Atomic force volumetric metrology device

Abstract

The present application relates to the technical fields of micro-nano structure measurement and detection, and particularly provides an atomic force volumetric measurement device, which comprises an elastic element, a piston probe, a force detection unit, a motion control unit and a feedback control unit, and needs to ensure that: after the piston probe enters a deep hole to be measured, the gap between the piston probe and the deep hole to be measured is less than 2 times the average free path of gas molecules under working environment, and there is no friction between the piston probe and the deep hole to be measured; the motion control unit drives the piston probe to move relatively in the axial direction of the deep hole to be measured; when the force acting on the elastic element is equal to a preset threshold value, the piston probe is relatively far away from the deep hole to be measured; and the volume of the inner cavity of the deep hole to be measured is calculated according to the displacement of the piston probe entering the deep hole to be measured and the force acting on the elastic element. The present application solves the problem that the traditional optical measurement method is limited by the optical diffraction limit, significantly improves the deep hole detection resolution, and can realize the detection of deep silicon blind holes with a diameter less than 100 nanometers.

Description

Technical Field

[0001] This invention belongs to the field of micro-nano structure metrology and detection technology, and particularly relates to an atomic force volume measurement device. Background Technology

[0002] Atomic force microscopy (AFM) is a high-resolution scanning probe technique widely used for surface and nanostructure characterization at the nanoscale and even atomic scale. Proposed in 1986 by Gerd Binning, Carl Quiet, and Christoph Gebel, this technique extends the concept of scanning tunneling microscopy, enabling high-resolution imaging of conductors and insulators. Since its inception, AFM has become one of the most important tools in nanoscience, materials research, semiconductor metrology, and bioimaging. US Patent No. US4724318, published on February 9, 1988, entitled "Atomic force microscope and method for imaging surfaces with atomic resolution," discloses an atomic force microscope and surface imaging method with atomic resolution. A sharp probe is mounted on the free end of a spring-loaded microcantilever, bringing the probe tip close to the sample surface. The interatomic forces between the atoms at the probe tip and the atoms on the sample surface cause the microcantilever to bend and deform, thus enabling the detection of the sample surface morphology. It discloses the basic working principle of AFM: scanning the sample surface with a sharp probe tip mounted on a flexible microcantilever. Interatomic forces between the tip and the sample cause bending deformation of the microcantilever. These deformations are typically detected using a beam deflection method: a laser beam is irradiated on the back of the microcantilever, reflected, and then incident on a position-sensitive photodetector. A feedback system maintains a constant interaction between the tip and the surface by controlling a piezoelectric scanner. By recording the vertical movement of the scanner, AFM reconstructs a high-resolution three-dimensional topography of the sample surface. AFM can achieve sub-nanometer vertical resolution and nanometer-level lateral resolution.

[0003] Over the years, various operating modes have been developed for measuring different physical properties. Common modes include contact mode, tapping mode, non-contact mode, and peak force tapping mode. For example, Chinese Patent No. CN102844666A, published on December 26, 2012, entitled "Method and Apparatus for Operating a Scanning Probe Microscope," discloses a peak force tapping mode that uses force as a feedback variable to reduce the interaction force between the probe tip and the sample, while maintaining the scanning speed achievable through all existing AFM operating modes, thereby achieving sample detection with improved resolution and high sample throughput.

[0004] In addition to surface morphology imaging, modern AFM technology can also measure mechanical properties, electrical conductivity, surface potential, magnetic force, and thermal behavior at the nanoscale. Force spectroscopy can also quantitatively measure the interaction forces between the probe and the sample.

[0005] Today, AFM is widely used in biological fields such as semiconductor device inspection, nanomaterials research, polymer science, and protein and cell membrane imaging. Continuous advancements in probe technology, high-speed scanning technology, and multifunctional measurement capabilities are further expanding the application scope of AFM as a multifunctional nanocharacterization platform.

[0006] With the development of advanced semiconductor packaging technology, through-silicon vias (TSVs), as a key structure for realizing vertical interconnects of chips, have seen their diameters continuously shrink (reaching the sub-100 nanometer scale) and their aspect ratios continuously increase (often greater than 5, even reaching 100). The internal volume integrity of TSVs directly determines the interconnect resistance, reliability, and yield. Common defects such as neck shrinkage, partial blockage, excessive sidewall roughness, or filling voids can all lead to a reduction in effective volume or impaired connectivity.

[0007] Existing technologies for detecting deep silicon blind vias (TSVs) include: FIB-SEM cross-sectional analysis, Mirau interferometry, focused beam microscopy / microspectroscopy, and X-ray transmission imaging. Among these, FIB-SEM is a destructive analysis method, unsuitable for manufacturing inspection, and suffers from slow speed, high cost, lack of wafer-level statistical representativeness, and susceptibility to artifacts such as gallium implantation, re-deposition, curtain effect, and geometric distortion. Mirau interferometry and focused beam microscopy / microspectroscopy are both limited by optical diffraction limits, unable to reliably penetrate deep vias with high aspect ratios, and their signals are easily interfered with by sidewall scattering, failing to effectively collect signal light reflected from the bottom of the TSV. While X-ray transmission imaging can penetrate silicon, its projection method lacks depth resolution, making it difficult to detect tiny gaps, voids, and minute volume changes. Furthermore, its resolution is limited by the focal spot size, and it also cannot effectively collect signal light reflected from the bottom of the TSV.

