

[0077] Hereinafter, the aforementioned aims, other aims, features, and advantageous effects of the present disclosure will be understood easily by referring to preferable embodiments related to the accompanying drawings. However, the present disclosure is not limited to embodiments described in this specification and may be embodied into other forms. Preferably, the embodiments in this specification are provided in order to allow disclosed contents to be exhaustive and to communicate the concept of the present disclosure to those skilled in the art.

[0078] In this specification, when a certain element is placed on another element, this means that it may be formed directly thereon or that the third element may be interposed between them. Further, in the drawings, the thickness of an element may be overstated in order to explain the technical content thereof efficiently.

[0079] The embodiments described in this specification will be explained with reference to a cross-sectional view and / or a plane view. In the drawings, the thickness of a film and a region may be overstated in order to explain the technical content thereof efficiently. Accordingly, the form of exemplary drawings for a fabrication method and / or an allowable error may be reformed. Thus, the embodiments according to the present disclosure are not limited to specific forms illustrated herein but may include variations in the form resulting from the fabrication method. For example, the region illustrated with perpendicular lines may have a form to be rounded or with a predetermined curvature. Thus, regions exemplified in the drawings have attributes, and shapes thereof exemplify specific forms rather than limiting the scope of the present disclosure. In the various embodiments of this specification, terms such as ‘first’ and ‘second’ et cetera are used to describe various elements, but these elements should not be limited to such terms. These terms are merely used to distinguish one element from others. The embodiments explained and exemplified herein may include complementary embodiments thereto.

[0080] The terms used in this specification are to explain the embodiments rather than limiting the present disclosure. In this specification, the singular expression includes the plural expression unless specifically stated otherwise. The terms, such as ‘comprise” and / or “comprising” do not preclude the potential existences of one or more elements.

[0081] When describing the following specific embodiments, various kinds of specific contents are made up to explain the present disclosure in detail and to help understanding thereof. However, it will be apparent for those who have knowledge to the extent of understanding the present disclosure that the present disclosure can be used without any of these specific contents. In a certain case when describing the present disclosure, the content that is commonly known to the public but is substantially irrelevant to the present disclosure is not described in order to avoid confusion.

[0082] Hereinafter, described are the configuration, function, and measurement methods of a three-dimensional shape measurement system using an interferometer, such as a phase shifting interferometer, and an AFM 100 according to an aspect of the present disclosure.

[0083] The present disclosure provides a three-dimensional shape measurement apparatus using, for example, a phase shift interferometer (PSI) 1 and an AFM 100. The apparatus comprises, in one aspect of the present disclosure, the phase shift interference unit 1 for measuring a shape of a measurement object 2, and an AFM unit 200 for measuring the measurement object 2. The AFM unit 200 has an active cantilever beam 150 which is moved by a 3-axis piezo actuator 140, and the AFM unit 200 is adapted to measure a boundary of a specific area of interest in the measurement object 2.

[0084] The high performance of the AFM 100, shown in more detail in Fig. 11) is enabled by combination of following features: (i) a high-frequency cantilever, (ii) a fast AFM controller implemented in a high-speed DSP FPGA device, (iii) a high-speed closed-loop scanner, and (iv) a quick approach technique.

[0085] The cantilever excitation unit for the cantilever beam 150 comprises high-precision, dedicated DDS generators and low-noise excitation drivers for bridge supply and self-actuation allowing a defined digital control. The analogue part for the read-out signal is designed to feature high bandwidth (up to 5 MHz), high gain and extremely low noise (less than 1.59 nV / Hz'A). The amplified signal is converted using a fast analog-digital converter (ADC) providing a conversion time in the range of 10 ns - 12 ns with high resolution. The digitized signal is fed to an all-digital fast lock-in amplifier. The output of the all-digital fast lock-in amplifier is used as feedback for the precise all-digital PI controller for fast Z-regulation.

