A probe for detecting the geometric parameters of the inner wall of a through-silicon via (TSV).

Abstract

This invention belongs to the field of through-silicon via (TSV) inspection technology, specifically relating to a probe for detecting the geometric parameters of the inner wall of a TSV. The probe includes a probe rod and a probe head; the aspect ratio of the probe rod is 10~50:1; the probe head includes a hemispherical portion and a tip, the hemispherical portion and the tip being integrally connected, with the tip of the tip located away from the hemispherical portion; the hemispherical portion is integrally connected to the probe rod, and the angle between the tip of the tip and the axis of the probe rod is 70°~110°; the radius of curvature of the tip is 10nm~50nm, and both the probe rod and the probe head are made of tungsten. The probe of this invention can meet the measurement requirements for critical dimensions and sidewall roughness of TSVs with an aspect ratio greater than 10:1.

Description

Technical Field

[0001] This invention belongs to the field of through-silicon via (TSV) detection technology, specifically relating to a probe for detecting the geometric parameters of the inner wall of a TSV. Background Technology

[0002] Through-Silicon Vias (TSVs) are a core technology in advanced chip packaging. Located in the later stages of chip manufacturing, defects in TSVs can cause entire wafer defects, determining the packaging quality and performance stability of 3D chips. A research report from the Semiconductor Equipment and Materials International (SEMI) indicates that as the number of wafer stacking layers increases and the aspect ratio of TSVs continues to improve, the overall chip defect rate caused by a single TSV defect increases exponentially. TSV process quality becomes a bottleneck for subsequent packaging yield. Therefore, how to measure and inspect TSVs and ensure high yield in this production stage through quality control is a pressing issue for the advanced chip packaging industry.

[0003] The mainstream TSV process is the Bosch process, which belongs to deep reactive ion etching (DRIE) technology. The first step of this process involves machining straight vias with diameters ranging from 10 to tens of micrometers on a silicon wafer substrate, with a maximum depth penetrating the wafer. The initial thickness of a 12-inch wafer is approximately 775 micrometers. Alternating cycles of SF6 fluorine gas and C4F8 fluorocarbons are used to longitudinally etch and sidewall protect the silicon substrate material, respectively, to achieve high aspect ratio TSV fabrication. Ideally, the inner walls of the TSV should be regular and smooth. However, during the alternating removal and protection of silicon material in the Bosch process, periodic serrated scallop-like morphology forms on the sidewalls, significantly increasing surface roughness by approximately 100nm to 200nm. Excessive sidewall roughness reduces the adhesion of the metal filler, hindering the uniform deposition of subsequent oxide layers and conductive metal materials, leading to problems such as dielectric leakage and voids in the filler layer. Furthermore, fluctuations in etching process parameters can induce other typical defects in TSV vias, such as notches, silica deposits, uneven depth / diameter, and sidewall cone angles. The aforementioned geometric and shape defects can lead to electrical failures in TSVs, impaired structural stability, and subsequent malfunctions such as uncontrolled thermal management in the chip. Therefore, after TSV via molding, sampling inspection must be carried out to accurately measure critical dimensions such as top and bottom hole diameters, hole depths, sidewall angles, and sidewall roughness to prevent defective products from entering the next production stage.

[0004] Atomic force microscopy (AFM) is a high-resolution technique commonly used for surface roughness measurement. However, it can only measure the outer surface of a sample perpendicularly, making it difficult to probe the interior of high aspect ratio holes, especially the sidewalls. Sejong University in South Korea achieved 3D imaging of through-holes with an aspect ratio of 4.3 and a resolution of 2 nm by using a high aspect ratio carbon nanotube (CNT) AFM probe to penetrate deep into high aspect ratio structures and detect sidewalls through real-time probe orientation adjustment. Su-Been et al. designed a scanner that can tilt left and right by tilting the AFM tip, improving it into a 3D-AFM that can rotate at a certain angle in the vertical plane, enabling sidewall scanning. However, current technology is limited to imaging the sidewalls of grooves. The core component of AFM is its probe tip. Xi'an Jiaotong University assembled carbon nanotubes (CNTs) on an AFM silicon probe, using CNTs to create nanoprobe tips with a diameter as low as 10 nm. These CNT tips are grown on silicon cantilever arms and have been successfully used in several metrology institutions in China. In addition, some researchers have designed and fabricated probes with special shapes, such as trumpet-shaped probes and triangular probes, to achieve 3D scanning of sidewalls. However, the longitudinal detection depth of the aforementioned AFM probes is insufficient, with lengths ranging from 125 μm to 225 μm and aspect ratios from 3 to 8. When measuring deeper TSV holes, existing AFM probes cannot simultaneously achieve high resolution and a large aspect ratio; even with tilted probes, the entire internal morphology of the hole cannot be characterized. Therefore, AFM probes are not suitable for measuring the internal dimensions of TSVs with aspect ratios greater than 10. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a probe for detecting the geometric parameters of the inner wall of a through-silicon via.