[0008] Therefore, there is an urgent need for a metrology technology with depth sensitivity that can directly detect high aspect ratio TSV structures at the sub-100 nanometer scale to meet the production metrology requirements of next-generation TSVs. Summary of the Invention

[0009] In view of this, the present invention aims to provide an atomic force volume measurement device that directly uses the ideal gas law to back-calculate the effective internal volume by measuring the mechanical response generated by the piston compressing the enclosed gas in the deep cavity. This solves the problem of traditional optical measurement methods being limited by the optical diffraction limit, significantly improves the detection accuracy of deep silicon blind holes, and can be adapted to the measurement needs of next-generation high aspect ratio TSV structures in the sub-100 nanometer scale.

[0010] To achieve the above objectives, the technical solution created by this invention is implemented as follows: This invention provides an atomic force volume measurement device, comprising: Elastic element; The piston probe is connected to one end of the elastic element. The shape and size of the piston probe must ensure that after the piston probe enters the deep hole to be measured, the gap between the piston probe and the deep hole to be measured is less than twice the mean free path of gas molecules under working conditions, and there is no friction between the piston probe and the deep hole to be measured. A force detection unit is used to acquire the force applied to an elastic element; The motion control unit is used to drive the elastic element or move the deep hole to be measured, so that the piston probe can move relative to the axial direction of the deep hole to be measured. The feedback control unit is configured to control the motion control unit to move the piston probe away from the deep hole to be measured when the force on the elastic element is equal to a preset threshold. The internal volume of the deep hole to be measured is calculated based on the displacement of the piston probe into the deep hole and the force exerted on the elastic element.

[0011] Preferably, the elastic element is a helical spring. Preferably, the elastic element is an AFM cantilever beam. Preferably, the mean free path of gas molecules is adjusted by changing the air pressure of the working environment to detect deep holes of different sizes. Preferably, the mean free path of gas molecules is reduced by increasing the air pressure of the working environment, thereby improving the detection accuracy.

[0012] Preferably, the deep hole to be tested is a deep silicon blind hole with a diameter of less than 2 micrometers.

[0013] Preferably, the motion control unit is an XYZ piezoelectric scanning stage, which drives the elastic element or the deep hole to be measured to perform grating scanning in the X and Y directions, and performs reciprocating detection at each detection point position in a direction perpendicular to the scanning direction.

[0014] Preferably, the force detection unit is a force gauge, which is mounted on the helical spring and used to measure the force acting on the helical spring.

[0015] Preferably, the force detection unit includes a laser and a photodetector. The laser emits a laser beam to illuminate the upper surface of the AFM cantilever beam, and the photodetector receives the reflected light spot reflected from the upper surface of the AFM cantilever beam. The deformation of the AFM cantilever beam is obtained based on the position change of the reflected light spot on the photodetector, and the force acting on the AFM cantilever beam is calculated based on the deformation of the AFM cantilever beam.

[0016] Preferably, the motion control unit subtracts the initial height of the piston probe and the deformation of the elastic element from the axial drive displacement of the deep hole to be measured, and obtains the displacement of the piston probe entering the deep hole to be measured.

[0017] Preferably, the internal volume of the deep hole to be measured is... The formula is: ; in, Let be the cross-sectional area of ​​the deep hole to be measured, n be the number of moles of gas in the deep hole, R be the ideal gas constant, and T be the thermodynamic temperature. This represents the displacement of the piston probe within the deep hole being measured. This represents the force exerted by the gas inside the deep hole on the piston probe.

[0018] Preferably, it also includes an atomic probe disposed at the center of the lower surface of the piston probe, wherein the atomic probe and the piston probe are fixed in a detachable manner or are obtained by integral fabrication.

[0019] Preferably, the upper surface of the sample is first probed with an atomic force microscopy to create a three-dimensional morphology model of the sample's upper surface, determine the shape and position of the deep hole to be measured on the sample, and make the central axis of the piston probe coincide with the central axis of the deep hole to be measured. Then, atomic force volume measurement is performed on the deep hole to be measured.

[0020] Compared with the prior art, the present invention can achieve the following beneficial effects: Compared to traditional deep silicon blind hole detection techniques that rely on optical refraction, interference, or X-ray absorption, this invention overcomes the limitations of optical diffraction on detection accuracy. It avoids the problem that photons or electrons cannot return from the bottom of the silicon blind hole and be received when detecting high aspect ratio deep silicon blind holes, significantly improving the detection resolution. Traditional detection methods relying on white light interference can only detect deep silicon blind holes with a diameter of about 10 micrometers, methods relying on X-ray tomography can only detect deep silicon blind holes with a diameter of about 7 micrometers, and methods based on reflectance measurement spectroscopy can only detect deep silicon blind holes with a diameter of about 3 micrometers. This invention not only breaks through the 3-micrometer limit of traditional methods but can even detect deep silicon blind holes with a diameter of less than 100 nanometers. Furthermore, by increasing the working gas pressure and reducing the mean free path of gas molecules, even smaller deep silicon blind holes can be detected.

[0021] Furthermore, compared to FIB-SEM cross-sectional analysis, the device of this invention for detecting deep silicon blind vias does not require cutting the sample and will not damage the deep silicon blind vias to be detected. It can achieve non-destructive and rapid detection, filling the gap in existing metrology technology in the field of next-generation advanced packaging.

