A defect detection method

Abstract

The application discloses a defect detection method, comprising: providing a measured substrate to be detected, the substrate being formed with a recess; filling the recess with a formable flexible material; performing heat treatment on the substrate filled with the material at a preset temperature to form a target detection object with a complementary topography of the recess; peeling the target detection object from the measured substrate; detecting and identifying a defect feature on a surface of the target detection object, and determining an abnormal topography of an inner wall of the recess on the measured substrate according to the defect feature. The defect detection method can realize more intuitive detection inside the recess and improve defect detection accuracy.

Description

Technical Field

[0001] This application relates to the field of semiconductor manufacturing technology, specifically to a defect detection method. Background Technology

[0002] During wafer manufacturing, defects can occur at any stage of the process. Deep trenches, as a core three-dimensional structure in advanced chips such as power devices, MEMS sensors, and 3D chips (e.g., TSV vias), play crucial roles in electric field isolation, current path control, mechanical support, and vertical interconnection. Therefore, deep trench inspection is an indispensable process in wafer manufacturing.

[0003] Existing deep trench inspection methods include conventional defect scanning, failure analysis cross-sectioning (FA slicing), wafer acceptance testing (WAT), and electrical testing. Conventional defect scanning typically performs rapid scanning and identification of microscopic physical defects inside and around the deep trench. However, defects in deep trenches or deep VIA vias, such as small silicon pillars, notches, cracks, or residual particles at the bottom, are difficult to detect, thus affecting subsequent WAT testing and even wafer yield. While FA slicing can visually display defects, this method is irreversible, rendering the entire wafer unusable. WAT and electrical testing methods struggle to detect defects unrelated to electrical properties but relevant to reliability engineering (RE).

[0004] Therefore, how to conduct more intuitive inspections of the interior of deep trenches is a problem that needs to be solved. Summary of the Invention

[0005] This application provides a defect detection method that can provide the morphology of deep trenches or through-walls, thereby enabling more intuitive detection. The specific solution is as follows: In a first aspect, this application provides a defect detection method, comprising: providing a substrate to be tested, wherein a recess is formed on the substrate; filling the recess with a formable flexible material; heat-treating the substrate filled with the material at a preset temperature to form a target detection object having a complementary morphology to the recess; peeling the target detection object from the substrate; detecting and identifying defect features on the surface of the target detection object, and determining the abnormal morphology of the inner wall of the recess on the substrate based on the defect features.

[0006] Optionally, the recess can be filled with a formable flexible material, specifically by pouring liquid formable flexible material onto the surface of the substrate under test, so that the formable flexible material flows into the recess of the substrate under test.

[0007] Optionally, the recess is filled with a formable flexible material, specifically including: providing an auxiliary substrate, forming a formable flexible material layer on the surface of the auxiliary substrate; the thickness of the formable flexible material layer being greater than the depth of the recess; adhering the test substrate to the surface of the auxiliary substrate; applying pressure to the test substrate and / or the auxiliary substrate, causing the formable flexible material layer to deform and fill the recess.

[0008] Optionally, the substrate filled with the material is heat-treated at a preset temperature to form a target detection object with a complementary morphology to the recess. Specifically, this includes: heat-treating the substrate filled with the material at a preset temperature to crosslink and cure the formable flexible material to form an elastomer; and using the elastomer as the target detection object.

[0009] Optionally, the substrate filled with the material is heat-treated at a preset temperature to crosslink and cure the formable flexible material to form an elastomer. Specifically, this includes heat-treating the test substrate filled with the formable flexible material at a temperature of 60°C to 80°C for 15 to 30 minutes to form silicone rubber, wherein the silicone rubber is the elastomer.

[0010] Optionally, peeling the target detection object from the substrate under test specifically includes: using a special peeling jig to peel the target detection object from the substrate under test along a preset peeling angle and at a preset peeling rate.