[0086] These elements are implemented in a high-speed DSP FPGA and provide an overall delay less than 5ps (as seen in Fig. 4). The scanning speed also depends on the X and Y positioning system which use high-resolution DDS generators. Three precision DAC channels and low-noise voltage drivers are used to fit the X, Y and Z output signals in a range from 0 to 10V. These elements provide an overall delay less than 25 ps.

[0087] The high-speed 3D closed-loop scanner is also part of the system. It is driven by a low- noise high-voltage amplifier which amplifies the X, Y and Z signals up to 150V. A fast approach motor is controlled by the digital motor driver providing high current and short reaction time. The combined delay of all elements results in total system delays of less than 40 ps and was confirmed experimentally. A high-speed Ethernet communication interface build in the controller provides a real-time data sampling and visualization using PC software. Summarizing all delay times of all system components (FPGA, DAC, ADC, Lock-in amplified, Pl-controller) the bandwidth of the system is as high as 200 kHz.

[0088] The phase detection systems can be employed as a method of measuring the critical dimensions (CD) of nano-features indirectly, by using the phase variation produced by the repeated x, y-shift of the samples (object) and accurate measuring of the shift of the samples. Thus, the precision of the measurement system depends on the accuracy of the measuring of the x-shift and y-shift of the samples.

[0089] FIG. 5 shows a flowchart of a three-dimensional shape measurement method using the phase shifting interferometer 1 and the AFM 100 according to an aspect of the present disclosure.

[0090] As shown in FIG. 5, the shape of the measurement object within the field of view (FOV) is measured by a phase shift interference unit 1 to acquire an interference measurement signal (e.g., FOV: lOOum x lOOurn) in a step S10.

[0091] Then, the active cantilever beam 150 is moved to the specific area of interest of the measurement object through a 3-axis piezo actuator of the AFM unit 200 to measure the boundary of the specific area of the measurement object in step S20. In other words, only the boundary of the specific area (e.g., Cu-SiO2 boundary) is measured by using the AFM unit 200. The AFM unit 200 is moved in parallel by the 3-axis (X, Y, Z) piezo actuator 140 in order to measure the measurement object 2 and align the optical axis of the interference unit 1.

[0092] In this case, since the degree of height difference at the boundary of the specific Cu- SiO2 area occurring within the same FOV is not expected to be significantly different, measuring one of the Cu-SiO2 boundaries and applying the same adjustment to all of the areas of interest. The key to the present disclosure is that, when acquiring the interference measurement signal and the AFM signal, the measurement point of the AFM is the same as the optical axis of the interference unit and is controlled by the 3-axis piezo actuator 140.

[0093] Hereinafter, described are the configuration, function, and interference signal measurement method of the interference unit according to an aspect of the present disclosure. The first, second and third aspects described below are described as illustrative aspects of the invention but are not limited thereto.

[0094] FIG. 6 shows a schematic view of an interference unit 1 according to the first aspect of the present disclosure. In the first aspect of the present disclosure, light 10 emitted from a light source 10 is partially reflected through a beamsplitter 30 and incident on a reference mirror 6, and the rest of the light 10 is passed through the beamsplitter 30 and incident on the measurement object 2. The light reflected onto the measurement object 2 is passed back through the beamsplitter 30, the light reflected onto the reference mirror 6 is reflected onto the beamsplitter 30, and interference is generated through quantum phase lag. An interference signal is measured through a camera 70 via a lens 60.

[0095] FIG. 7 shows a schematic view of an interference unit 1 according to the second aspect of the present disclosure. In the second aspect of the present disclosure, a Mirau objective lens 41 incorporating a Mirau lens is adopted without the reference mirror 6.

[0096] In other words, in the second aspect of the present disclosure, the light emitted from a light source 10 is reflected through the beamsplitter 30 and incident on the Mirau objective lens 41. Part of the light is reflected onto the Mirau lens and the rest of the light is passed through the Mirau objective lens 41 and incident on a measurement object 2. Interference is generated between the light reflected on to the Mirau lens 41 and the light reflected on to the measurement object 2, and an interference signal is measured through a camera 70 via a lens 60.