[0006] A probe for detecting the geometric parameters of the inner wall of a through-silicon via (TSV), comprising a probe rod and a probe head;

[0007] The length-to-diameter ratio of the probe rod is 10~50:1;

[0008] The probe head includes a hemispherical portion and a needle tip, the hemispherical portion and the needle tip are integrally connected, and the tip of the needle tip is away from the hemispherical portion;

[0009] The hemispherical part is integrally connected to the probe rod, and the angle between the tip of the needle and the axis of the probe rod is 70°~110°.

[0010] The radius of curvature of the needle tip is 10nm~50nm;

[0011] Both the probe rod and the probe head are made of tungsten.

[0012] This invention uses tungsten as the probe rod and probe tip, primarily because tungsten wire itself has high rigidity and hardness. Furthermore, excessively long tungsten wires can lead to insufficient probe rod rigidity, causing bending during contact measurement. A length-to-diameter ratio of 10–30:1 is sufficient for measuring the internal dimensions of TSVs with a depth-to-width ratio greater than 10, while still ensuring probe rigidity. The hemispherical portion is integrally connected to the probe rod, allowing the root of the hemisphere to effectively distribute bending moments when the probe scans within the hole or encounters lateral forces, preventing stress concentration cracks in the rod-needle transition zone. This ensures that the probe maintains good rigidity and structural strength even with a length-to-diameter ratio of 10–30:1. The integrated design of the hemispherical part and the tip further improves the overall structural strength and rigidity of the probe, ensuring that no deformation or wear occurs when measuring the internal dimensions of TSVs with a depth-to-width ratio greater than 10. The angle between the tip and the axis of the probe rod is 70°~110° to achieve accurate measurement of sidewall angles and sidewall roughness. The probe can be tilted during the inspection process to characterize the entire internal morphology of the hole. The radius of curvature of the tip is 10nm~50nm, which can improve the sharpness of the tip and achieve high-resolution measurement of the surface roughness of the TSV sidewall.

[0013] In another preferred embodiment, the diameter of the probe rod is 60μm to 100μm. This diameter ensures applicability to most through-silicon via (TSV) inspections. If the tungsten wire diameter is too small, the probe rod will lack sufficient rigidity and structural strength at a length-to-diameter ratio of 10 to 30:1, affecting inspection accuracy. Since the diameter of TSVs is generally below 100μm, if the tungsten wire diameter is too large, it cannot enter the TSV for inspection.

[0014] In another preferred embodiment, one side of the probe rod is tangent to the arc portion of the hemispherical part. This tangential arrangement prevents the hemisphere from experiencing multi-line contact or wedging on the borehole wall during detection, allowing the cantilever deflection signal to be directly mapped to the true borehole wall morphology, thus eliminating artifacts.

[0015] In another preferred embodiment, the ratio of the radius of the hemispherical portion to the diameter of the probe rod is 2 to 3:1.

[0016] In another preferred embodiment, the ratio of the length of the needle tip to the radius of the hemispherical portion is 2 to 3:1. This ratio ensures the rigidity of the needle tip during use, making the tip more robust and able to withstand TSV sidewall friction and scanning shear forces without bending or breaking.

[0017] In another preferred embodiment, the probe rod is cylindrical or conical.

[0018] In another preferred embodiment, when the probe rod is conical, the hemispherical portion is integrally connected to the smaller end of the probe rod.