[0011] Optionally, if the formation process of the target detection object involves pouring a liquid, formable, flexible material onto the surface of the substrate to be tested, then peeling the target detection object from the substrate to be tested specifically includes: providing an auxiliary substrate and coating the surface of the substrate with an adhesive; using the adhesive to bond the auxiliary substrate to the side of the target detection object opposite to the substrate to be tested; and peeling the target detection object from the substrate to be tested by pulling the auxiliary substrate.

[0012] Optionally, detecting and identifying defect features on the surface of the target object to be detected includes: providing an auxiliary substrate and crosslinking the target object to be detected onto the auxiliary substrate; scanning and / or re-examining the auxiliary substrate to detect and identify the defect features; after determining the abnormal morphology of the inner wall of the recess on the substrate to be tested, removing the crosslinked target object from the auxiliary substrate; the substrate after removal can be reused as an auxiliary substrate.

[0013] Optionally, detecting and identifying defect features on the surface of the target inspection object includes: if the coordinates of a suspected defect are found in the optical inspection process prior to SEM scanning, then sending an instruction to the SEM machine through the application programming interface of the SEM machine to view the defect features at the coordinates.

[0014] Optionally, the method further includes: before filling the recess with a formable flexible material, forming a low surface energy protective film layer on the surface of the substrate under test, the protective film layer covering the inner wall of the recess; wherein forming the low surface energy protective film layer on the surface of the substrate under test specifically includes: spin-coating perfluorooctyltrichlorosilane on the surface of the substrate under test to form the protective film layer with anti-adhesion properties; wherein the thickness of the protective film layer is not greater than 2 nanometers.

[0015] Optionally, the formable flexible material is liquid polydimethylsiloxane.

[0016] Optionally, the recess may include a deep groove and / or a through hole.

[0017] Compared with the prior art, this application has the following advantages: The defect detection method provided in this application involves providing a substrate to be tested, on which recesses are formed; filling the recesses with a formable flexible material; heat-treating the substrate filled with the material at a preset temperature to form a target detection object with a complementary morphology to the recesses; peeling the target detection object from the substrate; detecting and identifying defect features on the surface of the target detection object; and determining the abnormal morphology of the inner wall of the recesses on the substrate based on the defect features. By forming a target detection object with a complementary morphology to the recesses using a formable flexible material, the inner wall morphology of deep trenches or VIAs is mirrored and visually represented, facilitating the detection of small silicon pillars, notches, cracks, or tiny particles remaining at the bottom of the recesses that are difficult to detect with conventional scanning. This enables accurate scanning and / or review of defects in the inner walls of the recesses fabricated on the substrate, improving the substrate yield.

[0018] Furthermore, scanning and / or re-inspection can be performed by cross-linking the target object with an auxiliary substrate. This auxiliary substrate can be reused after the target object is removed, reducing defect detection costs. Moreover, during the process of peeling the target object from the substrate, particles from deep trenches or VIAs may be adsorbed and carried away, thereby mitigating substrate yield losses caused by particle defects. Attached Figure Description

[0019] Figure 1 This is a flowchart of a defect detection method provided in one embodiment of this application.

[0020] Figure 2A This is a schematic cross-sectional view of a stage in which a liquid formable flexible material is poured into a substrate according to one embodiment of this application.

[0021] Figure 2B This is a schematic cross-sectional view of an example of the stage of peeling an elastomer from a substrate under test, provided in one embodiment of this application.

[0022] Figure 2C This is a cross-sectional structural diagram of an example of the scanning and review stage of a target detection object provided in one embodiment of this application. Detailed Implementation

[0023] To enable those skilled in the art to better understand the technical solutions of this application, the application will be clearly and completely described below with reference to the accompanying drawings of the embodiments. However, this application can be implemented in many other ways different from those described below. Therefore, based on the embodiments provided in this application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this application.

[0024] It should be noted that the terms "first," "second," etc., in the claims, specification, and drawings of this application are used to distinguish similar objects and are not used to describe a specific order or sequence. Such data are interchangeable where appropriate so that the embodiments of this application described herein can be implemented in a sequence other than that shown or described herein. Furthermore, the terms "comprising," "having," and their variations are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0025] It should be noted that the thickness and shape in the accompanying drawings of the embodiments of this application do not reflect the actual proportions, and are only intended to illustrate the various embodiments.