[0022] This invention measures the mechanical response generated by the piston compressing the enclosed gas in the deep cavity, uses the ideal gas law to back-calculate the effective internal volume, and then determines the depth and state of the deep silicon blind hole based on the volume. It can reliably detect deep localized defects such as neck contraction and blockage that occur in the middle or bottom of the deep cavity.

[0023] This invention improves upon traditional atomic force microscopy (AFM) by allowing for the separate design of a piston probe, which can be magnetically attached to an existing AFM with extremely low modification costs and a mature manufacturing process. Furthermore, an atomic probe is designed below the piston probe, which also functions as a microscopic probe within the AFM. This atomic probe performs grating scanning and vertical probing on semiconductor packages with deep silicon blind vias, enabling three-dimensional morphological modeling of the semiconductor package. This allows for the precise location of the deep silicon blind vias, ensuring perfect insertion of the piston probe into the via during detection. The gap between the piston probe and the blind via is less than twice the mean free path of gas molecules under operating conditions, guaranteeing friction-free operation. This invention combines the functions of an atomic force microscope with the ability to detect ultra-small diameter deep silicon blind vias. Attached Figure Description

[0024] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of an atomic force volume measurement device using a helical spring according to Embodiment 1 of the present invention. Figure 2 This is a schematic diagram of a piston probe for detecting deep silicon blind vias according to Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of a hemispherical piston probe provided according to Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of the AFM cantilever beam and piston probe of the atomic force volumetric metering device based on the AFM cantilever beam provided in Embodiment 2 of the present invention; Figure 5 This is a schematic diagram of an atomic force volume measurement device based on an AFM cantilever beam using the beam deflection method, according to Embodiment 2 of the present invention. Figure 6This is a schematic diagram of an AFM cantilever beam-based atomic force volume measurement device according to Embodiment 3 of the present invention. Figure 7 This is a schematic diagram of an atomic force volume measurement device based on an AFM cantilever beam using the beam deflection method, according to Embodiment 3 of the present invention. Figure 8 This is a schematic diagram of an atomic force volumetric metering device based on an AFM cantilever beam and equipped with an atomic probe, provided in Embodiment 4 of the present invention.

[0025] The reference numerals in the figures include: 0. Deep silicon blind via, 1. Elastic element, 2. Piston probe, 3. Atom probe, 4. Motion control unit, 5. Feedback control unit, 6. Force detection unit, 61. Laser, 62. Photodetector. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and do not constitute a limitation thereof. Similar elements in different embodiments are referred to by associated similar element reference numerals. In the following embodiments, many details are described to facilitate a better understanding of the invention. However, those skilled in the art will readily recognize that some features may be omitted in different situations, or may be replaced by other elements, materials, or methods. In some cases, some operations related to the invention are not shown or described in the specification. This is to avoid obscuring the core parts of the invention with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; the relevant operations can be fully understood based on the description in the specification and general technical knowledge in the art.

[0027] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined to form various implementations. Furthermore, the order of the steps or actions in the method description can be changed or adjusted in a manner readily apparent to those skilled in the art. Therefore, the various orders in the specification and drawings are merely for the clear description of a particular embodiment and do not imply a mandatory order, unless otherwise stated that a particular order must be followed.

[0028] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0029] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0030] The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0031] Example 1: Please see Figure 1 and 2 In one embodiment of the present invention, an atomic force volume measurement device is provided, comprising: Elastic element 1; Piston probe 2 is connected to one end of elastic element 1. The shape and size of piston probe 2 must ensure that after piston probe 2 enters the deep hole to be measured, the gap between piston probe 2 and the deep hole to be measured is less than twice the mean free path of gas molecules under working conditions, and there is no friction between piston probe and deep hole to be measured. Force detection unit 6 is used to acquire the force applied to elastic element 1; The motion control unit 4 is used to drive the elastic element 1 or move the deep hole to be measured, so that the piston probe 2 moves relative to the axial direction of the deep hole to be measured. The feedback control unit 5 is configured to control the motion control unit 4 to move the piston probe 2 away from the deep hole to be measured when the force on the elastic element 1 is equal to a preset threshold. The internal volume of the deep hole to be measured is calculated based on the displacement of the piston probe 2 into the deep hole to be measured and the force exerted on the elastic element 1.

[0032] In this invention, the deep hole to be tested is a deep silicon blind hole 0, and the scanning plane is the sample surface on which deep silicon blind holes 0 are distributed. The atomic force volume measurement device based on a helical spring provided in Embodiment 1 can be applied to the detection of high aspect ratio deep silicon blind holes 0 on a semiconductor plane at the sub-100 nanometer scale. By measuring the mechanical response generated by the piston probe 2 compressing the closed gas inside the cavity of the deep silicon blind hole 0, the internal volume of the deep silicon blind hole 0 is deduced using the ideal gas law, thereby determining the depth and internal state of the deep silicon blind hole 0, and detecting whether there are deep localized defects such as neck contraction or blockage in the middle or bottom of the deep silicon blind hole 0.

[0033] In Embodiment 1, the elastic element 1 is a helical spring, whose function is to convert the gas compressive force exerted on the piston probe 2 within the deep hole to be measured into a precisely measurable elastic deformation. This deformation is then used to obtain the force exerted by the gas on the piston probe 2 within the deep hole using Hooke's Law, and combined with displacement detection to calculate the internal volume of the deep hole. In this embodiment, the deep hole to be measured is a deep silicon blind hole 0, with a diameter of 2 micrometers. The stiffness coefficient of the elastic element 1 is known, specifically the stiffness coefficient... Throughout the measurement process, the deformation of elastic element 1 should be within the elastic range, without plastic deformation.