[0097] FIG. 8 shows a schematic view of the interference unit 1 according to the third aspect of the present disclosure. In addition, FIG. 9 shows a flowchart of an interference signal measurement method according to this third aspect of the present disclosure.

[0098] As shown in FIG. 8, a single-shot phase shifting interferometry three-dimensional shape measurement apparatus using a polarized camera 100 according to this aspect of the present disclosure may be configured to include an illumination optics module 11, a linear polarizer 20, the beamsplitter 30, a polarizing beamsplitter 31, a reference mirror 6, a quarterwave plate (QWP) 50, a lens 60, a polarized camera 71.

[0099] In this third aspect of the present disclosure, multiple ones of the interference images with different polarized lights can be acquired in a single measurement.

[0100] According to this third aspect of the present disclosure, after setting a focus position with an AF laser, making a depth large enough within a measurement range of the measurement object 2 and securing an interference distance equal to the depth. Four images for applying the phase shifting algorithm can be acquired in a single image acquisition (One-shot) by using the polarized camera 71. This enables rapid measurement with minimal oscillation influence.

[0101] Further, according to this third aspect of the present disclosure, a polarizer, a quarterwave plate 50 and the polarized camera 71 are used to acquire an image by continuously moving the measurement object 2 in the X, Y direction through the stage, without actuating the reference mirror 6. The phase shifting algorithm enables simultaneous acquisition of 0°, 45°, 90°, and 135° polarized images.

[0102] In the third aspect of the present disclosure, the interference unit 1 may be configured to include a broadband light source 10 that emits light and an illumination optics module 11 passes the light emitted from the broadband light source 10 to the measurement object 2. As an exemplary, but non-limiting, specific aspect of the present disclosure, the broadband light source 10 is configured to emit light having a wavelength of 400 ~ 700nm.

[0103] The beamsplitter 30 is configured to reflect part of the light emitted from the light source 10 and to allow passage of the reflected light being incident on the polarizing beamsplitter 31.

[0104] The polarizing beamsplitter 31 is configured to reflect a first polarized light of light and penetrate a second polarized wave, i.e., to reflect an S-wave and penetrate a P-wave.

[0105] The linear polarizer 20 is configured to be provided between the beamsplitter 30 and the illumination optics module 11 to adjust the ratio of the S-wave and the P-wave.

[0106] The first reflected, polarized S-wave from the polarizing beamsplitter 31 is reflected onto the reference mirror 6 and then reflected again in the polarizing beamsplitter 31. On the other hand, the passed second polarized P-wave is reflected onto the measurement object 2 and then passed through the polarizing beamsplitter 31.

[0107] In addition, the quarter-wave plate 50 is configured to polarize the first polarized reflected light reflected from the reference mirror 6 and reflected by the polarizing beamsplitter 31, and the second polarized reflected light reflected from the measurement object 2 and passed through the polarizing beamsplitter 31.

[0108] The quarter-wave plate 50 generates a phase delay between the first polarized reflected light and the second polarized reflected light, enabling the generation of an interference signal. After penetrating the quarter-wave plate 50, the between the first polarized reflected light and the second polarized reflected light are incident on the polarized camera 71 via the lens 60.

[0109] The polarized camera 71 is configured to be positioned at the rear end of the quarterwave plate 5 and acquire the multiple interference images having the different polarization states.

[0110] The polarized camera 71 according to an aspect of the present disclosure interferes with the first polarized reflected light and the second polarized reflected light and acquires multiple interference images having different polarization states.

[0111] The micro-polarized camera 70 according to an aspect of the present disclosure comprises a pixelated polarizer mask and a 2D sensor array. The pixelated polarizer mask comprises a repeated pattern array of 2x2 unit cells across the entire mask.