[0026] To facilitate understanding of the various embodiments of this application, some concepts involved in the embodiments are given.

[0027] Deep trench: A three-dimensional structure with a high aspect ratio, formed on a semiconductor substrate (such as a silicon wafer) through an etching process. As device integration continues to increase, this structure can greatly improve functional density within a limited chip area.

[0028] Via Hole (VIA): In the semiconductor and advanced packaging fields, a via generally refers to a silicon via, which is a tiny conductive channel vertically penetrating the thickness of a silicon wafer and created inside the silicon substrate (or silicon interposer). Deep Via (TSV) refers to a through-silicon via.

[0029] Because recesses formed on semiconductors, such as deep trenches or vias, are closed and narrow, specific microscopic defects are easily generated during processing. For example, etching can cause sharp corners on the sidewalls, leading to electric field concentration and reducing device reliability. Therefore, mechanical defect scanning after recess etching is a crucial step. However, in deep trenches or vias with high aspect ratios, or other similar recess structures such as trenches, vias, or blind holes, defects such as small silicon pillars, notches, cracks, or residual particles at the bottom are difficult to detect. Furthermore, high aspect ratio recesses also present cleaning challenges, posing an even greater challenge to defect detection in these types of recesses. In addition, some application scenarios present challenges in detecting concave defects, making it difficult to identify them. Examples include: continuous / linear grooves, grid / intersecting grooves, large-area / planar grooves, continuous groove arrays, continuous / slit-like vias (such as slits), via arrays / dense vias, large-area / planar vias, large-area connecting holes / through holes / blind holes, light-trapping structures or light-trapping groove arrays, heat dissipation trench arrays, and microfluidic trench arrays.

[0030] In view of this, this application provides a defect detection method that uses a formable flexible material to reveal the inner wall morphology of a recess formed on a semiconductor, thereby improving the accuracy of recess defect detection.

[0031] The following combination Figure 1 and Figures 2A to 2C The defect detection method is described below.

[0032] Please refer to Figure 1 The defect detection method shown in the figure includes steps S101 to S105.

[0033] Step S101: Provide a substrate to be tested, wherein a recess is formed on the substrate; Step S102: Fill the recess with a formable flexible material; Step S103: Heat-treat the substrate filled with the material at a preset temperature to form a target detection object with a complementary morphology to the recess; Step S104: Peel the target object from the substrate being tested; Step S105: Detect and identify the defect features on the surface of the target object, and determine the abnormal morphology of the inner wall of the recess on the substrate under test based on the defect features.

[0034] A substrate, also known as a wafer, is the basic carrier used to grow semiconductor thin films or construct integrated circuits. The substrate is preferably a wafer. A wafer is a circular, thin-film substrate used in semiconductor manufacturing, and its material can be, but is not limited to, semiconductor or insulating materials such as silicon, gallium arsenide (GaAs), silicon carbide (SiC), and sapphire. In this embodiment, the wafer is preferably an extremely thin circular silicon wafer cut and polished from single-crystal silicon.

[0035] The recess includes deep trenches and / or through holes. The fabrication of these recesses is often required in the early or middle stages of substrate manufacturing. After fabrication, the recesses undergo defect inspection to ensure substrate yield.

[0036] In step S102, the moldable flexible material can be polydimethylsiloxane (PDMS) or other moldable materials. PDMS is preferably in liquid form. In this step, PDMS can be used to mold (or mirror) the inner wall morphology of the recesses created on the substrate. The process by which PDMS transforms from a liquid to an elastomer (silicone rubber) is called crosslinking. Preferably, an addition-cure curing system of PDMS is used, comprising two components: component A (base adhesive, i.e., prepolymer) and component B (curing agent); component A contains long chains of polydimethylsiloxane with vinyl groups (-CH=CH2); component B contains a crosslinking agent with multiple silicon-hydrogen bonds (Si-H), and may also include a platinum (Pt) catalyst. When A and B are mixed and heated, under the action of the platinum catalyst, the Si-H bonds open directly, undergoing an addition reaction with the vinyl groups, causing the independent polymer chains to be linked together by chemical bonds, forming a three-dimensional network structure. In this embodiment, the ratio of base adhesive to curing agent is in the range of 20:1 to 30:1 to obtain better fluidity and easy peeling.