[0034] The piston probe 2 is connected to the lower end of the elastic element 1. Unlike the design of traditional atomic force microscopes that connect micro- and nano-atomic-level probes via a cantilever, the shape and size of the piston probe 2 in this embodiment need to be designed according to the deep silicon blind hole 0 to be tested. Different sizes of deep silicon blind holes 0 require different piston probe 2 designs. Therefore, the elastic element 1 and piston probe 2 can be designed as detachable structures, allowing the piston probe 2 to be removed from the elastic element 1 when probing deep silicon blind holes 0 of different sizes. Alternatively, the upper end of the elastic element 1 can also be designed as a detachable structure, allowing the elastic element 1 and piston probe 2 to be replaced as a whole when probing deep silicon blind holes 0 of different sizes. Figure 1 The depth of the medium-deep silicon blind via 0 is d, the width is a, and the aspect ratio is d / a.

[0035] The shape of the elastic element piston probe 2 needs to be determined based on the opening shape of the deep silicon blind via 0. For example, if the opening of the via is circular, then the cross-sectional shape of the piston probe 2 also needs to be circular, and the overall shape is a cylinder; if the opening of the via is rectangular, then the cross-sectional shape of the piston probe 2 also needs to be rectangular, and the overall shape is a prism. A cylindrical piston probe 2 is commonly used, but other shapes can also be used... Figure 3 The hemispherical piston probe 2 is shown.

[0036] The piston probe 2 needs to be slightly smaller than the inner diameter of the deep silicon blind via 0 to ensure that after the piston probe 2 enters the deep silicon blind via 0, the gap between the piston probe 2 and the deep silicon blind via 0 is less than twice the mean free path of gas molecules under working conditions. ,in, The gap between piston probe 2 and deep silicon blind via 0. The mean free path of gas molecules under the operating environment ensures that the gap is in a slip flow or transition flow region. Within this region, the collision frequency between gas molecules and the wall is comparable to the intermolecular collision frequency, preventing the gas from escaping instantaneously during rapid piston movement. This creates a measurable adiabatic compressive pressure within the deep silicon blind hole 0. Simultaneously, the flow-limiting effect of the gap provides controllable leakage and damping, ensuring a gas spring effect within the deep silicon blind hole 0. Furthermore, it is necessary to ensure no actual friction between the piston probe 2 and the deep silicon blind hole 0 to avoid introducing frictional forces that could interfere with the detection results.

[0037] In this embodiment of the invention, the opening diameter of the deep silicon blind hole 0 is 2 micrometers, and the depth of the deep silicon blind hole 0 is 60 micrometers. Under normal working conditions, the mean free path of air molecules is about 69.1 nm. Therefore, the bottom diameter of the piston probe 2 is designed to be 1.8 micrometers. Thus, the gap between the deep silicon blind hole 0 and the piston probe 2 is 100 nm, which is less than twice the mean free path of gas molecules, thus meeting the design requirements.

[0038] When detecting deep silicon blind holes 0 with smaller diameters and larger aspect ratios, optional embodiments include: reducing the gap between the deep silicon blind hole 0 and the piston probe 2, such as designing the gap to be less than 1 times the mean free path of gas molecules; alternative embodiments include: changing the external environment, including air pressure and temperature, such as reducing the mean free path of gas molecules by increasing the working air pressure, thereby enabling the detection of smaller diameter deep silicon blind holes 0; alternative embodiments include: changing the working gas environment, for example, performing deep silicon blind hole 0 detection in an environment with a single gas or mixed gas where the mean free path of gas molecules is smaller. The above embodiments do not completely cover all optional methods. When detecting deep silicon blind holes 0 with smaller diameters, the core requirement is to reduce the mean free path of gas molecules in the test environment. Any method that can reduce the mean free path of gas molecules in the test environment can be used and is within the scope of disclosure and protection of the embodiments of this invention.

[0039] Through the above design, the deep silicon blind via 0 can be regarded as a compressible gas cavity. The pressure change can be converted into a measurable mechanical force through the piston probe 2. The adiabatic pressure as low as 0.1 nN can be measured through the elastic element 1 and the piston probe 2, and the volume change can be derived. Then, the internal volume of the deep silicon blind via 0 can be calculated based on the ideal gas law. By comparing the calculated internal volume of the deep silicon blind via 0 with the theoretical volume of the deep silicon blind via 0, it can be determined whether the deep silicon blind via 0 is qualified and whether there are problems such as neck shrinkage, partial blockage, excessive sidewall roughness, or filling voids.

[0040] To measure the elastic force of elastic element 1, a force detection unit 5 is also provided on elastic element 1. Specifically, the force detection unit 5 can be a force gauge, used to read the force acting on elastic element 1, i.e., the elastic force value, and output the elastic force value at each moment, thus forming the elastic force curve of elastic element 1. Since the bottom of elastic element 1 is connected to piston probe 2, it will be stretched by the gravity of piston probe 2, so elastic element 1 has an initial elastic force. Therefore, the force detection unit 5 will output an initial elastic force. Since the initial elastic force does not participate in subsequent calculations, the force detection unit 5 can be manually zero-calibrated. That is, after elastic element 1 is connected to piston probe 2 and is in a naturally stretched state, the force detection unit 5 outputs 0. At this time, the output of the force detection unit 5 is actually the change in elastic force based on the initial elastic force. Alternatively, zero-calibration can be omitted, and the force detection unit 5 can directly output the elastic force of elastic element 1. In subsequent data processing, the elastic force directly output by the force detection unit 5 is subtracted from the initial elastic force.