[0112] The 2x2 unit cell is a micro-polarizer pattern array with four different polarization axes, and the 2D sensor array is aligned with the individual polarization elements of each micropolarizer pattern array, enabling interference images having four different polarization states through the polarized camera 71. In addition, an analysing unit analyses the shape of the measurement object 2 from the interference image having the different polarization states. In this context, analysing means that the data from the PSI are correlated with the real physical data (metrological data) of the topology of the measurement object obtained using the AFM. In one aspect, this analysing unit is implemented in a software program which simply introducing the measured dimensions by the AFM with respect to the PSI measured data.

[0113] In other words, the analysing unit measures and analyses a three-dimensional shape of the measurement object 2 based on the phase difference between the reflected light of the reference mirror and the reflected light of the measurement object, based on the interference images having different polarization states. In addition, the stage is configured to move the measurement object 2 in a planar direction. Advances in semiconductor micro / nano-fabrication techniques have enabled the embedment of miniaturized sensors into the cantilever beams with sizes on the micrometre scale.

[0114] Hereinafter, described is the configuration, function, and measurement method of the AFM unit 200 according to an aspect of the present disclosure.

[0115] FIG. 10 shows a schematic view of the three-dimensional shape measurement system 100 using the exemplary phase shifting interferometer and an AFM according to an aspect of the present disclosure. FIG. 11 shows a schematic view and a partially enlarged view of an AFM unit 200 according to an aspect of the present disclosure. FIG. 12 shows a flowchart of a measurement method through an AFM unit according to an aspect of the present disclosure.

[0116] The active cantilever beam 150 of the AFM unit according to an aspect of the present disclosure is used to scan the surface of a measurement object 2 in various AFM measurement modes. In this aspect, the surface of the measurement object 2 is scanned by the cantilever beam 150 by using a 3-axis (XYZ) piezo actuator 140 in order to move the cantilever beam 150 along X and Y axes.

[0117] In addition, this system includes a Z-axis actuator 120 for moving the probe 150 along the Z-axis.

[0118] The 3 -axes piezo actuator 140 is used to move a cantilever along X, Y, Z-axes through an actuator 152 embedded in the cantilever beam 150 in a state that the measurement object 2 150 remains stationary.

[0119] As shown in FIG. 11, the main body of a scanner 130 is installed on a support frame 110. It is seen that the Z-axis actuator 120 is provided which actuates the scanner 130 in the direction of the Z-axis direction.

[0120] The active cantilever beam 150 of the AFM unit 200 is connected to the lower side of the scanner 150. As shown in the enlarged view of FIG. 11, the cantilever end of the cantilever beam 150 is provided with a tip 151.

[0121] The Z-axis actuator 152 is embedded in the cantilever beam 120 and is actuated to deform the cantilever beam 150 so that the tip 151 presses on a measurement point. A piezoresistance detection sensor 153 embedded in the cantilever beam 150 is configured to measure piezoresistance applied to a measurement object 2 by the tip 151.

[0122] In addition, as shown in FIG. 10 and FIG. 11, it is configured that one side of the active cantilever beam 150 projects outwardly from the side of the scanner 130, and an end portion thereof is tapered downwardly from a main body of the cantilever beam 150.

[0123] In the AFM unit 200 according to an aspect of the present disclosure, the AFM measurement point is controlled by the 3-axis piezo actuator 140 to align with the optical axis of the phase shifting interference unit 1 when acquiring an interference signal by the phase shifting interference unit 1 and an AFM signal.

[0124] As mentioned above, the phase shifting interference unit 1 measures the shape of the measurement object 2 within the field of view to acquire an interference measurement signal.

[0125] The active cantilever beam 150 is moved to the boundary of a specific area of the measurement object 2 using the 3-axis actuator 140 of the AFM unit 200 and the boundary of the measurement object 2 is measured. A measurement value for a boundary region is calibrated based on the AFM measurement signal.