[0019] In another preferred embodiment, the diameter of the cross-section at the junction of the needle tip and the hemispherical portion is the same as the diameter of the hemispherical portion.

[0020] In another preferred embodiment, both the probe rod and the probe head are made of tungsten.

[0021] Compared with the prior art, the present invention has the following beneficial effects.

[0022] In this invention, the probe head consists of a hemispherical portion and a tip portion. By controlling the angle between the tip and the probe shaft axis to be between 70° and 110°, when measuring deeper TSV holes, the probe can enter vertically to characterize the 3D dimensions and morphology inside the TSV hole, significantly improving the detectability of physical probes for the internal dimensions of micro-holes with high aspect ratios. The tip's radius of curvature of 10nm to 50nm improves its sharpness, enabling high-resolution measurement of the surface roughness of the TSV sidewalls. The probe shaft's length-to-diameter ratio of 10 to 50:1 allows for deep probing into the interior of TSV holes with large aspect ratios, meeting the measurement requirements for typical TSV critical dimensions and sidewall roughness with lateral dimensions of 50μm to 100μm and aspect ratios greater than 10:1. The probe rod is integrally connected to the hemispherical part, and the hemispherical part is integrally connected to the needle tip, which gives the probe good structural strength and rigidity. It is not easy to deform and wear during the measurement process, has a long service life, and can ensure the reliability of the measurement results during the service of the probe. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the probe structure of the present invention.

[0024] Figure 2 This is a schematic diagram of the probe head of the present invention.

[0025] Figure description: 1-Probe rod, 2-Probe head, 21-Hemispherical part, 22-Needle tip. Detailed Implementation

[0026] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. Unless otherwise specified, the experimental methods described in the embodiments of the present invention are conventional methods.

[0027] Currently, AFM (Automatic Through-Silicon Via) is limited by probe size, resulting in insufficient longitudinal detection depth. Existing AFM probes range in length from 125μm to 225μm, with aspect ratios of 3 to 8:1, as shown in Table 1. When measuring deeper TSV (Through-Silicon Via) holes, existing AFM probes suffer from low resolution due to insufficient tip sharpness (i.e., a large radius of curvature), making it impossible to accurately detect the geometric parameters of the TSV inner wall and thus reducing detection accuracy. While some methods assemble pyramid-shaped carbon nanotube tips onto AFM silicon probes to reduce tip diameter and increase tip sharpness for higher resolution of TSVs, they cannot achieve aspect ratios greater than 10. It is evident that existing AFM probes cannot simultaneously achieve high resolution and a large aspect ratio. Even with tilted probes, they can only reach the shallow layer of deep holes, failing to characterize the entire hole's interior. Therefore, existing AFM probes are unsuitable for measuring the internal dimensions of TSVs with aspect ratios greater than 10.

[0028] Table 1 Existing AFM probe parameters

[0029]

[0030] Therefore, the present invention provides a probe for detecting the geometric parameters of the inner wall of a through-silicon via (TSV). By using a length-to-diameter ratio of 10 to 50:1, the longitudinal detection depth is improved. The probe head is composed of a hemispherical part and a tip part. By controlling the radius of curvature of the tip, the sharpness of the tip is improved, thereby enabling more accurate detection of the TSV. Furthermore, by controlling the angle between the tip of the tip and the axis of the probe rod to be 70° to 110°, the probe does not need to be tilted during the detection process, thus improving the depth of the probe's reach and the detection accuracy.

[0031] The following is a detailed description of a probe used for detecting through-silicon vias.

[0032] This invention provides a probe for detecting through-silicon vias, such as... Figure 1 As shown, it includes a probe rod 1 and a probe head 2.

[0033] The length-to-diameter ratio of the probe rod 1 is 10 to 50:1. In this embodiment, the length-to-diameter ratio of the probe rod 1 is 10:1. The probe rod 1 is cylindrical or conical. In this embodiment, the probe rod 1 is conical with a taper of 85° to 89° and a diameter of 60μm, so as to facilitate insertion into the narrow space inside the TSV bore to measure its sidewall.