[0041] The motion control unit 4 is designed primarily to drive the piston probe 2 and the sample to achieve relative planar scanning and vertical detection. Therefore, it only needs to enable relative movement between the piston probe 2 and the sample. Based on this, this invention proposes two solutions: One is to place the motion control unit 4 at the top of the helical spring, attaching the helical spring to the motion control unit 4. The motion control unit 4 actively drives the helical spring and piston probe 2 to perform planar scanning and vertical detection, while the sample position remains unchanged. The other is to attach the helical spring to a fixed position, place the sample on the motion control unit 4, and drive the sample to perform planar scanning and vertical detection, while the positions of the helical spring and piston probe 2 remain unchanged. Both methods achieve relative movement between the piston probe 2 and the sample, and the driving process and gas metering principle are the same. The following description only uses the example of the helical spring being attached to the lower surface of the motion control unit 4.

[0042] The motion control unit 4 drives the helical spring and piston probe 2 to perform planar scanning of the sample with the deep silicon blind via 0. Specifically, the motion control unit 4 can be an XYZ piezoelectric scanning stage, which provides nanometer-level positioning of the piston probe 2 in the X, Y, and Z directions. The XYZ piezoelectric scanning stage drives the helical spring and piston probe 2 to perform controlled vertical and lateral scanning of the sample surface and the opening of the deep silicon blind via 0, i.e., moving the helical spring and piston probe 2 along the XY scanning plane. At each scanning point, the motion control unit 4 drives the helical spring and piston probe 2 to perform a periodic downward and reset movement along the Z direction, similar to the peak force operation used in advanced AFM technology. During the downward movement, the helical spring and piston probe 2 are controlled to move downwards, i.e., towards the scanning plane. When the force detection unit 5 measures that the elastic force generated by the helical spring equals a preset threshold, the motion control unit 4 drives the helical spring and piston probe 2 away from the scanning plane. Furthermore, the motion control unit 4 can record the downward driving displacement. The downward driving displacement is the Z-direction displacement of the motion control unit 4, but it is not the Z-direction displacement of the elastic element 1. This is because the elastic element 1 will be compressed during the vertical detection process. Therefore, the Z-direction displacement of the helical spring is actually the Z-direction displacement of the motion control unit 4 minus the compression of the elastic element 1.

[0043] When piston probe 2 descends into the deep silicon blind hole 0, its bottom surface is below the opening plane of the through hole and does not contact any solid. Because the gap between piston probe 2 and the deep silicon blind hole 0 is less than twice the mean free path of gas molecules under working conditions, the gas inside the deep silicon blind hole 0 cannot escape quickly. Piston probe 2 begins to compress the sealed gas inside the through hole, and the internal pressure of the deep silicon blind hole 0 begins to rise. The gas exerts an upward restoring force on piston probe 2, which is transmitted to the helical spring through piston probe 2, causing the helical spring to compress. As piston probe 2 continues to descend, the upward force exerted by the gas on piston probe 2 gradually increases, and the elastic force measured by force detection unit 5 also gradually changes. When the force on the helical spring equals a preset threshold, the motion control unit 4 is controlled to drive the helical spring and piston probe 2 to reset. When the elastic force generated by the helical spring equals the preset threshold, the displacement of piston probe 2 within the deep silicon blind hole 0 can be obtained based on the downward drive displacement of motion control unit 4, the compression amount of the helical spring caused by the gas force, and the initial position of piston probe 2 and the opening distance of the upper surface of the deep silicon blind hole 0. That is, the displacement of piston probe 2 within the deep silicon blind via 0. It equals the downward drive displacement recorded by motion control unit 4 minus the compression of the helical spring and the distance between the initial position of piston probe 2 and the opening of the upper surface of deep silicon blind hole 0.

[0044] To achieve zero internal volume in deep silicon blind vias The calculation requires first establishing the force exerted by the gas on the piston probe 2 when the piston probe 2 compresses the gas inside the deep silicon blind hole 0. The displacement of piston probe 2 within the deep silicon blind via 0 Quantitative relationship between them: First, determine the gas volume change. The displacement of piston probe 2 within the deep silicon blind via 0 The quantitative relationship between them is as follows: ; in, The cross-sectional area of ​​the deep silicon blind via 0 can be calculated based on the known opening diameter of the deep silicon blind via 0.

[0045] According to the ideal gas law, pressure is inversely proportional to volume: ; Where P represents gas pressure, V represents gas volume, n represents the number of moles of gas, R is the ideal gas constant, and T is the thermodynamic temperature.

[0046] The ideal gas law is further derived to obtain the gas pressure change inside a deep silicon blind via. With volume change The relationship is: ; In the process of measuring pressure, the positive or negative sign is usually omitted, i.e., the value is taken as... .

[0047] The gas pressure inside the deep silicon blind via 0 acts on the cross-section of piston probe 2, and the force exerted on piston probe 2 can be expressed as: .