[0126] In the acquisition of the AFM measurement signal through the AFM unit 200, a scanner 130 is first moved in the Z-axis direction throughout by the Z-axis actuator 120, and is positioned to the specific area of interest based on the initial position value of the probe tip 151 and the interference measurement signal so that the probe tip 151 is located at a specific measurement point of the boundary of the probe tip 151 through the 3-axis actuator 140. The optical axis of the interferometer is aligned with the measurement point (in step S21).

[0127] Then, the actuator 152 embedded in the cantilever beam 150 is actuated so that the tip presses on the measurement point (in step S22).

[0128] Then, the value of the piezoresistance at the measurement point by the tip 151 is measured through the piezoresistance detection sensor 153 embedded in the cantilever beam 150 (in step S23). In addition, the actuator embedded in the active cantilever beam 150 may be configured as an electrothermal actuator having a bimorph structure (two active layers) and a resistive heating element, as shown in Journal of Vacuum Science & Technology B 35, 06G101 (2017); DOI: 10.1116 / 1.4992073.

[0129] The electrothermal actuation embedded in the cantilever beam 150 employs a bimorph structure. This method employs a resistive heating element built into the bimorph structure instead of external laser as a heat source. The electrothermal actuation falls under the category of thermomechanical actuation, where thermally induced mechanical stress causes bending of the cantilever beam 150, and the key difference lies in the manner in which the temperature change is induced.

[0130] In this case, the temperature variation can be highly complex. This is primarily because the rate of heat dissipation depends on the temperature differential between the cantilever beam 150 and its environment. Generally, the integration of heating power is proportional to the temperature variation. The sinusoidal actuation terms excite the probe 150 resonance while the DC component can be utilized to control the probe 150’s static deflection. The build-up of the DC component in the energy input does not lead to an infinite temperature rise due to the increased heat dissipation power at higher temperatures.

[0131] In addition, the piezoresistance detection sensor 153 according to an aspect of the present disclosure has a Wheatstone bridge structure with four piezoresistive elements and measures the contact state and contact pressure of the tip 151.

[0132] That is, the deflection sensing of the AFM cantilever beam 150 can be implemented by using piezoresistive or piezoelectric sensing. Advances in semiconductor micro / nano- fabrication techniques have enabled the embedment of miniaturized sensors into cantilever beams 150 with sizes on the micrometre scale.

[0133] In an aspect of the present disclosure, multiple ones of the piezoresistive elements are incorporated into a cantilever base of the cantilever beam 150 where the maximum bending stress occurs. In general, four piezoresistive elements are used to form the full Wheatstone bridge configuration, which improves sensitivity and reduces thermal drift.

[0134] The piezoresistive sensing facilitates embedded measurement of the deflection of the cantilever beam 150 via resistance measurement, enabling both static and dynamic measurements with a wide bandwidth (from DC to megahertz). The sensitivity is comparable to that of optical methods, but is, however, not limited by the diffraction limit and can employ nanometre-scale cantilever beams. With the use of state-of-the-art semiconductor manufacturing technology, the geometric dimension of the sensing elements can be significantly smaller than that of conventional strain gauges when considering the effect of miniaturization. The reduction of the footprint enables specialized probes design for more accurate lateral force measurement.

[0135] The primary requirement for dynamic mode operation is the excitation of the cantilever resonance. Some actuation strategies can also allow control over static deflection. The active cantilever beam 150 according to an aspect of the present disclosure is configured by combining embedded self-sensing and self-actuation methods.

[0136] The active cantilever beam 150 eliminates the need for bulky external sensing and operation elements, which can minimize the physical footprint of the AFM unit 200. The aspect of the present disclosure includes all known probe design examples primarily created for AFM applications using external or embedded sensing and actuation methods.

[0137] In addition, diverse nanotechnology applications require nanopositioning capabilities. The specific positioning requirements can vary significantly depending on the application, such as micromanipulation, optical fibre alignment, wafer-scale lithography, etc. The positioning requirements for AFM operation are characterized by a unique combination of range, bandwidth, and resolution in three orthogonal directions.