[0037] To facilitate the removal of the target object formed from the moldable flexible material from the test substrate, an anti-adhesion treatment is required on the surface of the test substrate before filling the recess with the moldable flexible material. Specifically, a low surface energy protective film layer is formed on the surface of the test substrate before filling the recess, covering the inner wall of the recess. Low surface energy refers to a surface with low attractive force to other objects, thus preventing adhesion. Forming the low surface energy protective film layer on the surface of the test substrate specifically includes spin-coating perfluorooctyltrichlorosilane (FOTS) onto the surface of the test substrate to form the anti-adhesion protective film layer. Preferably, the thickness of the protective film layer is no greater than 2 nanometers.

[0038] There are several ways to fill the recess with a moldable flexible material. In one embodiment, filling the recess with a moldable flexible material specifically includes: pouring liquid moldable flexible material onto the surface of the substrate under test, such that the moldable flexible material flows into the recess of the substrate under test. That is, after spin-coating FOTS onto the surface of the substrate under test, a PDMS solution is poured into the substrate under test.

[0039] In another embodiment, the test substrate can be imprinted onto an auxiliary substrate coated with a moldable flexible material to transfer the recesses (deep trenches and / or vias) on the test substrate to the auxiliary substrate. This allows the morphology of the recesses to be more clearly displayed in the moldable flexible material layer of the auxiliary substrate, facilitating better defect detection. Specifically, filling the recesses with a moldable flexible material includes: providing an auxiliary substrate; forming a moldable flexible material layer on the surface of the auxiliary substrate; the thickness of the moldable flexible material layer being greater than the depth of the recess; adhering the test substrate to the surface of the auxiliary substrate; and applying pressure to the test substrate and / or the auxiliary substrate, causing the moldable flexible material layer to deform and fill the recess. Different imprinting pressures can be used depending on the curing method. If ultraviolet curing is used, the applied pressure is no higher than 0.1 MPa; if heat treatment imprinting is used, the applied pressure ranges from 5 to 20 MPa. The auxiliary substrate can be a bare wafer, i.e., a pure silicon wafer (or other semiconductor material wafer) without circuit clusters, device structures, or metal lines.

[0040] In step S103, the substrate filled with the material is heat-treated at a preset temperature to form a target detection object with a complementary morphology to the recess. Specifically, this includes: heat-treating the substrate filled with the material at a preset temperature to cross-link and cure the moldable flexible material to form an elastomer; using the elastomer as the target detection object. The preset temperature range is 60°C to 80°C. Further, heat-treating the substrate filled with the material at a preset temperature to cross-link and cure the moldable flexible material to form an elastomer specifically includes: heat-treating the substrate filled with the moldable flexible material at a temperature of 60°C to 80°C for 15 to 30 minutes to form silicone rubber, where the silicone rubber is the elastomer.

[0041] In step S104, different methods can be used to peel the target detection object from the substrate under test. One embodiment specifically includes: using a specialized peeling jig to peel the target detection object from the substrate under test along a preset peeling angle and at a preset peeling rate. The peeling angle, such as 180 degrees (or 90 degrees), and the peeling rate, such as 100 mm / min, can be locked by using a peeling jig, such as a peeling wedge, to achieve more precise peeling force data. In another embodiment, peeling is performed by carrier traction. Specifically, if the formation process of the target detection object involves pouring a liquid, formable, flexible material onto the surface of the substrate under test, peeling the target detection object from the substrate under test includes: providing an auxiliary substrate; coating the substrate surface with an adhesive (e.g., spin-coating or spraying); bonding the auxiliary substrate to the side of the target detection object opposite to the substrate under test using the adhesive; and peeling the target detection object from the substrate under test by traction of the auxiliary substrate.