[0048] Then and Substitution The force F exerted by the gas on the piston probe 2 and the displacement of the piston probe 2 within the deep silicon blind hole 0 can be obtained. The relationship is: ; Further analysis yielded the internal volume of the deep silicon blind via 0. The formula is: .

[0049] in, and All of these can be obtained by the atomic force volumetric metering device proposed in the embodiments of the present invention. Therefore, the volume of the deep silicon blind via 0 can be measured using the atomic force volumetric metering device, and the actual measured internal volume of the deep silicon blind via 0 can be obtained. By comparing it with its theoretical volume, the state of the deep silicon blind via 0 can be determined.

[0050] The internal volume of the deep silicon blind via 0 In the formula Equivalent to gas stiffness, let gas stiffness Then the calculation formula can be further transformed into As can be seen from this formula, no actual measurement recording is required. and It is only necessary to use the atomic force volume measurement device proposed in the embodiments of the present invention to measure and The ratio is sufficient.

[0051] Example 2: Please see Figure 4 and Figure 5 In Embodiment 2 of the present invention, an atomic force volume measurement device based on an AFM cantilever beam is provided. Embodiment 2 features a special design for the elastic element 1 and the force detection unit 6 without altering other structures or working principles. Embodiment 3 differs from Embodiment 2 in that the elastic element 1 is an AFM cantilever beam, which serves as the core force-displacement conversion device. The deformation of the AFM cantilever beam is proportional to the force it experiences, and it is configured as a force response device throughout the device. The force exerted by the gas within the deep silicon blind hole 0 on the piston probe 2 can be obtained through the AFM cantilever beam, and then combined with the displacement of the piston probe 2 within the deep silicon blind hole 0 to calculate the internal volume of the deep silicon blind hole 0. The AFM cantilever beam includes a free end and a fixed end, wherein the fixed end is integrated with the motion control unit 4, and the motion control unit 4 drives the AFM cantilever beam to perform controlled detection of through-hole structures with high aspect ratios, such as the deep silicon blind hole 0. The piston probe 2 is connected to the lower surface of the free end of the AFM cantilever beam.

[0052] The motion control unit 4 is connected to the fixed end of the AFM cantilever beam. During vertical detection, the piston probe 2 approaches the sample surface, and the force detection unit 6 collects the deformation of the AFM cantilever beam in real time, obtaining the change in force acting on the AFM cantilever beam through the deformation. This change in force is transmitted to the feedback control unit 5, which compares it with a preset threshold to control the vertical downward movement of the motion control unit 4. Specifically, during the downward movement, when the piston probe 2 interacts with the sample surface or enters a recessed feature such as a deep silicon blind hole 0, the resulting mechanical force causes the AFM cantilever beam to bend elastically. The force detection unit 6 collects the deformation of the AFM cantilever beam in real time and uses this to determine the change in force. When the obtained change in force equals the preset threshold, the feedback control unit 5 controls the motion control unit 4 to move the AFM cantilever beam and piston probe 2 away from the sample surface. The preset threshold is the peak force of the AFM cantilever beam during vertical detection.

[0053] For the force detection unit 6, the beam deflection method is used in the design of this embodiment of the invention. The force detection unit 6 includes a laser 61 and a photodetector 62. The laser 61 is used to emit laser light to irradiate the upper surface of the AFM cantilever beam, while the photodetector 62 is used to receive the reflected light spot reflected from the upper surface of the AFM cantilever beam, and the deformation of the AFM cantilever beam is obtained according to the position change of the reflected light spot on the photodetector 62. Specifically, the atomic force volumetric microscope provided in this embodiment of the invention operates using the force-controlled imaging principle during operation. During vertical detection, piston probe 2 descends into the deep silicon blind hole 0. The bottom surface of piston probe 2 enters below the opening plane of the deep silicon blind hole 0 without contacting any solid. Since the gap between piston probe 2 and deep silicon blind hole 0 is less than twice the mean free path of gas molecules under working conditions, the gas inside the deep silicon blind hole 0 cannot escape quickly. Piston probe 2 begins to compress the closed gas inside the through hole, and the internal pressure of deep silicon blind hole 0 begins to rise. The gas generates an upward restoring force on piston probe 2. The force on the lower surface of piston probe 2 is transmitted to the AFM cantilever beam, causing the AFM cantilever beam to deflect and undergo elastic deformation. This deformation is a measurable signal proportional to the interaction force. At this time, the illumination position and incident angle of laser 61 on the upper surface of the AFM cantilever beam change, which in turn causes a corresponding change in the exit angle of the reflected light spot. The position of the reflected light spot on the photodetector 62 changes. Based on the reflected light spot on the photodetector 62, the deformation of the AFM cantilever beam can be calculated, and further, based on the elastic characteristics of the AFM cantilever beam, the change in the force acting on the AFM cantilever beam can be calculated. The feedback control unit 5 monitors the change in the force acting on the AFM cantilever beam in real time. As the piston probe 2 continues to descend, the upward force exerted by the gas on the piston probe 2 gradually increases, and the deformation of the AFM cantilever beam also gradually increases. When the change in the force acting on the AFM cantilever beam reaches a preset threshold, it indicates that the vertical detection has reached its peak point. At this time, the vertical position of the motion control unit 4 is recorded, which corresponds to the downward position of the piston probe 2. Then, the piston probe 2 retracts to release the interaction force.