[0138] In an aspect of the present disclosure, the operation of an AFM nanopositioning system is described using a Cartesian coordinate system. The Z-axis represents the vertical out-of- plane direction in which the sample can bend the cantilever beam 150. The X-axis and Y-axis correspond to the in-plane directions in which the nanopositioning system scans the probe tip 151 over the measurement object 2. In typical in-raster-style line-by-line imaging, the X-axis is, in general, aligned with the high-frequency scan line.

[0139] The requirements of an AFM positioning system can vary significantly depending on factors such as the type of cantilever beam, measurement object conditions and imaging requirements. During AFM imaging, either the measurement object 2 or the probe 150 can be moved. Conventional AFM systems that use optical methods for tip 151 deflection often employ a sample scan configuration. In this case, the optical components used for scanning motion are too bulky, making a sample scan configuration is preferable.

[0140] The implementation of the active cantilever beam 150 can simplify the design of a probe 150 scanning AFM system. The scanning performance can be improved by combining the measurement object 2 scan and probe 150 scan configurations. For general imaging applications, the AFM positioning system is designed with a sample scan configuration that utilizes piezoresistive or optical cantilever readouts to achieve motion up to 100 pm x 100 pm in the in-plane and tens of microns of out-of-plan Z-axis range.

[0141] Fig. 12 shows an example of the cantilever beam 150 according to one aspect of the invention. The cantilever beam 150 comprises a sensing part 155 at the front of cantilever beam 150 having a resonance frequency of 900kHz (spring constant of <2N / m) and an integrated tip 151. The integrated tip 151 is made from silicon or diamond. The cantilever beam 150 comprises further an actuation part 156 which is provided with the thermomechanical actuator 157 for operation in off-resonance mode.

[0142] The actuation part 156 is usually implemented using poly crystalline piezo-stack z- actuators 152 for fast tracking and low-cost. One of the z-actuators is causing the cantilever beam 150 to move and another of the z-actuators 152 shakes the cantilever beam 150 close to its resonance frequency. It will be appreciated that these techniques are a compromise with respect to positioning accuracy, creep, nonlinearity, hysteresis, and scaling errors despite. Capacitive or strain gauge position sensors in closed-loop configuration in a nested feedback loop can cause a phase lag of the closed-loop system and thereby limit speed of measurement. In order to accelerate the response of the cantilever beam to DC-z-actuation (off-resonance) using the z-actuators, a lag-lead compensator can be implemented in a control system that generates operated DC-input on the thermomechanical actuator 152 to attain a desirable fast response (deflection output) of the active cantilever beam 150 in high dynamic bandwidth in the kHz range. This compensator was used and was able to increase the bandwidth of the cantilever beam 150 from 280 Hz to 4300 Hz.

[0143] The long-distance van der Waals forces from the surface of the measurement object 2 are sensed by the oscillating AFM probe. The AFM is excited at its resonance frequency by the thermoelectrical actuator 152 with oscillation amplitudes in the range of Inm and brought in close proximity to the surface of the measurement object 2. The resolution in this mode is defined by the separation between the tip 151 and the surface of the measurement object 2 and is of a few nanometres. For the scanning feedback either the vibration amplitude (amplitude modulation mode, AM) or the frequency shift (frequency modulation, FM) of the AFM probe can be used.

[0144] FIG: 14 shows the general set-up of the integrated PSI and AFM. The measurement object (wafer, substrate) 2 is under the PSI-objective 40 and the AFM-Probe (cantilever) 150 is in between the objective 40 and the measurement object (wafer, substrate) 2.