[0042] In step S105, defect detection is performed, wherein detecting and identifying defect features on the surface of the target object includes: providing an auxiliary substrate and crosslinking the target object onto the auxiliary substrate; scanning and / or re-examining the auxiliary substrate to detect and identify the defect features. Since the morphology of the target object and the recesses on the substrate being tested are complementary, a mirror image of the defect features of the target object can be used as an abnormal morphology within the corresponding recess, thereby identifying defects on the inner wall of the recesses in the substrate being tested. The defect features include one or more of silicon pillars, notches, cracks, and particles.

[0043] Furthermore, the method further includes: after determining the abnormal morphology of the inner wall of the recess on the substrate under test, removing the cross-linked target object on the auxiliary substrate; the substrate after removal can be reused as an auxiliary substrate. This can reduce the cost of defect detection.

[0044] Please refer to Figures 2A to 2C The figure shows a cross-sectional schematic diagram of three stages: casting a liquid formable flexible material into the substrate to form an elastomer, peeling off the elastomer, and scanning and re-examining defects.

[0045] Figure 2A The example test substrate schematically shows seven deep trenches, 1-7, which are formed by pouring liquid PDMS into the test substrate to fill the deep trenches; heating at 80 degrees Celsius for 20 minutes to cure the PDMS into silicone rubber; and the presence of defects in deep trenches 5-7, including a silicon pillar at the bottom of the inner wall of deep trench 5, a crack at the bottom of deep trench 6, and a notch in deep trench 7.

[0046] Figure 2B The figure shows the process of elastomer peeling, with PDMS pillars 8-14 corresponding to the morphology of each deep trench, i.e., the PDMS elastomer protrusions; PDMS pillar 12 corresponds to deep trench 5; PDMS pillar 13 corresponds to deep trench 6; and PDMS pillar 14 corresponds to deep trench 7. Accordingly, due to the silicon pillar at the bottom of deep trench 5, PDMS pillar 12 has a notch complementary to the silicon pillar at its corresponding position; PDMS pillar 13 has an additional portion complementary to the crack in deep trench 6 at its corresponding position; and PDMS pillar 14 has an additional portion complementary to the notch in deep trench 7 at its corresponding position.

[0047] Figure 2C After the intermediate elastomer is crosslinked onto the auxiliary substrate, the auxiliary substrate is scanned and re-examined. A notch in PDMS pillar 12 is detected, which indicates that there is a silicon pillar defect at the corresponding position of deep trench 5. A defect with multiple protrusions in PDMS pillar 13 is detected, and based on the shape of the defect, it can be determined that there is a crack at the corresponding position of deep trench 6. A defect with multiple protrusions in PDMS pillar 14 is detected, and based on the shape of the defect, it can be determined that there is a notch at the corresponding position of deep trench 7 that is complementary to the multiple protrusions.

[0048] Furthermore, before scanning and / or reviewing the auxiliary substrate, optical inspection can be performed. This optical inspection may reveal suspected defects, prompting further scanning and / or review. In this case, defects at specific locations can be directly viewed using the SEM machine without scanning. Specifically, detecting and identifying defect features on the surface of the target inspection object includes: if the coordinates of a suspected defect are found in the optical inspection process prior to SEM scanning, then sending instructions to the SEM machine via its application programming interface (API) to view the defect features at those coordinates.

[0049] Therefore, this embodiment provides a simple and low-cost reverse enhancement detection scheme for inner wall defects in recesses. The advantages of this scheme are: it can reflect the reverse morphology of deep trenches or deep through-holes on an auxiliary substrate cross-linked with a formable flexible material, PDMS. Furthermore, the auxiliary substrate can be reused after removing the formable flexible material following defect detection; moreover, if a suspected defect is found during the pre-scan optical inspection process, the specific location of the suspected defect can be directly viewed using the API of the SEM machine without scanning, allowing for more intuitive and accurate defect confirmation and improving defect detection accuracy; and, particles that cannot be removed from deep trenches can be adsorbed and removed using a formable flexible material such as PDMS columns, mitigating substrate yield loss caused by particle defects.

[0050] Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of this application. Therefore, the scope of protection of this application should be determined by the scope defined in the claims of this application.