[0034] like Figure 2As shown, the probe head includes a hemispherical portion 21 and a tip 22. By designing the hemispherical portion 21, its root, i.e., the arc portion, can effectively distribute the bending moment, avoiding stress concentration cracks in the rod-needle transition zone. Specifically, the hemispherical portion 21 and the tip 22 are integrally connected; and the tip of the tip 22 is far away from the hemispherical portion 21. The structural design of the hemispherical portion 21 being integrally connected to the probe rod 1 and the tip 22 being integrally connected can further improve the overall structural strength and rigidity of the probe. The angle between the tip of the tip 22 and the axis of the probe rod 1 is 70°~110°. This angle facilitates the probe to accurately measure the sidewall angle and sidewall roughness. In this embodiment, the angle is 90°. The radius of curvature of the tip 22 is 10nm~50nm, which can improve the sharpness of the tip. In this embodiment, the radius of curvature is 30nm. The hemispherical portion 21 is integrally connected to the smaller end of the probe rod 1, and one side of the probe rod 1 is tangent to the arc of the hemispherical portion 21. This tangency allows the root of the hemispherical portion 21 to effectively share the bending moment when the probe scans inside the hole or encounters lateral forces, preventing stress concentration cracks in the rod-needle transition zone. Furthermore, during the detection process, the hemispherical portion 21 will not produce multi-line contact or wedging phenomena on the hole wall, allowing the cantilever deflection signal to be directly mapped to the true shape of the hole wall, eliminating artifacts. The ratio of the radius of the hemispherical portion 21 to the diameter of the probe rod 1 is 2~3:1. In this embodiment, the ratio is 2:1. The diameter of the cross-section at the connection between the needle tip 22 and the hemispherical portion 21 is the same as the diameter of the hemispherical portion 21. By controlling the taper of probe rod 1, the angle between the tip of needle 22 and the axis of probe rod 1, and the radius of curvature, it is possible to ensure that the probe is both sufficiently slender and has high rigidity, so that the deformation can be kept negligible in nanoscale contact measurement, thereby ensuring measurement accuracy.

[0035] Both the probe rod 1 and the probe head 2 are made of tungsten, and the surface of the probe head 2 is coated with a nano-scale wear-resistant coating. Specifically, the nano-scale coating is an Al2O3 coating obtained by atomic layer deposition or chemical vapor deposition, and the thickness of the Al2O3 coating is 0.05μm.

[0036] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A probe for detecting the geometric parameters of the inner wall of a through-silicon via (TSV), characterized in that, The probe comprises a probe rod (1) and a probe head (2); The aspect ratio of the probe rod (1) is 10-50:1; The probe head (2) comprises a semi-spherical part (21) and a needle tip (22), the semi-spherical part (21) and the needle tip (22) are integrally connected, and the tip of the needle tip (22) is away from the semi-spherical part (21); The semi-spherical part (21) is integrally connected with the probe rod (1), and the included angle between the tip of the needle tip (22) and the axis of the probe rod (1) is 70-110°; The radius of curvature of the needle tip (22) is 10-50 nm; The probe rod (1) and the probe head (2) are both made of tungsten; One side of the probe rod (1) is tangent to the arc part of the semi-spherical part (21), and the ratio of the radius of the semi-spherical part (21) to the diameter of the probe rod (1) is 2-3:

1.

2. The probe for detecting the inner wall geometry of a through silicon via according to claim 1, wherein The diameter of the probe rod (1) is 60-100 μm.

3. The probe for detecting the inner wall geometry of a through silicon via according to claim 1, wherein The ratio of the length of the needle tip (22) to the radius of the semi-spherical part (21) is 2-3:

1.

4. The probe for detecting the inner wall geometry of a through silicon via according to claim 1, wherein The probe rod (1) is cylindrical or conical.

5. The probe for detecting the inner wall geometry of a through silicon via according to claim 4, wherein When the probe rod (1) is conical, the semi-spherical part (21) is integrally connected with the smaller end of the probe rod (1).

6. The probe for detecting the inner wall geometry of a through silicon via according to claim 1, wherein The diameter of the cross section of the connection between the needle tip (22) and the semi-spherical part (21) is the same as the diameter of the semi-spherical part (21).

7. The probe for detecting the inner wall geometry of a through silicon via according to claim 1, wherein The surface of the probe head (2) is coated with a nano-scale wear-resistant coating.

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