[0145] One example of the use of the system and method of this document is chemical mechanical polishing (CMP). CMP is a planarization technique used in semiconductor manufacturing, optics, and advanced materials processing to remove excess material, reduce surface roughness, and improve uniformity. CMP is designed to planarise (to make planar) the topography of the semiconductor wafer surfaces in order to meet the depth-of-focus requirements for advanced lithography and for building layer upon layer from front end transistors to back-end interconnects build through silicon vias (TSVs), and implement complex die-to-die interconnects, which are used to push scaling and future process nodes enabling the Moore's Law which without CMP would not be possible. CMP is used, for example, in multilayer device fabrication, where flat surfaces are required to ensure precise alignment of subsequent layers. CMP is a hybrid process that combines chemical etching and mechanical abrasion to achieve a smooth, flat surface on a substrate. The CMP process involves a rotating polishing pad, a slurry containing abrasive particles and reactive chemicals, and downward pressure applied to the substrate.

[0146] The morphology of the substrate surface refers to its topography, roughness, and uniformity, which directly impact device performance. Measurement of surface morphology is required in CMP to enable planarity and uniformity of the surface, as non-uniform surfaces can cause alignment issues in multilayer structures (e.g., photonic waveguides or semiconductor devices). CMP is also used to minimise surface defects. It is known that defects, such as scratches, pits, or residual particles can lead to electrical or optical failures in semiconductor and photonics applications. CMP can also help to fine-tune CMP parameters, such as pressure, slurry composition, and polishing time. This fine tuning of the CMP parameters prevents overpolishing or under-polishing, which can damage the substrate or leave residues. Finally, CMP has been found to enhance optical and electronic performance, by reducing optical scattering and loss in photonics, and by improving thin film deposition and electrical conductivity.

[0147] It will be appreciated that the apparatus and methods described above are not intended to be limited to the configurations and methods of the embodiments described above but may be configured with optional combinations of all or portions of each embodiment so that various variations may be made.

[0148] Figure Reference Numbers

[0149] 1 : Interference unit

[0150] 2: Measurement object

[0151] 3 : Si02 area

[0152] 4: Specific area, Cu area

[0153] 5: Boundary area

[0154] 6: Reference mirror

[0155] 10: Light source

[0156] 11 : Illumination Optics Module

[0157] 20: Polarizer

[0158] 30: Beamsplitter

[0159] 31 : Polarizing beamsplitter

[0160] 40: Objective lens

[0161] 41 : Mirau objective lens

[0162] 50: Quarter- wave plate

[0163] 60: (Tube) lens

[0164] 70: Camera

[0165] 71 : Polarized camera

[0166] 100: Three-dimensional shape measurement system using a phase shifting interferometer and an AFM

[0167] 110: Frame

[0168] 120: Z-axis actuator

[0169] 130: Scanner : 3 -axis PZT actuator : Cantilever Beam : Tip : Actuator : Piezoresistive detection sensor: Sensing part : Actuation part : Processing portion : AFM unit

Claims

CLAIMS1. A three-dimensional shape measurement system (100) using an interferometer and an atomic force microscope (AFM) comprising: an interference unit (1) for measuring a shape of a measurement object (2); and an AFM unit (200) for measuring the measurement object (2), wherein the AFM unit has a cantilever beam (150) moved by a 3-axis piezo actuator (140) and is adapted to measure a boundary of a specific area of the measurement object (2).

2. The three-dimensional shape measurement system using an interferometer and an AFM of claim 1, wherein the 3-axis piezo actuator (140) is aligned with an optical axis of the interferometer and controls a measurement point of the AFM.

3. The three-dimensional shape measurement system using an interferometer and an AFM according to claim 1 or 2, further comprising a cantilever beam (150) with a small sensing cantilever at a tip (151) and an actuating part (152).

4. The three-dimensional shape measurement system using an interferometer and an AFM of claim 3, wherein the cantilever beam (150) of the AFM is provided on one side of a scanner on a frame, comprising: a tip (151) that is provided on the end of the cantilever beam (150); an actuator (152) that is embedded in the cantilever beam (150) and is actuated to deform the cantilever beam (150) so as to cause the tip (151) to interact with the measurement point; and a piezoresistance detection sensor (153), embedded in the cantilever beam (150), for measuring piezoresistance applied to the measurement object (2) by the tip (151).