Claims

1. A defect detection method, characterized in that, include: A substrate to be tested is provided, wherein a recess is formed on the substrate; The recess is filled with a formable flexible material; The substrate filled with the material is heat-treated at a preset temperature to form a target detection object with a complementary morphology to the recess; The target object to be detected is peeled off from the substrate being tested; The defect features on the surface of the target object are detected and identified, and the abnormal morphology of the inner wall of the recess on the substrate under test is determined based on the defect features.

2. The defect detection method according to claim 1, characterized in that, The recess is filled with a formable flexible material, specifically including: Liquid formable flexible material is poured onto the surface of the substrate under test, causing the formable flexible material to flow into the recess of the substrate under test.

3. The defect detection method according to claim 1, characterized in that, The recess is filled with a formable flexible material, specifically including: An auxiliary substrate is provided, and a formable flexible material layer is formed on the surface of the auxiliary substrate; the thickness of the formable flexible material layer is greater than the depth of the recess. The surface of the substrate to be tested is placed against the surface of the auxiliary substrate; Pressure is applied to the substrate under test and / or the auxiliary substrate, causing the formable flexible material layer to deform and fill the recess.

4. The defect detection method according to any one of claims 1 to 3, characterized in that, The substrate filled with the material is heat-treated at a preset temperature to form a target detection object with a complementary morphology to the recess, specifically including: The substrate filled with the material is heat-treated at a preset temperature to crosslink and cure the formable flexible material to form an elastomer; the elastomer is used as the target detection object.

5. The defect detection method according to claim 4, characterized in that, The substrate filled with the material is heat-treated at a preset temperature to crosslink and cure the formable flexible material into an elastomer, specifically including: The substrate being tested, which is filled with a formable flexible material, is subjected to heat treatment at a temperature of 60°C to 80°C for 15 to 30 minutes to form silicone rubber, which is the elastomer.

6. The defect detection method according to claim 1, characterized in that, Peeling the target object from the substrate under test specifically includes: The target object is peeled from the substrate at a preset peeling angle and a preset peeling rate using a specialized peeling jig.

7. The defect detection method according to claim 1, characterized in that, If the formation process of the target detection object involves pouring a liquid, formable, flexible material onto the surface of the substrate being tested, then peeling the target detection object from the substrate being tested specifically includes: An auxiliary substrate is provided, and an adhesive is coated on the surface of the substrate; The adhesive is used to bond the auxiliary substrate to the side of the target object opposite to the substrate being tested. The target object is peeled off from the substrate being tested by pulling the auxiliary substrate.

8. The defect detection method according to claim 1, characterized in that, Detecting and identifying defect features on the surface of the target object includes: An auxiliary substrate is provided, and the target detection object is crosslinked onto the auxiliary substrate; The auxiliary substrate is scanned and / or re-examined to detect and identify the defect features; After determining the abnormal morphology of the inner wall of the recess on the substrate under test, the cross-linked target detection object on the auxiliary substrate is removed; The removed substrate can be reused as an auxiliary substrate.

9. The defect detection method according to claim 1, characterized in that, Detecting and identifying defect features on the surface of the target object includes: If the coordinates of a suspected defect are found in the optical inspection process prior to SEM scanning, an instruction is sent to the SEM machine via the application programming interface of the SEM machine to view the defect features at the coordinates.

10. The defect detection method according to claim 1, characterized in that, The method further includes: Before filling the recess with a formable flexible material, a low surface energy protective film layer is formed on the surface of the substrate under test, the protective film layer covering the inner wall of the recess; Specifically, forming a low surface energy protective film layer on the surface of the substrate under test includes: Perfluorooctyltrichlorosilane is spin-coated onto the surface of the substrate to form the protective film layer with anti-adhesion properties; The thickness of the protective film layer is no greater than 2 nanometers.

11. The defect detection method according to claim 1, characterized in that, The formable flexible material is liquid polydimethylsiloxane.

12. The defect detection method according to claim 1, characterized in that, The recess includes a deep groove and / or a through hole.

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