[0054] In this process, the displacement of the piston probe 2 within the deep silicon blind via 0 can be obtained by subtracting the initial height of the piston probe 2 and the deformation of the AFM cantilever beam from the total driving displacement of the motion control unit 4 perpendicular to the scanning direction. Similarly, Measure the internal volume of the deep silicon blind via 0.

[0055] Example 3: Please see Figure 6 and Figure 7In the atomic force volume measurement device based on an AFM cantilever beam provided in Embodiment 2 of the present invention, the motion control unit 4 is connected to the AFM cantilever beam. The motion control unit 4 drives the AFM cantilever beam and the piston probe 2 to actively approach the deep silicon blind hole 0 to achieve detection. If the force detection unit 6 is designed using a beam deflection method, it is necessary to ensure that the laser 61 and photodetector 62 move synchronously with the motion control unit 4 during the vertical detection process of the AFM cantilever beam. This coordinated movement reduces the robustness of the system. Therefore, Embodiment 3 of the present invention, without changing other structures and working principles, specially designs the driving target of the motion control unit 4. The only difference between Embodiment 3 and Embodiment 2 is: The motion control unit 4 is not connected to the AFM cantilever beam. Instead, the sample with the deep silicon blind hole 0 is placed on the motion control unit 4. The motion control unit 4 drives the sample to move actively along the axis of the deep silicon blind hole 0, achieving vertical detection. During this process, the spatial position of the AFM cantilever beam remains unchanged, so the laser 61 and photodetector 62 can remain stationary.

[0056] Example 4: Please see Figure 8 In Embodiment 4 of the present invention, the atomic force volumetric metrology device based on the AFM cantilever beam in Embodiment 3 is further improved. An atomic probe 3 is set at the center of the lower surface of the piston probe 2. This atomic probe 3 can be a probe from an existing atomic force microscope. The atomic probe 3 and the piston probe 2 can be integrally formed, or they can be manufactured separately and then fixed by precision bonding or magnetic attraction. The function of the atomic probe 3 is different from that of the piston probe 2. The atomic probe 3 is used for high-precision positioning and alignment, and for three-dimensional morphological modeling of the scanning plane. It is used to determine the position coordinates of the deep silicon blind hole 0 on the sample surface, ensuring that the piston probe 2 can accurately enter the center of the deep silicon blind hole 0, that is, the central axis of the piston probe 2 coincides with the central axis of the deep silicon blind hole 0. Since the diameter of the deep silicon blind hole 0 is less than 2 micrometers or even reaches the sub-100 nanometer level, and the diameter of the piston probe 2 is very close to the diameter of the deep silicon blind hole 0 (the gap is only 100nm), the alignment accuracy between the two is extremely high. Therefore, an atomic probe 3 is set at the center of the lower surface of the piston probe 2, and the three-dimensional morphology model of the scanning plane is modeled using the principle of atomic force microscopy.

[0057] To achieve 3D topographic modeling of the scanning plane, an XYZ piezoelectric scanning stage is used as the motion control unit 4. The sample with the deep silicon blind hole 0 is fixed on the XYZ piezoelectric scanning stage. The XYZ piezoelectric scanning stage drives the sample to actively perform grating scanning in the X and Y directions. Uniform detection points are set along the scanning path, and at each detection point, reciprocating detection is also required perpendicular to the scanning direction. That is, at each detection point, the motion control unit 4 drives the AFM cantilever beam and piston probe 2 to perform a periodic movement of downward movement and reset along the Z direction, similar to the peak force operation used in advanced AFM technology.

[0058] During the scanning process, the motion control unit 4 drives the atom probe 3 to perform lateral scanning and vertical probing (i.e., AFM mode) on the sample surface with deep silicon blind holes 0. At least three scenarios exist during the scanning process: The first method involves the atomic probe 3 contacting the upper surface of the sample. The second method involves the piston probe 2 contacting the upper surface of the sample. The third method involves the piston probe 2 entering the deep silicon blind hole 0 without friction.

[0059] In the three scenarios described above, when the atomic probe 3 contacts the upper surface of the sample, the solid contact will quickly trigger the reset process. When the piston probe 2 contacts the upper surface of the sample, the detection point is at the edge of the deep silicon blind hole 0. The atomic probe 3 enters the deep silicon blind hole 0, but the piston probe 2 is not aligned with the deep silicon blind hole 0, so the piston probe 2 contacts the edge of the deep silicon blind hole 0, triggering the reset process. When the piston probe 2 enters the deep silicon blind hole 0 without friction, the piston probe 2 is exactly aligned with the deep silicon blind hole 0. When the piston probe 2 probes down to a certain depth, the force of the gas on the piston probe 2 is equal to the preset threshold, triggering the reset process.

[0060] After scanning, the depth information of each detection point on the sample surface can be obtained, i.e., the motion matrix of the reflected light spot. Using the motion matrix of the reflected light spot, a high-resolution three-dimensional topographic model of the sample surface can be reconstructed. This allows the determination of the position coordinates of the deep silicon blind hole 0 and the contour line of its edge.

[0061] After determining the shape and position of the deep silicon blind via 0, the motion control unit 4 can move the sample until the central axis of the piston probe 2 coincides with the central axis of the deep silicon blind via 0, and control it to move vertically according to the formula. The internal volume of the deep silicon blind via 0 is measured to determine its internal state. Furthermore, since the atomic probe 3 is extremely small, it does not affect the accuracy of the calculation results.