5. The three-dimensional shape measurement system using an interferometer and an AFM of claim 4, wherein one side of the cantilever beam (150) projects outwardly from the side of a scanner(130), and an end portion of the cantilever beam (150) is tapered downwardly from a main body of the probe.

6. The three-dimensional shape measurement system using an interferometer and an AFM of claim 4 or 5, wherein the actuator (152) is an electrothermal actuator having a bimorph structure and a resistive heating element, and the piezoresistance detection sensor (153) has a Wheatstone bridge structure comprised of four piezoresistive elements and measures the connection state and contact pressure of the tip.

7. The three-dimensional shape measurement system using an interferometer and an AFM of any one of the above claims, wherein the interference unit comprises: an illumination optic module (11) with a light source (10) for emitting light; a polarizing beamsplitter (31) for reflecting a first polarized wave of the light (10) to a reference mirror (6) and passing a second polarized wave to the measurement object (2); a quarter-wave plate (50) for polarizing the first polarized reflected light reflected from the reference mirror (6) and reflected by the polarizing beamsplitter (31), and the second polarized reflected light reflected from the measurement object (2) and passed through the polarized beamsplitter (31); and a polarized camera (71), located on the back end of the quarter-wave plate (50), and acquiring multiple interferometric images having different polarization states.

8. A three-dimensional shape measurement method using an interferometer and an AFM comprising:Step 1, wherein a shape of a measurement object (2) within the field of view is measured using an interference unit and an interference measurement signal is acquired;Step 2, wherein a cantilever beam (150) is moved to a boundary of a specific area of the measurement object using a 3-axis actuator of an AFM unit (200) and the boundary of the measurement object (2) is measured; andStep 3, wherein a measurement value for a boundary region is calibrated based on the AFM measurement signal.

9. The three-dimensional shape measurement method using an interferometer and an AFM of claim 8, wherein the Step 2 comprises:Step 2-1, wherein a tip (151) is positioned at a measurement point of a boundary region of the specific area by the 3-axis actuator (140), and aligning an optical axis of the interferometer with the measurement point;Step 2-2, wherein an actuator (152) embedded in the cantilever beam (150) is actuated, and the tip (151) and scans a surface of the measurement object (2) in non-contact mode; andStep 2-3, wherein piezoresistance applied to the measurement point by the tip (151) is measured through a piezoresistance measurement sensor embedded in the cantilever beam (150).

10. The three-dimensional shape measurement method using an interferometer and an AFM of claim 8 or 9, wherein the actuator (152) is an electrothermal actuator having a bimorph structure and a resistive heating element, and in the Step 2-2, an AC voltage applied to the electrothermal actuator stimulates probe resonance, and then a DC voltage controls a static deflection.

11. The three-dimensional shape measurement method using an interferometer and an AFM of one of claims 8 to 10, wherein the Step 1 comprises steps of: emitting light from a light source (10); passing through the light (10) through an illumination optics module and passing the collimated light through a polarizer (20); reflecting a first polarized wave of the light (10) in a polarizing beamsplitter (31) to be incident on a reference mirror (6), and passing a second polarized wave to be incident on themeasurement object (2); reflecting the first polarized reflected light reflected from the reference mirror (6) onto the polarizing beamsplitter (31), and passing the second polarized reflected light reflected onto the measurement object (2) through the polarized beamsplitter (31); polarizing the first polarized reflected light and the second polarized reflected lights by passing through a quarter-wave plate (50); and interfering the first polarized reflected light and second polarized reflected light polarized in a polarized camera (71) and acquiring multiple interference images having different polarization states.12 An atomic force microscope (AFM) comprising a cantilever beam (150) with a small sensing cantilever at a tip (151) and an actuating part with electrothermal actuator (152).

13. Use of the method of the measurement system according to one of claims 1 to 7 or the method according to 8 to 11 for measuring the surface morphology of the measurement object (2) for chemical and mechanical polishing.

Images