[0062] It should be noted that the elastic element 1 of the present invention is not limited to the helical spring and AFM cantilever beam used in the above embodiments. Other structures or devices capable of measuring the force applied to the piston probe 2, such as elastic membranes and pressure sensors, are also applicable and fall within the scope of disclosure and protection of the present invention.

[0063] The atomic force volumetric metrology device of this invention measures the internal volume of a deep silicon blind hole 0, effectively solving the problem of traditional optical measurement being limited by the optical diffraction limit. It can measure features that cannot be reached by pure optical technology and can perform high-resolution volumetric metrology on deep and narrow structures such as TSVs, meeting the metrology requirements of next-generation high aspect ratio TSV structures at the sub-100 nanometer scale.

[0064] In summary, the above description is merely a preferred embodiment of this specification and is not intended to limit the scope of protection of this specification. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this specification should be included within the scope of protection of this specification.

[0065] The systems, apparatuses, modules, or units described in one or more of the above embodiments may be implemented by a computer chip or entity, or by a product having a certain function. A typical implementation device is a computer. Specifically, a computer may be, for example, a personal computer, a laptop computer, a cellular phone, a camera phone, a smartphone, a personal digital assistant, a media player, a navigation device, an email device, a game console, a tablet computer, a wearable device, or any combination of these devices.

[0066] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0067] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments.

Claims

1. An atomic force volume measurement device, characterized in that, include: Elastic element; A piston probe is connected to one end of the elastic element. The shape and size of the piston probe must ensure that: after the piston probe enters the deep hole to be measured, the gap between the piston probe and the deep hole to be measured is less than twice the mean free path of gas molecules under working conditions, and there is no friction between the piston probe and the deep hole to be measured. A force detection unit is used to acquire the force acting on the elastic element; A motion control unit is used to drive the elastic element or move the deep hole to be measured, so that the piston probe moves relative to the axial direction of the deep hole to be measured. The feedback control unit is configured to control the motion control unit to move the piston probe away from the deep hole to be measured when the force on the elastic element is equal to a preset threshold. The internal volume of the deep hole to be measured is calculated based on the displacement of the piston probe into the deep hole to be measured and the force exerted on the elastic element.

2. The atomic force volumetric metering device according to claim 1, characterized in that, The elastic element is a helical spring.

3. The atomic force volumetric metering device according to claim 1, characterized in that, The elastic element is an AFM cantilever beam.

4. The atomic force volumetric metering device according to claim 1, characterized in that, By adjusting the gas pressure in the working environment to regulate the mean free path of gas molecules, this method can be used to detect deep holes of different sizes.

5. The atomic force volumetric metering device according to claim 1, characterized in that, The detection accuracy is improved by reducing the mean free path of gas molecules by increasing the air pressure of the working environment.

6. The atomic force volumetric metering device according to claim 1, characterized in that, The deep hole to be tested is a silicon blind hole with a diameter of less than 2 micrometers.

7. The atomic force volumetric metering device according to claim 1, characterized in that, The motion control unit is an XYZ piezoelectric scanning stage. The XYZ piezoelectric scanning stage drives the elastic element or the deep hole to be measured to perform grating scanning in the X and Y directions. At each detection point, it performs reciprocating detection in a direction perpendicular to the scanning direction to ensure that the piston probe is in the center of the deep hole to be measured.

8. The atomic force volumetric metering device according to claim 2, characterized in that, The force detection unit is a force gauge, which is mounted on the helical spring and is used to measure the force acting on the helical spring.

9. The atomic force volumetric metering device according to claim 3, characterized in that, The force detection unit includes a laser and a photodetector. The laser emits a laser beam to illuminate the upper surface of the AFM cantilever beam. The photodetector is used to receive the reflected light spot reflected from the upper surface of the AFM cantilever beam. The deformation of the AFM cantilever beam is obtained based on the position change of the reflected light spot on the photodetector. The force acting on the AFM cantilever beam is calculated based on the deformation of the AFM cantilever beam.

10. The atomic force volumetric metering device according to claim 1, characterized in that, The motion control unit subtracts the initial height of the piston probe and the deformation of the elastic element from the axial driving displacement of the deep hole to be measured, and obtains the displacement of the piston probe entering the deep hole to be measured.

11. The atomic force volumetric metering device according to claim 1, characterized in that, Measuring the internal volume of the deep hole to be measured The formula is: ； in, Let be the cross-sectional area of ​​the deep hole to be measured, n be the number of moles of gas in the deep hole, R be the ideal gas constant, and T be the thermodynamic temperature. This refers to the displacement of the piston probe within the deep hole to be measured. The force exerted by the gas inside the deep hole on the piston probe is the force.

12. The atomic force volumetric metering device according to claim 7, characterized in that, It also includes an atomic probe disposed at the center of the lower surface of the piston probe, wherein the atomic probe and the piston probe are fixed in a detachable manner or are obtained by integral fabrication.

13. The atomic force volumetric metering device according to claim 12, characterized in that, First, atomic force microscopy is performed on the upper surface of the sample using the atomic probe to create a three-dimensional morphology model of the upper surface of the sample, determine the shape and position of the deep hole to be measured on the sample, and make the central axis of the piston probe coincide with the central axis of the deep hole to be measured. Then, atomic force volume measurement is performed on the deep hole to be measured.

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